Microchannel reaction evaluation method of pyromellitic dianhydride catalyst

Abstract

The invention provides a microchannel reaction evaluation method of a pyromellitic dianhydride catalyst. The microchannel reaction evaluation method comprises a feeding process, a vaporization process, a reaction process, a product separation process, a control process and an analysis process. Discharging a mixture of a reaction product and an unreacted reactant from the reaction tube, cooling, converting the reaction product and the unreacted durene from a gas phase into a liquid phase, separating in a gas-liquid separator, separating out gases such as air in a tail gas form, and feeding liquid into a liquid collecting tank; a reaction tube, a gas-liquid separator and a liquid collecting tank are sequentially arranged in a heat preservation box, the heat preservation box is divided into heat preservation sections with different temperatures according to different separation devices, the heat preservation sections can be integrated or arranged to be in a multi-body type according to needs, and the temperature of the reaction tube can be controlled in a multi-heat-preservation-box step-by-step temperature control mode and a heat preservation box, a heating belt and other combined temperature control modes. Accurate temperature control of reactants and reaction products is achieved, the reaction products can be efficiently collected, and guarantee is provided for accuracy of catalyst analysis and evaluation data.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst evaluation, in particular to a microchannel reaction evaluation method of a pyromellitic dianhydride catalyst. Background Art

[0002] The prior art uses a fixed-bed tubular reactor to generate anhydrides and by-products, which includes a gasification section, an oxidation section, a capture section, a hydrolysis section, a dehydration or sublimation purification section, a concentration section, a dehydration and drying section, and a recrystallization or sublimation section to generate pyromellitic acid or pyromellitic dianhydride. The process route is long, the steps are complex, and the time is very long, making it unsuitable for laboratory catalyst evaluation.

[0003] For example, Chinese patent CN214915974U discloses a device comprising a work platform and an air oxidation reactor equipped with a multifunctional feeder, a stirring assembly, and a discharger. By installing a multifunctional feeder assembly at the upper end of the air oxidation reactor and a ring-shaped adapter plate on the discharge pipe at the lower end of the reactor, the device addresses issues such as an unreasonable feed method and labor-intensive material removal. However, the device lacks a dedicated product insulation device, which can cause product solidification and blockage, hindering continuous experiments.

[0004] Chinese patent CN101735232A discloses a production method of pyromellitic dianhydride, which solves the problems of high energy consumption and high cost of three-waste treatment in existing production processes. The process of the present invention includes the following steps: 1. Oxidation, using durenyl and air as raw materials, an oxidation reaction is carried out by a catalyst at the temperature of a higher molten salt in the reactor to obtain a gas phase mixture, and a crude anhydride semi-finished product is recovered by three series-connected cooling traps; 2. Discharging, the crude anhydride in the trap is completely cleaned and raked out; 3. Hydrolysis and centrifugation, the crude anhydride obtained by oxidation is melted into a liquid by steam heating in a soft water hydrolysis kettle, hydrolyzed into pyromellitic acid, decolorized by activated carbon and recrystallized after hot filtration, and qualified pyromellitic acid and crude tetracarboxylic acid crystals are obtained by centrifugation; 4. Dehydration and sublimation are performed to obtain a refined homobenzene anhydride product. However, the device is not provided with a special product insulation device, which will cause the product to solidify, block the device, and affect continuous experiments; and the collected product needs to be post-processed to become pyromellitic dianhydride, and the steps are cumbersome.

