Method and system for predicting esterification reaction dehydration endpoint and energy consumption collaborative control

Abstract

The present application relates to esterification reaction process detection, stable isotope labeling analysis, industrial control system, industrial real-time control software, process control and advanced process control technical field, especially relates to a kind of esterification reaction dehydration end point prediction and energy consumption collaborative control method and system. According to the cumulative reaction water and acid value change into terminal candidate interval, the same reaction liquid sample is distributed to blank, acid challenge, alcohol challenge and double challenge microreaction unit, respectively, first isotopic labeled carboxylic acid, second isotopic labeled alcohol and two kinds of labels are added, first labeled ester, second labeled ester and double labeled ester are detected, background response is deducted and is corrected with double labeled ester generation rate, to obtain residual hydroxyl reaction ability and residual carboxyl reaction ability. According to two kinds of residual reaction ability to determine dehydration end point, and combine the main reactor condensate water rate to adjust heating load and vacuum load.

Description

Technical Field

[0001] This invention relates to the fields of esterification reaction process detection, stable isotope labeling analysis, industrial control systems, industrial real-time control software, process control and advanced process control technology, and in particular to a method and system for predicting the dehydration endpoint of an esterification reaction and coordinating energy consumption control. Background Technology

[0002] Esterification reactions typically require continuous removal of the water produced under heating, stirring, and reduced pressure to drive the reaction toward ester formation. Existing endpoint control methods mostly rely on parameters such as condensate volume, reaction time, acid value, temperature, or pressure to determine whether the reaction is complete.

[0003] Chinese patent document CN201444246U discloses an automatic control device for the endpoint of an esterification reaction. The gas phase outlet of the reactor is sequentially connected to a cooler, an automatic water separator, and a water metering alarm. The device controls the steam valve and cooling valve based on the liquid level signal from the water metering alarm. This scheme primarily determines the endpoint of the esterification reaction based on the amount of separated water, and also points out that when the esterification reaction approaches its endpoint, apparent parameters such as temperature, pressure, and flow rate may not show significant changes.

[0004] Furthermore, European patent document EP0680463B2, which discloses a process for the production of plasticizers and polyol esters, demonstrates that the water content and water removal status within the reactor affect the esterification reaction rate. Therefore, the actual amount of condensate collected depends not only on the amount of water generated by the chemical reaction but also on factors such as the water content within the reactor, gas-liquid mass transfer, reaction pressure, heating status, gas phase transport, and condensation capacity. When the condensate discharge rate decreases, it is difficult to accurately determine whether the esterification reaction has been completed or whether the decrease in discharge is due to reduced reactivity or insufficient dehydration capacity, based solely on the condensate discharge rate or apparent process parameters. This can easily lead to problems such as premature termination, delayed termination, deviations in product acid or hydroxyl value from targets, and continued ineffective energy input at the end of the reaction. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for predicting the dehydration endpoint and coordinating energy consumption control in esterification reactions, addressing the shortcomings of existing technologies. The technical problem to be solved is: when the esterification reaction is nearing its endpoint, how to separately identify the remaining hydroxyl reactivity, the remaining carboxyl reactivity, and the current chemical reactivity in the reaction solution, avoiding directly judging the decrease in the rate of condensation as the dehydration endpoint, and further adjusting the heating load and vacuum load according to the relative relationship between the chemical reactivity and the dehydration capacity of the main reactor, thereby improving the accuracy of the dehydration endpoint judgment and reducing endpoint misjudgment and ineffective energy consumption caused by reaction-limited states, mass transfer-limited states, and detection deviations.

[0006] The present invention specifically adopts the following solution: A method for predicting the dehydration endpoint of an esterification reaction and coordinating energy consumption control is executed by an esterification reaction control system, including a candidate triggering step, a homologous sample separation step, a labeling challenge step, a response identification step, and an endpoint control step.

[0007] In the candidate triggering step, the esterification reaction control system enters the endpoint candidate interval based on the cumulative reaction water volume and acid value changes. The gas phase outlet of the esterification reactor is connected to the condensation passage, which is equipped with a condensate quality detection mechanism. This mechanism outputs the condensate discharge rate of the main reactor according to a set sampling period. The sampling period can be set from 1 s to 30 s. The esterification reaction control system integrates the condensate discharge rate of the main reactor over time to obtain the cumulative reaction water volume.

[0008] The theoretical reaction water volume is determined based on the carboxyl equivalent of the fed carboxylic acid, the hydroxyl equivalent of the fed alcohol, and the stoichiometric relationship of the esterification reaction. For the esterification reaction of a monocarboxylic acid and a monohydric alcohol, 1 mol of water is generated for every 1 mol of ester bond formed. For polycarboxylic acids or polyhydric alcohols, the theoretical reaction water volume is determined according to the equivalent of the limiting functional groups that can participate in the esterification reaction. When the cumulative reaction water volume reaches 85% to 95% of the theoretical reaction water volume, the esterification reaction control system begins to detect changes in acid value.

[0009] Acid value detection can be performed using an automated sampling titration mechanism. The mechanism obtains a quantitative sample from the esterification reactor every 3 to 10 minutes, and calculates the acid value using the same titrant concentration and endpoint determination method. When the acid value change is below the set acid value change threshold for two or three consecutive times, and the cumulative reaction water volume reaches a set proportion, the esterification reaction control system enters the endpoint candidate range. The acid value change threshold can be set from 0.2 mgKOH / g to 1.0 mgKOH / g. Using both cumulative reaction water volume and acid value change as triggers avoids premature detection caused by short-term drops in condensate water, condensate retention, or sampling fluctuations.

[0010] In the homologous sampling step, the esterification reaction control system controls the sampling component to obtain the same reaction solution sample from the esterification reactor and distribute the same reaction solution sample equally to the blank microreactor unit, acid challenge microreactor unit, alcohol challenge microreactor unit, and double challenge microreactor unit. The sampling component includes an insulated sampling tube, a sampling pump, a metering chamber, and a dispensing valve. The temperature difference between the insulated sampling tube and the current reaction temperature of the esterification reactor is controlled within 2 °C. Before formal sampling, the sampling pump first discharges the residual reaction solution in the insulated sampling tube and then extracts the current reaction solution sample. The total volume of the same reaction solution sample can be set from 2 mL to 8 mL. The reaction solution sample volumes received by the four microreactor units are the same, and the reaction solution sample volume of a single microreactor unit can be set from 0.5 mL to 2 mL. The four microreactor units use the same reaction chamber volume, the same stirring speed, the same temperature program, the same pressure program, and the same detection time, so that the differences between the four detection paths are formed by the labeling conditions, rather than by the equipment conditions.

[0011] In the labeling challenge step, the labeling addition component adds a first isotope-labeled carboxylic acid with the same structure as the feed carboxylic acid to the acid challenge microreactor unit, adds a second isotope-labeled alcohol with the same structure as the feed alcohol to the alcohol challenge microreactor unit, and simultaneously adds the first isotope-labeled carboxylic acid and the second isotope-labeled alcohol to the double challenge microreactor unit. The blank microreactor unit does not add either the first isotope-labeled carboxylic acid or the second isotope-labeled alcohol. "Same structure as feed carboxylic acid" means that the first isotope-labeled carboxylic acid and the feed carboxylic acid have the same number of carboxyl groups, the same carbon skeleton connection relationship, and the same substituents, differing only in their stable isotope composition. "Same structure as feed alcohol" means that the second isotope-labeled alcohol and the feed alcohol have the same number of hydroxyl groups, the same carbon skeleton connection relationship, and the same substituents, differing only in their stable isotope composition. The first isotope-labeled carboxylic acid and the second isotope-labeled alcohol can use C13 labels, and the stable isotope purity can be set to 95% or higher.

[0012] The first isotope-labeled carboxylic acid reacts with hydroxyl groups in the reaction solution that can still participate in esterification to form a first-labeled ester. The formation rate of the first-labeled ester is used to characterize the reactivity of the remaining hydroxyl groups. The second isotope-labeled alcohol reacts with carboxyl groups in the reaction solution that can still participate in esterification to form a second-labeled ester. The formation rate of the second-labeled ester is used to characterize the reactivity of the remaining carboxyl groups. In the dual-challenge microreactor, the first isotope-labeled carboxylic acid and the second isotope-labeled alcohol form a dual-labeled ester. The formation rate of the dual-labeled ester is used to characterize the chemical reactivity resulting from the combined effects of the catalytic activity, temperature conditions, pressure conditions, and mixing conditions corresponding to the current reaction solution sample.

