Characterisation, surface hydrolysis and nitrogen stability in aluminophosphate oxynitride (AlPON) catalysts

摘要: Abstract Solid amorphous aluminophosphate oxynitride (AlPON) catalysts with a nitrogen content ranging from 0% up to 20% N (w/w) have been obtained by reaction between AlPO4 and NH3 at 800°C. Samples are analysed X-ray photoelectron (XPS) diffuse reflectance Fourier transform infrared (DRIFTS) spectroscopies, mass spectrometry (MS) thermogravimetry (TG). Similar that of AlPO4, AlPON local structure is pictured as network PO4 AlO4 tetrahedra in which preferentially replaces oxygen bonded phosphorous, although some contribution Al–N bonds an AlON phase also proposed. Nitridation stages yielding [PO3N] [PO2N2] building units characterised below 7.2% above 11% (w/w), respectively. Also terminal –PNH2 groups detected early nitridation stages. Freshly prepared readily undergo hydration (10–15% weight) hydrolysis atmospheric conditions. Hydration more intense on low containing samples sharply decreases (w/w). Ammonia the product both surface bulk decomposition. Hydrolysis almost independent while decomposition grows parallel percentage. Bulk 500°C than always involves either condensation around 230–240°C or through water 320–340°C. Condensation depends coverage preferred mechanism high AlPON.