Polymerization of Formaldehyde and Acetaldehyde on Ordered (WO₃)₃ Films on Pt(111)

Polymerization of formaldehyde, H 2 CO, and acetaldehyde, CH 3 CHO, was studied under ultrahigh vacuum conditions on a model catalyst consisting of an ultrathin WO 3 film supported on Pt(111). The onset of polymerization is observed at very low temperatures of 70 and 80 K for H 2 CO and CH 3 CHO, respectively, as documented by the evolution of the infrared reflection–absorption spectra. The amount of polymer increases with increasing coverage and saturates at 5 and 8 monolayers (ML) for the H 2 CO and CH 3 CHO multilayer films, respectively. Upon heating, the polymers decompose around 250 and 190 K for H 2 CO and CH 3 CHO, respectively, as evidenced mass spectrometrically by the desorption of their monomers and oligomers into the gas phase. The heats of H 2 CO and CH 3 CHO sublimation and polymerization determined on the basis of our experiments are in good agreement with previously published values.