MCM-41, MCM-48 and related mesoporous adsorbents: their synthesis and characterisation

MCM-41, MCM-48, MCM-41 analogue materials and disordered silica xerogels we re compared with respect to their long range and short range order, their s pecific surface area, pore structure and pore structural parameters, pore w all thickness and their surface hydroxyl group concentration. Based on X-ra y diffraction data it could be seen that the degree of long range order dec reased in the order MCM-41 > MCM-48 > MCM-41 analogues > amorphous silica x erogels. The particle porosity and pore wall thickness increased in the sam e sequence such that MCM-41 analogues and amorphous silica xerogels were mo re stable towards water and water vapour. The concentration of the surface hydroxyl groups increased when moving from MCM-41 to amorphous silica xerog els from 3 mu mol OH per m(2) (MCM-41, MCM-48) to 5-6 mu mol OH per m2 (MCM -41 analogue) and 8-9 mu mol OH per m(2) (amorphous silica xerogel). Rehydr oxylation of the materials (after calcination at 823 K) resulted in the los s of periodic structure for MCM-41. In contrast to this, the MCM-41 analogu e retained both its periodic structure and the concentration of surface hyd roxyl groups, alpha (OH). (C) 2001 Elsevier Science B.V. All rights reserve d.