Catalyst for converting ortho-hydrogen to para-hydrogen

Abstract

To provide an efficient catalyst capable of converting ortho-hydrogen into para-hydrogen.SOLUTION: There is provided a catalyst for converting ortho-hydrogen into para-hydrogen, the catalyst including nickel as an active ingredient, wherein the position of the strongest peak in an H2-TPR spectrum lies within 100°C to 350°C, and more preferably, the ratio (IHT / ILT) between the maximum peak intensity (ILT) observed in the low-temperature region of 100°C to 350°C and the maximum peak intensity (IHT) observed in the high-temperature region of 350°C to 600°C is less than 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a catalyst for converting orthohydrogen to parahydrogen. [Background technology]

[0002] Hydrogen can be produced from a variety of resources, and is therefore expected to be an energy source that can help reduce energy supply and procurement risks. Furthermore, hydrogen can be used as a carbon-free energy source by combining renewable energy-based water electrolysis and fossil fuels with carbon dioxide storage and reuse technologies, and is attracting attention as a substance that can play an important role in achieving carbon neutrality. However, because hydrogen is a gas at room temperature, its large volume and low transport efficiency pose a challenge. One known solution to this problem is to liquefy hydrogen to reduce its volume for transportation.

[0003] Due to the relationship between spin angular momentum, hydrogen exists in two states: ortho-hydrogen and para-hydrogen. In normal gaseous hydrogen (at room temperature), the spin equilibrium composition ratio between ortho-hydrogen and para-hydrogen is approximately 3:1. However, because para-hydrogen has less rotational energy, at low liquid hydrogen temperatures, almost all ortho-hydrogen is gradually converted to para-hydrogen over time (this reaction is called the "ortho-para-hydrogen conversion reaction"). A known issue is that the heat of reaction generated during this process vaporizes some of the liquefied hydrogen, reducing the efficiency of liquid hydrogen production. For this reason, there has been a demand for an ortho-para-hydrogen conversion catalyst that can increase the efficiency of ortho-hydrogen to para-hydrogen conversion and suppress the vaporization of liquid hydrogen, thereby increasing the efficiency of liquid hydrogen production.

[0004] Patent Document 1 describes the use of magnetic materials such as iron oxide and chromium oxide as catalysts to promote the conversion of ortho-hydrogen to stable para-hydrogen at low temperatures. Patent Document 2 discloses an ortho-para conversion catalyst obtained by heating and dehydrating a precipitate primarily composed of hydrous ferric oxide to form ferric oxide, which is then activated in a hydrogen stream. Patent Document 3 discloses a silica-nickel catalyst obtained by adding an aqueous solution of nickel sulfate to an aqueous solution of sodium silicate, neutralizing the mixture with an alkali, gelling the mixture, and then washing and drying it.

[0005] However, the catalysts described in Patent Documents 1 and 2, which use iron oxide as the active ingredient, have low efficiency in converting ortho-hydrogen to para-hydrogen, and the silica-nickel catalyst described in Patent Document 3 converts ortho-hydrogen to para-hydrogen by dispersing nickel oxide in silica gel and bringing the ortho-hydrogen in the silica gel into contact with the nickel oxide. Immediately before use, the catalyst is activated by reducing the nickel oxide, but because nickel oxide is more difficult to reduce than nickel with a thin oxide film, activation is insufficient and the ortho-para conversion efficiency is often low. As carbon neutralization progresses and liquid hydrogen usage is expected to increase in the future, highly active catalysts with high ortho-para conversion efficiency are needed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-12693 [Patent Document 2] Japanese Patent Publication No. 52-17383 [Patent Document 3] Japanese Patent Application Publication No. 49-41290 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention relates to an ortho-para-hydrogen conversion catalyst that can efficiently convert ortho-hydrogen into para-hydrogen. [Means for solving the problem]

[0008] The inventors discovered that the reduction state of nickel, the active component, has a significant impact on the conversion efficiency of ortho-para-hydrogen conversion. The present invention provides an ortho-para-hydrogen conversion catalyst containing nickel as an active component, which increases the ortho-para-hydrogen conversion efficiency by reducing the proportion of nickel, which is difficult to reduce, while increasing the proportions of metallic nickel and nickel, which is easily reduced, thereby using the H2-TPR spectrum as an indicator and positioning the peak with the highest intensity in the spectrum in the range of 100°C to 350°C.

