Ind. Eng. Chem. Process Des. Dev., Vol. 17, No. 3, 1978 373
R = gasconstant T = absolute temperature V = molar volume VA,VB,VC = coefficients of molar volume fit with temperature x = liquid phase mole fraction
X(1), X(2), . . . , X ( 6 ) = coefficients of temperature dependence relationship, eq l and 8 y = vapor phase mole fraction A12, Liz1 = defined by eq 2 y = liquid phase activity coefficient X = energy term in Wilson equation @ = fugacity coefficient
Maripuri, V. O., Ratcliff, G. A,, J. Chem. Eng. Data, 17, 366 (1972). Mrazek. R. V.. Van Ness, H. C.. AlChEJ., 7, 190 (1961). Nagata, I., J. Chem. Eng. Data, 14, 418 (1969). Nagata. I.,Yamada, T., J. Chem. Eng. Data, 18, 87 (1973). Nielsen, R. L., Weber, J. H., J. Chem. Eng. Data, 4, 145 (1959). Orye, R. V., Prausnitz, J. M., Ind. Eng. Chem., 57 (5),18 (1965). Perry, J. H., "Chemical Engineer's Handbook", 4th McGraw-Hill, New York, N.Y.,
1963. Powell, M. J. D., Comput. J., 7, 155 (1964). Rediich, O.,Kwong, J. N. S., Chem. Rev., 44, 233 (1949). Rossini, F. D., "Selected Values of Properties of Hydrocarbons & Related Compounds", A. P. I. Res. Project 44,Chemical Thermodynamic Properties Center, Texas A. & M. University, 1953. Sadler, L. Y., Luff, D. W., McKinley, M. D., J. Chem. Eng. Data, 16, 466
(1971). Scatchard, G.,Wood, S. E., Mochel J. M., J. Am. Chem. SOC., 68, 1957
(1946).
Subscripts cal = calculated value exp = experimental value 1 , 2 = components of binary mixture
Seetharamaswamy, V., Subrahmanyam, V., Chiranjivi, C., Dakshinamurthy, ?., J. Appl. Chem., 19 (9),258 (1969). Shirai, H., Nakanishi, K., Kagaku Kogaku, 29 (31,180 (1965). Smith, V. C., Robinson, R. L., J. Chem. Eng. Data, 15, 391 (1970). Strubi, K., Svoboda, V., Holub, R., Collect. Czech. Chem. Commun., 37, 3522
Superscripts E = excess L = liquid phase s = saturated
Timmermans, J., "Physico-Chemical Constants of Pure Organic Compounds", Elsevier Publishing Co., New York, N.Y., 1950,1965. Udovenko, V. V., Fatkulina, L. G., 2%. Fiz. Khim., 26, 719 (1952). Van Ness, H.C., Soczek, C. A., Peolquin. G. L., Machado, R. L., J. Chem. Eng. Data, 12, 217 (1967). Vijayaraghavan, S. V., Deshpande, P. K., Kuloor, N. R., lndian J. Techno/., 3 (9),
L i t e r a t u r e Cited
Wehe, A. H., Coates, J., AlChEJ., 1, 241 (1955). Weissberger, A., Proshkanes, E. D., Reddick, T. A,, Toops E. E., "Organic Solvents", Interscience, New York, N.Y., 1955. Wilson, G. M., J. Am. Chem., SOC.,86, 127 (1964).
(1972).
267 (1965).
