Yandan Chen

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.

Effect of silicone oil heat treatment on the chemical composition, cellulose crystalline structure and contact angle of Chinese parasol wood

The effect of silicone oil heat treatment (SOTH) on the chemical composition, cellulose crystalline structure, thermal degradation and contact angle of Chinese parasol wood were examined in this study. Samples were heated at 150°C, 180°C and 210°C for 2h and 8h, after SOHT chemical composition, fourier transformed infrared (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) of the treated samples were evaluated. Results showed that the chemical components of the wood were affected after SOHT particularly when treated at 210°C for 8h. Changes in the chemical components was due to the degradation of biopolymer components of the wood during SOHT. The crystallinity index of cellulose and contact angle of the SOHT samples was increased. The findings demonstrate the potential of SOHT for modification of wood. Thus an economical and eco-friendly approach to thermally modified wood was achieved in this study.

One-pot construction of cellulose-gelatin supramolecular hydrogels with high strength and pH-responsive properties

Inspired by the supramolecular structure of cellulose, cellulose-gelatin supramolecular hydrogels with high strength and pH-sensitivity were constructed in a basic-based solvent system, ethylene diamine/potassium thiocyanate (EDA/KSCN) with the aid of cyclic freezing-thawing. The investigation on the characteristics of supramolecular hydrogels revealed that repeated freezing-thawing cycles played an important role in the formation of the physical cross-linked supramolecular network structure between cellulose and gelatin. The mechanical properties of supramolecular hydrogels were much higher than pure cellulose and gelatin hydrogel, and the compressive strength was 9.6 times higher than that of pure gelatin hydrogel. The synergistic effect between hydrogen-bonding interaction and the reinforcement of regenerated cellulose nanofibrils (CNF) contributed to the superior mechanical performance. Furthermore, the swelling kinetics tests showed that the supramolecular hydrogels exhibited excellent pH-responsibility, indicating potential applications in biomedical fields. Thus, a straightforward route to construct natural polymer-based hydrogels with supramolecular structure through physical crosslinking strategy without employing hazardous crosslinking agents was developed, paving the way for the design of new types of hydrogels.

On preparing highly abrasion resistant binderless and in situ N-doped granular activated carbon

NaOH/urea, a cellulose solvent, has been applied for the preparation of binderless and in situ N-doped GACs (NaOH/urea-GACs). The dissolved cellulose binds lignin, hemicellulose and undissolved cellulose all together to form a granular precursor after kneading and extruding. During the process, NaOH and urea are dispersed in sawdust where the NaOH acts as an activator at high temperatures, and the urea plays the role of an in situ N-dopant. The results show that at a mass concentration ratio of 14 wt% NaOH/24 wt% urea which has been activated for 1 h at 850 °C after kneading for 2 h GACs with a specific surface area (SBET) of 811.299 m2 g−1, a microporosity of 59.20% and an abrasion resistance of 99.83% are obtained. The N content as well as its form of existence are also further explored. The desulfurization ability of the NaOH/urea-GACs is also investigated, and NaOH/urea-GACs, without removed alkali, are applied for desulfurization, and the adsorption process is appropriate for the Bangham model. The experimental results indicate that it is feasible to use an NaOH/urea solvent as a suitable chemical for the manufacture of GACs with good properties.