Acid catalyzed decomposition of C 5 and C 6 sugars has been considered an important source of biomass derived chemicals. An essential step in this process is the extraction of furfural, hydroxymethylfurfural and levulinic acid from aqueous phase. In this work, a computational screening of 178 organic solvents for simultaneous extraction of these chemicals from aqueous phase has been done with the continuum SMD (solvation model based on density) model. Our analysis has taken in account the partition coefficient, water miscibility, boiling point and toxicity of the organic solvents. The present theoretical results indicate that C 6 and C 7 ketones are the most adequate solvents, and 4-heptanone is predicted to be particularly useful.
Keywords: partition coefficient, green chemistry, MIBK, 4-heptanone, tributyl phosphate
IntroductionPetroleum remains as the main source of feedstock for manufacture of fuels and chemicals. Nevertheless, the increased concern on environmental problems related to carbon dioxide emissions and the petroleum dependence have encouraged the development of biomass based fuels and chemicals. [1][2][3][4][5] Among the different processes for biomass transformation, acid catalyzed hydrolysis of xylan and glycan components of wood to form C 5 and C 6 sugars have received attention. 6 In the catalytic process, xylose and glucose (or fructose) are transformed to furfural, 5-hydroxymethylfurfural (HMF) and levulinic acid via acid-catalyzed dehydration (Scheme 1).In the acid medium used for generation of the products, more degradation can take place, leading to formic acid. Scheme 1. Formation of furfural, HMF and levulinic acid from acid catalyzed dehydration of C 5 and C 6 sugars. Dalessandro and Pliego Jr. 431 Vol. 29, No. 2, 2018 Current processes for recovering of furfural makes use of steam. However, the yield is limited and recently the use of solvent extraction has been advocated as more effective process. 6,7 In the same way, extraction of HMF during the reaction is desirable because it avoids degradation of this compound. 5 An efficient extraction requires an adequate solvent, which should have low miscibility with water and lead to a high partition coefficient for each compound. Recent experimental studies have investigated different solvents for extraction [7][8][9][10] and some authors have suggested that 2-butanol and 2-butanone are effective for HMF, while methyl isobutyl ketone (MIBK) is effective for both HMF and furfural compounds. 5,6,9 Other possibility for identifying efficient solvents for extraction is via computational methods. Thus, Sandler and co-workers 11 have used the COSMO-SAC method to investigate the ability of several linear and branched alcohols to extract HMF from aqueous solution and have found that the method produces reasonable partition coefficients. Following this work, Blumenthal et al. 12 have reported a very extensive screening of solvents for extraction of HMF using the COSMO-RS method and they have suggested 110 potential solvents superior to that i...