Ordered and disordered zirconia-modified silica supports in diclofenac hydrodechlorination over palladium catalyst

The performance of Pd catalysts supported on ordered (ZrSBA) or disordered (ZS) ZrO₂-modified SiO₂ was evaluated in the hydrodechlorination of ecotoxic diclofenac with H₂ in an aqueous medium at 30 °C, after pre-reduction of the catalysts with H₂ at 320 °C or in water at 30 °C. The ordered 0.1 wt% Pd/ZrSBA catalysts with lower Pd content, reduced at both temperatures, showed similar diclofenac conversion rates that were comparable to or much higher than those of the 0.86 wt% Pd/ZS catalysts reduced at 320 or 30 °C, respectively. A comprehensive analysis using XRD, N₂ adsorption, TEM-EDA, TPR and XPS techniques revealed the presence of larger Pd nanoparticles, a reduced degree of Pd decoration with silica and slightly improved reducibility of Pd/ZrSBA at 30 °C compared to Pd/ZS, which resulted in a superior efficiency of the former catalyst.