Note: Descriptions are shown in the official language in which they were submitted.
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MOLECULAR SIEVE CATALYST COMPOSITION.
ITS MAKING AND USE IN CONVERSION PROCESSES
Field Of The Invention
(0001] The present invention relates to a molecular sieve catalyst
composition, to a method of making or forming the molecular sieve catalyst
composition, and to a conversion process using the catalyst composition.
Background Of The Invention
[0002] Olefins are traditionally produced from petroleum feedstock by
catalytic or steam cracking processes. These cracking processes, especially
steam
cracking, produce light olefins) such as ethylene and/or propylene from a
variety
of hydrocarbon feedstock. Ethylene and propylene are important commodity
petrochemicals useful in a variety of processes for making plastics and other
chemical compounds.
[0003] The petrochemical industry has known for some time that
oxygenates, especially alcohols, are convertible into light olefin(s). There
are
numerous technologies available for producing oxygenates including
fermentation
or reaction of synthesis gas derived from natural gas, petroleum liquids,
carbonaceous materials including coal, recycled plastics, municipal waste or
any
other organic material. Generally, the production of synthesis gas involves a
combustion reaction of natural gas, mostly methane, and an oxygen source into
hydrogen, carbon monoxide and/or carbon dioxide. Syngas production processes
are well known, and include conventional steam reforming, autothermal
reforming, or a combination thereof.
[0004] Methanol, the preferred alcohol for light olefin production, is
typically synthesized from the catalytic reaction of hydrogen, carbon monoxide
and/or carbon dioxide in a methanol reactor in the presence of a heterogeneous
catalyst. For example, in one synthesis process methanol is produced using a
copper/zinc oxide catalyst in a water-cooled tubular methanol reactor. The
preferred methanol conversion process is generally referred to as a methanol-
to-
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olefins) process, where methanol is converted to primarily ethylene and/or
propylene in the presence of a molecular sieve.
[0005] Molecular sieves are porous solids having pores of different sizes
such as zeolites or zeolite-type molecular sieves, carbons and oxides. The
most
commercially useful molecular sieves for the petroleum and petrochemical
industries are known as zeolites, for example aluminosilicate molecular
sieves.
Zeolites in general have a one-, two- or three- dimensional crystalline pore
structure having uniformly sized pores of molecular dimensions that
selectively
adsorb molecules that can enter the pores, and exclude those molecules that
are
too large.
[0006] There are many different types of molecular sieves well known to
convert a feedstock, especially an oxygenate containing feedstock, into one or
more olefin(s). For example, U.S. Patent No. 5,367,100 describes the use of a
well known zeolite, ZSM-5, to convert methanol into olefin(s); U.S. Patent No.
4,062,905 discusses the conversion of methanol and other oxygenates to
ethylene
and propylene using crystalline aluminosilicate zeolites, for example Zeolite
T,
ZKS, erionite and chabazite; U.S. Patent No. 4,079,095 describes the use of
ZSM-
34 to convert methanol to hydrocarbon products such as ethylene and propylene;
and U.S. Patent No. 4,310,440 describes producing light olefins) from an
alcohol
using a crystalline aluminophosphates, often represented by ALP04.
[0007] One of the most useful molecular sieves for converting methanol to
olefins) is a silicoaluminophosphate molecular sieves. Silicoaluminophosphate
(SAPO) molecular sieves contain a three-dimensional microporous crystalline
framework structure of [SiOz], [AIOzJ and [POz] corner sharing tetrahedral
units.
SAPO synthesis is described in U.S. Patent No. 4,440,871, which is herein
fully
incorporated by reference. SAPO is generally synthesized by the hydrothermal
crystallization of a reaction mixture of silicon-, aluminum- and phosphorus-
sources and at least one templating agent. Synthesis of a SAPO molecular
sieve,
its formulation into a SAPO catalyst, and its use in converting a hydrocarbon
feedstock into olefin(s), particularly where the feedstock is methanol, is
shown in
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U.S. Patent Nos. 4,499,327, 4,677,242, 4,677,243, 4,873,390, 5,095,163,
5,714,662 and 6,166,282, all of which are herein fully incorporated by
reference.
[0008] Typically, molecular sieves are formed into molecular sieve catalyst
compositions to improve their durability in commercial conversion processes.
The collisions within a commercial process between catalyst composition
particles
themselves, the reactor walls, and other reactor systems cause the particles
to
breakdown into smaller particles called fines. The physical breakdown of the
molecular sieve catalyst composition particles is known as attrition. Fines
often
exit the reactor in the effluent stream resulting in problems in recovery
systems.
Catalyst compositions having a higher resistance to attrition generate fewer
fines,
less catalyst composition is required for conversion, and longer life times
result in
lower operating costs.
[0009] Molecular sieve catalyst compositions are formed by combining a
molecular sieve and a matrix material usually in the presence of a binder. The
purpose of the binder is to hold the matrix material, often a clay, to the
molecular
sieve. The use of binders and matrix materials in the formation of molecular
sieve
catalyst compositions is well known for a variety of commercial processes. It
is
also known that the way in which the molecular sieve catalyst composition is
made or formulated affects catalyst composition attrition.
[0010] Example of methods of making catalyst compositions include: U.S.
Patent No. 5,126,298 discusses a method for making a cracking catalyst having
high attrition resistance by combining two different clay particles in
separate
slurries with a zeolite slurry and a source of phosphorous, and spray drying a
mixture of the slurries having a pH below 3; U.S. Patent No. 4,987,110 and
5,298,153 relates to a catalytic cracking process using a spray dried
attrition
resistant catalyst containing greater than 25 weight percent molecular sieve
dispersed in a clay matrix with a synthetic silica-alumina component; U.S.
Patent
Nos. 5,194,412 and 5,286,369 discloses forming a catalytic cracking catalyst
of a
molecular sieve and a crystalline aluminum phosphate binder having a surface
area less than 20 m2/g and a total pore volume less than 0.1 cc/g; U.S. Patent
No.
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4,542,118 relates to forming a particulate inorganic oxide composite of a
zeolite
and aluminum chlorhydrol that is reacted with ammonia to form a cohesive
binder; U.S. Patent No. 6,153,552 claims a method of making a catalyst, by
drying
a slurry of a SAPO molecular sieve, an inorganic oxide sol, and an external
phosphorous source; U.S. Patent No. 5,110,776 illustrates the formation of a
zeolite containing catalytic catalyst by modifying the zeolite with a
phosphate
containing solution; U.S. Patent No. 5,348,643 relates to spray drying a
zeolite
slurry with a clay and source of phosphorous at a pH of below 3; U.S Patent
Application No. 09/891,674 filed June 25, 2001 discusses a method for steaming
a
molecular sieve to remove halogen; U.S. Patent No. 5,248,647 illustrates spray
drying a SAPO-34 molecular sieve admixed with kaolin and a silica sol; U.S.
Patent No. 5,346,875 discloses a method for making a catalytic cracking
catalyst
by matching the isoelectric point of each component of the framework structure
to
the pH of the inorganic oxide sol; Maurer, et al, Aggregation and Peptization
Behavior of Zeolite Crystals in Sols and Suspensions, Ind. Eng. Chem. Vol. 40,
pages 2573-2579, 2001 discusses zeolite aggregation at or near the isoelectric
point; PCT Publication WO 99/21651 describes making ~a catalyst by drying a
mixture of an alumina sol and a SAPO molecular sieve; PCT Publication WO
02/05950 describes making a catalyst composition of a molecular sieve
containing
attrition particles with fresh molecular sieve; and WO 02/05952 discloses a
crystalline metallo-aluminophosphate molecular sieve and a matrix material of
an
inorganic oxide binder and filler where the molecular sieve is present in an
amount less than 40 weight percent relative to the catalyst weight and a
preferable
weight ratio of the binder to molecular sieve close to 1.
[0011] Although these molecular sieve catalyst compositions described
above are useful in hydrocarbon conversion processes, it would be desirable to
have an improved molecular sieve catalyst composition having better attrition
resistance and commercially desirable operability and cost advantages.
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Summary Of The Invention
[0012] This invention provides for a method of making or formulating a
molecular sieve catalyst composition and to its use in a conversion process
for
converting a feedstock into one or more olefin(s).
[0013] In one embodiment the invention is directed to a method for making
a molecular sieve catalyst composition by combining, contacting, mixing, or
the
like, a molecular sieve, a binder, and a matrix material in a slurry, wherein
the
slurry has a pH above or below an isoelectric point (IEP) of, independently or
in
combination, the molecular sieve, the binder and/or the matrix material. In
one
preferred embodiment, the slurry has a pH at least 0.3 above or below the IEP
of
the molecular sieve. In a preferred embodiment, the molecular sieve is
synthesized from the combination from at least two of the group consisting of
a
silicon source, a phosphorous source and an aluminum source, optionally in the
presence of a templating agent, more preferably the molecular sieve is a
silicoaluminophosphate or aluminophosphate, and most preferably a
silicoaluminophosphate.
[0014] In one embodiment the invention is directed to a method for
formulating a molecular sieve catalyst composition, the method comprising the
steps of: (a) introducing a molecular sieve to form a slurry; (b) introducing
a
binder to the slurry; (c) introducing a matrix material to the slurry; and (d)
spray
drying the slurry to produce the formulated molecular sieve catalyst
composition,
wherein a pH of the slurry is above or below an IEP of the molecular sieve. In
another embodiment, the pH of the slurry is at least 0.3 away, above or below,
the
isoelectric point of the molecular sieve. In another embodiment, the molecular
sieve catalyst composition has an Attrition Rate Index (ARI) less than 2
weight
percent per hour, preferably less than 1 weight percent per hour and most
preferably less than 0.5 weight percent per hour. Preferably the molecular
sieve is
a silicoaluminophosphate, an aluminophosphate and/or a chabazite structure-
type
molecular sieve.
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[0015] In yet another embodiment, the invention is directed to a process for
producing olefins) in the presence of any of the above molecular sieve
catalyst
compositions. In particular, the process involves producing olefins) in a
process
for converting a feedstock, preferably a feedstock containing an oxygenate,
more
preferably a feedstock containing an alcohol, and most preferably a feedstock
containing methanol in the presence of one or more of the molecular sieve
catalyst
compositions thereof.
Detailed Description Of The Invention
Introduction
[0016] The invention is directed toward a molecular sieve catalyst
composition, its making and to its use in the conversion of a hydrocarbon
feedstock into one or more olefin(s). The molecular sieve catalyst composition
is
made or formed from the combination of a molecular sieve, a binder, and
optionally, most preferably, a matrix material. It has been known generally in
the
art that with solid/liquid dispersions that particle aggregation is prevented
by
overcoming the van der Waals attraction potential between the solid or
particle
surfaces. Stabilization of dispersions by electrostatic repulsion is described
in
E.J. W. Verwey, et al., Theory of the Stabilization of Lyophobic Colloids,
Elsevier,
Amsterdam, 1948. The oxide surfaces are either negatively or positively
charged
depending on the pH of the oxides in an aqueous media; see Th. F. Tadros,
SolidlLiguid Dispersions, Academic Press, London, page S, 1987, which is fully
incorporated herein by reference. The isoelectric point (IEP) is that state
where
the surface of particles in a medium is not charged, which corresponds to a pH
value for a particular material, for example a molecular sieve catalyst
composition,
in a particular medium, for example water; see J. Lyklema, Structure of the
SolidlLiquid Interface and Electrical Double Layer, in SolidlLiquid
Dispersions
(Edited by Th.F. Tadors), Academic Press, London, pages 63-90, 1987, which is
fully incorporated herein by reference. It has been surprisingly discovered
that by
preparing a molecular sieve catalyst composition below or above the IEP of the
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molecular sieve, a catalyst composition having improved attrition resistance
is
formed. The pH at the IEP of a given surface is also an important
consideration in
selecting a binder, weight ratio of binder to molecular sieve, and total solid
particle content in a solid/liquid dispersion. Therefore, it has also been
discovered
that in addition to IEP, that the weight ratio of the binder to the molecular
sieve is
also important to producing an attrition resistance catalyst composition.
