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 oxidation (CPO) of m ethane to synthesis gas were designed at conditions suitable for the produc tion of methanol and hydrogen-for-fuel-cells. A steady-state, one-dimension al heterogeneous reactor model was applied in the simulations. Intra-partic le concentration gradients were taken into account explicitly, by solving t he continuity equations in the catalyst pellet at each position along the f ixed-bed reactor co-ordinate. The reactor designs are based on supported Ni catalysts, which catalyse the indirect formation of synthesis gas via tota l oxidation followed by steam reforming and watergas shift. In both cases w ater was added as a reactant. Atmospheric, air-based fixed-bed CPO reactors for fuel-cell applications are feasible due to low catalyst temperatures. At high-pressure methanol conditions, however, catalyst deactivation will b e very important as a result of the calculated high catalyst temperatures. The influence of the steam-reforming rate was investigated separately by pe rforming simulations with the kinetic reforming models proposed by Numaguch i and Kikuchi (Chem. Eng. Sci. 43 (1988) 2295) and Xu and Froment (AIChEJ. 35 (1989) 88). The influence of the oxidation kinetics was studied as well. Application of different reforming models leads to significantly different maximum catalyst temperatures. Also, the possible Occurrence of gas-phase reactions was investigated: homogeneous reactions will be very important at conditions suitable for methanol production. (C) 2001 Elsevier Science Ltd . All rights reserved.