A medium-temperature pyrophosphate type dense hydrogen permeable membrane material, a preparation method and application thereof

Abstract

The application discloses a medium-temperature pyrophosphate dense hydrogen-permeable membrane material and a preparation method and application thereof. 1‑x Mg x P2O7-delta@MO; delta is a non-chemically stoichiometric ratio: 0<=x<=0.5, 0<=delta<=1; wherein MO is a sintering aid, and the MO is one or more of zinc oxide, nickel oxide, copper oxide and boron oxide; the membrane material is prepared by a solid phase reaction method; the material of the application improves the oxygen vacancy concentration of the membrane material by doping the pyrophosphate with low-valence metal ions, so that the material still has good conductivity after high-temperature sintering; meanwhile, the doping also improves the compactness; and the membrane is more compact after high-temperature sintering by adding the sintering aid, so that the hydrogen can be separated in the medium temperature range of 200 DEG C to 400 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of separation membrane material technology, specifically relating to a medium-temperature pyrophosphate type dense hydrogen permeable membrane material, its preparation method, and its application. Background Technology

[0002] Rapid economic development, coupled with a massive demand for fossil fuels, has led to energy shortages and environmental pollution. In the context of carbon neutrality, seeking and developing clean energy sources is crucial for reducing carbon emissions. Hydrogen is an ideal clean energy carrier, producing no greenhouse gases or other harmful gases during its conversion. Furthermore, it boasts advantages such as high calorific value, renewability, and abundant resources, making it a promising energy source. Currently, hydrogen is primarily produced from fossil fuels, inevitably generating byproducts such as carbon dioxide, carbon monoxide, and methane. These byproducts require separation to improve hydrogen purity. Traditional separation methods such as distillation and absorption can be used to purify hydrogen, but they are costly and energy-intensive. Membrane separation technology, as an emerging approach, offers advantages such as low energy consumption, low cost, high efficiency, and high performance, making it a hot topic in cutting-edge research. In particular, dense proton-electron conductive hybrid ceramic membranes can theoretically achieve 100% hydrogen selectivity, demonstrating promising application prospects.

[0003] Current research primarily focuses on mixed proton-electron conductive films operating at temperatures above 800℃. Excessively high operating temperatures result in significant energy consumption, and maintaining these temperatures for extended periods places extremely high demands on equipment sealing, inevitably leading to a substantial increase in costs. Furthermore, hydrogen separation and purification processes that combine hydrogen production (such as water-gas shift reactions) with hydrogen applications (such as ammonia synthesis) can significantly reduce energy consumption, but these processes require intermediate temperatures (200℃–400℃). Tetravalent metal pyrophosphates are promising candidate materials, exhibiting good conductivity and stability in the intermediate temperature range, and have attracted widespread attention and research. Pyrophosphate materials are mainly classified into two categories: tin pyrophosphate-based and zirconium pyrophosphate-based. Compared to zirconium pyrophosphate-based materials, tin pyrophosphate-based materials have higher conductivity. Current applications of tin pyrophosphate-based materials often do not involve high-temperature sintering, leaving residual phosphate phases within the material to provide proton conductivity. However, tin pyrophosphate-based materials have poor sintering performance, making it difficult to achieve density and hindering hydrogen separation. Therefore, addressing the low density problem of tin pyrophosphate-based materials is crucial.

[0004] Therefore, we propose a method to address the poor sinterability of tin pyrophosphate-based materials, enabling their application in medium-temperature hydrogen separation. Summary of the Invention

[0005] The purpose of this invention is to provide a medium-temperature pyrophosphate-type dense hydrogen permeable membrane material, its preparation method, and its application.

[0006] The technical solution adopted in this invention is:

[0007] In a first aspect, the present invention provides a medium-temperature pyrophosphate-type dense hydrogen permeable membrane material, which is prepared from phase-forming powder and sintering aid, and the general chemical formula of the membrane material is: Sn 1-x Mg x P2O 7-δ @MO; Specifically, δ is a non-stoichiometric ratio: 0≤x≤0.5, 0≤δ≤1.

