US2739102A

US2739102A - Hydrocarbon desulfurization process by reacting the sulfur in the hydrocarbon with an olefin and a catalyst, then extracting the hydrocarbon with so2 and bf3

Info

Publication number: US2739102A
Application number: US368574A
Authority: US
Inventors: Paul N Rylander
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1953-07-17
Filing date: 1953-07-17
Publication date: 1956-03-20
Anticipated expiration: 1973-03-20

Description

March 20, 1956 P. N. RYLANDER 2,739,102

HYDROCARBON DESULFURIZATION PROCESS BY REACTING THE SULFUR IN THE HYDROCARBCN WITH AN OLEFIN AND A CATALYST, THEN EXTRACTING THE HYDROCARBON WITH SO2 AND B175 Filed July 17, 1955 /SEPAHA 70H DRYER DEAE/FA 70H y IN V EN TOR.

F Pau/ N. Ry/ander BY Hwy/@nes Feed HYDRCARBON DESULFURIZATION PROCESS BY REACTING THE SULFUR IN THE HYDRCAR- BGN WITH AN GLEFIN AND A CATALYST, THEN EXTRACTING THE HYDROCARBON WITH S02 AND BF2.

Paul N. Rylander, Chicago, Ill., assignor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application July 17, 1953, Serial No. 368,574

20 Claims. (Cl. 196-30) This invention relates to a process for refining hydrocarbon materials containing one or more undesired impurities, such as coloring matter, malodorous materials and organo-sulfur compounds. More particularly, this invention is concerned with a process for desulfurizing mercaptan and other organo-sulfur compound containing hydrocarbon oils, particularly sour petroleum distillates boiling in the heavier-than-gasoline range.

Patent application Serial Number 248,898, tiled September 29, 1951, now Patent 2,671,047, entitled Refining Hydrocarbon Materials with SO2 and BF3 by Robert C. Arnold and Arthur P. Lien discloses a process for desulfurizing organo-sulfur compound containing hydrocarbon materials by the treatment thereof with an agent consisting of liquid SO2 and BFs. This process gives a markedly greater amount of desulfurization than does an equivalent amount of liquid SO2 alone. Also, this process converts a sour, i. e., mercaptan containing, oil into an oil that is sweet to the doctor test. These improved results are obtained with substantially no increase in the amount of hydrocarbons taken into the extract phase. However, it has been found that the raffinate oil from this process, although of markedly lower organo-sulfur compound content, contains appreciable amounts of freesulfur. The free-sulfur is present in the raffinate oil even though none had been present n the sour oil feed to the process. The presence of free-sulfur in hydrocarbon oils such as naphthas, kerosenes, heater oils, or high solvency naphthas has an extremely bad effect on product quality as determined by the copper strip method.

One object of the present invention is to provide a process for refining and desulfurizing hydrocarbon oils containing organo-sulfur compounds. An additional object is to provide a process for decolorizing hydrocarbon materials, particularly hydrocarbon oils. A specific object of the invention is to provide a process for the treatment of a petroleum distillate containing objectionable amounts of organo-sulfur compounds and mercaptans to produce a product oil of low organo-sulfur compound content and also essentially free of free-sulfur. These and other objects of the invention will become apparent from the following description;

It has been discovered that free-sulfur is not present in the product of the treatment of hydrocarbon material containing organo-sulfur compounds with an agent consisting essentially of liquid SO2 and a promoter selected from the class of Lewis acids (Friedel-Crafts-type halides) l nite States Patent when the hydrocarbon oil is treated to substantially eliminate mercaptans prior to undergoing the liquid SO2-promoter treatment. Thus the combination process of this invention comprises: (1) Treating a hydrocarbon material containing mercaptans and other organo-sulfur compounds to substantially eliminate the mercaptans by treating the oil in the presence of a Friedel-Crafts metal halide catalyst with an olefin in an amount sufficient to substantially eliminate the mercaptans. (2) Contacting said substantially mercaptan-free oil with an agent consisting esl catalyst.

, (3) Separating a raffinate oil of markedly lower organosulfur compound content and essentially free of elemental sulfur from an extract phase comprising agent, sulfur compounds and extract hydrocarbons.

