Mechanical properties of mesoporous silicas and alumina-silicas MCM-41 and SBA-15 studied by N2 adsorption and 129Xe NMR

Purely siliceous and Al-containing MCM-41 and SBA-15 materials have been prepared with pore diameters of 2.4-3.0 nm for MCM-41 and 6.5-7.5 nm for SEA-15. The effect of compression on the mesopore structure has been studied by N-2 adsorption-desorption. X-ray diffraction and Xe-129 NMR experiments. The pore size distributions obtained from NZ adsorption data show that the mesopore structure is partially destroyed and that small size pores are formed at the expense of the original ones (in the loose powder) when the powder is compressed at high pressure (up to 520 MPa). The Xe-129 NMR spectra are interpreted in terms of an exchange between adsorbed Xe tin the channels) and gaseous Xe atoms tin the interparticle spaces), which depends on the particle size and the compaction of the powder. For both MCM-41 and SEA-15 materials. the Al-containing samples are more fragile than the purely siliceous materials. (C) 2001 Elsevier Science B.V. All rights reserved.