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Publication numberUS3755154 A
Publication typeGrant
Publication dateAug 28, 1973
Filing dateDec 7, 1970
Priority dateDec 10, 1969
Publication numberUS 3755154 A, US 3755154A, US-A-3755154, US3755154 A, US3755154A
InventorsAkabayashi H, Hoshiyama S, Takigawa S
Original AssigneeNissan Chemical Ind Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Separation of hydrocarbons from mixture thereof
US 3755154 A
Abstract
A process for separating at least one component of aromatics, olefins, naphthenes and paraffins from a mixed hydrocarbon stock containing the same by means of extraction with solvent characterized in that a solvent system selected from the group consisting of N-acetyl-morpholine, mixed solvent of N-acetylmorpholine and water, N-acetyl-2-pyrrolidone, mixed solvent of N-acetyl-2-pyrrolidone with water, dimethyl sulfoxide, diethylene glycol and other organic solvent is employed.
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United States Patent Akabayashi et al.

[ Aug. 1973 SEPARATION OF HYDROCARBONS FROM MIXTURE THEREOF Inventors: Hiroshi Akabayashi, Tokyo; Satoshi Hoshiyama, Ichikawa; Shinichiro Takigawa, Funabashi, all of Japan Nissan Kagaku Kogyo Kabushiki Kaisha, Tokyo, Japan Filed: Dec. 7, 1970 Appl. No.: 95,826

Assignee:

Foreign Application Priority Data Dec. 10, 1969 Japan 44/98926 June 29, 1970 Japan 45/5670l US. Cl 208/314, 208/323, 208/326,

1111. c1 Cl0g 21/00 Field of Search 208/314, 322, 323, 208/326, 317

References Cited UNITED'STATES PATENTS 10 1940 Lyons 208/314 2,484,305 10/1949 Mayland et al. 208/322 2,753,381 7/l956 Nelson 208/326 2,952,7l7 9/1960 Fleck et al..... 208/323 3,605,850 9/1971 Borst 208/325 Primary Examiner-Herbert Levine Att0rneyS.tevens, Davis, Miller & Mosher 57 ABSTRACT diethylene glycol and other organic solvent is employed.

3 Claims, 3 Drawing Figures WATER 8 F LE HYDROCARBON FEED 13 AROMATIC 1 PRODUCT 14 FX WATER l8 /-o121z1=m paooucr I 25 22 -1 l 2o 25 PARAFFIN L PRODUCT PATENTEDMIGZB ms SLY-55154 sum 1 use WATER HYDROCARBON FEED AROMATIC PRODUCT OLEFIN PRODUCT 25 PARAFFIN PRODUCT PAIENTEUmsea ma 3.755; 154

' sum 2 or 2 I-OLEFIN f CIB-HYDROCARBON soc c7- HYDROCARBON .8 N'ACETYL'2- |GHT PYRROLIDONE n-PARAFFIN .2 .4 .e .8 N-ACET -2- N-ACETYL-Z-PYRROLIDONE,BY WEIGHT PYRROL' SEPARATION OF HYDROCARBONS FROM MIXTURE THEREOF The present invention relates to a process for separating hydrocarbon mixtures into desired fractions by means of extraction. More particularly, the present invention relates to a process for extracting desired fractions selectively from hydrocarbon mixtures containing olefins, naphthenes, paraffms and aromatics in various proportions such as cracked petroleum oils or dehydrogenated paraffinic hydrocarbons.

Petroleum hydrocarbons which have been subjected to conversion treatments such as cracking contain olefins, naphthenes, paraffins and aromatic hydrocarbons in various proportions and, therefore, separation of the hydrocarbons into each fraction is demanded. Separation by means of extraction with solvents having high selective solvent power for aromatic hydrocarbons such as N-methylpyrrolidone has been proposed and, benzene, toluene, xylene, etc. are isolated according to this process.

However, there has been no solvent having satisfactory selectivity for olefins, naphthenes and paraffins.

ln separation of olefinic hydrocarbons, absorption method in which molecular sieve or silica gel is used, a method in which a complex with a heavy metal is formed and extraction-distillation method have so far been employed. However, all of those methods are largely influenced by impurities contained in the olefinic hydrocarbons and life of materials used for the separation is short. Accordingly, those methods are too expensive and uneconomical to be employed in treatment of cheap by-produced oils such as oils obtained by petroleum treatments.

On the other hand, in condensation-separation of olefinic hydrocarbons according to extraction with solvents, there has been proposed the use of liquid ammonia, liquid sulfurous acid, polyethylene glycols, sulfolan, dimethylsulfoxide and -butyrolactone. However, the solvents used on industrial scale have been those having only a relatively small carbon numbers (mainly those having five or less carbons). The reasons therefor are that as carbon number is increased, selectivity of solvents is decreased or dissolving power is decreased even if the selectivity is excellent. Thus, the solvents become very expensive and undesirable from industrial viewpoint.

An object of the present invention to provide a pro cess for collecting effectively desired fractions according to extraction with a solvent from olefin-containing hydrocarbon mixture by-produced in a large amount in thermal craking of petroleum or hydrocarbon mixtures containing olefins and paraffms obtained by dehydrogenation of paraffins.

Another object of the present invention is to provide extraction solvent systems which effectively extract desired fractions from said hydrocarbon mixtures.

