A method for preparing low-melting-point mixed liquid hydrogen storage materials and their applications

Abstract

This invention provides a method for preparing a low-melting-point mixed liquid hydrogen storage material and its application, relating to the field of organic liquid hydrogen storage materials technology. The low-melting-point mixed liquid hydrogen storage material of this invention is composed of at least two organic liquid hydrogen storage molecules selected from acridine, aziridine, and aziridine. By adjusting the raw material composition and preparation process, this invention achieves the technical effect of lowering the eutectic point of the material and increasing its hydrogen storage capacity. The theoretical hydrogen storage capacity of the mixed hydrogen storage material of this invention can reach 6.01 wt%, and the hydrogenation conditions are mild, allowing for complete dehydrogenation.

Description

Technical Field

[0001] This invention relates to the field of organic liquid hydrogen storage materials technology, and in particular to a method for preparing a low-melting-point mixed liquid hydrogen storage material and its application. Background Technology

[0002] Organic liquid hydrogen storage molecules are mainly nitrogen-containing fused heterocyclic aromatic compounds, especially carbazoles, which have mild dehydrogenation conditions and high hydrogen purity, making them excellent organic liquid hydrogen storage molecules. However, among carbazole molecules, propylcarbazole (NPCZ) has the lowest melting point at 48°C and a hydrogen storage capacity of 5.43 wt%, while ethylcarbazole (NECZ) has a melting point of 68°C and a hydrogen storage capacity of 5.79 wt%. This shows that carbazole molecules have relatively low hydrogen storage capacity and melting points above room temperature, thus limiting their application as organic liquid hydrogen storage molecules. Acridine (ACD) is a hydrogen storage molecule with high hydrogen storage capacity and a high melting point, with a theoretical hydrogen storage capacity of 7.25 wt% and a melting point of 111°C. However, its dehydrogenation reaction is difficult to carry out, making it unsuitable for use as a commonly used organic liquid hydrogen storage molecule.

[0003] In summary, current single-molecule hydrogen storage systems are generally solid at room temperature and have low hydrogen storage capacity, which does not meet the concept and requirements of liquid organic hydrogen storage. Therefore, how to provide a hybrid liquid hydrogen storage material with a melting point below room temperature that can maintain a liquid state at room temperature while possessing a high hydrogen storage capacity is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for preparing a low-melting-point mixed liquid hydrogen storage material and its application. By adjusting the raw material composition and preparation process, the technical effect of lowering the eutectic point of the material is achieved, and the hydrogen storage capacity of the material is increased. The method for preparing the low-melting-point mixed liquid hydrogen storage material of this invention is as follows: weigh organic liquid hydrogen storage molecules and mix them evenly to obtain a low-melting-point mixed liquid hydrogen storage material.

[0005] This invention utilizes differential scanning calorimetry to determine the eutectic point of a mixture and plots a eutectic point phase diagram of the mixed hydrogen storage material, thereby determining the proportion of the mixture with the lowest eutectic point.

[0006] Furthermore, the organic liquid hydrogen storage molecule is at least two of acridine, aziridine carbazole, and aziridine carbazole.

[0007] Furthermore, the organic liquid hydrogen storage molecule is acridine and aziridine-propylcarbazole, and the weight ratio of acridine to aziridine-propylcarbazole is 0.32:0.68.

[0008] Furthermore, the organic liquid hydrogen storage molecule is acridine and aziridine-ethylcarbazole, and the weight ratio of acridine to aziridine-ethylcarbazole is 0.43:0.57.

[0009] Furthermore, the organic liquid hydrogen storage molecule is aziridine carbazole and aziridine carbazole, and the weight ratio of aziridine carbazole to aziridine carbazole is 0.56:0.44.

[0010] Furthermore, the organic liquid hydrogen storage molecule is acridine, aziridine-propylcarbazole, and aziridine-ethylcarbazole, and the weight ratio of acridine, aziridine-propylcarbazole, and aziridine-ethylcarbazole is 0.207:0.433:0.360.

[0011] The eutectic point of the acridine and aziridine-ethylcarbazole mixture was found to be 26°C, the eutectic point of the acridine and aziridine-ethylcarbazole mixture was 49°C, the eutectic point of the aziridine and aziridine-ethylcarbazole mixture was 9°C, and the eutectic point of the acridine, aziridine-ethylcarbazole, and aziridine-ethylcarbazole mixture was 1°C.

