Organic liquid hydrogen storage method and organic liquid hydrogen storage continuous production system

Abstract

The invention relates to the technical field of organic liquid hydrogen storage, and discloses an organic liquid hydrogen storage method and an organic liquid hydrogen storage continuous production system.The organic liquid hydrogen storage method comprises the steps that 1, in the presence of an alkylation catalyst, carbazole makes contact with an alkylation reagent for an alkylation reaction, and mixed hydrogen oil is obtained; wherein the alkylating reagent comprises first alkylamine and second alkylamine; the structural general formula of the first alkylamine is represented as R1nNH3-n, n is an integer selected from 1-3, and R1 is selected from C3-C6 straight-chain or branched-chain alkyl; the structural general formula of the second alkylamine is R2mNH3-m, m is an integer selected from 1-3, R2 is selected from C1-C4 linear or branched alkyl, and the number of carbon atoms of R2 is smaller than that of R1; and (2) in the presence of a hydrogenation catalyst, contacting the mixed hydrogen oil with hydrogen for hydrogenation reaction. The method can realize continuous hydrogen storage of the organic liquid, and is high in hydrogenation rate and low in energy consumption.

Description

Technical Field

[0001] The invention relates to the technical field of organic liquid hydrogen storage, and in particular to an organic liquid hydrogen storage method and an organic liquid hydrogen storage continuous production system. Background Art

[0002] Hydrogen energy resources are abundant, easy to obtain, and the only combustion product is water. In addition, its excellent characteristics such as non-polluting, transportable, high calorific value, and low fuel value are considered to be the main energy source in the future. At present, the mainstream hydrogen storage and transportation methods mainly include high-pressure gaseous hydrogen storage, low-temperature liquid hydrogen storage, solid hydrogen storage, and organic liquid hydrogen storage. In recent years, organic liquid hydrogen storage has received great attention from scientific researchers. Organic liquid hydrogen storage technology is a way to achieve hydrogen energy utilization by reacting unsaturated organic matter with hydrogen under specific conditions, and releasing hydrogen through dehydrogenation reaction in the hydrogenation stage. The core of organic liquid hydrogen storage is to find a suitable hydrogen storage medium. As countries gradually deepen their research on hydrogen energy, N-alkyl carbazole has been developed as an organic liquid hydrogen storage carrier. Commonly used ones are N-ethyl carbazole and N-propyl carbazole. However, carbazole and N-alkyl carbazole have a high freezing point and are solid at room temperature. They need to be heated and melted before hydrogenation, which is a complex process and high cost.

[0003] In order to solve the above problems, on the one hand, some additives can be added to reduce the freezing point of organic liquid hydrogen storage materials. For example, CN112028014A discloses that by adding at least one of pyrazine and its derivatives or naphthyridine and its derivatives as a low melting point thermal conductive additive, the melting point of the entire hydrogen storage material can be reduced to below 0 ° C and the hydrogen storage density is not affected. CN104555914A discloses adding a low melting point compound having a melting point lower than 80 ° C, so that the melting point of the system is as low as room temperature. However, additives are generally inconsistent with the hydrogenation and dehydrogenation temperatures of the main components of the organic liquid, thereby affecting the selection of the catalyst and causing the decomposition of a certain component. On the other hand, it is also reported that the freezing point of the system is reduced by constructing a low eutectic system. For example, CN109353987A constructs a low eutectic system by doping at least one of carbazole, N-methyl carbazole, N-ethyl carbazole, N-n-propyl carbazole, N-isopropyl carbazole or N-n-butyl carbazole, which can significantly reduce the freezing point of the entire system. However, the traditional method of preparing a eutectic system requires the separate synthesis of different hydrogen storage materials, which are then mixed and melted. In addition, the compatibility of different hydrogen storage materials is poor, and the final hydrogenation effect is not ideal. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of complex process and low hydrogen storage efficiency of organic liquid hydrogen storage in the prior art, and to provide a method for organic liquid hydrogen storage and a continuous production system for organic liquid hydrogen storage. The method can realize continuous hydrogen storage of organic liquid with high hydrogen storage efficiency.

[0005] In order to achieve the above object, the present invention provides a method for storing hydrogen in an organic liquid in a first aspect, the method comprising: (1) contacting carbazole with an alkylating agent in the presence of an alkylating catalyst to carry out an alkylation reaction to obtain a mixed hydrogen oil; wherein the alkylating agent comprises a first alkylamine and a second alkylamine; The general structural formula of the first alkylamine is: 1 n NH 3-n , wherein n is an integer selected from 1 to 3, R 1 A straight or branched chain alkyl group selected from C3-C6; The general structural formula of the second alkylamine is: 2 m NH 3-m , wherein m is an integer selected from 1 to 3, R 2 is selected from a C1-C4 straight chain or branched alkyl group, and R 2 The number of carbon atoms is less than R 1 The number of carbon atoms; (2) In the presence of a hydrogenation catalyst, the mixed hydrogen oil is contacted with hydrogen to carry out a hydrogenation reaction.

