US3428701A

US3428701A - Alkylation-transalkylation process

Info

Publication number: US3428701A
Application number: US712333A
Authority: US
Inventors: Dennis J Ward
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1968-03-01
Filing date: 1968-03-01
Publication date: 1969-02-18
Anticipated expiration: 1986-02-18

Description

D. J. WARDv Feb. 18, 1969 3,428,701

ALKYLATION-TRANSALKYLATION PROCESS Filed March l, 1968- a: 1 1 1 Y s l b Q 1n l a: if

, 1 g t .S 1 E LQ [l5 g 1 1 E 1 03 1 1 N3 1 1 Q/ g q1 N 7 1. 03 y 0o //VV/VT0,?l Denn/'s J. Ward mw M 1' 1N 1` i; ATTORNEYS United States Patent O 3,428,701 ALKYLATION-TRANSALKYLATION PROCESS Dennis J. Ward, Lombard, Ill., assignor to Universal Oil Products Company, Des Plaines, Ill., a corporation of Delaware Continuation-impart of application Ser. No. 556,943, June 13, 1966. This application Mar. 1, 1968, Ser. No. 712,333 U.S. Cl. 260-671 10 Claims Int. Cl. C07c 3/56 ABSTRACT F THE DISCLOSURE An aromatic compound is produced utilizing the steps of alkylation, transalkylation and separation.

Cross-references to related applications This application is a continuation-in-part of my copending application Ser. No. 556,943, iiled June 13, 1966, and noW abandoned.

This invention relates to an improved process for the production of an aromatic compound, and more particularly relates to an improved process for the alkylation of an valkylatable aromatic compound with an olefinacting compound, and still more particularly relates to the lalkylation of an aromatic hydrocarbon with an olenic hydrocarbon which may 'be in lcombination wit-h other gases which are unreactive at the process conditions utilized. Further, this invention relates to a combination process including the steps of alkylation, transalkylation and separation.

An object of this invention is to provide an improved process for the alkylation of alkylatable aromatic compounds with olen-acting compounds in the presence of free and/or combined boron triuoride to produce alkylated aromatic hydrocarbons and more particularly to produce monoalkylated benzene hydrocarbons. A further object of this invention is to provide an improved process for the production of ethylbenzene, a desired chemical intermediate, which ethylbenzene is utilized in large quantities in dehydrogenation processes for the manufacture of styrene, one of the starting materials for the production of resins and some synthetic rubber. Another specic object of this invention is to produce alkylated aromatic hydrocarbons boiling within the gasoline boiling range having high anti-knock value and which may be used as such or as a component of gasoline suitable for use in automobile and Iairplane engines. Still another object of this invention 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 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. Still another object of this invention is an improved process in which molar excesses of aromatic hydrocarbons to be alkylated are utilized, and in which process the yield of monoalkylated aromatic hydrocarbon product is exceptionally high due to maximum consumption of polyalkylated aroirnatic hydrocarbon by-products in the process. The further object of maximum boron trifluoride utilization as a catalyst in this process, along with other objects of this invention, will be set forth hereinafter yas part of the accompanying specification.

One embodiment of the present invention relates to an ice improved process for the production of an aromatic compound which comprises alkylating an alkylatable aromatic compound with an olefin-acting compound in the presence of a catalytic amount of boron triuoride in an alkylation reaction zone containing a boron triiluoridemodified substantially anhydrous inorganic oxide, recirculating from about 33 to about 95 weight percent of the reacted and unreacted liquid alkylation zone eiuent from said alkylation reaction zone prior to fractionation back to said alkylation zone, comtmingling the balance of the efliuent of said alkylation zone with efuent from a transalkylation reaction zone as hereinafter set forth, passing the thus commingled efuents to a separation zone `and therein separating -uureacted aromatic compound, desired monoalkylated aromatic compound, higher molecular weight polyalkylated aromatic compounds and boron triiluoride, recycling at least a portion of said lunreacted aromatic compound to the alkylation zone, removing desired monoalkylated aromatic compound as product from the process, passing said polyalkylated aromatic compounds in admixture with at least a portion of said unreacted aromatic compound and boron triuoride to a transalkylation zone containing boron trifluoride-modified substantially anhydrous inorganic oxide and therein reacting the polyalkylated aromatic compounds with unreacted aromatic compound, and recycling the eiluent therefrom to said commingling step as aforesaid.

