US2208534A - Process for separating hydrocarbon mixtures - Google Patents

Description

l E. BsxNG July 16, 1940.

PROCESS FOR SEPARATING HYDR-OCARBON MIXTURES Filed Aug. 10, 1938 5y www Azomeys in use to accomplish separation of the oils.

Patented July 1.6, 1940 UNITED STATES PATENT OFFICE Ernst Bsing, Berlin, Germany, assignor to Edeleanu Gesellschaft, m. b. H., a corporation of Germany Application August 10, 1938, Serial No. 224,201 In Germany August 28, 1937 1o claims. (C1. 19e- 13) This invention relates to the production of high quali-ty lubricating oils-from raw stocks such as distillates or residual oils or low grade lubricating oil fractions whereby in addition to the lubricating oil, hydrocarbonmixtures of high specic gravity, having more or less asphaltic characteristics, are obtained simultaneously; f

VThe increasing demand for high quality lubricating oils of high viscosity index, low specific gravity and low carbon residue test has resulted in the development of various processes for separating the high quality products contained in crude natural or synthetic lubricating oil stocks from the low grade constituents. The 'low grade compounds associatedv with raw lubricating stocks possess undesirable physical "characteristics which make them unsuitable for lubricating purposes since they show a very poor temperature- Aviscosity relationship, sludging tendencies and great instability. It is knowntherefore that the presence of such oil fractions materially deprelci-ates the value of the lubricant and ever since it was observed that such low grade constituents 'show a greater solubility in certain solvents or solvent mixtures than the high grade components, the oil industry developed and ap-plied the various solvent refining processes that are now Generally speaking,- all such processes consist of mixing the oil to be treated with the specic solvent, allowing the mixture to rest afteragitationywhereupon two phases appear, namely a I rainate phase containing substantially all of -the high grade oil constituents associated with 'from by conventional means.

I have found now that a much more effective separation of oil constitutents of naturall or synthetic lubricating oil stocks can be obtained, if a `mixture of a selective solvent with said stock is chilled inl the presence of parafin to a temperature at which the high quality lubricating oil constituents are segregated together with the `paraffin fractions in such a form that the mass of oil and wax which results shows excellent iiltration. characteristics, and in which the lower `grade oil constituents remain in a liquid condition, i. e., dissolved within the selectivesolvent and removable therewith from'the mixture.,

ture of ltration showed no selective action upon the oil constituents, i. e., the mass of lterable precipitate of oil and paraffin was thrown out from a homogeneous solution( Prior investigators have further observed that Adcnyaxing processes which are carried out with a mixture of two solvents, one of which shows a selective, the other a non-selective action upon the oil constituents, produce a wax cake that retains somewhat higher quality oil constituents.

But these observers stress the fact that the two solvent constituents should be so blended with each other that, at the temperature of filtration, a diluent resul-ts4 which shows no selectivity towards the oil phase of the mixture. Contrarily to this known art my invention comprises filtering the cold mixture in the presence of only such a sol-vent or solvent mixture as will cause a separation of the oil into two mutually immiscible liquid phases one of which also contains wax, and I have observed that under such conditions the separation of high quality oil constituents, retained with the paraflin, is much more effective. The solvents should, however, be so selected and modiiied that the phase separation will occur only during the lower temperature ranges. I have found pyridine, especially technical pyridine which comprises a mixture of pyridine homologues, to be most useful for the purposes of this invention. I have further observed that pyridine is advantageous because it can be readily modied in its selectivity towards the oil treated by the addition4 of small amounts of water.

I may accomplish separation of that liquid phase which contains the wax simply by cold settling, but I prefer toaccelerate this process by filtration. If filtration is resorted to, the

Aiilter cake which results may conveniently be designated as low temperature oil-cake to distinguish it from a wax cake that is obtained during normal dewaxing operations wherein the `parailn wax is separated from a homogeneous solution of oil and solvent. 'Ihe filtrate produced during the first separation stepleaves,

uponevaporation of the solvent, a hydrocarbon Imixture of high specic gravity and low viscosity index'.

