US2671047A

US2671047A - Refining hydrocarbon materials with so2 and bf3

Info

Publication number: US2671047A
Application number: US248898A
Authority: US
Inventors: Robert C Arnold; Arthur P Lien
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1951-09-29
Filing date: 1951-09-29
Publication date: 1954-03-02
Anticipated expiration: 1971-03-02

Description

March 1954 R. c. ARNOLD ET AL REFINING HYDROCARBON MATERIALS WITH S0 AND BE;

2 Sheets-Sheet 1 Filed Sept. 29, 1951 Y s motcEEq 5& UPCXM h m EDEUCUE m d M t N m m W 0 i T hm \.VV H\mm. W AM L T L E55 m C.P. QM A wm \NN n .M H m. mm R .A 6

Y i B Q a 3 S S lLXr v 5 m m w mfiqmm mfi W H H 0 W I I .IXT NH\ M W a a M I. 3 3 ILXT @935 M w H u... H NW m P Q 1.2L 2 ON NW @m x m n? {N zotufitxm P MT mv March 1954 R. c. ARNOLD ET AL REFINING HYDROCARBON MATERIALS wiTH 50 AND BF I Filed Sept. 29, 1951 2 Sheets-Sheet 2 AWN w MOLS BF /GRAM ATOM OF SULFUR 0 0 O a 5 w a ZQEQN E31 SWMQ N INVENTORS: Roberf 0. Arnold Arthur P. Lienm 4 9% ATTORNEY Patented Mar. 2, 1954 REFINING HYDROCARBON MATERIALS WITH S02 AND BE;

Robert 0. Arnold, Park Forest, 111., and Arthur P. Lien, Highland, 1nd., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana Application September 29, 1951, Serial No. 248,898

14 Claims.

This invention relates to a process for refining organic materials containing one or more undesired impurities, such as coloring matter, malodorous materials, and sulfur or sulfur compounds. More particularly, this invention is concerned with a process for refining, and especially for desulfurizing, hydrocarbon materials such as sulfur-containing hydrocarbon oils, e. g. petroleum oil fractions.

One object of the present invention is to provide a process for refining and desulfurizing hydrocarbon materials containing sulfur and/or organic sulfur compounds. Another object of our invention is to provide a process for substantially deodorizing sour or mercaptan-containing hydrocarbon materials. An additional object is to provide a process for decolorizing hydrocarbon materials, particularly hydrocarbon oils. Still another object of our invention is to provide novel mixtures of chemical compounds characterized by a remarkably specific and selective interaction with organic sulfur compounds. These and other objects of our invention will become apparent from the ensuing description thereof.

The problems of refining hydrocarbon materials, particularly of decolorizing, deodorizing and desulfurizing said materials, have assumed increasing importance in the petroleum, coal derivatives and synthetic fuel industries. Attempts have heretofore been made to utilize the refining properties of BFa alone and in combination with various complex compounds of BFs and oxygenated organic compounds, such as ethers, esters and carboxylic acids, as set forth in U. S. Patent 2,495,851 of Arthur P. Lien and Bernard L. Evering, issued January 31, 1950. Although free BF3 in combination with complexes of BF3 and various oxygenated organic compounds has substantial utility for desulfurizing hydrocarbon oils, both the extent of desulfurization and selectivity of these combination solvents heretofore known has left something to be desired.

Briefly, we have made the surprising discovery that mixtures of BF3 and liquid sulfur dioxide exhibit a remarkable refining capacity for hydrocarbon materials containing sulfur or organic sulfur compounds and/or coloring impurities and/or odoriferous materials, particularly mercaptans. Especially remarkable is the ability of mixtures of BF3 and liquid sulfur dioxide to combine selectively with organic sulfur compounds contained in hydrocarbon oils, thereby producing solutions of said sulfur compounds in the BFa-liquid sulfur dioxide mixtures, which solutions are substantially insoluble in the resultant refined hydrocarbon oils at the refining temperatures which are employed in our process. We have discovered that refining agents comprising essentially BF3 and liquid sulfur dioxide are characterized by an unexpectedly high desulfurization capacity for hydrocarbon voils as compared with either reagent or the expected sum of their individual desulfurization capacities; moreover, that the combined refining agents exert this unexpectedly increased desulfurization capacity without exhibiting a substantially greater dearomatization capacity than liquid sulfur dioxide alone. As a result, the combined BFz-liquid sulfur dioxide treating agent of the present invention leads to extensive desulfurization of sulfur-containing hydrocarbon materials at surprisingly high raffinate yields.

In one particularly desirable aspect, our invention comprises contacting a hydrocarbon oil which is to be refined with a mixture of BF3 and liquid sulfur dioxide, said mixture being present in an amount sufficient to form a distinct liquid phase upon settling, and thereafter effecting stratification of the contacting mixture into a liquid layer comprising predominantly refined hydrocarbon oil, or raflinate, and a second, immiscible layer comprising predominantly a solution or chemical combination of BFs, liquid sulfur dioxide and impurities derived from the hydrocarbon oil charging stock, or extract.

