January. 1925
IND UXTRIAL A N D ENGINEERING CHEMIXTRY
25
Reclamation of Lubricating Oil from Used Crank-Case Oil By F. H. Rhodes and H. J. Haon, Jr. CORWLLUNIVERSITY, ITHACA, N. Y.
I
T IS well known that the lubricating oil which is used
solids to agglomerate so that they can be removed efficiently as crank-case oil in the lubrication of automobile engines by centrifuging. The lighter impurities which cause low undergoes more or less serious deterioration in service, viscosity can be eliminated by distillation. This distillation so that it is common practice to draw off and discard the should be effected in a current of steam so as to secure subused crank-case oil after about every thousand miles of stantially complete removal of the light fractions without driving. The total aggregate amount of lubricating oil cracking the lubricating oil itself. Since it is usually assumed thus discarded annually is very large and represents a very that the compounds which cause the formation of emulsions great economic waste; therefore any practicable method of with water are oxidation products that are acidic in character, recovering a good lubricatit should be possible to ing oil from this waste autoeliminate these- objectionA very satisfactory motor oil can be recovered from mobile crank-case oil would able impurities by agitating used crank-case oil by agitating the oil with a solution make possible a very great the used oil with an alkaline of sodium silicate (specific gravity 1 4 , centrifuging to economic saving. solution before centrifuging. remove the silicate solution and the agglomerated solids, Among the various causes and distilling the clarified oil with steam. From the of deterioration of automoExperimental distillate kerosene may be prepared. The yields of the bile crank-case oil in servarious products should be as follows: vice, the following are perI n order to obtain some haps the most important: Per cent i n f o r m a t i o n as to the of original amount of light material PRODUCT used oil (1) Accumulation of solid Recovered lubricating oil.. . . . . . . . . . . . . . 7 5 . 0 present in use2 crank-case 3.3 Residue from distillate of crude naphtha. impurities from the dust and oil, three samples were disLoss in refining crude kerosene. . . . . . . . . . 2 . 2 sand drawn in with the air Refined kerosene.. .................... 19.5 tilled with steam. All these through the carburetor and of &tal particles abraded samples were collected in from the bearings in the motor itself. February, one sample (Sample 1) being taken directly from (2) Dilution with unburned gasoline, with consequent lowering a car and the other two samples being taken from drums of the viscosity of the oil. (3) Partial thermal decomDosition or "cracking" of the oil of used oil which had been accumulated at the service stations. itself, due to contact with t h e h o t walls of the cylinder or to di- The light distillate from each sample was collected and measrect exposure of films of the oil to the burning fuel charge. This ured. In each distiIlation the oil was maintained at 356" cracking results in the formation of free carbon and in the proto 374" F. (180' to 190° C.), the entering steam was kept duction of liquid cracked products which may lower the lubriat 248' to 266' E". (120' to 130' C.), and the distillation was cating value and decrease the viscosity. continued until a running sample of the distillate showed (4) Partial oxidation of the oil or of some of its decomposition products, with the formation of oxidation products which are practically no oil. The results obtained in these preliminary acidic in character and which may tend to cause the oil to form persistent emulsions with water, to gum, or to show other ob- distillations may be summarized as follows: jectionable characteristics.
The exact extent to which deterioration from each of these causes may occur in any given case depends on a number of different factors: the nature of the original lubricating oil, the construction of the motor, the type of gasoline used as fuel, the temperature and weather conditions during driving, the type of carburetor used, the general manner in which the motor has been operated, etc. It is obvious that any satisfactory method for the recovery of lubricating oil from crank-case oil must provide for the removal of the suspended solid matter and of the gasoline and other light material which cause low viscosity, and must eliminate the objectionable products of the cracking and oxidation reactions. Suspended solids can be removed either by filtration or by centrifuging. Filtration is not, however, a very satisfactory method of removing these solids, because much of the solid material is so very finely divided that it can be removed only by a very fine filtering medium that would oppose great resistance t o the flow of the viscous oil and would clog quickly. Centrifuging the used oil directly is not altogether practicable, because the solid material is so fine that it separates only slowly even in a centrifuge driven at high speed. By the addition of a suitable coagulating agent, however, it should be possible to cause the suspended 1
Received June 7, 1924.
