Note: Descriptions are shown in the official language in which they were submitted.
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FCC PROCESS INCORPORATING
CRYSTALLINE MICROPOROUS OXIDE
CATALYSTS HAVING INCREASED LEWIS ACIDITY
BACKGROUND
This invention relates to catalyst components and compositions and methods of
making and using the composition which comprises a crystalline microporous
oxide
having a promoter metal compound that promotes dehydrogenation and increases
Lewis acidity without increasing the unit cell size of the crystalline
microporous oxide.
Crystalline microporous oxides, such as zeolitic materials, have been in
commercial use in a variety of industries for many years. These materials are
especially valuable for their fluid separation ability as molecular sieves, as
well as for
their ability to act as a catalyst.
Crystalline microporous oxides are particularly useful as catalysts which
convert the large paraffin molecules of a hydrocarbon mixture into smaller
more
unsaturated molecules such as olefins and aromatics. Typical conversion
processes
include fluid catalytic cracking and hydrocracking. To maximize this
conversion
process, many structural properties of the catalyst have to be balanced, such
as pore
size, pore volume, Lewis acidity, and Br~nsted acidity. If the structural
properties of
the conversion catalyst are not properly balanced, conversion of the
hydrocarbon
mixture to product may be low, product quality may be poor, or the conversion
catalyst
may be rapidly deactivated.
It would be of particular benefit to obtain a crystalline microporous oxide
catalyst high in catalytic activity by balancing the Bronsted acidity and the
Lewis
acidity of the framework and non-framework portions of the catalyst. By
balancing
the composition of the framework and non-framework portions of the crystalline
structure, catalytic activity can be efficiently optimized. In the case of a
cracking
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catalyst, olefin forming reactions of large paraffin molecules can be more
efficiently
coupled with the subsequent scission reactions which form the smaller
molecules in
the final product.
SUMMARY
One embodiment of the present invention comprises a catalyst comprising (i) a
matrix material, and (ii) a crystalline microporous oxide incorporated
into/with the
matrix material. The crystalline microporous oxide comprises a non-framework
portion and has a unit cell size. The non-framework portion comprises a
promoter
metal compound incorporated only into the non-framework portion of the
crystalline
microporous oxide. The promoter metal compound does not substantially increase
the
unit cell size of the crystalline microporous oxide.
In another embodiment of the catalyst, the crystalline microporous oxide
comprises a Y zeolite incorporated into the matrix material. The Y zeolite
comprises a
non-framework portion, has a unit cell size greater than about 24.30A, and
comprises
aluminum oxide incorporated only into the non-framework portion of the
crystalline
microporous oxide, such that the aluminum oxide increases Lewis acidity but
does not
substantially increasing the unit cell size of the zeolite.
In another embodiment of the catalyst, the crystalline microporous oxide
comprises a non-framework portion comprising a promoter metal compound capable
of increasing Lewis acidity incorporated only into the non-framework portion
of the
crystalline microporous oxide, such that the promoter metal compound does not
substantially increase the unit cell size of the crystalline microporous
oxide.
The embodiments of the catalyst can be used in an FCC unit, an isomerization
unit, or a hydrocracker by contacting the catalyst with a suitable feedstock.
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Another embodiment of the present invention comprises a process for making a
catalyst. The process comprises (a) contacting a crystalline microporous oxide
and a
promoter precursor comprising a promoter metal capable of forming a promoter
metal
compound, said crystalline microporous oxide comprising a non-framework
portion
and having a unit cell size; and, (b) heating the mixture of step (a) to a
temperature
between 150°C and 550°C; wherein a promoter metal compound
comprising said
promoter metal is incorporated only into the non-framework portion of the
crystalline
microporous oxide and wherein the promoter metal compound does not
substantially
increase the unit cell size of the crystalline microporous oxide.
Another embodiment of the present invention is a process comprising: (a)
contacting a crystalline microporous oxide and a promoter precursor, the
crystalline
microporous oxide comprising a non-framework portion and having a unit cell
size
and the promoter precursor comprising a promoter metal capable of forming a
promoter metal compound; (b) decomposing said promoter precursor thereby
forming
a promoter metal compound comprising an oxide form of said promoter metal; (c)
dispersing said promoter metal compound only into the non-framework portion of
said
crystalline microporous oxide; wherein the promoter metal compound does not
substantially increase the unit cell size of the crystalline microporous
oxide.
