Effect of Pore Connectivity of Pore-Opened Hierarchical MOR Zeolites on Catalytic Behaviors and Coke Formation in Ethanol Dehydration

Abstract

The hierarchical zeolite is one of the most promising materials for catalytic applications. However, the effect of its pore connectivity on catalytic behaviors and coke formation has not clearly been revealed. In this contribution, we demonstrate the visualization of the mesopore architecture in three-dimensional perspectives together with the pore connectivity network of poreopened hierarchical mordenite (MOR), fabricated by the seedassisted template-free synthesis followed by the fluoride treatment via the electron tomography (ET) technique. Interestingly, the pore-opened zeolites clearly display higher catalytic performance (approximately 80% of ethylene yield) in ethanol dehydration with respect to the parent one due to their additional pore-opened structures connected to the external surfaces of zeolites. In addition, the effect of pore connectivity network on the coke location and type obtained from ethanol conversion has been observed. It was found that the porous structure of the etched sample is directly connected to the external surface, and then, the large area of crystals can contribute to the reaction. Conversely, only a small amount of closed mesopores is observed inside the crystals in the case of the untreated sample, and therefore, the molecules cannot easily penetrate inside crystals for the catalytic reaction. These results open up promising perspectives for the development of hierarchical catalysts including fabrication by the template-free synthesis approach, pore-architecture characterization, and catalytic applications.

Bioethanol Upgrading to Renewable Monomers Using Hierarchical Zeolites: Catalyst Preparation, Characterization, and Catalytic Studies

“…It has been applied in many catalytic reactions such as the partial oxidation of methane to methanol [46], dimethyl ether carbonylation [47], and esterification with oleic acid [48]. Recently, the pore-opened mordenite (MOR) zeolite was also efficiently prepared using the similar NH 4 F etching method [49]. The parent MOR zeolite was treated with the NH 4 F aqueous solution to create the mesoporous network over the MOR crystals.…”

“…Recently, the visualization of zeolite pore architecture in three-dimensional views by electron tomography (ET) was revealed [49]. The MOR zeolites before and after the NH 4 F etching were characterized by the ET technique with the tilting angles from −70 • to + 70 • as shown in Figure 5.…”

“…In contrast, the parent MOR sample exhibited a small amount of closed mesopores inside the zeolite crystal. [49]. Copyright 2021 American Chemical Society.…”

Binder-free hierarchical zeolite pellets and monoliths derived from ZSM-5@LDHs composites for bioethanol dehydration to ethylene

“…4 Therefore, several strategies demonstrate the development of catalysts to achieve high catalytic performance in ethanol dehydration, for example, the fabrication of modified acid zeolites with hierarchical structures. 5,6 Although a rationally designed catalyst in powder form has been developed to improve the catalytic activity, it is still limited in terms of commercial use because of the pressure drop related to the fluid frictional flow of powder catalysts. 7 Therefore, catalyst powders are constructed into macroscopic objects, such as pellets, beads, and granules, well known as extruded catalysts.…”

“…4 Therefore, several strategies demonstrate the development of catalysts to achieve high catalytic performance in ethanol dehydration, for example, the fabrication of modified acid zeolites with hierarchical structures. 5,6…”