Primary and secondary hydrogen catalyst and method for its preparation

Abstract

The application discloses a primary and secondary hydrogen conversion catalyst and a preparation method thereof. The primary and secondary hydrogen catalyst comprises the following components in percentage by weight based on the catalyst weight: phenolic resin 10wt%-30wt%, hydrated ferric oxide 70wt%-90wt%; wherein the hydrated ferric oxide is a weakly crystalline state with a micro-particle size of 3-10nm. The preparation method of the primary and secondary hydrogen catalyst comprises the following steps: (1) preparing the weakly crystalline state hydrated ferric oxide; (2) mixing the weakly crystalline state hydrated ferric oxide powder with a phenolic resin aqueous solution into a plastic body, then performing extrusion molding, and conducting a heat curing reaction to obtain the primary and secondary hydrogen catalyst. The primary and secondary hydrogen catalyst has a large specific surface area, high physical strength and small abrasion, and the preparation method is simple, the reaction temperature is low, the energy consumption is small, the preparation efficiency is high, and the primary and secondary hydrogen conversion catalytic activity is high.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ortho-para hydrogen catalytic conversion, and particularly relates to an ortho-para hydrogen catalyst and a preparation method thereof. BACKGROUND

[0002] Hydrogen is an ideal clean energy, and is currently mainly used as a propellant for carrying rockets and has a broad application prospect in the field of hydrogen fuel cells. As a fuel and an important energy carrier, liquid hydrogen is a relatively ideal use and storage mode, and the production of liquid hydrogen is one of the important links in the development and application of hydrogen energy.

[0003] Due to the difference in nuclear spin and the limitation of symmetry, hydrogen molecules exhibit two different types, namely ortho-H2 and para-H2. Ortho-H2 refers to a hydrogen molecule composed of two hydrogen atoms with the same direction of nuclear spin, and para-H2 refers to a hydrogen molecule composed of two hydrogen atoms with opposite directions of nuclear spin. At high temperatures, the equilibrium composition of ortho-para state remains unchanged. At room temperature, hydrogen is composed of 25% ortho-H2 and 75% para-H2. At low temperatures, the equilibrium composition of ortho-para state will change with temperature. At the standard boiling point of liquid hydrogen, the content of para-H2 can reach 99.8%. During the liquefaction of hydrogen, if no ortho-para hydrogen catalytic conversion is performed, the produced liquid hydrogen is normal hydrogen. Liquid normal hydrogen will spontaneously undergo ortho-para state conversion and eventually reach the equilibrium hydrogen at the corresponding temperature. The ortho-para conversion of hydrogen is an exothermic reaction, and the heat released exceeds the latent heat of vaporization of liquid hydrogen, which will cause the vaporization loss of liquid hydrogen. Therefore, during the liquefaction of hydrogen, multi-stage ortho-para hydrogen conversion must be performed, and the development of high-performance ortho-para hydrogen conversion catalysts is crucial for the production and storage of liquid hydrogen.

[0004] Currently, amorphous hydrated iron oxide is mainly used as an ortho-para hydrogen conversion catalyst.

[0005] CN202210029537.5 provides a method for preparing nano hydrated iron oxide with high crystallinity by a hydrothermal method. However, the micro-particle size of the catalyst is 15-25 nm, the particle size is relatively large, and the specific surface area is low.

[0006] CN201910782910.2 discloses a preparation method of hydrated iron oxide. The method uses a weak base as a precipitating agent, iron trichloride as a reactant, and disperses the product in an ammonium bicarbonate solution, filters, and dries to obtain hydrated iron oxide. This method utilizes the pore-forming effect of ammonium bicarbonate pyrolysis to increase the specific surface area of the product, but it will cause a significant decrease in the particle strength of the dried material, resulting in high catalyst particle abrasion.

