Note: Descriptions are shown in the official language in which they were submitted.
i ~f~3,~'~
BACKGROl.lND OF THE INV~NTION
., . _
The invention is concerned with the combusting
of solid, sulfur-containing material in a manner to
effect ~ reduction in the emission of fiulfur oxides
to the atmosphere. ~n one specific embodiment, the
invention involves the catalytic cracking of ~ulfur-
containing hydrocarbon feedstocks in a manner to effect
a reduction in the amount of ~ulfur oxides emitted
from the regeneration zone of a hydrocarbon catalytic
crac~ing unit.
Typically, catalytic cracking of hydrocarbons
takes place in a reaction zone at hydrocarbon cracking
conditions to produce at least one hydrocarbon product
and to cause carbonaceous material Icoke) to be deposited
on the catalyst. Additionally, some sulfur, originally
present in the feed hydrocarbon~ may also be deposited,
e.g., as a component of the coke, on the catalyst.
It has been reported that approximately 504 of the
feed ~ulfur is converted to H2S in the FCC reactor,
40% remains in the liquid products and about 4 to
10% is deposited on the catalyst. Trhese amounts vary
with the type of feed, rate of hydrocarbon recycle, steam
stripping rate, the type of catalyst, reactor temperature,
etc.
Sulfur-containing coke deposits tend to deactivate
cracking catalyst. Cracking catalyst is advantaqeously
continu~usly regenerated, by combustion with oxygen-
containin~ gas in a regeneration zone, to low coke
levels, typically below about 0.4% by weight, to perform
satisfactorily when it is recycled to the reactor.
In the regeneration zone, at least a portion of sulfur,
along with carbon and hydrogen, which is deposited
on the catalyct, i~ oxidized and leaves in the form
--1--
r~)
of ~ulfur oxides (SO2 and SO3, hereinafter referred
to as ~SOxn~ along with substantial amount~ of CO,
C2 and H2O.
Considerable amount of ~tudy and research
effort ~as been directed to reducing oxide of sulfur
emissions from various gaseous streams, including those
from the stacks of the regenerators of FCC units. Rowever,
the results leave much to be desired. Many metallic com-
pounds have been proposed as materials to Pick uP oxides
10 of ~ulfur in FCC units (and other desulfurization appli-
cations) and a variety of supports, including particles
of cracking catalysts and ~inerts~, have been suggested
as carriers for active metallic reactants. Many of
the proposed metallic reactants lose effectiveness
when subjected to repeated cycling. Thus when Group
II metal oxides are impregnated on FCC catalysts or various
supports, the activity of the Group II metals is rapidly
reduced under the influence of the cyclic conditions.
Discrete alumina particles, when combined with silica-
containing catalyst particles and subjected to steam `at elevated temperatures, e.~., those present in FCC
unit regenerators, are of limited effectiveness in
reducing SOx emissions. Incorporation of sufficient
chromium on an alumina support to improv2 SOx sorption
results in undersirably increased coke and gas productionO
Accordingly, an object of the present inven$ion
is the provision of an improved composition and process
for reducing emissions o sulfur oxides.
An additional object of the present invention
is to provide an improved composiotn and process for
reducing the emissions of sulfur oxides from the regeneration
zones of hydrocar~on catalytic crackinq units.
--2--
Another object of the invention i6 to provide
an improved hydrocarbon conversion cataly~t. ~hese
and other objects of the invention will become apparent
from the followinq description and examples.
In one yeneral aspect, the present invention
involves a process for combusting ~olid, sulfur-containing
material by contacting the material with gaseous oxygen
in a combustion zone at combustion conditions to produce
c~mbustion products including sulfur oxide at least a portion
of which is sulfur trioxide. The present improvement com-
prises carrying out this contacting in the presence of dis-
crete entities containing an effective amount, preferably a
major amount by weight, of at least one metal-containing
spinel, preferably alkaline earth metal-containing spinel,
to thereby reduce the amount of sulfur oxide (relative to
combustion in the essential absence of the discrete entities)
emitted from the combustion zone. In another embodiment, the
present inprovement comprises carrying out this contacting
in the presence of discrete entities containing an effective
amount, preferably a major amount by weight, of at least one
alkaline earth metal-containing spinel and a minor amount of
at least one rare earth metal component associated with the
spinel to thereby reduce the amount of sulfur oxide ~relative
to combustion in the essential absence of the discrete
entities) emitted from the combustion zore.
In accordance with another aspect, the present
invention involves a converstion process which i5 carried
out, preferably in the substantial absence of added free
hydrogen, in at least one chemical reaction zone in which
sulfur-containing hydrocarbon feedstock is contacted
with particulate material to form at least one hydro-
carbon product and sulfur-containing carbonaceous material
deposi~ed on the particulate material and at least
~ ~2i,~.~
one regeneration zone in which at least a portion of
the 6ulfur-containing carbonaceous material deposited
on the ~olid particles is contacted with gaseous oxygen
to combust the sulfur-containing carbonaceous material and
to produce combustion products including sulfur oxid~ at
least a portion of which is sulfur trioxide.
The pres~nt improvement comprises u6ing a
particulate material comprising (A) a major amount
of solid particles capable of promoting the desired
hydrocarbon chemical conversion at hydrocarbon conver~ion
conditions and ~B) a minor amount of discrete entities
comprising an effective amount, preferably a major
amount of weight, i.e., at least about 50% by weight, of at
least one metal-containing spinel, preferably alkaline earth
metal containing spinel. In the event such discrete entities
comprise alkaline earth metal containing spinel, it is more
preferred that such discrete entities further comprise
a minor amount of at least one rate earth metal, preferably,
ceruim, component associated with the ~pinel. In one pre-
ferred e~mbodiment, the discrete entities also include a minor,
catalytically effective amount of at least one crystalline
aluminosilicate effective to promote hydrocarbon conversion,
e.g., cracking at hydrocarbon conversion conditions. The
discrete entities are present in an amount sufficient
to reduce the amount of sulfur oxides in the regeneration
zo~e effluen~ when used in a reaction zone-regeneration
zone system as described herein.
In one preferred embodiment, the particulate
material, more preferably the discrete entities, further
comprise a minor amount of at least one additional metal,
e.g., a Group VIII platinum group metal, component capable
of promoting the oxidation of sulfur dioxide to sulfur
trioxideatthe condition~ in the regeneration zone.
The preferred platinum group ~etals are palladium
and platinum, most prèferably platinum.
The prefelred relative amounts of the s~lid
particles and discrete entities are a~out 80 to about
99 parts and 1 to about 20 parts by weight, respectively~
This catalyst system is especially effective for the
catalytic cracking of a hydrocarbon feedstock to lighter,
lower boiling products. The present catalyst system prefer-
ably also has improved carbon monoxide oxidation catalytic
activity stabilitY-
The improvement of this invention can be used to
advanta~e with the cat~lyst being disposed in any conven-
tional reactor-regenerator system, in ebullating catalyst
bed systems, in systems which involve continuously convey-
ing or circulating catalyst between reaction zone and re-
generation zone and the like. Circulating cataylst systems
are preferred. Typical of the circulating catalyst bed
systems are the conventional moving bed and fluidized bed
reactor-regenerator systems. Both of these circulating
bed systems are conventionally used in hydrocarbon conver-
sion, e.g., hydrocarbon cracking, operations with the
fluidized catalyst bed reactor-regenerator systems being
preferred.