The low temperature oil cake may now be dissolved in a suitable dewaxing solvent, i. e., a`

diluent that aids the precipitation of solid wax from a homogeneous solution, and is subjected out at la lower temperature than the second filtration, thelow temperature oil-cake is partly dissolved while being contacted with the warmer dewaxing solvent. The temperature during the second filtration is fixed by the pour point of the refined lubricating oil desired. The solvent is removed from the second filtrate either` by means of distillation or if desired by extraction; andthe oil so produced represents thev desired high quality raffinate possessing a h igh viscosity index, a low carbon residue and a very good color at a substantial yield.

I have further observed that the quality of the hydrocarbon fractions which are precipitated with the paraiiin at low temperatures is a function of the amount of solvent used on the one hand and ofthe selectivity of the solvent relative to vthe oil constituents on the other hand. For example a solvent which shows a greater solvent power towards the oil constituents rejects only relatively small amounts of high quality hydrocarbons together with thel wax but retains a substantial quantity of medium quality products dissolved in it, whereas asolvent of greater selectivity causes separation of large quantities of paraffinic hydrocarbon oils and produces a filtrate which yields, upon levaporation of the solvent, hydrocarbon mixtures of high specific gravity and low viscosity index which resemble bodies of an asphaltic nature'. Thus it is possible to produce useful asphaltic bodies from asphalt v bearing residual oils or from extracts that are obtained by a conventional selective solvent rening process. It is therefore an object of my invention to process hydrocarbon mixtures with pyridine type solvents of such selectivity and in such quantities that the desired end products are obtained. In any event it is of importance that the solvents used to produce the separable mixture of oil and wax must be so adjusted in selectivity and 'amount that the separation into two phases occurs, preferably at the lower tem;

peratures. f

If it is intended to produce at the same time high quality lubricating oils on the one hand and hydrocarbon mixtures of high specic gravity and asphaltic nature on the other hand, it is advantageous to carry out this treating method in steps. For example the oil is first treated with a solvent which exhibits a high degree of selectivity as is the case when using more or less aqueous pyridine. This will result in the separation of substantial amounts of oil associated with the wax in such a form that it can be readily separated by filtration. The filtrate contains under such conditions of operation, hy-

drocarbon constituents of an asphaltic nature of high molecular weight. The low temperature oil-cake, which contains together with some medium quality products all of the high quality components, is now re-dispersed in solvent of a different selectivity having more solvent power fthan the one used in the rst separation step,

The process may be repeated once more if desired, whereupon a further improvement of the retained oil is obtained. In any event the nal step of recovering the high quality oils from the therewith associated wax consists of redispersing the `low temperature oil cake in a suitable dewaxing solvent; i. e., a diluent which -is nonselective towards the oil constituents,- filteringv and washing the cake. By subjecting the oil tosuch consecutive treating steps with solvents of increasing solvent power or decreasing selectivity, a fractionation of the charging stock into products of progressively improved quality is accomplished, and this fractionating is also an object of my invention.

This method may be modified in such manner that during the nrst separation step a solvent is applied which shows` greater solvent power towards the oil constituents, whereby only the highest quality components are retained with the wax to be separated by filtration and recovered from the wax by means of normal dewaxing processes. The ltrate under such conditions contains the medium quality products, together with the lowest grade compounds. This mixture may be further fractionated wtih the aid of wax addition and modification of the selectivity of the solvent contained in the filtrate as has been described in detail. I may `also combine the steps of fractionating the oil as set forth herein with conventional solvent extraction processes. In such a case the filtrate and the oil obtained from the wax are independently subjected to solvent extraction l As regards solvent circulation throughout the entire process itis advantageous to apply solvents that are capable of changing their selectivity by relatively simple means so that they may be used as selective solvents during the first separation step and/or for the de-oiling step of the low temperature oil-cake produced in the rst operation. For the nal filtering procedure the solvent must be of la non-selective type so as to permit complete removal of the oil from the wax. I prefer therefore to operate my process, using pyridine as a solvent, according to the following method:

A waxy lubricating oil stock is diluted with technical pyridine having a water content of from about 11/% to 3% byvolume and the mixture is cooled to approximately 10 F. At this temperature the aqueous pyridine is selective toward the medium and low quality oil constituents and the mixture of solid constituents and high quality oil is separated from the liquid oil-solvent mixture by filtration. The low temperature oilcake thus produced is dispersed in an anhydrous mixture of pyridine and pyridine homologues, hereinafter referred to as pyridine, which solvent acts as a normal dewaxing agent, i. e., shows no selectivity towards the oil constituents. 'Ihe volume ofl anhydrous pyridine used should be approximately equal to that used in the first step of .the process.

The mixture is next subjected to a second filttration for the purpose of separating oil and wax. T'he ltrate from this operation is modified with water causing thereby a separation into two only small amounts of oil are dissolved and this )15 lowerV phase is-re-cycled andi admixed with a new amount of charging stock to be treated. This method of operation brings about a considerable saving in solvent requirements,

To illustrate my method lof operation more specifically I refer to the attached diagrammatic iiow sheet wherein pyridine is used as a solvent.

The waxy material to be processed is caused -to ow from tank I through preheater 2 into mixer 3 where it is contacted with solvent from tank 4 and/or with re-cycle solvent from pipe line 27. The sotu'ce of origin of the re-cycle solvent will be described later. To start the process using anhydrous solvent from tank 4 a water modilication of the solvent is necessary to obtain the desired selectivity. When the process is in operation the re-cycle solvent carries the right amount of water. After charging stock and solvent are suiiiciently mixed with each other they pass through interchaangers 5 and 6 wherein the temperature of the mixture is lowered to labout -10 F. Leaving the interchangers the cold mass flows to filter 'I for the purpose of separating the ralinate oil-wax mixture from the liquid solvcnt-oilmixture. p

The filtrate from lter 'I is modified with an additional quantity of water, which enters the system through pipe line 8, for the purpose of increasing the selectivity of the solvent contained in the filtrate, resulting in the formation of two liquid phases in separator 9. The upper phase is composed of hydrocarbon constituents of low or medium quality and contains a relatively small amount of solvent, whereas the lower phase represents primarily solvent in which the extract constituents are dissolved. The upper vphase is removed through pipe line I0, the lower phase through pipe I4. The cold extract solution serves the purpose of pre-cooling the `charging mixture in heat exchanger 5.

The two liquid phases in separator 9 are transferred into their respective stills 'Il and I5 wherein the oils are freed of solvent. In each still there is produced as overhead distillate a `small quantity of aqueous pyridine which mixture is again used instead of pure water to serve as modifying agent of the solvent at the points `indicated hereinafter. As a side cut the fractionating columns produce in largey quantities `anhydrous pyridine which is collected and returned to pyridine storage tank fl through line I3. As distillation residues there are obtained a pseudo raflinate in still II and an extract of asphaltic characteristics in still I5, which products flow to their respective storage tanks I2 and I6.

f They low temperature oil-cake obtained from filter I is conveyed to a dispersing apparatus or mixer 22 where it isr contacted with anhydrous pyridine. This solvent is withdrawn from storage tank v4 over branchr I'I through line I8 to solvent cooler I9 and flows from there on through line 20 to mixer 22.

The mixture leaving mixer 22 is conducted to a second lter 23 wherein filtration is accomplished at about -10 F. As soon as the lter cake appears to dry up, cold wash liquid is applied to the cake to displace the remaining oil in the wax cake. The wash liquid is obtained from solvent cooler I9 through line 2|. The proportion of cold solvent added at mixer 22 to the amount of wash solvent depends of course upon the type of material` processed; the total volume of solvent used in lter 23 should, however, be equal to the volume of solvent that is .required as a selective diluent in mixer 3. The total ltrate leaving filter 23 is again modied with water which enters through line 24. The amount of water added is equal to the amount required during thev rst part of the operation over lter 7. The modied ltrate is passed through cooler 25 wherein the temperature is lowered a few degrees and passes from there on to separator 26. In separator 26 the liquid straties into two layers, namely, an upper layer or raffinate layer which contains substantially all of the oil in the ltrate, and a lower layer which consists primarily of aqueous solvent and contains but small amounts of oil. The ralnate layer contains only high quality oil fractions admixed with small amounts of solvent and this mixture is conducted to still 29 through line 28 and the topped refined oil ows from there to raiiinate storage tank 30. The pyridine fractions are collected as previously described.

