US2663674A - Refining sour hydrocarbon oils - Google Patents

Description

Dec. 22, 1953 .1. H. KRAUsE ErAL REFINING SOUR HYDROCARBON OILS Filed March 17, 1950 Patented Dec. 22, 1953 REFININGSOUR HYDROCARBON OILS Jack HKra'use and Russell HQ Brown, Hammond,

Ind.; assignors to Standard i! Company, Chill cago, Ill.,` "a corporation of Indiana. Application March 17, 1950, Serial No. 150,161?.`

hydrocarbon oils, such` as heavynaphtha, kerosene, diesel oil, heater oil and furnace oil, which farederi'vecl from Yfrom cracking processes, either` thermal orl catalytic.' More particularly the inventionr'elates to `a method of treating such stocksin orderto remove rrmercaptans with little or no degradation of thecolor of the oil.'

TheA removal of mercaptans from petroleum products'be'cause of their :objectionable odor has been a problem'oi longstanding with 'the` petroleurrrreners.l Many methods are known for the removal of the'merCaptaris,v as such; Vor for .their conversion 'to the' 'relatively` non-odo'rous disulfldfe's.'y Some of the more Well known methods are: Infthecase of the lightnaphth'as and `aasolines, the mercaptans Vare an aqueous alkali solution; solutizers` are added to increase/the of themercaptans Inthe'` case of distillates boiling' above'th'e gasoline range, the mercaptansare less alkali soluble andtheir removal is'much more diiii'c`ult.`V The removal of the mercaptans has been accomplished by the'u'se of solutized valkali'or by extraction with causticmethanol solutions. 'Anctherme'thod has involved converting the mercaptans to 'disuldes by air oxidation in the 'presence of tures. The elevated temperature caustic soluthe .distillation o fv crude oil orY removableby.- Washing with" sometimes, san-called solubilityv in the aqueous alkali solution.`

concentrated .sodiurii hydroxide solution at elevated"terru'ue'ra-V vtion process' formsa considerable amount of color vin'the Atreated oil and supplementary color improvenient procedures must be' resortedto.

KrauseTom application Ser.

.scribes a novel sweetening process Which comprises contacting the sour oil with air' and a No.` 141,391, leflY January 3l, 1950, now Patent No. 2,59L946, de?

'highlyconcentratel aqueous caustic solution in the presence of a copper catalyst.: The invention 'describedand claimed herein Ais an improvement ontherprocess of said application.

An object of this inventionV is toremove /mrcaptans from sour hydrocarbon distillates-With a minimum of color degradation. Anotherobject 1s to convert the niercaptans in sour hydrocarbonV f distillates into disuldes with little or no forma-` 'tion of objectionable color bodies. Stillanother yObjectis to treat sour hydrocarbon oils boiling f above'th'e g'asolineboiling range toproduce a substantially sweet oil with little ornocolor iormation.during'the treating process.-` Yet :another object is to `prevent the formationof objectionvm ablaCQlOlinfa sweetened .Oil during; the. .Si/@etening process by extracting the color forming ma- 9 Claims; (or 196429) terials withmethan'ol vbefore thepil'is sweetened.

It has been 'discovered thatrsourrhydrocarbon distillates and particularly those distillates' boiling above'the gasoline range; forexample; heater oil which boils between 350 andw650 can be made substantially doctor'sw'eet with little if any change'in color by the following `r'hetliod of treating: The sour distillate""is ex racted? with l10n-alkaline 4il@tli'aijl' lllvfl'lcfl olt'a'ishles than about 10 volume per centv oiwater in order yto remove materials which fap'pear to' 'be colorr formers'when the's'our oilfis contacte`d`v`vith` air and concentrated caustic solution; The methanol solution containingsaid materials is sepa'ratedf' from thev olla-nd the extractedoil'can` be Atva'teij washed to recover`any1-methanol 'disslvedf"and entrained therein.` Il h'e4 xtracte'dil;thenier captan 'number oft'vhich'has not changed aol-T preciably, is then contacted with airan'da higlriy concentrated aqueous" caustic solution in the pres-'1 ence of a catalytically active copper'conpound to produce a substantially sweet oil'of aboutilii` Sansepolcr as the sourvoilcharged to thc process.`

The inventionis 'illustrated by 'a'. dratv'n'g vili forms a part of this 'speciijlcationand i1s `a sch c matic vdiagram of anappa'ratus suitablel foc'arryingoutthe processi Q y u, i.