Another embodiment of the present invention is a process comprising: (a)
calcining a zeolite comprising a non-framework portion and having a unit cell
size; (b)
contacting the zeolite with a promoter precursor comprising a promoter metal
capable
of forming a promoter metal compound, wherein said promoter metal is selected
from
the group consisting of magnesium, chromium, iron, lanthanum, gallium,
manganese
and aluminum and wherein said promoter precursor is selected from the group
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consisting of aluminum acetylacetonate, aluminum isopropyloxide, aluminum
hexafluoroacetylacetonate, aluminum dichlorohydrol, aluminum ethoxides,
tris[2,2,6,6-tetramethyl-3-5, heptanedianoto]aluminum-III[Al(TMHD)~], aluminum
acetate, aluminum nitrate, aluminum propoxide, magnesium acetylacetonate,
chromium acetylacetonate, iron acetylacetonate, gallium acetylacetonate,
manganese
acetylacetonate, and lanthanide acetylacetonate; (c) heating the mixture of
step (b) to a
temperature between 1S0°C and 550°C; (d) incorporating the
product of step (b) into
a matrix material, wherein a promoter metal compound comprising said promoter
metal is incorporated only into the non-framework portion of the zeolite and
wherein
the promoter metal compound does not substantially increase the unit cell size
of the
zeolite.
Another embodiment of the present invention is a process comprising: (a)
contacting a calcined crystalline microporous oxide and a promoter precursor
1 S comprising a promoter metal capable of forming a promoter metal compound,
said
crystalline microporous oxide comprising a non-framework portion and having a
unit
cell size; and, (b) activating said promoter metal compound, wherein said
promoter
metal compound is incorporated only into the non-framework portion of the
crystalline
microporous oxide and wherein the promoter metal compound does not
substantially
increase the unit cell size of the crystalline microporous oxide.
Another embodiment of the present invention is a process comprising: (a)
calcining a crystalline microporous oxide, the crystalline microporous oxide
comprising a non-framework portion and having a unit cell size; (b) contacting
an
aluminum alkyl selected from the group consisting of trimethylaluminum,
triethylaluminum, tri(t-butyl)aluminum, and tri(i-butyl)aluminum; (c) treating
the
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product of step (b) with an oxygen-containing material to form a promoter
metal
compound, wherein the promoter metal compound does not substantially increase
the
unit cell size of the crystalline microporous oxide.
Other embodiments of the present invention include the products produced by
the processes of the present invention. These products may or may not be
incorporated into a matrix material, but are preferably incorporated into a
matrix
material before used in a process unit.
DETAILED DESCRIPTION
The catalytic activity of a crystalline microporous oxide, such as a zeolite,
can
be improved by effectively incorporating a promoter metal compound that
promotes
dehydrogenation and increases Lewis acidity of the crystalline microporous
oxide
without increasing its unit cell size. Although the crystalline microporous
oxide can
be used as a catalyst alone, the crystalline microporous oxide is preferably
incorporated into a matrix material, preferably an inorganic oxide. Other
catalytic or
non-catalytic components can also be present in the matrix material.
The crystalline microporous oxide of this invention can be used to catalyze
the
breakdown of primary products from the catalytic cracking reaction into clean
products such as naphtha for fuels and olefins for chemical feedstocks. The
crystalline
microporous oxide is preferably selected from the group consisting of
crystalline
aluminosilicate zeolites (hereafter zeolites), tectosilicates, tetrahedral
aluminophophates (ALPOs) and tetrahedral silicoaluminophosphates (SAPOs). More
preferably, the crystalline microporous oxide is a zeolite.
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Suitable zeolites include both natural and synthetic zeolites. Suitable
natural
zeolites include gmelinite, chabazite, dachiardite, clinoptilolite, faujasite,
heulandite,
levynite, erionite, cancrinite, scolecite, offretite, mordenite, and
ferrierite. Suitable
synthetic zeolites are zeolites X, Y, L, ZK-4, ZK-5, E, H, J, M, Q, T, Z,
alpha and
beta, ZSM-types and omega. Faujasites are preferred, particularly zeolite Y
and
zeolite X having a unit cell size greater than or equal to 24.30A, more
preferably
greater than or equal to about 24.40. The aluminum in the zeolite, as well as
the
silicon component, can be substituted for other framework components. For
example,
the aluminum portion can be replaced by boron, gallium, titanium or trivalent
metal .
compositions which are heavier than aluminum. Germanium can be used to replace
the silicon portion.
In a finished catalyst product, the crystalline microporous oxide is
preferably
included within an inorganic oxide matrix material that binds the catalyst
components
together so that the final catalyst is hard enough to survive interparticle
and reactor
wall collisions. An inorganic oxide matrix material can be made from an
inorganic
oxide sol or gel which is dried to "glue" the catalyst components together.