Molecular Sieves and Catalysts Thereof
[0017] Molecular sieves have various chemical and physical, framework,
characteristics. Molecular sieves have been well classified by the Structure
Commission of the International Zeolite Association according to the rules of
the
IUPAC Commission on Zeolite Nomenclature. A framework-type describes the
connectivity, topology, of the tetrahedrally coordinated atoms constituting
the
framework, and making an abstraction of the specific properties for those
materials. Framework-type zeolite and zeolite-type molecular sieves for which
a
structure has been established, are assigned a three letter code and are
described in
the Atlas of Zeolite Framework Types, 5th edition, Elsevier, London, England
(2001 ), which is herein fully incorporated by reference.
[0018] Non-limiting examples of these molecular sieves are the small pore
molecular sieves, AEI, AFT, APC, ATN, ATT, ATV, AWW, BIK, CAS, CHA,
CHI, DAC, DDR, EDI, ERI, GOO, KFI, LEV, LOV, LTA, MON, PAU, PHI,
RHO, ROG, THO, and substituted forms thereof; the medium pore molecular
sieves, AFO, AEL, EUO, HEU, FER, MEL, MFI, MTW, MTT, TON, and
substituted forms thereof; and the large pore molecular sieves, EMT, FAU, and
substituted forms thereof. Other molecular sieves include ANA, BEA, CFI, CLO,
DON, GIS, LTL, MER, MOR, MWW and SOD. Non-limiting examples of the
preferred molecular sieves, particularly for converting an oxygenate
containing
feedstock into olefin(s), include AEL, AFY, BEA, CHA, EDI, FAU, FER, GIS,
LTA, LTL, MER, MFI, MOR, MTT, MWW, TAM and TON. In one preferred
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embodiment, the molecular sieve of the invention has an AEI topology or a CHA
topology, or a combination thereof, most preferably a CHA topology.
[0019] Molecular sieve materials all have 3-dimensional framework
structure of corner-sharing T04 tetrahedra, where T is any tetrahedrally
coordinated canon. These molecular sieves are typically described in terms of
the
size of the ring that defines a pore, where the size is based on the number of
T
atoms in the ring. Other framework-type characteristics include the
arrangement
of rings that form a cage, and when present, the dimension of channels, and
the
spaces between the cages. See van Bekkum, et al., Introduction to Zeolite
Science
and Practice, Second Completely Revised and Expanded Edition, Volume 137,
pages 1-67, Elsevier Science, B.V., Amsterdam, Netherlands (2001).
[0020] The small, medium and large pore molecular sieves have from a fi-
ring to a 12-ring or greater framework-type. In a preferred embodiment, the
zeolitic molecular sieves have 8-, 10- or 12- ring structures or larger and an
average pore size in the range of from about 3A to 15 ~. In the most preferred
embodiment, the molecular sieves of the invention, preferably
silicoaluminophosphate molecular sieves have 8- rings and an average pore size
less than about SA, preferably in the range of from 3~ to about SA, more
preferably from 3A to about 4.St~, and most preferably from 3.5~ to about
4.2~.
[0021] Molecular sieves, particularly zeolitic and zeolitic-type molecular
sieves, preferably have a molecular framework of one, preferably two or more
corner-sharing [T04] tetrahedral units, more preferably, two or more [Si04],
[A104] and/or [P04] tetrahedral units, and most preferably [Si04], [A104] and
[P04] tetrahedral units. These silicon, aluminum, and phosphorous based
molecular sieves and metal containing silicon, aluminum and phosphorous based
molecular sieves have been described in detail in numerous publications
including
for example, U.S. Patent No. 4,567,029 (MeAPO where Me is Mg, Mn, Zn, or
Co), U.S. Patent No. 4,440,871 (SAPO), European Patent Application EP-A-0 159
624 (ELAPSO where El is As, Be, B, Cr, Co, Ga, Ge, Fe, Li, Mg, Mn, Ti or Zn),
U.S. Patent No. 4,554,143 (FeAPO), U.S. Patents No. 4,822,478, 4,683,217,
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4,744,885 (FeAPSO), EP-A-0 158 975 and U.S. Patent No. 4,935,216 (ZnAPSO,
EP-A-0 161 489 (CoAPSO), EP-A-0 158 976 (ELAPO, where EL is Co, Fe, Mg,
Mn, Ti or Zn), U.S. Patent No. 4,310,440 (A1P04), EP-A-0 158 350 (SENAPSO),
U.S. Patent No. 4,973,460 (LiAPSO), U.S. Patent No. 4,789,535 (LiAPO), U.S.
Patent No. 4,992,250 (GeAPSO), U.S. Patent No. 4,888,167 (GeAPO), U.S.
Patent No. 5,057,295 (BAPSO), U.S. Patent No. 4,738,837 (CrAPSO), U.S.
Patents Nos. 4,759,919, and 4,851,106 (CrAPO), U.S. Patents Nos. 4,758,419,
4,882,038, 5,434,326 and 5,478,787 (MgAPSO), U.S. Patent No. 4,554,143
(FeAPO), U.S. Patent No. 4,894,213 (AsAPSO), U.S. Patent No. 4,913,888
(AsAPO), U.S. Patents Nos. 4,686,092, 4,846,956 and 4,793,833 (MnAPSO),
U.S. Patents Nos. 5,345,011 and 6,156,931 (MnAPO), U.S. Patent No. 4,737,353
(BeAPSO), U.S. Patent No. 4,940,570 (BeAPO), U.S. Patents Nos. 4,801,309,
4,684,617 and 4,880,520 (TiAPSO), U.S. Patents Nos. 4,500,651, 4,551,236 and
4,605,492 (TiAPO), U.S. Patents No. 4,824,554, 4,744,970 (CoAPSO), U.S.
Patent No. 4,735,806 (GaAPSO) EP-A-0 293 937 (QAPSO, where Q is
framework oxide unit [Q02]), as well as U.S. Patents Nos. 4,567,029,
4,686,093,
4,781,814, 4,793,984, 4,801,364, 4,853,197, 4,917,876, 4,952,384, 4,956,164,
4,956,165, 4,973,785, 5,241,093, 5,493,066 and 5,675,050, all of which are
herein
fully incorporated by reference. Other molecular sieves are described in R.
Szostak, Handbook of Molecular Sieves, Van Nostrand Reinhold, New York, New
York (1992), which is herein fully incorporated by reference.
[0022] The more preferred silicon, aluminum and/or phosphorous containing
molecular sieves, and aluminum, phosphorous, and optionally silicon,
containing
molecular sieves include aluminophosphate (ALPO) molecular sieves and
silicoaluminophosphate (SAPO) molecular sieves and substituted, preferably
metal substituted, ALPO and SAPO molecular sieves. The most preferred
molecular sieves are SAPO molecular sieves, and metal substituted SAPO
molecular sieves. In an embodiment, the metal is an alkali metal of Group IA
of
the Periodic Table of Elements, an alkaline earth metal of Group IIA of the
Periodic Table of Elements, a rare earth metal of Group IIIB, including the
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Lanthanides: lanthanum, cerium, praseodymium, neodymium, samarium,
europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,
ytterbium and lutetium; and scandium or yttrium of the Periodic Table of
Elements, a transition metal of Groups IVB, VB, VIB, VIIB, VIIIB, and IB of
the
Periodic Table of Elements, or mixtures of any of these metal species. In one
preferred embodiment, the metal is selected from the group consisting of Co,
Cr,
Cu, Fe, Ga, Ge, Mg, Mn, Ni, Sn, Ti, Zn and Zr, and mixtures thereof. In
another
preferred embodiment, these metal atoms discussed above are inserted into the
framework of a molecular sieve through a tetrahedral unit, such as [MeOz], and
carry a net charge depending on the valence state of the metal substituent.
For
example, in one embodiment, when the metal substituent has a valence state of
+2,
+3, +4, +5, or +6, the net charge of the tetrahedral unit is between -2 and
+2.
[0023] In one embodiment, the molecular sieve, as described in many of the
U.S. Patents mentioned above, is represented by the empirical formula, on an
anhydrous basis:
mR:(MxAIYP~Oz
wherein R represents at least one templating agent, preferably an organic
templating agent; m is the number of moles of R per mole of (MxAIyPZ)OZ and m
has a value from 0 to 1, preferably 0 to 0.5, and most preferably from 0 to
0.3; x,
y, and z represent the mole fraction of Al, P and M as tetrahedral oxides,
where M
is a metal selected from one of Group IA, IIA, IB, IIIB, IVB, VB, VIB, VIIB,
VIIIB and Lanthanide's of the Periodic Table of Elements, preferably M is
selected from one of the group consisting of Co, Cr, Cu, Fe, Ga, Ge, Mg, Mn,
Ni,
Sn, Ti, Zn and Zr. In an embodiment, m is greater than or equal to 0.2, and x,
y
and z are greater than or equal to 0.01. In another embodiment, m is greater
than
0.1 to about 1, x is greater than 0 to about 0.25, y is in the range of from
0.4 to 0.5,
and z is in the range of from 0.25 to 0.5, more preferably m is from 0.15 to
0.7, x
is from 0.01 to 0.2, y is from 0.4 to 0.5, and z is from 0.3 to 0.5.
[0024) Non-limiting examples of SAPO and ALPO molecular sieves of the
invention include one or a combination of SAPO-S, SAPO-8, SAPO-11, SAPO-
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16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36,
SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44 (U.S. Patent No. 6,162,415),
SAPO-47, SAPO-56, ALPO-5, ALPO-11, ALPO-18, ALPO-31, ALPO-34,
ALPO-36, ALPO-37, ALPO-46, and metal containing molecular sieves thereof.
The more preferred molecular sieves include one or a combination of SAPO-18,
SAPO-34, SAPO-35, SAPO-44, SAPO-56, ALPO-18 and ALPO-34, even more
preferably one or a combination of SAPO-18, SAPO-34, ALPO-34 and ALPO-18,
and metal containing molecular sieves thereof, and most preferably one or a
combination of SAPO-34 and ALPO-18, and metal containing molecular sieves
thereof.
[0025] In an embodiment, the molecular sieve is an intergrowth material
having two or more distinct phases of crystalline structures within one
molecular
sieve composition. In particular, intergrowth molecular sieves are described
in the
U.S. Patent Application Serial No. 09/924,016 filed August 7, 2001 and PCT WO
98/15496 published April 16, 1998, both of which are herein fully incorporated
by
reference. For example, SAPO-18, ALPO-18 and RUW-18 have an AEI
framework-type, and SAPO-34 has a CHA framework-type. In another
embodiment, the molecular sieve comprises at least one intergrown phase of AEI
and CHA framework-types.
Molecular Sieve Synthesis
(0026] The synthesis of molecular sieves is described in many of the
references discussed above. Generally, molecular sieves are synthesized by the
hydrothermal crystallization of one or more of a source of aluminum, a source
of
phosphorous, a source of silicon, a templating agent, and a metal containing
compound. Typically, a combination of sources of silicon, aluminum and
phosphorous, optionally with one or more templating agents andlor one or more
metal containing compounds are placed in a sealed pressure vessel, optionally
lined with an inert plastic such as polytetrafluoroethylene, and heated, under
a
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crystallization pressure and temperature, until a crystalline material is
formed, and
then recovered by filtration, centrifugation and/or decanting.
[0027] In a preferred embodiment the molecular sieves are synthesized by
forming a reaction product of a source of silicon, a source of aluminum, a
source
of phosphorous, an organic templating agent, preferably a nitrogen containing
organic templating agent. This particularly preferred embodiment results in
the
synthesis of a silicoaluminophosphate crystalline material that is then
isolated by
filtration, centrifugation and/or decanting.
[0028] Non-limiting examples of silicon sources include a silicates, fumed
silica, for example, Aerosil-200 available from Degussa Inc., New York, New
York, and CAB-O-SIL M-5, silicon compounds such as tetraalkyl orthosilicates,
for example, tetramethyl orthosilicate (TMOS) and tetraethylorthosilicate
(TEOS),
colloidal silicas or aqueous suspensions thereof, for example Ludox-HS-40 sol
available from E.I. du Pont de Nemours, Wilmington, Delaware, silicic acid,
alkali-metal silicate, or any combination thereof. The preferred source of
silicon
is a silica sol.
