Co-Processing Methane and Biomass-Derived Oxygenates Over Mo/ZSM-5 Catalysts for Making Hydrocarbon Fuels

The concurrent deoxygenation of C₂-C₃ oxygenates and dehydroaromatization of CH₄ was accomplished using Mo/ZSM-5 catalysts at 950 K in order to suppress catalyst deactivation by carbon deposition and to minimize depletion of aromatic products due to deep scavenging of CH_x species by oxidants such as CO₂, O₂ and H₂O. A systematic study of C₂-C₃ oxygenates with varying Effective Hydrogen Index (EHI = (H-2(O))/C) and of reactant mixtures with varying oxygenate/CH₄ ratio (0.01-0.1) revealed that higher methane conversion is achieved in presence of  oxygenate co-feed and that the formation rate and selectivity to CO increased with increasing oxygenate/CH₄ ratio. The formation rate of C₂ hydrocarbons was not influenced by the identity of the C₂ or C₃ oxygenate at oxygenate/CH₄ ratio of 0.035. In contrast, the rate of formation of benzene varied depending on the carbon number and alcohol, aldehyde/ketone, or acid functionality of the co-reactant. These results show that CH₄ can be directly used for deoxygenation reactions of biomass compounds at high temperature conditions. Structural and chemical characterization of the catalyst by infrared and X-ray absorption spectroscopy as well as outstanding mechanistic questions pertaining to the tendency of the Mo/ZSM-5 system to shed off oxygen as CO, CO₂, or H₂O will be discussed.