【摘要】 采用溶胶凝胶法制备了用于草酸二甲酯加氢合成乙二醇的Cu/SiO2催化剂,在优化的反应条件下,当催化剂中Cu含量为15%～25%时,草酸二甲酯转化率和乙二醇选择性分别达到99.9%和95.0%.通过N2吸附-脱附、透射电镜、X射线衍射、氢气程序升温还原、N2O滴定法和X射线光电子能谱等手段对各Cu/SiO2催化剂进行了表征.结果表明,在相同反应条件下,随着Cu含量增加,硅胶对活性物种的包裹作用和Cu物种间的团聚作用对催化剂活性影响较大,当Cu含量≤10%时,硅胶对Cu物种的包裹作用强烈,是影响催化剂活性的主要因素;当Cu含量>10%时,催化剂表面Cu物种间的团聚作用变得突出,成为影响催化剂活性的主要因素,二者的消长对催化剂表面结构、活性物种的形态和化学环境的影响很大,并最终影响催化剂的性能.更多还原

【Abstract】 A series of Cu/SiO2 catalysts for the hydrogenation of dimethyl oxalate to ethylene glycol were prepared by the sol-gel method.Under optimized hydrogenation conditions,dimethyl oxalate conversion and ethylene glycol selectivity were found to reach 99.9% and 95.0%,respectively,upon varying the copper loading between 15% and 25%.The prepared catalysts were characterized by N2-physisorption,transmission electron microscopy,X-ray diffraction,H2-temperature-programmed reduction,N2O titration,and X-ray photoelectron spectroscopy.The results show that when the copper loading was increased under the same experimental conditions the factors that mostly affect the activities of the catalysts prepared by the sol-gel method are encapsulation and agglomeration.The encapsulation of silica is strong and it becomes the major factor when w(Cu) ≤ 10% while agglomeration among the copper species on the catalyst surface becomes more serious and is a major factor when w(Cu) > 10%.These two factors influence the surface structure,the morphology of the copper species,and the chemicals surroundings the catalysts and as a result the performance of the catalysts is affected too.更多还原