Abstract: The decomposition of CF4 in the absence of water on γ-Al2O3-based metal oxides was carried out to destruct the disposal perfluoro-carbons (PFCs) from industrial processes. In the present work, the conversion of CF4 was tested over bare γ-Al2O3 at different temperatures of 825, 850 and 900 ℃. It was found that the initial activity of Al2O3 increased in the order of 825 ℃<850 ℃<900 ℃CO2 yield declined quickly with time on stream because the un-reacted γ-Al2O3 was transformed into inactive α-Al2O3 phase that resulted from the highly exothermic effect of Al2O3-fluorination reaction. As for the CF4 decomposition on MgO-Al2O3, fluorination of Mg species and the highly exothermic effect produced led to the collapse of MgAl2O4 structure, in which the magnesium element was fluorinated into MgF2. Al2O3 modified with P or Ni could inhibit the transformation of un-reacted γ-Al2O3 into α-Al2O3 during CF4 decomposition, and consequently CF4 conversion reached a stable level with time on stream.

Key words: CF4 decomposition, Al2O3, Transformation of γ-Al2O3 into α-Al2O3, Modified Al2O3