A methyl acrylate-acetonitrile-water ternary azeotrope extractant and extraction separation method
By using methyl isobutyl ketone or butyl acetate as extractants, combined with COSMO-RS model screening and extractive distillation technology, the separation problem of methyl acrylonitrile-acetonitrile-water ternary azeotrope was solved, achieving efficient preparation of high-purity products with good industrial application potential.
Patent Information
- Application Number
- CN202610790861.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-03
- Publication Date
- 2026-08-25
AI Technical Summary
Existing technologies cannot effectively separate the ternary azeotrope of methacrylonitrile-acetonitrile-water, resulting in the inability to obtain high-purity methacrylonitrile and acetonitrile, which affects product purity and yield. Furthermore, traditional distillation cannot overcome the limitations of azeotropic composition.
Methyl isobutyl ketone or butyl acetate was used as the extractant. The extractant was screened using the COSMO-RS model through continuous or intermittent extractive distillation, and combined with thermodynamic and industrial applicability indicators, to achieve the separation of methacrylonitrile-acetonitrile-water ternary azeotrope.
The extraction process achieved a purity of over 99% and a yield of over 97% for methacrylonitrile and a purity of over 98.5% and a yield of over 96.5% for acetonitrile. Furthermore, the extractant is widely available, inexpensive, and easy to recover, demonstrating promising prospects for industrial applications.
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Figure CN122624929A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of methacrylonitrile-acetonitrile-water ternary azeotrope extraction technology, specifically to a methacrylonitrile-acetonitrile-water ternary azeotrope extractant and extraction separation method. Background Technology
[0002] Methacrylonitrile, also known as isobutylene nitrile, is an important organic synthesis raw material, mainly used to synthesize high-performance polymers and fine chemicals, such as polymethacrylimide, methyl methacrylate, and synthetic resins. Moreover, its polymer products are widely used in aerospace composite materials, high-end optical devices, and special coatings due to their excellent heat resistance, mechanical strength, and optical properties.
[0003] The isobutylene ammoxidation process is the mainstream technology for producing methacrylonitrile. In this process, isobutylene reacts with ammonia and oxygen under the action of a catalyst to produce methacrylonitrile, but a small amount of homologues such as acetonitrile is inevitably produced as byproducts. The gas mixture after the reaction needs to be treated by steps such as rapid cooling and absorption. During this process, water vapor is condensed or process water is introduced into the system, ultimately forming a complex mixture containing methacrylonitrile, acetonitrile, and water. How to economically and efficiently separate and purify these two high-value-added components from this mixture is directly related to the purity and yield of the main product, methacrylonitrile, and also determines whether the byproduct acetonitrile can be utilized as a resource. This issue has become a key factor restricting the economics of the entire process and the competitiveness of the product.
[0004] However, the methacrylonitrile-acetonitrile-water system exhibits complex azeotropic behavior at atmospheric pressure. This system contains two binary azeotropes and one ternary azeotrope. At atmospheric pressure, the methacrylonitrile-water azeotropic point is 76.13℃, the acetonitrile-water azeotropic point is 76.65℃, and the methacrylonitrile-acetonitrile-water azeotropic point is 75.47℃. For this system, conventional distillation cannot overcome the limitations of the azeotropic composition. Regardless of increasing the theoretical plate size or adjusting the reflux ratio, only products with near-azeotropic compositions can be obtained, and it is impossible to obtain any single high-purity component.
[0005] Based on this, the present invention proposes a ternary azeotropic extractant of methacrylonitrile-acetonitrile-water and an extraction and separation method thereof. Summary of the Invention
[0006] To solve the above-mentioned technical problems, the present invention provides an extractant and extraction separation method for methacrylonitrile-acetonitrile-water ternary azeotropes, which can achieve the separation of methacrylonitrile-acetonitrile-water ternary azeotropes with good separation effect.
[0007] The technical solution adopted in this invention is as follows: In a first aspect, the present invention provides a methacrylonitrile-acetonitrile-water ternary azeotrope extractant, wherein the extractant is one of methyl isobutyl ketone and butyl acetate.
[0008] Furthermore, the extractant was obtained based on the COSMO-RS model, and the screening steps included: Construct an extractant candidate library, wherein the extractants in the extractant candidate library include one or more of the following: alkanes, aromatic hydrocarbons, esters, ketones, ethers, alcohols, halogenated hydrocarbons, amides, and phosphorus-containing solvents; The surface charge density distribution curves and hydrogen bond acceptor region integrated areas of each extractant were calculated using COSMO-RS. The hydrogen bond acceptor region integrated areas were sorted from largest to smallest, and the extractants with the top 30-50% of the hydrogen bond acceptor region integrated areas were selected. The COSMO-RS was used to calculate the infinite dilution activity coefficients of the top 30-50% of the hydrogen bond acceptor regions of the selected extractants for methacrylonitrile, acetonitrile, and water, respectively. Liquid-liquid equilibrium simulations were performed on the methacrylonitrile-acetonitrile-water ternary system to obtain the partition coefficients and selectivity of each extractant for methacrylonitrile, acetonitrile, and water. The partition coefficients and selectivity were used as thermodynamic indicators. Collect or measure the industrial applicability indicators of the extractants whose integrated area of the selected hydrogen bond acceptor region ranks in the top 30-50%. Different weights are assigned to thermodynamic and industrial applicability indicators, and the overall score of each extractant is calculated. By combining the overall score ranking with the ranking of the integrated area of the hydrogen bond acceptor region, the extractants with the highest rankings in both categories were selected as the extractants for the methacrylonitrile-acetonitrile-water ternary azeotrope.
