Synthesis and Properties of Non-Aromatic Ionic Liquids and their Role in Cellulose Dissolution

Ran Liu, Zidan Chen, Hongwei Ren, Erhong Duan

Abstract


The dissolution of cellulose is an important pretreatment method required for some of its catalytic conversion processes. Morpholinium-based ionic liquids (ILs) are challenging solvent choices available for “greener” and “cheaper” dissolution of cellulose. In this study, morpholinium-based ILs were prepared, and their influencing factors were experimentally investigated. The unique bipolar chemical structure derived from oxygen (electron-rich center) and nitrogen (electron-poor center) considerably enhanced the Hammett acidity function (H0) of task-ILs. N-Methyl-N-allyl-morpholinium acetate IL showed the highest H0 (2.324) and polarizability power (1.096). The anion of ILs determined the hydrogen bond basicity (β). The acetate anion contributed to β (0.88) values. As to fluid properties, the morpholinium-based ILs exhibited much lower viscosity. The properties of ILs improved the dissolution efficiency. The cellulose was directly dissolved in morpholinium-based Ils, and no other derivatives were formed. The cations and the anions of ILs studied reacted with oxygen and hydrogen atoms on the hydroxyl groups of cellulose, respectively.

Keywords


Ionic liquids; Cellulose; Dissolution; Morpholinium

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