COUPLING PROCESS

Abstract: An ethylenically-unsaturated aliphatic hydrocarbon is coupled with an aromatic hydrocarbon having an active hydrogen on a saturated alpha-carbon in the presence of a supported alkali metal as a catalyst and 10-100 mol %, based on the amount of the alkali metal catalyst, of an oxide of sodium or potassium as a co-catalyst. In pre­ ferred embodiments of the invention, the ethylenically-­ unsaturated aliphatic hydrocarbon is an alkene of 2-20 carbons, such as ethene or propene; the active hydrogen-­ containing aromatic hydrocarbon is an alkylbenzene, such as toluene; the alkali metal is potassium or a potassium alloy; and the co-catalyst is sodium oxide.

Description: This invention relates to a process for coupling an ethylenically-unsaturated aliphatic hydrocarbon with an aromatic hydrocarbon having an active hydrogen on a saturated alpha-carbon. As disclosed, e.g., in U.S. Patent 4,179,580 (Cobb), European Specification 128001A (Kudoh et al.), and Eberhardt et al., Journal of Organic Chemistry , Vol. 30, pp. 82-84 (1965), it is known that supported alkali metals are useful as catalysts in the coupling of ethylenically-unsaturated hydrocarbons with aromatic hydrocarbons having an active hydrogen on a saturated alpha-carbon. For example, European Specification 128001A discloses the use of a sodium catalyst on a carrier of the formula K₂O. x Al₂O₃ where x is 0.5 to 11. The supported alkali metals are more effective than the corresponding unsupported alkali metals in such reactions but are still not as effective as might be desired. Claff et al., Journal of Organic Chemistry , Vol. 20, pp. 440-442 and 981-986 (1955) disclose the use of sodium oxide in the metalation of toluene by potassium. As object of this invention is to provide a novel process for coupling an ethylenically-unsaturated aliphatic hydrocarbon with an aromatic hydrocarbon having an active hydrogen on a saturated alpha-carbon. Another object is to provide such a process which utilizes a supported alkali metal as a catalyst. A further object is to provide such a process in which the reaction rate and product yield are increased. These and other objects are attained by coupling an ethylenically-unsaturated aliphatic hydrocarbon with an aromatic hydrocarbon having an active hydrogen on a saturated alpha-carbon in the presence of a supported alkali metal as a catalyst and 10-100 mol %, based on the amount of the alkali metal catalyst, of sodium oxide or potassium oxide as a co-catalyst. The ethylenically-unsaturated aliphatic hydrocarbon which is coupled with the aromatic hydrocarbon in the practice of the invention may be any of the ethylenically-unsaturated aliphatic hydrocarbons that are known to be useful in such reactions, such as ethene, propene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, 3-methyl-1-butene, 2-methyl-2-butene, 1-hexene, 2-hexene, 3-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-2-pentene, 1-heptene, 2-heptene, 2-octene, 4-nonene, 1-decene, 2-decene, 1-dodecene, 3-tetradecene, 5-hexadecene, 6-methyl-4-heptadecene, 1-eicosene, butadiene, isoprene, and 2,5-dimethyl-1,5-hexadiene. However, it is generally a hydrocarbon corresponding to the formula QQ′C=CTT′, in which Q, Q′, T, and T′ are independently selected from hydrogen and alkyl and alkenyl groups of up to 20 carbons; and it is apt preferably to be an alkene of up to 20 carbons. Particularly preferred ethylenically-unsaturated hydrocarbons are ethene and propene. The aromatic hydrocarbon having an active hydrogen on a saturated alpha-carbon may be any such compound that is known to be useful in such reactions, such as toluene, ethylbenzene, n-propylbenzene, isopropylbenzene, n-butylbenzene, sec-butylbenzene, isobutylbenzene, n-eicosylbenzene, o-, m-, and p-xylenes, o-, m-, and p-ethyltoluenes, 1,3,5-trimethylbenzene, 1,2,4,5- and 1,2,3,5-tetramethylbenzenes, p-diisopropylbenzene, 1- and 2-methylnaphthalenes, dimethylnaphthalenes, 1-ethyl-4-n-octadecylnaphthalene, 1,4-di-n-pentylnaphthalene, 1,2,3,4-tetrahydronaphthalene, indan, cyclohexylbenzene, methylcyclohexylbenzene, and diphenylmethane. However, it is generally a hydrocarbon corresponding to the formula RR′R″CH, in which R is an aryl group of up to 20 carbons and R′ and R″ are independently selected from hydrogen and alkyl and aryl groups of up to 20 carbons; and it is apt preferably to be an alkylbenzene having one or more aralkyl groups. A particularly preferred aromatic hydrocarbon is toluene. The mol ratio of ethylenically-unsaturated hydrocarbon to