Aniline oxidation reaction process and thermal safety risk assessment method

Abstract

The invention discloses an aniline oxidation reaction process which comprises the following steps: adding a solvent, aniline and a catalyst into a reaction kettle, stirring and dissolving, then adding an oxidizing agent, keeping the temperature and reacting for a period of time at a first temperature after charging, heating to a second temperature lower than 27 DEG C, and continuously reacting, wherein H2O2 is adopted as the oxidizing agent; na2WO4. 2H2O is adopted as the catalyst; dichloromethane is adopted as the solvent, and the invention further provides a safety risk assessment method for the aniline oxidation reaction process, and the safety risk assessment method comprises the following steps: respectively carrying out a material thermal stability test, a reaction calorimetry test of an oxidation reaction and a secondary decomposition test of an oxidation reaction completion liquid, and then carrying out safety risk assessment of the oxidation reaction. Therefore, the invention provides an aniline oxidation reaction process capable of realizing safe industrial production, and correspondingly provides a thermal safety risk assessment method for reliability assessment of safe production of the aniline oxidation reaction process.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production, and in particular to an aniline oxidation reaction process and a thermal safety risk assessment method. Background Art

[0002] While the chemical industry brings convenience to people, it also brings huge safety hazards. The raw materials and products involved in the production, storage, transportation, use and waste disposal processes are often flammable, explosive or toxic, harmful, corrosive and other characteristics. If they are misused, abused or improperly disposed, they are very likely to cause accidents such as combustion, explosion, poisoning, etc. Therefore, it is becoming increasingly necessary to conduct thermal safety risk assessment before scaling up production.

[0003] Although the oxidation process has been included in the high-risk process, the current thermal hazard assessment method for the oxidation process is slightly insufficient, and the reaction has the risk of material impact or even explosion in actual production. Based on this situation, many domestic users choose to use hydrogen peroxide as an oxidant and sodium tungstate as a catalyst (see "Organic Chemistry", 2004, Vol. 24, 319-321 and "Chemical Reagents", 2020, Vol. 42, 1509-1514). Since hydrogen peroxide is cheap and environmentally friendly, sodium tungstate can catalyze the oxidation reaction with better results and improve the yield. Although this new method is green, economical and efficient, it still has huge safety hazards. Due to the lack of domestic analysis and research under this system, the reaction may lose control in the process production, which is easy to cause heat accumulation or accidental release, and it is very easy to cause major production safety accidents. Therefore, it is extremely important for the chemical industry to explore and master more thermal safety risk assessment methods based on this oxidation reaction, and to identify and reduce the risks of the materials and reaction exothermic degassing processes involved before process production.

[0004] Chinese patent document CN115340475A discloses a method for preparing 1-diphenyldiazene oxide or its derivatives, wherein the raw material aniline is synthesized by catalytic oxidation in a system of zirconium hydroxide catalyst, hydrogen peroxide oxidation agent and solvents such as methanol, ethanol and acetonitrile, but the zirconium hydroxide used as the catalyst has a low reaction temperature of 30°C and a high reaction yield. However, the hydrogen peroxide used has obvious production safety risks, is not suitable for large-scale process production, and still has huge safety hazards. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, in order to solve the problems of high safety risk and unsuitability of process production of the existing aniline oxidation reaction, the present invention provides an aniline oxidation reaction process that can be safely produced industrially, and correspondingly provides a thermal safety risk assessment method to conduct a reliability assessment of safe production of the aniline oxidation reaction process.

[0006] To achieve one of the above purposes, a process for aniline oxidation reaction is provided, and the present invention adopts the following technical scheme:

[0007] An aniline oxidation reaction process comprises the following steps: adding a solvent, aniline and a catalyst into a reaction kettle, stirring and dissolving, then adding an oxidant, keeping the temperature at a first temperature for a period of time after the addition, heating to a second temperature and continuing the reaction; the second temperature is lower than 27°C.

[0008] Preferably, the oxidant is H2O2; the catalyst is Na2WO4.2H2O; and the solvent is dichloromethane.

[0009] Furthermore, the dropwise addition temperature of the solvent, aniline, catalyst and oxidant is controlled to be -5 to 5°C. After the addition is completed, the mixture is kept at -5 to 5°C for 0.25 to 1 hour.

[0010] Furthermore, the temperature is controlled to rise to 20-25° C. and kept warm for 3-7 hours. Furthermore, the volume of the solvent is 20 times the mass of the solute.

[0011] Furthermore, the mass ratio of the solvent to aniline is (2-25):1; the molar ratio of H2O2 to aniline is 2:1; and the molar ratio of the catalyst Na2WO4.2H2O to aniline is 0.1:1.

[0012] Furthermore, during the reaction process, the reaction system including the solvent, aniline, catalyst and oxidant is simultaneously subjected to evaporative cooling or decompression treatment.

[0013] A second object of the present invention is to provide a thermal safety risk assessment method for an aniline oxidation reaction, which is used to conduct a safety risk assessment on the aniline oxidation reaction process, including conducting a material thermal stability test, a reaction calorimetry test on the oxidation reaction, and a secondary decomposition test on the oxidation reaction completed liquid, and then conducting a safety risk assessment on the oxidation reaction.

