Abstract:
A method for the highly selective production of a p-alkylethylbenzene or 4,4&#39;-alkylethylbiphenyl involving the use of a Lewis acid or Bronsted acid alkylation catalyst and a highly regiospecific ethylating agent.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to the production of a p-alkylethylbenzene or a 4,4&#39;-alkylethylbiphenyl and more particularly concerns the highly selective production of p-ethyltoluene or p-diethylbenzene by the transethylation of benzene, toluene or ethylbenzene or the production of 4,4&#39;-diethyl- or methylethylbiphenyl by the transethylation of biphenyl, 4-methylbiphenyl or 4-ethylbiphenyl. 
     2. Description of the Prior Art 
     Dialkylbiphenyls are useful as high temperature heat transfer media. Dialkylbiphenyls, as well as dialkylbenzenes, are also desirable feedstocks for oxidation to the corresponding biphenyl or benzene dicarboxylic acids, which in turn are monomers that are known to be useful for the preparation of a variety of polymers. A known conventional process for producing a benzene dicarboxylic acid or a biphenyl dicarboxylic acid comprises the oxidation of a dialkylbenzene or a dialkylbiphenyl, respectively, with oxygen in the liquid phase in an acetic acid solvent at an elevated temperature and pressure and in the presence of a catalyst comprising cobalt, manganese and bromine components. In such cases, it is highly desirable that the alkyl groups on the benzene or biphenyl ring are methyl or ethyl. 
     Thus, there is a need for p-dialkylbenzenes and 4,4&#39;-dialkylbiphenyls and for highly selective processes for making specific p-dialkylbenzenes or 4,4&#39;-dialkylbiphenyls. Because of the great difficulty and expense of separating a p-dialkylbenzene or a 4,4&#39;-dialkylbiphenyl from its other dialkylbenzene isomers or other dialkylbiphenyl isomers, respectively, methods for producing a specific p-dialkylbenzene or 4,4&#39;-dialkylbiphenyl or mixtures of two or three specific p-dialkylbenzenes or 4,4&#39;-dialkylbiphenyls in high purity and quality are especially desirable. One such method is disclosed in Japanese Kokai Patent Application Publication No. 62-252733 (Nov. 4, 1987) and is a process for the transethylation of biphenyl with an ethylbenzene or ethyltoluene to form monoethylbiphenyl and diethylbiphenyl in the presence of a Friedel-Crafts catalyst, such as aluminum chloride, at 70°-150° C. This published Japanese patent application discloses that reaction temperatures of less than 70° C. delay the reaction rate. The ring positions of the ethyl substituents in the ethylated biphenyl products are not disclosed. Suitable ethylbenzenes and ethyltoluenes include ethylbenzene, diethylbenzene, triethylbenzene, tetraethylbenzene, other ethyl-substituted benzenes, ethyltoluene, diethyltoluene and other ethyl-substituted toluenes. Polyethylbenzenes containing relatively small amounts of monoethylbenzene, triethylbenzene and tetraethylbenzene can also be used advantageously. 
     Japanese Patent Application 35/391/48, published on Oct. 18, 1989, discloses a method for the preparation of ethyldiphenylethane or diethyldiphenylethane by the transethylation of diphenylethane with polyethylbenzene(s) in the presence of a Friedel-Crafts catalyst at 0°-150° C. Preferred catalysts are aluminum chloride, aluminum bromide and boron trifluoride. Transethylation of 1,1-diphenylethane by this method produces either 1-phenyl-1-ethylphenylethane, 1-phenyl-1-diethylphenylethane or 1,1-bis(ethylphenyl)ethane. The ring positions of the ethyl substituents in the ethylated products are not disclosed. 
     With regard to a different aromatic ring system, Olah et al., &#34;Alkylation of Naphthalene with Alkyl Halides,&#34; Journal of American Chemical Society, 98:7, pages 1839-1842 (Mar. 31, 1976), disclose that theretofore there was no clear understanding of directive effects and selectivities for the Friedel-Crafts alkylation of naphthalene. Olah et al. disclose poor selectivities and/or low conversions for the direct methylation of naphthalene or 2-methylnaphthalene using simple methylating agents such as methyl halides or methanol to provide beta-substituted products such as 2,6-dimethylnaphthalenes. 
     Since then, Japanese Kokai Patent Application Publication No. 61-83137 (Apr. 26, 1986) discloses a synthesis involving the transalkylation of naphthalene or 2-methylnaphthalene in the presence of an aluminum chloride catalyst at 0°-35° C. in the liquid phase to produce a 2,6-dialkylnaphthalene. Suitable alkylating agents are disclosed as including durene, diethylbenzene, triethylbenzene, triisopropylbenzene and isopropylxylene and dibutylbenzene. The reported results indicate a relatively low degree of selectivity for the formation of specific dialkylnaphthalenes. Furthermore, it is specifically stated that the disclosed alkylation method must be performed at 0°-35° C., preferably room temperature, and that the higher the reaction temperature, the lower the selectivity for the formation of beta-alkyl-substituted naphthalene and especially 2,6-dialkylnaphthalene. In addition, although this published patent application specifically mentions durene (1,2,4,5-tetramethylbenzene) as an example of an alkylation agent, it contains actual examples that illustrate only the use as alkylating agents in the method disclosed therein of polyalkylbenzenes where the alkyl groups are larger than methyl groups and indicates as follows that polyalkylbenzenes with alkyl groups other than methyl groups afford benefits in the method disclosed therein: &#34;Polyalkylbenzenes with ethyl, propyl, or butyl groups with high-carbon alkyl groups have high reaction rates . . . &#34; Moreover, this published Japanese patent application states that, when the naphthalene is solid at the reaction temperature, a solvent such as a paraffin or cycloparaffin should be employed. This published patent application discusses the use of halogenated alkyls in the alkylation of naphthalenes as a prior art method which did not produce a beta-alkyl naphthalene with the desired selectivity. 
