US3259669A - Hydrocarbon conversion process - Google Patents

Description

July 5, 1966 D. K. BEAvoN HYDROCARBON CONVERSION PROCESS 2 Sheets-Sheet l Filed June 28, 1963 July 5, 1966 D. K. BEAvoN 3,259,669

HYDROCARBON CONVERSION PROCESS Filed June 28, 1963 2 Sheets-Sheet 2 United States Patent O ,259 669 HYDRGCARBON COVERSION PROCESS David K. Beavon, Lockport, Ill., assigner to Texaco Inc., New York, N.Y., a corporation of Delaware Filed June 28, 1963, Ser. No. 291,435 8 Claims. (Cl. 26o-683.43)

This invention is directed to hydrocarbon conversion process and more particularly, to a process involving a combination of alkylation and aromatic extraction. In accordance with this invention, an aromatic hydrocarbon mixture is contacted with a sorbent and raffinate comprising unsorbed non-aromatic hydrocarbons is separated from sorbent and sorbed aromatic hydrocarbons. Olen is separately contacted with a stoichiome-tric excess of isoparafln reactant under alkylation conditions effecting formation of alkylation reaction mixture cornprising alkylate and excess isoparafn reactant. Sorbent and sorbed aromatics are contacted with said alkylation reaction mixture effecting transfer of aromatics from said sorbent to said alkylation mixture. Excess isoparains are then separated from the alkylation mixture containing aromatics forming a product comprising alkylate and aromatic hydrocarbons useful as a high octane constituent in gasoline blending.

The principal hydrocarbons which are valuable for use in the manufacture of high octane gasolines are aromatic hydrocarbons and highly branched parafnic hydrocarbons. These hydrocarbons are valued because of their high octane numbers. I n modern petroleum refining, aromatic hydrocarbons are obtained by catalytic reforming of straight run gasolines. Branched chain hydrocarbons are synthesized in large quantity from normally gaseous hydrocarbon streams by the alkylation of olefins for example propylene, butylenes, pentylenes, their polymers and copolymers with isoparains, for example, isobutane. Although aromatic hydrocarbons are of very high octane number, their combustion characteristics -result in relatively high carbon formation and high running temperatures in internal combusion engines. They also exhibit a relatively high octane sensitivity, the difference in octane number determined by the research method and the motor method, which is undesirable from the standpoint of road octane number performance. On the other hand, isoparaffin hydrocarbons are characterized by low octane sensitivity, clean combustion characteristics, and high lead appreciation. It is therefore desirable, in the manufacture of balanced motor fuels, to incorporate both aromatic and isoparaffin hydrocarbons in order to achieve the maximum production of motor fuels of optimum octane number, sensitivity, and clean burning characteristics.

Advantageously, aromatic hydrocarbons are concentrated by sorption using an adsorbent or absorbent. Examples of sorption processes employed in the petroleum industry for the separation or concentration of gasolinev boiling range aromatic hydrocarbons are liquid-liquid solvent extraction processes employing solvents which are selective for aromatic hydrocarbons, for example, glycols and glycol ethers and liquid-solid adsorption processes which employ solid adsorbents which are selective for aromatic hydrocarbons for example, silica gel. Exemplary of processes for the `separation of aromatics from gasoline boiling range hydrocarbons by liquid-liquid solvent extraction and by liquid-solid adsorption are the processes described in U.S. Patent 3,037,062, patented May 29, 1962 and in U.S. Patent 2,854,495, patented September 30, 1958 respectively. These sorption processes employ a large amount of energy in isolating the aromatic hydrocarbons from the low-octane constitutents of the catalytic reformate. Much of this energy is re- Vquired in effecting stripping of the extracted aromatics Patented July 5, 1966 from the sorbent. This energy is employed in distilling the aromatics away from the solvent in a liquid-liquid solvent extraction process or in distilling the desorbent from the aromatic product in a solid-liquid adsorption process. In accordance with the process of this invention, distillation of the aromatics is eliminated by transferring the aromatic hydrocarbons from the sorbent to the reaction mixture from an alkylation process. The reaction mixture and transferred aromatics are then passed to a deisobutanizing distillation which separates the excess isobutane from the reaction mixture and bottoms comprising alkylate and aromatic hydrocarbons .are Withdrawn for use as high octane blending components.