Preferably,
the inorganic oxide matrix material comprises oxides of silicon and aluminum.
The
.inorganic oxide matrix material can further comprise an active porous
inorganic oxide
catalyst component and an inert catalyst component. Preferably, each component
of
the catalyst is held together by attachment with the inorganic oxide matrix
material.
An active porous inorganic oxide catalyst component typically catalyzes the
formation of primary products by cracking hydrocarbon molecules that are too
large to
ft inside the crystalline microporous oxide. An active porous inorganic oxide
catalyst
component which can be incorporated into the cracking catalyst is preferably a
porous
inorganic oxide that cracks a relatively large amount of hydrocarbons into
lower
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molecular weight hydrocarbons as compared to an acceptable thermal blank. A
low
surface area silica (e.g., quartz) is one type of acceptable thermal blank.
The extent of
cracking can be measured in any of various ASTM tests such as the MAT
(microactivity test, ASTM # D3907-8). Compounds such as those disclosed in
Greensfelder, B. S., et al., Industrial and En~ineerin~ Chemistry, pp. 2573-
83, Nov.
1949, are desirable. Alumina, silica-alumina and silica-alumina-zirconia
compounds
are preferred.
An inert catalyst component typically densifies, strengthens and acts as a
protective thermal sink. An inert catalyst component which can be incorporated
into
the cracking catalyst of this invention preferably has a cracking activity
that is not
significantly greater than the acceptable thermal blank. Kaolin and other
clays as well
as a-alumina, titania, zirconia, quartz and silica are examples of suitable
inert
components.
The discrete alumina phases are preferably incorporated into the inorganic
oxide matrix material. Species of aluminum oxyhydroxides-y-alumina, boehmite,
diaspore, and transitional aluminas such as a-alumina, ~i-alumina, y-alumina,
8-
alumina, s-alumina, K-alumina, and p-alumina can be employed. Preferably, the
alumina species is an aluminum trihydroxide such as gibbsite, bayerite,
nordstrandite,
or doyelite.
In one embodiment of the present invention, the crystalline microporous oxide
catalyst component includes a compound for promoting dehydrogenation and
increasing Lewis acidity, referred to herein as a promoter metal compound. The
dispersal of the promoter metal compound into the crystalline microporous
oxide does
not result in any substantial increase in the unit cell size of the
crystalline microporous
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oxide, and the unit cell size of the crystalline microporous oxide material is
substantially the same.
The promoter metal compound is preferably in a chemical state to effectively
promote the dehydrogenation of paraffinic and naphthenic compounds in a
hydrocarbon feed stream to form olefinic compounds. For example, aluminum
oxide
(A1203), comprises a suitable promoter metal (aluminum). The oxide of aluminum
is
in such an effective chemical state.
The crystalline microporous oxide includes a framework portion and a non-
framework portion. Lewis acidity of the crystalline microporous oxide is
increased by
increasing the number of effective metal ration sites of the non-framework
portion of
the crystalline microporous oxide without increasing the unit cell size.
Typically,
when a material is incorporated into the framework portion of the material the
unit cell
size will be increased. When the promoter metal compounds of the present
invention
are incorporated into the crystalline micorporous oxide material of the
present
invention, the unit cell size remains substantially the same. Thus, the
promotar
materials are preferably incorporated only into the non-framework portion of
the
crystalline microporous oxide material. Cf., W.O. Haag, "Catalysis by Zeolites
-
Science and Technology", Zeolites and Related Micro~porous Materials, edited
by J.
Weitkamp, H.G. Karge, H. Pfeifer, and W. Holderich, Vol. 84, Elsevier Science
B.V.,
1994, with pp. 1375-1394 being incorporated herein by reference, which
discusses the
relevance of Lewis acid sites. As used herein, metal ration refers to either a
metal ion
or the metal ion plus oxide ion species.
One embodiment of the present invention is a process for making an activated
catalytic component. Other embodiments are the activated catalytic component
produced by the process and a final catalyst product that includes a matrix
material.
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One embodiment of the processes of the present invention comprises
contacting, by mixing or by other suitable methods, a crystalline microporous
oxide
and a promoter precursor capable of forming a promoter metal compound. As used
herein, mixing means combining components and does not necessarily require any
mechanical agitation. Contacting the promoter precursor with the crystalline
microporous oxide causes the promoter precursor to disperse within the non-
framework portion of the crystalline microporous oxide. The promoter metal
compound is then activated, preferably by decomposing the promoter precursor,
resulting in a residual organic portion and a promoter metal compound sorbed
or
dispersed into the non-framework portion of the crystalline microporous oxide.