The lower phase which accumulates in separator 26 consists almost entirely of cold solvent and this material is conducted through line 27 to heat exchanger or chiller 6 wherein the fresh charge of solvent-oil mixture is cooled to about *10 F. before passing to lter 1. .The solvent leaving chiller 6 is now passed to mixer 3 to be re-cycled with a new charge of stock.

The lter cake obtained from filter 23 is practically free of oil and this wax cake is conveyed to still'32 through line 3| to be topped free of solvent. The finished wax iiows into wax storage tank 33 and the pyridine fractions are collected as previously described.

To further illustrate my invention, I cite the following examples:

Ezrample I A lubricating oil distillate showing a parain content of 20% according to the Holde method and an A. P. I. gravity of 27.2 was dissolved in 300. vol. technical pyridine. The technical pyridine showed when subjected to an Engler distillation an end boiling point of 293 F. and it had a water content of 2% by volume. The mixture was cooled to 25 F., filtered and washed. The ltrate obtained is comparable in composition to an extract solution that results when subjecting the oil to selective extraction; it yields upon evaporation of the solvent, hydrocarbon mixtures of an asphaltic nature.

The low temperature oil-cake was thereupon dispersed in a new quantum of solvent which consisted in this case of equal volumes of pyridine and benzol, the mixture was agitated, cooled to 0 F., ltered and washed. This second filtering operation is similar in its procedure to a de-oiling or dewaxing process. The collected filtrate yielded a high quality raiinate oil upon topping oil" the solvent. The analytical data of the products obtained are shown in the following table. `'I'he table also shows Vfor comparative purposes in brackets the viscosity index of the conventionally dewaxed oil.

las

Example II The same lubricating oil distillate used in EX- arnple I was disolved in a technical pyridine fraction of 293 F. end point that had been dehydrated to such an extent that the water content was 0.1% by volume. The mixture was cooled to -30 F. and filtered at this temperature. The filtrate obtained from this operation was now modified with 2% by volume of water to effect phase separation. The upper layer which contained a small amount of solvent was removed and added to the low-temperature oilcake resulting from the ltering operation and the whole mass was now dispersed in a new quantum of solvent consisting in this case of equal volumes of pyridine and benzol, the mixture was cooled to -13 F. and the wax was separated by ltration. The products were recovered after distillng olf the solvent and the tabulated results given below show the yields and physical characteristics of the products. For comparison the viscosity index of the conventionally dewaxed oil is again given in brackets.

1 Waxy material.

This example shows the improvement in the quality and yield of raffinate by extracting a wax containing mixture in the presence of the wax as in Example I rather than after removal of the wax as in this example.

The following example shows the advantages to be derived from re-extracting, in the presence of an added amount of wax, a heavy extract previously obtained by conventional solvent extraction.

Example III To a substantially wax-free extract hydrocarbon mixture having a specific gravity at 60 F. of 1.026, which material had been obtained from a selective extraction operation on a Persian lubricating oil stock, were added 25 wt. of wax and the entire mass was dissolved in 300 vols. of technical pyridine containing 10% by vol. of water. The solution was cooled to -5 F. and filtered whereby the major portion of the original extract was retained with the wax. The highest molecular weight and. most unsaturated extract constituents remained in solution in the solvent and were recovered therefrom, yielding 23.2% by wt. of asphalt having a specific gravity of 1.097 at 60 F. From the low temperature oil-cake were obtained after de-oiling '76.8% by wt. of heavy oil showing a specific gravity of 0.998 at 60 F.

