A study on the thermal behavior of structured plate-type catalysts with metallic supports for gas/solid exothermic reactions

The heat transfer characteristics of seven different samples of coated plate-type structured catalysts with highly conductive metallic supports were investigated using the model reaction of CO oxidation over Pd/gamma -Al2O3. In the case of supports made of aluminum hot spot temperatures were moderate, and the thermal behavior of the structured catalysts was solely controlled by the heat transfer resistance at the interface between catalyst and reactor wall. Temperature gradients were markedly more significant in the case of a support with identical geometry but made of steel, due to a tenfold reduction of the intrinsic material conductivity. They were still greater in the case of a steel support with thinner plates. For aluminum supports, experiments with a fourfold more active catalytic washcoat and with a modified configuration of the structured support confirmed that an isothermal behavior is approached even for conditions corresponding to an adiabatic temperature rise of about 800 degreesC, and that such results can be scaled up to different geometries of the structured systems if the washcoat-to-support volume ratio is conserved. Finally, the wall heat transfer coefficient was enhanced by a design of the aluminum support with improved thermal contact at the wall. A simple 1D analysis, based on independent intrinsic kinetics, yielded estimates of the overall wall heat transfer coefficient in the range 80-120 W/(m(2) K). (C) 2000 Elsevier Science Ltd. All rights reserved.