A method for regenerating a continuous halogenated nitrobenzene hydrogenation catalyst

Abstract

The application provides a regeneration method of halogenated nitrobenzene continuous hydrogenation catalyst, and relates to the technical field of fixed bed halogenated nitrobenzene hydrogenation. The regeneration method mainly comprises the following steps: using alcohol, alkali, petroleum ether and ethyl acetate to preliminarily clean the bed layer, removing azo compounds and other pollutants on the surface of the catalyst by using the special properties of ionic liquids, and then completing the regeneration of the catalyst through the steps of pickling, precious metal solution treatment and drying. The application overcomes the defects of the prior art, has the advantages of simple operation, mild conditions and low cost, realizes the in-situ removal of surface impurities such as reaction intermediates and azo compounds on the catalyst surface without damaging the structure of the catalyst and disassembling the catalyst, further supplements the lost metal active components, and can effectively restore the catalyst activity.

Description

Technical Field

[0001] This invention relates to the field of fixed-bed halonitrobenzene hydrogenation technology, specifically to a method for regenerating a continuous halonitrobenzene hydrogenation catalyst. Background Technology

[0002] Fixed-bed catalytic hydrogenation has advantages such as mature technology, simple equipment and operation, and low investment. However, after long-term use, it is prone to local overheating and side reactions. The formation of byproducts such as azobenzene oxide, azobenzene, and hydrazine can lead to pore blockage of the catalyst, and active components often experience some loss during the reaction. These factors result in decreased catalytic activity, requiring periodic catalyst replacement, increasing production costs and generating a large amount of waste precious metal catalyst. Therefore, finding an effective method to clean and regenerate deactivated catalysts is of great significance for improving catalytic reaction efficiency.

[0003] Common methods for reactivating and regenerating deactivated catalysts generally involve high-temperature sham firing, which can effectively restore the catalyst's physicochemical properties. Solvent washing regeneration and acid treatment-high-temperature firing techniques also significantly restore deactivated catalysts, but their activity is difficult to recover to the level of fresh catalysts. In addition, traditional methods of adding metal often involve solution impregnation, but the metal distribution is uneven in different parts, resulting in poor effectiveness.

[0004] Patent 116139943A utilizes an acidic solution and a low-concentration sodium borohydride organic solution as the regeneration liquid to regenerate the deactivated catalyst under microwave conditions. The catalyst is then washed again with the organic solution and stored in a liquid seal. Ash and coke on the catalyst carrier are eluted, followed by calcination in a mixed atmosphere of oxygen and nitrogen to remove remaining coke. Finally, hydrogen reduction activates the oxidized metal components, further enhancing the catalytic activity of the regenerated catalyst. However, the acidic solution used in this method is hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid. These strong acid solutions often corrode the reaction tubes, affecting the reactor's lifespan.

[0005] Patent 115155673A uses a low-concentration sodium borohydride organic solution as the regeneration liquid to regenerate the deactivated catalyst under microwave conditions. The catalyst is then washed again with the organic solution and stored in a liquid seal. While this method is simple, efficient, and mild, it requires a regeneration vessel equipped with a microwave generator and a reflux device, making it unsuitable for in-situ catalyst regeneration in fixed beds and adding to the equipment cost.

[0006] Currently, existing solvents have some limitations in certain applications, such as insufficient dissolving capacity and slow dissolving rate, which bring certain difficulties to the actual catalyst regeneration and are not convenient for production use. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for regenerating a catalyst for the continuous hydrogenation of halonitrobenzene. This method addresses catalyst deactivation in the fixed-bed continuous catalytic hydrogenation reaction of halonitrobenzene, offering advantages such as simple operation, mild conditions, and low cost. It achieves in-situ removal of surface impurities such as reaction intermediates and azo compounds from the catalyst surface without damaging the catalyst structure or disassembling the catalyst, and further replenishes lost metal active components, effectively restoring catalyst activity.

[0008] To achieve the above objectives, the technical solution of the present invention is implemented through the following technical solution:

[0009] A method for regenerating a catalyst for the continuous hydrogenation of halonitrobenzene, the method comprising the following steps:

[0010] (1) Cleaning with mixed solvent: A mixed solvent is prepared by mixing alcohol, alkali, petroleum ether and ethyl acetate. The deactivated catalyst is initially cleaned using the mixed solvent.

[0011] (2) Ionic liquid cleaning: Ionic liquid is pumped into the fixed bed from top to bottom and washed away intermediates, azo compounds, etc. that block the pores at a certain temperature to perform secondary cleaning of the deactivated catalyst.

