Effect of calcination on the structure and catalytic activities of titanium incorporated SBA-15
Journal
Journal of Materials Chemistry
Journal Volume
21
Journal Issue
7
Pages
2255-2265
Date Issued
2011
Author(s)
Abstract
Well-ordered Ti-incorporated SBA-15 materials (shortly termed Ti-SBA-15) with Ti loading up to 10 mol% of Si were prepared by a one pot co-condensation method using tetraethyl orthosilicate (TEOS) as the silica source and titanium oxychloride as the Ti source in an acidic environment close to the isoelectric point of silanol groups (pH = 1.27-2.37). The Ti-SBA-15 materials with Ti/Si ratios smaller than 0.05 were curved solid tubes, while those with the Ti/Si ratios between 0.05-0.1 possessed platelet morphology and short mesochannels (ca. 150-500 nm). Titanium was homogeneously distributed in the silica framework of the as-made Ti-SBA-15 materials as isolated Ti species when the Ti/Si ratios were lower than 0.03. It formed small TiO2 nanocrystallites when the Ti loading was further increased or after the materials were calcined at temperatures higher than 500 °C. It is noteworthy that tetrahedrally coordinated Ti(iv) species were generated on the superficial areas of SBA-15 silica framework upon calcination at 600-1000 °C. These tetrahedrally coordinated Ti(iv) species not only stabilized the mesopore ordering up to 950-1000 °C, but also acted as effective catalytic sites in cyclohexene epoxidation. © The Royal Society of Chemistry.
Type
journal article