Utilization of sulfur dioxide in organic acids recovery and sulfur trioxide conversion with iron oxide as catalyst

摘要

Sulfur dioxide (SO2) is a primary air pollutant and its emission is strictly restricted by pertinent regulations. Methodology is to use SO 2 as a raw material to produce valuable chemicals while purifying the flue gas. Two approaches that use SO2 in the flue gas were put forward and examined. In the first approach, SO2 was used to recover acetic acid and lactic acid from the biological process. The second approach converted SO2 to SO3 through oxidation with iron oxide (Fe2O3) as catalyst. The experimental results of acetic and lactic acid recovery showed that both the reaction time and breakthrough time decreased with the increase of reaction temperature and SO2 flow rate. Analysis of the produced acetic and lactic acids demonstrated that the complete conversion of organic calcium salts to corresponding organic acids was not affected by the reaction conditions. The findings of this study indicated that recovering acetic acid and lactic acid with SO2 is both economical and environmentally beneficial. The oxidation of SO 2 was greatly enhanced by either microscale or nanoscale Fe2O 3 according to the experiment results. Nanoscale Fe2O 3 performed much better than its microscale counterpart in catalyzing the SO2 oxidation. The conversion of SO2 was temperature dependent for both types of Fe2O3. The reaction orders with respect to the reactants sulfur dioxide and oxygen were determined when using microscale and nanoscale iron oxides as catalysts. Empirical Arrhenius expressions of the catalytic oxidation of sulfur dioxide oxidation were derived based on rate constants obtained at different temperatures.