The catalyst ~ystem used in accordance with
certain embodLments of the invention is comprised of
a mixture of two types of solid particles.
Although the presently useful ~olid particles
and discrete entities may ~e used as a physical admixture
of separate particles, in one embodiment, the discrete
entities are combined as part of the solid particles.
That is, the discrete entities, e.g., comprising calcined
microspheres containing metal-containing spinel, and prefer-
ably, at least one additional metal component, are combined
2 ~
with the solid particles, e.g., during the manufacture of
the solid particles, to form combined particles which
function as both the presently useful solid particle~
and discrete entities i8 pre~erably a separate and
distinct phase. One preferred method for providing
the combined particles is to calcine the discrete
entities prior to incorporating the di~crete entitieæ
into the co~bined particles.
The form, i.e., particle size, of the present
catalyst particles, e.g., both fiolia particles and
discrete entities as well as the combined particles,
is not critical to the present invention and may vary
depending, for example, on the type of reaction-regeneration
~ystem employed. Such catalyst particles may be formed
into any desired shape such a pills, cakes, extrudates,
powders, granules, 6pheres and the like, using conventional
methods. With regard to fluidized catalyct bed systems, it
is preferred that the major amount by weight of the present
catalyst particles have a diameter in the range of about
10 microns to about 250 microns, more preferably about
20 microns to about 150 microns.
The solid particles are capable of promoting
the desired hydrocarbon conversion. The solid particles
are further characterized as having a composition (i.e.,
chemical ma~e-up) wh~ch is different from the discrete
entities. In one preferred embodiment, the ~olid
particles ~or the ~olid particles portion of the combined
particles described above) are substantially free of
metal~containing spinel, e.g.; alkaline earth metal-
containing spinel.
In one aspect of the present invention, the
discrete entitie~ comprise an effect;ve amount of at least
one metal-containing spinel, preferably alkaline earth
--6--
t 1~25~2
metal-containing spinel, and preferably, a minor,
catalytically effective amount of at least one crystalline
~luminosilica~e capable of promoting hydrocarbon conver-
sion at hydrocarbon conversion conditions. In the event
~uch discrete entities comprise alkaline earth metal-contain-
ing spinel, it is more preferred that such discrete entities
include a minor amount of at least one rare earth metal com-
ponent, preferably a cerium component, associated with the
spinel. In another aspect of the present invention, the
discrete entities, whether present as a separate and distinct
particle and/or combined with the solid particles in a single,
preferably substantially uniform, mass of combined particles,
and/or the solid particles and/or one or more other type of
particles (i.e., having compositions different from the
present solid particles and discrete entities) further com-
prise a minor amount of at least one additional metal, e.g.,
platinum group metal, component capable of promoting
the oxidation of sulfur dioxide to the sulfur trioxide
at the conditions in the combustion, e.g., catalyst regen-
eration, zone For example, an effective amount of at
least one sulfur oxide oxidation catalytic component, e.g.,
metal or compounds of metals selected from Group VI, IIB,
IVB, VIA, ~IB, VIIA and VIII and mixtures thereof, disposed
on a support, e.g., one or more inorganic oxides, may be in-
cluded with the present solid particles and discrete entities
and/or may be included on the solid particles and/or discrete
entities. As noted previously, the sulfur oxide oxidation
component may be associated with, e.g., deposited on, the
spinel com~onent ~f the present discrete entities.
The composition of the solid particles useful
in the present invention is not critical, provided
that such particles are capable of promoting the desired
hydrocarbon conversion. Particles having widely varying
l 16~522
compositions ~re conventionally used as catalyst in such
hydrocarbon conversion processes, the particular composition
chosen being dependent, for example, on the type of hydrocarbon
chemical conversion desired. Thus, the solid particles
suitable for use in the present invention include at least one
of the natural or synthetic materials which are capable of
promoting the desired hydrocarbon chemical conversion. For
example, when the desired hydrocarbon conversion involves one
or more of hydrocarbon cracking, disproportionation,
isomerization, polymerization, alkylation and dealkylation,
such suitabie materials include acid-treated natural clays
such as montmorillonite, kaolin and bentonite clays; natural
or synthetic amorphous materials, such as amorphous
silica-alumina, silica-magnesia and silica-zirconia
composites; crystalline aluminosilicate often referred to as
zeolites or molecular sieves and the like. In certain
instances, e.g., hydrocarbon cracking and disproportionation,
the solid particles preferably include such crystalline
aluminosilicate to increase catalytic activity. Methods for
preparing such solid particles and the combined solid
particles-discrete entities particles are conventional and
well known in the art. Certain of these procedures are
thoroughly described in U.S. Patents 3,140,253 and RE. 27,639.
Compositions of the solid particles which are
partisularly useful in the present invention are those in which
the crystalline aluminosilicate is incorporated in an amount
effective to promote the desired hydrocarbon conversion, e.g.,
a catalytically effective amount, into a porour matrix which
comprises, for example, amorphous material which may or may not
be itself capable of promoting such hydrocarbon conversion.
Included among such matrix materials are clays and amorphous
compositions of silica-alumina, magnesia, zirconia, mixtures
of these and the like. The crystalline aluminosilicate is
l 162~2
preferably incorporated into the matrix material in amounts
within the range of about 1% to about 75%, more preferably
about 2% to about 50%, by weight of the total solid particles.
The preparation of crystalline aluminosilicate-amorphous
matrix catalytic materials is described in the above-mentioned
patents. Catalytically active crystalline aluminosilicates
which are formed during and/or as part of the methods of
manufacturing the solid particles, discrete entities and/or
combined particles are within the scope of the present
invention. The solid particles are preferably substantially
free of added rare earth metal, e.g., cerium, component
disposed on the amorphous matrix material of the catalyst,
although such rare earth metal components may be associated
with the crystalline aluminosilicate components of the solid
particles.
As indicated above, the discrete entities utilized in
the present invention comprise an effective amount, preferably
a major amount, of at least one metal-containing spinel,
preferably alkaline earth metal-containing spinel. In another
aspect, the present discrete entities further comprise a minor
amount of at least one additional metal, e.g., platinum group
metal, component capable of promoting sulfur dioxide
oxidation.
The spinel structure is based on a cubic close-packed
array of oxide ions. Typically, the crystallographic unit cell
of the spinel structure contains 32 oxygen atoms; one-eighth of
the tetrahedral holes (of which there are two per anion) are
occupied by
~ 1~2522
divalent metal ion, and one-half of the octahedral holes
for which there are two per anion) are occupied by trivalent
metal ion 5 .
This typical spinel structure or a modification
thereof is adaptable to many other mixed metal oxides of
the type M M2 4 (e-g-, FeCr204,~nA1204 and Co Co2 04),
by some of the type MIVMII204 (e.g., Ti~n204, and SnCo204),
and by some of the type M2MVIO4 (e.g., Na2MoO4 and Ag2MoO4).
This structure is often symbolized as X[Y2]04, where square
brackets enclose the ions in the octahedral interstices.
