Milan Kekanović

Slip Modulus of Screws in Timber and Lightweight Concrete Composite Structures

NH4Cl was used to optimize the pretreatment conditions for biomass pretreatment to improve enzymatic saccharification and hemicellulose degradation of eucalyptus chips. After pretreatment, the solid substrate (SS) and pretreatment liquor (PL) were characterized, and the SS was enzymatically hydrolyzed to detect the conversion yield of cellulose (CYC). For the pretreatment using NH4Cl, the removal rate of hemicellulose reached up to 100% in some cases, but a great proportion of cellulose remained in the SS. The optimized conditions for pretreatment using NH4Cl were 0.3 M NH4Cl at 200 °C for 25 min. A comprehensive evaluation found that the most suitable severity parameter for pretreatment and enzymatic saccharification was 4.5, although a higher severity parameter could increase the CYC. XRD and FTIR analysis showed that the pretreatment had little influence on the cellulose crystalline region, and the lignin was well-retained in the pretreatment process.High biomass loading is a key technique to reduce the pretreatment cost of lignocellulosic biomass. In this work, various biomass species such as bagasse, erianthus, cedar, and eucalyptus were pretreated using an ionic liquid, 1-ethyl-3-methylimidazolium acetate, at different biomass loadings, particularly focusing on a high loading region. Cellulose structural changes in pretreated biomass were investigated via X-ray scattering and 13C solid-state nuclear magnetic resonance (SSNMR) spectroscopy. The structural behaviors roughly fell into two categories, corresponding to either grassy (bagasse and erianthus) or woody (cedar and hardwood) biomass. The grassy biomass gradually transformed from cellulose-I to cellulose-II in a monotonic manner against the biomass loading. In contrast, the transformation in the woody biomass occurred abruptly as solids was decreased within the high loadings range (50 wt% to 33 wt%). Below 33 wt%, a reformation of cellulose-I from cellulose-II proceeded readily. In terms of cellulose crystallinity, erianthus as well as bagasse showed a minimum value at 25 wt% loading, whereas the crystallinity for the woody biomass did not possess such a clear minimum. Acid hydrolysis of these pretreated biomass was also conducted and the relationship between the reactivity and the cellulose structural changes was discussed.