CN104056598A - MOFs based carbon dioxide adsorbent, preparation method and application thereof - Google Patents

Abstract

The invention discloses a MOFs-based carbon dioxide adsorbent, which comprises MOFs and organic amines loaded in the pores and surfaces of the MOFs, and the mass ratio of the MOFs to the organic amines is 0.1-10:1. The MOFs-based carbon dioxide adsorbent provided by the invention realizes the joint action of physical adsorption and chemical adsorption, absorbs and stores carbon dioxide at medium and low temperatures, and realizes regeneration and reuse of the adsorbent under certain conditions. The MOFs-based carbon dioxide adsorbent has good adsorption capacity, high selectivity and cycle stability for carbon dioxide, can overcome the shortcomings of organic amines that are easy to volatilize and corrode equipment, and meet the requirements of industrial treatment. The invention also discloses a preparation method of the MOFs-based carbon dioxide adsorbent and its application in carbon dioxide adsorption in flue gas.

Description

A kind of MOFs-based carbon dioxide adsorbent and its preparation method and application

technical field

The invention relates to the field of preparation of carbon dioxide adsorbents, in particular to a MOFs-based carbon dioxide adsorbent and its preparation method and application.

Background technique

In recent years, the increasing use of fossil fuels has led to increasing _CO2 emissions. In the past 250 years, the concentration of CO ₂ in the atmosphere has increased from 280ppm before the industrial revolution to 390ppm in 2010, especially in the past 50 years. Its excessive emissions have caused global warming, seriously affecting the earth's ecological environment and climate change. Therefore, _CO2 emission reduction has also become an urgent issue. The development of low-carbon new energy and the improvement of existing energy utilization efficiency are effective ways to reduce CO ₂ emissions, and CO ₂ capture and separation technology is undoubtedly an effective technology to reduce CO ₂ emissions.

Carbon dioxide capture and separation methods mainly include solvent absorption method, solid adsorption method, membrane separation method, cryogenic fractionation method and so on.

So far, the solvent absorption method is still the most widely used carbon dioxide separation method, among which the liquid solvent absorption-regeneration process is relatively mature and has been applied in industry. Liquid amine absorbent has the advantages of high thermal stability, high surface tension, and large adsorption capacity, but it has disadvantages such as high investment and operating costs, easy corrosion of equipment and pipelines, high energy consumption for regeneration of the adsorbent, and toxicity of the absorbent itself.

The solid adsorption method mainly uses the reversible adsorption of the solid adsorbent to the carbon dioxide in the raw material mixed gas to separate and recover carbon dioxide. The current solid adsorbent generally loads organic amines on hydrotalcite, activated carbon, zeolite molecular sieve and other carriers by impregnation method. s surface.

Metal-organic frameworks (MOFs, Metal-Organic Frameworks) refer to crystalline porous materials with a periodic network structure formed by self-assembly of transition metal ions and organic ligands. It has the advantages of high porosity, low density, large specific surface area, pore regularity, tunable pore size, topological structure diversity and tailorability, etc., and has a wide range of potential applications in the fields of gas storage, drug carrier, molecular recognition and catalysis.

However, when MOFs are used as carbon dioxide adsorbents, they need to be carried out at medium and high pressures, and the adsorption and separation capabilities of _CO2 at normal pressure are weak.

For example, MOF-74 has a carbon dioxide adsorption capacity of 15.86mmol/g at 3600KPa (Dietzel, P.D.C.; Besikiotis, V.; Blom, R.J.Mater.Chem.2009, 19, 7362), and 6.25mmol/g at 100KPa ( Bao, Z.; Yu, L.; Ren, Q.; Lu, X.; Deng, S.J.ColloidInterface Sci.2011, 353, 549), and when the carbon dioxide concentration in the flue gas is 15%, its adsorption capacity is only 0.42 mmol/g (Mason, J.A.; Sumida, K.; Herm, Z.R.; Krishna, R.; Long, J.R. Energy Environ. Sci. 2011, 4, 3030); the same situation appears in MIL-53, at 2500KPa, The adsorption capacity is 6.95mmol/g (Bourrelly, S.; Llewellyn, P.L.; Serre, C.; Millange, F.; Loiseau, T.; F_erey, G.J.Am.Chem.Soc.2005,127,13519), under 100KPa is 2.41mmol/g (Arstad, B.; Fjellv_ag, H.; Kongshaug, K.O.; Swang, O.; Blom, R.Adsorption2008,14,755), while the carbon dioxide concentration is 15%, the adsorption capacity is only 0.39mmol/g (Arstad, B.; Fjellv_ag, H.; Kongshaug, K.O.; Swang, O.; Blom, R. Adsorption 2008, 14, 755).

