Application of samarium-doped zirconium-titanium composite oxides in catalytic reactions of lactone ring-opening, amination, cyclization and N-alkylation

Abstract

This application discloses the application of samarium-doped zirconium-titanium composite oxides in catalyzing lactone ring-opening, amination, cyclization, and N-alkylation reactions. It belongs to the field of chemical synthesis technology. This invention uses a novel samarium-doped zirconium-titanium composite oxide as a catalyst. This catalyst possesses abundant oxygen vacancies and Lewis acid sites, enabling it to efficiently catalyze lactone ring-opening, amination, cyclization, and N-alkylation reactions, lowering the reaction energy barrier. Using this catalyst, N-butylcaprolactam, N-methylaniline, and 1-(3-methoxypropyl)-2-pyrrolidone were successfully prepared. The preparation method is simple, environmentally friendly, highly atom-economical, and suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and more specifically to the application of samarium-doped zirconium-titanium composite oxides in catalytic reactions of lactone ring-opening, aminolysis, cyclization and N-alkylation. Background Technology

[0002] N-substituted lactams and N-alkylated aromatic amines, whose general formulas can be represented as N-substituted lactams and N-monoalkylated amines respectively, are key advanced intermediates for constructing high-performance pharmaceuticals, dyes, and functional materials. For example, N-butylcaprolactam is a core fragment in the synthesis of antidepressants, N-methylaniline is an important precursor for azo dyes, and 1-(3-methoxypropyl)-2-pyrrolidone is a pharmaceutical intermediate in the synthesis of the sedative-hypnotic drug zopiclone. Although these target molecules differ in structure, their industrial synthesis routes all rely on the N-alkylation / amidation reaction of amine compounds with lactones or alkylating agents, and they all face the following major technical challenges:

[0003] First, poor atom economy and severe environmental pollution are common bottlenecks. Some existing technologies use halogenated hydrocarbons as alkylating agents. For example, the synthesis of 1-(3-methoxypropyl)-2-pyrrolidone requires the prior preparation of 3-methoxy-1-bromopropane; the synthesis of N-alkylcaprolactam or N-methylaniline also requires the use of corresponding halogenated hydrocarbons. This route is not only lengthy, but more critically, it introduces halogen atoms that do not ultimately enter the product, generating large amounts of halogen-containing wastewater and waste residue, severely violating green chemistry principles and incurring high subsequent treatment costs. For example, the production of 3-methoxy-1-bromopropane requires the discharge of approximately 5-8 tons of bromine-containing wastewater per ton of product produced, with bromide ion concentrations exceeding 1000 ppm, and treatment costs accounting for 15%-20% of the total cost.

[0004] Secondly, the selectivity control of the reaction process is difficult, leading to poor yield and purity. In the N-alkylation of amine compounds, achieving high selectivity in generating the target monoalkylated product (such as N-methylaniline) rather than the over-alkylated byproduct (such as N,N-dimethylaniline) is a major challenge. Simultaneously, in the aminolysis-cyclization reaction of lactones, competitive ring-opening side reactions, elimination reactions, and polymerization reactions significantly reduce the selectivity of the target lactam. Traditional processes rely on strong bases such as sodium hydride and sodium alkoxide, or noble metal catalysts (such as iridium catalysts) to activate the reactants. However, these catalytic systems are often difficult to precisely control the reaction pathway and pose safety hazards (such as the explosiveness of sodium hydride upon contact with water) or metal residue problems.

[0005] Furthermore, it is difficult to simultaneously achieve both universality and economic efficiency in catalysts and processes, and existing mainstream catalytic systems still have significant technical shortcomings. Although heterogeneous metal oxide catalytic systems have been developed in this field to replace traditional base catalysis and noble metal catalysis systems to address the above problems, such as the ZrTiO composite oxide catalyst disclosed in CN115646782A, which utilizes its Lewis acidic sites to catalyze the ring-opening and transesterification reactions of lactones, thus solving the problem of metal residue to some extent, this pure zirconium-titanium composite oxide catalyst suffers from problems such as low oxygen vacancy numbers, low catalytic activity, and poor regeneration stability. The lactone conversion rate is less than 90%, and the activity decays rapidly after multiple cycles, making it difficult to meet the needs of continuous industrial production. CN114872345A discloses a Ce-doped ZrTiO4 composite oxide catalyst, which improves catalytic activity by controlling the oxygen vacancy concentration through rare earth doping. However, it still suffers from insufficient selective control ability, easily generating over-alkylation byproducts in amine N-alkylation reactions, and the synergistic effect between rare earth and zirconium-titanium is weak, and the long-term regeneration stability of the catalyst has not been significantly improved. In addition to these, existing technologies include improved solutions such as biomass carbon-supported bimetallic catalysts and tin-based catalysts. However, these methods are generally limited by drawbacks such as high catalyst cost, complex preparation, harsh reaction conditions (e.g., high temperature and high pressure), or narrow substrate applicability. A prominent problem is that most catalysts are designed for a specific type of reaction, lacking universality and unable to adapt to different types of nitrogen functionalization reactions, from lactone amination to N-alkylation. This results in fragmented technological barriers and makes it difficult to form a platform-based solution.

[0006] Therefore, there is an urgent need in the field to develop a novel catalytic system with broad applicability that can efficiently catalyze a variety of nitrogen functionalization reactions (including the amination and cyclization of lactones and the selective N-alkylation of amines). For N-butylcaprolactam, N-methylaniline and 1-(3-methoxypropyl)-2-pyrrolidone, developing a green preparation process that is simple in steps, environmentally friendly, atom-economical and suitable for large-scale production is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention develops the application of samarium-doped zirconium-titanium composite oxides in catalytic lactone ring-opening, amination, cyclization and N-alkylation reactions, avoiding the use of haloalkanes and realizing green synthesis from the source; it has high activity and high selectivity, effectively suppressing side reactions; it is non-toxic, stable and recyclable, reducing production costs and environmental footprint.

