JP2000070723A - Ru-Al-Mg TYPE SYNTHETIC HYDROTALCITE, OXIDATION CATALYST AND PRODUCTION OF CARBONYL COMPOUND USING SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily prepare a recyclable catalyst for nonstoichiometric oxidation of an α,β-unsatd. alcohol. SOLUTION: The oxidation catalyst comprises a synthetic hydrotalcite represented by the formula Mg6Al2Ru0.5(OH)16.X (where X is a carbonate anion, a chlorine anion, an acetate anion, a sulfate anion, a terephthalate anion, a 1,5-naphthalenedisulfonate anion, a dodecylsulfate anion or a sebacate anion).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel synthetic hydrotalcite, an oxidation catalyst comprising the hydrotalcite, and a method for producing a carbonyl compound using the same.

[0002]

2. Description of the Related Art Conventionally, in the production of carbonyl compounds by oxidation of α, β-unsaturated alcohols such as allyl alcohol and benzyl alcohol, manganese dioxide, chromic acid, selenium dioxide, ruthenium-based catalyst, ruthenium-based catalyst +3 Secondary amine oxides, rhodium-based catalysts and the like are used.

Manganese dioxide (New Experimental Chemistry Course 15, Oxidation and Reduction [I-1], edited by The Chemical Society of Japan, Maruzen Co., Ltd., 7
In the production of carbonyl compounds using chromic acid (VI) (p. 105) and selenium dioxide (p. 331) as catalysts, manganese dioxide, chromic acid or selenium dioxide acts as an oxidizing agent, and the catalyst is stoichiometric. Manganese as a byproduct
Since chromium (IV) or a selenium derivative is generated, it is necessary to treat the chromium (IV) or selenium derivative.

[0004] Ruthenium-based catalysts (JP-A-57-1080)
No. 35) or a carbonyl compound using a ruthenium-based catalyst and a tertiary amine oxide (DE 440287) as a catalyst, a ruthenium-triphenylphosphine complex is used as a ruthenium-based catalyst, and a direct oxidizing agent is used. Is an oxygen atom, and the amount of the catalyst used is non-stoichiometric, that is, the amount of the catalyst is small, but has the disadvantage that the preparation of the catalyst is very complicated.

On the other hand, production of a carbonyl compound using a rhodium-based catalyst in an oxygen atmosphere (JP-A-3-93742)
In (2), the direct oxidizing agent is oxygen, and the amount of the catalyst used is non-stoichiometric. However, it is necessary to use a very expensive metal such as rhodium, and the preparation of the catalyst is complicated. is there.

[0006]

An object of the present invention is to provide a non-stoichiometric oxidation catalyst for α, β-unsaturated alcohols which is easy to prepare and which can be recycled.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and as a result, have been known as epoxidation catalysts for double bonds (Tetrahedron Letters, Vol. 36, No. 23, No. 4).
125-4128, 1995), the natural layered compound Mg-Al-based hydrotalcite was examined in various ways for its constituent metal components, and Ru-Al-Mg-based synthetic hydrotalcite was a novel substance. , Α, β-unsaturated alcohols, and found that the catalyst was very easy to prepare and recyclable. It was completed.

