CN109232781B

CN109232781B - Preparation method of nitrogen-containing porous organic polymer

Info

Publication number: CN109232781B
Application number: CN201811103897.5A
Authority: CN
Inventors: 刘福建; 米金星; 潘树法; 曹彦宁; 江莉龙
Original assignee: Fuzhou University
Current assignee: Fuzhou University
Priority date: 2018-09-21
Filing date: 2018-09-21
Publication date: 2021-03-30
Anticipated expiration: 2038-09-21
Also published as: CN109232781A

Abstract

The invention relates to preparation and application of an environmental catalyst, in particular to a preparation method of a nitrogen-containing porous organic polymer and application thereof in CO₂The application of adsorption and conversion. In the invention, under the catalysis of Lewis acid, a nitrogen-containing monomer and 1, 4-p-dichlorobenzyl or vinyl benzyl chloride are selected to synthesize the nitrogen-containing porous organic polymer through alkylation induced crosslinking. The obtained nitrogen-containing polymer has stable nitrogen-containing active sites, a large proportion of mesoporous macropores, unique carbon dioxide enrichment characteristic and high CO_2/N₂Selectively, the N-POPs adsorbent is subjected to CO in the industrial waste gas₂The high-selectivity adsorption has good application prospect.

Description

Preparation method of nitrogen-containing porous organic polymer

Technical Field

The invention relates to preparation and application of an environmental catalyst, in particular to a preparation method of a nitrogen-containing porous organic polymer and application thereof in CO₂The application of adsorption and conversion.

Background

After entering the industrial era from the world, the increasing concentration of carbon dioxide in the atmosphere and the resulting climate and environmental problems such as global warming and ocean acidification are receiving attention. The emission of acid gases such as carbon dioxide mainly comes from industrial activities, which mainly depend on the use of fossil fuels, for example, a great amount of carbon dioxide is removed from the tail gas of water gas shift reaction in coal gasification industry, so it is very important to eliminate carbon dioxide from industrial tail gas to alleviate various environmental problems. At present, the amine solution is due to the CO₂Has been widely used for CO at low cost and reversible chemical reaction₂Is selected fromAnd (4) selectively capturing. But has the problems of great solvent volatilization loss, serious corrosion of equipment and the like. Therefore, an efficient and pollution-free adsorption medium was developed to replace amine solutions for CO₂Selective capture is important.

In recent years, scientists have conducted extensive research work on the selective capture of CO from industrial flue gases₂The porous material is used as an absorbent, and the materials have the advantages of no volatility, no corrosion, easy regeneration and the like. Porous Organic Polymers (POPs), one of the most advanced materials, attract extensive attention of researchers due to their diversification in construction and synthesis routes, thereby providing an idea for structural and functional design. Furthermore, POPs covalently bound to them generally have high physical and chemical stability. Thus, POPs are in CO₂Has great application potential in capture. However, POPs are on CO₂The capture performance of (a) depends not only on its structural properties but also on the active sites it has. Specific functional groups, particularly nitrogen sites, are introduced into the POPs framework, so that the CO content of the POPs can be greatly improved₂Capture efficiency due to CO₂Unique Lewis acid-base interaction with nitrogen sites to achieve higher CO₂/N₂And (4) selectivity.

