Method for producing intermediate temperature water gas shift catalyst and method for producing hydrogen using the catalyst

Abstract

To provide a catalyst for a water gas shift reaction that maintains high activity of the catalyst within a temperature range of 200 to 450°C and has a high carbon monoxide shift rate, a method for preparing the catalyst, and a method for preparing hydrogen using the catalyst.SOLUTION: The present invention provides a catalyst for a water gas shift reaction, comprising a catalytic active component containing, relative to all metals of the catalyst, 40-80 mol% of copper (Cu), 15-50 mol% of zinc (Zn) and 1-13 mol% of aluminum (Al), wherein an aluminum-rich layer is present in the surface layer of the catalyst particle.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a highly active water-gas shift catalyst that can be used to convert carbon monoxide (CO) and water (HO) to carbon dioxide (CO) and hydrogen (H), a method for producing the same, and a method for converting a gas mixture containing carbon monoxide to hydrogen and carbon dioxide by a reaction containing water in the medium temperature range using the catalyst. [Background technology]

[0002] Hydrogen is a basic substance that can be applied to various industrial fields and can increase the added value of technologies, and it plays an important role not only in the petrochemical industry but also as a next-generation energy source for fuel cells, etc. Therefore, various types of research are being conducted on catalysts and process technologies that can produce high-purity hydrogen and reduce production costs.

[0003] There are two types of hydrogen production technologies: one is to produce hydrogen through the catalytic steam reforming of fossil fuels, and the other is to produce hydrogen using the water-gas shift catalytic reaction of a gas mixture containing carbon monoxide. Of these, the water-gas shift reaction is an exothermic reaction in which carbon monoxide reacts with water steam to convert it into hydrogen and carbon dioxide, and the reaction formula is as follows (1).

[0004] CO+H2O→H2+CO2, △H=-41.1kJ / mol(1)

[0005] The water-gas shift reaction generally produces hydrogen from carbon monoxide through two stages: the high-temperature water-gas shift (HTS) reaction and the low-temperature water-gas shift (LTS) reaction. In conventional processes, the high-temperature water-gas shift reaction is typically carried out at around 300-450°C and is used to convert large amounts of carbon monoxide, while the low-temperature water-gas shift reaction is carried out at around 200-300°C and, after the high-temperature water-gas shift reaction, the remaining carbon monoxide is converted and used for high-purity purposes.

[0006] The water-gas shift (WGS) reaction is sensitive to temperature, influenced by the equilibrium conversion rate, which determines the product composition. As mentioned above, the water-gas shift reaction is an exothermic reaction, and at high temperatures, the reverse reaction occurs, resulting in the reaction of hydrogen and carbon dioxide to produce carbon monoxide. Therefore, maintaining low temperatures in the water-gas shift reaction is advantageous from the perspective of hydrogen production.

[0007] Meanwhile, high-temperature water-gas shift catalysts are typically iron (Fe)-based, with a small amount of chromium (Cr) added to stabilize the reaction. The chromium prevents iron sintering and increases activity, accelerating the reaction rate and treating large amounts of carbon monoxide (CO). However, due to the high temperatures caused by the exothermic reaction, 2–4% of the initial molar amount of CO remains. Therefore, the use of low-temperature water-gas shift catalysts is required to remove the remaining CO. These low-temperature water-gas shift catalysts are copper-zinc (Cu-Zn)-based and achieve equilibrium conversion depending on the reaction conditions, demonstrating a CO conversion rate of over 99% at low temperatures.

[0008] Therefore, various copper-zinc-based water-gas shift catalysts have been developed and used. For example, a water-gas shift catalyst containing copper, zinc, and alumina has been developed, such as Korean Patent No. 1551509. However, there is still a need for a catalyst that can increase the carbon monoxide conversion rate. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention provides a catalyst for producing hydrogen gas from carbon monoxide, which maintains high catalytic activity at temperatures of 200 to 450°C and has a high carbon monoxide conversion rate, a method for producing the catalyst, and a method for producing hydrogen using the catalyst. [Means for solving the problem]

[0010] One aspect of the present invention provides a water gas shift reaction catalyst comprising catalytically active components including 40 to 80 mol % of copper (Cu), 15 to 50 mol % of zinc (Zn), and 1 to 13 mol % of aluminum (Al) relative to the total catalyst metals, and wherein an aluminum-rich layer is present on the surface of the catalyst particles.

