US2383057A - Extraction of hydrocarbons - Google Patents

Description

Aug. 21, 1 945. H. H. GROSS 'ET AL EXTRACTION OF HYDROCARBONS Filed Nov. 2, 1945 ARC A C5 SOLVENT RECYCLE WATER RECYCLE 7 HEATER OIL IRVINE F. GERMAN J HO RD H. GROSS VENTORS "THEIR ATTORNEY Patented Aug. 21, 1945 EXTRACTION I OF HYDROCARBON S Howard H. Gross, Fishkill, and Irvine F. German, Jr;, Beacon, N. Y., assignors to The Texas Company, New York, N. Y., a corporation oi Dela- 'ware Application November 2, 1943, Serial No. 508,704

8 Claims. (Cl. 196-13) This invention relates to the extraction of hydrocarbons and to the extraction of hydrocarbon mixtures with a solvent comprising a lactoneformlng acid such as levulinic acid.

The invention contemplates extracting a hydrocarbon mixture with a lactone-i'onning acid such as levulinic acid in the presence of a moditying agent such as water in an amount sufficient so that a two-phase system exists when'the solvent and hydrocarbon mixtures are in extractive contact within apredetermined temperature range. The resulting phases are separated and separately treated to remove the hydrocarbons and recover the acid solvent.

A lactone-i'orming acid such as levulinic acid tends to undergo decomposition to some extent when used as an extraction solvent at elevated temperatures, such decomposition involving lactone formation as evidenced by the presence of lactones in one of the liquid phases formed during the extraction.

In accordance with the present invention the liquid phase or hydrocarbon mixture containing lactones formed during the extraction is subsequently subjected to an elevated temperature in the presence 01' a substantial amount of added water so as to reconvert lactones present therein to the lactone-i'orming acid.

Thus, a mixture of aromatic and non-aromatic hydrocarbons may be extracted with a solvent comprising levulinic acid at a temperature in the range 150 to 225 F. for example to form extract and raflinate phases. The extract phase comprises aromatic hydrocarbons dissolved in the larger portion of the solvent while the railinate phase comprises non-aromatic hydrocarbons mixed with a minor proportion of the solvent.

The railinate phase will contain a small amount 01' lactones which are soluble in the ratlinate hydrocarbons. Accordingly, the rafllnate phase is withdrawn and commingled with a substantial amount of water, the water being present in an amount which is at least the molecular equivalent of the lactones present in the raillnate oil. The resulting mixture is then maintained at an elevated temperature in the range about 150 to 600 F. for a substantial period of time which may range from. a few minutes to several hours or for an even longer period of time. As a result of this heat treatment the lactones are substantially all reconverted. to levulinic acid.

- The treated mixture is then cooled to eiiect separation between the hydrocarbons and the levulinic acid solution. The separated hydrocarbons are discharged while the recovered acid is recycled to the extraction step. i

In ordbr to describe the invention in more detail reference will be made to the accompanying drawing comprising a flow diagram illustrating one method of practicing the process of the invention.

As indicated in the drawing, a mixture of arcmatic and non-aromatic hydrocarbons is drawn from a source not shown and conducted through a pipe I to a heater 2 wherein it is raised to a temperature in the range about 200 to 250 Fe The heated oil is then conducted through a pipe 3 to an intermediate portion of an. extraction tower 4.

Within the extraction tower 4 the oil is brought into intimate contact with levulinic acid introduced to the upper portion of the tower at one or more points as described later. Advantageously the treatment within the tower 4 involves countercurrent how of extraction solvent and oil undergoing treatment so that formation of extract and raflinate phases occurs.

The rafllnate phase comprising non-aromatic hydrocarbons mixed with a minor proportion of solvent accumulates in the top of the tower and is continuously drawn therefrom through a pipe 5 communicating with a pipe 6 leading to a heater 1. This railinate phase contains a small amount of lactones amounting to about 0.2 to 2.0% by weight of the raiiinate oil.

A quantity of water introduced to the system I through a pipe 8 is conducted through a branch pipe 9 communicating with the previously mentioned pipe 6 wherein the water so introduced is mixed with the rafllnate phase. The amount of water so added to the raflinate phase is sufficient to provide a mixture in which the water present is at least the molecular equivalent of the lactones present in the rafllnate oil. Advantageously the water is in substantial molar excess over the lactones and may amount to 20 mols per mol of lactone. V

The resulting mixture is passed through the heater 1 wherein it is raised to a temperature within the range to 600 F., preferably to a temperature 01' 250 to 300 F., and under suflicient pressure to maintain the system in a liquid state. The heated mixture is then drawn oil through a pipe l0 to a cooler II although it will be understood that where it is desired to employ lower temperatures with a longer time of heating provision may be made for maintaining the heated mixture at the elevated temperature for a substantial period of time ranging from 1 to 10 hours or more following which the mixture may be cooled.