[0014] Preferably, the reaction calorimetry test uses a fully automated chemical synthesis reactor to perform the following steps:

[0015] a. First, add solvent, aniline and catalyst to feed;

[0016] b. Lower the temperature to -5 to 5°C;

[0017] c. Perform stable calibration;

[0018] d. adding oxidant dropwise;

[0019] e. Raise the temperature to 20-25°C for reaction;

[0020] f. Keep the reaction at 20-25℃;

[0021] g. Stable calibration;

[0022] h.Data calculation and analysis;

[0023] Thus, the charging curve, the heat released curve, the reaction temperature curve and the jacket temperature curve in the oxidation reaction process are obtained;

[0024] The secondary decomposition test of the oxidation reaction completion liquid is to use an ES-ARC adiabatic accelerating calorimeter to perform a secondary decomposition test on the oxidation reaction completion liquid to obtain: a time-temperature-pressure curve of the exothermic section of the HWS mode test of the oxidation reaction completion liquid ARC, and a temperature-temperature rise rate-pressure rise rate curve of the exothermic section of the HWS mode test of the oxidation reaction completion liquid ARC;

[0025] The oxidation reaction safety risk assessment includes material decomposition heat assessment, severity assessment, possibility assessment, risk matrix assessment, and reaction process hazard assessment.

[0026] Further, the oxidation reaction safety risk assessment of the aniline oxidation reaction process is:

[0027] Material decomposition heat assessment: According to the thermal stability test results of the oxidation reaction completed liquid, the decomposition heat of the oxidation reaction completed liquid is <400J / g, which is assessed as Level 1, with potential explosion hazard;

[0028] Severity assessment: According to the adiabatic thermal test results of the oxidation reaction, the adiabatic temperature rise △Tad <50K, and the severity assessment of the runaway reaction of the oxidation reaction is level 1;

[0029] Possibility assessment: The possibility of uncontrolled reaction is assessed as level 1, and uncontrolled reaction is less likely to occur;

[0030] Risk matrix assessment: Based on the results of severity assessment and likelihood assessment, the risk matrix assessment is level 1, and level 1 risk is an acceptable risk;

[0031] Reaction process hazard assessment: The reaction process hazard assessment at the actual feeding rate is level 3.

[0032] Compared with the traditional technology, the present invention has the following beneficial effects:

[0033] 1) In common oxidation reactions, when H2O2 is used as an oxidant to participate in the reaction, most solvents react with it, which will lead to a decrease in the reaction yield. More importantly, when the solvent reacts with H2O2, a large amount of heat will be generated, which will bring unnecessary thermal risks to the reaction. The present invention effectively solves the problem of such reactions by mixing DCM solvent with H2O2.

[0034] 2) The reaction heat of the oxidation reaction is usually large, which leads to great risks in factory production. The present invention adopts a 20V solvent system to react while satisfying the balance between reaction efficiency and stability, thereby improving the thermal stability of the solution, greatly diluting the reaction heat and decomposition heat of the material, and greatly improving the safety of the process.

[0035] 3) The present invention adopts a thermal safety risk assessment method based on the process conditions of the aniline oxidation reaction to conduct an effective safety assessment, and obtains a reliable basis for clear risk classification. According to the assessment results, effective technical support and guarantee can be provided for the thermal safety of the production process of the oxidation process and the prevention and control of production safety accidents, which is of great significance to the safe production and major accident prevention in the chemical industry.

[0036] 4) The aniline oxidation reaction conditions of the present invention are excellent, and its products and by-products are clearly identified, which greatly improves the risk elimination of dangerous substances and further improves its safety in specific operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0038] Figure 1 This is the DSC test curve of aniline.

[0039] Figure 2 This is the DSC test curve of H2O2 solution.

[0040] Figure 3 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution.

[0041] Figure 4 This is the DSC test diagram of H2O2 and Na2WO4.2H2O solution in 5V DCM.

[0042] Figure 5 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V CH3OH.

[0043] Figure 6 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V 1,4-dioxane.

[0044] Figure 7 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V DMSO.

[0045] Figure 8 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V EA.

[0046] Fig. 9 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V EtOH.

[0047] Fig.10 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V H2O.

[0048] Fig.11 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V IPA.

[0049] Fig.12 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V THF.

[0050] Fig.13 This is a DSC test curve diagram of aniline oxidation post reaction mixture (2V DCM), wherein the oxidation reaction solution includes aniline, oxidant H2O2, catalyst Na2WO4.2H2O and solvent DCM.

[0051] Fig.14 This is a DSC test curve diagram of aniline oxidation post reaction mixture (10V DCM), wherein the oxidation reaction solution includes aniline, oxidant H2O2, catalyst Na2WO4.2H2O and solvent DCM.

[0052] Fig.15 This is a DSC test curve diagram of aniline oxidation post reaction mixture (20V DCM), wherein the oxidation reaction solution includes aniline, oxidant H2O2, catalyst Na2WO4.2H2O and solvent DCM.

[0053] Fig.16 This is the DSC test curve of compound 1 azobenzene oxide.

[0054] Fig.17 This is the DSC test curve of compound 2 nitrobenzene.

[0055] Fig.18 This is the DSC test curve of compound 3 nitrosobenzene.

[0056] Fig.19 These are the charging curve (Mr), heat release curve (qr_hf), reaction temperature curve (Tr), and jacket temperature curve (Tj) of the oxidation reaction process.

[0057] Fig. 20 The time-temperature-pressure curve of the exothermic phase of the ARC HWS mode test for the oxidation reaction completion liquid.

[0058] Fig.21 This is a temperature-temperature rise rate-pressure rise rate curve of the exothermic section of the ARC HWS mode test of the oxidation reaction completion liquid.

[0059] Fig. 22 This is the hydrogen spectrum of compound 1 azobenzene oxide.

[0060] Fig.23 This is the hydrogen spectrum of compound 2 nitrobenzene.

[0061] Fig.24 This is the hydrogen spectrum of compound 3 nitrosobenzene. Fig.25 The present invention is a reaction flow chart of the calorimetric test using a fully automatic chemical synthesis reactor. DETAILED DESCRIPTION

[0062] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer. Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art.

[0063] The H2O2 used in the present invention is 30 wt% H2O2 available on the market. The materials used as raw materials in the examples are all purchased.

