C O M M U N I CAT1 ON
PHASE EQUILIBRIA AND T H E T E L O M E R I Z A T I O N REACTION Two-component gas-liquid mixtures encountered in organic reactions performed at elevated pressures frequently deviate seriously from ideal solubility behavior. Three-phase systems of compositions very sensitive to pressure and temperature changes may b e produced. This phenomenon is exemplified with the system ethylene-ethyl bromoacetate, reactants applied to a telomerization reaction study, and its influence on the product composition is discussed.
ALTHOUGH many telomerization studies have been reported mith a variety of olefins and telogens, except for the work of Nesmeyanov et u l . (4,5) little attention has been given to the phase equilibria in such systems under pressure. For example, even though Todd and Elgin (8) have shown that ethylene. a commonly used taxogen, readily gives rise to three-phase systems with several organic liquids including alcohols, no mention of the possible influence of phase equilibria was made in studies of the telomerization of ethylene with alcohols (2,3). In these reactions the chain length distribution of the product telomers is of major interest and is largely determined by the reactants' ratio. FVith gaseous olefins (taxogens) producing two-phase systems, this ratio can be determined readily as a function of pressure. However, if phase separations occur in the liquid phase to give rise to three-phase systems, the ratio of reactants is no longer defined by the pressure. As such
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reactions are normally performed in metal pressure vessels which d o not permit direct visual observation, phase separations are seldom immediately obvious. T h e phase rule shows that a t constant temperature a twocomponent. three-phase system is invariant. T h e composition of each of the three phases is constant under these conditions, but the relative amount of each phase present is dependent on the ratio of the two components. Therefore the over-all composition can be changed by adding or removing gas without affecting the pressure. T h e results of reactions performed under such conditions have little correlative value unless the amounts of the individual phases are known. Furthermore, although it can be assumed that the small quantity of initiator used in these reactions has no effect on the phase behavior of the system, its distribution, as well as that of the reacting species, between the phases, presents a multireacting system with complicated interphase mass transfer effects. I n a study of the telomerization reaction between ethyl jromoacetate and ethylene ( 7 ) it was found that a three-phase system can exist under certain conditions. [In a comparable study using methyl bromoacetate ( 7 ) ! no similar observations were made.] This was indicated by plotting the ethylene content of the autoclave as a function of pressure as shown in Figure 1 . This curve was obtained by charging a 500-ml. rocking autoclave Lvith 46 ml. of ethyl bromoacetate and pressurizing to 1900 I1.s.i.with ethylene at 18' C. while rocking. Gas was then \vithdra\vn (at 18' C.), its volume measured, and the resulting prccsrirr change noted. After each sampling, the autoclave was rocked until no further pressure changp occurred ; 20 m i n u t e \vas wfficient. A s Figure 1 sho\vs. at 1000 p.s.i. the ethylene content of the autoclave could be rrducrtl by almost half without affecting the pressure. This indicatrs that a three-phase system exists under these conditions. Similar experiments prrformed between 38' and 106' C:. gave plots showing no c0nstar.t pressure lines. I t thrrrforr. appears that in this rcgion only two-phase systems exist. Hocvever. this method cannot be relied upon to indicate the atwnce of a three-phase system. For example. in Figure 1. if thr initial ethylene content of the autoclave had been only slighrly above 8 moles per liter, the
constant pressure line could have been too short to be observed. If a three-phase system exists a t ambient temperatures, the over-all compobition can be determined from the pressure at elevated temperatures (prior to reaction) where only two-phase systems exist. However, in such cases, the over-all composition can be predetermined only by actually measuring the amount of gas charged to the autoclave. Alternatively, the autoclave may be charged above the critical solution temperature, if the reaction temperature is well above the latter. It is also possible to charge the autoclave a t ambient temperature at some pressure other than the three-phase pressure. However, in this region the system may be sensitive to small temperature changes, and phase separations may occur which are not immediately apparent. In the study of the telomerization reaction between ethyl bromoacetate and ethylene it was found convenient to use a 500-ml. rocking autoclave as a reservoir from which a microreactor (6) was charged. This method permitted charging the reactor with a single phase of known composition and thus avoided complications arising from phase separations.
Literature Cited
(1) Baniel, A., Shorr, L. M. (to Maktsavei Israel), Israeli Patent 10,830 (Jan. 22, 1959); C.A. 53, 12185 (1959). (2) Gilliland. E. R., Kallal, R. J., Chem. Eng. Progr. 49, 647 (1953). (3)' Kirkland, E. V., Znd. Eng. Chem. 52, 397 (1960). (4) Nesmeyanov, A. N. et ai.. Chem. Technof. 9, 139 (1957). (5) Nesmeyanov, A. N., Freidlina, R.Kh., Zakhorkin, L. I., Quart. Rea. 10, 330 (1956). (6) Shorr, L. M., Rogozinski. M., Varsanyi, A , , Rev. Sci. Znstr. 33, 1468 (1962). (7) Skinner, LV, A , , Johnston, G. B., Fisher, M., J . Am. Chem. Soc. 79, 5790 (1957). (8) Todd, D. B., Elgin, J. C., A . I. Ch. E. J . 1, 20 (1955).
L. M . S H O R R MANFRED R O G O Z I N S K I ANDRE VARSAYYI AVRAHAM BANIEL
Israel Mining Industries Laboratories Haija, Israel
Acknowledgment
We are grateful to the Israel Mining Industries for permission to publish this work.
RECEIVED for review August 30, 1962 ACCEPTED September 10, 1963
C O M MUN I CAT1ON
N O N - N E W T O N I A N FLOW IN A ROLLING-BALL VISCOMETER A straightforward extension of the Lewis theory for Newtonian fluids which might be applied to other nonNewtonian models.
(2) has developed a theory for rolling-ball viscometers which seems to work rather well for Newtonian fluids. This theory can be paralleled for the power-law model ( 7 ) for non-Newtonian flow: LEWIS
TTy
= -m
dv 1 2
idyl
- ' dux
-
4
(1)
'The result is given as a relation among the following quantities: the linear speed of the rolling ball Ti, the diameter of the tube D , the diameter of the sphere d. the angle of inclination of the tube from the horizontal p. the acceleration of gravity g, and the densities of the fluid and the sphere p and p s :
Some values of J , are: J I = 0.531, J 1 , s = 1.082, J 1 / 3 = 1.440, J 1 / 4 = 1.697, J1;. = 1.892. The quantity J I is just 4/3 of the integral called I by Lewis. The algebraic and numerical details are given elsewhere ( 3 ) . literature Cited (1) Bird, R. B., Stewart, LV. E., Lightfoot, E. N., "Transport Phenomena," Second Corrected Printing, p. 11, bViley, New York. 1962 ( 2 ) - Lewis, H. \V., Anal. Chem. 2 5 , 507 (1953). (3) Turian, R. M., Ph.D. thesis, University of byisconsin, Madison, \Vis., 1964
R . BYRON BIRD RAFFI M . TURIAN Department of Chemical Engineering Uniaersitj of Ll'isconsin
Here the J , are integrals:
Madison, Wis. (3) where
RECEIVED for review November 13, 1963 ACCEPTED Xovember 13, 1963 Supported by National Science Foundation grant G-11996. VOL. 3
NO. 1
FEBRUARY 1964
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