Preparation of a cyclodextrin-based porous polymer and its application in adsorbing organic waste gas

Abstract

The present invention belongs to the technical field of organic waste gas adsorption, and relates to the preparation of a cyclodextrin-based porous polymer and its application in adsorbing organic waste gas. The present invention uses a water-in-oil high internal phase emulsion stabilized by a non-ionic surfactant as a template and is cured by ultraviolet light to prepare a cyclodextrin-based porous polymer, wherein the mass content of continuous phase water in the emulsion is 10-20%, the mass content of non-ionic surfactant is 0.1-1%, the emulsion uses a non-polar / weakly polar solvent as a dispersed phase and the dispersed phase content is 70-85%, and the continuous phase is dissolved with 2-5% of the mass of the emulsion double-bond-terminated cyclodextrin and 2-5% of the mass of the emulsion water-soluble polythiol; the double-bond-terminated cyclodextrin is obtained by reacting acryloyl chloride and / or vinyl isocyanate with the secondary hydroxyl group of cyclodextrin. The porous polymer of the present invention can absorb toluene up to 800 mg / g or more; and can be regenerated by high-temperature desorption, and its repeated adsorption capacity is maintained at more than 85% of the initial adsorption amount.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of environmentally friendly adsorption materials, and relates to the preparation of a cyclodextrin-based porous polymer and the application of the polymer in adsorbing organic waste gas. Background Art

[0002] At present, the control measures for VOCs mainly include source substitution, process control and end-of-pipe control. VOCs emissions can be reduced by improving industrial production processes and equipment, but the cost of improvement is high and end-of-pipe treatment is also required. Due to the low technical barriers and cost investment, end-of-pipe control technology has received widespread attention. End-of-pipe control technology can be divided into recovery method and destruction method according to whether VOCs are recycled. The destruction method is a method of decomposing VOCs molecules into carbon dioxide, water and non-toxic or low-toxic compounds using chemical or biological methods. Recovery methods include membrane separation, absorption, adsorption and condensation. The VOCs molecules treated by the recovery method are not destroyed themselves, but transferred. Among them, the adsorption method is considered to be a cost-effective VOCs control technology because it has the potential for adsorbents and VOCs recycling.

[0003] Cyclodextrin is produced by the degradation of starch by cyclodextrin glucosyltransferase. It is a cyclic oligosaccharide formed by connecting D-pyranose glucose residues through α-1,4-glycosidic bonds. The secondary hydroxyl groups on the secondary surface of cyclodextrin make its wider end and outer wall hydrophilic, while its cavity is hydrophobic, so it has a certain adsorption capacity. The hydrophobic cavity of cyclodextrin can include many inorganic, organic and chiral guest molecules to form host-guest or supramolecular complexes, and it is also easy to form inclusion complexes with various solid, liquid or gaseous substances.

[0004] High internal phase emulsions (HIPEs) refer to paste-like emulsions with a dispersed phase volume fraction exceeding 74%. They are composed of an internal dispersed phase and an external continuous phase and can exist stably. By "fixing" the continuous phase through polymerization reaction and removing the dispersed phase, a porous polymer, namely polyHIPEs, can be obtained. The prepared polyHIPEs have the characteristics of high porosity and interconnected pore structure, and have broad application prospects in the field of adsorption and separation. By utilizing the reactive hydroxyl groups on the surface of cyclodextrin, double bonds are introduced, and then a cyclodextrin-based porous polymer can be obtained through the emulsion template method. It has the macropores of the emulsion template method and the micropores of the cyclodextrin cavity, and can efficiently adsorb VOCs. In addition, cyclodextrin is a renewable biomass resource, and the resulting cyclodextrin-based porous polymer is bio-friendly, which is beneficial to the sustainable development of the industry.

[0005] At present, cyclodextrin-based adsorbents are still dominated by powder particles, which are inconvenient to operate when used and recycled, and have the problems of high cost, small absorption capacity, short saturation time, unstable purification rate, high regeneration difficulty, and easy secondary pollution. The porous polymer block prepared by the emulsion template method of the present invention is more convenient for absorption and recycling operations. The modified cyclodextrin can improve the cross-linking degree of the material, increase the specific surface area, and make it have better adsorption effect and faster adsorption speed. The raw materials used are cheap and easy to obtain, green and environmentally friendly. The preparation process of the cyclodextrin-based porous polymer is simple, does not produce secondary pollution, and has a wide range of applications. Summary of the invention

[0006] The present invention aims to utilize the secondary hydroxyl groups on the outer wall of cyclodextrin to chemically modify the carbon-carbon double bonds, and then obtain a cyclodextrin-based porous polymer through an emulsion template method; and utilize the hydrophobic cavity of cyclodextrin to achieve efficient and repeatable adsorption of VOCs.

