Design And Synthesis Of CuZn/UiO-66 Catalyst For CO₂ Hydrogenation To Methanol

In recent years,the massive exploitation and combustion of fossil fuels and the large amount of CO₂produced by human activities which discharged into the air are causing the content of CO₂in the atmosphere to increase year by year.The carbon dioxide is the main gas that causes the greenhouse effect,which leads to the aggravation of the greenhouse effect.At present,major countries around the world have successively formulated a series of measures to deal with the impact of climate change.While the conversion of CO₂into other substances has attracted more and more attention from researchers since it is also a rich carbon resource.Methanol is an ideal clean fuel as well as an extremely important chemical raw material.The catalytic synthesis of methanol by hydrogenation of CO₂can not only reduce CO₂emissions,but also effectively alleviate the energy crisis,which is an important strategic measure.The highly stable Zr-based MOFs material UiO-66 has a high specific surface area and abundant pore structure.In this paper,the structural characteristics of UiO-66 and UiO-67 are analyzed,using the deposition precipitation method to support Cu and Zn on UiO-66,which applied to catalyze the hydrogenation of CO₂to methanol.The effects of Cu+Zn（wt%）loading and Cu/Zn molar ratio on the activity of the catalyst,and the effect of the calcination temperature on the activity of the 35%CZ/U-2.5 catalyst with excellent activity were investigated.The above catalysts were characterized by low-temperature N₂adsorption and desorption,XRD,XPS,H₂-TPR,CO₂-TPD and TEM.The research results are as follows:（1）We used solvothermal method to prepare UiO-66 and UiO-67 materials,and analyzed their structures using characterization methods.The prepared UiO-66 and UiO-67have a large specific surface area and a perfect pore structure.Thermogravimetry also shows that the two materials will not start to decompose until the temperature reaches 500°C.Both materials have excellent thermal stability.Characterization analysis The results show that the pore structure of UiO-66 is more perfect.（2）Using UiO-66 as the carrier and under the premise of a Cu/Zn molar ratio of 2.5,a series of catalysts with different Cu+Zn（wt%）loadings were prepared,and the catalyst calcination temperature was set to 250°C.The research results show that the catalyst activity is the best when（Cu+Zn）is 35 wt%loading.The influence of Cu/Zn molar ratio on catalytic activity was explored on the basis of 35 wt%loading.Finally,35%CZ/U-2.5 catalyst has the best catalytic activity.The construction of the active interface between Cu-ZnO_xand Cu-Zr O_xin the catalyst is the key to improving the catalytic activity.（3）Taking 35%CZ/U-2.5 catalyst as the research object,explore the effect of different calcination temperature on the catalyst activity.The research results show that when the calcination temperature is increased from 400°C to 500°C,UiO-66 in the catalyst is decomposed into Zr O₂,and both Cu and ZnO particles in the catalyst are agglomerated.The catalyst calcination temperature at 400°C has excellent catalytic activity.The catalyst activity is closely related to the type of Zr material.