Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/3492
標題: Kinetics and Interfacial Characteristics for Phase-Transfer Catalyzed Benzylation in Liquid-Liquid System
液-液相相間轉移催化苯甲基化反應動力學與其界面特性之研究
作者: 林承亮
Lin, Cheng-Liang
關鍵字: Phase-transfer catalyst
相間轉移觸媒
Kinetics
liquid-liquid system
Esterification
Aliquat336
interficial tension
動力學
液-液系統
酯化反應
溴化四丁基銨
Aliquat 336
界面張力
出版社: 化學工程學系
摘要: 本研究主要探討液-液相與固-液相系統之溴化苯甲基與苯甲酸鈉在相間轉移觸媒催化下,合成苯甲酸苯甲酯之取代反應。在反應系統中,除了兩相反應物因素外,各項探討的變因包括:攪拌效應、觸媒添加量效應、有機溶劑種類效應、觸媒種類效應、溫度效應等,並進一步研究反應機構及求得反應動力學速率常數。 苯甲酸鈉本身添加至水中會降低水的表面張力,與溶劑之種類有關;四級鹽類類似界面活性劑,添加至有機溶液中會降低有機溶液的表面張力,兩種物質分別添加於水及有機溶液中則會降低水油之界面張力。在觸媒為氯化甲基三辛基銨( Aliquat 336 )系統中,氯化甲基三辛基銨在紡織工業上,常被應用於纖維的軟化劑。在液-液相系統中,利用氯化甲基三辛基銨較長團基親油的特性,可將水相反應物由水相質傳至油相。氯化甲基三辛基銨便可催化苯甲酸鈉與溴化苯甲基進行酯化反應。反應中間產物(PhCOOQ)的形成及探討反應的操作變數對其所產生的影響。實驗結果顯示反應速率隨著觸媒量的增加及溫度增加而增加。在有機溶劑效應方面,反應過程中,於具極性溶劑中反應3小時後苯甲酸苯甲酯的產率達95﹪以上;相反的,於低極性溶劑中反應3小時後苯甲酸苯甲酯的產率不達70﹪以上。實驗結果顯示利用氯化甲基三辛基銨在適當的條件下,能夠有效的進行液-液相之間的酯化反應。 在觸媒為Aliquat 336與其他四級銨鹽系統中,溴化苯甲基與苯甲酸鈉在液-液相系統反應生成苯甲酸苯甲酯。實驗結果在液-液相系統中,當攪拌速率超過200 rpm 時,在液-液相界面之間的質傳阻力可以忽略不計。不同觸媒反應活性大小為Aliquat 336 > TBPB > TBAI > TBAHS > TBAB > PEG系列。實驗結果可以以虛擬一階方程式完整而清楚的解釋此一系統。
The objectives of the present study are to apply phase-transfer catalytic technique in synthesizing benzyl benzoate by conducting nucleophilic substitutions in the organic solution in solid-liquid and liquid-liquid system. The operating conditions for investigation include agitation speeds , reaction temperatures, catalyst amounts, types of solvents, molar ratio of reactants, type of phase-transfer catalysts, volume ratio of aqueous to solvent , and so on. The reaction mechanism and apparent reaction rate constants were obtained from the experimental results. It will decrease interficial tension of two phases,while Aliquat 336 added to organic phase and sodium benzoate added to aquenous phase. Aliquat 336 is widely used as the fibers soften in textile industry. In liquid-liquid phase transfer system, the aqueous-phase reactant can be transported from aqueous-phase to organic-phase by the hydrophobic characters of catalytic Alliquat 336. The Aliquat 336 can catalyze sodium benzoate and benzyl bromide into esterification. The the formation of intermediate (PhCOOQ) and its the effects of the change on operating conditions were all investigate. The experimental results show that the more the amounts of catalyst, the faster the synthesizing reaction rate will be. Effects of different organic solvents for Aliquat 336 are carried out, and above 95% yield of benzyl benzoate is easily achieved within 3 hours as using chlorobenzene as the solvent. The kinetics of pseudo-first-order reaction can be applied to describe the overall reaction rate successfully. In the other quaternary ammonium system, the product selectivity and kinetics of sodium benzoate with benzyl bromide to produce benzyl benzoate via liquid-liquid phase-transfer catalysis were explored. When the agitation speed exceeds 200 rpm,the mass transfer resistance at the liquid-liquid interface can be ignored. Different phase-transfer catalysts were employed to compare their catalytic efficiency , and the reactivity order was found: Aliquat 336 > TBPB > TBAI > TBAHS > TBAB > PEG series.
URI: http://hdl.handle.net/11455/3492
Appears in Collections:化學工程學系所

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