February 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
densation can proceed to form either pyridine or acetonitrile and the present conditions are favorable t o the formation of acetonitrile. The following molten salt systems were not active catalysts for the condensation under the experimental conditions tested or were not suited to the present method: 33 mole % CdC12-43 mole % KC1-24 mole % NaCl 46 mole % PbC12-38 mole yo NC1-16 mole 7 0 NaCl 37 mole % FeC13-37 mole % KC1-26 mole % NaCl 50 mole % snCl~-50mole % KC1 ACKNOWLEDGMENT
The authors wish to thank JV. E. Winsche and W. $1. Langdon for their many helpful suggestions given during the course of this investigation. They also appreciate the cooperation of the Office of Production Research and Development of the War Production Board, under whose sponsorship the research was undertaken. LITERATURE CITED
(1) Clark, Am. J . Science, 207, 1 (1924). (2) Ellis, C., “Chemistry of Petroleum Derivatives,” Vol. 1,pp, 6834,New York, Chemical Catalog Co., 1934. (3) I. G. Farbenindustrie, Brit. Patent 321,177 (July 27, 1928). (4) Ibid., 334,193 (Feb. 23, 1929). (5) Ibid., 451,794 (Aug. 12, 1936). (6) I. G. Farbenindustrie, French Patent 38,072 (addition to 658,614, 1928). (7) International Critical Tables, Vol. 4, New York, McGraw-Hill Book Co., 1928.
331
Johnson, P. C., and Swann, S., Jr., IXD.ENG.CHEM.,38, 990 (1946). Kozlov, et a$., J . Gen. Chem. (U.S.S.R.), 6 , 250, 1089, 1341, 1346. 1349. 1352. 1897 11936): Ibid., 7,832,836, 1082, 1860, 2301 (1937). Ibid., 8, 366, 413, 419, 475 (1938). Meyer and Wesche, Be?., 50, 422 (1917). Nicodemus, Brit. Patent 283,163 (Jan. 5, 1927). Nioodemus, Ger. Patent 504,238 (Dec. 31, 1927), addition t o Ger. Patent 470,351. Ibid., 547,518 (March 8, 1929). I b i d . , 479,351 (June 20, 1929). Nioodemus and Schmidt, Ibid., 516,754 (Sept. 27, 1928), addition to Ger. Patent 479,351. Nikonova, Yavlenko, and Bergman, Bull. acad. sci. U.R.S.S., Classe sci. chim., 1941,391. Nosu, Kunitika, and Nisimura, J . Chem. SOC.J a p a n , 62, 179 (1941). Rotger, Ger. Patent 541,655 (Oct. 7, 1928). Ibid., 560,543 (April 10, 1930). Ibid., 525,652 (May 7, 1931). Schlecht and Rotger, Brit. Patent 295,276 (Aug. 8, 1927). Schlecht and Rotger, Ger. Patent 526,798 (Jan. 5,1929). I b i d . , 477,049 (May 8 , 1929). Schleoht and Rotger, U. S. Patent 2,012,174 (Aug. 12, 1936!; Shriner and Fuson, “Identification of Organic Compounds, 2nd ed., p. 170, New York, John Wiley & Sons, 1940. Smith, G. F., private communication. Stuer and Grog, Brit. Patent 109,983 (July 17, 1916). Winsche, W, E., private communication. Winsche and Johnscone,IND. ENG.CHEM., 36,435 (1944). RECEIVED September 18, 1947. Published by permission of the director of the Engineering Experiment Station, University of Illinois, Urbana, Ill.
Pure Hydrocarbons from Petroleum PREPARATION OF METHYLCYCLOHEXANE FROM STRAIGHT-RUN HEPTANE FRACTION JOHN GRISWOLD AND J. W. MORRIS’ University of Texas, Austin, Tex. Constructional details and performance of the improved Distex pilot plant are given. Methylcyclohexane of high purity was prepared from a narrow-boiling straight-run fraction by four successive operations: (1) a continuous fractionation removed most of the material boiling below n-heptane; (2) a Distex operation eliminated nearly all of the heptane with the remainder of the lighter materials; (3) a second Distex operation eliminated the toluene with part of the higher naphthenes; and (4) a batch fractionation recovered methylcyclohexane of purity about 99 mole 9%.
