US2079885A - Process for preparing lubricating oils - Google Patents

Description

May 11, 1937. v. vooRHEEs 2,079,885

PROCESS FOR PREPARING LUBRICATING OILS Filed Dec. 14, 1934' 2 Sheets-Sheet 1 SEPA/QA T0R\ EXTRACTO/Q 14 i i'f "fi .Soll/@nt INVENTOR K Vande/Veer Voorhees BY A EN "1 K ATTORNEY MaY 11, 1937 I v. vooRHEEs 2,079,885

vPROCESS FOR PREPARING LUBRICATING OILS Filed Dec. 14,v 1954' 2 sheets-sheet 2 a 0) Q 'N U) LA a f2 LLI- o ATTORN EY Patented May l l, 1937 UNITED STATES' PATENT 'OFFICE i y ,2,019,885 rnocEss ron rnrmumc Lunrca'mrc l Vandervcer Voorhees, Hammond, I nd., assignor to Standard Oil Company, Chicago, lll., a corporation of Indiana Application December 14, A1934, Serial No. '757,439 11 cams. (c1. 419e- 13) This invention relates to processes of extracting hydrocarbon oils with selective'solvents and it pertains more particularly to a process whereby certain parts of the extract and railinate are recycled to aid in the extraction oi the oil.

Petroleum is essentially a mixture of hydrocar A large number of individual compounds of each series are present in the oil but have diierent boiling points, physical and chemical properties.

In the various types of crude petroleums commanly known as paraiiln base, naphthene or asphalt base and mixed base oils, these various series of hydrocarbons are present in different proportions. For example, in the paraiiln'base oils such as those from the Appalachian ileld, there is a relatively highproportion of paraillnic hydrocarbons having chain structures and .high hydrogen to carbon ratios, whereas in the Gulf Coastal oils there isa high proportion of hydrocarbons with ring structures and low hydrogen to carbon ratio. 'I'he mixed base oils such as those from Oklahoma and Mid-Continent areas are in general intermediate these two extreme types of oil.

In the normal refining of crude petroleum, the fractions of varying distillation ranges, which are successively obtained by distillation of the oils, partake of the general character of the crude; for example, the heavy lubricating oil distillates derived from Appalachian crudes will show paraffinic characteristics, whereas the heavy distillates derived from Winkler crude show naphthenic characteristics. 'I'he distillates from the mixed base crudes, such as those from the Mid- Continent area, will show characteristics common to both the paraflnic and naphthenic oils. An importantA property of paraiiinic' lubricating oils is their low viscosity temperature coecients or rates'of change of viscosity with temperature. In other words, these oils have high viscosity indices. This property makes them particularly suitable for certain lubrication problems where high temperatures are encountered. At low temperatures also, these oilsretain their fluidity better, an important consideration in cold weather. For this reason, it is very desirable to separate from lubricating oils and from the mixed base oils in particular the undesirable naphthenic and aromatic constituents (compounds tending to form sludge) thereby making the` oil more parafflnic. Various methods have been proposed for doing this and some. have been used with partial success; thus, the oil may be subjected to vigorous treatmentv with sulfuric acid followed by neutralization and removal of harmful sulfuric acid derivatives.

