Method for preparing sterically hindered phenol antioxidant through ionic liquid catalysis

Abstract

The invention relates to the technical field of ionic liquid catalytic organic synthesis, and discloses a method for preparing a steric hindrance phenol antioxidant by ionic liquid catalysis, which comprises the following steps: dissolving a gaseous olefin alkylation reagent in an ionic liquid and a phenol reactant under pressure to form a transient homogeneous reaction system for reaction, and after the reaction, separating and purifying to obtain the steric hindrance phenol antioxidant. Under the condition that the pressure reduction rate is controlled in a closed-loop mode through an acoustic signal, the alkylation reagent is gasified and escaped, and therefore spontaneous separation of a product phase is triggered. According to the method, a non-mass-transfer limited environment required by chemical reaction and phase separation conditions required by product separation are unified in a single physical operation cycle, and closed-loop control is performed on a phase change process by using an acoustic signal generated in the process, so that spontaneous and rapid separation of the product is realized, and meanwhile, the stability of the whole process flow is maintained.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing hindered phenolic antioxidant by ionic liquid catalysis, belonging to the technical field of organic synthesis. BACKGROUND

[0002] In the field of organic synthesis, especially in the industrial preparation process of hindered phenolic antioxidant, using ionic liquid as a recyclable catalyst to replace traditional strong acid is a general technical strategy in this technical direction, and ionic liquid itself has the characteristics of designable acidity, low vapor pressure and good thermal stability.

[0003] In large-scale production, gaseous nonpolar olefin raw materials such as isobutylene are usually introduced into a liquid phase system of high-viscosity, strongly polar ionic liquid and phenolic reactants for reaction. In such a gas-liquid heterogeneous system, the rate of the entire chemical conversion process is not determined by the intrinsic activity of the catalyst, but is limited by the slow mass transfer process at the gas-liquid interface. In order to strengthen the mass transfer, vigorous mechanical stirring or increasing the reaction temperature is generally used, but such methods have an upper limit in improving the effect while bringing high energy consumption, and may cause side reactions. The method of introducing a cosolvent into the system to improve the compatibility will interfere with the product separation and catalyst recovery process after the reaction, increasing the complexity of subsequent processing.

[0004] Based on this, the prior art mainly has the following deficiencies: 1. The reaction process is controlled by the physical mass transfer rate, resulting in low utilization rate of the effective volume of the reaction kettle, and the total space-time yield is limited; 2. The energy consumption cost of the strong stirring for mass transfer is high, and it is difficult to avoid the uneven mixing area in the reaction system; 3. The product and the viscous ionic liquid form an emulsion or a close mixing system after reaction, and the subsequent separation step process is long, high energy consumption, and accompanied by cross contamination and loss of catalyst; analysis shows that in actual application, the physical conditions required for efficient reaction and the physical conditions required for efficient separation are mutually exclusive, the former requires good compatibility of each phase to eliminate the mass transfer interface, and the latter requires a clear phase interface between the product phase and the catalyst phase to facilitate separation, which constitutes a process contradiction: any measure to improve the compatibility of the reaction stage by strengthening stirring, heating or adding a cosolvent will inevitably increase the degree of emulsification of the product and the catalyst after the reaction is completed, making the subsequent separation step longer, higher energy consumption and more serious catalyst loss. Therefore, technical improvement usually has to choose between improving reaction efficiency and simplifying separation steps; in addition, the prior art also explores the idea of combining a hindered phenol structure with an ionic liquid to functionalize, for example, the Chinese invention patent with the authorization announcement number CN102060776B discloses an antioxidant ionic liquid containing a hindered phenol and its preparation method and application, which uses a hindered phenol group as part of the cation to prepare an ionic liquid with antioxidant function, and uses it as a lubricating oil additive, however, this technical idea focuses on the creation of new substances, and the purpose is to obtain a functional ionic liquid molecule, in the process of using ionic liquid as a catalyst to prepare traditional hindered phenol products, there is a core technical problem of mutual contradiction between reaction mass transfer and product separation. Therefore, how to provide a process method that can create a mass transfer-free environment for reactants and catalysts in the reaction stage, and then make the product and catalyst quickly separate after the reaction is completed, and this process does not introduce additional chemical separation aids, is the technical problem to be solved by the present application. SUMMARY

[0005] The present application provides a method for preparing a hindered phenol antioxidant catalyzed by ionic liquid, which mainly aims to solve the problem of how to make the reaction system homogeneous in the reaction stage to eliminate mass transfer limitation without introducing additional chemicals, while restoring the phase difference after the reaction to achieve spontaneous separation of the product.

[0006] To achieve the above purpose, the present application provides a method for preparing a hindered phenol antioxidant catalyzed by ionic liquid, which comprises the following steps: Step S1, in a pressure reactor, an ionic liquid and a phenolic reactant are introduced, followed by an alkylating agent, which is a gaseous alkene, and the reactor is pressurized until a transient homogeneous reaction system is formed, which is composed of the ionic liquid, the phenolic reactant and the alkylating agent; Step S2, the alkylating reaction is carried out in the transient homogeneous reaction system to generate a sterically hindered phenol product; Step S3, after the reaction is completed, the pressure of the reactor is reduced to make the alkylating agent gasify and escape from the transient homogeneous reaction system, and in the process of reducing the pressure of the reactor, an acoustic sensor arranged outside the reactor is used to monitor the acoustic signal in the reaction system in real time; the acoustic characteristics of critical foaming are identified based on the acoustic signal, and when the acoustic characteristics of critical foaming are identified, the reduction rate of the pressure is adaptively adjusted to inhibit the formation of macroscopic foam; Step S4, as the alkylating agent gasifies and escapes, the sterically hindered phenol product spontaneously phase separates from the ionic liquid to form a product phase that is immiscible with the ionic liquid, and the product phase is separated.