A specilic embodiment of the present invention relates to Ian improved process for the production of ethylbenzene which comprises alkylating benzene with ethylene at alkylation conditions including a temperature of from about 0 to about 250 C., a pressure of rfrom about atmospheric to about 200 atmospheres, a liquid hourly space velocity of from about 0.1 to about 20, in the presence of not more than 10.0 grams of boron triuoride per gram mol of ethylene in an alkylation reaction zone containing a boron tritluoride-.modied substantially anhydrous alumina, recirculating from about 33 to about weight percent of the reacted and unreacted liquid yalkylation zone efliuent from said alkylation reaction zone prior to fractionation back to said alkylation zone, commingling the balance of the eiuent of said alkylation zone with efliuent from a transalkylation reaction zone as hereinafter set eforth, passing the thus commingled effluents to a separationy zone, separating from the separation zone unreacted benzene, desired ethylbenzene, higher molecular weight polyethylbenzenes and boron triuoride, recycling at least a portion of said unreacted benzene to the alkylation zone, removing desired ethylbenzene as product from the process, passing said polyethylbenzenes in admixture with at least a portion of said unreacted benzene and-boron triuoride to a transalkylation zone containing boron trilluoride-modiied substantially anhydrous alumina and from about 0.0002 to about 1.2 grams of boron triuoride per gram mol of polyethyl'benzenes, therein reacting the polyethylbenzenes with unreacted benzene at transalkylation conditions, including a temperature of from about 50 C. to about 300 C., a pressure of from about atmospheric to about 200 atmospheres, and a liquid hourly space velocity of from about 0.1 to about 20 and recycling the eiiluent therefrom to said comuningling step as aforesaid.

Other embodiments of the present invention will become apparent in considering the specifications as hereinafter set forth.

This invention can be most clearly described and illustrated with reference to ith-e attached drawing. While of necessity, certain limitation must be present in such a schematic description, no intention is meant thereby to 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 compound with an olefin-acting compound in the presence of a catalytic amount of boron trifluoride in an alkylation reaction zone containing a boron trifluoride in an alkylation reaction zone containing a boro trifiuoride-modified substantially anhydrous inorganic oxide. In the drawing, this first step is represented as taking place in alkylation reaction zone 4 labeled alkylation. However, the mixture of `boron trifluoride, alkylatable aromatic compound, and olefin-acting compound must be furnished to this reaction zone. In the drawing, the boron trifluoride is represented as being furnished to reaction zone 4 through line 1. The olefin-acting compound is represented as being furnished to reaction zone 4 through lines 2 and 1. The alkylatable aromatic compound is represented as being furnished to reaction zone 4 through lines 3 and 1.

The olefin-acting compound, particularly olefin hydrocarbon, which may be charged to reaction zone 4 via lines 2 and 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 olefinacting compounds are olefinic hydrocarbons which comprise monoolefins containing one double bond per molecule. Monoolens which are utilized as olefin-acting compounds in the process of the present invention are either normally gaseous or normally liquid and include ethylene, propylene, l-butene, 2-butene, isobutylene, and higher molecular weight normally liquid olefins such as the various pentenes, hexenes, heptenes, octenes and mixtures thereof, and still higher molecular weight liquid olefins, the latter including various olefin polymers having from Iabout 9 to about 18 carbon atoms per molecule including propylene trimer, propylene tetramer, propylene pentamer, etc. Cycloolefins such as cyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, etc., may also be utilized. Also included within the scope of the olefin-acting compound are certain substances capable of producing olefinie 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 2 carbon atoms -per molecule. Examples of such `alkyl halides include ethyl fiuoride, npropyl fiuoride, isopropyl fluoride, n-butyl fiuoride, isobutyl fluoride, sec-butyl uoride, tert-butyl fiuoride, etc., ethyl chloride, n-propyl chloride, isopropyl chloride, nbutyl chloride, isobutyl chloride, sec-butyl chloride, tertbutyl chloride, etc., ethyl bromide, n-propyl bromide, isopropyl bromide, n-butyl bromide, isobutyl bromide, secbutyl 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 olefin-acting compound and may be successfully utilized as alkylating agents in the process of this invention.

