US2414252A - Solvent separation of hydrocarbons - Google Patents

Description

Patented Jan. 14, 1947 1. 2,414,252 SOLVENT SEPARATION or HYDROCARBONS Harry Virgil Ashburn, Beacon, N. mesne assignments, to The Y., assignor, by Texas Company,

New York, N. Y., a corporation of Delaware No Drawing. Application March 11, 1941, Serial No. 382,742

Claims. (Cl. 260-674) This invention relates to the solvent separation of hydrocarbon mixtures by extraction with a solvent comprising a glycol of high molecular weight.

The invention broadly contemplates separating unsaturated hydrocarbons including olefins and aromatics from a mixture of saturated and unsaturated hydrocarbons by extraction with a solvent comprising a high molecular weight glycol. Examples of glycols contemplated are those which are substantially completely soluble in water at normal room temperature and above and have a molecular weight in the range about 1000 to 4000 or higher. These glycols are characterized by having a specific gravity of about 1.0 to 1.25 relative to water at normal room temperature, a melting point of about 90 to 130 F., a Saybolt- Universal viscosity of about 70 to 420 seconds at 210 F. and a flash point temperature of about 400 to 550 F.

Specific examples of glycols of the foregoing character which have been. found effective as extraction solvents are known in the trade as "Carbowax 1500 and Carbowax 4000, and are commonly spoken of as poly-olefin glycols.

Carbowax 1500 is a soft, odorless solid having the consistency of petrolatum and is characterized by having a specific gravity of about 1.152, a melting point of about 95 to 99 F., a Saybolt- Universal viscosity of about 78 seconds at 210 F. and a flash point temperature of about 430 F.

Carbowax 4000 is a hard translucent solid resembling paraflin in appearance and texture'and is characterized by having aspecific gravity of about 1.203. a melting point ofabout 122 to 127 F., a Saybolt-Universal viscosity of about 418 seconds at 210 F. and a fiash point temperature of about 535 F.

These compounds are completely soluble in a substantially equal quantity of water at temperatures in the range of 68 to 122 F.

These particular compounds have been found particularly effective in extracting aromatic hydrocarbons such as benzol, toluol and xylol from hydrocarbon mixtures containing them such as cracked naphtha produced in the pyrolytic or vent. The resulting phases are separated and the hydrocarbons are thereafter separated from the solvent, the solvent advantageously being returnedfor treatment of fresh feed.

Other naphtha or hydrocarbon mixtures to which the invention may be applied comprise hydroformed naphtha, pyrolytically or catalytically reformed naphtha, polyformed naphtha and the like. It is also applicable to'the extraction of aromatic hydrocarbons from straight run naphthas or gasolines such as distilled from certain crudes.

It is also contemplated that the solvents of my invention may be employed in the extraction of to treatment with the solvent at above room temperature and under atmospheric pressure. The following are indicative of the results obtainable under such conditions when extracting toluene from a hydrocarbon mixture containing 20% olefins and 60% parafiflns by weight. The olefins used in this hydrocarbon mixture comprise a fraction having a boiling range of about 200 to 250 F. separated from polymer naphtha obtained in the catalytic polymerization of normally gaseous olefins. This olefin fraction has a specific gravity of 0.7228 at 68 F. relative to water at 392 F. The parafilns comprise a fractionhaving a boiling range of from about 200 to 250 F. separated from a-gasoline obtained by catalytically alkylating gaseous isoparaflins and olefins. This paraflln fraction has a specific gravity of 0.7063 at 68 F. relative to catalytic conversion of petroleum hydrocarbons.

The extraction is efiected at a temperature and under a pressure sufficient to maintain the solvent and hydrocarbons substantially in the liquid phase, thereby forming a solvent or extract phase comprising aromatic hydrocarbons dissolved in the bulk of the solvent and a hydrocarbon or raflinate phase comprising non-aromatic hydrocarbons mixed with a small amount of the sol- Extra? Weight tion tern ratio solvent perature to on Weight per cent oil in extract basis Weight Der cent toluene in extract oil lromine number Solvent vfextract Carbowax 1500 61 0 54 Carbowax 4000 The toluene content of the extract hydrocarbons is determined by calculation on the basis of is advantageously such exert substantial solvent other impurities.

density determinations, the toluene used in the feed mixture having a specific gravity of 0.8813

- at 68 F. relative to water at 39.2 1".

