US2081494A - Process for the production of lubricating oil - Google Patents

Description

D. R. MERRILL 2,081,494 PROCESS FOR THE PRODUCTIQN OF LUBRICATING OIL.

May 25, 1937.

Filed Oct. 24, 1932 2 Sheets-$heet l ww Aw INVENTOR. Dame 1? Merrill m BY flfi'gzvam r ATTORNEY \FC Patented May 25, 1937 UNITED STATES PATENT OFFICE PROCESS FOR THE PRODUCTION OF LUBRICATING OIL Application October 24, 1932, Serial No. 639,342

7 Claims.

This invention relates to a process for the production of lubricating oil. More specifically it relates to a process for the production of lubricating oil from petroleum by the use of solvents 5 One of the distinctive characteristicsof a lubricating oil is its viscosity. Its usefulness as a lubricant depends, at least in part upon its-viscosity. For many purposes lubricants are desired whose viscosity will vary as little as possible with 10 variations in temperature, 1. e., have low temperature viscosity susceptibilities. Those fractions which exhibit a low temperature viscosity susceptibility are ofttimes referred to as the parafiinic oils whereas the fractions which exhibit a. high 15 temperature viscosity susceptibility are referred to as the non-parafiinic oils.

The heavy oil fractions of many crude oils, from which lubricating oils are produced consist of a mixture of hydrocarbons some of which exhibit g a low temperature viscosity susceptibility. some of which exhibit an intermediate temperature viscosity susceptibility, and some of which exhibit a high temperature viscosity susceptibility. In order to produce superior lubricating oil from 25 hydrocarbon mixtures, as described above, those oils present having a high viscosity temperature susceptibility and'those having an intermediate temperature viscosity susceptibility are separated from the oilspresentwhich exhibit a low tem- 3 perature viscosity susceptibility. Solvent extraction is one of the methods employed to separate the undesirable oil from the desirable oil. Solvents, such as aniline, furfural, nitrobenzene, selenium oxychloride, sulphur dioxide or B B 3 dichlorethyl ether are capable, under the proper conditions of temperature and pressure, of dissolving the fractions present which are non-parafiinic in character.

The foregoing solvents under proper conditions 40 of temperature and pressure are capable of dissolving the oils present in the hydrocarbon mixture which exhibit intermediate, and low temperpature viscosity susceptibilities. These oils dissolved in the solvent may then be separated from 45 each otherby coolingin which case the oils exhibitingthe intermediate temperature viscositysusceptibility are forced .out of solution. X "These solventsform relatively heavy solutions with'the -nonparafiinic oil fractions and can be 501 separated from the insoluble parafiinic oil frac- :tions by settling. The, separated. parafiinic oil fractions orraifinatesand non-parafiinic oil fractions or extractsdissolved in solventare then distilled to separate the solvent from the oil,

further treatment as necessary to remove any remainingimpurities. Thenon-paraflinicoilfractions being relatively valueless are utilized as fuel or as cracking stock in conversion processes.

The separation of hydrocarbon mixtures into 5 parafflnic and non-parafiinic fractions by the use of solvents is not restricted to batch operation but may be carried out in a continuous manner. Where continuous extraction is employed it is customary to fiow the solvent countercurrently to the oil to be extracted. Hence the oil bein purified is progressively being contacted with solvent which is less contaminated with nonparaffinic fractions. The oil entering the extraction system is contacted with solvent containing a relatively high concentration of non-parafiinic fractions whereas the purified oil is finally contacted with pure solvent. .In this manner the maximum degree of refinement is usually obtained because at the final stage of the extraction relatively. pure oil is contacted with fresh solvent which has a high selective solvent power to separate the parafiinic and non-paraflinic fractions because it is not contaminated with non-parafiinic oil. When continuous countercurrent extraction is employed the extraction step may be carried out in one stage wherein the solvent and oil fiow countercurrently or it may be carried out in a plurality of stages wherein the extracts obtained from the later stages of the process are returned to the earlier stages of the process and employed therein as the extracting medium. Thus in the first extraction stage the oil to be extracted is contacted with solvent containing dissolved fractions from a later stage. The insoluble oil portion in the first stage passes to the second stage where it is contacted with solvent containing less of the extracted fractions. The insoluble oil from the second stage passes successively in the same manner as described above; to the remaining extraction stages until it reaches the final stagewherein it is extracted with pure solvent. In processes of this character the same temperature is employed throughout the system and as final products there are obtained avfraction consisting largely of the non-paramnic fractions and a fraction which. is in the main composed of-the paramnic fractions.

