US2955143A

US2955143A - Alkylation of aromatic hydrocarbons

Info

Publication number: US2955143A
Application number: US631523A
Authority: US
Inventors: Herman S Bloch
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1956-12-31
Filing date: 1956-12-31
Publication date: 1960-10-04
Anticipated expiration: 1977-10-04

Description

Oct. 4, 1960 H. s. BLOCH ALKYLATION oF ARoMATIc HYDRocARBoNs Filed Deo. 3l, 1956 United States Patent O ALKYmATIoN oF AnoMArrc HYDRooARBoNs Herman "S. Bloch, Skokie, Ill., assignor, by` mesne Vassignments, to Universal Oil lProducts Company, Des Plaines, Ill., a corporationof Delaware f Filed Dec. 31, 1956, Ser. No. 631,523

8 Claims. (Cl. Zoll-671) This invention relates to a process for the alkylation of aromatic hydrocarbons, and more particularly relates to a process for the alkylation of an a'lkylatable benzene hydrocarbon with an olefin-acting compound. Still more particularly, this invention relates to a combination process including the steps of liquid-liquid extraction, alkylation, and recovery of excess aromatic hydrocarbon utilized by gas-liquid extraction.

An `object of 4this invention is to produce al-kylated aromatic hydrocarbons, andmore particularly to produce alkylated benzene hydrocarbons. A specific object of this invention is to produce ethylbenzene, a desired chemical intermediate, which ethylbenzene is utilized in 'large quantities in .dehydrogenation processes for the manufacture of styrene, one starting material for the production of some synthetic rubbers. Another specific object of this invention is to produce alkylated aromatic hydrocarbons Within the gasoline boiling range having high antiknock values, which may be utilized `as such or as componentsof gasoline suitable for use in airplane or automobile engines. A further speciic objectV of this invention is the production of cumene byV the reaction of benzene with propylene, which cumene product is then oxidized to form cumene hydroperoxide which is readily oxidatively decomposed into phenol and acetone. Another object of this invention is to provide a process for the introduction of alkyl `groups into aromatic hydrocarbons of high vapor pressure at normal conditions with minimum loss of said high vapor pressurearomatic hydrocarbons. This and other-objects of this invention Will be set tforth hereinafter as part of the accompanying specication. y

In 'prior ar-t process for lthe alkylation of aromatic hydrocarbons with olefin hydrocarbons, it has been disclosed that it is .preferable to utilize molar excesses of aromatic hydrocarbons. In such processes itis generally preferred to utilize greater than 2 mols of aromatic hydrocarbon lper mol of olefin hydrocarbon and in many eases for best reaction it is preferred -to use greater than 3 mols of aromatic hydrocarbon per mol of olen hydrocarbon. This has been ffound necessary to prevent polymerization of the olefin 'hydrocarbon from taking place prior lto reaction of the olefin hydrocarbon` with the aromatic hydrocarbon. While generally satisfactory processes have resulted from such molar excesses of aromatic hydrocarbon, a problem has arisen when these molar excesses are utilized in connection with the alkylation of aromatic hydrocarbons of high vapor pressure at norma-l conditions, particularly when the olefin hydrocarbon is a normally gaseous olefin hydrocarbon such as ethylene, propylene, l-butene, 2-butene, or isobutylene.

Aethane,propane, n-butane, and isobutane. When these gas streams are used as the source of olefin hydrocarbon, after reaction of the Yolein'hydrocarbon with the i' I f '2,955,143 ce Patented oct. 4, 1960 aromatic hydrocarbon it is necessary to vent or otherwise dispose of these unreactive gases. If at 4the same time the -aromatic hydrocarbon utilized or alkylated is of al high vapor pressure at normal conditions, losses of said aro- -matic hydrocarbon occur due to vaporization thereof in thesel'unreactivev gases. As the molar quantity of aromatic hydrocarbon is increased to prevent polymerization of the olen hydrocarbon reacted, this problem becomes more acute. By means of the process of the present invention, this and .other disadvantages inherent in presently utilized processes can be overcome.

