Composite catalyst for synthesizing N-hydroxyethyl pyrrolidone from gamma-butyrolactone and ethanolamine and preparation method thereof

Abstract

The present invention belongs to the field of catalytic technology, and is specifically related to a composite catalyst for synthesizing N-hydroxyethyl pyrrolidone from γ-butyrolactone and ethanolamine, and its preparation method and application. The composite catalyst is composed of Hβ molecular sieve, auxiliary agent and active component, wherein Hβ molecular sieve accounts for 45-75% of the catalyst mass, auxiliary agent accounts for 20-50% of the catalyst mass, and active component accounts for 2-10% of the catalyst mass. The composite catalyst prepared by the present invention is highly acidic, has a large specific surface area, increases the contact area between the reactant and the active site, greatly improves the reaction efficiency, and is more conducive to the mass transfer of the reactant and the transportation of the product. Therefore, the catalyst is used to catalyze the reaction of synthesizing N-hydroxyethyl pyrrolidone from γ-butyrolactone and ethanolamine, and extremely high catalytic activity is embodied: at relatively low temperatures (200-300°C), relatively low pressures (0.1-5MPa) and under anhydrous conditions, the conversion rate of γ-butyrolactone can be achieved to reach 88%, the selectivity of NHP reaches 92.3%, and the purity of N-hydroxyethyl pyrrolidone product separated by subsequent rectification reaches 99.8%.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysis, and in particular relates to a composite catalyst for synthesizing N-hydroxyethyl pyrrolidone from gamma-butyrolactone and ethanolamine, and a preparation method thereof. Background Art

[0002] N-Hydroxyethylpyrrolidone (NHP) has hydroxyl (-OH), carbonyl (-CO-) and alkyl (-R) groups in its molecule. It is a transparent, colorless liquid with low viscosity and no special odor at room temperature. It has the advantages of strong polarity, strong solubility, good stability, non-corrosiveness, non-toxicity, and low volatility. Therefore, NHP is often used as an organic chemical solvent and auxiliary agent in the production of ink additives, detergents, coatings, adhesives and lithium-ion batteries. At the same time, NHP can also be used as a raw material for the synthesis of N-vinylpyrrolidone.

[0003] At present, the synthesis methods of NHP mainly include pyrrolidone method, acetylene method and γ-butyrolactone method. In the pyrrolidone method, α-pyrrolidone is used as the reaction raw material, and the compound such as alcohols and ethylene oxide is subjected to addition reaction under the catalysis of noble metal salts such as RhCl3, PtCl4, RuCl3 to generate NHP. This route has many by-products, environmental pollution, low product yield, and high cost of noble metal catalysts. The acetylene method is the main synthesis method of NHP. This method uses acetylene and formaldehyde as raw materials to carry out five-step reaction, which are respectively acetylene and formaldehyde addition reaction to synthesize 1,4-butynediol, 1,4-butynediol is subjected to catalytic hydrogenation reaction to synthesize 1,4-butanediol, 1,4-butanediol is subjected to catalytic dehydrogenation reaction to synthesize γ-butyrolactone, γ-butyrolactone is subjected to aminolysis reaction with liquid ammonia solution to synthesize pyrrolidone, and pyrrolidone and ethanol are reacted to generate NHP. This route has been developed since the 1930s and the process technology is relatively mature. It has the advantages of low raw material cost, high yield and large-scale production. However, this method has complex reactions, harsh operating conditions, high production technology requirements, large equipment investment, environmental pollution and acetylene raw materials are prone to explosion. In the 1960s, a simpler and cleaner synthesis method was successfully developed, namely the γ-butyrolactone method (GBL method). This method uses γ-butyrolactone and ethanolamine as raw materials, and γ-butyrolactone is aminized to form an intermediate N-hydroxyethyl-4-hydroxy-butyramide. The intermediate removes water molecules under high temperature and high pressure conditions to condense and close the ring to form NHP. The reaction principle is as follows:

[0004]

[0005]

[0006] This route has the advantages of simple operation, low toxicity, low pollution, high selectivity, and easy realization of continuous and automated industrial production. It is the main route for industrial production of NHP in my country.

