Effect of Temperature on Molecular Weight Distribution of Pyridinium Acetate Treated Kraft Lignin

The effect of temperature on the molecular weight distribution of kraft lignin during its dissolution in Pyridinium Acetate [PyAce] a protic ionic liquid was examined in detail by gel permeation chromatography. Lignin solubility increased with increasing temperature from 50 degrees C to 100 degrees C. The average molecular weight (M-w) of [PyAce] treated and recovered kraft lignin after thermal treatment with [PyAce] decreased from 4119 g mol(-1) to 1995 g mol(-1) within the temperature range of 50 degrees C-75 degrees C. A significant increase in molecular weight for [PyAce] treated lignin was observed as the process temperature was further increased from 75 degrees C to 100 degrees C. Results indicated that the condensation reactions occurred at elevated temperatures resulting in increased molecular weight during the dissolution process. (C) 2016 The Authors. Published by Elsevier Ltd.