U.S. patent application number 12/322485 was filed with the patent office on 2009-06-04 for fcc process using mesoporous catalyst.
Invention is credited to Jeffrey S. Beck, Stephen J. McCathy, David L. Stern, William A. Wachter.
Application Number | 20090139900 12/322485 |
Document ID | / |
Family ID | 38083448 |
Filed Date | 2009-06-04 |
United States Patent
Application |
20090139900 |
Kind Code |
A1 |
Wachter; William A. ; et
al. |
June 4, 2009 |
FCC process using mesoporous catalyst
Abstract
This invention relates to a FCC process using a mesoporous
catalytic cracking catalyst. The mesoporous fluidized catalytic
cracking catalyst is selective for minimizing the production of
coke and light gas. The catalyst comprises at least one amorphous,
porous matrix, each matrix having pores ranging in diameter from
about 1 .ANG. to about 10 .ANG. and pores ranging in diameter from
about 40 .ANG. to about 500 .ANG., wherein in the pore range from
50 .ANG. to 250 .ANG., there is a single maximum in differential
pore volume distribution over the 50 .ANG. to 250 .ANG. range.
Inventors: |
Wachter; William A.;
(Flemington, NJ) ; McCathy; Stephen J.; (Center
Valley, PA) ; Beck; Jeffrey S.; (League City, TX)
; Stern; David L.; (Baton Rouge, LA) |
Correspondence
Address: |
ExxonMobil Research & Engineering Company
P.O. Box 900, 1545 Route 22 East
Annandale
NJ
08801-0900
US
|
Family ID: |
38083448 |
Appl. No.: |
12/322485 |
Filed: |
February 3, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11106289 |
Apr 14, 2005 |
7504021 |
|
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12322485 |
|
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|
60577747 |
Jun 8, 2004 |
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Current U.S.
Class: |
208/118 |
Current CPC
Class: |
C10G 11/05 20130101;
C10G 11/04 20130101 |
Class at
Publication: |
208/118 |
International
Class: |
C10G 11/02 20060101
C10G011/02 |
Claims
1. A catalytic cracking process, comprising: contacting a
hydrocarbon feedstock with a catalytically effective amount of a
cracking catalyst under catalytic conversion conditions, wherein
the cracking catalyst comprises at least one amorphous, porous
matrix, each matrix having pores ranging in diameter from about 1
.ANG. to about 10 .ANG. and pores ranging in diameter from about 40
.ANG. to about 500 .ANG., wherein in the pore range from 50 .ANG.
to 250 .ANG., there is a single maximum in differential pore volume
distribution over the 50 .ANG. to 250 .ANG. range; and at least one
zeolite; wherein the catalytic conversion conditions include a
temperature of from about 450.degree. C. to about 700.degree. C., a
hydrocarbon partial pressure of from about 10 to 40 psia, a
cracking catalyst to feedstock (wt/wt) ratio of from about 3 to
100, where catalyst weight is total weight of the cracking
catalyst, a pressure ranging from about atmospheric pressure to
about 45 psig, and a feedstock residence time of from about 0.1 to
about 20 seconds.
2. The process of claim 1 wherein said matrix comprises at least
one clay, at least one aluminum hydroxide or oxyhydroxide and at
least one binder colloid.
3. The process of claim 2 wherein the zeolite is a Y zeolite or
zeolites isostructural with zeolite Y.
4. The process of claim 3 wherein the matrix is a silica-alumina
matrix.
5. The process of claim 2 wherein the matrix comprises gibbsite as
the aluminum hydroxide or oxyhydroxide.
6. The process of claim 1 wherein the cracking catalyst has been
ion-exchanged and calcined.
7. The process of claim 1 wherein the zeolite has pore diameters
ranging from 3 to 15 Angstroms.
8. The process of claim 2 wherein the clay is kaolin.
9. The process of claim 2 wherein the aluminum hydroxide is
alumina.
10. The process of claim 1 wherein the matrix is substantially free
of pores ranging in size from about 10 .ANG. to about 40 .ANG..
11. The process of claim 2 wherein the matrix is substantially free
of pores ranging in size from about 10 .ANG. to about 40 .ANG..
12. The process of claim 1 wherein an integrated maximum pore
volume for matrix pores having a diameter between about 10 .ANG.
and about 40 .ANG. is less than about 0.03 cc/g.
13. The process of claim 1 wherein an integrated maximum pore
volume for matrix pores having a diameter between about 10 .ANG.
and about 40 .ANG. is less than about 0.03 cc/g.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. non-provisional
application Ser. No. 11/106,289, filed Apr. 14, 2005, which claims
the benefit of U.S. provisional patent application Ser. No.
60/577,747 filed Jun. 8, 2004.
FIELD OF THE INVENTION
[0002] This invention relates to a process for utilizing mesoporous
catalytic cracking catalysts in cracking operations. In particular,
it relates a mesoporous fluidized catalytic cracking catalyst
selective for minimizing the production of coke and light gas, a
process for the production of such catalyst, and a process
utilizing such catalyst in fluidized catalytic cracking
operations.
BACKGROUND OF THE INVENTION
[0003] Catalytic cracking, notably fluidized catalytic cracking
("FCC"), is a conventional (i.e., well known) process for
converting higher average molecular weight, higher boiling
hydrocarbons to more valuable, lower average molecular weight,
lower boiling hydrocarbons. The products are useful as fuels for
transportation, heating, etc. In the process, the conversion step
is usually conducted by contacting a hydrocarbon feedstock, e.g., a
heavy gas oil, with a moving bed of particulate catalyst in the
substantial absence of hydrogen at elevated temperatures.
[0004] The FCC process is cyclic and includes, for example,
separate zones for catalytic feedstock conversion, steam stripping,
and catalyst regeneration. In the cycle, feedstock is blended with
the FCC catalyst in a catalytic reactor, typically a riser reactor,
for catalytic conversion into products. Lower boiling products are
separated from the catalyst in a separator, e.g., a cyclone
separator, and deactivated catalyst is conducted to a stripper and
contacted with steam to remove entrained hydrocarbons; the latter
can be combined with vapors from the cyclone separator, and both
can be conducted away from the process. Stripped deactivated
catalyst contains a carbonaceous residue, called "coke". Stripped
catalyst recovered from the stripper is conducted to a regenerator,
e.g., a fluidized bed regenerator, and contacted with a combusting
gas, e.g., air, at elevated temperature to burn off the coke and
reactivate the catalyst. Regenerated catalyst is then blended with
the feedstock entering the riser, completing the cycle.
[0005] In continuous, cyclic operation, exothermic coke combustion
in the regenerator provides at least a portion of the heat required
to balance the endothermic feedstock cracking in the reactor.
However, the presence of coke beyond that necessary for heat
balance is undesirable since converting feedstock hydrocarbon into
catalyst coke diminishes the quantity of hydrocarbon products
obtained from the feedstock. There is therefore a need for
catalysts that selectively make a greater quantity of hydrocarbon
products but less catalytic coke.
[0006] Mesoporous FCC catalysts, such as those described in U.S.
Pat. No. 5,221,648 are effective for feedstock conversion into high
value hydrocarbon products, such as light olefins. Such catalysts
have the desirable property that undesirably high catalyst coke
levels are avoided in FCC operation. However, such catalysts
contain a mesoporous silica-alumina matrix formed from silica sols
that undesirably add to the expense of catalyst production.
Moreover, conventional sols are acidic, and, consequently, can
undesirably affect catalytic constituents, such as zeolite, during
catalyst synthesis. There is therefore a need for improved
mesoporous catalysts.
SUMMARY OF THE INVENTION
[0007] The invention relates to (I) a cracking catalyst, (II) a
method for making the cracking catalyst, and (III) a catalytic
cracking process.
[0008] In an embodiment, the invention relates to a composition,
comprising at least one amorphous, porous matrix, each matrix
having pores ranging in diameter from about 1 .ANG. to about 10
.ANG. and pores ranging in diameter from about 40 .ANG. to at least
about 500 .ANG., wherein in the pore range from 50 .ANG. to 250
.ANG., there is a single maximum in differential pore volume
distribution over the 50 .ANG. to 250 .ANG. range. The matrix is a
single amorphous entity, or may be a blend of two or more
individual amorphous matrices provided that each matrix
individually meets the above-noted differential pore volume
distribution requirement.
