Method for producing catalyst for steam reforming of sulfur-containing methane gas and method for producing hydrogen using the catalyst

Abstract

This relates to a method for manufacturing a nickel-auxiliary metal composite metal catalyst using an alumina carrier having a mixture of different crystal phases, and a method for manufacturing hydrogen by steam reforming of sulfur-containing methane gas using the same. The composite alumina carrier has acid sites removed by heat treatment, and is manufactured by compositely and sequentially incorporating nickel and auxiliary metals into the composite alumina carrier using a pressurized injection method. The alumina carrier has an α-alumina / θ-alumina ratio of 10 or more and a specific surface area of ​​5 to 20 m. 2 The present invention relates to a nickel-transition metal / mixed alumina catalyst, the catalyst being prepared and used with a pore size distribution in the range of 10-50 nm, the nickel loading amount in the catalyst being 5-15 wt%, the nickel dispersion degree being 2-15%, and the nickel / auxiliary metal weight ratio being in the range of 5-10, and a method for producing hydrogen by steam reforming of sulfur-containing methane gas using the catalyst. By using the catalyst prepared according to the present invention, the large pores in the catalyst maximize the gas permeability between the reactants and the catalyst, thereby increasing the reaction rate, and the problems of carbon deposition and particle sintering at high temperatures, which are problems with nickel catalysts, are suppressed by combining with cerium, and barium is added to increase resistance to sulfur poisoning, thereby improving the durability of the catalyst and enabling stable hydrogen production for a long period of time.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a nickel-alumina catalyst used in a steam reforming process for producing hydrogen from methane, the main component of liquefied natural gas. Specifically, the present invention relates to a method for producing a macroporous nickel-auxiliary metal / alumina catalyst and a method for producing hydrogen by the steam reforming reaction of sulfur-containing methane gas using the same. [Background technology]

[0002] Recently, industrial development and population growth have led to an increase in energy demand worldwide. However, the fossil fuels currently used as energy sources are gradually becoming depleted. Furthermore, in order to combat global warming caused by greenhouse gases, countries around the world are continuing to conduct research into clean energy sources that can replace fossil fuels. Among these, the substance that is most actively researched as an environmentally friendly energy source is hydrogen. Hydrogen is believed to be able to replace almost all of the energy used today, and because it does not contain carbon, the main component of carbon dioxide, it has attracted attention as a clean energy source.

[0003] Hydrogen is also used as a raw material for fuel cells, a type of renewable energy, and its demand is expected to explode in the future. Hydrogen production methods include the traditional reforming of fossil fuels and the electrolysis of water using renewable energy. Currently, electrolysis produces approximately 5-10% of the total hydrogen required. However, due to its low economic viability, full-scale mass production is expected to be possible after 2030 or 2040. Therefore, the most widely used methods for producing hydrogen are natural gas, polyols such as glycerol, sorbitol, and xylitol, and biomass. Many researchers are focusing on improving the efficiency and reducing the cost of hydrogen production in this process. Representative methods for producing hydrogen using natural gas include autothermal reforming [Non-Patent Document 1: Jeongdong Kim et al., Ind. Eng. Chem. Res. 2021, 60, 19. 7257-7274], partial oxidation [Non-Patent Document 2: Anis Fakeeha et al., Processes 2020, 8, 499], carbon dioxide reforming [Non-Patent Document 3: Mun-Sing Fan et al., Int J Hydrogen Energy, 36, 8, 2011, 4875-4886], and steam reforming [Non-Patent Document 4: Kantilal Chouhan et al., Int J Hydrogen Energy, 46, 53, 2021, Among these, the steam reforming process is the most economical hydrogen production process when carbon dioxide separation and storage are not taken into consideration. It is also the most commonly used process commercially because the products after the reaction are simpler than those of other reactions and the selectivity for hydrogen is high.

[0004] Generally, the conversion of natural gas (mainly methane) to hydrogen is an endothermic reaction, so it is carried out at high temperatures to maintain the reaction temperature, and excess steam is injected to reduce the rate of coke formation during the reaction.

