The role of AgNPs in selective oxidation of benzyl alcohol in vapor phase using morphologically tailored MnO₂ nanorods in the presence of air

Abstract Vapor phase benzyl alcohol (BnOH) oxidation reaction is investigated over a pre–synthesised morphologically designed shape controlled spherical silver nanoparticles (AgNPs) decorated on manganese oxide nanorods (α–MnO₂NRs) in the presence of air. The combination of silver nanoparticles and the α–MnO₂NRs interface enabled the increased oxygen vacancies (Ov) and exhibited the strong metal–support interactions (SMSI) in surface oxygen activation. The effect of Ag loadings is significant and the optimal 1 wt% Ag loaded catalyst (1Ag/MnO₂NRs) showed excellent performance in benzyl alcohol oxidation due to high adsorption capacity, enhanced oxygen vacancies and red–ox properties. The DFT calculations confirmed that the high BnOH surface adsorption was exhibited over Ag modified MnO₂NRs than the bare α–MnO₂NRs. The optimized 1Ag/α–MnO₂NRs catalytic system achieved 2.6 fold higher activity compared to bare α–MnO₂NRs. These results provided novel insights on the rational design of shape dependent metal/metal oxide based heterogeneous catalysts

Designing versatile nanocatalysts based on PdNPs decorated on metal oxides for selective hydrogenolysis of biomass derived γ-valerolactone and reduction of nitro aromatics

Abstract In this work, we designed versatile heterogeneous nanocatalysts based on palladium nanoparticles (PdNPs) decorated on metal oxides supports (i.e., PdNPs/γ-Al₂O₃, PdNPs/WO₃ and PdNPs/Nb₂O₅) by step-wise controlled synthesis of novel monodispersed ∼2 nm PdNPs at room temperature and then impregnated over metal oxides. PdNPs supported catalysts were characterised by powder XRD, TEM, HRTEM, NH₃-TPD, N₂-BET, H₂-TPR, and XPS techniques. PdNPs based catalysts studied in two different model reactions were presented i.e., biomass platform chemical intermediate γ-valerolactone (GVL) conversion into pentanoic acid (PA) studied in vapor phase hydrogenolysis and 4-Nitrophenol (4-NP) reduction to 4-Aminophenol (4-AP) in liquid phase using NaBH₄ as reducing agent over 0.5 wt% Pd nanoparticles -based nanocatalysts. The relationship between the active sites and the catalytic performance was evaluated. The Under optimized reaction conditions, over 0.5 wt% PdNPs/γ-Al₂O₃ catalyst exhibited the highest PA yield of 100%, and over 0.5 wt% PdNPs/WO₃, 0.5 wt% PdNPs/Nb₂O₅ exhibited PA yields of 98% and 96% respectively. Over PdNPs/γ-Al₂O₃, PdNPs/WO₃, and PdNPs/Nb₂O₅, the reduction reaction rates in the 4-NP to 4-AP are 5.40 × 10⁻³ s⁻¹, 2.55 × 10⁻³ s⁻¹ and 2.30 × 10⁻³ s⁻¹ respectively. The calculated thermodynamic parameters of the Ea values for 4-NP to 4-AP reaction were 25.30, 26.75, and 27.81 KJ/mol for the PdNPs/γ-Al₂O₃, PdNPs/WO₃ and PdNPs/Nb₂O₅, respectively