US2031096A - Process for producing lubricating oil - Google Patents

Description

Feb. 18, 1936. u. B. BRAY PROCESS FOR PRODUCING LUBRICATING OIL Original Filed Oct. 6. 1950 INVENTOR //rlc r'g AORNEY.

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lPatented Feb. 18, 1936` Ulric B. Bray, Palos Verdes Estates, Calif., as-

signor to Union Oil Company of California, Los Angeles, Calif., a corporation of California Original application October 6, 1930, Serial No. 486,724. Divided and this application October 14, 1933, Serial No. 693,644

Claims. (Cl. 196-19) This y invention relates to the production lof lubricating oils from crude oils containing asphalt and wax. The invention relates particularly to the separation of wax from wax containing oils in 5 the presence of a chlorinated hydrocarbon solvent such as dichlorethylene and trichlorethylene. This case is a `division of my co-pending application Ser. No. 486,724, tiled Oct. 6, 1930.

It has been found advisable to cause the separation of asphalt from the oil by means of volatile solvents which are capable of dissolving the oil and any Wax and which do not dissolve the as- 'phalt Such solvents are lightr petroleum fractions, such as casinghead gasoline and naphtha and also petroleum fractions-normally vaporous at ordinary temperatures and pressures. Other solvents which may be used are alc'ohol, ether,

mixtures of alcohol and ether, acetone, etc. Il

prefer to use as solvent propane or liquid propane and by this I intend to include such hydrocarbons as are normally vaporous at ordinary temperature and pressure; such hydrocarbons include methane, ethane, propane, butane, isobutane and mixtures thereof. These normally gaseous hydroy carbon solvents maybe obtained by rectication of casinghead gasoline by the so-called stabilizin'g` method now conventional in the natural gasoline industry. They are liquefied bycom- .pression and cooled in the conventional manner and are drawn oi into pressure chamber where they are maintained in a liquid state until used.

A typical analysis of such a' fraction is 6.72%`

in an asphalt substantially free of oil and a solution of oil in the liquid petroleum fraction. This solution contains substantially all the wax present in the crude oil.

` A It has also been found that oil containing asphalt and impurities, such as Wax, may be first freed from the 'asphalt by a primary extraction with a light solvent, such as the solvent described I above, and that the impurities, such as wax, may

then be removed at a suitable temperature by the aid of a heavier solvent such as chlorinated light hydrocarbons as dichlorethylene and in particular, trichlorethylene in Which the wax is substantially insoluble at the low temperature employed.

By heavier solvent, I mean one of higher .bolling point than the light solvent previously described. l

Advantage is taken-of the high volatility of the light solvent 'to cause a cooling of the oil upon 5 a release of pressure to produce the separation of the contained wax. A` further advantage in cooling the oil in this manner is to bring the oil to a proper temperature for acid treatment. By acid treatment I intend to include treatment with 10 acid followed by the step of neutralization and/or clay treatment.

` also encountered in chemically treating oils of high viscosity. My invention avoids these diniculties by mixing the oil with trichlorethylene before dewaxing to reduce the viscosity and place the oil in proper condition for dewaxing. The re- 25 duced viscosityiis also advantageous in chemical treatment of the oil. Instead of trichlorethylene, I may use other solvents or diluents, for instance,

l benzol, alcohols, such as methyl, ethyl, propyl,

butyl alcohol or mixtures of the same, ketones 30 such as acetone or diethyl ketone, or mixtures of benzol with acetone or other ketones, or mixtures of benzol and butanol or other alcohols.

In addition to the power which trichlorethylene has of reducing'the viscosity of the asphalt-free 35 oil, it also is used as an extracting medium for Wax or other material whose presence is deleterious in a finished, high grade lubricating oil. The trichlorethylene, if used in suiiicient quantities, acts as a solvent for the oil during the red0 movalv of the Wax or other impurities in a marmer similar to the action of the propane solution during the removal of the asphalt. By regulating the quantity, substantially oil-free wax may be precipitated. In comparing their volatility and at' produce lubricating oil from oil containing asphalt and impurities by extracting the lubricating oil ilrst with a light solvent such as propaney .to precipitate the asphalt and then extracting the oil from the impurities such as wax with a heavier solvent such as trichlorethylene.

It is a'further object to produce lubricating oil from the oil described above by maintaining pressure on the oil and light solvent during the extraction of the asphalt and to extract the impurities such as wax from the asphalt free oil by means of a heavier solvent under reduced pressure.

It is furthermore an object of my invention to produce lubricating oil from oil containing asphalt and wax by mixing this oil with a solvent in which the lubricating oil fractions and wax are soluble, but in which the asphalt is insoluble, and subsequently separating the wax from the lubricating oil fractions in the presence of trichlorethylene.

