JPS5822016B2 - Method for producing alkylphenol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel process for alkylating phenols.

The reaction of selectively nuclear methylating the ortho and/or para positions of phenols such as phenol or substituted phenols is
It is useful in the synthesis of stabilizers, additives, and intermediates for organic drugs.

For example, 2,6-tert-butyl-p-cresol, which is useful as a stabilizer, is generally synthesized from p-cresol, but p-cresol is usually available in a mixture with m-cresol. Therefore, it is necessary to separate pure p-cresol from these mixtures, or to separate the tert-butylated derivative of p-cresol after tert-butylating the mixture, which increases separation costs and increases the amount of byproducts. The consumer of the resulting m-cresol or tert-butylated derivative of m-cresol becomes a problem, and if the supply and demand of the two is not balanced, there is a disadvantage that it will be expensive.

If phenol is used as a starting material, there is no such concern; for example, if phenol is used as a 2,6-sheet t
If a method of performing 4-methylation after ert-butylation can be performed with good yield, it can be replaced with the above method.

The method of using methanol as a nuclear methylating agent for phenols is known, but the reaction usually needs to be carried out at a fairly high temperature, and it is difficult to use methanol for groups that are easily removed thermally, such as tert-butyl groups and alkoxy groups. It is not suitable for nuclear methylation of phenols with

The present invention provides a method using aldehydes as an alkylating agent in order to obtain the desired alkylphenol at a relatively low temperature and in good yield.

Conventionally, methods using aldehydes as alkylating agents have been known.

For example, US Pat. No. 2,401,608 discloses a method for producing methylphenols by reacting phenols and formaldehyde in the presence of a basic catalyst, but this method does not involve side reactions. The yield of the target product is low.

Also, according to the specification of U.S. Patent No. 2,909,568, a two-step process in which phenols and formaldehyde are reacted in the presence of a basic catalyst to synthesize hydroxymethylphenols, and then methylphenols are produced by hydrogenation. is proposed.

According to this method, in the first stage of the reaction, hydroxymethylphenols are obtained in the form of salts, so it is necessary to produce free hydroxyphenols by acid precipitation, making the process long and complicated. The reaction had to be carried out under very mild conditions for a long time, and even in that case, the yield of hydroxymethylphenol was still not high enough, so it could not be said to be an excellent method.

Furthermore, the method described in Japanese Patent Publication No. 35-15359 is as follows:
This is an improved method of the above-mentioned US Pat. No. 2,401,608, in which an alcohol is further present in the reaction system of phenols, aldehydes, and bases.
After all, there were many side reactions, and the reaction temperature had to be maintained at a fairly high level, so it was still not a satisfactory method.

When reacting these aldehydes, in contrast to conventional methods that use basic catalysts, the present invention uses acid catalysts.

It is generally known that when phenols and formaldehyde are reacted in the presence of an acid catalyst, methylene-bridged multimers of two or more molecules are easily obtained. Although it is difficult to imagine alkylation with .

That is, the present invention provides a method for producing alkylphenol by reacting phenols, aldehydes, and hydrogen in the presence of an acid and a noble metal hydrogenation catalyst.

The phenols used as raw materials of the present invention are nuclear alkylatable, and therefore have at least a hydrogen atom directly connected to an aromatic nucleus.

Such phenols may have various substituents, and may be not only monohydric phenols but also polyhydric phenols.

Specifically, phenol, naphthol, cresol, xylenol, ethylphenol, flobylphenol,
Hydrocarbon-substituted phenols such as butylphenol, octylphenol, nonylphenol, dibutylphenol, cyclohexylphenol, phenylphenol, and cumylphenol Polyhydric phenols such as dicatechol, resorcinol, hydroquinone, bisphenol A1 dihydroxynaphthalene; methoxyphenol, ethoxyphenol, dimethoxyphenol Examples include alkoxy-substituted phenols such as; halogen-substituted phenols such as chlorophenol, bromophenol, and dichlorophenol.

Examples of the aldehyde used in the present invention include formaldehyde, acetaldehyde, and propionaldehyde, with formaldehyde being particularly preferred.

Formaldehyde may be used in monomeric form, but it can also be used in forms that liberate formaldehyde under the reaction conditions, such as trioxane or paraformaldehyde.

Alternatively, it can also be used as an aqueous solution (so-called formalin).

However, when an aqueous solution is used, depending on the reaction system, it may separate into two layers, an aqueous layer and an oil layer, in which case side reactions are likely to occur, so formaldehyde is usually used in the form of a polymer, as described above. is preferred.

The reaction of the present invention is carried out in the presence of an acid.

Although the acid varies depending on the type of hydrogenation catalyst used, it is generally one or two organic acids or inorganic acids with a pKa of 0.1 to 5.0, preferably 1.0 to 4.0. It is better to use more than one species.

Specifically, lower fatty acids such as acetic acid and propionic acid, halo lower fatty acids such as monochloroacetic acid and dichloroacetic acid, organic acids such as oxalic acid, succinic acid, and benzoic acid, hydrochloric acid,
Examples include inorganic acids such as phosphoric acid.

If an acid with a weak acid strength is used, the reaction rate will be slow, and if an acid with too strong an acid strength is used, a large amount of methylene cross-linked products of raw material phenols will be produced as a by-product. Therefore, it is recommended to use an acid with an appropriate acid strength. preferable.

For example, when only a lower fatty acid is used as the acid, the reaction selectivity is good, but the reaction rate is rather slow.

Furthermore, if only an acid with strong acid strength such as a halo-lower fatty acid is used, the reaction rate is fast but the selectivity is somewhat poor.

