The
development of an effective approach for methane utilization,
especially methane conversion to methanol, is a crucial challenge
that has remained unsolved satisfactorily. Herein, we propose an alternative
concept of methane utilization to methanol over Fe-ZSM-5@ZIF-8. The
concept is to use the designed composite as a dual catalyst in which
ZIF-8 and Fe-ZSM-5 act simultaneously as a gas adsorbent and catalyst,
respectively. In this case, methane can be adsorbed on ZIF-8 at 50
°C and subsequently converted to methanol at a moderate temperature
(150 °C) on Fe-ZSM-5. Interestingly, the promising catalytic
performance is observed on Fe-ZSM-5@ZIF-8, whereas only trace amounts
of produced methanol are detected on isolated Fe-ZSM-5 and ZIF-8.
Moreover, the designed composite also facilitates a facile methanol
desorption at the hydrophobic surface of the composite. This first
example opens up new promising horizons in combined perspectives for
gas storage and catalytic process applications.
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.
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