A catalyst for synthesizing sebacic dinitrile and a preparation method and application thereof
By using a modified alumina support combined with transition metal and rare earth metal oxide composite catalysts, the problems of low reaction efficiency and poor selectivity in the preparation of sebaonitrile were solved, achieving high selectivity and long lifespan catalytic performance, simplifying the process and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA TIANCHEN ENGINEERING CORPORATION LTD
- Filing Date
- 2026-04-28
- Publication Date
- 2026-07-03
AI Technical Summary
Existing sebacate preparation technologies suffer from problems such as low reaction efficiency, poor selectivity, high catalyst cost, and complex processes.
A modified alumina support combined with transition metal oxides and rare earth metal oxides was used as a catalyst. The catalyst was prepared by acidification of pseudoboehmite sol molding and combined with oil-ammonia column calcination. The catalyst had a pore size distribution of 10~50nm and an average pore size of 30~40nm. The catalyst was then used for the ammoniation and dehydration reaction of sebacic acid by immobilizing or spraying the active component with equal volume.
It significantly improves the selectivity of sebacate to over 95%, extends the catalyst life to over 1200 hours, simplifies the process, reduces costs, and is suitable for continuous production in fixed-bed reactors.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical synthesis technology, specifically to a catalyst for the synthesis of sebacate, its preparation method, and its application. Background Technology
[0002] Sebaconitrile (chemical formula C) 10 H 20 Sebaconitrile (N2) is an important aliphatic dinitrile compound, slightly soluble in water but readily soluble in organic solvents such as acetone and diethyl ether. Its most important industrial application is as a precursor in the synthesis of sebacic acid (decanediamine), a core monomer in the production of nylon-1010. In addition, sebaconitrile is widely used in pharmaceuticals, dyes, coatings, and analytical chemistry.
[0003] In existing technologies, sebacite is mainly prepared via three routes: 1) acetonitrile condensation with 1,6-dibromohexane; 2) sebacam dehydration; and 3) sebamic acid amination. Among these, sebamic acid amination has become the mainstream industrial route due to the readily available raw materials and high atom economy. The reaction mechanism of this route is as follows: sebamic acid is neutralized with ammonia to form an ammonium salt, which is then dehydrated at high temperature to form sebacam, and further dehydrated to obtain sebacite. However, since sebamic acid is a dicarboxylic acid, if the reactant molecules remain on the catalyst surface for too long, intramolecular cyclization can easily occur, generating sebacidiimide byproducts and reducing reaction selectivity.
[0004] To address the aforementioned issues, existing patent literature proposes several improvement solutions: Patent CN106824038A proposes a reaction apparatus and corresponding synthesis process for the synthesis of sebacate. This patent employs a specially structured ammonia-refining reactor combined with a heat transfer oil-based temperature control program, but suffers from long reaction times (≥10 hours) and complex operation. Patent CN107266335A provides a one-pot method for synthesizing sebacate, using urea and thionyl chloride as dehydrating agents. Although the yield can reach 74-79%, subsequent purification is difficult. Patent CN109206341A proposes a method for preparing sebacate, using ethylmethylimidazolium dihydrogen phosphate ionic liquid as a solvent and catalyst, shortening the reaction time to 40-70 minutes, but the ionic liquid has a complex structure and high cost. Patent CN116023299A discloses a method and apparatus for the continuous synthesis of sebacate from sebacic acid, employing a multi-pot continuous process to improve product quality, reduce energy consumption, increase yield, and reduce impurities. However, this approach suffers from high equipment investment and complex control. Patent CN117756668A proposes a continuous preparation method for sebacite and the catalyst used therein. This method employs a fluidized bed process, which is relatively complex and requires precise control of reaction conditions. Furthermore, the catalyst preparation is cumbersome. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention discloses a catalyst for the synthesis of sebacate, its preparation method, and its application, thereby solving the technical problems of low reaction efficiency, poor selectivity, high catalyst cost, and complex process in the existing sebacate amination method for preparing sebacate.
[0006] To achieve the above technical objectives, on the one hand, this invention proposes a catalyst for the synthesis of sebacate, the catalyst comprising a support and an active component, wherein the support is a modified alumina support, which is obtained by forming acidified pseudoboehmite sol using the oil-ammonia column method and then calcining it once; the modified alumina support has a pore size distribution of 10~50nm >90%, and an average pore size of 30~40nm; the active component is a composite metal oxide containing transition metal oxides and rare earth metal oxides; the mass ratio of the support, the transition metal oxide, and the rare earth metal oxide is 100:(1~10):(1~10).
