Highly effective fractionation chemistry to overcome the recalcitrance of softwood lignocellulose.

The efficient fractionation and thus production of individual biomass components are pivotal processes in the biorefinery concept. However, the recalcitrant nature of lignocellulose biomass, especially in the case of softwood, is one of the main obstacles to the wider application of biomass-based chemicals and materials. In this study, the use of aqueous acidic systems in the presence of thiourea was studied for the fractionation of softwood in mild conditions. Despite relatively low temperature (100 °C) and treatment times (30-90 min), notable high lignin removal efficiency (approximately 90 %) was obtained. Chemical characterization and the isolation of minor fraction of cationic, water-soluble lignin indicated that the fractionation proceed via nucleophilic addition of thiourea to lignin, resulting in dissolution of lignin in acidic water in relatively mild conditions. Besides high fractionation efficiency, both fiber and lignin fractions were obtained with bright color, significantly elevating their usability in material applications.

Amino-modified cellulose nanocrystals with adjustable hydrophobicity from combined regioselective oxidation and reductive amination.

The controlled revision of surface properties to alter the hydrophobic features of nanocellulose is a potential technique to obtain materials for many novel applications and to replace oil-based materials acting as amphiphilic polyelectrolytes, among others. In this study, linear amines with increasing chain length were used to adjust the hydrophobicity of amphiphilic cellulose nanocrystals (CNCs). Methyl-, ethyl-, n-propyl-, n-butyl-, n-pentylamine, and n-hexylamine were introduced into a cellulose backbone using combined periodate oxidation and reductive amination in an aqueous environment. A high-pressure homogenizer was used to liberate a highly transparent (over 85% at visible light range) nanocrystal dispersion containing CNCs with a length of 73-131 nm and a width of 5-6 nm. All of the CNCs had similar charge density but the hydrophobicity, indicated by the contact angle measurement from the films, increased gradually from 64° to 109° as a function of amine chain length. Thus, this study demonstrated the fabrication of uniform, amphiphilic nanosized polyelectrolytes with modifiable hydrophobicity.