12 Method for the synthesis of 12h-n-alkylcarbazoles and use of the products obtained by the synthesis method in the field of organic liquid dehydrogenation

Abstract

The application relates to the field of synthesis of 12H-N-alkylcarbazole, and discloses a synthesis method of 12H-N-alkylcarbazole and application of a product prepared by the synthesis method in the field of organic liquid dehydrogenation. The method comprises the following steps: reacting N-alkylaniline and 1,2-cyclohexanediol in the presence of a first catalyst to obtain a product containing 6H-N-alkylcarbazole; the first catalyst comprises a first carrier, a first active component and an auxiliary component, and the first active component is Pd; and the product containing 6H-N-alkylcarbazole is subjected to hydrogenation reaction in contact with a second catalyst under a hydrogen atmosphere to obtain 12H-N-alkylcarbazole; the second catalyst comprises a second carrier and a second active component, and the second active component is at least one of Pd, Pt, Rh, Ir and Ni. The synthesis method has the characteristics of simple steps and high yield of 12H-N-alkylcarbazole.

Description

Technical Field

[0001] This invention relates to the field of synthesis of 12H-N-alkylcarbazole, and more specifically to a method for synthesizing 12H-N-alkylcarbazole and the application of the product obtained by the synthesis method in the field of organic liquid dehydrogenation. Background Technology

[0002] Carbazole and its derivatives are an important class of nitrogen-containing heterocyclic compounds. Due to their unique electronic structure and optical properties, they have wide applications in organic optoelectronic materials (such as OLED light-emitting layers), pharmaceutical intermediates (such as anticancer drug carriers), and high-performance polymers (such as heat-resistant materials). Among them, 12H-N-alkylcarbazole is considered an ideal precursor for preparing high-purity optoelectronic materials due to its specific degree of hydrogenation and the solubility regulation ability conferred by the alkyl substituent. In addition, taking N-methylcarbazole as an example, hydrogenated N-methylcarbazole can achieve a hydrogen storage density of over 6.21 wt%, showing great potential in the field of organic hydrogen storage materials.

[0003] The traditional synthesis of dodecahydroN-alkylcarbazole involves alkylation followed by hydrogenation of carbazole, a route widely used in many organic liquid hydrogen storage studies. Currently, the main production method for carbazole is extraction from coal tar, especially the anthracene oil fraction of high-temperature coal tar, which often results in impurities such as naphthalene and anthracene in the product. Carbazole further reacts with alkylating agents to generate N-alkylcarbazole. Taking N-methylcarbazole as an example, the current mainstream process uses carbazole with halomethanes (such as iodomethane) or dimethyl sulfate as methylating agents, undergoing a nucleophilic substitution reaction catalyzed by strong bases (such as NaOH or KOH). This method has significant problems: iodomethane is expensive, volatile, and highly toxic; dimethyl sulfate is a strong carcinogen; and the reaction produces halide or sulfate byproducts, which is highly inconsistent with green chemistry requirements.

[0004] Sukata Kazuaki (Bulletin of the Chemical Society of Japan. 1983;56(1):280-284), Zhang Jun (Bioorganic & Medicinal Chemistry Letters. 2012;22(1):343-346), and Wu T.Y. (Journal of the Iranian Chemical Society. 2010;7(3):707-720) et al. disclosed the preparation of N by reacting haloalkanes with carbazole. Ethylcarbazole, however, these methods require the use of alkaline reagents (such as NaOH) to neutralize halogen byproducts, generating a large amount of waste salt, requiring large amounts of water for washing, posing environmental problems, and the products are prone to residual halogen elements.

[0005] N-alkylcarbazole is further hydrogenated in the presence of a hydrogenation catalyst to prepare 12H-N-alkylcarbazole. As can be seen from the above route, the product has a high content of impurities during the extraction of carbazole and the synthesis of N-alkylcarbazole, and the product is prone to residual halogens. This has a significant impact on the organic liquid hydrogen storage and dehydrogenation catalyst, and the route is also costly and does not conform to green chemistry.

