Ortho-hydrogen - para-hydrogen conversion catalyst and ortho-hydrogen - para-hydrogen conversion method

Abstract

An orthohydrogen-parahydrogen conversion catalyst according to the present invention contains a mixed valence manganese oxide in which the average oxidation number of manganese is more than +2 but less than +4, and can quickly perform conversion of orthohydrogen-parahydrogen essential for the production of liquid nitrogen.

Description

Technical Field

[0001] The present invention relates to an ortho-hydrogen - para-hydrogen conversion catalyst and an ortho-hydrogen - para-hydrogen conversion method.

Background Art

[0002] It is known that ortho-hydrogen remaining in liquefied hydrogen is converted into para-hydrogen over time, and the heat generated reduces the storage efficiency of liquefied hydrogen. Therefore, during the production of liquefied hydrogen, a process is carried out to increase the ratio of para-hydrogen in hydrogen gas, which has an ortho:para ratio of 3:1 (molar ratio) at room temperature. Usually, a solid catalyst is used for this process to improve efficiency. As such a solid catalyst, an iron-based compound is described in Non-Patent Document 1.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the studies of the present inventors, the iron-based compound described in Non-Patent Document 1 has a problem that the time required for the conversion of ortho-hydrogen - para-hydrogen (hereinafter also referred to as "OP conversion") is long. Therefore, an object of the present invention is to provide an OP conversion catalyst capable of quickly performing OP conversion. Another object of the present invention is to provide an OP conversion method.

Means for Solving the Problems

[0005] As a result of intensive studies to achieve the above problems, the inventors have found that the above problems can be achieved by the following configuration.

[0006] [1] An ortho-hydrogen - para-hydrogen conversion catalyst containing a mixed-valence manganese oxide in which the average oxidation number of manganese is more than +2 and less than +4. [2] The ortho-hydrogen - para-hydrogen conversion catalyst according to [1], wherein when 1 < x < 2 for the mixed-valence manganese oxide, it is MnO X represented as. [3] The measurement data of the peak derived from Mn2p in the XPS (X-ray photoelectron spectroscopy) measurement of the above ortho-hydrogen - para-hydrogen conversion catalyst is fitted with the following reference waveforms: Mn 3 / 2 The ortho-hydrogen - para-hydrogen conversion catalyst according to [1] or [2], wherein when fitted with the composite waveform of the peak waveform A derived from Mn 2+ O, the peak waveform B derived from Mn 3 / 2 O(OH), and the peak waveform C derived from Mn 3+ O2, the area fraction of the peak waveform B in the fitting waveform obtained as a result of the fitting is greater than 0. 3 / 2 4+ 3 / 2 [4] The ortho-hydrogen - para-hydrogen conversion catalyst according to [3], wherein the area fraction is 0.50 or more. [5] The ortho-hydrogen - para-hydrogen conversion catalyst according to [4], wherein the area fraction is 0.90 or less. [6] The ortho-hydrogen - para-hydrogen conversion catalyst according to any one of [3] to [5], wherein the area fraction of the peak waveform B is greater than at least one area fraction selected from the group consisting of the area fraction of the peak waveform A and the area fraction of the peak waveform C. [7] The ortho-hydrogen - para-hydrogen conversion catalyst according to [6], wherein the area fraction of the peak waveform B is greater than the area fraction of the peak waveform A and the area fraction of the peak waveform C. [8] The ortho-hydrogen - para-hydrogen conversion catalyst according to any one of [3] to [7], wherein the measurement data is in the range of 636 to 650 eV in binding energy. [9] The ortho-hydrogen - para-hydrogen conversion catalyst according to any one of [1] to [8], which contains a metal element other than manganese.

[10] The ortho-hydrogen - para-hydrogen conversion catalyst according to [9], wherein the metal element is at least one selected from the group consisting of lithium, chromium, iron, cobalt, nickel, and zinc.

[11] An ortho-hydrogen - para-hydrogen conversion method, which includes bringing gaseous hydrogen into contact with the ortho-hydrogen - para-hydrogen conversion catalyst according to any one of [1] to

[10] .

[12] The ortho-hydrogen - para-hydrogen conversion method according to

[11] , wherein the contact is carried out at 77 K or lower. [Advantages of the Invention]

[0007] According to the present invention, an OP conversion catalyst capable of quickly performing OP conversion can be provided. Further, according to the present invention, an OP conversion method can also be provided.

