Molded catalyst for ammonia decomposition and manufacturing method therefor

Abstract

The present invention relates to a molded catalyst for ammonia decomposition and a manufacturing method therefor and, more specifically, to an economical method for manufacturing a molded catalyst for ammonia decomposition and a molded catalyst manufactured thereby, wherein a catalyst carrier is prepared by coating various molded bodies such as beads, pellets, honeycombs, and the like with lanthanum and cerium and then ruthenium is supported on the catalyst carrier to produce an ammonia decomposition catalyst as a catalyst with superior activity in an ammonia decomposition reaction, whereby the strength of the coating can be sufficiently expressed, the catalytic activity can be improved or maintained even with a small amount of a catalytically active material (ruthenium), the loss of a coating solution can be reduced during a catalyst coating process, and the molded catalyst can be manufactured without a separate powder catalyst manufacturing process.

Description

Ammonia decomposition molding catalyst and method for producing the same

[0001] The present invention relates to a molded catalyst for ammonia decomposition and a method for producing the same, and more particularly, to an economical method for producing a molded catalyst for ammonia decomposition, which comprises coating one or more metals or metal oxides on various molded bodies such as beads, pellets, and honeycombs to produce a catalyst carrier, and then supporting a catalytically active substance thereon to produce an ammonia decomposition catalyst, wherein the strength of the coating can be sufficiently expressed, the catalytic activity can be improved or maintained even with a small amount of the catalytically active substance, the loss of a coating solution can be reduced during the catalyst coating process, and the molded catalyst can be produced without a separate powder catalyst production process, and to a molded catalyst produced thereby.

[0002] Hydrogen has attracted significant attention as a next-generation clean energy source due to its high gravimetric energy content and zero carbon emissions. However, hydrogen's low volumetric energy density, low boiling point, and handling (transportation and storage) difficulties have hindered its industrial and commercial application as an energy source.

[0003] These problems can be overcome by using hydrogen carriers that can be easily transported to consumption sites and reformed or decomposed to produce hydrogen on-site. Among various hydrogen carriers, ammonia is recognized as an excellent hydrogen carrier candidate due to its low production cost, high volumetric and gravimetric energy density, ease of liquefaction, clean molecular storage medium, and ability to be catalytically decomposed into carbon-free hydrogen.

[0004] Today, catalytic ammonia decomposition has become a promising approach for hydrogen production, and significant efforts are being made to develop highly efficient catalysts for this reaction. Commonly used ammonia decomposition catalysts typically consist of a catalyst carrier and a catalytically active metal supported on the catalyst carrier's surface. These catalysts are designed and optimized to provide selectivity and reactivity appropriate for the required process.

[0005] Such ammonia decomposition catalysts are manufactured in powder form by mixing a catalyst carrier and a catalytically active metal through various methods such as impregnation, co-precipitation, ion exchange, hydrothermal synthesis, and melting. The manufactured powder catalyst is then manufactured by mixing various additives and extruding it into various shapes through a multi-stage injection molding method. However, the injection molding method is not only very complicated in its manufacturing process, but also uses a large amount of powder catalyst and has difficulties in performing production, installation, and maintenance work due to the large amount of dust generated during the manufacturing process.

[0006] Recently, in order to reduce the pressure drop in the catalyst layer and increase the surface area of ​​the catalyst, a catalyst-containing material is coated on the channel surface inside a ceramic or metal molded body in the shape of a bead or honeycomb using dip coating, wash coating, or spray coating. For these ceramic or metal molded body-based coating catalysts, the adhesion between the catalyst and the molded body is a very important factor, and the adhesion can be determined by the molded body surface treatment method, the catalyst coating solution preparation method, the coating method, the drying and firing methods, etc.

[0007] Korean Patent No. 10-0807730 discloses a method for forming an adhesive layer on the interface between a molded body and a catalyst using atomic vapor deposition (ALD) or chemical vapor deposition (CVD) to form a material identical to the catalyst or a material having the same surface properties as the catalyst as the catalyst, in order to increase the adhesive strength between the molded body and the catalyst. Korean Patent No. 10-1403698 discloses a method for manufacturing a metal molded body catalyst by contacting a mixed solution containing a precursor and a precipitant of a metal catalyst with a metal molded body to form a metal precipitate on the metal molded body, and then heat-treating the metal molded body to uniformly disperse and support metal nanoparticles and enhance the bonding strength between the catalyst support layer and the surface of the metal molded body.

[0008] In addition, Korean Patent Publication No. 2023-0103587 provides a method of evenly distributing a catalyst coating solution on the surface of a molded body by deeply penetrating the catalyst coating solution into the surface of the molded body using an ultrasonic method, and then fixing the catalyst coating solution to the surface of the molded body at a constant and uniform thickness using an air knife combined with an infrared lamp.

[0009] However, these prior technologies have limitations in ease of use and commerciality because they require expensive reaction equipment or must be performed under a vacuum, and there are problems such as difficulty in evenly dispersing the catalyst coating solution on the surface of a molded body to obtain a catalyst coating layer having a uniform and constant thickness, or the coating strength between the catalyst coating layer and the molded body is still weak, and there are problems such as a lot of loss of the catalyst coating solution.

[0010] Due to these issues, when one or more metals or metal oxides are directly coated onto a shaped body such as a bead, pellet, or honeycomb, the coating may not adhere well to the body, or even if it is coated, it may easily detach, resulting in reduced catalyst activity and physical durability. This phenomenon is particularly pronounced when two or more components are chemically bonded to form composite metal oxides or metals directly on the body's surface.