It is a further object of this invention to mix the trichlorethylene with the oil either in the presence of substantially all the propane used to precipitate the asphalt, or in the presence of only a portion of said propane, or the trichlorethylene may be added after substantially all the propane has been separated from the oil and wax.

Another object of this invention is to produce lubricating oil from oil containing asphalt and wax by mixing a volatile solvent therewith under pressure to precipitate the asphalt and dissolve the lubricating oil fractions and wax, separate, the precipitated wax under pressure, and taking advantage of the highly volatile characteristics of the solvent by releasing the pressure and a1- lowing the solvent to vaporize and consequently cool the oil and wax, thereby precipitating thel latter, and to separate the wax from the oil in the presence of trichlorethylene. It is a particular object of my invention to separate the precipitated wax from the oil solvent solution by means of mechanical separating devices, particuf larly by means of a centrifuge. Other objects and advantages of my invention will be apparent from the following description of my invention taken from the drawing which shows a preferred schematic arrangement-of apparatus for carrying out my invention.

Referring to the drawing, topped residuum obtained by distilling crude oil at a temperature preferably not over 60G-625 F. to remove all fractions up to and including all or a portion of the light lubricating oil, is taken from tank I and is passed through line 2 to pump 3 and to T 4 where it meets a propane solution of lubricating oil coming through line I5. The propane and residuum pass through the turbulence or mixing coil 5 and then into decanter C. The asphalt in the residuum is precipitated by the propane and settles to the bottom of decanter 6. The precipitated asphalt resembling a slurry may be drawn oil from the bottom of the decanter with sufficient liquid propane to permitpumping. The asphalt propane slurry is passed through pump 'i and line I where it is mixed with propane from storage 8 via pump 9 and line I0. The mixture then is passed into mixing coil II and into decanter I2. Decanters 6 and I2 and propane storage 3 are maintained at the same pressure by vmeans of equilibrium lines Icontrolled by valves I1'. The pressures in Ii, I2 and 3 are sufilcient to maintain the solvent in liquid state at ordinary temperatures of about 75 F. -For the solvent given above, this pressure is about 125 to 175 lbs. per square inch. If it is desired to produce an lsphalt containing still less oil or wax, the countercurrent washing with propane may be extended to as many `steps as desired.

The clear overflow from decanter I2, consisting of liquid propane in which is dissolved a small amount of lubricating oil, is passed through linev I3, pump I4 to line I5 to T 4 where it is mixed with the incoming topped residuum and passes through turbulence coil 5 into decanter 6', as described above. The asphalt slurry from decanter I2 is drawn off through the pressure release valve I3 and flashed through coil I3 in furnace 20.

Suicient heat is supplied in coil I9 to cause vaporization of the propane and to melt the asphalt. The heatedmixture of asphalt and propane is now sent into evaporator 2I where superheated steam is introduced via 22 in order to complete the evaporation of the propane and to reduce the asphalt to satisfactory ilash and fire specifications. The overhead from evaporator 2i is sent through line 23 to condenser 24 which may be a heat exchanger or simple cooler or a combination of both.l The products from' condenser 24 consisting of condensed steam and oil together with uncondensed propane are sent to separator 2l. through 21 and condensed water through 26. The uncondensed propane from the separator is sent through line 28 to propane compressor 20. The compressed propane is sent through line 3I to line 32 to condenser 33 where it is liquefied and passes into propane storage 8. The reduced asphalt is sent to asphalt storage 23. The pressure in 2I is about atmospheric, although it may be higher, if desired.

The overflow from decanter 6,' consisting of a more concentrated solution of lubricating oil and propane is passed through pump 35 and line. 34 through pressure reduction valve 36 where it meets trichlorethylene from tank 31 passing through pump 38 and valve 39. In the operation of cooling chamber 4I, if a very large portion of the propane is evaporated, the remaining solution would be too viscous and not of suiiicient difierence in specific gravity between the oil and wax phases to permit satisfactory behavior in the dewaxing operation. Therefore, a suitable quantity of trichlorethylene is added in line 40 to the incoming propane solution. The addition of the trichlorethylene also reduces the loss of propane f in the centrifuging operation if the centrifuge Is not gas tight in construction.