[0007] CN202111354244.6 discloses a method for preparing a doped primary and secondary hydrogen conversion catalyst by high-temperature hydrothermal method. The method drops a metal ion solution to be doped into an iron salt solution in a certain proportion, then adds an appropriate amount of lye, obtains a precipitate through hydrothermal reaction, and then obtains a hydrated iron oxide catalyst through washing, drying and grinding treatment. However, the high-temperature reaction time of this preparation method is too long, the synthesis efficiency is low, the energy consumption is high, the obtained doped iron oxide has a large grain size (300-1000 nm), the product has high crystallinity, small specific surface area, and high wear of the formed particles.

[0008] CN202210832769.4 discloses a preparation method of a Fe atom doped fiber magnetic catalyst FeMnO x The method uses hydrothermal reaction, has high energy consumption, and has high preparation cost due to the need to prepare manganese oxide precursor. The catalyst has a fiber-like structure with a diameter of 2-5 nm and a length of 100 nm-500 nm, and the product has a large particle size and a low specific surface area.

[0009]

Fine Petroleum Chemical Industry Progress, 2010, 11 (7): 26-31

[0010] The specific surface area, particle strength and wear are important control indicators of catalytic materials. The hydrated iron oxide used in the above-mentioned primary and secondary hydrogen conversion catalyst has a low specific surface area, weak particle strength and high wear, which is not conducive to improving the performance of the primary and secondary hydrogen conversion catalyst. SUMMARY

[0011] In view of the deficiencies of the prior art, the present application provides a primary and secondary hydrogen conversion catalyst and a preparation method thereof. The primary and secondary hydrogen catalyst of the present application has a large specific surface area, high physical strength and small wear, the preparation method is simple, the reaction temperature is low, the energy consumption is small, the preparation efficiency is high, and the primary and secondary hydrogen conversion catalyst has high catalytic activity.

[0012] The primary and secondary hydrogen catalyst of the present application comprises the following components based on the weight of the catalyst: phenolic resin 10wt%-30wt%, hydrated iron oxide 70%-90%; wherein the hydrated iron oxide is a weakly crystalline crystal state, and the micro-particle size is 3-10 nm;

[0013] The primary and secondary hydrogen catalyst of the present application has the following properties: the particle radial crushing strength is 10-30 N / mm, the wear is 0.05%-0.18%, and the specific surface area is 150-250 m 2 / g; particle diameter 1.0~2.5mm.

[0014] In the positive and negative hydrogen catalyst of the present invention, the weakly crystalline state has the following characteristics: (1) In the XRD pattern, the peak intensity of all characteristic diffraction peaks is not greater than 2 and the half width at half maximum (FWHM) of the diffraction angle 2θ is less than 2º compared with the baseline intensity at the position (2θ); (2) There are distinguishable lattice fringes in high magnification (200,000 times and above) transmission electron microscopy images or distinguishable diffraction spots or diffraction rings in electron diffraction patterns.

[0015] The preparation method of the neutral-parahydrogen catalyst of the present invention includes the following steps:

[0016] (1) Preparation of weakly crystalline hydrated iron oxide;

[0017] (2) Weakly crystalline hydrated iron oxide powder is mixed with phenolic resin aqueous solution to form a plastic body, which is then extruded and thermosetting to obtain a secondary hydrogen catalyst.

[0018] In the method of the present invention, the preparation process of the weakly crystalline hydrated iron oxide in step (1) is as follows: under the simultaneous action of ultrasonic dispersion and mechanical dispersion, the iron salt solution and the inorganic alkali solution are mixed to form a colloidal mixture. Then, the colloidal mixture is allowed to stand for 0.5 to 5 hours, washed, separated, and dried. Then, it is crushed and sieved to obtain a certain mesh size of weakly crystalline hydrated iron oxide powder.

[0019] Furthermore, the iron salt is ferric chloride and / or ferric sulfate; the iron salt solution is in the form of Fe... 3+ The concentration is 0.10–1.5 mol / L, preferably 0.20–1.0 mol / L.

[0020] Further, the inorganic alkali is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, or ammonium bicarbonate, preferably sodium hydroxide or potassium hydroxide; the concentration of the inorganic alkali solution is expressed in terms of OH... - The concentration is calculated to be 0.5–2.0 mol / L, preferably 1.0–1.5 mol / L.