[0007] CN1712396 discloses a modified Y-type molecular sieve catalyst, which uses ethanolamine and γ-butyrolactone as raw materials to synthesize NHP at 240-300°C, gas phase, and normal pressure. The total yield of the product can reach more than 90%, the process is simple, and it is easy to realize industrial continuous automated production, and the separation and purification steps can be reduced. However, the single-pass yield of the product is only 46%, and the gasification process consumes a lot of energy.

[0008] Yang Wenzhong et al. (Shandong Chemical Industry, 2016, 45(18): 6-9) reported a SO4 2- / Al2O3 type solid superacid catalyst, in a fixed bed reactor, the factors affecting the reaction were analyzed by orthogonal test. The results showed that the product NHP had the best reaction effect when the reaction temperature was 280℃, the molar ratio of γ-butyrolactone to ethanolamine was 1:1.3, and the feed rate was 0.3mL / min, with a conversion rate of 78.3%. The synthesis method has fewer reaction steps, high catalyst efficiency, and can react continuously. However, the selectivity of the process is less than 45.6%.

[0009] CN107474003 discloses a method for continuously synthesizing N-methylpyrrolidone and NHP in a microchannel reactor using alkylamine and γ-butyrolactone as raw materials and ethylene glycol as solvent. Under the conditions of a molar ratio of alkylamine to γ-butyrolactone of 1.0 to 1.6, a reaction temperature of 240 to 300° C., and a pressure of 1.7 to 5.2 MPa, the product yield reaches more than 90%. This method can shorten the synthesis process from several hours to within 30 minutes. However, this method has a high reaction pressure and a high reaction temperature, resulting in high energy consumption in the reaction process, and it is difficult for the microchannel reactor to achieve continuous large-scale production of the product. Summary of the invention

[0010] In view of the problems and shortcomings in the prior art, the present invention aims to provide a composite catalyst and a preparation method thereof.

[0011] To achieve the purpose of the invention, the technical solution adopted by the present invention is as follows:

[0012] The first aspect of the present invention provides a composite catalyst for synthesizing N-hydroxyethyl pyrrolidone from γ-butyrolactone and ethanolamine, wherein the composite catalyst uses Hβ molecular sieve as a carrier, is loaded with an auxiliary agent and an active component, and the active component is tungsten oxide, molybdenum oxide, SO4 2- or S2O8 2- One or more of the following; the Hβ molecular sieve accounts for 45-75% of the catalyst mass, the additive accounts for 20-50% of the catalyst mass, and the active component accounts for 2-10% of the catalyst mass.

[0013] More preferably, the active component is SO42- or molybdenum oxide.

[0014] Preferably, the auxiliary agent is one or more of zirconium dioxide, titanium dioxide or iron oxide, and zirconium dioxide is most preferred.

[0015] Preferably, the SiO2 / Al2O3 molar ratio of the composite catalyst is 20-30, and the specific surface area is 250-350m 2 / g, pore volume 0.35~0.45cm 3 / g.

[0016] Preferably, the Hβ molecular sieve has a SiO2 / Al2O3 molar ratio of 20 to 100 and a specific surface area of ​​400 to 700 m 2 / g, total pore volume 0.35~0.75cm 3 / g, Na2O≦0.15wt%. More preferably, the SiO2 / Al2O3 molar ratio of the Hβ molecular sieve is 20-40, and the specific surface area is 450-550m 2 / g, total pore volume 0.60~0.70cm 3 / g, Na2O≦0.15wt%.