[0011] Another aspect of the present invention provides a method for producing a water gas shift catalyst, including: a copper-zinc coprecipitation step of mixing a metal precursor solution containing a Cu precursor and a Zn precursor with a precipitant solution to coprecipitate copper and zinc to produce a copper-zinc coprecipitate; an Al precipitation step of injecting an Al precursor solution into a solution containing the copper-zinc coprecipitate to precipitate aluminum on the surface of the copper-zinc coprecipitate to produce a CuZnAl catalyst precursor having an aluminum-rich layer on the surface; and a calcination step of calcining the CuZnAl catalyst precursor to produce a CuZnAl catalyst.

[0012] Yet another aspect of the present invention provides a method for producing hydrogen by reacting the catalyst of the present invention or the catalyst produced by the method of the present invention with a gas mixture for a water gas shift reaction. [Effects of the Invention]

[0013] The water-gas shift catalyst of the present invention operates easily in the intermediate temperature range of 250 to 350°C between the high-temperature water-gas shift reaction and the low-temperature water-gas shift reaction, has high catalytic activity, exhibits excellent CO conversion even under high-temperature conditions due to exothermic reactions, and exhibits stable high performance even under low steam / carbon dioxide ratio conditions.Furthermore, it has excellent hydrothermal durability and is not deactivated even when exposed to high-temperature steam for a long period of time. [Brief explanation of the drawings]

[0014] [Figure 1] 1 shows the process flow of a conventional one-step method for producing a water gas shift catalyst. [Figure 2] 1 shows the process flow of a two-step method for producing a water gas shift catalyst according to the present invention. [Figure 3]1 shows an image of a portion of the copper-based catalyst prepared according to Comparative Example 1 taken with a transmission electron microscope (TEM). [Figure 4] 1 shows an image of a part of the water gas shift catalyst prepared in Example 1 taken by a transmission electron microscope (TEM). [Figure 5] 1 is a graph showing the change in pH over time during the first and second aging processes in the preparation of the water gas shift catalyst of Example 1. [Figure 6a] 1 is a TEM image of catalyst particles prepared in Example 1. [Figure 6b] In the catalyst particle of FIG. 6a, an arbitrary position within the catalyst particle set for measuring the weight ratio or atomic ratio of aluminum is shown. [Figure 7] A graph comparing the CO conversion rates of Comparative Experimental Example 1 and Experimental Example 1 at 300° C. for 100 hours is shown in Table 1. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0016] As described above, the conventional continuous reaction system of high-temperature water-gas shift reaction-low-temperature water-gas shift reaction has a problem in that it is difficult to simplify the process because the operating temperatures of the continuous reaction system are different and different catalysts need to be used depending on the temperature.

[0017] Hydrogen is produced by the dissociation of water vapor, and according to Le Chatelier's principle, the higher the concentration of the reactants, the more likely the forward reaction will occur. Furthermore, because the dissociation rate of water vapor is slower than the rate of carbon dioxide production, a higher amount of water vapor than the stoichiometric ratio must be supplied to smoothly supply the oxygen atoms produced by dissociation in order to maintain a high CO conversion rate. Therefore, while the water-gas shift reaction involves a 1:1 mol stoichiometric ratio of carbon monoxide and water vapor, in actual conventional processes, an excess amount of water vapor is supplied.

[0018] If oxygen is not supplied smoothly, carbon deposition from carbon monoxide occurs on the Fe catalyst, which can easily cause catalyst deactivation. If water vapor is supplied in excess, the energy required to convert the initially supplied water into water vapor is much higher than the energy required for stoichiometric supply.

[0019] In addition, since the temperature of the reaction gas supplied to the reactor for the high-temperature water-gas shift reaction is 300°C or higher, a huge amount of energy is required to heat the steam, which has a steam / carbon dioxide molar ratio of 3.0. Even if the heat of reaction is recovered, the insufficient energy must be supplied by an external heat source such as a boiler.

