Catalyst for ammonia decomposition reaction with improved catalyst stability and hydrogen production method using same

Abstract

The present invention relates to a catalyst for an ammonia decomposition reaction and a hydrogen production method using same. More specifically, the present invention relates to: a catalyst for an ammonia decomposition reaction which, by containing cesium and cerium in a cobalt-molybdenum composite nitride, exhibits excellent catalytic activity in the ammonia decomposition reaction and thus enables an improved ammonia conversion rate, and which shows minimal degradation in activity even after high-temperature and long-duration reactions, offering excellent long-term stability; and a hydrogen production method using the catalyst.

Description

Catalyst for ammonia decomposition reaction with improved catalytic stability and method for producing hydrogen using the same

[0001] The present invention relates to a catalyst for an ammonia decomposition reaction and a method for producing hydrogen using the same, and more specifically, to a catalyst for an ammonia decomposition reaction having improved catalyst stability, which can improve the ammonia conversion rate in an ammonia decomposition reaction and exhibit long-term stability by suppressing catalyst deactivation, and a method for producing hydrogen using the same.

[0002] With climate change intensifying, hydrogen energy is attracting attention worldwide as an eco-friendly alternative to fossil fuels. To commercialize hydrogen energy, the development of technologies for safely and efficiently storing and transporting hydrogen is crucial. While various methods exist for storing hydrogen, methods utilizing hydrogen storage materials capable of reversibly storing and releasing hydrogen are expected to be promising as hydrogen storage media for fuel cell vehicles.

[0003] One way to efficiently store and transport hydrogen is to use ammonia as a hydrogen storage and supply source. Because the process of decomposing ammonia into hydrogen and nitrogen is endothermic, energy is required to produce the products. Conventional catalytic decomposition reactions require a large amount of heat to produce useful amounts of hydrogen gas, making hydrogen production expensive.

[0004] 2NH3→ 3H2+ N2 (endothermic reaction)...(1)

[0005] A catalyst for ammonia decomposition reaction is a catalyst that decomposes ammonia into nitrogen and hydrogen. In the past, when attempting to obtain high-purity hydrogen using ammonia decomposition catalysts proposed so far, the conversion rate was low, or catalysts that increased the conversion rate by increasing the reaction activity tended to have an excessive decrease in catalytic activity as the reaction time passed.

[0006] In accordance with such circumstances, the present invention aims to propose a novel ammonia decomposition catalyst having a high conversion rate from ammonia to nitrogen and hydrogen, while also having high stability.

[0007] As a prior art, first, European Patent Publication No. 2612706 relates to an ammonia oxidation / decomposition catalyst, and more specifically, a technology is presented regarding a catalyst that can reduce the cost of producing hydrogen by utilizing the heat generated in the ammonia oxidation reaction in the ammonia decomposition reaction, and which includes the precious metal ruthenium as a catalytically active component and lanthanum oxide and / or cerium oxide as a catalyst support.

[0008] In addition, Japanese Patent Application Laid-Open No. 2011-224556 relates to a catalyst for ammonia decomposition, a method for producing the catalyst, and a method for producing hydrogen using the catalyst. More specifically, a technology is presented regarding a catalyst that exhibits high activity for an ammonia decomposition reaction and can efficiently decompose ammonia into hydrogen and nitrogen, the catalyst including a Group 8 metal to which ruthenium belongs as a catalyst component, and including lanthanum oxide and / or cerium oxide as a catalyst support component.

[0009] However, these catalysts are precious metal catalysts based on ruthenium and other materials, and their rarity and high cost have limited their application to large-scale processes.

[0010] Accordingly, the inventors of the present invention, while studying a non-precious metal catalyst for ammonia decomposition reaction, confirmed that a catalyst for ammonia decomposition reaction containing a new type of composite nitride containing cerium and cesium in a cobalt and molybdenum composite nitride exhibited superior catalytic activity compared to existing catalysts and long-term stability that maintained activity even after a long period of time, thereby completing the present invention.

[0011] [Prior Art Literature]

[0012] [Patent Document]

[0013] (Patent Document 1) European Patent Publication No. 2612706 (Published: July 10, 2013)

[0014] (Patent Document 2) Japanese Patent Application Laid-Open No. 2011-224556 (Published: November 10, 2011)

[0015] The main purpose of the present invention is to solve the above-described problems, and to provide a catalyst for ammonia decomposition reaction that has high activity in ammonia decomposition reaction and can maintain activity for a long period of time, and a method for producing hydrogen using the same.

[0016] In order to achieve the above purpose, one embodiment of the present invention provides a catalyst for ammonia decomposition reaction with improved catalytic stability, characterized in that cesium and cerium are contained in a cobalt and molybdenum composite nitride.

[0017] In a preferred embodiment of the present invention, the cesium may be contained in an amount of 0.001 to 0.05 mol per 1 mol of the cobalt and molybdenum composite nitride.

[0018] In a preferred embodiment of the present invention, the cerium may be contained in an amount of 0.01 to 0.4 mol per 1 mol of the cobalt and molybdenum composite nitride.

[0019] In a preferred embodiment of the present invention, the cobalt and molybdenum composite nitride may be characterized in that cobalt is contained in an amount of 0.5 to 1.5 moles per mole of molybdenum.

