US2971992A

US2971992A - Alkylation of aromatic hydrocarbons

Info

Publication number: US2971992A
Application number: US705860A
Authority: US
Inventors: Herman S Bloch
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1957-12-30
Filing date: 1957-12-30
Publication date: 1961-02-14
Anticipated expiration: 1978-02-14
Also published as: ES246256A1

Description

Feb. 14, 1961 H. s. BLOCH 2,971,992

ALKYLATION 0F AROMATIC HYDROCARBONS Filed Dec. 30, 1957 Bottoms awn 0g auaumg Van! IN VE/V TOR.-

Herman .S. Bloch BY.- N n KMLZIZLM Off Gas Rena/0r Benzene ATTORNEYS.

United States Patent ALKYLATION OF AROMATIC HYDROCARBONS Herman S. Bloch, Skokie, 111., assignor, by mesne assignments, to Universal Oii Products Company, Des Plaines, 111., a corporation of Delaware Filed Dec. 39, 1957, Ser. No. 705,860

7 Claims. (Cl. 260-671) This invention relates to a process for the alkylation of an aromatic hyrocarbon, and more particularly relates to a process for the alkylation of an alkylatable benzene hydrocarbon with an olefin-acting compound, and still more particularly relates to the alkylation of benzene with ethylene and propylene in combination with unreactive gases. Further, this invention relates to a combination process including the steps of alkylation, gas-liquid separation, fractionation, countercurrcnt gas-liquid absorption, and selective recycle to obtain alkyl transfer.

An object of this invention is to produce alkyl-aromatic hydrocarbons, and more 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 a high antiknock value and which may be used as such or as a component of gasoline suitable for use in automobile and airplane engines. A further specific object is a process for the production of cumene by the reaction of benzene with propylene, which cumene product is oxidized in large quantities to form cumene hydroperoxide which is readily decomposed into phenol and acetone. Another object of this invention is a process for the production of para-diisopropylbenzene which diisopropylbenzene is oxidized to terephthalic acid, one starting material for the production of some synthetic fibers. Still 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 pressure aromatic hydrocarbons and maximum utilization thereof in the process. The further object of maximum boron trifiuoride recovery for reuse as a catalyst in this process, along with other objects of this invention, Will be set forth hereinafter as part of the accompanying specification.

In prior art processes for the 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 it is generally preferable to utilize greater than two mols of aromatic hydrocarbon per mol of olefin hydrocarbon, and in many cases, for best reaction, it is preferred to use three or more mols of aromatic hydrocarbon per mol of olefin hydrocarbon. This has been found necessary to prevent polymerization of the olefin hydrocarbon from taking place prior to the reaction of the olefin hydrocarbon with the aromatic hydrocarbon. While generally satisfactory proc esses have resulted from the utilization of such molar excesses of aromatic hydrocarbons in the presence of solid or liquid catalysts of the class known as Friedel-Crafts metal halides, a problem arises when these molar excesses are utilized in connection with the alkylation of aromatic hydrocarbons of high vapor pressure at normal conditions,

particularly when the olefin hydrocarbon utilized as the olefin-acting compound or alkylating agent is a normally gaseous olefin hydrocarbon such as ethylene, propylene, l-butene, Z-butene, or isobutylene, and the problem is further accentuated when this alkylation is carried out in the presence of a gaseous acidic catalyst such as exemplified by boron trifluoride. The above mentioned olefin hydrocarbons are often present as minor quantities in various refinery gas streams containing major quantities of other gases such as hydrogen, nitrogen, hydrogen sulfide, and hydrocarbons such as methane, ethane, propane, n-butane, and isobutane. It has been suggested in the prior art that the aromatic hydrocarbon to be alkylated can be utilized in a gas-liquid absorption zone for the absorption of the olefin hydrocarbon from such gas streams. When the aromatic hydrocarbon thus utilized has a high vapor pressure at normal conditions, concurrent loss of the aromatic hydrocarbon is observed due to the vapor pressure which the aromatic hydrocarbon exerts in the absorption zone, which aromatic hydrocarbon is then carried from the absorption zone along with the unreactive gases which the prior art suggests can be vented from the absorption zone. Furthermore, such a process is dependent upon the solubility coefficient of the olefin hydrocarbon in the aromatic hydrocarbon in the absorption zone at the conditions of temperature and pressure utilized therein. It is obvious that at best such a process is inefiicient. By means of the process of the present invention, these and other disadvantages in the hereinabove described processes can be overcome.

in one embodiment the present invention relates to a process for the production of an alkylated aromatic hydrocarbon which comprises passing to a reaction zone an alkylatable aromatic hydrocarbon, an unsaturated organic compound, and recycle polyalkylaromatic hydrocarbon absorber oil produced as hereinafter described and containing boron trifiuoride, reacting therein said alkylatable aromatic hydrocarbon with said unsaturated organic compound at alkylation conditions in the presence of boron trifluoride as the alkylation catalyst, passing efiiuent comprising boron trifiuoride, alkylatable aromatic hydrocarbon, alkylated aromatic hydrocarbon and polyalkylated aromatic hydrocarbon from said reaction zone to a gasliquid separation zone, separating gas from liquid in said separation zone, passing said gas to a lower region of a gas-liquid absorption zone hereinafter described, passing liquid from said separation zone to a fractionation zone, fractionating said liquid in said zone to separate overhead unreacted alkylatable aromatic hydrocarbon, recycling said unreacted alkylatable aromatic hydrocarbon to the reaction zone, passing alkylated aromatic hydrocarbon to a second fractionation zone, fractionating said alkylated aromatic hydrocarbon in said second fractionation zone to separate overhead desired alkylated aromatic hydrocarbon product, removing said product from the process, passing polyalkyiated aromatic hydrocarbon from said second fractionation zone to an upper region of a gas-liquid absorption zone as absorber oil therefor, countercurrently contacting said polyalkylaromatic hydrocarbon with the hereinabove described gas feed to said zone, venting from the process non-absorbed gas from said zone, and passing said absorber oil containing boron trifiuoride from said zone to the reaction zone as aforesaid.

In another embodiment the present invention relates to a process for the production of an alkylated aromatic hydrocarbon which comprises passing to a reaction zone an alkylatable aromatic hydrocarbon, an olefin, and re cycle polyalkylaromatic hydrocarbon absorber oil produced as hereinafter described and containing boron trifiuoride, reacting therein said alkylatable aromatic hydrocarbon with said olefin at alkylation conditions in the presence of boron trifiuoride as the alkylation catalyst, passing efi'luent comprising boron trifluoride, alkylatable aromatic hydrocarbon, alkylated aromatic hydrocarbon and polyalkylated aromatic hydrocarbon from said reaction zone to a gas-liquid separation zone, separating gas from liquid in said separation zone, passing said gas to a lower region of a gas-liquid absorption zone hereinafter described, passing liquid from said separation zone to a fractionation zone, fractionating said liquid in said zone to separate overhead unreacted alkylatable aromatic hydrocarbon, recycling said unreacted alkylatable aromatic hydrocarbon to the reaction zone, passing alkylated aromatic hydrocarbon to a second fractionation zone, fractionating said alkylated aromatic hydrocarbon in said second fractionation zone to separate overhead desired alkylated aromatic hydrocarbon product, removing said product from the process, passing polyalkylated aromatic hydrocarbon from said second fractionation zone to an upper region of a gas-liquid absorption zone as absorber oil therefor, countercurrently contacting said polyalkylaromatic hydrocarbon with the hereinabove described gas feed to said zone, venting from the process non-absorbed gas from said zone, and passing said absorber oil containing boron trifluoride from said zone to the reaction zone as aforesaid.

