# Patent

## Title
Process for producing cycloalkanol and/or cycloalkanone

## Abstract

The object of the present invention is to produce cycloalkanol and/or cycloalkanone with good selectivity by oxidizing cycloalkane with molecular oxygen. The method of the present invention contains the step of oxidizing cycloalkane with molecular oxygen in the presence of cobalt salt of carboxylic acid and cobalt complex with porphyrin as a ligand, the cobalt complex with porphyrin as a ligand being a compound represented by the formula (1):




    
    
        wherein each of X1 to X8 independently represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, a hydrocarbon group, a halogenated hydrocarbon group or a sulfonyl group, and each of R1 to R4 independently represents a hydrogen atom, a nitro group, a cyano group, a hydrocarbon group or a halogenated hydrocarbon group.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing cycloalkanol and/or cycloalkanone by oxidizing cycloalkane with molecular oxygen.
2. Description of the Related Art
As a method for oxidizing hydrocarbon such as alkane, cycloalkane and alkene with molecular oxygen, there has been known a method utilizing cobalt salt of carboxylic acid as a catalyst (e.g., see U.S. Pat. No. 3,957,876). In addition, recently, a method utilizing porphyrin complex as a catalyst has been proposed. As a such catalyst, for instance, EP 0 471 501 A discloses a complex of iron, chromium, manganese, ruthenium or copper with perhalogenated porphyrin as a ligand; EP 0 532 327 A discloses a complex of iron, chromium, manganese, ruthenium, cobalt or copper with cyanated porphyrin as a ligand; EP 0 532 326 A discloses a complex of iron, chromium, manganese, ruthenium, cobalt or copper with nitrated porphyrin as a ligand; and EP 0 704 447 A discloses a complex of iron with halogenated porphyrin as a ligand.
SUMMARY OF THE INVENTION
However, the sufficient selectivity of a product, for example the selectivity of cycloalkanol and/or cycloalkanone produced by oxidizing cycloalkane with molecular oxygen, has not been achieved by those previous methods described above.
The present invention provides a process for producing cycloalkanol and/or cycloalkanone by oxidizing cycloalkane with molecular oxygen in the presence of cobalt salt of carboxylic acid and cobalt complex with porphyrin as a ligand.
According to the present invention, cycloalkanol and/or cycloalkanone can be produced from cycloalkane with good selectivity.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In the present invention, cycloalkane is used as a starting material, which is oxidized with molecular oxygen in the presence of a catalyst to produce corresponding cycloalkanol and/or cycloalkanone.
Examples of the cycloalkane as the starting material include monocyclic cycloalkane with no substituent on the ring, such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane and cyclooctadecane; polycyclic cycloalkane such as norbornane, decalin and adamantane; cycloalkane with a substituent on the ring, such as methylcyclopentane and methylcyclohexane; and the like, which usually have about 3 to 20 carbon atoms. Two or more of them can be used together, if necessary.
Oxygen-containing gas is usually used as a source of the molecular oxygen. The oxygen-containing gas may be air or pure oxygen, or may be diluted air or pure oxygen with an inert gas such as nitrogen, argon, or helium. Alternatively, oxygen-enriched air, which can be obtained by adding pure oxygen to the air, may be used as the oxygen-containing gas.
In the present invention, cobalt salt of carboxylic acid (hereinafter, it may be referred to as cobalt salt) and cobalt complex with porphyrin as a ligand (hereinafter, it may be referred to as cobalt complex) are used together as catalysts for oxidizing cycloalkane with molecular oxygen. By employing such catalyst system, cycloalkane can be oxidized and cycloalkanol and/or cycloalkanone can be produced with good selectivity.
The cobalt salt used in the present invention may be a salt of monohydric or polyhydric aliphatic carboxylic acid, alicyclic carboxylic acid or aromatic carboxylic acid. Two or more of them can be used together, if necessary. Preferred examples of the cobalt salt include cobalt acetate, cobalt 2-ethylhexanoate, cobalt naphthoate, cobalt oxalate, cobalt laurate, cobalt palmitate, cobalt stearate and the like. The cobalt salt is preferably a salt of aliphatic carboxylic acid, more preferably a salt of aliphatic carboxylic acid having 2 to 20 carbon atoms, and further preferably a salt of aliphatic carboxylic acid having 6 to 10 carbon atoms.
Another catalyst component, cobalt complex is typically represented by the following formula (1):




(wherein, each of X1 to X8 independently represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, a hydrocarbon group, a halogenated hydrocarbon group or a sulfonyl group, each of R1 to R4 independently represents a hydrogen atom, a nitro group, a cyano group, a hydrocarbon group or a halogenated hydrocarbon group.)