The above described objects and other objects of the present invention can be attained by using a solvent system selected from the group consisting of N- acetylmorpholine, mixed solvent of N- acetylmorpholine and water, N-acetyl-2-pyrrolidone, mixed solvent of N-acetyl-Z-pyrrolidone and water or dimethylsulfoxide and mixed solvent of N-acetyl-2- pyrrolidone and other optional organic solvent as extraction solvent for hydrocarbon mixtures containing various proportions of aromatic hydrocarbons, olefinic hydrocarbons, naphthene hydrocarbons and paraffmic hydrocarbons.

The present invention will be understood more particularly by the following descriptions including attached drawings.

FIG. I is a diagram showing steps in continuously performing the process of the present invention;

FIG. 2 is a triangular diagram showing mutual solubilities of l-olefin, n-paraffine and N-acetyl-Z- pyrrolidone; and

FIG. 3 is a triangular diagram showing mutual solubilities of aromatic hydrocarbon, n-paraffme and N-acetyl-Z-pyrrolidone.

The inventors have found that anhydrous N- acetylmorpholine dissolves olefin-naphthene hydrocarbons but its dissolving power for paraffmic hydrocarbons is very poor and, therefore, it serves as effective solvent for extraction of olefin-naphthene hydrocarbons. I

The inventors have also found that N-acetylmorpholine in anhydrous state has remarkably high dissolving power for aromatic hydrocarbons but its selectivity is poor and that if five percent by weight of water is incorporated in N-acetylmorpholine, selectivity is improved though its dissolving power is decreased and the selectivity is inclined to be increased as water is increased. However, increase in amount of water is limited, since dissolving power of N-acetylmorpholine is gradually decreased as water content is increased. Favorable water content is five 20 percent by weight.

Since boiling point of N-acetylmorpholine is 243 C, this compound is capable of extracting aromatic hydrocarbons having relatively high boiling points such as cymenes and cumenes in addition to benzene, toluene, xylene, etc.

Extraction with using hydrous N-acetylmorpholine as solvent can be performed continuously in a counter current multistage extraction device at ambient temperature. Particularly, if reflux operation is added, aromatic hydrocarbons having a desired aromatic concentration can be obtained on the side of the extracting solvent and hydrocarbon mixture free of aromatic hydrocarbons is obtained in the extraction residue.

The separation of olefin-naphthene hydrocarbons by means of extraction with anhydrous N- acetylmorpholine is preferably effected after removal of aromatic hydrocarbons according to said method. However, if aromatic hydrocarbon content is less than three percent by weight, olefin-naphthene hydrocarbons can be directly extracted without necessity of previous removal of the aromatic hydrocarbons.

The extraction operation of olefin-naphthene hydrocarbons with anhydrous N-acetylmorpholine can be effected continuously by using a counter current multistage extraction device at ambient temperature. In case olefin-naphthene hydrocarbons are to be extracted from hydrocarbon mixtures having more than eight carbon atoms, extraction temperature may be elevated and solubilizing power may be increased. However, in any case, a temperature not damaging selectivity of solvents is preferably. Olefin-naphthene hydrocarbons having relatively high purities can be extracted out by adding reflux operation to the above extractingoperation. In such a case, paraffinic hydrocarbons having a purity of near percent can be obtained as extraction residue.

According to our presumption, relation between water content of N-acetylmorpholine and its solubilizing powers for xylene, heptene-l and n-heptane are as shown in Table 1.

TABLE 1 Solubilities in mixed solvent of Nacetylmorpholine and water Water content Solubility Solubility Solubility of solvent of xylene of heptene-l of N-heptane (8/ 8 (8 g (8/ g solvent) solvent) solvent) 00 16.0 0 287.0 10.6 0 10 14.2 6.6 O 8.2 6.5 0 30 6.2 O 40 5.2 0 50 4.5 0

The extraction with N-acetylmorpholine can be effected either batchwise or continuously. 1n continuous extraction, hydrocarbon mixture is first introduced in an aromatic extraction tower and an extract obtained by counter current operation is fractionated into aromatic hydrocarbons, water and N-acetylmorpholine in an aromatic distillation tower. N-acetylmorpholine is reused by adding therein water and circulating it into the aromatic extraction tower or by directly introducing it in an olefin extraction tower without adding water. On the other hand, extraction residue from the aromatic extraction tower is added with a necessary amount of water to washaway N-acetylmorpholine and then oil layer is introduced in the olefin extraction tower to extract olefins. After distillation or washing with water, olefins are obtained. The wash water can be reused by introducing it into the aromatic extraction tower.

In separating hydrocarbon mixtures according to extraction with a solvent such as N-acetylmorpholine, not only aromatic hydrocarbons and olefinic hydrocarbons but also aromatic hydrocarbons and olefin-naphthene hydrocarbons can be isolated at relatively high purities from paraffinic hydrocarbons.

The process of the present invention will be illustrated more concretely by way of examples.

Example 1 In 35.8 g (about 50 ml) of mixture of 20 wt. percent of xylene and 80 wt. percent of n-heptane, 110.3 g (about 100 ml) of N-acetylmorpholine having 5 wt.% water content are added at ambient temperature. After thorough agitation for about 5 minutes, the solution is allowed to stand whereby the solution is separated into two layers. The two layers are fractionated respectively. Thereafter, n-octane is added as internal standard into the upper layer extraction residue and the layer is analyzed according to gas chromatography. The results are shown in the following table.

