Synthesis method of N-alkyl carbazole

Abstract

The present invention relates to the technical field of preparation of N-alkyl carbazole, and discloses a synthesis method of N-alkyl carbazole, wherein the synthesis method comprises: in the presence of hydrogen, carbazole and alkyl aldehyde are contacted with a catalyst; the catalyst comprises a carrier, and an active metal component and an optional auxiliary component loaded on the carrier, wherein the active metal component is selected from at least one of group VIII and group IB metal elements, and the auxiliary component is selected from at least one of alkali metals, alkaline earth metals, group IVB metals, group VIIB metals and group VIII non-precious metals. The process can realize the continuous production of N-alkyl carbazole, the target product has high selectivity, and is in line with the green atomic economy.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of N-alkyl carbazole, and in particular to a method for synthesizing N-alkyl carbazole. Background Art

[0002] N-ethylcarbazole is a white needle-shaped crystal that is soluble in hot ethanol, ether, acetone, chlorobenzene and pentane, but insoluble in water. It is often used as a dye intermediate, agricultural chemical, and reagent. In the dye industry, it is used to produce Permanent Purple RL, Cyan Haichang Blue, etc. Taking N-ethylcarbazole as an example, the preparation routes of N-alkylcarbazole with the most industrial value are: ethyl chloride method, diethyl sulfate method, and diethyl carbonate method. Among them, the ethyl chloride method has the most industrial value and enterprises have completed industrial production as early as the 1990s.

[0003] (1) Haloalkane method

[0004] The halogenated alkyl method mainly utilizes carbazole to react with bromoethane or chloroethane at high temperature to generate N-ethylcarbazole. For example, EP0858995A1 discloses using o-dichlorobenzene as solvent, N,N,N',N'-tetramethyl-1,3-propylenediamine as catalyst, chloroethane and carbazole reaction, N-ethylcarbazole yield 99.3%, but the whole process is accompanied by the use of a large amount of toxic solvents, and the environmental pressure is relatively large. CN1184202C discloses a method using benzyltriethylammonium chloride, polyethylene glycol, surfactant and ethanol as phase transfer catalyst, using benzene and NaOH aqueous solution as mixed solvent, carbazole and bromoethane reaction, N-ethylcarbazole yield up to 98%. However, the above reaction process all generates a large amount of hydrochloric acid or bromic acid, so potassium hydroxide is often added in industry as acid binding agent neutralizing acid, but this method can cause a large amount of waste salt to be generated, and the waste liquid treatment difficulty is high.

[0005] (2) Diethyl sulfate method

[0006] US2783244A1 discloses a process for purifying anthracene and preparing N-ethylcarbazole, wherein anthracene pitch is used as a raw material, anthracene and carbazole are separated by a washing and crystallization method, and then anthracene and carbazole mixture are subjected to alkylation reaction with diethyl sulfate, acetone and 96% potassium hydroxide mixed solution as solvent for 2.5 hours. After the reaction, the product is purified to obtain anthracene with a purity of 93% and N-ethylcarbazole with a purity of 87%. The diethyl sulfate used in this process is toxic, a large amount of organic solvents are used, waste salts are generated, and the reaction time is long, so the application of diethyl sulfate is not as extensive as the alkyl halide method.

[0007] (3) Diethyl carbonate method

[0008] US5393894A1 and EP0635490A1 disclose a method for preparing N-ethylcarbazole, wherein 96% pure carbazole is used as a raw material, ethyl carbonate is used as an alkylating agent, the molar ratio of carbazole to ethyl carbonate is 1.1-2.5:1, and the reaction is carried out at 130-320°C for 24 hours in the presence of potassium hydroxide, potassium carbonate or potassium ethoxide, and then the product is distilled and purified to obtain a product with a purity of 96%. However, the reaction temperature of this process is high and the reaction time is long.