[0021] Furthermore, the iron salt solution contains Fe 3+ Calculated with inorganic alkaline solution as OH - Calculate, OH - / Fe 3+ The molar ratio is 3.0 to 4.5.

[0022] Further, the ultrasonic dispersion condition is that the ultrasonic frequency is 20-100 kHz, the ultrasonic power density acting on the reaction material is 20-1200 W / L, and the ultrasonic dispersion temperature is 10-45 DEG C; the preferred ultrasonic dispersion condition is that the ultrasonic frequency is 40-80 kHz, the ultrasonic power density is 40-600 W / L, and the ultrasonic dispersion temperature is kept at 20-35 DEG C.

[0023] Further, the mechanical dispersion includes but is not limited to mechanical stirring, magnetic stirring, shaking table, shear stirring and any mode and operation condition which are beneficial to fast and uniform mixing of the material.

[0024] Further, the separation is carried out by natural sedimentation, centrifugation, vacuum filtration or pressure filtration to separate the solid-liquid suspension after washing to obtain the solid phase material.

[0025] Further, the washing and filtering degree needs to meet that the mass content of sodium element in the finally obtained catalyst composition is less than 0.1% in terms of Na2O, preferably the Na2O content is less than 0.01%; and deionized water is generally used for washing operation.

[0026] Further, the drying condition is that the drying temperature is 20-60 DEG C, and the drying is carried out until the water content is not more than 40 wt%, preferably 10 wt%-25 wt%. The water content of the hydrated iron oxide is defined as follows: 5 grams of the washed hydrated iron oxide is placed in a 120 DEG C oven, and dried for 12 h under air atmosphere, and at this time, the sample is set to have a water content of 0.

[0027] Further, the crushing can be carried out by various means such as rolling, ball milling and the like, and the crushing process should keep the powder from changing the crystal form, and further preferably the powder has a mesh size of 200-800.

[0028] In the method, the mass percentage content of the phenolic resin aqueous solution in step (2) is 10 wt%-70 wt%, preferably 20 wt%-50 wt%.

[0029] The phenolic resin in step (2) of the method of the present application should be mixed with the hydrated iron oxide powder to form a viscous state suitable for extrusion molding by an extruder, generally in the form of a strip, which can be clover, four-leaf clover or cylindrical, and the diameter of the final strip-shaped product is 1.0-2.5 mm, preferably 1.2-2.0 mm. The phenolic resin is water-soluble phenolic resin, which can be prepared by itself or purchased as a commercial product. In the method of the present application, the heat curing conditions in step (2) are as follows: temperature 120-160℃, time 6-36 hours, generally in air atmosphere. The application of the primary and secondary hydrogen catalyst in the conversion of primary and secondary hydrogen, the reaction conditions are as follows: reaction temperature 20-80K, volume space velocity 200-2000min -1 , preferably 400-1800min -1 .

[0030] The present application uses weakly crystalline hydrated iron oxide and water-soluble phenolic resin as raw materials, which can be mixed and molded at a lower temperature to form an aqueous solution, which can maximize the catalytic activity of the active component of iron oxide, improve the effective contact area of hydrogen molecules and catalyst, and the catalyst has high strength and low wear, which is very suitable for the conversion of primary and secondary hydrogen. The present application does not use high-temperature hydrothermal synthesis method, the reaction temperature is low, the energy consumption is small, and the production cost is greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Transmission electron microscope image of the hydrated iron oxide prepared in Example 1.

[0032] Figure 2 X-ray diffraction spectrum of the hydrated iron oxide prepared in Example 1. DETAILED DESCRIPTION

