Method for industrially synthesizing acetophenone

Abstract

The invention provides a method for industrially synthesizing acetophenone, which relates to the field of fine chemical engineering and comprises the following steps: by taking benzoic acid and acetic acid as raw materials, enabling the benzoic acid and acetic acid to flow through a reactor filled with a solid catalyst to synthesize acetophenone; the invention initiatively provides a process route for catalytically synthesizing acetophenone in a fixed bed reactor by taking acetic acid and benzoic acid as raw materials, so that the acetophenone is prepared under the process, the raw materials benzoic acid and acetic acid in the process route are wide in source and easy to obtain, the process route is suitable for continuous production, the device flow is simple, and the product quality is stable.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fine chemical technology, and particularly relates to a method for industrial synthesis of phenyl methyl ketone. BACKGROUND

[0002] Phenyl methyl ketone is a colorless liquid with molecular formula C6H5COCH3, melting point 19.6 ℃, boiling point 202.6 ℃, which is widely used in soap and tobacco flavors, used for synthesis of phenyl glycolic acid, alpha-phenyl indole, isobutyl benzene propionic acid, and also used as a plasticizer for plastics. When used as a solvent, it has the characteristics of high boiling point, stability, and pleasant odor, and can dissolve nitrocellulose, cellulose acetate, ethylene resin, coumarone resin, alkyd resin, glycerol alkyd resin, etc., and is often used in combination with ethanol, ketones, esters and other solvents.

[0003] Friedel-Crafts acylation reaction is the most important and most commonly used method for preparing aryl ketones in the laboratory, and benzene is used as both a raw material and a solvent. Acylating agents commonly use acetic anhydride (such as CN201010185997.4), and catalysts generally use anhydrous AlCl3 or Fe2O3. CN201410571790.9 discloses the use of potassium chlorate, but the yield of phenyl methyl ketone is low due to harsh reaction conditions, and chlorine-containing waste is generated, which is not suitable for industrial production.

[0004] In industry, ethylbenzene oxidation method is generally used to produce phenyl methyl ketone. In the applied patents, the oxidizing agents include air or oxygen (CN201510090298.4, CN201410742237.7, CN201010223144.5, CN201010103414.9), tert-butyl hydroperoxide (CN201710885396.6, CN201610736766.5, CN201210169970.5), hydrogen peroxide (CN201110346787.3) and ozone (CN201910123279.5).

[0005] The catalysts for ethylbenzene oxidation include cobalt (II) salt (CN201910794908.7, CN201110346787.3, CN201480022480.X), Cu(II) salt (CN201110193501.2), nitrogen-doped nanocarbon (CN201810171406.4), magnesium oxide supported on modified nanometer diatomite (CN201610736766.5), at least one compound composed of an alkaline compound and water, and at least cobalt, manganese and bromine as active ingredients (CN201610983936.X), metal phthalocyanine (CN201510090298.4), mononuclear metalloporphyrin and μ-oxo-bicyclic metalloporphyrin with the structure of formula (III) (CN201010103414.9), molecular sieve supported solid base as a carrier, and metal salt loaded by impregnation method (CN201410742237.7), Dawson-type phosphomolybdovanadate polyoxometalate with cobalt and pyridine as counterions and bromide (CN201010223144.5), SBA15 mesoporous molecular sieve (mercury lamp irradiation, photocatalysis, CN200810200740.4).

[0006] Other raw materials for preparing acetophenone include α-methylstyrene without catalyst for photooxidation (CN200710046544.1), or titanium dioxide or aluminum oxide or zinc oxide or nickel oxide or iron oxide or copper oxide as catalyst for oxidation with hydrogen peroxide (CN201711297245.5); sec-butylbenzene for oxidation with molecular oxygen (CN201110263493.4); cumene for oxidation in alkaline solution (CN202111092372.8); phenylacetylene for hydration under the action of molecular sieve H-ZSM-5 catalyst (CN202011447897.4), or under the action of phosphorous acid as catalyst (CN201410808993.5).