[0020] Low-temperature water-gas shift catalysts are based on copper and can promote the water-gas shift reaction even at low temperatures. However, they have problems in that they are not durable when exposed to water vapor for long periods of time, and the supply of excess CO increases the heat of reaction, causing copper sintering when exposed to high temperatures, resulting in a decrease in activity.

[0021] Therefore, water gas shift catalysts containing copper, zinc, and aluminum, which are produced by a one-step method as shown in Figure 1, have been developed in the past, but the carbon monoxide conversion rate of the catalysts is not high.

[0022] Therefore, the present invention provides a catalyst that maintains catalytic activity over a certain temperature range and has a high carbon monoxide conversion rate, a method for producing the catalyst, and a method for producing hydrogen using the catalyst.

[0023] In the present invention, the term "coprecipitation" can also be referred to as "precipitation", which means precipitating the precipitation target or all precipitation targets in a solution.

[0024] In the present invention, medium temperature means 250 to 350°C.

[0025] The present invention provides a water gas shift reaction catalyst containing catalytically active components containing 40 to 80 mol % of Cu, 15 to 50 mol % of Zn, and 1 to 13 mol % of Al based on the entire metal catalyst.

[0026] The reason for controlling the components in the catalyst of the present invention as described above will be explained in detail below.

[0027] Cu is an active metal and an essential element for the water gas shift reaction catalyst, and if its content is less than 40 mol%, the number of active sites may decrease, while if its content exceeds 80 mol%, sufficient activity is achieved, but the size of Cu particles increases, which may reduce the catalytic activity.

[0028] Zn is an element that acts as a structural stabilizer for Cu in the water gas shift reaction, and if the Zn content is less than 15 mol%, there is a problem that Zn is insufficient to sufficiently stabilize the structure of Cu, while if the Zn content exceeds 50 mol%, the proportion of Cu decreases, which may reduce the catalytic activity.

[0029] Aluminum generally has the advantage of being hydrophilic and easily decomposing water.

[0030] If the aluminum content is less than 1 mol%, it is insufficient to enhance the structural or electronic activity of the catalyst, and if it exceeds 13 mol%, the crystalline structure of the aluminum precursor becomes hydrotalcite, which is not beneficial to activity.

[0031] The water gas shift catalyst preferably has an aluminum-rich layer on the surface of the catalyst particle. Therefore, the catalyst of the present invention has a large amount of hydrophilic aluminum on the surface, which easily decomposes water, and therefore protects the active metal copper even when exposed to water vapor for a long period of time, thereby improving the durability of the catalyst.

[0032] In this case, aluminum is distributed mainly on the outer surface of the water gas shift catalyst, and the aluminum-rich layer refers to a region that is approximately 0.1 to 10% of the radius of the catalyst particle from the surface layer of the catalyst particle.

[0033] The water gas shift catalyst according to the present invention has high activity at 200 to 450°C, more preferably 250 to 350°C, and provides a water gas shift catalyst with a carbon monoxide conversion rate of 98.5% or higher at the above temperatures.

[0034] The present invention provides a method for producing a water gas shift catalyst. The method for preparing a water gas shift reaction catalyst of the present invention includes a copper-zinc coprecipitation step of mixing a metal precursor solution containing a Cu precursor and a Zn precursor with a precipitant solution to coprecipitate copper and zinc to form a copper-zinc coprecipitate; an aluminum precipitation step of injecting an aluminum precursor solution into a solution containing the copper-zinc coprecipitate to precipitate aluminum on the surface of the copper-zinc coprecipitate to prepare a CuZnAl catalyst precursor having an aluminum-rich layer on the surface; and a calcination step of calcining the CuZnAl catalyst precursor to prepare a CuZnAl catalyst.

[0035] At this time, the Cu and Zn coprecipitation step is followed by the Al precipitation step, and the schematic flow of the manufacturing method is shown in FIG.

[0036] Cu, Zn coprecipitation step The Cu and Zn co-precipitation step synthesizes a precipitate by injecting a Cu precursor and a Zn precursor into a precipitant solution. First, a Cu precursor and a Zn precursor solution are prepared, and then the solution containing the Cu precursor and the Zn precursor is injected into a solution containing a precipitant, thereby coprecipitating Cu and Zn.

