Synthesis and Characterization of Ti—MCM-41-Type Mesoporous Molecular Sieves with High Titanium Contents

Abstract

By employing a sodium silicate + titanium tetrabutoxide + trimethylmyristylammonium bromide system, it has been possible to obtain mesoporous titanosilicateTt-MCM-41-type molecular sieves containing systematically varying titanium contents. The samples obtained possessed a high BET specific surface area and exhibited the perfect hexagonal mesoporous structure characteristic for MCM-41 materialseven when the titanium fraction present was as great as 20 mol%. It has been shown that most of the titanium can be expelled from the structure when the materials are treated with sulphuric acid solution. However. such treatment does not destroy their inherent hexagonal structure, thereby suggesting that the titanium is preferentially localized in the mesopore surface layer.The structure/sorption properties of the materials were investigated by X-ray diffractionmethods and by the adsorptionof n-hexaneand water vapour. A possible mechanism for the formation of such MCM-41-type molecular sieves is proposed which suggests that the use of organometallic ethers M(OR)n' accompanied by ether solubilization with organic micellar templates. leads to the preferential localization of M in the mesopore surface.

Uncommon Adsorption Isotherm of Methanol on a Hydrophobic Y-zeolite

“…It is conjectured that oxygen and hydroxyl surface contamination might contribute to this pore saturation, but it has remained unclear why the condensation pressures are so different from each other. The corresponding Type V adsorption isotherms are extremely rare. − Apart from adsorption of water over the cited two microporous adsorbents, true Type V isotherms have been only reported for water, benzene, and N 2 over mesoporous Vycor , and MCM-41 , with pore saturating steps at approximately p / p o ≈ 0.8 and 0.2, respectively. These steps are generally attributed to hydroxyl assisted condensation in the extremely narrow ( d ≈ 25 Å) mesopores.…”

Polymer Sol-Gel Synthesis of Hybrid Nanocomposites

“…Their specific surface area S sp varies from 130 to 1260 m 2 g -1 , depending on synthesis conditions. Titanium-containing silica mesoporous molecular sieves of hexagonal (MSM-41) and cubic (MSM-48) (designations of Mobil Corporation) types are of special interest including for catalysis; progress in this field is reviewed in [18,19]. Rather large size of their pores (2-3 nm and larger) provides versatile possibilities for the modification of internal surface to control hydrophobic-hydrophilic and acidic properties, as well as for the design of catalytically active sites.…”

Synthesis, Structure, and Acidic Properties of MCM-41 Functionalized with Phosphate and Titanium Phosphate Groups

“…11 Myristyltrimethylammonium bromide (MTMAB) (Fluka) was used as surfactant. The composition of the initial reaction mixture (mol) was as 9 To an aqueous solution of MTMAB were added a 1:1 mixture of TBOT with i-PrOH and an aqueous solution of sodium silicate with vigorous stirring. The suspension obtained was magnetically stirred at ambient temperature for 10-12 h and kept without agitation for another 10-12 h. The resulting precipitate was filtered off, washed with distilled water and dried in air at 100 °C (as-synthesized sample).…”

“…We proposed a direct synthesis of mesoporous titanosilicate with a hexagonal siliceous structure and TiO 2 layer localized on the surface of the mesopores . We studied the chemical structure and the acidic properties of the surface species of this material (denoted for the sake of simplicity as Ti - MCM-41 ).…”

“…8 We proposed a direct synthesis of mesoporous titanosilicate with a hexagonal siliceous structure and TiO 2 layer localized on the surface of the mesopores. 9 We studied the chemical structure and the acidic properties of the surface species of this material (denoted for the sake of simplicity as Ti-MCM-41). Furthermore, we reported the first example of post-functionalization of the resulting materials aiming at the introduction of new catalytic sites.…”