It is desired to release the pressure upon the propane solution so that propane will evaporate from the solution and thereby sufilciently lower the temperature of the remaining solution to permit a satisfactory dewaxing operation. The propane solution passing through pressure reduction valve 36 goes through line 40 into cooling chamber 4I which is in eiect a rectifying column held at a predetermined pressure corresponding to the desired dewaxing temperature. As the propane evaporatee, the temperature of the remaining solution falls to that in which the vapor pressure will correspond to that being maintained in the cooling chamber by propane compressor 43. The propane vapors pass out through line 42 to compressor 43. The conditions in rectifying column 4I are maintained by the proper manipulation of valve 38 by controlling the suction of compressor 43 so that only the solvent is removed and the lubricating oil and trichlorethylene are retained as bottoms. By reducing the pressure tov substantially atmospheric, a temperature of .-40" F. can be obtained; Substan-V The condensed light oils are removed tially all the propane may be .removed from the solution in rectifying column 4| or only the necessary quantity may be allowed to vaporize therefrom in order to provide for sufficient cooling to 'dewax the oil. The compressed vapors leaving ever, if desired, the mixture may be filter pressed -or cold settled to separate the precipitated wax In the event from the remaining oil solution. cold settling is employed for removing the precipitated Waxthe wax will settle upwardly and the 4 Wax free solution is decanted from the bottom of the settler. The centrifuge is operated by motor t1 Whichis positioned outside a gas tight insulated chamber t8 which contains centrifuge t6.

l Wax is discharged from the centrifuge through line ill connecting with the center of the centrifuge on account of the high specific gravity of the trichlorethylene solution of oil and the comparatively lower specific gravity of the precipitated wax. The discharged wax may be worked up in any' suitable manner for the recovery of propane, trichlorethylene and oil.. The dewaxed oil is discharged through line 5l] and is passed into heater 5 l The heater 5l may consist of any convenient equipment which will impart heat to the cold oil passing through line 5t, such as a heated coil set in a furnace or heat exchanger. As shown, it Ais a steam heated, steam entering at 52 and exiting at 5i; The 'dewaxed oil solution leaving heater 5l may be sent by either of two courses.

If it is desired to acid and alkali treat the devi/aired lubricating oil stock while in trichlorethylene solution, the oil is passed through valve 5d to evaporator 55. In evaporator 55 practically all of the remaining propane is removed from the solution, passed` through mist extractor .55', through line 55 to propane compressor 30, where it is compressed and sent through line 3l and line 32 to condenser 33 where it is liquefied and passed into propane storage t. The column 55 isoperated to keep the trichlorethylene in the oil by the proper manipulation of valve 5t and by controlling the suction of propane compressor 3. This is merely a simple rectifying step. Rectifying plates may be provided to assist in this operation as will be understood by those skilled in the art. If desired, the dewaxed trichlorethylene solution of oil may be chemically treated in the presence of the liquefied normally gaseous hydrocarbon solvent, i. e. propane, in which case the propane is retained in the trichlorethylene solution during the subsequent chemicall treatment hereinafter described. A temperature of about 40 F. is desirable in the following chemical treat- -ment and may be obtained by heating the cold temperature in heatacid sludge is withdrawn through line 68 controlled by valve 59. In agitator 13 it is first treated with water passing from 18 via pump 19 and line controlled by valve 80' through line 11. The water is withdrawn through 8l controlled by valve 82. The oil is then treated with caustic soda passing from 14 via pump 15 and line 16 controlled by valve 16 to line 11. The spent caustic is withdrawn through 8l. The alkali treated oil is then Washed with water as previously described. The treated trichlorethylene solution is carried from agitator 13 by line 33. T-he treated trichlorethylene solution passes through line 83, pump 8i, line 85, valve to heat interchanger 81.A

If it is not desired to perform the acid and alkali treatment in thel presence of the trichlorethylene, the Aoil leaving heater 5I is passed through valve 54 to heat interchanger 81, valves 54 and 86 being closed and valve 54 open.l Oil leaving 81, where its temperature is raised somewhat, is sent through line B8 to coil 89 in furnace 2li where its temperature is raised still further before being introduced into evaporator 9| through line 90. Steam isintroducedvia 92 in evaporator Sil to aid in the flashing of the trichlorethylene and residual propane and to reduce the remaining oil to satisfactory flash and fire specifications. The oil remaining in the bottom of evaporator 9i is drawn oir through line 93 and sent to dewaxed oil storage 95 via pump gli.

If the oil has not been chemically treated in trichlorethylene solution, it may now be treated free from trichlorethylene or, if desired, a quantity of liquefied normally gaseousA hydrocarbon solvent, such as liquid propane, may be added to the trichlorethylene free oil and the chemical treatment may be effected in the presence o f this solvent. i

The treated trichlorethylene solution travels from heat interchanger t1 in the same path described above in order to be free of trichlorethylene and residual propane.