Much research is currently done on CO₂The adsorbent mainly comprises active carbon, alumina, molecular sieve, silicon dioxide and the like. Patent No. CN107661748A discloses an organic amine functionalized macroporous silica CO₂The adsorbent is organic amine functional macroporous silicon dioxide CO formed by taking organic amine as an active component₂CO of adsorbent₂The adsorption capacity is greatly improved, the dynamic adsorption capacity reaches 208mg/g, and the regeneration cycle stability is good. But the organic amine in the functionalization process can affect human bodies and the environment, thereby influencing the further application and development of the adsorbent. Patent No. CN108079956A discloses a novel multi-stage micro/mesoporous solid amine adsorbent, which is prepared by mixing HZSM-5 and MCM-41 according to different mass ratios to obtain a composite molecular sieve carrier, and taking Tetraethylenepentamine (TEPA) as a modifier, wherein when the mass ratio of the HZSM-5 to the MCM-41 is 1: 1, the TEPA loading amount is 30%, and the adsorption temperature is highWhen the temperature is 55 ℃ and the air inlet flow is 30mL/min, the equilibrium adsorption amount is up to 3.57mmol/g, and after 10 times of adsorption and desorption cycles, the adsorption amount is reduced by 8.1 percent. Although the above adsorbent also has a good adsorption effect, it requires activation with an organic amine to obtain its active site, resulting in a lack of stability of its adsorption performance. Therefore, under the catalysis of Lewis acid, the nitrogen-containing monomer and 1, 4-p-dichlorobenzyl are selected to synthesize the nitrogen-containing porous organic polymer through alkylation induced crosslinking. The obtained nitrogen-containing polymer has stable nitrogen-containing active sites, a large proportion of mesoporous macropores, unique carbon dioxide enrichment characteristic and high CO_2/N₂Selectively, the N-POPs adsorbent is subjected to CO in the industrial waste gas₂The high-selectivity adsorption has good application prospect.

Disclosure of Invention

The invention aims to overcome the problems of insufficient adsorption capacity and poor stability of the existing adsorbent, and provides a preparation method of a high-nitrogen-content mesoporous macroporous organic polymer.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method of a nitrogen-containing porous polymer material comprises the following steps:

a. dissolving a certain mass of 1, 4-p-dichlorobenzyl or vinylbenzyl chloride in 1, 2-dichloroethane, wherein when the vinylbenzyl chloride is used as a raw material, an initiator azobisisobutyronitrile AIBN (azodiisobutyronitrile) is required to be added; then vigorously stirring for 30-120s at 0 deg.C, and adding a certain volume of Lewis acid catalyst into the mixture;

b. subsequently, adding a certain mass of nitrogen-containing monomer to the mixture;

c. in N₂Heat treating for a period of time in an atmosphere;

d. the solid formed is filtered off and washed thoroughly with hot anhydrous ethanol to remove residual reactants and lewis acid catalyst;

e. immersing the crude product in isopropylamine, treating at room temperature for 6-12h for activation, and then drying in vacuum;

preferably, the mass of the 1, 4-dichlorobenzyl in the step a is 0.5-2g, and the volume of the 1, 2-dichloroethane is 15-30 ml; the volume of vinylbenzyl chloride is 0.5-1.5 ml, and the mass of the initiator is 0.05g

Preferably, the volume of the Lewis acid catalyst in the step a is 2-5ml, and the type of the Lewis acid catalyst is SnCl₄Or TiCl_4。

Preferably, in the step b, the mass of the nitrogen-containing monomer is 0.5-1.5g, and the nitrogen-containing monomer is one of p-phenylenediamine, 4,4' -bipyridine, hexamethylenetetramine or 4-vinylpyridine.

Preferably, the heat treatment temperature of the step c is 60-90 ℃, and the heat treatment time is 2-6 h.

Preferably, in the step d, the number of times of washing with ethanol is 6-12.

Preferably, in the step e, the temperature of vacuum drying is 60-120 ℃ and the time is 6-24 h.

A nitrogen-containing porous organic polymer is prepared by the method, and the porous nitrogen-containing polymer is used for selectively adsorbing carbon dioxide with high efficiency.

Preferably, the porous nitrogen-containing polymer is used for CO₂In N₂Selective adsorption of (1).

Preferably, the CO is₂The adsorption temperatures of (A) were 0 ℃ and 25 ℃.

Preferably, the sorbent loading is 0.1 g; pretreating under vacuum condition at 160 deg.C for 12 hr before adsorption, and placing in Dewar flask at 0 deg.C and 25 deg.C for CO₂And N₂Adsorption of (3).

