JPS6239146B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing alkoxybenzaldehyde, phenoxybenzaldehyde, etc. by oxidizing alkoxybenzyl alcohol, phenoxybenzyl alcohol, etc. with an oxygen-containing gas. Alkoxybenzaldehyde, phenoxybenzaldehyde, and the like are very useful compounds as raw materials for fragrances, agricultural chemicals, and other intermediates in organic synthesis. Conventional methods for obtaining these aromatic aldehydes include oxidizing benzyl halides obtained by halogenating toluene derivatives with hexamethylenetetramine, and benzyl halides obtained by reacting halogens with toluene derivatives in the presence of phosphorus halide. In the case of anisaldehyde, a method of hydrolyzing halides, such as a method of oxidizing anethole extracted from fenugreek oil with a reagent, is carried out industrially. However, these methods have problems such as stoichiometric consumption of expensive reagents, very low yields, and complicated handling such as waste water treatment. It is also known to obtain the corresponding benzaldehyde by oxidizing alkoxybenzyl alcohol with an oxygen-containing gas in a basic aqueous solution in the presence of a platinum metal catalyst or a platinum metal-lead, bismuth, silver, or tin catalyst (JP-A Publication No. 55-59128). However, with this method, a yield of, for example, anisaldehyde is only 71% at most. Under high conversion conditions, oxidative decomposition of the aldehyde produced and subsequent reaction to acid occur, making it unsuitable for practical use. Therefore, there is a strong demand for a method for producing the above-mentioned aromatic aldehydes in good yield. The present invention aims to solve the above problems. Then, alkoxybenzyl alcohols or phenoxybenzyl alcohols obtained by hydrolysis of alkoxybenzyl halides or phenoxybenzyl halides or reduction of alkoxybenzoic acid esters or phenoxybenzoic acid esters are added to the liquid phase. It achieves its purpose through oxidation. The liquid phase oxidation is performed using the above raw materials in an organic solvent in the presence of a catalyst prepared by adding lead and/or copper to palladium and/or platinum. This liquid phase oxidation is preferably carried out in the absence of alkaline compounds. That is, the present invention is based on the general formula () (In the formula, X is an alkoxy group or a phenoxy group, n
represents an integer from 1 to 3. When n is 2 or 3, each X may be the same or different. In addition, when X is a methoxy group and is in the meta and para positions, these two methoxy groups are cyclized to form -O-CH ₂ -
It may also take the form of O-. ) in an organic solvent in the presence of a catalyst consisting of at least one type selected from palladium and platinum as component (A) and at least one type selected from lead and copper as component (B). Oxidized with medium oxygen-containing gas General formula () (In the formula, n, According to the present invention, alkoxy or phenoxybenzaldehyde can be produced in higher yield than conventional methods. In addition, the method of the present invention does not consume expensive reagents and does not cause problems in wastewater treatment, and is industrially very advantageous from the viewpoint of pollution problems. The raw material of the present invention is an alcohol represented by the formula (), examples of which include 4-methoxybenzyl alcohol, 3-ethoxybenzyl alcohol, and 3-ethoxybenzyl alcohol.
Phenoxybenzyl alcohol, 2,5-dimethoxybenzyl alcohol, 3,4-dimethoxybenzyl alcohol, 3,4,5-trimethoxybenzyl alcohol, 2-methoxy, 4-phenoxybenzyl alcohol, piperonyl alcohol, etc. be. The structural formula of piperonyl alcohol is as follows. The catalyst used in the present invention essentially contains palladium or platinum as component (A). Furthermore, at least one of lead and copper is essential as component (B). Generally, component (A) is used in a metallic state or in a slightly oxidized state, and component (B) is used in the form of an oxide or salt, or a mixture thereof. These active ingredients are usually supported on a carrier. As a carrier, calcium carbonate, activated carbon, alumina (α alumina, γ alumina, etc.), silica,
Those commonly used as carriers for platinum metal catalysts, such as silica, alumina, and zeolite, are used. The total loading of the active ingredients (A) and (B) on the carrier is preferably 0.1 to 30% by weight as metals.