[0005] Therefore, the currently commercialized methane steam reforming process (Reaction Scheme 1) produces synthesis gas of hydrogen and carbon monoxide at an operating temperature of 800°C to 1000°C by injecting steam to methane at a ratio of 2.0 to 3.0 over a reforming catalyst. Furthermore, the carbon monoxide produced after steam reforming is further converted into hydrogen through the water-gas shift reaction (Reaction Scheme 2), thereby increasing the hydrogen yield. The theoretical reaction scheme for converting natural gas to hydrogen is as follows:

[0006] Reaction 1 (methane steam reforming reaction): CH4 + H2O → CO + 3H2 Reaction 2 (carbon monoxide water-gas shift reaction): CO + H2O → CO2 + H2 Overall (Reaction 1 + Reaction 2) Reaction: CH4 + H2O → CO2 + 4H2

[0007] Catalysts for steam reforming reactions to produce hydrogen from natural gas must have high reaction activity, a certain life span, high heat transfer, low pressure drop, high thermal durability, and mechanical strength. To achieve this, catalysts are manufactured by incorporating active metals into a strong oxide support. To date, catalysts developed include precious metal catalysts (platinum, palladium, rhodium, ruthenium, iridium, etc.), non-precious metal catalysts (nickel, copper, etc.), and mixed precious and non-precious metal / non-precious metal catalysts (platinum-nickel, rhodium-nickel, ruthenium-nickel, nickel-copper, nickel-zinc, nickel-tin, etc.) (Non-Patent Document 5: Eugenio Meloni et al., Catalysts 2020, 10, 352). Precious metal catalysts have the advantage of lower coke generation during the reaction compared to non-precious metal catalysts, resulting in higher hydrogen production rates. However, the sustained rise in precious metal prices worldwide makes them less economical for commercial use. In the case of non-noble metal catalysts, nickel-containing catalysts are typically used in most reforming processes due to their reforming ability and low cost.

[0008] However, nickel catalysts are more susceptible to sulfur poisoning than precious metal catalysts (natural gas contains sulfur compounds such as thiophenes and mercaptans, which are removed using adsorbents before the reforming reaction. However, depending on the reforming method, sulfur remains in the gas after desulfurization at a level of 0.1 to 5 ppm, and the residual sulfur is adsorbed onto the catalyst during the reforming reaction, causing a decrease in activity). Furthermore, as summarized in Table 1, various forms of coke (whisker-type coke or pyrolytic coke) are actively produced at high temperatures, which can deposit on the metal and catalyst surfaces and continuously accumulate within the catalyst, ultimately destroying the catalyst itself, making them unsuitable for long-term use (Non-Patent Document 6: Qimin Ming et al., Catalysis Today, Vol. 77, Issue 1×2, 2002, Pages 51-64).

[0009] [Table 1]

[0010] In addition, due to its low thermal durability, nickel metal in the catalyst gradually aggregates and sinters during high-temperature reactions, increasing its particle size and gradually speeding up its deactivation rate over time. Regarding this technical point, JR Rostrup-Nielsen et al. (Advances in Catalysis 2002, 47:65-139) conducted research on the rate of coke formation as a function of nickel particle size and found that the larger the nickel particle size, the more rapidly the initial stage of coke formation occurs.

[0011] For these reasons, many researchers have been researching methods for manufacturing non-precious metal catalysts that can improve coke resistance, sulfur resistance, and long-term durability at high temperatures. Most of these studies have focused on increasing catalytic activity by diversifying the type of catalyst support or adjusting the metal-support interaction. Furthermore, research has been ongoing for a long time to increase activity by using composite metals in addition to nickel alone as the catalytically active metal. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Republic of Korea Patent No. 10-0781503 [Patent Document 2] Republic of Korea Patent No. 10-0962584 [Patent Document 3] Republic of Korea Patent No. 10-0980591 [Patent Document 4] Republic of Korea Patent No. 10-0394076 [Patent Document 5] Republic of Korea Patent No. 10-1625537 [Non-patent literature]

[0013] [Non-licensed document 1] Jeongdong Kim et al., Ind. Eng. Chem. Res. 2021, 60, 19. 7257-7274 [Non-licensed document 2] Anis Fakeeha et al., Processes 2020, 8, 499 [Non-licensed document 3] Mun-Sing Fan et al., Int J Hydrogen Energy, 36, 8, 2011, 4875-4886

Non-licensed Document 4

Non-licensed Document 5

Non-licensed Document 6

Non-licensed Document 7

Non-licensed literature 9

Non-licensed literature 10

[0014] As methods for suppressing coke deposition and enhancing activity by changing the type of support for nickel catalysts, catalysts in which nickel is supported on a silica-zirconia composite oxide support (Patent Document 1: Korean Patent No. 10-0781503), mesoporous nickel-alumina hybrid catalysts using anionic surfactants, sol-gel, and a templating method (Patent Documents 2-3: Korean Patent No. 10-0962584; Korean Patent No. 10-0980591), catalysts in which nickel is supported on a cerium-zirconia support (Patent Document 4: Korean Patent No. 10-0394076; Non-Patent Document 8: Ignacio Iglesias et al., Int J Hydrogen Energy, Vol. 44, Issue 16, 2019, Pages 8121-8132), and La catalysts using a template method have been reported. 1-x Ce x Catalysts using these supports have the advantage of improving catalyst durability, but they are limited in that their manufacturing process is more complicated and the manufacturing costs are higher than those of commercially available alumina supports, making them less competitive in terms of price.

