Binary Vapor-Liquid Equilibrium for C3 Hydrocarbons* By

Binary Vapor-Liquid Equilibrium for C3 Hydrocarbons*

by ToshikatsuHakuta**, KunioNagahama**, and MitsuhoHirata**

Summary: High-purity propylenefeedstock is required for manufacture of polypropylene. Accurate vapor-liquid equilibrium data of C3 hydrocarbonsare essentialfor the determination of fractionation requirementsto obtain high-purity propylenefrom a C3 hydrocarbonmixture. The apparatus used in this investigationwas a modificationof theforced-circulation type. It has been stated by Ruhemann1)that this type of apparatus is the most accurate and reliable of all low temperature method. Binary vapor-liquid equilibrium relationships for the propylenepropane, propylene- propadiene(allene) and propane-propadienesystems were determinedat isothermal conditionsof 0℃ and 20.1℃. In these three binary mixtures, the propanepropadiene systemforms a minimum boiling azeotropic mixture. Azeotropic conditionswere determinedusing a smoothingmethod proposed by Suda2)which was basedon a simplerelation in vapor-liquidequilibrium ratio of the constituents.

1 Introduction a minimum purity of 99%. The equilibrium data for the propylene-pro- 3 Experimental Apparatus and Experimen- pane system have been reported by Reamer and tal Method Sage3), by Hanson et al4), by Mann, Pardee and 3.1 Apparatus Smyth5) and by Hirata, Hakuta and Onoda8). But The experimental apparatus used in this in- data for propylene-propadiene and propane-pro- vestigation is illustrated in Figure 1. This ap- padiene systems have not been published. Hill et al.7) suggested that greater deviation from ideality paratus for measuring the vapor-liquid equilibrium might be expected for the system such as the is one of the types of forced circulation of the vapor phase. This is entirely made of stainless steel propane-propadiene, with greater differences in the degree of saturation of molecular structure. designed for operating conditions; temperatures as low as -200℃ and pressures up to 100 atm.. It is reported in "Azeotropic Data-II"8) that the The equilibrium cell has a capacity of 150ml. propane-propadiene system formed a minimum boiling azeotropic mixture, but vapor-liquid equi- with glass windows for inspection from outside. librium data are not unpublished. So the authors Both the vapor and liquid phase sampling cells investigated equilibrium relationships for propyl- have a capacity of 10ml., detailed descriptions of ene-propane, propylene-propadiene and propane- which were made previously9). The sampling propadiene systems, and determined azeotropic vessel, in which the liquid sample is allowed to points of the propane-propadiene system at 0℃ vaporize, has a capacity of about 100ml.. and 20.1℃. The circulation of the vapor phase is carried out by means of a magnetic pump provided with two 2 Materials check valves. The magnetic pump is shown in The propylene and propane samples were fur- Figure 2. The rate of circulation can be adjusted nished by Takachiho Chemical Industry Co.. at will between 0ml/min and 300ml/min. The propylene sample was specified to contain The measurement of temperature in this inves- 99.32% propylene, 0.05% ethane, 0.15% propane tigation was carried out by a mercury thermometer. and 0.49% air, and the propane sample was The pressure was read with a differential pressure specified to contain 99.85% propane, 0.05% ethane gauge and a dead weight pressure tester. and 0.10% air. The propadiene (allene) sample was furnished by The Matheson Co. Inc. and had 3.2 Experimental Method First, V in Figure 1, is connected to a vacuum * Received November 18, 1968. ** Faculty of Engineering, Tokyo Metropolitan Univer- pump for evacuation the system completely. A sity (2-1-1, Fukazawa, Setagaya-ku, Tokyo, Japan). high-boiling component is introduced into the

Bulletin of The Japan Petroleum Institute Hakuta, Nagahama and Hirata: Binary Vapor-Liquid Equilibrium for C3 Hydrocarbons 11

Fig. 1 Schematic Diagram of V-L Equilibrium Apparatus

Fig. 2 Magnetic Piston Pump

Fig. 3 Pressure-Composition Diagram of Propylene- Propane System system from a sample cylinder. The equlibrium cell is maintained at a desired temperature.The 0℃ run was taken with ice of 0.01kg/cm2 and the valves of the vapor phase and water in cooling bath and the 20.1℃ run was sampling cell are closed in order to sample the done in the constant temperature bath which was vapor-phase. As vapor phase is circulated through controlled by means of temperature controller. the by-pass in vapor phase sampling cell at this After the temperature desired was obtained, the time, the equilibrium condition is not broken. magnetic pump is operated to circulate the vapor Immediately thereafter, the liquid sample is col- phase, and high and/or low boiling components lected in the evacuated liquid phase sampling are fed into the system. When the liquid surface vessel and the sampling cell. in equilibrium cell was adjusted and pressure was The sample is subjected to gas chromatographic reached to a desired level, the feed valve is closed. analysis by valve operation. When a steady state was established for about The analysis was carried out by Yanagimoto half an hour, the pressure is read to an accuracy GCG-3DH Gas Chromatograph equipped with 4

Volume 11-May 1969 12 Hakuta, Nagahama and Hirata: Binary

Table 1 Vapor-Liquid Equilibrium Original Data System: Propylene (1)-Propane (2) at 0℃

