Catalyst and process for its preparation, purification of aniline

Abstract

The present application relates to a kind of catalyst and its preparation method, the refining method of aniline, wherein the catalyst includes core and shell, the core includes acidic microporous-mesoporous composite molecular sieve and metal oxide loaded on the molecular sieve, the shell includes hydrophobic porous carrier layer and metal element loaded on the porous carrier layer.The catalyst of the present application can promote the conversion of cyclohexylamine and phenol in aniline into macromolecule, high-boiling substance, which can be quickly removed by simple rectification subsequently, finally realizing the synchronous efficient removal of phenol and cyclohexylamine, significantly improving the quality of aniline, while reducing the energy consumption of refining system and aniline loss, and no new impurities are introduced throughout.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to catalysts and their preparation methods, as well as methods for refining aniline. Background Technology

[0002] Aniline, as an important organic chemical raw material, is a key intermediate in the polyurethane, synthetic rubber additives, fine chemicals, and pesticide industries. Currently, its industrial production mainly relies on nitrobenzene liquid-phase hydrogenation technology. Although this technology can achieve high yields of aniline, the reaction process generates byproducts such as phenol and cyclohexylamine, which seriously affect the purity of the product.

[0003] For the removal of phenol, since its boiling point (181.9℃) is very close to that of aniline (184℃), existing technologies mostly employ distillation for removal. For example, patent CN117756645A discloses a method for reducing the phenol content in the by-reaction products of liquid-phase hydrogenation of nitrobenzene (MNB), which ensures product quality by maintaining a high steam flow rate in the product refining tower for a long period. The research paper "Quality Improvement Study on the Production of MDI-grade Aniline by Liquid-Phase Hydrogenation of Nitrobenzene" proposes that phenol is mainly removed from the heavy aniline components, requiring the aniline refining tower to have sufficient theoretical plates to ensure the removal effect. This places high demands on the separation capacity of the aniline refining tower. If the refining tower cannot achieve the expected removal effect, it is necessary to increase the amount of heavy components collected from the bottom of the tower and connect an aniline recovery tower in series to recover the aniline. It is evident that the above methods all suffer from high energy consumption, cumbersome operation, and stringent requirements for distillation equipment. In addition, the method for reducing the phenol content in aniline disclosed in patent CN110627651A uses the residual heat of nitrobenzene gas-phase hydrogenation and excess hydrogen to catalytically hydrogenate phenol into more easily processed cyclohexanone in a catalytic reactor. However, this method requires an additional re-hydrogenation reaction, which has the drawback of excessive hydrogenation of aniline.

[0004] For the removal of cyclohexylamine, existing technologies mainly achieve this by removing light components through a dehydration tower. For example, the study on quality improvement of MDI-grade aniline produced by liquid-phase hydrogenation of nitrobenzene records that the cyclohexylamine content is mainly controlled by periodically removing light components through a dehydration tower. When the cyclohexylamine in the crude aniline of the system is enriched to 4000 ppm, a light component tower needs to be added to recover aniline from the bottom of the tower while ensuring the stability of the reactor. The cyclohexylamine discharged from the top of the tower is then incinerated. It can be seen that this process has the problems of cumbersome operation and high energy consumption.

[0005] Therefore, existing methods for removing cyclohexylamine and phenol from aniline generally suffer from drawbacks such as cumbersome operation, high cost, and excessive hydrogenation of aniline, and urgently need further improvement. Summary of the Invention

[0006] Therefore, it is necessary to provide a catalyst and its preparation method, as well as a method for purifying aniline, to address the above problems. The catalyst can react cyclohexylamine and phenol in aniline to generate macromolecular, high-boiling-point substances, which can then be quickly removed by simple distillation, thereby improving the quality of aniline.

[0007] A catalyst comprising a core and a shell, the core comprising an acidic microporous-mesoporous composite molecular sieve and a metal oxide supported on the molecular sieve, and the shell comprising a hydrophobic porous support layer and a metal element supported on the porous support layer.

[0008] In one embodiment, the molecule is screened from at least one of HZSM-5, HB, HY, and HMOR;

[0009] And / or, the molecular sieve is tested using an ammonia-based temperature-programmed desorption method, wherein the desorption temperature is 400℃~600℃.

[0010] And / or, the metal oxide is selected from oxides of Group VIB metals;

[0011] And / or, the metallic element is selected from Group VIII metals;

[0012] And / or, the porous support layer is selected from a silicon dioxide layer, a titanium dioxide layer, or a porous carbon layer;

[0013] And / or, the porous carrier layer has a water contact angle of 110°~130° at 25°C;

[0014] And / or, the surface of the porous carrier layer is modified with a hydrophobic compound.

[0015] In one embodiment, the metal oxide is selected from at least one of molybdenum oxide, tungsten oxide, and chromium oxide;

[0016] And / or, the metallic element is selected from at least one of palladium, platinum, nickel, and ruthenium;

[0017] And / or, the porous carrier layer is selected from a silicon dioxide layer;

[0018] And / or, the surface of the porous support layer is modified with a silane compound.

[0019] In one embodiment, the mass of the metal oxide is 1 wt% to 15 wt% of the mass of the molecular sieve;

[0020] And / or, the mass of the elemental metal is 2wt% to 35wt% of the mass of the porous carrier layer;

[0021] And / or, the mass of the metal element is 0.3wt% to 5wt% of the mass of the catalyst.

[0022] In one embodiment, the mass of the metal oxide is 3wt% to 7wt% of the mass of the molecular sieve;

[0023] And / or, the mass of the elemental metal is 3wt% to 10wt% of the mass of the porous carrier layer;

[0024] And / or, the mass of the metallic element is 0.5wt% to 1.5wt% of the mass of the catalyst.

