CN105348107A - Preparation method of p-nitrobenzaldehyde - Google Patents

Abstract

The invention discloses a method for preparing p-nitrobenzaldehyde. With p-nitrotoluene as a raw material, azobisalkylnitrile is used to catalyze bromine to bromine p-nitrotoluene to generate p-nitrobenzyl bromide and hydrogen bromide, carbonate aqueous solution is used to catalyze the hydrolysis of p-nitrobenzyl bromide to p-nitrobenzyl alcohol, and sodium hydroxide is used to catalyze hydrogen peroxide to oxidize p-nitrobenzyl alcohol to generate the target product p-nitrobenzaldehyde. The invention uses azobisalkylnitrile solid catalyst to replace peroxycarbonate liquid phase catalyst to catalyze bromination reaction, thereby improving the safety of industrial preparation reaction operation; using halogenated aromatic hydrocarbons as solvent medium avoids the use of halogenated alkane solvent medium and avoids the pollution of low-boiling volatile organic solvents; using hydrogen peroxide oxidation method improves the cleanliness of industrial preparation reaction and reduces environmental pollution. The invention improves the product yield, and the yield is about 3% higher than that of the current traditional industrial method, the total yield reaches 76%, and the product purity is above 99%.

Description

A kind of preparation method of p-nitrobenzaldehyde

technical field

The present invention relates to a kind of preparation method of known compound, is exactly a kind of industrial clean preparation method of p-nitrobenzaldehyde.

Background technique

p-Nitrobenzaldehyde is a light yellow crystalline powder with a melting point of 105-107°C. It is slightly soluble in water and soluble in organic solvents such as alcohols, aromatics, halogenated hydrocarbons, and carboxylates. Vapor volatility properties. The molecular formula is C ₇ H ₅ NO ₃ , and the relative molecular mass is 151.1. Its structural formula is:

p-Nitrobenzaldehyde is used as an important intermediate in the synthesis of fine organic functional materials such as medicines, dyes, and pesticides. It has a wide range of uses and can derive many important functional chemicals. In the field of important intermediates used in the synthesis of pesticides, medicines, dyes, photosensitive materials and liquid crystal materials, such as the preparation of p-nitrobenzene-2-butenone, p-aminobenzaldehyde, p-acetamidobenzaldehyde, and trimethoprim Pyrimidine, thiocarbazone, p-thiourea, acetaminophen, chloramphenicol, etc. In addition, the downstream products of p-nitrobenzaldehyde also have many new uses, such as p-nitrobenzaldehyde phenylhydrazone, an organic nonlinear optical material with high frequency doubling effect.

There are many ways to prepare p-nitrobenzaldehyde. Using p-nitrotoluene as raw material, chromium oxide, dichromate, or potassium permanganate is used as oxidizing agent in acetic anhydride medium to oxidize the side chain to synthesize p-nitrobenzaldehyde. The reaction selectivity of this method is poor, the by-product p-nitrobenzoic acid is formed, the yield is low, and a large amount of refractory acid waste water containing heavy metal salts is produced, causing serious environmental pollution. Using toluene as raw material, chlorination produces benzyl chloride, then nitration produces nitrobenzyl chloride, further hydrolysis and oxidation to obtain the target product. This method requires the application of chlorine, and benzyl chloride has a lacrimal effect; the second step of nitration reaction uses a mixture of nitric acid and niobium pentoxide solid superacid as a nitrating agent, although the para-nitration selectivity is improved compared with the traditional nitric acid sulfuric acid mixed acid system, but Three isomers of o-nitrobenzyl chloride, m-nitrobenzyl chloride and p-nitrobenzyl chloride are still formed, which are difficult to separate, and also have a strong lachrymatory effect, and metal oxides are difficult to recycle. Yu Yuanbin and others synthesized p-nitrobenzaldehyde in methanol-alkaline medium by using p-nitrotoluene as raw material, using metalloporphyrin biomimetic catalysts, and air oxidant. However, the selectivity of the synthesis reaction is poor, the yield is very low, more by-products are formed, the process conditions are under pressure, and the cost is high.

