Abstract:

A novel ionic liquid Caprolactam-trifluoromethanesulfonic acid ([CP]OTf) was prepared with trifluoromethanesulfonic acid and Caprolactam as raw material. The structure of the ionic liquid was characterized by 1HNMR and FTIR. It was used as the catalyst and solvent in the nitration of toluene. The effects of the amount of catalyst, reaction temperature, reaction time, the concentration of nitric acid and recycling of catalyst on product yield and para-selectivity for the nitration of toluene was investigated with the aid of gas chromatography. The results showed that, when the nitration temperature was 55℃, the reaction time was 6h, the molar ratio of toluene to 95% nitric acid was 1:1, the amount of catalyst was 15% of the molar of toluene, the ortho-para isomer ratio reached 1.12, far below 1.67 by using sulfuric acid, and gave a product yield of 78.41%. Ionic liquid [CP]OTf showed high regioselectivity and catalytic activity. The catalyst could be reutilized up to five times with little decrease in activity and regioselectivity.

Key words: toluene, ionic liquid, nitration, Caprolactam-trifluoromethanesulfonic acid