Synthesis method of N-butyl pyrrolidone

Abstract

The invention discloses a synthesis method of N-butyl pyrrolidone, and belongs to the technical field of compound synthesizing.The synthesis method comprises the steps that firstly, a ZSM-8 molecular sieve is soaked in a titanate solution, a part of titanium element is introduced into a framework of the molecular sieve through a liquid-solid phase reaction, and a titanium modified molecular sieve is obtained; the preparation method comprises the following steps: firstly, preparing a molecular sieve catalyst, then, carrying out co-doping modification on heteropoly acid cerium salt and nitrogen to obtain the modified molecular sieve catalyst, and then, applying the modified molecular sieve catalyst to a process for preparing N-butyl pyrrolidone from n-butylamine and gamma-butyrolactone through a nucleophilic addition reaction one-step method, so that the reaction conditions are obviously reduced, the reaction conversion rate is increased, and the yield of N-butyl pyrrolidone is increased. And the prepared modified molecular sieve catalyst can be repeatedly used.

Description

Technical Field

[0001] The invention belongs to the technical field of compound synthesis, and particularly relates to a method for synthesizing N-butylpyrrolidone. Background Art

[0002] As five-membered heterocyclic molecules, pyrrolidone compounds have unique properties in biological activity. The molecular skeleton of such heterocyclic compounds exists in many active natural products. Preliminary studies have shown that such compounds can effectively improve and prevent diseases such as arrhythmia induced by adrenaline and barium chloride, as well as coronary artery occlusion. For simple alkane-substituted pyrrolidone compounds (such as NMP, NEP, etc.), it is a polar non-proton transfer solvent. It has the advantages of low toxicity, high boiling point, outstanding solubility, strong selectivity and good stability. It is widely used in aromatic extraction, purification of acetylene, olefins, and dienes; solvents for polyvinylidene fluoride; electrode auxiliary materials for lithium-ion batteries; synthesis gas desulfurization, lubricant refining, lubricant antifreeze, olefin extraction agent; solvent for polymerization of insoluble engineering plastics; agricultural herbicides; insulating materials, integrated circuit production; cleaning of semiconductors, liquid crystal panels, and circuit boards; PVC tail gas recovery; paint removers, dye additives, dispersants, etc. It can also be used as a solvent for polymers and a medium for polymerization reactions, such as polyphenylene sulfide (PPS), polysulfone (polyethersulfone), polyimide (PI), aramid fiber, etc. It can also be used in pesticides and medicines.

[0003] Since pyrrolidone compounds have so many unique properties, the synthesis of this type of compound has always been one of the key and hot topics of chemists' research. Carrying out this research topic can promote the industrial production of pyrrolidone compounds, which is conducive to promoting efficient and economic technological upgrading in the fields of semiconductors, new energy batteries, polymer materials, coatings, and medicines in my country, and developing more technical devices for the industrial production of pyrrolidone products, which is of great significance to the development of my country's economy.

[0004] With the advancement of science and technology, people's demand for chemical products shows green consumption concepts such as low toxicity or non-toxicity, environmental protection, and biodegradability, which even become technical thresholds and technical barriers for developed countries abroad. At present, the green industrial development of chemical products has become the key to the development of the chemical industry. N-butylpyrrolidone products have the advantages of excellent high temperature stability and low toxicity to human body or environment, so they have broad market prospects in the fields of coatings, medicines, pesticides, inks, petrochemicals, etc. However, the existing N-butylpyrrolidone synthesis method has the problems of harsh reaction conditions and low conversion rate. Summary of the invention

[0005] In view of this, the present invention provides a method for synthesizing N-butyl pyrrolidone, which adopts a modified molecular sieve catalyst, reduces the reaction temperature, and shortens the reaction time.

