Synthesis of microporous titanosilicate ETS-10 from TiCl3 and TiO2: a comprehensive study

• Published in: Microporous and mesoporous materials Vol. 23; no. 5-6; pp. 253 - 263
• Main Authors: Rocha, João, Ferreira, Artur, Lin, Zhi, Anderson, Michael W
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.09.1998; Elsevier
• Subjects: Chemistry; Colloidal state and disperse state; ETS–10; Exact sciences and technology; General and physical chemistry; Microporous; Porous materials; Synthesis; Titanosilicate; Titanosilicate; ETS–10; Synthesis; Microporous; Scanning microscope; Micropore; Temperature effect; pH; Titanium chloride; NMR spectrometry; Fluorides; Experimental study; Chemical synthesis; Titanium oxide; X ray diffraction; Freeze
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/S1387-1811(98)00120-6

A comprehensive study of the hydrothermal synthesis conditions which afford pure and highly crystalline samples of microporous titanosilicate ETS-10 from TiCl3 and crystalline TiO2 (anatase) is reported. The following parameters have been studied: fluoride ions, temperature, pH of the parent gel, sodium and potassium cations, H2O/Si and Si/Ti molar ratios, seeds and time. The best ETS-10 samples are obtained after only ∼15h (TiCl3) and 24h (anatase) hours of synthesis at 230°C and pH≈10.5 with a Si/Ti molar ratio of 5–6. By carefully selecting the titanium sources and synthesis parameters, it is possible to obtain crystallites with sizes ranging from ∼0.5μm (anatase route) to ∼25μm (TiCl3 route). The latter are the largest ETS-10 crystals reported so far. The first step in the TiCl3 synthesis is the formation of a silica–titania gel which then transforms into ETS-10. The rate-limiting step of the TiO2 route is the slow dissolution of anatase followed by condensation with silicate species which are more readily available in solution. Good-quality ETS-10 is easily prepared in the presence of Na+ and K+, without the addition of fluoride ions. If K+ is absent, the synthesis becomes a difficult task and seems to be possible only in the presence of fluoride and under strict control of other synthesis parameters. When the precursor is TiCl3, seeding with good-quality ETS-10 is important, but this is not so when anatase is used.