[0013] The amount of labeled material added should be less than the expected remaining functional group equivalent in the same reaction solution sample to avoid altering the composition of the reaction solution due to excessive addition of labeled material. The amount of carboxylic acid labeled with the first isotope and alcohol labeled with the second isotope can be set to 5 μmol to 50 μmol, respectively. After the four microreactors complete the labeling, they should execute the same temperature and pressure program. The difference between the reaction temperature and the current reaction temperature of the esterification reactor should be controlled within 1 °C, and the difference between the reaction pressure and the current reaction pressure of the esterification reactor should be controlled within 2 kPa. The reaction time can be set to 60 s to 300 s.

[0014] In the response identification step, the labeling detection component detects the first labeled ester generated by the acid challenge microreaction unit, the second labeled ester generated by the alcohol challenge microreaction unit, and the dual-labeled ester generated by the dual-challenge microreaction unit. The labeling detection component can employ a gas chromatography-mass spectrometry (GC-MS) device, a liquid chromatography-mass spectrometry (LC-MS) device, or a detection device capable of distinguishing stable isotope mass channels. The blank microreaction unit is used to detect natural isotope peak clusters, detector baseline drift, and background responses formed by the original components of the reaction solution in the first labeled ester mass channel, the second labeled ester mass channel, and the dual-labeled ester mass channel. The labeling detection component obtains response curves for the four microreaction units within the same detection time. The mass channel module uses the slope of the linear interval of the response curves to determine the corresponding generation rate and subtracts the background response.

[0015] The activity correction module corrects the formation rates of the first and second labeled esters by correcting the formation rates of the dual-labeled esters, so that the remaining hydroxyl and carboxyl reactivity do not shift synchronously due to changes in catalyst activity, micro-reaction temperature deviations, or sampling delays.

[0016] In the endpoint control step, the esterification reaction control system determines whether the corrected bis-labeled ester formation rate has reached the effective challenge threshold, and whether the remaining hydroxyl and carboxyl reactivity have reached the target remaining range, respectively. The effective challenge threshold can be determined based on the corrected bis-labeled ester formation rate in the same batch of reaction, and can be set to 5% to 20% of the corrected bis-labeled ester formation rate in the reaction. The target remaining range is pre-calibrated based on the product acid value, product hydroxyl value, and product conversion rate requirements. The target remaining ranges for remaining hydroxyl and carboxyl reactivity can be expressed as molar concentrations or as a proportion relative to the initial functional group equivalents.

[0017] When the corrected dual-labeled ester formation rate reaches the challenge effective threshold, and the remaining hydroxyl and carboxyl reactivity enters the corresponding target remaining ranges, the esterification reaction control system determines the dehydration endpoint. If at least one condition is not met, the esterification reaction control system determines to continue the reaction and adjusts the heating and vacuum loads according to the relative relationship between the chemical reactivity characterized by the corrected dual-labeled ester formation rate and the dehydration capacity characterized by the condensate discharge rate from the main reactor.

[0018] When the reaction dehydration matching ratio is greater than the set upper limit, the chemical reaction capacity is higher than the physical dehydration capacity, and the controller maintains the heating load and increases the vacuum load or condensation load. When the reaction dehydration matching ratio is lower than the set lower limit, and at least one remaining reaction capacity exceeds the target remaining range, the controller increases the heating load and maintains the vacuum load. When the reaction dehydration matching ratio is between the set upper and lower limits, the controller maintains the current heating load and vacuum load.

[0019] The first stable isotope tag is placed at the non-exchangeable carbon skeleton position of the first isotope-labeled carboxylic acid, and the second stable isotope tag is placed at the non-exchangeable carbon skeleton position of the second isotope-labeled alcohol. The non-exchangeable carbon skeleton position indicates that the stable isotope tag is bonded to the carbon atom and will not be transferred due to proton exchange during esterification reactions, acid-base titrations, sampling, and mass spectrometry detection.

[0020] The first stable isotope label must not be placed in a position where it is easily exchanged with water in the reaction solution, and the second stable isotope label must not be placed at the hydroxyl hydrogen position. When using C13 to label the carbon skeleton, the first isotope-labeled carboxylic acid and the second isotope-labeled alcohol maintain their labeling relationship before and after the esterification reaction, making it easy to distinguish between the first-labeled ester, the second-labeled ester, and the dual-labeled ester.

[0021] The first and second stable isotope tags form non-overlapping first labeled ester mass channels, second labeled ester mass channels, and dual-labeled ester mass channels. These three mass channels are located outside the natural isotope peak clusters of the corresponding unlabeled esters. The labeling position and number of labels are determined according to the molecular weight of the unlabeled ester, the width of the natural isotope peak clusters, and the mass resolution of the labeling detection component.

[0022] Taking an unlabeled ester containing ten carbon atoms as an example, the natural isotope peak clusters of the unlabeled ester are usually concentrated near the unlabeled molecular ion peak. The first isotope labeling of carboxylic acids can include four or more carbon-thirteen atoms, and the second isotope labeling of alcohols can include two or more carbon-thirteen atoms, ensuring that the first-labeled ester, the second-labeled ester, and the dual-labeled ester differ by at least two mass units. The mass resolution of the labeling detection component should be able to separate adjacent mass channels.

[0023] Before detection, the quality channel module is calibrated using unlabeled ester standards, first-labeled ester standards, second-labeled ester standards, and dual-labeled ester standards. Each standard is injected into the labeling detection component, and the retention time, target quality channel, and peak area response are recorded. During formal detection, only detection peaks whose retention time deviation and quality channel deviation simultaneously meet the preset range are identified as the corresponding labeled esters.

[0024] The response identification steps include activity calibration, hydroxyl group calculation, and carboxyl group calculation. The activity correction module determines the challenge activity coefficient based on the added equivalents of the two labeled substances in the dual-challenge microreaction unit and the corrected dual-labeled ester formation rate. The capability calculation module determines the remaining hydroxyl group reactivity based on the formation rate of the first labeled ester after subtracting the background response and the challenge activity coefficient, and determines the remaining carboxyl group reactivity based on the formation rate of the second labeled ester after subtracting the background response and the challenge activity coefficient.

[0025] In the actual calibration process, reaction solution samples at three states—initial reaction, mid-reaction, and confirmed endpoint—can be selected and subjected to a four-way labeling challenge. The remaining functional group equivalents at the initial and mid-reaction stages can be calculated using acid and hydroxyl values, while the confirmed endpoint sample can be obtained by extending the reaction time and performing offline detection. The capability calculation results are correlated with the acid and hydroxyl value conversion results to establish calibration curves for the remaining hydroxyl and carboxyl reactivity.

[0026] The homologous sampling step also includes internal standard addition, recovery verification, and imbalance removal. The internal standard addition component adds the same mass of a third isotope internal standard that does not participate in the esterification reaction to each of the four microreaction units. The third isotope internal standard can be a stable isotope-labeled aromatic hydrocarbon. The third isotope internal standard remains chemically stable at the microreaction temperature and pressure and does not react with carboxyl groups, hydroxyl groups, catalysts, or the generated esters. The mass channel of the third isotope internal standard should be separate from the mass channels of the unlabeled ester, the first-labeled ester, the second-labeled ester, and the dual-labeled ester. The internal standard addition component can add the same amount of third isotope internal standard to each of the four microreaction units after homologous sampling but before the labeling challenge begins. The labeling detection component determines the detection peak area of ​​the third isotope internal standard in each of the four microreaction units and determines the detection recovery rate based on a pre-established peak area-mass correspondence. The detection recovery rate is equal to the ratio of the detected mass of the third isotope internal standard to the actual added mass.

[0027] When the difference in detection recovery rates between any two microreactors reaches the sampling deviation threshold, the controller discards the detection results of the current four microreactors and re-executes the same-source sampling step. The sampling deviation threshold can be set from 3% to 8%. When the difference in detection recovery rates is lower than the sampling deviation threshold, the controller retains the current detection results.

[0028] Differences in detection recovery rates can be caused by factors such as sample volume deviation, injection loss, residual samples in the detection pathway, and detector response drift. Before resplitting, the sample dispensing unit is flushed with the current reaction solution to rinse the insulated sampling tube and dispensing valve, and the marking detection unit is flushed with the cleaning solution to rinse the detection sampling pathway, preventing residual samples from the previous batch from entering the resplitting sample.

[0029] After the response identification step is completed, the sampling component obtains a second reaction solution sample from the esterification reactor and distributes the second reaction solution sample equally to the second group of blank microreaction units, the second group of acid challenge microreaction units, the second group of alcohol challenge microreaction units, and the second group of double challenge microreaction units. The four microreaction units in the second group use the same reaction chamber volume, heat exchange area, stirring components, gas phase volume, and detection sampling pathway as the four microreaction units in the first group. The four microreaction units in the first group perform the labeling challenge at the first reaction pressure, while the four microreaction units in the second group perform the same labeling challenge at a second reaction pressure different from the first reaction pressure. The difference between the two reaction pressures can be set from 5 kPa to 15 kPa. Except for the reaction pressure, both groups of microreaction units use the same reaction temperature, the same sample volume, the same amount of label added, the same stirring speed, and the same reaction time.