[0006] The first aspect of the present invention is to provide a method for preparing a modified molecular sieve catalyst, comprising the following steps:

[0007] First, the ZSM-8 molecular sieve is immersed in a titanate solution, and part of the titanium element is introduced into the framework of the molecular sieve through a liquid-solid phase reaction to obtain a titanium-modified molecular sieve; a soluble cerium salt is dissolved in an aqueous solution of phosphotungstic acid to obtain a mixed solution; the titanium-modified molecular sieve is then added to the mixed solution, and a hydrothermal reaction is carried out at 100 to 120° C. for 20 to 25 minutes; the solid product is separated, washed, and dried; and then calcined in an ammonia atmosphere to obtain the modified molecular sieve catalyst;

[0008] The mass ratio of the soluble cerium salt to the phosphotungstic acid in the mixed solution is (1-1.2):1; the mass ratio of the titanium modified molecular sieve to the mass ratio of the soluble cerium salt is 100:(1-1.5).

[0009] The modified catalyst of the present invention is based on ZSM-8 molecular sieve, the silicon (aluminum) oxygen tetrahedron of ZSM-8 molecular sieve forms a ten-membered oxygen heterocyclic system through a common vertex oxygen bridge, and the connecting tetrahedron forms a chain structure through the shared edge connection, and then the chain structure is connected to form a ZSM-8 three-dimensional skeleton structure. The ZSM-8 molecular sieve has a stable structure and high hydrothermal stability, and can be used for high temperature and high pressure reactions; the ZSM-8 molecular sieve is a medium-pore zeolite molecular sieve, which has excellent ion exchange performance and a high specific surface area, providing more adsorption points for metal ion loading. The present invention first introduces part of the titanium element into the skeleton of the molecular sieve through a liquid-solid phase reaction. Titanium is a transition metal with unique electronic properties and catalytic activity. The introduction of titanium can change the skeleton element composition of the molecular sieve, regulate the electronic structure of the molecular sieve, optimize the catalytic active site center point, and make the reactant easier to adsorb and convert on the molecular sieve. And titanium modification can also enhance the skeleton structure of the molecular sieve, improve its heat resistance, anti-toxicity and anti-hydrolysis performance, thereby avoiding the destruction of the skeleton structure in the subsequent modification process. In addition, titanium modification can also regulate the pore size and distribution of molecular sieves, enrich the types and number of acid centers, and thus help improve catalytic activity. Then, heteropoly acid cerium salts are doped on the molecular sieve matrix through hydrothermal reaction. Heteropoly acid cerium salts not only have strong acidity, but also can effectively catalyze reactions; in addition, heteropoly acid cerium salts also have good thermal stability, and their structure and performance can remain stable under high temperature conditions, without significant decomposition or inactivation. In a variety of chemical environments, they show good chemical stability, are not easy to react with other chemicals, and can maintain catalytic activity under acidic, alkaline or neutral conditions; finally, by calcining in an ammonia environment, nitrogen-containing groups are doped in the molecular sieve catalyst, and the number of active sites in the co-doped modified molecular sieve catalyst is greatly increased, and the types are enriched. These active sites can accurately locate the reactants on the active sites, promote the conversion efficiency and selectivity of the reactants, thereby avoiding the occurrence of side reactions, reducing the reaction temperature, and shortening the reaction time. Nitrogen doping can also adjust the acidity and alkalinity of the molecular sieve catalyst after being doped with heteropolyacid cerium salt. At the same time, co-doping with heteropolyacid cerium salt and nitrogen can also improve the stability of the molecular sieve catalyst, so that it can still maintain good catalytic activity under high temperature and high pressure conditions.

[0010] Furthermore, the titanium modified molecular sieve is prepared by an impregnation method.

[0011] Furthermore, the preparation method of the titanium modified molecular sieve comprises the following steps:

[0012] (1) firstly wash the ZSM-8 molecular sieve with alcohol (ethanol washing), and then dry it at 80-100°C; (2) dissolve cobalt titanate in ethanol to prepare a cobalt titanate solution with a concentration of 1 mol / L; (3) immerse the ZSM-8 molecular sieve treated in step (1) in the cobalt titanate solution for 30-45 min; (4) centrifuge and wash the impregnated molecular sieve with ethanol, and then dry it at 80-100°C to obtain the titanium modified molecular sieve.

[0013] Optionally, the calcination temperature is 300-350° C.; the calcination time is 30-45 min.

[0014] Optionally, the soluble cerium salt is cerium nitrate or cerium chloride.

[0015] Optionally, the drying is performed at 50-60°C.

[0016] The second aspect of the present invention is to provide a modified molecular sieve catalyst prepared by the above-mentioned preparation method.

