Low-temperature activation method and regeneration method of CO2 molecular sieve adsorbent

Abstract

The invention belongs to the technical field of molecular sieve activation, and particularly relates to a low-temperature activation method and regeneration method of a molecular sieve, and the method comprises the following steps: (1) mixing the molecular sieve with deionized water according to a mass volume ratio of 1: (20-30), and dipping at 25-35 DEG C for 20-40 minutes; (2) carrying out suction filtration, and drying for 10-14 hours in an air atmosphere at the temperature of 100-150 DEG C; and (3) activating the dried molecular sieve at 180-220 DEG C for 1.5-2.5 hours, and purging with inert gas. The obtained activated molecular sieve is used for adsorbing and penetrating mixed gas, the activated molecular sieve after adsorption is purged and regenerated by inert gas at 140-160 DEG C, and the regeneration time is 1.5-3 hours. The method has the characteristics of high adsorption performance, strong selectivity, obvious energy-saving effect and the like.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve activation technology, specifically to a low-temperature activation method for a CO2 molecular sieve adsorbent and its regeneration method. This method reduces the molecular sieve's activation temperature through water treatment, significantly improving its CO2 adsorption performance and reducing high-temperature potential energy consumption in industrial applications. Background Art

[0002] Molecular sieves are one of the primary adsorbents for industrial CO2 capture and absorption. Their efficient removal of CO2 is crucial for mitigating global climate change. However, long-term storage of molecular sieves in air can lead to the formation of carbonate and carbonate-like layers on their surfaces, which can clog the pores and reduce their adsorption capacity. High-temperature activation is commonly used in industry to revitalize their adsorption properties.

[0003] To lower the activation temperature of molecular sieves, high-temperature calcination (500-600°C) is generally used to activate molecular sieves. The high-temperature calcination activation process consumes a large amount of high-grade heat, and the lack of high-grade heat in restricted or low-pressure areas (such as plateaus) limits the decarburization efficiency of industrial molecular sieves.

[0004] Prior art research on lowering activation temperature has primarily focused on optimizing calcination conditions or introducing chemical additives, but these methods can introduce impurities or increase costs. Therefore, a cost-effective, environmentally friendly, and low-temperature activation method is urgently needed. Summary of the Invention

[0005] The present invention aims to overcome the deficiencies of the prior art and provide a low-temperature activation method and regeneration method for a CO2 molecular sieve adsorbent having high adsorption performance, strong selectivity, high-grade thermal energy and obvious energy-saving effect.

[0006] To solve the above-mentioned technical problems, the present invention is achieved as follows:

[0007] A low-temperature activation method for a CO2 molecular sieve adsorbent comprises the following steps:

[0008] (1) Mix the molecular sieve and deionized water in a mass volume ratio of 1:20-30 and soak at 25-35°C for 20-40 minutes;

[0009] (2) Filter and dry in air at 100-150°C for 10-14 hours;

[0010] (3) Activate the dried molecular sieve at 180-220°C for 1.5-2.5 hours and purge with inert gas.

[0011] Furthermore, in step (1), the molecular sieve is C-NaA molecular sieve.

[0012] Furthermore, in step (3), H-NaA molecular sieve is obtained after purging with inert gas.

[0013] Furthermore, in step (1), the mass volume ratio of the deionized water to the molecular sieve is 1:25.

[0014] Furthermore, in step (3), the activation temperature is 200° C. and the activation time is 2 hours.

[0015] Furthermore, the inert gas is helium or nitrogen, and the purge flow rate is 10 to 30 mL / min.

[0016] The regeneration method of the adsorbent obtained by the low-temperature activation method of the CO2 molecular sieve adsorbent is to use the obtained activated molecular sieve to adsorb and penetrate the mixed gas, and regenerate the activated molecular sieve after adsorption by purging with inert gas at 140-160°C, and the regeneration time is 1.5-3 hours.

[0017] Furthermore, the mixed gas is CO2 and CH4; the volume ratio of CO2 to CH4 is 15:85; the activated molecular sieve after adsorption is purged and regenerated with inert gas at 150°C, and the He flow rate is 14 mL / min.

