Preparation method of alpha-iron oxide nanosheet catalyst with controllable size, prepared catalyst and application

Abstract

The invention discloses a preparation method of a size-controllable alpha-iron oxide nanosheet catalyst, the prepared catalyst and application of the catalyst. Comprising the following steps: mixing ferric iron salt, ethanol, water and sodium acetate at room temperature, reacting in a closed container, centrifuging, washing, drying and roasting to obtain the size-controllable alpha-iron oxide nanosheet catalyst. The catalyst provided by the invention is controllable and uniform in size and is used for ortho-parahydrogen reaction, and an effective method is provided for structural design and development of the high-activity ortho-parahydrogen catalyst.

Description

Technical Field

[0001] The present application relates to a method for preparing a size-controllable α-iron oxide nanosheet catalyst, a catalyst prepared therefrom and applications thereof, and belongs to the field of chemistry and chemical engineering. Background Art

[0002] Hydrogen energy is an important renewable energy source with many advantages such as high energy density, high calorific value and environmental friendliness. Hydrogen energy is not only an effective supplement to traditional fossil energy, but also has great potential to gradually replace traditional carbon-based energy, which is of great significance to the realization of the country's "dual carbon" goals. In the large-scale use of hydrogen energy, safe and efficient storage and transportation is one of the key issues. Liquid hydrogen, as the most convenient storage and transportation form of hydrogen energy, is the basis of hydrogen energy application.

[0003] Hydrogen exists in two isomers, orthohydrogen and parahydrogen, which are orthohydrogen (o-H2) with the same nuclear spin direction and parahydrogen (p-H2) with the opposite nuclear spin direction. The two hydrogen isomers have the same chemical properties, but they differ in physical properties such as heat, magnetism and optics. In particular, the difference in the thermodynamic stability of ortho-parahydrogen caused by nuclear spin isomerism at different temperatures causes changes in the equilibrium ratio of ortho-parahydrogen. For example, ordinary hydrogen at room temperature is composed of 75% orthohydrogen and 25% parahydrogen; while at 77K (liquid nitrogen temperature), the equilibrium concentration of parahydrogen is 50.5%. Therefore, liquid hydrogen directly liquefied with room temperature equilibrium hydrogen can undergo spontaneous ortho-parahydrogen conversion during storage and transportation. Because the process is exothermic, when the temperature is lower than 150K, the conversion heat of ortho-parahydrogen is greater than the latent heat of vaporization of liquid hydrogen and causes the evaporation of liquid hydrogen. This causes the pressure in the hydrogen storage tank to increase, making the storage and transportation of liquid hydrogen a huge challenge. Therefore, accelerating the conversion of ortho-parahydrogen by ortho-parahydrogen catalysts during the hydrogen liquefaction process is the core of large-scale application of liquid hydrogen. Among the known para-hydrogen conversion catalysts, iron-based catalysts are the most widely used commercial catalysts. However, the role of the morphology of iron catalysts on the activity of para-hydrogen conversion is still unclear. Therefore, there is an urgent need to develop iron-based catalysts with characteristic exposed surfaces and apply them to para-hydrogen conversion. Summary of the invention

[0004] The purpose of the present application is to provide a catalyst for catalytic conversion of ortho-parahydrogen, which has the characteristics of high stability, controllable size and controllable activity for the catalytic conversion reaction of ortho-parahydrogen.

[0005] The object of the present invention is to provide a method for preparing a catalyst for catalytic conversion of normal parahydrogen, which method has the characteristics of simple operation, strong repeatability and strong universality.

[0006] According to one aspect of the present application, a method for preparing a size-controlled α-iron oxide nanosheet catalyst is provided, comprising the following steps:

[0007] At room temperature, trivalent iron salt, ethanol, water and sodium acetate are mixed, reacted in a closed container, centrifuged, washed, dried and calcined to obtain the size-controllable alpha-iron oxide nanosheet catalyst.

[0008] The ferric iron salt is selected from at least one of ferric chloride and ferric nitrate.

[0009] The usage ratio of the trivalent iron salt, ethanol, water and sodium acetate is 4-6 mmol: 40-70 ml: 0-20 ml: 2-6 g.

[0010] The reaction temperature is 120-200°C;

[0011] Optionally, the reaction temperature is selected from any value of 120°C, 140°C, 160°C, 180°C, 200°C or a range between any two of the above values.

[0012] The reaction time is 12 to 20 hours.

[0013] Optionally, the reaction time is selected from any value among 12h, 14h, 16h, 18h, 20h or a range between any two of the above.

[0014] The washing is performed with water and ethanol.

[0015] The drying temperature is 10 to 120° C.

