阅读说明：本技术 一种利用1，4-丁二醇制备n-甲基吡咯烷酮的方法 (Method for preparing N-methyl pyrrolidone by using 1, 4-butanediol ) 是由 王亚 赵建勇 刘龙波 于 2021-08-11 设计创作，主要内容包括：本发明涉及一种制备N-甲基吡咯烷酮的方法,具体涉及利用1,4-丁二醇制备N-甲基吡咯烷酮的方法。本发明首先制备Sm、Yb共掺杂多孔三维花状CuO催化剂,由于该催化剂特殊的结构和Sm、Yb共掺杂的协同作用,保证了该催化剂用于1,4-丁二醇制备γ-丁内酯时,在常压下较短的时间内,1,4-丁二醇具有较高的转化率以及γ-丁内酯具有较高的选择性,进而保证了γ-丁内酯产率和纯度,在使用γ-丁内酯时,仅需简单的精馏即可用于N-甲基吡咯烷酮的制备,在γ-丁内酯制备N-甲基吡咯烷酮时,由于超声空化和介孔二氧化硅负载Zn/Mn/Cu复合催化剂共同作用,保证了γ-丁内酯的转化率和N-甲基吡咯烷酮的选择性,进而制备出高纯度、高产率的N-甲基吡咯烷酮。(The invention relates to a method for preparing N-methylpyrrolidone, in particular to a method for preparing N-methylpyrrolidone by using 1, 4-butanediol. The invention firstly prepares Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst, and due to the special structure of the catalyst and the synergistic effect of Sm and Yb codoped, the catalyst ensures that when the catalyst is used for preparing gamma-butyrolactone from 1, 4-butanediol, the 1, 4-butanediol has higher conversion rate and the gamma-butyrolactone has higher selectivity within a shorter time under normal pressure, thereby ensuring the yield and purity of the gamma-butyrolactone, when the gamma-butyrolactone is used, the catalyst can be used for preparing N-methyl pyrrolidone only by simple rectification, when the gamma-butyrolactone is used for preparing N-methyl pyrrolidone, the conversion rate of the gamma-butyrolactone and the selectivity of the N-methyl pyrrolidone are ensured due to the combined action of ultrasonic cavitation and mesoporous silica loaded Zn/Mn/Cu composite catalyst, thereby preparing the N-methyl pyrrolidone with high purity and high yield.)

1. A method for preparing N-methylpyrrolidone by using 1, 4-butanediol is characterized by comprising the following steps:

step S1, preparing gamma-butyrolactone: loading an Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst into a fixed bed reactor, discharging air in the reactor by adopting nitrogen, heating the reactor, firstly introducing hydrogen for a period of time, keeping introducing the hydrogen, introducing 1, 4-butanediol, keeping the reaction temperature at 240-260 ℃, keeping the molar ratio of the hydrogen to the alcohol at 5, keeping the pressure at normal pressure, continuously discharging gas, collecting a product by condensation, and further purifying the product by rectification; the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is characterized in that the doping ratio of Sm is 3-5%, the doping ratio of Yb is 2-4%, the doping ratio of Sm and Yb is the molar ratio of Sm and Yb elements to Cu elements in the CuO catalyst respectively, the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is of a three-dimensional flower-shaped structure formed by mutually staggering nanosheets, a porous structure is arranged on each nanosheet, the average particle size of the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is about 1.5-1.8 mu m, the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is composed of nanosheets with the thickness of 14-22nm, and the specific surface area is about 156.3-188.4m 2/g;

step S2, preparing N-methyl pyrrolidone: continuously pumping the purified gamma-butyrolactone and methylamine liquid in the step two into a tubular reactor by using a high-pressure metering pump according to the molar ratio of 1: 1.2, adding a mesoporous silica loaded Zn/Mn/Cu composite catalyst, simultaneously performing ultrasonic cavitation, controlling the ultrasonic power to be 450 ion-doped 600W and the ultrasonic frequency to be 23-16kHz, performing condensation reaction, controlling the temperature to be 240 ion-doped 260 ℃, the pressure to be 6.2-6.3MPa and the reaction residence time to be 3-4h, and using nitrogen as a pressure supplementing gas source for the reaction to obtain the gamma-butyrolactone and methylamine liquid; wherein the total Zn loading amount of the mesoporous silica loaded Zn/Mn/Cu composite catalyst is 1.2-1.8% of the weight of the mesoporous silica, the total Mn loading amount is 1.3-1.8% of the weight of the mesoporous silica, the total Cu loading amount is 1.4-1.6% of the weight of the mesoporous silica, the specific surface area of the mesoporous silica is 242.6-265.4m2/g, and the average pore diameter is 23-28 nm.

2. The method according to claim 1, further comprising a step S0 before the step S1: preparing Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst: adding 0.1mol of copper acetate, 3-5mmol of samarium nitrate and 2-4mmol of ytterbium nitrate into 2L of mixed solvent of glycerol, methanol and water, wherein the volume ratio of glycerol to methanol to water is 1: 1: 2, adding 0.4-0.5mol of urea, performing magnetic stirring for 10-20min, then adding 0.4-0.5mol of sodium dodecyl benzene sulfonate, continuing magnetic stirring for 5-10min, then transferring into a high-pressure reaction kettle with a polytetrafluoroethylene lining for solvothermal reaction, sealing, controlling the pressure of the reaction kettle to be 1.3-1.5MPa, preserving the temperature for 8-10h at 180-200 ℃, cooling to room temperature, taking out, filtering, washing and drying to obtain the Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst.

