Preparation of surface-silylated and benzene-bridged Ti-containing mesoporous silica for cyclohexene epoxidation

Organic–inorganic hybrid Ti-containing mesostructured materials were directly synthesized from tetrabutyl titanate in acidic media by using a non-ionic surfactant P123 as a structure-directing agent, tetraethoxysilane as an inorganic silicon source and 1,4-bis-(triethoxysilyl)benzene as organicsilica. The benzene-bridged Ti-containing periodic mesoporous organosilica Ti-SBA-15-ben was further modified by surface silylation with trimethylchlorosilane. The products were characterized by various means. We find the materials maintained good mesoporous structure, their hydrophobic properties were significantly improved after silanization, and the organic silicon source in the pore walls was favorable for obtaining tetravalent active titanium ions. The catalysts were evaluated in cyclohexene epoxidation with tertbutyl hydroperoxide as an oxidant agent. With Ti-SBA-15-ben as the catalyst, the epoxide selectivity and cyclohexene conversion were improved to 59.9 and 34.7 % respectively. Moreover, surface hydrophobization by silylation treatments further increased the epoxide selectivity to 71.5 %.