[0064] According to a preferred embodiment of the present invention, an aniline oxidation reaction process comprises the following steps: adding a solvent, aniline and a catalyst into a reaction kettle, stirring and dissolving, then adding an oxidant, and after the addition is completed, keeping the temperature at a first temperature for a period of time, heating to a second temperature and continuing the reaction: the second temperature is lower than 27°C.

[0065] First, for the aniline oxidation reaction system, during the material addition and waiting process, the following risks may exist: first, hydrogen peroxide decomposes and releases heat at a very low temperature under the catalytic action of sodium tungstate; second, the oxidation reaction itself is an exothermic reaction, and the heat release of the reaction will accelerate its decomposition. Therefore, in order to avoid reaction rush and loss of control, based on the aniline oxidation reaction process of the present invention, the temperature is kept at a lower first temperature for a period of time to avoid initial decomposition; and the temperature of the entire reaction system is controlled below 27°C, which can avoid the risk of H2O2 decomposition, heat release and rush.

[0066] The oxidant is selected from any one of H2O2, PCC, NaClO, MnO2, and DMSO. The catalyst is preferably Na2WO4.2H2O. The solvent is selected from any one of 1,4-dioxane, CH3OH, DMSO, EA, EtOH, IPA, THF, H2O, or dichloromethane.

[0067] The oxidant is H2O2; the selected hydrogen peroxide system has the characteristics of being green, environmentally friendly, and generally stable, which are recognized in the industry. The catalyst is Na2WO4.2H2O; sodium tungstate is used as a catalyst to improve the reaction rate and yield in the process. Although the reaction system of hydrogen peroxide and sodium tungstate has the above technical advantages, hydrogen peroxide itself will decompose rapidly under the conditions of acid, alkali, high temperature, catalyst, etc., releasing a large amount of heat and posing the risk of thermal explosion. In recent years, there have been numerous reports on this dangerous reaction. While catalysts such as sodium tungstate bring convenience, they also cause risks such as low initial decomposition temperature. However, there are very few risk assessments for aniline oxidation reactions in the industry, so it is urgent to establish a safe production process based on the hydrogen peroxide / sodium tungstate system.

[0068] In order to reduce the risk of reaction, the present invention controls the temperature of adding solvent, aniline, catalyst and oxidant to -5 to 5°C, and after adding, the temperature is kept at -5 to 5°C for a period of time, such as 0.25 to 1 hour; then the temperature is controlled to rise to 20 to 25°C and the reaction is allowed to proceed for 3 to 7 hours until the reaction is completed. Combined with the DSC test analysis and verification below, by Figure 2 It can be seen that the exothermic peak of 30% hydrogen peroxide starts at 35.86℃ and ends at 113.63℃, releasing 476.64J / g of heat. Figure 3It can be seen that the exothermic peaks of H2O2 and Na2WO4.2H2O solutions start from 27.62°C and end at 87.89°C, with a heat release of 262.88 J / g. It can be seen that when the H2O2 and Na2WO4.2H2O systems exceed 27°C, there is a risk of decomposition and exothermic release (since the data itself is also affected by factors such as the sensitivity of the instrument and the heating rate, the initial decomposition temperature is very likely to be lower). At the same time, it was found during the experiment that hydrogen peroxide has the risk of material impact at around 50°C. Hydrogen peroxide, an oxidant, is incompatible with many solvents, reacts in the process, causes unnecessary heat, and brings unnecessary thermal risks. Therefore, the solvent of the present invention preferably uses dichloromethane, which can avoid the interference of the reaction between the solvent and hydrogen peroxide to the greatest extent, and further reduce the risk of decomposition. At the same time, hydrogen peroxide itself will decompose at a very low temperature, and sodium tungstate will reduce its initial decomposition temperature, so the present invention provides suitable temperature conditions. Under the above conditions, in order to reduce the thermal safety risk to a minimum, the present invention also provides a solvent volume that is more conducive to production. When the solvent volume value is 20 times the solute mass value (hereinafter recorded as 20V), the safety risk is relatively low, and it can be safely scaled up in the laboratory and factory. Therefore, based on this embodiment, the reduction of the greater risk of process production is achieved through the combination of temperature control of a specific gradient and a preferred solvent reaction system.

[0069] In addition, in order to further conduct safety risk assessment on the aniline oxidation reaction process, the present invention also provides a thermal safety risk assessment method for aniline oxidation reaction, including conducting material thermal stability test, oxidation reaction reaction calorimetry test, and secondary decomposition test on the oxidation reaction completion liquid respectively; and conducting oxidation reaction safety risk assessment based on the test results. More specifically:

[0070] The thermal stability test of the material is to use a differential scanning calorimeter to perform a thermal stability test on the aniline oxidation reaction solution;

[0071] The reaction calorimetry test of the oxidation reaction is performed using a fully automatic chemical synthesis reactor according to the following process. The reaction calorimetry test performs the following steps:

[0072] a. First, add solvent, aniline and catalyst to feed;

[0073] b. Lower the temperature to -5 to 5°C;

[0074] c. Perform stable calibration;

[0075] d. adding oxidant dropwise;

[0076] e. Raise the temperature to 20-25°C for reaction;

[0077] f. Keep the reaction at 20-25℃;

[0078] g. Stable calibration;

[0079] h.Data calculation and analysis;

[0080] Thus, the charging curve (Mr), the heat released curve (qr_hf), the reaction temperature curve (Tr), and the jacket temperature curve (Tj) during the oxidation reaction are obtained;

[0081] The secondary decomposition test of the oxidation reaction completion liquid is to use an ES-ARC adiabatic accelerating calorimeter to perform a secondary decomposition test on the oxidation reaction completion liquid to obtain: a time-temperature-pressure curve of the exothermic section of the HWS mode test of the oxidation reaction completion liquid ARC, and a temperature-temperature rise rate-pressure rise rate curve of the exothermic section of the HWS mode test of the oxidation reaction completion liquid ARC;

[0082] The oxidation reaction safety risk assessment includes material decomposition heat assessment, severity assessment, possibility assessment, risk matrix assessment, and reaction process hazard assessment.

