Temperature excursions in reactors packed with segregated layers of catalyst and inert solids

A recent numerical studies by Yakhnin and Menzinger (Proc. 8th Int. Symp. o n Catalyst Deactivation, Brugge, Belgium, 10-13 October, Vol. 126, 1999, pp . 291-298) suggests that activity inhomogeneity in a catalyst bed can creat e larger temperature excursions after changes in feed temperature than woul d be encountered in beds with homogeneous catalyst activity. Until now, thi s finding has not been confirmed experimentally. Inhomogeneous catalyst act ivity was simulated by constructing a packed bed reactor by successive laye rs of catalyst and the inert support. Oxidation of carbon monoxide (CO) wit h oxygen in a nitrogen carrier gas over an industrial 0.2 wt% Pt/gamma -alu mina catalyst was employed. This reaction is exothermic and inhibited by CO . Step changes and periodically varying inlet temperature were used to gene rate disturbances. Both wrong-way behaviour and differential flow instabili ty were observed. Temperature excursions in the layered bed significantly e xceeded those in a bed of homogeneous activity at the same operating condit ions. (C) 2001 Elsevier Science Ltd. All rights reserved.