[0008] To solve the above-mentioned technical problems, this application adopts the following technical solution: The primary objective of this application is to provide: the application of a samarium-doped zirconium-titanium composite oxide in the catalytic reaction of lactone compounds with amine compounds, wherein the general formula of the samarium-doped zirconium-titanium composite oxide is Smx Zr TizO2-δ, where x is x=0.05-0.15, y=0.5-0.7, z=0.25-0.35, and δ is oxygen vacancy; The reaction includes ring-opening, aminolysis and cyclization steps of the lactone; The lactone compound includes γ-butyrolactone or ε-caprolactone; The amine compounds include ammonia, aliphatic amines, or aromatic amines.

[0009] Another object of this application is to provide: the application of a samarium-doped zirconium-titanium composite oxide in catalytic N-alkylation reactions, wherein the general formula of the samarium-doped zirconium-titanium composite oxide is Sm x Zr TizO2-δ, where x=0.05-0.15, y=0.5-0.7, z=0.25-0.35, and δ represents an oxygen vacancy; the N-alkylation reaction is a reaction in which dimethyl carbonate is used as the alkylating agent.

[0010] Another object of this application is to provide a method for preparing the samarium-doped zirconium-titanium composite oxide, comprising the following steps: (1) Preparation of precursor solutions: Prepare aqueous solutions containing zirconium source, alcoholic solutions containing titanium source and aqueous solutions containing samarium source respectively; (2) Low-temperature co-precipitation: Mix the three solutions obtained in step (1), add ammonia dropwise to the mixture under ice-water bath cooling and stirring conditions until the pH is 9.5-10.0, age for 20-24 hours, centrifuge and wash until no Cl- is detected, and the resulting filter cake is vacuum dried to obtain the precursor; (3) Programmable temperature controlled calcination: The dried precursor is subjected to the following heat treatments in sequence: a. Dehydration stage: Heat to 245-265℃ at a heating rate of 1-1.5℃ / min, and dry for 2-3 hours; b. Crystal phase transformation stage: Under air atmosphere, heat to 530-560℃ at a heating rate of 2-4℃ / min and heat for 3 hours; c. Oxygen vacancy control stage: Replace the atmosphere in the furnace with nitrogen atmosphere, and raise the temperature to 730-760℃ at a heating rate of 4-6℃ / min, dry for 1.5-3.0h, and then cool to room temperature; (4) Molding and activation: Grind, sieve and press the calcined product obtained in step (3) into a tablet to obtain the samarium-doped zirconium-titanium composite oxide; activate it in an air atmosphere at 380-430℃ for 1.5-3.0 hours before use.

[0011] As a preferred technical solution, in step (1), the zirconium source is ZrOCl2·8H2O, the titanium source is Ti(OC4H9)4, and the samarium source is Sm(NO3)3·6H2O; the alcohol solution containing the titanium source is prepared under nitrogen protection, and the solvent used is anhydrous ethanol; the molar ratio of the zirconium source, titanium source and samarium source is 0.06 : 0.03 : 0.01.

[0012] As a preferred technical solution, the temperature of the ice-water bath in step (2) is maintained at 10±2℃; the vacuum drying time is 12h; As a preferred technical solution, in step (3), step c, the specific operation of the oxygen vacancy control stage is as follows: first, use high-purity nitrogen to replace the furnace 3 to 5 times to make the oxygen volume content in the furnace ≤0.3%, and then perform heat treatment under nitrogen atmosphere. As a preferred technical solution, in step (4), the sieving is sieved through a 200-mesh sieve; the tableting is pressed into granules with a diameter of 3 mm.

[0013] Another object of this application is to provide: samarium-doped zirconium-titanium composite oxide prepared by the above method.

[0014] Another object of this application is to provide: a method for synthesizing 1-(3-methoxypropyl)-2-pyrrolidone, using the aforementioned samarium-doped zirconium-titanium composite oxide as a catalyst, and catalyzing γ-butyrolactone, 3-methoxy-1-propanol and ammonia in a one-pot catalytic transesterification and aminolysis-cyclization tandem reaction to prepare 1-(3-methoxypropyl)-2-pyrrolidone; The molar ratio of γ-butyrolactone to 3-methoxy-1-propanol is 1:1-1.3; The amount of catalyst added is 2.5-5% of the total mass of the reactants.

[0015] As a preferred technical solution, the method for synthesizing 1-(3-methoxypropyl)-2-pyrrolidone includes the following steps: (1) Mix γ-butyrolactone, 3-methoxy-1-propanol and the pre-activated catalyst until homogeneous. Under the condition of oxygen content <0.1%, heat to 180±5℃ at 2-5℃ / min, and then carry out transesterification reaction under constant temperature and autogenous pressure to prepare 4-hydroxybutyric acid-3-methoxypropyl ester. (2) Ammonia gas was introduced into the reaction system of step (1) and the pressure was controlled at 2.8-3.5 MPa. The aminolysis-cyclization reaction was completed at 200±5℃ to prepare crude product 1-(3-methoxypropyl)-2-pyrrolidone. (3) The crude product was cooled and filtered to remove the catalyst, and then distilled under reduced pressure to prepare 1-(3-methoxypropyl)-2-pyrrolidone.

[0016] As a preferred technical solution, the stirring speed in step (1) is 260-360 rpm; the stirring time is 10-15 min; the self-generated pressure is in the range of 0.8-1.2 MPa; when the conversion rate of γ-butyrolactone is >99.9%, the transesterification reaction ends. As a preferred technical solution, the amount of ammonia gas used in step (2) is 3-4.5 times the molar amount of γ-butyrolactone; the aminolysis-cyclization reaction ends when the conversion rate of the intermediate product 4-hydroxy-N-(3-methoxypropyl)butyramide is ≥99.8%. As a preferred technical solution, the cooling temperature in step (3) is 25°C; the process of vacuum distillation is as follows: under the vacuum condition of maintaining the system pressure at 5 mmHg, the fraction with a boiling point temperature between 100-105°C is collected.

[0017] Another object of this application is to provide: a method for synthesizing N-butylcaprolactam, using the aforementioned samarium-doped zirconium-titanium composite oxide as a catalyst, and catalyzing ε-caprolactone and n-butylamine through a one-pot tandem reaction of transesterification and aminolysis-cyclization to prepare N-butylcaprolactam; The molar ratio of ε-caprolactone to n-butylamine is 1:0.9-1.3; The amount of catalyst added is 2-5% of the total mass of the reactants.