An important variant is the inverse spinel structure,
Y[XY]04, in which half of the Y ions are in tetrahedral
interstices and the X ions are in octahedral ones along
with the other half of the Y ions. The inverse spinel
structure is intended to be included within the scope of
the term "metal-containing spinel" as used herein. The
inverse spinel structure occurs often when the X ions have a
stronger preference for octahedral coordination than do the
Y ions. All MIVM2IIO~ are inverse, e.g., ~n(~nTi)04, and
many of the M M2 4 ones are also, e.g., Fe (Co Fe )04,
NiA124'Fe (Fe Fe )04 and Fe(NiFe)04. There are also
many compounds with distorted spinel structures in which
only a fraction of the X ions are in tetrahedral sites. This
occurs when the preference of both X and Y ions for octahedral
and tetrahedral sites do not differ markedly.
Further, details on the spinel structure are described
in the following references: "Modern Aspects of Inorganic
Chemistry" by H. I. Emeleus and A. G. Sharpe (1973), pp. 57-58
and 512-513; "Structural Inorganic Chemistry", 3rd edition, (1962)
by A. F. Wells, pp. 130, 487 490, 503 and 526; and "Advanced
Inorganic Chemistry", 3rd edition, by F. A. Cotton and ~.
--10--
1 ~82~22
Wilkinson 11972), PP. 54~55-
Metal-containing spinels include the following:
Mn~1204, FeA1204, CoA120~, NiA120~, 2 4
FeMgFeO4, FeTiFeO~ ZnSnZnO4, GaMg~aO~, ~nMg~nO4, BeLi2F4,
2 4 24~ SnMg204~ ~gA1204, CUA1204, (LiAl O )
ZnK2tCN)4, CdK2(CN~4~ ~gK2~N)4~ ZnTi2 4' 2 4 2 4
MnCr o , FeCr204, CoCr~04, NiCr204, ZnCr204, 2 4' 2 4
ZnCr2S4, cdCr2S4, TiMn~04 M~Fe24' FeFe24' CoF 24' 2 4
CuFe2~4, 2nFe20~, CdFe204~ ~gC24~ 2 4 2 4
2 4 2S4, CUC254~ Ge~i2o4~ NiNi2S4, ZnGa2o4, WAg o
and ZnSn204.
The preferred metal-containing spinel~ for use
in the present invention are alkaline earth metal spinels,
in particular magnesium aluminate spinel. Lithium containing
spinels,which may be produced using conventional techniques
are also preferred for use. With regard to magnesium alumi-
nate spinel, there often are eight Mg atoms and sixteen Al
atoms to place in a unit cell l8MgA1204). Other alkaline
earth metal ions, such as calcium, stronium, barium and mix-
tures thereof, may replace all or a part of the magnesiumions. Similarly, other trivalent metal ions, such as iron,
chormium, vanadium, manganese, gallium, boron, cobalt and
mixtures thereof, may replace all or a part of the aluminum
ions.
The metal~containing spinels useful in the present
invention may be derived from conventional and well known
sources. For example, these spinels may be naturally
occurring or may be ~ynthesized using techniques well known
in the art. Thus, a detailed description of such techniques
is not included herein. However, a brief description of
the preparation of the most preferred spinel, i.e., magnesium
aluminate spinel,is set forth below. Certain of the tech-
--11--
niques described, e.g., dryirg l~nd calcining, have applica-
bility to other metal-containing ~;pinels.
The magnesi~m aluminate spinel ~uitable for
use in the present invention can be prepared, for example,
according to the method di~closed in ~.S. Patent No.
2,992,191 The spinel can be formed by reacting, in
an aqueous medium, a water-soluble nagnesium inorganic
salt and a water-~oluble aluminum salt ~n which the
aluminum is present in the anion. Suitable salts are
exemplified by the strongly acidic magnesium salts ~uch
as the chloride~ nitrate or ~ulfate and the water soluble
alkali metal aluminates~ ~he magnesium and aluminate
~alts are dissolved in an aqueous medium and a spinel
precursor is precipitated through neutralization of
the aluminate by the acidic magnesium salt. Excesses of
acid salt or aluminate are preferably not employed, thus
avoiding the precipitation of excess magnesia or alumina.
Preferably, the precipi~ate is washed free of extraneous
ions before being further processed.
The precipitate can be dried and calcined to
yield the magnesium aluminate spinel. Dryinq and cal-
cination may take place simultaneously. However, it is
preferred that the drying take place at a temperature
below which water of hydration is removed from the spinel
precursor. Thus, this drying may occur at temperatures
~elow about 500~., preferably from about 220F. to about
450DF. Suitable calcination temperatures are exemplified
by temperatures ranging ~rom about 800F. to about 2000F.
or more. Calcination of the spinel precursor may take
place in a period of time o~ at least about one half hour
and preferably in a period of tLme ranging from about 1
hour to about 10 hours.
Another proceg for ~roducing the presently
~ 162~
Useful magnesium aluminate spinel i5 set forth in U.S.
Patent 3,791,992. This process includes mixing a solution
of a soluble acid salt of divalent magnesium with a
solution of an alkali metal aluminate; separating and
washing the resulting precipitate; exchanging the washed
precipitate with a solution of an ammonium compound to
decrease the alkali metal content; followed by washing,
drying, forming and calcination steps. In general, as
indicated previously, the metal-containing spinels useful
in the present invention may be prepared by methods which
are conventional and well known in the art.
The metal spinel-based composition may be formed
into particles of any desired shape such as pills, cake,
extrudates, powders, granules, spheres, and the like using
conventional methods. ~he size selected for the particles
can be dependent upon the intended environment in which the
final discrete entities are to be used -- as, for example,
whether in a fixed catalyst bed or circulating catalyst bed
reaction system or whether as a separate particle or as part
of a mass of combined particles.
Substantially non-interfering proportions of
other well known refractory material, e.g., inorganic oxides
such as silica, zirconia, thoria and the like may be included
in the present discrete entities. Free magnesia and/or
alumina (i.e., apart from the alkaline earth metal containing
spinel) also may be included in the discrete entities, e.g.,
using conventional techniques. For example, the discrete enti-
ties may include about 0.1% to about 25% by weight of free
magnesia (calculated as MgO). By substantially "non-inter-
ferring" is meant amounts of other material which do not have asubstantial deleterious effect on the present catalyst system
or hydrocarbon conversion proce~s. ~he inclusion of material~
~uch as silica, zirconia, ~horia and the like into ~he
present discrete entities may act ~o improve one or more
of the functions of the discrete entitie~.
The presently useful lithi~n containing spinels,
e.g., lithium aluminate spinel, preferably are associated
with a minor amount of at least one rare earth metal component.
Cerium or other suitable rare earth or rare earth
mixture may be associated with the spinel usin~ any suitable
technique or combination of techniques; for example, impregnation,
coprecipitation, ion-exchange and the like, well known in
the art, with impregnation beinq preferred. Impregnation
may be carried out by contacting the spinel with a solution,
preferably aqueous, of rare earth; for example, a solution
containing cerium ions lpreferably Ce~3, Ce+4 or mixtures
thereof~ or a mixture of rare earth cations containing a
substantial amount ~for example, at least 404) of cerium
ions. Water-soluble sources of rare earth include the nitrate
and chloride. Solutions having a concentration of rare earth
in the range of 3 to 30~ by weight are preferred. Preferably,
sufficient rare earth salt is added to incorporate about
0.05 to 254 (weiqht), more preferably about 0.1 to 15% rare
earth, and still more preferably about 1.0 to 15% rare earth,
by weight, calcula~ed as elemental metal, on the particles.
