A method for preparing modified silicon dioxide for adsorbing carbon dioxide

Abstract

The present invention relates to the technical field of silicon dioxide, and discloses a preparation method of modified silicon dioxide for adsorbing carbon dioxide, the present invention uses tetrabutylammonium bromide or benzyltriethylammonium bromide as a catalyst, catalyzes the carboxyl group of triazine thiophene modifier and the epoxy group of KH560 modified porous silicon dioxide to react, realizes the introduction of a large number of triazine rings and thiophene groups on the surface of porous silicon dioxide, nitrogen-rich triazine rings and thiophene structures as polar groups, have strong affinity and binding ability for carbon dioxide, can form dipole-dipole and other interactions with carbon dioxide, significantly improves the adsorption performance of porous silicon dioxide to carbon dioxide. Modified silicon dioxide is obtained, and it shows a very high adsorption capacity for carbon dioxide at different temperatures. The practical application of silicon dioxide in the adsorption, storage and other aspects of carbon dioxide is expanded.

Description

Technical Field

[0001] The invention relates to the technical field of silicon dioxide, in particular to a method for preparing modified silicon dioxide capable of absorbing carbon dioxide. Background Art

[0002] During industrial production and fossil fuel combustion, a large amount of carbon dioxide is released, which is the main cause of the greenhouse effect and climate warming. The adsorption, capture and storage of carbon dioxide are research hotspots. The development of high-performance carbon dioxide adsorbents is the key. At present, the materials used to adsorb carbon dioxide mainly include activated carbon, molecular sieves, microporous polymers, porous nanomaterials, etc. Among them, porous silica has the advantages of being green and pollution-free, diverse preparation methods, rich pore structure, and large specific surface area. It has broad application prospects in the adsorption and storage of carbon dioxide. There are various methods for preparing nano-silica. It can usually be prepared by precipitation method using sodium silicate and sulfuric acid; or it can be prepared by hydrolysis of tetraethyl orthosilicate.

[0003] Modifying the surface of porous silica and introducing functional groups such as active amines and thiophene can improve the affinity and adsorption capacity of silica for carbon dioxide. Patent CN104258828B discloses a carbon dioxide adsorbent and a preparation method thereof, wherein 3-aminopropyltrimethoxysilane is used to aminate the surface of a hollow silica sphere carrier, and then in situ polymerization is performed on the inner and outer surfaces of the hollow spheres to polymerize poly-L-arginine, and groups such as active amines such as guanidine are introduced, which has the advantages of fast adsorption speed and good long-term stability. The present invention aims to modify the surface of porous silica, introduce active groups such as triazine and thiophene, and improve the adsorption capacity of carbon dioxide. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a preparation method of modified silicon dioxide for adsorbing carbon dioxide.

[0005] Technical solution: A method for preparing modified silicon dioxide for adsorbing carbon dioxide: add solvent and KH560 modified porous silicon dioxide into a flask, add triazine thiophene modifier and catalyst after stirring, filter after stirring reaction, wash with ethanol, and dry to obtain modified silicon dioxide for adsorbing carbon dioxide. The reaction mechanism is:

[0006]

[0007] Furthermore, the solvent is propylene glycol methyl ether acetate, ethylene glycol monoethyl ether acetate or toluene.

[0008] Furthermore, the mass of the triazine thiophene modifier and the catalyst are 120-300% and 3.6-10.5% of the mass of the KH560 modified porous silica, respectively.

[0009] Furthermore, the catalyst is tetrabutylammonium bromide or benzyltriethylammonium bromide.

[0010] Further, the reaction is carried out at 100-120° C. for 12-24 h.

