A bifunctional solid acid catalyst for promoting desorption of CO2-rich liquid, and its preparation method and application

Abstract

A bifunctional solid acid catalyst for promoting CO2 desorption in rich solutions, its preparation method, and its application, comprising the following steps: preparing an aqueous solution of iron salt and an aqueous solution of phosphoric acid respectively; adding HZSM-5 to the aqueous solution of iron salt, followed by ultrasonication, heating and stirring, cooling, and centrifugation to separate the solid and liquid phases to obtain precipitate A, which is then washed, dried, and calcined to obtain calcined product A; adding calcined product A to the aqueous solution of iron salt, followed by ultrasonication, heating and stirring, cooling, and centrifugation to separate the solid and liquid phases to obtain precipitate B, which is then washed, dried, and calcined to obtain Fe-HZSM-5; adding Fe-HZSM-5 to the aqueous solution of phosphoric acid, followed by ultrasonication and stirring at room temperature, and centrifugation to separate the solid and liquid phases to obtain precipitate C, which is then washed, dried, and calcined to obtain PO4. 3‑ / Fe-HZSM-5. Applying the catalyst obtained by this method to the desorption process of CO2-rich solution can significantly improve the desorption rate and desorption efficiency, and reduce the regeneration energy consumption of CO2-rich amine solution.

Description

Technical Field

[0001] This invention belongs to the field of catalyst processing technology, specifically relating to a bifunctional solid acid catalyst that promotes CO2-rich liquid desorption, its preparation method, and its application. Background Technology

[0002] CO2 is a major contributor to global warming. To achieve the goal of limiting global warming to within 2°C of pre-industrial levels, it is imperative to reduce CO2 emissions, especially from coal-fired power plants. Carbon dioxide capture, utilization, and storage (CCUS) technology has been identified as an effective means to reduce CO2 emissions. Chemical absorption based on monoethanolamine (MEA) has become the most widely used CO2 capture technology in coal-fired power plants due to its high decarbonization efficiency and simple process. However, problems such as high regeneration heat load, equipment corrosion, solvent loss, and degradation during CO2 desorption seriously hinder its industrial development. Therefore, developing carbon capture technologies with excellent absorption performance and low regeneration energy consumption has become a hot topic both domestically and internationally. Adding molecular sieve catalysts to the CO2 desorption process has become one of the most promising carbon capture technologies. This technology can significantly improve the CO2 desorption rate, increase CO2 desorption efficiency, reduce regeneration time, and lower regeneration temperature, thereby reducing regeneration energy consumption. Currently, molecular sieve catalysts are mainly modified through alkali treatment, metal impregnation, metal ion exchange, and chemical vapor deposition. Among these, metal ion exchange has become a research hotspot in recent years. Summary of the Invention

[0003] The purpose of this invention is to provide a bifunctional solid acid catalyst for promoting CO2-rich liquid desorption, its preparation method and application. The preparation method is simple, and the solid acid catalyst prepared can significantly improve the desorption capacity and desorption efficiency when applied to the CO2-rich liquid desorption process, reduce the regeneration energy consumption of CO2-rich amine solutions, and thus reduce the cost of CO2 capture by organic amine method.

[0004] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0005] A method for preparing a bifunctional solid acid catalyst that promotes CO2-rich liquid desorption includes the following steps:

[0006] (1) Prepare an aqueous solution of iron salt with a concentration of 0.015-0.017 mol / L by dissolving iron salt in water; prepare an aqueous solution of phosphoric acid with a concentration of 0.25-1 mol / L by dissolving phosphoric acid in water;

[0007] (2) Add HZSM-5 molecular sieve to iron salt aqueous solution, wherein the solid-liquid ratio between the molecular sieve HZSM-5 and the iron salt aqueous solution is 1g:(10-20)ml, sonicate at room temperature, heat and stir to carry out the first ion exchange, cool, and centrifuge to separate the solid and liquid to obtain precipitate A.

