Green hydrodeoxygenation of biomass pyrolysis oil into cycloalkanes using Ni-Mo nanoparticles supported H-mesoporous beta catalysts

Significant challenges in upgrading biomass pyrolysis oil (BPO) include the directional cleavage of >C-O- linkages with high bond strength and the cascade hydrogenation of aromatic rings to prevent recondensation, ultimately maximizing the formation of cycloalkanes. We present the synthesis of H-mesoporous beta (HMB) supported Ni-Mo nanoparticles (NPs) catalysts (Ni-Mo/HMB) via a two-step synthetic strategy, including in-situ mesopores reconstruction and the uniform dispersion of bimetallic NPs under solvothermal conditions. The Ni-Mo/HMB catalyst efficiently converted BPO to cycloalkanes under mild conditions, attributable to the synergistic effect between accessible Lewis acidic sites (LASs) and bimetallic Ni-Mo active sites for catalyzing hydrodeoxygenation (HDO). Furthermore, the dispersion of bimetallic Ni-Mo NPs is most uniform with a Ni/Mo ratio of 10/3, and demonstrated the high HDO activity. The Ni-Mo/HMB, with a short distance between Ni-Mo NPs and accessible LASs, achieved the conversion of mequinol to cyclohexane with selectivity of 100 % at 140 °C for 2 h under 4 MPa initial hydrogen pressure (IHP). Correspondingly, BPO contains all heteroatom-containing organic species (including 92.4 % OCOCs, 3.4 % NCOCs, and 2.2 % SCOCs) and 2.0 % benzenes, which underwent catalytic HDO over 10Ni-3Mo/HMB at 140 °C for 16 h, yielding high amounts of cycloalkanes (61.5 %) and chain alkanes (CAs, 38.5 %). Additionally, first-principles show that 10Ni-3Mo/HMB exhibits high catalytic activity due to the active hydrogen species transfer within Ni-Mo NPs and accessible LASs. The repolymerization reactions and diffusion limitations of intermediates are effectively mitigated due to the mesoporous texture of Ni-Mo/HMB, which sustains excellent activity after 5 cycles of recycling.