JPS6152130B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing thymols, and more particularly to a method for simultaneously producing p-thymol and o-thymol from m-cresol and propylene. o-thymol, m-thymol, p-thymol, and vic-thymol referred to in the present invention refer to compounds of the following formula:

[Formula] Those in which the groups are in the o-position, m-position, p-position, and vic-position, respectively, i.e., 6-isopropyl-3-methyl-phenol, o-thymol, 5-isopropyl-3-methyl-phenol m-thymol, 4-isopropyl-3-methyl-phenol p-thymol, 2
-isopropyl-3-methyl-phenol vic
-It shall be called thymol. O-thymol and p-thymol are used in preservatives, disinfectants, cosmetics, etc. Among these, p-thymol has a stronger bactericidal power than o-thymol, phenol, cresol, etc.
It has excellent properties of low toxicity and odor. Several proposals have been made in the past regarding methods for producing thymols by reacting m-cresol and propylene in the presence of a catalyst. The use of calcium oxide as
Publication No. 46-3053 describes metal sulfate/γ- as a catalyst.
The use of alumina and the use of metallic cerium as a catalyst are described in Japanese Patent Publication No. 53-24408. However, these all relate to methods for selectively producing only o-thymol;
- Method for simultaneously producing thymol or p-
There is no mention of how to produce thymol. On the other hand, German Published Patent No. 2139622 discloses that m-cresol and propylene are combined with ZnBr ₂ −
A method for simultaneously obtaining o-thymol and p-thymol by reacting in the presence of HBr-H ₂ O has been described, but this method is not economical because it is difficult to recover and reuse the catalyst. The problem is that it is scarce. Another known method for simultaneously obtaining o-thymol and p-thymol is to react m-cresol and isopropyl alcohol in the presence of phosphoric acid, but this method requires a large amount of phosphoric acid. There are problems such as: the phosphoric acid is diluted by the produced water, making it difficult to recover, the disposal of waste acid is also a problem, and isopropyl alcohol is relatively expensive as a raw material. However, it still has the disadvantage of being uneconomical. Patent No. 182136 (Japanese Patent Publication No. 1821-4221) discloses that a mixture of phenols and isopropanol or propylene is used together with water or benzole to form a solid phosphoric acid catalyst or a naturally occurring or synthesized catalyst containing silica or alumina as active components. Alternatively, a method has been shown in which one propyl group is introduced into the nucleus of a phenol by reacting it in the gas phase over a catalyst containing zinc chloride as the active main ingredient, and at the same time, water is removed from benzol. The results of a similar experiment without addition are also shown. In this document, a phosphoric acid/silicic acid catalyst is cited as an example of a solid phosphoric acid catalyst, and the raw material is fed onto the catalyst in a gaseous state. However, according to the studies of the present inventors, m
- When the reaction between cresol and propylene or isopropanol is carried out in the gas phase, the production ratio of p-thymol to o-thymol is small, and the production ratio of m-thymol, which is difficult to separate from p-thymol, increases significantly. This results in the following result. Japanese Patent Publication No. 41-16781 discloses that phosphoric anhydride, condensed phosphoric acid and salts thereof, Also, it has been described that a phosphorus compound selected from the group consisting of phosphoric acid and its salts is allowed to coexist, but the catalytic effect is not necessarily good because the phosphorus compound is simply allowed to coexist without being supported on a carrier. Table 2 of this publication also lists comparative examples in which phosphoric acid is used together with diatomaceous earth, but it is stated that the catalytic effect is small. In addition, when phosphoric acid is simply used in the form of coexistence without being supported on a carrier, recovery is difficult, especially in the case of liquid phosphoric acid, and the tendency for corrosion of the reaction equipment increases. There is. Furthermore, when m-cresol and propylene are reacted in a liquid phase, the reaction rate is slow and p- The ratio of o-thymol to thymol is large, and furthermore, when the reaction temperature is raised to increase the reaction rate, there is a problem that the production ratio of m-thymol increases. Japanese Patent Publication No. 44-53 describes a method for producing alkylphenols by subjecting phenols and olefins to a gas-phase contact reaction in the presence of a phosphorus pentoxide-boric anhydride catalyst. There is no mention of its use, and the proportion of the meta form among the ortho form, meta form, and para form of the alkylphenol obtained reaches 30 to 100%, and the meta form is the main product in this method. It's summery. Now, when producing thymols mainly consisting of p-thymol and o-thymol, m-thymol, a by-product which is particularly thermally stable, can be produced by isomerization.