[0037] The Cu precursor is Cu 2+ is the cation, and the anion part is NO3 - , SO4 2- , CH3COO - , H.C.O.O. - , Cl - and I - and a metal precursor selected from the group consisting of:

[0038] The Zn precursor is Zn 2+ is the cation, and the anion part is NO3 - , SO4 2- , CH3COO - , H.C.O.O. - , Cl - and I - and a metal precursor selected from the group consisting of:

[0039] The Cu, Zn co-precipitation step includes an aging process, which involves synthesizing a solution containing a copper-zinc co-precipitate and aging it for 30 to 180 minutes at the same temperature as the initial temperature of the precipitant.

[0040] Cu and Zn precursor content In the method for producing the water gas shift catalyst, the concentration of the solution containing Cu and Zn precursors is 0.1M to 1.5M. If the concentration of the solution containing Cu and Zn precursors is less than 0.1M, the amount of Cu and Zn precursors is small, making it difficult to form the catalyst. If the concentration exceeds 1.5M, it is difficult to form a solution. The method for producing a water gas shift catalyst is provided, in which the molar ratio of Cu precursor to Zn precursor is 50:50 to 80:20. If the molar ratio of Cu precursor to Zn precursor is 0:100 to less than 50:50, the number of active sites is small, resulting in low catalytic activity. This can lead to problems such as a decrease in CO conversion. On the other hand, if the molar ratio of Cu precursor to Zn precursor is more than 80:20 to 100:0, the Zn content is low, resulting in an increase in Cu particles. This can lead to a problem of poor catalytic activity retention due to the increased exposed Cu.

[0041] Precipitant The precipitant used in the Cu and Zn co-precipitation step preferably has weak basicity, and includes at least one precipitant selected from the group consisting of carbonates or bicarbonates of alkali metals Li, Na, K, or ammonium, NaOH, and NH4OH.

[0042] A method for producing a water gas shift catalyst is provided, in which the temperature of the precipitant solution before the metal precursor is injected is between room temperature (20°C) and 80°C, and the pH is about 6 to 9. If the temperature of the precipitant solution before the metal precursor is injected exceeds 80°C, the water in the solution is likely to evaporate, accelerating the particle formation process and making it difficult to synthesize a uniformly dispersed catalyst. Furthermore, if the temperature is below 20°C, the precipitation reaction is difficult to occur, resulting in a long time required to produce the catalyst. Furthermore, if the pH exceeds 9, an oxide is immediately formed, while if the pH is below 6, no precipitate is formed.

[0043] Therefore, the initial concentration of the precipitant is 0.01 M to 1.2 M. If the initial concentration of the precipitant is less than 0.01 M, the volume of the precipitant aqueous solution increases significantly to precipitate the metal precursor, resulting in inefficient catalyst synthesis, while if the concentration exceeds 1.2 M, the desired pH cannot be achieved after the metal precursor is injected. However, it is preferable that the concentration of the precipitant is a concentration that can maintain the pH range specified above.

[0044] Cu and Zn precipitation stage In the Cu and Zn precipitation step, a solution containing Cu and Zn precursors is poured into a precipitant to prepare a copper-zinc coprecipitate. When the solution containing Cu and Zn precursors is injected into the precipitant, it is injected until the pH reaches 5 to 8. If the pH of the solution is less than 5, both Cu and Zn react with the precipitant, which causes a problem that Al cannot be precipitated later. If the pH of the solution is not 8 after injection, Cu and Zn are not sufficiently precipitated, which causes a problem that the activity of the catalyst is reduced.

[0045] Al precipitation stage In the Al precipitation step, an Al precursor is injected into a solution containing the copper-zinc coprecipitate, thereby precipitating Al on the surface of the Cu and Zn precipitates, thereby obtaining a catalyst having an aluminum-rich layer on the surface of the catalyst particles to be obtained in the present invention. The Al precursor is Al 3+ is the cation, and the anion part is NO3 - , SO4 2- , CH3COO - , H.C.O.O. - , Cl - and I - and a metal precursor selected from the group consisting of:

[0046] Al precursor content The concentration of the Al precursor solution is 0.01 to 1.5 M. If the concentration of the Al precursor solution is less than 0.01 M, the amount of Al precursor is small and the amount of solvent is large, making it difficult to form the catalyst since it takes a long time to produce the catalyst, and if the concentration exceeds 1.5 M, the solubility of the Al precursor is not high, making it difficult to form a solution.