     Shimada et al., &#34;Ethylation and Transethylation of Naphthalene,&#34; Bulletin of the Chemical Society of Japan, Vol. 48 (II), pages 3306-3308 (November 1975), disclose the transethylation of naphthalene by ethylbenzene or ethylxylenes to form monoethylnaphthalenes in the presence of an aluminum chloride catalyst at 20°-30° C. The rates of transethylation with ethylxylene isomers were reported to decrease in the order of 1,2-dimethyl-4-ethylbenzene≧1,3-dimethyl-4-ethylbenzene &gt;1,4-dimethyl-2-ethylbenzene ≧1,3-dimethyl-5-ethylbenzene. 
     Thus, until recently, no existing method was known for the highly selective production of 2,6-diethylnaphthalene or a mixture of 2,6- and 2,7-diethylnaphthalenes by a transethylation process. Then Hagen et al., U.S. Pat. No. 4,873,386, which issued on Oct. 10, 1989, disclosed a method for producing 2,6-diethylnaphthalene, which comprises: reacting in the liquid phase at least one of naphthalene or 2-ethylnaphthalene as the feed with at least one of 1,4-diethylbenzene, 1,2,4-triethylbenzene, or at least one tetraethylbenzene or pentaethylbenzene as the ethylating agent, in the presence of a Lewis acid catalyst selected from the group consisting of aluminum chloride, aluminum bromide, boron trichloride, tantalum pentachloride, antimony pentafluoride, and red oil at a level of from about 0.01 to about 1 mole of the catalyst (for red oil, based on the aluminum chloride content of the red oil) per mole of the feed and at a temperature in the range of from about -10° C. to about 100° C. In particular, Hagen et al., disclose that 1,2,3,4- and 1,2,3,5-tetraethylbenzenes, as well as 1,2,4,5-tetraethylbenzene (durene), are useful ethylating agents, but that hexaethylbenzene is not. Hagen et al. further disclose that 2,6-diethylnaphthalene is formed at a higher selectivity and yield when 2-ethylnaphthalene is transethylated and that pentaethylbenzene and any tetraethylbenzene are the preferred ethylating agents. However, Hagen et al. neither disclose nor suggest that the method disclosed therein would be useful for the selective ethylation to produce p-alkylethylbenzene or 4,4&#39;-alkylethylbiphenyl. 
     OBJECTS OF THE INVENTION 
     It is therefore a general object of the present invention to provide an improved method for the highly selective production of p-alkylethylbenzene or 4,4&#39;-alkylethylbiphenyl. 
     More specifically, it is an object of the present invention to provide an improved method for the highly selective production of p-ethyltoluene, p-diethylbenzene, 4,4&#39;-diethylbiphenyl, or 4,4&#39;-methylethylbiphenyl by ethylation under highly regiospecific conditions. 
     Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims. 
     SUMMARY OF THE INVENTION 
     These objects are achieved by an improved method for producing (a) p-alkylethylbenzene, where the alkyl group is methyl or ethyl, from benzene, toluene, ethylbenzene, or a mixture of benzene and ethylbenzene as the feed or (b) a 4,4&#39;-alkylethyldiphenyl, where the alkyl group is methyl or ethyl, from biphenyl, 4-methylbiphenyl, 4-ethylbiphenyl or a mixture of biphenyl and 4-ethylbiphenyl as the feed, comprising: reacting the feed in the liquid phase with at least one of 1,2,4-triethylbenzene, at least one tetraethylbenzene or pentaethylbenzene as the ethylating agent, at a level of from about 1 to about 10 moles of the ethylating agent per mole of the feed, in the presence of a Lewis acid or Bronsted acid alkylation catalyst or mixture thereof that is more acidic than ferric chloride and at least as acidic as ferric bromide at a level of from about 0.01 to about 1 mole of the catalyst per mole of the feed and at a temperature in the range of from about -10° C. to about 100° C. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Benzene, toluene, ethylbenzene, or a mixture of benzene and ethylbenzene is suitable for use as the feed in the method of this invention to make a p-alkylethylbenzene. Biphenyl, 4-methylbiphenyl, 4-ethylbiphenyl, or a mixture of biphenyl and 4-ethylbiphenyl is suitable for use as the feed in the method of this invention to make a 4,4&#39;-alkylethylbiphenyl. Preferably, a feed comprising toluene or ethylbenzene is employed to make p-alkylethylbenzene or a feed comprising 4-methylbiphenyl or 4-ethylbiphenyl is employed to make 4,4&#39;-alkylethylbiphenyl in the method of this invention. The feed must be either dissolved in a suitable solvent as described below or must be liquid at the reaction temperature employed. 
     As indicated in the examples hereinbelow, relative to the diethylbenzenes and 1,2,3- and 1,3,5-triethylbenzenes, polyethylated benzenes having from 3 up to 5 ethyl substituents on the benzene ring, two of which are para to one another, afford substantially improved yields of the desired p-alkylethylbenzene or 4,4&#39;-alkylethylbiphenyl in the method of this invention. Thus, 1,2,4-triethylbenzene, any tetraethylbenzene, pentaethylbenzene, and mixtures thereof are the only suitable ethylating agents in the method of this invention. Since all tetraethylbenzenes have at least one pair of ethyl substituents that are in ring positions that are located para to each other, all tetraethylbenzenes are suitable ethylating agents in the method of this invention, and therefore, mixtures of tetraethylbenzene isomers need not be separated and can be used as the ethylating agent in the method of this invention. Hexaethylbenzene forms an irreversible addition complex with the acid catalyst, and therefore, is not an effective ethylating agent in the method of this invention. Preferably, a tetraethylbenzene, and more preferably 1,2,4,5-tetraethylbenzene, is the ethylating agent in the method of this invention. 
