Core-shell type catalyst for synthesizing m-xylylenediamine as well as preparation method and application of core-shell type catalyst

Abstract

The invention discloses a core-shell catalyst for m-xylylenediamine synthesis and a preparation method and application thereof, and belongs to the technical field of catalysts. The catalyst is composed of a nanocrystal nucleus formed by silicon-aluminum oxide, an active component wrapping the surface of the nanocrystal nucleus, and an auxiliary shell layer. The active component is Ni, and the content of the active component is 5-30 wt%; the auxiliary agent is any one of Co, Mn and Mo, the content of the auxiliary agent is 0.1-5 wt%, the silicon-aluminum oxide crystal nucleus is synthesized by adopting a parallel flow coprecipitation method, and the silicon-aluminum ratio is 5-10; the salt of Ni and the auxiliary agent firstly generates a composite oxide on the surface of the crystal nucleus, and a shell layer containing the active component and the auxiliary agent is formed after reduction. The catalyst has high isophthalonitrile hydrogenation catalysis activity and good selectivity, the isophthalonitrile conversion rate reaches 99.9%, the m-xylylenediamine selectivity is 98% or above, and the catalyst is suitable for industrial production of m-xylylenediamine synthesized through isophthalonitrile fixed bed continuous catalytic hydrogenation.

Description

Technical Field

[0001] This application relates to a core-shell catalyst for the synthesis of m-phenylenediamine, its preparation method, and its application, belonging to the field of catalyst technology. Background Technology

[0002] m-Phenylenediamine (MXDA) is mainly used to manufacture high-performance epoxy resin curing agents that are heat-resistant, non-toxic, suitable for underwater construction, and rapidly cured by heating. It is a raw material for polyurethane resins and synthetic functional epoxy resins, and is also used in rubber additives, photosensitive plastics, pesticides, coatings, nylon products, fiber finishing agents, rust inhibitors, chelating agents, lubricants, paper processing, and other fields.

[0003] MXDA and its cyclic hydrides can be used as epoxy resin curing agents, exhibiting excellent room-temperature curing performance, good heat resistance, water resistance, and chemical corrosion resistance. They also produce well-cured resins with a transparent and extremely fine surface, low viscosity, and good handling properties. Simultaneously, MXDA is an important fine chemical intermediate, capable of synthesizing polyamides with diacids and the polyurethane monomer m-xylene diisocyanate. Its benzene ring hydrides can also be used to synthesize diisocyanates. Currently, it is used in the synthesis of rubber crosslinking agents, pesticides, fiber stabilizers, and surfactants, possessing significant industrial and commercial value.

[0004] Currently, MXDA is mostly produced using isophthalonitrile (IPN) catalytic hydrogenation. Common catalysts used include Raney nickel, modified Raney nickel, or amorphous nickel. In China, batch hydrogenation processes are predominantly employed. For example, patent 201010150757.0 discloses a method for preparing MXDA in a high-pressure reactor using Raney nickel as a catalyst and a mixture of aromatics and alcohols as a solvent via IPN hydrogenation. This method utilizes a hydrogen distributor to enhance gas-liquid mass transfer, achieving an MXDA yield exceeding 98%. However, due to the high production cost, poor safety, and unstable reaction associated with batch hydrogenation processes, China is focusing on developing fixed-bed continuous hydrogenation processes centered on heterogeneous catalysts. Patent 201910439999.2 discloses a hydrogenation catalyst for preparing MXDA and its application. The catalyst support is alumina or a magnesium-aluminum mixture, the active element is Ni, and it is activated after impregnation with an additive. Hydrogenation is performed in solvents such as N,N-dimethylcyclohexylamine (DMCHA), N,N-dimethylethanolamine (DMEA), and methylethanolamine (MMEA) to obtain m-phenylenediamine, achieving an IPN conversion rate of over 99.9% and an MXDA selectivity of over 98%. Patent 202311532329.8 provides an amination hydrogenation catalyst, its preparation method, and its application in the preparation process of m-phenylenediamine. By adding a desorption aid, coking and deactivation of the catalyst are avoided, wear resistance is improved, and an IPN conversion rate of over 99.2% and an MXDA yield of over 92.1% are obtained.