[0030] The capacity calculation module calculates the remaining hydroxyl reactivity and the remaining carboxyl reactivity for the two reaction pressures respectively. If the difference in remaining hydroxyl reactivity between the two reaction pressures is lower than the pressure replication threshold, and the difference in remaining carboxyl reactivity between the two reaction pressures is lower than the pressure replication threshold, the controller retains the detection results.

[0031] The pressure replication threshold can be an absolute difference or a relative difference. When using a relative difference, the pressure replication threshold can be set to 5% to 10%. When at least one residual reaction capacity difference reaches the pressure replication threshold, the controller determines the micro-reaction mass transfer disturbance and controls the temperature and pressure actuator to reset the temperature and pressure program.

[0032] Resetting the temperature and pressure program can include increasing the stirring speed of the microreactor, extending the reaction time, reducing the volume of the reaction solution sample, or reducing the difference between the two reaction pressures. After resetting, the sample distribution unit re-acquires the reaction solution sample and performs the two sets of labeling challenges again until the difference in remaining reactivity corresponding to the two reaction pressures is lower than the pressure replication threshold.

[0033] Pressure replication testing can eliminate detection biases caused by gas-liquid mass transfer, boiling state of the microreactor, and sample volatilization. The calculated capability, truly derived from the remaining hydroxyl and carboxyl equivalents of the sample, should remain consistent within the specified pressure variation range; the apparent formation rate due to mass transfer limitations will vary significantly with reaction pressure.

[0034] The response identification step also includes tag balance, exchange discrimination, and result retention. The tag verification module determines the stable isotope masses corresponding to the first isotope-labeled carboxylic acid, the second isotope-labeled alcohol, the first-labeled ester, the second-labeled ester, and the dual-labeled ester, respectively. The input mass corresponding to the first stable isotope tag is determined by the first isotope-labeled carboxylic acid added in the acid challenge microreaction unit and the dual challenge microreaction unit. The output mass corresponding to the first stable isotope tag is determined by the unreacted first isotope-labeled carboxylic acid, the first-labeled ester, the dual-labeled ester, and other components containing the first stable isotope tag detected.

[0035] The input mass corresponding to the second stable isotope tag is determined by the second isotope-labeled alcohol added in the alcohol challenge microreaction unit and the double challenge microreaction unit. The output mass corresponding to the second stable isotope tag is determined by the unreacted second isotope-labeled alcohol, the second-labeled ester, the double-labeled ester, and other components containing the second stable isotope tag detected.

[0036] The label mass balance error is determined by dividing the difference between the input mass and output mass of the stable isotope label by the input mass of the stable isotope label. The label mass balance error can be set to no more than 3% to 8%. During the exchange discrimination process, the label detection component detects the amount of label migration from the first and second stable isotope labels into components other than the preset esterification products. Components other than the preset esterification products include by-reaction products, cleavage products, exchange products, and labeled components that cannot be classified into the first labeled ester, second labeled ester, or dual-labeled ester.

[0037] When the mass balance errors of both the first and second stable isotope tags are below the tag balance threshold, and the tag migration is below the tag exchange threshold, the tag verification module retains the remaining hydroxyl and carboxyl reactivity. If the mass balance error of either tag reaches the tag balance threshold, or the tag migration reaches the tag exchange threshold, the tag verification module discards the test results.

[0038] When the tag migration reaches the tag exchange threshold, the stable isotope tag position should be reselected. The stable isotope tag should be adjusted from the exchangeable hydrogen position to the non-exchangeable carbon framework position. When the tag mass balance error reaches the tag balance threshold, the tag loading amount, detection sampling recovery rate, and mass channel integral range should be checked.

[0039] The endpoint control steps also include state determination and load adjustment. When the challenge activity coefficient reaches the activity threshold, at least one remaining reaction capacity exceeds the corresponding target remaining range, and the condensate effluent rate of the main reactor is lower than the dewatering matching threshold, the controller determines that the mass transfer is limited.

[0040] Mass transfer limitation indicates that the reaction solution still retains hydroxyl or carboxyl groups capable of continuing the reaction. The dual-challenge microreactor also demonstrates that the current reaction solution has effective esterification activity, but the condensate discharge rate of the main reactor is lower than the discharge rate matching the chemical reaction capacity. Mass transfer limitation can be caused by excessively high reaction pressure, insufficient condensation load, insufficient stirring intensity, increased resistance in the gas phase passage, or increased viscosity of the reaction solution.

[0041] Under mass transfer-limited conditions, the controller maintains the heating load and increases the vacuum load or condensation load. The vacuum load can be increased in stages, ranging from 3% to 8%. After each load adjustment, the controller waits for a response stabilization period before re-detecting the condensate discharge rate from the main reactor to avoid continuous adjustments causing the reaction pressure to exceed the equipment's operating range. The controller determines a reaction-limited state when the challenge activity coefficient is below the activity threshold and at least one remaining reaction capacity exceeds the corresponding target remaining range. A reaction-limited state indicates that unreacted functional groups still exist in the reaction solution, but the current temperature, catalyst activity, or reaction contact state is insufficient to maintain the required reaction rate.

[0042] Under limited reaction conditions, the controller increases the heating load while maintaining the vacuum load. The heating load can be increased in stages, ranging from 2% to 5% each time. When the reaction temperature reaches the upper limit of the equipment operating temperature, the controller stops increasing the heating load and outputs a catalytic activity check signal.

[0043] When the remaining hydroxyl and carboxyl reactivity reaches the target remaining range, the controller reduces the heating load and maintains the vacuum load, allowing water that has been generated in the esterification reactor but has not yet entered the condensation path to continue to be discharged. The maintenance time can be determined based on the gas phase volume of the esterification reactor, the length of the gas phase path, and the response time of the condensation path, and can be set from 60 s to 300 s.

[0044] The esterification reaction dehydration endpoint prediction and energy consumption coordinated control system includes a sample dispensing component, a labeling and dispensing component, a temperature and pressure execution component, a labeling detection component, a heating execution component, a vacuum execution component, and a controller.

[0045] The sample dispensing unit is connected to the esterification reactor. The dispensing unit obtains a sample of the same reaction solution from the esterification reactor and distributes the same sample equally to the blank microreactor, acid challenge microreactor, alcohol challenge microreactor, and double challenge microreactor. The insulated sampling tube of the dispensing unit is positioned between the sampling port and the quantitative chamber of the esterification reactor. The quantitative chamber is connected to each of the four microreactors via a dispensing valve.

[0046] The labeling and dispensing assembly is connected to the acid challenge microreactor, the alcohol challenge microreactor, and the dual challenge microreactor, respectively. The labeling and dispensing assembly includes a first label storage chamber, a second label storage chamber, and a metering injection mechanism. The metering injection mechanism dispenses a first isotope-labeled carboxylic acid into the acid challenge microreactor, a second isotope-labeled alcohol into the alcohol challenge microreactor, and simultaneously dispenses the first isotope-labeled carboxylic acid and the second isotope-labeled alcohol into the dual challenge microreactor.

[0047] The thermo-pressure actuator is connected to each of the four micro-reaction units. The thermo-pressure actuator includes a temperature detection mechanism, a heating mechanism, a pressure detection mechanism, and a pressure regulating mechanism. The thermo-pressure actuator causes the four micro-reaction units to execute the same thermo-pressure program and sends the detected temperature and pressure values ​​to the controller.

[0048] The labeling detection component is connected to each of the four microreaction units. The component sequentially acquires the detection samples from the four microreaction units and outputs the generation responses of the first labeled ester, the second labeled ester, and the dual-labeled ester. The component also outputs the background response of the blank microreaction unit in the three mass channels.

[0049] The heating actuator is connected to the esterification reactor and adjusts the reaction heat input according to heating control commands. The heating actuator may include a steam regulating valve, a heat transfer oil regulating valve, or an electric heating power regulator. The vacuum actuator is also connected to the esterification reactor and adjusts the reaction pressure according to vacuum control commands. The vacuum actuator may include a vacuum pump, a vacuum regulating valve, a pressure detection mechanism, and a gas phase passage. The controller is communicatively connected to the sample dispensing assembly, the labeling and dispensing assembly, the temperature and pressure actuator, the label detection assembly, the heating actuator, and the vacuum actuator. The controller outputs sampling and dispensing commands to the sample dispensing assembly, the amount of label added to the labeling and dispensing assembly, the temperature and pressure program to the temperature and pressure actuator, receives mass channel data from the label detection assembly, and outputs control commands to the heating and vacuum actuators.

