Deactivation and decoking of a naphtha reforming catalyst

Abstract

Summary The kinetics of decoking of two commercial naphtha reforming catalysts (Pt-Re-Al 2 O 3 ) were investigated under isothermal conditions as well as with the non-isothermal ignition point method. The reaction rate of decoking is first order with respect both to the concentration of oxygen and to the carbon load. Two types of coke can be distinguished: A very reactive coke, which is rapidly burned off, and a coke, which is by a factor of 100 less reactive. The amount of the more reactive coke, which is (according to literature) formed on the metal sites, is small (0.3 g c /100 g cat ), The decoking process is therefore determined by the reactivity of the coke formed on the acidic sites, especially for initial carbon loads, which are typical for the decoking of an industrial catalyst (>10 g c /100 g cat ). The reactivity of the coke, which is almost equal for both catalysts, is quite high and in the order of a typical activated char coal. The kinetic parameters (activation energy, pre-exponential factor) are given. At temperatures of more than 400°C, pore diffusion limitations have to be considered. External diffusion limitations can be neglected, at least for temperatures of technical relevance, as the temperature should not exceed 550°C to avoid an irreversible deactivation of the catalyst.