Composition of Composition Proportion (wt. 17) hydrocarbons by weight n-hep- Xy- Sol- (wt.%) (91;) tane lene vent n-hepxylene tane Upper layer 21.3 89.3 10.7 0 89.3 10.7 Lower layer 78.7 0.9 3.1 96.0 22.5

Example 2 Into 35.8 g (about 50 ml) of the same hydrocarbon mixture as in Example 1, 108.6 g (about 100 ml) of N- acetylmorpholine having 20 wt. percent water content are added at ambient temperature. After thorough agitation for about 5 minutes, the solution is allowed to stand whereby the solution is separated into two layers. The two layers are fractionated respectively. Thereafter, n-octane is added as internal standard into the upper layer (extraction residue) and the layer is analyzed according to gas chromatography. The results are shown in the following table.

Composition Composition of (wt. hydrocarbons Proportion (wt. by weight n-hep- Xy- 801- nxylene tane lene vent Heptane Upper layer 24.8 84.4 15.6 0 84.4 15.6 Lower layer 75.2 0 1.2 98.8 0 100 Example 3 Composition of Composition hydrocarbons Proportion (wt. (wt. by weight p- 801- np (96) Hep- C yvent Hep- Cytane mene tane mene Upper layer 24.8 81.0 19.0 0 81.0 19.0 Lower layer 75.2 0 0.9 99.1 0 100 Example 4 Into 34.0 g (about 50 ml) of mixture of 20 wt. percent of heptene-l and wt. percent of n-heptane, l 10 g (about ml) of anhydrous N-acetylmorpholine are added at 40 C. After thorough agitation for 5 minutes, the solution is allowed to stand whereby the solution is separated into two layers. The two layers are fractionated respectively. Thereafter, n-octane is added is added as internal standard into the upper layer (extractin residue) and the layer is analyzed according to gas chromatography. The results are shown in the following table.

Composition of Composition hydrocarbons Proportion (wt. (wt.%) by weight H n- Hep- Hepw Sol- Heptene-l tane l vent tane Upper layer 19.1 83.8 16.1 0.1 83.9 16.1 Lower layer 80.9 3.2 1.8 95.0 64.0 36.0

Example 5 lnto 37.4 g (about 50 ml) of hydrocarbon mixture containing 23 wt. percent of dodecene-l and 77 wt. percent of n-dodecane, 109.8 g (about 100 ml) of anhydrous N-acetylmorpholine are added. After thorough agitation at 80 C for about 5 minutes, the solution is allowed to stand whereby the solution is separated into two layers. The two layers are fractionated respectively. Thereafter, n-decane is added as internal standard into the upper layer (extraction residue) and the layer is analyzed according to gas chromatography.

The results are shown in the following table.

Composition Composition hydrocarbons Proportion (wt. (wt.%) by weight ndode- Solndodededcenevent dodecene-l cane 1 cane Upper 22.4 81.3 [8.2 0.5 8L7 18.3 Lower layer 77.6 1.8 2.3 95.9 43.9 56.1

Example 6 Thermally cracked gasoline having boiling point.

range of 53 -l04 C, olefinic content of 38.3 vol.%, aromatic content of 3.3 vol. percent and parafiinic content of 58.4 vol. percent was subjected to continuous multistage extraction with N-acetylmorpholine in about 3.0 liter multistage extraction device (40 stages) of rotating disk system under the following conditions:

Raw material-feeding speed: 366 g/hr. Raw material-feeding stage: 20th stage Solvent-feeding speed: 3,120 glhr. Temperature 40 C Rotating speed of disk: 600 r.p.m.

After extraction operation, extraction residue and extract were separated into the solvent and hydrocarbons by means of rectification. Thereafter composition of the hydrocarbon mixture was analyzed by FlA analysis according to MS K 2536. PM is the Fluorescent Indicator Adsorption and the JIS is the Japanese Industrial Standard for FM which has been published in 1969. The results are shown in the following table.

Hydrocarbon Com ition composition Weight (wt. (vol.%)

Hy- Sol- Ole- Par Aromag/hr. drovent fins aftics carbon fines Extraction residue 95 100 1.1 98.9 0 pp layer) Extract (Lower 3390 8.0 92.0 51.5 44.0 4.5 layer) Example 7 Hydrocarbon mixture of 20 wt. percent of toluene, 20 wt. percent of heptene-l and 60 wt. percent of nheptane is subjected to continuous extraction according to steps as shown in FIG. 1.

The hydrocarbon mixture is fed into an aromatic extraction tower 2 through 1 at ambient temperature (23 C). At the same time, acetylmorpholine having wt. percent water content is fed through a pipe and hydrocarbon mixture as reflux material containing 98 wt. percent of toluene and 2 wt. percent of n-heptane is fed through a pipe ll.

Extraction product is fed into a standing tank 5 through a pipe 3 and a distillation tower 7 through a pipe 6. After distillation, distillate from the top of the tower is separated from water and fed in part into an aromatic product tank through a pipe 8 and in part as reflux material into the 'aromatic extraction tower through the pipe 11. Extraction residue which is known as ratfinate is introduced in a water tank 12 through a pipe 4 and washed with water separated in the distillation tower 7 and freshly'fed water. Thereafter, the hydrocarbon mixture thus washed with water is introduced in an olefin extraction tower l6 kept at 40 C through a pipe 15. On' the other hand, water used for washing and then separated in the water tank l2 is fed into an-extraction solvent preparation tank 13 through a pipe 14- and combined with bottom distillate of the distillation tower 7 to'obtain 5 wt. percent water content which is again fed into the aromatic extraction tower 2 through the pipe 10.

