US2041677A - Process for the recovery and purification of lubricating oils from mineral oils - Google Patents

Description

May I9, -1936.

CONDENSER F. x. GoVERs 2,04L677 PROCESS FOR THE RECOVERY AND PURIFICATION OF LUBRICATING OILS vFROM MINERAL OILS Original Filed April 2, 1931 FRANCIS xfcovERs INVENTOR BY @www HIS ATTCRNEY Patented May 19, 1936 UNITED STATES PROCESS FOR THE RECOVERY AND PURI- FICATION OF LUBRICATING OILS FROM MINERAL OILS Francis X. Govers, Vincennes, Ind., assignor to Indian Refining Company, Lawrenceville, Ill.,

a corporation of Maine Original application April 2, 1931, Serial No.

527,104, now Patent No.

Divided and application June 10,

1,920,125, dated July 1932, Serial No. 616,502. Again divided and this application February 28, 1934, Serial No.

3 Claims.

This invention relates to the improvement in methods of obtaining from mineral oils, fractions suitable for the manufacture of lubricants and to so refining such fractions as to improve the lubricating characteristicsy of the resulting oils, and more particularly to such methods as applied to mineral oils containing a substantial amount of paraflin wax.

This application is a division of my application, Serial No. 616,502, filed June 10, 1932 as a division of my application Serial No. 527,104, led April 2, 1931, for Process for the recovery and purification of lubricating oils from mineral oils, and now matured into U. S. Patent No. 1,920,125, which latter is also designated as a division and continuation-impart of my application, Serial No. 313,346, now matured into U. S. Patent No. 1,802,942.

The method not only produces lubricating oils having markedly superior lubricating values, but in addition thereto gives greatly increased yields of lubricants and parain wax from a given amount of crude oil.

Lubricating oils must not only possess the property of forming coherent and adherent films but they must, in addition, possess body enough for the required duty. They should flow readily at low temperatures (say F.) and should retain at high temperatures (say 400 F.) enough body and oiliness (by oiliness is meant the property of being adsorbed by or wetting the surface of a metal) for the duty required. The components of lubricating oils should retain, at all times, under conditions of use their mutual solubility, and the oils should not become cloudy, opaque, or show signs of separation at low temperatures. They should not corrode or tend to dissolve the bearing metals under conditions of use, and should contain no free carbon.

In the cases of lubricants for internal combustion engines, they should retain their property of oiliness at high temperatures and under conditions of crank case dilution and should not form an emulsion with water.

As ordinarily manufactured, lubricants made from naphthene-base oils have the property of retaining at low temperatures the mutual solubility of component hydrocarbons and the formation of coherent films but are lacking in that they do not have the necessary degree of oiliness under conditions of crank case dilution or at elevated temperatures.

As ordinarily manufactured, lubricants made from paraffin-base crudes retain to a greater degree than the naphthene-base lubricants their oiliness at high temperatures and under crank oase dilution, but at low temperatures the components of the paraffin-base lubricants, as heretofore made, tend to lose their mutual solubility, and these oils show signs of cloudiness, due to the separation of solid hydrocarbons, and lose their oiliness As most of the loss of mutual solubility at low temperatures in lubricants made from Wax-containing crude oils is due to the separation of paraflin wax, these lubricants are put through a so-called dewaxing process, which consists of cooling or chilling a fraction containing lubricants down to a temperature where the wax separates out, and ltering out the separated wax. Due to diculties in manufacture, this dewaxing is seldom if ever complete.

The usual explanation of the lack of complete dewaxing is that wax exists in two states, an amorphous and a crystalline state, and that the wax in the amorphous state not only does not separate out, but prevents the otherwise crystallizable wax from separating.

It is common procedure, almost universal, in the manufacture of lubricants from parainbase crude oils, to distill from the crude, fractions containing the desired lubricants, and then to submit these fractions to a cracking operation whereby, it is claimed, the amorphous Wax is converted into the crystallizable body, and then to submit the cracked fractions to a de- Waxing process.

While this cracking operation results in a product that contains less Wax and is, therefore, easier to dewax, the dewaxing is never complete and the tendency to separation at lowering temperatures remains. This cracking operation not only breaks down the so-called amorphous wax but part of the crystallizable wax as well, and converts much of the valuable lubricating fraction into compounds of lower boiling point and of lessened value.

