催化学报 ›› 2018, Vol. 39 ›› Issue (8): 1303-1310.DOI: 10.1016/S1872-2067(18)63012-8

• 第十五届国际二氧化碳利用会议专栏 • 上一篇    下一篇

稀土三元催化体系ZnO/SiO2负载化及季铵盐催化CO2与环氧丙烷合成高分子量聚碳酸酯

程瑞华, 周宇杰, 侯侨丽, 刘柏平   

  1. 华东理工大学化学工程国家重点实验室, 上海 200237
  • 收稿日期:2018-01-12 修回日期:2018-02-27 出版日期:2018-08-18 发布日期:2018-07-04
  • 通讯作者: 程瑞华
  • 基金资助:

    浦江人才计划(16PJD016).

ZnO/SiO2-modified rare-earth-metal ternary catalyst bearing quaternary ammonium salts for synthesis of high molecular weight poly(propylene carbonate)

Ruihua Cheng, Yujie Zhou, Qiaoli Hou, Boping Liu   

  1. State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
  • Received:2018-01-12 Revised:2018-02-27 Online:2018-08-18 Published:2018-07-04
  • Contact: 10.1016/S1872-2067(18)63012-8
  • Supported by:

    This work was supported by the Pujiang Talent Projects (16PJD016).

摘要:

由环氧丙烷(PO)和CO2交替共聚合成脂肪族聚碳酸亚丙酯,CO2利用率高,所得产物具有一定的力学性能和生物降解性能,具有广泛应用前景.目前,用于CO2和环氧化合物共聚的催化体系主要包含锌、钴、镉、铬、铝和稀土等金属活性中心,结构、活性各异的催化剂体系,其催化性能和产物性能也各具特色.其中,稀土三元催化剂(ZnEt2-甘油-三氯乙酸钇)因合成聚碳酸酯产物的分子量高、碳酸酯单元含量高、聚醚及环碳酸酯副产物少的特点而受到关注.但是由于催化剂催化效率低,聚合时间长,产品成本高,使得工业化规模生产受到限制.
本文基于稀土三元催化体系,将催化剂负载于硅胶及锌改性硅胶,优化了其制备条件,同时考察了添加季铵盐对催化CO2/环氧丙烷共聚合成聚碳酸酯性能的影响.结果表明,在1L聚合釜中,于3.5MPa和70℃反应条件下,ZnO担载量及ZnO/SiO2添加量对反应性能均有影响.当3wt%ZnO/SiO2的添加量为5g时,稀土三元催化体系的活性为4845.2g/molZn..所得聚合物经过多次纯化处理后,能够有效提高材料的热学性能,即有效除去产物中的ZnO对聚合物的热稳定性有重要作用.添加含有不同阴离子(F-,Cl-和Br-)的季铵盐可显著影响稀土三元催化剂的活性.其中,仅四甲基氟化铵可以明显提高反应活性乃至聚合物分子量.在3wt%ZnO/SiO2载体和四甲基氟化铵的协同作用下,稀土三元催化体系的共聚性能明显提升,活性最高可达5223.0g/molZn.聚合物结构分析表明,在载体和四甲基氟化铵存在下,聚合物分子量明显提高,可达到20万以上,分子量分布明显变窄,且聚合物结构如碳酸酯的单元含量、副产物含量以及聚合物产品玻璃化温度基本不变,后者均保持在40-41?;C.基于此,我们提出了在ZnO改性硅胶载体及四甲基氟化铵存在下稀土三元催化体系催化CO2/环氧丙烷共聚的反应机理:ZnO/SiO2载体有利于稀土三元催化体系的分散,而四甲基氟化铵则有利于吸附在ZnEt2上的环氧丙烷开环.

关键词: CO2/环氧烷烃共聚, 稀土金属催化剂, ZnO改性硅胶, 季铵盐, 分子量

Abstract:

A modified rare-earth-metal catalyst system combined with quaternary ammonium salts (QASs) as cocatalysts was investigated in the alternating copolymerization of CO2/propylene oxide (PO) to produce poly(propylene carbonate) (PPC). In the presence of ZnO/SiO2, the ZnEt2-glycerine-Y(CCl3OO)3 catalyst presented higher activity for CO2/PO copolymerization, as well as a higher molecular weight of polycarbonate, while maintaining the high carbonate content originating from the neat ZnEt2-glycerine-Y(CCl3OO)3 catalyst. In the presence of QASs bearing different halide anions (F-, Cl-, and Br-), the type of the halide anion had a strong influence on the activity of the catalyst for CO2/PO alternating copolymerization. Only tetramethylammonium fluoride (TMAF) could promote the alternating copolymerization without increasing the by-product. Combined the ZnO/SiO2 catalyst and TMAF, the catalytic activity for CO2/PO polymerization increased dramatically compared to the basic ternary catalyst system. The improved catalyst system produced a polymer with a high carbonate unit level equivalent to that of the polycarbonate produced by the basic ZnEt2-glycerine-Y(CCl3OO)3 catalyst system.

Key words: CO2/epoxide copolymerization, Rare-earth-metal catalyst, ZnO-modified silica gel, Quaternary ammonium salt, Molecular weight