For the adsorption of carbon dioxide in flue gas, it is required that the adsorbent can have a high adsorption capacity and adsorption selectivity for _CO2 under normal pressure, and can realize multiple cycles. Therefore, it is necessary to design an adsorbent that can meet the above conditions Adsorbents are of great importance.

Contents of the invention

The invention provides a MOFs-based carbon dioxide adsorbent, which uses MOFs as a carrier and carries organic amines to realize the joint action of physical adsorption and chemical adsorption, absorb and store carbon dioxide at medium and low temperatures, and realize the regeneration and reuse of the adsorbent under certain conditions. The MOFs-based carbon dioxide adsorbent has good adsorption capacity, high selectivity and cycle stability for carbon dioxide, can overcome the shortcomings of organic amines being volatile and easy to corrode equipment, and meets the requirements of industrial treatment.

The invention discloses a MOFs-based carbon dioxide adsorbent, which comprises MOFs and organic amines loaded on the MOFs, and the mass ratio of the MOFs to the organic amines is 0.1-10:1.

The carrier material MOFs used in the MOFs-based carbon dioxide adsorbent provided by the invention has rich pores, a large specific surface area, and strong gas adsorption and storage capabilities, while the N atoms of organic amines make their molecular chains with Positive charges are beneficial to the loading of organic amines on the surface of MOFs. After the modification of MOFs by organic amines, it not only maintains the characteristics of large specific surface area and strong adsorption capacity of MOFs, but also combines the selectivity of organic amines for CO ₂ gas adsorption (-NH ₂ in organic amine molecules can interact with CO ₂ Adsorption due to weak reaction), and overcome the shortcomings of organic amines that are volatile and highly corrosive, and realize the combined adsorption of physical adsorption and chemical adsorption, and the purpose of selectively adsorbing carbon dioxide with chemical adsorption as the main, while heating Or in the case of decompression, this compound can also decompose and release the carbon dioxide stored in MOFs, so as to achieve the function of storing carbon dioxide at low temperature or releasing carbon dioxide at high temperature or decompression, so as to realize the regeneration of the adsorbent.

The MOFs are MOF-like MOFs, ZIF-like MOFs, and MIL-like MOFs. MOFs are composed of transition metals and organic ligands, the transition metals can be selected from Zn, Cu, Cr, Pd, Pt, Ru, Ni, Co, V, Fe, Mn, etc., and the organic ligands can be selected from terephthalic acid , 2,6-naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, etc.

Preferably, the MOFs are selected from MOF-74, ZIF-8, MIL-101.

The preparation of MOF-74 can refer to the literature Dietzel, P.D.C.; Besikiotis, V.; Blom, R.J.Mater.Chem.2009, 19, 7362;

The preparation of ZIF-8 can refer to Yazaydin, A.O.; Snurr, R.Q.; Park, T.-H.; Koh, K.; Liu, J.; LeVan, M.D.; .; Galloway, D.B.; Low, J.L.; Willis, R.R.J. Am. Chem. Soc. 2009, 131, 18198;

The preparation of MIL-101 can refer to literature Llewellyn, P.L.; Bourrelly, S.; Serre, C.; Vimont, A.; Daturi, M.; Hamon, L.; Weireld, G.D.; , D.-Y.; Hwang, Y.K.; Jhung, S.H.; F_erey, G. Langmuir 2008, 24, 7245.

Preferably, the organic amine is at least one of diethanolamine, triethanolamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, polyacrylamide, and polypropyleneamine. A sort of. Small molecular organic amines are further preferred, such as diethanolamine, triethanolamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. To prevent macromolecular organic amine polymers from clogging MOFs with small pores, resulting in a decrease in the ability to adsorb CO ₂ .

Further preferably, the MOFs are MIL-101 or MOF-74, and the organic amine is tetraethylenepentamine.