[0009] Furthermore, the alkane solvents in the candidate library of extractants include one or more of n-hexane, cyclohexane, n-heptane, and petroleum ether; Aromatic hydrocarbon solvents include one or more of toluene, o-xylene, and m-xylene; Ester solvents include one or more of ethyl acetate, butyl acetate, isobutyl acetate, propyl acetate, and butyl propionate; Ketone solvents include one or more of methyl isobutyl ketone (MIBK), methyl ethyl ketone (MEK), cyclohexanone, and isophorone; Ether solvents include one or more of methyl tert-butyl ether (MTBE), isopropyl ether, diethyl ether, and anisole; Alcohol solvents include one or more of n-butanol, isobutanol, n-pentanol, isooctanol, and cyclohexanol; Halogenated hydrocarbon solvents include one or more of dichloromethane, chloroform, and chlorobenzene; Amide solvents include N-methylpyrrolidone; Phosphorus-containing solvents include tributyl phosphate.
[0010] Furthermore, the industrial usability indicators include boiling point, toxicity, price, and viscosity.
[0011] Furthermore, when calculating the comprehensive score of each extractant based on thermodynamic and industrial applicability indicators, it is necessary to first normalize the parameters of each indicator in the thermodynamic and industrial applicability indicators.
[0012] Secondly, the present invention provides an extraction and separation method for a ternary azeotrope of methacrylonitrile-acetonitrile-water, wherein the steps of continuous extraction and distillation separation of the ternary azeotrope of methacrylonitrile-acetonitrile-water using an extractant are as follows: Extractive distillation was used to extract and distill the ternary azeotrope of methacrylonitrile-acetonitrile-water. The methacrylonitrile-acetonitrile-water ternary azeotrope was fed into the middle of the extractive distillation column, while the extractant was fed into the top of the extractive distillation column. The extractant was selectively solvated to break down the ternary azeotrope of methacrylonitrile-acetonitrile-water and the binary azeotrope of methacrylonitrile-water. After extractive distillation, methacrylonitrile was distilled off from the top of the extractive distillation column and high-purity methacrylonitrile was collected by condensation. The bottom of the column yielded a mixture of acetonitrile, water and extractant. The mixture at the bottom of the extractive distillation column is pumped to the extraction recovery column. By controlling the temperature of the extraction recovery column, acetonitrile is distilled off from the top of the column and high-purity acetonitrile is collected by condensation. The bottom of the column yields a mixture of extractant and a small amount of water. The mixture at the bottom of the extraction recovery tower is pumped to the extractant dehydration tower. By controlling the temperature of the extractant dehydration tower, water and a small amount of extractant are distilled off from the top of the tower. The mixture of water and a small amount of extractant is collected by condensation. The bottom of the tower yields the dehydrated extractant, which is then recycled back to the extractive distillation tower for reuse.
[0013] Furthermore, the mass ratio of the methylacrylonitrile-acetonitrile-water ternary azeotrope to the extractant in the extractive distillation column is 1:0.5~3; the operating pressure of the extractive distillation column is atmospheric pressure, the top temperature is 90~100℃, the bottom temperature is 110~130℃, the reflux ratio is 2~4, and the theoretical plate number is 30~50.
[0014] Furthermore, the operating pressure of the extraction and recovery tower is atmospheric or reduced pressure, the top temperature is 81~83℃, the bottom temperature is 110~130℃, the reflux ratio is 1~3, and the theoretical plate number is 15~25.
[0015] Furthermore, the operating pressure of the extractant dehydration tower is atmospheric pressure, the top temperature is 93~95℃, the bottom temperature is 110~120℃, the reflux ratio is 1~3, and the theoretical plate number is 10~15.
[0016] Thirdly, the present invention provides an extraction and separation method for a ternary azeotrope of methacrylonitrile-acetonitrile-water, wherein the steps of batch extraction and distillation separation of the ternary azeotrope of methacrylonitrile-acetonitrile-water using an extractant are as follows: In a batch distillation column, a ternary azeotrope of methacrylonitrile-acetonitrile-water and an extractant are added at a mass ratio of 1:0.5~3. The operating pressure, reflux ratio, and temperature of the batch distillation column are controlled. When the temperature inside the column stabilizes at 90~91℃, the methacrylonitrile vapor at the top of the column is collected and condensed to obtain the methacrylonitrile product. When the temperature inside the column drops to 81~82℃, the acetonitrile vapor at the top of the column is collected and condensed to obtain the acetonitrile product.
[0017] The beneficial effects of this invention are as follows: This invention proposes an extractant and extraction separation method for a ternary azeotrope of methacrylonitrile-acetonitrile-water. The extractant is methyl isobutyl ketone or butyl acetate. The extractant of this invention has a good extraction and separation effect on the methacrylonitrile-acetonitrile-water ternary azeotrope, resulting in a purity of over 99% and a yield of over 97% for the methacrylonitrile product obtained by extractive distillation, and a purity of over 98.5% and a yield of over 96.5% for the acetonitrile product. In addition, the extractant determined by this invention is a common industrial solvent, widely available, inexpensive, easy to recycle, environmentally friendly, and has stable recycling performance, showing good prospects for industrial application. Attached Figure Description
[0018] Figure 1 This is a σ-profile curve of methacrylonitrile, acetonitrile, water and methyl isobutyl ketone in Example 1 of the present invention; Figure 2 This is a radial distribution function curve of methyl isobutyl ketone with methacrylonitrile, acetonitrile, and water in Example 1 of the present invention; Figure 3 This is a schematic diagram of the continuous extraction distillation system in Embodiment 2 of the present invention; The image is labeled as follows: 1. Extractive distillation column; 2. Extraction recovery column; 3. Extractant dehydration column; 4. First condenser; 5. Second condenser; 6. Third condenser; 7. First reboiler; 8. Second reboiler; 9. Third reboiler; 10. Decanter. Detailed Implementation
[0019] This invention provides a ternary azeotrope extractant of methacrylonitrile-acetonitrile-water and an extraction and separation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0020] Unless otherwise specified, all COSMO-RS calculations used in the following examples were performed on COSMOthermX software at a temperature of 298.15 K. Liquid-liquid phase equilibrium experiments were conducted in a 298.15 K constant-temperature water bath shaker, shaken for 3 hours, and then allowed to stand for 12 hours until the phase interface stabilized. Gas chromatography analysis was performed using an Agilent 7890A, equipped with a DB-WAXETR capillary column (30 m × 0.25 mm × 0.25 μm) and a TCD detector. Chromatographic conditions were: injector temperature 433 K, detector temperature 443 K, column temperature 333 K held for 2 min, then increased to 373 K at a rate of 5 K / min and held for 5 min; carrier gas was H2. Batch distillation experiments were conducted in a distillation column with 18 theoretical plates (25 mm inner diameter, 1.5 m height), operating at atmospheric pressure, and starting collection after 1 hour of total reflux stabilization.