[0020] Another embodiment of the present invention provides a method for producing a catalyst for ammonia decomposition reaction with improved catalytic stability, characterized by comprising the steps of: (a) mixing a cobalt precursor, a molybdenum precursor, a cesium precursor, and a cerium precursor; (b) drying the mixture of step (a); and (c) nitriding the dried mixture of step (b) with a nitrogen source to produce a cobalt and molybdenum composite nitride containing cesium and cerium.

[0021] In another preferred embodiment of the present invention, it may be characterized by including a step of maturing the mixture of step (a) after step (a).

[0022] In another preferred embodiment of the present invention, the maturation may be characterized in that it is performed at 25°C to 100°C for 0.1 hour to 10 hours.

[0023] In another preferred embodiment of the present invention, the step (b) may further comprise a step of calcining after drying.

[0024] In another preferred embodiment of the present invention, the firing may be characterized by performing a first firing at 100°C to 400°C, followed by a second firing at 400°C to 700°C.

[0025] In another preferred embodiment of the present invention, step (a) may be characterized by mixing a cobalt precursor, a molybdenum precursor, a cesium precursor, and a cerium precursor using solvent-depleted milling.

[0026] In another preferred embodiment of the present invention, the nitriding treatment in step (c) may be characterized in that it is performed at 600°C to 800°C.

[0027] In another preferred embodiment of the present invention, the nitrogen source may be characterized by being at least one selected from the group consisting of ammonia, sodium cyanide, potassium cyanide, urea, and melamine.

[0028] Another embodiment of the present invention provides a method for producing hydrogen from ammonia, characterized in that a cobalt and molybdenum composite nitride containing cesium and cerium is brought into contact with a gas containing ammonia to cause an ammonia decomposition reaction.

[0029] In another preferred embodiment of the present invention, the contact of the ammonia and the cobalt and molybdenum composite nitride containing cesium and cerium may be performed at 300°C to 600°C.

[0030] The catalyst for ammonia decomposition reaction according to the present invention contains cesium and cerium in a cobalt and molybdenum composite nitride, thereby exhibiting excellent catalytic activity in ammonia decomposition reaction, and suppressing deactivation of the catalyst even after a high temperature and long-term reaction, so that the activity does not decrease significantly, resulting in excellent long-term stability of the catalyst.

[0031] In addition, the method for manufacturing a catalyst for ammonia decomposition reaction according to the present invention can reduce the time and cost required for drying the solvent by minimizing the use of solvent, facilitate mass production of the catalyst, and also manufacture the catalyst using solvent-depleted milling that can minimize the decrease in catalyst performance, thereby having the effect of enabling mass production on a commercial scale without deterioration in catalyst activity.

[0032] FIG. 1 is a graph showing the results of measuring the ammonia conversion rate of catalysts manufactured in Manufacturing Examples 1 to 7 according to the present invention. FIG. 1(a) is a graph showing the results of measuring the ammonia conversion rate of catalysts manufactured in Manufacturing Examples 1 to 4, and FIG. 1(b) is a graph showing the results of measuring the ammonia conversion rate of catalysts manufactured in Manufacturing Examples 5 to 7.

[0033] Figure 2 is a graph showing the results of measuring the ammonia conversion rate of the catalysts manufactured in Manufacturing Examples 5 and 8 to 11 according to the present invention.

[0034] FIG. 3 is a graph showing the results of measuring the ammonia conversion rate of the catalysts manufactured in Manufacturing Examples 5 and 12 to 16 according to the present invention. FIG. 3(a) is a graph showing the results of measuring the ammonia conversion rate of the catalysts manufactured in Manufacturing Examples 5 and 12 to 15, and FIG. 3(b) is a graph showing the results of measuring the ammonia conversion rate of the catalysts manufactured in Manufacturing Examples 5 and 16.

[0035] FIG. 4 is a graph showing the results of measuring the ammonia conversion rate of catalysts manufactured in Manufacturing Examples 5 and 17 to 24 according to the present invention. FIG. 4(a) is a graph showing the results of measuring the ammonia conversion rate of catalysts manufactured in Manufacturing Examples 5, 17 to 20, and 23, and FIG. 4(b) is a graph showing the results of measuring the ammonia conversion rate of catalysts manufactured in Manufacturing Examples 5 and 21 to 24.

[0036] Figure 5 is a graph showing the results of measuring the ammonia conversion rate of the catalysts manufactured in Manufacturing Examples 1, 5, 23, and 24 according to the present invention.

[0037] Figure 6 is a graph showing the results of measuring the long-term stability of the catalysts manufactured in Manufacturing Examples 1, 5, 23 and 24 according to the present invention. Figure 6(a) is a graph showing the ammonia conversion rate according to the reaction time, and Figure 6(b) is a graph showing the X according to the reaction time. NH3 / X 0 NH3 This is a graph that measures .

[0038] 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.

[0039] 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.

[0040] The reactions and mixing described below can be carried out at room temperature and pressure unless otherwise specified, and can be carried out under conventional 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.

[0041] The present invention provides, from one aspect, a catalyst for ammonia decomposition reaction with improved catalytic stability, characterized in that cesium and cerium are contained in a cobalt and molybdenum composite nitride.

[0042] Hereinafter, the catalyst for ammonia decomposition reaction according to the present invention will be described in detail.

[0043] The catalyst for ammonia decomposition reaction according to the present invention is characterized by containing cesium and cerium in a cobalt and molybdenum composite nitride, and is used for ammonia decomposition reaction and is economical compared to existing precious metal catalysts, has superior ammonia decomposition reaction efficiency compared to existing non-metal catalysts, and exhibits characteristics that can exhibit long-term stability of the catalyst by suppressing deactivation of the catalyst according to reaction time even at high temperatures and for a long time.