Olen hydrocarbons, particularly normally-gaseous hydrocarbons, are olefin-acting compounds for use in the process of this invention and are passed to reaction zone 4 via lines 2 and 1. The process of this invention may 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, 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 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 reforming units, coking units, polymerization units, `dehydrogenation 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 suggested by the prior art utilized such large quantities of alkylatable aromatic compound that they have not been economically feasible. This is particularly true for refinery gas streams known as off-gas streams containing relatively lminor quantities of olefin hydocarbons such as ethylene. Thus, it has been possible to catalytically polymerize propylene and/or butenes in the various refinery gas streams, but the off-gases from such processes still contain the utilizable olefin hydrocarbon, ethylene. In addition to containing ethylene in minor quantities, these off-gas streams contain other olefin hydrocarbons, depending upon their source, including propylene andbutenes. A refinery off-gas ethylene stream may contain varying quantities of hydrogen, nitrogen, methane 'and ethane with the ethylene in minor proportion, while a refinery off-gas propylene stream is normally 4diluted with propane and contains the propylene in minor quantity, and a refinery off-gas butene stream is normally diluted with butanes land contains the butenes in minor quantities. A typical analysis in mol percent for utilizable refinery off-gas from a catalytic cracking unit 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, 0.5%. It is readily observed that the total olefin content of this gas stream is 16.6 mol percent and the ethylene content is even lower, namely 10.3%. Such gas streams containing olefin hydrocarbons in minor or dilute quantities are particularly preferred alkylating agents within the broad scope of this invention. It is readily Iapparent that only the olefin content of such streams undergoes reaction at alkylation conditions of the process, 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 gases which do not react may lbe utilized in the separation zone as hereinafter described, or they may be vented from the process with minimum loss of boron triiiuoride and alkylatable aromatic compound due to their vapor pressure at the conditions of temperature and pressure utilized for venting the non-reactive gases.

Many aromatic compounds are utilizable as alkylatable aromatic compounds Within the process of this invention. The preferred aromatic compounds are aromatic hydrocarbons, and the preferred aromatic hydrocarbons are monocyclic aromatic hydrocarbons, that is, benzene hydrocarbons. Suitable aromatic hydrocarbons include benzene, toluene, ortho-Xylene, meta-xylene, para-xylene, ethylbenzene, orthoethyltoluene, meta-ethyltoluene, paraethyltoluene, 1,2,3-trirnethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, normal propylbenzene, isopropylbenzene, or cumene, normal butylbenzene, etc. Higher molecular Weight alkyl aromatic hydrocarbons are also suitable as starting materials and include aromatic hydrocarbons such as a-re produced by the alkylation of the aromatic hydrocarbons with olefin polymers. Such products are frequently referred to in the art as alkylate, and include hexylbenzene, nonylbenzenes, dodecylbenzenes, pentade-cylbenzenes, hexyltoluenes, nonyltoluenes, dodecyltoluenes, pentadecyltoluenes, etc. Very often ialkylate is obtained as a high boiling fraction in which the `alkyl group attached to the aromatic nucleus varies in size yfrom about C9 to C18. Other suitable alkylatable aromatic hydrocarbons include those with two or more aryl groups such as 4diphenyl, diphenylmethane, triphenyl, triphenylmeth-ane, liuorene, stilbene, etc. Examples of lalkyl-atable aromatic hydrocarbons within the scope of this invention utilizable as starting materials and contain ing condensed `aromatic rings include naphthalene, alkyl nap'hthalenes, anthracene, phen-anthrene, naphthacene, rubrene, etc. When the selected alkylated aromatic hydrocarbon is a solid, it may be heated by means not shown so that it passes as a liquid through line 3 as hereinafter described. Of the 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, boron trifluoride is added to alkylation zone 4 conveniently by passage through line 1. Boron triuoride is a gas, boiling point 101 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 1 so that it dissolves at least partially in the alkylatable aromatic compound passing into alkylation zone 4 via lines 3 and 1. The boron trifluoride may also be added as the solution of a gas in a suitable organic solvent. However, in the utilization of such solutions, care must be exercised So that the selective solvent is unreactive with the alkylating agent or normally gaseous olen hydrocarbon utilized in the process. Furthermore, boron trifluoride complexes with many organic compounds, particularly those containing sulfur or oxygen atoms. These complexes, while utilizable as catalysts, are very stable and thus will interfere with the recovery of boron triuoride in the separation zone hereinafter set forth. Therefore, further limit-ation upon the selection of such a solvent is that it be free from atoms or groups which form complexes with boron triliuoride. The amount of boron trifluoride which is -utilized is relatively small. It has been found that the amount necessary can be conveniently expressed as grams of boron trifluoride per gram mol -of olefin-acting compound, preferably olefin. This amount of boron triliuoride will not contain more than 10.0 grams of 'boron triuoride per gram mol of olefin utilized, and preferably not more than 3.0 grams of boron trifluoride per gram mol of olefin utilized. When the amount of boron trifluoride present in the alkylation zone is within the above expressed limit, substantially complete conversion of the oleiin-acting compound is obtained even when the olefin-acting compound is present in what might seem to be minor or dilute quantities in the gas stream. Furthermore, a portion of boron triliuoride then carries over lfrom the alkylation reaction zone to the transalkylation reaction zone yas hereinafter described wherein that amount will be utilized again, or in combination with further added boron triliuoride, to cause the transalkylation reaction to go forward. Thus, double use of the originally added quantity `of boron trifluoride is obtained in this process.

