U.S. patent application number 10/136904 was filed with the patent office on 2002-10-31 for zeolite-based catalyst material, the preparation thereof and the use thereof for the selective dehydrogenation of n-butane.
This patent application is currently assigned to Phillips Petroleum Company. Invention is credited to Drake, Charles A., Wu, An-hsiang.
Application Number | 20020161271 10/136904 |
Document ID | / |
Family ID | 22832245 |
Filed Date | 2002-10-31 |
United States Patent
Application |
20020161271 |
Kind Code |
A1 |
Wu, An-hsiang ; et
al. |
October 31, 2002 |
Zeolite-based catalyst material, the preparation thereof and the
use thereof for the selective dehydrogenation of n-butane
Abstract
A process in which a hydrocarbon feedstock containing n-butane
is selectively dehydrogenated to a product containing butenes. A
catalyst suitable for the selective dehydrogenation of a feedstock
containing n-butane to provide a product containing butenes. A
method for producing a catalyst suitable for the selective
dehydrogenation of a feedstock containing n-butane to provide a
product containing butenes.
Inventors: |
Wu, An-hsiang;
(Bartlesville, OK) ; Drake, Charles A.; (Nowata,
OK) |
Correspondence
Address: |
Chevron Phillips Chemical Company LP
Suite 3450
1301 McKinney
Houston
TX
77010
US
|
Assignee: |
Phillips Petroleum Company
Bartlesville
OK
|
Family ID: |
22832245 |
Appl. No.: |
10/136904 |
Filed: |
May 2, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10136904 |
May 2, 2002 |
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09798422 |
Mar 2, 2001 |
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09798422 |
Mar 2, 2001 |
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09222446 |
Dec 29, 1998 |
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6218328 |
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Current U.S.
Class: |
585/660 ;
502/74 |
Current CPC
Class: |
B01J 37/0009 20130101;
B01J 29/605 20130101; B01J 29/60 20130101 |
Class at
Publication: |
585/660 ;
502/74 |
International
Class: |
C07C 005/333; B01J
029/62 |
Claims
That which is claimed is:
1. A catalyst composition comprising: (A) an titania-modified
zeolite composition; (B) platinum and (C) tin.
2. A catalyst according to claim 1 wherein the titania-modified
zeolite composition comprises an air dried mixture of LTL zeolite,
aluminum hydroxychloride and Bentonite.
3. A catalyst according to claim 2 wherein the titania-modified
zeolite composition comprises an air dried mixture of LTL zeolite,
aluminum hydroxychloride and Bentonite to which a titanium organic
compound has been added to provide a titanium-modified LTL zeolite
composition.
4. A catalyst according to claim 3 wherein the titanium organic
compound is titanium ethoxide.
5. A catalyst according to claim 3 wherein the titania-modified LTL
zeolite composition comprises an air dried mixture of LTL zeolite,
aluminum hydroxychloride and Bentonite to which a titanium organic
compound has been added that has been calcined to provide a
titania-modified LTL zeolite.
6. A catalyst according to claim 4 wherein the titania-modifled LTL
zeolite composition comprises an air dried mixture of LTL zeolite,
aluminum hydroxychloride and Bentonite to which a titanium organic
compound has been added that has been calcined to provide a
titania-modified LTL zeolite.
7. A catalyst according to claim 5 wherein the titania-modified LTL
zeolite composition comprises a calcined air dried mixture of LTL
zeolite, aluminum hydroxychloride and Bentonite to which a titanium
organic compound has been added that has been further treated by
impregnation with a platinum-tin impregnating solution to provide a
titania-modified LTL zeolite composition impregnated with platinum
and tin.
8. A catalyst according to claim 6 wherein the titania-modified LTL
zeolite composition comprises a calcined air dried mixture of LTL
zeolite, aluminum hydroxychloride and Bentonite to which a titanium
organic compound has been added that has been further treated by
impregnation with a platinum-tin impregnating solution to provide a
titania-modified LTL zeolite composition impregnated with platinum
and tin.
9. A catalyst according to claim 7 wherein the platinum-tin
impregnating solution comprises chloroplatinic acid.