In a further embodiment the present invention relates to a process for the production of an alkylated benzene hydrocarbon which comprises passing to a reaction zone an alkylatable benzene hydrocarbon, a normally gaseous olefin, and recycle polyalkylbenzene hydrocarbon absorber oil produced as hereinafter described and containing boron trifluoride, reacting therein said alkylatable benzene hydrocarbon with said normally gaseous olefin at alkylation conditions in the presence of boron trifluoride as the alkylation catalyst, passing efiluent comprising boron trifluoride, alkylatable benzene hydrocarbon, alkylated benzene hydrocarbon, and polyalkylated benzene hydrocarbon from said reaction zone to a gasliquid separation zone, separating gas from liquid in said separation zone, passing said gas to a lower region of a gas-liquid absorption zone hereinafter described, passing liquid from said separation zone to a fractionation zone, fractionating said liquid in said zone to separate overhead unreacted alkylatable benzene hydrocarbon, recycling said unreacted alkylatable benzene hydrocarbon to the reaction zone, passing alkylated benzene hydrocarbon to a second fractionation zone, fractionating said alkylated benzene hydrocarbon in said second fractionation zone to separate overhead desired alkylated benzene hydrocarbon product, removing said product from the process, passing polyalkylated benzene hydrocarbon from said second fractionation zone to an upper region of a gasliquid absorption zone as absorber oil therefor, countercurrently contacting said polyalkylbenzene hydrocarbon with the hereinabove described gas feed to said zone, venting from the process non-absorbed gas from said zone, and passing said absorber oil containing boron trifluoride from said zone to the reaction zone as aforesaid.

In a specific embodiment the present invention relates to a combination process for the production of ethylbenzene which comprises passing to a reaction zone benzene, ethylene, and recycle diethylbenzene absorber oil produced as hereinafter described and containing boron trifluoride, reacting therein said benzene with said ethylene at alkylation conditions in the presence of boron trifluoride as the alkylation catalyst, passing effluent comprising boron trifluoride, benzene, ethylbenzene, and polyethylbenzene from said reaction zone to a gas-liquid separation zone, separating gas from liquid in said separation zone, passing said gas to a lower region of a gas liquid absorption zone hereinafter described, passing liquid from said separation zone to a fractionation zone,

zene to a second fractionation zone, fractionating said ethylated benzene in said second fractionation zone to separate overhead desired ethylbenzene product, removing said ethylbenzene product from the process, passing higher boiling polyethylated benzene from said second fractionation zone to a third fractionation zone, fractionating said polyethylated benzene in said third fractionation zone to separate overhead diethylbenzene, removing higher boiling polyethylated benzene'as bottoms from the process, passing said diethylbenzene from said third fractionation zone to an upper region of a gas-liquid absorption zone as absorber oil therefor, countercurrently contacting said diethylbenzene with the hereinabove described gas feed to said zone, venting from the process non-absorbed gas from said zone, and passing said absorber oil containing boron trifiuoride from said zone to the reaction zone as aforesaid.

In another specific embodiment the present invention relates to a process for the simultaneous production of ethylbenzene and cumene which comprises passing to a reaction zone benzene, ethylene and propylene diluted with unreactive gas, and recycle dialkylbenzene absorber oil produced as hereinafter described and containing boron trifluoride, reacting therein said benzene with said ethylene and propylene at alkylation conditions in the presence of boron trifluoride as the alkylation catalyst, passing effluent comprising boron trifluoride, unreactive gas, benzene, ethylbenzene, cumene, and polyalkylated benzene from said reaction zone to a gas-liquid separation zone, separating gas from liquid in said separation zone, passing said gas to a lower region of a gas-liquid absorp tion zone hereinafter described, passing liquid from said separation zone to a fractionation zone, fractionating said liquid in said zone to separate overhead unreacted benzene, recycling said unreacted benzene to the reaction zone, passing higher boiling alkylated benzene to a second fractionation zone, fractionating said alkylated benzene in said second fractionation zone to separate overhead desired ethylbenzene product, removing said ethylbenzene as one product from the process, passing higher boiling alkylated benzene from said second fractionation zone to a third fractionation zone, fractionating said higher boiling alkylated benzene in said third fractionation zone to separate overhead desired cumene product, removing said cumene as the second product from the process, passing still higher boiling polyalkylated benzene from said third fractionation zone to a fourth fractionation zone, fractionating said polyalkylated benzene in said fourth fractionation zone to separate overhead dialkylated benzene, removing higher boiling polyalkylated benzene as bottoms from the process, passing said dialkylated benzene from said fourth fractionation zone fractionating said liquid in said zone to separate overhead unreacted benzene, recycling said unreacted benzene to the reaction zone, passing higher boiling ethylated bento an upper region of a gas-liquid absorption zone as absorber oil therefor, countercurrently contacting said dialkylbenzene with the hereinabove described gas feed to said zone, venting from the process non-absorbed gas from said zone, and passing said absorber oil containing boron trifluoride from said zone to the reaction zone as aforesaid.

This invention can be most clearly illustrated with reference to the attached drawing. While of necessity certain limitations must be present in such a schematic description, no intention is meant to thereby limit the generally broad scope of this invention. As stated hereinabove, the first step of the process of the present invention comprises alkylating an alkylatable aromatic hydrocarbon with an unsaturated organic compound at alkylation conditions in the presence of a gaseous acidic catalyst, namely, boron trifluoride, In the drawing, this first step is represented as taking place in reaction zone 6. However, the mixture of alkylatable aromatic hydrocarbon, unsaturated organic compound, and make-up reaction zone 6 through line 1. The alkylatable aromatic hydrocarbon is combined therewith in line 1 by passage through line 2 which also provides means for continuous or discontinuous addition of boron trifiuoride through line 3. Line 4 in the drawing represents means by which unreacted alkylatable aromatic hydrocarbon is recycled to reaction zone 6. Line 5 in the drawing represents polyalkylaromatic hydrocarbon absorber oil containing boron trifluozide which is recycled to the reaction zone.