Kaneda et al. found that Ru(III)-loaded hydroxyapatite can catalyze the oxidation of various alcohols with good catalytic activity and selectivity. Liu Changchun and others applied this method to the synthesis of p-nitrobenzaldehyde, using RuHAP as a catalyst, oxygen oxidation of p-nitrobenzyl alcohol under normal pressure to prepare p-nitrobenzaldehyde, this method can significantly improve the synthesis of p-nitrobenzaldehyde Selectivity and increase product yield, but the catalyst is expensive and difficult to recycle and reuse. Peng Xinhua et al. used p-nitrotoluene as a raw material, reacted with bromine to form p-nitrobenzyl bromide, then catalyzed hydrolysis by sodium carbonate to form p-nitrobenzyl alcohol, and further synthesized p-nitrobenzene by oxygen oxidation catalyzed by metal-organic complexes. Formaldehyde, although significantly improved reaction selectivity, has improved productive rate, but the organic peroxide liquid catalyst of bromination reaction procedure, its thermal stability of industrial application is poor; The used metal organic complex catalyst of the 3rd step oxidation reaction procedure is difficult Regeneration, and oxygen oxidation is a gas-liquid phase reaction system, which needs to be reacted under certain pressure conditions. Therefore, there are no obvious advantages in terms of production cost and convenience in industrial operation.

Contents of the invention

The purpose of the present invention is to provide a clean method for preparing p-nitrotolualdehyde with mild reaction conditions, good selectivity and high yield, which is suitable for industrialization with low cost and safe operation, and meets the dual development requirements of environment and economy.

Technical scheme of the present invention is: a kind of preparation method of p-nitrobenzaldehyde comprises the steps:

(1) bromination reaction

Add p-nitrotoluene, solvent halogenated aromatic hydrocarbon, and catalyst azobisalkylnitrile into the reactor, and add bromine dropwise under constant stirring at a controlled temperature of 40-50°C. The dosage of bromine is 0.5-0.6 times the theoretical amount After dripping, heat and reflux to react until the color of bromine fades, then add hydrogen peroxide and reflux for no less than 2 hours to obtain a p-nitrobenzyl bromide reaction solution;

(2) Hydrolysis reaction

Add carbonate aqueous solution to the reaction liquid of the first step, heat and reflux hydrolysis reaction, generate p-nitrobenzyl alcohol target product and sodium bromide by-product, liquid-liquid separation organic phase and aqueous phase, obtain p-nitrobenzyl alcohol organic Mutually;

(3) oxidation reaction

Sodium hydroxide is added to the organic phase of p-nitrobenzyl alcohol, hydrogen peroxide is added dropwise at a temperature of 25-35° C. under continuous stirring, and the reaction is heated under reflux to generate the final product p-nitrobenzaldehyde.

The azobisalkylnitrile described in step (1) is selected from any one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanonitrile or azobisisooctanonitrile, preferably azobisisobutyronitrile Nitrogen diisovaleronitrile; the dosage of the catalyst is 1%-20% of the mass of p-nitrotoluene; the halogenated aromatic hydrocarbon is selected from chlorobenzene, o-dichlorobenzene or bromobenzene.

The carbonate described in the step (2) is potassium carbonate or sodium carbonate, preferably potassium carbonate, and the consumption of the carbonate is 5%-100% of the mass of p-nitrotoluene; the reflux reaction time is 20-30h.

The hydrogen peroxide mass percentage concentration described in step (3) is 10%-50%, preferably 20%-35%; the consumption of sodium hydroxide is 10%-20% of p-nitrotoluene mass.

The synthetic route of the present invention is as follows:

Using p-nitrotoluene as raw material, azobisalkylnitrile catalyzes bromine bromination of p-nitrotoluene to generate p-nitrobenzyl bromide and hydrogen bromide (hydrogen bromide is oxidized by hydrogen peroxide into elemental bromine and enters the reaction system for recycling ), the carbonate aqueous solution catalyzes the hydrolysis of p-nitrobenzyl bromide to p-nitrobenzyl alcohol, and the sodium hydroxide catalyzes the oxidation of p-nitrobenzyl alcohol with hydrogen peroxide to generate the target product p-nitrobenzaldehyde.

