ABSTRACT
Recovering lignin with high ß-O-4 content is of prime interest for further high yield depolymerization in low molecular weight phenolic compounds. Pretreatment of lignocellulosic biomass with deep eutectic solvents (DES) was studied to extract this type of tailored lignin from softwood and brewer's spent grains. In this work, choline chloride (ChCl) based DES with two different hydrogen bond donors (HBD) (lactic acid (LA) and Glycerol (Gly)), were investigated at mild temperatures (60 and 80 °C). The influence of DES pretreatment on extracted lignin molecular weight and structural characteristics was analysed. The acidity and density of DES were proved to affect lignin extraction yield and its features. The lignin characteristics (type of interunits, accessibility) were shown to impact their ability to be recovered. Acidic-DES ChCl:LA at 80 °C with woody biomass gave promising results with 78% of lignin extracted exclusively composed of G units with 61% of ß-O-4 linkages with narrow molecular weights distribution.
Subject(s)
Deep Eutectic Solvents , Lignin , Biomass , Hydrogen Bonding , Lignin/chemistry , Solvents/chemistry , TemperatureABSTRACT
Fractionation of phenolic compounds in thermomechanical pulp mills was performed with a coupling of a prior treatment realized by flotation and a ceramic membrane process. Two lines of membranes filtration were tested. After a common 150â kDa clarification, 1â kDa filtration was performed with or without previous 5â kDa filtration. Flotation was shown to be inevitable to retain lipophilic compounds which cause severe membrane fouling. 150â kDa permeate flux was 20% higher when process water was firstly floated and was around 260â Lâ h-1â m-2. 1â kDa membrane was fouled with 31% of irreversible fouling without previous 5â kDa filtration and phenolic compounds purity reached only 26% in this 1â kDa permeate. Phenolic compounds as lignin-like substances which might be attached to hemicelluloses were recovered in 5â kDa retentate. Retentate of 1â kDa might contain a major fraction of lignin derivatives with molecular weights around 1â kDa free or linked with phenolic acids. Permeate of 1â kDa contained 14% of phenolic compounds such as lignans and free phenolic acids purified at 50%.
Subject(s)
Water Purification , Water , Chemical Fractionation , Filtration , Membranes, Artificial , Polyphenols , WastewaterABSTRACT
A total synthesis of (Z,E)-D-Glucophosphoenolpyruvate and its carboxylic ester derivatives is described in four or five steps from 2,3:5,6-Di-O-isopropylidene-4-O-t-butydimethylsilyl-D-glucose.