[0007] Preferably, during the phase separation of the sterically hindered phenol product from the ionic liquid, one or more short-term high-pressure inert gas pulse injections are carried out through the gas inlet pipeline into the two-phase interface region or the ionic liquid phase below it, and the local pressure and flow field disturbance generated by the pulse injection accelerate the coalescence and macroscopic layering of the product phase.

[0008] Preferably, the pressurization in step S1 is such that the working condition of the alkylating agent is in a supercritical state or a near-critical state, wherein the near-critical state is defined as a pressure in the range of 0.8 to 1.2 times the critical pressure of the alkylating agent and a temperature in the range of 0.8 to 1.2 times the critical temperature of the alkylating agent.

[0009] Preferably, the alkylating agent is an alkene containing 2 to 4 carbon atoms.

[0010] Preferably, the acoustic characteristics of critical foaming in step S3 are defined as narrowband characteristic peaks with rapid energy concentration appearing in the acoustic signal in the frequency band of 3 kHz to 30 kHz.

[0011] Preferably, the adaptive adjustment of the reduction rate of the pressure in step S3 includes: when the acoustic characteristics of critical foaming are identified, the reduction rate of the pressure is temporarily increased, and then switched to a stable exhaust mode lower than the initial reduction rate, and after the acoustic signal returns to the background voiceprint without the acoustic characteristics of critical foaming, the initial reduction rate is restored.

[0012] Preferably, the introduction of the alkylating agent in step S1 is performed at a rate superimposed with a sinusoidal fluctuation of frequency ω set in the control program, and the formation of the transient homogeneous reaction system is determined by a dimensionless parameter R phase reaching a threshold value R crit set in the control program. phase wherein R phase is defined by the following equation: R lag = G / P lag wherein G is the gain of the response component of the pressure signal in the reactor at the same frequency ω, and P

[0013] Preferably, it further comprises identifying the occurrence of the abnormal exothermic side reaction based on the trajectory of the gain G and the phase delay Φ in the two-dimensional state space constituted by the gain and the phase delay, deviating from the characteristic region calibrated based on the reference physical dissolution process.

[0014] Preferably, it further comprises analyzing the harmonic response components of the pressure signal at integer multiples of the frequency ω; and determining the activity state of the ionic liquid catalyst online based on the characteristics of the harmonic response components.

[0015] Preferably, it further comprises adaptively adjusting the duration or the reaction temperature of the alkylation reaction in step S2 based on the activity state of the ionic liquid catalyst determined online, to compensate for the change in catalyst activity.

[0016] Compared with the prior art, the present application has the following beneficial effects: 1. By pressurizing the gaseous reactant as the alkylating agent, it is made to form a single homogeneous fluid together with the ionic liquid and the phenolic reactant in the reaction system, and after the reaction is completed, it is made to gasify and escape by depressurization. This reversible regulation of the physical state of the alkylating agent unifies the two conflicting requirements of the mass transfer conditions required in the chemical reaction stage and the phase separation conditions required in the product separation stage in the same physical operation cycle, so that the separation of the product is no longer an independent step dependent on external material or energy input, but a deterministic physical process that occurs with the end of the reaction.

[0017] 2. In the depressurization process, an acoustic sensor arranged outside the reactor is used to monitor the acoustic signal in the system in real time, and the pressure reduction rate is adaptively adjusted based on the identified critical foaming acoustic characteristics. This way converts an invisible and nonlinear phase change process into a controllable engineering operation with clear process characteristics, which uses the physical signal generated by the process itself to feed forward the process itself, avoiding the impact of uncontrolled foaming on product recovery rate and catalyst recovery rate, and maintaining the stability of the entire process flow.

[0018] 3. In the process of phase separation of the sterically hindered phenolic product from the ionic liquid, a short high pressure inert gas pulse is injected into the two-phase interface area through the gas inlet pipeline. This operation uses the existing fluid transportation hardware in the system to generate local pressure and flow field disturbance in the two-phase system. The disturbance provides external energy for the dispersed product microdroplets to overcome the interfacial energy barrier and coalesce, accelerating macroscopic delamination and shortening the time occupied by the equipment due to waiting for material sedimentation. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The integrated process and control logic flowchart of the present application; Figure 2 The acoustic feature recognition spectrum of critical foaming in the speed control and pressure reduction process of the present application; Figure 3 The integrated process control and information flow system architecture diagram of the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below combined with specific embodiments, and it should be understood that the specific embodiments described here are only used to explain the present application, and do not constitute a limitation on the protection scope of the present application.