[0008] (3) The precipitate A was washed, dried and calcined to obtain calcined product A;

[0009] (4) Add the calcined product A to the iron salt aqueous solution, wherein the solid-liquid ratio between the calcined product A and the iron salt aqueous solution is 1g:(10-20)ml, sonicate at room temperature, heat and stir to carry out a second ion exchange, cool, and centrifuge to separate the solid and liquid to obtain precipitate B.

[0010] (5) The precipitate B was washed, dried and calcined to obtain Fe-HZSM-5;

[0011] (6) Add Fe-HZSM-5 to a phosphoric acid aqueous solution, wherein the solid-liquid ratio between Fe-HZSM-5 and the phosphoric acid aqueous solution is 1g:(100-200)ml, sonicate at room temperature, stir at room temperature, and centrifuge to separate the solid and liquid to obtain precipitate C;

[0012] (7) The precipitate C was washed, dried and calcined to obtain the bifunctional solid acid catalyst PO4. 3- / Fe-HZSM-5.

[0013] Preferably, in step (2), the ultrasonic treatment time is 5 to 40 minutes, the heating reaction temperature is 30 to 120°C, and the heating reaction time is 4 to 20 hours.

[0014] Preferably, in step (3), the drying temperature is 60-120℃, the drying time is 8-24h, the calcination temperature is 400-800℃, and the calcination time is 3-10h.

[0015] Preferably, in step (4), the ultrasonic treatment time is 5 to 40 minutes, the heating reaction temperature is 30 to 120°C, and the heating reaction time is 4 to 20 hours.

[0016] Preferably, in step (5), the drying temperature is 60-120℃, the drying time is 8-24h, the calcination temperature is 400-800℃, and the calcination time is 3-10h.

[0017] Preferably, in step (6), the ultrasonic time is 10 min to 40 min and the stirring time is 12 to 48 h.

[0018] Preferably, in step (7), the drying temperature is 60℃~120℃, the drying time is 8~24h, the calcination temperature is 400℃~800℃, and the calcination time is 3h~10h.

[0019] The present invention also provides a bifunctional solid acid catalyst prepared by the above preparation method.

[0020] The present invention also provides the application of the above-mentioned bifunctional solid acid catalyst in the catalytic desorption of carbon dioxide. The bifunctional solid acid catalyst is added to a CO2-rich MEA aqueous solution and reacted at 92°C to desorb CO2, thereby regenerating the MEA. The mass fraction of the MEA aqueous solution is 30%. The CO2 content in the CO2-rich MEA aqueous solution is 0.58-0.60 mol CO2 / mol MEA.

[0021] Preferably, the mass concentration of the bifunctional solid acid catalyst in the CO2-rich MEA aqueous solution is 0.05%.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The preparation process of this invention is simple and low in cost;

[0024] (2) Lowering the desorption temperature and increasing the desorption rate: The addition of the bifunctional solid acid catalyst prepared in this invention enables CO2 desorption to be carried out at a lower desorption temperature (90-92℃), accompanied by a faster desorption rate, higher CO2 desorption capacity and lower regeneration energy consumption.

[0025] (3) Enhance catalytic activity and stability: The present invention uses a bifunctional solid acid catalyst prepared by metal ion exchange method. This method introduces metal active groups by adjusting the pore structure, pore size distribution and acidic site distribution of BASs and LASs. Due to the synergistic effect between metal oxide and molecular sieve, it exhibits excellent catalytic activity and stability, which is beneficial to improving the catalytic CO2 desorption performance. Attached Figure Description

[0026] Figure 1 The graph shows the change in CO2 desorption capacity catalyzed by Fe-HZSM-5 prepared in step (5) of Example 1 over time;

[0027] Figure 2 The graph shows the change in CO2 desorption rate catalyzed by Fe-HZSM-5 prepared in step (5) of Example 1 over time.

[0028] Figure 3 The PO4 prepared in Examples 1 to 4 respectively 3- / Fe-HZSM-5 catalyzed CO2 desorption capacity over time;

[0029] Figure 4 The PO4 prepared in Examples 1 to 4 respectively 3- / Fe-HZSM-5 catalyzed CO2 desorption capacity over time;

[0030] Figure 5 The HZSM-5 used in the examples, the Fe-HZSM-5 prepared in step (5) of Example 1, and the PO4 prepared in Example 1 are all mentioned. 3- XRD pattern of Fe-HZSM-5;

[0031] Figure 6 This is a diagram of a CO2 absorption and desorption device. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments.