     The mole ratio of the ethylating agent-to-benzene, toluene, ethylbenzene, biphenyl, 4-methylbiphenyl or 4-ethylbiphenyl, mixture of benzene and ethylbenzene, or mixture of biphenyl and 4-ethylbiphenyl is in the range of from about 1:1, preferably from about 2:1, to about 10:1, preferable to about 5:1, in the method of this invention. 
     The transethylation reaction of the present invention is conducted in the liquid phase in the presence or absence of a solvent. Any liquid that is inert under the reaction conditions employed and serves as an effective solvent for the reactants and products is suitable for use in the method of this invention. Suitable solvents include halocarbons, such as methylene chloride, chlorobenzene, 1,1-dichloroethane, 1,2-dichloroethane, and chloroform, or carbon disulfide, benzene, cyclohexane, and n-octane. Solvents which are basic and bind irreversibly with the catalyst are not suitable. Such unsuitable solvents include ketones, aldehydes, ethers, esters and alcohols. Preferably, the solvent is methylene chloride. If a solvent is employed, the weight ratio of solvent-to-feed compound is in the range of from about 1:1, preferably from about 2:1, to about 15:1, preferably to about 8:1. 
     Lewis acids and Bronsted acids or mixtures thereof that are conventionally used as alkylation catalysts and that are more acidic than ferric chloride and at least as acidic as ferric bromide, and preferably at least as acidic as aluminum chloride, and that do not decompose under the conditions employed in the method of this invention are suitable for use as the catalyst in the method of this invention. Suitable Lewis acid catalysts include aluminum chloride, aluminum bromide, tantalum pentachloride, antimony pentafluoride, boron trichloride, ferric bromide, sulfonated zirconia, trifluoromethanesulfonic acid, and &#34;red oil,&#34; a complex polar liquid catalyst phase which is synthesized by addition of ethyl chloride or bromide or hydrogen chloride or bromide to a slurry of aluminum chloride or some other aforesaid suitable Lewis acid in an aromatic solvent such as benzene, methylbenzene, ethylbenzene, mixed dimethylbenzenes, mixed diethylbenzenes, mixed tetramethylbenzenes or mixed tetraethylbenzenes and which forms a separate liquid phase below the phase containing the feed. Preferably, aluminum chloride or red oil containing aluminum chloride is the catalyst. Other conventional Lewis acids, such as antimony chloride, bismuth chloride, ferric chloride, tin chloride, titanium chloride, and zinc chloride, are not such effective catalysts in the method of the present invention. 
     The catalyst can be employed as a separate immiscible layer such as the aforementioned red oil, or it can be dissolved with the reactants and products in an organic solvent such as methylene chloride or chlorobenzene. Thus, depending upon the selection of solvent for the catalyst, the feed, ethylating agent and catalyst can be present in a single liquid phase, or the feed and catalyst can be present in separate liquid phases. In the alternative, the catalyst can be in the form of a solid, for example, aluminum chloride deposited or intercalated with graphite. The catalyst is employed in the method of this invention at a level in the range of from about 0.01, preferably from about 0.05, to about 1.0, preferably to about 0.2 mole per mole of the total content of benzene, toluene, ethylbenzene, biphenyl, 4-methylbiphenyl, 4-ethylbiphenyl, or mixture thereof. 
     If the reaction is performed continuously or batchwise, the residence time is from 0.1, preferably from about 1, to about 10, preferably to about 5 hours. The reaction temperature is in the range of from about -10° C., preferably from about -5° C., to about 100° C., preferably to about 20° C. The reaction pressure must be sufficiently high to maintain the reactants and products in the liquid phase at the particular reaction temperature employed and generally is in the range of from about 0.5, preferably from about 0.8, to about 10, preferably to about 5, atmospheres gauge. 
     Preferably, when a polar solvent is not used, a hydrogen halide, such as hydrogen chloride, or an alkyl, alkylene or alkylidene halide is employed as a promoter in the method of the present invention. Typically, such alkyl, alkylene, or alkylidene halides include a methyl halide, such as methyl chloride, or a methylene, ethylene, or ethylidene halide. The promoter is employed at a level of from about 0.1, preferably from about 0.5, up to about 100, preferably up to at least about 2 moles per mole of catalyst (for red oil, based on the aluminum chloride content of the red oil). When the solvent is an alkyl or alkylene halide, it also serves as a promoter in the method of the invention. 
    
    
     The present invention will be more clearly understood from the following specific examples: 
     EXAMPLES 1-47 
     Except as indicated hereinbelow, each of Examples 1-47 was performed using 250 milliliter, 3-neck, round-bottom flask equipped with a magnetic stirrer, purged with nitrogen and cooled in an ice bath. The components of the reaction mixture that are identified in Table 1 were introduced in the amounts and under the reaction conditions specified in Table 1. In each case, the catalyst was introduced last, at which point the transethylation reaction commenced immediately. Twenty-four hours after the catalyst was introduced, methanol, in a volume that was approximately twice the volume of the reaction medium, was introduced to quench the reaction. The product mixture was then analyzed to determine the weight percent of biphenyl, 4-methylbiphenyl or 4-ethylbiphenyl (identified as BP, 4-MBP or 4-EBP, respectively, in Table 4) that is converted, (&#34;Conversion&#34;), the &#34;Yield&#34; or mole percent of BP,4-MBP or 4-EBP that is converted selectively to 4,4&#39;-diethylbiphenyl or 4,4&#39;-methylethylbiphenyl (identified as 4,4&#39;-DEBP and 4,4&#39;-MEBP, respectively), and the &#34;Selectivity&#34; or relative mole percent of 4,4&#39;-DEBP or 4,4&#39;-MEBP in the combined amounts of products produced in each example. The Yield is also the quotient obtained by dividing 100 into the product of the Conversion multiplied by the Selectivity. In Tables 1 and 3, TeEB means a mixture of tetraethylbenzenes. 