It may not be necessary to wash the spinel after
certain soluble rare earth salts (such as nitrate or acetate)
are added. After impxegnation with rare earth salt, ~he
spinel can be dried and calcined to decompose the salt,fonn-
ing an oxide in the case of nitrate or acetate. Alternatively,
the spinel, e.g., in the form of discrete particles, can
be charged to a hydrocarbon conversion, e.g., cracking unit,
with the rare earth in ~alt form. In this case a rare earth
~alt with a thermally decomposable anion can decompose to
-14-
1 ~ 6~1~ $~2
the oxide in the reactor and be available $o associate with
S~x in the regenerator.
Especially good results were achieved using ~pinel
containing discrete entities 3uch that the concentration
of rare earth metal, e.g., cPrium, calculated as the metal,
is in the range of about 1 t~-25~, more preferably about
2% to about 15%, by weight of the total di~crete entities.
The present discrete entities preferably further
comprise a minor amount ~f at least one crystalline
aluminosilicate capable of promoting the desired hydrocarbon
conversion. Typical aluminosilicates have been described
above. Preferably, such aluminosilicates comprise about
1~ to about 30~, more preferably about 1% to about 10~,
by weight of the discrete er.tities. The presence of
~uch aluminosilicates in the present discrete entities acts
to increase the overall catalytic activity of the ~olid
particles-discrete entities mixture for promoting the
desired hydrocarbon conver~ion.
As indicated above, in one preferred embodiment
the presently useful particulate material, e.g., the
discrete entities utilized in the present invention, also
contain at least one additional metal, e.g., platinum
group metal, component. These additional metal components
are defined as being capable of prom~ting the oxidation of
sulfur dioxide to sulfur trioxide at combustion conditions~ e.g.,
the conditions present in the catalyst regenerator. Increased
carb~n monoxide oxidation may also be obtained by including
at least one of the additisnal metal components. ~uch
metal components are selected from the group consi~ting of
30 Group IB, IIB, IVB, YIA~ VIB, VIIA and VIII of the Periodic
Table, the rare earth metals, vanadium, iron, tin and antimony
and mLxtures thereof and may be incorporated into the presently
~ lS2~2
useful particulate material, e.g., the discrete entities,
in any suitable manner. Many techni~ues for including the
additional metal in ~he parti~ulate ~aterial are conventional
and well known ~n the art. The aaditional metal, e.g.,
platinum group metal, such 2s platinum, may exi~t within
the particula~e material, e.g., discrete entities, at
least in part as a compound ~uch a~ an oxide, ~ulfide,
halide and the li~e, or in the elemental fitate. Generally,
the amount of the platinum group metal component present
in the final discrete entities i5 ~mall compared to the
~uantity of the spinel. The platinum group metal component
preferably comprises fxom about 0,05 parts-per-million (ppm)
to about 1~, more preferably abGut 0.05 ppm. to about 1,000
ppm., and still more preferably about O.S ppm. to about
500 ppm., by weight of the discrete entities, calculated
on an elemental basis. Excellent results are obtained when
the discrete entities contain about 50 ppm. to about 200
ppm., and in particular about 50 ppm. to about gO ppm., by
weight of at least one platinum group metal component. The
other add,tional metals may be included in the particùlate
material in an amount effective to promote the oxidation
of at least a portion, preferably a major portion, of the
~ulfur dioxide present to sulfur trioxide at the conditions
of combustion, e.g., conditions present in the catalyst
regeneration zone of a hydrocarbon catalytic cracking unit.
Prefera~ly, the present di~crete entities comprise a minor
amount by weight of at least one additional ~etal component
~calculated as elemental metal). Of course the amount of
additional metal used will depend, for example, on the
de~ree of sulfur dioxide oxidation desired and the effective-
ness of the additional metal component to promote such
oxidation.
16-
~ ~6~
Alternately to inclu~ion in the discrete entities,
one or more additional metal components may be pre ent in
all or a portion of the above-noted golid particles ~nd/ox
may be included in a type of particle other than either
the present solid particles or discrete entities. For
example, separate particles comprising at least one additional
metal component and porous inorganic oxide support, e.g.,
platinum on alumina, may be included along with the solid
particle an~ discrete entities to prom~te sul~ur dioxide
10 oxidation.
The additional metal, e.g., platinum group metal,
component may be associated with the spinel based composi-
tion in any suitable manner, ~uch as by the impregnation of
the spinel at any stage in its preparation and either after
or hefore calcination cf the spinel based composition. As
indicated previously, vari~us procedures for incorporating
the additional metal component or componentsinto the par-
ticulate material are conventional an~ well known in the art.
Preferably, the additional metal component is substantially
uniformly disposed on the spinel of the present discrete
entities ~ne preferxed method for adaing the platinum
group metal to the spinel involves the utilization of a
water solu~le compound of the platinum group metal to
impregnate the spinel. For example, platinum may be added
to the spinel by comingling the spinel with an aqueous
solution ~f chloroplatinic ~cid. Other water-soluble compounds
of platinum may be employed a~ impregnatiOn 801utions, includ-
ing, for example, ammonium chloroplatinate and platinum
chloride.
Both inorganic and organic compounds of the
platinum group metals are useful for incorporating the
platinum group metal compon~nt into the present di~crete
entities. Platinum group metal compounds, ~uch as chlor-
-17-
~ ~6"522
platinic acid and palladium chloride are preferred.
It may be desirable to be able to separate the
discrete entitie~ fr~m the ~olid particle6, for example,
when it is desired to use the ~olid particles alone for
hydrocarbon conver~ion of where it is desired to recover
the discrete entities for other U6e8 or ~or example, for
p~atinum group metal rec~very. qhis can be conveniently
~c^D~plished by preparing the ~ec~nd solid particle~
in a manner such that they have a different ~ize thar.
the first ~olid particles. ~he separation of the first
2nd secDnd solid particles can then be easily effected
by ~creening or other reans ~f size segre~ation.
As noted above, the presently useful solid
particle5 and discrete entities can be employed in
a rass of cor~ined particles ~hich function as both
the EDlid particles, e.g., promotes hydrocarbon conversion,
and the discrete entities. Such combined particles ~,ay
~e produced in any suitable manner, certain of which methods
are c~nventional and ~nown in the art.
Although this invention i5 useful in m~ny
hydrocarb~n che~,ical conversions, the present
catalyst, i.e., mixture comprisinq ~olid part;cles and
oiscrete entities, and process ~ md particular applicability
in s~stems for the ca~alytic cracking of hydro~arbo~s
and the regenerati~n of cataly~t so empl~yed. Such
catalytic ~ydrocar~on crac~in~ often ~nvolves c~nverting,
i.e., cracking, hea~ier or ~i~her boilinq hydrocarbons
to ~asoline and ~ther l~wer boiling c~mpDnents, ~u~h
as he~ane, hexene, pentane, pentene, ~utane, butylene,
pr~pane, propylene; ethane, ethylene, methane and mixtures
thereo~. Often, the ~ubstantially hydrocarbon feedstock
c~mpris~s a gas oil fræction, e.g., derived fr~m petroleum,
~hale ~il, tar sand ~il, Cca~ and the like. S~ch feedstock
-18-
~ 162522
may comprise a mixture of straight run, e.g., virgin, gas oil.
