1.  Field of the Invention
This invention relates to a process for the alkylation of aromatic hydrocarbons with C.sub.2 to C.sub.4 olefins to produce mono-alkylaromatic compounds and a mixture of poly-alkylaromatic compounds and to the transalkylation of poly-alkylaromatic compounds to produce additional mono-alkylaromatic compounds. 
2.  Description of the Prior Art
Processes for the alkylation and/or transalkylation of aromatic compounds with a Friedel-Crafts type catalyst (i.e., aluminum chloride, sulfuric acid, liquid and supported phosphoric acid and the like) are known and are currently practiced commercially.  The above-described catalysts, however, suffer from the disadvantage of corrosion of process apparatus and waste disposal problems.  Also, the supported phosphoric acid must be kept optimally hydrated, imposing an extra control function. 
In addition to the above catalysts, the use of activated clays and solid zeolite catalysts has been suggested as suitable for the alkylation and transalkylation of aromatics to form alkylated aromatic compounds.  In using solid zeolite catalysts, two principal modes of operation have been described.  First, the catalyst may be utilized as a powder slurried in the liquid reactants.  This procedure is disadvantageous because it generally requires a batch as opposed to a continuous operation, and additionally requires expensive filtration or centrifuging units to separate the catalyst from product and unreacted compounds.  A more commercially feasible technique involves the use of a fixed-bed reactor containing relatively large catalyst particles through which the reacants are continuously passed. 
A process for the alkylation and transalkylation of benzene with olefinic compounds is disclosed in U.S. Pat.  No.  3,819,735 to Argento et al.  which relates to a liquid alkylation catalyst and process for alkylating benzene with propylene or n-butene to form cumene or secondary butylbenzene.  Additionally, the reference teaches a transalkylation reaction for producing secondary butylbenzene or cumene from the corresponding dialkylbenzene.  The catalyst comprises a liquid, aluminum chloride which forms a liquid complex with the reactants.  The liquid complex is described as having excellent room temperature stability. 
Another process for the alkylation of aromatic hydrocarbons is disclosed in U.S. Pat.  No.  4,169,111 to Wight which relates to a process for the manufacture of ethylbenzene.  In particular, benzene is alkylated with ethylene in the presence of a crystalline zeolite catalyst to produce ethylbenzene and polyethylbenzenes.  At least a portion of the diethylbenzene fraction is recycled to the alkylation zone while the remainder thereof plus higher polyethylbenzenes are subjected to a transalkylation reaction. 
U.S. Pat.  No.  3,417,148 to Fishel relates to an alkylation process wherein an aromatic compound, for example, benzene, toluene, xylene, etc.,  is alkylated with an olefin-acting compound utilizing a catalyst consisting of a crystalline aluminosilicate chemically combined with a metal subfluoride vapor.  The olefin-acting compounds include olefins, acetylenic hydrocarbons, alcohol, esters, ethers, and alkyl halides.  Metal subfluorides are described as aluminum monofluoride, silicon difluoride, etc. 
Another alkylation process is disclosed in U.S. Pat.  No.  3,586,729 to Juguin et al.  which relates to a process and catalyst for alkylating aromatic hydrocarbons and/or for producing oligomers from olefins.  In particular, an olefin and an aromatic hydrocarbon are contacted under alkylation conditions with a catalyst consisting of agglomerates or microballs impregnated with phosphoric anhydrides.  The microballs have a specific surface area of about 200 M.sup.2 /g to about 300 M.sup.2 /g.  The reference mentions the production of ethylbenzene, cumene, and butylbenzene by alkylation. 
U.S. Pat.  No.  3,205,276 to Toland discloses a process for producing secondary butylbenzene from ethylene and benzene, by reacting benzene and ethylene in the presence of a polymerization-alkylation catalyst comprising aluminum metal and the reaction product of aluminum metal with a halide. 
Ethylene and an aromatic compound, for example, benzene, are heated in the presence of a halide, such as hydrogen chloride, and an excess of metallic aluminum.  The major product of this reaction is secondary butyl benzene. 
A process for the alkylation or transalkylation of aromatic compounds is disclosed in U.S. Pat.  No.  4,070,407 to Haag et al.  which relates to an alkylation or transalkylation reaction wherein aromatic hydrocarbons are contacted with an alkylating or transalkylating agent in a reaction zone using a catalyst consisting of a crystalline aluminosilicate zeolite.  Suitable alkylating agents are olefins, alkyl halides and alcohols.  Transalkylation agents include alkyl or poly-alkylaromatic hydrocarbons. 
As can readily be determined from the above, there is an ongoing search for new and more efficient processes and catalysts for producing alkylated aromatics from olefins and aromatic compounds. 
Accordingly, it is an object of the present invention to provide an improved process for alkylating and transalkylating aromatic compounds. 
Another object of the present invention is to provide a process for separating mono-alkylated aromatic compounds from poly-alkylated aromatic compounds prior to transalkylation, thus reducing the amount of aromatic compound and catalyst needed to efficiently transalkylate poly-aromatic compounds. 
Other objects and advantages of the invention will be apparent from the following description.