JPS599531B2 - Method for producing phenols - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for obtaining phenols, particularly isomer-free substituted phenols, in high yields.

A method called the cumene method is generally used to produce phenol, in which cumene is first oxidized to produce cumene hydroperoxide (a type of tertiary hydroperoxide).
(hereinafter abbreviated as C-HPO) was obtained in high yield, and then the reaction solution was concentrated to a C-HPO concentration of 70 to 80 wt%.
-HPO concentrate is decomposed with acid to obtain phenol and acetone with a selectivity to cumene of 85 to 90 mol%. On the other hand, a method for producing substituted phenols such as cresol ゛5
However, the cymene method, which corresponds to the cumene method, is known, and the corresponding substituted phenols are obtained by performing a reaction similar to the cumene method on an aromatic compound having a substituent and an isoprobyl group. However, in the case of the cymene method, when an aromatic compound with a substituent (0) is alkylated with propylene to introduce an isopropyl group, substituted isomers are inevitably generated, and these are converted into substituted phenols in the final product. This results in a mixture of In contrast, one 5-methyl group of a methyl-substituted aromatic compound is oxidized to synthesize the corresponding primary hydroperoxide (hereinafter referred to as 1-■℃), which is then decomposed to produce the corresponding phenol. For example, a method for synthesizing p-methylbenzyl hydroperoxide (hereinafter referred to as pc-HPO) from p-xylene and then obtaining p-cresol from this is described in U.S. Patent No. 2,683,751, Journal
of the American Chemical Society, Vol. 77, p. 4035, etc.

According to this method, substituted phenols, such as p'35-
When producing p-cresol from ghylene, m-cresol from m-xylene, and 3,5-xylenol from mesitylene, it has the advantage of being able to obtain highly pure products that do not contain isomers, and is superior to the cymene method. It has high industrial value.
However, with this method, it is difficult to obtain 1-HPO in high yield in the oxidation process, and in the decomposition process, there are many side reaction products between formaldehyde, which is one of the decomposition products, and phenol. The yield of phenols is low;
It has not become an industrial manufacturing method.

As a method for solving these problems, the present inventors have developed a method for obtaining 1-HPO in high yield by allowing an aliphatic tertiary hydroperoxide to coexist as a reaction aid in the oxidation step (Japanese Patent Application No. 121643), and for the decomposition process, the coexistence of an organic solvent and boron trifluoride (Japanese Patent Application No. 52-480
20), coexistence of a specific proportion of alcohol and boron trifluoride (
Patent Application No. 5364105), coexistence of specific proportions of aliphatic alcohols and ketones with hydrogen fluoride (Japanese Patent Application No. 5312541)
We have discovered a method for obtaining phenols in high yield using 4).

However, in the case of the above-mentioned invention regarding the oxidation step, there remain problems such as the aliphatic tertiary hydroperoxide used at a high concentration is expensive and a large amount of excess must be recycled. In view of these points, the present inventors have conducted intensive research and found that the yield of 1-HPO can be increased by causing the oxidation reaction of methylbenzenes in the above-mentioned cumene method by allowing the C-HPO concentrate to coexist as a reaction aid. In addition, 1HP0 and C-HPO can be acid-decomposed without separating them from this oxidation reaction solution to produce their corresponding phenols (phenols derived from methyl-substituted aromatics as raw materials of the present invention are treated with toluene). In the following description, including the phenol derived from C-HPO, it will be referred to as phenol to distinguish it from the phenol derived from C-HPO.

) and phenol, and arrived at the present invention. That is, the present invention oxidizes a methyl-substituted aromatic compound in the liquid phase with a molecular oxygen-containing gas in the coexistence of a C-HPO concentrate obtained by concentrating the cumene oxidation reaction product solution, and One of the methyl groups is oxidized to form the corresponding 1-HPO, and the resulting reaction product is concentrated to a concentrated solution containing C-HPO and 1-HPO; In this method, a liquid is subjected to a decomposition reaction in the presence of an acidic catalyst to convert C-HPO and 1-HPO into phenol and phenols, respectively.