[0011] In order to solve the above-mentioned problem, the present invention provides an economical method for manufacturing a molded catalyst, in which lanthanum and cerium, as catalysts having excellent activity in an ammonia decomposition reaction, are coated on various molded bodies such as beads, pellets, and honeycombs, and then a catalytically active substance is supported thereon to manufacture an ammonia decomposition catalyst, and the lanthanum and cerium are directly formed on the molded body without forming a separate metal oxide or metal powder, while sufficiently exhibiting coating strength, and the catalytic activity can be improved or maintained even with a small amount of the catalytically active substance, and the loss of the catalyst coating liquid can be reduced, and a molded catalyst manufactured by the above-mentioned manufacturing method is proposed.

[0012] [Prior Art Literature]

[0013] [Patent Document]

[0014] (Patent Document 1) Korean Patent No. 10-0807730 (Published: October 1, 2007)

[0015] (Patent Document 2) Korean Patent No. 10-1403698 (Published: February 7, 2013)

[0016] (Patent Document 3) Korean Patent Publication No. 2023-0103587 (Published: July 7, 2023)

[0017] The present invention was created to solve the above-mentioned problem, and the purpose of the present invention is to provide a method for manufacturing a molded catalyst for ammonia decomposition, which can sufficiently exhibit coating strength when coating a coating component containing lanthanum and cerium on various molded bodies such as beads, pellets, and honeycombs, and then supporting a catalytically active substance thereon, and can improve catalytic activity for ammonia decomposition reaction even with a small amount of a catalytically active substance, and can minimize the use of a catalyst coating liquid while reducing the loss of a catalyst coating liquid, and a molded catalyst manufactured thereby.

[0018] In order to solve the above problem, the present invention comprises the steps of: (a) immersing a molded body in a coating solution containing a coating component including lanthanum and cerium and a first additive to form a wet layer containing the coating component on the surface of the molded body; (b) immersing the molded body on which the wet layer has been formed in a fixing solution containing an alkali metal hydroxide dissolved therein to fix the wet layer on the surface of the molded body; (c) heat-treating the molded body on which the wet layer has been fixed on the surface to form a coating layer containing the coating component on the surface of the molded body; (d) supporting ruthenium as a catalytically active material on the coating layer of the molded body; And (e) a step of drying the molded body carrying the catalytically active substance, or drying and calcining the molded body to produce the molded body carrying the catalytically active substance; wherein the first additive is at least one selected from the group consisting of methyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, refined starch, dextrin, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyethylene glycol, and silica sol. A method for producing a molded catalyst for ammonia decomposition is provided.

[0019] As one embodiment of the present invention, the molded body of step (a) is characterized in that it is made of an alumina material.

[0020] In addition, as one embodiment of the present invention, the molded body of step (a) is characterized in that it is surface-treated with an acid and / or a base.

[0021] In addition, as an embodiment of the present invention, the acid used in the surface treatment is at least one selected from the group consisting of HCl, HNO3, H2SO4, HF, H3PO4, and organic acids, and the base is at least one selected from the group consisting of LiOH, NaOH, KOH, NH4OH, and NaBH4.

[0022] In addition, as one embodiment of the present invention, the coating solution of step (a) is characterized in that the first additive is added in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the coating component.

[0023] In addition, as one embodiment of the present invention, the coating solution of step (a) is characterized in that it further includes one or more second additives selected from among polyhydric alcohols, waxes, and lubricants.

[0024] In addition, as one embodiment of the present invention, the coating solution of step (a) is characterized in that the second additive is added in an amount of 5 to 90 parts by volume with respect to 100 parts by volume of the coating component.

[0025] In addition, as one embodiment of the present invention, the fixing solution of step (b) is characterized in that it contains one or more alkali metal hydroxides selected from the group consisting of LiOH, NaOH, and KOH.

[0026] In addition, as one embodiment of the present invention, the step (b) is characterized in that the molded body on which the wet layer is formed is immersed in the fixing solution for 0.5 to 4 hours to fix the wet layer on the surface of the molded body.

[0027] In addition, the present invention provides a molded catalyst for ammonia decomposition, characterized in that ruthenium is supported on a support on which a coating layer containing lanthanum and cerium is formed on an alumina molded body.

[0028] In addition, the present invention provides an ammonia decomposition molding catalyst manufactured by the method for manufacturing an ammonia decomposition molding catalyst of the present invention.

[0029] In addition, the present invention provides an ammonia decomposition method characterized by contacting ammonia with a molded catalyst for ammonia decomposition according to the present invention.

[0030] According to the present invention, in order to manufacture a molded catalyst for ammonia decomposition, a catalyst carrier is manufactured by coating one or more metals or metal oxides on various molded bodies such as beads, pellets, and honeycombs, and then a catalytically active substance is supported thereon to manufacture a molded catalyst for ammonia decomposition, thereby improving or maintaining catalytic activity even with a small amount of a catalytically active substance, and there is an effect of being able to manufacture a molded catalyst for ammonia decomposition without a separate powder catalyst manufacturing process.

[0031] In addition, the present invention has the effect of improving the adhesion between the molded body and the coating layer by adding a first additive or a first additive and a second additive to the coating solution when coating metal oxides or metals on the surface of the molded body as described above, thereby sufficiently exhibiting the mechanical strength of the finally manufactured molded catalyst.

