Method of preparing low density-high micropore volume refractory inorganic oxide particles

Claim 1

A method of preparing spherical particles of alumina having an average bulk density of from about 0.1 to about 0.6 grams per cubic centimeter, with from about 0.7 to about 5.0 cubic centimeters per gram of the total pore volume being associated with pores having an average diameter of less than about 600 Angstroms, said method comprising the steps of: a. effecting the gelation of a hydrosol of said alumina in admixture with ammonia in a hot oil bath to form hydrogel spheres; b. percolating a water-miscible alcohol through said hydrogel spheres at a temperature of from about 20° to about 50° C. until the effluent alcohol is substantially free of acquired water; c. thereafter evaporating the resulting water-alcohol solution from the hydrogel spheres at a pressure of from about 300 to about 600 millimeters of mercury and at a temperature substantially equivalent to the boiling point of said alcohol-water solution at said pressure; d. further drying said spheres in a substantially water-free atmosphere to produce spheres characterized by less than about 10 wt. % loss on ignition at 900° C.; and e. calcining the dried spheres at a temperature of from about 425° to about 750° C. in a substantially water-free atmosphere.

Claim 2

A method of preparing spherical particles of alumina having an average bulk density of from about 0.1 to about 0.6 grams per cubic centimeter, with from about 0.7 to about 5.0 cubic centimeters per gram of the total pore volume being associated with pores having an average diameter of less than about 600 Angstroms, said method comprising the steps of: a. effecting the gelation of a hydrosol of said alumina in admixture with ammonia in a hot oil bath to form hydrogel spheres; b. percolating a water-miscible alcohol through said hydrogel spheres at a temperature of from about 20° to about 50° C. until the effluent alcohol is substantially free of acquired water; c. thereafter evaporating the resulting water-alcohol solution from the hydrogel spheres at a pressure of from about 300 to about 600 millimeters of mercury and at a temperature substantially equivalent to the boiling point of said alcohol-water solution at said pressure; d. further drying said spheres in a substantially water-free atmosphere to produce spheres characterized by less than about 10 wt. % loss on ignition at 900° C.; and e. calcining the dried spheres at a temperature of from about 425° to about 750° C. in a substantially water-free atmosphere.