Processes for preparing a catalyst

Abstract

Processes for purifying silicon tetrafluoride source gas by subjecting the source gas to one or more purification processes including: contacting the silicon tetrafluoride source gas with an ion exchange resin to remove acidic contaminants, contacting the silicon tetrafluoride source gas with a catalyst to remove carbon monoxide, by removal of carbon dioxide by use of an absorption liquid, and by removal of inert compounds by cryogenic distillation; catalysts suitable for removal of carbon monoxide from silicon tetrafluoride source gas and processes for producing such catalysts.

1 . A process for preparing a catalyst comprising an inert substrate and a catalytic metal oxide being at or near the surface of the inert substrate, the process comprising:
 impregnating catalytic metal on the surface of or throughout the bulk of an inert substrate; and   heating the metal-impregnated inert substrate to a temperature of at least about 250° C. to form a catalytic metal oxide at or near the surface of the inert substrate.   
     
     
         2 . A process as set forth in  claim 1  wherein the metal-impregnated inert substrate is heated to a temperature of from about 250° C. to about 1000° C. 
     
     
         3 . A process as set forth in  claim 1  wherein the inert substrate comprises an inert metal oxide and is prepared by reacting a first metal halide comprising an inert metal with hydrogen in an oxygen and hydrogen flame to produce a inert substrate powder. 
     
     
         4 . A process as set forth in  claim 3  wherein the catalytic metal is impregnated throughout the inert substrate by reacting a second metal halide comprising the catalytic metal with hydrogen in an oxygen and hydrogen flame concurrently with the reaction between the first metal halide and hydrogen. 
     
     
         5 . A process as set forth in  claim 1  wherein the catalytic metal is impregnated onto the inert substrate by precipitating catalytic metal from a metal salt solution onto the inert substrate. 
     
     
         6 . A process as set forth in  claim 1  wherein the catalytic metal oxide comprises a metal selected from the group consisting of copper, manganese, chromium, cobalt, thallium, molybdenum, silver and mixtures thereof. 
     
     
         7 . A process as set forth in  claim 6  wherein the catalytic metal oxide comprises a metal selected from the group consisting of copper, manganese or mixtures thereof. 
     
     
         8 . A process as set forth in  claim 1  wherein the inert substrate is selected from the group consisting of zirconia, alumina silicate, silica, alumina, yttria and mixtures thereof. 
     
     
         9 . A process as set forth in  claim 8  wherein the inert substrate is selected from the group consisting of zirconia, alumina silicate or mixtures thereof. 
     
     
         10 . A process as set forth in  claim 1  wherein the inert substrate comprises a metal oxide stabilizer comprising a metal selected from the group consisting of lanthanides, actinides, magnesium, yttrium, calcium, and mixtures thereof. 
     
     
         11 . A process as set forth in  claim 10  wherein the inert substrate comprises less than about 0.1% by weight stabilizer. 
     
     
         12 . A process as set forth in  claim 1  wherein the inert substrate comprises less than about 0.1% by weight yttrium oxide as a stabilizer. 
     
     
         13 . A process as set forth in  claim 1  wherein the catalyst comprises at least about 95% inert substrate by weight, less than about 3% catalytic metal by weight and less than about 0.5% stabilizer by weight. 
     
     
         14 . A process as set forth in  claim 1  wherein the catalyst comprises from about 0.001% to about 1.0% by weight catalytic metal. 
     
     
         15 . A process as set forth in  claim 1  wherein the catalyst comprises about 95% to about 99.999% by weight inert substrate. 
     
     
         16 . A process as set forth in  claim 1  wherein the substrate has a surface area from about 1 m 2 /g to about 1000 m 2 /g. 
     
     
         17 . A process as set forth in  claim 1  wherein the substrate has a bulk porosity of from about 30% to about 80%.