Studyies On NiO/MgO Solid Solution Catalyst In CH₄/CO₂ Reforming Reaction

Key problem for the research of CH4/CO2 reforming reaction is the development of practical catalysts with high activity, stability and no carbon deposition. Based on the literature, this paper prepared the solid solution catalysts using nickel as the active component, MgO as the supporters. The activity and stability of the catalysts was tested at 0.1 atm and 800℃ using a GHSV of 2×104mL·g-1·h-1. Combined with characterization means of XRD, H2-TPR, XPS, CO2-TPD, TPSR, TG, XPS to explore the form law and characteristic of NiO/MgO solid solution, several conclusions were obtained as follows:(1)In the impNiO/MgO catalysts, the impNiO/MgO800-1.5 catalyst not only formed solid solution,but also had highly activety and stablity. CO2 conversion was 94.6%,CH4 conversion was 93.6% after 6 hours. After reaction, the impNiO/MgO-800-1.5 catalyst had 23% carbon deposition.In the coNiO/MgO catalysts, the coNiO/MgO600-16 catalyst not only formed solid solution,but also had high activety and stablity. CO2 conversion was 95.9%,CH4 conversion was 95.7% after 6 hours. After reaction, the coNiO/MgO-600-16 catalyst had only 10% carbon deposition.The catalysts prepared by co-precipitation had higher activety and less carbon deposition than the catalysts prepared by impregnation.(2) In the solid solution catalysts, the impNiO/MgO-800-1.5 catalyst was more active than the impNiO/MgO-600-1.5 catalyst. The impNiO/MgO-800-1.5 catalyst was hard to be reduced according to the results of H2-TPR and XPS, so Ni2+ions had strong enough interaction with the support. The impNiO/MgO-800-1.5 catalyst had stronger CO2 adsorption site than the impNiO/MgO-600-1.5 catalyst.The coNiO/MgO-600-16 catalyst was more active than the coNiO/MgO-600-1.5 catalyst. The coNiO/MgO-600-16 catalyst was hard to be reduced according to the results of H2-TPR and XPS, so Ni2+ ions had strong enough interaction with the support. The impNiO/MgO-800-1.5 catalyst had stronger CO2 adsorption site than the impNiO/MgO-600-1.5 catalyst.(3) In the research of reaction mechanism, there is a popular belief that CH4 sequentially dissociates into the surface CHx (x=1-3) and an H on the reactive metal surface during the reaction. However, the reaction mechanism of CO2 remained some controversies from the reports. The reaction mechanism of CO2 will have a important meaning to the reasearch of reaction mechanism of this reaction. The impNiO/MgO-800-1.5 and the coNiO/MgO-600-16 catalysts were test by temperature programmed surface reaction (TPSR). When H2was pulsed in continuous 10%CO2/He mixture, CO was obviously detected. We obtained the conclusion that the surface H could promote the dissociation of CO2 on the NiO/MgO solid solution catalysts. So the surface H dissociated from CH4 could promote the dissociation of CO2. We directly proved that why the NiO/MgO solid solution catalysts had excellent capability.