Thermally stable phosphate containing alumina precipitates and their method of preparation

A method of preparing a thermally stable composite precipitate containing from 10 to 60 mole percent alumina and from 40 to 90 mole percent aluminum phosphate, which comprises:

• forming a first aqueous solution of aluminum cations and PO.sub.4.sup.--- anions wherein the molar ratio of the PO.sub.4.sup.--- anions to the aluminum cations is 0.82:1 to 0.25:1;
• neutralizing said first aqueous solution with ammonia gas or a second aqueous solution of an ammonia based material selected from the group consisting of ammonium hydroxide, ammonium carbonate, ammonium bicarbonate or urea in such a manner that the pH of the combined first aqueous solution and the neutralizing medium is controlled in the range of 7 to 10.0;
• recovering said precipitate;
• drying said precipitate;
• and
• calcining said precipitate at a temperature from 300.degree. C. to 500.degree. C. for a time up to 16 hours to form an amorphous aluminum phosphate composite material having a surface area from about 100 to about 200 m.sup.2 /g, an average pore radius from 75 to 150 A and wherein no more than a 30% decrease in surface area is obtained if said composite precipitate is calcined at 500.degree. C. for 16 hours and further calcined at a temperature up to about 900.degree. C. for up to 16 hours.