[0050] The controller subtracts the background response of the blank microreactor unit to correct the formation rates of the first and second labeled esters, respectively, to obtain the remaining hydroxyl and carboxyl reactivity. Based on these two remaining reactivity rates, the controller determines the dehydration endpoint and generates heating and vacuum control commands according to the relative relationship between the corrected dual-labeled ester formation rate and the condensate discharge rate from the main reactor.

[0051] The system comprises four micro-reaction units, all of which have identical reaction chamber volume, heat exchange area, stirring components, gas phase volume, and sampling pathway. Each of the four micro-reaction units is equipped with an independent marker injection port and a detection sampling port.

[0052] The reaction chamber volume can be set from 3 mL to 10 mL, and the reaction liquid sample volume can be set from 10% to 50% of the reaction chamber volume. The difference in reaction chamber volume among the four micro-reaction units should be controlled within 1%, the difference in heat exchange area should be controlled within 2%, the difference in gas phase volume should be controlled within 2%, and the difference in stirring speed should be controlled within 3%.

[0053] Separate labeling ports prevent premature mixing of first-isotope-labeled carboxylic acids and second-isotope-labeled alcohols in the dispensing pathway. Separate detection sampling ports prevent cross-contamination between blank microreactors, acid challenge microreactors, alcohol challenge microreactors, and dual challenge microreactors.

[0054] The pressure regulation assembly is connected to four microreactor units. The pressure regulation assembly enables the first group of four microreactor units and the second group of four microreactor units to perform the same marking challenge at different reaction pressures. The pressure regulation assembly includes two pressure regulation paths, two pressure sensing mechanisms, and isolation valves. The two pressure regulation paths maintain the first reaction pressure and the second reaction pressure, respectively.

[0055] The internal standard dispensing assembly is connected to each of the four microreactors. The assembly adds the same mass of a third isotope internal standard to each of the four microreactors. The assembly includes an internal standard storage chamber, a metering pump, and a four-way dispensing valve. The output volume of the four-way dispensing valve is calibrated by weighing before dispensing.

[0056] The controller includes a quality channel module, an activity calibration module, a capacity calculation module, and a label verification module.

[0057] The quality channel module is communicatively connected to the label detection component. It separates the first labeled ester quality channel, the second labeled ester quality channel, and the dual-labeled ester quality channel from the detection response output by the label detection component. The quality channel module then performs retention time matching, peak boundary determination, baseline subtraction, peak area integration, and generation rate fitting on each of the three quality channels.

[0058] The activity correction module is communicatively connected to the quality channel module. The quality channel module inputs the corrected first-labeled ester formation rate, the corrected second-labeled ester formation rate, and the corrected dual-labeled ester formation rate into the activity correction module. The activity correction module determines the challenge activity coefficient based on the corrected dual-labeled ester formation rate and uses the challenge activity coefficient to correct the corrected first-labeled ester formation rate and the corrected second-labeled ester formation rate, respectively.

[0059] The capacity calculation module communicates with the activity correction module. The activity correction module inputs the challenge activity coefficient and the corrected rates of formation of the first and second labeled esters into the capacity calculation module. The capacity calculation module determines the remaining hydroxyl group reactivity based on the corrected rate of formation of the first labeled ester and the remaining carboxyl group reactivity based on the corrected rate of formation of the second labeled ester.

[0060] The label verification module communicates with the quality channel module and the capability calculation module. The label verification module receives the first stable isotope label mass, the second stable isotope label mass, the recovery rate of the third isotope internal standard, and the label migration amount output by the quality channel module. The label verification module also receives the remaining hydroxyl reactivity and remaining carboxyl reactivity corresponding to the two reaction pressures output by the capability calculation module.

[0061] The label verification module generates a result retention signal or a re-detection signal based on the mass balance error of the first and second stable isotope labels, the amount of label migration, and the difference in the residual reactivity of the two types of labels under different reaction pressures. The result retention signal is input to the endpoint control process, and the re-detection signal is input to the sampling component, the labeling and dispensing component, and the temperature and pressure execution component, so that the system can re-perform homogeneous sampling, labeling challenge, and response identification.

[0062] The beneficial effects of the present invention are as follows: The present invention determines the candidate interval of the endpoint based on the cumulative reaction water volume and acid value change, so that the labeling challenge is concentrated in the stage of the esterification reaction near the endpoint. This avoids frequent sampling and detection in the early stage of the reaction and avoids the single fluctuation of condensate water directly triggering the endpoint determination, thereby providing stable start conditions for endpoint identification.

[0063] After entering the endpoint candidate region, the sampling component obtains the same reaction solution sample from the esterification reactor and distributes it equally to the blank microreactor unit, acid challenge microreactor unit, alcohol challenge microreactor unit, and double challenge microreactor unit. The four microreactor units execute the same temperature and pressure program, ensuring that the four detection pathways have the same raw material composition, catalyst state, water content, and reaction environment. Differences in detection results mainly originate from marker addition conditions, thus reducing the impact of batch variations, sampling time variations, and microreactor condition variations on endpoint identification results.

[0064] In the acid challenge microreactor, a first isotope-labeled carboxylic acid with the same structure as the feed carboxylic acid is added. This first isotope-labeled carboxylic acid reacts with the remaining hydroxyl groups in the reaction solution to form a first labeled ester, with the formation rate of the first labeled ester corresponding to the reactivity of the remaining hydroxyl groups. In the alcohol challenge microreactor, a second isotope-labeled alcohol with the same structure as the feed alcohol is added. This second isotope-labeled alcohol reacts with the remaining carboxyl groups in the reaction solution to form a second labeled ester, with the formation rate of the second labeled ester corresponding to the reactivity of the remaining carboxyl groups. By separately detecting the two types of remaining functional groups, the incomplete judgment of the one-sided reaction state caused by only detecting the acid value or only detecting the hydroxyl value can be avoided.

[0065] The dual-challenge microreaction unit simultaneously introduces a first isotope-labeled carboxylic acid and a second isotope-labeled alcohol, which react to form a dual-labeled ester. The dual-labeled ester formation rate reflects the effective esterification activity of the current reaction solution sample. The activity correction module uses the dual-labeled ester formation rate to correct for the first and second labeled ester formation rates, ensuring that changes in the common rate caused by decreased catalyst activity, sample temperature deviations, sampling delays, and changes in microreaction states are not directly interpreted as a reduction in residual hydroxyl or carboxyl groups, thereby improving the accuracy of identifying the two residual reactivity groups.

[0066] The blank microreaction unit does not contain the first isotope-labeled carboxylic acid or the second isotope-labeled alcohol. The mass channel module utilizes the background response of the blank microreaction unit to correct the first-labeled ester mass channel, the second-labeled ester mass channel, and the dual-labeled ester mass channel, respectively. This weakens the background signal generated by natural isotope peak clusters, instrument baseline drift, and the original components of the reaction solution, preventing the low-concentration labeled ester response from being covered or amplified by the background signal.

[0067] The first and second stable isotope tags are positioned at non-exchangeable carbon backbone locations, forming non-overlapping first-labeled ester mass channels, second-labeled ester mass channels, and dual-labeled ester mass channels, enabling the three labeled esters to be identified separately in the same detection process. The tag verification module further determines the validity of the detection results based on the stable isotope tag mass balance error and tag migration, thereby reducing detection errors caused by tag loss, tag exchange, side reactions, and misidentification of mass channels.

[0068] After the third isotope internal standard is added in equal amounts to the four microreaction units, the label verification module can compare the consistency of sampling and detection across the four detection pathways based on the detection recovery rate of the third isotope internal standard. When the difference in detection recovery rate reaches the sampling deviation threshold, the current detection result is discarded and the sample is resampled, thus avoiding incorrect endpoint determination caused by sample volume deviation, injection loss, and detection pathway residue.

[0069] Two groups of four microreactors performed the same labeling challenge at different reaction pressures, and the reactivity of residual hydroxyl and residual carboxyl groups under the two reaction pressures was compared. When the difference between the two sets of test results reached the pressure replication threshold, the controller determined that the microreactor process was affected by the mass transfer state and reset the temperature and pressure program. Pressure replication verification can prevent gas-liquid mass transfer, volatilization losses, or changes in the boiling state of the microreactors from being mistaken for changes in residual functional groups.

[0070] The controller determines the dehydration endpoint when the rate of formation of the dual-labeled ester reaches the effective threshold and the remaining hydroxyl and carboxyl reactivity enters the target remaining range, respectively. The endpoint determination is constrained by both the effective esterification activity and the state of the two remaining functional groups, avoiding premature termination of the reaction when the catalyst is deactivated, the detection response is insufficient, or there is still a significant residual functional group on one side.