[0025] A method for preparing the catalyst includes the following steps:

[0026] Provides acidic microporous-mesoporous composite molecular sieves;

[0027] Metal oxides are loaded onto the molecular sieve to obtain the core.

[0028] A porous carrier layer is formed by coating the surface of the core and then hydrophobically modified to obtain a hydrophobic porous carrier layer.

[0029] A catalyst is obtained by loading a metal element onto the porous support layer.

[0030] In one embodiment, the preparation method of the acidic microporous-mesoporous composite molecular sieve includes: treating the acidic molecular sieve with an alkaline solution and an acidic solution respectively, and then calcining it to obtain the acidic microporous-mesoporous composite molecular sieve;

[0031] And / or, the step of loading metal oxides onto the molecular sieve includes: impregnating the molecular sieve with an aqueous solution containing a metal precursor by an impregnation method, followed by calcination;

[0032] And / or, the porous carrier layer is selected from a silica layer, and the step of coating the core surface to form a silica layer includes: dispersing the core in a solvent and coating the core surface with a silica layer using a sol-gel method;

[0033] And / or, the hydrophobic modification step includes: after the core surface is coated to form a porous carrier layer, the gas phase hydrophobic modification is carried out using silane gas under inert gas protection;

[0034] And / or, the step of loading a metal element onto the porous support layer includes: impregnating the porous support layer with an aqueous solution containing a metal precursor using an impregnation method, and then carrying out a reduction reaction in a reducing atmosphere.

[0035] A method for refining aniline, the method comprising: passing aniline raw material into a reactor packed with the catalyst to react and obtain refined aniline.

[0036] In one embodiment, the liquid hourly space velocity (LHSV) is 0.5 h⁻¹ during the reaction step. -1 ~2.0h -1 The reaction temperature is 200℃~240℃, the pressure is 0.1MPa~2.0MPa, and the residence time is 0.5h~2h.

[0037] In one embodiment, the aniline raw material is selected from aniline prepared by liquid-phase hydrogenation of nitrobenzene.

[0038] The catalyst of this invention achieves precise spatial distribution of condensation, dehydrogenation and hydrogenation active sites through a partitioned core and shell structure design, successfully integrating the three types of reaction functions into one. The active sites work together in an orderly manner, greatly improving the overall reaction efficiency and selectivity.

[0039] When the catalyst is applied to aniline refining, the molecular sieve in the core efficiently catalyzes the condensation reaction of cyclohexylamine and aniline, while the supported metal oxide simultaneously catalyzes the dehydrogenation reaction to generate diphenylamine. The active hydrogen generated during dehydrogenation rapidly migrates to the shell through an internal hydrogen overflow network. The hydrophobic shell selectively enriches phenol, guiding its directional hydrogenation at the metal active sites within the shell to generate cyclohexanone. Simultaneously, the physical sieving and hydrophobic enrichment of the shell enables preliminary separation of cyclohexylamine / aniline from phenol, allowing different reactants to directionally contact their corresponding active sites, effectively suppressing side reactions such as phenol alkylation and reducing the formation of carbon precursors. Therefore, the catalyst of this invention can promote the conversion of cyclohexylamine and phenol in aniline into large, high-boiling-point substances, which can then be rapidly removed by simple distillation, ultimately achieving simultaneous and efficient removal of phenol and cyclohexylamine, significantly improving aniline quality, reducing energy consumption and aniline loss in the refining system, and introducing no new impurities throughout the process. Detailed Implementation

[0040] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0042] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0043] The catalyst provided by this invention comprises a core and a shell. The core comprises an acidic microporous-mesoporous composite molecular sieve and a metal oxide supported on the molecular sieve. The shell comprises a hydrophobic porous support layer and a metal element supported on the porous support layer. It is understood that the metal oxide can be supported on the outer surface and / or the inner surface of the pores of the molecular sieve, generally both the outer surface and the inner surface are supported; similarly, the metal element can also be supported on the outer surface and within the pores of the porous support layer, generally both the outer surface and the pores are supported.

[0044] The catalyst of this invention achieves precise spatial distribution of condensation, dehydrogenation and hydrogenation active sites through a partitioned core and shell structure design, successfully integrating the three types of reaction functions into one. The active sites work together in an orderly manner, greatly improving the overall reaction efficiency and selectivity.

[0045] Specifically, micropores refer to pore structures with a pore size less than 2 nm, while mesopores refer to pore structures with a pore size between 2 nm and 50 nm. Condensation reactions mainly occur on the mesoporous surface of molecular sieves. Compared to microporous molecular sieves, the mesoporous network constructed through alkali-acid treatment significantly improves the accessibility of active sites, directly shifting the reaction site from the mass-transfer-constrained micropores to the highly efficient mass-transfer mesoporous region. This structural optimization not only significantly improves the reaction rate but also allows intermediate products to rapidly diffuse away from the active sites, effectively suppressing deep side reactions caused by retention and reducing the formation of carbon precursors.

[0046] The dehydrogenation reaction mainly occurs at the active sites of the metal oxide anchored on the molecular sieve, ensuring that the intermediate products obtained from condensation can freely access the dehydrogenation active centers, eliminating the diffusion limitations imposed by the microporous structure. Simultaneously, the active hydrogen atoms generated in the dehydrogenation reaction dissociate from the active centers of the metal oxide and overflow along the mesoporous framework of the molecular sieve, rapidly reaching the porous support layer. From there, they are efficiently transported through the channels of the porous support layer to the active centers of the elemental metal, directly used in the hydrogenation reaction. Thus, the catalyst constructs a highly efficient internal hydrogen overflow circulation network, achieving in-situ recycling of hydrogen atoms.

