Study On Catalytic Performance Of Macroporous Copper Zinc - Zirconium Catalyst For Carbon Dioxide Hydrogenation

CO2is a mostly abundant potential raw material in nature, and major gases caused greenhouse effect, which lead to global warming. The environmental problem is more and more important today, people pay much attention to how to use to CO2efficiently. CO2hydrogenation to CH3OH is an efficient way for saving energy, reducing emission and recycling resource. As a base material of the C1chemical industry, methanol is a new kind of important and high competitive clear fuel. The synthesis of useful new energy (methanol) via hydrogenation of carbon dioxide not only can improve the living environmental condition, but also can mitigate the increasing resource problem.In this paper, a series of Cu-ZnO, Cu-ZrO2, Cu-ZnO-ZrO2catalysts were prepared by co-precipitation and studied the structure and performance of catalysts by means of XRD, H2-TPR, BET, the metallic copper surface areas and the assessment of activity. The results indicated that ZnO and ZrO2facilitated the crystallinity and dispersion of CuO, at the same time inhibited crystal growth and the integration of catalysts, which result in enhancing the acticity of catalysts. The activity of Cu-ZnO-ZrO2catalysts was better than the one of Cu-ZnO or Cu-ZrO2catalysts.In the next experiment, a series of macroporous Cu-ZnO-ZrO2catalysts were prepared by a template method, and characterized by the techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), H2temperature-programmed reduction (H2-TPR), N2adsorption, reactive N2O adsorption. The activity of the catalysts was tested for methanol synthesis from CO2hydrogenation. Firstly, a series of macroporous Cu-ZnO-ZrO2catalysts with different Zn/Zr ratios were investigated. It was found that, the macroporous CZZ catalysts with lower Zn/Zr ratio exhibiting a better morphology. The macroporous structure could inhibit the growth of the CuO crystallite size and avoid the sintering, which enhanced the acticity of catalysts. To a degree, the results were very different with the decrease of Zn/Zr. The decrease of Zn/Zr lead to the collapse of macroporous structure, and the CuO crystallite was sintering, which decreased the acticity of catalysts. In addition, the influence of the calcination temperatures was investigated. It was found that, the catalysts calcined at lower temperatures presented a disorderly structure, a lower crystallization degree and a lower catalytic activity. The catalysts calcined at450℃and550℃, exhibiting a three-dimensionally ordered macroporous structure and the walls were unfirm. In addition, the catalysts with a better crystallization degree presented a higher catalytic activity. The higher calcination temperatures could destroy the three-dimensionally ordered macroporous structure of the catalysts. Afterthat, the specific surface area and catalytic activity of catalysts also decreased.Finally, catalysts were investigated by in-situ DRIFT. With the in-situ DRIFT technique, the reaction intermediate species including carbonate, hydrogen carbonate, formate, surface-bound formaldehyde and methoxide can be detected, indicating the carbonate formed the formate and the formate formed the CH3OH. Combining with literature, put forward to the double activity center and the reaction route of CO2hydrogenation.