Prior to passage to the alkylation zone, unreacted aromatic compound substantially free of boron compound impurities is combined with the alkylatable aromatic compound via lines 9 and 3 as hereinafter set forth. Recycled unreacted aromatic compound is available in the process since it is preferred to utilize a molar excess of alkylatable aromatic compound over olefin-acting compound, preferably oleiin. This, as disclosed in the prior art, Ihas been found necessary to prevent side reactions from taking place such as for example, polymerization of the olefin-acting compound prior to reaction thereof with the alkylatable Iaromatic compound and to direct the reaction principally to monoalkylation. Any molar excess of alkylatable aromatic compound may be utilized, although best results are obtained when the alkylatable aromatic compound to olefin-acting compound molar ratio is from about 3:1 to about 20:1 or more. It is one of the features of this invention that unreacted aromatic compound substantially free of boron compound impurities is available for recycle to the alkylation reaction zone.

Alkylation zone 4 is of the conventional type with a boron trifluoride-modied inorganic oxide disposed therein inthe reaction zone. The alkylation zone may be equipped with heat transfer means, baffles, trays, heating means, etc. The alkylation reaction zone is preferably of the adiabatic type and thus feed to the alkylation zone will preferably be provided with the requisite amount of heat prior to passage thereof to said alkylation zone. As set forth hereinabove, the alkylation reaction zone is packed with a boron trifluoride-modiied inorganic oxide. The inorganic oxide with which the zone is packed may be selected from among diverse inorganic oxide including alumina, silica, boria, oxides of phosphorous, titanium dioxide, zirconium dioxide, chromia, zinc oxide, magnesia, calcium oxide, silica-alumina, silica-magnesia, silica-alumina-magnesia, 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 previously acid treated), diatomaceous earth, etc. Of the above-mentioned inorganic oxides, gamma-alumina and theta-alumina is most readily modified by boron triiiuoride, and thus the use of one or both of these boron trifluoride-modilied aluminas is preferred. The modification of the inorganic oxide, particularly alumina, may be carried out prior to or simultaneous with the passage of the reactants containing boron trifluoride to the reactor. The exact manner in which the inorganic oxides are modified by boron trifluoride is not completely understood. However, it has been found that the modification is preferably carried out at a temperature at least as high as that selected for use in the particular zone, so that the catalyst in said zone will not exhibit an activity induction period. If the inorganic oxide is modified prior to use, this modification may be carried out in situ in the reactor or in a separate catalyst preparation step. More simply, this modification is accomplished by mere passage of boron trifluoride gas over a bed of the inorganic oxide maintained at the desired temperature. If the modification of the inorganic oxide with Iboron triiiuoride is carried out during the passage of the reactant thereover, the catalyst will exhibit an induction period and thus complete reaction of the alkylating agent with the alkylatable aromatic compound, and transalkylation of the recycled polyalkylated aromatic compounds will not take place for some hours, say up to 12 or more.