[0033] Example 1

[0034] A method for preparing a bifunctional solid acid catalyst that promotes CO2-rich liquid desorption includes the following steps:

[0035] (1) Dissolve iron salt in deionized water, mix well, and prepare an aqueous solution of iron salt with a concentration of 0.015 mol / L; dissolve phosphoric acid in water to prepare an aqueous solution of phosphoric acid with a concentration of 0.25 mol / L;

[0036] (2) Add 2g of HZSM-5 powder to 30ml of 0.015mol / L iron salt aqueous solution, sonicate at room temperature for 15min, mix evenly to form a uniform suspension, stir at 70℃ for 12h for the first ion exchange, cool to room temperature, centrifuge and filter to separate precipitate A.

[0037] (3) The precipitate A was washed with deionized water and then dried at 100°C for 12 hours. The product was then placed in a muffle furnace for calcination at 500°C for 6 hours to obtain calcined product A, which is a brownish-yellow powder.

[0038] (4) Add 2g of calcined product A to 30ml of 0.015mol / L iron salt aqueous solution, sonicate at room temperature for 15min, mix evenly to form a uniform suspension, stir at 70℃ for 12h for a second ion exchange, cool to room temperature, centrifuge and filter to separate precipitate B.

[0039] (5) The precipitate B was washed with deionized water and then dried at 100°C for 12 hours. The product was then placed in a muffle furnace for calcination at 500°C for 6 hours to obtain Fe-HZSM-5, which was a brownish-yellow powder.

[0040] (6) Add 1g Fe-HZSM-5 to 100ml of 0.25mol / L phosphoric acid aqueous solution, sonicate at room temperature for 10min, stir at room temperature until homogeneous, stir at room temperature for 12h, centrifuge and filter to obtain precipitate C.

[0041] (7) The precipitate C was washed with deionized water and then dried at 100°C for 12 h. The resulting product was then calcined in a muffle furnace at 500°C for 6 h to obtain a brownish-yellow bifunctional solid acid catalyst PO4. 3- / Fe-HZSM-5.

[0042] The HZSM-5 used in this embodiment, the Fe-HZSM-5 prepared in step (5) of this embodiment, and the PO4 prepared in step (7) of this embodiment. 3- The XRD pattern of Fe-HZSM-5 is as follows: Figure 5 As shown in the figure, the XRD patterns before and after modification tend to be consistent, indicating that the Fe metal modification and phosphoric acid post-treatment did not change the structure of HZSM-5, and the framework of HZSM-5 did not undergo desiliconization and dealuminization due to high-temperature calcination, thus reducing its activity; no characteristic diffraction peaks of Fe and P were found in the XRD pattern, indicating that Fe and P are highly dispersed on the surface of HZSM-5.

[0043] Example 2

[0044] The only difference between this embodiment and Example 1 is that in step (1), a 0.5 mol / L phosphoric acid aqueous solution is prepared. All other steps are the same as in Example 1.

[0045] Example 3

[0046] The only difference between this embodiment and Example 1 is that in step (1), a 0.75 mol / L phosphoric acid aqueous solution is prepared; all other steps remain the same as in Example 1.

[0047] Example 4

[0048] The only difference between this embodiment and Example 1 is that in step (1), a 1 mol / L phosphoric acid aqueous solution is prepared; all other steps remain the same as in Example 1.

[0049] The brownish-yellow powder-like bifunctional solid acid catalyst prepared in the above examples was named PO4. 3- / Fe-HZSM-5(x), where x refers to the concentration of phosphoric acid, that is, the catalysts prepared in Examples 1 to 4 are named PO4. 3- / Fe-HZSM-5(0.25), PO4 3- / Fe-HZSM-5(0.5), PO4 3- / Fe-HZSM-5(0.75), PO4 3- / Fe-HZSM-5(1).