[0007] For industrial production, although ethylbenzene is easier to obtain than other raw materials, the oxidation of ethylbenzene is strictly regulated due to safety issues, and it is difficult for general enterprises to start the project. In addition, ethylbenzene is mainly used for the production of styrene, so it is necessary to develop a new process.

[0008] In addition, the mainstream of the current industrial production of acetophenone is the oxidation of ethylbenzene, and the product indicators produced by the method have three deficiencies: first, the purity is only 99%, which cannot meet the demand for higher purity such as ≥99.9% in the field of food-grade flavor and high-end ink; second, it is easy to contain 1-phenyl ethanol, benzaldehyde and other impurities, and some high-end flavors and pharmaceutical intermediates require the content of 1-phenyl ethanol to be ≤500ppm, and the conventional process is difficult to meet the standard, and the impurities such as α-methyl benzyl alcohol and phenol may also affect the application effect; third, the product quality stability is insufficient, and the reaction is greatly affected by the performance of the catalyst, the reaction conditions and the like, which easily leads to the fluctuation of the impurity content.

[0009] Based on this, the present application aims to provide a method for industrial synthesis of acetophenone with good purity, less impurities and more easy to industrial production. SUMMARY

[0010] The present application provides a method for industrial synthesis of acetophenone, which has simple raw materials, simple process and is easy to industrial production.

[0011] The technical scheme for solving the above technical problems is as follows: a method for industrial synthesis of acetophenone, characterized in that benzene carboxylic acid and acetic acid are used as raw materials, and the raw materials benzene carboxylic acid and acetic acid are flowed through a reactor with a solid catalyst inside to synthesize acetophenone.

[0012] The equation of the above reaction is: C6H5COOH + CH3COOH = C6H5COCH3+ H2O + CO2 The reaction mechanism of the above reaction may be that the carboxyl group (-COOH) of the phCOOH molecule is removed to become a phenyl group (ph-), and the removed carboxyl group becomes CO2, and the H atom combines with the hydroxyl group (OH) of the acetic acid CH3COOH to become water (H2O) and is also released, and the acetic acid without the hydroxyl group becomes acetyl group CH3CO-, and then couples (or condenses) with the phenyl group (ph-) to become acetophenone (phCOCH3'). In addition, it is also possible that the acetic acid is first decarboxylated, and then coupled with the benzoic acid.

[0013] Further, the reactor is a fixed bed reactor, and further, the feeding mode of the raw material is to put the solid benzoic acid into acetic acid, heat to 60-100℃, become a uniform solution, and then pump into the reactor. By controlling the reaction temperature and the reaction pressure, the raw material flows through the catalyst bed in the reactor in the form of gas, and the gas-solid phase catalytic reaction occurs.

[0014] A solid catalyst is placed inside the reactor. Benzoic acid and acetic acid are mixed and preheated to near the reaction temperature, becoming a gas. This gas then enters the reactor from the top of the fixed-bed reactor for reaction. The reaction product is drawn from the bottom of the reactor, where it exchanges heat with the raw materials to recover heat. After being cooled by water, it becomes a liquid. Unreacted raw materials and the byproduct acetone are removed by distillation to obtain acetophenone. (Acetic acid, in addition to reacting with benzoic acid to produce acetophenone, also reacts with another acetic acid molecule to produce acetone. Acetone and acetophenone have significantly different boiling points; by distilling the reaction product to remove the byproduct acetone and unreacted raw materials, the target product acetophenone can be obtained.)

[0015] Furthermore, the reaction is a continuous flow type, meaning the raw materials continuously flow into the reactor.