[0009] In summary, most of the N-alkyl carbazole preparation methods disclosed in the prior art have problems such as high environmental pressure, long reaction routes, and inability to achieve continuous production. Therefore, it is imperative to develop a low-cost, environmentally friendly, and commercially scalable synthesis route for high-quality N-alkyl carbazole. Summary of the invention

[0010] The purpose of the present invention is to overcome the problems of high raw material cost, poor environmental friendliness, complex preparation method and difficulty in continuous production in the prior art, and to provide a synthesis method of N-alkyl carbazole, which is environmentally friendly, highly selective, low cost and free of secondary salts.

[0011] In order to achieve the above object, the present invention provides a method for synthesizing N-alkyl carbazole, the method comprising: contacting carbazole and alkyl aldehyde with a catalyst in the presence of hydrogen;

[0012] The catalyst comprises a carrier, and an active metal component and an optional auxiliary component supported on the carrier, wherein the active metal component is selected from at least one of Group VIII and Group IB metal elements, and the auxiliary component is selected from at least one of alkali metals, alkaline earth metals, Group IVB metals, Group VIIB metals and Group VIII non-precious metals.

[0013] Preferably, the active metal component is selected from at least one of Ni, Fe, Co and Cu;

[0014] Wherein, based on the total amount of the catalyst, the content of the active metal component in terms of element is 10-30wt%, the content of the auxiliary component in terms of oxide is 0-10wt%, and the content of the carrier is 60-90wt%.

[0015] Preferably, the active metal component is selected from at least one of Pd, Pt and Ru;

[0016] Wherein, based on the total amount of the catalyst, the content of the active metal component in terms of element is 0.1-5wt%, the content of the auxiliary component in terms of oxide is 0-10wt%, and the content of the carrier is 85-99.9wt%.

[0017] The method for synthesizing N-alkyl carbazole provided by the present invention breaks through the inherent synthesis route of using halogenated hydrocarbons as alkylating agents in the prior art, creatively proposes that carbazole and alkyl aldehyde generate an imine intermediate under the action of a supported catalyst containing an active metal component selected from metal elements of Group VIII and Group IB, and further reduce the imine intermediate to N-alkyl carbazole in the presence of hydrogen. The method has technical versatility and can produce various types of N-alkyl carbazole.

[0018] The synthesis method provided by the present invention does not require the use of other organic solvents, greatly reduces the generation of organic waste liquid, reduces environmental pollution and operation difficulty, avoids the introduction of halogen, and halogen-free N-alkylcarbazole can be used as a hydrogen storage carrier. The process can realize the continuous production of N-alkylcarbazole, and the catalyst is easy to separate and regenerate, the product separation difficulty is low, and the traditional organic solvent extraction product step is avoided, with low pollution, environmental friendliness, and high product yield. The preparation method has high selectivity for the target product and is in line with the green atomic economy. DETAILED DESCRIPTION

[0019] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0020] The present invention provides a method for synthesizing N-alkyl carbazole, which comprises: in the presence of hydrogen, contacting carbazole and alkyl aldehyde with a catalyst;

[0021] The catalyst comprises a carrier, and an active metal component and an optional auxiliary component supported on the carrier, wherein the active metal component is selected from at least one of Group VIII and Group IB metal elements, and the auxiliary component is selected from at least one of alkali metals, alkaline earth metals, Group IVB metals, Group VIIB metals and Group VIII non-precious metals.

[0022] In the present invention, the selection range of the types of the alkyl aldehyde is relatively wide, and those skilled in the art can select the corresponding alkyl aldehyde according to the needs of the target N-alkyl carbazole.

[0023] According to some preferred embodiments of the present invention, the structure of the alkyl aldehyde is as shown in formula (1),

[0024] Formula (1),

[0025] Wherein, R is selected from C1-C11 alkyl groups, preferably C1-C4 straight-chain or branched alkyl groups, such as methyl, ethyl, propyl, isopropyl, butyl, etc.

[0026] According to some preferred embodiments of the present invention, the alkyl aldehyde is an alkyl aldehyde having 2-5 carbon atoms, preferably at least one of acetaldehyde, propionaldehyde, isobutyraldehyde, n-butyraldehyde and valeraldehyde.