     Comparison of Examples 1-3 illustrates that high yields of the desired product are achieved even at relatively low reaction temperatures at which the reaction proceeds relatively slower, provided that the reaction is allowed to proceed long enough. Comparison of the results of Examples 6-8, 18 and 22 illustrates that the highest yields of the desired product are attained at reaction temperatures of 25°-30° C. 
     Comparison of the results of Examples 13 and 18 illustrates that relatively higher yields and selectivities are attained at relatively higher catalyst concentrations than at lower catalyst concentrations. The results of Examples 41-44 illustrate that strong solid acids such as sulfonated zirconia are effective catalysts in the method of this invention. 
     Comparison of the results of Examples 11-13 and 33-35 illustrates that the yield and selectivity for producing the desired product increase as the number of ethyl groups on the ethylating agent increases from 2 to 4 and as the ring positions of such groups with respect to one another changes from meta to ortho and then to para. Comparison of the results of Examples 13 and 15-17 illustrate that the maximum yield and selectivity for producing the desired product occur when the mole ratio of ethylating agent to feed compound is about 2:1. 
     Comparison of the results of Examples 2, 3, 21 and 28-31 illustrates that, when a halocarbon solvent is not employed, relatively little conversion occurs unless a promoter is employed. 
     
                                           TABLE 1__________________________________________________________________________Example      Ethylating Agent                   CatalystNo.   Feed   Compound              Amount.sup.1                   Compound                           Amount.sup.1__________________________________________________________________________ 1    BP     TeEB  2.0  AlCl.sub.3.sup.5                            0.4 2    BP     TeEB  2.0  AlCl.sub.3.sup.5                            0.4 3    BP     TeEB  2.0  AlCl.sub.3.sup.5                            0.4 4    4-MBP  TeEB  2.0  AlCl.sub.3.sup.5                            0.4 5    4-MBP  TeEB  2.0  AlCl.sub.3.sup.5                            0.4 6    BP     TeEB  3.0  AlCl.sub.3.sup.5                            0.4 7    BP     TeEB  3.0  AlCl.sub.3.sup.5                            0.4 8    BP     TeEB  3.0  AlCl.sub.3.sup.5                            0.4 9    4-EBP  TeEB  1.5  AlCl.sub.3.sup.5                            0.410    BP     TeEB  3.0  AlCl.sub.3.sup.5                            0.411    4-EBP  P-DEB 2.0  AlCl.sub.3                            1.012    4-EBP  1,2,4-TEB              2.0  AlCl.sub.3                            1.013    4-EBP  1,2,4,5-TeEB              2.0  AlCl.sub.3                            1.014    BP     TeEB  4.0  AlCl.sub.3                            1.015    4-EBP  TeEB  1.0  AlCl.sub.3                            1.016    4-EBP  TeEB  3.0  AlCl.sub.3                            1.0__________________________________________________________________________ Footnotes .sup.1 moles per mole of feed .sup.2 dissolves reactants, product and catalyst .sup.3 dissolves reactants and product, but not catalyst .sup.4 milliliters of solvent per the actual number of moles of feed used .sup.5 red oil catalyst, with a separate liquid phase formed of AlCl.sub.3, formed when HCl or EtBr (ethylene bromide) is passed through the C.sub.6 H.sub.12 phase 
    
     
         Example Reaction      Solvent      PromoterNo.   Temp. (°)      Compound            Amount.sup.4                   Compound                         Amount__________________________________________________________________________ 1     0-20      C.sub.6 H.sub.12.sup.3            80/.2  EtBr   .4.sup.1 2    20   C.sub.6 H.sub.12.sup.3            80/.2  EtBr   .4.sup.1 3    30   None  0/.18  HCl   Sat&#39;d 4    20   C.sub.6 H.sub.12.sup.3            25/.01 HCl   Sat&#39;d 5    20   C.sub.6 H.sub.12.sup.3            25/.01 HCl   Sat&#39;d 6    20   C.sub.6 H.sub.12.sup.3            55/.13 EtBr   .4.sup.1 7    25-30      C.sub.6 H.sub.12.sup.3            55/.13 HCl   Sat&#39;d 8    40   C.sub.6 H.sub.12.sup.3            50/.12 HCl   Sat&#39;d 9    20   C.sub.6 H.sub.12.sup.3            110/.27                   HCl   Sat&#39;d10    15   C.sub.6 H.sub.12.sup.3            80/.13 HCl   Sat&#39;d11     0   CH.sub.2 Cl.sub.2.sup.2            20/.0025                   solvent                         20/.0025.sup.412     0   CH.sub.2 Cl.sub.2.sup.2            25/.0025                   solvent                         25/.0025.sup.413     0   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.414     0   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.415     0   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.416    0    CH.sub.2 Cl.sub.2.sup.2            25/.0025                   solvent                         25/.0025.sup.4__________________________________________________________________________ Footnotes .sup.1 moles per mole of feed .sup.2 dissolves reactants, product and catalyst .sup.3 dissolves reactants and product, but not catalyst .sup.4 milliliters of solvent per the actual number of moles of feed used .sup.5 red oil catalyst, with a separate liquid phase formed of AlCl.sub. when EtBr (ethylene bromide) or HCl (hydrogen chloride) is passed through the C.sub.6 H.sub.12 phase .sup.6 milliliters per milliliter per hour, liquid hourly space velocity. .sup.7 milligrams per millimole of feed 
    
     