[0016] Optionally, the drying temperature is 40 to 120°C;

[0017] Optionally, the drying temperature is 60 to 120°C;

[0018] Optionally, the drying temperature is selected from any value of 60°C, 70°C, 80°C, 90°C, 100°C, 120°C or a range between any two of the above values.

[0019] The drying time is 6 to 12 hours;

[0020] Optionally, the drying time is 8 to 12 hours.

[0021] Optionally, the drying time is selected from any value among 6h, 7h, 8h, 9h, 10h, 11h, 12h or a range between any two of the above.

[0022] The calcination temperature is 200-400°C;

[0023] Optionally, the calcination temperature is selected from any value of 200°C, 250°C, 300°C, 350°C, 400°C or a range between any two of the above values.

[0024] The calcination time is 2 to 6 hours.

[0025] Optionally, the calcination time is selected from any value among 2h, 3h, 4h, 5h, 6h or a range between any two of the above.

[0026] According to another aspect of the present application, an α-iron oxide nanosheet catalyst prepared by the above-mentioned preparation method is provided.

[0027] According to another aspect of the present application, there is provided a use of the above-mentioned α-iron oxide nanosheet catalyst in normal-parahydrogen conversion.

[0028] The conversion temperature is 21K~200K.

[0029] The catalyst provided in the present application is used for evaluating the performance of catalytic conversion of ortho-parahydrogen, and the reaction temperature range is 21-100K, and the preferred temperature is 21-80K. The prepared α-iron oxide nanosheet catalyst is used for catalytic conversion reaction of ortho-parahydrogen, and the catalyst significantly improves the activity and stability of catalytic conversion reaction of ortho-parahydrogen. The catalyst preparation method in the present application is simple and easy, with low cost, and the catalytic conversion efficiency of ortho-parahydrogen is controllable, and the catalytic conversion efficiency can be controlled and adjusted within the range of 20%-70%, and can be used as a model catalyst for theoretical research on ortho-parahydrogen conversion.

[0030] The beneficial effects of this application include:

[0031] The catalyst preparation method provided in the present application is simple to operate, reliable, and conducive to large-scale production and use. The catalyst provided in the present application has a simple material synthesis method, strong repeatability, and stable activity. The catalyst preparation method in the present application is simple and easy to operate, has low cost, and the catalytic conversion efficiency of normal and para hydrogen is controllable. The catalytic conversion efficiency can be controlled and adjusted within the range of 20%-70%, and can be used as a potential catalyst for the development of normal and para hydrogen conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 XRD diagrams of the catalysts prepared in Comparative Example 1 and Examples 1-2 of the present application.

[0033] Figure 2 This is a TEM image showing the morphology of the α-iron oxide nanosheet catalyst prepared in Comparative Example 1 of the present application at 100 nm.

[0034] Figure 3 This is a TEM image of the morphology characterization of the α-iron oxide nanosheet catalyst prepared in Example 1 of the present application at 100 nm.

[0035] Figure 4 This is a TEM image of the morphology characterization of the α-iron oxide nanosheet catalyst prepared in Example 2 of the present application at 100 nm. DETAILED DESCRIPTION

[0036] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0037] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0038] In the present application, room temperature refers to "25°C".

[0039] In the present application, the ortho-parahydrogen conversion rate = (initial ortho-hydrogen concentration - product ortho-hydrogen concentration) / initial ortho-hydrogen concentration.

[0040] Comparative Example 1:

[0041] Small-α-iron oxide nanosheet catalysts were prepared by hydrothermal method. The specific process is as follows:

[0042] 1) Accurately weigh 1.365g FeCl3·6H2O and place it in a clean beaker. Add 50mL ethanol, 20mL deionized water, and 10g sodium acetate in sequence. Ultrasonicate for 30 minutes and stir for 30 minutes. After stirring thoroughly, transfer the mixed solution to a polytetrafluoroethylene hydrothermal reactor liner with a volume capacity of 150mL and seal the liner;

[0043] 2) The reactor was then transferred to an electric heated forced air drying oven at 150° C. for reaction for 18 hours.

[0044] 3) After the reaction is completed, the mixture is cooled to room temperature naturally, the sample solution after hydrothermal treatment is separated by centrifugation, and washed three times with deionized water and ethanol respectively. The washed sample is then dried in a drying oven at 80° C. to obtain a Small-α-iron oxide nanosheet catalyst. Figure 2 It can be seen that the prepared Small-α-iron oxide nanosheet catalyst with special exposed crystal face

[001] is in the shape of a regular hexagon with good crystallinity, a side length of about 70 nm, and a uniform particle size distribution.