10. A catalyst according to claim 8 wherein the platinum-tin
impregnating solution comprises chloroplatinic acid.
11. A catalyst according to claim 7 wherein the platinum-tin
impregnating solution comprises tin chloride.
12. A catalyst according to claim 8 wherein the platinum-tin
impregnating solution comprises tin chloride.
13. A method for preparing a catalyst wherein the method comprises:
(A) admixing LTL zeolite, aluminum hydroxychloride and Bentonite to
provide an LTL zeolite composition and (B) calcining the LTL
zeolite composition to provide a calcined LTL zeolite composition;
(C) adding titanium to the calcined LTL zeolite composition by
impregnating with a titanium compound to provide a
titanium-modified LTL zeolite composition; (D) calcining the
titanium-modified LTL zeolite composition to provide a
titania-modified LTL zeolite composition and (E) adding platinum
and tin to the titania-modified LTL zeolite by impregnating the
titania-modified LTL zeolite composition with a platinum-tin
impregnating solution to provide a titania-modified LTL zeolite
composition impregnated with platinum and tin.
14. A method for preparing a catalyst according to claim 13 wherein
the titanium compound is chosen from the group consisting
essentially of titanium halides, tetraalkyl titanates of the
general formula Ti(OR).sub.4 wherein each R is an alkyl group,
titanium methoxide and titanium ethoxide.
15. A method for preparing a catalyst according to claim 14 wherein
the titanium compound is titanium ethoxide.
16. A method for preparing a catalyst according to claim 14 wherein
the platinum compound is chosen from the group consisting
essentially of chloroplatinic acid, platinic chloride, platinum
bromide, platinum iodide, tetramine platinum chloride, tetramine
platinum nitrate, tetramine platinum hydroxide, tetrachlorodiamine
platinum and combinations of any two or more thereof and the tin
compound is chosen from the group consisting essentially of
stannous acetate, stannic acetate, stannous bromide, stannic
bromide, stannous chloride, stannic chloride, stannous oxalate,
stannous sulfate, stannic sulfate, stannous sulfide and
combinations of any two or more thereof.
17. A method for preparing a catalyst according to claim 16 wherein
the platinum compound is chloroplatinic acid.
18. A method for preparing a catalyst according to claim 16 wherein
the tin compound is stannous chloride.
19. A method for preparing a catalyst according to claim 16 wherein
the platinum compound is chloroplatinic acid and the tin compound
is stannous chloride.
20. A method for dehydrogenating n-butane to butenes comprising
contacting n-butane with a catalyst prepared by the method of claim
13 under conditions for the production of butenes.
21. A method for dehydrogenating n-butane to butenes comprising
contacting n-butane with a catalyst prepared by the method of claim
14 under conditions for the production of butenes.
22. A method for dehydrogenating n-butane to butenes comprising
contacting n-butane with a catalyst prepared by the method of claim
15 under conditions for the production of butenes.
23. A method for dehydrogenating n-butane to butenes comprising
contacting n-butane with a catalyst prepared by the method of claim
16 under conditions for the production of butenes.
24. A method for dehydrogenating n-butane to butenes comprising
contacting n-butane with a catalyst prepared by the method of claim
17 under conditions for the production of butenes.
25. A method for dehydrogenating n-butane to butenes comprising
contacting n-butane with a catalyst prepared by the method of claim
18 under conditions for the production of butenes.
26. A method for dehydrogenating n-butane to butenes comprising
contacting n-butane with a catalyst prepared by the method of claim
19 under conditions for the production of butenes.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a catalyst suitable for the
selective dehydrogenation of n-butane, a process for the
preparation of a catalyst suitable for the selective
dehydrogenation of n-butane and the use of this catalyst in a
process for the selective dehydrogenation of n-butane.
BACKGROUND OF THE INVENTION
[0002] It is known that n-butane can be dehydrogenated to butenes
in the presence of variety of catalyst supports impregnated with a
variety of metals. The dehydrogenation often produces coke at a
rate that spoils the reactivity of the catalyst in a sufficiently
short period of time to render the commercial use of the catalysts
infeasible. A catalyst composition has newly been found to be
usefull for selectively dehydrogenating n-butane to butene products
without producing coke at a commercially inhibiting rate.
