Bifunctional Catalyst with a Yolk–Shell Structure Catalyzes Glucose to Produce Ethylene Glycol
The preparation of small molecule compounds with a high value from biomass has always been the focus of research, and catalysts with high activity and stability are an essential part of biomass conversion. In this work, yolk–shell nanospheres (YSNSs) with the high hydrogenation activity metal Pd as the core and mesoporous silica as the shell were prepared firstly, and then the bifunctional catalyst Pd@WOx–MSiO2 YSNSs was obtained by loading tungsten oxide on the surface of yolk–shell nanospheres. The structure characterization showed that the prepared Pd@WOx–MSiO2 YSNSs had a good shell–void–core structure, the amorphous WOx species was uniformly dispersed on the surface and channel of the mesoporous silica shell, and there were no bulky WO3 crystals. A series of Pd@WOx–MSiO2 YSNSs catalysts with different tungsten contents were used to catalyze the directional preparation of ethylene glycol (EG) from glucose. The conversion of glucose was 99.3% and the selectivity of EG was 59.4%. According to the analysis of the acidity of the catalyst and the valence state of the metal, the catalyst had weak Lewis acidity, which could promote the cleavage of the C–C bond in glucose, and W5+ could produce oxygen vacancy to adsorb oxygen into glucose, so that the tungsten species can effectively promote the selectivity of EG. Pd@WOx–MSiO2 YSNSs were very different from other supported catalysts in structure and the distribution of active sites. Compared with traditional supported catalysts, Pd@WOx–MSiO2 YSNSs had higher activity and stability due to their unique yolk–shell structures and the protection of the inner Pd nanoparticles by the mesoporous silica shell.
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