The alkylation reaction is effected in the liquid phase in the presence of an acid catalyst. The alkylation reaction is directed to the production of `a maximum yield of high product quality alkylate with minimum catalyst consumption by maintaining desirable operating conditions including conditions of intimate mixing, a low ternperature, and a high ratio of isoparafln to olefin. Intimate contact ofthe reactants and catalyst is effected by intensive mixing forming an emulsion of liquid hydrocarbon and catalyst. The alkylation reaction temperature is desirably maintained within a range of about 35 to 75 F. It is necessary to cool the reactants and reaction mixture to maintain a desirable reaction temperature since a large amountof heat is liberated as the heat of reaction of the olefin and isoparaffin. Mixing is typically obtained by rapid circulation of the reaction mixture by means of pumps as in pump and tank systems or by means of impellers or jets in internal circulating systems. Cooling may be provided by autorefrigeration, effluent refrigeration or with external coolers as is Well known in the art. In all of these systems, an emulsion of the reaction mixture is formed and circulated in the reaction zone. Reactant hydrocarbons and catalyst are continuously added to the reaction mixture, and a portion of the emulsion is continuously Withdrawn. The emulsion which is Withdrawn is separated into catalyst and hydrocarbon phases; the catalyst phase is recycled and alkylate product is recovered from the hydrocarbon phase. l

In the catalytic alkylation of olefins with isoparafiins, a preponderance of isoparaffn (typically about 60 to 80 volume percent or more of the hydrocarbons in the reaction mixture) over olefin material and hydrocarbon diluents including alkylate is used to direct the reaction towards production of the most valuable aviation or automotive fuels. Consequently a large quantity of isoparaffin must be recovered and recycled for reuse in the process. isobutane is generally used as the isoparafin for the manufacture of aviation or motor ffuels although other isoparaffins, for example lisopentane, may be employed.

The alkylation agent reacted with isoparain is olenbased, that is, it is an olefin for example, propylene, butylene, pentylene or the like, a low boiling polymer of a normally gaseous olefin, or an alkyl ester for example, an alkyl sulfate or fluoride which may be produced by absorption of an olefin in acid catalyst in the so-called two-stage alkylation process or by other means.

In catalytic alkylation, the mol ratio of isoparaffn to olefin-based material supplied to the alkylation zone is maintained substantially in excess of l to l, and preferably within the range of about 4 to 1 to about 20 to l. The catalyst to liquid hydrocarbon volume ratio is maintained within the range of about 0.5 to l to about 5 to 1 and preferably within the range of about 1 to 1 to about 3 to 1. Catalyst strength is maintained of at least about 88 percent acid strength when sulfuric acid is used, of at used. A liquid catalyst which is non-volatile under alkylation reaction conditions, for example, sulfuric acid, is preferred. Sulfuric acid strength is maintained within the range of about 88 to 95 percent by purging spent acid from the system and by adding make-up acid of about 98.0 to 99.9 percent purity.

An important part of the isobutane employed in alkylation processing is a recycle stream produced by fractional distillation of alkylation products in a deisobutanizing fractional distillation zone, the isobutane being recovered as a distillate fraction of high isobutane concentration, for example, about 85 to 95 liquid volume percent isobutane. The alkylate in such distillation zone is recovered in the liquid bottoms fraction. This liquid bottoms fraction may be fractionated in conventional manner to separate light ends and alkylate fractions for use as fuel blending stocks. In accordance with this invention, the alkylation products, prior to the deisobutanizing distillation, are employed to desorb the aromatics from the sorbent from an aromatic sorption process whereby said aromatics are transferred to the alkylation reaction mixture and appear in the bottoms product of the deisobutanizing distillation.

The accompanying drawings diagrammatically illustrate the process of this invention. Although the drawings illustrate arrangements of apparatus in which the process of this invention may be practiced, it is not intended to limit the invention to the particular apparatus and materials described.

