Design and preparation of palygorskite supported bimetallic palladium‑cerium catalysts for efficient catalytic combustion of toluene

Abstract

Toluene oxidation technology has been widely concerned because toluene can cause environmental pollution and affect human health. In this study, the palygorskite (Pal) was designed as a functional support to synthesize palladium‑cerium (PdCe) bimetallic catalyst through precipitation approach for reducing the amount of precious metal and maintaining catalytic activity of supported catalyst over toluene. The relationship between the structure properties and catalytic performance was analyzed by various characterization techniques. The introduction of Ce ions could significantly increase the amount of metallic Pd and the oxygen vacancies. The finely dispersion of metal active component and a large number of oxygen vacancies improve the catalyst reducibility and oxygen species activity of catalyst system. The obtained Pd₈Ce₂@A-Pal catalyst exhibits the best catalytic performance for toluene combustion, and the temperatures for 50 % and 90 % toluene conversion are 150 and 185 °C at space velocity of 30,000 mL/g/h, respectively. The space velocity, the long catalytic stability and the effect of water vapor on catalytic activity were investigated, which confirmed the good catalytic performance. The investigation of situ diffuse reflection Fourier transform spectroscopy measurements have confirmed the intermediates during toluene oxidation, and indicated that the toluene degradation pathway over Pd₈Ce₂@A-Pal is via benzyl alcohol-benzylic and aldehydic species-benzoate species-maleic anhydride, finally decayed to CO₂ and H₂O.