Effect of the thermal conductivity of metallic monoliths on methanol steam reforming

• Heat transfer characteristics and MSR performance in monoliths have been studied.
• Axial and radial thermal conduction play an important role in heat transfer and MSR.
• Monolith with lower cell density presents more marked temperature profiles.
• The average monolith temperature increment results in a higher MSR conversion.

We have studied the influence of cell density of two sets of metal monoliths coated with different amounts of Pd/ZnO in the methanol steam reforming (MSR). The results indicate that the conversion increases with increasing size of the channels that is accompanied by a decrease in the monoliths cell density. To explain this unexpected result, the longitudinal and radial temperature profiles were measured. It was observed that the thermal conductivity increased with increasing cell density and temperature profiles became more marked with increasing catalyst loading on the monolith. This last result was explained by the increase of the heat required for the reaction to maintain a constant space velocity. Being fixed central temperature of the monolith and being the MSR an endothermic reaction, the average temperature increases with decreasing thermal conductivity. To assess whether this increase in average temperature justifies the observed increase in conversion, a CFD modeling of the system was performed. The simulation results showed an excellent agreement with experimental values. This confirms the fundamental role of thermal conductivity, which is mainly controlled by the cell density of the monolith.

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