FIGURE l illustrates an embodiment employing liquidsolid adsorption in the process of this invention.

FIGURE 2 illustrates an embodiment employing liquidliquid extraction in the process of this invention.

Referring to FIGURE 1, olen in line 1 and isoparain in line 2 are contacted with an alkylation catalyst introduced through line 3 in catalytic alkylation zone 4. Spent catalyst is withdrawn through line 5 for regeneration or disposal, not shown. The catalyst and reaction mixture in alkylation zone 4 are maintained at a temperature of within the range of about 35 to 75 F., for example, about 45 F., by cooling the feed materials, contents of the reaction zone, or both as is well known in the art. Effluent hydrocarbon, referred to as reactedmix, contains an excess of isoparan and is discharged through line 6 at a temperature within the range of about 35 to about 90 F., for example, about 71 F. The reacted-mix is neutralized in neutralization zone 7, for example, by caustic and water washing or by contact with clay or bauxite. Neutralized reacted-mix is passed through line 8, switch valve 10 and line 11 to sorption tower 12.

Sorption tower 12 contains a solid adsorbent, for example, silica gel, which has previously been contacted with a hydrocarbon stream containing aromatics effecting sorption of the aromatics by the silica gel. Aromatics are displaced .from the solid adsorbent by the reacted-mix and the effluent mixture is discharged through line 15, switch valve 16 and line 17 to deisoparainizer 18. Deisoparafiinizer 18 yis a fractional distillation column effecting separation of isoparains as distillate which are discharged through line 20 and recycled to line 2 to comprise a portion of the isoparafln introduced into the catalytic alkylation zone. Distillation bottoms, comprising aromatics and alkylate, are withdrawn through line 21 for use as a high octane blending constituent.

An aromatic hydrocarbon stream, for example, a catalytic reformate, is passed through line 25, switch valve 10 and line 26 to sorption tower 27. Sorption tower 27, like tower 12, contains a solid adsorbent. Aromatics are sorbed on the adsorbent and parafnic hydrocarbons are discharged as raiiinate through line 28, switch valve 16 and line 29. Parains discharged through line 29 may be employed in the manufacture of low octane fuels, jet fuels, or solvent or may be further processed, for example, by isomerization, for the production of high octane blending components (not shown).

After the solid adsorbent in tower 27 has become saturated with aromatics and sorbed aromatics in tower 12 displaced, switch valves 10 and 16 are reversed so that reacted-mix is introduced into sorption tower 27 through lines 8 and 26, and aromatic hydrocarbon mixture is introduced into sorption tower 12 through lines 25 and 11. Correspondingly, efiluent parafns are discharged through lines 15 and 29 and desorbed aromatics and reacted-mix are passed tfnough lines 28 and 17. Although not shown, the mixing of effluent streams may be reduced by the use of a purge stream between cycles, for example, a stream of normal butane.

In FIGURE 2, a straight run gasoline is introduced through -line 40 into catalytic reforming zone 41. Catalytic reforming zone 41 may be, for example, a dehydroaromatization process employing a platinized alumina. Catalytic reformate containing aromatic hydrocarbons is discharged through line 42 to solvent extraction tower 43. Solvent extraction tower 43 may be a packed column, a rotating disc contactor, or other countercurrent liquid contacter as is well known in the art. A solvent which preferentially extracts aromatic hydrocarbons, for example, diethylene glycol, is introduced into the top of tower 43 through line 44 at a temperature within the range of about 200 to 400 F. Ranate hydrocarbons, comprising principally paraffin hydrocarbons, are discharged through line 45, contacted with water from line 46, and passed to separator 47. Solvent is washed from the paran hydrocarbons and the washings and hydrocarbon are separated in separator 47.` Water washings are withdrawn through line 48 and passed to solvent recovery facilities, not shown, where the solvent is separated for reuse. Parafn hydrocarbons, free of solvent, are discharged through line 49 for storage or use, not shown.