[0016] Furthermore, the flow rate of the feedstock (acetic acid and benzoic acid) is expressed as weight hourly space velocity (feedstock weight flow rate kg / catalyst weight kg·h, abbreviated as h). -1 The range is 0.2-3 h. -1 The weight hourly space velocity (WHSV) is the physical meaning of the weight of feedstock flowing over a unit weight of catalyst; therefore, it is also called catalyst load. The reaction temperature range is 350-450℃, and the reaction pressure is 0.1-1 MPa. At the same WHSV, increasing the pressure prolongs the contact time between the feedstock and the catalyst, thereby increasing the throughput. However, since this reaction is a molecular expansion reaction, excessively high pressure is detrimental to chemical equilibrium. Based on the actual operating temperature and pressure, the residence time of the feedstock on the catalyst can be calculated, ranging from a few seconds to tens of seconds.

[0017] Furthermore, the catalyst is a cerium-praseodymium-doped magnesium aluminum oxide catalyst. The active component of the catalyst is a cerium-praseodymium mixed rare earth oxide supported on an alkaline oxide MgO-modified Al2O3 support, denoted as CeO2-Pr6O. 11 / MgO-Al2O3, also abbreviated as CePr / MgAlO4, is a catalyst that enables the synthesis of acetophenone from benzoic acid and acetic acid.

[0018] Furthermore, the raw materials also contain water. The above reaction process generates water, but due to the high reaction temperature, the raw materials are prone to coking. Adding a certain amount of water to the raw materials can prevent the catalyst from becoming deactivated due to coking. Additionally, this reaction is strongly endothermic; the introduction of superheated steam into the reactor from the preheater can introduce some heat, preventing the catalytic bed temperature from becoming too low, making the reaction more stable and easier to control.

[0019] Furthermore, the acetic acid is in excess relative to benzoic acid, preferably with a molar ratio of 1.5. This is because the reaction between benzoic acid and acetic acid is an equimolecular reaction. Based on the same reaction mechanism, a side reaction occurs where two acetic acid molecules generate one acetone molecule, consuming some acetic acid; therefore, acetic acid needs to be in excess in the feedstock. Additionally, benzoic acid is a solid and has low solubility in acetic acid; an excess of acetic acid also facilitates feeding and ensures complete reaction, preventing residue from clogging the reactor outlet pipe.

[0020] The beneficial effects of this invention are: 1. This invention is the first to propose a process route for the catalytic synthesis of acetophenone in a fixed-bed reactor using acetic acid and benzoic acid as raw materials. This process route enables the preparation of acetophenone. The raw materials acetic acid and benzoic acid are widely available and easy to obtain, making it suitable for continuous production (benzoic acid can be obtained from toluene using existing mature processes, and toluene has a larger output in petrochemical enterprises, and can also be obtained from the methylation reaction of benzene and methanol. In addition, methanol carbonylation can provide a large amount of cheap acetic acid), which is more conducive to industrial promotion.

[0021] 2. The process of the present invention utilizes existing mature equipment, has a simple process flow, stable product quality, low investment, is suitable for small and medium-scale continuous production, and generates no polluting waste, which is beneficial to the environment.

[0022] 3. The reaction involved in this invention involves the reduction of carbon atoms, resulting in inexpensive raw materials and high industrial value of byproducts, giving it a significant price advantage. After the reaction is complete, acetophenone with a purity of over 99.9% can be obtained by combining it with conventional distillation processes. The impurities contained are only trace amounts of similar substances such as acetone and benzophenone, which can better meet the needs of downstream customers. The product yield calculated based on benzoic acid can reach over 70%. Attached Figure Description

[0023] Appendix Figure 1 This is a gas chromatogram of acetophenone prepared in Example 1; Appendix Figure 2 This is the gas chromatogram of acetophenone prepared in Comparative Example 1. Detailed Implementation

[0024] The principles and features of the present invention are described below. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] Example 1 The synthesis of acetophenone in this embodiment was carried out according to the following steps: S1. Preparation of catalyst support γ-Al₂O₃ modified with basic oxide MgO was prepared by precipitation method. 2.6 g of magnesium nitrate hydrate (Mg(NO₃)₂·6H₂O) and 149 g of aluminum nitrate hydrate (Al(NO₃)₂·9H₂O) were dissolved in 100 ml of deionized water. While stirring, 10% NaOH solution was added dropwise until the pH reached 8. The resulting precipitate was filtered and washed with deionized water to remove Na₂O. + Ions. After drying at 110℃ and calcining at 500℃ for 4 hours, approximately 41g of a support containing 1% MgO and 99% Al2O3 was obtained, denoted as 1%MgO-Al2O3, with a measured specific surface area of ​​200 M². 2 / g, water absorption rate 100%.

