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

► Cellulose nanocrystals are produced by cation exchange resin as catalyst. ► The optimization process of cation exchange resin hydrolysis is investigated. ► Resin-catalyzed process is easy to handle and environmentally friendly. 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 189min. Electron microscopy (EM) showed that the diameter of CNCs was about 10–40nm, and the length was 100–400nm. 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.