         Example      Ethylating Agent                   CatalystNo.   Feed   Compound               Amount                   Compound                           Amount__________________________________________________________________________17    4-EBP  TeEB  4    AlCl.sub.3                            1.018    4-EBP  TeEB  2    AlCl.sub.3                            0.219    4-EBP  TeEB  2    AlCl.sub.3                            0.220    4-EBP  TeEB  1    AlCl.sub.3                            0.521    4-EBP  TeEB  1    AlCl.sub.3                            0.3322    4-EBP  TeEB  2    AlCl.sub.3                            0.223    4-EBP  TeEB  2    AlCl.sub.3                            0.224    4-EBP  TeEB  2    AlCl.sub.3                            0.225    4-EBP  TeEB  3    AlCl.sub.3                            0.226    BP     TeEB  4    AlCl.sub.3                            0.127    4-EBP  TeEB  2    AlCl.sub.3                            0.228    4-EBP  TeEB  2    AlCl.sub.3                            0.129    BP     TeEB  4    AlCl.sub.3                            0.130    4-EBP  TeEB  2    AlCl.sub.3                            0.231    BP     TeEB  4    AlCl.sub.3                            0.232    4-EBP  TeEB  2    AlCl.sub.3                            0.233    BP     o-DEB 2    AlCl.sub.3                            0.234    BP     m-DEB 2    AlCl.sub.3                            0.2__________________________________________________________________________Example Reaction      Solvent      PromoterNo.   Temp. (°C.)      Compound            Amount.sup.4                   Compound                         Amount__________________________________________________________________________17     0   CH.sub.2 Cl.sub.2.sup.2            25/.0025                   solvent                         25/.0025.sup.418     0   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup. 419    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.420     0   CH.sub.2 Cl.sub.2.sup.2            30/.005                   solvent                         30/.005.sup.421     0   CH.sub.2 Cl.sub.2.sup.2            30/.0075                   solvent                         30/.0075.sup.422    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.423    reflux      CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.424    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   EtBr   1.0.sup.125    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.426    20   None  0/.005 None   027    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.428    20   None  0/.005 None   029    20   None  0/.005 None   030    20   None  0/.005 EtBr   1.0.sup.131    20   None  0/.005 EtBr   1.0.sup.132    20   CH.sub.2 Cl.sub.2.sup.2            1/.005 solvent                          1/.005.sup.433    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.434    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.4__________________________________________________________________________Example      Ethylating Agent                   CatalystNo.   Feed   Compound              Amount.sup.1                   Compound                           Amount.sup.1__________________________________________________________________________35    BP     p-DEB 2.0  AlCl.sub.3                            0.236    4-EBP  TeEB  2.0  AlCl.sub.3                            0.137    BP     TeEB  4.0  AlCl.sub.3                            0.138    4-EBP  TeEB  2.0  AlCl.sub.3                            0.239    BP     TeEB  4.0  AlCl.sub.3                            0.240    BP + 4-EBP        TeEB  3.3  AlCl.sub.3                            0.1741    4-EBP  TeEB  2.0  ZrO.sub.2 /SO.sub.4.sup.-2                            1.25.sup.642    4-EBP  TeEB  2.0  ZrO.sub.2 /SO.sub.4.sup.-2                            0.625.sup.643    4-EBP  TeEB  2.0  ZrO.sub.2 /SO.sub.4.sup.-2                            1.25.sup.644    BP     TeEB  4.0  ZrO.sub.2 /SO.sub.4.sup.-2                            0.938.sup.645    BP     TeEB  4.0  ZrO.sub.2 /SO.sub.4.sup.-2                            0.938.sup.646    4-EBP  TeEB  2.0  ZrO.sub.2 /SO.sub.4.sup.-2                           40.sup.747    BP + 4-EBP        TeEB  3.3  ZrO.sub.2 /SO.sub.4.sup.-2                           33.3.sup.7__________________________________________________________________________Example Reaction      Solvent      PromoterNo.   Temp. °C.      Compound            Amount.sup.4                   Compound                         Amount__________________________________________________________________________35    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   None   036    20   None  0/.005 EtBr   .1.sup.137    20   None  0/.005 EtBr   .1.sup.138    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   EtBr   .2.sup. 139    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.440    20   CH.sub.2 Cl.sub.2.sup.2             30/.0025 +                   solvent                          30/.0025 +            .0005        .0005.sup.441    20   CH.sub.2 Cl.sub.2.sup.2            24/.0025                   solvent                         24/.0025.sup.442    20   CH.sub.2 Cl.sub.2.sup.2            24/.0025                   solvent                         24/.0025.sup.443    20   CH.sub.2 Cl.sub.2.sup.2            24/.0025                   solvent                         24/.0025.sup.444    20   CH.sub.2 Cl.sub.2.sup.2            12/.0025                   solvent                         12/.0025.sup.445    20   None  0/.010 none   046    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.447    20   CH.sub.2 Cl.sub.2.sup.2             30/.0025 +                   solvent                         30/.0025.sup.4 +            .0005        .0005.sup.4__________________________________________________________________________ 
    
     
