Study On The Performance Of Modified SBA - 15 Mesoporous Supported Copper - Based Catalyst For Hydrogenation

As the CO₂ emissions is riseing rapidly, so the greenhouse effect resulting in the global temperature rises, which is a threat to the ecological balance of the planet. Meanwhile worldwide consumption of carbon-based energy lead to the carbon-based energy resources decrease more quickly. In recent years, scientists have been constantly exploring the effective ways to use the CO₂ to synthesis available carbon-based energy. Methanol was synthesized by hydrogenation of carbon dioxide, which is a non-nitrogen, sulfur-free clean energy,and it has an important meaning for the utilization of carbon dioxide.In this paper, Using SBA-15 and Al-SBA-15, Mg-SBA-15 mesoporous molecular sieve as supports, a series of Cu-Zn-Zr supported SBA-15 and Al/Mg modified SBA-15 mesoporous catalysts were prepared by impregnation method with different Cu-Zn-Zr oxides content and Al/Si,Mg/Si molar ratio.The-N2.adsorption-desorption（BET）, X-raydiffraction（XRD）,transmission electron-microscopy（TEM）, H2 temperature programmed reduction（H2TPR）, CO₂ temperature programmed desorption（CO₂-TPD） And N2O-titration-technique(N2O RFCwere used to determine the textual structure and physicochemical properties of the catalysts. The catalytic activities of these catalysts were determined on the hydrogenation of CO₂ to methanol in a fixed-bed reactor. Characterization results showed that all catalysts, except for CZZ5o%-SBA-15, having a mesoporous structure. The modification of SBA-15 not only have an influence on the acid-base properties of the catalysts, but also have an influence on the ddispersion of copper and grain size of loaded Cu-Zn-Zr oxides.Catalytical experimental results showed that, the methanol selecticity of the pure SBA-15 supported catalysts was increased firstly and then decreased as the increase of Cu-Zn-Zr loadings. The highest methanol selecticity was abtained when the loading is 35%.The decrease of the methanol selecticity with the continuous increase of Cu-Zn-Zr loadings may be attributed to the agglomerationof Cu-Zn-Zr oxides and the ddispersion of copper. The modification of Al not only increases the surface acid sites of the supports, but also improve the Dcu%、 Scu of the catalysts and promote the formation of Cu+-O-Zn active sites. CZZ/A1-SBA-15（0.03） catalyst showed the larger methanol selectivity （26%）, which increased by 11%as compared with non-doped aluminum CZZ/Al-SBA-15（0） catalyst. However, with the increasing of Al content, the acidity of the supports is increasing, which is not good for the absorption of CO₂, and resulting in the decrease of the catalytic activity. Compared to Al-modified supports, the modification of Mg has a little influence on the grain size and the dispersion of copper of supported Cu-Zn-Zr oxides. In addition, the desorption of CO₂ on the surface of catalysts become more difficult due to the existance of more base sites, which resulting in the decrease of catalytic activity.