Hydrothermal synthesis of titanosilicate ETS-10 using Ti(SO 4) 2

• Published in: Microporous and mesoporous materials Vol. 81; no. 1; pp. 1 - 10
• Main Authors: Ji, Zhaoxia, Yilmaz, Bilge, Warzywoda, Juliusz, Sacco, Albert
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 06.06.2005; Elsevier
• Subjects: Chemistry; Colloidal state and disperse state; Crystallization kinetics; ETS-10; Exact sciences and technology; General and physical chemistry; Porous materials; Surface structure; Synthesis; Titanosilicates; Synthesis; Titanosilicates; ETS-10; Crystallization kinetics; Surface structure; Crystallization; Kinetics; Hydrothermal condition; Titanium Silicates
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2005.01.006

The ternary reaction composition diagram in the SiO 2–Na 2O–TiO 2–KF–H 2SO 4–H 2O system was developed for static ETS-10 synthesis at 473 K utilizing Ti(SO 4) 2 and N-brand sodium silicate solutions as sources of Ti and Si, respectively. For KF/TiO 2 = 1.5 and H 2O/TiO 2 = 300, pure, crystalline (⩾95%) ETS-10 products were obtained in a narrow reaction composition zone (Na 2O/SiO 2 = 0.790–0.825, SiO 2/TiO 2 = 5.30–5.90, initial pH = 10.22–10.95). The presence of islands and terraces with heights of ∼1.2–1.7 nm suggests a layer growth mechanism via two-dimensional surface nucleation. The aspect ratio R = c/ a of typical ETS-10 crystals ( c is the axial length of the bi-pyramid and a is the linear dimension of the square basal plane shared by the two pyramids) and the roughness of crystal pyramidal side surface decreased with increasing initial synthesis mixture pH. The Si/Ti ratios in the ETS-10 products were close to the theoretical value of 5. The crystallization curves for this pure ETS-10 showed that the induction time decreased substantially from 36 to 19 h, whereas crystallization rate increased only slightly from 19% to 27% h −1 upon increasing initial pH. Increasing dilution of the initial synthesis mixture with water (5.50SiO 2:4.46Na 2O:1.00TiO 2:1.5KF:3.35H 2SO 4:450–750H 2O) resulted in progressively longer crystallizations, producing bi-pyramidal crystals of monotonically increasing dimensions. The results of experiments using NaF instead of either KF or KOH (i.e., conducted without K + and F +) suggested that in unseeded, organic-free ETS-10 syntheses, K + was necessary for the nucleation of ETS-10, while F − was not.