An ionic liquid extractive distillation separation process for separating a butyl acetate-butanol azeotrope

Abstract

The application discloses an ionic liquid extractive distillation separation process of butyl acetate-butanol azeotrope, and relates to the field of chemical separation technology.The specific steps of the process are as follows: firstly, a device is built and the pressure is calibrated to 101.3 kPa;then, a two-component synergistic extractant is prepared, mixed with the azeotrope after vacuum drying, and added to an equilibrium chamber to form a stable vapor-liquid equilibrium through heating and stirring; subsequently, samples are collected from gas and liquid phase sampling ports and sealed and labeled; finally, gas chromatography is used for analysis, NRTL model parameters are fitted, parameters are adjusted through thermodynamic testing, and optimal operation parameters are determined; through the use of the two-component synergistic extractant, the application strengthens the selective destruction capacity of the butyl acetate-butanol azeotrope and improves the stability of the system; a sealed vapor-liquid equilibrium device is built, precise sampling analysis is performed, model parameters are fitted and verified, and optimal operation parameters are determined through the optimization of the whole process, thereby providing support for the industrialization of the extractive distillation process.

Description

Technical Field

[0001] This invention relates to the field of chemical separation technology, specifically to an ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope. Background Technology

[0002] Butyl acetate and butanol are both widely used organic solvents in industrial production, playing important roles in fine chemicals, coatings preparation, pharmaceutical intermediate synthesis, and fragrance production. They readily form azeotropes during industrial synthesis and separation, and the presence of these azeotropic systems prevents effective separation using conventional distillation processes. Therefore, extractive distillation has become a core technology for separating these azeotropes. As the chemical industry moves towards green and low-carbon development, traditional organic solvent extractants are gradually being replaced due to their high volatility, significant environmental pollution, and difficulty in recovery. Ionic liquids and eutectic solvents, as novel green extractants, have become a research focus in the field of extractive distillation separation of ester-alcohol azeotropes due to their advantages such as low volatility, high selectivity, and designability. The industry urgently needs to develop green extractive distillation processes suitable for butyl acetate-butanol azeotropes to meet the industrial demand for the separation of high-purity monomer products, while also aligning with the requirements of green chemical development.

[0003] Traditional butyl acetate-butanol azeotropic separation processes, whether using a single ionic liquid or a single eutectic solvent as the extractant, have significant performance limitations. A single extractant is insufficient to enhance the selective destruction of the azeotrope, and the physical properties of some extractants can affect the mass transfer and flow efficiency of the mixture, resulting in separation effects and efficiencies that fall short of industrial production expectations. Furthermore, traditional processes lack standardized procedures for extractant pretreatment; the presence of impurities and moisture significantly reduces extractant performance and affects the stable establishment of vapor-liquid equilibrium. In addition, the control precision of vapor-liquid equilibrium devices in traditional processes is insufficient, and the sampling process is poorly standardized, easily leading to sample volatilization and contamination, resulting in biased detection data. Moreover, the fitting and optimization of process parameters lack systematic thermodynamic verification, leading to highly arbitrary parameter adjustments and an inability to achieve precise control of the separation process. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an ionic liquid extraction and distillation separation process for butyl acetate-butanol azeotropes. This process utilizes a compounded ionic liquid and a low-melting-point solvent to form a bicomponent synergistic extractant, relying on the synergistic effect of hydrogen bonding to disrupt the azeotropic system. Simultaneously, the pretreatment process of the extractant is optimized to ensure its performance. The process employs a precisely pressure-controlled vapor-liquid equilibrium device to achieve zoned, sealed sampling of the gas and liquid phases. Combined with gas chromatography, quantitative analysis of the components is performed. A professional algorithm is used to fit the NRTL model parameters of the compounded quaternary system, and the data is verified through thermodynamic consistency testing. After adjusting multi-dimensional process parameters, the optimal operating conditions are determined. This process improves the stability and accuracy of azeotropic separation. The extractant also possesses green and environmentally friendly characteristics, is adaptable to the modification of existing industrial equipment, and provides a technical reference for the separation of similar ester-alcohol azeotropes.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope, the process comprising: S1, Device setup and pressure calibration: The dryer, buffer tank, and pressure gauge are connected in series and then sealed to the balance chamber. Nitrogen gas is introduced and the moisture in the nitrogen gas is removed by the dryer. The nitrogen gas input is monitored and adjusted in real time by the pressure gauge to keep the internal pressure of the balance chamber stable at 101.3 kPa. S2, Raw material processing and vapor-liquid equilibrium construction: First, prepare the eutectic solvent DES, then combine the ionic liquid and the eutectic solvent DES in a specific molar ratio to form a bicomponent synergistic extractant. The bicomponent synergistic extractant is vacuum dried and set aside after moisture detection. The mixture of butyl acetate-butanol azeotrope and the bicomponent synergistic extractant is added to the equilibrium chamber after pressure calibration and stirred evenly. The equilibrium chamber is heated using a heating rod, and a thermometer is connected to the equilibrium chamber to monitor the temperature. The vapor generated in the equilibrium chamber is condensed through a serpentine condenser and then refluxed. The power of the heating rod is adjusted to stabilize the reflux drip rate, allowing the mixed system to run in steady state until a stable vapor-liquid two-phase equilibrium is formed. S3, Vapor-Liquid Two-Phase Sampling: After the vapor-liquid equilibrium is stable, a gas phase sample is collected through the gas phase sampling port and a liquid phase sample is collected through the liquid phase sampling port. After sampling, the sample is sealed and marked. S4, Data Analysis and Parameter Optimization: Gas samples are injected into a gas chromatograph for quantitative analysis to obtain gas-liquid mole fraction data. The Levenberg-Marquardt algorithm is used to fit the NRTL model parameters suitable for the quaternary system. Thermodynamic consistency tests are conducted in conjunction with the Fredenslund criterion. The process parameters are adjusted based on the test results to determine the optimal operating parameters. The quaternary system is composed of butyl acetate, butanol, ionic liquid, and eutectic solvent DES. The Levenberg-Marquardt algorithm was used to fit the NRTL model parameters suitable for the quaternary system composed of butyl acetate, butanol, ionic liquid, and eutectic solvent. Initial parameters were set, and the binary interaction parameters and non-randomness parameters were continuously optimized through iterative calculations until convergence was achieved, resulting in a complete NRTL model parameter set for the experimental quaternary system. Theoretical values ​​of gas phase mole fraction and activity coefficient under corresponding operating conditions were then calculated based on the fitted NRTL model. Thermodynamic consistency tests were conducted using the Fredenslund criterion to verify the deviations between experimentally measured values ​​and theoretically calculated values, thus validating the experimental data. To assess the reliability of the model fitting results, and based on the results of the thermodynamic consistency test, the relevant process parameters were adjusted one by one for the operating conditions that failed the consistency test. After each parameter adjustment was completed, a complete vapor-liquid equilibrium experiment and sample component detection were carried out again. The NRTL model parameter fitting and Fredenslund criterion thermodynamic consistency test were then performed again. This cycle of parameter adjustment, experimental verification, model fitting, and consistency testing was repeated until the experimental data for all operating conditions passed the Fredenslund criterion thermodynamic consistency test. At the same time, the model fitting deviation under different parameter combinations was compared, and finally the optimal operating parameters for the butyl acetate-butanol azeotrope bicomponent synergistic extraction distillation separation process were screened and determined.

