The structure-catalytic activity relationship for the transient layered zeolite MCM-56 with MWW topology

• Published in: Catalysis today Vol. 345; pp. 116 - 124
• Main Authors: Korzeniowska, Aleksandra, Grzybek, Justyna, Kałahurska, Katarzyna, Kubu, Martin, Roth, Wiesław J., Gil, Barbara
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2020
• Subjects: External Brønsted acid sites; Friedel-Crafts alkylation; MCM-56 zeolite; Structure-Catalytic activity relationship; Friedel-Crafts alkylation; MCM-56 zeolite; Structure-Catalytic activity relationship; External Brønsted acid sites
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2019.09.044

•MCM-56/49 zeolites were synthesized using Aerosil, Ultrasil and Ludox as silica sources.•MCM-56 synthesized with aniline showed enhanced availability of Brønsted acid centers.•Zeolites were tested in Friedel-Crafts alkylation of mesitylene with benzyl alcohol.•Catalytic activity depended on external Brønsted centers concentration.•Key role of IR spectroscopy in correlating physical characteristics with activity. [Display omitted] Zeolite MCM-56 is a high alumina, monolayered form of the commercially useful framework MWW but it is a transient product during crystallization, so many factors influence its state and quality. This work examines properties of a series of MCM-56 and MCM-49 samples synthesized for different times using Aerosil, Ultrasil and Ludox as silica sources, hexamethyleneimine as the structure directing agent and additionally aniline as structure promoting agent. It was found that the most important parameter, governing the catalytic activity in the test reaction of Friedel-Crafts alkylation of mesitylene with benzyl alcohol, was availability of the Brønsted acid centers located at the external surfaces of the crystals. The key role in correlating physical characteristic with activity was played by infrared spectroscopy as it enabled the study of many properties of the tested materials, starting from the total concentration of acid centers, and their type (Brønsted or Lewis acids) through the concentration of centers available for the reagent molecules, to investigating the correlation of acidity with the degree of zeolite crystallinity.