[0018] Furthermore, the mixed gas is CO2 and N2; the volume ratio of CO2 to N2 is 15:85; the activated molecular sieve after adsorption is purged and regenerated with inert gas at 150°C, and the He flow rate is 14 mL / min.

[0019] Furthermore, the adsorption temperature is 25°C.

[0020] This method reduces the activation temperature of molecular sieves through water treatment, making it particularly suitable for the activation of 4A molecular sieves (NaA molecular sieves). It significantly improves their CO adsorption performance and reduces energy consumption in industrial applications. At room temperature, water washing of the molecular sieves effectively removes carbonate and carbonate-like species from the surface of the NaA molecular sieve, which are difficult to remove.

[0021] Compared with the prior art, the present invention has the following characteristics:

[0022] (1) Improved adsorption performance: The penetration time of H-NaA for CO2 reached 45.28 min / g, which is 8.23 times that of untreated C-NaA (5.5 min / g); the saturated adsorption capacity increased from 0.94 mmol / g to 2.00 mmol / g.

[0023] (2) Enhanced selectivity: The dynamic selectivity in CO2 / CH4 mixed gas increased from 31.95 (C-NaA) to 66.08 (H-NaA).

[0024] (3) Energy-saving advantage: The activation temperature is reduced from the traditional 550℃ to 200℃, reducing high-grade heat energy consumption and is suitable for low-pressure or plateau areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be described in detail below through specific examples. These examples are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art. As mentioned throughout the specification and claims, "including" or "comprising" is an open-ended term and is interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims. Unless otherwise specified, the various reagents and materials used in the present invention can be purchased from the market.

[0026] Figure 1 Comparison of the adsorption breakthrough curves of C-NaA and H-NaA samples for CO2 mixed gas;

[0027] Figure 2 This is a comparison chart of the penetration adsorption capacity and saturation adsorption capacity of CO2 mixed gas by C-NaA and H-NaA samples of the present invention;

[0028] Figure 3 The relationship between the dynamic adsorption capacity and dynamic selectivity of the two samples of the present invention for CO2 / CH4;

[0029] Figure 4 is the recycling performance of the H-NaA sample of the present invention;

[0030] Figure 5 The CO2 signal acquisition diagram during the regeneration process of the H-NaA sample of the present invention and the CO2 and CH4 penetration curves of the C-NaA and H-NaA samples in the CO2 / CH4 mixed gas system;

[0031] Figure 6 The online mass spectrometry signal curves of CO2 and H2O during the activation process of C-NaA and H-NaA samples of the present invention are as follows;

[0032] Figure 7 Comparison of FTIR spectra under different temperature conditions of the present invention;

[0033] Figure 8 XPS spectra of C-NaA and C-NaA-lmin;

[0034] Figure 9 SEM images of C-NaA and H-NaA;

[0035] Figure 10 TEM images of C-NaA and H-NaA;

[0036] Figure 11 isotherm and pore size distribution of CO2 physical adsorption (0℃);

[0037] Figure 12 The adsorption kinetics curves and mass transfer coefficients Dc of C-NaA and H-NaA samples for CO2;

[0038] Figure 13 XRD patterns of H-NaA and C-NaA;

[0039] Figure 14 The thermogravimetric curve (TG) was repeated four times for the C-NaA molecular sieve sample;

[0040] Figure 15 The TG and DTG curves of H-NaA and C-NaA, as well as the CO2 and H2O signal diagrams during the in-situ mass spectrometry acquisition process from 20°C to 500°C; DETAILED DESCRIPTION

[0041] The technical solution of the present invention is illustrated by the following examples, but the protection scope of the present invention is not limited thereto. Any equivalent replacement or parameter adjustment based on the technical features of the present invention falls within the scope of protection of this patent.