That is, the present invention comprises the following eleven items. (A) Synthetic hydrotalcite represented by Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ · X. [X is a carbonate anion,
It represents chlorine anion, acetate anion, sulfate anion, terephthalate anion, 1,5-naphthalenedisulfonic acid anion, dodecyl sulfate anion or sebacate anion. (B) The synthetic hydrotalcite according to item (a), wherein X is a carbonate anion. (C) A magnesium salt (Mg salt), an aluminum salt (Al salt), and a ruthenium salt (Ru salt), which are inorganic metal salts, are dissolved in water, and sodium hydroxide and a salt of an anion represented by X are further added, followed by heating. A general formula of Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ · X wherein X is the same as that described in the item (a). ] The manufacturing method of the synthetic hydrotalcite represented by these. (D) The method for producing synthetic hydrotalcite according to item (c), wherein the inorganic metal salts are magnesium chloride, aluminum chloride and ruthenium chloride, respectively, and the anion salt is a sodium salt. (E) The method for producing a synthetic hydrotalcite according to item (c) or item (d), wherein X is a carbonate anion. (F) An oxidation catalyst comprising a synthetic hydrotalcite represented by Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ ×. [X
Is the same as that described in the item (a). (G) An oxidation catalyst comprising the synthetic hydrotalcite according to item (f), wherein X is a carbonate anion. (H) In an oxygen atmosphere, Mg ₆ Al ₂ Ru _0.5 (OH)
₁₆ · X [X are the same as those described in paragraph (a). A method for producing a carbonyl compound, comprising oxidizing an aromatic ring-conjugated allylic alcohol or benzylic alcohol to obtain a corresponding aldehyde or ketone using the synthetic hydrotalcite represented by the formula (I) as a catalyst. (I) The method for producing a carbonyl compound according to item (h), wherein X is a carbonate anion. (J) The aromatic ring conjugated allylic alcohol is cinnam alcohol, 2-methyl-3-phenyl-2-propen-1-ol, 3,3′-diphenyl-2-propene-
Item (h) or Item (i) which is 1-ol, 2-pyridylmethanol or 4-phenyl-3-buten-2-ol
The method for producing a carbonyl compound according to the above. (K) the benzylic alcohol is benzyl alcohol,
Item (h) or item (i) which is 4-methoxybenzyl alcohol, 3,4-methylenedioxybenzyl alcohol, 4-isopropylbenzyl alcohol, 4-chlorobenzyl alcohol, α-methylbenzyl alcohol or benzhydrol A method for producing a carbonyl compound. (L) Mg ₆ Al ₂ Ru _0.5 (O
H) A method for regenerating a synthetic hydrotalcite catalyst, comprising washing a synthetic hydrotalcite catalyst represented by ₁₆ CO ₃ with an aqueous solution of Na ₂ CO ₃ .

[0009]

DETAILED DESCRIPTION OF THE INVENTION Hydrotalcite, a naturally occurring mineral, is known as a layered compound, but is a synthetic hydrotalcite of the present invention represented by Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ .X. Talcite is also a layered compound like a natural product (analysis result by X-ray diffraction).

According to the present invention, Mg ₆ Al ₂ Ru _0.5 (OH)
_{As a} method for preparing 16.X, an inorganic metal salt as a raw material,
That is, magnesium salt (Mg salt), aluminum salt (Al
Salt) and a ruthenium salt (Ru salt) are dissolved in water, an alkali hydroxide and a salt of an anion represented by X are further added, and a heat treatment is performed to obtain a target synthetic hydrotalcite as a precipitate. Further, the obtained precipitate is dried under heating or at room temperature.

The molar ratio of the raw materials used is Ru salt / Mg
Salt / Al salt / OH ⁻ / X = 1/1 to 30/1 to 30/1
0 to 100/1 to 50, preferably Ru salt / Mg salt / Al salt / OH ⁻ / X ⁻ = 1/5 to 20/1 to 1
10/20 to 50/1 to 20, more preferably,
Ru salt / Mg salt / Al salt / OH ⁻ / X ⁻ = 1/10 /
3.4 / 30 / 17.4.

The kind of the inorganic metal salt (Ru salt, Mg salt, Al salt) is not particularly limited, and halides (Cl, B
r, I), sulfate, carbonate, nitrate and the like can be used, and among them, chloride (Cl) or nitrate is preferable.

The anions represented by X include carbonate anion, chloride anion, acetate anion (AcO), sulfate anion, terephthalate anion (TA), 1,5-naphthalenedisulfonic acid anion (ND), and dodecyl sulfate anion (DS ) or sebacic acid anion (SA), but these are in the time of preparation of the hydrotalcite, Na ₂
CO ₃ , NaCl, CH ₃ COONa, Na ₂ SO ₄ ,
It is recommended to incorporate into the reaction in the form of sodium terephthalate, sodium 1,5-naphthalenedisulfonic acid, sodium dodecylsulfonic acid or sodium sebacate.

The hydrotalcite according to the present invention can be prepared by using an alkali metal salt such as a potassium salt or a lithium salt instead of the sodium salt as the anion.

The alkali hydroxide used is NaO
H, KOH, LiOH and the like, preferably NaO
H.

