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 E_a 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.