Such gas oil fractions often boil primarily in the range of
about 400F. to about 1000F. Other substantially hydrocarbon
feedstocks, e.g., other high boiling or heavy fractions of
petroleum, shale oil, tar sand oil, coal and the like may be
cracked using the catalyst and method of the present invention.
Such substantially hydrocarbon feedstock often contains minor
amounts of contaminants, e.g., sulfur, nitrogen and the like.
In one aspect, the present invention involves converting a
hydrocarbon feedstock containing sulfur and/or sulfur
chemically combined with the molecules of hydrocarbon
feedstock. The present invention is particularly useful when
the amount of sulfur in such hydrocarbon feedstock is in the
range of about 0.01% to about 5%, preferably about 0.1% to
about 3%, by weight of the total feedstock.
Hydrocarbon cracking conditions are well known and
often include temperatures in the range of about 850F. to
about 110F., preferably about 900F. to about 1050F. Other
reaction conditions usually include pressures of up to about
100 psia.; catalyst ratios of about 1 to 2 to about 25 to 1,
preferably about 3 to 1 to about 15 to 1; and weight hourly
space velocities (WHSV) of from about 3 to about 60. These
hydrocarbon cracking conditions may be varied depending, for
example, on the feedstock and solid particles or combined
particles being used and the product or products wanted.
In addition, the catalytic hydrocarbon cracking system
includes a regeneration zone for restoring the catalytic
activity of the solid particles or combined particles of
catalyst previously used to promote hydrocarbon cracking~
Carbonaceous, in particular sulfur-containing carbonaceous,
deposit-containing catalyst particles from the reaction zone
are contacted with free oxygen-containing gas in the
-- 19 --
I lB~
regeneration zone at conditions to restore or maintain the
activity of the catalyst by -removing, i.e., combusting, at
least a portion o the carbonaceous material from the catalyst
particles. When the carbonaceous deposit material contains
sulfur, at least one sulfur-containing combustion product is
produced in the regeneration zone and may leave the zone with
the regenerator flue gas. The conditions at which such free
oxygen-containing gas contacting takes place may vary, for
example, over conventional ranges. The temperature in the
catalyst regeneration zone of a hydrocarbon cracking system is
often in the range of about 900F. to about 1500F., preferably
about 1100F. to about 1350F. and more preferably about
1100F. to about 1300F. Other conditions within such
regeneration zone may include, for example, pressures up to
about 100 psia., average catalyst contact times within the
range of about 3 minutes to about 120 minutes, preferably from
about 3 minutes to about 75 minutes. Sufficient oxygen is
preferably present in the regeneration zone to completely
combust the carbon and hydrogen of the carbonaceous deposit
material, for example, to carbon dioxide and water. The amount
of carbonaceous material deposited on the catalyst in the
reaction zone is preferably in the range of about 0.005% to
about 15%, more preferably about 0.1% to about 5% by weight of
the catalyst. The amount of carbonaceous material deposited on
the catalyst in the reaction zone is preferably in the range of
about 0.005% to about 15%, more preferably about 0.1% to about
10%, by weight of the catalyst. The amount of sulfur, if any
contained in the carbonaceous deposit material depends, for
example, on the amount of sulfur in the hydrocarbon feedstock.
This deposit material may contain about 0.01% to about 10% or
more by weight of sulfur. At least a portion of the regenerated
- 20 -
1 ~6~2
catalyst is often returned to the hydrocarbon cracking
reaction zone.
The solid particles useful in the catalytic hydrocarbon
cracking embodiment of the present invention may be any
conventional catalyst capable of promoting hydrocarbon
cracking at the conditions present in the reaction zone, i.e.,
hydrocarbon cracking conditions. Similarly, the catalytic
activity of such solid particles is restored at the conditions
present in the regeneration zone. Typical among those
conventional catalysts are those which comprise amorphous
silica-alumina and at least one crystalline aluminosilicate
having pore diameters of about 8A to about 15A and mixtures
thereof. When the solid particles and/or discrete entities to
be used in the hydrocarbon cracking embodiment of the present
invention contain crystalline aluminosilicate, the
crystalline aluminosilicate may include minor amounts of
conventional metal promoters such as the rare earth metals, in
particular, cerium.
As indicated previously, one embodiment of the present
invention involves contacting solid, sulfur-containing
material in a combustion zone at combustion conditions to
produce combustion products including at least one sulfur
oxide at least a portion of which is sulfur trioxide. Reduced
emissions of sulfur oxide from the combustion zone are achieved
by carrying out this contacting in the presence of discrete
entities containing at least one alkaline earth metal spinel
and at least one rare earth metal component.
Typical solid material combustion zones include, for
example, fluid bed coal burning steam boils and fluid sand bed
waste combustors. The present discrete entities have
sufficient strength to withstand the conditions in such
combustion zones. In the coal fired boiler application, the
- 21 -
~ 1625~
discrete entities are added, either separately or with the
sulfur-containing coal, to the combustion zone, e.g., boiler,
where combustion takes place and at least some sulfur trioxide
is formed. The discrete entities leave the combustion zone
with the coal ash and can be separated from the ash, e.g., by
screening, density separation, or other well known solids
separation techniques. The flue gases leaving the combustion
zone have reduced amounts of sulfur oxide, e.g., relative to
combustion in the absence of the discrete entities. The
discrete entities from the combustion zone can then be
subjected to a reducing environment, e.g., contacted with H2,
at conditions such that at least a portion of the sulfur
associated with the discrete entities disassociates with the
discrete entities, e.g., in the form of H2S, and is removed for
further processing, e.g., sulfur recovery. The discrete
entities, after sulfur removal may be recycled to the
combustion zone, e.g., boiler.
Conditions with the boiler may be those typically used
in fluid-bed coal burning boilers. The amount of discrete
entities used is sufficient to reduce sulfur oxide emissions in
the boiler flue gas, preferably, by at least about 50% and more
preferably by at least about 80%. Conditions within the
reducing zone are such that at least a portion, preferably at
least about 50% and more preferably at least about 80% of the
sulfu~ associated with the discrete entities is removed. For
example, reducing conditions may include temperatures in the
range of about 900F. to about 1800F.; pressures in the range
of about 14 to about 100 psia; and H2 to associated sulfur mole
ratio in the range of about 1 to about 10.
In the fluid sand bed waste combustion application, the
fluid sand, e.g., which acts as a heat sink, may be combined
with the discrete entities and circula-ted from the combustion
- 22 -
1 1~2522
zone to the reduction zone. Reduced emi.ssions of sulfur oxide
from the combustion zone are thus achieved.
Conditions in the combustion zone rnay be as typically
employed in fluid sand bed waste combustors. The amount of
discrete entities employed is sufficient to reduce sulfur
oxide emissions in the combustor flue gases, preferably by at
least about 50% and more preferably by at least about 80%.
