Method for producing N-methylpyrrolidine catalyst by NMP (N-Methyl Pyrrolidine) hydrogenation

Abstract

The invention discloses a method for producing an N-methylpyrrolidine catalyst through NMP hydrogenation, and relates to the technical field of catalyst production, and the method comprises the following steps: S1, carrier acid treatment; s2, roasting is carried out; s3, preparing impregnation liquid; s4, carrying out equivalent-volume impregnation; s5, drying; s6, temperature programming reduction is carried out; and S7, passivating treatment is conducted. The hydrogenation catalyst with high activity and high selectivity is prepared by taking nickel as a main active component, adding a small amount of noble metal as an auxiliary agent and optimizing pretreatment conditions of a carrier, physicochemical properties of impregnation liquid and activation and reduction procedures of the catalyst. The method is high in process parameter controllability and good in repeatability, the prepared catalyst keeps excellent catalytic performance, meanwhile, the use amount of precious metal is effectively reduced, and the method has remarkable industrial application value.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of catalyst production, in particular to a method for producing N-methyl pyrrolidine by hydrogenation of N-methyl pyrrolidone. BACKGROUND

[0002] N-methyl pyrrolidine is an organic compound, which has multiple uses, such as in the pharmaceutical industry, is a key intermediate for synthesizing the fourth-generation cephalosporin antibiotic cefepime; in the essence and perfume industry, is used for synthesizing various high-grade perfume and essence intermediates; in the pesticide industry, is used as an intermediate for synthesizing new high-efficiency low-toxicity pesticides; and in the field of organic synthesis, can be used as an alkaline reagent, a catalyst or a solvent to promote the performance of various organic chemical reactions.

[0003] When producing N-methyl pyrrolidine, a catalyst must be added, and the main methods are as follows: the first method is a kind of N-methyl pyrrolidine solvent-free continuous production method in patent application No. 2021111706776, and the raw material is N-methyl pyrrolidone hydrogenation method. In this method, N-methyl pyrrolidone and hydrogen are reacted in a high-pressure device under the action of a catalyst to prepare N-methyl pyrrolidine. The disadvantage of this method is that the raw material uses hydrogen, which has strict requirements on the transportation (or preparation) and storage of the raw material, and the reaction is carried out under high pressure, which has strict requirements on the equipment and operation, and the investment and production cost are large, which is not conducive to industrial production.

[0004] The second method is a kind of N-methyl pyrrolidine preparation method in patent application No. 2017109278798. The catalyst composition is copper 15-25%, cobalt 10-20%, nickel 5-10%, palladium 0.2-2.0%, and rare earth (lanthanum / cerium) accounts for 1-5%, which is used for catalyzing the dehydrogenation of N-methyl pyrrolidine to prepare N-methyl pyrrolidine. The catalyst does not specify the type of carrier, and the claims cover Cu-Co-Ni-Pd-rare earth multi-metal combination, which needs higher hydrogen pressure, and also has strict requirements on the equipment and operation, and the investment and production cost are large.

[0005] The third method is a kind of N-methyl pyrrolidine preparation method in patent application No. 2005100165541. In this process, 1.4-dichlorobutane and methylamine are added to the reactor to synthesize N-methyl pyrrolidine and hydrochloric acid, and then inorganic alkali is added for neutralization to obtain N-methyl pyrrolidine and hydrochloride. The disadvantages of this method are: 1. The equipment material requirements are high, and the equipment investment is large due to the production of by-product hydrochloric acid in the reaction process. 2. A large amount of sodium hydroxide is consumed, and the subsequent treatment is complex.

[0006] The fourth method is to use tetrahydro-pyrrole and methanol to prepare N-methyl pyrrolidine under the catalysis of a catalyst. This method is used more in China. For example, patent application number 2022106500886 discloses a preparation method of N-methyl pyrrolidine. The disadvantages of this method are: the price of raw materials is high, the process is complex, the treatment of "three wastes" is difficult, and the production cost is high. Other preparation methods have the disadvantages of low yield and serious pollution. The existing technology uses noble metal (such as Ru / C) catalyst DE, which has high cost and is easy to be poisoned; the catalyst with Cu and Ni and the carrier ZrO2 has low yield and fast activity decay.

[0007] Now the production of N-methyl pyrrolidine catalyst has the following problems: 1. In the impregnation method and the precipitation method, metal ions are easy to migrate and agglomerate due to solvent evaporation and surface tension, resulting in uneven particle dispersion and large particle size difference, which directly affects the number and consistency of active sites.

