A process for the synthesis of tetrahydropyrroles
By modifying the NaZSM-5 molecular sieve catalyst, the problems of low yield and low selectivity in the synthesis process of tetrahydropyrrole were solved, and the production of tetrahydropyrrole with high yield and high selectivity was achieved. The catalyst also showed good stability at high temperature.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INNER MONGOLIA ZHONGHUI BIOTECHNOLOGY CO LTD
- Filing Date
- 2026-04-30
- Publication Date
- 2026-07-21
AI Technical Summary
Existing tetrahydropyrrole synthesis processes suffer from low yields, low selectivity, and poor catalyst stability, making it difficult to meet the purity requirements of high-end applications.
Modified NaZSM-5 molecular sieves were used as catalysts. A hierarchical porous structure was formed through alkali treatment, ion exchange and calcination. Active components and modifying agents were loaded to form a catalyst with hydrodehydrogenation activity, which promoted the conversion of tetrahydrofuran to tetrahydropyrrole. The selectivity and stability were improved through acid synergy.
The yield and selectivity of tetrahydropyrrole were significantly improved, while the modified molecular sieve catalyst maintained good hydrothermal stability at high temperatures, avoiding side reactions and achieving efficient production.
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical raw material synthesis technology, and in particular to a synthesis process for tetrahydropyrrole. Background Technology
[0002] Tetrahydropyrrole (CAS 123-75-1), also known as pyrrolidine, is a secondary amine organic intermediate containing a five-membered nitrogen heterocycle. It is a colorless to pale yellow transparent liquid at room temperature with a characteristic amine odor. Its boiling point is 89.5±8.0℃, relative density is 0.8±0.1 g / cm³, refractive index is 1.428, and flash point is only 2.8℃. It is readily soluble in polar solvents such as water and ethanol. It is prone to discoloration upon exposure to light or humid air and must be stored in a sealed, light-protected container. As a core raw material in the fine chemical industry, tetrahydropyrrole has applications in many high-value-added fields, including pharmaceuticals, pesticides, electronic chemicals, polymer materials, and daily chemical products, and is a key building block for constructing complex molecular structures.
[0003] In the pharmaceutical field, tetrahydropyrrole is a core pharmacophore in the synthesis of anti-HIV drugs, antibiotics, anti-tumor drugs, and various cardiovascular drugs. Through alkylation and acylation reactions of its secondary amine groups, it can efficiently construct chiral centers and active molecular skeletons. Pharmaceutical-grade products have strict limitations on purity (≥99.0%), moisture content, and heavy metal content. In the pesticide field, it is a key raw material for synthesizing intermediates of neonicotinoid insecticides, fungicides, and herbicides, significantly improving the bioactivity and environmental compatibility of target products. In the electronic chemicals field, tetrahydropyrrole can serve as a precursor for ionic liquids, a monomer for OLED materials, and an additive for electrochemical energy storage electrolytes, exhibiting excellent conductivity and stability. In the polymer materials field, it acts as a crosslinking agent and functional monomer to enhance the mechanical strength and weather resistance of polyurethane, rubber, and other materials. It also has important applications in zeolite templates and desulfurizers. With the rapid development of downstream pharmaceutical and new energy materials industries, the market demand for tetrahydropyrrole continues to grow, placing higher demands on the efficiency, economy, and purity of its production processes.
[0004] Currently, the main industrial synthesis routes for tetrahydropyrrole include pyrrole catalytic hydrogenation, 1,4-butanediol / butanediamine ammoniation cyclization, γ-butyrolactone ammonolysis, and tetrahydrofuran ammoniation. Each route differs significantly in raw material cost, reaction conditions, yield, and equipment requirements. Pyrrole catalytic hydrogenation is the traditional mainstream process. Using pyrrole as a raw material, hydrogenation occurs under high pressure (3–5 MPa) and medium temperature (80–120 °C) conditions with noble metal catalysts such as Raney nickel and palladium on carbon (Pd / C). The product yield is ≥95% with high purity. However, this process has significant limitations: high-pressure hydrogen poses an explosion risk, requiring extremely high pressure resistance and safety protection for equipment; the noble metal catalyst is easily poisoned by impurities such as sulfur and chlorine in the raw materials, resulting in high regeneration costs and a complex recovery process, making it difficult to significantly reduce production costs.
