A process for measuring the polymerization enthalpy change of polyacrylic acid reaction based on micro-reaction calorimeter

Abstract

The invention discloses a polyacrylic acid reaction polymerization enthalpy change determination process based on a micro-reaction calorimeter, comprising the following steps: forming a continuous flow micro-reaction calorimeter by combining a microchannel reaction module, a local calorimetric module, a connecting fitting, and a material conveying device; configuring a reaction solution; using three different-sized pipes to deliver the configured sodium pyrosulfite solution, sodium persulfate solution, and acrylic acid solution into the continuous flow micro-calorimeter; preheating the reactants; mixing the reaction; converting the temperature during the reaction and the heat released by the reaction into electrical signals; allowing the hot start of sodium persulfate to generate free radicals at 70°C to interact with acrylic acid in the solution; and calculating the yield of polyacrylic acid under different initiator contents in the reaction system by nuclear magnetic hydrogen spectrum. The polyacrylic acid reaction polymerization enthalpy change determination process based on the micro-reaction calorimeter improves the reaction efficiency and obtains a higher yield and a polymerization reaction enthalpy value under the optimal yield.

Description

Technical Field

[0001] The invention belongs to the technical field of acrylic acid polymerization continuous flow process, and in particular relates to a polyacrylic acid reaction polymerization enthalpy change determination process based on a micro-reaction calorimeter. Background Art

[0002] Polyacrylic acid is obtained by polymerizing acrylic acid monomers. In actual production and life, it has a wide range of application prospects and is often used in adsorbents, rust removers, flocculants and other fields. Usually, acrylic acid has good solubility in water, so it is often polymerized in aqueous solution to obtain polyacrylic acid. At present, acrylic acid polymerization mainly adopts a kettle batch process, but there are certain limitations in heat transfer and mass transfer, such as slow reaction speed, easy to cause local heat accumulation, and even accidents such as reaction out of control. Therefore, in order to improve the above defects, it is necessary to measure the polymerization enthalpy change of polyacrylic acid reaction.

[0003] However, in the existing continuous flow synthesis process of polyacrylic acid in a micro-reaction calorimeter, acrylic acid is used as a raw material and sodium persulfate and sodium metabisulfite are used as initiators. Since the initiators added to the reaction are all peroxides with strong chemical properties and the reaction needs to be carried out under high pressure, if the traditional kettle intermittent operation is adopted, it is easy to cause local overheating or sudden pressure increase of the reactor, which has great safety hazards and product blockage defects. In addition, ordinary pipeline reactors are difficult to overcome the heterogeneous mass transfer barriers, resulting in low product yields. Summary of the invention

[0004] The object of the present invention is to provide a process for measuring the polymerization enthalpy change of polyacrylic acid reaction based on a micro-reaction calorimeter to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a process for determining the polymerization enthalpy change of polyacrylic acid reaction based on a micro-reaction calorimeter, comprising the following steps:

[0006] S1, forming a reaction calorimetric system suitable for the polymerization reaction by combining a microchannel reaction module, a local calorimetric module, connection accessories, and a material conveying device, that is, forming a continuous flow micro-reaction calorimeter;

[0007] S2. Prepare a reaction solution: prepare sodium metabisulfite and sodium persulfate into a solution according to the material ratio at room temperature;

[0008] S3, using three pipes of different sizes to deliver the prepared sodium metabisulfite solution, sodium persulfate solution and acrylic acid solution into the continuous flow microcalorimeter;

[0009] S4, preheating of reactants;

[0010] S5, mixed reaction;

[0011] S6, using microfluidic chips and Peltier elements to monitor the temperature during the reaction and convert the heat released by the reaction into electrical signals;

[0012] S7. Setting the experimental temperature at 70°C to allow the thermal start of sodium persulfate to generate free radicals to interact with acrylic acid in the solution, comprising the following steps:

[0013] A1. Calibrate and verify the device using acid-base reaction;

[0014] A2. Study the polymerization and thermal effects of the reaction system when the solid content of sodium hydroxide, sodium metabisulfite and sodium persulfate is 10%, 20%, 30% and 47%;

[0015] S8. The yield of polyacrylic acid under different initiator contents in the reaction system is calculated by hydrogen nuclear magnetic spectrum, and the effect of initiator content on the yield of polyacrylic acid is obtained.