[0029] Non-limiting examples of aluminum sources include aluminum-
containing compositions such as aluminum alkoxides, for example aluminum
isopropoxide, aluminum phosphate, aluminum hydroxide, sodium aluminate,
pseudo-boehmite, gibbsite and aluminum trichloride, or any combinations
thereof.
A preferred source of aluminum is pseudo-boehmite, particularly when producing
a silicoaluminophosphate molecular sieve.
[0030] Non-limiting examples of phosphorous sources, which may also
include aluminum-containing phosphorous compositions, include phosphorous-
containing, inorganic or organic, compositions such as phosphoric acid,
organic
phosphates such as triethyl phosphate, and crystalline or amorphous
aluminophosphates such as ALP04, phosphorous salts, or combinations thereof.
The preferred source of phosphorous is phosphoric acid, particularly when
producing a silicoaluminophosphate.
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[0031] Templating agents are generally compounds that contain elements of
Group VA of the Periodic Table of Elements, particularly nitrogen, phosphorus,
arsenic and antimony, more preferably nitrogen or phosphorous, and most
preferably nitrogen. Typical templating agents of Group VA of the Periodic
Table
of elements also contain at least one alkyl or aryl group, preferably an alkyl
or aryl
group having from 1 to 10 carbon atoms, and more preferably from 1 to 8 carbon
atoms. The preferred templating agents are nitrogen-containing compounds such
as amines and quaternary ammonium compounds.
[0032] The quaternary ammonium compounds, in one embodiment, are
represented by the general formula RQN+, where each R is hydrogen or a
hydrocarbyl or substituted hydrocarbyl group, preferably an alkyl group or an
aryl
group having from 1 to 10 carbon atoms. In one embodiment, the templating
agents include a combination of one or more quaternary ammonium compounds)
and one or more of a mono-, di- or tri- amine.
[0033] Non-limiting examples of templating agents include tetraalkyl
ammonium compounds including salts thereof such as tetramethyl ammonium
compounds including salts thereof, tetraethyl ammonium compounds including
salts thereof, tetrapropyl ammonium including salts thereof, and
tetrabutylammonium including salts thereof, cyclohexylamine, morpholine, di-n-
propylamine (DPA), tripropylamine, triethylamine (TEA), triethanolamine,
piperidine, cyclohexylamine, 2-methylpyridine, N,N-dimethylbenzylamine, N,N-
diethylethanolamine, dicyclohexylamine, N,N-dimethylethanolamine, choline,
N,N'-dimethylpiperazine, 1,4-diazabicyclo(2,2,2)octane, N', N',N,N-tetramethyl-
(1,6)hexanediamine, N-methyldiethanolamine, N-methyl-ethanolamine, N-methyl
piperidine, 3-methyl-piperidine, N-methylcyclohexylamine, 3-methylpyridine, 4-
methyl-pyridine, quinuclidine, N,N'-dimethyl-1,4-diazabicyclo(2,2,2) octane
ion;
di-n-butylamine, neopentylamine, di-n-pentylamine, isopropylamine, t-butyl-
amine, ethylenediamine, pyrrolidine, and 2-imidazolidone.
[0034] The preferred templating agent or template is a tetraethylammonium
compound, such as tetraethyl ammonium hydroxide (TEAOH), tetraethyl
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ammonium phosphate, tetraethyl ammonium fluoride, tetraethyl ammonium
bromide, tetraethyl ammonium chloride and tetraethyl ammonium acetate. The
most preferred templating agent is tetraethyl ammonium hydroxide and salts
thereof, particularly when producing a silicoaluminophosphate molecular sieve.
In one embodiment, a combination of two or more of any of the above templating
agents is used in combination with one or more of a silicon-, aluminum-, and
phosphorous- source.
[0035] A synthesis mixture containing at a minimum a silicon-, aluminum-,
and/or phosphorous- composition, and a templating agent, should have a pH in
the
range of from 2 to 10, preferably in the range of from 4 to 9, and most
preferably
in the range of from 5 to 8. Generally, the synthesis mixture is sealed in a
vessel
and heated, preferably under autogenous pressure, to a temperature in the
range of
from about 80°C to about 250°C, and more preferably from about
150°C to about
I 80°C. The time required to form the crystalline product is
typically from
immediately up to several weeks, the duration of which is usually dependent on
the temperature; the higher the temperature the shorter the duration.
Typically, the
crystalline molecular sieve product is formed, usually in a slurry state, and
is
recovered by any standard technique well known in the art, for example
centrifugation or filtration. The isolated or separated crystalline product,
in an
embodiment, is washed, typically, using a liquid such as water, from one to
many
times. The washed crystalline product is then optionally dried, preferably in
air.
[0036] In one preferred embodiment, when a templating agent is used in the
synthesis of a molecular sieve, it is preferred that the templating agent is
substantially, preferably completely, removed after crystallization by
numerous
well known techniques, for example, heat treatments such as calcination.
Calcination involves contacting the molecular sieve containing the templating
agent with a gas, preferably containing oxygen, at any desired concentration
at an
elevated temperature sufficient to either partially or completely decompose
and
oxidize the templating agent.
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[0037] Molecular sieves have either a high silicon (Si) to aluminum (Al)
ratio or a low silicon to aluminum ratio, however, a low Si/Al ratio is
preferred for
SAPO synthesis. In one embodiment, the molecular sieve has a Si/Al ratio less
than 0.65, preferably less than 0.40, more preferably less than 0.32, and most
preferably less than 0.20. In another embodiment the molecular sieve has a
Si/Al
ratio in the range of from about 0.65 to about 0.10, preferably from about
0.40 to
about 0.10, more preferably from about 0.32 to about 0.10, and more preferably
from about 0.32 to about 0.15.
Method for Making Molecular Sieve Catalyst Compositions
[0038] Once the molecular sieve is synthesized, depending on the
requirements of the particular conversion process, the molecular sieve is then
formulated into a molecular sieve catalyst composition, particularly for
commercial use. The molecular sieves synthesized above are made or formulated
into molecular sieve catalyst compositions by combining the synthesized
molecular sieves) with a binder and optionally, but preferably, a matrix
material
to form a molecular sieve catalyst composition or a formulated molecular sieve
catalyst composition. This formulated molecular sieve catalyst composition is
formed into useful shape and sized particles by well-known techniques such as
spray drying, pelletizing, extrusion, and the like.
[0039] The pH at the IEP for various materials including metal oxides are
discussed in J. Lyklema, Structure of the SolidlLiguid Interface and
Electrical
Double Layer, in SolidlLiquid Dispersions, Academic Press, London, pages 63-
90, 1987 and J.-E. Otterstedt and D. A. Brandreth, Small Particles Technology,
page 258, Plenum, New York, 1998, which are herein fully incorporated by
reference.
[0040] In one embodiment, the molecular sieve, preferably a
silicoaluminophosphate molecular sieve, and more preferably a SAPO-34
molecular sieve, has a pH in the range of from about 3 to 7 at its IEP
(measured as
an aqueous slurry), preferably in the range of from 4 to 6, and more
preferably in
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the range of from 4.5 to 5.5. In another embodiment, the binder, preferably an
alumina sol, has a pH of greater than about 9 at its IEP, preferably greater
than 10.
In yet another embodiment, the matrix material, preferably a clay, has a pH
less
than about 2 at its IEP.
[0041] In another embodiment, the slurry comprising a molecular sieve and
one or more of a binder or a matrix material has a pH above or below,
preferably
below the IEP of the molecular sieve, and one or more of the binder or the
matrix
material. Preferably the slurry comprises the molecular sieve, the binder and
the
matrix material and has a pH different from, above or below, preferably below,
the
IEP of the molecular sieve, the binder and the matrix material. In an
embodiment,
the pH of the slurry is in the range of from 2 to 7, preferably from 2.3 to
6.2; the
IEP of the molecular sieve is in the range of from 2.5 to less than 7,
preferably
from about 3.5 to 6.5; the IEP of the binder is greater than 10; and the IEP
of the
matrix material is less than 2. In a particularly preferred embodiment, the
IEP of
the molecular sieve is in the range of from 4.5 to 5.5.
[0042] In yet another embodiment, the binder, preferably a alumina sol, and
more preferably an aluminum chlorohydrate, is positively charged and/or at a
pH
in the range of from greater than 2 to less than 10. In still a further
embodiment,
the matrix material, a clay is negatively charged and/or has pH of less than 2
at its
IEP. In another embodiment, a binder and a matrix composition, preferably a 20
to 60 weight percent binder and 40 to 80 weight percent matrix material based
on
the total weight of the binder and matrix material, has a pH of about 9.8 at
its IEP.
[0043] In one preferred embodiment, the slurry has a pH at least 0.3 above
or below the IEP of the molecular sieve and/or the IEP of the binder and/or
the
IEP of the matrix material, preferably the slurry has a pH at least 0.5 above
or
below, preferably below, more preferably the slurry has a pH at least 1 above
or
below, preferably below, and most preferably the slurry has a pH at least 1.5
above or below, preferably a pH of at least 2 below. Preferably the pH of the
slurry is different from the IEP of the molecular sieve, the binder and matrix
material.
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[0044] In one embodiment, the weight ratio of the binder to the molecular
sieve is in the range of from about 0.1 to 0.5, preferably in the range of
from 0.1 to
less than 0.5, more preferably in the range of from 0.11 to 0.48, even more
preferably from 0.12 to about 0.45, yet even more preferably from 0.13 to less
than 0.45, and most preferably in the range of from 0.15 to about 0.4.
[0045] In another embodiment, the molecular sieve catalyst composition or
formulated molecular sieve catalyst composition has a micropore surface area
(MSA) measured in mz/g-molecular sieve that is greater than about 70 percent,
preferably greater than about 75 percent, more preferably greater than 80
percent,
even more preferably greater than 85 percent, and most preferably greater than
about 90 percent of the MSA of the molecular sieve itself. The MSA of the
molecular sieve catalyst composition is the total MSA of the composition
divided
by the fraction of the molecular sieve contained in the molecular sieve
catalyst
composition.
[0046] In another embodiment in the formulation of a molecular sieve
catalyst composition, that the amount of solids present in a slurry of the
molecular
sieve and the binder, optionally including a matrix material, used in a spray
drying
process for example is important. Also, it is preferred that the synthesized
molecular sieve contain an amount of a liquid medium, preferably water, not
calcined, prior to being used in the slurry. When the solids content of the
slurry is
too low or too high the attrition resistance properties of the molecular sieve
catalyst composition is reduced. The molecular sieve catalyst composition in a
preferred embodiment is made by preparing a slurry containing a molecular
sieve,
a binder, and, optionally while preferably, a matrix material. The solids
content of
the preferred slurry includes about 20% to about 50% by weight of the
molecular
sieve, preferably from about 30% to about 48% by weight of the molecular
sieve,
more preferably from about 40% to about 48% by weight molecular sieve, about
5% to about 20%, preferably from about 8% to about 15%, by weight of the
binder, and about 30% to about 80%, preferably about 40% to about 60%, by
weight of the matrix material.
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[0047] There are many different binders that are useful in forming the
molecular sieve catalyst composition. Non-limiting examples of binders that
are
useful alone or in combination include various types of hydrated alumina,
silicas,
and/or other inorganic oxide sol. One preferred alumina containing sol is
aluminum chlorhydrate. The inorganic oxide sol acts like glue binding the
synthesized molecular sieves and other materials such as the matrix together,
particularly after thermal treatment. Upon heating, the inorganic oxide sol,
preferably having a low viscosity, is converted into an inorganic oxide matrix
component. For example, an alumina sol will convert to an aluminum oxide
matrix following heat treatment.
[0048] Aluminum chlorhydrate, a hydroxylated aluminum based sol
containing a chloride counter ion, has the general formula of
Al",O~(OH)oCh,~x(HZO) wherein m is 1 to 20, n is 1 to 8, o is 5 to 40, p is 2
to 15,
and x is 0 to 30. In one embodiment, the binder is A1,304(OH)24C1~~12(Hz0) as
is
described in G.M. Wolterman, et al., Stud. Surf. Sci. and Catal., 76, pages
105-
144 (1993), which is herein incorporated by reference. In another embodiment,
one or more binders are combined with one or more other non-limiting examples
of alumina materials such as aluminum oxyhydroxide, y-alumina, boehmite,
diaspore, and transitional aluminas such as a-alumina, (3-alumina, y-alumina,
8-
alumina, s-alumina, x-alumina, and p-alumina, aluminum trihydroxide, such as
gibbsite, bayerite, nordstrandite, doyelite, and mixtures thereof.