[0005] Improving IPN conversion and MXDA yield, as well as enhancing catalyst stability for continuous fixed-bed production, has long been a key focus in the industry. Internationally, BASF and Mitsubishi Gas have pioneered continuous MXDA production, but domestic reports are scarce. Existing results show that many homogeneous catalysts exhibit good activity and selectivity. However, because IPN initially forms an imine intermediate during hydrogenation, if it cannot be rapidly further hydrogenated to MXDA, it is prone to further cross-linking, generating large molecular compounds that coat the catalyst surface, causing a rapid decline in activity and a short catalyst lifetime. Summary of the Invention

[0006] To address the problem in existing technologies for the catalytic hydrogenation of isophthalonitrile to prepare m-phenylenediamine that the slow hydrogenation rate of the imine intermediate leads to the formation of large molecular compounds that cover the catalyst, affecting its activity and lifespan, this application provides a preparation scheme for a core-shell catalyst for the synthesis of m-phenylenediamine. The prepared catalyst has strong basicity to promote the hydrogenation and desorption of imine, while also having well-developed pores to promote the diffusion of reactants and products, thereby improving the catalyst's lifespan.

[0007] The technical solution adopted in this application is as follows:

[0008] According to one aspect of this application, a core-shell catalyst for the synthesis of m-phenylenediamine is provided, the core-shell catalyst comprising a nanocrystalline nucleus formed of silicon aluminate oxide and a shell layer encapsulating the surface of the nanocrystalline nucleus;

[0009] The weight ratio of silicon to aluminum in the nanocrystalline nucleus is 5 to 10:1.

[0010] The shell layer includes active components and additives;

[0011] The active component is Ni;

[0012] The content of the active component in the core-shell catalyst is 15-30 wt%.

[0013] The auxiliary agent is selected from at least one of Co, Mn, and Mo;

[0014] The content of the auxiliary agent in the core-shell catalyst is 0.1-5 wt%.

[0015] The shell has a porous structure, through which the core-shell catalyst exposes part of the nanocrystal nuclei.

[0016] According to two aspects of this application, a method for preparing the aforementioned core-shell catalyst for the synthesis of m-phenylenediamine is provided, comprising the following steps:

[0017] S1. An aluminum source and an alkaline solution I are added concurrently to a slurry containing water and silica sol to obtain a mixed solution I. The mixed solution I is then aged to obtain a suspension containing the nanocrystal nuclei. The weight ratio of silicon to aluminum in the mixed solution I is 5 to 10:1.

[0018] S2. Add a mixture containing a nickel source and an additive precursor, and an alkaline solution II to the suspension in step S1 in parallel flow to obtain a mixed solution II. Aging the mixed solution II, filter, wash and dry the product to obtain an intermediate product. This step ensures that Ni and the additive are fully loaded on the surface of the silicon aluminum oxide.

[0019] S3. The intermediate product from step S2 is calcined in an oxidizing atmosphere to obtain a catalyst precursor.

[0020] S4. The catalyst precursor described in step S3 is reduced in a reducing atmosphere to obtain the core-shell catalyst for the synthesis of m-phenylenediamine.

[0021] Optionally, the oxidizing atmosphere is preferably air.

[0022] Optionally, the reducing atmosphere is preferably hydrogen or a mixture of hydrogen and nitrogen.

[0023] Optionally, in the mixture of hydrogen and nitrogen, the volume content of hydrogen is not less than 50%.

[0024] Optionally, the conditions for aging I and aging II independently include: a temperature of 80–95°C and a reaction time of 4–12 h under stirring.

[0025] Optionally, the pH values ​​of mixed solution I and mixed solution II are independently 7 to 9. The pH is adjusted during the preparation step by adding the raw materials along with a concurrent flow of alkaline solution.

