Mesoporous Metallosilicates Prepared by Nonhydrolytic Acetamide Elimination
| Autoři | |
|---|---|
| Rok publikování | 2014 |
| Druh | Konferenční abstrakty |
| Fakulta / Pracoviště MU | |
| Citace | |
| Popis | Non-hydrolytic sol-gel reactions are efficient alternatives to classical aqueous techniques for synthesis of multimetallic oxides and inorganic-organic hybrid materials. This processes provides better reaction control and higher homogeneity of prepared materials. We developed nonhydrolytic sol-gel routes to several groups of metallosilicate materials based on acetamide elimination reactions. This approach is based on the condensation reaction of silicon tetraacetate Si(OAc)4 and metal amides (Ti(NEt2)4, Zr(NEt2)4). Reactions were performed at different molar ratios. Nonhydrolytic condensation leads to formation the Si–O–Ti and Si–O–Zr bonds in the xerogel framework. Diethylacetamide and acetanhydride were confirmed (GC-MS, 1H NMR) as the reaction byproducts. To achieve the mesoporous nature of the material, the reaction was successfully modified by the addition of the Pluronic P123. This copolymer has structure-directing and protecting feature and allows to prepare tough gels. After heat treatment the Pluronic P123 is burned out and xerogels are mesoporous with high surface areas. The resulting xerogels and volatile byproducts were characterized by liquid and solid-state NMR, IR, GC-MS, surface area analysis, TGA, XRD and DRUV-Vis. The catalytic activity of titanosilicate xerogels for epoxidation of cyclohexene was studied. It was found that synthesized titanosilicates are very effective catalysts for the epoxidation. The effect of titanium loading on the xerogels homogeneity was observed. The homogeneity of gels increase with the lower content of Ti. It was observed, that samples with 10 mol % of Ti contain the highest amount of four-coordinated Ti atoms. These species are the active sites of catalyst. In the case of the xerogels synthesized with Pluronic P123, the best results are achieved for calcined xerogels (500 °C). In the model epoxidation reaction the yields of cyclohexene oxide were 96 %. |
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