[0033] The application is further described in detail below with reference to examples. The Na2O content in the catalyst is tested by XRF method; the specific surface area is tested by low-temperature nitrogen adsorption method, and the specific surface area value is calculated according to BET method; the size and lattice image of the hydrated iron oxide nanoparticles are observed by transmission electron microscopy; the radial crushing strength of the shaped sample is detected according to the relevant requirements in HG / T 3927-2007 method; the determination method of the hydrated iron oxide mass content is defined as follows: 5 g of sample and 50 mL of 25% hydrochloric acid are placed in a 250 mL conical flask, heated and refluxed at 60°C for 1 h, then filtered to obtain the insoluble phenolic resin, dried and weighed, and the hydrated iron oxide mass content is calculated; the determination method of the crystallization strength of the sample is defined as follows: (1) for a strong crystallization sample, in the XRD spectrum, at least one diffraction peak with a ratio greater than 2 exists between the peak intensity and the baseline intensity at the position (2θ), and the half-height width of the diffraction angle 2θ is less than 2º; (2) for a weak crystallization sample, no diffraction peak meeting the above strong crystallization determination condition exists in the XRD spectrum, but in the high-magnification transmission electron microscopy image, there should be distinguishable lattice stripe images, or in the electron diffraction spectrum, there should be distinguishable diffraction spots or diffraction rings. The para-hydrogen content is calculated by gas chromatography. The water-soluble phenolic resin is purchased from American Sheng Engineering Plasticization Company. Example 1

[0034] 1.2 mol / L sodium hydroxide solution and 0.9 mol / L ferric chloride solution are prepared respectively, and under the condition of mechanical stirring and ultrasonic dispersion (60 kHz, 30 W / L) at room temperature (25°C), a certain amount of sodium hydroxide solution is added to the ferric chloride solution, so that the molar ratio of OH - / Fe 3+ is 3.2, a suspension is formed, and after standing for 2 h, the precipitate is repeatedly washed and filtered with water to remove impurity ions in the sample. The washed material is dried in a forced air oven at 40°C until the water content is about 15%. The powder is crushed by a pulverizer, and the powder with a particle size of 300-200 mesh is obtained. Then, 35 wt% water-soluble phenolic resin is added, mixed uniformly, and then formed into a strip-shaped trilobate shape by using an extruder. Then, the sample is dried at 140°C for 12 h.

[0035] No obvious diffraction peak exists in the X-ray diffraction spectrum of the sample, indicating that the crystallinity is not high, but in the transmission electron microscopy image with a magnification of 400,000 times, obvious lattice stripe images can be observed, and in the selected area electron diffraction spectrum, some diffraction spots also exist, indicating that the obtained hydrated iron oxide is in a weak crystalline state.

[0036] The particle diameter of the catalyst is 1.4 mm, the radial crushing strength is 24.3 N / mm, the specific surface area is 197 m 2 / g. The hydrated iron oxide has a mass content of 83%, and an abrasion of 0.10%. The hydrated iron oxide is weakly crystalline, and the micro-particle size is 6.8 nm. The positive and secondary hydrogen conversion performance test is shown in Table 1. Example 2

[0037] A 1.5 mol / L sodium hydroxide solution and a 1.3 mol / L ferric chloride solution were prepared respectively. Under the condition of mechanical stirring (300 rpm) and ultrasonic dispersion (100 KHz, 160 W / L) at room temperature (30°C), a certain amount of the ferric chloride solution was added into the sodium hydroxide solution, so as to meet the molar ratio of OH - / Fe 3+ 3.2, and a suspension was formed. After standing for 4 h, the precipitate was repeatedly washed and filtered with water to remove sodium ions in the sample so as to meet the index requirements. The washed product was dried in a blast drying oven at 60°C until the water content was about 10%. The dried product was crushed by a crusher, and the powder with a mesh size of 600-500 was screened. Then, 25 wt% water-soluble phenolic resin was added, and the mixture was uniformly mixed and extruded into a strip-shaped clover shape. Then, the strip-shaped clover was dried at 150°C for 10 h.

