US2798842A

US2798842A - Sweetening hydrocarbon oils with air and caustic solution containing lead, bismuth, or thallium

Info

Publication number: US2798842A
Application number: US637316A
Authority: US
Inventors: Louis D Rampino
Original assignee: Tidewater Oil Co
Current assignee: Tidewater Oil Co
Priority date: 1957-01-30
Filing date: 1957-01-30
Publication date: 1957-07-09
Anticipated expiration: 1974-07-09

Description

Louis D. Ranrpino,

United States Patent O SWEETENING HYDROCARBON OILS WITH AER AND .CAUSTIC SOLUTION I CONTAINING LEAD, TBISMUTH; OR THALLIUM (Ioncord, Califi, assiguor to Tide- 'waterOil Company, SanFranciseo, Calif., a cerporation ofDelaware Application January .30, 1957, Serial No. 637,316 23-Claims. ((1196-29) solidated herein without additional disc'losure,'both now abandoned.

In the refining of petroleum, special problems are presented by the presence of mercaptans. Hydrocarbon .soils, especiallycracked gasolines, nearly "always contain small quantities of mercaptans,-which have a disagreeable odor and other undesirable properties.

Inpetroleumrefining, two generalmethodsare used to reduce the mercaptan content of hydrocarbonoils. One of these methods is to extract themercaptans with various alkaline solutions, and the other is to convert the mercaptans into more innocuous compounds which remain dissolved in the oil. In some operations, the majorpart of the mercaptans are extracted and the sweetening is completed by conversion of the remaining mercaptans.

A number of processes are available forthe reduction of the mercaptan content of oils. The besttknown of these sweetening processes are: the doctor process; the alkali hypochlorite process; copper sweetening; .the solutizer process; and, more recently, the .so-called inhibitor sweetening with phenylene diamine type inhibitor. However, each of these processes is subject to certain definite shortcomings. Thus, in the doctor process, in which a caustic-washed oil'is agitated with a little sulfur "and an aqueous alkaline solution :of sodium plumbite, it is difficult to control accurately the required mount of elemental sulfur. If too much sulfur is added the excess remains in the oil and, if greater than about parts per million, may render the gasoline corrosive. In addition, the free sulfur tends to react with disulfides formed during the processing to give polysulfides. The latter greatly reduces the susceptibility of the oilsfor tetraethyllead.

Treating with alkaline hypochlorite, while valuable for sweetening straight run gasolines, is little use on cracked petroleum products, primarily'because the strong oxidizing effect of the hypochlorite tends to produce unstable color and gum-forming compounds. As indoctonsweetening, it is also difficult to gauge the amount of hypochlorite to be added due to the everchanging mercaptan content of theoils undergoingtreatment. Copper sweetening is also little used since the slightest trace of excess copper in the oil will accelerate oxidation giving rise to gums.

The solutizer processes depend on the use .of a substance termed .solutizerj to increase the solubility of unneutralized mercaptans in the caustic wash solutions. Substances such as alkyltphenols and sodium-or potassium jectionable .mercaptans in Patented July 9, I957 ice salts of the lower molecular weight fatty acids are useful .as :solutizers. In addition to being expensive, these processes normally donot produce a doctor sweet product (mercaptan sulfur content of 0.0002 gm./ cc. of distillate, or less) since they depend on extraction of the mercaptans which is nevercomplete.

To a greater or lesser degree, all the aforementioned processes have an additional disadvantage of requiring extensive equipment forhandling large volumes of treating agent. In-some of these processes relatively "expensive treating or revivifying agents are used, and occasionally large losses of these reagents are encountered. As a result, these processes are apt to be'expensive, difficult to control and not always effective.

Recently, a process for sweetening certain hydrocarbon oils by means of oxygen dissolved in the oil in thepresence of an oil-soluble N alkyl derivative of paraphenylene diamine was developed. This process, often termed in- .hibitorsweetening, due to use of a compoundcommonly employed to inhibit the oil againstoxidation, has advantages over the sweetening processes just described since it is simply controlled, inexpensive, convenient and effective. However, a serious difiicu'lty often encountered in inhibitor sweetening operations is the by-product formation of organic peroxides which in turn lead to in- .creased gum formation and, in-use, dirtier engines. As .gum formation -also'tends to increase with increasedboiling range, with inhibitor sweetening, is-often necessary to control gum formation by reducing the end distillation temperature .of naphtha fractions to a lowerdegree than would otherwise be necessary. This latter procedure re- .sultsin poor-t manufacturing economies by curtailing the effective use of the heavierrefinerystoc ts.

Iheupresent inventionis directed to asimple, effective and inexpensive process for sweetening hydrocarbon liquids which is not subject-tothedefects of'the prior art, and which results in much lower gum formation and cleaner engines. Accordingly, oneobject ofthe present invention is to provide a process for rendering hydrocarbon liquids doctor-sweet without employing elemental sulfurand with .a minimum formation of peroxides. An-

.other tobjectof .t-he inventionis to provide such a process .thatis easily controlled, inexpensive and rapidly carried out. Another object of the invention is to provide an improved .sweetening process that maybe carried out simultaneously with caustic washing of the hydrocarbon liquid. Anotherlobjectoftthe invention isto provide a sweetening process in which the .capacity of i a caustic solution used to extract mercaptans.iscontinuously renewed withoutthe necessity of adding expensive revivifying agents. Astill further object of the invention is to provide an improved sweetening process, involving inhibitor sweetening, in

which both the consumption ofrinhibitor and the formation of peroxides and gums are reduced to a minimum. Another object is to provide a process for altering tobhydrocarbon liquids that is highly efiective regardless of substantial variations in the mercaptan content. t

Another object is'to provide a process for sweetening hydrocarbon oils of higher boiling range that cannot be satisfactorily'sweetened by conventional inhibitor sweetening.

Otherobjects and advantages of the present invention will be apparent from the following detailed description,

:from the specific examples enumerated herein, and from the drawing in which Figs. :1 ;and 2 are flow diagrams of two diifering forms of a process for sweetening hydro- .carbon oils. embodying the invention.

' going treatment.

' hibitor sweetening processes.