To
increase the effective number of metal cation non-framework acid sites, the
promoter
metal compound sorbs to the crystalline microporous oxide by a liquid or gas
phase
reaction, such as vapor phase transfer.
The promoter precursor and crystalline microporous oxide are contacted for an
amount of time sufficient for the crystalline microporous oxide to retain
between 40
and 60 wt%, preferably about 50 wt%, of the promoter metal oxide resulting
from
decomposition of the promoter precursor' The degree of retention can be
measured by
measuring the weight of the crystalline microporous oxidelpromoter precursor
mixture
during the activation/heating step. The crystalline microporous oxide and
promoter
precursor are mixed in a weight ratio of crystalline microporous
oxide:promoter precursor
is between 100:15 to 100:200, preferably 100:15 to 100:100. For example, in an
embodiment
contacting a zeolite and aluminum acetylacetonate, the aluminum
acetylacetonate will yield
about 15.7% A1203 upon decomposition/reaction. Assuming that about 55 wt% of
the A1a03
from the aluminum acetylacetonate disperses into the non-framework portion of
the zeolite
upon decomposition/reaction and is retained by the zeolite, to get 15 grams of
A1203 onto 100
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grams of zeolite (15% A1203 added), 100 grams of zeolite are mixed with about
175 grams of
aluminum acetylacetonate:
(15 g. A1203 / (0.157 A1203/ aluminum acetylacetonate x 0.55 (percent
decomposition))) =173.4 grams aluminum acetylacetonate.
The residual organic portion may be removed by contacting it with a suitable
oxygen containing gas to combust the organic portion. Other suitable methods
known
in the art are also acceptable.
The promoter metal compound is preferably multivalent metal compound.
Preferably, the multivalent metal compound is a compound containing a di-
valent or
tri-valent metal, preferably selected from the group consisting of magnesium,
chromium, iron, lanthanum, gallium, manganese and aluminum.
Preferably, the promoter precursor is stable in the gas phase and preferably
has
a boiling point less than about 550°C, more preferably less than about
500°C.
Examples of preferz-ed promoter precursors include, but are not limited to,
aluminum
acetylacetonate, aluminum isopropyloxide, aluminum hexafluoroacetylacetonate,
aluminum dichlorohydrol, aluminum ethoxides, tris[2,2,6,6-tetramethyl-3-5,
heptanedianoto]aluminum-III[Al(TMHD)3], aluminum alkyls such as trimethyl
aluminum, triethyl aluminum, and triisobutyl aluminum, aluminum acetate,
aluminum
nitrate, aluminum propoxide, gallium acetylacetonate, manganese
acetylacetonate,
magnesium acetylacetonate, chromium acetylacetonate, iron acetylacetonate, and
lanthanide acetylacetonate.
In one specific embodiment, the crystalline microporous oxide is preferably
calcined by methods laiown in the art before contacting it with a promoter
precursor
that may include, but is not limited to aluminum acetylacetonate, aluminum
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isopropyloxide, aluminum hexafluoroacetylacetonate, aluminum dichlorohydrol,
aluminum ethoxides, tris[2,2,6,6-tetramethyl-3-S, heptanedianoto]aluminum-
III[Al(TMHD)3], aluminum acetate, aluminum nitrate, aluminum propoxide,
magnesium acetylacetonate, chromium acetylacetonate, iron acetylacetonate,
manganese acetylacetonate, gallium acetylacetonate, and lanthanide
acetylacetonate,
which upon activation, form the promoter metal compounds.
The promoter metal compound is activated by heating the crystalline
microporous oxide/promoter precursor mixture to between about 150°C and
about
550°C. The heating step decomposes the promoter precursor into a
residual organic
portion and a promoter metal compound that is dispersed in the non-framework
portion of the crystalline microporous oxide. The resulting activated
crystalline
microporous oxide catalyst component can then be combined with a suitable
matrix
material and used as a catalytst. In this embodiment the preferred promoter
precursors
include In one embodiment, the crystalline microporous oxide is a zeolite,
preferably
Y zeolite, and the promoter precursor is aluminum acetylacetonate, resulting
in an
aluminum oxide promoter metal compound of aluminum oxide.
In another specific embodiment, the crystalline microporous oxide is
preferably
calcined by methods known in the art before contacting it with the promoter
precursor
comprising an aluminum alkyl. Suitable aluminum alkyls include, but are not
limited
to trimethylaluminum, triethylaluminum, tri(t-butyl)aluminum, tri(i-
butyl)aluminum.
