US2143405A - Method for purifying mercaptan oils - Google Patents

Description

Jan. 10, 1939.

.|.VA. CAMPBELL. JR., Er A1.

IETHOD FOR PURIFYING MERGAPTAN OILS lll' mkg

N om la A Filed Sept. 25, 1933 IMPM/11p@ g:

Qww Hmmm um .M5956 rma Jan. 1o, 1939 METHOD FOR. PUBIFYING MEBCAPTAN OILS Joseph A. Campbell, Jr., Manhattan Beach, and

Theodore Merle Phillips, Lomlta, Calif., assignorl to Union Oil Company of California. Los Angeles, Calif., a corporation of California.

Application September 25, 1933, Serial No. 690,866

20 Claims. (Ci. 196-29) This invention relates to the rening' of petroleum, particularly the removal of mercaptans from hydrocarbon oils such as petroleum distillate.

The object of the invention is to provide a simple and emcient procedure for the elimination or conversion of mercaptans in connection with the refining of gasoline and the like, whereby the well known doctor sweetening procedure may be avoided.

Briefly the invention comprises the addition of elementary sulfur to a distillate to be treated and the treatment of the distillate with caustic soda or other equivalent alkaline solution in the presence of 4the sulfur. The invention includes also the subsequent step oi revivifying the separated' used caustic solution to prepare it for further use, by treatment of the caustic with additional quantities of elementary sulfur for removal or conversion of accumulated materials which hinder or entirely inhibit its further effectiveness. The invention also includes a third step employed under some conditions of treating the sulfureted caustic solution where it has been in service for a long period of time with a small amount of litharge, thereby again rejuvenating and preparing the caustic solution for further use. This addition of small amounts of litharge speeds up the rate of reaction of the sulfureted caustic solution.

Considering the process in greater detail, the treatment according to this invention ordinarily follows acid treatment of the distillate (e. g. gasoline) according'to any usual or preferred procedure. In conducting the operation where a mercaptan-containing distillate is being treated, a quantity of gasoline (preferably nished gasoline) is passed through a sulfur cone in order that the gasoline may dissolve a desired quantity oi elementary sulfur, such as iiowers of sulfur. The gasoline so sulfureted may be introduced into the distillate reilning system at any one of several points. For example it may be introduced into the distillate feed to the acid treater and be carried on through the acid treating and subsequent water washing system. Or the sulfureted gasoline may be introduced to the acid treated distillate after all or part of the sludge has been separated and before water wash. Or the sulfureted gasoline may be introduced after the water wash either before the washed distillate has been passed to a caustic wash or as it is being passed to the caustic wash. In any one of these instances the treated distillatel containing elementary sulfur added through the medium of the sulfureted gasoline (or other sulfureted distillate as the case may be) is passed to the caustic wash so that the caustic treatment of the acldtreated distillate takes place in the presence of the added elementary sulfur. According to this treatment a complete conversion or removal of the mercaptans is eiected, enough elementary sulfur having been employed for the respective distillate to accomplish this result.

Referring to the accompanying drawing, ,and having reference to gasoline as the raw distillate being treated, the row gasoline feed is supplied to the system through the line IIJ, acid being supplied through the line I2. The acidulated gasoline is passed through a mixer I3 and through solution settling towers I4 according to any well known procedure. the acid treated gasoline being then water-washed as at tanks I5 and pumped thence to the caustic washing and settling tank I6, and if desired to a caustic settling. tank l1. The various solutions are withdrawn from the various tanks asindicated, the `caustic solution being recirculated through the caustic storage tank I8. Finished gasoline is withdrawn from the settling tank I'l, and a portion of this is bypassed to the sulfur cone 2U wherein the desired solution of elementary sulfur takes place. From the sulfur cone the sulfureted finished gasoline is pumped to the raw gasoline being treated through any one of a plurality of supply lines 2l,

22, 23 as indicated, or to any other point of introduction between the feed line I0 and the point of injection of the gasoline being treated into the caustic washing tank I6. Satisfactory treatment is obtained when the sulfureted finished gasoline stream is supplied to any one of the indicated points. Preferably, however, the sulfureted gasoline is supplied after the Water-wash and may be rst commingled with the recirculated caustic solution which is pumped by way of line 2li to the stream of gasoline being treated just prior to the passage through the mixing coil 25 leading to the tank I6.

