Nitrogen-containing porous carbon, preparation method thereof and application of nitrogen-containing porous carbon in selective catalytic oxidation of hydrogen sulfide

Abstract

The invention belongs to the technical field of catalyst preparation, and particularly relates to nitrogen-containing porous carbon, a preparation method thereof and application of the nitrogen-containing porous carbon in selective catalytic oxidation of hydrogen sulfide. According to the invention, nitrogen is doped in a carbon skeleton, and the main existence forms of the doped nitrogen comprise pyridine nitrogen, pyrrole nitrogen, graphite nitrogen and nitrogen oxide, so that the electron donating ability, surface alkalinity and chemical polarity of the carbon material can be effectively adjusted, and the catalytic oxidation ability of the carbon material to hydrogen sulfide is greatly improved. The nitrogen-containing porous carbon provided by the invention is used as a porous carbon material rich in pyridine nitrogen, can realize stable hydrogen sulfide conversion, oxidizes hydrogen sulfide into elemental sulfur, and efficiently produces sulfur while removing hydrogen sulfide. The preparation method provided by the invention is simple in steps, convenient to operate, high in feasibility and good in process stability, and has the potential of large-scale industrialization.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and in particular relates to nitrogen-containing porous carbon, a preparation method thereof, and application thereof in selective catalytic oxidation of hydrogen sulfide. Background Art

[0002] Hydrogen sulfide (H2S), a toxic, flammable, and corrosive acidic gas, is widely present in various natural environments and industrial production processes, including geothermal and volcanic areas, natural gas and oil reserves, oil hydrotreating, and natural gas and coal gasification. It generally poses certain hazards to the human body. In chemical production processes, hydrogen sulfide in the gas can corrode pipelines and equipment, causing failures in transportation and operating systems.

[0003] Due to the polluting characteristics of hydrogen sulfide, it is necessary to achieve precise removal at different concentrations. Methods for removing hydrogen sulfide mainly include catalytic oxidation, adsorption, and absorption. Catalytic oxidation has low investment costs and high desulfurization efficiency, making it particularly suitable for efficient and precise removal of hydrogen sulfide.

[0004] Selective catalytic oxidation (SCO) can directly catalyze the conversion of hydrogen sulfide into elemental sulfur. Because it is not subject to thermodynamic constraints and boasts high conversion rates, it has the potential to treat low-concentration hydrogen sulfide tail gas. Commonly used hydrogen sulfide catalysts include metal oxides and carbon materials. Carbon materials offer advantages such as a well-developed porous structure, large surface area, and modifiable surface chemical properties. However, their catalytic oxidation performance for hydrogen sulfide is limited and cannot fully meet the performance requirements of applications. Summary of the Invention

[0005] The purpose of the present invention is to provide a nitrogen-containing porous carbon and a preparation method thereof and an application thereof in selective catalytic oxidation of hydrogen sulfide. The nitrogen-containing porous carbon provided by the present invention has a strong catalytic oxidation ability for hydrogen sulfide.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a nitrogen-containing porous carbon, comprising a carbon skeleton and nitrogen doped in the carbon skeleton; the nitrogen exists in the form of pyridinic nitrogen, pyrrolic nitrogen, graphitic nitrogen and nitrogen oxide.

[0008] Preferably, the particle size of the carbon skeleton is not greater than 0.25 microns; the pore size of the carbon skeleton is 9.5 to 16.1 nm; the specific surface area of the carbon skeleton is 138 to 185 m 2 / g; the pore volume of the carbon skeleton is 0.43 to 0.67 cm 3 / g.

[0009] Preferably, the molar ratio of the carbon skeleton to nitrogen is 19-23:2-6.

[0010] The present invention also provides a method for preparing the nitrogen-containing porous carbon described in the above scheme, comprising the following steps:

[0011] The nitrogen source and the carbon source are mixed, ground, and then carbonized to obtain the nitrogen-containing porous carbon.

[0012] Preferably, the nitrogen source is an organic amine.

[0013] Preferably, the carbon source includes one or more of anhydrides, sugars and organic acids.

[0014] Preferably, the mass ratio of the carbon source to the nitrogen source is 1-10:1-20.

[0015] Preferably, the grinding time is 5 to 30 minutes; the grinding speed is 100 to 200 revolutions per minute; and the grinding ball milling ratio is 5 to 10:1.

[0016] Preferably, the carbonization temperature is 500-1000° C., and the heat preservation carbonization time is 2-5 hours; and the carbonization is carried out in a protective gas.

