Improved accessibility of Na-LTA zeolite catalytic sites for the Knoevenagel condensation reaction

• Published in: Microporous and mesoporous materials 2022-01, Vol.331, p.111640, Article 111640
• Main Authors: Floriano da Silva, Juliana, Deise da Silva Ferracine, Edilene, Cardoso, Dilson
• Format: Article
• Language: English
• Subjects: Mesopores; TPOAC and Activation energy; Zeolites
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2021.111640

The use of zeolites in basic catalysis is limited when large molecules are involved, such as in the manufacture of fine chemicals, due to difficulty in accessing the micropores of the catalyst. A solution to this problem is to synthesize zeolites containing mesopores that improve the accessibility of the active sites. This work investigates the synthesis of zeolites 4A according to a bottom-up method employing the organosilane surfactant [3-(trimethoxysilyl) propyl] octadecyldimethylammonium chloride (TPOAC), at different concentrations in the synthesis mixture (TPOAC/Al2O3 = 0–0.09), to produce mesopores. The zeolites were evaluated in the Knoevenagel condensation reaction, which is strongly influenced by the accessibility of the catalytic sites, due to the large sizes of the molecules involved. Zeolites 4A with mesopores, showing higher external surface areas, were formed in the presence of TPOAC at the different concentrations tested. Higher conversions were achieved using the zeolites with mesopores, compared to conventional zeolite 4A, due to improved access of the reactant molecules to the catalytic sites. In addition, the reaction catalyzed by the zeolite with mesopores had lower activation energy, compared to use of the conventional zeolite 4A. [Display omitted] •Type 4A zeolites containing mesopores were synthesized using the TPOAC organosilane surfactant.•The textural properties of these zeolites could be controlled by adjusting the amount of TPOAC used in the synthesis.•The zeolites containing mesopores provided higher conversions in the Knoevenagel condensation reaction.•The higher conversions are due to the increased access to the active sites, as a result of the higher external surface area.