哌嗪型双核酸性离子液体催化合成苯甲酸甲酯OA北大核心CSTPCD

Benzoates are important intermediates for preparing perfume essence and artificial essential oils.For conventional esterification of benzoic acid with methanol,protonic acids such as HCl,H2SO4,have been used,which is harmful to equipment and shows low product yield.Using ionic liquids as solvents or catalysts can make the reaction conditions stable,recyclable,and environment-friendly,and lead to high product yield.In this work,a series of sulfonic-acid-functionalized dual-core piperazine-based ionic liquids,such as 1,4-bis[N-methyl-N-(3-sulfopropyl)]piperazine bis(p-toluenesulfonate)([BMSP][PSA]),1,4-bis[N-methyl-N-(3-sulfopropyl)]piperazine dimethanesulfonate([BMSP][MSA]),and 1,4-bis[N-methyl-N-(3-sulfopropyl)]piperazine bis(hydrosulfate)([BMSP][SA]),were synthesized by a two-step process.The molecular structure of[BMSP][PSA]was characterized by FT-IR,1H NMR and TGA-DTG.It exhibited good thermal stability.The results showed that the three sulfonic-acid-functionalized dual-core piperazine-based ionic liquids had excellent catalytic activity,among which the synthesized[BMSP][PSA]exhibited the best catalytic activity.The conversion of benzoic acid reached 97.6%under the conditions of alcohol-acid ratio of 16∶1,reaction temperature of 70℃,reaction time of 3 h,and catalyst dosage of 3 mmol.The conversion for esterification still reached 93.9%after 4 cycles with the catalyst,which showed excellent catalytic activity.Therefore,it was a good candidate of green catalyst for industrial production.