[0017] The second aspect of the present invention provides a method for preparing the composite catalyst according to the first aspect, comprising the following steps:

[0018] (1) impregnating the Hβ molecular sieve in a metal salt solution for 8 to 12 hours, then drying at 60 to 120° C. for 8 to 12 hours, and then calcining at 200 to 400° C. for 3 to 6 hours to obtain a precursor;

[0019] (2) The precursor is added to a solution containing an active component and immersed for 10 to 15 hours, then dried at 60 to 120° C. for 10 to 24 hours, and then calcined at 500 to 650° C. for 3 to 6 hours to obtain a composite catalyst for synthesizing N-hydroxyethyl pyrrolidone from γ-butyrolactone and ethanolamine.

[0020] According to the preparation method, preferably, the concentration of the metal salt solution is 0.5 to 2 mol·L -1 The mass ratio of the metal salt to the Hβ molecular sieve carrier is 0.5 to 2.5:1.

[0021] According to the preparation method, preferably, the metal salt solution is any one of a zirconium oxychloride solution, a ferric nitrate solution or a titanium tetrachloride solution.

[0022] According to the preparation method, preferably, the concentration of the solution containing the active ingredient is 0.5 to 1 mol·L -1The mass ratio of the solution containing the active component to the precursor is 0.6 to 1:1.

[0023] According to the preparation method, preferably, the anions in the solution containing the active component are molybdate, tungstate, metatungstate, sulfate or persulfate, and the cations are hydrogen ions or ammonium ions.

[0024] According to the preparation method, preferably, the composite catalyst can be formed by extrusion, and the particle size after forming is 20 to 40 meshes.

[0025] The third aspect of the present invention provides a method for synthesizing N-hydroxyethyl pyrrolidone, comprising the following steps: adding the composite catalyst described in the first aspect of the present invention, γ-butyrolactone and ethanolamine into a reactor, maintaining the reaction temperature at 200-300°C and the reaction pressure at 0.1-5MPa, and obtaining N-hydroxyethyl pyrrolidone after the reaction is completed.

[0026] According to the method, preferably, the reactor is a fixed bed reactor, and the loading amount of the catalyst is 5% to 80% of the volume of the fixed bed reactor, more preferably 10% to 30%.

[0027] According to the method described, more preferably, the reaction temperature in the fixed bed reactor is 260°C, the reaction pressure is 5 MPa, and the reaction space velocity is 2 h -1 .

[0028] According to the method, preferably, the molar ratio of γ-butyrolactone to ethanolamine is 0.5-1.5:1, and more preferably, the molar ratio of γ-butyrolactone to ethanolamine is 1.04:1.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention uses Hβ molecular sieve as a carrier and adopts an impregnation method to prepare a composite catalyst with a solid superacid (auxiliary agent and active component) loaded on the surface of the molecular sieve. The composite catalyst has strong acidity and a larger specific surface area than ordinary metal catalysts, which increases the contact area between the reactant and the active site, greatly improves the reaction efficiency, and is more conducive to the mass transfer of the reactant and the transportation of the product. Therefore, the catalyst is used to catalyze the reaction of γ-butyrolactone and ethanolamine to synthesize N-hydroxyethyl pyrrolidone, and it exhibits extremely high catalytic activity: at a relatively low temperature (200-300°C), a relatively low pressure (0.1-5MPa) and anhydrous conditions, the conversion rate of γ-butyrolactone can reach 88%, the selectivity of NHP can reach 92.3%, and the purity of the N-hydroxyethyl pyrrolidone product separated by subsequent distillation can reach 99.8%.

[0031] (2) The preparation method of the composite catalyst provided by the present invention has the advantages of being simple, easy to operate, mild conditions, easy to control and suitable for industrial production.

