FEBRUARY, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
Acknowledgment The authors are indebted to H. hL Cooper, F. R. Abernethy7 and Other members Of the Section for analyses of the coals, fUSainS, insoluble residues, and Pitches.
Literature Cited AbernethY, F.9 Cooper, M.1 and TarPleY, E * c.2 IN=. ENC.CHEM.,Anal. Ed., 10, 389 (1938). Bakes, W. E.1 DePt. sei. Ind. Research, Tech. Paper 37 (1933). Beel, A. E., Fuel, 3, 390 (1924). Bone, w. A.7 and Bard, B. J. A.1 PrOC. Roy. SOC. (London), 162A, 495 (1937).
Boosere, M. de, Fuel, 5, 522 (1926). British Fuel Research Lab., Rept. for Year Ended March 31, 1937.
Davis, J. D., Fuel, 8, 375 (1929). Finn, C. P., Trans. Inst. Mining Engr8. (London), 80, 283 (1930-31).
Fisher, C. H., IND. ENG.CHEM.,Anal. Ed., 10, 374 (1938). Fisher, C. H., and Eisner, A., IND. ENO.CHEM.,29,1371 (1937). Fisher, C. H., Sprunk, G. C., Eisner, Abner, Clarke, Loyal, and Storoh, H. H., to be published. Francis, W., J . Inst. Fuel, 6, 301-8 (1933). Gordon, K., Trans. Inst. Mining E n g ~ s .(London), 82 (Pt. 4), 348-63 (1931).
Graham, J. G., and Skinner, D. G., J . SOC.Chem. Ind., 48, 129T (1929).
195
(15) Horton, L., Williams, F. A., and King, J. G., British Fuel Research Tech. Paper 42 (1935). (16) Hovers, T., Koopmans, H., and Pieters, H. A. J., Fuel, 15, 233 (1936). (17) Legrand, C., and Simonovitch, M., Ibid., 17, 145-60 (1938). (18) Macrae, J. c . , and Wandless, A. M., Ibid., 15. 68 (1936). (19) Petrick, A. J., Gaigher, B., and Groenewoud, P., J . Chent. Met. Minino Soc. S. Africa. 38, 122-4 ( S e d . 1937). (20) Rittmeisier, W., Glkckauf, 64, 624 (1928). (21) Selvig, W. A., and Seaman, H., Bur. Mines, Cooperative Bull. 43 (1929). (22) Seyler, C. A,, Colliery Guardian, 155, 990, 1046, 1087, 1137, 1231 (1937). (23) Shatwell, H. G., and Graham, J. I., Fuel, 4, 25, 75, 127, 252 (1925). (24) Sprunk, G. C., and Thiessen, R., IKD.ENG.CHBM.,27, 446 I1 51. ,-9 -x--, Storch, H. H., Ibid., 29, 1367 (1937). Thiessen, R., and Francis, W., Bur. Mines, Tech. Paper 446 (1929) ; Fuel, 8, 385-405 (1929). Wandless, A. M., and Macrae, J. C., Fuel, 13, 4 (1934).
. . Wright, C. C., and Gauger, A. W., Am. Mining Congress,
Yearbook, pp. 381-3 (1937). (29) Wright, C. C., and Gauger, A. W., Penna. State Coll., Tech. Paper 31 (Oct., 1936). RECEIVZD September 19, 1938. Presented before the Division of Gas and Fuel Chemistry at the 96th Meeting of the American Chemical Sooiety, Milwaukee, Wis., September 5 to 9, 1938. Published by permieaion of the Director, C.8.Bureau of Mines. (Not subject to oopyright.)
Glacial Acetic Acid in Petroleum Refining Glacial acetic acid has been found to have selective extraction characteristics for the removal of the undesirable materials present in petroleum fractions. It will remove by selective extraction materials which cause smoking in the burning of kerosene, and undesirable constituents in lubricating oil stocks. Experiments toward this end are reported, pilot-plant work is described, and a flow sheet of a plant erected is given.
