A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole

Abstract

The application belongs to the technical field of organic hydrogen storage material, and particularly relates to a synthesis method of an organic hydrogen storage material 3,6-dihydropyrrolo[3,2-e]indole. The synthesis method comprises the following steps: putting raw materials and a catalyst into a reactor, reacting at 25-250 DEG C for 0.1-72 hours, and obtaining 3,6-dihydropyrrolo[3,2-e]indole by separating and purifying the reaction product; wherein the raw materials are one of p-phenylenediamine and 5-aminoindole or a mixture of the two, and ethylene glycol; the catalyst is a combination of catalyst X and catalyst Y, or the catalyst is a composite catalyst C; catalyst X is a noble metal or a noble metal element supported by a carrier; catalyst Y is one or more of alkali metal oxides, alkali earth metal elements, alkali earth metal oxides, partial group IIIA or group IV A elements, zinc elements, copper elements, zinc oxide and copper oxide. The one-step synthesis method has high atom economy and is simple to operate without multi-step protection reaction.

Description

Technical Field

[0001] This invention belongs to the field of organic hydrogen storage materials technology, specifically relating to a method for synthesizing 3,6-dihydropyrrolo[3,2-e]indole, an organic hydrogen storage material. Background Technology

[0002] Among organic hydrogen storage materials, unsaturated aromatic hydrocarbons such as indoles, carbazoles, and benzyltoluenes are the most studied varieties. They achieve hydrogen energy storage and utilization through reversible reactions with hydrogen, and have the characteristics of large hydrogen storage capacity, high hydrogen energy utilization rate, recyclable hydrogen storage molecules, and long lifespan. However, existing organic hydrogen storage materials generally suffer from problems such as low hydrogen storage capacity, high reaction temperature, poor material stability, and high toxicity, among which the high dehydrogenation reaction temperature is a key bottleneck.

[0003] Patent CN113233413A reports that a benzodipyrrole compound system can lower the dehydrogenation temperature to below 150℃. Among these, the 3,6-dihydropyrrolo[3,2-e]indole ring has no substituents and boasts a hydrogen storage efficiency as high as 6.02%, making it one of the most promising organic hydrogen storage materials. However, the current synthesis process for this compound has many shortcomings, preventing mass production and meeting the demands of the hydrogen storage industry.

[0004] The literature MonatshChem (2013) 144:717-724 uses 5-nitroindole as the starting material and proceeds through multiple steps including nitro reduction, N protection, iodination, amino protection, coupling cyclization, and deprotection. The overall yield is <40%, and the starting material is dangerous and toxic.

[0005] The synthetic method for 3,6-dihydropyrrolo[3,2-e]indole described in this literature is as follows:

[0006] .

[0007] The literature Tetrahedron Letters, Vol. 38, No. 10, pp. 1673-1676, 1997 also uses 5-nitroindole, and the reaction involves four steps: BOM protection, addition of ethyl cyano group, hydrogenation reduction cyclization, and hydrolysis, with an overall yield of only about 30%.

[0008] The synthetic method for 3,6-dihydropyrrolo[3,2-e]indole described in this literature is as follows:

[0009] .

[0010] Medarex's patent WO2008103693A2 uses 4-aldehyde indole as a substrate, which is condensed with azidoacetic acid, followed by high-temperature cyclization and deacidification to obtain the product. The route is relatively short, but azidoacetic acid is explosive and the raw material 4-nitroindole is not easy to obtain.

[0011] The synthesis method described in patent WO2008103693A2 is as follows:

[0012] .

[0013] Patent CN121202883A uses diaminophenylethanol and diol compounds to synthesize through two cyclization processes, but diaminophenylethanol raw materials are not easy to obtain.

[0014] The synthesis method described in patent CN121202883A is as follows:

[0015] .

[0016] Therefore, developing a simple, low-cost, and high-yield synthesis process for 3,6-dihydropyrrolo[3,2-e]indole is of great significance for promoting the industrial application of organic hydrogen storage materials.

[0017] To address the above problems, this invention is proposed. Summary of the Invention

[0018] The purpose of this invention is to overcome the shortcomings of the prior art and provide a one-step method for synthesizing 3,6-dihydropyrrolo[3,2-e]indole, so as to achieve rapid, low-cost and large-scale preparation of this organic hydrogen storage material.