The unsaturated organic compound, particularly olefinacting compound, and still more particularly olefin hydrocarbon, which may be charged to reaction zone 6 via line 1 may be selected from diverse materials including monoolefins, diolefins, polyolefins, acetylenic hydrocarbons, and also alcohols, ethers, and esters, the latter including alkyl halides, alkyl sulfates, alkyl phosphates, and various esters of carboxylic acids. The preferred unsaturated organic compounds are olefinic hydrocarbons which comprise monoolefins containing one double bond per molecule and polyolefins which contain more than one double bond per molecule. Monoolefins which are utilized as unsaturated organic compounds or olefin-acting compounds in the process of the present invention are either normally gaseous or normally liquid and include ethylene, propylene, l-butene, Z-butene, isobutylone, and higher molecular weight normally liquid olefins such as the various penteues, heirenes, heptenes, octenes, and still higher molecular weight liquid olefins, the latter including various olefin polymers having from about 9 to about 18 carbon atoms per molecule including propylene trimer, propylene tctramer, propylene pentamer, etc. Cycloolcfins such as cyclopentene, methyl-cyclopentene, cyclohexene, methylcyclohexene, etc., may also be utilizcd. Also included within the scope of the term unsaturated organic compound or olefin-acting compound are certain substances capable of producing olefinic hydrocarbons or intermediates thereof under the conditions of operation utilized in the process. Typical olefin producing substances or olefin-acting compounds capable of use include alkyl halides capable of undergoing dehydrohalogenation to form olefinic hydrocarbons and thus containing at least two carbon atoms per molecule. Examples of such alkyl halides include ethyl fluoride, n-propyl fluoride, isopropyl fluoride, n-butyl fluoride, isobutyl fluoride, sec-butyl fluoride, tert-butyl fluoride, etc., ethyl chloride, n-propyl chloride, isopropyl chloride, n-butyl chloride, isobutyl chloride, sec-butyl chloride, tert-butyl chloride, etc., ethyl bromide, n-propyl bromide, isopropyl bromide, n-butyl bromide, isobutyl bromide, sec-butyl bromide, tert-butyl bromide, etc. As stated hereinabove, other esters such as alkyl sulfates including ethyl sulfate, propyl sulfate, etc., and alkyl phosphates including ethyl phosphate, etc. may be utilized. Ethers such as diethyl ether, ethyl propyl ether, dipropyl ether, etc., are also included within the generally broad scope of the term unsaturated organic compound or olefin-acting compound and may be successfully utilized as allrylating agents in the process of this invention.

Olefin hydrocarbons, particularly normally gaseous olefin hydrocarbons, are preferred olefin-acting compounds or unsaturated organic compounds for use in the process of this invention and for passage by means of line 1 to reaction zone a. The process of this invention can be successfully applied to and utilized for complete conversion of olefin hydrocarbons when these olefin hydrocarbons are present in minor quantities in various gas streams. Thus, in contrast to prior art processes, the normally gaseous olefin for use in the process of this invention need not be concentrated. Such normally gaseous olefin hydrocarbons appear in minor quantities in various refinery gas streams, usually diluted with various unreactive gases such as hydrogen, nitrogen, methane, ethane, propane, etc. These gas streams containing minor quantities of olefin hydrocarbons are obtained in petroleum refineries from various refinery installations including thermal cracking units, catalytic cracking units, thermal re forming units, coking units, polymerization units, etc. Such refinery gas streams have in the past often been burned for fuel value since an economical process for the utilization of their olefin hydrocarbon content has not been available, or processes which have been taught by the prior art utilize such large quantities of alkylatable aromatic hydrocarbon that they have not been economically feasible. This is particularly true for refinery gas streams known as off-gas streams containing relatively minor quantities or olefin hydrocarbons such as ethylene. Thus, it has been possible to catalytically polymerize propylene and/ or butenes in various refinery gas streams, but the off-gases from such processes still contain the utilizable olefin hydrocarbon, ethylene. Prior to my invention, it has been considered necessary to concentrate this ethylene for use as an alkylating agent. In addition to containing ethylene in minor quantities, these off-gas streams contain other olefin hydrocarbons, depending upon their source, including propylene and butenes. A refinery ofi-gas ethylene stream may contain varying quantities of hydrogen, nitrogen, methane, and ethane with the ethylene in minor proportion while a refinery elf-gas propylene stream is normally diluted with propane and contains the propylene in minor quantities, and a refinery off-gas butene stream is normally diluted with butanes and contains the butenes in minor quantities. A typical analysis in mol percent for a utilizable refinery off-gas from a catalytic cracking unit is as follows: nitrogen, 4.0%; carbon monoxide, 8.2%; hydrogen, 5.4%; methane, 37.8%; ethylene, 10.3%; ethane, 24.7%; propylene, 6.4%; propane, 10.7%; and C hydrocarbons, 0.5%. It is readily observed that the total olefin content of this gas stream is 16.7 mol percent and the ethylene content is even lower, namely 19.3 mol percent. Such gas streams containing olefin hydroca bons in minor or dilute quantities are particularly preferred unsaturated organic compounds or olefin-acting compounds within the broad scope of the invention. It is readily apparent that only the olefin content of such streams undergoes reaction in the process of this invention, and that the remaining gases free from olefin hydrocarbons are vented from the process. It is one of the features of this invention that the non-reactive gases are vented from the process with minimum loss of boron trifiuoride and alkylatable aromatic hydrocarbon due to their vapor pressure at the conditions of temperature and pressure utilized for venting the non-reactive gases.

The unsaturated organic compound or olefin-acting compound or normally gaseous olefin hydrocarbon has combined therewith in line 1 alhylatable aromatic hydrocarbon from line 2 which may or may not have boron trifiuoride combined therewith from line 3 as will be set forth further in detail hereinafter. Many aromatichydrccarbons are utilizable as alkylatable aromatic hydrocarbons within the process of this invention. Preferred aromatic hydrocarbons are monocyclic aromatic hydrocarbons, that is, benzene hydrocarbons. Suitable aromatic hydrocarbons include benzene, toluene, ortho- Xylene, meta-xylene, para-Xylene, ethyl-benzene, orthoethyltoluene, meta-ethyltoluene, para-ethyltoluene, 1,2,3- trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, normal-propylbenzene, isopropylbenzene, normal-butylbenzene, etc. Higher molecular Weight alkylaromatic hydrocarbons are also suitable as starting materials and include aromatic hydrocarbons such as are produced by the prior alkylation of aromatic hydrocarbons with olefin polymers. the art as alkylate, and include hexylbenzene, hexyltoluene, nonylbenzene, nonyltoluene, dodecylbenzene, dodecyltoluene, etc. Other suitable alkylatable aromatic hydrocarbons include those with two or more aryl groups such as diphenyl, diphenylmethane, triphenylmethane,

Such products are referred to in .acting compound, preferably olefin.

fiuorene, stilbene, etc. Examples of alkylatable aromatic hydrocarbons within the scope of this invention utilizable as starting materials and containing condensed benzene rings include naphthalene, alpha-methylnaphthalene, betamethylnaphthalene, etc., antbracene, phenanthrene, naphthacene, rubrene, etc. When the selected alkylatable aromatic hydrocrabon is a solid, it is heated by means not shown so that it passes as a liquid through line 2 to line 1 as hereinabove described. Of the above alkylatable aromatic hydrocarbons for use as starting materials in the process of this invention, the benzene hydrocarbons are preferred, and of the benzene hydrocarbons, benzene itself is particularly preferred.

