Microwave-Assisted Pretreatment of Lignocellulosic Biomass with a Low Transition Temperature Mixture: Choline Chloride/Glycerol

Biomass pretreatment can enhance the potential of the lignocellulosic structure. Corncob is an available agricultural biomass residue that can be found in many countries. The pretreatment can improve the efficiency of converting corncob into bioenergy. A novel approach using low transition temperature mixtures (LTTMs) based on choline chloride combined with glycerol as the solvent for microwave-irradiation heating pretreatment process was explored. The effectiveness of microwave-irradiation heating was investigated as an alternative pretreatment method, with variations in temperature (90 and 150 °C) and residence time (5 and 10 min). The results revealed that the lignin-carbohydrate complex could be effectively broken down, leading to the fractionation of lignin and hemicellulose. The obtained biomass is known as cellulose-rich material (CRM). The microwave-irradiation heating combined with LTTMs proved to be successful for the generation of CRMs, resulting in an increase in cellulose content and effective lignin removal. The microwave-irradiation heating exhibited high performance in lignocellulosic fractionation compared to conventional heating. The method allowed for the optional preservation of hemicellulose at lower temperatures or its extraction at higher temperatures. The parameters investigated in this study can be applied to biomass pretreatment using LTTMs with microwave-irradiation heating to obtain the desired CRM tailored for each specific biomass conversion process.