[0009] Specifically, the catalyst of the present invention is an ortho-para-hydrogen conversion catalyst that converts ortho-hydrogen to para-hydrogen, and is characterized by containing nickel as an active component and having the highest peak intensity in the H2-TPR spectrum in the range of 100°C to 350°C.

[0010] [Specific explanation] The invention will be described in detail below. In this specification, unless otherwise specified, the symbol "to" indicating a range includes the upper and lower limits of the range, for example, "X to Y" means "greater than or equal to X and less than or equal to Y." The elements, groups, and periods shown in this specification are based on the IUPAC periodic table.

[0011] The catalyst of the present invention converts orthohydrogen to parahydrogen and contains nickel as an active component. The nickel contained in the catalyst of the present invention is present in various forms, such as metallic state, state with an oxide film on the metal surface, and state of oxide. However, nickel with high catalytic activity is found in metallic nickel and easily reduced nickel. The catalyst of the present invention has a high proportion of metallic nickel and easily reduced nickel, and therefore has a peak with the highest intensity in the H2-TPR spectrum in the low temperature range of 100°C to 350°C.

[0012] H2-TPR is a method for examining the reducing properties of a catalyst by passing a constant flow of reducing gas through the catalyst while raising the temperature at a constant rate. Generally, hydrogen gas diluted with an inert gas such as argon is used as the reducing gas, and H2-TPR spectra corresponding to temperature changes can be obtained.

[0013] The catalyst of the present invention uses nickel as an active component, and its activity is determined using an H2-TPR spectrum as an index, with the position of the highest peak in the spectrum being in the range of 100° C. to 350° C. The activity of nickel varies greatly depending on factors such as the form of the nickel, the surface condition of the nickel, the interaction with the support, and the presence or absence of a co-catalyst. Nickel with high catalytic activity is metallic nickel and easily reduced nickel, and this easily reduced nickel is, for example, nickel with a thin oxide film.

[0014] The peak position of the H2-TPR spectrum varies depending on the state of nickel. For materials containing a large amount of metallic nickel or easily reduced nickel, the highest peak position of the H2-TPR spectrum appears in the low-temperature range of 100°C to 350°C, while for materials containing a large amount of nickel that is difficult to reduce, the highest peak position of the H2-TPR spectrum appears in the high-temperature range of above 350°C to 600°C.

[0015] The catalyst of the present invention has a high activity, with the highest peak in the H2-TPR spectrum located in the low temperature range of 100°C to 350°C, and contains a large amount of metallic nickel and nickel with a thin oxide film. The catalyst of the present invention also contains nickel with a thin oxide film on the metallic nickel surface, but the metallic nickel is present below the oxide film, resulting in a high metallic nickel content. The catalyst of the present invention preferably has a high peak in the H2-TPR spectrum located in the range of 100°C to 300°C, and more preferably in the range of 100°C to 250°C.

[0016] The reason why the high content of metallic nickel and easily reduced nickel leads to high activity in ortho-para hydrogen conversion reactions is not clear, but it is thought that this is because hydrogen penetrates into the interior of the nickel, which cannot be fully utilized in normal catalytic reactions, and both the surface and the interior act effectively as reaction fields.

[0017] The catalyst of the present invention has the highest peak intensity (I LT ) and the highest peak intensity (I HT ) ratio (I HT / I LT ) is preferably less than 1, more preferably less than 0.5. (Examples 1 to 4) When this peak intensity ratio is less than 1, more preferably less than 0.5, the activity for ortho-para-hydrogen conversion tends to be higher.

[0018] The content of nickel contained in the catalyst of the present invention is preferably in the range of 40% by mass to 80% by mass, more preferably 45% by mass to 75% by mass, and particularly preferably 50% by mass to 70% by mass, calculated as nickel relative to the total weight of the catalyst. When the nickel content is in the above range, the activity in the ortho-para hydrogen conversion reaction tends to be higher.

