Two-phase porous silica: Mesopores inside controlled pore glasses

The structural and textural properties of "Two-Phase Porous Silica" consist ing of a mesoporous pore system formed by finely dispersed silica-gel insid e the original pores of a macroporous glass framework have been carefully i nvestigated. Nitrogen adsorption at 77 K, Mercury Intrusion, Small Angle X- ray Scattering (SAXS), Temperature-Programmed Desorption (TPD) of ammonia a nd Al-27 MAS NMR spectroscopy were used. Different mesoporous glasses inves tigated show BET surface areas up to 300 m(2)/g, a total pore volume of abo ut 0.16 cm(3)/g and pore sizes of <2-10 nm, depending on the acid leaching conditions of the phase-separated sodium borosilicate initial glass. The te xture of the macroporous "frame" glass was characterized after removing the mesoporous finely dispersed silica-gel phase with alkaline solution. Leach ing of the phase-separated initial glass with Al(NO3)(3) solution and follo wed by thermal treatment lead to the formation of Bronsted acid sites at th e surface of the resulting mesoporous glasses by an incorporation of alumin ium in tetrahedral coordination in the silica framework. (C) 2001 Kluwer Ac ademic Publishers.