Polymeric triphenylboron Lewis acid catalyst for nitrating NO2 to prepare nitrobenzene as well as preparation method and application of polymeric triphenylboron Lewis acid catalyst

Abstract

The invention relates to a polymeric triphenylboron Lewis acid catalyst for nitrating NO2 to prepare nitrobenzene as well as a preparation method and application of the polymeric triphenylboron Lewis acid catalyst. The polymeric triphenylboron Lewis acid catalyst can be prepared through a Friedel-Crafts reaction between triphenylboron and dichloroethane. Polymerized triphenylboron lewis acid is used as a catalyst, NO2 is used as a nitrating agent, O2 is used as an oxidizing agent, dichloroethane is used as a solvent, and nitrobenzene can be prepared by nitrating benzene at the temperature of 0-50 DEG C and the pressure of 0.1-3 MPa. After the reaction is finished, the catalyst can be recycled through filtration. Compared with the existing nitration method, the benzene nitration clean production process provided by the invention has the advantages of weak heat release, low corrosion and low pollution.

Description

Technical Field

[0001] The invention relates to a polymeric triphenylboron Lewis acid catalyst and a preparation method thereof and a method for nitrifying benzene NO2 to prepare nitrobenzene, belonging to the field of fine chemicals. Background Art

[0002] Nitrobenzene is an important chemical raw material, which can be used as a raw material for preparing aniline, benzidine, azobenzene, etc. At present, the mixed acid nitration method is used in the industry to prepare nitrobenzene, that is, a mixed acid system composed of sulfuric acid and nitric acid is used as a catalyst and a nitrating agent to nitrate benzene to prepare nitrobenzene. For example, patent CN102516082A reports a method for preparing nitrobenzene by reacting benzene with mixed acid, and the mixed acid system used contains 3-30% nitric acid, 50-80% sulfuric acid, and 10-25% water; patent US4091042 reports a method for preparing nitrobenzene by nitration of benzene and mixed acid (HNO3 3.0-7.5wt%, H2SO458.5-66.5 wt%, H2O 28-37 wt%) at 80-120°C, and the conversion rate of this method reaches 98%. Although the above-mentioned method of nitration using mixed acid has a fast reaction rate and good reaction selectivity, it has problems such as strong reaction exotherm, strong corrosiveness of mixed acid, and poor process safety, which brings huge challenges to the environment and safe production.

[0003] In order to solve the environmental and safety problems caused by traditional mixed acid nitration, the method of using nitrogen oxides as nitrating agents for nitration has gained more and more attention. Although the catalytic system reported so far has a good catalytic effect on toluene, the effect of NO2 nitration of benzene is not ideal because benzene is more inert than toluene and NO2 is more inert than N2O4, N2O5, etc. in nitrogen oxides. For example, the document Chem. Commun. (2000, 1571–1572) reported a method of nitration of toluene using β molecular sieve as catalyst and NO2 as nitrating agent. Toluene can obtain a 100% conversion rate, but under the same reaction conditions and with a 1-fold extension of the reaction time, benzene can only achieve a 55% conversion rate. The method reported in the document e-EROS Encyclopedia of Reagents for Organic Synthesis (2009, 1-9) even requires a high temperature of 171°C to achieve NO2 nitration of benzene.

[0004] There has been no good solution for how to achieve efficient benzene NO2 nitration under mild conditions and obtain nitrobenzene with high selectivity. Summary of the invention

[0005] The present invention aims to provide a novel polymeric triphenylborane Lewis acid catalyst, and utilize the catalyst to achieve efficient benzene NO2 nitration under mild conditions and obtain nitrobenzene (attached Figure 1), this method can overcome the problems of low benzene conversion rate and high reaction temperature in the existing methods.

[0006] The main technical scheme of the present invention is a polymeric triphenylboron Lewis acid catalyst, characterized in that the catalyst is prepared from aluminum trichloride or ferric trichloride and triphenylboron, and the mass ratio of aluminum trichloride or ferric trichloride to triphenylboron in the catalyst is 5:1-0.5:1.

