Ammonia adsorbent and manufacturing method therefor

Abstract

An ammonia adsorbent according to an embodiment of the present invention may comprise MgCl2-supported reduced graphene oxide (RGO).

Description

Ammonia adsorbent and method of manufacturing the same

[0001] The present invention relates to an ammonia adsorbent and a method for manufacturing the same.

[0002] Conventional ammonia removal processes have been primarily used for ammonia recovery processes to improve the performance of the Haber-Bosch process and for ammonia removal processes to prevent emissions into the atmosphere.

[0003] The hydrogen production process using ammonia is a process in which ammonia is decomposed into nitrogen and hydrogen by a catalyst under high temperature conditions as shown in reaction equation 1 below, and depending on the decomposition rate, undecomposed ammonia is contained in the decomposition gas (N2, H2), and high-purity hydrogen is produced through a process to remove it.

[0004] [Reaction Equation 1]

[0005] 2NH3→ N2+ 3H2

[0006] To this end, undecomposed ammonia was removed by an adsorption process that adsorbs ammonia using an adsorbent for ammonia adsorption in adsorption processes such as PSA, TSA, and VPSA.

[0007] To this end, conventional studies have used various adsorbents to remove ammonia, and examples include studies that primarily used zeolite, alumina, silica gel, and activated carbon.

[0008] However, conventional adsorbents had a problem where their ammonia adsorption performance deteriorated during repeated regeneration processes.

[0009] Therefore, there is a need for an adsorbent that maintains excellent ammonia adsorption performance even after long-term use.

[0010] One embodiment of the present invention can provide an ammonia adsorbent that maintains stable performance without performance degradation by improving long-term stability, and a method for manufacturing the same.

[0011] One embodiment of the present invention can provide an ammonia adsorbent with excellent ammonia adsorption capacity and a method for manufacturing the same.

[0012] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall contents of this specification.

[0013] An ammonia adsorbent, which is one embodiment of the present invention, may include RGO (Reduced Graphene Oxide) supported with MgCl2.

[0014] The above MgCl2 may be included in an amount of 0.01 to 5 weight percent based on the total weight of the adsorbent.

[0015] The above adsorbent may additionally support a metal halide.

[0016] The metal halide may be at least one selected from the group consisting of CaCl2, SrCl2, MgBr2, CaBr2, and SrBr2.

[0017] A method for manufacturing an ammonia adsorbent, which is an embodiment of the present invention, may include a DGO synthesis step of synthesizing DGO (Defected Graphene Oxide) from graphite; an RGO synthesis step of synthesizing RGO (Reduced Graphene Oxide) from the DGO; and a step of supporting the RGO in an MgCl2 solution to support MgCl2 on the interface of the RGO.

[0018] The weight of MgCl2 relative to the total weight of the above MgCl2 solution may be included in an amount of 0.01 to 5 weight%.

[0019] The method may further include a step of additionally supporting the DGO loaded with MgCl2 on a metal halide to load the metal halide.

[0020] The metal halide may be at least one selected from the group consisting of CaCl2, SrCl2, MgBr2, CaBr2, and SrBr2.

[0021] The ammonia adsorbent and the method for manufacturing the same, which is an embodiment of the present invention, have improved long-term stability and can maintain stable performance without performance degradation.

[0022] An ammonia adsorbent and a method for manufacturing the same, which is an embodiment of the present invention, may have excellent ammonia adsorption capacity.

[0023] Figure 1 is a graph showing the breakthrough time of NH3 adsorption for each PSA cycle between the adsorbents of the example and comparative example.

[0024] Preferred embodiments of the present invention will be described below with reference to the attached drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0025] In addition, embodiments of the present invention are provided to more fully explain the present invention to those with average knowledge in the relevant technical field.

[0026] In drawings, the shapes and sizes of elements may be exaggerated for clearer explanation.

[0027] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limited in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form.

[0028] In this description, expressions such as “include” or “equipped” are intended to refer to certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts or combinations thereof other than those described.

[0029] Unless otherwise specifically defined in the specification of the present invention, % units mean weight %.

[0030] In this specification, terms such as 'top', 'upper', 'upper surface', 'lower', 'lower surface', 'lower surface', and 'side surface' are based on the drawings and may actually vary depending on the direction in which the elements or components are arranged.

[0031] Additionally, throughout the specification, when it is said that one part is 'connected' to another part, this includes not only cases where they are 'directly connected,' but also cases where they are 'indirectly connected' with other elements in between.

[0032] The present invention will be described in detail below through each embodiment or example of the invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may also be combined with other embodiments or examples. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0033] One embodiment of the present invention can provide an ammonia adsorbent with excellent ammonia adsorption capacity and improved long-term stability, maintaining stable performance without performance degradation, and a method for manufacturing the same.

[0034] Accordingly, an ammonia adsorbent of one embodiment of the present invention may include RGO supported with magnesium chloride (hereinafter MgCl2) and calcium chloride (hereinafter CaCl2).

