Method for preparing n-alkyl carbazole

Abstract

Provided is a method for preparing N-alkyl carbazole. The method comprises: with diphenylamine and an alkyl alcohol as raw materials, reacting same in the presence of a catalyst A to prepare N-alkyldiphenylamine, and then in the presence of a catalyst B and hydrogen, subjecting the N-alkyldiphenylamine to coupled dehydrogenation to prepare N-alkyl carbazole. Further provided is the use of a catalyst composition containing the catalyst A and the catalyst B for catalyzing a reaction of diphenylamine with an alkyl alcohol to prepare N-alkyl carbazole. In the present application, an alkyl alcohol is used as an alkylation reagent; the raw materials are easily available and inexpensive; few byproducts are produced and are easy to treat; the raw materials and products do not pollute the environment; and the used catalyst A and catalyst B are both heterogeneous catalysts, have good selectivity and high yield, are easy to separate, and can realize continuous production. The preparation method of the present application can achieve coproduction of carbazole, and solves the problem of carbazole having limited sources, low purity and a high price in the prior art.

Description

A preparation method of N-alkylcarbazole

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on June 13, 2023, with application number 202310695043.5 and invention name “A Method for Preparing N-Alkylcarbazole”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of fine chemical synthesis, and specifically relates to a method for preparing N-alkyl carbazole. Background Art

[0004] N-alkylcarbazole is an important class of organic intermediate raw materials with a wide range of uses. For example, N-ethylcarbazole is the raw material for synthesizing dyes such as Permanent Purple RL and Sulfide Reduction Blue GNX. In addition, it is also a carrier for liquid hydrogen storage. The hydrogen storage capacity of N-ethylcarbazole is 5.8wt%. Compared with liquid hydrogen storage systems such as toluene / cyclohexane, dibenzyltoluene, and naphthalene, N-ethylcarbazole has the advantage of a low hydrogen release reaction temperature and is considered to be a very promising hydrogen storage material. With the advancement of the national hydrogen energy plan, the demand for materials such as N-ethylcarbazole will increase significantly. The traditional N-ethylcarbazole production process is obtained by the N-alkylation reaction of carbazole. Carbazole is derived from coal tar and has limited production itself, which cannot meet the needs of large-scale production. More importantly, the traditional alkylation process uses halogen-containing raw materials such as ethyl bromide, which easily produces difficult-to-handle salt wastes that are difficult to dispose of. For example:

[0005] 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 TY (Journal of the Iranian Chemical Society. 2010; 7(3): 707-720) et al. disclosed the preparation of N-ethylcarbazole by the reaction of halogenated hydrocarbons with carbazole. However, these methods require the use of alkaline reagents (such as NaOH) to neutralize the halogen by-products, resulting in the generation of a large amount of waste salts that require washing with a large amount of water, posing environmental problems, and the product is prone to residual halogen elements.

[0006] Li J (Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 2009; 73(2): 221-225), Tsunashima Y (Journal of Heterocyclic Chemistry. 1981; 18(2): 315-318), Bergman J (Tetrahedron. 1990; 46(17): 6113-6124) et al. reported the preparation of N-ethylcarbazole by the reaction of esters with carbazole. This is also an important synthesis method, but it requires the use of an alkaline reagent to neutralize the by-product acid to generate by-product salts such as sodium sulfate, sodium phosphate, etc. The salt waste generated by the stoichiometric ratio is also a solid hazardous waste that is difficult to dispose of.

[0007] (Tetrahedron. 2012; 68(25): 5075-5080) reported the reaction of nitrobiphenyl with phosphate to prepare N-ethylcarbazole, but an alkaline reagent was required to neutralize the by-product phosphoric acid. This method also produced a stoichiometric by-product sodium phosphate.

[0008] Kashima C et al. (Journal of Heterocyclic Chemistry. 1987; 24(4): 913-916) disclosed the preparation of N-ethylcarbazole by reacting 2,5-dimethoxytetrahydrofuran with ethylamine hydrochloride. However, this method has a low conversion rate and a scarce source of raw materials, making it unsuitable for large-scale production.

[0009] Paria S (ChemCatChem. 2014; 6(9): 2477-2483) and Hernandez-Perez AC (Angewandte Chemie International Edition. 2013; 52(48): 1-6) et al. reported the synthesis of N-ethylcarbazole under photocatalytic conditions. However, due to the great uncertainty of the photocatalytic reaction and the extremely low space-time yield, it is difficult to meet the requirements of industrial production.

[0010] Chinese patent document CN107488140B discloses the preparation of N-ethylcarbazole by reacting acetylene with carbazole. While this method is environmentally superior to traditional diethyl sulfate and alkyl halide methods, it is a gas-liquid reaction with low conversion efficiency. Furthermore, acetylene is a highly explosive substance, and under the reaction conditions described in this patent, it exhibits the "Black Panther effect" known in the acetylene industry: a violent explosion can occur in the presence of metal ions, vibration, and other unknown factors, without the need for oxygen. Another Chinese patent document, CN112159345A, utilizes the reaction of ethylene with carbazole to prepare N-ethylcarbazole. However, the use of metallic sodium in this reaction makes it difficult to meet safety requirements and, therefore, difficult to meet mass production requirements.

[0011] At the same time, for high-carbon N-alkyl carbazoles such as N-propyl carbazole and N-butyl carbazole, the traditional synthesis process is insufficient for the preparation of corresponding raw materials. Therefore, the development of a universal N-alkyl carbazole synthesis process has great industrial value.

[0012] Based on the above analysis, existing N-alkyl carbazole preparation methods have the following drawbacks: The diethyl sulfate method and the alkyl halide method produce sulfuric acid and halides as byproducts, respectively, when producing N-ethyl carbazole, posing environmental concerns. The carbazole acetylene method and the ethylene method, however, pose safety risks. Furthermore, all of these methods also face issues with raw material sourcing, as they all use carbazole, which primarily comes from coal tar and is relatively expensive. Furthermore, most existing preparation methods lack the potential for large-scale production, especially for high-carbon N-alkyl carbazoles such as N-propyl carbazole and N-butyl carbazole, as corresponding technical routes are lacking. Therefore, the development of N-alkyl carbazole synthesis routes with inexpensive raw materials, widespread availability, environmental friendliness, and versatility is urgently needed.

[0013] Summary of the Invention

[0014] In view of this, the technical problem to be solved by the present application is to address the defects of existing N-alkyl carbazole preparation methods, such as expensive raw materials, difficult by-product treatment, poor environmental protection, and lack of versatility. Therefore, a method for preparing N-alkyl carbazole is provided, which has cheap and environmentally friendly raw materials, no salt waste is generated during the reaction process, high reaction yield and strong versatility.

[0015] To achieve the above objectives, this application adopts the following technical solutions:

[0016] According to an embodiment of the present application, in a first aspect, the present application provides an application of a catalyst composition in catalyzing the reaction of diphenylamine and an alkyl alcohol to prepare N-alkylcarbazole, wherein the catalyst composition comprises catalyst A and catalyst B:

[0017] The catalyst A comprises an active component MA and a carrier LA, wherein the active component MA is selected from at least one of Ni, Co, Ir, Pt, Pd, and Ru, and the carrier LA is at least one of Al2O3, activated carbon, SiO2, ZrO2, and SnO2;

[0018] The catalyst B includes an active component MB and a carrier LB, wherein the active component MB is selected from at least one of Ni, Pt, Pd, Fe, and Cu, and the carrier LB is at least one of TiO2, Al2O3, SiO2, activated carbon, ZrO2, molecular sieve, Mg-Al hydrotalcite, NiAl2O4 spinel, and CoAl2O4 spinel.

[0019] In the examples of the present application, in the catalyst A, the content of the active component MA is 0.5 to 36 wt%.

[0020] In an embodiment of the present application, in the catalyst A, the active component MA is at least one of Ni, Co, Ru, and Ir.

[0021] In an embodiment of the present application, in the catalyst A, the content of the carrier LA is 64 to 99.5 wt%.

[0022] In an embodiment of the present application, the catalyst A further includes an auxiliary agent NA, and the auxiliary agent NA is at least one of Zn, Sn, Cu, an oxide of an alkali metal or an alkaline earth metal, or Sn.