Lubricants made from oils so cracked tend to lose the peculiar and highly desirable quality of oi1iness, this tendency becoming greater as the degree of cracking increases.

In an attempt to retain to a high degree this quality, it has been proposed to limit the cracking effect, as far as possible, by the use of distillation methods calling for lower temperatures under diminished pressures.

The methods heretofore described, calling for the use of Idiminished pressures and a lowered temperature in distillation, do not entirely prevent the undesirable cracking effect, and in the case of crude oils containing considerable quantities of parain wax, the difculties of dewaxing are increased and it has, up to the development of the new method herein described, been impossible to produce a lubricating oil of the desired oiliness in which mutual solubility of its componentl parts at low temperatures is preserved.

I have discovered in the manufacture of lubricants that, in order to preserve fully their inherent oiliness and mutual solubility, under conditions of use, it is not only necessary to remove, in rening, such .portions or fractions as tend to separate under conditions of temperature or use, but it is important to so control the process that no portion of the lubricant has, in the course of manufacture, been heated above a definite and fixed point.

I have discovered that, by the use of controlled indirect heating, it is possible to distill and redistill the fractions of mineral oil suitable for lubrication under diminished pressure without decomposition or dissociation, and at the same *time preserve the natural oiliness inherent in lubricants made from parafn-base oils.

I havediscovered that, by the use of a suitable solvent treatment, it is possible to separate out from the main body of the lubricant fraction of ,the oil, such portions as will tend to separate out later under conditions of use and/or lowering temperature.

I have discovered that, by the use of a mixture yof solvents of diiering solvent properties, it is possible to get a better separation from the lubricating oils of the desirable portions from those `which are undesirable, from a lubricant standpoint.

I have discovered that, by the use of suitable solvents and the selection of particular fractions obtained by distillation under diminished pressure with controlled indirect heating, it is possible yto obtain from any given crude oil, lubricating oils characterized by a high degree of oiliness, and maintenance of the mutual solubility of the components even at low temperatures.

By selective solvent I means a liquid which at temperatures of approximately F. has substantially complete solvent action on a mineral oil wax distillate substantially free from constituents having a boiling point equal to or below that of gas oil, and at temperatures of -5 and below has substantially complete solvent action on the liquid hydrocarbons therein but substantially no solvent action on the solid hydrocarbons therein, and of such a nature that upon cooling a solution of such mineral oil wax distillate in the solvent liquid to 0 F. and removing the solid hydrocarbons so precipitated and the solvent liquid, the resulting oil has a cold test of substantially 0 F.

I have found that these constituents of lubricant containing oils, which have high specific gravities and relatively steep viscosity-temperaturerelationships, can be separated from those constituents which have low specic gravities and a relatively nat viscosity-temperature relationship by extracting the lubricating oil with a selective solvent, such as acetone, for example.

In the past the oil which probably was best suited to summer conditions was a lubricating oil made from Pennsylvania type crude oils but, due to the fact that the Pennsylvania type oils are wax-bearing oils, prior to my invention, oils from this source of sufciently low cold test for winter use were not available. On the other hand, the

lubricating oils made from the so-called naphthene-base crudes, which were not of the waxbearing type, or, if containing wax at all, are easily dewaxed, have the characteristic of having very high viscosity at low temperatures, as compared to oil made from Pennsylvania type crudes of like viscosity at 210 F.

I am able to produce lubricating oils having all the characteristics so much desired by the automobile industry and automotive engineer, viz., oils having a low pour test and combined with such low pour test, a low viscosity temperature relation at 0 F. as compared to an oil produced from the naphthene-base crudes, having the same viscosity at 210 F. I am able to produce lubricating oils from mixed base crudes, o1' crudes of the type from Mid-continent, vIllinois and Indiana fields, having characteristics of relatively low specific gravity with relatively narrow increase in viscosity from to 210 F. as cornpared with lubricating oils of the prior art. Prior to my discovery, lubricating oils have existed in the trade having relatively high specic gravity coupled with a low pour test and also oils of relatively low specific gravity coupled with relatively high pour test but no 10W pour test oils have appeared on the market or have been produced commercially having a. relartively low specific gravity as compared with viscosity at 210 F. The oils produced by the new method have the property of the right degree of oiliness and viscosity at a temperature at which they are used while flowing readily and with not too great a resistance to flow at temperatures of 0 F. and below.