The invention has the following advantages and beneficial effects:

1. the nitrogen-containing porous polymer has strong adjustability, high material thermal stability, simple and green preparation process, easy realization of industrial production and wide application prospect.

2. The surface area of the nitrogen-containing porous organic polymer is as high as 700-1200 m²Per g, has good activity and selectivity in carbon dioxide adsorptionSex;

3. the nitrogen-containing porous organic polymer material prepared by the invention does not need to load or add other active components, and nitrogen elements contained in the material can improve the surface alkalinity of the material, increase the number of carbon edge positions and defect positions and strengthen the adsorption of carbon dioxide.

Drawings

FIG. 1 shows examples 1 to 4 of the present invention in which CO is present at 0 ℃₂And N₂The adsorption curve of (c);

FIG. 2 shows examples 1 to 4 of the present invention in which CO is present at 25 ℃₂And N₂The adsorption curve of (c);

FIG. 3 is CO of example 2 of the present invention₂Performing a cyclic adsorption experiment; (adsorption conditions: pure CO)₂At 25 ℃, 50mL/min for 180 min; the desorption conditions are as follows: pure N₂, 75 ℃，150 mL/min, 120 min）；

FIG. 4 shows N at liquid nitrogen temperature for nitrogen-containing porous organic polymers in examples 1 to 4 of the present invention₂A physical adsorption-desorption curve;

FIG. 5 is a diagram showing the pore size distribution of porous organic nitrogen-containing polymers in examples 1 to 4 of the present invention;

FIG. 6 is an SEM image of porous nitrogen-containing organic polymers of examples 1 to 4 of the present invention; the a figure is N-POP-p-phenylenediamine, the b figure is N-POP-4,4' -bipyridyl, the c and d figures are N-POP-hexamethylene tetramine, and the e and f figures are N-POP-pyridine.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in detail below with reference to examples and accompanying drawings, which are provided for further illustration of the present invention and are not intended to limit the present invention.

Example 1

N-POP-p-phenylenediamine: 0.5g of 1, 4-p-dichlorobenzyl was dissolved in 20ml of 1, 2-dichloroethane, which was then stirred vigorously at 0 ℃ for 60s, and 2ml of SnCl was added to the mixture₄.1g of p-phenylenediamine monomer is then added to the mixture in N₂The reaction was carried out at 70 ℃ for 3h under an atmosphere. The solid formed after suction filtration was then washed 8 times with hot anhydrous ethanol to remove residual reactants and lewis acidA catalyst. Finally, the crude product is immersed in isopropylamine, treated for 12h at room temperature for activation, dried in vacuum at 80 ℃ for 18h to obtain a nitrogen-containing porous organic polymer, namely N-POP-p-phenylenediamine, and the specific surface area of the sample is 1116m²The content of nitrogen element is 3.5 percent per gram.

Example 2

N-POP-4,4' -bipyridine: 2.0g of 1, 4-dichlorobenzyl are dissolved in 25ml of 1, 2-dichloroethane, stirred vigorously at 0 ℃ for 30s and 4ml of TiCl are added to the mixture₄. 1.5g N-POP-4,4' -bipyridine monomer was then added to the mixture in N₂The reaction is carried out for 5h at 90 ℃ under the atmosphere. The solid formed after suction filtration was then washed 9 times with hot anhydrous ethanol to remove residual reactants and lewis acid catalyst. Finally, immersing the crude product in isopropylamine, treating for 9h at room temperature for activation, and drying in vacuum at 100 ℃ for 12h to obtain a nitrogen-containing porous organic polymer which is marked as N-POP-4,4' -bipyridyl. The specific surface area of this sample was 1047m²The content of nitrogen element is 5.1 percent per gram.

