porous material for use as component of the catalyst is one having initially after heating at 1000 u00b0 f in air for six hours a surface area greater than about 20 square meters per gram b e t method brunauer emmett and teller see van nostrand chemist 39 s dictionary 1953 edition preferably greater than 100 m 2 g more preferably at least 200 m 2 g and a pore volume greater than about 0 25 cc g desirably the inert porous material has at least 0 2 cubic centimeters per gram pore volume in pores having diameters ranging from about 90 to about 200 angstroms these stated physical characteristics are those of the porous inert material when taken separately after calcining 6 hours at 1000 u00b0 f and prior to being composited with the other components alternatively and optionally an alumina hydrosol or hydrogel or hydrous alumina slurry may be used provided that the ultimate porous inert component when dried and calcined separately has physical characteristics within the above stated ranges the catalysts of the present invention may be prepared by any one of several methods the preferred method of preparing one of the catalysts of the present invention that is a catalyst comprising silica alumina and as porous inert material alumina is to react sodium silicate with a solution of alumina sulfate to form a silica alumina.