In a simple embodiment, my invention contemplates distilling, under conditions of diminished pressure coupled with controlled indirect heating, from crude oils the lubricating oil fractions under a low absolute pressure, advantageously about 5 mm., removing from such fraction, by means of a selected and selective solvent treatment at a desired temperature, and subsequent cooling, such portions as tend to separate out under use of lowering temperature or tend to lessen the desired oiliness; removing from the lubricating portion of the solvent used; treating the portion remaining after the removal of the solvent to remove sulphur and sulphur-bearing bodies; and finally redistilling, under diminished pressure and controlled indirect heat, into fracr tions diifering, in accordance with the requirements of the trade, as to body and gravity.

The advantages of distilling mineral oils under diminished pressure or in a so-called vacuum have been recognized for many years, and the extra advantage of a very high degree of Vacuum due to the extreme lowering of the boiling point of the desired fraction has been recognized, but the adaptation of Very high vacuum operations to commercial products has been held back because of the peculiar characteristics of the material under treatment. Mineral oils having a relatively high viscosity are rather sluggish in heat transfer and under methods hitherto proposed much of the good effects of high vacuum are destroyed or rendered in part ineffective by reason of the method of heating. Direct heating of the distilling vessel by means of products of combustion does not wholly achieve the desired purpose, because, due to the low rate of heat transfer from gas to oil, high temperature differences are employed and parts of the mass are heated beyond the desired Jtemperature, this tendency to overheating being accentuated by the viscosity of the oil and its low heat conductivity. These diiculties can 75 be overcome in part by the use of indirect heating, and While this is effective, so far as permitting the control of the heating medium to a greater extent than in the case of direct lire apparatus and in the prevention of overheating, the capacity of the apparatus is limited by reason of the sluggishness of the oil to absorb and transmit heat in the ordinary type of still. I have discovered, however, that if the oil to be distilled is moved at high velocity over a heated surface maintained at or about the requisite degree of temperature, the temperature differences between the body of the oil under treatment and the heating medium, which may be a suitable vapor or liquid can be kept to a minimum, and that a high rate of heat transfer can be maintained at low temperature differences. This results in a minimum of change in the oil under treatment and the retention of all the desired qualities, both in the liquid and solid hydrocarbons.

As means for heating the surfaces over which the oil is rapidly circulated, I use instead of direct heating by flame or products of combustion, a suitable heated uid advantageously circulated to and from a source of heat supply, such as the condensable vapor of a high boiling compound such as diphenyl, which vapor is of stable composition at the temperature used, or a molten metal such as lead or a fusible alloy (as described in my U. S. Patent, No. 1,586,987, patented June 1, 1926). The method of carrying out distillation by means of diphenyl as a heating medium has been fully described in my U. S. Patent No. 1,864,349 issued June 21, 1932, for Method of evaporating liquids.

It has been proposed to fractionally separate liquid hydrocarbons by means of selective solvents and it has been proposed to use solvents as diluents in the manipulation of lubricating bearing fractions prior to and during the removal of wax. All the solvents hitherto proposed have not had suflicient selective solvent action as between the solid hydrocarbons and the liquid hydrocarbons under treatment. Acetone, both in a pure and diluted state, has been proposed as a solvent for the selective Separation of differing liquid portions of hydrocarbons. It has also been proposed to use various alcohols for such purpose. It has been proposed to use benzol and toluol as diluents. I'he use of acetone by itself results in the separation of the liquid hydrocarbons into various different fractions and the use of benzol by itself results in lubricating fractions which, after removal of the benzol, show great increase in temperature at which the finished lubricating oil shows cloudiness or separation of solid hydrocarbons.

I have discovered, however, that by combining the two solvents in proper proportions, there is no separation of the liquid hydrocarbons into several Varying fractions, and that upon chilling, the solid hydrocarbons are entirely separated in such a state as to permit of easy separation either by centrifugal force or by means of ltration, and that after removal of the solvents, the lubricating oils retain their oiliness at all temperatures and remain homogeneous at low temperatures.

