Study of the diffusion of liquids and their binary mixtures in mesoporous aluminosilicates under freezing conditions

The diffusion of n-decane, n-heptadecane and their binary mixtures of two different compositions confined in novel mesoporous aluminosilicates was investigated by the Pulsed Field Gradient (PFG) NMR technique. The temperature range studied was between −100 and 23 °C, comprising the bulk melting points of n-heptadecane at 23 °C and n-decane at −30 °C. The melting curves of all liquids measured by cryo-NMR allowed discrimination of the temperature ranges where non-frozen liquid existed in the pores. The study of n-decane and n-heptadecane mixtures of two different compositions by cryo-NMR does not reveal any preferential adsorption of one of the mixture components in the investigated material. In both the bulk and the pores, the diffusion coefficients follow Arrhenius dependencies with essentially identical activation energies. The diffusion coefficients of the liquids inside the pores are reduced by more than an order of magnitude.