CN1125020C

CN1125020C - Catalytic synthesizing process of toluyl aldehyde

Info

Publication number: CN1125020C
Application number: CN99119802A
Authority: CN
Inventors: 沈伟; 徐华龙
Original assignee: Fudan University
Current assignee: Fudan University
Priority date: 1999-10-21
Filing date: 1999-10-21
Publication date: 2003-10-22
Anticipated expiration: 2019-10-21
Also published as: CN1257060A

Abstract

The present invention relates to a method for synthesizing toluyl aldehyde by methyl benzoic acid ester gas-phase hydrogenation. Benzoic acid ester is hydrogenized to synthesize benzaldehyde in the prior art, and the methylbenzaldehyde synthesis effect by methylbenzoic acid is not ideal. The present invention adopts a MnO-Al2 O3-ZrO2 catalyst prepared by an attaching precipitation method, and the methylbenzoic acid ester is prepared into the methylbenzaldehyde by gas phase catalysis hydrogenation. The catalyst contains main components of MnO, Al2 O3 and ZrO2, and active constituents of manganese oxide and zirconium dioxide are dispersed on aluminum oxide in a single layer mode. When the molar ratio of hydrogen gas to the methylbenzoic acid ester is 20 to 100 at the reaction temperature of 350 to 430 DEG C, the conversion rate per pass of the methylbenzoic acid ester reaches 96%, and the selectivity of the methylbenzaldehyde reaches 89%.

Description

Catalytic synthesis method of methyl benzaldehyde

The invention relates to a method for synthesizing methyl benzaldehyde by gas-phase hydrogenation of methyl benzoate.

The methyl benzaldehyde can be o-methyl benzaldehyde, m-methyl benzaldehyde or p-methyl benzaldehyde, which are important organic chemical products and important synthetic raw materials of fine chemical products such as medicines, spices, resin additives and the like.

The traditional process for preparing methyl benzaldehyde adopts xylene indirect electrosynthesis method, which has high energy consumption and low yield. The key point of international research is the synthesis of methyl benzaldehyde by methyl benzoic acid or ester catalytic hydrogenation. European patent EP 0,150,961 describes a process for the catalytic hydrogenation of benzoates to benzaldehyde, in which ZrO is used₂Catalyst, modifying component one or more of the following elements, Al, Sc, Ga, In, La, Ce, Pr, Nd. U.S. Pat. No. 3, 4,585,900 describes the synthesis of benzaldehyde by catalytic hydrogenation of benzoic acid, In which α -Al is used₂O₃Y as a carrier₂O₃The reaction temperature of the CuO supported catalyst is 420 ℃, and when the hydrogen-acid ratio (molar ratio) is 50, the conversion rate of the benzoic acid is 87.5 percent, and the selectivity of the benzaldehyde is 92.9 percent. European patent EP 0,573,087 and U.S. Pat. No. 3, 5,336,810 describe 1MK₂CO₃Adding the solution into manganese nitrate, aluminum nitrate, copper nitrate and zinc nitrate solution to form mixed solution, coprecipitating at pH 4-10, filtering, drying, reducing, screening and roasting to obtain the catalyst, wherein the optimal component is MnO₂/ZnO-ZnAl₂O₄. US patent US 4,987,265 mentions the preparation of catalysts by co-precipitation of Mn salts with acidic salts (Al, Zr, Ti, Hf, Nb)at pH between 7 and 10. In the above patents the authors mention mostly that the invented process can also be used for the synthesis of tolualdehyde, but the results are not as good as for the synthesis of benzaldehyde.

The invention aims to provide a method for synthesizing methyl benzaldehyde by gas-phase hydrogenation of methyl benzoate.

In the presence of a catalyst, vaporized methyl benzoate and hydrogen are mixed and then continuously enter a catalytic bed for hydrogenation reaction, and the reaction formula is as follows:

wherein CH₃ArCOOR' is methylbenzoateAnd R' is an alkyl group.

The catalyst of the invention is MnO-Al₂O₃-ZrO₂The catalyst is prepared by integrating the advantages of a loading method and a precipitation method, and is called as an adhesion precipitation method. Manganese nitrate, zirconium nitrate and the prepared aluminum hydroxide are precipitated uniformlyMixing, washing to neutrality, drying at 200 deg.C and 100 deg.C, calcining at 600 deg.C and reducing and activating.

