Patent ID: 6723887
Filing Date: 2004-04-20
Classification: C07C

Abstract:
A process for the preparation of difluoromethane (HFC-32) by vapor phase fluorination of methylene chloride with anhydrous hydrogen fluoride (AHF) in the presence of a coprecipitated chromia-alumina impregnated with zinc salt as catalyst at a temperature ranging from 225-375Â° C. and contact time not exceeding 20 seconds, removing HCI and heavier components by distillation, subjecting HFC-32 rich cut to a further step of fluorination in presence of fluorination catalyst to convert chlorofluoromethane HCFC-31, an intermediate formed along with HFC -32, to HFC-32 thereby reducing the concentration of HCFC 31 in HFC-32 rich cut to obtain pure HFC-32.