I have found that it is highly desirable to extract oil in stages countercurrently with a solvent. Furthermore, I have found that a more economical use of solvent can be obtained where the solvent and dissolved fractions from a later stage of the extraction is partially deprivedof its dissolved fractions before passing it to an earlier stage to be employed therein as the extracting medium.

It is, therefore; an object of my invention to extract oil countercurrently stages with a solvent and to deprive the solvent passing from a later extraction stage of a portion of its dissolved fractions before employing it as a solvent medium in an earlier stage.

It is another object of my invention to extract oil countercurrently in stages with a solvent, to deprive the solvent passing from a later extraction stage of a portion of its dissolved fractions and then to pass this partially purified solvent to an earlier extraction stage operating at'the same or at a different temperature than said later stage.

Fig. 1 is a schematic arrangement of apparatus which may be employed in carrying out my process.

Fig. 2 is a schematic arrangement of another form of apparatus in which my process may be carried out. a

Fig. 3 is a cross section of an orifice mixer which I employ to produce an intimate mixture between two immiscible liquids. The fluids in pipe A pass successively through the diaphrams B, B, and B which are provided with openings 0, C, and C". After leaving the constricted openings C, C, and C", the fluid passes into chambers D, D, and D". The passage of the immiscible liquids through the diaphram into the enlarged chambers D, D, and D" produces suificient turbulence to insure intimate contact of these fluids.

Referring more particularly to Fig. l, the oil to be extracted enters the extraction apparatus through line I from a source not shown and enters pump 2 which forces it through line 3, and valve 4 to cooler 5. The cooled oil emerges from cooler 5 into line 6 where it meets a stream of solvent coming from heat exchanger 95 through line H1. The mixture of oil and solvent passes through orifice mixer I where they are intimately mixed. The mixture in orifice mixer I passes through line 8 into settling tower 9 where the solvent containing dissolved fractions settles to the bottom owing to its relatively high specific gravity, and the insoluble parafiinic oil fractions sent by pump 98 through line H4, valve I I5 and line H6 to distillation means where the solvent is separated from the extract. As a modification, the extract from line H4 may be passed to heat interchanger 93 where it is cooled to a point sufiiciently low to cause a separation of a portion of the most paraflinic oil fractions present, from the non-paraffinic fractions which are dissolved in the solvent. The cooled mass in interchanger 93 passes through line I00 to separator IOI where the insoluble oil fractions rise to the top and are removed through line I02. The solvent and dissolved fractions in separator IOI are removed through line I03, valve I04, line I05 and valve I08 into line H6 from which it passes to distillation means, not shown, to separate the solvent from the extract; or instead of passing to line H6, it may pass to cooler I01 where a further cooling of the solvent and dissolved fractions takes place and a further separation of oil fractions at this reduced temp rature talges place. The mixture in cooler I0I then passes through line I08 to separator I09 where the insoluble fractions rise to the top and are removed through line H0. The solvent containing the dissolved fractions may then be removed through 5 line III and valve H3 into line H6 where it passes to distillation means for separating the solvent and dissolved fractions; or it may pass through valve H2, line 90, valve 9| and line 92 to heat exchanger 93 where its temperature is 10 raised by indirect thermal contact with the relatively warm fluid in line H4. After passing from interchanger 93, the solvent and remaining dissolved fractions pass to heater 95 where their temperature is raised preferably to a point equ 15 to that of the oil being discharged from heater 5. The insoluble oil fraction in the uppermost zone of settling tower9, is removed through line I0 to orifice mixer I I where it is mixed with sol vent coming from heater I2 through line H8. 20 The mixed solvent and oil pass into settling chamber I3 where the light insoluble fraction rises to the uppermost zone and is removed through line I4. The solvent and dissolved fractions in settling chamber I3 gravitate to the lower 25 zone of chamber I3 and are removed through line I3, valve I4, pump I5 and line I8 to heat exchanger I0 where the temperature of the solvent and dissolved fractions is lowered sufficiently to. cause a portion of the fractions dissolved in the 30 solvent to be forced out of solution. The solvent containing the immiscible or undissolved fractions in exchanger I0 then passes through line 11 into separator I8 where the insoluble fractions owing to their lower specific gravity, rise to 35 the top and are withdrawn through line I9. The solvent and remaining dissolved fractions in separator I8 settle out and are withdrawn through line 80, valve 8I and line 82 to cooler 83 where the temperature of this solution is again lowered to cause a further separation of oil at this lowered temperature. The cooled mass in cooler 83 is withdrawn through line 84 into settling cham ber where the insoluble oil rises to the top and is withdrawn through line 86. The solvent 45 and remaining dissolved fractions in settling chamber 85 are withdrawn through line 81, valve 89, line 90, valve 9I, line 92, heat exchanger 93, line 94, heater and line III into line 8 where they are employed as solvent for the oil being 50 discharged from heater 5. If desired, a portion of the solvent and dissolved fractions in line I I I may be mixed with the solvent in line 90, which. has been obtained as previously described from settling chamber 85 through line 81, and valve 55 89, by opening valve H2.

