CN107488140B - Synthesis method of N-ethyl carbazole - Google Patents
Synthesis method of N-ethyl carbazole Download PDFInfo
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Abstract
A synthetic method of N-ethyl carbazole relates to N-ethyl carbazole. In an N-methylpyrrolidone solvent, carbazole and a proton removing agent are subjected to salt forming reaction to generate carbazole salt, and acetylene is continuously introduced for reaction to obtain N-vinylcarbazole; and adding a Pd catalyst into the generated N-vinyl carbazole organic solvent, and carrying out hydrogenation reaction in an auxiliary agent to obtain the N-ethyl carbazole. A series of special catalysts are optimized, the green synthesis of the N-ethyl carbazole can be effectively realized through the catalytic hydrogenation process, and the discharge of three wastes is reduced. In the hydrogenation process, the catalyst can be repeatedly used, and the cost is reduced. The N-ethyl carbazole product prepared by the hydrogenation process has higher quality. The traditional alkylating reagent (diethyl sulfate, ethyl carbonate, haloethane and the like) and toxic organic solvent are not needed, the problem of waste liquid discharge is avoided, and the production process is a green and clean production process.
Description
Technical Field
The invention relates to N-ethyl carbazole, in particular to a synthesis method of N-ethyl carbazole, which is green and does not discharge waste liquid.
Background
N-ethyl carbazole is used as intermediate of blue Haichang blue GC and permanent violet RL dyes. Among them, one of the downstream products has high permanent violet RL tinting strength and bright color, and is widely applied to the industries of paint, rubber, synthetic fiber, plastics and the like as a high-end pigment by virtue of excellent chemical properties such as heat resistance, sun resistance, migration resistance and the like.
The industrial synthesis of N-ethyl carbazole mainly comprises three methods: diethyl sulfate process, ethyl carbonate process, and haloethane process. The diethyl sulfate method adopts diethyl sulfate to ethylate carbazole to obtain N-ethyl carbazole, the diethyl sulfate has strong alkylation capacity, and the alkylation reaction on amino can be carried out under moderate reaction conditions without influencing the hydroxyl of a benzene ring. The literature (Telore R.D., Satam M.A., Sekar N.dyes and Pigments 2015; 122: 359-) 367) reports that diethyl sulfate and carbazole were reacted with acetone as the solvent and KOH as the deprotonating agent at reflux for 4h, giving a yield of 90%.
The ethyl carbonate method uses ethyl carbonate as an alkylating agent, and European patent EP 0635490 discloses a method for preparing N-ethyl carbazole, sodium hydroxide, potassium carbonate or potassium ethoxide is used as a proton removing agent to react for 24 hours, and the purity of the obtained product is 96%. Similar to the diethyl sulfate method, the alkylation reagent used in the method has high cost, and the reaction needs a toxic organic solvent to participate, so that the reaction yield is not high.
In contrast, the haloethane process is the most widely practiced process. The alkylation reagents commonly used are mainly ethyl chloride and ethyl bromide, and the reactions can be divided into homogeneous and heterogeneous syntheses: the homogeneous synthesis is that carbazole and proton removing agent generate carbazole salt, chloroethane is introduced under the condition of pressurization for ethylation, and the reaction temperature is higher; most reports mainly adopt a phase transfer catalysis method, namely, in a multiphase system, a phase transfer catalyst is used for realizing smooth reaction. The N-alkylation is usually carried out by taking alkyl quaternary ammonium salt as a phase transfer catalyst and taking 50% NaOH aqueous solution-benzene mixed solvent as a two-phase system. European patent EP 557993(1993) discloses that the traditional quaternary ammonium salt is replaced by amine organic substance triethylamine with lower price as a phase transfer catalyst, 48 percent of NaOH aqueous solution-o-dichlorobenzene is used as a solvent, the reaction is carried out for 9 hours at 100 ℃, and the reaction yield can reach 99.6 percent. Similarly, diethylamine, 2-phenyl-1-propylamine and the like are used as catalysts, and the reaction effect is also good. EP 858995(1998) uses o-dichlorobenzene as solvent and N, N, N ', N' -tetramethyl-1, 3-propanediamine as phase transfer catalyst, and the reaction is carried out at 100 ℃ for 4h, and the obtained yield is 99.3%.
