US2428695A - Hydrocarbon extraction process - Google Patents

Description

Patented Oct. 7, 1947 HYDROCARBON EXTRACTION PROCESS Donald 0. Bond, Northbrook, and Michael Savoy,

Chicago, Ill., assignors to The Pure Oil Company, Chicago, 111., a corporation of Ohio No Drawing. Application February 12, 1945, Serial No. 577,582

This invention relates to a method of separating ring-type hydrocarbons .fromopen-chain or aliphatic hydrocarbons.

We have discovered that aqueous alkali solutions containing in solution naphthenic acid salts or partially oxidized petroleum hydrocarbons,

have the ability to selectively dissolvearomatic the open-chain compounds, and by reason .of the difference in solubility, hydrocarbon,mi xtures containing open-chain and closed-ring hydrocarbons can be separated into one or more fractions more concentrated in closed-ring hydrocarbons than is .the original hydrocarbon mixture.

An objectof theinvention is to providea method for separating open-chain. hydrocarbons from closed-ring hydrocarbons.

Another object ofv the invention is to prepare from a mixture of open-chain and closed-ring hydrocarbons a fractionmore concentrated in open-chain hydrocarbons.

A further object of the invention is to prepare from a mixture of open-chain and closed-ring hydrocarbons a fraction more concentrated in closed-ring hydrocarbons.

Other objects of the invention will become apparent from the following description.

The extracting solution which is usedin ac-, cordance with our inyention is made by dissolving in aqueous alkali solution, preferably either sodium or potassium hydroxide solution, naphthenic acids and/or aqueous alkali soluble oxidation products resulting from the partial oxidation 7 14 Claims.- 6

of. When naphthenic acids are used, a solventizer, that is, a substance which will cause the naphthenic acids or soaps to go in solution in the aqueous alkali, is also added.

As solventizers to keep the naphthenic acids in solution, may be used such compounds as ethylene glycol, phenols including phenol, o-, mand pethyl phenol, normally liquid xylenols and mixtures thereof, cresols, 2,3,5-trimethyl phenol, butyl-pyrogallol, 3,4,.-dihydroxydiphenyl, p-chlormrc esol, alph ph h L thiophenols such as thiophenol, oand m-thiocresol, chlorpheno-ls such as oand p-chlorphenol and 2,4,5-trichlor phenol. Alkyl phenolssuch as the various cresols and mixtures of cresols have been found to be particularly'efiective solventizer's;

B the term naphthenic acids it is intended to include all alicyclic acids particularly those which occur naturally in crude petroleum and which are predominantly cyclic in structure such as carboxylic acids of cyclo-pentane and cyclohexane ring structure. These acids, generally speaking, fall within the empirical formulae CnH2n-1COQH, CnH2n-3COOH and cnnzmscoon and contain a cyclo-parafiinic ring having a carboxyl group attached to carbon in the ring or to n al ha c-chain which is i ur at ed t carbon in the ring. The acids may be mono or poly cyclic, usually the former. An increase .in the length of the aliphatic chain or in the number of aliphaticgroup substituents increases the tendency of the acids to behave as aliphatic acids. Since soaps of aliphatic acids, even those of as low molecular weight as heptylic acid, are too insoluble in sodium hydroxide solution to possess substantial merit as mercaptan solubility promoters, it is not desirable to have too many aliphat c carbon at ms-pe mo ecule prese t bevention.

'leum hydrocarbons.

cause of the concomitant low solubility. It is accordingly preferred to use those naphthenic acids which have at least a definite minimum solubility in aqueous alkali solution. Acids which have this alkali solubility are those acids which dissolve substantially completely to the extent of 18.7 pounds in a solution consisting of 18.3 pounds of sodium hydroxide, 6.3 pounds of commercial cresol and 56.7 pounds of water at temperatures of about 70 Fl It is apparent that in applying this solubility test to'compositions containing mixtures of naphthenic acids of varying molecular weight and structure, that some of the acids may dissolve and others remain undissolved. If the dissolved acids are soluble to the aforementioned extent, they are alkali-soluble within the meaning of this in- Naphthenic acids containing over about 8 or 9 carbon atoms per molecule, such as those containing between about 11 and 16 carbon atoms, are particularly effective.

