Aluminosilicate MCM-48 materials with enhanced stability via simple post-synthesis treatment in water

Abstract

The hydrothermal and mechanical stability of aluminosilicate MCM-48 may be remarkably enhanced by post-synthesis treatment of the as-synthesised materials in water. To obtain materials with enhanced stability, as-synthesised aluminosilicate MCM-48 samples, prepared via direct mixed-gel synthesis, were subjected to further hydrothermal treatment in water at various temperatures prior to calcination. The stability of the (calcined) treated materials, in boiling water and after compaction at high pressure, was investigated using a variety of techniques including powder XRD, N 2 sorption studies and elemental analysis. The stability of the treated materials was found, in all cases, to be higher than that of the primary materials. The improvement in stability was dependent on the temperature and duration of the post-synthesis treatment and was observed to go through a maximum within the temperature range 120–165 °C. The optimum post-synthesis temperature for enhancing stability was found to be 150 °C. The effect of the post-synthesis treatment on both the mechanical and hydrothermal stability is related to pore wall thickening and increased crosslinking within the aluminosilicate framework of the treated MCM-48 materials.