CA1253876A - Manufacture of aryl esters - Google Patents

Manufacture of aryl esters

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Publication number
CA1253876A
CA1253876A CA000473905A CA473905A CA1253876A CA 1253876 A CA1253876 A CA 1253876A CA 000473905 A CA000473905 A CA 000473905A CA 473905 A CA473905 A CA 473905A CA 1253876 A CA1253876 A CA 1253876A
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CA
Canada
Prior art keywords
acetate
catalyst
palladium
chromium
carboxylic acid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000473905A
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French (fr)
Inventor
Anil B. Goel
Peter E. Throckmorton
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ashland LLC
Original Assignee
Ashland Oil Inc
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Filing date
Publication date
Application filed by Ashland Oil Inc filed Critical Ashland Oil Inc
Priority to CA000473905A priority Critical patent/CA1253876A/en
Application granted granted Critical
Publication of CA1253876A publication Critical patent/CA1253876A/en
Expired legal-status Critical Current

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Abstract

ABSTRACT OF THE DISCLOSURE

The oxidation process for the manufacture of aryl esters comprising contacting the reaction mixture of an aromatic hydrocarbon, a carboxylic acid and molecular oxygen in the liquid phase at an elevated temperature with a catalyst composed of palladium or a compound of palladium, a chromium compound and a compound of at least one member selected from the group consisting of zinc, manganese, tin, cobalt and nickel is described.

Description

, .

MANUFACTU~E OF ARYL ESTERS

Background of the Invention ~ -Field of the Invention The present invention provides an improved process for making aryl esters from aromatic hydrocarbons such as benzene, naphthalene, anthracene, biphenyl, phenanthrene, fluorene, terphenyls, and the like, which comprises the reaction of a mixture of an aromatic hydrocarbon, molecular oxygen, a carboxylic acid, and optionally a hydrocarbon solvent, in the liquid phase in the presence of a catalyst which is composed of palladium or a compound of palladium, a compound of chromium and a compound of at least one metal selected from the group consisting of Zn, Mn, Sn, Co, and Ni.
':
. Description of the Prior Art The manufacture of phenol by the direct oxidation of benzene with oxygen is known. There are, for instance, thermal processes which are performed at very high temperatures in which the phenol formed is susceptible to further oxidation so that considerable loss of yield occurs as is disclosed in U.S. Patent No.
. 2,223,383. In the presence of catalysts, the oxidation can be carried out at somewhat lower temperatures as in . U.S. Patent No. 3,133,122 but the reactions have been i 30 plagued by low conversions and excessive production of unwanted by-products as is disclosed in U.S. Patent No.
, 2,392,875.
: It has been proposed to make phenyl acetate and '. biphenyl from benzene and acetic acid in the liquid phase in the presence of palladium acetate and without . - 1
2 ~253~7~
; added molecular oxygen by a stoichiometric reaction in Chem. and Ind., March 12, 1966, page 457a U.S. Patent No. 3,542,852 discloses the preparation of hydroxy aromatic compounds by reaction of an aromatic compound and oxygen in the presence of a !. r catalyst composed of iron, a noble metal or a compound 5 of either in the presence of a nitrate ion and a carboxylic acid. More recently 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 composed of a Group VIII
metal (U.S.. Patent No. 3,642,873) or a compound of such metal (U.S. Patent No. 3,651,127) have been disclosed. Similarly variations in this type of reaction ha~e been disclosed in U.S. Patent Nos.
3,646,111; 3,651,101; 3,772,383; 3,959,352 and 3,959,354. U.S. Patent No. 3,959,354 concludes that liquid phase reactions of this type, because of problems of catalyst elution, etc., are disadvantageous for an industrial process. U.S. Patent No. 3,772,383 describes a liquid phase reaction using a ~ery complex catalyst system which includes the use of nitric acid and a lower aliphatic carboxylic acid such as acetic, propionic, butyric, etc. U.S. Patent No. 3,644,486 describes the catalytic manufacture of oxacylation products and optionally hydroxylation products of condensed aromatic compounds, saturated aliphatic or cycloaliphatic carboxylic acids and molecular oxygen in ; the presence of a noble metal of Sub-Group VIII of the Mendeleef Periodic Table or compounds thereof. This Patent also discloses that transition metals can be used with the Group VIII metals and that carbonates or acylates of alkali or alkaline earth metals may also be used as activators in the catalyst system. Although extremely low yields of hydroxylation product are shown.
Generally speaking, these prior art processes deal for the most part with vapor phase oxidation reactions, ~ 253~
~~ or liquid phase reactions in which all of the reactants (except oxygen in some instancesj are initially included in the reaction mixture and they use lower alkyl carboxylic acids such as acetic acid and propionic acid. Moreover, in general the prior art catalytic processes have produced low conversions, 5 usually less than 10%, with poor selectivity to the desired aryl ester, and the hydroxy aromatic compound, such as phenol or naphthol, is often a primary product.
The use of the lower saturated carboxylic acids, primarily acetic acid, in the catalytic oxidation 10 process produces a highly corrosive system which can cause reaction equipment corrosion problems and excessive recyle costs as well as the extremely poor conversions and selectivities mentioned above. None o~
the prior art methods disclose the continuous addition 15 of the aromatic hydrocarbon, the continuous removal of water from the reaction mixture as it forms, nor do they disclose or suggest the use of a solvent or the applicants' catalyst for the higher aromatic compounds in Applicants' process.
Summary of the Invention ;
We have discovered an improved oxidation process L for the transformation of aromatic hydrocarbons such as 25 benzene, naphthalene, anthracene, biphenyl, phenanthrene, terphenyls, fluorene, and the like, molecular oxygen and a higher carboxylic acid to the corresponding aromatic carboxylate in good conversions and selectivities to the desired product by including 30 using a catalyst system composed of a compound of palladium, a compound of chromium and a compound of at least one metal selected from the group consisting of Zn, Mn, Sn, Co, and Ni. Our process also may use a solvent for the aromatic hydrocarbon, particularly when ; 35 the aromatic hydrocarbon is one containing 10 or more carbon atoms and two or more aromatic rings per .
4 ~253~7~