[0006] Therefore, although the traditional synthetic route of dodecahydro-N-alkylcarbazole is widely used, the synthesis of N-alkylcarbazole is costly, which limits the scope of research on N-alkylcarbazole hydrogen storage carriers. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of cumbersome steps, harsh conditions, numerous byproducts, and low yield in the synthesis route of 12H-N-alkylcarbazole in the prior art. This invention provides a method for synthesizing 12H-N-alkylcarbazole and the application of the product obtained by the synthesis method in the field of organic liquid dehydrogenation. The synthesis method is characterized by simple steps and high yield of 12H-N-alkylcarbazole.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for synthesizing 12H-N-alkylcarbazole, the method comprising:

[0009] (1) In the presence of a first catalyst, N-alkylaniline was reacted with 1,2-cyclohexanediol to obtain a product containing 6H-N-alkylcarbazole;

[0010] The first catalyst includes a first support, a first active component, and an auxiliary component, wherein the auxiliary component includes at least one of Cu, Zn, Ni, La, Co, and Ce, and the first active component is Pd;

[0011] The yield of 6H-N-alkylcarbazole in the product containing 6H-N-alkylcarbazole is ≥70%;

[0012] (2) Under a hydrogen atmosphere, the product containing 6H-N-alkylcarbazole is contacted with a second catalyst to carry out a hydrogenation reaction to obtain 12H-N-alkylcarbazole;

[0013] The second catalyst includes a second support and a second active component, wherein the second active component is at least one of Pd, Pt, Rh, Ir and Ni.

[0014] The second aspect of this invention provides the application of the product obtained by the synthesis method described in the first aspect in the field of organic liquid dehydrogenation.

[0015] Through the above technical solution, this invention adopts a palladium-based and auxiliary component dual-catalytic stepwise system. N-alkylaniline that has not fully reacted under the action of the first catalyst will continue to react under the action of the second catalyst to generate 6H-N-alkylaniline, which will then react with 1,2-cyclohexanediol to obtain 12H-N-alkylcarbazole. This achieves the direct and efficient synthesis of 12H-N-alkylcarbazole from N-alkylaniline. The reaction conditions are mild, the product does not contain halogens, and the yield is high, with a significant improvement in production efficiency. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] In this invention, unless otherwise specified, "first" and "second" do not indicate a sequence or limit the specific materials or steps; they are merely used to distinguish that these are not the same material or step. For example, in "first active component" and "second active component," "first" and "second" are used only to indicate that these are not the same active component; similarly, in "first carrier" and "second carrier," "first" and "second" are used only to indicate that these are not the same carrier.

[0018] The first aspect of this invention provides a method for synthesizing 12H-N-alkylcarbazole, the method comprising:

[0019] (1) In the presence of a first catalyst, N-alkylaniline was reacted with 1,2-cyclohexanediol to obtain a product containing 6H-N-alkylcarbazole;

[0020] The first catalyst includes a first support, a first active component, and an auxiliary component, wherein the auxiliary component includes at least one of Cu, Zn, Ni, La, Co, and Ce, and the first active component is Pd;

[0021] The yield of 6H-N-alkylcarbazole in the product containing 6H-N-alkylcarbazole is ≥70%;

[0022] (2) Under a hydrogen atmosphere, the product containing 6H-N-alkylcarbazole is contacted with a second catalyst to carry out a hydrogenation reaction to obtain 12H-N-alkylcarbazole;

[0023] The second catalyst includes a second support and a second active component, wherein the second active component is at least one of Pd, Pt, Rh, Ir and Ni.

[0024] In existing technologies, the synthetic route for 12H-N-alkylcarbazole generally tends to retain residual halogen elements. Taking the popular research product 12H-N-ethylcarbazole as an example, the synthetic route involves the halogenation reaction of carbazole with chloroethane or bromoethane to generate the intermediate N-ethylcarbazole; the second step is the synthesis of 12H-N-ethylcarbazole from N-ethylcarbazole under the action of a hydrogenation catalyst. Carbazole is extracted from coal tar, resulting in a high impurity content. The use of halogenated alkanes leads to a high halogen content in N-ethylcarbazole, which poisons the subsequent hydrogenation catalyst. Furthermore, the purification process required for the intermediate N-ethylcarbazole results in its high price.