Sample 1 2 3
Volume taken for distillate CC
.
2000 2000 1500
Volume naphtha distillate ec. 635 508 390
Naphtha distillate Per cent 31.7 25.4 26.0
These results indicate that, at least in cold weather, the average amount of light material in discarded crank-case oil is from 25 to 30 per cent. A comparatively large amount of average used lubricating oil from accumulated waste crank-case oil at a service station was collected and used in the following experiments. This original material was black in color and had a very distinct "cracked" smell. It contained a considerable amount of dirt and sediment, part of which settled rather rapidly when the oil was allowed to stand. The oil showed the following analysis :2 Flash point (Cleveland open cup). . . . . . . . . . . . . 131' F. (55' C.) Fire point (Cleveland open cup). . . . . . . . . . . . . . . 153' F. (67' C.) Gravity.. .................................. 29.9' A. P. I.
One portion (2000 cc.) of this oil was passed through a supercentrifuge at the rate of 100 cc. per minute, the centrifuge being operated at approximately 30,000 r. p. m. Other portions of the original oil, of 2000 cc. each, were mixed with 500-cc. portions of various solutions, agitated thoroughly, 2
Bur. Mines, Tech. Pager 828.
'
Vol. 17. No.1
INDUSTRIAL A N D ENGINEERING CHEMISTRY
26
and passed through the centrifuge a t the rate and speed stated above. The solutions used were as follows: distilled water; sodium carbonate, 5 per cent; sodium hydroxide, 1 per cent; sodium hydroxide, 20 per cent; sodium silicate (technical, specific gravity 1.192); calcium chloride, 20 per cent. Each of the centrifuged oils was then reduced by distillation with steam in a small iron still. The amount of oil taken for each distillation was 1500 cc. In each case the oil in the still was heated to 347' F. (175" C.). Steam superheated to 257" F. (125' C.) was then admitted and the distillation was continued a t 347' F. (175' C.) until a running sample of the distillate showed that practically no more naphtha was coming over. A sample of the original used crank-case oil was also distilled in the same manner. Each sample of steam-refined oil was analyzed. The results are summarized in Table I. The flash points and fire points were obtained with a Cleveland open cup tester. The carbon residue and the free acid were determined by the Bureau of Mines method.2 The sediment was determined by extracting 10-gram samples of the oil in alundum thimbles with benzene, using a Soxhlet extractor. Since the density, the flash and fire points, and the viscosity of the residual oils depend primarily upon the extent to which the steam distillation is carried and not upon the preliminary treatment of the sample, and since the steam distillations were made in substantially the same manner in each case, it was not considered necessary to determine the specific gravity, flash and fire points, and viscosity of every sample of reclaimed oil.
6
7
8
9 10 11 12
... ... ...
i5 :5
... 24.0
Flash Fire point point OF.
O F .
131 386
153 443
... ... 389 ... ...
... ... 440 ... ...
392
464
417 397 365
464 443 419
...
...
Free acid Carbon Mg.KOH/ residue gram Per cent oil
o:iis
0.030 0.650 0.499 0.458 0.523 0.485 0,499 0.596 0.491 0.274
.....................................
Color., Pale yellow Gravity. ..................................... 45.8'' A. P. I. Flash point (Pdnsky-Marteu closed cup tester). , ?,9" F. (37,: C.) Odor.. ......................... > ............ Cracked odor
o:Oiss
0.0122 0.0122 0.0000 0.0000 0.0000 0.0000 0.0013 0.0000 0.0013 0.0756
Sedi- Viscosity ment Saybolt Per seconds cent at 100' F. 0 0.57
0.030 0.021 0.021
0.020 0.0135 0 I000
0.0216 0.000 0.006
iiii
... ... ... ... 355
350
...