It is difficult to convert to -thymol or o-thymol, and separation by distillation is also difficult because p-thymol and m-thymol have close boiling points. Therefore, it is advantageous for p-thymol recovery to suppress the production of meta-forms as much as possible at the stage of the alkylation reaction and to keep the m-thymol/p-thymol production ratio small. As mentioned above, in the alkylation reaction of phenols in the presence of a catalyst, the same alkylation reaction can yield various results depending on the type of catalyst, reaction conditions, type of phenol, etc., and it is difficult to predict in advance. However, as a result of continued research aimed at industrially advantageously producing thymol compounds including p-thymol, the present inventors have arrived at the present invention described below. That is, the method for producing thymols of the present invention involves reacting m-cresol and propylene in the presence of a catalyst so that p-thymol and o-thymol are the main components, and the production ratio of o-thymol/p-thymol is 3/3. 1 or less, wherein the catalyst is at least one carrier selected from the group consisting of silica/alumina, diatomaceous earth, and silica/titania, and phosphoric acid is added to a P ₂ O ₅ /carrier mixture. A solid phosphoric acid catalyst supported at a weight ratio of 10/90 to 25/75 is used, and the reaction is carried out in a liquid phase under heating conditions and at a propylene pressure of normal pressure to 50 Kg/ ^cm2. It is characterized by this. The present invention provides excellent effects as listed below. p-thymol can be produced with good yield together with o-thymol. Furthermore, since the production ratio of o-thymol to p-thymol is 3/1 or less, the amount of p-thymol produced relative to o-thymol is significantly larger than in the conventional method. Although p-thymol and o-thymol are produced at the same time, their boiling points are different, so they can be easily separated from each other. In addition, the production rate of m-thymol, which is difficult to separate from p-thymol due to its small boiling point difference, is low;
- Separation and purification of thymol becomes easier. The solid phosphoric acid catalyst used can be recovered and used repeatedly, which is economically advantageous. In the present invention, a solid phosphoric acid catalyst is used as a catalyst in the reaction between m-cresol and propylene, and such a solid phosphoric acid catalyst is prepared by a conventional dipping method. For example, after soaking the carrier in a commercially available 85% phosphoric acid aqueous solution for several hours, the water is evaporated and dried at 100-150°C, and the carrier is left in the air at a temperature of 100-800°C, preferably 200-150°C. 500℃
It can be obtained by cooling after heat treatment. Examples of the carrier supporting the phosphoric acid include silica/alumina, diatomaceous earth, and silica/titania, and one or more of these may be used. In the case of silica/alumina, Al ₂ O ₃ /SiO ₂
In the case of diatomaceous earth, the weight ratio of Al ₂ O ₃ /SiO ₂ is 10/90 or less, especially 5/95 or less. , in the case of silica/titania, the weight ratio of TiO ₂ /SiO ₂ is
A ratio of 40/60 or less is preferred. Although silica alone has some effect, it has the disadvantage that the reaction rate is slow even when the propylene pressure is increased, and the reaction rate is even lower in normal pressure reactions. Next, the amount of phosphoric acid supported on these carriers is
In terms of P ₂ O ₅ , the weight ratio of P ₂ O ₅ / carrier is 10/90 to 25/
Set to a range of 75. The weight ratio of P ₂ O ₅ /support is
If it is less than 10/90, the production ratio of o-thymol/p-thymol becomes too large to meet the intended purpose; on the contrary, if the weight ratio of P ₂ O ₅ /carrier is increased to 25/75 or more. However, since the catalytic effect cannot be improved beyond a certain limit, it is economically disadvantageous, and the hygroscopicity of P ₂ O ₅ makes the surface of the catalyst sticky, making it difficult to handle. The shape or particle size of the catalyst may be either powder or granule, but when considering the reaction rate and the operability of filtering and recovering the used catalyst,
