Optimization of ethyl lactate‐based organosolv process for lignin recovery from the solid waste of a wheat straw biorefinery

Abstract

AbstractBACKGROUNDThe organosolv process promotes biomass delignification at relatively high temperatures using a wide variety of organic solvent solutions. Nevertheless, previous studies on organosolv processes have not dealt with the use of ethyl lactate as organic solvent. Thus the aim of the present contribution was to determine and to validate if the use of ethyl lactate has a positive influence on lignin recovery for organosolv processes whose feedstock is the solid waste from a wheat straw‐based biorefinery. The effect of operating conditions (temperature and time) on lignin recovery was also studied.RESULTSA mixed design of experiments was proposed as the strategy to maximize lignin recovery. The mathematical model derived from a multiple linear regression applied to the mixed design results indicates that 190 °C and a non‐aqueous solution containing ethyl lactate and ethanol (81.2% w/w ethyl lactate) could provide a maximum lignin recovery of 75.9% w/w. This theoretical maximum was validated. Thus the proposed model adequately describes the behavior of lignin recovery. Moreover, Fourier transform infrared (FTIR) characterization of the resultant lignin suggested that its structure is a function of the organic solvent solution used during the organosolv process.CONCLUSIONThe evidence from this study indicates that lignin recovery from the solid waste of a wheat straw‐based biorefinery in an organosolv process depends on temperature and ethyl lactate presence in the reaction medium. These findings enhance the understanding of organosolv processes and could be applied if eventual lignin valorization is desired. © 2019 Society of Chemical Industry