[0021] Reagents used: methacrylonitrile (purity ≥99.5%), acetonitrile (purity ≥99.5%), ultrapure water, and 30 industrial solvents from the candidate library of extractants (all commercially available analytical grade or industrial grade, purity ≥99.0%).
[0022] Example 1 In Example 1, the extraction agents suitable for the methacrylonitrile-acetonitrile-water ternary azeotrope were first screened based on the COSMO-RS model. The steps are as follows: S1. Construct a candidate library of extractants and set up COSMO structure files for methacrylonitrile (MAN), acetonitrile (ACN), water (H2O), and each extractant.
[0023] Specifically, the extractant candidate library includes n-hexane, cyclohexane, n-heptane, petroleum ether, toluene, o-xylene, m-xylene, ethyl acetate, butyl acetate, isobutyl acetate, propyl acetate, butyl propionate, methyl isobutyl ketone (MIBK), methyl ethyl ketone (MEK), cyclohexanone, isophorone, methyl tert-butyl ether (MTBE), isopropyl ether, diethyl ether, anisole, as well as n-butanol, isobutanol, n-pentanol, isooctanol, cyclohexanol, dichloromethane, chloroform, chlorobenzene, tributyl phosphate, and N-methylpyrrolidone.
[0024] The COSMO structure files for methacrylonitrile, acetonitrile, water, and various extractants can be directly accessed from the standard files in the COSMObase database built into the COSMOthermX software. If no corresponding file is found in the database, it is obtained through ab initio calculations using TurboMole quantum chemistry software. The calculation parameters are set as follows: the density functional is BP functional, the basis set is TZVP basis set with d orbital polarization functions (i.e., BP-TZVPD-fine level). The calculation process includes full optimization of molecular geometry, energy minimization, and calculation of COSMO surface charge distribution. The final output is a standard format .cosmo file, ensuring that the file can be directly imported into the COSMO-RS model for subsequent thermodynamic calculations.
[0025] S2. Calculate the surface charge density distribution curve and hydrogen bond acceptor region integrated area of each extractant using the COSMO-RS model. Sort the hydrogen bond acceptor region integrated areas from largest to smallest and select the top 40% of extractants by hydrogen bond acceptor region integrated area.
[0026] The specific steps are as follows: The COSMO structure files of each candidate extractant, methacrylonitrile, acetonitrile, and water obtained in step S1 were called and imported into the σ-profile analysis module of the COSMOthermX software. The calculation temperature was set to 298.15K and the calculation was performed. The surface charge density distribution curve P(σ) of each molecule was output. The σ axis was divided into three characteristic regions according to the charge density value, namely the hydrogen bond donor region (σ < -0.0082e / Å). 2 ), nonpolar region (-0.0082 < σ < 0.0082e / Å) 2 ) and hydrogen bond acceptor region (σ>0.0082e / Å) 2 Calculate the integral area of the hydrogen bond acceptor region for each candidate extractant. And press A HBA The extractants are sorted from largest to smallest, and the top 40% are selected for the next stage. This pre-screening step only requires molecular surface charge density distribution and does not require time-consuming thermodynamic calculations. It can quickly eliminate solvents with significantly insufficient acceptor capacity (such as alkanes, some ethers, and low-polarity aromatics), significantly reducing subsequent calculation costs. Extractant A HBA The larger the atom, the stronger its ability to form competitive hydrogen bonds with hydrogen atoms in water, which is more conducive to breaking the azeotropic reaction.
[0027] Based on the above calculations, the integral area of the hydrogen bond acceptor region of the selected top 40% of extractants is shown in Table 1 below.
[0028] Table 1. Integral area of hydrogen bond acceptor region for each candidate extractant S3. Using the COSMO-RS model, calculate the infinite dilution activity coefficients of the top 40% of the selected extractants in terms of the integral area of the hydrogen bond acceptor region for methacrylonitrile, acetonitrile, and water, respectively. Perform liquid-liquid phase equilibrium simulation on the methacrylonitrile-acetonitrile-water ternary system to obtain the partition coefficients and selectivity of each extractant for methacrylonitrile, acetonitrile, and water, and use the partition coefficients and selectivity as thermodynamic indicators.
[0029] The specific steps are as follows: import the generated COSMO file into the COSMOthermX software, set the temperature to 298.15K, calculate the infinite dilution activity coefficients of each extractant for methacrylonitrile, acetonitrile, and water, then perform a ternary system liquid-liquid phase equilibrium simulation, and calculate the partition coefficient (D) and selectivity (S) of each extractant for methacrylonitrile, acetonitrile, and water based on the simulation results. The COSMO-RS prediction results of each candidate extractant are shown in Table 2 below.
[0030] Table 2. Partition coefficients and selectivity of each candidate extractant to methacrylonitrile, acetonitrile, and water. S4. Collect or determine the industrial applicability indicators of the top 40% of the selected extractants by their integral area of hydrogen bond acceptor regions.