SUMMARY OF THE INVENTION
[0003] It is an object of this invention to at least partially
dehydrogenate n-butane to butenes.
[0004] Another object of this invention is to provide an improved
zeolite-based catalyst that can be utilized in the dehydrogenation
of n-butane to butenes.
[0005] A further object of this invention is to provide a method
for making a zeolite-based catalyst that can be utilized in the
dehydrogenation of n-butane to butenes.
[0006] A still further object of this invention is to accomplish
the dehydrogenation of n-butane while minimizing the co-production
of coke.
[0007] The invention is a zeolite-based catalyst in which an L-type
zeolite that has been modified with titania is impregnated with
platinum and tin to provide a catalyst composition and a process in
which a feedstock containing n-butane is passed in contact with
this catalyst composition under selective dehydrogenation
conditions to yield butenes as product while minimizing the
co-production of coke.
[0008] Other objects and advantages of the invention will become
apparent from the detailed description and the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The zeolite material used in making the inventive
compositions can be any zeolite which when contacted with a
feedstock containing n-butane under suitable operating conditions
is effective in the conversion of n-butane to butenes. Preferably,
the zeolite is of type L and more preferably is an LTL zeolite (as
defined in ATLAS OF ZEOLITE STRUCTURE TYPES, W. M. Meier and D. H.
Olson, Butterworth-Heinemann, Third Revised Edition 1992). The
preferred type of zeolite is described as Linde Type L,
K.sub.6Na.sub.3 [Al.sub.9Si.sub.27O.sub.72].21H.sub.2O.
[0010] The catalyst compositions described herein also contain an
inorganic binder (also called matrix material) preferably selected
from among alumina, silica, alumina-silica, aluminum phosphate,
clays (such as bentonite) and mixtures thereof. The content of the
zeolite component of the mixture of zeolite and inorganic binder is
about 50-99 (preferably about 50-80) weight percent. The content of
the above-listed inorganic binders in the mixture of zeolite and
inorganic binder is about 1-50 weight percent. Generally, the
zeolite and organic binder components are compounded and
subsequently shaped (such as by pelletizing, extruding or
tableting). Generally the surface area of the compounded
composition is about 50-700 m.sup.2/g, and the particle size is
about 1-10 mm. The compounded zeolite composition can be subjected
to heat treating as described below.
[0011] In the preferred embodiment of this invention the type L
zeolite is admixed with bentonite, Al.sub.2(OH).sub.5Cl.5H.sub.2O
and water and thoroughly blended to form a paste which is then
extruded, pelleted, dried in air to form a zeolite composition
suitable for use as catalyst in the dehydrogenation of
n-butane.
[0012] This zeolite composition can then be subjected to a heat
treatment, following the conditions set out below, before being
used in the preparation of a catalyst by the preferred embodiment
of this invention. In the heat treatment, the zeolite composition
is exposed, by any suitable method known in the art, to a gas
atmosphere under temperature and pressure conditions and for a
period of time that is suitable to provide a desired heat treated
product.
[0013] The gas used in the heat treatment of the zeolite
composition can be selected from the group consisting of inert
gases (nitrogen, helium, argon and the like), reducing gases
(carbon monoxide, hydrogen and the like), air, oxygen and steam.
The preferred gas is selected from among air, oxygen, nitrogen,
steam and mixtures thereof. Most preferably, the treatment gas is
selected from among air, oxygen, nitrogen and mixtures of two
thereof.
[0014] Generally, this heat treatment can be conducted at a
pressure in a range from below atmospheric pressure to about 1000
pounds per square inch absolute (psia). More typically, however,
the pressure range is from about atmospheric to about 100 psia. The
temperature of this heat treatment is generally in the range of
about 250.degree. C. to about 800.degree. C. Preferably, this
temperature range is from about 350.degree. C. to about 700.degree.
C. and, most preferably, the temperature of this heat treatment is
in a range of about 450.degree. C. to about 600.degree. C.