The insoluble oil fraction being removed from the upper zone of chamber I3 through line I4 passes to orifice mixer I5 where it is mixed with solvent from line H9. This mixed mass passes GC through line I6 to settling chamber I! where the insoluble oil fractions rise to the top, because of their lower specific gravity, and are removed through line I8. The heavy solvent with its dissolved fractions in settling chamber II is re- 65 moved through line 50, valve 5|, pump 52 and line 53 to heat exchanger 41 where its temperature is lowered sufficiently to cause a separation of a portion of the dissolved fractions. The

cooled mass in exchanger 41 passesthroughline 71 54 to settling chamber 55 where the insoluble oil fractions rise to the top and are removed through line 56. The solvent and remaining dissolved fractions in settling chamber 55 are removed through line 51, valve 58 and line. 59 to 7 cooler 60 where the solution of solvent and oil is further cooled sufhciently to cause further separation of oil from the solvent. The cooled mass is passed from. cooler 60 through line 6| to separator 62 where the insoluble oil rises to the top and is removed through line 63. The heavier solvent containing dissolved fractions gravitates to the bottom of settling chamber 62 andis removed through line 64, valve 66, line 61, valve 68 and line 69 to heat exchanger 10 where its temperature is raised by indirect heat exchange after which it passes through line H and heater 12 to line H8 where it is mixed with oilfrom line l0 as hereinbefore described. If desired, the solvent and dissolved fractions in line 64 may be mixed with a portion of the solvent and extracted fractions from chamber 85 by opening valve 88.

The oil in line .18 passes to mixer l9 where it is mixed with fresh solvent introduced through line 23, pump 24, line 25, heater 26 and line I20, passes into orifice mixer l9 along with the oil from line 18. Here the oil is thoroughly mixed with the solvent and passed into settling chamber 2|. The light insoluble oil fractions rise and are removed through line 22 to storage, not shown. This material constitutes the most parafinic fractions contained in the raw stock introduced through line I. This fraction may now be given any further treatment, such as with acid, alkali and/or clay for the production of a highly paraffinic lubricating oil. The solvent and.

dissolved fractions in settling chamber 2i gravitate to the bottom and are removed through line 21, valve 28, pump 29 and line 30 to cooler 3| where they are cooled sufficiently to cause separation of a part of the oil from solution. The cooled mass in cooler 3| is withdrawn through line 32 to settling chamber 33 where the insoluble oil rises to the top and is removed through line 34. The solvent containing dissolved fractions gravitates to the bottom of chamber 33 and is removed through line 35, valve 36 and line 31 to cooler 38 where it is again cooled sufliciently to cause a further separation of oil from the solvent and dissolved fractions. The mass in cooler 38 is withdrawn through line 39 to separator 40 where the insoluble oil, being lighter than the solvent, rises to the top and is removed through line 4|. The solvent and dissolved fractions gravitate to the bottom of separator 40 and are removed through line 42, valve 43, line 44, valve 45, line 46, interchanger 41, line 48, heater 49 and line H9 into mixer l5 where they are mixed with oil coming from line l4. If desired, the solvent and dissolved fractions withdrawn from settling'chamber 40 by way of line 42, valve 43 and line 44 may be mixed with solvent containing dissolved fractions removed from the bottom'of settling chamber 62 by opening valve 65.