[0035] Defected Graphene Oxide (DGO) contains many defects, which increases the number of sites capable of strongly binding with MgCl2. Consequently, the number of sites where ammonia can be adsorbed also increases significantly. Therefore, the combination of DGO and MgCl2 can provide higher ammonia adsorption performance.

[0036] Furthermore, DGO converted into RGO (Reduced Graphene Oxide) possesses a high surface area and excellent conductivity, which further enhances ammonia adsorption performance. Performance can also be continuously improved by increasing the concentration of MgCl2 to provide more active adsorption sites.

[0037] The above MgCl2 may be included in an amount of 0.01 to 5 weight% relative to the total weight of the adsorbent, specifically 0.1 to 3 weight%, and more specifically 0.8 to 1.2 weight%. If the weight of MgCl2 relative to the total weight of the adsorbent is less than 0.01 weight%, the ammonia adsorption performance may be reduced, and the reaction rate and efficiency may decrease due to a lack of catalyst active sites. If the weight of MgCl2 exceeds 5 weight%, ammonia may not permeate into the RGO, resulting in a decrease in adsorption capacity and efficiency, and some of the MgCl2 may remain on the surface in an inactive state, reducing the effective adsorption area and causing the RGO to collapse or break.

[0038] In addition, the ammonia adsorbent of one embodiment of the present invention may additionally support a metal halide. The metal halide may be at least one selected from the group consisting of CaCl2, SrCl2, MgBr2, CaBr2, and SrBr2.

[0039] The ammonia adsorbent of one embodiment of the present invention can be used in processes such as pressure swing adsorption (PSA), temperature swing adsorption (TSA), and vacuum swing adsorption (VPSA), and can possess not only ammonia adsorption capacity but also long-term stability.

[0040] Hereinafter, a method for manufacturing an ammonia adsorbent, which is an embodiment of the present invention, will be described.

[0041] A method for manufacturing an ammonia adsorbent, which is an embodiment of the present invention, may include a DGO synthesis step of synthesizing DGO (Defected Graphene Oxide) from graphite; an RGO synthesis step of synthesizing RGO (Reduced Graphene Oxide) from the DGO; and a step of supporting MgCl2-supported RGO in a CaCl2 solution to support CaCl2 on the interface of the RGO.

[0042] The above DGO synthesis step may be a step of intentionally creating defects in graphite through chemical, physical, or thermal treatment.

[0043] The above DGO synthesis step may include a step of repeatedly performing oxidation and reduction on graphite by treating it in a strong acid or strong base environment. Structural defects may be formed in the graphite through this step.

[0044] Nitric acid, sulfuric acid, etc., may be used as the strong acid mentioned above, but are not particularly limited. Sodium hydroxide, etc., may be used as the strong base mentioned above.

[0045] The above DGO synthesis step may include a step of heat-treating oxidized or reduced graphite to remove oxygen functional groups and induce defects.

[0046] The above DGO synthesis step may additionally include a step of ion irradiation (plasma treatment) and / or ultrasonical treatment of graphite.

[0047] The above DGO synthesis step can obtain DGO through a drying step.

[0048] The above RGO synthesis step can have excellent specific surface area and conductivity by reducing DGO while maintaining the defective structure through reduction.

[0049] First, the above RGO synthesis step may include a step of dispersing DGO in a solvent. The solvent may be water. The dispersion method is not particularly limited, but ultrasound or the like may be used.

[0050] The above RGO synthesis step may include a reduction step. The reducing agent is not particularly limited, but, for example, hydrazine, vitamin C, ascorbic acid, sodium hydroxide, etc. may be used.

[0051] The above RGO synthesis step may further include a heat treatment step.

[0052] The above RGO synthesis step can obtain RGO through a drying step.

[0053] The weight of MgCl2 relative to the total weight of the above MgCl2 solution may be included in an amount of 0.01 to 5 weight%, specifically 0.1 to 3 weight%, and more specifically 0.8 to 1.2 weight%. If the weight of MgCl2 relative to the above MgCl2 solution is less than 0.01 weight%, the ammonia adsorption performance may be reduced, and the reaction rate and efficiency may decrease due to a lack of catalyst active sites. If the weight of MgCl2 exceeds 5 weight%, the adsorption capacity and efficiency may decrease because ammonia cannot permeate into the RGO, and some of the MgCl2 remains on the surface in an inactive state, reducing the effective adsorption area and causing the RGO to collapse or break.

[0054] A method for manufacturing an ammonia adsorbent, which is an embodiment of the present invention, may further include the step of additionally supporting the metal halide by supporting the RGO supported with MgCl2 on the metal halide. The metal halide may be at least one selected from the group consisting of CaCl2, SrCl2, MgBr2, CaBr2, and SrBr2.

[0055] The ammonia adsorbent produced by the method for producing an ammonia adsorbent according to one embodiment of the present invention can be used in processes such as pressure swing adsorption (PSA), temperature swing adsorption (TSA), and vacuum swing adsorption (VPSA), and can possess not only ammonia adsorption capacity but also long-term stability.