The traditional N-ethyl carbazole synthesis method not only needs toxic organic solvents to participate in the alkylation process, but also is harmful to human bodies and pollutes the environment, and particularly serious environmental problems can be caused by improper treatment of halogen-containing waste water containing chlorine and the like brought by a haloethane method. At present, the country pays close attention to the aspect of environmental protection, and particularly, in recent years, serious environmental protection policies such as a new environmental protection law, an atmospheric pollution prevention law, ten earth laws and the like are developed intensively. Therefore, a green and environment-friendly N-ethyl carbazole synthetic route is provided, which is particularly important.
The hydrogenation synthesis of N-ethyl carbazole is an effective way to realize clean production and improve product quality, but so far, almost no one has synthesized N-ethyl carbazole through hydrogenation reaction. The reason is mainly the strong electron transfer capability of the carbazole group, so that the hydrogenation reduction of the vinyl group has certain difficulty. The carbazole which is more than 90 percent is from coal chemical products, and because the sulfur-containing species exist in the raw materials, the carbazole also puts new requirements on the anti-poisoning capability of the catalyst and is directly related to the indiscriminate activity of the catalyst.
Disclosure of Invention
The invention aims to provide a method for synthesizing N-ethyl carbazole, which applies a noble metal Pd catalyst to the hydrogenation reaction of N-vinyl carbazole, has high hydrogenation activity and can be recycled.
The invention comprises the following steps:
1) in an N-methylpyrrolidone solvent, carbazole and a proton removing agent are subjected to salt forming reaction to generate carbazole salt, and acetylene is continuously introduced for reaction to obtain N-vinylcarbazole;
2) and adding a Pd catalyst into the generated N-vinyl carbazole organic solvent, and carrying out hydrogenation reaction in an auxiliary agent to obtain the N-ethyl carbazole.
In the step 1), the mass concentration ratio of carbazole to proton-removing agent in the N-methylpyrrolidone solvent is 1: 0.02-0.5, preferably 1: 0.06-0.12; the temperature of the salt forming reaction can be 80-100 ℃, and the time of the salt forming reaction can be 20-30 min; the continuous acetylene feeding reaction condition can be 140-200 ℃ and the reaction time can be 4-6 h under 0.1-0.5 MPa.
In the step 2), the mass concentration ratio of the catalyst to the N-vinylcarbazole substance in the generated N-vinylcarbazole organic solvent can be 1: 1000-5000; the Pd catalyst can be selected from one of phosphate, MgO and the like; the auxiliary agent can adopt weak acid, and the weak acid can be selected from one of phosphoric acid, hypophosphorous acid and the like; the condition for carrying out the hydrogenation reaction in the auxiliary agent can be that the pH value is 5-7, and the hydrogenation reaction is carried out for 3-4 h at the temperature of 30-120 ℃ and under the pressure of 0.1-1.2 MPa; the condition for carrying out the hydrogenation reaction in the weak acid regulation system can be preferably that the hydrogenation reaction is carried out under the conditions of 0.2-0.6 MPa and 60-100 ℃.
The invention adopts two-step synthesis: the N-vinyl carbazole is prepared from carbazole, and then the N-ethyl carbazole is obtained by direct hydrogenation, so that the disadvantages of high price and high toxicity of the traditional alkylating reagent are avoided, and the problem of discharge of halogen-containing wastewater containing chlorine and the like caused by a haloethane method is avoided.
The invention has the outstanding advantages that:
1) a series of special catalysts are optimized, the green synthesis of the N-ethyl carbazole can be effectively realized through the catalytic hydrogenation process, and the discharge of three wastes is reduced.
2) In the hydrogenation process, the catalyst can be repeatedly used, and the cost is reduced.
3) The N-ethyl carbazole product prepared by the hydrogenation process has higher quality.
