Preparation method of dolomite derivative catalyst and application of dolomite derivative catalyst in catalyzing tertiary amine to absorb CO2

Abstract

The application discloses a preparation method of a dolomite derivative catalyst and application of the dolomite derivative catalyst in a reaction of absorbing CO2 by catalyzing a tertiary amine. The preparation steps of the dolomite derivative catalyst comprise the following steps: (1) drying, grinding and sieving dolomite to obtain dolomite fine material; and (2) calcining the dolomite fine material to obtain the dolomite derivative catalyst. The application has the advantages of simple operation, low cost, green cleanness, and the obtained catalyst has rich surface basic sites, large specific surface area, excellent performance in absorbing CO2 by catalyzing a tertiary amine solution, high cyclic stability and good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of gas separation technology, specifically relating to the application of a dolomite derivative catalyst for the rapid and low-energy capture of CO2 from a tertiary amine solution. Background Technology

[0002] With the acceleration of global industrialization, the large-scale combustion of fossil fuels has led to a continuous rise in atmospheric carbon dioxide (CO2) concentrations, triggering severe greenhouse effect and climate change problems. According to relevant research, CO2 emissions from industrial flue gas are one of the main sources, characterized by high flow rates and relatively low CO2 concentrations. Against this backdrop, developing efficient and economical CO2 capture technologies is of crucial strategic significance for achieving "dual carbon" goals and maintaining the sustainable development of traditional energy industries. Among numerous CO2 capture technologies, chemical absorption has become the mainstream choice for current industrial applications due to its high capture efficiency and mature technology. Among these, amine aqueous solution absorption is particularly prominent, with monoethanolamine (MEA) solutions widely used in practical engineering due to their excellent reaction kinetics. However, this method has significant drawbacks: the carbamate bond formed by the reaction of primary / secondary amines with CO2 has a high energy (about 305 kJ / mol), which leads to a large amount of energy being consumed during solvent regeneration. CO2 desorption usually needs to be carried out under high-temperature steam conditions of 120-140℃. This process accounts for 60-80% of the total energy consumption of the capture unit, which greatly increases the cost of CO2 capture and restricts its large-scale industrial promotion.

[0003] In contrast, tertiary amine absorbents such as N-methyldiethanolamine (MDEA) exhibit unique thermodynamic advantages. MDEA molecules lack NH bonds, and its CO2 absorption primarily occurs via the bicarbonate pathway. It boasts a high stoichiometric capture capacity of 1 mol CO2 / mol amine, with low regeneration energy consumption (only 58.8 kJ / mol), and also possesses better resistance to degradation and corrosion. However, a major drawback is the relatively slow CO2 absorption rate of MDEA, a kinetic bottleneck that severely limits its large-scale application in industrial settings.

[0004] To overcome the kinetic limitations of CO2 absorption in tertiary amine solutions, scholars both domestically and internationally have conducted extensive research. Early studies attempted to improve the mass and heat transfer characteristics of the absorption process by adding nanoparticle (NP) materials, such as metal oxide nanoparticles like MgO, TiO2, and CeO2 (KhdaryNH, AlayyarAS, Alsarhan LM, et al. Review. Catalysts, 2022, 12(3):300), as well as metal-organic frameworks (MOFs) (M. Usman, N. Iqbal, T. Noor, et al. Chem. Rec, 2022, 22, e202100230), carbon-based materials, etc. Studies have shown that Fe3O4 nanofluids can increase the CO2 absorption rate by 20% compared to pure MDEA solvent (Tavakoli, A, Rahimi, K, Saghandali, F, et al. Journal of Environmental Management, 2022, 313, 114955.), and Ni nanoparticles can increase the average CO2 absorption rate in MEA solvent by 34% (Seo, S, Lages, B, Kim, M. Journal of CO2 Utilization, 2022, 36, 244-252). However, the improvement effect of these nanofluids on CO2 absorption activity in MDEA solution is relatively limited, mainly because their mechanism of action relies more on physical enhancement.

[0005] In recent years, solid base catalysts have become a research hotspot due to their ability to transfer electrons to CO2 through their strongly basic surface sites, thus promoting the reaction between CO2 and amine solutions. Solid base catalysts such as CaCO3, K / MgO, and layered double hydroxides (LDH) have been applied to amine-based CO2 capture systems. Among them, LDH, with its abundant strongly basic sites, can increase the CO2 absorption rate by 92.7% (Zhang, X, Zhang, S, Tang, F, et al. Chemical Engineering Science, 2023, 278, 118889); CaO and MgO, rich in Lewis basic sites, increase the CO2 absorption rate by 17% and 16.4%, respectively (Nie, Y, Li, Y, Wang, H, et al. ACS Omega, 2023, 8, 11813-11823); MnO… xThe catalyst, possessing both abundant basic sites and unsaturated manganese sites, significantly increased the CO2 absorption rate by 360% (Zhang, X, Zhang, S, Tan, Z. et al., Chemical Engineering Journal, 2023, 465, 142878). To further improve the CO2 absorption rate of tertiary amine solutions, thereby reducing CO2 capture costs and enhancing the practicality of amine-based CO2 capture, it is crucial to develop inexpensive, efficient, and highly stable catalysts to enhance the CO2 absorption performance of tertiary amine solvents, achieving a high absorption rate and low energy consumption CO2 capture method. This has significant theoretical and practical value. Summary of the Invention

[0006] To address the problems of slow CO2 absorption rate and high catalyst cost in current tertiary amine solutions, this invention provides a method for preparing a dolomite derivative catalyst and its application. This catalyst has advantages such as high activity, good stability, inexpensive and readily available raw materials, and simple operation.

[0007] The technical solution of the present invention is as follows:

[0008] (1) Select dolomite from natural carbonate minerals with a purity of 95% or higher.

[0009] (2) The dolomite is dried, ground and sieved to obtain fine dolomite material.

[0010] (3) Dolomite fines are calcined to obtain dolomite derivative catalysts.

[0011] Preferably, in step (1), the dolomite is a natural carbonate mineral with a purity of 99%, and its origin is the Shanxi magnesia dolomite mining area;

[0012] Preferably, in step (2), the dolomite drying temperature is 80°C;

[0013] Preferably, in step (2), the dolomite drying time is 6 hours;

[0014] Preferably, in step (2), the particle size of the fine dolomite particles after grinding and sieving is 20-30 μm;

[0015] Preferably, in step (3), the calcination time of the dolomite fines is 8 hours;

[0016] Preferably, in step (3), the calcination temperature of the dolomite fines is 900℃ to obtain the dolomite derivative catalyst.

[0017] The tertiary amine solution is used as the catalyst for CO2 absorption reaction. N-methyldiethanolamine (MDEA) is preferred as the absorption solvent. The MDEA solution is prepared with a mass ratio of MDEA to pure water of 15-30 wt%, preferably 20 wt%.

[0018] The dolomite derivative catalyst of this invention can be represented as DOL-T, where T represents the calcination temperature (°C) and DOL represents dolomite. This catalyst, DOL-T, is used in the CO2 absorption process of MDEA solution in traditional organic amine solvent CO2 capture processes, and can significantly accelerate the absorption rate. The main reason for this is that DOL itself is alkaline, giving it a certain catalytic effect. After calcination, it forms a porous structure, greatly increasing its specific surface area and enriching its alkaline sites, effectively improving reaction and mass transfer efficiency.

[0019] The dolomite derivative catalyst of this invention is used to catalyze the absorption of CO2 from MDEA solution. The resulting DOL-900 exhibits a large specific surface area and abundant pore structure (specific surface area: 11.6 m²). 2 The catalyst (with an average pore size of 19.9 nm) exhibits excellent performance in catalyzing CO2 absorption in MDEA solution, increasing the instantaneous absorption rate by 168.3%, improving the absorption capacity by 68.9%, and demonstrating good cycle stability.

[0020] MDEA solution absorbs CO2 at a temperature of 25–40°C, while the flue gas from traditional coal-fired power plants is around 40°C. The methods for loading / supporting catalysts in traditional packed towers include, but are not limited to, wrapping with packing material, impregnating the packing surface, and random packing that replaces part of the packing material and the catalyst.

[0021] The beneficial effects of this invention are:

[0022] (1) The catalyst preparation process is simple and the raw materials are cheap and readily available.

[0023] (2) The catalyst has superior absorption performance and stronger catalytic performance than traditional catalysts such as physical mixtures of CaO and MgO and carbonates.

[0024] (3) The catalyst is easy to separate, has good stability, and good recyclability. Attached Figure Description

[0025] Figure 1 The diagram shows the rate of CO2 absorption in the tertiary amine solution catalyzed by the catalyst in the examples.

[0026] Figure 2 The diagram shows the amount of CO2 absorbed by the catalyst in the tertiary amine solution in the examples.

[0027] Figure 3 The X-ray diffraction pattern of the catalyst in the examples is shown.