[0023] In the examples of the present application, in the catalyst A, the content of the active component MA is 10-30 wt%, the content of the carrier LA is 69-89 wt%, and the content of the auxiliary agent NA is 0.05-1 wt%.

[0024] In the examples of the present application, the composition of the catalyst A is: Co 21.3 wt%, MgO 0.15 wt% and Al2O3 78.55 wt%.

[0025] In the examples of the present application, the composition of the catalyst A is: 30 wt% Ni, 1.0 wt% ZnO and 69 wt% SiO2.

[0026] In the examples of the present application, the composition of the catalyst A is: 0.5 wt% Ir and 99.5 wt% Al2O3.

[0027] In an embodiment of the present application, in the catalyst B, the content of the active component MB is 0.1 to 13 wt%; and / or the content of the carrier LB is 87 to 99.9 wt%.

[0028] In an embodiment of the present application, the catalyst B further includes a promoter NB, and the promoter NB is an oxide of at least one of Mn, Sn, Re, Mo, and K.

[0029] In the embodiments of the present application, in the catalyst B, the content of the active component MB is 1-10 wt%, and / or the content of the carrier LB is 90-95 wt%, and / or the content of the additive NB is 0.2-6 wt% in terms of metal.

[0030] In the embodiment of the present application, the additive NB is an oxide of Sn and K. Calculated as metal, the Sn content is 0.1-1 wt% of the mass of the catalyst B, and the K content is 0.1-1 wt% of the mass of the catalyst B.

[0031] In the embodiment of the present application, the active component MB is Pt and Ni, the Pt content is 0.1-3 wt% of the mass of the catalyst B, and the Ni content is 1-10 wt% of the mass of the catalyst B.

[0032] In the embodiment of the present application, the composition of the catalyst B is: Pt 1wt%, Re 0.2wt%, Sn 0.4wt%, Mn 2wt%, NiAl2O4 94% and ligand oxygen of Re, Sn and Mn 2.4wt%.

[0033] In the examples of the present application, Pt 0.8 wt%, Ni 2 wt%, Sn 0.1 wt%, K 0.1 wt%, TiO 2 96.9%, and oxygen as a ligand of Sn and K 0.1 wt%.

[0034] According to an embodiment of the present application, in a second aspect, the present application further provides a method for preparing N-alkylcarbazole, comprising the following steps:

[0035] S1. In the presence of catalyst A, diphenylamine reacts with an alkyl alcohol having a water content of not more than 10 wt %, wherein more than 85 wt % of the alkyl alcohol is in liquid form during the reaction, to produce N-alkyldiphenylamine;

[0036] S2. In the presence of catalyst B and hydrogen, N-alkyldiphenylamine undergoes a coupling dehydrogenation reaction to produce N-alkylcarbazole;

[0037] The catalyst A comprises an active component MA and a carrier LA, wherein the active component MA is selected from at least one of Ni, Co, Ir, Pt, Pd, and Ru, and the carrier LA is at least one of Al2O3, activated carbon, SiO2, ZrO2, and SnO2;

[0038] The catalyst B includes an active component MB and a carrier LB, wherein the active component MB is selected from at least one of Ni, Pt, Pd, Fe, and Cu, and the carrier LB is at least one of TiO2, Al2O3, SiO2, activated carbon, ZrO2, molecular sieve, Mg-Al hydrotalcite, NiAl2O4 spinel, and CoAl2O4 spinel.

[0039] In the preparation method of the present application, the reaction phase of the alkyl alcohol in step S1 is extremely important. The inventors have discovered that if the reaction is conducted after all the reaction raw materials have been vaporized to a gas phase, such reaction conditions can cause a large amount of diphenylamine to decompose and convert into benzene and aniline-like substances, and even produce triphenylamine, resulting in a decrease in the selectivity and yield of the N-alkylation reaction in step S1. Therefore, in the examples of the present application, it is preferred that at least 95 wt% of the alkyl alcohol be in a liquid state during the reaction, thereby improving the selectivity and reaction yield of N-alkyldiphenylamine.

[0040] Vaporization fraction is a concept well known to those skilled in the art and has a strict academic definition. Specifically, it is defined as the ratio of the mass of a substance in the vapor phase to the total mass of the substance when it is in a vapor-liquid two-phase state (including bubble point, dew point, supercooled liquid phase, or superheated gas phase), that is, the proportion of the vapor phase in the two-phase region. This is described in both "Principles of Chemical Engineering" and "Physical Chemistry." In the preparation method of the present application, the vaporization fraction of the alkyl alcohol must be strictly controlled below 15%. In other words, at least 85% by weight of the alkyl alcohol must be in the liquid phase in the reactor. Preferably, the vaporization fraction must be strictly controlled below 5%. In other words, at least 95% by weight of the alkyl alcohol must be in the liquid phase in the reactor.

[0041] In the preparation method of the present application, the alkyl alcohol raw material used in step S1 often contains water. The inventors have discovered that the water content of the alkyl alcohol is crucial to the reaction outcome, significantly affecting the conversion of diphenylamine and the selectivity of N-alkyldiphenylamine. Therefore, in the examples of the present application, the water content of the alkyl alcohol is preferably no more than 0.5 wt % to ensure high conversion and selectivity in the N-alkylation reaction.

[0042] The present inventors have discovered that in step S1, the reaction pressure has a significant impact on the N-alkylation reaction of diphenylamine and alkyl alcohol, especially when using a fixed-bed reactor. Although the reaction does not show a change in molecular weight during the process and should in principle be insensitive to the reaction pressure, in fact, this may be because under specific reaction pressure control, the vast majority of the alkyl alcohol can be present in liquid form, thereby allowing the reaction to proceed under liquid phase conditions, thereby improving the conversion rate and selectivity of the N-alkylation reaction. Therefore, in the embodiments of the present application, the reaction pressure is controlled so that the alkyl alcohol can maintain a liquid phase under these conditions. The reaction conditions can be calculated from the saturated vapor pressure of each alkyl alcohol. Specifically, in the embodiments of the present application, the preferred reaction pressure is 2 to 12 MPa, and the reaction temperature is a dependent variable of the reaction pressure. At this reaction pressure, the corresponding reaction temperature is 170 to 270°C. More preferably, the reaction pressure is 4.0 to 8.0 MPa and the reaction temperature is 200 to 250°C.

[0043] In the preparation method of the present application, in step S1, the N-alkylation reaction of diphenylamine and alkyl alcohol needs to be carried out in a reactor, that is, the mixed reaction raw materials need to be fully contacted with the heterogeneous catalyst A under the reaction conditions. The reactor used in the embodiments of the present application can be selected from a tank reactor or a fixed bed reactor, preferably a fixed bed reactor, and more preferably a fixed bed reactor with a partition wall heat exchange structure provided therein.

[0044] When a fixed bed reactor is used, since the N-alkylation reaction of diphenylamine with an alkyl alcohol is a liquid phase reaction, it is difficult to disperse the reaction materials on the catalyst bed. Therefore, conventional liquid-solid two-phase reactions use a bottom feeding method to facilitate uniform distribution. However, the inventors have found that the reaction results of bottom feeding are much worse than those of top feeding. That is, this reaction requires the reaction materials to enter the catalyst bed from the top of the fixed bed reactor. In the examples of the present application, the volume liquid hourly space velocity of the catalyst bed in the fixed bed reactor is 0.1 to 1.2 h -1 , preferably 0.6 to 0.9 h -1 The volume liquid hourly space velocity refers to the volume (in cubic meters) of liquid reaction raw materials processed per cubic meter of catalyst per hour.

[0045] When the N-alkylation reaction adopts a tank reactor, the mass of the catalyst A is 1-10 wt% of the total mass of the reaction raw materials, preferably 6-8 wt%; the reaction time is 6-24 h, preferably 12-24 h.

[0046] In the preparation method of the present application, in step S1, in principle, the reaction stoichiometric ratio of alkyl alcohol and diphenylamine is 1:1, but in practice it is found that the stoichiometric ratio of alkyl alcohol needs to be higher to obtain better reaction results. The inventors have obtained an optimized stoichiometric ratio through experiments and simulation calculations, that is, the molar ratio of alkyl alcohol to diphenylamine is 2 to 15:1, preferably 6 to 15:1.