[0018] The role of the catalyst in the synthesis of N-butylcaprolactam is as follows: (1) Lewis acid-catalyzed ring-opening of lactones at Zr-Ti heterostructures: The ring strain of ε-caprolactone (six-membered ring) requires the activation of the ester group (C=O) by the Lewis acid site. Zr in the catalyst... 4+ and Ti 4+ The valence difference forms a heterogeneous interface, generating strong Lewis acid sites that can polarize the C=O bond of ε-caprolactone and promote the nucleophilic attack of n-butylamine. (2) Sm 3+ The ammonia complexing ability accelerates aminolysis: The nitrogen atom in n-butylamine (R-NH2) has a lone pair of electrons, which can react with Sm 3+ The 4f empty orbitals form coordinate bonds ([Sm-NH2R)). 3+ This enhances the nucleophilicity of the amino group and lowers the activation energy of the aminolysis reaction; (3) Oxygen vacancies promote dehydration and cyclization: After ring opening, the intermediate undergoes dehydration and cyclization to form a lactam. Oxygen vacancies on the catalyst surface can adsorb the hydroxyl groups (-OH) of the intermediate, promoting intramolecular cyclization through hydrogen abstraction (generating H2O). Another object of this application is to provide: a method for synthesizing N-methylaniline, using the aforementioned samarium-doped zirconium-titanium composite oxide as a catalyst, and catalyzing the aminolysis and methyl transfer reaction of aniline and dimethyl carbonate in a "one-pot" process to prepare N-methylaniline; The molar ratio of aniline to dimethyl carbonate is 1:1.7-2.2; The amount of catalyst added is 1.8-5% of the total mass of the reactants.

[0019] The reaction between dimethyl carbonate (DMC) and aniline is a nucleophilic substitution-methyl transfer reaction: aniline (Ar-NH2) acts as a nucleophile to attack the methyl carbon of DMC, resulting in aminolysis (Ar-NH2 + CH3O-CO-OCH3 → Ar-NH-CH3 + CH3OH + CO2). A catalyst is required to simultaneously satisfy the following conditions: activate the carbonyl group of DMC (requiring a Lewis acid site); and inhibit overmethylation (avoiding the formation of N,N-dimethylaniline).

[0020] The role of catalysts in the synthesis of N-methylaniline is as follows: ① Zr-Ti heterostructure activation of DMC: The carbonyl group (C=O) of DMC can be converted to Lewis acidic sites (Zr) on the catalyst surface. 4+ / Ti 4+ Polarization forms positively charged carbon centers (δ). + C=O), enhancing the nucleophilic attack capability of aniline; ② Sm 3+ Selective regulatory effects: Sm 3+ The 4f orbital electron cloud density is low, and its coordination ability with aniline is weaker than that of NH3, which can avoid the deactivation of the amino group caused by excessive complexation. At the same time, it inhibits secondary methylation through steric hindrance (i.e., N-methylaniline is difficult to react further with DMC to generate N,N-dimethylaniline). ③ Removal capacity of byproducts from oxygen vacancies: The methanol (CH3OH) generated in the reaction can be removed from the catalyst surface through adsorption-desorption of oxygen vacancies, thus avoiding product inhibition.

[0021] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: (1) A novel samarium-doped zirconium-titanium composite oxide catalyst is used to catalyze the ring-opening, amination, cyclization and N-alkylation reaction steps of lactone. The catalyst has abundant oxygen vacancies and Lewis acid sites, which can efficiently catalyze the ring-opening, amination, cyclization and N-alkylation reactions of lactone and reduce the reaction energy barrier.

[0022] (2) The catalyst used in this application can be recycled and regenerated, and it remains active after being recycled, which reduces costs and is in line with the principles of green chemistry.

[0023] (3) The novel samarium-doped zirconium-titanium composite oxide was used to catalyze a variety of nitrogen functionalization reactions (including the amination and cyclization of lactones and the selective N-alkylation of amines), and the preparation of N-butylcaprolactam, N-methylaniline and 1-(3-methoxypropyl)-2-pyrrolidone was achieved. The method is simple, environmentally friendly, highly atom-economical and suitable for large-scale production. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 The structural formula is: 1-(3-methoxypropyl)-2-pyrrolidone. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0027] Example 1 Samarium-doped zirconium-titanium composite oxide (Sm-ZrTiO4, Sm 0.1 Zr 0.6 Ti 0.3 Preparation of O2-δ catalyst (coprecipitation-step calcination method) Catalyst reagent preparation: Zirconium oxychloride: purity ≥99.9%, Fe³ + <50ppm; Tetrabutyl titanate: purity ≥99.5%, hydrolytic stability qualified; Samarium nitrate: purity ≥ 99.99%, total rare earth impurities < 0.1%; Anhydrous ethanol: analytical grade, water content ≤0.1%; Ammonia solution: Heavy metals <5ppm, no sulfides; Deionized water: conductivity ≤1 μS / cm, see Table 1 for details.

[0028] Table 1. Reagents and their functions used in the preparation of samarium-doped zirconium-titanium composite oxides

[0029] (1) Preparation of precursor solution Zirconium solution: ZrOCl2·8H2O (22.32 g, 0.06 mol) dissolved in 200 mL of deionized water at 60 °C; Titanium solution: Ti(OC4H9)4 (10.21 g, 0.03 mol) dissolved in 50 mL of anhydrous ethanol (under nitrogen protection); Samarium solution: Sm(NO3)3·6H2O (4.44g, 0.01mol) dissolved in 100mL of deionized water.

