A method for preparing p-phenylenediamine from nitrobenzene

Abstract

The present invention provides a method for preparing p-phenylenediamine from nitrobenzene, comprising the following steps: S1) contacting nitrobenzene and urea with an MgO-based solid base catalyst and conducting a first reaction to obtain a mixture of p-nitroaniline and p-nitrosoaniline; S2) contacting the p-nitroaniline and p-nitrosoaniline mixture obtained in step S1) with an N-doped, C-supported, non-precious metal Ni-based bimetallic single-atom catalyst and conducting a second reaction under an H2 atmosphere to obtain p-phenylenediamine. The method for preparing p-phenylenediamine from nitrobenzene and urea provided herein has the advantages of low catalyst and raw material costs, good catalyst activity and reusability, high conversion rate and product selectivity, and a clean reaction process.

Description

Technical Field

[0001] The present invention relates to the technical field of organic chemical industry, in particular to a method for preparing p-phenylenediamine from nitrobenzene. Background Art

[0002] Paraphenylenediamine has a wide range of uses. It is a commonly used sensitive reagent for testing iron and copper. It is also used in the production of azo disperse dyes, acid dyes, direct dyes, sulfur dyes, fur dyes, rubber antioxidants and photographic developers. It is also used in the production of para-aramid, polyamide-imide resins, polyurethanes and other polymers. It is widely used in aircraft, rockets, missiles, fireproof and bulletproof equipment, automobiles, ships, rubber reinforcement materials, special ropes, high-temperature resistant filter materials, etc.

[0003] The industrial production method for p-phenylenediamine primarily involves the reduction of p-nitroaniline in the presence of a stoichiometric amount of a reducing agent, such as iron powder. p-Nitroaniline is primarily produced via the ammonolysis of p-chloronitrobenzene or the nitration-hydrolysis of N-acetanilide. This method is subject to severe equipment corrosion, long routes, high energy consumption and production costs, and generates large amounts of acidic gaseous, liquid, and solid waste, resulting in significant environmental pollution. Patents such as US6245943B1 and CN1332150A report a method for preparing p-phenylenediamine from nitrobenzene and urea. Nitrobenzene, urea, and a base react to produce 4-nitrosoaniline and 4-nitroaniline, which are then catalytically hydrogenated using a precious metal catalyst, such as Pd / C or Pt / C, to produce p-phenylenediamine. This method uses nitrobenzene and urea as raw materials to produce p-phenylenediamine, which is readily available and inexpensive. However, the use of stoichiometric amounts of bases, such as potassium hydroxide and potassium carbonate, results in high material consumption. Furthermore, the use of precious metal hydrogenation catalysts, such as Pd / C or Pt / C, results in high catalyst costs. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing p-phenylenediamine from nitrobenzene, which has low catalyst and raw material costs and good catalyst activity and reusability.

[0005] The present invention provides a method for preparing p-phenylenediamine from nitrobenzene, comprising the following steps:

[0006] S1) contacting nitrobenzene and urea with a MgO-based solid base catalyst and performing a first reaction to obtain a mixture of p-nitroaniline and p-nitrosoaniline;

[0007] S2) contacting the mixture of p-nitroaniline and p-nitrosoaniline obtained in step S1) with an N-doped C-supported non-noble metal Ni-based bimetallic single-atom catalyst, and performing a second reaction under a H2 atmosphere to obtain p-phenylenediamine.

[0008] According to the present invention, the reaction equation for preparing p-phenylenediamine from nitrobenzene and urea is as follows:

[0009]

[0010] According to the present invention, in the first reaction described above, a solid base catalyst is crucial for the reaction between nitrobenzene and urea. Without the solid base catalyst, nitrobenzene and urea do not react; and when the solid base catalyst is inactive, the conversion rate of nitrobenzene is very low. The solid base catalyst described in the present invention is a MgO-based solid base catalyst.

[0011] Optionally, the MgO-based solid base catalyst is prepared by using at least one of Sn salt, Al salt, and Zr salt and Mg salt as raw materials through a hydrothermal synthesis method and a heat treatment method.

[0012] Optionally, the Sn salt is selected from at least one of Sn hydrochloride, sulfate, nitrate and acetate.

[0013] Optionally, the Al salt is selected from at least one of Al hydrochloride, Al sulfate, Al nitrate and Al acetate.

[0014] Optionally, the Zr salt is selected from at least one of Zr hydrochloride, sulfate, nitrate and acetate.

[0015] Optionally, the Mg salt is selected from at least one of Mg hydrochloride, Mg sulfate, Mg nitrate and Mg acetate.

