U.S. patent number 3,875,049 [Application Number 05/355,607] was granted by the patent office on 1975-04-01 for platinum-tin catalyst regeneration process.
This patent grant is currently assigned to Chevron Research Company. Invention is credited to Harris E. Kluksdahl.
United States Patent |
3,875,049 |
Kluksdahl |
* April 1, 1975 |
Platinum-tin catalyst regeneration process
Abstract
Hydroconversion of hydrocarbons, particularly reforming of
naphthas, is conducted in the presence of hydrogen with a catalyst
comprising a platinum group component in an amount of from 0.01 to
5 weight percent, a tin component in an amount of from 0.01 to 5
weight percent and a halogen in an amount of from 0.1 to 3 weight
percent in association with a porous solid carrier.
Inventors: |
Kluksdahl; Harris E. (San
Rafael, CA) |
Assignee: |
Chevron Research Company (San
Francisco, CA)
|
[*] Notice: |
The portion of the term of this patent
subsequent to October 9, 1990 has been disclaimed. |
Family
ID: |
27358667 |
Appl.
No.: |
05/355,607 |
Filed: |
April 30, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
8663 |
Feb 4, 1970 |
|
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|
|
865010 |
Oct 9, 1969 |
|
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Current U.S.
Class: |
208/140; 208/139;
502/38; 502/37; 208/111.1; 208/111.35 |
Current CPC
Class: |
B01J
37/22 (20130101); C10G 35/09 (20130101); B01J
23/62 (20130101); B01J 23/626 (20130101); B01J
23/96 (20130101) |
Current International
Class: |
C10G
35/09 (20060101); C10G 35/00 (20060101); B01J
23/54 (20060101); B01J 23/62 (20060101); B01J
23/90 (20060101); B01J 23/96 (20060101); B01J
37/00 (20060101); B01J 37/22 (20060101); B01j
011/14 () |
Field of
Search: |
;208/139,111,140
;252/441,442,466PT,416 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gantz; Delbert E.
Assistant Examiner: Hellwege; James W.
Attorney, Agent or Firm: Magdeburger; G. F. Davies; R. H. De
Young; J. J.
Parent Case Text
CROSS REFERENCE
This is continuaton, of application Ser. No. 8,663, filed Feb. 4,
1970 which is a continuation-in-part of copending application Ser.
No. 865,010 filed Oct. 9, 1969, now abandoned.
Claims
I claim:
1. A regenerative process for the hydroconversion of hydrocarbons,
which comprises (1) contacting the hydrocarbons at hydroconversion
conditions in the presence of hydrogen with a catalyst comprising a
platinum group component in an amount from 0.01 to 5 weight
percent, a tin component in an amount from 0.01 to 5 weight
percent, and a halogen in an amount from 0.1 to 3 weight percent in
association with a porous solid carrier, until said catalyst has
become deactivated by carbonaceous deposits, and (2) contacting the
deactivated catalyst with an activating gas containing oxygen at
elevated temperatures for a time sufficient to activate the
catalytic composition.
2. A process as in claim 1 wherein the porous solid carrier is
alumina.
3. The process of claim 1, wherein said activating gas also
contains a halogen component.
4. The process of claim 1, wherein the catalyst is reduced in the
presence of hydrogen after contact with said activating gas.
Description
BACKGROUND OF THE INVENTION
1. Field
The present invention is directed to hydrocarbon hydroconversion
processes, and more particularly to reforming processes. Still more
particularly, the present invention is concerned with a catalytic
composition and a process for the hydroconversion of hydrocarbon in
the presence of the catalytic composition. The catalyst comprises a
platinum group component and a tin component in accociation with a
porous solid carrier.
2. Prior Art
Hydrocarbon hydroconversion processes, such as hydrocracking,
hydrogenation, hydrofining, isomerization, alkylation,
desulfurization and reforming, are of special importance in the
petroleum industry as a means for improving the quality and
usefulness of hydrocarbons. The requirement for a diversity of
hydrocarbon products, including, for example, high quality
gasoline, has led to the development of many catalysts and
procedures for converting hydrocarbons in the presence of hydrogen
to useful products. A particularly important hydrocarbon
hydroconversion process is reforming. Although many features of the
present invention are discussed in terms of reforming, it is to be
understood that the present invention relates to other hydrocarbon
hydroconversion processes as well.
