WO2003099755A1

WO2003099755A1 - Hydrocarbon, alcohol and/or ketone oxidation method

Info

Publication number: WO2003099755A1
Application number: PCT/FR2003/001549
Authority: WO
Inventors: Eric Fache; Jean-Pierre Simonato; Didier Bonnet
Original assignee: Rhodia Polyamide Intermediates
Priority date: 2002-05-23
Filing date: 2003-05-22
Publication date: 2003-12-04
Also published as: AU2003260563A1; FR2839973A1; TW200406379A

Abstract

The invention relates to a method for oxidation using oxygen or an oxygen-containing gas of hydrocarbons into corresponding carboxylic acids, alcohols and/or ketones or alcohols and/or ketones into corresponding carboxylic acids. More specifically, the invention relates to a hydrocarbon, alcohol and/or ketone oxidation method using oxygen or an oxygen-containing gas in liquid phase and in the presence of a catalyst. The invention is characterised in that said catalyst comprises at least one zirconium compound and at least one cerium compound.

Description

PROCESS FOR THE OXIDATION OF HYDROCARBONS, ALCOHOLS AND / OR KETONES

The present invention relates to the oxidation, by oxygen or a gas containing it, of hydrocarbons into carboxylic acids, corresponding alcohols and / or ketones or of alcohols and / or ketones into corresponding carboxylic acids.

The direct oxidation by oxygen of hydrocarbons, more particularly cycloalkanes, in the presence of a catalyst, is a process which has been studied for a long time. Indeed, there would be obvious advantages in avoiding the use of an oxidizing agent such as nitric acid, used in one of the stages of current industrial processes, which would spare the treatment of the nitrogen oxides generated.

In the many variants of such a catalytic oxidation process with oxygen, cobalt is the most frequently recommended catalyst.

Thus, US patent US-A-2 223 493, published in December 1940, describes the oxidation of cyclic hydrocarbons to corresponding diacids, in the liquid phase generally comprising acetic acid, at a temperature of at least 60 ° C. , using an oxygen-containing gas and in the presence of an oxidation catalyst such as a cobalt compound.

American patent US Pat. No. 4,902,827, published in February 1990, describes an improvement in the air oxidation of cyclohexane to adipic acid, in the liquid phase comprising acetic acid, at a temperature of 80 ° C. 160 ° C and in the presence of an oxidation catalyst comprising a soluble compound of cobalt and a soluble compound of zirconium and / or hafnium.

More recently, it has been recommended in patent EP-A-0 694 333 to use, in the context of the oxidation of hydrocarbons by oxygen, a catalyst comprising a cobalt salt and a ferric salt.

It was also recommended in patent EP0870751 to use a catalyst comprising a cobalt salt and a chromium salt to improve the selectivity.

As another usual catalyst for this oxidation reaction, there may be mentioned manganese. However, it turns out that if the selectivities and productivities obtained with the catalytic systems used in the previous processes described above are acceptable, new catalytic systems are always sought after, making it possible to improve productivity and selectivity as well as the ease of recovery and recycling of the catalyst. This is what the present invention proposes to achieve. More precisely, it consists of a process for the oxidation of hydrocarbon, alcohol and / or ketone using oxygen or a gas containing it, in the liquid phase and in the presence of a catalyst, characterized in that the catalyst comprises at least one zirconium compound and at least one cerium compound.

The hydrocarbons which are used as starting substrates in the process of the invention are more particularly alkanes, cycloalkanes, alkyl-aromatic hydrocarbons, alkenes and cycloalkenes having from 3 to 20 carbon atoms. Among these hydrocarbons, cycloalkanes, in particular those which have a ring having from 5 to 12 carbon atoms, are certainly the most important, because their oxidation leads to dicarboxylic acids or to intermediate cycloalkanols and cycloalkanones. The most interesting hydrocarbon is cyclohexane, the oxidation of which leads to adipic acid, one of the basic compounds of polyamide 6-6, but can also provide cyclohexanone leading to caprolactam and therefore to polyamide 6.

The present process can also be used for the oxidation of alcohols or intermediate ketones, in particular cycloalkanols and cycloalkanones having from 5 to 12 carbon atoms, preferably cyclohexanol and / or cyclohexanone, to prepare the corresponding dicarboxylic acids.

In what follows, the process will be more particularly described for the oxidation of hydrocarbons, essentially cycloalkanes, and in a preferred way for the oxidation of cyclohexane. The catalytic system comprising zirconium and cerium compounds makes it possible to directly prepare adipic acid with good selectivity when the oxidation of cyclohexane is carried out. These catalytic properties are obviously very advantageous for industrial exploitation of this oxidation reaction.

