A TPD-MS study of the interaction of coumarins and their heterocyclic derivatives with a surface of fumed silica and nanosized oxides CeO2/SiO2, TiO2/SiO2, Al2O3/SiO2.

The interactions between coumarins and the surface of fumed SiO(2), CeO(2)/SiO(2), TiO(2)/SiO(2) and Al(2)O(3)/SiO(2) were assessed by means of temperature-programmed desorption mass spectrometry. The different stages of the thermolysis of coumarin were identified and an analysis of the underlying reactions was performed. The kinetic parameters of the involved reactions were thus obtained. The decomposition of thiazolyl-substituted coumarins was found to proceed through a 'thiazole-thiazine' ring expansion in the adsorbed state. A linear correlation between the sigma constants (Sigma sigma) of the coumarin substituents and the activation energy of CO(2) formation was obtained.