In the development of catalysts for catalytic hydroconversion
processes, it is important that the catalyst exhibit not only the
capability to initially perform the specified functions but also
that it has the capability to perform satisfactorily for prolonged
periods of time. Thus, in the development of new catalysts,
attention must be directed to the activity, selectivity and
stability characteristics of the catalyst. The activity of a
catalyst is a measure of the catalyst's ability to convert
hydrocarbon reactants to products at a specified severity level,
i.e., at a particular temperature, pressure, hydrogen to
hydrocarbon mole ratio, etc. The selectivity of the catalyst refers
to the ability of the catalyst to produce high yields of desirable
products, and accordingly low yields of undesirable products. The
stability of a catalyst is a measure of the ability of the catalyst
to maintain the activity and selectivity characteristics over a
specified period of time. Thus, for example, a catalyst for
successful reforming must possess good selectivity, i.e., be able
to produce high yields of high octane number gasoline products and
accordingly low yields of light hydrocarbon gases. The catalyst
should also possess good activity in order that the temperature
required to produce a certain quality product need not be too high.
Also, the stability should be such that the activity and
selectivity characteristics can be retained during prolonged
periods of reforming operation. Thus, the temperature stability,
which is generally measured as the fouling rate of the catalyst,
should be such that the temperature need not be raised at an
excessively high rate in order to maintain conversion of the feed
to a constant octane product. Also, the yield stability of the
catalyst should be such that the production of valuable C.sub.5 +
gasoline products does not decrease appreciably during prolonged
operation at a constant conversion.
As indicated above, the present invention is particularly concerned
with catalytic reforming, that is, the treatment of naphtha
fractions or feeds to improve the octane rating. Most catalytic
reforming operations are characterized by employing catalysts
comprising dehydrogenation-promoting metal components associated
with porous solid carriers, which catalysts selectively promote
such hydrocarbon reactions as dehydrogenation of naphthenes to
aromatics, dehydrocyclization of paraffins to naphthenes and
aromatics, isomerization of normal paraffins to isoparaffins, and
hydrocracking of relatively long-chained paraffins. Most catalysts
used in reforming processes comprise platinum group components,
particularly platinum, in association with porous solid carriers,
for example, alumina. Research efforts have been expended to seek
substitutes for platinum and/or to seek catalytic promoters to use
with platinum catalysts to increase their activity, stability, and
selectivity characteristics.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved
hydroconversion process can be conducted in the presence of a
catalyst comprising a platinum group component, a tin component,
and a halogen associated with a porous solid carrier. The platinum
group component is present in an amount of from 0.01 to 5 weight
percent based on the finished catalyst; preferably the platinum
group component is platinum. Preferably the tin component is
present in an amount of from 0.01 to 5 weight percent and the
halogen in an amount of from 0.1 to 3 weight percent, based on the
finished catalyst. The hydrocarbon hydroconversion process is
preferably the reforming of naphtha or gasoline fractions to
produce high octane products.
Also, in accordance with the present invention, a novel catalytic
composition of matter has been discovered comprising a porous solid
carrier, preferably a porous inorganic oxide carrier, having
associated therewith from 0.01 to 5 weight percent of a platinum
group component, 0.01 to 5 weight percent of a tin component, and
0.1 to 3 weight percent of a halogen. The catalytic composition is
preferably in a reduced state. The novel catalyst of the present
invention is found to be highly active and stable for the reforming
of naphtha and gasoline boiling range hydrocarbons and, in fact, is
superior to commercial reforming catalysts containing only a
platinum group component.
Another of the several advantages of the present invention is that
the catalyst does not require presulfiding to reduce initial
formation of low molecular weight hydrocarbons during startup of
the reforming process, in contrast to other reforming catalysts
which often require such pretreatment for such purpose.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention may be better understood and will be further
explained hereinafter by reference to the Figures.
The graphs in FIGS. 1 and 2 show for comparison purposes data from
simulated life tests indicating the reforming activity and
stability of a conventional catalyst comprising platinum and
chloride on an alumina support and a catalyst comprising platinum,
tin, and chloride on an alumina support. Conditions of operation
were more severe than normally used in reforming operations in
order to simulate the response of the catalysts to much longer
tests (life tests). The graph in FIG. 1 shows the average catalyst
temperature as a function of the length of the test or hours
onstream required to maintain a 99 F-1 clear octane for each of the
two catalysts. The graph in FIG. 2 shows as a function of the time
onstream the yield of C.sub.5 + liquid product or gasoline having
99 F-1 clear octane rating produced during the reforming of each of
the two catalysts. From FIG. 2 it is seen that the process using
the platinum-tin catalyst yields significantly higher amounts of 99
F-1 clear octane product than the process using the platinum
catalyst without tin.