[0008] 2. The number of active sites is small or the strength of the active sites is insufficient, which cannot effectively activate the reactant molecules, resulting in the need for reaction at higher temperature and pressure, which not only consumes more energy but also increases equipment wear and tear.

[0009] 3. Traditional catalysts, such as molecular sieves and single-aluminum oxide carriers, will undergo skeleton hydroxylation or swelling when they come into contact with water, resulting in the blocking of the carrier's pores and a sharp decrease in the specific surface area. The active metal particles originally dispersed in the pores are exposed to the outside, which are easy to sinter or lose.

[0010] 4. Some catalysts rely on noble metals (such as pure Pt and Pd) or rare metals as active components, which are expensive and require a large amount (5%-10% by mass), significantly increasing the total production cost. At the same time, some preparation processes, such as high-pressure hydrogenation, need to be carried out under high temperature (300-400℃) and high pressure (5-10MPa) conditions, which require high-quality equipment and a 3-5 times higher investment cost than conventional equipment. At the same time, there is a risk of leakage and explosion under high temperature and high pressure, which requires additional safety protection facilities, further increasing the production cost.

[0011] There are still some defects in the current analysis methods for N-methyl pyrrolidine, which affect the sensitivity. For example, N-methyl pyrrolidine (NMP) is volatile and easy to oxidize, which brings a large error to the traditional titration method; the detection limit of the traditional gas chromatography method is high (only 16ppm), which cannot meet the requirements of high-purity chemicals. At the same time, the sample pretreatment relies on activated carbon / molecular sieve adsorption, which is complicated and may introduce impurities. Moreover, the problem of NMP separation and interference in N-methyl pyrrolidone production waste gas has not been solved. A high-sensitivity and anti-interference special analysis method is needed to realize efficient detection of N-methyl pyrrolidine. SUMMARY

[0012] The present application aims at solving the problems in the background art, and provides a method for producing N-methyl pyrrolidine catalyst by NMP hydrogenation.

[0013] In order to achieve the above-mentioned purpose, the present application specifically adopts the following technical scheme: The method for producing N-methyl pyrrolidine catalyst by NMP hydrogenation comprises the following steps: S1, carrier acid treatment: titanium dioxide and alumina are mixed in a three-dimensional mixer at a mass ratio of 3:7 for 2 hours, then 8% nitric acid solution is used for stirring at 80-100℃ for 2-4 hours, and ultrasonic auxiliary treatment is performed for 1 hour during the stirring; S2, calcination: the acid-treated material is washed with deionized water until neutral, i.e. pH=6.5-7.5, and then dried at 110-120℃ for 12-24 hours, followed by heating to 500℃ for calcination for 4 hours, to obtain a composite carrier with a specific surface area of 200±20 m2 / g and a pore size of 15±2 nm; S3, preparation of impregnation solution: nickel nitrate, chloroplatinic acid and cerium nitrate are dissolved in deionized water, citric acid is added, the addition amount of citric acid is 1.2 times the mass of the metal, ammonia water is used to adjust the pH to 3.8, and a mixed solution is obtained; S4, equal volume impregnation: the above-mentioned mixed solution is slowly added to the composite carrier, and an equal volume impregnation method is used, and the impregnated material is obtained by standing at room temperature for 10-13 hours and aging at 50-70℃ for 5-7 hours; S5, drying: the above-mentioned impregnated material is placed in an oven at 70-90℃ for 2-4 hours of pre-drying, and supercritical CO2 drying is used, with a temperature of 30-50℃ and a pressure of 9.5-11.0 MPa, to obtain dried material; S6, programmed temperature reduction: the above-mentioned dried material is placed in a tube furnace, heated to 120℃ at a rate of 5℃ / min and kept for 1 hour, heated to 300℃ at a rate of 2℃ / min and kept for 2 hours, and heated to 400℃ at a rate of 1℃ / min and kept for 3 hours, to obtain reduced material, wherein the atmosphere is a mixture of 10% H2 / 90% N2, and the flow rate is 50 mL / min; S7, passivation treatment: the reduced material is cooled to 140-160℃ under N2 protection, and a 1% O2 / N2 mixed gas is passed through for passivation for 2-3 hours, and then sealed after being cooled to room temperature, to obtain the finished catalyst.

[0014] Preferably, in the step S1, carrier acid treatment, the titanium dioxide has sharp parameters as follows: titanium ore type ≥98%, specific surface area ≥80 m2 / g, particle size range 20-50 nm, Fe2O3 (diiron trioxide) ≤0.01%, and particle size range 20-50 nm.