[0044] In the catalyst for ammonia decomposition reaction according to the present invention, the cobalt and molybdenum composite nitride is a nitride containing cobalt and molybdenum, and may contain 0.5 to 1.5 mol of cobalt, preferably 0.8 to 1.2 mol, per 1 mol of molybdenum. In the cobalt and molybdenum composite nitride, the cobalt and molybdenum contents satisfy the aforementioned content range, so that the largest amount of cobalt molybdenum composite nitride can be formed.

[0045] In addition, the cesium contained in the cobalt and molybdenum composite nitride may be included in an amount of 0.001 mol to 0.05 mol, preferably 0.004 mol to 0.015 mol, per 1 mol of the cobalt and molybdenum composite nitride.

[0046] When the above cesium content is less than 0.001 mol per 1 mol of the cobalt and molybdenum composite nitride, a problem may arise in which the effect of the cocatalyst is insufficient due to the small amount of cesium added, and when it exceeds 0.05 mol, a problem may arise in which the degree of exposure of the active material and the pores of the catalyst are blocked due to excessive cesium covering the catalyst surface.

[0047] In addition, cerium contained in the above cobalt and molybdenum composite nitride plays a positive role in activity and thermal stability as a cocatalyst, and may be included in an amount of 0.01 mol to 0.4 mol, preferably 0.05 mol to 0.20 mol, per 1 mol of the cobalt and molybdenum composite nitride.

[0048] When the above cerium content is less than 0.001 mol per 1 mol of the cobalt and molybdenum composite nitride, a problem may arise in which the effect of the cocatalyst is insufficient due to the small amount of cerium added, and when it exceeds 0.4 mol, a problem may arise in which the degree of exposure of the active material and the pores of the catalyst are blocked due to excessive cesium covering the catalyst surface.

[0049] In addition, from another aspect, the present invention provides a method for producing a catalyst for an ammonia decomposition reaction with improved catalytic stability, characterized by comprising the steps of: (a) mixing a cobalt precursor, a molybdenum precursor, a cesium precursor, and a cerium precursor; (b) drying the mixture of step (a); and (c) nitriding the dried mixture of step (b) with a nitrogen source to produce a cobalt and molybdenum composite nitride containing cesium and cerium.

[0050] Hereinafter, the method for manufacturing a catalyst for ammonia decomposition reaction according to the present invention will be described in detail for each step.

[0051] The above step (a) is a step of obtaining a mixture by mixing a cobalt precursor, a molybdenum precursor, a cesium precursor, and a cerium precursor.

[0052] The above step is a step of uniformly mixing a cobalt precursor, a molybdenum precursor, a cesium precursor, and a cerium precursor. Specifically, the cobalt precursor, the molybdenum precursor, the cesium precursor, and the cerium precursor may be obtained by using solvent-deficient milling or by dissolving the cobalt precursor, the molybdenum precursor, the cesium precursor, and the cerium precursor in a solvent.

[0053] In one embodiment, the solvent-deficient milling is a mixing method that uses no solvent or a small amount of solvent, and can be performed using a mixing device such as a ball mill, a planetary mill, a stirred ball mill, a vibrating mill, etc. that uses chemically inert beads. At this time, in order to maximize the mixing effect, a small amount of a solvent that can dissolve the precursor, such as water, methanol, and ethanol, can be selectively added.

[0054] In one embodiment, when mixing precursors using solvent-deficient milling according to the present invention, milling can be performed at a rotation speed of 100 rpm to 1000 rpm for 6 to 72 hours.

[0055] Mixing of cobalt precursors, molybdenum precursors, cesium precursors, and cerium precursors using solvent-deficient milling can reduce the cost of solvent removal required in subsequent processes by minimizing the use of solvent, and can achieve the effect of minimizing the decrease in catalyst performance while facilitating the production of large quantities of catalysts.

[0056] Meanwhile, in another embodiment, the solvent mixture of the cobalt precursor, molybdenum precursor, cesium precursor, and cerium precursor may be obtained by adding the required amount to each individual solvent, and mixing these solutions to obtain a mixture, or by adding the measured cobalt precursor, molybdenum precursor, cesium precursor, and cerium precursor all to one solvent to obtain a mixture of the cobalt precursor, molybdenum precursor, cesium precursor, and cerium precursor. At this time, the solvent is not limited as long as it can dissolve the precursors, and may preferably be water.

[0057] The above cobalt precursor, molybdenum precursor, cesium precursor and cerium precursor may be at least one selected from the group including organic compounds and inorganic compounds containing each metal (cobalt, molybdenum, cesium and cerium) element or ion, and specifically may be a chloride, hydrate, nitride, acetylacetonate, iodide, etc. of each metal, and as a preferred example, may be in the form of a nitride and hydrate, but is not limited thereto.

[0058] As a specific example, the cobalt precursor may be cobalt nitrate [Co(NO3)2], cobalt nitrate hydrate [Co(NO3)2ㆍxH2O], cobalt chloride (CoCl2), etc., and the molybdenum precursor may be ammonium molybdate [(NH4)2MoO4], ammonium molybdate hydrate [(NH4)6Mo7O 24 ㆍ4H2O], sodium molybdate (Na2MoO4), etc.

[0059] In addition, as a specific example, the cesium precursor may be cesium nitrate (CsNO3), cesium chloride (CsCl), etc., and the cerium precursor may be cerium nitrate [Ce(NO3)3], cerium nitrate hydrate [Ce(NO3)3ㆍxH2O], etc.