Then, the hydrocarbon mixture introduced into the olefin extraction tower kept at 40 C is extracted with anhydrous N-acetylmorpholine simultaneously introduced through a pipe 24 and reflux material (hydrocarbon mixture of 88 wt. percent of heptene-l, 11.5 wt. percent of n-heptane and 0.5 wt. percent of toluene) introduced through a pipe 25. The extract is fed into a standing tank 19 through a'pipe l7 and into a distillation tower 21 through a pipe 20. After distillation, the distillate from the top of the tower is sent in part into an olefin product tank through a pipe 22 and in part into the olefin extraction tower as reflux material through the pipe 25. The extraction residue which is known as raffinate is introduced into a water tank 26 through a pipe 18 and washed with water separated in the distillation tower 7 and freshly fed water. After completion of washing, the separated hydrocarbons are sent into a paraffin product tank through a pipe 27. On the other hand, the wash water separated after being used for washing in the water tank 26 is sent into the extraction solvent preparation tank 13 through the pipe 14 and utilized partially. 7

Operation conditions employed in the above steps are shown in Table 2. Extracted quantities of toluene, heptene-l and n-heptane obtained in the extraction operation and compositions revealed according to gas chromatography are as shown in Table 3.

TABLE 2 Operation conditions in the aromatic extraction tower:

Multistage extraction device of ro- 10 stages tating disk system. Raw material feeding 5th stage Raw material feeding speed 500 g./hr. Solvent feeding speed 1,810 g./hr. Reflux quantity 320 g./hr.

(feeding 1st stage) Operation conditions in the olefinic extraction tower:

Multistage extraction device of ro- 40 stages tating disk system. Raw material feeding 20th stage Raw material feeding speed 402 g./hr. Solvent feeding speed 6,040 g./hr. Reflux quantity 965 g./hr.

(feeding 1st stage) TABLE 3 Aromatic Oiefinic Parafflnic product tank product tank product tank Quantity by weight, grams/ hour 290 Composition, Toluene, 98.." Toluene, 2.7..." n-Heptnne, 99. weight percent. Heptene-l,2.. He tone-1,873.. Heptene-1,l.0.

. neptene, 10.0.

The inventors have also found that N-acctyl-Z- pyrrolidone is quite useful as extraction solvent for olefins.

N-acetyl-2-pyrrolidone has the following structural formula:

This compound is in the form of colorless liquid having boiling point of 236 C (760 mmHg) and specific gravity at room temperaure of 1.146. This compound has a high thermal stability and is distillable under normal pressure or reduced pressure. This compound is completely compatible with water and its toxicity is low. N-acetyl-Z-pyrrolidone has a high dissolving power for hydrocarbon mixtures and, particularly, it dissolves out olefinic hydrocarbons selectively from mixture of olefinic hydrocarbons and paraffinic hydrocarbons. FIG. 2 is a tri-angular diagram showing mutual solubilities of l-olefin, n-paraffine and N-acetyl-Z-pyrrolidone. This figure clearly suggests that N-acetyl-2-pyrro1idone has very excellent property as extraction solvent for olefinic hydrocarbons. There has been no compound in the past which can be used as solvent for olefinic hydrocarbons having such a wide range of carbon number.

As clearly shown in the figure, mutual solubility curve of a hydrocarbon having seven or less carbon atoms has so-called plate point at 25 C which gives a closed curve against the axis connecting n-paraffin with n-acetyl-Z-pyrrolidone. Mutual solubility curve of a hydrocarbon having eight or more carbon atoms at a temperature of at least room temperature gives an open curve against the axis connecting n-paraffin with N- acetylpyrrolidone.

Thus, the solvent having the above mutual solubilities with an olefinic hydrocarbon and a paraffinic hydrocarbon can be used effectively in industrially various manners.

(1) For extracting olefinic hydrocarbons having seven or less carbon numbers at a higher concentration, the triangular diagram of FIG. 2 can be revised by incorporating therein another solvent for improving selectivity of the solvent. Namely, the mutual solubility curve in FIG. 2 is revised to an open curve against the axis connecting n-paraffin with N-acetyl-Z-pyrrolidone so as to increase purity of the final extract by olefinic hydrocarbon reflux material. As such solvents used for revision, water and dimethyl sulfoxide are most suitable. Proportion of those solvents to N-acetyl-Z-pyrrolidone is as shown in Table 1. For an olefin having 7 carbon atoms, it is preferred to use a mixed solvent containing less than 1.0 wt. percent of water or 3.0 20.0 wt. percent of dimethyl sulfoxide.

TABLE 1 Solubility o1(g./100 g.

' solvent Content in mixed solvent (weight percent Heptenen-Heptane Water w TABLEI [Solubllltles in mixed solvent 01 N-ocvtyl-Z-pyrrollrlonu and water or dimethyl SUllOXltltl (25 C.)]

Content in (2) In extraction of olefinic hydrocarbons having eight 10 carbon atoms, the olefinic hydrocarbons of a high purity can be obtained as the final extract by using only N-acetyl-Z-pyrrolidone alone. However, it is advantageous to use mixed solvent of N-acetyl-Z-pyrrolidone and water or dimethyl sulfoxide for improving selectivity and for economy of the extraction operation. In such a case, it is preferred to effect the extraction operation at a temperature in the range of 40 60 C. Contents of water and dimethyl sulfoxide in the mixed solvents are preferably 0.5 1.0 wt. percent and 1.0 5.0 wt. percent, respectively. Tables 2-1 and 2-2 show solubilities of a l-olefin and an n-paraffin having 10 carbon atoms in mixed solvents of various proportions at various temperatures.

