Selective production of 2,6-diethylnaphthalene

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the production of a diethylnaphthalene and more particularly concerns the highly selective production of 2,6-diethylnaphthalene by the transethylation of naphthalene or 2-ethylnaphthalene by 1,4-diethylbenzene, 1,2,4-triethylbenzene, at least one tetraethylbenzene or pentaethylbenzene.
2. Description of the Prior Art
Naphthalene dicarboxylic acids are monomers that are known to be useful for the preparation of a variety of polymers. For example, poly(ethylene 2,6-naphthalate) prepared from 2,6-naphthalene dicarboxylic acid and ethylene glycol has better heat resistance and mechanical properties than polyethylene terephthalate and is useful in the manufacture of films and fibers.
Diethylnaphthalenes are desirable feedstocks for oxidation to the corresponding naphthalene dicarboxylic acids. A known conventional process for producing a naphthalene dicarboxylic acid comprises the oxidation of a diethylnaphthalene 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.
Diethylnaphthalenes can be found in low concentrations in refinery streams as mixtures of some or all of the ten possible diethylnaphthalene isomers. However, separation of these isomers is very difficult and expensive. Consequently, methods for producing specific diethylnaphthalenes or mixtures of two or three specific diethylnaphthalenes in high purity and quality are highly desirable. One such method is disclosed in Japanese Kokai Patent Application Publication No. 61-83137 (Apr. 26, 1986) and is a synthesis involving the transalkylation of naphthalene or a 2-methylnaphthalene in the presence of an aluminum chloride catalyst at 0.degree.-35.degree. C. in the liquid phase to produce a 2,6-dialkylnaphthalene. Suitable alkylating agents are disclosed as including durene, diethylbenzene, triethylbenzene, triisopropylbenzene and isopropylxylene dibutylbenzene. The reported results indicate a relatively low degree of selectivity for the formation of specific dialkylnaphthalenes.
Japanese Kokai Patent Application Publication No. 62-252733 (Nov. 4, 1987) discloses a process for the transethylation of biphenyl with an ethylbenzene to form monoethylbiphenyl and diethylbiphenyl in the presence of a Friedel-Crafts catalyst, such as aluminum chloride, at 70.degree.-150.degree. C. The Japanese patent discloses that reaction temperatures of less than 70.degree. C. delay the reaction rate. The ring positions of the ethyl substituents in the ethylated biphenyl products are not disclosed. Suitable ethylbenzenes 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.
Shimada et al., "Ethylation and Transethylation of Naphthalene," 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.degree.-30.degree. C. The rates of transethylation with ethylxylene isomers were reported to decrease in the order of 1,2-dimethyl-4-ethylbenzene .gtoreq., 1,3-dimethyl-4-ethylbenzene .gtoreq., 1,4-dimethyl-2-ethylbenzene .gtoreq.1,3-dimethyl-5-ethylbenzene.
Thus, no existing method is known for the highly selective production of 2,6-diethylnaphthalene or a mixture of 2,6- and 2,7-diethylnaphthalene by a transethylation process.
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 2,6-diethylnaphthalene or a mixture of 2,6- and 2,7-diethylnaphthalene.
More specifically, it is an object of the present invention to provide an improved method for the highly selective production of 2,6-diethylnaphthalene or a mixture of 2,6- and 2,7-diethylnaphthalene by transethylating naphthalene or 2-ethylnaphthalene under highly regeospecific conditions.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims and upon reference to the accompanying drawings.
SUMMARY OF THE INVENTION
These objects are achieved by an improved method for producing 2,6-diethylnaphthalene, comprising: 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, 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 by weight, in the presence of a Lewis acid catalyst selected from the group consisting of aluminum chloride, aluminum bromide, tantalum chloride, antimony fluoride, and red oil, at a level of from about 0.01 to about 1 mole of the catalyst per mole of the feed (for red oil, based on the content of aluminum chloride content of the red oil) by weight and at a temperature in the range of from about -10.degree. C. to about 100.degree. C.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Naphthalene or 2-ethylnaphthalene or mixtures thereof are suitable for use as the feed in the method of this invention. Preferably the feed comprises 2-ethylnaphthalene. As illustrated in the examples hereinbelow, relative to 1,2- and 1,3-diethylbenzenes, 1,2,3- and 1,3,5-triethylbenzenes, and hexaethylbenzene, polyethylated benzenes having from 2, preferably from 3, up to 5 ethyl substituents on the benzene ring, two of which are pra to one another afford substantially improved yields of 2,6- and 2,7-diethylnaphthalenes in the method of this invention. Thus, 1,4-diethylbenzene, 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 such as the ethylating agent in the method of this invention. Hexaethylbenzene forms an irreversible addition complex with the acid catalyst and therefore does not work in the preferred method of this invention.