Example 3

N-POP-hexamethylenetetramine: 1.0 g of 1, 4-p-dichlorobenzyl was dissolved in 30ml of 1, 2-dichloroethane, which was then stirred vigorously at 0 ℃ for 90s, and 3ml of SnCl was added to the mixture₄. 0.85 g N-POP-hexamethylenetetramine monomer was then added to the mixture in N₂The reaction was carried out at 75 ℃ for 3h under an atmosphere. The solid formed after suction filtration was then washed 6 times with hot anhydrous ethanol to remove residual reactants and lewis acid catalyst. And finally, immersing the crude product in isopropylamine, treating for 6h at room temperature for activation, and drying in vacuum at 70 ℃ for 24h to obtain a nitrogen-containing porous organic polymer, namely N-POP-hexamethylenetetramine. The specific surface area of this sample was 1177m²The content of nitrogen element is 3.3 percent per gram.

Example 4

N-POP-pyridine: 1mL of vinylbenzyl chloride and 0.78mL of 4-vinylpyridine were dispersed in 30mL of 1, 2-dichloroethane, followed by the addition of 0.05g of azobisisobutyronitrile AIBN initiator. The copolymerization is carried out by heating the mixture at 80 ℃ for 24 hours to give a viscous copolymer with linear characteristics. To obtain a hypercrosslinked network, it was then stirred vigorously at 0 ℃ for 90s and 4mL of TiCl were added₄Is introduced into the mixture and is in N₂Under the protection of atmosphere, the reaction is carried out at 90 ℃ for 6 hours. The resulting solid was filtered off and washed with hot anhydrous ethanol and hydrochloric acid to remove residual reactants and lewis acid catalyst. The crude product was then immersed in isopropylamine, treated at room temperature for 12h for activation, and then dried under vacuum at 80 ℃ for an additional 12 h. The synthesized sample is denoted as N-POP-pyridine. The specific surface area of this sample was 969 m²The content of nitrogen element is 3.0 percent per gram.

Comparative example 1

POP without nitrogen doping: 2.0g of 1, 4-dichlorobenzyl are dissolved in 15mL of 1, 2-dichloroethane, stirred vigorously at 0 ℃ and 5mL of TiCl are added to the mixture₄. Then, in N₂The reaction was carried out at 75 ℃ for 24 hours under an atmosphere. The solid formed by suction filtration was washed with hot absolute ethanol to remove residual reactants and lewis acid catalyst and dried under vacuum at 80 ℃ for 24 hours. The sample was designated as POP. The specific surface area of this sample was 592 m²/g。

Comparative example 2

PDVB-VP porous organic polymer: 0.065 g of azobisisobutyronitrile was weighed out and dissolved in 25mL of ethyl acetate, and then 2mL of Divinylbenzene (DVB) and 1mL of 4-Vinylpyridine (VP) were added successively, and after stirring at room temperature for 3 hours, all the mixtures were put in a pot at 120 ℃ and treated for 24 hours. After completion of the reaction, the solvent was evaporated at room temperature for 24h and the resulting solid was dried under vacuum at 80 ℃ for 24h to give a pale pink powder. The synthetic porous organic polymer is represented by PDVB-VP-0.5, where 0.5 is the volume ratio VP/DVB. The specific surface area of the polymer was 479m²In terms of a/g, the nitrogen content was 4.18%.

CO₂Adsorption Performance and selectivity test

Prior to testing, the samples were treated at 160 deg.C (0.1 Pa) for 12 h. Then transferred to a Mac 3020 physical adsorption apparatus and tested for CO at 0 and 25 deg.C, respectively₂And N₂Adsorption isotherm of (1). And CO₂The cyclic adsorption experiment of (A) was carried out in a Mettler TGA/SDTA 851eAbout 5mg (accurately weighed) of the sample was placed in a ceramic crucible and transferred to a TGA balance. When the sample was stable at 25 ℃, the gas was purged with nitrogen (150 ml/min) for 30 minutes and then switched to pure CO₂Gas (50 ml/min) and hold for 2 h. Subsequently, CO is introduced₂Gas switching to N₂And the temperature was raised to 75 ℃. CO 2₂The cycle experiment of adsorption was tested 10 times after the temperature and airflow were stable.