[0042] Example 1:

[0043] 1. Sample preparation process

[0044] 1.1 Sample preparation steps

[0045] (1) At 30°C, molecular sieve C-NaA was mixed with deionized water at a ratio of 1:25 (g:mL); (wherein, the C-NaA molecular sieve sample was a commercially available 4A molecular sieve)

[0046] (2) After the molecular sieve is immersed in deionized water for 30 minutes, it is filtered and placed in an oven at 120°C and dried in air atmosphere for 12 hours;

[0047] The molecular sieve sample obtained in the above steps is H-NaA molecular sieve.

[0048] 1.2 Sample activation conditions

[0049] The H-NaA molecular sieve sample was activated at 200 °C for 2 h with a He purge of 14 mL / min;

[0050] 1.3 Adsorption conditions

[0051] The adsorption temperature is 25℃, and the mixed gas composition is: CO2 / CH4 (15 / 85, v / v); CO2 / N2 (15 / 85, v / v)

[0052] 2. H-NaA molecular sieve has high selectivity and high adsorption capacity in CO2 / CH4 mixed gas

[0053] Comparison of the adsorption and penetration performance of C-NaA and H-NaA samples on mixed gases CO2 / CH4 (15 / 85, v / v) and CO2 / N2 (15 / 85, v / v) at 25℃ (e.g. Figure 1 shown). Figure 1 Comparison of the adsorption breakthrough curves of C-NaA and H-NaA samples for CO2 mixed gas: (A) CO2 / CH4; (B) CO2 / N2. Figure 2 Comparison of the penetration and saturation adsorption capacities of CO2 mixtures for C-NaA and H-NaA samples: (A) CO2 / CH4; (B) CO2 / N2. It can be seen that CH4 quickly penetrates both samples (the penetration times for C-NaA and H-NaA for CH4 are 0.21 min g -1 、0.26min g -1 ). In sharp contrast, there is a significant difference in the adsorption and penetration capacity of the two samples for CO2. In the CO2 / CH4 mixed gas system, the carbon dioxide penetration time of H-NaA is 8.23 times that of C-NaA. The adsorption and penetration times of C-NaA and H-NaA for carbon dioxide are 5.5 min / g and 45.28 min / g, respectively. Compared with the untreated commercial C-NaA, the adsorption and penetration capacity of H-NaA for CO2 is increased by more than 8 times. The penetration adsorption of carbon dioxide by C-NaA and H-NaA is 0.14 mmol g, respectively. -1 、1.21mmol g -1 , and the saturated adsorption capacity for CO2 was 0.94 mmol g -1 、2.00mmol g -1 .

[0054] Calculate the adsorption selectivity of two molecular sieve samples for CO2 in the CO2 / CH4 (15 / 85, v / v) binary mixture system, such as Figure 3 As shown. Figure 3 It can be seen that compared with the untreated commercial C-NaA molecular sieve, the dynamic selectivity of the -H-NaA molecular sieve sample for CO2 in the CO2 / CH4 mixture is significantly improved, among which the selectivities of C-NaA and H-NaA for CO2 / CH4 are 31.95 and 66.08, respectively.

[0055] 3. Molecular sieve regeneration method that maintains stable adsorption performance after multiple regeneration cycles

[0056] The H-NaA molecular sieve was regenerated at 150°C with a He purge flow rate of 14 mL / min. Ten regeneration cycles verified the good regeneration performance of the H-NaA molecular sieve. The results showed that it had stable regeneration performance at 150°C, with its saturated adsorption capacity basically maintained at around 2 mmol / g. Figure 4 The cyclic regeneration performance of the H-NaA sample: (a) CO2 / CH4 mixed gas breakthrough curve; (b) comparison of CO2 breakthrough adsorption amount.

[0057] See also Figure 5 , a is the CO2 signal acquisition diagram during the regeneration process of the H-NaA sample; b is the breakthrough curve of CO2 and CH4 for C-NaA and H-NaA samples in the CO2 / CH4 mixed gas system. Under the conditions of He purge, regeneration temperature of 150℃ and regeneration time of 1h, the H-NaA sample was regenerated. During the regeneration process, the online mass spectrometer of the BSD-MAB instrument was used to collect the signal value of the desorbed CO2 during the regeneration process, as shown in the figure. Figure 5 As shown in a. It can be seen from the figure that under the regeneration conditions, the sample basically completed the regeneration process at about 50 minutes. Figure 5 The penetration time of H-NaA sample to CO2 in a (45.28min g -1 ), the desorption time of CO2 is not longer than the adsorption time of CO2, which proves that the sample may be used in the adsorption-desorption cycle operation in industrial production.