[0006] Preferably, the molar ratio of the first alkylamine to the second alkylamine is (1-10):1, preferably (2-6):1.

[0007] A second aspect of the present invention provides a continuous production system for organic liquid hydrogen storage, the system comprising: a raw material supply unit, an alkylation reaction unit and a hydrogenation reaction unit connected in sequence along a logistics direction; The raw material supply unit includes a carbazole storage tank and an alkylating agent storage tank, which are used to provide carbazole and the alkylating agent to the alkylation reaction unit; The alkylation reaction unit includes an alkylation reactor, which carries out an alkylation reaction between carbazole from the raw material supply unit and an alkylation agent; The hydrogenation reaction unit comprises a hydrogenation reactor for contacting the stream from the alkylation reaction unit with hydrogen to carry out a hydrogenation reaction; Preferably, the alkylation reaction unit further comprises a distillation tower, the feed inlet of the distillation tower is connected to the outlet of the alkylation reactor, and the bottom outlet of the distillation tower is connected to the feed inlet of the hydrogenation reaction unit.

[0008] In the prior art, the mixed N-alkyl carbazole low melting point hydrogen storage hydrogen oil needs to be produced first, then mixed and finally heated and melted, and the process operation is difficult in actual process production. Through the above technical scheme, the present invention provides an integrated continuous organic liquid hydrogen storage method, firstly, a low melting point mixed hydrogen oil is obtained by contacting a mixed alkylating agent with carbazole for alkylation reaction, and then the obtained mixed hydrogen oil is hydrogenated. The reaction process is universal, and the mixed hydrogen oil can be prepared by matching the type and content of the alkylating agent, and the continuous synthesis and storage of the mixed N-alkyl carbazole low melting point hydrogen storage hydrogen oil can be realized. By mixing the hydrogenated materials, the melting point of the overall hydrogen oil can be reduced, which is beneficial to the separation of the reaction product and the initial material, and the synergistic effect of different hydrogen oil components makes it easier to complete the hydrogenation of the reactant product, which can provide higher conversion rate and selectivity than the traditional method, which is beneficial to industrial production and reduces production energy consumption. DETAILED DESCRIPTION

[0009] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0010] A first aspect of the present invention provides a method for storing hydrogen in an organic liquid, the method comprising: (1) contacting carbazole with an alkylating agent in the presence of an alkylating catalyst to carry out an alkylation reaction to obtain a mixed hydrogen oil; wherein the alkylating agent comprises a first alkylamine and a second alkylamine; The general structural formula of the first alkylamine is: 1 n NH 3-n , wherein n is an integer selected from 1 to 3, R 1 A straight or branched chain alkyl group selected from C3-C6; The general structural formula of the second alkylamine is: 2 m NH 3-m , wherein m is an integer selected from 1 to 3, R 2 is selected from a C1-C4 straight chain or branched alkyl group, and R 2 The number of carbon atoms is less than R 1 The number of carbon atoms; (2) In the presence of a hydrogenation catalyst, the mixed hydrogen oil is contacted with hydrogen to carry out a hydrogenation reaction.

[0011] According to some preferred embodiments of the present invention, R 1 The straight or branched alkyl group selected from C3-C5 is preferably at least one of n-propyl, isopropyl, n-butyl, isobutyl, pentyl and isopentyl. The corresponding first alkylamine is, for example, propylamine, butylamine, pentylamine, or the corresponding dialkylamine, trialkylamine, etc., which may include various isomers. Preferably, the first alkylamine is a normal alkylamine, for example, n-propylamine, n-butylamine, n-pentylamine or at least one of the dialkylamines and trialkylamines corresponding to the above substances. It is understood that, for example, the dialkylamine corresponding to n-propylamine is dipropylamine.

[0012] According to some preferred embodiments of the present invention, R 2 The straight or branched alkyl group selected from C2-C3 is preferably at least one of ethyl, n-propyl and isopropyl. The corresponding second alkylamine is, for example, ethylamine, diethylamine, triethylamine, propylamine, or the isomers of the above substances.

[0013] According to some preferred embodiments of the present invention, R 2 The number of carbon atoms and R 1 The difference in the number of carbon atoms is 1-3, for example, the difference can be any one of 1, 2, and 3.

