Catalytic performance and mechanism of a Pt/TiO2 catalyst for the oxidation of formaldehyde at room temperature

The performance of TiO2 supported noble metal (Pt, Rh, Pd and Au) catalysts was examined and compared for the catalytic oxidation of formaldehyde (HCHO). Among them, the Pt/TiO2 was the most active catalyst. The effects of Pt loading and gas hourly space velocity (GHSV) on Pt/TiO2 activity for HCHO oxidation were investigated at a room temperature (20 degrees C). The optimal Pt loading is 1 wt.%. At this loading, HCHO can be completely oxidized to CO2 and H2O over the Pt/TiO2 in a GHSV of 50,000 h(-1) at 20 degrees C. The 1% Pt/TiO2 was characterized using BET, XRD, high resolution (HR) TEM and temperature programmed reduction (TPR) methods. The XRD patterns and HR TEM image show that Pt particles on TiO2 are well dispersed into a size smaller than 1 nm, an important feature for the high activity of the 1% Pt/TiO2. The mechanism of HCHO oxidation was studied with respect to the behavior of adsorbed species on Pt/TiO2 surface at room temperature using in situ DRIFTS. The results indicate that surface formate and CO species are the main reaction intermediates during the HCHO oxidation. The formate species could decompose into adsorbed CO species on the catalyst surface without the presence Of O-2, and the CO was then oxidized to CO, with the presence of O-2. Based on these results, a simplified mechanism for the catalytic oxidation of HCHO over 1% Pt/TiO2 was proposed. (c) 2006 Elsevier B.V. All rights reserved.