A method for preparing a denitrifying agent

Abstract

The present invention relates to the technical field of denitrification agents, and in particular to a method for preparing a denitrification agent, wherein carbon dioxide, ammonia and water are subjected to a catalytic reaction in an organic solvent system to obtain a denitrification agent, wherein the catalyst is a Co-Ni catalyst. The reaction of the present invention increases the reaction rate under the action of a catalyst, greatly accelerates the reaction speed of the raw materials, and rapidly reacts to obtain micron-sized powder particles; the particle size of the denitrification agent generated by the reaction is concentrated in the range of 1-2 μm, which greatly accelerates the decomposition speed of the denitrification agent during use; the denitrification agent generated by the reaction has a high reaction activity, and according to experimental tests, it can be rapidly decomposed at 100-150° C., and the ammonia yield is greater than 95%.

Description

Technical Field

[0001] The invention relates to the technical field of denitrification agents, and in particular to a method for preparing a denitrification agent. Background Art

[0002] At present, the main technologies for denitrification of pulverized coal boiler flue gas in thermal power plants are selective catalytic reduction technology (SCR) and non-selective catalytic reduction technology (SNCR). Urea is widely used as a reducing agent in the denitrification and ammonia production process. Although the technology of urea ammonia production for power plant denitrification is relatively mature, it still has problems such as high cost, low pyrolysis efficiency, low denitrification efficiency, and easy corrosion of the system. In particular, the actual ammonia yield of urea pyrolysis ammonia production is only 83% to 93%, resulting in waste of urea and a series of derivative problems. Therefore, it is urgent to develop efficient denitrification agents and ammonia production technologies to improve ammonia production efficiency, reduce ammonia production temperature, and improve the economy of denitrification, which is of great significance. Summary of the invention

[0003] The present invention solves the problems in the related art, proposes a method for preparing a denitrifying agent, and obtains a denitrifying agent with good reaction activity and low cost, which can be applied to the pyrolysis system of SCR and SNCR denitrification processes.

[0004] In order to solve the above technical problems, the present invention is achieved through the following technical scheme: a method for preparing a denitrifying agent, wherein carbon dioxide, ammonia and water are subjected to a catalytic reaction in an organic solvent system to obtain a denitrifying agent, wherein the catalyst is a Co-Ni catalyst.

[0005] As a preferred solution, the mass percentages of the raw materials are: 50-55% carbon dioxide, 38-43% ammonia, 0.5-5% water, and 0.2-2% catalyst.

[0006] As a preferred embodiment, the ratio of Co to Ni in the Co-Ni catalyst is 1:10 to 10:1, wherein the Co:Ni ratio is preferably between 2:8 and 6:4, more preferably between 3:7 and 4:6, and the optimal ratio is between 3.5:6.5 and 4:6. The catalyst size is concentrated between 200-500nm.

[0007] As a preferred embodiment, the organic solvent is at least one of toluene, xylene, chlorobenzene, o-dichlorobenzene, 1,2-dichloroethane, paraffin oil, ethanol, methanol and carbon tetrachloride, among which toluene, xylene, o-dichlorobenzene and chlorobenzene are preferred, chlorobenzene and xylene are more preferred, and chlorobenzene is the best.

[0008] As a preferred embodiment, the reaction temperature is between -5 and 25°C, with 0-10°C being the most optimal.

[0009] As a preferred embodiment, the specific preparation steps are as follows:

[0010] S1. placing a mixture of cobalt hydroxide and nickel hydroxide in a muffle furnace and calcining at 1000-1200° C.;

[0011] S2, placing the obtained oxide powder in water containing a surfactant to react for 24 hours;

[0012] S3, filtering the product after the reaction, washing it and then vacuum drying it to obtain a Co-Ni catalyst;

[0013] S4, adding the catalyst to the organic solvent, adding water according to the ratio, controlling the reaction temperature between 0-10°C, and then introducing ammonia and carbon dioxide;

[0014] S5. After the reaction is completed, the obtained solid product is filtered and vacuum dried to obtain a denitrification agent powder.

