Preparation method of all-cis-N heterocyclic organic liquid storage isomer

Abstract

The invention belongs to the technical field of hydrogen energy storage and release, and relates to a preparation method of a full-cis-N heterocyclic organic liquid-state memory isomer, which comprises the following steps: adding a carrier into a solvent A, and carrying out ultrasonic treatment, the solvent A being one or two of methanol, ethanol, isopropanol and water; adding a noble metal source into the solvent A in the step 1, uniformly mixing, then removing the solvent A at 40-90 DEG C, and drying to obtain a precursor of which the surface contains metal ions; carrying out reduction treatment on the precursor to obtain a catalyst M / Support; and adding an M / Support catalyst and a reaction medium into the organic liquid storage body for hydrogenation reaction to obtain the all-cis-N heterocyclic organic liquid storage body isomer. The invention provides a method for selectively hydrogenating a nitrogen-containing heteroaromatic hydrogen storage body at a high conversion rate of 99.9% and a high total cis-isomer of 91.3% under a mild condition of 40-150 DEG C, and the product is easy to dehydrogenate quickly, so that the energy consumption and the cost of an LOHC hydrogen storage and release system are remarkably reduced.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy storage and release technology, and particularly relates to a method for preparing isomers of all-cis N-heterocyclic organic liquid storage. Background Technology

[0002] Hydrogen energy has a capacity of approximately 33.3 kWh·kg⁻¹. -1 The specific energy density and zero-carbon end-use characteristics of hydrogen have become one of the core supports for building a clean energy system. In the storage and transportation stage, organic liquid hydrogen storage (LOHC) technology uses catalytic hydrogenation of organic molecules at the production site to fix hydrogen in the form of chemical bonds for storage. It can be safely transported at ambient temperature and pressure using existing liquid fuel infrastructure. After catalytic dehydrogenation at the point of use, the carrier can be recycled, combining high safety with infrastructure compatibility. In LOHC systems represented by nitrogen-containing aromatic heterocycles such as N-ethylcarbazole, achieving highly selective hydrogenation under mild conditions to obtain a subsequent easily dehydrogenated configuration is the core key to determining the energy consumption and economics of the entire hydrogen storage and release cycle.

[0003] However, existing LOHC hydrogenation / dehydrogenation catalytic systems still face many bottlenecks: insufficient catalytic selectivity, the tendency to generate heterogeneous mixtures or non-preferred configurations during hydrogenation, directly raising the subsequent dehydrogenation energy barrier, leading to a significant increase in hydrogen release temperature and system energy consumption; in addition, poor control of the metal-support interface interaction of some catalysts easily triggers side reactions and supports structural degradation, shortening catalyst lifespan and further increasing application costs. Therefore, there is an urgent need to develop a catalytic system that can precisely control the hydrogenation configuration of nitrogen-containing aromatic molecules under mild hydrogen pressure and temperature conditions, preferentially generate all-cis isomers with lower dehydrogenation energy barriers, and possess high catalytic activity, long cycle life, and broad applicability, laying the foundation for the engineering and large-scale application of LOHC technology.

[0004] In summary, to reduce costs and increase efficiency in hydrogen storage systems and improve the efficiency of reversible hydrogen utilization, developing high-performance LOHC catalytic systems (such as M / CeO2) that can selectively add hydrogen under mild conditions and preferentially form easily dehydrogenated configurations (such as all-cis isomers) has become a key technical challenge for promoting the engineering implementation of organic liquid hydrogen storage technology. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing fully cis-N heterocyclic organic liquid isomers to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention provides the following solution: A method for preparing isomers of fully cis-N heterocyclic organic liquids includes: Step 1: Add 0.5-5.0g of carrier to solvent A and sonicate for 10-60 minutes, wherein solvent A is one or a mixture of two of methanol, ethanol, isopropanol and water; Step 2: Add the noble metal source to solvent A from step 1 and mix well. Then remove solvent A at 40-90℃ and dry to obtain a precursor containing metal ions on the surface. Step 3: The precursor is reduced in a hydrogen mixed atmosphere at a temperature of 100-800℃ or in an organic reducing agent at a temperature of 0-60℃ to obtain a high-performance noble metal supported catalyst M / Support. Step 4: Add 0.1g-1g of the high-performance M / Support catalyst and reaction medium to 3g-30g of organic liquid storage medium, and carry out hydrogenation reaction at 40-150℃ under hydrogen atmosphere to obtain the all-cis N heterocyclic organic liquid storage medium isomer.