In one embodiment the present invention relates to a combination process which comprises separating an aromatic hydrocarbon from a mixture thereof with a nonaromatic hydrocarbon of similar boiling range by contacting said mixture with an imrniscible organic solvent of higher boiling range in which said aromatic hydrocarbon selectively dissolves, recovering the thus purified aromatic hydrocarbon by fractionation from the higher boiling selective solvent, recycling -lean solvent lfor reuse in the process, alkylating the aromatic hydrocarbon with a normally -gaseous olefin hydrocarbon from a gas stream at alkylating conditions in Ithe presence of an acid-acting alkylation catalyst, said aromatic hydrocarbon being present in a molar quantity greater than that stoichiometrically necessary for said alkylation reaction, separating unreactive gases containing a portion of the excess aromatic hydrocarbon lfrom the alkylation zone effluent, contacting said gases with at least a portion of the lean solvent prior to its reuse as a selective solvent for an aromatic hydrocarbon as aforesaid, recovering another .portion of excess aromatic hydrocarbon for reuse in the process from the alkylation zone normally liquid eluent, and recovering alkylated aromatic hydrocarbon product.

In another embodiment, the present invention relates to a combination process rwhich comprises separating benzene `from a mixture thereof with a paraiiin hydrocarbon of similar boiling range by contacting said mixture with a .polyalkylene glycol solvent of higher boiling range in which said benzene selectively dissolves, recovering the thus purified benzene by fractionation from the polyalkylene glycol solvent, recycling the lean polyalkylene glycol solvent for reuse in the process, alkylating the benzene with ethylene from a gas steam containing minor quantities of ethylene at alkylating conditions in the presence of an acid-acting alkylation catalyst, said benzene being present in a molar quantity greater than that stoichiometrically necessary for said alkylation reaction, separating unreactive gases lcontaining a portion of the excess benzene from the alkylation zone efuent, con- -tacting said gases with at least a portion of the lean polyaikylene glycol solvent prior to its reuse as a selective solvent for benzene as aforesaid, recovering another portion of excess benzene ffor reuse in the process from the alkylation zone normally liquid eiuent, and recovering ethylbenzene.

In still another embodiment, the present invention relates to a combination process which comprises separating toluene from a mixture thereof with a paraiiin hydrocarbon of similar boiling range by contacting said mixture with a polyalkylene glycol solvent of higher boiling range Ain which said toluene selectively dissolves, recovering the thus purified toluene by fractionation from the polyalkylene glycol solvent, recycling the lean polyalkylene glycol solvent for reuse in the process, alkylating the toluene with ethylene from a gas stream containing minor quantities of ethylene at alkylating conditions in the presence of an acid-acting alkylation catalyst, said toluene being present in a molar quantity greater than that stoichiometvrically necessary for said alkylation reaction, separating lwith at least a portion of theilean polyalkylene glycol solvent prior to its reuse as a selective solvent for toluene as aforesaid, recovering another portion of excess toluene for reuse in the process from the alkylation zone normally liquid efuent, and recovering ethyltoluene. f

In a further embodiment, the present invention relates'.

solvent for reusein the process, alkylating the xylenewith ethylene from a Vgas stream containingminor quantities ofethylene'at alkylating conditions iin the presence of an acid-acting alkylation catalyst,1said xylene being present in a molar quantity greater than that stoichiometrically necessary forsaid alkylation reaction, separating unreacfive gases containing a portion of the excessxylene from the alkylation zone eluent, contacting said gases with at least a portion of the lean polyalkylene glycol solvent prior to its reuse as a'selective solvent for xylene as aforesaid, recovering another portion of excess xylene for reuse in the process from the alkylation zone normally liquid eiliuent, and recovering an ethylxylene.

In a specificembodiment, the present invention relates to a combination process which comprises separating benzene from a lmixture thereof with a parain hydrocarbon of similar boiling range by contacting said mixture with a diethylene glycol solvent of higher boiling range in which said benzene selectively dissolves, recovering the thus puriiied benzene by fractionation from the diethylene glycol solvent, recycling the lean diethylene glycol solvent for reuse in the process, alkylating the benzene with ethylene from a gas stream containing minor quantities of ethylene at alkylating conditions in the presence of an acid-acting alkylation catalyst, said benzene being present in a molar quantityV greater than that stoichiometrically necessary for said alkylation reaction, separating unreactive gases containing a portion of the excess benzene fromthe alkylation zoneeifluent, contacting said gases with at least a por- Vtion of the lean diethylene glycol solvent prior to its reuse as la selective solvent for benzene as aforesaid, recovering another portion of excess benzene for reuse in the process from the alkylation zone normally liquid eluent, and recovering .ethylbenzene. i