[0049] In another embodiment, the binders are alumina sots, predominantly
comprising aluminum oxide, optionally including some silicon. In yet another
embodiment, the binders are peptized alumina made by treating alumina hydrates
such as pseudobohemite, with an acid, preferably an acid that does not contain
a
halogen, to prepare sols or aluminum ion solutions. Non-limiting examples of
commercially available colloidal alumina sots include Nalco 8676 available
from
Nalco Chemical Co., Naperville, Illinois, and Nyacol AL20DW available from
Nyacol Nano Technologies, Inc., Ashland, MA.
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[0050] The molecular sieve described above, in a preferred embodiment, is
combined with one or more matrix material(s). Matrix materials are typically
effective in reducing overall catalyst cost, act as thermal sinks assisting in
shielding heat from the catalyst composition for example during regeneration,
densifying the catalyst composition, increasing catalyst strength such as
crush
strength and attrition resistance, and to control the rate of conversion in a
particular process.
[0051] Non-limiting examples of matrix materials include one or more o~
rare earth metals, non-active, metal oxides including titania, zirconia,
magnesia,
thoria, beryllia, quartz, silica or sols, and mixtures thereof, for example
silica-
magnesia, silica-zirconia, silica-titania, silica-alumina and silica-alumina-
thoria.
In an embodiment, matrix materials are natural clays such as those from the
families of montmorillonite and kaolin. These natural clays include
sabbentonites
and those kaolins known as, for example, Dixie, McNamee, Georgia and Florida
clays. Non-limiting examples of other matrix materials include: haloysite,
kaolinite, dickite, nacrite, or anauxite. In one embodiment, the matrix
material,
preferably any of the clays, are subjected to well known modification
processes
such as calcination and/or acid treatment and/or chemical treatment.
[0052] In one preferred embodiment, the matrix material is a clay or a clay-
type composition, preferably the clay or clay-type composition having a low
iron
or titania content, and most preferably the matrix material is kaolin. Kaolin
has
been found to form a pumpable, high solid content slurry, it has a low fresh
surface area, and it packs together easily due to its platelet structure. A
preferred
average particle size of the matrix material, most preferably kaolin, is from
about
0.05 ~.m to about 0.6 ~,m with a D9° particle size distribution of less
than about
1 ~,m.
[0053] In one embodiment, the binder, the molecular sieve, and the matrix
material are combined in the presence of a liquid to form the catalyst
composition,
where the amount of binder is from about 2% by weight to about 30% by weight,
preferably from about 5% by weight to about 20% by weight, and more preferably
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from about 7% by weight to about 15% by weight, based on the total weight of
the
binder, the molecular sieve and matrix material, excluding the liquid.
[0054] Upon combining the molecular sieve, the binder, and optionally the
matrix material, in a liquid to form a slurry, mixing, preferably rigorous
mixing is
needed to produce a substantially homogeneous mixture. Non-limiting examples
of suitable liquids include one or a combination of water, alcohol, ketones,
aldehydes, and/or esters. The most preferred liquid is water. In one
embodiment,
the slurry is subjected to high shear for a period of time sufficient to
produce the
desired slurry texture, sub-particle size, andlor sub-particle size
distribution.
Suitable means for subjecting the slurry to milling including colloid mills,
inline
mixers, and the like.
[0055] The preparation of the slurry comprising the molecular sieve, the
binder and the matrix material is carried out by mixing the molecular sieve,
the
binder and optionally the matrix material at a temperature in the range of
from
about -10°C to about 80°C. Depending on the particle size of the
molecular sieve
and the binder, in one embodiment, a particle size reduction step is
performed,
either before or after mixing. There are many ways to perform particle size
reduction on various powders using a variety of devices, including but not
limited
to an impingement mill (a micronizer available from Sturtevant, Inc. Boston,
Massachusetts), or a dry or wet mill, for example an Eiger mill (a wet mill
available from Eiger Machinery, In., Grayslake, Illinois), a jar rolling mill
for both
dry and wet milling (available from Paul O. Abbe, Inc., Little Falls, New
Jersey),
or by use of a high-shear mixer (available from Silverson Machines, Inc., East
Longmeadow, Massachusetts). The particle size distribution in the slurry is
measured using for example, a Microtrac laser scattering particle size
analyzer
53000 available from MicroTrac, Clearwater, Florida. To ensure the quality of
the slurry for spray drying to form the catalyst composition of the invention,
measurements of pH, surface area, solid content, bulk density, and viscosity
are
also preferably monitored using respectively, for example, a Cole Palmer pH
meter, Micromeritics Gemini 9375 surface area instrument available from
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Micometrics Instrument Corporation, Norcross, Georgia, CEM MAS 700
microwave muffle furnace for solid content determination available from CEM
Corporation, Mathews, North Carolina, and Brookfield LV-DVE viscometer for
viscosity. Zeta potential measurements were made on a Matec 9800
electrokinetic
instrument available from Matec Applied Science, Northboro, MA. Particle size
is but one factor in the effectiveness of the slurry in the formation of the
catalyst
composition of the invention. In addition, the sequence of adding each
individual
component, the molecular sieve, binder, matrix material, and other ingredient,
is
also important. Sequence of addition is most important when the surface of the
different particles, whether these are of the molecular sieve, the binder, or
the
matrix materials, have opposite charges, negative and positive, or different
charge
densities. As a general rule, after size reduction is completed, if necessary,
the last
step is the addition and mixing of the opposite charged particles. In one
preferred
embodiment, it is best to add the component selected from the molecular sieve,
the
binder or the matrix material, having a higher charge density per unit mass to
a
component having a lower charge density per unit mass.
[0056] The molecular sieve, the binder, and the matrix material, are in the
same or different liquid, and are combined in any order, together,
simultaneously,
sequentially, or a combination thereof. In the preferred embodiment, the same
liquid, preferably water is used. The molecular sieve, matrix material, and
the
binder, are added to a liquid as solids, or as slurries, together or
separately. If
solids are added together, it is preferable to add a limited and/or controlled
amount
of liquid.
[0057] In one embodiment, the slurry of the molecular sieve, the binder and
the matrix materials is mixed or milled to achieve a sufficiently uniform
slurry of
sub-particles of the molecular sieve catalyst composition that is then fed to
a
forming unit that produces the molecular sieve catalyst composition. In a
preferred embodiment, the forming unit is a spray dryer. Typically, the
forming
unit is maintained at a temperature sufficient to dry most of the liquid from
the
slurry, and from the resulting molecular sieve catalyst particles. The
resulting
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catalyst composition when formed in this way preferably takes the form of
microspheres.
[0058] When a spray dryer is used as the forming unit, typically, the slurry
of the molecular sieve, the binder and the matrix material is co-fed to the
spray
drying volume with a drying gas with an average inlet temperature ranging from
100°C to 550°C, and a combined outlet temperature ranging from
50°C to about
225°C. In an embodiment, the average diameter of the spray dried formed
catalyst
composition is from about 10 ~m to about 300 pm, preferably from about 30 pm
to about 250 p.m, more preferably from about 40 pm to about 150 Vim, and most
preferably from about 50 pm to about 120 pm.
[0059] During spray drying, the slurry is passed through a nozzle
distributing the slurry into small droplets, resembling an aerosol spray into
a
drying chamber. Atomization is achieved by forcing the slurry through a single
nozzle or multiple nozzles with a pressure drop in the range of from 100 psig
to
2000 psig (690 kPag to 13790 kPag). In another embodiment, the slurry is co-
fed
through a single nozzle or multiple nozzles along with an atomization fluid
such
as air, steam, flue gas, or any other suitable gas with a pressure drop in the
range
of from 1 psig to 150 psig (6.9 kPag to 1034 kPag).
[0060] In yet another embodiment, the slurry described above is directed to
the perimeter of a spinning wheel that distributes the slurry into small
droplets, the
size of which is controlled by many factors including slurry viscosity,
surface
tension, flow rate, pressure, and temperature of the slurry, the shape and
dimension of the nozzle(s), or the spinning rate of the wheel. These droplets
are
then dried in a co-current or counter-current flow of air passing through a
spray
drier to form a substantially dried or dried molecular sieve catalyst
composition,
more specifically a molecular sieve catalyst composition in a microspherical
form.
[0061] Generally, the size of the microspheres is controlled to some extent
by the solids content of the slurry. However, control of the size of the
catalyst
composition and its spherical characteristics are also controllable by varying
the
slurry feed properties and conditions of atomization.
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[0062] Other methods for forming a molecular sieve catalyst composition is
described in U.S. Patent Application Serial No. 09/617,714 filed July 17, 2000
(spray drying using a recycled molecular sieve catalyst composition), which is
herein incorporated by reference.
[0063] In another embodiment, the formulated molecular sieve catalyst
composition contains from about 1 % to about 99%, preferably from about 10 %
to
about 90%, more preferably from about 10% to about 80%, even more preferably
from about 20% to about 70%, and most preferably from about 20% to about 60%
by weight of the molecular sieve based on the total weight of the molecular
sieve
catalyst composition.
[0064] Once the molecular sieve catalyst composition is formed in a
substantially dry or dried state, to further harden and/or activate the formed
catalyst composition, a heat treatment such as calcination, at an elevated
temperature is usually performed. A conventional calcination environment is
air
that typically includes a small amount of water vapor. Typical calcination
temperatures are in the range from about 400°C to about 1,000°C,
preferably from
about 500°C to about 800°C, and most preferably from about
550°C to about
700°C, preferably in a calcination environment such as air, nitrogen,
helium, flue
gas (combustion product lean in oxygen), or any combination thereof. In one
embodiment, calcination of the formulated molecular sieve catalyst composition
is
carried out in any number of well known devices including rotary calciners,
fluid
bed calciners, batch ovens, and the like. Calcination time is typically
dependent
on the degree of hardening of the molecular sieve catalyst composition and the
temperature ranges from about 1 minutes to about 10 hours, preferably 15
minutes
to about 5 hours.
[0065] In one embodiment, the attrition resistance of a molecular sieve
catalyst composition is measured using an Attrition Rate Index (ARI), measured
in weight percent catalyst composition attrited per hour. An apparatus such as
described in S.A. Weeks and P. Dumbill, in Oil & Gas Journal, pages 38 to 40,
1987, which is herein fully incorporated by reference. ARI is measured by
adding
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6.0g of catalyst composition having a particles size ranging from about 53
microns
to about 125 microns to a hardened steel attrition cup. Approximately 23,700
cc/min of nitrogen gas is bubbled through a water-containing bubbler to
humidify
the nitrogen. The wet nitrogen passes through the attrition cup, and exits the
attrition apparatus through a porous fiber thimble. The flowing nitrogen
removes
the finer particles, with the larger particles being retained in the cup. The
porous
fiber thimble separates the fine catalyst particles from the nitrogen that
exits
through the thimble. The fine particles remaining in the thimble represent the
catalyst composition that has broken apart through attrition. The nitrogen
flow
passing through the attrition cup is maintained for 1 hour. The fines
collected in
the thimble are removed from the unit. A new thimble is then installed. The
catalyst left in the attrition unit is attrited for an additional 3 hours,
under the same
gas flow and moisture levels. The fines collected in the thimble are
recovered.
The collection of fine catalyst particles separated by the thimble after the
first hour
are weighed. The amount in grams of fine particles divided by the original
amount of catalyst charged to the attrition cup expressed on per hour basis is
the
ARI, in weight percent per hour (wt. %/hr). ARI is represented by the formula:
ARI = C/(B+C)/D multiplied by 100%, wherein B is weight of catalyst
composition left in the cup after the attrition test, C is the weight of
collected fine
catalyst particles after the first hour of attrition treatment, and D is the
duration of
treatment in hours after the first hour attrition treatment.