The methyl-substituted aromatic compound used as a raw material in the present invention refers to an aromatic compound having one or more methyl groups substituted on an aromatic ring, and a t-butyl group that does not participate in the oxidation reaction in addition to one or more methyl groups. It is an aromatic compound that has halogen etc. but does not have ethyl group or isopropyl group, such as toluene, o-, m-, or p-xylene, 1, 2, 3-, 1,
2.4- or 1.3.5-trimethylbenzene, diurene, d-methylnaphthalene, β-methylnaphthalene, o
- m- or p-t-butyltoluene, dimethyl-t-butylbenzene, o-, m- or p-chlorotoluene, o-
-, m-, p-nitrotoluene, etc. The oxidation reaction is preferably carried out using a molecular oxygen-containing gas at a pressure higher than atmospheric pressure, and the higher the pressure, the faster the reaction.
Pressures in the range 20k9/C7ilG are suitable.

The lower the reaction temperature, the higher the selectivity to 1-HPO but the lower the reaction rate, while the higher the reaction temperature, the higher the selectivity to 1-HPO.
90-140℃ as the decomposition of Oll-HPO increases.
The temperature range is industrially appropriate.

C-HPO concentrate, which is a reaction aid for the oxidation reaction and is ultimately a raw material for phenol, is a concentrate of the oxidation reaction product in the ordinary cumene process, and generally has a concentration of 70 to 8
Although the C-HPO content is approximately 0 wt%, the amount added is such that the pure C-HPO concentration in the reaction solution is 10 to 70 wt%.
%, preferably 10 to 40 wt%.

The appropriate reaction time is 0.5 to 10 hours, preferably 1 to 6 hours.

If the reaction rate of the raw materials is increased, the selectivity to 1-HPO will decrease, so from the point of view of selectivity it is desirable to keep the reaction rate as low as possible, but since this will reduce the yield per reactor volume, Preferably, the ratio is between 5 and 20%.

A solvent may be used in addition to the C-HPO concentrate and the reaction raw materials, but it is not particularly necessary.

The reaction format may be batch, semi-batch, or continuous, but in the case of continuous reaction, it is preferable to use a multi-stage tank reactor.

The material of the reactor is preferably an inert material that does not affect the production of 1-HPO, such as Teflon, glass, aluminum, titanium, etc.

Since the reaction is exothermic, heat is removed by cooling from the outside or by evaporating the internal liquid.

As the molecular oxygen-containing gas, pure oxygen or a mixture of oxygen and an inert gas can be used, with air being preferred.

It is appropriate to adjust the flow rate of the molecular oxygen-containing gas to such an extent that substantially no oxygen or only a small amount of oxygen remains in the exhaust gas from the reaction system. The reaction product liquid after the oxidation reaction has a raw material liquid composition,
4-10 wt% 1-HPOllO-7 depending on reaction rate
Although it contains 0 wt % of C-HPO, unreacted raw materials, by-products, etc., this is distilled under reduced pressure to remove most of the methyl-substituted aromatic compounds as raw materials.

As a result, the liquid is concentrated to about 30 to 70 wt% of the liquid before distillation, but by keeping the concentration temperature low, 1-HP
There is almost no loss of O and C-HPO ~ The concentrate obtained in this way is then subjected to a decomposition reaction, and 1-
HPO is converted to the corresponding phenols and CHPO is converted to phenol.

The decomposition reaction can be carried out by widely applying known and conventional methods used for this type of reaction, and can be carried out using various organic solvents, mineral acids such as hydrogen fluoride, boron fluoride, sulfuric acid, and hydrochloric acid, and ion exchange. It is carried out in the presence of a type solid acid catalyst, etc., and in particular, the above-mentioned combination of an organic solvent and boron trifluoride (Japanese Patent Application No. 1973-
48020) Alcohol and boron trifluoride in a ratio of 1 to 20:1
Combination used at molar ratio of
, 1 to 30 parts by weight of aliphatic alcohol and 99 parts by weight of aliphatic ketone
100 parts by weight of a solvent consisting of ~70 parts by weight and 0 parts by weight of hydrogen fluoride
．． Combination using 2 to 15 parts by weight (Patent Application 1987-1)
25414) etc. are suitable. The product liquid after the decomposition reaction is
After separating the catalyst, light boiling components such as solvents are removed by distillation, and then phenol and phenols are separated by rectification to produce a product. Note that when toluene is used as a raw material, only phenol is the product. The present invention can be realized in an embodiment in which it is combined with the cumene process for producing phenol, that is, in an embodiment in which the process of the present invention is combined with the process for producing C-HPO by oxidizing cumene, which is the first stage of the cumene process for producing phenol. The effect is significant.