[0058] See also Figure 6 As shown, Figure 6 Figure 2 shows the online mass spectrometry signal curves for CO2 and H2O during the activation of C-NaA and H-NaA samples in the present invention; a is the CO2 signal; b is the H2O signal. During the sample activation process, the CO2 and H2O signals were collected using an online mass spectrometer in a multicomponent competitive adsorption penetrometer (BSD-MAB).

[0059] See also Figure 7 , Figure 7 Comparison of FTIR spectra under different temperature conditions: a is C-NaA; b is H-NaA; c is the action mechanism diagram. Figure 8 The XPS spectra of C-NaA and C-NaA-1min are shown in Figure 2; a is the full spectrum; b is the high-resolution spectrum of C1s. To confirm the presence of carbonate and carbonate-like species on the sample surface, we performed in-situ FTIR and XPS characterization on the C-NaA and H-NaA samples.

[0060] At 30℃~320℃, with 30℃ as the temperature interval, the infrared spectrum of the sample was collected. Figure 7 In a, we can observe that the C-NaA spectrum contains peaks at 1557, 1412, and 1367 cm-1, which belong to bidentate carbonates and carbonate-like salts. -1 However, no such peaks were found in the infrared spectrum of H-NaA sample. + The element concentration of C-NaA samples at a certain depth was obtained by sputtering (1 min) by removing the surface layer layer by layer using XPS technology. The samples were named C-NaA-1min. The corresponding typical XPS broad spectrum and C1s spectrum are shown in the figure below. Figure 8 As shown in the figure, it can be seen that there is an obvious carbonate (CO3) peak at 288.8ev. + After sputtering, the peak almost disappeared, proving that carbonate and carbonate-like species existed on the surface of the C-NaA sample. It also proved that after washing with water, almost all carbonate and carbonate-like species on the sample surface were washed away.

[0061] See also Figure 9 and Figure 10 As shown, Figure 9 In the SEM images, a is C-NaA and b is H-NaA. Figure 1 In the OTEM image, a is C-NaA and b is H-NaA.

[0062] The SEM and TEM images of C-NaA and H-NaA samples are shown in Figure 2. Figure 9 and Figure 1 As shown in Figure 0, it can be seen from SEM and TEM that there is no obvious difference in the crystal morphology between C-NaA and H-NaA samples. The adsorption isotherms (0℃) of C-NaA and H-NaA samples for CO2 and the corresponding pore size distribution are shown in Figure 0. Figure 11 The most probable pore diameter of the C-NaA sample is 0.36 nm, while that of the H-NaA sample is 0.40 nm. This indicates that carbonates and carbonate-like species on the sample surface play a role in blocking the pores. After water treatment, the amount of carbonates and carbonate-like species on the sample surface decreases, and the most probable pore diameter increases.

[0063] The kinetic curves of CO2 adsorption on C-NaA and H-NaA samples at corresponding pressure points between 80 and 500 mbar (80 mbar, 100 mbar, 200 mbar, 300 mbar, 400 mbar, and 500 mbar) were measured by an intelligent gravimetric analyzer (IGA) (30°C). In addition, the mass transfer coefficient D of CO2 at different pressure values was calculated based on the kinetic curves using the Fick model. c Value, see Figure 12a is the C-NaA kinetic curve; b is the H-NaA kinetic curve; c is the D c value.

[0064] As can be seen from the figure, the adsorption capacity of CO2 by H-NaA sample is about 10 times that of C-NaA sample. At 300mbar, the mass transfer coefficient of CO2 in H-NaA sample is D c Value (2.05×10-11cm 2 s -1 ) is significantly higher than that of C-NaA sample (0.70×10-11cm 2 s -1 ). From the perspectives of CO2 equilibrium adsorption capacity and mass transfer coefficient, it is proved that after water treatment, the molecular sieve sample has better adsorption performance for CO2. It also indirectly shows that after water treatment, the blockage of pores by carbonate and carbonate-like species on the surface of the molecular sieve sample has been significantly improved.