[0005] Chinese patent CN110746435A discloses a method for producing pyromellitic dianhydride by continuous low-temperature liquid-phase oxidation of durenyl. The method comprises the following steps: first, continuously injecting a mixture of durenyl, acetic acid, and a cobalt-manganese-bromine-zirconium-guanidine catalyst into an oxidation reaction tower; simultaneously, oxygen-rich gas is continuously introduced into the tower body while the liquid is injected; the temperature in the oxidation reaction tower is maintained at 200-300°C and the pressure in the tower body is maintained at 0.5-3 MPa; durenyl reacts with oxygen to produce pyromellitic acid, which has a low density and floats on the upper surface of the liquid; the upper surface liquid with a high pyromellitic acid content is extracted and flash-evaporated to evaporate the light components, and crude pyromellitic acid is obtained at the bottom of the tank; the crude pyromellitic acid is recrystallized and centrifuged to obtain pyromellitic acid crystals, which are then dehydrated to obtain pyromellitic dianhydride. The catalyst uses a small amount of bromine, which reduces equipment corrosion; the process is simple and easy to implement, and is beneficial to the industrial production of pyromellitic dianhydride. The pyromellitic acid produced by this device also needs to be post-processed to obtain pyromellitic dianhydride, and it cannot be used for microchannel reaction evaluation of small amounts of catalyst. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a microchannel reaction evaluation method for pyromellitic dianhydride catalyst, which solves the problem of product collection difficulty caused by the high melting point of the reaction product through a specially designed heating and heat preservation device.

[0007] In order to achieve the above object, the present invention provides a microchannel reaction evaluation method for pyromellitic dianhydride catalyst, comprising the following steps: a feeding process, a vaporization process, a reaction process, a product separation process, a control process and an analysis process;

[0008] The product separation process includes: a mixture of the reaction product and the unreacted reactant is discharged from the reaction tube and cooled. Specifically, the reaction tube can be a fixed-bed tubular reactor. The reaction product and the unreacted durene are converted from a gas phase to a liquid phase and separated in a gas-liquid separator. Gases such as air are separated in the form of tail gas, and the liquid enters a liquid collection tank.

[0009] The reaction tube, gas-liquid separator and liquid collection tank are placed in an insulation box in sequence. The insulation box is divided into insulation sections with different temperatures according to different separation equipment. It can be a one-piece type or a multi-piece type as needed.

[0010] In some embodiments, the reaction tube and the gas-liquid separator are placed in an upper insulation box and a lower insulation box. The mixture of the reaction product and the unreacted reactant is discharged from the reaction tube and cooled. The reaction product and the unreacted tetramethylbenzene are converted from the gas phase to the liquid phase and are separated in the gas-liquid separator. After filtering, the air and other gases are separated in the form of tail gas. The liquid enters the liquid collection tank through a needle valve. The liquid collection tank is placed in a liquid collection insulation box. The filter is one or more and can be inside or outside the insulation box.

[0011] In some embodiments, the ambient temperature of the pipeline from the reaction tube to the liquid collection tank needs to be controlled at not less than 300° C. to ensure that the reaction product and unreacted tetramethylbenzene remain in liquid form and are separated in the gas-liquid separator, are not discharged with the gas, and remain in liquid form and enter the liquid collection tank.

[0012] In some embodiments, the control process includes the use of a supporting software control system, flow, temperature sensors and control systems, and switch valves. The temperature of the reactants and reaction products can be precisely controlled by multiple insulation boxes in a step-by-step manner, and the insulation boxes and heating belts are combined to control the temperature. The software control system can also realize temperature settings, flow and other parameters, and can obtain set, real-time and historical temperature and flow curves to facilitate laboratory operations.

[0013] In some embodiments, the analysis process includes taking out a sample from a liquid collection tank, dissolving it with a solvent, and performing liquid or gas chromatography analysis.

[0014] In some embodiments, durenyl is heated and melted and then mixed with hot air during the feeding process. Specifically, durenyl can be heated and melted or carried out by a carrier gas into a bubbler and mixed with air in a pipeline or a mixer before entering a preheating tube before the reaction tube. Alternatively, heated air and heated molten liquid durenyl can be added to the preheating tube before the reaction tube via a liquid raw material tank.

[0015] In some of the embodiments, the pipelines and equipment in the feeding process, such as the plunger pump, flow meter and liquid raw material tank, are heated or insulated, and the pipelines are wrapped with thermal insulation heating tapes.

[0016] In some embodiments, the preheating tube is heated during the vaporization process so that the durenyl is fully vaporized and mixed with the hot air. The device for heating the preheating tube can be a preheater, and the temperature is controlled at 300-400°C.

[0017] In some embodiments, the oxidation reaction process is carried out using a reaction tube, specifically a fixed bed tubular reactor, maintaining a reaction temperature of 320-500°C and a space velocity of 3000-10000.-1 .

