摘要
分别采用吡啶探针和乙腈探针红外光谱法研究了氯铝酸离子液体的酸性，结合固体酸表征方法，研究了离子液体的酸性对吡啶探针各振动模式的影响。发现当氯铝酸离子液体AlCl3的摩尔分数x为0．4～0．5时，离子液体显弱Lewis酸性，强碱性吡啶探针分子能很好地表征离子液体的酸性，而弱碱性乙腈探针分子只适用于表征酸性较强的离子液体。考察了氯铝酸离子液体酸强度对苯与长链烯烃烷基化反应的影响，结果发现，AlCl3的摩尔分数x≤0．5时，离子液体没有催化活性；x〉0．55时，随着离子液体酸性的增强，烯烃转化率升高，但2位烷基苯选择性下降。结合离子液体的酸强度对烷基化反应机理进行初步分析认为具有催化活性的物质是强Lewis酸Al2Cl7^-。
The acidity of chloroaluminate ionic liquids （ILs） was determined by using pyridine and acetonitrile as IR spectroscopic probes. Based on the characterization method of acidity of solid acid, IR VCCN absorption frequencies of pyridine in ionic liquids were assigned. By using the pyridine probe, it was found that when the anion molar composition x of ionic liquid varies within 0. 4-0. 5, ionic liquids exhibit weak Lewis acidity. Strongly basic molecular pyridine can be used as a probe to measure the acidity of ionic liquids whether their acidity is strong or weak, while weakly basic molecular acetonitrile is only fit for strong acid. In addition, the Lewis acidity-activity correlation for the chloroaluminate ionic liquids catalyst in the alkylation reaction was studied. The weakly acidic ILs with x≤0. 5 does not exhibit any catalytic activity in the alkylation reaction. When the anion molar composition x is more than 0. 55, the activity of ionic liquids is greatly enhanced due to the increase in the strength of the strong Lewis acidic species Al2Cl7^-. But with the increase in alkenes conversion, the selectivity of 2-alkylbenzene is slightly reduced.
出处
《光谱学与光谱分析》
SCIE
EI
CAS
CSCD
北大核心
2007年第3期460-464,共5页
Spectroscopy and Spectral Analysis
基金
国家自然科学基金重点项目(20436050)资助
关键词
氯铝酸离子液体
红外光谱法
酸性
吡啶
乙腈
烷基化反应
Chloroaluminate ionic liquids
IR spectroscopy
Acidity
Pyridine
Acetonitrile
Alkylation