[0008] MO is a sintering aid, and MO is one or more of zinc oxide, nickel oxide, copper oxide, and boron oxide.

[0009] Preferably, the intermediate-temperature pyrophosphate-type dense hydrogen permeable membrane material is composed of phase-forming powder and sintering aid, and the general chemical formula of the powder is: Sn 0.9 Mg 0.1 P2O 7-δ @MO; x=0.1, δ is a non-stoichiometric ratio: 0≤δ≤0.2. Wherein MO is a sintering aid, and MO is one or more of zinc oxide, nickel oxide, copper oxide, and boron oxide.

[0010] Preferably, the membrane material has a density of not less than 90%.

[0011] A second aspect of the present invention provides a method for preparing a medium-temperature pyrophosphate-type dense hydrogen-permeable membrane material according to the first aspect, the method comprising the following steps:

[0012] 1) Weigh diammonium hydrogen phosphate [(NH4)2HPO4], tin dioxide (SnO2), magnesium oxide (MgO) and phosphoric acid (H3OP4), mix them and perform wet ball milling. After wet ball milling, dry, calcine and grind to obtain phase-forming powder.

[0013] 2) The phase-forming powder and the sintering aid MO are subjected to wet ball milling, and then dried to obtain the precursor powder. The sintering aid MO is one or more of zinc oxide, nickel oxide, copper oxide or boron oxide.

[0014] 3) Inject the precursor powder into the mold and press it into shape to obtain the membrane preform.

[0015] 4) The membrane preform is calcined to obtain a medium-temperature pyrophosphate type dense hydrogen permeable membrane material.

[0016] Preferably, the grinding aid solvent used in the wet ball milling in step 1) is one or more of ethanol and acetone.

[0017] Preferably, the amount of the grinding aid solvent in step 1) is 100% to 150% of the total mass of diammonium hydrogen phosphate, tin dioxide, oxide of M, and phosphoric acid.

[0018] Preferably, the specific operation of roasting in step 1) is as follows: heating from room temperature to 600℃ to 800℃ at a heating rate of 1℃ / min to 3℃ / min, and then holding at that temperature for 5h to 10h.

[0019] Preferably, the amount of sintering aid mentioned in step 2) is 1% to 5% of the total mass of the phase-forming powder.

[0020] Preferably, the grinding aid solvent used in step 2) of wet ball milling is one or more of ethanol and acetone.

[0021] Preferably, the amount of grinding aid solvent used in step 1) is 100% to 150% of the total mass of the phase-forming powder and zinc oxide powder.

[0022] Preferably, the pressing and molding in step 3) is carried out under a pressure of 10MPa to 25MPa and a holding time of 8min to 15min.

[0023] Preferably, the sintering operation in step 4) is as follows: the temperature is increased from room temperature to 1000℃ to 1200℃ at a heating rate of 3℃ / min to 5℃ / min, and then held for 1h to 5h.

[0024] In some embodiments, the membrane material has a density of not less than 90%.

[0025] Preferably, the membrane material has a viscosity of 0.025-0.15 mL / min at 200-400°C and under humidification with purge gas. -1 cm -2 Hydrogen permeability.

[0026] A third aspect of the present invention provides a medium-temperature pyrophosphate-type dense hydrogen-permeable membrane material as described in the first aspect for selectively separating hydrogen from a hydrogen-containing gas mixture or for constructing a membrane reactor for hydrogen-related reactions.

[0027] The beneficial effects of this invention are:

[0028] 1. The medium-temperature pyrophosphate type dense hydrogen permeable membrane material of the present invention can achieve hydrogen separation in the medium temperature range, and the preparation method is simple.

[0029] 2. The medium-temperature pyrophosphate type dense hydrogen permeable membrane material of the present invention has well-developed surface cells, a compact intercellular structure, a large particle size, and no obvious pores, so that gas cannot pass through.