[0017] The present invention also provides the use of the nitrogen-containing porous carbon described in the above scheme or the nitrogen-containing porous carbon obtained by the preparation method described in the above scheme in the selective catalytic oxidation of hydrogen sulfide.

[0018] The present invention provides a nitrogen-containing porous carbon. The present invention dopes nitrogen into the carbon skeleton, and the main forms of the doped nitrogen include pyridinic nitrogen, pyrrolic nitrogen, graphitic nitrogen and nitrogen oxide, which can effectively adjust the electron donating ability, surface alkalinity and chemical polarity of the carbon material, and greatly improve the catalytic oxidation ability of the carbon material to hydrogen sulfide. The main forms of the doped nitrogen in the nitrogen-containing porous carbon of the present invention are pyridinic nitrogen, pyrrolic nitrogen, graphitic nitrogen and nitrogen oxide, among which pyridinic nitrogen plays a major role in the catalytic oxidation of H2S. It has a unique electron cloud distribution, and its lone pair electrons can interact with hydrogen sulfide molecules, adsorb hydrogen sulfide molecules and enrich them on the catalyst surface, thereby promoting the reaction. At the same time, pyridinic nitrogen can initiate the catalytic oxidation reaction by forming chemical bonds with other reactants or intermediates, reducing the activation energy of the reaction and accelerating the reaction rate. The chemical bonds formed by pyridinic nitrogen and adjacent carbon atoms have high bond energy. The electronegativity of nitrogen atom is greater than that of carbon atom, and the polarity of bond is enhanced when forming chemical bond, and electron cloud is more partial to nitrogen atom, so that the bond length between pyridinic nitrogen and carbon atom is shortened, and bond energy increases.This stronger chemical bond can improve the structural stability of carbon material, making it more difficult to be destroyed.The nitrogen-containing porous carbon provided by the present invention is a porous carbon material rich in pyridinic nitrogen, and stable hydrogen sulfide conversion can be achieved, and hydrogen sulfide is oxidized to elemental sulfur, and efficient sulfur production is produced while removing hydrogen sulfide.

[0019] Specifically, the change in the electron-donating ability of the carbon material is because the electronegativity of the nitrogen atom is greater than that of the carbon atom. When the nitrogen atom replaces some of the carbon atoms in the carbon material, the electron cloud distribution of the surrounding carbon atoms will change; the nitrogen atom has a strong ability to attract electrons, which makes the electron cloud density on the adjacent carbon atoms relatively reduced, while in the area far away from the nitrogen atom, the electron cloud density will increase, thereby changing the overall electron cloud distribution of the carbon material and regulating its electron-donating ability. The surface alkalinity of the carbon material depends on the basic sites. After the nitrogen atom is doped into the carbon material, its lone pair of electrons can accept protons to form basic sites. For example, nitrogen species such as pyridinic nitrogen and pyrrolic nitrogen can combine with hydrogen ions in water in aqueous solution, making the surface of the carbon material alkaline. The chemical polarity of the carbon material is generated because the introduction of nitrogen atoms introduces nitrogen-containing polar groups, such as amino groups and imino groups, into the carbon material. The presence of these polar groups increases the polarity of the carbon material surface, which can produce stronger interactions with polar substances.

[0020] The present invention also provides a method for preparing the nitrogen-containing porous carbon described in the above scheme. The preparation method provided by the present invention has simple steps, convenient operation, high feasibility, good process stability, and has the potential for large-scale industrialization.

[0021] The present invention also provides the use of the nitrogen-containing porous carbon described in the above embodiment, or the nitrogen-containing porous carbon obtained by the preparation method described in the above embodiment, in the selective catalytic oxidation of hydrogen sulfide. The nitrogen-containing porous carbon provided by the present invention can achieve stable hydrogen sulfide conversion and efficiently recover sulfur resources from hydrogen sulfide, which is of great significance for environmental catalytic applications and basic material development. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a diagram showing the catalytic activity of the nitrogen-containing porous carbon prepared in Example 1 of the present invention;

[0024] Figure 2 This is a diagram showing the catalytic activity of the nitrogen-containing porous carbon prepared in Example 2 of the present invention;

[0025] Figure 3 This is a diagram showing the catalytic activity of the nitrogen-containing porous carbon prepared in Example 3 of the present invention;

[0026] Figure 4 This is a diagram showing the catalytic activity of the nitrogen-containing porous carbon prepared in Example 4 of the present invention;

[0027] Figure 5 This is an SEM image of the nitrogen-containing porous carbon prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0028] The present invention provides a nitrogen-containing porous carbon, comprising a carbon skeleton and nitrogen doped in the carbon skeleton; the nitrogen exists in the form of pyridinic nitrogen, pyrrolic nitrogen, graphitic nitrogen and nitrogen oxide.

