Carbon capture and storage as gas hydrates: characterization and optimization of CO2-hydrates formation

The sequestration of carbon dioxide (CO2) in the form of gas hydrates presents a promising strategy for mitigating climate change by securely storing CO2 in marine environments. Gas hydrates are crystalline structures consisting of water molecules organized in cages which encapsulate different guest molecules, like CO2 [1]. Gas hydrates are formed at low temperature and high-pressure conditions, commonly found in deep-sea. Thus, the marine environment offers ideal conditions for hydrate formation, with natural sediments acting as reservoirs. This study explores the potential of hydrate-based CO2 storage in marine sediments, focusing on the mechanisms of hydrate formation, the influence of sediment properties and the long-term stability of stored CO2. In this context, CO2 gas hydrates were formed both in presence and in absence of natural sand of the Adriatico sea, the confirmation of CO2 uptake was obtained by Raman Analysis. Given the similarity of ice water with gas hydrates, water at different temperatures has been investigated by Raman spectroscopy and scanning electron microscopy to obtain information about the influence of sand and temperature on hydrates structure and formation [2]. The results show that CO2 hydrate formation is more efficient in natural sediments than in pure water, with higher gas uptake and formation density. The study of -OH water vibrations band by Raman measurements, and the SEM analyses confirms that the presence of sand reduces molecular disorder, promoting more stable and denser hydrate structures. This suggests that examining the microscopic ice structure and the behaviour of the vibrational bands, it is possible to provide valuable information for the prediction of the gas hydrates structure and to give a better understanding of the interactions between water molecules and sediments. The aim of this study falls within the PRIN 2022 PNRR project entitled «Reliable long-term CO2 storage as clathrate hydrates in seawater and marine sediments (CO2-RESTO)», funded by the European Union – Next Generation EU.