[0025] Therefore, the inventors of this invention have creatively discovered a method for synthesizing 6H-N-alkylcarbazole with a carbazole ring structure using N-alkylaniline and 1,2-cyclohexanediol as raw materials, followed by hydrogenation to obtain 12H-N-alkylcarbazole. The reaction process is shown in Formulas I and II.

[0026] Formula I,

[0027] Formula II;

[0028] During hydrogenation, unreacted feedstocks can undergo a secondary reaction under a second catalyst, as shown in Formulas III and IV.

[0029] Formula III,

[0030] Formula IV.

[0031] It should be noted that R in Formula I, Formula II, Formula III and Formula IV all represent alkyl groups as described above in this invention.

[0032] The method proposed in this invention not only has a high raw material utilization rate, but also a high yield of 12H-N-alkylcarbazole, and does not produce halogens, poison the catalyst, or have a low cost.

[0033] The present invention also includes a protective atmosphere in step (1). The present invention has a wide range of choices for the type of protective atmosphere, for example, it can be nitrogen and / or an inert gas.

[0034] In this invention, the yield of 6H-N-alkylcarbazole was obtained by gas chromatography. Based on 1,2-cyclohexanediol, the yield of 6H-N-alkylcarbazole = .

[0035] According to the present invention, preferably, the content of the first support is 93-98.5 wt%, more preferably 93-97 wt%, based on the total mass of the first catalyst.

[0036] According to the present invention, preferably, based on the total mass of the first catalyst and calculated by metal elements, the content of the first active component is 0.5-5 wt%, more preferably 1-4 wt%.

[0037] According to the present invention, preferably, the content of the auxiliary component is 1-10 wt%, more preferably 2.5-8 wt%, based on the total mass of the first catalyst and calculated by metal elements.

[0038] In this invention, the composition of the first catalyst is within the above-mentioned preferred range, which can improve the yield of 6H-N-alkylcarbazole, thereby further improving the yield of 12H-N-alkylcarbazole.

[0039] According to the present invention, preferably, the auxiliary component is selected from at least one of Cu, Ni, La and Ce.

[0040] According to the present invention, preferably, the first carrier is selected from at least one of alumina, silica, magnesium aluminum hydrotalcite and zeolite molecular sieve.

[0041] According to a preferred embodiment of the present invention, the zeolite molecular sieve comprises HZSM-5.

[0042] According to the present invention, preferably, the molar ratio of N-alkylaniline to 1,2-cyclohexanediol is 1-8:1, more preferably 3-6:1.

[0043] According to the present invention, preferably, the alkyl group in N-alkylaniline is selected from C1-C8 alkyl groups.

[0044] The present invention has a wide range of choices for alkyl groups. The alkyl group can be a straight-chain alkyl group or an isomeric alkyl group. Preferably, the C1-C8 alkyl group is selected from at least one of methyl, ethyl, propyl, butyl, and pentyl.

[0045] The present invention has a wide range of yield selection for 6H-N-alkylcarbazole. Preferably, the yield of 6H-N-alkylcarbazole is ≥80%, which is more conducive to improving the yield of 12H-N-alkylcarbazole.

[0046] According to the present invention, preferably, the reaction conditions in step (1) include: a temperature of 230-300°C, preferably 240-280°C.

[0047] According to the present invention, preferably, the reaction conditions in step (1) include: a pressure of 0-2 MPa, preferably 0.5-1.5 MPa.

[0048] According to the present invention, preferably, the reaction conditions in step (1) include: a volume hourly space velocity (VHSV) of 1,2-cyclohexanediol of 0.01-0.1 h⁻¹. -1 Preferably, it is 0.02-0.08h.-1 .

