US2017432A - Refining lubricating oils - Google Patents

Description

Oct. 15,1935. w. BAHLKE REFINING LUBRICATING OILS Filed Nov. 21, 1932 INVENTOR JtbahL/w A-ITORNEY J Before describing assists in the separation of solvent and oil.

of vaporizing propane is, of'

Patented Oct. 15, 1935 UNITED STATES PATENT OFFICE 2,017,432 REFINING LUBRICATING OILS William Herbert Bahlke, Hammond, Ind., assignor to Standard Oil Company, Chicago, R1,, a corporation of Indiana Application November 21, 1932, Serial No. 43,586

' 6 Claims.

wherein the dewaxing diluent aids in the extrac-{ tion and the extraction solvent aids in the de- ,waxing.

The object of this invention is to produce lubricating oils with low pour points and high viscosity indices from mixed base crude distillates or residues. A further object is to provide an improved means for separating naphthenic and/or asphaltic constituents from lubricating oils. A further object is to provide an improved means for separating wax from oils so that the solvent used in the extraction step may act as an antisolvent in the dewaxing, step. A further object is to provide an improved means for removing the extracting solvent from a finished lubricating oil. as the detailed description of ceeds. r

the invention pro- In solvent extraction processes heretofore used it has been difiicult to separate the raffinate phase from the extract phase because the wax separates out at extraction temperatures and entrains large amounts of both phases in a diflicultly workable slurry or buttery mass. Furthermore, the rafiinate phase is usually quite viscous,

especially at low temperatures, making it difiicult to handle. Also it has been dimcult to recover the extracting solvent from the separated oils without loss of solvent, and corrosion caused by decompositionof the solvent. The object of the present invention is to overcome all of these difficulties and-t improve the efiiciency of the recently developed propane dewaxing process.

the invention in detail it maybe well to state a few fundamental princk ples on which the invention is-based. In the first place, it has been found thatlight hydrocarbon diluents, such aspropane, butane, pentane, etc. increase oil and the extraction solvents,

a more intimate contact can be obtained between the solvent and the oil. Then when the diluent, or a portion thereof, is allowed to evaporate from the mixture a low temperature is obtained which v and other undesirable impurities, may be drawn The 'refrigerative effect course, well known but in the present invention the self evaporation serves another function,-

namely, by removing the propane from the mix- Other objects will be apparent the miscibility between the such as beta beta dichlordiethyl ether, hereinafter referred to as 'If desired, however,

ture of propane, oil and solvent, the miscibility temperature of the remaining components is increased to suchan extent that a separation of therafiinate and extract phases may be readily obtained. In the preferred embodiment of my invention a liquefied hydrocarbon gas, for example, propane, and a suitable extraction solvent, for example, Chlorex, are mixed under pressure with the oil to be extracted. In general, the components will be completely miscible. The temperature of the mixture is next reduced by allowingsa portion of the propane to expand, thereby causing a separation of the mixture into two layers which are separately treated for recovery of solvents, as hereinafter described.

Referring to the drawing which forms a part of-- this spefiification liquefied hydrocarbon gas which may suitably be propane, contained in tank I is conducted in regulated quantities by pump 2 and. line 3 to mixer 4 where it is intimately mixed withthe extraction solvent from tank 5 delivered by pump 6 and the oil to be treated .contained in tank l delivered by pump 8. The oil may suitably be a distillate from M-C crude or other mixed-base petroleum oil having a viscosity withinthe lubricating range and ordinarily containing paraffin wax in amounts usually between 1 and 10%,- but sometimes as gnuch as 20%. It may also suitably be treated with concentrated or fuming sulfuric acid before extraction. ,If desired, the oil may be mixed with the propane before'acid treating and the chlorex introduced afterward.

ill with or without reduction of pressure, depending on the method of opera.-'

tion. adapted. In one method of operation the chiller I0 is substantially filled with the mixture whereupon the incoming, supply is shut off and 40 the pressure is reduced by opening valve I] leading-from the vapor line I! in the top of the chiller. As the propane is withdrawn in this manner the mixture of extraction solvent and oil separates into two phases. Where the extraction solvent is heavier than the oil, as in the case 0 Chlorexi, the solvent formsa separate layer j at'the bottom of the chiller. This layer, containing the naphthenic fractions of the oil so off at intervals during the chilling operation, line l3 and pump l4 being provided for this purpose. the entire charge may be chilled down to the minimum temperature em- 70 are recompiessed by The extract fraction now freed from propane .2 ployed in the process before any separation of solvent phase is made.