[0017] The third aspect of the present invention is to provide the use of the modified molecular sieve in catalytic preparation of N-butylpyrrolidone.

[0018] The fourth aspect of the present invention is to provide a method for synthesizing N-butyl pyrrolidone, using γ-butyrolactone and n-butylamine as raw materials and the above-mentioned modified molecular sieve catalyst as a catalyst to prepare N-butyl pyrrolidone through a nucleophilic addition reaction; the added amount of the modified molecular sieve catalyst is 0.5-0.8% of the γ-butyrolactone.

[0019] The reaction mechanism for the synthesis of N-butylpyrrolidone is as follows:

[0020] The synthesis reaction of N-butylpyrrolidone belongs to the process of ring conversion from O-ring compounds to N-ring compounds, which specifically includes amination ring opening and condensation ring closing processes. In the ring opening process, butylamine replaces the ester oxygen-O- of γ-butyrolactone (GBL) to form an open-ring chain product, generate a chain amide, and complete the ring opening process. Ring closing condensation is the process of dehydration and condensation of chain hydroxybutyramide to form a five-membered ring. Since the energy barrier ΔE value that needs to be overcome when the intermediate generates butylpyrrolidone is relatively large, ring closing is much more difficult than amination ring opening. The use of an effective catalyst can reduce this activation energy, so that the reaction can proceed smoothly.

[0021] In a further preferred embodiment, the molar ratio of γ-butyrolactone to n-butylamine is 1:(1-1.8); the pressure during the reaction is 5.0-8.0 MPa; the reaction temperature is 150-200° C.; and the reaction time is 2.0-2.5 h.

[0022] In a further preferred embodiment, after the preparation of N-butylpyrrolidone is completed, a step of removing impurities by distillation under reduced pressure is also included.

[0023] The present invention has the following technical effects:

[0024] The invention co-dopes the molecular sieve catalyst with heteropoly acid cerium salt and nitrogen, thereby effectively improving the reaction efficiency of synthesizing N-butyl pyrrolidone from gamma-butyrolactone and n-butylamine through the amine method, reducing the reaction conditions, and making the catalyst easy to separate and reusable. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0026] Figure 1 The figure is a reaction mechanism diagram for synthesizing N-butylpyrrolidone according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0029] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0030] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0031] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0032] Unless otherwise specified, the normal temperature in the present invention is 25±2°C.

[0033] All raw materials used in the examples of the present invention are commercially available.

[0034] 1. The technical indicators of each raw material are as follows:

[0035] γ-Butyrolactone (GBL), CAS#96-48-0, C4H6O2, molecular weight 86.09. It is a colorless, transparent, oily liquid with a certain degree of hygroscopicity and an acetone-like odor. It is directly miscible in water, alcohol, ester, ether, ketone and aromatic hydrocarbons in any proportion, and slightly soluble in straight-linked alkanes and cycloalkanes. It is an excellent solvent for many polymers and also an excellent solvent for many gases.

[0036] Table 1 Physicochemical properties of γ-butyrolactone (GBL)

[0037]

[0038] n-Butylamine, CAS#109-73-9, C4H 11 N, molecular weight 73.14. It is a colorless transparent liquid at room temperature with a smell similar to ammonia. It is used as an intermediate in the synthesis of pesticides, surfactants, and medicines. The n-butylamine used in this study is an industrial-grade product purchased from Zhejiang Xinhua Company with a content of 99.5%. Common physical properties are shown in Table 2.

[0039] Table 2 Physical properties of n-butylamine

[0040]

[0041]

[0042] 2. Analysis and detection methods

[0043] (1) Purity analysis

[0044] Analytical instruments and conditions:

[0045] Analytical instruments: GC6820 gas chromatograph and CERITY NDS CHEMICAL chromatography data workstation (produced by Agilent Technologies, USA).

[0046] Detector: Flame ionization detector (FID).

[0047] Chromatographic column: INNOWAX type quartz capillary column (length 30m, inner diameter 0.32mm, liquid film thickness 0.5μm).

[0048] (2) Determination of chromaticity: (Platinum-cobalt color number)

[0049] Analysis method: GB / T 3143-1982 Color determination of liquid chemical products (Hazen unit - platinum-cobalt color number).