[0015] The time period for conducting this heat treatment must be
sufficient to provide a material that is substantially dry, i.e.,
free of water. Generally, the period of time during which the
zeolite is exposed to treating gas at appropriate conditions of
temperature and pressure can range from about 0.1 hour to about 30
hours. Preferably, this heat treatment is conducted for a time
period in the range of about 0.25 hour to about 20 hours and, most
preferably, from about 0.5 hour to about 10 hours.
Addition of Titanium
[0016] The zeolite composition is further treated to provide a
zeolite composition containing titanium. Titanium is incorporated
into the zeolite composition to form a mixture of the zeolite
composition and titanium. The titanium can be incorporated into the
zeolite by any suitable means or method known in the art for
incorporating metallic elements into a substrate material. One
method is to mix the zeolite composition with at least one
anhydrous compound, followed by a heat treatment preferably at
about 700-800.degree. C. for about 1-10 hours in an inert gas
stream. Another method, presently preferred for impregnating the
zeolite composition, uses a liquid impregnation solution containing
a concentration of titanium sufficient to ultimately provide the
final inventive composition with the concentration of titanium in
the required range.
[0017] When titanium is incorporated into the zeolite composition
with an aqueous solution of a titanium compound, the preferred
impregnation solution is an aqueous solution of titanium ethoxide.
The titanium-impregnated zeolite composition is then heat treated,
preferably at about 400-700.degree. C. for about 1-10 hours in an
inert gas stream. The titanium-impregnated zeolite composition is
then calcined in an oxidizing atmosphere, preferably at about
400-700.degree. C. for about 1-10 hours to produce a
titania-impregnated zeolite composition.
[0018] Any water soluble titanium compound is suitable for use in
the impregnation of the zeolite in this invention. Suitable
titanium compounds include, but are not limited to, titanium
halides, tetraalkyl titanates of the general formula Ti(OR).sub.4
wherein each R is an alkyl group (such as tetraethyl titanate,
tetraisopropyl titanate, tetrabutyl titanate), titanium methoxide
and titanium ethoxide. At present, titanium ethoxide is
preferred.
[0019] The amount of titanium incorporated or impregnated into the
zeolite should provide a concentration effective to assure
predetermined butene conversion yields employing the catalyst
composition in the selective dehydrogenation of feedstock that
contains n-butane. Generally, the weight percent of titanium
present both in the titanium impregnated zeolite composition and in
the zeolite composition containing additional metal impregnants is
in a range of about 0.001 to about 10 weight percent of the
impregnated zeolite composition. The preferred concentration of
titanium in both the titanium impregnated zeolite composition and
in the zeolite composition containing additional metal impregnants
is in the range of about 0.01 to about 5 weight percent and) more
preferably, from about 0.1 to about 2 weight percent.
[0020] The titanium impregnated zeolite composition is calcined to
provide a titania-modified zeolite composition. The calcination
process is conducted in an oxidizing atmosphere preferably in the
presence of oxygen or air although a non-interfering amount of a
carrier gas inert to the oxidation process can also be present.
This heat treatment can be conducted at a pressure in a range from
below atmospheric pressure to about 1000 pounds per square inch
absolute (psia), more typically from about atmospheric to about 100
psia. The temperature of this heat treatment is generally in the
range of about 250.degree. C. to about 800.degree. C. Preferably,
this temperature range is from about 350.degree. C. to about
700.degree. C. and, most preferably, the temperature of this heat
treatment is in a range of about 450.degree. C. to about
600.degree. C. The period of time during which the zeolite is
exposed to treating gas at appropriate conditions of temperature
and pressure can range from about 0.1 hour to about 30 hours,
preferably, from about 0.25 hour to about 20 hours and, most
preferably, from about 0.5 hour to about 10 hours.
