KR870001906B1 - Recovery of aromatic hydrocarbons and nonaromatic raffinate stream from a hydrocarbon charge stock - Google Patents

Abstract

This invention relates to an aquous extraction of solvent. The recovery of solvent from extraction residue is performed by secondary sovent extraction process. The used aromatic-selective solvent is sulfolane,(tetrahydrothiophene, 1-1 dioxide) (I) [R1, R2, R3, R4=hydrogen, C1-10 alkyl, C1-8 alkoxy , 2-sulfolene, 3-sulfolene or 2-methylsulfolane. The solvent composition is composed of selective solvent and water.

Description

Recovery of aromatic hydrocarbons and non-aromatic extract residues from hydrocarbon sources

Diagram of flow of a preferred process according to the invention.

The present invention relates to solvent extraction of aromatic hydrocarbons from hydrocarbon charge stock. The present invention also relates to the aqueous extraction of solvents from non-aromatic extract residues produced upon extraction of aromatics from a hydrocarbon source. The present invention also relates to an improved process for the aqueous extraction of solvents from non-aromatic extraction residues produced in the solvent of aromatics from a hydrocarbon source, i.e. pretreatment of the aqueous extracts with the extraction residues. .

It is well known that the effluent stream contains a solvent in the extraction zone of the extraction process of aromatic hydrocarbons. The solvent contained in the extract residues must be recovered, not only to interrupt the continuous process or to use the extract residues, but also to prevent the loss of the solvent in the aromatic extraction process. Recovery of the solvent from the extract residues is accomplished by a secondary solvent extraction process such as distillation of the extract residues or washing the extract residues.

Typical aromatic-selective solvents used in commercial aromatic extraction processes that can be recovered in the present invention are generally known as sulfolanes (tetrahydrothiophene, 1-1 dioxide). Also used are sulfolane derivatives corresponding to the following structural formulas;

Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represent hydrogen, alkyl radicals containing 1-10 carbon atoms, aralkyl radicals containing 7-12 carbon atoms, alkoxy containing 1-8 carbon atoms It is selected from radicals. Other solvents included in the present step include 2-sulfonene or 3-sulfonene of the following structural formula.

Other typical solvents with high selectivity to select aromatics from non-aromatic hydrocarbons and are within the scope of the present invention include 2-methylsulfonane, 2,4-dimethylsulfolan, methyl-2-sulfonyl ether, N-aryl 3-sulfonylamine, 2-sulfonyl acetate, diethylene glycol, various polyethylene glycols, dipropylene glycol, various polypropylene glycols, dimethyl- sulfoxide, N-methyl pyrrolidone, and the like.

Particularly preferred solvates in the process of the invention are sulfolane of the structure

The solvent composition in the present invention consists of a mixture of one or more of the solvents specified herein with water. Particularly preferred solvent compositions consist of water and sulfolane. In extracting aromatic hydrocarbons from hydrocarbon mixtures, the solubility of paraffins is assumed to be low and gradually increased in the following order; It is a technique to control the solubility of hydrocarbons in solvent compositions with naphthenes, olefins, diolefin acetylenes, sulfur-containing hydrocarbons, nitrogen-containing hydrocarbons, oxygen-containing hydrocarbons, aromatic hydrocarbons, and varying amounts of water. Therefore, by adding more water in the solvent, the solubility of all components in the hydrocarbon mixture is reduced but the solubility difference (selectivity) between the components is increased. The real effect is to reduce the number of binding stages necessary to achieve a given purity of the aromatic extract and to increase the final purity of the aromatic extract when the number of binding stages is unchanged.

The presence of water in the solvent composition provides the advantage of introducing volatiles into the fractionation system where the aromatic extract is separated from the thick solvent composition. Volatilization of water in the solvent composition aids in the removal of all non-aromatic hydrocarbons from the aromatic-rich solvents and substantially all of the aromatic extracts from the final lean solvent.

The solvent composition contains about 0.1 to about 20 weight percent water. When the solvent composition is composed of sulfolane, it is preferred to contain about 0.1-1.0% by weight of water, and in the case of a solvent composition consisting of polyalkylene glycols it is preferred to contain about 6-about 15% by weight of water.