[0047] Furthermore, since the water contact angle of the porous support layer is greater than 90° and it is hydrophobic, the target hydrogenation feedstock can be selectively enriched by utilizing polarity differences, resulting in a local high concentration within the shell pores. At the same time, it guides other reactants into the core to participate in the reaction, achieving preliminary separation of different reactants. Simultaneously, it can promote the preferential adsorption and distribution of the active metal components within the shell pores, achieving spatial isolation between hydrogenation sites and condensation / dehydrogenation sites. Combined with the hydrophobic enrichment effect, this enables highly selective and efficient hydrogenation of the target feedstock at the active metal sites, effectively suppressing the occurrence of non-target side reactions.

[0048] To further optimize the hydrophobic enrichment effect and reaction selectivity, the porous carrier layer has a water contact angle of 110°~130° at 25°C.

[0049] In this invention, the hydrophobicity of the porous support layer can be achieved by modifying the porous support layer with a hydrophobic compound. In some embodiments, the hydrophobic compound can be selected from silane compounds, such as trimethylchlorosilane.

[0050] This invention does not limit the selection of molecular sieves. When tested using the ammonia-programmed temperature desorption method, hydrogen-form molecular sieves such as HZSM-5, HB, HY, and HMOR exhibit desorption temperatures of 400℃~600℃, possessing suitable acid strength and quantity, and capable of efficiently catalyzing the condensation reactions of amino and hydroxyl compounds. Furthermore, their regular pore structure, after alkali-acid etching, can form a highly efficient mesoporous network, eliminating micropore diffusion limitations. Simultaneously, the molecular sieve exhibits excellent framework stability, forming good interfacial compatibility with the supported metal oxide and the outer porous support layer, ensuring the overall stability and lifespan of the catalyst. Therefore, in some embodiments, the molecular sieve is selected from at least one of HZSM-5, HB, HY, and HMOR, with HZSM-5 being more preferred.

[0051] Similarly, the present invention does not limit the selection of metal oxides and metals. Generally, the metal element used in the metal oxide is different from the elemental metal loaded in the shell.

[0052] Among them, Group VIB metal oxides such as molybdenum oxide, tungsten oxide, and chromium oxide possess excellent dehydrogenation active sites, enabling them to efficiently catalyze the dehydrogenation reaction of hydrogen-containing intermediates. Furthermore, their interaction with molecular sieves can further optimize the electronic structure of the active sites, enhancing the selectivity of the dehydrogenation reaction. In addition, these metal oxides can also serve as efficient mediums for the transfer of active hydrogen, facilitating the rapid overflow of active hydrogen generated during dehydrogenation along the mesoporous framework to the shell hydrogenation active sites, ensuring the overall cycle efficiency of the catalytic system.

[0053] Therefore, in order to endow the catalyst with efficient and stable dehydrogenation catalytic activity, and at the same time form functional synergy with the active metal components in the molecular sieve core and shell to construct a smooth internal hydrogen overflow circulation network, the metal oxide is preferably an oxide of a Group VIB metal, such as at least one of molybdenum oxide, tungsten oxide, and chromium oxide, and the mass of the metal oxide is preferably 1wt% to 15wt% of the mass of the molecular sieve, and more preferably 3wt% to 7wt%.

[0054] Group VIII metals possess excellent hydrogenation catalytic activity and hydrogen adsorption capacity, enabling them to rapidly capture and activate active hydrogen migrating from the core. Noble metals such as palladium and platinum also exhibit good catalytic selectivity, allowing for precise catalysis of hydrogenation reactions of target substrates while reducing the occurrence of side reactions. Metals such as nickel and ruthenium combine catalytic activity with cost advantages, meeting the needs of different application scenarios. Their synergistic effect with the core-shell structure can further enhance overall catalytic efficiency.

[0055] Therefore, in order to endow the catalyst with efficient and highly selective hydrogenation activity, while matching the dehydrogenation performance of the core metal oxide, and to construct an efficient internal hydrogen overflow circulation system, the metal element is preferably selected from Group VIII metals, and more preferably at least one of palladium, platinum, nickel, and ruthenium. The mass of the metal element is preferably 0.3wt% to 5wt% of the mass of the catalyst, and more preferably 0.5wt% to 1.5wt%.

[0056] Similarly, the present invention does not limit the selection of the porous support layer, which can be selected from a silica layer, a titanium dioxide layer, or a porous carbon layer. Among these, silica layers exhibit excellent chemical stability, maintaining structural integrity under acidic, alkaline, and high-temperature conditions, making them suitable for various reaction systems. They also possess a large specific surface area and tunable pore structure, which is beneficial for improving the dispersibility of active components and enhancing mass transfer efficiency. Furthermore, their surface is rich in silanol groups, facilitating subsequent modification with hydrophobic compounds. They also exhibit good thermal stability, adapting to high-temperature reactions and regeneration processes, and are widely available, relatively inexpensive, and have a mature preparation process. Therefore, in some embodiments, the porous support layer is preferably a silica layer. Simultaneously, the present invention does not limit the amount of the porous support layer. In some embodiments, the mass of the elemental metal is 2wt% to 35wt% of the mass of the porous support layer, more preferably 3wt% to 10wt%.