Conditions within the reducing zone are similar to those set
forth above for the coal fired boiler application.
The following examples are provided to better
illustrate the invention, without limitation, by presenting
several specific embodiments of the process of the invention.
EXAMPLE I
This example illustrates the production of discrete
entities useful in the present invention.
7.05 lb. sodium aluminate (analyzed as 29.8% by weight
Na20 and 44.85% by weight of Al203) was stirred with one gallon
deioni.zed water to bring as much as possible into solution.
This was filtered through cloth with a lO" Buchner funnel. The
filtered solution was diluted to 8 liters with deionized water.
7.95 lb. Mg(N03)26H20 was dissolved in one gallon
deionized water, and 166 ml. of concentrated HN03 was added.
The solution was diluted to 8 liters with deionized water.
The two final solutions were run simultaneously from
burettes into 32 liters deionized water in a 30 gallon rubber
lined drum. The mix was stirred vigorously during the
addition. Addition of the Mg(N03) 2 solution required 36
minutes. 2760 ml. of the sodium aluminate solution was added
during this period. The pH was held between 7.0 and 7.5. After
addition of all the magnesium nitrate-containing solution,
sodium aluminate solution was added to bring the pH to 8.5.
- 23 -
~,'
l 16~522
After this, 1080 ml. of sodium aluminate solution remained and
was discarded.
The mix was held overnight and then filtered with a
plate-frame press. The cake was washed in the press with 110
gallons deiGnized water. A solution of 26 grams Mg(NO326H20 in
200 ml. deionized water was added to the slurry. The slurry
was filtered and washed as before. After a repeat of the
slurry, filter, and wash, the cake was dried at about 250F. in
a forced air drying oven.
The dried product was then hammermilled, first on a
0.050" screen, then the 0-60 mesh portion was hammermilled
again, this time on the 0.010" screen. The desirable, fine
material was then screened through a 60 mesh screen. The
so-obtained product, magnesium aluminate spinel precusor, was
then transferred into a 59 mm diameter quartz tube, where it
was calcined, in a fluidized state, for 3 hours at 900F. with
an air flow rate of about 106 liters per hour to form magnesium
aluminate spinel.
The resulting magnesium aluminate spinel particles are
screened to produce final particles having diameters less than
lO0 microns.
_A_PLE II
Example I is repeated except that final magnesium
aluminate spinel particles are impregnated, using conventional
techniques, with an aqueous solution of chloroplatinic acid.
The resulting particles are dried and calcined and contain
about lO0 ppm. of platinum, by weight of the total
platinum-containing particles, calculated as elemental
platinum. The platinum is substantially uniform]y distributed
on the spinel-containing particles.
- 24 -
. ~ ~
1 ~62~2~
E~AMPLE III
Example I was repeated except that the calcined
magnesium aluminate spinel was impregnated with cerium.
For cerium impregnation, 0.39 lb. cerium carbonate was
slurried in 1820 mls. of water and mixed with 350 mls. of 70%
nitric acid slowly to dissolve the carbonate. 3.75 lbs. of the
calcined magnesium aluminate spinel was placed in a Pyrex tray
and impregnated with the cerium solution with hand mixing using
rubber gloves. After the impregnation was complete, the mix
was allowed to equilibrate overnight.
The impregnated product was dried under IR lamps and
finally in a 260F. oven overnight. The dried product was
calcined in a fluidized state in a 59 mm. diameter quartz
reactor, for 3 hours at 900F. with an air flow rate of about 83
l/hr. The resulting mangesium aluminate spinel particles were
screened to produce final particles having diameters less than
100 microns and these final particles contained 5% by weight of
cerium, calculated as elemental cerium.
EXAMPLE IV
A quantity of solid particles of a commercially
available hydrocarbon cracking catalyst containing about 6% by
weight of crystalline aluminosilicate, about 54% by weight
amorphous silica-alumina and 40% by weight alpha alumina, and
having the same approximate size as the final particles from
Examp.e I, is combined with the final particles of Example I so
that a mixture of 5 parts by weight of discrete entities and 95
parts by weight of the solid particles results. The catalytic
activity of the solid particles is equilibrated by using same
(prior to combining with the discrete entities) in commercial
fluid bed catalytic cracking service.
The mixture of solid particles and final particles is
loaded to a conventional fluid bed catalytic cracking unit
1 ~2~
(FCCU) and used to crack a petroleum derived gas oil fraction,
a combine~ fresh feed and recycle stream. The fresh gas oil
fraction boils ln the range of about 400F. to about 1000F. and
is substantially hydrocarbon in nature, containing minor
amounts of sulfur and nitrogen as contaminants. Conventional
hydrocarbon cracking and catalyst regeneration conditions are
employed in the reaction zone and regeneration zone,
respectively.
The weight ratio of catalyst particles to total (fresh
plus recycle) hydrocarbon feed entering the reaction zone is
about 6 to 1. Other conditions within the reaction zone
include:
Temperature, F. 930
Pressure, psia. 15
WHSV 15
Such conditions result in about 70% by volume conversion of the
gas oil feedstoc~ to products boiling at 400f. and below.
The catalyst particles from the reaction zone include
about 0.8% by weight of carbonaceous deposit material which is
at least partially combusted in the regeneration zone. This
carbonaceous material also includes a minor amount of sulfur
which forms SOz at the combustion conditions formed in the
regeneration zone. Air, in an amount so that amount of oxygen
in the regeneration zone is about 1.15 times the amount
theoretically required to completely combust this deposit
material, is heated to the desired temperature before being
admitted to the regeneration zone. Conditions within the
regeneration zone include:
Temperature, F.1100
Pressure, psia. 15
Average Catalyst
Residence Time, min. 30
- 26 -
~ 1~25~2
After a period of time, the catalyst is shown to remain
effective to promote hydrocarbon cracking in the reaction
zone, and reduced emissions of sulfur (as sulfur oxides) from
the flue gases of the regeneration zone are obtained (relative
to processing in the absence of the f:inal magnesium aluminate
spinel-containing particles).
EXAMPLE V
Example IV is repeated, except that the
platinum-containing particles of Example II are used instead
of the magnesium aluminate spinel particles of Example I.
After a period of time, the catalyst is shown to remain
effective to promote hydrocarbon cracking in the reaction zone
and carbon monoxide and sulfur dioxide oxidation in the
regeneration zone. In addition, reduced emissions of sulfur
(as sulfur oxides) from the flue gases of the regeneration zone
are obtained (relative to processing in the substantial
absence of the platinum-containing particles).
EXAMPLE VI
Example IV is repeated except that the
cerium-containing particles of Examp].e III are used in place of
the particles of Example I.
After a period of time, the catalyst is shown to remain
effective to promote hydrocarbon cracking in the reaction
zone, and reduced emissions of sulfur (as sulfur oxides~ from
the flue gases of the regeneration
z~n~ are obtained (relative to processing in the absence
of the final magnesium aluminate spinel-containing particles.