[0019] In the catalyst of the present invention, the nickel crystallite size is preferably 8.0 nm or less, more preferably 7.0 nm or less, and particularly preferably 6.0 nm or less. In the present invention, the nickel crystallite size can be calculated from an X-ray diffraction pattern. Specifically, it can be calculated using the peaks attributed to metallic nickel that appear in the X-ray diffraction pattern. Nickel crystallites within the above range have a short distance from the surface to the interior of the nickel, which facilitates hydrogen penetration, and is therefore thought to exhibit high activity in the ortho-para hydrogen conversion reaction. The lower limit of the nickel crystallite size may be 1.0 nm or more, 2.0 nm or more, or 3.0 nm or more.

[0020] The catalyst of the present invention may contain a promoter component in addition to nickel. The promoter component is preferably at least one element selected from Mg, Cu, Cr, Mn, and Zr, more preferably at least one element selected from Cu, Cr, and Mn, and particularly preferably contains all of Cu, Cr, and Mn. These promoter components are thought to exist in the catalyst of the present invention in the form of oxides, metals, or the like. Furthermore, some of them are thought to form alloys with Ni metal. The catalyst of the present invention containing such promoter components is likely to have higher activity in the ortho-para hydrogen conversion reaction.

[0021] In the catalyst of the present invention, the content of the promoter components is preferably in the range of 1 to 10 mass %, more preferably 2 to 8 mass %, and particularly preferably 3 to 7 mass %, calculated as the total oxide content of each element relative to the total mass of the catalyst of the present invention. By including a promoter with a content in the above range, the activity in the ortho-para-hydrogen conversion reaction can be increased.

[0022] The catalyst of the present invention has a specific surface area of ​​50 m 2 / g~400m 2 / g, and 75m 2 / g~300m 2 / g range is more preferable, and 100m 2 / g~210m 2 The specific surface area in the above range can enhance the activity in the ortho-para hydrogen conversion reaction.

[0023] The catalyst of the present invention preferably includes a carrier. The active component, nickel, is dispersed and supported on the carrier, resulting in higher activity in the ortho-para hydrogen conversion reaction. The carrier is preferably at least one selected from silica, alumina, and titania. Carriers made of these compounds allow nickel to be more easily dispersed. Silica-rich diatomaceous earth, or clay minerals such as sepiolite and attapulgite can also be used as the carrier.

[0024] The content of the support, calculated as the total amount of each oxide, is preferably 40 mass % or less, more preferably 35 mass % or less, and particularly preferably 30 mass % or less, relative to the total mass of the catalyst of the present invention. The catalyst of the present invention having a support content within the above range can have higher activity in the ortho-para hydrogen conversion reaction.

[0025] The catalyst of the present invention can be suitably used in the ortho-para hydrogen conversion reaction whether in powder form or in a molded form. By increasing the contact area with hydrogen by forming it in a powder-like form, the ortho-para hydrogen conversion reaction can be efficiently promoted. On the other hand, by forming it into a molded body, the pressure loss during hydrogen flow can be reduced, thereby reducing the load on the device. In this way, the shape can be appropriately selected according to the conditions of each device. Incidentally, depending on the application, the catalyst can be used in the form of a molded body or granules with a major axis of 0.5 mm to 5 mm, for example.

[0026] The catalyst of the present invention can be prepared, for example, by a production method having the following steps. (1) Reaction step for preparing nickel-containing precipitate (2) A calcination step of calcining the nickel-containing precipitate to produce nickel oxide. (3) A reduction step of reducing the nickel oxide to metallic nickel. (4) A stabilization step of forming an oxide film on the surface of the metallic nickel. Each step will be described in detail below. However, the method for producing the catalyst of the present invention is not limited to the following production method.

[0027] <Preparation step of nickel-containing precipitate> The nickel-containing precipitate can be prepared by adding a precipitant to an aqueous solution containing nickel, which serves as the active component, and adjusting the solubility to form a precipitate. For example, an acidic aqueous solution containing nickel sulfate or nickel nitrate is prepared, and a basic solution containing a precipitant such as sodium carbonate, sodium hydroxide, or ammonia is prepared, and then these are mixed to prepare a nickel-containing precipitate. At this time, a promoter component or a carrier can be added to the acidic or basic solution to prepare a precipitate containing the promoter component and the carrier component. For example, a basic aqueous solution containing sodium silicate dissolved therein or a basic aqueous solution containing diatomaceous earth dispersed therein can be used to prepare a precipitate containing the carrier component.