Example IV A petrolatum slack wax produced from a Pechelbronn lubricating oil stock by means of Sharples centrifuges having a wax content of 29.2%, an A. P. I. gravity of 23.0 and a melting point of 117 F. was treated in a semi-continuous series of tests as follows: The petrolatum was mixed at 115 F. with 300 vol.% of technical pyridine (end boiling Vpoint of solvent 293 F.) containing 2.5 vol.% of water. This solvent exhibited a sufficient selectivity between the saturated and naphthenic constituents of the oil components of the petrolatum to cause formation of two phases upon cooling the mixture. The solvent of the above specified characteristics was obtained from a stage of the process that will be described later. At the mixing temperature of 115 F. all constituents of the mixture of petrolatum and solvent were in a homogeneous solution but upon cooling the fluid to F. the saturated oil constituents were precipitated together with the wax in a readily filterable form. The ltration was accomplished in a specially cooled plate type filter and the cake was washed with 100 vol.% of solvent of the saine source of origin as was used to dilute the petrolatum. 'Ihe filter throughput obtained during this operation reached the exceptionally high value of 366 lbs/sq. ft./hr. based upon the petrolatum charged.

The resulting low .temperature oil-cake was now dispersed in 1'75 vol.% (based upon the original charge) of anhydrous technical pyridine which had been pre-chilled to -5 F. and after thorough mixing the mass was again subjected to filtration at .5 F. The cake was washed with 225 vol.% (based upon the original charge) of anhydrous pyridine and a practically oil-free wax cake was obtained. During this filtration step the ltei` throughput reached a value of 45 lbs./ sq. ft./hr. based upon the charging stock or 34 lbs/sq. ft./hr. basedupon the charge going to the second filter. p

To the nitrate from the second ltration step were added 2.5 vol.%.of water, i. e. the same amount of water that was required in the solvent to carry out successfully the lrstltering operation, causing vthe nitrate to separate into two phases. The second phase separation could be accelerated considerably by slightly lowering the temperature of the ltrate to about 12 F., whereby thev residual traces of wax still contained in the filtrate were precipitated in a fine flakyform. The flaky wax rises rapidly to the surface upon settling and while ascending gathers up the small rafnate globules and facilitates complete separation. The upper phase composed of high quality hydrocarbon constituents contained small amounts of solvent and yielded upon removal oi solvent a raffinate oil which shall be designated as R.1 to identify it in the appended tables.

The lower phase was primarily composed of solvent and contained substantially all of the water added and only approximately 3% of oil'. This material could therefore be continuously recycled instead of new solvent and constitutes the material previously referred to that was used as a diluent and precipitant during the initial separation.

The wax obtained from the second filtration was fractionated into a high melting fraction and into a low melting fraction. This was accomplished by again dispersing the cake from filter 23 in anhydrous pyridine ata higher teml low grade material was produced is not described herein since it represents a repetition of treating procedures already explained in Adetail. 'I'he slops Iare included in the wax as shown in the appended table.

The filtrate from the first filtering operation represents an extract solution from which a second grade oil or pseudo raiiinate was precipitated by means of additional water modification. For the purpose of identiiication this material is designated in the tabulations as R2. From this operation the iinal extract was obtained as the lower phase during pseudo railinate precipitation. The products produced `by this treating. method and their respective characteristics are tabulated below.

1 A. P. I. gravity and Viscosity index reicr to the conventionally dewaxed oil.

2 Melting point.

3 Specific gravity, Lilli.

Example V A Persian mixed base lubricating oil distillate having a Saybolt universal viscosity of 111 sec. at 210 F. was processed in a manner similar to that described in Example III with the only exception that 2 vol.% of water was used instead of 2.5 Vol.%. The results of this series of experiments are tabulated below. The wax content of the charging stock was 14% by weight as determined by the I-Iolde method.

1 A. P. l. gravity and viscosity index refer to tho conventionally dcwaxed cil.

f Specific gravity, 1.060.