The graphs in FIGS. 3 and 4 show, as a function of the onstream
time, the average catalyst temperature and the C.sub.5 + gasoline
yield produced, respectively, for an accelerated test (as defined
in Example 2) reforming process conducted in accordance with the
present invention using a freshly prepared platinum-tin-chloride
catalyst. The graphs in FIGS. 5 and 6 show the same information
using a catalyst that was regenerated and activated as later
described after being used in a pilot plant test. The reforming
conditions included an average reactor pressure of 125 psig, a
hydrogen-to-hydrocarbon molar ratio of 3, and a liquid hourly space
velocity of 3. The catalyst temperature was adjusted as fouling
occurred to maintain production of a 100 F-1 clear octane product.
The catalyst responded well to regeneration and the yield of
C.sub.5 + product remained high over the entire run length.
Furthermore, the reforming periods, both with fresh and regenerated
and activated catalyst, were of substantial duration, i.e., around
20 to 25 hours. This is significant considering the low pressure
and accelerated nature of the tests.
DESCRIPTION OF THE INVENTION
The porous solid carrier or support which is employed in the
preparation of the catalyst of the present invention can be any of
a large number of materials upon which catalytically active amounts
of a platinum group component, a tin component, and a halogen
component can be included. The porous solid carrier can be, for
example, charcoal, or carbon. preferably, the porous solid carrier
is an inorganic oxide. A high surface area inorganic oxide carrier
is particularly preferred, e.g., an inorganic oxide having a
surface area of greater than 50 m.sup.2 /gm and preferably greater
than about 150 m.sup.2 /gm. Generally, the porous inorganic oxides
which are useful as catalyst supports for the present invention
have surface areas of from about 50 to 750 m.sup.2 /gm. Natural or
syhthetically produced inorganic oxides or combinations thereof can
be used. Typical acidic inorganic oxide supports which can be used
are the naturally occurring aluminum silicates, particularly when
acid treated to increase the activity, and the synthetically
produced cracking supports, such as silica-alumina,
silica-zirconia, silica-alumina-zirconia, silica-magnesia,
silica-alumina-magnesia, and crystalline zeolitic aluminosilicates.
For hydrocracking processes it is generally preferred that the
carrier comprises a siliceous oxide. Generally, preferred
hydrocracking catalysts contain silica-alumina, particularly
silica-alumina having a silica content in the range of 30 to 99
weight percent.
For reforming processes, it is generally preferred that the
catalyst has low cracking activity, that is, has limited acidity.
It is preferred for reforming processes to use inorganic oxide
carriers such as magnesia and alumina. Alumina is particularly
preferred for purposes of this invention. Any of the forms of
alumina suitable as a support for reforming catalysts can be used,
e.g., gamma alumina, eta alumina, etc. Gamma alumina is
particularly preferred. Furthermore, alumina can be prepared by a
variety of methods satisfactory for the purposes of this invention.
Thus, the alumina may be prepared by adding a suitable alkaline
agent such as ammonium hydroxide to a salt of aluminum, such as
aluminum chloride, aluminum nitrate, etc., in an amount to form
aluminum hydroxide which on drying and calcining is converted to
alumina. Alumina may also be prepared by the reaction of sodium
aluminate with a suitable reagent to cause precipitation thereof
with the resulting formation of aluminum hydroxide gel. Also
alumina may be prepared by the reaction of metallic aluminum with
hydrochloric acid, acetic acid, etc., in order to form a hydrosol
which can be gelled with a suitable precipitating agent, such as
ammonium hydroxide, followed by drying and calcination.
The catalyst of the present invention comprises a platinum group
component, a tin component, and a halogen in association with a
porous solid carrier, particularly a porous inorganic oxide
carrier. The platinum group component should be present in an
amount of from 0.01 to 5 weight percent, preferably from 0.01 to 3
weight percent, based on the finished catalyst. The platinum group
component embraces all the members of Group VIII of the Periodic
Table having an atomic weight greater than 100, i.e., ruthenium,
rhodium, palladium, osmium, iridium, and platinum, as well as
compounds and mixtures of any of these. Thus, the platinum group
components are the Group VIII noble metals or compounds thereof.