[0005] The 1,4-butanediol ammoniation cyclization method uses 1,4-butanediol and ammonia as raw materials, undergoing an intramolecular dehydration cyclization reaction under the action of a solid acid catalyst. This route has readily available raw materials and a relatively mature process, but the reaction temperature needs to be controlled at 250–350℃, resulting in high energy consumption. Furthermore, the catalyst is prone to carbon deposition and deactivation, leading to a short continuous operating life. Product yields are mostly concentrated between 70% and 85%, which is insufficient to meet the purity requirements of high-end applications. The γ-butyrolactone ammonolysis method generates tetrahydropyrrole through lactone ring-opening, amination, and cyclization reactions. This reaction requires high temperatures of 200–300℃, produces numerous byproducts, and has high separation and purification costs, resulting in low overall energy efficiency. It is only suitable for small-scale production of specialty products. The electrolytic reduction method uses pyrrole as raw material, achieving reduction through electrolysis. However, it suffers from low current efficiency, high energy consumption, and difficulties in product separation, and has not yet achieved industrial-scale promotion.
[0006] Tetrahydrofuran ammoniation has become a key research and industrial application area in recent years due to its advantages such as low raw material cost, simple process, and high atom utilization. This method uses tetrahydrofuran and ammonia as raw materials, and a gas-phase catalytic amination cyclization reaction occurs under the action of a solid acid catalyst to directly generate tetrahydropyrrole. The core reaction pathway is as follows: tetrahydrofuran is first activated at the acidic site of the catalyst, undergoes a nucleophilic addition reaction with ammonia to generate an intermediate, and then undergoes intramolecular dehydration cyclization to form a five-membered nitrogen heterocycle, finally desorbing to obtain the tetrahydropyrrole product. Compared with other processes, tetrahydrofuran ammoniation does not require high-pressure hydrogen, resulting in lower equipment investment; the raw material tetrahydrofuran can be obtained through various pathways such as petroleum cracking and biomass conversion, making it widely available and cost-controllable, aligning with the modern industrial trend towards green and low-cost development.
[0007] For example, patent number CN121005668A discloses a "continuous flow process preparation method of tetrahydropyrrole", which includes: S101. Mixing porous Co3O4-based composite catalyst and CuAl metal oxide catalyst, and placing them in a continuous flow reactor, adjusting the reaction temperature to 300~350°C and the pressure to 0.5~1.5 MPa; S102. Continuously introducing tetrahydrofuran and ammonia into the continuous flow reactor to carry out a continuous catalytic reaction, and then collecting the reaction products in a gas-liquid separator after condensation to obtain tetrahydropyrrole. This method has the advantages of efficient mass and heat transfer, avoiding hot spot formation, shortening reaction time and reducing energy consumption, and can also reduce the use of organic solvents, which is green chemistry oriented. However, the highest yield of tetrahydropyrrole obtained by this method is 88.7%, which is relatively low.
[0008] Therefore, it is necessary to develop a synthesis process for tetrahydropyrrole with high yield, high selectivity, and stable catalyst. Summary of the Invention
[0009] The purpose of this invention is to provide a synthesis process for tetrahydropyrrole to solve the problems of low yield, low selectivity, and poor catalyst stability in current tetrahydropyrrole synthesis processes.
[0010] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a process for synthesizing tetrahydropyrrole, comprising the following steps: S1. NaZSM-5 molecular sieve is placed in sodium hydroxide solution and stirred, then filtered, washed and dried to obtain alkali-treated molecular sieve. S2. The alkali-treated molecular sieve obtained in step S1 is placed in an ammonium nitrate solution for ion exchange, filtered, washed, dried and then calcined to obtain hydrogen-form HZSM-5 molecular sieve. S3. The hydrogen-type HZSM-5 molecular sieve obtained in step S2 is placed in citric acid solution and stirred, filtered, washed and dried to obtain the modified hierarchical porous HZSM-5 molecular sieve. S4. Prepare an impregnation solution by mixing the active component and the modifying agent, impregnate the modified hierarchical porous HZSM-5 molecular sieve obtained in step S3 in the solution, and then dry and calcine to obtain the catalyst precursor. S5. The catalyst precursor obtained in step S4 is mixed with binder and additives, added to deionized water, kneaded and extruded into strips, dried and calcined to obtain the modified molecular sieve catalyst. S6. The modified molecular sieve catalyst obtained in step S5 is placed in a fixed bed. First, the air in the reactor is replaced with ammonia. Then, the temperature is raised and tetrahydrofuran and ammonia are continuously introduced. The reaction is carried out under positive pressure. After the reaction is completed, the crude tetrahydropyrrole is obtained by condensation. S7. Pump the crude tetrahydropyrrole obtained in step S6 into a distillation column and distill it under normal pressure. The concentration of tetrahydropyrrole to be measured is not less than 97%. Then, it enters a dehydration kettle, where calcium oxide is added for dehydration. Finally, it is distilled and condensed to obtain tetrahydropyrrole.