[0007] The technical solution adopted by the present invention includes the following characteristic steps:

[0008] The cyclodextrin used in the present invention includes any one of α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), and γ-cyclodextrin (γ-CD).

[0009] The invention first prepares double-bond terminated cyclodextrin, and utilizes acryloyl chloride and / or vinyl isocyanate to react with secondary hydroxyl groups on the outer wall of cyclodextrin to obtain double-bond terminated cyclodextrin.

[0010] The present invention uses a water-in-oil high internal phase emulsion stabilized by a nonionic surfactant as a template to prepare a cyclodextrin-based porous polymer, wherein water is a continuous phase, a nonpolar / weakly polar solvent is a dispersed phase, and the nonionic surfactant is an emulsion stabilizer.

[0011] The high internal phase emulsion of the present invention uses aqueous solution as the continuous phase, wherein the water accounts for 10-20% of the total mass fraction of the emulsion.

[0012] The high internal phase emulsion of the invention has double-bond-terminated cyclodextrin dissolved in the continuous phase, wherein the double-bond-terminated cyclodextrin accounts for 2-5% of the total mass fraction of the emulsion.

[0013] The high internal phase emulsion of the present invention also contains water-soluble polythiol dissolved in the continuous phase, including any one of tetra(ethylene glycol) disulfide, hexa(ethylene glycol) disulfide, polyethylene glycol disulfide, 2,2′-(1,2-ethylenedioxy) diethanethiol, trimethylolpropane tri(3-mercaptopropionate), pentaerythritol tetrakis-3-mercaptopropionate, etc., wherein the water-soluble polythiol accounts for 2-5% of the total mass fraction of the emulsion.

[0014] The nonionic surfactant used in the present invention includes any one of Pluronic P123, Pluronic F127, Tetronic 1307, Tetronic 1107, etc. The nonionic surfactant accounts for 0.1-1% of the total mass fraction of the emulsion.

[0015] The dispersed phase of the high internal phase emulsion prepared by the present invention is a non-polar / weakly polar solvent, including any one of toluene, xylene, paraffin, cycloparaffin, gasoline, diesel, liquid paraffin, etc. The non-polar / weakly polar solvent accounts for 70-85% of the total mass fraction of the emulsion.

[0016] The cyclodextrin-based cross-linked network selected in the present invention is obtained by "olefin-ene" click chemistry of double-bond-terminated cyclodextrin and water-soluble polythiol. The prepared high internal phase emulsion is exposed to ultraviolet light (600W, 120mW / cm 2 ,320~580nm) for 60~120s, and then purified and dried to obtain a cyclodextrin-based porous polymer.

[0017] The beneficial effects of the present invention are:

[0018] 1. The present invention uses cyclodextrin as the porous polymer main body and utilizes the hydrophobic annular cavity of cyclodextrin to achieve efficient adsorption of VOCs.

[0019] 2. The present invention utilizes ultraviolet light-induced "olefin-ene" click chemical curing, which has high production efficiency.

[0020] 3. The porous polymer of the present invention has a multi-level cellular structure, and can adsorb toluene up to 800 mg / g or more; and can be regenerated by high-temperature desorption, and its repeated adsorption capacity is maintained at more than 85% of the initial adsorption amount.

[0021] 4. The present invention is an adsorption material with bio-based cyclodextrin as the main body, which has a high adsorption capacity and can be regenerated by desorption for recycling, and is an environmentally friendly adsorption material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Example 5 Microscopic morphology of cyclodextrin-based porous polymer;

[0023] Figure 2 Example 6 Microscopic morphology of cyclodextrin-based porous polymer;

[0024] Figure 3 Example 7 Microscopic morphology of cyclodextrin-based porous polymer;

[0025] Figure 4 Example 8 Microscopic morphology of cyclodextrin-based porous polymer;

[0026] Figure 5Example 9 Microscopic morphology of cyclodextrin-based porous polymer;