[0047] In the embodiments of the present application, the alkyl alcohol is selected from a monohydric alcohol having 1 to 5 carbon atoms. The alkyl alcohol may be a normal alcohol or an isomer thereof. For example, the butanol may be selected from n-butanol, isobutanol, sec-butanol, or tert-butanol; the pentanol may be an isomer such as 3-pentanol, isopentanol, sec-pentanol, tert-pentanol, or neopentanol. Preferably, the alkyl alcohol is selected from a normal alcohol, specifically at least one of methanol, ethanol, n-propanol, n-butanol, and n-pentanol.

[0048] In the preparation method of the present application, the selection of a suitable catalyst in step S1 significantly influences the N-alkylation reaction results of diphenylamine. Previous studies often used acidic catalysts, resulting in the alkylation of diphenylamine occurring primarily on non-N atoms, that is, on the benzene ring. The present inventors conducted extensive high-throughput catalyst screening and unexpectedly discovered that when the active component MA is selected from at least one of metallic Ni, Co, Ru, Pt, or Pd, and the carrier LA is at least one of Al2O3, activated carbon, SiO2, or ZrO2, the reaction of alkyl alcohol and diphenylamine can achieve a relatively high N-alkylation yield. In particular, when the active component MA is at least one of metallic Ni, Co, Ru, or Ir, and the active component MA content is between 0.5 and 36 wt%, unexpectedly high N-alkylation yields can be achieved. The present inventors speculate that the reaction mechanism may be that the alkyl alcohol first undergoes dehydrogenation on the metal of the active component MA to form the corresponding aldehyde intermediate, which then couples with the NH in diphenylamine and, after dehydration and hydrogenation, is converted into N-alkyldiphenylamine.

[0049] In Catalyst A used in this application, the carrier provides support for the active components and may also play a significant synergistic role in the coupling-dehydration-hydrogenation reaction. In the examples of this application, the optional carrier LA is at least one of Al2O3, activated carbon, SiO2, and ZrO2, with the content of the carrier LA ranging from 64 to 99.5 wt%.

[0050] In an embodiment of the present application, the catalyst A further comprises an auxiliary agent NA, and the auxiliary agent NA is at least one of Zn, Sn, Cu, an oxide of an alkali metal, an alkaline earth metal, or Sn, preferably Mg or K.

[0051] In the examples of the present application, as an optional implementation, the content of the active component MA of the catalyst A is 10-30 wt%, the content of the carrier LA is 69-89 wt%, and the content of the auxiliary agent NA is 0.05-1 wt%.

[0052] As an optional specific example, the composition of the catalyst A is: Co 21.3wt%, MgO 0.15wt% and Al2O3 78.55wt%; or, Ni 30wt%, ZnO 1.0wt% and SiO2 69wt%; or, Ir 0.5wt% and Al2O3 99.5wt%.

[0053] In the examples of this application, Catalyst A can be prepared as an oxidized precursor by conventional methods such as coprecipitation and impregnation loading. Prior to use, it requires hydrogen reduction at 280-450°C to a metallic state, a process well known to those skilled in the art and not described in detail herein. Alternatively, Catalyst A can be obtained directly by alloy quenching followed by caustic soda extraction.

[0054] In an embodiment of the present application, step S1 further includes a purification step:

[0055] The reaction mixture of diphenylamine and alkyl alcohol is subjected to a first separation to obtain a first separated product and a second separated product; the first separated product is dehydrated to obtain unreacted alkyl alcohol, which is recycled as an alkylation reagent; the second separated product is subjected to a second separation to obtain N-alkyldiphenylamine and unreacted diphenylamine, respectively, and the unreacted diphenylamine is recycled as a substrate for an alkylation reaction.

[0056] In step S1, after the N-alkylation reaction is completed, the reaction mixture and the catalyst are separated and discharged. This separation step is well known to those skilled in the art. If a tank reactor is used, liquid-solid separation is achieved through sedimentation, filtration, or other methods. In a fixed-bed reactor, the catalyst is stationary, so separation is achieved upon discharge from the reactor. In an embodiment of the present application, the first and second separations can be achieved by vacuum distillation at a pressure of -70 to -98 kPa. Due to differences in melting points, separation can also be achieved by crystallization or other methods. The purity of the N-alkyldiphenylamine obtained by the second separation is 95.0 to 99.9%, with a diphenylamine content of no more than 3 wt%.

[0057] In the preparation method of the present application, in step S2, in the presence of catalyst B and hydrogen, N-alkyldiphenylamine undergoes an intramolecular coupling dehydrogenation reaction to produce N-alkylcarbazole, while simultaneously co-producing carbazole and hydrogen, and by-products include benzene, aniline and low-carbon hydrocarbons.

[0058] The coupling dehydrogenation reaction is carried out in the presence of hydrogen. Since most N-alkyldiphenylamines have a boiling point higher than the reaction temperature and cannot be vaporized under normal pressure, the inventors have discovered that the presence of an appropriate amount of hydrogen can significantly extend the service life of the catalyst. Therefore, in the examples of the present application, the molar ratio of N-alkyldiphenylamine to hydrogen is 1:1 to 30, preferably 1:4 to 20. This molar ratio is the key to obtaining a high yield of N-alkylcarbazole.

[0059] In the embodiments of the present application, the reaction temperature of the coupled dehydrogenation reaction is 200-300°C, preferably 230-270°C; the reaction pressure is negative pressure, normal pressure or slightly positive pressure, that is, -0.1-0.2 MPa in absolute pressure, preferably 5-150 KPa.

[0060] In the embodiment of the present application, step S2 is carried out in a fixed bed or fluidized bed. When a fixed bed reactor is used for the coupled dehydrogenation reaction, the volume liquid hourly space velocity is 0.01 to 0.8 h -1 .

[0061] In an embodiment of the present application, the active component MB of the catalyst B contains 0.1-13 wt %. Alternatively, the active component MB is Pt and Ni, with the Pt content being 0.1-3 wt % and the Ni content being 1-10 wt % of the catalyst B.

[0062] In an embodiment of the present application, the optional carrier LB of the catalyst B is at least one of TiO2, Al2O3, SiO2, activated carbon, ZrO2, molecular sieve, Mg-Al hydrotalcite, NiAl2O4 spinel, and CoAl2O4 spinel, preferably at least one of Al2O3, ZrO2, Mg-Al hydrotalcite, NiAl2O4 spinel, TS-1 molecular sieve, and CoAl2O4 spinel, further preferably at least one of Al2O3, NiAl2O4 spinel, TS-1 molecular sieve, and CoAl2O4 spinel, more preferably at least one of NiAl2O4 spinel and TS-1 molecular sieve, and the content of the carrier LB is 87 to 99.9 wt%.

[0063] In an embodiment of the present application, the catalyst B further comprises a promoter NB, which is an oxide of at least one of Mn, Sn, Re, Mo, and K. Preferably, the promoter NB is an oxide of Sn and K. Calculated as metals, the Sn content is 0.1 to 1 wt% of the mass of the catalyst B, and the K content is 0.1 to 1 wt% of the mass of the catalyst B. It should be noted that the promoters NB are all metal oxides, and the valence state of the metals cannot be confirmed by the present inventors.

[0064] In the examples of the present application, as an optional embodiment, the content of the active component MB of the catalyst B is 1-10 wt%, the content of the carrier LB is 90-95 wt%, and the content of the additive NB is 0.2-6 wt% in terms of metal.

[0065] As an optional specific example, the composition of the catalyst B is: Pt 1wt%, Re 0.2wt%, Sn 0.4wt%, Mn 2wt%, Al2O3 94% and 2.4wt% of ligand oxygen of Re, Sn and Mn; or, Pt 0.8wt%, Ni 2wt%, Sn 0.1wt%, K 0.1wt%, TiO2 96.9% and 0.1wt% of ligand oxygen of Sn and K.