The effects of the present invention are as follows.

(1) The coexistence of C-HPO concentrate improves the yield of 1-HPO in the oxidation reaction of methyl-substituted aromatic compounds,
By-products are also reduced.

Therefore, the yield of final phenols is improved. (2) C-
HPO concentrate can be obtained at low cost if a cumene process phenol manufacturing plant is nearby or combined as a process, and most of the HPO concentrate is converted to phenol without loss in the oxidation process of the present invention. Furthermore, the cumyl alcohol produced by partial decomposition can be regenerated into cumene in a cumene process phenol production apparatus, so the actual cost of C-HPO is low.

(3) Separation of the substituted phenol obtained when a methyl-substituted aromatic compound other than toluene is used as a raw material and the phenol obtained from CHPO can be easily carried out by distillation.

Example 1 p-xylene 2007, C-HPO concentrate 1007 (C
-HPO73.2wt%, cumyl alcohol 9.7wt
%, acetophenone 1.5wt%, cumene 13.8wt%
%) was charged into a titanium reactor having an internal volume of 500 cc, and an oxidation reaction was carried out at a reaction temperature of 120°C, air was blown in, and a pressure of 10 kg/DG for 4 hours.

From the composition analysis of the reaction product liquid, C-HPO74]7, Px-
HPOl was 9.57, p-gysylene 179.47, cumene 8.9yl acetophenone 2.47, cumyl alcohol 16.07, and others 2.17. The reaction rate of p-xylene is 10.3%, ? Selectivity to HPO is 72.7m
It was 0.1%. The increase in C-HPO is due to production from cumene. Next, this oxidation reaction product liquid was heated to a bottom temperature of 50°C under a reduced pressure of 10mT1LHg to remove light boiling components such as p-xylene and cumene, and C-H
123.57 of a concentrated liquid having a PO content of 60 wt% and a μmHPO content of 15.6 wt% was obtained. Px-H in the concentration process
The recovery rate of PO was 99%. Next, the internal volume is 250m
Acetone 100y and the above concentrated liquid 307 were collected in a polyethylene reactor No. 1 and cooled on ice. Add to this 30% of hydrogen fluoride.
A wt% methanol solution 207 was added. This mixture was heated to 50° C. for 30 minutes to perform a hydroperoxide decomposition reaction. After the reaction was completed, analysis of the reaction solution revealed that C-HPO and Px-HPO had completely reacted, and the yields of phenol and p-cresol from them were 98m01% and 96m01%, respectively. . The total selectivity of p-cresol from the raw material p-xylene was 69m01%.

Examples 2-6 The reaction was carried out by variously changing the raw materials, reaction conditions, etc.

The results were as shown in Table 1. In addition, C-HPO in the table
Concentrated liquid and hydrogen fluoride-metanol solution are as in Example 1.
means the same composition as.

Claims (1)

[Claims] 1 In the coexistence of cumene hydroperoxide added to the reaction product liquid in a proportion of 10 to 70% by weight,
A methyl-substituted aromatic compound in which only a methyl group is substituted on the aromatic nucleus as a substituent participating in the oxidation reaction is oxidized in a liquid phase using a molecular oxygen-containing gas, and one of the methyl groups of the methyl-substituted aromatic compound is oxidized. to produce the corresponding primary hydroperoxide, and the resulting reaction product liquid is concentrated to obtain a concentrated liquid containing cumene hydroperoxide and the primary hydroperoxide, and then the concentrated liquid is treated in the presence of an acidic catalyst. A method for producing phenols, which comprises converting cumene hydroperoxide and the primary hydroperoxide into phenol and corresponding phenols, respectively, by subjecting them to the decomposition reaction described below.