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TABLE V. PHASE RELATIONS IN
SYSTEM BUTADIENEISOBUTENE-SOLVENT' AT 50" F.
o/ Butadiene (SofvenbFree) in Hydrocarbon Phase 0 24.1 24.7 43.8 45.6
46.6 69.3 70.5 100
+ -
THE
Solvent Phase Lb. solvent %butadiene (solvent-free) Lb. hydrooarbons 0 32.68 34.3 25.5 35.0 55.5
58.1 50.7
77.6 78.3 100
Solvent 61.5% ethylene. lycol oyanide 5.5 cuprous ohlon$e. b Re-used aozent.
+ 26.4%
..
1416s
18.6 15.6s 15.6
10.lb
methanol
+ 6.6%
sodium
and 5 were obtained with a ratio of furfural to naphtha in the original mixture of about 1.5; the other tie lines represent a ratio of about 4.5. The three ternary solubility curves define the hetergeneous region on three sides of the tetrahedron. The solid section outlined by these curves and by the surfaces joining them on which the quaternary equilibrium points lie define the complete heterogeneous region. The equilibrium phases of tie lines 7 and 12 lie on the surfaces, but the compositions of the furfural-rich phase of the other lines plotted are apparently in error. Material balances are shown by the tie lines if the projected composition of the original mixture lies on the line, aa in ternary systems. The projected diagram has other properties equivalent to the ternary diagram, The mixture M resulting from the addition of naphtha and furfural of ratio S in Figure 9 to isobutene and butadiene in the projected ratio F lies on line FS. Its position on the line is in inverse ratio to the quantities of hydrocarbons and solvents mixed: pounds S/pounds F = M F / M S . The weights
Vol. 37, No. 11
of equilibrium phases H and L in which mixture M separates are in inverse ratio to distances M H and M L . The composition of a projected quaternary mixture changes on the addition of one of the components along the line connecting the original camp+ sition with the apex of the added component, Hunter (4) showed that, if the chloroform-acetone-acetic acid-water system was representative of systems with one immiscible pair, only two ternary diagrams need be established to define the quaternary system. The butadiene system has two immiscible pairs and, obviously, a quaternary tie line cannot be defined by equilibria in two of the ternary systems. The effect of the third ternary system is to rotate the quaternary tie line out of the intersection of the planes passing through ternary tie lines of two systems and the opposite apexes. ACKNOWLEDGMENT
The authors wish to express their thanks to E. H. Leslie for his interest and review of the manuscript; to the Blaw-Knox Company for permission to present the results of this investigation; and to Mercedes Zimmer for preparing the illustrations. LITERATURE CITED Brackner, A. V., Hunter, T. G., and Nash, A. W., IND.ENQ. CHEX.,3 3 , 8 8 0 (1941). Elli6, C., "Chemistry of Petroleum Derivatives", p. 160, New York, Chemical Catalog Co.,1934. Freeman, S.,U. S.Patent 2,278,309 (1942). Hunter, T. G., IND. ENQ.CHIOM.., 34,963 (1942). Joshua, W.P.,and Stanley, H. M., Brit. Patent 428,106 (1935). (6) Maloney, J. O., and Shubert, A. E., Trans. Am. Inst. Chem. Engrs., 36,741 (1940). (7) Poole, J. W..U. 9. Patent 2.273.661 (1942). (8j Smith, A. S:, and Funk, J: E.,' Trans. Am. Inst. Chem. Engrr., 40, 211 (1944).
Nonbenzenoid Hydrocarbons in Recvcle Benzene J
JOHN R. ANDERSON AND ALBERTA S. JONES Mellon Institute, Pittsburgh, Pa.
CARL J. ENGELDER University of P i t t s b u r g h , P i t t s b u r g h , P a .