[0007] In the above technical solution, an acidified pseudoboehmite sol is formed by an oil-ammonia column method combined with a single calcination process to obtain a modified alumina support with a pore size distribution of 10-50 nm, a pore ratio of more than 90%, and an average pore size of 30-40 nm. This pore structure matches the size of the macromolecular reactant sebacic acid and the product sebaconitrile, which is conducive to the diffusion of reactants and the rapid desorption of products, thereby shortening the residence time of reactants on the catalyst surface and inhibiting the formation of by-products such as sebacimide. In addition, the above technical solution uses transition metal oxides and rare earth metal oxides as composite active components, controlling the mass ratio of support, transition metal oxides and rare earth metal oxides to 100:(1-10):(1-10). The transition metal provides the active center for the ammoniation dehydration reaction, and the rare earth metal enhances the anti-coking ability of the catalyst surface. The two work synergistically to improve catalytic activity and extend the catalyst life.
[0008] In a further example of the invention, the pore structure characteristics of the catalyst were optimized. Optionally, the catalyst has a pore volume of 0.4~0.85 ml / g, preferably 0.5~0.7, and a specific surface area of 200~300 m² / g. 2 / g, preferably 220~260m 2 / g ensures both the number of active sites and provides sufficient reaction space and product diffusion channels.
[0009] In a further example of the present invention, the catalyst has an average pore size of 30-40 nm.
[0010] In a further example of the present invention, the mechanical strength of the catalyst is >60 N / particle, and the high hardness of the catalyst gives it excellent long-term continuous catalytic performance. In an optional example of the present invention, the mechanical strength of the catalyst is 60~70 N / particle.
[0011] In a further example of the present invention, the modified alumina support is one or a mixture of two of γ-Al2O3 or δ-Al2O3, and the modified alumina support of a specific crystal form can improve the catalytic performance of the catalyst.
[0012] In a further example of the invention, the transition metal is at least one selected from Cr, Zn, Mn, Fe, Co, Ni, and Zr. In an optional example of the invention, the transition metal is at least one selected from Cr, Zn, Mn, Fe, Ni, and Zr.
[0013] In a further example of the present invention, the rare earth metal is at least one selected from La, Ce, Sm, and Pr. Embodiments of the present invention illustrate a process for preparing catalysts using different transition metals and rare earth metals.
[0014] In a further example of the present invention, the preparation method of the acidified boehmite sol includes: dispersing boehmite, a pore-forming agent, and a pore-expanding agent in water to obtain a suspension; and acidifying the suspension with an acid solution to obtain the acidified boehmite sol. The use of the pore-forming and pore-expanding agents enables the obtained alumina support to possess a suitable surface pore structure, especially a large average pore size. This facilitates the desorption and adsorption of large organic molecules such as sebacic acid and sebaconitrile on the catalyst surface, shortens the reaction residence time of large reactant molecules on the catalyst surface, and avoids the formation of byproducts. Combined with the acidification treatment to form a stable boehmite sol system, this facilitates the obtaining of a highly active crystalline phase of the support, laying the foundation for the preparation of highly selective and long-life sebaconitrile synthesis catalysts.
[0015] Optionally, the pore-forming agent is at least one of methylcellulose, polyethylene glycol, polyacrylamide, and polyacrylamide.
[0016] Optionally, the pore-expanding agent is at least one of starch, guar gum powder, hexamethylenetetramine, and sodium hydroxyethyl sulfonate cocoate.
[0017] Optionally, the mass ratio of the pseudoboehmite, pore-forming agent, and pore-expanding agent is (80~90):(5~10):(5~10).
[0018] Optionally, the solid content of the suspension is 25% to 35%.
[0019] Optionally, the acidification treatment includes stirring at room temperature for 2-4 hours until a homogeneous slurry is formed.
[0020] In order to achieve better modification of aluminum chloride, the present invention explored and optimized the type and amount of acid solution.
[0021] Optionally, the acid solution is a nitric acid solution.
[0022] Optionally, the mass concentration of the acid solution is 20% to 30%, and the mass of the acid solution added is 15% to 25% of the total mass of the pseudoboehmite, pore-forming agent, and pore-expanding agent.
[0023] In order to obtain a carrier with better properties, this invention explores and optimizes the operation and parameter control of the oil-ammonia column method.
[0024] Optionally, the oil-ammonia column method includes: adding the acidified pseudoboehmite sol into an oil-ammonia column to form gel spheres and allowing them to stand for aging.
[0025] Optionally, the oil-ammonia column is composed of kerosene, ammonia, and water.