[0006] Furthermore, the dryer, buffer tank, pressure gauge, and balance chamber are sealed together by corrosion-resistant pipelines. Nitrogen gas is processed by the dryer and then enters the buffer tank, and is then transported to the balance chamber through pipelines. The pressure gauge is directly connected to the gas phase space of the balance chamber to collect pressure data inside the balance chamber in real time.

[0007] Furthermore, the vacuum drying treatment of the bicomponent synergistic extractant was carried out at 393K and 0.2kPa for 48 hours. After drying, the moisture content of the bicomponent synergistic extractant was detected by Karl Fischer titration. The ionic liquid was treated separately under the same vacuum drying conditions before compounding, and the eutectic solvent DES was vacuum dehydrated to a moisture content of less than 0.0005% by mass before compounding.

[0008] Furthermore, the eutectic solvent DES is synthesized from hydrogen bond acceptors and hydrogen bond donors in a molar ratio of 1:2 to 1:4, wherein the hydrogen bond acceptor is choline chloride or tetrabutylammonium chloride, and the hydrogen bond donor is ethylene glycol, glycerol, or urea; the molar ratio of the ionic liquid to the eutectic solvent DES is 1:0.5 to 1:2; the molar fraction of butyl acetate in the butyl acetate-butanol azeotrope ranges from 0.05 to 0.95, with a molar fraction increment of 0.05; the molar fraction of the bicomponent synergistic extractant in the mixed raw materials is 0.02, 0.04, or 0.06, and the viscosity of the bicomponent synergistic extractant is reduced by 30%-50% compared to the single ionic liquid; the mixed raw materials are continuously stirred after being added to the equilibrium chamber, and after stirring, the mixture is allowed to stand until no stratification occurs.

[0009] Furthermore, the heating rod is attached to the outer wall of the equilibrium chamber, the thermometer is inserted into the liquid phase region inside the equilibrium chamber, the inlet of the serpentine condenser is connected to the gas phase outlet of the equilibrium chamber, the outlet of the serpentine condenser is connected to the reflux port of the equilibrium chamber, the condensing medium is introduced into the jacket layer of the serpentine condenser, and the heating rate and reflux drip rate inside the equilibrium chamber are controlled by adjusting the power of the heating rod. By utilizing the synergistic effect of the hydrogen bond network between the ionic liquid and DES, the selective destruction ability of the mixed system on the butyl acetate-butanol azeotrope is enhanced.

[0010] Furthermore, the gas phase sampling port is located in the top gas phase region of the equilibrium chamber, and the liquid phase sampling port is located in the middle liquid phase region of the equilibrium chamber. The equilibrium chamber is kept closed during the sampling process. After the gas phase sample and the liquid phase sample are collected, they are placed in sealed containers and the sealed containers are marked with corresponding numbers.

[0011] Furthermore, the gas chromatograph is equipped with a KB-Wax capillary column and a flame ionization detector. The column oven temperature of the gas chromatograph is set to 353.15K, the injection port temperature is set to 403.15K, and the detector temperature is set to 423.15K. The area normalization method is used to quantitatively analyze the butyl acetate and butanol components in the gas phase and liquid phase samples.

[0012] Furthermore, the NRTL model, formally known as the non-stochastic two-liquid model, comprises the following calculation formulas: activity coefficient calculation equation, intermediate parameter calculation equation, and binary interaction parameter calculation equation. When fitting the NRTL model parameters using the Levenberg-Marquardt algorithm, the minimum objective function is used as the convergence condition, where: The formula for calculating the intermediate parameters of the model is as follows: The formula for calculating the binary interaction parameters is as follows: The formula for calculating the objective function is: in, Let be the activity coefficient of component i. , , These represent the mole fractions of components i, j, and k in the liquid phase, where i, j, and k are any one of the components: butyl acetate, butanol, ionic liquid, or eutectic solvent (DES). For the non-randomness parameters of the NRTL model, and Let be the binary interaction parameter between component i and component j, R be the universal gas constant, and T be the system temperature at vapor-liquid two-phase equilibrium. , As an intermediate variable in the NRTL model, represents the intermediate parameters of the NRTL model, F is the objective function of the Levenberg-Marquardt algorithm, and n is the number of measurement data sets in the vapor-liquid equilibrium experiment. Let i be the experimentally measured activity coefficient of component i. The activity coefficient for component i is calculated using the NRTL model. Subscript 1 represents the butyl acetate component, and subscript 2 represents the butanol component. The contribution of component k to the molecular / ionic / hydrogen bond interactions of the target component.

