Emerging green strategies for biogas upgrading through CO2 capture: From unconventional organic solvents to clathrate and semi-clathrate hydrates

Di Profio, Pietro; Ciulla, Michele; Di Giacomo, Stefano; Barbacane, Nadia; Wolicki, Rafal Damian; Fontana, Antonella; Moffa, Samanta; Pilato, Serena; Siani, Gabriella

doi:10.1016/j.molliq.2023.123196

Cited by 10 publications

(1 citation statement)

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“…Methods that consist of generating fine dispersions of the two phases are efficient because of the large water/guest interfacial area available for hydrate formation and growth, but it usually requires a lot of mechanical energy . Under quiescent conditions, one route for overcoming this mass-transfer limitation relies on the use of anionic surfactants added in tiny amounts (a few hundreds of ppmw) to the aqueous phase, which act to promote gas hydrate formation through mechanisms that are still poorly understood. − A better characterization and understanding of those mechanisms is key for increasing the TRL (technology readiness level) of gas-hydrate-based technologies, such as natural gas storage , and separation, − water treatment or desalination, , and secondary refrigeration. − Gas separation and water treatment or desalination involve a continuous flow that requires high gas hydrate throughputs, i.e., high conversion rates, whereas gas storage or secondary refrigeration requires high conversion levels; in the latter application, enough liquid water should be left unconverted to ensure flowability (see Figure ).…”

Section: Introductionmentioning

confidence: 99%

Growth Kinetics and Porous Structure of Surfactant-Promoted Gas Hydrate

Samar,

Venet,

Desmedt

et al. 2024

ACS Omega

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Surfactants present in tiny amounts in the aqueous phase are known to be efficient gas hydrate promoters; yet, the promotion mechanisms are still not fully understood. Understanding and directing those mechanisms is key to the implementation of gashydrate-based applications such as gas storage and separation, secondary refrigeration or water treatment, and desalination. In this work, the growth at the water/gas interface and the porous structure of surfactant-promoted methane hydrate are observed by optical microscopy and Raman imaging in glass capillaries used as optical cells. Hollow crystals are continuously generated and expelled from the methane/water meniscus into the water or surfactant solution, where they ultimately form the skeleton of a porous medium filled with the solution. Unprecedented information is gathered over a range of scales from the molecular scale (crystal structure and cage filling) to the mesoscale (crystal morphologies, growth habits and pore sizes) and macroscale (rates and amounts of water and gas converted into hydrate and hydrate porosity). Following an early steady-state growth regime, a sudden order-of-magnitude increase of the conversion rate occurs, which is related to gaseous methane microbubbles being directly incorporated across the meniscus in the aqueous solution and later converted to methane hydrate. An assessment and comparison are made of the mechanisms and performance of two common anionic surfactants known to be efficient gas hydrate promoters, SDS (sodium dodecyl sulfate) and AOT (dioctylsulfosuccinate sodium or AerosolOcTyl). AOT provides a quicker but more limited conversion into hydrate than SDS, suggesting that it is more appropriate for continuous flow processes while SDS is better suited for gas storage applications. Raman spectra reveal that cage filling by methane of structure I methane hydrate is not affected by surfactants.

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