The performance of titania-supported Wacker catalysts in the oxidation of 1-butene

The kinetics of l-butene oxidation over titania-supported catalysts has been investigated. The reaction rate shows a first-order dependence on I-butene and water coverage at low partial pressures. At higher partial pressures of water in the feed the reaction rate first strongly increases and then levels off, when the water coverage exceeds a monolayer, probably due to partial dissolution of PdSO4. The concentration of dioxygen in the feed has a slight positive influence on the activity up to 15 kPa. Heterogeneous Wacker catalysts consist of a palladium salt deposited on a vanadium pentoxide layer on a support material such as titania. The composition of the catalyst appears to be of major influence on its performance. For palladium acetate-based catalysts the activity shows a first order in the palladium coverage. The activity of the catalysts decreases with increasing vanadium oxide coverage. Temperature programmed reduction (TPR) shows that the reduction temperature of the vanadium oxide overlayer increases with increasing coverage. The easiness of reducibility of the titania-supported catalysts in comparison to the alumina-based ones is directly related to the one order of magnitude higher activity of the tinania-based catalysts. On oxidizing 1-butene to butanone, the activity of titania-supported catalysts decreases by approximately 60% during the first 100 h of operation. After this initial deactivation, the activity and selectivity of the catalyst remains stable for more than 700 h. TPR and high resolution electron microscopy (HREM) show that this deactivation is mainly caused by a slight sintering of the vanadium oxide layer.