[0066] In one embodiment, the molecular sieve catalyst composition or
formulated molecular sieve catalyst composition has an ARI less than 15 weight
percent per hour, preferably less than 10 weight percent per hour, more
preferably
less than 5 weight percent per hour, and even more preferably less than 2
weight
percent per hour, and most preferably less than 1 weight percent per hour. In
one
embodiment, the molecular sieve catalyst composition or formulated molecular
sieve catalyst composition has an ARI in the range of from 0.1 weight percent
per
hour to less than 5 weight percent per hour, more preferably from about 0.2
weight
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percent per hour to less than 3 weight percent per hour, and most preferably
from
about 0.2 weight percent per hour to less than 2 weight percent per hour.
Process For Using the Molecular Sieve Catalyst Compositions
[0067] The molecular sieve catalyst compositions described above are useful
in a variety of processes including: cracking, of for example a naphtha feed
to
light olefins) (U.S. Patent No. 6,300,537) or higher molecular weight (MW)
hydrocarbons to lower MW hydrocarbons; hydrocracking, of for example heavy
petroleum and/or cyclic feedstock; isomerization, of for example aromatics
such
as xylene, polymerization, of for example one or more olefins) to produce a
polymer product; reforming; hydrogenation; dehydrogenation; dewaxing, of for
example hydrocarbons to remove straight chain paraffins; absorption, of for
example alkyl aromatic compounds for separating out isomers thereof;
alkylation,
of for example aromatic hydrocarbons such as benzene and alkyl benzene,
optionally with propylene to produce cumeme or with long chain olefins;
transalkylation, of for example a combination of aromatic and
polyalkylaromatic
hydrocarbons; dealkylation; hydrodecylization; disproportionation, of for
example
toluene to make benzene and paraxylene; oligomerization, of for example
straight
and branched chain olefin(s); and dehydrocyclization.
[0068] Preferred processes are conversion processes including: naphtha to
highly aromatic mixtures; light olefins) to gasoline, distillates and
lubricants;
oxygenates to olefin(s); light paraffins to olefins and/or aromatics; and
unsaturated
hydrocarbons (ethylene and/or acetylene) to aldehydes for conversion into
alcohols, acids and esters. The most preferred process of the invention is a
process directed to the conversion of a feedstock comprising one or more
oxygenates to one or more olefin(s).
[0069] The molecular sieve catalyst compositions described above are
particularly useful in conversion processes of different feedstock. Typically,
the
feedstock contains one or more aliphatic-containing compounds that include
alcohols, amines, carbonyl compounds for example aldehydes, ketones and
carboxylic acids, ethers, halides, mercaptans, sulfides, and the like, and
mixtures
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thereof. The aliphatic moiety of the aliphatic-containing compounds typically
contains from 1 to about SO carbon atoms, preferably from 1 to 20 carbon
atoms,
more preferably from 1 to 10 carbon atoms, and most preferably from 1 to 4
carbon atoms.
[0070] Non-limiting examples of aliphatic-containing compounds include:
alcohols such as methanol and ethanol, alkyl-mercaptans such as methyl
mercaptan and ethyl mercaptan, alkyl-sulfides such as methyl sulfide, alkyl-
amines such as methyl amine, alkyl-ethers such as dimethyl ether, diethyl
ether
and methylethyl ether, alkyl-halides such as methyl chloride and ethyl
chloride,
alkyl ketones such as dimethyl ketone, formaldehydes, and various acids such
as
acetic acid.
[0071] In a preferred embodiment of the process of the invention, the
feedstock contains one or more oxygenates, more specifically, one or more
organic compounds) containing at least one oxygen atom. In the most preferred
embodiment of the process of invention, the oxygenate in the feedstock is one
or
more alcohol(s), preferably aliphatic alcohol(s) where the aliphatic moiety of
the
alcohol(s) has from 1 to 20 carbon atoms, preferably from 1 to 10 carbon
atoms,
and most preferably from 1 to 4 carbon atoms. The alcohols useful as feedstock
in
the process of the invention include lower straight and branched chain
aliphatic
alcohols and their unsaturated counterparts.
[0072] Non-limiting examples of oxygenates include methanol, ethanol, n-
propanol, isopropanol, methyl ethyl ether, dimethyl ether, diethyl ether, di-
isopropyl ether, formaldehyde, dimethyl carbonate, dimethyl ketone, acetic
acid,
and mixtures thereof. In the most preferred embodiment, the feedstock is
selected
from one or more of methanol, ethanol, dimethyl ether, diethyl ether or a
combination thereof, more preferably methanol and dimethyl ether, and most
preferably methanol.
[0073] The various feedstocks discussed above, particularly a feedstock
containing an oxygenate, more particularly a feedstock containing an alcohol,
is
converted primarily into one or more olefin(s). The olefins) or olefin
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27
monomers) produced from the feedstock typically have from 2 to 30 carbon
atoms, preferably 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms,
still
more preferably 2 to 4 carbons atoms, and most preferably ethylene an/or
propylene. Non-limiting examples of olefin monomers) include ethylene,
propylene, butene-1, pentene-1, 4-methyl-pentene-1, hexene-1, octene-l and
decene-1, preferably ethylene, propylene, butene-I, pentene-1, 4-methyl-
pentene-
l, hexene-1, octene-1 and isomers thereof. Other olefin monomers) include
unsaturated monomers, diolefms having 4 to 18 carbon atoms, conjugated or
nonconjugated dimes, polyenes, vinyl monomers and cyclic olefins.
[0074] In the most preferred embodiment, the feedstock, preferably of one or
more oxygenates, is converted in the presence of a molecular sieve catalyst
composition of the invention into olefins) having 2 to 6 carbons atoms,
preferably
2 to 4 carbon atoms. Most preferably, the olefin(s), alone or combination, are
converted from a feedstock containing an oxygenate, preferably an alcohol,
most
preferably methanol, to the preferred olefins) ethylene and/or propylene.
[0075] The are many processes used to convert feedstock into olefins)
including various cracking processes such as steam cracking, thermal
regenerative
cracking, fluidized bed cracking, fluid catalytic cracking, deep catalytic
cracking,
and visbreaking. The most preferred process is generally referred to as gas-to-
olefins (GTO) or alternatively, methanol-to-olefins (MTO). In a MTO process,
typically an oxygenated feedstock, most preferably a methanol containing
feedstock, is converted in the presence of a molecular sieve catalyst
composition
thereof into one or more olefin(s), preferably and predominantly, ethylene
and/or
propylene, often referred to as light olefin(s).
[0076] In one embodiment of the process for conversion of a feedstock,
preferably a feedstock containing one or more oxygenates, the amount of
olefins)
produced based on the total weight of hydrocarbon produced is greater than 50
weight percent, preferably greater than 60 weight percent, more preferably
greater
than 70 weight percent, and most preferably greater than 75 weight percent. In
another embodiment of the process for conversion of one or more oxygenates to
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one or more olefin(s), the amount of ethylene and/or propylene produced based
on
the total weight of hydrocarbon product produced is greater than 65 weight
percent, preferably greater than 70 weight percent, more preferably greater
than 75
weight percent, and most preferably greater than 78 weight percent.
[0077] In another embodiment of the process for conversion of one or more
oxygenates to one or more olefin(s), the amount ethylene produced in weight
percent based on the total weight of hydrocarbon product produced, is greater
than
30 weight percent, more preferably greater than 35 weight percent, and most
preferably greater than 40 weight percent. In yet another embodiment of the
process for conversion of one or more oxygenates to one or more olefin(s), the
amount of propylene produced in weight percent based on the total weight of
hydrocarbon product produced is greater than 20 weight percent, preferably
greater than 25 weight percent, more preferably greater than 30 weight
percent,
and most preferably greater than 35 weight percent.
(0078] The feedstock, in one embodiment, contains one or more diluent(s),
typically used to reduce the concentration of the feedstock, and are generally
non-
reactive to the feedstock or molecular sieve catalyst composition. Non-
limiting
examples of diluents include helium, argon, nitrogen, carbon monoxide, carbon
dioxide, water, essentially non-reactive paraffins (especially alkanes such as
methane, ethane, and propane), essentially non-reactive aromatic compounds,
and
mixtures thereof. The most preferred diluents are water and nitrogen, with
water
being particularly preferred.
(0079] The diluent, water, is used either in a liquid or a vapor form, or a
combination thereof. The diluent is either added directly to a feedstock
entering
into a reactor or added directly into a reactor, or added with a molecular
sieve
catalyst composition. In one embodiment, the amount of diluent in the
feedstock
is in the range of from about 1 to about 99 mole percent based on the total
number
of moles of the feedstock and diluent, preferably from about 1 to 80 mole
percent,
more preferably from about 5 to about 50, and most preferably from about 5 to
about 25.
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[0080] In one embodiment, other hydrocarbons are added to a feedstock
either directly or indirectly, and include olefin(s), paraffin(s), aromatics)
(see for
example U.S. Patent No. 4,677,242, addition of aromatics) or mixtures thereof,
preferably propylene, butylene, pentylene, and other hydrocarbons having 4 or
more carbon atoms, or mixtures thereof.
[0081] The process for converting a feedstock, especially a feedstock
containing one or more oxygenates, in the presence of a molecular sieve
catalyst
composition of the invention, is carried out in a reaction process in a
reactor,
where the process is a fixed bed process, a fluidized bed process (includes a
turbulent bed process), preferably a continuous fluidized bed process, and
most
preferably a continuous high velocity fluidized bed process.
[0082] The reaction processes can take place in a variety of catalytic
reactors
such as hybrid reactors that have a dense bed or fixed bed reaction zones
and/or
fast fluidized bed reaction zones coupled together, circulating fluidized bed
reactors, riser reactors, and the like. Suitable conventional reactor types
are
described in for example U.S. Patent No. 4,076,796, U.S. Patent No. 6,287,522
(dual riser), and Fluidization Engineering, D. Kunii and O. Levenspiel, Robert
E.
Krieger Publishing Company, New York, New York 1977, which are all herein
fully incorporated by reference. The preferred reactor type are riser reactors
generally described in Riser Reactor, Fluidization and Fluid-Particle Systems,
pages 48 to 59, F.A. Zenz and D.F. Othmo, Reinhold Publishing Corporation,
New York, 1960, and U.S. Patent No. 6,166,282 (fast-fluidized bed reactor),
and
U.S. Patent Application Serial No. 09/564,613 filed May 4, 2000 (multiple
riser
reactor), which are all herein fully incorporated by reference.
[0083] In the preferred embodiment, a fluidized bed process or high velocity
fluidized bed process includes a reactor system, a regeneration system and a
recovery system.
[0084] The reactor system preferably is a fluid bed reactor system having a
first reaction zone within one or more riser reactors) and a second reaction
zone
within at least one disengaging vessel, preferably comprising one or more
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cyclones. In one embodiment, the one or more riser reactors) and disengaging
vessel is contained within a single reactor vessel. Fresh feedstock,
preferably
containing one or more oxygenates, optionally with one or more diluent(s), is
fed
to the one or more riser reactors) in which a molecular sieve catalyst
composition
or coked version thereof is introduced. In one embodiment, the molecular sieve
catalyst composition or coked version thereof is contacted with a liquid or
gas, or
combination thereof, prior to being introduced to the riser reactor(s),
preferably
the liquid is water or methanol, and the gas is an inert gas such as nitrogen.
[0085] In an embodiment, the amount of fresh feedstock fed separately or
jointly with a vapor feedstock, to a reactor system is in the range of from
0.1
weight percent to about 85 weight percent, preferably from about 1 weight
percent
to about 75 weight percent, more preferably from about 5 weight percent to
about
65 weight percent based on the total weight of the feedstock including any
diluent
contained therein. The liquid and vapor feedstocks are preferably the same
composition, or contain varying proportions of the same or different feedstock
with the same or different diluent.
[0086] The feedstock entering the reactor system is preferably converted,
partially or fully, in the first reactor zone into a gaseous effluent that
enters the
disengaging vessel along with a coked molecular sieve catalyst composition. In
the preferred embodiment, cyclones) within the disengaging vessel are designed
to separate the molecular sieve catalyst composition, preferably a coked
molecular
sieve catalyst composition, from the gaseous effluent containing one or more
olefins) within the disengaging zone. Cyclones are preferred, however, gravity
effects within the disengaging vessel will also separate the catalyst
compositions
from the gaseous effluent. Other methods for separating the catalyst
compositions
from the gaseous effluent include the use of plates, caps, elbows, and the
like.
