2-甲基吡啶类离子液体结构与酸性关联及其酯化催化活性

The association of 2-Methylpyridinium Ionic liquids' structures,acidities and esterification catalytic performance

合成了由5种不同阳离子和2种不同阴离子组成的3类2-甲基吡啶类离子液体;采用FT-IR和UV-vis对所制备的离子液体进行了结构和酸性表征,考察了离子液体的结构与其酸性的关联,并以癸酸和三聚甘油的酯化反应为探针反应,考察了离子液体的酯化催化性能。结果表明:(a)阳离子结构相同时,离子液体酸性与阴离子酸性一致,即HSO_4^->H_2PO_4^-;阴离子结构相同时,3类离子液体酸性满足:引入烷基磺酸基>引入烷基>未引入;(b)阴离子主要通过酸性影响酯化催化活性,阳离子主要通过引入的基团影响酯化催化活性;而整个离子液体结构导致的与酯化反应体系的相溶性是影响催化活性的主要因素。

Three sorts of 2-methylpyridinium ionic liquids,which composed of five different kinds of cations and two kinds of anions,were synthesized via methods of one-or two-steps under existence of no solvent.The structures and acidities of these ionic liquids were characterized by FT-IR and UV-Vis spectroscopy.The association between the structure of ionic liquid and its acidity was investigated.The esterification reaction of capric acid and tripolyglycerol was used as the probe reaction,and the catalytic performance of these ionic liquids was examined.The results showed that：（a）When the cations are the same,the acidities of ILs meet the order HSO4-〉H2PO4-,which is in line with anionic acidity;while the anions are the same,the acidities of ILs meet the order：introduction of alkyl sulfonic groupsintroduction of alkyl no introduction;（b）The anion of the ionic liquid mainly affects the esterification and catalytic activity by the acidity mainly through the introduced groups;while the intermiscibility of the whole ILs molecule with the esterification reaction system is the key factor to the catalytic activity.