[0019] This application provides a method for synthesizing 3,6-dihydropyrrolo[3,2-e]indole, an organic hydrogen storage material, comprising the following steps: adding raw materials and catalyst to a reactor, reacting at 25-250℃ for 0.1-72 hours, and separating and purifying the reaction product to obtain 3,6-dihydropyrrolo[3,2-e]indole;

[0020] The raw materials are one or a mixture of two of p-phenylenediamine and 5-aminoindole, and ethylene glycol; the molar ratio of p-phenylenediamine and / or 5-aminoindole to ethylene glycol is 1:0.5-1:20.

[0021] The catalyst is a combination of catalyst X and catalyst Y, or the catalyst is a composite catalyst C;

[0022] The catalyst X is a noble metal, or a noble metal element supported on a support.

[0023] The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst X is 1:0.0005-1:0.1;

[0024] The catalyst Y is one or more of the following: alkali metal oxide, alkaline earth metal element, alkaline earth metal oxide, some group IIIA or IVA element, elemental zinc, elemental copper, zinc oxide, and copper oxide.

[0025] The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst Y is 1:0.001-1:0.1;

[0026] The composite catalyst C is prepared from catalyst X and catalyst Y;

[0027] The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst C is 1:0.0005-1:0.1.

[0028] Some Group IIIA or IVA elements are aluminum and silicon.

[0029] The chemical structural formula of 3,6-dihydropyrrolo[3,2-e]indole is as follows:

[0030] .

[0031] The reaction formula of this application is:

[0032] .

[0033] The reaction principle of this application is:

[0034] The principle of this invention is that catalyst X acts as the main catalyst to activate the substrate, while catalyst Y has a synergistic effect on catalyst X, enabling the reaction of m-phenylenediamine and aminoindole with ethylene glycol to prepare 3,6-dihydropyrrole[3,2-e]indole. Alternatively, composite catalyst C activates the substrate, enabling the reaction of m-phenylenediamine and aminoindole with ethylene glycol to prepare 3,6-dihydropyrrole[3,2-e]indole.

[0035] Preferably, a solvent is also added to the reactor, wherein the solvent is a liquid with a boiling point above 200°C at room temperature and pressure.

[0036] Preferably, in the raw materials, the molar ratio of p-phenylenediamine and / or 5-aminoindole to ethylene glycol is 1:1 to 1:10.

[0037] Preferably, the catalyst X is one or more of the following: carbon-supported palladium, molecular sieve-supported ruthenium, silicon oxide / alumina-supported rhodium, layered bimetallic hydroxide-supported platinum, and alumina-supported platinum; silicon oxide / alumina refers to silicon oxide and alumina.

[0038] The catalyst Y is one or more of sodium oxide, magnesium oxide, elemental magnesium, elemental zinc, zinc oxide, elemental aluminum, zinc-magnesium alloy, and elemental copper.

[0039] The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst X is 1:0.005-1:0.05;

[0040] The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst Y is 1:0.01-1:0.1.

[0041] Preferably, the composite catalyst C is prepared by one of the following two methods:

[0042] Method A: Load the elemental metal or metal alloy in catalyst Y together with the noble metal onto a support;

[0043] Method B: The oxide in the catalyst Y forms a composite support with the support, and the noble metal is loaded onto the composite support.

[0044] Preferably, the composite catalyst C is one of the following: alumina-supported platinum-magnesium, silica-supported palladium-calcium, magnesium oxide / alumina-supported palladium, potassium oxide / alumina-supported platinum, and silica-supported ruthenium-zinc;

[0045] The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst C is 1:0.005-1:0.05.

[0046] Preferably, the solvent is selected from one or a combination of N-methylpyrrolidone, sulfolane, ethylene carbonate, tetraethylene glycol dimethyl ether, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, and 1-ethyl-3-methylimidazolium tetrafluoroborate.

[0047] Preferably, the reaction temperature is 150-220℃ and the reaction time is 8-24 hours.

[0048] Preferably, stirring or no stirring is performed before the reaction.