[0027] The synthesis method of N-alkyl carbazole provided by the present invention breaks through the inherent synthesis route of using halogenated hydrocarbons as alkylating agents in the prior art, and creatively proposes that carbazole and alkyl aldehyde generate an imine intermediate under the action of a supported catalyst containing an active metal component selected from metal elements of Group VIII and Group IB, and further reduce the imine intermediate to N-alkyl carbazole in the presence of hydrogen. Taking N-ethyl carbazole as an example, the synthesis route of the synthesis method provided by the present invention is shown in reaction formula (2):

[0028] Formula (2).

[0029] Compared with the existing haloalkane synthesis route, the synthesis method provided by the present invention avoids the introduction of halogens, and the halogen-free N-alkylcarbazole can be used as a hydrogen storage carrier. In addition, the synthesis method provided by the present invention does not require the use of additional organic solvents, which greatly reduces the generation of organic waste liquid, reduces environmental pollution and reduces operational difficulty.

[0030] According to some preferred embodiments of the present invention, the molar ratio of the alkyl aldehyde to carbazole is 2-20:1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1 and other typical but non-limiting mass ratios or any range between the two. Preferably, the molar ratio of the alkyl aldehyde to carbazole is 5-15:1. Controlling the molar ratio of the alkyl aldehyde to carbazole within the above preferred range is conducive to improving the carbazole conversion rate and the alkyl carbazole selectivity.

[0031] The preparation method of the present invention can be carried out in any conventional device in the art, and the present invention has no particular limitation thereto. For example, a fixed bed reactor or a kettle reactor can be used.

[0032] According to some preferred embodiments of the present invention, the contact is carried out in a fixed bed reactor, and the contact conditions include: the reaction temperature is 180-250°C, preferably 200-230°C, the hydrogen pressure is 0.2-3MPa, preferably 0.5-2MPa, the total volume liquid hourly space velocity of the raw material is 0.05-0.3h -1 , preferably 0.1-0.2h-1 .

[0033] According to other preferred embodiments of the present invention, the contacting is carried out in a tank reactor, and the contacting conditions include: the reaction temperature is 220-270°C, preferably 240-260°C, the reaction pressure is 0.2-3MPa, preferably 0.5-2MPa; the mass ratio of catalyst to carbazole is (0.01-0.05):1, preferably (0.03-0.04):1, and the reaction time is 1-5h, preferably 2-3h.

[0034] The inventors of the present invention have found in their research that the hydrogenation step of the imine is the rate-limiting step of the reaction, and preferably the reaction hydrogen pressure is 0.2-3Mpa, which is conducive to improving the selectivity and yield of N-alkyl carbazole. When the hydrogen pressure is high, the product N-alkyl carbazole is further hydrogenated to obtain hydrogen-rich N-alkyl carbazole through GC-MS detection, and hydrogen is a dangerous gas, and too high hydrogen pressure increases safety risks.

[0035] According to the present invention, preferably, the preparation method further comprises optionally purifying the product obtained by the contacting. The purification can be carried out in any conventional manner in the art, and the present invention has no particular limitation thereto. Preferably, the purification can be carried out by distillation. The above preferred embodiment is adopted, which has low pollution and is environmentally friendly. Compared with the conventional alkyl halide synthesis method, the reaction system of the preparation method provided by the present invention does not contain organic substances such as benzene, acetone, and o-dichlorobenzene, so there is no need to carry out an additional organic solvent extraction step, and the product can be directly purified by distillation.

[0036] According to the present invention, the catalyst comprises a carrier, and an active metal component loaded on the carrier. Preferably, the catalyst further comprises an auxiliary component different from the active metal component. The auxiliary component is selected from at least one of alkali metals, alkaline earth metals, IVB group metals, VIIB group metals and VIII group metals. In the catalyst, the auxiliary component exists in the form of an oxide. The synergistic effect of the auxiliary component and the active metal component is beneficial to improving the catalyst activity, and is beneficial to preventing the active center metal from sintering and improving the service life of the catalyst. According to the present invention, in the catalyst, the auxiliary component exists in the form of an oxide.

[0037] According to some preferred embodiments of the present invention, the auxiliary component is selected from at least one of Na, Mg, Zn, Zr, Mn, Co, K and Cs, preferably at least one of Mg, Co, K and Zn.