The SO2-promoter process is applicable to various liquid or liquefied hydrocarbon materials which contain organo-Sulfur compounds. Thus it is applicable to various petroleum fractions for the purposes of removing sulfur, gums or other resinous materials, colored impurities and odoriferous compounds. 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. Particularly suitable charging stocks are petroleum distillates boiling in the heavier-than-gasoline range, i. e., between about 330 and 675 F.

This 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 hydrogenation in the presence of sulfur-sensitive catalysts and the like.

In addition the refining agents of the present invention may be applied to the desulfurization and decolorization of sour aromatic hydrocarbon fractions, for example, crude benzols, toluols, Xylols, naphthalene fractions or the like.

The process may also be applied to the refining of various coal tar fractions and coal tar distillates. n In the refning of shale oil fractions the refining agents serve not only to remove organic sulfur compounds from the feed stock, but also to remove oxygen compounds and nitrogen compounds.

It is to-be understood that the above specific examples of charging stocks which may be refined by the present invention are illustrative only and are not intended to limit the field of applicability of the process.

Although the mechanism is not understood, the mercaptans present in the feed oil appear to be the cause of the formation of free-sulfur in the SO2-promoter process. A product oil that is free of free-sulfur can be obtained if the mercaptans are eliminated from the oil.

The sweetening process is believed to involve the reaction of a mercaptau and an olefin in the presence of a Although any olefinic hydrocarbon can be utilized, sterically hindered olefins, such as tetramethylethylene, are not especially suitable. It is preferred to use pylene and butylene.

In general, at least about one `mol of olefin is used per mol of mercaptan present in the sour oil. Somewhat less than this amount may be used, as it is not necessary to produce an oil that is sweet to the doctor test. A substantially sweet oil, i. e., an oil having a mercaptan number below about S, canbe treated by the SO2-promoter process without the introduction of amounts of free-sulfur that can be detected by the reverse doctor test. The presence of olefin in excess of the about 1 mol minimum amount has a beneficial effect on the rate of sweetening. A large excess offolen is undesirable because of the introduction of side reactions, such as polymerization.l

The sweetening process can be carried out at temperatures as low as 60 C. and as high as +50 Low temperatures have an adverse effect on the rate of sweetening. `Elevated temperatures, in the presence of 'I C. Yor higher.Y

very active catalysts such as BFa, introduced undesirable side reactions. It is preferred to operate at about the same temperature as the subsequent SO2-promoter process.

, The rate of sweetening is dependent upon the amount .of olefin, the temperature, the catalyst and the degree ,of agitation. ln general the higher the temperature the ,faster the rate of sweetening. At the preferred condi- ;tions of operation, the sweetening time may be between ,about 5 minutes and 60 minutes. In any event, the ,contacting must be maintained for a time long enough .to substantially sweeten the sour oil feed.

The catalyst for the olefin-mercaptan reaction may be ,any Lewis acid. However, it is preferred to use those .Friedel-Crafts-type halides which are also effective desulfurization promoters for liquid SO2. As little as trace ,amounts of catalyst may be used. In order to increase the rate of sweetening (decrease contact time), it is ,desirable to use more than this amount, for example, .about l mol of catalyst per mol of mercaptan in the sour oil. In some cases, all of the promoter needed in the .SO2-promoter process, may be introduced into the olefinsour oil-catalyst contacting zone. The catalyst may `be different from the promoter but it is preferred to .operate using the same catalyst-promoter in cach proc- ,ess step of the combination process of this invention.

in general, the proportion of liquid sulfur dioxide used .-in the liquid SO2-promoter process varies with 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 miscibiliities being encountered at higher temperatures and lower :miscibilities at lower temperatures. At least a sufiicient amount of sulfur dioxide is used to exceed its solubility in the hydrocarbon material being treated at the par- =ticular treating temperature, thereby forming two dis- =tinct liquid phases, i. e., a predominantly hydrocarbon liquid phase containing a relatively small proportion of dissolved sulfur dioxide or rainate layer and a predominantly sulfur dioxide liquid phase or extract layer. Ordinarily, liquid sulfur dioxide is employed in the process :in amounts between about percent and about 200 percent by volume or more, based on the volume of :hydrocarbon charging stock. Preferably, between about and 75 volume percent of liquid SO2 is used. Y

