Method for continuously preparing nitrobenzene from benzene and NO2

Abstract

The invention provides a method for continuously preparing nitrobenzene by taking benzene and NO2 as raw materials. The method comprises the following steps: filling a solid catalyst capable of catalyzing NO2 nitration of benzene in 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. The route has the advantages of cheap and easily available raw materials, high reaction efficiency, good selectivity and easy continuous production, and is a safe, green, economic and efficient nitrobenzene synthesis route.

Description

Technical Field

[0001] The invention relates to a method for continuously preparing nitrobenzene by using benzene and NO2, belonging to the field of green chemical industry. Background Art

[0002] Nitrobenzene (CAS No.: 98-95-3) is an important chemical raw material, commonly used as a precursor compound for drugs, dyes and explosives, and has important uses in the field of organic synthesis. The process route currently used in industry is to nitrate benzene using a mixed acid system consisting of sulfuric acid and nitric acid to prepare nitrobenzene. Although this route has high reaction efficiency, it has problems such as strong heat release, strong corrosion, and high danger, making the corresponding nitration reaction a hazardous chemical process that is subject to key supervision.

[0003] N2O5 or N2O4 is a new type of nitration reagent. Using highly active N2O5 or N2O4 instead of nitric acid for nitration has the characteristics of mild reaction conditions, fast reaction rate, and no need for catalyst. For example, the paper Chinese Chemical Letters 23 (2012) 73–76 reported the use of N2O5 to nitrate toluene in the absence of a catalyst. The reaction can obtain a 64% yield at 20 oC. Although N2O5 and N2O4 have high activity, they are expensive and difficult to store, making their industrial application value small.

[0004] Relatively speaking, NO2 is cheap and can even be obtained from industrial waste gas. If NO2 can be used as a nitrating agent, it will have significant industrial value. Compared with N2O5 or N2O4, NO2 is very inert and requires a higher temperature to achieve NO2 nitration of benzene. For example, the document e-EROS Encyclopedia of Reagents for Organic Synthesis (2009, 1-9) reported a method for nitrifying benzene using NO2, but it required a high temperature of 171 °C to achieve NO2 nitration of benzene. Summary of the invention

[0005] The present invention aims at the defects of the existing nitrating reagents N2O5 or N2O4 being expensive and difficult to store, and adopts NO2 which is cheap and easy to store as the nitrating reagent. Meanwhile, the defect of high temperature in the prior art of benzene nitrification by NO2 is overcome, and a pipeline reactor filled with a solid catalyst is adopted to carry out the NO2 nitrification of benzene under mild conditions of -10-80°C to prepare nitrobenzene, which has the advantages of high benzene conversion rate and high nitrobenzene selectivity.

[0006] Different from the existing mixed acid nitration and high temperature nitration of benzene with NO2, the present invention provides a method for continuously preparing nitrobenzene with benzene and NO2. The main technical scheme of the present invention is to load a solid catalyst that can catalyze the nitration of benzene with NO2 into a pipeline reactor, continuously introduce benzene, NO2 and O2 into the pipeline reactor at a certain flow rate, and react at a certain temperature to obtain nitrobenzene.

[0007] The above method for continuously preparing nitrobenzene from benzene and NO2 is a further feasible scheme, wherein the catalyst loaded in the pipeline is H-type Amberlyst-15, Amberlyst-35, Amberlyst-36, Amberlyst-45 or perfluorosulfonic acid resin.

[0008] The above method for continuously preparing nitrobenzene from benzene and NO2, as a further feasible scheme, uses NO2 as a nitrating agent.

[0009] The above method for continuously preparing nitrobenzene from benzene and NO2 is a further feasible scheme, wherein the reaction space velocity is 0.1-6 g benzene / g catalyst / hour.

[0010] The above method for continuously preparing nitrobenzene from benzene and NO2, as a further feasible scheme, the reaction temperature is -10-80 o C (when the reaction temperature is below 10 o C, use a mixed solution with a mass ratio of benzene: ethylene dichloride = 1:1 instead of benzene).

[0011] The above method for continuously preparing nitrobenzene from benzene and NO2, as a further feasible scheme, has a mass ratio of feed NO2 to benzene of 5:1-0.5:1.

[0012] The above method for continuously preparing nitrobenzene from benzene and NO2, as a further feasible scheme, has a mass ratio of feed O2 to NO2 of 5:1-1:1.