T
HE use of selective solvents solvent for removhg unsaturated, S. S. BHATNAGAR &VD p. J. WARD naphthenic, and aromatic hydrofor improving the quality University of the Punjab, Lahore, India of aetroleum fractions has carbons (11. With intensive treatbecome Lwell-established practice ment, kerosene of the highest quality may be obtained from the stocks examined, and very in the refining industry during recent years. The first high yields of oils of moderate quality have been demonprocess Lo be adopted was that of Edeleanu (4) for prostrated with a relatively small percentage treatment. In the ducing high-grade kerosene from inferior stocks by extyaclatter case the excellent solvent powers of acetic acid for tion with liquid sulfur dioxide. More recently the prinresins and resin-forming compounds will produce an imciples of solvent extraction have been applied to lubricating provement in quality with respect to wick incrustation oil stocks to remove or reduce those constituents which are without excessive loss during treatment. responsible for poor temperature-viscosity characteristics The main and most reliable criterion of kerosene quality and bodies which form gummy and carbonaceous deposits in the cylinders of internal combustion engines. Usually is furnished by the smoke tendency test. The conditions for measuring smoke point have been fully described (8), a single solvent phase is employed such as Chlorex ( I @ , and the maximum flame height without smoke of a kerosene furfuraldehyde (g), or phenol (S),but in some cases a double may be accurately recorded by means of the smoke point solvent scheme is used as in the Duosol (11) or sulfur dioxidelamp used. Subject to other requirements such as viscosity, benzene @)processes. I n the course of an investigation on the properties of volatility, wick incrustation, etc., the determination of smoke various Indian and Burma kerosene fractions, one of the point serves to differentiate clearly between kerosenes of writers found that glacial acetic acid is a particularly effective different qualities.
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I
VOL. 31, NO. 2
0 KEROSENE
KEROSEN&
€2
FIGURE1. FLOWSHEETOF ACETIC ACID RECOVERY BY WATERWASHING The calculated smoke points of the main classes of constituents present in kerosene are reported to be: paraffns, 80 mm.; naphthenes, 24 mm.; aromatics, 7 mm. Goulston and Wilson (8) reported that only kerosenes with a smoke point of about 32 mm. can be regarded as having no tendency to smoke, so that the removal of aromatics is essential for the production of grades of the highest quality. But since the market does not demand such a high quality, the removal of resinous and unsaturated and a part of the aromatic hydrocarbons is usually sufficient.
layer was distilled, and the fraction distilling between 115" and 120" C. consisted of acetic acid with about 7 per cent oil. The residue of the distillation was sodium acetate and the heavy portion of the extract oil which may be regarded as fuel oil. The smoke point of the oil salted out may be controlled by the quantity of sodium acetate added. The results of these experiments are summarized in the following table; the measurements are on an acid-free basis: Acetic Acid
Raffinate
Smoke Point
Extract
Smoke Point
%
%
Mm
%
Mm.
%
76
20 5
6 0
47. 42 32 5
19'0 18 0 14 5
8'0
Oil Yield
600
The first laboratory experiments on glacial acetic acid extraction were carried out on a Burma kerosene fraction with the following characteristics:
200
0.824 S ecific gravit at 60/60" F. 125 F?mh point (&sed), F. 18.5 Smoke point mm. 8 0/500, 0.5/200 Lovibond aoior, 18-in. cell Distn. range (Inst. Petroleum Tech.), F.: 1st drop 320 366 444 518 536 561 Amount distd., % ' 98.5
In one series of experiments kerosene was mixed with acetic acid and thoroughly agitated in a mechanical shaker for 30 minutes. After settling, the clear layers were separated, the upper layer being washed free of acid by successive portions of water and measured. The lower layer, composed of acetic acid and extracted material, was "salted out" by the addition of anhydrous sodium acetate, and the oil separated was washed with water. The remainder of the extract
335 300 250
40 l8 45 50
150
71
66
36 0
31 0 29 0 28 0 25 0
24.0
Fuel 011
8 0 1 5
This table shows that very high yields of improved oil may be obtained by degrading a small percentage of the kerosene to fuel oil.
Raffinate Yield The next experiments were concerned with increasing the yield of r a f i a t e ; excessive distillation of acetic acid and the use of sodium acetate were avoided. As was to be expected, it was found possible to treat further quantities of kerosene by using the extract as a washing medium. In one experiment kerosene was dissolved in acetic acid until the mixture corresponded roughly to that obtained by distillation of the extract after salting out with sodium acetatethat is, a 7 per cent oil-acetic acid mixture. A 250 per cent treatment of kerosene was given with this solution, and the raffiate obtained was further treated with a similar volume of solution; the yield was 56 per cent acid-free raffiate.