3. The method as claimed in any one of claims 1 to 2, wherein the doping ratio of Sm to Yb in the Sm and Yb co-doped porous three-dimensional flower-like CuO catalyst is 4%, the doping ratio of Yb is 3%, the doping ratios of Sm to Yb are molar ratios of Sm element and Yb element to Cu element in the CuO catalyst respectively, the Sm and Yb co-doped porous three-dimensional flower-like CuO catalyst is formed by interleaving nanosheets to form a three-dimensional flower-like structure, the sheets have a porous structure, the Sm and Yb co-doped porous three-dimensional flower-like CuO catalyst has an average particle size of about 1.5 μm, is composed of nanosheets with a thickness of 20nm, and has a specific surface area of about 188.4m 2/g.

4. The method according to any one of claims 1 to 3, wherein the mesoporous silica supported Zn/Mn/Cu composite catalyst is prepared by a method comprising: soaking 100g of mesoporous silica in an aqueous solution of zinc nitrate, manganese nitrate and copper nitrate, continuously stirring for 4 hours, taking out, heating and drying at 100 ℃ for 2 hours, roasting the loaded mesoporous silica in a high-temperature furnace at 400-500 ℃ for 2-3 hours, and cooling to obtain the mesoporous silica loaded Zn/Mn/Cu composite catalyst.

5. The method according to any one of claims 1 to 4, wherein the mesoporous silica supports a Zn/Mn/Cu composite catalyst, wherein the total Zn loading is 1.2% by weight of the mesoporous silica, based on the weight of Zn; the total loading amount of Mn is 1.8 percent of the weight of the mesoporous silica, based on the weight of Mn; the total loading of Cu is 1.5 percent of the weight of the mesoporous silica, the specific surface area of the mesoporous silica is 265.4m2/g according to the weight of Cu, and the average pore diameter is 25 nm.

6. The method according to claim 2, wherein in step S0, 0.1mol of copper acetate, 4mmol of samarium nitrate and 3mmol of ytterbium nitrate are added to 2L of a mixed solvent of glycerol, methanol and water, wherein the volume ratio of glycerol, methanol and water is 1: 1: 2, adding 0.4mol of urea, carrying out magnetic stirring for 10min, then adding 0.4mol of sodium dodecyl benzene sulfonate, and continuing to carry out magnetic stirring for 10 min.

7. The method according to claim 2, wherein in step S0, the pressure in the reaction vessel is controlled to 1.5MPa, and the temperature is maintained at 200 ℃ for 8 hours.

8. The production method according to any one of claims 1 to 7, wherein in step S1, the reaction temperature is maintained at 250 ℃.

9. The process according to any one of claims 1 to 8, wherein in step S2, the condensation reaction is carried out at an ultrasonic frequency of 25kHz and an ultrasonic power of 600W, the temperature is controlled at 260 ℃, the pressure is 6.3MPa, and the reaction residence time is 3 hours.

10. The method according to claim 4, wherein the mesoporous silica supported Zn/Mn/Cu composite catalyst is prepared by a method in which the calcination temperature is 500 ℃ and the calcination time is 2 hours.

Technical Field

The invention relates to a method for synthesizing N-methyl pyrrolidone, in particular to a method for directly preparing a high-purity N-methyl pyrrolidone product by using 1, 4-butanediol to generate an intermediate product gamma-butyrolactone without purification.

Background

N-methyl pyrrolidone (NMP) belongs to nitrogen heterocyclic compounds, has a molecular formula of C5H9NO, a boiling point of 204 ℃, a flash point of 95 ℃, is a liquid with slight ammonia smell, is miscible with water in any proportion, and is almost completely mixed with all solvents (ethanol, acetaldehyde, ketone, aromatic hydrocarbon and the like). NMP is a polar aprotic solvent, has high boiling point, strong polarity, low viscosity, strong dissolving capacity, no corrosion, low toxicity, strong biodegradability, low volatility, excellent chemical stability and thermal stability, is mainly applied to various industries such as petrochemical industry, plastic industry, medicines, pesticides, dyes, lithium ion battery manufacturing industry and the like, is widely applied to aromatic extraction, purification of acetylene, olefin and diene, and is also applied to a solvent of a polymer and a medium of a polymerization reaction.

At present, the methods for synthesizing NMP at home and abroad include the synthesis of gamma-butyrolactone and monomethylamine, the preparation of N-methylpyrrolidone by dehydrogenation-amination of 1, 4-butanediol and the like, and the methods for synthesizing NMP by gas phase catalysis, synthesizing NMP by electrolysis and the like.

However, the catalyst used in the dehydrogenation-amination method of 1, 4-butanediol has low selectivity and low conversion rate, and as the chinese patent CN102029156B reports that 1, 4-butanediol is reacted in the presence of an oxide catalyst containing Cu, Zr and Ce to obtain γ -butyrolactone, the method has the problems of long reaction time, low selectivity and low yield of γ -butyrolactone. The catalyst used in CN11077317A has the following general formula: m1aM2bM3cOx, wherein M1 is Cu, M2 is at least one element selected from Al and Si, and M3 is at least one element selected from Na, Mg, Ce, Cr, Mn and Zn, but the conversion rate of 1, 4-butanediol is low, the selectivity of gamma-butyrolactone is low, the yield is low, and the like, and meanwhile, the preparation under a high-pressure state is required, and the requirement on equipment is high.