According to a first embodiment of the invention, the catalytic system comprises at least one zirconium compound soluble in the reaction medium, chosen for example without limitation from zirconium chloride, zirconium bromide, zirconium nitrate l zirconium acetylacetonate and zirconium carboxylates such as zirconium acetate tetrahydrate, zirconium propionate, zirconium adipate, zirconium glutarate, zirconium succinate, zirconium octoate, and at least one compound of the cerium soluble in the reaction medium, chosen for example without limitation from cerium chloride, cerium bromide, cerium nitrate, cerium acetylacetonate and cerium carboxylates such as cerium acetate, cerium, cerium adipate, cerium glutarate, cerium succinate, cerium octoate. The catalyst can also comprise, as doping elements, other metal compounds chosen from the group comprising Cu, Ag, Au, Mg, Ca, Sr, Ba, Zn, Cd, Hg, Al, Se, In, Tl, Y, Ga, Ti, Hf, Ge, Sn, Pb, V, Nb, Ta, Cr, Mo, W, Mn, Te, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt and combinations thereof. By compound of a metallic element is meant the compounds comprising at least one atom of said metal in association with other chemical elements such as, for example, oxygen, but also the metal alone. According to a second embodiment of the invention, the catalyst according to the invention comprises a support comprising at least one zirconium compound and at least one cerium compound. The zirconium and cerium compounds are supported or impregnated on the inert support according to conventional techniques for manufacturing the so-called supported catalysts. The catalyst can also be constituted by a mixture of zirconium and cerium oxides or by a mixed oxide of zirconium and cerium. It can also include as doping elements one or more metallic elements from the list indicated above for the first embodiment.

As suitable support for the invention, mention may be made of advantageously porous metal oxides such as aluminum oxides, silicon oxides, active carbons or graphites, zeolites, silicalites, aluminophosphates, silicoaluminophosphates, organic resins.

The molar ratio between zirconium and cerium can vary within wide limits. It is thus possible to implement a Zr / Ce molar ratio advantageously between 1 / 0.00001 and 1/100, preferably between 1 / 0.0001 and 1/10. The amount of the other metals, when present, may vary in molar ratios to zirconium, similar to those indicated above for cerium.

The catalyst can be obtained in situ by loading the zirconium and cerium compounds and possibly other metals into the reaction medium. It can also be prepared extemporaneously by mixing said compounds in the proportions necessary to obtain the Zr / Ce molar ratios and possibly the other metals.

Preferably, this mixture is produced using a solvent, advantageously a solvent of the same nature as that used for the oxidation reaction. The amount of catalyst, expressed as a percentage by weight of metallic elements (zirconium, cerium and possibly other metals) relative to the reaction mixture, is generally between 0.0001 and 10%, advantageously between 0.001 and 2%, without these values are critical. It is however a question of having sufficient activity without however using excessively large quantities. Indeed, the catalyst must be separated from the final reaction medium and recycled.

It is advantageous to also use a compound which initiates the oxidation reaction. The initiators are often hydroperoxides, such as example cyclohexyl hydroperoxide or tert-butyl hydroperoxide. They are also ketones or aldehydes, such as for example cyclohexanone which is one of the compounds formed during the oxidation of cyclohexane or acetaldehyde. Generally the initiator represents from 0.01% to 20% by weight of the weight of the reaction mixture used, without these proportions having a critical value. The initiator is especially useful when starting the oxidation and when carrying out the oxidation of cyclohexane at a temperature below 120 ° C and batchwise. It can be introduced at the start of the reaction.

The liquid reaction medium preferably contains an at least partial solvent for the carboxylic acid and / or alcohol and / or ketone, the preparation of which is targeted by the implementation of the method of the invention. This solvent can be very varied in nature insofar as it is not substantially oxidizable under the reaction conditions. It can in particular be chosen from polar protic solvents and polar aprotic solvents. As polar protic solvents, mention may, for example, be made of carboxylic acids having only primary or secondary hydrogen atoms, in particular aliphatic acids having from 2 to 9 carbon atoms such as acetic acid, perfluoroalkylcarboxylic acids such as trifluoroacetic acid, lipophilic acids such as hexanoic, heptanoic, octanoic, 2-ethylhexanoic, nonanoic, decanoic, undecanoic, dodecanoic, stearic (octadecanoic) acids and their permethyl derivatives (total substitution of hydrogen for methylene groups by methyl group), 2-octadecylsuccinic acid, 2,5-ditertiobutyl benzoic, 4-tertiobutylbenzoic, 4-octylbenzoic, tertiobutyl hydrogen orthophthalate, naphthenic or anthracene acids substituted by alkyl groups, preferably of the tertiobutyl type, substituted derivatives of phthalic acids, fatty diacids com me the fatty acid dimer. Mention may also be made of acids belonging to the preceding families and carrying different electron-donating substituents (groups with heteroatom of type O or N) or electro-acceptors (halogens, sulfonimides, nitro groups, sulfonato or the like), alcohols such as tertiobutanol. As polar aprotic solvents, mention may be made, for example, of lower alkyl esters (that is to say an alkyl radical having from 1 to 4 carbon atoms) of carboxylic acids, in particular of the carboxylic acids mentioned above, the tetramethylene sulfone (or sulfolane), acetonitrile, ketones such as acetone, halogenated hydrocarbons such as dichloromethane, chlorobenzene, dichlorobenzenes or fluorinated hydrocarbons.

