An investigation of lignocellulosic biomass including: Compositional modeling, novel pretreatments and extraction of cellulose nanocrystals

The thermal decomposition of three major components of lignocellulosic biomass: cellulose, hemicellulose, and lignin were studied using modulated thermogravimetric analysis (MTGA). It provided the activation energy of each component and showed that the composition of lignocellulosic biomass can be predicted by TGA measurements in an air atmosphere. 37 natural woods and 20 synthetic biomass mixtures were used to develop a compositional model based on their TGA measurements. A multivariate regression analysis with PLS model showed potential to predict the compositions of any unknown woody biomass. Further, sugar maple (Acer saccharum) woodchips were pretreated using high-energy electron beam (HEEB) irradiation with or without prior biodelignification and hot-water extraction. It was found that biomass recalcitrance was significantly reduced by HEEB irradiation. The digestibility of cellulase was effectively enhanced by HEEB irradiation, biodelignification and hot-water extraction. An irradiation of 500 kGy increased the enzymatic activity at least five fold compared to the control and decreased the break strength of woodchips by 80%. TGA study showed that the thermal stability of sugar maple woodchips was decreased as the irradiation dosage increased. X-ray diffraction and 13C solid-state NMR indicated that wood cellulose was decrystallized by irradiation, and consequently an improvement of cellulose accessibility. Size exclusion chromatograph (SEC) found that irradiation resulted in depolymerization of wood cellulose. Wood powder with irradiation (≥500 kGy) was completely dissolved in a DMSO/TBAF (10:1, v/w) solvent. 1D and 2D nuclear magnetic resonance (NMR) analysis of pretreated-wood solution showed a capability of detecting the effects of irradiation on individual biomass components including chain scissions of polysaccharides and S/G ratio changes of lignin. Finally, cellulose nanocrystals were prepared from wood pulps, holocellulose and cellulose that were isolated from maple wood, and microcrystalline cellulose from oil palm. Different acid hydrolysis conditions were applied to these cellulose sources. Micro-rods in cellulose II crystallographic form were obtained from acid hydrolysis of maple wood cellulose. A direct hydrolysis of maple wood holocellulose produced so-called nanowhiskers with high aspect ratio. The rod-like nanocrystals from hydrolysis of microcrystalline cellulose from oil palm were dispersed evenly with narrow size distribution.