[0015] In addition to nickel alone, methods for increasing activity by combining different metals as promoters with alumina supports have been used, such as Ni / Mg-Al2O3, Ni / Si-Al2O3, Ni / La-Al2O3, and Ni / Ce-Al2O3, which modify the properties of the support, or by adding auxiliary metals such as Ru, Au, Ce, Ir, Nb, Pt, Co, and Ag (Non-Patent Document 9: Haotian Zhang et al., Renewable and Sustainable Energy Reviews, 149, 2021, 111330). Non-Patent Document 10: Juliana da S. Lisboa et al. (Catalysis Today 101, 2005, pp. 15-21) and others demonstrated the effect of suppressing nickel particle agglomeration by adding alkali metals or alkaline earth metals to nickel catalysts, but also demonstrated the drawback of lower methane conversion and overall reaction activity. [Means for solving the problem]

[0016] As mentioned above, nickel catalysts developed to date have been improved in activity and durability through various methods. As part of these manufacturing methods, the present invention aims to manufacture a trimetal catalyst by adding nickel and other auxiliary metals to an alumina support with controlled pore characteristics, and to apply this catalyst to the steam reforming of sulfur-containing methane gas to demonstrate stable catalytic activity for a long period of time.

[0017] Therefore, a technical object of the present invention is to provide a method for manufacturing a catalyst used in producing hydrogen using the steam reforming reaction of sulfur-containing methane gas simulating natural gas, which has resistance to poisoning by trace amounts of sulfur components remaining in the reactants, minimizes deposition of coke generated during high-temperature reactions, and inhibits sintering of nickel metal, thereby maintaining stable reaction activity for a long period of time.

[0018] Another technical object of the present invention is to provide a method for stably producing hydrogen by steam reforming of sulfur-containing methane gas using the catalyst produced as described above.

[0019] In order to achieve the above technical objectives, the inventors have altered the pore distribution of a cost-competitive alumina carrier to allow natural gas, a reactant, to diffuse within the catalyst and for the product to quickly move out of the catalyst. They also fabricated a catalyst by positioning cerium, which can increase the dispersion of nickel, the main active site, and barium, which can suppress sulfur poisoning, in a tri-metallic form on the carrier to enable each metal to exhibit its own unique properties.

[0020] The alumina support used in the present invention is heat-treated to increase its strength so that it can withstand high temperatures during the reforming reaction, and the heat treatment temperature of the support is adjusted to have a surface area of ​​5 to 20 m2 so that 10 wt% or more of nickel and auxiliary metals can be supported. 2 The carrier was manufactured so that the average pore size was maintained in the range of 10-50 nm. The initial γ-alumina crystal phase was calcined at 1100-1150°C, and then the carrier was manufactured so that it consisted of a mixed α-alumina and θ-alumina crystal phase.

[0021] In the present invention, the catalyst is prepared by mixing 80-90 wt % of alumina carrier, 10-15 wt % of nickel metal, a weight ratio of nickel / cerium of 5-10, and a weight ratio of nickel / barium of 15-100, and the nickel metal is contained in the carrier at a concentration of 0.5-1.5 wt % / m 2 / g (weight % / specific surface area of ​​carrier 10-20m 2 / g basis), and the auxiliary metal cerium can be present uniformly in the carrier at an active metal density of 0.05 to 0.2 wt% / m 2 / g, and another auxiliary metal, barium, is added to the support at 0.005 to 0.03 wt% / m 2 The active metal density was uniformly distributed at 10 ...

[0022] The present invention also provides a method for preparing a support having an α-alumina / θ-alumina weight ratio of 10 or more (alpha 91% - theta 9%) to (alpha 100% - theta 0%) by heat treating spherical γ-alumina at 1100-1150°C, b) loading an alloy solution, in which nickel and cerium precursors are mixed and dissolved in a solvent, onto the prepared hybrid alumina support by pressurized spraying at room temperature, and c) drying the loaded support at 100-120°C in an air atmosphere and calcining it at 700-850°C. d) supporting the prepared nickel-cerium / mixed alumina material with a solution of a barium precursor at room temperature by a pressure spray method; e) drying the supported material in an air atmosphere at 100-120°C and calcining it at 500-600°C; and f) rapidly reducing the prepared nickel-cerium-barium / mixed alumina oxidation catalyst with hydrogen gas at a temperature in the range of 550-700°C to prepare a final catalyst.