and more preferably 0.2 to 25% by weight. The loading rate of component (A) on the carrier is preferably 0.1 to 20% by weight of the metal, more preferably
It is 0.1-10% by weight. Further, the supporting ratio of component (B) on the carrier is preferably 0.05 to 25% by weight as metal, and more preferably 0.1 to 20% by weight. To prepare these catalysts, for example, a palladium compound such as palladium nitrate, palladium chloride, palladium acetate, palladium acetylacetonate, or a platinum compound such as chloroplatinic acid is supported on a carrier by a conventional method such as dipping. , by supporting a lead and/or copper compound by a method such as dipping and drying. Examples of the above-mentioned lead compounds include lead acetate, lead nitrate, lead sulfate, lead oxide, lead hydroxide, and metallic lead, and examples of the copper compounds include copper chloride, copper sulfate, copper nitrate, and copper acetate. It can also be obtained by adding and mixing a lead and/or copper compound and a palladium or platinum compound together, supporting them on a carrier by a method such as dipping, and drying. Alternatively, it can be obtained by first supporting a lead and/or copper compound on a carrier and then supporting palladium or platinum thereon. As a catalyst activation treatment, reduction treatment with formalin, hydrazine, methanol, olefin, hydrogen, etc. is usually performed before or after drying. It goes without saying that this treatment is not limited to being carried out after all active ingredients have been loaded, but that the reduction treatment may be carried out each time each ingredient is loaded. In addition, commercially available palladium-activated carbon, palladium-calcium carbonate, platinum-activated carbon catalysts, etc., are supported by a method such as dipping a solution containing lead and/or copper components, and then dried, or catalysts that are subjected to treatment such as reduction or oxidation after being supported. , dried catalysts can likewise be used in the process of the invention. One of the characteristics of the oxidation reaction of the present invention is that the aromatic alcohol as a raw material is dissolved in an organic solvent. and those that dissolve the product under the reaction conditions are used. Specifically, aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene, aliphatic hydrocarbons such as n-heptane, n-octane, and n-decane, alicyclic hydrocarbons such as cyclohexane, and halogens such as chlorobenzene. hydrocarbon, ethyl acetate, isopropyl acetate, acetic acid n
- Esters such as butyl, ethers such as diethylene glycol dimethyl ether and dioxane, nitriles such as butyronitrile and benzonitrile,
Although it is preferable to use a solvent such as N.N dimethylformamide or dimethyl sulfoxide, raw alcohols can also be used as a solvent. Note that the solvent may contain a small amount of water before the reaction or water by-produced by the reaction. The concentration of aromatic alcohol used is 1 to 100% by weight, particularly preferably 5 to 50% by weight. The oxygen-containing gas used in the reaction not only means a mixed gas with other gases, but also includes a gas consisting only of oxygen. Any type of reactor such as a stirred tank, bubble column, fixed bed, etc. can be used, and the reaction can be carried out either batchwise or continuously. The appropriate reaction temperature is room temperature to 150℃, but 40 to 130℃
℃ is more preferable. The appropriate pressure is normal pressure to 10 kg/cm ² . The aromatic aldehyde obtained by the reaction is separated by a conventional method such as distillation, and the catalyst is separated by filtration,
It is separated by methods such as tilting and centrifugation and used repeatedly. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way. Example 1 10 g of anis alcohol dissolved in 90 g of toluene was charged into a four-necked flask equipped with a gas inlet, a stirrer, a condenser and a thermometer, and then 5% by weight of Pd-activated carbon was added to the liquid. A dried catalyst supported with 10% by weight of lead acetate as a metal was added to a catalyst (manufactured by Nippon Engelhard Co., Ltd.) so that the catalyst concentration was 1% by weight, air gas was introduced into the liquid, and the temperature was heated at 90℃3.
