US2495850A - Process of extracting aromatic hydrocarbons - Google Patents

Description

Jan. 31, 1950 A. P. LIEN Er AL 2,495,850

PRocEss oF EXTRACTING ARoMATIc HYDRocARBoNs Filed nec. 2v, 194e 2 sheets-sheet 1 5E TTL [H Jrg Feed

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Jan 31, 1950 A. P. LIEN Er A1.

PROCESS 0F EXTRACTING AROMATIC HYDROCARBONS Filed nec. 2v, 194e 2 Sheets-Sheet 2 ?aerrtecl Jan., Si, i195@ aaaassc PROCESS F EXTRCIING ROMTIC HYDRGCARBNS Arthur R Lien, Hammond, inail., and Bernard L, lEvering, Chicago, lill., assignors to Standard @il Company, Chicago, lill., a corporation ci indiana Application December 2'?, i946, Serial No. 718,854

11 Claims.

This invention relates to the treatment of organic materials, and more particularly to the relining of organic materials containing mixtures of hydrocarbons, such as aromatic, parafllnlc, naphthenic and/or olenic hydrocarbons to selectively extract therefrom the aromatic hydrocarbons. It relates still more particularly to the selective extraction of aromatic hydrocarbons from petroleum fractions containing the same.

The separation of aromatic hydrocarbons from parainic, naphthenic and/or olenic hydrocarbons in materials containing the same find application in many fields. Among the many possible specific applications of the invention are the treatment of petroleum cycle stocks to provide less refractory stocks for subsequent thermal or catalytic cracking operations. Other specific applications will be readily apparent.

It is an object of the present invention to provide a method of selectively separating aromatic hydrocarbons from paraflinic, naphthenic and/or oleilnic hydrocarbons in a mixture containing the same.

Still another object of the invention is to provide an improved method of refining petroleum fractions to separate therefrom undesirable aromatic hydrocarbons.

A still further object of the invention is to provide an effective method of refining hydrocarbons.

Other objects and advantages of the invention will become apparent from the following description thereof read in conjunction with the accompanying drawings which form a part of the specification and in which Figure 1 is a flow-diagram of one method of carrying out the invention, and

Figure 2 is a flow-diagram of a modied method of carrying out the invention.

- In accordance with the present invention aromatic hydrocarbons are selectively separated from a mixture containing non-aromatic hydrocarbons, such as parafilnic, naphthenic and/or olefinic hydrocarbons by extracting such materials with a complex of boron fluoride (BFa) with an oxygenated organic compound, and the halogen, preferably chlorine, derivatives of such oxygenated organic compounds. The aromatic hydrocarbons and the non-aromatic hydrocarbons subject tolseparation by the present invention may be normally liquid or liquid under existing operating pressures. While complexes of BF: with aliphatic or aromatic or oxygenat'ed compounds can be used, we prefer to employ complexes of BF; with an oxygenated alkane compound selected from the class consisting of ethers, esters and acids having not more than about 5,

Methyl ether Butyl formate Ethyl ether Ethyl propionate Propyl ether Formic acid Butyl ether Acetic acid Amyl ether Propionic acid Phenol Anisol Methylethyl ether Pyran Methyl acetate Tr- Ethyl acetate Tetra Propyl acetate Penta- Amyl acetate methylene Methyl formate oxides Ethyl formate and the halogenated, preferably chlorinated, derivatives of the above as for example, B,B dichloroethyl ether (Chlorex) chloroacetic acid, etc.

While complexes of boron fluoride with oxygenated organic compounds as a class are effective solvents for effecting a separation between aro-` matic hydrocarbons and paraiiinic, oleflnlc and/or naphthenic hydrocarbons, they are all not equal in their eifectiveness and selectivity since the degree'of selectivity and effectiveness may vary with different complexes with the composition of the mixture being extracted and with the conditions of extraction, as will be hereinafter described.

