关键词:

离子液体, 酸催化剂, 固定化, 酯化反应, 浸渍法, 溶胶-凝胶法

Abstract: Three designed and synthesized Brnsted acidic ionic liquids（ILs）［（n-Bu-SO₃H）MIm］［HSO₄］，［（n-Bu-SO3H）MIm］［p-CH₃C₆H₄SO₃］and ［Et₃NH］［HSO₄］，as well as another commercial ionic liquid ［HBIm］［CF₃SO₃］were used to catalyze the esterification reaction of hexanoic acid and ethanol.Among them（n-Bu-SO₃H)MIm］［HSO₄］exhibited the highest activity，which was later selected to be immobilized on the silica gel by both impregnation and sol-gel methods.The immobilized ILs were then characterized by ¹H NMR，elemental analysis，FTIR and activity test.The results showed that the loading amounts of ionic liquid by the impregnation method A，B and sol-gel methods were 15.5%，20.5 % and 40.5 %（mass），respectively.For the first time the three immobilized ILs were used to catalyze the esterification of hexanoic acid and ethanol，and the yields of ethyl hexanoate were 75.3%，92.6%and 92.6%，respectively.However，the activity of the ionic liquid immobilized impregnation decreased rapidly with recycle runs since the load amount of ionic liquid dropped to 3.0 %（mass）after 4 recycle runs for method A and dropped to 7.0 %（mass）after 8 cycle runs for method B.By contrast，the ionic liquid immobilized by the sol-gel method was much stable，and could be reused for 10 times with only little decrease in activity.Moreover，the sol-gel method immobilized ionic liquid also showed acceptable activity（ester yields>90.0%）for the esterification of other carboxylic acid with ethanol.Therefore，the sol-gel method is an excellent method for the immobilization of ionic liquid to catalyze esterification reactions..

Key words:

离子液体, 酸催化剂, 固定化, 酯化反应, 浸渍法, 溶胶-凝胶法