Research In Nickel-Based Composite Catalysts For Methane Dry Reforming

Rapid development of modern industry and the release of CO₂ has triggered a series of environmental and energy crisis.The industrial utilization of methane has been highlighted recent years due to the worldwide discovery and exploitation of shale gas.The dry reforming of methane is an effective route to convert the two greenhouse gases,carbon dioxide and methane into syngas for the later production of liquid fuel through Fischer-Tropsch synthesis and oxo-synthesis.This reaction simultaneously realizes the industrial transformation of methane to valuable chemical products,consumes these two destructive greenhouse gas and effectively reduce carbon emissions,being of great benefit to both environmental and commercial consideration?Nickel based catalysts are the most favorable catalysts for DRM for its high activity,abundant reserves and bargain price.However,Ni based catalysts usually undergo severe deactivation due to metal sintering and coke deposition duiring long-tem test under high reaction temperature.Many researches have been carried out from several main points which affect the catalyst performance to develop Ni based catalysts with high coke resistance and stability,promoting the industrialization of methane dry reforming reaction.In this work,we have synthesized Ni/MgO-SiO₂ catalyst with hierachical hollow sphere structure through one-pot hydrothermal method.The catalyst presents high surface area?477.4 m²/g?and Ni metal nanoparticles with small size?6.6 nm?.Comparing with Ni/SiO₂,we found that the addition of MgO promoter increases the alkaline of support,promotes the adsorption and activation of CO₂ on catalyst surface,and results in superior catalytic activity and coke resistance.The addition of Mg²⁺during the sample preparation promoted the SiO₂ dissolution and formation of hollow sphere structure.The phyllosilicate helps to stabilize the hollow hierarchical structure at high temperatures,leading to a good thermostability.Comparing with IM-Ni/MgO-SiO₂ and IM-Ni/SiO₂,we found that the hydrothermal route produces catalysts with larger surface areas and strong metal-support interaction which yield higher catalytic activity and carbon resistance.Besides,we have prepared Ni@MgO/SiO₂catalyst through chemical vapor deposition?CVD?based on magnesium reduction.The magnesium alloy was used as reducing agent and the precursor of promoter,and the nickel was reduced to metal by magnesium vapor in the high temperature gas phase environment,meanwhile MgO promoter was deposited on the catalyst surface.This sample shows special catalytic performance,and this special gas phase synthesis method also has the prospect of further promotion to other catalytic systems.On the whole,we have successfully introduced the support,Ni catalytic species and promoter to the hollow hierarchical Ni/MgO-SiO₂nanocomposite catalyst with uniform structure and good dispersion through hydrothermal method.This catalytic performance of the sample exceed other catalysts with the same components or the same structure that have already been reported.At the same time,we have synthesized Ni@MgO/SiO₂ through the combination of vapor deposition and hydrothermal method,the reduction of Ni species and promoter deposition were achieved in one step through the innovative application of vapor magnesium reduction.This method has broad research and exploration prospect.