In the aromatic extraction process of the present invention, the hydrocarbon inflow source is treated in an extraction zone consisting of a tower or column suitably equipped with burr saddle lashing or the like, or a column containing baffles, or a rotary plate connector (RDC).

In this zone, the hydrocarbon inlet is treated in combination with a lean solvent composition to yield a non-aromatic extract residue and an aromatic-rich solvent composition. The concentrated solvent composition is recovered from the extraction zone and passes through a separation zone consisting of at least one fractionation column operated to remove residual non-aromatic hydrocarbons and recover the high purity aromatic extract and the resulting lean solvent composition. do. The non-aromatics removed are generally recovered to the extraction zone to provide reflux of the non-aromatic, hydrocarbons. As the solvents used in the extraction process are generally suitable at elevated temperatures, it is common to recover the aromatic extracts with removal of evidence—aromatic extracts are subsequently separated from the steam concentrate and passed through a fractionation train where Are classified. The steam concentrate is subsequently used to rinse the mentioned primary non-aromatic extract residues of the extract and to recover the residual solvent contained therein.

The aromatic extraction process described extensively herein is clearly described in US Pat. No. 3,361,664, where the solvent composition consists of sulfolane and water. Typical aromatic extraction processes using solvent compositions composed of polyalkylene glycols and water are described in US Pat. No. 2,773,918. These patents and published patent applications are typical of aromatic extraction zones that produce non-aromatic extract residues and aromatic-rich solvents, and separation zones where the thick solvent is separated to yield non-aromatic fractions, high purity aromatic extracts and final lean solvents. The processing steps and operating conditions are clearly described.

As mentioned above, the non-aromatic extract residues exiting the extraction zone contain some solvent. The solvent is part of the low concentration of dissolved components, part of which is an influent dispersion in the free solvent due to turbulence, present in the extract residues in the extraction zone. Since the typical solvent compositions used for aromatic extraction are water soluble, the extraction process of the solvent contained in the non-aromatic extract residues is by combining the extract residues with liquids in a continuous extraction apparatus. The extraction of water and solvent from the extract residues is carried out by suitable liquid-liquid confinement determination, such as towers containing suitable devices such as burial saddles or lashings, or towers or rotary plate connectors containing suitable stages.

Extraction residue discharged from the aqueous extraction zone or the water washing zone is substantially liberated from the solvent composition. Non-aromatic hydrocarbon extract residues consisting of hexane and haptan are generally useful as solvents, although in some cases they are excluded because of the contamination of the introduced aromatics. One excluded use is in solvent extraction of vegetable oils. The contaminant amount of aromatics generated in the non-aromatic extract residues is removed from the aqueous extracts used in the solvent extraction process from the extract residues.

In terms of saving water, the aqueous extract is derived from the aforementioned stripper concentrate recovered from the aromatic extract. This stripper concentrate, wherein substantially all of the aromatic extract is isolated, contains about 300-about 400 ppm, aromatic, which flows into the non-aromatic extract residue in the extraction process of the solvent composition.

It is an object of the present invention to provide an improved process for solvent extraction of aromatic hydrocarbons and recovery of high purity non-aromatic extract residues from hydrocarbon sources. More specifically, the object of the present invention is an improved process for the aqueous extraction from non-aromatic extraction residues produced upon solvent extraction of aromatics from a hydrocarbon source, with high purity extraction residues being recovered.

It is an object of the present invention, together with the local portion of the original non-aromatic extract residues, to produce an aromatic-containing steam concentrate of the residue recovered from the aromatic extract, in which the concentrate recovers the solvent from the original extract residues. It can be achieved by pretreatment before use as an extract. In this process, only a very small amount of extract residues recovers the residual aromatics from the vapor concentrate-aromatics are also high purity solvents that are extracted from the original extract residues and thus impair the use.