[0015] As a preferred embodiment, the surfactant is at least one of polyethylene glycol, ammonium salts, and sulfonates, among which polyethylene glycol is preferred, polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600 and polyethylene glycol 800 are more preferred, and polyethylene glycol 200 is the best.

[0016] As a preferred embodiment, the denitrification agent is a micron-sized mixture including ammonium carbamate and ammonium carbonate.

[0017] As a preferred solution, the ammonium carbamate content is 85-95%, and the ammonium carbonate content is 5-15%. The higher the proportion of ammonium carbamate in the denitrification agent, the better the effect in practical use.

[0018] As a preferred solution, the particle size of the micron-sized mixture ranges from 1 to 2 μm.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The reaction rate is increased under the action of a catalyst, which greatly accelerates the reaction rate of the raw materials and quickly reacts to obtain micron-sized powder particles;

[0021] (2) The particle size of the denitrifier generated by the reaction is concentrated in the range of 1-2 μm, which greatly accelerates the decomposition rate of the denitrifier during use;

[0022] (3) The denitrification agent generated by the reaction has high reactivity. According to experimental tests, it can be rapidly decomposed at 100-150°C, and the ammonia yield is greater than 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a scanning electron microscope image of the Co-Ni catalyst of the present invention;

[0024] Figure 2 is a scanning electron microscope image of the Co-Ni catalyst of the present invention;

[0025] Figure 3 The molecular structure diagram (ammonium carbamate crystal) obtained by performing X-ray single crystal diffraction on the denitrifying agent obtained by the present invention;

[0026] Figure 4 The molecular structure diagram (ammonium carbonate crystal) of the denitrifying agent obtained by the present invention is obtained by performing X-ray single crystal diffraction. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0029] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0030] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0031] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0032] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0033] Example 1

[0034] The preparation method of Co-Ni catalyst is as follows:

[0035] Take 20g Co(OH)2 and 30g Ni(OH)2 as raw materials, place them in a muffle furnace and calcine them at 1000-1200°C for 2h to obtain a mixed powder of cobalt oxide and nickel oxide; then stir the powders of cobalt oxide and nickel oxide with 0.5g polyethylene glycol 200 and 200g pure water at room temperature for 24h to obtain a mixed solid slurry of oxides and hydroxides, and then filter the slurry and vacuum dry it to obtain catalyst I. Figure 1 and 2 As shown, it can be seen from the scanning electron microscope photograph that the obtained catalyst is a particle with regular shape and a particle size of about 500nm.

[0036] Embodiment 2-7

[0037] In the preparation method of Example 1, different ratios of Co to Ni and different surfactants were selected for preparation, and other conditions remained unchanged to obtain catalysts with different properties, as shown in the following table:

[0038] Table 1 Preparation of different catalysts in Examples 1-7

[0039]

[0040] Example 8

[0041] 200g of chlorobenzene was added to a 500mL four-necked round-bottom flask, and mechanical stirring was installed. The internal temperature was lowered to 0-5°C with an ice-water bath, and 0.1g of catalyst I and 0.4g of pure water were added. Then, ammonia and carbon dioxide were introduced, wherein ammonia was 100mL / min and carbon dioxide was 50mL / min. The reaction time was about 1h. After the reaction was completed, the denitrifier powder was filtered and then dried in a nitrogen atmosphere at 40°C to obtain the denitrifier. The average particle size of the denitrifier prepared in this embodiment was 1-2μm, and the proportion of ammonium carbamate in the denitrifier was 94%, and the proportion of ammonium carbonate was 6%. The denitrifier prepared in Example 8 was subjected to X-ray single crystal diffraction, and the molecular structure obtained was as follows Figure 3 As shown, the synthesized denitrification agent is a mixture of ammonium carbamate and ammonium carbonate, with blue representing nitrogen atoms, red representing oxygen atoms, and gray representing carbon atoms and hydrogen atoms.