The sulfur-removing powers of liquid SO2 are remark- -ably enhanced by the addition thereto of a promoter -selected from the class of Lewis acids (Friedel-Crafts- -type halides). Not all the members of the class of compounds known as the Friedel-Crafts-type halides can be -used in this process. Some members are completely ineffective, for example, aluminum triuoride, or are only feebly effective, for example, antimony trichloride, alumi- -num bromide and stannic chloride. A high degree of -solubility in the liquid SO2 is helpful. However, some members of low solubility are good promoters when used in the form of a liquid SO2-promoter slurry, for example, FeCls, HgCiz, and ZnClz. The members of the class which are effective as sulfur removal promoters in liquid SO2 extraction are AlCla, FeCls, TiClt, BFa, HgClz, BCls, and ZnClz. With the exception of BFS these promoters do not appear to give complete sweetening when a sour oil is contacted with the SO2-promoter agent. However, a sufficient amount of sweetening occurs with all the promoters to produce a Vdeleterious amount of freesulfur in the product oil if the sour oil is not sweetened -prior to contacting with the SO2-promoter agent. Because of its solubility in liquidSOz, ease of recovery from the extract phase and superior desulfurization obtained therewith, BFs is preferred.

The amount of promoter employed in the process will usually fall within the range of about 0.5 to about 5 mols per gram atom of sulfur contained in the hydrocarbon charging stock'. The proportions of promoter to sulfur within the above range, when employed with liquid sulfur dioxide, are suflicient not only to effect substantial desulfurization of sulfur-containing hydrocarbon materials but also to effect additional refining, particularly decolorization. For purposes of desulfurization it has been discovered that the optimum desulfurization can be effected by the employment of between about l and about 3 mols of promoter per gram atom of sulfur contained in the hydrocarbon charging stock. (It is to be understood that at least a sufiicient amount of liquid sulfur dioxide to form a liquid phase distinct from the rafiinate hydrocarbon material is also present in the contacting zone.)

The SO2-promoter process may be conducted at temperatures between about -{-l0 C. and 85 C. The preferred temperature range is between about 10 C. -40 C. The optimum temperature will vary not oniy with the type of charging stock but also with the desired product, i. e., maximum-desulfurization and maximum color improvement may require diferent temperatures at otherwise constant conditions of operation.

The SO2-promoter process is conducted under pressure sufficient at least to maintain a substantial proportion of the sulfur dioxide in the liquid state and likewise sufficient at least to maintain a substantial proportion of the gaseous promoters dissolved in the liquid phase. In the presence of liquid sulfur dioxide', BFa forms extremely stable addition compounds with organo-sulfur compounds and, as a result, a substantial proportion of BFS 'which is originally introduced into the refining zone as a gas is rapidly absorbed. The partial pressure of BFH in equilibrium with said BFS-sulfur compound addition compounds is very low at temperatures of 0 C. or less. In general, the SO2-promoter process can be operated at pressures which are commonly encountered in commercial process equipment, for example, between about l and about 30G p. s. i. g., although usually pressures between about l and about l5 p. s. i. g. are sufficient for the present purposes.

The contacting time required in the SO2-promoter process is dependent upon the intimacy of contacting with the refining agent of the hydrocarbon material being tree ed and upon the operating temperature. Ordinarily, the contacting time may be between about l and 6() minutes. The operating temperature will, to some extent, affect 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.

Various diluents, countersolvents or co-solvents can be employed in Yaddition to the 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 co-solvents, particularly benzol with liquid sulfur dioxide, is well known and these co-solvents may find application in the process.

