Solid‐State MAS NMR Study of Hydrated/Dehydrated Phosphorus‐modified ZSM‐5 Zeolite

Abstract

The chemical changes of the phosphorus‐modified ZSM‐5 zeolites in hydration/dehydration processes have been studied by using the solid‐state MAS NMR spectroscopy. The identification of the chemical species of the steamed or washed zeolite could be done by analyzing the spectral changes on the solid‐state multinuclear MAS NMR spectroscopy when the zeolite was hydrated and dehydrated. It was reconfirmed that the steaming process effectively remove Al‐attached polyphosphates from the zeolite framework even though the zeolite was modified with phosphorus but the washing process did not. Dehydration process led to a dramatic change of aluminum species by breaking the aluminum‐oxygen bond in the zeolite framework and to a formation of polyphosphate attached to aluminum.