[0047] The Al precursor solution is injected after the pH has decreased by about 0.05 to 0.2 and then recovered during the maturation of the Cu and Zn co-precipitation step, which means that the copper-zinc precipitate has changed from an amorphous to a crystalline form. Therefore, the Al precursor solution can be injected after the Cu-Zn precipitate has changed from an amorphous to a crystalline form during the maturation of the Cu and Zn co-precipitation step.

[0048] The Al precipitation step includes an aging process, which involves injecting an Al precursor solution into a solution containing a copper-zinc coprecipitate, and then aging the solution for 15 to 60 minutes at the same temperature as the initial temperature of the precipitant.

[0049] In this case, the Al precursor solution is injected until the pH reaches 5 to 7. If the pH falls below 5 after injecting the solution, a large amount of Al remains unprecipitated, resulting in a problem in process efficiency. If the pH does not reach 7 after injecting the solution, Al is not sufficiently precipitated, resulting in a problem in catalyst activity.

[0050] Filtration and washing steps The filtering and washing step includes a subsequent filtering and washing step following the Al precipitation step to remove unwanted ions other than the CuZnAl catalyst precursor, thereby obtaining the CuZnAl catalyst precursor. The CuZnAl catalyst precursor is then added to distilled water and stirred to dilute the unwanted ions remaining in the solid, and the solid is then recovered using a filter. This process is repeated several times.

[0051] Drying stage The drying step is necessary to remove moisture from the prepared CuZnAl catalyst precursor, and involves drying the CuZnAl catalyst precursor obtained from the filtering and washing steps in an oven at 100°C to 300°C for 22 to 24 hours. If the drying temperature is less than 100°C, it takes a long time to remove moisture, and if it exceeds 300°C, the crystal structure changes to an oxide state, making it difficult to determine the properties of the CuZnAl catalyst precursor.

[0052] Firing stage The calcination step is necessary to transform the catalyst into an oxide form before activation, and includes a calcination step at 300 to 500° C. If the temperature of the calcination step is less than 300° C., the transformation into an oxide form may not be sufficient, which may cause problems with the stability of the catalyst after activation, while if the temperature exceeds 500° C., there is a problem that the particles become large due to the high temperature.

[0053] The present invention provides a method for producing a water gas shift catalyst, which includes a reduction step of reducing the catalyst of the present invention or the catalyst produced by the production method of the present invention in a hydrogen atmosphere at 280 to 500°C.

[0054] The present invention provides a method for producing hydrogen. The present invention includes a reduction step in which the water gas shift catalyst according to the present invention is reduced in a hydrogen atmosphere at 280 to 500°C prior to the method for producing hydrogen.

[0055] In this case, the reduction step is necessary to transform copper oxide into active metallic copper. If the temperature of the reduction step is less than 280°C, reduction may not occur sufficiently, and if the temperature exceeds 500°C, problems may arise in that Cu and Zn may be alloyed or the particle size may become large due to the high temperature.

[0056] The composition of the mixed gas for the water gas shift reaction must contain carbon monoxide, and may be, for example, a mixed gas containing 1.5 mol % H2, 25.5 mol % N2, 60 mol % CO, and 13 mol % CO2.

[0057] The present invention provides a method for producing hydrogen using the catalyst according to the present invention or a catalyst produced by the production method according to the present invention.

[0058] The present invention provides a method for producing hydrogen, which comprises providing a catalyst according to the present invention or a catalyst produced by the production method of the present invention in a water gas shift reaction.

[0059] The catalyst may be reduced in a hydrogen atmosphere at 280 to 500°C.

[0060] In the hydrogen production method according to the present invention, the reaction temperature in the above step is 200 to 450°C, and the molar ratio of steam / carbon monoxide is 1.0 to 3.0, and hydrogen is produced using the water gas shift reaction.