In this embodiment, the promoter metal compound is activated by contacting the
crystalline microporous oxide/promoter precursor mixture with an oxygen
containing
material. Suitable oxygen containing materials include, but are not limited to
air,
oxygen gas, water, and aicohols such as methyl alcohol, ethyl alcohol,
isopropyl
alcohol, and butyl alcohol. The oxygen-containing material reacts with the
aluminum
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alkyl, thereby activating the promoter metal compound by forming aluminum
oxide
and a residual organic portion. The reaction step decomposes the promoter
precursor
into a promoter metal compound that is dispersed in the non-framework portion
of the
crystalline microporous oxide and into a residual organic portion that can be
removed
if necessary as described above. The resulting activated crystalline
microporous oxide
catalyst component can then be combined with a suitable matrix material and
used as a
catalytst. Preferably, the promoter metal comprises aluminum and the
crystalline
microporous oxide comprises a zeolite.
The product of the process of the preceeding paragraph comprising crystalline
microporous oxide material and promoter metal compound incorporated into the
non-
framework portion of the crystalline microporous oxide material can be added
to an
inorganic oxide matrix material as described above to form a catalyst,
preferably to
form a fresh non-contaminated catalyst. The catalyst is then passed to a
process unit
for suitable use as described below.
The matrix material may constitute the balance of the final catalyst
composition, although other catalyst components and materials can be
incorporated
into the catalyst. Preferably, the matrix material comprises about 40 to about
99 wt%,
more preferably from about 50 to about 80 wt% of the catalyst based on the
total
catalyst weight. It is also within the scope of the invention to incorporate
into the
catalyst other types of microporous oxides, clays, and carbon monoxide
oxidation
promoters. The catalyst of the present invention is preferably fresh when
passed into
the cracking process, that is, it is substantially free from the metals that
may
contaminate the catalyst during a catalytic cracking process. Such metals
include but
are not limited to, nickel, vanadium, sodium and iron.
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The catalysts of the present invention can be used is various petroleum and
chemical processes, particularly those in which dehydrogenation of paraffins
is
desired. For example, they can be used to catalyze reactions in fluid
catalytic
cracking, hydrocracking, and isomerization. The promoter metal compound sorbs
to
the crystalline microporous oxide portion of the catalyst in such a manner as
to
promote the dehydrogenation of paraffins and naphthenes. Preferably, large
paraff ns
are converted to olefins as a result of the paraffins having contacted the
crystalline
microporous oxide. The olefins are then preferably converted into smaller
paraffin
molecules, olefinic molecules, and aromatic molecules in ratios desired for
fuels
products.
Fluid catalytic cracking is used to convert high boiling petroleum oils to
more
valuable lower boiling products, including gasoline and middle distillates,
such as
kerosene, jet fuel and heating oil. Typical feeds to a catalytic cracker have
a high
boiling point an include residuum, either on its own, or mixed with other high
boiling
fractions. The most common feeds are gas oils with an initial boiling point
usually
above about 230°C, more commonly above about 350°C, with end
points of up to about
620°C. Typical gas oils include straight run (atmospheric) gas oil,
vacuum gas oil, and
coker gas oils. As appreciated by those of ordinary skill in the art, such
hydrocarbon
fractions are difficult to precisely define by initial boiling point since
there axe so
many different types of compounds present in a petroleum hydrocarbon fraction.
Hydrocarbon fractions in this range include gas oils, thermal oils, residual
oils, cycle
stocks, topped and whole crudes, tar sand oils, shale oils, synthetic fuels,
heavy
hydrocarbon fractions derived from coking processes, tar, pitches, asphalts,
and
hydxotreated feed stocks derived from any of the foregoing.
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Fluid catalytic cracking units will typically contain a reactor where the
feedstock
contacts a hot powdered catalyst heated in a regenerator. Transfer lines
connect the two
vessels for moving catalyst particles back and forth. The cracking reaction
will
preferably be carried out at a temperature from about 450° to about
680°C, more
preferably from about 480° to about 560°C; pressures from about
5 to 60 psig, more
preferably from about 5 to 40 psig; contact times (catalyst in contact with
feed) of about
0.5 to 15 seconds, more preferably about 1 to 6 seconds; and a catalyst to oil
ratio of
about 0.5 to 10, more preferably from about 2 to 8.
During the cracking reactions, lower boiling products are formed and some
hydrocarbonaceous material and non-volatile coke are deposited on the catalyst
particles.
The hydrocarbonaceous material is removed by stripping the catalyst,
preferably with
steam. The non-volatile coke is typically comprised of highly condensed
aromatic
hydrocarbons. As hydrocarbonaceous material and coke build up on the catalyst,
the
activity of the catalyst for cracking and the selectivity of the catalyst for
producing
gasoline blending stock are diminished. The catalyst particles can recover a
major
proportion of their original activity by removing most of the
hydrocarbonaceous material
by stripping and removing the coke by a suitable oxidative regeneration.
