A catalyst for preparing primary amine by hydrogenation of nitrile and a preparation method thereof

Abstract

The application provides a preparation method of a metal supported catalyst, and the process is divided into three steps: (1) high-temperature pretreatment of an oxide carrier under a reducing atmosphere to obtain a carrier S1; (2) mixing, drying and calcining of the S1 and a noble metal salt solution with a certain concentration to obtain a precursor C1 containing highly dispersed noble metals; and (3) mixing, drying, calcining and reduction of the C1 and a metal salt solution with a certain concentration to obtain a supported nanometer catalyst C2. The catalyst prepared by the method provided by the application is suitable for a primary amine reaction synthesized by hydrogenation of nitrile compounds, in particular, a 1,6-hexanediamine reaction prepared by hydrogenation of adiponitrile or 6-aminohexanenitrile, the catalyst does not need to add an alkali aid in the reaction process, can efficiently hydrogenate to obtain a primary amine product, reduces equipment corrosion and environmental pollution, and has industrial application value.

Description

Technical Field

[0001] This invention relates to the field of catalytic hydrogenation of nitrile compounds to primary amines, particularly to the preparation method and application of catalysts for the hydrogenation of adiponitrile and 6-aminohexanonitrile to 1,6-hexanediamine. Background Technology

[0002] Amines are an important class of chemical intermediates with wide applications in industries such as biopharmaceuticals, coatings, pesticides, and rubber. Compared with traditional organic synthesis routes, the selective hydrogenation of nitrile compounds to amines based on supported metal catalysts is a highly atom-economical and environmentally friendly synthetic route, thus attracting widespread attention. However, due to the high reduction potential of the C≡N triple bond in nitrile molecules, the selectivity of this catalytic route is generally low, often yielding a mixture of primary amines, secondary amines, imines, and low-value hydrogenolysis byproducts, significantly increasing subsequent separation costs. Therefore, designing a high-performance hydrogenation catalyst capable of achieving highly selective synthesis of a single amine compound while simultaneously avoiding hydrogenolysis byproducts remains a major challenge in the field of selective hydrogenation of nitrile compounds.

[0003] 1,6-Hexanediamine (HMD) is an important organic chemical intermediate, mainly used in the production of polyamides, such as Nylon-66 and Nylon-610. It can also be used as a curing agent and organic crosslinking agent for urea resins, epoxy resins, or urea-formaldehyde resins. In recent years, the demand for HMD in synthetic fibers and engineering plastics has been increasing, leading to a sustained rise in its price and a significant supply-demand gap in the market. Currently, the main production process for HMD is the adiponitrile catalytic hydrogenation method, which has attracted much attention due to its simplicity, high product quality, and low production cost. Industrially, adiponitrile hydrogenation mainly uses Raney nickel-based catalysts. Although these catalysts have good catalytic activity, they suffer from poor mechanical stability, are prone to sintering, are brittle, and are easily spontaneously combustible. During the reaction, large amounts of ammonia or inorganic bases need to be added to suppress side reactions, generating large amounts of alkaline waste liquid that not only corrodes production equipment but also puts enormous pressure on environmental protection. Chinese patent CN1417200A discloses an amorphous alloy catalyst composed of metals such as nickel, aluminum, phosphorus, and iron for the catalytic hydrogenation of adiponitrile to hexamethylenediamine in a stirred tank or fixed bed reactor, achieving a conversion rate of 87%, but with low selectivity. For example, CN104001516A discloses a catalyst composed of a silver-ammonia mixture (ammonia water and silver nitrate aqueous solution) and a porous aluminum support for the hydrogenation of adiponitrile to hexamethylenediamine, achieving a yield of 80%, but the catalyst cost is too high, hindering industrial application. Therefore, for the hydrogenation reaction of adiponitrile, it is necessary to develop novel catalysts with high activity, high selectivity, and easy product separation to meet the needs of industrial production.

[0004] Furthermore, noble metal catalysts have attracted continuous attention from researchers in nitrile hydrogenation systems due to their ability to activate H2 molecules at low temperatures and their excellent hydrogenation performance. For example, Wang et al. (H. Wang, et al. Nature Communications, 2019, 10, 4998) used atomic layer deposition technology to deposit single-atom Pd on the surface of Ni nanoparticles to prepare a core-shell Pd1Ni / SiO2 catalyst, which not only significantly improved the conversion rate of benzonitrile hydrogenation but also achieved high selectivity for secondary amine products. Liu et al. (ZB Liu, et al. Nature Communications, 2021, 12, 6194) used defect-rich graphene as a support to construct a single-atom Pd catalyst for benzonitrile hydrogenation. Under conditions without the addition of a base promoter, the single-atom Pd catalyst tended to generate secondary amine products.