[0013] Furthermore, the thermodynamic consistency test is based on the Fredenslund criterion, and the calculation formula is as follows: The formula for calculating the average relative deviation in synchronous calculations is: in: The mean absolute deviation of the gas phase mole fraction. This represents the number of measurement data sets in the vapor-liquid equilibrium experiment. The experimentally determined gaseous molar fractions of butyl acetate and butanol components are shown. The gas-phase mole fractions of butyl acetate and butanol are calculated using the NRTL model for a quaternary system. ARD represents the average relative deviation of the activity coefficients. Components The experimentally measured activity coefficient, Components Activity coefficients calculated using the NRTL model for quaternary systems, subscript These represent the butyl acetate component and the butanol component, respectively.

[0014] Furthermore, the process parameter adjustments include adjusting the heating power of the heating rod, the condensing medium flow rate of the serpentine condenser, the desiccant replacement cycle of the dryer, and the nitrogen input of the pressure gauge. It also includes optimizing the molar ratio of the ionic liquid to the eutectic solvent DES and the synthesis molar ratio of the eutectic solvent DES. After adjustment, the temperature and pressure of the equilibrium chamber are kept stable. The final optimal operating parameters include the molar fraction of the bicomponent synergistic extractant in the mixed raw materials, the molar ratio of the ionic liquid to the eutectic solvent DES, the heating power of the heating rod, and the condensation reflux drip rate of the serpentine condenser.

[0015] Compared with existing technologies, this ionic liquid extractive distillation separation process for butyl acetate-butanol azeotrope has the following advantages: I. This invention utilizes a compounded ionic liquid and a low-eutectic solvent to form a bicomponent synergistic extractant. Targeted drying and dehydration treatment is applied to the extractant and each raw material component, ensuring the purity and performance of the extractant. Simultaneously, leveraging the synergistic effect of the hydrogen bond network between the two components, the selective destructive ability of the butyl acetate-butanol azeotrope is enhanced, overcoming the performance limitations of traditional single extractants. The compounded extractant effectively reduces viscosity, improves the mass transfer and flow characteristics of the mixed system, and facilitates smoother construction of vapor-liquid equilibrium. After stirring and settling, the mixed raw materials form a homogeneous system without stratification, further enhancing the overall homogeneity of the system. This lays a solid foundation for subsequent stable vapor-liquid equilibrium, significantly improving the stability of the system in the early stages of azeotropic separation and the targeted nature of the extraction operation, allowing the core role of extractive distillation to be fully realized.

[0016] II. This invention constructs a sealed vapor-liquid equilibrium device with precisely adjustable pressure, performing zoned and fixed-point sampling of the gas and liquid phases and marking them with seals. This ensures the accuracy of sample testing from the sampling stage. Combined with specialized testing instruments, it achieves precise quantitative analysis of gas and liquid phase components. A professional algorithm is used to fit the parameters of an NRTL model suitable for quaternary systems, and thermodynamic consistency testing is used to scientifically verify the experimental data. Based on the test results, the process parameters are systematically adjusted to achieve full-process parameter optimization of the extractive distillation process. The parameter adjustment covers multiple dimensions such as the extractant compounding ratio, heating and condensation conditions, and gas source control. The final determined optimal operating parameters can maintain a stable vapor-liquid equilibrium state of the separation system in the long term, improving the accuracy and overall efficiency of extractive distillation separation. This provides reliable parameter support and a complete technical basis for the industrial application of this process.

[0017] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0019] Figure 1 A flowchart of an ionic liquid extraction distillation separation process for a butyl acetate-butanol azeotrope. Figure 2 This is a schematic diagram of the experimental setup; 1. Heating rod; 2. Liquid phase sampling port; 3. Equilibrium chamber; 4. Thermometer; 5. Gas phase sampling port; 6. Serpentine condenser; 7. Buffer tank; 8. Dryer; 9. Pressure gauge. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0021] Example 1: The ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope of the present invention is achieved using an experimental apparatus consisting of a heating rod 1, a liquid phase sampling port 2, an equilibrium chamber 3, a thermometer 4, a gas phase sampling port 5, a serpentine condenser 6, a buffer tank 7, a dryer 8, and a pressure gauge 9. Figure 2 As shown, through step-by-step operations including device setup and pressure calibration, raw material processing and vapor-liquid equilibrium construction, vapor-liquid two-phase sampling and data analysis and parameter optimization, combined with thermodynamic model fitting and algorithm calculation of the quaternary system, selective destruction and efficient separation of the azeotropic properties of butyl acetate-butanol azeotrope are achieved. The devices are sealed and coordinated, and the process steps are orderly connected and advanced step by step, ensuring the stability, accuracy and operability of the entire separation process.

[0022] S1, Equipment Setup and Pressure Calibration: The first step in this process is equipment setup and pressure calibration. First, the dryer 8, buffer tank 7, and pressure gauge 9 are connected in series. Then, this series assembly is sealed and connected to the balance chamber 3. All devices are connected via corrosion-resistant pipelines to ensure the airtightness of the entire gas path and prevent pressure fluctuations due to leakage. After the equipment setup is complete, nitrogen gas is introduced into the connected equipment. The nitrogen first enters the dryer 8, where it is treated to remove moisture. The dried nitrogen then enters the buffer tank 7 for flow stabilization and is then transported to the balance chamber 3 via corrosion-resistant pipelines.

[0023] Pressure gauge 9 is directly connected to the gas phase space of equilibrium chamber 3. Pressure gauge 9 is used to collect and monitor the pressure data inside equilibrium chamber 3 in real time. The amount of nitrogen input is adjusted in real time according to the monitored pressure value to keep the pressure inside equilibrium chamber 3 stable at 101.3 kPa. This provides a stable pressure environment for the subsequent construction of the vapor-liquid balance system and completes the pressure calibration operation of the entire device.