[0032] In addition, the present invention minimizes the use of the coating solution by adding a first additive or a first additive and a second additive to the coating solution when coating metal oxides or metals on the surface of a molded body as described above, and at the same time, the coating solution remaining after use for coating can be reused, and in the process of fixing the coating layer by immersing the coated molded body in a fixing solution, the components included in the coating layer on the surface of the molded body are not eluted into the fixing solution, so that the fixing solution can be reused, and unnecessary material loss can be reduced in the process of manufacturing a molded catalyst, and even if only a small amount of an expensive catalytically active substance and a component constituting the coating layer are used, the catalytic activity can be significantly improved, so that there is an effect that allows for the economical mass production of a molded catalyst for ammonia decomposition.

[0033] Figure 1 is a flow chart schematically illustrating a method for manufacturing a molded catalyst for ammonia decomposition according to one embodiment of the present invention.

[0034] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is well known and commonly used in the art.

[0035] The terms “comprising,” “including,” or “having” used in this specification indicate the presence of features, values, steps, operations, components, parts, or combinations thereof described in the specification, and do not exclude the possibility that other features, values, steps, operations, components, parts, or combinations thereof that are not mentioned may be present or added.

[0036] The reactions and mixing described below can be carried out at room temperature and pressure unless otherwise specified, and can be carried out under typical reaction and mixing conditions without additional additions. However, this should not be interpreted in a way that deviates from matters clearly understood by those skilled in the art.

[0037] The present invention relates to a method for producing a molded catalyst for decomposition of ammonia, comprising the steps of: (a) immersing a molded body in a coating solution containing a coating component including lanthanum and cerium and a first additive to form a wet layer containing the coating component on the surface of the molded body; (b) immersing the molded body on which the wet layer has been formed in a fixing solution containing an alkali metal hydroxide dissolved therein to fix the wet layer on the surface of the molded body; (c) heat-treating the molded body on which the wet layer has been fixed to the surface to form a coating layer containing the coating component on the surface of the molded body; (d) loading ruthenium as a catalytically active material onto the coating layer of the molded body; and (e) drying the molded body on which the catalytically active material is loaded, or drying and calcining the molded body to produce a molded body on which the catalytically active material is loaded. The present invention also relates to a molded catalyst for decomposition of ammonia, which is produced by the method.

[0038] Referring to the attached drawings below, the method for manufacturing a molded catalyst for ammonia decomposition according to the present invention and the molded catalyst for ammonia decomposition manufactured thereby are described in detail.

[0039] Figure 1 is a flow chart schematically illustrating a method for manufacturing a molded catalyst for ammonia decomposition according to one embodiment of the present invention.

[0040] As illustrated in FIG. 1, the method for manufacturing a molded catalyst for ammonia decomposition according to the present invention first immerses a molded body in a coating solution containing a coating component including lanthanum and cerium so that a wet layer containing lanthanum and cerium is formed on the surface of the molded body [step (a)].

[0041] The coating component containing lanthanum and cerium included in the above coating solution may be at least one selected from a carrier material capable of supporting a catalytically active material (ruthenium) or a precursor of the carrier material, and may be a metal or metal oxide of lanthanum and cerium.

[0042] At this time, the content of lanthanum and cerium in the entire coating solution is 1 mmol mL -1100 mmol mL -1 may be, preferably 5 mmol mL -1 10 mmol mL -1 It could be.

[0043] The content of lanthanum and cerium may be 0.2 to 0.5 times the mole number of lanthanum relative to the total mole number of lanthanum and cerium, and preferably 0.25 to 0.45 times.

[0044] The above lanthanum and cerium may be in the form of a metal or metal oxide in the final manufactured catalyst, and are preferably in the form of a metal oxide.

[0045] As the precursor of the above lanthanum or cerium oxide, any one or more of oxides, chlorides, hydroxides, bromides, iodides, nitrates, sulfates, carbonates, acetates, oxalates, fluorides, isopropoxides, and organometallic complexes of lanthanum and cerium can be used.

[0046] In the above coating layer, the coating component may be dissolved or dispersed in a solvent, and the solvent may be used without limitation as long as it is a solvent capable of dissolving or dispersing the coating component. For example, water such as distilled water or purified water, alcohol such as methanol, ethanol, isopropanol, glycol, etc. may be used, and preferably water.

[0047] The above-mentioned wet layer is formed by a dip coating method in which the molded body is immersed in a coating liquid so that the coating liquid penetrates into the inside of the molded body. At this time, dip coatings in which the molded body is dipped in the coating liquid to form a wet layer (200) having a coating liquid component on the surface of the molded body can be controlled by adjusting the coating temperature and time depending on the type, concentration, and amount of the coating liquid and the molded body. For example, the temperature of the coating liquid during the dipping can be 20 to 40°C, and the time can be performed for 0.5 to 4 hours. In addition, several coating processes can be repeatedly performed so that the coating layer can be formed on the surface of the molded body with a desired thickness and strong adhesive strength.

[0048] Additionally, the coating solution may include a first additive to bind the coating component to the surface of the molded article and provide cohesion and viscosity. The first additive prevents the coating component contained in the wet layer formed on the surface of the molded article in the fixing step described below from dissolving into the fixing solution.

[0049] The above first additive can be applied without limitation as long as it is an organic binder that can improve the adhesion of the coating material to the surface of the molded body and prevent the coating material in the wet layer from being eluted into the fixing reaction liquid during the fixing step, and for example, it can be at least one selected from the group consisting of methyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, refined starch, dextrin, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyethylene glycol, and silica sol, and in terms of forming a uniform wet layer, it can be preferably at least one selected from the group consisting of methyl cellulose, polyvinyl alcohol, polyethylene glycol, and silica sol, and more preferably, it can be methyl cellulose and / or polyvinyl alcohol.