[0016] Optionally, the MgO-based solid base catalyst is selected from at least one of MgO / SnO2, MgO / γ-Al2O3, and MgO / ZrO2.

[0017] Optionally, the molar ratio of nitrobenzene to urea is 1:2 to 1:4.

[0018] Optionally, the amount of the MgO-based solid base catalyst used is 2% to 10% of the mass of nitrobenzene.

[0019] Optionally, the temperature of the first reaction is 80-100°C.

[0020] Optionally, the first reaction time is 1 to 2 hours.

[0021] The solvent for the first reaction is selected from dimethyl sulfoxide, water or 50%-95% volume concentration of ethanol aqueous solution.

[0022] According to the present invention, in the second reaction, a hydrogenation catalyst is crucial for the hydrogenation of p-nitroaniline and p-nitrosoaniline. Without a catalyst, p-nitroaniline and p-nitrosoaniline do not undergo hydrogenation, resulting in no p-phenylenediamine product. Low catalyst activity results in very low conversion rates of p-nitroaniline and p-nitrosoaniline. The hydrogenation catalyst described herein is a non-precious metal Ni-based bimetallic single-atom catalyst supported by N-doped carbon.

[0023] Optionally, the N-doped C-supported non-noble metal Ni-based bimetallic single-atom catalyst is prepared using at least one of Cu salt, Co salt, and Cr salt, as well as Ni salt and a bidentate nitrogen-containing organic compound as raw materials.

[0024] Optionally, the Cu salt is selected from at least one of Cu hydrochloride, Cu sulfate, Cu nitrate and Cu acetate.

[0025] Optionally, the Co salt is selected from at least one of Co hydrochloride, sulfate, nitrate and acetate.

[0026] Optionally, the Cr salt is selected from at least one of Cr hydrochloride, sulfate, nitrate and acetate.

[0027] Optionally, the Ni salt is selected from at least one of Ni hydrochloride, sulfate, nitrate and acetate.

[0028] Optionally, the bidentate nitrogen-containing organic compound is at least one selected from o-phenanthroline, 2,2'-bipyridine, and disodium ethylenediaminetetraacetate.

[0029] Optionally, the N-doped C-loaded non-precious metal Ni-based bimetallic single atom catalyst is selected from one or more of N-doped C-loaded Ni-Cu bimetallic single atom catalyst, N-doped C-loaded Ni-Co bimetallic single atom catalyst, and N-doped C-loaded Ni-Cr bimetallic single atom catalyst.

[0030] Optionally, the amount of the N-doped C-supported non-noble metal Ni-based bimetallic single-atom catalyst used is 2% to 4% of the mass of nitrobenzene.

[0031] Optionally, the temperature of the second reaction is 60-100°C.

[0032] Optionally, the second reaction time is 1-2 hours.

[0033] Optionally, the pressure of H2 is 0.5-2 MPa.

[0034] The solvent for the second reaction is selected from methanol.

[0035] Compared to the prior art, the present invention provides a method for preparing p-phenylenediamine from nitrobenzene, comprising the following steps: S1) contacting nitrobenzene and urea with an MgO-based solid base catalyst and conducting a first reaction to obtain a mixture of p-nitroaniline and p-nitrosoaniline; S2) contacting the p-nitroaniline and p-nitrosoaniline mixture obtained in step S1) with an N-doped, C-supported, non-precious metal Ni-based bimetallic single-atom catalyst and conducting a second reaction under an H2 atmosphere to obtain p-phenylenediamine. The method for preparing p-phenylenediamine from nitrobenzene and urea provided herein has the advantages of low catalyst and raw material costs, good catalyst activity and reusability, high conversion rate and product selectivity, and a clean reaction process. DETAILED DESCRIPTION

[0036] To further illustrate the present invention, the method for preparing p-phenylenediamine from nitrobenzene provided by the present invention is described in detail below with reference to examples, but the present application is not limited to these examples.

[0037] Unless otherwise specified, the raw materials in the examples of this application were purchased from commercial sources. Unless otherwise specified, the testing methods were all conventional methods.

[0038] The conversion rate and selectivity in the examples of this application are calculated as follows:

[0039]

[0040]

[0041] Example 1

[0042] To a mixture of 0.1 mol (35.06 g) of SnCl4·5H2O and 200 mL of water, 0.1 mol / L KOH solution was added dropwise to a pH of 7 to generate a white precipitate. The mixture was filtered, and 0.5 mol / L KOH solution was added to a pH of 13. The resulting solution was added dropwise to a mixture of 0.1 mol (20.33 g) of MgCl2·6H2O, 3 g of P123 polymer and 200 mL of water. The mixture was stirred at room temperature for 6 h, heated at 200°C for 12 h, cooled to room temperature, filtered, dried, and calcined at 500°C under a N2 atmosphere for 4 h to obtain 19.10 g of the MgO / SnO2 solid base catalyst I.