[0032] (3) The present invention uses a composite catalyst as a heterogeneous catalyst to catalyze the synthesis of N-hydroxyethyl pyrrolidone from γ-butyrolactone and ethanolamine, which not only has high reaction activity and good selectivity, but also has the advantages of good stability, easy product separation, and recyclability. At the same time, the composite catalyst can be used to catalyze the synthesis of high-purity N-hydroxyethyl pyrrolidone under anhydrous conditions, reducing the subsequent separation of water and reducing environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a SEM image of the composite catalyst prepared in Example 1 of the present invention;

[0034] Figure 2 The present invention is a schematic diagram of the structure of a reaction device for preparing N-hydroxyethyl pyrrolidone, wherein 1 is a heating jacket, 2 is a fixed bed reaction tube, 3 is a condenser, and 4 is a product distillation tower. DETAILED DESCRIPTION

[0035] The following examples are only for further explanation of the present invention. It should be noted that all technical and scientific terms used in the present invention have the same meanings as in the technical field to which the present invention belongs unless otherwise specified. The experimental methods in the following examples without specifying specific conditions are all based on conventional techniques in the technical field, or according to the conditions recommended by the manufacturer; the reagents or instruments used without specifying the manufacturer are all conventional products that can be purchased commercially.

[0036] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0037] The Hβ molecular sieve selected in the present invention is commercially available, with a SiO2 / Al2O3 molar ratio of 25 and a specific surface area of ​​505.81 m 2 / g, total pore volume 0.65cm 3 / g, Na2O≦0.15wt%.

[0038] (I) Experimental study on the composition of catalyst

[0039] In order to explore the influence of the composition of the composite catalyst on the preparation of N-hydroxyethyl pyrrolidone from γ-butyrolactone and ethanolamine, the present invention conducted experiments of Examples 1 to 6 and Comparative Examples 1 to 4.

[0040] Example 1

[0041] This embodiment provides a method for preparing N-hydroxyethyl pyrrolidone, comprising the following steps:

[0042] 1. Preparation of composite catalyst

[0043] 20g Hβ molecular sieve was washed with 100mL 0.5mol·L -1 The zirconium oxychloride solution was impregnated for 12 hours, then dried at 100°C for 12 hours, and calcined at 350°C in an air atmosphere for 6 hours to obtain a precursor.

[0044] According to the mass ratio of ammonium sulfate solution to precursor of 0.8:1, 1 mol·L -1 The ammonium sulfate solution was added dropwise to the precursor and impregnated for 12 h using an equal volume impregnation method, consuming 17.0 mL of the ammonium sulfate solution. The precursor was then dried at 100 °C in an air atmosphere for 12 h and calcined at 600 °C in an air atmosphere for 5 h to obtain a composite catalyst.

[0045] The test results show that the SiO2 / Al2O3 molar ratio of the composite catalyst is 23.45 and the specific surface area is 300.87 m 2 / g, total pore volume 0.42cm 3 / g.

[0046] Figure 1 This is a SEM picture of the composite catalyst prepared in this example. It can be seen from the picture that the surface of the composite catalyst is rough and it is in the form of aggregated particles.

[0047] 2. Preparation of N-hydroxyethylpyrrolidone

[0048] like Figure 2 As shown, it is a schematic diagram of the structure of the reaction device for preparing N-hydroxypyrrolidone in this embodiment, in which 1 is a heating jacket, 2 is a fixed bed reaction tube, 3 is a condenser, and 4 is a product distillation tower. The fixed bed reactor is 800 mm long, 15 mm in inner diameter, and 140 mL in volume.

[0049] First, 15 mL (9.7 g, which is 10.7% of the fixed bed volume) of a composite catalyst with a particle size of 20 to 40 mesh after molding was loaded into the constant temperature section of a fixed bed reactor. After γ-butyrolactone and ethanolamine were prepared into a mixed solution at a molar ratio of 1.04:1, 30 mL / h was introduced into the fixed bed reactor containing the composite catalyst. The temperature of the constant temperature section of the reactor was 260° C., the reaction pressure was 5 MPa, the residence time was 0.5 h, and the composition of the reaction tube outlet was analyzed by gas chromatography. The experimental results are shown in Table 1.