Compared with the traditional process, this method has significant advantages. The main features are: (1) This method uses hydrogen peroxide oxidation method, which improves the cleanliness of industrial preparation reactions and reduces environmental pollution compared with other inorganic heavy metal salts and inorganic mineral acid oxidation methods. pollute. (2) This method uses the hydrogen peroxide oxidation method to realize the normal pressure liquid phase preparation reaction, which is milder than the gas-liquid phase pressurized reaction of the air (oxygen) oxidation method, which improves the safety of industrial preparation operations and saves energy. (3) The method improves the product yield, which is about 3% higher than the current industrial traditional method. The total yield of the method reaches 76%, and the product purity is more than 99%. (4) The method uses the inorganic solid alkali sodium hydroxide to catalyze the oxidation reaction, does not use metal-organic complex catalysts, improves the reaction stability, and greatly reduces the industrial preparation cost. (5) In this method, the azobisalkylnitrile solid catalyst is used to replace the peroxycarbonate liquid phase catalyst to catalyze the bromination reaction and improve the safety of the industrial preparation reaction operation. (6) The method uses halogenated aromatic hydrocarbon as solvent medium, avoids the use of halogenated alkane solvent medium, and avoids the pollution of low boiling point volatile organic solvent. (7) The method can be reacted under normal pressure, the reaction conditions are mild, and the industrial preparation is easy to operate. (8) The method reduces the generation of organic by-products and the discharge of inorganic salt (acid) wastewater. (9) The method can prepare and isolate high-purity intermediate compound p-nitrobenzyl alcohol according to market demand.

Description of drawings

Fig. 1 is process flow chart of the present invention.

detailed description

Below in conjunction with accompanying drawing 1, the new method is described in further detail.

With reference to accompanying drawing 1, the present invention comprises three unit reaction processes, i.e. bromination, hydrolysis, oxidation reaction. In the first bromination reaction process stage, azobisalkylnitrile is used to catalyze the reaction of bromine and p-nitrotoluene, and the hydrogen bromide by-product formed is oxidized by hydrogen peroxide into elemental bromine and then enters the reaction system for recycling, which not only reduces the Bromine consumption and waste reduction can reduce production costs. In this process, halogenated aromatic hydrocarbons are used instead of halogenated alkanes to avoid the use of volatile organic solvents. In the second hydrolysis reaction process stage, the reaction mixture of the first process stage directly enters the second reaction process stage, which reduces environmental pollution, saves energy and reduces emissions, simplifies the separation operation in the process, and is easy to implement engineering. In addition to nitrobenzyl alcohol, there is also a small amount of p-nitrobenzaldehyde final product. The p-nitrobenzyl alcohol at this stage can be isolated and extracted as a product, and its purity is very high. In the third oxidation reaction process stage, hydrogen peroxide is a cheap and environment-friendly oxidant. Sodium hydroxide is used to catalyze hydrogen peroxide to oxidize p-nitrobenzyl alcohol to generate p-nitrobenzaldehyde with high selectivity. The reaction is under normal pressure, the conditions are mild, and the operation is simple. , without the use of metal-organic complexes, greatly reducing the cost of raw materials. Compared with the traditional industrial method, the new method increases the yield by 3%, reduces the generation of organic by-products, avoids the impact of transition metal salts on the environment, and has dual characteristics of environment and economy.

The method uses three unit reaction processes to prepare p-nitrobenzaldehyde in detail below with specific examples, but it does not represent limiting the scope of the present invention.

Example 1

In the reactor, add 80g chlorobenzene, 13.7g p-nitrotoluene, 2.7g azobisisovaleronitrile, slowly add 9.6g bromine dropwise within 30min at 50°C, after the dropwise addition, stir and heat to reflux React until the bromine color fades. Slowly add 7.0 g of 27.5% hydrogen peroxide dropwise within 30 min, and stir and reflux for 3 h. Add 68.5g of 20% potassium carbonate aqueous solution to the reaction solution, stir and reflux for 30h, recover chlorobenzene by distillation, cool and stand to separate the water phase and the organic phase containing p-nitrobenzyl alcohol. Transfer the organic phase into the reactor, add 2.7g of sodium hydroxide, stir and control the temperature at 25°C, add 48.7g of 35% hydrogen peroxide dropwise within 30min, and heat to reflux for 26h. After the reaction was completed, it was cooled to room temperature, and the organic phase was separated by standing. After washing, the organic solvent was concentrated, and 11.5 g of p-nitrobenzaldehyde was obtained by refining with ethanol. The GC purity was 99.1%, and the yield was 76.2%.

Example 2

In the reactor, add 80g of chlorobenzene, 13.7g of p-nitrotoluene, and 1.2g of azobisisoheptanonitrile, and slowly add 9.0g of bromine dropwise within 30min at 45°C. After the dropwise addition, stir and heat to reflux React until the bromine color fades. Slowly add 7.0 g of 27.5% hydrogen peroxide dropwise within 30 min, and stir and reflux for 2 h. Add 41.5 g of 30% potassium carbonate aqueous solution to the reaction solution, stir and reflux for 21 h, recover chlorobenzene by distillation, and cool and stand to separate the water phase and the organic phase containing p-nitrobenzyl alcohol. Transfer the organic phase into the reactor, add 1.5g of sodium hydroxide, stir and control the temperature at 30°C, add 62.0g of 27.5% hydrogen peroxide dropwise within 30min, and heat to reflux for 26h. After the reaction was completed, cool to room temperature, stand to separate the organic phase, concentrate the organic solvent after washing, and refine with ethanol to obtain 11.3 g of p-nitrobenzaldehyde, with a GC purity of 99.0% and a yield of 74.8%.