[0060] Thereafter, the mixture obtained in step (a) may include an aging step so that the catalyst composition and crystals can be effectively formed before the drying step described below.

[0061] The above aging can be performed using various mixers and stirrers so that uniform mixing can be achieved, and can be performed at 25°C to 100°C, preferably 70°C to 90°C, for 0.1 to 10 hours.

[0062] When the above maturation temperature is less than 25 ℃, smooth mixing and nucleation speed are slow, so CoMoO, which is the main component of the catalyst, x There may be a problem that the formation of the compound is not smooth, and when it exceeds 100 ℃, the nucleation rate is fast, so CoMoO x A problem may arise where the compound particles are formed large, which may reduce the activity of the catalyst. In addition, if the maturation time is less than 0.1 hour, CoMoO may be formed due to the short maturation time. x Problems may arise where the compound is not sufficiently formed, and if it exceeds 10 hours, smooth CoMoO xAlthough compound formation can be expected, the long maturation time may cause unnecessary economic problems in the catalyst manufacturing stage.

[0063] Next, step (b) is a step of drying the above-described mixture, wherein the drying may be performed at a temperature of 25°C to 150°C, preferably 90°C to 120°C, after evaporating the solvent contained in the mixture. When the drying temperature is 90°C or higher, drying can be performed effectively, and when it is 120°C or lower, the cost can be relatively saved. In addition, the drying time is preferably adjusted within 24 hours according to the dry state of the mixture, but may include performing the drying for longer if necessary.

[0064] Thereafter, the dried mixture can be further calcined at 200°C to 800°C, preferably 350°C to 600°C, in an oxidizing atmosphere such as air or an oxygen-containing mixed gas. When the calcination temperature is 200°C or higher, impurities can be sufficiently removed, thereby improving ammonia decomposition efficiency, and by maintaining the temperature at 800°C or lower, the possibility of catalytic performance degradation due to sintering can be reduced. In addition, since the calcination time varies depending on the calcination amount, calcination device, etc., it may be difficult to quantitatively express it, and therefore, it is preferable to determine the calcination completion time based on the state of the calcined product. Nevertheless, if the calcination time is necessarily limited, it can be performed for 30 hours or less.

[0065] In addition, the above-mentioned firing may be performed within the aforementioned temperature range, but the firing step may be divided into a first firing and a second firing to prevent rapid shrinkage and structural change of various complex oxides (cesium, cerium, cobalt, and molybdenum). At this time, the first firing may be performed at 100°C to 400°C, and the second firing may be performed at 400°C to 700°C after the first firing.

[0066] By performing firing by dividing by temperature within the temperature range described above, it is possible to prevent rapid shrinkage of the complex oxide that occurs as impurities present in the mixture escape from the mixture due to rapid temperature changes, which is desirable for increasing and maintaining the specific surface area of ​​the catalyst.

[0067] The subsequent step (c) is a step of nitriding to maximize the ammonia decomposition reaction activity of cobalt and molybdenum, which are the main active components of the mixture dried in the step (b), and the nitriding can be performed at 300°C to 800°C, preferably 600°C to 750°C, under a nitrogen source for 0.1 to 8 hours.

[0068] If the above nitriding treatment is performed at a temperature below 300°C, a sufficient nitriding effect cannot be expected, and if it is performed at a temperature exceeding 800°C, the specific surface area may decrease due to the agglomeration of the catalyst material, which may cause a problem in that the efficiency of the ammonia decomposition reaction decreases. In addition, since the nitriding treatment time varies depending on the amount of reactants, etc., it may be difficult to quantitatively express it, so it is preferable to judge it based on the state of the nitride treated with nitriding. Nevertheless, if the calcination time is necessarily limited, it can be performed for 1 to 4 hours.

[0069] At this time, as the nitrogen source used in the above nitriding treatment, any compound containing nitrogen atoms commonly used in the field can be used without limitation, and examples thereof include ammonia, urea, melamine, etc.

[0070] The present invention provides, from another aspect, a method for producing hydrogen from ammonia using the catalyst for the ammonia decomposition reaction described above.

[0071] Specifically, the method for producing hydrogen according to the present invention can produce hydrogen through an ammonia decomposition reaction by bringing a cobalt and molybdenum composite nitride containing cesium and cerium, i.e., a catalyst for the ammonia decomposition reaction described above, into contact with a gas containing ammonia.

[0072] The above ammonia-containing gas is not particularly limited, but may be a gas containing a substance that generates ammonia through thermal decomposition, such as urea, as well as ammonia gas or ammonia-containing gas.

[0073] Additionally, the gas containing ammonia may contain other components as long as they do not poison the catalyst. The reaction temperature is preferably 300°C to 600°C. The reaction pressure may be 0.002 MPa to 2 MPa in absolute pressure, more preferably 0.004 MPa to 1 MPa.

[0074] The above catalyst for ammonia decomposition reaction exhibits an ammonia conversion rate of 50% or more at a temperature in the range of 450°C to 550°C, and specifically, can exhibit an ammonia conversion rate of 80% or more at a temperature in the range of 500°C to 550°C.

[0075] Hereinafter, the present invention will be described in more detail through specific examples. The following examples are merely illustrative examples to aid understanding of the present invention and are not intended to limit the scope of the present invention.