[0087) In one embodiment of the disengaging system, the disengaging
system includes a disengaging vessel, typically a lower portion of the
disengaging
vessel is a stripping zone. In the stripping zone the coked molecular sieve
catalyst
composition is contacted with a gas, preferably one or a combination of steam,
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31
methane, carbon dioxide, carbon monoxide, hydrogen, or an inert gas such as
argon, preferably steam, to recover adsorbed hydrocarbons from the coked
molecular sieve catalyst composition that is then introduced to the
regeneration
system. In another embodiment, the stripping zone is in a separate vessel from
the
disengaging vessel and the gas is passed at a gas hourly superficial velocity
(GHSV) of from 1 hr-' to about 20,000 hr-' based on the volume of gas to
volume
of coked molecular sieve catalyst composition, preferably at an elevated
temperature from 250°C to about 750°C, preferably from about
350°C to 650°C,
over the coked molecular sieve catalyst composition.
[0088] The conversion temperature employed in the conversion process,
specifically within the reactor system, is in the range of from about
200°C to about
1000°C, preferably from about 250°C to about 800°C, more
preferably from about
250°C to about 750 °C, yet more preferably from about
300°C to about 650°C, yet
even more preferably from about 350°C to about 600°C most
preferably from
about 350°C to about 550°C.
[0089] The conversion pressure employed in the conversion process,
specifically within the reactor system, varies over a wide range including
autogenous pressure. The conversion pressure is based on the partial pressure
of
the feedstock exclusive of any diluent therein. Typically the conversion
pressure
employed in the process is in the range of from about 0.1 kPaa to about 5
MPaa,
preferably from about 5 kPaa to about 1 MPaa , and most preferably from about
20 kPaa to about 500 kPaa.
[0090] The weight hourly space velocity (WHSV), particularly in a process
for converting a feedstock containing one or more oxygenates in the presence
of a
molecular sieve catalyst composition within a reaction zone, is defined as the
total
weight of the feedstock excluding any diluents to the reaction zone per hour
per
weight of molecular sieve in the molecular sieve catalyst composition in the
reaction zone. The WHSV is maintained at a level sufficient to keep the
catalyst
composition in a fluidized state within a reactor.
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32
[0091] Typically, the WHSV ranges from about 1 hr -' to about 5000 hr -',
preferably from about 2 hr~' to about 3000 hr', more preferably from about 5
hr-'
to about 1500 hr-', and most preferably from about 10 hr-' to about 1000 hr'.
In
one preferred embodiment, the WHSV is greater than 20 hr-', preferably the
WHSV for conversion of a feedstock containing methanol and dimethyl ether is
in
the range of from about 20 hr-' to about 300 hr-'.
[0092] The superficial gas velocity (SGV) of the feedstock including diluent
and reaction products within the reactor system is preferably sufficient to
fluidize
the molecular sieve catalyst composition within a reaction zone in the
reactor.
The SGV in the process, particularly within the reactor system, more
particularly
within the riser reactor(s), is at least 0.1 meter per second (m/sec),
preferably
greater than 0.5 m/sec, more preferably greater than 1 m/sec, even more
preferably
greater than 2 m/sec, yet even more preferably greater than 3 m/sec, and most
preferably greater than 4 m/sec. See for example U.S. Patent Application
Serial
No. 09/708,753 filed November 8, 2000, which is herein incorporated by
reference.
[0093] In one preferred embodiment of the process for converting an
oxygenate to olefins) using a silicoaluminophosphate molecular sieve catalyst
composition, the process is operated at a WHSV of at least 20 hr-' and a
Temperature Corrected Normalized Methane Selectivity (TCNMS) of less than
0.016, preferably less than or equal to 0.01. See for example U.S. Patent No.
5,952,538, which is herein fully incorporated by reference. In another
embodiment of the processes for converting an oxygenate such as methanol to
one
or more olefins) using a molecular sieve catalyst composition, the WHSV is
from
0.01 hr-' to about 100 hr-', at a temperature of from about 350°C to
550°C, and
silica to MeZ03 (Me is a Group IIIA or VIII element from the Periodic Table of
Elements) molar ratio of from 300 to 2500. See for example EP-0 642 485 B1,
which is herein fully incorporated by reference. Other processes for
converting an
oxygenate such as methanol to one or more olefins) using a molecular sieve
catalyst composition are described in PCT WO 01/23500 published April 5, 2001
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33
(propane reduction at an average catalyst feedstock exposure of at least 1.0),
which is herein incorporated by reference.
[0094] The coked molecular sieve catalyst composition is withdrawn from
the disengaging vessel, preferably by one or more cyclones(s), and introduced
to
the regeneration system. The regeneration system comprises a regenerator where
the coked catalyst composition is contacted with a regeneration medium,
preferably a gas containing oxygen, under general regeneration conditions of
temperature, pressure and residence time. Non-limiting examples of the
regeneration medium include one or more of oxygen, O~, 503, NZO, NO, NOZ,
NZOS, air, air diluted with nitrogen or carbon dioxide, oxygen and water (U.5.
Patent No. 6,245,703), carbon monoxide and/or hydrogen. The regeneration
conditions are those capable of burning coke from the coked catalyst
composition,
preferably to a level less than 0.5 weight percent based on the total weight
of the
coked molecular sieve catalyst composition entering the regeneration system.
The
coked molecular sieve catalyst composition withdrawn from the regenerator
forms
a regenerated molecular sieve catalyst composition.
[0095] The regeneration temperature is in the range of from about 200°C
to
about 1500°C, preferably from about 300°C to. about
1000°C, more preferably
from about 450°C to about 750°C, and most preferably from about
550°C to
700°C. The regeneration pressure is in the range of from about 15 psia
(103
kPaa) to about 500 psia (3448 kPaa), preferably from about 20 psia (138 kPaa)
to
about 250 psia (1724 kPaa), more preferably from about 25 psia (172kPaa) to
about 150 psia (1034 kPaa), and most preferably from about 30 psia (207 kPaa)
to
about 60 psia (414 kPaa). The preferred residence time of the molecular sieve
catalyst composition in the regenerator is in the range of from about one
minute to
several hours, most preferably about one minute to 100 minutes, and the
preferred
volume of oxygen in the gas is in the range of from about 0.01 mole percent to
about 5 mole percent based on the total volume of the gas.
[0096] In one embodiment, regeneration promoters, typically metal
containing compounds such as platinum, palladium and the like, are added to
the
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34
regenerator directly, or indirectly, for example with the coked catalyst
composition. Also, in another embodiment, a fresh molecular sieve catalyst
composition is added to the regenerator containing a regeneration medium of
oxygen and water as described in U.S. Patent No. 6,245,703, which is herein
fully
incorporated by reference. In yet another embodiment, a portion of the coked
molecular sieve catalyst composition from the regenerator is returned directly
to
the one or more riser reactor(s), or indirectly, by pre-contacting with the
feedstock,
or contacting with fresh molecular sieve catalyst composition, or contacting
with a
regenerated molecular sieve catalyst composition or a cooled regenerated
molecular sieve catalyst composition described below.
[0097] The burning of coke is an exothermic reaction, and in an
embodiment, the temperature within the regeneration system is controlled by
various techniques in the art including feeding a cooled gas to the
regenerator
vessel, operated either in a batch, continuous, or semi-continuous mode, or a
combination thereof. A preferred technique involves withdrawing the
regenerated
molecular sieve catalyst composition from the regeneration system and passing
the
regenerated molecular sieve catalyst composition through a catalyst cooler
that
forms a cooled regenerated molecular sieve catalyst composition. The catalyst
cooler, in an embodiment, is a heat exchanger that is located either internal
or
external to the regeneration system. In one embodiment, the cooler regenerated
molecular sieve catalyst composition is returned to the regenerator in a
continuous
cycle, alternatively, (see U.S. Patent Application Serial No. 09/587,766 filed
June
6, 2000) a portion of the cooled regenerated molecular sieve catalyst
composition
is returned to the regenerator vessel in a continuous cycle, and another
portion of
the cooled molecular sieve regenerated molecular sieve catalyst composition is
returned to the riser reactor(s), directly or indirectly, or a portion of the
regenerated molecular sieve catalyst composition or cooled regenerated
molecular
sieve catalyst composition is contacted with by-products within the gaseous
effluent (PCT WO 00/49106 published August 24, 2000), which are all herein
fully incorporated by reference. In another embodiment, a regenerated
molecular
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sieve catalyst composition contacted with an alcohol, preferably ethanol, 1-
propnaol, 1-butanol or mixture thereof, is introduced to the reactor system,
as
described in U.S. Patent Application Serial No. 09/785,122 filed February 16,
2001, which is herein fully incorporated by reference. Other methods for
operating a regeneration system are in disclosed U.S. Patent No. 6,290,916
(controlling moisture), which is herein fully incorporated by reference.
[0098) The regenerated molecular sieve catalyst composition withdrawn
from the regeneration system, preferably from the catalyst cooler, is combined
with a fresh molecular sieve catalyst composition and/or re-circulated
molecular
sieve catalyst composition and/or feedstock and/or fresh gas or liquids, and
returned to the riser reactor(s). In another embodiment, the regenerated
molecular
sieve catalyst composition withdrawn from the regeneration system is returned
to
the riser reactors) directly, preferably after passing through a catalyst
cooler. In
one embodiment, a carrier, such as an inert gas, feedstock vapor, steam or the
like,
semi-continuously or continuously, facilitates the introduction of the
regenerated
molecular sieve catalyst composition to the reactor system, preferably to the
one
or more riser reactor(s).
[0099) By controlling the flow of the regenerated molecular sieve catalyst
composition or cooled regenerated molecular sieve catalyst composition from
the
regeneration system to the reactor system, the optimum level of coke on the
molecular sieve catalyst composition entering the reactor is maintained. There
are
many techniques for controlling the flow of a molecular sieve catalyst
composition described in Michael Louge, Experimental Technigues, Circulating
Fluidized Beds, Grace, Avidan and Knowlton, eds., Blackie, 1997 (336-337),
which is herein incorporated by reference. Coke levels on the molecular sieve
catalyst composition is measured by withdrawing from the conversion process
the
molecular sieve catalyst composition at a point in the process and determining
its
carbon content. Typical levels of coke on the molecular sieve catalyst
composition, after regeneration is in the range of from 0.01 weight percent to
about 15 weight percent, preferably from about 0.1 weight percent to about 10
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36
weight percent, more preferably from about 0.2 weight percent to about 5
weight
percent, and most preferably from about 0.3 weight percent to about 2 weight
percent based on the total weight of the molecular sieve and not the total
weight of
the molecular sieve catalyst composition.
[00100] In one preferred embodiment, the mixture of fresh molecular sieve
catalyst composition and regenerated molecular sieve catalyst composition
and/or
cooled regenerated molecular sieve catalyst composition contains in the range
of
from about 1 to 50 weight percent, preferably from about 2 to 30 weight
percent,
more preferably from about 2 to about 20 weight percent, and most preferably
from about 2 to about 10 coke or carbonaceous deposit based on the total
weight
of the mixture of molecular sieve catalyst compositions. See for example U.S.
Patent No. 6,023,005, which is herein fully incorporated by reference.
[00101] The gaseous effluent is withdrawn from the disengaging system and
is passed through a recovery system. There are many well known recovery
systems, techniques and sequences that are useful in separating olefins) and
purifying olefins) from the gaseous effluent. Recovery systems generally
comprise one or more or a combination of a various separation, fractionation
and/or distillation towers, columns, splitters, or trains, reaction systems
such as
ethylbenzene manufacture (U.S. Patent No. 5,476,978) and other derivative
processes such as aldehydes, ketones and ester manufacture (U.S. Patent No.