In Fig. 1 the flow of the solvent is countercurrent' to the oil to be extracted. After each extraction step, the solvent is partially deprived of its dissolved fractions through cooling and settling. The partially purified solvent is then heated and employed as a solvent medium in an earlier extraction stage.

Referring more particularly to Fig. 2, the stock to be treated enters line 20l from a source not shown and passes through pump 202, line 203, valve 204, line 205 to cooler 206 where the temperature of the oil is decreased. From cooler 206 the oil passes to the lower zone of column 208. Here it is countercurrently extracted with solvent introduced into the upper zone of column 208 through line 293 and at a temperature substantially equal to that of the oil introduced into the lower zone of column 208. The solvent introduced at the top of the column 208 belng heavier than the oil passing downward through the rising column of oil introduced into the lower zone of column 208 and extracts therefrom certain of the non-paraffinie fractions. The insoluble oil from which there has been extracted the non-paraifinic fractions is removed from column 208 through line 209. The solvent and dissolved fractions are removed from column 208 through line 294, valve 295, pump 296, and line 291. At this point in the process, valve 298 may be opened and the solvent and extracted fractions or a portion thereof may be sent through line 306 to distillation means in order to separate the solvent from the extract, or the solvent and dissolved fractions may be passed through heat exchanger 290 which cools the solution and causes oil fractions to separate from the solvent solution. The cooled mass in exchanger 290 passes through line 300 to separator 30! where the light insoluble fractions rise to the top and are withdrawn through line 3l5. The heavy solvent and remaining dissolved fractions gravitate to the bottom of separator 30L The fractions or a portion thereof, are removed through line 302, valve 303, line 304 andvalve 305 to distillation means to separate the oil and solvent; or valve 5 305 may be closed, in which case, the solvent and dissolved fractions pass through cooler 301 to further separate oils dissolved therein. The cooled mass in separator 301 is removed through line 308 into separator 309 where the insoluble light oil fractions rise to the top and are removed through line 3I0. The solvent and remaining fractions are then removed from settling chamber 309 through line 3| I, valve 3l3 and line 306 to distillation means, to separate the solvent from the extract.

The oil fraction in line 209 passes to the lower zone of extraction column 2 I0 where it is countercurrently extracted with solvent introduced into the upper zone of column M0 by means of line 268.

The heavy 'solvent introduced into the upper zone of column 2l0 moves downward through the ascending column of relatively light oil and extracts therefrom certain non-parafiinic fractions. The oil from which the non-paraffinic oil has been extracted is removed from column 2I0 through line 2| I. The solvent and extracted fractions in column 2l0 are removed through line 269, valve 210, line 21!, pump 212 and line 213 to heat exchanger 265, which cools them and causes a portion of the oil to be forced out of solution.

The cooled mass in exchanger 265 is removed through line 214 into settling chamber 215 where the insoluble light oil rises to the top and is removed through line 216. The solvent and dissolved fractions are removed through line 211, valve 218 and line 219 intocooler 280 where a further separation of oil takes place. The cooled mass in cooler 280 passes through line 28l into settling chamber 282 where the oil rises to the top and is removed through line 283. The heavy solvent and extracted fractions are removed from the bottom of chamber 282 through line 284, valve 286, line 281, valve 288, line 289'to heat exchanger 290 where they are heated and then passes through line 291 to heater 292 where their temperature is again increased after which they pass by means of line 293 into extraction column 208. If desired, the solvent and dissolved fracrequired to give a railinate of the desired degree of parafiinicity. After the'relative proportions of solvent and feed stock are thus established, the temperature of the first stage will then be chosen so as to obtain the desired relationships of yield and quality between the extract and the intermediate raflinate. Thus if the first stage is operated at as low a temperature as is economically feasible, an extract phase will be obtained of maximum aromatic character and the intermediate rafiinate phase will be obtained in maximum yield. If at this low temperature an excessive quantity of extract of insufliciently aromatic character is produced, due to the use of an excessive amount of solvent in the first stage, the excess extract phase not required for the first stage may be bled ofi either before or after cooling and passed to a still for recovery of solvent and an intermediate grade of oil. If, on the other hand, the first stage is operated at a somewhat higher temperature but still substantially below the temperature employed for the second stage, the yield of. extract will be increased but it will not be so predominantly of aromatic character because of inclusion in the extract of compounds of intermediate paraiiinicity which under the previous conditions were obtained in the intermediate rafiinate. The yield of intermediate raflinate will be correspondingly reduced, but, its quality will be improved due to the more complete elimination of compounds of intermediate grade in the extract. Additional solvent may even be added between the two .stages to improve the quality of the intermediate raffinate, although ordinarily this is not as economical as adding all of the solvent in the last stage. For any particular stock and solvent, the ratio of solvent to stock and the temperatures of the two stages may be chosen in accordance with the principles just discussed to separate the oil into the three fractions of most suitable quality for any particular set of marketing conditions.