[0043] Example 2

[0044] 0.2 mol (51.28 g) of Mg(NO3)2·6H2O, 0.1 mol (37.51 g) of Al(NO3)3·9H2O, and 2 g of hexadecyltrimethylammonium bromide were mixed evenly with 400 mL of 50% ethanol solution, stirred at 60°C for 1 h, 25% ammonia water was added dropwise until the pH reached 9, and heating and stirring were continued for 6 h. The mixture was cooled to room temperature, filtered, dried, and calcined at 600°C under N2 atmosphere for 3 h to obtain 18.28 g of the MgO / γ-Al2O3 solid base catalyst II.

[0045] Example 3

[0046] 0.1 mol (21.45 g) of Mg(CH3COO)2·4H2O, 0.2 mol (70.48 g) of Zr(SO4)2·4H2O, 3 g of hexadecyltrimethylammonium bromide and 600 mL of 75% ethanol solution were mixed uniformly, stirred at 50°C for 2 h, 25% ammonia water was added dropwise until the pH reached 10, and heating and stirring were continued for 4 h. The mixture was cooled to room temperature, filtered, dried, and calcined at 700°C under N2 atmosphere for 2 h to obtain 28.61 g of the MgO / ZrO2 solid base catalyst III.

[0047] Example 4

[0048] 1mmol (0.24g) of NiCl2·6H2O, 1mmol (0.17g) of CuCl2·2H2O, 0.1mol (18.02g) of o-phenanthroline and 100mL of 75% ethanol were mixed, stirred at 60°C for 3h, and the solvent was evaporated and dried to obtain 18.28g of Ni and Cu complex of o-phenanthroline. The complex was evenly mixed with 91.40g of Na2CO3, calcined at 800°C for 4h under N2 atmosphere, cooled to room temperature, washed with water, and dried to obtain 16.32g of the N-doped C-supported Ni-Cu bimetallic single atom catalyst IV.

[0049] Example 5

[0050] 1mmol (0.28g) NiSO4·7H2O, 3mmol (0.72g) CoCl2·6H2O, 0.4mol (62.40g) 2,2'-bipyridine and 500mL 95% ethanol were mixed, stirred at 70°C for 1h, and the solvent was evaporated and dried to obtain 62.66g of nickel and cobalt complexes of 2,2'-bipyridine. The complexes were evenly mixed with 124.72g NaHCO3, calcined at 1000°C for 2h under N2 atmosphere, cooled to room temperature, washed with water, and dried to obtain 58.89g of the N-doped C-supported Ni-Co bimetallic single atom catalyst V.

[0051] Example 6

[0052] 3mmol (0.75g) Ni(CH3COO)2·4H2O, 1mmol (0.17g) Cr(NO3)3·9H2O, 0.2mol (67.24g) disodium ethylenediaminetetraacetate and 500mL 50% ethanol were mixed, stirred at 40°C for 5h, and the solvent was evaporated and dried to obtain 67.46g of Ni and Cr complex of disodium ethylenediaminetetraacetate. The complex was evenly mixed with 134.48g K2CO3, calcined at 900°C for 3h under N2 atmosphere, cooled to room temperature, washed with water, and dried to obtain 63.68g of the N-doped C-supported Ni-Cr bimetallic single atom catalyst VI.

[0053] Example 7

[0054] 0.1 mol (12.31 g) of nitrobenzene, 0.3 mol (18.02 g) of urea, 0.62 g of MgO / SnO2 solid base catalyst I and 30 g of dimethyl sulfoxide were mixed, heated and stirred at 90°C for 2 h. GC-MS analysis showed that the nitrobenzene conversion was 100%, and a mixture of p-nitroaniline and p-nitrosoaniline was obtained. The mixture was cooled to room temperature, allowed to stand, and then centrifuged. The obtained solid MgO / SnO2 solid base catalyst I was recycled. After the solvent was evaporated from the obtained liquid, 30 g of methanol and 0.25 g of N-doped C-loaded Ni-Cu bimetallic single atom catalyst IV were added, 2 MPa of H2 was injected, and the mixture was heated and stirred at 90°C for 2 h. GC-MS analysis showed that the selectivity for p-phenylenediamine was 100%. The mixture was cooled to room temperature, allowed to stand, and then centrifuged. The obtained N-doped C-loaded Ni-Cu bimetallic single atom catalyst IV was recycled.