[0013] The advantages and effects achieved by the present invention are as follows: compared with the existing method of preparing nitrobenzene by mixed acid nitration, the present invention provides a new process for preparing nitrobenzene with low heat release, low corrosion and good safety. Compared with the existing nitration method using N2O5 or N2O4 as a nitrating agent, the present invention provides a method for preparing nitrobenzene by efficient nitration using cheap NO2. Compared with the existing method of preparing nitrobenzene using NO2 as a nitrating agent, the present invention provides a method for continuously producing nitrobenzene under mild conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a schematic diagram of the process of continuously preparing nitrobenzene from benzene and NO2. Specific implementation plan

[0015] The embodiments of the present invention will be described in detail below in conjunction with examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. Without departing from the scope of the preceding and following purposes, variations are included within the technical scope of the present invention. Example 1

[0016] Amberlyst-35 resin 50.0g was loaded into a pipe reactor with a diameter of 1 cm. The pipe reactor temperature was set to 50℃, the benzene preheating temperature was 40℃, and the NO2 and O2 preheating temperatures were 40℃. The reactants were introduced at a benzene flow rate of 1.0 g / min (corresponding to a space velocity of 1.2 g benzene / g catalyst / hour), a NO2 flow rate of 2.0 g / min, and an O2 flow rate of 4.0 g / min. After the reaction system was stabilized for 20 minutes, the outflow product was collected. After NO2 was removed by decompression, the composition of the outflow product was analyzed by gas chromatography. The results showed that the benzene conversion rate was 68.9% and the nitrobenzene selectivity was 99.1%. Embodiment 2-5

[0017] Similar to Example 1, different catalysts were used to catalyze the benzene nitration reaction using NO2 as the nitrating agent. The results are shown in Table 1.

[0018] . Embodiment 6-8

[0019] Similar to Example 1, the reaction was carried out using different benzene flow rates. The results are shown in Table 2.

[0020] . Examples 9-13

[0021] Similar to Example 1, the reactions were carried out at different temperatures. The results are shown in Table 3.

[0022] .

[0023] Note: The temperature is -10 and 0 o C, a mixed solution with a mass ratio of benzene to ethylene dichloride = 1:1 is used instead of benzene. Examples 14-16

[0024] Similar to Example 1, the reaction was carried out using different NO2 flow rates. The results are shown in Table 4.

[0025] . Examples 17-19

[0026] Similar to Example 1, the reaction was carried out using different O2 flow rates. The results are shown in Table 5.

[0027] .

[0028] From the data analysis of the above embodiments, it can be seen that compared with the existing mixed acid nitration process, the present invention uses NO2 as a nitrating agent to nitrate benzene to produce nitrobenzene, which has the advantages of mild reaction conditions, low reaction heat release, and low material corrosiveness. Compared with the existing NO2 nitration process, the method provided by the present invention achieves efficient benzene NO2 nitration under mild conditions and obtains nitrobenzene with high selectivity. At the same time, the present invention greatly improves the preparation efficiency of nitrobenzene through continuous flow reaction.

Claims

1. A method for continuously preparing nitrobenzene using benzene and NO2 as raw materials, characterized in that The pipeline reactor is filled with a solid catalyst that can catalyze the nitration of benzene with NO2. Benzene, NO2 and O2 are continuously introduced into the pipeline reactor at a certain flow rate, and react at a certain temperature to produce nitrobenzene.

2. The method for continuously preparing nitrobenzene using benzene and NO2 as raw materials according to claim 1, characterized in that The catalyst filled in the pipeline is H-type Amberlyst-15, Amberlyst-35, Amberlyst-36, Amberlyst-45 or perfluorosulfonic acid resin.

3. The method for continuously preparing nitrobenzene using benzene and NO2 as raw materials according to claim 1, characterized in that Use NO2 as nitrifying agent.

4. The method for continuously preparing nitrobenzene using 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.

5. The method for continuously preparing nitrobenzene using benzene and NO2 as raw materials according to claim 1, characterized in that The reaction temperature is -10-80°C.

6. The method for continuously preparing nitrobenzene using benzene and NO2 as raw materials according to claim 1 or 5, characterized in that When the reaction temperature is lower than 10°C, a mixed solution with a mass ratio of benzene to ethylene dichloride = 1:1 is used instead of benzene.

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

1.

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

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