[0031] Specifically, the industrial applicability indicators include boiling point, toxicity (LD50, oral in rats), price (RMB / 100g, industrial grade), and viscosity (25℃, mPa·s). The industrial applicability indicators of each candidate extractant are shown in Table 3 below.
[0032] Table 3. Industrial Applicability Indicators of Each Candidate Extractant Note: Toxicity data are from the MSDS database, prices are reference prices for industrial-grade solvents, and viscosity data are from chemical handbooks (25℃).
[0033] S5. Assign different weights to thermodynamic and industrial applicability indicators, and calculate the comprehensive score of each extractant.
[0034] Specifically, when calculating the comprehensive score of each extractant based on thermodynamic indicators (indicator parameters: distribution coefficient and selectivity) and industrial applicability indicators (indicator parameters: boiling point, toxicity, price and viscosity), this step requires first normalizing each indicator parameter in the thermodynamic indicators and industrial applicability indicators (i.e., performing range normalization independently on each type of indicator parameter to eliminate the influence of dimensions), and then calculating the comprehensive score according to the weights.
[0035] In this embodiment, the weights of each indicator are allocated as follows: the total weight of the thermodynamic indicators is 0.6, where D MAN With a weight of 0.15, DACN Weight is 0.05, D H2O With a weight of 0.15, S MAN / H2O Weights of 0.1, S ACN / H2O Weight is 0.05, S MAN / CAN The weight of each indicator is 0.1; the total weight of practicality indicators is 0.4, with boiling point, toxicity, price, and viscosity each having a weight of 0.1. Based on this weight allocation, the comprehensive scores of each candidate extractant are calculated as shown in Table 4 below.
[0036] Table 4. Overall scores of each candidate extractant S6. Combine the overall score ranking with the hydrogen bond acceptor region integral area ranking, and select the top three extractants from the two categories as methacrylonitrile-acetonitrile-water ternary azeotropic extractants.
[0037] Specifically, based on the calculated integrated area of the hydrogen bond acceptor region for each candidate extractant in Table 1, the top three extractants are methyl isobutyl ketone (Methyl isobutyl ketone), butyl acetate, and tributyl phosphate. Based on the comprehensive score calculation in Table 4, the top three extractants are also Methyl isobutyl ketone (Methyl isobutyl ketone), butyl acetate, and isobutyl acetate. Although tributyl phosphate has a large integrated area of the hydrogen bond acceptor region, its practicality score is low (high boiling point, high viscosity), ranking eighth overall. While isobutyl acetate has a high comprehensive score, its integrated area of the hydrogen bond acceptor region is small, ranking sixth. Therefore, Methyl isobutyl ketone (Methyl isobutyl ketone) and butyl acetate were ultimately selected as the preferred extractants.
[0038] Based on the determination that methyl isobutyl ketone and butyl acetate are the preferred extractants, the results were verified by liquid-liquid phase equilibrium experiments and batch distillation experiments, and the optimal extractant was selected.
[0039] In this embodiment, a liquid-liquid equilibrium experiment was conducted to verify the accuracy of the partition coefficient and selectivity predicted by the COSMO-RS model. The specific steps were as follows: A ternary mixture of methacrylonitrile-acetonitrile-water was prepared at 298.15 K and atmospheric pressure, with a mass ratio of methacrylonitrile, acetonitrile, and water of 4:3:3 (simulating a typical industrial composition). 10.0000 g of the methacrylonitrile-acetonitrile-water mixture was accurately weighed into a 100 mL stoppered conical flask, and then 2.0000 g of extractant (methyl isobutyl ketone or butyl acetate) was added, making the extractant-to-raw material mass ratio 1:5. The conical flask was then placed in a 298.15 K constant-temperature water bath shaker and shaken at 150 r / min for 3 h, followed by standing for 12 h until the interface between the two phases was clear. Extraction and raffinate samples were taken separately using a syringe, dried with anhydrous sodium sulfate, and the content of each component was analyzed by gas chromatography. Each sample was measured in triplicate, and the average value was taken. Based on the equilibrium composition, the partition coefficient and selectivity were calculated. The experimental results of methyl isobutyl ketone were compared with the COSMO-RS predicted values in Table 5 below, and the experimental results of butyl acetate were compared with the COSMO-RS predicted values in Table 6 below.
[0040] Table 5 Comparison of experimental and predicted values of methyl isobutyl ketone liquid-phase equilibrium Table 6 Comparison of experimental and predicted values of butyl acetate liquid phase equilibrium Analysis of Tables 5 and 6 above shows that the relative deviations between the liquid-liquid equilibrium experimental values and the COSMO-RS predicted values for the two extractants, methyl isobutyl ketone and butyl acetate, are both less than 5%, indicating that the COSMO-RS model has high prediction accuracy for this system and the screening results are reliable.
[0041] In this embodiment, to verify the extraction effect of the selected methyl isobutyl ketone (Methyl isobutyl ketone) and butyl acetate extractants on the ternary azeotropic system of methacrylonitrile-acetonitrile-water, a batch distillation experiment was conducted. The batch distillation experimental apparatus used a glass distillation column with an inner diameter of 25 mm and a height of 1.5 m, filled with θ-ring stainless steel packing. The theoretical number of plates was 18, and the reboiler was a 500 mL three-necked flask equipped with an electric heating mantle. A total condenser and a reflux ratio controller were installed at the top of the column. During the experiment, a ternary mixture of methacrylonitrile-acetonitrile-water (mass ratio 4:3:3), with a total mass of 300 g, was first prepared. Then, 300 g of the raw material and 150 g of extractant were added to the reboiler. Heating and condensation were turned on, and total reflux operation was performed for 1 hour to stabilize the gas-liquid equilibrium within the column. Then, the reflux ratio was set to 3:1, and the extraction began. According to S... MAN / ACNFor a prediction greater than 1, methyl acrylonitrile is preferentially collected from the top of the column. The top temperature is recorded every 10 minutes, and fractions from each time period are collected using sampling bottles. When the top temperature drops from approximately 90°C to approximately 81°C, the sampling bottle is switched, and acetonitrile product collection begins. After distillation, each fraction is collected, weighed, and its purity is analyzed by gas chromatography to calculate the yield.