[0066] In the preparation method of the present application, the active component MB of the catalyst B is in a metal reduced state, which is generally obtained by reducing the oxidized precursor of the catalyst B in a hydrogen gas flow at 200-430°C, which is well known to those skilled in the art.

[0067] Compared with the existing technology, the technical solution of this application has the following advantages:

[0068] 1. The preparation method of N-alkylcarbazole provided in the embodiment of the present application uses diphenylamine and alkyl alcohol as raw materials, reacts in the presence of catalyst A to obtain N-alkyldiphenylamine, and then, in the presence of catalyst B and hydrogen, couples and dehydrogenates the N-alkyldiphenylamine to obtain N-alkylcarbazole. The present application uses alkyl alcohol, which is widely available in the industry, as an alkylating agent. The raw materials are easily available and inexpensive, and there is no problem of limited raw materials. In addition, the stoichiometric products are water and hydrogen, with few by-products and easy to handle. The raw materials and products do not pollute the environment. The raw materials recovered after the reaction can also be recycled, meeting the requirements of green process. The catalysts A and B used are both heterogeneous catalysts with good selectivity, high yield and easy separation, which can achieve continuous production. Furthermore, the preparation method of the present application can also co-produce carbazole, solving the problems of limited sources, low purity and high price of existing carbazole.

[0069] 2. In the method for preparing N-alkylcarbazole provided in the embodiments of the present application, by controlling more than 85 wt% of the alkyl alcohol to be present in liquid phase during the preparation of N-alkyldiphenylamine, the N-alkylation process of diphenylamine is carried out under liquid phase conditions. This avoids the problem of easy decomposition of diphenylamine caused by gas phase reaction, which leads to decreased selectivity and reaction yield.

[0070] 3. The preparation method of N-alkylcarbazole provided in the embodiment of the present application preferably adopts a fixed bed process, and breaks through the conventional liquid-solid two-phase reaction mode of bottom feeding to facilitate uniform distribution of the liquid phase. It is proposed that the reaction raw materials enter the catalyst bed from the top of the fixed bed reactor, which is more conducive to full contact between the reaction raw materials and the catalyst, and avoids the reaction raw materials from being immersed in the catalyst bed during bottom feeding, resulting in channeling, short circuiting, etc., so that part of the reaction raw materials cannot fully contact with the catalyst bed, resulting in reduced conversion rate, yield and other indicators; while when feeding from the top, under the condition of controlling the space velocity, the reaction raw materials basically pass through the catalyst bed in a manner of adhering to the wall and dripping, which can better ensure that the reaction raw materials are fully in contact with the catalyst bed, thereby improving indicators such as conversion rate and yield.

[0071] 4. In the preparation method of N-alkylcarbazole provided in the examples of the present application, the molar ratio of hydrogen to N-alkyldiphenylamine is controlled to be 1 to 30 during the preparation of N-alkylcarbazole, and is controlled to be 4 to 20 under optimized conditions. The dehydrogenation reaction process of N-alkyldiphenylamine to N-alkylcarbazole requires, according to conventional understanding, to minimize the hydrogen partial pressure. However, the present inventors have discovered that supplementing a certain amount of hydrogen, especially within a preferred range, can actually increase the yield of N-alkylcarbazole and also improve the operational stability of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0073] FIG1 is a mass spectrum fragmentation diagram of N-methyldiphenylamine prepared in Example 1 of the present application.

[0074] FIG2 is a chromatogram of a mixture of diphenylamine and N-methyldiphenylamine prepared in Example 1 of the present application.

[0075] FIG3 is a mass spectrum fragmentation diagram of N-methylcarbazole prepared in Example 1 of the present application.

[0076] FIG4 is a GC-MS analysis spectrum of the coupled dehydrogenation product of the mixture of N-methyldiphenylamine and diphenylamine in Example 1 of the present application.

[0077] FIG5 is a mass spectrum fragmentation diagram of N-ethyldiphenylamine prepared in Example 2 of the present application.

[0078] FIG6 is a chromatogram of a mixture of diphenylamine and N-ethyldiphenylamine prepared in Example 2 of the present application.

[0079] FIG7 is a mass spectrum fragmentation diagram of N-ethylcarbazole prepared in Example 2 of the present application.

[0080] FIG8 is a GC-MS analysis spectrum of the coupled dehydrogenation product of the mixture of N-ethyldiphenylamine and diphenylamine in Example 2 of the present application.

[0081] FIG9 is a mass spectrum fragmentation diagram of N-propyldiphenylamine prepared in Example 3 of the present application.

[0082] FIG10 is a chromatogram of a mixture of diphenylamine and N-propyldiphenylamine prepared in Example 3 of the present application.

[0083] FIG11 is a mass spectrum fragmentation diagram of N-propylcarbazole prepared in Example 3 of the present application.

[0084] FIG12 is a GC-MS analysis spectrum of the coupled dehydrogenation product of the mixture of N-propyldiphenylamine and diphenylamine in Example 3 of the present application. DETAILED DESCRIPTION

[0085] The following examples are provided to further better understand the present application, but are not limited to the best implementation mode described herein, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts shall fall within the scope of protection of the present application.

[0086] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be followed. If the manufacturer of the materials or instruments is not specified, they are all conventional products that can be purchased.

[0087] Regarding N-alkylation reactions, prior art CN113214146A discloses the use of a heterogeneous catalyst to catalyze the reaction of alcohols with aminopyridine to prepare N-methylaminopyridine. However, this method has a high reaction temperature and requires dilution with a carrier gas. The reaction solvent is water. Actual N-alkylation of diphenylamine and alcohol under these conditions yielded extremely low reaction yields. This is likely due to the greater steric hindrance of diphenylamine compared to a single pyridine ring, which increases the difficulty of N-alkylation. Furthermore, under these catalytic conditions, diphenylamine undergoes a cracking reaction to convert into aniline, benzene, or isomerizes into triphenylamine and aniline. Therefore, this application optimizes the catalyst and reaction conditions to address the low reaction yield.

[0088] In the examples of this application, the N-alkylation reaction was carried out in an autoclave or fixed-bed catalyst evaluation reactor. The reaction products were qualitatively analyzed using an Agilent 6890N / 5973N GC-MS, and quantitatively analyzed using the area normalization method. Aspen Plus is a large-scale, general-purpose process simulation system for production unit design, steady-state simulation, and optimization. In the examples of this application, Aspen Plus was used to simulate the liquid fraction of alkyl alcohols under reaction process conditions, thereby inferring the alkylation reaction process of alkyl alcohols with diphenylamine. The simulation results were consistent with the experimental results.

[0089] Preparation Example 1: Co-precipitation method was used to prepare the catalyst Co-MgO / Al2O3

[0090] Mix 105.2 g of Co(NO3)2·6H2O and 0.6 g of Mg(NO3)2 and dissolve them in 150 mL of water. Add 1 mol / L NaOH aqueous solution dropwise until the pH value is 6.7. Add 92.4 g of pseudo-boehmite while stirring and stir for 3 hours. Filter and wash three times with water. The filtrate is dried at 120°C for 3 hours and calcined at 400°C for 3 hours to obtain catalyst precursor A1.

[0091] Before use, catalyst precursor A1 was reduced in a hydrogen stream at 420°C for 3 hours to obtain Co-MgO / Al2O3, which was designated as catalyst A1. Analysis and testing revealed that the composition of catalyst A1 was: Co 21.3 wt%, MgO 0.15 wt%, and the balance being the carrier Al2O3.

[0092] Preparation Example 2: Preparation of Pt-Sn / ZrO2 catalyst by impregnation loading method

[0093] 2.1 g of H2PtCl6·6H2O and 0.2 g of SnCl2 were dissolved in water, mixed with 43 mL of 20% aqueous hydrochloric acid solution, and 98.9 g of nano-ZrO2 (commercially available) was added with stirring. Stirring was continued for 3 h, and the mixture was evaporated to dryness in a water bath with stirring, dried at 120°C overnight, calcined at 400°C for 3 h, and then washed four times with 90°C hot water and dried to obtain catalyst precursor A2.