As stated hereinabove, when desired, boron trifluoride is admixed with the alkylatable aromatic hydrocarbon prior to passage thereof to line 1. This is accomplished by passage of the boron triiluoride via line 3 to line 2. Boron trifiuoride is a gas, boiling point l01 C, melting point 126 C., and is somewhat soluble in most organic solvents. It may be and generally is utilized per se by mere passage thereof as a gas through line 3 under sufficient pressure so that it dissolves at least partially in the alkylatable aromatic hydrocarbon passing concurrently therewith through line 2. The boron trifiuoride may also be utilized as a solution of the gas in an organic solvent. However, in the utilization of such solutions care must be exercised so that the selected solvent is unreactive with the unsaturated organic compound or olefinacting compound or normally gaseous olefin hydrocarbon utilized in the process. Furthermore, boron trifiuoride complexes with many organic compounds, particularly those containing sulfur or oxygen atoms. Those complexes while utilizable as catalysts, are very stable and thus will interfere with the recovery of boron trifluoride in the ga s-liquid absorption zone hereinafter set forth. Therefore, a further limitation upon the selection of such a solvent is that it be free from atoms or groups which form complexes with boron trifiuoride. Gaseous boron trifluoride itself is the preferred catalyst. The amount of boron trifiuoride which is utilized is relatively small. It has been found that the amount necessary can be conveniently expressed as grams of boron trifiuoride per gram mol of unsaturated organic compound or olefin- This amount of boron trifiuoride will range from about 0.1 milligram to about 0.8 gram of boron trifluoride per gram mol of olefin utilized. When the amount of boron trifluoride present in'the reaction zone is within the above expressed range, substantially complete conversion of the olefinacting compound is obtained, even when the olefin-acting compound is present in what might seem to be minor or dilute quantities in a gas stream. Furthermore, while theboron trifluoride as shown in the drawing is added, when necessary, via linefi to line 2 it may, if desired, be added, when necessary, directly to line 1, or to reaction zone 6.

Prior to entry from line 1 to reaction zone 6, the reactants and catalyst, if any, have combined therewith recycle alkylatable aromatic hydrocarbon via line 4, and polyalkylaromatic hydrocarbon absorber oil containing boron trifiuoride via line 5. Recycle alkylatable aromatic hydrocarbon is generally available in the process since it is preferred to utilize a molar excess of alkylatable aromatic hydrocarbon over unsaturated organic compound, preferably olefin. This, as is disclosed in the prior art, has been found necessary to prevent side reactions from taking place, such as polymerization of the unsaturated organic compound prior to reaction thereof with the alkylatable aromatic hydrocarbon, and to direct the reaction principally to monoalkylation. Polyalkylaromatic hydrocarbon produced in the process is recycled to the reaction zone via line 5 for three reasons. First of all, some transfer of alkyl groups from polyalkylaromatic hydrocarbon to alkylatable aromatic hydrocarbon takes place in the reaction zone thus increasing the yield per pass of desired alkylated aromatic hydrocarbon product; Second, the polyalkylaromatic hydrocarbon, as will be described hereinafter, is a useful absorber oil to prevent loss of alkylatable aromatic hydrocarbon in the gas stream vented from the process. Third, and most important, since the polyalkylaromatic hydrocarbons are relatively strongly basic, they dissolve boron trifluoride by complex formation from the effluent unreactive gases effectively and their use permits a unitary combination process in which only minor quantites or no boron trifiuoride addition is necessary to maintain catalyst activity and desired reaction. The basic character of these polyalkylaromatic absorber oils is pronounced in comparison to recycle of unalkylated aromatic hydrocarbons or monoalkylated aromatic hydrocarbons. Furthermore, polyalkylaromatic hydrocarbons of certain structures are much more basic than other polyalkylaromatic hydrocarbons and it is a preferred embodiment of this invention to include such strongly basic polyalkylaromatic hydrocarbons in the recycle stream for maximum boron trifluoride recovery and recycle. Such strongly basic polyalkylarornatic hydrocarbons include those which have 1,3- dialkyl substitution, 1,3,5-trialkyl substitution, and 1,2,4,5- tetralkyl substitution. Examples of such polyalkylaromatic hydrocarbons include 1,3-diethylbenzene, 1,3,5-triethylbenzene, l,2,4,5-tetraethylbenzene and other polyalkylaromatic hydrocarbons in which the same structural configuration is present. Therefore, the polyalkylaro matic hydrocarbon produced in the process is first recycled to a gas-liquid absorption zone for boron trifiuoride recovery, and is then recycled back to the reaction zone via line 5.

The combined feed to the reaction zone comprising alkylatable aromatic hydrocarbon, unsaturated organic compound, boron trifluoride provided in the manner hereinabove specified, and polyalkylaromatic hydrocarbon is passed to reaction zone 6. Reaction zone 6 is of the conventional type and may be equipped with heat transfer means, bafiles, trays, metal packing, heating means, etc. The reaction zone preferably is of the adiabatic type and thus the feed to this zone will preferably be provided with the requisite amount of heat proir to passage thereof to said zone. In a preferred embodiment, this reaction zone will be adiabatic and packed with a refractory oxide. The refractory oxide with which said zone is packed may be selected from among various inorganic oxides including alumina, silica, boria, or oxides of phosphorus (which for the purposes of this specification along with silica are considered to be metal oxides), titanium dioxide, zirconium dioxide, chromia, zinc oxide, magnesia, calcium oxide, silica-alumina, silica-magnesia, silica-aluminamagnesia, silica alumina zirconia, chromia-alumina, alumina-boria, silica-zirconia, etc., and various naturally occurring inorganic oxides of various states of purity such as bauxite, clay (which may or may not have been acid treated), diatomaceous earth, etc. Of the above mentioned inorganic oxides for use as packing in reaction zone 6, alumina is preferred.

The conditions utilized in reaction zone 6 may be varied over a relatively wide range. Thus, the desired alkylation reaction in the presence of the above indicated boron trifiuoride catalyst may be effected at a temperature of from about 0 F. or lower to about 500 F. or higher, preferably at a temperature of from about F. to about 350 F. The alkylation reaction is usually carried out at a pressure of from about substantially atmospheric to about 200 atmospheres. The pressure utilized is usually selected to maintain the alkylatable aromatic hydrocarbon in substantially liquid phase. Within the above mentioned temperature and pressure ranges, it is not always possible to maintain the olefin-acting compound in liquid phase. Thus, when utilizing a refinery off-gas containing ethylene, the ethylene will be dissolved in the liquid phase alkylatable aromatic hydrocarbon (and alkylated aromatic hydrocarbon as formed) to the extent governed by temperature, pressure, and solubility considerations. However, a portion thereof will always be in the gas phase. Referring to the aromatic hydrocarbon to be alkylated, it is preferable to have present from about 2 up to about or more, sometimes up to 20, molar proportions per molar proportion of olefin-acting compound introduced therewith. The hourly liquid space velocity of the liquid through the reaction zone may be varied over a relatively wide range of from about 0.25 to about 20 or more.