[0024] S2, Feed Processing and Vapor-Liquid Equilibrium Construction: Raw material processing and vapor-liquid equilibrium establishment are key operational steps in this process to achieve azeotropic separation. This step sequentially completes the synthesis of the eutectic solvent DES, the formulation and drying of the bicomponent synergistic extractant, the preparation of the mixed raw materials, and the construction of the vapor-liquid equilibrium system. The specific implementation method is as follows: First, a eutectic solvent DES is synthesized. Choline chloride or tetrabutylammonium chloride is selected as the hydrogen bond acceptor, and ethylene glycol, glycerol, or urea is selected as the hydrogen bond donor. The hydrogen bond acceptor and hydrogen bond donor are mixed in a molar ratio of 1:2 to 1:4 to obtain the eutectic solvent DES. The synthesized eutectic solvent DES is then subjected to vacuum dehydration treatment until its water content is lower than 0.0005% by mass. After treatment, it is ready for use. Simultaneously, the ionic liquid is separately vacuum dried. Then, the dried ionic liquid is compounded with the above-treated eutectic solvent DES in a molar ratio of 1:0.5 to 1:2 to form a bicomponent synergistic extractant. This bicomponent synergistic extractant reduces the viscosity by 30%-50% compared to the single ionic liquid, effectively improving the mass transfer efficiency in the extractive distillation process.

[0025] The bicomponent synergistic extractant obtained above was subjected to vacuum drying at 393 K and 0.2 kPa for 48 hours. After drying, the moisture content of the bicomponent synergistic extractant was tested by Karl Fischer titration. After passing the test, it was sealed and stored for later use. Subsequently, a butyl acetate-butanol azeotrope was prepared. The molar fraction of butyl acetate in the azeotrope was controlled within the range of 0.05 to 0.95, with a molar fraction increment of 0.05. The butyl acetate-butanol azeotrope was mixed with the bicomponent synergistic extractant to obtain a mixed raw material. The molar fraction of the bicomponent synergistic extractant in the mixed raw material was 0.02, 0.04, or 0.06. The mixed raw material was added into the equilibrium chamber 3, which had been pressure calibrated, and the mixed raw material was continuously stirred. After stirring, it was allowed to stand until there was no stratification in the mixed system, ensuring the homogeneity of the raw material mixture.

[0026] After the mixed raw materials were added and processed, a vapor-liquid equilibrium system was constructed. Heating rod 1 was attached to the outer wall of equilibrium chamber 3 to provide a heat source. A thermometer 4 was inserted into the liquid phase region inside equilibrium chamber 3 to monitor temperature changes in real time. The inlet of the serpentine condenser 6 was connected to the vapor phase outlet of equilibrium chamber 3, and the outlet of the serpentine condenser 6 was connected to the reflux port of equilibrium chamber 3. A condensing medium was introduced into the jacket of the serpentine condenser 6. The vapor generated by heating inside equilibrium chamber 3 entered the serpentine condenser 6, was condensed into liquid, and returned to equilibrium chamber 3 through the reflux port. By adjusting the power of heating rod 1, the heating rate and reflux drip rate inside equilibrium chamber 3 were controlled to maintain a stable reflux drip rate, allowing the mixed system to operate in a steady state until a stable vapor-liquid two-phase equilibrium was formed. The synergistic effect of the hydrogen bond network between the ionic liquid and DES was utilized to enhance the selective destruction ability of the mixed system on the butyl acetate-butanol azeotrope, laying the foundation for subsequent sampling and analysis.

[0027] S3, Vapor-Liquid Two-Phase Sampling: After the vapor-liquid equilibrium state inside the equilibrium chamber 3 stabilizes, the vapor-liquid two-phase sampling operation is carried out. The gas phase sampling port 5 is set in the top gas phase area of ​​the equilibrium chamber 3, and the liquid phase sampling port 2 is set in the middle liquid phase area of ​​the equilibrium chamber 3. During the sampling process, the equilibrium chamber 3 is kept in a completely closed state to avoid the intervention of the external environment that may disrupt the vapor-liquid equilibrium system and ensure the accuracy of the collected samples.

[0028] Gas phase samples are collected through gas phase sampling port 5, and liquid phase samples are collected through liquid phase sampling port 2. After the gas phase and liquid phase samples are collected, they are immediately placed into dedicated sealed containers. The sealed containers containing different samples are marked with corresponding numbers to indicate the sample type, collection time, and other information to prevent sample confusion. After sampling, the sealed samples are stored in a suitable environment for subsequent analysis and testing.

[0029] S4, Data Parsing and Parameter Optimization: The data analysis and parameter optimization steps, through quantitative analysis of collected samples, parameter fitting of thermodynamic models, and thermodynamic consistency testing, enable the adjustment of process parameters and the determination of optimal operating parameters, providing accurate parameter basis for actual extractive distillation production. The specific implementation method is as follows: Sealed gas and liquid samples were injected into a gas chromatograph for quantitative analysis. The gas chromatograph was equipped with a KB-Wax capillary column and a flame ionization detector. Before detection, the parameters of the gas chromatograph were set: the column oven temperature was set to 353.15 K, the injection port temperature was set to 403.15 K, and the detector temperature was set to 423.15 K. The area normalization method was used to quantitatively analyze the butyl acetate and butanol components in the sample. The gas and liquid phase molar fraction data were obtained through analysis and used as the basis data for subsequent model fitting.

[0030] Based on the obtained gas-liquid phase mole fraction data, parameter fitting was performed on an NRTL model applicable to a quaternary system composed of butyl acetate, butanol, an ionic liquid, and a eutectic solvent DES. The Levenberg-Marquardt algorithm was used for fitting, with the minimum objective function as the convergence condition. The calculations were performed sequentially using the NRTL model's activity coefficient calculation equation, intermediate parameter calculation equation, and binary interaction parameter calculation equation. The activity coefficient calculation equation is as follows: The formula for calculating the intermediate parameters of the model is as follows: The formula for calculating the binary interaction parameters is as follows: The formula for calculating the objective function is: in, Let be the activity coefficient of component i. , , These represent the mole fractions of components i, j, and k in the liquid phase, where i, j, and k are any one of the components: butyl acetate, butanol, ionic liquid, or eutectic solvent (DES). For the non-randomness parameters of the NRTL model, and Let be the binary interaction parameter between component i and component j, R be the universal gas constant, and T be the system temperature at vapor-liquid two-phase equilibrium. , As an intermediate variable in the NRTL model, represents the intermediate parameters of the NRTL model, F is the objective function of the Levenberg-Marquardt algorithm, and n is the number of measurement data sets in the vapor-liquid equilibrium experiment. Let i be the experimentally measured activity coefficient of component i. The activity coefficient for component i is calculated using the NRTL model. Subscript 1 represents the butyl acetate component, and subscript 2 represents the butanol component. The contribution of component k to the molecular / ionic / hydrogen bond interactions of the target component.

