Selective methanation of CO over HZSM-5 supported Ni and Ni-Ru catalysts

Nickel and ruthenium catalysts supported on HZSM-5 of different SiO2/Al2O3 ratios were synthesized and their catalytic performance in the selective methanation of CO (CO-SMET) in a CO2 and H2 rich gas has been investigated, paying much attention to the effects of catalyst surface acidity on the reaction selectivity. H2-TPR and XPS were employed to identify the chemical states of nickel on HZSM-5 supports. NH3-TPD was used to determine the surface acidity of the prepared catalysts. The results show that higher CO methanation activity and selectivity can be obtained on the catalyst with higher surface acidity and a lower SiO2/Al2O3 ratio of the support. The Ni-Ru/HZSM-5 catalyst having a SiO2/Al2O3 ratio of 38 and with 15 wt% Ni and 0.5 wt% Ru loading exhibits the best catalytic performance. At the reaction temperature of 220 degrees C, this catalyst can reduce CO from 1 vol% to below 50 ppm while keeping the CO selectivity above 90%. Under the synergistic effect of acid sites and active metal sites, Ni/HZSM-5 and Ni-Ru/HZSM-5 performed excellent CO removal properties and CO methanation selectivity.