[0065] See also Figure 13 , Figure 13 The XRD patterns of H-NaA and C-NaA are shown in Table 2. From the XRD patterns, it can be seen that both C-NaA and H-NaA samples have characteristic peaks of LTA-type molecular sieves, and there is no obvious difference.

[0066] See also Figure 14 , Figure 14 The thermogravimetric curves of the C-NaA sample were repeated four times continuously. It can be seen from the figure that the thermal stability of the sample remains unchanged during the heating process. The thermogravimetric TG and differential thermogravimetric DTG curves of the C-NaA and H-NaA samples (see Figure 15 a and 15b), it can be seen that the difference in the weight loss ratio of the two samples is very small, and both samples have obvious weight loss at 110 ° C, indicating that most of the weight loss is mainly due to the desorption of physically adsorbed water. After water treatment, the thermal stability of the two samples is basically the same during the heating process. In addition, a multi-component competitive adsorbent (BAD-MAB) was used to record the signal peaks of CO2 and H2O in real time during the activation process of the samples from 20 ° C to 500 ° C (see Figure 15 c and 15d). Figure 15 Figures a and b: TG and DTG curves of H-NaA and C-NaA; c and d: CO2 and H2O signals during in situ mass spectrometry acquisition at a temperature ranging from 20°C to 500°C. The CO2 signal peak for the H-NaA sample is significantly weaker than that for the C-NaA sample. Furthermore, a distinct CO2 desorption peak is observed at 327°C for the C-NaA sample, attributed to the decomposition of carbonate and carbonate-like species.

[0067] See also Figure 15We roughly calculated and compared the energy balance of C-NaA and H-NaA samples during the activation process, where the calculation process was based on 1 kg of molecular sieve sample.

[0068] (1) The activation energy of the C-NaA sample is calculated as follows:

[0069] According to the weight loss rate of the C-NaA sample in the TG curve, the mass m2 of carbonate and carbonate-like species on the surface of the C-NaA sample can be estimated by formula (1):

[0070] m2≈(1 / 80%)×5%=0.06kg (1)

[0071] The temperature of sample C-NaA was raised from 25°C to 300°C and maintained at 300°C for 2 hours. Therefore, the energy Q1 (kJ) required for the activation of sample C-NaA can be estimated as:

[0072] Q1=C z ×m1×(300-25)+m2×ΔH1 (2)

[0073] =0.92×1×275+0.06×3020=441.75kJ

[0074] Among them, C z is the specific heat capacity of the C-NaA sample (here, the specific heat capacity of 4A molecular sieve is 0.92 kJ / (kg×K), 25°C and 1 atm). m1 and m2 represent the masses of C-NaA (1 kg) and carbonate / carbonate-like species, respectively. ΔH1 is the decomposition heat of the carbonate / carbonate-like species (here, the decomposition heat of Na2CO3 is 3020 kJ / kg).

[0075] (2) The activation energy of the H-NaA sample is calculated as follows:

[0076] According to the weight loss rate of the H-NaA sample in the TG curve, the water content m4 per unit mass of the dry molecular sieve sample in the C-NaA sample can be estimated by formula (3):

[0077] m4≈(1 / 80%)×15%=0.19kg (3)

[0078] The temperature of the H-NaA sample was raised from 25°C to 200°C and maintained at 200°C for 2 hours. Therefore, the energy Q2 (kJ) required for activation of the H-NaA sample can be estimated as:

[0079] Q2=C z ×m3×(200-25)+m4×[C w ×(100-25)+ΔH2] (4)

[0080] =0.94*1*175+0.19*[4.18*75+2257]

[0081] =652.90kJ

[0082] Among them, C w is the specific heat capacity of water (4.18kJ / (kg*K), 25℃ and 1atm), C z is the specific heat of H-NaA (here, the specific heat of 4A molecular sieve is 0.92 kJ / (kg×K), 25°C and 1 atm). m3 is the mass of H-NaA (1 kg), and ΔH2 is the heat of vaporization of water (2257 kJ / kg, 100°C, 1 atm).