Platinum is preferred because of its better performance in
reforming and other hydroconversion reactions. When platinum is
used, particularly in reforming processes, the preferred amount is
from 0.01 to 3, more preferably 0.1 to 2 weight percent, and still
more preferably 0.1 to 0.9 weight percent. Regardless of the form
in which the platinum group component exists on the carrier,
whether as metal or compound, e.g., as an oxide, halide, sulfide,
or the like, the weight percent is calculated as the metal.
Reference to "platinum," "platinum group component," etc., is meant
to refer to both the metal and the compound form.
The tin component is present on the catalyst in an amount of from
0.01 to 5 weight percent and preferably from 0.01 to 3 weight
percent and more preferably from 0.1 to 1.5 weight percent, based
on the finished catalyst. The tin component can exist on the
carrier in the metallic form or as a compound., e.g., as an oxide,
sulfide, or the like. Reference to "tin" is meant to refer to both
the metal and the compound form of tin. Regardless of the form in
which tin exists on the carrier, whether as the metal or compound
form, the weight percent is calculated as the metal.
The platinum group component and tin component can be intimately
associated with the porous solid carrier by suitable techniques
such as ion exchange, precipitation, coprecipitation, etc.
Preferably, however, the components are associated with the porous
solid carrier by impregnation. Furthermore, one of the components
can be associated with the carrier by one procedure, e.g., ion
exchange, and the other component associated with the carrier by
another procedure, e.g., impregnation. As indicated, however, the
components are preferably associated with the carrier by
impregnation. The catalyst can be prepared by either coimpregnation
of the platinum group component and tin component or by sequential
impregnation.
The platinum group component is preferably associated with the
porous solid carrier by impregnation of water soluble compounds of
the platinum group metals. For example, platinum may be added to
the support by impregnation from an aqueous solution of
chloroplatinic acid. Other water soluble compounds of platinum
which may be incorporated as part of the impregnation solution are,
for example, ammonium chloroplatinates, platinum chloride,
polyammine platinum salts, etc. Compounds of the other platinum
group components may be used as, for example, palladium chloride,
rhodium chloride, etc. Impregnation solutions using organic
solvents may also be used.
The tin component is preferably associated with the porous solid
carrier suitably by impregnation. Impregnation can be accomplished
using an aqueous solution of a suitable compound. However, when
using an aqueous tin impregnating procedure, the resulting
catalytic composition of matter is preferably activated in order to
obtain optimum catalytic activity. The preferred activation process
comprises reacting the catalytic composition with an activating gas
including oxygen at a temperature from 500.degree.F. to
1300.degree.F. for at least 0.5 hours to calcine it. A halogenating
component, for example, carbon tetrachloride, chloroform, t-butyl
chloride, t-butyl fluoride or the like, may preferably be added
during the activation. The activating gas may be slightly moist.
The use of a slightly moist activating gas is preferred if a
halogenating component is included with said activating gas.
As another embodiment, the tin component is impregnated on the
carrier, which has previously been impregnated with a decomposable
compound of a platinum group component and calcined, from an
organic solution. Thus, a tin compound dissolved in ether or
alcohol or other suitable organic solvent may be used as the
impregnation solution. Care should be exercised after impregnation
that the organic material is completely evaporated or removed from
the catalyst prior to heating of the catalyst in the presence of a
reducing atmosphere, for example, hydrogen. Thus, careful drying or
calcination should follow impregnation using an organic solvent in
order to thoroughly rid the catalyst of hydrocarbon molecules. The
presence of hydrocarbons on the catalyst during contact with a
hydrogen atmosphere appears to detrimentally affect the performance
of the catalyst during hydroconversion reactions as, for example,
reforming. The organic solution is preferably substantially
anhydrous. If it is not substantially anhydrous, then the catalytic
composition should preferably be activated as described above to
insure that it has substantially optimum activity. In general, if
the catalytic composition is contacted with a substantial amount of
moisture during or after impregnation with a tin component, it is
desirable to activate the composite as disclosed above to insure
that it has substantially optimum activity.
Suitable tin compounds which can be used for impregnation are the
chlorides, nitrates, sulfates, acetates and ammine complexes. Also,
useful tin compounds include the organic tin compounds, such as the
tetra-alkyl compounds (tetra-, butyl, phenyl, ethyl, propyl, octyl,
decyl, tin and the like), and the tetra-alkoxide compounds (tin
tetraethoxides, etc.). Other useful compounds are the stannates.