[0009] In a related embodiment, the composition's matrix has a
differential pore volume as a function of matrix pore diameter, and
this function has a maximum between 50 .ANG. and 250 .ANG.,
preferably between 50 .ANG. and 150 .ANG.. The integrated
differential pore volume for matrix pores having a diameter between
about 1 .ANG. and about 10 .ANG. cannot be distinguished from the
pore volume in zeolites typically used in the application. Thus it
is not feasible to estimate the pore volumes for pores below about
10 .ANG. because one cannot distinguish between the pore volume of
the matrix and that of the zeolite. The integrated maximum pore
volume for the volume of matrix pores having a diameter between
about 10 .ANG. and about 40 .ANG. is less than about 0.03 cc/g,
preferably less than about 0.01 cc/g, more preferably less than
about 0.006 cc/g.
[0010] In another embodiment, the invention relates to a method for
making a cracking catalyst precursor comprising:
[0011] (a) combining water, at least one molecular sieve, at least
one aluminum hydroxide or aluminum oxyhydroxide, at least one clay,
at least one urea compound having the formula
##STR00001##
where R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are individually H or
C.sub.1 to C.sub.4 alkyl and X is sulfur or oxygen, and at least
one phosphate to form a first mixture;
[0012] (b) combining the first mixture with sufficient aqueous
alkaline silicate solution to form a slurry having a pH sufficient
to prevent gellation of the aqueous alkaline silicate solution;
[0013] (c) drying the slurry at a drying temperature to remove
water to form a first solid, said solid preferably comprising
ammonium silicate, alkali silicate and alkali carbonate, urea
compound, clay, at least one aluminum hydroxide or aluminum
oxyhydroxide and molecular sieve;
[0014] (d) combining the first solid with water and an ion exchange
composition comprising one or more mineral acid, preferably
sulfuric acid, aluminum salts of mineral acids such as aluminum
sulfate, and/or ammonium salts of mineral acids such as ammonium
sulfate, to form the catalyst precursor, the catalyst precursor
having a lower concentration of alkali metal compared to the first
solid.
[0015] In a related embodiment, the invention relates to making
catalyst from the catalyst precursor comprising the further steps
of:
[0016] (e) combining the catalyst precursor with water and a
second, independently selected ion exchange composition comprising
one or more mineral acid such as sulfuric acid, aluminum salts of
mineral acids such as aluminum sulfate, and/or ammonium salts of
mineral acids such as ammonium sulfate, to form an ion-exchanged
catalyst precursor having a lower concentration of alkali metal
compared to the first and second solids;
[0017] (f) calcining the ion-exchanged catalyst precursor at a
temperature ranging from about 250 to about 850.degree. C. for a
calcination time to make a calcined, ion-exchanged catalyst
precursor; and
[0018] (g) contacting the calcined, ion-exchanged catalyst
precursor with steam at a temperature ranging from about 650 to
about 850.degree. C. for a steaming time. A preferred steaming time
is 4 to 48 hours. The steaming deactivates the cracking catalyst
and simulates the deactivation in a commercial FCC unit which runs
at significantly lower water pressures for a much longer time.
[0019] In yet another embodiment, the invention relates to a
catalytic cracking process, comprising contacting a hydrocarbon
feedstock with a catalytically effective amount of a cracking
catalyst under catalytic conversion conditions, wherein the
cracking catalyst comprises zeolite and an amorphous, porous matrix
having pores ranging in diameter from about 1 .ANG. to about 10
.ANG. and pores ranging in diameter from about 40 .ANG. to at least
about 500 .ANG., wherein in the pore range from 50 .ANG. to 250
.ANG., there is a single maximum in differential pore volume
distribution over the 50 .ANG. to 250 .ANG. range.
[0020] In another related embodiment the catalytic conversion
conditions include a temperatures of from about 450.degree. C. to
about 700.degree. C., a hydrocarbon partial pressure of from about
10 to 40 psia, a cracking catalyst to feedstock (wt/wt) ratio of
from about 3 to 100, where catalyst weight is total weight of the
cracking catalyst, a pressure ranging from about atmospheric
pressure to about 45 psig, and a feedstock residence time of from
about 0.1 to about 20 seconds.
[0021] In a related embodiment, the cracking catalyst is made
by:
[0022] (a) combining water, at least one molecular sieve, at least
one aluminum hydroxide, at least one clay, urea compound, and at
least one phosphate to form a first mixture, said urea compound
having the formula:
##STR00002##
where R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are individually H or
C.sub.1 to C.sub.4 alkyl and X is sulfur or oxygen;
[0023] (b) combining the first mixture with sufficient aqueous
alkaline silicate solution to form a slurry having a pH sufficient
to prevent gellation of the aqueous alkaline silicate solution;
[0024] (c) drying the slurry at a drying temperature to remove
water to form a first solid;
[0025] (d) combining the first solid with water and an ion exchange
composition comprising one or more of sulfuric acid, aluminum
sulfate, and/or ammonium sulfate, to form a catalyst precursor, the
catalyst precursor having a lower concentration of alkali metal
compared to the first solid;
[0026] (e) combining the catalyst precursor with water and a
second, independently selected ion exchange composition comprising
one or more of sulfuric acid, aluminum sulfate, and/or ammonium
sulfate, to form an ion-exchanged catalyst precursor having a lower
concentration of alkali metal compared to the first solid and
catalyst precursor;
[0027] (f) calcining the ion-exchanged catalyst precursor at a
temperature ranging from about 250 to about 850.degree. C. for a
calcination time to make a calcined, ion-exchanged catalyst
precursor; and
[0028] g) contacting the calcined, ion-exchanged catalyst precursor
with steam at a temperature ranging from about 650 to about
850.degree. C. for a steaming time in order to make the cracking
catalyst. The preferred steaming time is 4 to 48 hours.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a plot of the differential mercury pore volume
(dV/dD) vs. pore diameter for catalyst matrix between 40 and 10000
Angstroms.
[0030] FIG. 2 is a plot of integrated differential mercury pore
volume vs. pore diameter between 40 and 500 Angstroms for catalyst
matrix.
[0031] FIG. 3 is a plot of dV/dD vs. pore diameter showing the
extrapolation of pore volume for pores in the 10 to 40 Angstrom
range.
[0032] FIG. 4a is a plot showing a comparison of coke make vs.
221.degree. C.- plus coke make for the base case comparative
catalysts vs. catalysts of the invention.
[0033] FIG. 4b is a plot showing a comparison of coke make vs.
221.degree. C.- plus coke make for commercially available catalysts
vs. catalysts of the invention.
[0034] FIG. 5 is a plot showing a comparison of the coke yield
normalized to remove the influence of conversion vs. 221.degree.
C.- plus coke make for the base case comparative catalysts vs.
catalysts of the invention.
[0035] FIG. 6a is a plot showing a comparison of dry gas make vs.
221.degree. C.- +coke make for the base case comparative catalyst
vs. catalysts of the invention.
[0036] FIG. 6b is a plot showing a comparison of dry gas make vs.
221.degree. C.- +coke make for the commercially available catalysts
vs. catalysts of the invention.
[0037] FIG. 7a is a plot showing a comparison of propene make vs.
221-.degree. C.+coke conversion for catalysts of the invention vs.
base case comparative catalysts.
[0038] FIG. 7b is a plot showing a comparison of propene make vs.
221-.degree. C.+coke conversion for the commercially available
catalysts vs. catalysts of the invention.
[0039] FIG. 8a is a plot of dV/dD vs. pore diameter showing that
catalysts of the invention have a maximum occurring at pore
diameters above 50 Angstroms.
[0040] FIG. 8b is a plot of dV/dD vs. pore diameter showing that
the commercially available catalysts have a local maximum in the
dV/dD plot below 60 Angstroms regardless of the severity of the
steaming.
[0041] FIG. 8c is a plot of dV/dD vs. pore diameter showing that
commercially available catalyst when blended with other
commercially available catalysts from the same manufacturer has a
local maximum in the dV/dD plot below 60 Angstroms regardless of
the severity of the steaming.
[0042] FIG. 8d is a plot of dV/dD vs. pore diameter showing that
catalysts of this invention have a maximum in the dV/dD plot above
60 Angstroms and below 80 Angstroms unlike the commercially
available catalysts which have a local maximum below 60 Angstroms
in all cases and may have a local maximum above 80 Angstroms in
some cases.
DETAILED DESCRIPTION OF THE INVENTION
(I) The Catalytic Cracking Catalyst
[0043] In an embodiment, the invention relates to a catalytic
cracking catalyst composite ("composite" herein) comprising
cracking catalyst (generally in particle form) and, optionally,
other reactive and non-reactive components. More than one type of
catalyst may be present in the composite. Typically, the catalyst
comprises matrix and at least one crystalline molecular sieve, said
matrix comprising at least one clay, at least one aluminum
hydroxide or oxyhydroxide, and binder colloids. The molecular sieve
can be an aluminosilicate, such as zeolite, having an average pore
diameter between about 3 and 15 Angstroms. The pore diameter also
sometimes referred to as effective pore diameter can be measured
using standard adsorption techniques and hydrocarbons of known
minimum kinetic diameters. See Breck, Zeolite Molecular Sieves,
1974 and Anderson et al., J. Catalysis 58, 114 (1979) and the
"Atlas of Zeolite Structure Types," eds. W. H. Meier and D. H.