An olenic feed stock comprising butylenes and propylene in line 51 is charged to sulfuric acid alkylation facility 52. Isobutane in line 53 is combined with recycle isobutane from line 54 and passed to sulfuric acid alkylation facility 52. Makeup sulfuric acid is added through line 55 and spent acid is withdrawn through line 56. The isobutane and olefin reactants are emulsied with the acid catalyst and alkylation is effected at a temperature within the range of about 35 to 75 F. Hydrocarbon reacted-mix is separated and passed through line 59 t0 caustic and water wash facility 60 at a temperature within the range of about 75 to 90 F. The washed reacted mix is then passed through line 61 to transfer tower 62.

Extract from solvent extraction tower 44 comprising solvent and dissolved aromatic hydrocarbons is withdrawn from tower 44 through line 63 and introduced into the top of transfer tower 62. The solvent extract-mix and alkylation reacted-mix are contacted in countercurrent flow in tower 62. The solvent extract-mix at extraction temperature within the range of about 200 to 400 F. is cooled by the rising alkylation reacted mix establishing a temperature gradient through transfer tower 62. Since the solubility of hydrocarbons in a solvent such as diethylene glycol decreases with decreasing temperatures, this temperature gradient tends to reduce the solubility of the hydrocarbon in the solvent as it flows down the tower. The stripped solvent at the bottom of the tower is relatively cold and has little solubility for hydrocarbons. Stripped solvent is withdrawn from the bottom of tower 62 through line 65, passed through heater 66 where it is heated to extraction temperature and returned to tower 43 through line 44. Recovered and makeup solvent are added through line 67.

Alkylation reacted-mix and transferred aromatics are withdrawn from the top of tower 62 through line 68, washed with water introduced through line 69, and discharged to separator 70. Washed alkylation reacted-mix and aromatics are discharged through line 71 to deisobutanizer 72 and the washings containing dissolved solvent are withdrawn through line 72 to solvent recovery facilities, not shown. Isobutane is distilled overhead from deisobutanizer 72 and recycled to alkylation zone 51 through line 54. Deisobutanized alkylate comprising normal butane, alkylate and transferred aromatic hydrocarbons is withdrawn through line 73 for use as a high octane component is gasoline. Alternatively, aviation gasoline and motor gasoline may be separated by distilling the deisobutanizer bottoms to separate normal butane, light alkylate useful as a blending component of aviation gasoline and heavy hydrocarbons comprising heavy alkylate and aromatics for motor fuel manufacture by conventional distillation means, not shown.

Example A straight run gasoline having a 55.6 API gravity, as ASTM distillation boiling range of 207 to 385 F. and containing 65.1 percent parafins, 0.5 percent olefins, 20.6 percent naphthenes and 13.8 percent aromatics is charged at a rate of 12,200 barrels per day to a catalytic reforming process. In the-catalytic reforming process, the straight run gasoline and hydrogen are contacted with a conventional reforming catalyst comprising platinized alumina containing combined halogen at an inlet temperature of 965 F., a liquid hourly space velocity of 2.6, and with a mol ratio of hydrogen to hydrocarbon of 8.9: l. Heavy catalytic reformate in a yield of 41.5 percent basis feed is separated from the reforming products. The heavy catalytic reformate has a gravity of 38.2 API, an ASTM distillation boiling range of 194 to 398 F., and contains 29.0 percent paraiiins and naphthenes, 1.0 percent oleiins, and 70.0 percent aromatic hydrocarbons. The heavy catalytic reformate is charged to the bottom of a solvent extraction tower maintained at a temperature of 300 F. Diethylene glycol at a solvent to charge ratio of 5.1 and at a temperature of 300 F. is charged to the top of the solvent extraction tower. Raiinate having a gravity of 62.6 API, and ASTM distillation range of 200 to 382 F. and containing 2.9 volume percent aromatics is discharged. Extract and dissolved aromatic hydrocarbons are withdrawn as bottoms at a temperature of 300 F. and at a rate of 28,500 barrels per day.