The present invention includes a method for recovering aromatic hydrocarbons and non-aromatic extract residues from a hydrocarbon inlet source; Treating said aborigine in an extraction zone with an aromatic-selective solvent composition to yield a first residue and a residual solvent consisting of aromatic-rich solvents and non-aromatic hydrocarbons; Treating said aromatic-rich solvent stream in a first separation zone such that substantially all residual non-aromatic hydrocarbons are separated; Treating the above-mentioned aromatic-rich solvents in the first separation zone with the removal stream to yield a high purity aromatics, a first aqueous stream consisting of steam concentrate and residual aromatics and a substantially aromatic hydrocarbon free lean solvent; Recovering the lean solvents into the extraction zone; Treating the residual aromatic-containing first aqueous stream in the first fold zone to combine a small amount of the first extract residue to yield a second aqueous stream and an aromatic-containing second extract residue substantially free from aromatic hydrocarbons; Recovering the second extraction dregs into the extraction zone; Treating the residue of the first extract residues with the second aqueous zone in a second fold zone to yield solvent residues and solvent compositions that are free from solvent containing aqueous streams and substantially aromatic hydrocarbons; It is composed of recovering the aromatic-free extract residues.

Objects and examples of the present invention will become more apparent from the following.

The invention will also be explained in more detail by the accompanying drawings.

In this preferred example, the depentanized catalytic reformate is first reflowed to remove the high boiling fraction. The reflowed product is subjected to a sequential extraction to yield a nitrated grade aromatic fraction consisting of benzene, toluene and xylene, extract residues free of C ₆ -C ₈ paraffins and substantially aromatics. The reflowed source preferentially enters the initial aromatic extraction zone, which is not shown in the accompanying drawings, and is about 8730 b.psd (1390 m 3 psd) or 1063.6nb-mols / hi (48. 2.44 kmol / hr). Combine with sulfolane solvent composition. Non-aromatic extract residues yield about 4365 b.psd (690m 3 psd), or 470.8 nb-mols / hr (213.6 kmols / hr), while aromatic-rich solvents produce about 1191.9 nb-mols (540.6 kmols) hydrocarbons per hour. Recovered to yield an extract.

Referring to the figure, the concentrated solvent stream from the first extraction zone is introduced via line 1 into the apparatus according to the invention. The thick solvents provide a solvent composition consisting of about 1191.9 mols (540.6 kmols) of hydrocarbon extract and sulfolane fruit per hour. This thick solvent stream continues through line 1 and enters the solvent removal column 2 at a temperature of about 245 ° F. (118 ° C.) and a pressure of about 5 psig (34 kpa gauge). The solvent removal column 2 is operated to separate substantially all non-aromatic hydrocarbons from the introduced concentrated solvent stream. The supernatant of the removal column is thus recovered through line 3 at a temperature of about 659.1 mols / hr (299.0 kmols / hr) about 265 ° F. (129 ° C.) and a pressure of about 5 psig (34 kpa gauge). This upper vapor stream is cooled to about 120 ° F. (49 ° C.) in concentrator 4 and then flows through line 5 into phase separator 6 at substantially atmospheric pressure. The steam concentrate is settled in the phase separator 6 to yield an aqueous phase and a hydrocarbon phase. The hydrocarbon phase consisting substantially of non-aromatic hydrocarbons is discarded through line 7 at about 592.1 mols / hr (268.6 kmols / hr) and about 120 ° F. (49 ° C.). Although not shown in the figures, these hydrocarbons are recycled to the primary aromatic extraction regime to yield non-aromatic reflux. The aqueous phase recovered from the phase separator 6 consists of water evaporated from the sulfolane-water composition introduced into the solvent stripping column 2. The aqueous phase is recovered from the phase separator 6 via line 8 at about 67 mols / hr (30 kmols / hr) and the aqueous phase is treated by the method described herein.

In the thick solvent passing through the bottom of the solvent removal column 2, the temperature is raised by the rise of hot hydrocarbons and water vapor by a method suitable to yield substantially all non-aromatic hydrocarbons from the thick solvent. The aromatic thick-solvent is discarded from the bottom of the solvent stripping column 2 through line 9 at a temperature of about 300 ° F. (149 ° C.). The aromatic-rich solvent stream enters the afterboiler 10, where it is increased to a temperature of about 350 [deg.] F. (180 [deg.] C.). The resulting hot afterboiling and aqueous mixture is reintroduced through line 11 to the bottom of the desolving column 2 at a pressure of about 10 psig (70 kpa gauge).

