NMR transverse relaxation times and phase equilibria of methane hydrate in mesoporous alumina.

• Methane hydrate formation from water adsorbed in the pores of alumina was studied. • Low-field NMR spin–spin relaxation time (T 2) method was used. • No movement of water between pores during hydrate formation was detected. • Temperature decreases results in hydrate formation in smaller and smaller pores. • The size of hydrate particles previously formed in larger pores increases in parallel. The processes of formation (and decomposition) of methane hydrate from water adsorbed in the pores of spherical granules of mesoporous alumina (Al 2 O 3) have been investigated using the low-field NMR spin–spin relaxation time (T 2) and DSC methods. Analysis of the obtained data showed that changes observed in the relaxation time spectra represent a strong case in favor of the model envisaging hydrate growth in pore spaces without conspicuous water transfer through the volume content of the sample with mesoporous structure. As the supercooling strength of the liquid phase enhances, the size of the pores in which hydrate formation takes place decreases. At this, the size of the hydrate particles previously formed in larger pores tends to increase. Hydrate nucleation was shown to be followed by intensive and rapid hydrate formation in some parts of the alumina granules in the sample. The "skipping" mechanism of hydrate formation between granules remains unclear. [ABSTRACT FROM AUTHOR]