As extracting medium, I may employ such solvents as aniline, nitrobenzene, B B dichlorethyl ether, methyl cellosolve, sulphur dioxide or mixtures thereof. Furthermore, the process may be applied to distilled or residual oils or to oils which have been diluted with hydrocarbon diluents varying from heavy diluents such as kerosene to light diluents of the normally gaseous type, such as propane. The primary purpose of mixing the oil with diluents, is to reduce its viscosity so as to facilitate mixing and phase separation. It is therefore, evident that the use of diluents is of value primarily with the more viscous oils and in operation at fairly low temperatures such that the viscosity of the undiluted oil renders mixing and phase separation dimcult. Since it is ordinarily only the raiiinate phase which exhibits excessive viscosity, the diluents'employed should preferably be of the paraflinic type so they will tend to remain in the raifinate phase and from the standpoint of economy the quantity of diluent should be held to the minimum required to give the desired reduction in viscosity. It will ordinarily be found that the addition of one part naphtha to two parts of oil will give an adequate degree of fluidity.

As a specific example a dewaxed Santa Fe Springs lubricating oil stock was countercur- I rently extracted in a two stage extraction process with 200 volume per cent of B B dichlorethyl ether. The temperature in the first extraction stage was 44 F. and the temperature of the second stage was 120 F.

The products recovered from the two stage extraction consisted of an extract, an intermediate rafiinate and a final rafiinate. These products were then distilled to remove the solvent from the oil. As the final raffinate fraction withdrawn from the extraction process at 120 F. contains an appreciable quantity of solvent and extract fractions in solution, it may be found desirable to cool this fraction to a temperature of approximately 40 F., pass the cooled mass to settling means and allow the separated solvent and dissolved fractions to settle from the raffinate oil. The rafiinate oil from the cooler may then be sent to distillation means to separate the remaining solvent present and the solvent and extracted fractions may be returned to the first extraction stage where it may be employed therein as extraction medium for the incoming oil.

The following table shows the characteristics of the raw stock, the extract, the intermediate raflinate and the final rafiinate recovered from the two stage extraction process described above:

.2 a s: 5 5 5 4 a c a u :1 a a, q a N '0 E g as as gs 3 J, m 8 8 g, o, 8.2 s g i. u 2 El .5 0 1! B U D NJ Stock 100 19. 9 104 51 867 Extract 33 10. 2 202 -8 939 Intermediate raflinatom 36 24. 1 76 .835 Final raflinate 26 26. O 94 88 821 As will be noted the viscosity index of the final rafiinate is 88. With another stage of extraction this value can be somewhat increased.

The viscosity index referred to in the table is defined by Dean and Davis in Chemical and Metallurgical Engineering, vol. 36, 1929, page 618. The viscosity index of a lubricating oil is an indication of its composition or type, i. e., whether it is a paraffin or naphthene base oil. Paraflin base oils are arbitrarily assigned a viscosity index of 100, and certain naphthene base oils from the Gulf Coast are assigned a viscosity index of 0 and mixed base oils lie between these extremes.

