CN103145527B - Process for synthesizing p-methoxy benzaldehyde or p-tertbutyl benzaldehyde - Google Patents

Abstract

A kind of synthetic technique of p-methoxybenzaldehyde or p-tert-butylbenzaldehyde, it is to p-methoxytoluene or p-tert-butyltoluene, add acidifying agent glacial acetic acid and catalyzer cobalt acetate and sodium bromide, in heating Oxidation reaction is carried out by passing oxygen under the condition. After the reaction is finished, the feed liquid is washed with water twice to remove the catalyst and acetic acid. The oil phase after washing with water is added with a high boiling point solvent, and then subjected to step-by-step vacuum distillation. First, the excess p-methoxytoluene or p-tert-butyltoluene is evaporated from the solvent, then the vacuum degree and temperature are increased, and the gas phase condensate is collected to obtain p-methoxybenzaldehyde or p-tert-butylbenzaldehyde; continue to increase the rectification temperature, accept the gas phase condensate with water and undergo two recrystallizations to obtain p-methoxybenzoic acid or p-tert-butylbenzoic acid. The process of the invention reduces the discharge of waste water, avoids the generation of waste water containing sodium sulfate, and simultaneously does not extract p-methoxybenzoic acid or p-tert-butylbenzoic acid with toluene, thereby reducing the pollution of toluene to the environment.

Description

A kind of synthesis technique of p-methoxybenzaldehyde or p-tert-butylbenzaldehyde

technical field

The invention relates to a method for preparing substituted benzaldehyde by oxidation of substituted toluene.

Background technique

Using p-methoxytoluene or p-tert-butyltoluene as raw material, the process of synthesizing p-methoxybenzaldehyde or p-tert-butylbenzaldehyde and co-producing p-methoxyl or p-tert-butylbenzoic acid is exactly the same, only The process parameters are slightly different, and the process includes oxidation reaction, distillation to remove acetic acid, washing with water and alkali, separation of p-methoxyl or p-tert-butylbenzoic acid, rectification of p-methoxybenzaldehyde or p-tert-butylbenzaldehyde Separation and other steps. Taking p-methoxybenzaldehyde as an example, its reaction formula is as follows.

After a sufficient amount of p-methoxytoluene is acidified with acetic acid, catalyst sodium bromide and cobalt acetate are added, and oxygen is passed through at a certain temperature for oxidation reaction to generate p-methoxybenzaldehyde and p-methoxybenzoic acid. The synthetic material liquid is distilled to remove acetic acid, washed to remove the catalyst, and then washed with sodium carbonate alkali to separate the generated p-methoxybenzoic acid into sodium p-methoxybenzoate from the organic phase. The organic phase is p-methoxybenzaldehyde dissolved in excess p-methoxytoluene, the p-methoxybenzaldehyde is separated by rectification under reduced pressure, and the remaining p-methoxytoluene is recycled into units.

The soda ash washing water phase contains sodium p-methoxybenzoate, which is neutralized by sulfuric acid to obtain p-methoxybenzoic acid and sodium sulfate, which are extracted by adding toluene and layered. The water phase is wastewater containing sodium sulfate. The oil phase is precipitated, cooled and crystallized, centrifuged to obtain a wet product of p-methoxybenzoic acid, and dried to obtain qualified p-methoxybenzoic acid. The centrifuged mother liquor is distilled and recovered toluene, which is used mechanically. The process flow is shown in Figure 1.

The separation process of this process is complicated. In addition to synthetic wastewater, a considerable amount of high-concentration wastewater containing sodium sulfate and toluene non-condensable gas are produced. The unit consumption of toluene is about 0.068t/t.

Contents of the invention

The present invention intends to select a high-boiling-point organic solvent, and adopts a fractional distillation process to successively separate p-methoxytoluene, p-methoxybenzaldehyde and p-methoxybenzoic acid, simplify the separation process, and no longer consume toluene for extraction. And eliminate the generation of sodium sulfate wastewater.

Technical scheme of the present invention is as follows:

A kind of synthesis technique of p-methoxybenzaldehyde or p-tert-butylbenzaldehyde, its technological process sees, Fig. 2, will p-methoxytoluene, add glacial acetic acid acidification and catalyst cobalt acetate and sodium bromide, in heating condition Oxygen is passed through to carry out the oxidation reaction. After the reaction, the feed liquid is washed twice with water to remove the catalyst and acetic acid. The oil phase after washing is added with a high-boiling organic solvent with a boiling point above 330°C, and then subjected to step-by-step vacuum distillation. , first at -0.09MPa, 85-90°C desolvation and steaming to remove excess p-methoxytoluene or at -0.09MPa, 80-86°C to remove excess p-tert-butyltoluene, and then increase the vacuum and temperature , at -0.098MPa, collect the gaseous condensate at 100-105°C to obtain p-methoxybenzaldehyde or collect the gaseous condensate at 98-104°C to obtain p-tert-butylbenzaldehyde, continue to increase the rectification temperature, at -0.098 Under MPa, distill p-methoxybenzoic acid at 118-123°C or distill p-tert-butylbenzoic acid at 114-118°C, accept the gas phase condensate with water and recrystallize twice to obtain p-methoxybenzoic acid or p-tert-butylbenzoic acid.

