Some Properties of Mixed Paraffinic and Olefinic Hydrates

Abstract

Abstract An experimental investigation was made of the effect of temperature upon thethree-phase pressure associated with the propane-water and propene-watersystems when hydrates were present. In addition, the characteristics of thepropane-propene-water system were established over a limited range oftemperatures under conditions such that hydrate was formed. The hydrate phasefor this system may be a solid solution and the distribution of propane andpropene in it is similar to that found in the coexisting hydrocarbon liquidphase. Introduction A knowledge of the characteristics of hydrates of the hydrocarbonsencountered in industrial practice is of importance in connection with thedesign of process equipment. Villard carried out early studies of hydrates, andde Forcrand considered the more probable compositions of the hydrates ofhydrocarbons. Hammerschmidt presented information about the propane-water andthe isobutane-water systems. Scheffer studied the hydrate of hydrogen sulfidein detail, and de Forcrand reported on the hydrates of krypton, argon, andxenon. Roberts and co-workers determined the nature of the hydrates formed in themethane-water and ethane-water systems. Carson and Katz studied themethane-propane-water, methane-pentane-water, and the methane-hexane-watersystems in the four-phase region. The results of this rather extensiveinvestigation indicated that the paraffinic hydrates formed solid solutions.The experimental evidence now available does not support the existence ofhydrates of the pentanes-and heavier hydrocarbons but it cannot be stated withcertainty that such hydrates are not formed. Stackelberg made extensive studiesof the crystal structure of paraffinic hydrate, by means of x-ray techniquesand found that hydrates posses, a definite structure and composition. Theexistence of such a structure does not preclude the formation of solidsolutions of hydrates in aqueous systems containing two or morehydrocarbons. Wilcox, Carson and Katz reviewed the information on the hydrates ofimportance in the processing of natural gas and presented data concerning theirformation from natural gas. Kobayashi and Katz made studies at high pressure ofthe hydrate of methane, and Unruh and Katz investigated hydrates in mixtures ofcarbon dioxide and methane. Frost and Deaton contributed to the knowledge of the composition of theparaffinic hydrates. The irregularities in the experimental results wereseveral times the expected uncertainties. This experience confirms the behaviorencountered by other investigators indicating that hydrates tend to occludewater during their formation, thus rendering difficult the direct measurementof their composition. T.P. 3376