An apparatus has been designed and constructed to measure liquid hydrocarbon solubility in water. On-line analysis coupled with gas chromatography has been applied to the determination of binary mixtures of water with benzene and cyclohexane for the temperature range (70 to 150) °C. Measurements obtained for benzene show good agreement with literature values and allow us to validate this new method. Increasing the temperature from 70 °C to 150 °C increases the mole fraction solubility of cyclohexane in water from (19.7 ± 0.02) × 10-6 to (131 ± 3) × 10-6.

A solid-phase extraction method has been developed for measuring low solubilities of hydrocarbons in water. The solubilities in water of methylcyclohexane, ethylcyclohexane, trans-1,2-dimethylcyclohexane, and a mixture of 1,2-dimethylcyclohexane isomers (respectively, 89.3 mol % and 10.7 mol % of the cis and trans isomers) were determined at temperatures ranging from (30 to 180)°C. At 30°C, the mole fraction solubility is (2.96 ( 0.03) × 10 -6 for methylcyclohexane, (0.699 ( 0.007) × 10 -6 for ethylcyclohexane, and (0.80 ( 0.02) × 10 -6 for trans-1,2-dimethylcyclohexane. The mole fraction solubility is (1.09 ( 0.01) × 10 -6 and (0.91 ( 0.01) × 10 -6 , respectively, for cis-1,2-dimethylcyclohexane and trans-1,2-dimethylcyclohexane (from the mixture). Temperature effect on solubility in water for ethylcyclohexane and for the dimethylcyclohexanes is very similar. Increasing the temperature from (30 to 180)°C increases the solubilities by a factor of approximately 40. IntroductionWater is continuously present during the fluid-reservoir formation and the exploitation of oil and gas reservoirs. Also, knowledge of water-hydrocarbon phase behavior is of tremendous interest in the environmental sciences and in the chemical and petroleum industries.There is a large amount of solubility data in the literature, and nearly all available data are at ambient conditions, or these data are in poor agreement.In a previous paper, 1 we reported solubility measurements in water for benzene and cyclohexane over the temperature range of (70 to 150)°C. A static apparatus has been designed and constructed for these determinations. It allows for the on-line analysis by gas chromatography of the hydrocarbon saturated aqueous phase in equilibrium. But the solubility of alkanes and alkylcyclohexanes in water is lower than the solubility of aromatics or cyclohexane. The on-line method previously described and used 1 was not adapted and was modified. 2 Water saturation is still performed using the static method, but the sampling procedure is accomplished using the solidphase extraction method. 3 Trace hydrocarbon saturated water is trapped in a C18 column and then eluted by methanol. Methanol + hydrocarbon solutions are analyzed by gas-chromatography flame-ionization detection (GC-FID) using an internal standard calibration method.The present work reports the solubility in water of methylcyclohexane, ethylcyclohexane, trans-1,2-dimethylcyclohexane, and of a mixture of 1,2-dimethylcyclohexane isomers (cis + trans) at temperatures ranging from (30 to 180)°C.

A solid-phase extraction method has been developed for measuring low solubilities of hydrocarbon in water. The solubilities of hexane, heptane, and octane in water were determined at temperatures ranging from (30 to 180) °C. The solubilities of alkanes in water at 30 °C decrease with increasing carbon number. At 30 °C, the mole fraction solubility is (2.06 ± 0.01) × 10-6 for hexane and (0.120 ± 0.002) × 10-6 for octane. The temperature effect on solubility in water is much more important for octane than for hexane. Increasing the temperature from (30 to 180) °C increases the solubilities by a factor of 23 for hexane and 110 for octane.

An apparatus has been designed and constructed to measure mutual solubilities of (water + hydrocarbon). The solubility of water in toluene, cyclohexane, methylcyclohexane, ethylcyclohexane, and (cis + trans)-1,2-dimethylcyclohexane were determined at temperatures ranging from (30 to 180)°C. Measurements obtained for toluene show good agreement with literature values and allow us to validate this new method. As expected, increasing the temperature increases the solubilities of water in the alkylcyclohexanes. Furthermore, the solubility of water in alkylcyclohexanes increases with the number of carbon atoms.