Lignin Valorization through Thermochemical Conversion: Comparison of Hardwood, Softwood and Herbaceous Lignin

Abstract

In the present study, milled wood lignin (MWL) and organosolv lignin isolated from red oak (hardwood), loblolly pine (softwood) and corn stover (herbaceous biomass) were characterized by TGA, elemental analyzer, GPC, FTIR, 2D-HSQC NMR, and then pyrolyzed in the absence and presence of a zeolite catalyst. For all three biomass species, organosolv lignins contained fewer volatiles in comparison to the corresponding MWLs. Red oak lignin was affected most by the organosolv process, evident by the greatest decrease in volatile content and increase in carbon content of the organosolv lignin. Compared to the corresponding MWLs, organosolv lignins produced more char and less phenolic oil upon pyrolysis. Organosolv lignins also convert to catalytic coke and light hydrocarbons in higher selectivity in comparison to the MWLs during catalytic pyrolysis. When pyrolyzed, corn stover MWL produced 16.26% of phenolic monomers, which is a significantly higher yield compared to 8.61% from red oak MWL and 9.51% from loblolly pine MWL. During catalytic pyrolysis, corn stover lignins also produced higher yields of aromatic hydrocarbons in comparison to red oak or loblolly pine derived lignins. Overall, corn stover lignin had the highest potential for volatilization because it retains highly branched polymer structure enriched in tricin, ferulate and coumarate groups.

Agricultural residue‐derived lignin as the filler of polylactic acid composites and the effect of lignin purity on the composite performance

“…The T d ' s of the lignin were varied from 180 to 200.7 ° C for the three kinds of lignin, decreasing with increasing inorganic content in the lignin. The T d of corn stover lignin measured in this study was lower than that of softwood alkali lignin reported by Gordobil et al ., possibly attributed to the longer aliphatic side chains attached to aromatic rings . The range of T max was between 335.5 and 350.3 ° C for different corn stover lignin, which also decreased with increasing inorganic content.…”

“…Thus, corn stover‐derived lignin is one of the major byproducts in the biorefineries. It is also noteworthy that compared to woody‐biomass derived lignins, herbaceous biomass‐based lignin (such as corn stover lignin) has lower thermal stability and higher chemical reactivity due to its higher content of phenolic hydroxyl and branched aliphatic side chains . The aims of the present study are two folds: to investigate the role of the lignin impurities on the composite performance and evaluate the potential of the agricultural‐residue lignin in filler application.…”

Structural Characterization of Lignin and Its Degradation Products with Spectroscopic Methods

“…The EHL had the highest molecular weight (i.e., M w = 1429 g/mol; M n = 746.18 g/mol). In a comparison of pretreatments on hardwood (red oak), softwood (loblolly pine), and herbaceous biomass (corn stover) for lignin valorization through pyrolysis, organosolv lignins contained fewer volatiles in comparison to the corresponding MWLs for all the tested samples [51]. Red oak lignin was affected mostly by the organosolv process, since the greatest decrease in volatile content and increase in carbon content were observed.…”

Potential of producing carbon fiber from biorefinery corn stover lignin with high ash content

“…6,13 Lignin is an amorphous aromatic polymer and its physiochemical and thermal properties highly depend on the biomass origin and lignin isolation method. 14 Although lignin in general is biosynthesized from three main units, which are p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units, the ratios of H, G, and S units vary by biomass species. 15 S unit is dominant in hardwood lignin; thus hardwood lignin is chemically stable and less likely to crosslink when it is thermally processed.…”