It is preferable to use one prepared to about 200 meshes. The amount of the catalyst used in the reaction between m-cresol and propylene varies depending on the type of carrier, the amount of phosphoric acid supported, etc., but is 5 to 40% by weight, preferably 10 to 35% by weight, based on the raw material m-cresol. It is usually selected from a range of weight %. Next, the reaction conditions for the above reaction are as follows: reaction temperature is 100 to 400℃, preferably 150 to 250℃, reaction pressure is propylene pressure, normal pressure to 50Kg/cm ² reaction time is from 1 minute to 15 hours. It is desirable to choose. The molar ratio of propylene/m-cresol is preferably 3 or less. The reaction amount of propylene varies depending on the reaction time or reaction pressure, but the m-cresol conversion rate is preferably in the range of 80 to 30 mol%, and the reaction amount of propylene at this time is per 1 mol of m-cresol as a raw material. Approximately 0.8-0.3 mol. After the reaction, propylene is released from the reactor, and if necessary, reactions such as isomerization and rearrangement of by-products are performed, followed by known separation and purification methods such as filtration, distillation, recrystallization, and extraction. By taking, the target products o-thymol and p-thymol are obtained. By the way, the solid phosphoric acid catalyst used in the above reaction can be used repeatedly in the reaction between m-cresol and propylene. In this case, the reaction rate tends to decrease as the number of repeated uses increases.
No deterioration in the selectivity of the reaction product was observed even after repeated use. A decrease in the reaction rate can be prevented by increasing the reaction temperature, using a new solid phosphoric acid catalyst, etc. Next, the method of the present invention will be further explained with reference to Examples. In the following, the reaction products were analyzed by gas chromatography. Note that "others" in the reaction product mainly refer to high boiling point components, and the composition (mol %) of the reaction solution was calculated assuming that this was diisopropyl-m-cresol. The m-cresol conversion rate and the selectivity of each product were calculated according to the following formula. m-Cresol conversion rate (mol%) = 100-product in reaction solution (mol%) Product selectivity (mol%) = product in reaction solution (mol%)/100-m- in reaction solution Cresol (mol%) Examples 1 to 2, Reference Examples, Comparative Example 1 310 g of m-cresol and 46.5 g of a solid phosphoric acid catalyst as shown in Table 1 (all with particle size of 80 to 150 mesh) were placed in an autoclave. Preparation,
The reaction was allowed to proceed with stirring in the presence of propylene at a temperature of 250°C. During the reaction, the reaction pressure is
Propylene was introduced sequentially to reach a range of 12 to 18 Kg/cm ² to replenish the loss. The results are shown in Table 1 below. (See Table 1) From the results in Table 1, it is clear that both o-thymol and p-thymol can be obtained with high selectivity by using phosphoric acid/silica alumina or phosphoric acid/diatomaceous earth as the solid phosphoric acid catalyst. that the ratio of o-thymol to p-thymol is 1.9 to 2.3, and that the production ratio of p-thymol to o-thymol is larger than that of the conventional method as shown at the beginning;
It can also be seen that the amount of by-produced m-thymol is extremely small. Example 3 In an autoclave, 310 g of m-cresol and phosphoric acid/silica titania as a solid phosphoric acid catalyst (P ₂ O ₅ /SiO ₂ .TiO ₂ = 20/80, TiO ₂ /SiO ₂ =