[0023] The catalyst produced in the present invention is used in the steam reforming reaction of sulfur-containing methane gas, which simulates liquefied natural gas, and the steam / methane gas mixture is mixed at a volume ratio of 2.5 to 3.5 at a reaction temperature of 700 to 850°C and a gas hourly space velocity (GHSV) of 500 to 30,000 h -1 The present invention provides a method for producing hydrogen, characterized by carrying out a reaction under the following conditions: [Effects of the Invention]

[0024] The nickel-cerium-barium / alumina triple catalyst with controlled pore size and surface area prepared according to the present invention and the hydrogen production method using the same are applied to the steam reforming of sulfur-containing methane gas, and are designed to exhibit resistance to sulfur poisoning, catalyst sintering, and coke deposition, which are causes of catalyst deactivation, even under high-temperature reaction conditions. As a result, the agglomeration of nickel metal particles is suppressed, significantly reducing the rate of deactivation, and nickel metal is no longer poisoned by coke or sulfur, thereby maintaining a high and stable hydrogen conversion rate and selectivity over a long period of time during the steam reforming reaction. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a flowchart illustrating steps of a manufacturing method according to a first embodiment of the present invention. [Figure 2] 1 shows electron microscope (video microscopy) and electron probe X-ray microanalyzer (EPMA) photographs of the catalyst prepared in Example 1 of the present invention. [Figure 3] 1 shows the results of a long-term reforming reaction using the catalysts produced in Example 1 and Comparative Examples 4, 5, and 6. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention relates to a method for producing a catalyst for use in the steam reforming of sulfur-containing methane gas. The method comprises preparing a support with controlled acid sites and pore size, using nickel as an active metal, and supporting cerium and barium as auxiliary metals to enhance sulfur resistance and coke resistance.

[0027] The composite metal catalyst of the present invention, in which nickel-auxiliary metal is supported on an alumina support having controlled crystalline phase and pore characteristics, is a) heat-treating spherical γ-alumina at 1100-1150°C to prepare a carrier having an α-alumina / θ-alumina weight ratio of 10 or more, preferably 91% by weight or more of α-alumina and 9% by weight or less of θ-alumina; b) supporting an alloy solution, in which nickel and cerium precursors are mixed and dissolved in a solvent, on the prepared composite alumina support by a pressurized spray method at room temperature; c) After loading, drying at 100 to 120 ° C in an air atmosphere and calcining at 700 to 850 ° C; d) supporting a solution of a barium precursor dissolved in a solvent on the prepared nickel-cerium / mixed alumina by pressurized spraying at room temperature; e) After loading, drying at 100 to 120 ° C in an air atmosphere and calcining at 500 to 600 ° C; f) rapidly reducing the prepared nickel-cerium-barium / mixed alumina oxidation catalyst at a high temperature of 550 to 700°C using hydrogen gas to prepare a catalyst.

[0028] Each step will be explained in detail below. The temperature units indicated in this specification are in degrees Celsius.

[0029] In step a), the alumina support can be prepared by using boehmite, pseudoboehmite, or γ-alumina as a starting material. The support can be heat-treated in a heat treatment furnace at 1100-1150°C for 1-5 hours to remove acid sites and adjust the pore size, thereby changing the crystalline phase to α-alumina containing 1-10 wt% θ-alumina. The heat treatment temperature is closely related to the crystalline phase and pore structure of the support. When the heat treatment temperature is less than 1100°C, the crystalline phase of the alumina may be a mixture of θ-alumina and γ-alumina, and acid sites may still exist within the support. The pore size of the support is small, which may slow the diffusion rate of reactants within the support. When the heat treatment temperature exceeds 1150°C, the pore size increases, and the crystalline phase of the alumina becomes the alpha phase, which exists as a single crystalline phase, and all acid sites within the support are removed, but the specific surface area is reduced to 3 m. 2 The alumina support thus prepared has an average pore size distribution in the range of 20 to 50 nm, an α-alumina / θ-alumina ratio of 10 or more, and a specific surface area of ​​5 to 20 m 2 The carrier may be in the form of a sphere, a cylinder, a pellet, or a tube, and these shapes can be produced by oil-drop, tablet, or extrusion methods.

[0030] In step b), the nickel precursor can be any one of nickel nitrate hydrate, nickel chloride hydrate, nickel acetate hydrate, and nickel sulfate hydrate, and the cerium precursor can be any one of cerium nitrate hydrate, cerium chloride hydrate, cerium acetate hydrate, cerium sulfate hydrate, and cerium oxalate hydrate. Preferably, compounds having the same anion form can be sequentially supported or mixed to prepare a support solution. The active metal precursor can be prepared by dissolving the active metal precursor in ion water or a dihydric alcohol (e.g., ethanol, ethylene glycol) in a solvent equal to the pore volume of the support and then supporting it on the support using a pressurized spray method.