The following Table I is characteristic of naph thenic acids which are suitable for use in preparing solutions for use in practising this inven-v tion.

Table I A. P. I. gravity at 60 F Neutralization No. (Mg.

KOH per g.) I. B. P

Apparent molecular w Approximate formula 1 Cracking.

The acidic oxidation products of petroleum hydrocarbons which may be used in preparing the extracting solution may be formed by either the vapor or liquid phase, preferably the latter, partial oxidation of normally liquid or solid petro- This oxidation may be carried out with air or oxygen or other oxidizing agents, with or without catalysts, at any desired superatmospheric pressure but is ordinarily not in excess of about 160 (3., although higher temperatures may be employed.

The products produced by oxidation of petroleum oils ordinarily vary considerably in composition, although it is generally believed that a major portion of the oxidation products are acidic in character, probably of the nature of fatty acids. Crude oxidation. mixtures, resulting from the liquid phase oxidation of parafiin wax, have been known'to contain higher fatty acids, and their anhydrides, oxy-acids, alcohols, ketones, alcoholketones, lactones and unsaturated acids.

The petroleum acidic oxidation products may i be obtainedfor example, by blowing air through kerosene or melted parafiin wax in the presence of suitable catalysts such as potassium perm an- I ganate and other manganates and permanganates of preparing such acidic material is to melt crude free.

. by distillation under vacuum. A distillation may,

Tjao

' Weight.

4 scale wax derived from petroleum and mix therewith an aqueous solution containing a, small amount of potassium permanganate and soda ash. This mixture is heated to a temperature of about 110 C. and air forced through the mixture for a period of about 18 hours. This reduces the unsaponifiable content of the mixture to about 65%. The oxidized acidic materials are obtained by neutralizing the oxidation mixture with aqueous alkali at a temperature of about 170 C., and a pressure of about 100 p. s. i. The resulting water solution of the alkali reaction products is separated from the Water insoluble material and the aqueous solution extracted with naphtha to more completely remove unsaponified material. The aqueous solution is acidified with dilute sulphuric acid and the acidicoxidation products set These are driedand may be fractionated if desired, be carried out on the crude oxidation mixture prior to saponification.

The acidic products derived by oxidation of petroleum hydrocarbons differ as to odor and appearance from similar pure straight chain fatty acids of approximately the same molecular They also differ in that they do not readily solidify at low temperatures. Analysis of the crude mixtures obtained as a result of the oxidation process is particularly difficult because of the lack of stability of some of the oxidation products which products break down upon dis-' tillation, thus producingnew materials not originally present in the crude oxidation mixture.

The acidic oxidation mixture, whatever its exact composition may be, issoluble in aqueous alkali solutions and materially enhances the abil ity of such solutions to dissolve liquid hydrocarbons. .While oxidation mixtures from anyof the less volatile petroleum hydrocarbons are useful in accordance with this invention, it is preferred to use those oxidation products obtained by the oxidation of relatively high molecular weight petroleum hydrocarbons, such as those hydrocarbons of about 10 to 30 carbon atoms.

A petroleum oxidation product which wehave found particularly effective, hereinafter referred v .to as Product A, is prepared by catalytic air oxidation of 36 to 40 Baum gravity Pennsylvania petroleum distillate and has th following properties:

Table II In order to demonstratethe difference in solubility of open chain and ring hydrocarbons in alkali solutions containing naphthenic acids or oxidi'zed petroleum hydrocarbons, a series of tests" was made in which different hydrocarbons were 7 dissolved into different solutions and thefamount of solution of the hydrocarbon inthe extraction solvent determined. Two methods were used to determine the extent of solution of hydrocarbons intheaqueous'alkalisolution: (1) the vapor pres sure method, and (2) the settling method. In the vapor pressure method, small amounts of hydrocarbons were added to the alkali solution in an extraction burette and the mixture was shaken,-