[0038] In the present invention, the active metal component is selected from at least one of Group VIII and Group IB metal elements, and may be Group VIII and Group IB noble metals and / or non-noble metal elements. Preferably, the active metal component is selected from at least one of Ni, Fe, Co, Cu, Pd, Pt and Ru.

[0039] According to some preferred embodiments of the present invention, the active metal component is selected from at least one of Group VIII and Group IB non-precious metal elements, preferably at least one of Ni, Fe, Co and Cu.

[0040] Preferably, based on the total amount of the catalyst, the content of the active metal component in terms of element is 10-30wt%, preferably 15-25wt%, the content of the auxiliary component in terms of oxide is 0-10wt%, preferably 2-8wt%, and the content of the carrier is 60-90wt%, preferably 67-83wt%.

[0041] According to other preferred embodiments of the present invention, the active metal component is selected from at least one of the noble metal elements of Group VIII and Group IB, preferably at least one of Ru, Rh, Ir, Pt, Ag, Au and Pd, and further preferably at least one of Pd, Pt and Ru.

[0042] Preferably, based on the total amount of the catalyst, the content of the active metal component in terms of element is 0.1-5wt%, preferably 0.1-1wt%, the content of the auxiliary component in terms of oxide is 0-10wt%, preferably 2-8wt%, and the content of the carrier is 85-99.9wt%, preferably 91-97.9wt%.

[0043] In the present invention, the composition of the catalyst is tested by the ICP-OES method.

[0044] The present invention has a wide range of choices for the carrier in the catalyst, and any conventional catalyst carrier in the art can be applied to the present invention. For example, the carrier can be at least one of activated carbon, an oxide carrier and a molecular sieve.

[0045] According to some preferred embodiments of the present invention, the oxide support is selected from a single-component oxide support and / or a dual-component oxide support; the single-component oxide support is selected from at least one of Al2O3, CeO2, La2O3, MgO, SiO2, ZrO2, TiO2 and ZnO; more preferably at least one of Al2O3, ZrO2 and SiO2. The dual-component oxide support is selected from at least one of ZrO2-Al2O3, MgO-ZrO2, ZrO2-SiO2, ZnO-ZrO2, CeO2-ZrO2, SiO2-Al2O3, preferably at least one of ZrO2-Al2O3, SiO2-Al2O3 and ZrO2-SiO2. Preferably, the mass ratio of the two oxide components in the dual-component oxide support is 1-10:1-10.

[0046] The present invention has no particular limitation on the source of the oxide carrier, and a commercially available shaped carrier can be used. For example, the alumina carrier can be spherical alumina, and the specific surface area is preferably 100-200 m 2 / g. It can also be an oxide support prepared by a method known in the art.

[0047] The present invention has no particular limitation on the source of the catalyst, and the catalyst can be prepared by conventional methods in the art, such as impregnation method, precipitation method, ammonia evaporation method, sol-gel method, etc., which are well known to those skilled in the art. The present invention has no particular limitation on the specific preparation conditions and operation of the catalyst, and the catalyst preparation conditions known in the prior art can be used.

[0048] According to some preferred embodiments of the present invention, before the contacting, the step of activating the catalyst is further included, so that at least part of the active metal component exists in a single substance form.

[0049] Preferably, the activation treatment is carried out in a hydrogen-containing atmosphere, the temperature of the activation treatment is 230-255°C, preferably 240-250°C, the hydrogen pressure is 0.2-0.55MPa, preferably 0.25-0.35MPa, and the activation time is 1.5-2.5h, preferably 2-2.5h.

[0050] The present invention will be described in detail below through examples.

[0051] Unless otherwise specified, the raw materials used in the following examples are commercially available.

[0052] The following preparation examples are used to illustrate the preparation of the catalysts of the present invention.