[0094] Before use, catalyst precursor A2 was reduced in a hydrogen stream at 350°C for 3 hours to obtain Pt-Sn / ZrO2, which was designated as catalyst A2. Analysis and testing revealed that the composition of catalyst A2 was: Pt 1 wt%, Sn 0.1 wt%, and the balance being the carrier ZrO2.

[0095] Preparation Example 3 Preparation of catalyst Pd / AC by impregnation loading method

[0096] Dissolve 2.5 g of Pd(NO3)2·2H2O in 210 mL of water, add 99 g of activated carbon treated with 0.1 mol / L nitric acid (commercially available) under stirring, continue stirring for 3 h, evaporate to dryness with stirring in a water bath, dry at 120°C overnight, and calcine at 300°C under a nitrogen atmosphere for 3 h to obtain catalyst precursor A3.

[0097] Before use, the catalyst precursor A3 was reduced in a hydrogen stream at 250°C for 3 hours to obtain Pd / AC, which was designated as catalyst A3. Analysis and testing showed that the composition of catalyst A3 was: Pd 1 wt%, and the balance was carrier activated carbon.

[0098] Preparation Example 4: Preparation of Ru / Al2O3 Catalyst by Impregnation Loading Method

[0099] Dissolve 2.1 g of RuCl3 in 89 mL of 0.1 mol / L dilute hydrochloric acid solution at 65°C, add 116.5 g of pseudo-boehmite while stirring, continue stirring for 3 h, evaporate to dryness with stirring in a water bath, dry at 120°C overnight, and then calcine in a muffle furnace at 400°C for 4 h to obtain catalyst precursor A4.

[0100] Before use, catalyst precursor A4 was reduced with hydrogen in a tube furnace at 350°C for 4 hours to obtain Ru / Al2O3, which was designated as catalyst A4. The composition of the catalyst tested was: Ru 1 wt%, with the balance being the carrier Al2O3.

[0101] Preparation Example 5: Preparation of Ni-ZnO / SiO2-Al2O3 catalyst by coprecipitation method

[0102] 148.6 g of Ni(NO3)2·6H2O and 1.7 g of ZnCl2 were dissolved in water, and a 1 mol / L NaOH aqueous solution was added dropwise until the pH value was 6.5. 69 g of SiO2-Al2O3 (Si / Al molar ratio of 10) was added under stirring, and stirring was continued for 5 h. The mixture was filtered and washed five times with water. The filtrate was dried at 120°C overnight and calcined at 450°C for 3 h to obtain catalyst precursor A5.

[0103] Before use, catalyst precursor A5 was reduced in a hydrogen stream at 420°C for 3 hours to obtain Ni-Zn / SiO2, designated as catalyst A5. Analysis and testing revealed that the composition of catalyst A5 was: 30 wt% Ni, 1.0 wt% ZnO, and the balance being the SiO2-Al2O3 support.

[0104] Preparation Example 6 Preparation of Ir / Al2O3 Catalyst by Impregnation Loading Method

[0105] 0.9 g of IrCl3·3H2O was dissolved in 101 mL of 0.1 mol / L dilute hydrochloric acid solution at 40°C. 117 g of pseudo-boehmite was added with stirring and the mixture was stirred for 3 h. The mixture was evaporated to dryness with stirring in a water bath and dried at 120°C overnight. The mixture was then calcined in a muffle furnace at 600°C for 4 h to obtain catalyst precursor A6.

[0106] Before use, the catalyst precursor A6 was reduced with hydrogen in a tube furnace at 350°C for 4 hours to obtain Ir / Al2O3, which was designated as catalyst A6. Analysis and testing showed that the composition of catalyst A6 was: Ir 0.5 wt%, with the balance being the carrier Al2O3.

[0107] Preparation Example 7 Catalyst Pt-ReO x -SnO x -MnO x Preparation of / Al2O3

[0108] 4 g H2PtCl6·6H2O, 0.42 g SnCl2, and 0.3 g HReO4 were dissolved in 141 mL 1 mol / L hydrochloric acid solution at 80°C, combined with 26 g 50% Mn(NO3)2 aqueous solution under stirring, and then 200 g Al2O3 was added. The mixture was soaked for 3 h, the solvent was evaporated by rotary evaporation, and dried at 120°C overnight. Then, the mixture was calcined in a muffle furnace at 600°C for 4 h to obtain catalyst precursor B1.

[0109] Before use, the catalyst precursor B1 was placed in a tube furnace at 350 °C and reduced with hydrogen for 4 h to obtain the catalyst Pt-ReO x -SnO x -MnO x / Al2O3, denoted as catalyst B1. The composition of catalyst B1 is: Pt 1wt%, Re 0.2wt%, Sn 0.4wt%, Mn 2wt%, Al2O3 carrier is 94%, and the balance is Re, Sn and Mn ligand oxygen. In the oxides of Re, Sn and Mn, the valence state of Re, Sn and Mn cannot be determined individually, so they are respectively expressed as ReO x 、SnO x 、MnO x express.

[0110] Preparation Example 8 Catalyst Pt-Ni-SnO x Preparation of K2O / TiO2

[0111] 2.4 g H2PtCl6·6H2O and 0.28 g SnCl2 were dissolved in 60 mL of 2 mol / L hydrochloric acid solution at 60°C, and then combined with 33 g of an aqueous solution containing 13.66 g Ni(NO3)2·6H2O under stirring. 150 g TiO2 (containing approximately 0.1 wt% K2O) was added, and the mixture was soaked for 1 h, dried at 120°C overnight, and then calcined in a muffle furnace at 500°C for 2 h to obtain catalyst precursor B2.

[0112] Before use, the catalyst precursor B2 was placed in a tube furnace at 450 °C and reduced with hydrogen for 4 h to obtain the catalyst Pt-Ni-SnO x -K2O / TiO2, denoted as catalyst B2. The composition of catalyst B2 is: Pt 0.8wt%, Ni 2wt%, Sn 0.1wt%, K 0.1wt%, TiO2 carrier is 96.9%, and the balance is Sn and K ligand oxygen. In Sn oxide, the valence state of Sn cannot be confirmed alone, so SnO x express.

[0113] Example 1

[0114] In this embodiment, methanol is selected as an alkylating agent to perform an N-alkylation reaction with diphenylamine to prepare N-methyldiphenylamine, and then N-methylcarbazole is prepared by an intramolecular coupling dehydrogenation reaction of N-methyldiphenylamine. The process includes the following steps:

[0115] (1) 30 mL of catalyst A1 was crushed into 20-40 mesh and loaded into a fixed bed reactor. It was activated at 230-250 °C for 6 h. Then, the prepared raw materials (methanol and diphenylamine with a molar ratio of 6:1, in which the water content of methanol accounts for 0.5 wt% of the weight of methanol) 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 208°C and the reaction pressure was 4.2 MPa. According to Aspen Plus calculations, under these conditions, the proportion of methanol passing through the catalyst bed in liquid form was 97 wt%;

[0116] The reaction mixture of methanol and diphenylamine is condensed to 50°C at the bottom of a fixed-bed reactor and then enters a gas-liquid separator for gas-liquid separation. The separated liquid phase is subjected to reduced pressure distillation at -75 to -85 kPa to remove unreacted methanol, thereby obtaining a mixture of diphenylamine and N-methyldiphenylamine that is liquefied at room temperature. The unreacted methanol is dehydrated and purified and then recycled to the above step for use as an alkylating agent.

[0117] Figure 1 is a mass spectrum fragmentation diagram of N-methyldiphenylamine prepared in this example, wherein peak 1a is the molecular peak of N-methyldiphenylamine, peak 2 is the carbon cation fragmentation peak after demethylation of N-methyldiphenylamine, peak 3 is the fragmentation peak after dephenylation of N-methyldiphenylamine, and peak 4 is the fragmentation peak of benzene. These molecular peaks and fragmentation peaks prove that the intermediate N-methyldiphenylamine was successfully obtained in this example. Figure 2 is a chromatogram of a mixture of diphenylamine and N-methyldiphenylamine prepared in this example, wherein peak 1 is N-methyldiphenylamine, peak 2 is Peak 3 is diphenylamine, Peak 4 is Peak 5 represents methanol, and peak 6 represents water. Based on area normalization analysis and calculated as diphenylamine (mol %), the diphenylamine conversion is 54.10%, and the selectivity for N-methyldiphenylamine is 81.91%. As shown in Figure 2 , the alkylation reaction also occurs on the benzene ring, generating a product with a methyl group on the benzene ring (peak 4). Simultaneously, the generated N-methyldiphenylamine or the product of peak 4 undergoes further alkylation, introducing a methyl group on the benzene ring or the N atom, yielding the product represented by peak 2.

