Enzymatic and catalytic hybrid method for levulinic acid synthesis from biomass sugars

In this study, an enzymatic and catalytic integrated approach is presented for high yield levulinic acid (LA) production from saccharified biomass hydrolysate prepared from acid pretreatment of corn stover. In order to convert glucose from a biomass hydrolysate solution to fructose the simultaneous isomerization and reactive extraction (SIRE) and back-extraction (BE) method was implemented. The SIRE-BE process successfully overcomes unfavorable glucose to fructose equilibrium and produce fructose at 88% yield. Besides, fructose was transferred to an acidic ionic liquid (IL) and aqueous mixture reaction medium by this pathway. It was noticed that the aqueous mixture of the task specific IL, 1-(4-sulfobutyl)-3-methyl imidazolium hydrogen sulfate ([BMIM-SO3H]HSO4), provides a uniquely suitable reaction medium. The mixtures are not only very effective in back-extracting ketose from the organic phase (following SIRE), but also able to effect the conversion of fructose to LA without the extra need for an acid catalyst in the medium. This highlights a significant advantage of the process since the issues with the extraneous acid catalyst recovery are eliminated. Besides, in the acidic [BMIM-SO3H]HSO4 aqueous mixture, high LA yield of 70% was achieved at 95 °C for 1 h from 2.5 wt% fructose loading.