It is possible to heat the total extract phase from the process until substantially all the SO2 has been vaporized off without substantially decomposing the promoter-sulfur compound adduct, if the temperature of the extract phase does not exceed about 50 C. When using BFS as the promoter, the free BFS, i. e., the BFS existing in simple solution in the extract phase, passes off along the gascous SO2. Partial .removal of the SO2 results in the separation of a second rainate layer and the yield of the second raffinate reaches a. maximum when substantially all the SO2 has been removed. vVhen substantially all the SO2 has been removed from the iirst extract phase, the second raffinate consists essentially of all the aromatic hydrocarbons extracted from the feed stock and some 4sulfur compounds, as evidenced by the sulfur content thereof; and the secondiextract phase consists sub- 'mixed butylenes.

stantially of an adduct of promoter and sulfur compounds. The amount of SO2 present in the second extract phase may vary from about 1 to about 15 volume percent depending upon the temperature at which the first extract phase was heated in order to remove SO2 and free BFa. The sulfur content of the aromatic hydrocarbon containing second ratlinate obtained by this SO2 removal technique is less than the sulfur content of the total extract materials; and may be in some cases as low as 0.1 weight percent.

When the extract phase is treated so as toy remove substantially ail the SO2, the second extract material appears to consist essentially of organo-sulfur compounds. Treatment of a West Texas heater oil containing 0.6 weight percent sulfur with 2 mols of BFS per mol of sulfur dissolved in 25 volume percent of liquid SO2, separation of the resultant extract phase, removal of the SO2 and free BFS 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 SO2-promoter 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 effecting the alkylation of'isoparaftinic hydrocarbons with olens in the presence of liquid acid catalysts. It should be understood that the specific equipment forms no part of the present invention and that any equipment adaptable for the purposes of contacting the refining agent with the hydrocarbon charging stock yand thereafter separating spent refining agent from the refined charging stock can be employed for the purposes of the invention. Y

The invention is illustrated by one embodiment shown in the annexed drawing which forms a part of this specification. The feed stock to the process is a heater oil derived by distlation from West Texas crude. This feed boils between 375 and 560 F. and has a mercaptan number of 90. The feed should be HzS-free and lherein the HzS has been removed by washing with a dilute aqueous caustic solution. Other methods of removing H25 may be used.

The feed is passed from source 11 by way of line 12 into line 13. The olens in this illustration are refinery The butylenes from source 16 are passed by way of line 17 into line i3. Herein 1 mol of butylenes is added per mol of mercaptans in the feed. The combined streams are passed by way of line 13 into dryer 19.

Dryer 19 may comprise conventional equipment and drying reagents, for example, a vessel packed with calcium chloride, excelsior, ber glass, magnesium silicate drying agents (Florisil), alumina gei or the like. Drying of the oil canralso be effected by distillation, for example, Vacuum distillation prior to the addition of a dry butylene stream. Y

It' should 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 BFa to form hydrates, which complicates the recovery of BF3, and since the corrosive tendencies of the SO2-promoter agent tend to increase with increasing water concentration in the refining system.

The dried stream is passed through line 2i into deaeration equipment Z2 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 procd esses of liquid sulfur dioxide refining of hydrocarbon oils can be employed. The deaerated oil is passed through line 23 into heat exchanger 24 wherein the temperature of the stream is adjusted to the desired sweetening temperature.

The temperature of the butylene-feed stream is reduced to 20 C. by means of exchanger 24. The cooled stream is passed by way of line 26 into reactor 27. Reactor 27 herein is a vertical vessel designed to give intimate contacting of a gas and a liquid. Other methods of contacting may be employed.

BFS is introduced by way of line 23 into reactor near the point of butylene-feed entry. Herein about 1 mol of BFs per gram atom of sulfur present in the feed is ernployed. The BFB-butyIene-feed is maintained at about 20 C. in reactor Z7 for about 15 minutes.

A substantially sweet oil is withdrawn from the top ot reactor 27 and is passed by way of line 29 into heat exchanger 31..

If desired, the viscosity of the oil may be reduced by dilution with a saturated hydrocarbon such as n-pentane, isopentane, n-octane, petroleum ether, methylcyclcpentane, cyclohexane or the like. Diluent from source 33 may be introduced by way of valved line 3d into line 29. No diluent is used in this embodiment.

The substantially sweet oil is adjusted to a temperature of 20 C. in exchanger 31 and is then introduced by way of line 36 into the lower portion of extraction tower 37.v The extractor may be packed with suitable corrosionresistant packing materials to increase the efficiency .of contacting of the charging stock and refining agents. For example, the extractor can be packed with structural carbon in the form ot Berl saddles, glass or porcelain spheres, Monel metal fragments, mild carbon steel jack chain or the like, or may be provided with mechanicallyor magnetically-actuated agitators.

