The kinetics of hydrodeoxygenation (HDO) reaction in literature are mostly reported for single model compounds in bio-oil. However, these kinetic models may become invalid in the real bio-oil environment where other model compounds are present. This study investigates the effect of acetic acid, which is a major compound in bio-oil, on the liquid-phase HDO reaction kinetics of vanillin (VL). A synthesized bimetallic catalyst (PdRh/Al2O3) was utilized in a batch reactor at 308–328 K, 1–4 MPa H2 gas partial pressure (PH), 263–526 mM initial VL concentration (CVL0), and 1.9–4.6 kg/m3 catalyst loading with ethyl acetate as the reaction solvent. N2 adsorption–desorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), CO chemisorption, and mercury porosimetry methods were used to determine the physicochemical properties of the catalyst. Transport limitations in the system were ruled out via the Madon–Boudart test, Weisz–Prater criterion, agitation, and particle size test. ...