[0026] Optionally, the temperature of the oil-ammonia column is 80~100℃.
[0027] Optionally, the amount of oil-ammonia column used is such that the oil film thickness is 0.1~1mm and the ammonia water thickness is 100~200cm.
[0028] Optionally, the static aging temperature is 80~100℃ and the time is 12~20h.
[0029] To improve the surface properties and hardness of the modified alumina carrier, the calcination temperature is optionally 400-600℃ and the calcination time is 4-8h; further optionally, drying is performed before calcination; the drying temperature is 100-150℃ and the drying time is 5-10h; even further optionally, the aluminum chloride microspheres obtained by the oil-ammonia column method are washed with water before drying to remove impurities.
[0030] On the other hand, the present invention proposes a method for preparing the above-mentioned catalyst for synthesizing sebacate, the method comprising: loading the metal salt of the active component onto the support, and then subjecting it to secondary calcination and hydration treatment to obtain the catalyst.
[0031] Furthermore, the metal salt of the active component is loaded onto the modified alumina support using equal-volume impregnation or spray impregnation methods. Loading the active metal onto the support surface using equal-volume impregnation or spray impregnation methods improves the utilization rate of the active metal. The combined use of rare earth metals and transition metals enhances the catalyst surface's resistance to coking and extends the catalyst's lifespan.
[0032] To better neutralize the acidity on the catalyst surface and thus improve the selectivity of the catalytic process, this invention explores and optimizes the operation and parameter control of secondary roasting.
[0033] Furthermore, the secondary calcination temperature is 500~600℃, and the time is 6~8h.
[0034] Furthermore, it also includes drying before secondary roasting, with a drying temperature of 100~150℃ and a drying time of 4~6 hours.
[0035] To enhance the active sites of the crude catalyst, this invention explores and optimizes the operation and parameter control of the hydration treatment.
[0036] Furthermore, the hydration treatment is carried out at a temperature of 70-90°C for 5-10 hours.
[0037] Furthermore, it also includes drying after hydration treatment, with a drying temperature of 100~120℃ and a drying time of 4~6 hours.
[0038] On the other hand, the present invention proposes a method for synthesizing sebacite by ammonohydrolysis, wherein the method is carried out under the action of the catalyst described above.
[0039] Optionally, the method includes: mixing and preheating molten sebacic acid with ammonia, followed by an ammonia dehydration reaction under the action of a catalyst; the reacted material is then condensed and the liquid phase is separated to obtain sebaconitrile product. The method for synthesizing sebaconitrile of this invention eliminates the complex equipment configuration of traditional multi-reactor series or fluidized bed processes, resulting in a shorter reaction flow, simpler operation, and suitability for continuous industrial production; it also simplifies the post-processing steps, avoiding complex extraction and distillation separation steps in traditional methods, thereby improving production efficiency and reducing separation energy consumption.
[0040] Optionally, the method is carried out in a fixed-bed reactor.
[0041] In order to improve reaction efficiency, promote raw material conversion and improve the selectivity of sebacate, this invention explores and optimizes the process and parameter control of sebacate ammoniation and dehydration.
[0042] Optionally, the molar ratio of sebacic acid to ammonia is 1:(1~5).
[0043] Optionally, the feed space velocity of the sebacic acid is 0.2~1h. -1 .
[0044] Optionally, the preheating temperature is 300~350℃.
[0045] Optionally, the reaction temperature is 320~400℃ and the reaction pressure is 0~0.5MPa (gauge pressure).
[0046] Compared with the prior art, the beneficial effects of the present invention are as follows: The catalyst support of the present invention is a macroporous alumina support with a pore size of 10~50nm (>90%) and an average pore size of 30~40nm, which effectively matches the macromolecular size of sebacic acid, promotes reactant diffusion and product desorption, shortens residence time, significantly inhibits sebacimide side reactions, and achieves a selectivity of over 95%; through the synergistic cooperation of transition metal and rare earth metal composite oxide active components, the catalytic activity and anti-coking ability are improved, and the service life is extended to over 1200h; the catalyst preparation process is simple, the raw materials are readily available, and the cost is low, making it suitable for continuous production in a fixed-bed reactor; the method of synthesizing sebaconitrile in the present invention has mild reaction conditions, a simple process, and simple post-processing, solving the technical problems of low reaction efficiency, poor selectivity, high catalyst cost, and complex process in the prior art. Detailed Implementation
[0047] To facilitate understanding of the present invention, a more comprehensive description will be provided below, along with preferred embodiments. However, it should be understood that these embodiments are merely for more detailed explanation and should not be construed as limiting the invention in any way, i.e., not intended to limit the scope of protection of the invention.