Consequently,
the catalyst particles are sent to a stripper and then to a regenerator.
Catalyst regeneration is accomplished by burning the coke deposits from the
catalyst surface with an oxygen-containing gas such as air. Catalyst
temperatures during
regeneration may range from about 560°C to about 760°C. The
regenerated catalyst
particles are then transferred back to the reactor via a transfer line and,
because of their
heat, are able to maintain the reactor at the temperature necessary for the
cracking
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reactions. Coke burn-off is an exothermic xeaction; therefore, in a
conventional fluid
catalytic cracking unit with conventional feeds, no additional fuel needs to
be added.
The feedstocks used in the practice of the present invention, primarily
because of their
low levels of aromatics, and also due to the relatively short contact times in
the reactor
or transfer line, may not deposit enough coke on the catalyst particles to
achieve the
necessary temperatures in the regenerator. Therefore, it may be necessary to
use an
additional fuel to provide increased temperatures in the regenerator so the
catalyst
particles returning to the reactor are hot enough to maintain the cracking
reactions, iVon-
limiting examples of suitable additional fuel include Ca- gases from the
catalytic
cracking process itself, natural gas, and torch oil. The C2- gases are
preferred.
Isomerization is another process in which the catalysts of the present
invention
can be used. Hydrocarbons which may be isomerized by the process of the
present
invention include paraffinic and olefinic hydrocarbons typically having 4-20,
preferably
4-12, more preferably about 4-6 carbon atoms; and aromatics such as xylene.
The
preferred chargestock is comprised of paraffinic hydrocarbons typified by
butanes,
pentanes, hexanes, heptanes, etc. Isomerization conditions include
temperatures from
about 80°C to about 350°C, preferably from about 100°C to
260°C; a pressure from
about 0 to 1,000 psig, peferably from about 0 to 300 psig; a liquid hourly
space velocity
of about 0.1 to 20, preferably about 0.1 to 2; and a hydrogen rate, in
standard cubic feet
per barrel of about 1,000 to 5,000, preferably from about 1,500 to 2,500.
Operating
temperatures and catalyst activity are correlated with space velocity to give
reasonably
rapid processing of the feedstock at catalyst deactivation rates which insure
maximum
on-stream time of the catalyst between periods of regeneration.
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The catalysts of the present invention may also be used in hydrocracking
processing. Hydrocracking increases the overall refinery yield of quality
gasoline-
blending components. Hydrocracking can take a relatively low-quality gas oiI
feed that
otherwise would be blended into distillate fuel and converts it, in the
presence of
hydrogena and an appropriate catalyst in fixed-bed reactors. Typically, the
feedstock is
mixed with hydrogen vapor, heated to.about 140°C to 400°C,
pressurized to about 1,200
to 3,500 psi, and charged to a first-stage reactor where about 40 to 50% of
the feedstock
reacts to remove nitrogen and sulfur compounds that inhibit the cracking
reactions and
I O make lower quality products. The stream from the first stage is cooled,
liquefied, and
run through a separator where butanes and lighter gases are taken off. The
bottoms
fraction is passed to a second-stage reactor a cracked at higher temperatures
and
pressures wherein additional gasoline-blending components and a hydrocrackate
are
produced.
The invention will be further understood by reference to the following
Examples that illustrate embodiments of the invention.
EXAMPLE 1
Standard MAT tests (e.g., microactivity test, ASTM # D3907-8) were run on
three separate commercially available crystalline microporous oxides: USY
(obtained
from W.R. Grace, Davison Division, as Z14USY or UOP as LZY 82 or LZY 84); LZ-
210 (available from Katalystiks, Inc.); and calcined rare earth exchanged Y
(CREY,
available from W.R. Grace, Davison Division). Prior to running the MAT test,
the
crystalline microporous oxides were combined with matrix material (Ludox,
available
from DuPont) and steamed at 1400°F for 16 hours to produce a cracking
catalyst.
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Each catalyst tested comprised 20 wt% zeolite and 80 wt% matrix material. The
results are indicated in Table 1 below.
Table 1
MAT Results USY LZ-210 CREY
conversion(wt%, 400F minus) 42.5 47.7 64.1
H2 (wt%) 0.0113 0.0186 0.0064
C (wt%) 1.480 I.891 1.760
Surface Area (m2/g) 200 189 130
Pore Volume (cm3/g) 0.439 0.023 0.254
Unit Cell (A) 24.21 24.24 24.51
EXAMPLE 2
The crystalline microporous oxides of EXAMPLE 1 were metal ion exchanged
according to the method of cation exchange in zeolites as described in A.