The expression viscosity index, as used herein, refers specically to the index of lubricating oils, defined by Dean and Davis in Chemical and Metallurgical Engineering, volume 36, page 618, 1929. The viscosity index of a lubricating oil is an indication of its composition or type, that is, whether it is a parafn base or naphthene 'base oil. Paramn base oils are arbitrarily assigned a viscosity index of 100, naphthene base oils are assigned a viscosity index of zero, and mixed base oils lie between these extremes. By the present invention I have made it possible to obtain from mineral oils containing a mixture of paraiiinic and naphthenic compounds, a maximum yield of parain type hydrocarbons (with a high viscosity index) with the minimum amount of solvent and without the nuisance or cost of acid treating and without appreciable destruction of the naphthenic constituents of the oil. .f vThe term "naphthenic hydrocarbons is employed in this Yapplication andin the claims in a generic sense to include the hydrocarbons that are aromatic, aromatic-like, and oleflnic in composition as well s the polymethylene hydrocarbons. The above naphthenic compounds found in lubricating oils are responsible for the low viscosity indices and sludge-forming properties of these oils, whereas in the case of the W- boiling oils, such as naphthas and cracked naphthas, the naphthenic compounds are responsible for the anti-detonating characteristics of these distillates, In all crudes, the hydrocarbons in the lubricating oil range are mixtures in which all shades of naphthenicity and paraiiinicity are represented to a greater or lesser extent, depending on the type of crude. Therev is accordingly a fairly continuous distribution of hydrocarbons of low, intermediate and high viscosity index, making separation much more difficult than would be the case if the oils contained only two or three types of hydrocarbons.

An object of my invention is to produce an improved method for the continuous countercur- `rent extraction of mineral oils so that I can obtain a lubricating oil raffinate which has a high viscosity index or is highly paraflinic and stable y against sludge formation, and a second fraction,

-part of this specification.

the extract, which has a low viscosity index or which is highly naphthenic or aromatic in composition. l

A particular object of my invention is to provide a process for extracting mineral oils whereby a certainy part of the rafiinate and/or extract can be used .in combination with-a solvent to extract the oil; thereby .reducing the amount of solvent normally used to extract the oil.- My invention is illustrated by Figures 1 and 2, which form a Figure 1 is .a diagrammatic elevation of an apparatus for the extraction of oils by my improved process.

Briefly, the general outline of my new process is as follows: A mineral lubricatingoil containing parailinic and naphthenic constituents is given a countercurrent extraction with a suitable solvent, the railinate and extract fractions tothe extractor to aid in the further extraction of fresh oil. Likewise, a part. of the most parafnic raffinate is returned to the extractor to aid in the further extraction of fresh oil. Either or both oi these steps may be used.

The oil to be extracted, for example a mixed base mineral oil distillate having a gravity of 26.6 A. P. I., a Saybolt viscosity of 1,14 seconds fat 210 F. and a viscosity index of about 56, is forced by pump Il) through conduit II and introduced into `vertical extractor I2 at a point slightly below or at about the middle thereof by` perforated pipe I3. Before starting the process, extractor I2 may be filled with the oil or solvent and in this example I will assume that extractor I2 is lled with solvent as the continuous phase. The oil, being lighter than the solvent, passes up through the solvent which is continuously introducedinto the top7 part of the tower through perforated pipe I4.`l The solvent descends through the tower and thereby effects a countercurrent extraction of the ascending oil. Any suitable means, such as pump I5 and conduit I6, may be used to pass thevsolvent into perforated pipe I4. The oil and/or solvent may be heated before being introduced into the extractor so that the' extraction will be eiected at the desired temperature. ,The extractor may .also be heated and/or cooled at various points by coils or jackets (not shown). When a solvent like di(2chlorethyl) ether is used, the extraction is suitably carried out at a temperature ranging from 75 to 125 F. When a solvent like cresylic acid is used, the extraction temperature may range from to 175 F. Higher or lower temperatures may be used to suit the particular type of oil and solvent and to conform with the practice of the rener. The volume of solvent used may vary over a wide range, but due to my particular method of extracting, good yields of high viscosity index oils can be produced with small quantities of solvent, for example 0.5 to 1.5 volumes of solvent for each volume of oil. The process may also be operated with somewhat larger volumes of solvent, for example 1.5 to 3 volumes of solvent may be used for each volume of oil. Selective solvents such as phenol, nitrobenzene, furfural, chloraniline or mixtures of any of these may be used. Previous to extraction the oil may be rened by any of the usual refining agents such as sulfuric acid,

aluminum chloride, fullers earth, propane, etc. The solvent, with the dissolved extract or low viscosity index constituents, is withdrawn from the bottom of extractor I2 through conduit I'I and passed to cooler I8 where it is cooled to a temperature ranging from 25 to 80 F. below the temperature of extraction and thencethrough conduit I9A toextract separator- 20. The manner of using a part of.this extract in the further extraction of the oil in extractor I2 will be described hereinafter. f

