Double gas hydrate of isopropanol and methane

Composition and structure of isopropanol and methane double hydrate synthesized from isopropanol solutions with concentrations from 6.2 to 17.9 mass.% were studied by means of thermovolumetric and X-ray powder diffraction methods. It was found that the double hydrate has a cubic structure II within the whole concentration range. Composition of the double hydrate with the maximal methane content corresponds to 4.5 C3H7OH·17.0CH4·136H2O (274.2 K and 5.2 MPa). We studied the decomposition curve of this hydrate in the temperature range from 253 K to 280 K. At temperatures above 273.2 K, double hydrate decomposition temperatures are only 1–2 K higher than that of pure methane hydrate. However, at temperatures below 273.2 K, double hydrate decomposition temperatures are significantly higher in comparison with methane hydrate. For example, at 1 MPa, methane hydrate decomposes at 243 K while double hydrate decomposes at 267.0 K. Our findings show that isopropanol is a promising hydrate-forming component whose aqueous solutions may be advantageously used in separation processes using gas hydrate formation technology at temperatures below 273.2 K and for gas storage in the form of double gas hydrate.