6 ing a plain 20% sodium hydroxide solution and the solubility of the hydrocarbons in this solution was substantially m'l. Alkali solutions con taining other known solubility promoters, such after which the vapor pressure above the solution 5 as isobutyric acid,- and high boiling tar acids was determined. This procedur w c t nued were: tried but these materials had very little until further addition of hydrocarbon had no ef- Q1ubi-1i1;y effect on t hydroca bo feet on the V p pressure. As larger amounts In Table IV is given solubility at various tem-- of hydrocarbons are dissolved in the alkali solupera'tures of various open-chain and closed-ring tion, the partial pressure of the hydrocarbon in- 10 hydrocarbons in s t creases until the solution has become saturated with hydrocarbons. Further addition of hydro- Table IV carbon produces no further efiect on the vapor j. r V pressure: All measurements taken after t attractant: s:-staircases?startersf burette had been placed in a water bath maming 1 s.3 parts by weightofNaOH, 18.7 parts by weight of naphtained at constant temperature and the burette gi g gg g-f ge i ig mgg fifi 9501s and allowed to remain therein for a sufficient period a of time so that the pressure became constant. Temperature, O

In the settling method, the extraction solution Hydrocarbon was mixed with an excess of hydrocarbon and al- 32 60 84 100 126 lowed to stand at the temperature selected for solution. After several days standing, a sample of the caustic solution was withdrawn and the hy- 21 drocarbon content was determined by means of gfgggg g :2 the A. S. T. M. apparatus for determining the di- 25 Di-isobutylene. 7.1 6.2 lution of crank-case oils. In every case where the ggglggg ggg; 2:? settling method was used, the mixture of hydro- Methylcyclohexane 10I1 carbon and aqueous alkali solution was allowed i8 2 to stand in a constant temperature water bath Benzene. 9.5 until the concentration of hydrocarbon in the g gfi g 3:3 caustic solution became constant. Pinene 10.0 The naphthenic acid-containing solution is gfigfifi ig g 3:3 designated as Solution M and the Product A con- Tetrahydronaphthalene 8.2 taining solution is designated as Solution A.

Table III This table, like the preceding table, shows the v difierence in solubility in the alkali solution 106- m of Hydrocarbon tween open-chain and closed-ring hydrocarbons. dissolved, per on The difference in solubility is particularly marked gg fg j gg iggs with respect to cyclohexene. com osition of Extracting Hydrocrabon O. In order to demonstrate the ability of alkali Centby solutions containing naphthenic acids and oxi- Vapor Settling dized petroleum hydrocarbons to separate ring $21K; Method hydrocarbons from open-chain hydrocarbons, a blend of 30% by volume of toluene and 70% by NaOHAsB volume of normal heptane was prepared and the Naphthenic blend was subjected to extraction with Solution cresflkfifi j nheptane M. 800 cc. of Solution M was contacted with cyclohexene 16 0 17 6 140 cc. of hydrocarbon mixture and the mixture jj 1 1 was then permitted to settle and separate into Pinene two layers. The layers were separated and the mhemne 9 0 8 2 hydrocarbon was recovered by distillation from the lower layer. 59 cc. of distillate was recovered I ton c 18.0 from the lower layer and this was again ex- Y tracted with 300 cc. of Solution M and the hydro- SolutmnA dl-lsobutylenem carbon recovered by distillation from the lower layer as before, amounted to 24 cc. 24 cc. of hy- It is apparent from the table that cyclic hydrodrocarbon was again contacted with 125 cc. of carbons are more soluble in the alkali solution Solution M and 10 cc. of hydrocarbon was rethan are the open-chain hydrocarbons and that 60 covered from the lower layer. In the following this difference in solubility is even more marked Table V is given the data with respect to the in the case of the alkali solution containing quantity, refractive index and toluene content Product A than in the case of the solution conof the several extracts and raflinates produced in taining naphthenic acids. Tests were made usthe extraction.

