The thermal and chemical stability of a titanium-substituted MCM41 (TiMCM-41) with Si/Ti mole ratio of 39 and pore diameter of 2.4 nm was studied with the small-angle X-ray diffraction and X-ray absorption near-edge structure techniques. The TiMCM-41 was stable in helium flow below 1273 K and under gas-phase reaction conditions of ethanol dehydrogenation (ethanol/O-2 = 1 mol/mol, 373-723 K). Under liquid-phase reaction conditions of phenol hydroxylation (phenol/35% H2O2/acetone in moles = 3 : 1 :7, 333 K), however, it lost the MCM-41 structure and titanium was leached out of the silicalite framework.