Silicalite-1 Crystals Etched with Hydrofluoric Acid Dissolved in Water or Acetone

0346414 - ÚFCH JH 2011 RIV US eng J - Journal Article
Brabec, Libor - Kočiřík, Milan
Silicalite-1 Crystals Etched with Hydrofluoric Acid Dissolved in Water or Acetone.
Journal of Physical Chemistry C. Roč. 114, č. 32 (2010), s. 13685-13694. ISSN 1932-7447. E-ISSN 1932-7455
R&D Projects: GA AV ČR IAA400400909
Institutional research plan: CEZ:AV0Z40400503
Keywords : silicalite-1 crystals * acetone * hydrofluorid acid
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 4.520, year: 2010

Highly siliceous (Si/Al ≈ 350) MFI-type crystals of various sizes and morphologies were etched with HF dissolved either in water or in acetone. The highest concentration of HF used was 4 wt % in water and 5.5 wt % in acetone with etching time shorter than 1 h. After rapid etching, the lateral faces of coffin-shaped crystals exhibited differently resistant triangular areas. Slow etching lasting weeks or months was performed in 100× diluted solutions and provided oriented rectangular pits corresponding to the point-group symmetry of MFI structure. Our coffin-shaped crystals were found to be twins of lateral faces as {100} consisting of two pyramidal segments ingrown to the crystal bed. Inner resistant triangle skins were found in calcined crystals indicating preferential deposition of organic residues on the segment interface. Such skins also appeared in small flat monocrystals at the top of the calcined polycrystalline layer.
Permanent Link: http://hdl.handle.net/11104/0187451