Issue Date: June 11, 2012
Depolymerized Lignin Makes A Good Solvent
Chemical engineers have developed a catalytic process to mince lignin into its alkylphenol building blocks, which can serve as a solvent for biphasic processing of the hemicellulosic and cellulosic components of biomass (Green Chem., DOI: 10.1039/c2gc35203f). A team led by James A. Dumesic of the University of Wisconsin, Madison, envisions an integrated biorefinery process that would convert poplar wood into furfural, levulinic acid, and γ-valerolactone intermediates and from there make butene, which can be oligomerized to produce gasoline or jet fuel. In early-stage work, Dumesic’s team used 2-sec-butylphenol as an effective solvent for the continuous aqueous-organic biphasic reaction system that would be operating in such a biorefinery. But rather than purchasing a petroleum-derived solvent and transporting it to a future biorefinery, the researchers looked for a way to create a solvent from the biomass feedstock itself. They found that in hot aqueous acid solution standard palladium, ruthenium, or platinum catalysts selectively hydrolyze the C–O–C aromatic ether bonds in lignin. The result is a mix of the alkyl-substituted phenols propyl guaiacol and propyl syringol. The mixture or propyl guaiacol alone works efficiently in the continuous biphasic reactors, the researchers note, enabling the synthesis and separation of the intermediate compounds and catalyst recovery.
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