[0007] Preferably, the carrier is alumina, titanium dioxide, carbon, silicon dioxide, or cerium oxide; Preferably, the noble metal salt is any one of chloride, nitrate, acetylacetone, acetate, sodium chlorate, and ammonium chlorate.

[0008] Preferably, the inert gas in the hydrogen mixed atmosphere is argon or nitrogen, and the volume ratio of hydrogen to inert gas is 0.05-1:1.

[0009] Preferably, the organic liquid storage medium is one or a mixture of at least two of N-ethylcarbazole, N-propylcarbazole, or N-methylcarbazole.

[0010] Preferably, the reaction medium is cyclohexane, water, a mixture of water and methanol, a mixture of water and ethanol, or one or a mixture of at least two of ethanol, methanol, and solvent-free conditions.

[0011] Preferably, the mass ratio of the carrier to the noble metal salt is 1:0.001-0.2.

[0012] Preferably, the reduction treatment takes 0.5-6 hours and the heating rate is 0.5-20℃ / min.

[0013] Preferably, the organic reducing agent is selected from one or a mixture of at least two of sodium borohydride, hydrazine or hydrazine hydrate, formic acid or formate, hypophosphite, dimethylamine borane, and ascorbic acid.

[0014] Preferably, the mass ratio of the M / Support catalyst to the organic liquid storage medium is 1:1-100.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: The hydrogenation reaction conditions are mild and the conversion efficiency is excellent: This invention can achieve efficient hydrogenation of nitrogen-containing aromatic heterocyclic hydrogen storage materials such as N-ethylcarbazole, N-methylcarbazole, and N-propylcarbazole under mild temperature and mild hydrogen pressure of 40–150℃. The conversion rate of N-ethylcarbazole can reach 99.9%, and the selectivity of the all-cis isomer is as high as 91.3%. It effectively solves the core pain points of insufficient catalytic selectivity and high hydrogenation temperature in the existing technology, and significantly reduces the energy consumption of the hydrogenation process.

[0016] The target product exhibits outstanding dehydrogenation performance: the prepared all-cis N-heterocyclic organic liquid storage isomer has a lower dehydrogenation energy barrier and can rapidly dehydrogenate and release hydrogen at slightly higher temperatures of 120–220℃, significantly shortening the hydrogen release cycle, reducing the overall energy consumption and system operation complexity of organic liquid hydrogen storage (LOHC) storage / release cycle, and improving the efficiency of high-efficiency and reversible utilization of hydrogen.

[0017] The catalyst system boasts broad adaptability and stable performance: It employs a universal support system encompassing cerium oxide (CeO2), alumina (Al2O3), titanium dioxide (TiO2), silica (SiO2), carbon materials, and their composites or doped modified materials. Various noble metal salts, such as chlorides, nitrates, and acetylacetonates, are incorporated, and uniform dispersion of the noble metals on the support surface is achieved through impregnation, deposition-precipitation, and other methods. Oxide supports leverage the strong interaction between oxygen vacancies and the metal-support relationship to enhance the exposure of active sites and the synergistic adsorption effect between the substrate and hydrogen. Carbon supports optimize mass transfer efficiency and metal dispersion through surface functional groups and pore structure, ensuring the catalyst exhibits high activity, excellent selectivity, and good cycling stability, reducing side reactions and support degradation, and extending catalyst lifespan. Furthermore, the catalyst offers flexible reduction methods, employing gas-phase H2 reduction at 100–800℃ or liquid-phase chemical reduction at 0–60℃, supplemented by activation in a hydrogen-containing atmosphere at 150–400℃ when necessary, adapting to different production scenarios.

[0018] The preparation process is flexible and versatile: the reaction medium can be cyclohexane, ethanol, methanol, water or a mixture thereof, or it can be carried out under solvent-free conditions; the organic liquid storage medium can be selected from one or more of N-methylcarbazole, N-ethylcarbazole, and N-propylcarbazole according to actual needs, with a large range of process adjustment space, which can adapt to the personalized needs of different application scenarios.

