Study On Coke And Sintering Resistant Catalysts For Methane Synthesis And Conversion

The carbon deposition on the catalyst in the carbon-containing reaction atmosphere and the sintering of catalyst under high temperature reaction conditions are the two main factors leading to catalyst deactivation,which is a common problem in the field of heterogeneous catalysis research.The work of this thesis is to study the problem of catalyst deactivation due to carbon deposition and sintering in the two typical reactions of low H2/CO ratio syngas dry methanation to artificial natural gas and methane partial oxidation to syngas.The results are as follows:1.Created Ni based catalysts with high activity and high regeneration stability for dry methanation(1)The effect of nickel dispersion method on the structure and catalytic performance of Ni/MgAl2O4 catalyst was studied.It was found that the use of ethanol as the solvent for the nickel nitrate precursor immersion liquid can increase the dispersion degree of nickel than water as the solvent for the nickel nitrate precursor immersion liquid,thereby significantly increasing its activity in dry methanation reaction,but the carbon deposition deactivation is still relatively obvious.Further,the Ni/MgAl2O4 catalyst was modified by the second metal Au,and it was found that the coke resistant properties was enhanced after the addition of Au,but the addition of excess Au reduces the catalytic activity.It was found that Au and Ni formed?10 nm bimetallic nanoparticles with electron donation from Ni to Au.The nature and gasification behavior of the carbon deposited on the Au-Ni/MgAl2O4 is very similar to the carbon deposited on the Ni/MgAl2O4,but the amount of carbon formed is significantly less,indicating that the modification of Ni by Au inhibit CO disproportionation.(2)The Ni0.1Mg0.9Al2O4 catalyst with high activity and high regeneration stability was prepared via solvothermal method,and it was found that nickel can freely enter and exit the spinel lattice and redisperse during the calcination-reduction regeneration process,and the amount of small-sized nickel nanoparticles(?2 nm)increased after multiple reaction-regeneration operations.The carbon deposited on Ni0.1Mg0.9Al2O4 in the reaction does not cover the surface of the nickel nanoparticles,but on the surface of the support.Both the exposure of the active nickel surface and the formation of small-sized nickel nanoparticles contribute to the stability and activity of Ni0.1Mg0.9Al2O4 during dry methanation reaction-regeneration process.Conventional Ni/Al2O3 is also active in dry methanation reaction,but it is quickly deactivated due to carbon deposition and metal sintering2.Developed Pt/MgAl2O4 and Rh/MgAl2O4 catalysts with high activity and high temperature stability for partial oxidation of methaneMgAl2O4-HS supported Pt catalysts(Pt/MgAl2O4-HS)with MgAl2O4 support synthesized via hydrolysis solvothermal method shows high catalytic activity and stability during the 500 h life test at 900? in partial oxidation of methane via the combustion-reforming pathway and without detectable carbon deposits.The MgAl2O4-CP supported Pt catalyst(Pt/MgAl2O4-CP)with MgAl2O4 support prepared by the coprecipitation(CP)method shows continuous deactivation and carbon deposition.This is due to the fact that MgAl2O4-HS in Pt/MgAl2O4-HS has a purer spinel surface structure,which improves its efficiency in stabilizing Pt nanoparticles.In addition,Rh/MgAl2O4 also exhibits high activity and high temperature stability in POM reaction,and the content of Rh can be as low as 0.09 wt%.