The solvent or extract phase which is drawn off by pump I4 is conducted by line I5 to strip- 5 per l6 where the propane which it contains is removed by raising the temperature of the extract by means of heating coil H. The propane vapors from the heated mixture are led by line l6 and valve Hi to condenser 20 where they. are

rellquefied under pressure and the liquid is returned to storage tank When the pressure of the vapors is insuflicient, for proper liquefaction,

the vapors may be conducted by valve 2| and line 22 to compressor 23 which delivers them to the condenser under sufilcient pressure for liquefaction.

' After the removal of propane from the extract it is conducted by line 24 and pump 25 to still 26 for reclaiming the extraction solvent. Heat is 20 supplied to the still and the solvent is vaporized from the oil, the vapors being led, by line 21 to condenser 28 where they are condensed and the recovered solvent is collected in receiver 29 from which it flows by line 30 to pump 3| and is returned by line 32 to the solvent storage tank 5. .The oil freed from solvent is removed from the still by line 26a to cooler 26b and line 260 to extract storage 26d.

In order to facilitate the recovery of extraction solventfrom the naphthenic oil and reduce decomposition which would result from the use of high temperatures, a stripping gas is introduced into the still 26 by line 33. This gas may suitably be propane vapor withdrawn from the propane storage reservoir I by line 34, as illustrated. The propane which is carried over with the solvent vapors collects in receiver 29 and is withdrawn by line 35 and returned to the propane system by a line not shown.

After the extract layer is withdrawn from chiller ID the oil or rafilnate layer, which may suitably be at a low temperature, for example, zero to F., is transferred by pump 4 and valved line 36 to filter press 31,- valved line l5 being closed. To obtain lower viscosity and lower temperatures for the filtering operation, I may add additional propane to chiller l0 via line 3, mixer 4 and valve 9. The filter press 31 removes any crystallized wax from the ramnate fraction, the 50 wax being transferred by line where it is heated by steam coil 40 to melt it and remove propane therefrom. "The propane vapors are led by line 4| back to the propane vapor line 22 and compressor. 23, and the wax fraction is discharged from the stripper byline 42. Liquid propane from storage tank I may be led by valved line 43 to the filter for the purpose of washing the filter press cake and recovering the maximum quantity 01' oil therefrom.

The filtrate, containing a large quantity of propane and some extraction solvent, is led by line 44-andipump 45 to stripper 46 where it is heated by cell 41, expelled from the mixture. The propane vapors 6 are led-by lines 48 and 4| to the condenser 20 or the compressor 23 as desired, depending-on the pressure. When the pressure of the vapors is sufiicient for condensation they are led ,by valved line 49 directly to the ,-condenser, otherwise they compressor 23,

is withdrawn from stripper 46 by line 50, pump 5| and line 5la to settler 52 equipped with coil 53 which may be employed for cooling ifneces- 75 sary. Here the raflinate fraction will ordinarily it to storage tank 5.

38 to stripper 39 the propane being thereby "and the charge tovthese'units separate into two layers due to the removal of the liquefied hydrocarbon gas. When heavy solvents are used, such as Chlorex and nitrobenzene, the lower layer will consist principally of solvent containing some oil in solution. This 5 oil is more naphthenic in character than the oil remaining in the upper layer and it is therefore ordinarily desirable to make a separation between these two fractions. Accordingly, the lower layer may be withdrawn to tank 54 and 10 the upper layer may be charged directly to still 55 for recovery of solvent. This may be done by controlling valves and 60a, permitting the lower layer to pass through line 59 to tank 54 and thereafter diverting the upper layer to pump 6| and still 55. The solvent fraction in tank 54 may be returned directly to the process for reextraction, line 56, pump 51 and line 58 being used for this purpose. When desired, however, this fraction may likewise be charged to still for recovery of solvent as hereafter described.