Olson, Butterworth-Heineman, Third Edition, 1992. More than one
type of catalyst may be present in the composite. For example,
individual catalyst particles may contain large pore zeolite, shape
selective zeolite, and mixtures thereof. In addition to catalyst
particles, the composite may also include fines, inert particles,
particles containing a metallic species such as platinum and
compounds thereof.
[0044] In addition to matrix and molecular sieve, the catalyst can
further comprise metals such as platinum, promoter species such as
phosphorous-containing species, and species for imparting
additional catalytic functionality (additional to the cracking
functionality) such as bottoms cracking and metals passivation.
Such an additional catalytic functionality may be provided, for
example, by aluminum-containing species.
[0045] The inorganic matrix is a porous inorganic oxide matrix
component for (i) binding the components together so that the
catalyst is attrition resistant enough to survive inter-particle
and reactor wall collisions (i.e., attrition resistance) and (ii)
to provide a degree of size selectivity with respect to molecules
capable of cracking on or in the molecular sieve. The inorganic
oxide matrix may be made from, e.g., an inorganic oxide sol, which
is then dried. Conventional sols can be used. Examples of
conventional sols include silica sols derived from the reaction of
sodium silicate and sulfuric acid/aluminum sulfate solutions,
silica sols prepared through an ion-exchange process typified by
materials with trade names such as "Ludox" and "Nyacol", 5/6 basic
aluminum chlorhydroxide typified by materials such as
"Chlorhydrol", and peptized alumina slurries such as those that can
be made from the reaction of acid with materials such as the
"Versal" series of aluminum pseudoboehmites. The matrix itself may
possess catalytic properties, generally of an acidic nature, but
matrix catalytic activity is not required. In an embodiment, the
matrix comprises oxides of silicon and aluminum. The matrix can
comprise more than one oxide phase, for example, aluminum
oxyhydroxides-.gamma.-alumina, boehmite, diaspore, and transitional
aluminas such as .alpha.-alumina, .beta.-alumina, .gamma.-alumina,
.delta.-alumina, .epsilon.-alumina, .kappa.-alumina, and
.rho.-alumina can be employed. In a related embodiment, the alumina
species is an aluminum hydroxide such as gibbsite, bayerite,
nordstrandite, or doyelite. The matrix material may contain
phosphorous or aluminum phosphate, and while generally undesirable,
a small amount of sodium. The matrix may also comprise clays such
as kaolin, bentonite, attapulgite, montmorillonite, hectorite and
pyrophyllite.
[0046] The catalyst in the composite will now be described in more
detail. The catalyst comprises matrix, said matrix comprising at
least one clay, at least one aluminum hydroxide or oxyhydroxide,
and binder colloids, in an amount ranging from about 5 wt. percent
to about 100 wt. percent, preferably from about 8 wt. percent to
about 95 wt. percent, based on the total weight of the catalyst,
within which is dispersed a crystalline molecular sieve. In an
embodiment, the molecular sieve is a crystalline aluminosilicate,
i.e., zeolite, natural or synthetic, typically having a
silica-to-alumina mole ratio (Si/Al) of about 2, and greater, and
uniform pores with diameters ranging from about 3 .ANG. to about 15
.ANG.. The zeolite content of the catalyst ranges from about 0
percent to about 95 percent by weight, preferably from about 5
percent to about 92 percent, and more preferably from about 10
percent to about 60 percent, based on the total weight of the
catalyst.
[0047] Under the IUPAC, microporous refers to pores in the 2 to 20
.ANG. range and mesoporous in the 20 to 500 .ANG. range. As defined
in this invention, the respective ranges are about 1 to about 10
.ANG. for micropores and about 40 .ANG. to at least about 500
.ANG., preferably between 40 .ANG. and 250 .ANG. for mesopores. A
functional definition of "mesoporous" as used herein is that
porosity which extends above the range normally associated with the
adsorption of mid-distillate in FCC, in particular the porosity in
pores which have larger diameters than those associated with the
standard commercial FCC zeolite, structure type FAU as set forth in
the "Atlas of Zeolite Structure Types," ed. W. M. Meier, D. H.
Olson and Ch. Baerlocher, Elsevier, 1996.
[0048] The differential pore volume for matrix pores has a maximum
at a diameter between 40 .ANG. and 250 .ANG. as illustrated in FIG.
1. This Figure shows that in the pore range from 50 .ANG. to 250
.ANG., there is a single maximum in the differential mercury pore
volume over the 50 .ANG. to 250 .ANG. range.
[0049] The pore volume measured with mercury for matrix pores with
diameters less than 250 Angstroms comprises between 60 and 80% of
the pore volume measured by mercury below 500 Angstroms as
illustrated in FIG. 2.
[0050] Mercury is not capable of measuring pore volumes below about
35 Angstroms and while gas phase adsorption done under very
specific conditions may be able to capture the pore volume in this
range, interference from pores associated with the zeolites
contained in the system precludes accurate measurement of two
different types of pores within this range.
[0051] The matrix is substantially free of pores ranging in
diameter between about 10 .ANG. and about 40 .ANG., i.e., these
pore diameters are substantially absent from the matrix pore
distribution. By "substantially free of" is meant that the
integrated maximum pore volume for the volume of matrix pores
having a diameter between about 10 .ANG. and about 40 .ANG. is less
than about 0.03 cc/g, preferably less than about 0.01 cc/g, more
preferably less than about 0.006 cc/g. It has been discovered that
an adequate indication of the pore volume below 35 Angstroms is
given by the slope of the differential mercury porosimetry as is
indicated in FIG. 3. When lines tangent to the differential mercury
intrusion curve at points below 50 Angstroms intercept the pore
diameter axis with a positive slope at a value not less than 0
Angstroms and most preferentially at not less than 10 Angstroms
when the value of dV/dD is 0.0000, catalysts of this invention give
lower coke yields. The following plots in FIG. 3 for two different
materials of this invention show tangent lines which intercept the
pore diameter at values of 10 and 25 Angstroms respectively.
[0052] For FIG. 3, which is a plot of dV/dD vs. pore diameter, the
maximum volume of the pore volume of pores in the 10-40 .ANG. is
equal to 0.0004 ccHg/(g-Angstrom) times 30 Angstroms divided by
2=0.006 cc/g.
[0053] In an embodiment, the matrix is an amorphous, porous
silica-alumina matrix having pores ranging in size from about 1
.ANG. to about 10 .ANG. and from about 40 .ANG. to about 500 .ANG.,
but substantially free of pores ranging in size from about 10 .ANG.
to about 40 .ANG., provided that in the pore range from 50 .ANG. to
250 .ANG., there is a single maximum in differential pore volume
distribution over the 50 .ANG. to 250 .ANG. range.
[0054] In a related embodiment, the composition's matrix has a
differential pore volume as a function of matrix pore diameter, and
this function has a maximum between 50 .ANG. and 150 .ANG.. The
integrated differential pore volume for matrix pores having a
diameter between about 1 .ANG. and about 10 .ANG. cannot be
distinguished from the pore volume in zeolites typically used in
the catalyst. The integrated maximum pore volume for the volume of
matrix pores having a diameter between 40 .ANG. and about 500 .ANG.
ranges from about 0.06 cc/g to about 0.12 cc/g, and the integrated
pore volume for matrix pores having a diameter between about 10
.ANG. and about 40 .ANG. is less than about 0.03 cc/g, preferably
less than 0.01 cc/g.
[0055] Catalysts of these types are highly selective in the
production of liquids, notably olefins, during fluid catalytic
cracking operations, and coke make is low. The attrition resistance
of these catalysts is quite high, as indicated by the low Davison
Indices ranging from about 1 to about 8, most often and preferably
from about 1 to about 5 measured in terms of the Davison Index. See
"Advances in Fluid Catalytic Cracking," Catalytica, Mountain View,
Calif., Part 1, 1987. p. 355.
[0056] A preferred catalyst particle comprises (a) amorphous,
porous solid acid matrix, such as alumina, silica-alumina,
silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia,
silica-titania, silica-alumina-rare earth and the like; and (b) a
zeolite such as faujasite. The matrix can comprise ternary
compositions, such as silica-alumina-thoria,
silica-alumina-zirconia, magnesia and silica-magnesia-zirconia. The
matrix may also be in the form of a cogel. Silica-alumina is
particularly preferred for the matrix, and can contain about 10 to
40 wt. % alumina. As discussed, promoters can be added.