[0048] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.
[0049] Furthermore, it should be noted that although the various steps of the preparation method of the present invention are described in a specific order in the description of the present invention, these orders are not restrictive. Without departing from the basic principles of the present invention, those skilled in the art can perform the steps in different orders.
[0050] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" or "at least one" means two or more.
[0051] All numerical designations, such as temperature, time, flow rate, and range, are approximate values. It should be understood that, while not always explicitly stated, all numerical designations are preceded by the term "approximately." It should also be understood that, while not always explicitly stated, the reagents described herein are merely examples, and their equivalents are known in the art.
[0052] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.
[0053] Example 1
[0054] A method for preparing a catalyst for the synthesis of sebacate includes the following steps: (1) Weigh boehmite, methylcellulose, and starch in a mass ratio of 85:7.5:7.5. Mix these raw materials evenly, and add an appropriate amount of deionized water to form a suspension with a solid content of 30%. Then, add a 25% nitric acid solution to the suspension, the amount of which is 20% of the total mass of the powder, and stir at room temperature for 3 hours to ensure the homogeneity of the slurry. Subsequently, drop the above slurry into an oil-ammonia column preheated to 90°C to form spheres, and collect the generated 2 mm spherical materials. Next, age these spherical materials for 16 hours. After aging, remove the residue by washing with water, then dry at 120°C for 6 hours, and finally calcine at 500°C for 6 hours to obtain the modified alumina carrier.
[0055] (2) An aqueous solution containing chromium nitrate and lanthanum nitrate was prepared and loaded onto the primary alumina by an equal-volume impregnation method. The mass ratio of alumina to transition metal and rare earth metal oxides was set to 100:5:5. The catalyst was then dried at 120°C for 5 hours, calcined at 550°C for 7 hours, and finally hydrated at 80°C for 8 hours to enhance the active sites of the catalyst, thus obtaining a catalyst for the synthesis of sebacate.
[0056] The catalyst is supported by γ-Al₂O₃, with over 90% of the pores having a pore size distribution in the range of 10–50 nm, an average pore size of approximately 30 nm, a pore volume of 0.6 ml / g, and a specific surface area of 250 m². 2 / g, and the mechanical strength exceeds 62N / piece.
[0057] Example 2
[0058] A method for preparing a catalyst for the synthesis of sebacate includes the following steps: (1) Weigh boehmite, polyethylene glycol, and guar gum powder in a mass ratio of 80:10:10. Mix these raw materials evenly, and add an appropriate amount of deionized water to form a suspension with a solid content of 35%. Then, add a 30% nitric acid solution to the suspension, the amount of which is 25% of the total mass of the powder, and stir at room temperature for 4 hours to ensure the homogeneity of the slurry. Subsequently, drop the above slurry into an oil-ammonia column preheated to 100°C to form spheres, and collect the generated spherical materials. Next, age these spherical materials for 20 hours. After aging, remove the residue by washing with water, then dry at 150°C for 10 hours, and finally calcine at 600°C for 8 hours to obtain the modified alumina carrier.
[0059] (2) An aqueous solution containing ferric nitrate and cerium nitrate was prepared and loaded onto the modified alumina support by an equal-volume spray impregnation method. The mass ratio of alumina to transition metal and rare earth metal oxides was set to 100:6:6. The catalyst was then dried at 150°C for 6 hours, calcined at 600°C for 8 hours, and finally hydrated at 90°C for 10 hours to enhance the active sites of the catalyst, thus obtaining a catalyst for the synthesis of sebacate.
[0060] The catalyst is supported by δ-Al₂O₃, with over 90% of the pores having a pore size distribution in the range of 10–50 nm, an average pore size of approximately 32 nm, a pore volume of 0.7 ml / g, and a specific surface area of 280 m². 2 / g, and the mechanical strength exceeds 63N / piece.
[0061] Example 3
[0062] A method for preparing a catalyst for the synthesis of sebacate includes the following steps: (1) Weigh boehmite, polyacrylamide, and hexamethylenetetramine in a mass ratio of 90:5:5. Mix these raw materials evenly and add an appropriate amount of deionized water to form a suspension with a solid content of 25%. Then, add a 20% nitric acid solution to the suspension, the amount of which is 15% of the total mass of the powder, and stir at room temperature for 2 hours to ensure the homogeneity of the slurry. Subsequently, drop the above slurry into an oil-ammonia column preheated to 80°C to form spheres, and collect the generated spherical materials. Next, age these spherical materials for 12 hours. After aging, remove the residue by washing with water, then dry at 100°C for 5 hours, and finally calcine at 400°C for 4 hours to obtain the modified alumina carrier.
