Hydrothermal synthesis, description

Detailed description of the synthesis procedures as weh as thorough characterisation of the materials whl be described elsewhere. For both materials, hydrothermal synthesis procedures... 

The recent descriptions of the ALPO-n, SAPO-n and MeAPO-n families of microporous materials illustrate that hydrothermal syntheses can afford a wide and diverse range of four-coordinate framework structures based on nearregular tetrahedra [1,2]. As building blocks, octahedra and tetrahedra can also be combined, in various proportions, into a variety of structure types [3,4]. Reflecting the conditions used for conventional synthesis [3,4], most of these structures are condensed, with little accessible pore volume. There are, however, examples of both synthetic [5-7] and natural materials [8-11] that have microporous crystalline structures. Further, the formation chemistry of silicates and aluminosilicates [12,13] illustrates that the more open structures are generally produced under relatively mild conditions. Open octahedral-tetrahedral structures with large pore systems might therefore also be accessible under appropriate low temperature hydrothermal conditions. 

High-pressure methods are discussed in detail under High Pressure Synthesis of Solids. Hydrothermal methods are discussed in the previous Section. A few examples relative to oxide synthesis are given here. Descriptions of the equipment used are given by Rao and GopaUcrishnan and by Rooymans. ... 

The sodium form of the ZSM-5 zeolite samples with framework content 2.6 to 2.8 Alp/U.C were synthesized using TPABr and without using template in stainless steel autoclaves under autogeneous pressure at 423 K, under static conditions, with crystallization time of 72 h. Detailed description of the synthesis method has been given in our previous publication (10). The Na-ZSM-5 samples were converted to NH4-ZSM-5 by repeated ion exchange with 5N NH4NO4 solution. NH4-ZSM-5 having 4.5 AI. 7U.C has taken for hydrothermal treatment Proton form of the above mentioned catalysts were obtained from their respective ammonia forms by calcination in presence of air at 753 K for 6 h.( 10). 

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