[0053] Preparation Example 1 Preparation of Catalyst by Impregnation Method

[0054] 1.08 g of palladium nitrate solution (Pd mass fraction of 18.36%) and 1.975 g of cobalt nitrate hexahydrate were dissolved in 19.717 g of deionized water and then the metal mixture solution was poured into a 20 g Al2O3 carrier (spherical, specific surface area 165 m 2 / g) in a rotary evaporator, stirred for 30 min, and then allowed to stand at room temperature for 4 h. The catalyst was then dried at 120 °C for 12 h, and then calcined at 550 °C for 4 h. The resulting catalyst was crushed and sieved to 30-40 mesh, and the catalyst was recorded as Hywin-YL-1#.

[0055] Based on the total mass of the catalyst, the content of palladium element was 0.96 wt %, the content of cobalt oxide was 2.45 wt %, and the content of aluminum oxide carrier was 96.59 wt %.

[0056] Preparation Example 2 Preparation of Catalyst by Ammonia Evaporation

[0057] 19.87g nickel nitrate hexahydrate, 10.55g magnesium nitrate hexahydrate and 147.11g aluminum nitrate nonahydrate were dissolved in 150 ml deionized water and kept at a constant temperature of 65°C, then 1 mol / L ammonia water was added to a pH value of 11 and stirred for 30 minutes. Then the temperature was raised to 72°C, stirred and evaporated to a pH value of 8.5, and continued to stir and age for 2 hours. After aging, it was filtered and washed 3 times. The filter cake was dried at 120°C for 12 hours and then calcined at 450°C for 4 hours. The catalyst powder was pressed into tablets and sieved through 30-40 mesh. The catalyst was recorded as Hywin-YL-2#.

[0058] Based on the total mass of the catalyst, the content of nickel element is 15.63 wt %, the content of magnesium oxide is 6.46 wt %, and the content of aluminum oxide is 77.91 wt %.

[0059] Preparation Example 3 Preparation of Catalyst by Precipitation Method

[0060] 15.21g copper nitrate trihydrate, 2.89g zinc nitrate hexahydrate, 66.67g ammonium silica sol (silicon dioxide content 30wt%, Qingdao Haiyang Chemical Co., Ltd.) and 14.08g urea were dissolved in 200ml deionized water and ultrasonicated for 2h. Then nitric acid (67wt%) was added dropwise to adjust the pH to 2-3, and the temperature was raised to 95℃ for 24h. Filter, wash the filter cake 3 times, then dry at 120℃ for 12h, and finally calcine at 450℃ for 4h. The obtained catalyst powder was pressed into tablets and sieved through 30-40 mesh. The catalyst was recorded as Hywin-YL-3#.

[0061] Based on the total mass of the catalyst, the content of copper element is 16.14 wt %, the content of zinc oxide is 3.19 wt %, and the content of silicon dioxide is 80.67 wt %.

[0062] Preparation Example 4 Preparation of Catalyst by Sol-Gel Method

[0063] Place 18.04 g of ferric nitrate nonahydrate, 34.84 g of zirconium nitrate pentahydrate and 24.98 g of citric acid in a beaker and add 200 mL of deionized water to fully dissolve them. Then place them in a 500 mL rotary evaporator and perform rotary evaporation at 85°C. When the solution becomes a sol, place it at 120°C and dry it for 12 hours. After drying, calcine it at 550°C for 4 hours to obtain Fe-ZrO2.

[0064] Dissolve 1.43g potassium hydroxide in 7.85g deionized water, drop the solution into the Fe-ZrO2 obtained in the above step for equal volume impregnation, let stand for 2h, then dry in a 120℃ drying oven for 6h, and finally calcine at 550℃ for 4h. The obtained catalyst powder is pressed into tablets and sieved through 30-40 mesh, and the catalyst is recorded as Hywin-YL-4#.

[0065] Based on the total mass of the catalyst, the content of iron element is 17.35 wt %, the content of auxiliary potassium oxide is 5.82 wt %, and the content of carrier zirconium oxide is 76.83 wt %.

[0066] Preparation Example 5

[0067] The method of Preparation Example 1 was followed, except that cobalt nitrate hexahydrate was not added. The catalyst was denoted as Hywin-YL-5#.

