Kinetics for Synthesizing o-Hydroxybenzoic Acid Butyl Ester via Ultrasound Assisted Tri-Liquid Phase-Transfer Catalysis

• Main Authors: Chien-Hsing Chen, 陳建行
• Other Authors: 楊鴻銘
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/37851855402468358863

碩士 === 國立中興大學 === 化學工程學系所 === 95 === The kinetics of esterification of sodiume salicylate with butyl bromide to produce salicylic acid n-butyl ester were investigated via ultrasound-assisted tri-liquid phase-transfer catalysis. Third-liquid phase was formed with high catalytic intermediates to increase reaction rate. Sonochemistry is a technique to increase chemical reaction rate by ultrasounic irradiation. Ultrasonic irradiation can provide energy to promote the reaction. The subject of this research involves kinetics for synthesizing o-hydroxybenzoic acid butyl ester, the optimum condition of the reaction system, comparisons between ultrasound-assisted, stirring mixing and both operations. Only tetrabutylphosphonium bromide(TBPB) and tetrabutylammonium bromide(TBAB) can form third-liquid phase among the four catalysts tested in this study. Reaction activity increases with increasing organic reactant concentration as butyl bromide added but keeps constant with largely excess amounts. Activity increases with decreasing ultrasonic frequency. Using ultrasonic frequency 28 kHz the production yield was 82.3 % within 3 hours. Correlating the experimental data, the relation of the enhancement ratio (η) of ArCOOQ in third-liquid phase, and the product yield in organic phase is . The pseudo-first-order kinetic model was used to well describe the overall reaction, by the equation , and the apparent reaction rate constants (kapp) were obtained for with different conditions. We can obtain the activation energy of 31.5 kJ/mol by Arrehenius equation during 50~80 ℃. For high product yield, cost, easy analysis, the production yield was 97.3% as ultrasonic frequency 28kHz, power 300W, and 70℃. With ultrasound alone, the activity becomes lower the energy of higher frequency decreases quickly. Molecule collision raised by agitation can overcome mass transfer resistance. Combining two operations of ultrasound and agitaion make the activity better than with each single operation. Mass transfer resistance can be neglected by stirring speed more than 100 rpm, the yield increases and kapp increases 53.3 % as ultrasound assisted extra.