Decomposition and Raman spectrum of dimethyl ether hydrate

The thermal stability and decomposition of dimethyl ether (DME) and DME hydrate were studied using a self-designed instrument. The Raman spectra of DME, a solution mixture of DME and water (DME–water) and DME hydrate were measured. The result showed that the decomposition temperature of DME hydrate was dependent on the ambient pressure and H2O/DME molar ratio; DME hydrate tended to decompose at a higher temperature under a higher ambient pressure. The decomposition temperature of DME hydrate was −13.8 °C when the molar ratio of H2O/DME was 12.0, and the stoichiometric composition of DME hydrate was inferred to be DME·13H2O. Raman spectroscopy analysis showed that the vibration of DME hydrate shifted toward lower wave numbers in comparison with that of DME-water and DME. Moreover, the spectrum of DME hydrate showed a vibration band at 3151 cm−1, which was not observed for DME-water or DME.