In accordance with the first form of the invention to be discussed, mercaptans contained in hydrocarbon oils are caused to react with peroxides formed during inhibitor sweetening of the oils (or, if desired, by a direct addition of peroxides to the system), in the presence of aqueous caustic and small amounts of mercaptide-forming metals that easily undergo oxidation-reduction reactions. Such metals are known to include various forms of lead, bismuth, and thallium which apparently act as catalysts for the reaction, although the exact mechanism is not understood. An explanation presently advanced is that certain compounds of the metal are oxidized by the peroxides and the resulting compounds subsequently reduced by the mercaptans to compounds suitable for reacting with more peroxides. In effect the sweetening process becomes also a peroxide destroying process, resulting in lower gum formation and cleaner engines due to the lower peroxide content of the sweetened oil. .As an example, excellent results are obtained with lead in the plumbous form. Due primarily to the low cost and ready availability of commercial doctor solution, this is the preferred source of plumbous lead. The term doctor solution is used in this specification, as is commonly employed in the petroleum art, to denote aqueous alkaline solutions of sodium plumbite (NazPbOz).

In accordance with the second form of the invention to be discussed, a sour cracked hydrocarbon oil is inhibited with a hindered phenol type of inhibitor and also a phenylene diamine type of inhibtor and then contacted with aqueous caustic in the presence of air and a small amount of the aforementioned mercaptide-forming metals that easily undergo oxidation-reduction reactions and apparently act as catalysts for the reaction of mercaptans during inhibitor sweetening of the Hindered phenols found effective include 2,6-ditertiary butyl para cresol and 2,6-ditertiary butyl phenol. Other examples include 2,6-ditertiary amyl phenols and other 2,6-ditertiary alkyl phenols in which any or all of the remaining ring positions are substituted by alkyl groups. The hindered phenol prevents peroxide from being formed at too fast a rate. The ready availability of 2,6-ditertiary butyl para cresol makes this the preferred source of hindered phenol.

Also, in accordance with both forms of the invention, substantial amounts of the mercaptans are dissolved in the aqueous caustic as mercaptides and are thereupon converted to disulfides which are returned to the oil under- As a result, the caustic becomes to a large extent revivified and may again be used in the sweetening process without the necessity of expensive Although the chemical reactions involved in this revivification are not clearly understood, it is apparent that the metal catalysts used are highly effective in the aqueous phase to promote the reaction of peroxides with the mercaptides to form disulfides. The converted disulfides are then extracted from the caustic through contact with the hydrocarbon oil. In addition, a particular phenomenon of the present invention is a continuing, although lessened, catalytic eifect produced by recirculating caustic that has once been used in the new sweetening process. This is entirely contrary to prior experience and indicates that the presence of catalyst in the treating tank alters the caustic in some way not understood, permiting the process to be successfully carried out without a continuous injection of catalyst. Generally, however, continuous injection of catalyst is preferred.

In practicing the first-mentioned form of the invention, it is desirable to first contact the mercaptan-containing oil with a phenylenediamine type inhibitor in the presence of air and aqueous caustic, as is customary in in- A minute amount of the metal catalyst is mixed with the oil either before, simultaneously, or preferably after contacting the oil With the .4 caustic. The mixture of the oil, caustic and catalyst is then allowed to stand for a suflicient time to permit the desired amount of conversion of mercaptans and peroxides, after which the separated oil is passed to storage or blended with other components to form a finished fuel. The revivified caustic settling from the mixture may then be recycled for further use in the sweetening process.

In determining particular metals useful as catalysts in the present invention, it appears that the metal should not only have different states of oxidation, but also should be capable of readily reacting with mercaptans contained in the hydrocarbon oils to form mercaptides. Moreover, the mercaptides formed should be easily oxidizable; otherwise the eifect of catalysts, thought to result from the metal varying between its oxidized and reduced forms, cannot be achieved. Thus it is found that compounds of lead, bismuth and thallium will readily react with mercaptans to form mercaptides, with the hydrogen of the mercaptan (RSH) being replaced by the metal. Similarly, the mercaptides of these metals are readily oxidized.

Forms of metals useful in carrying out the present invention are illustrated in the following examples:

EXAMPLE 1 A number of tests were conducted by shaking 25 cc. of spent caustic (10 Baum) in a brown quart bottle with 500 cc. of caustic-washed, catalytically cracked naphtha having a boiling range of F. to 268 F. The naphtha employed was derived primarily from California and Middle East crudes and had previously been inhibited with NN' clisecbutyl paraphenylene diamine at the rate of 7.5 pounds per 1,000 barrels of naphtha. In each of the tests, metal in a form suitable as a catalyst Was added to the caustic before shaking. After shaking, the bottle was capped with a slotted cork to allow access to air. The metals were added to the caustic as follows:

(a) Blank, no metal added.

(b) 0.2 cc. of doctor solution having a concentration equal to 24 grams of PbO per liter of solution (4.8 mg. PbO).

(c) 7 mg. of solid PbOz (lead peroxide).

(d) 4.9 mg. PbOz heated to boiling with 4 cc. of 35 Baum NaOH and diluted to 25 cc. with the spent caustic (sodium plumbate).

(e) 5.6 mg. PbOz heated with the spent caustic.

(f) 10.9 mg. of Bi(OH)2NO3 (bismuth subnitrate) heated with 3 cc. of 35 Baum NaOH and diluted to 25 cc. with the spent caustic.

The tendency of the added metals to prevent or reduce peroxide formation and consequent gum formation in sweetened gasolines is shown in Table A:

Table A 4 DAYS AFTER SHAKING WITH OAUSIIC Form of Metal Added Test Performed (D Doctor Sodium Heated Bis- N o SOlld Solu- Plum- PbOz muth Metal tion Pb 02 bate Subnitrate Doctor Test Neg Neg. Neg. Neg. Neg. Neg. Peroxide N o 2. 48 0. 14 0. 62 0. 37 0. 87 0. 0 Blended Copper Dish Gum 18 14 27 14 26 12 25 DAYS AFTER SHAKING WITH GAUSTIO Peroxide N o 0. 82 0. 18 0. l8 0. 23 0. 36 0. l8 Blended Copper Dish Gum 39 11 21 20 oxide numbers were determined by U. 0. P. Method H-33-40; and blended copper dish gums by a modification of Federal Specification VV-L-791b, Method 330.1, in which the treated stock was blended in equal proportions with an acid treated solvent extract boiling between 190 and 270 F. Results obtained by said modified method are herein referred to as blended copper dish gum-1 EXAMPLE 2 The procedure of Example 1 was repeated using the same catalytically cracked stock. However, the metals added to the caustic were as follows:

(g) Blank, no metal added.

(h) 0.01 cc. of the doctor solution of Example 1.

(i) 1 cc. of the sodium plumbate solution (d) of Example 1.

(j) Solid PbzOs (lead sesquioxide) prepared by adding cumene hydroperoxide to 5 cc. of the doctor solution of Example 1, and filtering and water Washing the precipitate.

