Synthesis and characterization of Ti-containing mesoporous alumina molecular sieves

Ti-containing mesoporous alumina molecular sieves with a structure of MSU-2 have been synthesized using metal alkoxides as titanium and aluminum sources and Triton X-100 as templating surfactant, respectively. The structure of the products and the state of Ti species were characterized by XRD, TEM, N-2-sorption, UV-vis DRS and Laser Raman Spectroscopy. It is found that the surface area and the pore volume of sample increase when Ti is incorporated, suggesting an effect of Ti on stabilizing the alumina framework. It is also shown that most of Ti exists in the framework as an isolated mononuclear species at Ti/Alless than or equal to6%. As Ti content increases, polymerized Ti species and even TiO2 domains form. But these domains grow so difficultly within mesoporous walls that they graft to the surface of alumina walls at a higher Ti content level, leading to some degree of pore blocking. However, up to Ti/Al = 33%, no well-defined bulk TiO2 is found, meaning that Ti species can be dispersed better in mesoporous alumina than in conventional TiO2-Al2O3 composite.