Synthesis And Application Of Lignin Based Polyether Glycol

Lignin, which exists in the most ligneous structure of many plants, features renewable,non-toxic and low-cost. Its basic structural unit is phenylpropane, with methoxy, hydroxyl and carbonyl groups, attached to benzene rings and side chains. Lignin can be liquefied to polyhydric alcohol for the synthesis of biomass-based polyurethane. It has the potential to replace petroleum-based polyhydric alcohol. However, the low reactivity and high molecular weight of lignin make it difficult to be dissolved or dispersed. Furthermore, it will have an adverse effect on the quality of downstream polyhydric alcohol. To solve this problem, the oxidation pre-treatment has been proposed for the modification of lignin before it was used to synthesize polyhydric alcohol.In this paper, anovel approach for the oxidation of lignin catalyzed by graphene/MnO2 nanocomposites with hydrogen peroxide as the oxidant and dioxane as the solvent was explored. Hydroxyl values, which were affected by several factors, such as temperature,time, catalyst and oxidant input, were employed to evaluate reaction efficiency. Under the optimum conditions, the values were almost tripled, compared with that of the raw lignin.The oxidation has little influence on the main body structure of lignin.Furthermore, the lignin was used to prepare biomass-based polyether alcohol and the optimal reaction conditions were also investigated. The optimum liquefaction condition of modified lignin was:The temperature was 120 °C, the liquefaction time was 50 min, the liquefaction solvent/lignin ratio at 4:1 and sulfuric acid dosage was 0.4%. The optimum liquefaction condition of lignin was: The liquefaction temperature was 120 °C, the liquefaction time was 60 min, the liquefaction solvent/lignin ratio at 4:1 and sulfuric acid dosage was 0.5%. Comparing the performance of the liquefaction products with unmodified lignin. The results show that the hydroxyl value is increased, the viscosity, the residue ratio and the molecular weight are decreased, which proves that the modified lignin has better liquefaction effect.The modified lignin based polyether glycol was used to prepare the polyurethane foam.The influence of the adding amount of lignin based polyether glycol on the properties of foam density, compressive strength, thermal conductivity was investigated. When the amount was 30% the materials shown optimal performance.