(k) 1 gram of PbCOs (leadcarbonate).

(1) Metaplumbic acid (HzPbOa) prepared by adding an excess of 6 N nitric acid to 2 grams of red lead (Pb304) and washing the precipitate with dilute nitric acid.

The results of these tests are set forth in Table B:

Table B 3 DAYS AFTER SHAKING WITH CAUSTIC Form of Metal Added The procedure of Example 1 was again repeated with the following metals added to the caustic before shaking with the naphtha:

(m) Blank, no metal added.

(n) 13.1 mg. of bismuth trioxide (BizOs) heated with 3 cc. of 35 Baum NaOH.

(o) 13.1 mg. of bismuth tetroxide heated 35 Baum NaOH.

The results of these tests appear in Table C.

Table C 4 DAYS AFTER SHAKING WITH CAUSTIC with 3 cc. of

Form of Metal Added Test Performed (m) p N0 Bismuth Bismuth Metal Trioxide Tctroxide Doctor Test Neg. Neg. Neg. Peroxide No 0.84 0.26 0.17 Blended Copper Dish Gum 15 4 2 18 DAYS AFTER SHAKING WITH CAUSTIC Peroxide No Blended Copper Dish Gum EXAMPLE 4 To compare the effect of thallium compounds with lead compounds, under the procedure of Example 1, the following metals were added to 25 cc. of caustic before shaking with the naphtha:

(p) Blank, no metal added.

(q) 2.2 mg. of thallium in the dissolved in the caustic.

(r) 11.0 mg. of thallium in the form of thallous chloride,

dissolved in the caustic.

(s) 0.1 cc. of the doctor solution of Example 1 (equivalent to 2.2 mg. of Pb).

(t) 0.5 cc. of the doctor solution of Example 1 (equivalent to 11.0 mg. of Pb).

The effect of thallium compounds in preventing peroxide formation in sweetened gasolines is shown in the following table:

form of thallous chloride,

Table D 3 DAYS AFTER SHAKING WITH CAUS'IIC Form and Amount of Metal Added Test Performed (P) (q) (T) (s) Thallous Thallous Doctor Doctor No Chloride Chloride Solution Solution Metal (2.2 mg. (11.0 mg. (2.2 mg. (11.0 mg.

Th) Th) Pb) Pb) Grams mercaptans per 100 cc. of naphtha 0. 00035 0.00019 0.00026 0. 00013 0.00022 Peroxide No 0. 58 0. 20 0. 29 0. 29 0. 39

0 DAYS AFTER SHAKING WITH CAUSTIC Peroxide No 0. 45 0.11 0.11 0.11 0. 23

The results set forth in Examples 1 to 4 show that both bismuth and thallium are effective in reducing peroxide formation, and that lead is effective in either the plumbous (Pb++) or plumbic (Pb++++) form.

In practicing the second-mentioned form of the invention, it is desirable to first add to the mercaptan-containing oil a hindered phenol type of inhibitor and also a phenylene diamine type inhibitor and then contact the inhibited 'oil with aqueous caustic in the presence of air. A minute amount of the metal catalyst is mixed with the dually inhibited oil either before, simultaneousl \or preferably after contacting the oil with the caustic. The mixture of the oil, caustic and catalyst is then allowed to stand for a sulficient time to permit the desired amount of conversion of mercaptans and peroxides, after which the separated oil is passed to storage or blended with other components to form a finished fuel. The revivified caustic settling from the mixture may then be recycled for further use in the sweetening process. This form of the present invention is illustrated by the following examples:

EXAMPLE 5 A number of tests were conducted by shaking 35 cc. of 10 Baum caustic in a brown quart bottle with 700 cc. of heavy thermally cracked naphtha having a boiling range of 206 to 390 F. The naphtha employed was derived primarily from California and Middle East crudes and had been previously inhibited with phenylene diamine inhibitor or with ditertiary butyl para cresol inhibitor or both. In some of the tests pluinbous lead, in the form of 0.15 cc. of doctor solution, was added to the caustic before shaking with gasoline. After shaking, the bottle was capped with a slotted cork to allow access to air. Changes in mercaptan sulfur, gum, and peroxide number were measured over a period of 7 day with results shown in Table E.

stored in absence and presence remedy this situation. Table E also shows that when gasoline is inhibited with only 2,6-ditertiary butyl para cresol sweetening time is too slow to be of practical value.

Best results were obtained when the gasoline contained both inhibitors and when doctor solution was present in the caustic to speed up the rate of sweetening. Under these conditions product quality of the sweet gasoline was satisfactory.

It should be also noted that the concentration of mercaptans in the caustic layer was considerably lowered by the presence of doctor solution. It appears that one function of doctor solution is to accelerate the disappearance of mercaptans in the caustic and thereby accelerate the rate of gasoline sweetening by shifting the equilibrium of mercaptans between gasoline and caustic.

In the preparation of Table E, and subsequent tabulated data, peroxide number was determined by U. 0. P. method H3340; and blended copper dish gum by a modification of Federal Specification VV-L-79 Lb., Method 330.1, in which the treated stock was blended in equal proportions with an acid-treated solvent extract boiling between 190 and 270 F. Results obtained by said modified method are herein referred to as blended copper dish gum. Mercaptan sulfur was determined by the method given on page 618 of Ind. Eng. Chem. Ana1., 13th ed., No. 9 (September 15, 1941). ASTM gum was measured by Method D38152T.

EXAMPLE 6 with phenylene diamine inhibitor or with 2,6-ditertiary butyl para cresol or both. in one case 2,6-ditertiary butyl phenol was substituted for the cresol.

Tests were conducted by shaking 700 cc. of inhibited gasoline in a brown quart bottle with cc. of 10 Baum caustic to which no doctor solution was added in some cases and 0.1 cc. of doctor solution was added to others. After shaking, the bottle was capped with a slotted cork to allow access to air. Blank experiments were also performed in which uninhibited gasoline was of 10 Baum caustic. Changes in mercaptan sulfur, gums, and peroxide numbers were measured over a period of several days for each gasoline. Table F shows the results obtained with uninhibited gasoline.

