Phosphating alumina: A way to tailor its surface properties

Phosphated alumina with new surface properties was prepared by sol–gel synthesis. Aluminum coordinately unsaturated sites (CUS) were promoted and tuned through phosphate addition. Two phosphate species on alumina were disclosed by 31P MAS NMR spectroscopy. The population of aluminum CUS was related to the amount of phosphorus incorporated into the alumina network. The relative amount of phosphorus species was controlled by the alumina gel’s aging time. X-ray diffraction, performed on calcined solids, identified a microcrystalline structure of γ-alumina. Phosphated aluminas showed both high surface areas (364–394 m2/g) and total pore volume (1.0–1.2 cm3/g), even after calcining at 550 °C.