In the above synthesis process of p-methoxybenzaldehyde or p-tert-butylbenzaldehyde, the high-boiling organic solvent with a boiling point above 330° C. may be methyl biphenyl or biphenyl-biphenyl ether.

The p-methoxybenzaldehyde or p-tert-butylbenzaldehyde synthesis process of the present invention reduces the discharge of waste water, avoids the generation of sodium sulfate-containing wastewater, and at the same time, does not extract p-methoxybenzoic acid or p-tert-butylbenzene with toluene Formic acid reduces the pollution of toluene to the environment.

Description of drawings

Fig. 1 is the flow process of the synthesis technique of p-methoxybenzaldehyde of prior art;

Fig. 2 is the flow process of the synthetic technique of p-methoxybenzaldehyde of the present invention.

Detailed ways

The present invention is further illustrated below with examples.

Example 1

In a 1000mL reaction flask, add 525mL of p-methoxytoluene, 150mL of glacial acetic acid, 50g of cobalt acetate and 30g of sodium bromide, stir, heat to 45°C, and pass oxygen for 4h to complete the reaction; add 800mL of water twice to wash the reaction liquid, to remove catalyst and acetic acid.

Add 200mL of monomethylbiphenyl to the oil phase after water washing, mix evenly, and desolvate under reduced pressure (-0.09MPa, 85-90℃) to remove p-methoxytoluene; continue to increase the rectification temperature (-0.098MPa, 100 -105°C), gas phase condensation to obtain p-methoxybenzaldehyde (light yellow liquid, acid value: ≤1.0mgKOH/g, content 99.3%); increase the rectification temperature again (-0.098MPa, 118-123°C), distill P-methoxybenzoic acid is discharged, and the gas-phase p-methoxybenzoic acid is passed into the water absorption tower, cooled and crystallized, and p-methoxybenzoic acid (white powder crystals, melting point range 181-185°C) is obtained after recrystallization and drying , content 99.2%).

Example 2

In a 1000mL reaction flask, add 700mL of p-tert-butyltoluene, 20mL of glacial acetic acid, 10g of cobalt acetate and 4.5g of sodium bromide, stir, heat to 45°C, and pass oxygen for 4h to complete the reaction; add 1000mL of water twice to wash the reaction liquid , to remove catalyst and acetic acid.

Add 260mL of biphenyl-biphenyl ether low-melting mixture to the oil phase after water washing, mix well, and carry out desolvation under reduced pressure (-0.09MPa, 80-86°C) to remove excess p-tert-butyltoluene; continue to increase the rectification Temperature (-0.098MPa, 98-104°C), gas phase condensation to obtain p-tert-butylbenzaldehyde (light yellow liquid, content 99.2%); increase the rectification temperature again (-0.098MPa, 114-118°C), remove p-tert-butylbenzaldehyde tert-butylbenzoic acid, p-tert-butylbenzoic acid in the gas phase is passed into the water absorption tower, cooled and crystallized, recrystallized and dried to obtain p-tert-butylbenzoic acid (white powder crystals, melting point range 164.0-166.0°C, content 99.05%).

Claims (2)

1. a synthetic technique of p-methoxybenzaldehyde or p-tert-butylbenzaldehyde, with p-methoxytoluene or p-tert-butyltoluene, acidify with glacial acetic acid and catalyzer cobalt acetate and sodium bromide, in heating condition Oxygen is passed through to carry out the oxidation reaction. After the reaction, the feed liquid is washed twice with water to remove the catalyst and acetic acid. The feature is: the oil phase after water washing is added with a high-boiling organic solvent with a boiling point above 330 ° C, and then carried out step by step. Rectification under reduced pressure, first at -0.09MPa, 85-90°C desolvation and steaming out excess p-methoxytoluene or at -0.09MPa, 80-86°C desolventization and steaming out excess p-tert-butyltoluene, and then increase Vacuum degree and temperature, at -0.098MPa, collect gas phase condensate at 100-105°C to obtain p-methoxybenzaldehyde or collect gas phase condensate at 98-104°C to obtain p-tert-butylbenzaldehyde, continue to increase the rectification temperature , at -0.098MPa, distill p-methoxybenzoic acid at 118-123°C or distill p-tert-butylbenzoic acid at 114-118°C, receive the gas phase condensate with water and recrystallize twice to obtain p-methoxybenzoic acid Oxybenzoic acid or p-tert-butylbenzoic acid. 2. the synthesis technique of p-methoxybenzaldehyde or p-tert-butylbenzaldehyde according to claim 1 is characterized in that: the high-boiling point organic solvent with a boiling point above 330° C. is monomethylbiphenyl or Biphenyl-biphenyl ether.