The preparation time (heat treatment time) of the synthetic hydrotalcite is 1 to 100 hours, preferably 10 to 30 hours.

The preparation temperature (heat treatment temperature) of the synthetic hydrotalcite is 0 to 100 ° C., preferably 40 to 80 ° C.

The drying time of the obtained synthetic hydrotalcite is 1 to 100 hours, preferably 10 to 100 hours.
~ 30 hours.

The drying temperature of the obtained synthetic hydrotalcite is 0 to 200 ° C., preferably 80 to 200 ° C.
150 ° C.

According to the present invention, Mg ₆ Al ₂ R
A method for producing a carbonyl compound by oxidizing an allylic alcohol or a benzylic alcohol using a synthetic hydrotalcite represented by u _0.5 (OH) ₁₆ .X (X is the same as described above) as a catalyst. Also provide.

When a primary alcohol is oxidized, an aldehyde is obtained, and when a secondary alcohol is oxidized, a ketone is obtained.

The allylic alcohol is an alcohol represented by the general formula (1).

[0023] [Wherein, R ¹ , R ² , R ³ , and R ⁴ are the same or different,
A hydrogen atom or an alkyl group which may have a substituent,
It represents an alkenyl group, an aromatic group or a heterocyclic aromatic group.
Further, R ¹ and R ³ may be bonded to each other with or without a heteroatom via a carbon atom to which they are bonded to form a cyclic structure. ]

In the allylic alcohol represented by the general formula (1), specific examples of R ¹ , R ² , R ³ , and R ⁴ include a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and an alkyl group having 1 to 20 carbon atoms. And at least one of R ^{1 and} R ² is preferably an aromatic group (such an aromatic ring conjugated allylic alcohol). Especially a phenyl group, and R ³
Alternatively, preferably, R ⁴ is a hydrogen atom or a methyl group.

Examples of the group in which R ¹ and R ³ are bonded to each other via a hetero atom together with the carbon atom to which they are bonded to form a cyclic structure include a thienyl group, a tetrahydropyranyl group and a pyridine group. And the like.

On the other hand, examples of the group in which R ¹ and R ³ are bonded to each other together with the carbon atom to which they are bonded via no other heteroatom to form a cyclic structure include a cyclohexene group and a cyclopentene group. Is exemplified.

Specific allylic alcohols include allyl alcohol, cinnam alcohol, 2-methyl-3
-Phenyl-2-propen-1-ol, 3,3'-diphenyl-2-propen-1-ol, 4-phenyl-
3-buten-2-ol, 2-thienyl alcohol, 2
-Pyridylmethanol and the like, preferably aromatic ring conjugated (R ¹ or R ² is an aromatic group) allyl alcohol, ie, cinnam alcohol, 2-methyl-3-phenyl-2-propene-1- All, 3,3'-diphenyl-2-propen-1-ol, 4-phenyl-3-
Buten-2-ol and 2-pyridylmethanol are exemplified.

The carbonyl compounds obtained by oxidizing the allylic alcohol include allyl aldehyde, cinnamaldehyde, 2-methyl-3-phenyl-2-propenyl aldehyde, 3,3'-diphenyl-2-propenyl aldehyde, Phenyl-3-buten-2-one, 2
-Thienylaldehyde, 2-pyridylaldehyde and the like.

The benzylic alcohol is represented by the general formula (2)
Is an alcohol represented by

[0030] [Wherein, R ⁵ and R ⁶ are the same or different, and each represents a hydrogen atom or an optionally substituted alkyl group, alkenyl group, alkoxy group, halogen group, aromatic group, heterocyclic aromatic group, or the like. Show. ]

[0031] During benzylic alcohol represented by the general formula (2), as a specific ^{R 5,} a hydrogen atom, 1 to carbon atoms
20 alkyl groups and phenyl groups, preferably a hydrogen atom, a methyl group and a phenyl group, and R ⁶ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms and an alkoxy group having 1 to 10 carbon atoms. And a chlorine atom, and a hydrogen atom, a methoxy group, an isopropyl group, and a chlorine atom are recommended. The position of R ⁶ bonded to the benzene ring is as follows:
Any position of o, m and p can be used on the basis of benzyl alcohol.

