Framework and extra-framework aluminium in wet ion exchanged Fe-ZSM5 and the effect of steam during the decomposition of N2O

► 27Al 3QMAS identifies the Al species in hydrated and dehydrated H/Fe-ZSM5. ► Two types of Brønsted acid sites are observed. ► Fe-ions preferentially replace some of the Brønsted acid protons in their charge balancing role. ► Dealumination of Fe-ZSM5 in the decomposition reaction illustrated by 29Si and 27Al MAS NMR. ► Large amounts of water are catalytically detrimental and associated with dealumination.