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] The microchannel reaction evaluation method for a pyromellitic dianhydride catalyst provided by the present invention has a simple process and can be used to evaluate and screen catalysts. The method breaks away from traditional process simulation devices and obtains analytical data by realizing liquid collection of products. More specifically, the method recommends a step-by-step temperature control method using multiple insulation boxes and a combined temperature control method using insulation boxes, heating belts, etc., thereby realizing precise temperature control of reactants and reaction products, enabling efficient collection of reaction products, saving time, and ensuring the accuracy of catalyst analysis and evaluation data.

[0020] The present invention solves the problem of product collection difficulties caused by the high melting point of reaction products through a specially designed heating and heat preservation device, and provides a catalyst microchannel reaction evaluation method that can quickly and effectively collect products. The reaction products will not block the pipeline, and the reaction products can be smoothly collected, which is conducive to evaluating the performance of the catalyst and continuously analyzing the catalyst. DETAILED DESCRIPTION

[0021] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments to further understand the purpose, solution and effect of the present invention, but are not intended to limit the scope of protection of the claims attached to the present invention.

[0022] A specific embodiment of the present invention provides a microchannel reaction evaluation method for a pyromellitic dianhydride catalyst, comprising the following steps: a feeding process, a vaporization process, a reaction process, a product separation process, a control process, and an analysis process;

[0023] Among them, the product separation process includes: the mixture of the reaction product and the unreacted reactant after the reaction is discharged from the reaction tube and cooled. Specifically, the reaction tube can be a fixed bed tubular reactor, the reaction product and the unreacted tetramethylbenzene are converted from the gas phase to the liquid phase, and are separated in the gas-liquid separator, and the air and other gases are separated in the form of tail gas, and the liquid enters the liquid collection tank; the reaction tube, the gas-liquid separator, and the liquid collection tank are placed in an insulation box in sequence, and the insulation box is divided into insulation sections with different temperatures according to different separation equipment. It can be a one-piece type or a multi-body type as needed.

[0024] The reaction tube (specifically, a fixed-bed tubular reactor) and a gas-liquid separator are placed in an upper insulation box and a lower insulation box. After the reaction, the mixture of the reaction product and the unreacted reactant is discharged from the reaction tube and cooled. The reaction product and the unreacted tetramethylbenzene are converted from the gas phase to the liquid phase and separated in the gas-liquid separator. After being filtered by a filter, air and other gases are separated in the form of tail gas. The liquid enters a liquid collection tank through a needle valve. The liquid collection tank is placed in a liquid collection insulation box. The filter is one or more and can be inside or outside the insulation box. The pipeline from the reaction tube to the liquid collection tank needs to be controlled at an ambient temperature of not less than 300°C to ensure that the reaction product and the unreacted tetramethylbenzene remain in a liquid state in the gas-liquid separator and are separated, are not discharged with the gas, and remain in a liquid state and enter the liquid collection tank.

[0025] Specifically, the control process includes the use of a supporting software control system, flow and temperature sensors in the control system, and an on-off valve. Through step-by-step temperature control of multiple insulated boxes and a combined temperature control method of insulated boxes and heating belts, precise temperature control of reactants and reaction products is achieved, and reaction products are efficiently collected for subsequent analysis. The software control system also allows for temperature settings (40 temperature programming steps) and flow parameters, and can obtain set, real-time, and historical temperature and flow curves to facilitate laboratory operations.

[0026] Specifically, the analysis process includes removing a sample from a liquid collection tank, dissolving it in a solvent, and subjecting it to liquid or gas chromatography analysis. More specifically, the sample is dissolved in ethyl acetate. Similarly, the exhaust gas is collected and then fed into a gas chromatograph or flue gas analyzer. Specifically, the liquid chromatograph uses 10% acetonitrile, 15% potassium dihydrogen phosphate, and 75% water as the mobile phase, with a flow rate of 0.8 ml / min, a Shimadzu LC-20A chromatograph, an AQ-C18 column, a UV detector wavelength of 215 nm, and a column temperature of 40°C.