[0050] (3) Determination of moisture:

[0051] Analytical method: GB / T 6283 Determination of water content in chemical products Karl Fischer method (general method)

[0052] 3. Indicator calculation method

[0053]

[0054] The yield data of N-butyl pyrrolidone is obtained by the following formula, and the molar number of the product N-butyl pyrrolidone is calculated by weighing the distillation product:

[0055]

[0056] Example 1

[0057] A method for preparing a modified molecular sieve catalyst comprises the following steps:

[0058] S1. Titanium modification of ZSM-8 molecular sieve: (1) first alcohol wash (ethanol wash) the ZSM-8 molecular sieve, and then dry it at 80°C; (2) dissolve cobalt titanate in ethanol to prepare a cobalt titanate solution with a concentration of 1 mol / L; (3) immerse the ZSM-8 molecular sieve treated in step (1) in the cobalt titanate solution for 35 min; (4) centrifuge and ethanol wash the impregnated molecular sieve, and then dry it at 100°C to obtain a titanium-modified molecular sieve.

[0059] S2. Dissolving cerium nitrate in an aqueous solution of phosphotungstic acid to obtain a mixed solution; then adding a titanium-modified molecular sieve to the mixed solution, and subjecting the mixed solution to a hydrothermal reaction at 120°C for 25 min; separating the solid product, washing it with distilled water, and then drying it at 50°C for 2 h; and then calcining it at 300°C for 30 min in an ammonia atmosphere to obtain the modified molecular sieve catalyst;

[0060] The mass ratio of cerium nitrate to phosphotungstic acid in the mixed solution is 1.1:1; the mass ratio of the titanium-modified molecular sieve to the mass ratio of the cerium nitrate is 100:1.

[0061] Example 2

[0062] A method for preparing a modified molecular sieve catalyst comprises the following steps:

[0063] S1. Titanium modification of ZSM-8 molecular sieve: (1) first alcohol wash (ethanol wash) the ZSM-8 molecular sieve, and then dry it at 100°C; (2) dissolve cobalt titanate in ethanol to prepare a cobalt titanate solution with a concentration of 1 mol / L; (3) immerse the ZSM-8 molecular sieve treated in step (1) in the cobalt titanate solution for 45 min; (4) centrifuge and ethanol wash the impregnated molecular sieve, and then dry it at 100°C to obtain a titanium-modified molecular sieve.

[0064] S2. Dissolving cerium nitrate in an aqueous solution of phosphotungstic acid to obtain a mixed solution; then adding a titanium-modified molecular sieve to the mixed solution, and subjecting the mixed solution to a hydrothermal reaction at 120°C for 25 min; separating the solid product, washing it with distilled water, and then drying it at 60°C for 2 h; and then calcining it at 300°C for 45 min in an ammonia atmosphere to obtain the modified molecular sieve catalyst;

[0065] The mass ratio of cerium nitrate to phosphotungstic acid in the mixed solution is 1.2:1; the mass ratio of the titanium-modified molecular sieve to the mass ratio of the cerium nitrate is 100:1.5.

[0066] Example 3

[0067] A method for preparing a modified molecular sieve catalyst comprises the following steps:

[0068] S1. Titanium modification of ZSM-8 molecular sieve: (1) first alcohol wash (ethanol wash) the ZSM-8 molecular sieve, and then dry it at 100°C; (2) dissolve cobalt titanate in ethanol to prepare a cobalt titanate solution with a concentration of 1 mol / L; (3) immerse the ZSM-8 molecular sieve treated in step (1) in the cobalt titanate solution for 30 minutes; (4) centrifuge and ethanol wash the impregnated molecular sieve, and then dry it at 80°C to obtain a titanium-modified molecular sieve.

[0069] S2. Dissolving cerium nitrate in an aqueous solution of phosphotungstic acid to obtain a mixed solution; then adding a titanium-modified molecular sieve to the mixed solution, and hydrothermally reacting at 100°C for 25 minutes; separating the solid product, washing it with distilled water, and then drying it at 50°C for 2 hours; then calcining it at 300°C for 30 minutes in an ammonia atmosphere to obtain the modified molecular sieve catalyst;

[0070] The mass ratio of cerium nitrate to phosphotungstic acid in the mixed solution is 1:1; the mass ratio of the titanium-modified molecular sieve to the mass ratio of the cerium nitrate is 100:1.2.

