The surface-treatment of silica gels was performed by the refiux method where the water absorbed in the silica gels was removed previously by boiling them in the long carbon chain hydrocarbon with high boiling point, thereafter an alcohol having a similar boiling point as that of hydrocarbon was added to these suspensions and reacted with silica gels. The effect of surface-treatment by the reflux method on the surface properties, e.g., surface area and pore size distribution was investigated. The followings were confirmed; (1) both the adsorbed amounts of argon at 77K on the silica gels dehydrated in the boiling hydrocarbon and the surface areas showed the decrease in comparison with those of the original silica gel. These trends were appreciable with raising the temperature for dehydration and a 10% decrease was observed in both adsorbed amount on silica gel dehydrated at 250°C and the surface area. (2) both the adsorbed amount on the silica gels treated with alcohol after dehydration and the surface area showed an appreciable decrease according to the degree of surface-treatment and, the length of carbon chain of each surface group. After removing the surface group by the heat treatment, both adsorbed amount and surface area were found to be similar to those of the silica gel dehydrated in the boiling hydrocarbon, but showed still low value in comparison with those of original silica gel. From these results, it would be concluded that the dehydration of silica gels resulted in the surface contraction whereas the reaction of alcohol with silica gel did not affect the surface properties of the substrate.
