CN111943199A - A method for preparing sulfur-nitrogen co-doped porous carbon material with potassium hydroquinone sulfate as activator - Google Patents

Abstract

The invention provides a method for preparing a sulfur-nitrogen co-doped porous carbon material by using potassium hydroquinone sulfate as an activator. The thermal carbonization product of potassium hydroquinone sulfate and glucosamine hydrochloride salt or chitosan is ground and then carbonized at high temperature. The sulfur element in potassium hydroquinone sulfate and the nitrogen element in the carbon source material are used to realize sulfur Co-doping of carbon materials with nitrogen; at the same time, the chemical activation of potassium element in the reaction mixture is used to form porous structures in carbon materials through a one-step high temperature treatment. The preparation method proposed in the present invention avoids the use of strong corrosive activators such as potassium hydroxide, and only needs one-step high-temperature treatment to complete the activation and sulfur/nitrogen doping processes, which is more efficient than the traditional carbonization-activation two-step preparation process. Simultaneously, the prepared sulfur-nitrogen co-doped carbon material has high specific surface area and high pore capacity, and shows good adsorption characteristics for carbon dioxide.

Description

A method for preparing sulfur-nitrogen co-doped porous carbon material with potassium hydroquinone sulfate as activator

technical field

The invention belongs to the technical field of preparation and application of porous carbon materials, in particular to a method for preparing a sulfur-nitrogen co-doped porous carbon material by using potassium hydroquinone sulfate as an activator.

Background technique

Fossil energy sources such as coal and oil are the main forms of energy today, and their consumption forms a large amount of carbon dioxide, which leads to a continuous increase in the concentration of carbon dioxide in the atmosphere. Although a lot of manpower and material resources have been invested in the development of new clean and environmentally friendly energy at home and abroad, the dominance of fossil energy is still difficult to change in the short term. In this context, the use of carbon capture and storage technologies to control the continued rise in carbon dioxide concentrations is of great significance. The use of organic amine solution to absorb carbon dioxide is the most mature carbon capture method at present, but the regeneration process of amine solution requires a lot of energy, and there are safety hazards such as corrosiveness and toxicity (Environ.Sci.Technol.47 (Environ.Sci.Technol.47( 2013) 11960-11975). The adsorption and capture of carbon dioxide using porous carbon materials is another very promising method, because porous carbon materials have abundant porous structure types, good thermal and chemical stability, and low production cost, which is very suitable for carbon dioxide. Adsorption studies of (Carbon 148 (2019) 164-186).

Doping carbon materials can endow them with more functionality, and the most studied doping elements are mainly sulfur, nitrogen, phosphorus, boron, etc. (Energy Environ. Sci. 6 (2013) 2839-2855). The carbon dioxide adsorption performance of sulfur and nitrogen doped carbon materials has also been a research hotspot. Existing research results show that there is a strong interaction between doped sulfur in the oxidation state such as thiophene and carbon dioxide molecules, which can effectively improve the carbon dioxide adsorption performance of porous carbon materials (Carbon 66 (2014) 320-326 ); and nitrogen doping can form basic adsorption sites in carbon materials, which can selectively adsorb carbon dioxide and enhance the interaction with carbon dioxide molecules (J.Mater.Chem.A 4(2016)17299-17307). Sulfur/nitrogen-doped porous carbon materials are generally prepared by the following two methods: one is to use sulfur/nitrogen-containing organic compounds as raw materials for direct carbonization or activation treatment; the other is to use sulfur/nitrogen-containing compounds such as sulfur dioxide/ammonia and carbon at high temperature Doping is carried out under the reaction. The second preparation method has better versatility, but the first method has simpler requirements for preparation process and equipment.

The most common method for forming porous structures in carbon materials is activation. Generally, the raw materials are carbonized, and then activated with phosphoric acid, potassium hydroxide, etc. In addition to the need to go through two heating-cooling processes in this preparation method, the corrosiveness of the activator is also a problem that must be considered. Selecting suitable materials as preparation raw materials, simplifying the preparation process and saving production costs are still the research focus of the preparation of porous carbon materials.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a method for preparing a sulfur-nitrogen co-doped porous carbon material with potassium hydroquinone sulfate as an activator, and one-step high-temperature treatment completes the doping and activation process of sulfur and nitrogen elements on carbon. At the same time, the prepared carbon material has a high specific surface area and exhibits good carbon dioxide adsorption performance.

