Preparation method of titanium dioxide loaded sepiolite catalyst for catalyzing desorption of CO2-rich amine solution

Abstract

The invention discloses a preparation method of a titanium dioxide loaded sepiolite catalyst for catalyzing desorption of a CO2-rich amine solution, which comprises the following steps: fully mixing a proper amount of tetrabutyl titanate (TBT), absolute ethyl alcohol and glacial acetic acid at room temperature to obtain a precursor solution A; then slowly dropwise adding a regulating solution composed of a proper amount of absolute ethyl alcohol and distilled water into the precursor solution A, and stirring at a certain temperature to enable the two components to fully react, so as to obtain titanium dioxide (TiO2) gel B; carrying out vacuum drying on the obtained TiO2 gel at 100 DEG C for 24 hours to obtain a TiO2 solid C; fully mixing a proper amount of sepiolite (SEP) and the solid C in distilled water, standing for a period of time, and carrying out suction filtration and vacuum drying to obtain a mixture D; and finally, heating the substance D to a calcining temperature in an air atmosphere, calcining, and grinding after calcining to obtain the titanium dioxide loaded sepiolite catalyst. Compared with the existing catalyst, the catalyst provided by the invention has the advantages of abundant raw material reserves and low price; separation is convenient, and regeneration performance is good; the catalytic performance of the catalyst is superior to that of a single sepiolite and titanium dioxide catalyst; the catalytic cycle stability is good, and the absorption performance of an amine solution is not influenced.

Description

Technical Field

[0001] The present invention belongs to industrial CO 2 The technical field of emission reduction control is particularly related to a method for catalyzing a CO-rich 2 A method for preparing a titanium dioxide-supported sepiolite catalyst desorbed by an amine solution. Background Art

[0002] With the rapid development of industry, the combustion of fossil fuels such as coal, oil and natural gas produces carbon dioxide (CO 2 ) and automobile exhaust gases have led to a continuous increase in the concentration of greenhouse gases in the atmosphere, and the greenhouse effect caused by greenhouse gases has had a great impact on the environment. Organic amine solution chemical absorption is the most effective and widely used CO 2 Capture technology. This technology currently has the advantages of mature process, high absorption efficiency, high stability and low operating cost, but it also faces the key problem of high solvent regeneration energy consumption, which accounts for about CO 2 Capture accounts for 60% of the total cost, making CO 2 The high capture cost of CO limits the use of amine solvent chemical absorption to capture CO 2 In industrial applications, solid catalysts are used to catalyze CO 2 Desorption has received extensive attention. The use of solid catalysts can improve the CO 2 The desorption rate of CO 2 The desorption energy consumption has important economic and industrial significance.

[0003] Bhatti et al. 2 and ZnO were added to ethanolamine (MEA) solution to make CO 2 The regeneration energy consumption, cycle capacity and desorption rate increased by 32%, 56% and 54% respectively. 2 Materials with high desorption performance may require a complex preparation process, including doping, modification and other steps. This will increase the difficulty and cost of preparation (Bhatti UH et al. ACS Sustainable Chemistry & Engineering, 2019, 7 (12): 10234-10240). Zhang Xiaowen et al. added a variety of solid acid catalysts to MEA solvent to promote CO 2 During the desorption process, it was found that SO was added during the MEA solvent regeneration process. 4 2- / TiO 2And SAPO-34 can reduce the heat load by 17.1% and 24.3% respectively (Zhang X et al. Applied Energy, 2017, 202: 673-684; Zhang X et al. Environ Sci Technol, 2019, 53(10): 6094-6102). Although there are many types of catalysts for catalytic regeneration of rich CO 2 amine solution so far, the relative desorption energy consumption of most catalysts still cannot reach the ideal state. To further reduce the regeneration energy consumption of rich CO 2 amine solution, and thus reduce the CO 2 capture cost, developing and designing new and efficient solid catalysts for the regeneration process of rich CO 2 amine solution has great economic and industrial significance.