In the formula (1), when at least one of X1 to X8 existing on the pyrrole ring is a halogen atom, the halogen atom can be a fluorine atom, a chlorine atom, a bromine atom or an iodine atom. When at least one of X1 to X8 is a hydrocarbon group, the hydrocarbon group can be an aliphatic hydrocarbon group, an alicyclic hydrocarbon group or an aromatic hydrocarbon group.
As used herein, an aliphatic hydrocarbon group is a residue of aliphatic hydrocarbon whose hydrogen atom is removed therefrom, which usually has about 1 to 20 carbon atoms. Specific examples of the aliphatic hydrocarbon group include an alkyl group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a s-butyl group and a t-butyl group; an alkenyl group such as a vinyl group, an allyl group, and a methallyl group; an alkynyl group such as an ethynyl group and a propargyl group; and the like.
An alicyclic hydrocarbon group is a residue of alicyclic hydrocarbon whose hydrogen atom is removed therefrom, which usually has about 3 to 20 carbon atoms. The alicyclic hydrocarbon group may be the residue of alicyclic hydrocarbon whose hydrogen atom on the aliphatic ring is removed therefrom or may be the residue of alicyclic hydrocarbon having aliphatic chain whose hydrogen atom on the aliphatic chain is removed therefrom. Specific examples of the alicyclic hydrocarbon group include a cycloalkyl group such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group and a cyclohexyl group; a cycloalkyl alkyl group such as a cyclopentylmethyl group and a cyclohexylmethyl group; and the like.
An aromatic hydrocarbon group is a residue of aromatic hydrocarbon whose hydrogen atom is removed therefrom, which usually has about 6 to 20 carbon atoms. The aromatic hydrocarbon group may be the residue of aromatic hydrocarbon whose hydrogen atom on the aromatic ring is removed therefrom, or may be the residue of aromatic hydrocarbon having aliphatic chain whose hydrogen atom on the aliphatic chain is removed therefrom, or may be the residue of aromatic hydrocarbon having aliphatic ring whose hydrogen atom on the aliphatic ring is removed therefrom. Specific examples of the aromatic hydrocarbon group include an aryl group such as a phenyl group, a tolyl group and a naphthyl group; an arylalkyl group (an aralkyl group) such as a benzyl group and a phenethyl group; and the like.
When at least one of X1 to X8 is a halogenated hydrocarbon group, the halogenated hydrocarbon group can be a hydrocarbon group on which at least one hydrogen atom is substituted with a fluorine atom, a chlorine atom, a bromine atom or an iodine atom. When at least one of X1 to X8 is a sulfonyl group, the sulfonyl group can be a group having a hydrocarbon group bonding to unsubstituted (—SO2—) group. The hydrocarbon group in those halogenated hydrocarbon group and sulfonyl group can be an aliphatic hydrocarbon group, alicyclic hydrocarbon group or aromatic hydrocarbon group as in the case of the hydrocarbon group representing X1 to X8, and exemplified similarly as in the hydrocarbon group representing X1 to X8.
Whereas, in the formula (1), when at least one of R1 to R4 existing on carbons linking the pyrrole rings is a hydrocarbon group, the hydrocarbon group can also be an aliphatic hydrocarbon group, alicyclic hydrocarbon group or aromatic hydrocarbon group as in the case of the hydrocarbon group representing X1 to X8, and exemplified similarly as in the hydrocarbon group representing X1 to X8.
When at least one of R1 to R4 is a halogenated hydrocarbon group, similarly as in the halogenated hydrocarbon group representing X1 to X8, the halogenated hydrocarbon group can also be a hydrocarbon group on which at least one hydrogen atom is substituted with a fluorine atom, a chlorine atom, a bromine atom or an iodine atom. When at least one of X1 to X8 is a sulfonyl group, the sulfonyl group can also be a group having a hydrocarbon group bonding to unsubstituted (—SO2—) group, similarly as in the sulfonyl group representing X1 to X8. Moreover, the hydrocarbon group in those halogenated hydrocarbon group and sulfonyl group can also be an aliphatic hydrocarbon group, an alicyclic hydrocarbon group or an aromatic hydrocarbon group as in the case of the hydrocarbon group representing X1 to X8, and exemplified similarly as in the hydrocarbon group representing X1 to X8.
In the formula (1), at least one of X1 to X8 is preferably a halogen atom, and in this occasion, preferably others than the halogen atom are a hydrogen atom, a hydrocarbon group or a halogenated hydrocarbon group, and more preferably all of X1 to X8 are halogen atoms. R1 to R4 are preferably a hydrogen atom, a hydrocarbon group or a halogenated hydrocarbon group.
Such cobalt complex represented by the formula (1) can be prepared by known methods, for example a method described in Journal of Organic Chemistry, Vol. 32, p. 476, 1967, and a method described in Inorganic Chemistry, Vol. 31, p. 2044, 1992. The cobalt complex may be used with being carried on a carrier such as silica, alumina, titania, montmorillonite, zeolite, hydrotalcite and the like.
Oxidation reaction can be conducted by contacting cycloalkane with molecular oxygen in the presence of cobalt salt and the cobalt complex. Amounts of the cobalt salt used and the cobalt complex used are, in the total amount of both, usually 0.01 to 100 ppm by weight, preferably 0.1 to 50 ppm by weight to cycloalkane. Weight ratio of the cobalt salt to the cobalt complex is usually 100:1 to 1:100, preferably 20:1 to 1:20.
