ON THE STABILITY OF TYPE-I GAS HYDRATES IN THE PRESENCE OF METHANOL

Using computer simulations we have studied the stability of type I gas hydrates for different mixtures of methane/methanol at 270 K and atmo spheric pressure. In the nanosecond time regime the empty and the meth ane-filled hydrate are stable with only small perturbations to the wat er cavity structure. Inclusion of methane stabilizes the lattice struc ture over the empty hydrate. A hydrate filled with methanol melts in r oughly 1 ns with a concomitant destruction of the cavity structure. Th e resulting mixture is liquidlike in contrast to the icelike hydrate s tructure. Small amounts of methanol can be incorporated into the hydra te structure; thus a 4 wt % methanol solution is stable, whereas a 7 w t % solution melts. In the stable methanol hydrate cavity structure is maintained, but the perturbations relative to the empty hydrate empha size the inherent flexibility of these structures. More alcohol can be incorporated into the hydrate if methane is allowed to stabilize the hydrate.