Density functional theory was employed to study the hydrothermal stability of P-modified ZSM-5 zeolites using cluster models. The calculations of hydrolysis energies indicated that the introduction of phos-phorus increases the hydrothermal stability of ZSM-5 zeolites. The initial paths of dealumination were studied with explicit water molecules. It was found that the framework Al-O coordination bond can be replaced by coodination bonds between water molecules and the aluminium. One to three water molecules can form coordination bonds with framework Al and release energies. The P-modification restrain the dealumination. The calculated 27Al NMR chemical shifts for the obtained structures are consistent with the experimental measurements.
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