Total catalytic oxidation of chlorinated aromatics over bimetallic Pt–Ru supported on hierarchical HZSM-5 zeolite

Abstract

Combination of great redox-acidity and strong chlorine-resistant, are critical to constructing efficient catalyst for the total oxidation of chlorinated aromatics. Herein, bimetallic Pt–Ru supported on hierarchical HZSM-5 zeolites were prepared by an improved co-impregnation. The distinct catalytic properties of the well-characterized Pt–O–Ru structures were demonstrated for chlorobenzene (CB) oxidation. For CB streams containing 1000 ppm CB/dry air, GHSV = 40,000 mL/g h, T 50 of Pt 0 · 5 Ru 0.5 / m -HZ (234 °C) is significantly better than monometallic Pt 1 / m -HZ (294 °C) and Ru 1 / m -HZ (298 °C). Additionally, Pt 0 · 5 Ru 0.5 / m -HZ is stable during 50-h test with high selectivity for less toxic products (CO 2 and HCl) and scarce formation of chlorinated byproduct. In situ DRIFTS reveals that CB reacted with Brønsted acid sites to produce phenolates, which is sequentially converted into maleic anhydride, aldehyde and carboxylates under the synergetic effects of redox-acidity properties prompted by Pt–O–Ru structures. The partial oxidation products are finally oxidized into CO 2 , HCl and H 2 O by surface oxygen. • Pt x Ru y / m -HZ catalysts prepared by improved co-impregnation present Pt–O–Ru structure. • The interaction of SiAlOH with Pt–Ru precursors leads to the formation of Pt–O–Ru. • Pt–O–Ru shows the stronger acidity, enhanced redox property and surface oxygen. • Pt 0 · 5 Ru 0.5 / m -HZ catalyst presents high stable activity in both CB and toluene oxidation. • Adsorption and activation of CB occur under the synergism of Pt, Ru and HZSM-5.