[0011] Further, the preparation method of the triazine thiophene modifier is as follows: nitrogen is introduced into a flask, 1,4-dioxane solvent, cyanuric chloride, 5-aminothiophene-2-carboxylic acid methyl ester, N,N-diisopropylethylamine in a molar ratio of 1: (3-3.6): (3.3-4.2) are added, the substitution reaction is carried out at 65-75°C for 6-10 hours, and the product is distilled under reduced pressure. The product is washed with water, and then added to 120-150mL of methanol, and 120-150mL of sodium hydroxide solution with a molar concentration of 3-3.5mol / L is added, and the hydrolysis reaction is stirred at 70-90°C for 4-8 hours, and the methanol is removed by distillation under reduced pressure, and concentrated hydrochloric acid is added to adjust the pH to 3-4, and the precipitate is precipitated, filtered, and dried to obtain the triazine thiophene modifier. The reaction formula is:

[0012]

[0013] Further, the preparation method of KH560 modified porous silica is:

[0014] Step (1), adding ethanol, water, and hexadecyltrimethylammonium bromide into a flask, stirring, adding ethyl orthosilicate and concentrated ammonia water, stirring for reaction, filtering, washing with ethanol and water, and drying the product and calcining it in a muffle furnace to obtain porous nano-silica.

[0015] Step (2), add toluene and porous nano-silica into a flask, disperse by ultrasonic, then add KH550, stir and react after heating, filter, wash with ethanol, and dry to obtain KH560 modified porous silica.

[0016] The technical effect is as follows: the present invention uses cyanuric chloride and 5-aminothiophene-2-carboxylic acid methyl ester as reactants, and obtains a triazine thiophene modifier through substitution reaction and hydrolysis reaction. Then, tetrabutylammonium bromide or benzyltriethylammonium bromide is used as a catalyst to catalyze the reaction between the carboxyl group of the triazine thiophene modifier and the epoxy group of the KH560 modified porous silica, thereby introducing a large number of triazine rings and thiophene groups on the surface of the porous silica. The nitrogen-rich triazine ring and thiophene structure serve as polar groups, and have a strong affinity and binding ability for carbon dioxide, and can form dipole-dipole interactions with carbon dioxide, thereby significantly improving the adsorption performance of porous silica for carbon dioxide. The modified silica obtained shows a high adsorption capacity for carbon dioxide at different temperatures. The practical application of silica in the adsorption and storage of carbon dioxide has been expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the adsorption isotherm of modified silica for carbon dioxide at 25°C.

[0018] Figure 2 This is the adsorption isotherm of modified silica for carbon dioxide at 50°C.

[0019] Figure 3 This is the adsorption isotherm of modified silica for carbon dioxide at 75°C. DETAILED DESCRIPTION

[0020] The average particle size of the nano silicon dioxide of the present invention is 40nm. KH560 is γ-glycidyloxypropyltrimethoxysilane.

[0021] The CAS number of 5-aminothiophene-2-carboxylic acid methyl ester is 14597-58-1. The CAS number of thiophene-2-carboxylic acid is 527-72-0.

[0022] Preparation method of KH560 modified porous silica:

[0023] (1) Add 10 mL of ethanol, 45 mL of water, and 0.8 g of hexadecyltrimethylammonium bromide into a flask, stir, then add 4.5 mL of ethyl orthosilicate and 0.22 mL of 25% concentrated ammonia water, stir and react for 8 h, filter, wash with ethanol and water, dry, place the product in a muffle furnace, and calcine at 600 ° C for 4 h to obtain porous nano-silica.

[0024] (2) Add 80 mL of toluene and 2 g of porous nano-silica into a flask, disperse by ultrasonication, then add 0.85 g of KH550, heat to 80°C, stir and react for 18 h, filter, wash with ethanol, and dry to obtain KH560-modified porous silica.

[0025] Example 1

[0026] (1) Nitrogen was introduced into a flask, and 50 mL of 1,4-dioxane solvent, 15 mmol of cyanuric chloride, 54 mmol of 5-aminothiophene-2-carboxylic acid methyl ester, and 63 mmol of N,N-diisopropylethylamine were added. The mixture was stirred at 70° C. for a substitution reaction for 6 h, and the mixture was distilled under reduced pressure. The product was washed with water and then added to 150 mL of methanol. 150 mL of a sodium hydroxide solution with a molar concentration of 3 mol / L was added, and the mixture was stirred at 80° C. for a hydrolysis reaction for 5 h. The methanol was distilled under reduced pressure, and concentrated hydrochloric acid was added to adjust the pH to 3. The precipitate was filtered and dried to obtain a triazine thiophene modifier.