The-examples cited illustrate extensively my methods of operation and the treatments of the various types of oils demonstrate the flexibility of my process'. While I have specified certain denite conditions of operation such asI temperatures, solvent selectivity and process cycles, I do not limit myself to the aforesaid specific `examples since it is quite cbvious'that many modil iications may be made by those skilled in the art without deviating from the spirit and scope of my invention. I contemplate such variations in the conditions under which to operate my process as may be advantageous to carry out my invention as set forth herein, in particular when applying my process to treatment of hydrocarbon oils which differ materially from the products de scribed in the examples.

I claim:

1. A process of producing lubricating oil of` high quality from wax-free hydrocarbon mixtures containing low and high quality oil constituents, comprising dissolving said mixture in an aqueous substance of the class of pyridine and its homologues containing approximately 11/2%` to 3%' of` water which at normal. temperature exhibits' no selective solvent action upon any group of the oil constituents and which becomes a selective solvent for the low quality constituents upon coolirig, adding a substantial amount of Wax to said mixture and cooling it to a low temperature whereby an undissolvedphase, called rainate phase, and a dissolved phase, called extract phase, are obtained, the raiiinate phase containing the added solid wax, together with substantially all of the high quality lubricating oil, both being saturated with solvent, and the extract phase containing the bulk of the solvent and dissolved therein the low quality oil constituents, separating the phases from each other, recovering the solvent from the extract phase to obtain the low quality oil or extract, dispersing the ralnate phase at substantially the same low temperature in an additional quantity of cold solvent of the class described having such a low content of water that it exhibits a solvent action only upon the high quality oil constituents but not upon the added Wax, subjecting the mixture toa second separation step to separate the solution containing the high quality lubricating oil from the solid Wax and recovering t-he solvent from the solution and from the wax.

2. A process of producing a lubricating oil of high quality from hydrocarbon mixtures containing the same together with low quality oil constituents and wax, comprising dissolving said mixture in an aqueous substance of the class of pyridine and its homologues containing not to exceed about 3% of water so that it exhibits at normal temperature no selective solvent action upon any group of the oil constituents and the wax, and there being not less than about 11/% of water so that it becomes a selective solvent for the lovf quality oil constituents upon cooling, cooling the mixture to a low temperature, whereby an undissolved phase, called raiiinate phase, and a dissolved phase, called extract phase, are obtained, the ralinate phase containing the solid wax constituents together with substantially all of the high quality lubricating oil both being saturated with the aqueous solvent substance. the extract phase containing the bulk` of the aqueous solvent substance and `dissolved therein the low quality oil constituents,` separating the phases from each other, recovering `the solvent from the extract phase to obtain the low, quality cil or extract, dispersing the raiinate phase at substantially the same low temperature in an additional quantityof an anhydrous substance of the class of pyridine and its homologues which exhibits a solvent action only upon the high `quality oil constituents but not upon the wax, subjecting the mixture to a second separation step to separate the solution containing the high quality lubricating oil from the solid wax and recovering the anhydrous solvent substance from the solution and from the Wax.

3. A process of producing lubricating oil of high quality as per claim-2, wherein the hydrocarbon mixture is mixed with a solvent substance of the class of pyridine and its homologues containing water obtained by recycling a suitable amount of aqueous solvent recovered from the ltrate by water modification, said ltrate resulting from the filtration of the mixture obtained by the additional anhydrous solvent added to the raffinate phase to separate the wax from the high quality lubricating oil.

4. A process ofproducing lubricating oil of high quality and wax from hydrocarbon mixtures containing the same, together with low quality oil constituents, comprising dissolving said mixture in a substance of the class of pyridine and its homologues containing sufficient water so that it exhibits at normal temperature no solvent action upon any group of the oil constituents'and the wax but that it becomes a selective solvent for the low quality oil constituents upon cooling, cooling the mixture to obtain a rainnate phase and an extract phase in accordance with claim 2, wherein the raflinate phase is dispersed at a low temperature in an additional quantity of a cold anhydrous substance of the class of pyridine'and its homologues to dissolve the high quality oil and to leave undissolved the solid wax, ltering the mixture and adding to the solution of high quality oil in said anhydrous substance suicient water at a somewhat lower temperature to cause the highquality oil to separate out of the solution, and recycling the substantially oil-free, water-containing substance for reuse in the rst separation step.