The particular compound chosen will depend somewhat on the solvent
chosen, whether water, or an organic solvent. The tin can be in the
stannous or stannic oxidation state. It is particularly preferred
to use the chloride or halide compounds of tin inasmuch as the
impregnation not only distributes the tin component but also the
halide component, which is beneficial to most hydroconversion
reactions.
It is necessary to promote the catalyst for hydrocarbon
hydroconversion reactions by the addition of combined halogens
(halides), particularly fluorine or chlorine. Bromine may also be
used. The catalyst promoted with halogen usually contains from 0.1
to 10 weight percent, preferably 0.1 to 3 weight percent, total
halogen content. When the halogen is chlorine, it even more
preferably contains 0.5 to 2.0 weight percent and still more
preferably 0.8 to 1.6 weight percent, total chlorine content. The
preferred amounts are particularly desirable in reforming. The
halogens may be incorporated onto the catalyst at any suitable
stage of catalyst manufacture, e.g., prior to or following
incorporation of the platinum group component and tin component.
Generally, the halogens can be combined with the catalyst by
contacting suitable compounds such as hydrogen fluoride, ammonium
fluoride, hydrogen chloride, and ammonium chloride, either in the
gaseous form or in the water soluble form with the catalyst.
Preferably the fluorine or chlorine is incorporated with the
catalyst from an aqueous solution containing the halogen. Often
halogen is incorporated with the catalyst by impregnating with a
solution of a halogen compound of a platinum group metal or tin.
Thus, for example, impregnation with chloroplatinic acid normally
results in chlorine addition to the catalyst. Halogen may also be
incorporated during the activation process previously
described.
Following incorporation of the porous solid carrier with the
platinum group component, the tin component, and the halogen, the
resulting composite is usually treated by heating at a temperature
of, for example, no greater than 500.degree.F and preferably at
200.degree. to 400.degree.F. Thereafter the composite can be
calcined at an elevated temperature as, for example, up to
1,300.degree.F., if desired. In the case of sequential deposition
of the metal components onto the porous solid carrier, it may be
desirable to dry and calcine the catalyst after the introduction of
one of the metal components and prior to introduction of the
other.
Following calcination, the catalyst containing a platinum group
component and a tin component is preferably heated at an elevated
temperature in a hydrogen containing atmosphere, preferably dry
hydrogen to produce the catalyst in reduced form. It is
particularly preferred that this treatment with hydrogen be
accomplished at a range of 600.degree. to 1,300.degree.F and
preferably from 600 .degree. to 1000.degree.F. The heating in the
presence of hydrogen preferably continues until the partial
pressure of hydrogen substantially stabilizes. This will usually
take 5 minutes or longer. The treatment in the presence of hydrogen
should be accomplished in a hydrocarbon-free environment. Thus, any
hydrocarbon on the catalyst should be removed prior to contact with
the hydrogen. The environment should also be substantially free of
carbon oxides. By "reduced form" it is not meant to imply that the
entire catalyst or even all of the platinum group component and tin
component are reduced to a zero valence state, although the great
majority of the platinum group component is believed to be reduced
to the metal (zero valence). The reduction of the catalytic
composition as described above to form a reduced catalytic
composition enhances the usefulness of the catalytic composition
in, for example, reforming processes.
The novel catalytic composition of the present invention finds
utility for various hydrocarbon hydroconversion reactions including
hydrofining, hydrogenation, reforming, alkylation,
dehydrocyclization, isomerization, and hydrocracking. The catalyst
composition of the present invention is most advantageously used
for reforming. The hydrocarbon feeds employed and the reaction
conditions used will depend on the particular hydrocarbon
hydroconversion process involved and are generally well known in
the petroleum art. The conditions of temperature, pressure,
hydrogen flow rate, and liquid hourly space velocity in the
reaction zone can be correlated and adjusted depending on the
particular feedstock utilized, the particular hydrocarbon
hydroconversion process, and the products desired. For example,
hydrocracking operations are generally accomplished at a
temperature of from about 450.degree. to 900.degree.F and a
pressure between about 500 to 10,000 psig. Preferably pressures
between 1200 to 1600 psig are used. The hydrogen flow rate into the
reactor is maintained between 1000 to 20,000 SCF/bb1 of feed and
preferably in the range 4000 to 10,000 SCF/bb1. The liquid hourly
space velocity (LHSV) will generally be in the range of from 0.1 to
10 and preferably from 0.3 to 5.
