Preparation Of CuO-ZnO-ZrO₂ Catalyst By Polymer Precursor Method And Its Catalytic Performance For CO₂ Hydrogenation To Methanol

In recent years,the greenhouse effect resulted from CO₂ emissions becomes more and more serious.On the other hand,CO₂ is a valuable carbon resource in nature,which can be converted into useful chemicals and fuels.Accordingly,a large number of researchers have focused on CO₂ hydrogenation to methanol because methanol is an important solvent and feedstock for the production of chemicals and fuel additives,which is of great significance for the sustainable development of society.The polymer precursor method is widely used to prepare doped nano-powders,due to the fact that the prepared powder possesses a precise chemical ratio and a large specific surface area.But this method has not been applied to the preparation of CuO-ZnO-ZrO₂ catalysts.In this paper,the CuO-ZnO-ZrO₂ catalysts were prepared by the polymer precursor method and tested for the methanol synthesis from CO₂ hydrogenation.The content of ethylene glycol,the calcination temperature and the addition of different complexing agents were mainly considered.Meanwhile,this method was compared with other preparation methods.The main results are as follows:1.Effect of the content of ethylene glycol on the CuO-ZnO-ZrO₂ catalystsThe CuO-ZnO-ZrO₂ catalysts were prepared by the polymer precursor method with different proportions of ethylene glycol?EG?to citric acid?CA?under the molar ratio of CA to total amount of metal ions remaining constant of 2,and applied for the synthesis of methanol from CO₂ hydrogenation.The result indicates that the yield of methanol decreased gradually as the content of EG increasing.Furthermore,the catalytic activity was not only related to the surface area of metallic copper(S_Cu)but also to the interaction between copper and other oxides?ZnO and ZrO₂?.2.Effect of the calcination temperature on the CuO-ZnO-ZrO₂ catalystsThe effects of the calcination temperature on the phsico-chemical properties and catalytic performance of the CuO-ZnO-ZrO₂ catalysts prepared by the polymer precursor method were investigated.The results indicate that both the CO₂ conversion and the yield of methanol exhibit volcanic trend with the increase of calcination temperature.Meanwhile,the m-ZrO₂was gradually generated in catalysts which could improve the methanol selectivity.And the catalysts calcinated at 400°C owned larger S_Cu and thus the higher CO₂ conversion.In addition,the activity of methanol synthesis is mainly dependent on S_Cu.3.Effect of the complexing agent on the CuO-ZnO-ZrO₂ catalystsThe CuO-ZnO-ZrO₂ catalysts were prepared by polymer precursor method with different complexing agents?citric acid,tartaric acid,glycine,oxalic acid,and EDTA?,and used for the synthesis of methanol from CO₂ hydrogenation.The results indicate that the S_Cu of the catalysts were greatly influenced by the complexing agent,thus affecting the activity for methanol synthesis.Among the complexing agents investigated here,the catalyst prepared with citric acid owns the best catalytic performance.4.Effect of the preparation methods on the CuO-ZnO-ZrO₂ catalystsIn comparison with other methods including co-precipitation,EDTA-citric acid complexing,and polymer complexation solution,the CuO-ZnO-ZrO₂ catalyst prepared by the polymer precursor method possessed the better methanol selectivity and methanol yield.Moreover,this method has the merit of simple operation process,thus it is a practical method for the preparation of the CuO-ZnO-ZrO₂ catalyst for the synthesis of methanol from CO₂hydrogenation.