[0007] The present invention also provides a method for preparing the above-mentioned polymeric triphenylboron Lewis acid catalyst, which is characterized in that the catalyst preparation comprises the following steps: adding triphenylboron, dichloroethane, aluminum trichloride or ferric chloride into a pressure-resistant reactor, adding methanol for quenching after the reaction is completed, and performing Soxhlet extraction with dichloromethane, and the obtained solid is the polymeric triphenylboron Lewis acid catalyst.

[0008] As a further feasible scheme, the above-mentioned method for preparing the polymeric triphenylboron Lewis acid catalyst uses aluminum chloride or ferric chloride as the catalyst for catalyst synthesis.

[0009] The method for preparing nitrobenzene by nitrating benzene with NO2 using a polymeric triphenylboron Lewis acid catalyst provided by the present invention is characterized in that it comprises the following steps: adding benzene, a solvent, a polymeric triphenylboron Lewis acid catalyst and NO2 into a pressure-resistant reactor, filling with oxygen, reacting under vigorous stirring, and after the reaction is completed, removing unreacted NO2 under reduced pressure to obtain a nitrobenzene solution.

[0010] In the above-mentioned method for nitrifying benzene with NO2 to prepare nitrobenzene, as a further feasible scheme, the mass ratio of polymeric triphenylboron Lewis acid to benzene is 0.005:1-0.1:1.

[0011] The above-mentioned method for nitrifying benzene with NO2 to produce nitrobenzene, as a further feasible scheme, has a mass ratio of NO2 to benzene of 1:1-20:1.

[0012] The above-mentioned method for nitrifying benzene with NO2 to prepare nitrobenzene, as a further feasible scheme, the solvent is benzene, dichloromethane, chloroform, dichloroethane, trichloroethane.

[0013] The above-mentioned method for nitrifying benzene with NO2 to prepare nitrobenzene, as a further feasible scheme, the reaction temperature is -10-50 o C.

[0014] The above-mentioned method for nitrifying benzene with NO2 to produce nitrobenzene, as a further feasible scheme, has an oxygen pressure of 0.1-3MPa.

[0015] The above-mentioned method for nitrifying benzene with NO2 to prepare nitrobenzene, as a further feasible scheme, is that after the reaction is completed, the catalyst can be recovered and reused by filtering.

[0016] Compared with the existing method of preparing nitrobenzene by nitration of benzene, the present invention provides a clean production process of nitrobenzene with low corrosion and high safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The embodiment is a reaction process diagram of the nitration of benzene with NO2 using polymeric triphenylborane Lewis acid as catalyst to produce nitrobenzene.

[0018] Figure 2 The invention is a synthesis method and a schematic diagram of the structure of a polymeric triphenylboron Lewis acid catalyst.

[0019] Figure 3 It is the EDS-Mapping diagram of the catalyst synthesized in the example.

[0020] Figure 4 is an element distribution diagram of the catalyst synthesized in the example. DETAILED DESCRIPTION

[0021] 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

[0022] Catalyst preparation: 10.0 g triphenylborane, 100 mL dichloroethane, and 30.0 g aluminum chloride were added to a 500 mL pressure reactor at 80 o C for 24 hours. Then cool to 50 o C, slowly add 200 mL of methanol to quench the reaction. Stir for 2 h to remove the aluminum chloride. o The mixed system after the reaction was subjected to Soxhlet extraction with dichloromethane at 400 °C, and the obtained solid was dried to obtain 8.9 g of polymeric triphenylboron Lewis acid catalyst.

[0023] The characterization results of the obtained catalyst are shown in the attached Figure 3 and attached Figure 4 , by the attached Figure 3 It can be seen that elements such as C, B, and Cl are evenly distributed on the catalyst surface. Figure 4 It can be seen that element C accounts for 84.96%, element B accounts for 12.11%, and element Cl accounts for 1.30%. Example 2

[0024] 3.0 g benzene, 20.0 g 1,2-dichloroethane, 15.0 g NO2, and 0.03 g polymeric triphenylboron Lewis acid catalyst were added to a 100 mL pressure reactor in sequence, and 1.0 MPa of oxygen was added. The reaction was stirred vigorously at 0°C for 8 hours. After the reaction was completed, the unreacted NO2 was removed under reduced pressure to obtain a nitrobenzene solution. The reaction solution was analyzed by gas chromatography, showing a benzene conversion rate of 86.1% and a nitrobenzene selectivity of 99.3%. Embodiment 3-7

[0025] Similar to Example 1, a polymeric triphenylborane Lewis acid catalyst was synthesized by a different method. Then, benzene was nitrated with NO2 to produce nitrobenzene by a method similar to Example 2. The results are shown in Table 1.

