Phase Transfer Characteristics of PTC system with butyltriphenyl phosphonium bromide and butyltriphenyl phosphonium chloride

• Main Authors: Ying-Jay Chiang, 江英傑
• Other Authors: Chien-Li Chiang
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/npc5j8

碩士 === 國立成功大學 === 化學工程學系碩博士班 === 92 === 　Recently many researches have been dedicated to the study of phase transfer catalytic reaction systems. In view of the industrial applications, the stability of the dispersed system, involving two immiscible liquids, is of much importance in the industrial operations. Increasing the volume fraction of the dispersed phase will result in the increase of the mass transfer areas, promote the drops coalescence rate and eventually lead to the phase inversion, i.e. the dispersed phase becomes the continuous phase and vice versa. The characteristics of phase inversion will affect the reaction rate and the dispersion behavior of the system. 　For the system with two immiscible phases, characteristics of phase inversion are the major concerns from the view point of the system stability. Phase inversion means that the equilibrium of the continuous phase and the dispersion phase in the system was broken. The happening of phase inversion can be observed by the abrupt change of voltage in the system. 　Quaternary ammonium salts have been used in the majority of reported phase transfer studies, but quaternary phosphonium salts can be equally effective, and may be preferred under some extreme conditions of high temperature or concentrated bases when Hofmann Degradations occur. As the results, quaternary phosphonium salts is better than quaternary ammonium salts and more stable. Hence the quaternary phosphonium salts are selected to be the phase transfer catalysts in this text. 　In this thesis, we use the synthesis of phenyl benzoate from benzyl chloride in the organic phase and sodium phenolate in the water phase with butyltriphenyl phosphonium chloride and butyltriphenyl phosphonium bromide as the catalysts to study the variations of the characteristics of phase inversion upon the phase transfer catalyst concentrations and reactant concentrations. In the systems with phase transfer catalyst added only, we find that it tends to help water becoming the continuous phase when the rotor speed increases, i.e. it tends to form an oil in water emulsion. Therefore, the occurrence of oil in water transforming to water in oil is more difficult. In this study, the variations of the physical properties, characteristics of phase inversion, droplet coalescence time and delayed inversion time of the system are similar to those obtained by using the symmetrical quaternary phosphonium salts. In general, the hold up of phase inversion of systems with butyltriphenyl phosphonium bromide added is higher than those with butyltriphenyl phosphonium chloride added. It shows that it is easier to form an oil in water emulsion after butyltriphenyl phosphonium bromide are added. But as the concentration of butyltriphenyl phosphonium bromide is high, the interfacial tension of the system is getting more important. And the phase inversion curves move downward with increasing catalyst concentration. However this behavior is not observed in the system with butyltriphenyl phosphonium bromide as the catalyst due to it’s lower influence of interfacial tension.