The gravity-viscosity constant referred to in the table is defined by Hill and Coats in the Journal of Industrial and Engineering Chemistry, vol. 20, page 641 (1928). This constant represents the parafiinicity or naphthenicity of a given oil. A high value indicates a high degree of naphthenicity while low values indicate relatively greater parafiinicity. Lubricating oils from natural crudes range from .903 (for an extreme Gulf Coast type) to .807 for an extreme Pennsylvania type, or-even beyond.

The foregoing example is merely illustrative of one method of carrying out my invention and is not to be construed .as limiting the invention which I claim.

I claim:

1. A process for the separation of paraflinic from the non-paraflinic fractions of a hydrocarbon oil mixture which comprises extracting a raiiinate from an earlier extraction stage with a solvent into a second raflinate and fractions dissolved in said solvent, cooling said solvent containing dissolved fractions to separate an insoluble fraction therefrom, removing said solvent and remaining dissolved fractions from said insoluble fraction, subsequently passing the solvent and remaining dissolved fractions to said earlier extraction stage and extracting a hydrocarbon oil mixture passing to said earlier extraction stage into a plurality of fractions.

2. A process for the separation of paraflinic from the non-parafflnic fractions of a hydrocarbon oil mixture which comprises extracting a ramnate from an earlier extraction stage with a solvent into a second raffinate and fractions dissolved in said solvent, cooling said solvent containing dissolved fractions to separate an insoluble fraction therefrom, removing said solvent and remaining dissolved fractions from said insoluble fraction, subsequently passing said solvent and remaining dissolved fractions to said earlier extraction stage and extracting a hydrocarbon oil mixture passing to said earlier extraction stage into a raflinate and fractions dissolved in the solvent containing the remaining dissolved fractions.

3. A process for the separation of parafflnic from the non-paraflinic fractions of a hydrocarbon oil mixture which comprises extracting a raillnate passing from an earlier extraction stage into a plurality of fractions with a solvent, one of said fractions containing solvent and dissolved fractions, cooling said solvent containing dissolved fractions to separate an insoluble fraction therefrom, separating said solvent and remaining dissolved fractions from said insoluble fraction, subsequently passing said solvent containing the remaining dissolved fractions to said earlier extractionstage, and extracting oil passing to said earlier extraction stage into fractions dissolved in said solvent containing the remaining dissolved fractions and said raflfilnate passing from said earlier stage of extraction.

4. A process for the separation of parafiinic and non-parafiinic fractions from a hydrocarbon oil mixture containing the same which comprises extracting said oil with a solvent in a primary stage into a rafilnate and fractions dissolved in said soivent, passing said raflinate to a secondary extraction stage and extracting said raflinate with a solvent into a second raflinate and fractions dissolved in said solvent, cooling said solvent and dissolved fractions from said secondary extraction stage to separate an insoluble fraction therefrom, separating said solvent from said secondary extraction stage containing the remaining dissolved fractions from said insoluble fraction and passing said solvent from said secondary extraction stage containing remaining dissolved nate and a mixture of extract and intermediate.

raflinate dissolved in said solvent, cooling said latter mixture to separate said intermediate raffinate therefrom, separating said intermediate rafllnate from said solvent containing the remaining dissolved extract and passing said solvent containing said remaining dissolved ex-.

tract to said primary extraction stage to extract said 011 passing into said primary extraction stage.

6. A process for treating oil to produce lubricating oil which comprises extracting a raflinate produced by extraction of oil with a solvent with fresh solvent to produce a rafllnate and a mixture of extract and solvent containing an intermediate raflinate, cooling said nn'xture to separate said intermediate raiiinate from said solvent and extract, removing said intermediate rafinate from said solvent and extract and treating fresh oil with said extract and solvent free from said intermediate raflinate to produce said first mentioned rafilnate.

7. A process for the production of lubricating oil from a hydrocarbon oil mixture which comprises separating a second raffinate and B B dichlorethyl ether containing dissolved fractions in a later extraction stage, cooling said B B dichlorethyl ether containing dissolved fractions to separate an insoluble fraction therefrom, removing said insoluble fraction from the B B dichlorethyl ether and remaining dissolved fractions, passing said B B dichlorethyl ether containing the remaining dissolved fractions to an earlier extraction stage and extracting said hydrocarbon oil mixture passing to said earlier extraction stage into a ramnate and fractions dissolved in said B B dichlorethyl ether.

DAVID R. MERRIIJJ.

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