Study On The Preparation Of Cu-In/ZrO₂ Catalysts And Its Performance Of CO₂ Hydrogenation To Methanol

A large amount of carbon dioxide emissions caused the concentration in the atmosphere to rise,which led to the‘greenhouse effect’and threatened human survival.Carbon dioxide was an important chemical raw material of C1 chemical industry,widely used in industrial production and daily life.Synthesizing new chemicals through various means such as hydrogenation reduction,molecular polymerization,and reverse water-gas shift could achieve the resource utilization of CO₂.This study took carbon dioxide hydrogenation to methanol as the research object,used the amphoteric oxide ZrO₂ as the catalyst support,copper as the main active component and In₂O₃ as the co-catalysts.Through catalyst surface structure modified by low-temperature plasma,investigating the effect on the selectivity and conversion of the catalyst.The details were as follows:（1）To study the effect of the dispersibility and reduction performance of copper oxide on the carrier to the catalytic activity of CuO/ZrO₂.The catalysts with different Cu/Zr molar ratios were prepared by the sol-gel method.XRD and BET results about the Cu₁Zr₄-O（Cu/Zr=1/4）catalyst suggested that CuO was highly dispersed or amorphous on the surface of the catalyst carrier.At this time,the catalyst had good dispersibility and low crystallinity and the BET surface area of the catalyst was as high as 111.36 m²/g.XPS characterization showed that the binding energies of Cu 2p of the Cu₁Zr₄-O catalyst shifted to low binding energies,indicated the reduction ability of catalyst increased.The effects of process conditions such as reaction temperature,pressure and space velocity on the reaction were investigated.The catalytic test showed that the CO₂ conversion,the selectivity of CH₃OH and the yield of CH₃OH over the Cu₁Zr₄-O catalyst were 8.0%,59.5%and 4.7%at 250.0℃,2.0MPa,12000 mL/（g·h）and V（H₂）/V（CO₂）=3/1.（2）To investigate the existence form of the co-catalyst In₂O₃ in the catalyst and its effect on the catalytic activities.The Cu₁In_xZr₄-O catalyst was modified by adding main-group element In to improve the catalytic activity,CH₃OH selectivity and stability of catalyst.The Cu₁In_xZr₄-O catalysts were prepared by the sol-gel method,and the Cu/In/Zr molar ratio was adjusted to form a single alloy structure of copper and indium.XRD results proved that when Cu/In/Zr was 1/2/4,a new Cu₂In alloy structure was formed in Cu₁In₂Zr₄-O catalyst.H₂-TPR results showed that Cu₁In₂Zr₄-O catalyst had a better reduction performance.H₂-TPD and CO₂-TPD results proved that Cu₂In alloy could promote the adsorption of H₂ and CO₂ and reduce the desorption temperature of the catalyst.Under the reaction conditions of270.0℃,2.0 MPa,GHSV=12000 mL/（g·h）,V（H₂）/V（CO₂）=3/1,CO₂ conversion was12.8%,the methanol selectivity was 72.8%and the methanol yield reached 9.3%over Cu₁In₂Zr₄-O catalyst.The catalyst efficiency remained above 98%for 100 hours of reaction.（3）To discuss the influence of Cu₁In₂Zr₄-O catalyst surface modification on the catalytic performance by low temperature plasma.The Cu₁In₂Zr₄-O catalyst with better performance was used as the catalyst research.The modified Cu₁In₂Zr₄-O-PC catalyst before calcination and the modified Cu₁In₂Zr₄-O-CP catalyst after calcination were obtained through low temperature plasma,respectively.XRD,SEM and H₂-TPR results showed that the plasma modified catalyst had lower crystallinity,smaller particle size,better dispersion and good reduction performance,which proved that the Cu₁In₂Zr₄-O-PC catalyst had better catalytic activity and selectivity after plasma modification.Under the conditions of reaction 270.0℃,2.0 MPa,V（H₂）/V（CO₂）=3/1and GHSV=12000 mL/（g·h）,CO₂ conversion was 13.3%,the methanol selectivity was 74.3%and the methanol yield was 9.8%of Cu₁In₂Zr₄-O-CP catalyst.The CH₃OH yield increased about 5.4%than that in Cu₁In₂Zr₄-O catalyst.This study aimed to improve the catalytic activity and CH₃OH selectivity of copper-based catalysts.Through increasing the dispersibility of copper oxide,forming copper-indium alloyed structures and plasma modified,we could improve reducibility of catalyst and promote CO₂ to diffused to the catalyst surface,in order to improve the CH₃OH selectivity and CO₂ conversion for CO₂ hydrogenation to methanol.The results showed that the Cu₁In₂Zr₄-O-PC catalyst under conditions of 270.0℃,2.0MPa,GHSV=12000 mL/（g·h）and V（H₂）/V（CO₂）=3/1,CO₂ conversion was 13.3%and the CH₃OH selectivity was 74.3%,the Cu₁In₂Zr₄-O-PC catalyst could also be continuously reacted in a fixed bed for 100 h.