FI79295C - Preparation of higher aryl esters - Google Patents

Description

1 79295

Preparation of higher aryl ethers

The present invention relates to an oxidation process for the preparation of aryl esters in which the aroma, molecular oxygen and aliphatic carboxylic acid react in the presence of a metal catalyst.

The production of phenol by direct oxidation of benzene with oxygen is known. There are, for example, thermal processes carried out at relatively high temperatures, whereby the phenol formed is further sensitive to oxidation, with a significant reduction in yield, as disclosed in U.S. Patent 2,223,383. In the presence of catalysts, oxidation can be performed at somewhat lower temperatures, such as disclosed in U.S. Patent 2,133,122, but low conversions and excess production of unwanted by-products have been typical of reactions, as disclosed in U.S. Patent 2,392,875.

The preparation of phenylacetates and biphenyl from benzene and acetic acid in the liquid phase in the presence of palladium acetate and without the addition of molecular oxygen by stoichiometric reaction is described in Chem. and Ind., March 12, 1966, page 457.

U.S. Patent 2,792,952 discloses the preparation of oxyaromatic compounds by the reaction of an aromatic compound and oxygen in the presence of a catalyst consisting of iron, a noble metal, or either compound in the presence of a nitrate ion and a carboxylic acid. Still later, the preparation of phenyl esters and phenols by the reaction of benzene, molecular oxygen, and a lower aliphatic carboxylic acid in the presence of a catalyst comprising a Group VIII metal (U.S. Patent 3,642,873) or a compound of such a metal (U.S. Patent 3,651,127) is disclosed. Correspondingly, modifications of this type of reaction are disclosed in U.S. Patent 3,646,111, 3,651,101, 3,772,383, 3,959,352 and 3,959,354. U.S. Patent 3,959,354 concludes that liquid-type reactions of this type are disadvantageous due to catalyst elution problems, etc. industrial process. U.S. Patent 3,772,383 describes a liquid phase reaction using a highly complex catalyst system involving the use of nitric acid and a lower aliphatic carboxylic acid such as acetic, propionic, n-butyric, isobutyric or caproic acid. U.S. Patent 3,644,486 describes the catalytic preparation of oxacylation products and optionally hydroxylation products from condensed aromatic compounds, saturated aliphatic or cycloaliphatic carboxylic acids and molecular oxygen in the presence of subgroup 8 of the Mendeleyev Periodic Table or their compounds. This patent also discloses that transition metals can be used with Group 8 metals and that carbonates or acylates of alkali or alkaline earth metals can also be used as activators in catalyst systems. Although a liquid phase reaction has been reported, the need for the use of a hydrocarbon solvent or the removal of water from the reaction mixture has not been mentioned, and very low yields of acetoxylation products have occurred.

In general, prior art methods mostly deal with vapor phase oxidation reactions or liquid phase reactions, where all reactants (except oxygen in some cases) are initially included in the reaction mixtures and use 3,79295 lower alkyl carboxylic acids such as acetic acid and propionic acid. More specifically, prior art catalyst processes have produced low conversions, usually less than 10%, with poor selectivity for the desired aryl ester, and an oxyaromatic compound such as phenol or naphthols is often the primary product. The use of lower saturated carboxylic acids, especially acetic acid, in the catalytic oxidation process produces a highly corrosive system, which can cause corrosion problems in the reaction equipment and additional recycled precipitates, as well as very poor conversions and selectivities, as mentioned above. None of the prior art methods provide for the continuous addition of aromatic hydrocarbons, nor the continuous removal of water from the reaction mixture as it forms, nor do they suggest or suggest the use of a solvent or catalyst for higher aromatic compounds in this process.

An improved oxidation process has been invented for the conversion of higher aromatic hydrocarbons comprising 10 or more carbon atoms and two or more aromatic rings per molecule, such as naphthalene, anthracene, biphenyl, phenanthrene, terphenyls, fluorene and the like, to the carboxylic acid and higher carboxylic acid with selections over the desired product by incorporating the solvent into the aromatic hydrocarbon compound in the process.

The invention is mainly characterized by what is said in the characterizing part of claim 1.

Ko. the process is also based on the use of a mono- or polycarboxylic acid having 5 or more carbon atoms and a catalyst system consisting of a palladium compound, an antimony compound and a previously absorbed compound or an alkaline earth metal compound.

Said neetephasic reaction produces high conversions and substantial quantitative yields of higher aryl esters when the higher aromatic hydrocarbon either reacts with the carboxylic acid in the presence of an inert solvent or is continuously added as a solution in an inert solvent to the reaction mixture 4,79295 during the reaction. The solvent may be one which has the ability to remove water as droplets so that the water formed, after the higher aromatic hydrocarbon has been converted to the ester, is continuously removed from the reaction mixture in the process. If water, a by-product of the oxidation reaction, is allowed to remain in the reaction mixture, it can cause hydrolysis of the aryl ester to form aromatic hydroxy compounds, which in turn can cause catalyst spoilage and inactivation.

