Sorption-catalytic steam conversion of CO on a mechanical mixture of Pt/Ce0.75Zr0.25O2 catalyst and NaNO3/MgO sorbent

Abstract

The sorption-catalytic steam conversion of CO using a mechanical mixture of 5 wt.% Pt/Ce0.75Zr0.25O2 catalyst grains and 10 mol.% NaNO3/MgO sorbent was studied. It was shown under the model conditions that initially MgO adsorbs СО2 only slightly, whereas its promotion with NaNO3 leads to a considerable growth of the adsorption dynamic capacity in the temperature range of 300–350 °С with a maximum at 320 °С. High activity and selectivity of the catalyst in steam conversion of CO were demonstrated for a model mixture with the composition (vol.%) 11.6 CO, 61 H2 and 27.4 H2O: the concentration of СО at the reactor outlet did not exceed 1 vol.% in the temperature range of 220– 400 °С (the minimum value of 0.3 vol.% was observed at 240 °С), and СН4 – at temperatures below 320 °С (0.61 vol.% at this point). The use of the sorbent in a mixture with the catalyst in the sorption-catalytic steam conversion of CO at 320 °С led to a considerable decrease in its sorption capacity; this may be related to the conversion of all NaNO3 into Na2CO3, which decomposed incompletely during regeneration. Nevertheless, this made it possible to decrease twofold the outlet concentrations of СО and СН4 as compared to the values observed at the indicated temperature in the experiment without a sorbent: particularly, in the middle of the first adsorption cycle they were equal to 6.1·10–4 and 8.2·10–2 vol.%, respectively, on a dry gas basis. Thus, the indicated approach to the sorption-catalytic conversion of CO was shown to be promising; further studies are needed to increase the capacity and stability of the presented type of sorbents.