The cooled mixture is conducted from the cooler ll through a pipe I! to a settling vessel [3 wherein the mixture is permitted to stand at a temperature corresponding to about room temperature so that separation of the' aqueous acid mixture from the hydrocarbon occurs. The upper layer will comprise raflinate hydrocarbons which are drawn oil through a pipe l4.

The aqueous layer, consisting mainly of levu-' linic acid, is drawn oil through a pipe l5 through which it is returned to the upper portion of the extraction tower 4. Any make-up acid required can be added through a pipe IS.

The extract phase accumulating in the bottom portion of the extraction tower 4 is continuously drawn off through a pipe 20 to a stripper 2| wherein the aromatic hydrocarbons may be stripped from the acid solvent with the aid of steam under subatmospheric pressure, if desired.

Residual liquid, consisting of solvent from which the aromatic hydrocarbons have been stripped, is drawn off through a pipe 22 and recycled all or in part through the pipe 23 leading to the upper portion of the extraction tower 4. The acid solvent returned to the pipe 23 is 01' relatively high concentration and therefore may be introduced to the extraction tower 4 at a point intermediate between the point of feed oil introduction and the point of solvent return through the pipe l5.

The distillate removed in the stripper 2| is conducted through a pipe 30 to a cooler 3| wherein cooling and condensation is effected. The resulting condensate is conducted through a pipe 32 to a settler 33 wherein phase separation between aromatics and water occurs.

The separated aromatics which may still retain a small amount or trace of levulinic acid are conducted through a pipe 34 to a scrubber 35 wherein the aromatics may be subjected to countercurrent washing with a stream of water. The water may be introduced to the upper part of the scrubber through a pipe 36 in the proportion of about 1 volume of water to 1 volume of aromatics, so as to permit countercurrent contact between water and aromatics. The scrubbed aromatics are discharged jrom the top of the scrubber 35 through a pipe 31 while the wash water is removed from the bottom of the scrubber 35 through a pipe 38 communicating with a pipe 39. The pipe 39 communicates with the previously mentioned pipe 9 thereby providing means for recycling all or a portion of the water either to the top of the extraction tower 4 or for mixing with rafiinate phase flowing through the pipe 6. The portion of water not recycled through the pipe 39 may be discharged from the system through a pipe 40. Likewise, water separated from the settler 33 is drawn through a pipe H which communicates with the previously mentioned pipe 39. recycled through pipe 39 or removed from the system through pipe 40.

As previously mentioned, some water or recycled water containing a small amount of acid can be introduced to the upper portion of the extraction tower 4 through a pipe 43 which permits introducing the water at a point above that at which the solvent or more concentrated solvent solutions are introduced. In this way the railinate phase is subjected to washing with This water also may be water as it rises towards the top of the extraction tower 4.

Moreover, by introducing water or substantially pure water at the top of the tower while introducing solvent of progressively increasing concentration at successive points in the tower toward the point of feed oil introduction a concentration gradient may be maintained throughout this portion of the extraction tower.

The method of flow thus illustrated is applicable to the treatment of naphtha or fractions of naphtha containing aromatic constituents. It has been found that levulinic acid of not in excess of about 97% concentration, that is, containing at least about 3% water by weight of the acid, is effective in extracting toluene oi nitration grade from such hydrocarbon mixtures. The extraction may be effected in the presence of larger amounts of water, for example, using acid of about 75% concentration but under such conditions higher extraction temperatures are required since the about 60% acid.

More specifically, the invention concerns eifecting the extraction of aromatics from hydrocarbon mixtures containing them by treating the mixtures with a levulinic acid-water solvent having a concentration within the range about 60 to 97% acid, based on the mixture of acid and water, or with anhydrous acid in the presence of 3 to 60% water by weight of the anhydrous acid. The ratio of acid-water solvent to feed oil may vary over a wide range, for example, from 1 or less to 10 or more volumes of solvent per volume of oil.

The extraction temperature employed may range from about 20 to 300 F. although the present invention is particularly concerned with operations employing extraction temperatures in the upper portion of this range, namely, in the neighborhood of 200 F. and above, at which temperatures levulinic acid undergoes some decomposition with formation of lactones.