[0063] (2) An aqueous solution containing zinc nitrate and samarium nitrate was prepared and loaded onto the modified alumina support by an equal-volume impregnation method. The mass ratio of alumina to transition metal and rare earth metal oxides was set to 100:3:3. Then, it was dried at 100°C for 4 hours, calcined at 500°C for 6 hours, and finally hydrated at 70°C for 5 hours to enhance the active sites of the catalyst, thus obtaining a catalyst for the synthesis of sebacate.
[0064] The catalyst is supported by γ-Al₂O₃ or δ-Al₂O₃, with over 90% of the pores having a pore size distribution in the range of 10–50 nm, an average pore size of approximately 35 nm, a pore volume of 0.5 ml / g, and a specific surface area of 220 m². 2 / g, and the mechanical strength exceeds 65N / piece.
[0065] Example 4
[0066] A method for preparing a catalyst for the synthesis of sebacate includes the following steps: (1) Weigh boehmite, polyacrylamide, and sodium hydroxyethyl sulfonate cocoate in a mass ratio of 88:6:6. Mix these raw materials evenly and add an appropriate amount of deionized water to form a suspension with a solid content of 30%. Then, add a 28% nitric acid solution to the suspension, the amount of which is 22% of the total mass of the powder, and stir at room temperature for 3 hours to ensure the homogeneity of the slurry. Subsequently, drop the above slurry into an oil-ammonia column preheated to 95°C to form spheres, and collect the generated spherical materials. Next, age these spherical materials for 18 hours. After aging, remove the residue by washing with water, then dry at 130°C for 8 hours, and finally calcine at 550°C for 7 hours to obtain the modified alumina carrier.
[0067] (2) An aqueous solution containing nickel nitrate and praseodymium nitrate was prepared and loaded onto the modified alumina support by an equal-volume impregnation method. The mass ratio of alumina to transition metal and rare earth metal oxides was set to 100:4:4. The catalyst was then dried at 130°C for 5 hours, calcined at 550°C for 7 hours, and finally hydrated at 85°C for 7 hours to enhance the active sites of the catalyst, thus obtaining a catalyst for the synthesis of sebacate.
[0068] The catalyst is supported by γ-Al₂O₃, with over 90% of the pores having a pore size distribution in the range of 10–50 nm, an average pore size of approximately 39 nm, a pore volume of 0.65 ml / g, and a specific surface area of 260 m². 2 / g, and the mechanical strength exceeds 70N / piece.
[0069] Example 5
[0070] A method for preparing a catalyst for the synthesis of sebacate includes the following steps: (1) Weigh boehmite, methylcellulose, and starch in a mass ratio of 83:8.5:8.5. Mix these raw materials evenly and add an appropriate amount of deionized water to form a suspension with a solid content of 28%. Then, add a 22% nitric acid solution to the suspension, the amount of which is 18% of the total mass of the powder, and stir at room temperature for 3.5 h to ensure the homogeneity of the slurry. Subsequently, drop the above slurry into an oil-ammonia column preheated to 85°C to form spheres, and collect the generated spherical materials. Next, age these spherical materials for 15 h. After aging, remove the residue by washing with water, then dry at 110°C for 7 h, and finally calcine at 450°C for 5 h to obtain the modified alumina carrier.
[0071] (2) An aqueous solution containing manganese nitrate and zirconium nitrate was prepared and loaded onto the modified alumina support by an equal-volume impregnation method. The mass ratio of alumina to transition metal and rare earth metal oxides was set to 100:7:7. Then, it was dried at 110°C for 5 h, calcined at 520°C for 7 h, and finally hydrated at 80°C for 8 h to enhance the active sites of the catalyst, thus obtaining a catalyst for the synthesis of sebacate.
[0072] The catalyst is supported by δ-Al₂O₃, with over 90% of the pores having a pore size distribution in the range of 10–50 nm, an average pore size of approximately 31 nm, a pore volume of 0.6 ml / g, and a specific surface area of 250 m². 2 / g, and the mechanical strength exceeds 64N / piece.