[0049] Preferably, after the reaction is completed, the catalyst is recovered by filtration and can be reused after washing with ethanol, vacuum drying, and nitrogen storage. After complete deactivation, it can be regenerated by activation in a hydrogen environment at 400°C or above in a muffle furnace.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] 1. This application provides a one-step method for synthesizing 3,6-dihydropyrrolo[3,2-e]indole. This application employs a one-step synthesis method, eliminating the need for multiple protection reactions, resulting in high atom economy and simple operation.

[0052] 2. This application uses p-phenylenediamine, 5-aminoindole, and ethylene glycol as raw materials, which are widely available and inexpensive.

[0053] 3. The product yield of this application can reach up to 90.9%, which is much higher than that of the prior art (30%-40%).

[0054] 4. The catalyst in this application can be recycled and reused, and can be reactivated and regenerated after deactivation, thus reducing production costs.

[0055] 5. The reaction temperature and time of this application are controllable, no extreme reaction conditions are required, and it is easy to scale up for industrial production. Attached Figure Description

[0056] Figure 1 The one-dimensional H-NMR spectrum of 3,6-dihydropyrrolo[3,2-e]indole.

[0057] Figure 2 Two-dimensional H-NMR spectrum of 3,6-dihydropyrrolo[3,2-e]indole.

[0058] Figure 3 The chemical structural formula is 3,6-dihydropyrrolo[3,2-e]indole. Detailed Implementation

[0059] The present invention will be described below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. Experimental methods not specifically described in the embodiments generally use conventional conditions and conditions described in the manual, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified. The raw materials required in the following embodiments and comparative examples are all commercially available.

[0060] p-Phenylenediamine, ethylene glycol, and 5-aminoindole were purchased through the platform of Wuhan Xinshen Chemical Technology Co., Ltd.

[0061] Unless otherwise specified, all percentages in this application are mass percentages.

[0062] The synthesis method of the present invention is as follows: In a reactor, p-phenylenediamine or 5-aminoindole (which can be used alone or in combination) is added, along with ethylene glycol, a catalyst (a combination of catalyst X and Y, or a composite catalyst C) and a solvent (or no solvent is added) in a certain proportion. The reaction is carried out at 25-250°C for 0.1-72 hours. The reaction product is then simply separated and purified to obtain 3,6-dihydropyrrolo[3,2-e]indole.

[0063] The molar ratio of p-phenylenediamine or 5-aminoindole to ethylene glycol is 1:0.5-1:20, preferably 1:1-1:10;

[0064] The molar ratio of p-phenylenediamine or 5-aminoindole to catalyst X is 1:0.0005-1:0.1, preferably 1:0.005-1:0.05;

[0065] The molar ratio of p-phenylenediamine or 5-aminoindole to catalyst Y is 1:0.001-1:0.1, preferably 1:0.01-1:0.1;

[0066] The molar ratio of p-phenylenediamine or 5-aminoindole to catalyst C is 1:0.0005-1:0.1, preferably 1:0.005-1:0.05.

[0067] Catalyst X: mainly refers to noble metals and their compounds supported on a support in elemental form, preferably palladium-carbon, ruthenium-molecular sieve, rhodium-silica / alumina, Pt-LDH (layered double hydroxide), platinum-alumina, etc.

[0068] Catalyst Y: refers to alkali metal oxides, alkaline earth metal elements or oxides, some IIIA or IVA elements, zinc and copper elements and oxides in transition metals, or combinations thereof, preferably sodium oxide, magnesium oxide, elemental magnesium, elemental zinc, zinc oxide, elemental aluminum, zinc-magnesium alloys, elemental copper, etc.

[0069] Composite catalyst C: can replace the combination of catalysts X and Y, and its preparation method is as follows:

[0070] Method A: Alloys are formed by precious metals and alkali metal elements, alkaline earth metal elements, some IIIA or IVA elements, or zinc and copper elements in transition metals, and loaded onto a carrier, such as 2% platinum-magnesium-alumina, 2.5% palladium-calcium-silicon oxide, and 3% ruthenium-zinc-silicon oxide.

[0071] Method B: Noble metals are loaded onto a composite support consisting of alkali metal oxides, alkaline earth metal oxides, some IIIA or IVA oxides, or transition metals such as zinc oxide and copper oxide, and a support, such as 5% platinum-potassium oxide / aluminum oxide or 5% palladium-magnesium oxide / aluminum oxide.