An oxidation reaction temperature is usually in the range of 0 to 200° C., preferably 100 to 180° C., more preferably 130 to 180° C., further preferably 145 to 180° C. A reaction pressure is usually in the range of 0.01 to 10 MPa, preferably 0.1 to 2 MPa. A solvent can be employed in the reaction, if necessary. Examples of the solvent include a nitrile solvent such as acetonitrile and benzonitrile, and carboxylic acid solvent such as acetic acid and propionic acid, and the like.
The post treatment operation after the oxidation reaction is not particularly limited. Examples of the post treatment include a method comprising the steps of washing a reaction mixture with water to separate the cobalt salt and the cobalt complex therefrom, and then distilling the reaction product, and the like. When cycloalkyl hydroperoxide is contained in the reaction mixture, the reaction mixture may be subjected to an alkaline treatment, reduction treatment or the like, to convert the cycloalkyl hydroperoxide easily into a desired cycloalkanol or cycloalkanone.
The resulting cycloalkanol can be converted into cycloalkanone by a known method, and cycloalkanone is used as a starting material for producing oxime or lactam.
EXAMPLES
The present invention is described in more detail by following Examples, which should not be construed as a limitation upon the scope of the present invention. Analyses of cyclohexane, cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide in a reaction mixture were conducted by gas chromatography. Based on results of the analysis, conversion of cyclohexane and respective selectivities to cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide were determined.
Example 1
As catalysts, 0.0007 g (2.1×10−6 mol) of cobalt(II) 2-ethylhexanoate and 0.0035 g (2.1×10−6 mol) of cobalt(II) 5,10,15,20-tetrakis(pentafluorophenyl)-2,3,7,8,12,13,17,18-octabromoporphyrin (compound of the formula (1), wherein X1 to X8 are bromine atoms and R1 to R4 are pentafluorophenyl groups) were dissolved in 2499.6 g (29.7 mol) of cyclohexane to prepare feed liquid (catalyst/starting material solution). Into 1 L autoclave, 278 g of the feed liquid was introduced, and inside of the system was pressured to 0.6 MPa with nitrogen, and then, the temperature of the system was increased to 145° C. with flowing nitrogen. Continuous reaction was conducted for 4 hours with supplying the feed liquid at 4.6 g/min. with flowing air so as to make oxygen concentration in an exhaust gas 1 to 5% by volume under conditions of reaction temperature 145° C., reaction pressure 0.6 MPa, and residence time 60 minutes. From a result of analysis of the reaction mixture, a conversion of cyclohexane was 4.1%, and selectivities of cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide were 27.0%, 33.3% and 30.2%, respectively (total selectivity was 90.5%).
Example 2
A procedure was conducted similarly as in Example 1, except that residence time was 75 minutes. A conversion of cyclohexane was 5.7%, and selectivities of cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide were 31.4%, 34.4% and 19.2%, respectively (total selectivity was 85.0%).
Comparative Example 1
A procedure was conducted similarly as in Example 1, except that 0.0070 g (4.2×106 mol) of cobalt(II) 5,10,15,20-tetrakis(pentafluorophenyl)-2,3,7,8,12,13,17,18-octabromoporphyrin was used alone as a catalyst and cobalt(II) 2-ethylhexanoate was not used. A conversion of cyclohexane was 5.5%, and selectivities of cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide were 29.4%, 38.3% and 15.7%, respectively (total selectivity was 83.4%).
Comparative Example 2
A procedure was conducted similarly as in Comparative Example 1, except that residence time was 75 minutes. A conversion of cyclohexane was 7.5%, and selectivities of cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide were 31.7%, 35.7% and 10.7%, respectively (total selectivity was 78.1%).
Comparative Example 3
A procedure was conducted similarly as in Example 1, except that cobalt(II) 5,10,15,20-tetrakis(pentafluorophenyl)-2,3,7,8,12,13,17,18-octabromoporphyrin was not used and 0.0021 g (5.9×10−6 mol) of cobalt(II) 2-ethylhexanoate was used alone as a catalyst, and a reaction pressure was 0.9 MPa. A conversion of cyclohexane was 7.0%, and selectivities of cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide were 24.6%, 15.6% and 11.5%, respectively (total selectivity was 51.7%).
Comparative Example 4
A procedure was conducted similarly as in Comparative Example 3, except that residence time was 50 minutes. A conversion of cyclohexane was 6.4%, and selectivities of cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide were 26.0%, 22.2% and 16.7%, respectively (total selectivity was 64.9%).

## Claims

1. A process for producing cycloalkanol and/or a cycloalkanone, comprising the step of oxidizing cycloalkane with molecular oxygen in the presence of cobalt salt of carboxylic acid and cobalt complex with porphyrin as a ligand, wherein the cobalt complex with porphyrin as a ligand is a compound represented by the formula (1):



wherein each of X1 to X8 independently represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, a hydrocarbon group, a halogenated hydrocarbon group or a sulfonyl group, and each of R1 to R4 independently represents a hydrogen atom, a nitro group, a cyano group, a hydrocarbon group or a halogenated hydrocarbon group.

2. The process according to claim 1, wherein at least one of the X1 to X8 in the formula (1) is a halogen atom.

3. The process according to claim 1 or 2, wherein the cycloalkane is cyclohexane.