[0014] According to some preferred embodiments of the present invention, the molar ratio of the first alkylamine to the second alkylamine is (1-10):1, preferably (2-6):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, etc., which are specific but not limiting molar ratios, or any range between the two. The above preferred embodiments are adopted to facilitate the forward progress of the alkylation reaction, obtain a mixed hydrogen oil with more stable properties at room temperature, and further improve the hydrogen storage efficiency.

[0015] According to some preferred embodiments of the present invention, the molar ratio of the alkylating agent to carbazole is 10-20:1, preferably 14-17:1, preferably 14:1, 15:1, 16:1, 17:1 and other specific but non-limiting molar ratios or any range between the two. The above preferred embodiments are advantageous for generating mixed hydrogen oil with a higher freezing point, and hydrogen can be stored and transported at a lower temperature.

[0016] The present invention has a wide selection range for the alkylation catalyst, as long as it can catalyze the alkylation transfer process between the alkylation agent and the carbazole. Preferably, the alkylation catalyst comprises a carrier, and an active metal component supported on the carrier, and the active metal component is selected from at least one of the metal elements of Group VIII and Group IB, and can be a noble metal or a non-noble metal.

[0017] According to some preferred embodiments of the present invention, the active metal component is selected from at least one of Ni, Fe, Co and Cu. Preferably, based on the total amount of the catalyst, the content of the active metal component in terms of element is 15-70wt%, preferably 15-25wt%, and the content of the carrier is 30-85wt%, preferably 75-85wt%.

[0018] According to some other preferred embodiments of the present invention, the active metal component is selected from at least one of Ir, Pt and Pd. Preferably, based on the total amount of the catalyst, the content of the active metal component in terms of element is 0.1-15wt%, preferably 0.1-10wt%; the content of the carrier is 85-99.9wt%, preferably 90-99.9wt%.

[0019] The present invention has a wide range of choices for the carrier in the alkylation catalyst, and conventional catalyst carriers in the art can be applied to the present invention. Preferably, the carrier is at least one of activated carbon, an oxide carrier and a molecular sieve.

[0020] According to some preferred embodiments of the present invention, the oxide support is selected from a single-component oxide support and / or a dual-component oxide support; the single-component oxide support is selected from at least one of Al2O3, CeO2, La2O3, MgO, SiO2, ZrO2, TiO2 and ZnO; more preferably at least one of Al2O3, ZrO2 and SiO2. The dual-component oxide support is selected from at least one of ZrO2-Al2O3, MgO-ZrO2, ZrO2-SiO2, ZnO-ZrO2, CeO2-ZrO2, SiO2-Al2O3, preferably at least one of ZrO2-Al2O3, SiO2-Al2O3 and ZrO2-SiO2.

[0021] The present invention has no particular limitation on the source of the catalyst, and the catalyst can be prepared by conventional methods in the art, such as impregnation method, precipitation method, sol-gel method, etc., which are well known to those skilled in the art.

[0022] In the present invention, the alkylation reaction in step (1) can be carried out without introducing an additional solvent, and the alkylation agent can simultaneously act as an alkylation agent and a solvent, thereby eliminating the need to use additional solvents, which is beneficial for further reducing the generation of organic waste liquid, further reducing environmental pollution, and reducing the difficulty of post-processing.

[0023] According to some preferred embodiments of the present invention, the contacting in step (1) is carried out in the presence of an organic solvent, and the boiling point of the organic solvent is not higher than 80° C. Preferably, the organic solvent is selected from at least one of acetonitrile, dichloroethane and ethyl acetate. In the above preferred case, it is conducive to the alkylation reaction to proceed in the forward direction.

[0024] Preferably, the molar ratio of the organic solvent to carbazole is (1-15):1, preferably (2-7):1.

[0025] According to some preferred embodiments of the present invention, the conditions of the alkylation reaction in step (1) include: a reaction temperature of 250-450°C, preferably 300-400°C; a reaction pressure of 3-10 MPa, preferably 5-8 MPa, and a liquid hourly space velocity of carbazole of 0.3-1.5 h -1 , preferably 0.7-1h -1 .

[0026] In the present invention, the product obtained by the alkylation reaction can be directly subjected to the hydrogenation reaction described in step (2), or can be optionally purified before the hydrogenation reaction. Those skilled in the art can make the selection according to actual needs.

[0027] According to some preferred embodiments of the present invention, the method further comprises: distilling the product obtained by the alkylation reaction to obtain the mixed hydrogen oil. The present invention has no particular limitation on the conditions of the distillation, as long as the low-boiling byproducts and unreacted raw materials in the product obtained by the alkylation reaction can be removed.