Example 3

In the reactor, add 80g of o-dichlorobenzene, 13.7g of p-nitrotoluene, and 1.2g of azobisisooctanonitrile, and slowly add 9.0g of bromine dropwise within 30min at 45°C. After the dropwise addition, stir and heat The reaction was refluxed until the color of bromine faded. Slowly add 7.0 g of 27.5% hydrogen peroxide dropwise within 30 min, and stir and reflux for 2 h. Add 41.5 g of 30% potassium carbonate aqueous solution to the reaction solution, stir and reflux for 23 hours, recover o-dichlorobenzene by distillation, and cool and stand to separate the water phase and the organic phase containing p-nitrobenzyl alcohol. Transfer the organic phase into the reactor, add 1.5g of sodium hydroxide, stir and control the temperature at 30°C, add 34.1g of 50% hydrogen peroxide dropwise within 30min, and heat to reflux for 26h. After the reaction was completed, cool to room temperature, stand to separate the organic phase, concentrate the organic solvent after washing, and refine with ethanol to obtain 10.8 g of p-nitrobenzaldehyde, with a GC purity of 99.3% and a yield of 71.5%.

Example 4

In the reactor, add 80g of chlorobenzene, 13.7g of p-nitrotoluene, and 1.5g of azobisisovaleronitrile, and slowly add 9.0g of bromine dropwise within 30min at 45°C. After the dropwise addition, stir and heat to reflux for reaction until the bromine color fades. Slowly add 7.0 g of 27.5% hydrogen peroxide dropwise within 30 min, and stir and reflux for 2 h. Add 50.0 g of 25% potassium carbonate aqueous solution to the reaction solution, stir and reflux for 23 hours, recover 65 g of chlorobenzene by distillation, and cool and stand to separate the water phase and the organic phase containing p-nitrobenzyl alcohol. Transfer the organic phase into the reactor, add 2.0 g of sodium hydroxide, stir and control the temperature at 30° C., add 37.0 g of 27.5% hydrogen peroxide dropwise within 30 min, and heat to reflux for 26 h. After the reaction was completed, it was cooled to room temperature, allowed to stand to separate the organic phase, and purified by reaction and extraction with sodium bisulfite to obtain 11.4 g of p-nitrobenzaldehyde with a GC purity of 99.5% and a yield of 75.5%.

Example 5

In the reactor, add 80g of chlorobenzene, 13.7g of p-nitrotoluene, and 1.5g of azobisisovaleronitrile, and slowly add 9.0g of bromine dropwise within 30min at 45°C. After the dropwise addition, stir and heat to reflux for reaction until the bromine color fades. Slowly add 7.0 g of 27.5% hydrogen peroxide dropwise within 30 min, and stir and reflux for 2 h. Add 50.0 g of 25% potassium carbonate aqueous solution to the reaction solution, stir and reflux for 24 hours, recover chlorobenzene by distillation, and cool and stand to separate the water phase and the organic phase containing p-nitrobenzyl alcohol. Transfer the organic phase into a reactor, add 2.0 g of sodium hydroxide, stir to control the temperature at 30° C., add 68.7 g of 20% hydrogen peroxide dropwise within 30 min, and heat to reflux for 25 h. After the reaction was completed, it was cooled to room temperature, the organic phase was separated, and purified by steam distillation to obtain 11.0 g of p-nitrobenzaldehyde with a GC purity of 99.9% and a yield of 72.8%.