aromatic hydrocarbon varies with the particular reactants employed and the products desired, particularly since the aromatic hydrocarbon may have one or more active hydrogens, and it may be desired to react the ethylenically-unsaturated hydrogen with only one or with more than one active hydrogen in the aromatic hydrocarbon. It is frequently preferred to employ the reactants in the stoichiometric amounts appropriate for the preparation of the desired product. However, either reactant can be used in excess. As in Cobb, the alkali metal employed as a catalyst may be lithium, sodium, potassium, rubidium, or cesium; and it appropriately has its surface area increased by being finely divided or liquid as well as by being supported on any suitable support material, such as diatomaceous earth, activated charcoal, granular coke, silicon, pumice, porcelain, quartz, steel turnings, copper shot, sodium carbonate, and potassium carbonate. However, it is preferably potassium or a potassium alloy, e.g., a sodium/potassium alloy. The amount of alkali metal used is a catalytic amount, generally 2-10 mol %, based on the amount of either of the reactants when they are employed in equimolar amounts or on the amount of the major reactant when they are not utilized in equimolar amounts. The co-catalyst of the invention is an oxide of sodium or potassium. It is preferably sodium oxide, since potassium oxide is dangerous to make and is therefore less likely to be available. Like the alkali metal, it is used in finely divided form; and it may be incorporated into the reaction mixture as the oxide, or it may be generated in situ, e.g., by oxidizing supported sodium or potassium. The amount of co-catalyst used is 10-100 mol %, based on the amount of the alkali metal catalyst. The reaction is conducted by heating a mixture of the ethylenically-unsaturated aliphatic hydrocarbon, the active hydrogen-containing aromatic hydrocarbon, the supported catalyst, and the co-catalyst under substantially anhydrous conditions at a suitable temperature, generally 100-300°C., preferably 175-200., to couple the reactants. It is generally conducted in the absence of a diluent or in the presence of an excess of the active hydrogen-containing aromatic hydrocarbon as the sole diluent. However, an inert diluent can be used if desired. Exemplary of such diluents are liquid alkanes, cycloalkanes, and aromatic hydrocarbons, such as pentane, hexane, isooctane, cyclohexane, naphthalene, decahydronaphthalene, and white oils. The process of the invention proceeds at a faster rate and provides higher product yields with fewer by-products than comparable processes conducted in the absence of the co-catalyst, and it is particularly advantageous as a means of alkylating alkylaromatic compounds, especially alkylbenzenes, to form compounds useful in various applications such as solvents, internal standards, intermediates for polymers, pharmaceuticals, or pesticides. The following examples are given to illustrate the invention: COMPARATIVE EXAMPLE A A suitable reaction vessel was charged with 4.9g of diatomaceous earth, 92g (1.0 mol) of toluene, C₁₁ paraffin as a GC standard, and 1.0g of NaK (an alloy having a K content of 78% by weight). The mixture was stirred and heated to 185°C in 15 minutes, after which propene was charged until a pressure of 2758 kPa was reached; and the propene pressure was then maintained at 2689-2758 kPa throughout the reaction. Periodically the stirrer was stopped to allow the solids to settle; and samples were drawn, allowed to cool to room temperature, and subjected to GC analysis to determine the amounts of unreacted toluene, desired isobutylbenzene (IBB) product, and n-butylbenzene (NBB), methylindan (MI), and methylpentene (MP) by-products. Finally the reaction was stopped by cooling the reactor to 75°C, venting most of the propene, and injecting 10 mL of methanol under nitrogen pressure to quench the catalyst. The results of the analyses are shown below. Time (min.) Mols x 100 Toluene IBB NBB MI MP 0 100 0 0 0 0 40 100 0 0 0 0 80 93.0 3.5 0.2 0.46 0.4 120 78.3 11.3 0.53 2.56 1.2 160 66.0 17.4 0.81 4.12 1.7 200 62.1 21.2 0.98 4.90 2.0 240 60.3 22.8 1.05 5.18 2.2 COMPARATIVE EXAMPLE B Comparative Example A was repeated except that the diatomaceous earth support was replaced by 6.6g of sodium oxide having a particle size of -325 mesh. The analytical results are shown below. Time (min.) Mols x 100 Toluene IBB NBB MI MP 0 100 0 0 0 0 40 91.9 8.8 1.11 0.06 0.6 80 83.0 13.1 1.60 0.09 0.9 160 72.2 22.1 2.45 0.17 1.6 EXAMPLE