[0118] (2) The mixture of liquefied diphenylamine and N-methyldiphenylamine was subjected to batch distillation for purification at -94 to -96 kPa. The distillation was carried out using a packed tower with an effective packing height of 2.5 m and a fixed reflux ratio of 3. A fraction having a top temperature of 170 to 178° C. was obtained, namely, N-methyldiphenylamine (purity of about 97 wt%).

[0119] (3) 30 mL of catalyst B1 was loaded into a fixed bed reactor, and hydrogen and N-methyldiphenylamine obtained in step (2) were introduced into the reactor for coupling dehydrogenation reaction at a liquid hourly space velocity of 0.2 h -1 , reaction temperature 260 ° C, reaction pressure 0.12 MPa (absolute pressure), the molar ratio of N-methyldiphenylamine to hydrogen is 1:10; the reaction material is condensed to 70 ° C at the reactor outlet temperature, a certain amount of N-methylpyrrolidone (NMP) is added to dissolve it, and then gas chromatography-mass spectrometry analysis is performed while hot. The analysis results are shown in Figures 3 and 4.

[0120] Figure 3 is a mass spectrum fragmentation diagram of N-methylcarbazole obtained in this example, wherein peak 1a is the molecular peak of N-methylcarbazole, peak 2 is the fragment peak of carbazole ion, and peak 3 is the fragment peak of biphenyl ion. These molecular peaks and ion fragment peaks prove that N-methylcarbazole was successfully obtained in this example. Figure 4 is a GC-MS analysis spectrum of the coupled dehydrogenation product of N-methyldiphenylamine and diphenylamine mixture in this example, wherein peak 1 is N-methyldiphenylamine, peak 2 is diphenylamine, peak 3 is NMP (solvent), peak 4 is a byproduct with a molecular weight of 197, peak 5 is N-methylcarbazole, peak 6 is carbazole, and peak 7 is methanol. According to the area normalization method, the conversion rate of N-methyldiphenylamine is 81.33%, the selectivity of N-methylcarbazole is 67.41%, and the selectivity of carbazole is 12.11%.

[0121] Example 2

[0122] In this embodiment, ethanol is selected as an alkylating agent to perform an N-alkylation reaction with diphenylamine to prepare N-ethyldiphenylamine, and then N-ethylcarbazole is prepared by an intramolecular coupling dehydrogenation reaction of N-ethyldiphenylamine. The method comprises the following steps:

[0123] (1) 30 mL of catalyst A5 was crushed into 20-40 mesh and loaded into a fixed bed reactor. It was activated at 230-250 °C for 2 h. Then, the prepared raw materials (ethanol and diphenylamine with a molar ratio of 6:1, in which the water content of ethanol accounts for 0.5 wt% of the mass of ethanol) were introduced from the top of the reactor through a metering pump at a liquid hourly space velocity of 0.9 h -1 The reaction temperature was set at 248°C and the reaction pressure was 6 MPa. According to Aspen Plus calculations, under these conditions, 98 wt% of ethanol passed through the catalyst bed in liquid form.

[0124] The reaction mixture of ethanol and diphenylamine is condensed to 60°C at the bottom of a fixed-bed reactor and then passed into a gas-liquid separator for gas-liquid separation. The separated liquid phase is subjected to reduced pressure distillation at -75 to -85 kPa to remove unreacted ethanol, thereby obtaining a mixture of diphenylamine and N-ethyldiphenylamine that is liquefied at room temperature. The unreacted ethanol is dehydrated and purified and then recycled to the above step for use as an alkylating agent.

[0125] Figure 5 is a mass spectrum fragmentation diagram of N-ethyldiphenylamine obtained in this embodiment, wherein peak 1b is the molecular peak of N-ethyldiphenylamine, peak 1a is the N-methyldiphenylamine-like fragment peak formed after demethylation of N-ethyldiphenylamine, peak 2 is the fragment peak of diphenylamine cation after deethylation of N-ethyldiphenylamine, peak 3 is the fragment peak of diphenylamine cation after further dephenylation, and peak 4 is the fragment peak of benzene. These molecular peaks and fragment peaks prove that the intermediate N-ethyldiphenylamine was successfully obtained in this embodiment. Figure 6 is a chromatogram of a mixture of diphenylamine and N-ethyldiphenylamine in this embodiment, wherein peak 1 is N-ethyldiphenylamine, peak 2 is Peak 3 is diphenylamine, and peak 4 is Peak 5 is Peak 6 is ethanol. As shown in FIG6 , according to the area normalization method and calculated based on diphenylamine (mol %), the diphenylamine conversion rate is 67.79%, and the selectivity of N-ethyldiphenylamine is 75.65%.

[0126] (2) A mixture of diphenylamine and N-ethyldiphenylamine was subjected to intermittent distillation purification at -94 to -96 kPa using a packed tower with an effective packing height of 2.5 m and a fixed reflux ratio of 4. A fraction having a top temperature of 181 to 184° C. was obtained, which contained N-ethyldiphenylamine (purity of approximately 94 wt%).

[0127] (3) 30 mL of catalyst B2 was loaded into a fixed bed reactor, and hydrogen and N-ethyldiphenylamine obtained in step (2) were introduced into the reactor for coupling dehydrogenation reaction at a liquid hourly space velocity of 0.25 h -1 , reaction temperature 290 ° C, reaction pressure 0.12 MPa (absolute pressure), the molar ratio of N-ethyldiphenylamine to hydrogen is 1:10; the reaction material is condensed to 80 ° C at the reactor outlet temperature, a certain amount of N-methylpyrrolidone (NMP) is added to dissolve it, and then analyzed by gas chromatography-mass spectrometry. The analysis results are shown in Figures 7 and 8.

[0128] Figure 7 is a mass spectrometry fragmentation diagram of N-ethylcarbazole prepared in this example, wherein peak 1b is the molecular peak of N-ethylcarbazole, peak 1a is the fragment peak of N-methylcarbazole ion, peak 2 is the fragment peak of carbazole ion; peak 3 is the fragment peak of biphenyl ion. These molecular and fragment peaks demonstrate that N-ethylcarbazole was successfully obtained in this example. Figure 8 is a GC-MS analysis spectrum of the coupled dehydrogenation product of a mixture of N-ethyldiphenylamine and diphenylamine in this example, wherein peak 1 is N-ethyldiphenylamine, peak 2 is diphenylamine, peak 3 is the solvent NMP, peak 4 is the product with a molecular weight of 197, peak 5 is N-ethylcarbazole, peak 6 is carbazole, and peak 7 is ethanol. According to the area normalization method, the conversion rate of N-ethyldiphenylamine is 71.12%, the selectivity of N-ethylcarbazole is 56.51%, and the selectivity of carbazole is 23.04%.

[0129] Example 3

[0130] In this embodiment, propanol is selected as an alkylating agent to carry out an N-alkylation reaction with diphenylamine to prepare N-propyldiphenylamine, and then N-propylcarbazole is prepared by an intramolecular coupling dehydrogenation reaction of N-propyldiphenylamine. The method comprises the following steps:

[0131] (1) 30 mL of catalyst A1 was crushed into 20-40 mesh and loaded into a fixed bed reactor. It was activated at 230-250 °C for 4 h. Then, the prepared raw materials (propanol and diphenylamine with a molar ratio of 6:1, in which the water content of propanol accounts for 0.2 wt% of the mass of propanol) were introduced from the top of the reactor through a metering pump at a liquid hourly space velocity of 0.7 h -1 The reaction temperature was set at 225°C and the reaction pressure was set at 4.5 MPa. According to Aspen Plus calculations, under these conditions, the proportion of propanol passing through the catalyst bed in liquid form was 95 wt%;

[0132] After the bottom of the fixed-bed reactor is condensed to 60°C, a sample is taken out of the gas-liquid separator and unreacted propanol is removed by reduced pressure distillation at -75 to -85 kPa to obtain a mixture of diphenylamine and N-propyldiphenylamine that is liquefied at room temperature. The unreacted propanol is dehydrated and purified and then recycled to the above step for use as an alkylating agent.