[0026] S2, Preparation of catalyst Dissolve 5 g Ce(NO3)3·6H2O in 10 ml of deionized water, and 25 g Pr(NO3)3·6H2O in 50 ml of deionized water. After mixing, impregnate 40 g of the above-mentioned material with a specific surface area of ​​approximately 200 M². 2 / g of 1% MgO-Al2O3 support was impregnated for 12 hours. Then it was dried in an oven at 110℃ and finally calcined in a muffle furnace at 590℃ for 5 hours to obtain 51 g of composite oxide catalyst. The oxide weight composition was CeO2 4% and Pr6O 11 20%, 1%MgO-Al2O376%.

[0027] S3, Catalytic synthesis of acetophenone 50g of catalyst was placed in a single-tube reactor, with both ends filled with inert coarse quartz sand to fix its position. The reactor temperature was controlled by a temperature controller. Acetic acid / benzoic acid was mixed according to a formulation of 1.5 mol / L and heated to 70°C to completely dissolve the benzoic acid into a homogeneous solution. This solution was then pumped in by a metering pump, preheated to approximately 350°C by a preheater, and then introduced into the reactor. The reaction conditions were: raw material liquid hourly space velocity (LHSV) of 0.5 h⁻¹. -1 The reaction was carried out at a temperature of 350℃ and a pressure of 0.12 MPa. The resulting reaction solution mainly contained acetophenone, acetone (a byproduct), and a small amount of unreacted raw materials.

[0028] S4, distillation The above reaction solution can be separated into acetophenone product and acetone by-product by conventional distillation process.

[0029] Specifically, in this embodiment, a two-column combined process was used to purify the above reaction solution by distillation to successfully separate acetone and acetophenone. The process involved atmospheric distillation and vacuum distillation: the first distillation column operated at atmospheric pressure, and at a top temperature of approximately 56°C and a bottom temperature of approximately 100°C, acetone was obtained in the first distillation step. The residue after acetone removal was transferred to the second distillation column for vacuum distillation. At a vacuum of approximately 90 kPa, a top temperature of approximately 140°C, and a bottom temperature of approximately 150°C, acetophenone was obtained. Analysis was performed using a GC9890-ES gas chromatograph with a BP-1 column. The chromatogram is shown below. Figure 1 It can be seen that the purity of the obtained acetophenone is 99.94%.

[0030] The product results data are detailed in Table 1.

[0031] Example 2 The synthesis of acetophenone in this embodiment is carried out according to the following steps: S1. Preparation of catalyst support (Example 1) γ-Al₂O₃ modified with basic oxide MgO was prepared by precipitation method. 13g of magnesium nitrate hydrate (Mg(NO₃)₂·6H₂O) and 150g of aluminum nitrate hydrate (Al(NO₃)₂·9H₂)₂ were dissolved in 100ml of deionized water. While stirring, 10% NaOH solution was added dropwise until the pH reached 8. The resulting precipitate was filtered and washed with deionized water to remove Na₂O. + Ions. After drying at 110℃ and calcining at 500℃ for 4 hours, approximately 43.5 g of a support containing 5% MgO and 95% Al2O3 was obtained, denoted as 5%MgO-Al2O3, with a measured specific surface area of ​​180 M². 2 / g, water absorption rate 95%.

[0032] S2. Preparation of catalyst (Example 4) Dissolve 25g Ce(NO3)3·6H2O in 50ml of deionized water, and dissolve 5g Pr(NO3)3·6H2O in 50ml of deionized water. After mixing, impregnate 40g of the above-mentioned material with a specific surface area of ​​approximately 180M². 2 The catalyst was impregnated with a 5% MgO-Al2O3 support for 12 hours. It was then dried in an oven at 110°C and finally calcined in a muffle furnace at 590°C for 5 hours. Approximately 51 g of catalyst was obtained, with an oxide weight composition of 20% CeO2 and 60% Pr6O3. 11 4%, 5% MgO-Al2O3 76%.