[0083] The fully automatic chemical synthesis reactor is selected from EasyMax 402 or RC1mx. In the process of calorimetry, in order to obtain the parameter ΔT required for safety assessment ad The Easymax software was used to execute the “U-cpr-U determination with 10 min waiting and ΔTr to 3 K” program.

[0084] Based on the specific reaction conditions of the present invention, the oxidation reaction safety risk assessment result of the aniline oxidation reaction process is:

[0085] Material decomposition heat assessment: According to the thermal stability test results of the oxidation reaction completed liquid, the decomposition heat of the oxidation reaction completed liquid is <400J / g, which is assessed as Level 1, with potential explosion hazard:

[0086] Severity assessment: According to the adiabatic thermal test results of the oxidation reaction, the adiabatic temperature rise ΔTad < 50K, and the severity assessment of the runaway reaction of the oxidation reaction is level 1;

[0087] Possibility assessment: The possibility of uncontrolled reaction is assessed as level 1, and uncontrolled reaction is less likely to occur;

[0088] Risk matrix assessment: Based on the results of severity assessment and likelihood assessment, the risk matrix assessment is level 1, and level 1 risk is an acceptable risk;

[0089] Reaction process hazard assessment: The reaction process hazard assessment at the actual feeding rate is level 3.

[0090] Furthermore, the present invention can further utilize evaporative cooling or decompression treatment to prevent the reaction mass from being in a runaway state, using a distillation unit that can operate normally even in the event of a utility failure, and measures such as a backup cooling system, tilting the reaction mass or quenching. A pressure relief system that can handle possible two-phase flow conditions can also be used, and a collection tank needs to be installed to prevent the reaction mass from being thrown out of the equipment, and put into operation after a failure occurs.

[0091] Example 1

[0092] The reactants are mixed according to the following process: 7.5 g aniline, 189.13 g dichloromethane, 17.11 g Na2WO4.2H2O aqueous solution, 18.27 g H2O2, wherein: the mass ratio of the solvent to aniline is (2-25):1; the molar ratio of H2O2 to aniline is 2:1; the molar ratio of the catalyst Na2WO4.2H2O to aniline is 0.1:1.

[0093] The following steps are performed: solvent dichloromethane, aniline and catalyst Na2WO4.2H2O are added to the reaction kettle, stirred to dissolve, and then the oxidant H2O2 is added. After the addition is completed, the reaction is kept at 0°C for 0.5h, the temperature is raised to 21°C, and the reaction is continued for 5h until the reaction is completed. The chemical reaction formula is as follows:

[0094]

[0095] The aniline oxidation reaction was tested for thermal stability of materials, calorimetric test of the reaction after oxidation, and secondary decomposition test of the oxidation reaction completion liquid, and the safety risk assessment of the oxidation reaction was performed based on the test results. The details are as follows:

[0096] Test 1: Material thermal stability test

[0097] Using a differential scanning calorimeter, the thermal stability of aniline, oxidant H2O2, and H2O2 and catalyst Na2WO4.2H2O were first tested respectively; then, H2O2 was mixed with Na2WO4.2H2O solution and dichloromethane (abbreviated as DCM), and the thermal stability of the mixture was tested;

[0098] Figure 1 is the DSC test curve of aniline, Figure 1 It can be seen that an exothermic peak is detected between (0-400)°C, which starts from 199.03°C and ends at 264.50°C, with a heat release of 24.50 J / g.

[0099] Figure 2 is the DSC test curve of the oxidant H2O2; Figure 2It can be seen that one exothermic peak and one endothermic peak are detected between (0-400)℃. The exothermic peak starts from 35.86℃ and ends at 113.63℃, releasing 476.64J / g of heat; the endothermic peak starts from 151.87℃ and ends at 292.53℃.

[0100] Figure 3 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution; an exothermic peak is detected between (0-400)℃, starting from 27.62℃ and ending at 87.89℃, and the heat released is 262.88J / g.

[0101] Figure 4 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V DCM; an exothermic peak is detected between (0-400)℃, the exothermic peak starts from 289.15℃ and ends at 315.05℃, and the heat released is 12.02J / g; when H2O2 is added to the 5V DCM solution, no obvious phenomenon occurs.

[0102] Comparative Examples 1-12

[0103] The method is basically different from Example 1, except that the solvent is different. The solvent is replaced with one of methanol (abbreviated as MeOH), 1,4-dioxane (abbreviated as 1,4-Dioxane), dimethyl sulfoxide (abbreviated as DMSO), ethyl acetate (abbreviated as EA), ethanol (abbreviated as EtOH), H2O, isopropanol (abbreviated as IPA) and tetrahydrofuran (THF) solvents, and then the mixture is tested for thermal stability.

[0104] Figure 5 The DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V CH3OH; Figure 5 It can be seen that an exothermic peak is detected between (0-400)℃, the exothermic peak starts from 170.14℃ and ends at 287.30℃, and the heat released is 595.91J / g; when H2O2 is added to 5V CH3OH and Na2WO4.2H2O solution, exothermic phenomenon occurs, indicating that H2O2, Na2WO4.2H2O system reacts with solvent CH3OH; from the DSC spectrum, it can be seen that the decomposition exothermic peak of H2O2 disappears, and an exothermic peak is generated from 170.14℃, which means that when H2O2 is used as an oxidant and sodium tungstate is used as a catalyst, CH3OH as a solvent will introduce heat release and also lead to a decrease in the yield of the reaction.

