Hydrodechlorination of 4-Chlorophenol on Pd-Fe Catalysts on Mesoporous ZrO(2)SiO(2) Support

A mesoporous support based on silica and zirconia (ZS) was used to prepare monometallic 1 wt% Pd/ZS, 10 wt% Fe/ZS, and bimetallic FePd/ZS catalysts. The catalysts were characterized by TPR-H(2), XRD, SEM-EDS, TEM, AAS, and DRIFT spectroscopy of adsorbed CO after H(2) reduction in situ and tested in hydrodechlorination of environmental pollutant 4-chlorophelol in aqueous solution at 30 °C. The bimetallic catalyst demonstrated an excellent activity, selectivity to phenol and stability in 10 consecutive runs. FePd/ZS has exceptional reducibility due to the high dispersion of palladium and strong interaction between FeOx and palladium, confirmed by TPR-H(2), DRIFT spectroscopy, XRD, and TEM. Its reduction occurs during short-time treatment with hydrogen in an aqueous solution at RT. The Pd/ZS was more resistant to reduction but can be activated by aqueous phenol solution and H(2). The study by DRIFT spectroscopy of CO adsorbed on Pd/ZS reduced in harsh (H(2), 330 °C), medium (H(2), 200 °C) and mild conditions (H(2) + aqueous solution of phenol) helped to identify the reasons of the reducing action of phenol solution. It was found that phenol provided fast transformation of Pd(+) to Pd(0). Pd/ZS also can serve as an active and stable catalyst for 4-PhCl transformation to phenol after proper reduction.