CN1073542C - Method for synthesizing aromatic aldehyde by continuous catalytic hydrogenation of aromatic acid or aromatic ester - Google Patents

Abstract

A method for catalytically synthesizing corresponding aromatic aldehydes with aromatic acids or esters, in the presence of a modified manganese oxide catalyst with γ-Al ₂ O ₃ as the carrier, the aromatic acids or their esters are hydrogenated in the gas phase at atmospheric pressure to prepare the corresponding aromatic aldehydes , the activation of the catalyst and the hydrogenation reaction proceed continuously. The catalyst modifier is one or more of Zn, Zr and Cu. When the reaction temperature is 350-500°C and the molar ratio of hydrogen to aromatic acid or its ester is 10-200, it can be prepared with a content of up to 98%. Aromatic aldehyde products, the reaction yield is over 80%.

Description

A method for aromatic acid or ester catalyzed continuous hydrogenation to synthesize aromatic aldehyde

The invention relates to a method for synthesizing aromatic aldehydes by continuous catalytic hydrogenation of aromatic acids or their esters in gas phase.

Aromatic aldehyde is an important organic chemical product, and is an important synthetic raw material for fine chemical products such as medicine, spices, and resin additives. Chlorine-free aromatic aldehyde can also be used in flavors and food additives.

The traditional manufacturing process of aromatic aldehyde is the toluene branched methyl halogenation method, which is based on the organic synthesis process of adding super-equivalent halogen auxiliary raw materials, and the aromatic aldehyde product contains chlorine. In addition, there are formylation and oxidation of benzene, which are limited by the reaction substrate, and their use is limited to special occasions. European patent EP0,150,961 has described the method for aromatic acid or its ester catalytic hydrogenation synthesis aromatic aldehyde, has used _ZrO in this method Catalyst, modification component has selected one or several following elements in, Al, Sc, Ga, In, La, Ce, Pr, Nd. U.S. Patent No. 4,585,900 describes the method for aromatic acid catalytic hydrogenation to synthesize aromatic aldehydes. In this method, α-Al ₂ O ₃ is used as a carrier Y ₂ O ₃ /CuO catalyst, the reaction temperature is 420 ° C, and the hydrogen-acid ratio ( When the molar ratio) was 50, the benzoic acid conversion rate was 87.5%, and the benzaldehyde selectivity was 92.9%. The above-mentioned method has disadvantages such as high cost of catalyst, pollution to the environment, etc., so it still needs to be further improved.

The object of the present invention is to provide a method for continuously synthesizing aromatic aldehydes by gas-phase catalysis of aromatic acids or esters at atmospheric pressure.

The embodiment of the present invention relates to the preparation of corresponding aromatic aldehydes by hydrogenation of aromatic acids or their esters in gas phase at atmospheric pressure in the presence of a modified manganese oxide catalyst supported by γ-Al ₂ O ₃ . The reaction formula is as follows:

          

Among them, Rh is an aromatic group, and R' is an alkyl group.

The present invention uses γ-Al ₂ O ₃ as a carrier and modified manganese oxide as a catalyst. The catalyst can be modified by one or several elements of Cu, Zn and Zr, and can be reduced and activated under hydrogen or hydrogen-nitrogen mixed gas. The temperature rises slowly from 120°C to 420°C. After reduction, the aromatic acid or ester is continuously preheated and mixed with hydrogen into the catalytic bed for reaction. The hydrogenation temperature range is 350-500°C, the molar ratio of hydrogen to aromatic acid or ester is 10-200, and the liquid hourly space velocity of aromatic acid or ester is 0.05-0.5hr ^-1 .

Aromatic acids or esters in the present invention are derivatives of benzoic acid and benzoic acid esters such as benzoic acid, hydroxybenzoic acid, toluic acid, methyl benzoate, methyl hydroxybenzoate, and methyl toluate.

The better conditions for the above reaction are: the hydrogenation reaction temperature is 380-420°C, the molar ratio of hydrogen to aromatic acid or ester is 20-100, and the liquid hourly space velocity of aromatic acid or ester is 0.1-0.3hr ^-1 .

