Binary Mixtures for Testing Fractionating Columns at Atmospheric and Reduced Pressures L. B. BRAGG
The four liquids mere purified by distillation and redistillation and cuts from each distillation were saved until samples of constant physical characteristics were obtained. Known mixtures were prepared by weighing first one component and
Foster Wheeler Corporation, Carteret, N. J.
A. R. RICHARDS Trinidad Leaseholds Limited, Pointe-&Pierre, Trinidad, B. W. I.
TABLE11. 0-DICHLOROBESZESE-DIETHYLBEKZESE MIXTURES wt. % v01. % Mole 76
S PART of the program of determining the operating
A
characteristics of Stedman packed columns, it was desired that a series of determinations should be made a t pressures less than atmospheric. Before the fractionating ability of the packing could be ascertained under such conditions, it was necessary to have information on the relative volatility of test mixtures a t reduced pressures. Mixtures of benzene and ethylene dichloride were satisfactory for tests a t 400, 200, and 100 mm. of mercury absolute pressure, although a t the lowest pressure ice water had to be used to obtain complete condensation of the vapors leaving the top of the column. Since no data were known to be available, it mas necessary to investigate the relative volatility of this mixture a t these three pressures, and since it was known that the values of the relative volatility reported by Smith and RIatheson (6) were ideal and not entirely correct, data were also required a t 760 mm. of mercury absolute pressure. For tests at the lower pressures of 50 and 10 mm. of mercury absolute, mixtures of o-dichlorobenzene and diethylbenzene were used; these mixtures were chosen on account of satisfactory boiling point differences, boiling temperature levels, and differences in refractive indices. TABLEI. BEKZENE-ETHYLENE DICHLORIDE MIXTURES voi. % Mole % Sp. Gr. Refractive Wt. %
Benzene Detd. 100.00 87.45 86.76 86.01 83.23 78.50 69.66 66.70 62.12
(20/20" C.) Detd. 0.8791 0.9136 0.9153 0.9184 0.9252 0,9399 0.9668 0.9758 0,9881
Index (20' C.) Detd. 1.6008 1.4949 1.4944 1.4936 1,4923 1.4902 1.4853 1.4838 1.4813
Benzene Calcd. 100.00 90.89 90.34 89.77 87.63 83.90 76.63 74,09 70.07
Benzene Calcd. 100.00 89,86 89.29 88.63 86,29 82.24 74.43 71 75 67.52
57.30 51.23 49.32 49.23 43.20 41.61 38.90 38.32 37.37
1.0041 1.0238 1.0335 1,0349 1.0574 1,1541 1.0721 1,0758 1.0800
1.4792 1.4760 1.4744 1.474s 1,4712 1.4702 1.4688 1.4681 1.4680
66.70 59.99 58.14 58.05 52.06 50,43 47.61 47,Ol 46.00
62.98 57.11 55.23 55.14 49.09 47.47 44.66 44.07 43.07
32.27 30.25 26.25 22.99 18.18 10.72 7.96 0.00
1,1012 l.lOS2 1.1252 1.1406 1.1618 1 1967 1.2130 1.2550
1,4646 1.4636 1.4610 1.4692 1.4563 1.4516 1.4498 1 ,4447
40.48 38.24 33.69 29.88 24,08 16.63 10.99 0.00
37.66 35.48 31.09 27.46 21.98 13.21 9.88 0.00
o-Dichlorobenzene Detd. 100.00 98.38 95.31 93.15 89.55 85.13 81.92 78.48
Sp. Gr. (20/20" C.) Detd. 1.3079
73.80 73.41 71.24 65,OO 59.00 58.50 48.16 44.24
....
1.6331
....
1.5317
.... ....
1.5247
....
1.5116
,...
1.5102
....
1.5048 1.5016 1.5000 1.4965
33.64 31.05 31.04 21.28 18.81 11.74 7.53 0.00
TA4BLE 111.
....
.... ....
1.2437
....
1.2002
....
....
1,1656
....
1,1138
....
1,0884
1.5191
...
