A method for preparing a catalyst and applications thereof

Abstract

The application discloses a preparation method and application of a catalyst. The preparation method comprises the following steps: firstly, modifying microporous parent molecular sieves by using an auxiliary agent; secondly, treating the microporous parent molecular sieves by using water vapor; thirdly, obtaining hierarchical pore molecular sieves by using an alkali solution for alkali treatment; and finally, obtaining the catalyst by extruding and shaping the hierarchical pore molecular sieves and a binder. In a caprolactam ammoniation reaction, the catalyst exhibits excellent activity, selectivity and stability. The catalyst provided by the application overcomes the defects of low efficiency, rapid deactivation and high production cost of existing catalysts, and has the advantages of simple preparation process, cheap and easily available raw materials and large-scale industrial production.

Description

Technical Field

[0001] This application relates to a method for preparing a catalyst and its application, belonging to the field of chemical technology. Background Technology

[0002] Hexamethylenediamine is a key intermediate in the production of high-performance materials such as nylon. Currently, the main synthetic routes are the adiponitrile method and the caprolactam method. In the 1960s, Toray Industries of Japan pioneered the technology of preparing hexamethylenediamine from caprolactam by using waste nylon as raw material. In recent years, with the continuous expansion of caprolactam production capacity and the continuous reduction of costs, research on the direct catalytic amination and dehydration of caprolactam to synthesize the intermediate 6-aminohexanonitrile (which is then catalytically hydrogenated to obtain hexamethylenediamine) has been continuously advanced. Currently, there are two main methods for synthesizing 6-aminohexanonitrile from caprolactam: liquid-phase and gas-phase methods. The main processes of the caprolactam amination reaction are ring-opening and dehydration reactions.

[0003] CN107739318A discloses a liquid-phase synthesis process using phosphoric acid or phosphate as a catalyst, employing a batch method. The caprolactam conversion is 55%, and the 6-aminohexanonitrile selectivity is 97%, indicating a low conversion rate. Catalyst separation and recycling complicate the process, resulting in low overall equipment efficiency. CN111662210A discloses a two-step liquid-phase method for preparing 6-aminohexanonitrile, achieving a single-pass caprolactam conversion of 99%. However, the first step, crude product separation, is difficult and energy-intensive. In the gas-phase process, the early US patent US2234566A used silica gel supported copper as a catalyst, but the conversion rate was low, less than 25%, and the selectivity of 6-aminohexanonitrile was low, less than 90%. CN114832851A disclosed a catalyst with oxides of at least one element selected from iron, calcium, magnesium, phosphorus and zinc loaded on a support prepared by H USY molecular sieve, alumina and clay, and the surface was modified with titanium oxide. The resulting catalyst had a caprolactam conversion rate of about 80% and a selectivity of more than 98%, and could still maintain high activity after 1000h of operation. Summary of the Invention

[0004] To address the problems existing in the prior art, a method for preparing a catalyst is provided. The prepared catalyst exhibits excellent activity, selectivity, and stability in the caprolactam amination reaction. The catalyst proposed in this invention overcomes the shortcomings of existing catalysts, such as low efficiency, rapid deactivation, and high production costs. Moreover, the preparation process is simple, the raw materials are inexpensive and readily available, and it can be used for large-scale industrial production.

[0005] According to one aspect of this application, a method for preparing a catalyst is provided, comprising the following steps:

[0006] a) Add the microporous molecular sieve to the auxiliary agent solution and impregnate it by an equal volume, dry it by I, and calcine it by I to obtain substance a;

[0007] b) Treat substance a with water vapor to obtain substance b;

[0008] c) Subject the substance b to alkali treatment, ammonium exchange, and calcination II to obtain a hydrogen-type hierarchical porous molecular sieve;

[0009] d) The hydrogen-type hierarchical porous molecular sieve and binder are extruded into strips and calcined (III) to obtain the ammoniation catalyst.

[0010] Optionally, the microporous matrix molecular sieve is selected from at least one of ZSM-11 molecular sieve, ZSM-5 molecular sieve, and mordenite, and the silica-alumina ratio of the microporous matrix molecular sieve is 5 to 30.

[0011] Optionally, the additive solution is a soluble salt containing an additive element, wherein the additive element is selected from at least one of Fe, Ca, Mg, P, and Zn.