[0031] The nickel precursor can be supported at 10-15 wt% based on the final catalyst. If supported at less than 10 wt%, catalytic performance is difficult to achieve, while if supported at more than 15 wt%, the nickel precursor is not absorbed into the support and accumulates on the surface of the support, resulting in poor nickel dispersion and reduced durability. The cerium precursor can be supported at a nickel / cerium weight ratio of 5-10, preferably 5-7.

[0032] Step c) may include a step of drying the nickel-cerium / mixed alumina precursor prepared in step b) and then heat-treating it at a temperature in the range of 700 to 800°C to remove moisture and anions derived from the metal precursor. The heat-treatment temperature is common knowledge and may be within an appropriate range, so further detailed description will be omitted. However, it is preferable to perform the heat-treatment at a temperature equal to or higher than the reforming reaction temperature to prevent deformation of the metal in the catalyst during the steam reforming reaction.

[0033] In step d), the barium precursor can be any one of barium nitrate hydrate, barium chloride hydrate, barium acetate hydrate, and barium hydroxide hydrate. The active metal precursor can be prepared by dissolving it in a solvent of ionized water or a dihydric alcohol (e.g., ethanol or ethylene glycol) in an amount equal to the pore volume of the support and supporting it on the support using a pressurized spray method. The barium precursor can be supported at a nickel / barium weight ratio of 15 to 100, preferably 80 to 100. If the weight ratio is less than 15, excessive barium is supported in the catalyst, resulting in a low reaction conversion rate. If the weight ratio is more than 100, the sulfur resistance effect of barium may not be exhibited.

[0034] Step e) may include a step of drying the nickel-cerium-barium / mixed alumina precursor prepared in step d) and then heat-treating it in an air atmosphere at a temperature ranging from 500 to 600°C to remove moisture and anions derived from the metal precursor. The heat-treatment temperature may be within a suitable range according to common knowledge, and therefore further detailed description thereof will be omitted.

[0035] In step f), the nickel-cerium-barium / mixed alumina oxide prepared in step e) is rapidly reduced using hydrogen gas at a temperature between 550 and 700°C to obtain the final catalyst. If the reduction temperature is below 400°C, the metal oxide species may not be completely reduced. If the reduction temperature is above 700°C, the metal particles may aggregate and sinter, resulting in a decrease in active sites. The reduction process was carried out by raising the temperature to 600°C in a nitrogen atmosphere in a stepwise manner, followed by flowing hydrogen gas. When two or more active metal species are present in the catalyst, immediate exposure to hydrogen gas at a high temperature, as in the reduction method described above, can instantly convert the active metal species into an alloy. However, if the temperature is gradually increased from room temperature to a hydrogen atmosphere for reduction, each metal is reduced according to its own oxygen desorption temperature, making it difficult to convert the active metal species into an alloy.

[0036] In addition, the catalyst prepared in the present invention can be used for the steam reforming reaction of sulfur-containing methane gas after being introduced into a reactor. The steam / methane gas mixture is mixed at a volume ratio of 2.5 to 3.5 at a reaction temperature of 700 to 850°C and a gas hourly space velocity (GHSV) of 500 to 30,000 h -1 Hydrogen can be produced by a gas phase reaction under the conditions of (1) and (2). The higher the gas space velocity, the greater the amount of hydrogen produced, so the optimum value can be arbitrarily adjusted according to the volume of the reactor and the amount of catalyst, and therefore, there is no particular limit to the range.

[0037] The reactor for producing hydrogen through the reforming reaction is not particularly limited, but may be a fixed-bed catalytic reactor, in which a catalyst is packed inside the reactor. Furthermore, because the dehydrogenation reaction is an endothermic reaction, it is important that the catalytic reactor remain adiabatic. It is important that the reforming reaction process of the present invention is carried out under appropriate reaction conditions, including reaction temperature, pressure, and gas space velocity. If the reaction temperature is below 700°C, the reforming reaction will not proceed sufficiently, resulting in a very low amount of hydrogen. If the reaction temperature is above 850°C, side reactions such as agglomeration of the active metals of the catalyst introduced into the reactor, sintering, coke formation, and cracking reactions may occur, potentially resulting in poor catalyst durability.

[0038] The technical configuration of the present invention will be described in detail below with reference to the drawings, examples, and comparative examples.