[0026] Optionally, the calcination and reduction conditions independently include: a temperature of 300–600°C and a time of 4–6 hours.

[0027] Optionally, the roasting temperature is preferably 400–550°C.

[0028] Optionally, the aluminum source is aluminum nitrate.

[0029] Optionally, the alkaline solution I and alkaline solution II are independently selected from aqueous solutions of at least one of sodium hydroxide, sodium carbonate, and sodium bicarbonate.

[0030] Optionally, the nickel source is selected from at least one of nickel nitrate, nickel oxalate, nickel chloride, and nickel acetate.

[0031] Optionally, the auxiliary precursor is selected from at least one of Co precursor, Mn precursor, and Mo precursor;

[0032] The Co precursor is selected from at least one of the following: Co nitrate, chloride, oxalate, and acetate.

[0033] The Mn precursor is selected from at least one of the following: nitrate, chloride, oxalate, and acetate of Mn;

[0034] The Mo precursor is selected from ammonium molybdate and / or sodium molybdate.

[0035] In the core-shell catalyst preparation method described in this application, the silicon-aluminum oxide crystal nuclei are synthesized using a co-current co-precipitation method, with a silicon-to-aluminum ratio between 5 and 10. A salt of Ni and the promoter first forms a composite oxide on the surface of the crystal nuclei, which, after reduction, forms a shell layer containing the active component and the promoter, covering the surface of the silicon-aluminum oxide crystal nuclei. The catalyst exhibits high catalytic activity and excellent selectivity for the hydrogenation of isophthalonitrile, achieving a conversion rate of 99.9% for isophthalonitrile and a selectivity for isophthalic dimethylamine exceeding 98%. It is suitable for the industrial production of isophthalonitrile through continuous fixed-bed catalytic hydrogenation to synthesize isophthalic dimethylamine.

[0036] According to three aspects of this application, the application of the aforementioned core-shell catalyst for the synthesis of m-phenylenediamine or the core-shell catalyst for the synthesis of m-phenylenediamine obtained according to any of the foregoing preparation methods is provided in the catalytic hydrogenation of isophthalonitrile to prepare m-phenylenediamine.

[0037] Optionally, the catalytic hydrogenation of isophthalonitrile to prepare isophthalic acid is carried out in a fixed-bed reactor.

[0038] Optionally, the fixed-bed reactor is loaded with a catalyst of the target shape obtained by pressing a mixture containing the core-shell catalyst for the synthesis of m-phenylenediamine, cellulose, and graphite into tablets.

[0039] Optionally, the conditions for the catalytic hydrogenation of isophthalonitrile to prepare isophthalic dimethylamine include: a temperature of 40–130°C, a pressure of 1–8 MPa, and an isophthalonitrile space velocity of 0.1–1 h⁻¹. -1 .

[0040] Optionally, the catalyst with the target shape is preferably a cylindrical catalyst with a diameter of 3 mm to 6 mm and a length of 3 mm to 6 mm.

[0041] Optionally, in a fixed-bed reactor, liquid ammonia is added as an alkaline auxiliary agent to catalytically hydrogenate isophthalonitrile to m-phenylenediamine.

[0042] The beneficial effects of this application include:

[0043] The core-shell catalyst for the synthesis of m-phenylenediamine provided in this application involves forming a loosely structured shell containing active components and promoters on the surface of aluminosilicate crystal nuclei. The porous structure of the shell exposes part of the aluminosilicate crystal nuclei. The prepared core-shell catalyst exhibits strong basicity to promote the hydrogenation and desorption of imines, solving the problem of slow hydrogenation rates of imine intermediates leading to the formation of large molecular compounds that cover the catalyst, affecting its activity and lifetime. Simultaneously, it possesses well-developed pores to promote the diffusion of reactants and products, thereby improving catalyst lifetime. The core-shell catalyst of this application exhibits high catalytic activity and excellent selectivity for the hydrogenation of isophthalonitrile, achieving a conversion rate of 99.9% for isophthalonitrile and a selectivity for m-phenylenediamine exceeding 98%. It is suitable for the industrial production of m-phenylenediamine via continuous fixed-bed catalytic hydrogenation of isophthalonitrile. Attached Figure Description