515 480 22.1 552 0 * 000 20.6 Sample I-Original crank-case oil before centrifuging or distilling 2-Lubricating. oil residue from crank-case oil steam-distilled but not centnfuged 8-Lubricating oil residue from crank-case oil centrifuged alone and then steaq-distilled +Lubricating oil residue from crank-case oil mixed with water, centrifuged and steam-distilled +Lubricating oil residue from crank-case oil mixed with 5 per cent solution of sodium carbonate, centrifuged and steam-distilled 6-Lubricatin oil residue from crank-case oil mixed with 1 per cent sodium [ydroxide centrifuged and steam-distilled 7-Lubricating oil resid& from crand-case oil mixed with 20 per cent sodium hydroxide, centrifuged, and steam-distilled 8-Lubricating oil residue from crank-case oil mixed with sodium silicate solution (specific gravity 1.182), centrifuged, and stcam-distilled 9-Lubricating oil residue from crank-case oil mixed with 20 per cent calcium chloride solution, centrifuged, and steam-distilled 10, 11, 12-Three widely adyertised and commonly used brands of medium grade motor oils
The oil obtained by the steam distillation of the original crank-case oil without preliminary centrifuging was black in color and showed black particles of suspended solid material when diluted with benzene. Samples 3, 4, 5, 6, and 9 were rather dark brown and gave a faint black sediment when diluted with benzene and allowed to stand. Sample 7, which was agitated with a 20 per cent solution of sodium hydroxide before centrifuging and distillation, was brown in color but showed almost no sediment when diluted. Sample 8, prepared from oil that had been agitated with a solution of sodium silicate, was clear and of a dark red color, and gave no sediment on dilution. In fact, this sample of reclaimed oil was as clear and almost as light in color as two of the new oils selected for comparison.
.
Distillation:
Temperature F. OC.
Residue
TABCB 1 Gravity O A. P. I. Sample 60° F. 29.9 1 2 25.5 3 4 5 26.5
The reclaimed &Is showed viscosities considerably lower than any of the new oils, but well above the minimum viscosity usually specified for medium grade motor oils. I n flash point, fire point, and carbon residue the reclaimed oils compare very satisfactorily with the new ojls; while none of the recovered oils which had been agitated with alkaline solutions showed any free acidity. I n the distillation of the untreated or centrifuged oils the average yield of naphtha distilled over with the steam was 375 cc. from each 1500-cc. portion of the original used oil, or 25 per cent by volume of the used oil. The average volume of condensed steam collected with the steam dis, approximately 2.8 times the volume tillate was 1066 c ~ . or of the crude naphtha distillate. The crude naphthas from the various distillations were separated from water and combined. Five hundred cubic centimeters of this crude naphtha were distilled, from a glass flask, to a vapor temperature of 482' F. (250' C.). The crude kerosene distillate thus obtained measured 435 cc. and showed the following analysis:
Per cent
4.0 0.0
Loss
The residue from the distillation of the crude naphtha was a dark brown, oily liquid, consisting presumably of a mixture of rather heavy cracked products from the original lubricating oil together with some lubricating oil which had been carried over mechanically in the steam distillation. A portion (250 cc.) of the crude kerosene distillate was washed with four successive 10-cc. portions of 93 per cent sulfuric acid, then once with water, once with a 20 per cent solution of sodium hydroxide, and again with water. The amount of acid used in washing was more than would actually be required in plant practice. The washed material wa8 redistilled. The total loss of material in washing and redistillation was 9.6 per cent by volume of the crude kerosene distillate. The final purified and redistilled material was clear and water-white, with a clean, kerosene-like odor. It showed a flash point of 99' F. (37" C.) and gravity of 45.7" A. P. I. The distillation range was as follows: Temperature
0
F.
O C .
Residue
Per cent
2.0 0.0
Loss
Discussion of Results
It appears, therefore, that by agitating used crank-case oil with a solution of sodium silicate, centrifuging to remove the solution and the precipitated solids, and distilling with steam to remove volatile impurities, it is possible to recover a lubricating oil which compares very favorably in every respect with new oil. I n fact, it is possible that this recovered oil will be even better and more stable than new oil, since any very easily cracked or easily oxidized constituents in the fresh oil should be absent from the reclaimed oil. The
January, 1925
INDUSTRIAL AND ENGINEERING CHEMISTRY
action of the sodium silicate in facilitating the precipitation and removal of the finely divided solid matter from the oil is presumably due to the mutual coagulation of the suspended solids in the oil and the colloidal silica in the silicate solution. It is apparent that the low-boiling material which is present in used crank-case oil and which is principally responsible for the lowered viscosity of the used oil consists principally of the unburned "heavy end" of the gasoline used as motor fuel. This recovered light material, if suitably refined, could be blended with light naphtha or casinghead gasoline to make motor fuel, or could be disposed of as kerosene. By a fractional distillation of the refined, recovered naphtha to remove that part of the material which boils above 410" F.
