US2162963A

US2162963A - Process for desulphurizing mineral oils

Info

Publication number: US2162963A
Application number: US161456A
Authority: US
Inventors: Donald S Mckittrick
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1937-08-28
Filing date: 1937-08-28
Publication date: 1939-06-20
Anticipated expiration: 1956-06-20

Description

June 2 0, 1939. D. s. McKlTTRlcK PROCESS FOR DESULPHURIZING-MINERL OILSv Filed Aug. 28, 193'? 2 Sheets-Sheet l sought@ NM N@ 2 Sheets-Sheet 2 D. S. MCKITTRICK Filed Aug. 28, 1937 geld/trick June 20, 1939.

PRocEss FOR DESULPHURIZING MINERAL oILs vwv Patented June 2.0, 1939 UNITED STATES PATENT OFFICE Donald S. McKittrick, Oakland, Califmassignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application August 28, 1937, Serial No. 161,456

, Claims.

This invention relates to the treatment of hydro'carbon oils for the removal 'of sulphur, and is particularly-concerned with the removal of sulphur from low boiling distillates, such as naphthas, gasoline, and cracked orstraight-run distillates containing the same,- although other distillates, such as kerosene, gas oil, and polymerized low boiling oils, as well as higher boiling mineral oil fractions may also be desulphurized in accordance with the present process.

More specifically, the present process is concerned with the removal of sulphur compounds, particularly the more refractory sulphur compounds, such as thiophene and its homologues, like alkyl thiophenes, from lower distillates, but

may also be employedgto remove the less refrac-ftory sulphur compounds, such as thioethers, mercaptans, and 'sulphides The present invenv tion is especially useful in the refining of distillatesv containing aromatic hydrocarbons, ,in which it is desired to retain the aromatic hydrocarbons in the desulphurized oil together with other hydrocarbons, such as gasoline, wherein .the aromatic hydyrocarbons are desirable for improving the anti-knock properties of the fuel; but it may be applied to fractions containing little or no aromatics. Y

It has already been proposed to separate sulphur compounds from hydrocarbon oils by extracting the oli with a polar solvent which preferentially dissolves sulphur compounds and forms two liquid phases upon being mixed with the oil. (See U. S. Patent No. 2,024,117.) A disadvantage of sucha process has been that an appreciable quantity of valuable hydrocarbons, and

particularly of aromatic and unsaturated hydrocarbons, is lost together with the sulphur compounds. This is due to the fact that the prefvereiitialsolvents are not totally immiscible with the; hydrocarbons, under the conditions of the extraction, and a complete separation between sulphur compounds and hydrocarbons is not possibleeither in the usual batch or single counter- ,y current extractions.

countercurrently to the preferential solvent for sulphur compounds; introducing the second cut into the extraction zone at a point intermediate to the points of introduction of the rst cut and the solvent; and withdrawing rafiinate and extract phases at spaced points in the extraction zone, The rst cut may, optionally, be fractionally distilled to produce a modified cut containing the hydrocarbons of low carbon to hydrogen ratio in a more concentrated form, and this modified first cut employed in the extraction zone,

The fractionation to produce the aforesaid first and second cuts may be effected either by distillation or by solvent extraction, When distillation is employed for the preliminary fractionation, the initial sulphur-bearing oil is distilled in the presence of a separating agent of the type of preferential solvent for aromatic hydrocarbons to separate therefrom a distillate containing a concentrate of hydrocarbons of low carbon to hydrogen ratios, and constituting the first cut; the distillation residue constitutes the second cut, This distillation may, for example, be carried out in the manner described in the U. S. patent to Roelfsema, 2,069,329, the distillation temperature and/or the pressure being, however, preferably regulated so as to produce a distillate containing substantially only the most saturated hydrocarbons, particularly paraiiines, leaving the olenic and aromatic hydrocarbons in the residue.