TABLE 1 samples of N-POPs CO at different temperatures and pressures₂Adsorption amount and CO₂/N₂IAST selectivity

^[a]According to the mixture gas CO₂/N₂(0.15/0.85) was calculated from the IAST model at 1 bar.

FIGS. 1-2 show the measurement of CO at 0 ℃ and 25 ℃ for examples and comparative examples₂And N₂Adsorption isotherms. The CO at different temperatures and pressures is summarized in Table 1₂Adsorption capacity and selectivity thereof. As can be seen from the graph, N-POP-hexamethylene tetramine has higher CO₂Adsorption capacities (5.67 and 3.93mmol/g at 1 bar at 0 ℃ and 25 ℃ respectively) for CO corresponding to POP₂CO with adsorption capacities of 1.05 and 0.96 mmol/g, PDVB-VP-0.5₂The adsorption capacities are 1.84 and 1.48 mmol/g, which are both significantly lower than the N-POP-xCO of₂And (4) adsorption performance. The addition of the nitrogen-containing monomer is illustrated, more nitrogen active sites are provided, and therefore, the CO of the material is greatly improved₂And (4) adsorption performance. CO removal₂Adsorption of CO in addition to its capacity₂/N₂The selectivity is also a very important parameter, and Table 1 gives the examples and comparative examples for CO₂And N₂(0.15/0.85 v/v) CO of the gas mixture₂/N₂Adsorption selectivity, calculated according to ideal solution adsorption theory (IAST). The selectivity of the examples is obviously higher than that of the comparative examples, and particularly, the selectivity of the N-POP-4,4' -bipyridyl at 0 ℃ and 25 ℃ is respectively as high as 73.9 and 75.6. Illustrating the nitrogen produced in this exampleThe porous polymer has good CO₂Selective adsorption performance. The cycling experiment of N-POP-hexamethylene tetramine in figure 2 also proves that the material has good stability.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. The preparation method of the nitrogen-containing porous organic polymer is characterized in that the nitrogen-containing porous organic polymer is synthesized by alkylating, inducing and crosslinking a nitrogen-containing monomer and vinylbenzyl chloride under the catalysis of Lewis acid; the nitrogen-containing monomer is p-phenylenediamine or hexamethylenetetramine; the method comprises the following steps of synthesizing a nitrogen-containing porous organic polymer by alkylation induced crosslinking of a nitrogen-containing monomer and vinylbenzyl chloride under the catalysis of Lewis acid: firstly, dissolving vinylbenzyl chloride in 1, 2-dichloroethane, adding Azobisisobutyronitrile (AIBN) initiator, then violently stirring for 30-120s at 0 ℃, and adding Lewis acid catalyst into the mixture; subsequently adding a nitrogen-containing monomer to the mixture in N₂Heat treating for a period of time at an atmosphere and elevated temperature; the heat treatment temperature is 60-90 ℃, and the heat treatment time is 2-6 h; filtering to form a solid, washing the solid for 3-5 times by using hot absolute ethyl alcohol to remove residual reactants and Lewis acid catalyst; and finally, immersing the crude product into isopropylamine, treating at room temperature for 6-12h for activation, and drying in vacuum to obtain a nitrogen-containing porous organic polymer, namely N-POP-x, wherein x is a nitrogen-containing monomer.

2. The method according to claim 1, wherein the volume of the vinylbenzyl chloride is 0.5-1.5 ml, the mass of the initiator is 0.05g, the mass of the nitrogen-containing monomer is 0.5-1.5g, and the volume of the 1, 2-dichloroethane is 15-30 ml.

3. The method according to claim 1, wherein the Lewis acid catalyst is SnCl₄Or TiCl₄(ii) a The addition amount is 2-5 ml.

4. The method according to claim 1, wherein the temperature and time for vacuum drying are 60-120 ℃ and 6-24 hours, respectively.