The proportion of liquid sulfur dioxide, based on the hydrocarbon material being refined, can be varied between about 15 and about 200 volume percent, more or less, depending upon the specific hydrocarbon material being treated and the treating conditions, especially the temperature. The relative miscibility of liquid sulfur dioxide and hydrocarbon charging stocks varies with temperature, greater mutual miscibilities in general being encountered at higher temperatures and lower miscibilities at lower temperatures. In general we employ at least a sufficient amount of sulfur dioxide to exceed its solubility in the hydrocarbon material being treated at the treating temperature, thereby forming two distinct liquid phases, viz. a predominantly hydrocarbon liquid phase containing a relatively small proportion of dissolved sulfur dioxide and a predominantly sulfur dioxide liquid phase or extract layer. Ordinarily, liquid sulfur dioxide is employed in our process in amounts between about 25 percent and about 100 per cent by volume, based on the volume of hydrocarbon charging stock.

The amount of BF3 employed in our process will usually fall within the range of about 0.5 to about mols of BFa per gram atom of sulfur contained in the hydrocarbon charging stock. As will be shown hereinafter, proportions of BFa to sulfur within the above range, when employed with liquid sulfur dioxide, are suiiicient not only to eifect substantial desulfurization of sulfur-containing hydrocarbon materials but also to effect additional refining, particularly decolorization. For purposes of desulfurization We have discovered the unexpected fact that optimum desulfurization can be eiiected by the employment of between about 1 and about 3 mols of BF3 per gram atom of sulfur contained in the hydrocarbon charging stock, employing in addition a sufficient proportion of liquid sulfur dioxide to form a liquid phase distinct from the rafiinate hydrocarbon material.

The present refining process may be conduct-ed at temperatures of C. or less, e. g., within the range of about 0 C. to about 85 C. Usually we employ temperatures between about 10 C. and about 50 C. In any given instance, bearing in mind a specific object of the refining process, it is readily possible to determine both the absolute and economically optimum temperatures by means of relatively few tests and standard engineering calculations.

The present refining process is conducted under pressure sufficient at least to maintain a substantial proportion of the sulfur dioxide in the liquid phase and likewise sufficient at least tomaintain a substantial proportion of the BFa in the liquid phase in the presence of sulfur compounds. We have discovered that in the presence of liquid sulfur dioxide, BFs forms extremely stable addition compounds with sulfur compounds such as are frequently encountered in petroleum oils and, as a result, a substantial proportion of B35 which is originally introduced into the refining zone as a gas is rapidly absorbed. The partial pressure of BF; in equilibrium with said BFa-sulfur compound addition compounds is very low at temperatures of 0 C. or less. In general, the present process can be operated at pressures which are commonly encountered in commercial process equipment, for example between about 1 and about 300 p. s. i. g., although usually pressures between about 1 and about p. s. i. g. are sufiicient for the present purposes.

The time period required in the present refining process will be dependent, naturally, upon the intimacy of contacting with the refining agent of the hydrocarbon material being treated and upon the operating temperature. Ordinarily, the time period is selected between about and about 30 minutes. The operating temperature will, to some extent, afiect the intimacy of contacting by determining the liquid viscosities in the refining system and, probably to a more important extent, by determining the rate of interaction of sulfur compounds and other impurities in the feed stock with the refining agent. Although the present process has been referred to as a refining or extraction process, there is reason to believe that the actual mechanism of refining in the present process is a chemical or quasichemical union of organic sulfur compounds, colored impurities and the like with the chemically reactive BFs-litgnid sulfur dioxide refining agent. Interand intra-molecular conversions of sulfur compounds, especially of mercaptans,

also occur as shown by doctor-sweet rafifinates and extracts. Doctor-sweet products may even be obtained without diphasic separation.

Various diluents, countersolvents or co-solvents can be employed in the present process in addition to the SO2BF3 refining agent. Especially in the case of viscous or relatively high pour point hydrocarbon charging stocks it may be desirable to dilute said charging stocks with diluents or countersolvents such as liquefied propane, butanes, pentanes, hexanes, saturated naphthas or the like. The use of various cosolvents, particularly benzol with liquid sulfur dioxide, is well-known and these co-solvents may find application in the process of the present invention.

The present refining process is applicable to various liquid or liquefied hydrocarbon materials. Thus, it is applicable to various petroleum fractions for the purposes of removing sulfur, gums or other resinous materials, colorecl impurities and odoriferous compounds, particularly mercapt-ans. Suitable petroleum feed stocks may comprise light naphtha fractions, gasolines, heavy naphthas, kerosenes, transformer oils, heater oils, furnace oils, diesel fuels, gas oils, lube oils and crude oils. The present refining process can be applied for the purpose of desulfurizing various petroleum stocks which are to be subsequently treated in refining or conversion operations in which sulfur or sulfur compounds are undesirable, for example, catalytic cracking operations, catalytic reforming operations, catalytic hydroforming operations, catalytic hydro genation in the presence of sulfur-sensitive catalysts and the like.

In addition, the BFa-liquid sulfur dioxide refining agents of the present invention may be applied to the desulfurization and decolorization of aromatic hydrocarbon fractions, for example crude benzols, toluls, xylols, naphthalene fractions or the like.

The present process may also be applied to the refining of various coal tar fractions and coal tar distillates. In the refining of shale oil fractions the present refining agents serve not only to remove organic sulfur compounds from the feed stock, but also to remove oxygen compounds and nitrogen compounds. It should be understood that the above specific examples of charging stocks which may be refined in accordance with the present invention are illustrative only and are not intended to limit the field of applicability of the process of the present invention.