Table E SWEETENIN G OF HEAVY THERMAL NAPHTHA Experiment No .1 1 2 3 4 5 Phenylene Diamine inhibitor, lbs./

1,000 bbls 10 10 10 10 0 2,6-Ditert. butyl para cresol inhi tor, lbS./1,000 bbls O 0 2. 5 2. 5 2. 5 Doctor Solution in Caustic Absent Present Absent Present Absent Zero Days:

Mercaptan Sulfur (raw gasoline),

grns. 100 cc 0. 0013 0.0013 0. 0013 0.0013 0.0013 Two Days:

Mercaptan Sulfur 0.00040 0.00031 0.00048 0.00036 0 00053 Peroxide N o 0.43 0. 38 0.67 ASTM Gun1 5. 0 4. 8 0. 8 0. 6 1. 6 Blended Copper Dish 120 105 15 11 56 Seven Days:

Mercaptan Sulfur of gasoline. 0 00014 0. 00013 0 00014 0. 00013 0. 00042 Mercaptan Sulfur of Caustic- 0. 0016 0. 00016 0. 0021 0 00088 Peroxide N o 2. 0 1. 8 0.59 0.52 1. 2 ASTM Gum 6. 4 6. 6 0. 4 0.2 1. 4 Blended Copper Dish Gu m 181 176 78 31 82 The results in Table E show that the conventional in- Table F hibitor sweetening process produced a sweet product of SWEETENING OF UNINHIBITED LIGHT CATALYTIC too high gum content to be satisfactory and that even NAPHTHA the addition of doctor solution to the caustic did not 25 N Inhibitor Content" Caustic Absent Present Mercaptan Sulfur at start, gm 0.0 0.0039 After 1 day 0.00365 0.0002 After 2 days 0.0036 After 7 days 0. 00346 Copper dish gum: After 1 day 740 Table F shows that sweetening of uninhibited gasoline is impractical for the following reasons: in absence of caustic, sweetening time is extremely long; in presence of caustic, sweetening is accompanied by a large increase in gum.

Table G compares sweetening time, gum, and peroxide number of the same gasoline inhibited with different inhibitors and stored over caustic.

Table G SWEETENING OF INHIBITED LIGHT CATALYTIC GASOLINE Inhibitor, lbs/1,000 bbls:

Phenylene diarntne 10 0 10 10 2,6-Ditertiary Butyl para cresol 0 5 5 0 2,6-Ditertiary Butyl phenol 0 0 0 5 Caustic Present Present Present Present Mereaptan Sulfur at Start,

gins/100 cc 0.0039 0.0039 0.0039 0. 0039 After 2 days- 0.00086 0 0020 0.00083 0. 00098 After 4 days 0.00015 0.0015 0.00038 0. 00022 (sweet) (sour) (sour) After 7 days 0.0010 0.00015 0. 00015 (sour) (sweet) (sweet) Tests after 7 days- Peroxide N o 0. 38 0. 12 0. 22 0. 25 ASTM Gum 1 1 1 1 Blended Cu Dish Gum 33 6 6 8 The results in Table G show that when gasoline is inhibited with only 2,6-ditertiary butyl para cresol, sweetening time is too slow to be of practical value. Gasoline inhibited with only phenylene diamine inhibitor sweetens I erably lower than in the at the fastest rate but gives, with this type of gasoline, higher gum and peroxide number after sweetening.

Gasolines inhibited with both phenylene diamine and hindered phenols sweeten at an intermediate rate; gum and peroxide content of the sweet gasolines are considcase Where no hindered phenol is present. a

In accordance with the invention, advantage is taken of the product-improvement quality of the hindered phenol without the disadvantage of a decreased rate of sweetening. This involves having a small amount of doctor solution present in the caustic.

Table H shows the improvements obtained in both SWEETENING OF LIGHT CATALYTIC NAPHTHA: EFFECT OF DOCTOR SOLUTION Inhibitor, lbs/1,000 bbls.:

Phenylene diamine l 10 10 0 2,6-ditert. butyl para oresol 0 0 5 2,6;ditert. butyl phenol. 0 0 5 0 Doctor Solution Present Present Present Present Mercaptan Sulfur at start,

gms./100 cc 0. 0039 0.0039 0.0039 0.0030 Afterzdays 0.00013 1 0.00017 0.00015 0.00050 H (sweet) (sweet) (sweet) (sour) After 7 days 1 Peroxide No 0.11 0.06 0.05 0.05 ASTM Gum 1 1 1 1 Blended Cu Dish Gum Comparison of Table G and Table H reveals that doctor solution greatly accelerates the rate of sweetening in all cases; the retarding effect of a hindered phenol is practically absent when phenylene diamine inhibitor is also present; and, in addition, peroxide number and copper dish gum of the sweet gasoline are markedly lower.

The first-mentioned form of the invention may be better understood by reference to Fig. 1 which illustrates, in diagrammatic form, apparatus suitable for carrying out the invention. Sour naphtha (i. e., naphtha containing objectionable amounts of mercaptans) which may be taken directly from the fractionating system of a cracking plant or from storage, and which previously may have received a light wash with caustic soda solution to remove traces of fatty acids, H28, and other substances more acidic than mercaptans, is fed to pump 2 through line 1 whence it is forced through line 3, mixing device 8 (including mixing orifices 8), and line 4 to tank 9 and thence through line 10 to storage. Mixing in device 8 may advantageously be assisted by recycling through line 12 and recycle pump 13.

Prior to the entry of the naphtha stream into mixing device 8, a desired proportion of inhibitor is added as, for example, from tank 5 through valve 6 and proportioning pump 7. Oxygen to effect the reaction is preferably supplied, in the form of air or other gas containing free-oxygen, through line 11 after the introduction of the inhibitor in order that passage through the mixing device 8 may assist the solution of the oxygen in the naphtha. Simultaneously with the injection of inhibitor, the naphtha is preferably contacted with a quantity of aqueous caustic sufiicient to dissolve the more soluble of the mercaptans in the caustic as mercaptides. After settling, the caustic in tank 9 (below level 18) may be returned to the process through line 14 by recycle pump 15. Spent caustic passed to the drain through valve 16 may be replaced by fresh caustic from tank 17, as needed.

According to the invention, a minute quantity of metal catalyst is admixed with the oil, either before, simultaneously, or preferably after contacting the oil with caustic. In the illustrated process, the desired proportion of catalyst is added from tank 20 through valve 21 and proportioning pump 22. The intermixed oil and caustic containing respectively inhibitor and catalyst in solution are then allowed to stand in tank 9 a sufficient time to permit the mercaptans contained in the oil to react by catalysis with the peroxides formed through addition of the oxygen. Because of a continuing catalytic effect (believed to result from oxidation-reduction reactions of the metal catalyst) sweetening of the naphtha, as evidenced by conversion of the mercaptans to disulfides, is achieved simultaneously with conversion of the peroxides to alcohols. Thus, in the practice of the invention, cracked naphthas which normally tend to form gums are simultaneously treated to reduce mercaptan content and gum formation.