This invention can perhaps be best understood by refer- A v ence tothe attached drawing. VWhile of necessity certain limitations must berpresent in such a schematic description, 11o intention is meant tolmit thegenerally. broad scope of this invention. As stated hereinabove, the first step of the combination process of the present invention comprises separating an aromatic hydrocarbon from a mixture thereof with a non-aromatic hydrocarbon of similar boiling range by contacting said mixture with an immiscible organic solvent of higher boiling range in which said aromatic hydrocarbon selectively dissolves.

In the H drawing, this first step is represented as taking place in l' extraction zone 12. However, the mixture of aromatic hydrocarbon and non-aromatic hydrocarbon of similar boiling range must be furnished to this extraction zone. In the drawing this is accomplished by the reforming of a gasoline or naphtha or a selected fraction thereof. Thus, a full boiling range gasoline, a naphtha, or a selected fraction thereof is passed throughv line 1 to which is added make-up hydrogen through line 2 and recycled hydrogen from line 3 and this hydrogen and hydrocarbon mixture then passes through line 4 to reforming zone 5. As usually operated the amount of hydrogen charged along with .the hydrocarbons usually will-be from 0.5 to aboutrlS mols per mol of hydrocarbon.

Reforming zone 5 is packed with a reforming catalyst ,such as a platinum-alumina-combined halogen catalyst. v Such catalyst usually contain from about 0:01 t9 ,abllf 2 percent platinum, from about 0.1 to about 8 percent. combined halogen, preferably fluorine and/or chlorine, and the remainder alumina. However, other catalysts such as platinumsilica-alumina, molybdena-alumina, etc. may be utilized. The reforming process will be effected at a temperature within the range of from about 600 F. to about 1000" F., a pressure `within the range of from about 50 to about 500 p.s.i., and at a liquid hourlyspace velocity of from about 0.5 to about 10 or more. After reforming, thehydnocarbon mixtureY passes from reformingfzone Sthrough line V6 toV high pressure separator Y7 wherein hydrogen is separated from the hydrocarbon product via line3 and recycled for further use in the reforming process. The reformate passes from high pressure separator 7 through line 8 tov fractionation zone 9. Fractionation zone 9 is merely schematic and may comprise one or more fractionation towers as may be necessary 'in any particular case. VFor example, if the feed to the reforming zone is a fullboiling gasoline or naphtha fraction, it will be necessary to utilize several fractionation towers in order to separate the desired mixture of aromatic hydrocarbon and non-aromatc hydrocarbon of the same boiling range. In fractionation tower 9, the desired boiling range fraction is distilled overhead and passes through line 10 to extraction zone 12. The higher boiling fraction is removed from the process, through line 11 for uses such as a blending stock for automobile and aviation gasoline.

While the above description 4is illustrative of .the preparation of an aromatic hydrocarbon and non-aromatic hydrocarbon of similar boiling range by reforming, for use in the first step of the process of this invention, this mixture may also be provided from other sources, for example, as a selective fraction from the distillation of coal tar, as `a selective fraction from the dehydrogenation of naphthenic hydrocarbons, as a selective fraction which has been distilled from cracked gasoline, etc. Thus, the mixture of aromatic hydrocarbon and non-.aromatic hydrocarbonmay be provided from various sources. Further, this mixture may be a vclose boiling fraction comprisi-ng `mainly one aromatic hydrocarbon in admixture with non-aromatic hydrocarbons, such .as a benzenehexane fraction, or lthe mixture may be awider boiling fraction containing more than one aromatic hydrocarbon and more than one parain hydrocarbon homolog. An example of such a latter fraction is one containing benzene, toluene, and xylenes in radmixture with hexanes, heptanes, and octanes. The various mixtures of aromatic hydrocarbons and non-aromatic hydrocarbons of similar boiling range are well known to thosenskilled in the art.

