The catalytic decomposition of CHF 3 over ZrO 2-SO 4

Abstract

The destruction of CHF 3 over ZrO 2 and ZrO 2-SO 4 was studied in a fixed bed catalytic reactor system in dry and humid air streams. The addition of sulfate to the zirconia greatly improved the catalytic activity, decreasing the light-off temperature by approximately 40°C. The destruction of CHF 3 proceeded according to a catalyzed hydrolysis reaction, rather than an oxidation reaction, thereby necessitating that water be present in the feed stream. The presence of water in the feed stream had a significant effect on the stability of the catalyst. In dry air, the catalyst rapidly deactivated. Deactivation is attributed to the fluorination of the zirconium, which results in a loss of oxygen and sulfur from the catalyst and a significant decrease in surface area. The addition of 2.5% water to the feed stream greatly improves the catalyst’s stability; however, some deactivation was observed. Deactivation in humid air was attributed to a gradual accumulation of fluorine on the catalyst, which resulted in a loss of sulfate and oxygen from the zirconia, and a decrease in the surface area of the catalyst.