As indicated above, the catalyst of the present The is preferably
employed in reforming. the feedstock desirably used for reforming
is a light hydrocarbon oil, e.g., a naphtha fraction. Generally,
the naphtha will boil in the range falling within the limits of
from 70.degree. to 550.degree.F and preferably from 150.degree. to
450.degree.F. The feedstock can be, for example, either a
straight-run naphtha or a thermally-cracked or
catalytically-cracked naphtha or blends thereof. The feedstock can
preferably be low in sulfur, i.e., preferably contain less than 10
ppm sulfur and more preferably less than 5 ppm sulfur. In the case
of a feedstock which is not already low in sulfur, acceptable
levels can be reached by hydrogenating the feedstock in a
presaturation zone where the naphtha is contacted with a
hydrogenation catalyst which is resistant to sulfur poisoning. A
suitable catalyst for this hydrodesulfurization process is, for
example, an alumina-containing support with a minor proportion of
molybdenum oxide and cobalt oxide. Hydrodesulfurization is
ordinarily conducted at a temperature of from 700.degree. to
850.degree.F, a pressure of from 200 to 2000 psig, and a liquid
hourly space velocity of from 1 to 5. The sulfur contained in the
naphtha is converted to hydrogen sulfide which can be removed prior
to reforming by suitable conventional processes.
The feedstock can preferably be low in moisture i.e., preferably
contain less than 50 ppm water (by weight) and more preferably less
than 15 ppm moisture. This limits the amount of moisture that
contacts the catalyst and thereby serves to keep the activity of
the catalyst high for longer periods of time.
Reforming conditions will depend in large measure on the feed used,
whether highly aromatic, paraffinic or naphthenic, and upon the
desired octane rating of the product. The temperature in the
reforming process will generally be in the range of about
600.degree. to 1100.degree.F and preferably about 700.degree. to
1050.degree.F. The pressure in the reforming reaction zone can be
atmospheric or superatmospheric. The pressure will generally lie
within the range of from 25 to 1000 psig and preferably from about
50 to 750 psig. The temperature and pressure can be correlated with
the liquid hourly space velocity (LHSV) to favor any particularly
desirable reforming reaction as, for example, dehydrocyclization,
or isomerization. Generally, the liquid hourly space velocity will
be from 0.1 to 10, and preferably from 1 to 5.
Reforming of a naphtha is accomplished by contacting the naphtha at
reforming conditions and in the presence of hydrogen with the
desired catalyst. Reforming generally results in the production of
hydrogen. The hydrogen produced during the reforming process is
generally recovered from the reaction products and preferably at
least part of said hydrogen is recycled to the reaction zone.
Preferably, the recycle hydrogen is substantially dried, as by
being contacted with an adsorbent material such as a molecular
sieve, prior to being recycled to the reaction zone. Thus, excess
or make-up hydrogen need not necessarily be added to the reforming
process, although it is sometimes preferred to introduce excess
hydrogen at some stage of the operation, for example, during
startup. Hydrogen, either as recycle or make-up hydrogen, can be
added to the feed prior to contact with the catalyst or can be
contacted simultaneously with the introduction of feed to the
reaction zone. Generally, during startup of the process, hydrogen
is recirculated over the catalyst prior to contact of the feed with
the catalyst. Hydrogen is preferably introduced into the reforming
reaction zone at a rate of from about 0.5 to 20 moles of hydrogen
per mole of feed. The hydrogen can be in admixture with light
gaseous hydrocarbons.
Although, as previously pointed out, it is not necessary, it may be
desirable in some instances to presulfide the catalyst prior to use
in catalytic hydroconversion reactions, for example, reforming. The
presulfiding can be done in situ or ex situ by passing a
sulfur-containing gas, e.g., H.sub.2 S, and hydrogen through the
catalyst bed. A temperature of from 25 to 1100.degree.F or more can
be used for the presulfiding. Other presulfiding treatments are
known in the prior art. It may also be desirable on startup of the
reforming process to use a small amount of sulfur, e.g., H.sub.2 S
or dimethyl disulfide. The sulfur compound is added to the
reforming zone in the presence of the flowing hydrogen. The sulfur
can be introduced into the reaction zone in any convenient manner
and at any convenient location. It can be contained in the liquid
hydrocarbon feed, the hydrogenrich gas, the recycle liquid stream
or a recycle gas stream or any combination.
After a period of operation when the catalyst becomes deactivated
by the presence of carbonaceous deposits, the catalyst can be
regenerated, for example, by passing an oxygen-containing gas
having no more than about 2 percent oxygen, into contact with the
catalyst at an elevated temperature in order to burn carbonaceous
deposits from the catalyst. The method of regenerating the catalyst
will depend on whether there is a fixed bed, moving bed, or
fluidized bed operation.