[0015] Preferably, in the step S1, the parameters of the alumina in the carrier acid treatment are: γ-alumina≥99%, pore size distribution 5-15nm, Na2O≤0.02%, ignition loss≤8%.

[0016] Preferably, in the step S1, the parameters of the nitric acid in the carrier acid treatment are: 65-68% analytically pure, Cl - ≤0.0001%, heavy metals≤0.0005%.

[0017] Preferably, in the step S1, the parameters of the citric acid in the carrier acid treatment are: ≥99.5%, moisture≤0.5%, ignition residue≤0.05%, chlorides, sulfates≤10ppm, heavy metals≤075ppm, iron, calcium≤3ppm, organic impurities≤0.1%.

[0018] Preferably, in the step S1, the parameters of the nickel nitrate solution in the carrier acid treatment are: Ni 2+ content≥20.0wt%, pH 3.5-4.5, SO4 2- ≤0.001%, organic residue≤50ppm; the parameters of the chloroplatinic acid solution are: Pt≥37.5wt%, other noble metals≤0.5% water insoluble≤0.01%.

[0019] Preferably, in the step S1, the mass ratio of the nitric acid solution to the solid material in the carrier acid treatment is 10:1, and the parameters of the ultrasonic assisted treatment are 40kHz and a power of 200W.

[0020] Preferably, in the step S3, the molar ratio of chloroplatinic acid, nickel nitrate and cerium nitrate in the preparation of the impregnation solution is 1:6:4.

[0021] As the same inventive concept as the above technical solutions, the present application also claims a production method of N-methylpyrrolidine, using the catalyst prepared by the method for producing N-methylpyrrolidine catalyst of NMP.

[0022] As the same inventive concept as the above technical solutions, the present application also claims an analysis method of N-methylpyrrolidine, for detecting N-methylpyrrolidine prepared by the production method of N-methylpyrrolidine, comprising the following steps: Step 1, derivative reagent: take 100μL of the sample solution to be tested in a 2mL glass derivative bottle, and add 100μL of HFBA solution, immediately seal the bottle cap, vortex mix for 30 seconds, after mixing, place in a 40℃ water bath for 10 minutes, take out and cool to room temperature, add 800μL of chromatographic grade n-hexane for dilution, vortex mix well; Step 2, multi-dimensional chromatographic separation: a pre-column is DB-5MS, matrix interference is removed, an analysis column is DB-WAX, high-resolution separation of polar derivatives is realized, the reagent after mixing is added, the initial temperature is 50 DEG C, is maintained for 2 minutes, then is uniformly increased at a rate of 10 DEG C / min, medium-boiling substances are gradually eluted, the final temperature is increased to 240 DEG C, and is maintained for 5 minutes, and coexisting substances in waste gas are completely separated; Step 3, negative chemical source mass spectrometry detection: selected ion monitoring (SIM) m / z 254.

[0023] Compared with the prior art, the beneficial effects of the present application are that: 1. The combination of citric acid complexation and supercritical CO2 drying allows the metal nanoparticles (Ni, Pt) to be uniformly and firmly dispersed on the carrier surface, avoiding the problems of particle agglomeration and sintering in traditional preparation. This makes the number of active sites stable during the long-term reaction process, and the active sites are not quickly lost due to particle growth. At the same time, after acid treatment and high-temperature calcination, the TiO2-Al2O3 composite carrier forms a more rigid skeleton structure, which, combined with the porous network preserved by supercritical drying, can effectively resist the erosion of trace water in the reaction system, reduce the risk of collapse or swelling of the carrier pores, and provide stable support for the active sites.

[0024] 2. Compared with the first method of a solvent-free continuous production method of N-methyl pyrrolidine and the second method of a preparation method of N-methyl pyrrolidine, the use of hydrogen gas is avoided, which not only reduces the cost of using hydrogen gas, but also improves the convenience of production, which is conducive to industrialized production. Compared with the third method of preparing N-methyl pyrrolidine, the amount of sodium hydroxide solid material is saved, and the inert gas nitrogen can protect the reaction, and hydrogen can inhibit oxidation, which improves the effect during preparation. Compared with the fourth method of preparing N-methyl pyrrolidine, the use of expensive raw materials such as tetrahydrofuran is avoided, which not only saves the production cost, but also avoids complex production processes.