When the alkylation reaction has proceeded to the desired extent, the products from the alkylation zone, which may be termed alkylation zone eifiuent, are withdrawn from zone 6 through line 7, are indirectly heat exchanged in heat exchanger 8 with recycle unreacted alkylatable aromatic hydrocarbon produced as hereinafter described, and are passed through line 9 to separator 10, also known as the alkylation reaction zone effluent received. The akylation or reaction zone effluout which passes into separation zone 1% comprises unreactive gases, if any, which were introduced to the system along with the unsaturated organic compound, boron triiiuoride, excess allrylatable aromatic hydrocarbon, alkylated aromatic hydrocarbon, and polyalkylated aromatic hydrocarbon. The unreactive gases, if any, and the boron trifluoride are separated as gases in gasliquid separation zone 18, and passed through line 11 to gas-liquid absorption zone 51, hereinafter described. Since the alkylatable aromatic hydrocarbon was utilized in excess in the reaction zone, the excess alkylatable aromatic hydrocarbon will be present in separation zone 10 and a portion thereof will be vaporized overhead due to its vapor pressure at these conditions alongwith-the unreactive gases and boron trifiuorlde. The temperature of separation zone 19 will be somewhat less than that of the reaction zone, in most cases, due to the cooling which has taken place in heat exchanger 8 by indirect heat exchange with recycle alkylatable aromatic hydrocarbon. The liquid which is separated in separation zone 10 passes therefrom through line 12 to the first fractionation zone 13, labeled benzene column in the drawing.

Fractionation zone 13 is a conventional fractional distillation column or tower and is utilized for the purpose of recovering excess unreacted alkylatable aromatic hydrocarbon for recycle from the reaction zone effluents. The recovered unreacted alkylatable aromatic hydrocarbon passes overhead from first fractionation zone 13 through line 14 containing condenser 15 to overhead receiver 16. A vent is placed on this overhead receiver to remove any gases which have failed to be removed by means of the gas-liquid absorption zone. This amount, of course, is normally very small. These gases pass from overhead receiver 16 through line 17 containing, if desired, a pressure control valve as shown. These gases may be passed, if desired, from line 17 back to gas-liquid absorption zone 61, by means not shown, and if they are thus returned to the gas-liquid absorption zone, this return will be to a lower region thereof, as for example, by combination with and return through line 11. The thus recovered unreacted alkylatable aromatic hydrocarbon is withdrawn from overhead receiver 16 through line 18 by pump 19 which provides recycle to fractionation zone 13 by means of lines 20 and 21 and which also recycles the remainder of the recovered alkylatable aromatic hydrocarbon via lines 26 and 4 back to line 1 and reaction zone 6. The higher boiling alkylated aromatic hydrocarbons are withdrawn from fractionation zone 13 by means of line 22 and passed therethrough to a second fractionation zone 25. A portion of the higher boiling alkyiated aromatic hydrocarbons is withdrawn from line 22 by means of line 23 containing reboiler 24 and passed back to a lower region of fractionation zone 13. By means of reboiler 24 the lated aromatic hydrocarbon.

10 requisite amount .of heat is furnished to fractionation zone 13.

Second fractionation zone 25 is of the conventional type and is utilized for recovery of desired alkylated aromatic hydrocarbon from higher boiling homologs thereof. The desired alkylated aromatic hydrocarbon is withdrawn overhead from fractionation zone 25 through line 26 containing condenser 27 and is passed to overhead receiver 28. The liquid product from overhead receiver 28 comprises desired alkylated aromatic hydrocarbon which is withdrawn therefrom through line 29 by pump 30 which provides reflux for fractionation zone 25 through lines 31 and 32. Pump 30 also provides a means for passage of desired alkylated aromatic hydro carbon from the process by means of line 33. The still higher boiling alkylated aromatic hydrocarbons are withdrawn from fractionation zone 25 by means of line 34 and are passed to third fractionation zone 3?. A portion of the higher boiling alkylated aromatic hydrocarbons are withdrawn from line 34 through line 35 containing reboiler 36 and are passed back to a lower region of fractionation zone 25. By means of reboiler 36 the requisite amount of heat is supplied to this fractionation zone.

As stated hereinabove, the higher boiling alkylated aromatic hydrocarbons, in the preferred embodiment of this invention, are withdrawn from fractionation zone 25 through line 34 and passed to a third fractionation zone 37. However, these higher boiling polyalkylated aromatic hydrocarbons may be withdrawn from fractionation zone 25 through line 34 and passed directly by means not shown through line 57 to an upper region of gas-liquid absorption zone 61. This, of course, is a broad embodiment of the present invention and is utilized when no rerunning of the higher boiling polyalkylated aromatic hydrocarbons is desired and when the olefin-acting compound charged to the process as the alkylating agent is a single compound such as ethylene instead of a mixture of such compounds such as an ofigas containing both ethylene and propylene. In the broad embodiment, when the polyalkylated aromatic hydrocarbons are passed directly from the bottom of fractionation zone 25 to an upper region of gas-liquid ab sorption zone 61, a quantity thereof may be withdrawn, if so desired, by means not shown, when the quantity of these higher boiling alkylated aromatic hydrocarbons is more than is necessary for gas-liquid absorption zone 61.

Gas-liquid absorption zone 61 is a countercurrent contacting zone, of conventional design, the size of which is varied depending upon the quantity of recycle higher boiling alkylated aromatic hydrocarbons passed thereto and upon the quantity of unreacted alkylatable aromatic hydrocarbon, boron trifluoride, and unreactive gases passed to a lower region thereof. In gas-liquid absorption zone 61 the higher boiling alkylated aromatic hydrocarbons pass into an upper region thereof through line 57 and flow downward in a countercurrent manner to the gases which are introduced thereto in a lower region thereof, for example, via line 11. The unreacted alkylatable aromatic hydrocarbon vaporized in separation zone 10 and boron trifluoride are recovered, dissolved in and complexed with the higher boiling alky- The unreactive gases are vented from absorption zone 61 through line 62 containing a pressure control valve as shown. The higher boiling alkylated aromatic hydrocarbon containing d.ssolved unreacted alkylatable aromatic hydrocarbon and boron trifluoride is withdrawn from the bottom of gas-liquid absorption zone 61 through line 5 and recycled to re action zone 6 as hereinabove set forth.

Depending upon whether or not the unsaturated organic compound utilized in the process comprises one or more such compounds, and depending upon whether or not rerunning of the higher boiling alkylated aro matic hydrocarbons is deemed necessary or desirable, it

'unreactive gases. cumene are primary products of the process.

higher boiling alkylated aromatic hydrocarbons for use in the gas-liquid absorption zone for recovery of gases hereinabove described. In the simplest case, the unsaturated organic compound is an olefin such as ethylene and the higher boiling alkylated aromatic hydrocarbon is recycled to the gas-liquid absorption zone without rerunning. In the next case, the unsaturated organic com- 1 pound is an olefin such as ethylene and the higher boiling alkylated aromatic hydrocarbon is rerun to produce an overhead recycle fraction for the gas-liquid absorption zone and to produce a bottoms fraction for removal from the process. In another case, and in a preferred embodiment of this invention, the unsaturated organic compound utilized is a mixture of normally gaseou olefins comprising both ethylene and propylene diluted with In such a case, both ethylbenzene and This is the typical case when the normally gaseous olefin hydrocarbon feed stream comprise a so-called refinery offgas. In this case, the alkylated aromatic hydrocarbons higher boiling than the first desired product are passed from fractionation zone through line 34 to a third fractionation zone 37.

