The deactivation mechanism of Co/MgO catalyst for the reforming of methane with carbon dioxide was investigated. The conversion of CH4 displayed a significant decrease in the initial stage caused by carbon deposition....The deactivation mechanism of Co/MgO catalyst for the reforming of methane with carbon dioxide was investigated. The conversion of CH4 displayed a significant decrease in the initial stage caused by carbon deposition.There were two types of cokes, carbon nanotubes(CNTs) and carbon nano-onions(CNOs). The number of the CNO layers that coated on the surface of Co nanoparticles(NPs) increased rapidly in the initial reforming time,which was responsible for the deactivation of the Co/MgO catalyst. The deposition of CNOs was attributed to the oxidation of Co NPs. Therefore, the deactivation of the Co/MgO catalyst was originated from the first oxidization of the Co NPs into Co3 O4 by O species(OH intermediate, CO_2, H2 O) during the reforming reaction,which accelerates the formation of coke that blocked the active metal, thus led to catalyst deactivation.展开更多
CH4 dissociation on Co（0001） surfaces is an important step, which has been investigated at the level of density functional theory. It is found that CH4 is unfavorable to adsorb on Co（0001）, while CH4 favores to di...CH4 dissociation on Co（0001） surfaces is an important step, which has been investigated at the level of density functional theory. It is found that CH4 is unfavorable to adsorb on Co（0001）, while CH4 favores to dissociate to CH3, CH2 and CH on Co（0001） surface by sequential dehydrogenation. In the whole process of CH4 dehydrogenation, CH4 dissociate to CH3 and H is the rate-determining step. The calculated results show that CH2 and CH exist mainly on Co（0001） surface, while the dehydrogenation of CH into C and H is difficult.展开更多
基金Supported by the National Natural Science Foundation of China(21736010,U1462128,91334108)the State Key Development Program for Basic Research of China(2015CB251402)
文摘The deactivation mechanism of Co/MgO catalyst for the reforming of methane with carbon dioxide was investigated. The conversion of CH4 displayed a significant decrease in the initial stage caused by carbon deposition.There were two types of cokes, carbon nanotubes(CNTs) and carbon nano-onions(CNOs). The number of the CNO layers that coated on the surface of Co nanoparticles(NPs) increased rapidly in the initial reforming time,which was responsible for the deactivation of the Co/MgO catalyst. The deposition of CNOs was attributed to the oxidation of Co NPs. Therefore, the deactivation of the Co/MgO catalyst was originated from the first oxidization of the Co NPs into Co3 O4 by O species(OH intermediate, CO_2, H2 O) during the reforming reaction,which accelerates the formation of coke that blocked the active metal, thus led to catalyst deactivation.
文摘CH4 dissociation on Co（0001） surfaces is an important step, which has been investigated at the level of density functional theory. It is found that CH4 is unfavorable to adsorb on Co（0001）, while CH4 favores to dissociate to CH3, CH2 and CH on Co（0001） surface by sequential dehydrogenation. In the whole process of CH4 dehydrogenation, CH4 dissociate to CH3 and H is the rate-determining step. The calculated results show that CH2 and CH exist mainly on Co（0001） surface, while the dehydrogenation of CH into C and H is difficult.
