Preparation of catalysts of predetermined pore size distribution and pore volume

Claim 1

In a process for preparing a catalyst comprising a Group VI-B or Group VIII metal, or both, composited with alumina, the alumina being precipitated as an alumina hydrogel from a solution which contains a hydrous form of alumina and a compound having an anion soluble in an alkaline medium and which forms a soluble aluminum salt, the improvement comprising precipitating the hydrogel of alumina at temperatures ranging from about 15° F to about 120° F from the solution, which contains alumina in concentration ranging from about 1 to about 5 percent, based on the weight of solution, at pH ranging from about 8 to about 12, separating the alumina hydrogel from the solution, contacting the alumina hydrogel with a solution of a water-soluble polymer containing from about 2 to about 24 monomer units from the group consisting of (a) polyethylene glycols, (b) polypropylene glycols, and (c) polyethylene amines sufficient to absorb the polymer into the pores of the alumina hydrogel, displacing water from the pores until the weight ratio of polymer:alumina within the hydrogel ranges from about 0.5:1 to about 4:1, drying the hydrogel, and then calcining the dried hydrogel to form a gamma alumina catalyst composite characterized, when the catalyst is of size ranging from about 1/50 inch up to 1/25 inch average particle size diameter, at least about 15 percent of its total pore volume of absolute diameter within the range of about 150A to about 250A; when the catalyst is of size ranging from about 1/25 inch to about 1/8 inch average particle size diameter, at least about 15 percent of its total pore volume of absolute diameter within the range of about 175A to about 275A; wherein, in each of these catalysts of differing ranges of particle size distributions, the pore volumes resultant from pores of 50A, and smaller, are minimized; the surface areas and pore volumes of the catalysts being interrelated with particle size, and pore size distributions, surface areas ranging at least about 200 m 2 /g to about 600 m 2 /g with pore volumes ranging from about 0.8 to about 3.0 cc/g (B.E.T.).