Structural and sorption characteristics of the products from zeolitization of sba-15 in the presence of tetraalkylammonium hydroxides

Micro–mesoporous materials combining the structural and sorption characteristics of a mesoporous molecular sieve (MMS) and zeolite BEA were obtained by the “dry gel conversion” method – partial zeolitization of silica MMS SBA-15 in the presence of tetraethylammonium hydroxide. The volume of the mesopores reaches 0.65 cm³/g, while that of the micropores is in the region of 0.1 cm³/g. The acidity of the obtained zeolitized materials differs from that of BEA; the total concentration of medium-strength acid centers (maximum thermal desorption of ammonia at ~315 °C) amounts to 0.15 mmol/g.     

Effect of Production Conditions of Hierarchical SnAl-BEA Zeolites on Their Acidity and Catalytic Activity in Tandem Process for the Production of 4-Methoxybenzyl-sec-Butyl Ether

Theoretical and Experimental Chemistry - Hierarchical SnAl-silicate zeolites of the BEA structural type with Lewis (up to 130 μmol/g) and Brønsted (up to 330 μmol/g) acid sites, the...     

Crystallization kinetics of zeolite-like phosphates AIPO4-5 and SAPO-5

We show that the crystallization rate of isostructural zeolite-like phosphates AlPO₄-5 and SAPO-5 is considerably higher than for zeolites and polysilicates. We analyze the kinetic and energy parameters, taking into account the high structural lability of aluminophosphates, the effect of limiting processes of dissolution of the original pseudoboehmite and conversion of the intermediates, and also isomorphic inclusion of silicon atoms. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Nauki Prospekt, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 184–187. May–June, 1997.     

Influence of structure of the crystal lattice of nickel(II) complex with amide-containing ligand on its stability and adsorption properties

The characteristic of the crystal lattice of the hydrate of a nickel complex with a tetradentate amide-containing ligand is the presence of hexamers of the metal complex molecule, united by intermolecular hydrogen bonds which are retained during adsorption and desorption of polar molecules. The lattice of this material is characterized by a definite lability which arises during interaction with methanol. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 1, pp. 47–51, January–February, 2007.     

Characteristics of Template Formation in Silica in Acidic Media

Characteristics of template formation in silica at pH < 0.1 in the presence of a surface active substance (cetyltrimethylammonium bromide or chloride) have been investigated. Depending on the acidity of the reaction medium and some other factors, the synthesis of spontaneously growing particles of templated silica at interfacial surfaces led to the formation of fibers, spirals, spheres, and other forms, most of which appeared as hexagonally ordered bodies of revolution. It is possible to detemplate these forms of silica and to transform them to mesoporous molecular sieves without destroying their structures.