[0028] <Firing process> In this step, the nickel-containing precipitate is calcined to produce nickel oxide. The nickel contained in the nickel-containing precipitate exists as either a carbonate or a hydroxide, or both. In this calcination step, the nickel-containing precipitate is calcined to convert the nickel carbonate and nickel hydroxide contained in the precipitate into nickel oxide. For example, when the nickel-containing precipitate is calcined at a temperature of 300°C or higher, the nickel carbonate and nickel hydroxide contained in the precipitate become nickel oxide.

[0029] The calcination temperature is preferably in the range of 350°C to 500°C, more preferably in the range of 300°C to 400°C. Furthermore, when the nickel-containing precipitate is calcined at a temperature range of 300°C to 400°C, the nickel crystallite diameter of the final catalyst tends to fall within the preferred range (8.0 nm or less). The calcination time is adjusted appropriately depending on the amount of nickel-containing precipitate charged and the calcination temperature. For example, the calcination time is preferably 1 hour to 24 hours. If the calcination time is too long, the production efficiency decreases and the nickel crystallite diameter of the final catalyst tends to become large. The calcination atmosphere may be air or an inert gas atmosphere.

[0030] <Reduction process> In this step, nickel oxide contained in the precipitate (hereinafter referred to as the calcined product) that has undergone the calcination step is reduced to metallic nickel. For example, when the calcined product containing nickel oxide is reduced at a temperature of 350°C or higher in a hydrogen atmosphere, the nickel oxide is reduced to metallic nickel. By performing this operation, nickel oxide, which is difficult to reduce, is reduced, and the peak that appears in the H-TPR spectrum between 350°C and 600°C is also reduced.

[0031] The reduction temperature is preferably 350°C or higher, and more preferably in the temperature range of 400°C to 450°C. Furthermore, by carrying out the reduction treatment within this heating range, the nickel crystallite diameter of the finally obtained catalyst tends to fall within the preferred range (8.0 nm or less). The reduction time is adjusted appropriately depending on the amount of the calcined material containing nickel oxide charged and the reduction temperature. For example, the reduction time is preferably in the range of 1 hour to 48 hours. If the reduction time is too long, the production efficiency decreases and the nickel crystallite diameter of the finally obtained catalyst tends to become large.

[0032] <Stabilization process> In this step, an oxide film is formed on the surface of the metallic nickel contained in the calcined product (hereinafter referred to as the reduced product) that has undergone the reduction step, thereby stabilizing the metallic nickel. The metallic nickel contained in the reduced product is easily oxidized by reacting with oxygen in the air. The oxidation reaction of metallic nickel is a highly exothermic reaction, and if the reduced product containing metallic nickel is exposed to the air as is, it will ignite. Therefore, an oxide film is formed on the surface of the metallic nickel to stabilize it and prevent it from igniting even in the air. This stabilization treatment results in a catalyst that is easy to handle. The catalyst of the present invention is obtained through this stabilization step. The degree of the oxide film formed on the surface of the metallic nickel is controlled so that the position of the highest intensity peak in the H2-TPR spectrum is in the range of 100°C to 350°C.

[0033] For example, an oxide film can be formed on the surface of metallic nickel by keeping the above-mentioned reduced material containing metallic nickel at a temperature of 50°C to 150°C in an inert gas atmosphere and slowly adding a gas with an oxygen concentration of 1% or less. Another method is to have metallic nickel adsorb carbon dioxide and then gradually increase the oxygen concentration to form an oxide film. These methods can form a thin oxide film, so the H2-TPR spectrum of metallic nickel with this oxide film has a peak at a lower temperature.

