NOx adsorbent as well as preparation method and application thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-11-14
- Publication Date
- 2026-05-15
AI Technical Summary
When nitrogen-doped hydrothermal carbon is used directly as a NOx adsorbent, it suffers from problems such as insufficient adsorption capacity, insufficient water resistance, high calcination temperature, complex preparation composition, and high cost.
Using glucose as raw material, nitrogen-doped hydrothermal carbon was prepared through hydrothermal reaction, nitrogen source calcination, and alkaline activation. The pyridine nitrogen content was controlled to be above 25%, and the preparation process was optimized to improve the NOx adsorption capacity.
The prepared NOx adsorbent can adsorb more than 2.49 mmol/g at room temperature, and the adsorption capacity can be increased by more than 2 times after water vapor and oxygen are introduced, demonstrating a highly efficient NOx capture capacity.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of waste gas treatment, specifically relating to a NOx adsorbent, its manufacturing method, and its application. Background Technology
[0002] Contemporary China is continuously advancing the construction of ecological civilization, and environmental protection has always been one of the key focuses of the Chinese government's work. Nitrogen oxides (NOx) are one of the main components of air pollutants, and the harm they cause is extremely serious. NOx emissions from industrial flue gas are the main air pollutants, mainly including nitric oxide (NO) and nitrogen dioxide (NO2), with NO accounting for the majority. Therefore, reducing NOx emissions is an urgent task.
[0003] Commonly used NOx adsorbent materials include porous carbon materials, zeolite molecular sieves, metal-organic frameworks (MOFs), and metal oxides. Porous carbon materials, with their well-developed pore structure, good chemical stability, and recyclability, are widely used in air pollution control, gas separation, and energy storage. CN101641151A discloses a method for manufacturing a NOx adsorbent material and the NOx adsorbent material itself. The method involves impregnating zeolite with an aqueous solution of ferric chloride, heating it at 330℃–500℃ in a moisture-free atmosphere to allow for ion exchange of Fe, followed by heat treatment in a non-oxidizing atmosphere. This heat treatment in a non-oxidizing atmosphere results in high NOx adsorption performance, with an NO adsorption capacity reaching 0.3 mmol / g. CN101693192A discloses a method for preparing a high-capacity nitrogen oxide adsorbent. This method uses manganese (or cobalt) and cerium as the main catalytic oxidation components, and activated carbon as the NOx absorption component. The activated carbon material loaded with manganese (or cobalt) and cerium is obtained through impregnation, and then calcined under inert gas to obtain an adsorbent material that can effectively oxidize NO to NO2 at low temperatures and absorb it. Its NOx adsorption capacity (based on NO2) can reach over 30 mg / g. While the above techniques can achieve NOx adsorption, the adsorption capacity is relatively low.
[0004] Hydrothermal carbon has uniform dispersion, large specific surface area and abundant pore structure. Its surface contains a large number of oxygen-containing functional groups, which are conducive to the adsorption and oxidation of NO. As an ideal porous carbon precursor, it can be activated to form porous carbon materials with excellent adsorption performance.
[0005] CN109647474A relates to a nitrogen-doped carbon material, its preparation, and its application. Using glucose as a raw material and melamine as a nitrogen source, the method involves first calcining glucose at a certain temperature under an inert atmosphere to prepare a carbon substrate. Then, the calcined carbon substrate is mixed with melamine in a certain proportion in an aqueous solution, followed by heating and stirring. After drying, it is calcined again at a low temperature under an inert atmosphere to obtain the nitrogen-doped carbon material. This preparation method is simple, energy-efficient, and low-cost. The nitrogen-doped carbon material exhibits high reactivity and can selectively degrade a variety of organic pollutants, thus solving the technical problems of complex and costly preparation methods and limited degradation capabilities for organic pollutants in the environment associated with existing nitrogen-doped carbon materials.
[0006] Using nitrogen-doped hydrothermal carbon directly as a NOx adsorbent, as disclosed in existing technologies, has problems such as insufficient adsorption capacity, insufficient water resistance, high calcination temperature, complex preparation composition, and high cost. Summary of the Invention
[0007] To address the shortcomings of existing technologies, this invention provides a NOx adsorbent, its manufacturing method, and its applications. The adsorbent provided by this invention exhibits a high NOx adsorption capacity, and its raw materials are widely available, inexpensive, and simple to prepare, making it highly suitable for industrial production and widespread application.
[0008] The first aspect of the present invention provides a NOx adsorbent, wherein the adsorbent is a nitrogen-doped hydrothermal carbon material, and the nitrogen content is 1%-5% by mass, preferably 1.1%-4.5%, wherein pyridine nitrogen accounts for more than 25% of the nitrogen content, preferably more than 30%.