When solvent extraction is employed for the preliminary fractionation, the initial sulphur bearing oil is contacted with a solvent capable of causing the formation of immiscible liquid phases, one of which contains the most saturated in 'which Figures l and 2 are schematic flow diagrams illustrating the steps of` two specic-emsulphur-bearing low boiling hydrocarbon oil, suchas a cracked distillate boiling within .gasoline range, which may, if desired, have been given a preliminary light treatment with sulphuric acid or with an alkaline to remove the less reumn 5 through a conduit 6, which may be pro- Y vided -with a heating coil and with the usual 'ered with the overhead distillate.

phlegmating means, etc., not shown. In the column 5 the feed mixture is distilled to produce a distillate, withdrawn through lthe `lin'e 1, containing at least a portion of the most saturated hydrocarbons of thefeed mixture, and little or no sulphur. The expression saturatedhydrocarbons is intended to include both open chain and cyclic hydrocarbons, i. e., paraillnic and saturated naphthenic hydrocarbons. The distillate may, ,in addition, contain olenic hydrocarbons the quantity -of which is, however, kept to a minimum by careful operation of the column. The separating agent is preferably selected with regard to its boiling temperature to be distilled over, whereby all or the major portion is recov- I my, however, alsov employ higher boiling separating agents which are only' partially vaporized or which remain inthe liquid state.

The distillate is condensed in a condenser 8 and a portion of the condensate may, if desired, be returned to the column through a reflux line 9 and a valve I0; the remainder ilows through valve II and is treated in the separating stage I2 to remove the separating agent, 'if any, by further distillation, in situations where the formation of azeotropes is not a hindrance, or, in any case, by chilling the distillate and separating the resulting chilled condensate into an oil phase and a separating agent phase in a settling tank or a centrifugal separator, if necessary, in the presencel of an added essentially oil-immiscible solvent like water or aqueous alcohol which dissolves the separating agent. The `oil is withdrawn at I3, and the separating agent, or its solution in a solvent, at Il. 'I'he removal of the separating agent from the distillate is more specifically described in the U. S. patent to Roelfsema, 2,069,339.

When thedistillate contains little or no separatfrom the separating agent; or the same end may be achieved by separating the distillate into two liquid phases by cooling, and controlling the reflux of one or both of these phases to the column.

It is not,however, essential to remove all `of the separating agent overhead, because a small quantity does not interfere with the operation of the subsequent extraction step, especially when the not restric from the residue in a separating stage Il, similar to the stage Il. Y

The temperature and pressure in the"column I are regulated to produce a distillate which contains a concentrate of the most saturated hydrocarbons. Under these conditions sulphur compounds are usually for the greater part exeluded from the distillate, although it may contain certain amounts of low boiling Imercaptans when these are present in the oil fed through the valve I. If the initial oil contains aromatic hydrocarbons, as most low boiling distillates do,

the distillate from the column 5 is less aromatic than the initial oil. It may, for example, contain between about 30 and '15% of the original hydrocarbons, but since it is necessary to employ very exact fractionating control to void the distilla'tion of undesirable quantities of aromatic and other unsaturated hydrocarbons when a large distillate is produced, I prefer to take of! a 'distillate containing only between about 30 and 65% of the hydrocarbons. When the distillate contains large quantities of oleflnes, it is often desirable to distil even Ismaller quantities, such as 30|to 50%, to produce a distillate consisting substantially of, i. 'e., containing over about 85% of parailinic and/or naphthenic hydrocarbons. -Under any of originalhydrocarbons, lof which about 58% are y non-aromatics and 2% are aromatics. The sharpness of the separation effected in the column 6 may be improved by initially distilling the oil into a number of narrower boiling fractions having boiling ranges of about 25 C. to 80 C., and subiecting each narrow boiling fraction separately to the distillation in the column I.'

According to the preferred embodiment of the process, the distillate from the column l, constituting the first cut of the oil, is flowed through a valve Il into a second dlstilling column I1, which may be similar to the column l,vwherein the first a cut is distilled, substantially or totally in the absence o f a separating agent to produce a distillation bottom product, withdrawn at It, containing the most saturated hydrocarbons in .a more concentrated form, and constituting a modiiied first cut. The conditions in the column I'I are such as to produce distillate withdrawn at I 9, containing usually from about 10 to 50% of the feed to this column, although the process is to this range, since even greater amounts of oil may be taken of! overhead. vIn general, it is desirable .to take 'olf overhead only enough oil to cause a concentration of the saturated hydrocarbons vin the distillation residue. vThe distillate may be condensed in the condenser Il, flowed through the valve 2|, and withdrawn at 22 as'a separate product. If mercaptans and/or similar sulphur compounds are present. the distillate may be flowed through the valve 23, and the sweetening stage 24, wherein the distillate is treated by known methods, such as a sodium plumbite or a caustic soda treatment, preferably one whichi will remove sulphur.