[0031] After completing the parameter fitting of the NRTL model, thermodynamic consistency tests were conducted using the Fredenslund criterion to verify the reliability of the model fitting results. During the test, the mean absolute deviation of the gas phase mole fraction was calculated using the following formula: Simultaneously, the average relative deviation of the activity coefficient is calculated using the following formula: in: The mean absolute deviation of the gas phase mole fraction. This represents the number of measurement data sets in the vapor-liquid equilibrium experiment. The experimentally determined gaseous molar fractions of butyl acetate and butanol components are shown. The gas-phase mole fractions of butyl acetate and butanol are calculated using the NRTL model for a quaternary system. ARD represents the average relative deviation of the activity coefficients. Components The experimentally measured activity coefficient, Components Activity coefficients calculated using the NRTL model for quaternary systems, subscript These represent the butyl acetate component and the butanol component, respectively.

[0032] Based on the results of thermodynamic consistency testing, targeted adjustments were made to the process parameters. These adjustments included the heating power of heating rod 1, the condensing medium flow rate of serpentine condenser 6, the desiccant replacement cycle of dryer 8, and the nitrogen input rate of pressure gauge 9. Fine-tuning was also performed on the molar ratio of the ionic liquid to the eutectic solvent DES and the synthesis molar ratio of the eutectic solvent DES. During parameter adjustments, the temperature and pressure of equilibrium chamber 3 were kept stable to prevent imbalances in the vapor-liquid equilibrium system caused by sudden parameter changes. After completing all parameter adjustments and verifications, the optimal operating parameters for this process were determined. These optimal operating parameters included the molar fraction of the bicomponent synergistic extractant in the mixed feedstock, the molar ratio of the ionic liquid to the eutectic solvent DES, the heating power of heating rod 1, and the condensation reflux drip rate of serpentine condenser 6.

[0033] The ionic liquid extractive distillation separation process for butyl acetate-butanol azeotropes of this invention achieves efficient disruption of the azeotropic properties of butyl acetate-butanol azeotropes through a compounded bicomponent synergistic extractant. Compared to a single ionic liquid extractant, this effectively reduces the extractant viscosity and improves mass transfer efficiency. Simultaneously, relying on precise device calibration and vapor-liquid equilibrium construction, combined with NRTL model fitting and Fredenslund criterion verification, precise optimization of process parameters is achieved. This provides a stable, efficient, and scalable process for the extractive distillation separation of butyl acetate-butanol azeotropes, effectively improving the separation purity and efficiency of butyl acetate and butanol. Example 2: Ionic liquid extraction and distillation separation process for butyl acetate-butanol azeotrope.

[0034] This embodiment focuses on the separation of a butyl acetate-butanol azeotrope with a butyl acetate molar fraction of 0.05. The prepared eutectic solvent DES uses choline chloride as the hydrogen bond acceptor and ethylene glycol as the hydrogen bond donor, synthesized at a molar ratio of 1:2. The molar ratio of the ionic liquid to the eutectic solvent DES is 1:0.5. The molar fraction of the bicomponent synergistic extractant in the mixed feed is 0.02. This bicomponent synergistic extractant reduces viscosity by 30% to 50% compared to a single ionic liquid. Specific process steps are as follows... Figure 1 As shown S1. Setup and Pressure Calibration: The dryer 8, buffer tank 7, and pressure gauge 9 are connected in series via corrosion-resistant pipelines to the equilibrium chamber 3 for a sealed connection. The corrosion-resistant pipelines effectively prevent gas leakage and ensure the airtightness of the entire system. Nitrogen gas is introduced into this connected system. The nitrogen gas first passes through the dryer 8 to remove moisture, preventing moisture from entering the equilibrium chamber 3 and interfering with the subsequent vapor-liquid equilibrium process. The dehydrated nitrogen gas enters the buffer tank 7 for temporary storage and pressure stabilization, and then is smoothly delivered to the equilibrium chamber 3 through pipelines. The pressure gauge 9 is directly connected to the gas phase space of the equilibrium chamber 3, allowing the pressure data to be more closely approximated to the actual system conditions. The pressure data inside the equilibrium chamber 3 is monitored in real time by the pressure gauge 9, and the nitrogen input is precisely adjusted according to the monitored values ​​to maintain the pressure inside the equilibrium chamber 3 stably at 101.3 kPa, providing a constant pressure environment for the entire subsequent experimental process and completing the pressure calibration of the entire system.

