Preparation Of CuZnO-ZrO₂ Solid Solution And Its Catalytic Properties On Co₂ Hydrogenation To Methanol

Excessive consumption of fossil energy leads to excessive CO₂ content in the atmosphere.CO₂ is one of the major greenhouse gases,which leads to increasingly serious global temperature rise.Therefore,researchers have paid extensive attention to the resource utilization of CO₂.Among them,CO₂ hydrogenation to methanol is one of the important ways of resource utilization,and the core technology of this reaction lies in the development of catalysts with high activity and selectivity.In this paper,based on the ZnO-ZrO₂ solid solution catalyst obtained by regulating the molar ratio of Zn and Zr,the catalyst was modified by doping transition metal copper and plasma treatment.The crystal structure and other properties of the catalysts were systematically studied by some characterization methods.The catalytic performance of different catalysts were tested in a fixed-bed reactor.The details are as follows:?1?Preparation of ZnO-ZrO₂ solid solution catalyst and evaluation of its catalytic performance.The catalysts with different mole ratios of Zn/Zr were prepared by coprecipitation.It was proved by XRD and Raman that ZnO-ZrO₂ bimetallic oxide was a solid solution structure when molar ratios of Zn/Zr was 1/4.Through the characterization of H₂-TPR,it is proved that ZnO-ZrO₂ solid solution catalyst has better reduction performance compared with pure ZnO and ZrO₂.The performance of catalysts with different Zn/Zr molar ratios was tested in a high pressure fixed-bed reactor,the reaction temperature,pressure and other parameters were optimized,and the stability of the catalyst was tested.The CO₂ conversion of 8.6%,methanol selectivity of 85%and methanol yield reached 7.3%over the ZnO-ZrO₂ solid solution catalyst under the condition of reaction temperature at 270?,the reaction pressure of5 MPa,H₂/CO₂=3/1 and GHSV=12000 mL/?g h?,and it can run stably in fixed bed reactor for 100 h without inactivation.The characterization and performance analysis of the catalyst showed that the strong interaction and good reduction ability of metal oxides in the solid solution of ZnO-ZrO₂ catalyst,that provided a theoretical basis for its high methanol selectivity from CO₂ hydrogenation.?2?Study on the performance of copper-doped ZnO-ZrO₂ solid solution catalysts.On the basis of the research of ZnO-ZrO₂ solid solution catalyst,copper doping was further carried out for its low CO₂ conversion,a series of CuZnO-ZrO₂ solid solution catalysts with different amount of copper were prepared by coprecipitation.Under the condition of reaction temperature at 250?,the reaction pressure of 5 MPa,H₂/CO₂=3/1 and GHSV=12000 h^-1,the CO₂ conversion of 19.7%,methanol selectivity of 81.4%and methanol yield reached 16%over 3%CuZnO-ZrO₂ catalyst and it has the better catalytic stability.Through the characterization and performance analysis of Cu-doped ZnO-ZrO₂ solid solution catalysts show that 3%CuZnO-ZrO₂solid solution has the similar structure with ZnO-ZrO₂ solid solution catalyst,the highly dispersed CuO species in the solid solution structure can effectively reduce the catalyst reduction temperature and improved catalyst reduction performance,ensure it has high methanol selectivity and CO₂ conversion.?3?Modification of CuZnO-ZrO₂ solid solution catalyst by glow discharge plasma.In order to reduce the crystallinity of the catalyst and improve the dispersibility and reduction performance of the catalyst,based on 5%CuZnO-ZrO₂ catalyst,glow discharge plasma was used to modify the catalysts during the process of preparation.Under the condition of reaction 260?,5 MPa,H₂/CO₂=3/1 and GHSV=6000 h^-1,the CO₂ conversion of 20.1%,methanol selectivity of 82.5%and methanol yield reached16.6%over the CuZnO-ZrO₂-PC catalyst,and it has the better catalytic stability.The characterization and properties of the catalysts before and after plasma modification were studied show that the CuZnO-ZrO₂-PC solid solution catalyst has low crystallinity,good dispersion and good reduction performance,which provides a basis for the high catalytic performance.