[0105] Figure 6This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V 1,4-dioxane; an exothermic peak is detected between (0-400)℃, the exothermic peak starts from 180.25℃ and ends at 254.06℃, and the heat released is 529.04J / g; when H2O2 is added to 5V 1,4-dioxane and Na2WO4.2H2O solution, gas is released, indicating that the H2O2, Na2WO4.2H2O system reacts with the solvent 1,4-dioxane; from the DSC spectrum, it can be seen that the decomposition exothermic peak of H2O2 disappears, and an exothermic peak is generated from 180.25℃, which means that when H2O2 is used as an oxidant and sodium tungstate is used as a catalyst, 1,4-dioxane as a solvent will introduce heat release and also lead to a decrease in the reaction yield.

[0106] Figure 7 It is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V DMSO; 3 exothermic peaks are detected between (0-400)℃, the first exothermic peak starts from 194.14℃ and ends at 201.49℃, releasing 1.71J / g of heat, the second exothermic peak starts from 223.74℃ and ends at 291.10℃, releasing 96.86J / g of heat, the third exothermic peak starts from 295.86℃ and ends at 370.22℃, releasing 184.67J / g of heat; at 5V When H2O2 is added to DMSO and Na2WO4.2H2O solution, there is a violent release of heat and gas, indicating that the H2O2, Na2WO4.2H2O system reacts with the solvent DMSO; from the DSC spectrum, it can also be seen that the decomposition exothermic peak of H2O2 disappears, and three exothermic peaks are generated starting from 194.14℃, which means that when H2O2 is used as an oxidant and sodium tungstate is used as a catalyst, DMSO as a solvent will introduce exothermic heat and also lead to a decrease in the yield of the reaction.

[0107] Figure 8DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V EA; 3 exothermic peaks were detected between (0-400)℃, the first exothermic peak started from 169.52℃ and ended at 224.81℃, releasing 19.87J / g of heat, the second exothermic peak started from 237.99℃ and ended at 275.81℃, releasing 17.50J / g of heat, the third exothermic peak started from 279.48℃ and ended at 353.76℃, releasing 423.27J / g of heat; at 5V When H2O2 is added to EA and Na2WO4.2H2O solution, an exothermic phenomenon occurs, indicating that the H2O2, Na2WO4.2H2O system reacts with the solvent EA; from the DSC spectrum, it can also be seen that the decomposition exothermic peak of H2O2 disappears, and three exothermic peaks are generated starting from 169.52℃, which means that when H2O2 is used as an oxidant and sodium tungstate is used as a catalyst, EA as a solvent will introduce exothermic heat and also lead to a decrease in the yield of the reaction.

[0108] Fig. 9 It is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V EtOH; Fig. 9 It can be seen that an exothermic peak is detected between (0-400)℃, the exothermic peak starts from 204.63℃ and ends at 299.28℃, and the heat released is 539.68J / g; when H2O2 is added to 5V EtOH and Na2WO4.2H2O solution, exothermic phenomenon occurs, indicating that H2O2, Na2WO4.2H2O system reacts with solvent EtOH; from the DSC spectrum, it can also be seen that the decomposition exothermic peak of H2O2 disappears, and an exothermic peak is generated from 204.63℃, which means that when H2O2 is used as an oxidant and sodium tungstate is used as a catalyst, EtOH as a solvent will introduce heat release and also lead to a decrease in the yield of the reaction.

[0109] Fig.10 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V H2O; no obvious exothermic peak was detected between (0-400)℃.

[0110] Fig.11DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V IPA; 3 exothermic peaks were detected between (0-400)℃, the first exothermic peak started from 106.43℃ and ended at 118.31℃, releasing 3.34J / g of heat; the second exothermic peak started from 128.03℃ and ended at 183.76℃, releasing 35.14J / g of heat; the third exothermic peak started from 193.70℃ and ended at 292.07℃, releasing 358.97J / g of heat; at 5V When H2O2 is added to the IPA and Na2WO4.2H2O solution, it can be seen from the DSC spectrum that the decomposition exothermic peak of H2O2 disappears, and an exothermic peak is generated from 106.43℃, which means that when H2O2 is used as an oxidant and sodium tungstate is used as a catalyst, IPA as a solvent will introduce exotherm and also lead to a decrease in the yield of the reaction.

[0111] Fig.12 This is the DSC test curve of H2O2 and Na2WO4.2H2O solution in 5V THF; an exothermic peak is detected between (0-400)℃, the exothermic peak starts from 137.10℃ and ends at 178.99℃, and the heat released is 594.75J / g; when H2O2 is added to 5V THF and Na2WO4.2H2O solution, exothermic phenomenon occurs, indicating that H2O2, Na2WO4.2H2O system reacts with solvent THF; from the DSC spectrum, it can also be seen that the decomposition exothermic peak of H2O2 disappears, and an exothermic peak is generated from 137.10℃, which means that when H2O2 is used as an oxidant and sodium tungstate is used as a catalyst, EtOH as a solvent will introduce exothermicity and also lead to a decrease in the yield of the reaction.

[0112] Combined with the thermal stability test results of Example 1 and Comparative Examples 1-12, it can be seen from the DSC curves in different solvents when H2O2 is used as an oxidant and sodium tungstate is used as a catalyst that H2O2, sodium tungstate and 1,4-dioxane, CH3OH, DMSO, EA, EtOH, IPA and THF all have obvious heat release or gas. When H2O2 and DCM are mixed, there is no obvious large exothermic peak. The analysis is that hydrogen peroxide is an oxidant and is incompatible with various solvents, but not with DCM. Therefore, the present invention uses aniline, oxidant H2O2, catalyst Na2WO4.2H2O and solvent DCM to form an aniline oxidation reaction liquid.