I
N THE prepwation of ethylbenzene by catalytic ethylation of benzene, a large molar ratio of benzene to ethylene is maintained in order to minimize polyethylation. The excess benzene is recycled after rectification and the addition of virgin benzene. It has been observed that recycle benzene gradually deteriorates in quality; the boiling range and freezing point, especially the latter, finally reach values considerably outside the specifications for virgin benzene. It was believed that this deterioration in recycle benzene was caused, a t least in part, by the accumulation of saturated nonbenzenoid hydrocarbons present in virgin benzene. The impurities belonging to this classification in recycle benzene have therefore been characterized. The impurities in nitration benzene ( 1 ) were described in a previous paper (I?).. Sample A , employed in the present study, represented the accumulated recycled material from the ethylation of a considerable volume of refined coke-oven benzene from a large number of sources. The virgin benzene entering the reaction had a solidify-
ing temperature (1) of not less than 4.85" C. and a boiling range ( I ) of not more than 1.0" C. Figure 1 is a distillation curve, giving condensation temperatures of distillate a t 760 mm., of a sample of the saturated nonbenzenoid hydrocarbons secured from the recycle benzene, plus some n-pentane. Figure 1 also presents the results of determinations of refractive indices (n") of fractions of the distillate, and the normal boiling points (solid circles) and na2 (open circles) of the parafEns, cyclopentanes, and cyclohexanes whose normal boiling points are within the condensation temperature range of the bulk of the nonbenzenoid hydrccarbon sample. The methods and reagents used in this work were discussed in a previous paper (8). Sam le A (35.5 liters) was fractionally crystallized until 1005 ml. o r a highly contaminated product, B, and a purified fraction, C were obtained. The solidifying temperatures ( 1 ) were as foliows: A 1.95' C.; B, approximately -52" C.; C, 3.00' C. Fraction b was separated into two fractions by adsorption on silica gel, using n-pentane to displace the
Novedmr, 1945
I10
$100
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
1053
-
-
90-
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O 'B W
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2
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-
VOLUME OF DISTILLATE IN ML. Figure 1. Condensation Temperature and Refractive Index as a Function of Volume for Saturated Nonbenzenoid Hydrocarbons Secured from Recycle Benzene Plus Some n-Pentane Solid mirole. and o n circle.
boiling point.
give the normal boiling point. and refractive indime, reepsatirely, of the indicated pure h dmcarbon. known to witEn the condensation temperature range. Data on the pure hydrooarbone taken from report. of A.5.I. Rwearch Project 44 m t the National Bureau of Standard..
h8VO
paraffins and cycloparaffins, and methanol to displace the aromatic fraction. The parafiins and cycloparaffins, together with some of the n-pentane, were fractionated under high reflux in a still with a jacjketed and heated column, 2000 mm. high and 26 mm. in internal diameter, made of Pyrex and packed to a height of 1960 mm. with single-turn 4mm. (approximately) Pyrex helices. After the bulk of the displacing liquid (n-pentane) had been distilled, the distillation data shown in Figure 1 were obtained. A total of 600 ml. of the distillate indicated in Figure 1) was distilled from the column, after whic the remainder (140 ml.) was distilled using the still with the column of smaller diameter described in the revious paper (8). The last two fractions (indicated in the regactive index data of Figure 1)were obtained after Tetralin had been added to the contents of the still. Fifteen milliliters of ethylbenzene and 125 ml. of benzene were recovered from the aromatic fkaction from the separation by adsorption.
6
Fraction B (1005ml.), obtained from 35.5liters of recycle benzene by purification of the latter through a change of solidifying point of 1.05' C., consisted of approximately 680ml. of saturated nonbenzenoid hydrocarbons (Figure l), 125 ml. of benzene, 15 ml. of ethylbenzene, and 185 ml. of material unaccounted for in the analysis. These data show that the recycle benzene contained several volume per cent of saturated nonbenzenoid hydrocarbons, and that the bulk of the impurities in recycle benzene belong to this classification. However, the compositions of the nonbenzenoid hydrocarbon samples secured from recycle benzene and from virgin benzene, shown in the previous paper (B), are, in some respects, strikingly different. In general, the present sample is preponderantly paraffinic, while the previous sample was preponderantly naphthenic. The
data for the previous sample indicated the presence of a considerable quantity of methylcyclohexane, while its presence in the present sample in as large an amount has not been demonstrated. The condensation temperatures (Figure 1) point to the fact that about 26% of the sample of saturated nonbenzenoid hydrocarbon impurities in the present study is composed of compounds with boiling points below 80' C.; in contrast, the previous sample (8) was composed almost entirely of compounds boiling above 80' C. For the present sample, for the fractions of distillate in the boiling range above 80" C., the refraotive indices are, in general, considerably lower than corresponding fractions from the previous sample. These comparisons suggest that the gradual deterioration in the quality of the recycle benzene is attributable to the preferential accumulation of paraffins. Some lower-boiling p a r a n s (Z methylpentane, 3-methylpentane, and n-hexane) seem to have been introduced during the ethylation process; most of the naphthenes (except cyclohexane) present in the original benzene appear to have been removed to a large extent. LITERATURE CITED
(1) Altieri, V. J., "Gas Chemists Book of Standards for Light Oils and Light Oil Products", New York, Am. Gas h a . , 1943. (2) Anderson and Engelder, IND.ENO.CHIDM., 37,641 (1946). CONTBIBIJTION 664 of the Department of Chemistry, University of Pitbburgh. John R. Andenon and Alberta 8. Jones are on the staff of the Pittsburgh Steel Company's Induetrial Fellowship at Mellon Inatitute.
