Preparation Of The High Efficient Cu-ZnO/SBA-15 Catalyst For Methyl Acetate Hydrogenation And The Role Of ZnO

With the oil resources shrinking,ethanol is regarded as an ideal alternative energy source to notably reduce our dependence on foreign oil by utilized as fuel or additive of gasoline.Based on the unique energy structure of China,study on coal-to-ethanol route is extremely important for our energy multiple and security.A novel coal-to-ethanol route,including carbonylation of dimethyl ether(DME)to methyl acetate(MA)and hydrogenation of MA to ethanol,is a green and efficient method and has attracted many attentions because of mild reaction condition,high atom economy,low pollution and wild raw material sources.Cu-Zn based catalysts were generally used in hydrogenation of MA due to its excellent performance,but how to further enhance the dispersion and the interaction between copper and zinc species is still a challenge to improve catalytic activity.Furthermore,the mechanism of ZnO as a chemical contributor in the hydrogenation of MA is still unclear.In this dissertation,a new preparation method of high efficient Cu-ZnO/SBA-15 catalysts was proposed,the role of ZnO and its facets on Cu-Zn based systems for MA hydrogenation was studied in detail.Cu-ZnO/SBA-15 catalysts were fabricated by solid-state strategy.When the mass percentage of metal oxide was 30 wt.% and the molar ratio of Cu:Zn = 9:1,the best catalytic performance can be achieved,the conversion of MA reached 85% with a 82% selectivity of ethanol at 220 ?,2.0 MPa,H2/MA = 20.In comparison with other reported Cu-Zn based catalysts,Cu-Zn O/SBA-15 catalysts fabricated by solid-state strategy exhibited superior activity.It was found that there exists an extraordinary microenvironment between organic template and silica walls in as-prepared SBA-15.The supported oxide particles can be successfully introduced into the pores of parent SBA-15 by the use of organic template.To the best of our knowledge,this is the first report of such a high dispersion of Cu and ZnO.Additionally,the results indicated that interaction between copper and zinc species can be notably enhanced owing to their intimate contact with the help of organic template,which may open up a new inspiration in rational design of Cu-Zn based catalysts for hydrogenation of esters.Cu-ZnO/SBA-15 catalysts with different Cu/Zn ratios were used to further exploration of ZnO contributions.The results demonstrated that introduction of ZnO exhibited a promoting effect on generation of Cu-ZnOx which help to facilitate Cu+.The catalytic performance linearly increases with increasing Cu+/Cu0 ratio on the surface of reduced catalysts.These results were consistent with the hypothesis that the cooperation between Cu-Zn Ox and Cu0 is responsible for the enhanced catalytic performance.Compared to the Cu+ species from Cu-O-Si,XPS and XAES results have revealed that Cu+ species from Cu-ZnOx are more active in the adsorption of carbonyl with lower electron density and stronger Lewis acidity.Parent ZnO with different polarity ratios was used to prepare Cu/ZnO catalysts.Results indicated that the polarity ratio of ZnO strongly influenced the catalytic performance.Compared with non-polar facets,polar facts expose more ZnOx oxygen vacancies.A higher polarity ratio promotes hydrogenation of MA,which is attributed to a stronger interaction between copper and ZnO.