[0049] According to the present invention, preferably, the content of the second support is 95-99.5 wt%, more preferably 96-99 wt%, based on the total mass of the second catalyst.

[0050] According to the present invention, preferably, based on the total mass of the second catalyst, the content of the second active component, calculated by metal element, is 0.5-5 wt%, more preferably 1-4 wt%.

[0051] According to the present invention, preferably, the second active component is Pd.

[0052] In this invention, the content of each component in the second catalyst and the type of the second active component are selected within the above-mentioned preferred range, which is beneficial to further convert 6H-N-alkylcarbazole into 12H-N-alkylcarbazole. At the same time, it further enables the unreacted raw materials to undergo a secondary reaction under the second catalyst, thereby improving the yield of 12H-N-alkylcarbazole.

[0053] The present invention has a wide range of choices for the second carrier. Preferably, the second carrier is selected from at least one of alumina, silica, magnesium aluminum hydrotalcite, HZSM-5 and HY molecular sieve.

[0054] According to the present invention, preferably, the conditions for the hydrogenation reaction include a temperature of 170-230°C, more preferably 180-220°C.

[0055] According to the present invention, preferably, the conditions for the hydrogenation reaction include a pressure of 3-8 MPa, more preferably 4-7 MPa.

[0056] According to the present invention, preferably, the conditions for the hydrogenation reaction include: a hydrogen volume hourly space velocity of 1000-5000 h⁻¹. -1 Preferably 1500-4500h -1 .

[0057] According to the present invention, preferably, the method further includes vacuum distillation of the products of the hydrogenation reaction.

[0058] In this invention, the above-mentioned vacuum distillation operation can separate the light components containing the raw material, with the remainder being a mixture of hexahydro, octahydro, decahydro, and dodecahydro N-alkylcarbazole.

[0059] In this invention, the synthesis method described above does not involve the introduction of any halogen atoms.

[0060] The second aspect of this invention provides the application of the product obtained by the synthesis method described in the first aspect in the field of organic liquid dehydrogenation.

[0061] In this invention, the product obtained by the above synthesis method does not contain halogens, has little impact on organic liquid hydrogen storage and dehydrogenation catalysts, and is beneficial for application in the field of organic liquid dehydrogenation.

[0062] The present invention will be described in detail below through embodiments.

[0063] Unless otherwise specified, all examples and comparative examples below are conventional methods; the reagents, materials and instruments used are commercially available and / or prepared using methods known in the art, unless otherwise specified.

[0064] In the following comparative examples and embodiments, the yield of 12H-N-alkylcarbazole was obtained by gas chromatography. The yield of 12H-N-alkylcarbazole, calculated as 12H-N-alkylcarbazole, was = .

[0065] Example 1

[0066] N-methylaniline and 1,2-cyclohexanediol were mixed in a molar ratio of 3:1 and reacted with a first catalyst. The first catalyst consisted of Pd and Cu supported on a magnesium aluminum layered double hydroxide (Mg:Al atomic molar ratio = 3:1), with Pd accounting for 1.5% by mass and Cu as the first auxiliary agent accounting for 5% by mass. This yielded a first liquid mixture containing 6H-N-methylcarbazole, with a 6H-N-methylcarbazole yield of 96.78% (based on 1,2-cyclohexanediol). The reaction was carried out at a temperature of 280 °C, a pressure of 0.5 MPa, and a space velocity of 0.03 h⁻¹. -1 A first liquid mixture undergoes a hydrogenation reaction in contact with a second catalyst under a certain hydrogen pressure. The second catalyst is composed of Pd supported on an alumina carrier, with Pd comprising 2% by mass and alumina comprising 98% by mass. This yields a second liquid mixture containing 12H-N-methylcarbazole. The hydrogenation reaction is carried out at a temperature of 220℃, a pressure of 4 MPa, and a hydrogen space velocity of 4000 h⁻¹. -1 The second liquid mixture was subjected to distillation to obtain a mixture of 6H, 8H, 10H, and 12H-N-methylcarbazole, with 12H-N-methylcarbazole as the main component. The product was analyzed by gas chromatography, and the yield of 12H-N-methylcarbazole was 94.88%.