1 ,0254
....
0.9736
....
0.5387 0.9069
....
0.8710 VAPOR
AND
o-Dichlorobenzene Calcd. 100.00 98.22 94.88 92.55 88.66 83.93 80.53 76.89
65.23 64.77 62.26 56.29 48.94 48.42 38.21 34.57
71.99 71.59 69.33 62.89 56.77 56.26 45.87 42.00
25,24 23.07 23.06 15.26 13.37 8.22 5.20 0.00
31.63 29.13 29.12 19.79 17.46 10.83 6.86 0.00
LIQUIDEQUILIBRIA AND RELATIVE
VOLATILITIES OF BEKZENE-ETHYLEKE DICHLORIDE MIXTURES Mole % Benzene in: $ Liquid Vapor 760 Millimeters97.73 97.91 90.43 91.27 80.11. 81.11 68.72 70.02 59.69 61.32 48.61 50.21 40.17 42.92 40.15 41.94 30.12 32.61 25.13 26.48 20.12 22.11 10.49 11.20 10.30 11.50 2.60 2.83
--
----200 97.41 90.43 80 00 70.30 60.21 60.03 50.43 40.16 30.48 20.12 10.48 3.00
1088
Refractive o-DiohloroIndex (20' C . ) benzene Detd. Calcd. 1,5518 100.00 1.3505 97.59 1.6483 93.12 1.5467 90.06 .... 85.09 1.6408 79.22 .... 76.11 1.5362 70.83
Rliliinirteirs--. 97.62 51.93 82.20 73.78 62.39 63.33 53.28 43.61 33.54 22.85 12.83 3.62
~
a
1.088 1.111 1.066 1.063 1.071 1.070 1.120 1.077 1.123 1.073 1.127 1.076 1.132 1.091
1.091 1.206 1.154 1,189 1.096 1.150 1,121 1,152 1.151 1.176 1.257 1.214
~ Mole %~ Benzene ~ in: ~ Liquid Vapor Millimeters-400 57.41 57.73 90.43 91.66 90.18 90.88 89.53 90.82 80.00 81.69 70. 30 73.40 69.93 71.76 60.03 63.10 69,5l 61.44 59.31 61.52 59.51 61.77 60.43 53.06 49.91 52.26 40.51 43.27 40.15 42.90 30.48 32.63 21.41 23.57 21.03 23.17 20.12 22.34 10.68 12.21 10.68 12.21 10.49 10.98 3.00 3.38
-.-loo
95,08 84.90 74.84 65.00 65.03 44.98 34.98 24.96 15.05 5.10
Ullimeters-95.48 85.51 75.85 68.11 67.90 49.03 38.30 28.98 17.02 6.54
$$$& y a
1.146 1.163 1.085 1,108 1.115
1.166 1.093 1.139 1 , 084
1,088 1.095 1.111 1.058 1.120 1.120 1.100 1.132 1.132 1.142 1.163 1.163 1.053 1.131 1.093 1.050 1.056 1.150 1.124 1.177 1.154 1.227 1.158 1.302
September, 1942
INDUSTRIAL AND ENGINEERING CHEMISTRY
(y
then the mixture in a suitable small flask. The specific gravity of the mixture Was determined With a Pycnometer bottle and the refractive index with an Abbe refractometer. The mole per cent of the lower boiling constituent was then calculated from the molecular weights of the pure constituents, and the volume per cent was calculated assuming no contraction or expansion of volume on mixing and using the determined specific gravities of the individual liquids.
where a:
= z = y =
=
1089
(L) (+) 1--Y
relative volatility of two liquids of binary mixture mole fraction of more volatile component in liquid mole fraction of more volatile component in vapor
The data obtained on the two binary mixtures are given in Tables I11 and IV, and the values of relative volatility for the benzene-ethylene dichloride mixtures are presented graphi-
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
1090
Vol. 34, No. 9
1.3G 1.3 2
0-DICH LOROBENZENE DIETHYLBENZENE
1.28
Dl ETHY L B E N ZENE
1.24 4: 1.20
I
a
-I
a
1.16
I #I 2 1.08 1.04
1.00
0
IO 20 30 40 50 60 70 80 90 M O L PERCENT 0 - D I C H L O R O B E N Z E N E IN LIQUID
FIGURE 2.