[0050] Example 2

[0051] This embodiment provides a method for preparing N-hydroxyethyl pyrrolidone, comprising the following steps:

[0052] 1. Preparation of composite catalyst

[0053] 20g Hβ molecular sieve was washed with 100mL 1.5mol·L -1 The zirconium oxychloride solution was impregnated for 12 hours, then dried at 100°C for 12 hours, and calcined at 350°C in an air atmosphere for 6 hours to obtain a precursor.

[0054] According to the mass ratio of ammonium sulfate solution to precursor of 1:1, 1 mol·L -1 The ammonium sulfate solution was added dropwise to the precursor and impregnated for 12 h using an equal volume impregnation method, consuming 23.8 mL of the ammonium sulfate solution. The precursor was then dried at 100 °C in an air atmosphere for 12 h and calcined at 600 °C in an air atmosphere for 5 h to obtain a composite catalyst.

[0055] The test results show that the SiO2 / Al2O3 molar ratio of the composite catalyst is 21.13 and the specific surface area is 299.99m 2 / g, total pore volume 0.41cm 3 / g.

[0056] 2. The preparation method of N-hydroxyethyl pyrrolidone is the same as that in Example 1. The experimental results are shown in Table 1.

[0057] Example 3

[0058] This embodiment provides a method for preparing N-hydroxyethyl pyrrolidone, comprising the following steps:

[0059] 1. Preparation of composite catalyst

[0060] 20g Hβ molecular sieve was washed with 100mL 1.0mol·L -1 The zirconium oxychloride solution was impregnated for 12 hours, then dried at 100°C for 12 hours, and calcined at 350°C in an air atmosphere for 6 hours to obtain a precursor.

[0061] According to the mass ratio of ammonium sulfate solution to precursor of 1:1, 0.5 mol·L -1 The ammonium sulfate solution was added dropwise to the precursor and impregnated for 12 h using an equal volume impregnation method, consuming 20.0 mL of the ammonium sulfate solution. The precursor was then dried at 100° C. in an air atmosphere for 12 h and calcined at 600° C. in an air atmosphere for 5 h to obtain a composite catalyst.

[0062] The test results show that the SiO2 / Al2O3 molar ratio of the composite catalyst is 21.03 and the specific surface area is 286.76 m 2 / g, total pore volume 0.40cm 3 / g.

[0063] 2. The preparation method of N-hydroxyethyl pyrrolidone is the same as that in Example 1. The experimental results are shown in Table 1.

[0064] Example 4

[0065] This embodiment provides a method for preparing N-hydroxyethyl pyrrolidone, comprising the following steps:

[0066] 1. Preparation of composite catalyst

[0067] 20g Hβ molecular sieve was washed with 100mL 0.5mol·L -1 The zirconium oxychloride solution was impregnated for 12 hours, then dried at 100°C for 12 hours, and calcined at 350°C in an air atmosphere for 6 hours to obtain a precursor.

[0068] According to the mass ratio of ammonium sulfate solution to precursor of 1:1, 0.5 mol·L -1 The ammonium sulfate solution was added dropwise to the precursor and impregnated for 12 h using an equal volume impregnation method, consuming 16.0 mL of the ammonium sulfate solution. The precursor was then dried at 100 °C in an air atmosphere for 12 h and calcined at 600 °C in an air atmosphere for 5 h to obtain a composite catalyst.

[0069] The test results show that the SiO2 / Al2O3 molar ratio of the composite catalyst is 22.85 and the specific surface area is 319.32 m 2 / g, total pore volume 0.42cm 3 / g.

[0070] 2. The preparation method of N-hydroxyethyl pyrrolidone is the same as that in Example 1. The experimental results are shown in Table 1.

[0071] Example 5

[0072] This embodiment provides a method for preparing N-hydroxyethyl pyrrolidone, comprising the following steps:

[0073] 1. Preparation of composite catalyst

[0074] 20g Hβ molecular sieve was washed with 100mL 1.5mol·L -1 The precursor was obtained by impregnating the precursor in the ferric nitrate solution for 12 h, then drying at 100° C. for 12 h, and calcining at 350° C. in an air atmosphere for 6 h.