[0030] (2) Low-temperature coprecipitation Mix the three solutions and maintain the mixture in an ice-water bath at 10±2℃; add ammonia dropwise with stirring until the pH reaches 9.5-10.0, and age for 20-24 hours; centrifuge and wash until no Cl is visible. - (AgNO3 test negative), filter cake vacuum dried for 12 hours; (3) Programmable temperature controlled calcination a. Dehydration stage: Place the dried filter cake into a muffle furnace, control the heating rate to 1-1.5℃ / min, and dry at 245-265℃ for 2-3 hours; b. Crystal phase transformation: Then, in an air atmosphere, control the heating rate to 2-4℃ / min, raise the temperature to 530-560℃, and heat for 3 hours; c. Oxygen vacancy control: Replace with high-purity nitrogen 3-5 times until the oxygen volume content in the furnace is ≤0.3%. Under nitrogen atmosphere, control the heating rate at 4-6℃ / min and bake at 730-760℃ for 1.5-3.0h. Cool to room temperature.

[0031] (4) Molding and activation: The calcined product obtained in step (3) is ground through a 200-mesh sieve and pressed into particles with a diameter of 3mm to obtain samarium-doped zirconium-titanium composite oxide. Before use, it is activated in air at 380-430℃ for 1.5-3.0 hours.

[0032] To verify the catalytic performance of the samarium-doped zirconium-titanium composite oxide prepared in Example 1 of this application, its thermal stability, transesterification activity, amine decyclization activity, and target product selectivity were tested. The experimental results are shown in Table 2. Table 2 Sm 0.1 Zr 0.6 Ti 0.3 O2-δ catalytic performance indicators

[0033] Catalyst activity retention rate: Based on the yield at the time of first use (100%) Calculate the first n times The ratio of the yield of the cycle to the yield of the first cycle.

[0034] Target product yield: The purity of the product after vacuum distillation was determined by gas chromatography (GC, HP-5 column, FID detector), and the yield was calculated (yield = actual product mass / theoretical product mass × 100%).

[0035] Results analysis: As shown in Table 2, the samarium-doped zirconium-titanium composite oxide has good catalytic performance.

[0036] Example 2 Samarium-doped zirconium-titanium composite oxide (Sm-ZrTiO4, Sm 0.05 Zr 0.5 Ti 0.25 Preparation of O2-δ catalyst (coprecipitation-step calcination method) The other operations are the same as in Example 1, except that the molar ratio of samarium solution, zirconium solution and titanium solution is different during the preparation of the precursor solution, which is 0.05:0.5:0.25. The catalytic performance indicators are shown in Table 3.

[0037] Table 3 Sm 0.05 Zr 0.5 Ti 0.25 O2-δ catalytic performance indicators

[0038] Example 3 Samarium-doped zirconium-titanium composite oxide (Sm-ZrTiO4, Sm 0.15 Zr 0.7 Ti 0.35 Preparation of O2-δ catalyst (coprecipitation-step calcination method) The other operations are the same as in Example 1, except that the molar ratio of samarium solution, zirconium solution and titanium solution is different during the preparation of the precursor solution, which is 0.15:0.7:0.35. The catalytic performance indicators are shown in Table 4.

[0039] Table 4Sm 0.15 Zr 0.7 Ti 0.35 O2-δ catalytic performance indicators

[0040] Example 4 A method for preparing 1-(3-methoxypropyl)-2-pyrrolidone includes the following steps: Process route: γ-Butyrolactone → [transesterification] → 4-hydroxybutyric acid-3-methoxypropyl ester → [ammonolysis] → 4-hydroxy-N-(3-methoxypropyl)butyramide → [dehydration cyclization] → target product.

[0041] raw material: γ-Butyrolactone (CAS: 96-48-0): a five-membered ring lactone (molecular weight 86.1, purity ≥99%). 3-Methoxy-1-propanol (CAS: 3714-73-0): A methoxyl-containing fatty alcohol (molecular weight 90.1, purity ≥98%). Ammonia (NH3) (liquid ammonia or high-purity gaseous ammonia, purity ≥99.9%) (1) Clean the 316L stainless steel high-pressure reactor (500 mL) with dilute nitric acid (5%), rinse with deionized water until neutral, and dry at 120℃ for later use. Catalyst activation: Sm-ZrTiO4 catalyst (Sm 0.1 Zr 0.6 Ti 0.3 O2-δ) is activated in air at 380-430℃ in a muffle furnace for 1.5-3.0h (oxygen vacancy control), and then sealed for later use after cooling; (2) Transesterification reaction: Mechanism: γ-Butyrolactone undergoes transesterification with 3-methoxy-1-propanol under Sm-ZrTiO4 catalysis to generate 4-hydroxybutyric acid-3-methoxypropyl ester.

[0042] γ-Butyrolactone (86.1 g, 1 mol), 3-methoxy-1-propanol (117.1 g, 1.3 mol, 30% excess to promote equilibrium), and activated catalyst (Samarium-doped zirconium-titanium composite oxide prepared in Example 1) (8.2 g, 4 wt%) were added to the reactor. The mixture was stirred at 300 rpm for 10 min until homogeneous. Nitrogen gas was introduced into the reactor three times until the oxygen content was <0.1%. The temperature was slowly increased to 180±5℃ at a rate of 3℃ / min, and the pressure was increased to approximately 0.8-1.2 MPa. The reaction was carried out at the same temperature and pressure for 4 hours. When the conversion rate of γ-butyrolactone was >99.9% as monitored by HPLC, 4-hydroxybutyric acid-3-methoxypropyl ester was prepared. The reaction equation is as follows: (CH2)3OC=O+HO-(CH2)3-OCH3→HO-(CH2)3COO-(CH2)3-OCH3 (3) Amine hydrolysis-cyclization reaction: Mechanism: The precursor is first aminohydrolyzed in an ammonia environment to 4-hydroxy-N-(3-methoxypropyl)butyramide, and then dehydrated and cyclized.