[0034] The above-mentioned production method of the present invention may optionally include a separation step, a washing step, a molding step, and a step of adding a carrier or a co-catalyst component. For example, in the precipitation step, a nickel-containing precipitate is deposited in the aqueous solution, which can be separated and washed. The nickel-containing precipitate can also be molded into various shapes by extrusion molding, tableting, or the like. Furthermore, a carrier or a co-catalyst component can also be added. In this way, the above-mentioned production step can be combined with unit operations commonly performed in the field of catalyst preparation. [Effects of the Invention]

[0035] The catalyst of the present invention stabilizes metallic nickel by providing a thin oxide film on the surface, while reducing the amount of nickel oxide and nickel that is difficult to reduce due to a thick oxide film. In the catalyst of the present invention, metallic nickel is present below the oxide film, so the metallic nickel content is high, and nickel with a thin oxide film is easily reduced. Therefore, although the catalyst of the present invention exhibits an H2-TPR spectrum in the temperature range of 100°C to 600°C, the peak with the highest intensity in the spectrum is located in the low temperature range of 100°C to 350°C, and therefore has high activity in ortho-para hydrogen conversion.

[0036] The catalyst of the present invention preferably has a peak intensity (I LT ) and the highest peak intensity (I HT ) ratio (I HT / I LT) is less than 1, and more preferably less than 0.5. Therefore, the catalyst has higher activity in ortho-para hydrogen conversion. [Brief explanation of the drawings]

[0037] [Figure 1] 1 shows H2-TPR spectra (Example 1, Comparative Example 1). [Figure 2] 1 shows X-ray diffraction patterns (Example 1, Comparative Example 1). DETAILED DESCRIPTION OF THE INVENTION

[0038] The catalyst of the present invention will be specifically described below using examples. However, the catalyst of the present invention is not limited to the following examples. The catalysts obtained in each example and comparative example were evaluated and analyzed as follows.

[0039] [1] Composition analysis (Ni, Mg, Cu, Cr, Mn, Zr) The sample was dissolved in acid and the filtrate was prepared. If a colored residue occurred, the residue was melted and then dissolved in acid to prepare a solution. Both solutions were diluted with water to the appropriate concentration, and the contents of Ni, Mg, Cu, Cr, Ma, Zr, and Si were measured using an ICP optical emission spectrometer (Agilent Technologies, 730ICP-OES, inductively coupled plasma optical emission spectroscopy). The Si content was calculated in terms of SiO2. Note that each content was calculated based on the total amount of catalyst.

[0040] [2] H2-TPR measurement The sample was measured using a micro-flow reduction tester (Mitsubishi Heavy Industries Machinery Technology Co., Ltd.). 0.1 g of sample, sized to 355–710 μm, was loaded into a stainless steel reactor tube, a thermocouple was inserted at the sample position, and a mixture of hydrogen gas (3 mL / min) and nitrogen gas (27 mL / min) was passed through. The sample was heated from room temperature to 600°C at a heating rate of 600°C / hr using a tubular furnace. The change in gas concentration during heating was detected using a TCD, and the temperature at the position of the highest intensity peak was calculated from the resulting TPR spectrum.

[0041] [3] Nickel crystallite size measurement X-ray diffraction measurements were performed on the samples using a Rigaku X-ray diffractometer (Rigaku MultiFlex). First, the sample to be measured was crushed and packed onto a sample plate. X-ray diffraction (Cu-Kα radiation source) measurements were performed under the following conditions: tube voltage 40 kV, tube current 20 mA, scan range 10–70°, divergence slit 1.0 mm, scattering slit 1.0 mm, receiving slit 0.3 mm, and scan speed 4° / min. If peaks with tops at 2θ = 44° ± 1° and 2θ = 51° ± 1° were observed in the obtained diffraction pattern, it was determined to contain metallic nickel. Furthermore, the nickel crystallite size was calculated using the Scherrer equation by detecting diffraction peaks with tops near 2θ = 44° using analysis software (JADE Version 5.0).

[0042] [4] Specific surface area measurement The specific surface area of ​​the sample was calculated using the gas adsorption method (BET flow method). Specifically, a specific surface area measurement device (Mountec, Macsorb HM model-1220) was used. The sample was degassed in a pure nitrogen gas stream at 250°C for 40 minutes, and then maintained at liquid nitrogen temperature under a 30% nitrogen and 70% helium mixed gas flow to allow equilibrium adsorption of nitrogen. The sample temperature was raised to room temperature while this mixed gas was flowing, and the amount of nitrogen desorbed during this period was measured. The specific surface area was calculated by dividing this by the sample mass after measurement.