4) Compared with the traditional synthesis process, the method does not need the participation of traditional alkylating reagents (diethyl sulfate, ethyl carbonate, haloethane and the like) and toxic organic solvents, has no waste liquid discharge problem, and is a production process which really accords with green and cleanness.
Drawings
FIG. 1 is a high performance liquid chromatogram of N-vinylcarbazole, an intermediate product of example 1 of the present invention.
FIG. 2 is a high performance liquid chromatogram of the product N-ethylcarbazole of example 1 of the present invention.
Detailed Description
The following examples are intended to describe the invention in more detail, and these examples are merely illustrative of the best mode of carrying out the invention and do not limit the scope of the invention in any way.
Example 1
Adding 2g of carbazole, 0.04g of proton removing agent KOH and 10ml of N-methylpyrrolidone serving as solvents into a 50ml glass pressure-resistant bottle, starting stirring, heating to 80 ℃, carrying out a salt forming reaction for 30min to generate carbazole potassium salt, then introducing acetylene, and reacting at 160 ℃ and normal pressure for 2.5h to obtain N-vinylcarbazole, wherein the yield reaches 98.6%; in the next step, adding Pd catalyst (MgO as carrier) into N-vinylcarbazole at a concentration ratio of 1: 2000, and introducing 0.3MPaH2And carrying out hydrogenation reaction at 70 ℃ for 3h to obtain the N-ethyl carbazole, wherein the yield reaches 98.8%.
The high performance liquid chromatogram of the intermediate product N-vinylcarbazole of example 1 of the present invention is shown in FIG. 1, and the high performance liquid chromatogram of the product N-ethylcarbazole of example 1 of the present invention is shown in FIG. 2.
Example 2
Adding 2g of carbazole, 0.08g of proton removing agent KOH and 10ml of N-methylpyrrolidone serving as solvents into a 50ml glass pressure-resistant bottle, starting stirring, heating to 80 ℃, carrying out a salt forming reaction for 20min to generate carbazole potassium salt, then introducing acetylene, reacting for 5h at 160 ℃ and normal pressure to obtain N-vinylcarbazole, wherein the yield reaches 99.0%; in the next step, adding Pd catalyst (MgO as carrier) into N-vinylcarbazole at a concentration ratio of 1: 2000, and introducing 0.3MPaH2And carrying out hydrogenation reaction at 70 ℃ for 3h to obtain the N-ethyl carbazole, wherein the yield reaches 98.7%.
Example 3
Adding 2g of carbazole, 0.12g of proton removing agent KOH and 10ml of N-methylpyrrolidone serving as solvents into a 50ml glass pressure-resistant bottle, starting stirring, heating to 80 ℃, carrying out a salt forming reaction for 20min to generate carbazole potassium salt, then introducing acetylene, and reacting at 160 ℃ and normal pressure for 2.5h to obtain N-vinylcarbazole, wherein the yield reaches 98.9%; in the next step, adding Pd catalyst (MgO as carrier) into N-vinylcarbazole at a concentration ratio of 1: 2000, and introducing 0.3MPaH2And carrying out hydrogenation reaction at 70 ℃ for 3h to obtain the N-ethyl carbazole, wherein the yield reaches 98.4%.
Example 4
Adding 2g of carbazole, 0.04g of proton removing agent KOH and 10ml of N-methylpyrrolidone serving as solvents into a 50ml glass pressure-resistant bottle, starting stirring, heating to 80 ℃, carrying out a salt forming reaction for 30min to generate carbazole potassium salt, then introducing acetylene, and reacting at 160 ℃ and normal pressure for 2.5h to obtain N-vinylcarbazole, wherein the yield reaches 98.6%; in the next step, adding Pd catalyst (MgO as carrier) into N-vinylcarbazole at a concentration ratio of 1: 2000, and introducing 0.1MPaH2And carrying out hydrogenation reaction at 50 ℃ for 3.5h to obtain the N-ethyl carbazole, wherein the yield reaches 98.0%.