The upper layer in separator 52 which is comprised largelyof raflinate containing some solvent in solution is conducted by line 53. and valve 60 to pump 6| and still 55. This still, like still 26, may also be equipped with a supply of stripping gas introduced by valve 62 from line 34. Theextraction solvent is vaporized and stripped from the oil and carried by vapor line 63 to condenser coil 64 where it is condensed and conducted to receiver 65. The propane gas collecting in this receiver may be returned by valved line 66 to line 4| and thence to compressor 23, as previously described. The recovered solvent is withdrawn from the receiver by valved 35 line 6! leading to pump 3| and line 32, leading The rafllnate oil remaining in still 55 is withdrawn by line 68 to cooler 69, thence by line 10 and valve 1| to rafllnate storage reservoir 12. 40 When it is desired to recover the solvent from. the intermediate extract contained in tank 54 this material may be led by line 13 and valve 14 to still 55 where the extract is vaporized in a manner similar to that Just described. The intermediate oil freed from extract may be withdrawn through cooler '69, line 10 and valved line 15 to storage tank 16. This intermediate oil fraction may be discharged from the system or may be reprocessed by returning it through line 11, pump 51 and line 58 to the solvent extraction system. When it is not desired to make a separation of the intermediate oil fraction just described, the raflinate contained in stripper 46 may be led directly by line 50, pump 5| and line 18 to still 55 for recovery of solvent, as previously described.

The process just described is semi-continuous in nature and it should be understood that various units of the equipment may be employed in multiple when necessary to obtain a balanced working of the plant. Thus, for HI and filter press fl may suitably be in duplicate may be controlled by suitable manifolds not described but well understood in the art. In certain cases where the oil treated forms a mixture with the solvent which rapidly separates into two layers, I may operate the chiller It in av continuous fashion by reducing the pressure 01' the charge flowing f through valve 9. In this way I maintain a low ressure and corr'espondinglylow temperature thin the chiller ||lv which results in a continuous separation of the charge into two layers. The bottom layer may be continuously with- 7 .drawn by line l3 and pump II to line 15 and stripper l6, as previously described. The upper layer may likewise be continuously withdrawn by line 19 and pump 80 leading to filter press 31.

One of the principal advantages of this method of operation is that a continuous supply of hydrocarbon gas is available for compression and for other operations, such as stripping the solvent in stills 26 and 55 in which case the gas for this purpose may be led directly ffoiiline 22 to line 34 by a connection not shown. Another advantage of continuous operation is the possibility of employing smaller quantities of extraction solvent in the system and thus reducing the inventory on this expensive material.

One of the important advantages of my combination solvent extraction process is that the dewaxing and extraction operations may be carried out simultaneously without thenecessity of making a careful separation of extraction solvent and dewaxing diluent, in this case a liquefied hydrocarbon gas.

Another and still more important advantage is that the separation of wax from the oil and the diluent is greatly facilitated by the presence of the extraction solvent which, as previously indicated, acts as a wax antisolvent. The railinate layer which is charged to the filter is saturated with the extraction solvent which possesses a verylow solubility for wax. By subjecting this material to filtration at the separation temperature or critical solution temperature the maxi mum amount of wax is removed from the oil, thus producing an oil which is substantially entirely wax-free. In my preferred embodiment I filter the wax from the raffinate layer at the temperature of separation. At higher temperatures a part of the wax passes into solution in the oil and cannot be removed in the filter press. At lower temperatures a still further separation of solvent occurs and produces a second liquid phase which interferes with the filtration process.

Another advantage of my combination process of extraction and dewaxing lies in the dilutinga,

effect of the liquefied hydrocarbon gas on the oil. Many of the oils which it is desired to treat have, very high viscosities and are diflicult to separate from extraction solvents. The presence of the liquefied hydrocarbon gas in the oil reduces its viscosity to a very low value and permits solvent extraction at temperatures far below those heretofore available. As a result I am enabled to use oils and employ solvents which heretofore could not be handled,'or which could only be separated by expensivecentrifugal apparatus. The ready separation obtained by the use ofdiluents in my solvent extraction process enables 'it to be carried out without the use of centrifugal machines althoughsuch machines may be used in place of or in conjunction with gravity separa-' tion when desired.