The cause of coloriorm'ation during' 'sweet ning' by air orrfree oxygen inthe presence oifcaust'ic solution is not fully understood butfisthought to be due tothe oxidation vof ph'emilic "substances'f contained in i high' 'sulfur oilsl' These substances are present .111. only'vey' Small @maints .forex-g ample, extracting-'10P vlollimes. .Ofs'pur healer .5011. with five treats of lqvolumesfeach of substanj- Q tially anhydrous methanol removed; only'f about'` 0.2 volume of oxygenatedV hydrocarbons believedto be alkyl phenols; the colorof this extracted oil after sweetening with air in-the presence of`% KOH solution-anda copper catalyst fvvasfbetterv than the color of thcsournil: fs

' extracted oil was The same West Texas heater oil was used in obtaining the following data. One hundred volumes of the sour oil was extracted at about 80 F. with five treats of methanol in amounts and containing volume percentages of water hereinafter indicated; the solvent was separated from the oil and the extracted oil water washed to remove the methanol dissolved and entrained therein. The then treated as described in the previous paragraph except that all the treats were at about 80 F., to obtain a sweet product.

Solvent Composition Solvent, Color Vol. Saybolt Percent Product MeOH Water Per Treat Oil These data indicate that the color of the sweet oil can be maintained substantially unchanged or even improved by extracting the sour oil with from about to 100 volumes of solvent per 100 volumes of sour oil. The range of solvent usage should be from 5 to 200, preferably from about 25 to 100, volumes of solvent per 100 volumes of sour oil. The solvent composition can vary from substantially anhydrous methanol to about 90 volume per cent methanol and 10 volume per cent water. Preferably the water content should be less than 5% and for best results should be about It has been found that the use of highly concentrated aqueous solutions of KOH are superior to NaOH solutions in that not only may lower temperatures be used to obtain a substantially sweet oil but also better colored products are obtained. Also it has been found that the addition of a copper compound to the caustic solution or preferably to the sour oil before the caustic solution is added very markedly increases the rate of sweetening and also decreases the rate of color` formation. The best sweetening results are obtained with a substantially saturated--at the temperature of operation-aqueous caustic solution; a reaction temperature between 80 and 125 F.; a contact time of between 3 and 60 minutes, depending on the temperature, and from about 1% by volume to about 15% by volume of caustic solution. The copper catalyst can be any compound which is somewhat soluble in hot concentrated caustic solution or which can be dispersed in the form of a waterl solution in the sour oil before the caustic solution is added. In terms of weight per cent of caustic solution used, the copper compound added can vary from about 0.004 to about 0.3 weight per cent in terms of copper. The preferred copper compounds to be added are cupric chloride and cupric sulfate.

It was found that sour oils that had been extracted with caustic-methanol solutions and water washed did not sweeten when treated with air, caustic solution and copper catalyst. An oil of 65 mercaptan number was extracted with one 10 volume per cent treat of a solution consisting of 33 weight per cent, KOH; 29 weight per cent, methanol; and 38 weight per cent, water; the separated oil was water washed and then treated with l volume per cent of a 55% KOE solution containing 0.1 weight per cent of CuSO4.5I-I2O and air at F. for 30 minutes; the extracted oil was 28 mercaptan number and +15 color while the treated oil was 20 mercaptan number and +14 color. It is believed that the caustic-methanol removed not only the color forming bodies but also the natural oxidation accelerators present in the oil, which are thought to be somewhat acidic; the absence of the natural oxidation accel erators prevents the further removal cf the mercaptans by the air-caustic process. The use of non-alkaline methanol appears to remove the materialsthat cause serious color degradation without also removing enough of the natural oxidation accelerators to impair the subsequent oxidation of the mercaptans.