The rafnate comprising the highly paraiiinic constituents is withdrawn from the top part of the extractor through conduit 2i and passed to cooler 22 where it is cooled to a temperature from 25 to 80 F. below the temperature of extraction 'and thence through conduit 23 to rainate separator 2c. A small amount of solvent will be present in the raffinate. 'I'he use of a portion of -this raiiinate in the further extraction of the oil in extractor I2 will be described hereinafter.

The admixture of solvent and extract in separator 20 separates into two layers hereinafter referredto as extract #1 and extract #2". 'Ihe former collects in the upper part of separator 20 and the latter collects in the lower part of the separator. Extract #2 is composed of a part of the solvent and the most highly naphthenic constituents o'r the constituents having the lowest viscosity index., Extract #l is composed of a part of the solvent and the less naphthenic constituents which have a somewhat higher viscosity index than the constituents of extract #2. l

Likewise, the; raffinate separates into two fractions hereinafter referred to as rafllnate #2 and railinate #1. The former collects in the upper part of the separator 24 and the latter collects in the lower part of the separator. Rafnate #2 is composed of a small part of the solvent and the most paramnic constituents of the oil or the constituents having the highest viscosity index. Raflinate #1 is composed of a small part of the solvent and the less parafnic constituents which have a somewhat lower viscosity index than the constituents in rafilnate #2, If desired, several separators like 20 and 24 may be used in parallel to effect a separation of solvent they are prevented' from escaping from the top of the extractor with the raililnate in line 2|. v'I'he added naphthenic constituents and solvent descend through the extractor I2 and effect a countercurrent extraction of the ascending oil.

In effect, these added naphthenic constituents take the place of a part of the solvent and thereby reduce the quantity of the particular solvent normally used in the extraction of oils, and per- -mit the use of more hydrophyllic solvents such of the tower, forms a separate phase which rises through the tower and serves to absorb or extract from the solution therein, those constituents of intermediate viscosity index desired in the rafnate.

It should be understood that the extract removed by conduits 3l and 32 and the raffinate-removed by conduits 33 and 34 may be distilled or given any conventional treatment to recover the solvent from the oil. The recovered solvent is recycled through conduit I6. The conduits 30 and 35 should be spaced far enough above the lower end of the extracting tower l2 so that a quiescent zone may exist in the lower part of said tower. The same precaution should be followed with respect to conduits I4 and 21. Baiiles may be placed in either or both of these quiescent zones to prevent a turbulent action. I

In the accompanying diagram, Figure 2, I have shown a theoretical distribution of viscosity index throughout the lubricating oil range. Although this diagram is not based on actual data it is believed to be approximately correct in view of related data and observations on the behavior of lubricating oils partially separated into their constituents by selective solvents.

The diagram represents a typical lubricating, oil distillate from mixed base crude and is believed to show the results which would be obtained by separating this oil into small fractions on the basis of viscosity index, i. e., each fraction to be homogeneous or substantially homogeneous from the standpoint of the viscosity index of its constituents. In the separation of oils to improve the viscosity index, the maximum yield and/or viscosity index would be obtained by sharply separating the mixture between two hydrocarbon constituents, rejecting all hydrocarbons of lower viscosity index. This is not practicable commercially but is the aim in all commercial processes of this kind. It is illustrated in the chart by intersecting the area under the curve with the line ai-b, all hydrocarbons lying to the rightlbeing of higher viscosity index than any of those on the left of the line a-b.

It may be observed from this theoretical diagram that it would be very difficult to separate two oils whose Viscosity indices are close together because the chemical and physical differences in that case are very slight. Referring to the chart,

the letter a designates a fraction of about 55 i sents intermediate naphthenic material (between points a and c) G represents intermediate parafnic material (between points a and d), and H represents the most paraiiinicmaterial (to the right of point d). Let us assume that E and F are to be separated from G and H. A large amount of F, being intimately associated with G', is carried into the raflinate end of the system.