100
RELATIVE VOLATILITY OF 0-DICHLOROBENZENE-DIETEYLBENZENE SYSTEM AT Two PRESSURES
1
0
IO 20 30 40 50 60 70 8 0 90 M O L PERCENT 0-DICHLOROBENZENE IN LIQUID
0
l , ! , l- 1
1
0
1
1.5000
,
i 0-DICHLOROBENZENE-DIETYYLBENZENZENE 1
15100
PLATE DETERMINATION CURVESFOR FIGURE 3. THEORETICAL
cally in Figure 1. I n the graph for 760 mm. the data of Pahlavouni (3, 6), Rosanoff and Easley (4), and Zawidski (7) are also included. Using refractive index as a means of determining mole per cent benzene in both the liquid and the vapor, the readings were accurate to only *0.0001; as a result the mole per cent values were accurate to only *0.2. The resulting possible errors in the relative volatility figures are indicated by the dashed lines extending above and below the calculated values. The difficulty of obtaining accurate data when the mixture is very rich in one of the components is a t once apparent. The lines drawn on the graphs are those believed best to represent the data a t each pressure, taking into consideration the results obtained a t the other pressures so that the several lines are of the same general shape. I n the case of the data obtained at 100 mm. pressure considerable difficulty was encountered due to freezing of benzene onto the walls of the condenser in making the determinations a t the higher benzene
THE
I 5200 15300 REFRACTIVE INDEX
I5400
1
1
15500
Two ~IIXTURES
concentrations. Such freezing out of benzene results in low apparent values of vapor composition and relative volatility. For this reason the data above 70 mole per cent benzene were ignored and the line was drawn dashed by comparison with the data a t the higher pressures. The values of relative volatility for the o-dichlorobenzenediethylbenzene mixtures are presented graphically in Figure 2 . Values of relative volatility for both mixtures were taken from Figures 1 and 2 from the lines drawn through the data and used to calculate the curves of theoretical plates 21s. refractive index shown in Figure 3. I n constructing these curves the number of theoretical plates was calculated for small differences in mole per cent in the liquid, using the equation of Beatty and Calingaert (1) and taking the value of the relative volatility as that of the mid-point liquid mole per cent. The figures for the number of theoretical plates thus determined were then combined to give the curves shown, by means of which the number of theoretical plates may be di-
INDUSTRIAL AND ENGINEERING CHEMISTRY
September, 1942
1091
rectly determined from the difference of the refractive index TABLEIV. VAPOR AND LIQUIDEQUILIBRIA AND RELATIVE readings for liquid samples drawn from above and below the VOLATILITIESOF 0-DICHLOROBENZENE-DIETHYLBENZENE column under test. MIXTURES ~ ~ l Mole % o-DiohloroVolatility benzene in: Liauid VaDor U -5 0 Millimeters-
97,38 91.07 82.77 75.87 71.10 62.76 62,60 54.68 48,07 47.70 39.67 32.73 32,53 28.50 21.83 17.05 10.33 8.55 5.40 4.73 2.90
97.70 92.40 83.90 77.05 73.10 64.56 64.02 56.90 49.97 61.20 42.37 36.00 34.65 31.15 24.17 18.65 11.20 9.80 6.90 6.33 3.25
1.143 1.192 1,085 1.068 1,105 1.081 1.063 1.094 1.079 1,150 1.118 1.156 1.100 1.135 1.141 1.115 1.095 1.162 1.298 1.361 1.125
~ Mole t i7% o-Diohloro~ ~ ~ ~ l benzene in: Volatility Liquid Vapor LY -lo Millimeters-
97.23 95.03 91.20 90.04 80.23 79.95 70.27 70.26 60.40 59.87 50.90 49.97 40.05 39.48 30.14 28.90 20.98 20.56 15.16 10.33 7.13 6.19 2.89
97.67 95.45 91.88 91.00 81.58 81.84 73.70 73.02 63.17 61.68 54.30 53.28 42.93 42.74 34.12 32.60 24.60 23.10 18.54 11.60 8.55 6.54 3.24
1.194 1.097 1.092 1.119 1.091 1.130 1.186 1.146 1.125 1.079 1.146 1.142 1.126 1.144 1.200 1.190 1.229 1.161 1.274
i.im
1.218 1.279 1.125
~
t
i
~
~
Acknowledgment The authors wish to acknowledge the services of L. X I S sen, P. N. Heere, and S. Finelli in obtaining the data and preparing the plots.
