Synthesis Of Functionalized Heteropolyanion-based Ionic Liquids And Applications In Transesterification Of Methyl Acetate

Methyl acetate is a byproduct of the production of polyvinyl alcohol and the production is excessive.Because of the high energy consumption,traditional hydrolysis method limits its application.Therefore,using methyl acetate obtain esters of higher value by the transesterification method has an obvious advantage.Ionic liquids have been widely used in organic synthesis,electrochemistry,separation purification and other fields for their unique physical and chemical properties.Functionalized heteropolyanion-based ionic liquid which was obtained by combining organic cations and heteropolyanions overcomes the shortages of ionic liquid,such as hardly separating with reactants and large dosage,so it can be used as an acid catalyst with excellent performance.In this paper,a series of HPA-ILs were synthesized,and the preparation and characterization of these HPA-ILs were studied.We researched the catalytic performance of the HPA-ILs in the transesterification of methyl acetate to obtain esters of higher value.The main contents are as following:?1?A series of HPA-ILs were obtained by combining Keggin heteropolyanions and organic cations.We studied the characterization of HPA-ILs by IR and NMR.The thermal stability was analyzed by themogravimetric amalyzer.?2?The above six kinds of single-core HPA-ILs was chosen,which was used as a catalysts in the synthesis of isoamyl acetate from methyl acetate and isoamyl alcohol by transesterification.The effects of the type of catalyst,the temperature,catalyst dosage,reactant molar ratio and other factors in the reaction process were studied in detail.Compared to the traditional catalysts,namely H₂SO₄ and H₃PW₁₂O_40,[Bs Et₃N]₃PW₁₂O₄₀showed comparable catalytic activity.The conversion of methyl acetate was 52.34%under the appropriate conditions:the reaction temperature was328.15K,the reaction time was 6h,the dosage of[Bs Et₃N]₃PW₁₂O₄₀ was 5%?w?and molar ratio of methyl acetate and isoamyl alcohol was 1:1:5.A pseudo-homogeneous?PH?kinetic model was applied,and the calculated results was that the activation energy of the forward and reverse reaction were 53.29 k J/mol and 49.30 k J/mol,respectively;the forward and reverse reaction pre-exponential factor were 2.51×10⁵ L/?mol·g·min?and 8.21×10⁴ L/?mol·g·min?,respectively.Moreover,[Bs Et₃N]₃PW₁₂O₄₀ could be easily recovered,and reused for five times without any obvious decrease of catalytic activity.?3?Binuclear HPA-ILs was synthesized for the transesterification of methyl acetate and isooctyl alcohol.Compared with single-core HPA-ILs,H₂SO₄ and H₃PW₁₂O₄₀.the two binuclear HPA-ILs[Bis-Bs Im B][HPW₁₂O₄₀]and[Bs₂DABCO][HPW₁₂O₄₀]performed higher catalytic activities.Choosing[Bis-Bs Im B][HPW₁₂O₄₀]and[Bs₂DABCO][HPW₁₂O₄₀]as catalysts,and the effect of temperature,catalyst loading,and molar ratio of the reactants was studied in detail.A pseudo-homogeneous kinetic model was applied successfully to correlate the experimental data,and the kinetic parameters were estimated.Results showed that the calculated value by the reaction kinetic model was in good agreement with those obtained from experiments.Moreover,the two catalysts could be easily recovered and reused for five times without any obvious decrease in catalytic activity.