[0012] Optionally, the auxiliary agent solution is selected from at least one of ferric nitrate, ferric chloride, calcium nitrate, calcium chloride, magnesium nitrate, magnesium chloride, ammonium phosphate, diammonium hydrogen phosphate, diammonium dihydrogen phosphate, zinc nitrate, and zinc chloride.

[0013] Optionally, the additive in the additive solution is 0.01 to 30 wt% of the content of the microporous molecular sieve matrix, and the additive is based on the mass of the additive elements.

[0014] Optionally, the additive in the additive solution is any value or a range between two values ​​from 0.01wt%, 0.1wt%, 3wt%, 15wt%, and 30wt% of the content of the microporous matrix molecular sieve.

[0015] Optionally, the time for the equal-volume impregnation is 2 to 15 hours.

[0016] Optionally, the time for the equal-volume impregnation is any value among 2h, 5h, 8h, 12h, and 15h, or a range between two values.

[0017] Optionally, the temperature of the drying process I is 40–100°C, and the drying time is 10–50 h.

[0018] Optionally, the temperature of the drying I is selected from any value of 40°C, 60°C, 80°C, and 100°C, or a range between two values.

[0019] Optionally, the drying time I is selected from any value of 10h, 20h, 30h, 40h, 50h or a range between two values.

[0020] Optionally, the temperature of the calcination I is 400–650°C, and the calcination time is 2–5 hours.

[0021] Optionally, the temperature of the calcination I is any value among 400℃, 450℃, 500℃, 600℃, and 650℃, or a range between two values.

[0022] Optionally, the roasting time I is any value among 2h, 3h, 4h, and 5h, or a range between two values.

[0023] Optionally, the temperature of the steam treatment is 300–600°C, and the steam treatment time is 2–6 hours.

[0024] Optionally, the temperature of the steam treatment is any value among 300℃, 400℃, 500℃, and 600℃, or a range between two values.

[0025] Optionally, the steam treatment time is any value among 2h, 3h, 4h, 5h, and 6h, or a range between two values.

[0026] Optionally, the alkali used in the alkali treatment is selected from at least one of NaOH, KOH, Na2CO3, and K2CO3.

[0027] Optionally, the concentration of alkali in the alkali treatment is 0.1 to 1 mol / L.

[0028] Optionally, the concentration of the alkali in the alkali treatment is any value or a range between two values ​​from 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, and 1.0 mol / L.

[0029] Optionally, during the alkali treatment process, the solid-liquid ratio of substance b to the solution is 1:20 to 40.

[0030] Optionally, during the alkali treatment process, the solid-liquid ratio of substance b to the solution is any value among 1:20, 1:30, and 1:40, or a range between two values.

[0031] Optionally, the temperature of the alkali treatment is 30–90°C, and the time of the alkali treatment is 10–60 min.

[0032] Optionally, the temperature of the alkali treatment is any value among 30°C, 50°C, 70°C, and 90°C, or a range between two values.

[0033] Optionally, the alkali treatment time is any value among 10 min, 30 min, 50 min, and 60 min, or a range between two values.

[0034] Optionally, the ammonium salt exchanged is selected from at least one of ammonium nitrate, ammonium chloride, and ammonium carbonate.

[0035] Optionally, the concentration of the ammonium salt solution is 0.5–1.0 mol / L.

[0036] Optionally, the ammonium exchange temperature is 70–95°C, the ammonium exchange time is 1–3 hours, and the ammonium exchange is performed 1–5 times.

[0037] Optionally, the temperature of calcination II is 400–600°C, and the calcination time of calcination II is 2–5 hours.

[0038] Optionally, the temperature of the calcination II is any value or a range between two of 400°C, 450°C, 500°C, 550°C, and 600°C.

[0039] Optionally, the roasting time II is any value among 2h, 3h, 4h, and 5h, or a range between two values.

[0040] Optionally, the adhesive is selected from at least one of alumina, silica gel, and clay.

[0041] Optionally, the mass ratio of the hydrogen-type hierarchical porous molecular sieve to the binder is 1:0.1 to 10;

[0042] Optionally, the temperature of the third calcination is 400–600°C, and the calcination time is 2–5 hours.

[0043] Optionally, the mesopore size of the catalyst is 2 to 20 nm.

