Sorption-Enhanced Water Gas Shift Reaction over a Mechanical Mixture of the Catalyst Pt/Ce0.75Zr0.25O2 and the Sorbent NaNO3/MgO

Results of studying the sorption-enhanced water gas shift reaction over a mechanical mixture of grains of 5 wt % Pt/Ce0.75Zr0.25O2 catalyst and 10 wt % NaNO3/MgO sorbent are presented. It is shown that pure magnesium oxide sorbs virtually no СО2 under model conditions, while its promotion with NaNO3 substantially improves the dynamic sorption capacity in the 300–350°C range of temperatures with a maximum at 320°C. The catalyst shows high activity and selectivity in the water gas shift reaction for a model mixture (CO, 11.6; H2, 61; H2O, 27.4 vol %). The concentration of CO at the outlet from the reactor is less than 1 vol % in the 220–400°C range of temperatures (the minimum is 0.3 vol % at 240°C) with СН4 at the temperatures below 320°C (0.61 vol % at this point). Using this sorbent in mixtures with a catalyst in the sorption-enhanced water gas shift reaction at 320°C substantially reduces its sorption capacity, due probably to the full conversion of NaNO3 into Na2CO3 that is not completely decomposed at the stage of regeneration. This nevertheless allows the outlet СО and СН4 concentrations to be halved, relative to values observed at this temperature in experiments with no sorbent: 6.1 × 10−4 and 8.2 × 10−2 vol % per dry gas basis at the middle of the first adsorption cycle. Prospects for using this approach in the sorption-enhanced water gas shift reaction and the need for further studies on improving the capacity and stability of the presented sorbents are described.