以固定化相間轉移觸媒催化苯甲酸鈉之酯化反應動力學研究

Kinetics for Esterification of Sodium Benzoate over Immobilized Phase-Transfer Catalysts

許豪麟(Hao-Lin Hsu)

指導教授 ： 楊鴻銘

國立中興大學/工學院/化學工程學系所/碩士(2003年)

摘要

本研究探討的是於固定化相間轉移觸媒催化下進行苯甲酸鈉與溴化苯甲基之SN2親核取代反應，所使用之固體觸媒擔體是將苯乙烯及氯甲基苯乙烯進行共聚合反應而得，且使用不同官能基前驅物，如三級胺、三正辛基膦或三苯基膦，將其固定於巨孔口型或微孔口型觸媒的表面上，形成活性中心。在固-液-液相催化反應系統中，只需使用少量粒徑大小為40-80 mesh與1.38%交聯度之三正丁基季銨基巨孔口型固體觸媒，在反應三小時後產率即可達到86%以上，且總反應速率隨平均粒徑的增加而降低，顯示出在三相反應系統下，苯甲酸鈉之酯化反應同時受到顆粒內部擴散與本質反應之影響。然而觸媒之特性與結構也會影響觸媒反應活性，相同交聯度且官能基團為三正丁基季銨基時，巨孔口型觸媒活性較微孔口型觸媒催化活性為佳，以及探討操作變數的影響，包括攪拌效應、觸媒添加量效應、水量添加效應、有機溶劑種類效應、觸媒種類效應、溫度效應等，進而得到較適當的反應條件；隨著攪拌速率和溫度提高，觸媒添加量增加，反應速率隨之增快，當觸媒官能機使用為三級膦之反應效率較三級胺為佳。
離子交換反應也是重要的反應過程之一，故使用三相觸媒對苯甲酸鈉進行離子交換反應，可知在反應過程中觸媒中間體(QPhCOO)形成及變化情形；於3分鐘後其活性中間體就已經幾乎達定值，且隨著交聯度增加，形成觸媒活性中間體量隨之降低。提出此取代酯化反應之動力學模式，且由實驗結果知可由虛擬一階反應動力式可完整描述。
最後探討觸媒之再生還原方法，以達到降低成本及節省資源，進而改善傳統製成的目的。

關鍵字

相間轉移觸媒 ； 動力學 ； 酯化反應 ； 固定化觸媒 ； 觸媒再生及回收

並列摘要

The kinetics for SN2 nucleophilic substitution reaction of sodium benzoate with benzyl bromide catalyzed by immobilized phase-transfer catalyst was investigated. The support of solid phase-transfer catalyst was prepared from the copolymerization of polystyrene and chloromethylstyrene. Different functional groups were used as the active centers, such as trialkylamines, trioctylphosphine or triphenylphosphine, and that was immobilized onto the surface of the macroporous or microporous catalysts.
In solid-liquid-liquid system, the product yield was obtained above 86% within 3 hr of reaction using small amount of solid catalyst with the properties of 1.38% divinylbenzene crosslinked, particle size of 40-80 mesh ,tributylamine activated, and macropore-mouth type, and the overall reaction rate decreased with increasing the mean particle size. This demonstrates that the esterification of sodium benzoate is controlled by the combination of intraparticle diffusion and intrinsic reaction under triphase conditions. Moreover, the characteristics and structure of the catalyst support also affect the catalytic efficiency. With the same degree of crosslinking, macroporous catalyst with tributylamine activated has higher activities than microporous catalyst does. The effects of operating parameters, including agitation speed, reaction temperature, amounts of catalyst, types of solvents, molar ratio of reactants, type of phase-transfer catalysts, volume ratio of aqueous, and so on, were all performed to find the optimal reaction conditions. With increasing of agitation speed, reaction temperature and amounts of catalyst, the reaction rate increased. The catalytic efficiency of functional group used as trioctylphosphine was best than trialkylamines.
The ion-exchange reaction is one of the fundamental process of solid-liquid-liquid triphase reactions. We also proceed the ion-exchange reaction by triphase catalysts for sodium benzoate solution to know the formation and variation of the active intermediate (PhCOOQ) during the reaction. After induction period in 3 minutes, the active intermediate of the solid catalyst with 1.38% divinylbenzene crosslinked and macroporous type was also observed to keep at a near constant concentration. With increasing of cross-linking level, the formation of the active intermediate decreased.A kinetic model was developed to describe this esterification conducted in the solid-liquid-liquid triphase system, and the experimental data were well described by the pseudo-first-order kinetics.
Eventually, the methods of reuse and regeneration of the catalyst was also explored to reach the purpose of lowering processing cost and saving resources.

並列關鍵字

Phase-Transfer Catalysis ； Kinetics ； Esterification ； Immobilized Catalys ； Regeneration and Recycle of Catalyst

參考文獻

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