Application of Pd/α-Si3N4 catalysts to radiant panels using methane catalytic combustion to obtain infrared emission Original Research Article

Silicon nitride (α-Si3N4)-based radiant panels were prepared using the same process as that used industrially for present day alumina-based radiant panels. They were successfully tested under industrial conditions during the catalytic combustion of methane to obtain infrared emission. Both panels impregnated with palladium operated successfully at high power density (100 kW/m2; 950 °C) for 2500 h (15 weeks). From the first stages of emission, the silicon nitride-based panel exhibits a narrower power density operation range (75–100 kW/m2) than the alumina-based one (63–100 kW/m2). However, during ageing this difference decreases very slightly and after 2500 h of operation we observe a range of 83–100 kW/m2 for the silicon nitride-based panel and a range of 73–100 kW/m2 for the alumina-based one. The same tendency (lower activity of Pd/α-Si3N4) is observed in the laboratory tests during the reaction of total combustion of methane in a flow-reactor. The as-prepared Pd/α-Si3N4 exhibit poor morphological properties (size and distribution of metal particles) compared to those of Pd/alumina. This characteristic accounts for the lower activity of the former catalysts and efforts for further optimising this catalyst are currently in progress. Nevertheless, the silicon nitride-based radiant panels have operated under industrial conditions for 2500 h with rather encouraging performances.