[0016] As a further preferred embodiment, the continuous flow micro-reaction calorimeter in S1 includes a reaction chamber and a reference chamber formed by a stainless steel plate, and thermopiles are installed in the reaction chamber and the reference chamber, and a serpentine microchannel is fixed on the thermopiles. Insulating foam is arranged on the periphery of the stainless steel plate, and a heat transfer layer is arranged between the insulating foam and the stainless steel plate, and a heat exchange channel inlet and a heat exchange channel outlet of an external constant temperature circulating oil bath system are arranged on the lower end surface of the insulating foam.

[0017] As a further preferred embodiment, the thermopile is composed of Peltier elements, and the specifications of the S1 continuous flow microreaction calorimeter are: microchannel characteristic size R=2mm; calorimetric sensitive area composed of Peltier elements 50mm×50mm; reactor specific surface area 2500m2 / m3; heat transfer coefficient 1700kW / (m2·K).

[0018] As a further preferred embodiment, after the light oil in the constant temperature circulating oil bath system flows out, it flows into the heat transfer layer through the heat exchange channel inlet, and flows out from the heat exchange channel outlet and flows back into the constant temperature circulating oil bath system.

[0019] As a further preferred solution, the S3 uses a three-way pipe to nest the smallest tube into the larger tube, and the larger tube is nested into the largest tube. The three pipes of different sizes are respectively connected to the syringes on the laboratory injection pump.

[0020] As a further preferred embodiment, S4 comprises: preheating the sodium metabisulfite solution, sodium persulfate solution and acrylic acid solution configured in S3 and introduced into the continuous flow microcalorimeter using a preheating aluminum plate before mixing them on the serpentine reaction aluminum plate to reach the required reaction temperature.

[0021] As a further preferred embodiment, the sodium pyrosulfite solution, sodium persulfate solution and acrylic acid solution preheated by the preheating aluminum plate in S4 are mixed and reacted on the reaction aluminum plate.

[0022] As a further preferred embodiment, the molar ratio in S7 is defined as: n(sodium persulfate):n(acrylic acid)=1:40, n(sodium metabisulfite):n(acrylic acid)=1:20.

[0023] The present invention provides a process for measuring the polymerization enthalpy change of polyacrylic acid reaction based on a micro-reaction calorimeter, which has the following beneficial effects:

[0024] 1. The polyacrylic acid reaction polymerization enthalpy change measurement process based on micro-reaction calorimeter breaks the phase interface barrier and ensures sufficient mixing of reactants while maintaining good heat transfer efficiency through continuous flow micro-reaction calorimeter, which is very suitable for the development of acrylic acid reaction polymerization process.

[0025] 2. The polyacrylic acid reaction polymerization enthalpy change determination process based on the micro-reaction calorimeter utilizes the above-mentioned advantages of the continuous flow micro-reaction calorimeter to screen the initiator content, improve the reaction efficiency, and obtain a higher yield and the polymerization reaction enthalpy value at the optimal yield.

[0026] 3. Compared with the current continuous flow process, the semi-batch reaction calorimetry method is used for the determination of polymerization enthalpy change of polyacrylic acid reaction based on micro-reaction calorimeter. It can only obtain the total reaction heat, but not the exothermic change process of the actual process. Therefore, the evaluation based on semi-batch calorimetry often leads to the problem of overly conservative results. This determination process can obtain the maximum heat release rate in the reaction process through continuous flow calorimetry, simulate the maximum reaction enthalpy under different working conditions, etc., which provides data support for more reasonable evaluation of continuous flow reactions in the future. This has a good guiding significance for actual factory production, and can be equipped with a more suitable refrigeration system to ensure production safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the micro-reaction calorimeter of the present invention;

[0028] Figure 2 It is a schematic diagram of injection of the continuous flow reactant system of the present invention.

[0029] In the figure: 1. Insulating foam; 2. Stainless steel plate; 3. Reaction chamber; 4. Reference chamber; 5. Thermopile; 6. Serpentine microchannel; 601. Primary tube; 602. Secondary tube; 603. Tertiary tube; 604. Serpentine reaction aluminum plate; 60401. Preheating aluminum plate; 60402. Reaction aluminum plate; 605. Three-way pipe; 7. Heat exchange channel inlet; 8. Heat exchange channel outlet. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] like Figure 1 , Figure 2 As shown, the present invention provides a technical solution: a process for measuring the polymerization enthalpy change of polyacrylic acid reaction based on a micro-reaction calorimeter, comprising the following steps:

[0032] S1. A reaction calorimetric system suitable for the polymerization reaction is formed by combining a microchannel reaction module, a local calorimetric module, connecting accessories, and a material conveying device, that is, a continuous flow micro-reaction calorimeter. The continuous flow micro-reaction calorimeter includes a reaction chamber 3 and a reference chamber 4 formed by a stainless steel plate 2. A thermopile 5 is installed in each of the reaction chamber 3 and the reference chamber 4. A serpentine microchannel 6 is fixed on the thermopile 5. An insulating foam 1 is arranged on the periphery of the stainless steel plate 2. A heat transfer layer is arranged between the insulating foam 1 and the stainless steel plate 2. A heat exchange channel inlet 7 and a heat exchange channel outlet 8 of an external constant temperature circulating oil bath system are arranged on the lower end surface of the insulating foam 1. After the light oil in the constant temperature circulating oil bath system flows out, it flows into the heat transfer layer through the heat exchange channel inlet 7, and flows out from the heat exchange channel outlet 8 and flows back into the constant temperature circulating oil bath system, thereby realizing the closed-loop circulation of the light oil. Specifically, the thermopile 5 is composed of Peltier elements, and the specifications of the S1 continuous flow micro-reaction calorimeter are: microchannel characteristic size R=2mm; calorimetric sensitive area composed of Peltier elements 50mm×50mm; reactor specific surface area 2500m2 / m3; heat transfer coefficient 1700kW / (m2·K).

[0033] S2. Prepare a reaction solution: At room temperature, prepare sodium metabisulfite and sodium persulfate into a solution according to the material ratio.

[0034] S3. Use three pipes of different sizes to deliver the prepared sodium metabisulfite solution, sodium persulfate solution and acrylic acid solution into the continuous flow microcalorimeter. Specifically, the smallest tube is nested into the larger tube through a three-way tube, and the larger tube is nested into the largest tube. The three pipes of different sizes are respectively connected to the syringes on the laboratory injection pump. The laboratory injection pump can be selected from but not limited to the neMESYS injection pump.

[0035] For specific implementation, please refer to Figure 2The three pipes of different sizes are respectively a primary pipe 601 for sodium persulfate solution, a secondary pipe 602 for sodium pyrosulfite solution and a tertiary pipe 603 for acrylic acid solution, wherein the primary pipe 601 is made of HPFA material and has a size of 360 μm; 150 μm, the secondary pipe 602 is made of PEEK material and has a size of (800 μm; 510 μm), the tertiary pipe 603 is made of PFA material and has a size of (1.6 mm; 1 mm), and the primary pipe 601 is connected to the secondary pipe 602 through a tee pipe 605, and the secondary pipe 602 is connected to the tertiary pipe 603 through the tee pipe 605, so that the three pipes can be respectively injected with three solutions and mixed at appropriate positions in the tertiary pipe 603.

[0036] S4, preheating of reactants: The three pipes containing the three solutions in the above S3 are first passed to the serpentine reaction aluminum plate 604, and preheated by the serpentine preheating aluminum plate 60401 set on the serpentine reaction aluminum plate 604 to reach the required reaction temperature.

[0037] S5. Mixing reaction: The three preheated fluids in the above S4 can be mixed and reacted on the reaction aluminum plate 60402.

[0038] S6. Use microfluidic chips and Peltier elements to monitor the temperature during the reaction and convert the heat released by the reaction into electrical signals.

[0039] S7. The experimental temperature was set at 70°C to allow the hot start of sodium persulfate to generate free radicals to interact with acrylic acid in the solution. The device was first calibrated and verified using an acid-base reaction, and then the polymerization and thermal effects of the reaction system solid content (sodium hydroxide, sodium metabisulfite, sodium persulfate) at 10%, 20%, 30%, and 47% were studied. In the specific implementation, the molar ratio in the experiment was defined as: n (sodium persulfate): n (acrylic acid) = 1:40, n (sodium metabisulfite): n (acrylic acid) = 1:20.

[0040] S8. The yield of polyacrylic acid under different initiator contents in the reaction system is calculated by hydrogen nuclear magnetic spectrum, and the effect of initiator content on the yield of polyacrylic acid is obtained.

[0041] Through the above-mentioned measurement process, the industrial acrylic acid polymerization process was simulated under specific conditions, and the influence of the initiator dosage on acrylic acid polymerization was studied. The yield and enthalpy of acrylic acid polymerization under different initiator dosages were obtained, and it was found that with the increase of the initiator dosage, the polyacrylic acid yield and the polymerization enthalpy value showed a trend of first increasing and then decreasing. After conclusion analysis, it can be obtained that the optimal initiator dosage of the synthesis process is 30%. At this time, the maximum yield of acrylic acid polymerization reaction is 95%, and the polymerization reaction enthalpy △H=79.6kJ / mol.