[0043] 3 mol of liquid ammonia (or gaseous ammonia, controlled by a mass flow meter) was introduced into the reactor, and the pressure was adjusted to 3.0 MPa (maintaining the partial pressure of ammonia). The temperature was controlled at 200±5℃, and the reaction was carried out at a constant temperature for 6 hours. The reaction was terminated when the conversion rate of the intermediate 4-hydroxy-N-(3-methoxypropyl)butyramide was 99.8% as monitored by GC-MS, thus preparing the crude product 1-(3-methoxypropyl)-2-pyrrolidone. The reaction equation is as follows: HO-(CH2)3COO-(CH2)3-OCH3+NH3→HO-(CH2)3CO-NH-(CH2)3-OCH3+H2O HO-(CH2)3CO-NH-(CH2)3-OCH→(CH2)3CO-N-(CH2)3-OCH+H2O (4) Purification: The temperature of the reactor is rapidly reduced from 200℃ to 25℃ (room temperature) using an ice-water bath. After cooling to room temperature, the pressure relief valve of the reactor is slowly opened to release the gas (mainly ammonia) inside the reactor. The liquid mixture in the reactor is the "crude product" system. It mainly contains the following components: Target product: 1-(3-methoxypropyl)-2-pyrrolidone (liquid) Excess feedstock: Unreacted 3-methoxy-1-propanol (liquid) Byproducts: water (generated by aminolysis and cyclization reactions), and possibly trace amounts of olefins or polymers (liquid). Catalyst: Solid particles (solid, suspended or precipitated in a liquid) The crude product system was filtered to separate the solid (catalyst) and liquid (crude product). The obtained solid catalyst was washed three times with ethanol and regenerated by vacuum drying at 80°C for 4 hours. The separated liquid (crude product) was subjected to vacuum distillation. Under a vacuum condition maintained at 5 mmHg, the fraction with a boiling point between 100-105°C was collected to obtain a colorless and transparent liquid, namely 1-(3-methoxypropyl)-2-pyrrolidone, with the structural formula shown below. Figure 1 As shown. Analysis showed that the GC purity was ≥99.96% (high purity grade) and the yield was 96% (the difference in yield and purity from the corresponding yield in Table 2 is due to different batches).

[0044] (5) Catalyst regeneration The recovered catalyst was calcined in air at 550℃ (heating rate 5℃ / min) for 3 hours. After replenishing oxygen vacancies, the above experiment was repeated. The yield, purity and activity retention of the target product were measured each time. The experimental results are shown in Table 5.

[0045] Table 5 Catalyst Regeneration Experiment

[0046] Catalyst activity retention: The ratio of the yield of the nth cycle to the initial yield is calculated based on the yield at the first use (set as 100%).

[0047] Target product yield: The purity of the product after vacuum distillation was determined by gas chromatography (GC, HP-5 column, FID detector), and the yield was calculated (yield = actual product mass / theoretical product mass × 100%).

[0048] Example 5 A method for preparing N-butylcaprolactam includes the following steps: raw material: ε-caprolactone (purity ≥99%), n-butylamine, catalyst (Samarium-doped zirconium-titanium composite oxide prepared in Example 2) (5 wt%) Experimental procedure: (1) Catalyst preactivation: The catalyst Sm prepared in Example 2 was used to preactivate the catalyst Sm 0.05 Zr 0.5 Ti 0.25 O2-δ powder was placed in a crucible and then placed in a vacuum drying oven. The temperature was increased to 400℃ at a rate of 5℃ / min and calcined at this temperature for 4 hours (to remove surface-adsorbed water and impurities). After cooling to room temperature, it was transferred to a desiccator for later use. (2) Seal the reactor and check its airtightness: replace with an inert atmosphere, introduce high-purity nitrogen to 0.5 MPa, maintain for 5 minutes and then depressurize to atmospheric pressure, repeat 3 times; (3) After the airtightness test is passed, add the following to the high-pressure reactor in sequence: 11.4 g (0.10 mol) of ε-caprolactone, 9.5 g (0.13 mol, molar ratio 1:1.3) of n-butylamine, and 1.05 g (5% of the total mass of the reactants) of pre-activated catalyst. Start stirring (500 rpm) and heat to 140℃ (autogenous pressure about 0.8 MPa) at 3℃ / min. React at constant temperature for 1 hour to complete the ring opening and aminolysis of lactone, and generate 6-hydroxy-N-butylhexamide. (4) Continue to increase the temperature to 180℃ at 2℃ / min (the autogenous pressure increases to 1.2-1.5 MPa), and react at a constant temperature for 3 hours (oxygen vacancies promote dehydration and cyclization). (5) After the reaction is completed, cool the mixture to room temperature in an ice-water bath, press out the material with compressed nitrogen, filter the mixture to separate the catalyst (recovery rate > 98%), transfer the filtrate to a rotary evaporator, remove unreacted n-butylamine by vacuum distillation at 80°C, and purify the crude product by silica gel column chromatography (petroleum ether: ethyl acetate = 3:1) to obtain a colorless oily liquid, which is N-butylcaprolactam; its yield is 95.1% and the product purity is 99% (superior grade) (the yield and purity in Table 2 are due to batch differences).

[0049] The conversion rate of ε-caprolactone was determined to be >98% (Lewis acidic catalytic ring-opening); the selectivity of the target product was >98.6% (Sm³). + (Promotes aminolysis; oxygen vacancies accelerate dehydration and cyclization).

[0050] Example 6 A method for preparing N-methylaniline includes the following steps: raw material: Aniline, dimethyl carbonate, catalyst (Samarium-doped zirconium-titanium composite oxide prepared in Example 3) (5 wt%); Experimental procedure: (1) Catalyst preactivation: Take the catalyst Sm prepared in Example 3 0.15 Zr 0.7 Ti 0.35 O2-δ powder (the optimal ratio of this patented technology) is placed in a tube furnace; under a nitrogen atmosphere, the temperature is increased to 300℃ at 3℃ / min, and calcined at a constant temperature for 2 hours to remove surface adsorbed water; after cooling to 80℃, it is transferred to a desiccator for later use. (2) Seal the reactor and check its airtightness: replace with an inert atmosphere, introduce high-purity nitrogen to 0.5 MPa, maintain for 5 minutes and then depressurize to atmospheric pressure, repeat 3 times; (3) After the airtightness test is passed, add aniline (freshly distilled, 99.5%), dimethyl carbonate (DMC, water content <50 ppm), and pre-activated catalyst (5 wt% based on total material mass) sequentially to the high-pressure reactor. Start stirring (500 rpm) and raise the temperature to 150℃ at 3℃ / min (DMC decomposition temperature ≈90℃). Then adjust the temperature to 150-160℃, at which point the self-generated pressure is about 1.8-2.2 MPa. Reaction time: 3-4 hours. (Monitored by online sampling HPLC, target: aniline conversion rate >99%).