[0008] The OP conversion catalyst of the present invention contains a mixed-valence manganese oxide in which the average oxidation number of manganese exceeds +2 and is less than +4. Although the mechanism by which the effects of the present invention are obtained is not necessarily clear, it is presumed that a very limited region around manganese atoms having a predetermined electronic state serves as a reaction site and the catalytic effect is exhibited. Therefore, even if the OP conversion catalyst contains a metal other than manganese (for example, lithium, cobalt, zinc, copper, etc.), it has no particular effect on the activity of the catalyst itself. In addition, when the average oxidation number of manganese exceeds +2 and is +3 or less, an OP conversion catalyst having more excellent OP conversion efficiency can be obtained.

[0009] Further, when 1 < x < 2 for the OP conversion catalyst of the present invention, when it contains a mixed-valence manganese oxide represented by MnO X a more excellent OP conversion effect can be obtained.

[0010] In addition, for the Mn2p in the XPS measurement of the OP conversion catalyst of the present invention 3 / 2 the measurement data of the peak derived from is fitted with the following reference waveforms: Mn 2+ the peak waveform A derived from Mn2p of MnO 3 / 2 the peak waveform B derived from Mn2p of MnO(OH) 3+ and the peak waveform C derived from Mn2p of MnO2. When the fitting is performed with the composite waveform, if the area fraction of the peak waveform B in the fitting waveform obtained as a result of the fitting is greater than 0, a more excellent OP conversion effect can be obtained. 3 / 2 and the peak waveform C derived from Mn2p of MnO2. When the fitting is performed with the composite waveform, if the area fraction of the peak waveform B in the fitting waveform obtained as a result of the fitting is greater than 0, a more excellent OP conversion effect can be obtained. 4+ and the peak waveform C derived from Mn2p of MnO2. When the fitting is performed with the composite waveform, if the area fraction of the peak waveform B in the fitting waveform obtained as a result of the fitting is greater than 0, a more excellent OP conversion effect can be obtained. 3 / 2 In addition, when the area fraction of the peak waveform B is 0.50 (50%) or more, a more excellent OP conversion effect can be obtained.

[0011] In addition, when the area fraction of the peak waveform B is 0.50 (50%) or more, a more excellent OP conversion effect can be obtained.

[0012] In addition, when the area fraction of the peak waveform B is 0.90 or less, a more excellent OP conversion effect can be obtained.

[0013] In addition, when the area fraction of the peak waveform B is greater than at least one of the area fractions selected from the group consisting of the area fraction of the peak waveform A and the area fraction of the peak waveform C, a more excellent OP conversion effect can be obtained. This tendency is more remarkable when it is greater than both the area fraction of the peak waveform A and the area fraction of the peak waveform C.

[0014] In addition, when the measurement data is at a binding energy of 636 to 650 eV, a more excellent OP conversion effect can be obtained.

[0015] In addition, even when a metal element other than manganese (for example, lithium, chromium, iron, cobalt, nickel, and zinc) is included, an excellent OP conversion effect can be obtained.

[0016] The OP conversion method of the present invention includes bringing gaseous hydrogen into contact with the above OP conversion catalyst. Due to the excellent characteristics of the above OP conversion catalyst, when this method is used, the time required for OP conversion can be dramatically shortened.

[0017] In addition, when the above contact is carried out at 77K or lower, due to the excellent characteristics of the above OP conversion catalyst, the volume fraction of parahydrogen in the gas phase more readily reaches approximately 50% or more more quickly.

Brief Description of the Drawings

[0018]

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Mode for Carrying Out the Invention

[0019] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0020] [OP Conversion Catalyst] The OP conversion catalyst according to an embodiment of the present invention includes a mixed valence manganese oxide in which the average oxidation number of manganese is more than +2 and less than +4. In this specification, the mixed valence manganese oxide means an oxide containing manganese and containing manganese atoms having a plurality of oxidation numbers, and examples thereof include those containing manganese atoms selected from the group consisting of Mn(II), Mn(III), and Mn(IV).

[0021] Note that the valence of the manganese oxide can be measured by the method using HAXPE described later. The mixed-valence manganese oxide may contain metal elements other than those described above. Such metals are not particularly limited, and examples include alkali metals such as Li (lithium), Cr (chromium), Fe (iron), Co (cobalt), Ni (nickel), and Zn (zinc). Among them, alkali metals are preferred. Note that the mixed-valence manganese oxide is different from a mixture of manganese oxides having different oxidation numbers.