[0039] Example 1 The carrier used in Example 1 was a γ-alumina carrier (manufactured by BASF, Germany, specific surface area: 210 m 2 / g) was calcined at 1100°C for 5 hours to cause a phase transition before use. The phase-transformed support had a structure in which the θ-alumina crystalline phase and the α-alumina crystalline phase were mixed in a ratio of 1:9, and had a specific surface area of ​​19 m 2The catalyst has physical properties of 0.01g / g and a pore size of 32nm. To initially support the metals, nickel was used as a precursor (Ni(NO3)2·6H2O), and cerium, used as an auxiliary metal, was used as a precursor (Ce(NO3)3·6H2O). The nickel and cerium precursors were dissolved in water and impregnated into a phase-transformed theta-alpha hybrid alumina support using a spray-loading method. After impregnation, the catalyst underwent an aging process for approximately one hour to ensure that the metal solution was thoroughly distributed throughout the support. The catalyst was then dried at 120°C for 12 hours to completely remove moisture from the catalyst, and then heat-treated in an air atmosphere at 700°C for six hours to immobilize the metals. Thereafter, to support the metals again, barium acetate (Ba(C2H3O2)2) was supported on the internal pores of the alumina containing nickel and cerium using the spray support method. The metal-supported composition was heat-treated in an air atmosphere at 550°C for 4 hours to prepare a metal-supported catalyst. The heat-treated catalyst was heated to 600°C in an air atmosphere, purged with nitrogen for 5 minutes, and then subjected to rapid reduction in a hydrogen gas flow to prepare a catalyst. The catalyst prepared in Example 1 was confirmed to contain 10.0 wt% nickel, 1.5 wt% cerium, and 0.12 wt% barium. The nickel-cerium-barium mixture was uniformly distributed within the support.

[0040] <Example 2> In Example 2, a catalyst was produced in the same manner as in Example 1, except that the final catalyst contained 5.0 wt % nickel, 0.75 wt % cerium, and 0.06 wt % barium as metals.

[0041] Example 3 In Example 3, a catalyst was produced in the same manner as in Example 1, except that the final catalyst contained 15.0 wt % nickel, 2.25 wt % cerium, and 0.18 wt % barium as metals.

[0042] <Comparative Example 1> In Comparative Example 1, a catalyst was produced in the same manner as in Example 1, except that the carrier used in Example 1 was heat-treated at a temperature of 900°C during the preparation of the carrier. The carrier crystal phase of the catalyst was a mixture of γ and θ phases, and the specific surface area was 121 m 2 / g, and the pore size was 10 nm.

[0043] <Comparative Example 2> In Comparative Example 2, a catalyst was produced in the same manner as in Example 1, except that the carrier used in Example 1 was heat-treated at a temperature of 1000°C during the preparation of the carrier. The carrier crystal phase of the catalyst was a mixture of γ and θ phases, and the specific surface area was 84 m 2 / g, and the pore size was 14 nm.

[0044] <Comparative Example 3> In Comparative Example 3, a catalyst was produced in the same manner as in Example 1, except that the carrier used in Example 1 was heat-treated at a temperature of 1200°C during the preparation of the carrier. The carrier crystal phase of the catalyst was the alpha phase, and the specific surface area was 3m 2 / g and the pore size was 45 nm.

[0045] <Comparative Example 4> Comparative Example 4 was produced in the same manner as in Example 1, except that only nickel was used as the metal, and the final catalyst contained only 10.0 wt % of nickel as the metal.

[0046] <Comparative Example 5> Comparative Example 5 was produced in the same manner as in Example 1 except that only nickel and cerium were used as metals, and the final catalyst contained 10.0 wt % nickel and 1.5 wt % cerium as metals.

[0047] <Comparative Example 6> Comparative Example 6 was produced in the same manner as in Example 1 except that only nickel and barium were used as metals, and the final catalyst contained 10.0 wt % nickel and 0.12 wt % barium as metals.

[0048] <Comparative Example 7> Comparative Example 7 was produced in the same manner as in Example 1, except that the production temperature of the reduction catalyst was set to 650°C.

[0049] <Comparative Example 8> Comparative Example 8 was produced in the same manner as in Example 1, except that the production temperature of the reduction catalyst was set to 700°C.

[0050] <Comparative Example 9> Comparative Example 9 was produced in the same manner as in Example 1, except that the temperature was raised in a hydrogen atmosphere during production of the reduction catalyst.

[0051] <Comparative Example 10> Comparative Example 10 was produced in the same manner as in Example 1, except that nickel, cerium, and barium were separately supported.

[0052] <Comparative Example 11> Comparative Example 11 was produced in the same manner as Comparative Example 10, except that the temperature was raised in a hydrogen atmosphere during production of the reduction catalyst.

