Method for continuous preparation of nitrobenzene from benzene and NO2

Abstract

The application provides a method for continuously preparing nitrobenzene by using benzene and NO2 as raw materials. The method is characterized in that: a solid catalyst capable of catalyzing the nitration of benzene by NO2 is filled in a pipe reactor, benzene, NO2 and O2 are continuously fed into the pipe reactor at a certain flow rate, and the reaction is carried out at a certain temperature to obtain nitrobenzene. This route is safe, green, economical and efficient, and is a safe, green, economical and efficient nitrobenzene synthesis route.

Description

Technical Field

[0001] This invention relates to a method for the continuous preparation of nitrobenzene from benzene and NO2, which belongs to the field of green chemistry. Background Technology

[0002] Nitrobenzene (CAS No.: 98-95-3) is an important chemical raw material, commonly used as a precursor compound for pharmaceuticals, dyes, and explosives, and has significant applications in organic synthesis. The current industrial process for preparing nitrobenzene involves the nitration of benzene using a mixed acid system composed of sulfuric and nitric acids. While this route boasts high reaction efficiency, it suffers from strong exothermic, corrosive, and hazardous characteristics, making the corresponding nitration reaction a critically monitored and dangerous chemical process.

[0003] N₂O₅ or N₂O₄ are novel nitrating agents. Using highly reactive N₂O₅ or N₂O₄ instead of nitric acid for nitration reactions offers advantages such as mild reaction conditions, fast reaction rates, and the ability to carry out nitration without a catalyst. For example, the paper *Chinese Chemical Letters* 23 (2012) 73–76 reported an example of nitrating toluene using N₂O₅ without a catalyst, achieving a 64% yield at 20 °C. Although N₂O₅ and N₂O₄ exhibit high reactivity, their high price and difficulty in storage limit their industrial application value.

[0004] In comparison, NO2 is inexpensive and can even be obtained from industrial waste gas. Using NO2 as a nitrating agent would have significant industrial value. Compared to N2O5 or N2O4, NO2 is very inert and requires higher temperatures to achieve the NO2 nitration of benzene. For example, the literature e-EROS Encyclopedia of Reagents for Organic Synthesis (2009, 1-9) reports a method for nitrifying benzene using NO2, but this requires a high temperature of 171 °C. Summary of the Invention

[0005] This invention addresses the shortcomings of existing nitrating agents N2O5 or N2O4, which are expensive and difficult to store. It uses NO2, which is inexpensive and easy to store, as the nitrating agent. At the same time, it overcomes the high temperature defect of existing NO2 nitration technology for benzene. It uses a pipeline reactor filled with a solid catalyst to carry out the NO2 nitration of benzene to prepare nitrobenzene under mild conditions of -10-80℃, which has the advantages of high benzene conversion rate and high nitrobenzene selectivity.

[0006] Unlike existing methods that use mixed acid nitration and high-temperature nitration of benzene with NO2, this invention provides a method for the continuous preparation of nitrobenzene from benzene and NO2. The main technical solution of this invention involves loading a solid catalyst capable of catalyzing the nitration of benzene with NO2 into a pipeline reactor, continuously introducing benzene, NO2, and O2 into the pipeline reactor at a certain flow rate, and reacting at a certain temperature to obtain nitrobenzene.

[0007] As a further feasible option, the catalyst packed in the pipeline in the above-mentioned method for the continuous preparation of nitrobenzene from benzene and NO2 can be H-type Amberlyst-15, Amberlyst-35, Amberlyst-36, Amberlyst-45 or perfluorosulfonic acid resin.

[0008] The above-described method for the continuous preparation of nitrobenzene from benzene and NO2 can be further implemented by using NO2 as a nitrating agent.

[0009] The above-described method for the continuous preparation of nitrobenzene from benzene and NO2 is a further feasible scheme with a reaction space velocity of 0.1-6 g benzene / g catalyst / h.

[0010] The above-described method for the continuous preparation of nitrobenzene from benzene and NO2, as a further feasible approach, involves a reaction temperature of -10 to 80°C. o C (when the reaction temperature is below 10) o At step C, a mixed solution of benzene and dichloroethane with a mass ratio of 1:1 is used instead of benzene.

[0011] The above method for the continuous preparation of nitrobenzene from benzene and NO2 can be further implemented in which the mass ratio of NO2 to benzene in the feed is 5:1 to 0.5:1.

[0012] As a further feasible approach, the above method for the continuous preparation of nitrobenzene from benzene and NO2 can be implemented with a feed O2 to NO2 mass ratio of 5:1 to 1:1.

