Process for making hydrophobic silica with reduced surface area

Details Process for making hydrophobic silica with reduced surface area Process for making hydrophobic silica with reduced surface area

1998-02-11

1999-08-24

Marquis, Melvyn I.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

423338, 528 30, 528 32, 528490, C08G 7700

Patent

active

059425903

ABSTRACT:
The present invention is hydrophobic silica gels having a reduced surface area and a method for their preparation under neutral conditions. The method comprises two steps, where in the first step the pH of a mixture comprising a silica hydrosol and colloidal silica is adjusted with a base to within a range of pH 3 to pH 6 to facilitate formation of a silica hydrogel having incorporated therein colloidal silica. In the second step the silica hydrogel is contacted with an organosilicon compound in the presence of a catalytic amount of a strong acid to effect hydrophobing of the silica hydrogel to form a hydrophobic silica gel having a surface area within a range of about 100 m.sup.2 /g to 450 m.sup.2 /g in the dry state. In a preferred process the hydrophobic silica gel is contacted with a sufficient quantity of a water-immiscible organic solvent to convert the hydrophobic silica hydrogel into a hydrophobic silica organogel. A water soluble compound of cerium or iron may be added during conduct of the second step to improve heat stability of the hydrophobic silica gel.

REFERENCES:
patent: 4595578 (1986-06-01), Cohen et al.
patent: 5708069 (1998-01-01), Burns et al.

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