| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 95 === In this thesis, as a continued study, the solid-liquid-liquid phase transfer catalysis (SLL PTC) technique was adopted for synthesizing n-hexyl acetate(ROAc) from 1-bromohexane(RBr) and sodium acetate(NaOAc) by using a catalyst-rich liquid phase (crp). The SLL PTC system contained a solid phase (NaOAc), two liquid phases (catalyst-rich liquid phase and organic phase). The phase transfer catalysts used were polyethylene glycol-600(PEG-600) and the mixtures of PEG-600 and tetra-n-butylammonium bromide(QBr). The conditions for forming a solid-liquid-liquid system and the optimal conditions for the esterification of RBr and NaOAc were searched and analyzed. In this study, a 125 mL 3-necked glass bottle was used as the reactor. During the reaction, 25 mL n-heptane, suitable amount of water, sodium acetate, 1-bromohexane, and PEG-600 (or PEG-600 and QBr) were added.
The results showed that the PEG-600 catalysis system owned a much larger volume of crp than the one of QBr. Specific parts of RBr and ROAc were dissolved in the crp during the reaction but most of the reagents were dissolved in the organic phase. The conversion of RBr increased with the amount of PEG-600, but became a steady when a larger amount was added. In the later period of reaction, the fractional yield approached to 1. An added amount of 0.07 mol PEG-600 showed the best result. Slightly increasing the amount of water could increase the conversion of RBr but reduce the fractional yield of ROAc as a result. Though higher conversion of RBr could be obtained by increasing the amount of NaOAc properly, yet too much NaOAc would reduce the fractional yield of ROAc. The optimal amounts of water and NaOAc are 2 mL and 0.03 mol. Higher molecular weight of PEG would reduce the conversion of RBr and both PEG-400 and PEG-600 are good candidates as the catalyst in this system. Either fixing the amount or the concentration of RBr, the conversion of RBr would be increased with the reduction of the amount of heptane, and the fractional yields were all approaching to 1. Increaseing the reaction temperature would remarkably increase the conversion of RBr and the fractional yield could remain unity even in 90 oC. To avoid the vaporization of the solvent, a reaction temperature under 90 oC could be set. In the optimal condition, the total reaction rate of RBr catalysis system could be described by quasi-first order reaction model. As the amount of PEG-600 less than 0.03 mol, the crp/org phase dispersions were likely to be formed while the phase dispersions would be inversed into org/crp as the amount of PEG-600 was higher than 0.035 mol. Therefore, in the optimal condition in the system, the organic phase was the dispersed phase and the crp was the continuous phase.
In the PEG-600 and QBr coexistent catalysis system, the addition of QBr followed with PEG-600 could obtain conversion higher than QBr or PEG-600 catalysis system and even higher than the simultaneously added system did. The optimal amounts for QBr and PEG-600 were both 0.03 mol.
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