After the catalyst is reduced and activated, methyl benzoate and hydrogen are continuously preheated and mixed to enter a catalyst bed for reaction. The hydrogenation reaction temperature range is 300-500 ℃, the molar ratio of hydrogen to methyl benzoate is 10-200, and the liquid hourly space velocity of methyl benzoate is 0.08-0.8hr^-1。

The better conditions of the reaction are as follows: the hydrogenation reaction temperature is 350-430 ℃, the molar ratio of hydrogen to methyl benzoate is 20-100, and the liquid hourly space velocity of the methyl benzoate is 0.1-0.4hr^-1。

The methyl benzoate is alkyl benzoate such as methyl benzoate and ethyl benzoate, and the methyl group can be ortho-position, meta-position or para-position, i.e. ortho-methyl benzoate, meta-methyl benzoate or para-methyl benzoate.

The reaction adopts a gas phase hydrogenation method, so that methyl benzoate needs to be vaporized to participate in the reaction, the vaporization of the methyl benzoate is realized by heating the raw material to be above the boiling point or adopting a saturated steam method below the boiling point, and then the methyl benzoate is mixed with preheated hydrogen and enters a reactor to carry out hydrogenation reaction on a catalyst after being superheated.

The preferred three components of the catalyst of the present invention are manganese oxide in the range of 20 to 50 wt%, zirconium oxide in the range of 2 to 10 wt%, and alumina in the range of 40 to 78 wt%, with the manganese and zirconium being present in a single layer on the alumina. Experiments also prove that the catalyst manganese and zirconium prepared in the range can be dispersed in a single layer, and the catalytic effect is good.

The catalyst used in the invention is MnO-Al prepared by an adhesion precipitation method₂O₃-ZrO₂The catalyst is prepared through loading Mn ion and Zr ion onto the aluminum hydroxide precipitate to form single layer dispersion, and final dispersingAdding a precipitant such as ammonia water to form manganese and zirconium hydroxide precipitate, wherein the preparation method comprises the following steps:

(1) dissolving aluminum nitrate in deionized water, and dropwise adding ammonia water to adjust the pH value to 7-9 to obtain aluminum hydroxide

And (4) precipitating.

(2) Dissolving manganese nitrate and zirconium nitrate in deionized water, and uniformly precipitating the obtained solution and aluminum hydroxide

Mixing, so that manganese ions and zirconium ions are attached to the aluminum hydroxide to form single-layer dispersion.

(3) Adjusting pH of the mixture to 8-10 with ammonia water, and washing the precipitate with deionized water

Drying at 200 deg.C after sexual activation, and calcining at 600 deg.C at 400 deg.C for 1.5-3.5hr^-1。

(4) The above-mentioned roasted MnO-Al₂O₃-ZrO₂The mixture is mixed with reducing gas hydrogen or hydrogen-nitrogen

Reducing and activating the synthesis gas at the temperature of 200-500 ℃ to obtain the methyl benzene synthesized by the gas phase hydrogenation of methyl benzoate

A catalyst for formaldehyde.

The preparation of the catalyst adopts an adhesion precipitation method, the catalytic effect is superior to that of the catalyst in the prior art, and MnO-Al with active components of manganese oxide and zirconium oxide dispersed in a single layer is adopted₂O₃-ZrO₂A process for producing methylbenzaldehyde from methylbenzoate by gas phase hydrogenation in the presence of a catalyst. The method is characterized in that the catalytic hydrogenation reaction is continuously carried out, the methyl benzoate hydrogenation is completed in one step, the process is simple, the conversion rate of the catalytic hydrogenation can reach 96 percent, and the selectivity can reach 89 percent.

Example (b):

1.5 g of MnO-Al prepared by an adhesion precipitation method₂O₃-ZrO₂The catalyst was packed in a stainless steel reactor having a diameter of 14mm, and the content of manganese oxide in the catalyst was 20% (wt%), zirconium oxide was 2% (wt%) and aluminum oxide was 78% (wt%). The preparation method of the catalyst comprises the following steps:

(1) dissolving aluminum nitrate in deionized water, and dropwise adding ammonia water to adjust the pH value to 8, thereby obtaining aluminum hydroxide precipitate.

(3) Adjusting pH of the mixture to 8 with ammonia water, washing the precipitate with deionized water to neutrality

Oven drying at 150 deg.C, and baking at 500 deg.C for 3hr^-1。

(4) The above-mentioned roasted MnO-Al₂O₃-ZrO₂The mixture is slowly cooled from 120 ℃ by using a hydrogen-nitrogen mixture

Reducing and activating at 420 deg.c to obtain methyl benzaldehyde from methyl benzoate through gas phase hydrogenation

A catalyst.

Pumping methyl p-methylbenzoate into a gasifier by using a metering pump, mixing with preheated hydrogen, heating, and allowing the mixture to enter a catalytic bed for reaction, wherein the feeding amount of the methyl p-methylbenzoate is 4.0ml/hr, and the feeding flow of the hydrogen is 0.021M³The reaction temperature is 380-390 ℃, the conversion rate of methyl p-methylbenzoate is 96 percent, and the selectivity of p-methylbenzaldehyde is 89 percent.

