Influence of the preparation method on the properties of Fe-ZSM-5 for the selective catalytic reduction of NO by n-decane

The selective catalytic reduction of NO by n-decane was studied on Fe-ZSM5 catalysts prepared by chemical vapor deposition and solid-state ion exchange from FeCl₃, ligand exchange from iron acetylacetonate in toluene, and impregnation or ion exchange with iron nitrate in water. These catalysts were characterized using a wide variety of techniques. Activity tests were carried out by temperature-programmed surface reaction (TPSR) or at steady state. The most active materials were those characterized by the presence of iron species reducible at approximately 640 K, and assigned to cationic iron oxo species such as [(OH)-Fe-O-Fe-(OH)]²⁺. The NO conversion during steady-state experiments was lower than in TPSR tests, due to the build-up of a carbonaceous deposit. Water and SO₂ reversibly poisoned the NO conversion.