A method for nitroaromatics hydrogenation based on polyvinyl chloride degradation to prepare functional carbon materials

Abstract

A method for preparing functional carbon material based on polyvinyl chloride degradation and nitroaromatic hydrogenation, taking polyvinyl chloride and ethylenediamine as raw materials, different types of carbon materials are prepared by controlling the type of activator and the amount of ethylenediamine, and the carbon material is used for the hydrogenation reaction of nitro compounds, which has very excellent hydrogenation performance; through the method, polyvinyl chloride can be directly degraded into hydrogenation functional carbon material, avoiding the use of metal catalysts, by changing the amount of ethylenediamine and the activation procedure, different nitrogen-doped and different structure functional carbon materials can be obtained, the carbon material has good activity for the hydrogenation of nitroaromatic compounds; the application not only solves the degradation problem of chlorine-containing plastics, but also realizes the non-metal catalytic nitroaromatic hydrogenation reaction to prepare aromatic amine; the application provides a new reaction path and idea for the degradation of chlorine-containing plastics and nitro hydrogenation reaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical engineering and catalytic science, and relates to a method for hydrogenation of nitroaromatics based on preparation of functional carbon materials from polyvinyl chloride degradation. BACKGROUND

[0002] With the improvement of human science and living standards, the use of plastics is also more and more widely, most of the plastics are difficult to be decomposed in nature and dispersed in every corner of nature in the form of microplastics, causing serious pollution to human and biological world. Therefore, how to convert plastics into useful chemicals has attracted people's attention. In the current research, polyethylene, polypropylene and other plastics can be degraded into small molecules with multiple carbon chains under the participation of catalysts, and polyvinyl chloride is difficult to be directly degraded into small molecules due to containing heteroatoms, therefore, the method of dechlorination and nitrogen introduction for degrading polyvinyl chloride into nitrogen-containing functional carbon materials is one of the effective methods for degrading polyvinyl chloride.

[0003] Aromatic amines are an important class of chemical raw materials, which are mainly prepared by hydrogenation of nitroaromatics. The hydrogenation of nitroaromatics is mainly catalyzed by metals, and in industry, iron powder and hydrochloric acid are used as reducing agents to reduce nitroaromatics to prepare aromatic amines. The use of nitrogen-containing functional carbon materials prepared from polyvinyl chloride degradation as catalysts to catalyze the hydrogenation of nitroaromatics to aromatic amines not only can reduce the price of catalysts, but also can help to solve the pollution caused by chlorine-containing plastics to the environment. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a method for hydrogenation of nitroaromatics based on preparation of functional carbon materials from polyvinyl chloride degradation.

[0005] The present application adopts the following technical solutions:

[0006] A method for hydrogenation of nitroaromatics based on preparation of functional carbon materials from polyvinyl chloride degradation, comprising the following steps:

[0007] (1), ethylenediamine and polyvinyl chloride are mixed in proportion, stirred uniformly and heated to reflux in an oil bath for 12h, the obtained precursor is dried and ground into powder, then placed in a tube furnace, heated to 500℃ under inert atmosphere and calcined for 2h, the obtained solid is dispersed in an alkaline solution of activator, stirred at room temperature for 2h, then stirred in a 80℃ water bath and evaporated to dryness, the dried powder is ground into powder and placed in a tube furnace again, heated to 750℃ under inert atmosphere and calcined for 1h, the obtained solid powder is washed with dilute hydrochloric acid solution, then washed with water until neutral and dried, the obtained solid is ground into powder for use;

[0008] (2), the solid powder catalyst obtained in step (1) and the substrate nitroaromatics are weighed and placed in a high-pressure reaction kettle containing a solvent, the high-pressure reaction kettle is sealed and leak tested, then a certain pressure of hydrogen gas is injected, heated for a period of time, and then the reaction is stopped.

[0009] Further, in step (1), the mass ratio of ethylenediamine to polyvinyl chloride is 1.0-5.0.

[0010] Further, in step (1), the oil bath heating reflux temperature is 120-180℃.

[0011] Further, the activator alkali solution comprises KOH, NaOH, KHCO3, NaHCO3, K2CO3 or Na2CO3.