The above described caustic treat in the presence of elementary sulfur accomplishes an almost complete conversion of the mercaptan sulfur so that the iinished gasoline leaving the caustic settling tank Il is sweet to the doctor test. No plumbite or litharge in any form is required to effect this conversion. The caustic solution It has been found satisfactory also to .treat mercaptan-containing gasolines and similar light petroleum distillates without any previoim or subsequent acid treat, the present treatment being adequate for elimination or conversion of the mercaptans. v l

It is to be observed that other points of intro-v duction of the sulfureted gasoline to the gasoline being treated may include supplying the sulfureted finished gasoline to the treated gasoline stream after mingling of the caustic solution with the feed gasoline, as through line 30. Similarly, various other points of introduction may be selected with satisfactory results.

The caustic soda solution after separation from the treated distillate may be re-used as long as it is effective. VAfter a time however the caustic solution takes up a sufficient quantity of inhibiting materials to materially interfere with or completely check its effectiveness. When this condition occurs the interfering materials may be converted or removed by contacting the alkaline solution directly with additional quantities of elementary sulfur.- Thereupon the caustic solution so rejuvenated may be further re-used.

In some instances it has been found that where ,the sulfureted caustic solution has been in service for a long period of time, being continuously re-used in connection with the above described rejuvenation by the addition of elementary sulfur to the solution, such old solution becomes so affected that satisfactory rejuvenation by means of elementary sulfur is not accomplished. v It has been found that under these conditions the life of the solution may be further prolonged by the addition of a small quantity of litharge to the sulfureted caustic solution. Such, addition of litharge has also been found to conserve the amount of the old caustic solution that must be employed. It is to be understood however that up to this point no litharge in the form of plumbite or otherwise is to be used, only the sulfur being used in conjunction with the caustic.

In connection with the addition of the elementary sulfur to the mercaptan-bearing distillate to be treated, it is preferred that the suliurv be added to the distillate after acid treat and after a water wash following acid treat, although the other points of introduction have been found to be satisfactory at least under many conditions. While the use of sulfureted gasoline has been indicated above asbeing the method by which the sulfur is introduced, it is obvious that other known or preferred means of effecting the sulfur admixture may be employed satisfactorily. In connection with the rejuvenation of the caustic solution, it is not necessary that the solution be continuously re-used until it becomes largely or entirely ineffective. Instead, sulfur may be continuously added to the caustic solution supply tank. Likewise after this solution becomes quite old and it becomes necessary to add litharge, or if it is desired to increase the rate of reaction of the caustic solution, this litharge may be continuously added to the supply tank I8 in the very small quantities necessary to produce the desired results. This addition of small amounts of litharge, although far below the range necessary for the doctor treat of the distillate,

speeds up the rate of reaction of vthe fresh or sulfureted caustic solution to which the litharge has been added.

`The quantities of sulfur to be added to the dis'- tillate'being treated, or to be added to the reused caustic solution, and the quantities of lith- Aamamos arge later to be added to the caustic solution which has been in service for a long period of time, may be readily determined by those skilled in the art, and will depend to a considerable extent upon the nature of the distillate being treated, and also to some extentupon the character and effectiveness of the preceding 'acid treat. Again where the treatment here described is ernployed independently of any acid treat and-upon a.distillate which has not 4been acid treated, the quantities will again vary. However as a specinc example the following is given: A cracked gasoline distillate containing 0.035% mercaptans, after being passed through an acid treater and washed with water, was combined with a stream of finished sulfureted gasoline which had been contacted in a sulfur cone to dissolve 0.52% of elementary sulfur, the sulfureted gasoline being fed at a rate to supply 0.65 of a unit of elementary sulfur per unit of mercaptan sulfur in the distillate. 'I'he treated distillate so sulfureted was then passed to an ordinary caustic washing and settling apparatus from which the finished gasoline was withdrawn.l The settled caustic solution was continuously recirculated through the system by way of its supply tank, which contained large quantities of elementary sulfur.

It should be understood in connection with the foregoing that where particular reference has been had to the treatment of gasoline using sulfureted gasoline toaid the elementary sulfur, obviously other distillates may be so treated, and the procedure, such as points of addition may be varied in any obvious or desirable manner so long as the desired results may-be obtained. Simpotassium hydroxide or mixtures of sodium hydroxide may be employed as an equivalent. Thus potassium hydroxide or mixtures of sodium hydroxide and hydrated lime may be employed, or hydrated lime alone were so used as to be effective.

We claim:

1. A method for purifying mercaptan oils comprising contacting a quantity of mercaptan-bearing hydrocarbon oil with elementary sulfurand caustic alkali solution free from litharge to convert the mercaptans, removing the treated oil, contacting the resultant caustic lsolution with elementary sulfur and using the caustic solution so sulfureted for treatment of further quantities of such mercaptan-bearing oils.