[0071] Example 4

[0072] A method for preparing a modified molecular sieve catalyst comprises the following steps:

[0073] S1. Titanium modification of ZSM-8 molecular sieve: (1) first alcohol wash (ethanol wash) the ZSM-8 molecular sieve, and then dry it at 100°C; (2) dissolve cobalt titanate in ethanol to prepare a cobalt titanate solution with a concentration of 1 mol / L; (3) immerse the ZSM-8 molecular sieve treated in step (1) in the cobalt titanate solution for 45 min; (4) centrifuge and ethanol wash the impregnated molecular sieve, and then dry it at 100°C to obtain a titanium-modified molecular sieve.

[0074] S2. Dissolving cerium nitrate in an aqueous solution of phosphotungstic acid to obtain a mixed solution; adding a titanium-modified molecular sieve to the mixed solution, and subjecting the mixed solution to a hydrothermal reaction at 110°C for 20 min; separating the solid product, washing it with distilled water, and then drying it at 60°C for 2 h; and then calcining it at 350°C for 30 min in an ammonia atmosphere to obtain the modified molecular sieve catalyst;

[0075] The mass ratio of cerium nitrate to phosphotungstic acid in the mixed solution is 1.2:1; the mass ratio of the titanium-modified molecular sieve to the mass ratio of the cerium nitrate is 100:1.5.

[0076] Comparative Example 1

[0077] A method for preparing a modified molecular sieve catalyst comprises the following steps:

[0078] S1. Titanium modification of ZSM-8 molecular sieve: (1) first alcohol wash (ethanol wash) the ZSM-8 molecular sieve, and then dry it at 100°C; (2) dissolve cobalt titanate in ethanol to prepare a cobalt titanate solution with a concentration of 1 mol / L; (3) immerse the ZSM-8 molecular sieve treated in step (1) in the cobalt titanate solution for 45 min; (4) centrifuge and ethanol wash the impregnated molecular sieve, and then dry it at 100°C to obtain a titanium-modified molecular sieve.

[0079] S2. dissolving cerium nitrate in an aqueous solution of phosphotungstic acid to obtain a mixed solution; adding a titanium-modified molecular sieve to the mixed solution, and subjecting the mixed solution to a hydrothermal reaction at 110° C. for 20 min; separating the solid product, washing it with distilled water, and drying it at 60° C. for 2 h; and then calcining it at 350° C. for 30 min under a nitrogen atmosphere to obtain the modified molecular sieve catalyst;

[0080] The mass ratio of cerium nitrate to phosphotungstic acid in the mixed solution is 0.5:1; the mass ratio of the titanium-modified molecular sieve to the mass ratio of the cerium nitrate is 100:1.5.

[0081] Comparative Example 2

[0082] A method for preparing a modified molecular sieve catalyst comprises the following steps:

[0083] S1. Titanium modification of ZSM-8 molecular sieve: (1) first alcohol wash (ethanol wash) the ZSM-8 molecular sieve, and then dry it at 100°C; (2) dissolve cobalt titanate in ethanol to prepare a cobalt titanate solution with a concentration of 1 mol / L; (3) immerse the ZSM-8 molecular sieve treated in step (1) in the cobalt titanate solution for 45 min; (4) centrifuge and ethanol wash the impregnated molecular sieve, and then dry it at 100°C to obtain a titanium-modified molecular sieve.

[0084] S2. dissolving cerium nitrate in an aqueous solution of phosphotungstic acid to obtain a mixed solution; adding a titanium-modified molecular sieve to the mixed solution, and subjecting the mixed solution to a hydrothermal reaction at 110° C. for 20 min; separating the solid product, washing it with distilled water, and drying it at 60° C. for 2 h; and then calcining it at 350° C. for 30 min under a nitrogen atmosphere to obtain the modified molecular sieve catalyst;

[0085] The mass ratio of cerium nitrate to phosphotungstic acid in the mixed solution is 2.0:1; the mass ratio of the titanium-modified molecular sieve to the mass ratio of the cerium nitrate is 100:1.5.