[0057] In an embodiment, the catalyst's zeolite includes zeolites
which are iso-structural to zeolite Y. These include the
ion-exchanged forms such as the rare-earth hydrogen and ultrastable
(USY) form. The zeolite may range in crystallite size from about
0.1 to 10 microns, preferably from about 0.3 to 3 microns. The
relative concentrations of zeolite component and matrix on an
anhydrous basis may vary widely, with the zeolite content ranging
from about 1 to 100, preferably 10 to 99, more usually from about
10 to 80, percent by weight of the dry composite.
[0058] The amount of zeolite component in the catalyst particle
will generally range from about 1 to about 60 wt. %, preferably
from about 5 to about 60 wt. %, and more preferably from about 10
to about 50 wt. %, based on the total weight of the catalyst. As
discussed, the catalyst is typically in the form of a catalyst
particle contained in a composite. When in the form of a particle,
the catalyst particle size will range from about 10 to 300 microns
in diameter, with an average particle diameter of about 60 microns.
The surface area of the matrix material after artificial
deactivation in steam at pressures higher than in commercial
operations (i.e. at pressures of ca. 1 atmosphere) will be about
<350 m.sup.2/g, preferably 50 to 200 m.sup.2/g, more preferably
from about 50 to 100 m.sup.2/g. While the surface area of the
catalysts will be dependent on such things as type and amount of
zeolite and matrix components used, it will usually be less than
about 500 m.sup.2/g, preferably from about 50 to 300 m.sup.2/g,
more preferably from about 50 to 250 m.sup.2/g, and most preferably
from about 100 to 250 m.sup.2/g.
[0059] Another preferred catalyst contains a mixture of zeolite Y
and a second zeolite such as zeolite beta. The first and second
zeolite may be on the same catalyst particle, on different
particles, or some combination thereof. Zeolite amount and matrix
type and properties are as set forth in the description of the Y
zeolite catalyst. In a related embodiment the second zeolite is a
shape-selective zeolite species such as ZSM-5. Alternatively, the
shape-selective zeolite can be used in the catalyst without the
first zeolite. The Y zeolite, shape-selective zeolite, or both can
be on the same catalyst particle, on different particles, or some
combination thereof.
[0060] Shape-selective zeolite species useful in the invention
include medium pore size zeolites generally having a pore size from
about 0.5 nm, to about 0.7 nm. Such zeolites include, for example,
MFI, MFS, MEL, MTW, EUO, MTT, HEU, FER, and TON structure type
zeolites (IUPAC Commission of Zeolite Nomenclature). Non-limiting
examples of such medium pore size zeolites, include ZSM-5, ZSM-12,
ZSM-22, ZSM-23, ZSM-34, ZSM-35, ZSM-38, ZSM-48, ZSM-50, silicalite,
and silicalite 2. The most preferred is ZSM-5, which is described
in U.S. Pat. Nos. 3,702,886 and 3,770,614. ZSM-11 is described in
U.S. Pat. No. 3,709,979; ZSM-12 in U.S. Pat. No. 3,832,449; ZSM-21
and ZSM-38 in U.S. Pat. No. 3,948,758; ZSM-23 in U.S. Pat. No.
4,076,842; and ZSM-35 in U.S. Pat. No. 4,016,245.
[0061] While the shape-selective species has been described in
terms of zeolite, it can be a shape-selective (i.e., medium pore
size) molecular sieve. In an embodiment, suitable medium pore size
molecular sieve includes the silicoaluminophosphates (SAPO), such
as SAPO-4 and SAPO-11 which is described in U.S. Pat. No.
4,440,871; chromium silicates; gallium silicates; iron silicates;
aluminum phosphates (ALPO), such as ALPO-11 described in U.S. Pat.
No. 4,310,440; titanium aluminosilicates (TASO), such as TASO-45
described in EP-A No. 229,295; boron silicates, described in U.S.
Pat. No. 4,254,297; titanium aluminophosphates (TAPO), such as
TAPO-11 described in U.S. Pat. No. 4,500,651; and iron
aluminosilicates.
[0062] The large pore (e.g., zeolite Y) and shape-selective
zeolites in the catalytic species can include "crystalline
admixtures" which are thought to be the result of faults occurring
within the crystal or crystalline area during the synthesis of the
zeolites. Examples of crystalline admixtures of ZSM-5 and ZSM-11
are, for example, disclosed in U.S. Pat. No. 4,229,424. The
crystalline admixtures are themselves medium pore, i.e.,
shape-selective, size zeolites and are not to be confused with
physical admixtures of zeolites in which distinct crystals of
crystallites of different zeolites are physically present in the
same catalyst composite or hydrothermal reaction mixtures.
(II) Process for the Preparation of the Catalytic Cracking
Catalyst
A. Preparation of Starting Material, or Catalyst Precursor
Material
[0063] The catalyst of this invention comprises a catalytically
active molecular sieve dispersed in a mesoporous inorganic matrix.
In an embodiment, a crystalline aluminosilicate zeolite, or
zeolite, suitably a USY or high silica USY zeolite, is admixed,
preferably with water, urea compound, a phosphate, a clay, e.g.,
kaolin and an aluminum hydroxide, e.g. gibbsite, and these solids
slurried. An aqueous silica solution, e.g., a silica sol (a binder
colloid), is added to the aqueous slurry. The sol should not be
allowed to gel. The slurry of blended components is dried,
ion-exchanged to remove sodium, calcined, and then steamed to form
the catalyst.
[0064] A catalyst precursor can be made by: [0065] (a) combining
molecular sieve with (i) an aqueous solution containing alkali
silicate, e.g., sodium silicate; (ii) urea; (iii) a phosphate, such
as alkali metal phosphate, ammonium phosphate, or both; and (iv) a
clay component such as bentonite, kaolin, or both to form a slurry;
[0066] (b) spray drying the slurry; and [0067] (c) removing sodium
in an ion exchange operation.
[0068] Gibbsite may be added to the catalyst precursor as a
component in part (a) above. The order of addition of the
components (a) may be varied. A catalyst can be made from the
precursor by additional ion exchange, if necessary to further
remove sodium, and then calcining and steaming. The calcining and
steaming can be conventional. Calcining can take place at
temperatures in the range 250 to 850.degree. C. The time of
calcining depends on the temperature chosen but is typically
greater than 1 hr. Steaming is preferably done for about 4 to 48
hours at temperatures of about 650 to 850.degree. C.
[0069] The matrix, after steaming, can be characterized by pore
size distribution, as measured by mercury porosimetry (Structure of
Metallic Catalysts, J. R. Anderson. 1975, Chapter 6, Pages 384-385;
theta=140 degrees, Hg surface tension equals 474 ergs/cm.sup.2).
Under the IUPAC, microporous refers to pores in the 2 to 20
.ANG..
[0070] The urea compound has the general formula
##STR00003##
where R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are individually H or
C.sub.1 to C.sub.4 alkyl, preferably H and X is sulfur or oxygen,
preferably oxygen. The preferred urea compound is urea, i.e.,
H.sub.2NCONH.sub.2.
[0071] Urea may be added to the slurry in an amount which is
stoichiometric based on the reaction of urea with the sodium in
sodium silicate to form sodium carbonate and ammonia. The amount of
urea may vary from 0.8 to 1.2 times the stoichiometric amount based
on the amount of sodium silicate. The addition of urea to the
slurry generally leads to an increase in the pore volume of the
catalysts according to the invention.
[0072] The phosphates are water soluble phosphate salts, typically
sodium or ammonium phosphate salt, preferably sodium phosphate. The
salts may be primary, secondary or tertiary salts such as
NaH.sub.2PO.sub.4, (NH.sub.4).sub.2HPO.sub.4,
(NH.sub.4).sub.3PO.sub.4, Na.sub.2HPO.sub.4, Na.sub.3 PO.sub.4, as
well as polyphosphates such as (NaPO.sub.3).sub.n,
Na.sub.4P.sub.2O.sub.7 and the like. The amount of phosphate is
preferably less than that required to react with all the aluminum
present.
[0073] The clays used in the slurry may be kaolin, bentonite,
attapulgite, montmorillonite, hectorite and pyrophyllite. The
preferred clay is kaolin or bentonite, especially kaolin. In an
embodiment, zeolite, clay, phosphate, sodium silicate, at least one
aluminum hydroxide or aluminum oxyhydroxide and urea are added
together or in sequence, in any order, and slurried at ambient
temperature in a limited, controlled, and amount of water. In
general, it has been found that the weight ratio of water:solids in
the slurry can range between about 1:1 to about 4:1, preferably
between about 1.5:1 to about 3:1. A weight ratio of water:solids
approximating about 2:1 has been found highly successful in forming
high quality catalysts. When the weight ratio of water:solids is
less than about 1:1, the viscosity of the slurry is too high to
spray dry, while weight ratios of water:solids exceeding about 4:1
may lead under some circumstances to a loss in the
attrition-resistance of the catalyst. The pH of the slurry at this
time ranges between about 10 and about 12 in order to avoid
gellation of the silica sol. In an embodiment, the silica in the
sol ranges from about 1.0 nm (nanometers) to about 22.0 nm,
preferably from about 1.5 nm to about 15.0 nm average diameter.