[0133] Figure 9 is a mass spectrum fragmentation diagram of N-propyldiphenylamine obtained in this example, wherein peak 1c is the molecular peak of N-propyldiphenylamine, peak 1a is the N-methyldiphenylamine-like fragment peak formed after N-propyldiphenylamine is deethylated, peak 2 is the fragment peak of diphenylamine cation after N-propyldiphenylamine is depropylated, peak 3 is the fragment peak of diphenylamine cation after further dephenylation, and peak 4 is the fragment peak of benzene. These molecular peaks and fragment peaks prove that the intermediate N-propyldiphenylamine was successfully obtained in this example. Figure 10 is a chromatogram of a mixture of diphenylamine and N-propyldiphenylamine obtained in this example, wherein peak 1 is N-propyldiphenylamine, peak 2 is Peak 3 is diphenylamine, and peak 4 is propanol. As shown in FIG10 , according to the area normalization method and calculated based on diphenylamine (mol %), the diphenylamine conversion rate is 70.97%, and the selectivity of N-propyldiphenylamine is 87.01%.

[0134] (2) The mixture of diphenylamine and N-propyldiphenylamine was subjected to intermittent distillation and purification at -99 to -100 kPa. The distillation was carried out using a packed tower with an effective packing height of 2.5 m and a fixed reflux ratio of 8. A fraction with a top temperature of 176 to 179° C. was obtained, which was N-propyldiphenylamine (purity of about 97 wt%).

[0135] (3) 30 mL of catalyst B1 was loaded into a fixed bed reactor, and hydrogen and N-propyldiphenylamine obtained in step (2) were introduced into the reactor for coupling dehydrogenation reaction at a liquid hourly space velocity of 0.12 h -1 , reaction temperature 270 ° C, reaction pressure 0.04 MPa (absolute pressure), the molar ratio of N-propyldiphenylamine to hydrogen is 1:8; the reaction material is condensed to 80 ° C at the reactor outlet temperature, N-methylpyrrolidone (NMP) is added for dissolution, and then analyzed by gas chromatography-mass spectrometry. The analysis results are shown in Figures 11 and 12.

[0136] Figure 11 is a mass spectrometry fragmentation diagram of N-propylcarbazole prepared in this example, wherein peak 1c is the molecular peak of N-propylcarbazole, peak 1a is the fragment peak of N-methylcarbazole ion, peak 2 is the fragment peak of carbazole, and peak 3 is the fragment peak of biphenyl ion. These molecular peaks and ion fragment peaks demonstrate that N-propylcarbazole was successfully obtained in this example. Figure 12 is a GC-MS analysis spectrum of the coupled dehydrogenation product of a mixture of N-propyldiphenylamine and diphenylamine in this example, wherein peak 1 is N-propyldiphenylamine, peak 2 is diphenylamine, peak 3 is the solvent NMP, peak 4 is a byproduct with a molecular weight of 225, peak 5 is N-propylcarbazole, peak 6 is carbazole, and peak 7 is propanol. According to the area normalization method, the conversion rate of N-propyldiphenylamine was 69.46%, the selectivity of N-propylcarbazole was 40.32%, and the selectivity of carbazole was 34.17%.

[0137] Comparative Example 1

[0138] Except for the following contents, the rest are the same as Example 1.

[0139] In step (1), the reaction temperature was set to 208° C. and the reaction pressure was set to 1.0 MPa.

[0140] According to Aspen Plus calculations, under these conditions, the proportion of methanol passing through the catalyst bed in liquid form is 22 wt%.

[0141] The results showed that the reaction mixture sample was taken from the bottom of the fixed bed (sampled at 24 to 26 hours), and the conversion of diphenylamine was 14.10% based on diphenylamine (mol%), and the selectivity of N-methyldiphenylamine was 31.82%.

[0142] Comparative Example 2

[0143] Except for the following contents, the rest are the same as Example 1.

[0144] Methanol with a water content of 11 wt% was used as the alkylating agent.

[0145] The results showed that the reaction mixture sample was taken from the bottom of the fixed bed (sampled at 24-26 hours), and the conversion of diphenylamine was 28.31% and the selectivity of N-methyldiphenylamine was 78.72% calculated as diphenylamine (mol%).

[0146] Comparative Example 3

[0147] Except for the following contents, the rest are the same as Example 1.

[0148] In step (1), the prepared raw materials are fed into the fixed bed reactor from the bottom of the reactor.

[0149] The results showed that the reaction mixture sample was taken from the top of the fixed bed (sampled at 24 to 26 hours), and the conversion of diphenylamine was 38.93% based on diphenylamine (mol%), and the selectivity of N-methyldiphenylamine was 63.92%.

[0150] Comparative Example 4

[0151] Except for the following contents, the rest are the same as Example 1.

[0152] The introduction of hydrogen is omitted in step (3).

[0153] The results showed that the conversion rate of N-methyldiphenylamine was 21.33%, the selectivity of N-methylcarbazole was 31.01%, and the selectivity of carbazole was 21.42%.

[0154] Obviously, the above embodiments and comparative examples are merely examples for clarity of explanation and are not intended to limit the embodiments. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. Use of a catalyst composition in catalyzing the reaction of diphenylamine and alkyl alcohol to prepare N-alkylcarbazole, the catalyst composition comprising catalyst A and catalyst B: The catalyst A comprises an active component MA and a carrier LA, wherein the active component MA is selected from at least one of Ni, Co, Ir, Pt, Pd, and Ru, and the carrier LA is at least one of Al2O3, activated carbon, SiO2, ZrO2, and SnO2; The catalyst B includes an active component MB and a carrier LB, wherein the active component MB is selected from at least one of Ni, Pt, Pd, Fe, and Cu, and the carrier LB is at least one of TiO2, Al2O3, SiO2, activated carbon, ZrO2, molecular sieve, Mg-Al hydrotalcite, NiAl2O4 spinel, and CoAl2O4 spinel.

2. The use according to claim 1, characterized in that: In the catalyst A, the content of the active component MA is 0.5-36 wt %; and / or the active component MA is at least one of Ni, Co, Ru, and Ir; and / or the content of the carrier LA is 64-99.5 wt %.

3. The use according to claim 1, characterized in that: The catalyst A further includes an additive NA, and the additive NA is at least one of Zn, Cu, an oxide of an alkali metal or an alkaline earth metal, or Sn.

4. The use according to claim 3, characterized in that: In the catalyst A, the content of the active component MA is 10-30 wt%, the content of the carrier LA is 69-89 wt%, and the content of the auxiliary agent NA is 0.05-1 wt%.

5. The use according to claim 4, characterized in that: The composition of the catalyst A is: 21.3 wt% Co, 0.15 wt% MgO and 78.55 wt% Al2O3; or, 30 wt% Ni, 1.0 wt% ZnO and 69 wt% SiO2.

6. The use according to claim 2, characterized in that: The composition of the catalyst A is: 0.5 wt% Ir and 99.5 wt% Al2O3.

7. The use according to any one of claims 1 to 6, characterized in that: In the catalyst B, the content of the active component MB is 0.1 to 13 wt %; and / or the content of the carrier LB is 87 to 99.9 wt %.

8. The use according to claim 7, characterized in that: The catalyst B further includes a promoter NB, and the promoter NB is an oxide of at least one of Mn, Sn, Re, Mo, and K.

9. The use according to claim 8, characterized in that: In the catalyst B, the content of the active component MB is 1-10 wt%; and / or the content of the carrier LB is 90-95 wt%; and / or the content of the additive NB is 0.2-6 wt% in terms of metal.

