席夫碱Mo(VI)功能化介孔SiO2的制备及其催化烯烃环氧化研究

采用共缩聚法制备有机-无机杂化材料,以介孔SiO_2材料为载体,分别嫁接席夫碱配体和配位乙酰丙酮钼,得到Mo(VI)席夫碱修饰的介孔SiO_2(Mo-SB-Cl-SiO_2-0.5-1).所制备的材料采用XRD,SEM,N2吸附-脱附和TEM技术对其结构进行了表征.考察了Mo-SB-Cl-SiO_2-0.5-1催化液相烯烃环氧化性能,结果表明:Mo-SB-Cl-SiO_2-0.5-1催化剂对烯烃环氧化具有高的转化率和优良的催化活性.与后嫁接法制备的催化剂相比,Mo-SB-Cl-SiO_2-0.5-1催化剂催化活性得到明显提高,催化环己烯环氧化的转化率和选择性分别为85%和99%.在不同烯烃的研究中,环辛烯具有最高的转化率和选择性,分别为87%和99%.催化剂重复使用4次后,环己烯的转化率没有明显下降,选择性仍然高达98%,表明Mo-SB-Cl-SiO_2-0.5-1具有较好的催化稳定性.

Preparation of Mo(VI) Schiff Base Functionalization Mesoporous SiO2 and Catalytic Olefin Epoxidation

The co-condensation strategy was proposed to be adopted to prepare the organic/inorganic hybrid materials. In this preparation, mesoporous SiO₂ acted as the support. After grafting the Schiff base ligand and coordinating molybdenum acetylacetonate, the Mo (VI) Schiff base was modified mesoporous SiO₂ (Mo-SB-Cl-SiO₂-0.5-1) then formed under the condition of co-condensation. The XRD, SEM and N₂ adsorption-desorption and TEM techniques were applied to characterize the structure of materials. The catalytic performance of Mo-SB-Cl-SiO₂-0.5-1 was discussed in liquid olefins epoxidation system. The results showed a higher conversion and excellent catalysis activity in epoxidation of olefins. In comparison with that catalyst prepared by post-grafting method, the Mo-SB-Cl-SiO₂-0.5-1 catalyst showed an enhanced epoxidation activity and selectivity. In the reaction of cyclohexene, the conversion and selectivity were 85% and >99%, respectively. For the study on influences of different olefins, the highest conversion (87%) and selectivity (>99%) were found for cyclooctene had over Mo-SB-Cl-SiO₂-0.5-1. After being reused for 4 times, the conversion of cyclohexene hardly declined and the selectivity was still high to be 98%, which indicated that the good reusability of Mo-SB-Cl-SiO₂-0.5-1.