[0051] Reaction endpoint monitoring: After 3 hours of reaction, a 0.2 mL sample was taken half an hour later, quenched with ice-cold methanol, and analyzed by HPLC. Chromatographic conditions: acetonitrile / water (60:40), flow rate 1.0 mL / min, detection wavelength 254 nm; Judgment criteria: The aniline peak area disappears (conversion rate > 99%), and the proportion of the N-methylaniline peak area is ≥ 98% (N,N-dimethylaniline < 2%).

[0052] Product separation and purification: After the reaction is completed, cool to 50°C and use compressed nitrogen to expel the material; filter to recover the catalyst (which can be reused more than 5 times); The filtrate is transferred to a distillation apparatus: atmospheric distillation: first recover unreacted DMC (boiling point 90℃); vacuum distillation: under a vacuum of 5 mmHg, collect the fraction at 100-105℃ (N-methylaniline boiling point 196℃ / 760 mmHg); product purity ≥99.5% (superior grade), yield ≥92.9%.

[0053] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0054] Example 7 Comparative experiment on the catalytic performance of samarium-doped zirconium-titanium composite oxide, pure zirconium-titanium composite oxide, and cerium-doped zirconium-titanium composite oxide. Reagents: The reagents used in this example are identical in specifications and purity to those used in Examples 1-6, and the instruments used are identical to those used in Examples 1-6. Cerium nitrate (Ce(NO3)3·6H2O, purity ≥99.99%, total rare earth impurities <0.1%) is added.

[0055] catalyst Sm 0.1 Zr 0.6 Ti 0.3 Preparation of O2-δ Prepared according to the coprecipitation-step calcination method of Example 1 of this application.

[0056] Comparative Example 1 Preparation of pure ZrTiO4 catalyst Based on Example 1 of this application, the samarium source is removed, and only the zirconium and titanium sources are retained, with a zirconium-titanium molar ratio of 0.6:0.3. The remaining preparation processes, parameters, and steps are completely identical. Preparation of zirconium solution (ZrOCl2) 8H2O 22.32g, 0.06mol dissolved in 200mL 60℃ deionized water; titanium solution (Ti(OC4H9)4 10.21g, 0.03mol dissolved in 50mL anhydrous ethanol, nitrogen protection); samarium-free solution; Low-temperature coprecipitation: Mix the two solutions, incubate in an ice-water bath at 10±2℃, add ammonia dropwise until pH 9.5-10.0, age for 24 hours, centrifuge and wash until no Cl is found. - Vacuum dry for 12 hours; Programmable temperature controlled calcination: dehydration stage at 255℃ for 2.5h, crystal phase transformation stage at 545℃ in air for 3h, oxygen vacancy regulation stage at 745℃ in nitrogen atmosphere for 2h, with the heating rate consistent with that of this application. Molding and activation: Grind through a 200-mesh sieve, compress into 3mm granules, activate in air at 380-430℃ for 2 hours, and seal for later use.

[0057] Comparative Example 2 Ce 0.1 Zr 0.6 Ti 0.3 Preparation of O2-δ catalyst Based on Example 1, the samarium source was replaced with an equimolar cerium source, and the Ce:Zr:Ti molar ratio was 0.1:0.6:0.3 (consistent with the Sm ratio in this application). The remaining preparation processes, parameters, and steps were exactly the same. Prepare zirconium solution, titanium solution (consistent with this application), and cerium solution (Ce(NO3)3). 4.34 g of 6H₂O (0.01 mol dissolved in 100 mL of deionized water). The subsequent low-temperature co-precipitation, programmed temperature-controlled calcination, molding and activation steps were completely consistent with those in Example 1 of this application, and 3 mm particulate catalysts were prepared and sealed for later use after activation.

[0058] Parallel testing of catalytic activity and product selectivity Parallel catalytic experiments were conducted using three typical reactions—γ-butyrolactone transesterification-amine decyclization, ε-caprolactone ring-opening-amine decyclization, and aniline N-methylation—as test models. The experimental procedures were strictly performed in accordance with Examples 4, 5, and 6 of this application, with only the catalyst type being replaced.

[0059] Test of γ-butyrolactone transesterification-amine decyclization reaction (refer to Example 4 of this application) The nitrogen purging reactor was repeated three times until the oxygen content was <0.1%. 86.1 g (1 mol) of γ-butyrolactone and 117.1 g (1.3 mol) of 3-methoxy-1-propanol were added sequentially to a 500 mL high-pressure reactor, along with 8.2 g of each of the three types of catalysts (4% of the total mass of the materials). The mixture was stirred (300 rpm) for 10 min until homogeneous. The temperature was increased to 180±5 °C at 3 °C / min, and the transesterification reaction was carried out at an autogenous pressure of 0.8-1.2 MPa for 4 h. 3 mol of liquid ammonia was introduced to adjust the pressure to 3.0 MPa, and the temperature was increased to 200±5 °C for 6 h of amine decyclization reaction. The mixture was cooled to 25 °C in an ice-water bath, the catalyst was recovered by filtration, and the crude product was distilled under reduced pressure at 5 mmHg (collecting the fraction at 100-105 °C). The conversion rate of γ-butyrolactone and the yield and purity of 1-(3-methoxypropyl)-2-pyrrolidone were determined by GC, and the data were recorded.

[0060] ε-Caprolactone ring-opening catalytic performance test (refer to Example 5 of this application) Nitrogen gas was applied to the high-pressure reactor three times until the oxygen content was <0.1%. 11.4 g (0.10 mol) of ε-caprolactone and 9.5 g (0.13 mol) of n-butylamine were added sequentially to the high-pressure reactor, along with 1.05 g of each of the three types of catalysts (5% of the total mass of materials). The mixture was stirred, heated to 140 °C at 3 °C / min, and subjected to an autogenous pressure of 0.8 MPa for 1 hour. The temperature and pressure were then increased to 180 °C at 2 °C / min, and the autogenous pressure was maintained at 1.2-1.5 MPa for 3 hours. The mixture was then cooled with ice water and filtered. The crude product was purified by silica gel column chromatography (petroleum ether: ethyl acetate = 3:1). GC was used to determine the conversion rate of ε-caprolactone and the yield and purity of N-butylcaprolactam, and the data were recorded.

