Synthesis, characterization, and evaluation of the CO₂ adsorption capacities of beta, ZSM-12, ZSM-48, and silicalite-1 zeolites obtained in the presence of tetraethylammonium hydroxide and 1,6-diaminohexane as organic structure-directing agents

Zeolites synthesis using a combination of tetraethylammonium hydroxide (TEAOH) and 1,6-diaminohexane (DAH) as organic structure-directing agents (OSDAs) has been studied in order to understand how they acted during the synthesis. This combination can crystallize four zeolites: beta, ZSM-12, ZSM-48, and silicalite-1. TEAOH is found to direct the synthesis of beta, and ZSM-12 zeolites, whereas DAH directs the synthesis of ZSM-48 zeolite. On the other hand, the two organic components are found to have a cooperative role in the crystallization process of silicalite-1, with greater templating ability for TEAOH compared to DAH. The use of a supplementary organic component does not affect the degree of filling of the primary OSDA in the structure or the morphology of the obtained zeolites. The carbon dioxide (CO₂) adsorption capacity of the zeolites obtained was evaluated at a temperature of 293 K in a pressure range of 0 to 1 atm. The relationship between the surface properties of the zeolites and their adsorption behavior was studied. Beta zeolite had the highest adsorption capacity with 2.9 mmol/g, while ZSM-48 zeolite had the lowest adsorption capacity with only 0.7 mmol/g.