[0028] The present invention has no particular limitation on the hydrogenation catalyst used in step (2), and any conventional catalyst in the art capable of catalyzing the hydrogenation of alkyl-substituted carbazole can be applied to the present invention. Preferably, the hydrogenation catalyst comprises a carrier and a hydrogenation active metal component.

[0029] Preferably, the hydrogenation active metal component is selected from at least one of Co, Pt, Pd, Cu, Ru and Ni.

[0030] Preferably, based on the total amount of the hydrogenation catalyst, the carrier content is 60-99.9wt%, preferably 70-99.5wt%; the content of the hydrogenation active metal component in terms of element is 0.1-40wt%, preferably 0.5-30wt%.

[0031] According to the present invention, preferably, the conditions of the hydrogenation reaction include: a reaction temperature of 75-175°C, preferably 80-120°C; a reaction pressure of 2-7MPa, preferably 2.5-4.5MPa; a liquid hourly space velocity of the mixed hydrogen oil of 0.2-1.5h -1 , preferably 0.2-0.7h-1 ; The hydrogen-to-oil ratio is (2-15):1, preferably (4-8):1.

[0032] A second aspect of the present invention provides a continuous production system for organic liquid hydrogen storage, the system comprising: a raw material supply unit, an alkylation reaction unit and a hydrogenation reaction unit connected in sequence along a logistics direction; The raw material supply unit includes a carbazole storage tank and an alkylating agent storage tank, which are used to provide carbazole and the alkylating agent to the alkylation reaction unit; The alkylation reaction unit includes an alkylation reactor, which carries out an alkylation reaction between carbazole from the raw material supply unit and an alkylation agent; The hydrogenation reaction unit comprises a hydrogenation reactor, which is used for contacting the stream from the alkylation reaction unit with hydrogen to carry out a hydrogenation reaction.

[0033] In the present invention, the alkylation reactor may be any reactor in the art. Preferably, the alkylation reactor is a fixed bed reactor.

[0034] Preferably, the alkylation reaction unit further comprises a distillation tower, the feed inlet of the distillation tower is connected to the outlet of the alkylation reactor, and the bottom outlet of the distillation tower is connected to the feed inlet of the hydrogenation reaction unit.

[0035] The present invention will be described in detail below through examples.

[0036] The alkylation catalyst used in the following examples is a 0.5 wt % Pd / C catalyst, denoted as Hywin-2024-1#.

[0037] The hydrogenation catalyst used in the following examples and comparative examples is a 0.5 wt% Ni / Al2O3 catalyst, denoted as Hywin-2024-0#.

[0038] Example 1 (1) A mixed solution of triethylamine and n-propylamine (molar ratio of 1:3) was selected as an alkylating agent, and acetonitrile was selected as a reaction solvent to carry out an N-alkylation reaction with carbazole, wherein the molar ratio of the mixed solution of triethylamine and n-propylamine to carbazole was 15:1, and the molar ratio of acetonitrile to carbazole was 15:1.

[0039] 10 mL of Hywin-2024-1# catalyst was loaded into the fixed bed reactor, and then the prepared raw materials were pumped into the reactor from the top with a liquid hourly space velocity of 0.9 h -1 , the reaction temperature was set to 300 °C, and the reaction pressure was set to 6 MPa.

[0040] After 2 hours of reaction, the sample was taken out of the gas-liquid separator after condensation to 60°C from the bottom of the fixed bed, dissolved in N-methylpyrrolidone (NMP) and analyzed by gas chromatography. The GC-MS graph shows that the target products N-ethylcarbazole and N-propylcarbazole were obtained. According to the area normalization method, the conversion rate of carbazole was 99.21 mol%, the selectivity of N-ethylcarbazole and N-propylcarbazole was 99.51 mol% (the molar ratio of N-ethylcarbazole to N-propylcarbazole was 1.4:1), and the by-products were mainly 3-ethylcarbazole and 3-propylcarbazole. After the reaction, the mixture was simply distilled to distill off the low-boiling alkyl alkane and solvent to obtain a liquid mixed hydrogen oil.

[0041] (2) The liquid mixed hydrogen oil obtained above was sent to a fixed bed reactor for hydrogenation reaction. The fixed bed reactor was filled with 10 mL of Hywin-2024-0# catalyst. The liquid hourly space velocity was 0.4 h -1 , the reaction temperature is 250 ℃, the reaction pressure is 3MPa, and the hydrogen-to-oil ratio is 4:1. After 6 hours of reaction, the product composition is tested by gas chromatography, and the hydrogenation efficiency of the mixed hydrogen-to-oil is calculated by calculating the content of the product after hydrogenation of the mixed hydrogen-to-oil. The results are shown in Table 1.