[0050] When the molded body having the wet layer formed by the first additive is immersed in a fixing solution to perform a fixing process, the coating components of the wet layer are not eluted into the fixing solution, thereby preventing loss of the coating components. In addition, the fixing solution may not be contaminated, thereby making the manufacturing method of the molding catalyst economical and simple.

[0051] The first additive may be added to the coating solution in an amount of 0.5 to 10 parts by weight, preferably 1 to 3 parts by weight, relative to 100 parts by weight of the coating component. If the first additive is contained in an amount of less than 0.5 parts by weight relative to 100 parts by weight of the coating component, the function of the binder may be difficult, and if it exceeds 10 parts by weight relative to 100 parts by weight of the catalyst carrier component, problems may occur in the reduction of the content of the coating component and the fixation step due to the excessive amount of the first additive.

[0052] Meanwhile, the coating solution may further include a second additive including one or more selected from among polyhydric alcohols, for example, glycerol, ethylene glycol, propylene glycol, etc., or waxes and lubricants, in order to suppress shrinkage or peeling of the coating layer that may occur during the drying process described below.

[0053] The second additive may be added in an amount of 5 to 90 parts by volume based on 100 parts by volume of the coating component, and the second additive in the above content range acts to form a uniform coating layer without deteriorating the catalyst properties.

[0054] The molded body coated with the above coating solution can use molded bodies of various shapes depending on the reaction to which the molding catalyst is applied, and specifically, it can be in the shape of a bead, pellet, felt, mat, mesh, foam, foil, honeycomb, pin, etc., and preferably, it can be in the shape of a bead or a honeycomb. In addition, it is preferable that the molded body material is alumina.

[0055] In addition, the molded body may be subjected to chemical surface treatment using a surface treatment agent such as an acid and / or a base to uniformly disperse the coating component on the surface by forming a polar functional group such as a hydroxyl group and an unstable surface state. At this time, the acid that can be used for the surface treatment of the molded body may be at least one selected from the group consisting of HCl, HNO3, H2SO4, HF, H3PO4, and an organic acid, and the organic acid is not limited thereto, but may be, for example, acetic acid, formic acid, lactic acid, citric acid, acrylic acid, sulfonic acid, carboxylic acid, and the like. The base may be at least one selected from the group consisting of a base solution containing LiOH, NaOH, KOH, NH4OH, and NaBH4, and may be preferably KOH or NH4OH.

[0056] As described above, the present invention utilizes a dip coating method to form a coating layer on the surface of a molded article. This allows for the formation of a uniform and thin coating layer on the surface of even complexly structured articles, and facilitates the control of the coating amount. Furthermore, the use of the first and second additives minimizes coating liquid loss while simultaneously enabling continuous use of the coating liquid, thereby enabling the economical mass production of molded catalysts.

[0057] In addition, in the present invention, the strength of the coating layer is increased by removing the excess coating liquid of the wet layer remaining on the surface of the molded body after immersing the coating liquid, and in order to secure an appropriate thickness of the coating liquid layer, the strength and time of the air blow for removing the excess coating liquid can be controlled, or the viscosity of the coating liquid can be controlled according to the additive content.

[0058] Thereafter, the molded body having a wet layer formed by the dip coating is immersed in a fixing solution containing dissolved alkali metal hydroxide to fix the wet layer [step (b)].

[0059] The step (b) above can strongly bind the coating component contained in the wet layer to the surface of the molded body by fixing the wet layer on the surface of the molded body created in step (a) using a fixing solution.

[0060] As the above-mentioned fixing solution, an alkali metal hydroxide that enables a wet layer of a coating component contained in a coating solution to be fixed to the surface of a molded body can be applied without limitation as long as it is dissolved in a solvent, and specifically, the alkali metal hydroxide may be one or more alkali metal hydroxides selected from the group consisting of LiOH, NaOH, and KOH, and may be preferably NaOH and / or KOH in terms of ease of fixing and cost.

[0061] The solvent of the above-mentioned fixing solution may be used without limitation as long as it is a solvent capable of dissolving alkali metal hydroxides such as LiOH, NaOH, and KOH, and examples thereof include water such as distilled water or purified water; alcohol such as methanol, ethanol, and isopropanol; glycol, and the like, and water is preferred.

[0062] The concentration of alkali metal hydroxide in the above fixing solution is 0.5 mol L -1 4 mol L -1 may be, preferably 0.75 mol L -1 1.25 mol L -1 It could be.

[0063] At this time, the fixation can be performed by immersing the molded body on which the wet layer is formed in a fixation solution at 20 to 60°C for 0.5 to 4 hours, preferably 1 to 3 hours. When the fixation is performed within the temperature range and for the time, a coating layer with a uniform and strong bond is formed, and the problem of the wet layer being excessively exposed to the reaction solution, causing the components contained in the wet layer to be dissolved, preventing the formation of the coating layer from proceeding well, and the contamination of the reaction solution, which makes it impossible to reuse the product, can be prevented.

[0064] Thereafter, the molded body to which the above wet layer has been fixed is heat-treated to form a carrier coating layer on the surface of the molded body [step (c)].

[0065] In the above step (c), the molded body, which has been immersed in the fixing solution in the above step (b) and has undergone fixation of the wet layer, is separated from the fixing solution and the fixed wet layer is heat-treated. The heat treatment may further include a drying step in detail. That is, the solvent in the fixing solution can be completely removed through drying. The drying may be performed, for example, at 40 to 120°C for 4 to 48 hours, and may be performed using a conventional method such as hot air, constant temperature and humidity, etc. When the drying temperature is within the above range, the fixed wet layer can be sufficiently dried, and the detachment of the dried wet layer due to excessive drying or a rapid reaction of the components contained in the wet layer can be prevented.