In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is;

A method for preparing a sulfur-nitrogen co-doped porous carbon material with potassium hydroquinone sulfate as an activator, comprising the following steps:

(1) Glucosamine hydrochloride is dissolved in 50mL water, the solution that forms is added 100mL hydrothermal reactor, and at 200 ℃, carry out hydrothermal carbonization;

(2) repeatedly washing the product obtained in step (1) with deionized water, and drying at 100°C;

(3) take chitosan or the dried product of step (2), grind and mix it with potassium hydroquinone sulfate, the formed mixture is placed in a tube furnace, protected by an inert gas, and the tube furnace is heated to a high temperature for carrying out Treatment, and then naturally cooled to room temperature under the protection of an inert atmosphere;

(4) The product prepared in step (3) is added to hydrochloric acid for treatment, then repeatedly washed with deionized water, and dried to obtain a sulfur-nitrogen co-doped porous carbon material.

Preferably, in step (1), the amount of glucosamine hydrochloride added is 5.0g, and the hydrothermal carbonization treatment time is 6 hours;

Preferably, in step (3), the mass ratio of the added hydroquinone potassium sulfate and chitosan or glucosamine hydrochloride thermal carbonization product is 2-4:1, the nitrogen flow rate is 60mL/min, and the high temperature treatment temperature is 700-900℃, the treatment time is 1-2h, and the heating rate is 5℃/min

Preferably, in step (4), the mass percentage concentration of hydrochloric acid used is 10%, the drying temperature is 100° C., and the drying time is 4 hours.

Compared with the prior art, in the present invention, the thermally carbonized product of hydroquinone potassium sulfate and glucosamine hydrochloride or chitosan is ground and carbonized at a high temperature, and the sulfur element and carbon in the hydroquinone potassium sulfate are utilized. The nitrogen element in the source material realizes the co-doping of sulfur and nitrogen on the carbon material; at the same time, the chemical activation of potassium element in the reaction mixture is used to form a porous structure in the carbon material after a one-step high temperature treatment. The preparation method proposed in the present invention avoids the use of strong corrosive activators such as potassium hydroxide, and only needs one-step high-temperature treatment to complete the activation and sulfur/nitrogen doping processes, which is more efficient than the traditional carbonization-activation two-step preparation process. Simultaneously, the prepared sulfur-nitrogen co-doped carbon material has high specific surface area and high pore capacity, and shows good adsorption characteristics for carbon dioxide. The advantages of the present invention are:

(1) Potassium hydroquinone sulfate is used as a source of sulfur element, and at the same time as an activator, the process of doping and activation is completed at high temperature at the same time;

(2) using nitrogen elements contained in chitosan and glucosamine hydrochloride to realize nitrogen doping of carbon materials to prepare sulfur-nitrogen co-doped carbon materials;

(3) The process of doping, carbonization and activation is completed in one step, which simplifies the traditional two-step preparation process of carbonization and reactivation.

Description of drawings

Fig. 1 is the scanning electron microscope photograph of the sulfur-nitrogen co-doped porous carbon material of the specific embodiment 1 of the present invention;

Fig. ₂ is the N adsorption-desorption isotherm of the sulfur-nitrogen co-doped porous carbon material at 77K according to the specific embodiment of the present invention;

Fig. 3 is the X-ray photoelectron spectrum N1s spectrum of the sulfur-nitrogen co-doped porous carbon material according to the specific embodiment 2 of the present invention;

Fig. 4 is the X-ray photoelectron spectrum S2p spectrum of the sulfur-nitrogen co-doped porous carbon material according to the specific embodiment 2 of the present invention;

₅ is the N adsorption and desorption isotherm of the sulfur-nitrogen co-doped porous carbon material at 77K according to the specific embodiment of the present invention;

Fig. 6 is the _CO adsorption isotherm of the sulfur-nitrogen co-doped porous carbon material at 298K according to the specific embodiment 3 of the present invention;

Fig. ₇ is the N adsorption isotherm of the sulfur-nitrogen co-doped porous carbon material at 298K according to the specific embodiment 3 of the present invention;

8 is a schematic diagram showing the results of CO ₂ /N ₂ adsorption selectivity of the sulfur-nitrogen co-doped porous carbon material according to the specific embodiment 3 of the present invention;

FIG. 9 is a schematic diagram of the preparation process of the sulfur-nitrogen co-doped porous carbon material of the present invention.