The distillation residue withdrawn at 2l,- which may be passed either through the unit v2l' to remove the separating agent or through the by- 1| oil, and is fed into an extraction zone 28 at an intermediate point thereof. A preferential solvent for sulphur compounds, which is capable of forming two liquid phases when contacted with the oil, is introduced at 29 near one end of the extraction zone, and` the residue from the column I1, constituting the modified first cut of the original oil, at 30 near the other end. If desired, the distillation in the column I1 may be eliminated, the distillate from the column 5 may be introduced at 30, by by-passing the column I1 through.

The extraction zone is arranged' the valve 3|. for the countercurrent flow of the distillate and the preferential solvent through a plurality of stages, which-may be virtual, as in the case of a packed tower, or real, as in the case of a series of mixers and settlers. In the extraction zone,

railinate and extract phases (consisting predomi-v nantly of hydrocarbons and of a solution of sulphur compounds .in the solvent, respectively,) are formed and flow countercurrently to one another. and are withdrawn at spaced points 32 and 33, respectively. The section between the intermediate inlet for the second cut and the inlet 29 for the preferential solvent is designated as the rectifying section of the extraction zone, and the section between the inlets for the rst and second cuts as the stripping section, it being understood that, raffinate phase from the stripping section flows into the rectifying section, and extract phase from the rectifying section iiows into the stripping section. The temperature is regulated so that a minimum quantity of hydrocarbons is removed in the ultimate extract phase withdrawn l from the stripping section, this quantity of hydrocarbons being in most cases between about 0.5 and 4% of the initial oil. Temperature regulating means, such as a cooling coil 34' may be provided for this purpose.

The solvent may be recovered from the separated phases in the

units

35 and 36 by any suitable means, such as distillation or washing with water, etc. The desulphurized oil is withdrawn at 31 and the sulphur compounds at 38; the recovered preferential solvent is withdrawn at 39 and 40 and may be reused. The desulphurized oil may be blended with the distillate from the column I1 by meansof the valve 4I.

Instead of feeding only the first cut, i. e., distillate from the coiunm 5, or the residue from the column I1 into the extraction unit at 30, the feed at this point may be augmented by introduc- -ing a parainic solvent having a boiling temperature range Well outside of the distillate being desulphurized from a source 42 through a valve 43, and may be recovered from the raffinate phase at 44. Only negligible quantities of this solvent are usually in the extract phase, so that its separation from the preferential solvent in the unit 36 is not necessary; it may, however, be separated therein and withdrawn at 45. This may consist predominantly of parafllnic or naphthenic hydrocarbons, or their mixtures, the former being preferred. Thus, paraflinic hydrocarbons like light naphtha, pentane, isopentane, iso-octane, and highly refined white oils may be employed.

Referring to Figure 2, 5I represents an extraction zone, which may comprise one or more stages, for the countercurrent flow of a preferential solvent for aromatic hydrocarbons, fed into the extraction zone near one end ythrough a valve 52 from a tank 53, and the feed of sulphur-bearing oil, fed through a valve 54, either at the other end of the zone, when the zone comprises only a rectifying section, or at an intermediate point as shown, when the zone lcoprises both rectifying and stripping sections. The rates of flow and temperature are regulated to produce counterflowing ramnate and extract phases which are withdrawn at 55 and 56, and constitute the first and second cuts of the initial oil, respectively, a suilicient quantity of solvent, or a solvent of sulcient solvent power being used to dissolve the 5 unsaturated olenic and aromatic hydrocarbons produce a raflinate which contains the most saturated hydrocaaons in a lhighly concentrated form, and amounting to between about 30 and 75% and, preferably, between about 30 and 65% of the hydrocarbons; when treating oils rich in .olefines, raflinates containing less than 50% of the feed are preferred, as described above in connection with` the process according to Figure 1.