[0012] Further, in step (1), the temperature for twice calcination in the tube furnace is 500-900℃.

[0013] Further, in step (2), the reaction conditions are that the hydrogen pressure is 1-5 MPa, the temperature is 230℃, and the reaction time is 4-12h.

[0014] Further, in step (2), the nitroaromatics comprise nitrobenzene, p-nitrotoluene, p-nitrobenzoic acid or p-nitrostyrene.

[0015] From the above description of the present application, compared with the prior art, the beneficial effects of the present application are: the present application mixes polyvinyl chloride with ethylenediamine, carries out dechlorination reaction at low temperature to introduce reticular nitrogen elements on the polyvinyl chloride carbon chain, and carbonizes under inert atmosphere to realize the dechlorination degradation of polyvinyl chloride and prepare nitrogen-doped functional carbon materials. By changing the amount of ethylenediamine and the activation procedure, functional carbon materials with different nitrogen doping and different structures can be obtained, and the carbon materials have good activity for the hydrogenation of nitroaromatic compounds. This invention not only solves the degradation problem of chlorine-containing plastics, but also realizes the non-metallic catalytic hydrogenation of nitroaromatics to prepare aromatic amines; it provides a new reaction path and idea for the degradation of chlorine-containing plastics and the hydrogenation of nitro compounds;

[0016] In this method, the amount of ethylenediamine and the type of activator will affect the content and structure of nitrogen in the catalyst, thereby affecting its hydrogenation performance; when the ratio of ethylenediamine to polyvinyl chloride is 2:1 and NaHCO3 is used as the activator, the nitrogen-doped carbon material prepared has the best hydrogenation performance, in which the pyrrole structure nitrogen is the main active center. Under the conditions of 200℃ and 2 MPa hydrogen pressure, the reaction time is 8h, the conversion rate of nitrobenzene can reach 97%, and the yield of aniline can reach 96%. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The synthesis route map of the functional carbon material. DETAILED DESCRIPTION

[0018] The present application is further described below through specific embodiments.

[0019] A method for hydrogenating nitroaromatics based on the degradation of polyvinyl chloride to prepare functional carbon materials includes the following steps:

[0020] (1) Mix ethylenediamine and polyvinyl chloride in proportion, stir evenly and heat under reflux in an oil bath for 12 hours. Dry and grind the obtained precursor into powder and place it in a tube furnace. Calcinate at 500°C for 2 hours under an inert atmosphere. Disperse the obtained solid in an activator alkaline solution, stir at room temperature for 2 hours, and then stir and evaporate to dryness in an 80°C water bath. Grind the dried powder into powder and place it in a tube furnace again. Calcinate at 750°C for 1 hour under an inert atmosphere. Wash the obtained solid powder with dilute hydrochloric acid solution, then wash with water until neutral and dry. Grind the obtained solid into powder for later use.

[0021] (2) Weigh the solid powder catalyst obtained in step (1) and the substrate nitroaromatic hydrocarbon into a high-pressure reactor containing solvent. After sealing the high-pressure reactor and checking for leaks, purge with hydrogen gas at a certain pressure. Heat for a period of time and then stop the reaction.

[0022] The synthesis route diagram for step (1) is referenced. Figure 1 Specifically, in step (1), the mass ratio of ethylenediamine to polyvinyl chloride is 1.0-5.0; the reflux temperature of the oil bath heating is 120-180℃; the activator alkaline solution contains KOH, NaOH, KHCO3, NaHCO3, K2CO3 or Na2CO3; and the temperature of the two calcinations in the tube furnace is 500-900℃.

[0023] In step (2), the reaction conditions are a hydrogen pressure of 1-5 MPa, a temperature of 230°C, and a reaction time of 4-12 h; specifically, nitroaromatics include nitrobenzene, p-nitrotoluene, p-nitrobenzoic acid, or p-nitrostyrene.