Therefore, the existing solid catalyst still has the major defects, the solid catalyst still has the problems of low conversion rate of the raw material 1, 4-butanediol and low selectivity of the product gamma-butyrolactone, and the requirement on equipment is high under a high-pressure state.

Disclosure of Invention

The invention aims to provide a method for preparing N-methylpyrrolidone by using 1, 4-butanediol, firstly preparing Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst, ensuring that 1, 4-butanediol has higher conversion rate and gamma-butyrolactone has higher selectivity in a shorter time under normal pressure when the catalyst is used for preparing the gamma-butyrolactone by using the 1, 4-butanediol due to the special structure of the catalyst and the synergistic effect of the Sm and Yb codoping, further ensuring the yield and the purity of the gamma-butyrolactone, only needing simple rectification to prepare the N-methylpyrrolidone when the gamma-butyrolactone is used, and under the combined action of ultrasonic cavitation and mesoporous silica loaded Zn/Mn/Cu composite catalyst when the gamma-butyrolactone is used for preparing the N-methylpyrrolidone, ensures the conversion rate of gamma-butyrolactone and the selectivity of N-methyl pyrrolidone, and further prepares the N-methyl pyrrolidone with high purity and high yield.

The technical scheme for solving the problems is as follows:

a method for preparing N-methylpyrrolidone by using 1, 4-butanediol comprises the following steps:

step S1, preparing gamma-butyrolactone: loading an Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst into a fixed bed reactor, discharging air in the reactor by adopting nitrogen, heating the reactor, firstly introducing hydrogen for a period of time, keeping introducing the hydrogen, introducing 1, 4-butanediol, keeping the reaction temperature at 240-260 ℃, keeping the molar ratio of the hydrogen to the alcohol at 5, continuously discharging gas, keeping the pressure at normal pressure, continuously discharging the gas, collecting a product by condensation, and further purifying the product by rectification; the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is characterized in that the doping ratio of Sm is 3-5%, the doping ratio of Yb is 2-4%, the doping ratio of Sm and Yb is the molar ratio of Sm and Yb elements to Cu elements in the CuO catalyst respectively, the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is of a three-dimensional flower-shaped structure formed by mutually staggering nanosheets, a porous structure is arranged on each nanosheet, the average particle size of the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is about 1.5-1.8 mu m, the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is composed of nanosheets with the thickness of 14-22nm, and the specific surface area is about 156.3-188.4m 2/g;

step S2, preparing N-methyl pyrrolidone: continuously pumping the gamma-butyrolactone obtained by purification in the step two and methylamine liquid into a tubular reactor by using a high-pressure metering pump according to the molar ratio of 1: 1.2, adding a mesoporous silica loaded Zn/Mn/Cu composite catalyst, simultaneously performing ultrasonic cavitation with the ultrasonic power of 450 ion-doped 600W and the ultrasonic frequency of 23-16kHz, performing condensation reaction at the temperature of 240 ion-doped 260 ℃, the pressure of 6.2-6.3MPa and the reaction residence time of 3-4h, and taking nitrogen as a pressure supplementing gas source for the reaction to obtain the gamma-butyrolactone and methylamine liquid; wherein the total Zn loading amount of the mesoporous silica loaded Zn/Mn/Cu composite catalyst is 1.2-1.8% of the weight of the mesoporous silica, the total Mn loading amount is 1.3-1.8% of the weight of the mesoporous silica, the total Cu loading amount is 1.4-1.6% of the weight of the mesoporous silica, the specific surface area of the mesoporous silica is 242.6-265.4m2/g, and the average pore diameter is 23-28 nm.

Further, before the step S1, there is a step S0: preparing Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst: adding 0.1mol of copper acetate, 3-5mmol of samarium nitrate and 2-4mmol of ytterbium nitrate into 2L of mixed solvent of glycerol, methanol and water, wherein the volume ratio of glycerol to methanol to water is 1: 1: 2, adding 0.4-0.5mol of urea, performing magnetic stirring for 10-20min, then adding 0.4-0.5mol of sodium dodecyl benzene sulfonate, continuing magnetic stirring for 5-10min, then transferring into a high-pressure reaction kettle with a polytetrafluoroethylene lining for solvothermal reaction, sealing, controlling the pressure of the reaction kettle to be 1.3-1.5MPa, preserving the temperature for 8-10h at 180-200 ℃, cooling to room temperature, taking out, filtering, washing and drying to obtain the Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst.

Furthermore, in the adopted Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst, the doping ratio of Sm is 4%, the doping ratio of Yb is 3%, the doping ratio of Sm and Yb is the molar ratio of Sm and Yb elements to Cu elements in the CuO catalyst respectively, the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is a three-dimensional flower-shaped structure formed by mutually staggering nanosheets, a porous structure is arranged on a lamella, the average particle size of the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is about 1.5 mu m, the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is composed of the nanosheets with the thickness of 20nm, and the specific surface area is about 188.4m 2/g.