[0057] The present invention also provides a method for preparing the catalyst, comprising the following steps:

[0058] S1 provides acidic microporous-mesoporous composite molecular sieves;

[0059] S2, a metal oxide is loaded onto the molecular sieve to obtain the core;

[0060] S3, a porous carrier layer is formed by coating the surface of the core and then hydrophobically modified to obtain a hydrophobic porous carrier layer;

[0061] S4, a metal element is loaded onto the porous support layer to obtain a catalyst.

[0062] In step S1, the preparation method of the acidic microporous-mesoporous composite molecular sieve includes: treating the acidic molecular sieve with alkaline solution and acidic solution respectively, and then calcining it to obtain the acidic microporous-mesoporous composite molecular sieve.

[0063] For example, acidic molecular sieves are mixed with alkaline solutions such as NaOH and stirred at 60℃~85℃ for 15min~60min, more preferably 25min~35min. The mixture is immediately cooled, centrifuged, and washed with deionized water until neutral. The resulting solid is then mixed with acidic solutions such as HCl and treated at room temperature for 0.5h~2h, more preferably 0.8h~1.5h. After centrifugation, washing, and drying, the solid is calcined at 400℃~600℃, more preferably 500℃~580℃ for 2.5h~5.5h, more preferably 3.5h~4.5h to obtain acidic microporous-mesoporous composite molecular sieves. The preferred mass ratio of acidic molecular sieve to alkaline solution is 1:5 to 150. When NaOH solution is selected, the preferred mass fraction of NaOH is 0.5% to 5.0%, more preferably 0.8% to 3.0%. The preferred mass ratio of alkali-treated molecular sieve to acidic solution is 1:5 to 150. When HCl solution is selected, the preferred mass fraction of HCl is 0.2% to 2.0%, more preferably 0.3% to 1.0%.

[0064] In step S2, the step of loading metal oxides onto the molecular sieve includes: impregnating the molecular sieve with an aqueous solution containing a metal precursor using an impregnation method, and then calcining it.

[0065] For example, using an impregnation method, an aqueous solution containing a metal precursor is impregnated onto the molecular sieve, then aged at room temperature for 10-14 hours, more preferably 11-13 hours, then dried at 90-130°C, more preferably 100-120°C for 8-12 hours, more preferably 9-11 hours, and then calcined in air at 400-600°C, more preferably 450-550°C for 3-5 hours, more preferably 3.5-4.5 hours, to obtain the core. The metal precursor is preferably at least one of ammonium molybdate, ammonium metatungstate, or chromium hydroxide.

[0066] In step S3, when a porous carrier layer is formed by coating the surface of the core, the coating method is matched according to the material selection of the porous carrier layer. For example, when the porous carrier layer is selected from the silica layer, the step of forming a silica layer by coating the surface of the core includes: dispersing the core in a solvent and forming a silica layer by coating the surface of the core using the sol-gel method.

[0067] For example, the core is dispersed in a mixed solvent of ethanol and water, and an alkaline compound such as ammonia is added as a catalyst. A silicon source such as tetraethyl orthosilicate is slowly added dropwise under stirring. The reaction is carried out at room temperature for 16-20 hours, more preferably 17-19 hours. After the reaction, the core is centrifuged, washed, dried, and calcined at 400-600°C, more preferably 450-500°C, for 2-4 hours, more preferably 2.5-3.5 hours, thereby forming a silica layer on the surface of the core. The preferred mass ratio of ethanol to water in the mixed solvent is 3-6:1, the mass ratio of the mixed solvent to the core is 50-150:1, the amount of alkaline compound such as ammonia added is 0.5%-3% of the mass of the core, and the amount of silicon source such as tetraethyl orthosilicate added is 50%-100% of the mass of the core.

[0068] In step S3, the hydrophobic modification step includes: after the core surface is coated to form a porous carrier layer, under the protection of an inert gas, hydrophobic compound gas such as silane gas is used to perform gas-phase hydrophobic modification.

[0069] For example, under the protection of inert gases such as nitrogen and argon, at a temperature of 100℃ to 300℃, more preferably 150℃ to 250℃, the mixture is contacted with silane compound gases such as trimethylchlorosilane vapor for 1h to 3h, more preferably 1.5h to 2.5h, to perform vapor-phase hydrophobic modification. The amount of silane compound gas such as trimethylchlorosilane vapor added is 1% to 10% of the mass of the core.

[0070] In step S4, the step of loading the metal element on the porous support layer includes: using an impregnation method to impregnate the porous support layer with an aqueous solution containing the metal precursor, and then carrying out a reduction reaction in a reducing atmosphere.

[0071] For example, using an impregnation method, an aqueous solution containing a metal precursor is impregnated onto the porous support layer, then aged at room temperature for 10-14 hours, more preferably 11-13 hours, followed by drying at 90-130°C, more preferably 100-120°C for 8-12 hours, more preferably 9-11 hours, and then reduced in a reducing atmosphere for 1-3 hours, more preferably 1.5-2.5 hours. The metal precursor is selected from nitrates, chlorides, or acetates, preferably at least one of chloropalladium acid, chloroplatinic acid, nickel nitrate, or ruthenium chloride. During reduction in the reducing atmosphere, the reducing atmosphere is selected from hydrogen or a mixture of hydrogen and an inert gas, and the reduction temperature is 200-400°C, more preferably 250-350°C.

[0072] Therefore, this invention successfully anchors metal oxide particles in the core and precisely fixes elemental metal particles in a porous support layer through sequential loading and surface selective modification techniques. This effectively avoids the concentrated loading of active components on the same support, which not only plays a key role in preventing pore blockage, maintaining catalyst deactivation, and extending catalyst life, but also achieves precise spatial distribution of condensation, dehydrogenation, and hydrogenation active sites through partitioned design. This successfully integrates the three types of reaction functions into one, with each active site working synergistically and in an orderly manner, significantly improving the overall reaction efficiency and selectivity.

