Deactivation by coking of supported palladium catalysts. Effect of time and temperature Original Research Article

The coking reaction with cyclopentane was investigated on silica supported palladium catalysts in the temperature range 400–500°C at various times. After reaction, the catalysts were characterized by temperature programmed oxidation by the fouling effect of coke on the reaction of cyclohexane dehydrogenation and by infrared spectroscopy of chemisorbed CO. TPO profiles of coked catalysts show the presence of two oxidation peaks corresponding to coke deposition on the metallic function: the first one near 250°C which would correspond to coke deposited on palladium atoms of high coordination number, depends very little on the temperature or the time of the coking reaction. On the other hand, the second TPO peak near 400°C which would involve palladium atoms of low coordination number, is enhanced by an increasing time or temperature of the reaction. These results clearly indicate that low coordinated palladium atoms are more resistant to the deactivation by coke under reforming conditions.