[0011] This application first involves alkali treatment of NaZSM-5 molecular sieves. In an alkaline environment, OH... - It preferentially and selectively attacks and hydrolyzes the Si-O-Si bonds, removing some framework silicon atoms. Mesoporous channels are then etched into the originally well-ordered microporous framework, resulting in a hierarchical porous structure. Subsequently, ion exchange is performed using ammonium nitrate, and the remaining H₂ after calcination... +By combining with the negative charge of the framework, Brønsted acidic active centers are formed, which can catalyze the activation and ring-opening of the CO bond in tetrahydrofuran and the dehydration and cyclization of the ammoniation intermediate. Then, a ternary weak acid is used to remove the amorphous non-framework aluminum remaining in the pores, repairing framework defects, clearing the silica-alumina debris in the pores, and improving the hydrothermal stability of the molecular sieve, resulting in a modified hierarchical porous HZSM-5 molecular sieve. The modified hierarchical porous HZSM-5 molecular sieve is then impregnated with a loading of active components and modifying agents. The active components and modifying agents diffuse uniformly into the micropores and mesopores of the molecular sieve with the solution, and through electrostatic adsorption and anchoring with the hydroxyl and acid centers on the surface of the molecular sieve, they are uniformly distributed throughout the pore surface. After reduction, elemental metal active centers with hydrogenation and dehydrogenation activity are generated, in which transition metals are selected as active components for catalysis. The imine species generated by the dehydration of the amination intermediate is rapidly hydrogenated to form tetrahydropyrrole, which simultaneously promotes the forward shift of the dehydrogenation-hydrogenation equilibrium of the reaction, significantly improving the conversion rate of tetrahydrofuran and the selectivity of tetrahydropyrrole, and avoiding side reactions of the intermediate. The modifier forms a strong interaction with the metal active center through electronic effects. On the one hand, it can anchor the metal nanoparticles and inhibit agglomeration and sintering during the high-temperature reaction process. On the other hand, it can further fine-tune the distribution of acid centers in the molecular sieve, supplement a small number of weak Lewis acid centers, and form acid synergy with Brønsted acid centers to further improve the selectivity of the cyclization reaction. At the same time, rare earth additives can improve the hydrothermal stability of the catalyst and reduce skeleton dealumination under high-temperature hydrothermal conditions.
[0012] In some embodiments, the concentration of the sodium hydroxide solution is 0.1~0.5 mol / L.
[0013] In some embodiments, the mass ratio of the NaZSM-5 molecular sieve to the volume ratio of the sodium hydroxide solution is 1 g:(5~15) ml.
[0014] In some embodiments, in step S1, the stirring conditions are stirring at 60~90°C for 0.5~3 hours.
[0015] In some embodiments, the concentration of the ammonium nitrate solution is 0.1~0.5 mol / L.
[0016] In some embodiments, in step S2, the mass ratio of the alkali-treated molecular sieve to the volume ratio of the ammonium nitrate solution is 1 g:(5~15) ml.
[0017] In some embodiments, in step S2, the ion exchange conditions are 80-90°C for 2-3 hours, and the process is repeated 2-3 times.
[0018] In some embodiments, in step S2, the calcination conditions are 500~600℃ for 3~5 hours.
[0019] In some embodiments, the concentration of the citric acid solution is 0.1~0.3 mol / L.
[0020] In some embodiments, in step S3, the mass ratio of the hydrogen-form HZSM-5 molecular sieve to the volume ratio of the citric acid solution is 1:(5~15).
[0021] In some embodiments, in step S3, the stirring conditions are stirring at 50~80°C for 1~4 hours.
[0022] In some embodiments, the active component is any one or more of copper nitrate, nickel nitrate, and cobalt nitrate.
[0023] In some embodiments, the modifying agent is lanthanum nitrate.