Table 2 Vapor-Liquid Equilibrium Original Data System: Propylene (1)-Propadiene (2) at 0℃

Bulletin of The Japan Petroleum Institute Vapor-Liquid Equilibrium for C3 Hydrocarbons 13

Table 3 Vapor-Liquid Equilibrium Original Data System: Propane (1)-Propadienc (2) at 0℃

Fig. 4 Pressure-Composition Diagram of Propylene- Propadiene System

m. Activated Aluminum/Squalane column. Hy- drogen was used as a carrier gas and the flow rate

was 80ml/min. The column temperature was Ｆig. 5 Pressure-Composition Diagram of Propane-

about 60℃ and the filament current was 200mA. Propadiene System

Volume 11-May 1969 14 Hakuta, Nagahama and Hirata: Binary

Table 4 Azeotropic Data for Propane-Propadiene System

Fig. 6 α-χ1 Diagram of Propylene -Propane System

Fig. 9 γ1, γ2-χ1 Diagram of Propylene -Propane Sys- tem at 20.1℃

Fig. 7 α-χ1 Diagram of Propylene-ProPadiene System

Fig. 10 γ1, γ2-χ1 Diagram of Propylene -Propadiene System at 0℃

Fig. 8 α-χ1 Diagram of Propane-Propadiene System

4 Experimental Results and Discussion

Experimental results of vapor-liquid equilibrium measurements for the propylene-propane, Fig. 11 γ1, γ2-χ1 Diagram of Propane-Propadiene Sys- propylene-propadiene and propane-propadiene tem at 20.1℃

Bulletin of The Japan Petroleum Institute Vapor-Liquid Equilibrium for C3 Hydrocarbons 15

system were tabulated in Table 1, Table 2 and volatility with temperatures was small in the Table 3, respectively. In these tables, Ki, a propylene-propane system, but was considerably and γi were calculated in the following equations. large in the propylene-propadiene and propane- yi propadiene systems. The propane-propadiene Ki (1) χi system formed a minimum boiling azeotropic mix- yi (1-χi) ture and the azeotropic points were determined. αij (2) χi (1-yi) πyi Acknowledgement γi (3) Ｐiχi The author's thanks are due to Y. Misaki, N. Figure 3, 4 and 5 show the pressure-composition Tanaka and T. Mori who helped us in the experi- diagram for the above systems. Figure 6, 7 and 8 mental work of this investigation, and also to show the relative volatility (α)-liquid composition Chisso Co., Ltd. for the supply of high-purity C3 diagrams. As shown in Figure 6, 7 and 8, relative hydrocarbons used in this work. volatility of the propylene-propane system is not affeced by the variation of temperature. On Nomenclature the other hand, the relative volatility for the K Vapor-liquid equilibrium ratio P Pressure, kg/cm2. abs. propylene-propadiene and propane-propadiene P゜ Vapor pressure of pure component, kg/cm2・abs. systems is considerably affected. T Temperature,℃ In these systems the propane-propadiene system x Mole fraction in liquid phase formed a minimum boiling azeotropic mixture. y Mole fraction in vapor phase α Relative volatility Azeotropic points at 0℃ and 20.1℃. are shown γ Activity coefficient in Table 4. Figure 9, 10 and 11 show the activity π System pressure, kg/cm2・abs. Subscripts coefficients-liquid composition diagrams for each Subscripts system. These systems have a crosspoint in activity coefficients, but the propylene-propadiene 1 Low boiling component 2 High boiling component system at 20.1℃ has not. In this system the i i component activity coefficients for propylene (γ1) are scattered around unity. So it is impossible to test the soun- Literature Cited dness of the data for the propylene-propadiene ) Ruhemann, M., "The Separation 1 of Gases", 2nd., system at 20.1℃ with Redlich-Kister's10) formula. Oxford Univ. Press, England (1949).

ｘ=1 2) Suda, S., Thesis of Dr. Eng., Tokyo Metropolitan University (Dec. 1966). logγ1/γ2=0 (4) ｘ:=0 3) Reamer, H. H., Sage, B. H., Ind. Eng. Chem., 43, The solid lines in all figures and the determina- 1628 (1951). 4) Hanson, G. H., Hogan, R. J., Nelson, W. T., tion of azetropic points are based on a simple Cines, M. R. ibid., 44, 604 (1952). smoothing method using K values of the consti- 5) Mann, A. N., Pardee, W. A., Smyth, R. W., J. tuents. Chem. Eng. Data, 8, 499 (1963). 6) Hirata, M., Hakuta, T., Onoda, T., J. Petrol. Inst., 10, 440 (7), (1967). 5 Conclusion 7) Hill, A. B., McCormick, R. H., Barton, P., Fenske, M. R., A. I. Ch. E. Journal, 8, 681 (1962). The isothermal vapor-liquid equilibrium data 8) Horsley, L., " Azeotropic Data-II ", 32 (1962) Am. for the propylene-propane, propylene-propadiene Chem. Soc., Washington. 9) Hirata, M., Suda, S., Kagaku Kogaku, 31, 759 (1967). and propane-propadiene systems were obtained in 10) Redlich, O., Kister, T., Ind. Eng., Chem. 40, 345 this investigation. The variation of the relative (1948).

Volume 11-May 1969