Nucleation curves of methane - propane mixed gas hydrates in hydrocarbon oil

The second generation High Pressure Automated Lag Time Apparatus (HP-ALTA MkII) was used to measure the nucleation curves of Structure II (sII)-forming methane-propane mixed gas hydrates on the surface of a quasi-free water droplet suspended in involatile hydrocarbon oil, squalane. The measured nucleation curves were then compared to the previously obtained nucleation curves of the same guest gas hydrate on a quasi-free water droplet supported by perfluorodecalin. The comparison of the two sets of data sets showed that the nucleation rates of the two systems were broadly similar to each other. A simple master nucleation curve was derived for each system as a function of the system subcooling. The model-independent empirical equation that relates the nucleation rate to the system subcooling was Jwater-guest (s−1 m−2)=2.38×10−39ΔT26.746 for a quasi-free water droplet suspended in squalane and Jwater-guest (s−1 m−2)=7.70×10−11ΔT7.931 for a quasi-free water droplet supported by perfluorodecalin. The nucleation rates predicted by these empirical equations are then compared to the nucleation rates of other relevant systems in the literature. The model-independent analysis method for the derivation of nucleation curves we have developed can be applied to constant cooling ramp data obtained by any experimental techniques.