Effects of the radial distribution of platinum in spherical alumina catalysts on the oxidation of CO in air

Abstract

The oxidation of CO in air has been studied using spherical alumina pellets with varying radial platinum distributions. Shell and homogeneous catalysts have been prepared with the same total amount of platinum. Co-impregnation of chloroplatinic acid and citric acid was used to obtain the homogeneous distribution. Temperature ramp experiments in a flow reactor showed significant differences in light-off behavior for the two catalysts. Compared to the shell catalyst, the conversion of CO started at lower temperatures when using the homogeneous catalyst, but higher temperatures were needed for total conversion. Stedy-state experiments performed in a micro Berty tank reactor with the homogeneous catalyst were used to derive two different kinetic models for the oxidation. One of the kinetic expressions was used to simulate the catalytic activity in a steady-flow reactor system. The maximum temperature gain which can be achieved by placing the active material at the optimum position in the pellet, in comparison to an infinitesimal shell distribution, was found to be 48°C at 95% conversion for 1.0% CO. (C) 2000 Elsevier Science Ltd. All rights reserved.