[0042] The batch distillation results of methyl isobutyl ketone (Methyl IBE) are as follows: 118.3 g of methacrylonitrile (99.7% purity, 98.6% yield) and 88.1 g of acetonitrile (99.5% purity, 97.9% yield) were obtained, along with 7.8 g of transition fraction. The top temperature stabilized at 90-91℃ within 30-90 min, corresponding to the collection of methacrylonitrile; and stabilized at 81-82℃ within 120-150 min, corresponding to the collection of acetonitrile. The batch distillation results of butyl acetate under the same operating conditions were: methacrylonitrile purity 99.3%, yield 97.3%; and acetonitrile purity 98.9%, yield 96.6%, significantly lower than that of Methyl IBE. Therefore, Methyl IBE was determined to be the optimal extractant.
[0043] In addition, this embodiment, based on determining methyl isobutyl ketone (Methyl Iobutyl ketone) as the optimal extractant, also verifies its recycling performance to evaluate the industrial application stability of Methyl Iobutyl ketone. Specifically, the bottom liquid (mainly water and Methyl Iobutyl ketone) after the above batch distillation experiment was subjected to atmospheric distillation, and the fraction collected at 120-130℃ was used to obtain recovered Methyl Iobutyl ketone (gas chromatography analysis showed the recovered Methyl Iobutyl ketone purity was greater than 99.0%). The recovered Methyl Iobutyl ketone was then reused in the above batch distillation experiment for a total of 5 cycles, with the product purity and yield recorded each time. The results are shown in Table 7 below.
[0044] Table 7 Results of the recycling performance test of methyl isobutyl ketone Analysis of the test results in Table 7 shows that after five cycles of methyl isobutyl ketone, the purity of methacrylonitrile only decreased from 99.7% to 99.4%, the yield decreased from 98.6% to 97.4%, and the extractant recovery rate remained above 97%, indicating that it has good recycling performance and industrial application potential.
[0045] In addition, to reveal the molecular mechanism by which the selected optimal extractant, methyl isobutyl ketone, exhibits high selectivity for methacrylonitrile, the following mechanism analysis was performed in this embodiment: (1) σ-profile analysis The σ-profile of each substance was calculated using COSMO-RS, and σ-profile curves for methacrylonitrile (MAN), acetonitrile (ACN), water (H2O), and methyl isobutyl ketone (MIBK) were plotted, as shown below. Figure 1As shown. According to the COSMO-RS theory, the σ axis is divided into three characteristic regions: the hydrogen bond donor region (σ < -0.0082e / Å). 2 ), nonpolar region (-0.0082 < σ < 0.0082e / Å) 2 ) and hydrogen bond acceptor region (σ > 0.0082e / Å) 2 ).from Figure 1 As can be seen from the data, (a) water exhibits a double peak in the hydrogen bond donor region (σ≈-0.019e / Å). 2 Intensity 3.8 Å 2 The second peak is located at σ ≈ -0.014e / Å. 2 Intensity 4.5 Å 2 (a) Corresponding to two hydrogen atoms, this indicates that water has an extremely strong hydrogen bond donor capacity and is the core of azeotropic formation. Methacrylonitrile, acetonitrile, and methyl isobutyl ketone all contribute zero in this region, and the three can only participate in the interaction as hydrogen bond acceptors; (b) In the nonpolar region, methacrylonitrile reaches its peak at σ=0 (20.5 Å). 2 ), significantly higher than acetonitrile (12.0 Å), 2 ) and methyl isobutyl ketone (12.5 Å) 2 This is due to the combined contribution of the methyl group and the carbon-carbon double bond in its molecule; the nonpolar peak of methyl isobutyl ketone comes from the alkyl chain, and the nonpolar peak of acetonitrile (12.0 Å) is also present. 2 (c) From the methyl group, water contributes almost zero in this region, consistent with its strong polarity; (d) In the hydrogen bond acceptor region, acetonitrile has a σ≈0.010e / Å 2 The strength of the hydrogen bond acceptor reaches its peak at the α-hydroxyl group and remains high throughout the entire hydrogen bond acceptor region, making it the strongest hydrogen bond acceptor among the four substances; the carbonyl oxygen of methyl isobutyl ketone has a strength of σ≈0.007~0.009e / Å. 2 A strong peak appears at σ, indicating a slightly lower acceptor ability than acetonitrile but still a strong acceptor, and the peak position is positive, suggesting its specific affinity for hydrogen bond donors; the acceptor peak of methacrylonitrile is located at σ≈0.004~0.006e / Å. 2 (Peak 26.8Å) 2 However, it is located closer to the nonpolar region and decays rapidly after σ > 0.008 (it has dropped to 20.0 Å at σ = 0.008). 2 This indicates that its receptor ability is coupled with the overall nonpolar molecular environment, and its affinity for strongly polar donors is relatively weak.
[0046] The strong donor bimodal peaks of water and the strong acceptor peaks of acetonitrile / methacrylonitrile form a perfect complement, resulting in a strong hydrogen bond network between water and nitrile, generating binary and ternary azeotropes that are difficult to separate under normal pressure. MIBK, as a pure acceptor, can competitively disrupt the original water-nitrile hydrogen bonds due to its strong carbonyl oxygen acceptor ability, while achieving selective extraction by virtue of the difference in nonpolar affinity for MAN and ACN.
