U.S. patent number RE35,166 [Application Number 08/240,156] was granted by the patent office on 1996-03-05 for catalyst.
This patent grant is currently assigned to Unilever Patent Holdings B.V.. Invention is credited to Paul Chapple.
United States Patent |
RE35,166 |
Chapple |
March 5, 1996 |
Catalyst
Abstract
The invention provides a catalyst composition useful in treating
hydrocarbons contaminated with vanadium residues, the catalyst
comprising a zeolite, a matrix and certain heavier alkaline earth
metal oxides.
Inventors: |
Chapple; Paul (Clwyd,
GB7) |
Assignee: |
Unilever Patent Holdings B.V.
(Rotterdam, NL)
|
Family
ID: |
10580221 |
Appl.
No.: |
08/240,156 |
Filed: |
May 10, 1994 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
328715 |
Mar 27, 1989 |
4948769 |
|
|
|
153482 |
Feb 2, 1988 |
|
|
|
|
870545 |
Jun 4, 1986 |
|
|
|
Reissue of: |
533443 |
Jun 5, 1990 |
05021145 |
Jun 4, 1991 |
|
|
Foreign Application Priority Data
Current U.S.
Class: |
208/120.1;
208/52CT; 208/149; 208/121; 208/120.25; 502/521 |
Current CPC
Class: |
B01J
29/06 (20130101); B01J 29/166 (20130101); C10G
11/05 (20130101); B01J 29/088 (20130101); B01J
2229/42 (20130101); Y10S 502/521 (20130101) |
Current International
Class: |
B01J
29/08 (20060101); B01J 29/00 (20060101); B01J
29/06 (20060101); B01J 29/16 (20060101); C10G
11/05 (20060101); C10G 11/00 (20060101); C10G
011/04 () |
Field of
Search: |
;208/113,118,119,120,121,149,52CT ;502/521 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Brunsman; David
Attorney, Agent or Firm: Cushman Darby & Cushman
Parent Case Text
This is .Iadd.a reissue of U.S. Pat. No. 5,021,145, application
07/533,443, filed Jun. 5, 1990, which is .Iaddend.a division of
application Ser. No. 07/328,715, filed Mar. 27, 1989, now U.S. Pat.
No. 4,948,769 which is a continuation of Ser. No. 07/153,482, filed
Feb. 2, 1988, abandoned, which is a continuation of Ser. No.
06/870,545, filed Jun. 4, 1986, abandoned.
Claims
I claim:
1. A method of cracking vanadium containing hydrocarbon feedstocks
wherein the feedstock is contacted with a catalyst composition
comprising:
(i) a crystalline zeolite,
(ii) a matrix material, and
(iii) a single phase crystalline mixed oxide selected from calcium
and barium tin oxides, the strontium tin oxides Sr.sub.2 SnO.sub.4
and Sr.sub.3 Sn.sub.2 O.sub.7, strontium titanium oxides and .[.the
barium titanium oxides BaTi.sub.2 O.sub.5, BaTi.sub.4 O.sub.9,
BaTi.sub.5 O.sub.11, Ba.sub.2 TiO.sub.4, Ba.sub.2 Ti.sub.5
O.sub.12, Ba.sub.2 Ti.sub.9 O.sub.20, Ba.sub.4 Ti.sub.13 O.sub.30,
and Ba.sub.6 Ti.sub.17 O.sub.40, and.]. mixtures thereof.
Description
FIELD OF THE INVENTION
The invention relates to cracking catalysts and to catalytic
cracking, which is a major refinery process for the conversion of
hydrocarbons to lower boiling fractions. More specifically, the
invention relates to catalyst compositions which are particularly
resistant to degradation by vanadium deposited on the catalyst in
the course of the cracking reaction, and to an improved process for
cracking vanadium containing feedstocks by using these
catalysts.
BACKGROUND TO THE INVENTION
Catalysts containing crystalline zeolites dispersed in an inorganic
oxide matrix have been used for the catalytic cracking of
petroleum-derived feedstocks for many years. During this time, it
has been widely recognised in the industry that certain
contaminants (notably vanadium, nickel, and iron), initially
dissolved or dispersed in the hydrocarbon feedstock, are deposited
on the catalyst during the catalytic cracking process, and the
accumulated deposits lead to undesirable changes in the activity
and selectivity of the thus contaminated catalysts. Typically, the
harmful effects noted have been increased yields of coke and
hydrogen, a phenomenon ascribed to the action of the deposited
metals as centres of dehydrogenation. More recently, however, it
has been appreciated that vanadium also has other harmful
properties, as well as increasing dehydrogenation activity, it
reacts with and destroys the zeolite component of the catalyst,
leading to a severe decrease in the activity of the catalyst.
