(416g) Hydrogenolysis of C-O Bond Over Ni-Based Bimetallic Nps: Application in Lignin Valorization

As lignin contains ca. 40% energy in lignocellulose biomass, its conversion to small molecules (mostly aromatics), which can serve as either fuels or chemicals, has received significant attention recently. Catalytic hydrogenolysis of the aryl ether bonds is a crucial step for lignin conversion. Previous studies are mostly focused on precious metal catalysts with a handful of others that use nickel-based catalysts. Nevertheless, identification of more efficient, yet affordable catalysts for C_Ar-O bond cleavage is still the bottleneck for lignin valorization via hydrogenolysis.

In this study, thirteen monometallic nanoparticle catalysts and twelve bimetallic nanoparticle catalysts were employed to catalyze the hydrogenolysis of 2-phenoxy-1-phenethanol, which is a typical lignin model compound with β-O-4 type linkage. All the nanoparticle catalysts were prepared by wet chemical reduction method with NaBH4 as the reductant and polyvinylpyrrolidone (PVP) as the stabilizer. The reactions were carried out at 100-160 °C and 1-20 bar H₂. The products were analyzed by GC, GC-MS and major products are also isolated by liquid chromatography and versified by NMR. Among catalysts being screened, NiPd, NiRu and NiAu exhibited superior catalytic performance over the other catalysts. In particular, NiAu nanoparticles were significantly more active than pure Au and Ni catalysts, and were effective in the hydrogenolysis of a variety of lignin model compounds and real lignin. TEM, XPS, XRD and EXAFS were employed to characterize the morphology, structure and electronics of the NiAu catalysts, revealing the interactions between Au and Ni atoms. The promotion effect of Au decorated Ni was proposed to be the electron donating of the slightly electron deficient Ni atoms on the NiAu nanoparticles that facilitating C-O bond break, providing implications on future catalyst design.