[0045] Embodiment 1:

[0046] Middle-α-iron oxide nanosheet catalyst was prepared by hydrothermal method, and the specific process is as follows:

[0047] 1) Accurately weigh 1.365g FeCl3·6H2O and place it in a clean beaker. Add 60mL ethanol, 10mL deionized water, and 10g sodium acetate in sequence. Ultrasonicate for 30 minutes and stir for 30 minutes. After stirring thoroughly, transfer the mixed solution to a polytetrafluoroethylene hydrothermal reactor liner with a volume capacity of 150mL and seal the liner;

[0048] 2) The reactor was then transferred to an electric heated forced air drying oven at 150° C. for reaction for 18 hours.

[0049] 3) After the reaction is completed, the sample solution is cooled naturally to room temperature, and the sample solution after hydrothermal treatment is separated by centrifugation, and then washed with deionized water and ethanol for three times. The washed sample is then placed in a drying oven at 80° C. to obtain a Middle-α-iron oxide nanosheet catalyst. Figure 3 It can be seen that the prepared Middle-α-iron oxide nanosheet catalyst with special exposed crystal face

[001] is in the shape of a regular hexagon with good crystallinity, a side length of about 120 nm, and a uniform particle size distribution.

[0050] Embodiment 2:

[0051] Large-α-iron oxide nanosheet catalysts were prepared by hydrothermal method. The specific process is as follows:

[0052] 1) Accurately weigh 1.365g FeCl3·6H2O and place it in a clean beaker. Add 70mL ethanol and 10g sodium acetate in sequence. Ultrasonicate for 30 minutes and stir for 30 minutes. After stirring thoroughly, transfer the mixed solution to a polytetrafluoroethylene hydrothermal reactor liner with a volume capacity of 150mL and seal the liner;

[0053] 2) The reactor was then transferred to an electric heated forced air drying oven at 150° C. for reaction for 18 hours.

[0054] 3) After the reaction is completed, the sample solution is cooled naturally to room temperature, and the sample solution after hydrothermal treatment is separated by centrifugation, and then washed with deionized water and ethanol for three times. The washed sample is then placed in a drying oven at 80°C to obtain a Large-α-iron oxide nanosheet catalyst. Figure 4 It can be seen that the prepared Large-α-iron oxide nanosheet catalyst with special exposed crystal face

[001] is in the shape of a regular hexagon with good crystallinity, a side length of about 180 nm, and a uniform particle size distribution.

[0055] Embodiment 3:

[0056] Parahydrogen conversion reaction

[0057] When the reaction was carried out in a low-temperature Dewar tank under a temperature environment of 77 K, liquid nitrogen was used as a cooling medium to ensure that the catalyst could carry out the catalytic reaction at a temperature of 77 K. 0.2-3 g of the α-iron oxide nanosheet catalyst prepared in Comparative Example 1 and Examples 1 and 2 were used, and the reaction space velocities were 250, 500, and 2000 mL·g, respectively. -1 ·min -1 The specific reaction conditions are shown in Table 1.

[0058] Table 1: Comparative Example 1: Effect of the catalysts prepared by α-iron oxide nanosheets and Examples 1 to 2 on the conversion of normal parahydrogen

[0059]

[0060]

[0061] As can be seen from Table 1, the catalytic activity of the α-iron oxide nanosheet catalyst for the conversion of normal parahydrogen gradually increases as the grain size increases, and the Large-α-iron oxide nanosheet with the largest particle size has the highest catalytic activity.

[0062] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a size-controllable α-iron oxide nanosheet catalyst, characterized in that: The following steps are involved: At room temperature, trivalent iron salt, ethanol, water and sodium acetate are mixed, reacted in a closed container, centrifuged, washed, dried and calcined to obtain the size-controllable alpha-iron oxide nanosheet catalyst.

2. The preparation method according to claim 1, characterized in that: The ferric iron salt is selected from at least one of ferric chloride and ferric nitrate.

3. The preparation method according to claim 1, characterized in that: The usage ratio of the trivalent iron salt, ethanol, water and sodium acetate is 4-6 mmol: 40-70 ml: 0-20 ml: 2-6 g.

4. The preparation method according to claim 1, characterized in that: The reaction temperature is 120-200°C; The reaction time is 12 to 20 hours.

5. The preparation method according to claim 1, characterized in that: The washing is washing with water and ethanol.

6. The preparation method according to claim 1, characterized in that: The drying temperature is 10 to 120° C. Preferably, the drying temperature is 40 to 120°C; The drying time is 6 to 12 hours; Preferably, the drying time is 8 to 12 hours.

7. The preparation method according to claim 1, characterized in that: The calcination temperature is 200-400°C; The calcination time is 2 to 6 hours.

8. An α-iron oxide nanosheet catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the α-iron oxide nanosheet catalyst according to claim 8 in normal-parahydrogen conversion.

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