FEBRUARY, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
The combined extracts were added, in two equal stages, to a further volume of kerosene, and a second raffinate was obtained. The extracts were then applied to a third volume of kerosene, and a further r a f i a t e was obtained. The final extracts were distilled, a fraction was obtained by dilution of the distillate with an excess of water, and the residue of the distillation, consisting of material suitable for fuel oil, formed the balance of the initial oil. A summary of these operations shows the following: Per Cent 56 92 99
Raffinate First Second Third
Smoke Point, Mm. 30.5 25.5 22.0
Combining the results and including all the kerosene used, the over-all treatment was 137 per cent, yielding 73.2 per cent r a f i a t e . A percentage of 9.3 was obtained from the distillation of the extract, giving 82.5 per cent of improved kerosene with a calculated smoke point of 24.8 mm. The extract residue had a smoke point of 9 mm. and represented 16.3 per cent of the kerosene treated; the balance of 1.2 per cent was manipulation loss.
Loss of Reagent and Acid Recovery Succeeding experiments were concerned not only with yields of raffinate and percentage treatment but with the problems of loss of reagent and commercially feasible methods of acid recovery. A heavier grade of kerosene was also used with an initial boiling point much higher than that of acetic acid. I t s characteristics were as follows: S ecific gravity at 60/60° F.
0.840 150 15 9.0/500
Ffash point (closed), F. Smoke point, mm. Lovibond color, Win. cell
Distn. range (Inst. Petroleum Tech.), F.:
IDop 80 95%, m.-.
E lllel
Amount distd., %
During the course of water washing experiments, it was proved that raffinates could be washed almost free of acid with a total of 10 per cent by volume of water used in several successive portions. These raffinate washings could then be added to the extract to liberate a part of the dissolved oil and the separated oil could likewise be washed practically free of acid by about 10 per cent of water. Figure 1 shows the flow sheet of a scheme of washing with limited volumes of water and, a t the same time, obtaining raffinate and extract oil in a substantially acid-free state. Supplementary information follows: Experiment No. Oil treated, cc. Acid used, cc. Unwashed raffinate, cc. Extract, cc. Fresh water to wash raffinate, cc. Raffinate after washing, CC. Wash water CC. Acid conteni of washed raffinate, % Acid content of wash waters, % Smoke point of neutral raffinate, mm.
I1
I
200 600 159 (Ra) 645 (Ed 96
I11
96 138 (WRi) 104 (Wi) 0.0021 22.23
0.0021 14.12
200 600 159 (Ra) 648 (Ea) 96 139 (WRa) 109 (WS) 0.0032 15.71
20.0
18.0
18.0
200 600
! : A &?I
E {E?)
It appears probable that the acid used in experiments I1 and I11was slightly contaminated with water, since smoke points are much lower than in experiment I. The inference from these experiments is that, with a 300 per cent treatment, 48 per cent of water (based on the original kerosene volume) will reduce the acid content of the separated fractions to below 0.01 per cent under the conditions employed. The yield of oil was 91-92 per cent and, apart from transfer losses, the deficit remained dissolved in the aqueous acid.
197
After a considerable amount of data had been couected, the possibilities of acetic acid as a commercial solvent were then examined: It is chemically stable under the conditions of an extraction process. Its selectivity is good and permits the extraction of undesirable constituents without excessive loss of useful fractions, Physical characteristics, such as specific gravity and surface tension, are very suitable for obtaining a sharp separation of the extract and raffinate. It is generally available at moderate cost. It is easily and completely recoverable from raffinate and extract phases by distillation or water extraction. It is corrosive in steel equipment; copper or alloy construction must be used throughout and air be excluded. Factors such as toxicity, specific heat, latent heat, and vapor pressure are favorable.