2. In this example, the catalyst prepared in example 1 was used, 5 g of the catalystwas charged in a stainless steel reactor having a diameter of 14mm, the catalyst was reduced and the raw material ethyl M-methylbenzoate was fed in the same manner as in example 1, the feeding amount of ethyl M-methylbenzoate was 3.5ml/hr, and the feeding flow rate of hydrogen was 0.021M³The reaction temperature is 390 ℃ and 400 ℃, the conversion rate of the ethyl m-methylbenzoate is 97 percent, and the selectivity of the benzaldehyde is 86 percent.

3.5 g of MnO-Al prepared by an adhesion precipitation method₂O₃-ZrO₂The catalyst was packed in a stainless steel reactor having a diameter of 14mm, and the content of manganese oxide in the catalyst was 35% (wt%), zirconium oxide was 5% (wt%) and aluminum oxide was 60% (wt%). The catalyst reduction method was the same as in example 1,the o-methyl ethyl benzoate adopts a saturated steam feeding mode, the evaporation temperature is controlled to be 120 ℃, and the feeding flow of hydrogen is 0.040M³The reaction temperature is 390 plus 400 ℃, the conversion rate of the ethyl o-methylbenzoate is 98 percent, and the selectivity of the benzaldehyde is 85 percent.

4.5 g of MnO-Al prepared by an adhesion precipitation method₂O₃-ZrO₂The catalyst was packed in a stainless steel reactor having a diameter of 14mm, and the content of manganese oxide in the catalyst was 32% (wt%), zirconium oxide was 8% (wt%) and aluminum oxide was 60% (wt%). The catalyst reduction and the raw material methyl p-methylbenzoate feeding method were the same as in example 1, the feeding amount of methyl p-methylbenzoate was 4.5ml/hr, and the feeding flow of hydrogen was 0.045M³The reaction temperature is 370 and 380 ℃, the conversion rate of methyl p-methylbenzoate is 95 percent, and the selectivity of p-methylbenzaldehyde is 85 percent.

Claims

1. A catalytic synthesis method of methyl benzaldehyde by using methyl benzoate in MnO-Al₂O₃-ZrO₂The gas phase hydrogenation synthesis is carried out in the presence of a catalyst, and the specific reaction conditions are as follows:

(1) the molar ratio of the hydrogen to the methyl benzoate is 10-200;

(2) the liquid hourly space velocity of methyl benzoate is 0.08-0.8hr^-1；

(3) The hydrogenation reaction temperature is 300-500 ℃;

(4) the catalyst is in Al₂O₃Upper monolayer dispersing MnO and ZrO₂Is prepared from manganese nitrate and nitric acid

Loading zirconium on aluminum hydroxide in a single layer, adding a precipitator, washing to neutrality, and drying at 100-200 deg.C

Drying, roasting at 400-600 ℃, and reducing and activating.

2. The catalytic synthesis process for methylbenzaldehyde according to claim 1, wherein the molar ratio of hydrogen to methylbenzoate ester is 20 to 100.

3. The catalytic synthesis process of methylbenzaldehyde according to claim 1, wherein the liquid hourly space velocity of methylbenzoate is 0.1 to 0.4hr^-1。

4. The catalytic synthesis process for tolualdehyde according to claim 1, wherein the reaction temperature is preferably 350-430 ℃.

5. The catalytic synthesis process for methylbenzaldehyde according to claim 1, wherein the vaporization of the methylbenzoic acid esters is carried out by heating the starting materials to a temperature above or below the boiling point using saturated steam.

6. The catalytic synthesis method of methylbenzaldehyde according to claim 1, wherein the content of manganese oxide in the catalyst is 20 to 50% (wt%), the content of zirconium oxide is 2 to 10% (wt%), and the content of aluminum oxide is 40 to 78% (wt%).

7. The catalytic synthesis process for tolualdehyde according to claim 1, characterized in that the catalyst is prepared as follows:

Precipitating;

(2) dissolving manganese nitrate and zirconium nitrate in deionized water, and uniformly mixing the obtained solution and aluminum hydroxide precipitate

Combining, so that manganese ions and zirconium ions are attached to the aluminum hydroxide; (3) adjusting the pH value of the mixed solution to 8-10 with ammonia water, washing the obtained precipitate with deionized water to neutrality, drying at 200 ℃ and roasting at 600 ℃ for 1.5-3.5 hr; (4) reducing and activating the roasted solid by using reducing gas hydrogen or hydrogen-nitrogen mixed gas at the temperature of 200-500 ℃ to obtain the catalyst.