Allowed time to react. The Pd-activated carbon catalyst described above is a commercially available product, but it has been reduced in advance. The same applies to the following descriptions. After completion of the reaction, analysis by gas chromatography showed that an anis alcohol conversion rate of 98.6%, an anisaldehyde yield of 97.3%, and an anisaldehyde selectivity of 98.6% were obtained. Trace amounts of anisic acid, anisole, esters, etc. were observed as by-products. Examples 2 and 3 and Comparative Examples 1 and 2 Table 1 shows the results of Examples 2 and 3 and Comparative Examples 1 and 2, which were reacted under the same conditions as Example 1 except that the solvent and reaction time were changed.

【table】

[Table] Comparative Example 3 5% Pd- as component (A) without supporting component (B)
Using the activated carbon catalyst (manufactured by Nippon Engelhard Co., Ltd.) as is, the reaction was carried out under the same conditions as in Example 1, resulting in an anis alcohol conversion rate of 99.3%, anisaldehyde yield, and anisaldehyde selectivity of 49.0%.
The yield was 49.4%, and the by-product of anisole was 41.2% (yield). When the reaction time was 1 hour, the anis alcohol conversion rate was 75.5%, the anisaldehyde yield was 58.2%, the anisaldehyde selectivity was 77.1%, and the anisole by-product was 14.2% (yield). Example 4 A catalyst in which 1% by weight of copper nitrate was supported as a metal on a 5% Pd-activated carbon catalyst (manufactured by Nippon Engelhard Co., Ltd.) was dried and decomposed to make the copper component into an oxide, and the catalyst concentration was 1% by weight. As a result, the anis alcohol conversion rate was 84.9%, the anisaldehyde yield was 71.8%, and the anisaldehyde selectivity was 84.6%. When the reaction time was 5 hours, the anis alcohol conversion rate was 95.6%.
The anisaldehyde yield was 76.3% and the anisaldehyde selectivity was 79.8%. Example 5 The reaction was carried out under the same conditions as in Example 1, except that a catalyst in which 10% by weight of lead acetate was supported as a metal on a 5% Pt-activated carbon catalyst (manufactured by Nippon Engelhard Co., Ltd.) was used. Alcohol conversion rate 97.3%,
The anisaldehyde yield was 95.9% and the anisaldehyde selectivity was 98.6%. Example 6 3 g of m-phenoxybenzyl alcohol was converted into p-
The reaction was carried out under the same conditions as in Example 1, except that the catalyst concentration was 1.5% by weight, the reaction temperature was 100°C, and the reaction time was 2 hours.
- Phenoxybenzyl alcohol conversion rate 99.9%,
m-Phenoxybenzaldehyde yield 97.6%, m
-The phenoxybenzaldehyde selectivity was 97.8%. Comparative Example 4 The reaction was carried out under the same conditions as in Example 6 except that a 5% Pd-activated carbon catalyst (manufactured by Nippon Engelhard Co., Ltd.) was used as a catalyst, and as a result, the m-phenoxybenzyl alcohol conversion rate was 98.9, m -Phenoxybenzaldehyde yield was 26.2%, m-phenoxybenzaldehyde selectivity was 26.5%, and 65.4 (yield) of diphenyl ether was produced as a by-product.

Claims (1)

[Claims] 1 General formula () (In the formula, X is an alkoxy group or a phenoxy group, n
represents an integer from 1 to 3. When n is 2 or 3, each X may be the same or different. In addition, when X is a methoxy group and is in the meta and para positions, these two methoxy groups are cyclized to form -O-CH ₂ -
It may also take the form of O-. ) with an oxygen-containing gas in an organic solvent in the presence of a catalyst consisting of at least one selected from palladium and platinum as component (A) and at least one selected from lead and copper as component (B). Oxidized, general formula () (In the formula, n,