Catalyst for preparing azobenzene oxide from nitrobenzene through one-step method and preparation method

Abstract

The invention discloses a catalyst for preparing azobenzene oxide from nitrobenzene by a one-step method and a preparation method, the catalyst is an amorphous phase composite oxide, the chemical formula of the catalyst is Nix-Aly-Oz, x, y and z are numbers of Ni, Al and O respectively, x is equal to 1-20, y is equal to 80-99, and z is equal to 2-3; the preparation method comprises the following steps: dissolving the nickel salt, the aluminum salt and the complexing agent in water, heating to 60-80 DEG C, stirring for 3-6 hours, drying by distillation at 80-110 DEG C, and roasting in air at 400-700 DEG C for 3-5 hours; the molar ratio of the nickel salt to the aluminum salt is 1: (4-99), and the molar ratio of the complexing agent to the metal ions is (1-4): 1. When the azobenzene oxide is prepared from nitrobenzene through a one-step method as a catalyst, the reaction activity and the yield of the azobenzene oxide can be remarkably improved, the highest nitrobenzene conversion rate is 88.0%, the selectivity of the azobenzene oxide is 86.1%, and meanwhile the azobenzene oxide has the advantages of being small in dosage, low in cost, simple in process, high in yield and selectivity and the like.

Description

Technical Field

[0001] The invention belongs to the field of heterogeneous catalysis, and in particular relates to a catalyst for preparing azobenzene oxide from nitrobenzene in one step and a preparation method thereof Background Art

[0002] As an important organic intermediate, azobenzene oxide compounds are widely used in dyes, medicines and other fields. There are two methods for preparing azobenzene oxide using nitrobenzene as raw material, namely, a one-step method and a two-step method. The one-step method is to mix nitrobenzene solution with a hydrogen donor and a catalyst, and condense under mild conditions to directly obtain azobenzene oxide; the two-step method is to first obtain the reduction product aniline in the catalytic reduction process with nitrobenzene as the substrate, and then oxidize aniline to prepare azo products. Compared with the two-step method, the one-step method has the advantages of simple reaction process, high efficiency and selectivity, and is more economically valuable.

[0003] At present, there are reports on the one-step preparation of azobenzene from nitrobenzene using sodium / potassium borohydride as hydrogen donor. Chong et al. reported a cerium oxide-supported nanocluster catalyst with a gold to substrate ratio of 1:394, 70°C, 180 minutes, nitrobenzene conversion of 91%, and azobenzene selectivity of 89% (Nanoscale, 2013, 5(16): 7622-7628.). Diab et al. reported a Ni-PHI catalyst with a nickel to substrate ratio of 1:747, 50°C, 120 minutes, nitrobenzene conversion of 92%, and azobenzene selectivity of 87% (Chemical Engineering Journal, 2023, 460: 141068.). These catalysts have complex system structures, rely on precious metals and require external additives, and are expensive.

[0004] A Chinese invention patent application with publication number CN111333550A discloses a method for preparing an oxidized azobenzene derivative, wherein nitrobenzene is reacted with an aqueous glucose solution in an ethanol solution containing an alkaline compound at 50-80°C in air for 12-48 hours to obtain an oxidized azobenzene derivative with a yield of only 50%.

[0005] The Chinese invention patent application with publication number CN101851175A discloses a method for preparing oxyazobenzene compounds, wherein 1 mmol of nitrobenzene compound requires 0.2-8 mL (preferably 1-3 mL) of polyethylene glycol-400; preferably, the molar ratio of nitrobenzene to solid sodium hydroxide is 1:1-10 (preferably 1:2-6), and the reaction is preferably carried out at 85-95°C.

[0006] The Chinese invention patent with announcement number CN103265450B discloses a method for photocatalytic synthesis of oxyazobenzene and azobenzene compounds. First, nitrobenzene compounds, bases and alcohols are uniformly mixed in a molar ratio of 1:0.1-20:10-1000 to form a solution. Then, a copper / stone black catalyst is added to the solution at a mass ratio of nitrobenzene compounds to catalysts of 1:0.001-2, and ultrasonic dispersion is performed for 5-240 minutes. Then, the dispersed solution is heated to 20-80°C under inert gas protection and stirring conditions at an intensity of 0.001-5p / cm and reacted for 3-10 hours to obtain oxyazobenzene compounds.