Fractionation zone 37 is a conventional fractional distillation column and is utilized, as set forth hereinabove. for either of two purposes. One purpose is to rerun higher boiling alkylated aromatic hydrocarbons. In this case, the higher boiling alkylated aromatic hydrocarbons are passed overhead through line 38, condensed in condenser 39, and are passed to overhead receiver 40. From overhead receiver 40 these higher boiling alkylated aromatic hydrocarbons are withdrawn through line 41 by pump 42 which provides reflux to the fractionation zone through lines 43 and 44.- The higher boiling alkylated aromatic hydrocarbon for recycle purposes is pumped from pump 42 through

lines

43 and 44 to line 57 by means not shown. The bottoms from the process in this case are withdrawn through line 46. 'In the preferred embodiment, this fractional distillation column is utilized to remove overhead a second desired alkylated aromatic hydrocarbon and to provide means for its recovery from the process. This second desired alkylated aromatic hydrocarbon passes overhead from fractionation zone 37 through line 38 containing condenser 39 to overhead receiver 40. The liquid product from overhead receiver 40 is withdrawn therefrom through line 41 by pump 42 which in this embodiment also provides reflux to the fractionation zone through

lines

43 and 44. This pump also removes this second desired product from the process by passage thereof through line 45. The still higher boiling alkylated aromatic hydrocarbons are withdrawn from fractionation zone 37 by means of line 46 and are passed to fourth fractionation zone 49. A portion of -the higher boiling alkylated aromatic hydrocarbon is withdrawn from line 46 through line 47 containing rcboiler 48 and is passed back to a lower region of fractionation zone 37. By means of reboiler 48, the requisite amount of heat is supplied to this fractionation zone.

As stated hereinabove, the'higher boiling alkylated aromatic hydrocarbons, in the preferred embodiment of this invention, are withdrawn from fractionation zone 37 through line 46 and passed to a fourth fractionation zone 49. However, these higher boiling polyalkylated aromatic hydrocarbons may be withdrawn from fractionation zone 37 through line 46 and passed directly by means not shown through line 57 to an upper region of gas-liquid absorption zone 61. This embodiment of the prment invention is utilized when no rerunning of these higher boiling polyalkylated aromatic hydrocarbons is desired and when the olefin-acting compound charged to the process is a mixture of two alkylating agents such as ethylene and propylene instead of being simply a single compound. In this embodiment when the polyalkylated aromatic hydrocarbons are passed directly from the bottom of fractionation zone 37 to an upper region of gas-liquid absorption zone 61, a quantity thereof may be withdrawn through line 46, if so desired, by means not shown, when the quantity of these higher boiling alkylated aromatic hydrocarbons is more than is necessary for gas-liquid absorption zone 61.

In a further and preferred embodiment of this process wherein two products are produced as hereinabove described and where it is desirable and/or advisable to fractionate the absorption zone recycle to remove tar therefrom, a still further fourth fractionation zone can be utilized as shown in the drawing. The second desired product from the process is removed via lines 43 and as described hereinabove. The bottoms from fractionation zone 37 are passed through line 46 to a recycle fractionation zone 49. Recycle fractionation zone 49 is a conventional fractional distillation column by means of which polyalkylaromatic hydrocarbon absorber oil is produced and by means of which tar is removed from the process. The desired absorber oil, generally polyalkylaromatic hydrocarbons, and more particularly those of the structural configurations set forth hereinabove, is separated overhead from fractionation zone 49 through line 50 containing condenser 51 and passed to overhead receiver 52. This liquid absorber oil is withdrawn from overhead receiver 52 through line 53 by means of pump 54 which provides recycle to this fractionation zone by means of

lines

55 and 56. The net absorber oil separated overhead is also passed by pump 54 through

lines

55 and 57 to absorption zone 61. The tar and still higher boiling polyalkylaromatic hydrocarbons are removed from the process from the bottom of recycle zone 49 through line 58. A portion thereof is withdrawn through line 59 containing reboiler 60 and is passed back to a lower region of zone 49. Reboiler 60 provides the necessary amount of heat for proper op eration of this fractionation zone.

The following example is introduced for the purposes of illustration with no intention of unduly limiting the generally broad scope of this invention. This example illustrates the utilization of the process of the present invention for the production of 500 barrels per day of ethylbenzene and 69 barrels per day of cumene. The catalyst utilized comprises about 0.5 gram of boron trifluoride per gram mol of olefin in a reaction zone packed with gamma-alumina. This example utilizes olfgas from a catalytic cracking unit containing both ethylene and propylene as alkylating agents for benzene. The production of the hereinabove described quantities of ethylbenzene and cumene are hereinafter set forth with reference to the attached drawing.

Referring to the drawing, off-gas from a catalytic cracking unit in the quantity of 676 pound mols per hour, after compression, is fed to the plant through line 1. These 676 pound mols per hour are made up as follows: 72 mols of hydrogen, 151 mols of nitrogen and carbon monoxide, 281 mols of methane, 62.7 mols of ethylene, 96 mols of ethane; 9.3 mols of propylene, and 4 mols of propane. There is also charged to the reactor 71.3 pound mols 'per hour of fresh benzene through line 2 and 0.05 pound mols per hour of makeup boron trifluoride through line 3. Also charged to the reactor are 558.5 pound mols per hour of recycle benzene supplied through line 4. This 558.5 pound mols per hour of re cycle benzene contains 0.055 mol of boron trifluoride,

0.7 mol of methane, 6.7 mols of ethane, 1.3 mols of propane, 549.0 mols of benzene, and 0.7 mol of ethylbenzene. By means of line 5 there is also charged to the reactor through line 1 absorber rich recycle oil containing boron trifiuoride and condensed separator vapors, produced as hereinafter described, in the quantity of 412 pound mols per hour. This 41.2 mols per hour is made of 0.412 mol of boron trifluoride, 0.3 mol of methane,

