Study On Copper Based Catalyst For Catalytic Performance Of Carbon Dioxide Hydrogenation To Methanol

With the development of industrial society,people's demand for material is becoming more and more abundant.Industrial development is inseparable from fossil fuels such as coal,oil and natural gas.It is well known that fossil fuels are non-renewable resources and will eventually be depleted.In addition,the use of fossil fuels will increase the concentration of greenhouse gases,mainly CO₂,in the atmosphere,resulting in a greenhouse effect,which will eventually lead to a worse climate.Therefore,under catalysis,using CO₂ as the carbon source and H₂ as the reducing gas can reduce CO₂ to methanol under the reaction conditions of high pressure and heating,which can solve the problem of climate warming and alleviate the depletion of fossil fuels.The first of this paper,discusses the effect of different preparation methods on the catalytic performance of the catalyst.The Cu O-Zn O-Zr O₂-Al₂O₃?CZZA?catalysts prepared by carbonate coprecipitation,oxalic acid gel,and urea hydrolysis were selected for this study.The XRD,N₂-adsorption desorption,H₂-TPR,H₂-TPD,CO₂-TPD,XPS characterization methods were used to compare the structural properties of the catalyst,and the effects of different preparation methods on the catalyst crystal structure,specific surface area,pore volume,adsorption and desorption performance,and the electronic state of the catalyst surface were analyzed.The research results show that the main reason for the different catalyst structures is that the catalyst precursors prepared by different preparation methods are different,which in turn leads to different catalyst structural properties.The CZZA catalyst prepared by the oxalic acid gel method has large mesoporous pores,which helps methanol molecules diffuse from the surface of the catalyst.In addition,there is a stronger interaction between the Cu O particles in the catalyst and other metal oxides on the catalyst,and oxalic acid The surface of the CZZA catalyst prepared by the gel method has more oxygen vacancies,which helps the catalyst generate more active sites for CO₂ hydrogenation.Adsorption performance studies show that CZZA-3 by this catalyst prepared method has stronger adsorption performance for reaction gases?H₂ and CO₂?.Can greatly promote the reaction conversion of the reaction gas.The microreactor-chromatography unit was used to study the catalytic performance of the catalyst,CZZA-3 catalyst prepared by oxalic acid gel method is excellent in catalytic performance.Under the reaction conditions of2MPa and a reaction space velocity of 6000m L/(g_cat·h),the CO₂ conversion was13.67%,the CH₃OH selectivity was 62.59%,and the CH₃OH yield was 8.56%.After that,the effect of alumina content on the structural properties and catalytic performance of the CZZA catalyst was discussed.The oxalic acid gel method was used to prepare CZZA catalysts with different alumina content.The study found that with the increase of alumina content in the CZZA catalyst,Cu O crystal particle size did not change significantly,while the specific surface area and pore volume of the catalyst both increased,and the dispersion of Cu O particles increases,and the interaction between Cu O and other metal oxides also increases.Through the hydrogenation experiment to test the catalytic performance of the catalyst,it was found that as the reaction temperature increased,the CO₂ conversion rate on all catalysts increased,while the CH₃OH selectivity decreased,the CO selectivity increased,and the methanol yield increased first and then decreased.The maximum methanol yield of CZZA catalyst is240?.At the same reaction temperature,with the increase of alumina content in the CZZA catalyst,the CO₂ conversion rate increases,while the methanol selectivity gradually decreases,the CO selectivity gradually increases,the methanol yield increases first and then decreases,and the CZZA catalyst containing 20%wt Al₂O₃?CZZA-3-20?.The catalytic effect is the best,under the reaction conditions of T=240?,P=2MPa,GHSV=6000m L/(g_cat·h),H₂/CO₂=3,CO₂ conversion rate is17.37%,CH₃OH selectivity is 54.13%,The yield of CH₃OH was 9.4%,and the CH₃OH space-time yield was 201.5 mg/gcat·h.The methanol yield of CZZA-3-20 catalyst is84.31%more than CZZA-3-0 catalyst,which fully shows that the addition of alumina greatly improves the catalyst activity and methanol synthesis efficiency.Finally,the effect of reaction process conditions on the catalytic performance of the CZZA-3-20 catalyst was discussed.The study found that increasing the reaction pressure helps to catalyze the hydrogenation of CO₂ to methanol.Although increasing the reaction space velocity will decrease the CO₂ conversion rate,it can improve the selectivity of the target product CH₃OH.Increasing the H₂:CO₂ ratio of the reaction gas increases the CO₂ conversion and CH₃OH selectivity,but the methanol space-time yield increases first and then decreases.When the H₂:CO₂ ratio is 3,the methanol space-time yield is the largest.The CZZA-3-20 catalyst has undergone a nearly 120-hour reaction test,and its catalytic performance remains basically unchanged,indicating that the catalyst has good stability.