These problems have become more acute as refiners have faced the
need to process heavier feedstocks which contain increased amounts
of the metal contaminants, and various strategies have been
employed to alleviate the deleterious effects and facilitate smooth
running of catalytic cracking units. These approaches have
included.
(1) more frequent replenishment of the circulating catalyst
inventory;
(2) withdrawal of the regenerated catalyst and treatment with
various chemicals to passivate the metals;
(3) changes in the design or operation of the catalytic cracker to
reduce the poisoning activity of the contaminant metals;
(4) addition to the feedstock of compounds of elements such as
antimony, tin, barium, manganese, germanium and bismuth.
Examples of these approaches will be found in the following
patents: U.S. Pat. Nos. 4,111,845, 4,101,417, 4,377,494, 4,367,136,
3,977,963.
Further attempts to cope with harmful effects of metals, especially
vanadium, have related to modifications of the cracking catalyst
itself; these have included admixture with sacrificial catalyst
particles, careful control of the zeolite composition, and
inclusion in the catalyst of specified amounts of vanadium trapping
additives, including alumina, titanium dioxide (titania) and
zirconium dioxide (zirconia) and certain compounds of calcium and
magnesium. Disclosures of such catalysts will be found in U.S. Pat.
Nos. 4,432,890, 4,451,355 and BE 899,446.
GENERAL DESCRIPTION OF THE INVENTION
The present invention provides a catalyst composition comprising a
i) crystalline zeolite, ii) a matrix material, and iii) certain
crystalline mixed oxides, derived from the heavier alkaline earth
elements (calcium, strontium, barium) and certain combinations with
elements of group IV of the periodic table, which oxides have
themselves no harmful effects on the catalytic properties but are
present in amounts sufficient to act as a vanadium passivator.
Accordingly, the present invention provides a catalyst composition
comprising i) a crystalline zeolite, ii) a matrix material and iii)
a mixed oxide selected from calcium, strontium and barium tin
oxides and strontium and barium titanium oxides and mixtures
thereof.
The crystalline zeolite component of the present invention, which
is usually present in the range from about 5% to about 40% by
weight, may generally be described as a crystalline, three
dimensional, stable structure enclosing cavities of molecular
dimensions. Most zeolites are based on aluminosilicate frameworks,
the aluminium and silicon atoms being tetrahedrally coordinated by
oxygen atoms. However, for the purposes of our invention we include
as "zeolites" similar materials in which atoms of other elements
are present in the framework, such as boron, gallium, germanium,
chromium, iron, and phosphorus. Further we include materials such
as pillared interlayered clays ("PILCS"), which have many of the
catalytically valuable characteristics of the aluminosilicate
zeolites. We also include all modifications to the above materials,
whether obtained by ion-exchange, impregnation, hydrothermal or
chemical treatments.
Zeolites which can be employed in the catalysts and processes of
this invention can be natural or synthetic in origin. These
naturally occurring zeolites include gmelinite, chabazite,
dachiardite, clinoptilolite, faujasite, heulandite, analcite,
levynite, erionite, sodalite, canorinite, mepheline, lazurite,
scolecite, natiolite, offretite, mesolite, mordenite, brewsterite,
fevierite, and the like. Suitable synthetic zeolites are zeolites
A,B,E,F,H,J,L,Q,T,W,Z,Y,Z, alpha, beta, omega, the EU types, the Fu
types, the Nu types, the 2K types, the ZSM types, the ALPO types,
the SAPO types, the L2 series, and other similar materials will be
obvious. The effective pore size of the synthetic zeolites are
preferably between 0.6 and 1.5 nanometers, and the prefered
zeolites are those with the faujasite framework and silica/alumina
ratios >3, thus including synthetic zeolite Y and the various
form of Y which have been made more siliceous by chemical,
hydrothermal or thermal treatments.
