以相間轉移觸媒催化技術進行苯乙醇氧化反應之研究

Oxidation of Phenylethanol by Phase-Transfer Catalysis

溫鴻凱(Hong Kan Wen)

指導教授 ： 吳和生

元智大學/工程學院/化學工程與材料科學學系/碩士(2001年)

摘要

本文主要研究，1-苯乙醇反應物在不同溶劑下以三級丁基過氧化氫(tert-butyl hydroperoxide ,TBHP)為氧化劑，氧化成苯乙酮產物。此反應必需加入CuCl2當做觸媒才能反應，但反應速率緩慢，如再加入溴化四丁基銨(tetrabutylammonium bromide ,TBAB)或自行合成的固體觸媒反應可增加催化速率。所運用的固體觸媒是利用苯乙烯，氯甲基苯乙烯為聚合反應物，加入二乙烯苯當交聯劑，利用懸浮共聚合法合成觸媒擔體。再將具有催化性質之三丁基胺固定於高分子擔體上，得到四級銨化苯甲基-氯甲基苯乙烯樹脂觸媒，以此自行合成的固體觸媒與商用的可溶性觸媒TBAB相互比較。
不同的反應方式會影響氧化反應的反應速率及氧化劑對反應物的氧化效能，因此以不同觸媒的型態及不同的溶劑種類進行不同的反應方式，分為有均相反應、兩相反應(液-液相、固-液相)、三相反應(液-固-液三相)，分別探討這些不同反應模式各變因之影響，進而觀察在每個反應中CuCl2觸媒與TBAB相間轉移觸媒或苯乙烯樹脂三相轉移觸媒相互之間所扮演的角色。
結果可以發現，很明顯的可溶性觸媒TBAB的反應無論是是在產率及反應速率在相同條件下大都比苯乙烯樹脂固體觸媒還要好。但在某些反應是固體觸媒比可溶性觸媒反應還要好，如在溶劑量多時、觸媒量增大時、溫度升高時等，雖然兩者反應產率及速率都是呈現下降趨勢，而固體觸媒卻比TBAB平緩許多，使得產率及反應速率固體觸媒的較高。在不同的反應方式中可以明顯的比較出何種方式反應較為好的，在均相反應及液-固兩相反應較快，在五個小時內能達到產率為60%以上，而液-液兩相及液-固-液三相反應都要在15小時以後甚至24小時以後達產率60%以上，因此在反應機構中，由實驗中可以看出其反應效能上均相反應＞兩相反應(固-液)＞兩相反應(液-液)＞三相反應(液-固-液)。
觸媒的壽命與改質也是此研究重點之一，由於可溶性觸媒不能回收重複使用且對於產物的純化有著相當大的問題，便發展出固體觸媒。將固體觸媒一再的使用觀察其活性的損失情況，發現重複反應達五次雖然反應速率逐漸變慢但是在相同時間內所得產率變少不到10%。另外在固體觸媒上若能加以改質發展出能使反應更接近於可溶性觸媒。

關鍵字

相間轉移觸媒 ； 氧化反應 ； 氯化銅

並列摘要

The oxidation of 1-phenylethanol with TBHP (tert-butyl hydroperoxide) in to acetophenone different kinds of solvents was investigated by phase transfer catalysis. When only CuCl2 used as catalyst was added, the reaction rate was slowly. However if extra addition of phase transfer catalyst such as TBAB (tetrabutylammonium bromide) or triphase catalyst synthesized by our lab could enchance dramatically the reaction rate. Triphase catalyst was synthesized with styrene, vinyl chlorobenzyl and divinyl benzene(crosslinkage agent) using suspension polymerization. Then, tri-n-butylamine was immobilized on polymer particle . The characterization and reactivity of polyer-supported catalyst compared with that of commercial TBAB.
Different reaction conditions would resulted in different the reaction rate of oxidation and the efficacy of oxidant to reagent. Four reaction systems were studied to achive the optimum reaction condition, including homogenous reaction, two phase reaction (liquid-liquid, solid-liquid) and triphase reaction. Meanwhile, the reactive roles of catalyst CuCl2, TBAB and triphase catalyst were observed for each reaction systems.
According to the experimental result, the yield and the reaction rate in the presence of TBAB catalyst were better than these of the triphase catalyst in most condition, but some conditions the triphase catalyst better than TBAB e.g. high volume of solvent, high amount of catalyst obsered or high temperature. The yield and the reaction rate were oberved to descend tendency for both catalysts, but the tendency for the triphase catalyst was more gently decrease than that for TBAB. The reaction rate of homogenous and two-phase (solid-liquid) reaction were rapid than that of the other reaction system and the yield of acetophenone could be upto 60% after 5 hours. The yield of acetophenone for liquid-liquid and liquid-solid-liquid reaction were upto 60% after 15 hours or more time. The squence of the reactivity of the reaction system was homogenous＞two-phase (solid-liquid)＞two-phase (liquid-liquid) triphse reaction (liquid-solid-liquid).
The degradation and reuse of the triphase catalyst were also conducted in this study. Because dissoluble catalyst can’t reuse easilywhich is a diffcult program in order to obtain. Triphase catalyst was used to overcome the separation problem and the properties of polymer resins were defermimed. It is found that reaction rate was slowly decreasingly with increasing reuse time of triphase catalyst and the yield was decrease less than 10% after five recycle times. In addition, the reactivity of triphase catalyst was more close to that the dissoluble catalyst if triphase catalyst was transnatured propenty, for example changing the hipophilic-hydrophilic balance.

並列關鍵字

phase-transfer catalysis ； oxidation ； CuCl2

參考文獻

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