[0076] <Manufacturing Example 1: CoMoO x -N catalyst>

[0077] Co(NO3)2ㆍ6H2O 2.5 g and (NH4)6Mo7O 24 ㆍ1.51 g of 4H2O was dissolved in 100 ml of deionized water to obtain a homogeneous mixture, and then the obtained mixture was aged while stirring at 80°C for 1 hour. The aged mixture was evaporated of moisture using a rotary evaporator and dried at 100°C for 20 hours. Thereafter, the dried mixture was first calcined at 350°C for 15 hours and then secondarily calcined at 600°C for 5 hours. The calcined product was nitrided at 700°C for 3 hours under ammonia gas to obtain CoMoO. x -N catalyst was prepared. At this time, the CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0078] <Manufacturing Examples 2 to 4: CoMoO x -N catalyst>

[0079] A catalyst was prepared in the same manner as in Manufacturing Example 1, but the maturation time was changed to CoMoO as described in Table 1. x -N catalysts were prepared respectively.

[0080] <Manufacturing Example 5: Cs 0.007 Ce 0.1 -CoMoO x -N catalyst>

[0081] Manufacturing method of Manufacturing Example 5: 2.5 g of Co(NO3)2ㆍ6H2O, (NH4)6Mo7O 24ㆍ4H2O 1.51 g, Ce(NO3)3ㆍ6H2O 0.38 g, and CsNO3 0.011 g were dissolved in 100 ml of deionized water to obtain a homogeneous mixture, and then the obtained mixture was aged while stirring at 80°C for 3 hours. The moisture of the aged mixture was evaporated using a rotary evaporator, and dried at 100°C for 20 hours. The dried mixture was then first calcined at 350°C for 15 hours, and then secondarily calcined at 600°C for 5 hours. The calcined product was nitrided at 700°C for 3 hours under ammonia gas to obtain Cs 0.007 Ce 0.1 -CoMoO x -N catalyst was prepared. At this time, the Cs 0.007 Ce 0.1 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0082] <Manufacturing examples 6 to 10: Cs 0.007 Ce 0.1 -CoMoO x -N catalyst >

[0083] Cs in the same manner as in Manufacturing Example 5 0.007 Ce 0.1 -CoMoO x - Manufacture N catalyst, but change the manufactured catalyst to the conditions in Table 1 below and Cs 0.007 Ce 0.1 -CoMoO x -N catalyst was prepared.

[0084] <Manufacturing Example 11: Cs 0.007 Ce 0.1 -CoMoO x -N catalyst >

[0085] Cs in the same manner as in Manufacturing Example 5 0.007 Ce 0.1 -CoMoO x-N catalyst was manufactured, but only the nitriding step was performed after drying at 100°C for 20 hours, excluding the calcination step, to obtain Cs 0.007 Ce 0.1 -CoMoO x -N catalyst was prepared.

[0086] <Manufacturing Examples 12 to 16: Cs 0.007 Ce 0.1 -CoMoO x -N catalyst >

[0087] Cs in the same manner as in Manufacturing Example 5 0.007 Ce 0.1 -CoMoO x -N catalyst is manufactured, but the conditions in Table 1 below are changed to Cs 0.007 Ce 0.1 -CoMoO x -N catalyst was prepared.

[0088] [Table 1]

[0089]

[0090] <Manufacturing Example 17: Cs 0.007 Ce 0.01 -CoMoO x -N catalyst>

[0091] A catalyst was prepared in the same manner as in Manufacturing Example 5, but instead of 0.38 g of Ce(NO3)3ㆍ6H2O, 0.037 g of Ce(NO3)3ㆍ6H2O was mixed to obtain Cs 0.007 Ce 0.01 -CoMoO x -N catalyst was prepared. At this time, the Cs 0.007 Ce 0.01 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0092] <Manufacturing Example 18: Cs 0.007 Ce 0.05 -CoMoO x -N catalyst>

[0093] A catalyst was prepared in the same manner as in Manufacturing Example 5, but instead of 0.38 g of Ce(NO3)3ㆍ6H2O, 0.186 g of Ce(NO3)3ㆍ6H2O was mixed to obtain Cs 0.007 Ce 0.05 -CoMoO x -N catalyst was prepared. At this time, the Cs 0.007 Ce 0.05 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0094] <Manufacturing Example 19: Cs 0.007 Ce 0.20 -CoMoO x -N catalyst>

[0095] A catalyst was prepared in the same manner as in Manufacturing Example 5, but instead of 0.38 g of Ce(NO3)3ㆍ6H2O, 0.745 g of Ce(NO3)3ㆍ6H2O was mixed to obtain Cs 0.007 Ce 0.20 -CoMoO x -N catalyst was prepared. At this time, the Cs 0.007 Ce 0.20 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0096] <Manufacturing Example 20: Cs 0.007 Ce 0.50 -CoMoO x -N catalyst>

[0097] A catalyst was prepared in the same manner as in Manufacturing Example 5, but instead of 0.38 g of Ce(NO3)3ㆍ6H2O, 1.86 g of Ce(NO3)3ㆍ6H2O was mixed to obtain Cs 0.007 Ce 0.50 -CoMoO x -N catalyst was prepared. At this time, the Cs 0.007 Ce 0.50 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0098] <Manufacturing Example 21: Cs 0.004 Ce 0.10 -CoMoOx -N catalyst>