Literature Cited (1) Beatty, H. A., and Calingaert, G., IND. ENG.CHEM.,26, 504-8
(1934). (2) Cornell, Wallace, and Montonna, R. E., Ibid., 25, 1331-5 (1933). (3) Pahlavouni, E., Bull. SOC. chim. Belg., 36, No. 11, 533-47 (1927). (4) Rosanoff, M. A., and Easley, C. W., J . Am. Chem. SOC.,31, 953-87 (1909). ( 5 ) Smith, E. R., and Matheson, H., J . Research Natl. Bur. Standards, 20, 641-50 (1938). (6) Tables annuelles de constantes et donn6s numbriques, Vol. V I I I , p. 270 (1931). (7) Zawidski, Jan von, 2. physik. Chem., 35, No. 2 , 129-203 (1900).
Nitroparaffins as Solvents in the Coating Industry CHARLES BOGIN AND H. L. WAMPNER Commercial Solvents Corporation, Terre Haute, Ind. Four nitroparaffins-nitromethane, nitroethane, 1-nitropropane, and 2-nitropropane-are now produced on a commercial scale. Their mild odor and low degree of toxicity, coupled with high solvent strength and medium rate of evaporation, offer a combination of properties heretofore not obtainable in any series of solvents. While these materials are nitro-containing organic compounds, they are not so flammable as hydrocarbon solvents of equal rates of evaporation. The nitroparaffins are among the most powerful solvents known for the organic esters of cellulose, such as cellulose acetate and cellulose acetobutyrate. Solutions of these materials tolerate appreciable proportions of cheap diluents, such as alcohols and hydrocarbons. Their ideal rates of evaporation make it possible to formulate finishes which duplicate those of nitrocellulose for drying
T
HE commercial production of four nitroparaffinsnitromethane, nitroethane, and 1- and 2-nitropropanes -was started in the summer of 1940. Since that time they have become of considerable importance in the chemical industry. The synthesis of these materials and of many of their derivatives, their physical properties, and many suggested uses have been described in previous articles (47, IO, 11). The present paper will be limited to considering certain of the solvent uses of the nitroparaffins. Organic liquids find use as solvents in two large fields: the extraction of various materials by selective-solvent action,
speed and leveling properties. It is no longer necessary to use the customary combinations of fast- and extraslow-evaporating solvents to apply satisfactory films. The nitroparaffins show unusual solvent strength for vinyl copolymer resins and are being used in large quantities for this purpose. They are also of interest in practically every other coating problem. Thus, while they show no advantage over the ester-type solvents in most nitrocellulose coatings, there are certain specialty applications where their mild odor and different solvent properties have given them commercial applications. The nitroparaffins are also of interest in a number of miscellaneous coating applications-with shellac, synthetic and processed rubber, paint and varnish removers, alkyd resins, and other high-polymer coatings.
and the dissolving of materials to aid in carrying out reactions or to produce desired effects such as the deposition of films of protective coatings. In any of these applications the physical properties of the solvent are important. The nitroparaffins belong to the medium-boiling class of solvents, and their rates of evaporation lie between those of toluene and butyl acetate. Table I, which compares the evaporation rates of the nitroparaffins with the more commonly used lacquer solvents, gives a better picture of their exact position. The nitroparaffins are definitely not hygroscopic, and these materials and water have very low mutual solubilities.