The conditions utilized in reaction zone 4 may be varied over a relatively wide range. Thus, the desired alkylation reaction in the presence of the above indicated catalyst may be effected at a temperature of from about 0 or lower to about 300 C. or higher, and preferably from about 0 to about 250 C. The alkylation reaction is usually carried out at a pressure of from about substantially atmospheric, preferably from about 15 to about 200 atmospheres or more. The pressure utilized is usually selected to maintain the` alkylatable aromatic compound in substantially liquid phase. However, 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 as the olefin-acting compound, the ethylene will be dissoved in the liquid phase alkylatable aromatic compound (and alkylated aromatic compound as formed) to the extent governed lby temperature,- pressure, and solubility considerations. However, a portion thereof will always be in the gas phase. The hourly liquid space velocity of the liquid through the alkylation zone may be varied over relatively Wide range of from about 0.1 to about 20 or more.

When the alkylation reaction has proceeded to the desired extent, preferably with conversion of the ole- :lin-acting compound, the product (which may comprise both reacted and unreacted materials) from the alkylation zone which may be termed alkylation zone eiluent is withdrawn from alkylation reaction zone 4 via line 5 so that from about 33 to about 95 weight percent and preferably from about 50 to about 90 weight percent of the liquid alkylation zone effiuent prior to fractionation is recirculated back to said alkylation zone via lines a and 1, as hereinafter described, and the balance of the alkylation zone effluent passes via line 5, to a conimingling step hereinafter described, to separation and fractionation is separation zone 6.

In separation zone 6, unreacted aromatic compound, desired monoalkylated aromatic compound, higher molecular weight polyalkylated aromatic compound and boron trifiuoride are separated by, for example, conventional fractionator-distillation columns or toweers in combination, if desired, with various stripping towers and treating agents. At least a portion of said unreacted aromatic compound is recycled via

lines

9, 3 and 1 to alkylation zone 4 and via

lines

9 and 10 to transalkylation zone 13. Desired monoalkylated aromatic compound is removed as product from the process via line from separation zone 6. Boron trifluoride recovered from separation zone 6 is removed via line 7 where at least a portion of said boron trifluoride is returned to the separation zone and the remainder or net amount is passed via line 8 to

lines

1 and 12 as hereinafter set forth. Polyalkylated aromatic compound is passed to transalkylation zone 13 from separation zone 6 via line 11.

Transalkylation zone 13 is of the conventional type with a boron trifiuoride-modified inorganic oxide disposed therein in the reaction zone. The transalkylation zone may be equipped with heat transfer means, bafiies, trays, heating means, etc. The transalkylation reaction zone is preferably of the adiabatic type and thus feed to the transalkylation zone will preferably be provided with the requisite amount of heat prior to passage thereof to said transalkylation zone. As set forth hereinabove, the transalkylation reaction zone is packed with a boron trifluoridemodified inorganic oxide. The particular boron trifiuoridemodified inorganic oxide is generally selected so that the same material is utilized in both the alkylation reaction zone and the transalkylation reaction zone. Since the conditions necessary for transalkylation are generally more severe than for alkylation, one effective means for increasing severity is by utilization of a bed of boron trifluoridemodified inorganic oxide in transalkylation zone 13 of greater depth than was utilized as in the alkylation zone 4. By the utilization of such greater bed depth, one effectively decreases the liquid hourly space velocity of the combined feed therethrough and thus increases reaction zone severity. As was the case with the conditions utilized in the alkylation reaction zone, the conditions utilized in transalkylation reaction zone 13 may be varied over a relatively wide range, but, as set forth hereinabove, are usually of greater severity than prevail in the alkylation reaction zone. Various means other than increasing catalyst bed depth and decreasing liquid hourly space velocity may be utilized for increasing this reaction zone severity. For example, the mol concentration of boron trifluoride in transalkylation zone 13 may be greater than for alkylation zone 4 by passage of additional boron trifluoride thereto via