Dyer, An
Introduction to Zeolite Molecular Sieyes, Chapter 6, "Zeolites as Ion
Exchangers",
John ~iley & Sons, 1988, which chapter is incorporated herein by reference.
After
the crystalline microporous oxides were ion exchanged, they were combined with
matrix material and steamed as in EXAMPLE 1, and run according to a standard
MAT
test. The results are shown in Table 2.
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Table 2
MAT Results USY LZ-210 GREY
+ AI203 + AI203 + AI203
conversion (wt%, 400F minus)29.8 38.5 51.1
H2 (wt%) 0.0047 O.OOSS O.OOS6
C (wt%) 1.119 1.737 1.516
Surface Area (m2/g) 194 172 161
Pore Volume (cm3/g) 0.346 0.314 0.318
Unit Cell (A) 24.25 24.22 24.36
The results indicate that the metal ion exchanged crystalline microporous
oxides have a significant reduction in conversion to product compared to the
non-
exchanged crystalline microporous oxides of EXAMPLE 1. This indicates that the
metal ion exchange procedure results in the loss of effective metal cation
sites of the
non-framework portion of the crystalline microporous oxides in that the
balance
between Brccnsted sites and Lewis sites is not favorable for the desired
activity.
EXAMPLE 3
Standard MAT tests were run on three separate commercially available
crystalline microporous oxides: rare earth exchanged CREY (RECREY) made by
' exchanging a portion of the GREY of Example 1 with a rare earth ion solution
by the
method of Dyer; hydrogen calcined rare earth exchanged Y (HCREY) made by
exchanging the approximately 4 wt% Na+ of the CREY with NH4+ according to the
method of Dyer; and ultrastabilized calcined exchanged rare earth Y (LTSCREY)
made
by calcining NH4CREY according to the method described in references 6-13 of
R.
Szostak, "Modified Zeolites" (Chapter 5), Introduction to Zeolite Science and
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Practice, Vol. 58, Ed. by H. Van Bekkum, E.M.Flanigan, and J.C. Jansen,
Elsevier,
1991. Prior to running the MAT test, the zeolites were combined with matrix
material
(10 wt% zeolite; 30 wt% Si02 as IMSIL-A-8, available from Unimin Specialty
Minerals, Inc.; 60 wt% Si02-A1203 made from a gel obtained from W.R. Grace,
Davison Division, which gives a 25 wt% A1203, Si02-A1203 when dried and
washed) to produce a cracking catalyst. The results are indicated in Table 3.
Table 3
MAT Results RECREY HCREY USCREY
conversion (wt%, 430°F minus) 45.3 50.1 44.0
C (wt%) 1.34 1.39 1.33
650°F+ prod. (wt%) 32.4 27.4 32.7
Surface Area (m2/g) 101 129 113
Unit Cell (A) 24.49 24.45 -
EXAMPLE 4
Each of the crystalline microporous oxides of EXAMPLE 3 was blended in a
separate container with aluminum acetylacetonate (ratio of zeolite to aluminum
acetylacetonate approximately 1:1.4; decomposition temperature of aluminum
acetylacetonate slightly greater than 320°C). Each container was placed
in an oven
and heated to 150°C, held for one hour, and the oven was purged with an
amount of
nitrogen sufficient to flush out the potentially flammable decomposition
products of
the acetylacetone decomposition. After purging, the oven was heated to
500°C, held
for one hour, and allowed to cool. The oven was then heated in air for 2 hours
at
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500°C. Based on the weight of the product, it was calculated that about
45 wt% of the
alumina expected from the amount of aluminum acetylacetonate remained with the
zeolite as a result of the addition process. The zeolite containing the added
alumina
was then made into catalyst as in Example 3 and then run under standard MAT
conditions. The results are shown in Table 4.
Table 4
MAT Results RECREY HCREY USCREY
+ A1203 + A1203 + A1203
conversion (wt%, 430°F minus) 55.2 58.2 60.8
C (wt%) 1.63 1.57 1.65
650°F+ prod. (wt%) 22.6 19.3 17.4
Surface Area (m2/g) 118 81 143
Unit Cell (A) - 24.43 24.46
The results indicate that the crystalline microporous oxides which contain the
added metal compound for promoting dehydrogenation and Lewis acidity show a
significant increase in conversion to gasoline product compared to the non-
metal
added crystalline microporous oxides of EXAMPLE 3. This indicates that the
addition
of the metal compound increased the number of effective metal cation sites of
the non-
framework portion of the crystalline microporous oxide. In other words,
addition of
the metal compound resulted in a significant increase in Lewis acid sites.
