Production of polyols via direct hydrolysis of kraft lignin: Effect of process parameters

•Bio-polyols were produced via alkaline hydrolysis of kraft lignin for polyurethanes.•A high yield of polyols up to 92% was obtained, with suitable −OH numbers and Mw.•The Mw of lignin was reduced from 10,000g/mol to ∼3300g/mol at low temperature.•A higher temperature especially 350°C favored polyol...

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Bibliographic Details
Published in:	Bioresource technology 2013-07, Vol.139, p.13-20
Main Authors:	Mahmood, Nubla, Yuan, Zhongshun, Schmidt, John, (Charles) Xu, Chunbao
Format:	Article
Language:	eng
Subjects:	Analyzers Biological and medical sciences Biotechnology - methods Carbon Catalyst Depolymerization Fundamental and applied biological sciences. Psychology Hydrogen-Ion Concentration - drug effects Hydrolysis Hydrolysis - drug effects Kraft lignin Lignin - chemistry Magnetic Resonance Spectroscopy Polymerization - drug effects Polymers - chemical synthesis Polyols Polyurethane foam Process parameters Reaction time Sodium Hydroxide - pharmacology Spectroscopy, Fourier Transform Infrared Temperature Time Factors
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Summary:	•Bio-polyols were produced via alkaline hydrolysis of kraft lignin for polyurethanes.•A high yield of polyols up to 92% was obtained, with suitable −OH numbers and Mw.•The Mw of lignin was reduced from 10,000g/mol to ∼3300g/mol at low temperature.•A higher temperature especially 350°C favored polyols of lower Mw ∼1400g/mol.•A longer reaction time produced polyols with lower aliphatic −OH number. Kraft lignin (KL) was successfully depolymerized into polyols of moderately high hydroxyl number and yield with moderately low weight-average molecular weight (Mw) via direct hydrolysis using NaOH as a catalyst, without any organic solvent/capping agent. The effects of process parameters including reaction temperature, reaction time, NaOH/lignin ratio (w/w) and substrate concentration were investigated and the polyols/depolymerized lignins (DLs) obtained were characterized with GPC-UV, FTIR-ATR, 1H NMR, Elemental & TOC analyzer. The best operating conditions appeared to be at 250°C, 1h, and NaOH/lignin ratio ≈0.28 with 20wt.% substrate concentration, leading to
ISSN:	0960-8524 1873-2976