[0022] The OP conversion catalyst containing the above mixed-valence manganese oxide has, in the Mn2p in the XPS (X-ray photoelectron spectroscopy) measurement of the OP conversion catalyst, 3 / 2 the measurement data of the peak derived from ·Mn 2+ O's Mn2p 3 / 2 the peak waveform A derived from ·Mn 3+ O(OH)'s Mn2p 3 / 2 the peak waveform B derived from ·Mn 4+ O2's Mn2p 3 / 2 the peak waveform C derived from When fitted by the composite waveform of, it is preferable that the area fraction of the peak waveform B in the fitting waveform obtained as a result of the above fitting is greater than 0.

[0023] The fact that the area fraction of the peak waveform B is greater than 0 suggests that Mn with an oxidation number of +3 is present in the mixed-valence manganese oxide in the OP catalyst. The area ratio of the peak waveform B is preferably greater than 0, and is preferably 0.50 or more in terms of obtaining an OP conversion catalyst having a more excellent effect of the present invention. The upper limit is not particularly limited, but generally, it is preferably 0.90 or less.

[0024] Next, the method for calculating the area fraction of the peak waveform B will be described. First, the reference waveform will be described. The reference waveform is calculated from "Fig. 1" in Applied Surface Science 366 (2016) 475-485. First, in the above “Fig. 1”, the drawings are arranged in a 3×3 matrix. Among these, three drawings in the left column are used. That is, Mn 2+ Mn2p of Mn 3 / 2 O, Mn 3+ Mn2p of Mn 3 / 2 O(OH), and Mn 4+ Mn2p of Mn 3 / 2 O2.

[0025] Next, the method for calculating the reference waveform in the case of Mn 2+ Mn2p of Mn 3 / 2 O will be described. First, in “Fig. 1”, the measured values are plotted as white circles “data”. These are read as digital data, and automatic peak separation is performed by BIC (Bayesian information criterion)-fitting, and the fitting result is obtained using the sum of pseudo-Voigt functions as the basis function. Note that the number of peaks is automatically selected using the BIC value as the evaluation criterion.

[0026] In this way, the reference waveform (peak waveform A) of Mn 2+ Mn2p of Mn 3 / 2 O, the reference waveform (peak waveform B) of Mn 3+ Mn2p of Mn 3 / 2 O(OH), and the reference waveform (peak waveform C) of Mn 4+ Mn2p of Mn 3 / 2 O2 are obtained. Fig. 1 is a diagram showing the peak waveform A thus obtained. Similarly, Fig. 2 is a diagram showing the peak waveform B, and Fig. 3 is a diagram showing the peak waveform C. In each of Figs. 1 to 3, the white circles marked with “spectrum” are the citation data from the above-mentioned literature. Also, “background” represents the white radiation from the background, and “fitted” represents each obtained reference waveform. Note that each reference waveform is separated into 4 to 5 peak waveforms.

[0027] Next, the analysis process of the XPS measurement results (actual measurement data) of the OP conversion catalyst will be described. The XPS measurement method of the OP conversion catalyst follows the method described in the subsequent examples. Specifically, it is performed by hard X-ray photoelectron spectroscopy (HAXPES) using hard X-rays as the excitation light.

[0028] First, among the XPS measurement results (measurement data) of the OP conversion catalyst, a range of binding energy (BE) from 636 to 650 eV is cut out. In this specification, the measurement data in the above range is defined as the signal derived from Mn2p 3 / 2 and the peak in that range is defined as the peak derived from Mn2p 3 / 2 .

[0029] Next, the peak (measurement data) derived from Mn2p 3 / 2 obtained from the measurement data is fitted with the composite waveform of peak waveforms A to C. Figure 4 is a diagram showing the XPS measurement data of Mn3O4 and the fitting waveform obtained by synthesizing the reference waveforms. In Figure 4, the black circles (described as "spectrum" in Figure 4) represent the actual measurement data. In contrast, "fitting_spectrum" is the result of fitting by synthesizing three reference waveforms. In Figure 4, this composite waveform is formed by overlapping peak waveform A and peak waveform B, and peak waveform C is not used. In Figure 4, the waveform marked as MnO is the peak waveform A component in the composite waveform. Similarly, the waveform marked as MnO(OH) represents the peak waveform B component, and the waveform marked as MnO2 represents the peak waveform C component. The area fraction of peak waveform B in the composite waveform was 1.203 / (1 + 1.203 + 0) = 0.546 (54.6%).