[0075] According to the mass ratio of ammonium molybdate solution to precursor of 1:1, 0.5 mol·L -1 The ammonium molybdate solution was added dropwise to the precursor and impregnated for 12 h using an equal volume impregnation method, consuming 20.2 mL of the ammonium molybdate solution. The precursor was then dried at 100 °C in an air atmosphere for 12 h and calcined at 600 °C in an air atmosphere for 5 h to obtain a composite catalyst.

[0076] The test results show that the SiO2 / Al2O3 molar ratio of the composite catalyst is 21.46 and the specific surface area is 279.18 m 2 / g, total pore volume 0.46cm 3 / g.

[0077] 2. The preparation method of N-hydroxyethyl pyrrolidone is the same as that in Example 1. The experimental results are shown in Table 1.

[0078] Example 6

[0079] This embodiment provides a method for preparing N-hydroxyethyl pyrrolidone, comprising the following steps:

[0080] 1. Preparation of composite catalyst

[0081] 20g Hβ molecular sieve was washed with 100mL 1.0mol·L -1 The precursor was obtained by immersing in titanium tetrachloride solution for 12 hours, drying at 100° C. for 12 hours, and calcining at 350° C. in air atmosphere for 6 hours.

[0082] According to the mass ratio of ammonium sulfate solution to precursor of 1:1, 1.0 mol·L -1 The ammonium sulfate solution was added dropwise to the precursor and impregnated for 12 hours using an equal volume impregnation method, consuming 17.4 mL of the ammonium sulfate solution. The precursor was then dried at 100°C in an air atmosphere for 12 hours and calcined at 600°C in an air atmosphere for 5 hours to obtain a composite catalyst.

[0083] The test results show that the SiO2 / Al2O3 molar ratio of the composite catalyst is 22.68 and the specific surface area is 286.74 m 2 / g, total pore volume 0.38cm 3 / g.

[0084] 2. The preparation method of N-hydroxyethyl pyrrolidone is the same as that in Example 1. The experimental results are shown in Table 1.

[0085] Comparative Example 1

[0086] First, 15 mL (9.3 g, which is 10.7% of the fixed bed volume) of Hβ molecular sieve with a particle size of 20-40 mesh was placed in the constant temperature section of the fixed bed reactor. After γ-butyrolactone and ethanolamine were prepared into a mixed solution with a molar ratio of 1.04:1, 30 mL / h was introduced into the fixed bed reactor equipped with Hβ molecular sieve. The temperature of the constant temperature section of the reactor was 260°C, the reaction pressure was 5 MPa, the residence time was 0.5 h, and the composition of the reaction tube outlet was analyzed by gas chromatography. The experimental results are shown in Table 1.

[0087] Comparative Example 2

[0088] 1. Preparation of composite catalyst

[0089] 52 g of zirconium oxychloride octahydrate was directly dried at 100° C. in an air atmosphere for 12 h, and calcined at 350° C. in an air atmosphere for 6 h to obtain a precursor.

[0090] According to the mass ratio of ammonium sulfate solution to precursor of 0.6:1, 1 mol·L -1 The ammonium sulfate solution was added dropwise to the precursor and impregnated for 12 h using an equal volume impregnation method, consuming 11.9 mL of the ammonium sulfate solution. The precursor was then dried at 100 °C in an air atmosphere for 12 h and calcined at 600 °C in an air atmosphere for 5 h to obtain a composite catalyst.

[0091] The specific surface area of ​​the composite catalyst is 69.33 m 2 / g, with a total pore volume of 0.13 cm 3 / g.

[0092] 2. The preparation method of N-hydroxyethyl pyrrolidone is the same as that in Example 1. The experimental results are shown in Table 1.

