Layer-Like Zeolite X as Catalyst in a Knoevenagel Condensation: The Effect of Different Preparation Pathways and Cation Exchange

Abstract

This study is dedicated to the comparative investigation of the catalytic activity of layer-like Faujasite-type (FAU) zeolite X obtained from three different synthesis routes (additive-free route, Li2CO3 route, and TPOAC route) in a liquid-phase Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate to ethyl trans-α-cyanocinnamate. It is shown that the charge-balancing cations (Na+ and K+) and the morphological properties have a strong influence on the apparent reaction rate and degree of conversion. The highest initial reaction rate could be found for the layer-like zeolite X synthesised by the additive-free route in the potassium form. In most cases, the potassium-exchanged zeolites enabled higher maximum conversions and higher reaction rates compared to the zeolite X catalysts in sodium form. However, very thin crystal plates (below 100 nm thickness), similar to those obtained in the presence of TPOAC, did not withstand the multiple aqueous ion exchange procedure, with the remaining coarse crystals facilitating less enhancement of the catalytic activity.

Zeolites Derived from Natural Kaolinite for CO2 Adsorption

“…The 27 Al MAS NMR spectrum of ZEO X (Figure 2, left panel) contains two signals at 3 and 63 ppm. The band at 63 ppm is assigned to the 27 Al nuclei in a tetrahedral coordination within the framework of zeolite X [49,50], whereas the shoulder at ca. 60 ppm might arise from different tetrahedral Al species within the sample derived from the slow dissolution of the parent kaolinite in alkali condition [48].…”

“…Processes 2024, 12, x FOR PEER REVIEW 7 of 15 nation within the framework of zeolite X [49,50], whereas the shoulder at ca. 60 ppm might arise from different tetrahedral Al species within the sample derived from the slow dissolution of the parent kaolinite in alkali condition [48].…”

A post-sulfonated one-pot synthesized magnetic cellulose nanocomposite for Knoevenagel and Thorpe–Ziegler reactions

“…6,7 Conventionally, different amines, organometallic catalysts, Lewis acids, such as, TiCl 4 , ZnCl 2 , and Al 2 O 3 , ionic liquids, and amino acids have been efficiently utilized as homogeneous catalysts for Knoevenagel condensation. [7][8][9] Due to the difficulty in recycling and harsh reaction conditions for homogeneous catalysts, heterogeneous catalysts, such as incorporating zeolites, 10,11 metal-organic frameworks (MOFs), 12,13 ionic liquids, hetero-poly acids, 14 functionalized mesoporous silica, 15 and carbon-based materials, 16,17 have been developed for Knoevenagel condensation. Thorpe-Ziegler cyclization is an intramolecular cyclization of aliphatic carbonitriles into amines, and is useful in synthesizing bioactive heterocycles.…”

A New Mixed-Metal Phosphate as an Efficient Heterogeneous Catalyst for Knoevenagel Condensation Reaction

“…In this context, the heterogeneous path is considered to be the most convenient due to the scope of the recyclability of catalyst, the ease of catalyst separation, and the cost-effectiveness of the process. Several heterogeneous catalysts displayed good performances in Knoevenagel condensation reactions such as the surfactant-mesoporous silica composite [16], functionalized MCM-41 [17], indium-doped AlMCM-41 [18], mesoporous carbon nitride [19], zeolites [20,21], porous organic polymers [22], metal-organic framework [2], phosphate complexes [23], coordination polymers [24], etc. However, use of these materials as catalysts may often lead to metal contamination in the final product.…”