It may be desirable to activate the catalyst after if has been
regenerated by reacting it with an activating gas including oxygen.
The activating technique is that disclosed above for increasing the
activity of a catalyst where tin has been included by an aqueous
impregnating procedure. It is generally preferred to include a
halogenating component with the activating gas when activating a
deactivated and regenerated catalyst. The reason for this is that
the deactivated and regenerated catalyst may have lost some halogen
content during its use in a hydrocarbon hydroconversion process.
The catalyst may be analyzed for halide content to determine
whether a halogenating component should be included with the
activating gas.
After regeneration, or regeneration and activation if the catalyst
is activated, the catalyst is preferably heated at an elevated
temperature in a hydrogen containing atmosphere to reduce it.
Preferably the heating is performed in the presence of a
substantially hydrocarbon-free, hydrogen containing gas that is
preferably substantially dry at a temperature from 600.degree.F. to
1,300.degree.F., and more preferably from 600.degree.F. to
1000.degree.F. The substantially hydrocarbon-free
hydrogen-containing gas is preferably also free of carbon oxides
and water.
The process of the present invention will be more readily
understood by reference to the following Examples.
EXAMPLE 1
A catalyst comprising platinum, tin, and chlorine in association
with alumina was prepared as follows: Stannic tetrachloride
(anhydrous) in an amount of 0.5 ml was diluted to 65 mls by the
addition of absolute ethanol. The stannic tetrachloride-ethanol
solution was then contacted with 125 grams of a commercially
available 0.3 weight percent platinum-0.6 weight percent
chlorine-alumina catalyst. The impregnated composite was then left
for 2 hours in a closed vessel at room temperature. Thereafter the
composite was dried in a vacuum oven for approximately 16 hours at
about 250.degree.F. The catalyst was then calcined in flowing air
for about 2 hours at 900.degree.F and then reduced in one
atmosphere of hydrogen for 1 hour at 900.degree.F. The resulting
catalyst contained about 0.5 weight percent tin and about 1.0
weight percent chlorine.
The catalyst was tested for reforming of a naphtha feed having a
boiling range of 151.degree. to 428.degree.F comprising 23.4 volume
percent aromatics, 36.5 volume percent paraffins, and 40.1 volume
percent naphthenes. The feed was essentially sulfur free. Reforming
conditions included a pressure of 125 psig, a liquid hourly space
velocity of 3 and hydrogen to hydrocarbon mole ratio of 3;
once-through hydrogen was used. The temperature was adjusted to
maintain conversion to 99 F-1 clear octane product.
For comparison purposes, the commercially available 0.3 weight
percent platinum-0.6 weight percent chlorine-alumina catalyst was
also tested for reforming at the same reaction conditions and with
the same feed as that described above for the platinum-tin
catalyst.
The reforming processes were conducted under conditions to simulate
an accelerated life test for the catalyst. These conditions were
not necessarily maintained at levels used in a commercial reforming
process but, in general, were much more severe to test in a
relatively few hours how well the catalyst would perform. The
increase in temperature necessary to maintain conversion to 99 F-1
clear octane product was measured for each catalyst to give an
indication of the activity and temperature stability of each
catalyst. The results are shown in the graph in FIG. 1. The change
in yield of C.sub.5 + gasoline product over the period of the run
was measured for each catalyst to give an indication of the yield
stability of each catalyst. The C.sub.5 + gasoline yield product
having an octane rating of 99 F-1 clear is shown in FIG. 2.
The response of the platinum-containing catalyst to the simulated
life test was very poor compared to the performance of the
platinum-tin catalyst. As seen in FIG. 1, it was necessary to
increase the temperature very rapidly for the process using the
platinum catalyst without tin in order to maintain a 99 F-1 clear
octane. Moreover, the yield of C.sub.5 + liquid product having the
desired octane rating decreased significantly for the process using
the platinum catalyst without tin as shown in FIG. 2. On the other
hand, the catalyst comprising platinum and tin performed remarkably
well during the reforming test. From FIG. 1 it can be seen that the
reforming temperature required to maintain a 99 F-1 clear octane
product increased much slower as compared to the temperature
increase when reforming with the platinum catalyst without tin.