After injection of the metal catalyst, the naphtha is allowed to stand in time tank 9, or in other storage, for a period suflicient' to permit the desired amount of conversion of mercaptans and peroxides, usually from 1 to 10 days. While the process is illustrated as continuous, in the sense that sweetened naphtha may be periodically withdrawn from tank 9, it will be understood that the treated fuel may be introduced into more than one time tank so as to obtain the benefits of longer periods of standing in contact with the caustic. Thus, when tank 9 is substantially full, the treated stock flowing through line 4 may be introduced into another time tank (not shown), and tank 9 isolated for a desired time by shutting

valves

23, 24, and 25.

In the second-described form of the invention, shown in Fig. 2, the same general procedure is followed, except that prior to the entry of the naphtha stream into mixing device 8, a desired proportion of the two inhibitors phenylene diamine and a hindered phenol is added separately or as a mixture as, for example, from tanks 5 and. 5 through valves 6 and 6 and proportioning pump 7. Oxygen to eflect the reaction is again preferably supplied, in the for of air or other gas containing free-oxygen, through line 11 after the introduction of the inhibitor in order that passage through the mixing device 8 may assist the solution of the oxygen in the naphtha.

Where a heavy naphtha is to be sweetened, a light hydrocarbon or mixture of light hydrocarbons is injected to increase the vapor pressure to 5 to 6 lbs. prior to the entry of oxygen into the system. In this way explosion hazards are safely eliminated.

It may be advantageous to keep the gasoline moving while in contact with the caustic. This may be conveniently done by continuously withdrawing a portion of the gasoline in the time tank and injecting this: into line 4 either before or after injection of the catalyst, as for example through valve 26, pump 27 and line Z81 of Fig. 2.

Both forms of the invention are particularly adapted, though not restricted, to the treatment of naphthas containing relatively low (in the order of 0.01% of mercaptan sulfur) but objectionable amounts of mercaptans. Such naphthas may result from the cracking of low sulfur stocks, or they may result from the treatment of higher mercaptan content naphthas by any one of several mercaptan removal processes, such as extraction with caustic soda solution, with or without a so-called solutizer.

The amount of catalyst required to sharply reduce gum formation is extremely small. For example, when using a commercial doctor solution containing approximately 15 grams PbO per liter of solution, from about 1.5 to 15 gallons of solution per 1000 barrels of oil has been found to be effective. Stated otherwise, a continuous injection of from about 0.00005 part to about 0.00 part by weight lead in the plumbous form per parts of hydrocarbon oil will produce the desired result. On the other hand, too large an injection of lead, that is, more than about 0.003 part per 100, may unnecessarily retard the rate of sweetening. When using various forms of bismuth or thallium as the catalyst, similarly low amounts of catalyst appear satisfactory.

The following are examples of the practice of the first mentioned form of the invention according to the general procedure outlined in the drawing, and, with particular reference to lead, illustrate the effect of different concentrations of the catalyst metals.

EXAMPLE 7 A catalytically cracked naphtha, from the cracking of a mixture of gas oils derived primarily from California and Middle East crudes with a boiling range of 106 F. to 266 F., and having a mercaptan content (as sulfur) of 0.006 gram per 100 cc. of stock is processed as in the drawing. The sour naphtha is charged at a rate of 250 barrels per hour and injected with 19 pounds per hour of MN disecbutyl paraphenylene diamine inhibitor. A 2.9 percent solution of aqueous caustic soda from the time tank is recycled with the charge at 60 barrels per hour. Air at the rate of 90 standard cubic feet per hour is then injected into the charge. After thorough mixing, catalyst in the form of doctor solution of a concentration of 9.25 grams PbO per liter of solution is injected at a rate of 1.4 gallons per hour (0.000135 percent Pb by weight). Tests on samples taken just before the treated naphtha enters the time tank, and at various periods after entering the tank, are set forth in Table I.

Table I At En- After 2 After 8 Data Collected trance To days in days in Time Tank Time Tank Time Tank Grams mercaptans S per 100 cc. Less than Less than of naphtha 0.0012 0. 0002 0.0002 Peroxide Number 0. 45 0. 13 0. 06 Blended Copper Dish Gum. 10 7 4 ASTM Gum 0.2 0.0 0.0

In Table I and subsequent tables, mercaptan sulfur is determined bu the method set forth on page 618 of Ind. Eng. Chem. Analysis, 13th ed., No. 9 (September 15, 1941), and ASTM Gum by Method D38152T.

Example 8 A catalytically cracked naphtha similar to that in Example 5 but having an initial mercaptan content (as sulfur) of 0.0068 gram per 100 cc. of naphtha is processed in the same manner as in Example 7, except the concentration of the doctor solution is increased to 14.3 grams of PhD per liter (0.00021 percent Pb by weight) and a 4.5 percent solution of caustic soda is employed. Samples are Withdrawn from the time tank and tested as shown in Table I.

The procedure of Example 7 is repeated on catalytically cracked naphtha, similar to that in Example 7, having an an initial mercaptan content (as sulfur) of 0.0055 gram per cc. of naphtha with the following variations, the caustic being circulated is increased in concentration to a 6 percent solution, and the concentration of the doctor solution to 19.6 grams of PbO per liter (0.00029 percent Pb by weight). Tests on samples taken just before and at various periods after the naphtha entered the time tank produce the following results:

Table K At En- After 1 day After 4 Data Collected trance To in Time days in Time Tank Tank Time Tank Grams Mercaptans S per 100 cc. Less than of naphtha 0. 00090 0. 00070 0. 00020 Peroxide Number 0.62 0.25 0. l1 Blended Copper Dish Gum up 9 5 2 M The results of Examples 7, 8 and 9 demonstrate that an increase in the amount of metal present does not necessarily tend to further reduce peroxide and gum formation and, consequently, indicate the catalytic nature of the metal.

EXAMPLE 10 Prior to any injection of the catalyst metals of the invention, catalytically cracked naphtha (from a mixture of gas oils derived primarily from California and Middle 12 East crudes andhaving a mercaptan content (as sulfur) of from 0.005 to 0.007), is charged to thesystem shown in the drawing. The naphtha is then injected with inhibitor and air and mixed with caustic in the amounts and proportions set forth in Example 7. Mercaptan sulfur is determined in a series of tests on samples taken at the entrance to the time tank. Similarly, peroxide and gum formation is determined in another series of tests on samples of sweetened naphtha drawn from the time tank (approximately 2 days after entrance into the time tank). The entire procedure is then repeated with the additional injection of 1.42 gallons per hour of doctor solution (containing from 9.5 to 19 grams PbO per liter). A comparison of these series of tests is set forth below:

Table L Data Collected N 0 Metal Doctor Solu- Injection tion Injected Mercaptans S per 100 cc. of entering naphtha 0. 002-0. 0025 0. 0005-0. 001 Peroxide N o. of sweetened naphtha. 0. 8-1. 5 0. 1-0. 4 Blended Copper Dish Gums 20-40 0-8 ASTM Gums 0. 4-1 00.4

These results indicate clearly that not only are the gasolines sweetened with a minimum formation of peroxides and a consequent reduction in the formation of gums, but also that the gasolines are sweetened more rapidly than is possible merely with inhibitor sweetening.