[0021] The present application provides a method for preparing sterically hindered phenolic antioxidant by ionic liquid catalysis, the process flow is designed as a closed loop physical and chemical process executed in a single pressure reactor, which mainly includes: system initialization and transient homogeneous construction stage, intrinsic kinetics controlled alkylation reaction stage, acoustic signal guided speed control and pressure reduction and phase transition triggering stage, and product spontaneous separation and coalescence acceleration stage. In the industrial preparation of sterically hindered phenolic antioxidant, a common technical problem is that the gaseous nonpolar olefin raw material has mass transfer resistance in the viscous and strong polar ionic liquid catalyst system, which limits the rate of chemical conversion process to physical diffusion rather than the intrinsic chemical activity of the catalyst. The method of the present application temporarily uses the gaseous reactant as the key medium for reconstructing the physical phase state of the whole reaction system by reversible physical state regulation of the gaseous reactant as the alkylation reagent, so as to unify the mass transfer-free environment required in the reaction stage and the phase separation conditions required in the separation stage in the same pressurization-reaction-depressurization physical operation cycle.

[0022] In one embodiment, the ionic liquid as catalyst and the phenolic reactant as substrate are first introduced into a pressure reactor, then the gaseous olefin as alkylating agent, which can be an olefin containing 2 to 4 carbon atoms, such as isobutylene, is introduced into the reactor, the reactor is pressurized until the working condition of the alkylating agent reaches its supercritical state or near-critical state, where the near-critical state is defined as the pressure being in the range of 0.8 to 1.2 times the critical pressure of the alkylating agent and the temperature being in the range of 0.8 to 1.2 times the critical temperature of the alkylating agent, under this high density fluid state, the alkylating agent is completely miscible with the ionic liquid and the phenolic reactant, the original gas-liquid interface in the system disappears, thus forming a single liquid phase, low viscosity, transient homogeneous reaction system, which eliminates the physical mass transfer bottleneck, so that the subsequent chemical reaction can be carried out in the mode of intrinsic kinetic control; in order to accurately determine the formation of the transient homogeneous reaction system, the method uses an online phase state identification procedure based on dynamic excitation response, during the introduction of the alkylating agent, the introduction rate is not constant, but a sinusoidal fluctuation rate superimposed on the preset frequency ω in the control program, at the same time, the control module analyzes the pressure signal in the reactor in real time, extracts the gain G and phase delay P of the response component with the same frequency ω as the excitation frequency lag Since when the two phases coexist, the dissolution process of the alkylating agent is accompanied by mass transfer delay, the system shows higher P lag and lower G, while after the formation of the homogeneous phase, the system response mainly reflects the rapid compression of the fluid, showing lower P lag and higher G, therefore, the method defines a dimensionless parameter R phase which is calculated by the following formula: R phase =G / P lag The formation of the transient homogeneous reaction system is determined by the dimensionless parameter R phase reaching the threshold value R crit set in the control program, which provides a clear quantitative basis for the start of the subsequent alkylization reaction stage.

[0023] After the alkylation reaction to produce the sterically hindered phenol product in a transient homogeneous reaction system, the process enters a depressurization separation stage, after the reaction is completed, the pressure of the reactor is reduced, and the alkylating agent as a temporary solvent is vaporized and escaped from the reaction system. The rapid release of high-pressure dissolved gas from the high-viscosity liquid can easily cause uncontrolled foaming and may cause the loss of ionic liquid catalyst entrained with the gas mist. To avoid this situation, in the depressurization process, an acoustic sensor is set outside the reactor to monitor the acoustic signals in the system in real time. When a narrow-band characteristic peak with rapid energy concentration in the 3 kHz to 30 kHz frequency band is identified, the acoustic feature is judged as a precursor of critical foaming of the system. Once the acoustic feature of critical foaming is identified, the control system adaptively adjusts the pressure reduction rate. The operation procedure is as follows: first, temporarily increase the pressure reduction rate to shock and destroy the foam structure being formed, then switch to a stable exhaust mode lower than the initial reduction rate, and after the acoustic signal returns to the background voiceprint without the critical foaming acoustic feature, return to the initial reduction rate to continue depressurization. With the continuous vaporization and escape of the alkylating agent, the solvent environment of the reaction system returns to the high-polarity ionic liquid environment, so that the originally dissolved non-polar sterically hindered phenol product spontaneously phase separates due to the reduced solubility, forming a product phase that is immiscible with the ionic liquid and has a lower density, and is layered on the ionic liquid phase. This self-layering process may be relatively slow due to the high viscosity of the ionic liquid. To speed up this process, the method can also include a physical disturbance step, that is, during the phase separation of the sterically hindered phenol product, one or more short-term high-pressure inert gas pulse injections are performed through the gas inlet pipeline of the reactor to the two-phase interface region or the ionic liquid phase below it. The local pressure wave and flow field shear generated by the pulse injection provide the energy for the coalescence of dispersed product microdroplets, thereby accelerating the macroscopic layering of the product phase. Finally, the product phase is separated by decantation or interfacial suction, and the sterically hindered phenol antioxidant is obtained, while the ionic liquid catalyst can be directly used for the next batch reaction.