Silica sols are described in "The Chemistry of Silica: Solubility,
Polymerization, Colloid and Surface Properties, and Biochemistry,"
by Ralph K. Iler. A Wiley Interscience Publication, 1979. Water may
be added to the sodium silicate sol to maintain the water:solids
weight ratio between about 1:1 and 3:1. The preferred solids
contents are between 28 and 45 wt. %, based on catalyst precursor.
The density of the slurry, on completing the addition of the
starting materials, preferably ranges from about 1.2 to 1.4, and
more preferably from about 1.20 to 1.35. Preferably also, the
viscosity of the slurry at this time ranges from about 60 to 300
cPs, more preferably from about 80 to about 200 cPs at 22.degree.
C.
[0074] After blending zeolite, clay(s), at least one aluminum
hydroxide or aluminum oxyhydroxide, urea, sodium silicate, and
phosphate, with adjustment of the water content, density, and
preferably also the pH and viscosity, the slurry can be dried in
conventional process equipment, e.g., a spray drier, to form
catalyst precursor.
[0075] In an embodiment, the slurry, preferably at/or below ambient
temperature is conducted to a drier, preferably a spray drier, at a
temperature sufficient to remove the water and form microspheres of
average particle diameter ranging from about 10 microns to about
200 microns, preferably from about 60 microns to about 100 microns.
The temperature is sufficiently high to dry the slurry and form a
rigid structure, but insufficiently high as to cause alkali metal
components (e.g., sodium from the sodium silicate) to be occluded
within the zeolite and prevent it from being washed, ion-exchanged,
and removed from the zeolite. Typically, the slurry is fed to a
drier, preferably a spray drier at an average inlet temperature
ranging from about 250.degree. C. to about 500.degree. C., and an
outlet temperature ranging from about 125.degree. C. to about
225.degree. C.
[0076] Following drying, catalyst precursor, preferably in the form
of a powder of microspherical particles, are washed with deionized
water, e.g., between ambient temperature and 100.degree. C. The
washed precursor is then ion-exchanged for a time sufficient to
remove the alkali metal, e.g., sodium, from the zeolite. In an
embodiment, one or more of sulfuric acid, aluminum sulfate, and
ammonium sulfate, are used. Preferably, aluminum sulfate hydrate
and ammonium sulfate are used. Preferably, a stoichiometric amount
of aluminum sulfate hydrate to ammonium sulfate is used, based on
the amount of sodium present. Preferably, a 2/3 atomic ratio of
Al.sup.3+/NH.sub.4.sup.30 in sulfate salts is used. Data in Tables
2.3 and 2.5 following indicate that the optimum
Al.sup.3+/NH.sub.4.sup.+ molar ratio lies at this atomic ratio for
the removal of sodium from the catalyst precursor.
[0077] When necessary, a second ion-exchange step can be used to
further lower the amount of sodium. The ion-exchanged particles are
generally again washed, e.g., between ambient temperature and
100.degree. C. The zeolite portion of the catalyst, after
ion-exchange, and washing, typically contains less than about 0.4
percent alkali metal, based on the weight of the catalyst. It is
believed that a small amount of aluminum from the aluminum sulfate
hydrate is incorporated into the catalyst during ion exchange.
[0078] While not wishing to be bound by any theory or model, the
presence of phosphate in the slurry is believed to affect the
matrix microporosity. It is believed that the phosphate interacts
with aluminum species in the slurry to make aluminum phosphate.
Since aluminum phosphate has an isoelectric point similar to
silica's, particles in the slurry appear to have a similar charge
and agglomeration is avoided. Agglomeration, it is believed, would
lead to a degradation in the microporosity characteristics of the
catalyst. Other factors, which are believed to lead to the unusual
pore distribution of the catalysts of the invention, relate to the
use of sodium silicate in the binder system in combination with
urea as the directing compound.
(III) The Catalytic Cracking Process
[0079] In yet another embodiment the invention relates to a
catalytic cracking process. The catalytic cracking process may be
carried out in a fixed bed, moving bed, ebullated bed, slurry,
transfer line (dispersed phase) or fluidized bed operation.
Suitable hydrocarbon feedstocks (i.e., the primary feed) for the
catalytic cracking process described herein include natural and
synthetic hydrocarbonaceous oils boiling in the range of about
430.degree. F. to about 1050.degree. F., such as gas oil; heavy
hydrocarbonaceous oils comprising materials boiling above
1050.degree. F.; heavy and reduced petroleum crude oil; petroleum
atmospheric distillation bottoms; petroleum vacuum distillation
bottoms; pitch, asphalt, bitumen, other heavy hydrocarbon residues;
tar sand oils; shale oil; liquid products derived from coal
liquefaction processes, naphtha, and mixtures thereof.
[0080] In an embodiment, the catalytic cracking process is
performed in one or more FCC process units. Each unit comprises a
reaction zone, usually a riser reaction zone, a stripping zone, a
catalyst regeneration zone, and at least one separation zone. In an
FCC process, the feedstock is conducted to and injected into the
reaction zone wherein the primary feed contacts a flowing source of
hot, regenerated catalyst. The hot catalyst vaporizes and cracks
the feed at a temperature from about 450.degree. C. to 650.degree.
C., preferably from about 500.degree. C. to 600.degree. C. The
cracking reaction deposits carbonaceous hydrocarbons, or coke, on
the catalyst, thereby deactivating the catalyst. The cracked
products may be separated from the coked catalyst and a portion of
the cracked products may be conducted to a separation zone such as
a fractionator. Fractions such as a naphtha fraction can be
separated from the cracked products in the separation zone and
conducted away from the process.
[0081] FCC process conditions in the riser reactor's reaction zone
include temperatures from about 450.degree. C. to about 700.degree.
C., hydrocarbon partial pressures from about 10 to 40 psia (69 to
276 kPa), preferably from about 20 to 35 psia (138 to 241 kPa); and
a catalyst to primary feed (wt/wt) ratio from about 3 to 100, where
catalyst weight is total weight of the catalyst composite. The
total pressure is from atmospheric to about 45 psig (411 kPa).
Though not required, it is also preferred that steam be
concurrently introduced with the feedstock into the reaction zone,
with the steam comprising up to about 50 wt. %, preferably about 2
to about 10 wt. % of the primary feed. Also, it is preferred that
the feedstock's residence time in the reaction zone be less than
about 20 seconds, preferably from about 0.1 to about 20 seconds,
and more preferably from about 1 to about 5 seconds.
[0082] The present process and catalyst provides both economic and
technical advantages over state of the art commercial FCC
catalysts. There are three major binders currently used to make FCC
catalysts. These are the acidified silica sol binder, aluminum
chlorhydrol, and peptized alumina. These three binding systems are
acidic, and this acidity can adversely affect the physical
properties of acid susceptible active materials. Previous
mesoporous catalysts based on silica used Ludox.RTM. as the silica
source. This is a more expensive ingredient than basic sodium
silicate.
[0083] In the present process, sodium silicate (a basic system) can
successfully bind FCC catalysts. Furthermore, the incorporation of
urea with sodium silicate into the spray drier feed produces
catalysts which are more mesoporous and more selective than
catalysts which have not been so treated. Neutralization of the
sodium contained in the sodium silicate is done with the ammonium
salt of an acid which is stronger than silicic acid. The cheapest
acid source is sulfuric acid. Neutralization with sulfuric acid
requires careful control or gellation will occur with consequent
loss in catalyst strength and integrity. Carbonic acid is a
somewhat stronger acid than silicic acid and as such can also be
used to neutralize sodium silicate. However, neutralization with
carbonic acid leads to gellation because the carbonic acid forms a
silica sol at a pH at which gellation readily occurs. Urea is the
anhydride of diammonium carbonate and hydrolyzes slowly to form
ammonia and sodium carbonate in basic solutions. Incorporation of
urea in the binder system allows reaction to take place after
drying so that a silica gel does not form prior to drying leading
to weaker products. Incorporation of urea also may also assist in
the formation of the present mesoporous pore structures, which
improve product selectivity. Alkali metal salts of phosphate seem
to be especially efficacious in forming pore structure, which leads
to improved selectivity to products other than coke. Comparative
Examples 1, 2, and 3 following show that materials made with
ammonium phosphate fail to produce beneficial product
selectivities. FIGS. 4 and 5 show the selectivity to products other
than coke on conversion to 221.degree. C.- is poorer for materials
made with ammonium phosphate, viz. materials labeled "1.11",
"2.11", "3.11", "1.12", "2.12", and "3.12", than for those made
with alkali metal phosphates, viz. materials labeled "4.11" and
"5.11". FIG. 8 shows the porosity in the region below 50 Angstroms
is larger for the materials made with ammonium phosphate.
