Hydrophobic-Organophilic Silica Powders

This discussion is limited to silica powders which have been surface-modified by chemisorbed molecules that profoundly change the adsorption characteristics or 

In more recent times interest in surface-modified silicas has increased in connection with adsorbents and column packings for gas and liquid phase chromatography. There are five types of surface modifications that have received attention  

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A partly hydrophobic and organophilic silica can be made very simply by a process patented by Goebel (507b). Fine silica powder is dehydrated and the surface dehydroxylated to an optimum degree by heating it for 1.5 hr in air at 470-530 C. The BET area was 297 m g" but the resulting specific hydroxylated area was 184 m g . When this powder was cooled and refluxed at 118 C in butanol at atmospheric pressure or even when simply exposed to butanol vapor in a closed container for a week, esterification occurred and the surface became about half covered with attached butoxy groups. 

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