Novel Catalytic Transformation of Lignin that Enables Consolidated Conversion of Biomass

Lignin comprises 40% of the energy content in biomass, but is primarily burned to generate process heat in the biorefinery rather than utilized to make high-value fuels and co-products. To convert all cell wall components, including lignin, to hydrocarbon fuels and low molecular weight aromatic compounds, hydrogenation and hydrogenolysis catalysts are needed that are highly robust, efficient and with low toxicity. We developed a bimetallic Palladium/Zinc/Carbon catalytic system for the disassembly of lignin via β-O-4 ether bond cleavages and characterized the reaction mechanism.

Cell Wall Molecules

Dimeric lignin model compounds and synthetic lignin polymers are cleaved with near quantitative conversions and yields of 80–90% (Parsell et al. 2013). Disassembly of about half of the lignin even from intact woody biomass into two methoxy-substituted propylphenols as major products is the technology basis of the C3Bio start-up company, Spero Energy (Provisional Patent Application 61/896,110). Presently manufactured from petroleum feedstock via a multi-step process, methoxypropylphenols are high-value fragrance and flavor compounds with an annual production volume of >30MM lbs and market value of $450 MM. The Spero Energy graduate students and post-doc team placed first in the Indiana Clean Energy Student Challenge and was awarded the $50K Aviation Biofuels Award supported by Boeing, United and Honeywell UOP in the Chicago Regional Clean Energy Challenge. The two reaction products have been further deoxygenated to high-octane molecules, propylbenzene and propylcyclohexane, using a selective Platinum/Molybdenum catalyst on multi-walled carbon nanotubes with >98% C9 hydrocarbon yield. The ability to deconstruct lignin first from intact biomass revolutionizes the conventional concept of the biorefinery by capturing high-value products from lignin as the first step and enhancing conversion of the cellulosic residue to fuel intermediates (Parsell et al. 2015).

References

Parsell TH, Owen BC, Klein I, Jarrell TM, Marcum CL, Haupert LJ, Amundson LM, Kenttämaa HI, Ribeiro F, Miller JT, Abu-Omar MM (2013) Cleavage and hydrodeoxygenation (HDO) of C–O bonds relevant to lignin conversion using Pd/Zn synergistic catalysis. Chem. Sci. 4:806-813.

Parsell T, Yohe S, Degenstein J, Jarrell T, Klein I, Gencer E, Heweston B, Hurt M, Kim JI, Choudhari H, Saha B, Meilan R, Mosier N, Ribeiro F, Delgass WN, Chapple C, Kenttämaa HI, Agrawal R, Abu-Omar MM (2015) A synergistic biorefinery based on catalytic conversion of lignin prior to cellulose starting from lignocellulosic biomass. Green Chemistry. [10.1039/C4GC01911C] December 2104

Provisional Patent Application 61/896,110. Delglass W N, Agrawal R, Ribeiro FH, Yohe SL, Abu-Omar M, Dietrich PJ. Catalytic Biomass Conversion Methods, Catalysts, and Method of Making the Same (2014)

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