T
HE principles of and general Distex procedure for obtain-
ing pure hydrocarbons from narrowboiling straight-run fractions have been discussed ( 1 ) . Briefly, the method consists of separating the fraction into groups of single structural types of hydrocarbons by solvent fractionation (the Distex operation), then recovering the pure compounds by conventional fractionation of the individual groups. I n the preceding article of this series (S), the second Distex pilot plant was described with its application to the separation of 1 Present address, E. I. du P o n t de S e m o u r s & Company, Cleveland, Ohio.
a commercial straight-run heptane fraction (Skellysolve C) for the preparation of pure n-heptane. During the course of the work, the capacity of the pilot plant column slowly but steadily decreased because of an accumulation of and clogging by sedimentlike material. For the present work, the new column was built with removable plate sections and most of the accessories were reconstructed t o avoid difficulties experienced earlier and to give higher capacity and better control of the operation. IMPROVED PILOT PLANT
A detailed flow diagram of the pilot plant is shown in Figure 1. The construction, insulation, heat compensation, and thermocouple details of column 3 are given in an earlier article ( 2 ) . It contained 150 removable screen plates as 50-plate sections mounted in 2-inch standard pipe, and had approximately double the capacity of the earlier column of the same diameter. (Actually, steel conduit tubing of the same dimensions was used. Each section contained two strings of 25 plates.) At the higher rates obtained, the earlier solvent recovery column proved to be of inadequate capacity. The new solvent recovery column is shown in Figure 2. The section above the feed contained six screen plates of the same design as for the main column. The
Vol. 41, No. 2
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
332
SOLVENT
G
TC-THERMOCOUPLE RAFFINATE RECEIVER
CONDENSER
;'"
I
1 1
I/
1)
1
FEED
R A FFI N AT E PRODUCT
Y
EXTRACT PRODUCT
PUMP
Figure 1.
Schematic Flow Diagram of Distex Pilot Plant
THERMOCOUPLE ASS E M B LY I
FLANGE FOR C O N N E C T I N G TO C O L U M N
A
)
TO
m
A
M A N O M E T E R S AND
LEVEL
CONTROLLER
GAGE
HEATER WINDING N O i 8 GHROHEL C WiRE. SPACED Y O R E CLOSELY N E A R BOTTOM
45'
GLASS
,
~
ALTERNATIVE MAhiFOLD roYNECTIoNS
TO L E V E L C O N T R O L L E R .
OYEqFLOYI TYPE L E Y E L ADJUSTER
COOLER
chi
/'TO SOLVENT R U N TANK
CARTRI D O E HEATER W E L L S
. .
Figure 2. Solvent Recovery Column for Distex Pilot Plant
TO S T E A M TRBP
M U
HYDROCARBON INLET
Figure 3. Take-Off Cup and Vaporizer for Distex Operation
333
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1949
THERMOCOUPLE WELL
3 I' VAPOR OUTLET T O CONDENSER ALTERNATIVE HYDROCARBON REFLUX I N L E T
If' PIPE VAPOR RISER 30" LONG
UNINSULATED T O PROVIDE INTERNAL REFLUX
CONDENSER ALL BRASS AND COPPER, BRAZED JOINTS C O P P E R TUBES.+"
I N L E T FOR M I X E D SOLVENT A N 0 HYDROCARBON REFLUX
Figure 4.
MAGNESIA INSULATION
BRASS SHELL
2 " X 14"
Column Head for Distex Operation
section below the feed was of standard 3-iqch pipe, packed t o a depth of 42 inches. The packing was made of 0.0625 X 0.3125 inch copper ribbon formed into 0.42-inch diameter single-turn helices. The performance of this section approximated seven equivalent theoretical plates. Various reboilers and column heads were used for the Distex operation for continuous fractionation and for batch fractionation of the hydrocarbons, as follows. In the Distex operations, positive control of the vapor rate was obtained by pumping the bottoms hydrocarbons through a steam heated vaporizer (Figure 3). The column head was a 5-plate section with top and bottom inlets and a top outlet (Figure 4). The top inlet was not used because with the head uninsulated, heat loss provided sufficient reflux and almost quantitative separation of the solvent from the overhead vapors. The hydrocarbon vapor passed t o a total condenser that consisted of a 0.376-inch pipe mounted in a ,jacket of 1-inch pipe, 36 inches long. For hydrocarbon fractionation, the reflux-type total condenser shown in Figure 5 was used in all cases. For continuous fractionation and batch fractionation of small samples, a 2.5-liter welded steel pot reboiler was used; this was heated by a 800-watt carridge heater in an integral well, and a 1000-watt hotplate mounted underneath. For batch fractionation of large samples, a 4-gallon welded steel pot reboiler was employed, 'heated by an internal steam coil and an outside electric hot plate underneath. Each pot was equipped with two thermowells (for liquid and vapor temperatures), sight glasses, and drain plugs. Small rotameters (Fisher & Porter tubes Nos. 0000, 000, and 00) with floats constructed in this laboratory were used to observe hydrocarbon flows. The small floats of these meters were caused to fluctuate by gas bubbles and extraneous matter in the liquid streams. Hence the rotameter readings were used only for control, and all flow rates reported later were based on tank measurements. Solvent flow rate was observed by calibrating friction drop across a length of 0.125-inch steel tubing connected to a mercury filled U-tube. Details of the latter are shown in Figure 6. The pumping system was not altered. Liquid temperatures were observed by bare-tip thermocouples whose construction is shown in Figure 6. Vapor rates were calculated from a heat balance on the feed and bottoms, and were checked against a heat balance around the condenser. Adiabatic conditions of the column were not difficult t o maintain, and the wall thermocouple temperatures agreed with the fluid temperatures to within 1" C. With the differential thermocouples, i t was not necessary t o predict temperature level and temperature gradient up and down the column before starting a run.
