Effect of ternary deep eutectic solvents on delignification of stone pine cone

Abstract

Due to their cost-effectiveness and environmentally friendly nature, deep eutectic solvents (DESs) hold great potential for applications in biomass conversion and the production of green chemicals. In this study, the delignification of the stone pine (Pinus pinea L.) cone was performed using seven different ternary deep eutectic solvents (TDESs). TDES treatments of stone pine cone samples were carried out in a microwave for 30 min. at 150 °C. The two-based components of TDESs were choline chloride (ChCl - 1 mol) and lactic acid (LA - 9 mol). The formic acid (FA – 2 mol), boric acid (BA – 1 mol), acetic acid (AA – 2 mol), sorbitol (S – 1 mol), triethylene glycol (TEG – 2 mol), ethylene glycol (EG – 2 mol), and glycerol (G – 2 mol) were used as third component of TDES. ChCl:LA:BA gave the lowest solid residue yield (57.90%) and highest lignin purity (86.89%). Klason lignin content of control was 35.08%. The lowest lignin content (19.42%) and highest delignification (68.89%) were obtained with ChCl:LA:FA treatment. The lowest and the highest L* values were obtained from ChCl:LA:BA and ChCl:LA:EG treatments with 21.76 and 37.36, respectively. This results showed that the third component of TDES affects the delignification efficiency of stone pine cone.