[0099] A catalyst was prepared in the same manner as in Manufacturing Example 5, but 0.006 g of CsNO3 was mixed instead of 0.011 g of CsNO3. 0.004 Ce 0.10 -CoMoO x -N catalyst was prepared. At this time, the Cs 0.004 Ce 0.50 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0100] <Manufacturing Example 22: Cs 0.015 Ce 0.10 -CoMoO x -N catalyst>

[0101] A catalyst was prepared in the same manner as in Manufacturing Example 5, but 0.023 g of CsNO3 was mixed instead of 0.011 g of CsNO3. 0.015 Ce 0.10 -CoMoO x -N catalyst was prepared. At this time, the Cs 0.015 Ce 0.10 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0102] <Manufacturing Example 23: Cs 0.007 -CoMoO x -N catalyst>

[0103] A catalyst was prepared in the same manner as in Manufacturing Example 5, but without adding a cerium precursor, and Cs 0.007 -CoMoO x -N catalyst was prepared. At this time, the Cs 0.007 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0104] <Manufacturing Example 24: Ce 0.10 -CoMoO x -N catalyst>

[0105] A catalyst was prepared in the same manner as in Manufacturing Example 5, but without adding a cesium precursor, and Ce 0.10 -CoMoO x -N catalyst was prepared. At this time, the Ce 0.10 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0106] <Manufacturing Example 25: Cs 0.007 Ce 0.1 -CoMoO x -N catalyst>

[0107] Co(NO3)2ㆍ6H2O 14.85 g, (NH4)6Mo7O 24 ㆍ4H2O 8.83 g, Ce(NO3)3ㆍ6H2O 2.19 g, and CsNO3 0.069 g were dissolved in 200 ml of deionized water to obtain a homogeneous mixture, and then the obtained mixture was aged while stirring at 80°C for 3 hours. The moisture in the aged mixture was evaporated using a rotary evaporator, and dried at 100°C for 20 hours. The dried mixture was then first calcined at 350°C for 15 hours, and then secondarily calcined at 600°C for 5 hours. The calcined product was nitrided at 700°C for 3 hours under ammonia gas to obtain Cs 0.007 Ce 0.1 -CoMoO x -N catalyst was prepared. At this time, the Cs 0.007 Ce 0.1 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0108] <Manufacturing Example 26: Cs 0.007 Ce 0.1 -CoMoO x -N catalyst>

[0109] Co(NO3)2ㆍ6H2O 29.70 g, (NH4)6Mo7O 24ㆍ4H2O 17.66 g, Ce(NO3)3ㆍ6H2O 4.39 g and CsNO3 0.1378 g were dissolved in 300 ml of deionized water to obtain a homogeneous mixture, and then the obtained mixture was aged while stirring at 80°C for 3 hours. The moisture of the aged mixture was evaporated using a rotary evaporator and dried at 100°C for 20 hours. The dried mixture was then first calcined at 350°C for 15 hours and then secondarily calcined at 600°C for 5 hours. The calcined product was nitrided at 700°C for 3 hours under ammonia gas to obtain Cs 0.007 Ce 0.1 -CoMoO x -N catalyst was prepared. At this time, the Cs 0.007 Ce 0.1 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0110] <Manufacturing Example 27: Cs 0.007 Ce 0.1 -CoMoO x -N catalyst>

[0111] Co(NO3)2ㆍ6H2O 14.85 g, (NH4)6Mo7O 24 ㆍ4H2O 8.83 g, Ce(NO3)3ㆍ6H2O 2.19 g and CsNO3 0.0689 g were dissolved in 10 ml of deionized water to obtain a uniform mixture, and then the obtained mixture was put into a ball milling device (LM-BS750, LK LABKOREA) and ball milled at a rotation speed of 350 rpm for 24 hours. The ball-milled mixture was vacuum-dried at 150°C for 24 hours, and then the dried mixture was calcined at 600°C for 5 hours. The calcined product was nitrided at 700°C for 3 hours under ammonia gas to obtain Cs 0.007 Ce 0.1 -CoMoO x -N catalyst was prepared. At this time, the Cs0.007 Ce 0.1 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0112] <Manufacturing Example 28: Cs 0.007 Ce 0.1 -CoMoO x -N catalyst>

[0113] Co(NO3)2ㆍ6H2O 29.70 g, (NH4)6Mo7O 24 ㆍ4H2O 17.66 g, Ce(NO3)3ㆍ6H2O 4.39 g and CsNO3 0.1378 g were dissolved in 20 ml of deionized water to obtain a uniform mixture, and then the obtained mixture was put into a ball milling device (LM-BS750, LK LABKOREA) and ball milled at a rotation speed of 350 rpm for 24 hours. The ball-milled mixture was vacuum-dried at 150°C for 24 hours, and then the dried mixture was calcined at 600°C for 5 hours. The calcined product was nitrided at 700°C for 3 hours under ammonia gas to obtain Cs 0.007 Ce 0.1 -CoMoO x -N catalyst was prepared. At this time, the Cs 0.007 Ce 0.1 -CoMoO x - In the N catalyst designation, the subscript indicates the mole of the corresponding component.

[0114] <Experimental Example 1: Measurement of ammonia decomposition reaction according to catalyst aging conditions>

[0115] In order to measure the effect of maturation time on the ammonia decomposition reaction as a catalyst for the ammonia decomposition reaction, the ammonia conversion rate for the ammonia decomposition reaction was measured using the catalyst manufactured in the manufacturing example, and the results are shown in Fig. 1.

