Brθnsted-lewis Acidic Ionic Liquids Catalytic Property For Transesterification

The transesterification is an important reaction in organic chemistry, traditionalcatalysts basic exist shortcomings of catalyst and product difficult separation anddifficult to reuse, and the development of catalytic performance is high, reusablecatalyst become the research focus. Base on the structural designability and acidictenability of ionic liquids （ILs）, in this paper, Several ionic liquids （ILs） weresynthetized, and identified Br nsted and Lewis acidity though pyridine probe FT-IR,using acetonitrile probe FT-IR compared the same kind of ILs Lewis acid size anddifferent kinds of ILs Lewis acid size. The synthesized ILs applied to thetransesterification gets the following conclusions:ILs as catalyst for catalytic polyethylene terephthalate （PET） and isooctanoltransesterification products dioctyl terephthalate （DOTP）, and the traditionalcatalysts were compared, the results indicated that the Br nsted-Lewis acidic IL（3-sulfonic acid）propyltriethylammonium chlorozincinate [HSO₃-（CH₂）3-NEt₃]Cl-ZnCl₂（ZnCl₂mole fraction is0.67） catalytic performance was better than traditionalcatalysts. Under the conditions of this IL, the optimum conditions were obtained:n（PET repeat unit）∶n（isooctanol）=1∶5，m（PET）∶m（IL）=5∶2，reactiontemperature210℃and time8h, PET conversion was almost100%and the yields ofboth DOTP and ethylene glycol （EG） were94.6%and95.6%.Catalytic performance of ILs and a variety of traditional catalysts werecompared in PET and n-butanol transesterification preparation dibutylterephthalate（DBTP）, and. the results indicated that the Br nsted-Lewis acidic ILs（3-sulfonic acid）propyltriethylammonium chlorozincinate [HSO₃-（CH₂）3-NEt₃]Cl-ZnCl₂（ZnCl₂mole fraction is0.67） and （3-sulfonic acid）propyl-3-methylimidazolechlorozincinate [HSO₃-（CH₂）3-mim]Cl-ZnCl₂（x=0.67）were better. Under theconditions of IL [HSO₃-（CH₂）3-NEt₃]Cl-ZnCl₂（x=0.67）, the optimum conditions were obtained: n（PET unit）∶n（n–butanol）=1∶3, m（PET）∶m（IL）=5∶1, reactiontemperature205℃and reaction time8h, the PET conversion was almost100%, andthe yields of DBTP and EG were95.3%and95.7%.The traditional catalysts were compared with ILs in reaction of soybean oil andmethanol preparation biodiesel, the results showed that although the traditionalcatalyst NaOH and IL [HSO₃-（CH₂）3-NEt₃]Cl-ZnCl₂（x=0.67） catalytic propertieswere better, NaOH was restricted to material acid value while IL was not. Under theconditions of this IL, the optimum conditions were obtained: n（soybean oil）∶n（methanol）=1∶8, m（soybean oil）∶m（IL）=20∶3, reaction temperature140℃and reaction time6h, the yield of biodiesel was95.7%.Better catalytic performance of ILs filtrated in the above experiments were donerecycling and reuse experiments and found that the reusability of the ILs were goodand after they were used several times, products yields wrer not obvious decrease.The structures of ILs before and after reuse which were characterized using FT-IR,NMR were compared, the results show that the ILs structures of reuse before andafter donot change significantly, good stability.