The catalysts useful in the process are preferably formed from palladium metal or palladium compounds and usually palladium carboxylate for convenience in conjunction with an antimony compound and a compound, usually an alkali metal-alkaline earth metal carboxylate. The catalysts of this invention may be used alone or in conjunction with supports. Suitable carriers include silica, alumina, carbon, quartz, pumice, diatomaceous earth and the like, as well as others known in the art.

Useful carboxylic acids according to the invention are mono- and polycarboxylic acids having 5 to 30 carbon atoms, corresponding to the formula R (COOH) n, where n is an integer from 1 to 2 and R is a hydrocarbon group having at least 5 carbon atoms. More preferred are monocarboxylic acids in which n is 1 and R is an aliphatic hydrocarbon group comprising 7 to 19 carbon atoms.

A carboxylic acid anhydride may be included in the reaction with the carboxylic acid, if necessary.

Higher organic solvents for aromatic hydrocarbons that may be useful for removing water from the reaction mixture include linear hydrocarbons of formula H2n + 2, where n is 4-14, such as heptane, pentane, octanes, and the like, cyclic hydrocarbons of formula ^ 2nr where n is 4-14, and linear and cyclic aliphatic ethers.

The process of this invention produces carboxylic acid conversions of about 10% greater with naphthalene as the reactant, with selectivities to naphthyl ester of about 79295 being about 100%. Thus, the the process produces the desired product in such significant quantities that it is immediately competitive with the best industrial processes currently in place for the production of alpha-bethanaphthyl esters and the naphthalenes themselves. Naphthyl esters, which can be prepared by our method, can be easily converted to the corresponding naphthols and the corresponding carboxylic acid by known means by hydrolysis and pyrrolysis. Naphthols can be readily recovered by known means, and the carboxylic acid, ketene, or acid anhydride is readily recyclable for use in the oxidation reaction of this invention.

In a typical reaction according to the present invention, a solution of naphthalene in heptane and a carboxylic acid is contacted with the catalyst under oxygen-containing conditions at a reaction temperature of about 100-300 ° C, and preferably about 140-200 ° C, and 1-100 preferably at 1-10 atmospheric pressure and most preferably at atmospheric pressure. at or near pressure. The molecular oxygen may be oxygen, or some gaseous mixture containing molecular oxygen. For example, molecular oxygen may be in the form of air for ease. The catalyst may be in the form of a mixture of (CH 3 COO) 2 Pd, (CH 3 COO) 3 Sb and CH 3 GOOM and / or (CH 2 COO) 2 M ', wherein M is at least one alkali metal and M' is at least one alkaline earth metal. The molar ratio Pd: Sb: M or M 'should be between 1: 0.1: 0.01-1: 100: 100 and preferably between 1: 0.2: 0.2-1: 40: 40. The water formed during the reaction is continuously removed dropwise readily with an organic solvent, which is continuously distilled from the reaction mixture as the reaction is carried out. The main reaction product (and in many cases the only product) in the reaction, naphthyl carboxylate, far exceeds the best yields achieved in the art, mainly in quantitative selectivity. As previously mentioned, the naphthyl carboxylate thus obtained can be hydrolyzed, if desired, to produce naphthol or naphthols by known means, and the carboxylic acid and catalyst can be recycled back to the oxidation reaction.

6 79295

Since substantially no naphthol is produced in the process of this invention, the catalyst activity is believed to be maintained for extended periods of time in continuous use. The rapid removal of water from the reaction mixture is likely to be at least in part due to the absence of naphthol in the reaction product. The presence of naphthol in the reaction product, if it were to occur, is believed to be the cause of the catalyst deterioration and consequently the short catalyst life. The method of the present invention is described in more detail in the following examples.

Example 1

The reaction was carried out in a glass reactor equipped with a thermometer, a mechanical stirrer, a Dean Stark-type collector with a reflux condenser and gases with liquid pipes. 40 g of octanoic acid, 10 g (78 mmol) of naphthalene, 8 g of heptane, 0.34 g (1.5 mmol) of Pd (OAc) 2, 0.45 g (1.5 mmol) of Sb ( OAcJ and 0.15 g (1.5 mmol) of KOAc The Dean Stark collector was charged with heptane The reaction was performed at 170 ° C with vigorous stirring for 5 hours GLC analysis showed that 57 moles (73% yield) ) naphthyl octanoate was completed.

Example 2

The procedure of Example 1 was repeated except that 10 g (78 mmol) of naphthalene was fed initially and then an additional 5 g (39 mmol) after a reaction time of 2 hours, and another 5 g (39 mmol) was added after the third hour and a further 5 g after the fourth hour. . Thus, a total of 25 g (195 mmol) of naphthalene was used in the reaction. Analysis of the final reaction mixture after a reaction period of 5 hours showed the formation of 134 mmol (69%) of naphthyl octanoate (97% alpha-acryl octanoate, 3% betanaphthyl octanoate).