Specific benzylic alcohols include:
Benzyl alcohol, 4-methoxybenzyl alcohol, 3,4-methylenedioxybenzyl alcohol, 4
-Isopropylbenzyl alcohol, 4-chlorobenzyl alcohol, α-methylbenzyl alcohol, benzhydrol and the like.

Examples of the carbonyl compound obtained by oxidizing a benzylic alcohol include benzaldehyde, 4-methoxybenzaldehyde, 3,4-methylenedioxybenzaldehyde, 4-isopropylbenzaldehyde, 4-chlorobenzaldehyde, α-methylbenzaldehyde, Examples include diphenyl ketone.

The specific oxidation method is as follows.

An allylic alcohol or benzylic alcohol (2 mmol), a synthetic hydrotalcite catalyst (0.3 g) and a reaction solvent are reacted at 60 ° C. in an oxygen atmosphere. After completion of the reaction, the catalyst was filtered off, and the filtrate was analyzed by GC to confirm that the corresponding carbonyl compound was obtained. Then, the filtrate was concentrated, and the residue was purified by a purification means such as column chromatography. Yields the desired carbonyl compound.

As a synthetic hydrotalcite oxidation catalyst
Is Mg₆Al₂Ru_0.5(OH) ₁₆CO_3,Mg
₆Al₂Ru_0.5(OH)₁₆Cl, Mg₆Al₂R
u_{0. 5}(OH)₁₆AcO, Mg₆Al₂Ru_0.5
(OH)₁₆SO₄, Mg₆Al₂Ru_0.5(OH)
₁₆TA, Mg₆Al₂Ru_0.5(OH)₁₆ND,
Mg₆Al₂Ru_0.5(OH)₁₆DS, Mg₆Al
₂Ru_0.5(OH)_{1 6}SA, and preferably
Mg₆Al₂Ru_0.5(OH)₁₆CO₃It is.

The composition ratio of the substrate (alcohol) and the catalyst used in the reaction is 0.05 to 1 g of the catalyst per 2 mmol of the reaction substrate, preferably 0.1 to 0.5 g.
g, more preferably 0.3 g.

As a reaction solvent, toluene, chlorobenzene, benzene, n-hexane, acetonitrile, 1,
Examples thereof include 2-dichloroethane, cyclohexane, and methanol, and preferably include toluene, chlorobenzene, and benzene.

The amount of the solvent is 1 to 50 ml, preferably 1 to 30 ml, more preferably 20 ml, per 1 g of the reaction substrate.

The reaction temperature varies depending on the reaction substrate and the reaction solvent, but it is 0 to 150 ° C., preferably 20 to 100 ° C., more preferably 60 to 80 ° C.

The reaction time varies depending on the reaction substrate and the reaction solvent, but may be 1 to 48 hours, preferably 1 to 24 hours.

After completion of the reaction, the catalyst is removed by filtration or centrifugation, the obtained filtrate is concentrated by a conventionally known method, and the residue is purified by liquid-liquid extraction, crystallization, chromatography and the like. A carbonyl compound can be obtained.

On the other hand, the synthetic hydrotalcite, which is the catalyst used in the oxidation reaction, can be reused without losing its oxidation activity and oxidation selectivity by washing with an aqueous alkali solution, followed by washing with water and drying. .

As the aqueous alkaline solution used for washing,
An aqueous alkali solution of about 10% can be mentioned, and examples of the alkali include NaOH, KOH, Na ₂ CO ₃ , K ₂ CO _{3, and the} like, and a 10 wt% Na ₂ CO ₃ solution is preferable.

After washing with the aqueous solution, the recovered catalyst is dried and used.

The drying time of the obtained regenerated catalyst is from 1 to
The time is 100 hours, preferably 10 to 30 hours.

The drying temperature of the obtained regenerated catalyst is from 0 to
The temperature is 200 ° C., preferably 80 to 150 ° C.

[0048]

The present invention will be described below in detail with reference to examples.

The basicity of hydrotalcite was evaluated by measuring the heat of adsorption of benzoic acid with Setram Micro DSC. The larger the value, the higher the basicity.