[0068] Based on the total mass of the catalyst, the content of palladium is 0.95wt%, and the content of the carrier alumina is 99.05wt%.

[0069] The following examples are used to illustrate the synthesis method of N-alkyl carbazole in the present invention.

[0070] Example 1

[0071] (1) Add Hywin-YL-1# catalyst into a 100 mL reactor, seal the reactor, replace the air in the reactor with nitrogen through the air inlet valve three times, then replace the nitrogen in the reactor with hydrogen three times, and flush 0.3 MPa hydrogen for the last time, set the pressure holding temperature to 240 °C, and the pressure holding time to 2 h to activate the catalyst;

[0072] (2) After the insulation is completed, the hydrogen in the reactor is emptied, 4.17 g of carbazole and 16.5 g of acetaldehyde are added to the reactor, the reactor is sealed, and the air in the reactor is replaced by nitrogen through the air inlet valve three times, and then the nitrogen in the reactor is replaced by hydrogen three times, and 2 MPa of hydrogen is injected for the last time. The reaction temperature is set to 260 °C, the stirring speed is 150 rpm / min, and the reaction time is 3 h;

[0073] (3) After the reaction was completed, an appropriate amount of NMP was added to dissolve, and the product composition was analyzed by gas chromatography (area normalization method). The carbazole conversion rate and NEC selectivity were calculated, and the results are shown in Table 1.

[0074]

[0075] Wherein, A1 is the chromatographic peak area of ​​carbazole, A2 is the chromatographic peak area of ​​NEC, and A3 is the total chromatographic peak area of ​​other by-products except NEC.

[0076] Embodiment 2-5

[0077] The method of Example 1 was followed, except that the reaction conditions were as shown in Table 1.

[0078] An appropriate amount of NMP was added to the reactor to dissolve all the substrates, and the product composition was analyzed by gas chromatography (area normalization method). The carbazole conversion rate and NEC selectivity were calculated, and the results are shown in Table 1.

[0079] Table 1 Reactor reaction conditions and results

[0080]

[0081] Example 6

[0082] 10 mL of Hywin-YL-2# catalyst was loaded into a fixed bed reaction tube, and the catalyst was reduced at 400°C using nitrogen (200 mL / min) and hydrogen (20 mL / min) for 3 h.

[0083] The hydrogen pressure was adjusted to 0.5 MPa through the back pressure valve, and then the mixed liquid of carbazole and acetaldehyde was introduced from the top of the reactor through a metering pump (the mass ratio of acetaldehyde to carbazole was 4:1), and the total liquid hourly space velocity was 0.1 h -1 , the reaction temperature was set at 220°C and the reaction was carried out for 2 hours.

[0084] After the reaction was completed, samples were collected from the gas-liquid separation tank at the bottom of the fixed bed, and an appropriate amount of N-methylpyrrolidone (NMP) was added to dissolve them. The samples were analyzed by gas chromatography (area normalization method). The results are shown in Table 1.

[0085] Examples 7-10

[0086] The method of Example 6 was followed, except that the reaction conditions were as shown in Table 2.

[0087] After the reaction was completed, samples were collected from the gas-liquid separation tank at the bottom of the fixed bed, and an appropriate amount of N-methylpyrrolidone (NMP) was added to dissolve them. The samples were analyzed by gas chromatography (area normalization method). The results are shown in Table 2.

[0088] Table 2 Fixed bed reaction conditions and results

[0089]

[0090] Comparative Example 1

[0091] (1) Add 0.15 g of Hywin-YL-1# catalyst into a 100 mL reactor, seal the reactor, replace the air in the reactor with nitrogen through the air inlet valve three times, then replace the nitrogen in the reactor with hydrogen three times, and flush 0.3 MPa of hydrogen for the last time. Set the pressure holding temperature to 240 °C and the pressure holding time to 2 h to activate the catalyst;

[0092] (2) After the insulation is completed, the hydrogen in the kettle is emptied, 4.17 g of carbazole, 24.19 g of ethyl chloride and 41.7 mL of dichloromethane solvent are added to the reactor, the reactor is sealed, and nitrogen is used to replace the air in the reactor through the air inlet valve three times, and then the nitrogen in the reactor is replaced with hydrogen three times, and 2 MPa of hydrogen is injected for the last time. The reaction temperature is set to 260 ° C, the stirring speed is 150 rpm / min, and the reaction time is 3 h;

[0093] (3) After the reaction was completed, an appropriate amount of NMP was added to the reactor to dissolve all the substrates, and the product composition was analyzed by gas chromatography (area normalization method). The calculated carbazole conversion rate was 62.31%, and the NEC selectivity was 77.11%.