[0025] 3. From the temperature and time of carrier acid treatment, to the pH value of the immersion liquid, to the rate and holding time of programmed temperature reduction, the parameters of each step are clear and quantifiable, which makes the performance difference of catalysts produced in different batches small, improves the control precision during production, and at the same time, uses low-cost Ni as the main active component, only adds a small amount of Pt as an additive, the mass fraction is usually ≤1%, and the prices of citric acid, nitric acid and other auxiliary materials are low and easy to obtain, which greatly reduces the cost pressure of industrialized production. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The chromatogram of the present application for preparing N-methyl pyrrolidine; Figure 2A flow chart of the analysis method of the present application; Figure 3 A flow chart of the embodiment of the present application. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0028] The materials and instruments used in the following embodiments are commercially available.

[0029] One kind of NMP hydrogenation production N-methyl pyrrolidine catalyst method, including the following steps: S1, carrier acid treatment: titanium dioxide and alumina are mixed in a three-dimensional mixer at a mass ratio of 3:7 for 2 hours, then washed with 8% nitric acid solution at 80-100℃ for 2-4 hours, and ultrasonic assisted treatment for 1 hour during the period; S2, calcination: the acid treated material is washed with deionized water to neutral, i.e. pH = 6.5-7.5, dried at 110-120℃ for 12-24 hours, then heated to 500℃ for 4 hours to obtain a composite carrier with a specific surface area of 200±20 m2 / g and a pore size of 15±2 nm; S3, preparation of impregnation solution: dissolve nickel nitrate, chloroplatinic acid and cerium nitrate in deionized water, add citric acid, the addition amount of citric acid is 1.2 times the mass of metal, adjust the pH to 3.8 with ammonia water to obtain a mixed solution; S4, equal volume impregnation: slowly drop the above mixed solution onto the composite carrier, use equal volume impregnation method, stand at room temperature for 10-13 hours, and age at 50-70℃ for 5-7 hours to obtain impregnated material; S5, drying: place the above impregnated material in an oven at 70-90℃ for 2-4 hours, and dry with supercritical CO2, the temperature is 30-50℃, the pressure is 9.5-11.0 MPa, to obtain dried material; S6, programmed temperature reduction: place the above dried material in a tube furnace, increase the temperature to 120℃ at a rate of 5℃ / min, keep for 1 hour, increase the temperature to 300℃ at a rate of 2℃ / min, keep for 2 hours, increase the temperature to 400℃ at a rate of 1℃ / min, keep for 3 hours, to obtain reduced material, wherein the atmosphere is a mixture of 10% H2 / 90% N2, and the flow rate is 50 mL / min; S7, passivation treatment: the reducing material is cooled to 140-160 DEG C under N2 protection, and 1% O2 / N2 mixed gas is passed for 2-3 hours, and after being reduced to room temperature, it is sealed and stored, to obtain the finished catalyst.

[0030] The material parameters used are as follows: The titanium dioxide sharp parameters are: titanic ore type > 98%, specific surface area > 80 m2 / g, particle size range 20-50 nm, Fe2O3 (diiron trioxide) < 0.01%, particle size range 20-50 nm; The alumina parameters are: gamma alumina > 99%, pore size distribution 5-15 nm, Na2O < 0.02%, ignition loss < 8%; Nitric acid (65-68% analytically pure, Cl - < 0.0001%, heavy metals (calculated as Pb) < 0.0005%); Citric acid: > 99.5% (GB / T8269), moisture < 0.5% ignition residue < 0.05%, chlorides, sulfates < 10 ppm, heavy metals < 075 ppm, iron, calcium < 3 ppm, organic impurities < 0.1%; Nickel nitrate solution: (Ni 2+ content > 20.0 wt%, pH 3.5-4.5, SO4 2- < 0.001%, organic matter residue < 50 ppm); Chloroplatinic acid solution: (Pt > 37.5 wt%, other noble metals (Pd, Rh) < 0.5% water-insoluble substance < 0.01%, HB / T3465-2012 ICP-MS filtration weighing).

[0031] In the step S1, carrier acid treatment, the mass ratio of nitric acid solution to solid material is 10:1, and the ultrasonic auxiliary treatment parameters are 40 kHz and a power of 200 W.

[0032] In the step S3, the molar ratio of chloroplatinic acid, nickel nitrate and cerium nitrate in the impregnation solution is 1:6:4, specifically, the mass percentage of chloroplatinic acid is 0.3-0.5 wt%, which is the hydrogenation active center; the mass percentage of nickel nitrate is 2.0-3.0 wt%, which is used for synergistic catalysis and reduces the Pt dosage; and the mass percentage of cerium nitrate is 1.0-2.0 wt%, which is used to improve the anti-coking capacity.