[0019] Significant potential for industrial application: The entire preparation method is simple and easy to implement, requiring no complex process equipment. The amount of all reagents can be flexibly scaled up or down proportionally. The product has good stability and wide matrix applicability. It can realize the efficient and large-scale preparation of hydrogen-rich and easily dehydrogenated materials, effectively reducing the overall cost and complexity of hydrogen storage systems, and providing reliable technical support for the engineering and large-scale application of LOHC technology.

[0020] In summary, this invention provides a method for achieving a high conversion rate of 99.9% and a high selectivity of 91.3% for hydrogenation of nitrogen-containing aromatic heterocyclic hydrogen storage materials under mild conditions of 40-150℃ using a noble metal supported catalyst, with the product readily and rapidly dehydrogenated, significantly reducing the energy consumption and cost of LOHC hydrogen storage and release systems. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 The chromatogram of cis-dodecyl N-ethylcarbazole prepared in Example 1; Figure 2 The 1H NMR spectrum of cis-dodecyl N-ethylcarbazole prepared in Example 1; Figure 3 The two-dimensional COSY NMR spectrum of all-cis-dodecyl N-ethylcarbazole prepared in Example 1; Figure 4 The mass spectrum of cis-dodecyl N-ethylcarbazole prepared in Example 1; Figure 5 Transmission electron microscopy (TEM) image of the Rh / CeO2 catalyst prepared in Example 1. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1 This embodiment provides a method for preparing a fully cis-N heterocyclic organic liquid reservoir isomer, and the method is as follows: S1: Disperse 0.2gCeO2 in 50mL ethanol (AR) and sonicate for 20 minutes.

[0025] S2: Add 350 μL of a 10 mg / mL rhodium chloride aqueous solution to the solution obtained in step 1, and sonicate for 20 minutes.

[0026] S3: Subsequently, the precursor A containing metal ions on its surface is obtained by oil bath heating treatment at 60°C to remove the solvent ethanol and drying.

[0027] S4: In a hydrogen-argon (10 / 90 vol%) atmosphere, precursor A is reduced at 350°C for 1 h, then naturally cooled to room temperature and passivated in air for 10 min to obtain the high-performance Rh / CeO2 catalyst.

[0028] S5: Weigh 0.1g of Rh / CeO2 catalyst, 1.0g of N-ethylcarbazole and 20mL of cyclohexane (AR) as solvents and add them to a high-pressure reactor. Charge the reactor with 5MPa of hydrogen gas and carry out the reaction at a temperature of 80℃. After the reaction is completed, cis-decahydro-N-ethylcarbazole is obtained.

[0029] Example 2 This embodiment provides a method for preparing a fully cis-N heterocyclic organic liquid isomer, which differs from Example 1 only in that: in step S2, 1400 μL of a 10 mg / mL rhodium chloride aqueous solution is added to the solution obtained in step S1.

[0030] The noble metal supported cerium oxide (CeO2) catalyst prepared in this embodiment is named 2.8Rh / CeO2.

[0031] Example 3 This embodiment provides a method for preparing a fully cis-N heterocyclic organic liquid isomer, which differs from Example 1 only in that: In step S2, 700 μL of chloroplatinic acid aqueous solution (H2PtCl6·6H2O) with a concentration of 10 mg / mL is added to the solution obtained in step S1. In step S4, the reduction treatment temperature of the precursor is 300℃; In step S5, the hydrogenation reaction is carried out at a temperature of 120°C.

[0032] The noble metal supported cerium oxide (CeO2) catalyst prepared in this embodiment is named Pt / CeO2.

[0033] Example 4 This embodiment provides a method for preparing a fully cis-N heterocyclic organic liquid isomer, which differs from Example 1 only in that the hydrogenation reaction temperature in step S5 is 120°C.

[0034] Example 5 This embodiment provides a method for preparing a fully cis-N heterocyclic organic liquid isomer, which differs from Example 1 only in that, in step S4, rhodium acetylacetone is used as the metal source. The noble metal-supported cerium oxide (CeO2) catalyst prepared in this embodiment is named AC-Rh / CeO2.

[0035] Example 6 This embodiment provides a method for preparing a fully cis-N heterocyclic organic liquid reservoir isomer, which differs from Example 1 only in that: in step S5, N-propylcarbazole is used as the organic liquid reservoir.

