A = a = = ideal gas state Subscripts c = critical property i, i, k = component identifications o = reference state A group contribution molecular model is developed for the thermocluding energy of vaporization, pVT relations, excess properties, and activity coefficients. The model is based on the cell theory in which the repulsive forces of molecules are expressed with a modified cell partition function derived from the Carnahan-Starling equation of state for hard spheres. The attractive forces are made u p of group pair interaction contributions. Group and interaction properties have been determined for methyl, methylene, hydroxyl, and carbonyl. Extensive comparisons are School of Chemical Engineering made of predictions of the model with data for pure liquids and their solu-Purdue University tions. West Lofayette, Indiana 47907 1. To develop a comprehensive theory of group contribution for the estimation of various thermodynamic

A general correlation of vapor-liquid equilibria in hydrocarbon mixtures is developed. The vaporization equilibrium ratio (K-value) is calculated through a combination of three factors (Qr) (@) K=-The quantity YO is a pure liquid component property and is correlated within the framework of Pitzer's modified form of the principle of corresponding states. The quantity y is calculated from Hildebrand's equation, with regular liquid solutions assumed. The necessary parameters in this equation are specially determined for the very light components. The vapor state quantity @ is calculated from Redlich and Kwong's equation of state. The correlation is in the form of o compact set of equations which are especially suitable for application with on electronic digital computer. The correlation applies to hydrocarbons of various molecular types, including paraffins, olefins, aromatics, and naphthenes. Hydrogen in hydrocarbon mixtures is likewise correlated. The correlation has been tested with a systematic compilation of literature data on mixtures of these components. The over-all average deviation from 2.696 data Doints is 8.7%. -J. D. Seader is with Rocketdyne,

y z X = ratio of R2 to R1 = ratio of the derivative time constant to y l / y z ; = positive constant.used to multiply each process see Equation ( 7 4 time constant in a set = defined by Equation (7b) = defined by Equation ( 7 c ) , s = product of the process time constants; T 1 ' 7 2 . 7 3 , s = sum of process time constants; 71 + 72 + T3, s = smallest process time constant, s = second largest process time constant, s = largest process time constant, s = reset or integral action time constant, s = derivative action time constant, s Greek Letters al a2 y1 y3 TI Q TS vi TD T~Z -N ; T D Z -N = values of 7 1 and T D suggested by the Zieg-7 2 = 7172 + 7173 + 72T.3, s2 ler-Nichol's rules, s rib = all lower values of Ti will lead to operation in the split stability region; defined by Equation = lowest value of T~ for z = 1 for which any value = critical frequency (that is, 180 deg phase lag), (lo), s T~~ oC of K , will lead to stable operation, s

A flow type of apparatus is built to give equilibrium gas and liquid samples at elevated pressures and temperatures while minimizing thermal decomposition. Saturated vapor and liquid compositions and K values are determined with this apparatus for the binary system hydrogen/tetralin (1,2,3,4-tetrahydronaphthalene) at SCOPEThis work extends experimental investigation of phase equilibrium of hydrogedheavy solvent systems to elevated pressures and temperatures of interest in hydro treating processes, particularly coal liquefaction processes. Information on the amount of dissolved hydrogen in the liquid phase is useful for analysis of reaction mechanism and for engineering design of blowdown and associated separation systems.Previous studies of the phase equilibrium of hydrogen/ solvent systems have been limited to relatively low temperatures. An exception is found in the work by Grayson and Streed (1963) in which a correlation of K values of hydrogen in heavy oils was presented for temperatures and pressures comparable to this work, but no detailed experimental data were given.The system hydrogedtetralin reported here is the first system studied in the new flow type of apparatus we have just built. The study is being continued with other hydrogen mixture systems. The data gathered with various types of solvents will contribute to the development of general quantitative description of the solubility of hydrogen in complex liquid mixtures. CONCLUSIONS AND SIGNIFICANCEVapor-liquid equilibrium in hydrogen/solvent systems has been the subject of a great deal of investigation owing to their industrial importance and scientific interest. The development of hydro treating and coal liquefaction processes generated renewed interest focused on conditions of high temperature and pressure and on heavy solvents. In this work we built a new flow type of apparatus and showed that equilibrium data can be obtained from it with small residence times of the samples in the high temperature zone. Thermal decomposition is minimized as residence time is reduced, making possible determination of equilibrium data at high temperatures that would otherwise lead to excessive decomposition.That equilibrium is attained in the apparatus at the conditions of operation is supported by the positive results obtained from three tests:1. The sample compositions are independent of flow rates within the range of flow rates employed.2. Data on hydrogedbenzene from our apparatus agree with results obtained by Connolly (1962) from a static apparatus.3. The new data on hydrogedtetralin satisfy the GibbsDuhem equation.Equilibrium saturated liquid and gas compositions and K values are determined for the binary system hydrogen/ tetralin at four temperatures (189. 6O, 268.7O, 348.6O, 389.1OC) and seven pressures (20, 30, 50, 100, 150, 200, 250 am). Henry constant of hydrogen is determined from the data. The results are useful for modeling the phase behavior of hydro treating and coal liquefaction processes. Since tetralin is widely used as a hydrogen-donor s...

Gas-liquid equilibrium data are determined for mixtures ofCOz 4toluene at five temperatures from 120 to 270 OC and for mixtures of CO, + m-xylene at four temperatures from 190 to 310 O C . The pressures were up to 50 atm for both systems.

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Compositions of saturated equilibrium liquid and vapor phases are determined In a flow apparatus for mixtures of methane and n-decane at 150, 240, 270, 290, and 310 OC, for methane and benzene at 150, 190, and 230 OC, and for methane and toluene at 150, 190, 230, and 270 OC. Pressures extend to near the crltlcals of the mixtures starting from 20 atrn or from somewhat above the vapor pressure of the solvent Whichever is higher.

Equations A4 and A5 have a feasible solution Dad > 0 i = 1,2,. . ,N ('48) if and only if the hyperplane defirxed by these equations intersects at least one of the planes bounding the positive region. Thus, at least one set of equations (A91 a