As hereinabove set forth, the selected aromatic hydrocarbon and non-aromatic hydrocarbon mixture is passed through line 10 to extraction zone 12. Extraction zone V12 is a .liquiddiquid :type contacting zone of a type fami-liarto those skilled in the art. To this zone is fed .an organic solvent for .the aromatic hydrocarbon through 13 and 14. In addition, recycle solvent is fed to this zone through line 23 as hereinafter described. The preferred organic solvents are those which are immiscible vwith hydrocarbons, those in which aromatic hydrocarbons selectively dissolve, and those of higher boiling range than the yaromatic hydrocarbon to be extracted therein. The solvent must not be completely miscible with hydrocarbons so that proper operation yof the liquid-liquid countereurrent extraction zone .can be realized. 'I'he solvent vmust have the property of selectively dissolving aromatic hydrocarbons for successful operation of the process. The solvent is preferably of higher boiling range than the aromatic hydrocarbon which is dissolved ithcreinso4 that the aromatic hydrocarbon can be readily separated Vfrom the solvent by fractionation overhead. AA solvent having these characteristics can be utilized economically in .an isothermal extraction process, which ,is ,thevmost desirable type. Suitable solvents include particularly the polyallzylene glycols, preferably diluted with 95ans t? varying amounts of water, say up to yabout 20 percent by volume of water. Typical polyalkylene glycols which can be lutilized successful-ly in the lpresent process are diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, mixtures of diethylene glycol and dipropylene glycol, etc. Another suitable class of solvents which may be utilized include higher boiling nitriles such as oxydipropionitn'le. Other selective solvents, such as, for example, phenylethanolamine, dimethylformamide, .and the like, may also be used, either by Ithemselves o-r in combination with one or more of the other named solvent components.

As stated hereinabove Ithe selective solvent is added to the upper section of extraction zone 12 through line 14 and passes downwardly therethrough in liquid-liquid contact with the mixture of aromatic hydrocarbon and nonaromatic hydrocarbon. The aromatic hydrocarbon selectively ldissolves in the solvent and passes from extraction zone 12 through line 16 to stripping zone 17. The portion of the feed stock to the extraction zone which is not dissolved Iby Ithe selective solvent is removed overhead from the extraction zone through line 15. This fraction, normally termed ranate, is suitable for `various uses such as stove oil, jet fuel, etc. The extraction zone is usually maintained at somewhat elevated temperatures, say 200- 500 F. and under slight pressure so that some ashing of the aromatic hydrocarbon from the selective solvent takes place -in the .st-ripping zone. The stripping zone 17 is normally operated at about atmospheric Vpressure so that pressures in the extraction zone will range Lfrom about atmospheric to about 200 p.s.i. The rates of addition of the feed stock and the selective solvent Ito extraction zone 12 will be varied depending upon the aromatic hydrocarbon to be extracted, upon the particular solvent utilized, and upon the Ytemperature of this portion of the isothermal process. However, the feed rates will be adjusted so that substantially all of the aromatic hydrocarbon is extracted by the selective solvent.

The mixture of selective solvent and aromatic hydrocarbon, .as hereinabove stated, vpasses from extraction zone 12 through line 16 to stripping zone 17. Stripping zone 17 maintained at approximately atmospheric pressure is heated -by a solvent reboiler not shown. AThe aromatic hydrocarbon in extremely .pure form passes overhead 'from stripping zone 17 through line I18. The selective solvent which does not need to be yfractionated because of its higher boiling range than the extracted aromatic hydrocarbon passes las a bottoms fraction from stripping zone 17 through

lines

19 and 20, valve 21, and line 22 back :through line 23 for recycle to the extraction zone as hereinabove described. Valve 21 is adjusted so that at -least a portion of the recycle solvent passes through line 24 to extraction zone 32 Which will b-e described hereinafter. It can be seen that full closure of valve 21 will result in passage of all of this recycle solvent through line 24 to extraction zone 32. Such valve adjustment is seldom necessary and Valve 21 is usually cracked in a manner to -allow passage of some of the recycle solvent to extraction zone 12.