[0030] Note that the area fraction of peak waveform B in the composite waveform is calculated from the following formula: Formula: (Area fraction of peak waveform B in the composite waveform) = (Area of peak waveform B in the composite waveform) / (Total area of peak waveforms A to C in the composite waveform)

[0031] When the area fraction of the peak waveform B in the obtained fitting waveform (composite waveform) is greater than 0, the OP conversion catalyst has a better OP conversion efficiency.

[0032] Also, from the viewpoint of obtaining an OP conversion catalyst having a better effect of the present invention, the area fraction of the peak waveform B is preferably greater than at least one selected from the group consisting of the area fraction of the peak waveform A and the area fraction of the peak waveform C (the calculation method for both is the same as the above formula), and more preferably greater than both.

[0033] Also, from the viewpoint of obtaining an OP conversion catalyst having a better effect of the present invention, the composite waveform is preferably represented by the combination of the peak waveform A and the peak waveform B.

[0034] According to the study by the present inventors, it is presumed that the OP conversion by the OP conversion catalyst of the present invention uses a very narrow region near the Mn atom in a predetermined electronic state as its reaction site. In the Mn2p 3 / 2 spectrum measured by the above method, when the area fraction of the peak waveform B is greater than 0, it means that there are Mn atoms in the electronic state as described above, and it can exhibit the function as an excellent OP conversion catalyst. From such a viewpoint, even when the OP conversion catalyst contains Mn atoms in other electronic states and / or other metal elements, since the reaction site is a very narrow region near the Mn atoms in a predetermined electronic state, it does not affect the function as an OP conversion catalyst, and an excellent OP conversion effect can be obtained.

[0035] As the mixed valence manganese, from the viewpoint of obtaining an OP conversion catalyst having a better effect of the present invention, when 1 < x < 2, it is preferably represented by MnO X Examples of such mixed valence manganese include Mn3O4. In other forms, the mixed-valence manganese includes MMn2O4 (alkali metal manganate; M is an alkali metal), and those in which a part of the above Mn sites are substituted with Cr, Fe, Co, Ni, Zn, etc.

[0036] The shape of the OP conversion catalyst is not particularly limited and may be appropriately selected according to the form of use, and such a selection is known to those skilled in the art. For example, if the OP conversion catalyst is in the form of particles with an average particle diameter of 1 to 10,000 nm, it can be filled into a sealed casing equipped with a gas inlet and outlet, and typically, gaseous hydrogen can be passed through while cooling.

[0037] As the OP conversion catalyst according to the embodiment of the present invention, a commercially available product may be used, or it may be manufactured by a known method and used. The manufacturing method of the OP conversion catalyst is not particularly limited, but Mn metal, Mn oxide, Mn nitride, Mn carbide, etc. can be mixed with a dopant metal component (pure metal, metal compound, etc.) as necessary, and then fired in an oxidizing atmosphere, for example.

[0038] [OP Conversion Method] The OP conversion method according to the embodiment of the present invention is an OP conversion method including bringing hydrogen gas into contact with the OP conversion catalyst described above. Examples of the method of bringing hydrogen gas into contact with the OP conversion catalyst include a method of supporting the OP conversion catalyst on the inner surface of the flow path of hydrogen gas. At this time, typically, the hydrogen gas is cooled. The cooling method is not particularly limited, and for example, it may be cooled with liquid nitrogen or the like.

[0039] By this method, at least a part of ortho-hydrogen is converted into para-hydrogen. In this method, since the above OP catalyst is used, the OP conversion efficiency is high, and OP conversion can be realized in a shorter time.

Examples

[0040] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto.

[0041] Mn3O4 powder (spinel structure; (Mn 2+ )(Mn 3+ )2O4; particle size ~100 nm) was used in the OP catalyst test without any pretreatment after purchase. As comparative samples, in addition, MnO powder (NaCl structure) with a particle size of about 100 nm, MnO2 powder (distorted rutile structure), FeO powder (NaCl structure), and Fe2O3 (corundum structure) were all used in the catalyst test without any special pretreatment after purchase. Hereinafter, each of the above samples will also be referred to as "sample powder".