[0035] S2, Raw Material Processing and Vapor-Liquid Equilibrium Construction: First, using choline chloride as a hydrogen bond acceptor and ethylene glycol as a hydrogen bond donor, a eutectic solvent, DES, was synthesized at a molar ratio of 1:2. The DES was then subjected to vacuum dehydration until its water content was below 0.0005% by mass to remove trace amounts of water and ensure its compatibility with the ionic liquid. The ionic liquid was then separately subjected to vacuum drying at 393 K and 0.2 kPa for 48 hours to fully remove water and prevent moisture from affecting the synergistic performance of the extractant. Finally, the dried ionic liquid was combined with the above-treated... DES was compounded at a molar ratio of 1:0.5 to form a bicomponent synergistic extractant. This bicomponent synergistic extractant was also subjected to vacuum drying at 393 K and 0.2 kPa for 48 hours to further remove trace amounts of moisture introduced during the compounding process. After drying, the moisture content was determined by Karl Fischer titration to accurately determine the drying standard of the extractant. Once qualified, it was sealed for later use. A mixture of butyl acetate-butanol azeotrope with a butyl acetate molar fraction of 0.05 and the prepared bicomponent synergistic extractant was added to the equilibrium chamber 3 after pressure calibration. The molar fraction of the bicomponent synergistic extractant in the mixed raw materials is 0.02. The mixed raw materials are continuously stirred to ensure that the azeotrope and the bicomponent synergistic extractant are fully contacted and integrated. After stirring, the mixture is allowed to stand until there is no stratification, ensuring the homogeneity of the mixture. The heating rod 1 is attached to the outer wall of the equilibrium chamber 3 to ensure that the equilibrium chamber 3 is heated evenly and to avoid local overheating or underheating affecting the system equilibrium. The thermometer 4 is inserted into the liquid phase region inside the equilibrium chamber 3 to ensure that the temperature monitoring value is closer to the actual reaction temperature of the system. The inlet of the serpentine condenser 6 is connected to the gas phase outlet of the equilibrium chamber 3, and the outlet of the serpentine condenser 6 is connected to the reflux port of the equilibrium chamber 3, and the reflux is directed to the jacket layer of the serpentine condenser 6. A condensing medium is introduced to ensure that the steam generated in the equilibrium chamber 3 can be fully condensed. The heating rod 1 is started to heat the equilibrium chamber 3. The internal temperature of the equilibrium chamber 3 is monitored in real time by the thermometer 4. The steam generated in the equilibrium chamber 3 is condensed by the serpentine condenser 6 and then refluxed. The heating rate inside the equilibrium chamber 3 is controlled by adjusting the power of the heating rod 1, while keeping the condensation reflux drip rate stable, so that the mixed system gradually reaches a dynamic stable state. Relying on the synergistic effect of the hydrogen bond network between the ionic liquid and DES, the selective destruction ability of the mixed system on the butyl acetate-butanol azeotrope is enhanced, making the difference between the vapor and liquid phase components in the system more significant, and allowing the mixed system to operate in a steady state until a stable vapor-liquid two-phase equilibrium is formed.

[0036] S3, Vapor-Liquid Two-Phase Sampling: After the vapor-liquid equilibrium in the equilibrium chamber 3 has stabilized, the equilibrium chamber 3 is kept closed to prevent outside air from entering and interfering with the established vapor-liquid equilibrium, while also preventing the volatilization and loss of components within the system. Gas phase samples are collected through the gas phase sampling port 5 located in the gas phase region at the top of the equilibrium chamber 3. This location can accurately collect samples that represent the overall composition of the gas phase. Liquid phase samples are collected through the liquid phase sampling port 2 located in the liquid phase region in the middle of the equilibrium chamber 3. This location avoids interference from sediment at the bottom or floating layer at the top of the equilibrium chamber 3, and the collected liquid phase samples are more representative. After the gas phase and liquid phase samples are collected, they are placed in dedicated sealed containers. Each sealed container is numbered and marked accordingly to prevent the samples from volatilizing or becoming contaminated during storage, ensuring that the sample composition remains unchanged for subsequent detection and analysis.

[0037] S4, Data Analysis and Parameter Optimization: The sealed gas and liquid samples were injected into a gas chromatograph equipped with a KB-Wax capillary column and a flame ionization detector. This configuration allows for effective separation of butyl acetate and butanol components during detection, improving accuracy. The column oven temperature was set to 353.15 K, the injection port temperature to 403.15 K, and the detector temperature to 423.15 K. This temperature setting ensures optimal vaporization and detection of the sample within the chromatograph. Area normalization was used for quantitative analysis of butyl acetate and butanol components in the sample, resulting in more accurate and reliable gas-liquid molar fraction data. Based on the obtained data, the Levenberg-Marquardt algorithm was used to fit non-random two-liquid model parameters suitable for the butyl acetate-butanol ionic liquid eutectic solvent DES quaternary system. The minimum objective function was used as the convergence condition during the fitting process, ensuring the fitted model parameters closely match the actual experimental data. The formula for calculating the intermediate parameters of the model is as follows: The formula for calculating the binary interaction parameters is as follows: The formula for calculating the objective function is: in, Let be the activity coefficient of component i. , , These represent the mole fractions of components i, j, and k in the liquid phase, where i, j, and k are any one of the components: butyl acetate, butanol, ionic liquid, or eutectic solvent (DES). For the non-randomness parameters of the NRTL model, and Let be the binary interaction parameter between component i and component j, R be the universal gas constant, and T be the system temperature at vapor-liquid two-phase equilibrium. , As an intermediate variable in the NRTL model, represents the intermediate parameters of the NRTL model, F is the objective function of the Levenberg-Marquardt algorithm, and n is the number of measurement data sets in the vapor-liquid equilibrium experiment. Let i be the experimentally measured activity coefficient of component i. The activity coefficient for component i is calculated using the NRTL model. Subscript 1 represents the butyl acetate component, and subscript 2 represents the butanol component. The contribution of component k to the molecular / ionic / hydrogen bond interactions of the target component is represented by the Fredenslund criterion. The thermodynamic consistency of the fitting results is then tested, and the mean absolute deviation of the gas phase mole fraction and the mean relative deviation of the activity coefficient are calculated to verify the reliability and rationality of the fitting results. The calculation formula is as follows: The formula for calculating the average relative deviation in synchronous calculations is: in: The mean absolute deviation of the gas phase mole fraction. This represents the number of measurement data sets in the vapor-liquid equilibrium experiment. The experimentally determined gaseous molar fractions of butyl acetate and butanol components are shown. The gas-phase mole fractions of butyl acetate and butanol are calculated using the NRTL model for a quaternary system. ARD represents the average relative deviation of the activity coefficients. Components The experimentally measured activity coefficient, Components Activity coefficients calculated using the NRTL model for quaternary systems, subscript Representing the butyl acetate and butanol components respectively, the process parameters were adjusted based on the results of thermodynamic consistency testing. These adjustments included the heating power of heating rod 1, the condensing medium flow rate of serpentine condenser 6, the desiccant replacement cycle of dryer 8, and the nitrogen input controlled by pressure gauge 9. Simultaneously, the molar ratio of the ionic liquid to the eutectic solvent DES and the synthesis molar ratio of DES were fine-tuned. During the adjustment process, the temperature and pressure of equilibrium chamber 3 were kept stable to ensure the mixed system remained in a stable reaction environment. Ultimately, the optimal operating parameters for this embodiment were determined: a molar fraction of 0.02 for the bicomponent synergistic extractant in the mixed raw materials, a molar ratio of 1:0.5 for the ionic liquid to the eutectic solvent DES, an appropriate heating power for heating rod 1, and a stable reflux dripping rate in serpentine condenser 6. This provides a precise process reference for the separation of butyl acetate-butanol azeotropes with this component proportion.

