Highly conductive “packed foams”: A new concept for the intensification of strongly endo- and exo-thermic catalytic processes in compact tubular reactors

We report a preliminary assessment of the heat transfer properties of innovative structured tubular reactors based on the conductive "packed foams" concept. In such reactors the catalyst is loaded in the form of small pellets packed in the voids of a highly conductive open-cell foam. This enables a catalyst inventory which is significantly higher than that of reactors loaded with the same structured substrate washcoated with catalytic material, while still exploiting the potential of enhanced heat removal through a highly conductive structured skeleton. By comparing the heat transfer performances of the packed foams with those of conventional packed beds of pellets and with those of bare (naked) open cell-foams, we show that the presence of the conductive foam within the packed bed of pellets grants optimal heat transfer performances as a result of a synergy between the enhanced conductive heat transfer in the solid structure of the foam and the effective heat transfer at the wall-bed boundary typical of packed beds. The former mechanism, which is flow independent, controls the effective radial conductivity. The latter one enhances the wall heat transfer coefficient and contributes to increase the overall heat transfer coefficient, particularly at high flow rates. This opens new perspectives for the intensification of highly exothermic/endothermic catalytic processes which require greater catalyst inventories in the reactor than those achievable with washcoated open-cell foams.