[0042] Figure 5 is a diagram showing the configuration of an OP conversion catalyst activity evaluation apparatus used in the catalyst test. The OP conversion catalyst activity evaluation apparatus 10 includes a sample tube 11, a Raman spectrometer 12 incorporating a gas cell 13, a pipeline 14 connecting the sample tube 11 and the gas cell 13, and a pump 15 disposed between the sample tube 11 and the Raman spectrometer 12. The sample tube 11 is disposed in a cooling chamber 16.

[0043] When using the above apparatus, the pump 15 can circulate gaseous hydrogen in the pipeline 14 and the sample tube 11 (in the direction of arrow "F" in the figure), and the ortho-para composition thereof can be measured by the Raman spectrometer 12. At this time, the cooling chamber 16 (for example, a container filled with liquid nitrogen or the like) can also be used.

[0044] The specific experimental method is as follows. First, 100 mg of the sample powder was filled into a sample tube made of Pyrex (registered trademark) glass with an inner diameter of 4 mm and sandwiched from above and below with a pinch of quartz wool to form a sample tube. A gas cell (volume 50 ml; quartz window) incorporated in a Raman spectrometer (JASCO RMP-510) and the sample tube were connected with a plastic tube, and a circulation system with a plunger pump sandwiched between them was constructed, and hydrogen (H2) gas was circulated repeatedly in such a way as to pass through the sample powder.

[0045] The cooling of the sample was started by immersing the sample tube in a Dewar flask filled with liquid nitrogen. From that point on, the abundance ratio of ortho-hydrogen and para-hydrogen in hydrogen gas was quantitatively measured as a function of time by a Raman spectrometer. The abundance ratio of ortho-hydrogen and para-hydrogen was calculated from the intensity ratio of the peaks (ortho-hydrogen: 588 cm -1 ; para-hydrogen: 353 cm -1 ) that characterize each on the Raman spectrum.

[0046] Figure 6 is a diagram showing the state of OP conversion by the Fe2O3 catalyst. Raman spectra of hydrogen gas at room temperature (RT), 0.0 hours after the start of cooling at 77K (“77K 0hr”), 1.5 hours (“77K 1.5hr”), and 2.0 hours (“77K 2.0hr”) are shown.

[0047] Figure 7 is a diagram showing the OP conversion efficiency of the Fe2O3 catalyst, with the volume fraction of para-hydrogen [para-hydrogen / (ortho-hydrogen + para-hydrogen)] calculated based on the peak intensities of 588 cm -1 ·353 cm -1 for ortho-hydrogen and para-hydrogen respectively on the vertical axis and the elapsed time from the start of cooling on the horizontal axis. The volume fraction of para-hydrogen gradually increases from the thermodynamic equilibrium value at room temperature (RT) (= 25%) towards the thermodynamic equilibrium value at 77K (= 50%).

[0048] Figures 8 to 13 are diagrams showing the OP conversion efficiency of FeO (Figure 8), Fe2O3 (Figure 9), FeOOH (Figure 10), MnO (Figure 11), Mn3O4 (Figure 12), and MnO2 (Figure 13) at liquid nitrogen temperature (77K). In each figure, the vertical axis corresponds to the volume fraction of para-hydrogen and the horizontal axis corresponds to the elapsed time from the start of cooling.

[0049] In the case of FeO (Figure 8) and MnO (Figure 11), the volume fraction of ortho-hydrogen hardly changed from the initial 25% over 3 hours from the start of cooling. On the other hand, in the case of MnO2 (Fig. 13) and Fe2O3 (Fig. 9), the volume fraction of ortho-hydrogen showed an increasing trend from 25% and reached 40% at the time point of 3 hours elapsed. However, in any case, the para-hydrogen volume fraction did not reach the target 50% after 3 hours from the start of cooling.

[0050] In contrast, in the case of Mn3O4 (Fig. 12), the volume fraction of ortho-hydrogen rapidly increased immediately after cooling and reached 50% at the time point of 30 to 45 minutes elapsed.

[0051] Figs. 14 and 15 show the Mn2p and O1s regions of the Hard X-ray Photoemission Spectroscopy (HAXPES) spectra in the inner shell region of the Mn3O4 catalyst.