[0071] When at least one remaining reaction capacity exceeds the target remaining range, the controller determines the state based on the relative relationship between the chemical reaction capacity characterized by the dual-labeled ester formation rate and the dehydration capacity characterized by the condensate discharge rate of the main reactor. If the chemical reaction capacity is effective but the condensate discharge rate of the main reactor is insufficient, the controller maintains the heating load and increases the vacuum load or condensation load to improve the physical dehydration conditions. If the chemical reaction capacity is insufficient and the remaining functional groups have not yet reached the target, the controller increases the heating load and maintains the vacuum load to improve the reaction conditions. This achieves coordinated regulation of the heating load and vacuum load corresponding to the chemical reaction process and the physical dehydration process, respectively, reducing the ineffective energy consumption caused by continuously increasing the heating load or vacuum load at the end of the reaction.

[0072] In summary, this invention obtains the remaining hydroxyl reactivity, remaining carboxyl reactivity, and current chemical reactivity through homologous sampling, four-way labeling challenge, dual-label activity correction, background response subtraction, internal standard recovery verification, pressure replication verification, and stable isotope label verification. The detection results are then combined with the condensate discharge rate of the main reactor to form a closed loop for endpoint determination and load control, thereby improving the reliability of the esterification reaction dehydration endpoint determination and reducing the risks of premature termination, delayed termination, product index deviation, and invalid energy input at the end of the reaction. Attached Figure Description

[0073] Figure 1 This is a schematic diagram of the signal flow for the execution steps of the control method of the present invention.

[0074] Figure 2 This is a schematic diagram of the overall structure of the control system of the present invention.

[0075] Figure 3 This is a schematic diagram of the tag challenge and response identification of the present invention. Detailed Implementation

[0076] The following combination Figures 1 to 3 The technical solution of the present invention will be described in detail below.

[0077] This embodiment uses the esterification reaction of hexanoic acid and n-butanol as an example. The first isotopically labeled carboxylic acid is hexanoic acid with a carbon skeleton entirely labeled with C13, and the second isotopically labeled alcohol is n-butanol with a carbon skeleton entirely labeled with C13. The first isotopically labeled carboxylic acid and the second isotopically labeled alcohol have the same chemical structure and reactive functional groups as their corresponding feedstocks. The stable isotopic tag is located at a non-exchangeable carbon skeleton position and does not transfer due to proton exchange under esterification conditions. For esterification systems of other carboxylic acids and alcohols, the same principle can be followed to select the first isotopically labeled carboxylic acid with the same structure as the feedstock carboxylic acid and the second isotopically labeled alcohol with the same structure as the feedstock alcohol.

[0078] This embodiment uses a 50 L esterification reactor. 11.616 kg of hexanoic acid, 7.412 kg of n-butanol, and 5.8 g of p-toluenesulfonic acid are added to the reactor. The feed amounts of hexanoic acid and n-butanol are both 100 mol, and the theoretical mass of reaction water is 1.8015 kg. The initial reaction temperature of the esterification reactor is set to 135 °C, and the initial absolute pressure is set to 40 kPa. The heating actuator adjusts the heating power of the esterification reactor, and the vacuum actuator adjusts the absolute pressure of the esterification reactor. The water generated in the reaction is condensed and separated, and the condensate flow rate of the main reactor is determined by a mass flow rate detection mechanism.

[0079] like Figure 1 As shown, the esterification reaction control system sequentially executes the candidate triggering step, the homologous sample separation step, the labeling challenge step, the response identification step, and the endpoint control step. Figure 1 The vertical arrows indicate the execution order of the steps. The "Yes" branch on the left of the decision box indicates that all endpoint conditions are met simultaneously, while the "No" branch on the right indicates that at least one endpoint condition is not met. The right-hand return arrow indicates that after the heating load and vacuum load adjustments are completed, the esterification reaction control system continues to execute the candidate triggering steps.

[0080] In the candidate triggering step, the esterification reaction control system continuously collects the condensate discharge rate of the main reactor and integrates the condensate discharge rate over time to obtain the cumulative reaction water volume. The cumulative reaction water volume can be determined according to the following formula: ; in, The cumulative reaction water volume at the current moment represents the mass of condensate collected from the start of the esterification reaction to the current moment. The current time indicates the point at which the integral of the cumulative reacted water volume ends; The integral time variable represents any detection time between the start of the esterification reaction and the current time. The corresponding main reactor condensate discharge rate represents the mass of water discharged from the esterification reactor and collected by condensation per unit time. Let be the integral time infinitesimal.

[0081] Acid value was measured every 5 minutes using an automated sampling titration system. The candidate triggering condition was set to the cumulative reaction water volume reaching 90% of the theoretical reaction water mass, and the decrease in acid value between two consecutive measurements not exceeding 0.5 mg KOH / g. When the cumulative reaction water volume reached 1.621 kg and the acid value change met the above conditions, the esterification reaction control system entered the endpoint candidate range. Using both cumulative reaction water volume and acid value change as triggers avoids premature activation of the marking challenge during the initial reaction stage or when there are short-term fluctuations in the condensate flow rate from the main reactor.

[0082] In the homologous sampling step, the sampling component obtains the same reaction solution sample from the esterification reactor through an insulated sampling pipeline. The temperature of the insulated sampling pipeline is maintained at the current temperature of the esterification reactor, and the stagnant liquid in the sampling pipeline is drained before formal sampling to reduce the influence of the previous reaction solution on the current detection results. The sampling component distributes the same reaction solution sample equally to the blank microreaction unit, acid challenge microreaction unit, alcohol challenge microreaction unit, and double challenge microreaction unit.

[0083] Each of the four microreactor units has a reaction chamber volume of 5 mL, and each microreactor unit receives a 1.00 mL sample of reaction solution. The four microreactor units have identical reaction chamber volumes, heat exchange areas, stirring components, gas phase volumes, and detection sampling pathways. The temperature and pressure control unit maintains the temperature of the four microreactor units at the current temperature of the esterification reactor, with the temperature difference controlled within 0.5℃; the temperature and pressure control unit also maintains the absolute pressure of the four microreactor units at the current absolute pressure of the esterification reactor, with the pressure difference controlled within 1 kPa. The stirring speed of all four microreactor units is set to 750 r / min.

[0084] In the labeling challenge step, the blank microreaction unit does not contain the first isotope-labeled carboxylic acid or the second isotope-labeled alcohol. The labeling and adding assembly adds 20 μmol of the first isotope-labeled carboxylic acid to the acid challenge microreaction unit, 20 μmol of the second isotope-labeled alcohol to the alcohol challenge microreaction unit, and simultaneously adds 20 μmol of the first isotope-labeled carboxylic acid and 20 μmol of the second isotope-labeled alcohol to the double challenge microreaction unit.

[0085] The first isotope-labeled carboxylic acid reacts with the remaining unreacted hydroxyl groups in the reaction solution to form a first labeled ester. Therefore, the formation rate of the first labeled ester can characterize the reactivity of the remaining hydroxyl groups in the reaction solution. The second isotope-labeled alcohol reacts with the remaining unreacted carboxyl groups in the reaction solution to form a second labeled ester. Therefore, the formation rate of the second labeled ester can characterize the reactivity of the remaining carboxyl groups in the reaction solution. In the dual-challenge microreactor, the first isotope-labeled carboxylic acid and the second isotope-labeled alcohol react with each other to form a dual-labeled ester. The formation rate of the dual-labeled ester is mainly affected by the catalyst activity, reaction temperature, reaction pressure, and mixing state of the current reaction solution, and therefore can be used as an endogenous reaction benchmark to correct the formation rates of the first and second labeled esters.

[0086] In this embodiment, the nominal mass-to-charge ratio (M / C ratio) of the unlabeled n-butyl hexanoate molecular ion is 172. The first isotopically labeled carboxylic acid contains six carbon thirteen atoms, corresponding to a nominal M / C ratio of 178 for the first labeled ester; the second isotopically labeled alcohol contains four carbon thirteen atoms, corresponding to a nominal M / C ratio of 176 for the second labeled ester; and the dual-labeled ester contains ten carbon thirteen atoms, corresponding to a nominal M / C ratio of 182 for the dual-labeled ester. The labeling detection component specifically employs a gas chromatography-mass spectrometry (GC-MS) detection device, and the detection responses of the second labeled ester, the first labeled ester, and the dual-labeled ester are collected in the mass channels corresponding to M / C ratios of 176, 178, and 182, respectively.

[0087] In the response identification step, the four microreaction units react continuously for 120 seconds after labeling. The labeling detection component collects the detection response every 10 seconds. The quality channel module generates the first labeled ester formation curve, the second labeled ester formation curve, and the dual-labeled ester formation curve based on the peak area at each detection time, and uses the linear fitting slope in the interval from 60 s to 120 s as the corresponding labeled ester formation rate.

