氯铝酸盐离子液体催化甲苯与氯代叔丁烷烷基化反应合成对叔丁基甲苯

合成Me3NH]Cl-2.0AlCl3、PyH]Cl-2.0AlCl3、Bmim]Cl-2.0AlCl3以及Et3NH]Cl-2.0AlCl3氯铝酸盐离子液体,对Et3NH]Cl-2.0AlCl3和PyH]Cl-2.0AlCl3两种离子液体进行系列改性,并考察氯铝酸盐离子液体催化甲苯与氯代叔丁烷的烷基化反应,反应合成对叔丁基甲苯的催化性能。结果表明,未经改性的氯铝酸离子液体催化烷基化反应,对位产物选择性均较低,经FeCl3、CuCl以及CH3NO2改性的Et3NH]Cl-2.0AlCl3离子液体对叔丁基甲苯选择性显著提高,而PyH]Cl-2.0AlCl3离子液体经CuCl改性后的对叔丁基甲苯选择性则提高到85%以上。采用乙腈、吡啶为探针的红外光谱对离子液体酸性表征的结果表明,改性后离子液体的L酸和B酸均有所降低,其中B酸是影响对叔丁基甲苯选择性的主要因素,并对离子液体酸性催化甲苯与氯代叔丁烷烷基化反应合成对叔丁基甲苯的作用机制进行分析。

Synthesis of p-tert-butyltoluene from alkylation of toluene and tert-butyl chloride catalyzed by chloroaluminate ionic liquid

The chloroaluminate ionic liquids,including Me₃NH]Cl-2.0AlCl₃,PyH]Cl-2.0AlCl₃,Bmim]Cl-2.0AlCl₃,Et₃NH]Cl-2.0AlCl₃,were synthesized and characterized.The Et₃NH]Cl-2.0AlCl₃ and PyH]Cl-2.0AlCl₃ ionic liquids were modified by FeCl₃,CuCl,CH₃NO₂ and C₂H₅-S-C₂H₅.Alkylation of toluene with 2-chloro-2-methylpropane catalyzed by the prepared ionic liquids was investigated.The results showed that p-tert-butyltoluene selectivity over unmodified chloroaluminate ionic liquid was lower,and p-tert-butyltoluene selectivity over Et₃NH]Cl-2.0AlCl₃ ionic liquids modified by FeCl₃,CuCl and CH₃NO₂ were improved significantly.Moreover,selectivity of p-tert-butyltoluene reached more than 85% over PyH]Cl-2.0AlCl₃ modified by CuCl.Acidity characterization using acetonitrile and pyridine as probe showed that Lewis acid and Brönsted acid of the ionic liquid were decreased after modification,and Brönsted acid was the main factor to selectivity of p-tert-butyl toluene.The synthesis mechanism of p-tert-butyltoluene by alkylation of toluene with chloro-isobutane catalyzed by ionic liquid was also discussed.