[0012] (3) Acid cleaning: Inject the acid cleaning solution into the fixed bed, and let the acid cleaning solution circulate in the fixed bed to eliminate the residual ionic liquid and acidify the catalyst surface;

[0013] (4) The noble metal solution is flowed through the catalyst bed to adsorb the noble metal onto the surface of the support, and then dried under a nitrogen atmosphere.

[0014] (5) Using a mixture of hydrogen / nitrogen or hydrogen / argon, the catalyst after metal addition is heated to perform in-situ reduction to obtain a regenerated catalyst.

[0015] Preferably, the ratio of each component in the mixed solvent in step (1) is alcohol (ml): alkali (g): petroleum ether (ml): ethyl acetate (ml) = X: Y: Z: W, where X, Y, Z, and W are real numbers and satisfy X+Y+Z+W=100%, and the alcohol in the mixed solvent is either methanol or ethanol, the alkali is either sodium hydroxide or potassium hydroxide, and the pH of the final mixed solvent is ≤14.

[0016] Preferably, the preliminary cleaning method in step (1) is to use a water bath of 5-15m. 3 The mixed solvent is pumped into the reaction tube at a flow rate of / h to clean the deactivated catalyst from top to bottom for 3-5 hours.

[0017] Preferably, the ionic liquid is composed of the following proportions: 1-ethyl-3-methylimidazolium acetate (ml) : 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate (ml) : 1-hexyl-3-methylimidazolium hexafluorophosphate (ml) = A : B : C, where A, B, and C are real numbers and satisfy A + B + C = 100%.

[0018] Preferably, the secondary cleaning in step (2) is specifically performed by controlling the ionic liquid flow rate to be 1–15 m / s. 3 The cleaning process continues at a rate of 30–65°C per hour, until the azo content in the cleaning solution drops below 50 ppm.

[0019] Preferably, the acidic cleaning solution in step (3) is a mixture of an acidic component and a solvent, wherein the acidic component is any one of citric acid, malic acid and ascorbic acid, the solvent is methanol or ethanol, and the concentration of the acidic component in the acidic cleaning solution is 1-20%.

[0020] Preferably, in step (3), the acidic cleaning solution is used to clean at a temperature of 25–50°C, with the flow rate of the acidic cleaning solution controlled at 2–30 m / s. 3 / h, clean for 2-5 hours.

[0021] Preferably, nitrogen purging is performed after the steps of mixed solvent cleaning, ionic liquid cleaning, and acid cleaning, with the temperature controlled at 30–80°C and the air velocity at 200–500 m / s. 3 / h, until no liquid flows out from the bottom of the catalyst bed.

[0022] Preferably, in step (4), the concentration of the precious metal component in the precious metal solution is 0.01–0.05 mg / mL, and the specific method of using the precious metal solution is to first use a liquid pump to pump the precious metal solution at a flow rate of 5–25 mL. 3 A flow rate of 0.5 m / h is pumped from the bottom of the catalyst bed until the noble metal solution flows out from the top. The pump is then shut off, and the bed is allowed to stand for 2–5 hours at a temperature of 60–85°C. After impregnation with the metal solution from bottom to top, a reverse top-to-bottom circulation is performed through the bed, during which the flow rate of the noble metal solution is 0.5–2 m / h. 3 The impregnation temperature is 60-85℃, and the impregnation time is 2-4 hours. During the entire precious metal solution impregnation process, the total amount of precious metal components is 1%-5% of the original fresh catalyst precious metal content.

[0023] Preferably, in step (5), the hydrogen volume ratio is 60-75%, and the total gas flow rate is 300-500 m / s. 3 / h, the reduction temperature is preferably 120~350℃, and the reduction time is 2~4h.

[0024] This invention provides a method for regenerating a catalyst in the continuous hydrogenation of halonitrobenzene, which has the following advantages compared with the prior art:

[0025] (1) This invention addresses the catalyst deactivation caused by azo compounds clogging catalyst channels by proposing an in-situ regeneration and activation technology. The bed is initially cleaned with alcohol, alkali, petroleum ether and ethyl acetate. Then, the special properties of ionic liquids are used to remove azo compounds and other contaminants from the catalyst surface. By adding metal active components and reducing, the activity of the catalyst is restored to a level comparable to that of a fresh catalyst. This invention uses ionic liquids as a cleaning medium, which can efficiently and environmentally clean deactivated catalysts, restore their activity, and extend their service life.

[0026] (2) In this invention, alcohol as a polar solvent can provide good dissolution performance, base as a catalyst can promote the dissolution reaction, petroleum ether as a neutral solvent can increase the dissolution rate, and ethyl acetate as a polar solvent can improve the dissolution performance and stability. By reasonably adjusting the proportion range of the above components, the best dissolution effect can be obtained.

