Catalytic decomposition of CFC-12 over solid acids WO3/MxOy (M = Ti, Sn, Fe)

Catalytic decomposition of dichlorodifluoromethane (CFC-12) in the presence of water vapor was investigated over a series of pure and WO3-promoted metal oxides. Although pure TiO2, SnO2 and Fe2O3 showed less activity for the decomposition of CFC-12, obvious enhancement in activity was actualized by supporting WO, on them using Ti(OH),, Sn(OH), and Fe(OH), as support precursors. The decomposition activity depended on the calcination temperature obviously and attained to a maximum as the content of WO, reached its utmost dispersion capacity on different supports. The 95% conversion temperature of WTi, WSn and WFe catalysts prepared by optimum conditions were 260%, 315 degrees C and 345 degrees C, respectively. CO, was;the main-product and no CO was detected as by-product. The selectivity to by-product CFC-13 on WO3-modified metal oxides was much lower than on unmodified metal oxides and it also exhibited a coverage-dependent effect. The catalytic activity of WO3/TiO2, WO3/SnO2 and WO3/Fe2O3 all remained steady for 120 h on stream. (C) 2000 Elsevier Science B.V. All rights reserved.