Thethus purified aromatic hydrocarbons from stripping zone 117 are passed through line 18 and line 27 to alkylation zone 28. Recycle aromatic Yhydrocarbon produced as hereinafter described passes through line 26 and line 27 to alkylation zone 28. The gas stream containing the olen hydrocarbon is introduced to the aromatic hydrocarbon via line 25 and passes therewith through line 27 to alkylation zone 28. As stated hereinabove, it is preferred to utilize a molar ratio of aromatic hydrocarbon to olefin hydrocarbon of greater than 2, and preferably of greater than 3 to preclude olefin polymerization prior to alkylation. As stated hereinabove, various aromatic hydrocarbons can be utilized within the Ygenerally broad scope of this invention. Of these aromatic hydrocarbons, benzene hydrocarbons are preferred, and of these, those which are particularly preferred include benzene, toluene, o-xylene, m-xylene, p-xylene, and ethyl; benzene. However, other aromatic hydrocarbons are operable including n-propylbenzene, iso-propylbenzene, butylbenzenes, naphthalene, ce methylnaphthalene, -methylnaphthalene,etc. The gas stream containing the olefin hydrocarbon, such as ethylene or propylene may be any refinery gas stream. Such refinery gas streams havein the past often been burned since an economical process for their utilization as alkylating agents has not been available. Such a typical gas is known as refinery off-gas. These refinery olf-gases in addition to containing varying amounts of ethylene, propylene, and the various butenes, depending on their source, contain varying quantities ofparatlnic hydrocarbons, nitrogen, hydrogen, etc. Thus, a refinery `off-gas ethylene stream may contain varying quantities, of methane and ethane while a refinery off-gas propylene stream is normally diluted with propane and a ibutylene stream is normally diluted with butanes. Typical analysis fora refinery gas from a catalytic cracking unit in mol per cent is as follows: nitrogen, 4.0%; carbon monoxide, 0.2%; hydrogen, 5.4%; methane, 37.8%; ethylene, 10.3%; ethane, 24.7%; propylene, 6.4%; propane, 10.7%; and C4 hydrocarbons, 0.4%.

Thus, the aromatic hydrocarbon and the normally gaseous olen hydrocarbon from a gas stream are passed through line 27 to alkylation zone 28. Alkylation zone 28 will contain an acid-acting .alkylation catalyst and the alkylating conditions utilized will depend upon the particular acid-acting alkylation catalyst selected. The acidacting alkylation catalyst may be selected from diverse materials including sulfuric acid, phosphoric acid, hydrogen uoride, aluminum chloride, aluminum bromide, boron trifluoride, ferrie chloride, zinc chloride, synthetically prepared silica-alumina, silica-zirconia, and various acid-acting aluminas including activated alumina of commerce, Tonsil, Porocel, etc. With the utilization of such diverse materials as alkylation catalysts, the temperature utilized in the alkylation zone will range from about 0 C. or lower to about 250 C. or higher and the pressure may vary from about atmospheric to about 500 p.s.i. or more. In a batch type process, the amount of catalyst in the alkylation zone may vary from about 1 percent by weight based on the reactants to about 500 percent by weight or more. If the alkylation catalyst is a solid, such as solid phosphoric acid, or silica-alumina, the amount of catalyst utilized is ordinarily designated by means of hourly liquid space velocity which may vary from about 0.1 to about 10 or more. When the alkylation reaction has proceeded to the desired extent, the

products from the alkylation zone, termed alkylation zone eiuent, are Withdrawn from alkylation zone 28 through line 29 to separator 30, also the alkylation zone eiiuent receiver. From this separator or receiver is Withdrawn overhead the unreactive gases introduced with Vthe olefin Vhydrocarbon gas stream and which merely pass through the reactor unchanged..