[0094] From the comparison of the above examples and comparative examples, it can be seen that the synthesis method provided by the present invention can realize the continuous production of N-alkyl carbazole, the product separation difficulty is low, and the traditional organic solvent extraction product step is avoided, the pollution is small, the environment is friendly, and the product yield is high. The preparation method has high selectivity for the target product and conforms to the green atom economy.

[0095] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for synthesizing N-alkyl carbazole, characterized in that: The synthesis method comprises: contacting carbazole and alkyl aldehyde with a catalyst in the presence of hydrogen; The alkyl aldehyde is selected from at least one of acetaldehyde, propionaldehyde and butyraldehyde; The catalyst comprises a carrier, and an active metal component and an auxiliary component supported on the carrier, wherein the active metal component is selected from at least one of Ni, Fe, Cu and Pd; and the auxiliary component is selected from at least one of Mg, Zn, K and Co.

2. The method for synthesizing N-alkylcarbazole according to claim 1, wherein: The molar ratio of the alkyl aldehyde to carbazole is 2-20:

1.

3. The method for synthesizing N-alkylcarbazole according to claim 2, wherein: The molar ratio of the alkyl aldehyde to carbazole is 5-12:

1.

4. The method for synthesizing N-alkylcarbazole according to claim 1, wherein: The contact is carried out in a fixed bed reactor, and the contact conditions include: a reaction temperature of 180-250° C., a hydrogen pressure of 0.2-3 MPa, and a total volume liquid hourly space velocity of 0.05-0.3 h -1 .

5. The method for synthesizing N-alkylcarbazole according to claim 1, wherein: The contact is carried out in a tank reactor, and the contact conditions include: reaction temperature of 220-270° C., hydrogen pressure of 0.2-3 MPa, mass ratio of catalyst to carbazole of (0.01-0.05):1, and reaction time of 1-5 h.

6. The method for synthesizing N-alkylcarbazole according to claim 1, wherein: The active metal component is selected from at least one of Ni, Fe and Cu; Wherein, based on the total amount of the catalyst, the content of the active metal component in terms of element is 10-30wt%, the content of the auxiliary component in terms of oxide is 2-10wt%, and the content of the carrier is 60-90wt%.

7. The method for synthesizing N-alkylcarbazole according to claim 1, wherein: The active metal component is selected from Pd; Wherein, based on the total amount of the catalyst, the content of the active metal component in terms of element is 0.1-5wt%, the content of the auxiliary component in terms of oxide is 2-10wt%, and the content of the carrier is 85-99.9wt%.

8. The method for synthesizing N-alkylcarbazole according to claim 1, wherein: The carrier is at least one of activated carbon, an oxide carrier and a molecular sieve.

9. The method for synthesizing N-alkylcarbazole according to claim 8, wherein: The oxide support is selected from a single-component oxide support and / or a two-component oxide support; The single-component oxide support is selected from at least one of Al2O3, CeO2, La2O3, MgO, ZrO2, TiO2, SiO2 and ZnO; the two-component oxide support is selected from at least one of ZrO2-Al2O3, MgO-ZrO2, ZnO-ZrO2, CeO2-ZrO2, ZrO2-SiO2 and SiO2-Al2O3.

10. The method for synthesizing N-alkylcarbazole according to claim 1, wherein: The synthesis method further comprises: before the contacting, activating the catalyst; The activation treatment is carried out in a hydrogen-containing atmosphere, the temperature of the activation treatment is 230-255° C., the hydrogen pressure is 0.2-0.55 MPa, and the activation time is 1.5-2.5 h.

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