We have found that it is possible to heatv the total extract phase from our process until substantially all the S02 has been vaporized ofi without substantially decomposing the BFs-suifur compound adduct, if the temperature of the extract phase does not exceed about 50 C. The free BFs, i. e. the BF3 existing in simple solution in the extract phase, passes off along with the gaseous S02. We have found that partial removal of the S02 will result in the separation of a second raffinate layer and the yield of the second raihnate reaches a maximum whensubstantially all the S02 and free BFs have been removed. When substantially all the S02 and free BFz have been removed from the. first extract phaee, the second rairinate consists essentially of all the aromatic hydrocarbons extracted from the feed stock and some sulfur compounds, as evidenced by the sulfur content thereof; and" the second extract phase consists of an adduct of BFs and sulfur compounds and some S02 con- When the extract phase is treated so as to-re- 7 move substantially all the S02 and free BFs,-'the second extract material appears to consist essentially of organo sulfur compounds. Treatment of a West Texas heater oil containing 0.6wt. per cent sulfur with 2 mols of BFa Der mol of-sulfur dissolved in 25 volume percent of liquid S02, separation of the resultant extract phase and removal of the S02 and free BF: from the extract phase at about 25 C. gave a second extract material with a sulfur content of 12.1%. The second raffinate consisted of aromatic hydrocarbons and enough organo sulfur compounds to give a sulfur content of 4%.

The present process can be carried out in batch, continuous or semi-continuous operating cycles, and in one or more stages, employing'contacting and separation equipment such as has heretofore been employed in the selective solvent refining of petroleum lubricating oil stocks or in efiecting the alkylation of isoparafiinic hydrocarbons with-olefins in the presence of liquid acid catalysts. It should be understood that the specific equipment employed forms no part of the present invention and that any equipment adaptable for the purposes of contacting the-BFa-liquid sulfur dioxide refining agent with the hydrocarbon charging stock and thereafter separating spent refining agent from the refined charging stock can be employed for the purposes of the invention.

In order more fully to describe one specific embodiment of our invention, reference is made to Figure 1. The feed stock, for example a sulfurbearing hydrocarbon material such as a West Texas virgin'heater oil'derived from distillation of a West Texas crude oil, is passed through valved line I0 into a drying zone ll wherein it is substantially dehydrated. Drying zone I I may comprise conventional equipment and drying reagents and may, for example, take the form of a vessel packed with calcium chloride, excelsior, fiber glass, magnesium silicate drying agents (Florisil), alumina gel or the like. Drying of the charging stock can also be effectedbydistillation, for example vacuumdistillation. Itshould be understood that the specific drying treatment forms no part of the present invention and that any drying treatment may be used which substantially eliminates water from the charging stock. The presence of water in the charging stock and in the treating system is extremely undesirable since water combines with BF: to form hydrates, which complicates the recovery of BF3, and since the corrosive tendencies of the present BFz-sulfur dioxide refining agent tend to increase with increasing water concentration in the refining system.

The dried charging stock is passed through line 12 into deaeration equipment [3 wherein air dissolved in or entrained in the charging stock is substantially removed. The specific deaeration process and equipment form no part of the present invention. Vacuum deaeration equipment such as is ordinarily employed in commercial 6. processes of liquid sulfur dioxide refining of hydrocarbon oils can be employed.v The deaerated charging stock is passed through line l4- into heat exchanger l5 wherein the temperature of the stock is'lowered to the desired treating temperature. r

If desired, the viscosity of the hydrocarbon charging stock can be reduced by dilution with a saturated hydrocarbon such as n-pentane, isopentane, n-octane, petroleum ether,'methylcyclopentane, cyclohexane or the like which may be introduced into line l4 through valved lin 16.

The hydrocarbon charging stock thus pretreat-' edis introduced into the lower portion of refining or extraction tower IT. The extraction tower may :be packed with suitable corrosion-resistant packing materials to increase the efficiency of contacting of the charging stock and refining agents. be packed with structural carbon in the form of Berl saddles, glass or porcelain spheres, Monel metal fragments, mild carbon steel jack chain or the like, or may be provided with mechanically or magnetically-actuated agitators.

In tower I! the hydrocarbon charging stock is contacted with liquid sulfur dioxide and BF3. If desired the combined reagents may be introduced into the upper portion of tower I! through valved line 18 leading from storage drum I9. Alternatively, liquid sulfur dioxide alone may be introduced through line l8 and BF3 may be introduced into the extraction zone through valved line 20 and manifold 2|.