                       TABLE 2______________________________________Ex-ample Reaction   Con-    Desired ProductNo.   Time (min) version Compound                            Yield Selectivity______________________________________ 1    420        4.56    4,4&#39;-DEBP                            4.56  100 660        16.90           16.25 96.1 960        32.71           30.66 93.8 1500       57.17           51.52 98.11 3240       72.70           63.08 86.76 2     90        7.68    4,4&#39;-DEBP                            7.54  98.13 180        26.91           25.39 94.32 300        44.41           40.73 91.71 540        51.49           46.92 91.13 2070       67.53           59.35 87.89 3    120        13.89   4,4&#39;-DEBP                            13.36 96.23 240        33.65           31.33 93.09 540        57.84           51.63 89.25 960        68.50           59.76 87.25 1530       78.88           66.13 83.84 4     30        10.59   4,4&#39;-MEBP                            10.42 98.36  60        20.32           19.93 98.06 180        51.08           47.32 92.65 870        84.68           65.82 77.73 5     60        10.14   4,4&#39;-MEBP                            10.14 100.00 120        21.31           21.08 98.91 180        33.19           32.18 96.96 360        44.08           42.16 95.64 720        61.70           57.09 92.53 1320       81.69           70.92 86.81 6     90        13.62   4,4&#39;-DEBP                            13.22 97.02 150        33.40           31.51 94.33 330        60.70           55.29 91.10 630        66.69           60.04 90.03 690        93.50           60.68 64.90 7     30        25.14   4,4&#39;-DEBP                            23.48 93.40  60        45.59           41.80 91.67 120        60.99           54.32 89.06 210        72.83           63.11 86.66 870        89.70           72.78 81.14 1260       94.65           69.28 73.20 8     30        10.27   4,4&#39;-DEBP                            9.83  95.70  60        21.06           19.66 93.39 120        29.48           26.93 91.33 300        40.73           35.40 86.93 600        64.89           50.68 78.10 1120       80.80           60.68 75.10 9     45        6.03    4,4&#39;-DEBP                            6.03  100.00  90        16.21           15.84 97.74 510        62.89           58.22 92.57 1050       75.42           67.86 89.9710    120        3.88    4,4&#39;-DEBP                            3.88  100.00 180        9.88            9.70  98.19 300        23.33           22.07 94.62 480        39.90           36.36 93.45 960        53.60           49.42 92.19 1495       67.03           60.41 90.1111     30        56.3    4,4&#39;-DEBP                            39.9  70.9  60        49.2            40.8  83.0  90        58.2            34.2  58.8 210        60.4            30.5  50.4 1200       76.6            39.3  51.412     30        48.9    4,4&#39;-DEBP                            45.7  93.5  60        63.3            57.5  90.9 120        70.9            64.4  90.8 240        75.7            65.7  86.813     30        30.1    4,4&#39;-DEBP                            27.2  90.8  60        61.7            55.1  89.3 120        77.7            71.2  91.6 210        90.2            86.9  96.4 240        89.4            86.1  96.314     30        13.76   4,4&#39;-DEBP                            4.75  34.52  90        44.25           30.3  68.60 150        55.96           40.69 72.71 210        74.21           58.50 78.83 420        94.52           70.32 74.4015     30        18.1    4,4&#39;-DEBP                            15.8  87.2  60        40.9            33.7  82.3  90        56.6            47.4  83.7 120        65.7            54.9  83.6 420        88.7            70.7  79.716     30        31.4    4,4&#39;-DEBP                            22.8  72.8  60        54.3            42.7  78.7 120        73.3            60.3  82.3 180        84.8            72.1  85.1 420        97.4            75.8  77.917     30        30.3    4,4&#39;-DEBP                            22.8  75.3  60        49.9            39.8  79.8   90       63.3            50.8  80.2 180        84.6            62.3  73.6 420        98.2            51.2  52.218     30        6.7     4,4&#39;-DEBP                            2.2   32.8  60        12.2            7.1   58.2  90        23.1            17.2  74.5 180        35.1            29.2  83.1 240        42.1            36.3  86.3 420        54.0            49.0  90.7 1200       63.1            50.8  80.519     30        34.8    4,4&#39;-DEBP                            27.6  79.4  60        49.7            42.4  85.4  90        57.1            51.5  90.2 240        69.4            65.4  94.3 1200       80.3            63.2  78.820     30        6.4     4,4&#39;-DEBP                            2.8   43.1  90        26.3            20.1  76.3 180        49.7            39.0  78.5 240        60.1            46.9  78.0 420        86.7            60.0  69.221     30        11.0    4,4&#39;-DEBP                            6.9   62.6  90        33.4            25.9  77.4 180        54.1            43.8  80.9 240        62.0            50.2  80.9 420        85.0            63.4  74.622     24        76.3    4,4&#39;-DEBP                            60.4  79.2  42        77.2            61.0  79.123     30        9.2     4,4&#39;-DEBP                            3.3   36.4  60        16.0            9.7   60.8  90        15.5            9.6   62.1 120        16.0            10.3  64.524     30        5.4     4,4&#39;-DEBP                            0.8   14.1  90        18.5            11.4  61.6 180        59.6            47.9  80.4 420        77.3            61.1  79.1 1200       80.3            66.3  82.625    No Reaction            0       4,4&#39;-DEBP                            0     026    No Reaction            0       4,4&#39;-DEBP                            0     027     90        77.3    4,4&#39;-DEBP                            60.9  78.928    No Reaction            0       4,4&#39;-DEBP                            0     029    No Reaction            0       