When the initial oil contains suicient open chain parafdnic hydrocarbons (including branched and straight chain), to produce a raffinate containing only or over 85% of such hydrocarbons, the raffinate amounting Ato over about 30% of the initial oil, I prefer-to remove all or most of. the naphthenic hydrocarbons (i. e., cyclic parafdnes) in the second cut; the /naphthenic `hydrocarbons may, however, be present in the first cut. -In the stripping section, i. e., between the point of introduction of the feed and 56, the point of withdrawal of the extract phase, the extract phase may, if desired, b e cooled by means of a coil 51 or otherwise treated to strip out saturated hydroi valve 58 to separating unit 59 for the removal of the preferential solvent, which may be returned to the tank 53 via the line 60; if desired, the unit 59 may be 'by-passed through a'valve 6|, especially when the preferential solvent for sulphur compounds employed in the subsequent extraction in the zone 28 is the same as that employed in the extraction zone 5| and the distilling unit 65 lis by-passed. The extract phase maybe similarly treated in the separating unit 62 for the removal of the preferential solvent, or by-passed via the valve 63.

The most saturated hydrocarbons in the first cut may be concentrated by passing through valve 64 into a distilling column 65, which may be similar to the column I1 of Figure 1, wherein the raiiinate phase or first cut is distilled preferably in the absence of a separating agent or prefer- -ential solvent to produce a distillate, withdrawn at 66, containing the most saturated hydrocarbons in a more concentrated form, and constituting a modified first cut. The conditions in the column 65 are such as to produce a distillation residue, withdrawn at 61, containing usually from about 10 to 50% of the feed to this column, although the process is not restricted to this range, since even greater amounts of residue may be produced. In general, it is desirable to produce the largest possible distillate; therefore, prefer- Il, if desired, after a sweetening or other mild desulphurizing treatment.

' The arrangement and operation of the extraction zone 28.'are similar to those of the zone 28 already described in connection with Figure 1; the second cut of the original oil is introduced at an intermediate point 10, the modified first cut,.

. or, if desired, the original first cut, by by-passing the column 85 through 4the valve 1I near one end at 80, and the preferential solvent for sulphur compounds near the other end at 28,

reference numerals

28, 2S, 30 and 32 to l5 designating the same elementsas in Figure 1.

The process according to Figure 2 involves two extractions: In the zone-5| the conditions are such that all of the initial'oil save the most paraflinic portion is dissolved in the solvent and is inthe extract phase; in the zone 28 substantially no hydrocarbons, or only a minor amount, i. e., less than about 4%'of the initial, are dissolved in the preferential solvent together with the sulphur compounds, the remaining hydrocarbons passing into the raffinate phase. While about 4% is the maximum quantity of hydrocarbons which is dissolved in the extract phase from the zone 28 under the preferred operating conditions, both in the process according to Figure 1 and according to Figure 2, my invention is not limited thereto, but is intended to include also operations wherein a lower yield of desulphurized oil is obtained, for example, operation wherein vis as much as 10% ofthe initial 'hydrocarbons are present in the extract phase from the zone 28.

The extract phase may, particularly when it contains larger amounts of hydrocarbons, be subjected to an intensive desulphurization treatment, such as, sulphuric acid, hydrogenation, oxidation, treatment with carbon monoxide, etc., and the desulphurized hydrocarbons may then be blended with the ramnate.

By preferential solvent for sulphur compounds ls meant a solvent possessing such characteristlcs that the distribution ratio between the solvent or extract phase and the oil or ramnate phase is greater for sulphur compounds than for most soluble hydrocarbons, when the solvent is contacted with the oil under conditions causing the formation of liquid phases. It is not necessary that all sulphur compounds be preferentially dissolved, but only those which it is desired to extract, such as thiophenes. In the usual case the most soluble hydrocarbons present in the oil are aromatics. Most polar selective solvents employed for the extraction of mineral oils to separate them into relatively more paraillnic and armatic portions, respectively, fall within this class, since thiophenes are generally more polar and are therefore more readily dissolved in such sol,

