Gas-Phase Total Oxidation of Benzene, Toluene, Ethylbenzene, and Xylenes Using Shape-Selective Manganese Oxide and Copper Manganese Oxide Catalysts

Abstract

Volatile organic compounds (VOCs) continue to be the major source of direct and indirect air pollution. Here, cryptomelane-type octahedral molecular sieve (OMS-2) manganese oxide, amorphous manganese oxide (AMO), and mixed copper manganese oxide (CuO/Mn2O3) nanomaterials were synthesized and, together with commercial MnO2, characterized by various techniques. These catalysts were investigated for gas-phase total oxidation of six VOCs under air atmosphere. Using OMS-2 at 250 °C, the average conversions for toluene, benzene, ethylbenzene, p-xylene, m-xylene, and o-xylene were 75%, 61%, 45%, 23%, 13%, and 8%, respectively, whereas using CuO/Mn2O3, 72%, 44%, 37%, 29%, 27%, and 26%, respectively, were obtained. Generally, the conversion of VOCs to CO2 using the synthesized catalysts increased in the order: o-xylene ≈ m-xylene < p-xylene < ethylbenzene < benzene < toluene. However, using commercial MnO2, benzene (44% conversion) was more reactive than toluene (37%), and the xylenes showed similar reactivities (...