[0024] In some embodiments, in step S4, the mass ratio of the active component, the modifying agent, and the modified hierarchical porous HZSM-5 molecular sieve is (0.2~0.3):(0.02~0.04):1.
[0025] Preferably, in step S4, the mass ratio of the active component, the modifying agent, and the modified hierarchical porous HZSM-5 molecular sieve is 0.25:0.03:1.
[0026] In some embodiments, in step S4, the immersion conditions are immersion at 25~30°C for 6~24 hours.
[0027] In some embodiments, in step S4, the calcination conditions are calcination at 400~550℃ for 3~5 hours.
[0028] In some embodiments, in step S5, the mass ratio of the catalyst precursor to the binder is 1:(0.1~0.3).
[0029] Preferably, in step S5, the mass ratio of the catalyst precursor to the binder is 1:0.2.
[0030] In some embodiments, in step S5, the calcination conditions are calcination at 500~600℃ for 4~6 hours.
[0031] In some embodiments, the mass ratio of the additive is 1 to 3% of the total mass of the catalyst precursor and the binder.
[0032] Preferably, the mass ratio of the additive is 2% of the total mass of the catalyst precursor and the binder.
[0033] In some embodiments, the modified molecular sieve catalyst has a diameter of 1.5 to 3 mm and a length of 3 to 5 mm.
[0034] In some embodiments, in step S6, the molar ratio of tetrahydrofuran to ammonia is 1:(9~12).
[0035] Preferably, in step S6, the molar ratio of tetrahydrofuran to ammonia is 1:11.
[0036] In some implementations, the heating condition in step S6 is 300~350°C.
[0037] Preferably, in step S6, the heating condition is 320°C.
[0038] In some implementations, the positive pressure condition in step S6 is 1~1.5MPa.
[0039] Preferably, in step S6, the positive pressure condition is 1.3 MPa.
[0040] In some embodiments, in step S6, the liquid hourly space velocity (LHSV) of the tetrahydrofuran is 0.3 to 0.8 h⁻¹. -1 .
[0041] In some embodiments, the distillation temperature in step S7 is 85~95°C.
[0042] Preferably, in step S7, the distillation condition is 90°C.
[0043] Compared with the prior art, the present invention has the following beneficial effects: (1) The tetrahydropyrrole synthesis process of the present invention has a high yield and high selectivity of tetrahydropyrrole, and the self-made modified molecular sieve catalyst has good hydrothermal stability and can exert a long-lasting catalytic effect.
[0044] (2) The modified molecular sieve catalyst of the present invention first undergoes alkali treatment of NaZSM-5 molecular sieve, followed by ion exchange with ammonium nitrate, and then removal of amorphous non-framework aluminum remaining in the pores by a ternary weak acid, thereby repairing framework defects, clearing silicon-aluminum debris in the pores, and improving the hydrothermal stability of the molecular sieve. It is then impregnated with active components and modifying agents to form a loading. The active components are used to catalyze the rapid hydrogenation of imine species generated from the dehydration of the ammoniation intermediate to tetrahydropyrrole, while simultaneously promoting a positive shift in the dehydrogenation-hydrogenation equilibrium of the reaction, significantly improving the efficiency of the reaction. The conversion rate of tetrahydrofuran and the selectivity of tetrahydropyrrole are improved, and side reactions of intermediates are avoided. The modifier forms a strong interaction with the metal active center through electronic effects. On the one hand, it can anchor the metal nanoparticles and inhibit agglomeration and sintering during the high-temperature reaction process. On the other hand, it can further fine-tune the distribution of acid centers in the molecular sieve, supplement a small number of weak Lewis acid centers, and form acid synergy with Brønsted acid centers to further improve the selectivity of cyclization reaction. At the same time, rare earth additives can improve the hydrothermal stability of the catalyst and reduce skeleton dealumination under high-temperature hydrothermal environment. Detailed Implementation
[0045] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.
[0046] Unless otherwise specified, the post-processing operations described below, such as "mixing", "dispersing", "purging", "pressurizing", "depressurizing", "spinning", "stretching", "bundling and oiling", "circular blowing", "centrifugation", "filtration", and "drying", can be selected by those skilled in the art based on actual conditions, and are not further limited.