I Contacting in extraction tower I! may, for example, be effected at temperatures between about -10 and about -40 C. at pressures between about 0 and about p. s, i. g. The amount of liquid sulfur dioxide introduced into tower I! may, for example, be between about 25 and about 100 percent by volume, based on th volume of hydrocarbon charging stock and the amount of BFs may, for example, be between about 1 and about 3 mols per gram atom of sulfur contained in the hydrocarbon charging stock. Tower I! may be operated raffinate-rich or extract-rich but we prefer the latter mode of operation. Meniscus 22 is shown in Figure 1 as the separation boundary between a lower liquid extract phase and a supernatant liquid raffinate phase comprising predominantly refined hydrocarbon stock. The contacting period in tower I! can be varied between about and about 30 minutes and may, for example, be about 5 minutes. j

Rafiinate is withdrawn from the upper end of tower I] through line 23 into stripping tower 24 communicating at its lowest end with a reboiler 25. Tower 24 may be unpacked or may optionally contain bubble trays, packing materials or other fractionating devices. Raflinate is controllably withdrawn from the lower end of tower 24 through reboiler '25 and recycled to tower 24 to maintain temperatures therein within the desired range.- Relatively small amounts of liquid S02 and BFa which have been occluded in the raffinate are vaporized in tower 24, usually at temperatures between about 30 C. and about C. and withdrawn through line 26 for reuse. Stripped raifinate is withdrawn through valved line 21 for removal from the process or for such further treatment as may be desired, for example treatment with concentrated sulfuric acid or with selective solvents, redistillation to separate diluent which was introduced through valved line I6, alkali treatment, clay treatment, water washing or other refining treatment.

For example, the extraction tower can Extractis withdrawn from the lower portion of extraction tower I! through valved. line 28. for treatment to separate extract materials and the components of the refining reagent, respectively. In one mode of operation theextract layeris passed from line 28 into stripping tower 29, which may be unpacked or which may be provided with packing or fractionating materials such as bubble cap plates. Tower 29 is provided with a reboiler 39 through which liquid materials from the lower end of the tower are controllably circulated to maintain a desired temperature within the tower. The extract layer may be subjected to a sufficiently high temperature in tower 29 tovaporize substantially its entire content of sulfur dioxide and. 133%. Such temperatures fall within the range of about 50 C; to about 250 C. Sufficient pressure must be maintained in tower 29 to prevent vaporization of the lower boiling portions of the extract. The sulfur dioxide-and BF-sv pass overhead from tower 29 through line 3| thence through valved line 32, through purification equipment schematically illustrated. by 33, thence through line 34, compressor 35 and condenser 3.6 into pressure storage vessel Hi. When the gas stream passing through valved line 32 contains little or nohydrogen sulfide, it may be passed around purification equipment 33 through valved" by-pass line 3?. Stripped extract materials are withdrawn from the lower end of tower 29 through

lines

38 and 39. V

In another mode of operation, separation of the extract layer is effected in two stages. In the two-stage method of separating the extract layer,

said layer is subjected in the first stage to relati'vely low temperature to effect vaporization of free sulfur dioxide and 3E3, which can be circulated after compression and cooling to extraction zo ne ll without requiring purification; the liquid residue of the first stage extract layer treatment is then subjected to a higher temperature to efiect decomposition of BF: adducts with sulfur compounds and aromatic hydrocarbons, containing more or less sulfur dioxide. The high temperature extract treating stage results in some decomposition of sulfur compounds to form hydrogen sulfide and, as a consequence it is desirable separately to treat the gas stream derived from the second stage extract treatment to remove hydroaen sulfide therefrom prior to 'liquefaction and recirculation of said stream for reuse in extraction tower H. The boiling points of sulfur dioxide, hydrogen sulfide and boron trifluoridelie sufiicientlyfar apart to permit their ready separation by fractional liquefactionmethods.

In the two-stage method of extract layer treatment, the first stage of treatment can be effected in tower 29, wherein it is desirable tomaintain temperatures between about 20 C'. and about 50 C. and pressures between about 1- and about 100 p. s. i. g. in order to prevent vaporization of. the lower boiling portions of the extract. The partially stripped extract layer is then withdrawn from the lower end of tower 29 through line 33, thence through valved line 48 into tower 4| communicating with reboiler 42. Tower M is suitably maintained at a temperature between about 80 C. and about 250 C. and a pressure between about 1 and about 100- p. s. i. g. The gases evolved in tower 4| usually contain, in addition to 13F:- and sulfur dioxide, more or less hydrogen sulfide which is produced by partial thermal decomposi' tion of sulfur compounds in tower 4|. Gases are taken overhead from tower A l through valved line 8'. 3 and can berecycled, in part, through. line 45 into: heat exchanger 46 and. dehydrator 41., and, in? part, through line 49 to extraction tower ll. Stripped'extract materials are withdrawn from the. lower end of tower 4| through valved line 44'.

It is desirable from: time to time to withdraw at least a portion of. the stream passing through

lines

31 and 43 through valved line 25 and heat exchanger 46 into a dehydrating tower 47 provided; with reboiler 48 and its accompanying circuit. Suitable conditions are maintained in tower 4? to withdraw S02 and BFa as gases overhead through line 59 for recycle to extraction zone I1. A liquid. bottoms fraction comprising water, sulfur dioxide andv BF3 hydrates is withdrawn from the lower portion of. tower 11-1 through reboiler 48,. whence an aliquot portion. is withdrawn from. time to time through valved line 58' for discharge from the system.