Since the aromatic hydrocarbon was utilized in .molar excess in the alkylation zone, the excess aromatic hydrocarbon will be present in separator 30 and a portion thereof will be vaporized overhead along with the unreactive gases. To prevent loss of this excess aromatic hydrocarbon vaporized along with the unreactive gases, these gases and vaporized aromatic hydrocarbon are directed via line 311 to extraction zone 32. Y

Extraction zone 32 is a gas-liquid countercurrent contacting zone, the size of which is varied depending upon the quantity of aromatic hydrocarbon in the unreactive gases and the particular liquid solvent utilized. In extraction zone 32 at least a portion of therecycle selective solvent passes into the'upper portion thereof through line 24 in countercurrent flow to the unreactive gases containing vaporized aromatic hydrocarbon. The vaporized aromatic-hydrocarbon is selectively dissolved in the selective solvent and the unreactive gases free from aromatic hydrocarbon are vented through line 33. This extraction,` zone 32 vis preferentially maintained at the same temperature as extraction zone 12 and stripping zone 17 In other words, these three pieces of apparatus are utilized in an isothermal operation which results in added advantage for the process. This added advantage is that there is no heat input to these vessels so that the operatingA costis'minimized.- Y

The selective solvent containing dissolved aromatic hydrocarbon is `withdrawn from extraction zone 32 through line 34 and passes through valve 35 and line 36 to line 23 forreuse in the extraction zone. In some cases it vmay be desirable to directv all or a Yportion of selective solvent containing dissolved aromaticY hydrocarbonfrom extraction zone 32 through line 37,

valve 38and lines

39 and 16 to stripping zone 17 for direct recoveryof the aromatic hydrocarbon from the selective solvent. In another case, valves 38 and 3S may be adjusted so as Yto direct a desired portion ofthisiselective solvent back to extraction 'zone 12 stripping zone 17.

The remaining alkylation zone. eiuents. are withdrawn from separator 30 through line 40 to fractionation zone 41. In fractionation zone 41 the remainder of the excess aromatic hydrocarbon utilized in the alkylation zone 28 is fractionated overhead and recycled by means of

lines

26 and 27, hereinabove described. The desired product is separated as abottoms fraction from fractionation zone andto direct another portion to 41 and if further purification is desired may be passed to 4another fractionation zone not shown, via line 42.

The following example is introduced for vthe purpose of villustration but -with no intention of unduly limiting the generally broad scope of this invention. In this example,

10,000 barrels per day of a full boiling range naphtha is introduced tothe reforming zone. This naphtha has a boiling range of 125 -400 F. The reforming zone is packed witha platinum-alumina-combined-halogen catalyst and reforming of the naphtha is accomplished at a pressure of 500 p.s.i., a temperature of 925 F., an hourly liquid space velocity oi 4.0, and a hydrogen to hydrocarbon ratio vof 6:1. From the reforming zone, the re- ;formed naphtha is separated from the recycled'hydrogen vand is passed to a series of fractionation zones.

naphtha is 'debutanized and a C5 to 190 F. cutis isolated The therefrom as an overhead fraction in a quantity of 2000 barrels per day. By analysis,`this fraction Vis found to convtain 18% by'volume ofV benzene, amounting to 360'barrels per day.'.V c This C5 to 190 F. fraction in the quantity of 2000 ybarrels per day. is passed Vto a liquid-liquidextraction zone utilizing a solvent comprising 94% diethylene glycol and 6% Water. VThis extraction zoneis maintained at atemperature of 260 F., a pressure of 90 p.s.i.g.,.and a 7:1

4solvent to feed ratio (by volume). Thus, if extraction zone 12in Figure I represents the solvent extraction zone, 2000 barrels per -day of 'benzene ,containing hydrocarbons pass thereto through line and 14,000barrels `per Vday of solvent ,is circulatedthereto Vthrough line,14.

Afterv extraction and recovery of benzene in a fractionation or strippingzone, there is obtained 3 60 barrels per day of benzene or aromatic concentrate. Y

This 360 barrels per day of benzene, equivalent to 27,000Ugramn1ols perhour is passed, for` example,