5,675,041 ), and other associated equipment for example various condensers,
heat
exchangers, refrigeration systems or chill trains, compressors, knock-out
drums or
pots, pumps, and the like. Non-limiting examples of these towers, columns,
splitters or trains used alone or in combination include one or more of a
demethanizer, preferably a high temperature demethanizer, a dethanizer, a
depropanizer, preferably a wet depropanizer, a wash tower often referred to as
a
caustic wash tower and/or quench tower, absorbers, adsorbers, membranes,
ethylene (C2) sputter, propylene (C3) splitter, butene (C4) sputter, and the
like.
[00102] Various recovery systems useful for recovering predominately
olefin(s), preferably prime or light olefins) such as ethylene, propylene
and/or
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37
butene are described in U.S. Patent No. 5,960,643 (secondary rich ethylene
stream), U.S. Patent Nos. 5,019,143, 5,452,581 and 5,082,481 (membrane
separations), U.S. Patent 5,672,197 (pressure dependent adsorbents), U.S.
Patent
No. 6,069,288 (hydrogen removal), U.S. Patent No. 5,904,880 (recovered
methanol to hydrogen and carbon dioxide in one step), U.S. Patent No.
5,927,063
(recovered methanol to gas turbine power plant), and U.S. Patent No. 6,121,504
(direct product quench), U.S. Patent No. 6,121,503 (high purity olefins
without
superfractionation), and U.S. Patent No. 6,293,998 (pressure swing
adsorption),
which are all herein fully incorporated by reference.
(00103] Generally accompanying most recovery systems is the production,
generation or accumulation of additional products, by-products and/or
contaminants along with the preferred prime products. The preferred prime
products, the light olefins, such as ethylene and propylene, are typically
purified
for use in derivative manufacturing processes such as polymerization
processes.
Therefore, in the most preferred embodiment of the recovery system, the
recovery
system also includes a purification system. For example, the light olefins)
produced particularly in a MTO process are passed through a purification
system
that removes low levels of by-products or contaminants. Non-limiting examples
of contaminants and by-products include generally polar compounds such as
water, alcohols, carboxylic acids, ethers, carbon oxides, sulfur compounds
such as
hydrogen sulfide, carbonyl sulfides and mercaptans, ammonia and other nitrogen
compounds, arsine, phosphine and chlorides. Other contaminants or by-products
include hydrogen and hydrocarbons such as acetylene, methyl acetylene,
propadiene, butadiene and butyne.
[00104] Other recovery systems that include purification systems, for
example for the purification of olefin(s), are described in Kirk-Othmer
Encyclopedia of Chemical Technology, 4th Edition, Volume 9, John Wiley &
Sons, 1996, pages 249-271 and 894-899, which is herein incorporated by
reference. Purification systems are also described in for example, U.S. Patent
No.
6,271,428 (purification of a diolefin hydrocarbon stream), U.S. Patent No.
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38
6,293,999 (separating propylene from propane), and U.S. Patent Application No.
09/689,363 filed October 20, 2000 (purge stream using hydrating catalyst),
which
is herein incorporated by reference.
[00105] Typically, in converting one or more oxygenates to olefins) having 2
or 3 carbon atoms, an amount of hydrocarbons, particularly olefm(s),
especially
olefins) having 4 or more carbon atoms, and other by-products are formed or
produced. Included in the recovery systems of the invention are reaction
systems
for converting the products contained within the effluent gas withdrawn from
the
reactor or converting those products produced as a result of the recovery
system
utilized.
[00106] In one embodiment, the effluent gas withdrawn from the reactor is
passed through a recovery system producing one or more hydrocarbon containing
stream(s), in particular, a three or more carbon atom (C3+) hydrocarbon
containing
stream. In this embodiment, the C3+ hydrocarbon containing stream is passed
through a first fractionation zone producing a crude C3 hydrocarbon and a CQ+
hydrocarbon containing stream, the C4+ hydrocarbon containing stream is passed
through a second fractionation zone producing a crude C4 hydrocarbon and a CS+
hydrocarbon containing stream. The four or more carbon hydrocarbons include
butenes such as butene-1 and butene-2, butadienes, saturated butanes, and
isobutanes.
[00107] The effluent gas removed from a conversion process, particularly a
MTO process, typically has a minor amount of hydrocarbons having 4 or more
carbon atoms. The amount of hydrocarbons having 4 or more carbon atoms is
typically in an amount less than 20 weight percent, preferably less than 10
weight
percent, more preferably less than S weight percent, and most preferably less
than
2 weight percent, based on the total weight of the effluent gas withdrawn from
a
MTO process, excluding water. In particular with a conversion process of
oxygenates into olefins) utilizing a molecular sieve catalyst composition the
resulting effluent gas typically comprises a majority of ethylene and/or
propylene
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39
and a minor amount of four carbon and higher carbon number products and other
by-products, excluding water.
[00108] Suitable well known reaction systems as part of the recovery system
primarily take lower value products and convert them to higher value products.
For example, the C4 hydrocarbons, butene-1 and butene-2 are used to make
alcohols having 8 to 13 carbon atoms, and other specialty chemicals,
isobutylene
is used to make a gasoline additive, methyl-t-butylether, butadiene in a
selective
hydrogenation unit is converted into butene-1 and butene-2, and butane is
useful
as a fuel. Non-limiting examples of reaction systems include U.S. Patent No.
5,955,640 (converting a four carbon product into butene-1 ), U.S. Patent No.
4,774,375 (isobutane and butene-2 oligomerized to an alkylate gasoline), U.S.
Patent No. 6,049,017 (dimerization of n-butylene), U.S. Patent Nos. 4,287,369
and
5,763,678 (carbonylation or hydroformulation of higher olefins with carbon
dioxide and hydrogen making carbonyl compounds), U.S. Patent No. 4,542,252
(multistage adiabatic process), U.S. Patent No. 5,634,354 (olefin-hydrogen
recovery), and Cosyns, J. et al., Process for Upgrading C3, C~ and CS Olefinic
Streams, Pet. & Coal, Vol. 37, No. 4 (1995) (dimerizing or oligomerizing
propylene, butylene and pentylene), which are all herein fully incorporated by
reference.
[00109] The preferred light olefins) produced by any one of the processes
described above, preferably conversion processes, are high purity prime
olefins)
products that contains a single carbon number olefin in an amount greater than
80
percent, preferably greater than 90 weight percent, more preferably greater
than 95
weight percent, and most preferably no less than about 99 weight percent,
based
on the total weight of the olefin. In one embodiment, high purity prime
olefins)
are produced in the process of the invention at rate of greater than S kg per
day,
preferably greater than 10 kg per day, more preferably greater than 20 kg per
day,
and most preferably greater than 50 kg per day. In another embodiment, high
purity ethylene and/or high purity propylene is produced by the process of the
invention at a rate greater than 4,500 kg per day, preferably greater than
100,000
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kg per day, more preferably greater than 500,000 kg per day, even more
preferably
greater than 1,000,000 kg per day, yet even more preferably greater than
1,500,000 kg per day, still even more preferably greater than 2,000,000 kg per
day, and most preferably greater than 2,500,000 kg per day.
[00110] Other conversion processes, in particular, a conversion process of an
oxygenate to one or more olefins) in the presence of a molecular sieve
catalyst
composition, especially where the molecular sieve is synthesized from a
silicon-,
phosphorous-, and alumina- source, include those described in for example:
U.S.
Patent No. 6,121,503 ( making plastic with an olefin product having a paraffin
to
olefin weight ratio less than or equal to 0.05), U.S. Patent No. 6,187,983
(electromagnetic energy to reaction system), PCT WO 99/18055 publishes April
15, 1999 (heavy hydrocarbon in effluent gas fed to another reactor) PCT WO
01/60770 published August 23, 2001 and U.S. Patent Application Serial No.
09/627,634 filed July 28, 2000 (high pressure), U.S. Patent Application Serial
No.
09/507,838 filed February 22, 2000 (staged feedstock injection), and U.S.
Patent
Application Serial No. 09/785,409 filed February 16, 2001 (acetone co-fed),
which are all herein fully incorporated by reference.
[00111] In an embodiment, an integrated process is directed to producing
light olefins) from a hydrocarbon feedstock, preferably a hydrocarbon gas
feedstock, more preferably methane and/or ethane. The first step in the
process is
passing the gaseous feedstock, preferably in combination with a water stream,
to a
syngas production zone to produce a synthesis gas (syngas) stream. Syngas
production is well known, and typical syngas temperatures are in the range of
from about 700°C to about 1200°C and syngas pressures are in the
range of from
about 2 MPa to about 100 MPa. Synthesis gas streams are produced from natural
gas, petroleum liquids, and carbonaceous materials such as coal, recycled
plastic,
municipal waste or any other organic material, preferably synthesis gas stream
is
produced via steam reforming of natural gas. Generally, a heterogeneous
catalyst,
typically a copper based catalyst, is contacted with a synthesis gas stream,
typically carbon dioxide and carbon monoxide and hydrogen to produce an
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41
alcohol, preferably methanol, often in combination with water. In one
embodiment, the synthesis gas stream at a synthesis temperature in the range
of
from about 150°C to about 450°C and at a synthesis pressure in
the range of from
about 5 MPa to about 10 MPa is passed through a carbon oxide conversion zone
to
produce an oxygenate containing stream.
[00112] This oxygenate containing stream, or crude methanol, typically
contains the alcohol product and various other components such as ethers,
particularly dimethyl ether, ketones, aldehydes, dissolved gases such as
hydrogen
methane, carbon oxide and nitrogen, and fusel oil. The oxygenate containing
stream, crude methanol, in the preferred embodiment is passed through a well
known purification processes, distillation, separation and fractionation,
resulting
in a purified oxygenate containing stream, for example, commercial Grade A and
AA methanol. The oxygenate containing stream or purified oxygenate containing
stream, optionally with one or more diluents, is contacted with one or more
molecular sieve catalyst composition described above in any one of the
processes
described above to produce a variety of prime products, particularly light
olefin(s), ethylene and/or propylene. Non-limiting examples of this integrated
process is described in EP-B-0 933 345, which is herein fully incorporated by
reference. In another more fully integrated process, optionally with the
integrated
processes described above, olefins) produced are directed to, in one
embodiment,
one or more polymerization processes for producing various polyolefins. (See
for
example U.S. Patent Application Serial No. 09/615,376 filed July 13, 2000,
which
is herein fully incorporated by reference.)
[00113] Polymerization processes include solution, gas phase, slurry phase
and a high pressure processes, or a combination thereof. Particularly
preferred is a
gas phase or a slurry phase polymerization of one or more olefins) at least
one of
which is ethylene or propylene. These polymerization processes utilize a
polymerization catalyst that can include any one or a combination of the
molecular
sieve catalysts discussed above, however, the preferred polymerization
catalysts
are those Ziegler-Natta, Phillips-type, metallocene, metallocene-type and
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advanced polymerization catalysts, and mixtures thereof. The polymers produced
by the polymerization processes described above include linear low density
polyethylene, elastomers, plastomers, high density polyethylene, low density
polyethylene, polypropylene and polypropylene copolymers. The propylene based
polymers produced by the polymerization processes include atactic
polypropylene,
isotactic polypropylene, syndiotactic polypropylene, and propylene random,
block
or impact copolymers.
[00114] In preferred embodiment, the integrated process comprises a
polymerizing process of one or more olefins) in the presence of a
polymerization
catalyst system in a polymerization reactor to produce one or more polymer
products, wherein the one or more olefins) having been made by converting an
alcohol, particularly methanol, using a molecular sieve catalyst composition.
The
preferred polymerization process is a gas phase polymerization process and at
least one of the olefins(s) is either ethylene or propylene, and preferably
the
polymerization catalyst system is a supported metallocene catalyst system. In
this
embodiment, the supported metallocene catalyst system comprises a support, a
metallocene or metallocene-type compound and an activator, preferably the
activator is a non-coordinating anion or alumoxane, or combination thereof,
and
most preferably the activator is alumoxane.
[00115] In addition to polyolefins, numerous other olefin derived products are
formed from the olefins) recovered any one of the processes described above,
particularly the conversion processes, more particularly the GTO process or
MTO
process. These include, but are not limited to, aldehydes, alcohols, acetic
acid,
linear alpha olefins; vinyl acetate, ethylene dicholoride and vinyl chloride,
ethylbenzene, ethylene oxide, cumene, isopropyl alcohol, acrolein, allyl
chloride,
propylene oxide, acrylic acid, ethylene-propylene rubbers, and acrylonitrile,
and
trimers and dimers of ethylene, propylene or butylenes.