As indicated by the foregoing tabulation the toluene content of the extract hydrocarbons ranged from about 24 to 46% by weight of the toluene in the feed mixture.

While batch extractions have been, described specifically it is contemplated that the extraction may be carried out in a continuous operation employing concurrent or countercurrent flow in conventional single or multistage extraction apparatus comprising packed towers or combinations of mixing and settling vessels.

It is also contemplated that mixtures of Carbowax and water may be'used as the extraction solvent. The proportion of water and Carbowax that, the mixture will action upon aromatic hydrocarbons at temperatures substantially above normal room temperature, for example, at temperatures of 200 F. and above, and at which temperatures the solvent-m"ixt1"1re exerts relatiyely little solvent action upon non-aromatic hydrocarbons. The extraction with such a solvent mixture is effected at the desired elevated temperature and the resulting extract and rafllnate phases are removed from the extraction zone. The separated phases are then subjected to cooling to about room temperature or somewhat above so that there is a substantial separation between solvent and hydrocarbons. The separated recovere fresh feed.

The proportion'of solvent to hydrocarbon feed employed in the extraction may be varied over a wide range as desired, for example, in the range of about 1 to 20 parts of solvent to 1 part of feed hydrocarbon mixture.

Where it is desired to obtain toluene substantially free from olefins the extract hydrocarbons may be subjected to treatment with a suitable agent such as sulfuric acid for the purpose of removing the olefins. The acid treatment may also be employed for the purpose of removing sulfur compounds such as mercaptans as'well as Other reagents maybe employed for this purpose including solid adsorptive material such as acid treated clay.

In extracting aromatic hydrocarbons such as toluene from naptha the light naptha fraction may be subjected to extraction with solvent followed by distillation of the resulting extract hydrocarbons to segregate a fraction rich in the desired aromatic constituents. As an alternative procedure the naphtha may be fractionated to segregate a fraction rich in the desired aromatic constituents, i. e., toluene or consisting essentially of hydrocarbons having a boiling range of drocarbons are discharged, leaving a solvent suitable for the extractionbf about 200 to 250 F. and this fraction then subjected to'solvent extraction in order to separate the toluene.

It is contemplated that the naphtha or naphtha fraction rich in the desired aromatics may be subjected to preliminary treatment to remove gum forming bodies and sulfur compounds prior to extraction with solvent. For example, the naphtha or suitable fraction thereof may be passed directly from the fractionating tower of the conversion unit in which the naphtha is produced to a conventional clay treatin tower for the removal of dioleflns or gum forming bodies. This clay treatment or a separate clay treatment may be carried out at temperatures sufllciently elevated to effect desulfurizing of the hydrocarbon mixture. Thereafter, the treated hydrocarbon mixture is subjected to extraction with solvent to remove the aromatic constituents in a 5 manner similar to that already described. The naphtha hydrocarbons from which the desired aromatics have been extracted can be run to gasoline or motor fuel production.

In addition to the foregoing the processhas application to the extraction of high antiknock aromatic blending stocks from wide boiling range naphthas or naphtha mixtures. It mayalso be applied to the treatment 'of high boiling petroleum fractions to obtain rafilnates of desired cetane number, kerosene having superior buming properties or lubricating oils of high viscosity index.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may

be made without departing from the spirit and scope thereof, and therefore only such limita-' tions should be imposed as are indicated in the appended claims.

I claim: 1. A process for separating unsaturated hydrocarbons including oleflnand aromatic hydrocarbons from a mixture of saturated and unsaturated hydrocarbons which comprise extracting the hydrocarbon mixture with a solvent comprising a poly-olefin glycol having a molecular weight of at least 1000, said poly-olefin glycol being substantially completely soluble in a substantially equal quantity of water at normal room tempera- 35 ture and above, effecting the extraction at a temperature andpressure sufficient to maintain the solvent and hydrocarbons substantially in the liquid phase, forming a solvent phase comprising unsaturated hydrocarbons dissolved in the bulk of the solvent and a hydrocarbon phase comprising saturated hydrocarbons mixed with a small amount of the solvent, separating the phases and recovering the hydrocarbons fromthe' solvent.