[0056] The present invention will be described in detail below through examples. However, it should be noted that the examples described below are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0057] Preparation Example

[0058] 1. Invention Example 1

[0059] (1) Synthesis of DGO

[0060] First, 200g of natural graphite powder was mixed with a 50% sodium hydroxide solution (1L) and stirred at 80°C for 6 hours to prepare surface-treated graphite. The oxidized graphite was filtered, washed with distilled water, and dried at 60°C to obtain oxidized graphite.

[0061] Afterwards, 20g of surface-treated graphite was mixed with 10g of sodium nitrate and 500mL of 5% hydrogen peroxide, and the surface-treated graphite was uniformly oxidized by stirring under conditions of 25℃ or lower.

[0062] Afterwards, the mixture was heated to 35°C and maintained for 3 hours while stirring, then 1 L of distilled water was slowly added to stop the reaction.

[0063] The above mixture was filtered, washed with distilled water, and dried at 60°C to obtain DGO.

[0064] (2) Synthesis of RGO

[0065] 20g of the above-mentioned synthesized DGO was dispersed in 2L of distilled water and then homogeneously dispersed through ultrasonic treatment. An RGO sheet was formed by stirring at 80°C using an eco-friendly reducing agent such as Vitamin C. The formed RGO sheet was centrifuged, washed, and dried at 100°C to obtain RGO.

[0066] (3) Preparation of adsorbent

[0067] 1 wt% MgCl2 was dissolved in distilled water and loaded onto the RGO. Subsequently, the RGO was treated under the same conditions in a rotary evaporator at 50°C and 50 rpm, and then dried and heat-treated in an oven at 100°C for 10 hours to ensure that the MgCl2 was stably bonded to the surface of the RGO.

[0068] The weight of MgCl2 relative to the total weight of the manufactured MgCl2 / RGO adsorbent is 1 wt%.

[0069] 2. Comparative Example 1

[0070] (1) CMS manufacturing

[0071] CMS was washed at 100℃ and dried to remove impurities, and then completely dried in an oven to obtain CMS.

[0072] (2) Adsorbent manufacturing

[0073] After dissolving MgCl2 in distilled water in a flask at a concentration of 1 wt%, the CMS was added to the same flask. Subsequently, distilled water was evaporated for 10 hours in a rotary evaporator at 50°C and 50 rpm to ensure that MgCl2 was evenly deposited on the surface of the CMS, and then dried in a drying oven at 100°C for 10 hours to remove moisture and stabilize the bonding, thereby preparing an MgCl2 / CMS adsorbent.

[0074] The weight of MgCl2 relative to the total weight of the manufactured MgCl2 / CMS adsorbent is 1 wt%.

[0075] Experimental Example (Measurement of breakthrough time)

[0076] The adsorbents of Invention Example 1 and Comparative Example 1 were prepared under different drying and wetting conditions, and the prepared adsorbents were loaded into a PSA ammonia adsorber.

[0077] Subsequently, the ammonia adsorption breakthrough time per cycle was measured when a gas containing 11.1 mol% ammonia, 22.2 mol% nitrogen, and 66.7 mol% hydrogen was introduced at a rate of 4 LPM (L / min) and adsorbed using a PSA ammonia adsorber at a pressure of 7 bar, and this is shown in Figure 1.

[0078] Referring to Fig. 1, it can be seen that the adsorbent of Invention Example 1, in which MgCl2 is supported on RGO, has a higher ammonia adsorption performance than the adsorbent of Comparative Example 1, in which MgCl2 is supported on CMS, and that even when the cycle is performed, the breakthrough time does not become shorter, but rather the breakthrough time increases.

Claims

1. An ammonia adsorbent comprising RGO (Reduced Graphene Oxide) supported with MgCl2.

2. In Paragraph 1, The above MgCl2 is an ammonia adsorbent in an amount of 0.01 to 5 weight percent based on the total weight of the adsorbent.

3. In Paragraph 1, The above adsorbent is an ammonia adsorbent additionally supported with a metal halide.

4. In Paragraph 1, The above metal halide is at least one selected from the group consisting of CaCl2, SrCl2, MgBr2, CaBr2 and SrBr2, an ammonia adsorbent.

5. DGO synthesis step for synthesizing DGO (Defected Graphene Oxide) from graphite; RGO synthesis step for synthesizing RGO (Reduced Graphene Oxide) using the above DGO; and A method for manufacturing an ammonia adsorbent, comprising the step of immersing the above RGO in an MgCl2 solution to support MgCl2 on the interface of the above RGO.

6. In Paragraph 5, A method for manufacturing an ammonia adsorbent, wherein the weight of MgCl2 relative to the total weight of the above MgCl2 solution is 0.01 to 5 weight%.

7. In Paragraph 5, A method for manufacturing an ammonia adsorbent, further comprising the step of additionally supporting an RGO loaded with MgCl2 onto a metal halide to support the metal halide.

8. In Paragraph 7, A method for preparing an ammonia adsorbent, wherein the metal halide is at least one selected from the group consisting of CaCl2, SrCl2, MgBr2, CaBr2 and SrBr2.

Images