[0066] Thereafter, the heat treatment of the above-mentioned molded body can be varied in consideration of the unique glass transition temperature of the molded body or catalyst carrier component, but in order to obtain a molded body having a support coating layer formed without cracks, it can be preferably fired at 350 to 700°C for a predetermined time in an oxidizing atmosphere. The heat treatment time can vary depending on conditions such as the firing temperature, coating amount, size and quantity of the molded body, but can be, for example, 2 to 6 hours.

[0067] If the heat treatment temperature is less than 350°C, a problem may arise in which the additives contained in the dried wet layer are not properly removed due to the low sintering temperature, and if it exceeds 700°C, excessive deformation of the coating layer and the shape of the molded body may occur due to the excessive sintering temperature. In addition, rapid temperature changes during the heat treatment process cause rapid combustion and oxidation of the additives, which causes cracks and detachment in the formation of the coating layer, significantly reducing the strength of the coating layer. Therefore, it is preferable to manufacture by gradually increasing the temperature by 5°C or less per minute.

[0068] Thereafter, ruthenium is loaded as a catalytically active material on the coating layer of the molded body [step (d)].

[0069] In the above step (d), any method that can support ruthenium on the molded body on which the coating layer is formed can be applied without limitation, and specifically, it can be a hydrothermal synthesis method, a co-precipitation method, an impregnation method, a mechanical mixing method, a deposition method, etc., and preferably, it can be an impregnation method, etc.

[0070] In one embodiment, the impregnation among the above-mentioned supporting methods may be performed by dissolving a catalytically active substance or a precursor thereof in a solvent, then evenly dispersing the solution on a carrier coating layer, and evaporating the solvent. At this time, the solvent may be any solvent that can evenly disperse the catalytically active substance precursor, and examples thereof include water, methanol, ethanol, propanol, butanol, acetone, and the like, and the content thereof may be used without limitation as long as it can evenly disperse the catalytically active substance.

[0071] The content of the ruthenium to be supported varies depending on the reaction applied, but may be 0.1 to 40 wt%, and preferably 0.1 to 10 wt%, based on the total weight of the molded body.

[0072] Thereafter, the molded body carrying the catalytically active material is dried or dried and fired to manufacture a molded body carrying the catalytically active material [step (e)].

[0073] The drying in the above step (e) can be performed at 50 to 120°C for 2 to 48 hours, and can be performed using a conventional method such as an oven, hot air, or constant temperature and humidity.

[0074] Although it may vary depending on the situation, if the drying temperature is below 50°C, the solvent used in the deposition process cannot be sufficiently removed due to the low drying temperature, and if it exceeds 120°C, the solvent used in the deposition process may rapidly evaporate due to the excessive drying temperature, causing the coating layer to collapse, so it is desirable to maintain the above temperature range.

[0075] The above-described dried molded body can be calcined. The calcination can be performed at a temperature of 300 to 500°C for a predetermined period of time in an oxidizing atmosphere, preferably to obtain a molded catalyst without cracking of the catalyst. The calcination time may vary depending on conditions such as the calcination temperature, the amount of support, the size and quantity of the molded body, etc., but may be, for example, 1 to 4 hours.

[0076] The above-mentioned sintering temperature range is desirable to avoid problems such as insufficient stabilization of the catalytically active material due to low sintering temperatures, or poor dispersion of the catalytically active ingredient material and deformation of the molded body due to high sintering temperatures. In addition, rapid temperature changes during the sintering process can cause cracks and pores in the molded body and the coating layer formed on the surface of the molded body, significantly reducing strength. Therefore, it is desirable to manufacture the molded body by gradually increasing the temperature at a rate of 10°C or less per minute.

[0077] In addition, the present invention provides a molded catalyst for ammonia decomposition, characterized in that it is manufactured by a manufacturing method including: (a) a step of immersing a molded body in a coating solution containing a coating component including lanthanum and cerium and a first additive to form a wet layer containing the coating component on the surface of the molded body; (b) a step of immersing the molded body on which the wet layer has been formed in a fixing solution containing an alkali metal hydroxide dissolved therein to fix the wet layer on the surface of the molded body; (c) a step of heat-treating the molded body on which the wet layer has been fixed to the surface to form a coating layer containing the coating component on the surface of the molded body; (d) a step of supporting ruthenium as a catalytically active material on the coating layer of the molded body; and (e) a step of drying the molded body on which the catalytically active material is supported, or drying and calcining the molded body to produce a molded body on which the catalytically active material is supported.

[0078] Since the details of the manufacturing method according to steps (a) to (e) above are the same as those described above, repeated description is omitted.

[0079] The molded catalyst for ammonia decomposition manufactured by the manufacturing method according to the present invention can sufficiently exhibit coating strength by improving the adhesion between the molded body and the coating layer, and the uniformity of the coating layer is improved while reducing the loss of the catalyst coating liquid through the use of the first additive and / or the second additive. In addition, the molded catalyst for ammonia decomposition manufactured by the manufacturing method according to the present invention can significantly improve the ammonia decomposition catalytic activity even with a small amount of the catalytically active substance by supporting ruthenium as a catalytically active substance on the coating layer.

[0080] In addition, the present invention provides an ammonia decomposition molded catalyst characterized in that ruthenium is supported on a support having a coating layer containing lanthanum and cerium formed on an alumina molded body, or an ammonia decomposition molded catalyst manufactured by the method for manufacturing an ammonia decomposition molded catalyst of the present invention.

[0081] In addition, the present invention provides an ammonia decomposition method characterized by contacting ammonia with a molded catalyst for ammonia decomposition according to the present invention.