[0073] Comparative Example 1 A method for preparing a catalyst includes: weighing boehmite, methylcellulose, and starch in a mass ratio of 85:7.5:7.5. After uniformly mixing these raw materials, an appropriate amount of deionized water is added to form a suspension with a solid content of 30%. Next, a 25% nitric acid solution is added to the suspension, amounting to 20% of the total powder mass, and the mixture is stirred at room temperature for 3 hours to ensure the homogeneity of the slurry. Subsequently, the slurry is dropwise into an oil-ammonia column preheated to 90°C to form spheres, and the resulting 2mm spherical materials are collected. These spherical materials are then aged for 16 hours. After aging, residues are removed by washing with water, followed by drying at 120°C for 6 hours, and finally calcined at 500°C for 6 hours to obtain an alumina spherical catalyst. This catalyst has a γ-type crystalline phase, with over 90% of the pores distributed in the 10-50nm range, an average pore size of approximately 30nm, a pore volume of 0.48ml / g, and a specific surface area of 255m². 2 / g, and the mechanical strength exceeds 61N / piece.
[0074] Comparative Example 2 A method for preparing a catalyst, comprising: (1) Weigh boehmite, methylcellulose, and starch in a mass ratio of 85:7.5:7.5. Mix these raw materials evenly, and add an appropriate amount of deionized water to form a suspension with a solid content of 30%. Then, add a 25% nitric acid solution to the suspension, the amount of which is 20% of the total mass of the powder, and stir at room temperature for 3 hours to ensure the homogeneity of the slurry. Subsequently, drop the above slurry into an oil-ammonia column preheated to 90°C to form spheres, and collect the generated 2mm spherical materials. Next, age these spherical materials for 16 hours. After aging, remove the residue by washing with water, then dry at 120°C for 6 hours, and finally calcine at 500°C for 6 hours to obtain the primary alumina carrier.
[0075] (2) Prepare an aqueous solution containing chromium nitrate and load it onto the primary alumina by an equal-volume impregnation method. The mass ratio of alumina to transition metal oxide is set to 100:5. Then, dry at 120°C for 5 hours, calcine at 550°C for 7 hours, and finally hydrate at 80°C for 8 hours to obtain alumina spherical catalyst.
[0076] This spherical alumina catalyst exhibits a γ-type crystalline phase, with over 90% of its pores ranging from 10 to 50 nm in size. The average pore size is approximately 29 nm, the pore volume is 0.36 ml / g, and the specific surface area reaches 223 m². 2 / g, and the mechanical strength exceeds 60N / piece.
[0077] Comparative Example 3 A method for preparing a catalyst, comprising: (1) Weigh the pseudoboehmite, mix these raw materials evenly, and add an appropriate amount of deionized water to form a suspension with a solid content of 30%. Then, add a 28% nitric acid solution to the suspension, the amount of which is 22% of the total mass of the powder, and stir at room temperature for 3 hours to ensure the homogeneity of the slurry. Subsequently, drop the above slurry into an oil-ammonia column preheated to 95°C to form spheres, and collect the generated spherical materials. Next, these spherical materials are aged for 18 hours. After aging, remove the residue by washing with water, dry at 130°C for 8 hours, and finally calcine at 550°C for 7 hours to obtain the primary alumina carrier.
[0078] (2) An aqueous solution containing nickel nitrate and praseodymium nitrate was prepared and loaded onto the primary alumina by an equal-volume impregnation method. In this process, the mass ratio of alumina to transition metal and rare earth metal oxide was set to 100:4:4. Afterward, the impregnated sample was dried at 130°C for 5 hours, then calcined at 550°C for 7 hours, and finally hydrated at 85°C for 7 hours to enhance the active sites of the catalyst, thus obtaining the catalyst.
[0079] The catalyst support has a γ-type crystalline phase, with over 43% of the pores having a pore size distribution in the 10–50 nm range, an average pore size of approximately 19 nm, a pore volume of 0.47 ml / g, and a specific surface area of 236 m². 2 / g, and the mechanical strength exceeds 47N / piece.
[0080] Comparative Example 4 A method for preparing a catalyst, comprising: (1) Weigh boehmite and polyacrylamide at a mass ratio of 88:12. Mix these raw materials evenly, and add an appropriate amount of deionized water to form a suspension with a solid content of 30%. Then, add a 28% nitric acid solution to the suspension, the amount of which is 22% of the total mass of the powder, and stir at room temperature for 3 hours to ensure the homogeneity of the slurry. Subsequently, drop the above slurry into an oil-ammonia column preheated to 95°C to form spheres, and collect the generated spherical materials. Next, these spherical materials are aged for 18 hours. After aging, remove the residue by washing with water, dry at 130°C for 8 hours, and finally calcine at 550°C for 7 hours to obtain the primary alumina carrier.
