Synthesis, characterization, and catalytic properties of Ti-containing SBA-15 mesoporous materials

Abstract

Titanium-containing SBA-15 mesoporous materials with Si/Ti molar ratios of 25, 50 and 100 (Ti-SBA-15) were successfully prepared by direct synthesized method using P123 as surfactant. The samples were characterized by XRD, BET, TEM and UV-Vis. It revealed at low Ti-loading (Si/Ti of 50-100), titanium was completely incorporated into SBA-15 framework, whereas at high Ti-loading (Si/Ti of 25) titanium was partially incorporated into SBA-15 framework, one part of Ti existed as extra-framework Ti (anatase phase). For comparison, Ti impregnated on Si-SBA-15 (Ti/SBA-15) was also prepared by postsynthesis method. In (*) this case, titanium was well dispersed onto the surface of SBA-15. The catalytic activities of Ti-SBA-15 with different Ti-content and Ti/SBA-15 samples were tested in the photocatalytic oxidation of red-phenol and in the photocatalytic reduction of Cr(VI) to Cr(III). The catalytic results showed that both the Ti-SBA-15 and Ti/SBA-15 solids are also the good catalysts for total photooxidation of red phenol. Especially, the tetrahedral coordinated titanium can oxidize red phenol much deeper than well dispersed titanium particles does. For photocatalytic reduction, the activities mainly depend on the number of Ti, not the state of Ti.

Anatase TiO2 nanocrystals anchored at inside of SBA-15 mesopores and their optical behavior

“…In terms of preparation techniques, two methods are commonly employed for obtaining SBA-15 modified with TiO 2 nanocrystals: post-synthesis and one-pot methods. The first one is able to promote the formation of metal oxides in the channels or external surfaces of support, which could block the channels and not allows the easy access of reactant molecules to the reaction sites in the porous matrix [29][30][31][32][33][34][35][36][37][38][39]. In the second one, it occurs the simultaneous addition of the precursors of silica and titanium oxides in the synthesis gel.…”