Extraction of Lignin from a Coproduct of the Cellulosic Ethanol Industry and Its Thermal Characterization

Abstract

Lignin was extracted from the solid coproduct of a lignocellulosic ethanol production by a solid-liquid extraction method using N,N-dimethyl formamide. This coproduct was the residue of a steam explosion pretreatment followed by enzymatic hydrolysis process. The coproduct was used as received and also after washing. Lignin content of the solid coproduct was reduced from 63% to 43% after lignin extraction. Fourier transform infrared spectroscopy (FTIR), molecular weight measurement (GPC), and elemental analysis provided information about the chemical structure and molecular weight of the fractions. The extracted lignin had lower molecular weight (~ 5000 Da.) and higher carbon content (63%) compared to the residue of extraction (M w ≈ 8000 Da. and carbon % = 48%). Thermal stability measurements of the samples by thermogravimetry (TGA) showed that the extracted lignin had the highest carbon residue. Effects of different heating cycles on the glass transition temperature (T g ) were measured. The T g of the soluble fraction was lower than that of the coproduct. Results of the X-ray diffraction (XRD) showed the crystalline structure of cellulose in both the coproduct and the solid residue after extraction. This extraction and material characterization is helpful for liquid processes such as solution spinning or electrospinning. The thermal properties can be used for optimization of heat treatment processes such as carbonization.

Processing, Carbonization, and Characterization of Lignin Based Electrospun Carbon Fibers: A Review

“…Cellulosic ethanol and paper/pulp production are two leading industries that produce lignin as their coproducts (Hu and Hsieh, 2013;Poursorkhabi et al, 2013;Chen et al, 2014;Abdelwahab et al, 2015Abdelwahab et al, , 2019Adams et al, 2018). Alkaline pulping (soda and kraft) are the most common methods to extract lignin from cellulose in paper/pulp manufacturing (Suhas et al, 2007).…”

Isolation and Characterization of Organosolv and Alkaline Lignins from Hardwood and Softwood Biomass

“…When focusing on lignin isolation, two general strategies for recovery are currently available. The first is to recover the water-insoluble lignin remaining at the end of the bioconversion following the biomass pretreatment and enzymatic hydrolysis. , Pretreatment methods in this case target mainly removal of hemicellulose as a means of improving enzymatic saccharification of cellulose; the lignin collected after these operations, however, suffers from low purity due to high content in recalcitrant carbohydrates, proteins, and salts limiting its suitability for further valorization. It can be mainly used as a low cost and high energy content solid fuel for heat or power generation .…”

Refining of Ethanol Biorefinery Residues to Isolate Value Added Lignins

“…The recent literature contains examples where postbioconversion techniques have been examined, including extraction with aqueous sodium hydroxide (NaOH) 14 or organic solvents such as dimethylformamide (DMF). 15 Notably, prebioconversion isolation protocols have received more attention over their postbioconversion counterparts. This is because lignin is a cellulase enzyme inhibiting moiety that may hinder the hydrolytic conversion process.…”