Decomposition of chlorofluorocarbons over metal phosphate catalysts Part I. Decomposition of CCl_2F_2 over metal phosphate catalysts

摘要

In the decomposition of chlorofluorocarbons (CFCs), HF produced in the decomposition reacts with and deactivates the catalyst. Metal phosphates were chosen as the catalyst from #DELTA#G calculations. Zr-P-O and AlPO_4 showed high catalytic activity for the decomposition of CCl_2F_2 above 350 deg C. The essential reaction of the decomposition is hydrolysis. On increasing the CCl_2F_2 concentration in the feed, the formation of CClF_3 as a by-product is promoted. AlPO_4 has both weak acid sites and those of intermediate strength and these acid sites may participate in the hydrolysis of CCl_2F_2. No reaction between AlPO_4 and formed HF was observed during 1000 h reaction at 400 deg C, AlPO_4 promises to be of practical use.