[0024] Example 1

[0025] A method for hydrogenating nitroaromatics based on the degradation of polyvinyl chloride to prepare functional carbon materials includes the following steps:

[0026] (1) Weigh ethylenediamine and polyvinyl chloride in a ratio of 2.0 into a round-bottom flask, stir evenly, and heat under reflux in a preheated oil bath at 160°C for 12 hours. The resulting solid is dried in a vacuum drying oven at 60°C. The solid is then ground into powder and placed in a tube furnace. Inert gas is introduced and the temperature is programmed to rise to 500°C for 2 hours. The resulting solid powder is dispersed in KOH solution and stirred at room temperature for 2 hours. Then it is evaporated to dryness in a water bath at 80°C. The resulting solid powder is placed in a tube furnace. Inert gas is introduced and the temperature is programmed to rise to 750°C for 1 hour. The calcined powder is washed with dilute hydrochloric acid and water until neutral, then dried and ground into powder. The resulting solid is denoted as NAC-1.

[0027] (2) Take 0.05 g of the above NAC-1 catalyst and 0.1 g of nitrobenzene dispersed in 30 ml of isopropyl alcohol and place in a high-pressure reaction kettle. Replace the reaction kettle with inert gas for 3 times, then charge 2 MPa of H2, heat to 200°C and react for 8 h. The obtained liquid is filtered with an organic filter membrane and then subjected to gas phase analysis. The results show that the conversion rate of nitrobenzene is 93% and the yield of aniline is 79%.

[0028] Example 2

[0029] A method for hydrogenation of nitroaromatics based on polyvinyl chloride degradation to prepare functional carbon materials, comprising the following steps:

[0030] (1) Take ethylenediamine and polyvinyl chloride in a ratio of 2.0 in a round-bottom flask, stir uniformly, then place in a preheated oil bath at 160°C and heat to reflux for 12 h. Dry the obtained solid in a vacuum drying box at 60°C, then grind the solid into powder, place in a tube furnace, pass inert gas and program to heat to 500°C for calcination for 2 h. Disperse the above obtained solid powder into a K2CO3 solution, stir at room temperature for 2 h, then evaporate in a water bath at 80°C. Place the obtained solid powder in a tube furnace, pass inert gas, program to heat to 750°C and calcine for 1 h. Wash the calcined powder with dilute hydrochloric acid and water until neutral, then dry and grind into powder. The obtained solid is recorded as NAC-2;

[0031] (2) Take 0.05 g of the above NAC-2 catalyst and 0.1 g of nitrobenzene dispersed in 30 ml of isopropyl alcohol and place in a high-pressure reaction kettle. Replace the reaction kettle with inert gas for 3 times, then charge 2 MPa of H2, heat to 200°C and react for 8 h. The obtained liquid is filtered with an organic filter membrane and then subjected to gas phase analysis. The results show that the conversion rate of nitrobenzene is 54% and the yield of aniline is 43%.

[0032] Example 3

[0033] A method for hydrogenation of nitroaromatics based on polyvinyl chloride degradation to prepare functional carbon materials, comprising the following steps:

[0034] (1) ethylenediamine and polyvinyl chloride in a ratio of 1.3 were weighed into a round-bottom flask, stirred uniformly, and then placed in an oil bath preheated to 160°C to heat and reflux for 12 h. The obtained solid was dried in a vacuum drying box at 60°C, then ground into powder, and placed in a tube furnace, inert gas was introduced, and the temperature was programmed to 500°C for calcination for 2 h. The obtained solid powder was dispersed in a KHCO3 solution, stirred at room temperature for 2 h, then evaporated in a water bath at 80°C, and the obtained solid powder was placed in a tube furnace, inert gas was introduced, and the temperature was programmed to 750°C for calcination for 1 h. The calcined powder was washed with dilute hydrochloric acid and water until neutral, dried, and ground into powder. The obtained solid was denoted as NAC-3. After being ground into powder, XPS characterization was performed, and the results showed that the N content was 1.8%, of which pyridine nitrogen accounted for 20.7%, pyrrole nitrogen accounted for 38.0%, oxidized graphite nitrogen accounted for 32.3%, and graphite phase nitrogen accounted for 9.0%;

[0035] (2) 0.05 g of the above-mentioned NAC-3 catalyst and 0.1 g of nitrobenzene were dispersed in 30 ml of isopropyl alcohol and placed in a high-pressure reaction kettle. The reaction kettle was replaced with inert gas for 3 times, then 2 MPa of H2 was charged, the temperature was raised to 200°C, and the reaction was carried out for 8 h. The obtained liquid was filtered with an organic filter membrane, and gas phase analysis was performed. The results showed that the conversion rate of nitrobenzene was 71%, and the yield of aniline was 62%.