2. A method according to claim 1 comprising the additional steps of treating further quantities of oil until the effectiveness of the sulfureted caustic solution becomes impaired, contacting such impaired solution with litharge to improve its effectiveness, and employing the so treated caustic solution for treatment of furtherquantities of said mercaptan-bearing oils.

3. A method for refining petroleum distillates comprising acid treating a mercaptan-bearing distillate, contacting the acid treated distillate with caustic solution, in the presence of elementary sulfur free from and in the absence of litharge, separating the treated distillate from caustic, contacting the separated caustic solution with additional elementary sulfur to restore the effectiveness of the caustic solution,. and continuously re-using the solution.

4. A method for refining petroleum distillates comprising acid treating a mercaptan-bearing distillate, contacting the acid treated distillate with caustic solution, in the presence of elementary sulfur initially free from and in the absence of litharge, separating the treated disanimos tillate from the caustic solution, rejuvenating the separated caustic solution by the addition o! elementary sulfur to restore its eectiveness, reusing the rejuvenated solution until sulfur rejuvenation becomes inadequate, contacting such re-used solution with litharge to improve the eectiveness of the solution, and using the litharge treated solution for further treatment of the mercaptan-bearing distillates.

5. A method of purifying mercaptan-bearing hydrocarbon oils comprising contacting the oils with elementary sulfur and caustic solution initially free from litharge to convert the mercaptans, removing the treated oil, contacting the thus separated caustic solution with additional elementary sulfur, contacting the resultant sulfureted caustic solution with litharge to improve the effectiveness of the solution, and using the caustic solution so sultureted and revivified for treatment of further-quantities, of such mercaptan-bearing oils.

6. A continuous cyclic process for purifying mercaptan-bearing petroleum distillates which comprises acid treating said mercaptan-bearing distillates, contacting said acid treated distillate with caustic soda solution in the presence of sulfur free from and in the absence of litharge, separating the caustic solution and the puriiied petroleum distillates, revivifying the said separated caustic solution by the addition of elementary. sulfur thereto and continuously returning the so revlvifled solution for treatment oi further amounts of -mercaptan-bearing petroleum distillates.

7. A cyclic process for purifying mercaptanbearing petroleum distillates comprising acid `treating said distillates, contacting the acid treated distillate with caustic soda solution in the presence of elementary sulfur initially free from and in the absence of litharge, separating the puried distillates from the caustic soda solution, reactivating the separated caustic soda solution by the addition of elementary sulfur thereto,.contacting the reactivated caustic solution with additional distillate until sulfur addition becomes inadequate, separating the last mentioned distillate from such spent caustic solution, adding to such separated spent caustic solution a quantity of litharge to reactivate further the aforesaid caustic soda solution and sulfur, and continuously returning the reactivated reagent for treatment o! further amounts of mercaptan-bearing petroleum distillates.

8. A continuous cyclic process for purifying mercaptanbearing hydrocarbon oils which comprises contacting said oils with elementary sulfur and aqueous caustic solution initially free from litharge to convert the mercaptans, remov- V ing the puriled oil, contacting the resultant separated caustic solution which has become inactive due to the presence of materials rasen up from the hydrocarbon oil with elementary sulfur to. reactivate the solution, treating further quantities of mercaptan-bearing oil with said reactivated solution, separating the last mentioned oil from the spent previously reactivated caustic solution, subsequently contacting said spent caustic solution with litharge in an amount substantially below that required to form a doctor solution but sulcient to reviviiy the aforesaid caustic solution, and continuously returning the so revivified solution for treatment of further amounts of mercaptan-bearing hydrocarbon oils.

9. A continuous cyclic process for refining mercaptan-bearing petroleum distillates which comprises adding eiementary sulfur to a partially spent solution of sodium hydroxide and sulfur tree from litharge which has been contacted with a mercaptan-bearing petroleum distillate, and treating further amounts of said-petroleum distillates with the solution obtained by the aforesaid addition oi elementary sulfur.

10. A process for revivifying a partially spent solution oi sodium hydroxide and sulfur tree from litharge which has been previously used in reiining mercaptan-bearing petroleum distillates comprising adding elementary sulfur to said solution in an amount sumcient to restore activity to the treating reagent.

11. A process according to claim l0 comprising the additional step of adding litharge in an amount substantially below that required to obtain a doctor solution to the solution of caustic soda and sulfur at a time when, after continued reuse oi.' the said suliurized caustic solution, the addition of elementary sulfur is no longer adequate in revivifying the said solution and treating further quantities of such distillates therewith.

