The Catalytic Oxidation of Hydrogen on Titanium Dioxide; Anatase and Rutile

Abstract

Abstract To clarify the reaction mechanism of catalytic oxidation of hydrogen on titanium dioxide, the rate of catalytic oxidation of hydrogen by oxygen and the reduction rate of titanium dioxide by hydrogen have been measured by a static method in temperature range of 400–650°C at 10−2 mmHg. The results were compared with those of carbon monoxide which were reported in the previous papers. The oxidation reactions of hydrogen on anatase and rutile were first order with respect to hydrogen and independent of the oxygen pressure. The oxidation rate was almost the same as the reduction rate of titanium dioxide by hydrogen. The activation energy was 29.2 kcal/mol for anatase and 17.8 kcal/mol for rutile, and the difference between these values for two crystal forms was nearly equal to that of the oxidation of carbon monoxide. Therefore, it may be considered that the mechanism of oxidation of hydrogen is analogous to that of carbon monoxide. The electric conductivity of the catalyst during the oxidation of hydrogen was larger than that in oxygen at the same temperature, and was still larger than that during the oxidation of carbon monoxide except for a few cases on anatase. There were close correlations between the electric conductivity and the amount of active oxygen of the catalyst and the reduction rate constant of titanium dioxide by both hydrogen and carbon monoxide.