[0043] [5] Evaluation of ortho-para hydrogen conversion Approximately 0.1 mL of catalyst was packed into an 8 mm inner diameter reactor tube. The catalyst bed temperature was adjusted to 250 °C under a 70 cc / min hydrogen gas flow, and reduction treatment was performed for 1 hour. The reactor tube was then cooled to -196 °C with liquid nitrogen, and hydrogen gas was passed through at 200 cc / min to convert a portion of the ortho-hydrogen to para-hydrogen. The hydrogen that passed through the catalyst bed was passed through an activated alumina column to separate the ortho- and para-hydrogen. The ortho- and para-hydrogen that passed through the column were passed through a copper oxide column to convert them to water, and the data were recorded as a chart using a TCD detector. The first peak detected in the chart for hydrogen that passed through the catalyst bed was designated para-hydrogen, and the second peak was designated ortho-hydrogen. The ratio of the area of ​​the peak attributable to para-hydrogen to the sum of the areas of the respective peaks (Outlet) was calculated. In addition, the proportion of the peak area (Inlet) attributable to para-hydrogen was calculated using the same method for hydrogen before it passed through the catalyst layer, and the increase in para-hydrogen, Δ (Δ = Outlet para-hydrogen amount - Inlet para-hydrogen amount), calculated by subtracting the amount of para-hydrogen in the Inlet from the amount of para-hydrogen in the Outlet, was used as the conversion activity from ortho-hydrogen to para-hydrogen.

[0044] Example 1: Ni-CuCrMn / Dieselguhr <Preparation step of nickel-containing precipitate> A 15-L stirring vessel was filled with 6.3 L of tap water, and 1,800.0 g of nickel sulfate hydrate [NiSO4·6H2O] (Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in the water and adjusted to 73°C. Then, 212.7 g of diatomaceous earth [Celite 505: Imerys] was added, and the mixture was stirred for 60 minutes to disperse the diatomaceous earth, preparing an acidic suspension. Next, 1,266.7 g of sodium carbonate (Na2CO3, Kanto Chemical Co., Ltd.) was dissolved in 6.1 L of tap water, and the mixture was adjusted to 73°C to prepare a basic aqueous solution. The basic aqueous solution was added to the acidic suspension over 80 minutes using a tube pump, obtaining a mixed solution. The mixture was maintained at 73°C and stirred for 2 hours. 20.0 g of sodium hydroxide (Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in 0.06 L of tap water to prepare a basic aqueous solution. This was added all at once to the mixed solution, and stirring was continued for 0.5 hours while maintaining the temperature at 73°C to obtain a slurry. The slurry was filtered under reduced pressure using a Nutsche filter to obtain a cake-like solid. The entire amount of the solid was added to 6 L of warm water adjusted to 40°C to prepare a slurry, and this filtration process was repeated. When the electrical conductivity of the slurry reached 0.4 mS / cm, 16.0 g of copper (II) oxide (Fujifilm Wako Pure Chemical Industries, Ltd.), 15.6 g of chromium (III) oxide (Fujifilm Wako Pure Chemical Industries, Ltd.), and 1.4 g of manganese (IV) oxide (Fujifilm Wako Pure Chemical Industries, Ltd.) were added. The slurry was then filtered under reduced pressure, and the resulting solid was added to 6 L of warm water adjusted to 40°C and filtered to obtain a cake-like solid. This process was repeated, and washing was completed when the electrical conductivity of the filtrate reached 0.2 mS / cm. The cake-like solid was then dried at 120°C for 12 hours using a box dryer. The dried solid was pulverized using a hammer crusher mill to obtain a nickel-containing precipitate. <Firing process> The nickel-containing precipitate was formed into a cylindrical shape with a diameter of 3.2 mm and a height of 3.2 mm using a tableting machine, and the formed body was fired in a muffle furnace at 370°C for 6 hours to obtain a fired product. <Reduction and stabilization process> The calcined product was reduced in a hydrogen atmosphere at 430°C for 10 hours and then cooled to 80°C. After that, the atmosphere was changed to nitrogen, and air was gradually added until the oxygen concentration reached 0.5% to 21%, and a stabilization treatment was carried out to form a thin oxide film, thereby obtaining an ortho-para hydrogen conversion catalyst.

