A method for long-term preservation of C12A7 electronic compounds on a large scale

Abstract

The application belongs to the technical field of electronic compound preservation, and specifically relates to a C12A7 electronic compound large-scale long-acting preservation method. The application does not depend on permanent solid-phase isolation coating, but through reversible physical / weak chemical adsorption of organic molecules, anions of C12A7:e- on the surface are 'locked' into a non-reactive state in a preservation state, so that the anions are no longer sensitive to H2O and O2; when C12A7:e- is used, through mild conditions 'unlocking', the C12A7:e- is restored to a high-activity surface electron state. The application fundamentally bypasses the technical path of solid-phase isolation, avoids the blockage of the protective layer to the catalytic activity of C12A7:e-, and simultaneously realizes reversible switching between the preservation state and the working state, thereby providing a feasible scheme for large-scale long-term high-quality preservation of C12A7:e- electronic compounds and practical application of the electronic compounds as catalyst carriers.

Description

Technical Field

[0001] This invention belongs to the field of electronic compound preservation technology, specifically a method for large-scale long-term preservation of C12A7 electronic compounds. Background Technology

[0002] C12A7:e⁻([Ca 24 Al 28 O 64 ] 4+ C12A7:e⁻ is an inorganic electronic compound with a mayenite crystal structure. Its unit cell consists of 12 sub-nanometer cages with a diameter of approximately 0.4 nm. Through chemical reduction, four electrons can be injected into four of these cages, acting as anions. C12A7:e⁻ exhibits a low work function (approximately 2.4 eV) and high local electron density, showing broad application prospects in electron emission, superconductivity, catalyst supports, and ion devices.

[0003] Due to the high chemical reactivity of C12A7:e⁻, its environmental stability remains a key challenge restricting its practical application. When exposed to air, the anionic electrons of C12A7:e⁻ react with oxygen and water molecules, leading to the destruction of its electronic structure and the degradation of its unique properties. Its degradation pathway mainly includes the oxidation pathway (O₂ captures anionic electrons and forms O₂). - (Iso-oxygen species) and hydrolysis pathway (reaction of H2O with anionic electrons). To address the aforementioned stability issues, researchers have developed various protection strategies. On a macroscopic level, electron compounds are encapsulated in vacuum quartz tubes or glove boxes for storage by isolating them from air and water. On a microscopic level, graphene is used to coat C12A7:e⁻ (CN116253558B, J. Mater. Chem. A, 2023, 11, 12802-12810) to isolate them from air and water. Alternatively, carbon nanoreactor technology is used to prepare carbon-coated C12A7:e⁻, enabling the carbon-coated particles to resist sintering at temperatures as high as 1450°C (J. Phys. Chem. C, 2017, 121, 22268-22273).

[0004] However, quartz tube encapsulation and glove box storage are only suitable for storing small quantities of C12A7:e⁻ in the laboratory and are difficult to adapt to large-scale applications. Existing protection principles based on "physical isolation" through microscopic inorganic solid-phase coating—forming an inorganic protective layer on the C12A7:e⁻ surface to physically isolate it from H₂O and O₂ in the environment—have inherent drawbacks: while isolating harmful atmospheres, the protective layer also physically blocks the contact between the C12A7:e⁻ surface and the external environment. When C12A7:e⁻ is used as a catalyst support, its surface states are significantly passivated, failing to fully utilize its unique chemical reactivity and thus reducing performance. More importantly, existing coating protection is usually irreversible; once formed, it is difficult to remove the protective layer without damaging the microstructure to restore the original surface state of C12A7:e⁻.

[0005] In industry, the current storage method for C12A7:e⁻ is to place C12A7:e⁻ in a sealed container. However, it is difficult for a sealed container to completely isolate the air, which eventually leads to the failure of C12A7:e⁻. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a method for the large-scale, long-term preservation of C12A7 electron compounds. Compared to existing technologies, this invention offers a novel protection approach—it does not rely on permanent solid-phase isolation coating, but instead utilizes the reversible physical / weak chemisorption of organic molecules to "lock" the anionic electrons on the C12A7:e⁻ surface into a non-reactive state during preservation, rendering them insensitive to H₂O and O₂. When using C12A7:e⁻, it is "unlocked" under mild conditions, restoring the highly active surface electronic state of C12A7:e⁻. This invention fundamentally bypasses the technical path of solid-phase isolation coating, avoiding the blocking of catalytic activity of C12A7:e⁻ by the protective layer, while simultaneously achieving reversible switching between the preserved and working states. This provides a feasible solution for the large-scale, long-term, high-quality preservation of C12A7:e⁻ electron compounds and their practical application as catalyst supports.