I have also found that the property of oiliness can be advantageously increased by the removal of undesired fractions of liquid hydrocarbons by means of a selective solvent.

Reference will now be made to the accompanying drawing which illustrates a flow diagram for the process of my invention.

Crude oil is delivered from storage I to a tube still 2 wherein it is subjected to distillation to remove fractions comprising gasoline, gas oil, or cracking stock and bottoms.

The bottoms are then conducted to a vacuum still 3 wherein they are subjected to distillation 5 under vacuum to removev therefrom distillate fractions comprising gas oil suitable for cracking stock and a wax distillate lubricating fraction. The undistilled portion, comprising the residue, is removed for such further treatment as may 10 be desired.

The wax distillate fraction above referred to is then conducted to a mixing tank 4 wherein it is mixed with acetone and benzol in proportions such that the mixture has a selective action as 15 between wax and oil at temperatures of 0 F. and below.

From the mixer 4, the mixture of oil and solvent liquid is delivered to a chiller 5, wherein it is cooled to temperatures of around 0 F. or below in order to precipitate the solid hydrocarbons.

The resulting chilled mixture is then delivered to a graining tank 6, and from there to a filter press l. The solid hydrocarbons are removed as 25V a wax cake which is withdrawn to storage as shown.

The resulting dewaxed filtrate, comprising dewaxed cil, acetone and benzol, is then delivered to a soivent recovery unit 8 wherein the acetone 30 and benzol is removed from the dewaxed oil. The dewaxed oil from which the solvent has been removed is then conducted to a solvent treating zone 9, wherein it is extracted with acetone in such proportion that the mixture of oil and sol- 35 vent separates into layers.

The two layers are separately removed and delivered to stills l0 and Il, respectively, wherein the solvent is removed from the oil.

'I'he oil remaining in still Il, comprising con- 40 stituents of the oil extracted by the acetone, is drawn to storage, as indicated, while the refined oil accumulating in the still I0 comprises dewaxed lubricating oil stock. This stock is then conducted to the chemical treating zone l2, wherein it is treated with acid and alkali to produce a nal oil which may be run to storage as shown.

A specific example of the operation of the process and apparatus is as follows: 1000 bbls. (42 gals. each) of Illinois crude oil are topped in a pipe still in which is distilled off at a-temperature not in excess of 675 F. about 28% (of the body of the oil) in the form of a gasoline cut, and 17% in the form of a cut suitable 55 for cracking. The remaining 550 bbls. are transferred to a vacuum still advantageously maintained under about 5 millimeters pressure.

There are first distilled 01T 170 bbls. under this low pressure, from an initial temperature of approximately 220 F. to a nal temperature of approximately 400 F. This material can be separated by distillation, into fractions for various uses, or may be run off in one fraction for cracking stock.

There is then distilled olf under low pressure (advantageously 5 mm. absolute) at an initial temperature of approximately 400 F. and a final temperature of approximately 620 F., 250 bbls. which fraction constitutes a wax distillate. My invention is not limited to the use of a cut within this range, as a cut within a wider or a cut or cuts within narrower ranges, may be used as considerations may require.

The residue of bbls. remaining in the vac- 75 luum still may be burned or worked up `in a special form of Vacuum evaporator for still heavier oils.

To this wax distillate fraction may be added its own volume (or more) of acetone, and thoroughly mixed at a temperature of 100 F. It is then cooled to 80 F. or lower and allowed to stand. Ihere is a sharp separation into twoV layers, and the top layer containing most of the solvent and about 10% of the wax distillate, is drawn off. From this portion, the acetone is evaporated and the residue treated according to the use to which it is to be put.

The amount of acetone used depends upon the desired fractional separation of the liquid hydrocarbons, and may be more or less than the amount above stated. This fractional separation using acetone may be effected in one or more operations.

The bottom layer, consisting of about 90% of the original wax distillate and 15% of the acetone used, is mixed with r1000 gals. of benzol and 5,425 gals. of acetone, heated to 90 F. and stirred thoroughly.

