文献类型：期刊文献

中文题名：ZnO/SiO_2-modified rare-earth-metal ternary catalyst bearing quaternary ammonium salts for synthesis of high molecular weight poly (propylene carbonate)

英文题名：稀土三元催化体系ZnO/SiO_2负载化及季铵盐催化CO_2与环氧丙烷合成高分子量聚碳酸酯（英文）

作者：Ruihua Cheng[1];Yujie Zhou[1];Qiaoli Hou[1];Boping Liu[1]

机构：State Key Laboratory of Chemical Engineering,East China University of Science and Technology,Shanghai200237,China

年份：2018

卷号：39

期号：8

起止页码：1303

中文期刊名：Chinese Journal of Catalysis

外文期刊名：催化学报（英文）

收录：CSTPCD;;Scopus;北大核心:【北大核心2017】；CSCD:【CSCD2017_2018】；

基金：supported by the Pujiang Talent Projects(16PJD016)~~

语种：英文

中文关键词：CO2/epoxide copolymerization;Rare‐earth‐metalcatalyst ZnO‐modifiedsilica gel;Quaternaryammoniumsalt;Molecularweight

外文关键词：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

摘要：A modified rare-earth-metal catalyst system combined with quaternary ammonium salts（QASs） as cocatalysts was investigated in the alternating copolymerization of CO_2/propylene oxide（PO） to produce poly（propylene carbonate）（PPC）. In the presence of ZnO/SiO_2, the ZnEt_2-glycerine-Y（CCl_3OO）_3 catalyst presented higher activity for CO_2/PO copolymerization, as well as a higher molecular weight of polycarbonate, while maintaining the high carbonate content originating from the neat ZnEt_2-glycerine-Y（CCl_3OO）_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 CO_2/PO alternating copolymerization. Only tetramethylammonium fluoride（TMAF） could promote the alternating copolymerization without increasing the by-product. Combined the ZnO/SiO_2 catalyst and TMAF, the catalytic activity for CO_2/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 ZnEt_2-glycerine-Y（CCl_3OO）_3 catalyst system.
由环氧丙烷(PO)和CO_2交替共聚合成脂肪族聚碳酸亚丙酯,CO_2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CO_2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(ZnEt_2-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CO_2/环氧丙烷共聚合成聚碳酸酯性能的影响.结果表明,在1 L聚合釜中,于3.5 MPa和70 ℃反应条件下,ZnO担载量及ZnO/SiO_2添加量对反应性能均有影响.当3 wt%ZnO/SiO_2的添加量为5 g时,稀土三元催化体系的活性为4845.2 g/mol_(Zn).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3 wt%ZnO/SiO_2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5223.0 g/mol_(Zn).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℃.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CO_2/环氧丙烷共聚的反应机理:ZnO/SiO_2载体有利于稀土三元催化体系的分散。