Study On Carbon Deposition Of Ni Based Bimetallic Catalysts In CH₄/CO₂ Reforming Reaction

The CH₄/CO₂ reaction,which is the industrial production of gas?H2 and CO?,is one of the important reaction in the field of steel smelting.The combination of direct reduction of iron and steelmaking gained rapid development of short process technology of clean steel production.In the direct reduction of iron production,in order to improve the conversion of CH₄/CO₂ reforming reaction rate and improve the quality of reducing gas and improve the quality of DRI,usually use Ni catalyst.In the CH₄/CO₂ reforming reaction,Ni catalyst has been widely used in industry because of its low cost and high catalytic activity.However,the existence of carbon deposition in Ni catalyst leads to deactivation.How to ensure the activity of Ni catalyst and reduce the formation of carbon dioxide in CH₄/CO₂ reforming reaction has attracted widespread attention.This paper use the method based on the density functional theory?DFT?calculation method of the first principle.The research on the Ni based catalyst in different catalytic reforming reaction of CH₄/CO₂ properties and anti carbon deposition characteristics,the main contents and conclusions are as follows:?1?For the Ni catalyst and three kinds of Ni based bimetallic catalysts?NiFe catalyst,NiCu catalyst,Ni Ag catalyst?,the structure model of the catalyst surface in the CH₄/CO₂ reforming reaction was established.In the model,according to the characteristics of different metal catalysts,the influence of partial energy on the structure model of the catalyst is considered while the two metals form the alloy.Three kinds of Ni based bimetallic catalysts,the formation of alloy segregation energy are:NiFe catalyst: 18.85kJ/mol,NiCu catalyst,NiAg catalyst:-16.73kJ/mol:-23.79kJ/mol,established the corresponding structure model,respectively NiFe homogeneous catalyst structure model,homogeneous and heterogeneous NiCu catalyst structure model,homogeneous and the heterogeneous NiAg catalyst structure model.?2?The adsorption capacity of different Ni-based catalysts was calculated by using the structural model of the Ni-based catalyst,and the CH₄ step-by-step dissociation reaction during the CH₄ / CO₂ reforming reaction was carried out.Effect of Metal Catalyst on Catalytic Properties in CH₄ Phase-dissociation Reaction.The results show that the adsorption energy?Eads?of CHx?x = 0-3?on different catalysts is: NiFe catalyst>Ni catalyst> NiAg catalyst> NiCu catalyst,which indicates that in CH₄ / CO₂ reforming reaction,NiFe catalyst is better than Ni catalyst,but the catalytic properties of NiCucatalyst and NiAg catalyst are not as good as Ni catalyst.?3?The maximum activation energy of CH₄ step-by-step dissociation reaction during the CH₄ / CO₂ reforming process under different Ni-based catalysts was calculated.The effects of different Ni-based bimetallic catalysts on the CH₄ phase dissociation reaction On the carbon deposition characteristics of the catalyst.The results show that the order of maximum activation energy?Ea?of CH₄ cascade dissociation on different catalyst surfaces is: heterogeneous NiCu catalyst> heterogeneous NiAg catalyst> homogeneous NiCu catalyst> homogeneous NiAg catalyst> Ni catalyst NiFe catalyst,which indicates that NiCu catalyst and NiAg catalyst have stronger carbon deposition resistance than Ni catalyst,while NiFe catalyst is more prone to carbon deposition than Ni catalyst.Based on the calculated results,the determination steps of different Ni-based catalysts in the catalytic dissociation of CH₄ were determined.?4?The adsorption energy and migration activation energy of O atoms on different catalyst surfaces were calculated for pyrolysis C elimination?CO₂+*?CO+O* and O*+C?CO+*?.The results show that the order of adsorption energy of O atoms on different Ni-based catalysts is NiFe catalyst> Ni catalyst> heterogeneous NiCu catalyst> heterogeneous NiAg catalyst> homogeneous NiCu catalyst> homogeneous NiAg catalyst,and Ni catalyst The reaction of CO₂ +*?CO+ O* on the surface of NiFe catalyst is more likely to occur,and the reaction of NiCu catalyst and CO₂+*?CO + O*on NiAg catalyst is not easy to occur.?5?The results show that the activation energy of O atoms on the surface of Ni-based catalysts is: NiAg catalyst> NiCu catalyst> NiFe catalyst> Ni catalyst.This indicates that the three bimetallic catalysts?Ni Fe catalyst,NiCu catalyst,NiAg catalyst?can reduce the migration of O atoms compared to Ni catalyst,which means that the three bimetallic catalysts can not be reduced by increasing the migration ability of O atoms Enhanced carbon deposition resistance of the catalyst.?6?The results show that the activation energy of the reaction on the surface of each catalyst is: NiCu catalyst> Ni catalyst> NiFe catalyst> NiAg catalyst.It is shown that NiCu catalyst is beneficial to the elimination of pyrolysis C compared with Ni catalyst,and NiFe catalyst and NiAg catalyst are not as good as Ni catalyst in pyrolysis C removal.?7?The results show that the catalytic properties of NiFe catalyst are better than that of Ni catalyst,but the carbon deposition resistance of NiFg catalyst is better than that of Ni catalyst.NiAg catalyst and Ni The catalyst is similar to the catalyticproperties,but its anti-carbon deposition ability is very poor;in general,NiCu catalyst has both good catalytic properties,but also has good resistance to carbon deposition capacity..