Through the matching of the above-mentioned preferred MOFs framework and organic amines, higher adsorption efficiency and cycle stability can be obtained at the same time.

The invention also discloses a preparation method of the MOFs-based carbon dioxide adsorbent, comprising the following steps:

Mix the organic amine with the solvent, disperse evenly, add MOFs to obtain the dispersion liquid, react with stirring or ultrasonic for 2-10 hours, heat to remove the solvent, then dry and grind to obtain the MOFs-based carbon dioxide adsorbent;

The mass ratio of the MOFs to the organic amine is 0.1-10:1, and the concentration of the MOFs in the dispersion liquid is 10 ^-4 -1.0 g/ml.

Preferably, the concentration of MOFs in the dispersion liquid is 0.001-0.016 g/ml.

The solvent is water, methanol, ethanol, benzene or chloroform; preferably methanol or ethanol.

Preferably, the temperature for removing the solvent by heating is 50-90°C.

Using the above preparation method, organic amines will be loaded in the pores of MOFs and on the surface of MOFs.

The present invention also discloses the application of the MOFs-based carbon dioxide adsorbent. Since the MOFs-based carbon dioxide adsorbent prepared by the present invention has excellent adsorption capacity and adsorption selectivity for carbon dioxide under normal pressure, it can be directly used in the flue Adsorption of carbon dioxide in air.

Specifically:

Under normal pressure, the MOFs-based carbon dioxide adsorbent is directly mixed with the flue gas. After the adsorption amount is stable, the desorption of carbon dioxide is realized through post-treatment, and the desorbed MOFs-based carbon dioxide adsorbent is reused;

The temperature of the flue gas is 40-80°C, and the volume concentration of carbon dioxide in the flue gas is 10-20%;

The post-treatment is heat treatment, microwave treatment or vacuum treatment.

The above-mentioned adsorption process is mainly chemical adsorption, and the organic ligands on the MOFs and the organic amines loaded on the MOFs selectively adsorb carbon dioxide.

Beneficial effects of the present invention:

(1) The MOFs-based carbon dioxide adsorbent prepared by the present invention realizes the combined action of physical adsorption and chemical adsorption, and selectively adsorbs carbon dioxide based on chemical adsorption, and has high adsorption performance and adsorption selectivity for carbon dioxide, and can pass through Low-temperature adsorption and storage of carbon dioxide, high temperature, decompression or microwave release of carbon dioxide, to achieve regeneration and reuse of adsorbents;

(2) By matching the MOFs framework and organic amines, a carbon dioxide adsorbent with high adsorption efficiency and high cycle stability is obtained. The preferred MOFs framework has high strength and is still intact after 5 cycles of adsorption, and the adsorption efficiency decreases rate below 15%.

(3) In the MOFs-based carbon dioxide adsorbent prepared by the present invention, the organic amine is loaded on the MOFs through chemical bonds or hydrogen bonds, which is not easy to volatilize, has little corrosion to equipment, and meets the requirements of industrial processing;

(4) The preparation process of the present invention is simple and controllable.

Detailed ways

The present invention is further illustrated by the following examples.

Adsorption capacity determination method in the embodiment:

The _CO2 adsorption experiments were carried out in a fixed adsorption bed. The adsorption column used in the test is made of high temperature resistant quartz glass, with a diameter of 1 cm and a length of 25 cm. The MOFs-based carbon dioxide adsorbent required for the experiment was weighed and filled into the adsorption column, and then the adsorption column was placed in a temperature-controlled tube furnace. Before the first experiment, the adsorbent was first activated at high temperature (413K) under the protection of N ₂ . The adsorption experiment was started after the temperature was cooled to the required temperature for the experiment. The experimental gas is prepared by mixing high-purity N ₂ (99.99%) and pure CO ₂ (99.9%) at a volume ratio of 1:9. The _CO concentration was determined online by gas chromatography (GC).

The _CO2 dynamic adsorption capacity q (mmol/g) is calculated by the following formula:

$\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; [</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; t</span>}}\mathrm{<span\; class="notranslate">\; Q</span>}\frac{{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; c</span>}}\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; ]</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; T</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}$

Among them, M is the mass of adsorbent (g), Q is the gas flow rate ( ^cm3 /min), _c0 is the _CO2 concentration at the inlet of the adsorption column (vol%), c is the _CO2 concentration at the outlet of the adsorption column (vol%), and t It is the time (min) to reach adsorption equilibrium, T is the gas temperature (K), T ₀ is 273K, and V _m is 22.4cm ³ /mmol.