[0093] Comparative Example 3

[0094] 1. Preparation of composite catalyst

[0095] 20g Hβ molecular sieve was washed with 100mL 1.5mol·L -1 The zirconium oxychloride solution was impregnated for 12 hours, then dried at 100°C for 12 hours, and calcined at 600°C in an air atmosphere for 5 hours to obtain a composite catalyst.

[0096] The test results show that the SiO2 / Al2O3 molar ratio of the composite catalyst is 23.87 and the specific surface area is 300.12 m 2 / g, total pore volume 0.41cm 3 / g.

[0097] 2. The preparation method of N-hydroxyethyl pyrrolidone is the same as that in Example 1. The experimental results are shown in Table 1.

[0098] Comparative Example 4

[0099] 1. Preparation of composite catalyst

[0100] According to 1 mol·L -1 The mass ratio of ammonium sulfate solution to Hβ molecular sieve is 1.25:1. -1 The ammonium sulfate solution was added dropwise to 20 g of Hβ molecular sieve and impregnated for 12 h using an equal volume impregnation method, consuming 19.6 mL of the ammonium sulfate solution. The mixture was then dried at 100° C. in an air atmosphere for 12 h and calcined at 600° C. in an air atmosphere for 5 h to obtain a composite catalyst.

[0101] The test results show that the SiO2 / Al2O3 molar ratio of the composite catalyst is 24.59 and the specific surface area is 503.64m 2 / g, total pore volume 0.63cm 3 / g.

[0102] 2. The preparation method of N-hydroxyethyl pyrrolidone is the same as that in Example 1. The experimental results are shown in Table 1.

[0103] Table 1 Effect of catalyst composition on the reaction

[0104]

[0105] As can be seen from Table 1, compared with Comparative Example 1, the silicon-aluminum ratio of the composite catalyst prepared in the present invention is slightly reduced. This is because the auxiliary agent (oxide) and active component (SO4 2- or MoO3) will cause it to remove part of the framework aluminum, resulting in an increase in the aluminum oxide content on the molecular sieve surface, thereby increasing the acid strength of the Hβ molecular sieve. At the same time, the specific surface area and pore volume of the composite catalyst prepared by the present invention have a downward trend, indicating that the auxiliary agent and the active component are successfully loaded on the surface of the Hβ molecular sieve, and the combination of the active component and the auxiliary agent will increase the total acid content and acid strength of the catalyst prepared by the present application at the same time.

[0106] Compared with Comparative Example 2, the catalyst prepared by the present invention retains the characteristics of large specific surface area and large pore volume of Hβ molecular sieve. During the reaction process, it is more conducive to the mass transfer and transportation of reactants and products, while increasing the contact area between reactants and active sites, greatly increasing the reaction efficiency.

[0107] Compared with Comparative Examples 3 and 4, the catalyst prepared by the present invention retains the strong acidity characteristics of the solid superacid, provides more active sites during the reaction process, and significantly improves the conversion rate of the reactants and the selectivity of N-hydroxyethyl pyrrolidone.

[0108] Therefore, compared with Comparative Examples 1 to 4, the catalyst prepared by the present invention is more efficient in the reaction of synthesizing N-hydroxyethyl pyrrolidone, and both the conversion rate and the selectivity are significantly improved, wherein the conversion rate is as high as 88%, and the selectivity is as high as 92.3%. At the same time, it can also achieve efficient catalytic synthesis of high-purity N-hydroxyethyl pyrrolidone under low temperature, low pressure and anhydrous conditions, thereby reducing the subsequent separation of water and reducing environmental pollution.

[0109] (II) Experimental study on the selectivity of catalysts under different raw material ratios

[0110] In order to explore the effect of the molar ratio of γ-butyrolactone to ethanolamine on the conversion rate of γ-butyrolactone, the selectivity of N-hydroxyethylpyrrolidone and the purity of the N-hydroxyethylpyrrolidone product separated by subsequent distillation, the present invention conducted experiments in Examples 7 to 9.