[0073] The catalyst of this invention can be applied to fields such as condensation, dehydrogenation and hydrogenation. For example, it can be used for the purification of aniline, and can also be used in coupled dehydrogenation and hydrogenation tandem reactions, such as the coupling of dehydrogenation reactions of alcohols or cycloalkanes with hydrogenation reactions of unsaturated compounds, or in the deep removal of oxygen- or nitrogen-containing impurities in organic liquids, such as the deep conversion and removal of organic impurities in pyridine, tetrahydrofuran or aromatics.

[0074] Specifically, the present invention also provides a method for refining aniline, the method comprising: passing aniline raw material into a reactor filled with the catalyst to react and obtain refined aniline.

[0075] The aniline raw material is selected from aniline prepared by liquid-phase hydrogenation of nitrobenzene, and the main impurities are phenol and cyclohexylamine. During the purification process, in the presence of a catalyst, cyclohexylamine and aniline first undergo a condensation reaction to generate N-cyclohexylaniline and ammonia. Then, two molecules of N-cyclohexylaniline lose four hydrogen atoms to generate two molecules of diphenylamine. Simultaneously, phenol loses four hydrogen atoms to generate cyclohexanone. The specific reaction process is as follows:

[0076]

[0077]

[0078] Specifically, the condensation reaction of cyclohexylamine and aniline mainly occurs on the mesoporous surface of the molecular sieve. At the same time, the product N-cyclohexylaniline can rapidly diffuse and detach through the mesopores. The dehydrogenation reaction of N-cyclohexylaniline mainly occurs on the active sites of the metal oxide anchored to the molecular sieve. The active hydrogen generated by the dehydrogenation reaction is efficiently transported to the active sites of the metal element through the pores of the hydrophobic porous support layer via the hydrogen overflow network. Meanwhile, the hydrophobic porous support layer has a selective enrichment effect on phenol molecules, thereby achieving highly selective and efficient hydrogenation of phenol at the metal active sites.

[0079] It is evident that the catalyst of this invention creates a dedicated reaction environment for the tandem reaction of cyclohexylamine-phenol-aniline to synthesize diphenylamine and cyclohexanone, wherein the core is responsible for condensation and dehydrogenation, and the shell is responsible for hydrogenation, thus realizing the division of labor in the reaction space.

[0080] Therefore, the purification method of this invention can simultaneously reduce the content of phenol and cyclohexylamine in crude aniline, specifically reducing both to below 10 ppm. Furthermore, the cyclohexanone and diphenylamine generated in the reaction can be rapidly removed by simple distillation, achieving simultaneous and efficient removal of phenol and cyclohexylamine. This method requires no hydrogen consumption throughout the process, fundamentally avoiding excessive hydrogenation of aniline. Moreover, the reaction raw materials and products are all pre-existing substances within the system, preventing the introduction of new impurities and effectively improving the quality of the aniline product. Simultaneously, it eliminates the need for a aniline recovery device in the light components, significantly reducing the energy consumption of the purification system, thus combining the dual advantages of process economy and high product quality.

[0081] To more thoroughly remove phenol and cyclohexylamine, the liquid hourly space velocity (LISH) is set to 0.5 h⁻¹ during the reaction step. -1 ~2.0h -1 Preferably 0.8h -1 ~1.5h -1 The reaction temperature is 200℃~240℃, preferably 210℃~230℃, the pressure is 0.1MPa~2.0MPa, preferably 0.3MPa~1.2MPa, and the residence time is 0.5h~2h, preferably 0.67h~1.25h.

[0082] The technical solution of the present invention will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0083] Example 1

[0084] 80g of HZSM-5 molecular sieve was mixed with 2.4kg of NaOH solution (mass fraction 0.8%), treated at 70℃ for 30min, cooled, centrifuged, and washed with deionized water until neutral. After washing, it was mixed with 2.4kg of HCl solution (mass fraction 0.37%) at room temperature for 1h, centrifuged, washed, dried, and calcined at 550℃ for 4h to obtain acidic microporous-mesoporous composite molecular sieve.

[0085] Take 70g of acidic microporous-mesoporous composite molecular sieve, impregnate it with 50mL of aqueous solution containing 5.15g of ammonium molybdate, age it at room temperature for 12h, dry it at 110℃ for 10h, and then calcine it in air at 500℃ for 4h to obtain the core, wherein the mass of molybdenum oxide is 5.03wt% of the mass of acidic microporous-mesoporous composite molecular sieve.

[0086] Take 60g of the core, add a mixed solvent of 4.8kg ethanol and 1.2kg water, add 4.8g of ammonia water with a mass fraction of 25%, and then slowly add 36g of tetraethyl orthosilicate. React at room temperature for 24h. After the reaction is completed, centrifuge, wash and dry the core, calcine it at 500℃ for 2h, and then treat it with 3g of trimethylchlorosilane vapor at 150℃ for 2h to coat the core with a hydrophobic silica layer.

[0087] Take 50g of the core coated with a hydrophobic silica layer, impregnate it with 40mL of chloropalladic acid aqueous solution (containing 0.61g of Pd), then age it at room temperature for 12h, then dry it at 110℃ for 10h, and then reduce it at 300℃ in a reducing atmosphere composed of H2 / N2 for 2h to obtain the catalyst, wherein the mass of Pd is 1.04wt% of the mass of the catalyst, denoted as Cat-1.

