β-Irradiation in the presence of 1,3-dialkylimidazolium ionic liquids causes covalent cellulose derivatization with simultaneous nitrogen incorporation

Abstract

Abstractβ-Irradiation (“e-beaming”) as well as swelling in ionic liquids, each process by itself, are common pretreatments in biorefinery scenarios. A combination of both, such as occurs with β-irradiation of biomass that was insufficiently washed and still contains traces of ionic liquids, causes covalent derivatization of the contained cellulose and incorporation of nitrogen. The nitrogen uptake occurred only in the presence of the ionic liquid and correlated linearly with both the irradiation dose and the concentration of the contained ionic liquid. The presence of other wood constituents during β-irradiation decreased nitrogen uptake, but did not prevent it. The derivatization of cellulose did not depend on the degree of crystallinity, but appeared to depend on the content of oxidized groups (carbonyl functionalities), also with a linear correlation. Future work must now clarify the mechanism of this reaction and the influence of other wood constituents, and address the possible potential of e-beaming in the presence of imidazolium ionic liquids for cellulose chemistry.