vents than even aromatic hydrocarbons. The" selectivity of these selective solvents between aromatics and sulphur compounds is, however, not the same for all, so that some are more suitable than others. The following solvents were found to be very suitable for the removal of sulphur by extracting such distillates: Lower aliphatic sulphonic acids, particularly methyl-sulphonic acid, ethyl-sulphonic acids, and isopropyl-sulphonic acid, thiophene aldehyde, ethyl cyanide, ethyl cyanoacetate, nitroaniline, aniline, methyl cyanide, ethylene diamine, liquid sulphur dioxide, a mixture of equal parts of liquid sulphur dioxide and acetone, methoxy methyl cyanide, methyl carbi# tol, and their mixtures. Solvents which are too or with a highly polar oxygenated aliphatic-com-` pound like methyl alcohol, ethyl alcohol, acetone, or their aqueous solutions. My invention. which resides in the combinationV of steps defined in the the distribution ratio -between the solvent phasel andthe oil phase is greater for the .aromatica than for the saturated hydrocarbons, solvents of this type being well known in the art. These solvents may be employed either in the distilling unit 5 of Figure 1 or in the first extraction zone 5I of Figure 2. As explained above, nearly all of these solvents are also preferential solvents for sulphur compounds and the same solvents can,

be employed for'both purposes; but since the effectiveness of these solvents for the speciflcfunctions of extracting sulphur compounds on the one ogy is made. Thus, a solvent like ethylene glycol. while operative to extract sulphur compounds, is -only very slightly selective between aromatica and sulphur compounds, and is, for this reason. not

preferred in that capacity; but it has a fair selectivity between paraiilnic hydrocarbons on the one hand, and aromatic hydrocarbons 'on the other hand, and may, therefore, be employed in the distilling unit 5. However, other substances which .do not form two layers when commingled with the oil, but which have a preferential solvent affinityl for aromatic hydrocarbons, and therefore cause the hydrocarbons of lower carbon to hydrogen ratiosv to be distilled over at a lower temperature than aromatic hydrocarbons of the same normal boiling temperature may also be vemployed for the distilling step in the embodiment according to Figure 1. The designation separating agent 'of the type of preferential solvent for aromatic hydrocarbons" is, in the present specification and claims,v used to include both of these typesof separating agents. While any separating agent of this type may be employed inthe distilling unit 5, it is preferable, in order to obtain a substantial yield of a distillate containing a concentrate of paraiiinic hydrocarbons without the distillation of unduly largel quantities of the separating agent or of the necessitating a very long column, it'is desirable to use a separating 4agent which boils within or near, i. e., not more than about C. below or 25 C. above the boiling range of the oil being distilled, the preferred hand, and aromatics, on the other, is not the` same, some ybeing more effective for one purpose, and some for the other, a distinction in terminolboiling point being within the range: 25 C. below y the initial boiling point of the fraction to the midpoint of the boiling temperature range of the fraction.

Any polar liquid which has the above described boiling temperature characteristics, and which has a preferential solvent attraction for aromatic hydrocarbons as compared with the more saturated hydrocarbons may be employed as the separating agent, such liquids having been found to cause the concentration in the distillation residue not only of the aromatics, but of the sulphur compounds as well; ythese same agents will also cause the more saturated parainic hydrocarbons to be distilled' at a lower temperature than the less saturated aliphatic hydrocarbons, such as oleflnes. These agents may, for example, be the solvents commonly employed for the solvent extraction of mineral oils, s'uch as organic compounds, either aliphatic, carbocycllc, or heterocyclic, containing one or more of the following groups: -NO2, -CN, SCN, =,=CO, CEOE :CI-ICH, ECOH, EC-Cl, 'NHn, =O, =CS, -COOH. -OR. and -COOR, wherein R designates an alkyl or aryl radical. Examples of these separating agents are: Nitrobenzene, benzonitrile, monochloracetonitrile, phenyl thiocyanate, plienolthiocyanate, formate, of pyridine,-benzald hyde, acetone, furfural, furfuryl alcohol, chlorisopropyl alcohol, diacetone` alcohol, methyl alcohol, ethyl alcohol, aniline, methyl lactate, triacetin, diacetln, methyl nitrobenzoate, formic acid, acetic acid, ethylenchlorhydrin, glycol monoacetate, glycol diacetate, lactic acid nitrile, toluidine, chlor pyridine, BB' dichloroethyl ether, chlor aniline, sulphur doxide, quinoline, isoquinoline, pyridine, chlorophenoll etc. My invention is not, however, limited to the specific solvents enumerated, nor to solvents containing the enumerated chemical groups, but may be used withV any separating agent having a preferential solvent attraction for aromatics.

