Session: ENFL General Posters:

The rising need for methane storage and transportation drives research on solid storage methods, such as gas hydrates. To exploit the potential of gas hydrates, the induction time for hydrate growth must be minimized and the extent of water-to-hydrate conversion maximized. One approach is using the class of porous materials called metal-organic frameworks (MOFs), which consists of metal ions connected by organic linkers. The advantageous properties of MOFs are the following: large surface area (increases gas-to-water contact area, reducing gas diffusion limitations), surface chemistry (promote nucleation due to how it interacts with methane and water), and the pores (act as nucleation sites for hydrate growth). This study focuses on two MOFs: ZIF-67 and ZIF-8. These MOFs share the same sodalite topology and organic linker, whereas ZIF-67 contains cobalt ions and ZIF-8 contains zinc ions. The effect of the MOFs on water-to-hydrate conversion and induction time were evaluated using a high-pressure differential scanning calorimeter (HP-DSC). Excellent performance was observed in terms of the overall water-to-hydrate conversion, as ZIF-8 increased it by 80% while ZIF-67 increased it by 82%. As for the induction time, the combined effects of the large surface area and good methane adsorption of both materials led to a decrease in hydrate nucleation induction time by 2.9 hours for ZIF-8 and 4.2 hours for ZIF-67. The shorter induction time associated with ZIF-67 stems from having a higher surface area than ZIF-8 (1585 m²/g versus 1052 m²/g) coupled with a higher methane adsorption (0.41 mmol/g versus 0.33 mmol/g). The adsorbed methane readily engages in hydrate formation, thus the higher methane content reduces the mass transfer limitations. Overall, ZIF-67 and ZIF-8 show excellent performance as methane hydrate growth promoters, and the cobalt and zinc ions, respectively, do not considerably effect the performance.

Moises Carreon

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