[0036] Example 4

[0037] A method for nitroaromatics hydrogenation based on polyvinyl chloride degradation to prepare functional carbon materials, comprising the following steps:

[0038] (1) ethylenediamine and polyvinyl chloride in a ratio of 2.7 were weighed into a round-bottom flask, stirred uniformly, and then placed in an oil bath preheated to 160°C to heat and reflux for 12 h. The obtained solid was dried in a vacuum drying box at 60°C, then ground into powder, and placed in a tube furnace, inert gas was introduced, and the temperature was programmed to 500°C for calcination for 2 h. The obtained solid powder was dispersed in a KHCO3 solution, stirred at room temperature for 2 h, then evaporated in a water bath at 80°C, and the obtained solid powder was placed in a tube furnace, inert gas was introduced, and the temperature was programmed to 750°C for calcination for 1 h. The calcined powder was washed with dilute hydrochloric acid and water until neutral, dried, and ground into powder. The obtained solid was denoted as NAC-4. After being ground into powder, XPS characterization was performed, and the results showed that the N content was 2.0%, of which pyridine nitrogen accounted for 17.4%, pyrrole nitrogen accounted for 43.6%, oxidized graphite nitrogen accounted for 27.3%, and graphite phase nitrogen accounted for 11.7%.

[0039] (2) Take 0.05 g of the above NAC-4 catalyst and 0.1 g of nitrobenzene dispersed in 30 ml of isopropyl alcohol and place it in a high-pressure reaction kettle. Replace the reaction kettle with inert gas for 3 times, then charge 2 MPa of H2, heat to 200℃ and react for 8 h. The obtained liquid is filtered with an organic filter membrane and then subjected to gas phase analysis. The results show that the conversion rate of nitrobenzene is 85% and the yield of aniline is 73%.

[0040] Example 5

[0041] A method for hydrogenation of nitroaromatics based on functional carbon materials prepared by degradation of polyvinyl chloride, comprising the following steps:

[0042] (1) Take ethylenediamine and polyvinyl chloride in a ratio of 2.0 in a round-bottom flask, stir uniformly, and then place it in a preheated oil bath at 160℃ for heating and refluxing for 12 h. The obtained solid is dried in a vacuum drying box at 60℃. Then the solid is ground into powder and placed in a tube furnace, inert gas is introduced and the temperature is programmed to 500℃ for calcination for 2 h. The obtained solid powder is dispersed in a KHCO3 solution, stirred at room temperature for 2 h, and then evaporated to dryness in a water bath at 80℃. The obtained solid powder is placed in a tube furnace, inert gas is introduced, the temperature is programmed to 750℃ for calcination for 1 h. The calcined powder is washed with dilute hydrochloric acid and water until neutral, dried and ground into powder. The obtained solid is denoted as NAC-5. After being ground into powder, XPS characterization is performed. The results show that the N content is 2.2%, among which the pyridine nitrogen accounts for 20.6%, the pyrrole nitrogen accounts for 57.0%, the oxidized graphite nitrogen accounts for 13.4%, and the graphite phase nitrogen accounts for 9.0%;

[0043] (2) Take 0.05 g of the above NAC-5 catalyst and 0.1 g of nitrobenzene dispersed in 30 ml of isopropyl alcohol and place it in a high-pressure reaction kettle. Replace the reaction kettle with inert gas for 3 times, then charge 2 MPa of H2, heat to 200℃ and react for 8 h. The obtained liquid is filtered with an organic filter membrane and then subjected to gas phase analysis. The results show that the conversion rate of nitrobenzene is 97% and the yield of aniline is 96%.