Further, the preparation method of the mesoporous silica supported Zn/Mn/Cu composite catalyst comprises the following steps: soaking 100g of mesoporous silica in an aqueous solution of zinc nitrate, manganese nitrate and copper nitrate, continuously stirring for 4 hours, taking out, heating and drying at 100 ℃ for 2 hours, roasting the loaded mesoporous silica in a high-temperature furnace at 400-500 ℃ for 2-3 hours, and cooling to obtain the mesoporous silica loaded Zn/Mn/Cu composite catalyst.

Further, the mesoporous silica supports a Zn/Mn/Cu composite catalyst, wherein the total Zn supporting amount is 1.2% of the weight of the mesoporous silica, and is calculated by the weight of Zn; the total loading amount of Mn is 1.8 percent of the weight of the mesoporous silica, based on the weight of Mn; the total loading of Cu is 1.5 percent of the weight of the mesoporous silica, the specific surface area of the mesoporous silica is 265.4m2/g according to the weight of Cu, and the average pore diameter is 25 nm.

Further, in step S0, 0.1mol of copper acetate, 4mmol of samarium nitrate, and 3mmol of ytterbium nitrate are added to 2L of a mixed solvent of glycerol, methanol, and water, wherein the volume ratio of glycerol, methanol, and water is 1: 1: 2, adding 0.4mol of urea, carrying out magnetic stirring for 10min, then adding 0.4mol of sodium dodecyl benzene sulfonate, and continuing to carry out magnetic stirring for 10 min.

Further, in step S0, the pressure in the reaction vessel was controlled to 1.5MPa, and the temperature was maintained at 200 ℃ for 8 hours.

Further, in step S1, the reaction temperature is maintained at 250 ℃.

Further, in step S2, the condensation reaction is carried out with the ultrasonic power of 600W and the ultrasonic frequency of 25kHz, the temperature is controlled to be 260 ℃, the pressure is 6.3MPa, and the reaction residence time is 3 h.

Further, in the preparation method of the mesoporous silica supported Zn/Mn/Cu composite catalyst, the roasting temperature is 500 ℃ and the time is 2 hours.

Further, in step S1, the conversion of 1, 4-butanediol is 100%, the selectivity of γ -butyrolactone is 99.92% or more, and the yield of γ -butyrolactone is 99.92% or more.

Further, in step S2, the conversion rate of γ -butyrolactone is 99.90% or more, and the selectivity of the target product, N-methylpyrrolidone, is 99.74% or more.

The invention has the beneficial effects that:

(1) the invention uses mixed solvent of glycerol, methanol and water as mixed solvent, sodium dodecyl benzene sulfonate as surfactant and urea as alkaline regulator, and adopts solvothermal method to effectively prepare the CuO catalyst with Sm and Yb codoped porous three-dimensional flower-ball structure, wherein CuO has a three-dimensional flower-like structure formed by interlacing nano sheets, a sheet layer has a porous structure and has a larger specific surface area, and a micro-reactor is formed in pores on the sheet layer and interlaced pores between the sheet layers to promote the generation and the proceeding of reaction, increase the active sites, increase the conversion rate of 1, 4-butanediol, and enhance the selectivity of gamma-butyrolactone to a certain extent, and because of the special structure of the catalyst and the Co-doping of Sm and Yb, the catalyst can ensure that the gamma-butyrolactone has higher selectivity and 1 of gamma-butyrolactone under normal pressure when preparing the gamma-butyrolactone by 1, 4-butanediol, conversion of 4-butanediol.

(2) The Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst is used for preparing the gamma-butyrolactone from the 1, 4-butanediol, and the Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst has good synergistic effect, so that the selectivity of the gamma-butyrolactone and the conversion rate of the 1, 4-butanediol can be remarkably improved; compared with the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst used for preparing the gamma-butyrolactone from the 1, 4-butanediol, the Sm or Yb co-doped porous three-dimensional flower-shaped CuO catalyst prepared by independently doping Sm or Yb has the advantages that the selectivity of the gamma-butyrolactone and the conversion rate of the 1, 4-butanediol are obviously reduced, so that the yield of the gamma-butyrolactone is obviously reduced, the Sm and Yb co-doping plays a good synergistic effect, the lattice structure is synergistically improved, and the structure of a pore channel is changed, so that the selectivity of the gamma-butyrolactone and the conversion rate of the 1, 4-butanediol are influenced.

(3) The invention utilizes the structure of the ultrasonic cavitation and mesoporous silica loaded Zn/Mn/Cu composite catalyst to play a good synergistic role, can form a microreactor, accelerates the reaction, increases active sites, and further increases the conversion rate of the composite catalyst gamma-butyrolactone and the selectivity of the N-methylpyrrolidone.

Description of the figures

Fig. 1 is an SEM image of Sm, Yb co-doped porous three-dimensional flower-like CuO catalyst of example 1 of the present invention.

