前驱液浓度对制备的草酸二甲酯加氢催化剂性能的影响

Influence of Precursor Concentration on Performance of Catalysts Prepared for the Hydrogenation of Dimethyl Oxalates

采用尿素均匀沉淀法制备了草酸二甲酯加氢合成乙二醇的Cu/SiO_2催化剂,并考察了催化剂制备时前驱液中铜离子浓度、尿素浓度以及铜负载量等因素对催化剂活性的影响。采用比表面孔隙度及化学吸附分析(BET)、X射线衍射(XRD)等对催化剂的结构进行了表征。实验结果表明,所制备的催化剂对草酸二甲酯加氢合成乙二醇反应均有较高的反应活性及乙二醇选择性。初始铜离子浓度的增大将增大催化剂的孔容以及孔径,易于出现过度加氢造成乙二醇的选择性下降。尿素浓度对制得的催化剂性能影响不大。铜负载量的增加易使催化剂中的铜晶聚集,造成催化剂的活性位覆盖使活性下降,负载量不宜超过25%。在铜离子浓度为0.3mol/L,尿素浓度为0.9mol/L,铜负载量为25%时制备的催化剂具有最高的反应活性,在实验条件下草酸二甲酯转化率为100%,乙二醇的收率达50%。

Silica-supported copper-based catalysts were prepared by means of homogeneous depositionprecipitation, and urea was used as precipitate. Influence of the copper ion and urea concentrations of the precursor solution and copper loading on performance of the prepared catalysts was investigated and BET and X-ray diffraction （XRD） were used to characterize the structure of the catalysts. The results showed that the prepared catalysts had high activity and high selectivity of ethylene glycol. Pore volume and diameter of the catalyst increased and the selectivity of ethylene glycol decreased because of over-hydrogeneration with increasing of initial copper ion concentration. Effect of urea concentration on the performance of prepared catalyst was slight. Copper-grain in the catalyst got together with over copper loading, which resulted in the decrease of catalytic activity. And the best performance catalyst was obtained under the conditions of copper ion concentration 0.3 mol/L, urea concentration 0.6 mol/L and 25% conner loading.