The guest molecular replacement method in hydrates offers dual advantage such as retention of their structural stability, and as a sink for carbon dioxide (CO2). However, the molecular exchangeability shows significant variance and the mechanism is also incomprehensible. This study is aimed at probing the stability of gas (CH4 & CO2) hydrates in the presence of CO2/CH4, N2 and their mixtures at low-pressure (~1.0 MPa) conditions. The selected experimental conditions help gain insight into the guest-guest exchange. Evaluation of gas pressure during the dissociation process indicates the presence of mixed hydrates. The micro-Raman investigations elucidate the occurrence of mixed hydrate seed crystals, encasing both CH4/CO2 molecules of initial hydrates, and also the molecules from the injected gas. The characteristic signatures of CH4 & CO2 molecules in hydrate systems broadly agree with the literature data, while that of N2 pointedly closer to the gas phase signature, indicating its role as a help-gas to promote replacement/rearrangement of guests in hydrate lattice.
Citation: Pinnelli S.R. Prasad, Burla S. K.; 2020, Stability and exchange of guest molecules in gas hydrates under the influence of CH4, CO2, N2 and CO2+N2 gases at low-pressures, Journal of Natural Gas Science and Engineering, 78, 103311, https://doi.org/10.1016/j.jngse.2020.103311