Hebei Provincial Key Laboratory of Green Chemical Technology and Efficient Energy Saving, School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130, China
Abstract To clarify the reaction mechanism of n-butyraldehyde self-condensation catalyzed by anatase TiO2, the catalysis of acidic sites and basic sites was investigated by the combination of in situ Fourier transform-infrared spectroscopy (FT-IR) analysis and poisoning acidic or basic sites on TiO2 surface by a probe molecule. The adsorption behavior of gaseous n-butyraldehyde molecule and the variation of reaction species on TiO2 surface indicated that two n-butyraldehyde molecules were adsorbed separately on Ti4+ and Ti-OH active sites and then reacted to 2-ethyl-2-hexenal. NH3 and CO2 were respectively used as the probe molecule to poison the acidic and basic sites on TiO2 surface and the catalytic performance of the poisoned catalyst for n-butyraldehyde self-condensation was evaluated to clarify the role of the acidic and basic sites. The results showed that the acidic sites played a major catalytic role while the basic sites promoted side-reactions. On this basis, the reaction mechanism of n-butyraldehyde self-condensation catalyzed by anatase TiO2 was established.