The catalyst used in _the invention is manganese oxide modified with gamma- _Al2O3 as the carrier, and the modification element is one or more of Cu, Zn and Zr. When preparing, dissolve manganese nitrate or acetate and aluminum nitrate in aqueous solution. The temperature of the solution should be 50-70°C when dissolving. After dissolving, add copper, zirconium or zinc nitrate, and adjust the pH value of the solution with ammonia water. , generally adjusted to pH = 9-11 to obtain coprecipitate, the coprecipitate was rinsed with deionized water until neutral, then dried, and roasted at 400-500°C in a muffle furnace for 1.5-3.5 hours to obtain The modified manganese oxide catalyst supported by γ-Al ₂ O ₃ can be loaded into the reactor for reduction and activation, and then used to catalyze the hydrogenation reaction.

The modified manganese oxide catalyst supported by γ-Al ₂ O ₃ after calcination and reduction is denoted as MnO-M/γ-Al ₂ O ₃ catalyst. Wherein M is modifier metal element.

The content of manganese in the catalyst is 10%-50% (wt%), and the content of the modifier is 0.1-5.0% (wt%). The experiment proves that the catalyst prepared in this range has better catalytic effect.

This reaction adopts atmospheric gas phase hydrogenation method, so the aromatic acid or its ester needs to be gasified to participate in the reaction. The gasification of the aromatic acid or its ester is carried out by heating the raw material above or below the boiling point and using saturated steam. Realized, and then mixed with preheated hydrogen into the reactor for reaction.

The invention uses gamma-Al ₂ O ₃ as the carrier in the presence of a modified manganese oxide catalyst to prepare the corresponding aromatic aldehyde through atmospheric pressure gas phase hydrogenation of aromatic acid or ester. The feature of this method is that the catalyst reduction and hydrogenation reactions can be carried out continuously, the process is simple, the conversion rate and selectivity of catalytic hydrogenation are high, the reaction yield is kept above 80%, the product is high in purity and does not contain chlorine, and can be prepared with a content greater than 98% chlorine-free aromatic aldehydes can be used as raw materials and additives in various industries of chemical industry, fragrance and food.

Example:

1. One of the preparation methods of the catalyst is to dissolve manganese nitrate and aluminum nitrate in an aqueous solution, adjust the solution to alkaline with ammonia water, and generally adjust the pH to 10-11. Precipitate, the co-precipitate was rinsed with deionized water until neutral, dried, and roasted in a muffle furnace at a temperature of 500 ° C for 3 hours, and the obtained modified manganese oxide catalyst based on γ-Al ₂ O ₃ was It can be loaded into a reactor for reduction activation, and then used for catalytic hydrogenation reaction.

2. The second preparation method of the catalyst is to dissolve manganese acetate and aluminum nitrate in an aqueous solution, adjust the solution to be alkaline with ammonia water, and generally adjust the pH to 9-10. Precipitate and co-precipitate were rinsed with deionized water until neutral, then dried, and then roasted in a muffle furnace at 450°C for 3 hours to obtain a modified manganese oxide catalyst supported by γ-Al ₂ O ₃ that is It can be loaded into a reactor for reduction activation, and then used for catalytic hydrogenation reaction.

3. This example adopts the MnO/γ-Al ₂ O ₃ catalyst prepared by the method of Example 1.

Put 5 grams of Mn ₂ O ₃ /γ-Al ₂ O ₃ catalyst into a stainless steel reactor with a diameter of 14 mm, and first reduce it with hydrogen and nitrogen mixed gas, and the reduction temperature slowly rises from 120°C to 420°C. After the reduction is complete, the methyl benzoate is injected into the gasifier with a metering pump, mixed with the preheated hydrogen, and then enters the catalytic bed for reaction after being heated. The feed rate of the methyl benzoate is 3.5ml/hr. The hydrogen feed flow rate is 0.021M ³ /h, the reaction temperature is 410°C, the conversion rate of methyl benzoate is 97%, and the selectivity of benzaldehyde is 86%.

4. In this example, the catalyst of Example 1 is used, and 2% of Zr element is added for modification.

5 grams of Mn ₂ O ₃ -Zr/γ-Al ₂ O ₃ catalysts are packed into a stainless steel reactor with a diameter of 14mm, the catalyst reduction and feeding method are the same as in Example 3, and the feeding amount of methyl benzoate is 3.5ml /hr, the hydrogen feed flow rate is 0.021M ³ /h, the reaction temperature is 395°C, the conversion rate of methyl benzoate is 100%, and the selectivity of benzaldehyde is 87.5%.