[0113] Comparative Examples 13-15

[0114] The method is basically the same as Example 6, except that the solvent is different. The solvent volume is replaced with 2V, 10V, and 20V respectively to test the thermal stability of the reaction solution of aniline oxidation.

[0115] Fig.13 is a DSC test curve diagram of the reaction mixture (2V DCM) after aniline oxidation, i.e., the aniline oxidation reaction solution; Fig.13 It can be seen that two exothermic peaks are detected between (0-400)℃. The first exothermic peak starts from 95.21℃ and ends at 195.54℃, releasing 197.94J / g of heat. The second exothermic peak starts from 219.33℃ and ends at 376.59℃, releasing 1164.74J / g of heat. 400J / g<decomposition heat<1200J / g. The decomposition heat is large and the potential explosion hazard is high.

[0116] Fig.14 is a DSC test curve diagram of the reaction mixture (10V DCM) after aniline oxidation, i.e., the aniline oxidation reaction solution; Fig.14 It can be seen that two exothermic peaks are detected between (0-400)℃. The first exothermic peak starts from 92.67℃ and ends at 182.56℃, releasing 85.55J / g of heat. The second exothermic peak starts from 232.91℃ and ends at 374.17℃, releasing 651.64J / g of heat. 400J / g<decomposition heat<1200J / g. The decomposition heat is large and the potential explosion hazard is high.

[0117] Fig.15 is a DSC test curve diagram of the reaction mixture (20V DCM) after aniline oxidation, i.e., the aniline oxidation reaction solution; Fig.15 It can be seen that three exothermic peaks are detected between (0-400)℃. The first exothermic peak starts from 116.46℃ and ends at 177.62℃, releasing 20.00J / g of heat; the second exothermic peak starts from 260.64℃ and ends at 323.98℃, releasing 190.68J / g of heat; the third exothermic peak starts from 324.62℃ and ends at 396.70℃, releasing 150.95J / g of heat.

[0118] In the DSC test curve of the aniline oxidation reaction liquid composed of aniline, oxidant H2O2, catalyst Na2WO4.2H2O and solvent DCM, when DCM is 2V, the maximum heat released is 1164.74J / g, 400J / g<decomposition heat<1200J / g, the decomposition heat is large, and the potential explosion hazard is high; when DCM is 10V, the maximum heat released is 651.64J / g, 400J / g<decomposition heat<1200J / g, the decomposition heat is large, and the potential explosion hazard is high; when DCM is 20V, the maximum heat released is 190.68J / g, the enthalpy value is greatly reduced, the safety is increased, and it can be safely scaled up in the laboratory and factory.

[0119] Test 2: Reaction calorimetry test of oxidation reaction

[0120] Use the fully automated chemical synthesis reactor EasyMax 402 according to the following process Fig.25 The reaction calorimetry was tested for the reaction mixture consisting of 7.5 g aniline, 189.13 g dichloromethane, 17.11 g Na2WO4.2H2O aqueous solution, and 18.27 g H2O2.

[0122] Thus, the charging curve (Mr), the heat released curve (qr_hf), the reaction temperature curve (Tr), and the jacket temperature curve (Tj) during the aniline oxidation reaction are obtained, such as Fig.19 As shown in the figure, the qr_hf curve is the thermal effect curve of the exothermic process. After integrating the time, the total heat release of the reaction is obtained. After calculation, it can be known that during the feeding process of this reaction, the temperature in the kettle increases, and during the insulation reaction process, the temperature in the kettle is stable. The total heat released is 18.04kJ, and the total mass of the materials participating in the reaction is 232.01g. Therefore, the specific heat release of the reaction is 77J / g.

[0123] According to the heat flow calorimetry principle, values ​​such as U (heat transfer coefficient) and Cpr (specific heat capacity) can be obtained during stable calibration of the program, and according to formulas such as ΔH (exothermic enthalpy) = m CpΔT, where m is mass (the amount of feed), and MTSR (maximum temperature of the synthesis reaction) = Tp (process temperature) + Xac·ΔT, the system can calculate values ​​such as ΔH (exothermic enthalpy) and MTSR.

[0124] ΔT ad is the adiabatic temperature rise, which is the total heat released by the synthesis reaction or material decomposition, and the temperature at which the system can rise under adiabatic conditions. ΔT of this reaction ad 55K;

[0125] MTSR is the highest temperature that the system can reach under adiabatic conditions when the material accumulation is maximum. Through calculation, the highest temperature MTSR corresponding to the runaway reaction in the oxidation reaction process is 76°C.

[0126] Since the aniline oxidation reaction is a normal pressure reaction, the technical maximum temperature MTT is the boiling point of the largest material in the reaction system under normal pressure, that is, the boiling point of dichloromethane: 39.75°C.

[0127] Test 3: Secondary decomposition test of the oxidation reaction completed liquid

[0128] The oxidation reaction completion liquid was subjected to secondary decomposition test using ES-ARC adiabatic accelerating calorimeter to obtain the following results: The exothermic time-temperature-pressure curve of the oxidation reaction completion liquid ARC HWS mode test ( Fig. 20, the curves are respectively temperature, pressure), the temperature-temperature rise rate-pressure rise rate curve of the exothermic section of the oxidation reaction completion liquid ARC HWS mode test ( Fig.21 ).

[0129] Depend on Fig. 20 and Fig.21 It can be seen that the oxidation reaction liquid exothermically decomposes into two stages. The initial decomposition temperature of the first stage is 170.60℃, and it stops at 175.70℃. The heat release is 28.26J / g, and the adiabatic temperature rise ΔT ad is 14.13K (corrected); the initial decomposition temperature of the second stage is 180.60℃, stops at 181.60℃, the heat release is 5.54J / g, and the adiabatic temperature rise ΔT ad is 2.77K (corrected); Fig. 20 Calculation shows that T D24 is 110.60℃, and when the process temperature is 21℃, the maximum reaction rate of the runaway reaction reaches time TMR ad >24h, when the temperature reaches the maximum temperature of the system (MTSR), the maximum reaction rate of the runaway reaction reaches the time TMR ad >24h.