[0009] The second aspect of the present invention provides a method for manufacturing the NOx adsorbent, comprising the following steps: (1) placing a glucose aqueous solution in a pressure-resistant container for hydrothermal reaction, and then washing and drying to obtain hydrothermal carbon; (2) grinding the hydrothermal carbon and a nitrogen source evenly, and calcining them under a nitrogen atmosphere to obtain nitrogen-doped hydrothermal carbon; (3) activating the nitrogen-doped hydrothermal carbon in step (2), and then drying and calcining it to obtain the NOx adsorbent.
[0010] In the method of the present invention, the mass concentration of the glucose aqueous solution in step (1) is 0.05-0.1 g / mL.
[0011] In the method of this invention, the hydrothermal reaction conditions in step (1) are: a temperature of 160℃-220℃, preferably 180℃-200℃, and a time of 4-18 hours, preferably 4-12 hours. The pressure-resistant container is generally a high-pressure reactor, preferably a high-pressure reactor with a polytetrafluoroethylene liner.
[0012] In the method of the present invention, the washing in step (1) is first performed with ethanol, followed by vacuum filtration, and then with deionized water, followed by filtration, until the solution becomes completely clear.
[0013] In the method of the present invention, the drying temperature in step (1) is 80-100℃ and the drying time is 8-12h.
[0014] In the method of the present invention, the nitrogen source in step (2) is one or more of melamine, hexamethylenetetramine, dicyandiamine, pyrrole, polypyrrole, etc., preferably melamine.
[0015] In the method of the present invention, the mass ratio of nitrogen source to hydrothermal carbon in step (2) is 1:1-4:1.
[0016] In the method of the present invention, the calcination temperature in step (2) is 300℃-600℃ and the calcination time is 2h-6h.
[0017] In the method of the present invention, the activation in step (3) is carried out with an alkaline solution, wherein the alkaline solution is KOH and / or NaOH, preferably KOH, and the mass ratio of KOH to nitrogen-doped hydrothermal carbon is 1:1-4:1, and the concentration of the alkaline solution is 0.8-3.0 mol / L.
[0018] In the method of this invention, the drying temperature in step (3) is 80℃-110℃, and the drying time is 8h-14h. The calcination is carried out under an inert atmosphere, with a calcination temperature of 600℃-800℃ and a calcination time of 1h-4h. The inert atmosphere is generally an inert gas and / or nitrogen.
[0019] A third aspect of the present invention provides a method for using the NOx adsorbent described above to adsorb NOx in a gas, wherein the NOx is NO and / or NO2.
[0020] In the application of this invention, the adsorption of the adsorbent is carried out under conditions of 1%-3% water vapor volume content, more preferably 1.8%-2.5%.
[0021] In the application of this invention, the adsorption of the adsorbent is carried out under the conditions of 1%-3% water vapor volume content and 1%-3% oxygen volume content.
[0022] Compared with the prior art, the present invention has the following beneficial effects:
[0023] (1) The adsorbent provided by the present invention has a high proportion of pyridine nitrogen, which helps to capture and adsorb NOx and has a high NOx adsorption capacity. The adsorption capacity can reach more than 2.49 mmol / g at room temperature.
[0024] (2) When a certain amount of water vapor is introduced into the adsorbent during the adsorption process, the adsorption capacity can be increased by more than 2 times. When a certain amount of oxygen is further introduced, the adsorption capacity can be increased by more than 2.2 times. Detailed Implementation
[0025] The technical solution and its effects of the present invention will be further described in detail below with reference to specific embodiments. The embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.
[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples were purchased from conventional biochemical reagent stores.
[0027] Example 1
[0028] A 0.054 g / mL glucose aqueous solution was placed in a high-pressure reactor and hydrothermally reacted at 200 °C for 4 h. After filtration, the solution was first washed with ethanol, then vacuum filtered, followed by washing with deionized water and filtration until the solution became completely clear. The solution was then dried at 80 °C for 8 h to obtain hydrothermal carbon. The hydrothermal carbon was mixed with melamine at a mass ratio of 1:2 and calcined at 350 °C for 3 h under a nitrogen atmosphere to obtain nitrogen-doped hydrothermal carbon. The nitrogen-doped hydrothermal carbon was then uniformly mixed with KOH at a mass ratio of 1:1 in an aqueous solution with an alkali concentration of 0.89 mol / L and dried at 100 °C for 10 h. After drying, the prepared adsorbent was calcined at 700 °C for 2 h under a nitrogen atmosphere to obtain a NOx adsorbent. The nitrogen content of the prepared adsorbent was 3.34%, of which pyridine nitrogen accounted for 35.4% of the nitrogen content.
