Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1998-11-03
2001-01-23
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S224000, C502S226000, C502S227000, C502S230000, C502S231000, C502S304000, C502S328000, C502S329000, C502S330000, C502S332000, C502S334000, C502S339000, C502S349000, C502S351000, C502S352000, C502S353000, C502S354000, C428S403000, C428S404000, C428S701000, C428S702000
Reexamination Certificate
active
06177381
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a layered catalyst composition, a process for preparing the composition and hydrocarbon conversion processes using the composition. The layered composition comprises an inner core such as alpha alumina, and an outer layer, comprising an outer refractory inorganic oxide, bonded to the inner core. The outer layer has uniformly dispersed thereon at least one platinum group metal, and a promoter metal. The catalyst composition further contains a modifier metal.
BACKGROUND OF THE INVENTION
Platinum based catalysts are used for numerous hydrocarbon conversion processes. In many applications promoters and modifiers are also used. One such hydrocarbon conversion process is the dehydrogenation of hydrocarbons, particularly alkanes such as isobutane which are converted to isobutylene. For example, U.S. Pat. No. 3,878,131 (and related U.S. Pat. Nos. 3,632,503 and 3,755,481) discloses a catalyst comprising a platinum metal, a tin oxide component and a germanium oxide component. All components are uniformly dispersed throughout the alumina support. U.S. Pat. No. 3,761,531 (and related U.S. Pat. No. 3,682,838) discloses a catalytic composite comprising a platinum group component, a Group IVA metallic component, e.g., germanium, a Group VA metallic component, e.g., arsenic, antimony and an alkali or alkaline earth component all dispersed on an alumina carrier material. Again all the components are evenly distributed on the carrier.
U.S. Pat. Nos. 3,558,477, 3,562,147, 3,584,060 and 3,649,566 all disclose catalytic composites comprising a platinum group component and a rhenium component on a refractory oxide support. However, as before, these references disclose that the best results are achieved when the platinum group component and rhenium component are uniformly distributed throughout the catalyst.
It is also known that for certain processes selectivity towards desirable products is inhibited by excessive residence time of the feed or the products at the active sites of the catalyst. Thus, U.S. Pat. No. 4,716,143 describes a catalyst in which the platinum group metal is deposited in an outer layer (about 400 &mgr;m) of the support. No preference is given to how the modifier metal should be distributed throughout the support. Similarly U.S. Pat. No. 4,786,625 discloses a catalyst in which the platinum is deposited on the surface of the support whereas the modifier metal is evenly distributed throughout the support.
U.S. Pat. No. 3,897,368 describes a method for the production of a noble metal catalyst where the noble metal is platinum and the platinum is deposited selectively upon the external surface of the catalyst. However, this disclosure describes the advantages of impregnating only platinum on the exterior layer and utilizes a specific type of surfactant to achieve the surface impregnation of the noble metal.
The art also discloses several references where a catalyst contains an inner core and an outer layer or shell. For example, U.S. Pat. No. 3,145,183 discloses spheres having an impervious center and a porous shell. Although it is disclosed that the impervious center can be small, the overall diameter is ⅛″ or larger. It is stated that for smaller diameter spheres (less than ⅛″), uniformity is hard to control. U.S. Pat. No. 5,516,740 discloses a thin outer shell of catalytic material bonded to an inner core of catalytically inert material. The outer core can have catalytic metals such as platinum dispersed on it. The '740 patent further discloses that this catalyst is used in an isomerization process. Finally, the outer layer material contains the catalytic metal prior to it being coated onto the inner core.
U.S. Pat. Nos. 4,077,912 and 4,255,253 disclose a catalyst having a base support having deposited thereon a layer of a catalytic metal oxide or a combination of a catalytic metal oxide and an oxide support. WO98/14274 discloses a catalyst which comprises a catalytically inert core material on which is deposited and bonded a thin shell of material containing active sites.
Applicants have developed a layered catalyst composition which differs from the prior art in several ways. The composition comprises an inner core such as alpha alumina and an outer layer such as gamma alumina. The outer layer has uniformly distributed thereon at least one platinum group metal such as platinum and a modifier metal such as tin. The platinum group metal to modifier metal atomic ratio varies from about 0.1 to about 5. The outer layer has a thickness of about 40 to about 400 microns. A modifier metal, e.g., lithium, is also present on the catalyst composition and may be present either entirely in the layer or distributed throughout the catalyst composition. Finally, the composition is prepared using an organic bonding agent such as polyvinyl alcohol which increases the bond between the layer and the inner core thereby reducing loss of the layer by attrition.
SUMMARY OF THE INVENTION
The present invention relates to a layered catalyst composition, a process for preparing the composition and hydrocarbon conversion processes using the composition. One embodiment of the invention is a hydrocarbon conversion process comprising contacting a hydrocarbon fraction with a layered composition under hydrocarbon conversion conditions to give a converted product, the layered composition comprising an inner core, an outer layer bonded to said inner core to the extent that the attrition loss is less than 10 wt. % based on the weight of the outer layer and, the outer layer comprising an outer refractory inorganic oxide having uniformly dispersed thereon at least one platinum group metal and at least one promoter metal, the catalyst composition further having dispersed thereon at least one modifier metal.
Another embodiment of the invention is a process for preparing the layered catalyst composition described above, the process comprising:
a) coating an inner core with a slurry comprising the outer refractory inorganic oxide and an organic bonding agent, said outer oxide having uniformly dispersed thereon at least one promoter metal, drying the coated core and calcining at a temperature of about 400° C. to about 900° C. for a time sufficient to bond the outer layer to the inner core and provide a layered support; and
b) uniformly dispersing on the layered support of step (a) a modifier metal and a platinum group metal to give a product; and
c) reducing the product of step (b) at reduction conditions to provide said layered catalyst composition.
A further embodiment of the invention is a process for preparing a layered catalyst composition comprising an inner core, an outer layer bonded to said inner core, the outer layer bonded to the inner core to the extent that the attrition loss is less than 10 wt. % based on the weight of the outer layer and the outer layer comprising an outer refractory inorganic oxide, having uniformly dispersed thereon at least one platinum group metal and at least one promoter metal, the catalyst composition further having dispersed thereon at least one modifier metal; the process comprising uniformly dispersing on the outer refractory oxide at least one modifier metal, at least one platinum group metal and at least one promoter metal, and coating an inner core with a slurry comprising the outer refractory oxide containing said platinum group metal, promoter metal, modifier metal and an organic bonding agent, drying and then calcining the coated core at a temperature of about 400° C. to about 900° C. for a time sufficient to provide a layered catalyst composition.
A still further embodiment is a layered catalyst composition comprising an inner core, an outer layer bonded to said inner core, the outer layer comprising an outer refractory inorganic oxide having uniformly dispersed thereon at least one platinum group metal, a promoter metal and the catalyst composition further having dispersed thereon a modifier metal and where the inner core is selected from the group consisting of alpha alumina, theta alumina, s
Bricker Jeffrey C.
Chen Qianjun
Hara Koji
Jensen Robert H
Kikuchi Kenji
Bell Mark L.
Hailey Patricia L.
Molinaro Frank S.
Tolomei John G.
UOP LLC
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