Study On The Performance Of CO₂ Adsorption Material And Catalyst For Hydrogen Production By CO₂ Methane Reforming

The excessive emission of global greenhouse gases（mainly CO₂ and CH₄）,mainly due to the excessive combustion and consumption of fossil fuels and other energy sources,has led to air pollution and greenhouse effect,which has caused a variety of problems,such as climate change and global warming,and has had a profound impact on human life and social and economic development.To further reduce excessive greenhouse gas emissions,various strategies have been proposed,including the adsorption and conversion of CO₂.These strategies not only reduce the concentration of CO₂ in the atmosphere,but also generate renewable energy（syngas）,which has broad application prospects in addressing the energy and environmental crisis caused by population growth.Therefore,the adsorption and conversion of CO₂ is a promising method.As an emerging sunrise industry,photovoltaic industry uses pollution-free and inexhaustible solar energy instead of traditional fossil energy with high energy consumption and high pollution.With the development of photovoltaic industry,polysilicon industry also rises.As a raw material for solar photovoltaic cells and semiconductor integrated circuits,high-purity polysilicon is known as the"food of modern industry".China’s Xinjiang region has a large number of polysilicon enterprises.At present,polysilicon is mainly produced by improved Siemens process,which will produce a large number of by-products of silicon tetrachloride（Si Cl₄）,which is in urgent need of treatment and resource utilization.In this paper,high specific surface area porous nano silica（SiO₂）spherical materials were prepared by using polysilicate by-product Si Cl₄ as raw material to interact with"hydroxy-rich"compounds.Its performance in CO₂ adsorption and CO₂ methane reforming was studied.The details are as follows:（1）Preparation and properties of high temperature CO₂ adsorption material Li₄SiO₄.In this study,an alcohol-water-ammonia system was constructed,and the effects of different surfactants on pore volume,pore size and specific surface area of SiO₂ porous nanospheres were studied.The experimental results show that when CTAB,P123,SLS and PEG are used as surfactants,the pore size of SiO₂ porous nanospheres increases gradually,while the pore volume and specific surface area decrease gradually.When CTAB is used,the maximum specific surface area can reach 1049.6 m²/g.The adsorption capacity of lithium silicate（Li₄SiO₄）prepared by SiO₂-CTAB for CO₂ adsorption can reach 35.2%at 700℃,which is 95.9%of the theoretical value.（2）Preparation and properties of Ni/SiO₂ catalyst for hydrogen production from CO₂ and CH₄reforming.In this chapter,the loading capacity of Ni and the influence of homemade SiO₂ and commercial SiO₂ as the support on catalyst performance were investigated.The results showed that the CH₄ conversion rate of the catalyst at 800℃was 79.14%when the loading capacity of Ni was 10 wt%with homemade SiO₂ as the support.The larger specific surface area and smaller pore size improved the dispersion of Ni.The production of carbon deposition is reduced and the catalyst has better catalytic performance.Then,a high dispersion SiO₂ supported nickel base catalyst was synthesized by L-arginine ligand-assisted impregnation method.The results showed that LA-Ni/SiO₂-HM had the best catalytic performance,and the conversion rates of CH₄ and CO₂ were 92.56%and 90.47%,at 800℃.The stability test at 700℃for 12 h showed that the H₂ yield was still 72.53%.Compared with the Ni/SiO₂-HM catalyst prepared by ordinary impregnation method,LA-Ni/SiO₂-HM catalysts developed by L-arginine ligand-assisted impregnation showed significantly higher catalytic stability due to high Ni sintering resistance and changes in coke properties.（3）Preparation and properties of Ni-M/SiO₂（M=Fe,Co,Cu,Ce）catalyst for hydrogen production by reforming CO₂ and CH₄.In this paper,the supported bimetallic Ni-M/SiO₂（M=Fe,Co,Cu,Ce）bimetallic catalysts were prepared by ordinary impregnation method with SiO₂ porous nanospheres with high specific surface area.The performance test results show that the Ni-Ce/SiO₂ catalyst has excellent catalytic activity of CO₂ methane reforming,and the conversion rate is always better than the other three catalysts in the range of 500℃to 800℃.The stability test results show that the Ni-Ce/SiO₂ catalyst has stable H₂ yield and H₂/CO ratio at 800℃after 12 h stability test.In addition,TG test showed that the carbon accumulation of Ni-Ce/SiO₂ catalyst was only 5.16%,which was due to the strong oxygen storage capacity and unique redox performance of Ce,which improved the carbon accumulation resistance of the catalyst.