[0111] Embodiments 7 to 9

[0112] The contents of Examples 7 to 9 are substantially the same as those of Example 2, except for the molar ratio of γ-butyrolactone to ethanolamine. For the specific molar ratio, conversion rate of γ-butyrolactone, selectivity and purity of N-hydroxyethylpyrrolidone, see Table 2.

[0113] Table 2 Catalytic effect of the catalyst prepared by the present invention on the reaction under different raw material ratios

[0114]

[0115] It can be seen from Table 2 that as the molar ratio of γ-butyrolactone to ethanolamine continues to decrease, the conversion rate of γ-butyrolactone remains at 85% to 88%, while the selectivity of NHP and the purity of the NHP product separated by subsequent distillation show a trend of first increasing and then decreasing. When the molar ratio of γ-butyrolactone to ethanolamine is 1.04:1, the catalytic effect is optimal.

[0116] The above embodiments are specific implementation methods of the present invention, but the implementation methods of the present invention are not limited to the above embodiments. Any other combination, change, modification, substitution and simplification that does not exceed the design concept of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for synthesizing N-hydroxyethyl pyrrolidone, characterized in that: The method comprises the following steps: adding a composite catalyst, γ-butyrolactone and ethanolamine into a reactor, maintaining a reaction temperature of 200-300°C and a reaction pressure of 0.1-5 MPa, and obtaining N-hydroxyethyl pyrrolidone after the reaction is completed; The composite catalyst uses Hβ molecular sieve as a carrier, loaded with additives and active components, and the active components are tungsten oxide, molybdenum oxide, SO4 2- or S2O8 2- One or more of the following; the Hβ molecular sieve accounts for 45-75% of the total mass of the composite catalyst, the additive accounts for 20-50% of the mass of the catalyst, and the active component accounts for 2-10% of the mass of the catalyst.

2. The method according to claim 1, characterized in that The auxiliary agent is one or more of zirconium dioxide, titanium dioxide or iron oxide.

3. The method according to claim 2, characterized in that The SiO2 / Al2O3 molar ratio of the composite catalyst is 20-30, and the specific surface area is 250-350 m 2 / g, pore volume 0.35~0.50 cm 3 / g.

4. The method according to any one of claims 1 to 3, characterized in that: The preparation method of the composite catalyst comprises the following steps: (1) Immersing the Hβ molecular sieve in a metal salt solution for 8 to 12 hours, then drying at 60 to 120°C for 8 to 12 hours, and then calcining at 200 to 400°C for 3 to 6 hours to obtain a precursor; (2) The precursor is added to a solution containing active components and immersed for 10 to 15 hours, then dried at 60 to 120 °C for 10 to 24 hours, and then calcined at 500 to 650 °C for 3 to 6 hours to obtain a composite catalyst for the synthesis of N-hydroxyethyl pyrrolidone from γ-butyrolactone and ethanolamine.

5. The method according to claim 4, characterized in that The concentration of the metal salt solution is 0.5 to 2 mol·L -1 The mass ratio of the metal salt to the Hβ molecular sieve carrier is 0.5 to 2.5:

1.

6. The method according to claim 5, characterized in that The concentration of the solution containing the active component is 0.5 to 1 mol·L -1 The mass ratio of the solution containing the active component to the precursor is 0.6 to 1:

1.

7. The method according to claim 6, characterized in that The metal salt solution is any one of a zirconium oxychloride solution, a ferric nitrate solution or a titanium tetrachloride solution.

8. The method according to claim 7, characterized in that The anions in the solution containing the active component are molybdate, tungstate, metatungstate, sulfate or persulfate, and the cations are hydrogen ions or ammonium ions.

9. The method according to claim 1, characterized in that: The reactor is a fixed bed reactor, and the loading amount of the catalyst is 5% to 80% of the volume of the fixed bed reactor.

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