[0026] . Embodiment 8-10

[0027] Similar to Example 2, different catalyst amounts were used to catalyze the nitration of benzene with NO2 to produce nitrobenzene. The results are shown in Table 2.

[0028] . Examples 11-13

[0029] Similar to Example 2, different amounts of NO2 were used to nitrate benzene to produce nitrobenzene. The results are shown in Table 3.

[0030] . Examples 14-17

[0031] Similar to Example 2, different solvents were used to nitrate benzene with NO2 to produce nitrobenzene. The results are shown in Table 4.

[0032] . Examples 18-20

[0033] Similar to Example 2, different temperatures were used to nitrate benzene with NO2 to produce nitrobenzene. The results are shown in Table 5.

[0034] . Examples 21-23

[0035] Similar to Example 2, different pressures were used to nitrate benzene with NO2 to produce nitrobenzene. The results are shown in Table 6.

[0036] . Embodiment 24

[0037] Catalyst recovery and application: Similar to Example 2, after the reaction is completed, the polymerized triphenylboron Lewis acid catalyst (recovered) is obtained by filtration and separation.

[0038] 3.0 g benzene, 20.0 g 1,2-dichloroethane, 15.0 g NO2, and 0.03 g polymeric triphenylboron Lewis acid catalyst (recovered) were added to a 100 mL pressure reactor in sequence, and 1.0 MPa of oxygen was added. The reaction was stirred vigorously at 0°C for 8 h. After the reaction was completed, the unreacted NO2 was removed under reduced pressure to obtain a nitrobenzene solution. The reaction solution was analyzed by gas chromatography, showing a benzene conversion rate of 86.0% and a nitrobenzene selectivity of 99.2%.

[0039] 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.

Claims

1. A polymeric triphenylboron Lewis acid catalyst, characterized in that The catalyst is prepared from aluminum trichloride or ferric trichloride and triphenyl boron, and the mass ratio of aluminum trichloride or ferric trichloride to triphenyl boron in the catalyst is 5:1-0.5:

1.

2. The method for preparing a polymeric triphenylboron Lewis acid catalyst according to claim 1, characterized in that The catalyst preparation comprises the following steps: adding triphenylboron, dichloroethane, aluminum trichloride or ferric chloride into a pressure-resistant reactor, adding methanol for quenching after the reaction is completed, and performing Soxhlet extraction with dichloromethane to obtain a solid which is a polymerized triphenylboron Lewis acid catalyst.

3. The preparation method according to claim 2, characterized in that The catalyst used in the synthesis of polymeric triphenylboron Lewis acid is aluminum chloride or ferric chloride.

4. The method of preparing nitrobenzene by nitration of benzene with NO2 using a polymeric triphenylboron Lewis acid catalyst according to claim 1, characterized in that The method comprises the following steps: adding benzene, solvent, polymerized triphenylboron Lewis acid catalyst and NO2 into a pressure-resistant reactor, introducing oxygen, reacting under vigorous stirring, and after the reaction is completed, removing unreacted NO2 under reduced pressure to obtain a nitrobenzene solution.

5. The method according to claim 4, characterized in that The solvent is benzene, dichloromethane, chloroform, dichloroethane or trichloroethane.

6. The method according to claim 4, characterized in that When benzene is nitrated with NO2 to produce nitrobenzene, the mass ratio of polymeric triphenylboronic Lewis acid to benzene is 0.005:1-0.1:

1.

7. The method according to claim 4, characterized in that When benzene is nitrated with NO2 to produce nitrobenzene, the mass ratio of NO2 to benzene is 1:1-20:

1.

8. The method according to claim 4, characterized in that The reaction temperature for nitration of benzene with NO2 to produce nitrobenzene is -10-50℃.

9. The method according to claim 4, characterized in that When benzene NO2 is nitrated to produce nitrobenzene, the oxygen pressure is 0.1-3MPa.

10. The method according to claim 4, characterized in that After the reaction is completed, the catalyst is recovered and reused by filtering.

Images