[0053] <Reaction example> The catalysts prepared in the Examples and Comparative Examples were evaluated for their performance as follows. To measure catalytic activity, a reforming reaction was carried out using a methane and hydrogen mixed gas. The reactor was evaluated using a fixed-bed reactor. 1.57 g of the catalyst was packed into a tubular reactor. Prior to the reaction, hydrogen gas was supplied at a constant rate of 30 cc / min to remove oxygen species from the catalyst surface, and the catalyst was reduced at 800°C for 1 hour. The reactor temperature was then maintained at a constant reaction temperature of 800°C, and a mixture of methane and hydrogen, the raw materials used in the reaction, was continuously supplied to the reactor at a constant volume ratio of 1:1, with a gas space velocity of 2000 h. -1The temperature was fixed at a constant value. In addition, to suppress the generation of coke during the catalytic reaction, steam and carbon were injected together at a ratio of 0.85:1. The reaction pressure was maintained at a constant 1.0 atmosphere using a pressure regulator. The substances produced after the reaction were transferred to a gas chromatography (GC) system via an injection line wrapped with a hot wire, and quantitative analysis was performed using a flame ionization detector (FID) and a thermal conductivity detector (TCD).

[0054] In the sulfur tolerance experiment, hydrogen sulfide was injected continuously at 5~15 ppm per minute together with methane / hydrogen mixed gas to simulate the sulfur components present in natural gas, and activity was compared.

[0055] The conversion rate of methane to the reactants was calculated according to the following criteria to compare the activity of the catalysts.

[0056] Methane conversion rate (%) = [number of moles of methane before reaction - number of moles of methane after reaction] / [number of moles of methane before reaction] x 100

[0057] Table 2 shows the manufacturing methods of the examples and comparative examples, and Table 3 shows the activity evaluation results for the catalysts manufactured by the examples and comparative examples without sulfur injection.

[0058] [Table 2]

[0059] [Table 3]

[0060] <Evaluation> Examples 2 and 3 and Comparative Examples 1 to 11 were compared with Example 1. The nickel dispersion and particle size were analyzed by carbon monoxide chemisorption (CO chemisorption), and the conversion rate and coke were analyzed by performing a methane reforming reaction without sulfur injection.

[0061] In Examples 1 to 3, the ratios of nickel, cerium, and barium were the same, but the total metal content ratios within the catalyst were adjusted to produce catalysts. Example 2 showed a significantly low methane conversion rate due to the low nickel content. In Example 3, excessive amounts of nickel and cerium were contained in the catalyst, resulting in low nickel dispersion, and thus the performance was lower than that of Example 1, despite the nickel content being 15 wt. This indicates that an appropriate amount of active metal is supported for the methane reforming reaction.

[0062] In Example 1 and Comparative Examples 1 to 3, catalysts were produced using different carrier calcination temperatures. In Comparative Examples 1 and 2, when the calcination temperature was 1000°C or less, the γ-alumina crystalline phase and the θ-alumina crystalline phase were mixed before calcination, and the specific surface area was 100 m 2 / g or more, and a considerable amount of micropores existed within the support, resulting in high nickel dispersion. As a result of the methane reforming reaction, Comparative Examples 1 and 2, which contained a γ-alumina crystalline phase, showed high coke generation, which is believed to be due to the acid sites on the surface of the γ-alumina, causing a large amount of coke generation during the reforming reaction. In contrast, Comparative Example 3, which was calcined at 1200°C, showed a pure α-alumina crystalline phase, resulting in very low nickel dispersion due to its low specific surface area. When the α-alumina crystalline phase was present, the coke generation during the reforming reaction was low, but the methane conversion rate was low. This indicates that the low specific surface area of ​​α-alumina causes nickel metal to aggregate, resulting in a low specific surface area and therefore low activity. This indicates that the θ-alumina or higher crystalline phase must be transformed before the reforming reaction, indicating that the surface area within the support must be adequate.

[0063] Example 1 and Comparative Examples 4 to 6 were prepared by individually supporting active metals within the catalyst and comparing them. Comparative Examples 4 and 6, which are catalysts without cerium support, were analyzed to have slightly lower nickel dispersion than Example 1, and the amount of coke after the reaction was also higher in Comparative Examples 4 and 6. This indicates the effect of supporting cerium in Example 1, while Comparative Example 5 showed values ​​similar to those in Example 1, indicating that barium is not involved in activity or coke formation.

[0064] In Example 1 and Comparative Examples 7 and 8, catalysts were prepared by adjusting the temperature of hydrogen reduction, which is the metal activation step of the prepared catalyst. In Comparative Examples 7 and 8, it was found that the nickel dispersion decreased due to the high reduction temperature, which resulted in a low methane conversion rate during the reforming reaction.

[0065] Example 1 and Comparative Example 9 were prepared using different reduction methods during hydrogen reduction, which is the metal activation step of the prepared catalyst. In Comparative Example 9, the temperature was raised to 600°C, the reduction temperature, in a hydrogen atmosphere. As a result, the nickel dispersion and methane conversion rate were similar to those of Comparative Example 4, which was a catalyst supported solely on nickel. This indicates that when reduction was performed while raising the temperature, alloying with cerium did not occur, and the effect of adding cerium was not achieved.