[0036] Example 7 This embodiment provides a method for preparing a fully cis-N heterocyclic organic liquid isomer, which differs from Example 1 only in that: In step S1, solvent A is a mixture of water and methanol (AR); In step S4, pure hydrogen is used as the reducing atmosphere for the reduction process; In step S5, the solvent for the hydrogenation reaction is water.

[0037] Example 8 This embodiment provides a method for preparing a fully cis-N heterocyclic organic liquid isomer, which differs from Example 1 only in that: In step S1, solvent A is a mixture of water and ethanol (AR); In step S2, the metal salt used is ruthenium acetylacetonate; In step S4, the reduction treatment temperature is 400℃ and the reduction time is 30 min; In step S5, the hydrogenation reaction is carried out at a temperature of 100°C.

[0038] Next, experimental verification was carried out on Example 1, including chromatographic analysis and nuclear magnetic resonance (NMR) spectroscopy (NMR). 1 H NMR analysis, two-dimensional correlation nuclear magnetic resonance (H NMR) 1 H- 1 The experiments, including H COSY analysis, mass spectrometry (MS) analysis, transmission electron microscopy (TEM) characterization, and hydrogenation reaction performance testing, are all routine procedures in this field and can be performed without question by those skilled in the art; therefore, the specific experimental procedures will not be elaborated upon. The experimental results are shown in Figures 1-5. Figure 1 The chromatogram shows the cis-dodecylhydro-N-ethylcarbazole isomer prepared in Example 1. As can be seen from the chromatogram, the characteristic peaks corresponding to the target product have regular shapes and no obvious interference from other peaks, indicating that the prepared cis-dodecylhydro-N-ethylcarbazole isomer has high purity and content.

[0039] Figure 2The image shows the 1H NMR spectrum of the cis-dodecylhydro-N-ethylcarbazole isomer prepared in Example 1. The spectrum indicates that the chemical environment of the hydrogen atoms in the product molecule is homogeneous, with no anisotropic hydrogen signals. Furthermore, the sum of all the peaks perfectly matches the theoretical total number of hydrogen atoms (25) in the cis-dodecylhydro-N-ethylcarbazole molecule, confirming that the product has a single component, a regular structure, and no other configurational impurities.

[0040] Figure 3 The image shows a two-dimensional COSY NMR spectrum of the all-cis-dodecylhydro-N-ethylcarbazole isomer prepared in Example 1. The coupling correlation signals between hydrogen atoms in this spectrum allow for precise analysis of the spatial connection and arrangement of adjacent hydrogen atoms in the molecule, directly confirming the all-cis configuration of the product and ruling out the possibility of a mixed cis-trans configuration.

[0041] Figure 4 The mass spectrum of the cis-dodecylhydro-N-ethylcarbazole isomer prepared in Example 1 is shown. The molecular ion peak of the target product in the spectrum corresponds to a molecular weight of 207, which is completely consistent with the theoretical molecular weight of cis-dodecylhydro-N-ethylcarbazole, clearly verifying the molecular identity of the prepared product and confirming the successful formation of the target product.

[0042] Figure 5 The image shows a transmission electron microscope (TEM) image of the Rh / CeO2 catalyst prepared in Example 1. It can be clearly observed from the image that the active component Rh (rhodium) does not exhibit obvious particle agglomeration on the CeO2 (cerium oxide) support surface, but is mainly uniformly dispersed in single-atom form. This confirms that the catalyst has excellent dispersibility of the active component, providing structural support for its high-efficiency catalytic performance.

[0043] Table 1 shows the performance data of the hydrogenation reaction of the cis-dodecylhydro-N-ethylcarbazole isomer in Example 1. The corresponding reaction conditions are as follows: catalyst dosage 1g, reactant N-ethylcarbazole dosage 5g, solvent cyclohexane 20mL, reaction temperature 60℃, hydrogen pressure 5MPa, and reaction time 8h.