[0012] Another object of the present invention is to provide an application of the mixed liquid hydrogen storage material prepared according to the above method in hydrogen storage.

[0013] The application method of the mixed liquid hydrogen storage material is as follows:

[0014] (1) Hydrogenation of materials:

[0015] S1. Mix the mixed liquid hydrogen storage material with the hydrogenation catalyst and add it to the reactor;

[0016] S2. Charge hydrogen into the reactor to purge the air from the reactor and bring the pressure inside the reactor back to atmospheric pressure.

[0017] S3. Increase the temperature and pressure of the reactor and carry out the hydrogenation reaction at a fixed rotation speed to obtain a fully hydrogenated mixed hydrogen storage molecule product;

[0018] (2) Material dehydrogenation:

[0019] S4. Add the fully hydrogenated mixed hydrogen storage molecule product and the dehydrogenation catalyst to the reaction apparatus;

[0020] S5. The dehydrogenation reaction is carried out in an oil bath. After the reaction is complete, the dehydrogenation product is obtained.

[0021] Furthermore, the hydrogenation catalyst in S1 is 5 wt% Ru / Al2O3, and the amount added is 10% of the total weight of the hydrogen storage molecules.

[0022] Furthermore, the hydrogenation reaction temperature in S3 is 130℃~170℃, the hydrogenation reaction time is 3h, and the rotation speed is 600r / min.

[0023] Furthermore, the dehydrogenation catalyst in S4 is 3wt% Pd / Ce3La7Al, and the amount added is 20% of the total weight of the hydrogen storage molecules.

[0024] Furthermore, the dehydrogenation reaction temperature in S5 is 230℃~260℃.

[0025] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0026] (1) By adjusting the raw material composition and preparation process of the material, the present invention achieves the technical effect of reducing the eutectic point of the material and increasing the hydrogen storage capacity of the material;

[0027] (2) The theoretical hydrogen storage capacity of the hybrid hydrogen storage material of the present invention can reach 6.01 wt%;

[0028] (3) The hydrogen storage material of the present invention has mild hydrogenation conditions and can achieve complete dehydrogenation. Attached Figure Description

[0029] The present invention will be further described below with reference to the accompanying drawings.

[0030] Figure 1 This is a graph showing the hydrogen storage capacity versus time variation during the hydrogenation process of the aziridine / acridine mixed hydrogen storage system at different temperatures in Example 1 of the present invention.

[0031] Figure 2 This is a graph showing the hydrogen storage capacity versus time variation during the hydrogenation process of aziridine carbazole alone in Example 1 of the present invention.

[0032] Figure 3 This is a graph showing the hydrogen storage capacity versus time variation during the acridine hydrogenation process in Example 1 of this invention.

[0033] Figure 4 This is a graph showing the hydrogen storage capacity versus time variation during the hydrogenation process of the aziridine / acridine mixed hydrogen storage system under different pressures in Example 2 of the present invention.

[0034] Figure 5 This is a graph showing the hydrogen storage capacity versus time variation during the hydrogenation process of aziridine carbazole alone in Example 2 of the present invention.

[0035] Figure 6 This is a graph showing the hydrogen storage capacity versus time variation during the acridine hydrogenation process in Example 2 of this invention.

[0036] Figure 7 This is a graph showing the change in hydrogen release over time during the dehydrogenation process of the fully hydrogenated propylcarbazole / acridine mixed hydrogen storage system at different temperatures in Example 3 of the present invention. Detailed Implementation

[0037] This invention provides a method for preparing a low-melting-point mixed liquid hydrogen storage material and its application. The method for preparing the low-melting-point mixed liquid hydrogen storage material of this invention is as follows: weigh organic liquid hydrogen storage molecules and mix them evenly to obtain a low-eutectic-point mixed liquid hydrogen storage material.

[0038] In one embodiment, the organic liquid hydrogen storage molecule is at least two of acridine, aziridine-propylcarbazole, and aziridine-ethylcarbazole.

