High-purity hydrogen production via a water-gas-shift reaction in a palladium-copper catalytic membrane reactor integrated with pressure swing adsorption

A Pd-Cu catalytic membrane reactor (CMR) integrated with pressure swing adsorption (PSA) was developed to produce fuel cell grade hydrogen from syngas. The enhanced water-gas-shift reaction in the Pd-Cu CMR packed with a high-temperature shift catalyst was experimentally conducted by using a carbon monoxide (CO)/ hydrogen (H2)/carbon dioxide (CO2) mixture (65:30:5 vol%) at 360-380 degrees C, 6-10 bar, and a steam/carbon (s/c) ratio of 1-5. Since H-2 was used as the sweeping gas, pure H2 could be directly obtained from the permeate side. The temperature inside the packed catalysts was well distributed in the developed CMR module without any specific hotspots during the reaction and separation. The CO conversion in the CMR increased from 85.4% to 94.8% with the recovery of 53.4% to 56.1% when the s/c ratio increased from 1 to 5. The conversion rate was enhanced by 10.0-16.7% compared with the fixed catalytic bed reactor. When four-bed PSA using activated carbon and zeolite was integrated to recover more H-2 from the retentate flow, the recovery of H-2 was additionally improved by 31.2-35.7%. The integrated Pd-Cu CMR with four-bed PSA could produce H-2 of over 99.9991% with a recovery of 91.37% and 8.67 ppm CO. For H-2 produced with less than 0.2 ppm CO, the recovery was reduced to 85.99% with 0.15 ppm CO. The feasibility of CMR with PSA to enhance CO conversion and H-2 recovery is suggested for the production of fuel cell grade H-2 for a proton-exchange membrane fuel cell (ISO 14687).