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.

The sensitivity to hydrogen and the catalytic activity in the oxidation of hydrogen of sensor materials based on tin dioxide and doped with cobalt, nickel, iron, and copper have been studied. The sensitivity of the sensors and the degree of conversion of hydrogen pass symbatically through a maximum with increasing quantity of each of the dopants. The results are explained by the influence of grain boundaries between tin dioxide and the dopants applied during the course of the oxidation reaction of hydrogen on the sensor material and on the sensitivity of the sensor to H 2 .Adsorption-semiconductor sensors based on metal oxides are widely used to measure the concentration of hydrogen in air [1][2][3][4].The aim of the present work was to investigate the sensitivity to hydrogen and the catalytic activity in the oxidation of hydrogen of sensor materials based on tin dioxide, alloyed with antimony doped with 3d metals (Co, Cu, Ni, Fe).The sensor materials were prepared by co-precipitation of tin and antimony hydroxides, drying, calcining in air at 973 K, and crushing to size of 40 mm. Samples were impregnated with hydrochloric acid solutions of Co, Cu, Ni, and Fe salts of different concentrations and fused in air at 863 K. Catalysts were prepared from the sensor materials formed into tablets and ground into 0.25-0.5 mm granules. The content of the 3d metals in the samples was determined by atomic absorption spectroscopy, the values of the specific surfaces (S sp ) were determined from the heat of absorption of argon. The state of the elements and their content in the surface layer of the samples were determined by XPS (Kratos-800 XPS spectrophotometer). The catalytic activity of the samples was determined on a flow set-up at atmospheric pressure in a gas mixture containing 0.004 vol.% H 2 and 20 vol.% O 2 . H 2 was determined chromatographically (Shimadzu GC-14B chromatograph). The degree of conversion of hydrogen at a given temperature served as a measure of the catalytic activity. Kinetics of the oxidation of H 2 were studied in a gradient-less reactor. The H 2 concentration was varied from 1.1·10 -4 to 6.7·10 -4 mol/L at an O 2 concentration of 8.9·10 -3 mol/L, an O 2 concentration was 1.1-8.9·10 -3 mol/L with an H 2 concentration of 4.5·10 -4 mol/L. Study of the kinetics was carried with 40-65% conversion of hydrogen.The sensors consisted of ceramic plates with a platinum heater and measuring electrodes, between which there is a gas-sensitive layer [5] based on a paste of a finely divided powder of the sensor material. The ratio of the electrical resistance of 128 0040-5760/08/4402-0128

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