' Table V Hydrocarbons Recov- H-ydrqearbons f c6 Soution cc of lgydrm cred from Extract Layer f g g fg ig MUM are 1stExtraction 800 140 1. 4228 33.5 59 2nd Extraction 300 59 1. 4259 36.5 24 3rd Extraction"--. 24. ,1. 4290 39.5 10

' sion difiiculties.

. It Will be seen from. Table V that by a threestage extraction it was possible to produce a fraction containing 39.5% of toluene.

[A portion of th same toluene-heptane blend 8 geneous We have found that the solutions of the composition given in Table I will remain homogeneous over the usual atmospheric temperature range. I

was extracted with the Solution A, the compo- '5 Extraction may be effected over the range sition of which is given in Table I. 110 cc. of of :"atmospheric temperatures. Temperatures hydrocarbon mixture was mixed with 270 cc. of ranging from 32 to'126 F. have been usedsatis- Solution A in the first-stage extraction- In the factorily. 7 The pressure maintained need only be second-stage extraction 35 cc. of hydrocarbon, sufficient to keep the hydrocarbons from vaporobtained from the extractlayer, was again 'ex- 10 izin'g; tracted with Solution A and 19 cc. of hydrocar- It is claimedr bons was recovered from the extract layer and in if The'method of separating a mixture'of'opem the third-stage extraction, the 19 cc. of hydrochain and closed-ring hydrocarbons into a plu-- carbons from the extract layer was recovered rality'of fractions at least one of which contains having a toluene content of 40.5%. Table VI a higher proportion of open-chain hydrocarbons gives the data for the extraction showing the reand at least one of which contains a higher pro fractive index, toluene content and quantity of portion of closed-ring hydrocarbons than'the hydrocarbon extract from each step of the procoriginal mixture comprising contacting saidmixess. ture withat leastabout 2 volumes of an aqueous Table VI Hydrocarbons Remain- V cclsolution cc. of Hydroeggggggggggiger mg ifi n t e ligy er AUsed gggg V v V an fii'i gg cc. 7 m)" 2%533 -00.

1st Extraction" V 270 110 1. 4234' 34.0 5 35 2nd Extraction. 200 1.4273 38.0. 19 3rd. Extraction..." 125 19 1.4300 40.5 14

It will be seen, therefore, that by employing aqueous alkali solutions containing naphthenic acids or oxidation petroleum hydrocarbons in solution, fractions respectively richer in open-chain and closed-ring hydrocarbons can be prepared from a mixture of open-chain and closed-ring hydrocarbons. A j

Extraction solutions for use in our process should contain a substantial amount of free alkali metal hydroxide, and preferably at least 10% by weight should be present. The solution'shouldalso contain a substantial amount of naphthenic acid orv oxidized petroleum soaps, preferabl not less than 10% by weight and generally in excess of 15% by weight. The naphthenic acids or ox idized petroleum products may be added to the solution in the acidic form or in the form of the alkali metal soap thereof. Sufficient solventizers should be present to keep the naphthenic acid' solution containing not less than about 10%. by.

weight of free alkali metal hydroxide and not less than about 10% by weight of a substance selected from the group consisting of alkali metal soaps of naphthenic acids and petroleum partial oxidation products, separatingthe resulting mixture into two layers and recovering hydrocarbons from the extract layer.

2. The method of separating a mixture of aro matic hydrocarbons and open-chain hydrocarbons into at least two fractions one of which is richer in aromatic hydrocarbons and the other of which is poorer in aromatic hydrocarbons than the original mixture comprising contacting said mixture with at least about 2 volumes of an aqueous alkali solution containing not lessthan about 10% by weight of free alkali metal hydroxide and not less than about 10% by weight of a substance; selected from the group consisting of soaps of naphthenic acids and of petroleum partial oxida- Care "should be centrated as to be too viscous and causeemul- Solutions containing up to 25% by weight'of free alkali'metal hydroxide and up to the maximum amount of soap soluble in the solution under extraction conditions work satisfactorily.