[0067] Example 2

[0068] N-methylaniline and 1,2-cyclohexanediol were mixed at a molar ratio of 6:1 and reacted with a first catalyst. The first catalyst consisted of Pd and Ni supported on HZSM-5 (silicon-aluminum atomic molar ratio 40), with Pd accounting for 2% by mass and Ni as the first auxiliary agent accounting for 3% by mass. The reaction was carried out at a temperature of 240℃, a pressure of 1.5 MPa, and a space velocity of 0.03 h⁻¹. -1A first liquid mixture containing 6H-N-methylcarbazole was obtained, with a 6H-N-methylcarbazole yield of 95.82% (based on 1,2-cyclohexanediol). The first liquid mixture underwent a hydrogenation reaction in contact with a second catalyst under a certain hydrogen pressure. The second catalyst consisted of Pd supported on an alumina support, with Pd comprising 4% by mass and alumina content of 96%. The hydrogenation reaction was carried out at a temperature of 180℃, a pressure of 7 MPa, and a hydrogen space velocity of 1500 h⁻¹. -1 A second liquid mixture containing 12H-N-methylcarbazole was obtained. This second liquid mixture was then distilled to obtain a mixture of 6H, 8H, 10H, and 12H-N-methylcarbazole, with 12H-N-methylcarbazole as the main component. The product was analyzed by gas chromatography, and the yield of 12H-N-methylcarbazole was 93.59%.

[0069] Example 3

[0070] N-methylaniline and 1,2-cyclohexanediol were mixed in a molar ratio of 4:1 and reacted with a first catalyst at a reaction temperature of 260 °C, a pressure of 1.2 MPa, and a space velocity of 0.06 h⁻¹. -1 The first catalyst used consisted of Pd and Ce supported on HZSM-5 (silicon-to-aluminum atomic molar ratio 40), with Pd accounting for 2.3% by mass and Ce, the first auxiliary agent, accounting for 2.5% by mass. A first liquid mixture containing 6H-N-methylcarbazole was obtained, with a 6H-N-methylcarbazole yield of 95.14% (based on 1,2-cyclohexanediol). The first liquid mixture underwent a hydrogenation reaction with a second catalyst under a certain hydrogen pressure. The hydrogenation reaction temperature was 190℃, the pressure was 6 MPa, and the hydrogen space velocity was 3000 h⁻¹. -1 The product was analyzed by gas chromatography. The second catalyst consisted of Pd supported on an alumina carrier, with Pd accounting for 3% of the mass. A second liquid mixture containing 12H-N-methylcarbazole was obtained. The second liquid mixture was then distilled to obtain a mixture of 6H, 8H, 10H, and 12H-N-methylcarbazole, with 12H-N-methylcarbazole as the main component. The yield of 12H-N-methylcarbazole was 94.78%.

[0071] Example 4

[0072] The method was followed in Example 3, except that the reaction temperature was 230°C, the yield of 6H-N-methylcarbazole was 78.14% (based on 1,2-cyclohexanediol), and the yield of 12H-N-methylcarbazole was 74.95%.

[0073] Example 5

[0074] The method is the same as in Example 3, except that the mass of Pd in ​​the second catalyst is replaced with Ir.

[0075] The yield of 6H-N-methylcarbazole was 92.14%.

[0076] The yield of 12H-N-methylcarbazole was 81.77%.

[0077] Example 6

[0078] The method is the same as in Example 3, except that the mass of Ce in the first catalyst is replaced with Co.

[0079] The yield of 6H-N-methylcarbazole was 83.18%.

[0080] The yield of 12H-N-methylcarbazole was 79.35%.

[0081] Example 7

[0082] The method is the same as in Example 3, except that the Pd content in the second catalyst is replaced with 0.5% based on the total mass of the second catalyst.

[0083] The yield of 6H-N-methylcarbazole was 92.85%.

[0084] The yield of 12H-N-methylcarbazole was 75.23%.