Stripped extract materials from lines 39 and #4- can be recirculated in part, optionally after dilution with a diluent such as a parafiinic naphtha, to the lower portionof extraction tower ll to serve as a backwash. The employment of a back.- washing operation increases the selectivity of the extraction operation in tower H, particularly increasing the selectivity of the extraction operationfor sulfur compounds as compared with. aromatic hydrocarbons. The extent of backwash may vary from between about 5 to about 25 percent. by volume of the hydrocarbon charge entering the lower portion of tower l'l At least a portion of the extract materials passing through lines 39 and 46 can be subjected to various desired refining after-treatments; For example, a portion of the extract materials. can be subjected to catalytic hydrofin-ing treatment, employing a conventional catalyst, e, g.,, cobalt molybdate, and conventional operatingcondi-tions These extract materials are a surprisingly good feed to a catalytic cracking operation; a high yield of very high octane gasoline is obtained, which gasoline has the remarkably low sulfur content of less than 0.1 wt. percent.

When a maximum yield of low sulfur rafiinate oil is desired without regard to the'presence of aromatic hydrocarbons therein, our-process can be carried out inthe following manner. The ex.- tract phase passes from extraction tower it through line 28 into stripper 29'. In stripper 2% pressor 35 and condenser 36 into storage ves=- sel 19.

The extract phase denuded of S02 and BFa passes out of stripper 29 through line 38 and line 6i into settler 52. In settler 6 2 the denuded extract phase. separates. into a second ralfinate phase and a second extract. phase. The second extract phase passes out of settler 2 t'l'lrouglzr line 64- and line 48 into stripper M The second extract phase which consists chiefly or organo sulfur compounds, BF3. and some S0: is decomposed in stripper M by being heatedto a. temperature between about '75 and 250 C. under a. pressure sufiicient to keep the lower boilin portions of. said second extract in the liquid state.

9 The products of the decomposition of the second extract phase pass overhead through valve line 43 or line 45 for treatment as previously described. The bottoms from tower 41 pass out through line 44 to storage not shown. The second extract material consists essentially of organo sulfur compounds. 7 7 I The second raffinate phase passes out of settler 62 through line 66 and may be recycled back to extraction tower I! by way of valved line 51.

The second rafiinate phase consists substantially y 7 caustic.

of aromatic hydrocarbons and some organo sulfur compounds. When this material is introduced into the initial extraction tower either at a low point in the tower or along with the feed stock, the sulfur content thereof is extracted and passes out of the tower in the extract phase; a

terials pass through line 65 and; 69- into stripper H, which stripper is provided with a reboiler I2.

In stripper II the BFs'and S02 dissolved in the second rafiinate are removed and pass overhead through line 13 to zone 33 for purification or through line H to line 45' for further purification. From the bottom of stripper H through line 16 the second rafinate materials pass to storage not shown. Dependent upon the feed stock and th conditions of operation of the extraction tower 11, this material consists of aromatic hydrocarbons and some organo sulfur compounds. The sulfur content of the bottoms from stripper 1| may vary from 0.1 wt. per cent to some amount less than the sulfur content of the total extract material from the initial extraction operation.

Numerouspumps, valves, heat exchangers and other engineering details have been omitted from Figure 1 in the interests of simplifying the descript on of the invention. Common engineering process expedients, particularly those which have heretofore been employed in processes of refining hydrocarbon oils with liquid sulfur dioxide will, no doubt, suggest themselves to those skilled in the art and it should be understood that such engineering expedients are within thepurview of the present invention. The following specific examples are supplied in the interests of illustrating but not unduly limiting the present invention. The table, below, presents data obtained in runs which are illustrative of the present invention. The charging stock was a West Texas virgin heater oil having the following inspections: ASTM distillation Per cent S-0.'73 IBP=332 F. n 1.4585 10%:390" F. API gravity=40.2

(sp. gr. (BO/60 F.)=0.8241) 50%=446F. Color Saybolt=+l3 90%=502 F. Mercaptan number=5'7.4 max.=548- F.

The extraction procedure consisted of adding the indicated amount of liquid sulfur dioxide to 500 cc. of oil contained in a reactor provided with a cooling jacket and mechanical agitator. The temperature of the reactor contents was maintained at -20 C. except in Runs 14 and 15 in which temperatures of 35 C. and 0 0., respectively, were employed. The indicated amount 10"? of BFa was metered into the reactor and the reactor was closed. At this point a pressure of from 10 to p. s. i. g., due largely to BF3, prevailed in the reactor, but when agitation was started, the pressure fell rapidly to about 0 p. s. i. g. Agitation'was continued for. 5 minutes, followed by a 30-minute settling period to furnish ample time for the extract and raffinate phases to separate. The extract phase was drawn off at the bottom of the reactor and the rafiinate phase was washed with water and then with 10% Finally the rafiinate was again washed with water and dried.

The following factors have been developed to indicate the selectivity of the refining process for sulfur compounds and aromatic hydrocarbons. respectively:

