Promotional effects of Cu and Zn in hydrotalcite-derived methane tri-reforming catalyst

Abstract

This work aims at development of a highly active and stable catalyst for tri-reforming of methane, wherein the performance of hydrotalcite-derived Mg-Al mixed oxide supported Ni catalysts and promotional effects of Cu and Zn were evaluated at 800 °C, 1 atm, SV 49,200 mLh−1g−1 and molar feed composition CH4:CO2:H2O:O2:N2 = 1:0.23:0.46:0.07:0.28. The non-promoted Ni catalyst displayed lower activity due to the low degree of reducibility. Although by adopting memory effect in preparation of hydrotalcite-derived Ni catalysts, the degree of reducibility was improved and higher catalyst activity was achieved, but the catalysts were vulnerable to deactivation due to Ni re-oxidation, metal sintering and carbon formation. The addition of Cu resulted in formation of Ni-Cu alloy. It reduced the ensemble size of Ni and occupied kink and edge Ni sites, which resulted in higher activity and stability. However, post reaction characterization results revealed Ni re-oxidation of Mg-Al mixed oxide supported Ni-Cu catalyst. The addition of Zn was found more effective in keeping the Ni in its metallic state thereby enhancing its stability. Moreover, the XPS results revealed that Zn addition electronically modified the Ni catalyst by charge transfer phenomenon and made Ni electron rich. As a result, Ni-Zn catalyst exhibited remarkable tri-reforming activity.