Combined silica sources to prepare preferentially oriented silicalite-1 layers on various supports

Abstract

Direct in-situ hydrothermal synthesis was optimized via combination of monomeric (TEOS) and colloidal (TOSIL) silica sources to prepare preferentially b-oriented high silica MFI zeolite (silicalite-1) layers on different supports using conventional heating. Crystallographic Preferred Orientation (CPO) indices and our created Preferred Orientation Coverage (POC) values were used to determine preferred orientation and its surface coverage. Particle size distribution of precursor species was measured with Dynamic Light Scattering technique. Crystal intergrowth and zeolite phase purity were checked with Scanning Electron Microscope and X-ray diffraction. Solid and (a+b)-oriented self-supported silicalite-1 layers were synthesized on mercury surface at static and vibration conditions. Additional self-assembled and oriented silicalite-1 layers floating in bulk solution were prepared from solutions with enhanced silica content. Preferentially b-oriented silicalite-1 layers were prepared on silicon wafer and polished non-porous stainless steel. Partial b-orientation was achieved for polished porous stainless steel supports. Remarkably intergrown and b-oriented silicalite-1 layers were synthesized on porous stainless steel covered by TiO2 layer that was impregnated with tetrabutylorthotitanate acting as a coupling agent and/or surface charge modifier.