Facile synthesis of uniform FeZSM-5 crystals with controlled size and their application to N2O decomposition

FeZSM-5 zeolites with crystal sizes ranging from 70 nm to 20 μm were synthesized by adjusting the alkalinity of the synthesis system and optimizing the crystallization conditions. After steam-activated treatment, these zeolites were used as catalysts in the direct decomposition of N2O, showing that the larger the zeolite crystal size, the higher the reaction temperature required for the complete decomposition of N2O. Moreover, N2O decomposition over the FeZSM-5 catalysts with crystal sizes larger than 5 μm at high temperatures shows that the conversion of N2O decreases with increasing the zeolite crystal size, implying that the internal mass transfer limitations are available. However, under the applied conditions, the diffusion limitations are absent and the observed reaction rates are controlled by the intrinsic kinetics of N2O decomposition over the FeZSM-5 catalysts with crystal sizes smaller than 2 μm.

The conversion of N2O over FeZSM-5 catalysts at 525 °C decreases with increasing the zeolite crystal size.Figure optionsDownload as PowerPoint slideHighlights
► Tailored synthesis of FeZSM-5 crystals with different sizes.
► Investigation on internal mass transfer limitations for N2O decomposition.
► The crystal size of FeZSM-5 significantly affects its observed activity.
► Diffusion limitations are available over the zeolite crystals larger than 5 μm.