[0029] The nitrogen-containing porous carbon provided by the present invention includes a carbon skeleton; the particle size of the carbon skeleton may be no greater than 0.25 microns, specifically 0.25 microns, 0.20 microns, 0.15 microns, 0.10 microns or 0.05 microns.

[0030] In the present invention, the pore diameter of the carbon skeleton may be 9.5 to 16.1 nm, specifically 9.5 nm, 12.6 nm, 14.6 nm or 16.1 nm.

[0031] In the present invention, the specific surface area of the carbon skeleton can be 138 to 185 m 2 / g, specifically 164m 2 / g; the pore volume of the carbon skeleton can be 0.43 to 0.67 cm 3 / g, specifically 0.56cm 3 / g.

[0032] The nitrogen-containing porous carbon provided by the present invention includes nitrogen; the molar ratio of the carbon skeleton to nitrogen can be 19-23:2-6, specifically 19:6, 20:4, 22:3 or 23:2.

[0033] In the present invention, the particle size of the nitrogen-containing porous carbon may be no greater than 0.25 micrometers, specifically 0.25 micrometers, 0.20 micrometers, 0.15 micrometers, 0.10 micrometers or 0.05 micrometers.

[0034] The present invention also provides a method for preparing the nitrogen-containing porous carbon described in the above scheme, comprising the following steps:

[0035] The nitrogen source and the carbon source are mixed, ground, and then carbonized to obtain the nitrogen-containing porous carbon.

[0036] In the present invention, a nitrogen source and a carbon source are mixed (referred to as a first mixing) and ground (referred to as a first grinding) to obtain a mixed powder. In the present invention, the nitrogen source is preferably an organic amine; the organic amine preferably includes one or more of dicyandiamide, melamine, urea, and ethylenediamine.

[0037] In the present invention, the carbon source preferably includes one or more of anhydrides, sugars and organic acids; the anhydride is preferably pyromellitic dianhydride (PMDA); the sugar preferably includes one or more of monosaccharides and polysaccharides; the monosaccharide is preferably glucose; the polysaccharide is preferably cellulose; and the organic acid is preferably trimesic acid.

[0038] In the present invention, the mass ratio of the carbon source to the nitrogen source may be 1-10:1-20, specifically 10:1, 5:1, 1:1, 1:5, 1:10, 1:15 or 1:20.

[0039] In the present invention, the first grinding time can be 5 to 30 minutes, specifically 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes; the first grinding speed can be 100 to 200 rpm, specifically 100 rpm, 120 rpm, 150 rpm, 170 rpm or 200 rpm; the first grinding ball milling ratio can be 5 to 10:1, specifically 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1.

[0040] After obtaining the mixed powder, the present invention carbonizes the mixed powder to obtain the nitrogen-containing porous carbon.

[0041] In the present invention, the carbonization temperature can be 500-1000°C, specifically 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C, and the heat preservation carbonization time can be 2-5h, specifically 2h, 3h, 4h or 5h.

[0042] In the present invention, the carbonization can be carried out in a protective gas; the protective gas can be nitrogen.

[0043] In the present invention, the carbonization preferably further includes heating; the heating rate is preferably 5°C / min.

[0044] In the present invention, after the carbonization, the obtained carbide is preferably cooled and then ground (referred to as the second grinding) and sieving in sequence; the cooling is preferably carried out under nitrogen protection; the final temperature of the cooling is preferably room temperature; the mesh number of the sieve used for sieving is preferably 60 to 80 meshes.

[0045] The present invention also provides the use of the nitrogen-containing porous carbon described in the above scheme or the nitrogen-containing porous carbon obtained by the preparation method described in the above scheme in the selective catalytic oxidation of hydrogen sulfide.

[0046] In the present invention, the application method may include the following steps: introducing H2S into nitrogen-containing porous carbon to perform a catalytic oxidation reaction.

[0047] In the present invention, the amount of the nitrogen-containing porous carbon can be 0.1 to 0.3 g, specifically 0.1 g, 0.2 g or 0.3 g.