In extractor 37 the oil is contacted with liquid sulfur dioxide and BFa. If desired the combined reagents may be introduced into the upper portion of extractor 37 from storage drum 38 through line 39. Alternatively, liquid sulfur dioxide alone may be introduced through line 39 and BFa may be introduced into the extraction zone from source 41 by way of valved line t2 and manifold. 43.

Contacting in extractor 37 is effected at a temperature of 20 C. and at a pressure of about 50 p. s. i. g. rthe amount of liquid sulfur dioxide introduced into extractor 37 is 70 percent by volume, based on the volume of oil. The amount of BF3 is 2.5 mols per gram atom of sulfur contained in the oil. Extractor 37 may be operated rainate-rich or extract-rich; the latter mode of operation is preferred. The contacting time in extractor 37 is about 10 minutes.

The rafnate phase is withdrawn fromthe upper end of extractor 37 through line 46 into stripping tower 47 which-is provided with internal reboiler 43. Stripper e7 may be unpacked or may optionally contain bubble trays, packing materials or other fractionating devices. Retatively small amounts of liquid S02 and BF which have been occluded in the raiinate are vaporized in stripper 47 and are withdrawn through line 49 for reuse. Product oil is withdrawn through line 5l. to storage not shown.

Further treatment of the product oil may be desired,

for example, treatment with concentrated sulfuric acid or with selective solvents, alkali treatment, clay treatment, water washing or other refining treatment. If diluent has been used, this may be removed'by distillation.

kThe extract phase is withdrawn from the lower portion of extractor 37 through line 52 for treatment to separate extract materials and the components of the agent, respectively. Herein the extract phase is passed from line 52 into stripper 53 which is provided with internal reboiler 54. Stripper 53 is similar in construction to stripper 47. The extract phase is subjected to a sutliciently high temperature in stripper S3 to vaporize essentially its entire content of sulfur dioxide and BFS. Such temperatures fall within the range of about 50 C. to about 250 C. Sufficient pressure must be maintained in stripper 53 to prevent vaporization of the lower boiling portions of the extract. The sulfur dioxide and BF3 are passed overhead frorn stripper 53 by way of line 56.

Stripped extract is withdrawn from stripper 53 and is passed to storage not shown by way of line 58. A portion of the extract may be recycled by Way of valved line 59 to a lower point of extractor 37 as a reflux stream.

The SO2 and BFs are passed from line 56 through valved line 61 and line 62 into purification zone 63. Here non-condensible gases, HzS, etc. are removed by means well known to the liquid SO2 extraction art. The purified SO2 and BF3 are passed into line 66 where they meet the material from line 49 and the combined stream is passed by way of condenser 67 and line 68 in storage drum 38.

Makeup SO2 from source 71 is passed by line 72 into storage drum 38.

When the stream in line 56 contains little or no HzS, the purification zone may be by-passcd and the SO2 and BF3 passed by way of valved line 74 directly to line 66.

.lt is desirable from time to time to dehydrate at least a portion of the stream passing through line 56. A part of this stream is passed by way of valved line 76 into dehydrator 77 which is provided with internal reboiler 7S. Dehydrated SO2 and EP3 are withdrawn overhead through line 81 and are passed by way of line 62 to puritication zone 63. A liquid bottoms fraction comprising water, sulfur dioxide and BF3 hydrates is withdrawn from the limer portion of dehydrator 77 by way of line 83 for discharge from the system.

Some BF-.z and seme gaseous SO2 are withdrawn from drum 38 and are passed through line 86 in gas-liquid separator S7. BFa, free of SO2, is passed from separator by way of lines S3 and 23 to reactor 27. Liquid SO2 is passed from separator 87 by way of line 89 back to drum 38.

Makeup BF?. may be introduced from source 41 by way of valved line 91 into line 2S and/ or by way of valved line 92 in line 39.

The extract may be subjected to various refining operations. For example, it can be given a catalytic hydrotining treatment, employing a conventional catalyst, e. g., cobalt molybdate, and conventional operating conditions. rl'he extract is 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 weight percent.