molecule such as naphthalene, anthracene, biphenyl, phenanthrene, terphenyls, fluorene, and the like. It is in our preferred process that a mono or ; polycarboxylic acid having 5 or more carbon atoms be used.
; ~ Our liquid phase reaction produces good yields of aryl esters, particularly when the water that is formed as the aromatic hydrocarbon is converted to ester is continuously removed in the process. If water, which is a by-product of the oxidation reaction, is allowed to remain in the reaction mixture, it can cause hydrolysis of the aryl ester to prvduce aromatic hydroxy compounds which in turn can cause fouling and inactivation of the catalyst.
The catalysts useful in our process are preferably composed of palladium metal or compounds of palladium and usually a palladium carboxylate for convenience in conjunction with a chromium compound and a compound of at least one metal selected from the group consisting of zinc, manganese, tin, cobalt and nickel. The catalysts of this invention may be used alone or may be supported on a carrier or support material. Suitable carriers include silica, alumina, carbon, quartz, pumice, diatomaceous earth, and the like and others ; which are known in the art.
The carboxylic acids useful in our invention include mono and poly-carboxylic acids having from 5 to 30 carbon atoms which correspond to the formula - R(COOH~n wherein n is an integer of 1 to 5 and R is a hydrocarbon group having at least 5-n carbon atoms.
Most preferred are monocarboxylic acids in which n is 1 3~ and R is an aliphatic hydrocarbon group having from 7 i to 19 carbon atoms. Some carboxylic acid anhydride can be included with the carboxylic acid in the reaction if desired.
For the higher aromatic hydrocarbons organic solvents which may be useful for the entrainment and removal of water from the reaction mixture include ~253~6 --~ linear hydrocarbons having the formula CnH2n+2 wherein n is from 4 to 14 such as heptane, pentane~ octanes, and the like, cyclic hydrocarbons having the formula Cn~n wherein n is from 4 to 14, and linear and cyclic aliphatic ethers.
The process of this invention produces ~n the case of benzene reactant conversions of the carboxylic acid to ester in the order of about 10% with selectivities to the phenyl ester on the order of 95% The phenyl esters which are produced by our process can be readily converted to the corresponding phenol and the corresponding carboxylic acid b~ known methods for hydrolysis. Phenol is easily recovered by known means and the corresponding carboxylic acid is readily recycled for further use in the oxidation reaction of this invention.
Description of the Preferred Embodiment In a typical reaction in accordance with this invention benzene and the carboxylic acid are contacted with the catalyst in an oxygen containing atmosphere at a reaction temperature in the range of from about 100 to 300C. and preferably from about 140 to 200C. and at from about 1 to 100, preferably 1 to 10 atmospheres ; and most preferably at or near atmospheric pressure.
The molecular oxygen can be oxygen, per se, or any gaseous mixture containing molecular oxygen. For instance, molecular oxygen can be in the form of air for convenience. The catalyst can be in the form of a mixture of palladium acetate, chromium acetate and at least one of zinc acetate, manganese acetate, tin acetate, cobalt acetate and nickel acetate. The molar ratio of Pd:Cr:M wherein M is a member selected from : the group consisting of zinc, manganese, tin, cobalt, ` and nickel should be in the range of from 1.0 : 0.1:
0.1 to 1 : 20 : 20 and preferabl~ in the range of from 35 1 : 0.2 : 0.2 to 1 : 10 : 10. During the reaction the water formed as a by-product is continuously removed 6 ~3876 conveniently by entrainment with excess benzene or with the organic solvent when it is used. The benzene or organic solvent is continuously distilled from the reaction mixture as the reaction proceeds The major product, phenyl carboxylate, can be hydrolyzed to produce phenol and the carboxylic acid and catalyst can be recycled back for reuse in the oxidation reaction.
Because essentially no phenol is produced directly in the oxidation reaction of this invention, it is believed that catalyst activity is maintained for long periods of time under continuous use. The rapid removal of water from the reaction mixture is probably at least partly responsible for the absence of phenol in the oxidation reaction product. The presence of phenol in the oxidation reaction mixture is believed to be detrimental in causing catalyst fouling and catalyst inactivation which result in very short catalyst life.
The process of this invention is further illustrated in the following examples.

