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

Abstract

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.