[0085] Example 8

[0086] The method is the same as in Example 3, except that the mass percentage of Pd in ​​the first catalyst is 0.3% and the mass percentage of Ce is 20%.

[0087] The yield of 6H-N-methylcarbazole was 28.19%.

[0088] The yield of 12H-N-methylcarbazole was 22.04%.

[0089] Example 9

[0090] The method of Example 3 was followed, except that the raw material was dodecylaniline, the yield of 6H-octadecylcarbazole was 32.81% (based on 1,2-cyclohexanediol), and the yield of 12H-octadecylcarbazole was 25.32%.

[0091] Comparative Example 1

[0092] The method of Example 3 is followed, except that the first catalyst does not contain any auxiliary components. Based on the total mass of the first catalyst, the Pd content is 4.8%, the support is alumina, the yield of 6H-N-methylcarbazole is 25.14% (based on 1,2-cyclohexanediol), and the yield of 12H-N-methylcarbazole is 21.05%.

[0093] Comparative Example 2

[0094] The method is the same as in Example 3, except that in the first catalyst, Pd is replaced by Pt by mass and Ce is replaced by Fe by mass.

[0095] The yield of 6H-N-methylcarbazole was 16.92%.

[0096] The yield of 12H-N-methylcarbazole was 12.09%.

[0097] The results above show that, compared with the comparative example, the synthesis method of 12H-N-alkylcarbazole provided by the present invention can improve the yield of 12H-N-methylcarbazole, and the route is simple, solving the problems of cumbersome steps, harsh conditions, many by-products and low yield of the synthesis route of 12H-N-alkylcarbazole in the prior art.

[0098] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for synthesizing 12H-N-alkylcarbazole, characterized in that, The method includes: (1) In the presence of a first catalyst, N-alkylaniline is reacted with 1,2-cyclohexanediol to obtain a product containing 6H-N-alkylcarbazole; wherein the alkyl group in the N-alkylaniline is a C1-C8 alkyl group; The first catalyst includes a first support, a first active component, and an auxiliary component, wherein the auxiliary component is selected from at least one of Cu, Ni, and Ce, and the first active component is Pd; The first carrier is selected from magnesium aluminum hydrotalcite and / or zeolite molecular sieves; Based on the total mass of the first catalyst, the content of the first support is 93-98.5 wt%; the content of the first active component, calculated by metal element, is 0.5-5 wt%; and the content of the auxiliary component, calculated by metal element, is 1-10 wt%. The reaction temperature in step (1) is 240-280℃; The yield of 6H-N-alkylcarbazole in the product containing 6H-N-alkylcarbazole is ≥70%; (2) Under a hydrogen atmosphere, the product containing 6H-N-alkylcarbazole is contacted with a second catalyst to carry out a hydrogenation reaction to obtain 12H-N-alkylcarbazole; The second catalyst includes a second support and a second active component, wherein the second active component is Pd; The second carrier is aluminum oxide; Based on the total mass of the second catalyst, the content of the second support is 96-99 wt%; and based on metal elements, the content of the second active component is 1-4 wt%.

2. The synthesis method according to claim 1, wherein, Based on the total mass of the first catalyst, the content of the first support is 93-97 wt%; the content of the first active component is 1-4 wt% based on metal elements; and the content of the auxiliary component is 2.5-8 wt% based on metal elements.

3. The synthesis method according to claim 1, wherein, The molar ratio of N-alkylaniline to 1,2-cyclohexanediol is 1-8:

1.

4. The synthesis method according to claim 1, wherein, The reaction conditions in step (1) include: a pressure of 0-2 MPa; and a volume hourly space velocity (VHSV) of 0.01-0.1 h⁻¹ for 1,2-cyclohexanediol. -1 .

5. The synthesis method according to any one of claims 1-4, wherein, The conditions for hydrogenation reactions include: a temperature of 170-230℃; a pressure of 3-8 MPa; and a hydrogen volume hourly space velocity of 1000-5000 h⁻¹. -1 .