Comparative study of structures of lignins using dioxane method and ionic liquids,by FTIR, chromatography techniques and¹³C NMR

In this study,extraction of the lignins of the flour of Poplus nigra and bagasse with dioxane and a suitable ionic liquid was performed to investigate and compare these three kinds of lignin .Then, the main identified structural units and different bonds between such structural units were used to conclude which of these two kinds of lignin (DL or IL ) is more unchanged and similar to original lignin using FTIR, (GPC) and ¹³ C NMR analysis. In fact, this study can play an important role in R&D of woodand pulping industries and inhibit photo-yellowing effect in papers. Comparative results showed thatthe dominant structural units of the two kinds of lignin are obtained from the cleavage of β-o-4 bondsespecially in dioxane lignins. The dominant structural units identified in bagasse was 4-hydroxy-3-methoxy-1-phenyl-γ-hydroxypropene(guaiacyl structures).The main structural units identified inP.nigra and bagasse is 4-hydroxy-3,5-dimetoxy-1-phenyl-γ-hydroxypropene (syringyl structures).Also, para hydroxyl phenylpropene structure was observed in lignin of bagasse. The content of cleavage of β-o-4 bonds and acetylation process in two kinds of dioxane lignins was more than in two kinds of ionic lignins.

کلیدواژه ها:

Poplus nigra ، Bagasse ، Dioxane ، Ionic liquid