[0007] Based on the above technical objectives, the present invention adopts the following technical solution: This invention protects a method for large-scale long-term preservation of C12A7 electronic compounds, comprising the following steps: Freshly prepared C12A7:e⁻ is mixed with cyclic saturated organic protective molecules, which are then adsorbed onto the surface of the C12A7:e⁻ particles and the openings of the cage channels by van der Waals forces, forming a hydrophobic protective layer and thus obtaining protected C12A7:e⁻. The protected C12A7:e⁻ consists of a C12A7:e⁻ matrix and cyclic saturated organic protective molecules adsorbed on the matrix surface and the openings of the cage channels. Compared with the microscopic materials of the prior art, the C12A7:e⁻ protected by this invention does not contain inorganic oxides or inorganic salts as permanent passivation coatings.

[0008] Among them, the cyclic saturated organic protected molecules do not chemically react with the free electrons in the C12A7:e⁻ cage, but only have an adsorption effect, and they are nonpolar / weakly polar saturated cyclic structures.

[0009] Under vacuum or inert atmosphere conditions, the protected C12A7:e⁻ is subjected to low-temperature heat treatment, which causes the cyclic saturated organic protective molecules to evaporate and be removed, yielding C12A7:e⁻ that retains its original free electron activity.

[0010] Preferably, the cyclic saturated organic protecting molecule is selected from at least one of methylcyclohexane, cyclooctane, tetrahydropyran, and 2-methyltetrahydrofuran.

[0011] Preferably, the adsorption method is selected from gas phase adsorption or anhydrous inert solvent liquid phase impregnation adsorption.

[0012] Preferably, the anhydrous inert solvent liquid-phase impregnation adsorption operation involves impregnating C12A7:e⁻ in a cyclic saturated organic protecting molecule; wherein the volume ratio of C12A7:e⁻ to the cyclic saturated organic protecting molecule is 1:1~3. In the anhydrous inert solvent liquid-phase impregnation adsorption, the volume ratio of C12A7:e⁻ to the cyclic saturated organic protecting molecule is 1:1~3. Too few cyclic saturated organic protecting molecules will result in insufficient protection of C12A7:e⁻; too many cyclic saturated organic protecting molecules will cause C12A7:e⁻ to precipitate, resulting in uneven and wasteful precipitation.

[0013] Preferably, the gas-phase adsorption operation is as follows: C12A7:e⁻ is placed in a cyclic saturated organic protective molecular atmosphere and adsorption is performed; if the cyclic saturated organic protective molecular atmosphere is a flowing atmosphere, the total carrier gas space velocity is 100 mL / (g). C12A7:e⁻ •h)~3000mL / (g C12A7:e⁻ •h), continuous flow adsorption at room temperature for 0.5h~5h, because the specific surface area varies greatly depending on the synthesis method of C12A7:e⁻, and the corresponding space velocity will be different; if the atmosphere of cyclic saturated organic protective molecules is a static atmosphere, static adsorption is performed for 2h~24h under the condition of 1vol%~6vol% of cyclic saturated organic protective molecules (the volume percentage of cyclic saturated organic protective molecules is 1%~6%, and the balance is carrier gas).

[0014] Preferably, C12A7:e⁻ is selected from C12A7:e⁻ powder, C12A7:e⁻ tablet, or C12A7:e⁻ porous carrier. The large-scale long-term preservation method of the present invention does not have requirements on the morphology of C12A7:e⁻.

[0015] Preferably, the method for large-scale long-term preservation of C12A7 electronic compounds is as follows: at room temperature, the protected C12A7:e⁻ is preserved according to conventional industrial methods, that is, sealed in an anhydrous and oxygen-free sealed container. Under the condition that the sealed container cannot completely isolate air, compared with bare C12A7:e⁻, the hydrophobic protective layer of C12A7:e⁻ protected by the present invention effectively isolates C12A7:e⁻ from direct contact with air, thus achieving long-term storage and transportation at room temperature.

[0016] Preferably, the low-temperature heat treatment conditions are: holding at 80℃~180℃ for 0.5h~4h, and the cyclic saturated organic protective molecules generated by desorption can be recovered by condensation and recycled.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention achieves reversible protection without permanent blockage: Unlike inorganic passivation technology, the protective layer of this invention is combined with the reversible physical / weak chemical adsorption of organic molecules. After desorption, the cage opening and surface are completely open, preserving the original catalytic carrier function of C12A7:e⁻.