[0030] 3. This invention increases the oxygen vacancy concentration in the material by doping with low-valence metal elements, reducing the sharp drop in conductivity after high-temperature sintering and also playing a certain role in densification; at the same time, the addition of sintering aids makes the material more dense; these two operations enable the membrane material to separate and purify hydrogen in the medium temperature range, which is expected to be coupled with a medium-temperature hydrogen-related membrane reactor, reducing energy consumption. Attached Figure Description

[0031] Figure 1 The images show the XRD patterns of the phase-forming powders in Example 1 and Comparative Example 1.

[0032] Figure 2 The images show SEM images of the surface and cross-section of the medium-temperature pyrophosphate-type dense hydrogen permeable membrane material in Example 1.

[0033] Figure 3 The images show SEM images of the surface and cross-section of the fresh pyrophosphate membrane material in Comparative Example 1.

[0034] Figure 4 The images show SEM images of the surface and cross-section of the pyrophosphate membrane material in Comparative Example 2.

[0035] Figure 5 The images show SEM images of the surface and cross-section of the pyrophosphate-type membrane material in Comparative Example 3.

[0036] Figure 6 The diagram shows the conductivity-temperature relationship of the membrane materials in Examples 1 and 2.

[0037] Figure 7 SEM images of the surface and cross-section of a pyrophosphate-type material mixed with other sintering aids in Comparative Example 4.

[0038] Figure 8 The density histograms are for Example 1 and Comparative Examples 1-4.

[0039] Figure 9 The hydrogen permeation rate-temperature curves are for Example 1 and Comparative Example 5. Detailed Implementation

[0040] The present invention will be further explained and described below with reference to specific embodiments. Example 1

[0041] A medium-temperature pyrophosphate-based dense hydrogen-permeable membrane material is prepared by the following steps:

[0042] 1) Mix 10.6965g of (NH4)2HPO4, 4.0692g of SnO2, 0.1209g of MgO and 0.7mL of H3PO4, add 20mL of anhydrous ethanol, and then wet ball mill at 400r / min for 24h. Then dry naturally in ventilation. Put the dried powder into a muffle furnace and heat it from room temperature to 650℃ at a heating rate of 2℃ / min. Hold it at that temperature for 6h, then cool it to room temperature at a cooling rate of 2℃ / min. Then grind it again to obtain the phase-forming powder.

[0043] 2) Mix the phase-forming powder with 1% of its total mass of zinc oxide powder, add 20 mL of anhydrous ethanol, and then perform wet ball milling for 12 h at a ball mill speed of 400 r / min. Then, air dry to obtain the precursor powder.

[0044] 3) Inject 0.8g of phase-forming powder into a cylindrical stainless steel mold with an inner diameter of 16mm, and then maintain it under a pressure of 25MPa for 8min to obtain a film preform.

[0045] 4) Place the membrane preform in a muffle furnace and heat it from room temperature to 1100℃ at a heating rate of 5℃ / min, hold it at that temperature for 2 hours, and then cool it back to room temperature at a cooling rate of 5℃ / min to obtain the medium-temperature pyrophosphate type dense hydrogen permeable membrane material (chemical formula Sn). 0.9 Mg 0.1 P2O 7-δ @ZnO; δ is a non-stoichiometric ratio, 0≤δ≤1), and the sintering aid MO is zinc oxide.

[0046] The membrane material obtained in Example 1 has a density of 94.5% and a viscosity of 0.02552 mL / min at 200 °C under purge gas humidification. -1 cm -2 The hydrogen permeability is 0.07429 mL / min at 300 °C. -1 cm -2 The hydrogen permeability, and the 0.15076 mL / min at 400 °C. -1 cm -2 Hydrogen permeability. Example 2

[0047] The medium-temperature pyrophosphate-type dense hydrogen-permeable membrane material prepared in Example 1 is used to selectively separate hydrogen from hydrogen-containing gas mixtures or to construct membrane reactors for hydrogen-related reactions.

