The Study Of Carbon Monoxide Hrdrogenation To Higher Alcohols Over Cu-based Catalysts

Higher alcohols,an important basic raw material in the chemical industry,can not only be used as an alternative fuel and a clean gasoline additive,but also as chemicals and chemical materials,exhibiting good application prospect.Synthesis of higher alcohols from syngas?CO+H₂?has attracted a great deal of attention under the background of energy shortage,so it has become a hot topic in the field of modern coal chemical industry.Owing to the low cost and mild reaction conditions,Cu-based catalysts are favored by researchers.In the CuZnAl catalysts prepared by complete liquid-phase method,the Al component existed in the form of AlOOH rather than the conventional?-Al₂O₃.In our previous work,AlOOH was prepared separately and mechanically mixed with industrial methanol catalyst C302 for CO hydrogenation.Higher alcohols were obtained,but the selectivity was low.In order to strengthen the interaction between the components of catalyst,and further to increase the selectivity of C₂₊OH.In this paper,CuZnAlOOH catalysts were prepared by impregnation method to combine Cu,Zn with AlOOH.Moreover,CuZnAl catalysts were prepared by a one-step precipitation method.The above two types of catalysts were used for CO hydrogenation reaction and characterized by XRD,H₂-TPR,N₂ adsorption,TG-DTG,CO₂-TPD-MS and CO-TPD-MS.The main conclusions are as follows:1?The content of AlOOH affected the product distribution.When Cu:Zn:AlOOH was 2:1:0.8,the catalyst was conducive to synthesis of C₂₊OH.The preparation method of AlOOH had a great influence on the dispersion of reducible Cu species in the catalysts.The impregnation sequence had an effect on the base content on the catalyst surface.2?CuZn Al catalysts were prepared by precipitation method.It was found that the catalysts had a hydrotalcite-like structure.And the p H value during the precipitation process was an important factor in hydrotalcite-like precursors synthesis process.The alteration of pH value had a significant effect on the reducible Cu species,specific surface area,surface basic strength and the adsorption capacity for CO.With the calcination temperature rising,the selectivity of C₂₊OH increased.Compared with hydrothermal-precipitation method,precipitation method was simple.And the CO conversion was high,but the main product was methanol and the selectivity of C₂₊OH in the products was low.3?The catalysts with highly dispersed Cu species and larger specific surface area were favorable for the increase of CO conversion.The synergistic effect of medium base and strong base as well as appropriate CO dissociation and non-dissociation ability was essential to the production of C₂₊OH.