[0038] In summary, this embodiment demonstrates the successful separation of a low-molar-fraction butyl acetate-butanol azeotrope using ionic liquid extractive distillation. Strict control of process parameters was maintained throughout the process. Choline chloride and an ethylene glycol-based eutectic solvent were synthesized at a 1:2 molar ratio, and the ionic liquid was compounded with this solvent at a 1:0.5 molar ratio, resulting in an extractant molar fraction of 0.02% in the mixed feedstock. Standardized equipment calibration, feedstock processing, vapor-liquid equilibrium establishment, and sampling procedures were implemented. The azeotropic equilibrium was disrupted by the synergistic effect of hydrogen bonding networks. Precise data was obtained through quantitative gas chromatography. The parameters of a non-random two-liquid model were fitted using the Levenberg-Marquardt algorithm, and thermodynamic consistency was tested using the Fredenslund criterion. After targeted adjustments to process parameters, the optimal operating scheme was determined, successfully achieving the effective separation of this low-molar-fraction butyl acetate-butanol azeotrope. This provides a specific and replicable process reference for the separation of similar low-molar-fraction systems.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope, characterized in that, The process includes: S1, Device setup and pressure calibration: Connect the dryer (8), buffer tank (7), and pressure gauge (9) in series and seal them together with the balance chamber (3). Then, introduce nitrogen gas. After the dryer (8) removes the moisture in the nitrogen gas, the pressure gauge (9) monitors and adjusts the nitrogen gas input in real time to keep the internal pressure of the balance chamber (3) stable at 101.3 kPa. S2, Raw material processing and vapor-liquid equilibrium construction: First, prepare the eutectic solvent DES, then mix the ionic liquid and the eutectic solvent DES in a specific molar ratio to form a bicomponent synergistic extractant. The bicomponent synergistic extractant is vacuum dried and then stored after moisture detection. The mixture of butyl acetate-butanol azeotrope and the bicomponent synergistic extractant is added to the equilibrium chamber (3) after pressure calibration and stirred evenly. The equilibrium chamber (3) is heated by heating rod (1), and the temperature is monitored by thermometer (4) connected to the equilibrium chamber (3). The steam generated in the equilibrium chamber (3) is condensed and refluxed through serpentine condenser (6). The power of heating rod (1) is adjusted to stabilize the reflux drip rate and allow the mixed system to run in steady state until a stable vapor-liquid two-phase equilibrium is formed. S3, Vapor-liquid two-phase sampling: After the vapor-liquid equilibrium is stable, a gas phase sample is collected through the gas phase sampling port (5), and a liquid phase sample is collected through the liquid phase sampling port (2). After sampling, the sample is sealed and marked. S4, Data Analysis and Parameter Optimization: Gas samples are injected into a gas chromatograph for quantitative analysis to obtain gas-liquid mole fraction data. The Levenberg-Marquardt algorithm is used to fit the NRTL model parameters suitable for the quaternary system. Thermodynamic consistency tests are conducted in conjunction with the Fredenslund criterion. The process parameters are adjusted based on the test results to determine the optimal operating parameters. The quaternary system is composed of butyl acetate, butanol, ionic liquid, and eutectic solvent DES. The Levenberg-Marquardt algorithm was used to fit the NRTL model parameters suitable for the quaternary system composed of butyl acetate, butanol, ionic liquid, and eutectic solvent. Initial parameters were set, and the binary interaction parameters and non-randomness parameters were continuously optimized through iterative calculations until convergence was achieved, resulting in a complete NRTL model parameter set for the experimental quaternary system. Theoretical values ​​of gas phase mole fraction and activity coefficient under corresponding operating conditions were then calculated based on the fitted NRTL model. Thermodynamic consistency tests were conducted using the Fredenslund criterion to verify the deviations between experimentally measured values ​​and theoretically calculated values, thus validating the experimental data. To assess the reliability of the model fitting results, and based on the results of the thermodynamic consistency test, the relevant process parameters were adjusted one by one for the operating conditions that failed the consistency test. After each parameter adjustment was completed, a complete vapor-liquid equilibrium experiment and sample component detection were carried out again. The NRTL model parameter fitting and Fredenslund criterion thermodynamic consistency test were then performed again. This cycle of parameter adjustment, experimental verification, model fitting, and consistency testing was repeated until the experimental data for all operating conditions passed the Fredenslund criterion thermodynamic consistency test. At the same time, the model fitting deviation under different parameter combinations was compared, and finally the optimal operating parameters for the butyl acetate-butanol azeotrope bicomponent synergistic extraction distillation separation process were screened and determined.

2. The ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope according to claim 1, characterized in that, In step S1, the dryer (8), buffer tank (7), pressure gauge (9) and balance chamber (3) are sealed together by corrosion-resistant pipelines. Nitrogen gas is processed by the dryer (8) and then enters the buffer tank (7), and is then transported to the balance chamber (3) through pipelines. The pressure gauge (9) is directly connected to the gas phase space of the balance chamber (3) to collect pressure data inside the balance chamber (3) in real time.