[0084] The following examples are presented to illustrate the
invention and should not be considered limiting in any way.
COMPARATIVE EXAMPLE 1
No Urea, Diammonium Hydrogen Phosphate
[0085] This is a comparative (base case) example using sodium
silicate as the silica source in the binder but without adding urea
during catalyst preparation.
[0086] To 3000 g of water in a 2-gallon plastic bucket was added:
1319.3 g of zeolite Z-14 G NaUSY, 12.5 g diammonium hydrogen
phosphate, 728 g of Hydrite UF kaolin clay, and 560 g of Spacerite
S-11 Gibbsite. The resulting mixture was stirred 30 min with a
Cowles mixer.
[0087] 1742.2 g of "N" brand Sodium Silicate was diluted with 1700
g of deionized water and added to the water/zeolite/diammonium
hydrogen phosphate/clay slurry and then colloid milled. The pH of
colloid-milled slurry was 10.8 at 22.degree. C. The viscosity of
the slurry was 188 cPs at 100 rpm, and the density of the slurry
was 1.322 g/cc.
[0088] The slurry was spray dried in a Bowen #1 Tower Spray Drier
(rated at 7/35 kg/hr with an airflow of 250 cfm at 80.degree. C.)
with an exit temperature of 121.degree. C.
787 g of solids with 50% above 74.4 microns were collected from the
Main Tower Pot. The properties of the slurry and product are
summarized in Table 1.1.
TABLE-US-00001 TABLE 1.1 Base Case (No Urea) Total Dried Product
Desired 2500 Wt % in Catalytic Na Water Solids Prod Weights Solids
Water Na.sub.2O (moles) (g) (g) Zeolite 40 1319.26 0.758 0.22 0.03
1.72 290.2 1029.0 "N" Sodium Silicate 20 1742.16 0.287 0.624 0.089
5.00 1087.1 655.1 Hydrite .RTM. UF 25 728.44 0.858 0.142 0 103.4
625.0 Spacerite .RTM. S-11 Gibbsite 15 559.70 0.67 0.33 184.7 375.0
Wgt % solids (must be 100) 100 4563.74
[0089] To ion-exchange this material, the following solution of
ammonium sulfate and aluminum sulfate was used:
[0090] 360 g Al.sub.2(SO.sub.4).sub.3.16H.sub.2O was dissolved in
2040 g DI water
[0091] 106.2 g (NH.sub.4).sub.2SO.sub.4 was dissolved in 2294 g DI
water.
[0092] To 120 g of the spray drier product was added 200 g of the
Al.sub.2(SO.sub.4).sub.3.16H.sub.2O solution and 200 g of the
(NH.sub.4).sub.2SO.sub.4 solution. This mixture was shaken at
80.degree. C. in a shaker bath @ 260 rpm for 1 hour, cooled and
then washed 3.times. with 500 g of DI (deionized) water at
80.degree. C. on the filter and air dried. The product from this
first ion exchange, Example 1.1, was analyzed. The remaining sample
was added to 200 g of the dilute aluminum sulfate solution and then
200 g of the dilute ammonium sulfate solution was added. This was
shaken for 1 hour at 80.degree. C. at 260 rpm, washed 3.times.500 g
of deionized water, dried at 120.degree. C. for 2 hours and
calcined to give Example 1.2. Table 1.2 contains the analyses for
these samples.
TABLE-US-00002 TABLE 1.2 Example 1.1 Example 1.2 SiO2 (wt %) 62.04
63.39 Al2O3 (wt %) 36.99 36.29 Na (wt %) 0.72 0.24
COMPARATIVE EXAMPLE 2
Urea, Diammonium Hydrogen Phosphate
[0093] This is a further comparative example. Unlike standard
commercial FCC catalysts, the preparation takes place in a basic
environment. It is assumed that 1 mole of urea neutralizes 2 moles
of sodium by decomposing to form ammonium silicate and sodium
carbonate.
[0094] To 2500 g of water in a 2 gallon plastic bucket was added:
1319.3 g of zeolite Z-14 G NaUSY, 12.5 g diammonium hydrogen
phosphate, 728 g of Hydrite UF kaolin clay, and 560 g of Spacerite
S-11 Gibbsite. The resulting mixture was stirred 30 min with a
Cowles mixer.
[0095] 1742.2 g of "N" brand Sodium Silicate was diluted with 2275
g of deionized water and added to the water/zeolite/diammonium
hydrogen phosphate/clay slurry and then colloid milled. The pH of
colloid-milled slurry was 11.0 at 21.degree. C. The viscosity of
the slurry was 247 cPs at 100 rpm. The slurry was spray dried in a
Bowen #1 Tower Spray Drier (rated at 7/35 kg/hr with an airflow of
250 cfm at 80.degree. C.) with an exit temperature of 145.degree.
C.
[0096] 1436 g of solids was collected from the Main Tower Pot. The
composition of the slurry and product are summarized in Table
2.1.
TABLE-US-00003 TABLE 2.1 Total Dried Product Desired 2500 Wt % in
Catalytic Na Prod Weights Solids Water Na2O (moles) Water (g)
Solids (g) Zeolite 40 1319.26 0.758 0.22 0.03 1.72 290.2 1029.0 "N"
Sodium Silicate 20 1742.16 0.287 0.624 0.089 5.00 1087.1 655.1
Hydrite .RTM. UF kaolin 25 728.44 0.858 0.142 0 103.4 625.0
Diammonium hydrogen phosphate 12.50 0.0 12.5 Spacerite .RTM. S-11
Gibbsite 15 559.70 0.67 0.33 184.7 375.0 Urea to match Na 201.67 0
0 201.7 Wt % solids (must be 100!) 100 4563.74 Wgt Fraction Solids
in Spray Drier Feed 0.31 Total Water to be added 4775.07
[0097] 52.4 g H.sub.2SO.sub.4 was dissolved in 1548 g of DI water
to make a dilute sulfuric acid solution.
[0098] 270 g Al.sub.2(SO.sub.4).sub.3.16H.sub.2O was dissolved in
1530 g of DI water to make a dilute aluminum sulfate solution with
4.5.times.10.sup.-4 moles Al.sup.3+/g solution.
[0099] 70.8 g (NH.sub.4).sub.2SO.sub.4 was dissolved in 1529.2 g of
DI water to make a dilute ammonium sulfate solution with
6.7.times.10.sup.-4 moles NH.sub.4.sup.+/g solution.
[0100] To 100 g of spray drier product was added solutions
according to Table 2.2.
TABLE-US-00004 TABLE 2.2 Example 2.1 Example 2.2 Example 2.3
Example 2.4 Example 2.5 200 g dilute 100 g dilute 200 g dilute 100
g dilute 200 g dilute sulfuric acid sulfuric acid aluminum aluminum
ammonium solution solution/ sulfate sulfate sulfate 100 g dilute
solution solution/ solution aluminum 100 g dilute sulfate ammonium
solution sulfate solution
[0101] These were shaken at 80.degree. C. for 1 hour; filtered,
washed 3.times. with 400 g of DI water at 80.degree. C. for 0.5
hours on the shaker bath and warmed to 120.degree. C. at 1.degree.
C./min and dried at 120.degree. C., 6 h.
[0102] The elemental analyses on these samples are contained in
Table 2.3.
TABLE-US-00005 TABLE 2.3 Exam- Exam- Exam- Example 2.1 Example 2.2
ple 2.3 ple 2.4 ple 2.5 SiO2 (wt %) 64.82 63.67 63.22 62.00 63.01
Al2O3 (wt %) 33.88 35.34 36.00 37.35 34.84 Na (wt %) 0.96 0.74 0.57
0.49 1.59
[0103] Note that the Al.sub.2O.sub.3/SiO.sub.2 weight ratio is 0.60
with example 2.4, the NH.sub.4.sup.+/Al.sup.3+ preparation, and
only 0.55 with example 2.5, the NH.sub.4.sup.+ preparation. This
indicates that the system is incorporating roughly 0.60/0.55-1=9.1%
more alumina or that ca. 0.091.times.35=3.2% alumina (1.6 g
alumina) has been added to the original weight of the catalyst.
This alumina comes from the 100/1800.times.270.times.102/666=2.3 g
in the exchange solution.