0.5 mol of ethane, 24.6 mols of benzene, 0.5 mol of ethylbenzene, 12.7 mols. of diethyl benzene, and2.2 mols of ethylisopropylbenzene. The combined feed is passed from line 1 to reactor 6 in the quantity of 1347.1 pound mols per hour. Reactor 6 is maintained at a pressure of 550 p.s.i.g. and at a temperature of 250 F. The 1347.1 pound mols per hour of combined feed passing to reactor 6 contains 0.517 mol of boron trifluoride, 72.0 mols of hydrogen, 151.0 mols of nitrogen and carbon monoxide, 282.0. mols of methane, 62.7 mols of ethylene, 103.2 mols of ethane, 9.3 mols of propylene, 5.3 mols of propane, 644.9 mols of benzene, 1.2 mols of ethylbenzene, 12.7 mols of diethylbenzene, and 2.2 mols of ethylisopropylbenzene. The benzene to olefin ratio is 9-1 In reactor 6 the olefin content of the off-gas stream reacts with the benzene and alkyl groups are transferred from dialkylbenzene to benzene to form monoalkylbenzene hydrocarbons. The reactor effluent passes from reaction zone 6 through line 7, is heat exchanged with recycle benzene, as hereinafter described, in heat exchanger 8 and passes through line 9 to gas-liquid separation zone 10. This reactor efiiuent in the quantity of 1275.0 pound mols per hour contains 0.513 mol of boron trifluoride, 72.0 mols of hydrogen, 151.0 mols of nitrogen and carbon monoxide, 282.0 mols of methane, no ethylene, 103.2 mols of ethane, no propylene, 5.3 mols of propane, 576.2 mols of benzene, 60.9 mols of ethylbenzene, 7.3 mols of cumene, 12.7 mols of diethylbenzene, 2.2 mols of ethylisopropylbenzene, 1.2 mols of diethylisopropylbenzene, 0.2 mol of triethylisopropylbenzene, and 0.3

mol of diisopropylbenzene. In separator 10 the gaseous products from the reaction zone effluent are separated from the liquid products. The gaseous products from the eilluent in the quantity of 618.2 pound mols per hour are passed from separator 10 to absorber 61, hereinafter described. The liquid reactionzone efiiuent passesfrom separator 10 through line 12 to fractionation zone 13, called the benzene column.

The benzene column 13 is fed with 656.8 pound mols per hour of separator liquid. This 656.8 pound mols per hour contains 0.097 mol of boron trifluoride, 0.5' mol of hydrogen, 0.5 mol of nitrogen and carbon monoxide, 5.0 mols of methane, 13.5 mols of ethane, 1.7 mols of propane, 551.1 mols of benzene, 60.4 mols of ethylbenzene, 7.3 mols of cumene, 12.7 molsof-diethylbenzene, 2.2 mols of ethylisopropylbenzene, 1.2 mols of diethylisopropylbenzene, 0.2 mol of triethylisopropylbenzene, and 0.3 mol of diisopropylbenzene. In this benzene column 13 the benzene and lighter (or. lower boiling.

materials) are separated from the remaining liquid. Thus, there is passed overhead from column 13 through 14 containing condenser 15 to receiver 16 maintained at' 100 F., 573 pound mols per hour containing 0.097 mol of boron trifluoride, 0.5 mol of hydrogen, 0.5 mol of nitrogen and carbon monoxide, 5.0 mols of methane, 13.5 mols of ethane, 1.7 mols of propane, 551.1 mols of benzene, and 0.7 mol of ethylbenzene. From receiver 16 there is vented 14.5 pound mols per hour of gas through line 17 containing a pressure control valve operating at 10 p.s.i.g. This 14.5 pound mols contains 0.042 mol of boron trifluoride, 0.5 mol of hydrogen, 0.5 mol of nitrogen and carbon monoxide, 4.3 mols of methane, 6.8 mols of ethane, 0.4 mol of propane, and 2.0 mols of benzene. This vent gas is utilized for fuel or sent to a flare tower, or as hereinabove set forth may be recycled, by means not shown, to line 11 and gas-liquid absorption zone 61.

The liquid in benzene column receiver 16 is withdrawn therefrom through line 18 by pump 19.vvhichv discharges through line and supplies reflux to benzene column 13 by means of line 21. Net recycle benzene is pumped by pump 19 through lines 20 and 4 back through heat exchange zone 8 to line 1 hereinabove described. The composition of this recycle benzene..in

the quantity of '558.5-'pound mols per hour has been described hereinabove. Aromatic hydrocarbons higher boiling than benzene are withdrawn from the bottom of benzene column 13 through line 22 and passed to ethylbenzene column 25. A portion thereof is passed via line 23 through reboiler 24 to supply heat to the column.

Ethylbenzene column 25 is fed with 83.7 pound mols per hour of benzene column bottoms contaning 59.7 mols of ethylbenzene, 7.3 mols of cumene, 12.7 mols of diethylbenzene, 2.2 mols of ethylisopropylbenzene, 1.2 mols of diethylisopropylbenzene, 0.2 mol of triethylisopropylbenzene, and 0.3 mol of diisopropylbenzene. This ethylbenzene column 25 separates overhead the net ethylbenzene produced. This ethylbenzene in the quantity of 59.7 pound mols per hour or 498 barrels per day passes through line 26, is condensed in condenser27 and passes to receiver 28. From receiver 28 this ethylbenzene is withdrawn through line 29 by pump 30 which supplies reflux to column 25 through lines 31 and 32. The net ethylbenzene passes through line 33 to storage. The bottoms from ethylbenzene column 25 pass through line 34 to cumene column 37. A portion'thereof passes through line 35 and reboiler 36 to supply heat to this ethylbenzene column.

Curnene column 37 is fed with 24 pound mols per hour from line 34. This 24 pound mols per hour contains 7.3 mols of cumene, 12.7 mols of diethylbenzene, 2.2 mols of ethylisopropylbenzene, 1.2 mols of diethylisopropylbenzene, 0.2 mol of triethylisopropylbenzene, and 0.3 mol of diisopropylbenzene. The function of this column is to separate the cumene from the higher boiling liquids. Thus, 7.3 mols per hour of cumene passes overhead from columnv 37 through line 38, is cooled in condenser 39 and passed to receiver 40. The liquid from receiver 40 is withdrawn through line 41 by pump 42 which supplies reflux to column 37 through

lines

43 and 44. The net cumene is withdrawnthrough line 45 to storage in the quantity of 69.3 barrels per day. The bottoms from cumene column 37 are withdrawn therefrom through line 46 and passed to recycle column 49. Cumene column 37 is heated by reboiling a portion of these bottoms which pass through line 47 and reboiler 48 back to the column.

Recycle column 49'is fed with 16.7 pound'mols per hour of polyalkylaromatic hydrocarbons containing 12.7 mols of diethylbenzene, 2.2 mols of ethylisopropylbenzene, 1.2 mos of diethylisopropylbenzene, 0.2 mol of triethylisopropylbenzene, and 0.3 mol of diisopropylbenzene. The. purpose ofthis recycle column, in addition to removing tar as bottoms from the process, is to separate overhead polyalkylaromatic hydrocarbons for use as absorber oil, and as a source of alkyl groups for alkyl transferreactions, as hereinbefore set forth. From recycle column 49 there' is separated overhead 14.9 pound mols per hour of polyalkylaromatic hydrocarbons through line 50. These hydrocarbons are condensed in condenser 51, and passed to overhead receiver 52. These 14.9 pound mols per hour contain 12.7 mols of diethylbenzene and 2.2 mols oiethylisopropylbenzene. The'liquid polyalkylaromatic hydrocarbons are withdrawn from receiver 52 through line 53 by means of pump 54 which supplies reflux to column 49bymeans of

lines

55 and 56. The bottoms'from column 49 in the quantity of 1.7 pound mols per hour-are withdravm therefrom through line 58. A portion of these bottoms are circulated throughline 59 containing reboiler 69 for the purpose of supplying heat to the column. The 1.7 pound mols per hour containing 1.2 mols of diethylisopropylbenzene, 0.2 mol of triethylisopropylbenzene, and 0.3 mol of diisopropylbeuzene are withdrawn as bottoms from the process.

