University of Kansas Background
Agricultural biomass is largely composed of lignin and cellulose. The cellulose is often used as a feedstock for fermentation, which produces ethanol or other fuel products. However, there is currently no viable commercial solution for valorizing the lignin. It is typically considered a low-value waste and is often burned to produce energy. Conversion of lignin to valuable products is thus a key enabler for the development of renewable fuels and specialty chemicals.
The KU invention uses a novel mesoporous silicate catalyst to depolymerize the lignin. Monomeric aromatic compounds including eugenol, vanillin, methyl vanillate, and guaciacyl acetone can then be isolated. Vanillin is notable because it is currently a high value commercial product. All of these monomers can be converted to other functionalized aromatics or BTX.
The lignin is suspended in a solvent along with the novel catalyst. The slurry is heated in a closed system under inert atmosphere. The solvent system has been optimized to produce higher monomer yields than the previously known methods. The catalysts and residual lignin solids are then separated, with the potential for the catalyst to be reused. The solvent is removed from the resulting mixture of monomers and other soluble molecules. This mixture can be separated via chromatographic or other methods.
Lignin is converted to higher value products through a clean and safe process
Monomer yields are higher than alternative solid acid catalysts
The catalyst is a solid, which can easily be separated from the lignin
The catalysts used are non-toxic and do not include leachable transition metals
Lab testing has shown that the yields of monomers and low molecular species is higher with this catalyst than with other microporous zeolites evaluated.
This technology can be part of an overall scheme for converting non-edible biomass to renewable chemicals. It can be incorporated into integrated bio refineries or used to process existing lignin sources.
The catalyst could potentially be used with unseparated lignocellulose feeds. It could be applied to higher temperature pyrolysis-type systems. It could serve as the acid component in a hydrocracking type catalyst.