[0047] The analytical methods used in the embodiments and comparative examples of this application are as follows: Selectivity of tetrahydropyrrole = number of carbon atoms in tetrahydropyrrole in the product / (number of carbon atoms in tetrahydrofuran in the reactants - number of carbon atoms in tetrahydrofuran in the product) × 100%; The yield of tetrahydropyrrole = (number of moles of tetrahydropyrrole carbon in the product / number of moles of tetrahydrofuran carbon in the reactants) × 100%.
[0048] Example 1 A process for synthesizing tetrahydropyrrole includes the following steps: S1. Place 100g of NaZSM-5 molecular sieve in 1L of 0.3mol / L sodium hydroxide solution, heat to 80℃ and stir for 2h, filter, wash with deionized water until pH=7, and dry at 120℃ for 4h to obtain alkali-treated molecular sieve. S2. Place 100g of the alkali-treated molecular sieve obtained in step S1 in 1L of 0.3mol / L ammonium nitrate solution and heat to 85℃ for ion exchange for 2.5h. Repeat twice. Filter, wash with deionized water until pH=7, dry at 120℃ for 4h, and then calcine at 550℃ for 4h to obtain hydrogen-form HZSM-5 molecular sieve. S3. Place 100g of the hydrogen-form HZSM-5 molecular sieve obtained in step S2 into 1L of 0.2mol / L citric acid solution, heat to 70℃ and stir for 3h, filter, wash with deionized water until pH=6.5, and dry at 120℃ for 4h to obtain the modified hierarchical porous HZSM-5 molecular sieve. S4. Prepare an impregnation solution by mixing 25g of active component, 2.7g of lanthanum nitrate and 150ml of deionized water. Impregnate 100g of the modified hierarchical porous HZSM-5 molecular sieve obtained in step S3 in the solution. Impregnate at 27℃ for 12h, dry at 120℃ for 6h, and calcine at 500℃ for 4h to obtain the catalyst precursor. S5. Mix 100g of the catalyst precursor obtained in step S4 with 20g of pseudoboehmite and 2.4g of guar gum powder, add 50ml of deionized water, knead and extrude into strips, dry at 120℃ for 6h, and calcine at 550℃ for 5h to obtain a modified molecular sieve catalyst with a diameter of 2mm and a length of 4mm. S6. Place 100g of the modified molecular sieve catalyst obtained in step S5 into a fixed bed. First, replace the air in the reactor with ammonia, then raise the temperature to 320℃ and continuously introduce tetrahydrofuran and ammonia (molar ratio of 1:11, liquid hourly space velocity of tetrahydrofuran of 0.5h). -1 The reaction was carried out at 1.3 MPa, and the crude tetrahydropyrrole was obtained by condensation after the reaction was completed. S7. Pump the crude tetrahydropyrrole obtained in step S6 into a distillation column and distill it under atmospheric pressure (top temperature 70℃, bottom temperature 100℃, feed temperature 85℃, side stream temperature 88℃, reflux ratio 3:1). The concentration of tetrahydropyrrole to be tested is not less than 97%. Then, it enters a dehydration kettle, and 5% calcium oxide is added to it for dehydration for 4 hours. Finally, it is distilled at 90℃ and condensed to obtain tetrahydropyrrole.
[0049] The active components are copper nitrate and nickel nitrate mixed in a mass ratio of 1:1.15.
[0050] The yield of tetrahydropyrrole was 95.7%, the gas chromatographic purity of tetrahydropyrrole was 98.9%, and the selectivity of tetrahydropyrrole was 93.8%. After 10 cycles without catalyst replacement, the selectivity of tetrahydropyrrole was 92.3%.
