In this study, we developed a series of bimetallic Ni metal nanoparticle catalysts that are highly active, stable catalyst in the hydrogenolysis of lignin into aromatic compounds under mild conditions in water. Unexpected, Ni7Au3 catalyst is three times more active than pure Ni catalyst in the hydrogenolysis of a lignin �-O-4 model compound. The structure of the catalysts were thoroughly characterized and the structure-activity relationship were rationalized. This enhancement of catalytic activity is partially due to the fact that Au reduces Ni particle size and result in a significant increase in Ni dispersion. Furthermore, Au increases the turnover frequency (TOF) of Ni by 50 %. DFT calculation and kinetic study suggest that surface reaction between phenoxy species and hydride is rate-determining and Au decrease the activation energy of this step by 20 kcal/mol. At 170 �C, the organosolve lignin is depolymerized into a mixture of monomers (> 10 wt% yield) and oligomers over Ni7Au3 catalyst in one hour, which is the best yield ever obtained under similar conditions.  Similarly, NiCu, NiAg, NiRu and NiRh catalysts are identified to be superior in the lignin depolymerization in the presence of H2, based on which we propose the designing strategies for lignin C-O bond hydrogenolysis. Obtaining feedstock chemicals from biomass such as lignin via advanced catalysis is essential to initiate a paradigm shift in green manufacturing and the development of cheap metal based, highly effective bimetallic Ni catalysts described herein represents a step forward.

Nickel based bimetallic catalysts for lignin hydrogenolysis into aromatic chemicals

247th National Meeting (2014)

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