19/81, particle size 80-150 mesh) was charged, and the reaction was allowed to proceed at a temperature of 150° C. while stirring in the presence of propylene. During the reaction, propylene was successively introduced so that the reaction pressure was in the range of 12 to 18 Kg/cm ² to replenish the amount consumed. The results are shown in Table 2 below. (See Table 2) Example 4 310 g of m-cresol and the entire amount of solid phosphoric acid catalyst recovered by filtration from the reaction product of Example 3 were placed in an autoclave, and the same procedure as in Example 3 was carried out. The first reaction using the recovered catalyst was carried out. Next, the entire amount of the solid phosphoric acid catalyst recovered by filtration from the reaction product and 310 g of m-cresol were placed in an autoclave, and a second reaction using the recovered catalyst was carried out in the same manner as in Example 3. Thereafter, the reaction using the recovered catalyst was repeated up to the fourth time in the same manner. The results are also shown in Table 2. (See Table 2) From the new catalyst column in Table 2, even if phosphoric acid/silica titania is used as the solid phosphoric acid catalyst, o-thymol and p-thymol are The ratio of o-thymol to p-thymol is 1.87, and the production ratio of p-thymol to o-thymol is higher than that of the conventional method. It can be seen that the amount is extremely small. Furthermore, from the recovered catalyst column in Table 2, the solid phosphoric acid catalyst used in the reaction can be used repeatedly in the next reaction, and both o-thymol and p-thymol can be obtained with high selectivity. Moreover, at that time o
-The production ratio of thymol and p-thymol is 1.8 to 1.9
It can be seen that the ratio is not large. Comparative Examples 2-3 Pyrex glass reaction tube (inner diameter 250m/m)
As a catalyst, silica/alumina catalysts or solid phosphoric acid catalysts shown in Table 3 (both with particle size 10~
Fill 100 ml of m-cresol and isopropyl alcohol (molar ratio
1.0) was preheated and vaporized at a rate of 0.5 to 1.0 ml/min, and then fed into a reaction tube at a reaction temperature of 250°C under normal pressure. The results are shown in Table 3. (See Table 3) From the results in Table 3, when the reaction is carried out in the gas phase using silica-alumina or solid phosphoric acid catalyst as a catalyst, the ratio of o-thymol to p-thymol and the ratio of m-thymol It can be seen that the ratio of p-thymol and p-thymol is significantly larger than that in the liquid phase reactions shown in Examples 1 and 2 and Reference Examples. Comparative Examples 4 to 5 Example 1, except that commercially available activated clay or solid phosphoric acid catalysts (all with particle size of 80 to 150 mesh) as shown in Table 4 were used as catalysts, and the reaction time was 4 hours. The same operation as in 2 was performed. The results are shown in Table 4. (See Table 4) From the results in Table 4, it can be seen that when activated clay alone is used, the reaction rate of m-cresol is extremely slow, and the production ratio of o-thymol and p-thymol, and of m-thymol and p-thymol is extremely large. I understand that. In the case of phosphoric acid/activated clay, the reaction rate is also slow and o-
It can be seen that the ratio of thymol and p-thymol is also large.

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Claims (1)

[Claims] 1 By reacting m-cresol and propylene in the presence of a catalyst, p-thymol and o-
A method for producing thymols mainly composed of thymol and having an o-thymol/p-thymol production ratio of 3/1 or less, wherein the catalyst is selected from the group consisting of silica-alumina, diatomaceous earth, and silica-titania. Using a solid phosphoric acid catalyst in which phosphoric acid is supported on at least one selected carrier at a weight ratio of P ₂ O ₅ /carrier of 10/90 to 25/75, and the reaction is carried out under heating conditions. A method for producing thymols, which is carried out in a liquid phase under conditions of normal propylene pressure to 50 kg/cm ² . 2. The method according to claim 1, wherein the solid phosphoric acid catalyst after the reaction is recovered and used repeatedly for the reaction between m-cresol and propylene.