5. This example adopts the catalyst prepared by Example 2 method.

5 grams of Mn ₂ O ₃ /γ-Al ₂ O ₃ catalysts are packed into a stainless steel reactor with a diameter of 14 mm, the catalyst reduction method is the same as in Example 3, benzoic acid is fed with saturated steam, and the evaporation temperature is controlled at 160 ° C. The feed flow rate of hydrogen is 0.040M ³ /h, the reaction temperature is 420°C, the conversion rate of benzoic acid is 100%, and the selectivity of benzaldehyde is 95%.

6. This example adopts the catalyst prepared by Example 2 method.

5 grams of Mn ₂ O ₃ /γ-Al ₂ O ₃ catalysts are packed into a stainless steel reactor with a diameter of 14 mm, the catalyst reduction and feeding method are the same as in Example 3, and the raw material methyl o-hydroxybenzoate is injected with a metering pump. The carburetor is mixed with the preheated hydrogen, and then enters the catalytic bed for reaction after being heated. The feeding amount of methyl o-hydroxybenzoate is 3.2ml/hr, and the hydrogen feeding flow rate is 0.025M ³ /h, and the reaction temperature At 400°C, the conversion rate of methyl o-hydroxybenzoate is 100%, and the selectivity of benzaldehyde is 85%.

7. In this example, the catalyst prepared by the method in Example 1 was used, and 3% of Zn was added for modification. 5 grams of Mn ₂ O ₃ /γ-Al ₂ O ₃ catalysts are packed into a stainless steel reactor with a diameter of 14mm. Catalyst reduction and feeding method can be example 3, and the feeding amount of methyl benzoate is 3.5ml/hr , the hydrogen feed flow rate is 0.021M ³ /h, the reaction temperature is 405°C, the conversion rate of methyl benzoate is 100%, and the selectivity of benzaldehyde is 87.0%.

8. In this example, the catalyst prepared by the method in Example 2 was used, and 5% Cu element was added for modification.

5 grams of Mn ₂ O ₃ -Cu/γ-Al ₂ O ₃ catalysts are packed into a stainless steel reactor with a diameter of 14mm, the catalyst reduction and feeding method are the same as in Example 3, and the feeding amount of methyl benzoate is 3.5ml /hr, the hydrogen feed flow rate is 0.021M ³ /h, the reaction temperature is 400°C, the conversion rate of methyl benzoate is 100%, and the selectivity of benzaldehyde is 85%.

Claims (4)

1. A process for synthesizing aromatic aldehyde by continuous hydrogenation of aromatic acid ester or gas phase catalyst features use of gamma-Al₂O₃Manganese oxide modified by a carrier is used as a catalyst, a modifying element of the catalyst is one or more of Zn, Zr and Cu, the content (weight percentage content) of manganese in the catalyst is 10-50%, the content (weight percentage content) of a modifying agent is 0.1-5.0%, reducing gas hydrogen or a hydrogen-nitrogen mixed gas is used for reduction and activation, gasified aromatic acid or ester is mixed with the hydrogen and then continuously enters a catalyst bed for hydrogenation reaction, and the activation and reaction conditions are as follows:

(1) the reduction activation temperature of the catalyst is 120-420 ℃;

(2) the molar ratio of hydrogen to aromatic acid or its ester is 10-200, and the liquid hourly space velocity of aromatic acid or its ester is 0.05-0.5hr^-1；

(3) The hydrogenation reaction temperature is 350-500 ℃.

2. The method of claim 1The gas phase continuous hydrogenation process of synthesizing aromatic aldehyde with aromatic acid or ester features the molar ratio of hydrogen to aromatic acid or ester of 20-100 and the liquid hourly space velocity of aromatic acid or ester of 0.1-0.3hr^-1The reaction temperature is 380-420 ℃.

3. The method for synthesizing aromatic aldehyde by gas-phase continuous hydrogenation of aromatic acid or ester according to claim 1, wherein the catalyst is prepared by dissolving nitrate or acetate of manganese and aluminum nitrate in water, adding nitrate of copper, zirconium or zinc after dissolving, adjusting the solution to be alkaline to obtain coprecipitate, washing the precipitate to be neutral, drying, roasting at 400-500 ℃ for 1.5-3.5 hours, and then putting the precipitate into a reactor for reduction treatment.

4. The method for synthesizing aromatic aldehyde by the gas-phase continuous hydrogenation of aromatic acid or ester according to claim 1, wherein the gasification of aromatic acid or ester is carried out by heating the raw material to a temperature above or below the boiling point with saturated steam.