Asselineau, L., Renon, H., Chem. Eng. Sci., 25, 1211 (1970). Brinkman, N. D.. Tao, L. C., Weber, J. H., Can. J. Chem. Eng., 52,(1974). Brown, I., Smith F.. Aust. J. Chem., 7, 264 (1954). Brown, I., Smith, F., Aust. J. Chem., 12, 407 (1959). Dewan, A. R., M.S. Thesis, University of Nebraska, 1976. Duran, J. L., Kaliaguine, S., Can. J. Chem. Eng., 49, 273 (1971). Fu, S.J., Lu, B. C. Y., J. Appl. Chem. (London), 16, 324 (1966). Holmes, M. J., Van Winkle, M., Ind. Eng. Chem., 62 (l),21 (1970). Kemme, H. R., Kreps, S. I., J. Chem. Eng. Data, 14, 98 (1969). Landwehr, J. C.,Yerazunis, S., Steinhauser, H. H., Chem. Eng. Data Ser., 3,231
Department of Chemical Engineering University o f Nebraska Lincoln, Nebraska 68588
Ashokkumar R. Dewan Luh C. Tao James H. Weber*
Received for reuieu! October 11, 1977 Accepted March 8,1978
(1958). Lu. B. C. Y., Can. J. Techno/., 34, 468 (1957).
Revised Acentric Factor Values
Passut and Danner (1973) have published a set of recommended acentric factors for hydrocarbons. Revised values, based on improved extrapolation procedures, are given for a few of these acentric factors which have been found to be inconsistent.
Passut and Danner (1913) have published a set of recommended acentric factors for many hydrocarbons. These acentric factors were calculated on the basis of the best available experimental data using the exact definition of Pitzer (1955a,b). Since these values were published, some inconsistencies have been observed and further evaluations have been done for the misbehaving compounds. The compounds which were in question are listed in Table I. A review of the data indicated that the vapor pressure data for these compounds were consistent except those for 1-butyne. In addition, experimental critical properties were available for these compounds, and no reason was found to reject the critical values reported. Thus the acentric factors for these compounds were reexamined in terms of the extrapolation procedures used t o determine their vapor pressures a t a reduced temperature of 0.7. Passut and Danner had generally determined the acentric factors from the Frost-Kalkwarf (1953) equation if this value was in agreement with the values determined by interpretating (or extrapolating) the experimental data and calculated from the Antoine equation. Upon further examination of the
Table I. Recommended Acentric Factors
ComDound Methane 2,2,3,3-Tetramethylbutane cis- 1,3-Dimethylcyclohexane t r a n s - 1,3-Dimethylcyclohexane cis- 1,4-Dimethylcyclohexane t r a n s - 1,4-Dimethylcyclohexane
1-Methyl-2-ethylbenzene 1-Methyl-3-ethylbenzene 1-Methyl-4-ethylbenzene Vinylbenzene (styrene) Cyclopropane Cyclobutane 1-Butyne Propadiene
Acentric factors PassutThis Danner work 0.0072 -
0.2237 0.1886 0.2338 0.2419 0.2937 0.3598 0.3219 0.2572 0.2645 0.2089 0.0501" 0.3125"
0.0115 0.2467 0.2414 0.2356 0.2348 0.2429 0.2941 0.3232 0.3221 0.2302 0.1279 0.1857 -
a These values appear to be in error. Because of inadequate data, however, no better values can be recommended.
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results it has been concluded, however, that extrapolation with the Antoine equation gives more consistent results than extrapolation with the Frost-Kalkwarf equation. On this basis the values in the last column of Table I are recommended as the best acentric factors for these compounds. The Antoine coefficients used to obtain these values were generally those of API Research Project 44 (1977). The values reported by Passut and Danner for the acentric factors of 1-butyne and propadiene also appear t o be in error. However, the vapor pressure data for these compounds are either unavailable or appear to be in error in the reduced temperature range of 0.7. In addition there are problems with the critical properties for these compounds. Thus although these acentric factors are highly suspect and probably should not be used, no better values could be obtained.
Literature Cited American Petroleum Institute Research Project 44, “Selected Values of Physica! and Thermodynamic Properties of Hydrocarbons and Related Compounds, Thermodynamic Research Center, Texas A&M University, College Station, TX (loose-leaf sheets extant 1977). Passut, C. A . , Danner, R. R., Ind. Eng. Chem. Process Des. Dev., 12, 365 (1973). Pitzer, K . S.,J. Am. Chem. SOC.,77, 3427 (1955a). Pitzer, K. S., J. Am. Chem. SOC.,77, 3433 (1955b).