In a preferred embodiment of the invention, the zeolite is
converted to a form which is most applicable for catalytic
cracking. In general this involves a sequence of ion-exchange and
calcination treatments to introduce acid groups into the zeolite,
stabilise the structure, and remove alkali metal cations. The
prefered method of achieving this end, well known in the art, is to
exchange the zeolite with solutions containing ammonium ions and/or
rare earth ions (either a pure rare earth compound or a
mixture).
Such treatment can be carried out either on the zeolite before it
is incorporated in the catalyst, or on the finished catalyst
containing the zeolite, it can be carried out on a filter press,
filter table, or filter belt, or by slurrying the zeolite/catalyst
in a tank.
The matrix into which the zeolite is incorporated can have a wide
range of compositions. Suitable components include: naturally
occurring or synthetic clays, including kaolin, halloysite and
montmorillonite; inorganic oxide gels, including binary gels such
as silica, silica-alumina, silica-zirconia, silica-magnesia,
aluminium phosphates, or ternary combinations such as
silica-magnesia-alumina; and crystalline inorganic oxides such as
silica, alumina, titania, zirconia.
Suitable mixed oxides for use as component (iii) are:
CaSnO.sub.3
Ca.sub.2 SnO.sub.4
SrTiO.sub.3
SrTi.sub.12 O.sub.19
Sr.sub.2 TiO.sub.4
Sr.sub.3 Ti.sub.2 O.sub.7
Sr.sub.4 Ti.sub.3 O.sub.10
SrSnO.sub.3
SR.sub.2 SnO.sub.4
Sr.sub.3 S.sub.2 O.sub.7
BaTiO.sub.3
BaTi.sub.2 O.sub.5
BaTi.sub.4 O.sub.9
BaTi.sub.5 O.sub.11
Ba.sub.2 TiO.sub.4
Ba.sub.2 Ti.sub.5 O.sub.12
Ba.sub.2 Ti.sub.9 O.sub.20
Ba.sub.4 Ti.sub.13 O.sub.30
Ba.sub.6 Ti.sub.17 O.sub.40
BaSnO.sub.3
Ba.sub.2 SnO.sub.4
The mixed oxide additive is a discrete component of the final
catalyst, and is readily identifiable in the fresh catalyst by
x-ray diffraction analysis. These materials are insoluble, and are
not decomposed into their component oxides over a wide range of
thermal and hydrothermal treatments, and, as such are readily
identifiable in hydrothermally deactivated catalyst samples.
Preferably the mixed oxide is present at a level of least about 1%
by weight of the catalyst and up to about 20% by weight.
The chemical form of the additive is central to determining the
concentration in which it is used in the catalyst composition, or
indeed its method of incorporation into the catalyst
formulation.
It is a possibility that the alkaline earth mixed oxide additive
reacts with vanadium on the catalyst through a displacement type
reaction resulting in the formation of high melting point alkaline
earth vanadates, thus immobilising the vanadium, and preventing its
further reaction with, and destruction of the zeolite component of
the catalyst, but there might also be another explanation. In this
manner, the alkaline earth compound is involved in a competitive
reaction for the vanadium with the zeolite. The alkaline earth
compounds of this invention are successful as passivators as a
result of their high reactivity towards vanadium compared to the
zeolite.
The use of crystalline mixed oxides containing titanium or tin, is
to render the alkaline earth additive inert to catalyst processing
procedures, and yet active in vanadium passivation on the final
catalyst, thus producing catalysts of increased vanadium tolerance,
with little or no adverse changes in catalytic and physical
properties, when compared to conventional catalysts.
Preferably, the concentration of the additive in the catalyst will
be in at least 1:1 molar proportion of alkaline earth to vanadium
with respect to the maximum vanadium level deposited on the
catalyst during use. Thus, the concentration of the alkaline earth
additive in the catalyst, can be tailored to best suit the process
in which it is used, thereby allowing the operation of the
catalytic cracking unit to be optimised.
The additives of this invention can be prepared by various
processes; for example, by calcination of intimate mixtures of the
oxides or carbonates of the component elements, in the appropriate
molar quantities, as disclosed by J Arjomand, J Less Common Met 61
133 1978, or by coprecipitation, or metathesis of salts of the
appropriate elements.