[0086] Comparative Example 3

[0087] A method for preparing a modified molecular sieve catalyst comprises the following steps:

[0088] S1. Titanium modification of ZSM-8 molecular sieve: (1) first alcohol wash (ethanol wash) the ZSM-8 molecular sieve, and then dry it at 100°C; (2) dissolve cobalt titanate in ethanol to prepare a cobalt titanate solution with a concentration of 1 mol / L; (3) immerse the ZSM-8 molecular sieve treated in step (1) in the cobalt titanate solution for 45 min; (4) centrifuge and ethanol wash the impregnated molecular sieve, and then dry it at 100°C to obtain a titanium-modified molecular sieve.

[0089] S2. Dissolving cerium nitrate in an aqueous solution of phosphotungstic acid to obtain a mixed solution; adding a titanium-modified molecular sieve to the mixed solution, and subjecting the mixed solution to a hydrothermal reaction at 110°C for 20 min; separating the solid product, washing it with distilled water, and drying it at 60°C for 2 h; and then calcining it at 350°C for 30 min under an argon atmosphere to obtain the modified molecular sieve catalyst;

[0090] The mass ratio of cerium nitrate to phosphotungstic acid in the mixed solution is 1.2:1; the mass ratio of the titanium-modified molecular sieve to the mass ratio of the cerium nitrate is 100:1.5.

[0091] Comparative Example 4

[0092] A method for preparing a modified molecular sieve catalyst comprises the following steps:

[0093] S1. Titanium modification of ZSM-8 molecular sieve: (1) first alcohol wash (ethanol wash) the ZSM-8 molecular sieve, and then dry it at 100°C; (2) dissolve cobalt titanate in ethanol to prepare a cobalt titanate solution with a concentration of 1 mol / L; (3) immerse the ZSM-8 molecular sieve treated in step (1) in the cobalt titanate solution for 45 min; (4) centrifuge and ethanol wash the impregnated molecular sieve, and then dry it at 100°C to obtain a titanium-modified molecular sieve.

[0094] S2. The titanium-modified molecular sieve was calcined at 350° C. for 30 min in an ammonia atmosphere to obtain a modified molecular sieve catalyst.

[0095] Comparative Example 5

[0096] The only difference from Example 1 is that the titanium modification process is omitted.

[0097] Application Example 1

[0098] A method for synthesizing N-butyl pyrrolidone, comprising the following steps:

[0099] First, add GBL into the autoclave, then add n-butylamine (the molar ratio of n-butylamine to GBL is 1.1:1), then add a certain amount of catalyst (the amount of catalyst added is 0.5wt% of GBL), seal the autoclave, pass high-purity, high-pressure nitrogen, and stir to increase the temperature. The reaction temperature is 200°C, the pressure in the autoclave is 6.5-7.5MPa, the reaction time is 120min, and the speed is 600 rpm. After the reaction is completed, the water produced by the reaction and a small amount of unreacted butylamine are first evaporated at normal pressure, and then vacuum distillation is performed to collect the fraction at 210-218°C / 6000Pa. The experimental results using different catalysts are shown in Table 3.

[0100] Table 3

[0101]

[0102]

[0103] It can be seen from Table 3 that, under the same reaction conditions, the conversion rate of the catalysts of Examples 1 to 4 of the present invention when catalyzing the synthesis of N-butyl pyrrolidone from n-butylamine and GBL is much higher than that of the catalysts of Comparative Examples 1 to 5 and conventional catalysts such as sulfonic acid ammonia, benzenesulfonic acid ammonia, phosphoric acid, etc. Among them, the catalyst of Example 1 has the best effect, so the catalyst of Example 1 is selected for subsequent tests.

[0104] Application Example 2

[0105] A method for synthesizing N-butyl pyrrolidone, comprising the following steps:

[0106] First, add GBL into the autoclave, then add n-butylamine in a certain molar ratio, and then add a certain amount of the catalyst of Example 1 (the amount of catalyst added is 0.5wt% of GBL), seal the autoclave, introduce high-purity, high-pressure nitrogen, and stir to raise the temperature. The reaction temperature is 200°C, the pressure in the autoclave is 6.5-7.5MPa, the reaction time is 120min, and the speed is 600 rpm. After the reaction is completed, the water produced by the reaction and a small amount of unreacted n-butylamine are first evaporated at normal pressure, and then vacuum distillation is performed to collect the fraction at 210-218°C / 6000Pa. The effect of different amine ratios on the reaction is shown in Table 4.