I have, however, found that when refining sulphur-bearing hydrocarbon mixtures boiling within gasoline range, superior results con be obtained by employing the following substances as separating agents, and their use constitutes the preferred form of my invention: Furfural. methyl cyanide, ethylene diamine, nitromethane and` Aand hydrocarbons of different ratios of carbon to hydrogen, which comprises the steps of separating said fraction into a flrst` out containing a concentrate of hydrocarbons of relatively low ratios of carbon to hydrogen and a second cut containing the remainder of the fraction, fiowlng said first cut through anextraction zone countercurrently to a preferential solvent for sulphur compounds under conditions causing the formation of counterfiowing raffinate and extract phases, introducing the second cut into the extraction zone at an intermediate point thereof, the conditionswithin `the extraction zone being such that the first cut washes hydrocarbons from the extract'phase to produce a washed extract phase containing the solvent sulphur compounds and not more than a minor amount of the hydrocarbons contained in the initial fraction and withdrawing raflinate and washed extract phases from said extraction zone at spaced points.

2. The process for refining` an initial hydrocarbon fraction containing sulphur compounds and hydrocarbons of different ratlos of carbon to hydrogen, which comprises the steps of separating said lfraction into a first cut containing a concentrate of hydrocarbons of relatively low ratios of carbon to hydrogenv and comprising between about 30 and '75% of the hydrocarbons of the initial fraction and 'a second cut containing the remainder of the fraction, flowing said firstl cut through an extraction zone countercurrently to a preferential solvent for sulphur compounds under conditions causing the formationA of counterflowing raflinate. and extract phases, introducing the second cut into the extraction zone at an intermediate point thereof, the conditions within the extraction zone being such that the first cut washes hydrocarbons from the extract phase to produce a washed extract phase containing the solvent, sulphur compounds,

. tillation product containing the hydrocarbons of low ratios of carbon to hydrogen in a more concentrated form than said first cut, and a second distillation product, flowing said first distillation product through an extraction zone countercurrently to a preferential solvent for sulfur compounds under conditions causing the formation of counterflowing raffinate and extract phases, introducing the second cut into the extraction zone at an intermediate point thereof, the conditions within the extraction zone being such that the distillation product Washes hydrocarbons from the extract phase to produce a washed extract phase containing the solvent, sul'- phur compounds, and less than about 10% of the hydrocarbons contained inthe initial fraction and withdrawing rainate and washed extract phases from said extraction zone at spaced points.

4. The process for refining an initial hydrocarbon fraction containing sulphur compounds andhydrocarbons of different ratios of carbon to hydrogen, which comprisesdistilling said initial fraction together with a polar separating agent of the type of preferential solventfor aromatic hydrocarbons in a distillation zone, maintaining conditions of temperature "and pressure in said zone to distil over a top product containing a concentrate of hydrocarbonsl of relatively low ratios of carbon to hydrogen'and forming a distillation bottom product in which the sulphur compounds and hydrocarbons of relatively high ratios of carbon to hydrogen are concentrated, owing hydrocarbons from said top product through an extraction zone countereurrently to a preferential solvent for sulfur compounds under conditions causingk `the formation of counterflowing raiiinate and extract phases, introducing, the concentrate of sulfur compounds and hydrocarbons from said bottom product into the extracfraction together with a polar separating agent of the type of preferential solvent for aromatic hydrocarbons in a distillation zone, maintaining conditions of temperature and pressure 'in said zone to distil over a rst top product containing a concentrate of hydrocarbons of relatively low ratios of carbon to hydrogen and forming a first distillation bottom product in which the sulfur compounds and hydrocarbons of relatively high ratios of carbon to hydrogen are concentrated, distilling the rst top product substantially in the absence of a polar separating agent to produce a second top product and a second distillation bottom product, flowing hydrocarbons from said second bottom product through an extraction zone countercurrently to a .preferential solvent for sulphur compounds under conditions causing the formation of counterflowing ramnate and extract phases, introducing the concentrate of sulphur compounds and hydrocarbons from said rst bottom product into the extraction zone at an intermediateI point thereof, the conditions within the extraction zone being such that the hydrocarbons from said second bottomproduct wash hydrocarbons from the extract phase to produce a washed extract phase and containing the solvent, sulphur compounds, and less than about 10% of the hydrocarbons contained in the initial fraction and 'withdrawing rafllnate and washed extract phases from said extraction zone at spaced points.