[0044] Figure 1 It is nano-silicon aluminum oxide and catalyst Ni 30 SEM images of -Co5 / Si5AlO-4, where (a) and (b) are SEM images of the synthesized nano-silicon aluminum oxide at scales of 100 nm and 10 nm, respectively, and (c) and (d) are SEM images of Ni. 30 SEM images of Co5 / Si5AlO-4, all at a scale of 100 nm;

[0045] Figure 2 It is a catalyst Ni 30 SEM-EDS mapping image of -Co5 / Si5AlO-4. Detailed Implementation

[0046] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0047] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased commercially. Unless otherwise specified, all testing methods were conventional methods, and all instrument settings were as recommended by the manufacturer.

[0048] In the embodiments and comparative examples of this application, the cylindrical catalyst was prepared by mixing 96 wt% of the catalyst with 3 wt% of cellulose and 1 wt% of graphite and pressing it into a cylindrical sheet with a diameter of 3 mm and a length of 3 mm.

[0049] Example 1

[0050] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 110.7g of aluminum nitrate solution with a concentration of 30wt% and 62.3g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 85℃ and the mixture was stirred and aged for 8 hours to obtain a suspension of nano-silica alumina oxide. 244.3g of nickel nitrate solution with a Ni content of 10wt% and 40.7g of cobalt nitrate solution with a Co content of 10wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 138.6g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 8 hours to allow Ni and Co to be loaded onto the surface of the silica alumina oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm. The catalyst was designated as Ni. 30 -Co5 / Si5AlO.

[0051] Example 2

[0052] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 110.7g of aluminum nitrate solution with a concentration of 30wt% and 62.3g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 85℃ and the mixture was stirred and aged for 4 hours to obtain a suspension of nano-silica alumina oxide. 244.3g of nickel nitrate solution with a Ni content of 10wt% and 40.7g of cobalt nitrate solution with a Co content of 10wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 138.6g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 4 hours to allow Ni and Co to be loaded onto the surface of the silica alumina oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm. The catalyst was designated as Ni. 30 -Co5 / Si5AlO-2.

[0053] Example 3

[0054] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 110.7g of aluminum nitrate solution with a concentration of 30wt% and 62.3g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 85℃ and the mixture was stirred and aged for 12 hours to obtain a suspension of nano-silica aluminate oxide. 244.3g of nickel nitrate solution with a Ni content of 10wt% and 40.7g of cobalt nitrate solution with a Co content of 10wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 138.6g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 12 hours to allow Ni and Co to be loaded onto the surface of the silica aluminate oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm. The catalyst was designated as Ni. 30 -Co5 / Si5AlO-3.

[0055] Example 4

[0056] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 110.7g of aluminum nitrate solution with a concentration of 30wt% and 62.3g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 95℃ and the mixture was stirred and aged for 12 hours to obtain a suspension of nano-silica aluminate oxide. 244.3g of nickel nitrate solution with a Ni content of 10wt% and 40.7g of cobalt nitrate solution with a Co content of 10wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 138.6g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 12 hours to allow Ni and Co to be loaded onto the surface of the silica aluminate oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm. The catalyst was designated as Ni. 30 -Co5 / Si5AlO-4.

[0057] Example 5

[0058] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 110.7g of aluminum nitrate solution with a concentration of 30wt% and 62.3g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 85℃ and the mixture was stirred and aged for 8 hours to obtain a suspension of nano-silica alumina oxide. 244.3g of nickel nitrate solution with a Ni content of 10wt% and 7.67g of cobalt nitrate solution with a Co content of 10wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 109.7g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 8 hours to allow Ni and Co to be loaded onto the surface of the silica alumina oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm. The catalyst was designated as Ni. 30 -Co1 / Si5AlO.