[0048] Comparative Example 1

[0049] A fresh pyrophosphate-based membrane material is prepared by the following steps:

[0050] 1) Mix 10.6965g of (NH4)2HPO4, 4.521g of SnO2 and 0.7mL of H3PO4, add 20mL of anhydrous ethanol, and then wet ball mill at 400r / min for 24h. Then dry naturally by ventilation. Put the dried powder into a muffle furnace and heat it from room temperature to 650℃ at a heating rate of 2℃ / min. Hold it at that temperature for 6h, then cool it to room temperature at a cooling rate of 2℃ / min. Then grind it to obtain the phase-forming powder.

[0051] 2) Inject 0.8g of phase-forming powder into a cylindrical stainless steel mold with an inner diameter of 16mm, and then hold it under a pressure of 25MPa for 8min to obtain a film preform.

[0052] 3) Place the membrane preform into a muffle furnace and heat it from room temperature to 1100℃ at a heating rate of 5℃ / min. Hold it at that temperature for 2 hours and then cool it back to room temperature at a cooling rate of 5℃ / min to obtain a fresh pyrophosphate membrane material (chemical formula SnP2O7).

[0053] Comparative Example 2:

[0054] A pyrophosphate-type membrane material is prepared by the following steps:

[0055] 1) Mix 10.6965g of (NH4)2HPO4, 4.0692g of SnO2, 0.1209g of MgO and 0.7mL of H3PO4, add 20mL of anhydrous ethanol, and then wet ball mill at 400r / min for 24h. Then dry naturally in ventilation. Put the dried powder into a muffle furnace and heat it from room temperature to 650℃ at a heating rate of 2℃ / min. Hold it at that temperature for 6h, then cool it to room temperature at a cooling rate of 2℃ / min. Then grind it again to obtain the phase-forming powder.

[0056] 2) Inject 0.8g of phase-forming powder into a cylindrical stainless steel mold with an inner diameter of 16mm, and then hold it under a pressure of 25MPa for 8min to obtain a film preform.

[0057] 3. Place the membrane preform in a muffle furnace and heat it from room temperature to 1100℃ at a heating rate of 5℃ / min, hold it at that temperature for 2 hours, and then cool it back to room temperature at a cooling rate of 5℃ / min to obtain the medium-temperature pyrophosphate membrane material (chemical formula Sn). 0.9 Mg 0.1 P2O 7-δ ; δ is a non-stoichiometric ratio, 0≤δ≤1).

[0058] Comparative Example 3:

[0059] A pyrophosphate-type membrane material is prepared by the following steps:

[0060] 1) Mix 10.6965g of (NH4)2HPO4, 4.521g of SnO2 and 0.7mL of H3PO4, add 20mL of anhydrous ethanol, and then wet ball mill at 400r / min for 24h. Then dry naturally by ventilation. Put the dried powder into a muffle furnace and heat it from room temperature to 650℃ at a heating rate of 2℃ / min. Hold it at that temperature for 6h, then cool it to room temperature at a cooling rate of 2℃ / min. Then grind it to obtain the phase-forming powder.

[0061] 2) Mix the phase-forming powder with 1% of its total mass of zinc oxide powder, add 20 mL of anhydrous ethanol, and then perform wet ball milling for 12 h at a ball mill speed of 400 r / min. Then, air dry to obtain the precursor powder.

[0062] 3) Inject 0.8g of precursor powder into a cylindrical stainless steel mold with an inner diameter of 16mm, and then hold it under a pressure of 25MPa for 8min to obtain a membrane preform.

[0063] 4) Place the membrane preform in a muffle furnace and heat it from room temperature to 1100℃ at a heating rate of 5℃ / min, hold it at that temperature for 2 hours, and then cool it back to room temperature at a cooling rate of 5℃ / min to obtain a pyrophosphate type membrane material (chemical formula SnP2O7@ZnO). The sintering aid MO is zinc oxide.

[0064] Performance testing:

[0065] 1) The X-ray diffraction (XRD) patterns of the phase-forming powders in Example 1 and Comparative Example 1 are shown below. Figure 1 As shown.