Numerous pumps, valves, heat exchangers and other engineering details have been omitted from the combined operation in the interests of simplifying the description. Common engineering process expedients, particularly those which have heretofore been employed in processes of refining hydrocarbon oils with liquid sulfur dioxide will readily suggest themselves to those skilled in the art; it is to be understood that such engineering expedients are within the purview of the present invention.

The results obtainable with the process of this invention are illustrated by the following comparative experiments. The charging stock used in all the experiments below was a West Texas virgin heater oil distillate, characterized as follows:

API 40 Sulfur (total), wt. percent 0.56 Mercaptan number 57.1 Color, Saybolt 16 Free suli'ur None ASTM Distillation, F.:

Initial 332 10% 390 50% 446 90% 502 Max. 565

The extraction procedure consisted of adding liquid sulfur dioxide to oil contained in a reactor provided with a cooling jacket and mechanical agitator. The temperature of the reactor contents was maintained at 20 C. When used, BFS was metered into the reactor and the reactor was closed. At this point a pressure of from l0 to 100 p. s. i. g., due largely to BFa, prevailed in the reactor, but when agitation was started, the pressure fell rapidly to about 0 p. s. i. g. Agitation was continued for 20 minutes at 20 C. followed by a 30-minute settling period to furnish ample time for the extract and raflinate phases to separate. The extract phase was drawn ofr at the bottom of the reactor and the rafiinate phase was washed with water and then with 10% caustic. Finally the raffinate was again washed with water and dried.

Run 1 In this run the feed was contacted with liquid SO2 alone (50 volume percent of liquid SO2). The oil from the raffinate phase was sour to the doctor test. About onehalf of the mercaptans has been removed by the extraction. A reverse doctor test indicated that the product oil contained no free-sulfur.

Run 2 In this run 400 ml. of sour oil, 200 ml. of liquid SO2 and 8.0 g. of BFg were charged to the reactor. The product oil had a total sulfur content of 0.17 weight percent 69% reduction in sulfur content) and was sweet to the doctor test. However, the product oil had a free-sulfur content of 14 milligrams per 100 ml. of oil.

Run 3 The conditions of this run were identical with those of Run 2 except that 40 g. of diisobutylene were also added to the reactor. The product oil had a total sulfur content of 0.08 weight percent (86% reduction in sulfur content) and was doctor sweet. The free-sulfur content was 4 mg. per 100 ml. of oil.

Run 4 In the rst step, 400 ml. of sour oil, 8.5 g. of BF3 and 21.0 g. of propylene were charged to the reactor. The contents were agitated at -20 C. for l hour. A sample was withdrawn and tested for mercaptan content; the oil was doctor sweet.

in the second step, 200 ml. of liquid SO2 was added to the reactor containing the sweet oil, BFs and some propylene. The contents were treated according to the extraction procedure above. The product oil was doctor sweet and contained no free-sulfur, as determined by the reverse doctor test.

These runs show that the presence of free-sulfur can be avoided if the mercaptan containing oil is first rendered substantially doctor sweet prior to treatment with liquid :G2- B133 agent. l

. Thus having described the invention, what lSI l. A process for retining a mercaptan-containing hydrocarbon oil, which process comprises (l) contacting said oil with at least an effective amount of an oleinic hydrocarbon, in the presence of at least a catalytic amount of a Eriedel-Crafts-type halide, for a time at least sutiicient to render said oil substantially mercaptan-free, (2) contacting said substantially mercaptan-frec oil with an agent consisting essentially of liquid SO2 and a promoter, wherein the liquid SO2 is present in an amount at least suicient to form an extract phase and the promoter is selected from the class of Friedel-Crafts balides consisting ot' AlCls, FeCls, TiCli, B133, HgClz, BCla and ZnClz at a temperature below about -l-l0 C. and (3) separating a refined ratiinate containing essentially no freesuii'ur from an extract phase.

2. The process of claim l wherein at least about l mol ot olefin is present per mol of mercaptan in said oil.

3. The process oi claim l wherein said mercaptan t is claimed 9 elimination process is carried out at a temperature below about +50 C.

