CO2-selective water gas shift membrane reactor for fuel cell hydrogen processing

In this study, a water gas shift membrane reactor containing both a CO2-selective polymeric membrane and a commercial Cu/ZnO/Al2O3 catalyst was developed for hydrogen processing for fuel cells, especially for the proton-exchange membrane fuel cells (PEMFCs). The polymeric CO2-selective membrane was synthesized by incorporating fixed and mobile carriers in cross-linked poly(vinyl alcohol). The membrane showed good CO2/H-2 and CO2/CO selectivities and high CO2 permeabilities at 110 - 170 degrees C. In the water gas shift (WGS) membrane reactor, the membrane removed CO2, one product of the WGS reaction, while the commercial Cu/ZnO/Al2O3 catalyst was used to catalyze the WGS reaction. By removing CO2 simultaneously, the reversible WGS reaction was shifted toward the products so that the CO concentration was converted and reduced significantly to less than 10 ppm, which met the purity requirement of hydrogen for PEMFCs. A one-dimensional model was used to simulate the reaction and the transport process in a rectangular flat-sheet membrane reactor with well-defined countercurrent gas flows. The modeling results agreed well with the experimental data. A CO concentration of less than 10 ppm and a H-2 concentration of greater than 50% (dry basis) were achieved at various flow rates of a simulated autothermal reformate in the membrane reactor.