新型两亲性HZSM-5沸石催化剂对环己烯水合相界面反应的催化研究

Amphiphilic HZSM-5 Zeolite Catalyst for Hydration of Cyclohexene on Phase-boundary Interface

采用三甲基氯硅烷对HZSM-5沸石样品进行外表面修饰,制得两亲性沸石样品,该类两亲性沸石能分布于水、油两相界面处.改性后样品的红外光谱中末端硅羟基峰的强度明显降低,并出现CH3基团的C_H伸缩振动吸收峰,证实部分亲水性表面硅羟基被亲油性硅烷基团取代.这类两亲性样品在不加共溶剂及静置条件下,对环己烯水合相界面催化反应的催化活性远远高于改性前的HZSM-5沸石.由于该相界面反应是以孔道内为主的反应,三甲基氯硅烷经改性制备出的亲油性HZSM-5沸石也呈现出较高的活性.

Amphiphilic HZSM-5 zeolite particles were prepared by a partial modification of the external surface of HZSM-5 zeolite with trimethylchlorosilane. These amphiphilic zeolite particles were oriented at the water-organic boundary when they were added to the mixture of cyclohexene and water or water with CCl_4. IR spectra indicated that the intensity of the band for the terminal silanols decreased significantly and the band for the methyl groups(C_H stretching vibration) emerged after modification, which gave a direct evidence that partial hydrophilic silanol groups on the surface of the zeolite were replaced by the hydrophobic alkylsilyl groups. This amphiphilic HZSM-5 zeolite exhibited a much higher catalytic activity than the parent HZSM-5 zeolite in the hydration of cyclohexene phase-boundary reaction without adding co-solvents and stirring. Because this phase-boundary reaction was proceeding through a channel-reaction mechanism, the hydrophobic HZSM-5 particles modified by trimethylchlorosilane also showed the better catalytic performance than the parent zeolite.