CO removal via selective methanation over the catalysts Ni/ZrO₂ prepared with reduction by the wet H₂-rich gas

The wet H₂-rich gas was used as reducing gas instead of the H₂/N₂ gas in the reduction step of the catalyst preparation. It is found that the selectivity for CO methanation over the catalysts 0.4Ni/ZrO₂ so-obtained was decreased in comparison to the case of the H₂/N₂ gas used as reducing gas. Even though, the samples with the different feed atomic ratios of Ni/Zr prepared by the impregnation method and the co-precipitation method, respectively, were evaluated with the wet H₂-rich gas both as reducing gas and as reactant gas. The catalysts Ni/ZrO₂-CP prepared by the co-precipitation method exhibited a high catalytic activity for CO removal at a lowered reaction temperature with increasing the Ni loading. Over the catalyst 3.0Ni/ZrO₂-CP, CO in the reactant gas could be removed to below 10 ppm at reaction temperatures of 220–260 °C with the selectivity higher than 50%. And the selectivity was kept at 100% during the 100 h test at 220 °C. The catalysts were characterized by XRD, XPS, XRF and the adsorption isotherm measurement. In addition, effect of water vapor in reactant gas was studied over the catalysts 0.4Ni/ZrO₂ with the wet H₂-rich gas and the dry H₂-rich gas as reactant gas, respectively, in the case of the H₂/N₂ gas fixed as reducing gas. It is seen that presence of water vapor in the reactant gas retarded methanation reactions of CO and CO₂ on the catalysts.