EXAMPLES
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[00116] In order to provide a better understanding of the present invention
including representative advantages thereof, the following examples are
offered.
Constituents of a mixture used for formulating catalysts will generally
contain
volatile components, including, but not limited to, water and, in the case of
molecular sieve, organic template. It is common practice to describe the
amount
or proportion of these constituents as being on a "calcined basis".
Calcination
involves heating a material in the presence of air at an elevated temperature
sufficient to dry and remove any contained volatile content (650°C for
one or more
hours). On a "calcined basis" is defined, for the purposes of the current
invention,
as the amount or fraction of each component remaining after it has been
mathematically reduced to account for losses in weight expected to occur if
the
component had been calcined. The term LOI (Loss-On-Ignition) is used herein
interchangeably with the fractional loss during calcination, a "calcined
basis".
Thus, 10 grams of a component containing 25% volatiles would be described as
"7.5 g on a calcined basis" with an LOI of 2.5g. Synthesis of a SAPO-34
molecular sieve is well known, and the SAPO-34 used in the Examples below was
measured to have a MSA of about 550 mZ/g-molecular sieve.
[00117] MSA is determined using a MICROMERITICS Gemini 2375 from
Micromeritics Instrument Corporation, Norcross, Georgia is used. An amount
O.lSg to 0.6g of the sample is loaded into the sample cell for degassing at
300°C
for a minimum of 2 hours. During the analysis, the Evacuation Time is 1.0
minute, no free space is used, and sample Density of 1.0 g/cc is used.
Thirteen
(13) adsorption data points are collected with adsorption targets of:
Data Point Adsorption Data Adsorption
Target (p/p)Point Target (p/p)
1 0.00500 8 0.25000
2 0.07500 9 0.30000
3 0.01000 10 0.40000
4 0.05000 11 0.60000
0.10000 12 0.75000
6 0.15000 13 0.95000
0.20000
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[00118] The correction factor used in the t-plot is 0.975. No de-sorption
points are collected. Other analysis parameters include, Analysis Mode:
Equilibrate; Equilibration Time: S second; Scan Rate: 10 seconds. A t-plot
from
0.00000 to 0.90000 is constructed using the ASTM certified form of the Harkins
and Jura equation (H-J Model): t(p) _ (13.99/(0.034-
log(p/p°)))°.s. It is shown by
Cape and Kibby [J.A. Cape and C.L. Kibby, J. Colloids and Interface Science,
138, 516-520 (1990)] that the conventional BET surface area of a microporous
material can be decomposed quantitatively into the external area and the
micropore volume, as expressed by equation given below: S",~cro - S~o~-SeX~ =
vm/d; ,
where v", is the micropore volume, S",~~~o is the micropore area calculated
from S,o,
and 5~~,. S,o, is given by the conventional BET method, and SeX, is the
external area
taken from the t-plot. d~ is a nonphysical length the value of which depends
on the
pressure used in the experiments. The proportionality factor, d~, is
determined
quantitatively by the pressures used in the BET fits.
[00119] For purposes of this patent application and appended claims "solids
content" is measured by weighing a sample of a slurry, calcining the slurry
sample, preferably at 550°C to 750°C, re-weighing the calcined
sample; the solids
content is equal to the calcined sample weight divided by the weight of the
slurry
sample multiplied by 100.
Example 1
[00120] A slurry was prepared by mixing 45.8 kg of a SAPO-34 molecular
sieve containing a template (Loss-on-Ignition (LOI) of 46.6%) to 25.1 kg of de-
ionized water under vigorous stirring conditions using a turbo-blade mixer at
60 to
300 rpm for a period of 2 hours, at which time the solid was totally
disintegrated.
A high-shear mixing step was applied on this mixture using a Silverson high-
shear
in-line mixer for two passes depending on the size reduction. Particle size
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analysis of a one-pass high-shear treated slurry is given in Table 1.
Example 2
[00121] A slurry of aluminum chlorohydrate (available from Reheis,
Berkeley Heights, New Jersey ) was prepared by adding 13.4 kg of
aluminum chlorohydrate (LOI: 51.6%) into 12.5 kg of de-ionized water
using a turbo-blade mixer at 60 to 300 rpm for a period of 0.2 to 12 hours
or until a translucent sol was obtained. This aluminum chlorohydrate sol
was then added to the slurry of Example 1 using a feed pump and mixed
for 0.2 to 5 hours before kaolin clay (ASP grade available from Engelhard
Corporation, Macon, Georgia) was added. An amount of 35.1 kg of kaolin
clay (LOI: 13.9%) and an additional amount of 4.2 kg of de-ionized water
was added to the mixture of SAPO-34 molecular sieve and aluminum
chlorohydrate. The resultant mixture was mixed using the turbo-blade
mixer at 60 to 300 rpm for a period of 2 hours, then passed through high-
shear in-line mixer twice. This slurry was aged at 40°C in a feed tank
under constant mixing using a turbo-blade mixer at 60 to 300 rpm for a
period of 15 hours. Particle size analysis of the aged slurry is given in
Table 1.
Table 1
Exampled,o (pm)DS (pm) d9o (pm) Solid Content
a a a b
1 1.08 1.75 2.74 18.7%
I2 10.93 11.85 3.24 46.7%
a~ d 10,x50, d90~ ~ ~ ~o, ~u%, yU% of the particles are at or smaller than the
size gwen.
b. Solid content was determined by calcining the slurry in a microwave muffle
furnace to 650oC.
Example 3
[00122] The IEP of the materials used in the formulation of the
catalyst composition was determined from the measurements of zeta-
potential using a Matec ESA 9800 electrokinetic instrument available from
Matec Applied Science, Northboro, MA. Zeta-potentials are calculated
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from measurements of an ultrasonic signal originating from distortion of
the colloidal particle's double in a high frequency ac field. Conversion of
the ultrasonic signal into a zeta-potential value factors in particle size,
particle density, and volume fraction of the suspended solid.
Example 4
[00123] Particle size dependence in a very dilute slurry (less than 1
weight percent) of a colloidal silicalite having an average particle size of
60 to 70 nanometers as a function of pH was determined using a Zeta Sizer
3000 (Malvern Instrument as above). At pH's away from the IEP, silicalite
particles were in the form of individual particles. However, these
individual particles aggregated to 1.45~m (25 to 30 times bigger than the
primary particle size) when the pH was adjusted to near the IEP.
Table 2
ExamplepH Viscosityd~o(~m)dso(~m)d9o(~m)Solid Density
(cP) a a a Contentof Slutry
b d (g/cc)
3.6 1840 0.28 1.45 3.54 44.5% 1.44
6 3.7 2940 0.38 0.90 6.48 44.8% 1.46
7 4.2 720 0.25 1.42 3.80 43.0% 1.42
'
8 3.7 3920 0.37 0.91 7.94 46.9% 1.48
~
a. d 10,d50 d90: 10%, 50%, 90% of the particles are at or smaller this size
given.
b. Viscosity was measured using a Brookfield LV viscometer: spindle #3, room
temperature, and
30 RPM.
c. Using the procedure of Example 5 except its pH was adjusted from 3.7 to 4.2
using an ammonia
solution;
d. Solid content was determined by calcining the slurry in a microwave muffle
furnace to 650oC.
Example 5
[00124] A slurry as prepared as in Examples 1 and 2 but added to a
slurry of SAPO-34 molecular sieve (B) to give a total solid content of
44.5% while maintained a weight ratio of sieve to aluminum chlorohydrate
and kaolin clay at 40/10.6/49.4. Viscosity, pH, and particle size
measurements of this Example 5 are given in Table 2.
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Example 6
0[ 0125] A slurry was prepared as in Examples 1 and 2 but using a
SAPO-34 molecular sieve (C) to give a total solid content of 44.8% while
maintained a weight ratio of sieve to aluminum chlorohydrate and kaolin
clay at 40/10.6/49.4. Viscosity, pH, and particle size measurements of this
Example 6 are given in Table 2.
Example 7
[00126] A slurry was prepared using the same composition and
procedure of Example 6 and its pH was increased from 3.7 to 4.2 using a
diluted ammonia aqueous solution. Viscosity, pH, and particle size
measurements for this Example 7 are given in Table 2.
Example 8
[00127] A slurry as prepared as in Examples 1 and 2 but using a
SAPO-34 molecular sieve (D) to give a total solid content of 46.9% while
maintaining a weight ratio of molecular sieve to aluminum chlorohydrate
and kaolin clay at 40/10.6/49.4. Viscosity, pH, and particle size
measurements of this Example 8 are given in Table 2.
Example 9
[00128] Zeta-potential measurement of SAPO-34 molecular sieve
(A) used in Example 2 after being calcined in air at 550°C for 5 hours.
It
was found that the presence of template in SAPO-34 resulted in a
substantially lower IEP pH than SAPO-34 free of template.
Example 10
[00129] The slurry made in Example 5 was spray dried using a lab-
scale spray dryer (Yamato DL-41 available from Yamato Scientific
America, Inc., Orangeburg, N.Y.). Slurry feed rate was at 40 to 50 g/min,
inlet temperature of 350°C and product temperature of 80 to
85°C,
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atomization pressure of 1 bar. The spray dry product was calcined at
650°C. This catalyst composition of this Example 10 had an ARI of 0.33.
Comparative Example 11
[00130] In contrast to the invention, a typical commercial FCC
catalyst, for example, a W. R. Grace Ultima 447 catalyst has an ARI of
7.94.
Comparative Example 12
[00131] A slurry prepared the same as Example 8, its pH was
attempted to be increased to 4.5 to 4.6 using a diluted ammonia solution
(5-15 wt%). It precipitated and solidified when the pH of the mixture
reached of about 4.6. The targeted pH value approached the IEP of the
SAPO-34 molecular sieve of Example 9, thus leading to destabilization of
the slurry. The resultant material could not be spray dried.
Example 13
[00132] The slurry made in Example 6 was spray dried using a lab-
scale spray dryer (Yamato DL-41 ). Slurry feed rate was at 40 to 50 g/min,
inlet temperature of 350°C and product temperature of 80 to
85°C,
atomization pressure of 1 bar. The spray dried catalyst composition was
calcined at 650°C for 1 hr. This formulated molecular sieve catalyst
composition had an ARI of 0.32.
Example 14
[00133] The slurry made in Example 7 was spray dried using a lab-
scale spray dryer (Yamato DL-41 ). Slurry feed rate was at 40 to 50 g/min,
inlet temperature of 350°C and product temperature of 80 to
85°C,
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atomization pressure of 1 bar. The spray dried catalyst composition was
calcined at 650°C. This formulated molecular sieve catalyst composition
had an ARI of 0.41.
Example 15
Oj 0134] The slurry made in Example 8 was spray dried using a lab-scale
spray dryer (Yamato DL-41). Slurry feed rate was at 40 to 50 g/min, inlet
temperature of 350°C and product temperature of 80 to 85°C,
atomization pressure
of 1 bar. The spray dried catalyst composition was calcined at 650°C.
This
formulated molecular sieve catalyst composition had an ARI of 0.29.
0[ 0135] While the present invention has been described and illustrated by
reference to particular embodiments, those of ordinary skill in the art will
appreciate that the invention lends itself to variations not necessarily
illustrated
herein. For example, it is contemplated that the molecular sieve catalyst
composition is useful in the inter-conversion of olefin(s), oxygenate to
gasoline
conversions reactions, malaeic anhydride, phthalic anyhdride and acrylonitrile
formulation, vapor phase methanol synthesis, and various Fischer Tropsch
reactions. It is further contemplated that a plug flow, fixed bed or fluidized
bed
process are used in combination, particularly in different reaction zones
within a
single or multiple reactor system. It is also contemplated the molecular sieve
catalyst compositions described herein are useful as absorbents, adsorbents,
gas
separators, detergents, water purifiers, and other various uses such as
agriculture
and horticulture. Additionally contemplated the molecular sieve catalyst
compositions include one or more other molecular sieves in combination. For
this
reason, then, reference should be made solely to the appended claims for
purposes
of determining the true scope of the present invention.
