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Preparation and characterization of thermally stable cellulose nanocrystals via a sustainable approach of FeCl3-catalyzed formic acid hydrolysis

Du, Haishun, Liu, Chao, Mu, Xindong, Gong, Wenbo, Lv, Dong, Hong, Yimei, Si, Chuanling, Li, Bin
Cellulose 2016 v.23 no.4 pp. 2389-2407
Eucalyptus, acid hydrolysis, cellulose, crystal structure, dimethyl sulfoxide, dispersibility, economic feasibility, ferric chloride, ferric hydroxide, formic acid, kraft pulp, nanocrystals, particle size, sulfuric acid, temperature, thermal stability, thermogravimetry, value-added products
Cellulose nanocrystals (CNCs) can be used as building blocks for the production of many renewable and sustainable nanomaterials. In this work, CNCs were produced from bleached eucalyptus kraft pulp with a high yield over 75 % via FeCl₃-catalyzed formic acid (FA) hydrolysis process. It was found that the particle size of resultant CNC products (F-CNC) decreased with the increase of FeCl₃ dosage in FA hydrolysis, and a maximum crystallinity index of about 75 % could be achieved when the dose of FeCl₃ was 0.015 M (i.e. about 7 % based on the weight of starting material). Thermogravimetric analyses revealed that F-CNC exhibited a much higher thermal stability (the decomposition temperature was over 260 °C) than S-CNC prepared by typical sulfuric acid hydrolysis. In the FeCl₃-catalyzed FA hydrolysis process, FA could be easily recovered and reused, and FeCl₃ could be transferred to Fe(OH)₃ as a high value-added product. Thus, the FeCl₃-catalyzed FA hydrolysis process could be sustainable and economically feasible. In addition, F-CNC could be well dispersed in DMSO and its dispersibility in water could be improved by a cationic surface modification.