[0083] By comparing the energy required for activation of H-NaA and C-NaA samples, it is shown that from the perspective of the required activation heat, the H-NaA sample has no advantage. However, what this patent work aims to solve is that in industrial applications, the molecular sieve adsorbent needs to be activated at high temperature before adsorbing the target molecules, and in some low-pressure areas or special application environments, due to the lack of high-grade thermal energy, sufficient high-temperature activation cannot be carried out. Comparing the activation process of the two samples, the H-NaA sample can achieve a better activation effect at 200°C, which is lower than the temperature range of medium-pressure steam (230-250°C, about 2.6-4.0MPa). The C-NaA sample needs to achieve a better activation effect at a temperature range equivalent to high-pressure steam (250-311°C, about 4.1-10.0MPa). Therefore, this method of activating molecular sieves can reduce the amount of high-grade thermal energy used in the activation process of molecular sieve adsorbents.

[0084] Comparison of CO2 adsorption performance of some molecular sieve adsorbents under different activation conditions

[0085]

[0086] aThe results are from single-component adsorption isotherms, and the rest are from mixed gas adsorption.

[0087] The above description is only a specific embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent transformation made using the present invention, or directly or indirectly applied in other related technical fields, is also included in the patent protection scope of the present invention.

Claims

1. A low-temperature activation method for a CO2 molecular sieve adsorbent, characterized in that: The following steps are involved: (1) Mix the molecular sieve and deionized water in a mass volume ratio of 1:20-30 and soak at 25-35°C for 20-40 minutes; (2) Filter and dry in air at 100-150°C for 10-14 hours; (3) Activate the dried molecular sieve at 180-220°C for 1.5-2.5 hours and purge with inert gas.

2. The low-temperature activation method of CO2 molecular sieve adsorbent according to claim 1, characterized in that: In step (1), the molecular sieve is C-NaA molecular sieve.

3. The low-temperature activation method of CO2 molecular sieve adsorbent according to claim 2, characterized in that: In step (3), H-NaA molecular sieve is obtained after purging with inert gas.

4. The low-temperature activation method for a CO2 molecular sieve adsorbent according to claim 3, characterized in that: In step (1), the mass volume ratio of the deionized water to the molecular sieve is 1:

25.

5. The low-temperature activation method of CO2 molecular sieve adsorbent according to claim 4, characterized in that: In step (3), the activation temperature is 200° C. and the activation time is 2 hours.

6. The low-temperature activation method for a CO2 molecular sieve adsorbent according to claim 5, characterized in that: The inert gas is helium or nitrogen, and the purge flow rate is 10 to 30 mL / min.

7. A method for regenerating a product obtained by the low-temperature activation method of a CO2 molecular sieve adsorbent according to any one of claims 1 to 6, characterized in that: The obtained activated molecular sieve is used to perform adsorption penetration on the mixed gas, and the activated molecular sieve after adsorption is purged with an inert gas at 140-160° C. and regenerated for 1-3 hours.

8. The method for regenerating the product obtained by the low-temperature activation method of the CO2 molecular sieve adsorbent according to claim 7, characterized in that: The mixed gas is CO2 and CH4; the volume ratio of CO2 to CH4 is 15:85; the activated molecular sieve after adsorption is purged with inert gas at 150°C and regenerated, with a He flow rate of 14 mL / min.

9. The method for regenerating the product obtained by the low-temperature activation method of the CO2 molecular sieve adsorbent according to claim 7, characterized in that: The mixed gas is CO2 and N2; the volume ratio of CO2 to N2 is 15:85; the activated molecular sieve after adsorption is purged and regenerated with an inert gas at 150°C, and the inert gas is He with a He flow rate of 14 mL / min.

10. The method for regenerating the product obtained by the low-temperature activation method of the CO2 molecular sieve adsorbent according to claim 7, characterized in that: The adsorption temperature is 25°C.

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