Crystalline and amorphous aluminosilicates with different pore structures for the synthesis of pyridines

Abstract

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.

Template-free synthesis of high degree crystallinity zeolite Y with micro–meso–macroporous structure

“…There were also the weak acidic OH-groups of the two types bound to the extraframework aluminum atoms. 63 In HY-mmm(60) zeolite the strong BAS are present both inside the pores and on the external surface of the crystals. The issues associated with the effect of the nature, concentration, and acid site strength studies of HY and HY-mmm(60) zeolites on the selectivity of the alkylpyridine formation demanded more thorough investigation.…”

Unusual Acid Sites in LSX Zeolite: Formation Features and Physico-Chemical Properties

“…It is worth noting that the intensity of bands at 3575 and 3665 cm −1 decreases, and the broad band of H-bounded OH groups appears in the range of 3200–3800 cm −1 with a maximum intensity at 3466 cm −1 . According to Equation (2), the shift of 200 cm −1 (compared to the HF band, 3665 cm −1 ) corresponds to the strength of acid sites in the proton affinity scale of 1240 kJ/mol, which is significantly less than the shift of 250–300 cm −1 which is characteristic for HY [ 97 , 99 , 100 , 101 ]. This characterizes LSX zeolite in partially decationized form as a material with less strong Brønsted acidity, which corresponds to a smaller Si/Al ratio [ 102 , 103 , 104 , 105 , 106 ].…”

A Review on Deactivation and Regeneration of Catalysts for Dimethyl Ether Synthesis

“…The most common metallic part consists of CuO-ZnO-Al 2 O 3 with various additives, which are presented later in this work. The acidic part is usually γ-Al 2 O 3 [5][6][7][8][9] zeolites [6,8,[10][11][12], aluminium phosphates [13][14][15] or amorphous aluminium silicates [16][17][18][19]. The metallic part is responsible for methanol synthesis (Equation (3)) and the water-gas conversion reaction (Equation ( 2)), and the acid part is responsible for methanol dehydration (Equation (4)).…”