Care should be exercised notto increase the concentration of alkali metal hydroxide and/or naphthenic acids or petroleum oxidation products 1- to thepoint where thesolution is no longer homotion products, separating the resulting mixture into an extract layer and a raffinate layerand recovering hydrocarbons from the extract layer. 3. Method in accordance with claim 2 in which the free alkali metal hydroxide content of the solution is in excess of 10% by weight and the content of said substance is in excess of approximately 15% by weight. 7

4;. Method in accordance with claim l'in which the substance comprises naphthenic acid soaps and the solution contains sufficient solventizer to keep the soaps in solution. a

' 5. Method in accordance with claim 1 in which -the substance comprises naphthenic acid soaps and the solution contains sufficient cresols to keep the soaps in solution. 7 r

6. Method in accordance with claim 2 in which the substance comprises naphthenic acid soaps and the solution contains'suflicient solventizer V to keep the soaps in solution. 1 s a r 7. Method in accordance with claim 2 in which the substance comprisesnaphthenic 'acid soaps and the solution contains sufllcient cresols to keep the soaps in solution.

8. The method of separating a mixture of hydrocarbons containing cyclohexene into at least two fractions one of which is richer in cyclohexene and the other of which is poorer in cyclohexene than the original mixture comprising contacting said mixture with at least about 2 volumes of an aqueous solution containin not less than about by weight of free alkali metal hydroxide and not less than about 10% by weight of a substance selected from the group consisting of soaps of naphthenic acids and soaps of partial oxidation petroleum products, separating the resulting mixture into an extract layer and a raffinate layer and recovering hydrocarbons from the extract layer.

9. Method in accordance with claim 8 in which the substance comprises naphthenic acid soaps and the solution contains cresols in sufiicient amount to keep the soaps in solution.

10. The method of separating a mixture of open-chain and closed-ring hydrocarbons into at least two fractions one of which is richer in closed-ring hydrocarbons and the other of which is poorer in closed-ring hydrocarbons than the original mixture comprising contacting said mixture at atmospheric temperature with at least about 2 volumes of an aqueous solution containing not less than 10% by weight of free alkali metal hydroxide, not less than by weight of alkali metal-naphthenie acid soaps and a sufficient amount of solutizer to keep the soaps in solution, separating the resulting mixture into an extract layer and a rafiinate layer, and recovering hydrocarbons from the extract layer.

11. Method in accordance with claim 10 in which the solventizer is cresol.

12. The method of separating a mixture of open-chain and closed-ring hydrocarbons into at least two fractions one of which is richer in closed-ring hydrocarbons and the other of which is poorer in closed-ring hydrocarbons comprising contacting said mixture at atmospheric temperature with at least about 2 volumes of an aqueous solution containing not less than about 10% by weight of free alkali metal hydroxide and not less than 10% by weight of alkali metal soaps of petroleum partial oxidation products, separating the resulting mixture into an extract and a rafiinate layer, and recovering hydrocarbons from the raflinate layer.

13. Method in accordance with claim 12 in which the soaps of petroleum partial oxidation products are soaps of a product prepared by catalytic air oxidation of 36 to 40 Baum gravity Pennsylvania petroleum distillate, which product has the following properties:

B-. gravity at 158 F l1-9 Specific gravity at 158 F 1007-09930 Viscosity (Saybolt) at 210 F 91-101 Cold test (A. S. T, M.) 20-25 F. Flash (0. O. C.) 250-270 F. Fire (C. O. C.) 280-300 F. Acid number -130 Saponification number -210 Iodine number 20 maximum Ash 0.5-1.0

14. Method in accordance with claim 1 in which the aqueous solution is composed of:

Per cent by weight Sodium hydroxide 18 Naphthenic acids 18.7 Cresols 6.3 Water 1 56.7

DONALD C. BOND. MICHAEL SAVOY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS