Preparation method of metal oxide loaded sepiolite catalyst for catalyzing desorption of CO2-rich amine solution

Abstract

The invention discloses a preparation method of a metal oxide loaded sepiolite catalyst for catalyzing desorption of a CO2-rich amine solution, which comprises the following steps: dispersing a proper amount of metal salt and sepiolite (SEP) into 400mL of deionized water, and mixing at room temperature to obtain a mixed solution A; stirring the mixed solution A at a certain temperature for 12 hours to obtain a mixed solution B; raising the temperature of the mixed solution B, and continuously stirring for 4 hours to obtain a mixed solution C; performing solid-liquid separation on the mixed solution C, performing vacuum drying, and grinding into powder to obtain a substance D; and finally, heating the substance D to a calcining temperature in an air atmosphere, and calcining to obtain the metal oxide loaded sepiolite catalyst. The obtained catalyst is used for catalyzing desorption of an amine-rich solution, and after the desorbed amine-poor solution is cooled, the CO2 loading capacity is measured by a titration method. CO2 is introduced into the amine-poor solution again for an absorption-desorption experiment, and the CO2 is recycled for 20 times. Compared with the existing catalyst, the catalyst provided by the invention has the advantages of abundant raw material reserves and low price; the performance of catalyzing CO2 desorption is superior to that of a traditional single metal oxide catalyst; and the catalyst has good cycle stability and can be recycled.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial CO2 emission reduction control, and in particular relates to a method for preparing a metal oxide-loaded sepiolite catalyst for catalyzing the desorption of a CO2-rich amine solution. Background Art

[0003] Carbon capture, utilization and storage (CCUS) technology plays an increasingly important role in reducing CO2 emissions, especially in power plants and heavy industries such as steel, cement and chemical manufacturing. Existing studies have shown that chemical absorption based on organic amine solvents is currently the most mature and convenient method for achieving low partial pressure separation of CO2. The main constraint of the organic amine solvent chemical absorption process is the high energy consumption required during the desorption process. The desorption temperature of traditional ethanolamine chemical capture technology is usually higher than 120°C, and the energy loss in the desorption process is more than 70%, accounting for more than 2 / 3 of the total operating cost of the CO2 capture device. The addition of a catalyst can reduce the energy consumption in the desorption process, and sepiolite is a natural mineral material with a special structure, which has a large specific surface area, rich pore structure and good thermal stability. By modifying sepiolite with different metal oxides, active sites can be introduced on its surface to enhance its CO2 desorption performance. The modified sepiolite catalyst can reduce the activation energy of the CO2 desorption reaction and achieve efficient CO2 desorption at a relatively low temperature, thereby reducing the energy consumption in the desorption process and improving the economy and feasibility of the entire CO2 capture and desorption cycle.

[0004] According to the research of Zhang et al., SAPO-34 molecular sieve and SO4 2- / TiO2 solid acid catalyst can reduce the heat load of blank MEA by 24.3% and 17.1%, increase the desorption rate by 28.3% and 20.0%, and increase the cycle capacity by 28.2% and 14.1%, respectively. In addition, adding four solid acid catalysts (three Acid catalysts: H-mordenite, HZSM-5 and H-β, and a Lewis acid catalyst: Al2O3), the cycle capacity, desorption rate, and desorption factor increased by 120.1-147.3%, 80.9-100.4%, 832.9-1360.8%, respectively, and the energy consumption decreased by 57.4-66.1%. In addition, Zhang et al. also studied H-ZSM-5, γ-Al2O3, SAPO-34, and SO4 2- / TiO2 and other four catalysts in the 3M MEA-2.5MAMP-0.5M PZ mixed amine system catalytic regeneration performance. The results showed that the addition of catalysts can reduce energy consumption by 11.1-20.1%, increase the desorption rate by 1.3-14.2%, and increase the cycle capacity by 3.8-22.8%. Among them, H-ZSM-5 has the best catalytic desorption performance. Bhatti et al. further modified H-ZSM-5 with NaOH. The results showed that the use of a certain concentration of alkali modification can improve the mesoporosity and surface acid sites of H-ZSM-5, and has better catalytic desorption performance.