[0051] Example 2 A process for synthesizing tetrahydropyrrole includes the following steps: S1. Place 100g of NaZSM-5 molecular sieve in 500ml of 0.5mol / L sodium hydroxide solution, heat to 60℃ and stir for 3h, filter, wash with deionized water until pH=7, and dry at 120℃ for 4h to obtain alkali-treated molecular sieve. S2. Place 100g of the alkali-treated molecular sieve obtained in step S1 in 500ml of 0.5mol / L ammonium nitrate solution and heat to 80℃ for ion exchange for 3h. Repeat twice. Filter, wash with deionized water until pH=7, dry at 120℃ for 4h, and then calcine at 500℃ for 5h to obtain hydrogen-form HZSM-5 molecular sieve. S3. Place 100g of the hydrogen-form HZSM-5 molecular sieve obtained in step S2 into 500ml of 0.3mol / L citric acid solution, heat to 50℃ and stir for 4h, filter, wash with deionized water until pH=6.5, and dry at 120℃ for 4h to obtain the modified hierarchical porous HZSM-5 molecular sieve. S4. Prepare an impregnation solution by mixing 20g of active component, 2g of lanthanum nitrate and 150ml of deionized water. Impregnate 100g of the modified hierarchical porous HZSM-5 molecular sieve obtained in step S3 in the solution. Impregnate at 25℃ for 24h, dry at 120℃ for 6h, and calcine at 400℃ for 5h to obtain the catalyst precursor. S5. Mix 100g of the catalyst precursor obtained in step S4 with 10g of pseudoboehmite and 1.1g of guar gum powder, add 50ml of deionized water, knead and extrude into strips, dry at 120℃ for 6h, and calcine at 500℃ for 6h to obtain a modified molecular sieve catalyst with a diameter of 1.5mm and a length of 3mm. S6. Place 100g of the modified molecular sieve catalyst obtained in step S5 into a fixed bed. First, replace the air in the reactor with ammonia, then raise the temperature to 300℃ and continuously introduce tetrahydrofuran and ammonia (molar ratio of 1:9, liquid hourly space velocity of tetrahydrofuran of 0.3h). -1 The reaction was carried out at 1 MPa, and the crude tetrahydropyrrole was obtained by condensation after the reaction was completed. S7. The crude tetrahydropyrrole obtained in step S6 is pumped into a distillation column and distilled at atmospheric pressure (top temperature 70℃, bottom temperature 100℃, feed temperature 85℃, side stream temperature 88℃, reflux ratio 3:1). The concentration of tetrahydropyrrole to be tested is not less than 97%. It is then introduced into a dehydration kettle, where 5% calcium oxide is added for dehydration for 4 hours. Finally, it is distilled at 85℃ and condensed to obtain tetrahydropyrrole.
[0052] The active components are copper nitrate and nickel nitrate mixed in a mass ratio of 1:1.15.
[0053] The yield of tetrahydropyrrole was 94.8%, the gas chromatographic purity of tetrahydropyrrole was 98.5%, and the selectivity of tetrahydropyrrole was 92.6%. After 10 cycles without catalyst replacement, the selectivity of tetrahydropyrrole was 91.2%.
[0054] Example 3 A process for synthesizing tetrahydropyrrole includes the following steps: S1. Place 100g of NaZSM-5 molecular sieve in 1.5L of 0.1mol / L sodium hydroxide solution, heat to 90℃ and stir for 0.5h, filter, wash with deionized water until pH=7, and dry at 120℃ for 4h to obtain alkali-treated molecular sieve. S2. Place 100g of the alkali-treated molecular sieve obtained in step S1 in 1.5L of 0.1mol / L ammonium nitrate solution and heat to 90℃ for ion exchange for 2h. Repeat 3 times. Filter, wash with deionized water until pH=7, dry at 120℃ for 4h, and then calcine at 600℃ for 3h to obtain hydrogen-form HZSM-5 molecular sieve. S3. Place 100g of the hydrogen-form HZSM-5 molecular sieve obtained in step S2 into 1.5L of 0.1mol / L citric acid solution, heat to 80℃ and stir for 1h, filter, wash with deionized water until pH=6.5, and dry at 120℃ for 4h to obtain the modified hierarchical porous HZSM-5 molecular sieve. S4. Prepare an impregnation solution by mixing 30g of active component, 4g of lanthanum nitrate and 150ml of deionized water. Impregnate 100g of the modified hierarchical porous HZSM-5 molecular sieve obtained in step S3 in the solution. Impregnate at 30℃ for 24h, dry at 120℃ for 6h, and calcine at 550℃ for 3h to obtain the catalyst precursor. S5. Mix 100g of the catalyst precursor obtained in step S4 with 30g of pseudoboehmite and 3.9g of guar gum powder, add 50ml of deionized water, knead and extrude into strips, dry at 120℃ for 6h, and calcine at 600℃ for 4h to obtain a modified molecular sieve catalyst with a diameter of 3mm and a length of 5mm. S6. Place 100g of the modified molecular sieve catalyst obtained in step S5 into a fixed bed. First, replace the air in the reactor with ammonia, then raise the temperature to 350℃ and continuously introduce tetrahydrofuran and ammonia (molar ratio of 1:12, liquid hourly space velocity of tetrahydrofuran of 0.8h). -1 The reaction was carried out at 1.5 MPa, and the crude tetrahydropyrrole was obtained by condensation after the reaction was completed. S7. Pump the crude tetrahydropyrrole obtained in step S6 into a distillation column and distill it under atmospheric pressure (top temperature 70℃, bottom temperature 100℃, feed temperature 85℃, side stream temperature 88℃, reflux ratio 3:1). The concentration of tetrahydropyrrole to be tested is not less than 97%. Then, it enters a dehydration kettle, and 5% calcium oxide is added to it for dehydration for 4 hours. Finally, it is distilled at 95℃ and condensed to obtain tetrahydropyrrole.