[0066] Depend on Figure 1 It can be seen that the phase-forming powder of Comparative Example 1 has a cubic phase structure. After being doped with low-valence metal elements, Example 1 maintained its original cubic phase and no impurity phase was generated.

[0067] 2) Scanning electron microscope (SEM) images of the surface and cross-section of the medium-temperature pyrophosphate-type dense hydrogen permeable membrane material in Example 1, the fresh pyrophosphate-type membrane material in Comparative Example 1, the pyrophosphate-type membrane material in Comparative Example 2, and the pyrophosphate-type membrane material in Comparative Example 3 are shown below. Figure 2 (a is the surface, b is the cross-section) Figure 3 (a is the surface, b is the cross-section) Figure 4 (a is the surface, b is the cross-section) and Figure 5 (a is the surface, b is the cross-section) as shown.

[0068] Depend on Figure 2 It can be seen that the surface cells of the medium-temperature pyrophosphate-type dense hydrogen permeable membrane material in Example 1 are well developed, the intercellular structure is compact, the particle size is large, and there are no obvious pores, so gas cannot pass through. It can also be seen from the cross-section that the cells are closely connected, indicating that the membrane material is very dense after high-temperature sintering and can be used for hydrogen separation in the medium temperature range.

[0069] Depend on Figure 3 It can be seen that the surface of the fresh pyrophosphate membrane material in Comparative Example 1 has many pores, small particle size, no continuous cell, and is not dense; the cross-section also shows that there are many pores, indicating that the fresh pyrophosphate membrane material is not dense after high-temperature sintering and cannot achieve hydrogen separation in the medium temperature range.

[0070] Depend on Figure 4 It can be seen that pyrophosphate materials that are only doped with low-priced metal elements but do not use sintering aids still have a small number of pores on the surface and do not have the high density of film materials that do not use sintering aids.

[0071] Depend on Figure 5 It can be seen that pyrophosphate materials mixed with only sintering aids also have a small amount of porosity.

[0072] Depend on Figure 8 As shown in the figure, the density of various materials is as follows: the theoretical density is calculated by XRD refinement, and the actual density is determined by Archimedes' displacement method. The actual density is equal to the theoretical density. Therefore, it can be seen that simultaneous doping and use of sintering aids can achieve a higher density.

[0073] 3) The membrane materials from Example 1 and Comparative Examples 1-2 were polished to a thickness of 1 mm using 400, 800, and 2000 grit SiC sandpaper. The membranes were then ultrasonically cleaned for 0.5 hours. After ultrasonic cleaning, both ends of the membrane were coated with silver paste, and a silver wire was used to collect the current and fix it to one end of a φ16 corundum tube. A φ30 quartz glass tube was used as the feed tube. The mold was placed in a high-temperature tube furnace. The heating program was as follows: the temperature was increased from room temperature to 400°C at a rate of 5°C / min, held at that temperature for testing, and then gradually decreased to the desired temperature at a rate of 5°C / min for further testing. The other end of the silver wire was connected to a Gramy electrochemical workstation. The workstation recorded the current and calculated the conductivity after providing voltage. The flow rate of the gas used in the test was precisely controlled by a mass flow controller, and hydrogen gas was introduced at a flow rate of 50 ml / min on the feed side. The relationship between conductivity and temperature is as follows: Figure 6 As shown.

[0074] Therefore, it can be seen that the membrane material in Comparative Example 1 is not dense and does not contain low-valence metal ion doping, resulting in very low conductivity. In contrast, the membrane material in Comparative Example 2, after low-valence metal ion doping, has an increased oxygen vacancy concentration, leading to increased conductivity. The membrane material in Example 1 is more dense than the membrane material in Comparative Example 2, hence its slightly improved conductivity.

[0075] Comparative Example 4

[0076] A pyrophosphate-type material mixed with other sintering aids is prepared by the following steps:

[0077] 1) Mix 10.6965g of (NH4)2HPO4, 4.521g of SnO2 and 0.7mL of H3PO4, add 20mL of anhydrous ethanol, and then wet ball mill at 400r / min for 24h. Then dry naturally by ventilation. Put the dried powder into a muffle furnace and heat it from room temperature to 650℃ at a heating rate of 2℃ / min. Hold it at that temperature for 6h, then cool it to room temperature at a cooling rate of 2℃ / min. Then grind it to obtain the phase-forming powder.

