The Study Of The Adsorption Properties For Metal Ions And The Triphase-tansfer Catalysis Properties Of The Immobilized Crown Ethers Dibenzo-18-crown-6

Crown ether can be immobilized on the surface of polymer microspheres after modified by chemical means, which is an important direction of the development of crown ether chemistry. The adsorption for metal ions and the phase-transfer catalysis properties are two important areas of application of immobilized crown ether . In this work, Dibenzo-18-crown-6 (DBC) was successfully chemical modified and immobilized on crosslinked polyvinyl alcohol (CPVA) microspheres. The adsorption for metal ions and the phase-transfer catalytic esterification reaction of benzoic acid butyl ester were studied, and some valuable research results were found.Firstly, Crown ether dibenzo-18-crown-6 (DBC) was chloromethylated using 1,4-bis(chloromethoxy)butane (BCMB) as chloromethylation reagent and in the presence of Lewis acid catalyst, and DBC was transferred into chloromethylated crown ether CMDBC. Its chemical structure was characterized with FTIR, MS, 13C-NMR and 1H-NMR methods. The experimental results show that the chloromethylation reaction of DBC is easy to be conducted, and symmetrical disubstituted product on each benzene ring is obtained, namely, CMDBC is a symmetrical tetra-substituted chloromethylation product.Crosslinked polyvinyl alcohol (CPVA) microspheres were prepared via direct crosslinking and balling reaction of polyvinyl alcohol with glutaraldehyde as crosslinker in a reverse phase suspension system; Via the nucleophilic substitution reaction of the chloromethyl groups of CMDBC with the hydroxyl groups of CPVA microspheres, DBC can be easily immobilized on the surface of CPVA microspheres, and immobilized crown microspheres DBC-CPVA can be obtained. Based on founding the method to determine the immobilization amount of DBC, bromothymol blue-solid extraction method, the effects of main factors on the immobilization reaction were mainly investigated. Results show that the reaction temperature and solvent polarity affect the immobilization reaction greatly, and the microspheres DBC-CPVA with a DBC immobilization amount of 1.72 mmol/g can be obtained at 70℃and in DMF solvent with stronger polarity.In this work, the complex adsorption behaviors of the immobilized crown microspheres DBC-CPVA for metal ions were investigated in detail, and the effect of temperature on the adsorption property of DBC-CPVA microspheres was examined. The experimental results reveal that in those alkali metal ions, the complex adsorption ability of DBC-CPVA microspheres towards K+ ion is much stronger than towards other ions, and the adsorption capacities are in the order: K⁺>>Na⁺>LI⁺>Rb⁺>Cs⁺. In various bivalent metal ions, DBC-CPVA microspheres exhibit stronger adsorption ability for Zn²⁺ and Co²⁺ ions, and it was found that the adsorbed molar amount of DBC-CPVA microspheres for the two ions is in the proportion of 1:2 with the immobilized molar amount of DBC. This implys a sandwich-type complex to be formed between DBC-CPVA and Zn²⁺ or Co²⁺ ions. The adsorption capacities of DBC-CPVA microspheres for different bivalent metal ions are in the order: Zn²⁺>Co²⁺>>Cu²⁺>Cd²⁺ >Mg²⁺. The adsorption capacity of DBC-CPVA microspheres for metal ion decreases with raising temperature.The phase-transfer catalysis behavior of DBC-CPVA was mainly studied using the esterification reaction of 1-bromobutane in organic phase and benzoic acid in water phase as a model system, and the effects of main factors on the triphase phase-transfer catalytic esterification reaction were examined. The experimental results show that after benzoic acid in water phase reacts with KOH to form potassium benzoate, a complex cation will be formed between the immobilized DBC and K+ ion. This complex cation will effectively carry negative benzoate ion from water phase into organic phase, and enable the esterification reaction between benzoate ion and 1-bromobutane to favorably carry out. The solvent polarity is advantageous to the esterification reaction. As the ratio of organic phase to water phase is equal to 1:4, a maximum conversion (about 70%) of 1-bromobutane can be obtained. As benzoic acid and KOH in water phase are excessive, the esterification reaction in organic phase follows a pseudo-first-order rate law. The catalyst DBC-CPVA has excellent recycle and reuse property, and the catalytic activity remains stable in reusing of eight recycles.