[0081] (2) Prepare an aqueous solution containing nickel nitrate and praseodymium nitrate, and load it onto the primary alumina by an equal-volume impregnation method. In this process, the mass ratio of alumina to transition metal and rare earth metal oxide is set to 100:4:4. Afterward, the impregnated sample is dried at 130°C for 5 hours, then calcined at 550°C for 7 hours, and finally hydrated at 85°C for 7 hours to enhance the active sites of the catalyst.
[0082] The catalyst support has a γ-type crystalline phase, with more than 72% of the pores having a pore size distribution in the range of 10-50 nm, an average pore size of about 24 nm, a pore volume of 0.55 ml / g, a specific surface area of 215 m² / g, and a mechanical strength of more than 33 N / particle.
[0083] Furthermore, the present invention evaluates the performance of the catalysts prepared in the above embodiments and comparative examples. The evaluation method is as follows: 5-50g of catalyst is loaded into a fixed-bed reactor. The reactor is a DN10-40 stainless steel pipe with a length of 0.5-1m. The reaction pipe is jacketed with heat transfer oil, and the reactor is heated by a high-temperature heat transfer oil system. Molten sebacic acid is pumped by a metering pump and mixed with ammonia in a vaporizer and preheated to 300-350°C before entering the reactor containing the catalyst. The feed space velocity of sebacic acid is 0.2-1 h⁻¹. -1 The reaction temperature was controlled at 320~400℃, the reaction pressure (gauge pressure) was 0~0.5MPa, and the molar ratio of sebacic acid to ammonia was 1:(1~5). The reaction products were condensed in a condenser and then introduced into a gas-liquid separator to separate the gas and liquid phases. The liquid phase was collected and analyzed by gas chromatography. The evaluation results are shown in Table 1. The gas chromatography analysis conditions are as follows: Equipment: Shimadzu Chromatography System Column: HP-5 30m × 320um × 1um Detector: Temperature 330℃, Air flow rate 200 sccm, Hydrogen flow rate 30 sccm Inlet: Temperature 300℃, Pressure 15psi Column oven temperature: 50℃ (heating rate 25℃ / min) → 150℃ (hold for 5 min) → 150℃ (heating rate 25℃ / min) → 330℃ (hold for 5 min).
[0084] Table 1
[0085] As shown in Table 1, the catalysts prepared in Examples 1-5 of this invention exhibit excellent comprehensive performance in the synthesis reaction of sebacate. Under the reaction conditions, the conversion rate of sebacate in each example reached over 96%, with a maximum of 98.53%; the selectivity of sebacate was over 95%, with a maximum of 98.13%; and the catalyst lifespan was significantly extended, reaching 1220-1550 hours, far superior to conventional catalysts.
[0086] Compared with Example 1, Comparative Example 1, which does not contain transition metals and rare earth metals, has a conversion rate of only 89.25%, a selectivity of 89.17%, and a lifetime of only 240 hours. Comparative Example 2, which contains only transition metals, has a higher conversion rate (91.98%), but its selectivity has decreased to 85.83%. This demonstrates that the synergistic effect of transition metals and rare earth metals plays a key role in simultaneously improving catalytic activity, selectivity, and stability.
[0087] Compared to Example 4, Comparative Example 3 did not use pore-forming and pore-expanding agents, resulting in an average pore size of only 19 nm and poor pore size distribution concentration (10-50 nm accounted for only >43%). This led to a significant reduction in conversion rate (90.84%) and selectivity (78.36%), as well as insufficient mechanical strength (>47 N / particle). Comparative Example 4 used only pore-forming agents without pore-expanding agents, resulting in an average pore size of 24 nm and a 10-50 nm proportion of >72%. Although its performance was better than Comparative Example 3, its conversion rate (92.14%), selectivity (83.93%), and lifetime (510 h) were still significantly lower than those of the examples in this application. This confirms the importance of a specific pore structure (average pore size 30-40 nm, 10-50 nm proportion >90%) for the diffusion and desorption of macromolecular reactants and the suppression of side reactions.
[0088] It should be noted that the above description is a further detailed explanation of the present invention in conjunction with specific embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple improvements can be made without departing from the concept of the present invention, and all such improvements should be considered to fall within the scope of protection of the present invention.
