Formation kinetics of propane hydrates

Propane hydrates are rarely considered by scientists. Despite the narrow borders of the formation region, they can form during storage and transportation of the liquefied petroleum gases. Therefore, it is important to know the induction time for solid hydrate formation. The present paper has considered the formation both from melting ice (at 1degreesC and 4 bar) and from water (at 2degreesC and 3.6-4.8 bar) in a stirred vessel. The formation from ice was quite instantaneous, while the production from water took about 15 h to start (and about 3 days to be completed) and depended on the pressure: in fact, it was slower at low pressure. All hydrates contained a high amount of ice (75-80%). The modulated differential scanning calorimetry was used for hydrate characterization: the reversing (heat-capacity) curves permitted one to quickly distinguish between hydrate and ice, also allowing a semiquantitative evaluation of the hydrate content.