[0088] Example 2

[0089] 80g of HZSM-5 molecular sieve was mixed with 2.4kg of NaOH solution (mass fraction 0.8%), treated at 70℃ for 30min, cooled, centrifuged, and washed with deionized water until neutral. After washing, it was mixed with 2.4kg of HCl solution (mass fraction 0.37%) at room temperature for 1h, centrifuged, washed, dried, and calcined at 550℃ for 4h to obtain acidic microporous-mesoporous composite molecular sieve.

[0090] Take 70g of acidic microporous-mesoporous composite molecular sieve, impregnate it with 50mL of aqueous solution containing 4.99g of ammonium metatungstate, age it at room temperature for 12h, dry it at 110℃ for 10h, and then calcine it in air at 500℃ for 4h to obtain the core, wherein the mass of tungsten oxide is 5.01wt% of the mass of acidic microporous-mesoporous composite molecular sieve.

[0091] Take 60g of the core, add a mixed solvent of 4.8kg ethanol and 1.2kg water, add 4.8g of ammonia water with a mass fraction of 25%, and then slowly add 36g of tetraethyl orthosilicate. React at room temperature for 24h. After the reaction is completed, centrifuge, wash and dry the core, calcine it at 500℃ for 2h, and then treat it with 3g of trimethylchlorosilane vapor at 150℃ for 2h to coat the core with a hydrophobic silica layer.

[0092] Take 50g of the core coated with a hydrophobic silica layer, impregnate it with 40mL of chloroplatinic acid aqueous solution (containing 0.59g of Pt), then age it at room temperature for 12h, then dry it at 110℃ for 10h, and then reduce it at 300℃ in a reducing atmosphere composed of H2 / N2 for 2h to obtain the catalyst, wherein the mass of Pt is 0.98wt% of the mass of the catalyst, and is denoted as Cat-2.

[0093] Example 3

[0094] 80g of HZSM-5 molecular sieve was mixed with 2.4kg of NaOH solution (mass fraction 0.8%), treated at 70℃ for 30min, cooled, centrifuged, and washed with deionized water until neutral. After washing, it was mixed with 2.4kg of HCl solution (mass fraction 0.37%) at room temperature for 1h, centrifuged, washed, dried, and calcined at 550℃ for 4h to obtain acidic microporous-mesoporous composite molecular sieve.

[0095] Take 70g of acidic microporous-mesoporous composite molecular sieve, impregnate it with 50mL of aqueous solution containing 5.22g of chromium hydroxide, age it at room temperature for 12h, dry it at 110℃ for 10h, and then calcine it in air at 500℃ for 4h to obtain the core, wherein the mass of chromium oxide is 5.06wt% of the mass of acidic microporous-mesoporous composite molecular sieve.

[0096] Take 60g of the core, add a mixed solvent of 4.8kg ethanol and 1.2kg water, add 4.8g of ammonia water with a mass fraction of 25%, and then slowly add 36g of tetraethyl orthosilicate. React at room temperature for 24h. After the reaction is completed, centrifuge, wash and dry the core, calcine it at 500℃ for 2h, and then treat it with 3g of trimethylchlorosilane vapor at 150℃ for 2h to coat the core with a hydrophobic silica layer.

[0097] Take 50g of the core coated with a hydrophobic silica layer, impregnate it with 40mL of chloroplatinic acid aqueous solution (containing 0.59g of Pt), then age it at room temperature for 12h, then dry it at 110℃ for 10h, and then reduce it at 300℃ in a reducing atmosphere composed of H2 / N2 for 2h to obtain the catalyst, wherein the mass of Pt is 1.05wt% of the mass of the catalyst, and is denoted as Cat-3.

[0098] Example 4

[0099] 80g of HZSM-5 molecular sieve was mixed with 2.4kg of NaOH solution (mass fraction 0.8%), treated at 70℃ for 30min, cooled, centrifuged, and washed with deionized water until neutral. After washing, it was mixed with 2.4kg of HCl solution (mass fraction 0.37%) at room temperature for 1h, centrifuged, washed, dried, and calcined at 550℃ for 4h to obtain acidic microporous-mesoporous composite molecular sieve.

[0100] Take 70g of acidic microporous-mesoporous composite molecular sieve, impregnate it with 50mL of aqueous solution containing 5.15g of ammonium molybdate, age it at room temperature for 12h, dry it at 110℃ for 10h, and then calcine it in air at 500℃ for 4h to obtain the core, wherein the mass of molybdenum oxide is 4.98wt% of the mass of acidic microporous-mesoporous composite molecular sieve.

[0101] Take 60g of the core, add a mixed solvent of 4.8kg ethanol and 1.2kg water, add 4.8g of ammonia water with a mass fraction of 25%, and then slowly add 36g of tetraethyl orthosilicate. React at room temperature for 24h. After the reaction is completed, centrifuge, wash and dry the core, calcine it at 500℃ for 2h, and then treat it with 3g of trimethylchlorosilane vapor at 150℃ for 2h to coat the core with a hydrophobic silica layer.

[0102] Take 50g of the core coated with a hydrophobic silica layer, impregnate it with 40mL of nickel nitrate aqueous solution (containing 1.15g of Ni), then age it at room temperature for 12h, then dry it at 110℃ for 10h, and then reduce it at 300℃ in a reducing atmosphere composed of H2 / N2 for 2h to obtain the catalyst, wherein the mass of Ni is 2.04wt% of the mass of the catalyst, and is denoted as Cat-4.

[0103] Example 5

[0104] The only difference between Example 5 and Example 1 is that the molecular sieve is replaced with HY instead of HZSM-5, and the resulting catalyst is denoted as Cat-5.

