VOCs catalytic removal over hierarchical porous zeolite NaY supporting Pt or Pd nanoparticles

Abstract

The present work reports the impregnation of palladium (Pd) or platinum (Pt) on hierarchical porous zeolite catalysts for Volatile Organic Compounds (VOCs) oxidation. The hierarchical porous zeolite (NaYmod) was synthesized via a top-down approach to incorporate mesoporosity into the microporous zeolite NaY. This process was achieved through a three steps synthesis: dealumination, desilication and alkaline treatment. 0.5 wt% of Pd and Pt precursors were then added to NaY and NaYmod supports by wet impregnation in order to elaborate efficient catalysts for the total oxidation of two types of VOCs, ethanol and toluene, which are probe molecules for oxygenated VOCs and BTEX compounds respectively. The supported and unsupported samples were characterized by X-Ray Diffraction (XRD), N2-physisorption, Transmission Electron Microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS). The modified mesostructured support ensures a better dispersion of the active phases and led to a partial presence of highly reactive Pt(II) species in the case of platinum-based samples. Whatever the oxidation reaction, these latter demonstrate higher conversions compared to palladium-based ones. The presence of Pt(II) species provided a high catalytic performance, with a total degradation of both VOC probe molecules at temperatures lower than 170 °C. Such temperatures have not been recorded before for NaY supported materials.