[0072] Solvents may or may not be added. When adding solvents, choose high-boiling-point solvents (boiling point above 200℃), such as N-methylpyrrolidone, sulfolane, ethylene carbonate, tetraethylene glycol dimethyl ether, 1-butyl-3-methylimidazolium trifluoromethanesulfonate (ionic liquid), 1-ethyl-3-methylimidazolium tetrafluoroborate (ionic liquid), etc.

[0073] The reaction temperature is 25-250℃, preferably 150-220℃; the reaction time is 0.1-72 hours, preferably 8-24 hours.

[0074] After the reaction is complete, the catalyst is recovered by filtration, washed with ethanol, vacuum dried, and stored in nitrogen for reuse. After complete deactivation, the catalyst can be regenerated by activation in a muffle furnace at above 400°C in a hydrogen environment. The filtered reaction solution is then purified to obtain the target product.

[0075] The following examples and comparative examples further illustrate the solution of this application.

[0076] All load values ​​mentioned in this article refer to the mass ratio of the load to the carrier. Unless otherwise specified, all percentages are mass percentages.

[0077] Example 01

[0078] The preparation method of catalyst C 2% platinum magnesium-alumina is as follows:

[0079] Carrier pretreatment: γ-alumina was calcined in a muffle furnace at 550℃ for 4 hours and dried for later use to obtain γ-alumina carrier.

[0080] Impregnation solution preparation: The precursor was prepared with a platinum loading of 2 wt% and a platinum / magnesium atomic ratio of 1:2. The precursors were chloroplatinic acid and magnesium nitrate, dissolved in water according to the saturated water absorption capacity of the support. The pH was adjusted to 2-3 with dilute hydrochloric acid to prevent hydrolysis, resulting in the impregnation solution. The 2 wt% platinum loading refers to a mass ratio of platinum to γ-alumina support of 2 wt%.

[0081] Co-impregnation: The γ-alumina support is added to the impregnation solution and allowed to stand at room temperature for 16 hours with intermittent stirring.

[0082] Drying and calcination: The impregnated carrier is dried at 110℃ for 12 hours and then calcined in air at 450℃ for 3 hours to ensure uniform dispersion of elements.

[0083] Reduction: Using 10 vol% H2 / N2 as the reducing gas, the dried and calcined material was reduced at 500℃ for 3 hours. During this time, magnesium atoms diffused into the platinum lattice, completing the catalytic preparation of 2% platinum-magnesium-alumina. 2% platinum-magnesium-alumina is also called alumina-supported platinum-magnesium material with a platinum loading of 2wt%. 10 vol% H2 / N2 refers to a hydrogen to nitrogen volume ratio of 10:90.

[0084] The same method was used to prepare 2.5% palladium-calcium silicate (silica-supported palladium-calcium, palladium loading 2.5 wt%, palladium-calcium atomic ratio 1:2) and 3% ruthenium-zinc silicate (silica-supported ruthenium-zinc, ruthenium loading 3 wt%, ruthenium-zinc atomic ratio 1:2). Silica was used instead of alumina as the carrier during preparation.

[0085] Example 02

[0086] Catalyst C 5% Platinum-Potassium Oxide / Aluminum Oxide was prepared by a stepwise impregnation method:

[0087] Preparation of composite carrier: Using potassium loading of 3wt% to alumina as the ratio, potassium nitrate solution was impregnated onto alumina in equal volume, then dried at 110℃ and calcined at 600℃ for 4 hours to obtain potassium oxide / alumina composite carrier.

[0088] Noble metal loading: Using 5 wt% platinum loading as the quantitative ratio, chloroplatinic acid was used as the precursor and impregnated onto a potassium oxide / alumina composite support in equal volume. The impregnation was carried out at room temperature for 12 hours to obtain the catalyst precursor.

[0089] The 5wt% platinum loading refers to the mass ratio of platinum to the potassium oxide / alumina composite carrier being 5wt%.