GLASS MANOMETER
Figure 5.
Total Condensing Still Head
Distex tests on the lowest 37 plates of the column a t an aniline
rate of 140 ml. per minute gave an average plate efficiency of 48%, and tests on the same section using n-heptane-methylcyclohexane alone gave an average plate efficiency of 54% ( 1 ) . The relatively high Distex efficiency an compared to the hydrocarbon efficiency is explainable on the basis that foam provides most of the vapor-
COMPRESSION
f
STEEL TUBING FOR FRICTION
MANOMETER
RUBBER PORCELAIN INSULATOR
Figure 6.
GASKETS
(Top) Friotion Loss Flowmeter; Bare Tip Thermocouple
(Bottom)
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
334
Vol. 41, No. 2
heptane and 15% methylcyclohexane as the tTvo most abundant hydrocarbons. The analysis indicated no compounds boiling betmeen 3-methylhexane (91.95' C.) and n-heptane (98.43" C,). The distillation temperature break between those two hydrocarbons occurred a t about 52% on the original stock. Since operational considerations for the preparation of pure n-heptane had already been worked out, the principal objoctive of thc present investigation was to obt.ain similar information for methylcyclohcsane. The pure compound was obtained by I h c four steps already noted. The quantit,ics and concentrat,ions in the charge and intermediate product's are shown diagrammatically in Figure 7. O P x u r I o x 1. To conccntrate tho metliylcyelohexane, a large quantit*y(86.6 liters) of Skellysolvc C was subjected to a continuous fractionation a t a feed rate of 10 ml. per minute and with a reflux ratio (L/D) of 20 to-1. The split was calcuiatcd Figure 7 . Steps in Separation of A l e t h y Icyclohexane to take about half of the feed overhead. The bottoms analysis data from the Ileligrid column distillation are plotted in Figure 8. A summary of the operaliquid contact. This is probable since the plates were designed tion and the calculated analysis of thc bottoms are given in with zero liquid seal (for minimum holdup in batch fractionation), Table I. Separation 1TTas sharp, and a higher percentage of the and foam from the aniline solutions is more abundant and persistent than foam from the straight hydrocarbons. feed could have been taken overhead without loss of nicthylcyclohexane. ACCESSORY EQUIPMENT A I D PROCEDURES Although the isolation of 2,2,4-trimethylpentane and of cis-1,2-dimethylcyclopentane from virgin petroleum fractions have not Refractive indexes were determined with a Bausch and Lomb been reported, these two hydrocarbon- boil and have refractive precision oil refractometer. The various intermediate samples weie analyzed for toluene by nitrating a small portion and then restoring it to its original refractive index by the addition of measured amounts of the pure TABLE 11. N.4PHl"ENE-PARAFFIN DISTEX SEP &RATIOS aromatic. (Operation 2) Purpose Analytical distillations with refractive index curves Tvere obRemoval of n-heptane from naphthenic conccntrat,c tained on the paraffin-naphthene (toluene-free) samples of Operating conditions Hydrocarbon reflux ratio, approx. 10: I bottoms products from operation 1 (continuous fractionation for Solvent concentration a t top of column, mole So 81 Solvent rate, ml./min. 140 removal of low-boiling hydrocarbons), and fioni operation 2 (DisHydrocarbon feed rate, ml./min. 8 tex for removal of paraffins). Further details of the accessory AIS. % 70 equipment and techniques are given in previous articles (1-8). Material balance on hydrocarbons Feed t o column Overhead product Bottoms product
PREPARATION OF RIETAYLCY CLOIIEX Ah F,
Thc Skellysolvc C was from the same batch oi material n-hose complete analysis has b e m reported (5). Tt contained 25% n-
TABLEI. CONTINGOUS D I ~ T ~ L L A T OF I O NSICEI.I.YSOI,CB C (Oneration 1) . . Purpose l t e m o r a l of most material lighter t h a n n-heptane Operating conditions Reflux ratio ( L / D ) C u t point, 7b Liquid rate in column, ml./niin. Column effectiveness, theoretical plates Material balance Feed t o column Overhead product Bottoms product Recoiery of unproceqsed inaterial Loss
20 to-1
%
86,02.5 40,545 41,720
100 46.9 48.1 2.4 2.6
2,120 2,240
1
in"?