[0039] In one embodiment, the organic liquid hydrogen storage molecule is acridine and aziridine-propylcarbazole, wherein the weight ratio of acridine to aziridine-propylcarbazole is 0.32:0.68.

[0040] In one embodiment, the organic liquid hydrogen storage molecule is acridine and aziridine-ethylcarbazole, wherein the weight ratio of acridine to aziridine-ethylcarbazole is 0.43:0.57.

[0041] In one embodiment, the organic liquid hydrogen storage molecule is aziridine carbazole and aziridine carbazole, wherein the weight ratio of aziridine carbazole to aziridine carbazole is 0.56:0.44.

[0042] In one embodiment, the organic liquid hydrogen storage molecule is acridine, aziridine-propylcarbazole, and aziridine-ethylcarbazole, wherein the weight ratio of acridine, aziridine-propylcarbazole, and aziridine-ethylcarbazole is 0.207:0.433:0.360.

[0043] Another object of the present invention is to provide an application of the mixed liquid hydrogen storage material prepared according to the above method in hydrogen storage.

[0044] The application method of the mixed liquid hydrogen storage material is as follows:

[0045] (1) Hydrogenation of materials:

[0046] S1. Mix the mixed liquid hydrogen storage material with the hydrogenation catalyst and add it to the reactor;

[0047] S2. Charge hydrogen into the reactor to purge the air from the reactor and bring the pressure inside the reactor back to atmospheric pressure.

[0048] S3. Increase the temperature and pressure of the reactor and carry out the hydrogenation reaction at a fixed rotation speed to obtain a fully hydrogenated mixed hydrogen storage molecule product;

[0049] (2) Material dehydrogenation:

[0050] S4. Add the fully hydrogenated mixed hydrogen storage molecule product and the dehydrogenation catalyst to the reaction apparatus;

[0051] S5. The dehydrogenation reaction is carried out in an oil bath. After the reaction is complete, the dehydrogenation product is obtained.

[0052] In one embodiment, the hydrogenation catalyst in S1 is 5 wt% Ru / Al2O3, and the amount added is 10% of the total weight of the hydrogen storage molecules.

[0053] In one embodiment, the hydrogenation reaction temperature in S3 is 130℃~170℃, the hydrogenation reaction time is 3h, and the rotation speed is 600r / min.

[0054] In one embodiment, the dehydrogenation catalyst in S4 is 3 wt% Pd / Ce3La7Al, and the amount added is 20% of the total weight of the hydrogen storage molecules.

[0055] In one embodiment, the dehydrogenation reaction temperature in S5 is 230°C to 260°C.

[0056] The technical solution provided by the present invention will be further described below with reference to the embodiments.

[0057] Example 1

[0058] A method for preparing a mixed liquid hydrogen storage material includes the following steps:

[0059] (1) Weighing: Accurately weigh different proportions of aziridine and acridine and mix them;

[0060] (2) Testing the eutectic point: The eutectic point of mixed liquid hydrogen storage materials with different proportions was determined using a differential scanning calorimeter;

[0061] (3) Find the optimal ratio: Based on the eutectic point of the liquid hydrogen storage materials mixed in different ratios, draw the eutectic point phase diagram of the mixed system of propylcarbazole and acridine, and find the lowest eutectic point and the optimal mixing ratio from the phase diagram;

[0062] (4) Preparation of mixed liquid hydrogen storage material: According to the optimal mixing ratio obtained in step (3), weigh 1.36g of propylcarbazole and 0.64g of acridine and 0.2g of 5wt% Ru / Al2O3, mix them evenly to obtain a binary mixed liquid hydrogen storage material of propylcarbazole and acridine.

[0063] (5) Hydrogenation:

[0064] Install the reactor: Place the binary mixed liquid hydrogen storage material of propylcarbazole and acridine from step (4) and 40 ml of n-hexane solvent into the reactor. First, install the parts. In order to ensure the airtightness of the reactor, tighten the screws diagonally. Then install the inlet and outlet water pipes, stirrer, connect the temperature sensing device, and finally close all the valves.

[0065] Adjustment: Open the inlet and outlet water pipes, check for leaks at the screw connections, and adjust the water flow; open the main hydrogen valve, adjust the pressure valve to 2MPa, and purge the reactor 3-4 times to remove all air from the reactor until the pressure inside the reactor is the same as atmospheric pressure.