[0005] Therefore, the present invention provides a catalyst preparation method for the hydrogenation of nitriles to prepare primary amines. Through a two-step loading method, the morphology of the active metal component of the catalyst is effectively controlled and adjusted, thereby achieving highly selective hydrogenation of adiponitrile or 6-aminohexanonitrile to prepare 1,6-hexanediamine under alkali-free conditions.

[0006] Purpose of the invention The purpose of this invention is to address the problems existing in the prior art by providing a catalyst and its preparation method for the hydrogenation synthesis of 1,6-hexanediamine from adiponitrile or 6-aminohexanenitrile. The supported catalyst prepared by this method has a stable and uniform active component, possessing both highly dispersed noble metal active sites and nanoparticle metal active sites. The presence of these dual active sites helps to regulate the adsorption capacity of raw materials and products at each stage, improving the selectivity of the target product 1,6-hexanediamine. The catalyst also has the advantage of not requiring the addition of strong base auxiliaries during the reaction, thus better protecting equipment, reducing environmental pollution, and improving the operability for industrial applications.

[0007] To achieve the above-mentioned objectives, the present invention provides the following specific technical solutions: A catalyst for the hydrogenation of adiponitrile to hexamethylenediamine is characterized by being prepared using a two-step supported method, the specific steps of which are as follows: (1) The oxide support is subjected to high temperature pretreatment under a reducing atmosphere to obtain oxide support S1 with certain surface defects; (2) S1 is mixed with a certain concentration of noble metal salt solution, dried and calcined to obtain precursor C1 containing highly dispersed noble metal; (3) It is mixed again with a certain concentration of metal salt solution, dried, calcined and reduced to obtain the supported nanocatalyst C2.

[0008] In this invention, the oxide carrier mentioned in step (1) is one or a mixture of several of cerium oxide, aluminum oxide, silicon oxide, zirconium oxide, titanium oxide, and magnesium oxide. The high-temperature pretreatment temperature range is 600-900 ℃, and the reducing gas is H2 or H2 / N2.

[0009] Generally, catalyst deactivation is mainly caused by the sintering of metal active centers (manifested as the growth of active metal nanoparticles before and after the reaction) and the deactivation of active centers by carbon deposits or organic polymers. The catalyst prepared using the method of this patent has a support with surface defects that facilitates the anchoring of noble metals, preventing their growth during the reaction. Furthermore, secondary loading can form metal active centers with different particle size distributions, resulting in a synergistic catalytic effect that improves the conversion capacity of intermediate products, reduces the formation of carbon deposits or polymers, and thus enhances the stability of the catalyst.

[0010] In this invention, in step (2), the precious metal salt is one of platinum chloride, rhodium chloride, palladium chloride, iridium chloride, ruthenium chloride, platinum acetylacetonate, rhodium acetylacetonate, iridium acetylacetonate, palladium acetylacetonate, ruthenium acetylacetonate, platinum nitrate, palladium nitrate, palladium acetate, rhodium nitrate, and ruthenium nitrate. The precious metal salt is dissolved in water or acetone solution with a concentration of 0.1-1 mg / mL and a metal loading range of 0.01-0.5 wt%.

[0011] In this invention, the metal salt mentioned in step (3) is one of nickel nitrate, cobalt nitrate, iron nitrate, copper nitrate, manganese nitrate, zinc nitrate, ruthenium chloride, platinum chloride, and palladium chloride. The metal salt is dissolved in water or dilute hydrochloric acid solution, with a concentration of 1-100 mg / mL and a metal loading range of 0.5-10 wt%.

[0012] In this invention, the method for bonding the metal to the support is a stepwise impregnation method, with a drying temperature of 80-120 ℃, a calcination temperature of 300-700 ℃, and a reduction temperature of 200-600 ℃. The catalyst prepared using the above method exhibits a highly dispersed noble metal in the first step and a nanoparticle state in the second step.

[0013] The above catalyst is used in the hydrogenation of nitriles to prepare primary amines, and the specific steps are as follows: (1) Place catalyst C2 in H2 or H2 / N2 mixture and reduce it at a certain temperature; (2) The reduced catalyst C2 is added to the reactor. At a certain temperature, the raw material liquid and hydrogen react with the catalyst to generate hexamethylenediamine.