Sulfur selectivity factor: [(Percent S in feed) (Percent S in rafiinate)-] lOi (Percent S in feed)(100V. percent rafiina'teljj which is equivalent to (Percent desulfurization Aromatic selectivity factor= l v H U [(n feed) (11. rafiinate)]. 10 v I (11 feed) (12 aromaticfree feed)] [IOU-V. percent raffinate] which is the substantial equivalent of' W (100-V. percent rafiinate) i It was found that complete dearomatization' of the feed stock ,with silica gel resulted in ajr'e fractive index of 1.4391 as compared withjthe initialrefractiveindexof1.4585. The runs set forth in the table were obtained by the'treatment. of the

heater oilw'ith

25, 50 and IOU-volume percent, respectively, of liquid sulfur dioxide, with and withoutthe addi!- tion of BF3 in the amounts. indicated; the re-'- sultantdesulfurization, dearornatization and raffinate yield values were determined. The percentage ofv desulfurization asa function..iof-BF3 and sulfur. dioxide concentration is presented in Figure 2, except for Runs 14 and 15. It will readily be apparent from thetable and-Figure 2 that the addition of BF to liquid S02 greatly increases the extent of desulfurization which is obtainable. The addition of BF to liquid sulfur dioxide results in a. verysharp increase, in desulfurization of the charging stock up to the point at which about 2 mols of BFs per. gram atom of sulfur contained in the heater oil charg-I- ing stock have been'added and thereafter the-extent of desulfurization increasesveryl-little. In the case of this particular heateroill (specific gravity, 0.8241; sulfur content, 0,73 weightpercent) 2 mols of BF3 per gram atom of,,sulf ur corresponds to about 9 pounds of BFs per-.42; gallon barrelof heater oil- It will furtherbe notedfthat the large and unexpected, increase in desulfurization effected byfth'e addition .of .BFs to liquid sulfur dioxide was obtainedw-ithout-sub stantialdecrcasein the yield of raffinate obtained by sulfur dioxidetreatment alone-" Thus, itwill be apparent from the runs. set forth in the table that. with decreased raffinateyields in the range of only 1 to 3, percent, .very large andun expected increases of desulfurization were readily obtained, as will be noted, for example, by come I! parison of

Runs

1 and 2, Runs 4 and 6, or Runs 10 and 12. It will further 'be noted that the percenta-ge of dearomatization is essentially determined by the liquid sulfur dioxide concentration in the treating zone, being but little affected by thecddition of even large molar excesses .of boron fluoride as will be apparent, for example, by the vapor pressure of BFa, indicating complex formation. Surprisingly, liquid sulfur dioxide, which is apparently structurally similar to the dimethylsulfolane, does not form a complex with BFs. The extent of desulfurization obtained in this experiment is about what would be expected from BA-dimethylsulfolane alone.

TABLE Extraction of West Texas mrgm heater Oll wzth SO2BF3 Ralfinate IerccntS Percent Percent Sulfur Aromatic D u 4 Run g M y t us (Lamp Dcsulfuri- Dearoma- Selectivity Selectivity gw atom of S 6:23 Method) zation tization Factor Factor Gamma 13-13011 25 96 l. 4533 0. 550 25 26. 8 620 670 0. 93 25 1. 7 94 1. 4529 0. 193 .74 28.8 1, 230 480 .157 25 3.8 94 1.4528 0.154 79 -29.4 1,320 490 2.69 50 0 91 1. 4501 0. 420 43 43. 2 470 480 '1 50 0.78 89 l. 4496 0. 274 G3 45. l 570 4l0 1.4 50 1.7 '88 1.4498 0.149 80 44. 4 660 37.0 1-8 50 2. 2 90 1. 4497 0. 123 83 45. 0 840 450 1.84 50 3. 8 88 1. 4498 0. 105 86 44. 4 710 37.0 1. 9. 50 6. 7 38 1.4494 0. 100 87 46. 8 720 390 1,..8 100 0 86 1. 4470 0. 311 58 58. 8 410 420 0.99 100 0.53 v85 1. 4463 0.218 70 63.0 470 420 1. 11 100 2.0 85 1. 4468 0. 102 .86 50.0 580 400 1. 13 1.0 2:3 35 1. 4460 0. 072 90 64. 5 600 430 1. 40 1 50 2. 0 90 l. 4498 0. 106 86 45. 0 850 450 1.121 1 50 2.0 90 l. 4516 0. 164 78 35.0 780 350 2. 23

1 Temp, 35 C. Temp, 0 6.

comparison of Runs 4 and 9. It appears from RUN 16 the data in the table that the extent of sulfur extraction is much greater than could be expected from a knowledge of the individual desulfurization capacities of sulfur dioxide and BFa. A comparison of Run 14 with

Runs

6 and 7 which are comparable but were effected at 20 C. as compared with the -35 C. temperature .of R411 14, shows that somewhat increased desulfurization at high raffinate yield was obtained by using the lowered temperature. on the other hand. increasing the temperature to 20 .C. in Run 15 resulted in a somewhat reduced extent of deufurization as compared with operations at c. as in Runs 6 and .7.

Although not indicated in the table. the color of sulfur dioxide-BR raffinates is generally very good, ranging from to Saybolt (from +13 of feed). The only runs which failed to produce a good colored rafiinate were those made at very high BFa treats. .6 to 8 111018 BFs per gram atom of sulfur. and the run made at 0 C. (Rim :15). Also not shown in the table is the effect of sulfur dioxide-BE: on mercaptan extras. tlon. It was observed that Doctor sweet raffinates were obtained when the amount of BFs was equivalent to at least .2 mols per mol of sulfur. Lesser amounts of BFs gave slightly sour prod- Ho as determined by the standard Doctor test. When the West Texas virgin heater oil was treated at 20 with BFa alone. in the proportion of 2.3!. mols per gram atom of sulfur contained in the oil. a sludge was produced, which was filtered from the refined oil. Analysis showed that only .19 percent desulfurization was attained. Repetition of the BE: treatment in the presence of 1 volume of hexane per. volume of oil, showed that no phase separation could be obtained and no ludge form d; analysis of the oil thus treated failed to reveal any desuliurization whatever.