[0044] According to another aspect of this application, a method for ammoniation is provided, in which a mixture of caprolactam and ammonia is contacted with a catalyst and reacted to obtain a 6-aminohexanonitrile product.

[0045] The catalyst is selected from those obtained according to the preparation method described above.

[0046] Optionally, the space velocity of the caprolactam is 1–20 h⁻¹. -1 .

[0047] Optionally, the molar ratio of caprolactam to ammonia in the mixed gas is 1:2 to 20.

[0048] Optionally, the reaction temperature is 150–450°C, and the reaction pressure is 0.01–1.0 MPa.

[0049] Optionally, the temperature of the reaction is any value among 150°C, 250°C, 350°C, and 450°C, or a range between two values.

[0050] Optionally, the pressure of the reaction is any value or a range between two of 0.01 MPa, 0.05 MPa, 0.1 MPa, 0.5 MPa, and 1.0 MPa.

[0051] Optionally, the reaction is carried out in a fixed-bed reactor, and the number of fixed-bed reactors is at least one.

[0052] The beneficial effects that this application can produce include:

[0053] 1) The catalyst preparation method provided in this application uses silica-alumina molecular sieves and alumina as binders and inexpensive salt active component precursors as catalyst raw materials. The raw materials are readily available and inexpensive. After extrusion molding and impregnation loading, the catalyst has good mechanical stability and long life. The molecular sieve has specific acidity and pore structure. By adjusting the ratio of molecular sieve to binder and the amount of phosphorus loading, the acidity of the catalyst can be effectively controlled. The hierarchical porous molecular sieve can improve the diffusion of reactants and products, thereby slowing down the deactivation rate and extending the catalyst life.

[0054] 2) The ammoniation method provided in this application can obtain the product with only one catalytic reaction, which is simple and helps to reduce costs.

[0055] 3) The ammoniation method provided in this application, using the catalyst prepared in this application, has an initial conversion rate and selectivity of over 90%, and after 1000 hours of cycling, the conversion rate and selectivity still remain at around 90%, demonstrating good stability. Attached Figure Description

[0056] Figure 1 The images shown are scanning electron microscope (SEM) images of the catalyst prepared in Example 1 of this application; wherein image a) is a scanning electron microscope image magnified 2000x, image b) is a scanning electron microscope image magnified 20000x, and images c) and d) are scanning electron microscope images magnified 200000x.

[0057] Figure 2 The attached diagrams are for the physical adsorption and desorption of N2 and the BJH pore size distribution of the catalyst in Example 1 of this application, where a) is the attached diagram for the physical adsorption and desorption of N2 and b) is the BJH pore size distribution diagram. Detailed Implementation

[0058] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0059] Unless otherwise specified, the experimental reagents used in the embodiments of the present invention are all conventional biochemical reagents and are all purchased through commercial channels; unless otherwise specified, the experimental methods are all conventional methods.

[0060] This invention utilizes the ASAP 2020PLUS HD88 physical adsorption instrument from Micron Technology Co., Ltd. to characterize the catalyst by nitrogen physical adsorption. The analytical conditions are as follows: 0.10 g of molecular sieve is loaded into a quartz adsorption tube and vacuum-treated at 350 °C for 10 h to remove moisture and impurities adsorbed by the molecular sieve material. Nitrogen adsorption / desorption experiments are then conducted at 77.4 K.

[0061] The analysis method in this embodiment of the invention is as follows:

[0062] The products were analyzed using an Agilent 7890B gas chromatograph, an FID detector, and a PLOT / Q column.

[0063] In the embodiments of this application, the caprolactam conversion rate and 6-aminoacetonitrile selectivity are calculated based on the normalization method: the caprolactam conversion rate and 6-aminoacetonitrile selectivity are calculated as follows:

[0064] Caprolactam conversion rate: (1-w)×100%

[0065] 6-Aminohexanonitrile selectivity:

[0066] Where w represents the percentage content of caprolactam in the chromatographic analysis results of the reaction product, and w* represents the percentage content of 6-aminohexanonitrile in the chromatographic analysis results of the reaction product.

