Catalytic decomposition of perfluorocarbons Part II. Decomposition of CF4 over AlPO4-rare earth phosphate catalysts

Catalytic activity of various metal phosphates were studied and it was found that Zr and Al phosphates are effective for CF4 decomposition in the presence of water vapor at above 600°C and the specific surface areas of these active catalysts were remarkably large after calcination at 1000°C for 5 h. No CF4 decomposition took place up to 700°C over the Mg2P2O7, Ca2P2O7, BPO4, FePO4 or the BiPO4 catalysts. The catalysts prepared from the solutions containing Al and rare earth (RE) nitrates and phosphoric acid are mixtures of the AlPO4 and RE phosphates. The mixtures of AlPO4 and phosphates of Y, La, Ce, Pr, Nd, and Gd increased in activity. Heavy rare earth elements (Er and Yb) showed little promotion effects. The catalytic activity of the Ce10%-AlPO4 slightly declined within the initial 40 h and then reached a steady value. 4.2 mol% of water vapor in the feed is sufficient for CF4 decomposition over Ce10%-AlPO4.