Conventional catalyst processing procedures encompass a wide range
of pH conditions, typically pH 3 to pH 10, and require that any
additives be resistant to such environments without themselves
being decomposed, or resulting in changes in the properties of
other catalyst components. The effect of additives not resistant to
such environments can be to render the catalyst processing
procedure inoperable, or to adversely affect both the physical and
catalytic properties of the finished catalyst.
As the form of the additives of the present invention are insoluble
and inert to any catalyst processing procedures, the catalysts
containing these additives may be prepared by any of the
conventional methods used for the manufacture of FCC catalysts. For
example, catalyst may be prepared by making an inorganic oxide sol
at pH 3 and adding to this, aqueous slurries of the other catalyst
components including zeolite and alkaline earth additive. The
homogenised slurry can then be spray dried to produce catalyst
microspheres, and washed free of soluble salts using for example
aqueous ammonium sulphate and water.
The catalyst compositions of this invention are employed in the
cracking of vanadium containing heavy hydrocarbon feedstocks, to
produce gasoline, and light distillate fraction. Typical feedstocks
would have an average boiling point greater than 316.degree. C.,
and include such materials as gas oils, and residual oils.
Because the catalysts of this invention are effective in cracking
processes even when contaminated with vanadium to levels in excess
of 5000 ppm, these catalysts can be used to process feedstocks
containing significantly higher concentrations of vanadium than
those employed in conventional catalytic cracking operations.
These catalysts may be employed in any catalytic cracking process
capable of operating with conventional microsphere fluid
catalysts.
SPECIFIC DESCRIPTION OF THE INVENTION
The following examples illustrate the advantages of the invention.
However, it is not intended that the invention be limited to the
specific examples given.
EXAMPLE 1
A calcium stannate additive was prepared by mixing together, with
constant agitation, a solution of 236 g of
Ca(NO.sub.3).sub.2.4H.sub.2 O, in 500 g of deionised water, and a
solution of 267 g Na.sub.2 SnO.sub.3.3H.sub.2 O in 500 g of
deionised water. The resulting precipitate was filtered, and washed
repeatedly, until the filtrate was free of Na.sup.+. The filter
cake was then dried at 100.degree. C., and finally calcined at
1000.degree. C. for 4 hrs, to give crystalline CaSnO.sub.3 which
was identified by X-ray diffraction. The crystalline CaSnO.sub.3
was finally finely ground prior to incorporation into the
catalyst.
The catalyst composition was prepared by combining together 75 g
Al.sub.2 O.sub.3, 276 g kaolin, 138 g CaSnO.sub.3, and 165 g CREY
(Calcined Rare Earth Y zeolite), in 2175 g of a silica sol (8%
SiO.sub.2) at pH 3.2 to provide a homogeneous slurry. The slurry
was then spray dried to form catalyst microspheres with an average
particle size of 60 microns.
The spray-dried catalyst was then washed with deionised water, ca
0.25M ammonium sulphate, and finally deionised water to remove
sodium, until the conductivity of the filtrate fell below 1 milli
mho.
EXAMPLE 2
The strontium titanate additive was prepared by grinding together
104 g of SrCO.sub.3, and 80 g of TiO.sub.2 to give a homogeneous
mixture. The mixture was then calcined at 1000.degree. C. for 20
hrs to give crystalline SrTiO.sub.3 which was identified by X-ray
diffraction. The crystalline SrTiO.sub.3 was finally finely ground
prior to incorporation into the catalyst.
The catalyst composition was prepared by combining together 100 g
Al.sub.2 O.sub.3, 478 g kaolin, 89 g SrTiO.sub.3, and 219 g CREY in
2871 g of a silica sol (8% SiO.sub.2) at pH 3.2 to provide a
homogeneous slurry.
The slurry was then spray dried into microspheres of catalyst, and
the catalyst finally washed according to the procedure in the
previous example to remove soluble Na.sup.+ ions.
EXAMPLE 3
The barium titanate additive was prepared by grinding together 197
g of BaTiO.sub.3, and 79.9 g of TiO.sub.2 to give a homogeneous
mixture. The mixture was then calcined at 1000.degree. C. for 16
hrs to give crystalline BaTiO.sub.3, which was identified by X-ray
diffraction.
The catalyst composition was prepared by combining together 100 g
Al.sub.2 O.sub.3, 494 g kaolin, 76 g BaTiO.sub.3, and 219 g CREY in
2850 g of a silica sol (8% SiO.sub.2) at a pH of 3.2 to provide a
homogeneous slurry.
