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Lignin Valorization through Thermochemical Conversion: Comparison of Hardwood, Softwood and Herbaceous Lignin
journal contribution
posted on 2016-09-14, 00:00 authored by Shuai Zhou, Yuan Xue, Ashokkumar Sharma, Xianglan BaiIn 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.