Example 5
In a 50ml glass pressure bottle, 2g of carbazole, 0.04g of proton-removing agent KOH and 10ml of N-methylpyrrolidone were added as solvents, andstirring and heating to 80 ℃ for salt forming reaction for 30min to generate carbazole potassium salt, introducing acetylene, reacting at 160 ℃ under normal pressure for 2.5h to obtain N-vinyl carbazole, wherein the yield reaches 98.6%; in the next step, adding Pd catalyst (gamma-Al as carrier) at a concentration ratio of 1: 2000 between the catalyst and the N-vinylcarbazole substance in the course of continuously hydrogenating to generate N-ethylcarbazole2O3) Introduction of 0.1MPaH2And carrying out hydrogenation reaction at 50 ℃ for 3.5h to obtain the N-ethyl carbazole, wherein the yield reaches 98.4%.
Example 6
Adding 2g of carbazole, 0.04g of proton removing agent KOH and 10ml of N-methylpyrrolidone serving as solvents into a 50ml glass pressure-resistant bottle, starting stirring, heating to 80 ℃, carrying out a salt forming reaction for 30min to generate carbazole potassium salt, then introducing acetylene, and reacting at 160 ℃ and normal pressure for 2.5h to obtain N-vinylcarbazole, wherein the yield reaches 98.6%; in the next step, adding Pd catalyst (magnesium phosphate as carrier) at a concentration ratio of 1: 2000 to N-vinylcarbazole substance, and introducing 0.3MPa H2And carrying out hydrogenation reaction at 70 ℃ for 3h to obtain the N-ethyl carbazole, wherein the yield reaches 99.1%.
The invention discloses a green synthesis method of N-ethyl carbazole. Carbazole is taken as a raw material, and the carbazole is added into an organic solvent to carry out a salt forming reaction to generate carbazole salt. Continuously introducing acetylene under normal pressure to react to obtain the N-vinyl carbazole. Then, adding a noble metal catalyst into an organic solvent of the N-vinyl carbazole, and carrying out catalytic hydrogenation reaction under mild conditions to obtain the N-ethyl carbazole. The invention avoids the disadvantages of high price and large toxicity of the traditional alkylating reagent, has no waste liquid discharge, and has the yield of the N-ethyl carbazole of more than 98 percent.
Claims (3)
1. A synthetic method of N-ethyl carbazole is characterized by comprising the following steps:
1) in an N-methylpyrrolidone solvent, carbazole and a proton removing agent are subjected to salt forming reaction to generate carbazole salt, and acetylene is continuously introduced for reaction to obtain N-vinylcarbazole; in an N-methylpyrrolidone solvent, the mass concentration ratio of carbazole to proton removing agent is 1: 0.06-0.12; the temperature of the salt forming reaction is 80-100 ℃, and the time of the salt forming reaction is 20-30 min;
2) adding a Pd catalyst into the generated N-vinyl carbazole organic solvent, and carrying out hydrogenation reaction in an auxiliary agent to obtain N-ethyl carbazole; in the generated N-vinyl carbazole organic solvent, the mass concentration ratio of the catalyst to the N-vinyl carbazole substance is 1: 1000-5000; the auxiliary agent adopts weak acid, and the weak acid is selected from one of phosphoric acid and hypophosphorous acid; the condition for carrying out the hydrogenation reaction in the auxiliary agent is that the pH value is 5-7, and the hydrogenation reaction is carried out for 3-4 h at the temperature of 30-120 ℃ and under the pressure of 0.1-1.2 MPa; the Pd catalyst is selected from Pd catalysts supported on magnesium oxide or magnesium phosphate.
2. The method for synthesizing N-ethylcarbazole according to claim 1, wherein in the step 1), the continuous acetylene feeding reaction is carried out at 140-200 ℃ and 0.1-0.5 MPa for 4-6 h.
3. The method for synthesizing N-ethylcarbazole according to claim 1, wherein in the step 2), the hydrogenation reaction is performed in the weak acid regulation system under a condition of 0.2 to 0.6MPa and at a temperature of 60 to 100 ℃.
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