MCM-41嫁接离子液体催化CO_(2)环加成反应

CO_(2) Cycloaddition Catalyzed by Ionic Liquids Grafted on MCM-41

以介孔分子筛(MCM-41)为载体,采用嫁接的方法制备了咪唑类离子液体功能化催化剂MCM-41-ImBr,采用X射线衍射(XRD)、傅里叶红外光谱(FT-IR)和元素分析(EA)对所得催化剂进行了表征,并将其用于催化CO_(2)与环氧氯丙烷(ECH)的环加成反应。考察了不同反应条件下CO_(2)与环氧氯丙烷(ECH)的环加成反应结果和催化剂重复使用的稳定性。表征结果表明:催化剂保持介孔结构,离子液体成功嫁接到了MCM-41表面,离子液体负载量为53.6 mmol/g。环加成反应结果表明:由于咪唑环与Br−的协同作用,在CO_(2)压力为0.7 MPa,反应温度为150℃,反应时间为4 h,催化剂用量为0.10 g,无添加助催化剂的条件下,ECH转化率高达100.0%,氯丙烯碳酸酯选择性为98.2%。当CO_(2)过量,反应温度为150℃时,ECH一级反应的表观速率常数为1.40 h^(-1),催化剂至少可以使用3次。

A kind of heterogeneous catalyst MCM-41-ImBr was prepared by grafting imidazolium-based ionic liquids on the surface of MCM-41.The catalyst was characterized by X-ray diffraction(XRD),Fourier infrared spectroscopy(FT-IR)and elemental analysis(EA),and was used to catalyze the cycloaddition reaction of CO_(2)with epichlorohydrin(ECH).The cycloaddition reaction results under different reaction conditions and the stability of catalyst reuse were investigated.The characterization results showed that the ionic liquids were successfully grafted on MCM-41 with intact mesoporous structure and the loading of ionic liquids was 53.6 mmol/g.Moreover,the catalyst exhibited high catalytic activity for catalyzing CO_(2)into cyclic carbonates due to the synergistic effect of the imidazole ring and Br−.The conversion of ECH and the selectivity of cyclic carbonate was 100.0%and 98.2%respectively,under the conditions of CO_(2)pressure of 0.7 MPa,reaction temperature of 150℃,reaction time of 4 h,catalyst dosage of 0.10 g and without co-catalyst.The approximate apparent rate constant of first order reaction with respect to ECH was 1.40 h^(-1) when CO_(2)was excessive and the reaction temperature was 150℃,and the catalyst could be used at least 3 times.