Addition of Platinum and Tin
[0021] After the heat treatment the titania-modified zeolite
composition is further treated to provide a catalyst composition
containing platinum and tin. Both platinum and tin are incorporated
into the titania-modified zeolite composition to form a mixture of
titania-modified zeolite, platinum and tin. The platinum and tin
can be incorporated into the titania-modified zeolite composition
by any suitable means or method known in the art for incorporating
metallic elements into a substrate material. One method is to mix
the titania-modified zeolite composition with at least one
anhydrous compound, followed by a heat treatment preferably at
about 700-800.degree. C. for about 1-10 hours in an inert gas
stream. Another method, presently preferred for impregnating the
titania-modified zeolite composition, uses a liquid impregnation
solution containing a concentration of platinum and tin sufficient
to ultimately provide the final inventive composition with the
concentration of platinum and tin in the required range.
[0022] Generally, any platinum-containing compound can be employed
in the process of this invention. Examples of suitable platinum
compounds include, but are not limited to, chloroplatinic acid,
platinic chloride, platinum bromide, platinum iodide, tetramine
platinum chloride, tetramine platinum nitrate, tetramine platinum
hydroxide, tetrachlorodiamine platinum and combinations of any two
or more thereof.
[0023] Any tin-containing compound can be employed in the process
of this invention. Examples of suitable tin compounds include, but
are not limited to, stannous acetate, stannic acetate, stannous
bromide, stannic bromide, stannous chloride, stannic chloride,
stannous oxalate, stannous sulfate, stannic sulfate, stannous
sulfide and combinations of any two or more thereof.
[0024] When platinum and tin are incorporated into the
titania-modified zeolite with an aqueous solution of a platinum or
a tin compound, the preferred impregnation solution is an aqueous
solution, preferably chloroplatinic acid for the impregnation with
platinum, or an aqueous solution formed by dissolving a salt of
tin, preferably hydrated stannous chloride (SnCl.sub.2.2H.sub.2O),
in water. It is acceptable, however, to use a somewhat acidic
solution to aid in the dissolution of the metal salt. The platinum-
and tin-impregnated, zeolite is then heat treated, preferable at
about 400-700.degree. C. for about 1-10 hours in an inert gas
stream.
[0025] The amount of platinum and tin incorporated or impregnated
into the zeolite should provide a concentration effective to assure
predetermined butene conversion yields employing the catalyst
composition in the selective dehydrogenation of feedstock that
contains n-butane. Generally, the weight percent of platinum or tin
present in the impregnated zeolite is in a range of about 0.001 to
about 10 weight percent of the impregnated zeolite composition. The
preferred concentration of platinum or tin in the impregnated
zeolite is in the range of about 0.01 to about 5 weight percent
and, more preferably, from about 0.1 to about 2 weight percent of
the impregnated zeolite composition.
[0026] Generally, this heat treatment can be conducted at a
pressure in a range from below atmospheric pressure to about 1000
pounds per square inch absolute (psia). More typically, however,
the pressure range is from about atmospheric to about 100 psia. The
temperature of this heat treatment is generally in the range of
about 500.degree. C. to about 1000.degree. C. Preferably, this
temperature range is from about 600.degree. C. to about 900.degree.
C. and, most preferably, the temperature of this heat treatment is
in a range of about 650.degree. C to about 850.degree. C.
[0027] Generally, the period of time during which the zeolite is
exposed to treating gas at appropriate conditions of temperature
and pressure can range from about 0.1 hour to about 30 hours.
Preferably, this heat treatment is conducted for a time period in
the range of about 0.25 hour to about 20 hours and, most
preferably, from about 0.5 hour to about 10 hours and results in a
calcined, steam treated product suitable for use in a catalyst
bed.
[0028] The process of this invention applies most specifically to
the conversion of n-butane to butenes. The feedstock can be any
feedstock that contains n-butane. The higher the content of
n-butane the more preferred is a feedstock for this invention.
