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. OMS-2 was the most active for toluene, benzene, ethylbenzene oxidation; whereas CuO/Mn2O3 was the most active for xylenes. Generally, the conversion of VOCs to CO2 using the synthesized catalysts increased in the order:  o-xylene~m-xylene<p-xylene<ethylbenzene<benzene<toluene. Differences in reactivity among VOCs were rationalized in terms of degree of substrate adsorption and structural effects. The higher oxidative activities exhibited by OMS-2, AMO, and CuO/Mn2O3 as compared to commercial MnO2 were attributed to a combination of factors including structure, morphology, hydrophobicity, and redox properties. The mobility and reactivity of active oxygen species are strongly correlated with catalytic activities. Lattice oxygen was involved in the VOC oxidation suggesting a Mars-van Krevelen mechanism.

Gas-phase total oxidation of benzene, toluene, ethylbenzene, and xylenes using shape-selective manganese oxide and copper manganese oxide catalysts

244th National Meeting (2012)

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