Synthesis of Hierarchical MOR-Type Zeolites with Improved Catalytic Properties

Zeinab Mcheik; Ludovic Pinard; Joumana Toufaily; Tayssir Hamieh; T Jean Daou

doi:10.3390/molecules26154508

Synthesis of Hierarchical MOR-Type Zeolites with Improved Catalytic Properties

Molecules. 2021 Jul 27;26(15):4508. doi: 10.3390/molecules26154508.

Authors

Zeinab Mcheik^{1

2

3

4}, Ludovic Pinard³, Joumana Toufaily⁴, Tayssir Hamieh⁴, T Jean Daou^{1

2}

Affiliations

¹ Axe Matériaux à Porosité Contrôlée (MPC), Institut de Science des Matériaux de Mulhouse (IS2M), UMR 7361, CNRS, University of Haute Alsace (UHA), F-68093 Mulhouse, France.
² University of Strasbourg (Unistra), F-67000 Strasbourg, France.
³ Institut de Chimie des Milieux et Matériaux de Poitiers, UMR 7285 CNRS, 4 Rue Michel Brunet, Bâtiment B27, CEDEX 09, 86073 Poitiers, France.
⁴ Laboratory of Materials, Catalysis, Environment and Analytical Methods Faculty of Sciences, Section I, Lebanese University Campus Rafic Hariri, Hadath, Lebanon.

Abstract

Hierarchical MOR-type zeolites were synthesized in the presence of hexadecyltrimethylammonium bromide (CTAB) as a porogen agent. XRD proved that the concentration of CTAB in the synthesis medium plays an essential role in forming pure hierarchical MOR-type material. Above a CTAB concentration of 0.04 mol·L^-1, amorphous materials are observed. These hierarchical mordenite possess a higher porous volume compared to its counterpart conventional micrometer crystals. Nitrogen sorption showed the presence of mesoporosity for all mordenite samples synthesized in the presence of CTAB. The creation of mesopores due to the presence of CTAB in the synthesis medium does not occur at the expense of zeolite micropores. In addition, mesoporous volume and BET surface seem to increase upon the increase of CTAB concentration in the synthesis medium. The Si/Al ratio of the zeolite framework can be increased from 5.5 to 9.1 by halving the aluminum content present in the synthesis gel. These synthesized hierarchical MOR-type zeolites possess an improved catalytic activity for n-hexane cracking compared to large zeolite crystals obtained in the absence of CTAB.

Keywords: hierarchical zeolites; mordenite; n-hexane cracking; zeolites.