水楊酸酯是一類重要的化合物，廣泛用於化粧品、防曬劑、食品、醫藥等領域。在工業上合成水楊酸酯大多使用濃硫酸為催化劑，由水楊酸與醇類進行酯化反應而製得。儘管濃硫酸價格便宜也易取得，但其容易腐蝕反應設備、後處理複雜及易造成環境汙染。因此開發一個高催化能力且對環境無毒的催化劑是近年來熱門的研究主題。
本研究利用1-乙烯基咪唑或咪唑與不同碳鏈烷基溴化物或雙鹵基烷類化合物進行反應，製備出不同類型之離子液體單體化合物，接著分別進行自由基聚合或自聚合反應，得到側鏈型(PVImCmBr)或直鏈型(PImCmCl)高分子聚合物，再分別與硫酸(H2SO4)或磷酸(H3PO4)進行陰離子交換，共製備出十二種聚離子液體催化劑。
由催化水楊酸酯試驗結果顯示聚離子液體在催化方面具有不錯的催化效果；陰離子為HSO4-的催化能力遠大於陰離子為H2PO4-，而烷基碳鏈長度並不會影響其催化能力。在本研究中，以16a與22a為催化劑的催化產率分別為89%與90%；當此二種催化劑經過五次循環使用產率可達70%與73%。綜合所有實驗結果得知此二種聚離子液體具有高的催化效果以及可以回收再使用。 Salicylate, a type of important compound that widely applied for various fields with cosmetics, sunscreen, food, and medicine. Most methods for synthesis of salicylate use concentrated sulfuric acid as a catalyst to proceed esterification of salicyclic acid and alcohol. Although the concentrated sulfuric acid is cheap and available, it causes that the reaction equipments are easily corroded, the post-processing is more complicated, and the environment is easily polluted. Therefore, developing a catalyst with high catalysis ability and environment-friendly is more interested with research.
This study is using 1-vinylimidazole (or imidazole) to react with alkyl bromide (or alkyl dihalide) with different alkyl chain and to different types of ionic liquid monomers. The brush chain types (PVImCmBr) or main chain types (PImCmCl) ionic polymers would be obtained by radical polymerization or self polymerization with these different types of ionic liquid monomers, and then through are anion-exchanged by sulfuric acid or phosphate acid to prepare twelve poly(ionic liquid) catalysts.
The experiment results reveal the poly(ionic liquid) catalysts perform good catalysis ability with esterfication reaction of salicyclic acid and alcohol. The catalysis ability of HSO4- anion is much higher than H2PO4-, and the alkyl chain length will not influence the catalysis ability. In this research, using 16a and 22a as catalyst can respectively achieve the catalysis yield of 89% and 90% and the yield of catalysis can also be achieved 70%~73% through five cycles. All experiment results show that the compounds 16a and 22a contain the highiest catalysis ability and reusability.