[0050] CO2-rich MEA aqueous solution: CO2 is introduced into the MEA aqueous solution, the absorption temperature is 40℃, and the absorption is carried out until saturation to obtain a CO2-rich MEA aqueous solution; the concentration of the MEA aqueous solution is 4.9 mol / L; the CO2 content in the CO2-rich MEA aqueous solution is 0.58-0.60 mol CO2 / mol MEA.

[0051] Blank experiment: The CO2-rich MEA aqueous solution was heated to 92℃ for desorption. The desorption results are shown in [the table below]. Figure 1 , Figure 2 .

[0052] Ethanolamine (MEA) is one of the fundamental methods for capturing carbon dioxide (CO2) using organic amines. Its stable carbamate products are a major obstacle to the high energy consumption required for amine solution regeneration, and also serve as a standard for verifying the good performance of the catalyst in this invention. By increasing the desorption rate at the same desorption temperature, using a wet flow meter for indirect measurement, and providing heat through an oil bath, the energy consumption for amine solution regeneration can be reduced.

[0053] A CO2 absorption and desorption device was built to simulate the actual decarbonization process, using... Figure 6 The MEA solution thermal desorption apparatus shown consists primarily of a 250 mL three-necked flask. The left neck is sealed with a rubber stopper (or glass stopper) to ensure the apparatus is airtight. A 300 mm long serpentine condenser is connected to the central neck. This condenser prevents amine loss due to evaporation during high-temperature desorption. A wet scrubber is connected after the condenser to measure the amount of amine desorbed in real time. A thermometer is installed on the right neck to monitor the temperature change of the amine solution. The amine solution is heated via an oil bath, while a rotor stirrer ensures thorough mixing of the catalyst and the amine solution.

[0054] To complete the experiment, CO2 was first bubbled into 100g of 30% MEA aqueous solution at a flow rate of 200ml / min. The CO2 absorption temperature was 40℃, and absorption was continued until saturation (CO2 loading was 0.58-0.60 mol / mol). -1 MEA); after this treatment, the CO2 loading of the MEA aqueous solution was between 0.58-0.6 mol CO2 / mol MEA. Next, HZSM-5 used in the examples, Fe-HZSM-5 prepared in step (5) of Example 1, and PO4 were added to these CO2-rich MEA aqueous solutions respectively. 3- / Fe-HZSM-5(0.25), PO4 3- / Fe-HZSM-5(0.5), PO4 3- / Fe-HZSM-5(0.75), PO4 3- / Fe-HZSM-5(1), with a catalyst addition amount of 0.05g. A blank control group was also added, i.e., no catalyst was added for desorption.

[0055] The three-necked flask was placed in an oil bath at 92°C for the reaction until desorption was complete. Generally, the end of desorption can be considered when the wet scrubber has remained stationary for about 5 minutes. The desorbed CO2 gas passes through a condenser and then returns to the wet scrubber. Finally, the experimental results were plotted using Origin plotting software. The results are shown below. Figures 1 to 4 .

[0056] Depend on Figures 1 to 4 It is clear that the bifunctional solid acid catalysts prepared in Examples 1 to 4 enable the CO2 desorption process to proceed at lower temperatures, accompanied by higher desorption rates, higher desorption capacities, and lower energy consumption. Among them, Fe-HZSM-5 significantly improves CO2 desorption performance, with a maximum desorption rate of 0.19 mmol / mol. -1 MEA s -1 Compared with the blank control group, the desorption rate increased by approximately 33%. Examples 1 to 4 show that phosphoric acid post-treatment can improve the catalytic activity of Fe-HZSM-5, with the optimal catalytic desorption performance at a phosphoric acid concentration of 0.5 mol / L, exhibiting a maximum desorption rate of 0.19 mmol / L. -1 MEA s -1 Compared with the blank control group, the desorption rate increased by about 50%. The desorption temperature in this experiment was 92℃, while the conventional desorption temperature is 110℃, which can significantly reduce water vaporization and thus reduce regeneration energy consumption.