The mole ratio of the ethylating agent-to-naphthalene and/or 2-ethylnaphthalene feed is in the range of from about 1:1, preferably from about 2:1, to about 10:1, preferably 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 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.
Certain specific Lewis acids are suitable for use as the catalyst of the method of this invention. Suitable Lewis acid catalysts include aluminum chloride, aluminum, bromide, tantalum pentachloride, antimony pentafluoride, boron trichloride, and "red oil," a complex polar liquid catalyst phase which is synthesized by addition of ethylchloride or bromide to a slurry of aluminum chloride or some other aforesaid suitable Lewis Acid in an aromatic solvent such as benzene, ethylbenzene, or mixed diethylbenzenes or mixed tetraethylbenzenes. Preferably aluminum chloride is the catalyst. The catalyst can be employed either dissolved in a suitable solvent or in an immiscible phase in a hydrocarbon medium.
Other conventional Lewis acids such as antimony chloride, bismuth chloride, ferric chloride, tin chloride, titanium chloride, zinc chloride and zirconium chloride are not effective catalysts in the preferred method of the present invention. Ethyl bromide and ethyl chloride are useful promoters.
The catalyst is employed in the method of this invention at a level in the range of from abou 0.01, preferably from about 0.05, to about 1.0, preferably to about 0.2 mole per mole of the total of naphthalene and 2-ethylnaphthalene employed.
If the reaction is performed continuously or batchwise, the residence time is from about 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.degree. C., preferably from about -5.degree. C., to about 100.degree. C., preferably to about 20.degree. 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.

The present invention will be more clearly understood from the following specific examples.
EXAMPLES 1-35
Except as indicated hereinbelow, each of Examples 1-35 was performed using a 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 Tables 1, 3 and 5 were introduced in the amounts specified in Tables 1, 3 and 5. In each case, the catalyst was introduced last, at which pont the transethylation reaction commenced immediately, and essentially identical reaction conditions were employed in each example. 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 combined weight percent of naphthalene (identified as Np in Tables 2, 4 and 6), and 2-ethylnaphthalene (identified as 2-ENp in Tables 2, 4, and 6) that is converted, the combined weight percent of naphthalene and 2-ethylnaphthalene that is converted selectively to 2,6- and 2,7-diethylnaphthalenes (identified as 2,6-DENp and 2,7-DENp, respectively, in Tables 2, 4, and 6) combined, and the relative concentrations of each of 2,6-diethylnaphthalene and 2,7-diethylnaphthalene in the combined amounts of 2,6-diethylnaphthalene and 2,7-diethylnaphthalene produced in each example.
TABLE 1______________________________________Amounts.sup.1 of Components Employed in Reaction Mixture______________________________________Exam- 2-Ethyl- 1,4-ple Naphtha- naphtha- Aluminum Methylene Diethyl-No. lene lene Chloride Chloride benzene______________________________________1 6.37 6.37 1.27 25 50.942 6.37 6.37 2.54 25 25.473 6.37 6.37 1.27 25 38.204 6.37 6.37 2.54 255 6.37 6.37 2.54 256 3.82 8.91 2.54 257 3.82 8.91 2.54 258 3.82 8.91 2.54 259 3.82 8.91 2.54 2510 3.82 8.91 1.27 1011 12.73 2.54 1.27 2512 12.73 1.27 1013 6.37 6.37 1.27 1014 3.82 8.91 1.27 2515 3.82 8.91 2.54 2316 6.37 6.37 2.54 25______________________________________ 1,2- 1,3- 1,2- 1,2,4- Dimethyl-Example Diethyl- Ethyl- Triethyl- 4-ethylNo. benzene benzene benzene benzene______________________________________234 50.945 50.946 38.207 39.488910111213141516______________________________________ 1,3,5- Tri- Tetra- Penta- Hexa-Example ethyl- ethyl- ethyl- ethyl-No. benzene benzene benzene benzene______________________________________2345678 25.479 38.2010 38.2011 25.4712 38.2013.sup.2 38.2014.sup.2 38.2015 38.2016 12.73______________________________________ Footnotes .sup.1 In millimoles, except in milliliters for methylene chloride .sup.2 A mixture of 72 weight percent of tetraethylbenzenes and 21 weight percent of pentaethylbenzene.
