Study On Reactive Distillation For Transesterification Using Br(?)nsted Acidic Ionic Liquids As Catalyst

The development of energy saving and environmental friendly chemical processes is an important research area in chemical engineering. In this project, the ionic liquid（IL） is used as catalyst in the reactive distillation process. The reactive distillation combines the reaction and distillation in the same device to save energy, and the ionic liquid catalyst is considered as “green” catalyst, so the process is environmental friendly. In this paper, the catalytic activities of single ionic liquids and mixed ionic liquids for the transesterification of methyl acetate and n-butanol were studied. The reaction kinetics of methyl acetate and n-butanol catalyzed by 1-sulfobutyl-3-methylimidazolium trifluoromethanesulfonate（[HSO₃bmim][OTF]） and 1-sulfobutyl-3-methylimidazolium tosylate（[HSO₃bmim][p-TS]） were investigated, respectively. The reaction kinetics of methyl acetate and iso-amyl alcohol catalyzed by 1-sulfobutyl-3-methylimidazolium hydrogensulfate（[HSO₃bmim][HSO₄]） were also measured, and a reactive distillation process for he transesterification of methyl acetate and iso-amyl alcohol catalyzed by ionic liquid was proposed and simulated. An experiment of the reactive distillation in a lab-scale column was then conducted to validate the simulation results.The acidity of 1-sulfobutyl-3-methylimidazolium chloride（[HSO₃bmim][CL]）, N-sulfobutylpyridinium trifluoromethanesulfonate（[HSO₃bpy][OTF]）, 1-sulfobutyl-3-methylimidazolium trifluoromethanesulfonate（[HSO₃bmim][OTF]）, 1-sulfobutyl-3-methylimidazolium tosylate（[HSO₃bmim][p-TS]） and 1-sulfobutyl-3-methylimidazolium hydrogensulfate（[HSO₃bmim][HSO₄]）, were measured and their catalytic activities for the transesterification of methyl acetate and n-butanol were compared. Meanwhile, the mixed ionic liquids [HSO₃bmim][CL]+[omim][PF₆] and [HSO₃bmim][p-TS]+[omim][PF₆] were used to catalyze the above reaction, and compared with the single ionic liquids. The results showed that the acidity and solubility are two important factors that influence the catalytic performance of ILs.The reaction kinetics of transesterification of methyl acetate and n-butanol catalyzed by [HSO₃bmim][OTF] and [HSO₃bmim][p-TS], as well as the reaction kinetics of the transesterification of methyl acetate and iso-amyl alcohol catalyzed by [HSO₃bmim][HSO₄] were measured and correlated by ideal homogeneous（IH） model and nonideal homogeneous（NIH） model, respectively. The results showed that the NIH model was more reliable to describe these transesterification reaction rates.Based on the analysis of residue curve map（RCM）, a reactive distillation（RD） process was proposed to conduct the transesterification of methyl acetate and iso-amyl alcohol using [HSO₃bmim][HSO₄] as catalyst. The process was simulated by ASPEN PLUS, and the effects of the structural and operational parameters of RD column were also investigated. The results show that the RD process can obtain high purity and high yield products of methanol and iso-pentyl acetate, and the purity of methanol and iso-pentyl acetate and the yield of iso-pentyl acetate increase with the theoretical plates, tray holdup and reflux ratio, and there exist optimal feed location and optimal amount of IL catalyst. An experiment of reactive distillation in a lab-scale column was conducted, and the experimental results were compared with the simulation results. The results agreed well, which indicates that the simulation method is reliable.