[0042] Examples 9-16

[0043] The denitrification agent preparation scheme is the same as that of Example 8, except that the solvent is replaced with xylene, o-dichlorobenzene, 1,2-dichloroethane, etc., and some of the catalysts obtained in Examples 1-7 are selected to prepare the denitrification agent, as shown in the following table:

[0044] Example Solvents Catalyst Model Ammonium carbamate ratio Ammonium carbonate ratio Example 8 chlorobenzene I 95％ 5％ Example 9 Xylene I 90％ 10％ Example 10 1.2-Dichloroethane I 88％ 12％ Embodiment 11 chlorobenzene II 64％ 36％ Example 12 chlorobenzene III 78％ 22％ Example 13 chlorobenzene IV 82％ 28％ Embodiment 14 chlorobenzene V 93％ 7％ Embodiment 15 chlorobenzene VI 74％ 26％ Example 16 chlorobenzene VII 78 22％

[0045] Embodiment 17

[0046] Pyrolysis experiment:

[0047] 10 g of the denitrifier prepared in Example 8 was placed in a heating tube furnace at 100-150° C. and completely decomposed within 1 minute by naked eye observation. The ammonia produced by the decomposition was absorbed by 5% dilute sulfuric acid and then back-titrated with sodium hydroxide solution to obtain a final ammonia value, which was almost consistent with the ammonia value of the denitrifier initially added. At the same time, the denitrifiers obtained in Examples 9-16 were pyrolyzed by the same method, and the ammonia production rate was calculated to be in the range of 97% to 99%.

[0048] The above are preferred implementation modes of the present invention. Those skilled in the art to which the present invention belongs can also change and modify the above implementation modes. Therefore, the present invention is not limited to the above specific implementation modes. Any obvious improvements, substitutions or modifications made by those skilled in the art on the basis of the present invention belong to the protection scope of the present invention.

Claims

1. A method for preparing a denitrifying agent, characterized in that: Carbon dioxide, ammonia and water are reacted in an organic solvent system via a catalyst to obtain a denitrifying agent, wherein the catalyst is a Co-Ni catalyst.

2. The method for preparing a denitrifying agent according to claim 1, characterized in that: The mass percentages of the raw materials are: 50-55% carbon dioxide, 38-43% ammonia, 0.5-5% water, and 0.2-2% catalyst.

3. The method for preparing a denitrifying agent according to claim 1, characterized in that: The ratio of Co to Ni in the Co-Ni catalyst is 1:10 to 10:

1.

4. The method for preparing a denitrifying agent according to claim 1, characterized in that: The organic solvent is at least one of toluene, xylene, chlorobenzene, o-dichlorobenzene, 1,2-dichloroethane, paraffin oil, ethanol, methanol and carbon tetrachloride.

5. The method for preparing a denitrifying agent according to claim 1, characterized in that: The reaction temperature is between -5 and 25°C.

6. The method for preparing a denitrifying agent according to claim 2, characterized in that: The specific preparation steps are as follows: S1. placing a mixture of cobalt hydroxide and nickel hydroxide in a muffle furnace and calcining at 1000-1200° C.; S2, placing the obtained oxide powder in water containing a surfactant to react for 24 hours; S3, filtering the product after the reaction, washing it and then vacuum drying it to obtain a Co-Ni catalyst; S4, adding the catalyst to the organic solvent, adding water according to the ratio, controlling the reaction temperature between 0-10°C, and then introducing ammonia and carbon dioxide; S5. After the reaction is completed, the obtained solid product is filtered and vacuum dried to obtain a denitrification agent powder.

7. The method for preparing a denitrifying agent according to claim 6, characterized in that: The surfactant is at least one of polyethylene glycol, ammonium salts and sulfonates.

8. The method for preparing a denitrifying agent according to claim 1, characterized in that: The denitrification agent is a micron-sized mixture including ammonium carbamate and ammonium carbonate.

9. The method for preparing a denitrifying agent according to claim 8, characterized in that: The content of ammonium carbamate is 85-95%, and the content of ammonium carbonate is 5-15%.

10. The method for preparing a denitrifying agent according to claim 8, characterized in that: The particle size of the micron-sized mixture ranges from 1 to 2 μm.

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