TABLE 2______________________________________Reac- Conversion.sup.2tion of Selectivity.sup.3 to Yield.sup.4 ofTime.sup.1 Np + 2-Np 2,6-DENp 2,7-DENp 2,6-DENp 2,7-DENp______________________________________Example 130 23.6 53.5 38.2 12.63 9.0260 42.4 51.6 37.5 21.88 15.90120 64.0 49.4 37.7 31.62 24.13Example 230 29.3 49.5 42.0 14.50 12.3160 50.7 46.9 44.2 23.78 22.41120 59.6 43.2 41.8 25.75 24.91Example 330 26.0 52.9 39.1 13.75 10.1760 40.3 51.1 39.1 20.59 15.76120 54.5 49.5 38.8 26.98 21.15Example 430 11.4 32.5 31.6 3.71 36.0260 15.3 30.3 32.3 4.64 4.94120 16.6 32.7 37.2 5.43 6.18Example 530 9.4 25.0 30.9 2.35 2.9060 13.3 21.6 36.2 2.87 4.81120 24.0 23.4 28.5 5.62 6.84Example 630 55.8 61.0 30.9 34.03 17.2460 67.7 57.0 31.5 38.59 21.33120 80.1 50.4 30.8 40.37 24.67Example 730 61.5 50.1 37.9 30.81 23.3160 63.1 47.5 38.1 29.97 24.04120 63.4 43.9 38.0 27.83 24.09Example 830 trace -- -- -- --60 1.3 33.1 17.5 0.43 0.23120 4.7 45.8 29.1 2.15 1.37Example 930 38.8 72.4 21.0 28.09 8.1560 76.7 60.2 18.5 46.17 14.19120 94.6 39.0 13.5 36.89 12.77Example 1030 7.0 77.6 21.5 5.43 1.5160 23.2 75.4 20.9 17.49 4.85120 71.6 63.2 19.3 45.25 13.81Example 1130 4.6 82.3 17.7 3.79 0.8160 23.9 65.3 19.0 15.61 4.54120 74.3 58.0 18.9 43.09 14.04Example 1230 trace -- -- -- --60 2.9 60.4 13.1 1.75 0.38120 82.3 31.4 22.8 25.84 18.76Example 1330 trace -- -- -- --60 16.9 73.7 21.3 12.45 3.60120 70.4 56.5 20.0 39.78 14.08Example 1430 2.5 65.3 23.8 1.63 0.6060 6.7 78.4 21.6 5.25 1.45120 30.9 73.8 21.8 22.80 6.73Example 1530 trace -- -- -- --60 11.4 76.3 20.8 8.70 2.37120 45.8 68.0 21.2 31.14 9.71Example 1630 trace -- -- -- --60 trace -- -- -- --120 trace -- -- -- --______________________________________ Footnotes .sup.1 Minutes .sup.2 Weight percent of feed compound converted .sup.3 Weight percent of feed compound converted that is converted to 2,6 or 2,7DENp .sup.4 Product of conversion and selectivity to 2,6 or 2,7DENp
TABLE 3______________________________________Amounts.sup.1 of Components Employed in Reaction Mixture______________________________________ 2-Ethyl- 1,4-Di Tetra-Example Naphtha- naphtha- ethyl- ethyl- MethyleneNo. lene lene benzene benzene Chloride______________________________________17 6.37 6.37 25.47 25.sup.218 6.37 6.37 25.47 25.sup.319 6.37 6.37 25.47 2520 6.37 6.37 25.47 2521 6.37 6.37 25.47 2522 6.37 6.37 25.47 2523 6.37 6.37 25.47 2524 6.37 6.37 25.47 2525 6.37 6.37 25.47 2526 6.37 6.37 25.47 2527 6.37 6.37 25.47 2528 3.82 8.91 38.20 2529 12.73 38.20 1030 12.73 38.20 10.sup.331 12.73 12.73 76.40______________________________________Example Aluminum Tantalum Zinc Stannic TitaniumNo. Bromide Chloride Chloride Chloride Chloride______________________________________17 2.5418 6.3719 2.5420 2.5421 2.5422 2.54232425262728293031______________________________________Exam- Anti- Anti- Ferric Zirco-ple mony mony Chlo- Bismuth nium Red.sup.5No. Chloride Fluoride ride Chloride Chloride Oil______________________________________17181920212223 2.5424 3.5725 8.2726 12.7327 2.5428 1.2729 2.54.sup.430 2.54.sup.431 2.54.sup.4______________________________________ Footnotes .sup.1 In millimoles, except in milliliters for methylene chloride .sup.2 Carbon disulfide instead of methylene chloride .sup.3 Benzene instead of methylene chloride .sup.4 Contains additionally 2.45 3.81 millimoles of ethyl bromide as a promoter .sup.5 Millimoles of aluminum chloride in red oil