[0130] Assessment Method: Oxidation Reaction Safety Risk Assessment

[0131] The safety risk assessment of oxidation reactions includes the following: material decomposition heat assessment, severity assessment, possibility assessment, risk matrix assessment, and reaction process hazard assessment. The assessment method comes from the "Guidelines for Safety Risk Assessment of Fine Chemical Reactions" (DB13 / T 5617-2022). The "Guidelines for Safety Risk Assessment of Fine Chemical Reactions" (DB13 / T 5617-2022) stipulates:

[0132] The explosiveness of materials is evaluated based on their decomposition heat and is divided into the following four levels (see Table 1).

[0133] Table 1. Material decomposition heat assessment standards

[0134] grade Decomposition heat J / g Consequences and explanations 1 Decomposition heat <400 Potential explosion hazard 2 400≤Decomposition heat≤1200 Decomposition releases large amounts of heat and has a high potential for explosion 3 1200<Decomposition heat<3000 Decomposition releases large amounts of heat and has a high potential for explosion 4 Decomposition heat ≥3000 The decomposition releases a lot of heat and has a high potential explosion risk

[0135] Decomposition heat assessment: Based on the material stability test results of the oxidation reaction completed liquid (see DSC test and Fig.15 ), the heat released by decomposition of the oxidation reaction is less than 400 J / g, which is assessed as Level 1, with potential explosion hazard;

[0136] The severity of the runaway reaction is evaluated using the adiabatic temperature rise ΔTad, which is divided into the following four levels (see Table 2).

[0137] Table 2. Evaluation criteria for severity of uncontrolled reactions

[0138]

[0139] Severity Assessment: Based on the results of the adiabatic test for oxidation reactions (see ARC Test 3 and Fig. 20 ), adiabatic temperature rise ΔT ad =16.90K,ΔT ad <50K, the runaway reaction severity assessment for oxidation reaction is level 1;

[0140] The possibility of reaction is evaluated based on the time to reach the maximum reaction rate and can be divided into the following four levels (see Table 3).

[0141] Table 3. Evaluation criteria for the possibility of runaway reactions

[0142]

[0143] Possibility assessment: Based on the adiabatic calorimetric test results of the oxidation reaction completed liquid (see Test 3 ARC test and Fig. 20 ), the reaction solution T D24 110.60℃(from Fig. 20 It can be seen that when the system process temperature is 21°C, the maximum reaction rate of the runaway reaction reaches the time TMR ad (The time required for an exothermic reaction to reach the maximum reaction rate from the start under adiabatic conditions)>24h, when the temperature reaches the maximum temperature of the system (MTSR), the maximum reaction rate of the runaway reaction reaches the time TMR ad >24h, the possibility of uncontrolled reaction is assessed as level 1, and uncontrolled reaction is less likely to occur;

[0144] The acceptability of uncontrolled reactions was evaluated based on the possibility and severity of the uncontrolled reactions and the results are shown in Table 4.

[0145] Table 4. Acceptability of runaway reactions

[0146]

[0147] Risk matrix assessment: According to the results of severity assessment and possibility assessment, the risk matrix is ​​assessed as Level Ⅰ, and Level Ⅰ risk is an acceptable risk: control measures are taken according to design requirements during the production process, and the level of safety management is improved.

[0148] Based on Tp, MTSR, MTT and T D24 Four temperature parameters are used as rating basis to assess the process hazard level (see Table 5).

[0149] Table 5. Process hazard level

[0150]

[0151] Reaction process hazard assessment: According to the reaction calorimetry test results of the oxidation reaction, the process temperature Tp = 21 ° C, the maximum temperature that the synthesis reaction may reach under the actual feeding rate (0-10g / min) under adiabatic conditions MTSR = 76 ° C, the technical maximum temperature MTT = 39.75 ° C, and the secondary decomposition test T of the oxidation reaction completion liquid D24 =110.60℃, we get Tp<MTT<MTSR<T D24 (21℃<39.75℃<76℃<110.60℃), that is, the reaction process hazard assessment at the actual feeding rate is level 3.

[0152] When the process hazard level is Level 4 and Level 5, the risk is relatively high and the factory is generally prohibited from production; below Level 3, production is allowed under certain engineering conditions.

[0153] Combined with the thermal stability test of Comparative Examples 9-11, in the later experiment, when the amount of aniline was 320 g, the reaction was still controllable, and the reaction temperature could be controlled by dropping hydrogen peroxide.

[0154] Therefore, from Td 24 and ΔH (see Fig.13 , 14 and 15), under the 20V solvent system of the present invention, the reaction risk is smaller and the reaction efficiency is guaranteed (when the reaction volume is enlarged, the reaction can be completed overnight at 2V, 5V and 20V).

[0155] In addition, based on the chemical reaction of the present invention:

[0156]

[0157] After the target reaction is out of control, the temperature reaches the technical limit (MTSR>MTT), but does not trigger the decomposition reaction (MTSR <T D24 ). In this case, process safety depends on the exothermic rate of the target reaction at MTT.