[0088] Although no label was added in the blank microreaction unit, the natural isotope peaks of the unlabeled product, instrument background, and original components of the reaction solution could still generate background responses in the three mass channels. To eliminate background responses, the mass channel module determined the corrected labeled ester formation rate according to the following formula: ; ; ; in, To correct for the formation rate of the first labeled ester, the formation rate is represented by the formation rate of the first labeled ester in the acid challenge microreaction unit minus the background change rate of the corresponding mass channel in the blank microreaction unit. The first labeled ester detection rate represents the rate of first labeled ester formation detected by the labeling detection component from the acid challenge microreaction unit. The first background rate represents the rate of change of the background in the first labeled ester mass channel of the blank microreaction unit.

[0089] To correct for the formation rate of the second labeled ester, the formation rate is represented by the formation rate of the second labeled ester in the alcohol challenge microreaction unit minus the background change rate of the corresponding mass channel in the blank microreaction unit. The second labeled ester detection rate represents the rate of second labeled ester formation detected by the labeling detection component from the alcohol challenge microreaction unit. The second background rate represents the rate of change of the background in the second labeled ester mass channel of the blank microreaction unit.

[0090] To correct for the double-labeled ester formation rate, the formation rate is represented by the formation rate obtained by subtracting the background change rate of the corresponding mass channel of the blank microreaction unit from the double-challenge microreaction unit's double-labeled ester formation rate. The detection rate of the dual-labeled ester represents the rate of dual-labeled ester formation detected by the labeling detection component from the dual-challenge microreaction unit. The background rate is denoted as the double-labeled background rate, representing the rate of change of the background of the blank microreaction unit in the double-labeled ester mass channel.

[0091] The activity correction module determines the challenge activity coefficient based on the dual-labeled ester formation rate and the equivalent addition of the two labels:

[0092] in, The activity coefficient represents the effective esterification activity of the current reaction solution sample under the current reaction temperature, current reaction pressure, current catalyst activity, and current mixing conditions. To correct for the rate of formation of the dual-labeled ester, the rate of formation of the dual-labeled ester is expressed after subtracting the background response corresponding to the blank microreaction unit; The equivalent amount of labeled carboxylic acid added represents the amount of the first isotope-labeled carboxylic acid added to the double-challenge microreaction unit; The equivalent amount of labeled alcohol added represents the amount of substance of the second isotope-labeled alcohol added to the double-challenge microreaction unit.

[0093] The capability calculation module uses challenge activity coefficients to correct the formation rates of the first and second labeled esters, respectively, to obtain the remaining hydroxyl reactivity and the remaining carboxyl reactivity. ; ; Among them, the reactivity of the remaining hydroxyl group This represents the hydroxyl equivalent in the same reaction solution sample that can react with the first isotope-labeled carboxylic acid, correcting for the formation rate of the first-labeled ester. This indicates the rate of formation of the first labeled ester after subtracting the background response; remaining carboxyl reactivity. This indicates the carboxyl equivalent in the same reaction solution sample that can react with the second isotope-labeled alcohol, correcting for the formation rate of the second-labeled ester. This represents the rate of formation of the second labeled ester after deducting the background response.

[0094] After activity correction using the dual-labeled ester formation rate, even if there is a short time delay between the detection time of the four micro-reaction units and the sampling time of the main reactor, or if the catalyst activity in the current reaction solution decreases, the capability calculation module can still separate the changes caused by the common reaction conditions from the first labeled ester formation rate and the second labeled ester formation rate.

[0095] In the endpoint control step, the effective threshold for the challenge was set at 10% of the rate of formation of the dual-labeled ester in the middle stage of the same batch of reaction. The target remaining range for the reactivity of the remaining hydroxyl groups was set at 0 mol / L to 0.020 mol / L, and the target remaining range for the reactivity of the remaining carboxyl groups was set at 0 mol / L to 0.020 mol / L.

[0096] When the rate of formation of the dual-labeled ester reaches the challenge threshold, and the remaining hydroxyl and carboxyl reactivity enters the corresponding target remaining range, Figure 1 When the endpoint determination conditions in the decision box are met simultaneously, the esterification reaction control system determines the dehydration endpoint along the "Yes" branch and outputs an endpoint confirmation signal. After receiving the endpoint confirmation signal, the controller reduces the heating load to 20% of the heating load before the endpoint determination, maintains the current vacuum load for 120 s, allows the remaining water vapor in the esterification reactor to continue entering the condensation path, and then stops the heating and vacuum actuators.

[0097] When the rate of formation of the dual-labeled ester fails to reach the effective threshold, or when at least one remaining reactivity fails to enter the target remaining range, the esterification reaction control system determines that the endpoint determination condition has not been met by following the "No" branch. The controller adjusts the heating load and vacuum load based on the relative relationship between the chemical reactivity characterized by the rate of formation of the dual-labeled ester and the dehydration capacity characterized by the rate of condensate discharge from the main reactor.

[0098] To ensure that the two capabilities are comparable, the controller determines the reaction dehydration matching ratio according to the following formula: ; in, The reaction dehydration matching ratio represents the relative relationship between chemical reactivity and physical dehydration capacity. The current corrected double-labeled ester formation rate represents the double-labeled ester formation rate after deducting the double-labeled background rate in the current detection cycle; The corrected bilabeled ester formation rate is represented by a pre-recorded bilabeled ester formation rate in the middle of the esterification reaction, serving as a reference bilabeled ester formation rate. The current condensate discharge rate of the main reactor represents the mass of condensate collected per unit time within the current detection cycle. The reference condensate discharge rate represents the condensate discharge rate of the main reactor, which was recorded in advance during the esterification reaction. To prevent zero parameters, this is used to prevent division by zero or abnormal amplification results when the current condensate discharge rate of the main reactor is zero or close to zero.

[0099] When the reaction dehydration match ratio is greater than 1.2, the chemical reaction capacity is higher than the current dehydration capacity. The controller maintains the heating load constant and increases the load of the vacuum actuator by 5%. When the reaction dehydration match ratio is less than 0.8 and at least one remaining reaction capacity exceeds the target remaining range, the current process exhibits reaction limitation. The controller increases the heating load by 3% and maintains the vacuum load constant. When the reaction dehydration match ratio is between 0.8 and 1.2 and at least one remaining reaction capacity exceeds the target remaining range, the controller maintains the current heating load and vacuum load. After completing the load adjustment, the esterification reaction control system continues to execute the candidate triggering step.

[0100] like Figure 2 As shown, the esterification reaction dehydration endpoint prediction and energy consumption co-control system includes an esterification reactor, a sample dispensing component, a blank micro-reaction unit, an acid challenge micro-reaction unit, an alcohol challenge micro-reaction unit, a dual challenge micro-reaction unit, a labeling and dispensing component, a temperature and pressure execution component, a labeling detection component, a heating execution component, a vacuum execution component, and a controller.

[0101] Figure 2 In the diagram, the arrow pointing from the esterification reactor to the sample dispensing assembly indicates the flow direction of the reaction liquid sample; the arrows from the sample dispensing assembly to the four microreactors indicate the direction of equal distribution of the same reaction liquid sample; and the arrows from the four microreactors to the labeling and detection assembly indicate the output direction of the detected sample or detection response. The connection between the labeling and dispensing assembly and the four microreactors indicates the labeling relationship, and the connection between the temperature and pressure control assembly and the four microreactors indicates the temperature and pressure control relationship. The connections between the heating and vacuum control assemblies and the esterification reactor represent the reaction heat input regulation relationship and the reaction pressure regulation relationship, respectively.

[0102] Figure 2 The dashed box indicates that the four microreactors functionally constitute a common counterfactual challenge group. The dashed box does not imply that the four microreactors must be housed in the same physical enclosure. The four microreactors can be housed in the same thermostatic metal block, or they can be housed in four separate reaction chambers with independent temperature and pressure control channels.

[0103] The sampling assembly includes an insulated sampling tube, a metering pump, a four-way dispensing valve, and four metering injection chambers. The metering pump draws 4.20 mL of reaction solution from the esterification reactor, of which 0.20 mL is used to flush the dispensing pathway, and the remaining 4.00 mL is injected into the four microreactors. The single output volume of each of the four metering injection chambers is 1.00 mL, and the difference in single output volume is controlled within 1%.

[0104] The labeling and dispensing assembly includes a first labeling reservoir, a second labeling reservoir, and a metering injection mechanism. The first labeling reservoir stores a first isotope-labeled carboxylic acid solution, and the second labeling reservoir stores a second isotope-labeled alcohol solution. The metering injection mechanism outputs a predetermined amount of label to the acid challenge microreactor, the alcohol challenge microreactor, and the dual challenge microreactor, respectively.