As far as the corrosion factor is concerned, the problem has been successfully dealt with in established processes for the manufacture of acetic acid. The cost of equipment in copper is naturally higher than corresponding steel construction; nevertheless, if the operations do not require elaborate or intricate plant, the material cost is not exorbitant. Othmer (IO) and others have described economical processes for the recovery of glacial acetic acid from its aqueous solutions by use of azeotropic agents which form constantboiling mixtures with the water present. This method has been successfully applied on a commercial scale for recovering glacial acetic acid from the products of wood distillation. Since it has been established that acetic acid may be recovered from treated kerosene fractions by a limited expenditure of water, and since the percentage acid treatment and the volume of water required could be substantially reduced by suitable countercurrent equipment, pilot-plant tests were undertaken in conjunction with the Vulcan Copper and Supply Company. On completion of these tests, it was decided to erect a unit with a daily capacity of 300 barrels of unrefined heavy kerosene; the flow sheet is shown in Figure 2. Pilot Plant The pilot plant treatment may be conveniently divided into the following six operations: 1. Continuous countercurrent extraction of the kerosene fraction with glacial acetic acid. 2. Continuous countercurrent washing of the raffinate from operation 1 with recovered wash water from an azeotropic distilling system. 3. Continuous countercurrent precipitation of oil from the extract of operation 1, using the combined aqueous acid solutions from the raffinate, precipitated oil, and fuel oil washings. 4. Continuous countercurrent washing of precipitated oil with recovered wash water from the azeotro ic distilling system. 5. Continuous azeotropic distillation o? the aqueous acidfuel oil solution obtained from the precipitation stage, to recover glacial acetic acid and substantially acid-free wash water and to obtain a residue containing some acetic acid. 6. Continuous countercurrent washin of the residual fuel oil-acid solution from the azeotropic dist3lation with recovered wash water.
Operating on a heavy kerosene fraction of the type previously described here, it was found that 125 per cent treatment by volume of glacial acetic acid effected an increase in smoke point from 14.5 to 24.5 mm. With a laboratory single addition of acid, 350 per cent treatment would have been required to achieve the same result. Yields are also increased, and 70 to 75 per cent of raffinate may be obtained by countercurrent treatment. By the application of countercurrent principles, all the water washing operations were accomplished by 10 per cent of water based on the original kerosene volume; the acid content of the separated oils was 0.01 per cent or less.
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21
REFINED KEROSENE OIL
The aqueous acid delivered to the azeotropic column for dehydration exceeded 90 per cent strength, and no difficulty was experienced in separating 99f per cent acid on the one hand and wash water containing below 0.5 per cent acid on the other. Several azeotropic agents are available for this purpose, and the selection is decided by cost and the consumption of fuel in the dehydrating process. These aspects of the question have been fully described by Othmer (10). The pilot-plant tests were not solely concerned with producing a maximum yield of oil of a given quality. In the local markets there is a demand for an inferior grade of kerosene which commands a price higher than fuel oil. This demand is satisfied by the oil precipitated by limited water addition to the extract, and the total yield of salable kerosene is approximately 90 per cent; the remaining 10 per cent obtained from the base of the azeotropic column is a fuel fraction. Although the extraction of acetic acid leaves only traces of the acid, it is essential to give the products a slight alkali wash to prevent corrosion of storage tanks. The application of water washing in an economical manner, followed by well-established methods of azeotropic recovery
2ND ORADE OIL STORAGE
FUEL OIL STORAGE
of the acid, forms the basis for a commercial application of the process. Losses of the azeotropic agent are extremely small and have been consistently maintained below 0.1 pound per 100 pounds of acid recovered in the manufacture of glacial acetic acid. The wash water recovered from the azeotropic system contains a little acid, but this is not a loss to the process since the water is recycled; its acid content does not affect materially the extraction efficiency.
Lubricant Treatment The investigations have been mainly directed to kerosene treatment, although some experimental work on lubricants has been carried out. Ferris, Birkhimer, and Henderson (6) studied a large number of solvents and rejected acetic acid on account of its miscibility-temperature characteristics with lubricating oil stocks. It is known, however, that acetic acid is a good solvent for asphaltic and resinous materials, and in certain cases the solubility of other materials of low viscosity index may be sufficient to produce highgrade stocks in good yields.
FEBRUARY, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
199
TABLEI. EXTRACTIONS OF INDIAN LUBRICANT Per Cent
-Redwood
66:6 66.6 32.0
looo F.
Yield
Treatment Original stock 600 aoetic aoid at 90° C. 600% acetio acid at 50-60° C . in three sta ea 100% nitro%enzene at 350 C. Air Ministry test, modified.