12. A continuous cyclic process ior refining mercaptan-bearing petroleum distillates which comprises initially subjecting such distillates to the action of an aqueous caustic solution and elementary sulfur sumcient to render the solution active and in the absence oi litharge, separating the spent caustic' solution from the treated distillate, adding further sulfur to the separated spent caustic solution to regenerate the solution, then treating further quantities ot distillate with the regenerated solution, separating' the treated distillate therefrom, then adding to such separated spent caustic solution a quantity of litharge in an amount less than that required to produce a doctor 'solution thereby activating said spent caustic solution, and then treating further quantities of distillate therewith.

13. A continuous process for purifying mercaptan-bearing petroleum distillates which comprises effecting solution o! elementary sulfur in the distillate, treating the thus sulfurized distillate with a caustic alkali solution in the absence of litharge, thereby converting the mercaptans, said solution of sulfur in the oil being effected apart from any sulfur content of the caustic solution, removing the treated oil from the resultant caustic solution, introducing elementary sulfur into the resultant caustic solution and using such sulfur-treated caustic solution to treat further quantities of said mercaptan-bearing distillate containing elementary sulfur in solution.

14. A continuous process for treating mercaptan-bearing petroleum distillates which comprises dissolving a quantity of elementary sulfur in a petroleum distillate, commingling said solution with a mercaptan-bearing petroleum distillate to sulfurize the latter, treating the thus sulfurized mercaptan-bearing petroleum distillate with a caustic alkali solution in the absence of litharge, thereby converting the mercaptans, removing the treated distillate from the resultant caustic solution, introducing elementary sulfur into the resultant separated caustic solution to regenerate the latter, and using such regenerated sulfur-treated caustic solution to treat further quantities of said sulfurized mercaptan-bearing petroleum distillate.

15. A continuous process according to claim 13 wherein the solution of elementary sulfur in the mercaptan-bearing distillate is eilected prior to addition of the caustic solution to the distillate.

-16. In the sweetcning of 'mercaptan-bcaring hydrocarbon distillates with caustic soda and sulfur. the method oi' regenerating the caustic soda solution for repeated re-use which includles.I the step oi adding sulfur thereto, in the absenceof distillate to be sweetened, prior to reuse-oi the solution.

17. In the sweetening o! mercaptan-bearing hydrocarbon distillates with caustic soda and sulfur, the method o! regenerating the caustic soda solution for repeated re-use which includes the step of adding sulfur thereto-in the absence of distillate to be sweetened. prior to the re-use of the solution until the` solution can no longer be regenerated by the addition of sulfur only, and then regenerating the solution for further reuse by adding litharge thereto in the absence of distillate to be sweetened.

18. A cyclic process for reilning mercaptanbearing petroleum distillates which comprises adding velementary sulfur to a partially spent solution oi' sodium hydroxide free from litharge which has previously been contacted with a mercaptan-bearing petroleum distillate in the presence'of sulfur, and without removing reaction products treating further amounts of said petroleum distillates with the resultant solution obtained by said sulfur addition.

19. A method according to claim 18 wherein patent No. 2.115,1;05.

lamentan sulfur u dass w um petroleum sistillate before treatment with said caustic solution.

20. A continuous process for purifying mercaptan-bearing petroleum distillata which comprises etlecting solution of elementary sulfur in the distillate,'initially treating the thus sulfur-v ized distillate with a caustic alkali solution in the absence ot litharge, thereby converting the mercaptans, saidsolution of sulfur in the oil being elected apart from any sulfur content oi' the caustic solution, removing the treated oil from the resultant caustic solution. introducing elementary sulfur into the resultant caustic solution and using such sulfur-treated caustic solution to treat further quantities oi.' said mercaptanbearing distillate `containing elementary sulfur in solution, then treating successive quantities of the sulfurized mercaptan-bearing distillate with said sulfurized caustic solution until said caustic alkali solution becomes inetllcient, then regenerating such caustic alkali solution by the addition of small quantities oi' litharge insuillcient to form doctor solution, and treating additional successive quantities of said sulfurized mercaptan-bearing petroleum distillate with said litharge-treated caustic solution.

JOSEPH A. CAMPBELL, Jn. THEODQRE MERLE PHILLIPS.

January 1959 JOSEPH A. CAMPBELL, JR., ET AL.

It is nerebyertified 'that error appears 1n' the printed specification of thef'above numbered patent requiring correction as follows: Page 1, second column, line 15., for the word "row" read raw; page 2, second column, line 56, strike out "potassium hydroxide or mixtures of and insert' instead the syllable and words `iler-ily any caustic solution otherv than; page 5, first column, line 71,-l claim', before "`caustic"" insert spent; and that the said Letters Patent should be read with this correction therein that the same may conform to therecord of the case in the Patent Office.

signed and sealed this 21st day of Merch., A. D. 1939.

(Seal') Henry Van Arsdale. y

Acting Commissioner of Patents.

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