TABLE 2-2.-SOLUBILITIES IN MIXED SOLVENT OF N- ACETYL-2-PYRROLIDONE AND DIMETHYL SULFOXIDE Dlrnethyl sulfoxide content Solubility (g./i00 g. solvent) mixed ofsolvent (weight n-Decane Decene-l Temperature percent) (A) (B) (B)/(A) (3) As in the case of hydrocarbons having eight 10 carbon atoms, olefinic hydrocarbons having 11 or more carbon atoms can be treated with either N-acetyl-Z-pyrrolidone alone or mixed solvent of N-acetyl-Z-pyrrolidone and water or dimethyl sulfoxide. If a mixed solvent is to be used, it is necessary to elevate temperature in order to increase solubility of the olefinic hydrocarbons. Tables 3-1 and 3-2 show solubilities of a l-olefin and an n-paraffin having 11 and 13 carbon atoms in N-acet-yl-Z- pyrrolidone and in mixed solvents at various temperatures.

Thus, olefinic hydrocarbons of a narrow carbon number range can be fractionated and extracted from various hydrocarbon mixtures having a wider carbon number range by using two or more extraction towers and proper combination of solvent mixture and temperatures.

TABLE 3-1.Solubillties Cu compounds in N-acetyl-2-pyrrolidoneand mixed solvents Proportion by weight in mixed Solubility (gJlOO g. solvent (percent) solvent Temperature, Dimethyl n-Undec- Undec 0. Water sulfoxide ane (A) ene-l (B) (B)/(A) TABLE 32.Solubilities of C 1 compounds in N-acetyl-2-pyrrolidone and mixed solvents Proportion by weig tin mixed Solubility (g./100 g. solvent (percent) solvent) ol- Tempern- Dirnethyl n-Tridec- Tridec ture, 0. Water sulloxide one (A) one-1(8) (B)/(A) 0 0 2. 8 9. l 3. 3 0 0 4. 5 ll. 9 2. 6 0 0 5. 2 l4. 0 2. 7 0 0 7. 0 23. 6 3. 4 l 0 7. 0 l1. 7 1. 7 5 0 5. 5 8. 0 1. 6 0 5 7. 5 15. 1 2. 0 0 10 7. 4 13. 5 1. 8 0 5 10. 4 21. 4 2. l 0 l0 9. 6 14. 9 l. 6

Separation of olefinic hydrocarbons and solvent(s) from an extract can be performed by rectification for hydrocarbons having 12 or less carbon atoms or and for ones having more 13 carbon atoms by allowing the extract to stand at room temperature and adding water in the solvent (s) till water content becomes higher than 5 wt. percent to separate the hydrocarbons. Those methods can be effected both in case of using only N-acetyl-Z-pyrrolidone and in case of using mixed solvent of N-acetyl-2-pyrrolidone and water. The recovered water-containing solvent can be used as solvent for extraction of olefinic hydrocarbons having 12 or less carbon atoms. In case of using mixed sovent of N-acetyl-Z-pyrrolidone and dimethyl sulfoxide, hydrocarbons having l0 or less carbon atoms can be separated by rectification and hydrocarbons having 11 or more carbon atoms can be separated by allowing them to stand at room temperature and adding water so that water content in the solvent to be recovered becomes less than 5 wt. percent. The recovered watercontaining mixed solvent canbe used as solvent for extraction of olefinic hydrocarbons having 10 or less carbon atoms.

Thus, use of N-acetyl-2-pyrrolidone as extraction solvent for olefinic hydrocarbons as in the process of the present invention is quite efiective from industrial viewpoint.

N-acetyl-2-pyrrolidone used in the process of the present invention has a high dissolving power also'for aromatic hydrocarbons and its selectivity can e increased by incorporating therein various other solvents. Thus, it be usable also as an extraction solvent for aromatic hydrocarbons. More particularly, if N-acetyl-Z-pyrrolidone is used as solvent for hydrocarbon'mixture composed of olefinic, aromatic and paraffinic hydrocarbons, it exhibits a very high selectivity at an aromatic hydrocarbon content of less than 40 wt. percent and it selectively dissolves and extracts aromatic hydrocarbons. However, if aromatic hydrocarbon is required to be concentrated to higher than 40 wt. percent, it is preferred to use mixed solvent of N-acetyl-2-pyrrolidone and another solvent such as water or diethylene glycol.

Thus, the solvent according to the process of the present invention, N-acetyl-2-pyrrolidone, is quite excellent as a solvent for extracting aromatic hydrocarbons from hydrocarbon mixtures. Extracting effect of N-acetyl-Z-pyrrolidone can be increased further by incorporating therein another solvent.

Aromatic'hydrocarbons have so far been fractionated by means of extraction with various extraction solvents on industrial scale. Aromatic hydrocarbons such as benzene, xylene and toluene have actually been fractionated according to this method. As known solvents used for this extraction operation, there may be mentioned diethylene glycols, sulfolane liquid ammonia, dinitrile, cyano ether, y-butyrolactone, methylpyrrolidone and N-methyl-2-pyrrolidone.

Though all of those extraction solvents can be used as extraction solvents for aromatic hydrocarbons, if those solvents are used, the extraction process becomes expensive due to their physical and chemical stability or toxicity or other economical problems occur such as large recovery loss of solvent.