[0018] The desorption conditions of this invention are mild: low-temperature desorption at 80℃~180℃, avoiding the chemical reaction between C12A7:e⁻ and cyclic saturated organic protective molecules caused by high temperature.

[0019] This invention exhibits excellent chemical compatibility: the cyclic saturated organic protective molecule has no active functional groups, does not consume free electrons within the C12A7:e⁻ cage, and does not damage the bulk structure of C12A7:e⁻ during storage.

[0020] The process of this invention is suitable for industrialization: it can process powders in batches and compress tablets into carriers; in addition, the cyclic saturated organic protective molecules can be recycled and reused, and the cost is controllable.

[0021] Significant novelty: Existing literature and patents only report on sealed storage and inorganic permanent coating. This invention is the first to propose a technical solution for the protection of C12A7:e⁻ by adsorbing cyclic saturated organic protective molecules to construct a reversible hydrophobic barrier. Attached Figure Description

[0022] Figure 1 XRD patterns of C12A7:e⁻, C12A7:e⁻ protected in Example 1, and C12A7:e⁻ protected in Example 2.

[0023] Figure 2 SEM images of C12A7:e⁻, C12A7:e⁻ protected in Example 1, and C12A7:e⁻ protected in Example 2.

[0024] Figure 3 Infrared spectra of C12A7:e⁻, C12A7:e⁻ protected in Example 2, and C12A7:e⁻ obtained after in-situ low-temperature deprotection and activation of C12A7:e⁻ protected in Example 2.

[0025] Figure 4 The graph shows a comparison of the catalytic performance of C12A7:e⁻ and C12A7:e⁻ after in-situ low-temperature deprotection and activation of the protected C12A7:e⁻ in Example 1, and the catalytic performance of C12A7:e⁻ after Ru loading. Detailed Implementation

[0026] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention. Unless otherwise specified, the experimental methods and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials described are commercially available.

[0027] Since quartz tubes and glove boxes have limited storage capacity for C12A7:e⁻, and considering the problem that existing technologies "use quartz tube encapsulation and glove box storage only for small-scale laboratory storage of C12A7:e⁻", this invention provides protected C12A7:e⁻. The hydrophobic protective layer can protect C12A7:e⁻ even in air / oxygen environments, thus overcoming the deficiency of small-scale laboratory storage.

[0028] Considering the problem that existing micromaterial designs not only block the contact between the C12A7:e⁻ surface and the external environment, but also result in irreversible coating protection, this invention employs cyclic saturated organic protective molecules to form a hydrophobic protective layer on the surface of C12A7:e⁻ particles and at the opening of the cage channels. This provides a reversible and low-temperature removable protection method for long-term preservation of C12A7:e⁻. While achieving long-term storage with protection against hydrolysis and oxidation, it also ensures the complete recovery of the original catalytic activity of C12A7:e⁻ after deprotection, overcoming the shortcomings of existing technologies.

[0029] Considering that existing technologies make it difficult to completely isolate C12A7:e⁻ from air in industrial applications, which leads to the failure of C12A7:e⁻, this invention uses cyclic saturated organic protective molecules to protect C12A7:e⁻, thus achieving large-scale long-term preservation of C12A7:e⁻.

[0030] The technical solution of the present invention will be studied below using examples and comparative examples. The specific research methods and results are shown below: Example 1 A method for large-scale long-term preservation of C12A7 electron compounds includes the following steps: S1. Inert atmosphere pretreatment: Under an anhydrous and oxygen-free Ar atmosphere, the freshly prepared C12A7:e⁻ powder is vacuum-purged at 150℃ to remove impurities pre-adsorbed on the surface.

[0031] S2. Constructing a reversible temporary protective layer: Maintaining an anhydrous and oxygen-free environment, pretreated C12A7:e⁻ is mixed with cyclic saturated methylcyclohexane at a volume ratio of 1:1.2. Through anhydrous inert solvent liquid phase impregnation, the cyclic saturated organic molecules are uniformly adsorbed onto the surface of C12A7:e⁻ particles and the openings of the cage channels by van der Waals forces, forming a hydrophobic protective layer on the outer layer of C12A7:e⁻ and protecting the C12A7:e⁻.

[0032] Example 2 A method for large-scale long-term preservation of C12A7 electron compounds includes the following steps: S1. Inert atmosphere pretreatment: Under an anhydrous and oxygen-free Ar atmosphere, the freshly prepared C12A7:e⁻ powder is vacuum purged at 150℃ to remove impurities such as water and carbon dioxide pre-adsorbed on the surface; after pretreatment, it is vacuum cooled to room temperature and transferred to the adsorption column for flat packing under high-purity Ar protection.