[0055] The active components are copper nitrate and nickel nitrate mixed in a mass ratio of 1:1.15.
[0056] The yield of tetrahydropyrrole was 95.6%, the gas chromatographic purity of tetrahydropyrrole was 98.2%, and the selectivity of tetrahydropyrrole was 93.1%. After 10 cycles without catalyst replacement, the selectivity of tetrahydropyrrole was 92.0%.
[0057] Example 4 A synthesis process for tetrahydropyrrole, the specific implementation method is the same as in Example 1, except that the active component is 15g.
[0058] The yield of tetrahydropyrrole was 90.5%, the gas chromatographic purity of tetrahydropyrrole was 97.5%, and the selectivity of tetrahydropyrrole was 87.9%. After 10 cycles without catalyst replacement, the selectivity of tetrahydropyrrole was 82.2%.
[0059] Example 5 A synthesis process for tetrahydropyrrole, the specific implementation method is the same as in Example 1, except that the active component is 35g.
[0060] The yield of tetrahydropyrrole was 93.8%, the gas chromatographic purity of tetrahydropyrrole was 98.2%, and the selectivity of tetrahydropyrrole was 89.5%. After 10 cycles without catalyst replacement, the selectivity of tetrahydropyrrole was 83.9%.
[0061] Comparative Example 1 A synthesis process for tetrahydropyrrole is described, with the specific implementation method being the same as in Example 1, except that step S1 is omitted and NaZSM-5 molecular sieve is directly used instead of the alkali-treated molecular sieve in step S2.
[0062] The yield of tetrahydropyrrole was 78.9%, the gas chromatographic purity of tetrahydropyrrole was 98.3%, and the selectivity of tetrahydropyrrole was 83.2%. After 10 cycles without catalyst replacement, the selectivity of tetrahydropyrrole was 73.9%.
[0063] Comparative Example 2 A synthesis process for tetrahydropyrrole is described, with the specific implementation method being the same as in Example 1, except that step S3 is omitted, and the hydrogen-form HZSM-5 molecular sieve obtained in step S2 is directly used to replace the modified hierarchical porous HZSM-5 molecular sieve in step S4.
[0064] The yield of tetrahydropyrrole was 85.2%, the gas chromatographic purity of tetrahydropyrrole was 97.9%, and the selectivity of tetrahydropyrrole was 87.3%. After 10 cycles without catalyst replacement, the selectivity of tetrahydropyrrole was 83.1%.
[0065] Comparative Example 3 A synthesis process for tetrahydropyrrole, the specific implementation method is the same as in Example 1, except that lanthanum nitrate is not added in step S4.
[0066] The yield of tetrahydropyrrole was 90.0%, the gas chromatographic purity of tetrahydropyrrole was 98.6%, and the selectivity of tetrahydropyrrole was 88.8%. After 10 cycles without catalyst replacement, the selectivity of tetrahydropyrrole was 84.2%.
[0067] Comparative Example 4 A synthesis process for tetrahydropyrrole is described, with the specific implementation method being the same as in Example 1, except that no active component is added in step S4.
[0068] The yield of tetrahydropyrrole was 48.6%, the gas chromatographic purity of tetrahydropyrrole was 97.2%, and the selectivity of tetrahydropyrrole was 72.2%. After 10 cycles without catalyst replacement, the selectivity of tetrahydropyrrole was 61.8%.