[0044] Example 6

[0045] A method for hydrogenation of nitroaromatics based on functional carbon materials prepared by degradation of polyvinyl chloride, comprising the following steps:

[0046] Take 0.05 g of the solid NAC-5 catalyst obtained in Example 5 and 0.1 g of nitrobenzene dispersed in 30 ml of isopropyl alcohol and place it in a high-pressure reaction kettle. Replace the reaction kettle with inert gas for 3 times, then charge 2 MPa of H2, heat to 160℃ and react for 8 h. The obtained liquid is filtered with an organic filter membrane and then subjected to gas phase analysis. The results show that the conversion rate of nitrobenzene is 33% and the yield of aniline is 25%.

[0047] Example 7

[0048] A method for hydrogenation of nitroaromatics based on polyvinyl chloride degradation to prepare functional carbon materials, comprising the following steps:

[0049] Take 0.05 g of the solid NAC-5 catalyst obtained in Example 5, 0.1 g of nitrobenzene is dispersed in 30 ml of methanol and placed in a high-pressure reaction kettle, the reaction kettle is replaced with inert gas for 3 times, then 2 MPa of H2 is filled, heated to 200℃ and reacted for 8 h, the obtained liquid is filtered with organic filter membrane and then subjected to gas phase analysis, the results show that the conversion rate of nitrobenzene is 35% and the yield of aniline is 30%.

[0050] Example 8

[0051] A method for hydrogenation of nitroaromatics based on polyvinyl chloride degradation to prepare functional carbon materials, comprising the following steps:

[0052] Take 0.05 g of the solid NAC-5 catalyst obtained in Example 5, 0.1 g of p-nitrotoluene is dispersed in 30 ml of isopropanol and placed in a high-pressure reaction kettle, the reaction kettle is replaced with inert gas for 3 times, then 2 MPa of H2 is filled, heated to 200℃ and reacted for 8 h, the obtained liquid is filtered with organic filter membrane and then subjected to gas phase analysis, the results show that the conversion rate of p-nitrotoluene is 82% and the yield of p-aminotoluene is 78%.

[0053] Example 9

[0054] A method for hydrogenation of nitroaromatics based on polyvinyl chloride degradation to prepare functional carbon materials, comprising the following steps:

[0055] Take 0.05 g of the solid NAC-5 catalyst obtained in Example 5, 0.1 g of p-nitrobenzoic acid is dispersed in 30 ml of isopropanol and placed in a high-pressure reaction kettle, the reaction kettle is replaced with inert gas for 3 times, then 2 MPa of H2 is filled, heated to 200℃ and reacted for 8 h, the obtained liquid is filtered with organic filter membrane and then subjected to gas phase analysis, the results show that the conversion rate of p-nitrobenzoic acid is 100% and the yield of p-aminobenzoic acid is 76%.

[0056] Comparative Example 1 (without adding ethylenediamine)

[0057] A method for hydrogenation of nitroaromatics, comprising the following steps:

[0058] (1) 1.0 g of polyvinyl chloride is ground into powder and placed in a tube furnace, inert gas is introduced and the temperature is programmed to 500℃ for calcination for 2 h; the obtained solid powder is dispersed in a KHCO3 solution, stirred at room temperature for 2 h, then evaporated to dryness in a water bath at 80℃, the obtained solid powder is placed in a tube furnace, inert gas is introduced and the temperature is programmed to 750℃ for calcination for 1 h, the calcined powder is washed with dilute hydrochloric acid and water until neutral, then dried and ground into powder; the obtained solid is recorded as NAC-6;

[0059] (2) Take 0.05 g of the above NAC-6 catalyst and 0.1 g of nitrobenzene dispersed in 30 ml of isopropyl alcohol and place in a high-pressure reaction kettle, use inert gas to replace the reaction kettle for 3 times, then charge 2 MPa of H2, heat to 200℃ and react for 8 h, the obtained liquid is filtered by organic filter membrane and then subjected to gas phase analysis, the result shows that the conversion of nitrobenzene is 0%.