[0033] S2. Dynamic vapor flow adsorption constructs a reversible temporary protective layer: The entire gas path is kept anhydrous and oxygen-free, with the pipeline heated to 38°C throughout to prevent vapor condensation. High-purity Ar is used as the carrier gas, with two controlled flow paths: one path introduces Ar into a 36°C constant-temperature 2-methyltetrahydrofuran vaporization bottle carrying saturated organic vapors; the other path uses Ar as a dilution carrier gas to mix and adjust vapor pressure. The mixed vapor and gas continuously pass uniformly from top to bottom through the C12A7:e⁻ powder bed, with a total carrier gas space velocity of 700 mL / (g). C12A7:e⁻ •h), continuous flow adsorption at a constant temperature of 35℃ for 2h; 2-methyltetrahydrofuran molecules are uniformly adsorbed on the surface of C12A7:e⁻ particles and at the opening of the cage channel by van der Waals forces, forming a complete hydrophobic protective layer on the outer layer of C12A7:e⁻ powder. The unadsorbed 2-methyltetrahydrofuran in the tail gas is recovered by ice water condensation to obtain gas-phase protected C12A7:e⁻.

[0034] Example 3 A method for large-scale long-term preservation of C12A7 electron compounds includes the following steps: S1. Inert atmosphere pretreatment: Under an anhydrous and oxygen-free Ar atmosphere, the freshly prepared C12A7:e⁻ powder is vacuum purged at 150℃ to remove impurities such as water and carbon dioxide pre-adsorbed on the surface. After purging, the powder is vacuum cooled to room temperature and transferred to a porous tray in a sealed static adsorption vessel under high-purity Ar protection, and then spread out flat.

[0035] S2. Constructing a reversible temporary protective layer through closed static adsorption: After evacuating the adsorption vessel, high-purity Ar is replaced three times. Methylcyclohexane liquid is added to the bottom storage tank of the vessel, and the mass ratio of C12A7:e⁻ powder to methylcyclohexane is controlled at 1:0.4, so that the powder and liquid do not come into direct contact. The vessel is completely locked to form a closed static system. The water bath is turned on to control the temperature inside the vessel at 35°C. The vessel is statically adsorbed for 12 hours under closed static conditions with 6 vol% cyclic saturated organic protective molecules. The saturated vapor of methylcyclohexane volatilized inside the vessel is uniformly adsorbed on the surface of C12A7:e⁻ particles and the opening of the cage channel through molecular diffusion and van der Waals forces, forming a continuous hydrophobic protective layer on the outside of the C12A7:e⁻ powder, thus obtaining C12A7:e⁻ with gas-phase static protection.

[0036] The method for large-scale long-term preservation of C12A7 electronic compounds in this invention is sealed storage and transportation: after adsorption, the compounds are sealed in an airtight container and stored and transported in batches at room temperature for a long time.

[0037] The following study uses C12A7:e⁻ protected in Examples 1 and 2 as examples. The specific research methods and results are shown below: Figure 1 The results show that the crystal structure of C12A7:e- after protection with methylcyclohexane and 2-methyltetrahydrofuran did not change significantly compared with the initial C12A7:e-. After treatment in Examples 1 and 2, the peak position and peak intensity of C12A7:e- remained in the state of the original electron compound, indicating that the preservation method of the present invention does not destroy the phase state and crystal structure of C12A7:e-.

[0038] Figure 2 The results show that the morphology and structure of C12A7:e- after protection with methylcyclohexane and 2-methyltetrahydrofuran are completely consistent with the initial C12A7:e- structure. The particle diameter and particle distribution do not change significantly. This indicates that the adsorption protection of methylcyclohexane and 2-methyltetrahydrofuran will not cause negative effects such as dissolution, aggregation, or phase separation of C12A7:e- particles. This shows that the protection method of the present invention can perfectly maintain the morphology of C12A7:e-.

[0039] The protected C12A7:e⁻ prepared in Example 2 was subjected to in-situ low-temperature deprotection and activation: heat treatment was carried out at 80°C under vacuum for 2 hours to obtain a highly active C12A7:e⁻ catalyst support with open cage channels and no decay of free electron concentration; the cyclic organic protective molecules were fully desorbed, condensed and collected for recycling. Figure 3 The results showed that after dynamic adsorption of 2-methyltetrahydrofuran, a significant characteristic peak attributable to 2-methyltetrahydrofuran appeared in the infrared spectrum of the C12A7:e- material. After desorption treatment, the relevant characteristic peak of 2-methyltetrahydrofuran disappeared, indicating that 2-methyltetrahydrofuran can achieve reversible adsorption-desorption on the C12A7:e- surface, thus verifying the effectiveness of the present invention.

