Xuerong Chen

Ultrasonication-assisted manufacture of cellulose nanocrystals esterified with acetic acid

Esterified cellulose nanocrystals (E-CNCs) are cellulose derivatives that could be applied in biomedical and chemical industries. E-CNCs were prepared with cellulose pulp using a mixture of 17.5M acetic and 18.4M sulfuric acid with the aid of ultrasonication. The effects of esterification time (3-7h), ultrasonication time (with a frequency of 40 kHz, 0 to 6h) and temperature (68-75 °C) on the yield and degree of substitution (DS) of E-CNCs were evaluated. The sample obtained without ultrasonication had the lowest yield and DS value of 48.16% and 0.22, respectively, whereas ultrasonication for 5h at 70 °C resulted in a yield of 85.38% and a DS value of 0.46. Characterization indicated the successful esterification of hydroxyl groups of cellulose, and the width of rod-shaped E-CNCs was from 10 to 100 nm. The study provides a simple and convenient method to manufacture E-CNCs.

Manufacture of cellulose nanocrystals by cation exchange resin-catalyzed hydrolysis of cellulose

Cellulose nanocrystals (CNC) were prepared from microcrystalline cellulose (MCC) by hydrolysis with cation exchange resin (NKC-9) or 64% sulfuric acid. The cation exchange resin hydrolysis parameters were optimized by using the Box-Behnken design and response surface methodology. An optimum yield (50.04%) was achieved at a ratio of resin to MCC (w/w) of 10, a temperature of 48 °C and a reaction time of 189 min. Electron microscopy (EM) showed that the diameter of CNCs was about 10-40 nm, and the length was 100-400 nm. Regular short rod-like CNCs were obtained by sulfuric acid hydrolysis, while long and thin crystals of cellulose were obtained with the cation exchange resin. X-ray diffraction (XRD) showed that, compared with MCC, the crystallinity of H2SO4-CNC and resin-CNC increased from 72.25% to 77.29% and 84.26%, respectively. The research shows that cation exchange resin-catalyzed hydrolysis of cellulose could be an excellent method for manufacturing of CNC in an environmental-friendly way.

Organic solvent-free and efficient manufacture of functionalized cellulose nanocrystals via one-pot tandem reactions

An environmentally benign approach for the manufacture of maleic anhydride functionalized cellulose nanocrystals (MA-CNCs) via one-pot tandem reactions with H2SO4 as a catalyst under organic solvent-free conditions was put forward. The effects of ball milling time, ultrasonication temperature and time on the yield and degree of substitution (DS) have been explored.