[0024] To exclude the influence of external interference on acoustic signal monitoring and quantify the control logic, a corresponding calibration procedure can also be performed before the first run, which includes: first, under the static condition of only ionic liquid in the reactor, run all auxiliary equipment such as stirring, heating and valve alone, collect and establish a device background noise database covering the frequency band of 3kHz to 30kHz, and in the actual pressure reduction process, the signal processing module calls the adaptive noise cancellation algorithm to filter out the background soundprint irrelevant to the phase change in the kettle in real time; secondly, in the homogeneous system formed, the critical foaming is actively induced by increasing the exhaust rate, the average value of the narrowband characteristic peak energy as a precursor is recorded, and 80% of the average value is set as the acoustic threshold for triggering the control logic, at the same time, the control parameters are optimized in the induction experiment, and the duration of the short-term pressure increase is determined to be 0.5 seconds to 2 seconds, and the rate is 150% to 300% of the initial pressure reduction rate, and the subsequent stable exhaust mode is 30% to 70% of the initial pressure reduction rate, and these determined values are written into the process control system as curing parameters; it should be noted that the method of the present application can also use dynamic excitation response signals for online diagnosis of catalyst state, and the catalytic reaction process has nonlinear characteristics, when the signal carrying the fundamental excitation frequency passes through the system, the harmonic response components with frequency of integer multiple of the excitation frequency ω will be generated in the output pressure signal, the characteristics of these harmonic components can be used as fingerprint information representing the micro-activity state of the catalyst, therefore, the method can also include analyzing the harmonic response components with frequency of integer multiple of ω in the pressure signal, and determining the activity state of the ionic liquid catalyst online based on its characteristics, for example, when fresh catalyst is used, record its harmonic response characteristics as a reference, in subsequent cyclic use, the activity attenuation of the catalyst is quantified by tracking the drift of the harmonic characteristics, accordingly, the duration or reaction temperature of the alkylation reaction can also be adaptively adjusted based on the online determination of the catalyst activity state to compensate for the change of catalyst activity, in addition, the fundamental response characteristics of the pressure signal can also be used to identify abnormal working conditions, when the gain G and the phase delay P lag When the trajectory in the two-dimensional state space deviates from the calibration area of the reference physical dissolution process, it can be used to identify the occurrence of abnormal exothermic side reactions, thereby providing a monitoring means for safe operation of the system.

[0025] In some embodiments, the ionic liquid is an acidic proton-functionalized ionic liquid, which plays a dual technical role of catalyst and high-polarity solvent in the reaction system, the phenolic reactant is the reaction substrate, the gaseous alkene as an alkylating agent, after being pressurized and dissolved in the reaction system, in addition to being a reactant, also serves as a temporary non-polar cosolvent, which reduces the polarity and viscosity of the entire system, and promotes the formation of a transient homogeneous reaction system; the molar ratio of the phenolic reactant to the alkylating agent is set to be in the range of 1:1.1 to 1:3.0, when the molar ratio is lower than 1:1.1, the stoichiometric amount of the alkylating agent in the system is insufficient, resulting in the conversion rate of the phenolic reactant cannot reach more than 99%, increasing the purification load of the unreacted raw materials in the subsequent product separation step; when the molar ratio is higher than 1:3.0, the excess alkylating agent no longer has a significant effect on the selectivity of the reaction, but in order to form a homogeneous system, a higher system pressure needs to be applied, which increases the manufacturing cost and operating energy consumption of the equipment; at the same time, the excess concentration of the alkene also increases the probability of its own oligomerization and other side reactions, which will cover the active sites of the ionic liquid catalyst, resulting in a faster deactivation rate of the catalyst, therefore, the molar ratio range of 1:1.1 to 1:3.0 is determined after weighing the three technical indicators of the conversion rate of the phenolic reactant, equipment and energy consumption cost, and catalyst service life; in the cluster deployment scenario including multiple pressure reactors, a central process control system is set up for collaborative management of the cluster, when a total production task is assigned, the central process control system will dynamically allocate the total feed amount of the alkylating agent according to the difference between the non-dimensional parameter R phase value and the set threshold value R crit value of each independent reactor pressure sensor in real time, the allocation logic makes the reactor with a lower R phase value, which is further away from the homogeneous state, obtain a higher proportion of the feed rate in the next control cycle, while the reactor that approaches or has reached the R crit threshold value, the feed rate is correspondingly reduced, this procedure replaces the static strategy of uniform feed rate for all reactors, to deal with the problem of inconsistent homogenization process caused by the slight differences in initial state, heat transfer efficiency or catalyst activity of each reactor.