[0014] Preferably, the nitrile compound is one of adiponitrile or 6-aminohexanonitrile.

[0015] Preferably, the reactor is one of a batch reactor, a fixed-bed reactor, a fluidized-bed reactor, or a slurry-bed reactor.

[0016] Preferably, the catalyst reduction conditions in step (1) are: temperature of 200-600 ℃, heating rate of 1-10 ℃ / min, H2 or H2 / N2 flow rate of 10-100 mL / min, and reduction time of 1-6 h.

[0017] Preferably, the raw material solution in step (2) is a nitrile-solvent mixture, wherein the solvent is at least one of methanol, ethanol, propanol, isopropanol, and butanol, and the mass concentration of the nitrile compound is 10-50 wt%.

[0018] Preferably, the hydrogenation reaction conditions in step (2) are: a reaction temperature of 50-150 ℃, preferably 80-120 ℃; and a reaction pressure of 1.0-10.0 MPa, preferably 3.0-7.0 MPa.

[0019] The beneficial effects of this invention are as follows: (1) Pretreatment of the support can increase the degree of surface defects of the support, which provides a guarantee for the first step of high dispersion loading of precious metals; the catalyst has a low precious metal loading, thereby reducing the cost of the catalyst.

[0020] (2) The two-step loading strategy of the present invention enables the surface of the support to simultaneously contain highly dispersed noble metal active sites and metal nanoparticle active sites. The highly dispersed noble metal active sites are single-atom or nanocluster structures with a size of less than 1 nm, which is beneficial to the adsorption of raw materials. The metal nanoparticles have a size of 2-5 nm, which is beneficial to the adsorption and activation of hydrogen. The synergistic effect of the two can reduce the competitive adsorption of reaction intermediates, improve the conversion efficiency of intermediates, thereby reducing the occurrence of side reactions and promoting the reaction to proceed in the direction of generating primary amines.

[0021] (3) The catalyst of the present invention can achieve high conversion rate and selectivity without the need for additional alkali additives in the whole reaction process, which can effectively avoid equipment damage and subsequent maintenance, and reduce the difficulty of subsequent product separation; the reaction conditions are mild, which can reduce the difficulty and risk factor in process operation. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to embodiments. It should also be understood that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. The specific mass, reaction time, temperature, process parameters, etc., in the examples are merely examples within a suitable range. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention.

[0023] Unless otherwise specified, the raw materials and reagents used in the following examples and comparative examples were all purchased through commercial channels.

[0024] Example 1 Catalyst preparation: 6 g of TiO2 support was reduced at 700℃ for 4 h under H2 atmosphere. After cooling, 12 mL of 0.5 mg / mL RuCl3 aqueous solution was added, and the mixture was stirred and evaporated to dryness at 80℃. The solution was then dried in an oven at 100℃ for 12 h and calcined at 500℃ for 4 h to obtain a highly dispersed noble metal catalyst precursor. 18 mL of 3 mg / mL RuCl3 aqueous solution was then mixed with the catalyst precursor, stirred and evaporated to dryness at 80℃, and dried in an oven at 100℃ for 12 h. The solution was then calcined at 500℃ for 4 h to obtain a two-step loaded noble metal catalyst with a Ru loading of (0.1 + 0.9) wt%.

[0025] Catalyst performance evaluation: The prepared catalyst was pressed into tablets and sieved to 20-40 mesh. Then, the catalyst was placed in an H2 / N2 atmosphere and heated to 250 °C at 3 °C / min for 4 h for reduction. The reduced catalyst was then placed in a reactor for hydrogenation performance evaluation. Specific conditions were as follows: 4.0 g of activated catalyst was added to a high-pressure reactor, the reactor was closed, and leaks were checked. 160 g of methanol and 40 g of adiponitrile were added to the reactor, and the mixture was purged three times sequentially with nitrogen and then hydrogen. The reaction was carried out at 100 °C, 4 MPa, and 1300 rpm for 5 h. The results are shown in Table 1.

[0026] Example 2 Catalyst preparation: 10 g of CeO2 support was reduced at 900 °C for 2 h under H2 atmosphere. After cooling, 50 mL of 1 mg / mL PdCl2 dilute hydrochloric acid solution was added, and the mixture was stirred and evaporated to dryness at 80 °C. The solution was then dried in an oven at 100 °C for 12 h and calcined at 250 °C for 4 h to obtain a highly dispersed noble metal catalyst precursor. 20 mL of 25 mg / mL copper nitrate aqueous solution was then mixed with the catalyst precursor, stirred and evaporated to dryness at 80 °C, and dried in an oven at 100 °C for 12 h. The solution was then calcined at 250 °C for 4 h to obtain a two-step loaded catalyst with a metal loading of (0.5 + 5) wt%.