4,4&#39;-DEBP                            0     030    No Reaction            0       4,4&#39;-DEBP                            0     031    No Reaction            0       4,4&#39;-DEBP                            0     032    No Reaction            0       4,4&#39;-DEBP                            0     033     30        11.8    4,4&#39;-DEBP                            5.2   43.8  90        21.1            10.2  48.1 180        30.8            15.6  50.7 360        36.9            18.1  49.034    30         5.3     4,4&#39;-DEBP                            0.7   4.4  60        10.1            3.0   29.4  90        15.9            5.6   35.5 120        24.0            8.9   37.2 180        31.7            12.4  39.2 360        43.8            18.4  42.035     30        32.6    4,4&#39;-DEBP                            20.8  63.9  60        47.7            30.0  62.9 120        58.9            34.2  58.1 240        63.6            35.2  55.4 360        66.3            21.9  33.136    No Reaction            0       4,4&#39;-DEBP                            0     037    No Reaction            0       4,4&#39;-DEBP                            0     038    No Reaction            0       4,4&#39;-DEBP                            0     039     30        25.1    4,4&#39;-DEBP                            7.0   27.8  60        34.4            13.9  40.5 120        40.8            21.5  52.8 240        51.1            29.5  57.8 1440       59.0            35.5  60.140     30        33.7    4,4&#39;-DEBP                            17.5  52.0  60        45.5            27.9  61.3 120        59.2            38.6  65.2 240        70.7            47.8  67.6 1440       80.2            53.1  66.241     60        34.3    4,4&#39;-DEBP                            29.5  85.9 120        17.7            14.6  82.3 180        10.9            8.2   74.9 240        10.1            8.1   90.242     15        79.3    4,4&#39;-DEBP                            63.3  79.8  75        74.4            61.7  82.9 135        35.2            29.4  83.6 195        18.9            15.3  80.8 255        13.1            10.8  82.443     15        60.2    4,4&#39;-DEBP                            51.6  85.7 135        36.7            31.9  86.8 195        22.8            19.3  84.5 255        18.9            15.4  81.244     15        6.6     4,4&#39;-DEBP                            1.9   28.945    No Reaction            0       4,4&#39;-DEPP                            0     046    No Reaction            0       4,4&#39;-DEBP                            0     047    No Reaction            0       4,4&#39;-DEBP                            0     0______________________________________ 
    
     EXAMPLES 48-65 
     Except as indicated hereinbelow, each of Examples 48-65 was performed using 250 milliliter, 3-neck, round-bottom flask equipped with a magnetic stirrer, purged with nitrogen and cooled in an ice bath. The components of the reaction mixture that are identified in Table 3 were introduced in the amounts and under the reaction conditions specified in Table 3. In each case, the catalyst was introduced last, at which point the transethylation reaction commenced immediately. Twenty-four hours after the catalyst was introduced, methanol, in a volume that was approximately twice the volume of the reaction medium, was introduced to quench the reaction. The product mixture was then analyzed to determine the weight percent of toluene or ethylbenzene (identified as TOL and EB, respectively, in Table 3) that is converted (&#34;Conversion&#34;), the &#34;Yield&#34; or mole percent of TOL or EB that is converted selectively to p-methylethylbenzene or p-diethylbenzene (identified as p-MEB or p-DEB, respectively), and the &#34;Selectivity&#34; or relative mole percent of p-MEB or p-DEB in the combined amounts of products produced in each example. The Yield is also the quotient obtained by dividing 100 into the product of the Conversion multiplied by the Selectivity. 
     When ethylbenzene is the feed, comparison of the results of Examples 48-50 illustrates that the use of reactants at a mole ratio of 1.5:1 of ethylating agent-to-feed compound affords the highest yield and selectivity of the desired product, and comparison of the results of Examples 54-56 illustrates that the use of a higher catalyst concentration affords a higher yield and selectivity for the desired product. By contrast, when methylbenzene is the feed, comparison of the results of Examples 57-59 illustrates that comparable yields and selectivities of the desired product are obtained even when the mole ratio of ethylating agent-to-feed compound was varied from 1:1  to 2:1, and comparison of the results of Examples 63-65 illustrates that similar yield and selectivities of the desired product are obtained even when the concentration of the catalyst was varied from a high level to a low level. 
     Comparison of the results of Examples 49, 52, 58 and 60 illustrates that the use of tetraethylbenzene instead of triethylbenzene as the ethylating agent affords greater yields and selectivities of the desired product regardless of whether ethylbenzene or methylbenzene is the feed compound. Comparison of the results of Examples 57, 58, 61, and 62 illustrates that, even though the reaction rate is higher at higher reaction temperatures, the yields and selectivities for the desired product obtained at lower reaction temperatures are comparable to those obtained at higher reaction temperatures if the reaction is allowed to proceed for a long enough period. 
     Comparison of the results of Examples 50 and 57 illustrates that comparable yields and selectivities of the desired product are obtained when the reaction system involves a single liquid phase in a methylene chloride solvent or two liquid phases with no solvent. 