[0107] Table 4

[0108] Amine ratio 1∶1 1.05∶1 1.1∶1 1.2∶1 1.5∶1 1.7∶1 1.8∶1 GBL conversion rate 92.6％ 99.0％ 98.99％ 98.9％ 98.7％ 98.6％ 98.8％

[0109] It can be seen from Table 4 that when other reaction conditions are the same, when the equivalent ratio of n-butylamine to γ-butyrolactone increases from 1.0 to 1.8, the reaction conversion rate also increases from 92.6% to 99.8%, but when the amine ratio is above 1.2, the reaction conversion rate hardly increases. Therefore, 1.1 is selected as the best reaction equivalent amine ratio.

[0110] Application Example 3

[0111] A method for synthesizing N-butyl pyrrolidone, comprising the following steps:

[0112] First, add GBL into the autoclave, then add n-butylamine (amine ratio 1.1:1), then add a certain amount of the catalyst of Example 1 (the amount of catalyst added is 0.5wt% of GBL), seal the autoclave, pass high-purity, high-pressure nitrogen, start stirring and heat up. The reaction temperature is 150-175°C, the pressure in the autoclave is 6.5-7.5MPa, the reaction time is 120min, and the speed is 600 rpm. After the reaction is completed, the water produced by the reaction and the small amount of unreacted butylamine are first evaporated under normal pressure, and then vacuum distillation is performed to collect the fraction at 210-218°C / 6000Pa. The experimental results at different temperatures are shown in Table 5.

[0113] Table 5

[0114]

[0115]

[0116] As can be seen from Table 5, the temperature of the system has a significant effect on the reaction. When the reaction temperature increases from 150°C to 170°C, the GBL conversion rate increases from 95.68% to 98.83%. When the temperature continues to increase to 175°C, the conversion rate does not improve significantly. Considering the feasibility and safety of industrial production, 165°C-170°C is selected as the optimal reaction temperature condition.

[0117] Application Example 4

[0118] A method for synthesizing N-butyl pyrrolidone, comprising the following steps:

[0119] First, add GBL into the autoclave, then add n-butylamine (amine ratio 1.1:1), then add a certain amount of the catalyst of Example 1 (the amount of catalyst added is 0.5wt% of GBL), seal the autoclave, pass high-purity, high-pressure nitrogen, start stirring and heat up. The reaction temperature is 165-170°C, the pressure in the autoclave is 5.5-8.0MPa, the reaction time is 120min, and the speed is 600 rpm. After the reaction is completed, the water produced by the reaction and the small amount of unreacted butylamine are first evaporated under normal pressure, and then the reduced pressure distillation is performed to collect the fraction at 210-218°C / 6000Pa. The experimental results under different reaction pressures are shown in Table 6.

[0120] Table 6

[0121]

[0122]

[0123] It can be seen from Table 6 that when the reaction pressure gradually increases from 5.5MPa to 7.5MPa, the conversion rate of γ-butyrolactone (GBL) increases from 96.5% to 98.56%. When the pressure continues to increase to 8.0MPa, the conversion rate of the reaction does not increase significantly. Therefore, we believe that maintaining the reaction pressure at around 6.5MPa-7.5MPa can obtain a better conversion rate and higher economy.

[0124] Application Example 5

[0125] A method for synthesizing N-butyl pyrrolidone, comprising the following steps:

[0126] First, add GBL into the autoclave, then add n-butylamine (amine ratio 1.1:1), then add a certain amount of the catalyst of Example 1 (the amount of catalyst added is 0.5wt% of GBL), seal the autoclave, pass high-purity, high-pressure nitrogen, start stirring and heat up. The reaction temperature is 165-170°C, the pressure in the autoclave is 7.0-7.5MPa, and the speed is 600 rpm. After the reaction is completed, the water produced by the reaction and a small amount of unreacted butylamine are first evaporated under normal pressure, and then vacuum distillation is performed to collect the fraction at 210-218°C / 6000Pa. The experimental results at different reaction times are shown in Table 7.

