Template-free synthesis of zeolite Y with hierarchical porous structure.

The synthesis of pyridines has been performed by a multi-component reaction of ethanol, formaldehyde, and ammonia in the presence of H-Beta, H-ZSM-12, and H-ZSM-5 zeolite catalysts. The maximum activity in the reaction is revealed by H-Beta zeolite; the conversion of ethanol induced by it reached 70% (400°C, 2 h -1 ). The main products of the reaction in the presence of H-Beta and H-ZSM-5 zeolites are pyridine and picolines; on H-ZSM-12 picolines and lutidines. Thus, the results of the studying the effect of reaction parameters are showed that the yield of lutidine and heavy products increases with the increase of the temperature (from 200 to 400°C) and the decrease of the weight hourly space velocity (from 10 to 2 h -1 ).

The heterogeneous catalytic synthesis of pyridine and methylpyridines (picolines) was carried out by the reaction of ethanol with formaldehyde and ammonia over aluminosilicates with different acidic properties and textural characteristics: zeolite framework-type FAU in H-form with microporous (H-Y) and micro-meso-macroporous structure (H-Y-mmm) and mesoporous aluminosilicates, obtained by sol-gel synthesis in an alkaline medium (ASM-1) and under variable pH (ASM-2). It is shown that the highest catalytic activity is characteristic of ASM-2 (Si/Al = 40) with a narrow pore size distribution within the range 2 to 5 nm and containing strongly acidic bridging Si–OH–Al groups on the surface. The products of the reaction of ethanol with formaldehyde and ammonia on the catalysts studied are dominated by picolines; the maximum amount of picolines (60%) is formed on the H-Y-mmm and aluminosilicate ASM-2 samples.

The microstructure, acid properties and characteristics of the porous structure of sol-gel-synthesized mesoporous aluminosilicates with Si/Al ratios of 40, 80, and 120 have been investigated. It was illustrated that the main reason for the formation of a narrow mesopore size distribution in the investigated aluminosilicates is related to the close size of the secondary particles of the prepared xerogels. The research revealed that an increase in the Si/A1 ratio leads to a slight decrease in the specific surface and mesopore volume. An increase in the Si/Al ratio from 40 to 120 has proved to reduce the total acidity in ammonia from 554 to 324 μmol/g. It is shown that mesoporous aluminosilicates prepared by two-step sol-gel synthesis show high activity and selectivity in the synthesis of 3,5-dialkylpyridines.

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