Inhibiting effects of transition metal salts on methane hydrate stability

The behavior of clathrate hydrates in the presence of transition metal salts was investigated using a Differential Scanning Calorimeter (DSC). Specifically, a DSC was employed to determine the onset temperature for methane hydrate decomposition in the presence of ferric chloride hexahydrate, [FeCl2(H2O)4]Cl·2H2O, anhydrous ferric chloride, FeCl3, MnSO4, FeSO4, CuSO4, and AgNO3, and to compare the inhibiting properties of these transition metal salts with NaCl and CaCl2, two well-known salt inhibitors. The degree of methane hydrate inhibition induced by the salts that were studied (as indicated by the reduction in dissociation temperature at a given pressure), when compared between mixtures with the same mole percentages of the salt, increases in the following order: FeSO4≈CuSO4