[0060] Comparative Example 2 (without secondary activation)

[0061] The method for hydrogenation of nitroarene includes the following steps:

[0062] (1) Take ethylenediamine and polyvinyl chloride in a ratio of 2.0 in a round-bottom flask, stir uniformly, then place in a preheated oil bath at 160℃ and heat to reflux for 12 h, the obtained solid is dried in a vacuum drying box at 60℃, then the solid is ground into powder and placed in a tube furnace, inert gas is introduced and the temperature is programmed to 500℃ for calcination for 2 h; the above obtained solid powder is dispersed in deionized water, stirred at room temperature for 2 h, then evaporated to dryness in a water bath at 80℃, the obtained solid powder is placed in a tube furnace, inert gas is introduced and the temperature is programmed to 750℃ for calcination for 1 h, the calcined powder is washed to neutral with water, dried and ground into powder. The obtained solid is recorded as NAC-7;

[0063] (2) Take 0.05 g of the above NAC-7 catalyst and 0.1 g of nitrobenzene dispersed in 30 ml of isopropyl alcohol and place in a high-pressure reaction kettle, use inert gas to replace the reaction kettle for 3 times, then charge 2 MPa of H2, heat to 200℃ and react for 8 h, the obtained liquid is filtered by organic filter membrane and then subjected to gas phase analysis, the result shows that the conversion of nitrobenzene is 18%, and the yield of aniline is 14%.

[0064] In summary, the present application introduces reticular nitrogen elements on the carbon chain of polyvinyl chloride by mixing polyvinyl chloride with ethylenediamine and carrying out dechlorination reaction at low temperature, and realizes the dechlorination degradation of polyvinyl chloride and the preparation of nitrogen-doped functional carbon material by carbonization under inert atmosphere. By changing the amount of ethylenediamine and the activation procedure, functional carbon materials with different nitrogen doping and different structures can be obtained, and the carbon material has good activity for the hydrogenation of nitroarene compounds. The present application not only solves the degradation problem of chlorine-containing plastics, but also realizes the non-metallic catalytic hydrogenation of nitroarene to prepare aromatic amine; and provides a new reaction path and idea for the degradation of chlorine-containing plastics and the hydrogenation of nitro.

[0065] The above description is only a preferred embodiment of the present application, and therefore cannot limit the scope of the present application, i.e. equivalent changes and modifications made according to the scope of the present application and the content of the specification shall still be within the scope covered by the present application.

Claims

1. A method for the catalytic hydrogenation of nitroaromatic hydrocarbons in the preparation of functional carbon materials by degradation of polyvinyl chloride, characterized in that: Includes the following steps: (1) Ethylenediamine and polyvinyl chloride were mixed in proportion, stirred evenly and heated under reflux in an oil bath for 12 h. The resulting precursor was dried, ground into powder and placed in a tube furnace. It was calcined at 500 °C for 2 h under an inert atmosphere. The resulting solid was dispersed in an activator alkaline solution, stirred at room temperature for 2 h and then stirred and evaporated in an 80 °C water bath. The dried powder was ground into powder and placed in a tube furnace again. It was calcined at 750 °C for 1 h under an inert atmosphere. The resulting solid powder was washed with dilute hydrochloric acid solution, washed with water until neutral and dried. It was then ground into powder to obtain a solid powder catalyst. (2) Weigh the solid powder catalyst obtained in step (1) and the substrate nitroaromatic hydrocarbon into a high-pressure reactor containing solvent. After sealing the high-pressure reactor and checking for leaks, purge with hydrogen gas at a certain pressure. Heat for a period of time and then stop the reaction.

2. The method according to claim 1, characterized in that: The synthesis route diagram for step (1) is as follows: 。 3. The method according to claim 1, characterized in that: The mass ratio of ethylenediamine to polyvinyl chloride is 1.0-5.0:

1.

4. The method according to claim 1, characterized in that: The reflux temperature for oil bath heating is 120-180 ℃.

5. The method according to claim 1, characterized in that: The activator alkaline solution contains KOH, NaOH, KHCO3, NaHCO3, K2CO3, or Na2CO3.

6. The method according to claim 1, characterized in that: In step (2), the reaction conditions are: hydrogen pressure 1-5 MPa, reaction temperature 230℃, and reaction time 4-12 h.

7. The method according to claim 1, characterized in that: In step (2), the nitroaromatic hydrocarbons include nitrobenzene, p-nitrotoluene, p-nitrobenzoic acid, or p-nitrostyrene.

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