The following example, in contrast to Examples 7 to 10, illustrates sweetening of naphtha over longer periods of time under batch process conditions.

EXAMPLE 11 A catalytically cracked naphtha, similar to that in Example 7 but having a boiling range of 104 F. to 269 F., and having a mercaptan content (as sulfur) of 0.0029 gram per 100 cc. of stock is charged at a rate of 250 barrels per hour and injected with 1.9 pounds per hour of NN' disecbutyl paraphenylene diamine inhibitor. A 6.5 percent solution of aqueous caustic soda is mixed with the charge at 60 barrels per hour. Air at the rate of standard cubic feet per hour is then injected into the charge. After thorough mixing, catalyst in the form of doctor solution of a concentration of 15.6 grams PbO per liter of solution is injected at a rate of 1.4 gallons per hour. The intermixed naphtha, caustic, inhibitor, and metal catalyst are introduced into an isolated time tank and allowed to stand. Tests on samples taken just before the treated naphtha enters the time tank, and at various periods after entering the tank, are set forth in continues to achieve the catalytic effect even though the injection of catalyst is discontinued. This phenomenon is not clearly understood, particularly since, on analysis, no metal has been found in the recycled caustic. The following examples, with particular reference to prior Examples 7 to 9, illustrate the effects subsequent to discontinuing the injection of catalyst.

EXAMPLE 12 Operations are conducted as described in Example 7 ma'ining constant.

p with a boiling range of 106 As in Example 8,

the rate of 90 standard cubic feet per hour.

rm a period of 12 days, after which time the injection or doctor solution is discontinued while maintaining the other cohditions Constant. Fifteen minutes thereafter samples of naphtha are taken at the entrance to the time tank, and tested. Tests, repeated at intervals, on the samples so taken are shown in Table N.

Table N At 1211- After 2 After 7 Data Collected trance to Days Days Time T 7 Standing Standing Grams Mercaptans S per 100 cc. 0110083 Le'ssthaii Less than of naphtha. 0. 0002 0. Peroxide Number 0. 54 0. 43 0. 23 Blended Copper Dish Gum 6 .28 8 ASTM Gum 0.2 0.2 0.0

EXAMPLE 13 Operations are conducted as described in Example 8 for a period of 2 days. The injection of doctor solution is then discontinued while maintaining the other con- The injection of doctor solution, described in Example 9; is discontinued after 5 days, all other conditions re- Two and one-half hours later samples are taken and tested as shown in Table P.

Table P At En- After 1 After 2 Data Collected trance to Day in Days in Time Tank Time Tank Time Tank Grams Mercaptans 8 per 100 cc. Less than of naphtha 0. 0013 0. 00070 0. 00020 Peroxide Number 0. 63 0.30 i 0.08 Blended Copper Dish Gum 8 l 2 A comparison of data, as for example in Tables K and P, indicates that a substantial reduction in peroxide and gum formation within the naphtha can be achieved at intervals of at least 2 /2 hours after the injection of catalyst is discontinued.

A further advantage of the metal catalyst resides in its power to effect a regeneration of the mercaptan extractive powers of the aqueous caustic during the period of contact with the naphtha. This effect is illustrated in the following example. 1

EXAMPLE l 1 Prior to any injection of catalyst, a catalytically cracked naphtha, from the cracking of a mixture of gas oils derived primarily from California and Middle East crudes F. to 266 F., and having a mercaptan content (as sulfur) of 0.006 gram per 100 cc. of stock is processed substantially as in the drawing. the sour naphtha is charged at a rate of 250 barrels per hour, injected with 1.9 pounds per hour 1 of NN disecbutyl paraphenylene diamine inhibitor,

mixed with 60 barrels of a 4.5 percent solution of aqueous caustic soda solutiori per hour, and injected with air at Subsequently, the entire process is repeated exactly as in the drawing with doctor solution of a concentration of 14.3 grams are 14 P120 per liter of solutionalso being injected at a rate of 1.4 gallons per hour (0.00021 percent Pb by weight). In each case, samples of caustic are taken just before the intermixed caustic and naphtha enters the time tank, and

one day after entering the tank.

Table Q i No" Metal Iniected Doctor Solution Injected Data Collected At En- After 1 At En- After 1 trance day In trance day In To Time Time To Time Time Tank Tank Tank Tank Grams mercaptan S per, 100 j V cc. of caustic 0.08 0. 06 0. 04 0. 007

The above results were verified in additional tests in which the addition of the catalyst metal was found to reduce the mercaptan sulfur in the caustic from about 0.07 to 0.10 gram at the entrance to the tank to about 0.02 to 0.05 gram, and after one day in the tank from about 0 .5 to 0.8 grain to about 0.005 to 0.01 gram.

The second-mentioned form of the invention has important advantages.

Contrary to the conventional use of doctor solution to sweeten gasoline, where a large excess of doctor solution is required to react with the mercaptans to form mercaptides and the mercaptides in turn are reacted with elemental sulfur to produce disulfides, the present invention uses only catalytic amounts of doctor solution (i. e., less lllhl the stoichiornetr'ic amounts of sodium plumbite are use l The amount of the two inhibitors will vary but, in general, the hindered phenol is added at the rate of 2.5 to 5 lbs. of 1000 bbls. of naphtha and the p'henylene diamine is' added at the rate of 5 to 10 lbs. per 1000 bbls. though more may be used if desired.

The following examples illustrate, according to the general procedure outlined in the drawing, the effect of using hindered phenol in conjunction with a phenylene diamine inhibitor compared to similar processing without the hindered phenol.