[0067] Example 1: Preparation of Catalyst

[0068] Prepare 27 mL of a phosphoric acid aqueous solution containing 4.5 g of phosphorus. The resulting liquid is the precursor solution. Weigh 30.0 g of ZSM-5 molecular sieve (Si / Al = 13), add the precursor solution to the molecular sieve, impregnate for 10 h, dry at 60 °C for 24 h, and calcine at 550 °C for 3 h. The phosphorus loading calculated based on the molecular sieve mass is 15% by mass. Press the modified molecular sieve powder into tablets, break them into fragments, and place them in a quartz tube. Then, steam treat the molecular sieve with water at 500 °C for 3 h. Take 25 g of the water-treated molecular sieve and add it to 750 mL of a 0.2 m³ solution. The molecular sieve was treated in a 1 mol / L NaOH solution at 80℃ for 30 min, centrifuged and washed until neutral, and dried at 100℃ for 12 h. The resulting molecular sieve solid was added to a 0.8 mol / L NH4NO3 solution at a solid-liquid ratio of 1:20 (g / mL), stirred at 85℃ for 2 h, and repeated 3 times. Then it was centrifuged and washed again, dried at 100℃ for 12 h, and finally calcined at 550℃ for 3 h. The resulting solid was the hierarchical porous molecular sieve, denoted as HZ-1.

[0069] 14.00g of multi-level porous molecular sieve HZ1 and 6.00g of alumina were physically mixed. After the mixture was homogeneous, an appropriate amount of 10wt% nitric acid solution was added. After the mixture was homogeneous, it was placed in a mold for extrusion molding. After the strips were dried, they were calcined at 500℃ for 2h and then crushed to 20-40 mesh. The resulting solid was the catalyst, and the sample was named Cat-1.

[0070] The scanning electron microscope image of HZ1 is shown below. Figure 1 As shown in the attached diagram of N2 physical adsorption / desorption and the BJH pore size distribution diagram, see below. Figure 2 As shown, the sample has a mesoporous structure with a pore size of about 4 nm, which is conducive to the diffusion of reactants and products.

[0071] Example 2: Preparation of Catalyst

[0072] The catalyst was prepared according to the method of Example 1, except that the precursor solution was an aqueous solution of ammonium dihydrogen phosphate, the phosphorus content in the aqueous solution was 2.1 g, and the loading of P calculated based on the molecular sieve mass was 7% by mass. The resulting sample was denoted as Cat-2.

[0073] Example 3: Preparation of Catalyst

[0074] The catalyst was prepared according to the method in Example 1, except that the temperature of the steam treatment was 400°C, the alkali for the alkali treatment was KOH, and the mass ratio of the hierarchical porous molecular sieve to alumina was 3:2. The resulting sample was denoted as Cat-3.

[0075] Example 4: Preparation of Catalyst

[0076] The catalyst was prepared according to the method of Example 1, except that the precursor solution was an aqueous solution of ferric nitrate, the aqueous solution contained 2.1 g of iron, and the Fe loading calculated based on the molecular sieve mass was 7% by mass. The steam treatment temperature was 600 °C and the steam treatment time was 2 h. The resulting sample was denoted as Cat-4.

[0077] Example 5: Preparation of Catalyst

[0078] The catalyst was prepared according to the method of Example 1, except that the precursor solution was an aqueous solution of zinc chloride, the zinc content in the aqueous solution was 3.0 g, the Zn loading based on the molecular sieve mass was 10% by mass, the molecular sieve used was ZSM-11 molecular sieve (Si / Al = 12), the steam treatment temperature was 400 °C, the steam treatment time was 5 h, and the resulting sample was denoted as Cat-5.

[0079] Example 6 Preparation of Catalyst

[0080] The catalyst was prepared according to the method of Example 1, except that the precursor solution was an aqueous solution of diammonium hydrogen phosphate, the phosphorus content in the aqueous solution was 3.6 g, the P loading based on the molecular sieve mass was 12% by mass, the molecular sieve used was ZSM-11 molecular sieve (Si / Al = 12), the steam treatment time was 5 h, the alkali used was Na2CO3, the alkali treatment temperature was 90 °C, the alkali treatment time was 60 min, and the obtained sample was denoted as Cat-6.

