Regulating catalytic stability of PtSnM/CeO2 (M = Mn, W, Nb) catalysts via the closely coupled multi-active sites to promote multicomponent VOCs oxidation

Abstract

Pt-based commercial catalysts tend to be poisoned by chlorine species in the oxidation of chlorinated volatile organic compounds (CVOCs), which greatly limits their wide applications. It is vital to develop the active catalysts with good chlorine resistance. In the present work, the novel supported ternary metallic catalysts (PtSnM/CeO2; M = Mn, W, Nb) with the closely coupled multi-active sites show good catalytic performance and excellent chlorine resistance for the oxidation of toluene and chlorobenzene (CB), and can effectively inhibit formation of the toxic chlorine-containing by-products. The catalytic activity for toluene oxidation in the mixed VOCs system follows the sequence: PtSnMn/CeO2 > PtSnW/CeO2 ≈ PtSnNb/CeO2 > PtSn/CeO2 > Pt/CeO2. The change of the electron structure around Pt results in the difference in adsorption capacity of toluene and CB. The C−Cl bond is first dissociated at the Brønsted acid sites, and the non-chlorinated organic compounds are oxidized at the Pt sites that contact with the acid sites in the proximity. Additional water provides sufficient protons to react with Cl species, enhancing the desorption amount of HCl; furthermore, the water also reacts with the adsorbed oxygen to generate new oxygen species, which participates in the oxidation of VOCs, so as to accelerate the removal of Cl species on the catalyst surface and reduce the more toxic polychlorine by-products. This work is helpful for developing the supported noble metal catalysts with good chlorine-resistant performance in the oxidation of multicomponent VOCs under the actual industrial conditions.