[0007] The Chinese invention patent with announcement number CN105085329B discloses a method for preparing aromatic oxyazobenzene by oxidation of aromatic amines. The method uses oxygen as an oxygen source and a catalyst of cerium dioxide or a composite oxide formed by V, Fe, Co, Mn, Cu and cerium dioxide to realize the method of preparing aromatic oxyazobenzene compounds by oxidation of aromatic amines. The molar ratio of the catalyst to the aromatic amine is 0.1-30 mol%, the oxygen pressure is 0.3-2 MPa, the reaction temperature is 100-180°C, and the reaction time is 4-48 hours.

[0008] Although the catalyst systems disclosed in the above four patents (applications) have lower costs compared to precious metal catalysts, they still have problems such as a relatively complicated reaction process and / or low yield and selectivity of the target product. Summary of the invention

[0009] The present invention aims to solve the above technical problems existing in the prior art and provides a catalyst and a preparation method for preparing oxyazobenzene from nitrobenzene in one step.

[0010] The catalyst for preparing azoxybenzene from nitrobenzene in one step is an amorphous composite oxide with a chemical formula of Ni x -Al y -O z , wherein x, y, and z are the number of Ni, Al, and O, respectively, x = 1-20, y = 80-99, and z = 2-3.

[0011] Preferably, the amorphous composite oxide is loaded on a carrier in a mass ratio of 1-30% to the carrier, and the carrier is ZSM-5, MCM-41 or porous carbon.

[0012] A preparation method of a catalyst for preparing azoxybenzene from nitrobenzene in one step, which is carried out in sequence according to the following steps: dissolving a nickel salt, an aluminum salt and a complexing agent in water, slowly heating to 60-80°C, stirring for 3-6 hours, evaporating to dryness at 80-110°C, and roasting in air at 400-700°C for 3-5 hours; the molar ratio of the nickel salt to the aluminum salt is 1:4-99, and the molar ratio of the complexing agent to the metal ion is 1-4:1.

[0013] The preferred calcination temperature is 500°C.

[0014] Preferably, the nickel salt or aluminum salt is nitrate, chloride or acetate.

[0015] Preferably, the complexing agent is one or two of citric acid, glucose, ethylene glycol, and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

[0016] The Nix-Aly-Oz amorphous phase composite oxide prepared by the present invention is used as a catalyst for preparing azobenzene oxide from nitrobenzene in a one-step process, which can significantly improve the reaction activity and the yield of azobenzene oxide, and the highest nitrobenzene conversion rate is 88.0%, and the selectivities of azobenzene oxide, azobenzene and aniline are 86.1%, 7.5% and 6.4% respectively; meanwhile, it has the advantages of small dosage, low cost, simple process, high yield and selectivity, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the XRD diffraction pattern of the catalyst of Example 1 of the present invention.

[0018] Figure 2 It is the XRD diffraction pattern of the comparative example catalyst of the present invention.

[0019] Figure 3 This is an activity evaluation graph of the 0.2 wt% Ni / γ-Al2O3-400 catalyst prepared in the comparative example of the present invention.

[0020] Figure 4 It is an activity evaluation graph of four catalysts prepared in Example 1 of the present invention.

[0021] Figure 5 It is a graph showing the stability test results of the catalysts prepared in Examples 1 and 2 of the present invention. DETAILED DESCRIPTION Example 1

[0022] Weigh 0.035 g nickel nitrate, 3.526 g aluminum nitrate and 17.930 g citric acid monohydrate, dissolve in deionized water; place in a 70°C oil bath and stir (age) for 5 h, dry at 110°C overnight; then grind the dried sample and place in a muffle furnace for calcination at 400°C, 500°C, 600°C and 700°C for 3 h each.

[0023] Four catalysts were obtained and named Ni1-Al 87 -O z -400, Ni1-Al 87 -O z -500, Ni1-Al 87 -O z -600, Ni1-Al 87 -O z -700.