[0029] The adsorbent was used for the adsorption treatment of four gases: one containing NO (1000 ppm), one containing NO (1000 ppm) and water vapor (2%), one containing NO (1000 ppm), water vapor (2%) and oxygen (3%), and one containing NO (1000 ppm) and CO (1000 ppm). Adsorption was carried out at room temperature and pressure.
[0030] The breakthrough adsorption amounts were measured to be 2.98 mmol / g, 9.1 mmol / g, 9.65 mmol / g, and 2.56 mmol / g on a flue gas analyzer (Kane, KM905, UK).
[0031] Example 2
[0032] A 0.054 g / mL glucose aqueous solution was placed in a high-pressure reactor and hydrothermally reacted at 200 °C for 4 h. After filtration, the solution was first washed with ethanol, then vacuum filtered, followed by washing with deionized water and filtration until the solution became completely clear. The solution was then dried at 80 °C for 8 h to obtain hydrothermal carbon. The hydrothermal carbon was mixed with hexamethylenetetramine at a mass ratio of 1:2 and calcined at 350 °C for 3 h under a nitrogen atmosphere to obtain nitrogen-doped hydrothermal carbon. The nitrogen-doped hydrothermal carbon was then uniformly mixed with KOH at a mass ratio of 1:1 in an aqueous solution with an alkali concentration of 0.89 mol / L and dried at 100 °C for 10 h. After drying, the prepared adsorbent was calcined at 700 °C for 2 h under a nitrogen atmosphere to obtain a NOx adsorbent. The nitrogen content of the prepared adsorbent was 1.13%, of which pyridine nitrogen accounted for 32%.
[0033] The adsorbent was used for adsorption treatment of gases containing NO (1000 ppm), gases containing NO (1000 ppm) and water vapor (2%), and gases containing NO (1000 ppm), water vapor (2%), and oxygen (3%). Adsorption was carried out at room temperature and pressure.
[0034] The breakthrough adsorption capacity was measured to be 2.57 mmol / g, 5.42 mmol / g, and 5.68 mmol / g on a flue gas analyzer (Kane, KM905, UK).
[0035] Example 3
[0036] A 0.1 g / mL glucose aqueous solution was placed in a high-pressure reactor and hydrothermally heated at 180℃ for 12 h. After filtration, the solution was first washed with ethanol, then vacuum filtered, followed by washing with deionized water and filtration until the solution became completely clear. The solution was then dried at 100℃ for 8 h to obtain hydrothermal carbon. The hydrothermal carbon was mixed with melamine at a mass ratio of 1:1 and calcined at 500℃ for 2 h under a nitrogen atmosphere to obtain nitrogen-doped hydrothermal carbon. The nitrogen-doped hydrothermal carbon was uniformly mixed with KOH at a mass ratio of 1:2 in an aqueous solution for activation. The alkali concentration was 1.78 mol / L, and the solution was dried at 80℃ for 14 h. After drying, the prepared adsorbent was calcined at 600℃ for 4 h under a nitrogen atmosphere to obtain a NOx adsorbent. The nitrogen content of the prepared adsorbent was 1.6%, of which pyridine nitrogen accounted for 26% of the nitrogen content.
[0037] The adsorbent was used for the adsorption treatment of NO gas (1000 ppm). Adsorption was carried out at room temperature and pressure. The breakthrough adsorption capacity was measured to be 2.64 mmol / g on a flue gas analyzer (Kane, KM905, UK).
[0038] Example 4
[0039] A 0.8 g / mL glucose aqueous solution was placed in a high-pressure reactor and hydrothermally heated at 180℃ for 12 h. After filtration, the solution was first washed with ethanol, then vacuum filtered, followed by washing with deionized water and filtration until the solution became completely clear. The solution was then dried at 80℃ for 12 h to obtain hydrothermal carbon. The hydrothermal carbon and melamine were thoroughly ground at a mass ratio of 1:3 and calcined at 300℃ for 6 h under a nitrogen atmosphere to obtain nitrogen-doped hydrothermal carbon. The nitrogen-doped hydrothermal carbon was uniformly mixed with KOH at a mass ratio of 1:3 in an aqueous solution for activation. The alkali concentration was 2.67 mol / L. The solution was dried at 110℃ for 8 h. After drying, the prepared adsorbent was calcined at 800℃ for 1 h under a nitrogen atmosphere to obtain a NOx adsorbent. The nitrogen content of the prepared adsorbent was 3.7%, of which pyridine nitrogen accounted for 28% of the nitrogen content.
