이온성 액체 촉매를 이용한 단당류 및 다당류 바이오매스의 5-히드록시메틸푸르푸랄로의 전환 반응 연구

Abstract

The purpose of this study, which involves ionic liquid, was to investigate not only solvents but also catalysts for the conversion of cellulose to 5-Hydroxymethylfurfural (5-HMF). Two kinds of ionic liquid catalysts were prepared; one an immobilized acidic ionic liquid catalyst and the other a Lewis acid ionic liquid catalyst containing metal chloride. The structure and acidic properties of the catalysts were examined by using Hydrogen nuclear magnetic resonance (1H-NMR) and Fourier transform inrared spectroscopy (FT-IR) measurements. The first result was to prepare immobilized acidic ionic liquid catalysts for conversion of fructose to 5-HMF. Generally, 5-HMF is formed through the process of dehydration of fructose in an acid catalyst. Acidic ionic liquids (ILs)-modified silica gels with ？SO3H and-SO2Cl functional groups (SiO2-[ASBI][HSO4], SiO2-[ASCBI][HSO4], SiO2-[ASBI][TfO], SiO2-[ASCBI] [TfO]), were used in fructose dehydration. The effects of the reaction time, temperature, reactant concentration (molar ratio of [BMIM]Cl solvent to fructose) were studied. The results showed that the performance of SiO2-[ASBI][HSO4] (immobilized by the grafting of 3-allyl-1-(4-sulfobutyl) imidazolium hydrogen sulfate on silica gel) was better than those of the well known Amberlyst-15 and DOWEX50x8 catalysts at 383 K for 2 h, after which a 5-HMF yield of 73% was obtained. In the second result, a Lewis acid ionic liquid catalyst containing metal chloride was investigated for its catalytic activity in the dehydration of glucose. Metal chloride salts, such as SnCl2, ZnCl2, AlCl3, FeCl3 and CuCl were screened, and used to obatin 5-HMF from glucose. During 2 h of reaction at 393 K, the glucose was selectively converted to 5-HMF, and the 5-HMF yield was 63% from [Me3NC2H4OH]-2AlCl4 (choline chloride ionic liquid containing AlCl3). It is well known that direct production of 5-HMF from cellulose is difficult to achieve because of its complicated reaction steps, such as hydrolysis, isomerization and dehydration. In the third result, a environmental benign method was investigated for enhancing the 5-HMF yield from cellulose using metal chloride (CrCl3-6H2O) and an immobilized acidic ionic liquid catalyst (SiO2-[ASBI][HSO4]). The results showed that 40% of the 5-HMF yield was obtained under reaction at 403 K for 2 h. Futhermore, SiO2-[ASBI][HSO4] catalyst was also recycled three times. These results suggest that the SiO2-[ASBI][HSO4] catalyst contributes to the reactions of hydrolysis and dehydration, and that the Cr cations of CrCl3-6H2O play a role enediol formation from glucose.