[0026] The harmonic response component analysis procedure for online determination of the activity state of the ionic liquid catalyst in the method of the present application also has a time effectiveness guarantee and reconstruction mechanism inside, the control system records the reaction time Δt adjusted to compensate for the catalyst activity decay index D in each production batch; when the Δt values of three consecutive production batches all exceed 30% of the standard reaction time set based on the initial active catalyst, the system will automatically trigger a reference harmonic fingerprint H initialre-calibration procedure, which requires a new set of highly active ionic liquid catalyst to be temporarily adopted in the next batch, and the reference harmonic fingerprint to be re-collected and calculated during the stable reaction phase of this batch, in order to update the H initial value stored in the control system, this mechanism is used to correct the reference drift caused by the difference between catalyst batches or irreversible physicochemical changes; in order to deal with the situation where the acoustic sensor signal is interrupted due to failure, the process control system also integrates an alternative rate and pressure reduction implementation; when the system detects that the acoustic sensor signal is lost or its signal-to-noise ratio is lower than the preset threshold during the pressure reduction phase, the control logic will automatically switch from the acoustic signal guided mode to a preset time-based gradient pressure reduction mode; in this mode, the system pressure will be reduced according to a programmed curve consisting of three stages, which does not rely on any real-time feedback: in the first stage, within the initial 30 minutes, the pressure is slowly reduced at 50% of the initial pressure reduction rate; in the second stage, within the next 15 minutes, the pressure reduction rate is increased to 150% of the initial pressure reduction rate; in the third stage, the pressure is reduced at 70% of the initial pressure reduction rate until it reaches atmospheric pressure. The rate curve of this alternative mode is determined through experiments during the process development stage, and it is a conservative pressure reduction strategy that can effectively suppress uncontrolled foaming in most cases, which is used to ensure the continuity and safety of the process when the core sensor fails.

[0027] Example 1: In an industrial application for producing high molecular weight, high purity steric phenolic antioxidants, the initial mixture of ionic liquid catalyst and phenolic reactants has high viscosity, and the target product is sensitive to reaction temperature. When using traditional gas-liquid bubbling stirring and increasing temperature to enhance mass transfer, it will be accompanied by side reactions such as olefin oligomerization or etherification, which will affect product yield and may cause catalyst deactivation, which constitutes a technical constraint between improving space-time yield and maintaining product purity and catalyst life. The technical solution of the present invention is applied to this scenario, the high viscosity ionic liquid and phenolic reactants are added to the pressure reactor, and isobutene is introduced as an alkylating agent. By continuously pressurizing and maintaining the temperature at the near-critical point of isobutene, until the dimensionless parameter R phase reached the preset threshold R crit , the system formed a low-viscosity transient homogeneous reaction system, in which isobutene molecules and phenolic reactant molecules obtained mass transfer-free contact in the ionic liquid catalyst environment, and the alkylation reaction was carried out rapidly at a much lower temperature than the traditional process, thereby avoiding the high-temperature induced side reaction conditions.

[0028] After the reaction is completed, the system enters the depressurization stage. At this time, due to the dissolution of a large amount of isobutene in the homogeneous system in the early stage, there is a high risk of foaming in the depressurization process. The acoustic sensor set outside the reactor monitored the appearance of narrow-band characteristic peaks in the acoustic signal in the early stage of depressurization, which represented critical foaming. The control system immediately executed the adaptive control procedure of short and rapid depressurization and subsequent stable and slow exhaust to inhibit the formation of violent foaming. The smooth progress of this process created non-emulsified initial conditions for the subsequent spontaneous phase separation of the product, so that the potential process risk generated by the high reactant load in the homogeneous reaction stage was controlled by the acoustic-guided depressurization stage. With the smooth escape of isobutene, the high molecular weight hindered phenol product was phase separated from the ionic liquid to form dispersed microdroplets, but due to the viscosity of the system, the macroscopic layering process was relatively slow. At this time, three short high-pressure nitrogen gas pulses were injected below the two-phase interface through the gas inlet pipeline, and the local pressure and flow field disturbance generated by the pulses accelerated the coalescence of the product microdroplets. The acoustic-guided smooth depressurization in the previous step avoided the close emulsification caused by violent bubbling, providing a premise for the efficient coalescence of the gas pulse injection step. Finally, the reactor showed a clear two-phase stratification, with the upper layer being a high-purity target hindered phenol product phase and the lower layer being an ionic liquid catalyst phase that could be directly used for the next batch production without obvious contamination. The reaction selectivity and catalyst recovery rate of the entire production batch were improved compared with the traditional stirred tank process.

[0029] Example 2: To objectively verify the technical effects of the method of the present application in terms of reaction efficiency and catalyst recovery compared with the traditional gas-liquid heterogeneous reaction method, a set of comparative tests were conducted. The test platform was a 5L volume pressure reactor equipped with a pressure sensor with a pressure range of 0-20MPa, a jacket heating system with a temperature control accuracy of ±0.5, and an acoustic sensor with a frequency range covering 3-30kHz, which was fixed to the outside of the reactor body. The quantitative analysis of product components used gas chromatography, and the residual amount of ionic liquid in the product phase was determined by measuring the concentration of key elements by inductively coupled plasma mass spectrometry. The test set up one control group and one test group using the method of the present application. The control group simulated the traditional gas-liquid heterogeneous stirring reaction method, and the same amount of ionic liquid catalyst and 2,4-di-tert-butyl phenol as the test group were added to the reactor. Under the conditions of normal pressure and continuous mechanical stirring (500rpm), the reaction system was heated to 120, and isobutene gas was introduced at a fixed flow rate to react for 5h to obtain a high conversion rate. The test group followed the technical solution of the present application, and after adding the same amount of materials into the reactor, the reactor was sealed and isobutene was pumped into it at a temperature of 80, and the pressure was continuously increased to 15MPa. After confirming that the system had formed a transient homogeneous reaction system through the online phase identification procedure based on dynamic excitation response, the reaction was maintained for 2h. After the reaction was completed, the acoustic signal guided pressure reduction program was started, and after the pressure was reduced to normal pressure and the product phase was preliminarily separated, three nitrogen gas pulses with a pressure of 5MPa and a duration of 100ms were injected below the two-phase interface. In the two groups of tests, the key process parameters and the final results were recorded and analyzed, and Table 1 is a comparison of the core data of the two groups of tests.