Viscosity-
749.4 538.3
140' F. 211.7 171.3
210' F. 60.1 56.4
505.8 502.4
165.7 163.9
55.4 55.5
Light and medium grades of mid-continent distillate lubricants have been treated with 175 to 200 per cent acetic acid by volume in a countercurrent system with a contacting temperature of 60' C., yields of approximately 80 per cent of refined oil being obtained. Brief characteristics of the treated and untreated oils are as follows: Physical Characteristica Viscosi tv. Savbolt Univirsal, Seo.: 210' F.
looo F.
Viscosity index 8 gr. (60/60° F.) onradson carbon, $6
d.
7200-Viscosity Oil- 7400-Viscosity OilUntreated Treated Untreated Treated
46.5
47.0 240.0 70.7
212.0
0.906
0.007
87.1 0.890 0.016
53.8 405.0 63.4 0.911 0.259
52.1
347.0 79.0
0.901
0.142
Laboratory extractions were also carried out with a distillate lubricant of Indian origin, and a comparison was made using nitrobenzene as an extractant on the same stock (Table I). The results show that the raffinate from nitrobenzene was superior in resistance t o oxidation with a smaller percentage treatment, and a similar viscosity index was obtained. In contrast, the yield with acetic acid is considerably higher, and the high percentage treatment may be reduced by appropriate countercurrent treatment. The extraction of the same Indian stock by furfural and acetic acid was also compared; it was carried t o a stage producing oils of almost identical gravity. The constants are given in the following table: Original Stock
Furfural
Ra5nste 0.911
Viscosity
Sp. Gr.
Index 40.7 73.4
(60/60° F.) 0 927 0.907
75.4 76.8
0.903 0.906
--Oxidation Viscosity, ratio
TestaCarbon residue, % Before After
1:1.36
0.15
0.25
1.27 0.79
1:1.39 1:1.25
0.10 0.06
0.00
1:1.56
0.82
to be in the direction of improved yields of raffinate for a given degree of improvement in viscosity index. It is recognized, however, that a comprehensive study of countercurrent conditions of contacting using acetic acid and other solvents will be necessary before a conclusive evaluation can be made. These conditions will include temperature variations and other known schemes of processing for increasing selectivity.
Acknowledgment The writers wish to acknowledge the cooperation of A. E. Duck, T. K. Lahiri, and N. G. Mitra in the laboratory work, and of J. G. A. Jeffrey and B. V. Fenton for their valuable assistance in developing recovery methods. Acknowledgment is also due D. F. Othmer, Polytechnic Institute of Brooklyn, N. Y., and the Vulcan Copper & Supply Company, Cincinnati, Ohio, for their development work in translating laboratory results to the plant stage. The authors also wish to thank Steel Brothers and Company, Ltd., of London, for permission to publish this paper. Literature Cited \I
Bhatnagar, U. S. Patent 2,100,707 (Nov. 30, 1937). Bryant, Manley, and McCarty, Refiner Natural Gasoline Mfr., 14, 299 (1935).
Dickinson, Oil Gas J.,33 (15), 1 (1935). Edeleanu, British Patent 11,140 (May 22, 1908) and later patents. Ferris, Birkhimer, and Henderson, IND.ENG.CHEM., 23, 753 (1931).
Acetic Acid Raffinate 0.910
Specific gravjty (!30/60° F.) 0.927 Kinematic viscosity, centlstokes: 10.37 11.35 10 10 210' F. 128.80 132.00 174.60 100' F. Kinematic viscosity indexs 22.1 43.8 45.7 Yield of rafinate, % 70 81 0 Calculated according t o the table of Hersh, Fisher, and Fenske (7).
....
From the work so far completed, the advantage of acetic acid as compared with other solvents for lubricants appears
Goulston, W. W., and Wilson, W. J., World Petroleum Congr., London, 1983,Proc. 2, 693-8. Hersh, Fisher, and Fenske, IND. ENG.CHEM..27, 1441 (1935). Inst. Petroleum Tech., Standard Methods for Testing Petroleum and Its Products, 1932. Kain, Refiner Natural Gasoline Mfr., 11, 553 (1932). Othmer, IND. ETCG. CHEM.,27, 250 (1935). Tuttle, Refiner Natural Gasoline Mfr., 14, 289 (1936). Williams, Ibid., 14, 293 (1935); Natl. Petroleum News, 27 (18), 26 (1935).
RECEIVED March 9, 1938.