[0042] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A process for measuring the polymerization enthalpy change of polyacrylic acid reaction based on a micro-reaction calorimeter, characterized in that: The following steps are involved: S1, forming a reaction calorimetric system suitable for the polymerization reaction by combining a microchannel reaction module, a local calorimetric module, connection accessories, and a material conveying device, that is, forming a continuous flow micro-reaction calorimeter; S2. Prepare a reaction solution: prepare sodium metabisulfite and sodium persulfate into a solution according to the material ratio at room temperature; S3, using three pipes of different sizes to deliver the prepared sodium metabisulfite solution, sodium persulfate solution and acrylic acid solution into the continuous flow microcalorimeter; S4, preheating of reactants; S5, mixed reaction; S6, using microfluidic chips and Peltier elements to monitor the temperature during the reaction and convert the heat released by the reaction into electrical signals; S7. Setting the experimental temperature at 70°C to allow the thermal start of sodium persulfate to generate free radicals to interact with acrylic acid in the solution, comprising the following steps: A1. Calibrate and verify the device using acid-base reaction; A2. Study the polymerization and thermal effects when the solid content of the reaction system, i.e., sodium hydroxide, sodium metabisulfite and sodium persulfate, is 10%, 20%, 30% and 47%; S8. Calculate the yield of polyacrylic acid at different initiator contents in the reaction system by hydrogen nuclear magnetic spectrum, and obtain the effect of initiator content on the yield of polyacrylic acid; The continuous flow micro-reaction calorimeter in S1 comprises a reaction chamber (3) and a reference chamber (4) formed by a stainless steel plate (2), wherein a thermopile (5) is installed in each of the reaction chamber (3) and the reference chamber (4), wherein a serpentine microchannel (6) is fixed on the thermopile (5), an insulating foam (1) is arranged on the periphery of the stainless steel plate (2), a heat transfer layer is arranged between the insulating foam (1) and the stainless steel plate (2), and a heat exchange channel inlet (7) and a heat exchange channel outlet (8) of an externally connected constant temperature circulating oil bath system are arranged on the lower end surface of the insulating foam (1); The S3 uses a three-way pipe to nest the smallest tube into the larger tube, and the larger tube is nested into the largest tube. The three pipes of different sizes are respectively connected to the syringes on the laboratory injection pump.

2. The process for determining the polymerization enthalpy change of polyacrylic acid reaction based on micro-reaction calorimeter according to claim 1, characterized in that: The thermopile (5) is composed of Peltier elements, and the specifications of the S1 continuous flow micro-reaction calorimeter are as follows: microchannel characteristic dimension R=2 mm; calorimetric sensitive area composed of Peltier elements 50 mm×50 mm; reactor specific surface area 2500 m2 / m3; heat transfer coefficient 1700 kW / (m2•K).

3. The process for determining the polymerization enthalpy change of polyacrylic acid reaction based on micro-reaction calorimeter according to claim 1, characterized in that: After the light oil in the constant temperature circulating oil bath system flows out, it flows into the heat transfer layer through the heat exchange channel inlet (7), and flows out from the heat exchange channel outlet (8) and flows back into the constant temperature circulating oil bath system.

4. The process for determining the polymerization enthalpy change of polyacrylic acid reaction based on micro-reaction calorimeter according to claim 1, characterized in that: The S4 comprises: preheating the sodium metabisulfite solution, sodium persulfate solution and acrylic acid solution configured in the S3 and introduced into the continuous flow microcalorimeter using a preheating aluminum plate before mixing them on the serpentine reaction aluminum plate to reach the required reaction temperature.

5. The process for determining the polymerization enthalpy change of polyacrylic acid reaction based on micro-reaction calorimeter according to claim 4, characterized in that: In S4, the sodium pyrosulfite solution, sodium persulfate solution and acrylic acid solution preheated by the preheating aluminum plate are mixed and reacted on the reaction aluminum plate.

6. The process for determining the polymerization enthalpy change of polyacrylic acid reaction based on micro-reaction calorimeter according to claim 1, characterized in that: The molar ratios in S7 are defined as follows: n(sodium persulfate):n(acrylic acid)=1:40, n(sodium metabisulfite):n(acrylic acid)=1:20.

Images