An Investigation of CFC12 (CCl 2F 2) Decomposition on TiO 2 Catalyst

Abstract

The catalytic oxidation of CFC12 was studied over a titania (TiO 2) catalyst in a fixed-bed reactor at temperatures ranging from 200 to 400°C and space velocity of 10,500 h −1. Results showed substantially complete conversion of CFC12 (>90%) to CO 2 and halogen acids at and above 300°C. Longer term deactivation studies carried out in the presence of water vapor as a cofeed at 300°C showed less than 5% change in activity and selectivity of the titania catalyst even after 4 days of operation. Nevertheless, a 75% reduction in catalyst surface area was observed after 4 days, most of which (50%) took place during the initial 1-1.5 h of reaction. Despite the 50% drop in surface area, the activity of the titania catalyst increased during the initial 1-1.5 h. Results of various experiments indicated that the increased activity of the catalyst was brought about by an increase in surface acidity due to surface fluorination. In situ FTIR techniques were employed to study the reaction mechanism of CFC12 destruction on the titania catalyst. Results indicated adsorption of CFC12 on the surface hydroxyls with further reaction between adsorbed CFC12 and surface hydroxyls leading to the formation of complete oxidation products through COFCl and COCl 2 intermediates.