Example 3 This experiment, which is outside the scope of the present invention, is a variant of Example 1 except that Sb (0Ac) 3 was not used. After 5 hours of reaction, it was found that 7,79295 only 5.5 mmol of naphthyl ester were found in the reaction mixture (5%).

Example 4

The procedure of Example 1 was repeated except that the catalyst used consisted of 0.67 g (3 mmol) of Pd (OAc), 0.9 g (3 mmol) of Sb (OAcJ) and 0.66 g (3 mmol) of Zn (OAc After 3 hours of reaction, an additional 5 g (39 mmol) of naphthalene was added to the reaction mixture, and at the end of the 5 hour reaction period, the reaction mixture was analyzed and found to contain 80 mmol of naphthyl octanoate (68% yield).

Example 5

The procedure of Example 4 was followed except that 20 g (156 mmol) of naphthalene was fed in 4 additions over a reaction time of 5 hours. GLC analysis showed that 101 mmol of naphthyl octanoate were formed in the reaction.

Example 6

The procedure of Example 1 was followed except that 0.17 g (0.75 mmol) of PdfOAc, 0.23 g (0.75 mmol) of Sb (OAc) 2 and 0.14 g (0.75 mmol) of mmol) of CsOAc, and the reaction was performed for only 3 hours. GLC analysis of the final reaction mixture indicated that 24 mmol of naphthyl octanoate was formed.

Example 7

The procedure of Example 6 was followed except that 0.75 mmol of NAOAc was used instead of CsOAc. Analysis of the final reaction mixture showed the formation of 17.3 irmoles of naphthyl octanoate.

Example 8

The procedure of Example 6 was followed except that 0.75 mmol of LiOAc was used instead of CsOAc. At the end of the reaction, 9.9 mmol of naphthyl octanoate were found to be present in the reaction mixture.

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Example 9

The procedure of Example 1 was repeated except that 0.068 g (0.3 mmol) of Pd (OAc) 2, 2.69 g (9 mmol) of Sb (OAc) 2 and 0.0314 (0.3 mmol) of Pd (OAc) 2 were fed as catalyst. ) KOAc. The Pd: Sb: K molar ratio was about 1: 30: 1. The reaction was performed at 165 at 3 ° C for 2 1/2 hours. Analysis of the reaction mixture showed that 31 mmol of naphthyl octanoate was formed.

Example 10 This example, which is outside the scope of the present invention, shows that lower carboxylic acids are not effective in the oxidation process of this invention. The procedure of Example 1 was followed using 50 g of acetic acid, 10 g (78 mmol) of naphthalene, 0.34 g (1.5 mmol) of Pd (0Ac) 2, 0.46 g (1.5 mmol) of Sb (OAc) 2 and 0.6 g (6 mmol) of KOAc. The reaction was carried out for 3 hours at 120-6 ° C (reflux) and oxygen was blown into the reaction mixture during the reaction in an amount of 50 cm -1. Vmin. Analysis of the final reaction mixture showed that less than 1 mmol (less than 2%) of the naphthalene had been converted to naphthyl acetate. .

Example 11 This example, which is outside the scope of the present invention, shows that the absence of an organic solvent in the process of the present invention leads to unsatisfactory results. The procedure of Example 1 was followed except that no heptane or any other organic solvent was used. At the end of the 3 hour reaction time, GLC analysis of the reaction mixture showed that only 1 mmol of naphthyl octanoate was formed and only 0.5 mmol of binaphthyl.

Claims (9)

9,79295 A process for the preparation of aryl esters in which an aromatic, molecular oxygen and aliphatic carboxylic acid react in the presence of a metal catalyst, characterized in that to produce a higher aryl ester a higher aromatic hydrocarbon having at least 10 carbon atoms and at least two rings R <C00H> n, where n is an integer from 1 to 2 and R is a hydrocarbon group having at least 5 carbon atoms, and the reaction mixture of the molecular oxygen is contacted in the liquid phase at a temperature of 100 to 300 ° C with a catalyst consisting of palladium or a palladium compound, an antimony compound and a compound of at least one element selected from the group consisting of alkali metals and alkaline earth metals, and that the water formed in the oxidation reaction is continuously removed from the reaction mixture by continuous azeotropic distillation of an organic solvent of the reaction mixture. Process according to Claim 1, characterized in that the higher aromatic hydrocarbon is naphthalene. Process according to Claim 2, characterized in that the organic solvent is heptane. Process according to Claim 3, characterized in that the carboxylic acid is octanoic acid. Process according to Claim 4, characterized in that the catalyst consists of palladium carboxylate, antimony carboxylate and potassium carboxylate. Process according to Claim 4, characterized in that the catalyst consists of palladium carboxylate, antimony carboxylate and cesium carboxylate. 10 79295 Process according to Claim 4, characterized in that the catalyst consists of palladium carboxylate, antimony carboxylate and sodium carboxylate. Process according to Claim 4, characterized in that the catalyst consists of palladium carboxylate, antimony carboxylate and lithium carboxylate. Process according to Claim 4, characterized in that the catalyst consists of palladium carboxylate, antimony carboxylate and zinc carboxylate.