[0061] If the reaction temperature is below 200°C, the supplied energy may be lower than the activation energy required to produce hydrogen, and if it exceeds 450°C, the hydrogen production reaction is an exothermic reaction, so the higher the temperature, the more the reverse reaction proceeds, limiting the reaction. Also, if the steam / carbon monoxide molar ratio is less than 1.0, the carbon monoxide cannot be used up, resulting in a corresponding under-synthesis of hydrogen, and if it exceeds 3.0, the unreacted excess steam must be separated.

[0062] In the method for producing hydrogen according to the present invention, the water gas shift reaction can be used to produce hydrogen from by-product gas, synthesis gas, gas produced by producing hydrogen and carbon monoxide through a reforming reaction of fossil fuel, a fuel reformer for a fuel cell, or a petrochemical process.

[0063] The present invention will be described in more detail below with reference to specific examples. The following examples are merely illustrative examples to aid in understanding the present invention, and are not intended to limit the scope of the present invention.

[0064] Example 1. Preparation of water-gas shift catalyst Example 1 First, a metal precursor solution containing Cu precursor and Zn precursor and an Al precursor solution were prepared. The molar ratio of Cu precursor to Zn precursor was 70:30, and the molar ratio of Al precursor was 4% of the total metal ions. The concentration of the metal precursor solution, in which the Cu precursor and Zn precursor were mixed, was 1.2M, and the concentration of the Al precursor solution was also 1.2M. In addition, the anion portion of each metal precursor was NO 3- For precipitation, a 0.1 M aqueous solution (precipitant solution, pH about 8) was prepared using basic NaHCO3.

[0065] Once all the solutions were prepared, the precipitant solution was heated to about 70°C, and then a metal precursor solution containing Cu precursor and Zn precursor was injected until the pH reached about 6. This corresponds to about 0 to about 15 minutes in Figure 5, and it was found that the pH tended to decrease because the injected solution (solution containing Cu and Zn precursors) was acidic.

[0066] The aging process begins when the pH no longer decreases (approximately 15 minutes in Figure 5). Next, once the precipitate is formed, it undergoes a first aging process at the same temperature for approximately one hour. During the aging process, the pH decreases to approximately 0.1 and then recovers, indicating that the precipitate has changed from an amorphous form to a crystalline form (pH at approximately 30 minutes in Figure 5).

[0067] After this phenomenon occurred, the Al precursor solution was injected 45 minutes later (approximately 75 minutes in FIG. 5). After the Al precursor solution was injected, an aging process was carried out for approximately 30 minutes.

[0068] The precipitate that had undergone the aging process was collected by filtration using filter paper, and unnecessary ions were removed by washing the collected precipitate with distilled water.

[0069] Thereafter, the recovered precipitate was dried in an oven set at 105° C. for about 12 hours to produce a catalyst precursor. The catalyst precursor prepared above was calcined in a muffle furnace at a temperature of 400°C (5°C / min) for 3 hours to prepare a catalyst.

[0070] A schematic diagram of the catalyst preparation process of Example 1 is shown in FIG. An image obtained by transmission electron microscopy (TEM) of a portion of the water gas shift catalyst prepared according to Example 1 is shown in FIG.

[0071] Comparative Example 1 A 1.2M metal precursor solution (175 mL) containing a mixture of Cu, Zn, and Al precursors was prepared. The mixture was then poured into a precipitant solution at the same temperature and pH as in Example 1 to carry out a precipitation process. The aging process was carried out for 1 hour and 30 minutes. The catalyst was then synthesized by filtering, washing, drying, and calcining under the same conditions as in Example 1.

[0072] A schematic diagram of the catalyst manufacturing process of Comparative Example 1 is shown in FIG. An image obtained by transmission electron microscopy (TEM) of a portion of the water gas shift catalyst prepared according to Comparative Example 1 is shown in FIG.