[0105] Example 6

[0106] The only difference between Example 6 and Example 1 is that the molecular sieve is replaced with HB instead of HZSM-5, and the resulting catalyst is designated Cat-6.

[0107] Comparative Example 1

[0108] 80g of HZSM-5 molecular sieve was mixed with 2.4kg of NaOH solution (mass fraction 0.8%), treated at 70℃ for 30min, cooled, centrifuged, and washed with deionized water until neutral. After washing, it was mixed with 2.4kg of HCl solution (mass fraction 0.37%) at room temperature for 1h, centrifuged, washed, dried, and calcined at 550℃ for 4h to obtain acidic microporous-mesoporous composite molecular sieve.

[0109] Take 70g of acidic microporous-mesoporous composite molecular sieve, impregnate it with 50mL of aqueous solution containing 5.15g of ammonium molybdate, age it at room temperature for 12h, dry it at 110℃ for 10h, and then calcine it in air at 500℃ for 4h to obtain the core, wherein the mass of molybdenum oxide is 5.05wt% of the mass of acidic microporous-mesoporous composite molecular sieve.

[0110] Take 50g of kernels, impregnate them with 40mL of chloropalladic acid aqueous solution (containing 0.61g of Pd), then age them at room temperature for 12h, then dry them at 110℃ for 10h, and then reduce them at 300℃ in a reducing atmosphere composed of H2 / N2 for 2h to obtain the catalyst, wherein the mass of Pd is 1.03wt% of the mass of the catalyst, and is denoted as Cat-7.

[0111] Comparative Example 2

[0112] 80g of HZSM-5 molecular sieve was mixed with 2.4kg of NaOH solution (mass fraction 0.8%), treated at 70℃ for 30min, cooled, centrifuged, and washed with deionized water until neutral. After washing, it was mixed with 2.4kg of HCl solution (mass fraction 0.37%) at room temperature for 1h, centrifuged, washed, dried, and calcined at 550℃ for 4h to obtain acidic microporous-mesoporous composite molecular sieve.

[0113] Take 70g of acidic microporous-mesoporous composite molecular sieve, impregnate it with 50mL of aqueous solution containing 5.15g of ammonium molybdate, age it at room temperature for 12h, dry it at 110℃ for 10h, and then calcine it in air at 500℃ for 4h to obtain a catalyst. The catalyst includes the acidic microporous-mesoporous composite molecular sieve and molybdenum oxide supported on the acidic microporous-mesoporous composite molecular sieve, wherein the mass of molybdenum oxide is 5.01wt% of the mass of the acidic microporous-mesoporous composite molecular sieve, and is denoted as Cat-8.

[0114] Take 60g of silica powder, add a mixed solvent of 4.8kg ethanol and 1.2kg water, add 4.8g of ammonia water with a mass fraction of 25%, and then slowly add 36g of tetraethyl orthosilicate. React at room temperature for 24h. After the reaction is completed, centrifuge, wash and dry the sample, calcine at 500℃ for 2h, and then treat with 3g of trimethylchlorosilane vapor at 150℃ for 2h to obtain a hydrophobic silica support.

[0115] Take 50g of hydrophobic silica support, impregnate it with 40mL of chloropalladic acid aqueous solution (containing 0.61g of Pd), then age it at room temperature for 12h, then dry it at 110℃ for 10h, and then reduce it at 350℃ in a reducing atmosphere composed of H2 / N2 for 3h to obtain a catalyst. The catalyst includes a silica support and Pd supported on the silica support, wherein the mass of Pd is 1.02wt% of the mass of the catalyst, and is denoted as Cat-9.

[0116] Performance evaluation:

[0117] Application Example 1

[0118] 50 mL of catalyst Cat-1 was loaded into a fixed-bed reactor. After purging with nitrogen five times, the pressure was increased to 0.5 MPa and maintained for 30 min. The airtightness of the apparatus was checked. Then, under a nitrogen atmosphere, the reactor was heated to 300 °C at a rate of 5 °C / min and activated at this temperature for 2 h to remove impurities physically adsorbed on the catalyst surface. After activation, the reactor temperature was adjusted to 220 °C, and nitrogen pressure was maintained at 0.6 MPa through a back pressure valve. The feed rate of the reaction solution (containing 93.09 wt% aniline, 6.43 wt% water, 385 ppm cyclohexylamine, 235 ppm phenol, and some high-boiling-point substances) was 1 mL / min (i.e., liquid hourly space velocity of 1.2 h⁻¹). -1 The residence time was 0.83 h, and the nitrogen to reaction liquid volume ratio was 100:1. After the reaction stabilized, gas-phase external standard method was used to sample and analyze the product at the outlet of the fixed-bed reactor. The results showed that the cyclohexylamine at the outlet was 5 ppm and phenol was 2 ppm.

[0119] Application Example 2

[0120] The only difference between Application Example 2 and Application Example 1 is that the catalyst is replaced with Cat-2, the outlet cyclohexylamine is 5 ppm, and the phenol is 3 ppm.

[0121] Application Example 3

[0122] The only difference between Application Example 3 and Application Example 1 is that the catalyst is replaced with Cat-3, and the outlet cyclohexylamine is 6 ppm and phenol is 4 ppm.

[0123] Application Example 4

[0124] The only difference between Application Example 4 and Application Example 1 is that the catalyst is replaced with Cat-4, and the outlet cyclohexylamine is 8 ppm and phenol is 6 ppm.

[0125] Application Example 5

[0126] The only difference between Application Example 5 and Application Example 1 is that the catalyst is replaced with Cat-5, and the outlet cyclohexylamine is 7 ppm and phenol is 5 ppm.