[0042] In Table 1, the conversion rate, selectivity and hydrogenation rate are the average values ​​of different hydrogen oils in the mixed hydrogen oil. The calculation formulas for the conversion rate, selectivity and hydrogenation rate of a single hydrogen oil are as follows: Conversion rate (%) = ×100%; Selectivity (%) = ×100%; Hydrogenation rate (%) = ; Where A0 is the chromatographic peak area of ​​carbazole, A2 is the chromatographic peak area of ​​the target N-alkylcarbazole, A3 is the total chromatographic peak area of ​​other by-products except NEC, and A4 is the chromatographic peak area of ​​the specific N-alkylcarbazole after 12H hydrogenation.

[0043] Example 2 (1) A mixed solution of triethylamine and n-butylamine (molar ratio of 1:2) was selected as an alkylating agent, and acetonitrile was selected as a reaction solvent to carry out an N-alkylation reaction with carbazole, wherein the molar ratio of the mixed solution of triethylamine and n-butylamine to carbazole was 16:1, and the molar ratio of acetonitrile to carbazole was 12:1.

[0044] 10 mL of Hywin-2024-1# catalyst was loaded into the fixed bed reactor, and then the prepared raw materials were pumped into the reactor from the top with a liquid hourly space velocity of 1.2 h -1 , the reaction temperature was set at 320 °C, and the reaction pressure was set at 5 MPa.

[0045] After 2 hours of reaction, the sample was taken out from the bottom of the fixed bed after condensation to 60°C, and then dissolved in N-methylpyrrolidone (NMP) and analyzed by gas chromatography. The GC-MS graph shows that the target products N-ethylcarbazole and N-butylcarbazole were obtained. According to the area normalization method, the conversion rate of carbazole was 99.12 mol%, the selectivity of N-ethylcarbazole and N-butylcarbazole was 99.42 mol% (the molar ratio of N-ethylcarbazole to N-butylcarbazole was 0.6:1), and the by-products were mainly 3-ethylcarbazole and 3-butylcarbazole. After the reaction, the mixture was simply distilled to distill off the low-boiling alkyl alkane to obtain a liquid mixed hydrogen oil.

[0046] (2) A hydrogenation reaction was carried out according to the method of Example 1. The results are shown in Table 1.

[0047] Example 3 (1) A mixed solution of triethylamine and n-pentylamine (molar ratio of 1:3) was selected as an alkylating agent, and acetonitrile was selected as a reaction solvent to carry out an N-alkylation reaction with carbazole, wherein the molar ratio of the mixed solution of triethylamine and n-pentylamine to carbazole was 25:1, and the molar ratio of acetonitrile to carbazole was 10:1.

[0048] 10 mL of Hywin-2024-1# catalyst was loaded into the fixed bed reactor, and then the prepared raw materials were pumped into the reactor from the top with a liquid hourly space velocity of 0.5 h -1 , the reaction temperature was set at 350 °C, and the reaction pressure was set at 5 MPa.

[0049] After 2 hours of reaction, the sample was taken out of the gas-liquid separator after condensation from the bottom of the fixed bed to 60°C, dissolved in N-methylpyrrolidone (NMP) and analyzed by gas chromatography. The GC-MS graph shows that the target products N-ethylcarbazole and N-pentylcarbazole were obtained. According to the area normalization method, the conversion rate of carbazole was 99.22 mol%, the selectivity of N-ethylcarbazole and N-pentylcarbazole was 99.25 mol% (the molar ratio of N-ethylcarbazole to N-pentylcarbazole was 1.1:1), and the by-products were mainly 3-ethylcarbazole and 3-pentylcarbazole. After the reaction, the mixture was simply distilled to distill off the low-boiling alkyl alkane to obtain a liquid mixed hydrogen oil.

[0050] (2) A hydrogenation reaction was carried out according to the method of Example 1. The results are shown in Table 1.

[0051] Example 4 (1) A mixed solution of n-propylamine and n-butylamine (molar ratio of 1:1) was selected as an alkylating agent, and acetonitrile was selected as a reaction solvent to carry out an N-alkylation reaction with carbazole, wherein the molar ratio of the mixed solution of triethylamine and n-pentylamine to carbazole was 20:1, and the molar ratio of acetonitrile to carbazole was 8:1.

[0052] 10 mL of Hywin-2024-1# catalyst was loaded into the fixed bed reactor, and then the prepared raw materials were pumped into the reactor from the top with a liquid hourly space velocity of 0.5 h -1 , the reaction temperature was set to 300 °C, and the reaction pressure was set to 8 MPa.