[0055] Example 8

[0056] 0.1 mol (12.31 g) of nitrobenzene, 0.2 mol (12.01 g) of urea, 0.24 g of MgO / γ-Al2O3 solid base catalyst II and 30 g of dimethyl sulfoxide were mixed, heated and stirred at 100°C for 1 h. GC-MS analysis showed that the nitrobenzene conversion was 100%, and a mixture of p-nitroaniline and p-nitrosoaniline was obtained. The mixture was cooled to room temperature, allowed to stand, and then centrifuged. The obtained solid MgO / γ-Al2O3 solid base catalyst II was recycled. After the solvent was evaporated from the obtained liquid, 30 g of methanol and 0.50 g of N-doped C-loaded Ni-Co bimetallic single atom catalyst V were added. 1 MPa of H2 was injected, and the mixture was heated and stirred at 100°C for 1 h. GC-MS analysis showed that the selectivity for p-phenylenediamine was 100%. The mixture was cooled to room temperature, allowed to stand, and then centrifuged. The obtained N-doped C-loaded Ni-Co bimetallic single atom catalyst V was recycled.

[0057] Example 9

[0058] 0.1 mol (12.31 g) of nitrobenzene, 0.4 mol (24.02 g) of urea, 1.23 g of MgO / ZrO2 solid base catalyst III and 40 g of dimethyl sulfoxide were mixed, heated and stirred at 80°C for 2 h. GC-MS analysis showed that the nitrobenzene conversion was 100%, and a mixture of p-nitroaniline and p-nitrosoaniline was obtained. The mixture was cooled to room temperature, allowed to stand, and then centrifuged. The obtained solid MgO / ZrO2 solid base catalyst III was recycled. After the solvent was evaporated from the obtained liquid, 30 g of methanol and 0.49 g of N-doped C-loaded N-doped C-loaded Ni-Cr bimetallic single atom catalyst VI were added, 0.5 MPa of H2 was injected, and the mixture was heated and stirred at 60°C for 2 h. GC-MS analysis showed that the selectivity for p-phenylenediamine was 100%. The mixture was cooled to room temperature, allowed to stand, and then centrifuged. The obtained N-doped C-loaded Ni-Cr bimetallic single atom catalyst VI was recycled.

[0059] Example 10

[0060] Example 10 is similar to Example 7, except that a different catalyst was used. Other reaction conditions were the same as those of Example 7. Example 10 used the MgO / SnO2 solid base catalyst I and the N-doped C-supported Ni-Cu bimetallic single atom catalyst IV, which were centrifuged after the reaction in Example 7. The results showed a nitrobenzene conversion of 100% and a p-phenylenediamine selectivity of 100%. Even after the catalyst was recycled 10 times, the nitrobenzene conversion and p-phenylenediamine selectivity remained 100%.

[0061] Comparative Examples 1-3

[0062] Comparative Examples 1-3 are similar to Example 2, except that different types of metal salts are used in the preparation of the solid base catalyst. Other preparation conditions are the same as those in Example 2.

[0063] The difference between Comparative Example 1 and Example 2 is that only 0.2 mol (51.28 g) of Mg(NO 3 ) 2 · 6H 2 O was used in the preparation of the catalyst, and no Al(NO 3 ) 3 · 9H 2 O was used, resulting in 7.98 g of MgO solid base catalyst VII.

[0064] The difference between Comparative Example 2 and Example 2 is that only 0.1 mol (37.51 g) of Al(NO 3 ) 3 · 9H 2 O was used in the preparation of the catalyst, and no Mg(NO 3 ) 2 · 6H 2 O was used, resulting in 10.15 g of γ-Al 2 O 3 catalyst VIII.

[0065] The difference between Comparative Example 3 and Example 2 is that 0.2 mol (51.28 g) of Mg(NO3)2·6H2O and 0.1 mol (22.81 g) of Ti(CH3CH2O)4 were used in the preparation of the catalyst, resulting in 15.97 g of MgO / TiO2 solid base catalyst IX.

[0066] Comparative Examples 4-6

[0067] Comparative Examples 4-6 are similar to Example 7, except that different catalysts are used and other reaction conditions are the same as Example 7.

[0068] The difference between Comparative Example 4 and Example 7 is that Comparative Example 4 uses 0.62 g of MgO solid base catalyst VII, and the conversion rate of nitrobenzene is 58%.

[0069] The difference between Comparative Example 5 and Example 7 is that Comparative Example 5 uses 0.62 g of γ-Al 2 O 3 catalyst VIII, and the conversion rate of nitrobenzene is 17%.

