Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

CH4 Adsorption in Wet Metal-Organic Frameworks Under Gas Hydrate Formation Conditions Using Large Reactor

Version 1 : Received: 15 April 2024 / Approved: 15 April 2024 / Online: 16 April 2024 (09:23:44 CEST)

A peer-reviewed article of this Preprint also exists.

Pandey, J.S.; Öncü, N.; von Solms, N. CH4 Adsorption in Wet Metal-Organic Frameworks under Gas Hydrate Formation Conditions Using A Large Reactor. Energies 2024, 17, 3509. Pandey, J.S.; Öncü, N.; von Solms, N. CH4 Adsorption in Wet Metal-Organic Frameworks under Gas Hydrate Formation Conditions Using A Large Reactor. Energies 2024, 17, 3509.

Abstract

Nanoporous materials, such as Metal-Organic Frameworks (MOFs), are renowned for their high selectivity as gas adsorbents due to their specific surface area, nanoporosity, and active surface chemistry. A significant challenge for their widespread application is their behavior and reduced gas uptake in wet conditions, attributed to competitive adsorption between gas and water. The current understanding of gas adsorption in wet materials is constrained by studies that utilize only small amounts of powdered porous materials (in the milligram range) within very small reactors (1-5 mL). This leaves a significant gap in knowledge about gas adsorption behaviors in larger reactors and when MOF sample sizes are increased (to the gram scale) for scaling up the process. Additionally, there is a notable dearth of experimental research in situations where MOFs are heavily saturated with water. To address these gaps, this study measures CH4 adsorption in MOFs under conditions of high moisture content, using larger samples of MOFs (in grams) and a large volume reactor. We selected commercially available MOFs, including HKUST-1, ZIF-8, MOF-303, and activated carbon. A high-pressure isotherms (at T = 274.15 K) using volumetric approach were measured to qualitatively compare the moles of gas adsorbed under both dry and wet conditions across different MOFs and weights. Experimental results show that the presence of water led to a decrease in total CH4 mmol adsorption in MOFs, with a more significant decrease observed in hydrophilic MOFs compared to hydrophobic ones. For hydrophilic MOFs, presence of crossover isotherms at crossover pressure provided evidence of water's conversion to hydrate and its positive role in enhancing total gas uptake, which varied among different hydrophilic MOFs. Oversaturated MOFs showed a larger deviation between dry and wet cases at higher pressures. The high-pressure isotherm data confirm the positive role of hydrophilic MOFs in the conversion of water to hydrate in oversaturated MOFs when MOFs sample size is large.

Keywords

Metal Organic Framework; high pressure isotherms; gas hydrates; CH4 storage

Subject

Engineering, Chemical Engineering

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