Synthesis of titanosilicate ETS-4 with controlled morphology and investigation of its crystallization kinetics

Bilge Yilmaz, Peter Q. Miraglia, Juliusz Warzywoda, Albert Sacco

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

ETS-4 crystals with controlled morphology were hydrothermally synthesized at 448 K under static conditions by changing their pH through variation of the amount of sulfuric acid added (x=3.3-4.4). The overall molar composition was 3.6SiO2 : 1TiO2 : 5.5Na2O : xH2SO4 : 230.2H2O. An increase of the initial pH from 11.50 (x=4.4) to 12.90 (x=3.3) resulted in a change of morphology of the ETS-4 product from spherulitic particles of submicron crystallites to monolithic crystals with rectangular prism morphology (average dimensions ∼1 × 15 × 2 μm). With the increase of initial pH, the polycrystalline particles resulted in progressively fewer and larger crystallites. The presence of growth spirals on the {1 0 0} surfaces of monolithic crystals suggested that high alkalinities resulted in low supersaturation of the (titano)silicate species, producing monolithic crystals with the largest dimension coinciding with linear -OTiOTiO- chains running in the [0 1 0] direction. Crystallization kinetics of ETS-4 was found to depend on the alkalinity of the synthesis mixture. The induction period decreased from ∼30 to ∼4 h when the initial pH increased from 11.50 to 12.90. The crystallization rate increased somewhat upon increase of the initial pH from 11.50 to 12.60 (x=3.6) only to decrease substantially upon further increase of the initial pH. These results indicate a complex growth process of ETS-4 spherulites, including both branching and spiral growth mechanisms.

Original languageEnglish
Pages (from-to)167-175
Number of pages9
JournalMicroporous and Mesoporous Materials
Volume71
Issue number1-3
DOIs
StatePublished - Jun 17 2004

Keywords

  • Crystal growth
  • Crystallization kinetics
  • ETS-4
  • Synthesis
  • Titanosilicates

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