4. The process of claim 3 r. herein said olen is propylene.

5. The process of claim 1 wherein said olefin is disobutylene.

6. The process of claim l wherein said olen is a butylene.

7. The process of claim 1 wherein said catalyst is BFs.

8. The process of claim 1 wherein said catalyst is AlCls.

9. The process of claim 1 wherein said catalyst is FeCls.

l0. A process for rening a hydrocarbon oil containing mercaptans and other organo-sulfur compounds, which process comprises (1) contacting said oil with at least about 1 mol of olefinic hydrocarbons per mol of mercaptan in said oil, in the presence of at least a catalytic amount of a Friedel-Crafts halide selected from the class consisting of AlCl3, FeCls, TiCl4, BF2., HgClz, BCla and ZnClz, at a temperature between about -60 and +50 C. for a time sutcient to render said oil substantially doctor sweet, (2) contacting the substantially sweet oil from step (l) with an agent consisting essentially of liquid SO2, in an amount between about 15 and 200 volume percent based on oil, and a promoter selected from the class of Friedel-Crafts halides consisting of AlCls, FeClx, TiCl-i, BFa, HgClz, BC13 and ZnClz, in an amount between about 0.5 and 5 mols per gram atom of sulfur in the oil, at a temperature between about and -40 C., (3) separating a raiinate phase from an extract phase, and (4) recovering a product oil markedly reduced in organo-sulfur compound content and containing essentially no free-sulfur as measured by the reverse doctor test from said rafnate phase.

11. The process of claim 10 wherein said hydrocarbon oil is a petroleum distillate boiling in the heavier-thangasoline range.

12. The process of claim 10 wherein said promoter is BFS and the BFs is'present in an amount between about 1 and 3 mols per gram atom of sulfur in the oil.

13. The process of claim 10 wherein the oil from step` (1) has a mercaptan number below about 5.

14. The process of claim 10 wherein said catalyst is present in an amount of about 1 mol per mol of mercaptan.

15. The process of claim l0 wherein the temperature of step (l) is substantially the same as the temperature in step (2).

16. The process of claim 10 where the catalyst of step (l) is the promoter of step (2). p

17. The process of claim 16 wherein the promoter is BFa.

18. A process for refining a sour petroleum distillate boiling in the heavier-than-gasoline range which also contains other organo-sulfur compounds, which process comprises 1) contacting said distillate with at least 1 m01 of a lower molecular weight olen per mol of mercaptans in said distillate, in the presence of between about 1 and 3 mols of BFa per gram atom of sulfur in said distillate, at a temperature between about --l0 and -40 C. for a time suicient to reduce the mercaptan number of said distillate to below about 5, (2) contacting the substantially sweet oil with between about 25 and 75 volume percent, based on said oil, of liquid SO2 and between about 1 and 3 mols of BFS per gram atom of sulfur in said oil, at a temperature between about 10 and -40 C. for a time sulcient to effect a substantial amount of desulfurization, 3) separating a raffinate phase from an extract phase, and (4) recovering from said ratlinate .phase a sweet oil containing essentially no freesulfur.

19. The process of claim 18 wherein said olefin is propylene.

20. The process of claim 18 wherein said oletn is disobutylene.

References Cited in the le of this patent UNITED STATES PATENTS 2,560,330 Brandon Jury 1o, 1951 2,646,390 Arnold er a1 July 21, 1953 2,671,046 Arnold et al. Mar. 2, 1954

Claims

1. A PROCESS FOR REFINING A MERCAPTAN-CONTAINING HYDROCARBON OIL, WHICH PROCESS COMPRISES (1) CONTACTING SAID OIL WITH AT LEAST AN EFFECTIVE AMOUNT OF AN OLEFINIC HYDROCARBON, IN THE PRESENCE OF AT LEAST A CATALYTIC AMOUNT OF A FRIEDEL-CRAFTS-TYPE HALIDE, FOR A TIME AT LEAST SUFFICIENT TO RENDER SAID OIL SUBSTANTIALLY MERCAPTAN-FREE, (2) CONTACTING SAID SUBSTANTIALLY MERCAPTAN-FREE OIL WITH AN AGENT CONSISTING ESSENTIALLY OF LIQUID SO2 AND A PROMOTER, WHEREIN THE LIQUID SO2 IS PRESENT IN AN AMOUNT AT LEAST