Formaldehyde Polymerization on (WO3)3/TiO2(110) Model Catalyst

Polymerization of formaldehyde, H2CO, was studied under ultrahigh vacuum conditions on a model catalyst consisting of monodispersed (WO3)(3) clusters anchored on TiO2(110). Formaldehyde oligomers, (H2CO)(n,) desorbing from the polymer that formed on the catalyst surface are detected between 250 and 325 K in ten-me:mime-programmed desorption experiments. At least two monolayers (ML) of H2CO tire required on the surface to observe (H2CO)(n), desorption and the amount saturates for H2CO coverages excess of similar to 40 ML. The presence of H2CO multilayers is required for the polymerization to take place indicating that it had to occur below 100 K. The saturation amount increases with increasing coverage of (WO3):( clusters with the highest amount of similar to 13 ML observed on 1.2 (WO3)(3)/nm(2). No (H2CO)(n) desorption was observed on the bare TiO2(110) surface.