[0053] After 2 hours of reaction, the sample was taken out from the bottom of the fixed bed after condensation to 60°C, and then dissolved in N-methylpyrrolidone (NMP) and analyzed by gas chromatography. The GC-MS graph shows that the target products N-propyl carbazole and N-butyl carbazole were obtained. According to the area normalization method, the conversion rate of carbazole was 99.1 mol%, and the selectivity of N-propyl carbazole and N-butyl carbazole was 99.12 mol% (the molar ratio of N-propyl carbazole to N-butyl carbazole was 1.3:1). The by-products were mainly 3-propyl carbazole and 3-butyl carbazole. After the reaction, the mixture was simply distilled to distill off the low-boiling alkyl alkane to obtain a liquid mixed hydrogen oil.

[0054] (2) A hydrogenation reaction was carried out according to the method of Example 1. The results are shown in Table 1.

[0055] Example 5 (1) A mixed solution of n-propylamine and n-pentylamine (molar ratio 1:2) was selected as an alkylating agent, and acetonitrile was selected as a reaction solvent to carry out an N-alkylation reaction with carbazole, wherein the molar ratio of the mixed solution of tripropylamine and n-pentylamine to carbazole was 15:1, and the molar ratio of acetonitrile to carbazole was 5:1.

[0056] 10 mL of Hywin-2024-1# catalyst was loaded into the fixed bed reactor, and then the prepared raw materials were pumped into the reactor from the top with a liquid hourly space velocity of 0.4 h -1 , the reaction temperature was set at 350 °C, and the reaction pressure was set at 7 MPa.

[0057] After 2 hours of reaction, the sample was taken out from the gas-liquid separator after condensation to 60°C from the bottom of the fixed bed, dissolved in N-methylpyrrolidone (NMP) and analyzed by gas chromatography. The GC-MS graph shows that the target products N-propylcarbazole and N-pentylcarbazole were obtained. According to the area normalization method, the conversion rate of carbazole was 99 mol%, and the selectivity of N-propylcarbazole and N-pentylcarbazole was 99.01 mol% (the molar ratio of N-propylcarbazole to N-pentylcarbazole was 1.4:1), and the by-products were mainly 3-propylcarbazole and 3-pentylcarbazole. After the reaction, the mixture was simply distilled to distill off the low-boiling alkyl alkane to obtain a liquid mixed hydrogen oil.

[0058] (2) A hydrogenation reaction was carried out according to the method of Example 1. The results are shown in Table 1.

[0059] Example 6 (1) A mixed solution of n-butylamine and n-pentylamine (molar ratio 1:3) was selected as an alkylating agent, and acetonitrile was selected as a reaction solvent to carry out an N-alkylation reaction with carbazole, wherein the molar ratio of the mixed solution of tripropylamine and n-pentylamine to carbazole was 20:1, and the molar ratio of acetonitrile to carbazole was 3:1.

[0060] 10 mL of Hywin-2024-1# catalyst was loaded into the fixed bed reactor, and then the prepared raw materials were pumped into the reactor from the top with a liquid hourly space velocity of 0.3 h -1 , the reaction temperature was set at 350 °C, and the reaction pressure was set at 7 MPa.

[0061] After 2 hours of reaction, the sample was taken out from the bottom of the fixed bed and condensed to 60°C. The sample was then dissolved in N-methylpyrrolidone (NMP) and analyzed by gas chromatography. The GC-MS graph shows that the target products N-butyl carbazole and N-pentyl carbazole were obtained. According to the area normalization method, the conversion rate of carbazole was 98.87 mol%, and the selectivity of N-propyl carbazole and N-butyl carbazole was 98.21 mol% (the molar ratio of N-ethyl carbazole to N-pentyl carbazole was 1:1.2). The by-products were mainly 3-butyl carbazole and 3-pentyl carbazole. After the reaction, the mixture was simply distilled to distill off the low-boiling alkyl alkane to obtain a liquid mixed hydrogen oil.

[0062] (2) A hydrogenation reaction was carried out according to the method of Example 1. The results are shown in Table 1.

[0063] Example 7 The method of Example 1 is followed, except that acetonitrile is not added in the alkylation reaction in step (1).

[0064] After 2 hours of reaction, the sample was taken out from the gas-liquid separator after condensation to 60°C from the bottom of the fixed bed, dissolved in N-methylpyrrolidone (NMP) and analyzed by gas chromatography. The GC-MS graph shows that the target products N-ethylcarbazole and N-propylcarbazole were obtained. According to the area normalization method, the conversion rate of carbazole was 99.6 mol%, and the selectivity of N-ethylcarbazole and N-propylcarbazole was 98.89 mol% (the molar ratio of N-ethylcarbazole to N-propylcarbazole was 1.2:1). After the reaction, the mixture was simply distilled to distill off the low-boiling alkyl alkane and solvent to obtain a liquid mixed hydrogen oil.