[0024] The XRD diffraction patterns of the four catalysts in Example 1 of the present invention are as follows: Figure 1 The results show that: Ni1-Al 87 -O z -400, there is an obvious large peak at 15.0°−35.0°, indicating an amorphous structure; while Ni1-Al 87 -O z -500, Ni1-Al 87 -O z -600, Ni1-Al 87 -O z -700 ℃ this package peak disappears, even after calcination at 700 ℃, still no diffraction peaks belonging to the crystalline Al2O3 structure are detected, indicating that the product of Example 1 of the present invention is an amorphous composite oxide with a chemical formula of Ni x -Al y -O z . Example 2

[0025] Weigh 0.001 g nickel nitrate, 0.099 g aluminum nitrate, 0.503 g citric acid monohydrate and 5 g carrier in deionized water, the carriers are ZSM-5-50, MCM-41, porous carbon respectively; place in a 70 ° C oil bath and stir (age) for 5 h, dry at 80 ° C overnight; then grind the dried sample and calcine in a muffle furnace at 500 ° C for 3 h to obtain Ni1-Al 87 -O z Amorphous composite oxide / support, Ni1-Al 87 -O z The ratio of the amorphous phase composite oxide to the support is 20 wt%.

[0026] Three catalysts were obtained and named as: (Ni1Al 87 O z / ZSM-5-50-500, (Ni1Al 87 O z ) / MCM-41-500, (Ni1Al 87 O z ) / C-500.

[0027] Comparative Example: Weigh the corresponding mass of nickel nitrate into deionized water, add commercial γ-Al2O3 (Shanghai McLean Biochemical Technology Co., Ltd.), stir thoroughly for 10 min, seal and let stand for 24 h; heat and stir at 80 °C to evaporate to dryness, then grind the dried sample and place it in a muffle furnace for calcination at 400 °C, 500 °C, 600 °C, and 700 °C for 3 h each.

[0028] Four catalysts were obtained, named as 0.2 wt% Ni / γ-Al2O3-X series catalysts, where X is the corresponding calcination temperature of 400, 500, and 600 ℃.

[0029] The XRD diffraction patterns of 0.2 wt% Ni / γ-Al2O3-400, 0.2 wt% Ni / γ-Al2O3-500, and 0.2 wt% Ni / γ-Al2O3-600 catalysts prepared in the comparative example are shown in FIG. Figure 2 shown. Figure 2 The characteristic diffraction peaks at 37.5°, 45.4°, and 67.0° are attributed to the (311), (400), and (440) crystal planes of γ-Al2O3 (PDF#29-0063), indicating that the comparative example 0.2 wt% Ni / γ-Al2O3-400 is a crystalline phase. As the calcination temperature increases, the crystals grow and the crystalline phase becomes more obvious.

[0030] experiment: Reaction experiments with different dosages of comparative catalyst 0.2 wt% Ni / γ-Al2O3-400 Use a pipette to take 4 mL of anhydrous ethanol, 1 mmol of nitrobenzene, and 1 mmol of n-decane (internal standard) in a beaker, seal it in a dark place, and stir for 20 min to form a mixed solution. Transfer the mixed solution to a brown bottle and seal it for storage. Take NaBH4, catalyst 0.2wt% Ni / γ-Al2O3-400, the mixed solution, and a magnet in a sealed glass bottle, place it on a magnetic stirrer, and stir at 60°C for 1 hour, where n (NaBH4) :n (NB)= 2, the amount of catalyst used was 1:93, 1:187, 1:373, 1:746. After each reaction, centrifuge for 3 min, take the supernatant, and perform qualitative and quantitative analysis by gas chromatography using the internal standard method. The results of the effect of different nickel to substrate molar ratios on the catalytic reduction reaction performance of nitrobenzene are shown in Figure 3 As shown, Figure 3 AOB is azoxybenzene, AB is azobenzene, and AN is aniline.

[0031] Figure 3 The results show that as the molar ratio of nickel to substrate increases, the conversion of nitrobenzene and the selectivity of aniline gradually increase, while the selectivity of azo products gradually decreases. On the 0.2 wt% Ni / γ-Al2O3-400 catalyst, when the molar ratio of nickel to substrate increases from 1:746 to 1:93, the conversion of nitrobenzene increases from 37.4% to 73.4%, the selectivity of the main product azobenzene oxide is above 80.0%, and the selectivity of aniline increases from 0.4% to 2.0%.