[0045] Example 2: Ni-Zr / Diatomaceous Earth <Nickel-containing precipitate preparation step> 3.1 L of tap water was poured into a 15 L stirring vessel, and 333.0 g of sodium carbonate (Na2CO3, Kanto Chemical Co., Ltd.) was dissolved in it and the temperature was adjusted to 80°C. 129.4 g of diatomaceous earth (Celite 505, Imerys) was then added and stirred for 60 minutes to disperse the diatomaceous earth, preparing a basic suspension. 1418.0 g of nickel sulfate hydrate (NiSO4·6H2O) (Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in 5.4 L of tap water, and 94.0 g of zirconium sulfate solution (Daiichi Kigenso Kagaku Kogyo Co., Ltd.) was added. The temperature was adjusted to 80°C to prepare an acidic aqueous solution. Using a tube pump, the acidic aqueous solution was poured into the basic suspension over 80 minutes to obtain a mixed solution. Stirring was continued for 1 hour while maintaining the mixed solution at 80°C. A basic aqueous solution for pH adjustment was prepared by dissolving 645.0 g of sodium carbonate (manufactured by Kanto Chemical Co., Inc.) in 3.0 L of tap water and adjusting the temperature to 80°C. This was poured into the mixed solution over 10 minutes using a tube pump. After the pouring was completed, stirring was continued for 120 minutes while maintaining the temperature at 80°C to obtain a slurry. The slurry was filtered under reduced pressure using a Nutsche filter to obtain a cake-like solid. The entire amount of the solid was added to 6 L of warm water adjusted to 40°C, and the filtration operation was repeated. When the electrical conductivity of the filtrate reached 1.5 mS / cm, the washing was stopped to obtain a cake-like solid. Thereafter, the cake-like solid was dried at 120°C for 12 hours using a box dryer. The dried solid was pulverized using a hammer crusher mill to obtain a nickel-containing precipitate. The subsequent steps were carried out in the same manner as in Example 1 to obtain an ortho-para hydrogenation catalyst.

[0046] Example 3: Ni-Mg / Silica <Nickel-containing precipitate preparation step> A 15-L stirring tank was filled with 3.3 L of tap water, and 143.3 g of sodium silicate No. 3 (Fuji Chemical Co., Ltd.) was dissolved therein. The temperature was adjusted to 80°C to prepare a sodium silicate aqueous solution. A 15-L stirring tank was filled with 6.3 L of tap water, and 1800.0 g of nickel sulfate hydrate [NiSO4·6H2O] (Fujifilm Wako Pure Chemical Co., Ltd.) was dissolved therein. The temperature was adjusted to 80°C to prepare an acidic aqueous solution. A basic aqueous solution was prepared by dissolving 1433.3 g of sodium carbonate (Na2CO3, Kanto Chemical Co., Ltd.) in 5.9 L of tap water and adjusting the temperature to 80°C. Using a tube pump, the acidic aqueous solution and the basic aqueous solution were added to the sodium silicate aqueous solution over 80 minutes to obtain a mixed solution. 266.7 g of magnesium sulfate (manufactured by Mai Chemical Co., Ltd.) was added to this mixed solution, and stirring was continued for 1.5 hours while maintaining the temperature at 80°C to obtain a slurry. The slurry was filtered under reduced pressure using a Nutsche filter to obtain a cake-like solid. The entire amount of the solid was poured into 6 L of warm water adjusted to 40°C, and the filtration operation was repeated. When the electrical conductivity of the filtrate reached 1.5 mS / cm, washing was stopped, and a cake-like solid was obtained. The cake-like solid was then dried at 120°C for 12 hours using a box dryer. The dried solid was pulverized using a hammer crusher mill to obtain a nickel-containing precipitate. <Firing process> The nickel-containing precipitate was formed into a cylindrical shape with a diameter of 3.2 mm and a height of 3.2 mm using a tableting machine, and the formed body was fired in a muffle furnace at 370°C for 6 hours to obtain a fired product. <Reduction and stabilization process> The calcined product was reduced in a hydrogen atmosphere at 430°C for 10 hours and then cooled to 80°C. After that, the atmosphere was changed to carbon dioxide, and air was gradually added until the oxygen concentration reached 0.5% to 21%, to perform a stabilization treatment to form a thin oxide film, thereby obtaining an ortho-para hydrogen conversion catalyst.