[0004] Sepiolite (SEP) is an economical and green natural fiber clay with rich reserves and wide distribution, and it is a basic material for modern industry. Sepiolite is composed of interconnected Si-O tetrahedra and Mg-O octahedral layers, forming fibrous crystals. These crystals are arranged in parallel bundles, forming voids and channels along the fiber axis. This porous structure increases the surface area and significantly enhances the adsorption capacity, enabling sepiolite to absorb and retain a large amount of water and positively charged metal ions. In addition, this structure also ensures that silanol groups (-Si-OH) are located at the edges of each block, becoming the main active catalytic sites. Based on these characteristics, sepiolite is an important carrier for fixing active catalytic sites in the liquid phase system. After thermal, inorganic or organic modification, the adsorption performance of sepiolite has been greatly improved, and its recovery ability has also been improved, showing excellent application prospects in the fields of process industry, agriculture, medicine and environmental remediation. Summary of the Invention

[0005] The technical problem solved by the present invention is to design and synthesize a new type of titanium dioxide supported sepiolite catalyst to improve the desorption rate of monoethanolamine (MEA) solution in the desorption of CO 2 process and reduce the desorption energy consumption by aiming at the problem of high regeneration energy consumption of rich amine solution.

[0006] The technical solution of the present invention is to provide a preparation method of a titanium dioxide supported sepiolite catalyst for catalyzing the desorption of rich CO 2 amine solution, and it is used for the desorption of rich CO 2 amine solvent. The main steps for synthesizing the catalyst by sol-gel method and impregnation method are as follows:

[0007] (1) Mix tetrabutyl titanate, absolute ethanol and glacial acetic acid at room temperature to obtain precursor solution A;

[0008] (2) Mix absolute ethanol and distilled water to form a regulating solution, and drop the regulating solution into the precursor solution A and continuously stir to obtain TiO 2 gel B;

[0009] (3) Vacuum-dry the gel B to obtain TiO 2 solid C;

[0010] (4) Mix SEP and TiO 2 solid C in distilled water. After standing for a period of time, perform suction filtration and vacuum drying to obtain solid D;

[0011] (5) Heat D to the calcination temperature and calcine it. After calcination, grind it to obtain the composite catalyst.

[0012] Further, in step (1), the volume ratio of tetrabutyl titanate, absolute ethanol and glacial acetic acid is 2.8:12:1.

[0013] Further, in step (2), the volume ratio of absolute ethanol and distilled water is 1:1. The regulating solution needs to be dropped into the precursor solution A at a rate of 50 - 60 drops per minute, the stirring time is 4 h, and the stirring temperature is 30 °C.

[0014] Further, in step (3), the drying temperature is 100 °C and the drying time is 24 h.

[0015] Further, in step (4), the mass ratio of TiO 2 to SEP is 1:2, 1:1, 2:1 respectively; the stirring time is 4 h, the standing time is 1 h, the drying temperature is 100 °C, and the drying time is 4 h.

[0016] Further, in step (5), the heating rate of substance D is 5 °C / min; the calcination temperature is 400 °C and the calcination time is 4 h.

[0017] The present invention synthesizes TiO by the sol-gel method 2 , and then synthesizes the above composite catalyst by the impregnation method. The main process is: fully mix an appropriate amount of tetrabutyl titanate (TBT), absolute ethanol, and glacial acetic acid at room temperature to obtain a precursor solution A; then slowly drop a regulating solution composed of an appropriate amount of absolute ethanol and distilled water into the precursor solution, and stir at a certain temperature to make the two components fully react, and then TiO₂ (TiO 2 ) gel B can be obtained; vacuum-dry the obtained TiO 2 gel at 100 °C for 24 h to obtain TiO 2Solid C; then an appropriate amount of sepiolite (SEP) and solid C were fully mixed in distilled water, and after standing for a period of time, suction filtration and vacuum drying were carried out to obtain mixture D; finally, substance D was heated to the calcination temperature and calcined in an air atmosphere, and after calcination, it was ground to obtain a titanium dioxide-supported sepiolite catalyst.

[0018] The catalyst of the present invention can be expressed as TiO 2 @SEP, where TiO 2 has a variety of advantageous properties, including a large surface area, remarkable thermochemical stability, inherent acidity, non-toxicity, and economic feasibility, and thus has become a widely used catalyst. The surface of sepiolite contains a large number of basic centers ([MgO 6 ) and acidic centers ([SiO 4 ), is a surface with dual centers, has strong polarity, which is conducive to the progress of the reaction, and the combination of the two can well play the synergistic effect of the catalytic reaction. Using this catalyst in the regeneration process of the rich amine solution in the traditional organic amine solvent to capture CO 2 process can effectively improve the CO 2 desorption rate, thereby reducing the energy consumption for the regeneration of the rich amine solution.