[0059] Example 6

[0060] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 110.7g of aluminum nitrate solution with a concentration of 30wt% and 62.3g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 85℃ and the mixture was stirred and aged for 8 hours to obtain a suspension of nano-silica alumina oxide. 237.1g of nickel nitrate solution with a Ni content of 10wt% and 7.67g of manganese acetate solution with a Mn content of 10wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 108.3g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 8 hours to allow Ni and Mn to be loaded onto the surface of the silica alumina oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm, denoted as Ni. 30 -Mn1 / Si5AlO.

[0061] Example 7

[0062] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 110.7g of aluminum nitrate solution with a concentration of 30wt% and 62.3g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 85℃ and the mixture was stirred and aged for 8 hours to obtain a suspension of nano-silica alumina oxide. 228.6g of nickel nitrate solution with a Ni content of 10wt% and 3.81g of manganese acetate solution with a Mn content of 10wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 105.7g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 8 hours to allow Ni and Mn to be loaded onto the surface of the silica alumina oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm, denoted as Ni. 30 -Mn 0.5 / Si5AlO.

[0063] Example 8

[0064] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 110.7g of aluminum nitrate solution with a concentration of 30wt% and 62.3g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 85℃ and the mixture was stirred and aged for 8 hours to obtain a suspension of nano-silica aluminate oxide. 237.1g of nickel nitrate solution with a Ni content of 10wt% and 7.62g of ammonium molybdate solution with a Mo content of 5wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 103.8g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 8 hours to allow Ni and Mo to be loaded onto the surface of the silica aluminate oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm, denoted as Ni. 30 -Mo 0.5 / Si5AlO.

[0065] Example 9

[0066] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 110.7g of aluminum nitrate solution with a concentration of 30wt% and 62.3g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 85℃ and the mixture was stirred and aged for 8 hours to obtain a suspension of nano-silica aluminate oxide. 227.2g of nickel nitrate solution with a Ni content of 10wt% and 1.51g of ammonium molybdate solution with a Mo content of 5wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 103.2g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 8 hours to allow Ni and Mo to be loaded onto the surface of the silica aluminate oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm, denoted as Ni. 30 -Mo 0.1 / Si5AlO.

[0067] Example 10

[0068] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 55.3g of aluminum nitrate solution with a concentration of 30wt% and 31.2g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 85℃ and the mixture was stirred and aged for 8 hours to obtain a suspension of nano-silica alumina oxide. 91.8g of nickel nitrate solution with a Ni content of 10wt% and 30.6g of cobalt nitrate solution with a Co content of 10wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 62.5g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 8 hours to load Ni and Co onto the surface of the silica alumina oxide. The mixture was cooled, filtered, and the filter cake was washed. After drying at 120℃, the cake was calcined in a muffle furnace at 500℃ for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550℃ for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was then mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm. The catalyst is denoted as Ni. 15 -Co5 / Si 10 AlO.

[0069] Comparative Example 1

[0070] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 110.7g of aluminum nitrate solution with a concentration of 30wt% and 62.3g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 95℃ and the mixture was stirred and aged for 12 hours to obtain a suspension of nano-silica alumina oxide. 252.1g of nickel nitrate solution with a Ni content of 10wt% and 154.4g of sodium hydroxide solution with a concentration of 30wt% were prepared and added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 12 hours to allow Ni to be loaded onto the surface of the silica alumina oxide. The mixture was cooled, filtered, and the filter cake was washed. After drying at 120℃, the cake was calcined in a muffle furnace at 500℃ for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550℃ for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was then mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm. The catalyst is denoted as Ni. 30 / Si5AlO.

