PHOTOCATALYTIC REDUCTION OF CARBON DIOXIDE IN GAS STEAMS BY UV/TiO_2 PROCESS

摘要

The reduction of carbon dioxide in gas streams by UV/TiO_2 process was studied in a flow reactor under various retention time, humidity contents, initial carbon dioxide concentrations, and UV light intensities. TiO_2 particles were used as photocatalyst and impregnated on the non-woven fabric textile for the reduction of carbon dioxide in gas streams under the irradiation of 365 nm UV light. The primary products from carbon dioxide reduction were determined to be methane and methanol. The photocatalytic reduction rate of carbon dioxide was found to be increased linearly with increasing initial of carbon dioxide concentration and can be well described by a Langmuir-Hinshelwood type rate equation suggesting that the adsorption of CO_2 on TiO_2 is the rate-determining step. The reduction rate of gaseous carbon dioxide was increased with increasing humidity content present in the gas stream for experiments conducted with humidity less than 55%. However, the reduction rate was decreased with increasing humidity content for experiments conducted with the presence of more than 55% humidity. Combing the equations of continuity and surface catalyst kinetics, a quasi-global kinetic model is developed for modeling the reduction of carbon dioxide by UV/TiO_2 process at various operation conditions.