| Summary: | The word energy outlook 2017 of the International Energy Agency (IEA) predicted an increase in natural gas energy demand until reaching a quarter of global energy demand in the new policies scenario by 2040, becoming the second-largest fuel in the global mix after oil.1 Nevertheless, the EIA annual report of 2022 reports a change in the scenario due to the war highlighting that the demand for natural gas will not follow the trend predicted in 2017, but it should slightly increase until 2050 (Figure 1). In this regard, the first two chapters of this thesis aim for two different solutions to contrast CO2 emissions and simultaneously obtain an energy source. Chapter 1 concerns the study of gas hydrates for CO2 storage and CH4 harvesting; the results reported in this chapter are also related to the PRIN 2017 (Progetti di Rilevante Interesse Nazionale) project. Gas hydrates are ice-like compounds present in nature that contain high amounts of methane; therefore, there is great interest in studying these compounds to understand how to exploit this energy resource without impacting the environment where they are present. The CO2 injection in CH4-hydrate reservoirs represents an attractive solution. This method allows the substitution of CH4, initially present, with CO2 by exploiting the greater stability of CO2-hydrates compared to methane ones. Accordingly, an imbalance of the natural deposits would not be created, and it would be possible to obtain CH4 to be used as an energy source and simultaneously store the CO2 to limit the greenhouse effect. Therefore, extracting natural gas from CH4-hydrate reservoirs and simultaneously storing CO2 can be considered a valid strategy for the energy transition phase. Natural gas hydrates are mostly found in sediments under the seabed or in the permafrost region, and the physical and chemical properties of marine water influence the phase behavior of NGHs due to the perturbation of the hydrogen bonds during the formation of hydrate structures. In this regard, Section 1.2 reports ...
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