[0027] (2) Add 80 mL of propylene glycol methyl ether acetate and 2 g of KH560 modified porous silica into a flask, stir, add 2.4 g of triazine thiophene modifier and 0.072 g of catalyst benzyltriethylammonium bromide, stir and react at 100° C. for 18 h, filter, wash with ethanol, and dry to obtain modified silica that adsorbs carbon dioxide.

[0028] Example 2

[0029] (1) Nitrogen was introduced into a flask, and 50 mL of 1,4-dioxane solvent, 15 mmol of cyanuric chloride, 45 mmol of 5-aminothiophene-2-carboxylic acid methyl ester, and 49.5 mmol of N,N-diisopropylethylamine were added. The mixture was stirred at 75° C. for 10 h for substitution reaction. The mixture was distilled under reduced pressure. The product was washed with water and then added to 150 mL of methanol. 150 mL of a sodium hydroxide solution with a molar concentration of 3.5 mol / L was added. The mixture was stirred at 70° C. for hydrolysis reaction for 8 h. The methanol was distilled under reduced pressure. Concentrated hydrochloric acid was added to adjust the pH to 4. The precipitate was filtered and dried to obtain a triazine thiophene modifier.

[0030] (2) Add 80 mL of toluene solvent and 2 g of KH560-modified porous silica into a flask, stir, add 3.8 g of triazine thiophene modifier and 0.12 g of catalyst tetrabutylammonium bromide, stir and react at 100° C. for 24 h, filter, wash with ethanol, and dry to obtain modified silica that adsorbs carbon dioxide.

[0031] Example 3

[0032] (1) Nitrogen was introduced into a flask, and 60 mL of 1,4-dioxane solvent, 15 mmol of cyanuric chloride, 48 mmol of 5-aminothiophene-2-carboxylic acid methyl ester, and 60 mmol of N,N-diisopropylethylamine were added. The mixture was stirred at 65° C. for 10 h for substitution reaction. The mixture was distilled under reduced pressure. The product was washed with water and then added to 120 mL of methanol. 120 mL of a sodium hydroxide solution with a molar concentration of 3.5 mol / L was added. The mixture was stirred at 90° C. for 4 h for hydrolysis reaction. The methanol was distilled under reduced pressure. Concentrated hydrochloric acid was added to adjust the pH to 4. The precipitate was filtered and dried to obtain a triazine thiophene modifier.

[0033] (2) Add 100 mL of ethylene glycol monoethyl ether acetate and 2 g of KH560-modified porous silica into a flask, stir, add 4.7 g of triazine thiophene modifier and 0.17 g of catalyst benzyltriethylammonium bromide, stir and react at 120° C. for 12 h, filter, wash with ethanol, and dry to obtain modified silica that adsorbs carbon dioxide.

[0034] Example 4

[0035] (1) 120 mL of propylene glycol methyl ether acetate and 2 g of KH560 modified porous silica were added to a flask, and after stirring, 6 g of triazine thiophene modifier (prepared in Example 1) and 0.21 g of catalyst tetrabutylammonium bromide were added. The mixture was stirred at 110° C. for 24 h, filtered, washed with ethanol, and dried to obtain modified silica that adsorbed carbon dioxide.

[0036] In Comparative Example 1, porous nano-silica is used as a carbon dioxide adsorbent.

[0037] In Comparative Example 2, KH560 modified porous silica was used as a carbon dioxide adsorbent.

[0038] Comparative Example 3

[0039] (1) Add 80 mL of propylene glycol methyl ether acetate and 2 g of KH560 modified porous silica into a flask, stir, add 2.4 g of thiophene-2-carboxylic acid and 0.072 g of catalyst benzyltriethylammonium bromide, stir and react at 100° C. for 18 h, filter, wash with ethanol, and dry to obtain modified silica that adsorbs carbon dioxide.

[0040] Comparative Example 4

[0041] (1) Add 80 mL of toluene and 2 g of KH560-modified porous silica into a flask, stir and then add 2.4 g of melamine, use the amino group of melamine to react with the epoxy group of KH560-modified porous silica to undergo a ring-opening reaction, stir and react at 100° C. for 24 h, filter, wash with ethanol, and dry to obtain modified silica that adsorbs carbon dioxide.