[0005] Bhatti et al. reported that adding metal oxide catalysts such as V2O5, MoO3, WO3, ZrO2, TiO2, MnO2, ZnO, etc. to MEA solvent can increase the CO2 desorption of rich amine solution by about 31-94% and reduce energy consumption by 20-48%. Similar research was also conducted on the bifunctional catalyst Al2O3-HZSM-5 (Al-ZSM), and the CO2 desorption performance of Al2O3, H-ZSM-5 and mixed catalysts was tested. The results showed that the cycle capacity can be increased by 26.4-51.7%, the CO2 desorption rate can be increased by 15.4-29.2%, the relative heat load can be reduced by 19.1-34.2%, and the desorption coefficient can be increased by 2-2.97 times.

[0006] Bairq et al. studied the catalytic CO2 desorption performance of multiphase catalysts (CMK-3-SiO2, CMK-3-SBA-15 and CMK-3-MCM-41) synthesized from CMK-3, SiO2, SBA-15 and MCM-41. Compared with the blank MEA solution system, the heat load of the CMK-3-SiO2 catalytic system was reduced by 37.41%, and the desorption rate and cycle capacity were increased by 95.1% and 68.97%, respectively. Summary of the invention

[0007] The technical problem solved by the present invention is to design and synthesize a metal oxide-loaded sepiolite catalyst to increase the desorption rate of monoethanolamine (MEA) solution in the process of desorbing CO2 and reduce the desorption energy consumption by targeting the problem of high regeneration energy consumption of rich amine solution.

[0008] The technical solution of the present invention is to provide a method for preparing a metal oxide-supported sepiolite catalyst for catalyzing the desorption of a CO2-rich amine solution, and to use the catalyst for desorption of a CO2-rich amine solvent. The main steps of preparing the catalyst by an impregnation method are as follows:

[0009] (1) dispersing metal salt and SEP in deionized water and mixing at room temperature to obtain a mixed solution A;

[0010] (2) stirring the mixed solution A at a certain temperature to obtain a mixed solution B;

[0011] (3) raising the temperature of mixed solution B and continuing stirring to obtain mixed solution C;

[0012] (4) separating the mixed solution C into solid and liquid and drying it in vacuum to obtain substance D;

[0013] (5) Heating substance D to a calcination temperature and calcining to obtain the metal oxide-supported sepiolite catalyst.

[0014] Furthermore, in step (1), the mass ratios of metal oxide to SEP are 1:2, 1:1, and 2:1, respectively, and the amount of deionized water used is 400 ml.

[0015] Furthermore, in step (2), the stirring temperature is 40° C. and the stirring time is 12 h.

[0016] Furthermore, in step (3), the stirring temperature is 80° C. and the stirring time is 4 h.

[0017] Furthermore, in step (4), the drying temperature is 100° C. and the drying time is 8 h.

[0018] Furthermore, in step (5), the heating rate of substance D is 5°C / min; the calcination temperature is 500°C, and the calcination time is 5h.

[0019] The present invention synthesizes the metal oxide-supported sepiolite catalyst by an impregnation method, and the main process is: disperse an appropriate amount of metal salt and sepiolite (SEP) into 400 mL of deionized water, and mix at room temperature to obtain a mixed solution A; then stir the mixed solution A at a certain temperature for 12 hours to obtain a mixed solution B; then raise the temperature of the mixed solution B and continue to stir for 4 hours to obtain a solution C; separate the mixed solution C into solid and liquid, vacuum dry it, and grind it into powder to obtain a substance D; finally, heat the substance D to the calcination temperature and calcine it in an air atmosphere to obtain the metal oxide-supported sepiolite catalyst. The catalyst of the present invention can be expressed as MO@SEP. Metal oxide MO is a very typical super-strong solid acid catalyst, which has the advantages of super-strong acid sites (B acid sites) and easy synthesis; the surface of sepiolite contains a large number of basic centers ([MgO6]) and acid centers ([SiO4]), which is a dual-center surface with strong polarity, which is conducive to the reaction. The combination of the two can well play the synergistic effect of the catalytic reaction. Using this catalyst in the regeneration process of rich amine solution in the traditional organic amine solvent CO2 capture process can effectively increase the CO2 desorption rate and thus reduce the energy consumption of rich amine solution regeneration.