Detailed Description

Example 1: a method for preparing N-methylpyrrolidone by using 1, 4-butanediol comprises the following specific steps:

step one, preparing Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst: adding 0.1mol of copper acetate, 4mmol of samarium nitrate and 3mmol of ytterbium nitrate into 2L of a mixed solvent of glycerol, methanol and water (the volume ratio of glycerol to methanol to water is 1: 1: 2), adding 0.4mol of urea, carrying out magnetic stirring for 10min, then adding 0.4mol of sodium dodecyl benzene sulfonate, continuing magnetic stirring for 10min, then transferring into a high-pressure reaction kettle with a polytetrafluoroethylene lining for carrying out solvothermal reaction, sealing, controlling the pressure of the reaction kettle to be 1.5MPa, preserving heat at 200 ℃ for 8h, cooling to room temperature, taking out, filtering, washing and drying to obtain the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst. The doping ratio of Sm to Yb in the obtained Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is 4 percent, the doping ratio of Yb is 3 percent, and the doping ratios of Sm to Yb are the molar ratios of Sm and Yb elements to Cu elements in the CuO catalyst respectively. An SEM image of the obtained Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is shown in figure 1, and the CuO is formed by interleaving nanosheets to form a three-dimensional flower-shaped structure, the nanosheets are provided with the porous structure, and the interleaved pores are formed among the nanosheets, so that the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is about 1.5 mu m in average particle size and is formed by the nanosheets with the thickness of 20nm, and the specific surface area reaches 188.4m 2/g.

Step two, preparing gamma-butyrolactone: and (2) filling the Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst (30g) prepared in the step one into a fixed bed reactor, discharging air in the reactor by adopting nitrogen, heating the reactor, introducing hydrogen for a period of time, keeping the introduction of the hydrogen, introducing 1, 4-butanediol, keeping the reaction temperature at 250 ℃, the molar ratio of the hydrogen to the alcohol at 5, keeping the pressure at normal pressure, continuously discharging gas, condensing and collecting products, analyzing the selectivity of gamma-butyrolactone and the conversion rate of the 1, 4-butanediol by using gas chromatography, keeping the conversion rate of the 1, 4-butanediol at 100%, the selectivity of the gamma-butyrolactone at 99.96%, and the yield of the gamma-butyrolactone at 99.96%, and further purifying the products by rectifying.

Step three, preparing N-methyl pyrrolidone: and (2) continuously pumping the purified gamma-butyrolactone and methylamine liquid in the step two into a tubular reactor by using a high-pressure metering pump according to the molar ratio of 1: 1.2, adding a mesoporous silica loaded Zn/Mn/Cu composite catalyst (30g), simultaneously performing ultrasonic cavitation with the ultrasonic power of 600W and the ultrasonic frequency of 25kHz, performing condensation reaction at the temperature of 260 ℃, the pressure of 6.3MPa and the reaction residence time of 3h, wherein nitrogen is used as a pressure supplementing gas source for the reaction. After the reaction, the conversion rate of the gamma-butyrolactone is 99.93 percent, and the selectivity of the target product N-methyl pyrrolidone is over 99.82 percent.

The preparation method of the mesoporous silica loaded Zn/Mn/Cu composite catalyst comprises the following steps: 100g of mesoporous silica is soaked in an aqueous solution of zinc nitrate, manganese nitrate and copper nitrate, continuously stirred for 4 hours, taken out and heated and dried at 100 ℃ for 2 hours. Roasting the loaded mesoporous silica in a high-temperature furnace at 500 ℃ for 2 hours, and cooling to obtain the mesoporous silica loaded Zn/Mn/Cu composite catalyst, wherein the total Zn loading is 1.2% of the weight of the mesoporous silica, and is calculated by the weight of Zn; the total loading amount of Mn is 1.8 percent of the weight of the mesoporous silica, based on the weight of Mn; the total Cu loading is 1.5 percent of the weight of the mesoporous silica, the specific surface area of the mesoporous silica is 265.4m2/g, and the average pore diameter is 25 nm.

Example 2: a method for preparing N-methylpyrrolidone by using 1, 4-butanediol comprises the following specific steps:

step one, preparing Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst: adding 0.1mol of copper acetate, 3mmol of samarium nitrate and 4mmol of ytterbium nitrate into 2L of a mixed solvent of glycerol, methanol and water (the volume ratio of glycerol to methanol to water is 1: 1: 2), adding 0.5mol of urea, carrying out magnetic stirring for 20min, then adding 0.5mol of sodium dodecyl benzene sulfonate, continuing magnetic stirring for 5min, then transferring into a high-pressure reaction kettle with a polytetrafluoroethylene lining for carrying out solvothermal reaction, sealing, controlling the pressure of the reaction kettle to be 1.3MPa, preserving heat at 180 ℃ for 10h, cooling to room temperature, taking out, filtering, washing and drying to obtain the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst. The doping ratio of Sm to Yb in the obtained Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is 3 percent, the doping ratio of Yb is 4 percent, and the doping ratios of Sm to Yb are the molar ratios of Sm and Yb elements to Cu elements in the CuO catalyst respectively. The obtained Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst is formed by mutually staggering nanosheets to form a three-dimensional flower-shaped structure, the lamella has a porous structure, staggered pores are formed among the lamellae, the average particle size of the Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst is about 1.6 mu m, the Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst is formed by the nanosheets with the thickness of 22nm, and the specific surface area reaches 156.3m 2/g.

Step two, preparing gamma-butyrolactone: and (2) filling the Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst (30g) prepared in the step one into a fixed bed reactor, discharging air in the reactor by adopting nitrogen, heating the reactor, introducing hydrogen for a period of time, keeping the introduction of the hydrogen, introducing 1, 4-butanediol, keeping the reaction temperature at 260 ℃, the molar ratio of the hydrogen to the alcohol at 5, keeping the pressure at normal pressure, continuously discharging gas, condensing and collecting products, analyzing the selectivity of gamma-butyrolactone and the conversion rate of the 1, 4-butanediol by virtue of gas chromatography, keeping the conversion rate of the 1, 4-butanediol at 100%, the selectivity of the gamma-butyrolactone at 99.94%, and the yield of the gamma-butyrolactone at 99.94%, and further purifying the products by rectification.

