In situ FTIR Study of the Adsorption of Formaldehyde, Formic Acid, and Methyl Formiate at the Surface of TiO2 (Anatase)

Abstract

The catalytic properties of TiO2 (anatase) in the reactions of formaldehyde oxidation and formic acid decomposition are examined. At 100–150°C, formaldehyde is converted into methyl formate with high selectivity regardless of the presence of oxygen in the reaction mixture. Formic acid is decomposed to CO and water. Surface compounds formed in the reactions of formaldehyde, formic acid, and methyl formate with TiO2 (anatase) are identified by in situ FTIR spectroscopy. In a flow of a formaldehyde-containing mixture at 100°C, H-bonded HCHO, dioxymethylene species, bidentate formate, and coordinatively bonded HCHO are observed on the TiO2 surface. In the adsorption of formic acid, H-bonded HCOOH and two types of formates (bidentate and unsymmetrical formates) are formed. In the adsorption of methyl formate, H-bonded HCOOCH3, HCOOCH3 coordinatively bonded via the carbonyl oxygen, and bidentate formate are identified.