438307 Methane Dehydro-aromatization (DHA) to Aromatic Liquids and Hydrogen by Supported MOx/ZSM-5 (M=V, Cr, Mo, W and Re) Catalysts: Structure-Activity Relationships

Monday, November 9, 2015: 12:30 PM
155D (Salt Palace Convention Center)
Israel Wachs1, Yadan Tang1, Jih-Mirn Jehng2, James Gallagher3, Jeffery A. Miller3, Jie Gao4 and Simon G. Podkolzin4, (1)Departments of Chemical & Biomolecular Engineering, Lehigh University, Bethlehem, PA, (2)Chemical Engineering, lehigh, bethlehem, PA, (3)Argonne National Laboratory, Argonne, IL, (4)Stevens Institute of Technology, Hoboken, NJ

The structure and reactivity of the supported MOx/ZSM-5 catalysts for methane dehydro-aromatization (DHA) were investigated with the aid of in situ UV-vis spectroscopy and temperature programmed operando Raman-MS spectroscopy. The initial surface MOx sites are dispersed as isolated surface metal oxides on the ZSM-5 support. The surface metal oxide sites undergo reduction and/or carburization during the methane DHA reaction to benzene and hydrogen. The supported CrO3/ZSM-5 and V2O5/ZSM-5 catalysts only reduce to sub-oxides without forming carbides and are not selective to benzene and form only carbon monoxide and hydrogen. Supported Re2O7/ZSM-5 catalysts reduce to metallic Re nanoparticles that activate CH4 for benzene and H2 production. The supported WO3/ZSM-5 catalysts only partially reduce and carburize to W-carbides, yielding selective and low activity catalysts for DHA of methane to benzene. The supported MoO3/ZSM-5 catalysts are the most efficient catalysts for CH4 DHA because of the complete reduction and carburization of the MoOx sites to catalytic active MoOxCy clusters. These dual site catalysts activate CH4 to C2Hx hydrocarbon intermediates on the metal carbide/metal sites and oligomerization of C2Hx hydrocarbons to aromatics takes place on the Brønsted acid sites of the ZSM-5 support. Consequently, efficient catalysts must possess both sites for activating CH4 to C2Hx and sites for oligomerizing C2Hx to aromatics.

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