Characterization of Organosolv Birch Lignins: Toward Application-Specific Lignin Production

Abstract

Organosolv pretreatment represents one of the most promising biomass valorization strategies for renewable carbon-based products; meanwhile, there is an overall lack of holistic approach to how extraction conditions affect the suitable end-usages. In this context, lignin extracted from silver birch ( Betula pendula L.) by a novel hybrid organosolv/steam-explosion treatment at varying process conditions (EtOH %; time; catalyst %) was analyzed by quantitative NMR ( 1 H– 13 C HSQC; 13 C NMR; 31 P NMR), gel permeation chromatography, Fourier transform infrared (FT-IR), Pyr-gas chromatography–mass spectroscopy (GC/MS), and thermogravimetric analysis, and the physicochemical characteristics of the lignins were discussed regarding their potential usages. Characteristic lignin interunit bonding motifs, such as β- O -4′, β-β′, and β-5′, were found to dominate in the extracted lignins, with their abundance varying with treatment conditions. Low-molecular-weight lignins with fairly unaltered characteristics were generated via extraction with the highest ethanol content potentially suitable for subsequent production of free phenolics. Furthermore, β-β′ and β-5′ structures were predominant at higher acid catalyst contents and prolonged treatment times. Higher acid catalyst content led to oxidation and ethoxylation of side-chains, with the concomitant gradual disappearance of p -hydroxycinnamyl alcohol and cinnamaldehyde. This said, the increasing application of acid generated a broad set of lignin characteristics with potential applications such as antioxidants, carbon fiber, nanoparticles, and water remediation purposes.

Salicornia dolichostachya organosolv fractionation: towards establishing a halophyte biorefinery

“…35 When using birch chips, the M w ranged from 2700 Da (200 C for 15 min with 60% ethanol and 1% w/w biomass H 2 SO 4 ) to 8000 Da (200 C for 30 min with 60% ethanol without catalyst). 36 Pine wood pretreated at 190 C for 60 min with 60% v/v ethanol and 1% w/w biomass H 2 SO 4 generated lignins with M w of 7700 Da; whereas cotton stalks pretreated at 200 C for 45 min with 50% v/v ethanol and 1% w/w biomass H 2 SO 4 , as well as sweet sorghum bagasse pretreated at 180 C for 30 min with 60% v/v ethanol produced lignins with M w of 16 800 Da and 6600 Da, respectively. 37 Comparatively, organosolv-pretreated lignin isolated from Salicornia had a much smaller molecular weight, which can be explained by the catalytic action of transition metals (e.g., iron, cobalt, manganese, platinum, ruthenium, and rhodium) during oxidative cleavage of b-O-4 linkages.…”

“… 35 When using birch chips, the M w ranged from 2700 Da (200 °C for 15 min with 60% ethanol and 1% w/w biomass H 2 SO 4 ) to 8000 Da (200 °C for 30 min with 60% ethanol without catalyst). 36 Pine wood pretreated at 190 °C for 60 min with 60% v/v ethanol and 1% w/w biomass H 2 SO 4 generated lignins with M w of 7700 Da; whereas cotton stalks pretreated at 200 °C for 45 min with 50% v/v ethanol and 1% w/w biomass H 2 SO 4 , as well as sweet sorghum bagasse pretreated at 180 °C for 30 min with 60% v/v ethanol produced lignins with M w of 16 800 Da and 6600 Da, respectively. 37 …”

Catalytic conversion of high S-lignin to a sustainable tri-epoxide polymer precursor

“…31,38–41 More importantly, the properties of organosolv lignins are often altered during these fractionation treatments, including re-condensation reactions forming unnatural and recalcitrant C–C bonds. 30,31,40–43…”

“…30,[35][36][37][38][39] However, the drawbacks of these methods are obvious given that they require extra usage of solvents, time, and energy. 31,[38][39][40][41] More importantly, the properties of organosolv lignins are often altered during these fractionation treatments, including re-condensation reactions forming unnatural and recalcitrant C-C bonds. 30,31,[40][41][42][43] The extra-step suffers from two problems.…”

“…31,[38][39][40][41] More importantly, the properties of organosolv lignins are often altered during these fractionation treatments, including re-condensation reactions forming unnatural and recalcitrant C-C bonds. 30,31,[40][41][42][43] The extra-step suffers from two problems. With the exception of the FPL method, the efficiency of lignin extraction was relatively low so that considerable material loss was experi- enced as illustrated in Fig.…”