In this specification I have referred specifically to propane as my preferred light hydrocarbon diluent. It should be understood, however, that I may .use other light hydrocarbons, such as ethane, butane, pentane, hexane, iso-butane, isopentane, butylene, propylene, ethylene, etc. Also the diluent may contain or consist of substituted light hydrocarbons, particularly low boiling ethers and halogenated compounds, such as methyl chloride, dichlor-difluor methane, etc. Although I prefer to use those hydrocarbons which are normally gaseous in order to obtain conveniently the refrigeration necessary, it will be understood that certain advantages of the process may be obtained by using even heavy diluents, such as light naphtha. -With heavier diluents whose volatility is insumcient to provide self-refrigeration by evaporation, I may add 5 a portion of a lighter solvent, e. g. propane, or I may supply indirect cooling to eflect separation when necessary.

The extraction solvents which I may use all belong to the class of organic liquids which are 10 incompletely miscible with petroleum lubricating oils at ordinary temperature, e. g. 70 F. These solvents, when mixed with a lubricating oil and allowed to separate, extract from it certain constituents undesired in the finished oil 15 and which impart to the oil a high viscosity temperature coefficient or low viscosity index as defined by Dean and Davis in Chemical 8: Metallurgical Engineering, 1929 volume 36, page 618-619. v The extraction solvents vary a great deal among themselves in their emciency and those. which I prefer to use belong chiefly to the classof ketones, phenols, ethers, esters, nitro and chloro compounds and amines. Examples of those I may employ in addition to Chlorex 25 and nitrobenzene, hereinbefore mentioned,are phenol, furfural, aniline, pyridine, ethyl chlor acetate, cresol, xylidine, alpha naphthol, acetone, ethylene diamine, glycol, diacetate, cellosolvc acetate, benzonitrile or mixtures of these.

Although the advantages of my process are most apparent. when treating a wax-containing oil, it can also be applied to a wax-free oil or one which has been previously dewaxed. The 5 ting ready separation of the extract, particularly as the diluent remains chiefly in the oil or rafii-. nate layer. Also the diluent facilitates mixing as previously described and in the case of the liquefied hydrocarbon gases, the diluent aids incooling the mixture below the miscibility temperature.

As an example of the results which may be obtained by my process, a mid-continent lubricating distillate having a viscosity of l22 seconds at 210 F. and'2682 seconds at 100 F'. was mixed under pressure with two volumes of Chlorex and three volumes of liquid propane. The mix.- ture was cooled to 15 F. and was allowed to separatev into two layers, The lower layer contains the non-paraflinoid' components and the upper layer contains the paraffinoid components. The lower layer was removedand the upper layer was freed from solvent and propane as it was not necessary to dewax for the reason that the initial lubricating distillate had already been subjected to a dewaxing operation. The resulting oil was obtained in a yield of 84% and had a viscosity of 95 seconds at 210 F. and 1350 seeonds at 100 F. equivalent'to a viscosity index of '79. The viscosity index of the originalv oil was 555, showing the improvement obtained in the process. The extract fraction after removal of solvent and diluent was a dark colored, heavy tar valuable as a fuel oil, impregnating or paving oil. It is characterized by a high fluidity when heated, a high specific gravity and freedom from paraffin wax.

- In another exampleof the advantages obtained by the use of liquefied hydrocarbon gases in-solvent extraction of lubricating-oils, the same'midcontinent lubricating distillate described above.

' skilled in the art and they v the separation was made at minus 18 spect to valves, pipe fittings,

two volumes of propane to one volume of oil. The mixture was separated at a temperature 01 minus 18 F. giving a yield of 79% oi railinate, having a viscosity of 97 at 210 F. and 1310 at 100 F. The viscosity index was 86.8 and the A. P. I. gravity was 25.3. Aiter percolation through clay the viscosity index rose to 90.7.