[0065] The hydrogenation reaction was carried out according to the method of Example 1. The results are shown in Table 1.

[0066] Example 8 The method of Example 1 is followed, except that the molar ratio of triethylamine to n-propylamine is 1:7.

[0067] After 2 hours of reaction, the sample was taken out from the bottom of the fixed bed after condensation to 60°C, and then dissolved in N-methylpyrrolidone (NMP) and analyzed by gas chromatography. The GC-MS graph shows that the target products N-ethylcarbazole and N-propylcarbazole were obtained. According to the area normalization method, the conversion rate of carbazole was 97.76 mol%, and the selectivity of N-ethylcarbazole and N-propylcarbazole was 89.57 mol% (the molar ratio of N-ethylcarbazole to N-propylcarbazole was 0.2:1). After the reaction, the mixture was simply distilled to distill off the low-boiling alkyl alkane and solvent to obtain a liquid mixed hydrogen oil.

[0068] The hydrogenation reaction was carried out according to the method of Example 1. The results are shown in Table 1.

[0069] Comparative Example 1 According to the existing implementation method, the production of N-alkyl carbazole low melting point hydrogen storage hydrogen oil requires the production of N-ethyl carbazole and N-propyl carbazole first.

[0070] 10 mL of catalyst was loaded into the fixed bed reactor, and then the prepared raw materials (i.e., a mixture of carbazole and ethyl bromide, with a molar ratio of 1:5) were pumped into the reactor from the top with a liquid hourly space velocity of 0.6 h -1 , the reaction temperature was set at 240 °C, and the reaction pressure was set at 6 MPa. After 4 h of reaction, the sample was taken out from the bottom of the fixed bed and condensed to 60 °C. The sample was dissolved in N-methylpyrrolidone (NMP) and analyzed by gas chromatography. As shown in the GC-MS graph, the target product N-ethylcarbazole was obtained with a purity of 99%.

[0071] To produce N-propylcarbazole, 10 mL of catalyst was loaded into a fixed bed reactor, and then the prepared raw materials (i.e., a mixture of carbazole and bromopropane, with a molar ratio of 1:5) were introduced from the top of the reactor through a metering pump at a liquid hourly space velocity of 0.6 h -1 , the reaction temperature was set at 240 °C, and the reaction pressure was set at 6 MPa. After 4 h of reaction, the sample was taken out from the bottom of the fixed bed and condensed to 60 °C. The sample was dissolved in N-methylpyrrolidone (NMP) and analyzed by gas chromatography. The GC-MS graph showed that the target product N-propylcarbazole was obtained with a purity of 99%.

[0072] The obtained N-ethylcarbazole and N-propylcarbazole were mixed in a molar ratio of 0.2:1 to obtain mixed carbazole-0, and the obtained carbazole-0 was put into a melt heating reactor and heated to 100°C to obtain mixed N-alkyl carbazole low melting point hydrogen storage oil.

[0073] The hydrogenation reaction was carried out according to the method of Example 1. The results are shown in Table 1.

[0074] Comparative Example 2 N-ethylcarbazole was used as a hydrogen storage carrier for hydrogenation reaction, N-ethylcarbazole was put into a preheater for melting, the preheater was heated to 250 ° C, and the preheated liquid hydrogen oil was sent to a fixed bed reactor for hydrogenation reaction, and 10 mL of Hywin-2024-1# catalyst was loaded in the fixed bed reactor. The hydrogenation reaction was carried out in the manner of Example 1, the product composition was tested by gas chromatography, and the hydrogenation rate of N-ethylcarbazole was calculated, and the results are shown in Table 1.

[0075] Table 1

[0076] By comparing the above examples and comparative examples, it can be seen that the method for storing hydrogen in an organic liquid provided by the embodiments of the present invention can improve the hydrogenation efficiency. The present invention can reduce the melting point of the overall hydrogen oil by mixing the hydrogenation materials, which is beneficial to the separation of the reaction product and the initial material, and through the synergistic effect of different hydrogen oil components, the reactant products are easier to complete hydrogenation, which can provide higher conversion rate and selectivity than traditional methods.

