Revealing Zeolites Active Sites Role as Kinetic Hydrate Promoters: Combined Computational and Experimental Study

Abstract

Clathrate hydrates are emerging as a novel storage medium for safe and compact methane storage. However, their industrial-scale applicability is hindered by relatively lower gas uptake and sluggish formation kinetics. In this study, we have employed zeolites with acidic (H-Y, FAU-type) and basic (Na-X, FAU-type) surface properties as kinetic hydrate promoters (KHPs). The impact of physical parameters as pressure and the gas-to-liquid ratio has also been studied. In a combined experimental and computational study, we assessed the performance of the two types of zeolites in different concentrations and pressures for binary CH 4 -THF clathrate hydrate synthesis in 1 a non-stirred configuration. The kinetic study results showed that the acidic zeolite (H-Y) exhibited superior performance over the basic one (Na-X), reaching its optimum at 0.5 wt% zeolite, which agreed well with the DFT calculations. The methane conversion reached 94.25% at this concentration and a relatively mild pressure (6 MP). The induction time and t 90 (time to reach 90% of final gas uptake) were reduced by 35% and 31%, respectively. Our results open the door for a better understanding of the role of acidic zeolites as possible environmental benign KHPs that can help the utilization of water as a medium for green energy storage and transportation.

Toward Economical Seawater-Based Methane Hydrate Formation at Ambient Temperature: A Combined Experimental and Computational Study

“…Such an explanation is also applicable to hydrophilic surface silanol groups and agrees with the literature 76 . However, our previous studies showed that such hydrogen-bonding interactions due to BAS are much lower than that of alkali metal extra framework cations such as sodium which can cause the clathrate structure to collapse 45 .…”

“…Among porous materials, zeolites are green materials with low cost, large surface area, tunable acidity and hydrophobicity, and above all high stability in aqueous medium 42,43 . The above properties of zeolites can significantly affect the kinetics of hydrate formation 44,45 . For example, the zeolite hydrophobicity and acidity can be tuned by changing Si/Al ratio , synthesis conditions or healing the defect sites 46,47 .…”

“…Recently, Omran et al revealed that acidic zeolite (H-Y, FAU-type) exhibited superior KHP performance over the basic one 13X (Na-X, FAU-type) for at relatively mild pressure (6 MP) without the need for SDS 45 . While there are many studies that investigated saline-based hydrate formation at elevated pressures and lower temperatures 22 , it has been rarely studied at ambient temperature.…”

“…In addition to amino acids, porous materials that can act as nucleation sites that accelerate the nucleation process were employed as KHPs. − Among porous materials, zeolites are green materials with a low cost, large surface area, tunable acidity and hydrophobicity, and above all high stability in aqueous medium. , These properties of zeolites can significantly affect the kinetics of hydrate formation. , For example, the zeolite hydrophobicity and acidity can be tuned by changing the Si/Al ratio, tuning the synthesis conditions, or healing the defect sites. , Moreover, zeolites are stable in aqueous medium in comparison to the most common MOFs, which suffer from structural deformation with their metal-coordinated linkers being replaced by water molecules . In spite of the advantages mentioned above, only a few studies have investigated the performance of zeolites as KHPs, with zeolite Na-X (FAU-type) being reported as the best performing zeolite in comparison to different ion-exchange forms (3A and 5A) of zeolite A (LTA-type).…”

Zeolitic ice: A route toward net zero emissions

“…In general, these materials can be utilized in two different ways: (1) in low concentrations as a nucleation site for heterogeneous nucleation to reduce the induction time [127] and (2) as host for hydrate using the confinement effect [128]. In the first approach, the porous material increases the surface area by adding another interface (or third surface) that facilitates crystallization and gas diffusion [129]. For example, hollow silica was also examined in many studies and showed kinetic improvement.…”