Lignin is a heterogeneous, alkyl-aromatic polymer found in plant cell walls which, given effective depolymerization and upgrading strategies, could eventually serve as a feedstock for the production of hydrocarbon fuels and aromatic chemicals. However, lignin depolymerization to upgradable intermediates remains challenging in a process context. Base catalyzed depolymerization (BCD) of lignin using sodium hydroxide as well as other basic media has been shown to be a reasonably effective depolymerization strategy when using isolated lignins. To gain more insight into using BCD in lignin-rich, process relevant feedstock, here we apply BCD with sodium hydroxide to residual biomass from a typical biochemical conversion process, namely the remaining solids after dilute-acid or disk refining pretreatment and enzymatic hydrolysis of corn stover. The bulk of this feedstock is highly lignin-rich, as shown by standard biomass compositional analysis assays. We conducted BCD reactions in a batch reactor with 10wt% solid loading in 2-4wt% NaOH at 270-330°C for 40 min. We performed a mass balance on each fraction from the BCD process, and characterized the resulting aqueous and solid residue using gel-permeation chromatography, NMR, and GC-MS, which when taken together suggest that a significant fraction (45-78%) of the starting lignin-rich material was depolymerized to small molecular weight, soluble species. Overall, this study demonstrates that BCD of residual, lignin-rich biomass after a conventional biochemical conversion process can be depolymerized in sodium hydroxide to produce significant yields of small molecular weight aromatics that potentially can be upgraded to fuels or chemicals.

Base-catalyzed depolymerization of residual solid biomass from a biochemical conversion process

249th National Meeting (2015)

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