If it is desired to make fractional separation of the liquid portions of the wax distillate hydrocarbons, the step of extracting the wax distillate may be omitted, and the wax distillate mixed directly with one and one-half times its volume of a mixture of equal parts of acetone and benzol, and heated to about 90 F. Depending upon the nature of the wax-bearing mixture being treated, other proportions of acetone to benzol may be used as, for example, a mixture comprising about 35% acetone and 65% benzol.

The mixture of Wax distillate and mixed solvents is then cooled, in a flo-wing stream and under mild agitation, to a low temperature, such as 5 F. or less, and run into grainers where it is stirred until there is a complete separation between the soluble and insoluble constituents.

This mixture of lubricating oil stock and solvents containing finely divided separated matter is then run through filter presses in which the suspended matter is separated out. The iilter cake is worked up for the reco-very and purification of the paraffin Wax, and the filtrate is run to evaporators where the solvents are evaporated ofi. The remainder of the filtrate may then be treated with 66 sulphuric acid, and acid and sludge centrifuged ofi", treated at 250 F. with an alkaline solution and the alkaline solution and separated matter centrifuged off.

While acid treatment of the oil following removal of the wax has thus been described, it is frequently advantageous to chemically treat the Wax distillate prior to the steps of fractionally separating by extracting with a solvent and of removing the wax in the presence of a selective solvent.

The thus treated distillate or lubricating oil stock, about 8500 gals., is transferred to a vacuum still of the type above described, where it is separated by distillation under low pressure, advantageously of the order of 5 mm., into the required fractions. This distillation is preferably conducted in the presence of alkali, as for example, caustic soda, either in solution or as a finely divided solid, in the approximate proportion of about l lb. of caustic soda to about 100 gals. of oil. For some grades of lubricating oils, the acid and alkali treatment may be omitted. During such distillation the temperature of the heating medium is not allowed to exceed '730 F.

An example of fractional distillation under an absolute pressure of about 5 mm.' is shown in the following' table:

` Gais. distilled Initial B. P. Finn B. P. Vsglstiifgty' 380 410 200 410 440 300 440 480 450 48o 54o 85o 54o son noo Residue The residue can be accumulated until there is enough for distillation and then be redistilled to a heavier oil than the 1100 viscosity in the above example, giving at an initial boiling point temperature of 600 F., and a final boiling point of 640 F., a lubricant of approximately 1700 Saybolt viscosity at 100 F.

' The lfractions as given in the above example are distinguished and differentiated from the lubricating oils ordinarily found in commerce by the comparative absence of red (when viewed by transmitted light in a Lovibond tintometer), by their retention of mutual solubility under low temperature conditions, by their oiliness under high temperature conditions, by their absence of bloom, in their relation of gravity to absolute viscosity, by their relatively low coefficient of friction under heavy loads, by their freedom from sulphur compounds, and by their absence of corrosive action. Lubricating oils, as found in commerce, may have grouped together in a given oil a few of the desirable properties above enumerated, but up to the discovery of the above described method for the recovery and refining of lubricating fractions of mineral oils, no lubricating oils have been known to possess, in any given oil, all of the above enumerated desirable qualities and properties.

Examples of the finished lubricating oils produced by this method are shown in the accompanying table:

Vapor tem. at l0 mm.

abs Color M" cell While in the above examples the mixture of solvent and wax distillate was cooled to -a temperature of 5 F. and the solid hydrocarbons removed by filtration to produce lubricating oil of 0 F. or 5 F. pour po-int, it is to be understood that lower chilling and filtering temperatures may equally well be employed for the production of oil having correspondingly lower pour points, as for example, a pour point of 20 F. or lower if desired.

