Study on application of CuZn/CeO2 catalysts in CO2 hydrogenation to methanol
The presence of by-product water produced during the CO2 hydrogenation to methanol reaction will accelerate the aggregation and sintering of CuZn species,resulting in serious deactivation of the catalyst.CeO2 has weak hydrophilicity and high hydrothermal stability,which can enhance the dispersion of CuZn species.Consequently,a series of CuZn-based catalysts with controllable crystal planes of CeO2 carriers were synthesized by hydrothermal method,and appropriate concentrations of oxygen vacancy were strategically introduced.The physicochemical properties such as morphologies and structures and reduction performances of the synthesized CeO2 carriers and CuZn/CeO2-y catalysts(y represents rod、cube or otca)were studied by characterization methods such as TEM,XRD and H2-TPR.The catalytic performances of CuZn/CeO2-y catalysts in CO2 hydrogenation to methanol were also investigated.The results show that the CeO2 carrier with nanorod structure and exposed(110)crystal plane(CeO2-rod)is more conducive to the dispersion of CuZn-based species.Moreover,CeO2-rod and Cu species form Cu—O—Ce interface,which enhances the ability of the catalyst to adsorb and activate CO2 and H2 simultaneously.Therefore,CuZn/CeO2-rod catalyst exhibits high CO2 conversion and methanol selectivity.Under the conditions of 260 ℃ and 3 MPa,the space-time yield of methanol is up to 433.4 g/(kg·h),and methanol selectivity is up to 68.5％.Simultaneously,the reaction paths and evolution of intermediates in CO2 hydrogenation to methanol were thoroughly delineated by in situ diffuse reflectance infrared Fourier transform spectroscopy.It is found that under the action of CuZn/CeO2 catalysts,the reaction mainly follow the formate path.The crystal plane effect of the carrier does not change the reaction paths,but it increases the equilibrium rate of important intermediate species.
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