Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1999-09-09
2002-04-09
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S300000
Reexamination Certificate
active
06368998
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process for the preparation of catalyst with improved catalytic properties, particularly improved initial activity, initial selectivity and/or activity performance over time and/or selectivity performance over time.
BACKGROUND OF THE INVENTION
The presence of certain species contained in the carriers of catalysts can be detrimental to the metal deposition process and/or catalyst performance and it is commonly believed that the concentration of these detrimental species must be controlled throughout the bulk of carrier. One way of controlling the amount of impurities through the bulk, although expensive, is by the use of purer raw materials. For example, U.S. Pat. No. 4,797,270 discloses water washing to reduce the sodium content of an alumina powder. The pH of the wash water may need to be adjusted for extraction of other metals and Japanese patent JP56164013 discloses the use of a low pH (acid) to extract uranium and thorium from a calcined &agr;-alumina raw material.
Several procedures in the art teach that washing after deposition of the catalytic metal is helpful. U.S. Pat. Nos. 4,361,504 and 4,366,092 suggest that ethylene oxide catalyst be water washed after the deposition of silver or silver/gold on the carrier. EP-211521 discloses washing of a catalyst with hot water to remove basic materials left on the catalyst from a silver impregnation process or the physical deposition of alkali metals. U.S. Pat. No. 4,367,167 discloses a process for preparing a supported catalyst wherein an impregnated support is immersed in an inert water immiscible organic solvent containing a dissolved aliphatic amine. U.S. Pat. No. 4,810,689 discloses depositing a silver compound, decomposing the silver compound to silver in the presence of an alkali metal compound, removing organic deposits by washing and introducing fresh alkali metal by impregnation during or after the washing stage. U.S. Pat. Nos. 4,186,106 and 4,125,480 disclose washing with an inert liquid after deposition of the catalytic metal and before deposition of a promoter material.
U.S. Pat. No. 4,908,343 teaches that it may be desirable to remove cations which are exchangeable with the alkali and alkaline earth metals contained in the impregnating solution, to allow for ease of repeatability in the use and reuse of the impregnating solution. No methods are taught for such removal; however, it is commonly known in the art that acids are highly effective cation removal solutions. U.S. Pat. No. 2,901,441 teaches washing a carrier with lactic acid then flushing with water.
The prior art remains concerned with the total amount of impurities; i.e., impurities throughout the bulk. Unfortunately, the impurity removal techniques taught typically attack the carrier itself. It has surprisingly been found that the metal deposition and/or catalytic properties of a catalyst may be greatly improved by controlling the purity of the surface of the carrier rather than the purity of the carrier bulk, such that the total amount of impurities may actually be high as long as the surface amount of impurities are maintained at a low level.
SUMMARY OF THE INVENTION
According to one embodiment of the invention, there is provided a process for improving the properties of a carrier, said process comprising selecting a carrier; and lowering a concentration of one or more ionizable species present on a surface of said carrier.
There is further provided a process for improving a carrier comprising selecting one or more materials; lowering a concentration of one or more ionizable species present in at least one of said one or more materials; forming a carrier comprising said one or more materials; and lowering a concentration of one or more ionizable species present on a surface of said carrier.
There is still further provided a process for improving the catalytic properties of a catalyst, said process comprising:
selecting a carrier;
lowering a concentration of one or more ionizable species on a surface of said carrier by a means effective in solubilizing the ionizable species and removing that species, or rendering the ionizable species insoluble, or rendering the ionizable species immobile;
optionally drying said carrier;
depositing a catalytically effective amount of one or more catalytically reactive metals on said carrier, thereby forming a catalyst precursor; and
optionally drying said catalyst precursor.
In another embodiment of the invention, there is provided a process for improving the catalytic properties of a catalyst, said process comprising:
selecting one or more materials;
lowering a concentration of one or more ionizable species present in at least one of said one or more materials by a means effective in solubilizing ionizable species and removing that species, or rendering the ionizable species insoluble, or rendering the ionizable species immobile;
forming a carrier comprising said one or more materials;
optionally lowering a concentration of one or more ionizable species on a surface of said carrier by a means effective in solubilizing and removing said ionizable species or rendering said ionizable species insoluble;
optionally drying said carrier;
depositing a catalytically effective amount of one or more catalytically reactive metals on said carrier, thereby forming a catalyst precursor; and
optionally drying said catalyst precursor.
In yet another embodiment of the invention there is provided a process for preparing a catalyst suitable for the vapor phase production of epoxides, said process comprising:
selecting a carrier;
lowering a concentration of one or more ionizable species present on a surface of said carrier;
optionally drying said carrier; and
depositing a catalytically effective amount of one or more catalytically reactive metals on said carrier.
The invention also provides for catalyst made by the processes of the embodiments herein described.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
It has been found that carriers which have been treated to reduce certain undesirable ionizable species, particularly anionic species, which are present on the surface of the carrier provide catalysts with improved catalytic properties, such as activity, selectivity and activity and/or selectivity performance over time, when compared with the performance of catalysts made from carriers which have not been so treated. The process is believed to work to improve the properties of most catalysts, no matter how impure the bulk carrier material, compared to a catalyst made with an untreated carrier. Further, the process will work for organic or inorganic carriers.
The process is effective in improving one or more of the catalytic properties of a catalyst wherein a catalytically reactive metal is deposited or impregnated upon a carrier which contains ionizable species on its surface. “Improvement in catalytic properties” as used herein means the properties of the catalyst are improved as compared to a catalyst made from the same carrier which has not been treated to lower surface ionizable species. Catalytic properties include catalyst activity, selectivity, activity and/or selectivity performance over time, operability (resistance to runaway), conversion and work rate.
The process requires that the concentration of undesirable ionizable species present on the surface of the carrier be reduced. As used herein, the “surface” of the carrier is that area of the carrier which may be measured by the standard method of Brunauer, Emmett and Teller (BET). Specifically, the surface of the carrier is the site at which reaction takes place. An “ionizable” species is a species which is capable of being rendered ionic, where the term “ionic” or “ion” refers to an electrically charged chemical moiety.
Carriers are commonly inorganic materials such as, for example, alumina-, silica-, or titania-based compounds, or combinations thereof, such as alumina-silica carriers. Carriers may also be made from carbon-based materials such as, for example, charcoal, activated carbon, or fullerenes. Ionizable species typically pr
Griffin Steven P.
Idebrando Christina
Shell Oil Company
Steinberg Beverlee G.
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