6. The process for refining an initial hydrocarbon fraction containing sulphur compounds and hydrocarbons of different ratios of carbon to hydrogen, which comprises distilling said initial fraction together with a polar separating agent of the type of preferential solvent for aromatic hydrocarbons in a distillation zone, maintaining conditions of temperature and pressure in said zone to distil over a first top product containing a concentrate of hydrocarbons of relatively low `ratios of carbon to hydrogen and forming a first distillation bottom product in which the sulphur compounds and hydrocarbons of relatively high ratios of carbon to hydrogen are concentrated, distilling the first top product substantially in the absence of a polar separating agent to produce asecond top product and a second 4distillation bottom product, flowing hydrocarbons from said second bottom product through an extraction zone countercurrently to va preferential solvent for sulphur compounds under conditions causing the formation of counterflowing railinate and extract phases, introducing the concentrate of' sulphur compounds and hydrocarbons from said first bottom product into the extraction zone at an intermediate point thereof, the conditions within the extraction zone being such that the hydrocarbons from said second bottom product wash hydrocarbons from the extract phase to .produce a washed extract phase and containing the solvent, sulphur compounds, and less than about 10% of the hydrocarbons contained in the initial fraction, withdrawing raiiinate and washed extract phases from said extraction zone at spaced points, subjecting said second top product to a sweetening treatment, and blending the sweetened top product with oil contained in said raiiinate phase.

7. The process for refining an initial hydrocarbon fraction containing sulphur compounds and hydrocarbons of different ratios of carbon `than about 25 C. above the end point of Said initial fraction, in a distillation zone, maintaining the conditions of temperature and pressure in said zone to distil at least a substantial portion of the separating agent'together with hydrocarbons of relatively low ratios of carbon to hydrogen, thereby forming a rectified top product derived from the combined mixture containing a concentrate of hydrocarbons of low ratios to carbonto hydrogen and a distillation bottom product in which the sulphur compounds'are concentrated and containing a concentrate of hydrocarbons of relatively high ratios of carbon to hydrogen, flowing hydrocarbons from saidtop product through an extraction zone countercurrently to preferential solvent for sulphur compounds under conditions causing the formation of counterowing raffinate and extract phases, introducing the concentrate of sulphur compounds and hydrocarbons from said bottom product into the extraction zone at an intermediate point thereof, the conditions within the extraction zone being such that the hydrocarbons from said top product wash hydrocarbons from the extract phase to produce a washed extract phase containing the solvent, sulphur compounds, and less than about 10% of the hydrocarbons contained in the initial fraction and withdrawing ramnate and washed extract phases from said extraction zone at spaced points.

8. The process according to claim 7 in which the separating agent has a boiling point falling within the range: 25 C. below the initial boiling point of the initial fraction to themidpoint of the boiling temperature range of the initial fraction. y

9. The process according to claim 7 in which la parafflnic solvent which is substantially immiscible with the preferential solvent for 4sulphur compounds is flowed through at least a portion of the extraction zone concurrently with the hydrocarbons from the topproduct.

10. The process according to claim 7 in which the separating agent is separated from the top product, and only the hydrocarbons thereof are introduced into the extraction zone.

1,1. 'Ihe process for refining an initial hydrocarbon fraction including components boiling within gasoline range and containing sulphur compounds and aromatic and non-aromatic hydrocarbons, which comprises distilling said initial fraction together with a polar separating agent of the type of preferential solvent for aromatic hydrocarbons in a distillation zone, maintaining the conditions of temperature and pressure in said zone to distil at least a substantial portion of the separating agent together with non-aromatic hydrocarbons, thereby forming a rectified. top product derived from the combined mixture containing a concentrate of non-aromatic hydrocarbons and a distillation bottom product containing a concentrate of sulphur compounds and aromatic hydrocarbons, flowing hydrocarbons from said top product through an extraction zone countercurrently to a preferential solvent for sulphur compounds under conditions causing the formation of counter-flowing railinate and extract phases, introducing the concentrate of sulphur compounds and aromatic hydrocarbons from said bottom product into the extraction zone at an intermediate point thereof, the conditions within the extraction zone being such that the'hydrocarbons from said top product wash hydrocarbons from the extract phase to produce a washed extract phase containing the solvent, sulphur compoundsfand less than the top product contains, between about 30 andl of said hydrocarbons.

