ZSM5 growth on a FeCrAl steel support. Coating characteristics upon the catalytic behavior in the NOx SCR

Abstract

The search for more efficient catalytic processes requires the development of new structured catalytic systems. Along these lines, a study was conducted to produce and characterize a structured catalyst composed of an ordered ZSM5 catalytic coating onto an FeCrAl alloy steel support. The film obtained by secondary hydrothermal synthesis without templates was studied by SEM, EPMA, and XRD; then, it was catalytically tested for the SCR of NOx with CH4. The growths were polycrystalline, dense, continuous and fast produced with a noticeable c-axis orientation perpendicular to the support surface. The FeCrAl surface made it possible to produce an adherent, Cr, Al, Fe-enriched coating. The indium-exchanged system had a good performance in the SCR of NOx with CH4 although the NOx to N2 conversion was somehow lower than for the powder catalyst. This could be due to a lower accessibility of the active sites given the unfavorable orientation of the zeolitic channels. On the contrary, the catalyst behavior was better in terms of selectivity to N2 and CO emission, probably due to both the low amount of non-selective indium species and the presence of oxidizing Fe species. The results obtained with this system indicate the importance of considering the crystalline spatial position of the coating and the chemical influence of the support in the search for the optimized performance of a structured catalyst.