[0048] In the present invention, the H2S can be introduced in the form of a mixed gas; the mixed gas can include hydrogen sulfide, oxygen and nitrogen; the concentration of H2S in the mixed gas can be 500-2000 ppm, specifically 500 ppm, 1000 ppm, 1500 rpm or 2000 rpm; the concentration of O2 in the mixed gas can be 500-2000 ppm, specifically 500 ppm, 1000 rpm, 1500 rpm or 2000 rpm.

[0049] In the present invention, the mass space velocity (WHSV) of the H2S introduced can be 30 to 120 L·g -1 h -1 , specifically 30 L·g -1 h -1 、40L·g -1 h -1 、50L·g -1 h -1 、60L·g -1 h -1 、75L·g -1 h -1 、90L·g -1 h -1 、105L·g -1 h -1 or 120 L·g -1 h -1 .

[0050] In the present invention, the equipment for the catalytic oxidation reaction may be a fixed bed reactor; the fixed bed reactor may be a fixed bed quartz reactor; the specification of the fixed bed quartz reactor may be Φ4mm×100mm.

[0051] In the present invention, the temperature of the catalytic oxidation reaction can be 30-240°C, specifically 30°C, 45°C, 60°C, 75°C, 90°C, 105°C, 120°C, 140°C, 160°C, 180°C, 200°C, 210°C, 220°C, 230°C or 240°C, and the insulation time can be 30-60 min, specifically 30 min, 40 min, 50 min or 60 min.

[0052] The nitrogen-containing porous carbon provided by the present invention can achieve stable conversion of hydrogen sulfide and efficiently recover sulfur resources in hydrogen sulfide, which is of great significance to environmental catalytic applications and basic material development.

[0053] In order to further illustrate the present invention, the scheme of the present invention is described in detail below with reference to the accompanying drawings and embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0054] In a specific embodiment of the present invention, the catalyst activity is expressed by H2S removal rate and S selectivity.

[0055] Example 1

[0056] Trimesic acid (25 g) and melamine (5 g) were ground in a mass ratio of 5:1 for 5 min at a grinding speed of 100 rpm and a grinding ratio of 5:1. The mixture was thoroughly mixed. The resulting white powder was then heated to 800°C at a rate of 5°C / min in a N2 atmosphere and calcined for 2 h for carbonization. The mixture was cooled to room temperature under nitrogen protection and then ground. After grinding, the mixture was sieved to obtain nitrogen-containing porous carbon with a particle size of no more than 0.25 μm.

[0057] Catalyst activity test: carried out in a Φ4mm×100mm fixed bed quartz reactor, the reaction conditions are: H2S concentration of 1000ppm, catalyst dosage of 0.1g, reaction temperature of 180℃, the results are as follows Figure 1 As shown. Figure 1 It can be seen that the H2S removal rate is above 40% for a long time, the catalytic activity of H2S is high, and the S selectivity is maintained at 100%. Because the H2S conversion rate is low, fewer sulfur-containing products are generated, thereby reducing the possibility of side reactions, making the generated products almost all S.

[0058] Example 2

[0059] Grind pyromellitic dianhydride (5 g) and ethylenediamine (5 g) in a mass ratio of 1:1 for 10 min, at a grinding speed of 150 rpm and a grinding ball mill ratio of 5:1, and mix thoroughly. Then, heat the obtained white powder to 700 ° C at a rate of 5 ° C / min in a N2 atmosphere and calcine for 4 h for carbonization. After cooling to room temperature under nitrogen protection, grind it and sieve it after grinding to obtain nitrogen-containing porous carbon with a particle size of no more than 0.25 microns.

[0060] Catalyst activity test: carried out in a Φ4mm×100mm fixed bed quartz reactor, the reaction conditions are: H2S concentration of 1000ppm, catalyst dosage of 0.1g, reaction temperature of 180℃, the results are as follows Figure 2 As shown. Figure 2 It can be seen that the H2S removal rate reached 100% for 30 h, the catalytic activity of H2S was very high, and the S selectivity was maintained at around 93% for a long time.

[0061] Example 3

[0062] Glucose (0.5 g) and dicyandiamide (5 g) were ground in a mass ratio of 1:10 for 20 min at a grinding speed of 200 rpm and a grinding ball mill ratio of 5:1. The mixture was thoroughly mixed. The resulting white powder was then heated to 900 °C at a rate of 5 °C / min in a N2 atmosphere and calcined for 3 h for carbonization. The powder was cooled to room temperature under nitrogen protection and then ground. After grinding, it was sieved to obtain nitrogen-containing porous carbon with a particle size of no more than 0.25 μm.