When the West Texas virgin heater oil was treated at 20 .C. with 3,4-dimethvlsu1folane and 2 mols 33% per gram atom of sulfur in the feed, only 21% desulfurization and a raifinate yield of '9'! volume percent of feed were observed. The dimethylsulfolane markedly reduces the The charging stock was a light catalytically cracked cycle .oil or gas oil containing 1.45 weight percent sulfur and having a refractive index (1%) of 1.5003. Extraction of this oil with 50 percent by volume of sulfur dioxide at -20 C. yielded 65 percent by volume of a railinate containing 0.59 weight percent sulfur .and havin a refractive index of 1.4695. Extraction of the charging stock with 50 percent by volume of liquid sulfur dioxide and 1.9 mols BFs per gram atom of sulfur likewise yielded 65 percent of raflinate but the sulfur content thereof was reduced to 0.45 weight percent and the refractive index was increased to 1.4705. Thus, the inclusion of BF: in the refining agent increased the desulfurization of the charging stock from 59 percent to 69 per cent without loss of ramnate yield and resulted in a more highly aromatic raflinate than the proc-- ess employing liquid sulfur dioxide alone as the refining agent.

RUN 17 The charging stool; was a naphtha obtained by distilling petroleum oils to coke, containing 0.66 weight percent of sulfur. Extraction of this stock with 50 percent by volume of liquid sulfur dioxide yielded percent by volume of railinate containing 0.413 weight percent of sulfur. Extraction of the charging stock with 50 percent by volume of liquid sulfur dioxide and 2.5 mols BFs per gram atom. of sulfur yielded the same proportion of rafiinate having the reduced sulfur content of 0.344 weight percent. Thus, the inclusion of BF: in the refining agent increased desulfurization of the charging stock from 37 to 48 percent without reduction in the proportion of rafiinate.

While certain specific applications of the process of the present invention have been described above, it will be appreciated that numerous other applications of the present refining process can be made. As an example, th present process may be applied to rafiinates from conventional liquid sulfur dioxide extraction processes which are known to contain residual sulfur compounds.

Moreover, the present process can be applied to extracts of conventional liquid sulfur dioxide refining processes, preferably in the following manher. The liquid sulfur dioxide extract phase is partially stripped of sulfur dioxide. Although suflicient sulfur dioxide may be retained to maintain a homogeneous liquid phase at temperatures between about 25 C. and about 40 C., it is preferred to regulate sulfur dioxide removal to the point where two liquid phases just begin to appear at the temperatures indicated. The liquid bottoms from this stripping operation are then contacted with BE; in amounts between about 0.5 and about 4, preferably about 1.5 to about 2.5 mols, per gram atom of sulfur present in the extract material, whereupon a substantial proportion of the aromatic hydrocarbons in said extract material is thrown out of solution and may be separated as a supernatant phase. If desired, during the BE; contacting operation, a non-aromatic hydrocarbon stream boiling outside the range of the organic material of the liquid sulfur dioxide extract phase can be introduced as a countersolvent in order to increase the selectivity of aromatic separation from extract materials. The sulfur dioxide-BFs-sulfur compound secondary extract which is produced by the BF3 contact ing operation can be stripped to remove BE: and sulfur dioxide and a high sulfur concentrate can be withdrawn from the process.

It will also be apparent that the refining process of the present invention can be applied to a wide variety of aromatic and sulfur-containing materials, for example extracts obtained by known solvent extraction processes, for example processes for the selective extraction of hydrocarbon oils with organic solvents such as furfural, nitromethane, dimethyl formamide, methanol and the like, or with inorganic solvents such as SbClz, liquid hydrogen fluoride, etc.

It will be apparent from the discoveries underlying our refinin process that the recovery of BF3 from its mixtures with other gases, e. g.,

hydrocarbon gases, can be readily effected by selectively absorbing it in a liquid mixture of sulfur dioxide and a sulfur compound, e. g., a dialkyl sulfide, or in sulfur-containing sulfur dioxide extracts.

This is a continuation in part of our co-pending application, No. 182,613, filed August 31, 1950, now abandoned.

We claim:

1. A process for refining a hydrocarbon material, which process comprises contacting said hydrocarbon material with liquid sulfur dioxide in an amount in excess of its solubility in said hydrocarbon material under the conditions of said contacting and with BFa at a temperature between about C. and about 85 C. under a pressure sufficient at least to maintain the liquid phase, and thereafter separating a refined hydrocarbon material and an extract solution in liquid sulfur dioxide and B193.

2. A process for desulfurizing a sulfur-containing hydrocarbon material, which process comprises contacting said hydrocarbon material with liquid sulfur dioxide in an amount in excess of its solubility in said hydrocarbon material under the conditions of said contacting and with BF: in an amount between about 0.5 and about 5 mols per gram atom of sulfur contained in said hydrocarbon material at a temperature between about 0 C. and about 85 C. under a pressure sufficient at least to maintain the liquid phase, and thereafter separating a substantially desulfurized hydrocarbon material and an extract solution of 14 sulfur compounds in liquid sulfur dioxide and BFa.