The carboxylic acids, whether lipophilic or not, are preferably used as solvent for the cyclohexane oxidation reaction. It is convenient to set uses a catalyst, the zirconium and cerium constituents of which are in the form of compounds derived from the carboxylic acid used as solvent or from the acids produced by the oxidation reaction, insofar as said compounds are soluble in the reaction medium. The solvent, as defined above, generally represents from 1% to 99% by weight of the reaction medium, preferably from 5% to 90% and even more preferably from 10% to 80%.

The oxidation can also be carried out in the presence of water introduced from the initial stage of the process or during the reaction. The temperature at which the oxidation reaction is carried out is variable, in particular depending on the substrate used. It is generally between 50 ° C and 200 ° C and preferably between 80 ° C and 140 ° C.

Pressure is not a critical process parameter. It can be lower, equal or higher than atmospheric pressure. Generally it will be between 0.1 MPa (1 bar) and 20 MPa (200 bar), without these values being mandatory.

It is possible to use pure oxygen, air, air enriched or depleted in oxygen or alternatively oxygen diluted by an inert gas.

The following examples illustrate the invention.

EXAMPLE 1

In a 125 ml autoclave, we load:

- 22.4 g of cyclohexane - 27.3 g of acetic acid

- 0.22 g of cyclohexanone

- 1 g of catalyst formed by an alumina on which have been impregnated with zirconium oxide and cerium oxide allowing 7370 ppm of cerium and 6700 ppm of zirconium to be present in the reaction medium. After closing the reactor, the mixture is heated to 105 ° C., with shaking.

After 180 minutes of reaction, the autoclave is cooled and then degassed. The reaction mixture is analyzed to determine the conversion rate and the selectivity. These analyzes are carried out by gas chromatography. By selectivity (ST) is meant the molar ratio expressed in percent of the number of moles assayed for a species relative to the theoretical number of moles of the species calculated from the number of moles of cyclohexane actually transformed:. The following results are obtained:

- conversion rate (TT) of cyclohexane: 5.5%

- ST in cyclohexanol relative to the transformed cyclohexane: 24.6%

- ST in cyclohexanone relative to the transformed cyclohexane: 1, 3%

- ST in adipic acid relative to the transformed cyclohexane: 51.4%

- adipic acid / total molar ratio of the diacids formed: 80.8%

COMPARATIVE EXAMPLE 2

Example 1 is repeated in the same apparatus and under the same operating conditions, with the following load of reagents: - 22.1 g of cyclohexane

- 27.2 g of acetic acid

- 0.22 g of cyclohexanone

- 0.49 g of zirconium acetylacetonate allowing to have 1860 ppm of Zr in the reaction medium. The reaction time is 180 minutes and the temperature 105 ° C. The following results are obtained:

- conversion rate (TT) of cyclohexane: 4.4%

- ST in cyclohexanol relative to the transformed cyclohexane: 28.4% - ST in cyclohexanone relative to the transformed cyclohexane: 45.1%

- ST in adipic acid relative to the cyclohexane transformed: 9.2%

- adipic acid / total molar ratio of diacids formed: 56.4%

EXAMPLE 3

Example 1 is repeated in the same apparatus and under the same operating conditions, but adding the following charge: - 22.5 g of cyclohexane

- 27.5 g of acetic acid

- 0.24 g of cyclohexanone - 0.43 g of zirconium acetylacetonate and 0.1616 g of cerium acetonate allowing to have 1600 ppm of zirconium and 1320 ppm of cerium in the reaction medium. The reaction time is 180 minutes and the temperature 105 ° C. The results obtained are:

- conversion rate (TT) of cyclohexane: 2.5%

- ST in cyclohexanol relative to the transformed cyclohexane: 16.2%

- ST in cyclohexanone relative to the transformed cyclohexane: 0%

- ST in adipic acid relative to the transformed cyclohexane: 27.9%

This test shows, in comparison with Example 2, the positive effect of the presence of cerium on the selectivity to adipic acid of catalysis by zirconium.

