Oxidative Fixation of SO2 into Aqueous H2SO4 over a Pitch-Based Active Carbon Fiber above Room Temperature

Oxidative fixation of SO 2 into aqueous H 2 SO 4 was examined at 50−70 °C over a pitch-based active carbon fiber (ACF) of large surface area. A higher temperature was found to require higher humidity and a longer contact time for the complete removal of SO 2 at the stationary state. Smaller adsorption of SO 2 and less condensed water on the ACF make it difficult to fix SO 2 on the ACF and to elute aqueous H 2 SO 4 continuously from the ACF, as revealed by the adsorbed SO 2 on ACF and the eluted aqueous H 2 SO 4 from the bed. Among the ACFs of different calcination temperatures, a particular ACF of the largest surface area calcined at 1100 °C showed the largest activity regardless of the reaction temperatures and humidity, indicating a major influence of the number of active sites. The hydrophilicity of the ACF has little influence on condensing water on the ACF above room temperature.