[0027] During the feeding process, durenyl is heated and melted and then mixed with hot air. Specifically, the durenyl can be heated and melted or carried out by a carrier gas into a bubbler and mixed with air in a pipeline or a mixer before entering a preheating tube before the reaction tube. Alternatively, the heated air and the heated and melted liquid durenyl are separately added to the preheating tube before the reaction tube via a liquid raw material tank. The pipes and equipment in the feeding process, such as the plunger pump, flow meter, and liquid raw material tank, are preferably heated or insulated, and the pipes are wrapped with insulating heating tape.

[0028] Specifically, during the vaporization process, the preheating tube is heated so that the durene is fully vaporized and mixed with the hot air. The device for heating the preheating tube can be a preheater, and the temperature is controlled at 300-400°C.

[0029] Specifically, the oxidation reaction process is carried out using a reaction tube, specifically, a fixed bed tubular reactor, maintaining a reaction temperature of 320-500°C and a space velocity of 3000-10000. -1 .

[0030] In summary, the prior art uses a fixed bed tubular reactor to generate anhydride and by-products, including a gasification section, an oxidation section, a capture section, a hydrolysis section, a dehydration or sublimation refining section, a concentration section, a dehydration and drying section, and a recrystallization or sublimation section to generate pyromellitic acid or pyromellitic dianhydride. The process route is long, the process is complicated, and the time is very long, which is not suitable for laboratory evaluation of catalysts. The present invention provides a catalyst microchannel reaction evaluation method that can quickly and effectively collect products. The process is simple and can be used to evaluate and screen catalysts. Durene and air are used as raw materials. The raw materials are vaporized and mixed and then enter a chamber filled with a test sample. The fixed-bed tubular reactor of the catalyst has a reaction temperature of about 350-450°C. After the reaction, the mixture of the reaction product and the unreacted reactant is discharged from the reaction tube and cooled. The reaction product and the unreacted durene are converted from gas phase to liquid phase, and are separated in a gas-liquid separator. Air or other carrier gases are separated, and the liquid enters a liquid collection tank. The ambient temperature of the pipeline from the reaction tube to the liquid collection tank needs to be controlled at no less than 300°C to ensure that the reaction product and the unreacted durene remain in liquid form in the gas-liquid separator and are separated, and are not discharged with the gas, and remain in liquid form and enter the liquid collection tank.

[0031] Since the melting point of pyromellitic dianhydride is as high as 285°C, which is much higher than room temperature, if the product collecting device is not optimized specifically, the oxidation products will solidify and accumulate in the reactor and pipeline, which not only affects the analysis of catalyst conversion and selectivity, but also ultimately causes the pipeline to be completely blocked. The present invention has been specifically designed with product heating, insulation and collecting devices to ensure that the temperature of the product will not be lower than 300°C before entering the collection tank, even if its temperature remains above the melting point throughout the entire process to maintain a liquid state, effectively solving the problem of product blockage and incomplete collection. Specifically, the temperature of the pipeline connecting the reaction tube and the gas-liquid separator of the microchannel reaction device, the pipeline connecting the gas-liquid separator and the needle valve, the pipeline connecting the needle valve and the liquid collection tank, the gas-liquid separator, the needle valve and the liquid collection tank is not lower than 300°C, which is higher than the melting point of pyromellitic dianhydride, thereby preventing pyromellitic dianhydride from solidifying and blocking the pipeline.

[0032] The microchannel reaction evaluation method for a pyromellitic dianhydride catalyst provided by the present invention has a simple process and can be used to evaluate and screen catalysts. The method breaks away from traditional process simulation devices and obtains analytical data by realizing liquid collection of products. More specifically, the method recommends a step-by-step temperature control method using multiple insulation boxes and a combined temperature control method using insulation boxes, heating belts, etc., thereby realizing precise temperature control of reactants and reaction products, enabling efficient collection of reaction products, saving time, and ensuring the accuracy of catalyst analysis and evaluation data.

[0033] The present invention solves the problem of product collection difficulties caused by the high melting point of reaction products through a specially designed heating and heat preservation device, and provides a catalyst microchannel reaction evaluation method that can quickly and effectively collect products. The reaction products will not block the pipeline, and the reaction products can be smoothly collected, which is conducive to evaluating the performance of the catalyst and continuously analyzing the catalyst.