[0033] Second, the performance parameters of the catalyst prepared in the application The performance of the prepared catalyst is as follows: The NMP hydrogenation catalyst prepared in the present application for producing N-methyl pyrrolidine is compared in performance with Pt / C catalyst and Cu-Ni / ZrO2 catalyst. The Pt / C catalyst is a kind of N-methyl pyrrolidine solvent-free continuous production method with application number 2021111706776. The Cu-Ni / ZrO2 catalyst is a kind of N-methyl pyrrolidine preparation method with application number 2017109278798.

[0034] The comparison results are shown in the following table: As can be seen from the above table, the NMP hydrogenation catalyst prepared in the present application for producing N-methyl pyrrolidine has a high conversion rate of 99.8% compared with the catalyst used in the N-methyl pyrrolidine solvent-free continuous production method with application number 2021111706776. After testing, the service life is 5000h. The comparison of the catalysts used in the present application and the N-methyl pyrrolidine solvent-free continuous production method with application number 2021111706776 is as follows: 1. Active site action: The catalyst only relies on Pt single component to provide active site, the number of sites is limited and easy to agglomerate. The present application improves the low-temperature activity by efficient activation of H2 of Pt, reduces the Pt dosage by enhancing the hydrogenation ability of Ni, and forms a "three-in-one" active site by adjusting the electronic structure of Ce to inhibit side reactions.

[0035] 2. Carrier and reaction mass transfer: The active carbon carrier of the catalyst used in the N-methyl pyrrolidine solvent-free continuous production method has uneven pore size (mostly microporous / mesoporous), the diffusion resistance of NMP molecules (large volume) is large, and carbon deposition is easy to occur due to retention. The present application can match the diffusion requirements of NMP and product, and improve the mass transfer efficiency.

[0036] In terms of production cost, compared with the catalyst used in the N-methyl pyrrolidine solvent-free continuous production method, the Pt dosage can be reduced. Pt is scarce and expensive, and the cost of a single ton of catalyst is as high as tens of thousands of yuan, which puts a lot of pressure on industrial application. By introducing low-cost Ni as the main active component and Pt as a trace amount of additive (loading amount ≤0.5%), the activity is improved through "Pt-Ni cooperation" - Ni enhances the hydrogenation ability, and Pt reduces the reaction activation energy.

[0037] The comparison of the catalysts used in the present application and the N-methyl pyrrolidine preparation method with application number 2017109278798 is as follows: According to the comparison of 1000h activity attenuation in the table, the 1000h activity attenuation of the present application is significantly lower than 15.1 of the patent Cu-Ni / ZrO2 of 2017109278798, and the TiO2-Al2O3 composite carrier ensures the mechanical stability and thermal stability. The composite design (noble metal + additive + stable carrier) of the present application is specially optimized for prolonging the service life of 2017109278798.

[0038] On the other hand, the present application has a long catalyst life, and the cost index (33) after cost allocation is significantly lower than (38) of the comparative example 2017109278798 patent Cu-Ni / ZrO2.

[0039] The table data shows that the conversion rate of the present application catalyst (conversion rate 99.8%, selectivity 99.9%) is 1.3 percentage points higher than that of the comparative example 2017109278798 patent technology Cu-Ni / ZrO2 (conversion rate 98.5%, selectivity 98.4%), and the selectivity is 1.5 percentage points higher.

[0040] Three, a production method of N-methyl pyrrolidine, using the catalyst prepared by the method of producing N-methyl pyrrolidine catalyst.

[0041] The specific production method is: Step 1, preheat and vaporize N-methyl pyrrolidone at 205-210℃, then mix with hydrogen gas in a static mixer, and then pass into a fixed bed reactor filled with catalyst to obtain N-methyl pyrrolidine crude product, the reaction pressure in the reactor is maintained at 0.1-0.3Mpa, the reaction temperature is 90-110℃, wherein the molar ratio of hydrogen to N-methyl pyrrolidone is 10-5:1, and the liquid hourly space velocity of N-methyl pyrrolidone to catalyst bed is 1-10h-1; S2, the N-methyl pyrrolidone crude product obtained in step S1 is subjected to vacuum rectification in a rectification column, and the unreacted N-methyl pyrrolidone light component is purified by collection, and the N-methyl pyrrolidone product collected from the top of the rectification column is obtained.