[0066] Heating and pressurizing: Set the reaction temperature (130℃~170℃), turn on the rapid heating switch, and stir at 50r / min to ensure uniform heating; once the temperature reaches the set temperature, increase the pressure to 8MPa, and adjust the speed to 600r / min. Start timing, and ensure that the pressure is maintained at 8MPa throughout the reaction process.

[0067] Sampling and testing: Samples are taken at preset time intervals and numbered until the reaction is completed; samples are obtained with a capillary tube, then diluted 10,000 times with chromatographic grade n-hexane, and detected by GC-MS to monitor the reaction progress in real time.

[0068] Reaction complete: When all reactants have been converted into fully hydrogenated products, stop the reaction, close the hydrogen partial pressure valve and the total pressure valve, set the temperature sensor to 20°C, turn off the heating button and stir, and wait for cooling; after cooling is complete, clean the reactor and its components.

[0069] Product separation: After the hydrogenation reaction is completed, the hydrogenated liquid and the catalyst are separated by filtration and collected separately; then the solvent and hydrogenation product are separated by rotary evaporator, and the hydrogenation product is used for dehydrogenation.

[0070] Data processing: Obtain and record the peak area percentage of each product based on the chromatographic data, and use data plotting to determine the influence of changes in relevant factors on the reaction; investigate the optimal hydrogenation conditions.

[0071] In this embodiment, under constant conditions such as reaction pressure, catalyst type, and feedstock ratio, the time required for the mixed hydrogen storage material of aziridine and acridine to reach the fully hydrogenated product at different temperatures (130℃, 140℃, 150℃, 160℃, 170℃) was studied. The results are as follows: Figure 1 As shown. In the mixed system, at 130℃, 140℃, 150℃, 160℃, and 170℃, the hydrogen storage density of the overall system reached 5.50wt%, 5.93wt%, 5.97wt%, 6.01wt%, and 6.00wt% after 150 min of reaction, respectively; the hydrogen storage density of NPCZ after 150 min of reaction was 5.31wt%, 5.37wt%, 5.43wt%, and 5.41wt%; and the time for ACD to reach the fully hydrogenated product was 40 min, 30 min, 25 min, 16 min, and 20 min, respectively.

[0072] Under the same conditions, when NPCZ and ACD were hydrogenated separately at different temperatures (130℃, 140℃, 150℃, 160℃, 170℃), the hydrogen storage densities of NPCZ alone after reacting for 150 min at 130℃, 140℃, 150℃, 160℃, and 170℃ were 5.21wt%, 5.30wt%, 5.38wt%, and 5.40wt%, respectively. However, ACD alone could not achieve 100% hydrogenation even after reacting for 8 hours at 130℃, 140℃, 150℃, 160℃, and 170℃.

[0073] Depend on Figure 1-3 It can be seen that, under the same conditions, the hydrogen storage rate of propylcarbazole and acridine in the mixed hydrogen storage system is significantly higher than that of propylcarbazole and acridine alone.

[0074] Example 2

[0075] A specific method for hydrogenating a mixed liquid hydrogen storage material includes the following steps:

[0076] (1) Weighing: Accurately weigh 1.36g of aziridine, 0.64g of acridine, and 0.2g of 5wt% Ru / Al2O3 and place them in the reaction vessel;

[0077] (2) Install the reactor: First install the parts. To ensure the reactor is airtight, tighten the screws diagonally. Then install the inlet and outlet water pipes, the agitator, connect the temperature sensing device, and finally close all the valves.

[0078] (3) Adjustment: Open the inlet and outlet water pipes, check for leaks at the screw connections, and adjust the water volume; open the main hydrogen valve, adjust the pressure valve to 2MPa first, and charge and discharge the reactor 3 to 4 times to exhaust the air in the reactor until the pressure inside the reactor is consistent with atmospheric pressure.

[0079] (4) Heating and pressurizing: Set the reaction temperature to 160℃, turn on the rapid heating switch, and stir at 50r / min to ensure uniform heating; when the temperature reaches the set temperature, increase the pressure to the set value, and adjust the speed to 600r / min, start timing, and ensure that the pressure is maintained at the set value during the reaction process.