Total
9 .2
hIet,hylcyclohexane Toluene IIeavy hydrocarbons
bI~iliGlcyciopentane n-Hexane
100.0 Fraction of light material going to bottoms product, 10.3%.
100 47 3 32.2 20.5
* ,
50 5 40 5 . I
Product Compositions Overhead Vol. % hy material balance Vol. 70 '1,4 tra?~s-1,2-dilnethslcyc~opentane 8.4 69.3 3-RIethylhexano 10.0 10 .?I n-Heptane 79.1 18.7 Heavy hydrocarbons 2.5
100.0
100,o
TABLE 111. METHYLCYCLOHEXAXE-TOLCESE DISTEX SEPARATION
.do
300 60-70 All.
18,:40 12,623 8,032
,
Bottoms b y analysis n-Heptane
Total
Product Coinpositions Bot t oms Overhead b y analysis Vol. % b y material balance 2-Methslhexane 6.0 90' t o 92' paraRins trans-l,2-dimethylcyclopentam 5.0 S O D t o H 2 O naphthenes n-Heptane 47.9 Benzene M e t hylcyolohexane 27.5 Cycloherane Toluene 4,4 2 , 2 - a n d 2,4-dimethylpenH e a v y hydrocarbons
LOSS
39,195
(OperaLion 3) Purpose Rcnioral of toluene from methylcyclohexane conccntrate Operating conditions IIydrocarhon reflux ratio a t top, approx. Solvent concentration a t top, aver. mole Yo Solrent rate ml. 'min. Hydrocarbo; feeb. rate, ml./min.
VoI, Yo 43.3
36.5 0.4
11.1 i n
2.6 5,t
100.0
Material balance on hydrocarbons T o t a l feed t o product Overhead product Bottoms product Loss
BI1. 11,95.5 9,205
2,112 638
10: 1 81 11.5
10
/C
%
100 77.1 17.6 5.3
8i:3 18.7
(r
Product Compositions Overhead from batch distillation n-heptane 2.2 hIethylcyclohexane 73.2 Heavy hydrocarbons 24.6
Bottoms (tolucnc by analybis balance by refracti7.e index) Toluene 58.0 Nethylcyclohexane 29,O Heavy hydrocarbons 13 .O
100.0
100.0
Total
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1949
335
indices between the values for heptane and methylcyclohexane. The presence of such compounds would affect the analytical distillation and refractive in2-METHYLMEXIYE dex curves. ANALYTICAL DlSTl LLATION OPERATION 2. OF The bottoms from operation 1 were next subjected to a Distex separation to eliminate n-heptane a n d other paraffins. The hydrocarbon reflux ratio (L/D) was 10 t o 1 with a feed rate of 8 ml. Figure 8. Analytical Distillation of Bottoms per minute and a Aromatics removed by nitration before distillation split calculated to take about 8% of OPERATION3. New conditions for toluene removal were the total methylcyclohexane overhead so as to ensure as nearly estimated, and the second Distex run followed operation 2 withcomplete elimination of the heptane as possible. The analytical distillation of the bottoms is plotted in ’Figure out shutting down the column. The split was calculated to remove about twice the percentage of bottoms as there was toluene 9, and a summary of the operation and the calculated analysis of in the charge to avoid any possibility of toluene in the overhead. the bottoms are given in Table 11. A high loss occurred in this (The presence of toluene would prevent pure methylcyclohexane operation because of trouble with the pumps. This introduces an from being obtained in the subsequent batch fractionation.) uncertainty into the overhead composition since the loss may The bottoms actually tested 58% toluene, and the refractive not have been exactly proportional for the material balance index of the overhead was not lowered by the analytical nitration calculation. procedure; this indicated quantitative elimination of the aroA small amount of light impurity remained in the bottoms, and matic. The operation is summarized in Table 111. the material balance indicated no methylcyclohexane in the overOPERATION4. The overhead from operation 3 was frachead. The trans-l,2-dimethylcyclopentaneis appreciably more volationated batchwise, using a reflux ratio (L/D) between 50 and tile than the n-heptane as none was found in the bottoms. The 75 to 1. The data are plotted on Figure 10. As shown by this figure, the last traces of lighter and heavier components were not refractive index of the high-boiling portion of the bottoms was distinctly higher than that of the same portion in the charge; easy to eliminate. From the refractive index-boiling point relations and the hydrocarbons known t o occur in petroleum, the this indicated that paraffins of boiling points higher than that of heavy material consists essentially of trimethylcyclopentanes n-heptane were present and were taken overhead.
