Liquid-phase reactions catalyzed by heterogeneous catalysts are important in the chemical conversion of non-volatile chemical feedstocks, such as biomass. The presence of reactive solutes, solvents, and spectator species present significant challenges in understanding adsorption and reactions at solid-liquid interfaces, particularly under conditions involving elevated temperatures and pressures. However, the conversion chemistry is lack of molecular understanding especially at the solid-liquid interface, mostly owing to the demanding reaction conditions including high temperature/pressure. Customized high temperature/pressure solid-state NMR rotors developed at PNNL, were adapted, allowing operando solid-state NMR measurements of conversion of lignin catalyzed with supported metal catalysts. For example, benzylphenylether (BPE) as the lignin α-O-4 model compound was studied with Ni/γ-Al2O3 at 120-225 °C with 50 bar H2. Selective 13C labeling of BPE allows quantification of the BPE and the corresponding products. The kinetic profiles of BPE hydrogenolysis follow pseudo-first-order rate law, and the activation energy was measured to be (86 ± 8) kJ/mol. Selective isotope labeling of hydrogen gas and solvent 2-PrOH with 2H allows the investigation of reactive participation of solvents and product toluene on the Ni surfaces.

Operando solid-state NMR spectroscopy for biomass conversion with solid catalysts

255th National Meeting (2018)

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