[0104] To further demonstrate the specific nature of this
interaction the spray dried product of Example 2 was exchanged in a
second series in which only the dilute aluminum sulfate solution
and the dilute ammonium sulfate solution were used as outlined in
Table 2.4. To 50 g of spray drier product was added solutions
according to Table 2.4:
TABLE-US-00006 TABLE 2.4 Example 2.6 Example 2.7 Example 2.8 150 g
dilute aluminum 100 g dilute aluminum 50 g dilute aluminum sulfate
solution/ sulfate solution/ sulfate solution/ 50 g dilute ammonium
100 g dilute ammonium 150 g dilute sulfate solution sulfate
solution ammonium sulfate solution
[0105] These were shaken at 80.degree. C. for 1 hour; filtered,
washed 3.times. with 400 g of DI water at 80.degree. C. for 0.5
hours on the shaker bath and warmed to 120.degree. C. at 1.degree.
C./min and dried at 120.degree. C., for 6 hours. Table 2.5 clearly
shows that for these sodium silicate bound catalysts, sodium
removal is most efficient with a combination of an aluminum salt
and an ammonium salt in a specific ratio, namely, 2 moles of Al/3
moles of ammonia.
TABLE-US-00007 TABLE 2.5 Example 2.6 Example 2.7 Example 2.8 SiO2
(wt %) 63.29 62.24 61.89 Al2O3 (wt %) 36.04 37.14 37.11 Na (wt %)
0.50 0.46 0.74
[0106] To demonstrate that successive ion exchanges complete the
removal of sodium from the catalyst, 120 g of the spray drier
product of Example 2 was added to 200 g of the dilute aluminum
sulfate solution and then 200 g of the dilute ammonium sulfate
solution was added. This was shaken for 1 hour at 80.degree. C. at
260 rpm, washed 3.times.500 g of deionized water, dried at
120.degree. C. for 4 hours to give Example 2.9. The remaining
sample was added to 200 g of the dilute aluminum sulfate solution
and then 200 g of the dilute ammonium sulfate solution was added.
This was shaken for 1 hour at 80.degree. C. at 260 rpm, washed
3.times.500 g of deionized water, dried at 120.degree. C. for 2
hours and calcined to give Example 2.10. The volatile free analyses
for examples 1.9 and 1.10 are contained in Table 2.6.
TABLE-US-00008 TABLE 2.6 Example 2.9 Example 2.10 SiO2 (wt %) 61.55
62.68 Al2O3 (wt %) 37.54 37.01 Na (wt %) 0.68 0.23
COMPARATIVE EXAMPLE 3
2.times. Urea, Diammonium Hydrogen Phosphate
[0107] This comparative example illustrates the removal of sodium
by ion exchange from the product from the spray drier which is
prepared as follows. To 3000 g of water in a 2-gallon plastic
bucket was added 1319.3 g of zeolite NaUSY, 12.5 diammonium
hydrogen phosphate, 728 g of Hydrite UF.RTM. kaolin clay, 403.5 g
of urea 560 g of Spacerite.RTM. S-11 Gibbsite. The resulting
mixture was stirred 30 minutes with a Cowles mixer.
[0108] 1742.2 g of "N".RTM. brand Sodium Silicate was diluted with
1700 g of deionized water and added to the water/zeolite/diammonium
hydrogen phosphate/clay slurry and then colloid milled. The pH of
colloid-milled slurry was 10.79 at 17.degree. C. The viscosity of
the slurry was 199 cP at 100 rpm, and the density of the slurry was
1.293 g/cc.
[0109] The slurry as spray dried in a Bowen #1 Tower Spray Drier
(rated at 7/35 kg/hr with an airflow of 250 cfm at 80.degree. C.)
with an exit temperature of 160.degree. C. After drying, collection
and weighing of the solids from the bottom of the main tower and
the solids from the bottom of the cyclone yielded 1129 g of solids
with 50% above 66.0 microns. The nominal slurry and product
compositions are shown in Table 3.1.
TABLE-US-00009 TABLE 3.1 Total Dried Product Desired 2500 Wt % in
Catalytic Na Water Solids Prod Weights Solids Water Na.sub.2O
(moles) (g) (g) Zeolite 40 1319.26 0.758 0.22 0.03 1.72 290.2
1029.0 "N" Sodium Silicate 20 1742.16 0.287 0.624 0.089 5.00 1087.1
655.1 Hydrite UF .RTM. kaolin 25 728.44 0.858 0.142 0 103.4 625.0
Spacerite S-11 .RTM. Gibbsite 15 559.70 0.67 0.33 184.7 375.0 Urea
404 0 0 201.7 Wt % solids (must be 100) 100 4563.74
[0110] 120 g of the spray drier product of Example 3 was added to
200 g of the dilute aluminum sulfate solution and then 200 g of the
dilute ammonium sulfate solution was added. This was shaken for 1
hour at 80.degree. C. at 260 rpm, washed 3.times.500 g of deionized
water, dried at 120.degree. C. for 4 hours to give Example 3.1. The
remaining sample was added to 200 g of the dilute aluminum sulfate
solution and then 200 g of the dilute ammonium sulfate solution was
added. This was shaken for 1 hour at 80.degree. C. at 260 rpm,
washed 3.times.500 g of deionized water, dried at 120.degree. C.
for 2 hours and calcined to give Example 3.2. The volatile free
analyses for examples 3.1 and 3.2 are contained in Table 3.2.
TABLE-US-00010 TABLE 3.2 Example 3.1 Example 3.2 SiO2 (wt %) 61.46
62.04 Al2O3 (wt %) 37.73 37.69 Na (wt %) 0.60 0.20
EXAMPLE 4
Urea, Disodium Hydrogen Phosphate
[0111] This example is a catalyst of this invention. In its
preparation, an alkali phosphate salt, urea, and sodium silicate
were employed to make a spray dried product which was ion-exchanged
using the optimum mix of aluminum and ammonium salts to make a
finished catalyst. When this catalyst was then deactivated using
steam, it had a pore structure according to the catalyst and
process of the invention. To 3000 g of water in a 2 gallon plastic
bucket was added: 13.4 g disodium hydrogen phosphate, 200 g of
urea, 373 g Alcoa C-33 gibbsite, 1319.3 g of zeolite NaUSY, 874 g
of Hydrite UF kaolin clay. The resulting mixture was stirred with a
Cowles mixer until it flowed smoothly.
[0112] 1742.2 g of "N" brand Sodium Silicate was diluted with 2400
g of deionized water and to this was added the water/disodium
hydrogenphosphate/urea/gibbsite/zeolite/clay slurry. This slurry
was then colloid milled twice. The pH of colloid-milled slurry was
10.8 at 22.degree. C. The viscosity of the slurry was 188 cPs at
100 rpm, and the density of the slurry was 1.288 g/cc. The slurry
was spray dried in a Bowen #1 Tower Spray Drier (rated at 7/35
kg/hr with an airflow of 50 cfm at 80.degree. C.) with an exit
temperature of 150.degree. C. 939 g of solids were collected from
the Main Tower Pot.
[0113] 120 g of the spray drier product of Example 4 was added to
200 g of the dilute aluminum sulfate solution and then 200 g of the
dilute ammonium sulfate solution was added. This was shaken for 1
hour at 80.degree. C. at 260 rpm, washed 3.times.200 g of deionized
water. The wet cake was added to 200 g of the dilute aluminum
sulfate solution and then 200 g of the dilute ammonium sulfate
solution was added. This was shaken for 1 hour at 80.degree. C. at
260 rpm, washed 3.times.200 g of deionized water, dried at
150.degree. C. for 1 hour and calcined at 760.degree. C. for 1 hour
to give Example 4.1. Table 4.1 contains the analyses:
TABLE-US-00011 TABLE 4.1 Example 4.1 SiO2 (wt %) 61.22 Al2O3 (wt %)
38.38 Na (wt %) 0.29
EXAMPLE 5
Urea, Tetrasodium Pyrophosphate
[0114] This example is a catalyst according to the catalyst and
process of the invention. To 3000 g of water in a 2-gallon plastic
bucket was added: 21.0 g tetrasodium pyrophosphate, 200 g of urea,
373 g Alcoa C-33 gibbsite, 1319.3 g of zeolite NaUSY, 874 g of
Hydrite UF kaolin clay. The resulting mixture was stirred with a
Cowles mixer until it flowed smoothly.
