Investigation into chromia-based catalyst and its application in preparing difluoromethane

The air-calcined chromia-based catalysts and nitrogen-calcined chromia-based catalysts are prepared and used for a vapor-phase catalytic fluorination reaction in preparing difluoromethane. It has been found that the air-calcined catalysts show much higher catalytic activity than that of nitrogen-calcined catalysts in the above mentioned reaction, which is attributed to the formation of a Cr species with high oxidation state on the air-calcined catalyst. Moreover, when the catalyst precursor is treated with anhydrous hydrogen fluoride at low temperature, the crystallized catalyst is easily formed and the catalytic reaction activity is decreased.