[0030] Table 1: Comparison of key performance data of test group and control group.

[0031] Test grouping Reaction temperature (°C) Reaction pressure (MPa) Reaction time (h) Conversion of phenolic reactant (%) Selectivity to target product (%) Catalyst residue in product phase (ppm) Macroscopic delamination time (min) Control group 120 0.1 5 85.2 76.5 550 >60 Inventive group 80 15 2 99.1 98.6 <50 5 Referring to Table 1, the data comparison shows that the experimental group using the method of this invention achieved a phenolic reactant conversion rate of 99.1%, higher than the 85.2% of the control group, and the reaction time was shortened by 60%. Simultaneously, the target product selectivity of the experimental group was 98.6%, higher than the 76.5% selectivity of the control group caused by side reactions due to higher reaction temperatures. This data confirms that by constructing a transient homogeneous reaction system, the reaction can be intrinsically kinetic controlled at lower temperatures, thereby increasing the reaction rate while suppressing the formation of by-products. Furthermore, regarding catalyst recovery and product separation efficiency, the catalyst in the product phase of the experimental group... The residual amount was less than 50 ppm, far lower than the 550 ppm residual amount of the control group caused by partial emulsification due to vigorous stirring and gas-liquid mass transfer. This result verifies the role of the acoustic signal-guided rate-controlled pressure reduction process in suppressing mist entrainment. In addition, after nitrogen pulse injection, the experimental group formed a clear macroscopic two-phase interface within 5 minutes, while the control group still had an emulsion layer after standing for 60 minutes. This phenomenon indicates that the high-pressure inert gas pulse injection step has the effect of accelerating phase separation of high viscosity systems. The experimental results confirm the performance of the method of the present invention in improving reaction efficiency, product purity and catalyst recovery rate.

[0032] Example 3: This example combines Figures 1 to 3 A method for preparing sterically hindered phenolic antioxidants using ionic liquid catalysis is described, such as... Figure 1 As shown, the process begins by introducing two initial materials—an ionic liquid, phenolic reactants, and a gaseous olefin alkylating agent—into the reaction system. First, a transient homogeneous system construction stage is initiated. By pressurizing the gaseous olefin, it dissolves in the reactants to form a single liquid phase, thus eliminating physical mass transfer limitations. The completion of this stage is determined by the dynamic excitation response online diagnostic module based on the logic of identifying the homogeneous state using gain and phase delay according to the pressure response. Subsequently, the system enters the intrinsically kinetic-controlled alkylation reaction stage, reacting efficiently in the homogeneous system to generate sterically hindered phenolic products. During this stage, the dynamic excitation response online diagnostic module also adaptively adjusts the reaction parameters based on the logic of determining the catalyst activity state online using harmonic components. The reaction concludes with... After the initial phase, the system enters an acoustically guided rate-controlled depressurization stage. By reducing the pressure, the alkylating reagent is vaporized and escaped, triggering product separation. This depressurization process is guided by a critical foaming acoustic feature recognition module. This module monitors the acoustic signal in real time, identifies critical foaming features, and adaptively adjusts the depressurization rate to maintain process stability. As the alkylating reagent escapes, the system enters the product self-separation stage, forming a product phase that is immiscible with the ionic liquid. To accelerate this process, a high-pressure inert gas pulse injection step can be selectively introduced. The local pressure and flow field disturbance generated by the injection are used to accelerate the aggregation of the product phase. Ultimately, this process produces two substances: the target sterically hindered phenolic antioxidant product and a recyclable ionic liquid catalyst recovery product.

[0033] like Figure 2 As shown in the figure, the horizontal axis represents frequency in kHz, and the vertical axis represents signal strength in dB. The figure shows the acoustic signal characteristic curves under three different operating conditions. The solid line marked with circular data points represents the normal step-down state, where the signal strength is generally low and has no obvious peak in the frequency band from 3kHz to 30kHz. The dashed line marked with triangular data points represents the critical pre-bubbling state, where the signal strength is generally increased and a narrow band characteristic peak with concentrated energy appears at about 11kHz. The dotted line marked with square data points represents the bubbling state, where the signal strength is further amplified compared to the pre-bubbling state, forming a sharper and higher intensity characteristic peak.

[0034] like Figure 3 As shown, the system uses a pressure reactor as its core physical device. The reactor is equipped with acoustic and pressure sensors and is connected to an external jacketed heating system and gas inlet / pulse pipeline. The sensors transmit the collected acoustic and pressure signals to the process control system in real time. The system contains four core logic modules: a data acquisition and signal processing module preprocesses the raw signals; a dynamic excitation response analysis module is responsible for phase identification and catalyst activity diagnosis; an acoustic feature identification and control logic module performs critical foaming precursor identification and adaptive adjustment of the depressurization rate; and a safety interlock and alarm module is responsible for monitoring abnormal operating conditions and executing safety procedures. Based on the analysis and decisions of the internal modules, the process control system issues control commands to the jacketed heating system and gas inlet / pulse pipeline, thus forming a closed-loop control. The operation status of the entire system is centrally managed and monitored by the operation and monitoring terminal central control room.