TABLE 4______________________________________Reac- Conversion.sup.2tion of Selectivity.sup.3 to Yield.sup.4 ofTime.sup.1 Np + 2-Np 2,6-DENp 2,7-DENp 2,6-DENp 2,7-DENp______________________________________Example 1730 5.2 70.5 29.5 3.67 1.5360 17.5 63.9 36.1 11.18 6.32120 38.5 53.2 44.4 20.48 17.09240 57.8 40.1 40.7 23.18 23.52Example 1830 14.5 45.8 42.4 6.64 6.1460 20.8 42.6 45.0 8.86 9.36120 36.1 33.4 47.5 12.06 17.15Example 1930 25.1 42.9 25.2 10.77 6.3360 35.8 41.6 27.0 14.89 9.67120 45.3 42.6 31.7 19.30 14.36Example 2030 trace -- -- -- --60 trace -- -- -- --120 trace -- -- -- --Example 2130 trace -- -- -- --60 trace -- -- -- --120 trace -- -- -- --Example 2230 trace -- -- -- --60 trace -- -- -- --120 trace -- -- -- --Example 2330 trace -- -- -- --60 trace -- -- -- --120 trace -- -- -- --Example 2430 28.8 52.9 43.0 15.24 12.3860 39.0 49.6 41.7 19.34 16.26120 44.8 46.6 42.4 20.88 19.00Example 2530 trace -- -- -- --60 trace -- -- -- --120 trace -- -- -- --Example 2630 trace -- -- -- --60 trace -- -- -- --120 trace -- -- -- --Example 2730 trace -- -- -- --60 trace -- -- -- --120 trace -- -- -- --Example 2830 trace -- -- -- --60 trace -- -- -- --120 trace -- -- -- --Example 2930 1.4 53.8 12.8 0.75 0.1860 3.3 75.6 19.2 2.49 0.63120 17.5 73.9 21.8 12.93 3.81180 86.3 45.5 20.3 39.27 17.52Example 3030 trace -- -- -- --60 trace -- -- -- --120 2.1 75.6 16.6 1.59 0.35240 29.7 65.6 25.0 19.48 0.741440 89.6 34.1 23.7 30.55 21.24Example 3130 1.4 79.4 18.6 1.11 0.2660 4.8 81.2 18.8 3.90 0.90120 18.2 77.6 19.6 14.12 3.57240 42.7 71.5 21.5 30.53 9.18360 55.7 65.4 21.2 36.43 11.81______________________________________ Footnotes .sup.1 Minutes .sup.2 Weight percent of feed compound converted .sup.3 Weight percent of feed compound converted that is converted to 2,6 or 2,7DENp .sup.4 Product of conversion and selectivity to 2,6 or 2,7DENp
TABLE 5______________________________________Amounts.sup.1 of Components Employed in Reaction Mixture______________________________________ 2-Ethyl- 1,4-Di- Tetra-Example Naphtha- naphtha- ethyl- ethyl- AluminumNo. lene lene benzene benzene Chloride______________________________________17 6.37 6.37 25.4718 6.37 6.37 25.4732 6.37 6.37 25.47 1.2733 12.73 38.20 1.2734 12.73 38.20 1.27______________________________________Exam- Alumi- Carbon 1,2-Di- 1,2-Di-ple num Disul- Chloro- chloro- chloro-No. Bromide fide Benzene benzene ethane form______________________________________17 2.54 2518 6.37 2532 2533 2534 10______________________________________ Footnotes .sup.1 In millimoles, except in milliliters for methylene chloride
TABLE 6______________________________________Reac- Conversion.sup.2tion of Selectivity.sup.3 to Yield.sup.4 ofTime.sup.1 Np + 2-Np 2,6-DENp 2,7-DENp 2,6-DENp 2,7-DENp______________________________________Example 1730 5.2 70.5 29.5 3.67 1.5360 17.5 63.9 36.1 11.18 6.32120 38.5 53.2 44.4 20.48 17.09Example 1830 14.5 45.8 42.4 6.64 6.1560 20.8 42.6 45.0 8.86 9.36120 36.1 33.4 47.5 12.06 17.15Example 3230 37.0 47.8 42.0 17.69 15.5460 47.8 45.4 40.7 21.70 19.4590 51.8 43.1 40.3 22.33 20.88Example 3330 13.2 60.4 26.6 7.97 2.7260 42.7 60.6 23.6 25.88 10.0890 78.9 48.8 22.2 38.50 17.52Example 3430 trace 0 -- -- -- --60 trace 0 -- -- -- --90 64.5 48.3 18.2 31.15 18.26Example 35______________________________________ Footnotes .sup.1 Minutes .sup.2 Wt. % of feed compound conv. .sup.3 Wt. % of feed compound conv. that is converted to 2,6 or 2,7DENp .sup.4 Product of conv. & select. to 2,6 or 2,7DENp