Example 1

Dissolve 1g of tetraethylenepentamine in 100ml of absolute ethanol, stir for 0.5h, add 1g of MOF-74, stir for 4h, put the sample in an oven, dry at 80°C to remove ethanol, and then dry at 105°C, denoted as M1. In the obtained sample, the content of organic amine was 50 wt%. The adsorption data was measured by using a fixed bed, the adsorption temperature was 70°C, and the simulated gas flow rate was 50ml/min. The results are shown in Table 1.

Example 2

Dissolve 1g of tetraethylenepentamine in 100ml of absolute ethanol, stir for 0.5h, add 1g of ZIF-8, stir for 4h, put the sample in an oven, dry at 80°C to remove ethanol, and then dry at 105°C, denoted as M2 . In the obtained sample, the content of organic amine was 50 wt%. The test conditions are the same as in Example 1, and the results are shown in Table 1.

Example 3

Dissolve 1g of tetraethylenepentamine in 100ml of absolute ethanol, stir for 0.5h, add 1g of MIL-101, stir for 4h, put the sample in an oven, dry at 80°C to remove ethanol, and then dry at 105°C, record as M3. In the obtained sample, the content of organic amine was 50 wt%. The adsorption capacity data was determined by using a fixed bed, and the results are shown in Table 1. When the adsorption temperature was adjusted to 20, 30, 40, 50, 60, 70, and 80°C, and the simulated gas flow rate was 50ml/min, the adsorption results of M3 are shown in Table 2. Adjust the adsorption temperature to 50°C, the simulated gas flow rate to 50ml/min; the desorption temperature to 150°C, the nitrogen purge flow rate to 50ml/min, and the desorption time to 30min. The cycle adsorption results of M3 are shown in Table 3.

Example 4

Dissolve 1g of polyethyleneimine in 100ml of absolute ethanol, stir for 0.5h, add 1g of MIL-101, stir for 4h, put the sample in an oven, dry at 80°C to remove ethanol, and then dry at 105°C, denoted as M4. In the obtained sample, the content of organic amine was 50 wt%. The test conditions are the same as in Example 1, and the results are shown in Table 1.

Example 5

Dissolve 1g of diethanolamine and 1g of polyethyleneimine in 500ml of absolute ethanol, stir for 5h, add 8g of MOF-74, stir for 12h, put the sample in an oven, dry at 80°C to remove ethanol, and then dry at 105°C. Record it as M5. In the obtained sample, the content of organic amine was 20 wt%. The test conditions are the same as in Example 1, and the results are shown in Table 1.

Example 6

Dissolve 1g of diethanolamine and 1g of tetraethylenepentamine in 500ml of absolute ethanol, add 3g of ZIF-8 after stirring for 5 hours, ultrasonicate for 12 hours, put the sample in an oven, dry at 80°C to remove ethanol, and then dry at 105°C. Record it as M6. In the obtained sample, the content of organic amine was 40 wt%. The test conditions are the same as in Example 1, and the results are shown in Table 1.

Example 7

Dissolve 1g of tetraethylenepentamine and 1g of polyethyleneimine in 500ml of absolute ethanol, stir for 5h, add 0.5g of MIL-101, stir for 12h, put the sample in an oven, dry at 80°C to remove ethanol, and then dry at 105°C Under drying, denoted as M7. In the obtained sample, the content of organic amine was 80 wt%. The test conditions are the same as in Example 1, and the results are shown in Table 1.

Example 8

Dissolve 1g of tetraethylenepentamine in 100ml of absolute ethanol, add 1g of MIL-101 after ultrasonication for 0.5h, ultrasonication for 4h, put the sample in an oven, dry at 80°C to remove ethanol, and then dry at 105°C, denoted as M8. In the obtained sample, the content of organic amine was 50 wt%. The test conditions are the same as in Example 1, and the results are shown in Table 1.

