UDC 544.723.21 V. L. Struzhko, P. S. Yaremov, E. V. Senchylo, V. M. Solomakha, and V. G. Ilyin XRD, TPDA, and IR spectroscopy of pyridine were used to study the effect of the synthesis conditions on the formation, adsorption characteristics, and acid properties of composite micro/mesoporous materials. Spatially well-ordered phases such as Beta, were found to exist in our samples. Variation of the preparation conditions permitted us to regulate the porosity and adsorption characteristics of the composite materials and the type, concentration, and strength distribution of the acid sites in the samples. The strength of the acid sites of the composite micro/mesoporous materials and their concentration are much higher than for mesoporous AlSi-MCM-41 but somewhat less than in the initial zeolites. Analysis of the results suggested that the samples obtained under similar conditions are not ordinary mechanical mixtures of two phases (zeolite and AlSi-MCM-41), but rather unique composites with tightly bound nanoparticles due to formation in a single reaction medium.Zeolites are commonly used as catalysts in the petrochemical and petroleum refining industry due largely to their crystal structure, porosity, and acid properties. However, small pore diameter (<0.75 nm) limits their use in the catalytic conversion of bulky molecules, in particular, in extensive catalytic cracking reactions and fine organic synthesis [1]. It was assumed that mesoporous molecular sieves (MMS), in particular, MCM-41-type materials with pore diameter £3-5 nm, possessing high specific surface (up to 1000 m 2 /g) could be used in such and similar processes. However, further investigation showed that the amorphous nature of the framework-forming substance and relatively low condensation lead to weak acidity and relatively low hydrolytic stability. Hence, the development of new materials with hybrid micro/mesoporous structure, combining the advantages of zeolites and MMS, holds considerable interest in regard to their possible application in adsorption and catalytic processes.There are presently several approaches being explored for the preparation of meso/microporous materials. One of them involves the creation of mesopores in zeolite crystals by dealumination and/or disilication upon acid, hydrothermal, or alkaline treatment [2]. Other approaches involve, somewhat generalizing, the preparation of micro/mesoporous composites from precursor zeolite crystal seeds formed in the first stages of the synthesis, the use of delaminated (fragmentized) zeolite particles as construction units, partial zeolitization of the MMS framework upon hydrothermal treatment in the presence of suitable
UDC 544.723.21 E. V. Senchylo, V. L. Struzhko, and V. N. SolomakhaWe have studied the effect of synthesis conditions on formation of thermally stable mesoporous zirconium phosphate. We have used X-ray diffraction, temperature-programmed desorption of ammonia, IR spectroscopy, NMR, and DTA to establish that formation of hexagonally ordered materials which are stable during detemplating is possible only when using cationic and nonionic surfactants, a temperature of 20°C, and post-synthesis treatment with a solution of orthophosphoric acid. We have established that, depending on the ordering, there is a change in both the adsorption characteristics of the zirconium phosphate as well as the concentration of acid sites and their strength distribution.In recent years, inorganic ion-exchange materials, in particular zirconium phosphates, have attracted increasing attention mainly due to their ability to meet a number of requirements imposed by modern technology. They are characterized by higher stability (compared with organic ion exchangers) at elevated temperatures and when exposed to rather intense radioactive radiation. Zirconium phosphate is also quite resistant to acids, except for HF, H 2 SO 4 , and H 2 C 2 O 4 , which form complexes with zirconium. Furthermore, zirconium phosphates and its modified forms, along with metal oxides, zeolites, molecular sieves, activated carbons, and other porous materials, are widely used as catalyst supports and catalysts in isomerization reactions [1], Friedel-Crafts acylation using benzyl chloride [2], and also as a matrix for controlled assembly of semiconductor clusters and organic molecules [3,4]. These materials can be used in nonlinear optics, in electronic and optical processes [5], and also as proton conductors in proton exchange membranes in fuel cells for direct conversion of chemical energy to electrical energy [6].Most widely studied have been zirconium phosphates with a layered structure which, depending on the synthesis method, have different crystal structures of the a-zirconium phosphate type (a-ZrP) of composition Zr(HPO 4 ) 2 ·H 2 O, g-zirconium phosphate (g-ZrP) of composition Zr(PO 4 )·(H 2 PO 4 )·2H 2 O, or zirconium pyrophosphate ZrP 2 O 7 [7]. Owing to the presence on the surface of layers of POH groups, a-zirconium phosphate is stable at high temperatures (700-800°C) [8]. The method for obtaining layered zirconium phosphates involves precipitation from acidic solutions of zirconium salts with the help of phosphoric acid, differently substituted sodium or ammonium phosphates. Phosphates of tetravalent metals are formed in strongly acidic medium (pH 0-1) [3]. Zr 4+ ions in solution are usually hydrated by six water molecules, while in Zr(HPO 4 ) 2 ·H 2 O they are found in an octahedral environment of six oxygen atoms of HPO 4 2-anions. Therefore the process of
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