Synthesis and characterization of a new oxynitride catalyst: The ZrPON solids

A new family of phosphate oxynitrides can be prepared by nitridation of X-ray amorphous zirconophosphate precursors under ammonia flow. By varying both nitridation time and temperature, ZrPON oxynitrides with different wt% nitrogen content were obtained. Acid-base characterizations have shown that the substitution of nitrogen for oxygen modifies their surface properties. It has thus been evidenced that the surface acidity sharply decreases with bulk nitrogen enrichment. The condensation rate in the Knoevenagel reaction also heavily depends on O/N ratio. (C) 1997 Elsevier Science Limited.