[0040] Figure 4 The results showed that when the C12A7:e⁻ protected in Example 1 was placed in a glass bottle, occupying half of the bottle's volume, and the bottle was not deoxygenated or dehydrated, but only the bottle opening was sealed with a stopper, desorption activation was performed after one week (desorption activation conditions: heat treatment at 80℃ under vacuum for 2 hours). The catalyst activity obtained after loading 1.2Ru% was comparable to that of the fresh C12A7:e- loaded 1.2Ru% catalyst at 0.1 MPa and 18000 mL·g. -1 h -1 Under the conditions of 2435 μmol·g -1 h -1 and 2570 μmol·g -1 h -1 1MPa, 18000mL·g -1 h -1 Under the conditions of 8152 μmol·g -1 h -1 and 8139 μmol·g -1 h -1 Within the measurement error range, they can be considered the same. This comparison shows that the activity of C12A7:e- as a catalyst support after protection with methylcyclohexane is not affected, indicating that the activity of C12A7:e- can be effectively maintained during storage, and that desorption activation can effectively restore the electronic properties of C12A7:e-.

[0041] Obviously, the above embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for large-scale long-term preservation of C12A7 electronic compounds, characterized in that, Includes the following steps: Freshly prepared C12A7:e⁻ is mixed with cyclic saturated organic protective molecules, which are then adsorbed onto the surface of C12A7:e⁻ particles and the openings of cage channels by van der Waals forces, forming a hydrophobic protective layer and thus protecting C12A7:e⁻. Among them, the cyclic saturated organic protected molecules do not chemically react with the free electrons in the C12A7:e⁻ cage; Under vacuum or inert atmosphere conditions, the protected C12A7:e⁻ is subjected to low-temperature heat treatment, which causes the cyclic saturated organic protective molecules to evaporate and be removed, yielding C12A7:e⁻ that retains its original free electron activity.

2. The method for large-scale long-term preservation of C12A7 electronic compounds according to claim 1, characterized in that, The cyclic saturated organic protected molecule is selected from at least one of methylcyclohexane, cyclooctane, tetrahydropyran, and 2-methyltetrahydrofuran.

3. The method for large-scale long-term preservation of C12A7 electronic compounds according to claim 1, characterized in that, The adsorption method is selected from gas phase adsorption or anhydrous inert solvent liquid phase impregnation adsorption.

4. The method for large-scale long-term preservation of C12A7 electronic compounds according to claim 3, characterized in that, The operation of anhydrous inert solvent liquid phase impregnation adsorption is as follows: C12A7:e⁻ is impregnated in a cyclic saturated organic protective molecule; The volume ratio of C12A7:e⁻ to the cyclic saturated organic protected molecule is 1:1~3.

5. The method for large-scale long-term preservation of C12A7 electronic compounds according to claim 3, characterized in that, The gas-phase adsorption process involves placing C12A7:e⁻ in a cyclic saturated organic protective molecular atmosphere and allowing it to adsorb. If the atmosphere of the cyclic saturated organic protective molecule is a flowing atmosphere, and the total carrier gas space velocity is 100 mL / (g) C12A7:e⁻ •h)~3000mL / (g C12A7:e⁻ •h), continuous flow adsorption at room temperature for 0.5h~5h; If the atmosphere of the cyclic saturated organic protective molecule is a static atmosphere, static adsorption is performed for 2h to 24h under conditions of 1vol% to 6vol% of the cyclic saturated organic protective molecule.

6. The method for large-scale long-term preservation of C12A7 electronic compounds according to claim 1, characterized in that, C12A7:e⁻ is selected from C12A7:e⁻ powder, C12A7:e⁻ tablet, or C12A7:e⁻ porous carrier.

7. The method for large-scale long-term preservation of C12A7 electronic compounds according to claim 1, characterized in that, The method for large-scale long-term preservation of C12A7 electronic compounds is as follows: at room temperature, the protected C12A7:e⁻ is preserved according to conventional industrial methods.

8. The method for large-scale long-term preservation of C12A7 electronic compounds according to claim 1, characterized in that, The conditions for low-temperature heat treatment are: holding at 80℃~180℃ for 0.5h~4h.

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