The boron fluoride complexes are readily prepared by bubbling a slight molar excess of boron fluoride through the oxygenated compound, e. g. ether, ester, acid, etc., and then subjecting the mixture to reduced pressure to remove the excess boron fluoride. In some cases, it is desirable to carry out the BF; stripping step at lower than room temperature in order to avoid decomposition of the complex. The residual product is a complex of a mol to mol ratio of boron fluoride to the oxygenated organic compound. The complexes suitable for the herein described inven.

tion are liquid or solids which melt slightly above room temperature, e. g. about F. to about F. A small amount, sufllcient to give a partial pressure of at least 15 pounds, and preferably from about 15 to 500 pounds, per square inch, of boron fluoride may be used in conjunction with the herein described complexes, in order to effect increased extraction, e. g. of higher molecular 55 weight aromatics.

The choice of anv particular organic oxygenated compounds used in forming the boron iiuoride complex will depend upon the feed to be treated, with due consideration being given to the boiling point of the complex in relation to the boiling range of the feed material and the extract to be obtained therefrom. For example, the boron fluoride-methyl ether or boron fluorideethyl ether complexes boil at relatively low temperatures, namely 258 to 262 F. Therefore, if the extracted material boils in this temperature range. it is preferable to use a higher boiling f complex. for example the adduct of boron fluoride with a halogenated methyl ethyl ether. Of course, under some conditions complexes having a boiling point lower than that of the extracted material may be used, in which case the complex can be recovered by distilling or flashing off the same from the extract.

The extraction can be carried out over a wide temperature range. of about 50 F. to about 150 F. or higher, and preferably from about '10 F. to about 100 F. The quantity of complex used should be suilcient to give a diphasic separation and depending upon the material being extracted can vary from 10 volume percent to about 200 volume percent or more, based on hydrocarbon feed, and preferably from about 50 volume percent to about 100 volume percent, although in some cases as little as 5 volume percent or less will give a satisfactory diphasic separation. A pressure sufficient to keep the' materials in a liquid phase should be maintained in the extractor. In the extraction of heavier stocks, such as for example lubricating stocks or in separation of aromatics and olens, improved selectivity can be attained under certain conditions by the addition to the extraction mixture of an inert paraiiin hydrocarbon diluent, such as for example pentane, hexane or heptane.

'Ihe following procedure of extracting a highly aromatic, relatively low-boiling hydrocarbon feed stock with a boron fluoride-ethyl acetate complex is given by way of illustration only and is not intended to be a limitation of our invention. Referring to Figure l, a highly aromatic, low-boiling hydrocarbon feed stock is introduced through a line I into the bottom portion of an extractor and countercurrently contacted with a boron fluoride-ethyl acetate complex introduced into the upper portion of the extractor I| through a line I2. The extractor I is suitably a packed column, although other known suitable means of obtaining intimate contact can be employed. A raffinate is removed overhead from the extractor I through a line I3 and introduced into a settler Il wherein any carryover complex is settled out and returned to the extractor I I through line |5. The raffinate, free of carryover complex, is withdrawn from the separator I4 through line I6 and introduced into the bottom portion of a still I1 provided with suitable heating means such as heating coil |8. The rannate substantially freed of aromatics is taken oif overhead through a line I9. The bottoms from the still |1 comprising a boron fluoride-ethyl acetate complex is withdrawn from still I1 through a line 20 and introduced into the complex storage tank 2|. If the hydrocarbon feed stock distills above the boiling point of the complex, the aromatic-free raffinate is withdrawn as bottoms and the complex is taken overhead. Still I1 may be operated under reduced pressure.