[0066] Example 1 and Comparative Examples 10 and 11 compare the effect of sequential metal loading and the effect of temperature-programmed reduction after sequential metal loading during active metal loading. Comparative Examples 10 and 11 both exhibited the same nickel dispersion as Comparative Example 4, but showed lower reactivity than Example 1. This is thought to be because cerium and barium did not form an alloy with nickel, but rather blocked the surface of the nickel metal in the catalyst and the surface area within the support, causing a decrease in activity.

[0067] As a result, as in Example 1, the crystal phase of the support was a θ-alumina / α-alumina mixture, and the specific surface area of ​​the support was approximately 20 m 2 / g, nickel content was approximately 10 wt%, nickel / cerium weight ratio was 6.7, nickel / barium weight ratio was 83, metal loading was performed in the order of primary nickel-cerium and barium, and reduction step was performed by rapid reduction at 600°C, which enabled the production of a catalyst with high methane conversion rate and low coke formation.

[0068] Meanwhile, Table 4 and FIG. 3 show the results of evaluation of the deactivation degree and long-term durability after catalytic reaction with respect to the sulfur content for the catalysts prepared in Example 1 and Comparative Examples 4 to 6.

[0069] [Table 4]

[0070] <Evaluation> In Table 4 and FIG. 3, the reforming reaction of methane gas containing sulfur was carried out for Example 1 and Comparative Examples 4 to 6.

[0071] Table 3 shows that for all catalysts in Example 1 and Comparative Examples 4 to 6, deactivation clearly occurred 24 hours after the start of the reaction as the sulfur content increased. However, at the same sulfur injection amount, the catalyst in Example 1 showed the lowest deactivation degree, while Comparative Examples 4 and 5, which did not contain barium, showed high deactivation degrees, indicating that barium helps suppress catalyst deactivation. In terms of methane conversion, Example 1 and Comparative Example 5, which carried cerium to promote nickel dispersion, showed higher values ​​than the catalysts not carrying cerium.

[0072] Next, a long-term activity evaluation was carried out for Example 1 and Comparative Examples 4 to 6 at the same sulfur injection amount, and the results are shown in FIG.

[0073] In both Example 1 and Comparative Examples 4 to 6, rapid deactivation occurred during the initial 24 hours of the reaction, but activity gradually decreased thereafter. In particular, Example 1 showed a performance decrease of approximately 7% from 24 hours to 100 hours, while the catalysts of Comparative Examples 4 to 6 showed a performance decrease rate of approximately 10%.

[0074] Therefore, Example 1, which contained cerium to increase nickel dispersion and barium to increase sulfur resistance, not only showed the highest activity and the lowest deactivation rate, but also high durability in long-term evaluation.

Claims

1. A method for producing a catalyst for steam reforming of sulfur-containing methane gas, comprising: a) heat-treating γ-alumina at 1100-1150°C to prepare a hybrid alumina support having an α-alumina / θ-alumina ratio of 10 or more; b) supporting an alloy solution in which a nickel precursor and a cerium precursor are mixed and dissolved in a solvent on the prepared composite alumina support; c) supporting the nickel-cerium / mixed alumina obtained by drying and calcining the support with a solution containing a barium precursor; d) drying and calcining the support to produce a nickel-cerium-barium / mixed alumina catalyst, and reducing the catalyst at a temperature in the range of 550 to 600°C. A method characterized by:

2. The mixed alumina contains 91% by weight or more of α-alumina and 9% by weight or less of θ-alumina. The method of claim 1.

3. The loading steps b) and c) are carried out at room temperature by pressurized injection. The method of claim 1.

4. In the step c), the drying and firing are carried out in an air atmosphere at 100 to 120°C and then at 700 to 850°C. The method of claim 1.

5. In the step d), drying and calcination are carried out in an air atmosphere at 100 to 120°C and calcination at 500 to 600°C. The method of claim 1.

6. The reduction is carried out using hydrogen gas. The method of claim 1.

7. A method for producing hydrogen by steam reforming of sulfur-sulfate methane gas in a reactor containing a catalyst, comprising: At a reaction temperature of 700 to 850°C, a mixture of steam and methane gas in a volume ratio of 2.5 to 3.5 is reacted at a gas space velocity of 500 to 30,000 h －１ A gas phase reaction is carried out under the conditions of The catalyst is produced by the method of claim 1. A method characterized by:

8. The reactor is a fixed-bed catalytic reactor in which a catalyst is packed. The method of claim 7.

9. The fixed bed catalytic reactor is maintained adiabatic. The method of claim 8.

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