JPS6239144B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing aromatic aldehydes by oxidizing aromatic alcohols with oxygen-containing gas. Aromatic aldehydes are very useful compounds as raw materials for perfumes, agricultural chemicals, resins, dyes, etc., and as intermediates for other organic synthesis. Conventionally, methods for obtaining aromatic aldehydes include
Industrial methods include oxidizing benzyl halides obtained by halogenating toluene derivatives, and hydrolyzing benzyl halides obtained by reacting toluene derivatives with halogens in the presence of phosphorus halide. ing. However, these methods have problems such as stoichiometric consumption of expensive reagents, low yields, and complicated wastewater treatment. It is also known to obtain benzaldehyde by oxidizing benzyl alcohol obtained by hydrolysis of benzyl halide with oxygen-containing gas in the presence of a platinum catalyst (for example, RPASneeden, J.
Am.Chem.Soc., 77.190 (1955)). However, even with this method, the yield is only 72% at most. When a palladium catalyst is used, elimination of substituents occurs and selectivity is low, making it difficult to put it to practical use. On the other hand, JP-A-54-138886 discloses a catalyst composition for oxidation reactions in which lead, tin, indium, and tellurium are added as promoter components to a noble metal catalyst. The main product of the oxidation reaction of alcohol is the corresponding acid, and there is no description of the production of the corresponding aldehyde, and the production is either not recognized or is minimal. Therefore, a method for obtaining aromatic aldehydes in good yield is strongly desired. The present invention aims to provide a solution to the above-mentioned problems, and attempts to achieve this purpose by using a catalyst in which lead and/or copper are added to palladium. That is, the present invention provides the following general formula (n is an integer of 1 to 3, R represents hydrogen, an alkyl group, or an aryl group.) This is a method for producing aromatic aldehydes, which is characterized by oxidizing them with an oxygen-containing gas in a reactor. According to the present invention, aromatic aldehydes can be produced in higher yields than conventional methods, and expensive reagents are not consumed, so there are no problems with wastewater treatment. The aromatic alcohol that is the raw material of the present invention has the general formula (n is an integer of 1 to 3, R is hydrogen, an alkyl group, or an aryl group.) It is a monohydric to trihydric alcohol represented by, specifically, benzyl alcohol, methylbenzyl alcohol, ethylbenzyl alcohol. ,
These include isopropylbenzyl alcohol, tert-butylbenzyl alcohol, dimethylbenzyl alcohol, trimethylbenzyl alcohol, phenylbenzyl alcohol, benzenedimethanol, and benzenedrimethanol. The catalyst used in the present invention essentially contains palladium as an active component, and also contains at least one of lead and copper. These active ingredients are usually supported on a carrier. The supporting ratio of the palladium component to the carrier is about 0.1 to 20% by weight as metal, preferably 0.2% by weight.
~10% by weight. In addition, the loading rate of lead and/or copper components on the carrier is 0.05 to 0.05 as metals.
About 25% by weight, preferably 0.1 to 20% by weight
That's about it. As a carrier, alumina (γ-alumina, α-
Alumina, etc.), silica, silica-alumina, calcium carbonate, barium sulfate, magnesia, activated carbon, and the like, which are commonly used as supports for platinum metal catalysts, are used. In the catalyst used in the present invention, the palladium component is supported on the carrier by a conventional method such as immersing the carrier in an aqueous solution of a palladium compound such as palladium nitrate, palladium chloride, palladium acetate, or palladium acetylacetonate. , followed by immersing the palladium-loaded support in an aqueous solution of lead and/or copper compounds, such as lead acetate, lead nitrate, lead sulfate, lead oxide, lead hydroxide, metallic lead, copper acetate, copper sulfate, etc. It can be obtained by allowing lead and/or copper components to be supported thereon, and further drying. Alternatively, it can also be obtained by adding and mixing a lead and/or copper compound and a palladium compound at any time, supporting it on a carrier by a method such as dipping, and drying it. Alternatively, it can be obtained by first supporting a lead and/or copper compound on a carrier, then supporting a palladium compound thereon, and drying the support. As a catalyst activation treatment, a reduction treatment using formalin, hydrazine, methanol-saturated nitrogen gas, hydrogen, etc. is usually performed before or after drying. It goes without saying that this reduction treatment is not limited to being carried out after all active ingredients have been supported, but may be carried out each time each ingredient has been supported. In addition, lead and/or copper components are supported on a commercially available catalyst such as palladium-activated carbon or palladium-calcium carbonate by a method such as dipping,
A dried catalyst, or a catalyst that has been subjected to a treatment such as oxidation or reduction after durability and dried as necessary, can be similarly used in the method of the present invention. Although the oxidation reaction of the present invention can be carried out without using a solvent depending on the raw material, it is usually preferable to dissolve or disperse the aromatic alcohol as a raw material in a solvent. As a reaction solvent, aromatic hydrocarbons such as benzene, toluene, ethylbenzene, kyumene, tert-butyltoluene, xylene, trimethylbenzene, tetramethylbenzene, phenyltoluene; n-hexane, n-heptane, n-octane, etc. aliphatic hydrocarbons such as cyclohexane; halogenated hydrocarbons such as chlorobenzene; esters such as methyl acetate and ethyl acetate; ethers such as diethylene glycol dimethyl ether and dioxane; ketones such as methyl ethyl ketone A substance that dissolves or disperses raw materials and products, such as the following, is used. The concentration of aromatic alcohol is suitably 0.1 to 100% by weight, particularly preferably about 0.5 to 50% by weight. Air is generally used as the oxygen-containing gas used in the reaction. Note that the oxygen-containing gas of the present invention does not mean only a mixed gas of oxygen and other gases;
It also includes a gas consisting only of oxygen. Any type of reactor can be used, such as a stirred tank, bubble column, fixed bed, etc.
It can be carried out either batchwise or continuously. The reaction temperature is suitably from room temperature to 150°C, preferably from 40 to 130°C. Further, the reaction pressure is about normal pressure to 10 kg/cm ² G, but it is usually advantageous to carry out the reaction at normal pressure. The aromatic aldehyde obtained by the reaction is separated by a conventional method such as distillation, and the catalyst is
Separated by filtration, decanting, etc., and used repeatedly. The resulting aromatic aldehyde has a structure in which at least one hydroxymethyl group of the aromatic alcohol as a raw material is substituted with a formyl group. For example, when benzenedimethanol is used as a raw material, when terephthalaldehyde and hydroxymethylbenzaldehyde are used as raw materials, and when para-tertiary butylbenzyl alcohol is used as raw materials,
Examples include para-tert-butylbenzaldehyde. 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 6.3 g of 1,4-benzenedimethanol was dissolved in 116 g of p-xylene, 5% by weight of lead acetate was supported as a metal on a 5% PD activated carbon catalyst (manufactured by Engelhard), and the dried catalyst was prepared at a catalyst concentration. A four-necked flask equipped with a gas inlet, a stirrer, a condenser, and a thermometer was charged to a concentration of 3.2% by weight, air was introduced, and the reaction was carried out at 80°C for 5 hours. After completion of the reaction, analysis by gas chromatography showed that the conversion rate of benzenedimethanol was 100%, the yield of terephthalaldehyde was 80.4%, and the yield of hydroxymethylbenzaldehyde was 8.9%. By-products were benzaldehyde, esters, and acids, and benzaldehyde was produced as a by-product at a yield of 3.2%. Comparative Example 1 The reaction was carried out under the same conditions as in Example 1 except that a 5% PD activated carbon catalyst (manufactured by Engelhard) was used without supporting a metal component. As a result, the benzenedimethanol conversion rate was 97.4%, and terephthalaldehyde was Yield 14.9%, hydroxymethylbenzaldehyde yield 7.9%, benzaldehyde 60.5%
(Yield) As a by-product. Example 2 The reaction was carried out in the same manner as in Example 1, except that lead nitrate was used instead of lead acetate and a catalyst supported at 1% by weight as metal was used, and the reaction time was 3 hours. As a result, benzene was produced. Dimethanol conversion rate 97.2
%, terephthalaldehyde yield was 66.1%, hydroxymethylbenzaldehyde yield was 13.9%, and benzaldehyde yield was 12.5%. Examples 3 to 6 Using a commercially available Lindlar catalyst (pd-pb/CaCO ₃ , manufactured by Engelhard), the reaction was carried out in the same manner as in Example 1, except that the catalyst concentration, reaction temperature, and reaction time were changed. are shown in Table 1.