[0158] Therefore, the present invention can further prevent the reaction materials from being in a runaway state by further utilizing evaporative cooling or decompression treatment. In order to reduce the risk of the process, the following comparative example test is further performed:

[0159] Through the above examples, the present invention further determines the products and by-products of aniline oxidation reaction, such as Fig. 22 The hydrogen spectrum of compound 1 azobenzene oxide is presented, such as Fig.23 is the hydrogen spectrum of compound 2 nitrobenzene, such as Fig.24 This is the hydrogen spectrum of compound 3 nitrosobenzene. And the corresponding thermal stability test was done:

[0160] Fig.16 is the DSC test curve of compound 1 azobenzene oxide; Fig.16 It can be seen that two exothermic peaks are detected between (0-400)℃. The first exothermic peak starts from 265.19℃ and ends at 351.68℃, releasing 1004.10J / g of heat. The second exothermic peak starts from 360.98℃ and ends at 400.06℃, releasing 85.38J / g of heat.

[0161] Fig.17 is the DSC test curve of compound 2 nitrobenzene; Fig.17 It can be seen that two exothermic peaks are detected between (0-400)℃. The first exothermic peak starts from 297.00℃ and ends at 362.70℃, releasing 15.72J / g of heat. The second exothermic peak starts from 371.78℃ and ends at 400.13℃, releasing 15.20J / g of heat.

[0162] Fig.18 is the DSC test curve of compound 3 nitrosobenzene; Fig.18 It can be seen that three exothermic peaks are detected between (0-400)℃. The first exothermic peak starts from 98.11℃ and ends at 210.08℃, releasing 740.05J / g of heat; the second exothermic peak starts from 218.51℃ to 321.63℃, releasing 478.63J / g of heat; the third exothermic peak starts from 325.96℃ to 400.20℃, releasing 288.25J / g of heat.

[0163] Figure 16-18 This indicates that compounds 1-3 have good thermal stability and safety under this process condition.

[0164] The above-mentioned ideal embodiments of the present invention are inspirations. Through the above-mentioned description content, relevant personnel can make various changes and modifications without departing from the technical idea of ​​the present invention. These equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A process for aniline oxidation reaction, characterized in that: The method comprises the following steps: adding a solvent, aniline and a catalyst into a reaction kettle, stirring and dissolving, then adding an oxidant, maintaining the temperature for a period of time after the addition, heating to a second temperature and continuing the reaction; the second temperature is lower than 27°C.

2. The reaction process according to any one of claim 1, characterized in that: The oxidant is H2O2; the catalyst is Na2WO4.2H2O; and the solvent is dichloromethane.

3. The reaction process according to claim 2, characterized in that: The dropwise addition temperature of the solvent, aniline, catalyst and oxidant is controlled at -5 to 5°C. After the addition is completed, the temperature is kept at -5 to 5°C for 0.25 to 1 hour.

4. The reaction process according to claim 2, characterized in that: Control the temperature to 20-25°C and keep the reaction for 3-7 hours.

5. The reaction process according to claim 2, characterized in that: The volume of the solvent is 20 times the mass of the solute.

6. The reaction process according to claim 2, characterized in that: The mass ratio of the solvent to aniline is (2-25):1; the molar ratio of H2O2 to aniline is 2:1; and the molar ratio of the catalyst Na2WO4.2H2O to aniline is 0.1:

1.

7. The reaction process according to claim 2, characterized in that: The reaction system of the solvent, aniline, catalyst and oxidant is subjected to evaporative cooling or decompression treatment during the reaction process.

8. A method for thermal safety risk assessment of aniline oxidation reaction, used for conducting safety risk assessment on the aniline oxidation reaction process according to any one of claims 1 to 5, characterized in that: It includes material thermal stability test, reaction calorimetry test of oxidation reaction, secondary decomposition test of oxidation reaction completed liquid, and then safety risk assessment of oxidation reaction.

9. The thermal safety risk assessment method according to claim 8, characterized in that: The thermal stability test of the material is performed by DSC test to evaluate the heat of decomposition of the material; the reaction calorimetry test uses a fully automatic chemical synthesis reactor to perform the following steps: a. First, add solvent, aniline and catalyst to feed; b. Lower the temperature to -5 to 5°C; c. Perform stable calibration; d. adding oxidant dropwise; e. Heat to 20-25℃ for reaction; f. Keep the reaction at 20-25℃; g. Stable calibration; h.Data calculation and analysis; Thus, the charging curve, the heat released curve, the reaction temperature curve and the jacket temperature curve in the oxidation reaction process are obtained; The secondary decomposition test of the oxidation reaction completion liquid is to use an ES-ARC adiabatic accelerating calorimeter to perform a secondary decomposition test on the oxidation reaction completion liquid to obtain: a time-temperature-pressure curve of the exothermic section of the HWS mode test of the oxidation reaction completion liquid ARC, and a temperature-temperature rise rate-pressure rise rate curve of the exothermic section of the HWS mode test of the oxidation reaction completion liquid ARC; The oxidation reaction safety risk assessment includes material decomposition heat assessment, severity assessment, possibility assessment, risk matrix assessment, and reaction process hazard assessment.

10. The thermal safety risk assessment method for aniline oxidation reaction according to claim 9, characterized in that: The oxidation reaction safety risk assessment of the aniline oxidation reaction process is: Material decomposition heat assessment: According to the test results of the oxidation reaction completed liquid, the decomposition heat of the oxidation reaction completed liquid material is <400J / g, which is assessed as Level 1, with potential explosion hazard: Severity assessment: According to the adiabatic thermal test results of the oxidation reaction, the adiabatic temperature rise △Tad <50K, and the severity assessment of the runaway reaction of the oxidation reaction is level 1; Possibility assessment: Based on the adiabatic calorimetric test results of the oxidation reaction completion liquid, the possibility of a runaway reaction is assessed to be level 1, which means that the runaway reaction is less likely to occur. Risk matrix assessment: Based on the results of severity assessment and likelihood assessment, the risk matrix assessment is level 1, which is an acceptable risk; Reaction process hazard assessment: The reaction process hazard assessment at the actual feeding rate is level 3.

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