[0052] The HAXPES measurement was carried out using X-rays with an incident energy of 5.95 keV at the undulator-type beamline of Harima "SPring-8 (registered trademark)". For the measurement, a hemispherical electron spectrometer (VG SCIENTA R4000; energy resolution 220 meV) was used under ultrahigh vacuum at room temperature. The binding energy of the photoelectrons was calculated with the Fermi level of the gold thin film as the zero point.

[0053] In the Mn2p region of Mn3O4, a strong peak of 642.2 eV derived from the photoelectron emission from Mn 3+ and a weak shoulder derived from Mn 2+ were observed at 641.1 eV, indicating that it is a mixed valence manganese. That is, a photoelectron peak with a binding energy of 642.2 eV having one shoulder consisting of strong Mn 3+ photoelectron emission and weak Mn 2+ photoelectron emission was observed.

[0054] Fig. 16 is a diagram showing the OP conversion efficiency at the liquid nitrogen temperature (77K) of Mn3O4, Mn2O3, LiMnO2, LiMn2O4, and MnO measured by the same method as above. The horizontal axis represents the elapsed time, and the vertical axis represents the para-hydrogen conversion efficiency.

[0055] For Mn2O3, LiMnO2, and LiMn2O4, powder samples manufactured by Aldrich were used without any pretreatment. Here, the average oxidation number of Mn in Mn2O3 and LiMnO2 is only +3 (not a mixed-valence manganese oxide). Similarly, the average oxidation number of Mn in MnO is only +2 (not a mixed-valence manganese oxide). On the other hand, the average oxidation number of Mn in Mn3O4 is +8 / 3, and it is a mixed-valence manganese oxide containing Mn with an oxidation number of +2 and Mn with an oxidation number of +3. Also, the average oxidation number of Mn in LiMn2O4 is +7 / 2, and it is a mixed-valence manganese oxide containing Mn with an oxidation number of +3 and Mn with an oxidation number of +4.

[0056] From the above results, Mn3O4 and LiMn2O4, which are mixed-valence manganese oxides with an average oxidation number of Mn exceeding +2 and less than +4, have an average oxidation number of Mn of +3 and are not mixed-valence manganese oxides, such as Mn2O3 and LiMnO 2、 And, compared with MnO, which has an average oxidation number of Mn of +2 and is not a mixed-valence manganese oxide, they had excellent OP conversion efficiency.

[0057] Also, Mn3O4, with an average oxidation number of Mn exceeding +2 and less than or equal to +3, had more excellent OP conversion efficiency compared with LiMn2O4.

Industrial Applicability

[0058] The current OP catalyst has the highest efficiency with Fe-based catalysts and has remained at that level, showing no dramatic progress in the past few decades. Although Fe is resource-rich, Fe-based OP conversion catalysts have an upper limit in conversion efficiency. Although Cr may show excellent OP conversion efficiency compared to Fe, its resource amount is about 1 / 1000 of that of Fe.

[0059] In contrast, although the production volume of Mn is lower than that of iron, there are many undeveloped aspects such as large-scale deposits being distributed in the sea. Therefore, with the increase in mining volume in the future, a decrease in raw material costs is expected. The OP conversion catalyst containing the mixed-valence manganese oxide of the present invention has a conversion efficiency far exceeding that of conventional Fe-based catalysts and is valuable enough to displace existing Fe-based catalysts.

[0060] By using this OP conversion catalyst and the OP conversion method, it is possible to significantly reduce the time and cost related to storage, which accounts for most of the cost in the production of liquefied hydrogen, and has great potential for future hydrogen society.

Explanation of Reference Signs

[0061] 10: OP conversion catalyst activity evaluation device 11: Sample tube 12: Raman spectrometer 13: Gas cell 14: Pipeline 15: Pump 16: Cooling chamber

Claims

1. A LiMn ortho-hydrogen - para-hydrogen conversion catalyst comprising a mixed-valence manganese oxide in which the average oxidation number of manganese is more than +2 and less than +4 ２ O ４ ​

2. A LiMn ortho-hydrogen - para-hydrogen conversion catalyst composed of a mixed-valence manganese oxide in which the average oxidation number of manganese is greater than +2 and less than +4. ２ O ４ ​

3. A method for ortho-hydrogen - para-hydrogen conversion, comprising contacting the ortho-hydrogen - para-hydrogen conversion catalyst according to Claim 1 or 2 with gaseous hydrogen.

4.

4. The method for ortho-hydrogen - para-hydrogen conversion according to Claim 3, wherein the contacting is carried out at 77 K or lower.

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