[0081] Example 7 Preparation of Catalyst

[0082] The catalyst was prepared according to the method of Example 1, except that the mass ratio of hierarchical porous molecular sieve to alumina was 1:1, the precursor solution was an aqueous solution of ammonium phosphate containing 3.0 g of phosphorus, and the phosphorus loading based on the molecular sieve mass was 10% by mass. The molecular sieve used was mordenite (Si / Al = 10). The steam treatment time was 4 h, the alkali treatment temperature was 90 °C, and the alkali treatment time was 45 min. The resulting sample was designated Cat-7.

[0083] Example 8: Preparation of Catalyst

[0084] The catalyst was prepared according to the method of Example 1, except that the precursor solution was an aqueous solution of ammonium phosphate, the phosphorus content in the aqueous solution was 3.0 g, the loading of P calculated based on the support was 10% by mass, the binder used was silicon oxide, and the resulting sample was designated as Cat-8.

[0085] Preparation of catalyst in Comparative Example 1

[0086] Take multi-level porous molecular sieve HZ1, compress it into tablets, and then crush it to 20-40 mesh. The resulting sample is denoted as Cat-9.

[0087] Preparation of catalyst in Comparative Example 2

[0088] The catalyst was prepared according to the method in Example 1, except that the molecular sieve treated with the additives was directly extruded with alumina, and the resulting sample was designated Cat-10.

[0089] The components of each catalyst are shown in Table 1.

[0090] Table 1

[0091]

[0092] Application of catalysts in Examples 9-18

[0093] The catalyst obtained in this invention was evaluated for its catalytic performance using a fixed-bed reactor. 1.0 g of catalyst was loaded, and the evaluation was conducted using caprolactam and ammonia as raw materials. The reaction temperature was 350 °C, the reaction pressure was 0.01 MPa, and the caprolactam space velocity was 3 h⁻¹. -1 The catalysts used in each example and the reaction results are shown in Table 2.

[0094] Table 2

[0095]

[0096] As shown in Table 2, the catalyst prepared by the present invention with hierarchical porous molecular sieve as the active component can achieve efficient production of 6-aminohexanonitrile compared with the catalyst prepared in the comparative example. The catalyst has good stability and long life, improves the diffusion of reactants and products, thereby slowing down the deactivation rate and extending the catalyst life.

[0097] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a catalyst, characterized in that, Includes the following steps: Prepare 27 mL of phosphoric acid aqueous solution containing 4.5 g of phosphorus. The resulting liquid is the precursor solution. Weigh 30.0 g of ZSM-5 molecular sieve with Si / Al = 13. Add the precursor solution to the molecular sieve, impregnate for 10 h, dry at 60 °C for 24 h, and calcine at 550 °C for 3 h. The P loading calculated based on the molecular sieve mass is 15% by mass. Press the molecular sieve powder modified with additives into tablets, break them into fragments, and place them in a quartz tube. Then, steam treat the molecular sieve with water at 500 °C for 3 h. Take 25 g of the water-treated molecular sieve and add it to 750 mL of 0.2 mol / L NaOH solution. Treat at 80 °C for 30 min, centrifuge and wash until neutral, and dry at 100 °C for 12 h. Add the obtained molecular sieve solid to 0.8 mol / L NH4NO3 solution with a solid-liquid ratio of 1:

20. The mixture was stirred at 85℃ for 2 hours with g / mL, repeated 3 times, then centrifuged and washed, dried at 100℃ for 12 hours, and finally calcined at 550℃ for 3 hours. The resulting solid was the multi-level porous molecular sieve. 14.00g of multi-level porous molecular sieve and 6.00g of alumina were physically mixed. After the mixture was homogeneous, an appropriate amount of 10wt% nitric acid solution was added. After the mixture was homogeneous, it was placed in a mold for extrusion molding. After the strips were dried, they were calcined at 500℃ for 2h and then crushed to 20-40 mesh. The resulting solid was the catalyst.

2. A method of ammoniation, characterized in that, A mixture of caprolactam and ammonia was contacted with a catalyst to react and give 6-aminohexanonitrile. The catalyst is selected from the catalyst obtained by the preparation method according to claim 1.

3. The method according to claim 2, characterized in that, The space velocity of the caprolactam is 1-20 h⁻¹. -1 ; The molar ratio of caprolactam to ammonia in the mixed gas is 1:2~20; The reaction temperature is 150~450℃, and the reaction pressure is 0.01~1.0 MPa.

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