[0042] The prepared N-methyl pyrrolidone chromatogram is as follows: Figure 1 .

[0043] Four, an analysis method of N-methyl pyrrolidine, for detecting N-methyl pyrrolidine prepared by the production method of N-methyl pyrrolidine, comprising the following steps: Step 1, Derivative reagent: Take 100 μL of the sample solution to be tested in a 2 mL glass derivatization bottle, and add 100 μL of HFBA solution, immediately seal the bottle cap, vortex mix for 30 seconds, after mixing, place in a 40°C water bath for 10 minutes, take out and cool to room temperature, add 800 μL of chromatographic grade n-hexane for dilution, vortex mix well. Among them, the reaction time is accurately controlled ± 0.5 min to avoid over-derivation or by-product generation, and the derivative product is stable for > 24 hours under the condition of avoiding light at -20°C. It should be analyzed on the same day.

[0044] Step 2, multidimensional chromatographic separation: the pre-column is DB-5MS, the matrix interference is removed, the analysis column is DB-WAX, the polar derivative is high-resolution separated, the mixed reagent is added, the initial temperature is 50°C, and it is kept for 2 minutes, then it is uniformly heated at a rate of 10°C / min, the medium boiling point substances are gradually eluted, the final temperature is increased to 240°C, and it is kept for 5 minutes, and the coexisting substances in the waste gas are completely separated. The auxiliary parameters are: carrier gas: high-purity helium (He), constant flow mode, flow rate 1.2 mL / min; injection port temperature: 250°C, no split injection (no split time 1 min); injection amount: 1.0 μL.

[0045] Step 3, negative chemical source mass spectrometry detection: selected ion monitoring (SIM) m / z 254, other mass spectrometry conditions are: Ion source: negative chemical ionization (NCI) mode.

[0046] Reaction gas: methane (CH4), purity ≥ 99.999%, flow rate 2.0 mL / min.

[0047] Ion source temperature: 150°C.

[0048] Electronic energy: 70 eV (after optimization).

[0049] Selected ion monitoring (SIM) Target ion: m / z 254 ([M-HF]⁻ characteristic fragment, HFBA-NMPy derivative HF product).

[0050] Residence time: 100 ms / ion.

[0051] System suitability verification: Retention time confirmation: the retention time of HFBA-NMPy derivative on DB-WAX column should be stable within ± 0.1 min (typical value about 18-20 min).

[0052] Specificity check: through blank matrix spiking experiment, it is confirmed that there is no m / z 254 interference peak for coexisting substances (such as aldehydes, ketones) in the waste gas.

[0053] Sensitivity calibration: calibration curve was established with derivatized standard solution (0.1-100 ng / mL), R 2 > 0.995.

[0054] Operation flow chart reference Figure 2 .

[0055] Five, examples (1) Example 1: Trace NMPy detection in high-purity N-methyl pyrrolidone Sample pretreatment Take 1 g of sample, add 0.1 mL of HFBA derivatization reagent, react at 40°C for 10 min; extract the derivative with n-hexane, no need for adsorption purification.

[0056] Instrument conditions Quantification and verification Calibration curve: 0.1-100 ppb linear (R 2 = 0.9995); Limit of detection (LOD): 0.05 ppb (320 times higher than 1); Spiked recovery: 96.2-103.8% (n=6).

[0057] Example 2: Online monitoring of NMPy in waste gas (waste gas treatment device) Waste gas sample collection Sampling equipment: vacuum sampling bottle (2L, silanized to avoid adsorption) + constant flow sampling pump (flow rate 500 mL / min).

[0058] Sampling volume: according to the expected concentration, collect 10-30 L of waste gas (e.g. collect 30 L when the concentration is low, to ensure that the target concentration after derivatization is within the calibration curve range).

[0059] Sample storage: immediately add 1 mL of anhydrous acetonitrile after sampling, store at -4°C for transportation, and complete derivatization within 24 hours.

[0060] Derivatization operation (according to method step 1) Key controls: Derivatization reagent (10% HFBA acetonitrile solution) is prepared fresh and used immediately to avoid hydrolysis (HFBA reacts with water to form heptafluorobutyric acid, reducing the derivatization efficiency).

[0061] Accurately control the water bath temperature (40±0.5°C) using a constant temperature water bath with stirring function to ensure uniform reaction.

[0062] When 800 μL of n-hexane is added after derivatization, the upper organic phase (derivatized product is dissolved in n-hexane, and the aqueous phase is discarded) is separated, and the organic phase is filtered through a 0.22 μm filter membrane before being loaded onto the machine.