[0038] Test results show that the obtained hydrated iron oxide is weakly crystalline, the particle diameter of the catalyst is 1.2 mm, the radial crushing strength is 22.1 N / mm, the specific surface area is 202 m 2 / g, the mass content of the hydrated iron oxide is 85%, the abrasion is 0.13%, and the micro-particle size is 6.2 nm. The positive and secondary hydrogen conversion performance test is shown in Table 1. Example 3

[0039] A 1.0 mol / L sodium carbonate solution and a 0.6 mol / L ferric chloride solution were prepared respectively. Under the condition of mechanical stirring (300 rpm) and ultrasonic dispersion (80 KHz, 120 W / L) at 45°C, a certain amount of the sodium hydroxide solution was added into the ferric chloride solution, so as to meet the molar ratio of OH - / Fe 3+ 3.2, and a suspension was formed. After standing for 0.5 h, the precipitate was repeatedly washed and filtered with water to remove sodium ions in the sample so as to meet the index requirements. The washed product was dried in a blast drying oven at 60°C until the water content was about 13%. The dried product was crushed by a crusher, and the powder with a mesh size of 500-400 was screened. Then, 30 wt% water-soluble phenolic resin was added, and the mixture was formed into a strip-shaped column. Then, the strip-shaped column was dried at 160°C for 8 h.

[0040] Test results show that the obtained hydrated iron oxide is weakly crystalline, the particle diameter of the catalyst is 1.0 mm, the radial crushing strength is 20.3 N / mm, the specific surface area is 212 m 2 / g. The mass content of the hydrated iron oxide was 89%, the abrasion was 0.15%, and the micro-particle size was 5.7 nm. The conversion performance of the normal and para-hydrogen was tested and is shown in Table 1. Comparative Example 1

[0041] The preparation conditions were the same as in Example 1, except that a large amount of water-soluble phenolic resin was added, and the content of the phenolic resin was 45 wt%. It was found that the phenolic resin could not be extruded into strips due to the excessive amount of the phenolic resin. After drying treatment without extruding into strips, the specific surface area of the product was only 105 m 2 / g, and the excessive amount of the phenolic resin also damaged the pore structure of the material, which was not conducive to catalytic application. The conversion performance of the normal and para-hydrogen was tested and is shown in Table 1. Comparative Example 2

[0042] The preparation conditions were the same as in Example 1, except that a certain amount of clay was added, and after mixing, the extruder was used to form a strip-shaped trilobate shape. It was tested that the obtained hydrated iron oxide had a weak crystalline state, the particle diameter of the catalyst was 1.5 mm, the radial crushing strength was 8.4 N / mm, and the specific surface area was 220 m 2 / g. The mass content of the hydrated iron oxide was 82%, the abrasion was 0.19%, and the micro-particle size was 6.5 nm. The conversion performance of the normal and para-hydrogen was tested and is shown in Table 1. Comparative Example 3

[0043] The iron oxide was prepared according to the method provided in Example 1 of CN202210029537.5, the grain size of the iron oxide was 23 nm, the crystallinity was high, and it was tested that the specific surface area was only 66 m 2 / g. It was pressed into a 1 mm thick sheet, and then slightly crushed. The conversion performance of the normal and para-hydrogen was tested and is shown in Table 1. Comparative Example 4

[0044] The hydrated iron oxide was prepared according to the method of Example 3 of CN201910782910.2. It was tested that the obtained hydrated iron oxide was in an amorphous state, the average particle diameter of the hydrated iron oxide was 5.4 nm, and the specific surface area was 238 m 2 / g. The phenolic resin was added in the manner and under the conditions of Example 1 to form a shape. The particle diameter of the obtained catalyst was 1.5 mm, the radial crushing strength was 17.2 N / mm, the specific surface area was 212 m 2 / g, the mass content of the hydrated iron oxide was 85%, and the abrasion was 0.17%. The conversion performance of the normal and para-hydrogen was tested and is shown in Table 1.

[0045] Table 1 Conversion rate of para-hydrogen of catalyst

[0046] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Parahydrogen conversion % 97.7 98.3 98.9 86.8 98.2 84.7 96.3

[0047] Test conditions: The activation condition was vacuum drying at 130°C for 12h, the evaluation temperature was 77K, and the volume space velocity was 400min-1 。

