Hydrolytic depolymerization of hydrolysis lignin: Effects of catalysts and solvents

Hydrolytic depolymerization of hydrolysis lignin (HL) in water and water-ethanol co-solvent was investigated at 250 degrees C for 1 h with 20% (w/v) HL substrate concentration with or without catalyst (H2SO4 or NaOH). The obtained depolymerized HLs (DHLs) were characterized with GPC-UV, FTIR, GC-MS, H-1 NMR and elemental analyzer. In view of the utilization of depolymerized HL (DHL) for the preparation of rigid polyurethane foams/resins un-catalyzed depolymerization of HL employing water-ethanol mixture appeared to be a viable route with high yield of DHL similar to 70.5 wt.% (SR yield of similar to 9.8 wt.%) and with M-w as low as similar to 1000 g/mole with suitable aliphatic (227.1 mg KOH/g) and phenolic (215 mg KOH/g) hydroxyl numbers. The overall % carbon recovery under the selected best route was similar to 87%. Acid catalyzed depolymerization of HL in water and water-ethanol mixture lead to slightly increased M-w. Alkaline hydrolysis helped in reducing M-w in water and opposite trend was observed in water-ethanol mixture. (C) 2015 Elsevier Ltd. All rights reserved.