The lactones so formed when extracting naphtha or naphtha hydrocarbon mixtures are usually found in the raflinate phase.

It has been found that by subjecting such lactones to elevated temperatures in the presence of a molar excess of water they are substantially completely reconverted to levulinic acid. For example, 1 mol of lactone is mixed with 1.32 mols of water. This mixture is maintained at a temperature of 300 F. for about 184 hours and then cooled to room temperature. The resulting product will comprise about 92.6% by weight of levulinic acid, 1.9% lactone and 5.5% water.

Consequently, and in accordance with the present invention, the raflinate phase containing a small amount of lactones is mixed with water and subjected to elevated temperature with continued agitation under conditions so as to effect substantial reconversion of the lactones to the acid.

l'ihile mention has been made of applying the process to the treatment of naphtha hydrocarbons it is also contemplated that it may be applied to the treatment of other hydrocarbons or hydrocarbon mixtures derived from petroleum or solme other source such as animal and vegetable 01 s.

Although the invention is particularly useful for the extraction of aromatic hydrocarbons from mixtures containing aromatic and non-aromatic hydrocarbons, it is contemplated that it ma be used in the treatment of other types of hydrocarbon mixtures as indicated above. It may be used to effect separation between olefinic and paraffinic hydrocarbons.

In connection with the extraction tower 4, pro vision may be made for the employment of extract recycle, rafilnate recycle, temperature gradient throughout the extraction zone, etc. One or more towers may be employed or the process may be carried out in a stage system, each stage compristhe extract phase or any portion thereof likewise may be treated to effect conversion of lactones contained therein.

For example, provision may be made for diverting all or a portion of the liquid mixture flowing through pipe to a conversion zone wherein it is maintained under suitable conditions such as employed in treating the raflinate phase to effect conversion of lactones to the corresponding acids. The so-treated mixture can then be cooled and subjected to settling so as to separate the solution of acid in water from the extract oil.

The separated solution may be recycled to the extraction tower 4 or otherwise disposed of. The extract oil can be removed or passed to the scrubber to remove any retained acid.

While not shown, it is also contemplated that means maybe provided for eiiecting thorough mixing of the heated lactone-containing mixture so as to facilitate the conversion to acid.

Obviously many modifications and variations of the invention as above set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated by the appended claims.

We claim:

1. A process for effecting separation between hydrocarbon bodies of difierent chemical constitution by solvent extraction which comprises extracting a mixture'orhydrocarbons with relatively concentrated aqueous levulinic acid at a temperature in the range about 150 to 300 F., forming an extract phase comprising soluble hydrocarbons dissolved in a larger proportion of the acid and a raiflnate phase comprising relatively insoluble hydrocarbons mixed with a minor proportion of the acid, said rafllnate phase containing a small amount of lactones formed from the acid during said extraction, separating said phases, commingling the separated raflinate phase with water in substantial molar excess over the lactones present, maintaining the commingled mixture at a temperature in the range 150 to 600 F. for a substantial period of time such that lactones therein are converted to acid, separating the resulting acid from the rafllnate hydrocarbons and returning the separated acid to the extraction step.

2. The method according to claim 1 in which the commingled mixture of water and railinate phase is maintained at a temperature of about 250 to 300 F. for a substantial period of time such that lactones therein are converted to acid.

3. A process for effecting separation between hydrocarbon bodies of different chemical constitution by solvent extraction which comprises extracting a mixture of hydrocarbons with relaforming an extract phase comprising soluble hydrocarbons dissolved in a larger proportion of the acid and a rafllnate phase comprising relatively insolublehydrocarbons mixed with a minor proportion of the acid, said raffinate phase containing a small amount of lactones formed from the acid during said extraction, separating said phases, separating the bulk of the solvent from the extract phase, returning the separated solvent to the extraction step, washin the extract hydrocarbons from which the bulk of the solvent has been separated with water to remove residual solvent, commingling a portion of the wash water containing residual solvent with said separated raifinate phase in an amount such that the water is in substantial molar excess over the lactones present, maintaining the commingled mixture at a temperature in the range to 600 F. for a substantial period of time such that lactones contained therein are converted to acid, separating the resulting acid from the raflinate hydrocarbons and returning the separated acid to the extraction step.