[0078] 2) Mix the phase-forming powder with 1% of boron oxide powder by mass, add 20 mL of anhydrous ethanol, and then perform wet ball milling for 12 h at a ball mill speed of 400 r / min. Then, air dry to obtain the precursor powder.

[0079] 3) Inject 0.8g of phase-forming powder into a cylindrical stainless steel mold with an inner diameter of 16mm, and then maintain it under a pressure of 25MPa for 8min to obtain a film preform.

[0080] 4) Place the film preform into a muffle furnace and heat it from room temperature to 1100℃ at a heating rate of 5℃ / min. Hold it at that temperature for 2 hours and then cool it back to room temperature at a cooling rate of 5℃ / min. This yields a pyrophosphate-type material (chemical formula SnP2O7@B2O3) mixed with other sintering aids. The sintering aid is B2O3.

[0081] Performance testing:

[0082] Scanning electron microscope (SEM) images of the surface and cross-section of a pyrophosphate-type material mixed with other sintering aids in Comparative Example 4 are shown below. Figure 7 (a is the surface, b is the cross-section) as shown.

[0083] It can be clearly observed that boron oxide, as a sintering aid, is not suitable for pyrophosphate materials. The surface and cross-section have a large number of pores, which cannot meet the densification requirements.

[0084] Depend on Figure 8 Its density can be determined.

[0085] Comparative Example 5:

[0086] A magnesium-doped zirconium pyrophosphate-based hybrid conductor hydrogen permeable membrane material Zr 0.9 Mg 0.1 P2O 7-δ The preparation method, wherein δ = 0 to 0.2, specifically includes the following steps:

[0087] 1) Weigh 9.98g ZrO2, 0.36g MgO and 11.62ml H3PO4, mix them and add 15ml ethanol. Ball mill at 500r / min and remove and air dry after 12h.

[0088] 2) The raw material powder obtained by ball milling is placed in a high-temperature muffle furnace and heated to 750°C at a heating rate of 2°C / min, and held at that temperature for 5 hours. Then it is cooled to room temperature at a rate of 2°C / min to obtain phase-forming powder.

[0089] 3) Weigh 1g of the phase-forming powder from step 2) and mix it with an ethanol solution of 0.05g / mL polyvinyl butyral ester. After natural drying, a mixed powder is obtained. The mixed powder is placed in a cylindrical stainless steel mold with an inner diameter of 16mm and pressed into shape under a pressure of 15MPa to obtain a film preform.

[0090] 4) The pressed membrane preform is placed in a high-temperature muffle furnace for sintering. The heating rate is 1℃ / min. First, the temperature is raised to 500℃ and held for 5h. Then, the temperature is raised to 1200℃ at a heating rate of 2℃ / min and held for 10h. Finally, the temperature is lowered to room temperature at a rate of 2℃ / min to obtain a magnesium ion-doped zirconium pyrophosphate-based hybrid conductor hydrogen permeable membrane material.