[0047] (2) Decomposition of interaction energy The interaction energies between methyl isobutyl ketone and methacrylonitrile, acetonitrile, and water were calculated using the COSMO-RS model and decomposed into mismatch energies (Ei). misfit ), hydrogen bond energy (E hb ) and van der Waals (E vdW The calculation results are shown in Table 8 below. The total interaction energy between methyl isobutyl ketone (MEK) and methacrylonitrile (-7.45 kcal / mol) is significantly stronger than that with water (-3.79 kcal / mol), and the total energy with acetonitrile (-6.72 kcal / mol) is also slightly lower than that with methacrylonitrile. Table 8 shows that hydrogen bond energy is the largest contributor: the hydrogen bond energy of methacrylonitrile (-3.45 kcal / mol) is higher than that of acetonitrile (-3.02 kcal / mol), and much higher than that of water (-1.28 kcal / mol). This indicates that MEK mainly achieves selective affinity for methacrylonitrile by forming strong hydrogen bonds between its carbonyl oxygen and the nitrile hydrogen of methacrylonitrile. The contribution of van der Waals energy also indicates the importance of nonpolar interactions. The van der Waals energy of methacrylonitrile (-2.18 kcal / mol) is slightly higher than that of acetonitrile (-2.05 kcal / mol), consistent with its stronger nonpolar characteristics. The mismatch energy reflects the degree of electrostatic matching, and the differences among the three are small.
[0048] Table 8. Interaction energies between methyl isobutyl ketone and each component. (3) Radial Distribution Function (RDF) Analysis To verify the strength of intermolecular interactions from a spatial structure perspective, a mixed system model containing methyl isobutyl ketone (MBE), methacrylonitrile (MAK), acetonitrile (AAK), and water was constructed using Materials Studio software (each molecule was set in an equimolar ratio). The initial configuration was built using the Amorphous Cell module, and geometry optimization was performed using the Forcite module. Then, molecular dynamics simulations were conducted for 200 ps in the NVT ensemble (temperature 298.15 K, time step 1 fs). Finally, the radial distribution function was calculated. The calculated radial distribution function g(r) between the carbonyl oxygen (O=C) of MBE, the nitrile carbon (C≡N) of MAK, the nitrile carbon of MAK, and the oxygen atoms in the water is shown below. Figure 2 As shown.
[0049] from Figure 2The results show that the first characteristic peak of methyl isobutyl ketone (MBE) and methacrylonitrile appears at 2.81 Å with an intensity g(r) = 2.35; the first characteristic peak of MBE and acetonitrile appears at 2.93 Å with an intensity g(r) = 2.12; and the first characteristic peak of MBE and water appears at 3.52 Å with an intensity g(r) = 1.28. It is generally believed that a distance of less than 3.5 Å with a significant peak indicates a strong intermolecular interaction. Therefore, the RDF results clearly confirm from a spatial distance perspective that MBE has the shortest binding distance and the highest interaction probability with methacrylonitrile, followed by acetonitrile, and the weakest interaction with water, with the interaction distance exceeding the range of strong hydrogen bonds. This order is completely consistent with the results of interaction energy decomposition.
[0050] Comprehensive analysis reveals that methyl isobutyl ketone (Methyl isobutyl ketone) leverages the strong hydrogen bond acceptor ability of its carbonyl oxygen group to form the strongest and closest specific hydrogen bond with methacrylonitrile (MAT), while exhibiting relatively weak affinity for water, thus achieving highly selective extraction of MAT. This mechanism is entirely consistent with the results from σ-profile, interaction energy, and RDF analysis.
[0051] Example 2 Reference Figure 3 In this embodiment, methyl isobutyl ketone (Methyl isobutyl ketone) selected in Example 1 is used for continuous extractive distillation of a ternary azeotropic system of methacrylonitrile-acetonitrile-water. The continuous extractive distillation system includes: an extractive distillation column 1, an extractive recovery column 2, and an extractive dehydration column 3. The top outlets of the extractive distillation column 1, the extractive recovery column 2, and the extractive dehydration column 3 are respectively connected to a first condenser 4, a second condenser 5, and a third condenser 6. The outlet of the third condenser 6 is connected to a decanter 10. The bottom outlets of the extractive distillation column 1, the extractive recovery column 2, and the extractive dehydration column 3 are respectively connected to a first reboiler 7, a second reboiler 8, and a third reboiler 9.