Example 6

In the reactor, add 80g of chlorobenzene, 13.7g of p-nitrotoluene, and 1.5g of azobisisovaleronitrile, and slowly add 9.0g of bromine dropwise within 30min at 45°C. After the dropwise addition, stir and heat to reflux for reaction until the bromine color fades. Slowly add 7.0 g of 27.5% hydrogen peroxide dropwise within 30 min, and stir and reflux for 2 h. Add 50.0 g of 25% potassium carbonate aqueous solution to the reaction solution, stir and reflux for 24 hours, recover chlorobenzene by distillation, and cool and stand to separate the water phase and the organic phase containing p-nitrobenzyl alcohol. Transfer the organic phase into the reactor, add 10.0g of 20% sodium hydroxide aqueous solution, stir and control the temperature at 30°C, add 49.0g of 35% hydrogen peroxide dropwise within 30min, and heat to reflux for 26h. After the reaction was completed, it was cooled to room temperature, the organic phase was separated, and purified with ethanol to obtain 11.1 g of p-nitrobenzaldehyde with a GC purity of 99.3% and a yield of 73.5%.

Example 7

In the reactor, add 80g of bromobenzene, 13.7g of p-nitrotoluene, 0.1g of azobisisobutyronitrile, and slowly add 8.0g of bromine dropwise within 30min at 40°C. After the dropwise addition, stir and heat to reflux React until the bromine color fades. Slowly add 7.0 g of 27.5% hydrogen peroxide dropwise within 30 min, and stir and reflux for 2 h. Add 3.4g of 20% sodium carbonate aqueous solution to the reaction solution, stir and reflux for 20 hours, recover bromobenzene by distillation, cool and stand to separate the water phase and the organic phase containing p-nitrobenzyl alcohol. Transfer the organic phase into the reactor, add 1.5g of sodium hydroxide, stir to control the temperature at 35°C, add 170.5g of 10% hydrogen peroxide dropwise within 30min, and heat to reflux for 26h. After the reaction was completed, it was cooled to room temperature, and the organic phase was separated by standing. After washing, the organic solvent was concentrated, and 8.2 g of p-nitrobenzaldehyde was obtained by refining with ethanol. The GC purity was 99.1%, and the yield was 54.2%.

Claims (7)

1. a preparation method of p-nitrobenzaldehyde, is characterized in that, comprises the steps: (1) bromination reaction Add p-nitrotoluene, solvent halogenated aromatic hydrocarbon, and catalyst azobisalkylnitrile into the reactor, and add bromine dropwise under constant stirring at a controlled temperature of 40-50°C. The dosage of bromine is 0.5-0.6 times the theoretical amount After dripping, heat and reflux to react until the color of bromine fades, then add hydrogen peroxide and reflux for no less than 2 hours to obtain a p-nitrobenzyl bromide reaction solution; (2) Hydrolysis reaction Add carbonate aqueous solution to the reaction liquid of the first step, heat and reflux hydrolysis reaction, generate p-nitrobenzyl alcohol target product and sodium bromide by-product, liquid-liquid separation organic phase and aqueous phase, obtain p-nitrobenzyl alcohol organic Mutually; (3) oxidation reaction Sodium hydroxide is added to the organic phase of p-nitrobenzyl alcohol, hydrogen peroxide is added dropwise at a temperature of 25-35° C. under continuous stirring, and the reaction is heated under reflux to generate the final product p-nitrobenzaldehyde. 2. the preparation method of p-nitrobenzaldehyde as claimed in claim 1 is characterized in that, the azobisalkylnitrile described in step (1) is selected from azobisisobutyronitrile, azobisisoamyl Any one of nitrile, azobisisoheptanonitrile or azobisisooctanonitrile; the amount of the catalyst is 1%-20% of the quality of p-nitrotoluene; the halogenated aromatic hydrocarbon is selected from chlorobenzene, o- dichlorobenzene or bromobenzene. 3. the preparation method of p-nitrobenzaldehyde as claimed in claim 1 or 2 is characterized in that, the azobisalkylnitrile described in step (1) is selected from azobisisovaleronitrile. 4. the preparation method of p-nitrobenzaldehyde as claimed in claim 1 is characterized in that, the carbonate described in step (2) is salt of wormwood or sodium carbonate, and the consumption of carbonate is p-nitrotoluene 5%-100% of the mass; the reflux reaction time is 20-30h. 5. the preparation method of p-nitrobenzaldehyde as claimed in claim 1 or 4 is characterized in that, the carbonate described in step (2) is salt of wormwood. 6. the preparation method of p-nitrobenzaldehyde as claimed in claim 1 is characterized in that, the hydrogen peroxide mass percent concentration described in step (3) is 10%-50%; The consumption of sodium hydroxide is p-nitro 10%-20% of the mass of toluene. 7. the preparation method of p-nitrobenzaldehyde as claimed in claim 1 or 6 is characterized in that, the hydrogen peroxide mass percentage concentration described in step (3) is 20%-35%.