Claims

1. A method for preparing a bifunctional solid acid catalyst that promotes CO2-rich liquid desorption, characterized in that, Includes the following steps: (1) Prepare an aqueous solution of iron salt with a concentration of 0.015-0.017 mol / L by dissolving iron salt in water; prepare an aqueous solution of phosphoric acid with a concentration of 0.25-1 mol / L by dissolving phosphoric acid in water; (2) Add HZSM-5 molecular sieve to iron salt aqueous solution, wherein the solid-liquid ratio between the molecular sieve HZSM-5 and the iron salt aqueous solution is 1g:(10-20)ml, sonicate at room temperature, heat and stir to carry out the first ion exchange, cool, and centrifuge to separate the solid and liquid to obtain precipitate A. (3) The precipitate A was washed, dried and calcined to obtain calcined product A; (4) Add the calcined product A to the iron salt aqueous solution, wherein the solid-liquid ratio between the calcined product A and the iron salt aqueous solution is 1g:(10-20)ml, sonicate at room temperature, heat and stir to carry out a second ion exchange, cool, and centrifuge to separate the solid and liquid to obtain precipitate B. (5) The precipitate B was washed, dried and calcined to obtain Fe-HZSM-5; (6) Add Fe-HZSM-5 to a phosphoric acid aqueous solution, wherein the solid-liquid ratio between Fe-HZSM-5 and the phosphoric acid aqueous solution is 1g:(100-200)ml, sonicate at room temperature, stir at room temperature, and centrifuge to separate the solid and liquid to obtain precipitate C; (7) The precipitate C was washed, dried and calcined to obtain the bifunctional solid acid catalyst PO4. 3- / Fe-HZSM-5.

2. The method for preparing a bifunctional solid acid catalyst for promoting CO2-rich liquid desorption according to claim 1, characterized in that, In step (2), the ultrasonic treatment time is 5 to 40 minutes, the heating reaction temperature is 30 to 120°C, and the heating reaction time is 4 to 20 hours.

3. A method for preparing a bifunctional solid acid catalyst for promoting CO2-rich liquid desorption according to claim 1 or 2, characterized in that, In step (3), the drying temperature is 60-120℃, the drying time is 8-24h, the calcination temperature is 400-800℃, and the calcination time is 3-10h.

4. The method for preparing a bifunctional solid acid catalyst for promoting CO2-rich liquid desorption according to claim 1, characterized in that, In step (4), the ultrasonic treatment time is 5 to 40 minutes, the heating reaction temperature is 30 to 120°C, and the heating reaction time is 4 to 20 hours.

5. A method for preparing a bifunctional solid acid catalyst for promoting CO2-rich liquid desorption according to claim 1 or 2, characterized in that, In step (5), the drying temperature is 60-120℃, the drying time is 8-24h, the calcination temperature is 400-800℃, and the calcination time is 3-10h.

6. The method for preparing a bifunctional solid acid catalyst for promoting CO2-rich liquid desorption according to claim 3, characterized in that, In step (6), the ultrasonic time is 10 min to 40 min and the stirring time is 12 to 48 h.

7. A method for preparing a bifunctional solid acid catalyst for promoting CO2-rich liquid desorption according to claim 1 or 2, characterized in that, In step (7), the drying temperature is 60℃~120℃, the drying time is 8~24h, the calcination temperature is 400℃~800℃, and the calcination time is 3h~10h.

8. A bifunctional solid acid catalyst prepared by any one of the preparation methods described in claims 1-7.

9. The application of the bifunctional solid acid catalyst according to claim 8 in the catalytic desorption of carbon dioxide, characterized in that, The bifunctional solid acid catalyst is added to a CO2-rich MEA aqueous solution, and the reaction is carried out at 92°C to desorb CO2 and regenerate the MEA. The mass fraction of the MEA aqueous solution is 30%. The CO2 content in the CO2-rich MEA aqueous solution is 0.58-0.60 mol CO2 / mol MEA.

10. The application according to claim 9, characterized in that, The mass concentration of the bifunctional solid acid catalyst in a CO2-rich MEA aqueous solution is 0.05%.

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