Enhanced performance of the OMS-2 catalyst by Ag loading for the oxidation of benzene, toluene, and formaldehyde

Abstract

Cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2)-supported Ag (xAg/OMS-2; x = 1.0, 3.0, 5.0, 7.0, 9.0, and 10.0 wt%) catalysts were prepared by a pre-incorporation method. These materials were used as catalysts for benzene, toluene, and formaldehyde oxidation to investigate the effects of support structures on the interaction between Ag and OMS-2 and the catalytic activity. The physicochemical properties of the samples were characterized by XRD, FT-IR, BET, TEM, XPS, O₂-TPD, H₂-TPR, and NH₃-TPD techniques. The results show that the loaded Ag exerted an important influence on the physicochemical properties of the sample. The Ag particles were homogeneously dispersed on the surface of xAg/OMS-2. The catalytic activity of OMS-2 was greatly improved after loading silver. The 9 wt% Ag/OMS-2 sample showed the best activity (T_90% was 362, 270, and 168 °C for benzene, toluene, and formaldehyde oxidation, respectively), which was due to the higher surface Mn³⁺/(Mn⁴⁺ + Mn³⁺) atomic ratio, a greater amount of active oxygen species, better low-temperature reducibility, and higher acidity. It is concluded that the excellent catalytic performance of 9 wt% Ag/OMS-2 was associated with the interaction between the Ag particles and the OMS-2 support.