[0090] Post-processing: The catalyst precursor was dried at 110℃ for 12 hours, then calcined at 400℃ in air for 3 hours, and finally reduced with hydrogen at 350℃ for 2 hours to obtain a highly dispersed 5% platinum-potassium oxide / alumina catalyst. This 5% platinum-potassium oxide / alumina catalyst is also called a platinum-supported material with a platinum loading of 5 wt% (potassium oxide / alumina).

[0091] The same method was used to prepare 5% palladium-magnesium oxide / aluminum oxide.

[0092] Example 1

[0093] In this embodiment, the 5% ruthenium-molecular sieve is a molecular sieve-supported ruthenium material purchased from Shaanxi Ruike New Material Co., Ltd., named ruthenium molecular sieve catalyst, CAS number 7440-18-8, with a ruthenium loading of 5wt%.

[0094] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0095] Add 10.8g (0.1mol) of p-phenylenediamine, 12.41g (0.2mol) of ethylene glycol, 2.02g (0.001mol) of 5% ruthenium-molecular sieve catalyst X, 0.048g (0.002mol) of magnesium powder catalyst Y, and 50ml of sulfolane to a 100ml pressure-resistant bottle. Heat to 200℃ and react for 24 hours. Cool down and stop the reaction. Then filter the solid-liquid mixture.

[0096] The catalyst can be recovered by filtration. It can be washed with ethanol, vacuum dried, and stored under nitrogen for reuse. If the catalyst is completely deactivated, it can be reactivated in a muffle furnace at 400°C or higher in a hydrogen environment.

[0097] The filtered reaction solution, after purification, yielded 10 g of 3,6-dihydropyrrolo[3,2-e]indole, with a yield of 64.1%. One-dimensional and two-dimensional H-NMR spectra are attached. Figure 1 and attached Figure 2 .

[0098] Specific purification methods:

[0099] Add twice the amount of deionized water to the filtered reaction solution, stir to extract the solid, filter again, collect the solid, and dry at 80°C. Dissolve the crude solid in 5 times the amount of 75% ethanol at 80°C until clear, slowly cool to room temperature to precipitate crystals, filter again, and vacuum dry at 60°C to obtain 3,6-dihydropyrrole[3,2-e]indole.

[0100] The following purification method is used in all subsequent embodiments of this application.

[0101] Figure 1 The one-dimensional H-NMR spectrum of 3,6-dihydropyrrolo[3,2-e]indole. Figure 2 Two-dimensional H-NMR spectrum of 3,6-dihydropyrrolo[3,2-e]indole. Figure 1 and Figure 2 The successful synthesis of 3,6-dihydropyrrolo[3,2-e]indole can be demonstrated.

[0102] Example 2

[0103] The 2% platinum magnesium-alumina mixture uses catalyst C material prepared in Example 01.

[0104] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0105] Add 13.2 g (0.1 mol) of 5-aminoindole, 6.2 g (0.1 mol) of ethylene glycol, 4.8 g (0.0005 mol) of 2% platinum magnesium-alumina, and 50 ml of tetraethylene glycol dimethyl ether to a 100 ml pressure-resistant bottle. Heat to 150 °C and stir for 8 hours. Cool down and stop the reaction, then filter the solid-liquid mixture.

[0106] The catalyst can be recovered by filtration. It can be washed with ethanol, vacuum dried, and stored in nitrogen for reuse. If it is completely deactivated, it can be reactivated in a muffle furnace at a temperature above 400°C in a hydrogen environment.

[0107] The filtered reaction solution was purified to yield 13 g of 3,6-dihydropyrrolo[3,2-e]indole, with a yield of 83.3%.

[0108] Example 3

[0109] 5% palladium-carbon, i.e., carbon-supported palladium with a palladium loading of 5wt%, is purchased through a reagent platform.

[0110] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0111] The method was the same as in Example 1, except that 1 mol of ethylene glycol was added, catalyst X was replaced with 0.005 mol of 5% palladium-carbon, catalyst Y was replaced with 0.001 mol of magnesium oxide, and the solvent sulfolane was not added. The temperature was raised to 180°C, and the reaction was carried out for 12 hours.