3. The ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope according to claim 1, characterized in that, In step S2, the vacuum drying treatment of the bicomponent synergistic extractant is carried out at 393K and 0.2kPa for 48 hours. After drying, the moisture content of the bicomponent synergistic extractant is detected by Karl Fischer titration. The ionic liquid is treated separately under the same vacuum drying conditions before compounding, and the eutectic solvent DES is vacuum dehydrated to a moisture content of less than 0.0005% by mass before compounding.

4. The ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope according to claim 1, characterized in that, In step S2, the eutectic solvent DES is synthesized from hydrogen bond acceptor and hydrogen bond donor in a molar ratio of 1:2 to 1:

4. The hydrogen bond acceptor is choline chloride or tetrabutylammonium chloride, and the hydrogen bond donor is ethylene glycol, glycerol or urea. The molar ratio of the ionic liquid to the eutectic solvent DES is 1:0.5 to 1:

2. The molar fraction of butyl acetate in the butyl acetate-butanol azeotrope ranges from 0.05 to 0.95, with a molar fraction increment of 0.

05. The molar fraction of the bicomponent synergistic extractant in the mixed raw materials is 0.02, 0.04 or 0.06, and the viscosity of the bicomponent synergistic extractant is reduced by 30%-50% compared to the single ionic liquid. After the mixed raw materials are added to the equilibrium chamber (3), they are continuously stirred. After stirring, the mixture is allowed to stand until there is no stratification.

5. The ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope according to claim 1, characterized in that, In step S2, the heating rod (1) is attached to the outer wall of the equilibrium chamber (3), the thermometer (4) is inserted into the liquid phase region inside the equilibrium chamber (3), the inlet of the serpentine condenser (6) is connected to the gas phase outlet of the equilibrium chamber (3), the outlet of the serpentine condenser (6) is connected to the reflux port of the equilibrium chamber (3), the condensing medium is introduced into the jacket layer of the serpentine condenser (6), the heating rate and reflux drip rate inside the equilibrium chamber (3) are controlled by adjusting the power of the heating rod (1), and the selective destruction ability of the mixed system on the butyl acetate-butanol azeotrope is enhanced by utilizing the synergistic effect of the hydrogen bond network between the ionic liquid and DES.

6. The ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope according to claim 1, characterized in that, In step S3, the gas phase sampling port (5) is set in the top gas phase area of ​​the equilibrium chamber (3), and the liquid phase sampling port (2) is set in the middle liquid phase area of ​​the equilibrium chamber (3). During the sampling process, the equilibrium chamber (3) is kept closed. After the gas phase sample and the liquid phase sample are collected, they are placed in sealed containers respectively, and the sealed containers are marked with corresponding numbers.

7. The ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope according to claim 1, characterized in that, In step S4, the gas chromatograph is equipped with a KB-Wax capillary column and a flame ionization detector. The column oven temperature of the gas chromatograph is set to 353.15K, the injection port temperature is set to 403.15K, and the detector temperature is set to 423.15K. The area normalization method is used to quantitatively analyze the butyl acetate and butanol components in the gas phase sample and the liquid phase sample.

8. The ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope according to claim 1, characterized in that, In step S4, the NRTL model, formally known as the non-random two-liquid model, is calculated using the following formulas: activity coefficient calculation equation, intermediate model parameter calculation equation, and binary interaction parameter calculation equation. When fitting the NRTL model parameters using the Levenberg-Marquardt algorithm, the minimum objective function is used as the convergence condition, where: The formula for calculating the intermediate parameters of the model is as follows: The formula for calculating the binary interaction parameters is as follows: The formula for calculating the objective function is: in, Let be the activity coefficient of component i. , , These represent the mole fractions of components i, j, and k in the liquid phase, where i, j, and k are any one of the components: butyl acetate, butanol, ionic liquid, or eutectic solvent (DES). For the non-randomness parameters of the NRTL model, and Let be the binary interaction parameter between component i and component j, R be the universal gas constant, and T be the system temperature at vapor-liquid two-phase equilibrium. , As an intermediate variable in the NRTL model, represents the intermediate parameters of the NRTL model, F is the objective function of the Levenberg-Marquardt algorithm, and n is the number of measurement data sets in the vapor-liquid equilibrium experiment. Let i be the experimentally measured activity coefficient of component i. The activity coefficient for component i is calculated using the NRTL model. Subscript 1 represents the butyl acetate component, and subscript 2 represents the butanol component. The contribution of component k to the molecular / ionic / hydrogen bond interactions of the target component.

9. The ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope according to claim 1, characterized in that, In step S4, the thermodynamic consistency test is based on the Fredenslund criterion, and the calculation formula is as follows: The formula for calculating the average relative deviation in synchronous calculations is: in: The mean absolute deviation of the gas phase mole fraction. This represents the number of measurement data sets in the vapor-liquid equilibrium experiment. The experimentally determined gaseous molar fractions of butyl acetate and butanol components are shown. The gas-phase mole fractions of butyl acetate and butanol are calculated using the NRTL model for a quaternary system. ARD represents the average relative deviation of the activity coefficients. Components The experimentally measured activity coefficient, Components Activity coefficients calculated using the NRTL model for quaternary systems, subscript These represent the butyl acetate component and the butanol component, respectively.

10. The ionic liquid extraction distillation separation process for butyl acetate-butanol azeotrope according to claim 1, characterized in that, In step S4, the process parameter adjustment includes adjusting the heating power of the heating rod (1), adjusting the condensing medium flow rate of the serpentine condenser (6), adjusting the desiccant replacement cycle of the dryer (8), adjusting the nitrogen input of the pressure gauge (9), and also includes parameter optimization adjustment of the compound molar ratio of ionic liquid and eutectic solvent DES, and the synthesis molar ratio of eutectic solvent DES; after the adjustment is completed, the temperature and pressure of the equilibrium chamber (3) are kept stable, and the final determined optimal operating parameters include the molar fraction of the bicomponent synergistic extractant in the mixed raw materials, the compound molar ratio of ionic liquid and eutectic solvent DES, the heating power of the heating rod (1), and the condensation reflux drip rate of the serpentine condenser (6).

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