While either caustic soda or caustic potash can be used in this process, caustic potash is preferred. Sour oils can be sweetened more quickly when concentrated, for example, 50-60 weight per cent, potassium hydroxide solutions are used in the sweetening step.

The odor of the oil obtained by this improved process has been found to be satisfactory and the color stability and burning qualities are excellent.

A fuller understanding of the treating process and the preferred conditions of operation will be obtained from the iigure which is only one form of the many that the process can assume. Referring to the figure, the sour oil, which may be given a preliminary wash with a weak alkaline solution, for example 4.0 to 10.0% by weight of NaOH in water, to remove hydrogen sulfide if this is present in the oil, is introduced by line I0 and the temperature is suitably adjusted by heat exchanger H, a preferred temperature is about F. The sour oil passes into a contacting tower l2 near the top of the tower which may be filled with crushed rock, Raschig rings, or other suitable material or even may be of the bubble tray type. The solvent in this illustration is by volume of methanol and 5% by volume of water; this ratio is chosen in order to reduce the miscibility of the methanol in the oil and reduce the losses of the solvent into the oil and the amount of wash water needed; the solvent is introduced by line I3 and passes through heat exchanger i4 where the temperature is adjusted to about 90 and then passes into tower l2 at about the verti cal midpoint of the tower; about 50 volumes of solvent are added per volumes of oil. While a packed tower is illustrated, the same degree of contacting can be obtained by using several stages of batch extraction with a portion of the solvent used in each stage; 4 to 6 stages are considered suitable. The solvent is added at the midpoint of the tower because its specific gravity is less than that of the oil and it will flow up against the descending oil stream.

The solvent, less that dissolved and entrained in the oil, passes out from the tower l2 through line l5 and passes through heater I5 where it is heated to about F., about the boiling point of anhydrous methanol, and passes through line il into fractionator I8 about the vertical midpoint; fractionator I8 is suitably a bubble tower but may be a packed tower. If additional heat is needed in the fractionator, this can be supplied through the reboiler coil IS shown in the bottom of the fractionator. Substantially anhydrous degradation which comprises contacting the sourdistillate with about to 200 per cent by volume of non-alkaline methanol solvent which con-l tains not more than about volume per cent of "water, separating the solvent and dissolved colorforming bodies from. the extracted oil, water washing the extracted Voil to remove dissolved methanol solvent, treating the washed oil with about 1 to 15 per cent by volume of a concentrated aqueous caustic solution, introducing a free-oxygen containing gas into the` mixture of oil and caustic solution, maintaining the temperature of treating atV between about 30 to 125 F., said caustic solution also containing an eifective amount of a copper compound which is active as an oxidation catalyst, and separating spent caustic solution and associated reaction products from the treated oil.

2. The process of claim 1 wherein the copper catalyst consists of from about 0.004 to 0.3 weight per cent as copper based on the caustic solution of a copper salt which forms a copper compound that is active as an oxidation catalyst when contacted with the caustic solution.

3. The process of removing mercaptans from a sour hydrocarbon distillate which is higher boiling than gasoline with a minimum of color degradation which comprises intimately7 contacting the sour distillate with about 25 to 100 volume per cent of a non-alkaline methanol solvent which comprises from about 5 volume per cent to substantially no water, separating the solvent and associated material removed from the sour oil, water washing the extracted sour oil to remove dissolved methanol solvent, intimately contacting' the washed oil with about 5 to 10 volume per cent of concentrated aqueous caustic solution, introducing into the mixture oxygen in excess or the stoichiometric amount needed to react with the mercaptans present in the oil, maintaining said mixture at a temperature of about 80-125 F. wherein said caustic solution contains an active copper catalyst which is effective as an oxidation promoter in an amount of 0.004 to 0.3 weight per cent of copper based on the caustic solution present in said mixture, which active copper catalyst is in the form of a copper compound and not in the form of metallic copper, continuing the oontacting until the oil is substantially sweet, and then separating spent caustic solution and associated reaction products from the treated oil.

i. The process of claim 3 wherein the time of contact between the extracted oil and the causticcopper catalyst solution is about 3 to 60 minutes.