Step three, preparing N-methyl pyrrolidone: and (2) continuously pumping the purified gamma-butyrolactone and methylamine liquid in the step two into a tubular reactor by using a high-pressure metering pump according to the molar ratio of 1: 1.3, adding a mesoporous silica loaded Zn/Mn/Cu composite catalyst (30g), simultaneously performing ultrasonic cavitation with the ultrasonic power of 550W and the ultrasonic frequency of 23kHz, performing condensation reaction at the temperature of 260 ℃, the pressure of 6.2MPa and the reaction residence time of 3h, wherein nitrogen is used as a pressure compensating gas source for the reaction. After the reaction, the conversion rate of the gamma-butyrolactone is over 99.91 percent through detection, and the selectivity of the target product N-methyl pyrrolidone is over 99.78 percent.

The preparation method of the mesoporous silica loaded Zn/Mn/Cu composite catalyst comprises the following steps: 100g of mesoporous silica is soaked in an aqueous solution of zinc nitrate, manganese nitrate and copper nitrate, continuously stirred for 4 hours, taken out and heated and dried at 100 ℃ for 2 hours. Roasting the loaded mesoporous silica in a high-temperature furnace at 400 ℃ for 3 hours, and cooling to obtain the mesoporous silica loaded Zn/Mn/Cu composite catalyst, wherein the total Zn loading is 1.6% of the weight of the mesoporous silica, and is calculated by the weight of Zn; the total loading amount of Mn is 1.5 percent of the weight of the mesoporous silica, based on the weight of Mn; the total Cu loading is 1.6 percent of the weight of the mesoporous silica, the specific surface area of the mesoporous silica is 245.4m2/g, and the average pore diameter is 28 nm.

Example 3: a method for preparing N-methylpyrrolidone by using 1, 4-butanediol comprises the following specific steps:

step one, preparing Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst: adding 0.1mol of copper acetate, 5mmol of samarium nitrate and 2mmol of ytterbium nitrate into 2L of a mixed solvent of glycerol, methanol and water (the volume ratio of glycerol to methanol to water is 1: 1: 2), adding 0.6mol of urea, carrying out magnetic stirring for 15min, then adding 0.5mol of sodium dodecyl benzene sulfonate, continuing magnetic stirring for 8min, then transferring into a high-pressure reaction kettle with a polytetrafluoroethylene lining for carrying out solvothermal reaction, sealing, controlling the pressure of the reaction kettle to be 1.8MPa, preserving the heat at 220 ℃ for 5h, cooling to room temperature, taking out, filtering, washing and drying to obtain the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst. The doping ratio of Sm to Yb in the obtained Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst is 5 percent, the doping ratio of Yb is 2 percent, and the doping ratios of Sm to Yb are the molar ratios of Sm and Yb elements to Cu elements in the CuO catalyst respectively. The obtained Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst is formed by mutually staggering nanosheets to form a three-dimensional flower-shaped structure, the lamella has a porous structure, staggered pores are formed among the lamellae, the average particle size of the Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst is about 1.8 mu m, the Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst is formed by the nanosheets with the thickness of 14nm, and the specific surface area reaches 161.2m 2/g.

Step two, preparing gamma-butyrolactone: and (2) filling the Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst (30g) prepared in the step one into a fixed bed reactor, discharging air in the reactor by adopting nitrogen, heating the reactor, introducing hydrogen for a period of time, keeping the hydrogen introduction, introducing 1, 4-butanediol, keeping the molar ratio of the hydrogen to the alcohol at 5, keeping the reaction temperature at 240 ℃, keeping the pressure at normal pressure, continuously discharging gas, condensing and collecting products, analyzing the selectivity of gamma-butyrolactone and the conversion rate of the 1, 4-butanediol by using gas chromatography, keeping the conversion rate of the 1, 4-butanediol at 100%, the selectivity of the gamma-butyrolactone at 99.92%, and the yield of the gamma-butyrolactone at 99.92%, and further purifying the products by rectifying.

Step three, preparing N-methyl pyrrolidone: and (2) continuously pumping the purified gamma-butyrolactone and methylamine liquid in the step two into a tubular reactor by using a high-pressure metering pump according to the molar ratio of 1: 1.3, adding a mesoporous silica loaded Zn/Mn/Cu composite catalyst (30g), simultaneously performing ultrasonic cavitation with the ultrasonic power of 450W and the ultrasonic frequency of 26kHz, performing condensation reaction at the temperature of 240 ℃, the pressure of 6.3MPa and the reaction residence time of 4h, wherein nitrogen is used as a pressure compensating gas source for the reaction. After the reaction, the conversion rate of the gamma-butyrolactone is 99.90 percent, and the selectivity of the target product N-methyl pyrrolidone is over 99.74 percent.