Detailed ways

A method for preparing sulfur-nitrogen co-doped porous carbon materials by using potassium hydroquinone sulfate as an activator proposed by the present invention will be described in more detail below in conjunction with the schematic diagram of the preparation process, which shows the preferred embodiments of the present invention, and It is not intended to limit the present invention.

A method for preparing a sulfur-nitrogen co-doped porous carbon material with potassium hydroquinone sulfate as an activator, as shown in Figure 9, includes the following steps:

(1) Dissolve 5.0 g of glucosamine hydrochloride in 50 mL of water, add the resulting solution to a 100 mL hydrothermal reactor, and carry out a hydrothermal carbonization reaction at 200° C. for 6 h;

(2) repeatedly washing the product obtained in step (1) with deionized water, and drying at 100°C;

(3) Take chitosan or the product after drying in step (2), grind and mix it with potassium hydroquinone sulfate, and place the resulting mixture in a tube furnace, pass nitrogen for protection (60 mL/min), and the tube type The furnace is heated to 700-900 °C and kept at a constant temperature for 1-2 hours, and then naturally cooled to room temperature under the protection of an inert atmosphere;

(4) The product prepared in step (3) was added to 10% hydrochloric acid for treatment, then repeatedly washed with deionized water, and dried at 100° C. for 4 hours to obtain a sulfur-nitrogen co-doped porous carbon material.

The carbon dioxide adsorption characteristic test of the obtained sulfur-nitrogen co-doped porous carbon material is carried out according to the following steps:

(1) Add about 100 mg of carbon material to the test sample chamber, heat to 250°C for vacuum degassing for 3 hours;

(2) Set the ambient temperature of the test sample chamber, gradually increase the carbon dioxide pressure, and test the complete carbon dioxide adsorption isotherm;

(3) After the carbon dioxide adsorption test is completed, the sample chamber is heated to 100 °C for 1 hour of vacuum treatment to complete the carbon dioxide desorption;

(4) The nitrogen adsorption isotherm of the carbon material was tested using a similar method, and the adsorption selectivity was calculated.

Example 1

The preparation steps of the sulfur-nitrogen co-doped porous carbon material in this embodiment are as follows: 5.0 g of glucosamine hydrochloride is dissolved in 50 mL of water, the transparent solution formed is added to a 100 mL stainless steel hydrothermal reactor, and the hydrothermal carbonization treatment is carried out at 200° C. for 6 hours. . The resulting product was filtered, washed repeatedly with deionized water, and finally dried at 100 °C for 4 h. 1.0 g of the dried hydrothermal carbonization product was taken and uniformly ground with 3.0 g of potassium hydroquinone sulfate. The resulting mixture was placed in a tube furnace and protected by nitrogen (60 mL/min). The furnace temperature of the tube furnace was raised from room temperature to 900°C at a rate of 5°C/min, and kept at a constant temperature for 2 hours. After natural cooling, the product was treated with 10% hydrochloric acid, washed repeatedly with deionized water, and dried at 100° C. for 4 hours to obtain the final product.

The scanning electron microscope photo of the sulfur-nitrogen co-doped porous carbon material prepared from glucosamine hydrochloride and potassium hydroquinone sulfate according to this example is shown in Figure 1. The carbon material exhibits irregular shapes and sizes, and the surface Large holes of different sizes are formed. The nitrogen adsorption-desorption isotherm of the carbon material at 77 K is shown in Fig. 2, and its specific surface area is 1303 m ² /g, which proves that the use of potassium hydroquinone sulfate can form a rich porous structure in the carbon material, namely can act as an activator.

Example 2

The preparation steps of the sulfur-nitrogen co-doped porous carbon material of the present embodiment are as follows: 1.0 g of chitosan and 4.0 g of potassium hydroquinone sulfate are ground, and the ground mixture is placed in a tube furnace, under nitrogen protection ( 60mL/min) furnace temperature was increased from room temperature to 800°C at a rate of 5°C/min, and was heated at a constant temperature of 800°C for 2 hours. After natural cooling, the product was treated with 10% hydrochloric acid, washed repeatedly with deionized water, and dried at 100° C. for 4 hours to obtain the final product.