[0027] (3) The solubility of the ionic liquid in this invention can be adjusted by regulating its composition and concentration, and appropriate cleaning conditions can be selected according to the characteristics and deactivation degree of the catalyst to improve the cleaning effect.

[0028] (4) Traditional cleaning methods often use strong acid solutions, which have high corrosiveness and environmental pollution risks. The acid cleaning solution used in this invention can not only efficiently remove ionic liquids, but is also environmentally friendly and reduces negative impacts on the environment.

[0029] (5) In this invention, the metal is uniformly distributed in the catalyst by combining top-down impregnation and reverse flow, thereby improving the activity and stability of the catalyst. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1:

[0032] This is used for in-situ activation and regeneration of catalysts after continuous hydrogenation catalysis of chloronitrobenzene; in the continuous hydrogenation catalytic reaction of chloronitrobenzene, when the conversion rate is less than 90%, it indicates that the catalyst has been deactivated, the reaction is stopped, and the catalyst is activated and regenerated.

[0033] The specific methods for catalyst regeneration are as follows:

[0034] (1) First, the deactivated catalyst was cleaned using a mixed solvent at room temperature and pressure. A mixed solution containing methanol, sodium hydroxide, petroleum ether, and ethyl acetate was prepared, with the proportions of methanol, sodium hydroxide, petroleum ether, and ethyl acetate being 49.9%, 0.1%, 15%, and 35%, respectively. At 15m 3 The mixed solution was pumped into the reaction tube at a flow rate of / h to wash the deactivated catalyst from top to bottom for 3 hours; the solution was then pumped at 200m at 60℃. 3 Nitrogen gas is introduced at a rate of / h until no liquid flows out from the bottom of the catalyst bed;

[0035] (2) Prepare ionic liquids with proportions of 10%, 30%, and 60% for 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac), 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([HOEMIM]BF4), and 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF6), respectively, using 10m 3 Ionic liquid is pumped into the reaction tube at a flow rate of / h to clean the intermediates and azo compounds on the catalyst. The cleaning temperature is 60℃, and the flow continues until the azo content in the cleaning solution is below 50ppm. The ionic liquid flow is then stopped, and the solution is pumped at 200m³ / h at 60℃. 3 Nitrogen gas is introduced at a rate of / h until no liquid flows out from the bottom of the catalyst bed;

[0036] (3) Prepare a methanol solution containing 5% citric acid, using 5m 3 The residual ionic liquid was flushed into the reaction tube at a flow rate of / h to clean it. The cleaning temperature was 30℃, and the cleaning time was 2h. Subsequently, the solution was flushed at 60℃ with a flow rate of 200m³ / h. 3 Nitrogen gas is introduced at a rate of / h until no liquid flows out from the bottom of the catalyst bed;

[0037] (4) A noble metal solution with a Pt concentration of 0.02 mg / mL was pumped into the catalyst bed from the bottom at a flow rate of 5 m / s. 3 / h, until the precious metal solution flows out from the top; then turn off the liquid pump, the immersion temperature is 85℃, and let stand for 4 hours; then perform reverse immersion, so that the precious metal flows out at 1m 3 The catalyst bed is filled with a flow rate of / h from top to bottom, the impregnation temperature is 60℃, and the impregnation time is 4h.

[0038] (5) After replenishing the precious metal active components, at 200m3 Nitrogen gas was introduced at a flow rate of / h for drying at a temperature of 60℃ for 12h. Finally, the regenerated catalyst was activated by introducing a hydrogen / nitrogen mixture with a hydrogen volume ratio of 60% and reducing it at 300℃ for 2h to obtain the regenerated and activated catalyst.

[0039] Example 2:

[0040] Taking the catalyst regeneration method in Example 1 above as an example, catalyst regeneration methods under different process conditions in experimental groups 1-8 were designed. The specific process conditions are shown in Table 1 below:

[0041] Table 1

[0042]

[0043]

[0044]

[0045] For the different catalyst regeneration process conditions mentioned above, different groups were set up using different reaction substrates, and the conversion rates of fresh catalyst, deactivated catalyst, and catalyst regenerated and activated using the above process were measured. The specific results are shown in Table 2 below:

[0046] Table 2

[0047]

[0048]

[0049] As shown in Table 2 above, the catalyst regeneration treatment in Example 1 and Experimental Groups 1-8 can effectively improve the conversion rate of the regenerated and activated catalyst.