The extract from the extractor is withdrawn therefrom through line 22 and introduced into still 23 equipped with suitable heating means,

4 such as heating coil 2l. Still 23 may be operated at sub-atmospheric pressure. A fraction comprising substantially aromatic hydrocarbons is removed overhead from still 23 through line 25,

5 while the complex, substantially free of aromatics, is withdrawn through line 26 and either introduced into the complex storage' tank 2| through line 21, or recycled to the extractor through line 28. VComplex from storage tank 2| is introduced into the extractor through lines 28, 29 and I2. In order to supply make-up boron fluoride complex. boron fluoride is introduced into the storage tank 2| through line 30 and ethyl acetate is added through line 3|. f

The foregoing example illustrates a method of carrying out the herein described invention in which the boron fluoride complex is not decomposed by distillation. However, certain boron .fluoride complexes are decomposed into boron fluoride and the oxygenated organic compound when subjected to distillation, even vacuum distillation. When employing such complexes they cannot `be recovered as in the hereinbefore described method. The following example illusz5 trates one method of carrying out the invention employing a boron fluoride complex which is decomposable under distillation conditions. For ythe purpose of illustration, the following procedure provides a method of carrying out the invention employing as the solvent a boron fluoride-beta beta dichloroethyl ether complex hereinafter referred to as the boron fluoride-Chlorex complex.

Referring to Figure 2, the feed to be extracted,

for example highly refractory aromatic cycle stock, is introduced through line ||0 into the bottom portion of extraction tower and countercurrently contacted with a boron fluoride- Chlorex complex introduced into the upper pornon of the tower In through une H2. A temperature of about 40 to 90 F. is maintained in the extraction tower The raffinate from the extraction tower III is removed overhead through line |`l3 to a settler Ill, wherein any entrained boron fluoride-Chlorex complex is settled out and recycled to tower I through lines I I5 and IIB, or may be passed through lines ||5 and ||1 to a complex recovery unit hereinafter described. The raffinate from the settler III is passed through o une Ha to a boron fluoride stripper H9 provided with suitable heating means such as a heating coil |20, wherein any small amount of dissolved boron fluoride complex is decomposed by heating and the boron fluoride is removed overhead through lines |2| and |22 to a boron fluoride- Chlorex mixer |23. The bottoms from the stripper l I9 are withdrawn through line |24 to a fractionator |25, provided with suitable heating o means such as a heating coil |26, wherein the Chlorex is taken overhead through lines |21 and |28 to the boron fluoride-Chlorex mixer |23. 'I'he raffinate, freed of boron fluoride and Chlorex, is removed from the tower |25 through line |29. If

35 a light hydrocarbon diluent has been used it may be removed as an overhead stream from the top of the fractionator |25 and the Chlorex taken off as a higher boiling side stream. Obviously, in the event the hydrocarbon product has a lower boiling point than the Chlorex, the hydrocarbon will be taken overhead from the fractionator |25 and the Chlorex will be withdrawn from the fractionator |25 as a bottom and passed to the boron ucride-Chlorex mixer.

The extract from the extractor tower comprising boron fluoride-Chlorex complex and the extracted material from the feed is removed from tower through line |30, and introduced into a stripper |3| provided with suitable heating means such as heating coil |32 for maintaining a bottom temperature of 180 F. to 400 F. in the stripper. Boron fluoride-Chlorex complex from the settler ||4 may be introduced into the stripper 13| through lines ||1 and |30. Boron fluoride is taken overhead through line |33 and passed via line |22 to the boron iluoride-Chlorex mixer |23. Bottoms from the stripper |3| are withdrawn through line |34 to fractionating tower |35, provided with suitable heating means such as heating coil |35, wherein the separation is made between the organic extracted* material and the Chlorex. Chlorex from the fractionator |35 is taken overhead through line |37 and lntroduced via line |28 to the boron fluoride-Chlorex mixer |23. 'I'he extracted organic material is withdrawn from the fractionating tower |35 through line |38. Alternately, the Chlorex may be withdrawn as bottom product if the boiling range of the extract is below the boiling point of Chlorex.