EXAMPLE VII
Examples I, II and I~l are repeated, except that
the final magnesium aluminate spinel particles, the platinum-
containing particles and the cerium-containing particlesr
respectively, each include about 7~ by weight of a crystal-
line aluminosilicate known to be catalytically active to
promote hydrocarbon cracking. The crystalline aluminosili-
1~ cate is incorporated into the pàrticles using conventional,well known techniques. The platinum, and particularly the
cerium, components are included in the particles so that a
substantial amount, e.g., greater than about 50%, of the
platinum and cerium is associated with the magnesium alumi-
nate spinel of the particles, rather than with the crystal-
line aluminosilicate. Cerium associated with the crystalline
aluminosilicate is substantially less effective, e.g., in
reducing SOx emissions, relative to cerium deposited on the
magnesium aluminate spinel portion of the particles.
EXAMP~E VIII
Example IV is repeated three times except that the
magnesium aluminate-containing Rpinel particles produced in
Example VII are used in place of the particles of Example I.
After a period of time in hydrocarbon cracking service, these
catalyst mixtures are shown to be effective to promote hydro-
carbon cracXing and reduced sulfur emissions from the regen-
eration zone are obtained. In particular, it is found that
the crystalline aluminosilicate present in the discretè en-
tities improves the hydrocarbon cracking in the reaction
zone beyond that occurring in a system with discrete entities
containing ~ubstantially no zeolitic component.
-28-
l 16~$~2
EXAMPLE IX
A mass of combined particles is prepared as follows:
The magnesium aluminate spinel-based discrete
entitie~ are prepared by forming an aq~eous slurry of magnesium
aluminate spinel precursor (produced as in Examplc I) 50
that the ~pinel concentration, calculated as MgAl2o4~ is
about 9~ by weigh~. S~fficient crystalline alumin~silicate
known to be effective to prcmote hydrocarbon cracking i6
added to the slurry ~o that t~e ~inal magnesium alumin~te
spinel-based discrete entities contain, on a dry weight basis,
about 10~ of ~uch crystalline aluminosilicate. This slurry
is ~tirred for about 1 hour to insure uniformity and then
~pray dried at a temperature less than that required to eliminate
a substantial portion of the water of hydration to form discrete
entities. These diserete entities are calcined in an electric
muffle furnace using a programmed timer to increase the
temperature 300F. per h~ur to 1050CF. and maintain this
te~perature fox 3 hours. The discrete entities are impregnated
with platinum and cerium as in Examples II and III. Thefinal
discrete entities contain about 7~ by weight of cerium calculated
as elemental cerium; and about lQ0 ppm. by weight of platinum.
A major portion of the cerium and platinum is associated with the
~pinel, rather than the crystalline aluminosilicate.
Essenti~ly all the calcined discrete entities
have a maximum dimension of less than about 200 microns.
~he discrete entities larger ~han 60 microns are discarded.
The solid particles-binderrmaterial is prepared
by adding 6000 parts by weight of a solution containing
Philadelphia Quartz Company "E" brand sodium silicate solution
diluted with an equal weight of water to 3000 parts by weight of
dilute (density-1.23~) H2SO4. After these two solutions
are thoroughly mixed, 4000 parts by weight of a solution
containing 1200 parts by weight of Al2(SO4)3 18H2O is added.
-29-
2 ~
Sufficient crystalline aluminosilicate, known to be effective
to promote ~ydrocarbon cracking, i6 added to the mixture
so that the final solid particles-binder material contains,
on a dry weight basis, about ~ ~f such crystalline alumino-
silicate. The resulting mixture is let stand to gel.
~he resulting hydrogel is cut into about 3~4~ cubes and covered
with concentrated NH40H diluted with an e~ual vol~me of water.
This material is let stand overnight and has a final pH of
ll. The material is then washed by percolation until free
of Na~ and S04=ion.
500 parts (on a dry weight basis) of the washed
hydrogel and 80 parts (on a dry weiqht basis) of the remaining
calcined discrete entities and lO,000 parts by weight of
water are thoroughly mulled, ground and mixed with agitation.
The resulting slurry is dried in a spray drier. This drier
is equipped with a two-fluid nozzle system which uses air
at about 20 psig.to disperse the slurry into the drying chamber.
The drying gas, i.e., flue gas from an inline burner, enters
the drying chamber at about 750F. and exits the chamber
20 at a temperature which ranges from about 305F. to 315F.
This drying gas in introduced into the top of the drying
chamber while the slurry is dispersed upward from near the
bottom of the cham~er. In this way, the material to be dried
is exposed to both counter-current flow ~during assent from
the nozzle system) and co-current flow (during qravity dissent)
relative to the downward drying gas flow. The resulting
dried particles are calcined in a manner similar to the calcination
~f the spinel based discrete entities described above. The
resulting combined particles ~re screened to provide particles
proper~y sized for use in a fluidized catalytic bed reaction
zone-regenerator hydrocarbon cracking system.
EXAMPLE X
Example IV i~ repeated except that the physical
-30-
~ ~2~2
mixture of discrete entities and catalyst particles used
in Example IV ~re replaced ~y the combined particle~ produced
in Example IX. After a period of time, these combined particles
are shown to remain effective to promote b~th hydrocarbon
cracking in the react~n z~ne ~nd to reduce the amount of
~ulfur atmospheric emission~ in the regeneration zone flue
g~ses.
EXAMPLE XI
Example I is repeated except that Li(NO3)-3H2o
is substituted for the Mg(~O3)2 6H2O. The resulting final
lithiu~ aluminate spinel particles have diameters less than
100 microns.
- ExAMpLE XII
The final particles of Example XIare impregnated,
using conventional techniques with ch~oroplatinic acid. The
resulting spinel-containing particles are dried and calcined
and contain about 100 ppm. of platinum, by weight of the
total platinum-containing particle~, calculated as elemental
platinum. The platinum is substantially uniformly distxibuted
on the spinel-containing particles.
EXAMPLE XIII
The final particles of Example XI are impregnated,
using conventional techniques, with cerium-using as ague~us
cerium nitrate solution. The resulting spinel-containing
particles are dried and calcined and contain about 10~ by
weight of cerium, calculated as elemental cerium.
EXAMPL~S XIV to XVI
Example IV is xepeated three times excep~ that
the final particles Pf Example I are replaced by the resulting
spinel-containing particles of Examples XI, XII and XIII,
reSpectively. In each instance, reduced emissions of sulfur
(as sulfur oxides) from the flue gases of the regenerator
-31-
5 2 2
zone is obtained.
EXAMPLES XVII to XXI
Particles having diameter~ of less than 100 microns
of the following ~pinel materials are prepared using
conventi~nal techniques:
Example
._
XV~I FeA12O4
XVIII MnA 24
XIX MgCr2O4
10XX Fe2TiO4
XXI MgFe204
EXAMPLES XXII to XXVI
Example ~V is repeated five additional tLmes except
that the final particles of Example I are replaced by the
6pinel-containing particl~s of Examples XVII, XVIII, XIX, XX
and XXI, respectively. In each instance, reduced emissions
of sulfur (as sulfur oxides) from the flue gases of the re-
generator zone is obtained~
EXAMPLES XXVII AND XXVIII
These examples illustrate certain of the surprising
benefits of the present invention.
Two blends of particles were prepared for testing.
