Mixed metal oxide catalysts are important for many industrial applications, for instance, for chemical and fuel productions from C1 feedstock such as CH3OH and CH4, and for environmental protection by removal of CH4 as a significant greenhouse gas. Experimental and computational studies on the catalytic mechanisms of mixed metal oxide catalysts are very challenging due to the complexity of their surface and electronic structure. In collaboration with the experimental team, we constructed extended surface models for several mixed oxide catalysts, including anatase TiO2 supported vanadia, Sr-doped La2O3, and Pd-doped Co3O4, and investigated their thermodynamic stability under relevant reactive environments and their catalytic mechanisms for the activation and oxidation of CH4 and CH3OH. For the VOx/TiO2 catalyst, we explained the selective formation of methyl formate and dimethoxymethane from CH3OH oxidation and the possible role of the sulfate promoter. For the Sr-doped La2O3 catalyst, we established its catalytic mechanism in the oxidative coupling of methane reaction and attributed the promoting effect of the Sr dopant to the creation of surface oxygen species with radical character as well as the increase in the surface basicity. For the Pd-doped Co3O4 catalyst, we compared its reactivity with pure Co3O4 surfaces and found the Pd dopant to significantly promote CH4 activation, consistent with the experimental observation. In our computational studies, we found it often useful to combine simulations with the extended surface model and the molecular cluster model for the elucidation of the complex mechanisms of heterogeneous catalytic oxidation reactions.

Computational studies on the surface structure and reactivity of mixed metal oxide catalysts: VOx/TiO2, SrOx/La2O3, and PdOx/Co3O4 for CH3OH and CH4 oxidation

254th National Meeting (2017)

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