The effect of some hydrocarbon liquids on methane hydrate nucleation

Abstract

The effect of some liquid hydrocarbon components on the nucleation process of methane clathrate hydrate has been investigated during isochoric, constant temperature nucleation experiments. The detected nucleation times were analyzed statistically and the key properties of nucleations were estimated through regression Most of the investigated components had a delaying effect on the nucleation, but with little difference between the components. This was the case for iso-pentane, n-hexane, n-octane, pentyl-benzene and n-dodecane. n-pentane showed virtually no effect, while cyclohexane had a nucleation propagating effect, though this may be because it can form a different hydrate structure (sII). Melting point tests indicated the formation of both sII and sI in the system when cyclo-hexane was present. The experimental results showed generally low reliability and it was concluded that this was because of the highly stochastic nature of the investigated phenomenon combined with statistical analysis on too little data. A novel method of detecting hydrate formation was used: a small but distinct pressure pulse was the first sign of hydrate formation, and this was successfully utilized to identify the time of hydrate formation in all the experiments. The activation energy of stable hydrate nuclei formation was successfully calculated using the Arrhenius plot method, and this could be used to calculate the critical radius of 31,8 Å.