Hydrate dissociation enthalpy and guest size

A heuristic is proposed to estimate one of the most important physical properties of hydrates, namely the heat of hydrate dissociation (Δhd) at temperatures above 273.2 K. It is shown that it is possible to estimate ΔHd by knowledge of the size of the hydrate guest molecule. To a first approximation, the enthalpy of dissociation is independent of the type and concentration of the guest gas, within a broad size constraint. While predicted values are neither as accurate nor as difficult as calorimetric measurements, the values are acceptable for many engineering calculations, and the prediction may serve in the absence of measurements. The hypothesis of the paper is demonstrated for single and mixed components of natural gases and for argon, krypton, xenon, oxygen, and nitrogen. As one notable outcome, most natural gases containing appreciable amounts of methane and propane should have essentially the same heat of dissociation.