[0063] (2) Multi-dimensional chromatography-mass spectrometry system implementation parameters Instrument configuration Gas chromatography: Agilent 7890B equipped with Deans Switch multi-dimensional chromatography switching system (realizes automatic switching of pre-column and analytical column).

[0064] Pre-column: DB-5MS (30 m x 0.25 mm x 0.25 μm), used to remove non-polar interferents (such as toluene, xylene, long-chain alkanes) in waste gas.

[0065] Analytical column: DB-WAX (60 m x 0.32 mm x 0.5 μm), realizes separation of derivatized product (HFBA-NMPy) and polar interferents (such as acetone, butanone, ethyl acetate) under programmed temperature (50°C→240°C, 10°C / min).

[0066] Mass spectrometry: Agilent 5977B, negative chemical source (NCI) mode, methane reaction gas (purity 99.999%), SIM mode monitors m / z 254.

[0067] System suitability verification results Retention time stability: 6 consecutive injections of standard (10 ng / mL), the retention time of HFBA-NMPy derivative is 19.2 ± 0.05 min (RSD = 0.2%), which meets the requirement of ± 0.1 min.

[0068] Specificity: blank waste gas matrix (after activated carbon adsorption and desorption) spiking experiment shows that coexisting substances (such as isopropyl alcohol, cyclohexanone) have no interference peaks at m / z 254, and the signal-to-noise ratio (S / N) of the target peak is > 10.

[0069] Calibration curve: the linear equation in the range of 0.1-100 ng / mL is y = 1234x + 56.7 (R 2 = 0.9992), the method detection limit (LOD) reaches 0.03 ng / mL (equivalent to 0.01 mg / M 3 in waste gas, when the sampling volume is 30 L).

[0070] (3) Actual sample analysis results 1. Sample detection Waste gas at the exhaust port of the workshop: 3 parallel samples were collected, and after derivatization, they were detected on the machine, and the NMPy concentrations were 0.32, 0.35, and 0.33 mg / M 3, RSD=4.5%, all lower than the emission standard limit value (1.0 mg / M 3 ).

[0071] Spiked recovery rate: at 0.5 mg / M 3 The recovery rate was 89%-95% (n=3) at the spiked level, meeting the environmental monitoring requirements (80%-120%).

[0072] 2. Interference exclusion cases High concentration of acetone interference: the concentration of acetone in a batch of samples reached 500 mg / M 3 After removing by DB-5MS pre-column, the acetone peak (retention time 8.5 min) on the DB-WAX column was completely separated from the target (19.2 min), without m / z 254 interference.

[0073] Flowchart reference Figure 3 .

[0074] Through the above comparison, the conversion rate of the present application can reach 99.8%, the conversion rate of Cu-Ni / ZrO2 is 98.5%, and the conversion rate of the catalyst used in the application number 2021111706776 N-methyl pyrrolidine solvent-free continuous production method is 99.3%.

Claims

1. A method for producing a catalyst for the hydrogenation of NMP to N-methylpyrrolidine, characterized in that The method comprises the following steps: S1, carrier acid treatment: mixing titanium dioxide and aluminum oxide in a three-dimensional mixer at a mass ratio of 3:7 for 2 hours, then stirring with 8% nitric acid solution at 80-100°C for 2-4 hours, and ultrasonic auxiliary treatment for 1 hour during the stirring; S2, calcination: washing the acid-treated material with deionized water until neutral, i.e. pH=6.5-7.5, drying at 110-120°C for 12-24 hours, then heating to 500°C for calcination for 4 hours to obtain a composite carrier with a specific surface area of 200±20 m2 / g and a pore size of 15±2 nm; S3, impregnation solution preparation: dissolving nickel nitrate, chloroplatinic acid and cerium nitrate in deionized water, adding citric acid, the addition amount of citric acid being 1.2 times the mass of the metal, adjusting the pH to 3.8 with ammonia water to obtain a mixed solution; S4, equal volume impregnation: slowly dropping the above-mentioned mixed solution onto the composite carrier, using equal volume impregnation method, standing at room temperature for 10-13 hours, aging at 50-70°C for 5-7 hours to obtain an impregnated material; S5, drying: placing the above-mentioned impregnated material in an oven at 70-90°C for pre-drying for 2-4 hours, and using supercritical CO2 drying at a temperature of 30-50°C and a pressure of 9.5-11.0 MPa to obtain a dried material; S6, programmed temperature reduction: placing the above-mentioned dried material in a tube furnace, heating to 120°C at a rate of 5°C / min and maintaining for 1 hour, heating to 300°C at a rate of 2°C / min and maintaining for 2 hours, and heating to 400°C at a rate of 1°C / min and maintaining for 3 hours to obtain a reduced material, wherein the atmosphere is a mixture of 10% H2 / 90% N2 with a flow rate of 50 mL / min; S7, passivation treatment: cooling the reduced material to 140-160°C under N2 protection, passing 1% O2 / N2 mixed gas for passivation for 2-3 hours, and sealing after cooling to room temperature to obtain a finished catalyst.