'through line 18 wherein 4itis combined with 79,800 gram mols per hour of recycle benzene from line 26. In addi- `8 solid phosphoric acid catalyst is a calcined mixture of phosphoric acid and kieselguhr. Alkylation zone 28 is maintained at a temperature of 575 F., Va. pressure of 600 p.s.i., and the liquid Vhourly space velocity based on the benzene is 2.0. From this alkylation there is obtained 25,320 gram mols per hour of ethylbenzene, 1050 gram mols per hour of diethylbenzene, and 630 gram mols per hour of triethylbenzene. In the alkylation zone, 100 percent of the ethylene charged, or 29,310 gram mols per hour is converted to alkylaromatic-hydrocarbons.V These alkylaromatic hydrocarbons along with excess benzene and the unreactive gases pass from alkylation zone 28 torseparator 30. The unreactive gases comprising nitrogen, hydrogen, methane, and ethane in the quantity of 205,190 gram mols per hour are discharged fromseparator 30 which is maintained at 100 F. and a pressure of 600 p.s.i. Along with these unreactive gases, due to its own vapor pressure, passes 1200 gram mols per hour of benzene. -This quantity of benzene would be lostrfromthe process in these vent gases were it not for `the presence of extraction zone 32 wherein this quantity of benzene is recovered by gas-liquid contact with a portion of the lean solvent from the bottom of stripping zone 17. This 1200 gram mols per hour is equivalent to a 4.5% loss based on the benzene charged to the Vprocess and would be equal to 16 barrels per day in a plant of l the indicated size.

tion to this 106,800 gram mols per hour of benzene, there v is provided an additional .recycle of 1200 gram mols of benzene per hour as hereinafter described.V YThis total quantity of benzene in theY amount of 108,000 gram mols per hour is combined with 234,500 gram mols per hour of a gas stream containing 12.5 mol percent ethylene or l ,29,310 gram mols per hour of ethylene to give an aromatic' to olefin ratio of 3.8/1. This combined feed passes i through line 27 to. alkylationV zone 28 containing what is known injthe art as solid phosphoric acid catalyst. This As stated hereinabove, the products and 79,800 gram mols of excess benzene are removed from separator 30 to a fractionation zone and the excess benzene is recycled to the process.

I claim as my invention:

v1. A process for producing alkylated aromatic hydrocarbonfrom a mixture of an aromatic hydrocarbon with a n0n-aromatic hydrocarbon of similar boiling point, Which comprises contacting said mixture in an extraction zone with an immiscible organic solvent of higher boiling point than and in which said aromatic hydrocarbon is selectively soluble, fractionating the resultant solution of aromatic hydrocarbon and solvent in a stripping zone to separate the aromatic hydrocarbon from lean higher Aboiling solvent, subjecting the thus separated aromatic hydrocarbon to catalytic alkylation with a gas stream containing a normally gaseous olefin in admixture with other gases While maintaining a molarexcess of said. aromatic hydrocarbon over said normally gaseous olefin, separating from the resultant alkylation eiluent unreacted gases containing excess aromatic hydrocarbon, contacting said unreacted gases with lean solvent from said stripping zone to dissolve therein excess aromatic hydrocarbon which would otherwise be vented and lost from the process in therunreacted gases, and introducing thus enriched solvent to one of said zones whereby recovered excess aromatic hydrocarbon is separated from the solvent in the stripping zone and subsequently supplied to the alkylating step. v 2. The process of claim 1 further characterized in that said enriched solvent is iirst introduced to said extraction zone and thence passed to said stripping zone.

3. The Vprocess of claim l further.characterized in that lsaid enriched solvent is introducedV directly Vto said strippingzone.Y Y .Vf

4. A process for producing alkylated aromatic hydrocarbon from a mixture of abenzene hydrocarbon With a parainic hydrocarbon of similar boiling point,Y which .compriseslcontacting said Ymixture in'anY extraction Yzone with an immiscible org-anic solvent of ,higher boiling point than ,and in which said benzene hydrocarbon is selectively soluble, fractionating the resultant solution of benzene hydrocarbon and solvent in a strippingzone to separate the 'benzene hydrocarbon from lean h ighernboilingsolvent, subjecting the thus .separated benzene hydrocarbon 'to catalytic alkylation with a gas streamcontaining a nor- Y mally gaseous olefin in admixture vvith other gases While maintaining a molar excess of said benzene hydrocarbon over said normally gaseous olen, separating from the resultant alkylaticn efuent unreacted gases containing excess benzene hydrocarbon, contacting said unreacted gases with lean solvent lfrom said stripping zone to dissolve therein excess benzene hydrocarbon which would otherwise be vented and lost -frorn the process in the unreacted gases, and fractionating thus enriched solvent in said Stripping zone whereby recovered excess benzene hydrocarbon is separated from the solvent and subsequently supplied to the alkylating step.

