Design of adiabatic fixed-bed reactors for the partial oxidation of methane to synthesis gas. Application to production of methanol and hydrogen-for-fuel-cells

Adiabatic fixed-bed reactors for the catalytic partial oxidn. (CPO) of methane to synthesis gas were designed at conditions suitable for the prodn. of methanol and hydrogen-for-fuel-cells. A steady-state, one-dimensional heterogeneous reactor model was applied in the simulations. Intra-particle concn. gradients were taken into account explicitly, by solving the continuity equations in the catalyst pellet at each position along the fixed-bed reactor coordinate. The reactor designs are based on supported Ni catalysts, which catalyze the indirect formation of synthesis gas via total oxidn. followed by steam reforming and water-gas shift. In both cases water was added as a reactant. Atm., air-based fixed-bed CPO reactors for fuel-cell applications are feasible due to low catalyst temps. At high-pressure methanol conditions, however, catalyst deactivation will be important as a result of the calcd. high catalyst temps. The influence of the steam-reforming rate was investigated sep. by performing simulations with the kinetic reforming models proposed by Numaguchi and Kikuchi (Chem. Eng. Sci. 43 (1988) 2295) and Xu and Froment (AIChE J. 35 (1989) 88). The influence of the oxidn. kinetics was studied as well. Application of different reforming models leads to significantly different max. catalyst temps. Also, the possible occurrence of gas-phase reactions was investigated: homogeneous reactions will be important at conditions suitable for methanol prodn