Selectivity and delignification kinetics for oxidative short‐term lime pretreatment of poplar wood, part I: Constant‐pressure

Abstract

Kinetic models applied to oxygen bleaching of paper pulp focus on the degradation of polymers, either lignin or carbohydrates. Traditionally, they separately model different moieties that degrade at three different rates: rapid, medium, and slow. These models were successfully applied to lignin and carbohydrate degradation of poplar wood submitted to oxidative pretreatment with lime at the following conditions: temperature 110-180°C, total pressure 7.9-21.7 bar, and excess lime loading of 0.5 g Ca(OH)2 per gram dry biomass. These conditions were held constant for 1-6 h. The models properly fit experimental data and were used to determine pretreatment selectivity in two fashions: differential and integral. By assessing selectivity, the detrimental effect of pretreatment on carbohydrates at high temperatures and at low lignin content was determined. The models can be used to identify pretreatment conditions that selectively remove lignin while preserving carbohydrates. Lignin removal≥50% with glucan preservation≥90% was observed for differential glucan selectivities between ∼10 and ∼30 g lignin degraded per gram glucan degraded. Pretreatment conditions complying with these reference values were preferably observed at 140°C, total pressure≥14.7 bars, and for pretreatment times between 2 and 6 h depending on the total pressure (the higher the pressure, the less time). They were also observed at 160°C, total pressure of 14.7 and 21.7 bars, and pretreatment time of 2 h. Generally, at 110°C lignin removal is insufficient and at 180°C carbohydrates do not preserve well.

Analysis of Primary Reactions in Biomass Oxidation with O2 in Hot-Compressed Alkaline Water

“…1 – X at t ≥ 150 min is described well by the following kinetic equation The amount of solid residue after 260 min extraction was insufficient for the analysis of chemical composition, but from a white color of the solid, it seemed that it consisted mainly of cellulose but probably also very smaller fractions of lignin and hemicellulose. This was consistent with previous studies that showed difficulty of complete delignification and also slow delignification on the final stage. , It is also known that complexes of lignin and cellulose are refractory, being inaccessible to oxygen-containing active species . The chemical composition of the solid residue is shown and discussed quantitatively later.…”

“…This was consistent with previous studies that showed difficulty of complete delignification and also slow delignification on the final stage. 12,25 It is also known that complexes of lignin and cellulose are refractory, being inaccessible to oxygen-containing active species. 26 The chemical composition of the solid residue is shown and discussed quantitatively later.…”

Short‐term oxidative lime pretreatment of palm pruning waste for use as animal feedstuff

“…These radicals attack the biomass by introducing hydrophilic groups into the lignin structure, thereby increasing lignin solubility. As a result of nucleophilic attack from a hydroxyl peroxide anion, ring opening may occur …”

Perspectives of Hydrogen Production from Corn Wastes in Poland by Means of Dark Fermentation

“…Nasr et al [11] models include hydrogen production profile over time using the Artificial Neuron Network (ANN) method. Sierra et al, Sangian et al, and Taufiq-Yap et al [12][13][14] analyzed the energy potential of wood. The net energy generated by dark fermentation and microbial fuel cell is given by Perera et al [15].…”