[0052] The steps for continuous extractive distillation of the methylacrylonitrile-acetonitrile-water ternary azeotropic system using the above-mentioned continuous extractive distillation system are as follows: (1) The ternary azeotrope of methacrylonitrile-acetonitrile-water (mass ratio 4:3:3) was extracted and distilled using an extractive distillation column. The theoretical plate number was set to 40, the operating pressure was atmospheric pressure, and the reflux ratio was 3. The methacrylonitrile-acetonitrile-water ternary azeotrope was fed from the middle of the extractive distillation column (the 25th theoretical plate), and the extractant methyl isobutyl ketone was fed from the top of the extractive distillation column (the 10th theoretical plate). The mass ratio of the methacrylonitrile-acetonitrile-water ternary azeotrope to the extractant was set to 1:1. The top temperature of the column was 90.3℃, and the bottom temperature of the column was 121.3℃. After extractive distillation, the vapor at the top of the column was methacrylonitrile. After the methacrylonitrile was condensed by the first condenser, part of it was refluxed back to the extractive distillation column, and part of it was collected as methacrylonitrile product. The bottom of the column yielded a mixture of acetonitrile, water and methyl isobutyl ketone. After the mixture was heated by the first reboiler, part of it was refluxed and part of it was pumped to the extraction recovery column. (2) The bottom mixture of the extractive distillation column is pumped to the extraction recovery column, which is set to have 20 theoretical plates, an operating pressure of atmospheric pressure, and a reflux ratio of 2.5. In the extraction recovery column, the boiling point of acetonitrile (81.6℃) is significantly lower than that of methyl isobutyl ketone (116.5℃), and methyl isobutyl ketone and acetonitrile do not form an azeotrope. In the presence of a large amount of methyl isobutyl ketone, the acetonitrile-water azeotrope is also significantly suppressed. The temperature at the top of the column is controlled at 81.6℃ and the temperature at the bottom of the column is controlled at 116.5℃, so that acetonitrile is collected from the top of the column as a light component. After the acetonitrile vapor at the top of the column is condensed by the second condenser, part of it is refluxed to the extraction recovery column and part of it is collected as acetonitrile product. A mixture of methyl isobutyl ketone and a small amount of water (almost no acetonitrile) is obtained in the bottom of the column. After the mixture is heated by the second reboiler, part of it is refluxed and part of it is pumped to the extractant dehydration column. (3) The mixture from the bottom of the extraction and recovery tower is pumped to the extractant dehydration tower, which is set to have 12 theoretical plates, an operating pressure of atmospheric pressure, and a reflux ratio of 2. Water and methyl isobutyl ketone form a low-boiling-point azeotrope (azeotropic point approximately 94°C). The temperature at the top of the extraction tower is controlled at 94.0°C, and the temperature at the bottom of the tower is controlled at 116.5°C, so that the azeotrope of water and methyl isobutyl ketone evaporates from the top of the tower. The azeotropic vapor at the top of the tower is condensed by the third condenser and then enters the decanter. After settling and separating, the upper layer rich in methyl isobutyl ketone is returned to the top of the dehydration tower as reflux liquid, and the lower layer of water phase is discharged from the system. The bottom of the tower yields dehydrated methyl isobutyl ketone with a water content of less than 0.1 wt%. All the dehydrated methyl isobutyl ketone is recycled back to the extractive distillation tower for reuse, forming a continuous and stable closed-loop circulation system.
[0053] In step (3) above, the low-boiling-point azeotrope formed by water and methyl isobutyl ketone is a heterogeneous azeotrope. After its vapor is condensed, it is placed in a decanter (separator) to achieve separation by utilizing the density difference and extremely low miscibility between the two. The upper layer is an organic phase rich in MIBK, and the lower layer is an aqueous phase rich in water.
[0054] In addition, during the operation of the above system, a small amount of fresh methyl isobutyl ketone needs to be added periodically to maintain the total balance of the extractant.
[0055] The extraction and distillation results of this embodiment were tested, and the purity of the methacrylonitrile product was 99.5 wt%, with a yield of 98.2%; the purity of the acetonitrile product was 99.3 wt%, with a yield of 97.4%.
[0056] Example 3 This embodiment uses butyl acetate, the extractant screened in Example 1, for continuous extractive distillation of a tertiary azeotropic system of methacrylonitrile-acetonitrile-water. The difference between this embodiment and Example 2 is that the extractant in this embodiment is butyl acetate, while the rest are the same.
[0057] The extraction and distillation results of this embodiment were tested, and the purity of the methacrylonitrile product was 99.3% and the yield was 97.1%; the purity of the acetonitrile product was 98.9% and the yield was 96.2%.
[0058] Comparative Example 1 This comparative example compares the batch extractive distillation of a ternary azeotropic system of methacrylonitrile-acetonitrile-water. The difference between this comparative example and Example 1 is that the extractant in this comparative example is chlorobenzene.
[0059] Comparative Example 2 This comparative example compares the batch extractive distillation of a ternary azeotropic system of methacrylonitrile-acetonitrile-water. The difference between this comparative example and Example 1 is that the extractant in this comparative example is toluene.
[0060] The extractive distillation results (purity and yield of methacrylonitrile and acetonitrile, and selectivity of methacrylonitrile and acetonitrile) of Comparative Examples 1 and 2 in Example 1 were tested, and the test results are shown in Table 9 below.
[0061] Table 9. Results of batch extractive distillation of Example 1 and Comparative Examples 1 and 2 Analysis of Table 9 above shows that the extraction and separation effects of chlorobenzene and toluene are significantly worse than those of methyl isobutyl ketone and butyl acetate. Furthermore, chlorobenzene has high toxicity (LD50 1110 mg / kg), limiting its industrial application. Toluene, on the other hand, exhibits low selectivity for methacrylonitrile and acetonitrile (S...). MAN / AC With N=1.03, the temperature fluctuation at the top of the column during the distillation process was large, and the cross-contamination of the fractions was serious, resulting in low purity and yield of methacrylonitrile and acetonitrile.
[0062] It should be noted that any parts not mentioned in this invention can be achieved by using or referencing existing technologies.
[0063] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.
Claims
1. A ternary azeotropic extractant of methacrylonitrile-acetonitrile-water, characterized in that, The extractant is one of methyl isobutyl ketone and butyl acetate.