The preparation method of the mesoporous silica loaded Zn/Mn/Cu composite catalyst comprises the following steps: 100g of mesoporous silica is soaked in an aqueous solution of zinc nitrate, manganese nitrate and copper nitrate, continuously stirred for 4 hours, taken out and heated and dried at 100 ℃ for 2 hours. Roasting the loaded mesoporous silica in a high-temperature furnace at 400 ℃ for 3 hours, and cooling to obtain the mesoporous silica loaded Zn/Mn/Cu composite catalyst, wherein the total Zn loading is 1.8% of the weight of the mesoporous silica, and is calculated by the weight of Zn; the total loading amount of Mn is 1.3 percent of the weight of the mesoporous silica, based on the weight of Mn; the total loading amount of Cu is 1.4 percent of the weight of the mesoporous silica, the specific surface area of the mesoporous silica is 242.6m2/g, and the average pore diameter is 23 nm.

Comparative example 1: the specific steps of a method for preparing N-methylpyrrolidone by using 1, 4-butanediol are the same as those of example 1, except that sodium dodecyl benzene sulfonate is not added in the step one, and the other steps are the same. The Sm and Yb codoped CuO nanoparticles are obtained in the first step, the average particle size of the nanoparticles is about 184nm, and three-dimensional flower-shaped CuO cannot be obtained. The selectivity of gamma-butyrolactone and the conversion of 1, 4-butanediol in step two were analyzed by gas chromatography, the conversion of 1, 4-butanediol was 86.44%, the selectivity of gamma-butyrolactone was 99.29%, and the yield of gamma-butyrolactone was 85.83%.

Comparative example 2: the specific steps of a method for preparing N-methylpyrrolidone by using 1, 4-butanediol are the same as those of example 1, except that glycerol is not added in the step one, and other steps are the same. The Sm and Yb codoped CuO nanoparticles are obtained in the first step, the average particle size of the nanoparticles is about 196nm, and three-dimensional flower-shaped CuO cannot be obtained. The selectivity of gamma-butyrolactone and the conversion of 1, 4-butanediol in step two were analyzed by gas chromatography, the conversion of 1, 4-butanediol was 83.21%, the selectivity of gamma-butyrolactone was 99.13%, and the yield of gamma-butyrolactone was 82.49%.

Comparative example 3: the specific steps of a method for preparing N-methylpyrrolidone by using 1, 4-butanediol are the same as those of example 1, except that methanol is not added in the step one, and the other steps are the same. The Sm and Yb codoped CuO nanoparticles are obtained in the first step, the average particle size of the nanoparticles is about 175nm, and three-dimensional flower-shaped CuO cannot be obtained. The selectivity of gamma-butyrolactone and the conversion of 1, 4-butanediol in step two were analyzed by gas chromatography, the conversion of 1, 4-butanediol was 87.23%, the selectivity of gamma-butyrolactone was 99.36%, and the yield of gamma-butyrolactone was 86.67%.

Comparative example 4: the specific steps of a method for preparing N-methylpyrrolidone by using 1, 4-butanediol are the same as those of example 1, except that water is not added in the step one, and the other steps are the same. The Sm and Yb codoped CuO nanoparticles are obtained in the first step, the average particle size of the nanoparticles is about 215nm, and three-dimensional flower-shaped CuO cannot be obtained. The selectivity of gamma-butyrolactone and the conversion of 1, 4-butanediol in step two were analyzed by gas chromatography, the conversion of 1, 4-butanediol was 82.32%, the selectivity of gamma-butyrolactone was 99.12%, and the yield of gamma-butyrolactone was 81.60%.

As can be seen from example 1 and comparative examples 1 to 4, it is demonstrated that the mixed solvent of glycerol, methanol, water and sodium dodecylbenzenesulfonate plays a crucial role in preparing the porous three-dimensional flower-like structure CuO catalyst with a large specific surface area, and one or two solvents and sodium dodecylbenzenesulfonate can not prepare the porous three-dimensional flower-like structure CuO catalyst with a large specific surface area, thereby seriously affecting the conversion rate of 1, 4-butanediol and affecting the selectivity of γ -butyrolactone, because the prepared Sm and Yb co-doped porous three-dimensional flower-like CuO catalyst has a special three-dimensional flower-like structure and a large specific surface area, and a microreactor is formed in the pores on the lamella and the pores staggered between the lamellae to promote the occurrence and progress of the reaction, increase the active sites and increase 1, 4-butanediol conversion rate, and enhances the selectivity of gamma-butyrolactone to a certain extent, and because of the special structure of the catalyst and Sm and Yb codoping, the catalyst can ensure that the gamma-butyrolactone prepared from 1, 4-butanediol has higher gamma-butyrolactone selectivity and 1, 4-butanediol conversion rate under normal pressure.

Comparative example 5: the specific steps of a method for preparing N-methylpyrrolidone by using 1, 4-butanediol are the same as those of example 1, except that samarium nitrate is not added in the step one, and the other steps are the same. The porous three-dimensional flower-shaped CuO catalyst doped with Yb is obtained in the first step, wherein the doping ratio of Yb in the CuO is 3%, and the doping ratio of Yb is the molar ratio of Yb element to Cu element in the CuO catalyst. The selectivity of gamma-butyrolactone and the conversion of 1, 4-butanediol in step two were analyzed by gas chromatography, the conversion of 1, 4-butanediol was 92.12%, the selectivity of gamma-butyrolactone was 81.32%, and the yield of gamma-butyrolactone was 74.91%.