[0069] According to the experimental results, the synthesis processes of tetrahydropyrrole in Examples 1-3 of this application have high yield, purity, and high selectivity, and the process still maintains good selectivity after 10 cycles. Examples 4 and 5 changed the mass ratio of active component, modifier, and modified hierarchical HZSM-5 molecular sieve. The reduction of active component resulted in insufficient hydrogenation active center density in the prepared catalyst, leading to a decrease in catalytic performance. The higher proportion of active component caused severe agglomeration of metal nanoparticles, a sharp drop in the utilization rate of active sites, and the possible generation of by-products, resulting in a decrease in catalytic effect. Comparative Example 1, due to the omission of step S1, had high catalyst diffusion resistance, resulting in a significant decrease in yield and selectivity, and severe deactivation after the cycle process. Comparative Example 2, due to the omission of step S3, had a mismatch in acid center distribution, exacerbated side reactions, and significantly decreased yield, selectivity, and stability. Comparative Example 3, due to the absence of lanthanum nitrate, had metal active centers that were prone to sintering, resulting in decreased hydrothermal stability of the catalyst and a decrease in catalytic performance. Comparative Example 4, due to the absence of active component, could not achieve rapid hydrogenation of imine intermediates, resulting in a decrease in catalyst performance.
[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A process for synthesizing tetrahydropyrrole, characterized in that, Includes the following steps: S1. NaZSM-5 molecular sieve is placed in sodium hydroxide solution and stirred, then filtered, washed and dried to obtain alkali-treated molecular sieve. S2. The alkali-treated molecular sieve obtained in step S1 is placed in an ammonium nitrate solution for ion exchange, filtered, washed, dried and then calcined to obtain hydrogen-form HZSM-5 molecular sieve. S3. The hydrogen-type HZSM-5 molecular sieve obtained in step S2 is placed in citric acid solution and stirred, filtered, washed and dried to obtain the modified hierarchical porous HZSM-5 molecular sieve. S4. Prepare an impregnation solution by mixing the active components and modifying agents, impregnate the modified hierarchical porous HZSM-5 molecular sieve obtained in step S3 in the solution, and then dry and calcine to obtain the catalyst precursor. S5. The catalyst precursor obtained in step S4 is mixed with binder and additives, added to deionized water, kneaded and extruded into strips, dried, and calcined to obtain the modified molecular sieve catalyst. S6. The modified molecular sieve catalyst obtained in step S5 is placed in a fixed bed. First, the air in the reactor is replaced with ammonia. Then, the temperature is raised and tetrahydrofuran and ammonia are continuously introduced. The reaction is carried out under positive pressure. After the reaction is completed, the crude tetrahydropyrrole is obtained by condensation. S7. The crude tetrahydropyrrole obtained in step S6 is pumped into a distillation column and distilled at atmospheric pressure. The concentration of tetrahydropyrrole to be measured is not less than 97%. The product is then transferred to a dehydration vessel, where calcium oxide is added for dehydration. Finally, the product is distilled and condensed to obtain tetrahydropyrrole.
2. The synthesis process of tetrahydropyrrole according to claim 1, characterized in that, The active component is any one or more of copper nitrate, nickel nitrate, and cobalt nitrate.
3. The synthesis process of tetrahydropyrrole according to claim 1, characterized in that, The modifying agent is lanthanum nitrate.
4. The synthesis process of tetrahydropyrrole according to claim 1, characterized in that, In step S4, the mass ratio of the active component, the modifying agent, and the modified hierarchical porous HZSM-5 molecular sieve is (0.2~0.3):(0.02~0.04):
1.
5. The synthesis process of tetrahydropyrrole according to claim 1, characterized in that, In step S5, the mass ratio of the catalyst precursor to the binder is 1:(0.1~0.3).
6. The synthesis process of tetrahydropyrrole according to claim 1, characterized in that, In step S5, the mass of the additive is 1-3% of the total mass of the catalyst precursor and the binder.
7. The synthesis process of tetrahydropyrrole according to claim 1, characterized in that, In step S6, the molar ratio of tetrahydrofuran to ammonia is 1:(9~12).
8. The synthesis process of tetrahydropyrrole according to claim 1, characterized in that, In step S6, the heating condition is 300~350℃.
9. The synthesis process of tetrahydropyrrole according to claim 1, characterized in that, In step S6, the positive pressure condition is 1~1.5MPa.
10. The synthesis process of tetrahydropyrrole according to claim 1, characterized in that, In step S7, the distillation temperature is 85~95℃.
Citation Information
Patent Citations
Continuous flow process preparation method of pyrrolidine
CN121005668A