The boron uoride-Chlorex mixer is operated under cooling conditions to prevent excessive temperature due to the heat of reaction between the boron fluoride and Chlorex. Make-up boron fluoride is introduced t the mixer through line |33 and the make-up Chlorex through line |40 in sumcient quantity to maintain a stoichiometric ratio of the components of the complex. The boron uoride-Chlorex complex from mixer |23 is recycled to the extraction tower through lines MI and ||2. Although the boron iluoride stripper and the Chlorex fractionator have been shown as separate towers, a single tower may be used.

The applicability of boron uoride-complexes to the separation of aromatics from paraffin hydrocarbons is demonstrated by the data in Table I below. 'I'he data presented therein were obtained in a one step extraction of blends of 50% heptane and 50% benzene, ortho xylene, and meta xylene with complexes of boron iluoride and various oxygenated organic compounds.

While the data in Table I are based on a single step extraction, an improvement can be obtained by carrying out the extraction in a number of stages. This improvement'is illustrated by the data in Table II, in which a blend of 50% benzene and 50% heptane was extracted with boron iluoride-ethyl ether and boron uoride-propyl acetate complexes in one and four stages, using a total of one volume of complex to one volume oi' the hydrocarbon mixture in each case.

TABLE II One stage vs. four stage extraction o! 50% n-C1-50% CeHe mixture Total Extraction, Complex Per Cent 1 stage' 4 Stage' Brr-Ethyl Ether 54. 2 79. 1 BFf-Propyl Acetate 55. 6 77. 1

TABLE III One stage vs. four stages extraction of 50% cetane-50% CeHe mixture 1 Stage 4 Stages The extraction of a polynuclear aromatic from BF. Ethyl Ether TABLE I Selective extraction of aromatic-Parafia blends with Bln-complexes 50% n-C1 50% n-01 60% n-C1 n-Heptane 50% CeHa 50% o-xylene 50% m-xylene Test Mix no* l. 3871 1.4301 1.4461 1. 4417 Bry-Ethyl Acetate:

Ramnate np* 1.3871 1. 4128 1. 4342 1. 4319 Treating Loes, Vol. Per Cent-..- 4 30 14 12 Per Cent Aromatics extracted l 50. 5 20. 2 17. 9 selectivity factor 1. 5B 1. 44 BFa-Propyl Acetate:

Ramnate no 1. 3871 1. 4102 1. 4301 1. 4276 Treating Lou, Vol. Per Cent 5 55 30 36- Per Cent Aromatics extracted 1 55. 6 27. 2 25.8 selectivity factor I l. 01 70 BFz-Acetlc Acid:

Rsnate nu 1.3871 1.4330 Treating Los, Vol. Per Cent 2 7 Per Cent Aromati extracted l 11. 7 selectivity factor 1. 87 BFr-Ethyi Ether:

Ralnate np l. 3871 1. 4103 1. 42% 1. 4276 Treating Loss, Vol. Per Cent 5 58 4l 38 Per Cent Aromatics Extracted 1 54. 2 27. 6 25. 8 selectivity Factor l 93 67 BFa-Anisole:

Railinate no 1. 3m 1. B40 L 4437 1. 4387 Treating Loss, Vol. Per Cent 3 86 55 51 Per Cent Aromatics extracted l 8. 1 4. 1 5. 5 selectivity factor L--- 12 0. 07

Baeedonn i n i l selectivity lector-aromatica extracted divided by treating lose; perfect selectivity equals 2. 0.

guasto a mixture containing polynuclear aromatica and non-aromatic hydrocarbons is demonstrated by the data in Table IV, in which a mixture of 20% anthracene oil and 80% heptane was extracted with an equal volume oi' boron fluoride-ethyl ether complex in one stage.