[0061] Catalytic performance test of aniline N-methylation (refer to Example 6 of this application) The high-pressure reactor was purged with nitrogen three times until the oxygen content was <0.1%. Aniline and dimethyl carbonate (molar ratio 1:2) were added, along with three types of catalysts (5% of the total mass of the materials). The mixture was stirred, heated to 150-160℃ at 3℃ / min, and subjected to an autogenous pressure of 1.8-2.2 MPa for 3-4 hours, until the aniline peak area disappeared as monitored by HPLC. The mixture was cooled to 50℃, the catalyst was recovered by filtration, and DMC was recovered by atmospheric distillation of the filtrate. The fraction distilled under reduced pressure (5 mmHg) was collected at 100-105℃. The aniline conversion rate and N-methylaniline selectivity were detected by HPLC, and the N,N-dimethylaniline content was quantitatively determined and the data were recorded.

[0062] Parallel testing of catalyst regeneration stability Using the γ-butyrolactone transesterification-amine decyclization reaction as a stability testing model, the three types of catalysts recovered in step 2 were uniformly regenerated, and cyclic catalytic experiments were carried out.

[0063] Catalyst regeneration: The three types of recovered catalysts were washed once with anhydrous ethanol, dried under vacuum at 80°C for 4 hours, and then calcined in air at 550°C for 3 hours (heating rate 5°C / min) in a muffle furnace to complete the regeneration and activation. 1. Cyclic catalysis: The three types of regenerated catalysts were subjected to repeated γ-butyrolactone transesterification-amine decyclization reaction tests (refer to Example 4 of this application), and 10 and 20 cycles of regeneration tests were completed respectively; 2. Data calculation: Based on the yield of the target product 1-(3-methoxypropyl)-2-pyrrolidone at the first use (100%), the catalyst activity retention rate after each cycle was calculated (activity retention rate = yield of the nth cycle / yield of the nth cycle × 100%). The cycle test of each catalyst was repeated twice, and the average value was recorded.

[0064] Parallel testing of catalyst space-time yield Using the γ-butyrolactone transesterification-amine decyclization reaction as a model, fixed-bed continuous catalytic testing was conducted on three types of catalysts, and the space-time yield was determined.

[0065] 1. The three types of catalysts were respectively loaded into a fixed-bed reactor, with a catalyst loading of 50g each. Before use, all catalysts were activated in air at 380-430℃ for 2 hours. 2. The reaction was continuously fed at a molar ratio of γ-butyrolactone to 3-methoxy-1-propanol of 1:1.3, with the reaction temperature controlled at 180±5℃, the pressure during the aminolysis stage at 3.0 MPa, and the reactor space velocity at 2 h⁻¹. - ¹, Continuous operation for 24 hours; 3. Collect the reaction products periodically, purify them by vacuum distillation, and then use GC to determine the yield of the target product. Calculate the space-time yield of the catalyst (space-time yield = the yield of the target product per unit mass of catalyst per unit time, unit: kg / (kg)). h), take the average data record of 24 hours.

[0066] Parallel determination of apparent activation energy of reaction Using the decyclization reaction of γ-butyrolactone amine as a model, the apparent activation energies of three types of catalysts were determined.

[0067] The conditions for controlling the reaction raw material ratio, catalyst addition amount, stirring rate, etc., were consistent with those for the γ-butyrolactone transesterification-amine decyclization reaction test (refer to Example 4 of this application). The reaction temperature of the amine decyclization stage was changed and set to 160℃, 170℃, 180℃, 190℃, and 200℃, respectively.

[0068] The reaction rates of the three types of catalysts were measured at different temperatures, and the apparent activation energy (unit: kJ / mol) was calculated by fitting the Arrhenius equation. Each temperature point was tested three times, and the average value was used for calculation.

[0069] Table 6. Experimental data compared with existing technologies 1.

[0070] This embodiment illustrates that the Sm of this application 0.1 Zr 0.6 Ti 0.3The O2-δ catalyst significantly outperforms the pure ZrTiO4 catalyst in Comparative Example 1 and the Ce-doped zirconium-titanium composite oxide catalyst in Existing Technology 2 in terms of catalytic activity and product selectivity. It achieves conversion rates of over 98% for substrates such as γ-butyrolactone, ε-caprolactone, and aniline, with target product yields increased by over 16% compared to existing technologies. Furthermore, it effectively suppresses side reactions such as excessive alkylation, with the byproduct N,N-dimethylaniline content <0.5%, demonstrating a significant selectivity advantage. 0.1 Zr 0.6 Ti 0.3 The O2-δ catalyst exhibits significantly superior regeneration stability compared to the two existing technologies, with an activity retention rate of >95% after 10 regenerations and >90% after 20 regenerations, representing an improvement of over 34.7% compared to Comparative Example 2. This addresses the technical challenge of poor regeneration stability in existing zirconium-titanium composite oxide catalysts; Sm 0.1 Zr 0.6 Ti 0.3 O2-δ catalysts can significantly reduce the apparent activation energy of the reaction (≤60kJ / mol), improve the reaction energy efficiency, and achieve a space-time yield of ≥0.5kg / (kg) for continuous fixed-bed reactions. h), far exceeding the two existing technologies, and more suitable for industrial continuous production; Sm 0.1 Zr 0.6 Ti 0.3 O2-δ achieves a synergistic improvement in catalytic activity, selectivity, and stability.

Claims

1. The application of a samarium-doped zirconium-titanium composite oxide in the catalytic reaction of lactone compounds with amine compounds, characterized in that, The general formula of the samarium-doped zirconium-titanium composite oxide is Sm x Zr Ti z O2-δ, where x is x=0.05-0.15, y=0.5-0.7, z=0.25-0.35, and δ is oxygen vacancy; The reaction includes ring-opening, aminolysis and cyclization steps of the lactone; The lactone compound includes γ-butyrolactone or ε-caprolactone; The amine compounds include ammonia, aliphatic amines, or aromatic amines.