[0080] (5) Sampling and testing: Sampling is carried out at preset time intervals and the samples are numbered until the reaction is completed; the samples are obtained with capillary tubes and then diluted 10,000 times with 40 mL of chromatographic grade n-hexane. The reaction process is monitored in real time using GC-MS.

[0081] (6) End of reaction: When all reactants are converted into fully hydrogenated products, stop the reaction, close the hydrogen partial pressure valve and the total pressure valve, set the temperature sensor temperature to 20°C, turn off the heating button and stir, and wait for the temperature to drop; after the temperature drops, clean the reactor and its parts; repeat the above experiment to investigate the effects of catalyst ratio and hydrogen partial pressure and other factors.

[0082] (7) Product separation: After the hydrogenation reaction is completed, filter to separate the hydrogenated liquid and the catalyst, and collect them separately; then use a rotary evaporator to separate the solvent from the hydrogenation product, and the hydrogenation product is ready for dehydrogenation and use.

[0083] (8) Data processing: Obtain and record the peak area percentage of each product based on the chromatographic data, and draw the effect of changes in relevant factors on the reaction by plotting the data; study the optimal hydrogenation conditions.

[0084] This embodiment studies the effect of hydrogen pressure on the hydrogenation process of a catalytically modified propylcarbazole and acridine mixed hydrogen storage material under optimal temperature conditions and by controlling pressure as a single variable. Accurate hydrogenation process data were obtained. By selecting a method of heating first and then pressurizing, the direct participation of hydrogen in the catalytic hydrogenation reaction during the heating process was avoided. Hydrogenation pressures of 6.0 MPa, 7.0 MPa, 8.0 MPa, and 9.0 MPa were investigated for the propylcarbazole and acridine mixed hydrogen storage material. The results are as follows: Figure 4 As shown. In the mixed system, at 6 MPa, 7 MPa, 8 MPa, and 9 MPa, the hydrogen storage density of the overall system after 150 min was 5.89 wt%, 5.97 wt%, 5.99 wt%, and 5.98 wt%, respectively; the hydrogen storage density of NPCZ after 150 min was 5.26 wt%, 5.38 wt%, 5.40 wt%, and 5.38 wt%, respectively; and ACD reached full hydrogenation within half an hour.

[0085] Under identical conditions, when NPCZ and ACD were hydrogenated separately, the hydrogen storage densities of NPCZ alone at 6 MPa, 7 MPa, 8 MPa, and 9 MPa after 150 min of reaction were 5.20 wt%, 5.28 wt%, 5.31 wt%, and 5.35 wt%, respectively. For ACD alone, the times to reach full hydrogenation products at 6 MPa, 7 MPa, 8 MPa, and 9 MPa were 480 min, 360 min, 260 min, and 80 min, respectively.

[0086] Depend on Figure 4-6 It can be seen that, under the same conditions, the hydrogen storage rate of propylcarbazole and acridine in the mixed hydrogen storage system is significantly higher than that of propylcarbazole and acridine alone.

[0087] Example 3

[0088] A specific method for dehydrogenating a mixed liquid hydrogen storage material includes the following steps:

[0089] (1) Weighing: Weigh 3.4g of aziridine, 1.6g of acridine and 1g of 3wt% Pd / Ce3La7Al into a three-necked round-bottom flask, place a magnetic ball in it and set the rotation speed to 60r / min;

[0090] (2) Install the reactor: First install the parts. To ensure the reactor is airtight, tighten the screws diagonally. Then install the inlet and outlet water pipes, the agitator, connect the temperature sensing device, and finally close all the valves.

[0091] (3) Adjustment: Open the inlet and outlet water pipes, check for leaks at the screw connections, and adjust the water volume; open the main hydrogen valve, adjust the pressure valve to 2MPa first, and charge and discharge the reactor 3 to 4 times to exhaust the air in the reactor until the pressure inside the reactor is consistent with atmospheric pressure.

[0092] (4) Heating and pressurizing: Set the reaction temperature to 160℃, turn on the rapid heating switch, and stir at 50r / min to ensure uniform heating; after the temperature rises to 230-260℃, increase the pressure to the set value, and adjust the speed to 600r / min. Start timing. During the reaction, ensure that the pressure is maintained at the set value.

