An in-situ DRIFTS study of acetone adsorption mechanism on TiO2 nanoparticles.

In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) has been used to investigate the adsorption and catalytic reaction of acetone on TiO2 surfaces. The adsorption of acetone has been investigated on hydrated (as-received from the provider) as well as dehydrated TiO2 nanoparticles. On both samples, acetone shows absorption bands results from the vibrational modes of acetone adsorbed molecules. The DRIFTS spectra indicate that acetone goes into a self-condensation reaction then it dehydrated yielding mesityl oxide. Formation of formaldehyde was observed only on as received sample and it was probably activated as a result to suppress mesityl oxide formation. This suppressed formation is a result of the existence of adsorbed H2O on the surface of as received TiO2. Adsorbed water is not favorable for aldolization/dehydration reaction because it can block the active sites for mesityl oxide formation. Outcomes of the current study provide fundamental insight into acetone adsorption and catalytic reaction on TiO2 nanoparticles. Specifically, this investigation demonstrates the adsorption mechanism of acetone on TiO2 surface and the role of presenting hydroxyl group on the TiO2 surface.