4. A process for effecting separation between oil constituents of different chemical constitution by solvent extraction which comprises extracting said oil with relatively concentrated aqueous levulinic acid at a temperature in the range 150 to 300 F'., forming an extract phase comprising constituents of the oil soluble in the major portion of the acid and a rafiinate phase comprising relatively insoluble constituents of the oil mixed with a minor portion of the acid, said railinate phase containing a small. amount of lactones formed from the acid during said extraction, separating said phases, commingling the separated railinate phase with up to about 20 mols of water per mol of lactone, maintaining the commingled mixture at a temperature in the range about 250 to 300 F. for a substantial period of time such that lactones therein are converted to acid, separating the resulting acid from the raflinate hydrocarbons and returning the separated acid to the extraction step.

5. A process for effecting separation between oil constituents of different chemical constitution by solvent extraction which comprises extracting said oil with aqueous levulinic acid having a concentration of about 60 to 97 weight per cent acid at 4 a temperature in the range about 150 to 300 F., forming an extract phase comprising constituents of the oil soluble in the major portion of the acid and a rafllnate phase comprising relatively insoluble constituents of the oil mixed with a minor portion of the acid, said raflinate phase containing a small amount of lactones formed from the acid during said extraction, separating said phases, corn-mingling the separated raflinate phase cent acid at a temperature substantially above the melting point of anhydrous levulinic acid, forming an extract phase comprising aromatic hydrocarbons dissolved in a major portion of the acid and a raflinate phase comprising nonaromatic hydrocarbons mixed with a minor portion of the acid, said rafilnate phase containing a small amount of lactones formed from the acid during said extraction, separating such phases, commingling the separated rafllnate phasewith up to about mols of water per mol of lac- -tone, maintaining the commingled mixture at a temperature of about 250 to 300 F. for a substantial period of time such that lactones therein are converted to acid, separating the resulting acid from the rafilnate hydrocarbons and returning the separated acid to the extraction step.

'7. A continuous process for effecting separation between oil constituents of different chemical constitution by solvent extraction which comprises introducing a stream of feed oil to an intermediate point of an extraction column maintained at an elevated temperature substantially above the melting point of anhydrous levulinic acid, introducing relatively concentrated aqueous levulinic acid to the upper portion of said column, eil'ecting countercurrent contact between feed oil and acid within the column at said elevated temperature such that a rafllnate phase comprising relatively insoluble constituents of feed oil mixed with a minor portion of acid and an extract phase comprising soluble constituents of the oil dissolved in a major portion of the acid are formed, continuously withdrawing extract phase from the lower portion of the column below the point of feed oil introduction, injecting water to the upper portion oi said column above the point of acid introduction, subjecting raffinate phase rising therein to washing with said injected water, continuously withdrawing from the upper portion of the column above the point of water injection a stream of washed rafllnate phase containing a small amount of lactones formed from the acid during said extraction, subjecting withdrawn rafilnate phase containing water in substantial molar excess over the lactones present in the rafllnate phase to an elevated temperature for a time suflicient to reconvert lactones to acid, cooling the heated raifinate phase to a temperature sufilciently low to cause separation into an oil phase and an aqueous phase comprising acid, and recycling separated acid phase to the upper portion of said column substantially below the point of water injection.

8.- A continuous process for extracting toluene from naphthawhichcompgises introducing a stream ornaph-tha hydrocarboiis fiantaining toluene to an intermediate point of an extraction column maintained at an elevated temperature in the range 150 to 225 F., introducing aqueous levulinic acid of about 97.0 concentration to the upper portion of said column, effecting countercurrent contact between feed naphtha and acid within the column at the aforesaid elevated temperature such that non-aromatic hydrocarbons mixed with a minor portion of the acid and an extract phase comprising aromatic hydrocarbons dissolved in a major portion of the acid are formed, withdrawing extract phase from the lower portion of the column below the point of naphtha introduction, injecting water to the upper portion of said column above the point of acid introduction, subjecting raffinate phase rising therein to washing with said injected water, withdrawing from the upper portion of the column above the point of water injection a stream of washed raifinate phase containing a small amount of lactones formed from the acid during said extraction, subjecting withdrawn rafflnate phase containing water in substantial molar excess over the lactones present in the raflinate phase to a temperature in the range about 250 to 300 F. for a period of time suflicient to reconvert lactones to acids, cooling the heated rafllnate phase mixture to about room temperature to form a hydrocarbon phase consisting essentially of nitration grade toluene and an aqueous phase comprising acid, separating said phases and recycling the separated acid phase to the upper portion of said column at a point substantially below the point of water injection.

HOWARD H. GROSS.

IRVINE 'F. GERMAN, Ja.

Images