Sulfation of ethanol lignin of abies wood by sulfamic acid in N,N-dimethylformamide medium

The sulfation of ethanol lignin of abies wood by sulfamic acid–urea mixture in N,N-dimethylformamide (DMF) medium was studied for the first time. The effect of the duration of lignin sulfation process on the yield and sulfur content in resulted lignin sulfates was studied. It was shown that the reaction of ethanol lignin sulfation begins and ends in a homogeneous medium. At temperature 100 °C, the sulfur content in lignin varies from 5.4 to 6.8% mass, depending on the process time. The introduction of sulfate groups into the lignin structure was confirmed by FTIR and 2D NMR spectroscopy. It was found that both alcohol and phenolic hydroxyl groups of lignin enter the sulfation reaction. The molecular weight distribution of sulfated ethanol lignin was determined by gel permeation chromatography. The optimized method of synthesis allows to obtain sulfated ethanol lignin with low polydispersity (1.31) and narrow molecular weight distribution (3.25–3.75 kDa).