双金属氰化物/稀土配合物催化二氧化碳和环氧丙烷的共聚合

Copolymerization Between Propylene Oxide and Carbon Dioxide under Rare Earth Metal Complex/Double Metal Cyanide Complex Catalyst

使用双金属氰化物/稀土配合物复合催化剂催化二氧化碳和环氧丙烷共聚合,其催化效率比双金属氰化物催化剂有显著提高,得到了数均相对分子质量大于1.0×105的聚合物。研究了复合催化剂的组成(如稀土的种类、稀土与锌的比例(Ln/Zn)、稀土配合物中酸根离子的酸性等)对共聚反应的影响,同时研究了反应体系的压力及反应时间对催化活性的影响。采用Y(CCl3COO)3稀土金属配合物有利于共聚反应的进行。当n(Y)/n(Zn)=6、聚合4 h后,其催化活性比单纯的双金属氰化物提高了31.5%,聚合物的相对分子质量则没有太大变化,而副产物碳酸丙烯酯的质量分数低于2%,而在该温度下单独采用稀土三元催化剂时副产物碳酸丙烯酯的生成量通常在10%以上。聚合物中碳酸酯含量低于双金属氰化物的催化产物,说明稀土配合物只是起到活化金属与环氧丙烷配位的作用,没有提高共聚物的碳酸酯含量,整个共聚合反应依然遵循双金属氰化物催化的共聚反应机理。

Double metal cyanide/rare earth metal complex was used to catalyze the copolymerization between propylene oxide and carbon dioxide. It was found that the catalytic activity was much higher than that using rare earth ternary catalyst alone. The method could produce resultant polymer with average relative molecular mass above 1.0×105 using the as-prepared catalyst with less than 2% propylene carbonate by product, which was remarkably decreased from over 10% mass fraction using the rare earth ternary catalyst alone. The effects of complex catalyst component, including the category of rare earth metal, the molar ratio of n（Y）/n（Zn）, the acidity of the ligand of rare earth metal salt, as well as the reaction pressure and reaction time on the copolymerization were investigated. It was found that Y（CCl3COO）3 could improve catalytic activity of double metal cyanide, when n（Y）/n（Zn）=6 and reaction time was 4 h, compared with the double metal cyanide, the catalytic activity was increased by 31.5% while the carbonate unit content in the polymer was reduced. Our results indicate that the rare earth metal complexes only activated the complexation of propylene oxide, and the catalytic process still followed that of the double metal cyanide complex.