EXAMPLE 16 A catalytically cracked naphtha, from the cracking of a mixture of gas oils derived primarily from California and Middle East crudes with a boiling range of 110 F. to 290 F., and having a mercaptan content (as sulfur) of 0.0055 gram per 100cc. of stock is processed as in the drawing. The sour naphtha is charged at a rate of 250 barrels per hour and injected with 2.5 pounds per hour of NN disecondary butyl paraphenylene diamine inhibitor. 'A 40 percent solution of aqueous caustic soda from the time tank is recycled with the charge at 50 barrels per hour. Air at the rate of standard cubic feet per hour is then injected into the charge. After thorough mixing, catalyst in the form of doctor solution of a concentration of 11.1 grams Pb O per liter of solution is injected at a rate of 1.0 gallons per hour (0.000162 percent Pb by weight). Tests on samples taken just before the treated naphtha enters the time tank, and at various periods after entering the tank, are set forth in Table R.

Table R At En- After 2 After 8 Data. Collected trance To days in days in Time Tank Time Tank Time Tank Grams mercaptans S per cc. Less than 0.0012 0. 00020 0.0002 0. 52 0. 25 0. 18 22 15 13 0.2 0.0 0.0

15 EXAMPLE 17 'phenylene diamine inhibitor, and a 4.5 percent solution of caustic soda is employed. Samples are withdrawn from the time tank and tested as shown in Table S.

The procedure of Example 16 is repeated with heavy thermally cracked naphtha having an initial mercaptan content (as sulfur) of 0.00092 gram per 100 cc. of naphthe and a boiling range of 205 to 395 F. The sour naphtha is charged at the rate of 175 barrels per hour and by volume of butane is injected to raise the vapor pressure. NN' disecondary butyl para phenylene diamine inhibitor is then injected at the rate of 1.5 pounds per hour. A 4.5 percent solution of aqueous caustic soda from the time tank is recycled with the charge at 40 barrels per hour. Air at the rate of 40 standard cubic feet per hour and catalyst in the form of doctor solution of a concentration of 18.1 gms. of PhD per liter is injected at a rate of 1 gallon per hour. Tests on samples taken just before and at various periods after the naphtha entered the time tank produce the following results:

Table T At En- After 2 After 4 Data Collected trance To days in days in Time Tank Time Tank Time Tank Grams Mercaptans S per 100 cc.

of naptha 0. 00068 0.00035 0. 00020 Peroxide Number 3. 6 3.1 2. 8 Blended Copper Dish Gum 162 172 175 The results of Example 18 show that sweetening of heavy thermal naphtha inhibited with only phenylene diamine inhibitor leads to unsatisfactory product quality.

EXAMPLE 19 The procedure of Example 18 is repeated with heavy thermally cracked naphtha similar to that in Example 18, except that the gasoline having an initial mercaptau sulfur content of 0.0011 gm. per 100 cc. is further inhibited, before contact with air or caustic, with 0.8 pound per hour of 2,6-ditertiary butyl para cresol. Results obtained in the time tank are shown in Table U.

Table U At En- After 2 After 4 Data Collected trance To days in days in Time Tank Time Tank Time Tank Grams Mercaptans S per 100 cc.

of naphtha 0. 00079 0. 00046 0.00027 Peroxide Number 0. 58 O. 47 0. 40 Blended Copper Dish G 43 40 37 EXAMPLE 20 The procedure of Example 19 is repeated on heavy thermally cracked naphtha, having an initial mercaptan content of 0.00095 except that a stream of gasoline is con- 16 tinuously withdrawn from the time tank and injected into line 4 previous to the injection of doctor solution at the rate of 50 barrels per hour. Results obtained in the time tank are shown in Table V.

Table V At En- After 2 After 4 Data Collected trance To days in days in Time Tank Time Tank Time Tank Grams Mercaptans S per 100 cc.

of naphtha 0.00040 0.00023 Less than 0.00020 Peroxide Number 0. 31 0. 23 0. 15 Blended Copper Dish Gum 22 15 i 10 These results indicate clearly that recirculation of part of the gasoline in the time tank accelerates sweetening and leads to improved product quality.

To those skilled in the art of which this invention relates, it will be clear that the invention makes possible a rapid, efficient sweetening of gasolines, using a modified inhibitor sweetening procedure with greatly reduced by-product formation of organic peroxides thereby resulting in decreased gum formation and cleaner engines. The invention also makes possible the regeneration of caustic wash solutions, in situ, without the necessity of expensive or involved regeneration procedures. However, it will be understood that the disclosures and the descriptions herein, such as those relating to the destruction of peroxides formed during inhibitor sweetening, are purely illustrative and are not intended to be in any sense limiting. Thus, organic peroxides necessary to the efiicient performance of the disclosed process could be supplied independently of inhibitor sweetening processes, as (for example) by a direct addition of peroxides to the caustic recirculation line 14 through valve 19. Thus, the injection of the catalyst may occur at other points in the system, such as prior to mixing tank 8 or mixing tank 8 could be eliminated, without appreciably varying the success achieved by the new process.

Similarly, the point of injection of the air, or other oxygen-containing gas, may be varied and may be either before, simultaneously or after the catalyst injection. Accordingly, all such changes in construction or variations and applications of the invention, which would naturally suggest themselves to a worker in the art are considered within the spirit and scope of the invention.

I claim:

1. The process of simultaneously sweetening and reducing the content of gum-producing peroxides in a sour hydrocarbon oil which comprises reacting mercaptans and organic peroxides contained in the oil in the presence of an aqueous alkaline solution containing in the form of va salt a catalytic amount less than about 0.003%

by weight of a metal selected from the group consisting of lead, bismuth, and thallium.

2. The process of claim 1 in which said peroxides are formed in said hydrocarbon oil by contacting the oil with air in the presence of a phenylene diamine type inhibitor and a hindered phenol type of inhibitor.

3. The process of claim 2 in which the hindered phenol type inhibitor is a member of the group consisting of 2,6-ditertiary butyl para cresol and 2,6-ditertiary butyl phenol.

4. The process of claim 2 in which the phenylene diamine type inhibitor is added to the oil at a rate in the order of 5 to 10 pounds per 1000 barrels and the hindered phenol type of inhibitor is added to the oil at a rate in the order of2.5 to 5 pounds per 1000 barrels.

5. The process of claim 1 in which said peroxides are formed in said hydrocarbon oil by contacting the oil with air in the presence of a phenylene diamine type inh bit 6. The process of claim 1 in which said peroxides are added to said oil from an extraneous source.

7. The process of claim 1 in which said hydrocarbon oil is a cracked naphtha.

8. In a process of sweetening light petroleum hydrocarbon oils of a type suitable for motor fuels in which a small amount of an oil-soluble phenylene diamine inhibitor is dissolved in said oil, the step of contacting the oil with an aqueous alkaline solution containing in the form of a salt a catalytic amount less than about 0.003% by weight of metal selected from the group consisting of lead, bismuth and thallium.