In practicing my invention I introduce E into this raffinate end because it is so naphthenic that it is immiscible with the good oil leaving that part of the system and at the same time it is relatively miscible With-F and ity therefore has the effect of extracting F from the ramnate and returning -it to the extract. It should be noted that I am not recycling that portion of the extract which contains desirable parafilnic mate- 4In order to prevent the loss of this material with the extract, I recycle part of the most highly parainic material H to the extract end of the tower. This material H is so dissimilar to E that it is immiscible therewith in the presence of the solvent and therefore it is not carried away with the extract. At the same time this material H, more closely resembling G, becomes intimately associated with G and carries it back to the raffinate end of the extraction system. Here again it should be noted that I am not returning an insufciently extracted paraillnic fraction for further extraction,-I am returning the most parailinic fraction to the extract end of the system for preventing the loss of fractions of intermediatel parainicity. My invention contemplates either the recycling of highly parafiinic rainate to the extract end of the system or the recycling of highly naphthenic extract to the raiiinate end of the system or both.

Referring again to Figure 1, I may employ more eective fractionating means for separating extract #1 from extract #2 and railinate #l from rafiinate #2. In place of separators 20 and 24, for example, Imay use countercurrent towers with progressive cooling and recycling. I may also employ an additional solvent, for example, light naphtha, hexane, butane or propane for improving the separation. I may likewise introduce hexane or propane into the base of extractor i2 through the perforated conduit 35 to assist in removing paraffinic material which may be mechanically or otherwise carried out of the extractor with the extract. The volume of propane, butane, hexane, or light hydrocarbon fraction may Vary over a Wide range, depending upon the oil and solvent used, but 0.1 to 0.5 volume of such solvents may be employed for each volume of oil extracted. Such additional solvent may bev recovered by distillation froml the extract fractions, and, of course, the principal solvent may be recovered and recirculated by pump l5.

While I have described this invention in relation to a particular application thereof, I intend that it shall be limited only by the following claims:

1'. The method of refining a hydrocarbon oil containing a plurality of components of varying degrees of paraiiinicity and naphthenicity which comprisesl countercurrently extracting said oil with a selective solvent to give a raiiinate and an extract, separating the rafiinate into highly -paraiiinic and less parafnic fractions, and returning the highly parafiinic fraction to the countercurrent extraction system for recovering less parailnic materials which would otherwise be lost in the extract.

2. The method of reiining a hydrocarbon oil containing a plurality of components voi! varying degrees of parailinicity and naphthenicity which comprises countercurrently extracting said oil with a selective solvent to give a rafElnate and al-.extract, separating the ratlinate into highly paraillnic and less paramnic fractions, and re fraction of highly naphthenic constituents, the

steps comprising countercurrently extracting the oil in an elongated vertical extracting zone with a selective solvent whereby there are obtained a raiiinate fraction and an extract fraction, removing said extract fraction and rafnate fraction to separate zones, separating said rainate fraction further into a more paraflinic and a less paraiiinic fraction, returning to a point near the extract end of the extracting zone a part of the more paraiinic fraction and permitting it to pass countercurrently through saidy extracting zone wherebyt supplements the countercurrent extraction of the oil by the selective solvent.

4. Steps according to claim 3 in which said separating step is accomplished by cooling said rafnate fraction about to 80 F.

5. Inthe process of separating a mixture of mineral lubricating oil hydrocarbons into fractions of low viscosity index and high viscosity I index, the steps comprising countercurrently extracting the low viscosity index hydrocarbons q tion, and returning to the initial countercurrent extraction operation a part of .the more naphthenic extract fraction and a part of the more parafnic rafnate fraction.