[0019] Compared with the existing technologies, the present invention has the following advantages:

[0020] (1) The catalyst raw materials are rich in reserves and low in price.

[0021] (2) The catalyst preparation process is simple and easy to operate.

[0022] (3) The catalytic CO 2 desorption performance is superior to that of traditional single metal oxide catalysts and sepiolite catalysts.

[0023] (4) The catalyst has good cycle stability and can be recycled repeatedly. Description of the Drawings

[0024] Figure 1 Represents the cycle regeneration performance of the catalyst in Example 1. Detailed Embodiments

[0025] Example 1: TiO 2 @SEP-2 / 1 catalyst

[0026] An appropriate amount of tetrabutyl titanate, absolute ethanol, and glacial acetic acid were mixed according to a volume ratio of 2.8:12:1, and stirred at room temperature for 30 min to obtain precursor solution A; then an adjustment solution composed of absolute ethanol and distilled water in a volume ratio of 1:1 was added dropwise to precursor solution A at a rate of 50 - 60 drops per minute, and stirred at 30 °C for 4 h to obtain TiO 2Gel; The gel was dried under vacuum at 100 °C for 24 h to obtain TiO 2 Solid; An appropriate amount of SEP was mixed with TiO 2 in a certain amount of distilled water, stirred at room temperature for 4 h, allowed to stand for 1 h, then subjected to suction filtration. After suction filtration was completed, it was dried under vacuum at 100 °C for 4 h to obtain solid D; Solid D was heated in an air atmosphere at a heating rate of 5 °C / min to the calcination temperature of 400 °C and calcined for 4 h. After calcination, it was ground to obtain the target product catalyst TiO 2 @SEP, where the mass ratio of TiO 2 and SEP is 2:1, abbreviated as TiO 2 @SEP-2 / 1, and the addition amount in the application example is 2 g.

[0027] Comparative Example 1: TiO 2 Catalyst

[0028] As a comparison, TiO 2 catalyst was synthesized. The synthesis process was the same as that of Example 1 above, except that SEP was not added in the fourth step.

[0029] Comparative Example 2: SEP

[0030] Example 2: TiO 2 @SEP-1 / 1 catalyst

[0031] Same as Example 1, the difference is that during the catalyst preparation process, the mass ratio of TiO 2 and SEP is 1:1, and the obtained catalyst is labeled as TiO 2 @SEP-1 / 1.

[0032] Example 3: TiO 2 @SEP-1 / 2 catalyst

[0033] Same as Example 1, the difference is that during the catalyst preparation process, the mass ratio of TiO 2 and SEP is 1:2, and the obtained catalyst is labeled as TiO 2 @SEP-1 / 2.

[0034] Application Example:

[0035] Catalytic desorption of rich CO 2 Monoethanolamine solvent

[0036] The operation steps of the absorption experiment are as follows: First, add the freshly prepared 5 mol / L MEA solution to a three-necked flask and heat it to 40 °C. Adjust the gas mass flowmeter to pass 200 mL / min of pure CO 2The gas is introduced into the MEA solution until it is saturated to obtain a rich amine solution, and the CO loading in the rich amine solution is measured by titration with 1M HCl solution. 2 For the absorption experiment, it is necessary to ensure that the CO loading is the same after each absorption. 2 The initial loading of the rich CO amine solution is 0.535 mol CO 2 / mol amine. 2 / mol amine.

[0037] CO 2 The method for measuring the CO loading is as follows: Place 1 mL of the rich amine solution to be measured and 10 mL of deionized water in a 250 mL conical flask containing a magnetic stir bar. Add 1 - 2 drops of methyl orange solution indicator. Place the conical flask in the middle position of the magnetic stirrer. Then add 1M HCl to the burette and connect it to the conical flask. Under the condition that the three-way valve is open, place an open glass bottle (containing a red indicator solution) at a certain height so that the indicator solution in the bottle is at the same horizontal position as the red indicator solution in the glass tube, and mark it as the 0 scale. Then close the three-way valve to ensure good airtightness of the device. Slowly place the open glass bottle containing the red indicator solution on the table and start titration. The specific steps of titration are as follows: First, time for 8 minutes and titrate with 1.0M HCl. Record the initial value (V 0 ), the equivalence point (V 1 ), and the volume of HCl consumed in excess (V 2 ). After stopping the timing, turn off the stirrer. Wait until the liquid level of the red indicator solution in the glass tube remains unchanged. Place the indicator solution in the glass bottle and the liquid level in the glass tube parallel, and read the indication (V) mL of the glass tube.