[0040] The adsorbent was used to adsorb NO gas (1000 ppm). Adsorption was carried out at room temperature and pressure. The breakthrough adsorption capacity was measured to be 2.49 mmol / g on a flue gas analyzer (Kane, KM905, UK).
[0041] Comparative Example 1
[0042] Similar to Example 1, except that urea was used as the nitrogen source to prepare the final adsorbent. The pyridine nitrogen in the prepared adsorbent accounted for 22% of the nitrogen content. The adsorbent was used to adsorb NO gas (1000 ppm), and its breakthrough adsorption capacity was measured to be 0.53 mmol / g on a flue gas analyzer (Kane, KM905, UK).
[0043] Comparative Example 2
[0044] Same as Example 1, except that the hydrothermal carbon was replaced with activated carbon to prepare the adsorbent. The adsorbent was used for adsorption treatment of gases containing NO (1000 ppm) and gases containing NO (1000 ppm) and water vapor (2%). The breakthrough adsorption capacities were measured to be 2.56 mmol / g and 1.47 mmol / g, respectively, on a flue gas analyzer (Kane, KM905, UK).
Claims
1. A NOx adsorbent, characterized in that... The adsorbent is a nitrogen-doped hydrothermal carbon material with a nitrogen content of 1%-5% by mass, of which pyridine nitrogen accounts for more than 25% of the nitrogen content.
2. The NOx adsorbent according to claim 1, characterized in that: The adsorbent has a nitrogen content of 1.1%-4.5% by mass, of which pyridine nitrogen accounts for more than 30% of the nitrogen content.
3. A method for manufacturing the NOx adsorbent according to any one of claims 1-2, characterized in that... The following contents are included: (1) A glucose aqueous solution is placed in a pressure-resistant container for hydrothermal reaction, and after washing and drying, hydrothermal carbon is obtained; (2) Hydrothermal carbon and nitrogen source are ground evenly and calcined under nitrogen atmosphere to obtain nitrogen-doped hydrothermal carbon; (3) The nitrogen-doped hydrothermal carbon in step (2) is activated, dried and calcined to obtain NOx adsorbent.
4. The manufacturing method according to claim 3, characterized in that: The mass concentration of the glucose aqueous solution in step (1) is 0.05-0.1 g / mL.
5. The manufacturing method according to claim 3, characterized in that: The conditions for the hydrothermal reaction in step (1) are: temperature of 160℃-220℃, preferably 180℃-200℃, and time of 4-18 hours, preferably 4-12 hours.
6. The manufacturing method according to claim 3, characterized in that: The washing process described in step (1) involves first washing with ethanol, then vacuum filtration, followed by washing with deionized water and filtration until the solution becomes completely clear.
7. The manufacturing method according to claim 3, characterized in that: The drying temperature in step (1) is 80-100℃ and the drying time is 8-12h.
8. The manufacturing method according to claim 3, characterized in that: The nitrogen source in step (2) is one or more of melamine, hexamethylenetetramine, dicyandiamine, pyrrole, polypyrrole, etc., with melamine being preferred.
9. The manufacturing method according to claim 3 or 8, characterized in that: The mass ratio of nitrogen source to hydrothermal carbon in step (2) is 1:1 to 4:
1.
10. The manufacturing method according to claim 3, characterized in that: The roasting temperature in step (2) is 300℃-600℃, and the roasting time is 2h-6h.
11. The manufacturing method according to claim 3, characterized in that: The activation in step (3) is carried out using an alkaline solution, wherein the alkaline is KOH and / or NaOH, preferably KOH, and the mass ratio of KOH to nitrogen-doped hydrothermal carbon is 1:1-4:1, and the concentration of the alkaline solution is 0.8-3.0 mol / L.
12. The manufacturing method according to claim 3, characterized in that: The drying temperature in step (3) is 80℃-110℃, and the drying time is 8h-14h.
13. The manufacturing method according to claim 3, characterized in that: The calcination in step (3) is carried out under an inert atmosphere, with a calcination temperature of 600℃-800℃ and a calcination time of 1h-4h.
14. A method for adsorbing NOx from a gas using the NOx adsorbent according to any one of claims 1-2 or the NOx adsorbent prepared by the method according to any one of claims 3-13, characterized in that: The NOx mentioned is NO and / or NO2.
15. The method according to claim 14, characterized in that: The adsorption of the adsorbent is carried out under conditions of 1%-3% water vapor volume content, more preferably 1.8%-2.5%.
16. The method according to claim 14, characterized in that: The adsorption of the adsorbent is carried out under the conditions of 1%-3% water vapor volume content and 1%-3% oxygen volume content.