Among the feedstocks for which this invention is useful are those
having a content of cracked hydrocarbon feedstocks from the
catalytic cracking (e.g., fluidized catalytic cracking and
hydrocracking) of gas oils and the thermal cracking of light
hydrocarbons, naphthas, gas oils, reformates and straight-run
gasoline. The cracked gasoline feedstock generally comprises
hydrocarbons containing 2-16 carbon atoms per molecule chosen from
among paraffins (alkanes) and/or olefins (alkenes) and/or
naphthenes (cycloalkanes). A more preferred feedstock for the
process of this invention is a cracked gasoline derived from the
fluidized catalytic cracking of gas oil, suitable for use as at
least a gasoline blend stock generally having a boiling range of
from about 80.degree. F. to about 430.degree. F. The boiling range
of the cracked hydrocarbon feedstock is determined by the standard
ASTM method for measuring the initial boiling point and the
end-point temperatures. Generally the content of paraffins exceeds
the combined content of olefins, naphthenes, and aromatics (if
present).
[0029] Feedstock containing n-butane and the catalyst compositions
can be contacted within a reaction zone in any suitable manner. The
contacting can be operated with a catalyst bed in a reactor vessel
as a batch process or, preferably, as a continuous process. In
either a batch or a continuous process a solid catalyst bed can be
employed. Both the batch and continuous modes of operation have
known advantages and disadvantages so that one skilled in the art
can select the mode most suitable for a particular feedstock to be
contacted with the inventive catalyst arrangement.
[0030] Contacting the feedstock containing n-butane and the
catalyst composition is carried out in a reaction zone containing
the catalyst compositions while employing reaction conditions that
promote the dehydrogenation of n-butane with the formation of
butenes. The reaction temperature employed in the contacting is in
the range of from about 300.degree. C. to about 800.degree. C.,
preferably, from about 400.degree. C. to about 700.degree. C. and,
more preferably, from 500.degree. C. to about 600.degree. C. The
pressure employed in the contacting can range from subatmospheric
up to about 500 psia and, preferably, from about atmospheric to
about 400 psia.
[0031] The flow rate at which the cracked hydrocarbon feedstock is
charged to the conversion reaction zone for contact with the
catalyst composition is selected to provide a weight hourly space
velocity (WHSV) in a range having an upward limit of about 1000
hour.sup.-1. The term "weight hourly space velocity", as used
herein, shall mean the numerical ratio of the rate at which a
cracked hydrocarbon feedstock is charged to the conversion reaction
zone in pounds per hour divided by the pounds of catalyst contained
in the conversion reaction zone to which the hydrocarbon is
charged. The preferred WHSV of the feed to the conversion reaction
zone, or contacting zone, can be in the range of from about 0.25
hour.sup.-1 to about 250 hour.sup.-1 and, more preferably, from
about 0.5 hour.sup.-1 to about 100 hour.sup.-1.
[0032] The following examples are presented to further illustrate
this invention and are not to be construed as unduly limiting its
scope.
EXAMPLE I
[0033] This example illustrates the preparation of catalysts which
were subsequently tested as catalysts in the selective
dehydrogenation of n-butanes to butenes.
Catalyst A (Control)-LTL Zeolite Impregnated with Platinum and
Tin
[0034] A quantity of 400 gm of commercially available LTL-K zeolite
catalyst provided by C. U. Chemie Euticon A. G., a Swiss
corporation, under their product designation "L-Zeocat" was admixed
with 12.0 gm of Bentonite, 48.0 gm of
Al.sub.2(OH).sub.5Cl.5H.sub.2O and 216 g of water. The mixture was
blender mixed into a paste and extruded into 1/16 inch pellets
which were air dried at 125.degree. for 3 hours and then calcined
at 500.degree. C. for 3 hours to yield an alumina-bound zeolite
catalyst.
[0035] A 37 percent solution of HCl in water was added to a mixture
of chloroplatinic acid and hydrated tin chloride
(SnCl.sub.2.2H.sub.2O) to form a solution having 1 wt percent of
chloroplatinic acid, 0.65 wt percent of tin chloride, 8.35 wt
percent HCl and 90 wt percent water.
[0036] A quantity of 50 gm of the aluina-bound zeolite catalyst was
admixed with an 11.1 gm quantity of the aqueous solution containing
platinum and tin. The impregnated zeolite was dried and calcined
with air flow at a temperature of 538.degree. C. for 6 hours to
produce 20.0 gm of alumina-bound zeolite impregnated with 0.21 wt.
percent platinum and 0.15 wt. percent tin.
