Efficient preparation of polyethylene glycol (PEG)-modified lignin from steam exploded hardwood biomass

The structures and characteristics of lignin derivatives prepared from steam exploded beech under alkali delignification and acid catalyzed polyethylene glycol (PEG) solvolysis were studied in detail. An efficient method for directly isolating PEG-modified lignin from wood was proposed to improve its thermal stability. The effects of steam explosion (SE) parameters and delignification process on lignin structure were studied by high performance anion exchange chromatograph, fourier transform infrared spectroscopy (FTIR), heteronuclear single quantum coherence (HSQC) NMR spectroscopies, ultraviolet and visible spectrophotometry, size exclusion chromatography (SEC) and thermogravimetric analysis (TGA). The results showed that SE pretreatment can greatly promote the yield of PEG-modified lignin. The PEG-modified lignin, isolated from steam exploded wood at 210 °C for 2.5 min, was ∼14% yield. The PEG moiety was located at the alpha carbon position of the β-O-4 linkage. The PEG-modified lignin exhibited improved thermal properties with a maximum weight loss temperature (Tdmax) greater than 380 ℃, and a degradation starting temperature (Tdst) in the range of 258–277 °C, met the temperature for polymer processing and contribute to improve the added value of lignin.