The resulting eliminator bottom fraction, consisting of aromatic-rich solvent, exits the bottom of the desolving column 2 through line 11 at a temperature of about 350 ° F. (180 ° C.). The aromatic-rich solvents are liberated from substantially non-aromatic hydrocarbons in the operating state of the solvent removal column 2. Aromatic thick solvents are transferred to extract recovery column 13 via line 12 at a temperature of about 325 ° F. (163 ° C.) and about 300 mmHg (40 kpa absolute) pressure. The aromatic-rich solvents contain sulfolane solvent compositions containing about 599.8 mols / hr (272.1 kmols / hr) of substantially pure aromatic hydrocarbon water.

The extract recovery column 13 is operated in a state suitable for substantially all aromatic hydrocarbons to be separated into the sulfolane composition. The upper vapor stream is discarded from the extract recovery column 13 across line 14 at a temperature of about 180 ° F. (82 ° C.) and about 300 mmHg absolute (40 kpa absolute) pressure. The hot steam stream enters concentrator 15, where it is cooled to a temperature of about 100 [deg.] F. (38 [deg.] C.) before it enters recoverer 17 through line 16. The resulting concentrate is separated in the aromatic hydrocarbon phase and the lower aqueous phase in the recoverer 17, the latter being due to the removal steam used in the extract recovery column 13. The first part of the hydrocarbon phase is discarded from the recoverer 17 via line 18 and returned to the extraction recovery column 13 as reflux. The second fraction of hydrocarbon phase is discarded via line 19 at about 602.8 mols / hr (273.4 kmols / hr). The part on this hydrocarbon consists of about 599.8 mols / hr (272.1 kmols / hr) of high purity aromatics and 3 mols / hr (1.4 kmols / hr) of dissolved influent water. The aqueous phase settled in the recoverer 17 contains about 400 ppm of the residual oil aromatic hydrocarbons. This aqueous phase consisted of a stripped steam concentrate that was discarded through a line 20 of about 621.9 mols / hr (282.1 kmols / hr) and entered the aromatic extract column 21.

The aromatic-rich solvent passing down the extract recovery column 13 is concentrated by stripping steam and hot aromatic hydrocarbon vapor and substantially all hydrocarbons are removed from the solvent. The resulting lean solvent is withdrawn from the extract recovery column 13 via line 22 at a temperature of about 325 ° F. (163 ° C.). The combined aqueous stream consisting of water, sulfolane and a small amount of non-aromatic hydrocarbons is passed through line 8 and line 23 from the above mentioned phase separator 6 and through line 23 from the mentioned circle. Flows into line 22. The resulting vapors and solvents are also introduced into the afterboiler 24 where they are heated to about 336 ° F. (168 ° C.). The produced after-boiling steam and liquid complex are discharged from the after-boiling apparatus 24 through the line 25 and flow into the bottom of the extract recovery column 13.

The pure lean solvent was withdrawn from the extract recovery column 13 via a line 26 at a temperature of about 325 ° F. (163 ° C.) and recovered to the primary aromatic extraction zone mentioned above, not shown in this figure.

The aqueous phase recovered in the recoverer 17 and introduced into the aromatic extract column 21 via line 20 combines with some of the non-aromatic extract residues recovered therefrom from the primary aromatic extraction zone mentioned above. Non-aromatic extract residues exit the primary aromatic extraction zone and enter the apparatus of the present invention via line 27 at about 470.8 mols / hr (213.6 kmols / hr). A small amount of extract residues of about 23.5 mols / hr (10.7 kmols / hr) is converted via line 28 and flows into the bottom of the aromatic extract column 21. Bonding is effected by the column at a temperature of about 100 ° F. (38 ° C.) and a pressure of about 60 psig (400 kpa gauge), which consists of a tumbler splice device or other suitable mixed-chip steel device. In the aromatic extract column 21, the non-aromatic component in the extract residues introduced therein extracts the substantial aromatic components of the aqueous phase introduced therein via line 20. It is discharged from the bottom of the aromatic extract column 21 of about 100ppm (29) or less and flows into the upper layer of the extract residue flush column 30. The supernatant is recovered from the column 21 via line 32 at about 23.5 mols / hr (10.7 kmols / hr) and with the above-mentioned lean solvents of line 26 for recovery to the primary aromatic extraction zone. Combined.