[0020] Compared with the existing technology, the present invention has the following advantages:

[0021] (1) Catalyst raw materials are abundant in reserves and low in price.

[0022] (2) The catalyst preparation process is simple and easy to operate.

[0023] (3) The catalytic CO2 desorption performance is better than that of traditional single metal oxide catalysts

[0024] (4) The catalyst has good cyclic stability and can be reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It shows the recycling performance of the catalyst in Example 1. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the embodiments.

[0027] Example 1: CoO@SEP catalyst

[0028] Appropriate amounts of Co(NO3)2·6H2O and SEP were dissolved in deionized water and mixed at room temperature to obtain a mixed solution A; then the mixed solution A was stirred at 40°C for 12 hours to obtain a mixed solution B; then the mixed solution B was stirred at 80°C for 4 hours to obtain a mixed solution C; the mixed solution C was subjected to solid-liquid separation, vacuum dried at 100°C for 8 hours, and then the powder was heated to 500°C at a heating rate of 5°C / min in an air atmosphere, and maintained at 500°C for 5 hours to obtain the calcined target product catalyst CoO@SEP, which was prepared in mass ratios of 1:2, 1:1, and 2:1, respectively, and the amount added in the application example was 2g.

[0029] Comparative Example 1: SEP catalyst, commercial product, the amount added in the application example is 2g.

[0030] Example 2: NiO@SEP catalyst

[0031] The same as Example 1, except that during the catalyst preparation process, the metal salt is Ni(NO3)2·6H2O, the obtained catalyst is marked as NiO@SEP, and catalysts with mass ratios of 1:2, 1:1, and 2:1 are prepared respectively, and the amount added in the application example is 2g.

[0032] Example 3: Al2O3@SEP catalyst

[0033] The same as Example 1, except that during the catalyst preparation process, the metal salt is Al(NO3)3·9H2O, the obtained catalyst is marked as Al2O3@SEP, and catalysts with mass ratios of 1:2, 1:1, and 2:1 are prepared respectively, and the amount added in the application example is 2g.

[0034] Example 4: CeO@SEP catalyst

[0035] The same as Example 1, except that during the catalyst preparation process, the metal salt is Ce(NO3)2·6H2O, the obtained catalyst is marked as CeO@SEP, the catalyst is prepared with a mass ratio of 1:1, and the amount added in the application example is 2g.

[0036] Application examples:

[0037] Catalytic desorption of CO2-rich monoethanolamine solvent

[0038] The operating steps of the absorption experiment are as follows: first, add a freshly prepared 5 mol / L monoethanolamine (MEA) solution into a three-necked flask and heat it to 40°C. By adjusting the gas mass flowmeter, 200 mL / min of pure CO2 gas is passed into the MEA solution for absorption saturation to obtain a rich amine solution. The CO2 loading capacity of the rich amine solution is measured by titration with 1 M HCl solution. The absorption experiment must ensure that the CO2 loading capacity is the same after each absorption. The required initial loading capacity of the CO2-rich amine solution is 0.535 mol CO2 / mol amine.

[0039] The CO2 load determination method is as follows: 1 mL of the rich amine solution to be tested and 10 mL of deionized water are placed in a 250 mL conical flask with a magnet, 1-2 drops of methyl orange solution indicator are added, the conical flask is placed in the middle of the magnetic stirrer, and then 1M HCl is added to the burette and connected to the conical flask. With the three-way valve open, an open glass bottle (containing a red indicator liquid) is placed at a certain height so that the indicator liquid in the bottle and the red indicator liquid in the glass tube are at the same horizontal position, and the 0 scale is recorded. Then, the three-way valve is closed to ensure that the device is airtight, and the open glass bottle containing the red indicator liquid is slowly placed on the table, and titration is started. The specific steps of the titration are as follows: first, start timing for 8 minutes, titrate with 1.0M HCl, and record the initial value (V0), equivalence point (V1), and excess HCl volume consumed (V2). After stopping the timing, turn off the stirring, wait until the red indicator liquid level in the glass tube remains unchanged, place the indicator liquid in the glass bottle and the liquid level in the glass tube parallel to each other, and read the glass tube indication (V) mL.

