Preparation Of Supported Copper-Based Catalysts And Their Catalytic Performance For CO 2 Hydrogenation To Methanol Synthesis

As a kind of greenhouse gas,the excessive emission of CO₂ had been destroyed the present ecological balance that would affect the survival and development of mankind seriously.What's more,CO₂ as an important carbon source,it is a desirable way to make CO₂ convert into methanol which has industrial application value.This process can not only alleviate the greenhouse effect but also promote cyclic utilization of CO₂.As the high stability of the CO₂ is difficult to be activated,thus the one of keys to realize the industrialization of methanol synthesis from CO₂ hydrogenation is to obtain high efficiency catalysts.In this paper,two different carriers were used to prepare supported copper-based catalysts.The physicochemical properties,catalytic activity and catalytic mechanism of the copper-based catalysts were investigated.Firstly,we adopted chemical reduction and impregnation method to prepared Au-CuO/SBA-15 catalysts with different Au contents?0.5?3wt.%?and SBA-15 modified by organic silane reagent APTES was act as the support.The results showed that the ordered mesoporous structure of SBA-15 was not destroyed after loaded with Au-CuO NPs,and the as-prepared catalysts have high specific surface area.The introduction of Au NPs improved the catalytic activity,which can be ascribed to both the hydrogen spillover at Au-CuO interface and the promoting effect of Au on intermediate products CO hydrogenation to methanol.With the increase of Au content,the catalytic activity increased first and then decreased,and 2%Au-CuO/SBA-15 catalyst showed the best catalytic activity with 13.5%methanol selectivity and 24.2%CO₂ conversion,respectively.The introduction of suitable amount of Au was beneficial to generate strong Au-CuO interaction,which can help to improve the sintering resistance of the catalyst,reduce the catalyst size and promote the hydrogen spillover at Au-CuO interface.Secondly,based on the importance of catalyst structure and ZnO,CZ catalysts were prepared by deposition-precipitation method.ZnO with different morphologies?flower,flower-sword and sword?were act as the support.The results showed that the catalytic activity was influenced by the morphology.The best catalytic performance was of f-CZ catalyst,followed by f/s-CZ catalyst and s-CZ catalyst gave the poor performances.f-CZ catalyst showed the best catalytic activity with 29.5%CO₂ conversion and 35.9%methanol selectivity.It was found that there was no linear relationship between Scu and space time yield of methanol,indicating that Scu was not the only factor affecting the catalytic performance.The strong interaction between f-ZnO and CuO in the f-CZ catalyst with high polarity ratio improved the Scu of the catalyst,which ehanced the amount of dissociatived hydrogen and then promoted the hydrogenation of the carbon species.On the other hand,the surface of f-CZ catalyst contained more oxygen vacancies and strong basic sites,which were contributed to generate the aimed product methanol and ultimately improve the catalytic activity.