Claims
1. A catalyst for the synthesis of sebacate, characterized in that, Includes a carrier and an active component, wherein, The carrier is a modified alumina carrier, which is obtained by forming acidified pseudoboehmite sol by oil-ammonia column method and then calcining it; the modified alumina carrier has a pore size distribution of 10~50nm accounting for >90%, and an average pore size of 30~40nm. The active component is a composite metal oxide containing transition metal oxides and rare earth metal oxides. The mass ratio of the carrier, the transition metal oxide, and the rare earth metal oxide is 100:(1~10):(1~10).
2. The catalyst for synthesizing sebacate according to claim 1, characterized in that, The catalyst has a pore volume of 0.4~0.85 ml / g, preferably 0.5~0.7 ml / g, and a specific surface area of 200~300 m² / g. 2 / g, preferably 220~260m 2 / g; And / or, the average pore size of the catalyst is 30~40 nm; And / or, the mechanical strength of the catalyst is >60N / particle, preferably 60~70N / particle.
3. The catalyst for synthesizing sebacate according to claim 1, characterized in that, The modified alumina support is one or a mixture of two of γ-Al2O3 or δ-Al2O3; And / or, the transition metal is at least one of Cr, Zn, Mn, Fe, Co, Ni, and Zr, preferably at least one of Cr, Zn, Mn, Fe, Ni, and Zr; And / or, the rare earth metal is at least one of La, Ce, Sm, and Pr.
4. The catalyst for synthesizing sebacate according to claim 1, characterized in that, The preparation method of the acidified boehmite sol includes: dispersing boehmite, a pore-forming agent, and a pore-expanding agent in water to obtain a suspension; and acidifying the suspension with an acid solution to obtain the acidified boehmite sol. Preferably, the pore-forming agent is at least one selected from methylcellulose, polyethylene glycol, polyacrylamide, and polyacrylamide; Preferably, the pore-expanding agent is at least one of starch, guar gum powder, hexamethylenetetramine, and sodium hydroxyethyl sulfonate cocoate. Preferably, the mass ratio of the pseudoboehmite, pore-forming agent, and pore-expanding agent is (80~90):(5~10):(5~10); Preferably, the solid content of the suspension is 25% to 35%; Preferably, the acid solution is a nitric acid solution; Preferably, the mass concentration of the acid solution is 20% to 30%, and the mass of the acid solution added is 15% to 25% of the total mass of the pseudoboehmite, pore-forming agent, and pore-expanding agent.
5. The catalyst for synthesizing sebacate according to claim 1, characterized in that, The oil-ammonia column method includes: adding the acidified pseudoboehmite sol into an oil-ammonia column to form gel spheres and allowing them to stand and age. Preferably, the temperature of the oil-ammonia column is 80~100℃; Preferably, the amount of oil-ammonia column used is such that the oil film thickness is 0.1~1mm and the ammonia water thickness is 100~200cm; Preferably, the static aging temperature is 80~100℃ and the time is 12~20h.
6. The catalyst for synthesizing sebacate according to claim 1, characterized in that, The calcination temperature is 400~600℃, and the calcination time is 4~8h; Preferably, the process also includes drying before the roasting operation; the drying temperature is 100~150℃, and the drying time is 5~10h.
7. A method for preparing the catalyst according to any one of claims 1-6, characterized in that, The preparation method includes: loading the metal salt of the active component onto the support, and then subjecting it to secondary calcination and hydration treatment to obtain the catalyst.
8. The preparation method according to claim 7, characterized in that, The metal salt of the active component is loaded onto the modified alumina support by means of equal volume impregnation or spray impregnation. And / or, the secondary calcination temperature is 500~600℃ and the time is 6~8h; Preferably, the process also includes drying before the second calcination, with a drying temperature of 100~150℃ and a drying time of 4~6 hours; And / or, the hydration treatment is performed at a temperature of 70~90℃ for a time of 5~10h; Preferably, the process further includes drying after hydration treatment at a temperature of 100-120°C for 4-6 hours.
9. A method for synthesizing sebacite nitrile by ammonolysis of sebacite, characterized in that, The method is carried out under the action of the catalyst described in any one of claims 1 to 6.
10. The method for synthesizing sebacite nitrile by ammonodehydration of sebacite according to claim 9, characterized in that, The method includes: mixing molten sebacic acid with ammonia gas and preheating it, then conducting an ammonia dehydration reaction under the action of a catalyst; the reacted material is condensed and the liquid phase is separated to obtain sebaconitrile product; Preferably, the molar ratio of sebacic acid to ammonia is 1:(1~5). Preferably, the feed space velocity of the sebacic acid is 0.2~1h. -1 ; Preferably, the preheating temperature is 300~350℃; Preferably, the reaction temperature is 320~400℃ and the reaction pressure is 0~0.5MPa.