[0063] Catalyst activity test: carried out in a Φ4mm×100mm fixed bed quartz reactor, the reaction conditions are: H2S concentration of 1000ppm, catalyst dosage of 0.1g, reaction temperature of 180℃, the results are as follows Figure 3 As shown. Figure 3 It can be seen that the H2S removal rate reached 100% for 18 h, the catalytic activity of H2S was high, and the S selectivity was maintained at about 97% for a long time.

[0064] Example 4

[0065] Trimesic acid (0.25 g) and dicyandiamide (5 g) were ground for 30 min at a mass ratio of 1:20, at a grinding speed of 200 rpm and a grinding ball mill ratio of 10:1, and thoroughly mixed. The resulting white powder was then heated to 800 ° C at a rate of 5 ° C / min in a N2 atmosphere and calcined for 2 h for carbonization. After cooling to room temperature under nitrogen protection, the powder was ground and sieved after grinding to obtain nitrogen-containing porous carbon with a particle size of no more than 0.25 μm.

[0066] Catalyst activity test: carried out in a Φ4mm×100mm fixed bed quartz reactor, the reaction conditions are: H2S concentration of 1000ppm, catalyst dosage of 0.1g, reaction temperature of 180℃, the results are as follows Figure 4 As shown. Figure 4 It can be seen that the H2S removal rate reached 100% for 63 h, the catalytic activity of H2S was very high, and the S selectivity was maintained at 95% for a long time (within 30 h), and then the selectivity increased slightly.

[0067] Test Example 1

[0068] The nitrogen-containing porous carbon prepared in Example 4 was analyzed by SEM electron microscope. The results are as follows: Figure 5 As shown. Figure 5 The material exhibits a relatively loose flaky and layered structure with abundant interconnected pores. This three-dimensional porous structure can increase the specific surface area of the carbon material, increase the active sites for the reaction with hydrogen sulfide, and promote the surface adsorption and mass transfer of reactant molecules.

[0069] It can be seen from the above examples that the nitrogen-containing porous carbon provided by the present invention, as a porous carbon material rich in pyridinic nitrogen, can achieve stable conversion of hydrogen sulfide, oxidize hydrogen sulfide into elemental sulfur, remove hydrogen sulfide and efficiently produce sulfur, and has broad application prospects.

[0070] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A nitrogen-containing porous carbon, characterized in that It comprises a carbon skeleton and nitrogen doped in the carbon skeleton; the nitrogen exists in the form of pyridinic nitrogen, pyrrolic nitrogen, graphitic nitrogen and oxidized nitrogen.

2. The nitrogen-containing porous carbon according to claim 1, characterized in that The particle size of the carbon skeleton is not greater than 0.25 microns; the pore size of the carbon skeleton is 9.5 to 16.1 nm; the specific surface area of the carbon skeleton is 138 to 185 m 2 / g; the pore volume of the carbon skeleton is 0.43 to 0.67 cm 3 / g.

3. The nitrogen-containing porous carbon according to claim 1 or 2, characterized in that The molar ratio of the carbon skeleton to nitrogen is 19-23:2-6.

4. The method for preparing nitrogen-containing porous carbon according to any one of claims 1 to 3, characterized in that: The following steps are involved: The nitrogen source and the carbon source are mixed, ground, and then carbonized to obtain the nitrogen-containing porous carbon.

5. The preparation method according to claim 4, characterized in that The nitrogen source is an organic amine.

6. The preparation method according to claim 4, characterized in that The carbon source includes one or more of acid anhydrides, sugars and organic acids.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The mass ratio of the carbon source to the nitrogen source is 1-10:1-20.

8. The preparation method according to claim 4, characterized in that The grinding time is 5 to 30 minutes; the grinding speed is 100 to 200 revolutions per minute; and the grinding ball milling ratio is 5 to 10:

1.

9. The preparation method according to claim 4 or 8, characterized in that The carbonization temperature is 500-1000° C., and the heat preservation carbonization time is 2-5 hours; the carbonization is carried out in a protective gas.

10. Use of the nitrogen-containing porous carbon according to any one of claims 1 to 3 or the nitrogen-containing porous carbon obtained by the preparation method according to any one of claims 4 to 9 in the selective catalytic oxidation of hydrogen sulfide.

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