1 research outputs found
Alkaline Peroxide Delignification of Corn Stover
Selective
biomass fractionation into carbohydrates and lignin is
a key challenge in the conversion of lignocellulosic biomass to fuels
and chemicals. In the present study, alkaline hydrogen peroxide (AHP)
pretreatment was investigated to fractionate lignin from polysaccharides
in corn stover (CS), with a particular emphasis on the fate of the
lignin for subsequent valorization. The influence of peroxide loading
on delignification during AHP pretreatment was examined over the range
of 30–500 mg H<sub>2</sub>O<sub>2</sub>/g dry CS at 50 °C
for 3 h. Mass balances were conducted on the solid and liquid fractions
generated after pretreatment for each of the three primary components,
lignin, hemicellulose, and cellulose. AHP pretreatment at 250 mg H<sub>2</sub>O<sub>2</sub>/g dry CS resulted in the pretreated solids with
more than 80% delignification consequently enriching the carbohydrate
fraction to >90%. Two-dimensional nuclear magnetic resonance (2D-NMR)
spectroscopy of the AHP pretreated residue shows that, under high
peroxide loadings (>250 mg H<sub>2</sub>O<sub>2</sub>/g dry CS),
most
of the side chain structures were oxidized and the aryl-ether bonds
in lignin were partially cleaved, resulting in significant delignification
of the pretreated residues. Gel permeation chromatography (GPC) analysis
shows that AHP pretreatment effectively depolymerizes CS lignin into
low molecular weight (LMW) lignin fragments in the aqueous fraction.
Imaging of AHP pretreated residues shows a more granular texture and
a clear lamellar pattern in secondary walls, indicative of layers
of varying lignin removal or relocalization. Enzymatic hydrolysis
of this pretreated residue at 20 mg/g of glucan resulted in 90% and
80% yields of glucose and xylose, respectively, after 120 h. Overall,
AHP pretreatment is able to selectively remove more than 80% of the
lignin from biomass in a form that has potential for downstream valorization
processes and enriches the solid pulp into a highly digestible material