Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And additional al or si containing component
Reexamination Certificate
1998-12-29
2001-04-17
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
And additional al or si containing component
C502S060000, C502S064000, C502S074000
Reexamination Certificate
active
06218328
ABSTRACT:
FIELD OF THE INVENTION
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
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 useful for selectively dehydrogenating n-butane to butene products without producing coke at a commercially inhibiting rate.
SUMMARY OF THE INVENTION
It is an object of this invention to at least partially dehydrogenate n-butane to butenes.
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.
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.
A still further object of this invention is to accomplish the dehydrogenation of n-butane while minimizing the co-production of coke.
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.
Other objects and advantages of the invention will become apparent from the detailed description and the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
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
6
Na
3
[Al
9
Si
27
O
72
].21H
2
O.
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
2
/g, and the particle size is about 1-10 mm. The compounded zeolite composition can be subjected to heat treating as described below.
In the preferred embodiment of this invention the type L zeolite is admixed with bentonite, Al
2
(OH)
5
Cl.5H
2
O 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.
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.
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.
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° C. to about 800° C. Preferably, this temperature range is from about 350° C. to about 700° C. and, most preferably, the temperature of this heat treatment is in a range of about 450° C. to about 600° C.
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
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° 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.
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° 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° C. for about 1-10 hours to produce a titania-impregnated zeolite composition.
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)
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.
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
Drake Charles A.
Wu An-hsiang
Griffin Steven P.
Ildebrando Christina
Phillips Petroleum Company
Richmond, Hitchcock, Fish & Dollar
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