2. The application of a samarium-doped zirconium-titanium composite oxide in catalytic N-alkylation reaction, characterized in that, The general formula of the samarium-doped zirconium-titanium composite oxide is Sm x Zr Ti z O2-δ, where x=0.05-0.15, y=0.5-0.7, z=0.25-0.35, and δ represents oxygen vacancies; The N-alkylation reaction is a reaction in which dimethyl carbonate is used as the alkylating agent.

3. The method for preparing the samarium-doped zirconium-titanium composite oxide according to any one of claims 1-2, characterized in that, Includes the following steps: (1) Preparation of precursor solutions: Prepare aqueous solutions containing zirconium source, alcoholic solutions containing titanium source, and aqueous solutions containing samarium source respectively; (2) Low-temperature co-precipitation: Mix the three solutions obtained in step (1), and under the conditions of cooling in an ice-water bath and stirring, add ammonia dropwise to the mixture until the pH is 9.5-10.

0. Aging for 20-24 hours, centrifugation and washing until no Cl is found. - The filter cake was detected and then vacuum dried to obtain the precursor. (3) Programmable temperature controlled calcination: The dried precursor is subjected to the following heat treatments in sequence: a. Dehydration stage: Heat to 245-265℃ at a heating rate of 1-1.5℃ / min, and dry for 2-3 hours; b. Crystal phase transformation stage: Under air atmosphere, heat to 530-560℃ at a heating rate of 2-4℃ / min and heat for 3 hours; c. Oxygen vacancy control stage: Replace the atmosphere in the furnace with nitrogen atmosphere, and raise the temperature to 730-760℃ at a rate of 4-6℃ / min, dry for 1.5-3.0h, and then cool to room temperature; (4) Molding and activation: Grind, sieve and press the calcined product obtained in step (3) into a tablet to obtain the samarium-doped zirconium-titanium composite oxide; activate it in an air atmosphere at 380-430℃ for 1.5-3.0 hours before use.

4. The preparation method according to claim 3, characterized in that, In step (1), the zirconium source is ZrOCl2·8H2O, the titanium source is Ti(OC4H9)4, and the samarium source is Sm(NO3)3·6H2O; the alcohol solution containing the titanium source is prepared under nitrogen protection, and the solvent used is anhydrous ethanol; the molar ratio of the zirconium source, titanium source and samarium source is 0.06 : 0.03 : 0.

01.

5. The preparation method according to claim 3, characterized in that, The temperature of the ice-water bath in step (2) is maintained at 10±2℃; the vacuum drying time is 12h; In step (3), step c, the specific operation of the oxygen vacancy control stage is as follows: first, use high-purity nitrogen to replace the furnace 3 to 5 times to make the oxygen volume content in the furnace ≤0.3%, and then perform heat treatment under nitrogen atmosphere. In step (4), the sieving is sieved through a 200-mesh sieve; the tableting is pressed into granules with a diameter of 3 mm.

6. The samarium-doped zirconium-titanium composite oxide prepared by the method of any one of claims 3-5.

7. A method for synthesizing 1-(3-methoxypropyl)-2-pyrrolidone, characterized in that, Using the samarium-doped zirconium-titanium composite oxide as described in claim 1 as a catalyst, 1-(3-methoxypropyl)-2-pyrrolidone was prepared by catalyzing the transesterification and aminolysis-cyclization tandem reaction of γ-butyrolactone, 3-methoxy-1-propanol and ammonia in a "one-pot" process. The molar ratio of γ-butyrolactone to 3-methoxy-1-propanol is 1:1-1.3; The amount of catalyst added is 2.5-5% of the total mass of the reactants.

8. The method according to claim 7, characterized in that, Includes the following steps: (1) Mix γ-butyrolactone, 3-methoxy-1-propanol and the pre-activated catalyst until homogeneous. Under the condition of oxygen content <0.1%, heat to 180±5℃ at 2-5℃ / min, and then carry out transesterification reaction under constant temperature and autogenous pressure to prepare 4-hydroxybutyric acid-3-methoxypropyl ester. (2) Ammonia gas was introduced into the reaction system of step (1) and the pressure was controlled at 2.8-3.5 MPa. The aminolysis-cyclization reaction was completed at 200±5℃ to prepare crude product 1-(3-methoxypropyl)-2-pyrrolidone. (3) The crude product was cooled and filtered to remove the catalyst, and then distilled under reduced pressure to prepare 1-(3-methoxypropyl)-2-pyrrolidone.

9. The method according to claim 7, characterized in that, The stirring speed in step (1) is 260-360 rpm; the stirring time is 10-15 min; the autogenous pressure is in the range of 0.8-1.2 MPa; the transesterification reaction ends when the conversion rate of γ-butyrolactone is >99.9%. The amount of ammonia used in step (2) is 3-4.5 times the molar amount of γ-butyrolactone; the aminolysis-cyclization reaction ends when the conversion rate of the intermediate product 4-hydroxy-N-(3-methoxypropyl)butyramide is ≥99.8%. The cooling temperature in step (3) is 25°C; the vacuum distillation process is as follows: under the vacuum condition of maintaining the system pressure at 5 mmHg, the fraction with a boiling point temperature between 100-105°C is collected.

10. A method for synthesizing N-butylcaprolactam, characterized in that, Using the samarium-doped zirconium-titanium composite oxide as described in claim 1 as a catalyst, N-butylcaprolactam is prepared by catalyzing the transesterification and aminolysis-cyclization tandem reaction of ε-caprolactone and n-butylamine in a one-pot process. The molar ratio of ε-caprolactone to n-butylamine is 1:0.9-1.3; The amount of catalyst added is 2-5% of the total mass of the reactants.

11. A method for synthesizing N-methylaniline, characterized in that, Using the samarium-doped zirconium-titanium composite oxide as described in claim 2 as a catalyst, N-methylaniline is prepared by catalyzing the aminolysis and methyl transfer reaction of aniline and dimethyl carbonate in a one-pot process. The molar ratio of aniline to dimethyl carbonate is 1:1.7-2.2; The amount of catalyst added is 1.8-5% of the total mass of the reactants.

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