[0027] Catalyst performance evaluation: The prepared catalyst was pressed into tablets and sieved to 20-40 mesh. 3.0 g of the tablets were weighed and packed into a quartz tube in a fixed-bed reactor. A H2 / N2 mixture was introduced and the reactor was heated to 250 °C at a rate of 5 °C / min for reduction for 4 h. The specific conditions of the fixed-bed reactor were: using a 40 wt% adiponitrile ethanol solution as raw material, at a reaction temperature of 90 °C, a reaction pressure of 3 MPa, and a mass hourly space velocity of 2.0 h⁻¹. -1The hydrogenation reaction was carried out under the condition that the molar ratio of hydrogen to adiponitrile was 20, and the results are shown in Table 1.

[0028] Example 3 Catalyst preparation: 100 g of Al2O3 support was reduced at 600 °C for 2 h under H2 atmosphere. After cooling, 200 mL of acetone solution of 1 mg / mL platinum acetylacetonate was added, and the mixture was stirred and evaporated to dryness at 50 °C. The solution was then dried in an oven at 100 °C for 12 h and calcined at 250 °C for 4 h to obtain a highly dispersed noble metal catalyst precursor. 200 mL of 100 mg / mL nickel nitrate aqueous solution was then mixed with the catalyst precursor, stirred and evaporated to dryness at 80 °C, and dried in an oven at 100 °C for 12 h. The solution was then calcined at 500 °C for 4 h to obtain a two-step loaded catalyst with a metal loading of (0.2 + 10) wt%.

[0029] Catalyst performance evaluation: The prepared catalyst was granulated to 10-20 mesh. 50 g of catalyst was weighed and placed in an H2 atmosphere, heated to 450 ºC at 10 ℃ / min for 6 h for reduction. The catalyst was then loaded onto a fluidized bed for hydrogenation reaction performance evaluation. Specific conditions were as follows: methanol was used as the solvent, adiponitrile was dissolved in methanol to form a 50 wt% working solution, and the mass ratio of catalyst to working solution was 1:100. The volume ratio of hydrogen to nitrogen in the mixed gas was controlled at 70:30, the hydrogen-nitrogen ratio at 60, the reaction pressure at 4 MPa, the bed reaction temperature at 80 ℃, and the residence time at 30 min. The H2 / N2 mixed gas was dispersed by a gas distributor and mixed with the working solution entering from the bottom of the reactor. Under the action of the catalyst in the reactor, the H2 / N2 mixture underwent a hydrogenation reaction with adiponitrile. The results are shown in Table 1.

[0030] Example 4 The catalyst preparation method is the same as in Example 2.

[0031] The catalyst performance evaluation method is the same as that in Example 1, and the results are shown in Table 1.

[0032] Example 5 The catalyst preparation method is the same as in Example 3.

[0033] The catalyst performance evaluation method is the same as in Example 2, and the results are shown in Table 1.

[0034] Example 6 The catalyst preparation method is the same as in Example 1.

[0035] The catalyst performance evaluation method is the same as in Example 2, and the results are shown in Table 1.

[0036] Example 7 The catalyst preparation method is the same as in Example 1.

[0037] The catalyst performance evaluation method was the same as in Example 1, except that the raw material was 6-aminohexanonitrile. The results are shown in Table 1.

[0038] Example 8 The catalyst preparation method is the same as in Example 2, except that the support is ZrO2.

[0039] The catalyst performance evaluation method was the same as in Example 2, except that the raw material was 6-aminohexanonitrile. The results are shown in Table 1.

[0040] Comparative Example 1 Catalyst preparation: 6 g of supported TiO2 was reduced at 700 °C for 4 h under H2 atmosphere. After cooling, 20 mL of RuCl3 aqueous solution with a concentration of 3 mg / mL was added and mixed with the above catalyst precursor. The mixture was stirred and evaporated to dryness at 80 °C, and then dried in an oven at 100 °C for 12 h. Finally, it was calcined at 500 °C for 4 h to obtain a one-step supported noble metal catalyst with a Ru loading of 1 wt%.

[0041] The catalyst performance evaluation method is the same as that in Example 1, and the results are shown in Table 1.

