Catalytic pyrolysis of methane on Mo/H-ZSM5 with continuous hydrogen removal by permeation through dense oxide films

A dense SrCe0.95Yb0.05O3-alpha thin film (similar to2 mum) was used to remove H-2 during non-oxidative conversion of methane to higher hydrocarbons on Mo/H-ZSM5 in order to overcome kinetic and thermodynamic constraints. At 950 K, these films removed only a small fraction of the H-2 produced and hydrocarbon synthesis rates were unaffected by H-2 removal. Higher temperatures led to a modest increase in CH4 conversion rates, but also to slightly lower C-2-C-12 hydrocarbon selectivities and to higher catalyst deactivation rates. These undesired effects were eliminated by the addition of small amounts of CO2 to the CH4 reactants. The combination of dense SrCe0.95Yb0.05O3-alpha thin films, chain-limiting catalytic pyrolysis reactions on Mo/H-ZSM5, and CO2 co-reactants led to stable catalyst performance and modestly higher hydrocarbon synthesis rates than in conventional reactors. The improvements achieved by continuous H-2 removal are in agreement with prediction of kinetic-transport model simulations in tubular reactors with permeable walls.