[0112] Example 4

[0113] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0114] The method was the same as in Example 1, except that catalyst X was replaced with 0.0008 mol of 5% Pt-LDH (layered bimetallic hydroxide supported on platinum, Pt loading 5 wt%), catalyst Y was replaced with 0.01 mol of zinc-magnesium alloy, and solvent was replaced with 1-butyl-3-methylimidazolium trifluoromethanesulfonate (ionic liquid). The temperature was raised to 190°C and the reaction was carried out for 12 hours.

[0115] 5% Pt-LDH (layered double hydroxide) was prepared by precipitation method: the layered double metal hydroxide (LDH) support was dispersed in deionized water to form a uniform suspension. Chloroplatinic acid precursor was weighed at 5 wt% of Pt loading and dissolved in water. It was slowly added dropwise to the LDH suspension. The pH of the system was adjusted to 8.0–9.0 with dilute urea solution under stirring. The system was aged at room temperature for 2–4 h to allow platinum species to be uniformly deposited on the LDH surface. Then, the system was filtered, washed twice with deionized water, and vacuum dried at 60–80 °C for 12 h. Finally, the system was reduced at 200–300 °C for 2 h in a hydrogen / argon mixed gas to obtain the 5% Pt / LDH catalyst.

[0116] Example 5

[0117] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0118] The method was the same as in Example 1, except that 0.3 mol of ethylene glycol was added, and catalyst X (5% ruthenium-molecular sieve) and catalyst Y (magnesium powder) were replaced with catalyst C 2.5% palladium-calcium-silica (silica-supported palladium-calcium, palladium loading 2.5 wt%, palladium-calcium atomic ratio 1:2) 0.003 mol, and the solvent was replaced with N-methylpyrrolidone. The temperature was raised to 220°C, and the reaction was carried out for 8 hours.

[0119] 2.5% palladium-calcium-silica was prepared by the method of Example 01.

[0120] Example 6

[0121] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0122] The method was the same as in Example 1, except that 1 mol of ethylene glycol was added, catalyst X was replaced with 0.0005 mol of 5% rhodium-silica / alumina, catalyst Y was replaced with 0.003 mol of elemental aluminum, and sulfolane solvent was not added. The temperature was raised to 150°C, and the reaction was carried out for 16 hours.

[0123] 5% rhodium-silica / alumina, i.e., rhodium supported on silica / alumina, with a rhodium loading of 5 wt%. The preparation method for 5% rhodium-silica / alumina is conventional; in this embodiment, it is prepared by ion exchange: a pre-activated SiO2-Al2O3 composite support, calcined at high temperature, is dispersed in deionized water to form a homogeneous suspension. The pH of the system is adjusted to weakly acidic with dilute hydrochloric acid to facilitate ion exchange. A 5% (w / w) rhodium trichloride precursor solution is added, and the exchange is carried out under continuous stirring for 6-12 h at room temperature or with mild heating, allowing Rh to... 3+ After sufficient exchange with hydroxyl or cation sites on the support surface, the catalyst is filtered, repeatedly washed with deionized water, dried at 100-120℃ for 10-12h, calcined at 350-450℃ in air for 3h, and then reduced at 300-350℃ in hydrogen / argon atmosphere for 2-3h to obtain a highly dispersed 5%Rh / SiO2-Al2O3 catalyst.

[0124] Example 7

[0125] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0126] The method was the same as in Example 1, except that catalyst X was replaced with 0.001 mol of 5% platinum-alumina, catalyst Y was replaced with 0.003 mol of zinc oxide, and the solvent was replaced with 1-ethyl-3-methylimidazolium tetrafluoroborate (ionic liquid). The temperature was raised to 170°C, and the reaction was carried out for 10 hours.

[0127] Example 8

[0128] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0129] The method was the same as in Example 7, except that the ratio of p-phenylenediamine to ethylene glycol was changed to 1:1. In the raw materials, p-phenylenediamine was 10.8 g (0.1 mol) and ethylene glycol was 14.2 g (0.1 mol).

[0130] Example 9

[0131] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0132] The method was the same as in Example 1, except that catalyst X and catalyst Y were replaced with catalyst C, i.e., 0.0006 mol of the 5% platinum-potassium oxide / alumina prepared in Example 02, with the solvent remaining unchanged. Furthermore, the raw materials included 10.8 g (0.1 mol) of p-phenylenediamine and 18.6 g (0.3 mol) of ethylene glycol. The temperature was raised to 180°C, and the reaction was carried out for 18 hours.