10. The use according to claim 9, characterized in that: The additive NB is an oxide of Sn and K, and the content of Sn is 0.1-1 wt% of the mass of the catalyst B, and the content of K is 0.1-1 wt% of the mass of the catalyst B, calculated as metal; and / or, The active component MB is Pt and Ni, the Pt content is 0.1-3 wt% of the mass of the catalyst B, and the Ni content is 1-10 wt% of the mass of the catalyst B.

11. The use according to claim 8, characterized in that: The composition of the catalyst B is: Pt 1wt%, Re 0.2wt%, Sn 0.4wt%, Mn 2wt%, Al2O3 94% and ligand oxygen of Re, Sn and Mn 2.4wt%; or, Pt 0.8wt%, Ni 2wt%, Sn 0.1wt%, K 0.1wt%, TiO2 96.9% and ligand oxygen of Sn and K 0.1wt%.

12. A method for preparing N-alkyl carbazole, characterized in that: The steps include: S1. In the presence of catalyst A, diphenylamine reacts with an alkyl alcohol having a water content of not more than 10 wt %, wherein more than 85 wt % of the alkyl alcohol is in liquid state during the reaction, to obtain N-alkyldiphenylamine; S2, in the presence of catalyst B and hydrogen, N-alkyl diphenylamine undergoes a coupling dehydrogenation reaction to obtain N-alkyl carbazole; The catalyst A comprises an active component MA and a carrier LA, wherein the active component MA is selected from at least one of Ni, Co, Ir, Pt, Pd, and Ru, and the carrier LA is at least one of Al2O3, activated carbon, SiO2, ZrO2, and SnO2; The catalyst B includes an active component MB and a carrier LB, wherein the active component MB is selected from at least one of Ni, Pt, Pd, Fe, and Cu, and the carrier LB is at least one of TiO2, Al2O3, SiO2, activated carbon, ZrO2, molecular sieve, Mg-Al hydrotalcite, NiAl2O4 spinel, and CoAl2O4 spinel.

13. The method for preparing N-alkyl carbazole according to claim 12, characterized in that: During the reaction, more than 95 wt % of the alkyl alcohol is in liquid state; and / or the water content of the alkyl alcohol is not higher than 0.5 wt %.

14. The method for preparing N-alkyl carbazole according to claim 12, characterized in that: In step S1, the reaction temperature is 170-270°C, and the reaction pressure is 2-12 MPa.

15. The method for preparing N-alkyl carbazole according to claim 14, characterized in that: In step S1, the reaction temperature is 200-250° C., and the reaction pressure is 4-8 MPa.

16. The method for preparing N-alkyl carbazole according to claim 12, characterized in that: When a fixed bed reactor is used in step S1, the reaction raw materials enter the catalyst bed from the top of the reactor, and the volume liquid hourly space velocity is 0.1 to 1.2 h -1 ; or, When a kettle reactor is used in step S1, the mass of the catalyst A is 1 to 10 wt % of the total mass of the reaction raw materials, and the reaction time is 6 to 24 h.

17. The method for preparing N-alkyl carbazole according to claim 16, characterized in that: In step S1, the volume liquid hourly space velocity is 0.6 to 0.9 h -1 ; Alternatively, the mass of the catalyst A is 6 to 8 wt% of the total mass of the reaction raw materials, and the reaction time is 12 to 24 h.

18. The method for preparing N-alkyl carbazole according to claim 12, characterized in that: In step S1, the molar ratio of the alkyl alcohol to the diphenylamine is 2 to 15:

1.

19. The method for preparing N-alkyl carbazole according to claim 18, characterized in that: In step S1, the molar ratio of the alkyl alcohol to the diphenylamine is 6 to 15:

1.

20. The method for preparing N-alkyl carbazole according to claim 12, characterized in that: The alkyl alcohol is selected from monohydric alcohols having 1 to 5 carbon atoms.

21. The method for preparing N-alkyl carbazole according to claim 12, characterized in that: In step S2, the reaction temperature is 200 to 300°C, and the reaction pressure is -0.1 to 0.2 MPa.

22. The method for preparing N-alkyl carbazole according to claim 21, characterized in that: In step S2, the reaction temperature is 230-270°C, and the reaction pressure is 5-150 KPa.

23. The method for preparing N-alkyl carbazole according to claim 12, characterized in that: The volumetric space velocity when feeding liquid in step S2 is 0.01~0.8h -1 .

24. The method for preparing N-alkyl carbazole according to claim 12, characterized in that: In step S2, the molar ratio of the N-alkyl diphenylamine to the hydrogen is 1:1-30.

25. The method for preparing N-alkyl carbazole according to claim 24, characterized in that: In step S2, the molar ratio of the N-alkyl diphenylamine to the hydrogen is 1:4-20.

26. The method for preparing N-alkyl carbazole according to claim 12, characterized in that: In step S2, the purity of the N-alkyl diphenylamine is 95.0-99.9%, wherein the diphenylamine content is not higher than 3wt%.

27. The method for preparing N-alkyl carbazole according to claim 12, characterized in that: In the catalyst A, the content of the active component MA is 0.5-36 wt %; and / or the active component MA is at least one of Ni, Co, Ru, and Ir; and / or the content of the carrier LA is 64-99.5 wt %.

28. The method for preparing N-alkyl carbazole according to claim 27, characterized in that: The catalyst A further includes an additive NA, and the additive NA is at least one of Zn, Cu, an oxide of an alkali metal or an alkaline earth metal, or Sn.

29. The method for preparing N-alkyl carbazole according to claim 28, characterized in that: In the catalyst A, the content of the active component MA is 10-30 wt%, the content of the carrier LA is 69-89 wt%, and the content of the auxiliary agent NA is 0.05-1 wt%.

30. The method for preparing N-alkyl carbazole according to claim 29, characterized in that: The composition of the catalyst A is: 21.3 wt% Co, 0.15 wt% MgO and 78.55 wt% Al2O3; or, 30 wt% Ni, 1.0 wt% ZnO and 69 wt% SiO2.

31. The method for preparing N-alkyl carbazole according to claim 27, characterized in that: The composition of the catalyst A is: 0.5 wt% Ir and 99.5 wt% Al2O3.

32. The method for preparing N-alkyl carbazole according to claim 12, characterized in that: In the catalyst B, the content of the active component MB is 0.1 to 13 wt %; and / or the content of the carrier LB is 87 to 99.9 wt %.

33. The method for preparing N-alkyl carbazole according to claim 32, characterized in that: The catalyst B further includes a promoter NB, and the promoter NB is an oxide of at least one of Mn, Sn, Re, Mo, and K.

34. The method for preparing N-alkyl carbazole according to claim 33, characterized in that: In the catalyst B, the content of the active component MB is 1-10 wt %, the content of the carrier LB is 90-95 wt %, and the content of the auxiliary agent NB is 0.2-6 wt % in terms of metal.

35. The method for preparing N-alkyl carbazole according to claim 34, characterized in that: The additive NB is an oxide of Sn and K, and the content of Sn is 0.1-1 wt% of the mass of the catalyst B, and the content of K is 0.1-1 wt% of the mass of the catalyst B, calculated as metal; and / or, The active component MB is Pt and Ni, the Pt content is 0.1-3 wt% of the mass of the catalyst B, and the Ni content is 1-10 wt% of the mass of the catalyst B.

36. The method for preparing N-alkyl carbazole according to claim 32, characterized in that: The composition of the catalyst B is: Pt 1wt%, Re 0.2wt%, Sn 0.4wt%, Mn 2wt%, Al2O3 94% and ligand oxygen of Re, Sn and Mn 2.4wt%; or, Pt 0.8wt%, Ni 2wt%, Sn 0.1wt%, K 0.1wt%, TiO2 96.9% and ligand oxygen of Sn and K 0.1wt%.

37. The method for preparing N-alkyl carbazole according to any one of claims 12 to 36, characterized in that: Step S1 also includes a purification step: performing a first separation on a reaction mixture of diphenylamine and alkyl alcohol to obtain a first separation and a second separation; Dehydrating the first separated product to obtain unreacted alkyl alcohol, which is recycled as an alkylating agent; The second separated product is subjected to a second separation to obtain N-alkyldiphenylamine and unreacted diphenylamine, respectively. The unreacted diphenylamine is recycled as a substrate for alkylation reaction.

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