Department of Chemical Engineering T h e Pennsylvania S t a t e University University Park, Pennsylvania 16802
W. P. Henry R. P. Danner*
Receiued f o r reuieu, January 16, 1978 Accepted January 31, 1978
DISCUSSION
Electrolytic Reduction of Alumina with Activated Cryolite S i r : When Acton et al. (1976) initiated a small-scale test of the Diller patents, it was presumed that they were seeking to duplicate my 3000% enhancement of the overall conductivity of a Hall cell, operating a t an industrial voltage. In their experiment no. 6, they show data for a lower, but still substantive, activation, Le. 400% current a t 3.6 V, or 50% voltage reduction from a normal of 5.3 v. The greater activation would have enabled both the lower voltage and the higher current. However, in the same experiment, there is an incidental 2 V transient. They inexplicably selected this datum as their sole basis of evaluation. Thus, they derived an apparently sweeping and unconstructive position. Diller (1977) responded with an analysis of the constructive part of the experiment, and he related the data to the copious normal-state data of Schlain e t al. (1963), the progenitors of the particular cell. Printing back to back, the Acton group explained the rationale of selecting the 2 V datum as the basis for evaluation. The rationale pertains to small voltages and small power supplies. In this paper, I will continue to draw upon my experience with the more than 150 experiments I have personally conducted with respect to the Diller effect. I will validate the pertinent readings, establish the normals, and show my computations. I will discuss the new reactions, the back emf as a major variable in my activation, and the alleged rationale.
Data Interpretation The interpretation of the Acton data is dependent upon a clear, activation-free normal base. The data of experiment no. 1,Figure 3, which may have been intended for this purpose, had to be discarded. As Schlain had demonstrated ample tolerance for mixing data from different cells of this group, and since the tolerance is negligible in relation to the gains that have been achieved, the Schlain data are a reservoir from which a suitable comparison base could be drawn. The significant variables in the Schlain tables are (a) anode material and (b) voltage. On p 25, they otherwise summarize that “operation is not greatly affected by relatively large changes in temperature, electrode spacing, current density, 0019-7882/78/1117-0374$01.00/0
and alumina content”. The anode material of this inquiry is graphite and the voltage range of special concern is 2.85-3.6 V. The Schlain experiments that are compatible with these conditions are no. 8-15,17-21,24,26-28,34-35. The current densities of these experiments were averaged and multiplied by Schlain’s (and Acton’s) anode area, as determined by them. This current, 11.8 A, and the average corresponding voltage, 3.18 V, become the normal base for this inquiry. Figure 3 requires a moderately activated cell in which a straight line balances the opposing Tafel and Diller curvatures. At its maximum 2.62 V, the current density is about 300% of a normal base for that cell. The same cell was deactivated in experiment no. 5, where it shows current density comparable to the normal base derived from Schlain. No pulse was reported. The failure of Acton et al. to notice the enormous and stable currents a t their 2.85 and 3.6 V, respectively, was not understood. They now explain that they wanted to save energy by operating a t 2 V normal, notwithstanding that the normalstate industrial voltages range from 3.9 to 5.3 V, and that the pots have to sustain their temperature through the in situ production of heat. Had they attained Diller’s 3000% level of activation, they could obtain the normal 5 V current a t 1.7 V and twice that current a t 2.1 V (Diller, 1969). Moreover, they state that they wanted to be able to use a 50-A power supply. Figure 1of my (1969) paper required 2400 A. My supply was capable of 3000 A steady and 6000 A for timed short periods. Back emf is an important variable in the Diller effect. The altered emf is indicative of the new reactions that have been induced. In high level activation, the emf actually reverses and feeds the system and, in part, enables the enormous current densities. Its measurement is more history-dependent and responsive to current density than usual. I t cannot be determined by extrapolation to zero current density. Ordinarily, it does not vary much. In commercial cells, it centers about 1.6 V. It is determined by shutting off the electrolysis and reading rapidly so as to catch the preceding cell dynamics. The Acton group did not monitor the back emf. Fortunately, in this case, I was able to calculate it, as will be seen in the section on
0 1978 American Chemical Society