lines

1 and 12. Also, when the alkylation reaction zone and transalkylation reaction zone are separate as shown in the drawing, one may effectively increase the temperature by proper placement of heating means before each reactor. The transalkylation reaction may be effected at temperatures of from about 50 to about 350 C. or higher, and preferably from about 50 to about 300 C., and at a pressure of from about substantially atmospheric, preferably from about l5 to about 200 atmospheres. Here again, the pressure utilized is selected to maintain the alkylatable aromatic compound in substantially liquid phase. Referring to the alkylatable aromatic compound, it is preferable to have present in the transalkylation reaction zone from about 1 to about 10 or more, sometimes up to 20, molar proportions per molar proportion of alkyl group in the polyalkylated aromatic hydrocarbon introduced therewith. The hourly liquid space velocity of the liquid through transalkylation zone 13 may be varied over a relatively wide range of from 0.1 to about 20 or more. The alkylatable aromatic compound to polyalkylated aromatic compound ratio in the transalkylation reaction zone can be varied independently of the alkylation reactor rates. W'hen the transalkylation reaction has proceeded to the desired extent so that a suficient quantity of polyalkylated aromatic compounds are converted to monoalkylated aromatic compounds by reaction with alkylatable aromatic compound, the gas-free products from transalkylation zone 13 are withdrawn through line 14 and cornmingled with at least a portion of the gas-free effluent from alkylation zone `4 via line 5 and passed to separation zone 6 for recovery of the desired components therefrom. By the utilization of the commingling step, the unreacted aromatic compound, monoalkylated aromatic compound and polyalkylated aromatic compound are fed directly to the separation zone for separation into the desired components as hereinabove described.

As set forth hereinabove, from about 33 to about 95 weight percent, and preferably from about 50 to about 90 weight percent of the liquid efiiuent of alkylation zone 4 is recirculated back to said alkylation zone via lines 5, 5a and 1 prior to fractionation. An unusual problem was encountered in the commercial application of an alkylationtransalkylation process necessitating the utilization of the present invention. When a relatively concentrated (greater than 50 mol percent) olefin-acting compound feed stream was introduced into such an alkylation-transalkylation process, side reactions occurred so that the overall efficiency of the alkylation-transalkylation decreased. However, when from about 33 to about 95 weight percent of the liquid effluent of the alkylation zone was pumped back to the alkylation zone prior to fractionation; there was a reduction in the side reactions occurring and the efficiency of the operation was improved. Further, there was a reduction in the temperature rise across the catalyst bed in alkylation zone 4 which in turn reduced the unreacted aromatic compound recycle to the alkylation zone. The reduction in temperature rise across the catalyst bed in turn prolonged catalyst life due to the less severe operating conditions as well as provided better and more efficient temperature control of the process. Further, by recirculating this portion of the alkylation zone efiiuent, the overall average molal ratio of benzene rings to C2 groups was unchanged, while the ratio of benzene rings to ethylene gro-ups was drastically reduced at a very low cost.

The following example is introduced for the purpose of illustration only with no intention of unduly limiting the generally broad scope of the present invention. The alkylation-transalkylation flow scheme was set up so that the flow scheme included those components as described with reference to the attached drawing. In the alkylation of benzene with a concentrated ethylene stream (99}-% ethylene) utilizing a boron trifluoride-modified substantially anhydrous inorganic oxide, namely boron trifluoridemodified substantially anhydrous gamma-alumina in both reactions zones, 67 weight percent of the reacted and unreacted liquid alkylation zone eiuent prior to fractionation was recirculated back to alkylation reaction zone 4 via lines 5, 5a and 1 which resulted in the substantial reduction (more than ten-fold) of undesired side products such as butylbenzene which were formed when benzene was alkylated with this concentrated ethylene stream without the process of the present invention.

Further, there was about a 70 C. reduction in temperature rise across the catalyst bed which reduced benzene recycle requirements which in turn prolonged catalyst life as well as provided better temperature control. Also, the ratio of benzene rings to ethylene groups was drastically reduced at very low cost. The alkylation-transalkylation process, utilizing the process of this invention, thus overcame an unusual commercial problem and regaining of high conversion to desired alkylated aromatic compound made the process become more efficient and more economical.