Comparison of the results from Examples 1-16, 32 and 33 illustrates that the superiority of tetra- and pentaethylbenzenes as selective ethylating agents and the superiority within the same compound class of p-substituted isomers over their non-parasubstituted isomers. Comparison of the results from Examples 1-3 illustrates that the effect of the ratio of ethylating agent-to-feedstock compounds on activity, with higher such ratios affording higher activity and reaction rates. Comparison of the results from Examples 9-12 illustrates (1) higher catalytic activity at higher catalyst loadings but with little change in selectivity and (2) higher selectivity and yield with 2-ethylnaphthalene present in the feed. Comparison of the results from Examples 13-14 illustrates that a mixture of tetraethylbenzenes prepared by the ethylation of a lower ethylbenzene with ethylene is a suitable ethylating agent for the selective production of 2,6-diethylnaphthalene.
Example 15 illustrates that pentaethylbenzene, like tetraethylbenzenes, is a highly selective ethylating agent in the method of the present invention. Comparison of the results from Examples 17-31 illustrates that Lewis acids that are at least as acidic as aluminum chloride exhibit significant activity for the production of 2,6-diethylnaphthalene. Comparison of the results from Examples 17-18 illustrates that soluble cataysts in nonpolar solvents are effective in the method of this invention for the production of 2,6-diethylnaphthalene. The results of Examples 19 and 24 illustrate that tantalum, pentachloride and antimony pentafluoride, although less active than aluminum chloride, are more selective than aluminum chloride and afford high ratios of 2,6- to 2,7-diethylnaphthalene.
Comparison of the results from Examples 25-28 illustrates that ferric chloride, bismuth chloride and zirconium chloride are inactive under the reaction conditions employed. Comparison of the results from Examples 29-31 illustrates that "red oil"--complexes of aluminum chloride with an alkyl halide (or with hydrogen chloride and an olefin) and an aromatic compound are highly selective catalysts in the present invention.
Examples 17, 18, 29-31 and 32-35 illustrate that the method of the present invention can be carried out as either (1) a homogeneous catalytic reaction in a solvent in which both the catalyst and reactants are dissolved or (2) a heterogeneous catalytic reaction with either a nonpolar solvent or no solvent, in which case the catalyst comprises a polar liquid phase--for example red oil--which exhibits little or no solubility for the reactants.
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 alternatives are considered equivalents and within the spirit and scope of the present invention.

Number	Name	Date
2739991	Hervert	Mar 1956
2837583	Lien et al.	Jun 1958
4288646	Olah	Sep 1981

Selective production of 2,6-diethylnaphthalene

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