The Effect Of Interaction Between NiM（M=Fe,Co,Cu） Bimetal And MgO Support On Carbon Deposition Of CH₄/CO₂ Reforming

Ni-based catalyst catalyzes the CH₄/CO₂ reforming synthesis gas,which has good initial activity and selectivity.However,due to the carbon deposition produced during the reaction to deactivate the catalyst,hindering the commercial application.It was found that the addition of the second metal and the selection of the appropriate carrier to modify the Ni-based catalyst structure can improve suppress carbon deposition performance.In this paper,the reaction of carbon deposition in CH₄/CO₂ reforming on the catalysts of Ni₂M₂（M = Fe,Co,Cu）bimetallic supported on different surface MgO supports was studied by DFT method,and the key factors to suppress carbon deposition were found.To provide valuable theoretical clues of suppressing carbon deposition of CH₄/CO₂ reforming catalyst.The following main conclusions are drawn from the study:The binding energy of bimetallic cluster supported on the defective surface MgO is greater than that on the perfect surface;one can conclude that the interaction between the defective support and the active component is stronger,and the active component is not easy to accumulate.In the actual preparation of the catalyst,the oxygen defect sites can be increased by the reduction treatment of the support,so that the active component is more stable.The activation energy of CH₄ dissociation rate determining step on Ni₂Co₂ supported on defective MgO is larger than that of oxidative activation energy,and the activation energy of pyrolysis C oxidation is less than that of pyrolysis C.Therefore,it is considered that the catalyst is inhibition of carbon deposit by CH₄/CO₂ reforming.The activation energy of CH₄ dissociation rate determining step on Ni2Cu2 suooprted on perfect and defective MgO are similar to that of oxidation,but the activation energy of pyrolysis C oxidation are less than that of pyrolysis C,it is believed that the catalyst can resist carbon deposition during the catalytic reforming of CH₄/CO₂.Based on the above analysis,it is proposed that the second metal Co is added to the supported Ni catalyst and the surface of the MgO support is reduced to have more O defects.The second metal Cu is added to the supported Ni catalyst,no special treatment of MgO support,the preparation of the catalyst in the CH₄/CO₂ catalytic reforming process can resist carbon deposition.This paper presents a new idea of suppressing coke.First,comparing CH_x（x=0³）oxidation and dissociation of activation energy.If the activation energy of CH_x（x=1³）oxidation（CH_x+O→CH_xO）is lower than the activation energy of CH_x dissociation(CH_x→ CH_x-1+H),CH_x species are easily oxidized to form CH_xO,thus changing CH₄ dissociation path of producing pyrolysis C,which suppresses the formation of carbon.Second,comparing the activation energy of the pyrolysis C polymerization and oxidation.If the activation energy of pyrolysis C oxidation（C+O→CO）is less than the activation energy of pyrolysis C（C+C→ C₂）,pyrolysis C can not be polymerized to produce carbon deposition precursors.Such a catalyst can inhibit carbon deposition.