Claims

1) Process for the oxidation of hydrocarbons, alcohols and / or ketones into carboxylic acids, using oxygen or a gas containing them, in the liquid phase in a solvent chosen from polar protic solvents and polar aprotic solvents and in the presence of a catalyst, characterized in that the catalyst comprises a zirconium compound and at least one cerium compound.

2) Process according to claim 1, characterized in that the hydrocarbon used as starting substrate is chosen from cycloalkanes which have a cycle having from 5 to

12 carbon atoms, and is preferably cyclohexane.

3) Process according to claim 1, characterized in that the alcohol and / or the ketone used as starting substrate are chosen from cycloalkanols and cycloalkanones which have a ring having from 5 to 12 carbon atoms, and are preferably the cyclohexanol and / or cyclohexanone.

4) Method according to one of claims 1 to 3, characterized in that the zirconium and cerium compounds are soluble in the reaction medium.

5) Method according to one of claims 1 to 4, characterized in that the catalyst comprises at least one zirconium compound soluble in the reaction medium, chosen from zirconium chloride, zirconium bromide, zirconium nitrate, l zirconium acetylacetonate and zirconium carboxylates such as zirconium acetate tetrahydrate, zirconium propionate, zirconium adipate, zirconium glutarate, zirconium succinate, zirconium octoate.

6) Method according to one of claims 1 to 5, characterized in that the catalyst comprises at least one compound of cerium soluble in the reaction medium, chosen from cerium chloride, cerium bromide, cerium nitrate, l cerium acetylacetonate and cerium carboxylates such as cerium acetate, cerium propionate, cerium adipate, cerium glutarate, cerium succinate, cerium octoate.

7) Method according to one of claims 1 to 3, characterized in that the catalyst comprises a support comprising at least one zirconium compound and at least one cerium compound. 8) Method according to claim 7, characterized in that the inert support is chosen from the group comprising aluminum oxides, silicon oxides, active carbon, zeolites, silicalites, aluminophosphates, silicoaluminophosphates, resins organic.

9) Method according to one of claims 1 to 3, characterized in that the catalyst comprises zirconium oxide and cerium oxide or a mixed oxide of zirconium and cerium.

10) Method according to one of claims 1 to 9, characterized in that the molar ratio between zirconium and cerium is between 1 / 0.00001 and 1/100.

11) Method according to one of claims 1 to 6 and 10, characterized in that the amount of catalyst, expressed as a percentage by weight of metallic elements relative to the reaction mixture, is between 0.0001 and 10%, preferably between 0.001 and 2%.

12) Method according to one of the preceding claims, characterized in that the catalyst comprises at least one metallic doping element chosen from the group comprising the metallic elements Cu, Ag, Au, Mg, Ca, Sr, Ba, Zn, Cd, Hg, Al, Se, In, Tl, Y, Ga, Ti, Hf, Ge, Sn, Pb, V, Nb, Ta, Cr, Mo, W, Mn, Te, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt and combinations thereof

13) Method according to one of claims 1 to 12, characterized in that the liquid reaction medium contains a solvent chosen from aliphatic carboxylic acids having from 2 to 9 carbon atoms and their esters, perfluoroalkylearboxylic acids and their esters, lipophilic acids and their esters, alcohols, halogenated hydrocarbons, ketones, tetramethylene sulfone (or sulfolane), acetonitrile.

14) Method according to one of claims 1 to 13, characterized in that the solvent used is chosen from the group comprising acetic acid, hexanoic, heptanoic, octanoic acids, 2-ethyl hexanoic, nonanoic, decanoic, undecanoic, dodecanoic, stearic (octadecanoic) and their permethyl derivatives, 2-octadecylsuccinic acid, 2,5-ditertiobutyl benzoic, 4-tertiobutylbenzoic, 4-octylbenzoic, tertiobutyl hydrogen orthophthalate, naphthenic acids or anthracene substituted by alkyl groups, substituted derivatives of phthalic acids, fatty diacids.

15) Method according to one of claims 1 to 14, characterized in that the solvent represents from 1% to 99% by weight of the reaction medium, preferably from 5% to 90%.

16) Method according to one of claims 1 to 15, characterized in that the temperature at which the oxidation reaction is carried out is between 50 ° C and 200 ° C and preferably between 80 ° C and 140 ° C.

17) Method according to one of claims 1 to 16, characterized in that the pressure at which the oxidation reaction is carried out is between 0.1 MPa (1 bar) and 20 MPa (200 bar).