Evaluation of the water gas shift reaction in a palladium membrane reactor

The water gas shift (WGS) reaction of a syngas mixture has been carried out in a tubular palladium membrane reactor at a temperature of 410–414 °C. A composite palladium-porous stainless steel membrane, 29 μm thick, obtained by electroless plating, has been first extensively tested with pure gases (H2, He, CO2) and syngas mixtures in the 310–455 °C temperature range and up to 800 kPa. Long-term stability of the membrane in H2 at 400 °C has also been checked over a period of 1200 h. The membrane has been then used for WGS tests in a membrane reactor. The membrane reactor, packed with a pulverized Fe/Cr commercial catalyst, has been operated at a reaction pressure of 100–600 kPa in the counter-current mode, with a nitrogen sweep-gas. The reactor has been fed with a shift gas mixture with a 7.6% CO concentration and H2O/CO ratio in the 2.7–3.6 range. The membrane reactor was able to achieve up to the 85.0% of CO conversion, while only the 37% as a maximum, was reached with the traditional reactor in the same operating conditions. Up to the 82% of hydrogen has been recovered with a purity exceeding the 97%.