[0077] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for storing hydrogen in an organic liquid, characterized in that: The method comprises: (1) contacting carbazole with an alkylating agent in the presence of an alkylating catalyst to carry out an alkylation reaction to obtain a mixed hydrogen oil; wherein the alkylating agent comprises a first alkylamine and a second alkylamine; The general structural formula of the first alkylamine is: 1 n NH 3-n , wherein n is an integer selected from 1 to 3, R 1 A straight or branched chain alkyl group selected from C3-C6; The general structural formula of the second alkylamine is: 2 m NH 3-m , wherein m is an integer selected from 1 to 3, R 2 is selected from a C1-C4 straight chain or branched alkyl group, and R 2 The number of carbon atoms is less than R 1 The number of carbon atoms; (2) In the presence of a hydrogenation catalyst, the mixed hydrogen oil is contacted with hydrogen to carry out a hydrogenation reaction.

2. The method according to claim 1, wherein: R 1 A straight or branched chain alkyl group selected from C3-C5, preferably at least one of n-propyl, isopropyl, n-butyl, isobutyl, pentyl and isopentyl; and / or, R 2 A straight or branched chain alkyl group selected from C2-C3, preferably at least one of ethyl, n-propyl and isopropyl; and / or, R 2 The number of carbon atoms and R 1 The difference in the number of carbon atoms is 1-3.

3. The method according to claim 1 or 2, wherein: The molar ratio of the first alkylamine to the second alkylamine is (1-10):1, preferably (2-6):1; Preferably, the molar ratio of the alkylating agent to carbazole is 10-20:1, preferably 14-17:

1.

4. The method according to any one of claims 1 to 3, wherein: The alkylation catalyst comprises a carrier, and an active metal component supported on the carrier, wherein the active metal component is selected from at least one of Group VIII and Group IB metal elements; Preferably, the active metal component is selected from at least one of Ni, Fe, Co and Cu; wherein, based on the total amount of the catalyst, the content of the active metal component in terms of element is 15-70wt%, and the content of the carrier is 30-85wt%; Preferably, the active metal component is selected from at least one of Ir, Pt and Pd; wherein, based on the total amount of the catalyst, the content of the active metal component in terms of element is 0.1-15wt%, and the content of the carrier is 85-99.9wt%; Preferably, the carrier is at least one of activated carbon, an oxide carrier and a molecular sieve.

5. The method according to any one of claims 1 to 4, wherein: The contacting in step (1) is carried out in the presence of an organic solvent, wherein the boiling point of the organic solvent is not higher than 80° C.; Preferably, the organic solvent is selected from at least one of acetonitrile, dichloroethane and ethyl acetate; Preferably, the molar ratio of the organic solvent to carbazole is (1-15):1, preferably (2-7):

1.

6. The method according to any one of claims 1 to 5, wherein: The conditions of the alkylation reaction in step (1) include: a reaction temperature of 250-450°C, preferably 300-400°C; a reaction pressure of 3-10 MPa, preferably 5-8 MPa; a liquid hourly space velocity of carbazole of 0.3-1.5 h -1 , preferably 0.7-1h -1 .

7. The method according to any one of claims 1 to 6, wherein: The method further comprises: distilling the product obtained from the alkylation reaction to obtain the mixed hydrogen oil.

8. The method according to any one of claims 1 to 7, wherein: The hydrogenation catalyst comprises a carrier and a hydrogenation active metal component; Preferably, the hydrogenation active metal component is selected from at least one of Co, Pt, Pd, Cu, Ru and Ni; Preferably, based on the total amount of the hydrogenation catalyst, the content of the carrier is 60-99.9 wt %, and the content of the hydrogenation active metal component in terms of element is 0.1-40 wt %.

9. The method according to any one of claims 1 to 8, wherein: The conditions of the hydrogenation reaction include: a reaction temperature of 75-175°C, preferably 80-120°C; a reaction pressure of 2-7MPa, preferably 2.5-4.5MPa; a liquid hourly space velocity of the mixed hydrogen oil of 0.2-1.5h -1 , preferably 0.2-0.7h -1 ; The hydrogen-to-oil ratio is (2-15):1, preferably (4-8):

1.

10. An organic liquid hydrogen storage continuous production system, the system comprising: The raw material supply unit, the alkylation reaction unit and the hydrogenation reaction unit are sequentially connected along the logistics direction; The raw material supply unit includes a carbazole storage tank and an alkylating agent storage tank, which are used to provide carbazole and the alkylating agent to the alkylation reaction unit; The alkylation reaction unit includes an alkylation reactor, which carries out an alkylation reaction between carbazole from the raw material supply unit and an alkylation agent; The hydrogenation reaction unit comprises a hydrogenation reactor for contacting the stream from the alkylation reaction unit with hydrogen to carry out a hydrogenation reaction; Preferably, the alkylation reaction unit further comprises a distillation tower, the feed inlet of the distillation tower is connected to the outlet of the alkylation reactor, and the bottom outlet of the distillation tower is connected to the feed inlet of the hydrogenation reaction unit.

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