[0091] The membrane materials from Example 1 and Comparative Example 5 were first sanded to a thickness of 1 mm using 400-grit SiC sandpaper, and then polished with 800-grit and 2000-grit SiC sandpaper. The membranes were then ultrasonically cleaned in an ultrasonic cleaner for 0.5 hours. After ultrasonic cleaning, the membranes were sealed to one end of a φ16 corundum tube using high-temperature ceramic adhesive. A φ30 quartz glass tube was then placed over the corundum tube for feeding. The mixture was left to stand for 24 hours to allow the high-temperature ceramic adhesive to dry completely. After complete drying, the mold was placed in a high-temperature tube furnace. Before testing, the airtightness of the device was checked; if no leaks were found, the next step of the temperature rise test could proceed. The temperature rise program was as follows: the temperature was increased from room temperature to 80°C at a rate of 1°C / min and held for 2 hours; then increased to 150°C at a rate of 1°C / min and held for 2 hours; after the holding period, the temperature was increased to 400°C at a rate of 1°C / min for the holding test. The flow rate of the gas used in the test was precisely controlled by a mass flow controller. A hydrogen-helium mixture with a volume ratio of 1:1 was introduced into the feed side, with a total flow rate of 100 mL / min. Argon gas was used as the purge gas at a flow rate of 100 mL / min. The purge exhaust gas was introduced into an Agilent 7890A gas chromatograph for hydrogen concentration determination, and the flow rate of the exhaust gas was measured using a soap bubble flow meter. The purge gas in Example 1 was humidified. The hydrogen permeation-temperature curves obtained in Example 1 and Comparative Example 5 are shown below. Figure 9 As shown.

[0092] Depend on Figure 9 It can be seen that at 300°C and above, the hydrogen permeation of Example 1 is higher than that of Comparative Example 5, while at 300°C and below, the hydrogen permeation is lower than that of Comparative Example 5. This may be due to the decrease in membrane material stability caused by temperature rise and fall, which leads to a faster rate of decrease in hydrogen permeation of Example 1.

[0093] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0094] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A medium-temperature pyrophosphate-type dense hydrogen-permeable membrane material, characterized in that, The membrane material is prepared from phase-forming powder and sintering aids, and its general chemical formula is: Sn 1-x Mg x P2O 7-δ @MO; where δ is a non-stoichiometric ratio: 0<x≤0.5, 0≤δ≤1; where MO is a sintering aid and MO is zinc oxide.

2. The intermediate-temperature pyrophosphate-type dense hydrogen-permeable membrane material according to claim 1, characterized in that, The general chemical formula of this membrane material is: Sn 0.9 Mg 0.1 P2O 7-δ @MO; x=0.1, δ is a non-stoichiometric ratio: 0≤δ≤0.2; where MO is a sintering aid and MO is zinc oxide.

3. A method for preparing a medium-temperature pyrophosphate-type dense hydrogen-permeable membrane material as described in any one of claims 1-2, characterized in that, Specifically, the following steps are included: 1) Weigh out diammonium hydrogen phosphate, tin dioxide, magnesium oxide and phosphoric acid, mix them and perform wet ball milling. After ball milling, dry, calcine and grind to obtain phase-forming powder; 2) The phase-forming powder and zinc oxide sintering aid are wet ball-milled, and then dried to obtain the precursor powder; 3) Inject the precursor powder into a mold and press it into shape to obtain a membrane preform; 4) The membrane preform is calcined to obtain a pyrophosphate-type dense membrane material.

4. The method according to claim 3, characterized in that: The membrane material has a density of not less than 90%.

5. The method according to claim 3, characterized in that: In steps 1) and 2), the grinding aid solvent used in wet ball milling is one or more of ethanol or acetone.

6. The method according to claim 3, characterized in that: The specific operation of the roasting in step 1) is as follows: the temperature is increased from room temperature to 600℃ to 800℃ at a heating rate of 1℃ / min to 3℃ / min, and then kept at that temperature for 5h to 10h.

7. The method according to claim 3, characterized in that: Step 2) The zinc oxide content is 1% to 5% of the total mass of the phase-forming powder.

8. The method according to claim 3, characterized in that: Step 3) The pressing and molding process is carried out under a pressure of 10MPa to 25MPa and a holding time of 8min to 15min.

9. The method according to any one of claims 3-8, characterized in that: The specific operation of the roasting in step 4) is as follows: the temperature is increased from room temperature to 1000℃ to 1200℃ at a heating rate of 3℃ / min to 5℃ / min, and then kept at that temperature for 1h to 5h.

10. A medium-temperature pyrophosphate-type dense hydrogen-permeable membrane material as described in any one of claims 1-2, used for selectively separating hydrogen from a hydrogen-containing gas mixture or for constructing a membrane reactor in a hydrogen-related reaction.

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