2. The methacrylonitrile-acetonitrile-water ternary azeotrope extractant according to claim 1, characterized in that, The extractant was obtained based on the COSMO-RS model, and the screening steps included: Construct an extractant candidate library, wherein the extractants in the extractant candidate library include one or more of the following: alkanes, aromatic hydrocarbons, esters, ketones, ethers, alcohols, halogenated hydrocarbons, amides, and phosphorus-containing solvents; The surface charge density distribution curves and hydrogen bond acceptor region integrated areas of each extractant were calculated using COSMO-RS. The hydrogen bond acceptor region integrated areas were sorted from largest to smallest, and the extractants with the top 30-50% of the hydrogen bond acceptor region integrated areas were selected. The COSMO-RS was used to calculate the infinite dilution activity coefficients of the top 30-50% of the hydrogen bond acceptor regions of the selected extractants for methacrylonitrile, acetonitrile, and water, respectively. Liquid-liquid equilibrium simulations were performed on the methacrylonitrile-acetonitrile-water ternary system to obtain the partition coefficients and selectivity of each extractant for methacrylonitrile, acetonitrile, and water. The partition coefficients and selectivity were used as thermodynamic indicators. Collect or measure the industrial applicability indicators of the extractants whose integrated area of the selected hydrogen bond acceptor region ranks in the top 30-50%. Different weights are assigned to thermodynamic and industrial applicability indicators, and the overall score of each extractant is calculated. By combining the overall score ranking with the ranking of the integral area of the hydrogen bond acceptor region, the extractants with the highest rankings in both categories were selected as the extractants for the methacrylonitrile-acetonitrile-water ternary azeotrope.
3. The methacrylonitrile-acetonitrile-water ternary azeotrope extractant according to claim 2, characterized in that, The alkane solvents in the candidate library of extractants include one or more of n-hexane, cyclohexane, n-heptane, and petroleum ether; Aromatic hydrocarbon solvents include one or more of toluene, o-xylene, and m-xylene; Ester solvents include one or more of ethyl acetate, butyl acetate, isobutyl acetate, propyl acetate, and butyl propionate; Ketone solvents include one or more of methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, and isophorone; Ether solvents include one or more of methyl tert-butyl ether, isopropyl ether, diethyl ether, and anisole; Alcohol solvents include one or more of n-butanol, isobutanol, n-pentanol, isooctanol, and cyclohexanol; Halogenated hydrocarbon solvents include one or more of dichloromethane, chloroform, and chlorobenzene; Amide solvents include N-methylpyrrolidone; Phosphorus-containing solvents include tributyl phosphate.
4. The methacrylonitrile-acetonitrile-water ternary azeotrope extractant according to claim 2, characterized in that, The industrial applicability indicators include boiling point, toxicity, price, and viscosity.
5. The methacrylonitrile-acetonitrile-water ternary azeotrope extractant according to claim 2, characterized in that, When calculating the comprehensive score of each extractant based on thermodynamic and industrial applicability indicators, it is necessary to first normalize the parameters of each indicator in the thermodynamic and industrial applicability indicators.
6. A method for extraction and separation of a ternary azeotrope of methacrylonitrile-acetonitrile-water, using the extractant according to any one of claims 1-5, characterized in that, The ternary azeotrope of methacrylonitrile-acetonitrile-water was separated by continuous extractive distillation using an extractant, as follows: Extractive distillation was used to extract and distill the ternary azeotrope of methacrylonitrile-acetonitrile-water. The methacrylonitrile-acetonitrile-water ternary azeotrope was fed into the middle of the extractive distillation column, while the extractant was fed into the top of the extractive distillation column. The extractant was selectively solvated to break down the ternary azeotrope of methacrylonitrile-acetonitrile-water and the binary azeotrope of methacrylonitrile-water. After extractive distillation, methacrylonitrile was distilled off from the top of the extractive distillation column and high-purity methacrylonitrile was collected by condensation. The bottom of the column yielded a mixture of acetonitrile, water and extractant. The mixture at the bottom of the extractive distillation column is pumped to the extraction recovery column. By controlling the temperature of the extraction recovery column, acetonitrile is distilled off from the top of the column and high-purity acetonitrile is collected by condensation. The bottom of the column yields a mixture of extractant and a small amount of water. The mixture at the bottom of the extraction recovery tower is pumped to the extractant dehydration tower. By controlling the temperature of the extractant dehydration tower, water and a small amount of extractant are distilled off from the top of the tower. The mixture of water and a small amount of extractant is collected by condensation. The bottom of the tower yields the dehydrated extractant, which is then recycled back to the extractive distillation tower for reuse.
7. The extraction and separation method for a ternary azeotrope of methacrylonitrile-acetonitrile-water according to claim 6, characterized in that, The mass ratio of the methylacrylonitrile-acetonitrile-water ternary azeotrope to the extractant in the extractive distillation column is 1:0.5~3; the operating pressure of the extractive distillation column is atmospheric pressure, the top temperature is 90~100℃, the bottom temperature is 110~130℃, the reflux ratio is 2~4, and the theoretical plate number is 30~50.
8. The extraction and separation method for a ternary azeotrope of methacrylonitrile-acetonitrile-water according to claim 6, characterized in that, The extraction and recovery tower operates at atmospheric or reduced pressure, with a top temperature of 81-83°C, a bottom temperature of 110-130°C, a reflux ratio of 1-3, and a theoretical plate number of 15-25.
9. The extraction and separation method for a ternary azeotrope of methacrylonitrile-acetonitrile-water according to claim 6, characterized in that, The operating pressure of the extractant dehydration tower is atmospheric pressure, the top temperature is 93~95℃, the bottom temperature is 110~120℃, the reflux ratio is 1~3, and the theoretical plate number is 10~15.
10. A method for extraction and separation of a ternary azeotrope of methacrylonitrile-acetonitrile-water, using the extractant according to any one of claims 1-5, characterized in that, The ternary azeotrope of methacrylonitrile-acetonitrile-water was separated by batch extractive distillation using an extractant, as follows: In a batch distillation column, a ternary azeotrope of methacrylonitrile-acetonitrile-water and an extractant are added at a mass ratio of 1:0.5~3. The operating pressure, reflux ratio, and temperature of the batch distillation column are controlled. When the temperature inside the column stabilizes at 90~91℃, the methacrylonitrile vapor at the top of the column is collected and condensed to obtain the methacrylonitrile product. When the temperature inside the column drops to 81~82℃, the acetonitrile vapor at the top of the column is collected and condensed to obtain the acetonitrile product.