[0115] 1742.2 g of "N" brand Sodium Silicate was diluted with 2400
g of deionized water and to this was added the water/tetrasodium
pyrophosphate/urea/gibbsite/zeolite/clay slurry. This slurry was
then colloid milled twice. The pH of colloid-milled slurry was 11.0
at 22.degree. C. The viscosity of the slurry was 189 cPs at 100
rpm, and the density of the slurry was 1.26 g/cc. The slurry as
spray dried in a Bowen #1 Tower Spray Drier (rated at 7/35 kg/hr
with an airflow of 250 cfm at 80.degree. C.) with an exit
temperature of 150.degree. C. 980 g of solids were collected from
the Main Tower Pot.
[0116] 120 g of the spray drier product of Example 5 was added to
200 g of the dilute aluminum sulfate solution and then 200 g of the
dilute ammonium sulfate solution was added. This was shaken for 1
hour at 80.degree. C. at 260 rpm, and washed 3.times.200 g of
deionized water. The wet cake was added to 200 g of the dilute
aluminum sulfate solution and then 200 g of the dilute ammonium
sulfate solution was added. This was shaken for 1 hour at
80.degree. C. at 260 rpm, washed 3.times.200 g of deionized water,
dried at 150.degree. C. for 1 hour and calcined at 760.degree. C.
for 1 hour to give Example 5.1. Table 5.1 contains the
analyses:
TABLE-US-00012 TABLE 5.1 Example 5.1 SiO2 (wt %) 62.28 Al2O3 (wt %)
37.32 Na (wt %) 0.29
EXAMPLE 6
[0117] Examples 1, 2, 3, 4, and 5 were calcined at 760.degree. C.
Examples 1, 2, and 3 were then steamed at a temperature of
760.degree. C. for 16 hours to give Examples 1.11, 2.11, and 3.11
in Table 6, then at a temperature of 788.degree. C. for 16 hours to
produce examples 1.12, 2.12, and 3.12 respectively, in Table 6.
Examples 4 and 5 were steamed at 788.degree. C., 16 hours to
produce the catalysts 4.11 and 5.11 for evaluation in an ACE FCC.
An ACE unit is a commercially available unit made for FCC
laboratory evaluations and is manufactured by Xytel Co., Elk Grove
Village, Ill. The properties of the steamed catalysts are set forth
in Table 6.
TABLE-US-00013 TABLE 6 Total Normal- Surface Zeolite Matrix Normal-
ized Normal- Area Surface Surface ized Alu- ized (BET) Area Area
Silica mina Na m2/g (m2/g) (m2/g) (wt %) (wt %) (wt %) Example 1.11
205.3 150.0 55.4 62.57 37.11 0.24 Example 2.11 213.6 155.8 57.7
62.53 37.17 0.22 Example 3.11 225.6 166.4 59.2 62.18 37.55 0.20
Example 1.12 144.0 102.0 42.1 Example 2.12 155.0 112.8 42.69
Example 3.12 151.3 114.9 36.37 Example 4.11 180.2 143.6 36.6 62.15
37.48 0.28 Example 5.11 184.0 147.3 36.8 58.72 40.87 0.31
[0118] Examples 1.11, 2.11, 3.11, 1.12, 2.12, and 3.12 as
comparison catalysts and 4.11 and 5.11 of this invention were then
evaluated by injecting a vacuum gas oil with the following physical
properties over the catalyst in a fixed fluidized bed reactor whose
operations are described in the open literature. The conditions
under which the unit operated follow:
TABLE-US-00014 REACTOR INIT TEMP F. 1030 REACTOR MIN TEMP F. 1010
FLUID BED REGEN TEMP F. 1250 CAT STRIP TIME SEC 330-610 s LIQ STRIP
TIME SEC 350-1050 s N.sub.2 DURING RXN TOP FEED SCCM 20 N.sub.2
DURING RXN TOP FLUID SCCM 20 N.sub.2 DURING RXN BTM FLUID SCCM 100
N.sub.2 DURING RXN TOT PURGE SCCM 41 N.sub.2 DURING REM LIQ STRIP
SCCM 100 CAT TO OIL RATIO WT/WT 3.0-9.0 CATALYST CHARGE WT GMS 9.0
OIL CHARGE WT GMS 1-3
[0119] The feedstock used was a Gulf Coast vacuum gas oil having
the following properties:
TABLE-US-00015 GRAVITY, API 23.9 CARBON 85.81 HYDROGEN 12.55
NITROGEN, SYRINGE INLET (ppm) 909 N (basic) wppm 313 SULFUR IN OILS
0.968 Ni (wppm) 0.42 V (wppm) 0.37 CARBON RESIDUE (MICRO) 0.22
TEMP. @ 5.0 WT % 658.4 TEMP. @ 10.0 WT % 701.7 TEMP. @ 20.0 WT %
755.7 TEMP. @ 30.0 WT % 795.7 TEMP. @ 40.0 WT % 829 TEMP. @ 50.0 WT
% 860.1 TEMP. @ 60.0 WT % 892.9 TEMP. @ 70.0 WT % 931.2 TEMP. @
80.0 WT % 970.7 TEMP. @ 90.0 WT % 1014 TEMP. @ 95.0 WT % 1033.1
SATS 55.4-56.56 1 RING AROM 20.4-20.9 2 RING AROM 11.7-11.1 3 RING
AROM 5.7-5.5 4 RING AROM 3.1-3.1 POLARS 3.8-2.9 SATS (UV CORES)
0.04 1 RING AROM (UV CORES) 3.3-3.0 2 RING AROM (UV CORES) 4.4-3.7
3 RING AROM (UV CORES) 3.4-2.9 4 RING AROM (UV CORES) 2.1-2.2
POLARS (UV CORES) 1.9-1.3
Consistent with the observed differences in the pore size
distribution of the steamed, artificially deactivated catalysts,
the base case and the two examples of this invention show
significantly different selectivities for coke in the cracking of a
Vacuum Gas Oil in a small captive fixed fluidized bed unit. (ACE).
FIG. 4a is a graph of coke make vs. 430.degree. F.- (221.degree.
C.-)+coke make for base case comparative catalysts vs. catalysts of
the invention. FIG. 4b shows that the catalysts of this invention
are more coke selective than the average coke selectivity seen from
commercially available state of the art catalysts.
[0120] FIG. 4a shows that the catalysts of this invention (Examples
4 and 5) differ from the similar comparative catalysts in that they
produce less coke for a given conversion level than other catalysts
made with ammonium phosphates. In FIG. 5, the same data are
normalized for conversion which removes the slopes for coke vs.
conversion seen in FIG. 4.
[0121] If light hydrocarbon moieties (such as methyl groups)
associated with heavy polynuclear aromatics in coke are cracked off
as a result high temperature, coke yields can fall while light gas
yields rise. Since either coke or light gas can constrain unit
operations, trading off coke for light gas is not a clear win. With
the catalysts of this invention, it appears that both coke and
light gas are lower than the base case comparative catalysts as
shown in FIG. 6a which is a plot of dry gas make vs. 430.degree.
F.- (221.degree. C.-)+coke make. FIG. 6b shows that the catalysts
of this invention make less dry gas than commercially available
state of the art catalysts.
[0122] FIG. 7a shows that the catalysts of this invention make more
valuable propene than do similar base case comparative catalysts
when they achieve the same conversion. FIG. 7b shows that the
catalysts of this invention make more propene than commercially
available state of the art catalysts.
[0123] FIG. 8a shows that the catalysts of this invention (Examples
4 and 5) differ from the similar base case comparative catalysts in
that:
[0124] 1. The maximum in the dV/dD vs. pore diameter plot occurs at
pore diameter greater than 50 Angstroms for the catalysts of this
invention.
[0125] 2. The tangents to the dV/dD vs. pore diameter curves below
50 Angstroms for steamed catalysts of this invention are positive
and intercept the pore diameter axis (dV/dD=0) at greater than 10
Angstroms.
[0126] 3. The catalysts of this invention are made with sodium
silicate, urea, and a sodium salt of phosphate as well as a
faujasite and alumina.
[0127] FIG. 8b shows that the commercially available state of the
art catalysts have a local maximum in the dV/dD plot below 60
Angstroms (about 50 Angstroms) regardless of the severity of the
steaming, and that above 60 Angstroms, there may be more than one
maximum in the 60 to 200 Angstrom range.
[0128] FIG. 8c is a plot of dV/dD vs. pore diameter showing that
commercially available state of the art catalysts when blended with
other catalysts from the same manufacturer have a local maximum in
the dV/dD plot below 60 Angstroms regardless of the severity of the
steaming.
[0129] FIG. 8d is a plot of dV/dD vs. pore diameter showing that
catalysts of this invention have a maximum in the dV/dD plot above
60 Angstroms and below 80 Angstrom unlike the commercially
available state of the art catalysts which have a local maximum in
the dV/dD plot below 60 Angstroms regardless of the severity of the
steaming and may have one or more maxima above 80 Angstroms.
* * * * *