After investigation on solvents more excellent than conventional solvents, the inventors have found that N-acetyl-2-pyrrolidone serves as a quite excellent solvent for extraction of aromatic hydrocarbons.

N-acetyl-2-pyrrolidone according to the present invention is capable of selectively extracting aromatic hydrocarbons and this compound is characterized in that dissolving power at the time of extraction is very high. Another feature of N-acetyl-Z-pyrrolidone is that this compound is also capable of extracting durene, pseudocumene, various alkylbenzenes and polycyclic aromatic compounds such as high boiling compounds. for example, tetralin and naphthalene in addition to benzene, toluene and xylene which have been obtained by means of extraction. Mutual solubility curves of aromatic hydrocarbon, paraffinic hydrocarbon and N-acetyl-2-pyrrolidone are as shown in FIG. 3. Plate point of any aromatic hydrocarbon resides at 25 C and, a closed curve is given against the axis connecting n-paraffin with N-acetyl-Z-pyrrolidone.

Accordingly, N-acetyl-Z-pyrrolidone can be used as extraction solvent for almost all aromatic hydrocarbons. In case N-acetyI-Z-pyrrolidone is used for the purpose of concentrating aromatic hydrocarbons on industrial scale, the above mutual solubility curve can be revised to an open curve against the axis connecting n-parafi'm and N-acetyl-pyrrolidone by using mixed solvent of N-acetyl-2-pyrrolidone and other selective solvent.

As such selective solvents which are useful in the form mixed with N-acetyl-Z-pyrrolidone, diethylene glycol, propylene glycol, sulfolane, dimethyl sulfoxide and N-methylpyrrolidone are suitable and, diethylene glycol is particularly effective. Water can be also used as a component of mixed solvent.

Proper extraction temperature when N-acetyl-2- pyrrolidone found by the inventors is used as extraction solvent is around room temperature (about 25 C). Heating or cooling is unnecessary at all. If the extraction is effected under heating, selectivity for aromatic extraction is lowered.

Aromatic hydrocarbons extracted with N-acetyI-2- pyrrolidone can be separated completely from the solvent and thereby recovered either by distillation or by adding water (if some water is already contained, water necessary for reducing solubility is added).

In separation of solvent and extract oil from extract layer, at least 95 wt. percent of the extract oil can be separated by adding water in a quantity 0.8 1.5 times as much as the solvent.

In performing aromatic extraction operation on industrial scale by using N-acetyl-2-pyrrolidone according to the present invention, roughly, the following two steps can be employed.

(1) In case N-acetyI-Z-pyrrolidone is used for the purpose of concentrating out aromatic hydrocarbons from various hydrocarbon mixtures containing cracked petroleum oil and aromatic hydrocarbons, a solvent mixture containing 40 wt. percent of the diethylene glycol is introduced into a multistage extraction tower and the hydrocarbon mixtures are refluxed till a desired concentration is obtained. The extract phase in which the aromatic hydrocarbons are dissolved in a concentrated form can be separated or recovered in a distillation tower or the extract phase can be separated into oil layer and solvent layer by adding therein water. Water can be separated from the water-containing solvent by means of distillation in solventpurificiation step.

(2) In case hydrocarbons other than aromatic hydrocarbons such as olefinic hydrocarbons are to be concentrated by means of extraction from various hydrocarbon mixtures including cracked petroleum oils and aromatic hydrocarbons, the aromatic hydrocarbons become undesirable contaminant in the extraction operation and they are to be removed. In such a case N-acetyl-2-pyrrolidone (used alone but not in the form of mixture) is very effective as extracting agent for pretreatment. Utilizing selective dissolving power of N-acetyl-2- pyrrolidone for aromatic hydrocarbons in a hydrocarbon mixture, extraction residue remaining not dissolved can be regarded to be hydrocarbon mixture hardly containing aromatic hydrocarbon compounds and the hydrocarbon mixture can be regarded to be compounds from which industrially valuable hydrocarbons such as monoolefinic hydrocarbons can be extracted.

In view of the above steps, it is understood that N-acetyl-Z-pyrrolidone in the present invention can be used effectively for manner aromatic hydrocarbons.

Solvent systems mainly composed of N-acetyl-2- pyrrolidone are capable of extracting naphthenic hydrocarbons contained in hydrocarbon mixtures in the same manner as in the case of extracting olefinic hydrocarbons.

Example 8 Into 38.0 g (about 50 ml) of mixture of 18.8 wt. percent of heptene-l and 81.2 wt. percent of n-heptane, 1 16.0 g (about ml) of mixed solvent of N-acetyl-2- pyrrolidone containing 5 wt. percent of dimethyl sulfoxide are added at 25 C. After thorough agitation for about 5 minutes, the solution is allowed to stand whereby the solution is separated into two layers. The two layers are separated from each other. Thereafter, n-octane is added as internal standard into both upper layer (extraction residue) and lower layer (extract) and both layers are analyzed according to gas chromatography. The results are shown in the following table.

Composition of hydrocarbons Proportion Composition (wt.%) (wt. by weight hepn- 501- Hepntene hepvent tene hep -l tane -l tane Upper layer 19.4 14.3 79.8 5.9 l5.2 84.8 Lower layer 80.6 2.2 5.3 92.5 29.3 70.7 Example 9 Into 38.1 g (about 50 ml) of mixture of 25.0 wt. percent of octene-l and 75.0 wt. percent of n-octane, g (about 100 ml) of N-acetyI-Z-pyrrolidone are added at 25 C. After thorough agitation for about 5 minutes, the solution is allowed to stand whereby the solution is separated into two layers. The two layers are separated from each other. Thereafter, n-decane is added as internal standard into boty upper both (extraction residue) and lower layer (extract) and the layers are analyzed according to gas chromatography. The results are shown in the following table.