In comparison with this result another sample of oil was extracted with three volumes of "Chlorex, without propane. The separation was made at a temperature of 100 F. and the resulting oil had a viscosity index of 87.7, almost identical with that obtained when propane was used and F. In this case, however, the yield was only 58.2%, a loss of over 20% compared with the yield obtained when propane was used. In another example, the same mixture without propane was separated at 10 F. in which case a yield of 80.4% was obtained, practically the same as that obtained previously with However the viscosity index was only propane.

86.8 previously obtained 82.3 in comparison with when propane was used. 1

The finished oil may be given a treatment with acid and finally with clay to improve its color stability and its anti-sludgin'g qualities. Any acid treatment, however, will be slight, preferably less than A; pound of concentrated acid per gal- Ion. If desired, the acid treatment may be applied before the solvent extraction process as previously mentioned.

In the above description I have not gone into detail or described the most desirable arrangement of heat exchangers, etc. and I have not attemptedto provide a working drawing with restorage means, etc. well known to those form no part of the All of these features will be present invention. I have scription of a preferred embodiment 01' this invention which will enable those skilled -in the art to practice it. I do not limit myself to these particular details and it should be understood that many modifications are possible, for instance, I may separate the rafiinate and wax from the Chlorate extract by means of settlers or centrii'uges. Likewise I may partially dewax at an ingiven a complete de-' termediate point in'the process and then complete the extraction anddewaxing thereafter. In either case, the diluent servesto reduce the viscosity in both stages, acts as a refrigerant and serves the important function of stripping the solvent from the oil in the final distillation step. I may also conduct the process in stages, first extracting the propane-oil mixture with Chlorex" toremove undesired low viscosity index-constituents, then further cooling the raflinate fraction to separate a wax-free oil extract of intermediate grade after-which the remaining raflinate fraction may be dewaxed in the manner previously described.

I claim:

1. A process of oil containing parafhnoid and non-parafllnoid components which comprises mixing liquid proproducing lubricating oil from nents in'said dichlorethyl more naphthenic than the raflinate phase pane and dichlorethyl ether with said oil and separating the solution 01' non-paramnoid compoether from the solution of paraflinoid components in said liquid propane. 5

2. A process of producing lubricating oil from oil containing paraflinoid and non-paramnoid components which comprises mixing liquid propane and dichlorethyl ether with said oil, separating the solution of non-parafllnoid components in said dichlorethyl ether from the solution of paraflinoid components in said liquid propane and separating the dichlorethyl ether and propane from their respective solutions.

3. A process of producing lubricating oil from 15 oil containing paramnoid and non-paraillnoid components which comprisesmixing liquid propane and dichlorethyl ether with said 011, reducing the viscosity of said mixture by heating the same and separating the solution or non-paraifinoid components in said dichlorethyl ether from the .solution of paraflinoid components in said liquid propane.

4. In a process of separating mineral oil containing parafllnic and naphthenic constituents 25 into fractions, respectively, more parafllnic and original oil, the stepcomprising mixing the oil with beta beta dichlorethylether and a liquid diluent selected from the group consisting of propane, butane, pentane, and hexane, cooling the admixture to eil'ect a two-layer liquid system, separating the upper layer which contains the paraflinic constituents from the lower layer which contains the naphsystem, and separating the upper layer from the lower layer.

6. The method of refining mineral lubricating oils containing naphthenic compounds, -parafllnic compounds and wax, which comprises diluting said oil with liquid oil with beta beta dichlorethylether, cooling the diluted mixture by vaporization of a-portion of the propane whereby an extract phase containing the naphthenic compounds separates from a compounds, separating said rafiiriate phase from said extract phase, precipitating wax from the raflinate phase in the presence or the liquid propane and beta beta dichlorethylether, mechanically separating .the precipitated wax from the oil solution, and recovering the propane and beta beta dichlorethylether from said raflinate phase.

I WILLIAM HERBERT BAHLKE.

propane, admixing the diluted which contains the parafllnic

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