Adamantane and diamantane; phase diagrams, solubilities, and rates of dissolution

Properties of adamantane and diamantane relevant to their occurrence in and removal from gas pipelines have been determined. The phase diagrams for these two diamondoids have been determined between ambient temperature and the estimated critical point using vapor pressure measurements, S-S and S-L phase transition observations, and solubilities in dense carbon dioxide. Diamantane exhibited three different solid phases. Although many common organic liquids were strong solvents for adamantane and diamantane, cyclohexane was particularly effective due to the similarity between its structure and the fused cyclohexane ring structure of the diamondoids. A generalized correlation for the mass transfer coefficient governing the dissolution of extremely thick diamantane deposits from the inter wall of pipelines developed in this study can be used to provide accurate estimates of the amount of solvent required to remove the deposit. Reasonable estimates can also be obtained with the analytical solution derived in this study if an invariant, average mass transfer coefficient is used.