[0027] Figure 6 Example 6 Static saturated adsorption capacity of cyclodextrin-based porous polymers for different VOCs;

[0028] Figure 7 Cyclic static saturated adsorption capacity of toluene by the cyclodextrin-based porous polymers of Example 5, Example 8, Example 9 and Comparative Example 1;

[0029] Figure 8 Example 7: Breakthrough curve of p-xylene adsorbed by cyclodextrin-based porous polymer. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with embodiments:

[0031] Examples 1 to 4 Preparation of Double-bond End-capped Cyclodextrin

[0032] Example 1

[0033] Take 10g of α-cyclodextrin (α-CD) and dissolve it in 500mL of sodium hydroxide aqueous solution (NaOH, 0.5M), transfer it to an ice water bath and stir it for 10min, add 10mL of acryloyl chloride drop by drop, and after the addition is completed, transfer it to room temperature for reaction for 1h, concentrate the reaction stock solution to remove water, and then dissolve it in 20mL of N,N-dimethylformamide (DMF) to filter and remove salt. The filtrate is precipitated with a large amount of acetone, and the double-bond terminated α-cyclodextrin (α-CD-TA) is collected and vacuum dried at 40°C for 12h.

[0034] Example 2

[0035] Take 10g of β-cyclodextrin (β-CD) and dissolve it in 500mL of NaOH aqueous solution (0.5M), transfer it to an ice water bath and stir it for 10min, add 10mL of acryloyl chloride drop by drop, and after the addition is completed, transfer it to room temperature for reaction for 1h, concentrate the reaction stock solution to remove water, then dissolve it in 20mL of DMF and filter to remove salt, precipitate the filtrate with a large amount of acetone, collect the double-bond terminated β-cyclodextrin (β-CD-TA), and dry it in vacuum at 40℃ for 12h.

[0036] Example 3

[0037] Take 10g of β-cyclodextrin (β-CD) and dissolve it in 500mL of NaOH aqueous solution (0.5M), transfer it to an ice water bath and stir it for 10min, add 10mL of methacryloyl chloride drop by drop, and after the addition is completed, transfer it to room temperature for reaction for 1h, concentrate the reaction stock solution to remove water, then dissolve it in 20mL of DMF and filter to remove salt, precipitate the filtrate with a large amount of acetone, collect the double-bond terminated β-cyclodextrin (β-CD-MA), and dry it in vacuum at 40℃ for 12h.

[0038] Example 4

[0039] Take 10g of γ-cyclodextrin (γ-CD) and dissolve it in 500mL of NaOH aqueous solution (0.5M), transfer it to an ice water bath and stir it for 10min, add 10mL of acryloyl chloride drop by drop, and after the addition is completed, transfer it to room temperature for reaction for 1h, concentrate the reaction stock solution to remove water, then dissolve it in 20mL of DMF and filter to remove salt, precipitate the filtrate with a large amount of acetone, collect the double-bond terminated γ-cyclodextrin (γ-CD-TA), and dry it in vacuum at 40℃ for 12h.

[0040] Examples 5 to 9 Preparation of Cyclodextrin-Based Porous Polymers

[0041] Example 5

[0042] A high internal phase emulsion was prepared in proportion, α-CD-TA, tetra(ethylene glycol) disulfide and Pluronic P123 were dissolved in water as the continuous phase, and toluene was used as the dispersed phase. The mass fractions of the components are: 10% water, 2% α-CD-TA, 2% tetra(ethylene glycol) disulfide, 1% Pluronic P123 and 85% toluene. A continuous phase aqueous solution was prepared, and shearing was maintained at 10,000 rpm using a high-speed shearing machine. Toluene was gradually dripped in to form a gel-like high internal phase emulsion and then maintained at high-speed shearing for 3 minutes. The formed gel-like high internal phase emulsion was transferred to the corresponding mold, cured by ultraviolet irradiation for 60 seconds, and then purified and dried to obtain a cyclodextrin-based porous polymer. The microscopic morphology of the corresponding cyclodextrin-based porous polymer is shown in Figure 1 .