2. The method according to'claim 1 in which 5 the solvent comprises a solid poly-olefin glycol having a specific gravity of about 1.0 to 1.25, melting point of about 90 to 130 F. and a Saybolt-Universal viscosity at 210 F. of about 70 to 420 seconds.

5o 3. A process for separating aromatic hydrocarbons including toluene from a hydrocarbon mixture containing aromatic hydrocarbons which comprises extracting a hydrocarbon mixture of aliphatic, alicyclic and aromatic hydrocarbons car-bons mixed with a small amount of the solvent, separating the phases and recovering the hydrocarbons from the solvent.

4. The method according to claim 3 in which the poly-olefin glycol has a specific gravity of about 1.152, a melting point of about to 99 F. and a Saybolt-Universal viscosity of about 78 seconds at 210 F.

5. The method according to claim 3 in which the poly-olefin glycol has a specific gravity of 7 about 1.203, melting point of about 122 to 127 properties, for example, Diesel fuel having a high I 6. A processifor separatin aromatic hydrocarbons from a-hydrocarbon mixture containing aromatic hydrocarbons and non-aromatic hydrov carbons which comprises extracting said hydrocarbon mixture with a solvent comprising a poly-olefin glycol having a molecular weight tion at a temperature and pressure suflicient to maintain the solvent and hydrocarbons in the liquid phase, forming a solvent phase comprising aromatic hydrocarbons dissolved in the bulk of the solvent and a hydrocarbon phase comprising non-aromatic hydrocarbons mixed with a small amount of the solvent, separating the phases and recovering the hydrocarbons from the solvent.

7. A process for separating aromatic hydrocarbons from a hydrocarbon mixture containing aromatic hydrocarbons and non-aromatic hy-' drocarbons which comprises extracting said hydrocarbon mixture with a solvent comprising a normally solid poly-olefin glycol, effecting the extraction at a temperature and pressure sufficient to maintain the solvent and hydrocarbons in the liquid phase, forming a solvent phase comprising aromatic hydrocarbons dissolved in the bulk of the solvent and a hydrocarbon phase comprising non-aromatic hydrocarbons mixed with a small amount of the solvent, separating the phases and recovering the hydrocarbons from the solvent.

8. A process for separating aromatic hydrocarbons from a hydrocarbon mixture containing aromatic hydrocarbons and now-aromatic hydrocarbons which comprises extracting said hydrocarbon mixture with Carbowax 'in the presence of water, effecting the extraction at a temperature and pressure sufllcient to maintain the Carbowax and hydrocarbons in the liquid phase,

forming a solvent phase comprising aromatic hydrocarbons dissolved in the bulk or the Carboranging from 1500 to 4000, efiecting the extrachydrocarbons from the solvent.

wax and a hydrocarbon phase comprising nonaromatic hydrocarbons mixed with a small amount of Carbowax, separating the phases and recovering the hydrocarbons therefrom.

- 9. A process for effecting fractional separation oi ahydrocarbon mixture containing saturated and unsaturated hydrocarbons which comprises extracting said hydrocarbon mixture with a solvent comprising a normally solid poly-olefin glycol, effecting said extraction at a temperatureand pressure suflicient to maintain the solvent and hydrocarbons in the liquid phase, forming a solvent phase comprising unsaturated hydrocarbons dissolved in the bulk of the solvent and a hydrocarbon phase comprising saturated hydrocarbons mixed with a small amount of the solvent, separating the phases and recovering the '10. A process for effecting fractional separa tion of a hydrocarbon'mixture containing saturated and unsaturated hydrocarbons which comprises extracting said hydrocarbon mixture with a solvent comprising a normally solid polyolefin glycol in the presence of water ata temperature and pressure suflicient to maintain the solvent and hydrocarbons in.the liquid phase, forming a solvent phase comprising unsaturated hydrocarbons dissolved in the bulk 01 the solvent and a hydrocarbon phase comprising saturated hydrocarbons mixed with a small amount oi. the solvent, separating the phases and recovering the hydrocarbons from the solvent. 1

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