5. A process for producing alkylating aromatic hydrocarbon from a mixture of a benzene hydrocarbon with a paranic hydrocarbon of `similar boiling point, which comprises contacting said mixture in an extraction zone with a polyalky-lene glycol solvent of higher boiling point than and in which said benzene hydrocarbon is selectively soluble, fractionating the resultant solution of benzene hydrocarbon and solvent in a stripping zone to separate the benzene hydrocarbon from lean higher boiling solvent, subjecting the thus separated benzene hydrocarbon to catalytic alkylation with a gas stream containing a norrnallyv gaseous olefin in -admixture with other gases while maintaining a molar excess of said benzene hydrocarbon over said normally gaseous olen, separating from the resultant alkylation ei'lluent unreacted gases containing excess benzene hydrocarbon, contacting said unreacted gases with at least -a portion of the lean solvent from. said stripping zone to dissolve therein excess benzene hydrol0 carbon which would otherwise -be vented and lost froml the process in the unreacted gases, and fractionating thus enriched solvent in said stripping zone whereby recovered excess benzene hydrocarbon is separated from the solvent and subsequently supplied to the alkylating step.

6. The process of claim 5 Ifurther characterized in that said enriched `solvent is first introduced to said extraction zone and thence supplied to the stripping zone yfor fnactionation in the latter.

7. The process of claim 5 -further chanacterized in that said enriched solvent is introduced directly to the stripping Zone for fractionation therein.

8. 'The process of claim 5 further characterized in that said normally gaseous olefin is ethylene.

References Cited in the le of this patent UNITED STATES PATENTS 2,276,171 Ewell Mar. 10, 1942 2,386,969 Mattox Oct. 16, 1945 2,393,895 Fleming Ian. 29, 1946 2,395,775 Anderson et al Feb. 26, 1946 2,396,965 Plassino Mar. 19, 1946 2,688,630 Wadley et al. Sept. 7, 1954 2,766,300 Weedinan Oct. 9, 1956 FOREIGN PATENTS 564,059 Great Britain Sept. 12, 1944

Claims

1. A PROCESS FOR PRODUCING ALKYLATED AROMATIC HYDROCARBON FROM A MIXTURE OF AN AROMATIC HYDROCARBON WITH A NON-AROMATIC HYDROCARBON OF SIMILAR BOILING POINT, WHICH COMPRISES CONTACTING SAID MIXTURE IN AN EXTRACTION ZONE WITH AN IMMISCIBLE ORGANIC SOLVENT OF HIGHER BOILING POINT THAN AND IN WHICH SAID AROMATIC HYDROCARBON IS SELECTIVELY SOLUBLE, FRACTIONATING THE RESULTANT SOLUTION OF AROMATIC HYDROCARBON AND SOLVENT IN A STRIPPING ZONE TO SEPARATE THE AROMATIC HYDROCARBON FROM LEAN HIGHER BOILING SOLVENT, SUBJECTING THE THUS SEPARATED AROMATIC HYDROCARBN TO CATALYTIC ALKYLATION WITH A GAS STREAM CONTAINING A NORMALLY GASEOUS OLEFIN IN ADMIXTURE WITH OTHER GASES WHILE MAINTAINING A MOLAR EXCESS OF SAID AROMATIC HYDROCARBON OVER SAID NORMALLY GASEOUS OLEFIN, SEPARATING FROM THE RESULTANT ALKYLATION EFFLUENT UNREACTED GASES CONTAINING EXCESS AROMATIC HYDROCARBON, CONTACTING SAID UNREACTED GASES WITH LEAN SOLVENT FROM SAID STRIPPING ZONE TO DISSOLVE THEREIN EXCESS AROMATIC HYDROCARBON WHICH WOULD OTHERWISE BE VENTED AND LOST FROM THE PROCESS IN THE UNREACTED GASES, AND INTRODUCING THUS ENRICHED SOLVENT TO ONE OF SAID ZONES WHEREBY RECOVERED EXCESS AROMATIC HYDROCARBON IS SEPARATED FROM THE SOLVENT IN THE STRIPPING ZONE AND SUBSEQUENTLY SUPPLIED TO THE ALKYLATING STEP.