[0044] catalyst Conversion rate (%) Selectivity (%) reactants <![CDATA[Rh / CeO2]]> 99.9 91.3 N-ethylcarbazole Table 1. Results of selective hydrogenation of chloronitrobenzene using different catalysts (selectivity is the selectivity of cis-dodecyl N-ethylcarbazole). The data in the table show that when using the Rh / CeO2 catalyst for the hydrogenation of N-ethylcarbazole, the conversion rate of the reactant N-ethylcarbazole is as high as 99.9%, and the selectivity of the target product, all-cis-dodecyl-N-ethylcarbazole, reaches 91.3%. This result fully demonstrates the high catalytic activity and excellent all-cis isomer selectivity of the Rh / CeO2 catalyst for nitrogen-containing aromatic heterocyclic molecules under low temperature and mild conditions.

[0045] In summary, the preparation method of this invention, utilizing a noble metal-supported catalyst, enables efficient hydrogenation of nitrogen-containing aromatic heterocyclic hydrogen storage media under mild conditions of 40-150℃, achieving a conversion rate of 99.9% and a selectivity of 91.3% for the all-cis isomer. This isomer can be rapidly dehydrogenated at 120-220℃. The method is highly universal, simple to prepare, and produces stable products, addressing the pain points of existing technologies, significantly reducing the energy consumption and cost of LOHC systems, and facilitating their engineering applications.

[0046] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing isomers of all-cis N-heterocyclic organic liquids, characterized in that, include: Step 1: Add 0.5-5.0g of carrier to solvent A and sonicate for 10-60 minutes, wherein solvent A is one or a mixture of two of methanol, ethanol, isopropanol and water; Step 2: Add the noble metal source to solvent A from step 1 and mix well. Then remove solvent A at 40-90℃ and dry to obtain a precursor containing metal ions on the surface. Step 3: The precursor is reduced in a hydrogen mixed atmosphere at a temperature of 100-800℃ or in an organic reducing agent at a temperature of 0-60℃ to obtain a high-performance noble metal supported catalyst M / Support. Step 4: Add 0.1g-1g of the high-performance M / Support catalyst and reaction medium to 3g-30g of organic liquid storage medium, and carry out hydrogenation reaction at 40-150℃ under hydrogen atmosphere to obtain the all-cis N heterocyclic organic liquid storage medium isomer.

2. The method for preparing the fully cis-N heterocyclic organic liquid isomer according to claim 1, characterized in that: The carrier is aluminum oxide, titanium oxide, carbon, silicon oxide, or cerium oxide.

3. The method for preparing the fully cis-N heterocyclic organic liquid isomer according to claim 1, characterized in that: The precious metal salt is any one of chloride, nitrate, acetylacetone, acetate, sodium chlorate, and ammonium chlorate.

4. The method for preparing the fully cis-N heterocyclic organic liquid isomer according to claim 1, characterized in that: The inert gas in the hydrogen-mixed atmosphere is argon or nitrogen, and the volume ratio of hydrogen to inert gas is 0.05-1:

1.

5. The method for preparing the fully cis-N heterocyclic organic liquid isomer according to claim 1, characterized in that: The organic liquid storage medium is one or a mixture of at least two of N-ethylcarbazole, N-propylcarbazole, or N-methylcarbazole.

6. The method for preparing the fully cis-N heterocyclic organic liquid isomer according to claim 1, characterized in that: The reaction medium is one or a mixture of at least two of the following: cyclohexane, water, a mixture of water and methanol, a mixture of water and ethanol, or ethanol, methanol, or solvent-free conditions.

7. The method for preparing the fully cis-N heterocyclic organic liquid isomer according to claim 1, characterized in that: The mass ratio of the carrier to the noble metal salt is 1:0.001-0.

2.

8. The method for preparing the fully cis-N heterocyclic organic liquid isomer according to claim 1, characterized in that: The reduction treatment lasts for 0.5-6 hours, and the heating rate is 0.5-20℃ / min.

9. The method for preparing the fully cis-N heterocyclic organic liquid isomer according to claim 1, characterized in that: The organic reducing agent is selected from one or a mixture of at least two of the following: sodium borohydride, hydrazine or hydrazine hydrate, formic acid or formate, hypophosphite, dimethylamine borane, and ascorbic acid.

10. The method for preparing the fully cis-N heterocyclic organic liquid isomer according to claim 1, characterized in that: The mass ratio of the M / Support catalyst to the organic liquid storage medium is 1:1-100.

Images