An olefin feed stream containing 8.4 liquid volume percent propylene, 11.9 percent propane, 37.9 percent isobutane, 22.6 percent butylenes, 17 percent normal butane and 2.2 percent pentanes is charged to a sulfuric acid alkylation process at a rate of 2,270 barrels per day together with 10,650 barrels per day of an isobutane stream containing 1.9 percent propane, 90.5 percent isobutane and 7.6 percent normal butane and heavier. The olefin and isobutane feed streams are contacted with sulfuric acid of 92.1 weight percent strength in emulsion comprising 50 volume percent acid at a reaction temperature of 45 F. Hydrocarbon is separated from the acid catalyst and 5,200 barrels per day of light hydrocarbons are evaporated from the reaction mixture in cooling the reaction zone. The remaining liquid hydrocarbon fraction, referred to as reacted-mix, comprises 1 percent propane, 63 percent isobutane, 18 percent normal butane and 18 percent alkylate is withdrawn at a rate of 8,500 barrels per day, neutralized with caustic, and water washed.

The water Washed reacted-mix at 75 F. is contacted with the extract-mix from the solvent extraction tower at 300 F. in countercurrent flow in a liquid-liquid contactor. A temperature gradient from 75 F. at the Ibottorn to 300 at the top is established in the contactor. Solvent freed of hydrocarbon is withdrawn from the bottom of the contacting tower and returned to the solvent extraction tower. Hydrocarbon raffinate comprising the reacted-mix and aromatics transferred from the extractmixare Withdrawn as ratiinate at a rate of 12,000 barrels per day. The rafiinate is charged to a deisobutanizing distillation separating an isobutane recycle stream as distillate and aromatics and alkylate as bottoms. The isobutane recycle stream, comprising about 90 percent isobutane, is distilled overhead at a rate of 5,450 barrels 6 per day, and is recycled to provide a portion of the isobutane feed to the alkylation process.

The bottoms comprise an unseparated mixture of 1,525 barrels per day of normal Ibutane, 1,525 barrels` per day of alkylate and 3,500 barrels per day of yaromatics. The unseparated mixture may be used directly as a gasoline blending stock or may be debutanized forming 5,025 barrels per day of butane-free gasoline product having a distillation range of F. to 400 F. and an octane number of 104 to 107 by ASTM research procedure after adding 3 cc. per gallon of tetraethyl lead.

I claim:

1. In the manufacture of motor fuels comprising aromatic hydrocarbons and alkylate wherein said aromatic hydrocarbons are separated from mixtures containing para'inic and aromatic hydrocarbons and said alkylate is formed by isoparain olefin alkylation, the combination which comprises contacting a hydrocarbon mixture containing paraiinic and aromatic hydrocarbons with a sorbent affecting sorption of said aromatics,

withdrawing unsorbed hydrocarbons comprising said paratfnic hydrocarbons, contacting an olen and a stoichiometric excess of isoparain reactant under alkylation conditions with an alkylation catalyst forming an alkylation reaction mixture comprising alkylate and isoparaiin reactant,

contacting said sorbent and sorbed aromatics with said alkylation reaction mixture effecting transfer of said aromatic hydrocarbons from said sorbent to said alkylation reaction mixture,

separating said alkylation reaction mixture containing said aromatic hydrocarbons into a iirst fraction comprising said isoparaiiin reactant and a second fraction comprising alkylate and said aromatic hydrocarbons,

recycling said lirst fraction to provide at least a part of said stoichiometric excess of isoparatin reactant, and

withdrawing said second fraction as a product.

2. The process of claim 1 wherein said second fraction is separated into a third fraction comprising alkylate and coboiling aromatics and a fourth fraction comprising high boiling aromatic hydrocarbons.

3. The process of claim 1 wherein said sorbent is a solid adsorbent.

4. The process of claim 1 wherein said sorbent is a liquid solvent.

5. The process of claim 1 wherein said hydrocarbon mixture is a catalytic reformate.

6. The process of claim 1 wherein said sorbent and sorbed hydrocarbon are contacted with said alkylation mixture at a temperature below that at which said hydrocarbon mixture and said sorbent are contacted.