[0116] In the above Figure 1, Figure 1(a) is a graph measuring the ammonia conversion rate by ammonia decomposition reaction temperature according to maturation time, and Figure 1(b) is a graph measuring the ammonia conversion rate by ammonia decomposition reaction temperature according to maturation temperature.

[0117] At this time, the ammonia decomposition reaction was measured at atmospheric pressure in a quartz fixed-bed continuous-flow straight-tube reactor equipped with a thermocouple. The reactor was equipped with a quartz cotton layer, and 0.1 g of the catalyst sample prepared in the manufacturing example was loaded therein, and then 6,000 mL / g cat. Pure NH3 (30 mL / min) corresponding to a gas hourly space velocity (GHSV) of / h was introduced into the reactor.

[0118] The catalytic activity was evaluated at temperatures ranging from 300°C to 600°C in steps of 50°C (60 min at each temperature). The concentration of the outlet gas was monitored using an online gas chromatograph (YL6500GC, YL Instrument Co., Korea) equipped with a thermal conductivity detector (TCD) and Porapak-N and Molesieve 13X columns. Ammonia conversion X NH3 (%) was calculated using Equation 1. In Equation 1 below, (NH3) in is the ammonia concentration entering the reactor, (NH3) out is the ammonia concentration discharged from the reactor.

[0119] X NH3 (%)={[(NH3) in -(NH3) out ] / (NH3) in}× 100 ....(1)

[0120] As shown in Fig. 1, there was no significant difference in the ammonia conversion rate according to the maturation time, but the catalysts of Preparation Examples 5 and 7, which were aged at 80°C and 90°C, respectively, showed higher ammonia activity than the catalyst of Preparation Example 6.

[0121] <Experimental Example 2: Measurement of ammonia decomposition reaction according to catalyst calcination conditions>

[0122] In order to measure the influence of calcination conditions on the ammonia decomposition reaction as a catalyst for the ammonia decomposition reaction, the ammonia conversion rate for the ammonia decomposition reaction was measured using the catalyst manufactured in the manufacturing example, and the results are shown in Fig. 2. At this time, the ammonia decomposition reaction was measured for the ammonia conversion rate for the ammonia decomposition reaction using the same method as in Experimental Example 1, and the results are shown in Fig. 2.

[0123] As shown in Fig. 2, the catalyst of Manufacturing Example 5 manufactured through first and second calcinations showed higher ammonia activity compared to the catalysts of Manufacturing Examples 8 to 11 manufactured through calcination at a single temperature or without calcination.

[0124] <Experimental Example 3: Measurement of ammonia decomposition reaction according to nitrification treatment conditions of the catalyst>

[0125] In order to measure the influence of nitrification treatment conditions on the ammonia decomposition reaction as a catalyst for the ammonia decomposition reaction, the ammonia conversion rate for the ammonia decomposition reaction was measured using the catalyst manufactured in the manufacturing example, and the results are shown in Fig. 3.

[0126] In the above Figure 3, Figure 3(a) is a graph measuring the ammonia conversion rate by ammonia decomposition reaction temperature according to the nitrification treatment time, and Figure 3(b) is a graph measuring the ammonia conversion rate by ammonia decomposition reaction temperature according to the nitrification treatment temperature.

[0127] At this time, the ammonia decomposition reaction was measured for the ammonia conversion rate in the ammonia decomposition reaction in the same manner as in Experimental Example 1, and the results are shown in Fig. 3.

[0128] As shown in Fig. 3, the catalysts of Manufacturing Examples 5, 12, and 13 manufactured by nitriding for 2 hours or more were found to have superior ammonia decomposition activity compared to the catalysts of Manufacturing Examples 15 and 14 manufactured by not performing nitriding or by nitriding for 1 hour, and in terms of the temperature of nitriding, the catalyst of Manufacturing Example 5, which was nitrided at 700°C, was found to have higher ammonia decomposition activity than the catalyst of Manufacturing Example 16, which was nitrided at 750°C.

[0129] <Experimental Example 4: Measurement of ammonia decomposition reaction according to the molar ratio of Ce and Cs in the catalyst>

[0130] In order to measure the influence of the molar ratio of cerium (Ce) and cesium (Cs) as catalysts for ammonia decomposition reaction, catalysts were manufactured while keeping the contents of cobalt and molybdenum nitride the same, but varying the contents of cerium (Ce) and cesium (Cs), respectively, and the ammonia conversion rate for the ammonia decomposition reaction was measured using the same method as Experimental Example 1, and the results are shown in Figures 4 and 5.

[0131] In the above FIG. 4, FIG. 4(a) is a graph showing the ammonia conversion rate of catalysts manufactured with different cerium (Ce) contents, FIG. 4(b) is a graph showing the ammonia conversion rate of catalysts manufactured with different cesium (Cs) contents, and FIG. 5 is a graph showing the ammonia conversion rate of a cobalt and molybdenum composite nitride catalyst that does not contain cerium and / or cesium and a cobalt and molybdenum composite nitride catalyst that contains cerium and cesium.

[0132] As shown in Fig. 4(a), the catalysts manufactured in Preparation Examples 5, 18 and 19 showed higher ammonia conversion rates than the catalysts containing no cerium (Preparation Example 23) or containing 0.01 mol (Preparation Example 17) and 0.50 mol (Preparation Example 20) of cerium even when the cesium content was the same, and as shown in Fig. 4(b), the catalysts manufactured in Preparation Examples 5, 21 and 22 showed higher ammonia conversion rates than the catalyst of Preparation Example 24 containing no cesium even when the cerium content was the same.

