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Page RESEARCH DIRECTOR:
Enrique Iglesia, Professor of Chemical Engineering, University of California at Berkeley and Faculty Scientist, Lawrence Berkeley Laboratory
SUMMARY:
This project explores the catalytic conversion of natural gas to higher hydrocarbons (olefins and aromatics) by coupling chemical reactions and separations. Our research specifically addresses the mechanistic details and feasibility of activating methane at relatively low temperatures (< 873 K) via cyclic methane decomposition and hydrogen scavenging cycles or by selective hydrogen removal through proton-conducting non-porous inorganic membranes. These membranes consist of thin films of oxides with perovskite structures and low oxygen-atom mobility. In this approach, the selective synthesis of higher hydrocarbons is carried out by combining selective catalysts based on cation-exchanged zeolites [e.g., Zn(Mo)/H-ZSM5] for the non-oxidative conversion of light paraffins (methane, ethane) to olefins and aromatics with the continuous removal of either H2 (to increase equilibrium yields) or hydrocarbons (to prevent full combustion) using separation devices contained within catalytic reactors. Such separations are carried spatially by using inorganic hydrogen transport membranes with paraffin activation on M/H-ZSM5 in one side and H2 oxidation on the opposite side of thin oxide films used as membranes. Separations can also be carried out temporally in cyclic feed reactors using porous inorganic solids that scavenge hydrogen or hydrocarbon products before undesired combustion reactions occur. These reactors minimize contact between reaction products and oxygen and prevent the undesired formation of CO2. Our initial experimental data and kinetic-transport simulations confirm that these coupled reaction-separation schemes increase olefin and aromatic yields during methane and ethane conversion. Our approach includes the synthesis and characterization of novel catalysts based on isolated exchanged cations held within constrained pore structures; these shape-selective pore structures limit chain growth and prevent carbon formation. It also includes the design and preparation of thin films of hydrogen-conducting perovskite oxides, and the rigorous simulation and experimental evaluation of coupled reaction-separation processes in order to increase hydrocarbon yields during activation reactions of light paraffins.
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Last Updated 10/29/98.