[0127] Application Example 6

[0128] The only difference between Application Example 6 and Application Example 1 is that the catalyst is replaced with Cat-6, and the outlet cyclohexylamine is 9 ppm and phenol is 7 ppm.

[0129] Application Comparative Example 1

[0130] The only difference between Comparative Example 1 and Application Example 1 is that the catalyst was replaced with Cat-7, and the outlet cyclohexylamine was 85 ppm and phenol was 28 ppm.

[0131] As can be seen from Comparative Example 1, if the hydrophobic silica layer is missing, not only will the physical sieving and hydrophobic enrichment functions be lost, causing various reactants to compete disorderly for nucleic acid sites, triggering side reactions such as deep conversion of raw materials and generating carbon precursors, but also the random distribution of metal active components will lead to direct contact with non-target reactants, resulting in the aggravation of side reactions.

[0132] Application Comparative Example 2

[0133] The only difference between Comparative Example 2 and Example 1 is that the catalyst was replaced with 20 mL of Cat-8 and 20 mL of Cat-9, with an outlet concentration of 138 ppm cyclohexylamine and 41 ppm phenol.

[0134] As can be seen from Comparative Example 2, if the core and shell are mixed and filled together, it will cause the hydrogen cycle system to be damaged. It will take a long time for hydrogen to overflow from the Cat-8 catalyst to the Cat-9 catalyst, which cannot guarantee the progress of the phenol hydrogenation reaction.

[0135] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0136] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A catalyst, characterized in that, The catalyst comprises a core and a shell. The core comprises an acidic microporous-mesoporous composite molecular sieve and a metal oxide supported on the molecular sieve. The shell comprises a hydrophobic porous support layer and a metal element supported on the porous support layer.

2. The catalyst according to claim 1, characterized in that, The molecules are screened from at least one of HZSM-5, HB, HY, and HMOR; And / or, the molecular sieve is tested using an ammonia-based temperature-programmed desorption method, wherein the desorption temperature is 400℃~600℃. And / or, the metal oxide is selected from oxides of Group VIB metals; And / or, the metallic element is selected from Group VIII metals; And / or, the porous support layer is selected from a silicon dioxide layer, a titanium dioxide layer, or a porous carbon layer; And / or, the porous carrier layer has a water contact angle of 110°~130° at 25°C; And / or, the surface of the porous carrier layer is modified with a hydrophobic compound.

3. The catalyst according to claim 2, characterized in that, The metal oxide is selected from at least one of molybdenum oxide, tungsten oxide, and chromium oxide; And / or, the metallic element is selected from at least one of palladium, platinum, nickel, and ruthenium; And / or, the porous carrier layer is selected from a silicon dioxide layer; And / or, the surface of the porous support layer is modified with a silane compound.

4. The catalyst according to claim 1, characterized in that, The mass of the metal oxide is 1 wt% to 15 wt% of the mass of the molecular sieve; And / or, the mass of the elemental metal is 2wt% to 35wt% of the mass of the porous carrier layer; And / or, the mass of the metal element is 0.3wt% to 5wt% of the mass of the catalyst.

5. The catalyst according to claim 4, characterized in that, The mass of the metal oxide is 3wt% to 7wt% of the mass of the molecular sieve. And / or, the mass of the elemental metal is 3wt% to 10wt% of the mass of the porous carrier layer; And / or, the mass of the metallic element is 0.5wt% to 1.5wt% of the mass of the catalyst.

6. A method for preparing a catalyst according to any one of claims 1 to 5, characterized in that, Includes the following steps: Provides acidic microporous-mesoporous composite molecular sieves; Metal oxides are loaded onto the molecular sieve to obtain the core. A porous carrier layer is formed by coating the surface of the core and then hydrophobically modified to obtain a hydrophobic porous carrier layer. A catalyst is obtained by loading a metal element onto the porous support layer.

7. The method for preparing the catalyst according to claim 6, characterized in that, The preparation method of the acidic microporous-mesoporous composite molecular sieve includes: treating the acidic molecular sieve with alkaline solution and acidic solution respectively, and then calcining it to obtain the acidic microporous-mesoporous composite molecular sieve; And / or, the step of loading metal oxides onto the molecular sieve includes: impregnating the molecular sieve with an aqueous solution containing a metal precursor by an impregnation method, followed by calcination; And / or, the porous carrier layer is selected from a silica layer, and the step of coating the core surface to form a silica layer includes: dispersing the core in a solvent and coating the core surface with a silica layer using a sol-gel method; And / or, the hydrophobic modification step includes: after the core surface is coated to form a porous carrier layer, the gas phase hydrophobic modification is carried out using silane gas under inert gas protection; And / or, the step of loading a metal element onto the porous support layer includes: impregnating the porous support layer with an aqueous solution containing a metal precursor using an impregnation method, and then carrying out a reduction reaction in a reducing atmosphere.

8. A method for purifying aniline, characterized in that, The refining method includes: passing aniline raw material into a reactor packed with a catalyst as described in any one of claims 1 to 7 to carry out a reaction, thereby obtaining refined aniline.

9. The method for purifying aniline according to claim 8, characterized in that, In the reaction step, the liquid hourly space velocity was 0.5 h⁻¹. -1 ~2.0h -1 The reaction temperature is 200℃~240℃, the pressure is 0.1MPa~2.0MPa, and the residence time is 0.5h~2h.

10. The method for purifying aniline according to claim 8, characterized in that, The aniline raw material is selected from aniline prepared by liquid-phase hydrogenation of nitrobenzene.

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