Claims

1. A primary-sec ondary hydrogen catalyst characterized in that: The catalyst includes the following components based on the weight of the catalyst: 10-30 wt% of phenolic resin and 70-90% of hydrated iron oxide; wherein the hydrated iron oxide is in a weakly crystalline state with a micro-particle size of 3-10 nm; the weakly crystalline state has the following characteristics: (1) in the XRD spectrum, the peak intensity of all characteristic diffraction peaks is not greater than 2 times the baseline intensity at the position 2θ, and the half-height width of the diffraction angle 2θ is less than 2º; (2) in the 200,000 times or more transmission electron microscope image, there are distinguishable crystal lattice stripe images or distinguishable diffraction spots or diffraction rings in the electron diffraction spectrum; the preparation method of the primary and secondary hydrogen catalyst includes the following steps: (1) preparing the weakly crystalline state hydrated iron oxide; (2) mixing the weakly crystalline state hydrated iron oxide powder and the aqueous phenolic resin solution into a plastic body, then extruding into a strip shape, and performing a heat curing reaction to obtain the primary and secondary hydrogen catalyst.

2. The catalyst of claim 1, wherein: The catalyst particle radial crushing strength is 10-30 N / mm, and the catalyst abrasion is 0.05%-0.18%.

3. The catalyst of claim 1, wherein: The catalyst has a specific surface area of 150-250 m 2 / g; the catalyst particles have a diameter of 1.0-2.5 mm.

4. A process for the preparation of the primary-sec ondary hydrogen catalyst according to any one of claims 1 to 3, characterized in that The preparation method of the primary and secondary hydrogen catalyst includes the following steps: (1) preparing the weakly crystalline state hydrated iron oxide; (2) mixing the weakly crystalline state hydrated iron oxide powder and the aqueous phenolic resin solution into a plastic body, then extruding into a strip shape, and performing a heat curing reaction to obtain the primary and secondary hydrogen catalyst.

5. The method of claim 4, wherein: The preparation process of the weakly crystalline state hydrated iron oxide in step (1) is as follows: under the simultaneous action of ultrasonic dispersion and mechanical dispersion, an iron salt solution is mixed with an inorganic lye to form a colloidal mixture, then the colloidal mixture is left to stand for 0.5-5 h, washed, separated, dried, and then crushed and sieved to obtain weakly crystalline state hydrated iron oxide powder with a certain mesh size.

6. The method of claim 5, wherein: The iron salt is ferric chloride and / or ferric sulfate; the iron salt solution has a Fe 3+ concentration of 0.10-1.5 mol / L.

7. The method of claim 5, wherein: The inorganic base is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate or ammonium bicarbonate; the inorganic base solution concentration is 0.5-2.0 mol / L as OH - .

8. The method of claim 5, wherein: The iron salt solution is in a molar ratio of Fe 3+ to the inorganic base solution in a molar ratio of OH - , OH - / Fe 3+ of 3.0 to 4.

5.

9. The method of claim 5, wherein: The ultrasonic dispersion conditions are as follows: the ultrasonic frequency is 20-100 kHz, the ultrasonic power density acting on the reaction material is 20-1200 W / L, and the ultrasonic dispersion temperature is 10-45℃.

10. The method of claim 5, wherein: The drying is performed at a drying temperature of 20-60℃ until the water content is not greater than 40 wt%.

11. The method of claim 4, wherein: The mass percentage content of the aqueous phenolic resin solution in step (2) is 10-70 wt%.

12. The method of claim 4, wherein: The phenolic resin in step (2) should be fully mixed with the hydrated iron oxide powder, and the viscous state should be suitable for extruding into a strip shape by using an extruder; the cross-sectional shape of the strip is clover, four-leaf clover or circular, and the diameter of the finally obtained strip is 1.0-2.5 mm; wherein the phenolic resin is water-soluble phenolic resin, and the aqueous phenolic resin solution is prepared by itself or by using a commercially available product.

13. The method of claim 4, wherein: The heat curing conditions in step (2) are as follows: the temperature is 120-160℃, the time is 6-36 hours, and the heat curing is performed in an air atmosphere.

14. Use of the primary-sec ondary hydrogen catalyst according to any one of claims 1 to 3 in a primary-sec ondary hydrogen conversion reaction, characterized in that: The primary-secondary hydrogen conversion reaction conditions are: reaction temperature 20-80 K, volume space velocity 200-2000 min -1 .

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