[0070] The difference between Comparative Example 6 and Example 7 is that Comparative Example 6 uses 0.62 g of MgO / TiO2 solid base catalyst IX, and the conversion rate of nitrobenzene is 59%.

[0071] The results of Comparative Examples 4-6 demonstrate that the catalyst composition significantly influences the reaction of urea with nitrobenzene in the reaction described herein. Using γ-Al2O3 catalyst VIII, the conversion of nitrobenzene is very low; using MgO solid base catalyst VII and MgO / TiO2 solid base catalyst IX, the conversion of nitrobenzene does not exceed 60%. However, in Examples 7-9, using MgO-based solid base catalysts such as MgO / SnO2, MgO / γ-Al2O3, and MgO / ZrO2, the conversion of nitrobenzene all reached 100%.

[0072] In summary, the present invention involves contacting nitrobenzene and urea with an MgO-based solid base catalyst to react and obtain a mixture of p-nitroaniline and p-nitrosoaniline. This mixture is then contacted with an N-doped, carbon-supported, non-precious metal Ni-based bimetallic single-atom catalyst in the presence of H2 to react and obtain p-phenylenediamine. Both the p-nitrobenzene conversion rate and p-phenylenediamine selectivity can reach 100%, and the catalytic activity remains unchanged after 10 cycles of catalyst use. This method has the advantages of low catalyst and raw material costs, good catalyst activity and reusability, high conversion rate and product selectivity, and a clean reaction process.

[0073] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing p-phenylenediamine from nitrobenzene, characterized in that: The following steps are involved: S1) contacting nitrobenzene and urea with a MgO-based solid base catalyst and performing a first reaction to obtain a mixture of p-nitroaniline and p-nitrosoaniline; S2) contacting the mixture of p-nitroaniline and p-nitrosoaniline obtained in step S1) with an N-doped C-supported non-noble metal Ni-based bimetallic single-atom catalyst, and performing a second reaction under a H2 atmosphere to obtain p-phenylenediamine; The MgO-based solid base catalyst is selected from at least one of MgO / SnO2, MgO / γ-Al2O3, and MgO / ZrO2; The molar ratio of nitrobenzene to urea is 1:2 to 1:4; The amount of the MgO-based solid base catalyst is 2% to 10% of the mass of nitrobenzene; The temperature of the first reaction is 80-100° C.; the time of the first reaction is 1-2 hours; The N-doped C-supported non-noble metal Ni-based bimetallic single-atom catalyst is prepared using at least one of Cu salt, Co salt, and Cr salt, as well as Ni salt and a bidentate nitrogen-containing organic compound as raw materials; The bidentate nitrogen-containing organic compound is selected from at least one of o-phenanthroline, 2,2'-bipyridine, and disodium ethylenediaminetetraacetate; The N-doped C-loaded non-noble metal Ni-based bimetallic single-atom catalyst is selected from one or more of an N-doped C-loaded Ni-Cu bimetallic single-atom catalyst, an N-doped C-loaded Ni-Co bimetallic single-atom catalyst, and an N-doped C-loaded Ni-Cr bimetallic single-atom catalyst; The temperature of the second reaction is 60-100° C.; the time of the second reaction is 1-2 hours.

2. The method according to claim 1, characterized in that The MgO-based solid base catalyst is prepared by using one of Sn salt, Al salt, Zr salt and Mg salt as raw materials through a hydrothermal synthesis method and a heat treatment method.

3. The method according to claim 2, characterized in that The Sn salt is selected from at least one of Sn hydrochloride, sulfate, nitrate, and acetate; The Al salt is selected from at least one of Al hydrochloride, Al sulfate, Al nitrate, and Al acetate; The Zr salt is selected from at least one of Zr hydrochloride, sulfate, nitrate, and acetate; The Mg salt is selected from at least one of Mg hydrochloride, Mg sulfate, Mg nitrate and Mg acetate.

4. The method according to claim 1, wherein The Cu salt is selected from at least one of Cu hydrochloride, Cu sulfate, Cu nitrate and Cu acetate; The Co salt is selected from at least one of Co hydrochloride, sulfate, nitrate, and acetate; The Cr salt is selected from at least one of Cr hydrochloride, sulfate, nitrate, and acetate; The Ni salt is selected from at least one of Ni hydrochloride, Ni sulfate, Ni nitrate and Ni acetate.

5. The method according to claim 1, wherein The amount of the N-doped C-supported non-noble metal Ni-based bimetallic single-atom catalyst is 2% to 4% of the mass of nitrobenzene; The pressure of H2 is 0.5-2 MPa.

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