The blends were as follows:
Blend A - 5~ by weight cerium impregnated
magnesium aluminate spinel final particles pro-
duced as in Example I, plus 95% by weight of
a conventional zeolite-containing hydrocarbon
cracking catalyst which had been equilibràted
in commercial fluid bed catalytic cracking
service.
Blend B - 5% ~y weight cerium impregnated gamma
alumina particles containing 5~ by weight of
-32-
~ 1~;2~
cerium, calculated a~ elemental cerium, and
having a particle size in the range of 25 to
100 microns, plus 95~ by weight of the same
conventional zeolite-containing catalyst as
to prepare blend A. Cerium-alumina particles
are known to possess good initial sulfur oxide
removal acti~ity w~en u~ed in fluid catalytic
cracking service.
~oth blends were tested to determine their ability
to continue to remove sulfur oxides over a period of time.
This test procedure was as follows: Step 1 involved an initial
determination of the ability of the blend to remove ~ulfur
oxides Erom regenerator flue gases. Step one was carried
out in a fluid bed catalytic cracking pilot plant known to
provide results which are correlatable to results obtained
in commercial ~ized systems. The feedstock and conditions
for step 1 were as follows:
Feedstock - mid-continent gas oil containing
2.04 by weight sulfur
Reactor temperature - 930F.
Regenerator temperature - 1100`F.
Stripper temperature - 930F.
Pressure - 15 psia.
Approximate catalyst reqeneration time - 30 minutes
Approximate stripping time - 10 minutes
Approximate reaction time - lminute
Steam as inerts in reactcr, 3 mole ~.
Step 2 ~f the test procedure involved continuous and
accelerated aging in a fluidized-bed reactor to ~imulate
the type of aqinq which occurs in commercial fluid-bed
catalytic crackin~ ~ervice. The feedstock and conditions
utilized in step 2 were as ~ollows:
-33-
2~
Feedstock - Gulf Coast ga~ oil c~ntaining
2 . 0~ by weight ~ulfur
r Reactor temperature - 930~F.
Reactor pressuxe - 15 psia.
D Reac~ion residence time v 1 minute
Reaction catalyst/oil weight ratio 6
D Stripping temperature - 930~.
Regenerator temperature - 1100F.
~egenerator pressure 15 psia.
~ Catalyst regenerator residence time - 30
D Regenerator combustion air flow ratio -20 lbs.air/
lb.coke
Step 3 of the test procedure involved periodically
repeating step 1 to determine how much of the blend's
acti~ity to remove sulfur oxide had ~een lost during the aging
of step 2.
The amount of sulfur oxides emitted wit~ the flue gases
from the regeneration using the blend was used as the basis
for determining the blend' 6 ability ~or activity) to remove
~u~ ~ulfur oxides.
Results o testing Blends A and ~ following the
above procedures were as follows:
Days Aged at Conditions(l) ~ of Initial Activity to Remove
of Step 2 Sulfur Oxide Retained
Blend A Blend
0 100 100
2 93 43
4 89 1
6 ~1 ~
(l)One day of aging at the condition of step 2
is more severe than the aging which would occur
in commercial FCC service. Therefore, there
is no direct one-on-one correlation between
aging in these two aging modes.
-34-
~ 162~22
These results indicate very clearly that the cerium-
magnesium alumina-te spinel particles of Blend A maintain sul-
fur oxide removal activity much longer than the cerium-alumina
particles of Blend s. Relatively rapid loss of sulfur removal
activity has been one of the major problems with prior art
attempts, e.g., cerium on alumina particles, to reduce sulfur
oxide emissions. Therefore, these results show that the pre-
sent invention provides substantial and surprising advantages
in reducing sulfur oxide emissions from combustion zones, e.g.,
regeneration zones of fluid bed hydrocarbon catalytic cracking
units.
While this invention has been described with respect
to various specific examples and embodiments, it is to be
understood that the invention is not limited thereto and that
it can be variously practiced within the scope of the follow-
ing claims.
SUPPLEMENTAR~ DISCLOSURE
The foregoing description indicates various metal-
containing spinels which may be used in the process of this
invention.
The presently useful metal-containing spinels include
a first metal and a second metal having a valence (oxida-
tion state) higher than the valence of the first metal. The
first and second metals may be the same metal or different
metals. In other words, the same metal may exist in a given
spinel in two or more different oxidation states. As indi-
cated above, the atomic ratio of the first metal to the second
metal in any given spinel need not be consistent with the
classical stoichiometric formula for such spinel. In one
embodiment, the atomic ratio of the first metal to the second
metal in the metal-containing spinel useful in the present in-
- 35 -
1 lB2~X2
vention is at least ahout 0.17 and preferably at least about
0.25. If the first metal is a mono-valent metal, the atomic
ratio of the first metal to the second metal is pxeferably at
least about 0.34, more preferably at least about 0.5.
When the spinel includes a divalent metal (e.g., alu-
minum), it is preferred that the atomic ratio of divalent to
trivalent metals in the spinel be in the range of about 0.17
to about l, more preferably about 0.25 to about 0.75, still
more preferably about 0.35 to about 0.65 and still further
more preferably about 0.45 to about 0.55.
The inventive process as claimed herein is furthermore
intended to be in a hydrocarbon conversion process for con-
verting a sulfur-containing hydrocarbon feedstock which com-
prises (l) contacting the feedstock with solid particles cap-
able of promoting the conversion of the feedstock at hydro-
carbon conversion conditions in at least one reaction zone to
produce at least one hydrocarbon product and to cause deacti-
vating sulfur-containing carbonaceous material to be formed
on the solid particles thereby forming deposit-containing
particles; (2) contacting the deposit-containing particles
with an oxygen-containing vaporous medium at conditions to
combust at least a portion of the carbonaceous deposit material.
in at least one regeneration zone to thereby regenerate at
least a portion of the hydrocarbon conversion catalytic acti-
vity of the solid particles and to form a regeneration zone
flue gas containing sulfur trioxide; and (3) repeating step
(l) and (2) periodically, the improvement which comprises:
using, in intimate admixture with the solid particles, a minor
amount of discrete entities having a composition different
from the solid particles and comprising at least one metal-
containing spinel including a first metal and second metal
having a valence higher than the valence of the first metal,
- 35a -
t ~62522
the atomic ratio of the first metal to the second metal in
the spinel is at least about 0.17, the discrete entities being
present in an amount sufficient to reduce the amount of sulfur
oxides in the flue gas.
In an alkaline earth metal-containing spine:L, the
atomic ratio of the first metal to the second metal is pre-
ferably at least about 0.2.
In a spinel containing magnesium and aluminum, the
atomic ratio of magnesium to aluminum is preferably in the
range of about 0.25 to about 0.75, more particularly in the
range of about 0.35 to about 0.65, and especially in the range
of about 0.45 to about 0.55.
The magnesium aluminate spinel prepared in Example I
was found to have an atomic ratio of magnesium to aluminum of
about 0.48.
The lithium aluminate spinel prepared in Example XI
was found to have an atomic ratio of lithium ions to aluminum
ions of about 0.2.
In Examples XVII to XXI the spinel materials therein
prepared are substantially stoichiometric spinel materials
prepared using conventional techniques.
- 35b -