[0082] In the ammonia decomposition method of the present invention, the gas containing ammonia to be treated is not particularly limited, but may be not only ammonia gas or ammonia-containing gas, but also gas containing a substance that generates ammonia through thermal decomposition, such as urea.

[0083] Additionally, the gas containing ammonia may contain other components as long as they do not poison the catalyst. The reaction temperature is preferably 300 to 600°C. The reaction pressure is 0.002 to 2 MPa in absolute pressure, more preferably 0.004 to 1 MPa.

[0084]

[0085] Hereinafter, the present invention will be described in more detail by way of preferred embodiments to aid understanding; however, the following embodiments are merely illustrative of the present invention, and the scope of the present invention is not limited to the following embodiments.

[0086]

[0087] <Example 1>

[0088] A solution of coating components, 4 mmol (1.7544 g) of Ce(NO3)3ㆍ6H2O (Sigma, 99%) and 2 mmol (0.8661 g) of La(NO3)3ㆍ6H2O (Sigma, 99%), was dissolved in 10 mL of deionized water to prepare a coating solution. 1 g of methyl cellulose as a first additive was dissolved in 10 mL of deionized water and 30 mL of ethanol (99.9%), and 11 mL of the solution was added to the solution of coating components, and 5 mL of glycerol was additionally mixed to prepare a coating solution.

[0089] Afterwards, 15 g of alumina beads (average diameter 3 mm) were dip-coated in the prepared coating solution at room temperature for 60 minutes, and then fixed by immersing in a fixing solution of 20 mL of 1 M KOH at room temperature for 30 minutes.

[0090] After fixation, the fixed alumina beads were dried in an oven at 60°C for 24 hours, and then heat-treated at 600°C (heating rate, 5°C / min) for 6 hours.

[0091] Afterwards, 12 g of heat-treated alumina beads were suspended in a solution of 1.5 wt.% Ruthenium nitrosyl nitrate solution (15.2586 mL) diluted with 50 mL of deionized water, and the solvent was evaporated at 80°C and 400 mbar. The resulting solution was dried in an oven at 100°C for 24 hours and calcined at 350°C (heating rate, 10°C / min) for 2 hours to produce a Ru / La-Ce / Al2O3 molded catalyst.

[0092]

[0093] <Examples 2 to 4>

[0094] A Ru / La-Ce / Al2O3 molded catalyst was manufactured using the same method as Example 1, except that fixation was performed by immersion for 1 hour, 2 hours, and 3 hours, respectively, for the fixation time.

[0095]

[0096] <Examples 5 to 7>

[0097] A Ru / La-Ce / Al2O3 molded catalyst was manufactured using the same method as Example 1, except that polyvinyl alcohol (manufacturer: Sigma Aldrich, average molecular weight: 89,000 to 98,000), polyethylene glycol (manufacturer: Sigma Aldrich, average molecular weight: 400), and silica sol (manufacturer: Sigma Aldrich, model name: Ludoxⓡ-AS40) were used instead of methyl cellulose as the first additive.

[0098]

[0099] <Example 8>

[0100] A Ru / La-Ce / Al2O3 molded catalyst was manufactured using the same method as in Example 1, except that the surface was treated by immersing the alumina beads in 1 M KOH for 1 hour before immersing them in the coating solution.

[0101]

[0102] <Comparative Example 1>

[0103] A Ru / Al2O3 molded catalyst was prepared by suspending 12 g of alumina beads (average diameter 3 mm) in a solution diluted with 15.2586 mL of a 1.5 wt% Ruthenium nitrosyl nitrate solution in 50 mL of deionized water, evaporating the solvent at 80°C and 400 mbar, drying in an oven at 100°C for 24 hours, and calcining at 350°C (heating rate, 10°C / min) for 2 hours.

[0104]

[0105] Comparative Example 2

[0106] A solution was prepared by dissolving 3.202 g La(NO3)3ㆍ6H2O and 6.4865 g Ce(NO3)3ㆍ6H2O in 100 mL of deionized water, suspending 15 g of alumina beads (average diameter 3 mm) and evaporating the solvent at 80°C and 400 mbar. The molded body containing the coating component was dried in an oven at 100°C for 24 hours and then heat-treated at 500°C for 3 hours. Afterwards, 12 g of heat-treated alumina beads were suspended in a solution of 1.5 wt.% Ruthenium nitrosyl nitrate solution (15.2586 mL) diluted with 50 mL of deionized water, and the solvent was evaporated at 80°C and 400 mbar. The resulting solution was dried in an oven at 100°C for 24 hours and calcined at 350°C (heating rate, 10°C / min) for 2 hours to produce the Ru / La-Ce / Al2O3 molded catalyst.

[0107]

[0108] <Comparative Example 3>

[0109] A solution of coating components, 4 mmol (1.7544 g) of Ce(NO3)3ㆍ6H2O (Sigma, 99%) and 2 mmol (0.8661 g) of La(NO3)3ㆍ6H2O (Sigma, 99%), was dissolved in 10 mL of deionized water to prepare a coating solution. A solution of 1 g of methyl cellulose as a first additive in 10 mL of deionized water and 30 mL of ethanol (99.9%) was taken as an 11 mL aliquot and added to the solution of coating components, and an additional 5 mL of glycerol was added and mixed to prepare a coating solution.

[0110] Afterwards, 15 g of alumina beads (average diameter 3 mm) were dip-coated on the prepared coating solution at room temperature for 60 minutes, and then the alumina beads were dried in an oven at 60°C for 24 hours, followed by heat treatment at 600°C (heating conditions, 5°C / min) for 6 hours.