[0133] In addition, as shown in FIG. 5, the catalyst of Preparation Example 5 was found to have a higher ammonia conversion rate than the catalyst containing neither cerium nor cesium (Preparation Examples 23 and 24) or containing neither cerium nor cesium (Preparation Example 1).

[0134] <Experimental Example 5: Measurement of Long-Term Stability of Catalysts>

[0135] In order to measure the long-term stability of a catalyst according to the content of cerium and / or cesium as a catalyst for an ammonia decomposition reaction, an ammonia decomposition reaction was performed for 100 hours using the catalysts prepared in Preparation Examples 1, 5 and Preparation Examples 23 to 24, and the long-term stability of the catalyst was measured, and the results are shown in Fig. 6.

[0136] In the above 6, Fig. 6(a) is a graph measuring the ammonia conversion rate according to the reaction time, and Fig. 6(b) is a graph measuring the initial ammonia conversion rate (X 0 NH3 ) Ammonia conversion rate (X) changed according to reaction time NH3 ) is a graph that measures the

[0137] X NH3 / X 0 NH3 = Ammonia conversion rate over time / Initial ammonia conversion rate

[0138] The above measurement was performed at atmospheric pressure, an ammonia space velocity of 54,000 ml / gcat. / h, and an indicator temperature of 550°C for 100 hours, and the results are shown in Fig. 6 as an ammonia conversion rate.

[0139] As shown in Fig. 6, it was confirmed that the catalyst manufactured in Manufacturing Example 5 maintained catalytic activity stably for 100 hours at a higher conversion rate than Manufacturing Examples 1, 23 to 24.

[0140] <Experimental Example 6: Measurement according to catalyst manufacturing method>

[0141] In order to measure the effect of the ammonia decomposition reaction according to the manufacturing method as a catalyst for the ammonia decomposition reaction, the catalysts of Manufacturing Example 5 and Manufacturing Examples 25 to 28, which were manufactured by keeping the contents of cobalt and molybdenum nitride the same but using different manufacturing methods, were used to measure the ammonia conversion rate for the ammonia decomposition reaction at different temperatures in the same manner as Experimental Example 1, and the results are shown in Table 2.

[0142] [Table 2]

[0143]

[0144] As shown in Table 2, it was confirmed that the catalyst performance of the catalysts of Manufacturing Examples 27 and 29 manufactured by the solvent-depleted milling method using ball milling was not reduced even when the manufacturing scale was increased, compared to the catalysts of Manufacturing Examples 5, 25, and 26 manufactured by the precipitation method.

[0145] While the present invention has been described with reference to the above-described embodiments, various embodiments may be constructed within the spirit and scope of the present invention. Accordingly, the scope of the present invention is defined by the appended claims and their equivalents, and is not limited to the specific embodiments described herein.

Claims

1. A catalyst for ammonia decomposition reaction with improved catalytic stability, characterized by containing cesium and cerium in a cobalt and molybdenum composite nitride.

2. In paragraph 1, A catalyst for ammonia decomposition reaction with improved catalytic stability, characterized in that the above cesium is contained in an amount of 0.001 mol to 0.05 mol per 1 mol of cobalt and molybdenum composite nitride.

3. In paragraph 1, A catalyst for ammonia decomposition reaction with improved catalytic stability, characterized in that the above cerium is contained in an amount of 0.01 mol to 0.4 mol per 1 mol of cobalt and molybdenum composite nitride.

4. In paragraph 1, A catalyst for ammonia decomposition reaction with improved catalytic stability, characterized in that in the above cobalt and molybdenum composite nitride, cobalt is contained in an amount of 0.5 to 1.5 mol per 1 mol of molybdenum. 5.(a) A step of mixing a cobalt precursor, a molybdenum precursor, a cesium precursor and a cerium precursor; (b) a step of drying the mixture of step (a); and (c) a step of nitriding the dried mixture in step (b) using a nitrogen source to produce a cobalt and molybdenum composite nitride containing cesium and cerium; a method for producing a catalyst for ammonia decomposition reaction with improved catalyst stability, characterized in that it comprises:

6. In paragraph 5, A method for producing a catalyst for ammonia decomposition reaction with improved catalyst stability, characterized in that it comprises a step of maturing the mixture of step (a) after step (a).

7. In paragraph 6, A method for producing a catalyst for ammonia decomposition reaction with improved catalyst stability, characterized in that the above aging is performed at 25°C to 100°C for 0.1 to 10 hours.

8. In paragraph 5, A method for producing a catalyst for ammonia decomposition reaction with improved catalyst stability, characterized in that the step (b) further includes a step of calcining after drying.

9. In paragraph 8, A method for producing a catalyst for ammonia decomposition reaction with improved catalyst stability, characterized in that the above calcination is performed first at 100 ℃ to 400 ℃ and then second at 400 ℃ to 700 ℃.

10. In paragraph 5, A method for producing a catalyst for ammonia decomposition reaction with improved catalyst stability, characterized in that the mixing in step (a) above uses solvent-deficient milling.

11. A method for producing hydrogen from ammonia, characterized in that a cobalt and molybdenum composite nitride containing cesium and cerium is brought into contact with a gas containing ammonia to cause an ammonia decomposition reaction.

12. In paragraph 11, A method for producing hydrogen from ammonia, characterized in that the contact of the above ammonia with the cobalt and molybdenum composite nitride containing cesium and cerium is performed at 300°C to 600°C.

Images