[0043] Example 6

[0044] A high internal phase emulsion was prepared in proportion, β-CD-TA, trimethylolpropane tris(3-mercaptopropionate) and Pluronic F127 were dissolved in water as the continuous phase, and xylene was used as the dispersed phase. The mass fractions of the components are: 15% water, 2% α-CD-TA, 2% trimethylolpropane tris(3-mercaptopropionate), 0.5% Pluronic F127 and 80% xylene. A continuous phase aqueous solution was prepared, and shearing was maintained at 10,000 rpm using a high-speed shearing machine. Xylene was gradually dripped in to form a gel-like high internal phase emulsion and then maintained at high-speed shearing for 3 minutes. The formed gel-like high internal phase emulsion was transferred to the corresponding mold, cured by ultraviolet irradiation for 60 seconds, and then purified and dried to obtain a cyclodextrin-based porous polymer. The microscopic morphology of the corresponding cyclodextrin-based porous polymer is shown in Figure 2 .

[0045] Example 7

[0046] A high internal phase emulsion was prepared in proportion, β-CD-MA, hexa(ethylene glycol) disulfide and Tetronic 1307 were dissolved in water as the continuous phase, and n-heptane was used as the dispersed phase. The mass fractions of the components are: 20% water, 2% β-CD-MA, 2% hexa(ethylene glycol) disulfide, 0.1% Tetronic 1307 and 76% n-heptane. A continuous phase aqueous solution was prepared, and shearing was maintained at 10,000 rpm using a high-speed shearing machine. n-heptane was gradually dripped in to form a gel-like high internal phase emulsion and then maintained at high-speed shearing for 3 minutes. The formed gel-like high internal phase emulsion was transferred to the corresponding mold, cured by ultraviolet irradiation for 60 seconds, and then purified and dried to obtain a cyclodextrin-based porous polymer. The microscopic morphology of the corresponding cyclodextrin-based porous polymer is shown in Figure 3 .

[0047] Example 8

[0048] A high internal phase emulsion was prepared in proportion, γ-CD-TA, polyethylene glycol disulfide and Tetronic 1107 were dissolved in water as the continuous phase, and cyclohexane was used as the dispersed phase. The mass fractions of the components are: 15% water, 3% γ-CD-TA, 3% polyethylene glycol disulfide, 1% Tetronic 1107 and 78% cyclohexane. A continuous phase aqueous solution was prepared, and shearing was maintained at 10,000 rpm using a high-speed shearing machine. Cyclohexane was gradually dripped in to form a gel-like high internal phase emulsion and then maintained at high-speed shearing for 3 minutes. The formed gel-like high internal phase emulsion was transferred to the corresponding mold, cured by ultraviolet irradiation for 60 seconds, and then purified and dried to obtain a cyclodextrin-based porous polymer. The microscopic morphology of the corresponding cyclodextrin-based porous polymer is shown in Figure 4 .

[0049] Example 9

[0050] A high internal phase emulsion was prepared in proportion, β-CD-TA, trimethylolpropane tris(3-mercaptopropionate) and Tetronic 1307 were dissolved in water as the continuous phase, and diesel was used as the dispersed phase. The mass fractions of the components are: 20% water, 5% β-CD-TA, 5% trimethylolpropane tris(3-mercaptopropionate), 0.1% Tetronic 1307 and 70% n-heptane. A continuous phase aqueous solution was prepared, and a high-speed shearing machine was used to maintain shearing at 10,000 rpm, and diesel was gradually dripped in to form a gel-like high internal phase emulsion and then maintained at high-speed shearing for 3 minutes. The formed gel-like high internal phase emulsion was transferred to the corresponding mold, cured by ultraviolet irradiation for 60 seconds, and then purified and dried to obtain a cyclodextrin-based porous polymer. The microscopic morphology of the corresponding cyclodextrin-based porous polymer is shown in Figure 5 .

[0051] Comparative Example 1

[0052] Prepare an aqueous solution in proportion, dissolve β-CD-TA, pentaerythritol tetra-3-mercaptopropionate and Tetronic1307 in water. The mass fractions of each component are: water is 68%, β-CD-TA is 15%, pentaerythritol tetra-3-mercaptopropionate is 15% and Pluronic P123 is 2%. Prepare a continuous phase aqueous solution, and use a high-speed shearing machine to maintain 10000rpm shearing for 3min. Transfer the formed aqueous solution to the corresponding mold, cure it by ultraviolet irradiation for 60s, and then purify and dry to obtain a cyclodextrin-based porous polymer.