[0105] The thermo-pressure actuator includes four heating units, four temperature detection units, four pressure regulating valves, and four pressure detection units. The thermo-pressure actuator receives the current reaction temperature and pressure from the controller and causes the four micro-reaction units to execute the same thermo-pressure program.

[0106] The labeling detection component specifically employs a gas chromatography-mass spectrometry (GC-MS) detection device. The sampling ports of the four microreaction units are sequentially connected to the injection valves of the GC-MS detection device. The labeling detection component outputs mass channel data for the first labeled ester, the second labeled ester, and the dual-labeled ester at fixed time intervals.

[0107] The controller is communicatively connected to the sample dispensing component, the labeling and dispensing component, the temperature and pressure execution component, the labeling detection component, the heating execution component, and the vacuum execution component. The controller outputs sample dispensing control commands to the sample dispensing component, labeling and dispensing commands to the labeling and dispensing component, temperature and pressure programs to the temperature and pressure execution component, receives three quality channel data output by the labeling detection component, and outputs load control commands to the heating execution component and the vacuum execution component.

[0108] The controller includes a quality channel module, an activity calibration module, a capacity calculation module, and a label verification module. Figure 2 The arrow pointing from the quality channel module to the activity correction module indicates that the corrected rates of the three labeled esters are input from the quality channel module to the activity correction module; the arrow pointing from the activity correction module to the capability calculation module indicates that the challenge activity coefficient and the corrected rates of the labeled esters are input to the capability calculation module; the connection between the label verification module and the quality channel module, the activity correction module, and the capability calculation module indicates that the label verification results can determine whether the test results are retained.

[0109] The mass channel module performs peak identification, baseline subtraction, and time fitting on the mass spectrometry data. The activity correction module determines the challenge activity coefficient based on the dual-labeled ester formation rate. The capability calculation module determines the remaining hydroxyl and carboxyl reactivity based on the challenge activity coefficient, the formation rate of the first and second labeled esters.

[0110] The label verification module is used to perform detection recovery rate verification, stable isotope mass balance calculation, and label migration verification. In one embodiment, the labeling and dispensing component also adds 10 μmol of a third isotope internal standard to each of the four microreaction units. The third isotope internal standard is specifically deuterated toluene. The third isotope internal standard does not participate in the esterification reaction and is used to verify the sampling, collection, and detection recovery processes of the four microreaction units. When the difference in the detection recovery rate of the third isotope internal standard between any two microreaction units reaches 5%, the label verification module discards the current detection result and outputs a resampling instruction to the sampling component.

[0111] In another embodiment, the controller controls the sampling assembly to acquire a second reaction solution sample and distributes it to four microreaction units in a second group. The first group of four microreaction units performs a labeling challenge at 40 kPa absolute pressure, and the second group of four microreaction units performs the same labeling challenge at 50 kPa absolute pressure. When the difference in residual hydroxyl reactivity and the difference in residual carboxyl reactivity corresponding to both pressures are less than 8%, the label verification module retains the test results; when at least one difference reaches 8%, the label verification module determines microreaction mass transfer interference and controls the temperature and pressure execution assembly to reset the stirring speed or reaction pressure of the microreaction units.

[0112] The label verification module also calculates the stable isotope masses corresponding to the first isotope-labeled carboxylic acid, the second isotope-labeled alcohol, the first-labeled ester, the second-labeled ester, and the dual-labeled ester. When the mass balance error of the first or second stable isotope label reaches 5%, or when the label migration of the stable isotope label into components other than the preset esterification product reaches 2%, the label verification module discards the test results and outputs a label re-addition instruction to the labeling component.

[0113] like Figure 3 As shown, the same reaction solution sample, after being dispensed by the sampling assembly, forms four parallel detection paths. Since the four detection paths originate from the same sampling time, the raw material composition, catalyst concentration, ester content, water content, and impurity composition remain consistent across the four microreactor units. The main difference between the four detection paths stems from the labeling conditions.

[0114] The first detection pathway consists of a blank microreaction unit and a background response. The blank microreaction unit does not contain the first isotope-labeled carboxylic acid or the second isotope-labeled alcohol. The blank microreaction unit is used to detect the natural isotope responses and instrument background of the same reaction solution sample in the three labeled mass channels. Figure 3 The background response is output to the background response processing box for subtracting blank micro-reaction units, indicating that the corresponding background response needs to be subtracted from each of the three quality channels.

[0115] The second detection pathway consists of an acid challenge microreactor, a first isotope-labeled carboxylic acid, and a first labeled ester. The first isotope-labeled carboxylic acid is added from the input side of the acid challenge microreactor. It reacts with the remaining hydroxyl groups in the reaction solution to form the first labeled ester. A higher rate of first labeled ester formation indicates a higher reactivity of the remaining hydroxyl groups in the reaction solution that can continue to participate in the esterification reaction.

[0116] The third detection pathway consists of an alcohol challenge microreaction unit, a second isotope-labeled alcohol, and a second-labeled ester. The second isotope-labeled alcohol reacts with the remaining carboxyl groups in the reaction solution to form the second-labeled ester. The higher the rate of second-labeled ester formation, the higher the reactivity of the remaining carboxyl groups in the reaction solution.

[0117] The fourth detection pathway consists of a dual-challenge microreaction unit, two labels, and a dual-labeled ester. The dual-challenge microreaction unit simultaneously receives a first isotope-labeled carboxylic acid and a second isotope-labeled alcohol. The dual-labeled ester is generated by the reaction of the two externally added labels; therefore, the rate of dual-labeled ester formation does not directly depend on the residual carboxyl or hydroxyl equivalents in the original reaction solution, but primarily characterizes the effective esterification activity under the current microreaction environment.

[0118] The outputs of the four detection paths are Figure 3 The lower part converges. The quality channel module first subtracts the background response of the blank microreaction unit, and then the activity correction module corrects the first labeled ester formation rate and the second labeled ester formation rate respectively using the dual-labeled ester formation rate. The capability calculation module finally outputs the remaining hydroxyl group reactivity and the remaining carboxyl group reactivity.

[0119] use Figure 3 The four-channel homogeneous detection structure shown avoids relying solely on the formation rate of the first or second labeled ester to determine the endpoint. When catalyst activity decreases, the sample temperature changes, or the microreaction mixing state alters, the formation rates of both the first and second labeled esters may decrease simultaneously. The dual-labeled ester formation rate reflects changes in common reaction conditions, enabling the controller to distinguish between two states: a reduction in remaining functional groups and a decrease in common reaction activity.

[0120] As an example, the feasible parameter range is given in Table 1 below, which provides a set of parameters that can be directly implemented. Figures 1 to 3The parameter ranges for the proposed scheme are shown. Specific parameters can be calibrated based on the type of carboxylic acid, alcohol type, reaction temperature, catalyst activity, and the detection sensitivity of the labeling and detection component.

[0121]

[0122] In the example of re-state determination and load control, Table 2 below shows how the controller performs control based on remaining reaction capacity, challenge effective state, reaction dehydration matching ratio, and label verification results.

[0123]

[0124] Through the above implementation method, the esterification reaction control system no longer directly equates the decrease in the rate of condensate discharge from the main reactor to the reaction endpoint. Instead, it establishes four counterfactual detection paths—blank challenge, acid challenge, alcohol challenge, and double challenge—using the same reaction solution sample. The blank microreaction unit is used to subtract the background response, the acid challenge microreaction unit is used to detect the remaining hydroxyl reactivity, the alcohol challenge microreaction unit is used to detect the remaining carboxyl reactivity, and the double challenge microreaction unit is used to correct the common activity of the current reaction environment. The controller determines whether the chemical reaction is complete based on the corrected two remaining reactivity levels and allocates heating and vacuum loads according to the relative relationship between chemical reactivity and physical dehydration capacity, thereby reducing endpoint misjudgments caused by changes in catalytic activity, limited mass transfer, or fluctuations in condensate discharge.