The slurry was then spray dried into microspheres of catalyst, and
the catalyst finally washed according to the procedure in example
1, to remove soluble Na.sup.+ ions.
EXAMPLE 4
Comparative
A catalyst composition containing no alkaline earth mixed oxide
additive was prepared by combining together 200 g Al.sub.2 O.sub.3,
1164 g kaolin, and 438 g CREY, in 5966 g of a silica sol (8%
SiO.sub.2) at pH 3.2 to provide a homogeneous slurry. The slurry
was then spray dried into microspheres, and finally washed
according to the procedure in example 1 to remove soluble Na.sup.+
ions.
EXAMPLE 5
A sample of catalyst of example 1. previously thermally treated to
538.degree. C. for 2 hrs was impregnated with 5000 ppm vanadium
according to the following procedure. 50 g of the dried catalyst
was slurried in 50 ml of an aqueous solution containing 1.24 g
VOSO.sub.4 in a rotary evaporator. The slurry was allowed to fully
mix for 30 mins at room temperature with constant agitation. The
slurry was then dried under vacuum to yield the vanadium
impregnated catalyst. The impregnated catalyst was finally calcined
at 538.degree. C. for 2 hrs (Catalyst IM).
EXAMPLE 6
50 g of catalyst of Example 2, thermally treated to 538.degree. C.
for 2 hrs was impregnated with 5000 ppm V using the procedure
detailed in example 5 (Catalyst IIM).
EXAMPLE 7
50 g of catalyst of Example 3, thermally treated to 538.degree. C.
for 2 hrs, was impregnated with 5000 ppm V, using the procedure
detailed in example 5 (Catalyst IIIM).
EXAMPLE 8
50 g of catalyst of Example 4, thermally treated to 538.degree. C.
for 2 hrs, was impregnated with 5000 ppm V, using the procedure
detailed in example 5 (Catalyst IVM).
The catalysts from the above examples were evaluated in a
microactivity test (MAT) unit. Prior to testing, the catalyst
samples were thermally treated at 538.degree. C. for 3 hrs and then
deactivated in steam, at atmospheric pressure, at a temperature of
788.degree. C. (1450.degree. F.) for a period of 4 hrs. The
cracking conditions used for the MAT were 482.degree. C.
(900.degree. F.), a space velocity of 16.0 WHSV and a catalyst to
oil ratio of 3. The gas oil feed used in all of the tests was
characterised as follows:
______________________________________ Gravity .degree.API 27.6
Sulphur wt % 0.64 Nitrogen wt % 0.09 Carbon residue wt % 0.39
Aniline point .degree.F. 182.00 Distillation .degree.F. 10% at 760
mm Hg 574 30% at 760 mm Hg 682 50% at 760 mm Hg 773 70% at 760 mm
Hg 870 90% at 760 mm Hg 991 Initial Boiling Point 338 Final Boiling
Point 1061 ______________________________________
TABLE 1 ______________________________________ Catalyst No Wt % I
II III IV ______________________________________ Conversion 75.5
76.3 76.2 75.3 Gasoline 56.9 58.2 57.8 57.5 LCO 15.2 14.7 14.4 15.7
H.sub.2 0.08 0.033 0.046 0.019 Coke 4.78 4.21 4.14 3.78
______________________________________
TABLE 2 ______________________________________ Catalyst No Wt % IM
IIM IIIM IVM ______________________________________ Conversion 53.2
44.9 31.8 19.0 Gasoline 43.1 36.3 25.1 12.9 LCO 19.4 23.1 24.3 23.1
H.sub.2 0.11 0.19 0.22 0.31 Coke 2.83 2.58 2.17 3.14
______________________________________
line yield are effectively unaltered by the addition of the
additives, while coke and H.sub.2 yields are slightly
increased.
The performance of catalysts containing the alkaline earth
additives of this invention, in the presence of vanadium show
considerable benefits over catalysts containing no such additives,
as can be seen by comparison of the results for catalysts (IM-IIIM)
with catalyst (IVM) (Table 2) all in the presence of 5000 ppm
Vanadium. These results show substantial improvements in vanadium
tolerance for the catalyst compositions containing the additives as
seen by higher conversion levels, improved gasoline selectivity,
and reduced coke and hydrogen production.
* * * * *