27
(210' C.) it would also be possible to prepare a very satisfactory paint thinner from this material. Application
The process described in this article is of course most suitable for the reclamation of crank-case oil on a comparatively small scale. In case small amounts of used oil were to be reclaimed by a petroleum refinery the used oil could be added directly to the paraffin distillate and worked up along with the fresh stock from crude material. In this case no change in the procedure normally used on fresh stocks would be necessary. Acid treatment and in some cases filtration must be included in the process.
Some Observations on the Transition of Coal to Coke' By Eric Sinkinson LEHIGHUNIVERSITY, BETHLEHEM, PA. Note-The pitch used in these HE experiments reA study of the electrical conductivity in the formation experiments was obtained by the corded in this paper of coke from coals of Spanish and British origin has been low temperature distillation under were undertaken with extended to Pennsylvanian and other American coals. reduced pressure of a Malayan the object of extending the lignite, and it was afterwards The conductivity method has aIso been applied to study specially washed to remove free scope of an earlier investithe gases produced by a thermal decomposition of coal. carbon. gation that promised to inThe gases first decompose and give a nucleus of carbon The r e s i s t a n c e s of a dicate something of the in fine state of division. The carbon particles are assumed centimeter cross section causes of coke formation by to be in so fine a state of division that forces of cohesion were measured in ohms. a further study of the nature come into play between them, which bind them into the The results are given in of the changes taking place foundational structure of a coke. Experiments are deTable I. in coal when it is heated and scribed to confirm this as far as possible. Durham (English) and thus becomes a conductor An attempt has been made to show that the humic Welsh coals were carbonof electricity. bodies in coal are the principal source of the olefins and ized to prepare a series of It has been pointed outZ other unsaturated gaseous compounds from which free cokes, the carbonizing temthat the change brought carbon is deposited within the range of temperatures peratures of which ranged about i s one in which free found for the decomposition of coal. from 400" to 900" C . The carbon liberated by the electrical resistances of this thermal decomposition of coal forms an electrically conducting bridge in the non- series were measured as described in the aforementioned conducting medium. Two conditions a t least are necessary paper. Table I1 summarizes the results obtained. before this can take place: (a) a minimum quantity of coke must be formed; (b) the particles of free carbon forming the TABLEI-ELECTRICAL RESISTANCESOF BRIQUETSOF FINELYDIVIDED COKEIN PITCH coke must be in a fine state of division. Consider the case ---DURHAM COKE-WELSH COKEwhere all the particles are spherical. Then if in a state of Coke Pitch Resistance Coke Pitch Resistance Per cent Per cent Ohms Per cent Per cent Ohms maximum coarseness, where all the particles are combined into one large one, evidently there cannot be a bridge across the nonconducting medium, but if the conglomerate is finely ground the particles will touch and form a bridge. Beyond a certain degree of fineness, the size of the particles should not affect the conductance. It seems reasonable to assume that carbon formed by heating coal will be in such a TABLE11-ELECTRICALRESISTANCES OS CARBONIZED COALS -WELSH-DURHAMstate as required by (b). CarboniCarboniExperiments were made to find out how coke itself in a fine zation zation Temperature Temperature state of division distributed in a nonconducting medium such c. Ohms c. Ohms as pitch would behave with different applied potentials from 900 0.13 900 0.20 800 0.60 800 0.75 conductors embedded in it. Two British cokes were selected, 700 100.00 700 140.00 600 4,300.00 600 6,000.00 namely, a Durham (Langley Park) and a Welsh-and these 550 7,900.00 550 40,000.00 were ground in a mill to pass a mesh of 200 to the linear 500 > 500,000.00 500 >500,000.00 400 > 500,000.00 400 > 500,000.00 inch (80 t o the em.), and dried at 105" C.in the ordinary way. A series of briquets was made with pitch in increments of 10 The results signify that the two coals investigated must be per cent by weight, up to 90 per cent of pitch. heated to a temperature in the region of 500' C. before a suffiI 1 Received May 5, 1924. cient quantity of free carbon is deposited to cause them to * Sinkinson, J . Chem. SOG.(London), 117, 185 (1920).
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