I claim as my invention:

1. An improved process for the production of an aromatic compound which comprises alkylating an alkylatable aromatic compound with an olen-acting compound in the presence of a catalytic amount of boron triuorde in an alkylation reaction zone containing a boron triuoride-modified substantially anhydrous inorganic oxide, recirculating from about 33 to about 95 weight percent of the reacted and unreacted liquid alkylation zone eluent from said alkylation reaction zone prior to fractionation back to said alkylation zone, comminglng the balance of the eiuent of said alkylation zone with eiuent from a transalkylation zone as hereinafter set forth, passing the thus commingled eluents to a separation zone and therein separating unreacted aromatic compound, desired monoalkylated aromatic compound, higher molecular weight polyalkylated aromatic compounds and boron tritluoride, recycling at least a portion of said unreacted aromatic compound to the alkylation zone, removing desired monoalkylated aromatic compound as product from the process, passing said polyalkylated aromatic compounds in admixture With at least a portion of said unreacted aromtic compound and boron trifluoride to a transalkylation zone containing boron triuoride-modified substantially anhydrous inorganic oxide and therein reacting the polyalkylated aromatic compounds with unreacted aromatic compound, and recycling the eluent therefrom to said commingling step as aforesaid.

2. The process of claim 1 further characterized in that said alkylatable aromatic compound is an alkylatable aromatic hydrocarbon, that said olefin-acting compound is an oleiinic hydrocarbon, that said inorganic oxide is a substantially anhydrous alumina, that said alkylation reaction zone contains not more than 10.0 grams of boron trifluoride per gram mol of olefin-acting compound, that the alkylation conditions are a temperature of from about 0 to about 250 C., a pressure of from about atmospheric to about 200 atmospheres, and a liquid hourly space velocity of from about 0.1 to about 20, that said transalkylation zone contains from about 0.0002 to about 1.2 grams of boron trifluoride per gram mol of polyalkylated aromatic compound, and that the transalkylation conditions are a temperature of from about 50 to about 300 C., a pressure of from about atmospheric to about 200 atmospheres, and a liquid hourly space velocity of from about 0.1 to about 20.

3. The process of claim 2 further characterized in that said alkylatable aromatic hydrocarbon is an alkylatable benzene hydrocarbon, that said olelinic hydrocarbon is a normally gaseous oleiin, and that said substantially anhydrous alumina is gamma-alumina.

Cil

4. The process of claim 2 further characterized in that said alkylatable aromatic hydrocarbon is benzene, that said olenic hydrocarbon is ethylene, that said desired monoalkylated aromatic compound is ethylbenzene, and that said higher molecular weight polyalkylated aromatic compounds are polyethylbenzenes.

5. The process of claim 2 further characterized in that said alkylatable aromatic hydrocarbon is benzene, that said olenic hydrocarbon is propylene, that said desired monoalkylated aromatic compound is cumene, that said higher molecular weight polyalkylated aromatic compounds are polypropylbenzenes.

6. The process of claim 2 further characterized in that said alkylatable aromatic hydrocarbon is benzene, that said olenic hydrocarbon is a butene, that said desired monoalkylated aromatic compound is butylbenzene, and that said higher molecular weight polyalkylated aromatic compounds are polybutylbenzenes.

7. The process of claim 3 further characterized in that said alkylatable benzene hydrocarbon is benzene, that said normally gaseous olefin comprises a refinery olf-gas containing a minor quantity of ethylene, that said desired monoalkylated aromatic compound is ethylbenzene, and that said higher molecular weight polyalkylated aromatic compounds are polyethylbenzenes.

8. The process of claim 1 further characterized in that the alkylation and transalkylation zone are confined within separated reaction vessels.

9. The process of claim 1 further characterized in that the quantity of boron triuoride present in the alkylation zone is less than that present in the transalkylation zone.

10. The process of claim 1 further characterized in that the boron triuoride furnished to the transalkylation zone is supplied solely from the alkylation zone.

References Cited UNITED STATES PATENTS 2,995,611 8/1961 Linn et al 260--672 XR 3,200,163 8/1965 Penske 260-671 3,200,164 8/1965 Gerald 260-671 3,205,277 9/ 1965 Pollitzer et al. 260-671 3,296,322 l/l967 Soderquist et al 260-671 DELBERT E. GANTZ, Primary Examiner.

CURTIS R. DAVIS, Assistant Examiner..

U.S. Cl. X.R.