Catalyst B and C (Invention)-Titania-modified LTL Zeolite
Impregnated with Platinum and Tin
[0037] A quantity of 10.0 g of the alumina-bound zeolite catalyst
produced for Catalyst A was admixed with 5.56 g of a 3 wt percent
aqueous solution of titanium ethoxide and calcined for 6 hours at
538.degree. C. to provide 9.43 g of titania-modified alumina-bound
zeolite.
[0038] A quantity of 6.05 g of the aqueous solution containing
platinum and tin produced for Catalyst A was admixed with the 9.43
g of titania-modified alumina-bound zeolite produced above and
calcined at 538.degree. C. for 6 hours to yield 9.25 g of
titania-modified alumina-bound zeolite impregnated with 0.25 wt
percent platinum and 0.22 wt percent tin.
Example II
[0039] This example illustrates the use of the Zeolite materials
described in Example I as catalysts in the selective
dehydrogenation of n-butane to butenes.
[0040] For each of the test runs, a 3.0 g sample of the catalyst
materials described in Example I was placed into a stainless steel
tube reactor (length: about 18 inches; inner diameter: about 0.5
inch). An n-butane feedstock was passed through the reactor at a
flow rate of about 5 WHSV, at a temperature of about 550.degree. C.
and at atmospheric pressure (about 0 psig). The runs using
Catalysts A and B were done without use of a carrier gas. Hydrogen
at a rate of 18.6 L/hr and a mol ratio of hydrogen to hydrocarbon
of about 3 was used a carrier gas for the run using Catalyst C. The
formed reaction product exited the reactor tube and passed through
several ice-cooled traps. The liquid portion remained in these
traps and was weighed. The volume of the gaseous portion which
exited the traps was measured in a "wet test meter". Liquid and
gaseous product samples (collected at hourly intervals) were
analyzed by means of a gas chromatograph. Results of the test runs
for Catalysts A through C are summarized in Table I. All test data
were obtained up to about 7 hours on stream except for Catalyst A
which was obtained up to about 6 hours on stream.
1TABLE I Ti PT Sn H.sub.2/n-C.sub.4 n-Butane Butenes Coke Catalyst
Wt %.sup.1 Wt %.sup.1 Wt %.sup.1 Mol Ratio Wt % Conv. Wt % Prod.
Avg. Wt %/hr A (Cont.) 0.000 0.211 0.146 0.000 20.668 17.149 0.282
B (Inv.) 0.144 0.249 0.244 0.000 30.079 24.839 0.106 C (Inv.) 0.144
0.249 0.244 3.000 23.102 20,696 0.025 .sup.1Wt % of composition
[0041] The tests show that Catalyst A (Control), an LTL zeolite
impregnated with platinum and tin, was not as efficient in the
selective dehydrogenation of n-butane to butenes as Catalysts B and
C (Invention), a titania-modified LTL zeolite impregnated with
platinum and tin. The inventive catalyst was used in the selective
dehydrogenation of n-butane both without using hydrogen as a
co-feed in the dehydrogenation (with Catalyst B) and with hydrogen
as a co-feed in the dehydrogenation (with Catalyst C). The
dehydrogenation employing catalyst without titania modification
converted a lesser weight percentage of the n-butane and produced a
lesser weight percentage of butenes with a greater average hourly
production of coke than employing the titania-modified zeolite
either with or without hydrogen co-fed to the dehydrogenation. The
titania-modified zeolite converted a greater weight percentage of
n-butane in the feedstock to a greater weight percentage of butenes
in the product while producing a better than satisfactory average
amount of coke per hour. Although the use of hydrogen co-feed
reduced the coke production, as expected, the n-butane conversion
and butenes production were less than without the hydrogen co-feed.
The relatively low cost of operation without using the hydrogen
co-feed makes the platinum and tin impregnated titania-modified
zeolite very attractive as catalyst for the selective
dehydrogenation of n-butane.
[0042] Reasonable variations, modifications and adaptations can be
made within the scope of the disclosure and the appended claims
without departing from the scope of this invention.
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