NITROGEN ADSORPTION AND SMALL-ANGLE NEUTRON-SCATTERING STUDIES WITH CAPPED ALUMINA

Nitrogen isotherms at 77 K have been measured for a series of gamma-aluminas with different particle sizes and organic capping groups. The isotherms were all of IUPAC Type IV in shape with Type H1 hysteresis. Different particle sizes did not alter the isotherms, whereas the addition of a capping group to the surface resulted in a reduction in the amount of nitrogen adsorbed. Calculations of the BET surface areas and pore size were in reasonable agreement with results from a small-angle neutron scattering (SANS) analysis, although SANS did not observe any surface capping groups. Thus SANS may be of use for surface area determinations where adsorption studies are inappropriate. The pores were shown to be homogeneous and predominantly spherical in shape.