[Table] Here, dimethanol, dialdehyde, monoaldehyde, and aldehyde refer to benzenedimethanol, terephthalaldehyde, hydroxymethylbenzaldehyde, and terephthalaldehyde+hydroxymethylbenzaldehyde, respectively. In addition, the benzaldehyde yield was 1.6 in Example 3.
%, 4 and 5 are only traces, and 6 is 0.7%
It was hot. Comparative Example 2 A commercially available 5% PD catalyst (supported by CaCO ₃ ,
The reaction was carried out under the conditions of Example 1, except that the catalyst concentration was 3.2% by weight, the reaction temperature was 80°C, and the reaction time was 3 hours. The conversion rate of benzenedimethanol was 85.6%. The selectivity was 29.4%, the same yield was 25.2%, the hydroxymethylbenzaldehyde selectivity was 9.2%, the same yield was 7.9%, and the benzaldehyde yield was 31.5%. Example 7 As a catalyst, 1% by weight of copper nitrate was supported as a metal on a 5% PD activated carbon catalyst (manufactured by Engelhard),
The reaction was carried out under the same conditions as in Example 1, except that a catalyst in which the copper component was made into an oxide by decomposition after drying was used at a catalyst concentration of 1.6% by weight, and the reaction time was 3 hours. As a result, benzenedimethanol conversion was achieved. The yield of terephthalaldehyde was 56.4%, the yield of hydroxymethylbenzaldehyde was 21.4%, and the benzaldehyde yield was 9.3%. When the reaction time was further extended for 4 hours and the reaction was continued for a total of 7 hours, the yield of terephthalaldehyde was
It became 63.2%. Example 8 Para-tertiary butylbenzyl alcohol
10.4 g, 120.0 g of para-tert-butyltoluene as a solvent, and 4.0 g of the catalyst of Example 3 as a catalyst.
When the reaction was carried out under the same conditions as in Example 1 except that the reaction was carried out at 85°C for 7 hours, the yield of para-tert-butylbenzaldehyde was 93.3%.
I got it. There were very few by-products including para-tert-butylbenzene. Comparative Example 3 The reaction was carried out in the same manner as in Example 8, except that 4.0 g of a commercially available 5% PD catalyst (the carrier was activated carbon, manufactured by Engelhard) was used as a catalyst, and the reaction time was 5 hours. Ta. As a result, the yield of para-tertiary butylbenzaldehyde was 53.5%, but the yield of para-tertiary butylbenzene was 41.5%.
% (yield) was produced as a by-product.

Claims (1)

[Claims] 1. The following general formula (n is an integer of 1 to 3, R is hydrogen, an alkyl group, or an aryl group.) An aromatic alcohol represented by A method for producing an aromatic aldehyde, which is characterized by oxidation with an oxygen-containing gas in a solvent.