Composition of hydrocarbons Proportion Composition (wt. (wt.%) bweight ocnsol- Ocntene ocvent tene Oc- -l tane Upper layer 20.4 2L7 72.0 6.3 23.1 76.9 Lower layer 79.6 2.4 4.8 92.8 33.3 66.7

Example 10 Into 38.0 g (about 50 ml) of the same hydrocarbon mixture as in Example 8, 117 g (about 100 ml) of mixed solvent of N-acetyl-Z-pyrrolidone containing 1 wt. percent of water are added at 25 C. After thorough agitation for about 5 minutes, the solution is allowed to stand whereby the solution is separated into two layers. The two layers are separated from each other. Thereafter, n-octane is added as internal standard into both upper layer (extraction residue) and lower layer (extract) and both layers are analyzed according to gas chromatography. The results are shown in the following table.

Example 13 into 1 1.5 g of mixture of 24.4 wt. percent of durene, 51.7 wt. percent of n-decane and 21.1 wt. percent of 5 decene-l 35.8 g of N-acetyl-Z-pyrrolidone were added at 2 5 C. After thorough agitation'for about 5 minutes, Proportion Composition (wt.%) (wt. the solution is allowed to stand whereby the solution is by welsh he? separated into two layers. The two layers are separated (9b) tene hep vent tene hep i me We from each other. The upper layer (extraction residue) pp l9 5 4 I 8 3 10 and the lower layer (extract) are analyzed according to 83$; l gas chromatography. The results are shown in the follayer 80.5 2.2 4.6 93.2 32.4 67.6 lowing table.

Composition of hydrocarbons Iroppf- Composition (weight percent) (weight percent) on Y weight Durn-Dec- Dec- 801- Durn-Dec- Dec- (percent) ene ane ene-1 vent ene ane ene-1 Upper layer 10.1 14.3 60.4 21.2 4.1 15.0 63.0 22.0 Lower layer 83.9 4.5 3.8 2.2 89.5 42.8 36.1 21.1

Example 11 Example 14 into 38.5 g (about 50 ml) of hydrocarbon mixture obtained by collecting straight chain hydrocarbons having 15 carbon atoms from cracked petroleum oil composed of 14.7 wt. percent of olefins, and 85.3 wt. percent of paraffins, 119 g (about 100 ml) of N-acetyLZ-pyrrolidone are added at temperatures given below. After thorough agitation for about 5 minutes, the solution is separated into two layers. The two layers are separated from each other. The upper and lower layers (extraction residue and extract, respectively) are analyzed according to gas chromatography. The results are shown in the following table.

Extraction on various mixture of n-parafi'in and aromatic hydrocarbon is effected once in the same manner as in Examples 8 and 9 by using mixed solution of N-acetyl-2-pyrrolidone and diethylene glycol. The results are as shown in the following table, wherein NAP shows N-acetyl-2-pyrrolidone and DEG shows diethylene glycol.

Example 15 into 50 ml of hydrocarbon mixture (cracked petroleum oil) having boiling point range of 76 144 C composed of 11.3 vol. percent of aromatic hydrocarbons, 29.3 vol. percent of olefinic hydrocarbons and Composition of hydrocarbons Composition (weight Propor- (weight percent) percent) tion by weight Ole- Paral- Sol- Ole- Paraf- Temperature, 0. Layer (percent) fln fin vent fln fin Upper layer... 23.4 13.0 79.7 7.3 14.0 80.0 Lower layer-.- 76. 6 1.0 4. 1 94. 9 19. 6 80. 4

00 Upper layer... 22.8 12.3 80.5 7.2 13.3 86.7 Lower layer... 77. 2 1. 3 4. 7 04. 0 21. 7 78. 3

70 Upper layer.-- 21. 2 12.3 79.0 8. 7 13.5 86.5 Lower layer... 78. 8 1. 4 5. 3 93. 3 20. 9 79. 1

Example 12 59.4 vol. percent of paraffinic hydrocarbons, 100 ml of Into 14.5 g of mixture of 29.8 wt. percent of toluene and 70.2 wt. percent of n-heptane, 45.4 g of N-acetyl- 2-pyrrolidone are added at 25 C. After thorough agitation for about 5 minutes, the solution is separated into two layers. The two layers are separated from each other. The upper layer (extraction residue) and the lower layer (extract) are analyzed according to gas chromatography. The results are shown in the follow ing table.

Composition of hydrocarbons Composition (wt. (wt. Proportion by weight Tdnsoltolnuene hepvent uene heptane tane Upper layer 24.9 16.6 77.8 5.6 17.6 82.4 Lower layer 75.] 4.7 1.1 94.2 81.0 19.0

N-acetyl-Z-pyrrolidone containing 1 wt. percent of water are added at 40 C. After thorough agitation for about 5 minutes, the solution is allowed to stand whereby the solution is separated into two layers. The two layers are separated from each other. The upper layer (extraction residue) and the lower layer (extract) are analyzed according to gas chromatography and HA (according to .11S-K-2536). The results are as shown in the following table.