[0047] Example 4: Ni / Diatomaceous Earth <Nickel-containing precipitate preparation step> A 15-L stirring vessel was charged with 6.3 L of tap water, and 1800.0 g of nickel sulfate hydrate [NiSO4·6H2O] (Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in it and adjusted to 73°C. Then, 220.0 g of diatomaceous earth [Celite 505: Imerys] was added, and the mixture was stirred for 60 minutes to disperse the diatomaceous earth, preparing an acidic suspension. Next, 1433.3 g of sodium carbonate (Na2CO3, Kanto Chemical Co., Ltd.) was dissolved in 5.9 L of tap water, and the mixture was adjusted to 73°C to prepare a basic aqueous solution. The basic aqueous solution was added to the acidic suspension over 80 minutes using a tube pump, obtaining a mixed solution. The mixture was maintained at 73°C and stirred for 2 hours. 20.0 g of sodium hydroxide (Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in 0.06 L of tap water to prepare a basic aqueous solution. This was added all at once to the mixed solution, and stirring was continued for 0.5 hours while maintaining the temperature at 73°C to obtain a slurry. The slurry was filtered under reduced pressure using a Nutsche filter to obtain a cake-like solid. The entire amount of the solid was added to 6 L of warm water adjusted to 40°C, and the filtration operation was repeated. When the electrical conductivity of the filtrate reached 1.5 mS / cm, the washing was stopped to obtain a cake-like solid. Thereafter, the cake-like solid was dried at 120°C for 12 hours using a box dryer. The dried solid was pulverized using a hammer crusher mill to obtain a nickel-containing precipitate. The subsequent steps were carried out in the same manner as in Example 1 to obtain an ortho-para hydrogenation catalyst.

[0048] [Comparative Example 1: NiO-CuCrMn / Dieselguhr] An ortho-para hydrogenation catalyst was obtained in the same manner as in Example 1, except that the reduction and stabilization steps were not carried out.

[0049] For the catalysts of Examples 1 to 4 and Comparative Example 1, the active component and co-catalyst component, their contents, and the type of carrier are shown in Table 1. The maximum peak position and peak intensity ratio (I HT / I LT), the presence or absence of metallic nickel, nickel crystallite size, specific surface area, the amount of para-hydrogen in the inlet and outlet, and the increase in the amount of para-hydrogen (activity Δ) are shown in Table 1. Furthermore, for the catalysts of Example 1 and Comparative Example 1, the H2-TPR spectra are shown in Figure 1, and the X-ray diffraction patterns are shown in Figure 2.

[0050] 1, the catalyst of Example 1 has a maximum peak position in the H2-TPR spectrum at 237°C, contains a large amount of metallic nickel and easily reducible nickel, and has a significantly higher efficiency of ortho-para-hydrogen conversion.The catalysts of Examples 2 to 4 also contain a large amount of metallic nickel and easily reducible nickel, and have a significantly higher efficiency of ortho-para-hydrogen conversion. On the other hand, in the catalyst of Comparative Example 1, the reduction step and stabilization step were not performed after calcining the nickel-containing precipitate, so the nickel was in the form of an oxide and the peak of the H-TPR spectrum was in the high temperature range (454°C). Therefore, the efficiency of ortho-para-hydrogen conversion was significantly lower, at approximately half or less of those in Examples 1 to 4.

[0051] [Table 1]

Claims

1. A catalyst for converting orthohydrogen to parahydrogen, comprising nickel as an active component, ２ A catalyst characterized in that the position of the most intense peak in the TPR spectrum is in the range of 100°C to 350°C.

2. The highest peak intensity (I ＬＴ ) and the highest peak intensity (I ＨＴ ) ratio (I ＨＴ / I ＬＴ 2. The catalyst according to claim 1, wherein the number of carbon atoms is less than 1.

3. 3. The catalyst according to claim 1, wherein the crystallite size of the nickel is 6.0 nm or less.

4. Specific surface area is 50m 2 / g~400m 2 The catalyst according to any one of claims 1 to 3, wherein the SiO2 content is in the range of / g.

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