Example 1 RuCl₃・ 3H₂O (4.3 mmol), MgCl₂
・ 6H₂O (43.2 mmol), AlCl₃・ H₂O
(14.4 mmol) was dissolved in 100 ml of distilled water.
a₂CO₃(74.7 mmol), NaOH (0.13
mol), and the mixture was stirred at 65 ° C for 18 hours. Generation slur
After filtration, the residue is washed with distilled water and further heated at 110 ° C. for 1 hour.
Mg by drying by heating for 2 hours₆Al₂Ru_0.5
(OH) ₁₆CO₃5.25 g was obtained.

Elemental analysis value Mg ₆ Al ₂ Ru
_{0.5 (OH) 16 CO 3 ·} 8H 2 O: Calculated Mg; 20.1, Al; 7.4, Ru; 7.0 analysis Mg; 19.5, Al; 7.4, Ru; 7 .3

Heat of adsorption of benzoic acid: 32.1 (J / g)

X-ray diffraction: interlayer distance 7.9 °

X-ray photoelectron spectrum: Ru 3d _5/2 = 28
1.0 eV, peak half width = 2.5 eV

Example 2 Cinnam Alcohol (0.26 g), Mg ₆ Al ₂ Ru
_0.5 (OH) ₁₆ CO ₃ hydrotalcite (0.3
g) and toluene (5 ml) in an oxygen atmosphere at 60 ° C. for 5 minutes.
Reacted for hours. After 5 hours, the reaction solution was analyzed by GC and the conversion to aldehyde was measured, and it was 73%. Then, after removing the catalyst by filtration, the filtrate was distilled off under reduced pressure,
The residue was purified by column chromatography to obtain cinnamaldehyde (isolation yield: 68%).

Examples 3 to 9 Instead of carbonate anions, chlorine anions were used as the anions.
, Acetate anion (AcO), sulfate anion, terephthalate
Luic acid (TA) anion, 1,5-naphthalenedi sulfone
Acid (ND) anion, dodecyl sulfonic acid (DS) ani
Example, except using ON, sebacic acid (SA) anion
In the same manner as in Example 1, Mg₆Al₂Ru _0.5(O
H)₁₆Cl, Mg₆Al₂Ru_0.5(OH)₁₆A
cO, Mg₆Al₂Ru_0.5(OH)₁₆SO₄, M
g₆Al₂Ru_0.5(OH)₁₆TA, Mg₆Al₂
Ru_0.5(OH)₁₆ND, Mg₆Al₂Ru_0.5
(OH)₁₆DS, Mg₆Al₂Ru_0.5(OH)
₁₆SA was obtained.

X-ray diffraction: interlayer distance Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ DS: 26.0 ° Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ TA: 14.1 ° Mg ₆ Al ₂ Ru _{0. 5} (OH) ₁₆ ND: 8.6Å Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ SA: 8.1Å Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ Cl: 7.95Å Mg ₆ Al ₂ Ru _{0 .5 (OH)} 16 AcO: 7.94
Å Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ SO ₄ : 7.92
Å

Heat of adsorption of benzoic acid Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ Cl: 28.8
(J / g) Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ AcO: 10.2
(J / g) Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ SO ₄ : 1.7
(J / g)

Examples 10 to 16 The oxidation reaction was carried out in the same manner as in Example 2 except that the hydrotalcite obtained in Examples 3 to 9 was used as the oxidation catalyst. Table 1 shows the amount of cinnamaldehyde produced (conversion rate) after 5 hours and the isolation yield of the aldehyde obtained from the reaction solution.

[0060]

Example 17 Cinnam Alcohol (0.80 g), Mg ₆ Al ₂ Ru
_0.5 (OH) ₁₆ CO ₃ hydrotalcite (0.9
g) and toluene (15 ml) were reacted at 60 ° C. for 24 hours in an oxygen atmosphere. The hydrotalcite was filtered off, and the filtrate was analyzed by GC. As a result, aldehyde was obtained quantitatively. After concentrating the filtrate, the oily residue was purified by silica gel column chromatography to obtain 0.734 g of cinnamaldehyde in a 92% isolated yield.

