催化学报

催化学报 ›› 2014, Vol. 35 ›› Issue (5): 631-643.DOI: 10.1016/S1872-2067(14)60094-2

• 研究论文 • 上一篇    下一篇

Cu-ZnO-Al2O3复合催化剂上甘油选择氢解合成丙二醇

王帅, 刘海超   

  1. 北京大学化学与分子工程学院, 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, 北京100871
  • 收稿日期:2014-03-20 修回日期:2014-03-27 出版日期:2014-04-18 发布日期:2014-04-24
  • 通讯作者: 刘海超
  • 基金资助:

    国家重点基础研究发展计划（973计划，2011CB201400，2011CB808700）；国家自然科学基金（21173008，21373019，51121091）.

Selective hydrogenolysis of glycerol to propylene glycol on hydroxycarbonate-derived Cu-ZnO-Al2O3 catalysts

Shuai Wang, Haichao Liu   

  1. Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
  • Received:2014-03-20 Revised:2014-03-27 Online:2014-04-18 Published:2014-04-24
  • Supported by:

    This work was supported by the National Basic Research Program of China (973 Program, 2011CB201400, 2011CB808700) and the National Natural Science Foundation of China (21173008, 21373019, 51121091).

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摘要：

分别采用均匀共沉淀法、沉积-沉淀法和传统的共沉淀法制备了3种具有相似组成的Cu-ZnO-Al2O3催化剂（CZA-HP，CAZ-DP和CZA-CP）; 同时还采用均匀共沉淀法制备了Cu-ZnO催化剂（CZ-HP）以用于比较. X射线衍射表征结果表明，以上方法制备的Cu-Zn-Al碱式碳酸盐前体中Cu2+，Zn2+和Al3+的混合均匀程度的顺序为CZA-DP < CZA-HP < CZA-CP. Al3+分散程度的提高和Al2O3与ZnO的紧密接触使得Cu-ZnO-Al2O3催化剂中金属Cu和ZnO具有更小的粒径. 但ZnO-Al2O3间紧密接触也阻隔了Cu-ZnO-Al2O3催化剂中金属Cu与ZnO之间的相互作用. 因此Al2O3的添加使得CZA-HP样品上的Cu粒子表现出最强的氧化还原能力. 在473 K和6.0 MPa H2的反应条件下，以上三种Cu-ZnO-Al2O3催化剂均高选择性地催化甘油氢解为丙二醇（30%甘油转化率下的选择性 > 90%）. Cu-ZnO-Al2O3催化剂表面单位Cu原子的本征活性顺序为CZA-DP < CZA-CP < CZ-HP < CZA-HP，与它们的氧化还原能力相一致. 此外，Al2O3的添加还显著地抑制了Cu粒子在反应过程中的聚集，提高了催化剂的稳定性. 经6次循环使用后，CZ-HP中Cu粒子的粒径从13.2增至45.2 nm，活性相应下降了45%；而CZA-HP中Cu粒子的粒径从8.3增至19.0 nm，活性仅下降了10%.

关键词: 甘油, 选择性氢解, 丙二醇, 铜, 氧化锌, 氧化铝, 碱式碳酸盐前体, 构效关系, 催化剂稳定性

Abstract:

Three Cu-ZnO-Al2O3 catalysts with similar compositions were prepared by homogeneous coprecipitation (CZA-HP), deposition-precipitation (CZA-DP), and conventional coprecipitation (CZA-CP). A Cu-ZnO catalyst was also prepared by homogeneous coprecipitation (CZ-HP) for reference. X-ray diffraction results showed that the degree of mixing of Cu2+, Zn2+, and Al3+ ions in the Cu-Zn-Al hydroxycarbonate precursor followed the order of CZA-DP < CZA-HP < CZA-CP. A more homogeneous aluminum distribution and intimate contact between Al2O3 and ZnO led to smaller CuO and ZnO crystallites in the CuO-ZnO-Al2O3 composite oxides, and consequently smaller Cu and ZnO crystallites in the final Cu-ZnO-Al2O3 catalysts. However, the intimate ZnO-Al2O3 contact hindered the interaction between Cu and ZnO in the Cu-ZnO-Al2O3 catalysts. As a result of these effects of Al2O3, for the samples other than CZA-CP, the Cu particles on CZA-HP showed the highest redox activity, which was characterized by N2O chemisorption-H2 temperature-programmed reduction. These catalysts catalyzed glycerol hydrogenolysis to propylene glycol with high selectivities above 90% at 30% glycerol conversion (473 K and 6.0 MPa H2). Their activities normalized per exposed surface Cu atom to give turnover frequencies increased in the order CZA-DP < CZA-CP < CZ-HP < CZA-HP, which was the order of the redox ability of the Cu particles. The addition of alumina increased the stability of Cu-ZnO catalysts. After six cycles (6 h per run), the activity of CZ-HP decreased by 45% accompanied by an increase of Cu crystallite size from 13.2 to 45.2 nm, while that of CZA-HP decreased only by 10% with an increase of the Cu crystallite size from 8.3 to 19.0 nm. These results demonstrated the promoting effects of Al2O3 on the activity and stability of Cu-ZnO catalysts derived from the hydroxycarbonates.

Key words: Glycerol, Selective hydrogenolysis, Propylene glycol, Copper, Zinc oxide, Alumina, Hydroxycarbonate precursor, Structure-activity relationship, Stability