Relationship between Pt particle size and catalyst activity for catalytic oxidation of ultrahigh-concentration formaldehyde

The effects of particle size and kinetics of Pt/activated carbon (AC) catalysts on catalytic oxidation of formaldehyde (HCHO) were investigated. AC, f-SiO 2 and MCM-41 were used as supports to prepare low-Pt-content catalysts using H 2 reduction. Pt/AC catalyst shows the highest activity with the largest Pt particle size. By contrast, 0.1 wt% Pt/AC reduced using KBH 4 has much higher activity than that reduced using H 2 , which can oxidize HCHO completely over 6000 ppm at 60°C in a fixed bed reactor. Transmission electron microscopy and X-ray photoelectron spectroscopy results indicate that Pt/AC-KBH 4 has larger Pt particles and lower valence state than Pt/AC-H 2 , which may be attributed to the ligand effect between Pt 4+ and the AC support. The result of O 2 temperature-programmed oxidation suggests that highly dispersed Pt 4+ ions have stronger interaction with AC support and thus are harder to be reduced by H 2 . Furthermore, Pt/AC is structure-sensitive and larger-sized Pt particles result in a high conversion of HCHO. Investigation of kinetics indicated that it is a zero-order reaction for such a high HCHO concentration condition for Pt/AC-KBH 4 .