The net liquid from receiver 52 in the quantity of 14.9 pound mols per hour as described hereinabove is pumped by pump 54 through

lines

55 and 57 to anupper region of absorption zone 61.. Absorption zone 61 is a gas-liquid contacting zone for recovery of boron trifluoride and benzene from the separator gas. This separator gas in the quantity of 618.2 pound mols per hour contains 0.416 mol of boron tn'fiuoride, 71.5 mols'of hydrogen, 150.5 mols of nitrogen and carbon monoxide, 277.0 mols of methane, 89.7 mols of ethane, 3.6 mols of propane, 25.1 mols of benzene, and 0.5 mol of ethylbenzene. This separator gas entering absorption zone 61 through line 11 in a lower region of the absorption zone is passed countercurrently to the 14.9 pound mols per hour of polyalkylaromatic hydrocarbon supplied through line 57. Recycle absorber oil passed from absorption zone 61 through lines 5 and 1 back to reaction zone 6. This rich absorption oil in the quantity of 40.8 mols per hour has been described hereinabove and contains 0.412 mol per hour of boron trifluoride which is greater than 99% of the boron trifluoride which separates as a gas overhead from separation zone 10. There is vented from absorption zone 61, 592 pound mols per hour of gas through line 62. This absorption zone 61 operates at a temperature of 100 F. and is maintained at a pressure of 100 p.s.i.g. by means of a pressure control valve in vent line 62. The 592. pound mols per hour of vent gas from line 62 contains 0.004 mol of boron trifluoride, 71.5 mols of hydrogen, 150.5 mols of nitrogen and carbon monoxide, 276.7 mols of methane, 89.2 mols of ethane, 3.6 mols of propane, and 0.5 mol of benzene.

The mol balances in and out of the 500 barrel per day ethylbenzene plant are presented in the following table:

'16 boron trifluoride catalyst used in the reaction zone, or only 0.05 mol per 67 .mols of combined ethylbenzene and cumene produced. V

I claim as my invention:

1. In the alkylation of an aromatic hydrocarbon in the presence of boron trifluoride in a reaction zone, the process which comprises separating from the reaction zone eflrluent a gaseous fraction containing boron trifluoride, a liquid mono-alkylated aromatic hydrocarbon fraction and a liquid basic polyalkylated aromatic hydrocarbon fraction, scrubbing said gaseous fraction with an absorber liquid consisting essentially of at least a portion of said liquid polyalkylated aromatic fraction to absorb boron trifluoride in the last-named fraction, and supplying the resultant BF -containing polyalkylated aromatic hydrocarbon fraction to the reaction zone.

2. The process of claim 1 further characterized in that said aromatic hydrocarbon is a benzene hydrocarbon.

3. The process of claim 1 further characterized in that said aromatic hydrocarbon is benzene which is alkylated with ethylene in said reaction zone.

4. The process of claim 1 further characterized in that said aromatic hydrocarbon is benzene which is alkylated with propylene in said reaction zone.

5. The process of claim 1 further characterized in that said aromatic hydrocarbon is benzene which is alkylated with a butene in said reaction zone.

6. The process of claim 1 further characterized in that Table Mols/Hour Lean Gas Ofi Benzene BF; Ethyl- Cumene Bottoms Gas Benzene In Out 131%.- 0.048 0. 004 0. 042 H, 72 71. 5 0. 5 151 150. 5 0. 5 CH4 281 276. 7 4.3 C2H4- 62. 7 0 0 C2115. 96.0 89. 2 6. 8 C3Hu- 9. 3 0 0 03133. 4. O 3. 6 0. 4 0 H; 71. 3 0. 5 2. 0 CeHsC 59. 7 Ca 501 7- 7- 3 C5Ha(C2 5)r(CaH'/)- 1. 2 o 2(C2 a)s( a 1) 0.2 Ca KCaHfi' 0. 3

Alkyl Aromatic Yield (Molar):

On Benzene Percent Ethylb 83.9 94 1 Cumenn 10. 2} Bottoms-l-Loss- 5. 9

On Ethylene- Ethylb 95. 2 95. 2 Bofl'nm 4 8 Total 100. 0

On Propylene- Cumene. 78. 5 78. 5 Bnffnm 2L 5 Total 100. 0

From the table the following yield picture is observed: ethylbenzene yield (molar) on benzeneis 83.9%. Cumene yield on benzene is 10.2%. Yield of monoalkylaromatic hydrocarbons is 94.1%. Benzene bottoms plus loss are 5.9%. Cumene yield based on propylene is 78.5%. Ethylbenzene yield based on ethylene is 95.2%. Thus, high yields of alkyl aromatics based both on benzene and olefin charged to the process are obtained by the process of the present invention. Furthermore, these yields. are attained with a net loss of about 1% of the said aromatic hydrocarbon is toluene which is alkylated with ethylene in said reaction zone.

7.v A process which comprises subjecting benzene to alkylation with a gas containing ethylene and propylene in the presence of boron trifluoride in a reaction zone, separating from the reaction zone efliuent a gaseous fraction containing boron trifinoride, an ethylbenzene fraction, a cnmene fraction and a basic polyalkylbenzene fraction, scrubbing said gaseous fraction with an absorber liquid consisting essentially of at least a portion of said poly- 17 18 alkylbenzene fraction to absorb boron trifluoride in the 2,406,869 Upham Sept. 3, 1946 last-named fraction, and supplying the resultant BFyCOntaining polyalkylbenzene fraction to the reaction zone. F PATENTS 564,059 Great Bntam Sept. 12, 1944 References Cited in the file of this patent 5 OTHER REFERENCES UNITED STATES PATENTS Thomas: Anhydrous Aluminum Chloride in Organic 2,397,495 Lien et a1. Apr. 2, 1946 Chemistry (1941), pp. 458-61 relied on.

Claims

1. IN THE ALKYLATION OF AN AROMATIC HYDROCARBON IN THE PRESENCE OF BORON TRIFLUORIDE IN A REACTION ZONE, THE PROCESS WHICH COMPRISES SEPARATING FROM THE REACTION ZONE EFFLUENT A GASEOUS FRACTION CONTAINING BORON TRIFLUORIDE, A LIQUID MONO-ALKYLATED AROMATIC HYDROCARBON FRACTION AND A LIQUID BASIC POLYALKYLATED AROMATIC HYDROCARBON FRACTION, SCRUBBING SAID GASEOUS FRACTION WITH AN ABSORBER LIQUID CONSISTING ESSENTIALLY OF AT LEAST A PORTION OF SAID LIQUID POLYALKYLATED AROMATIC FRACTION TO ABSORB BORON TRIFLUORIDE IN THE LAST-NAMED FRACTION, AND SUPPLYING THE RESULTANT FB3-CONTAINING POLYALKYLATED AROMATIC HYDROCARBON FRACTION TO THE REACTION ZONE.