[0033] S3 and S4 are the same as in Example 1.

[0034] The product results data are detailed in Table 1.

[0035] Example 3 The synthesis process of acetophenone in this embodiment is basically the same as that in Example 1. The difference is that water is added to the mixture of raw materials acetic acid and benzoic acid in the catalytic synthesis of acetophenone, wherein the weight of the added water is 20% of the weight of benzoic acid. The results are shown in Table 1.

[0036] Example 4 The synthesis process of acetophenone in this embodiment is basically the same as that in Example 1. The difference is that the weight composition of the prepared oxide is CeO2 5% and Pr6O. 11 25%, 1% MgO-Al2O3 70%. The results are shown in Table 1.

[0037] Example 5 The synthesis process of acetophenone in this embodiment is basically the same as that in Example 1. The difference is that the weight composition of the prepared oxide is CeO2 3.3% and Pr6O. 11 16.7%, 1%MgO-Al2O3 80%. The results are shown in Table 1.

[0038] Example 6 The synthesis process of acetophenone in this embodiment is basically the same as that in Example 1, except that the reaction conditions in step S3 are: liquid hourly space velocity of raw material 0.5 h⁻¹. -1 The reaction temperature was 450℃ and the reaction pressure was 0.1MPa. The results are shown in Table 1.

[0039] Example 7 The synthesis process of acetophenone in this embodiment is basically the same as that in Example 1, except that the reaction conditions in step S3 are: liquid hourly space velocity of raw material 0.5 h⁻¹. -1 The reaction temperature was 450℃ and the reaction pressure was 1.0MPa. The results are shown in Table 1.

[0040] Example 8 The synthesis process of acetophenone in this embodiment is basically the same as that in Example 1, except that the reaction conditions in step S3 are: liquid hourly space velocity of raw material 0.2 h⁻¹. -1 The reaction temperature was 450℃ and the reaction pressure was 1.0MPa. The results are shown in Table 1.

[0041] Example 9 The synthesis process of acetophenone in this embodiment is basically the same as that in Example 1. The difference is that the reaction conditions in step S3 are: liquid hourly space velocity of raw material 3 h⁻¹. -1 The reaction temperature was 450℃ and the reaction pressure was 1.0MPa. The results are shown in Table 1.

[0042] Comparative Example 1 The synthesis process of acetophenone in this comparative example is basically the same as that in Example 1, except that the catalyst support 1% MgO-Al2O3 is replaced with unmodified γ-Al2O3. The results are shown in Table 1. Chromatographic analysis was performed on the acetophenone product obtained in this comparative example; the chromatogram is shown in Table 1. Figure 2 It can be seen that the purity of the obtained acetophenone is 99.73%.

[0043] Comparative Example 2 The synthesis process of acetophenone in this comparative example is basically the same as that in Example 1, except that the catalyst support 1%MgO-Al2O3 is replaced with MgO. The results are shown in Table 1.

[0044] Comparative Example 3 The synthesis process of acetophenone in this comparative example is basically the same as that in Example 1. The difference is that Pr(NO3)3·6H2O was not used in the catalyst preparation process. That is, the catalyst is a cerium-doped magnesium-aluminum composite oxide, which does not contain Pr6O. 11 The results are shown in Table 1.

[0045] Comparative Example 4 The synthesis process of acetophenone in this comparative example is basically the same as that in Example 1, except that Ce(NO3)3·6H2O was not used in the catalyst preparation process. That is, the catalyst is praseodymium-doped magnesium-aluminum composite oxide, which does not contain CeO2. The results are shown in Table 1.

[0046] Comparative Example 5 The synthesis process of acetophenone in this comparative example is basically the same as that in Example 1, except that the reaction temperature for the catalytic synthesis of acetophenone in step S3 is adjusted to 300°C.