This is also
shown in Table 5 below by direct determination of the number of acidic sites
per gram
of catalyst.
If after steaming as in Example 3 hereof, pyridine is adsorbed onto the
catalysts, then heated to 250°C under vacuum to desorb any pyridine
from the more
weakly acidic at non-acidic sites, infrared spectroscopy can be used to
measure the
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relative amounts of pyridine adsorbed as the pyrindinium ion onto Bronsted
acidic
sites, and the amount sorbed as coordinated pyridine on the strong Lewis
sites. When
this is done on the catalysts as desorbed, the following band intensities of
the adsorbed
pyridine on the three catalysts is observed.
In Table 5 there are three different materials: 1) RECREY, a rare-earth
exchanged zeolite of the FAU structure type. This is the starting material for
the next
two samples of this table. 2) RECREY + added alumina -I, is a sample of the
RECREY to which alumina has been added by the methods taught herein, as
effective
added alumina. 3) RECREY + added alumina -II, is a sample of the RECREY to
which alumina has been added in a way that is not effective as additional
Lewis acid.
The methods taught by R.J. Gone, et al, [Journal of Catalysis 148, 213-223
(1994), and referenced therein] and G.L. Price, et al. [Journal of Catalysis
148, 228-
236, (1994)] are used to quantitatively determine the total acidity,
characterized as
both the amount of strongly acid sites (strong enought to effect n-propylamine
to
decompose to propylene and ammonia upon thermal desorption) and weakly acid
sites
(acidic because it will interact with n-propylamine at 50°C to retain
the amine, but will
desorb the n-propylamine as the temperature is raised). This determination
measures
both the Bronstad and Lewis acid sites. The measure of acidity is expressed as
milliequivalents of acid per gram of material (each millimole of amine is
counted as
reacting with one millimole of acid sites).
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Table 5
RECREY RECREY + RECREY +
Added A1203 Added A1z03
Total A1203 (wt.%) 19.7 30.5 27.0
Strong Acidity, MEQV/G 0.46 0.38 0.40
Weak Acidity, MEQV/G 2.64 2.99 2.59
Total Acidity, MEQV/G 3.10 3.37 2.99
Table 5 shows that only in the case of the effectively added alumina (I) is
the
weak acidity increased, along with the total acidity. The other example (II)
shows that
simply increasing the amount of alumina does not necessarily increase the
acidity.
Each of the zeolite samples described above are used to prepare catalysts as
described in Example 3, and then these composite catalysts are steamed to
deactivate
them at the same conditions described in Example 3.
A portion of each catalyst sample was then pressed into a thin disk. Each disk
was weighed and its' diameter and thickness measured. Each disk was then
placed in
a vacuum chamber and heated to remove any water or other sorbed gases. It was
then
cooled to 50°C and exposed to pyridine vapor for a short period. The
sample was then
held in vacuum for several hours and its infrared spectrum obtained,
particularly
between 1400crri' and 1600crri'. The sample was then heated to 250°C
and held for
several hours, and the spectrum was again obtained. This increased temperature
and
high vacuum removed any pyridine that was physically sorbed.
The infrared spectrum between 1400crri' and 1600crri' was measured on the
material before the pyridine sorption and the spectrum was subtracted from the
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spectrum of the sample containing the pyridine. The resulting spectrum was
that due
to the pyridine interacting with the acidic sites of the catalyst.
In this spectral region, peaks at 1540crri' to 1550crri' were assigned to the
pyridine that is coordinated to the protons from Bronsted acid sites. Peaks
between
1440crri' to 1460crri' were assigned to pyridine with which the pair of
electrons on
the nitrogen were interacting with the electron accepting sites (Lewis Acids)
of the
solid. In this spectral region 1440crri' to 1660cni' other bands between
1480crri'
and 1500crri' are due to combinations of bands of pyridine sorbed on both
Brr~nsted
and Lewis sites.
For the steamed, composite catalysts made with the zeolites shown in Table 5,
Table 6 lists the intensities observed for the bands due to the presence of
Bronsted and
Lewis sites on the catalysts.
Table 6
RECREY RECREY + ADA RECREY + ADA
I II
Band intensities due to:
(abs. units/gram)
Bronsted sites 22 33 33
Lewis Acid sites 55 104 60
These results show the effective addition of this metal compound does increase
the Lewis acidity of the active catalyst.
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Having now fully described this invention, it will be appreciated by those
skilled in the art that the invention can be performed within a wide range of
parameters within what is claimed.