     
                                           TABLE 3__________________________________________________________________________Example      Ethylating Agent                   CatalystNo.   Feed   Compound              Amount.sup.1                   Compound                           Amount.sup.1__________________________________________________________________________48    EB     TeEB  2.0  AlCl.sub.3.sup.5                           0.449    EB     TeEB  1.0  AlCl.sub.3.sup.5                           0.450    EB     TeEB  1.5  AlCl.sub.3.sup.5                           0.451    EB     TeEB  2.0  AlCl.sub.3.sup.5                           0.452    EB     1,2,4-TEB              1.0  AlCl.sub.3.sup.5                           0.453    EB     TeEB  2.0  AlCl.sub.3.sup.5                           0.454    EB     TeEB  2.0  AlCl.sub.3                           1.055    EB     TeEB  2.0  AlCl.sub.3                           0.256    EB     TeEB  1.5  AlCl.sub.3                           0.557    TOL    TeEB  2.0  AlCl.sub.3.sup.5                           0.458    TOL    TeEB  1.0  AlCl.sub.3.sup.5                           0.459    TOL    TeEB  1.5  AlCl.sub.3.sup.5                           0.460    TOL    1,2,4-TEB              1.0  AlCl.sub.3.sup.5                           0.461    TOL    TeEB  1.0  AlCl.sub.3.sup.5                           0.462    TOL    TeEB  2.0  AlCl.sub.3.sup.5                           0.463    TOL    TeEB  2.0  AlCl.sub.3.sup.5                           0.264    TOL    TeEB  2.0  AlCl.sub.3                           1.065    TOL    TeEB  2.0  AlCl.sub.3                           1.0__________________________________________________________________________ Footnotes .sup.1 moles per mole of feed .sup.2 dissolves reactants, product and catalyst .sup.3 dissolves reactants and product, but not catalyst .sup.4 milliliters of solvent per mole of feed .sup.5 red oil catalyst, with a separate liquid phase formed of AlCl.sub. when HCl is passed through the C.sub.6 H.sub.12 phase 
    
     
         Example Reaction      Solvent      PromoterNo.   Temp. (°C.)      Compound            Amount.sup.4                   Compound                         Amount__________________________________________________________________________48    20   C.sub.6 H.sub.12.sup.3            20/.047                   HCl   sat&#39;d49    20   C.sub.6 H.sub.12.sup.3            20/.141                   HCl   sat&#39;d50    20   None  0/.267 EtBr  0.4.sup.151     0   None  0/.196 EtBr  0.4.sup.152    20   C.sub.6 H.sub.12.sup.3            20/.062                   HCl   sat&#39;d53     0   None  0/.134 EtBr  0.4.sup.154     0   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.455    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.456    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.457    20   None  0/.892 HCl   sat&#39;d58    20   None  0/.892 HCl   sat&#39;d59    20   None  0/.089 HCl   sat&#39;d60    20   C.sub.6 H.sub.12            20/.062                   HCl   sat&#39;d61     0-15      None  0/.268 EtBr  0.4.sup.162     0   None  0/.196 EtBr  0.4.sup.163    20   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.464     0   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.465     0   CH.sub.2 Cl.sub.2.sup.2            30/.0025                   solvent                         30/.0025.sup.4__________________________________________________________________________ Footnotes .sup.1 moles per mole of feed .sup.2 dissolves reactants, product and catalyst .sup.3 dissolves reactants and product, but not catalyst .sup.4 milliliters of solvent per the actual number of moles of feed used .sup.5 red oil catalyst, with a separate liquid phase formed of AlCl.sub. when HCl or EtBr is passed through the C.sub.6 H.sub.12 phase 
    
     
                       TABLE 4______________________________________Ex-ample Reaction   Con-    Desired ProductNo.   Time (min) version Compound                            Yield Selectivity______________________________________48    30         17.00   p-DEB   14.39 84.65 60         37.68           31.57 37.68 90         57.78           47.88 82.87 130        76.26           61.27 81.52 225        94.66           71.28 75.3049    30         67.75   p-DEB   38.19 56.38 60         72.95           37.25 51.06 90         75.05           35.36 47.12 360        80.06           26.21 32.7450    30         44.09   p-DEB   36.07 81.80 60         79.81           63.15 79.13 90         91.87           68.83 74.92 240        96.34           55.41 57.5251    30         9.91    p-DEB   7.68  77.56 60         16.96           13.87 81.76 90         23.45           19.57 83.47 135        33.98           28.88 84.99 225        59.98           49.83 83.08 480        95.37           70.10 73.5152    30         67.77   p-DEB   26.60 39.25 60         68.94           24.76 35.92 90         69.56           23.43 33.68 210        70.50           21.23 30.12 405        71.97           21.30 29.6053    30         0       p-DEB   0     0 60         0               0     0 90         0               0     054    30         0.8     p-DEB   0.6   74.2 60         11.7            9.8   83.7 120        87.0            67.8  78.0 180        92.7            67.5  72.8 240        97.5            43.5  44.655    30         0       p-DEB   0     0 60         0               0     0 90         0               0     056    30         26.6    p-DEB   20.0  75.3 60         90.5            66.7  73.6 90         92.5            61.7  66.7 120        93.4            57.3  61.3 240        95.3            47.1  49.5 1440       96.7            38.2  39.557    30         23.50   p-MEB   17.4  73.9 60         68.83           50.4  73.3 90         88.51           50.6  57.2 165        98.12           28.75 29.3058    30         15.87   p-MEB   14.0  88.4 60         44.25           38.6  87.2 90         71.01           56.5  79.6 210        94.18           26.18 27.8059    30         8.81            6.48  73.5 60         24.56   p-MEB   20.78 84.6 90         52.29           43.36 82.9 120        77.92           56.93 73.07 180        96.28           41.45 43.0560    30         72.70   p-MEB   31.1  42.8 60         76.28           27.1  35.6 90         78.54           24.3  30.9 210        82.38           18.3  22.2 360        85.25           14.8  17.461    30         4.29    p-MEB   2.11  49.0 60         5.03            2.97  59.0 120        7.13            4.60  64.5 405        52.98           42.49 80.21 535        63.18           49.83 78.87 655        84.82           58.78 69.30 775        92.56           51.20 55.3262    30         7.24    p-MEB   4.6   63.7 60         11.59           8.1   69.8 150        31.49           25.0  79.3 240        43.12           35.92 83.30 300        50.98           41.79 81.96 360        58.33           46.86 80.33 575        87.48           47.41 54.2063    30         1.50    p-MEB   1.5   100 90         22.40           36.5  81.0 120        45.10           20.0  89.3 180        72.4            53.3  73.6 240        84.0            53.4  66.564    30         0       p-MEB   0     0 90         3.00            3.0   100.0 120        62.1            45.6  73.5 180        80.7            53.1  65.8 240        91.9            48.0  52.3 360        98.6            12.6  12.865    30         68.6    p-MEB   49.8  72.6______________________________________ 
    
     From the above description, it is apparent that the objects of the present invention have been achieved. While only certain embodiments have been set forth, alternative embodiments and various modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered equivalents and within the spirit and scope of the present invention.