Preparation Of Highly Active And Stable Perovskite-type Nickel-based Catalyst For Dry Reforming Of Methane

Dry reforming of methane（DRM）is one of the clean and efficient energy conversion process,which can convert methane and carbon dioxide to generate carbon monoxide and hydrogen.It can not only alleviate the greenhouse effects,but also improve energy efficiency,therefore it has attracted extensive attention of researchers.Nickel-based catalysts are the most likely catalysts to achieve industrialization at present,because low price Ni catalysts have high catalytic activity comparable to noble metals.However,Ni catalysts are prone to cause coke deposition,which leads to deactivation.Therefore,improving the coke resistance and stability of nickel-based catalysts are the main goal for DRM.The purpose of this paper is to improve the coke resistance of the catalysts,and the work is mainly carried out in two aspects:（1）The catalysts with perovskite structure,NiTiO₃and Ni_xCo_1-xTiO₃（X=0.8,0.9）,were synthesized using titanium carbide and metal nitrate as raw materials.The phase change of the catalyst during the synthesis was studied.（2）The stability of the three catalysts in DRM was studied,and the reasons for the performance differences were explored,and the relationship between performance and structure of Ni catalysts are established.The following results are obtained through experiments and analysis:TiC changed to NiTiO₃ with the increase of temperature.Below 300℃,it was mainly TiC species.Between 300～400℃,TiC was converted to NiTiO₃.At 500℃,the characteristic diffraction peaks of NiTiO₃were observed,and the characteristic diffraction peaks of TiC disappeared completely,which indicats that the catalysts had obvious perovskite structure.Inaddition,Ni_xCo_1-xTiO₃has strong metal-support interaction in comparison with NiTiO₃.The particles of active site Ni grew in a topological mode during reduction and Ni-TiO₂interface structure formed simutaneously.Furthermore,NiTiO₃has low activity at 700℃,but Ni_0.9Co_0.1TiO₃had a CH₄conversion of 29%,a CO₂conversion of 42%and a H₂/CO ratio of0.6.The catalytic activity of Ni_0.8Co_0.2TiO₃is higher,but Ni_0.9Co_0.1TiO₃is more stable than Ni_0.8Co_0.2TiO₃.This is because the higher content of Co in Ni_0.8Co_0.2TiO₃,which is beneficial to the Boudouard reaction and the electron density of Ni after the reduced Ni_0.8Co_0.2TiO₃is greater than that of Ni_0.9Co_0.1TiO₃,which is conducive to CH₄cracking.Meanwhile,the oxygen vacancy content in Ni_0.8Co_0.2TiO₃is less than that of Ni_0.9Co_0.1TiO₃,where unsufficient O*species from a sluggish CO₂activation cannot effectively eliminate carbon deposition,leading to a higher carbon deposition rate and the decline of catalyst activity.Notably,the carbon deposition rate and carbon elimination rate of Ni_0.9Co_0.1TiO₃maintained a dynamic balance,leading to an stable catalytic activity.