The lubricating oil may be subjected to extraction after removal of the Wax constituents to separate the constituents having a high specific gravity and steep viscosity-temperature relation from those having a low specific gravity and relatively flat viscosity-temperature relation, as outlined in the following example. A lubricating oil produced from llVlid-continent crude and from which the Wax was removed, according to the above method, had the following characteristics:

Vacuum redistillation of a sample of this oil gave fractions with the following characteristics:

Gravity A. P. I. 22. 4 22. 3 22. 4 22. 4 22. 4 22. 1 Vis. at 100 598 787 892 978 l, 198 1, 514 Vis. at 130- 233 302 327 370 416 560 59% 66% 67 7l 8(8i Viscosity index 48 50 32 41 34 47 The above lubricating oil was treated or extracted at 60 F. with acetone until the undissolved constituents comprised 30% of the whole, and after removal of the acetone therefrom, this undissolved portion had the following characteristics:

Gravity A. P. I 28.1` Vis. at 100 393 Vis. at 130 180 Vis. at 210 58.5 Flash F 440 Fire F 490 Pour test F 5 Conradsen carbon percent .0'12

Vacuum distillation of the above treated oil gave fractions with the following characteristics:

Gravity A. P. I 30.1 29.0 28.8 27. Viscosity at 100 235 382 578 950 Viscosity at 130-. 119 176 256 396 Viscosity at 210.. 48% 56 65 83 F1ashF 455 460 470 485 Fire QF 510 540 560 570 Pour test "F -5 -5 -5 -5 Conradsen carbon percent 012 010 012 012 Viscosity index 97 91 86 89 The viscosity index of each of the foregoing fractions has been calculated by the method of El. W. Dean and G. H. B. Davis, described in an article entitled, Viscosity variations of oils with temperature published on pages 618-619 of Chemical and Metallurgical Engineering, Volume 36, No. 10, October 1929.

An important advantage of my dewaxing process over the methods of the prior art resides in the fact that oil dewaxed by my process may be subjected to subsequent solvent or other refining treatment without appreciably affecting the pour test of the dewaxed oil. It has been observed that the pour test of oil dewaxed by other methods may increase substantially as a result of subsequent treating operations whereas the pour test of oil dewaxed by the method of my invention, in many instances, remains unchanged as a result of subjecting the dewaxed oil to subsequent treatment.

It will be obvious from the foregoing that many modifications may be made in the details of the process without departing from the spirit and scope of my invention.

For instance, certain other fractions of crude oil, such as lubricant concentrates from Pennsylvania type crude oils, or chemically treated lubricants containing concentrates from mixed base crude oils, are equivalents of the wax distillate given in the foregoing example with respect to the dewaxing treatment above described.

I claim:

1. The method of manufacturing low pour test high viscosity index oil from viscous wax-bearing mineral oil comprising mixing said oil with a solvent liquid composed of acetone and benzol mixed with the oil in proportions su'cient to yield an oil of around zero pour test when dewaxed at 0 F., chilling the mixture to precipiate the wax, separating the wax thus precipitated, removing the solvent from the dewaxed oil, mixing the dewaxed oil with a further quantity of acetone to provide a solvent mixture adapted to dissolve constituents of low viscosity index, and separating from the mixture a fraction of low pour test comprising constituents of high viscosity index.

2. The method of manufacturing low pour test high viscosity index oil from viscous wax-bearing mineral oil comprising mixing said oil with a solvent liquid composed of acetone and benzol mixed with the oil in proportions suicient to yield an oil of around zero pour test when dewaxed at 0 F., chilling the mixture to precipitate the wax, separating the wax thus precipitated, removing the solvent from the dewaxed oil, extracting the dewaxed oil with a solvent comprising mainly acetone to dissolve the low viscosity index constituents, and separating from the mixture a fraction of low pour test comprising constituents of high viscosity index.

3. The method of manufacturing low pour test high viscosity index lubricating oil from viscous wax-bearing mineral oil which comprises mixing with the oil a solvent liquid composed of an aliphatic ketone of the character of acetone and having selective solvent action as between liquid constituents of the oil of differing viscosity indices and a modifying solvent having solvent action for oil substantially of the character of benzol mixed in such proportions that at temperatures of around 0 F. and below the mixture has substantially complete solvent action upon the liquid hydrocarbon constituents and substantially no solvent action on the solid hydrocarbon constituents of the oil, chilling the mixture to 0 F. and below to precipitate solid hydrocarbons, removing the solid hydrocarbons thus precipitated, removing the solvent from the dewaxed oil, extracting the dewaxed oil with said selective solvent comprising mainly aliphatic ketone, and separating therefrom a fraction comprising low pour test oil of high viscosity index.

FRANCIS X. GOVERS.

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