Hydrolysis driving redox reaction to synthesize Mn-Fe binary oxides as highly active catalysts for the removal of toluene

Abstract

A novel hydrolysis driving redox reaction via combining selective reduction of KMnO4 by H2O2 and hydrolysis of Fe salts has been successfully applied to rapidly prepare a series of homogenous Mn-Fe binary oxides (xMn1Fe). The 3Mn1Fe catalyst exhibits better catalytic activity for toluene oxidation compared to MnO2, Fe2O3 and Cop-3Mn1Fe. The improved performance of 3Mn1Fe could arise from higher surface area, higher amount of Mn3+ ions, higher concentration of lattice defects and oxygen vacancies, and better low-temperature reducibility, as well as homogenous distribution of Mn and Fe. In terms of Mn/Fe ratio in xMn1Fe, the 5Mn1Fe catalyst exhibits a higher catalytic activity in toluene conversion. At 137 and 147°C, the conversion efficiency of toluene by 5Mn1Fe can reach 50% and 90%, respectively, while at 215°C a complete mineralization of toluene (20000mL/(gh), 1000ppm) can be achieved. The application of high GHSV of 240000mL/(gh) confirms that the 5Mn1Fe catalyst still has high catalytic ability in the removal of toluene, showing complete mineralization at 250°C. The endurability test (240000mL/(gh)) and the water effect test of the 5Mn1Fe catalyst show that it has good stability, renewability, and high toleration of high-moisture. With the combination of in situ Raman, in situ FTIR characterizations and on-line MS, the mechanism for catalytic oxidation of toluene over xMn1Fe is revealed.