[0073] 2. Comparison of metal distribution in CuZnAl catalysts The TEM image of the catalyst particles prepared in Example 1 is shown in Figure 6a, and the aluminum content was analyzed by analyzing the aluminum concentration at each position within the catalyst particles using an EDS (Energy Dispersive Spectrometer) of a scanning electron microscope (TEM), and the results are shown in Table 1. Figure 6b shows the positions within the catalyst particles of spectra 1 to 6 in Table 1.

[0074] [Table 1]

[0075] As shown in Table 1, the surface layer of the catalyst particles prepared by the method of the present invention has a significantly higher Al content or ratio than Cu and Zn. The aluminum-rich layer also exhibits mass and atomic ratios similar to spectra 1, 3, and 5 in Figure 6b.

[0076] 3. Comparative evaluation of carbon monoxide conversion rate depending on catalyst structure Test pieces of each catalyst from Example 1 and Comparative Example 1 were molded to a size of 2 cm in diameter and 3 cm in height and calcined at 600°C for 1 hour. Prior to evaluation, the catalysts were reduced with hydrogen. H2 and N2 were mixed at 250 mL / min and 450 mL / min using a mass flow controller and introduced into the catalyst bed. The catalysts were reduced at atmospheric pressure (1 atm) while the temperature was increased to 400°C at a rate of 1°C / min.

[0077] The performance of each of the calcined and reduced catalysts from Example 1 and Comparative Example 1 was evaluated in a fixed-bed catalytic reaction system consisting of a reaction gas supply section, liquid evaporator section, water gas shift reactor section, cooling section, and analysis section. The reaction gas was supplied using a mass flow controller and had a composition of 1.5 mol% H2, 25.5 mol% N2, 60 mol% CO, and 13 mol% CO2. Liquid reactants, such as water, were supplied to the evaporator section using a high-pressure metering pump and preheated to 250°C before being supplied to the reaction section. The reaction gas containing water vapor was supplied to a SUS316 tube filled with catalyst, and the reaction temperature was controlled by measuring the temperature with a thermocouple at the top of the catalyst.

[0078] Experimental Examples 1-3 Five milliliters (approximately 6 g) of the calcined and reduced catalyst of Example 1 was loaded into a catalytic reaction system, and the steam to carbon monoxide molar ratio (S / C) of the feed gas was changed to 2.0 (Experimental Example 1), 2.5 (Experimental Example 2), and 3.0 (Experimental Example 3). The catalytic activity was measured, and the water gas shift reaction was carried out while changing the reaction temperature from 200 to 450°C for each experiment.

[0079] Comparative Experimental Examples 1-3 The water gas shift reaction was carried out in the same manner as in Experimental Examples 1 to 3 above, using the catalyst produced in Comparative Example 1, while varying the steam to carbon monoxide ratio (S / C ratio) of the feed gas to 2.0 (Comparative Experimental Example 1), 2.5 (Comparative Experimental Example 2), and 3.0 (Comparative Experimental Example 3).

[0080] The product was passed through a condenser to condense the remaining steam into water, and the remaining product gas was quantitatively analyzed using a TCD analyzer for gas chromatography (GC, USA, Agilent 7890). The CO conversion rates for Experimental Examples 1 to 3 and Comparative Experimental Examples 1 to 3 are shown in Table 2 at intervals of 50°C.

[0081] [Table 2]

[0082] To compare the durability of the catalysts, the water-gas shift reaction was carried out at 300°C for 100 hours with an S / C of 2. The CO conversion rates obtained as a result are shown in Figure 7. After a long-term (50-hour) performance evaluation, the CO conversion rates of the catalysts as a function of reaction temperature are summarized in Table 3.

[0083] [Table 3]

[0084] As shown in Table 3 above, the CuZnAl catalyst of Experimental Example 1 according to the present invention had a significantly higher carbon monoxide conversion rate depending on the reaction temperature than the CuZnAl catalyst of Comparative Experimental Example 1, and even after 50 hours, it still showed a better carbon monoxide conversion rate than the CuZnAl catalyst of Comparative Experimental Example 1.

[0085] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and it is obvious to those skilled in the art that various modifications and variations are possible within the scope that does not deviate from the technical idea of ​​the present invention described in the claims.