14. The process according to claim 11 in which the initial fraction is a fraction containing saturated, olenic, and aromatic hydrocarbons, the top product contains between about 30 and 50% of said hydrocarbons, and the hydrocarbons in said top product contain over about of saturated hydrocarbons.

15. The process according to claim l1 in which the conditions within the extraction zone are such that thel extract phase contains less than about 4% of the hydrocarbons contained in the initial fraction.

16. The process for rening an initial hydrocarbon fraction containing sulphur compounds and hydrocarbons of diierent ratios of carbon to hydrogen, which comprises the steps of extracting said fraction in a first extraction zone with -a selective solvent, which, when contacted therewith, is capable of forming two liquid phases containing concentrates of hydrocarbons of dierent ratios of carbon to hydrogen, under conditions causing the formation of a first cut containing a concentrate of hydrocarbons of relatively 10W ratios of carbon to hydrogen and a second cut containing the remainder of the fraction, said first cut containing over about 85% of saturated hydrocarbons, flowing said rst cut through a second extraction zone countercurrently to a preferential solvent for sulphur compounds, under conditions causing the formation of counterflowing rainate and extract phases, introducing the second cut into the second extraction zone at an intermediate point thereof, the conditions within Vsaid second extraction zone being such that the first cut washes hydrocarbons from the extract to produce a washed extract phase containing the preferential solvent, sulphur compounds, and less than about 10% of the hydrocarbons contained in the initial fraction and withdrawing the ralnate phase and the washed extract phase from said second extraction zone at spaced points.

17. The process for rening an initial hydrocarbon fraction containing sulphur compounds and hydrocarbons of different ratios of carbon to hydrogen, which comprises the steps of extracting said fraction in a rst extraction zone with a selective solvent for aromatic hydrocarbons which, when contacted therewith, is capable ofl containing a concentrate of relatively low carbon to hydrogen ratios, under conditions to produce a rafllnate containing between about 30 and '75% of the hydrocarbons of the initial fraction, and a rst extract containing the remainder of the fraction, flowing said first raffinate through a second extraction zone countercurrently toA a preferential solvent -for sulphur compounds, under conditions causing the formation of counterflowing second raffinate and extract phases, introducing said first extract into the second extraction zone at an intermediate point thereof, the conditions within said second extraction zone being such that the first raffinate washes hydrocarbons from the second extract to produce a washed second extract phase containing the preferential solvent, sulphur compounds, and less than about 10% of the hydrocarbons containe, in the initial fraction and withdrawing the second raflinate phase and the washed extract phase from said second extraction zone at spaced points.

18. The process according to claim 17 in which the rst raffinate contains over about 85% of saturated hydrocarbons.

19. The process according to claim 17 inf which the second extract phase contains less than 4% of the hydrocarbons contained in the initial fraction.

20. The process for refining an initial hydrocarbon fraction containing sulphur compounds and hydrocarbons of different ratios of carbon to hydrogen, which comprises the steps of extracting said fraction in a rst extraction zone with a selective solvent for aromatic hydrocarbons which, when contacted therewith, is capable of forming an extract phase containing a concentrate of hydrocarbons of relatively high carbon to hydrogen ratios, and a rst raidnate phase containing a concentrate of relatively low carbon to hydrogen ratios, under conditions to produce a ralnate containing between about 30 and 75% of the hydrocarbons of the initial fraction, and a rst extract containing the remainder of the fraction, distilling said irst rafnate to produce a distillate and a distillation residue, flowing said distillate through a second extraction zone countercurrently to a preferential solvent for sulphur compounds, under conditions causing the formation of counterowing second railinate and extract phases, introducing said rst extract in to the second extraction zone at an intermediate point thereof, the conditions within said second extraction zone being such that the distillate washes hydrocarbons from the second extract phase to produce a washed second extract phase containing the preferential solvent, sulphur compounds, and less than about 10% of the hydrycarbons contained in the initial fraction and withdrawing the second ralnate phase and the washed extract phase from the second extraction zone at spaced points.

DONALD S. MCKITIRICK.