Zn-EDTA-2Na配合物催化环氧丙烷与CO2反应合成碳酸丙烯酯的研究

Synthesis of Propylene Carbonate from CO_2 and Propylene Oxide Using Zn-EDTA-2Na Complexes as Catalysts

以水为溶剂,利用无毒、稳定、廉价易得且具有强配位能力的乙二胺四乙酸钠盐(EDTA-nNa)与金属卤化物配位,构建了多种配合物MX_2-EDTA-nNa(M=Zn、Fe、Co、Ni;X=Cl、Br、I、NO_3;n=0、2、4)。配合物催化环氧丙烷与CO_2反应合成碳酸丙烯酯研究表明,配合物中金属中心Lewis酸性和阴离子离去能力越强,其催化活性越高;其中ZnBr_2-EDTA-2Na表现出最优异的催化性能,碳酸丙烯酯的收率和选择性分别为96.9%和99.3%,TOF达96.9 h^(-1)。通过复合氧化石墨烯,可以进一步提高ZnBr_2-EDTA-2Na的耐水性。另外,结合Redlich-Kwong方程和实验结果探讨了溶于反应液中CO_2的量,在25℃和1.25MPa下溶于反应液中的CO_2量超过9.3 mmol,将有利于CO_2转化为碳酸丙烯酯。

A series of novel MX2-EDTA-nNa（M=Zn, Fe, Co, Ni; X=Cl, Br, I, NO3; n=0, 2, 4） complexes were prepared through the coordination of metal halides with ethylenediaminetetraacetic acid sodium salts（EDTA-nNa）in aqueous solution. These prepared complexes were non-toxic, cheap, and stable. Based on the activities of MX2-EDTA-nNa, it was deduced that a strong acidity of metal and a strong leaving ability of anion were favorable for the cycloaddition reaction of CO2 with propylene oxide. In the case of using ZnBr2-EDTA-2Na as the catalyst,propylene carbonate（PC） selectivity and yield are 99.3% and 96.9%, respectively, showing a turnover frequency of96.9 h～（-1）. The stability of ZnBr2-EDTA-2Na could be improved by graphene oxide. Furthermore, the mount of CO2 dissolved in the liquid phase was calculated using the Redlich-Kwong equations on the basis of PC yield. It was found that the amount of CO2 dissolved in the reaction solution was higher than 9.3 mmol at a temperature of 25℃and a pressure of 1.25 MPa. The good solubility of CO2 in the reaction liquid was favorable for CO2 conversion.