Ionic liquid-mediated technology to produce cellulose nanocrystals directly from wood

Author

HatemAbushammalaabIngoKrossingbcMarie-PierreLaborieab

a

Chair of Forest Biomaterials, University of Freiburg, Werthmannstr. 6, 79085 Freiburg, Germany

b

Freiburg Materials Research Center, University of Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Germany

c

Institute of Inorganic and Analytical Chemistry, University of Freiburg, Albertstr. 21, 79104 Freiburg, Germany

Received 10 April 2015, Revised 18 June 2015, Accepted 22 July 2015, Available online 26 July 2015.

Highlights

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Cellulose nanocrystals can be directly extracted from wood using a low temperature pulping process with [EMIM][OAc].

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The CNCs extracted from wood maintain cellulose I microstructure (CrI of 70–75%), display large aspect ratios (22–65) and are surface acetylated.

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Wood polymers acetylation and the heterogeneous conditions for wood cellulose appear critical to the efficiency of the ionic liquid assisted extraction of CNCs directly from wood.

Abstract

We report for the first time the direct extraction of cellulose nanocrystals (CNCs) from wood by means of a 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]) treatment. A native cellulosic product could be recovered in 44% yield with respect to wood cellulose content. The product was analyzed for morphological (TEM, AFM, XRD), chemical (FTIR, 13C CP/MAS NMR), thermal (DSC, TGA) and surface properties (Zeta potential, contact angle). These analyses evidenced the presence of partially acetylated (surface DS = 0.28) nanocrystals of native cellulose I microstructure, with a crystallinity index of about 75% and aspect ratio of 65. Direct production of CNCs from wood is ascribed to the simultaneous capability of [EMIM][OAc] to (1) dissolve lignin in situ while only swelling cellulose, (2) decrease intermolecular cohesion in wood via acetylation, and (3) to catalyze cellulose hydrolysis.

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