(275c) Catalytic Depolymerization of Lignin over Mesoporous Solid Lewis Acid Catalysts

Catalytic
Depolymerization of Lignin over Mesoporous Solid Lewis Acid Catalysts

Kakasaheb
Y. Nandiwale^1,2, Andrew M. Danby¹, Anand
Ramanathan¹, Raghunath V. Chaudhari^1,2,
and Bala Subramaniam^1,2

¹Center for Environmentally Beneficial
Catalysis, The University of Kansas, Lawrence, Lawrence, Kansas 66047, United
States

²Department of Chemical and Petroleum
Engineering, The University of Kansas, Lawrence, Kansas 66045, United States.

Keywords: Biomass,
Lignin depolymerization, Lewis acid

In this work, we report the performances
of predominantly Lewis acidic, Zr-incorporated
mesoporous silicates (Zr-KIT-5 and Zr-KIT-6)^1-2 for deconstruction
of lignin into value added aromatic monomers. This work is motivated by several
factors. First, homogeneous Lewis acidic catalysts metal triflates³
have been shown to be effective in selective cleavage of ether linkages in
lignin. Further, Brønsted acid sites are known to
promote undesired condensation of the depolymerized products that may form
during lignin deconstruction.⁴ We therefore hypothesized that the
use of a predominantly Lewis-acidic solid catalyst should increase the yield of
the monomeric products compared to a predominantly Brønsted
acidic catalyst such as H-ZSM-5. Indeed, high yields of monomeric and dimeric oxoaromatic compounds (up to 75 wt%)
were observed during depolymenrization of dealkaline lignin on Zr-KIT-5 catalysts at 250°C. At
similar operating conditions, the Zr-KIT-5 catalyst outperforms reported yields
on H-ZSM-5 catalyst⁵ with much lower formation of heavier residues.
The effects of various solvents (1, 4-dioxane, acetic acid, methanol + water) and
operating conditions on the depolymerization of various lignins
[including corn stover lignin, PC 1369 hardwood
lignin (MeadWestvaco), Indulin 80 and dealkaline lignin, (TCI chemicals)] along with the product
selectivity and catalyst stability will be presented.

References:

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R. V.; Subramaniam, B., Ind Eng Chem Res 2013,
52, 15481-15487.

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