[0040] The CO2 loading α (mol CO2 / mol amine) is calculated by the following formula:

[0041]

[0042] Among them C HCl is the standard HCl solution concentration of 1.0 mol / L, V m is the gas molar volume, 22.4 L / mol, and T is room temperature (℃).

[0043] The main reaction body of the catalytic CO2-rich amine solution desorption experiment is a 500mL three-necked flask, in which a cleaned olive-shaped magnet is placed, a condensation reflux device is installed at the middle neck to prevent the volatilization of the amine solution, a temperature probe of a magnetic stirring electric heating jacket is inserted into the side bottle mouth to measure the desorption temperature of the solution, and the third neck mouth is plugged with a glass stopper to prevent leakage. 200mL of MEA solution with the required initial CO2 loading (for example, 0.535mol CO2 / mol amine) is added to the three-necked flask, and 0.25-1.25wt% of the catalyst (the catalyst used is the catalyst in the above embodiment and comparative example) is added, and the regeneration temperature is 80-100°C.

[0044] The operating steps of the desorption experiment are as follows: first, 500 mL / min of N2 is introduced into a new three-necked flask by adjusting the gas mass flowmeter to replace the air in the device, then 2 g of the above catalyst and 200 mL of rich amine solution are added to the three-necked flask, and the flask mouth is plugged with a glass stopper. The three-necked flask is placed in an 88°C intelligent magnetic stirring electric heating mantle, and the electric heating mantle and the electric energy meter are connected in series, where the function of the electric energy meter is to record the consumed electricity to calculate the relative desorption energy consumption of the CO2 desorption process.

[0045] After the desorption experiment, the CO2-poor amine solution was cooled to room temperature, and CO2 was introduced again for absorption and saturation before desorption. The absorption and desorption cycles were repeated 20 times.

[0046] The experimental results are shown in the following table.

[0047] Table 1 Comparison of relative desorption energy consumption of catalysts in Examples and Comparative Examples at 25 min

[0048]

[0049] It can be seen from the above table that, compared with blank MEA, the desorption energy consumption of MEA amine solvent is significantly reduced after adding the catalyst, and the catalytic performance of the catalyst prepared in the examples is far superior to that of a single catalyst.

Claims

1. A method for preparing a metal oxide-supported sepiolite catalyst for catalyzing the desorption of a CO2-rich amine solution, characterized in that The metal oxide is loaded on a sepiolite catalyst carrier and used to catalyze the desorption of a rich amine solution. The preparation method is as follows: (1) dispersing metal salt and SEP in deionized water and mixing at room temperature to obtain a mixed solution A; (2) stirring the mixed solution A at a certain temperature to obtain a mixed solution B; (3) raising the temperature of mixed solution B and continuing stirring to obtain mixed solution C; (4) separating the mixed solution C into solid and liquid and drying it in vacuum to obtain substance D; (5) Heating substance D to a calcination temperature and calcining to obtain the metal oxide-supported sepiolite catalyst.

2. The use according to claim 1, characterized in that In step (1), the mass ratio of metal oxide to SEP is 1:2, 1:1, and 2:1, and the amount of deionized water used is 400 mL.

3. The use according to claim 1, characterized in that In step (2), the stirring temperature is 40° C. and the stirring time is 12 h.

4. The use according to claim 1, characterized in that In step (3), the stirring temperature is 80° C. and the stirring time is 4 h.

5. The use according to claim 1, characterized in that In step (4), the drying temperature is 100° C. and the drying time is 8 h.

6. The use according to claim 1, characterized in that In step (5), the heating rate of substance D is 5°C / min; the calcination temperature is 500°C, and the calcination time is 5h.

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