TABLE IV con. heptane-aber, antnncene 011 n 1.4326 mante no 1.4083 Aromatic extracted based on nl,o n

per cent.- 53.4 Treating loss -do Aromatic based on treating loss -do.-- 50 The foregoing data demonstrate the eil'ectiveness o! complexes of boron iluoride and an oxygenated organic compound in extracting polynuclear aromatic hydrocarbons from a mixture containing paraillnic, naphthenic and/cr. oleilnic hydrocarbons The degree of extraction to be obtained with a complex mixture of higher molecular weight aromatica, parafllns, naphthenes and oleilns is demonstrated in Table V 4by a number of experlments carried out on a sample of highly refractory gas oil cycle stock, obtained by multiple recycling of East Texas naphthenic gas oil in a catalytic cracking process.

- TABLE V of cycle stock and BF: ethyl ether complex. Comparison of this run with run 6 shows that aromatic extraction is markedly increased over that obtained with RF1. ethyl ether complex in the absence of excess BF: and this without attendant loss in selectivity. The results in run 'I indeed approach closely those obtained with the relatively highly dissociated BFa. Chlorex cornplex (run 8). Although the presence of free BF: increases' the degree of extraction when used in conjunction with a BF: oxygen complex, it is seen from run 1 that BF: alone has little eiect in aromatic removal.

The effect of multiple stage contacting is shown by run 11. In this case a given sample of the cycle stock was contacted with equal volumes of fresh BFaethyl ether complex in 4 successive treats. Examination of the physical properties o! the ilnal rainate shows it to be less aromatic Extraction of cycle stock from East Texas naphthenic gas oil (one volume BF: complex volume oil) i Ramnate Run No. man; Agent V'lfgef't selectivity l no* D4 Gas 011 l- {Bycie Stock... "mm-"i5 ""mmil 1. 13 16. 6 23 16. 4

14.1 16.3 30 16. BF1.Propyl Ether- 45 12.4 BFLADISOIG 33 15. 0 BF1.Ethy1 Ether, 4-Stage l. 0. 840 38 l0. 0

l selectivity-ratio no* divided by treating lossXlO.

The measure of selectivity in the above experiments is shown as the ratio of index change to treating loss. It is seen that most of the complexes show about the same degree of selectivity, in direct contrast to the results on the lower moiecular weight aromatics as shown in Table I. Thus, anisole which is entirely unsatisfactory for extraction of benzene or xylene because of extremely poor selectivity (Table I), effects a high degree of extraction of aromatica from cycle stock with a good selectivity.

In the case of aromatics in the gas oil range, the degree of extraction increases markedly with increase in molecular weight of the organic portion of the BF: complex. Thus with the ethers (ROR), there is a dennite progression as R is changed from methylto ethylto propyl. The same eilect is noted in comparing the esters.

These eil'ects, holding only for the higher mocomplexes of boron fluoride and oxygenated compounds of the type herein described are effective in removing organic sulfur compounds, and colorforming bodies from organic materials, particularly hydrocarbons.

While we have described our invention with reference to certain specific embodiments thereof, the invention is not to be considered limited thereto, but includes within its scope such modifications as come within the appended claims.

We claim:

1. The method of extracting aromatic hydrocarbons from a mixture comprising normally lic| uid aromatic hydrocarbons and normally liquid non-aromatic hydrocarbons, comprising extracting said mixture at a temperature `within the range of from about 50 F. to about 150 F. with a complex of boron uoride with an oxygenated organic compound in suillcient quantity to form a diphasic separation, separating a fraction comprising essentially said non-aromatic hydrocarbons and a minor amount of said complex, and

a fraction comprising essentially aromatic hydrocarbons dissolved in said complex, and separating said complex from said fractions.

