Method for making hydrophobic silica gels under neutral conditions

A method for preparing a hydrophobic silica gel comprising:

• (A) adjusting the pH of a silica hydrosol comprising about 0.02 to 0.5 g of SiO.sub.2 per milliliter with a base to within a range of about pH 3 to pH 7 at a temperature within a range of about 10.degree. C. to 250.degree. C. to facilitate formation of a silica hydrogel and (B) mixing the silica hydrogel with (1) a catalytic amount of a strong acid and (2) an organosilicon compound selected from the group consisting of organosilanes described by formula
• R.sup.2.sub.a H.sub.b SiX.sub.4-a-b
• and organosiloxanes described by formula
• R.sup.2.sub.n SiO.sub.(4-n)/2,
• where each R.sup.2 is independently selected from a group consisting of hydrocarbon radicals comprising about 1 to 12 carbon atoms and organofunctional hydrocarbon radicals comprising about 1 to 12 carbon atoms, each X is independently selected from a group consisting of halogen and alkoxy radicals comprising 1 to 12 carbon atoms, a=0, 1, 2, or 3, b=0 or 1, a+b=1, 2, or 3 with the proviso that when b=1 then a+b=2 or 3, n is an integer of from 2 to 3 inclusive to form a hydrophobic silica hydrogel having a surface area within a range of about 100 m.sup.2 /g to 850 m.sup.2 /g as measured in the dry state.