[0133] Example 10

[0134] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0135] The method was the same as in Example 2, except that 0.2 mol of ethylene glycol was added, and catalyst C was replaced with catalyst X and catalyst Y, namely 0.001 mol of 5% platinum-alumina and 0.005 mol of elemental zinc. The solvent was replaced with 50 ml of sulfolane. The temperature was raised to 180°C and the reaction was carried out for 12 hours.

[0136] Example 11

[0137] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0138] The method was the same as in Example 2, except that 1 mol of ethylene glycol was added, and catalyst C was replaced with catalyst X and catalyst Y, namely 0.005 mol of 5% ruthenium-molecular sieve and 0.001 mol of elemental copper. No solvent was added. The temperature was raised to 220°C and the reaction was carried out for 18 hours.

[0139] Example 12

[0140] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0141] The method was the same as in Example 2, except that catalyst C was replaced with catalyst X and catalyst Y, namely: 0.0008 mol of 5% Pt-LDH (layered double hydroxide) and 0.008 mol of sodium oxide, and the solvent was replaced with 50 ml of sulfolane. The temperature was raised to 200°C and the reaction was carried out for 8 hours.

[0142] Example 13

[0143] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0144] The method was the same as in Example 2, except that 0.5 mol of ethylene glycol was added, and catalyst C was replaced with catalyst X and catalyst Y, namely 0.001 mol of 5% palladium-carbon and 0.006 mol of zinc-magnesium alloy. The solvent was replaced with 1-butyl-3-methylimidazolium trifluoromethanesulfonate (ionic liquid). The temperature was raised to 180°C and the reaction was carried out for 12 hours.

[0145] Example 14

[0146] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0147] The method was the same as in Example 2, except that 0.2 mol of ethylene glycol was added, catalyst C was replaced with 0.004 mol of 5% palladium-magnesium oxide / aluminum oxide, and the solvent was replaced with N-methylpyrrolidone. The 5% palladium-magnesium oxide / aluminum oxide was sourced from Example 02. The temperature was raised to 160°C, and the reaction was carried out for 24 hours.

[0148] Example 15

[0149] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0150] The method was the same as in Example 2, except that 0.2 mol of ethylene glycol was added, catalyst C was replaced with 0.002 mol of 3% ruthenium zinc-silica, and the solvent was replaced with N-methylpyrrolidone. The 3% ruthenium zinc-silica was sourced from Example 02. The temperature was raised to 220°C, and the reaction was carried out for 12 hours.

[0151] Example 16

[0152] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0153] The method is the same as in Example 2, except that 5-aminoindole is replaced with a 1:1 molar ratio mixture of p-phenylenediamine and 5-aminoindole, i.e., 0.05 mol of p-phenylenediamine and 0.05 mol of 5-aminoindole. The amount of ethylene glycol added is changed to 0.2 mol.

[0154] Comparative Example 1

[0155] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0156] The method was the same as in Example 1, except that catalyst X (2.02 g of 5% ruthenium-molecular sieve, 0.001 mol) was added, and catalyst Y was not added.

[0157] Comparative Example 2

[0158] A method for synthesizing an organic hydrogen storage material, 3,6-dihydropyrrolo[3,2-e]indole, includes the following steps:

[0159] Same as in Example 10, except that 0.001 mol of elemental zinc Y catalyst was replaced with 0.005 mol of p-toluenesulfonic acid.

[0160] The experimental conditions and yields of 3,6-dihydropyrrolo[3,2-e]indole for the above examples and comparative examples are shown in Table 1 below.

[0161] Table 1

[0162]

[0163] Note 1: The amino-ol ratio refers to the ratio of p-phenylenediamine and / or 5-aminoindole to ethylene glycol. When the raw material contains both phenylenediamine and 5-aminoindole, it refers to the ratio of phenylenediamine and 5-aminoindole to ethylene glycol.

[0164] When the raw material contains either phenylenediamine or 5-aminoindole, it refers to the ratio of p-phenylenediamine or 5-aminoindole to ethylene glycol.