[0047] The results are shown in Table 1.

[0048] Comparative Example 6 The synthesis process of acetophenone in this comparative example is basically the same as that in Example 1, except that the reaction temperature for the catalytic synthesis of acetophenone in step S3 is adjusted to 480°C.

[0049] The results are shown in Table 1.

[0050] Comparative Example 7 The synthesis process of acetophenone in this comparative example is basically the same as that in Example 1, except that the reaction pressure for the catalytic synthesis of acetophenone in step S3 is adjusted to 1.2 MPa.

[0051] The results are shown in Table 1.

[0052] Comparative Example 8 The synthesis process of acetophenone in this comparative example is basically the same as that in Example 1, except that the feed weight space velocity for the catalytic synthesis of acetophenone in step S3 is adjusted to 3.5 h⁻¹. -1 .

[0053] The results are shown in Table 1.

[0054] The gas chromatograms of the acetophenone products obtained in Examples 2-9 above show basically the same pattern. Figure 1 The purity of the acetophenone obtained was all above 99.9%, which will not be elaborated here. The purity of the acetophenone obtained in Comparative Examples 2-8 was all below 99.9%, which will not be elaborated here.

[0055] The yield data of acetophenone from the above examples and comparative examples are shown in Table 1, where the yield of acetophenone = benzoic acid conversion rate * acetophenone selectivity.

[0056] Table 1

[0057] As shown in Table 1, the process route of this invention successfully prepares acetophenone in a fixed-bed reactor using acetic acid and benzoic acid, which are more cost-effective and readily available, as raw materials. Furthermore, by combining the specific reaction conditions of this invention with conventional distillation techniques, high-purity (greater than 99.9%) acetophenone can be obtained with a yield exceeding 70%, suitable for industrial production, while simultaneously yielding acetone as a byproduct. Comparative Examples 1-4 characterize the role of the specific catalyst used in this process, ensuring the smooth progress of the reaction and the purity and yield of the product. Comparative Examples 5-8 characterize the synergistic effect of the process conditions of this invention, especially temperature, pressure, and feed weight hourly space velocity, in balancing benzoic acid conversion, yield, and selectivity.

Claims

1. A method for the industrial synthesis of acetophenone, characterized in that, Acetophenone is synthesized by passing benzoic acid and acetic acid through a reactor containing a solid catalyst.

2. The method for industrial synthesis of acetophenone according to claim 1, characterized in that, The reactor is a fixed-bed reactor.

3. The method for industrial synthesis of acetophenone according to claim 2, characterized in that, By controlling the reaction temperature and / or reaction pressure, the raw materials are made to flow through the catalyst bed in the reactor in gaseous form, resulting in a gas-solid phase catalytic reaction.

4. The method for industrial synthesis of acetophenone according to any one of claims 1-3, characterized in that, The raw material is fed by placing solid benzoic acid into acetic acid, heating it to 60-100℃ to form a homogeneous solution, and then pumping it into the reactor.

5. The method for industrial synthesis of acetophenone according to any one of claims 1-3, characterized in that, The reaction is a continuous flow type, meaning that the raw materials flow into the reactor continuously.

6. The method for industrial synthesis of acetophenone according to any one of claims 1-3, characterized in that, The reaction temperature is 350-450℃ and the reaction pressure is 0.1-1MPa.

7. The method for industrial synthesis of acetophenone according to claim 6, characterized in that, The feed weight space velocity is 0.2-3 h. -1 .

8. The method for industrial synthesis of acetophenone according to any one of claims 1-3, characterized in that, The catalyst is a cerium-praseodymium-doped magnesium aluminum oxide catalyst.

9. The method for industrial synthesis of acetophenone according to any one of claims 1-3, characterized in that, The raw materials also contain water.

10. The method for industrial synthesis of acetophenone according to any one of claims 1-3, characterized in that, The acetic acid is in excess relative to benzoic acid.

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