The extract residue from line 27 to the extract residue wash column 30 consists of 440.6 mols / hr (199.8 kmols / hr) of hydrocarbon and 6.6 mols / hr (3.0 kmols / hr) of sulfolane solvent. Extraction debris enters the column at a temperature of about 100 ° F. (38 ° C.) and a pressure of about 60 psig (400 kpa gauge). The extract residues are washed in a flush column 30 with 621.9 mols / hr (282.1 kmols / hr) 100 ° F. (38 ° C.) water entering the upper column of the column from line 29 and the water described in the method described herein. It was pretreated to contain up to about 100 ppm of aromatic hydrocarbons. Substantially the sulfolane free extract residues are extracted in flush residue column 30 through line 31 at about 440.18 mols / hr (199.66 kmols / hr), about 100 ° F. (38 ° C.) and about 30 psig (200 kpa gauge). Discharged. This extract residue is increased to about 4320 b.p.s.d (690㎥ p.s.d) and discharged.

The aqueous stream exits the extract residue wash column 30 at about 628.97 mols / hr (285.30 kmols / hr) and about 100 ° F. (38 ° C.). 621.9 mols / hr (282.1 kmols / hr) water, 7.0 mols / hr (3.2 kmols / hr) solvent and 0.07 mols / hr (0.032 kmols / hr) non-aromatic extract residues.

This aqueous stream is transferred through wine 23 and combined with the lean solvent of line 22 as mentioned herein and subsequently introduced into extract recovery column 13.

Those skilled in the process will be able to determine the particular operating conditions for separating the non-aromatic extracts required for any given component of the hydrocarbon source.

Claims (5)

(a) treating the inlet and the aromatic-selective solvent composition in the extraction zone to produce a primary extract residue and a residual solvent consisting of aromatic-rich solvents and non-aromatic hydrocarbons; (b) treating said aromatic-rich solvents in a primary separation zone such that the non-aromatic hydrocarbons formed above are substantially separated; (c) combining the aromatics-rich solvents in the stripping steam and the second separation zone to yield lean solvents free of primary aromatics consisting of high purity aromatics, steam concentrates and residual aromatics and substantially aromatic hydrocarbons. To be processed; (d) recovering the lean solvent to the extraction zone; (e) extracting the residual aromatic-containing primary aqueous stream in a small amount of the primary extract residue and in the primary separation zone so as to yield substantially secondary aqueous streams free of aromatic hydrocarbons and aromatic-containing secondary extract residues. To combine; (f) recovering the secondary extract residues to the extraction zone; (g) treating the residues of the primary extract residues in the secondary aqueous zone and the secondary tangent zone to yield an extract residue and a solvent composition in which the solvent-containing aqueous stream and substantially the aromatic hydrocarbon are free; And (h) recovering the aromatic hydrocarbons and the non-aromatic extract residues from the hydrocarbon inlet consisting of recovering the aromatic-free extract residues. A process according to claim 1, wherein the aromatic-selective solvent composition consists of a sulfolane chemical compound of the formula

Wherein R ₁ , R ₂ , R ₃ and R ₄ are hydrogen, alkyl radicals containing 1-10 carbon atoms, aralkyl radicals containing 7-12 carbon atoms, alkoxy radicals containing 1-8 carbon atoms It is chosen as original source from. The method of claim 1 wherein the aromatic-selective solvent composition is a sulfolane of the structure:

The process of claim 1, wherein the solvent-containing aqueous stream of step (g) is recovered to the extraction zone of step (a). The process of claim 1, wherein the solvent-containing aqueous stream of step (g) is recovered to the secondary separation zone of step (c).

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