[0165] Note 2: The amine / X or C ratio refers to the ratio of p-phenylenediamine and / or 5-aminoindole to catalyst X or catalyst C;

[0166] Note 3: The amine / Y ratio refers to the ratio of p-phenylenediamine and / or 5-aminoindole to catalyst Y;

[0167] The comparative examples show that without catalyst Y or by using an acidic catalyst, the yield of 3,6-dihydropyrrolo[3,2-e]indole is low, with the main product being the isomer 1,5-dihydropyrrolo[2,3-f]indole, the structural formula of which is as follows:

[0168] .

Claims

1. A method for synthesizing 3,6-dihydropyrrolo[3,2-e]indole, an organic hydrogen storage material, characterized in that, The process includes the following steps: adding raw materials and catalyst to a reactor, reacting at 25-250℃ for 0.1-72 hours, and separating and purifying the reaction product to obtain 3,6-dihydropyrrolo[3,2-e]indole; The raw materials are one or a mixture of two of p-phenylenediamine and 5-aminoindole, and ethylene glycol; the molar ratio of p-phenylenediamine and / or 5-aminoindole to ethylene glycol is 1:0.5-1:

20. The catalyst is a combination of catalyst X and catalyst Y, or the catalyst is a composite catalyst C; The catalyst X is a noble metal, or a noble metal element supported on a support. The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst X is 1:0.0005-1:0.1; The catalyst Y is one or more of the following: alkali metal oxide, alkaline earth metal element, alkaline earth metal oxide, some group IIIA or IVA element, elemental zinc, elemental copper, zinc oxide, and copper oxide. The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst Y is 1:0.001-1:0.1; The composite catalyst C is prepared from catalyst X and catalyst Y; The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst C is 1:0.0005-1:0.

1.

2. The synthesis method according to claim 1, characterized in that, A solvent is also added to the reactor, which is a liquid with a boiling point above 200°C at room temperature and pressure.

3. The synthesis method according to claim 1, characterized in that, In the raw materials, the molar ratio of p-phenylenediamine and / or 5-aminoindole to ethylene glycol is 1:1 to 1:

10.

4. The synthesis method according to claim 1, characterized in that, The catalyst X is one or more of the following: carbon-supported palladium, molecular sieve-supported ruthenium, silica / alumina-supported rhodium, layered bimetallic hydroxide-supported platinum, and alumina-supported platinum; silica / alumina refers to silica and alumina. The catalyst Y is one or more of sodium oxide, magnesium oxide, elemental magnesium, elemental zinc, zinc oxide, elemental aluminum, zinc-magnesium alloy, and elemental copper.

5. The synthesis method according to claim 1, characterized in that, The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst X is 1:0.005-1:0.05; The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst Y is 1:0.01-1:0.

1.

6. The synthesis method according to claim 1, characterized in that, The composite catalyst C is prepared by one of the following two methods: Method A: Load the elemental metal or metal alloy in catalyst Y together with the noble metal onto a support; Method B: The oxide in the catalyst Y forms a composite support with the support, and the noble metal is loaded onto the composite support.

7. The synthesis method according to claim 1, characterized in that, The composite catalyst C is one of the following: alumina-supported platinum-magnesium, silica-supported palladium-calcium, magnesium oxide / alumina-supported palladium, potassium oxide / alumina-supported platinum, and silica-supported ruthenium-zinc; The molar ratio of p-phenylenediamine and / or 5-aminoindole to catalyst C is 1:0.005-1:0.

05.

8. The synthesis method according to claim 1, characterized in that, The solvent is selected from one or more of the following: N-methylpyrrolidone, sulfolane, ethylene carbonate, tetraethylene glycol dimethyl ether, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, and 1-ethyl-3-methylimidazolium tetrafluoroborate.

9. The synthesis method according to claim 1, characterized in that, The reaction temperature is 150-220℃, and the reaction time is 8-24 hours.

10. The synthesis method according to claim 1, characterized in that, After the reaction is complete, the catalyst is recovered by filtration, washed with ethanol, dried under vacuum, stored in nitrogen, and then recycled. If the catalyst is completely deactivated, it can be reactivated and regenerated in a hydrogen environment at 400°C or above in a muffle furnace.

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