The X-ray photoelectron spectrum N1s spectrum of the sulfur-nitrogen co-doped porous carbon material prepared from chitosan and potassium hydroquinone sulfate according to this example is shown in Figure 3, and its nitrogen content is 4.49wt%, which proves that it can be used The nitrogen element contained in the raw material is doped with nitrogen; the X-ray photoelectron spectrum S2p spectrum of the carbon material is shown in Figure 4, and its sulfur content is 6.70 wt%, which proves that it is possible to use the nitrogen contained in potassium hydroquinone sulfate. The carbon material is sulfur-doped with elemental sulfur. The nitrogen adsorption and desorption isotherm of the carbon material at 77K is shown in Figure 5, its specific surface area is 1186m ² /g, and its pore volume is 0.889cm ³ /g, indicating that potassium hydroquinone sulfate can be used as the activator to prepare high Specific surface area sulfur-nitrogen co-doped porous carbon materials.

Example 3

The preparation steps of the sulfur-nitrogen co-doped porous carbon material of the present embodiment are as follows: 1.0 g of chitosan and 3.0 g of potassium hydroquinone sulfate are ground, and the ground mixture is placed in a tube furnace, under nitrogen protection ( 60mL/min) furnace temperature was increased from room temperature to 900°C at a rate of 5°C/min, and was heated at a constant temperature of 900°C for 2 hours. After natural cooling, the product was treated with 10% hydrochloric acid, washed repeatedly with deionized water, and dried at 100° C. for 4 hours to obtain the final product.

The steps for testing the carbon dioxide adsorption performance of the sulfur-nitrogen co-doped porous carbon material prepared in this example are as follows: add 100 mg of carbon material into the test sample chamber, and heat at 250°C for 3 hours in a vacuum to remove impurities such as moisture adsorbed on the surface. Place the test sample chamber in a 25°C constant temperature water bath, gradually increase the equilibrium adsorption pressure of carbon dioxide, obtain a complete adsorption isotherm, and calculate the equilibrium adsorption amount of carbon dioxide. Then, the test gas used was changed to nitrogen, the nitrogen adsorption isotherm of the prepared nitrogen-doped porous carbon material was tested, and the nitrogen adsorption amount and adsorption selectivity were calculated.

The carbon dioxide adsorption isotherm at 298K of the sulfur-nitrogen co-doped porous carbon material prepared from chitosan and potassium hydroquinone sulfate according to this example is shown in Figure 6, and the carbon dioxide adsorption amount under one atmosphere is 1.3 mmol /g, the carbon dioxide adsorption amount is 11.5mmol/g under 20bar pressure. The nitrogen adsorption isotherm of the carbon material at 298K is shown in Figure 7, and the nitrogen adsorption amount under one atmospheric pressure is 0.2 mmol/g. Figure 8 shows the adsorption selectivity values calculated from the carbon dioxide and nitrogen adsorption test results, and the adsorption selectivity at 1 atmosphere is 9.1.

Claims (5)

1. a method for preparing sulfur-nitrogen co-doped porous carbon material with potassium hydroquinone sulfate as activator, is characterized in that, comprises the following preparation steps: (1) Glucosamine hydrochloride is dissolved in water, the solution that forms adds hydrothermal reactor, carries out hydrothermal carbonization; (2) the product obtained in step (1) is repeatedly washed with deionized water and dried; (3) take chitosan or the dried product of step (2), grind and mix it with potassium hydroquinone sulfate, the formed mixture is placed in a tube furnace, protected by an inert gas, and the tube furnace is heated to a high temperature for carrying out Treatment, and then naturally cooled to room temperature; (4) The product of step (3) is added to hydrochloric acid for treatment, then repeatedly washed with deionized water, and dried to obtain a sulfur-nitrogen co-doped porous carbon material. 2. a kind of method for preparing sulfur-nitrogen co-doped porous carbon material with potassium hydroquinone sulfate as activator according to claim 1, is characterized in that, in step (3), potassium hydroquinone sulfate and The mass ratio of glucosamine hydrochloride thermal carbonization product or chitosan is 2-4:1. 3. a kind of method for preparing sulfur-nitrogen co-doped porous carbon material with potassium hydroquinone sulfate as activator according to claim 1, is characterized in that, in step (3), the temperature of high temperature treatment is 700- 900℃, the treatment time is 1-2h. 4. a kind of method for preparing sulfur-nitrogen co-doped porous carbon material with potassium hydroquinone sulfate as activator according to claim 1, is characterized in that, in step (1), hydrothermal carbonization is carried out at 200 ℃ deal with. 5 . The method for preparing a sulfur-nitrogen co-doped porous carbon material using potassium hydroquinone sulfate as an activator according to claim 1 , wherein in step (2), the drying temperature is 100° C. 6 .

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