Methanol steam reforming in single-fiber packed bed Pd-Ag membrane reactor: Experiments and modeling

The steam reforming of methanol was carried out in both a packed bed reactor (PBR) and single-fiber packed bed Pd-Ag membrane reactor (PBMR) utilizing a 3.9 mu m thick Pd-Ag membrane. A systematic comparison of the two reactor types was made for key performance metrics such as conversion, productivity, and hydrogen utilization at different pressures (3-5 bars) and temperatures (250-300 degrees C) on a commercial Cu/ZnO/Al2O3 catalyst. The reactor diameter and catalyst loadings of the PBMR were varied in order to determine the rate limiting process. A two-dimensional model was used to simulate the experiments and to identify the rate limiting process(es). A recently developed model of H-2 flux inhibition by competitive adsorption of the primary methanol reforming species (CO, CO2, CH3OH, H2O) was incorporated into the PRMR model [20]. Using the H-2 flux parameters and independently determined reforming kinetics from the PBR studies, very good agreement between the measured and predicted concentration and temperature dependence on space velocity was obtained. The simulations reveal that the rate limiting process is the permeation of H-2 through the membrane as a result of the competitive adsorption of CO in particular. The findings provide guidance on the design improvements needed to achieve higher productivity and hydrogen utilization. (C) 2010 Elsevier B.V. All rights reserved.