[0053] VOCs static adsorption simulation of the present invention

[0054] Taking Example 6 as an example, a porous polymer with a mass of about 0.5 g was first dried at 100°C in vacuum for 2 hours and then placed in a desiccator filled with saturated organic solvent (toluene, p-xylene, dichloromethane, dichloroethylene and chloroform) vapor at 20°C for 24 hours of adsorption. The experiment was repeated 5 times, and the static saturated adsorption capacity was shown in FIG. Figure 6 .

[0055] Repeated VOCs static adsorption performance test of the present invention

[0056] Taking Example 5, Example 8, Example 9 and Comparative Example 1 as examples, a certain mass of porous polymer was taken and placed in a desiccator filled with gas (toluene). After adsorption for 24 hours, the change in the mass of the porous polymer before and after adsorption was compared to calculate its adsorption amount; the adsorption was repeated after vacuum drying at 100°C for 12 hours, and the adsorption amount was recorded; 5 regeneration-adsorption cycles were repeated, and a graph showing the change in the adsorption amount of the porous polymer with the number of cycles was plotted ( Figure 7 ).

[0057] VOCs dynamic adsorption simulation of the present invention

[0058] Taking Example 7 as an example, it is loaded into a small fixed bed with an inner diameter of 3 cm and a loading height of 5 cm; the raw gas (paraxylene) enters the adsorption bed through a flow meter; the adsorption column is heated by an oil bath circulating outside to maintain a constant temperature of the bed; the tail gas after adsorption is absorbed by the tail gas absorption device and then discharged, and the concentration of paraxylene is detected online by a gas chromatograph before discharge. The designed processing capacity of the adsorption column is 10L / min, the operating pressure is 103.25kPa, and the operating temperature is 10-150°C. The experiment was repeated 5 times, and the adsorption breakthrough curve is shown in FIG. Figure 8 .

[0059] Table 1 Formulation of cyclodextrin-based porous polymer

[0060]

[0061]

[0062] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An application of a cyclodextrin-based porous polymer, characterized in that: Used for adsorbing organic waste gas; the preparation method of the cyclodextrin-based porous polymer comprises using a water-in-oil high internal phase emulsion stabilized by a non-ionic surfactant as a template and curing the cyclodextrin-based porous polymer by ultraviolet light, wherein the emulsion has water as a continuous phase with a mass content of 10-20%, the mass content of the non-ionic surfactant is 0.1-1%, the emulsion has a non-polar / weakly polar solvent as a dispersed phase with a dispersed phase content of 70-85%, and the continuous phase contains 2-5% of the mass of the emulsion double-bond-terminated cyclodextrin and 2-5% of the mass of the emulsion water-soluble polythiol; The double-bond terminated cyclodextrin is obtained by reacting acryloyl chloride and / or methacryloyl chloride with the secondary hydroxyl group of cyclodextrin; The water-soluble polythiol includes any one of tetra(ethylene glycol) disulfide, hexa(ethylene glycol) disulfide, polyethylene glycol disulfide, 2,2′-(1,2-ethylenedioxy)bis(ethylenethiol), trimethylolpropane tris(3-mercaptopropionate), and pentaerythritol tetrakis-3-mercaptopropionate; The organic waste gas is any one of toluene, p-xylene, dichloromethane, dichloroethylene, and chloroform; The light curing conditions are to use ultraviolet light to cure for 60~120s.

2. The use of the cyclodextrin-based porous polymer according to claim 1, characterized in that: The cyclodextrin is α - Cyclodextrin, β - Cyclodextrin, γ - Any of the cyclodextrins.

3. The use of the cyclodextrin-based porous polymer according to claim 1, characterized in that: The method for obtaining double-bond terminated cyclodextrin also includes the following steps: taking 10 g of β -Cyclodextrin was dissolved in 500 mL of 0.5 mol / L NaOH aqueous solution, transferred to an ice water bath and stirred for 10 min, 10 mL of acryloyl chloride was added dropwise, and after the addition was completed, the mixture was transferred to room temperature for reaction for 1 h, and then purified and dried.

4. The use of the cyclodextrin-based porous polymer according to claim 1, characterized in that: The nonionic surfactant includes any one of Pluronic P123, Pluronic F127, Tetronic 1307, and Tetronic 1107.

5. The use of the cyclodextrin-based porous polymer according to claim 1, characterized in that: The non-polar / weakly polar solvent includes any one of toluene, xylene, paraffin, cycloparaffin, gasoline, diesel, and liquid paraffin.

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