Process for the preparation of 1,1,1,2-tetrafluoroethane

Abstract

The present invention relates to a process for preparing a co-precipated Cr 2 O 3 /Al2O 3 catalyst promoted by Zinc, said process comprising co-precipatation of chromium and aluminum metal hydroxides from corresponding trivalent metal salt solutions using NH4OH, NaOH or KOH as a base and followed by calicination to give mixed oxide precatalyst in amorphous from which is impregnated with an activity promoting amount of Zinc compound. The catalyst is used for the preparation of HFC-134a by fluorination of trichloroethylene and fluorination of intermediate of the former reaction (HCFC-133a)

1 . A process for preparing a co-precipitated Cr 2 O 3 /Al 2 O 3  catalyst promoted by zinc, said process comprising co-precipitation from chromium and aluminum metal hydroxides from corresponding trivalent metal salt solutions using NH 4 OH, NaOH or KOH as a base and followed by calcination to provide a mixed oxide precatalyst in amorphous form, wherein the ratio of Cr:Al is in the range of 1:1 to 1:14, which is then impregnated with an activity promoting amount of zinc compound. 
     
     
         2 . A process as claimed in  claim 1 , wherein the metal hydroxide used is a bulk chromia. 
     
     
         3 . A process as claimed in  claim 1 , wherein the percent of zinc content in the catalyst is in the range of 2-12% by weight. 
     
     
         4 . A process as claimed in  claim 1 , wherein the ratio of Cr:Al is in the range of 4:1 to 38:1. 
     
     
         5 . A process for preparing a co-precipitated Cr 2 O 3 /Al 2 O 3  catalyst promoted by zinc, said process comprising co-precipitation from chromium and aluminum metal hydroxides from corresponding aqueous trivalent metal salt solutions using NH 4 OH, NaOH or KOH as a base, wherein the hydroxides are precipitated at a pH in the range of 7-8 by the addition of 1 to 6 molar solution of a base over a period of 0.2 to 20 hours, and followed by calcination to provide a mixed oxide precatalyst in amorphous form, which is then impregnated with an activity promoting amount of zinc compound. 
     
     
         6 . A process as claimed in  claim 1  wherein in step (a) the ratio of HF:TCE is in the range of 6:1 to 12:1 and preferably in the ratio of 7:1 to 10:1. 
     
     
         7 . A process as claimed in  claim 1 , wherein the weight ratio of water to trivalent metal salt is in the range 4:1 to 19:1. 
     
     
         8 . A process as claimed in  claim 1 , wherein the weight ratio of water to trivalent metal salt is in the range 4:1 to 10:1.