[0042] Comparative Example 2 The catalyst preparation method is the same as that in Comparative Example 1, except that the TiO2 support was not reduced.

[0043] The catalyst performance evaluation method is the same as that in Example 1, and the results are shown in Table 1.

[0044] Comparative Example 3 The catalyst preparation method is the same as in Example 1, except that the TiO2 support was not reduced.

[0045] The catalyst performance evaluation method is the same as that in Example 1, and the results are shown in Table 1.

[0046] Table 1. Reaction results of Examples 1-6 and Comparative Examples 1-3

[0047] Based on the data in Table 1, we can see that: The results of Examples 1, 2, and 3 show that the catalyst prepared by the method of the present invention is suitable for batch reactors, fixed-bed reactors, and fluidized-bed reactors.

[0048] The results of Example 1 and Comparative Example 1 show that the two-step loading of noble metals better reflects the synergistic effect of active centers of different sizes of noble metals compared with the one-step loading, reduces competitive adsorption, and results in a higher yield of the target product hexamethylenediamine.

[0049] The results of Comparative Examples 2 and 3 show that the support was not subjected to high-temperature pre-reduction treatment, making it difficult to form defect sites, which is not conducive to subsequent noble metal loading. The noble metal particle size is too large, and the catalyst performance is reduced.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. The application of a catalyst for the hydrogenation of adiponitrile to prepare hexamethylenediamine, characterized in that, This includes using a catalyst for the hydrogenation of adiponitrile to prepare hexamethylenediamine in the reaction of adiponitrile with hydrogen to produce hexamethylenediamine, with the following steps: (1) The supported nanocatalyst C2 is placed in H2 or H2 / N2 mixture and reduced at a certain temperature; (2) The reduced supported nanocatalyst C2 is added to the reactor. At a certain temperature, the raw material liquid and hydrogen react with the catalyst to generate hexamethylenediamine. The raw material solution is an adiponitrile-solvent mixture, and the solvent is at least one selected from methanol, ethanol, propanol, isopropanol, and butanol. The catalyst for the hydrogenation of adiponitrile to hexamethylenediamine is prepared by a two-step supported method, the specific steps of which are as follows: (a) The oxide support is subjected to high-temperature pretreatment under a reducing atmosphere to obtain an oxide support S1 with certain surface defects; the oxide support is one or a mixture of several of cerium oxide, aluminum oxide, silicon oxide, zirconium oxide, titanium oxide, and magnesium oxide; the high-temperature pretreatment temperature range is 600-900 ℃, and the reducing gas is H2 or H2 / N2. (b) S1 is mixed with a noble metal salt solution of a certain concentration, dried and calcined to obtain a precursor C1 containing highly dispersed noble metals; (c) Mix again with a metal salt solution of a certain concentration, dry, calcine and reduce to obtain supported nanocatalyst C2, which is a catalyst for the hydrogenation of adiponitrile to prepare hexamethylenediamine; the metal salt is one of nickel nitrate, cobalt nitrate, iron nitrate, copper nitrate, manganese nitrate, zinc nitrate, ruthenium chloride, platinum chloride and palladium chloride.

2. The application according to claim 1, characterized in that, In step (b), the precious metal salt is one of platinum chloride, rhodium chloride, palladium chloride, iridium chloride, ruthenium chloride, platinum nitrate, palladium nitrate, palladium acetate, rhodium nitrate, and ruthenium nitrate, and the precious metal loading ranges from 0.01 to 0.5 wt%.

3. The application according to claim 1, characterized in that, In step (c), the metal loading ranges from 0.5 to 10 wt%.

4. The application according to claim 1, characterized in that, The reactor is one of the following: batch reactor, fixed bed reactor, fluidized bed reactor, or slurry bed reactor.

5. The application according to claim 1, characterized in that, The catalyst reduction conditions in step (1) are: temperature of 200-600 ℃, heating rate of 1-10 ℃ / min, H2 or H2 / N2 flow rate of 10-100 mL / min, and reduction time of 1-6 h.

6. The application according to claim 1, characterized in that, In step (2), the mass concentration of adiponitrile is 10-50 wt%.

7. The application according to claim 1, characterized in that, The hydrogenation reaction conditions in step (2) are: reaction temperature of 50-150 ℃; reaction pressure of 1.0-10.0 MPa.

8. The application according to claim 7, characterized in that, The hydrogenation reaction conditions in step (2) are: reaction temperature of 80-120 ℃; reaction pressure of 3.0-7.0 MPa.

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