[0035] Example 4: When applying the method of the present invention to a new production equipment or using a new ionic liquid catalyst formulation, an offline calibration procedure can be performed to determine some core control parameters. This process aims to determine the dimensionless parameter threshold R used to determine the formation of a transient homogeneous reaction system for a specific system. crit The calibration process involves the addition of an acoustic signal characteristic threshold for triggering critical foaming control, and the calibration is performed in a pressure reactor of the same specifications as described above. The reactor is also equipped with a pressure sight glass for observing the internal fluid state. First, the ionic liquid and phenolic reactants used in the production batch are added to the reactor. The injection program for the alkylating agent, isobutylene, is then initiated, with its introduction rate superimposed with a sinusoidal fluctuation of a preset frequency ω. Simultaneously, the control system begins to calculate and record the dimensionless parameter R in real time. phase The dynamic changes of are calculated as defined in the specific implementation method.

[0036] During the process of continuously injecting isobutene and slowly increasing the pressure, the phase state of the fluid in the reactor was continuously observed through the pressure gage. When the last bubble in the reactor disappeared and the whole system appeared as a single, clear liquid phase, the calculated R phase value at this moment was recorded as R obs . After the system was depressurized and emptied, the aforementioned process of increasing the pressure to a homogeneous phase was repeated three times to obtain a set of R obs values. The threshold value R crit for production control was set as 95% of the average value of the set of observed R crit values. After the calibration of R crit , the calibration of the threshold value of the acoustic characteristics was continued using the homogeneous phase system. The pressure of the reactor was stabilized above the pressure at the homogeneous phase point, the pressure was decreased through the exhaust valve at an initial rate, and the acoustic signals in the reactor were continuously collected using an external acoustic sensor. The rate of pressure decrease was gradually increased at a fixed gradient until the appearance of persistent and rising foam on the liquid surface in the reactor was observed through the gage. Before the appearance of the foam, a narrow-band characteristic peak in the frequency band of 3 kHz to 30 kHz was stably observed in the spectral analysis diagram of the acoustic signals. The energy of the peak value of the precursor signal was recorded. The process of inducing foaming and signal collection was repeated several times. The average value of the characteristic peak energy stably observed as a precursor of foaming was taken as the critical foaming acoustic characteristic reference of the specific system, and 80% of the reference value was set as the trigger threshold of the acoustic regulation logic in the production process. Through the above calibration procedure, the control parameters originally used as a general range were determined as a set of quantitative operation data corresponding to a specific device and material system, thereby providing a determined process procedure for subsequent production.

[0037] Example 5: In order to quantify and compensate for the changes in the catalytic activity of the ionic liquid catalyst during long-term cyclic use, a reference harmonic fingerprint characterizing the initial activity of the catalyst needs to be established. The establishment process of the reference harmonic fingerprint is performed in an initial production batch using a brand-new ionic liquid catalyst with high activity. When the system reaches a stable transient homogeneous reaction system confirmed by the threshold R crit , the pressure response signal is continuously collected during the reaction stage. The gain G1 and the phase Φ1 of the fundamental frequency ω response component, and the gain G2 and the phase Φ2 of the second harmonic 2ω response component are extracted through the signal processing module. Then, a set of dimensionless harmonic parameters for characterizing the initial activity state is calculated and recorded. The set of parameters constitutes a reference harmonic fingerprint H initial =[G2 / G1, Φ2-2Φ1] in the form of a two-dimensional vector, which is stored in the control system as a reference for comparison of the activity of the catalyst in subsequent batches.

[0038] In the subsequent continuous production process, the control system calculates the current harmonic fingerprint H current at the same reaction stage of each batch in real time according to the foregoing manner, and obtains a catalyst activity attenuation index D in the form of a scalar by calculating the Euclidean distance between H initial and the reference harmonic fingerprint H initial , which is used to adaptively adjust the reaction time of the batch to compensate for the change in reaction rate caused by the decrease in catalyst activity, and the adjustment amount Δt of the reaction time and the attenuation index D follow a preset linear relationship Δt=k×D, wherein the proportionality coefficient k is a parameter preset in the control program by experimental calibration in the process development stage, and this procedure enables catalysts with different activities to achieve consistent final product conversion rates by adjusting the reaction time in different batches.

[0039] In the application of the method of the present application to a new product system with different physical properties, a set of procedures for determining separation process parameters and verifying safety response logic can be performed. After a simulated reaction is completed, the product microdroplets are dispersed in a two-phase system formed in the ionic liquid phase, and gradient experiments are performed on the three parameters of pressure, duration, and pulse number of high-pressure inert gas pulse injection. The macroscopic layering time and the amount of catalyst residue in the product phase are used as evaluation indicators. This experimental data is used to determine a set of process parameter combinations that can obtain a shorter macroscopic layering time and do not cause an increase in catalyst residue under this system, and this parameter combination is used as the set value for subsequent production.

