Wang Xin, Xue Jianyue, Wang Xinyun, Liu Xiaoheng
College of Chemistry and Materials Engineering, Chaohu University, Chaohu, Anhui, China.
Institute of Novel Functional Materials and Fine Chemicals, Chaohu University, Chaohu, Anhui, China.
PLoS One. 2017 May 11;12(5):e0176332. doi: 10.1371/journal.pone.0176332. eCollection 2017.
TiO2-SiO2 composites were synthesized using cetyl trimethyl ammonium bromide (CTAB) as the structure directing template. Self-assembly hexadecyltrimethyl- ammonium bromide TiO2-SiO2/(CTAB) were soaked into silver nitrate (AgNO3) aqueous solution. The Ag-TiO2-SiO2(Ag-TS) composite were prepared via a precipitation of AgBr in soaking process and its decomposition at calcination stage. Structural characterization of the materials was carried out by various techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption and ultraviolet visible spectroscopy (UV-Vis). Characterization results revealed that Ag particles were incorporated into hierarchical TiO2-SiO2 without significantly affecting the structures of the supports. Further heating-treatment at 723 K was more favorable for enhancing the stability of the Ag-TS composite. The cyclohexene oxide was the major product in the epoxidation using H2O2 as the oxidant over the Ag-TS catalysts. Besides, the optimum catalytic activity and stability of Ag-TS catalysts were obtained under operational conditions of calcined at 723 K for 2 h, reaction time of 120 min, reaction temperature of 353 K, catalyst amount of 80 mg, aqueous H2O2 (30 wt.%) as oxidant and chloroform as solvent. High catalytic activity with conversion rate up to 99.2% of cyclohexene oxide could be obtainable in water-bathing. The catalyst was found to be stable and could be reused three times without significant loss of catalytic activity under the optimized reaction conditions.
以十六烷基三甲基溴化铵（CTAB）为结构导向模板合成了TiO₂-SiO₂复合材料。将自组装的十六烷基三甲基溴化铵TiO₂-SiO₂/（CTAB）浸泡在硝酸银（AgNO₃）水溶液中。通过浸泡过程中AgBr的沉淀及其在煅烧阶段的分解制备了Ag-TiO₂-SiO₂（Ag-TS）复合材料。采用X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、N₂吸附-脱附和紫外可见光谱（UV-Vis）等多种技术对材料进行了结构表征。表征结果表明，Ag颗粒被引入到分级结构的TiO₂-SiO₂中，而对载体结构没有显著影响。在723K下进一步热处理更有利于提高Ag-TS复合材料的稳定性。在Ag-TS催化剂上，以H₂O₂为氧化剂进行环氧化反应时，环氧环己烷是主要产物。此外，在723K煅烧2h、反应时间120min、反应温度353K、催化剂用量80mg、以H₂O₂水溶液（30wt.%）为氧化剂、氯仿为溶剂的操作条件下，获得了Ag-TS催化剂的最佳催化活性和稳定性。在水浴中可获得高达99.2%的环氧环己烷转化率的高催化活性。发现在优化的反应条件下，该催化剂稳定，可重复使用三次，催化活性无明显损失。