5. In a process for treating a sour hydrocarbon distillate which is higher boiling than gasoline and which contains a large amount of mercaptan sulfur, in which process the distillate is intimately contacted with an amount of oxygen stoichiometrically equivalent to about one and one-half to two and one-half times the amount of mercaptans present in the distillate and in which process the contacting is effected in the presence of a concentrated Yaqueous caustic solution at a temperature of about E50-125 F. for a contact time of between 5-60 minutes and wherein said caustic solution contains an active copper catalyst which is eiective as an oxidation promoter in an amount of 0.004 to 0.3 weight per cent of copper based on caustic solution present in the contacting step, the improvement which comprises contacting the sour distillate before the sweetening step with about 25-109 volume per cent of `non-alkaline methanol solvent containing less than about 10 volume per cent of water in order to remove bodies that cause color formation during the sweetening step and water washing the extracted oil to remove dissolved methanol solvent.

6. The process of claim 5 wherein the concentrated aqueous caustic solution is a 50-50 weight per cent potassium hydroxide solution.

7. The process of treating a sour heater oil distillate containing a large amount of mercaptan sulfur, which process comprises intimately contacting the distillate with about 50 volume per cent of a non-alkaline methanol solution containing about 2 volume per cent of water, separating the methanol solution from the Idistillate, water washing the extracted distillate to remove dissolved methanol solvent intimately contacting the extracted distillate with about 5 volume per cent of a solution containing a substantially satu rated aqueous KOH solution and about 0.004 to 0.3 weight per cent, based on said solution, of copper in the form of a copper compound which active as an oxidation promoterV and which copper has been derived from copper sulfate, introducing sufficient oxygen to convert the mercaptans, maintaining the reaction mixture at a temperature of about -125" F. for a contact time sufcient to render the distillate substantially doctor sweet, and then separating the spent caustic solution and associated reaction products from the treated oil.

8. The process of claim 2 wherein said copper salt is copper sulfate.

9. The process of claim 2 wherein said copper salt is copper chloride.

JACK 1-1. KRAUSE. RUSSELL H. BROWN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,791,521 Bjerregaard Feb. 19, 1931 1,970,583 Stager Aug. 21, 1934 2,013,083 Welsh Sept. 3, 1935 2,228,041 Yabroii et al Jan. 7, 1941 2,394,652 Alves et al Feb. 12, 1946 2,556,836 Browder et al June 12, 1951

Claims (1)

1. THE PROCESS OF REMOVING MERCAPTANS FROM A SOUR HYDROCARBON DISTILLATE WHICH IS HIGHER BOILING THAN GASOLINE WITH A MINIMUM OF COLOR DEGRADATION WHICH COMPRISES CONTACTING THE SOUR DISTILLATE WITH ABOUT 5 TO 200 PER CENT BY VOLUME OF NON-ALKALINE METHANOL SOLVENT WHICH CONTAINS NOT MORE THAN ABOUT 10 VOLUME PER CENT OF WATER; SEPARATING THE SOLVENT AND DISSOLVED COLORFORMING BODIES FROM THE EXTRACTED OIL, WATER WASHING THE EXTRACTED OIL TO REMOVE DISSOLVED METHANOL SOLVENT, TREATING THE WASHED OIL WITH ABOUT 1 TO 15 PER CENT BY VOLUME OF A CONCENTRATED AQUEOUS CAUSTIC SOLUTION, INTRODUCING A FREE-OXYGEN CONTAINING GAS INTO THE MIXTURE OF OIL AND CAUSTIC SOLUTION, MAINTAINING THE TEMPERATURE OF TREATING AT BETWEEN ABOUT 80* TO 125* F., SAID CAUSTIC SOLUTION ALSO CONTAINING AN EFFECTIVE AMOUNT OF A COPPER COMPOUND WHICH IS ACTIVE AS AN OXIDATION CATALYST, AND SEPARATING SPENT CAUSTIC SOLUTION AND ASSOCIATED REACTION PRODUCTS FROM THE TREATED OIL.

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