To a 250 ml 3-neck flask equipped with a mechanical stirrer, reflux condenser and Dean-Stark tube were charged 0.67 g. (0.003 mol) of palladium ~II) acetate, 0.66 g. (0.003 mol) of zinc acetate, 0.74 g.
(0.003 mol) of chromium (III) acetate monohydrate, 39.81 g. (0.276 mol) of octanoic acid and 4.09 g.
(O.OSl mol) of benzene. The resulting mixture was stirred and heated to 170C. and oxygen was bubbled 30 through the reaction mixture at a flow rate of about 50 s cc/minute. Water formed during the reaction and was ' removed continuosly as it formed by azeotropic ; distillation with the excess benzene. The reaction temperature was maintained at 170C. + 2C. during the 35 course of the reaction and additional benzene was fed to the reactor by pump at a slow rate. The reaction ~as carried out ; 6 7 ~:253E~
for 5 hours and the total benze~e was 17.5 gO (0.225 mol). GLC analysis of the reaction mixture after 5 hours reaction time showed the formation of phenyl octanoate (19 millimols) and of some phenylene bis -octanoyloxy esters o,m,p, combined) (3.9 millimols total) for a total of 26.8 m mol of phenyl ester (about 10% conversion of the octanoic acid).

This example demonstrates that a catalyst composed only of palladium and chromium compounds is inferior to the catalysts composed of compounds of palladium, chromium and a compound of a member from the group consisting of zinc, manganese, tin, cobalt and nickel.
The procedure given in Example 1 was followed except that the catalyst was composed of 0.67 g. of palladium (II) acetate (0.003 mol), and 0.74 g. of chromium (III) acetate. GLC analysis of the reaction mixture after 5 hours reaction time showed that only 5 millimols of the phenyl ester of octanoic acid (2% conversion) had taken place.

The procedure of Example 1 was followed except that instead of .003 mol of zinc (II) acetate the same ; amount (.003 mol) of the acetates listed in the following table were used as part of the catalyst system. The amount of phenyl ester and the mols of phenyl ester per mol of palladium (in 5 hours reaction time) for each example are also given in the following '~ table:

~L~5~8~
TABLE

Metal Acetate Phenyl Ester Mols of Ester Per Example in CatalystM Mols Mol of Palladium - 3 Sn I 22 7.3 i . 4 MnII 19 6.2 ; 55 CoII 20 6.6 6 NiII 17.5 5.8

Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows:
1. An oxidation process for the manufacture of aryl esters comprising contacting the reaction mixture of an aromatic hydrocarbon, a carboxylic acid and molecular oxygen in the liquid phase at a temperature in the range of from 100° to 300°C with a catalyst composed of a palladium carboxylate, a chromium carboxylate and a carboxylate of at least one member selected from the group consisting of zinc, manganese, tin, cobalt and nickel wherein the molar ratio of Pd:Cr:Zn,Mn,Sn, Co or Ni is in the range of from 1.0:0.1:0.1 to 1:20:20.
2. The process of claim 1 wherein the aromatic compound is selected from the group consisting of benzene, naphthalene, anthracene, biphenyl, phenanthrene, fluorene, and terphenyls.
3. The process of claim 2 wherein the carboxylic acid is one which corresponds to the formula R(COOH)n wherein n is an integer of from 1 to 5 and R is a hydrocarbon group having at least 5-n carbon atoms.
4. The process of claim 3 wherein n is 1 and R is an aliphatic hydrocarbon group having from 7 to 11 carbon atoms.
5. The process of claim 4 wherein the water formed in the oxidation reaction is continuously removed from the reaction mixture.
6. The process of claim 5 wherein the aromatic hydrocarbon is benzene.
7. The process of claim 6 wherein the carboxylic acid is octanoic acid.
8. The process of claim 7 wherein the catalyst is composed of palladium acetate, chromium acetate and zinc acetate.
9. The process of claim 7 wherein the catalyst is composed of palladium acetate, chromium acetate and tin acetate.
10. The process of claim 7 wherein the catalyst is composed of palladium acetate, chromium acetate and manganese acetate.
11. The process of claim 7 wherein the catalyst is composed of palladium acetate, chromium acetate and cobalt acetate.
12. The process of claim 7 wherein the catalyst is composed of palladium acetate, chromium acetate and nickel acetate.
CA000473905A 1985-02-08 1985-02-08 Manufacture of aryl esters Expired CA1253876A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA000473905A CA1253876A (en) 1985-02-08 1985-02-08 Manufacture of aryl esters

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000473905A CA1253876A (en) 1985-02-08 1985-02-08 Manufacture of aryl esters

Publications (1)

Publication Number Publication Date
CA1253876A true CA1253876A (en) 1989-05-09

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Family Applications (1)

Application Number Title Priority Date Filing Date
CA000473905A Expired CA1253876A (en) 1985-02-08 1985-02-08 Manufacture of aryl esters

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CA (1) CA1253876A (en)

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