A study of hydrothermal stability, performed in boiling water under static conditions, of
MCM-41 materials containing different titanium content, prepared by direct synthesis at ambient
temperature and pressure, using tetraethoxysilane, titanium ethoxide and octadecyltrimethylammonium
bromide is presented. The behaviour is compared with pure silica grades prepared by a
similar procedure. The samples were characterised by X-ray diffraction, adsorption of nitrogen at
77K and diffuse reflectance UV–Vis spectroscopy. It was found that the stability improves as the
amount of titanium increases and that Ti-MCM-41 samples prepared with Si/Ti≤50 are significantly
stable. After 12h in boiling water the pore size uniformity was practically maintained and only a
small decrease in pore volume (5-9%), total surface area (2-7%) and mesopore width (3%) and a
slight increase in pore wall thickness (3-6%) occurred. In contrast, some degradation of the MCM-
41 structure for the pure silica and the lower Ti content (Si/Ti=100) samples was observed with the
effect being less pronounced for the latter. The higher hydrothermal stability of titanium substituted
samples is probably correlated with a higher degree of polymerisation of the pore walls and with the
presence of extra framework titanium
