Flame made low Pt loading catalysts supported on different metal oxides for catalytic combustion of CO and CH₄

Abstract

Catalytic combustion is an effective approach to remove air pollutants from various emission sources. For this purpose, supported noble metal catalysts are preferred in commercial applications due to their outstanding catalytic activity for eliminating CO, hydrocarbon compounds and NOx. In this paper, we employ the flame spray pyrolysis method to prepare a series of Pt-based catalysts with four different supports (TiO₂, ZrO₂, MgO and ZnO) and variable low Pt loadings for catalytic combustion of CO and CH₄. The performance of 0.5 Pt/TiO₂ is the best in all samples, in which the T₉₀ temperatures are 107 and 500 °C for 90% conversion of CO and CH₄, respectively. To examine its thermal stability, a time-on-stream test at 700 °C for 420 min is carried out, resulting in a decrease of about 5% in the final conversion of CH₄. The X-ray diffraction results show that TiO₂ support is a mixed phase with a major amount of anatase and a small amount of rutile other than a pure phase of ZrO₂, MgO and ZnO. Furthermore, X-ray photoelectron spectroscopy analysis and high-angle annular dark-field scanning transmission electron microscopy observation show that when the Pt loading is low, the Pt species exist as highly dispersed single atoms on the surface of the TiO₂ support. As the Pt loading gradually increases, the state of the Pt species transitions from single atoms to Pt clusters, resulting in a decrease in dispersion. Ultimately, the Pt can successfully accumulate on the surface of the TiO₂ nanoparticles, providing abundant active sites for efficient catalytic combustion reactions.

Keywords

Platinum catalyst / flame spray pyrolysis / catalytic combustion / methane / carbon monoxide

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