Claims

1. a copper-zinc coprecipitation step in which a metal precursor solution containing a Cu precursor and a Zn precursor is added to a precipitant solution until the pH reaches 5 to 8, thereby coprecipitating copper and zinc to form a copper-zinc coprecipitate; an Al precipitation step of injecting an Al precursor solution into a solution containing the copper-zinc coprecipitate to precipitate aluminum on the surface of the copper-zinc coprecipitate, thereby producing a CuZnAl catalyst precursor having an aluminum-rich layer on the surface; and a calcination step of calcining the CuZnAl catalyst precursor at 300°C to 500°C to prepare a CuZnAl catalyst; Including, The copper-zinc co-precipitation step is carried out by aging a mixture of the metal precursor solution containing the Cu precursor and the Zn precursor and the precipitant solution at room temperature (20° C.) to 80° C. for 30 to 180 minutes. The metal precursor solution has a molar ratio of Cu ions to Zn ions of 50:50 to 80:20; The Al precursor solution is injected after the pH value decreases to a range of 0.05 to 0.2 during aging and then recovers. The CuZnAl catalyst comprises catalytically active components including 40 to 80 mol % of copper (Cu), 15 to 50 mol % of zinc (Zn), and 1 to 13 mol % of aluminum (Al) based on the total catalyst metals.

2. 2. The method for producing a water gas shift catalyst according to claim 1, wherein the Al precursor solution is injected after the copper-zinc coprecipitate has changed from an amorphous form to a crystalline form during aging.

3. 2. The method for producing a water gas shift catalyst according to claim 1, wherein the Al precipitation step is performed by injecting an Al precursor solution into a solution containing the copper-zinc coprecipitate, and then aging the solution at a temperature of room temperature (20° C.) to 80° C. for 15 to 60 minutes.

4. 2. The method for preparing a water gas shift catalyst according to claim 1, wherein the metal precursor solution containing the Cu precursor and the Zn precursor has a concentration of 0.01M to 1.5M.

5. The Cu precursor, Zn precursor, and Al precursor are each prepared by adding NO ３ － , S.O. ４ ２－ , C.H. ３ COO － , HCOO － , Cl － and I － 2. The method for producing a water gas shift catalyst according to claim 1, wherein the catalyst is a salt having at least one anion selected from the group consisting of:

6. The precipitating agent is a carbonate or bicarbonate of an alkali metal, Li, Na, K or ammonium, NaOH and NH ４ 2. The method for preparing a water gas shift catalyst according to claim 1, wherein the precipitating agent is at least one selected from the group consisting of OH.

7. 2. The method for producing a water gas shift catalyst according to claim 1, wherein the precipitant solution has a temperature of room temperature (20° C.) to 80° C. and a pH of 6 to 9.

8. 2. The method for producing a water gas shift catalyst according to claim 1, wherein the precipitant solution has a concentration of 0.01M to 1.2M.

9. The method for producing a water gas shift catalyst according to claim 1, wherein the concentration of the Al precursor solution is 0.01 to 1.5M.

10. The method for producing a water gas shift catalyst according to claim 1, wherein the Al precursor solution is added until the pH reaches 5 to 7.

11. a filtering and washing step of filtering and washing the solution containing the CuZnAl catalyst precursor obtained in the Al precipitation step to obtain a CuZnAl catalyst precursor; 2. The method for preparing a water gas shift catalyst according to claim 1, further comprising a drying step of drying the obtained CuZnAl catalyst precursor in an oven at 100° C. to 300° C. for 22 to 24 hours.

12. The method for producing the water gas shift catalyst according to any one of claims 1 to 11, comprising a reduction step of reducing the CuZnAl catalyst in a hydrogen atmosphere at 280 to 500°C.

13. 12. A method for producing hydrogen, comprising the step of carrying out a water gas shift reaction by providing a catalyst produced by the method of any one of claims 1 to 11.

14. The method for producing hydrogen according to claim 13, wherein the catalyst is reduced in a hydrogen atmosphere at 280 to 500°C.

15. The method for producing hydrogen according to claim 13, wherein the water gas shift reaction is carried out at a reaction temperature of 200 to 450°C and a steam / carbon monoxide molar ratio of 1.0 to 3.0.

Images