β-Factor Based Separation Characteristics of Bio-derived Chemicals Present in Lignocellulosic Hydrolysates Using Vacuum Distillation

A chief shortcoming in the bioconversion of lignocellulosic feedstock is the immanent formation of byproducts such as organic acids, furans, and phenols during the pretreatment process, and these byproducts restrict subsequent microbial fermentation and spent stream disposal. Thus, a green and alternative technique for simultaneous removal and recovery of inhibitors is indispensable. This study explored the separation characteristics of organic acids (acetic acid and formic acid), and furans (furfural and 5-hydroxymethylfurfural) present in simulated and crude lignocellulosic acid-hydrolysates using vacuum distillation. The operation parameters selected for distillation experiments were low temperature (333.15 K) and subatmospheric pressure (13.7 +/- 1.3 KPa). A modified separation factor beta was introduced in a microlevel model to specify the separation characteristics. Furfural had the highest separation factor (value = 1), whereas acetic acid and formic acid had separation factors in the ranges of 0.17 to 0.24 and 0.05 to 0.07, respectively. After two distillation processes of poplar acid-hydrolysates, 100% of furfural was removed in the first stage, and then 76% of acetic acid and 93% of formic acid were simultaneously recovered after the second stage. Regarding vacuum distillation, the separation factor enhanced the condensation efficiency and provided guidance for the detoxification of lignocellulosic hydrolysates.