[0125] Finally, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for predicting the dehydration endpoint of an esterification reaction and coordinating energy consumption control, characterized in that, Performed by the esterification reaction control system, including: Candidate triggering steps: Enter the endpoint candidate interval based on the cumulative reaction water volume and acid value change; Same-source sampling step: Obtain the same reaction solution sample from the esterification reactor and distribute it equally to the blank microreactor, acid challenge microreactor, alcohol challenge microreactor and double challenge microreactor, so that the four microreactors perform the same temperature and pressure program; Labeling challenge steps: Add a first isotope-labeled carboxylic acid with the same structure as the feed carboxylic acid to the acid challenge microreactor unit, add a second isotope-labeled alcohol with the same structure as the feed alcohol to the alcohol challenge microreactor unit, and add both labels to the double challenge microreactor unit simultaneously; Response identification steps: Detect the first labeled ester of the acid challenge microreaction unit, the second labeled ester of the alcohol challenge microreaction unit, and the double labeled ester of the double challenge microreaction unit. Subtract the background response of the blank microreaction unit. Correct the generation rates of the first labeled ester and the second labeled ester with the generation rate of the double labeled ester to obtain the remaining hydroxyl reactivity and the remaining carboxyl reactivity. Endpoint control steps: The dehydration endpoint is determined when the rate of formation of the dual-labeled ester reaches the effective threshold and the remaining reactivity of the two reactors reaches the target remaining range. If the dehydration endpoint is not reached, the heating load and vacuum load are adjusted according to the relative relationship between the chemical reactivity characterized by the rate of formation of the dual-labeled ester and the dehydration capacity characterized by the rate of condensate discharge from the main reactor.

2. The method for predicting the dehydration endpoint of esterification reaction and coordinating energy consumption control according to claim 1, characterized in that, The tagging challenge step also includes the following sub-steps: The labeling and locating step is as follows: a first stable isotope tag is placed at the non-exchangeable carbon skeleton position of the first isotope-labeled carboxylic acid, and a second stable isotope tag is placed at the non-exchangeable carbon skeleton position of the second isotope-labeled alcohol. Channel separation sub-step: Based on the first stable isotope label and the second stable isotope label, a first labeled ester mass channel, a second labeled ester mass channel, and a double labeled ester mass channel are formed without overlap, and the three mass channels are located outside the natural isotope peak clusters of the corresponding unlabeled esters.

3. The method for predicting the dehydration endpoint of esterification reaction and coordinating energy consumption control according to claim 2, characterized in that, The response identification step further includes the following sub-steps: Activity labeling step: Determine the challenge activity coefficient corresponding to the current reaction solution sample based on the added equivalents of the two labels in the dual-challenge microreaction unit and the dual-labeled ester formation rate; Hydroxyl solution operator step: Determine the remaining hydroxyl reactivity based on the first labeled ester formation rate after subtracting the background response and the challenge activity coefficient; Carboxyl group solution operator steps: Determine the remaining carboxyl group reactivity based on the second labeled ester formation rate after subtracting the background response and the challenge activity coefficient.

4. The method for predicting the dehydration endpoint of esterification reaction and coordinating energy consumption control according to claim 3, characterized in that, The homologous sampling step also includes the following sub-steps: Internal standard addition sub-step: Add the same mass of a third isotope internal standard that does not participate in the esterification reaction to each of the four micro-reaction units; Recovery verification steps: Determine the detection recovery rate of the third isotope internal standard in each of the four micro-reaction units; Imbalance Rejection Sub-step: When the difference between any two detection recoveries reaches the sampling deviation threshold, discard the detection results of the current four micro-reaction units and re-execute the homologous sampling step.

5. The method for predicting the dehydration endpoint of esterification reaction and coordinating energy consumption control according to claim 4, characterized in that, The response identification step is followed by the following sub-steps: Pressure replication sub-step: Obtain a second reaction liquid sample from the esterification reactor, distribute the second reaction liquid sample equally to the four micro-reaction units in the second group, and subject the four micro-reaction units in the second group to the same labeling challenge under a reaction pressure different from that of the four micro-reaction units in the first group; Capacity comparison sub-step: Compare the reactivity of the remaining hydroxyl group and the reactivity of the remaining carboxyl group, corrected for the rate of ester formation under two reaction pressures; Mass transfer exclusion sub-step: When the difference in the reactivity of the remaining hydroxyl groups and the difference in the reactivity of the remaining carboxyl groups corresponding to the two reaction pressures are both below the pressure replication threshold, the detection results are retained. When at least one difference reaches the pressure replication threshold, micro-reaction mass transfer interference is identified and the temperature and pressure program is reset.

6. The method for predicting the dehydration endpoint of esterification reaction and coordinating energy consumption control according to claim 5, characterized in that, The response identification step further includes the following sub-steps: Tag balance operator steps: Determine the stable isotope masses corresponding to the first isotope-labeled carboxylic acid, the second isotope-labeled alcohol, the first-labeled ester, the second-labeled ester, and the dual-labeled ester, and establish the mass balance for each of the two stable isotope labels; Exchange discrimination sub-step: Detect the amount of tag migration of the first stable isotope tag and the second stable isotope tag into components other than the preset esterification product; The result retention sub-step is as follows: when the mass balance error of both stable isotope tags is below the tag balance threshold and the tag migration is below the tag exchange threshold, the remaining hydroxyl and carboxyl reactivity are retained.

7. The method for predicting the dehydration endpoint of esterification reaction and coordinating energy consumption control according to claim 6, characterized in that, The endpoint control step further includes the following sub-steps: State determination sub-steps: When the challenge activity coefficient reaches the activity threshold, at least one remaining reaction capacity exceeds the corresponding target remaining range, and the main reactor condensate effluent rate is lower than the dehydration matching threshold, the mass transfer-limited state is determined; when the challenge activity coefficient is lower than the activity threshold and at least one remaining reaction capacity exceeds the corresponding target remaining range, the reaction-limited state is determined. Load regulation sub-steps: Maintain heating load and increase vacuum load or condensation load under mass transfer-limited conditions; increase heating load and maintain vacuum load under reaction-limited conditions; reduce heating load and maintain vacuum load when the two remaining reaction capacities enter the target remaining range respectively.

8. A coordinated control system for predicting the dehydration endpoint of an esterification reaction and coordinating energy consumption, characterized in that, include: The sample dispensing component, connected to the esterification reactor, is used to distribute the same reaction solution sample equally to the blank microreactor, acid challenge microreactor, alcohol challenge microreactor, and double challenge microreactor. The labeling and dispensing assembly is connected to the acid challenge microreactor unit, the alcohol challenge microreactor unit and the dual challenge microreactor unit, respectively, and is used to dispense a first isotope-labeled carboxylic acid with the same structure as the feed carboxylic acid and a second isotope-labeled alcohol with the same structure as the feed alcohol. The temperature and pressure actuator is connected to four micro-reaction units respectively, and is used to enable the four micro-reaction units to execute the same temperature and pressure program; The labeling detection component is connected to four microreaction units respectively, and is used to output the generation response of the first labeled ester, the second labeled ester and the dual labeled ester; The heating actuator and the vacuum actuator are respectively connected to the esterification reactor; The controller is communicatively connected to the sample dispensing component, labeling and dispensing component, temperature and pressure execution component, labeling detection component, heating execution component, and vacuum execution component. It is used to subtract the background response of the blank micro-reaction unit, correct the first and second labeled ester generation rates with the dual-labeled ester generation rate, obtain the remaining hydroxyl and carboxyl group reactivity, determine the dehydration endpoint based on the two remaining reactivity, and generate heating and vacuum control commands based on the relative relationship between the dual-labeled ester generation rate and the condensate discharge rate of the main reactor.

9. The synergistic control system for predicting the dehydration endpoint of esterification reaction and coordinating energy consumption according to claim 8, characterized in that, Also includes: The four micro-reaction units have the same reaction chamber volume, heat exchange area, stirring component, gas phase volume and sampling passage. Each of the four micro-reaction units is equipped with an independent marker injection port and detection sampling port. The pressure regulating component is connected to four micro-reaction units respectively, and is used to enable the first group of four micro-reaction units and the second group of four micro-reaction units to perform the same marking challenge under different reaction pressures; The internal standard injection assembly is connected to four micro-reaction units respectively, and is used to add the same mass of the third isotope internal standard to the four micro-reaction units.

10. The esterification reaction dehydration endpoint prediction and energy consumption coordinated control system according to claim 9, characterized in that, The controller includes: The mass channel module, which is communicatively connected to the labeling detection component, is used to separate the first labeled ester mass channel, the second labeled ester mass channel, and the dual-labeled ester mass channel from the detection response. The activity correction module, which is connected in communication with the mass channel module, is used to determine the challenge activity coefficient based on the dual-labeled ester formation rate, and to correct the formation rate of the first labeled ester and the formation rate of the second labeled ester respectively using the challenge activity coefficient. The capability calculation module is connected in communication with the activity correction module and is used to determine the remaining hydroxyl reactivity and the remaining carboxyl reactivity based on the corrected first and second labeled ester formation rates, respectively. The tag verification module communicates with the quality channel module and the capacity calculation module. It is used to generate a result retention signal or a re-detection signal based on the mass balance error of the two stable isotope tags, the tag migration amount, and the difference between the two remaining reactivity under different reaction pressures.

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