JPS62153240A - Production of p-hydroxybenzaldehyde - Google Patents

Abstract

PURPOSE:In the production of the title compound by oxidation of p-cresol with molecular oxygen in the presence of a cobalt compound and a base, the reaction is carried out substantially in the absence of iron ion to avoid the activity of catalytic oxidation from lowering whereby the objective compound is selectively obtained. CONSTITUTION:In the production of p-hydroxybenzaldehyde by the oxidation of p-cresol with molecular oxygen in the presence of a cobalt compound and a base, the reaction is carried out substantially in the absence of iron ion, less than 6 ppm, preferably less than 3 ppm, calculated as Fe2O3 to avoid the oxidation activity of the catalyst from lowering and obtain the objective compound advantageously in an amount of less than 1/10 of the conventionally required quantity, namely more than 0.000001 mole or more, preferably 0.0005-0.05 mole per mole of the starting substance. The process according to the present invention can remarkably improve the reaction time and selectivity compared with the conventional processes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing parahydroxybenzaldehyde. More specifically, the present invention relates to an improved method for producing para-hydroxybenzaldehyde by oxidizing the alkyl group of para-cresol with molecular oxygen.

[Prior art]

A method for selectively producing para-hydroxybenzaldehyde or para-hydroxybenzaldehyde derivatives by oxidizing para-cresol or para-cresol m-form with molecular oxygen is described in Angew, Chem, 86,586.
(1975); Collection of lecture abstracts of the 12th Oxidation Reaction Symposium,
P74 (197B): There is a method introduced in Japanese Patent Application Laid-Open No. 55-81832. These methods are characterized by oxidation with molecular oxygen in an organic solvent containing a basic compound in the presence or absence of a cobalt catalyst.

[Means to solve the problem]

The prior art, especially the method disclosed in Japanese Patent Application Laid-Open No. 55-81832, is at a high level of technology.

The present inventor completed the present invention by confirming that a trace amount of iron ions increases (decreases) the oxidation catalytic ability of the cobalt compound used as a catalyst in this method.

Iron ions greatly reduce the oxidation catalytic ability of cobalt compounds, exhibiting a negative catalytic effect even in small amounts, and not only reduce the reactivity of para-cresol (but also reduce the selectivity to parahydride-oxybenzaldehyde, Increase the production of by-products, especially polymers.

According to the present invention, the amount of cobalt compound used can be adjusted according to the reaction substantially in the absence of iron ions.
Even one-tenth of the amount stated in 832, that is, 1 times the mole of O,OOOOOO to para-cresol, is effective.

In addition, by selecting reaction conditions that do not substantially contain iron ions, it is possible to improve the reaction time and selectivity of JP-A-55-81.
A significant improvement can be expected compared to 832.

The present invention is carried out under reaction conditions in which iron ions are substantially absent.
, 6 ppm or less, preferably 3 ppm or less in terms of 0.03.

The method of the invention uses para-cresol as a starting material. Also, the amount of cobalt compound used as a catalyst is
It is desirable that the amount is o,oooooi times or more in mole relative to para-cresol, and preferably in the range of 0.0005 to 0.05 times in mole.

Examples of the base used in the present invention include alkali metal hydroxides such as caustic soda, caustic potash, and lithium hydroxide, and metal alkoxides such as sodium alkoxide and potassium alkoxide. The amount used is 1.5 times mole or more, preferably 2 times mole to 5 times mole, relative to para-cresol.

As the alcohol used as the reaction solvent, lower alcohols such as methanol and ethanol isopropanol can be used. Particularly preferred is methanol. Of course, when selecting these bases and alcohols, consideration must be given to iron ions.

The method of the present invention is preferably carried out in the temperature range of 60 to 80°C; below 50°C, the reaction rate decreases;
At temperatures above 0°C, by-products due to solvent oxidation or side reactions increase.

Molecular oxygen used as an oxidizing agent includes oxygen gas,
There is air, etc., and the pressure is usually 1 atm or more.

The target product can be separated and purified from the reaction mixture by extraction with an organic solvent or recrystallization method.

The present invention will be specifically explained below using Examples.

Example 1 Para-cresol (59.5 N, 0.55 mol) and cobalt chloride filtrate (1°4 recommended) were placed in advance in an autoclave equipped with a thermometer, a stirrer, and an internal volume of 1 g, equipped with a thermometer, a supply pipe for liquid and gas, and a discharge pipe. g, 0.000006 mol), caustic soda (70,98, ), 1.65 mol) and methanol (
180 ml) was charged and stirred for 4 hours at a reaction temperature of 60° C. under an oxygen atmosphere of 1 atm.

The content of iron ions (Fc, .0.0.0) in the reaction solution in this example was 3 ppm.

The reaction mixture was analyzed by high performance liquid chromatography, and the results were as follows.

Conversion rate of para-cresol 65.4% Selectivity of para-hydroxybenzaldehyde 72.0% Example 2 In Example 1, the amount of cobalt chloride filtrate was changed to 1.51%.
! ! The reaction was carried out in the same manner as in Example 1, except that the amount was changed to (0,0O55 mol). In this example, iron ions (Fe
203 conversion) was 5 ppm.

The results of the reaction were as follows.

Conversion rate of para-cresol 95.1% Selectivity of para-hydroxybenzaldehyde 82.6 Comparative Example 1 In Example 1, caustic soda with a high iron content was used, and the content of iron ions (Fe20° conversion) in the reaction solution was 7p
The reaction was carried out as pm.

The results of the reaction were as follows.

Conversion rate of para-cresol 57.3% Selectivity of para-hydroxybenzaldehyde 55.8% Comparative Example 2 In Example 2, 1. D. Using method caustic soda, the content of iron ions (Fe203 equivalent) in the reaction solution was reduced to 10p.
The reaction was carried out as pm.

The results of the reaction were as follows.

Conversion rate of para-cresol 894% Selectivity of para-hydroxybenzaldehyde 70.0%

Claims (1)

[Claims] 1. A method for producing para-hydroxybenzaldehyde, which comprises oxidizing para-cresol with oxygen or an oxygen-containing gas in the presence of a cobalt compound and a base, the reaction being carried out in the substantial absence of iron ions.