I Comparative Example A was repeated except that 2.2 mols of sodium oxide having a particle size of -325 mesh was mixed with the diatomaceous earth and ground together with it prior to charging them to the reaction vessel. The analytical results are shown below. Time (min.) Mols x 100 Toluene IBB NBB MI MP 0 100 0 0 0 0 80 84.0 5.2 0.57 0.12 0.5 120 72.0 20.8 2.25 0.39 2.4 160 50.4 37.5 4.17 0.62 4.4 200 39.8 49.7 5.14 0.73 6.0 240 29.5 57.2 5.57 0.82 7.1 EXAMPLE II Example I was repeated except that the amount of sodium oxide was increased to 4.3 mmols. The analytical results are shown below. Time (min.) Mols x 100 Toluene IBB NBB MI MP 0 100 0 0 0 0 80 90.2 7.8 0.95 0.13 0.8 120 71.7 23.9 2.95 0.35 2.7 160 50.8 41.0 4.83 0.48 4.9 200 35.8 53.3 5.89 0.56 7.0 240 27.4 60.5 6.30 0.61 8.9 EXAMPLE III Example I was repeated except that the amount of sodium oxide was increased to 8.6 mmols. The analytical results are shown below. Time (min.) Mols x 100 Toluene IBB NBB MI MP 0 100 0 0 0 0 80 84.9 9.3 1.13 0.13 1.1 120 68.2 25.5 3.22 0.30 2.8 160 48.1 42.5 5.09 0.35 5.5 200 33.3 54.1 6.10 0.38 7.6 240 25.0 61.1 6.45 0.43 9.6 EXAMPLE IV Example III was repeated except that the amount of NaK used was 1.3g. The analytical results are shown below. Time (min.) Mols x 100 Toluene IBB NBB MI MP 0 100 0 0 0 0 80 87.9 11.5 1.44 0.14 0.9 120 65.2 29.4 3.78 0.31 3.0 160 46.5 47.5 5.85 0.35 5.7 200 27.9 60.7 6.96 0.35 8.4 240 18.6 69.0 7.35 0.35 11.5 EXAMPLE V Example III was repeated except that the sodium oxide employed had a particle size of +80 to -325 mesh. The analytical results are shown below. Time (min.) Mols x 100 Toluene IBB NBB MI MP 0 100 0 0 0 0 80 84.0 9.1 0.94 0.28 0.8 120 66.6 24.7 2.71 0.56 2.2 160 53.4 37.0 3.81 0.67 3.5 200 42.3 45.7 4.46 0.80 4.3 240 36.0 51.4 4.76 0.91 5.2 EXAMPLE VI Example III was repeated except that the NaK was replaced with 1.0g of potassium. The analytical results are shown below. Time (min.) Mols x 100 Toluene IBB NBB MI MP 0 100 0 0 0 0 40 99.6 1.7 0.18 0 0.1 80 85.6 11.5 1.48 0.15 1.2 120 63.1 29.0 3.76 0.32 3.1 160 43.4 46.1 5.68 0.36 5.3 200 30.1 57.8 6.61 0.38 7.5 240 21.5 63.4 6.94 0.42 9.2 EXAMPLE VII Example III was repeated except that the propene pressure was about 2069 kPa. The analytical results are shown below. Time (min.) Mols x 100 Toluene IBB NBB MI MP 0 100 0 0 0 0 120 80.5 18.0 2.29 0.20 1.0 160 64.9 33.4 4.13 0.26 1.8 200 47.6 45.8 5.40 0.31 2.8 240 39.3 52.9 5.89 0.37 3.4 EXAMPLE VIII Example III was repeated except that the reaction temperature was 165°C. The analytical results are shown below. Time (min.) Mols x 100 Toluene IBB NBB MI MP 0 100 0 0 0 0 120 97.7 3.4 0.38 0 0.4 160 93.9 7.4 0.90 0.06 0.9 200 86.2 13.4 1.70 0.14 1.9 240 77.1 20.5 2.63 0.21 2.9

Claims: A process for coupling an ethylenically-unsaturated aliphatic hydrocarbon with an aromatic hydrocarbon having an active hydrogen on a saturated alpha-carbon by contacting the said unsaturated aliphatic hydrocarbon with the said aromatic hydrocarbon in the presence of a supported alkali metal as catalyst, characterized in that the contact is conducted in the presence of 10-100 mol %, based on the alkali metal catalyst, of sodium oxide or potassium oxide as co-catalyst. The process of claim 1 wherein the ethylenically-unsaturated aliphatic hydrocarbon is a hydrocarbon corresponding to the formula QQ′C=CTT′, in which Q, Q′, T, and T′ are each hydrogen or alkyl or alkenyl groups of up to 20 carbons each. The process of claim 2 wherein the ethylenically-unsaturated aliphatic hydrocarbon is an alkene of 2-20 carbons. The process of any one of claims 1 to 3 wherein the aromatic hydrocarbon is a hydrocarbon corresponding to the formula RR′R″CH, in which R is an aryl group of up to 20 carbons and R′ and R″ are each hydrogen or alkyl or aryl groups of up to 20 carbons each. The process of claim 4 wherein the aromatic hydrocarbon is an alkylbenzene. The process of any one of claims 1 to 5 wherein the alkali metal catalyst is potassium or a potassium alloy. The process of any one of claims 1 to 6 wherein the co-catalyst is sodium oxide. The process of any one of claims 1 to 7 which is conducted at a temperature of 100-300°C. The process of claim 1 wherein propene is coupled with toluene at 175-200°C in the presence of a supported potassium or sodium/potassium catalyst and an oxide of sodium or of potassium as co-catalyst.

Inventors: SMITH, ROBERT SCOTT
Applicants: ETHYL CORPORATION
Application year: 1988
Main classification: C07C2
IPC codes: C07C2, B01J23, C07B61, C07C15, C07C1, C07C67