Acta Chimica Sinica ›› 2012, Vol. 70 ›› Issue (18): 1897-1903.DOI: 10.6023/A12050249 Previous Articles     Next Articles



王帅, 李洋, 刘海超   

  1. 北京分子科学国家实验室 分子动态与稳态结构国家重点实验室 北京大学化学与分子工程学院绿色化学研究中心 北京 100871
  • 投稿日期:2012-05-28 发布日期:2012-08-17
  • 通讯作者: 刘海超
  • 基金资助:

    项目受国家自然科学基金(Nos. 20825310, 21173008)和国家重点基础研究发展计划(973 计划, Nos. 2011CB201400, 2011CB808700)资助.

Selective Hydrogenolysis of Glycerol to Propylene Glycol on MgO-Al2O3 Dispersed Cu Catalysts

Wang Shuai, Li Yang, Liu Haichao   

  1. Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Green Chemistry Center, Peking University, Beijing 100871
  • Received:2012-05-28 Published:2012-08-17
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Nos. 20825310, 21173008) and the National Basic Research Project of China (Nos. 2011CB201400, 2011CB808700).

Cu/MgO-Al2O3 (Mg/Al atomic ratio=1/1, 3/1, 4/1), Cu/MgO and Cu/Al2O3 catalysts with high Cu dispersions were prepared by an impregnation method using ethanol as solvent instead of water. Compared to water, ethanol as solvent was favorable not only for obtaining the high dispersions of the Cu clusters on the basic oxide supports, but also for retaining the basicity and structures of the supports during the catalyst preparation. The density of the basic sites for the dispersed Cu catalysts increased with increasing the MgO contents in the basic supports. These catalysts catalyzed glycerol hydrogenolysis to propylene glycol with a high selectivity (>90%), and showed slight deactivation in dioxane at 200℃ and 6.0 MPa H2. Their reaction rates normalized by per exposed Cu atom increased with increasing the ratios of the basic sites to Cu atoms on the catalyst surfaces. The intrinsic hydrogenolysis activity of the Cu atoms were probed by N2O chemisorption-H2 temperature programmed reduction, which did not change essentially with the Cu loadings (2-6 wt%) and the Mg/Al atomic ratios of the MgO-Al2O3 supports. Meanwhile, the basic sites alone on the supports were inactive for the glycerol conversion. Taken together, we propose a synergetic effect that the basic sites at the interfaces between the Cu sites and the supports assist the cleavage of α-C-H bonds of glycerol on the Cu surfaces leading to the faster dehydrogenation of glycerol to glyceraldehyde, a kinetically-relevant step in glycerol hydrogenolysis to propylene glycol. These active basic sites appear to be the Br?nsted OH- sites, i.e. the hydroxyl groups bonded to the surface Mg2+cations on MgO-Al2O3. The understanding on such synergy between the basic sites and Cu sites in glycerol hydrogenolysis provides a basis for the rational design of superior hydrogenolysis catalysts and selective removal of oxygen from biomass-derived feedstocks.

Key words: glycerol, selective hydrogenolysis, propylene glycol, Cu/MgO-Al2O3, support effect