Surface OH—density

Thus, the isolated single silanols on thermally treated sample ACi would be located on the ex-GP sites (Table I). The density of these hydroxyls gives an estimate of the density of sites SP-GP on silica A to be about 0.65 per square nanometer. As a consequence, the OH density on initial sample ACi would be about 1.3 per square nanometer. The sum of this value and 2.9 (the methoxyl density) gives a total larger than the surface OH density on silica A. Thus when sample ACi is prepared, some methanol is added to siloxane bonds according to... 

Fig. 3.34 Surface OH —density of aluminas as a function of pretreatment temperature.

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