Studies On The Preparation Of Triphase-transfer Catalysts With Grafting-type And Catalytic Activity

The grafting polymerization of styrene on micron-sized silica gel particles was performed in solution polymerization system with the manner of "grafting from", and grafting particles PSt/SiO₂ were obtained. Chloromethylation reaction for the polystyrene grafted on silica gel particle surfaces was allowed to be carried out by using novel chloromethylation reagent, 1,4-bis (chloromethoxy) butane, and chloromethylated polystyrene-grafted silica gel particles, CMPS/SiO₂, were prepared and this composite particles also can be called as "composite-type chloro-sphere" The grafting degree of PSt/SiO₂ was analyzed with thermal gravimetric analysis(TG), and the morphology of PSt/SiO₂ particle was examined with scanning electron microscope (SEM). The chemical structure and composition of CMPSt/SiO₂ particle were characterized using infrared spectrum (FTIR) and Volhard method. The effects of various factors on the chloromethylation reaction of PSt/SiO₂ were mainly examined. The experimental results show that the CMPSt/SiO₂ with about 16% (wt%) of chlorine content (based on the grafted polystyrene) can be prepared when the reaction was carried out at room temperature for about 10h using CH₂Cl₂ as solvent and SnCl₄ as catalyst.The composition particle CMPSt/SiO₂ was quaternized with triethylamine(TEA), tributylamine(TBA) and triphenyl-phosphine(TPP). The effects of various factors on the quaternized reaction were mainly examined. Finally, triphase-transfer catalysts with grafting-type, which carried the quaternary ammonium salt and the quaternary phosphonium salt , were prepared. The chemical structure and composition of the catalysts were characterized by infrared spectrum (FTIR) and Volhard titration. The experimental results show that the quaternized reaction occurred easier when TEA was took as quaternized reagent for its smaller steric hindrance. The temperature also played an important role in the quaternazied reaction. While using different reagent, appropriate reaction temperature were diverse (TEA appropriate reaction temperature is 60℃, TBA is 60℃,TPP is 50℃). By controlling the reaction time, the catalysts with different quaternary degree have been prepared.The catalysts, prepared with grafting-type were used in the phase transfer catalytic reaction of benzyl chloride and sodium acetate to form benzyl acetate, and the catalytic activity were examined. The effects of various factors, such as solvent species, temperature and catalyst property, were also studied. The experimental results show that tricatalysts QN-PSt/SiO₂ and QP-PSt/SiO₂, have obvious catalytic activity in the synthesis of benzyl acetate, and can efficiently transfer acetates from aqueous phase into organic phase. The catalyst QN-PSt/SiO₂ (TEA) has higher catalytic activity in the synthesis of benzyl acetate, and it can effectively transfer acetic acid radical among tri-phases of liquid-solid-liquid. The conversion of benzyl chloride can get up to 66.1% at 60℃for 7h. It was found that the quaternization degree of polystyrene grafted on SiO₂ has a great effect on the catalytic activity. The catalytic activity is lower as the quaternization degree is too great or small, and QN-PSt/SiO₂ (TEA) has the highest catalytic activity as the quaternization degree of polystyrene grafted on SiO₂ is about 20 mol%, and the further research found that catalyst structure took remarkable effect on its activity. The catalytic activity is QP-PSt/SiO₂ (TPP) >QN-PSt/SiO₂ (TBA) > QN-PSt/SiO₂ (TEA) in turn. The prepared catalysts have excellent reusing property.The kinetics of the reaction have been investigated furthermore, and found that the phase transfer catalysis reaction has a characteristic of pseudo first order reaction when NaAC in the aqueous phase was excessive; With the reaction temperature became higher, the reaction rate was greater, the reaction temperature hoist per 10℃, the rate constant became 2～3 times primary. At the same reaction temperature, the reaction rate constant was QP-PSt/SiO₂(TPP)>QN-PSt/SiO₂(TBA)>QN-PSt/SiO₂(TEA), but the activation energy was absolutely contrary.