[0040] At the same time, in the dynamic excitation response analysis module of the system, according to the characteristic region calibrated by the reference physical dissolution process, a chemical alarm area in the gain-phase delay two-dimensional state space is set, and the control system is configured to automatically trigger a safety interlock when the dynamic response characteristic parameter trajectory enters the chemical alarm area and the duration exceeds a time threshold set to filter transient signal interference. The response action of the safety interlock is to immediately stop the introduction of the alkylating agent, simultaneously start the emergency cooling program of the reactor jacket, and send an alarm signal to the central control room. In this way, a definite response mechanism is provided for the process method when facing potential chemical abnormal conditions.

[0041] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application.

[0042] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application.

Claims

1. A process for the catalytic preparation of sterically hindered phenolic antioxidants from ionic liquids, characterized in that, The method comprises the following steps: Step S1, in a pressure reactor, an ionic liquid and a phenolic reactant are added, followed by introduction of an alkylating agent, the alkylating agent being a gaseous alkene, and the pressure of the reactor is increased until a transient homogeneous reaction system is formed, which is composed of the ionic liquid, the phenolic reactant and the alkylating agent; Step S2, an alkylation reaction is carried out in the transient homogeneous reaction system to generate a sterically hindered phenol product; Step S3, after the reaction is completed, the pressure of the reactor is reduced to make the alkylating agent gasify and escape from the transient homogeneous reaction system, and in the process of reducing the pressure of the reactor, an acoustic sensor arranged outside the reactor is used to monitor the acoustic signal in the reaction system in real time; The acoustic signal is used to identify the acoustic characteristics of critical foaming of the system, and when the acoustic characteristics of critical foaming are identified, the reduction rate of the pressure is adaptively adjusted; Step S4, as the alkylating agent gasifies and escapes, the sterically hindered phenol product spontaneously phase separates from the ionic liquid to form a product phase that is immiscible with the ionic liquid, and the product phase is separated.

2. The process for the preparation of hindered phenolic antioxidant catalyzed by ionic liquid as claimed in claim 1 wherein, In the process of phase separation of the sterically hindered phenol product from the ionic liquid, one or more short-term high-pressure inert gas pulse injections are carried out through a gas inlet pipeline into the ionic liquid phase at or below the two-phase interface region, and local pressure and flow field disturbance generated by the pulse injection are used to accelerate the coalescence and macroscopic layering of the product phase.

3. The process for the preparation of hindered phenolic antioxidant catalyzed by ionic liquid as claimed in claim 1 wherein, The pressurization in step S1 is to make the working condition of the alkylating agent be in a supercritical state or a near-critical state, wherein the near-critical state is defined as the pressure being in the interval of 0.8 times to 1.2 times of the critical pressure of the alkylating agent, and the temperature being in the interval of 0.8 times to 1.2 times of the critical temperature of the alkylating agent.

4. The process for the preparation of hindered phenolic antioxidant catalyzed by ionic liquid as claimed in claim 1 wherein, The alkylating agent is an alkene containing 2 to 4 carbon atoms.

5. The process for the preparation of hindered phenolic antioxidant catalyzed by ionic liquid as claimed in claim 1 wherein, The acoustic characteristics of critical foaming in step S3 are defined as narrowband characteristic peaks with rapid energy concentration appearing in the acoustic signal in the frequency band of 3 kHz to 30 kHz.

6. The process for the preparation of hindered phenolic antioxidant catalyzed by ionic liquid as claimed in claim 1 wherein, The adaptive adjustment of the reduction rate of the pressure in step S3 includes: when the acoustic characteristics of critical foaming are identified, the reduction rate of the pressure is temporarily increased, and then a stable exhaust mode lower than the initial reduction rate is switched to, and after the acoustic signal returns to the background voiceprint without the acoustic characteristics of critical foaming, the initial reduction rate is restored.

7. The process for the preparation of hindered phenolic antioxidant catalyzed by ionic liquid as claimed in claim 1 wherein, In step S1, the alkylating agent is introduced at a rate superimposed on a sinusoidal fluctuation of frequency ω set in the control program. Furthermore, the formation of the transient homogeneous reaction system is determined by a dimensionless parameter R characterizing the phase state of the system. phase The threshold R set in the control program is reached. crit To determine, where R phase R is defined by the following formula: phase =G / P lag Where G is the gain of the response component with the same frequency ω in the pressure signal inside the reactor, and P... lag This is the phase delay of the response component in the pressure signal that has the same frequency as frequency ω.

8. The process for the preparation of hindered phenolic antioxidant catalyzed by ionic liquid according to claim 7, characterized in that, Further comprising that the trajectory of the gain G and the phase delay Φ in the two-dimensional state space composed of the gain and the phase delay deviates from the characteristic region calibrated based on the reference physical dissolution process.

9. The process for the preparation of hindered phenolic antioxidant catalyzed by ionic liquid as claimed in claim 7 wherein, Further comprising: analyzing harmonic response components with frequencies being integer multiples of the frequency ω in the pressure signal; and determining the activity state of the ionic liquid catalyst online based on characteristics of the harmonic response components.

10. The process for the preparation of hindered phenolic antioxidant catalyzed by ionic liquid as claimed in claim 9 wherein, Further comprising: Based on the activity state of the ionic liquid catalyst determined online, the duration or the reaction temperature of the alkylation reaction in step S2 is adaptively adjusted.

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