[0127] Table 7 Experimental results at different reaction times

[0128]

[0129] It can be seen from Table 7 that under certain reaction conditions, after the reaction time is gradually increased from 2h to 2.5h, the GBL conversion rate is increased from 85.70% to 98.83%. When the reaction time continues to increase, the conversion rate of GBL does not increase significantly. Considering the economy and safety of the project, it is more appropriate to choose a reaction time of 140min to 150min.

[0130] Application Example 6

[0131] A method for synthesizing N-butyl pyrrolidone, comprising the following steps:

[0132] First, add GBL into the autoclave, then add n-butylamine (amine ratio 1.1:1), then add 0.5wt% of the catalyst of Example 1, seal the autoclave, introduce high-purity, high-pressure nitrogen, start stirring and heating. The reaction temperature is 165℃-170℃, the pressure in the autoclave is 6.5-7.5MPa, the reaction time is 140min, and the speed is 600rpm. After the reaction is completed, the catalyst is recovered by washing the solid components in the reaction system with ethanol and distilled water alternately for 3 times, and drying at 150℃ for 30min. After the reaction is completed, the water produced by the reaction and the small amount of unreacted butylamine are first distilled off at normal pressure, and then the reduced pressure distillation is performed to collect the fraction at 210-218℃ / 6000Pa. The relationship between the number of times the catalyst is used and the conversion rate is shown in Table 8.

[0133] Table 8

[0134] Catalyst application times first Second time The third time Fourth Fifth Conversion rate 97.85％ 96.72％ 95.98％ 95.78％ 95.42％

[0135] It can be seen from Table 8 that the number of times the catalyst is used has no obvious effect on the conversion rate. It can be seen that the catalyst of the present invention has excellent stability and can be reused.

[0136] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a modified molecular sieve catalyst, characterized in that: The following steps are involved: First, the ZSM-8 molecular sieve is immersed in a titanate solution, and part of the titanium element is introduced into the framework of the molecular sieve through a liquid-solid phase reaction to obtain a titanium-modified molecular sieve; a soluble cerium salt is dissolved in an aqueous solution of phosphotungstic acid to obtain a mixed solution; and the titanium-modified molecular sieve is added to the mixed solution, and a hydrothermal reaction is carried out at 100 to 120° C. for 20 to 25 minutes; The solid product is separated, washed, and dried; and then calcined in an ammonia atmosphere to obtain the modified molecular sieve catalyst; The mass ratio of the soluble cerium salt to the phosphotungstic acid in the mixed solution is (1-1.2):1; the mass ratio of the titanium modified molecular sieve to the mass ratio of the soluble cerium salt is 100:(1-1.5).

2. The method for preparing the modified molecular sieve catalyst according to claim 1, characterized in that: The calcination temperature is 300-350° C. and the calcination time is 30-45 minutes.

3. The method for preparing the modified molecular sieve catalyst according to claim 1, characterized in that: The soluble cerium salt is cerium nitrate or cerium chloride.

4. The method for preparing the modified molecular sieve catalyst according to claim 1, characterized in that: The drying is performed at 50-60°C.

5. A modified molecular sieve catalyst, characterized in that: The preparation method is described in any one of claims 1 to 4.

6. Use of the modified molecular sieve according to claim 5 in catalytic preparation of N-butylpyrrolidone.

7. A method for synthesizing N-butylpyrrolidone, characterized in that: Using γ-butyrolactone and n-butylamine as raw materials and the modified molecular sieve catalyst according to claim 5 as a catalyst, N-butylpyrrolidone is prepared by a nucleophilic addition reaction; The added amount of the modified molecular sieve catalyst is 0.5-0.8% of gamma-butyrolactone.

8. The synthesis method according to claim 7, characterized in that The molar ratio of γ-butyrolactone to n-butylamine is 1:(1-1.8); the pressure during the reaction is 5.0-8.0 MPa; the reaction temperature is 150-200° C.; and the reaction time is 2.0-2.5 hours.

9. The synthesis method according to claim 7, characterized in that: After the preparation of N-butyl pyrrolidone is completed, the process further comprises the step of removing impurities by distillation under reduced pressure.

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