[0050] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0051] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for regenerating a catalyst for the continuous hydrogenation of halonitrobenzene, characterized in that, The catalyst regeneration method includes the following steps: (1) Cleaning with mixed solvent: The four reagents, alcohol, alkali, petroleum ether and ethyl acetate, are mixed to obtain a mixed solvent, which is used to preliminarily clean the deactivated catalyst; (2) Ionic liquid cleaning: Ionic liquid is pumped into the fixed bed from top to bottom to perform secondary cleaning of the deactivated catalyst; (3) Acid cleaning: Inject the acid cleaning solution into the fixed bed, and let the acid cleaning solution circulate in the fixed bed to eliminate the residual ionic liquid and acidify the catalyst surface; (4) The noble metal solution is passed through the catalyst bed to adsorb the noble metal onto the surface of the support, and then dried under a nitrogen atmosphere; the concentration of the noble metal component in the noble metal solution is 0.01~0.05 mg / mL, and the specific method of using the noble metal solution is to first use a liquid pump to pump the noble metal solution at a flow rate of 5~25 m 3 A flow rate of 0.5 m / h is pumped from the bottom of the catalyst bed until the noble metal solution flows out from the top. The pump is then shut off, and the bed is allowed to stand for 2-5 hours at 60-85°C. After impregnation with the noble metal solution from bottom to top, a reverse top-to-bottom circulation is performed through the bed, during which the flow rate of the noble metal solution is 0.5-2 m / h. 3 The impregnation temperature is 60~85℃, the impregnation time is 2~4h, and the total amount of precious metal components during the entire precious metal solution impregnation process is 1%-5% of the original fresh catalyst precious metal content; the ionic liquid is composed of the following proportions: 1-ethyl-3-methylimidazolium acetate ml∶1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ml∶1-hexyl-3-methylimidazolium hexafluorophosphate ml=A∶B∶C, where A, B, and C are real numbers, and satisfy A+B+C=100%, where A, B, and C are all non-zero; (5) Using a mixture of hydrogen / nitrogen or hydrogen / argon, the catalyst after metal addition is heated to perform in-situ reduction to obtain a regenerated catalyst.

2. The method for regenerating a continuous hydrogenation catalyst for halonitrobenzene according to claim 1, characterized in that: In step (1), the ratio of each component in the mixed solvent is alcohol ml: alkali g: petroleum ether ml: ethyl acetate ml = X: Y: Z: W, where X, Y, Z, and W are real numbers and satisfy X+Y+Z+W=100%, where X, Y, Z, and W are not zero, and the alcohol in the mixed solvent is either methanol or ethanol, the alkali is either sodium hydroxide or potassium hydroxide, and the final mixed solvent pH is ≤14.

3. The method for regenerating a continuous hydrogenation catalyst for halonitrobenzene according to claim 1, characterized in that: The specific method for preliminary cleaning in step (1) is to use a 5-15m... 3 The mixed solvent is pumped into the reaction tube at a flow rate of / h to clean the deactivated catalyst from top to bottom for 3-5 hours.

4. The method for regenerating a continuous hydrogenation catalyst for halonitrobenzene according to claim 1, characterized in that: The specific method for the secondary cleaning in step (2) is to control the flow rate of the ionic liquid to 1~15m. 3 The cleaning process continues at a rate of 30~65℃ per hour, until the azo content in the cleaning solution is below 50ppm.

5. The method for regenerating a continuous hydrogenation catalyst for halonitrobenzene according to claim 1, characterized in that: The acidic cleaning solution in step (3) is a mixture of acidic components and solvents, wherein the acidic component is any one of citric acid, malic acid and ascorbic acid, the solvent is methanol or ethanol, and the concentration of the acidic component in the acidic cleaning solution is 1-20%.

6. The method for regenerating a continuous hydrogenation catalyst for halonitrobenzene according to claim 1, characterized in that: The specific method for using acidic cleaning solution in step (3) is to control the flow rate of the acidic cleaning solution to 2-30 m / s at a cleaning temperature of 25-50°C. 3 / h, clean for 2-5 hours.

7. The method for regenerating a continuous hydrogenation catalyst for halonitrobenzene according to claim 1, characterized in that: After the steps of mixed solvent cleaning, ionic liquid cleaning, and acid cleaning, nitrogen purging was performed, with the temperature controlled at 30~80℃ and the air velocity at 200~500m. 3 / h, until no liquid flows out from the bottom of the catalyst bed.

8. The method for regenerating a continuous hydrogenation catalyst for halonitrobenzene according to claim 1, characterized in that: In step (5), the hydrogen volume ratio is 60-75%, and the total gas flow rate is 300-500 m / s. 3 / h, reduction temperature is 120~350℃, reduction time is 2~4h.

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