The Preparation And Performance Of Cu/ZnO-In₂O₃ Catalytic CO₂ Hydrogenation To Methanol

Over the past time,the burning of fossil resources releases excessive CO₂into the atmosphere,which directly led to the increasingly serious climate and environmental degradation.Catalytic hydrogenation of captured CO₂with H₂generated from renewable energy sources such as solar and wind power to methanol is an effective solution to carbon emissions.The method of carbon capture and utilization can complete the recycling process of carbon resources,and finally it is possible to realize the complete replacement of fossil fuels by renewable resources to meet the energy needs of human beings.In the context of carbon neutrality and energy sustainability,methanol production and synthesis become extremely attractive.In the CO₂hydrogenation to methanol reaction,the most widely used catalyst is Cu-based materials,but it has the problem of long-term reaction deactivation in industrial production.In recent years,various oxide catalysts have also been gradually found to have good catalytic performances,such as Zn O-Zr O₂,In₂O₃-Zr O₂,etc.Among them,In₂O₃catalyst has aroused widespread heated discussion because of its high selectivity to methanol in high temperature reaction.However,the conversion efficiency of pure In₂O₃for CO₂is too low,resulting in a low reaction yield.Therefore,it will be very valuable to find a catalyst for CO₂hydrogenation to methanol with good stability and excellent reaction performance.In this paper,indium was added to the traditional industrial methanol synthesis Cu/Zn O catalyst.The effects of different indium contents and preparation methods on the phase and electronic structure of Cu/Zn O catalysts were investigated.The catalytic performance of modified Cu-Zn-In catalysts were investigated for CO₂hydrogenation to methanol reaction.The specific research contents are as follows:（1）A series of catalysts with different amount of In₂O₃addition were synthesized by hydrothermal method using urea as precipitant,and the catalytic performance of CO₂hydrogenation to methanol reaction was tested.It was found that the U-CZ0.8I catalyst achieved the highest methanol yield(2.9 mmol/g_cat/h)under the reaction conditions of280°C,and at the same time,the methanol selectivity reached 66.8%.The characterization results of XRD and XPS showed that the addition of indium in the catalyst changed the original phase,crystallinity and electronic structure characteristics of the Cu/Zn O catalyst.There was a certain strong electronic interaction between In₂O₃and Cu/Zn O,which made In 3d shift to higher binding energy.However,excessive In₂O₃would reduce the crystallinity of the catalyst and the catalytic performance.（2）The Cu-Zn-In catalysts were synthesized by different precipitation methods while keeping the addition amount of indium unchanged.And the influence of different preparation methods on the catalytic performances of the Cu-Zn-In catalysts was explored.It can be seen from XRD that the precursor of CP-CZ0.8I catalyst was in an amorphous state.Both IS-CZ0.8I catalyst and U-CZ0.8I catalyst contained Cu Zn（CO₃）（OH）₂and(Cu_0.3Zn_0.7)₅（CO₃）₂（OH）₆phases.In terms of reactivity,the CO₂conversion,methanol selectivity and yield of U-CZ0.8I catalyst was significantly better than those of CP-CZ0.8I,however,IS-CZ0.8I catalyst had the highest methanol selectivity at 280℃.（3）In order to promote the dispersion of Cu species in the catalyst,oxalic acid,formic acid,and citric acid,were added to the metal nitrate,respectively.And the OG-CZI,FG-CZI,and CG-CZI catalysts were synthesized by the solid-state grinding method.The test results of the catalytic performance of CO₂hydrogenation showed that the addition of oxalic acid had the best dispersion effect on the catalyst,and the reaction performance was the best(300℃,methanol yield up to 2.1 mmol/g _cat/h).The addition of formic acid made the indium species fully involved in the formation of the Cu₇In₃alloy,so the reaction activity was the lowest.