Also, from FIG. 2 the catalyst comprising platinum and tin
displayed remarkable stability during the reforming process. Thus,
the C.sub.5 + product remained very high during the reforming test
compared to the C.sub.5 + yield when reforming with the platinum
catalyst without tin. As another advantage of the platinum-tin
catalyst, it is noted that the initial startup temperature for the
process using the platinum-tin catalyst was significantly lower
than that of the process using the platinum catalyst without tin.
Also, production of low molecular weight hydrocarbons was low even
though the platinum-tin catalyst was not sulfided.
EXAMPLE 2
A catalyst (Catalyst A) comprising 0.3 weight percent platinum, 0.6
weight percent tin, and about 0.9 weight percent chlorine supported
on an alumina carrier was used in reforming a hydrofined,
catalytically cracked naphtha under accelerated conditions. The
catalyst was reduced prior to use. The process was conducted at
reforming conditions including an average reactor pressure of 125
psig, a hydrogen-to-hydrocarbon molar ratio of 3.0 and a liquid
hourly space velocity of 3. The temperature of the catalyst was
adjusted throughout the run to maintain production of a 100 F-1
clear octane product. The run was made using oncethrough hydrogen.
The hydrofined, catalytically cracked naphtha had an initial
boiling boint of 151.degree.F, an end boiling point of
428.degree.F, and a 50 percent boiling point of 307.degree.F. The
research octane number of the feed, without antiknock additives
(F-1 clear), was 64.6. The naphtha contained less than 0.1 ppm
nitrogen and less than 0.1 ppm sulfur. The feed was specifically
chosen because of its severe deactivating effect upon reforming
catalysts. Using this feed and the above reaction conditions, tests
of reforming catalysts can be accelerated, i.e., performed in a
fraction of the time needed with a less severely deactivating feed
and less severe conditions.
The results of reforming the naphtha at the accelerated conditions
specified, using Catalyst A, are shown in FIGS. 3 and 4. The graph
in FIG. 3 shows the average catalyst temperature in degrees
Farenheit as a function of the run length. The graph in FIG. 4
shows the C.sub.5 + yield decline as a function of the run
length.
A catalyst (Catalyst B) comprising 0.3 weight percent platinum, 0.6
weight percent tin, and about 1.35 weight percent chlorine
supported on an alumina carrier was used in reforming the same
hydrofined, catalytically cracked naphtha under the same
accelerated conditions as was Catalyst A. Catalyst B was a
regenerated and activated catalyst that had previously become
deactivated by use in a pilot plant run.
The regeneration of Catalyst B was accomplished by passing a gas
comprising nitrogen-oxygen, the oxygen being present in about 0.5
volume percent, through a bed of the catalyst at a temperature of
750.degree.F. The temperature in the bed increased to about
800.degree.F as the combustion flame travelled through the bed. The
temperature of the bed was then increased to about 850.degree.F and
a small amount of additional burning off of coke occurred.
The catalyst was contacted with an air-nitrogen-carbon
tetrachloride mixture having about 5 percent oxygen at a
temperature of about 950.degree.F to activate it. The
air-nitrogen-carbon tetrachloride mixture contained about 0.3
percent moisture. The catalyst was then flushed of air, moisture,
nitrogen, and carbon tetrachloride, heated in pure dry hydrogen at
900.degree.F to reduce it, and then contacted with the feed at
reforming conditions.
The results of reforming the naphtha at the conditions specified
with Catalyst B are shown in FIGS. 5 and 6. The graph in FIG. 6
shows the average catalyst temperature in degrees Farenheit as a
function of run length. The graph in FIG. 6 shows the C.sub.5 +
yield decline as a function of run length.
As can be seen from FIGS. 3-6, regeneration and activation of a
platinum-tin-chlorine catalyst results in the restoration of
substantially the initial activity of the catalyst, i.e., initial
catalyst temperature of Catalyst B was within a few degrees
Farenheit of the initial catalyst temperature of Catalyst A. It is
noted that a run length of approximately equal time can be obtained
after regeneration and activation.
The graphs in FIGS. 4 and 6 show the C.sub.5 + liquid yield
produced during the reforming process as a function of run length.
It can be seen that the yield remained at least about 85 volume
percent throughout the runs with both Catalyst A (fresh) and
Catalyst B (regenerated and activated).
The foregoing disclosure of this invention is not to be considered
as limiting since many variations can be made by those skilled in
the art without departing from the scope or spirit of the appended
claims. Thus, the catalyst of the present invention can be used for
isomerization of alkyl aromatics, e.g., the isomerization of
xylenes to other xylene isomers.
* * * * *