Example 18 The used hydrotalcite filtered off in Example 17 was replaced with 3
Washed with 0 ml of a 10% by weight Na ₂ CO ₃ solution and then with water. Furthermore, it dried at 110 degreeC for 12 hours. Using the dried hydrotalcite and repeating the same oxidation reaction as in Example 17, the cinnamaldehyde showed a reaction rate of 95% or more by GC analysis even in the second use and the third use.

Examples 19 to 30 Various carbonyl compounds were obtained in the same manner as in Example 2 except that the starting alcohols shown in Table 2 were used and the reaction time was set to the times shown in Table 2. Table 2 shows the results.

[0064]

[0065]

According to the present invention, it has become possible to provide a metal catalyst for oxidation of α, β-unsaturated alcohol which is easy to prepare and can be reused. Further, by oxidizing the α, β-unsaturated alcohol using the catalyst, it has become possible to obtain the corresponding α, β-unsaturated carbonyl compound in high yield and at low cost. Furthermore, the catalyst once used for the oxidation reaction can be easily regenerated.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C07C 45/37 C07C 45/37 47/232 47/232 47/52 47/52 49/217 49/217 49/76 49 / 76 A C07D 213/48 C07D 213/48 317/54 317/54 // C07B 61/00 300 C07B 61/00 300

Claims (12)

[Claims] 1. The method according to claim 1, wherein Mg ₆ Al ₂ Ru _0.5 (OH) _16.
X [X is a carbonate anion, a chloride anion, an acetate anion,
It represents a sulfate anion, terephthalate anion, 1,5-naphthalenedisulfonic acid anion, dodecyl sulfate anion or sebacate anion. ] The synthetic hydrotalcite represented by this. 2. The synthetic hydrotalcite according to claim 1, wherein X is a carbonate anion. 3. A magnesium salt (Mg) which is an inorganic metal salt.
Salt), aluminum salt (Al salt), ruthenium salt (Ru
Salt), dissolved in water, further added with sodium hydroxide and a salt of an anion represented by X, followed by heat treatment, characterized by the general formula Mg ₆ Al ₂ Ru _0.5 (OH) ₁₆ · X [X Is the same as that described in claim 1. ] The manufacturing method of the synthetic hydrotalcite represented by these. 4. The method according to claim 3, wherein the inorganic metal salt is magnesium chloride, aluminum chloride and ruthenium chloride, respectively, and the anion salt is a sodium salt. 5. The method for producing a synthetic hydrotalcite according to claim 3, wherein X is a carbonate anion. 6. Mg ₆ Al ₂ Ru _0.5 (OH) _16.
X [X is the same as that described in claim 1. An oxidation catalyst comprising a synthetic hydrotalcite represented by the formula: 7. The oxidation catalyst comprising a synthetic hydrotalcite according to claim 6, wherein X is a carbonate anion. 8. An oxygen atmosphere containing Mg ₆ Al ₂ Ru _0.5
(OH) 16 · X [X are the same as described in claim 1. A method for producing a carbonyl compound, comprising oxidizing an aromatic ring-conjugated allylic alcohol or benzylic alcohol to obtain a corresponding aldehyde or ketone using the synthetic hydrotalcite represented by the formula (I) as a catalyst. 9. The method for producing a carbonyl compound according to claim 8, wherein X is a carbonate anion. 10. The aromatic ring conjugated allylic alcohol is cinnam alcohol, 2-methyl-3-phenyl-
2-propen-1-ol, 3,3'-diphenyl-2
9. Propene-1-ol, 2-pyridylmethanol or 4-phenyl-3-buten-2-ol.
Or a method for producing a carbonyl compound according to any one of claims 9 to 13. 11. The benzylic alcohol is benzyl alcohol, 4-methoxybenzyl alcohol, 3,4-
The method for producing a carbonyl compound according to any one of claims 8 or 9, which is methylenedioxybenzyl alcohol, 4-isopropylbenzyl alcohol, 4-chlorobenzyl alcohol, α-methylbenzyl alcohol or benzhydrol. . 12. The Mg ₆ Al ₂ Ru used in the oxidation reaction
_A method for regenerating a synthetic hydrotalcite catalyst, comprising washing a synthetic hydrotalcite catalyst represented by _0.5 (OH) ₁₆ CO ₃ with an aqueous solution of Na ₂ CO ₃ .