[0111] Afterwards, 12 g of heat-treated alumina beads were suspended in a solution of 1.5 wt.% Ruthenium nitrosyl nitrate solution (15.2586 mL) diluted with 50 mL of deionized water, and the solvent was evaporated at 80°C and 400 mbar. The resulting solution was dried in an oven at 100°C for 24 hours and calcined at 350°C (heating rate, 10°C / min) for 2 hours to produce a Ru / La-Ce / Al2O3 molded catalyst.

[0112]

[0113] <Comparative Example 4>

[0114] A Ru / La-Ce / Al2O3 molded catalyst was prepared in the same manner as in Example 1, except that the fixation step was performed using 20 mL of deionized water instead of the fixation solution, in the same manner as in Example 3.

[0115]

[0116] Comparative Example 5

[0117] A Ru / La-Ce / Al2O3 molded catalyst was manufactured in the same manner as in Example 3, except that NH4OH was used instead of KOH as the fixing solution.

[0118]

[0119] Below, Table 1 shows the conditions for manufacturing the molding catalysts of Examples 1 to 11 and Comparative Examples 1 to 5.

[0120]

[0121] <Experimental Example 1: Performance Measurement of Ammonia Decomposition Catalyst>

[0122] The ammonia decomposition reaction was performed using the molded catalysts manufactured in the examples and comparative examples, and the ammonia conversion rate was measured. The measurement was performed at atmospheric pressure and an ammonia space velocity of 3000 mL / g. cat.Hydrogen, nitrogen, and unreacted ammonia gas generated after the ammonia decomposition reaction were measured using gas chromatography under the conditions of / h and reaction temperatures of 350 ℃, 400 ℃, 450 ℃, 500 ℃, and 550 ℃, and the ammonia conversion rate was calculated based on the equation below.

[0123]

[0124]

[0125] <Influence of molded body coating method>

[0126] In order to see the effect according to the molded body coating method, the catalysts manufactured in the manufacturing methods of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, which used the same manufacturing method except that the molded body was not coated or only the coating method was different, were applied to the ammonia conversion reaction in Experimental Example 1, and the results are shown in Table 2 below.

[0127]

[0128] Referring to Table 2, it can be confirmed that the molded catalyst manufactured in Example 1 showed a higher ammonia conversion rate than Comparative Example 1 in which the molded body was not coated with lanthanum and cerium, indicating that coating the molded body with lanthanum and cerium has advantageous ammonia decomposition catalytic activity. In addition, in the case of Example 1 using the dip coating method, the amount of precursors of cerium and lanthanum included in the coating solution was only about 27% of that in Comparative Example 2 using the impregnation method, and since the dip coating method was also used when forming the coating layer (less than 10% of the coating solution was consumed per coating), the amount of cerium and lanthanum used was significantly lower than that of the molded catalyst of Comparative Example 2, so the specific surface area of ​​the La-Ce coating layer will have an absolutely higher value in Comparative Example 2. Therefore, when the same amount of Ru is supported, it is expected that Ru will be better dispersed in Comparative Example 2, resulting in a higher ammonia conversion rate. However, the experimental results showed that Example 1 showed a higher conversion rate. From this, it can be confirmed that the method of the present invention can manufacture a highly efficient catalyst through the synergistic effect of the mutual bonding of the composite oxide layer of La-Ce and alumina while reducing the amount of a relatively expensive coating component such as La-Ce.

[0129] In addition, even if a La-Ce coating layer is formed on a molded body by a dip coating method, it can be seen that if a fixation step is not performed as in Comparative Example 3, the coating material is detached, resulting in a decrease in catalytic activity.

[0130]

[0131] <Influence of the type of fixative solution>

[0132] In order to see the effect according to the type of fixing solution, the catalysts manufactured in the manufacturing methods of Example 3, Comparative Example 3, Comparative Example 4, and Comparative Example 5, which used the same manufacturing method except that only the fixing solution was changed, were applied to the ammonia conversion reaction in Experimental Example 1, and the results are shown in Table 3 below.

[0133]

[0134] Referring to Table 3, it can be confirmed that Example 3, which used an alkali metal hydroxide such as KOH as the fixing solution of the present invention, showed the highest activity. In Comparative Example 4, which used water without using the fixing solution of the present invention, and Comparative Example 5, which used ammonia water, it can be confirmed that the reaction activity in the ammonia decomposition reaction was lower than when the alkali metal hydroxide was used. In addition, it can be confirmed that the reaction activity in the ammonia decomposition reaction was low even in Comparative Example 3, which did not perform the fixing step. This confirms that a fixing step using a fixing solution containing an alkali metal hydroxide is necessary in the production of a molded catalyst for ammonia decomposition.

[0135]

[0136] <Effect of fixation processing time>

[0137] In order to see the effect according to the fixation treatment time, the catalysts manufactured in the manufacturing methods of Examples 1, 2, 3, 4 and Comparative Example 1, which used the same manufacturing method except that only the fixation time was changed, were applied to the ammonia conversion reaction in Experimental Example 1, and the results are shown in Table 4 below.

[0138]

[0139] Referring to Table 4, it was found that the catalysts manufactured in the manufacturing methods of Examples 1 to 4 in which fixation was performed showed a large difference in ammonia conversion rate compared to the catalyst manufactured in the manufacturing method of Comparative Example 1 in which fixation was not performed. This shows that even if a coating layer is formed as described above, if the fixation step is not performed, the coating material is detached, resulting in a decrease in catalytic activity. In addition, it was found that the ammonia decomposition catalytic activity was further improved in the catalyst in which fixation was performed for 1 to 2 hours.