[0028] Figure 4 The infrared spectrum of the catalyst in the examples is shown.

[0029] Figure 5The diagram shows the N2 isothermal adsorption-desorption curves of the catalyst in the examples.

[0030] Figure 6 The figure shows the CO2 temperature-programmed desorption curve of the catalyst in the examples.

[0031] Figure 7 The diagram shows a schematic of the device for absorbing CO2 with a tertiary amine solution in the embodiment.

[0032] Table 1 shows a comparison of the instantaneous increase rate and instantaneous increase amount of CO2 in the catalytic absorption of tertiary amine solution by the catalysts in the examples and the control examples. Detailed Implementation

[0033] Example 1: Preparation and Catalytic Performance Testing of DOL-900 Catalyst

[0034] (1) Catalyst preparation: 5g of industrial dolomite was placed in a crucible and placed in a muffle furnace, and calcined at 900℃ for 8h to obtain DOL-900 catalyst.

[0035] (2) Catalyst characterization: The obtained catalyst was characterized by X-ray diffraction analysis, infrared spectroscopy and N2 adsorption-desorption curves, CO2 temperature-programmed desorption and other characterization tests.

[0036] (3) Catalytic performance test: The experimental setup for the catalyst-catalyzed CO2 absorption of tertiary amine solution is as follows: Figure 7 As shown. The experimental procedure is described as follows: Weigh a certain amount of MDEA solution into a 1L volumetric flask and dilute to volume. Shake the solution evenly to obtain a 20% MDEA solution. Measure 100ml of the 20% MDEA solution into a three-necked flask using a graduated cylinder, and then weigh 1g of DOL-900 into the MDEA solution using an electronic balance. Use two mass flow meters to control the flow rates of CO2 and N2 to 250mL / min respectively, with a total flow rate of 500mL / min. Turn the valve to dual-channel mode and mix CO2 and N2 for 5min, then introduce them into the MDEA solution. The glass tube connecting the three-necked flask is a frosted glass tube, which allows CO2 to enter the MDEA solution in the form of dispersed small bubbles. Simultaneously, turn on the magnetic stirrer at 500rpm to ensure more uniform mixing of the solution and gas. The mixed gas passing through the MDEA solution is then passed through a drying tube to remove entrained moisture and prevent it from affecting the CO2 content measurement results. The dried mixed gas is introduced into the CO2 detection device, and the CO2 outlet volume fraction is recorded. The absorption temperature is set to 25℃, and the experimental duration is set to 1h.

[0037] Comparative Example 1: DOL catalyst

[0038] In contrast, the DOL catalyst is made from uncalcined industrial dolomite.

[0039] Comparative Example 2: DOL-600 catalyst

[0040] In contrast, the DOL-600 catalyst was obtained by calcining at 600℃ for 8 hours under the same equipment conditions.

[0041] Table 1. Comparison of the instantaneous increase rate and instantaneous increase amount of CO2 in CO2 absorption by the catalyst in the examples and control examples.

[0042]

[0043] As shown in the table above, compared with blank MDEA, the addition of catalysts significantly increased the absorption rate and absorption amount of MDEA, and the performance of the catalysts prepared in the examples was better than that of the comparative catalysts.

Claims

1. A method for preparing a dolomite derivative catalyst, characterized in that, Includes the following steps: (1) Dolomite is selected from natural carbonate minerals with a purity of 95% or higher. (2) The dolomite is dried, ground and sieved to obtain fine dolomite material; (3) Dolomite fines were calcined to obtain dolomite derivative catalysts.

2. As described in claim 1, characterized in that, In step (1), the dolomite origin includes, but is not limited to, Shanxi magnesia dolomite, Hebei metallurgical dolomite, and dolomite ore from eastern Hebei, with w(CaO)≥30%, w(MgO)>19%, CaO to MgO mass ratio of 1.40-1.68, and low impurity content.

3. As described in claim 1, characterized in that, In step (2), the drying temperature of the dolomite is 60-100 ℃ and the drying time is 4-8 h.

4. As described in claim 1, characterized in that, In step (2), the dolomite is ground and sieved to a particle size range of 20-60 μm.

5. As described in claim 1, characterized in that, In step (3), the calcination time of the dolomite fines is 6-10 hours.

6. As described in claim 1, characterized in that, In step (3), the calcination temperature of the dolomite fines is 600-900 ℃.

7. The dolomite derivative catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the dolomite derivative catalyst as described in claim 7 in the catalytic absorption of CO2 by a tertiary amine solution.

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