[0093] (5) Sampling and testing: Sampling is carried out at preset time intervals and the samples are numbered until the reaction is completed; the samples are obtained with capillary tubes and then diluted 10,000 times with 40 mL of chromatographic grade n-hexane. The reaction process is monitored in real time using GC-MS.

[0094] (6) End of reaction: When all reactants are converted into fully hydrogenated products, stop the reaction, close the hydrogen partial pressure valve and the total pressure valve, set the temperature sensor temperature to 20°C, turn off the heating button and stir, and wait for the temperature to drop; after the temperature drops, clean the reactor and its parts; repeat the above experiment to investigate the effects of catalyst ratio and hydrogen partial pressure and other factors.

[0095] (7) Product separation: After the hydrogenation reaction is completed, filter to separate the hydrogenated liquid and the catalyst, and collect them separately; then use a rotary evaporator to separate the solvent from the hydrogenation product, and the hydrogenation product is ready for dehydrogenation and use.

[0096] (8) Data processing: Obtain and record the peak area percentage of each product based on the chromatographic data, and draw the effect of changes in relevant factors on the reaction by plotting the data; study the optimal hydrogenation conditions.

[0097] like Figure 7As shown, in the mixed system, at 230℃, 240℃, 250℃, and 260℃, the hydrogen release densities of the overall system after 480 min of reaction were 5.88wt%, 5.90wt%, 5.98wt%, and 6.01wt%, respectively; the times for complete dehydrogenation of 12H~NPCZ were 180 min, 150 min, 120 min, and 60 min, respectively; and the hydrogen release densities of 14H~ACD after 480 min of reaction were 6.83wt%, 6.90wt%, 7.15wt%, and 7.25wt%, respectively.

[0098] Under otherwise identical conditions, NPCZ alone has a dehydrogenation rate comparable to that of NPCZ in the mixed system at 230℃, 240℃, 250℃, and 260℃. ACD alone, after hydrogenation, is a solid, has a high dehydrogenation temperature, and is difficult to achieve dehydrogenation.

[0099] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a low-melting-point mixed liquid hydrogen storage material, characterized in that, The specific steps are as follows: Weigh the organic liquid hydrogen storage molecules and mix them evenly to obtain a mixed liquid hydrogen storage material with a low eutectic point; The organic liquid hydrogen storage molecules are acridine and aziridine carbazole; The weight ratio of acridine to aziridine is 0.32:0.

68.

2. The application of the mixed liquid hydrogen storage material according to claim 1, characterized in that, The application method is as follows: (1) Hydrogenation of materials: S1. The mixed liquid hydrogen storage material is mixed with the hydrogenation catalyst and added to the reactor; S2. Charge hydrogen into the reactor to purge the air from the reactor and bring the pressure inside the reactor back to atmospheric pressure. S3. Increase the temperature and pressure of the reactor and carry out the hydrogenation reaction at a fixed rotation speed to obtain a fully hydrogenated mixed hydrogen storage molecule product; (2) Material dehydrogenation: S4. Add the fully hydrogenated mixed hydrogen storage molecule product and the dehydrogenation catalyst to the reaction apparatus; S5. The dehydrogenation reaction is carried out in an oil bath. After the reaction is complete, the dehydrogenation product is obtained.

3. The application of the mixed liquid hydrogen storage material according to claim 2, characterized in that, The hydrogenation catalyst in S1 is 5 wt% Ru / Al2O3, and the amount added is 10% of the total weight of the hydrogen storage molecules.

4. The application of the mixed liquid hydrogen storage material according to claim 2, characterized in that, The hydrogenation reaction temperature in S3 is 130℃~170℃, the hydrogenation reaction time is 3h, and the rotation speed is 600r / min.

5. The application of the mixed liquid hydrogen storage material according to claim 2, characterized in that, The dehydrogenation catalyst in S4 is 3wt% Pd / Ce3La7Al, and the amount added is 20% of the total weight of the hydrogen storage molecules.

6. The application of the mixed liquid hydrogen storage material according to claim 2, characterized in that, The dehydrogenation reaction temperature in S5 is 230℃~260℃.

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