Direct Nonoxidative Methane Conversion in an Autothermal Hydrogen-Permeable Membrane Reactor

Direct nonoxidative methane conversion (DNMC) transforms CH4 to higher (C2+) hydrocarbons and H-2 in a single step, but its utility is challenged by low CH4 equilibrium conversion, carbon deposition (coking), and its endothermic reaction energy requirement. This work reports a heat-exchanged autothermal H-2-permeable tubular membrane reactor composed of a thin mixed ionic-electronic conducting SrCe0.7Zr0.2Eu0.1O3-delta membrane supported on a porous SrCe0.8Zr0.2O3-delta tube in which a Fe/SiO2 DNMC catalyst is packed, that concurrently tackles all of these challenges. The H-2-permeation flux drives CH4 conversion. O-2 from an air simulant (O-2/He mixture) sweep outside the membrane reacts with permeated H-2 to provide heat for the endothermic DNMC reaction. The energy balance between the endothermic DNMC and exothermic H-2 combustion on opposite sides of the membrane is achieved, demonstrating the feasibility for autothermal operation using a simple air sweep gas. Moreover, the back diffusion of O-2 from the sweep side to the catalyst side oxidizes any deposited carbon into CO. Thus, for the first time demonstrating all the desired attributes, a heat-exchanged H-2-permeable membrane reactor capable of achieving single-step auto-thermal DNMC catalysis while simultaneously improving CH4 conversion and preventing coking is achieved.