[0013] The advantages and effects of this invention are as follows: Compared with existing mixed acid nitration methods for preparing nitrobenzene, this invention provides a new process for preparing nitrobenzene with low exothermic activity, low corrosion, and good safety. Compared with existing nitration methods using N2O5 or N2O4 as nitrating agents, this invention provides a method for producing nitrobenzene using inexpensive NO2 at high efficiency. Compared with existing methods using NO2 as a nitrating agent, this invention provides a method for the continuous production of nitrobenzene under mild conditions. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the continuous preparation process of nitrobenzene from benzene and NO2 in an embodiment of the present invention. Detailed Implementation Plan

[0015] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Variations are included within the technical scope of the present invention without departing from the general spirit and intent. Example 1

[0016] 50.0 g of Amberlyst-35 resin was packed into a 1 cm diameter tubular reactor. The reactor temperature was set to 50 °C, and the benzene, NO2, and O2 preheating temperatures were all 40 °C. The reactants were simultaneously introduced at flow rates of 1.0 g / min (corresponding to a space velocity of 1.2 g benzene / g catalyst / h), 2.0 g / min NO2, and 4.0 g / min O2. After the reaction system stabilized for 20 minutes, the elution product was collected. After NO2 removal under reduced pressure, the composition of the elution product was analyzed by gas chromatography. The results showed a benzene conversion rate of 68.9% and a nitrobenzene selectivity of 99.1%.

[0017] Examples 2-5

[0018] Similar to Example 1, different catalysts were used to catalyze the benzene nitration reaction with NO2 as the nitrating agent, and the results are shown in Table 1.

[0019] .

[0020] Examples 6-8

[0021] Similar to Example 1, the reaction was carried out at different benzene flow rates, and the results are shown in Table 2.

[0022] .

[0023] Examples 9-13

[0024] Similar to Example 1, the reaction was carried out at different temperatures, and the results are shown in Table 3.

[0025] .

[0026] Note: Temperatures are -10 and 0. o At time C, a mixed solution of benzene and dichloroethane with a mass ratio of 1:1 is used instead of benzene.

[0027] Examples 14-16

[0028] Similar to Example 1, the reaction was carried out using different NO2 flow rates, and the results are shown in Table 4.

[0029] .

[0030] Examples 17-19

[0031] Similar to Example 1, different O2 flow rates were used for the reaction, and the results are shown in Table 5.

[0032] .

[0033] Analysis of the data from the above embodiments shows that, compared to existing mixed acid nitration processes, the present invention, using NO2 as a nitrating agent to nitrate benzene to nitrobenzene, has advantages such as mild reaction conditions, low exothermic reaction, and low material corrosivity. Compared to existing NO2 nitration processes, the method provided by the present invention achieves efficient benzene NO2 nitration under mild conditions and obtains nitrobenzene with high selectivity. Furthermore, the present invention significantly improves the preparation efficiency of nitrobenzene through continuous flow reaction.

Claims

1. A method for the continuous preparation of nitrobenzene from benzene and NO2, characterized in that... A solid catalyst capable of catalyzing the nitration of benzene with NO2 is packed into a pipeline reactor. Benzene, NO2, and O2 are continuously fed into the pipeline reactor at a certain flow rate. nitrobenzene is produced by reacting NO2 as the nitrating agent at a certain temperature. The solid catalyst packed in the pipeline reactor is H-type Amberlyst-15, Amberlyst-35, Amberlyst-36, Amberlyst-45, or perfluorosulfonic acid resin.

2. The method for continuously preparing nitrobenzene from benzene and NO2 as raw materials according to claim 1, characterized in that... The reaction space velocity is 0.1-6 g benzene / g catalyst / hour.

3. The method for continuously preparing nitrobenzene from benzene and NO2 as raw materials according to claim 1, characterized in that... The reaction temperature is -10 to 80℃.

4. The method for continuously preparing nitrobenzene from benzene and NO2 as raw materials according to claim 1 or 3, characterized in that... When the reaction temperature is below 10℃, a mixed solution of benzene and dichloroethane with a mass ratio of 1:1 is used instead of benzene.

5. The method for continuously preparing nitrobenzene from benzene and NO2 as raw materials according to claim 1, characterized in that... The mass ratio of NO2 to benzene in the feed is 5:1 to 0.5:

1.

6. The method for continuously preparing nitrobenzene from benzene and NO2 as raw materials according to claim 1, characterized in that... The mass ratio of O2 to NO2 in the feed is 5:1 to 1:1.

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