2. The method for producing a catalyst for N-methylpyrrolidine production by NMP hydrogenation according to claim 1, characterized by, In the step S1, carrier acid treatment, the anatase parameters of titanium dioxide are: titanium ore type ≥98%, specific surface area ≥80 m2 / g, particle size range 20-50 nm, Fe2O3 (diiron trioxide) ≤0.01%, particle size range 20-50 nm.

3. The method for producing a catalyst for N-methylpyrrolidine production by NMP hydrogenation according to claim 1, characterized by, In the step S1, carrier acid treatment, the parameters of aluminum oxide are: γ-type aluminum oxide ≥99%, pore size distribution 5-15 nm, Na2O ≤0.02%, ignition loss ≤8%.

4. The method for producing a catalyst for N-methylpyrrolidine production by NMP hydrogenation according to claim 1, characterized by, The step S1, the parameter of nitric acid in carrier acid treatment is: 65-68% analytically pure, Cl - ≤0.0001%, heavy metals ≤0.0005%.

5. The method for producing a catalyst for N-methylpyrrolidine production by NMP hydrogenation according to claim 1, characterized by, In the step S1, carrier acid treatment, the parameters of citric acid are: ≥99.5%, moisture ≤0.5%, ignition residue ≤0.05%, chlorides, sulfates ≤10 ppm, heavy metals ≤075 ppm, iron, calcium ≤3 ppm, and organic impurities ≤0.1%.

6. The method for producing a catalyst for N-methylpyrrolidine production by NMP hydrogenation according to claim 1, characterized by, The parameters of the nickel nitrate solution in the step S1, carrier acid treatment are: Ni 2+ content ≥ 20.0 wt%, pH 3.5-4.5, SO4 2- ≤ 0.001%, organic residue ≤ 50 ppm; the parameters of the chloroplatinic acid solution are: Pt ≥ 37.5 wt%, other noble metals ≤ 0.5% water insoluble ≤ 0.01%.

7. The method for producing a catalyst for N-methylpyrrolidine production by NMP hydrogenation according to claim 1, characterized by, In the step S1, carrier acid treatment, the mass ratio of nitric acid solution to solid material is 10:1, and the parameters of ultrasonic auxiliary treatment are 40 kHz and a power of 200 W.

8. The method for producing a catalyst for N-methylpyrrolidine production by NMP hydrogenation according to claim 1, characterized by, In the step S3, impregnation solution preparation, the molar ratio of chloroplatinic acid, nickel nitrate and cerium nitrate is 1:6:

4.

9. A method for producing N-methylpyrrolidine, characterized by, The catalyst is prepared by using the method of claim 1 for producing N-methyl pyrrolidine catalyst by NMP hydrogenation.

10. A method of analyzing N-methylpyrrolidine, characterized by, A method for detecting N-methylpyrrolidine prepared by the production method of claim 9, comprising the following steps: Step 1, derivative reagent: take 100 μL of the sample solution to be tested in a 2 mL glass derivative bottle, and add 100 μL of HFBA solution, immediately seal the bottle cap, vortex mix for 30 seconds, after mixing, place in a 40°C water bath for reaction for 10 minutes, take out and cool to room temperature, add 800 μL of chromatographic grade n-hexane for dilution, vortex mix well; Step 2, multidimensional chromatographic separation: the pre-column is DB-5MS, the matrix interference is removed, the analysis column is DB-WAX, the polar derivative is high-resolution separated, the mixed reagent is added and mixed well, the initial temperature is 50°C, maintained for 2 minutes, then uniformly heated at a rate of 10°C / min, the medium-boiling substances are gradually eluted, the final temperature is increased to 240°C, and maintained for 5 minutes, and the coexisting substances in the waste gas are completely separated; Step 3, negative chemical source mass spectrometry detection: selected ion monitoring (SIM) m / z 254.

Images