7. The process of claim 1 wherein said hydrocarbon mixture is contacted with said sorbent at a temperature of at least 200 F., said alkylation mixture is formed at a temperature less than F., and said sorbent .and said sorbed aromatics are contacted with said alkylation reaction mixture at a temperature below the temperature at which said hydrocarbon mixture and said sorbent are contacted.

8. In the manufacture of motor fuels comprising aromatic hydrocarbons .and alkylate wherein said aromatic hydrocarbons are separated from mixtures containing paratinic and aromatic hydrocarbons and said alkylate is formed sby isoparaflin-olen alkylation, the combination which comprises contacting a hydrocarbon mixture containing paraffinic and aromatic hydrocarbons with diethylene glycol at a temperature within the range of 200 to 400 F. effecting extraction of aromatic hydrocar bons from non-aromatic hydrocarbons,

withdrawing a raffinate comprising unextracted hydrocarbons,

withdrawing an extract-mix comprising aromatic hydrocarbons dissolved in said solvent,

contacting .an olefin and a stoichiometric excess of isoparan reactant under alkylation conditions with an alkylation catalyst forming alkylation reaction mixture comprising alkylate and isoparain reactant,

withdrawing said reaction mixture at a temperature within the range of about 35 to 100 F.,

contacting said alkylation reaction mixture with said extract rnix at a contacting temperature within the range of 35 to 400 F.,

separating diethylene glycol stripped of aromatic hydrocarbons and a ranate comprising alkylation reaction mixture and aromatic hydrocarbons,

passing said diethylene glycol solvent to said extraction zone,

passing said ranate to a deisoparanization zone cffecting separation of isoparafn,

recycling isoparain to said alkylation zone, and

withdrawing a mixture of alkylate and aromatic hydrocarbons as .a bottoms product from said deisoparafnization zone.

References Cited by the Examiner UNITED STATES PATENTS DELBERT E. GANTZ, Primary Examiner.

ALPHONSO D. SULLIVAN, Examiner.

C. R. DAVIS, Assistant Examiner.

Claims (1)

1. IN THE MANUFACTURE OF MOTOR FUELS COMPRISING AROMATIC HYDROCARBONS AND ALKYLATE WHEREIN SAID AROMATIC HYDROCARBONS ARE SEPARATED FROM MIXTURES CONTAINING PARAFFINIC AND AROMATIC HYDROCARBONS AND SAID ALKYLATE IS FORMED BY ISOPARAFFIN OLEFIN ALKYLATION, THE COMBINATION WHICH COMPRISES CONTACTING A HYDROCARBON MIXTURE CONTAINING PARAFFINIC AND AROMATIC HYDROCARBONS WITH A SORBENT AFFECTING SORPTION OF SAID AROMATICS, WITHDRAWING UNSORBED HYDROCARBONS COMPRISING SAID PARAFFINIC HYDROCARBONS, CONTACTING AN OLEFIN AND A STOICHIOMETRIC EXCESS OF ISOPARAFFIN REACTENT UNDER ALKYLATION CONDITIONS WITH AN ALKYLATION CATALYST FORMING AN ALKYLATION REACTION MIXTURE COMPRISING ALKYLATE AND ISOPARAFFIN REACTENT,, CONTACTING SAID SORBENT AND SORBED AROMATICS WITH SAID ALKYLATION REACTION MUXTURE EFFECTING TRANSFER OF SAID AROMATIC HYDROCARBONS FROM SAID SORBENT TO SAID ALKYLATION REACTION MIXTURE, SEPARATING SAID ALKYLATION REACTION MIXTURE CONTACTING SAID AROMATIC HYDROCARBONS INTO A FIRST FRACTION COMPRISING SAID ISOPARAFFIN REACTANT AND A SECOND FRACTION COMPRISING ALKYLATE AND SAID AROMATIC HYDROCARBONS, RECYCLING SAID FIRST FRACTION TO PROVIDE AT LEAST A PART OF SAID STOICHIOMETRIC EXCESS OF ISOPARAFFIN REACTANT, AND WITHDRAWING SAID SECOND FRACTION AS A PRODUCT.

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