2. The method of extracting aromatic hydroing said mixture at a temperature within the range of from about 50 F. to about 150o F. with a complex of boron fluoride with an oxygenated alkane compound having not more than about carbon atoms in the alkyl group, in suilicient quantity to form a diphasic separation, separating a fraction comprising essentially said nonaromatic hydrocarbons and a minor amount of said complex, and a fraction comprising essenltially aromatic hydrocarbons dissolved in said complex. v

3. The method described in claim 2 in which the oxygenated alkane compound is an alkane ester. l

4. The method described in claim 3 in which the alkane ester is ethyl acetate.

5. The method described in claim 2 in which the oxygenated alkane compound is an alkane ether.

6. The method described in 'claim 5 in vvhich the alkane ether is an ethyl ether.

7. The method described in claim 6 in which the alkane ether is beta, beta dichloroethyl ether.

uid aromatic hydrocarbons and normallyliquid non-aromatic hydrocarbons, comprising contacting said mixture at a. temperature within the range of from about 50 F. to about 150 F. with a complex of boron uoride and an oxygenated organic compound in suilicient quantity to form a diphasic separation,'separating a raiinate fraction comprising essentially non-aromatic 'hydrocarbons and a minor amount of said complex and an extract fraction comprising essentiallyl aromatic hydrocarbons dissolved in said complex and separating said complex from the railinate and extract fraction. l

l11. The method of extracting high molecular weight polycyclic aromatic hydrocarbons from a mixture comprising normally liquid high molecular weight polycyclic aromatic hydrocarbons and normally liquid non-aromatic hydrocarbons, comprising contacting said mixture at a temperature within therange of from about 50 F. to

about 150 AF. with a solventi comprisingessen- 81 The method described in claim 2 in which I the oxygenated alkane is an alkane acid.

9. The method of extracting aromatic hydrocarbons from a mixture comprising aromatic hydrocarbons and parailinic hydrocarbons comprising extracting said mixture at a temperature within the range of from about 50 F. to about 150YF. with a complex of boron fluoride with an oxygenated alkane compound having not more than about 5 carbon atoms in the alkyl group in 'suicient quantity to form a diphasic separation, separating a rafdnate comprising vessentially paraillnic hydrocarbons and said complex and an xtract comprising essentially aromatic hydrocarbons, and said complex, and separating said complex from the raillnate and extract fractions.

10. The method of extracting aromatic hydrocarbons from a mixture comprising normally liqtially a complex of boron uoride with an oxygenated organic compound, and an excess of boron fluoride suilcient to give` a partial pressure of at least 15 pounds per square inch, separating a raffinate comprising essentially non-aromatic hydrocarbons and a small amount of said solvent and an extract comprising essentially aromatic hydrocarbons and said solvent, and separating said solvent from said raffinate and extract.

ARTHURP. LIEN. BERNARD lL. EVERING.

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

UNITED STATES PATENTS Number Name Date 2,246,257 .Kohn June 17, 1941 2,257,086 A'twell Sept. 30, 1941 2,260,279 D'Ouville et al Oct. 21, 1941 2,343,744l Burk Mar. 7, 1944 2,415,171 Horeczy Feb. 4. 19.47

Claims (1)

1. 2. THE METHOD OF EXTRACTING AROMATIC HYDROCARBONS FROM A MIXTURE COMPRISING NORMALLY LIQUID AROMATIC HYDROCARBONS AND NORMALLY LIQUID NON-AROMATIC HYDROCARBONS, COMPRISING EXTRACTING SAID MIXTURE AT A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 50*F. TO ABOUT 150*F. WITH A COMPLEX OF BORON FLUORIDE WITH AN OXYGENATED ALKANE COMPOUND HAVING NOT MORE THAN ABOUT 5 CARBON ATOMS IN THE ALKYL GROUP, IN SUFFICIENT QUANTITY TO FORM A DIPHASIC SEPARATION, SEPARATING A FRACTION COMPRISING ESSENTIALLY SAID NONAROMATIC HYDROCARBONS AND A MINOR AMOUNT OF SAID COMPLEX, AND A FRACTION COMPRISING ESSENTIALLY AROMATIC HYDROCARBONS DISSOLVED IN SAID COMPLEX.

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