[0038] CO 2 The CO loading α (mol CO 2 / mol amine) is calculated by the following formula:

[0039]

[0040] Where C HCl is the concentration of the standard HCl solution, 1.0 mol / L, V m is the molar volume of the gas, 22.4 L / mol, and T is the room temperature (°C).

[0041] The reaction vessel for the catalytic desorption experiment of the rich CO amine solution is a 500 mL three-necked flask. Place a cleaned olive-shaped magnetic stir bar inside the flask. Install a condensing reflux device at the middle neck to prevent the volatilization of the amine solution. Insert the temperature probe of the magnetic stirrer heating mantle into the side neck to measure the desorption temperature of the solution. Plug the third neck with a glass stopper to prevent air leakage. Add 200 mL of the required CO 2 amine solution with the initial loading (for example, 0.535 mol CO 2 / mol amine) into the three-necked flask.2 MEA solution with a concentration of 30 wt% (30 wt% MEA in terms of mol amine), and 0.25 - 1.25 wt% of a catalyst (the catalysts used are the catalysts in the above examples and comparative examples) is added, and the regeneration temperature is 80 - 100 °C.

[0042] The operating steps of the desorption experiment are as follows: First, adjust the gas mass flowmeter to pass 500 mL / min of N 2 into a new three-necked flask to displace the air in the device. Then, add 2 g of the above catalyst and 200 mL of the rich amine solution into the three-necked flask, and stopper the flask with a glass stopper. Place the three-necked flask in an 88 °C intelligent magnetic stirring electric heating mantle, and connect the electric heating mantle and the watt-hour meter in series. The role of the watt-hour meter is to record the consumed electricity to calculate the relative desorption energy consumption during the CO 2 desorption process.

[0043] After the desorption experiment, cool the lean CO 2 amine solution to room temperature, and then pass CO 2 again to saturate it with absorption and then desorb it. Repeat the absorption and desorption cycle 12 times.

[0044] The experimental results are shown in the following table.

[0045] Table 1 Comparison of relative desorption energy consumption of catalysts in examples and comparative examples at 25 min

[0046]

[0047] As can be seen from the above table, compared with the blank MEA, the desorption energy consumption of the MEA amine solvent is significantly reduced after adding the catalyst, and the catalytic performance of the catalysts prepared in the examples is far superior to that of the single catalyst.

Claims

1. A method for preparing a titanium dioxide-supported sepiolite catalyst for catalyzing the desorption of a CO2-rich amine solution, characterized in that Titanium dioxide is loaded on a sepiolite catalyst carrier and used to catalyze the desorption of rich amine solution. The preparation method is as follows: (1) mixing tetrabutyl titanate, anhydrous ethanol and glacial acetic acid at room temperature to obtain a precursor solution A; (2) adding a mixture of anhydrous ethanol and distilled water to form a regulating solution dropwise into the precursor solution A and continuously stirring to obtain TiO2 gel B; (3) vacuum drying B to obtain TiO2 solid C; (4) SEP and TiO2 solid C are mixed in distilled water, and after standing for a period of time, the solid D is obtained by suction filtration and vacuum drying; (5) heating D to a calcination temperature and calcining it, and grinding it after calcination to obtain the composite catalyst.

2. The use according to claim 1, characterized in that In step (1), the volume ratio of tetrabutyl titanate, anhydrous ethanol and glacial acetic acid is 2.8:12:

1.

3. The use according to claim 1, characterized in that In step (2), the volume ratio of anhydrous ethanol to distilled water is 1:1, and the regulating liquid is added to the precursor liquid A at a rate of 50 to 60 drops per minute, the stirring time is 4 hours, and the stirring temperature is 30°C.

4. The use according to claim 1, characterized in that In step (3), the drying temperature is 100° C. and the drying time is 24 h.

5. The use according to claim 1, characterized in that In step (4), the mass ratios of TiO2 and SEP are 1:2, 1:1, and 2:1, respectively. The mixture is stirred for 4 hours, allowed to stand for 1 hour, and then filtered. The drying temperature is 100°C and the drying time is 4 hours.

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 400°C, and the calcination time is 4h.

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