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Novel and facile synthesis of transparent-monolithic TiO2 gels by sol-gel method based on an esterification reaction

Elghniji K., Rabah Z. A., Elaloui E

Materials Science Poland

2016

Vol. 34, No. 3

633--640

Transparent TiO2 monoliths were obtained through a modified sol-gel route from titanium isopropoxide as a precursor. By controlling the hydrolysis of this precursor through the intermediate of esterification reaction between acetic acid and isopropanol at 40 °C, transparent TiO2 xerogel monoliths were obtained. The monoliths prepared by this method were transparent in the wavelengths between 400 nm and 700 nm. Fourier transform infrared (FT-IR) spectroscopy suggested that the acetic acid played also an active role as a chelating agent, forming Ti[(OH)y(OOCCH3)x] less reactive species. Powder X-ray diffraction confirmed the amorphous-to-anatase phase transformation with the formation of unknown Ti-containing complex at 90 °C. Only anatase TiO2 could be observed in the samples calcined at 250 °C and 450 °C. Optical aspects of the gel (transparent-transluscent transformation of monolithic gel) and gelation time were controlled by changing the amount of external water.

Nanomaterials with a Multimodal Pore Structure Based on the MFI-type Zeolite

Burkat-Dulak A., Pashkova V., Pudło W., Włoch E., Jarzębski A., Derewinski M.

Polish Journal of Chemistry

2008

Vol. 82, nr 9

1809-1822

Synthesis and characterization of new multimodal porous systems containing thin MFI zeolitic films is reported. These films cover the internal surface of the meso- and macroporous silica-alumina monoliths. They are easily accessible through the open porous structure retained in the partially recrystallized, originally amorphous monolith. When the mesoporous Al-SBA-15 sieves are used in stead of monoliths, a controlled hydrothermal process results in the formation of the MFI nanodomains dispersed in the walls that separate mesopores hexagonally arranged. These do mains possess strong acidic sites of the zeolitic type, but the original ordering of mesopores in the parent material is very well retained. A simple method for the synthesis of the MFI crystals containing both meso- and macrovoids is also proposed. It makes use of the suspended mono- and polydispersed carbon particles that serve as porogens. Thus, the porous MFI crystals obtained can be used for the preparation of effective bifunctional catalysts by the de position of a highly dispersed metallic (Pd) phase.