3. A process for desulfurizing a sulfur-containing hydrocarbon material, which process comprises contacting said hydrocarbon material with between about 15 and about 200 percent by volume of liquid sulfur dioxide and with BE; in an amount between about 1 and about 3 mols per gram atom of sulfur contained in said hydrocarbon material at a temperature between about 0 C. and about C. under a pressure sufiloient at least to maintain the liquid phase, and thereafter separating a substantially desulfurized hydrocarbon material and an extract solution of sulfur compounds in liquid sulfur dioxide and BFa.

4. The process of claim 3 wherein about 2 mols of BF3 are employed per gram atom of sulfur contained in said hydrocarbon material and the temperature is between about 10 C. and about -50 C.

5. The process of claim 3 wherein said hydrocarbon material is a naphtha.

6. The process of claim 4 wherein said hydrocarbon material is a kerosene.

7. The process of claim 4 wherein said hydrocarbon material is a heater oil.

8. The process of claim 4 wherein said hydrocarbon material is a furnace oil.

9. The process of claim 4 wherein said hydrocarbon material is a gas oil.

10. A process for the selective desulfurization of a hydrocarbon material containing both organic sulfur compounds and aromatic hydrocarbons which process comprises contacting said hydrocarbon material with between about 15 and about 200 percent by volume of liquid sulfur dioxide and with BFs in an amount between about 1 and about 3 mols per gram atom of sulfur contained in said hydrocarbon material at a temperature between about -10 C. and about 50 C. under a pressure suflicient at least to maintain the liquid phase, and thereafter separating a substantially desulfurized hydrocarbon material containing aromatic hydrocarbons and an extract solution of organic sulfur compounds and aromatic hydrocarbons in liquid sulfur dioxide and BFx, said extract solution being characterized by a ratio of organic sulfur compounds to aromatic hydrocarbons between about 1.5 and about 2.5.

11. A process for refining a hydrocarbon oil containing organic-sulfur compounds, which process comprises contacting said oil in the liquid phase, at a temperature below about +10 C., with liquid sulfur dioxide in an amount at least sufiicient to form distinct extract and raffinate phases and in the presence of sufficient BF3 to form complexes, and thereafter separating a raffinate phase containing a refined hydrocarbon oil from the extract phase containing said complexes.

12. The process of claim 11 which includes further steps of removing sufiicient BFs and S02 from the extract phase to effect separation thereof into a second raflinate phase and a second extract phase which consists predominantly of organo-sulfur compounds, and separating said phases from each other.

13. The process of claim 12 wherein a portion of said second rafilnate phase is recycled to said contacting step.

14. In the process of refining a hydrocarbon material containing organo-sulfur compounds and aromatic hydrocarbons by contacting said hydrocarbon material with liquid SO: in an amount in excess of its solubility in said hydrocarbon material under the conditions oi said contacting and with BFs in an amount between about 0.5 and about 5 mols per gram atom of sulfur contained in said hydrocarbon material at a temperature between about 0 C. and about -85 C. under a pressure suflicient at least to maintain the liquid phase and thereafter separating a rafiinate phase consisting of a hydrocarbon material with a lower organo-sulfur compound content and an extract phase consisting of .organo-sulfur compounds adducted with BFa, S02, free BE; and aromatic hydrocarbons, the improvement wherein said extract phase is treated to remove free BF: and S02 in order to obtain References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,069,329 Roelfsema Feb.2, 1937 2,495,851 Lienet 'et a1 Jan. 31, 1950

Claims

1. A PROCESS FOR REFINING A HYDROCARBON MATERIAL, WHICH PROCESS COMPRISES CONTACTING SAID HYDROCARBON MATERIAL WITH LIQUID SULFUR DIOXIDE IN AN AMOUNT IN EXCESS OF ITS SOLUBILITY IN SAID HYDROCARBON MATERIAL UNDER THE CONDITIONS OF SAID CONTACTING AND WITH BF3 AT A TEMPERATURE BETWEEN ABOUT 0* C. AND ABOUT -85* C. UNDER A PRESSURE SUFFICIENT AT LEAST TO MAINTAIN THE LIQUID PHASE, AND THEREAFTER SEPARATING A REFINED HYDROCABON MATERIAL AND AN EXTRACT SOLUTION IN LIQUID SULFUR DIOXIDE AND BF3.

3. A PROCESS FOR DESULFURIZING A SULFUR-CONTAINING HYDROCARBON MATERIAL, WHICH PROCESS COMPRISES CONTACTING SAID HYDROCARBON MATERIAL WITH BETWEEN ABOUT 15 AND ABOUT 200 PERCENT BY VOLUME OF LIQUID SULFUR DIOXIDE AND WITH BF3 IN AN AMOUNT BETWEEN ABOUT 1 AND ABOUT 3 MOLS PER GRAM ATOM OF SULFUR CONTAINED IN SAID HYDROCARBON MATERIAL AT A TEMPERATURE BETWEEN ABOUT 0* C. AND ABOUT -85* C. UNDER A PRESSURE SUFFICIENT AT LEAST TO MAINTAIN THE LIQUID PHASE, AND THEREAFTER SEPARATING A SUBSTANTIALLY DESULFURIZED HYDROCARBON MATERIAL AND AN EXTRACT SOLUTION OF SULFUR COMPOUNDS IN LIQUID SULFUR DIOXIDE AND BF3.