6. In the process of separating a mixture oi lubricating oil hydrocarbons containing a 'large number of hydrocarbons of different viscosity index distributed continuously throughout the composition range of said mixture, the steps comprising separating said mixture by extraction into four fractions according to viscosity index and employing the most parainic fraction as an agent for absorbing hydrocarbons of intermediate viscosity index in one part of the extraction system and employing the most naphthenic fraction for absorbing naphthenic hydrocarbons in another part of the extraction system.

7. In a continuous process for separating mineral lubricating oils containing parainic and naphthenic constituents into a rainate fraction of highly parailinic constituents and an extract fraction of highly naphthenic constituents, the

lsteps comprising countercurrently extracting the oil in an elongated Vertical extracting zone with a selective solventwhereby there are obtained a raiinate fraction and an extract fraction, removing said extract fraction and raffinate fraction to separate zones, separating said ranate fraction further into a more paranic and a less parailinic fraction,v separating said extract fraction further into a inore naphthenic and a'less naphthenic fraction, returning to the raillnate-end of the extracting zone a part of the more naphthenic fraction, returning to the extract end of the extracting zone apart of the more paralnic fraction and permitting the more paraffinic and more naphthenic fractions to pas's countercurrently through said extracting zone whereby they supplement the countercurrent extraction of the oil by the selective solvent.

8. In a process for separating mineral lubricating oils containing parafnic and naphthenic constituents into a rainate fraction of highly paraiiinic constituents and an extract fraction of highly naphthenic constituents, the steps comprising countercurrently extracting the oil in an elongated extracting zone with a selective organic solvent whereby there are obtained a raiilnate fraction and an extract fraction, removing said extract fraction .and raffinate fraction to separate zones, separating said raiiinate fraction further into a more parafnic and a less parafiinic fraction, separating said extract fraction further into a more naphthenic and a less naphthenic fraction, returning to a point near one end of the extraction zone a part of the more naphthenic fraction, returning to the other end of the extracting zone a part of the more paraffinic fraction and permitting the more parafnic and more naphthenic fractions to pass countercurrently through said extracting zone whereby they supplement the countercurrent extraction of the oil by the selective solvent.

9. Steps according to claim 8 in which said separating steps are accomplished by separately cooling said fractions about 25 to 80 F.

10. In the process of separating mineral lubricating oils containing paranic and naphthenic constituents into a raffinate fraction of highly paraiiinic constituents and an extract fraction of highly naphthenic constituents, the steps comprising countercurrently extracting the oil in an elongated vertical extracting zone with a selective solvent and propane, said selective solvent being introduced into the upper part of the extracting zone and said propane being introduced into the lower part of said extracting zone, wherel by there are obtained a raffinate fraction and an extract fraction, removing said extract fraction and ramate-fraction from the extracting zone, cooling these fractions to temperatures from about 25 to 80 F. below the temperature used in the extracting zone, passing said cooled extract fraction and raiinate fraction to separate zones, permitting 'said railinate fraction to separate further into a more parafiinic and a less parafnic fraction, permitting said extract fraction to separate further into a more naphthenic and a less naphthenic fraction, returning to the upper part of the extraction zone a part of the more naphthenic fraction, returning to the lower part of the extracting zone a part of the more paranic fraction, and permitting the more naphthenid and more paranic fractions to pass countercurrently through said extracting zone whereby they supplement the countercurrent extraction of the oil by the selective solvent and propane.

11. The process as described in claim 10A Wherein a low boiling paraiiinic hydrocarbon is used in the place of propane.

VANDERVEER VOORHEES.

CERTIFICATE OF CORRECTION. 5

Patent No. 2,079,885. May l1 1937.

fI VANDERVEER VOORHEES.

It is hereby certified that error appears in the printed specification of' the above numbered patent requiring correction as follows: Page l, first column, line I5, for "whereby" read wherein; page 4, second column, line 28, claim 8, after "to" insert the words a point nearj and line 51, Claim lO, for "raffiate" read raffinate; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of Ythe case .in the Patent Office.

Signed and sealed this 29th day of June, A. D. 1937.

Henry Van Arsdale (Seal) Acting Commissioner of Patents.

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