-
DISTEX FOR PARAFFIN REMOVAL
Figure 9.
Analytical Distillation of Naphthenic Fraction
Toluene removed by nitration before distillation
Vol. 41, No. 2
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
336 I
either refractive index or density, if the impurity is chiefly n-heptane.
I
CUT 22
b.
IkIO
I
BATCH
-
ACKNOW LEDGMENT
FRACTIONATION
The University of Texas Ibo5 FINAL M ETHYLCYGLOH EX AN E CONCENTRATE sponsored the 1 I work by awards of University Research Institute assistantships to J. \T. Morris and to B. R. Randall in 1943-44. IFr. W,Akerq, H. H. Hurmence, M . E. Kleclra, and Figure 10 J. E. Walkey also devoted and iso-octanes. Cut No. 22 (200 nil.) from the center of the many hours to the construction and operation of the Distex methylcyclohexane plateau was set aside and cuts 17 to 21 and column and to the distillation analyses. 23 to 26 (total 1.9 liters) were composited. A flow sheet of the four operations showing the relative quantiLITERATURE ClTED ties and percentages of the various hydrocarbons is given in Figure 11. (1) Griswold, Andres, Van Berg, and Kasch, IND.ENC.CHEM.,38, 65 (1946). Densities and refractive indices of cut 22 and the composite, ( 2 ) Griswold, hforris, and Van Berg, Ibid., 36,1119 (1944). compared to the latest values for methylcyclohexane are (3) Griswold and Van Berg, Ibid., 38, 170 (1946). OF
(4)IL'atZ. Bur. Standards, A.P.I. Research Project 44, table 7a (June 30, 1945).
cut No.
0,7692 0,7692 0.76939
1.42308 1.42294 1.42312
22
Composite A.P.1.-NBS (4)
The purities of both samples are above 99% calculated from
'
FEED, SKELLYSCLVE ' c "
V K +
[@ASIS)
25 1 3 05
N-HEXANE METHYLCYCLOPENTANE 2 3 - B 2,4-DIMETHYLPENTANE BENZENE CYCLOHEXANE 2,3- OIMETHYLPENTANE 2- a 3 -METHYLHEXANE TRANS Ip.8 I ~ M M € T f N W C L W E N T A N € N- ~ E P T A N E METHYLCYCLOHEXANE TOLUENE HEAVY M I F F I N S 6 NAPHTHENES
02
}
TOTAL
a
VOMES
LOCO
PRODUCTS
DISTEX
25 I3 5 2
5s 229
I93
2 7
I93 249 I50 27
A
-32
-eL
Io00
1000
100 0
1
60
50 479 27 S 44
I33 21 2
482
14
20
69 3 ID 6
101 2
22 7 3.2
15s
I&z
w
100 0
1460
REJECTS
100.0
~
5.1
N -HEXANE METHYLCYCLOPENTANE 12-a 2,o- DIMETHYLPENTANE BENZENE CYCLOHEXANE 2 3- DIMETHYLPENTANE 8 3-METHYLHEXANE TRANS 1,3-8 I,2-MMETWGYCCOPENTANC N- HEPTANE METHYLCYCLOHEXANE TOLUENE HEAVY PIRAFFINS B NAPHTHENES
2.6 I.o
0.4 11.1
}
2:
a
VOLS
DISTEX
55
I50
a
VOLS.
CONTINUOUS OISTILLATI ON
22 9
24 9
R ~ C E I Y EJanuary II 11, 1947. Presented as part of the Thirteenth Annual Chemical Engineering Symposium of the Division of Industiial and Engineering Chemistry, AMERICAN C H E X I C ASOCIETY, L Pittsburgh, Pa. Earlier articles of this series appeared in Volumes 35, pp. 117, 247, and 854 (1943): 36, p. 1119 (1944); and 38, pp. 65 and 170 (1946) of this journal.
47 19 SI 9
43.3
202
3as
I7 1
lw.o
TOTAL
238 12 2
468 50
UNRECOVERABLE (LOSSES. SAMPLES. ETC.1
Figure 11.
r
10.0
21 4
8.4 79. I
180 169.4
-
214
2.5
100.0
5.2
122
Purification of Methylcyclohexane
29 56
12
71 14.2
% IS