[0140]

[0141] <Effect of the first additive type>

[0142] In order to see the effect according to the type of the first additive, the catalysts manufactured in the manufacturing methods of Examples 1, 5, 6, and 7, which used the same manufacturing method except that only the first additive was changed, were applied to the ammonia conversion reaction in Experimental Example 1, and the results are shown in Table 5 below.

[0143]

[0144] Referring to Table 5, in addition to methyl cellulose as the first additive, examples using polyvinyl alcohol, polyethylene glycol, and silica sol also showed improved ammonia decomposition catalytic activity. This indicates that even when polyvinyl alcohol, polyethylene glycol, and silica sol were used, the coating components were not eluted during the fixation stage, allowing the catalytically active substance to be sufficiently supported in the coating layer.

[0145]

[0146] <Effect of pretreatment of molded body>

[0147] In order to see the effect depending on the presence or absence of pretreatment of the molded body, the catalysts manufactured in the manufacturing methods of Examples 1 and 8, which used the same manufacturing method except that only the presence or absence of pretreatment of the molded body was different, were applied to the ammonia conversion reaction in Experimental Example 1, and the results are shown in Table 6 below.

[0148]

[0149] Referring to Table 6, the molded catalyst of Example 8, which was surface-treated in advance with 1 M KOH, showed a significantly higher ammonia conversion rate at a low temperature of 350°C, which was approximately 1.45 times higher than the molded catalyst of Example 1, which was not surface-treated. This shows that treating the surface of the molded body with acid or base in advance during the production of the molded catalyst can improve the ammonia decomposition catalytic activity.

[0150]

[0151] While the present invention has been described above with reference to the attached drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent embodiments are possible. Accordingly, the technical protection scope of the present invention is defined by the following claims and their equivalents, and is not limited to the specific embodiments described herein.

[0152]

[0153] The present invention relates to a molded catalyst for ammonia decomposition and a method for producing the same, which can improve or maintain catalytic activity even with a small amount of a catalytically active substance, can produce a molded catalyst for ammonia decomposition without a separate powder catalyst production process, can sufficiently exhibit the mechanical strength of the final molded catalyst by improving the adhesion between the molded body and the coating layer, and can reduce unnecessary material loss in the process of producing the molded catalyst by enabling the reuse of the molded body coating solution and the fixing solution, and can thus be widely used in industrial fields requiring ammonia catalytic decomposition technology.

Claims

1. (a) A step of immersing a molded body in a coating solution containing a coating component including lanthanum and cerium and a first additive to form a wet layer containing the coating component on the surface of the molded body; (b) a step of immersing the molded body on which the above wet layer is formed in a fixing solution containing dissolved alkali metal hydroxide to fix the wet layer on the surface of the molded body; (c) a step of heat-treating a molded body with a wet layer fixed on the surface to form a coating layer containing the coating component on the surface of the molded body; (d) a step of supporting ruthenium as a catalytically active material on the coating layer of the molded body; and (e) a step of drying a molded body containing a catalytically active material, or manufacturing a molded body containing a catalytically active material by drying and calcining; including, A method for producing a molding catalyst for ammonia decomposition, characterized in that the first additive is at least one selected from the group consisting of methyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, refined starch, dextrin, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyethylene glycol, and silica sol.

2. In paragraph 1, The molded body of step (a) above is: A method for manufacturing a molded catalyst for ammonia decomposition, characterized in that it is made of alumina material.

3. In paragraph 1, The molded body of step (a) above is: A method for producing a molded catalyst for ammonia decomposition, characterized in that the surface is treated with an acid and / or a base.

4. In paragraph 3, A method for producing a molded catalyst for ammonia decomposition, characterized in that the acid is at least one selected from the group consisting of HCl, HNO3, H2SO4, HF, H3PO4 and organic acids, and the base is at least one selected from the group consisting of LiOH, NaOH, KOH, NH4OH and NaBH4.

5. In paragraph 1, The coating solution of step (a) above, A method for producing a molding catalyst for ammonia decomposition, characterized in that the first additive is added in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the coating component.

6. In paragraph 1, The coating solution of step (a) above, A method for producing a molding catalyst for ammonia decomposition, characterized in that it further comprises at least one second additive selected from among polyhydric alcohols, waxes, and lubricants.

7. In paragraph 6, The coating solution of step (a) above, A method for producing a molding catalyst for ammonia decomposition, characterized in that the second additive is added in an amount of 5 to 90 parts by volume with respect to 100 parts by volume of the coating component.

8. In paragraph 1, The fixing solution of step (b) above is A method for producing a molded catalyst for ammonia decomposition, characterized in that it comprises at least one alkali metal hydroxide selected from the group consisting of LiOH, NaOH and KOH.

9. In paragraph 1, Step (b) above, A method for manufacturing a molded catalyst for ammonia decomposition, characterized in that the molded body on which the above-mentioned wet layer is formed is immersed in the above-mentioned fixing solution for 0.5 to 4 hours to fix the wet layer on the surface of the molded body.

10. A molded catalyst for ammonia decomposition, characterized in that ruthenium is supported on a support on which a coating layer containing lanthanum and cerium is formed on an alumina molded body.

11. An ammonia decomposition molding catalyst characterized by being manufactured by a method for manufacturing an ammonia decomposition molding catalyst according to any one of claims 1 to 9.

12. In the ammonia decomposition method An ammonia decomposition method characterized by contacting ammonia with a molded catalyst for ammonia decomposition manufactured by a manufacturing method according to any one of claims 1 to 9 or a molded catalyst for ammonia decomposition according to claim 10.

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