[0071] Comparative Example 2

[0072] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 110.7g of aluminum nitrate solution with a concentration of 30wt% and 62.3g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 95℃ and the mixture was stirred and aged for 12 hours to obtain a suspension of nano-silica alumina oxide. 252.1g of nickel nitrate solution with a Ni content of 10wt% and 58.8g of cobalt nitrate solution with a Co content of 10wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 154.4g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 12 hours to allow Ni and Co to be loaded onto the surface of the silica alumina oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm. The catalyst was designated as Ni. 30 -Co7 / Si5AlO.

[0073] Comparative Example 3

[0074] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 138.3g of aluminum nitrate solution with a concentration of 30wt% and 77.9g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 95℃ and the mixture was stirred and aged for 12 hours to obtain a suspension of nano-silica aluminate oxide. 253.6g of nickel nitrate solution with a Ni content of 10wt% and 42.3g of cobalt nitrate solution with a Co content of 10wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 143.8g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 12 hours to allow Ni and Co to be loaded onto the surface of the silica aluminate oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm. The catalyst was designated as Ni. 30 -Co5 / Si4AlO.

[0075] Comparative Example 4

[0076] 100g of deionized water and 150g of silica sol with a SiO2 content of 30wt% were added to a 1L reactor and stirred until homogeneous. 55.3g of aluminum nitrate solution with a concentration of 30wt% and 31.2g of sodium hydroxide solution with a concentration of 30wt% were added dropwise to the reactor, maintaining the pH at 7–9. After the addition was complete, the temperature was raised to 95℃ and the mixture was stirred and aged for 12 hours to obtain a suspension of nano-silica aluminate oxide. 57.6g of nickel nitrate solution with a Ni content of 10wt% and 28.8g of cobalt nitrate solution with a Co content of 10wt% were prepared and mixed. This mixture was then added dropwise to the reactor along with 45.7g of sodium hydroxide solution with a concentration of 30wt%, maintaining the pH at 7–9. After the addition was complete, the mixture was stirred and aged for 12 hours to allow Ni and Co to be loaded onto the surface of the silica aluminate oxide. The mixture was cooled, filtered, and washed. After drying at 120°C, it was calcined in a muffle furnace at 500°C for 6 hours to obtain the catalyst precursor. The precursor was reduced at 550°C for 4 hours under pure hydrogen conditions to obtain a core-shell catalyst. The catalyst was mixed with cellulose and graphite and pressed into cylindrical sheets with a diameter of 3 mm and a length of 3 mm. The catalyst was designated as Ni. 10 -Co5 / Si 10 AlO.

[0077] SEM images of typical catalysts are as follows: Figure 1 As shown. Figure 1 (a) and (b) are SEM images of the nano-silicon aluminum oxide synthesized in Example 4, and (c) and (d) are Ni 30The SEM image of Co5 / Si5AlO-4 shows that Ni and Co cover the surface of the nano-silicon aluminum oxide particles, forming a relatively loose shell.

[0078] like Figure 2 Ni 30 The SEM-EDS mapping image of Co5 / Si5AlO-4 shows that the catalyst surface has a high content of Co and Ni, indicating that Co and Ni tend to be distributed on the surface of the catalyst particles, forming a shell. The low Si content indicates that Si and Al are encapsulated inside the catalyst, forming crystal nuclei.

[0079] Catalytic performance testing: The catalysts of the examples and comparative examples were tested separately in a fixed-bed reactor under the condition of IPN space velocity of 0.5 h⁻¹. -1 The conversion and selectivity of four Ni alloys with the same composition were evaluated under the conditions of 4 MPa pressure, 110 °C temperature, and an ammonia-to-nitrile ratio of 20. Samples were taken at 500 h and 1000 h for chromatographic analysis. The results are listed in Table 1. 30 -Co5 / Si5AlO catalysts showed overall conversion rates exceeding 99.7%, with conversion rates still above 98.0% after 1000 hours of operation, and selectivity generally exceeding 98%. However, Ni catalysts with longer aging times... 30 -Co5 / Si5AlO-3 and Ni 30 The Co5 / Si5AlO-4 catalysts exhibited the best performance, indicating that extending the aging time helps improve the catalyst's activity, selectivity, and stability. Reducing the Co content to 1% resulted in a slight decrease in catalyst activity. Compared to catalysts with only Ni as the active component, the addition of Co, Mn, and Mo promoters all demonstrated a better ability to enhance catalytic activity. Further increasing the Co loading to 7% did not result in a particularly significant performance improvement, while reducing the Ni loading decreased the catalyst activity.