5. The process according to claim 2 in which an aqueous substance of the class cf pyridine and its homologues is used as the solvent in the first separation step and a mixture of a like substance and benzol is used as the solvent in the raffinate dispersion step.

6. The process according to claim 2 for producing high quality lubricating oil and wax in which the hydrocarbon mixture to be rened is a petrolatum containing waxY and low and high quality lubricating oil as produced from unrened hydrocarbon oil stocks/by known dewaxing processes.

7. A process of producing lubricating oil of high quality as per claim 2, wherein the second separation step is followed by the addition, to the anhydrous substance in which the high quality oil constituents are dissolved, of water in suflicient quantity to cause a separation of the solvent and water from the oil constituents into layers from which the latter can readily be drawn off for topping to form the finished high quality lubricating oil.

8. A process of producing lubricating oil of high quality from hydrocarbon mixtures containing the same together with low and medium'quality oil constituents and wax, comprising dissolving said mixture in an aqueous substance of the class of pyridine and its homologues containingenough water so that at normal temperature it exhibits no selective solvent action upon any groupy of the oily constituents and the wax, and becomes a selective solvent for the loW and medium quality oil constituents upon cooling, cooling the mixture to a low temperature whereby an undissolved phase, called raiinate phase, and a dissolved phase, called extract phase, are obtained, the raflinate phase containing the solid wax constituents together With substantially all of the high quality lubricating oil, both being saturated with said aqueous solvent substance, and the extract phase containing the bulk of the aqueous solvent substance and dissolved therein the low and medium quality oil constituents, separating the phases from each other, dispersing the raiinate phase at substantially the same low temperature in an additional quantity of a cold anhydrous substance of the class of pyridine and its homologues to dissolve the high quality oil constituents but not the wax, subjecting the mixture to a second separation step to separate the solution containing the high quality lubricating oil from the solid wax and recovering the anhydrous solvent substance fromfthe solution and from the wax, adding to the extract phase from 2 to 10% of water to cause a second separation into two phases, one containing the medium quality oil constituents and the other containing the low quality oil constituents dissolved in the aqueous solvent substance, separating the phases from each other and recovering the solventy from both phases.

9. The process according to claim 8 for producing high quality lubricating oil and Wax in which the hydrocarbon mixture to be refined is a petrolatum containing wax and low and high quality lubricating oil as produced from unrefined hydrocarbon oil stocks by known dewaxing processes.

10. A process of producing a lubricating oil of higher quality from hydrocarbon mixtures containing the same together with lower quality oil constituents in preponderating amount andwax, comprising dissolving said mixture in an aqueous substance of the class of pyridine and its homologues containing from 2% to 10% of Water so that it exhibits at normal temperature no selective solvent action upon any group of the oil constituents and the wax, and becomesv a selective solvent for the lower quality oil constituents upon cooling, cooling the mixture to a low temperature, whereby an undissolved phase, called raflinate phase, and a dissolved phase, called extract phase, are obtained, the ralinate phase containing the solid wax constituents together with substantially all of the higher quality lubricating oil both being saturated with the aqueous solvent substance, the extract phase containing the bulk of the aqueous solvent substance and dissolved therein the lower quality oil constituents, separating the phases from each other, recovering the solvent from the extract phase to obtain the lower quality oil or extract, dispersing the rafnate phase at substantially the same low temperature in an additional quantity of an anhydrous substance of the class of pyridine and its homologues which exhibitsa solvent action only upon the higher quality oil constituents but not upon the wax, subjecting the mixture to a second separation step toY separate the solution containing the higher quality lubricating oil from the solid Wax and recovering the anhydrous so-lvent substance from the solution and from the wax.

ERNEST BsrNG.

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