On the interpretation of temperature programmed reduction patterns of transition metals sulphides

Transition metal sulphides show the temperature programmed reduction (TPR) patterns consisting of multiple reduction domains: those at lower temperatures are attributed to the "weakly bonded" sulphur, whereas the "bulk reduction" peaks are usually placed at high temperatures. The present paper is focusing attention on the last type TPR maxima. Due to the positive free energy of reduction of catalytically important sulphides, their TPR at high temperatures is controlled by thermodynamics. For several bulk and supported sulphides, the ascending branch of the "bulk reduction" event might be transformed to a linear (ln[H2S]-1/T) plot from which standard enthalpy of reduction can be reliably extracted with good precision. Thermodynamics of sulphur abstraction from mixed sulphides (Mo-W sulphides, chromium thiospinels), or from highly dispersed bulk and supported systems can be estimated and compared using this approach. (c) 2006 Elsevier B.V. All rights reserved.