Corn ition of hy rocarbons Proportion Composition (wt.%) (vol. b weight hyparafdrosol aroolefinic carvent matic tinbons ic Upper layer 14.8 87.0 13.0 0.9 33.7 65.4 Lower layer 85.2 13.4 86.6 20.6 25.4 54.0

Composition of Solvent hydrocarbons (g.) or Propor- Composition (weight percent) (weight percent) raw tion by Composition of raw material mateweight Soln-Hep- (weight percent) Solvent riel (g.) Layers (percent) Toluene n-Heptane vent Toluene tene Toluene, 70.5 NAP 90 34. Upper, layer.. 17. 9 57. 2 38.3 4.5 60.0 40. 0 n-Hept'ane, 29.6 DEG 11.9 Lower layer..- 82.1 9. 6 0.9 89. 6 91. 4 8. 6

n-Hep- Soln-Hep- Benzene tane vent Benzene tane Benzene, 43.4. NAP 70 32.2 Upper layer... 13. 2 15.3- 80.0 4. 7 16. 1 83.9 n-Heptane, 66.6 DEG 30 ll. 8 Lower layer... 86. 8 11. 0 5. 4 83.6 67. 0 33. 0

Oe- 801- Oe- Xylene tene-l vent Xylene tene-l Xylene, 44.0 NAP 70 32.8 Upper layer... 13.0 23.1 60.5 16.4 27.6 72.4 Octene-l, 56.0 DEG 30 12.6 Lower layer... 87. 0 10.4 8. 8 80.8 64. 2 45.8

Naphthan-Do- Sol- Nephthan-Dolene decene vent lene decane Naphthalene, 31.4 NAP 70 34.0 Upper layer... 18.4 11. 1 87.1 1.8 11.3 88.7 n-Dodecane, 68.6 12. 1 Lower layer.. 81. 6 7. 6 2. 2 90. 2 77. 6 22. 4

Example 16 0 We claim:

into 50 ml of hydrocarbon mixture having 10 carbon atoms (cracked petroleum oil) composed of 17.0 vol. percent of aromatic hydrocarbons, 30.2 vol. percent of olefinic hydrocarbons and 52.8 vol. percent of parafiinic hydrocarbons, 100 ml of N-acetyl-2- pyrrolidone are added at 60 C. After thorough agitation for about 5 minutes, the solution is allowed to stand whereby the solution is separated into two layers. The two layers are separated from each other. The upper layer (extraction residue) and the lower layer (extract) are analyzed according to gas chromatography and HA (according to JIS-K-2536). The results are as shown in the following table.

Composition of hydrocarbons Proportion Composition (wt.%) (vol. by weight hyarooleparafsoldromatic finfinic car vent ic bons Upper layer 15.0 87.2 l2.8 9.5 29.6 60.9 Lower layer 85.0 16.6 83.4 23.2 30.6 46.2

Example 17 Composition of hydrocarbons Proportion Composition (wt.%) (vol. by weight hy- Solarooleparafdrovent matic fifinic carl'llC bons Upper layer 17.4 87.0 [3.0 32.0 25.7 42.3 Lower layer 82.6 13.4 86.6 0 35.4 64.6

l. A process for separating at least one component of aromatics, olefins, naphthenes and paraffins from a mixed hydrocarbon stock containing the same, comprising extracting at least an aromatic or olefin compo nent with a mixed solvent of N-acetyl-2-pyrrolidone and dimethyl sulfoxide.

2. A process according to claim 1 in which a mixture of N-acetyl-pyrrolidone and from l.0% to 5.0% by weight of dimethyl sulfoxide based on the mixture is used.

3. A process according to claim 2 wherein the aromatics and the olefins are extracted successively in separate extractors comprising,

a. feeding the mixed solvent and hydrocarbon stock into a continuous countercurrent multistage aromatic extractor, separating the aromatic containing extract from an effluent from the aromatics extractor and recovering the aromatics from said extract by distillation water washing,

recycling the separated solvent to the aromatic extractor,

recycling solvent which does not contain water to the olefin extractor,

washing the effluent from the aromatic extractor not containing aromatics with water,

b. passing the water washed effluent from the aromatic extractor not containing aromatics into the continuous countercurrent multistage olefin extractor, separating the olefin containing extract and recovering the olefins from the solvent by distillation or water washing, recycling the recovered solvent to either the aromatic extractor or the olefin extractor, and recycling as additive water for the solvent employed in the aromatic extractor the water used in washing the effluent from the aromatic extractor and the water used when the extract from the aromatic extractor is washed.

* C I t t

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4001107 *Jun 18, 1975Jan 4, 1977The Dow Chemical CompanySolvent extraction, separation of benzene, toluene, xylene
US4267034 *Nov 14, 1979May 12, 1981Phillips Petroleum CompanySeparating olefins from paraffins with dimethyl sulfoxide extractant
US4333824 *Jun 27, 1980Jun 8, 1982Texaco Inc.Refining highly aromatic lube oil stocks
US5186817 *Apr 15, 1991Feb 16, 1993The Standard Oil CompanyConverting the hydrocarbon feed to a water in oil emulsion and solvent extracting
US6146520 *Apr 2, 1997Nov 14, 2000Mobil Oil CorporationSelective re-extraction of lube extracts to reduce mutagenicity index
Classifications
U.S. Classification208/314, 208/332, 208/326, 208/333, 208/323
International ClassificationC10G21/00, C10G21/12
Cooperative ClassificationC10G21/12
European ClassificationC10G21/12