Characterization and Photocatalytic Properties：Ti-containing SBA-15 Prepared by Modified Direct Hydrothermal Method
Date Issued
2006
Date
2006
Author(s)
Chang, Ren-Wei
DOI
zh-TW
Abstract
Titanium-containing SBA-15 (Ti-SBA-15) was synthesized via a modified hydrothermal method, prepared as following: an amount of triblock copolymer P123 (EO20PO70EO20) was dissolved in 1 M HCl solution, followed by the dropwise addition of a mixture of tetraethylorthosilicate (silicon source, TEOS) and tetraethylorthotitanate (titanium source, TBOT) with the desired ratio of Ti and Si (in mole). After stirring 24 h, adding some amount of 2 M NaOH solution to adjust the desired pH of the synthesis system, and then hydrothermal treatment at 80 ℃ for 24 h. The final solid was collected by filtration, washed with water, and dried at room temperature, and then calcinated at 550 ℃ for 6 h. The structure characterization of Ti-SBA-15 and its photocatalytic properties was investigated.
The element analysis results indicated that the amounts of titanium in pH-adjusted Ti-SBA-15 are higher than that of Ti-SBA-15 as much as one order of magnitude. HRTEM images of all Ti-SBA-15 show well-ordered hexagonal arrays of mesopore with one-dimensional channels, and TiO2 aggregated layer at outside surface of pH-adjusted Ti-SBA-15 was observed. With increasing the pH value of the synthesis system, some TiO2 aggregated seriously to form nanoparticles anchored on the surface of Ti-SBA-15. N2 adsorption isotherm (77 K) shows the adsorption type of all Ti-SBA-15 are type Ⅳ with H1 hysteresis loop, which is typical for mesoporous materials with 2-D-hexagonal structure. From UV-Visible spectrum, Ti/Si = 0.05 shows the absorption band at 200-250 nm, indicated that titanium at framework site. When Ti/Si ratio increased, another adsorption band at about 300 nm emerges, indicated titanium distributed at extraframework site. X-ray adsorption spectrum evidenced that titanium at four coordination state in Ti-SBA-15, and titanium mainly at six coordination state in pH-adjusted Ti-SBA-15. From pyridine adsorption IR spectrum, all Ti-SBA-15 show Lewis acid properties.
Nitric oxide photocatalytic analysized by in-situ Electron Paramagnetic Resonance (in-situ EPR) indicated that Ti-SBA-15 adjusted pH=1 has the best photocatalysis for NO degradation with high nitrogen selectivity in products. Simultaneously, the photodegradation test of salicylic acid also shows that Ti-SBA-15 adjusted pH=1 exhibited the best performance. The high photocatalytic activity of Ti-SBA-15 adjusted pH=1 is contributed to TiO2 layer distributed uniformly at the outside surface of molecular sieves.
Subjects
含鈦SBA-15
一氧化氮光分解
柳酸光分解
Titanium-containing SBA-15
NO photodecomposition
photodegradation of salicylic acid
Type
thesis
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