It is most preferable to use a mixture of a lower fatty acid and an organic acid having a stronger acid strength, such as a lower halo fatty acid.

The mixing ratio in this case is arbitrary, but generally 1 part by weight of lower fatty acid is mixed with 0.0 parts by weight of a stronger acid.
It is preferable to use them by mixing them in a proportion of about 0.01 to 2 parts by weight.

The reaction of the present invention is carried out by bringing phenols, aldehydes, and hydrogen into contact in the presence of the acid,
At this time, it is necessary to coexist a hydrogenation catalyst.

The hydrogenation catalyst is preferably one that is highly active in an acidic medium and is inactive for nuclear hydrogenation of phenol nuclei. Therefore, hydrogenation catalysts based on noble metals such as baradium, platinum, ruthenium, rhodium, osmium, and iridium are preferred. used.

A particularly preferred hydrogenation catalyst is a palladium catalyst.

Palladium may be used alone, such as palladium black, but in order to improve the catalyst efficiency, it is preferable to use palladium supported on a suitable carrier.

Examples of such carriers include silica, alumina, silica-alumina, silica-magnesia, chromia-alumina, clay, and activated carbon.

In carrying out the reaction, in addition to the above components, inert diluents such as hydrocarbons such as hexane, heptane, kerosene, cyclohexane, benzene, toluene, and xylene, and ethers such as ethyl ether and isopropyl ether are allowed to coexist. It's okay.

The ratio of phenols and aldehydes to be used can be selected arbitrarily, but usually 0.00 molar ratio of aldehyde to 1 mole of phenol.
It is used in a proportion of 1 to 100 mol, preferably 0.5 to 10 mol.

The reaction can be carried out under any pressure, but generally the hydrogen partial pressure is 1 to 300 atm, preferably 10 to 150 atm.
It is best to carry out the process under atmospheric pressure conditions.

The reaction temperature is usually 50 to 250°C, preferably 1
00 to 150°C.

The method of the present invention is particularly useful as a method for 0- or p-alkylation of phenols.

Next, an example will be explained.

Example 1 103 g of 2.6-tert-butylphenol (0
, 5 moles), 18 g of paraformaldehyde, 5 oml of monochloroacetic acid, 50 m of acetic acid, and 5.4 g of palladium carbon supporting 15% palladium were charged into a 5007 nl autoclave.

Hydrogen pressurized at 50 kg/crit, heated to 120°C,
When the reaction was continued for an hour, the pressure inside the vessel had decreased to 201 y/i.

As a result of analyzing the reaction solution by gas chromatography, 2.
67tert-butyl-p-cresol 89.1 g,
4.3 g of 2,6-2',6'-tetra-tert-butyldihydroxyphenylmethane were obtained, and 15.3 g of unreacted 2,6-tert-butylphenol was obtained.
There was 2g.

Example 2; 2,6-tert-butylphenol 103g
.

32.6 g of paraformaldehyde, 56 g of acetic acid, 1.4 g of concentrated hydrochloric acid, 5 g of 5 wt% palladium carbon
It was charged into a ml autoclave.

When the hydrogen pressure was increased to 50 kg/ff1G, the temperature was raised to 80°C, and the reaction was continued for 5 hours, the internal pressure was 25 kg/cf.
It was down to flG.

As a result of the analysis, 66.0 g of 2,6-di-tert-butyl-p-cresol was produced, and unreacted 2,6-tert-butyl-p-cresol was produced.
It was found that there were 20.6 g of rt-butylphenol.

・Example 3 2.113 g of 6-tert-butylphenol.

3.3 g of paraformaldehyde, 10 g of oxalic acid, and 0.5 g of palladium carbon were charged into a 5Qcc mini autoclave, and reacted for 6 hours at an initial hydrogen pressure of 50 kg/cm and a reaction temperature of 120°C.

2,6-tert-butyl-p-cresol 3.8
5 g was obtained, and it was found that there were 4.63 g of unreacted 2,6-tert-butylphenol.

Example 4 2.6-tert-butylphenol 10.3 g
(0.05 mol), paraformaldehyde (92%) 0
．． 82 g (0,025 mol), 5 g of acetic acid, 5 g of monochloroacetic acid, and platinum carbon (containing 5 wt%) Ig in a 5 Qcc mini autoclave at an initial hydrogen pressure of 50 Iy/c/
? LG, the reaction was continued for 6 hours at a reaction temperature of 120°C.

2.6-tert-butyl-p-cresol 1.1
It was found that 0 g was produced and 5.2 g of unreacted 2,6-di-tert-butylphenol.

Examples 5-8 Ru-activated carbon, Rh-activated carbon, O8 as hydrogenation catalyst
p-methylation of 2,6-tert-butylphenol was carried out in exactly the same manner and under the same conditions as in Example 1, except that = activated carbon and Ir-activated carbon (coupled amounts of each were 5 wt%).

The results are summarized in Table 1.

Claims (1)

[Claims] 1. A method for producing alkyphenols, which comprises reacting phenols, aldehydes, and hydrogen in the presence of an acid and a noble metal hydrogenation catalyst. 2 Claim 1 using an organic carboxylic acid as the acid
Method described. 3. The method according to claim 2, wherein a mixture of lower fatty acids and halo-lower fatty acids is used as the organic carboxylic acid. 4. The method according to claim 1, wherein formaldehyde is used as the aldehyde. 5. The method according to claim 1, wherein the reaction is carried out under pressure. 6. The method according to claim 1, wherein the reaction is carried out at a temperature of 50 to 250°C. 1. The method according to claim 1, in which a palladium-based catalyst is used as the hydrogenation catalyst.