[0042] The adsorption isotherm of modified silica to carbon dioxide was tested using a gas adsorption instrument at 25°C, 50°C, and 75°C. Before the test, the modified silica was treated at 100°C for 2 hours in a nitrogen atmosphere.

[0043] From the instruction manual Figure 1-3 It can be seen that at an adsorption temperature of 25-70°C, the adsorption capacity of the modified silica of Examples 1-4 for carbon dioxide is significantly higher than that of Comparative Examples 1-4. When the relative pressure is 1.0 and the adsorption temperature is 25°C, the adsorption capacity of Example 4 for carbon dioxide reaches 57.8 mg / g. At an adsorption temperature of 50°C, the adsorption capacity of Example 3 for carbon dioxide reaches 158.3 mg / g. At an adsorption temperature of 75°C, the adsorption capacity of Example 3 for carbon dioxide reaches 207.3 mg / g.

Claims

1. A method for preparing modified silicon dioxide for adsorbing carbon dioxide, characterized in that: The preparation method comprises the following steps: adding a solvent and KH560 modified porous silica into a flask, adding a triazine thiophene modifier and a catalyst after stirring, filtering after stirring for reaction, washing with ethanol, and drying to obtain modified silica that adsorbs carbon dioxide; The structural formula of the triazine thiophene modifier is: ; The catalyst is tetrabutylammonium bromide or benzyltriethylammonium bromide.

2. The method for preparing modified silicon dioxide for adsorbing carbon dioxide according to claim 1, characterized in that: The solvent is propylene glycol methyl ether acetate, ethylene glycol monoethyl ether acetate or toluene.

3. The method for preparing modified silicon dioxide for adsorbing carbon dioxide according to claim 1, characterized in that: The mass of the triazine thiophene modifier and the catalyst are respectively 120-300% and 3.6-10.5% of the mass of the KH560 modified porous silica.

4. The method for preparing modified silicon dioxide for adsorbing carbon dioxide according to claim 1, characterized in that: The reaction is carried out at 100-120°C for 12-24h.

5. The method for preparing modified silicon dioxide for adsorbing carbon dioxide according to claim 3, characterized in that: The preparation method of the triazine thiophene modifier comprises the following steps: introducing nitrogen into a flask, adding 1,4-dioxane solvent, cyanuric chloride, 5-aminothiophene-2-carboxylic acid methyl ester, and N,N-diisopropylethylamine, stirring to carry out a substitution reaction, performing reduced pressure distillation, washing the product with water, then adding the product to 120-150 mL of methanol, and adding 120-150 mL of a sodium hydroxide solution with a molar concentration of 3-3.5 mol / L to carry out a hydrolysis reaction, removing the methanol by reduced pressure distillation, adding concentrated hydrochloric acid to adjust the pH to 3-4, precipitating a precipitate, filtering, and drying to obtain the triazine thiophene modifier.

6. The method for preparing modified silicon dioxide for adsorbing carbon dioxide according to claim 5, characterized in that: The molar ratio of cyanuric chloride, 5-aminothiophene-2-carboxylic acid methyl ester and N,N-diisopropylethylamine is 1:(3-3.6):(3.3-4.2).

7. The method for preparing modified silicon dioxide for adsorbing carbon dioxide according to claim 5, characterized in that: The substitution reaction is carried out at 65-75°C for 6-10 hours; the hydrolysis reaction is carried out at 70-90°C for 4-8 hours.

8. The method for preparing modified silicon dioxide for adsorbing carbon dioxide according to claim 3, characterized in that: The preparation method of the KH560 modified porous silica is: Step (1), adding ethanol, water, and hexadecyltrimethylammonium bromide into a flask, stirring, adding tetraethyl orthosilicate and concentrated ammonia water, stirring for reaction, filtering, washing, and drying, and placing the product in a muffle furnace for calcination to obtain porous nano-silicon dioxide; Step (2), add toluene and porous nano-silica into a flask, disperse by ultrasonic, then add KH560, stir and react after heating, filter, wash and dry to obtain KH560 modified porous silica.

Images