The overhead from evaporator 9i is passed through 95 and heat interchanger B1 into line 91 The trichlorlineill to trichlorethylene storage 31. Any uncondensed propane in separator 99 passes through line Wil to propane compressor 3. The compressed propane passes through lines 3 and 32 to condenser Siti where it lquenes and passes to propane storage t. The condensed steam is withdrawn through itl.

In the vforegoing description of my invention, I have described a chemical treatment of the oil as taking 4place subsequent to the removal of the wax from the oil. be hunted to this exact procedure. Ii' desired, the chemical treatment of 'the oil mayprecede the wax separation step and may be effected in the presence or substantial absence of trichlorethylene and/or liquid propane. ethylene and/or liquid propane may be added to the oil subsequent to the chemical treatment if the latter has been accomplished in the absence of either or both of these solvents.

The following is an example of one mode of carrying out my process for the production ofA lubricating oil employingl trichlorethylene as a solvent to aid in the separation of the precipitated wax from the oil.v However, it is to be-'understood that this example is to be considered merely as illustrative and not as limiting m'yinvention:

A topped residuum containing both asphalt and wax -such as Santa Fe Springs residuum which has been topped to approximately 400 However, I do not wish to The trichlor-` seconds Saybolt furol viscosity at 210 I". is comtaining the same which comprises commingling mingled with approximately 4 volumes of liquid propane at a temperature of about F. and under a pressure of about to 175 lbs. per square inch which is sumkcient to maintain the propane in a liquid state at the above temperature. The propane dissolves the oil and wax but precipitates the asphalt contained in the oil. After permitting the mixture to settle for a sumcient time, the oil propane solution is decanted away from the settled precipitated asphalt.

The oil propane solution is then mixed with approximately two volumes of trichlorethylene based on the one volume of the original topped residuum. 'Ihe pressure on the. mixture is gradually released to approximately atmospheric to permit evaporation of propane which reduces the temperature of the remaining solution of oil. wax, trichlorethylene and remaining propane to about -40 F. The reduction in temperature causes the wax to precipitate from the mixture. Approximately 2.5 -to 3 volumes of liquid propane are evaporated during their refrigeration down to -40 F. leaving from 0.9 to 1.4 volumes of liquid propane associated with 2 volumes of trichlorethylene and approximately 0.8 volumes of wax and de-asphaltized viscous oil. This mixture is then centrifuged to separate the precipitated wax from the oil, propane and trichlorethylene. Due to the high specific gravity of the trichlorethylene solution of oil and propane, the wax will appear at the center of the centrifuge and the solution of dewaxed oil will appear at the periphery of the centrifuge bowl. Discharge of wax and the solution of dewaxed oil as separate phases is accomplished continuously from the centrifuge. The oil solvent solution is then chemically treated with acid and alkali and/or clay and then the chemically treated solution of oil is distilled to remove the'liquid propane and trichlorethylene to leave a lubricating oil substantially free from asphalt and wax and having a .low Conradson carbon value and low pour point.

It is to be understood that the above description is merely illustrative of preferred embodiments of my invention of which many variations may be made by those skilled in the art within the scope of the following claims without departing from the spirit thereof.

I claim:

1. A process for separating wax from oil conthe precipitated wax from the oil and subsequently separating the liquefied normally gaseous hydrocarbon and chlorinated ethylene from the oil.

2. A process for separating wax from oil containing ythe same which comprises commingling said oil with a liquefied normally gaseous hydrocarbon and dichlorethylene, chilling the mixture to precipitate the wax, separating the precipitated wax from the oil in the presence of substantial quantities of liquefied normally gaseous hydrocarbon and dichlorethylene to aid in the separation of the precipitated wax from the oil and subsequently separating the liquefied normally gaseous hydrocarbon and dichlorethylene from the oil.

3. A process for separating wax from oil containing the same'which comprises commingling said oil with a liquefied normally gaseous hydrocarbon and trichlorethylene, chilling the mixture to precipitate the wax, separating the precipitated wax from the oil in the presence of substantial quantities of liquefied normally gaseous hydrocarbon and trichlorethylene to aid in the separation of the precipitated wax from the oil and subsequently separating the liquefied normally gaseous hydrocarbon and trichlorethylene from the oil.

4. A process for separating wax from oil containing the same which comprises commingling said oil with liquid propane and trichlorethylene, vaporizing a portion of the propane to chill the oil and precipitate the wax, separating the precipitate wax from the oil in the presence of substantial quantities of liquid propane andrtrichlorethylene to aid in the separation of the precipitated wax from the oil and subsequently separating the liquid propane and chlorinated ethylene from the oil.

5. A process as in claim 4 in which the separation of the precipitated wax is accomplished 50 by means of a centrifuge.

ULRIC B. BRAY.

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