[0080] Table 1. Conversion and selectivity of catalysts

[0081]

[0082]

Claims

1. A core-shell catalyst for the synthesis of m-phenylenediamine, characterized in that, The core-shell catalyst comprises a nanocrystalline nucleus formed of silicon aluminate oxide and a shell layer encapsulating the surface of the nanocrystalline nucleus; The weight ratio of silicon to aluminum in the nanocrystalline nucleus is 5 to 10:

1. The shell layer includes active components and additives; The active component is Ni; The content of the active component in the core-shell catalyst is 15-30 wt%. The auxiliary agent is selected from at least one of Co, Mn, and Mo; The content of the auxiliary agent in the core-shell catalyst is 0.1-5 wt%. The shell has a porous structure, through which the core-shell catalyst exposes part of the nanocrystal nuclei.

2. The method for preparing the core-shell catalyst for the synthesis of m-phenylenediamine according to claim 1, characterized in that, Includes the following steps: S1. Add aluminum source and alkaline solution I in parallel to a slurry containing water and silica sol to obtain mixed solution I. Aging solution I is then performed to obtain a suspension containing the nanocrystal nuclei. S2. Add a mixture containing a nickel source and an auxiliary precursor and an alkaline solution II to the suspension in step S1 in parallel to obtain a mixed solution II. Aging the mixed solution II, filter, wash and dry the product to obtain an intermediate product. S3. The intermediate product from step S2 is calcined in an oxidizing atmosphere to obtain a catalyst precursor. S4. The catalyst precursor described in step S3 is reduced in a reducing atmosphere to obtain the core-shell catalyst for the synthesis of m-phenylenediamine.

3. The preparation method according to claim 2, characterized in that, The conditions for aging I and aging II independently include: a temperature of 80–95°C and a reaction time of 4–12 h under stirring.

4. The preparation method according to claim 2, characterized in that, The pH values ​​of the mixed solution I and mixed solution II are independently 7 to 9.

5. The preparation method according to claim 2, characterized in that, The calcination and reduction conditions independently include a temperature of 300–600°C and a time of 4–6 hours.

6. The preparation method according to claim 2, characterized in that, The alkaline solution I and alkaline solution II are independently selected from aqueous solutions of at least one of sodium hydroxide, sodium carbonate, and sodium bicarbonate.

7. The preparation method according to claim 2, characterized in that, The nickel source is selected from at least one of nickel nitrate, nickel oxalate, nickel chloride, and nickel acetate.

8. The preparation method according to claim 2, characterized in that, The auxiliary precursor is selected from at least one of Co precursor, Mn precursor, and Mo precursor; The Co precursor is selected from at least one of the following: Co nitrate, chloride, oxalate, and acetate. The Mn precursor is selected from at least one of the following: nitrate, chloride, oxalate, and acetate of Mn; The Mo precursor is selected from ammonium molybdate and / or sodium molybdate.

9. The use of the core-shell catalyst for the synthesis of m-phenylenediamine according to claim 1 or the core-shell catalyst for the synthesis of m-phenylenediamine obtained by the preparation method according to any one of claims 2 to 8 in the catalytic hydrogenation of isophthalonitrile to prepare m-phenylenediamine.

10. The application according to claim 9, characterized in that, The preparation of m-phenylenediamine by catalytic hydrogenation of isophthalonitrile is carried out in a fixed-bed reactor; The fixed-bed reactor is loaded with a catalyst of the target shape obtained by pressing a mixture containing the core-shell catalyst for the synthesis of m-phenylenediamine, cellulose, and graphite into tablets.

Images