Comparative example 6: the specific steps of a method for preparing N-methylpyrrolidone by using 1, 4-butanediol are the same as those of example 1, except that samarium nitrate is not added in the step one, and the other steps are the same. The porous three-dimensional flower-shaped CuO catalyst doped with Yb is obtained in the first step, wherein the doping ratio of Yb in the CuO is 7%, and the doping ratio of Yb is the molar ratio of Yb element to Cu element in the CuO catalyst. The selectivity of gamma-butyrolactone and the conversion of 1, 4-butanediol in step two were analyzed by gas chromatography, the conversion of 1, 4-butanediol was 93.21%, the selectivity of gamma-butyrolactone was 82.56%, and the yield of gamma-butyrolactone was 76.95%.

Comparative example 7: the specific steps of a method for preparing N-methylpyrrolidone by using 1, 4-butanediol are the same as those of example 1, except that ytterbium nitrate is not added in the step one, and the other steps are the same. And step one, obtaining Sm-doped porous three-dimensional flower-shaped CuO, wherein the doping ratio of Sm in the CuO is 4%, and the doping ratio of Sm is the molar ratio of Sm to Cu. The selectivity of gamma-butyrolactone and the conversion of 1, 4-butanediol in step two were analyzed by gas chromatography, the conversion of 1, 4-butanediol was 91.05%, the selectivity of gamma-butyrolactone was 83.89%, and the yield of gamma-butyrolactone was 76.38%.

Comparative example 8: the specific steps of a method for preparing N-methylpyrrolidone by using 1, 4-butanediol are the same as those of example 1, except that ytterbium nitrate is not added in the step one, and the other steps are the same. And step one, obtaining Sm-doped porous three-dimensional flower-shaped CuO, wherein the doping ratio of Sm in the CuO is 7%, and the doping ratio of Sm is the molar ratio of Sm to Cu. The selectivity of gamma-butyrolactone and the conversion of 1, 4-butanediol in step two were analyzed by gas chromatography, the conversion of 1, 4-butanediol was 92.14%, the selectivity of gamma-butyrolactone was 84.78%, and the yield of gamma-butyrolactone was 78.12%.

Comparative example 9: the specific steps of a method for preparing N-methylpyrrolidone by using 1, 4-butanediol are the same as those of example 1, except that samarium nitrate and ytterbium nitrate are not added in the step one, and other steps are the same. And step one, obtaining the porous three-dimensional flower-shaped CuO. The selectivity of gamma-butyrolactone and the conversion of 1, 4-butanediol in step two were analyzed by gas chromatography, the conversion of 1, 4-butanediol was 70.88%, the selectivity of gamma-butyrolactone was 83.23%, and the yield of gamma-butyrolactone was 58.99%.

As can be seen from example 1 and comparative examples 5 to 9, experiments surprisingly found that the Sm and Yb codoped porous three-dimensional flower-shaped CuO catalyst is used for preparing gamma-butyrolactone from 1, 4-butanediol, and the gamma-butyrolactone has good synergistic effect, so that the selectivity of gamma-butyrolactone and the conversion rate of 1, 4-butanediol can be remarkably improved; compared with the Sm and Yb co-doped porous three-dimensional flower-shaped CuO catalyst used for preparing the gamma-butyrolactone from the 1, 4-butanediol, the Sm or Yb co-doped porous three-dimensional flower-shaped CuO catalyst prepared by independently doping Sm or Yb has the advantages that the selectivity of the gamma-butyrolactone and the conversion rate of the 1, 4-butanediol are obviously reduced, so that the yield of the gamma-butyrolactone is obviously reduced, the Sm and Yb co-doping plays a good synergistic effect, the lattice structure is synergistically improved, and the structure of a pore channel is changed, so that the selectivity of the gamma-butyrolactone and the conversion rate of the 1, 4-butanediol are influenced.

Comparative example 10: the specific steps of the method for preparing the N-methylpyrrolidone by using the 1, 4-butanediol are the same as those of the example 1, except that the ultrasonic cavitation is not carried out in the step three, and other steps are the same. The detection shows that the conversion rate of gamma-butyrolactone is above 81.36% and the selectivity of the target product N-methylpyrrolidone is 96.45% after the reaction in step three.

Comparative example 11: a method for preparing N-methylpyrrolidone from 1, 4-butanediol, which has the same specific steps as example 1, and is different from the preparation method of the mesoporous silica supported Zn/Mn/Cu composite catalyst in that the mesoporous silica is replaced by a solid silica carrier, and the other steps are the same. And step one, obtaining the porous three-dimensional flower-shaped CuO. The detection shows that the conversion rate of gamma-butyrolactone is above 80.21% and the selectivity of the target product N-methylpyrrolidone is 90.14%.

It can be seen from example 1 and comparative examples 10 to 11 that the conversion rate of γ -butyrolactone and the selectivity of N-methylpyrrolidone are both significantly reduced without ultrasonic cavitation or loading with solid silica, mainly because the ultrasonic cavitation effect is combined with the mesoporous structure to have a good synergistic effect, a microreactor can be formed, the reaction is accelerated, the active sites are increased, and further the conversion rate of γ -butyrolactone and the selectivity of N-methylpyrrolidone, which are a composite catalyst, are increased. In addition, researches show that any one of Zn, Mn and Cu is omitted from the mesoporous silica supported Zn/Mn/Cu composite catalyst, and when the mesoporous silica supports any two composite catalysts, the conversion rate of gamma-butyrolactone and the selectivity of N-methylpyrrolidone are reduced.

The present invention is not limited to the above exemplary embodiments, and any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.