9. The process of claim 8 in which said metal is present in the alkaline solution in the form of sodium plumbite.

10. A process of sweetening sour hydrocarbon oils, containing objectionable amounts of mercaptans, which comprises contacting the oil containing a phenylene diamine type inhibitor with aqueous caustic containing a small amount less than 0.003% by weight of a catalyst in the presence of air, said catalyst being a metal in soluble form selected from the group consisting of lead, bismuth and thallium.

11. The process of claim 10 in which said metal catalyst is present in the aqueous caustic in an amount between about 0.00005 parts and 0.001 parts metal per 100 parts of hydrocarbon oil.

12. The process of claim 1 in which said metal catalyst is lead, added in the form of doctor solution.

13. In the process of sweetening hydrocarbon oils which have been treated by conventional sweetening processes tending to produce gum-forming peroxides and which still contain small but objectionable amounts of mercaptans the finishing step which includes contacting the oil with an aqueous caustic solution of a metal catalyst selected from the group consisting of lead, bismuth and thallium for a reaction between said peroxides and mercaptans which has the properties of easily undergoing oxidation-reduction reactions and of readily forming mercaptides on contact with mercaptans, the catalyst being present in an amount at least 0.00005% and less than about 0.003% by weight.

14. In combination with a process wherein a stream of sour cracked hydrocarbon oil is contacted with a stream of caustic soda solution and the resulting mixture is permitted to settle, the resulting phases remain in contact in the presence of oxygen dissolved in the oil under conditions which result in the simultaneous formation of peroxides in the oil and conversion of mercaptans to disulfides, and a stream of the separated caustic soda phase is recycled to contact further quantities of oil, the method of increasing the rate of formation of disulfides and decreasing the final peroxide content of the oil, which comprises adding doctor solution to the caustic soda stream in an amount sufficient to increase the rate of formation of said disulfides but not substantially more than a rate of about 0.003 parts by weight of lead per 100 parts hydrocarbon oil.

15. The method of claim 14 wherein the oil contains a phenylene diamine type inhibitor effective to promote the formation of disulfides.

16. The method of claim 14 wherein the oil contains both a phenylene diamine type inhibitor and a hindered phenol type inhibitor.

17. In a process of sweetening light petroleum hydrocarbon oils of a type suitable for motor fuels in which a small amount of an oil-soluble phenylene diamine inhibitor and a small amount of an oil-soluble hindered t phenol inhibitor are dissolved in said oil, the step of contacting the oil with an aqueous alkaline solution containing in the form of a salt a catalytic amount less than about 0.003% by weight of metal selected from the group consisting of lead, bismuth and thallium.

18. A process of sweetening sour hydrocarbon oils, containing objectionable amounts of mercaptans, which comprises contacting the oil containing a phenylene diamine type inhibitor and a hindered phenol type inhibitor with aqueous caustic containing a small amount less than 0.003% by weight of a catalyst in the presence of air, said catalyst being a metal in soluble form selected from the group consisting of lead, bismuth and thallium.

19. In combination with a process wherein a stream of sour cracked hydrocarbon oil is contacted with a stream of caustic soda solution and the resulting mixture is permitted to settle, the resulting phases remain in contact in the presence of oxygen dissolved in the oil under conditions which result in the simultaneous formation of peroxides in the oil and conversion of mercaptans to disulfides, and a stream of the separated caustic soda phase is recycled to contact further quantities of oil, the method of increasing the rate of formation of disulfides and decreasing the final peroxide content of the oil, which comprises: adding doctor solution to the caustic soda stream in an amount suflicient to increase the rate of formation of said disulfides but not substantially more than a rate of about 0.003 parts by weight of lead per parts hydrocarbon oil, adding to the oil a phenylene diamine type inhibitor in an amount effective to promote the formation of disulfides, and adding to the oil a hindered phenol type of inhibitor in an amount sufficient to substantially suppress the formation of peroxides.

20. The method of claim 19 in which the hydrocarbon oil phase is maintained in motion While it remains in contact with the caustic soda phase, by transferring oil phase from one locus to a second locus in a time tank.

21. The process of claim 19 in which the hindered phenol type inhibitor is a member of the group consisting of 2,6-ditertiary butyl para cresol and 2,6-ditertiary butyl phenol.

22. The process of claim 19 in which the phenylene diamine type inhibitor is added to the oil at a rate in the order of 5 to 10 pounds per 1000 barrels.

23. The process of claim 19 in which the hindered phenol type inhibitor is added to the oil at a rate in the order of 2.5 to 5 pounds per 1000 barrels.

References Cited in the file of this patent UNITED STATES PATENTS 1,840,269 Borgstrom Jan. 5, 1932 2,042,055 Hoover May 26, 1936 2,149,035 Von Fuchs et al. Feb. 28, 1939 2,340,157 Thacker Jan. 25, 1944 2,367,178 Apgar Jan. 16, 1945 2,552,399 Browder May 8, 1951 2,616,831 Rosenwald Nov. 4, 1952 2,670,319 Ayers et al. Feb. 23, 1954 2,756,184 Brehm et al July 24, 1956 FOREIGN PATENTS 627,984 France June 20, 1927 263,381 Great Britain Dec. 30, 1926 Great Britain July 3, 1936 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,798,842 July 9, 1957 Louis D. Rampino It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Let mere Patent should read as corrected below.

Column 4, line 14, for "catalysts" read catalysis column 6, line 74, for "day" read days column 11, line 22, for "bu the" read by the column 14, line 55, for "40 percent" read 4.0 percent line 61, for "1.0 gallons" read 1.4 gallons column 15, line 4, after "sulfur" insert a closing parenthesis; column 17,

line 28, for the claim reference numeral 'l' read lO Signed and sealed this 10th day of September 1957.

Attest:

KARL H. AXLINE ROBERT C. WATSON Atteating Officer C'nnmisaioner of Patents

Claims

1. THE PROCESS OF SIMULTANEOUSLY SWEETINING AND REDUCING THE CONTENT OF GUM-PRODUCING PEROXIDES IN A SOUR HYDROCARBON OIL WHICH COMPRISES REACTING MERCAPTANS AND ORGANIC PEROXIDES CONTAINED IN THE OIL IN THE PRESENCE OF AN AQUEOUS ALKALINE SOLUTION CONTAINING IN THE FORM OF A SALT A CATALYTIC AMOUNT LESS THAN ABOUT 0.003% BY WEIGHT OF A METAL SELECTED FROM THE GROUP CONSISTING OF LEAD, BISMUTH, AND THALLIUM.