Effects of the Mg addition on characteristics and catalytic activity of Ni/-Al2O3 in dry reforming of methane

Abstract

Effectively using CO₂-containing natural gas is an urgent requirement in Vietnam. Therefore, producing hydrogen and syngas by dry reforming of methane (СН₄+СО₂ = 2Н₂+2СО) has gained renewed interest in recent years. In this paper, Ni/α- Al₂O₃ and Ni-Mg/α-Al₂O₃ catalysts were prepared by impregnation. Physico-chemical characteristics of catalysts were investigated via nitrogen physisorption (BET), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Temperature Programmed Reduction (TPR) methods. The activities of catalysts in CO₂ reforming of CH₄ were studied in a micro-flow reactor in the temperature range 550 –800^oC, and content of CH₄ and CO₂ of 3 % mol. It was found that the conversion of CH₄ and CO₂ remarkably increased with the increase of reaction temperature from 550 to 700^oC, but increased inconsiderably when the temperature reached more than 700^oC. The selectivities of CO and H₂ reached over 91 %. The modification of Ni/α- Al₂O₃ catalyst with Mg led to reduce the NiO particle size forme the new ZnO-MgO solid solution and increase the reductivity of catalyst. These improve the activity, selectivity and stability of catalyst. At the reaction temperature of 700^oC, the conversions of CH₄ and CO₂ on Ni-Mg/α-Al₂O₃ reached 88.5 % and 72.3 %, respectively. The activities of catalysts were stable for 30 hours of reaction. Moreover, the role of Mg in the resistance to the coke formation on the catalyst surface was clarified via the results of temperature programmed oxidation (TPO) of spent catalysts after running the reaction for 30 hours at 700^oC