Claims

1. A microchannel reaction evaluation method for a pyromellitic anhydride catalyst, characterized in that: The process includes the following steps: feeding process, vaporization process, reaction process, product separation process, control process and analysis process; The product separation process includes: the mixture of the reaction product and the unreacted reactant after the reaction is discharged from the reaction tube and cooled. Specifically, the reaction tube can be a fixed bed tubular reactor. The reaction product and the unreacted durene are converted from gas phase to liquid phase and separated in a gas-liquid separator. Gases such as air are separated in the form of tail gas, and the liquid enters a liquid collection tank; The reaction tube, gas-liquid separator and liquid collection tank are placed in an insulation box in sequence. The insulation box is divided into insulation sections with different temperatures according to different separation equipment. It can be an integrated type or a multi-body type as required.

2. The microchannel reaction evaluation method of pyromellitic anhydride catalyst according to claim 1, characterized in that: The reaction tube and the gas-liquid separator are placed in an upper insulation box and a lower insulation box. The mixture of the reaction product and the unreacted reactant is discharged from the reaction tube and cooled. The reaction product and the unreacted tetramethylbenzene are transformed from gas phase to liquid phase and separated in the gas-liquid separator. After being filtered by a filter, the air and other gases are separated in the form of tail gas. The liquid enters the liquid collection tank through a needle valve, and the liquid collection tank is placed in a liquid collection insulation box.

3. The microchannel reaction evaluation method of the pyromellitic anhydride catalyst according to claim 2, characterized in that: The filter may be one or more and may be inside or outside the incubator.

4. The microchannel reaction evaluation method of pyromellitic anhydride catalyst according to claim 1, characterized in that: The ambient temperature of the pipeline from the reaction tube to the liquid collection tank needs to be controlled at no less than 300°C to ensure that the reaction product and unreacted tetramethylbenzene remain in liquid form and are separated in the gas-liquid separator, are not discharged with the gas, and remain in liquid form and enter the liquid collection tank.

5. The microchannel reaction evaluation method of pyromellitic anhydride catalyst according to claim 1, characterized in that: The control process includes the use of a matching software control system, flow, temperature sensors and control systems, and switch valves. The temperature of the reactants and reaction products can be accurately controlled by multiple insulation boxes, and the insulation boxes and heating belts are combined to control the temperature. The software control system can also realize temperature settings, flow and other parameters, and can obtain set, real-time and historical temperature and flow curves to facilitate laboratory operations.

6. The microchannel reaction evaluation method of pyromellitic anhydride catalyst according to claim 1, characterized in that: The analysis process includes taking out the sample from the liquid collection tank, dissolving it with a solvent, and entering the liquid phase or gas chromatography for analysis.

7. The microchannel reaction evaluation method of pyromellitic anhydride catalyst according to claim 1, characterized in that: In the feeding process, durenyl is heated and melted and then mixed with hot air. Specifically, durenyl can be heated and melted or carried out by a carrier gas into a bubbler and mixed with air in a pipeline or in a mixer and then enter the preheating tube in front of the reaction tube; or the heated air and the heated and melted liquid of durenyl can be added to the preheating tube in front of the reaction tube through a liquid raw material tank.

8. The microchannel reaction evaluation method of pyromellitic anhydride catalyst according to claim 7, characterized in that: The pipelines and equipment in the feeding process, such as the plunger pump, flow meter and liquid raw material tank, are all heated or insulated, and the pipelines are wrapped with insulation heating belts.

9. The microchannel reaction evaluation method of pyromellitic anhydride catalyst according to claim 1, characterized in that: In the vaporization process, the preheating tube is heated so that the durene is fully vaporized and fully mixed with the hot air. The device for heating the preheating tube can be a preheater, and the temperature is controlled at 300-400°C.

10. The microchannel reaction evaluation method of pyromellitic anhydride catalyst according to claim 1, characterized in that: The oxidation reaction process is carried out using a reaction tube, specifically, a fixed bed tube reactor, maintaining a reaction temperature of 320-500°C and a space velocity of 3000-10000. -1 .