Example 9

Dissolve 1g of tetraethylenepentamine in 100ml of anhydrous methanol, stir for 0.5h, add 1g of MIL-101, stir for 4h, put the sample in an oven, dry at 70°C to remove methanol, and then dry at 105°C, denoted as M9. In the obtained sample, the content of organic amine was 50 wt%. The test conditions are the same as in Example 1, and the results are shown in Table 1.

Example 10

Dissolve 1g of tetraethylenepentamine and 1g of polyethyleneimine in 500ml of absolute ethanol, add 0.5g of MIL-101 after ultrasonication for 5h, ultrasonication for 12h, put the sample in an oven, dry at 80°C to remove ethanol, and then Dry it under the hood and record it as M10. In the obtained sample, the content of organic amine was 80 wt%. The test conditions are the same as in Example 1, and the results are shown in Table 1.

Example 11

Dissolve 1g of tetraethylenepentamine and 1g of polyethyleneimine in 500ml of anhydrous methanol, stir for 5h, add 0.5g of MIL-101, stir for 12h, put the sample in an oven, dry at 70°C to remove methanol, and then dry at 105°C Dry it under the hood and record it as M11. In the obtained sample, the content of organic amine was 80 wt%. The test conditions are the same as in Example 1, and the results are shown in Table 1.

Table 1 is a list of the carbon dioxide adsorption capacities of the MOFs-based carbon dioxide adsorbents prepared in Examples 1 to 11 at the same adsorption temperature and the same simulated gas flow.

Table 2 is a list of carbon dioxide adsorption capacities of the MOFs-based carbon dioxide adsorbent prepared in Example 3 at different temperatures.

Table 3 is a list of the carbon dioxide adsorption capacity of the MOFs-based carbon dioxide adsorbent prepared in Example 3 for five cycles.

Table 1

Table 2

table 3

Claims (10)

1. a MOFs group carbonic anhydride adsorption agent, is characterized in that, comprises MOFs, and is carried on the organic amine on MOFs; The mass ratio of described MOFs and organic amine is 0.1～10:1.

2. MOFs group carbonic anhydride adsorption agent according to claim 1, is characterized in that, described MOFs is MOF series class MOFs, ZIF series class MOFs, MIL series class MOFs.

3. MOFs group carbonic anhydride adsorption agent according to claim 1, it is characterized in that, described organic amine is at least one of diethanol amine, triethanolamine, diethylenetriamine, triethylene tetramine, TEPA, five ethene hexamines, polymine, polyacrylamide, polypropylene amine.

4. MOFs group carbonic anhydride adsorption agent according to claim 3, is characterized in that, described organic amine is diethanol amine, triethanolamine, diethylenetriamine, triethylene tetramine, TEPA, five ethene hexamines.

5. according to the MOFs group carbonic anhydride adsorption agent described in the arbitrary claim of claim 1～4, it is characterized in that, described MOFs is MIL-101 or MOF-74, and organic amine is TEPA.

6. a preparation method for MOFs group carbonic anhydride adsorption agent according to claim 1, is characterized in that, comprises the following steps:

By organic amine and solvent, after being uniformly dispersed, add MOFs to obtain dispersion liquid, stir or ultrasonication under react 2～10h, heating is except desolventizing, then drying, obtains MOFs group carbonic anhydride adsorption agent after grinding; In described dispersion liquid, the concentration of MOFs is 10 ^-4～1.0g/ml.

7. the preparation method of MOFs group carbonic anhydride adsorption agent according to claim 6, is characterized in that, in described dispersion liquid, the concentration of MOFs is 0.001～0.016g/ml.

8. the preparation method of MOFs group carbonic anhydride adsorption agent according to claim 6, is characterized in that, described solvent is water, methyl alcohol, ethanol, benzene or chloroform.

9. an application for MOFs group carbonic anhydride adsorption agent according to claim 1, is characterized in that, for the absorption of carbon dioxide in flue gas.

10. application according to claim 9, is characterized in that, under normal pressure, described MOFs group carbonic anhydride adsorption agent is directly mixed with flue gas, after adsorbance is stable, realize the desorption of carbon dioxide through post processing, the MOFs group carbonic anhydride adsorption agent after desorption is reused;

The temperature of described flue gas is 40～80 DEG C, and carbon dioxide in flue gas volumetric concentration is 10～20%;

Described post processing is heat treatment, microwave treatment or application of vacuum.