[0032] 2. Activity evaluation of the prepared catalyst in Example 1 Use a pipette to take 4 mL of anhydrous ethanol, 1 mmol of nitrobenzene, and 1 mmol of n-decane (internal standard) in a beaker, seal it in a dark place, stir it for 20 min to form a mixed solution, and transfer the mixed solution to a brown bottle and seal it for storage. Take NaBH4, catalyst, mixed solution, and magnet in a sealed glass bottle, place it on a magnetic stirrer, and stir and react at 60 °C for 1 hour, where n (NaBH4) :n (NB) = 2, the amount of catalyst used is nickel to substrate molar ratio of 1:373. After each reaction, centrifuge for 3 min, take the supernatant, and perform qualitative and quantitative analysis by gas chromatography using internal standard method. Example 1 Effect of different catalysts on the catalytic reduction reaction performance of nitrobenzene Figure 4 As shown, Figure 4 AOB is azoxybenzene, AB is azobenzene, and AN is aniline.

[0033] Figure 4 The results show that the change of calcination temperature has little effect on the catalytic activity of the catalyst. In the calcination temperature range of 400-700 °C, the conversion rate of nitrobenzene and the selectivity of the main product azoxybenzene on the four catalysts in Example 1 of the present invention can be maintained above 80.0%, indicating that this series of catalysts has a high selectivity for the reduction of nitrobenzene to azoxybenzene. 87 O zThe highest nitrobenzene conversion rate obtained on the Ni1Al-500 catalyst is 88.0%, and the selectivities of azobenzene oxide, azobenzene, and aniline are 86.1%, 7.5%, and 6.4%, respectively. In the comparative example, only when the molar ratio of nickel to substrate is increased from 1:746 to 1:93, the nitrobenzene conversion rate can reach 73.4%, and the selectivity of azobenzene oxide can be increased to more than 80.0%. This shows that the Ni1Al prepared by the present invention 87 O z -X catalyst is used for one-step preparation of azoxybenzene from nitrobenzene, and has high activity, and the conversion rate and selectivity of azoxybenzene are higher than those of the comparative example.

[0034] III. Example 2 Activity evaluation on the prepared catalyst Use a pipette to take 4 mL of anhydrous ethanol, 1 mmol of nitrobenzene, and 1 mmol of n-decane (internal standard) in a beaker, seal it in a dark place, and stir for 20 min to form a mixed solution. Transfer the mixed solution to a brown bottle and seal it for storage. Take NaBH4, catalyst, mixed solution, and magnet in a sealed glass bottle, place it on a magnetic stirrer, stir and react at 60°C for 1 hour, where n (NaBH4) :n (NB) =2, the amount of catalyst used is nickel to substrate molar ratio of 1:1867. After each reaction, centrifuge for 3 min, take the supernatant, and use gas chromatography to perform qualitative and quantitative analysis using internal standard method. Example 2 The effect of different catalysts on the catalytic reduction reaction performance of nitrobenzene is shown in Table 1. Figure 4 AOB is azoxybenzene, AB is azobenzene, and AN is aniline.

[0035] Table 1

[0036] From the data in Table 1, it can be seen that due to the difference in the properties of the carrier, the conversion rate of nitrobenzene on different catalysts is different, but the selectivity of the main product azoxybenzene is higher than 80.0%. The conversion rate of nitrobenzene on the catalyst with ZSM-5 as the carrier is 85.2%, and the conversion rate of nitrobenzene on the catalyst with mesoporous MCM-41 as the carrier is 75.2%. When the activated carbon material with a large specific surface area is used as the carrier, the conversion rate of nitrobenzene can also reach 56.4%. 87 O z The / support series catalysts have good activity for the catalytic reduction of nitrobenzene. Even when the molar ratio of nickel to substrate is as small as 1:1867, the conversion rate and selectivity of azoxybenzene are higher than or equal to the experimental results of the comparative example and Example 1.

[0037] Ni1Al prepared in Example 1 of the present invention 87 O z-500 and 20 wt% (Ni1Al 87 O z Cyclic stability of nitrobenzene reduction over ZSM-5-50-500 catalyst Take the Ni1Al prepared in Example 1 of the present invention 87 O z -500 catalyst, after 5 cycles of reaction according to the method of Experiment 2, the catalytic performance is as follows Figure 5 (A) As shown. The results show that (Ni) :n (NB) = 1:373, after 5 cycles of reaction, the conversion rate of nitrobenzene remained at about 80.0%, and the product was mainly azoxybenzene (AOB), indicating that the Ni1Al prepared in Example 1 of the present invention 87 O z -500 catalyst has good cycle stability for the catalytic reduction of nitrobenzene.

[0038] Take 20 wt% (Ni1Al 87 O z ) / ZSM-5-50-500 catalyst, after 5 cycles of reaction according to the method of Experiment 3, the catalytic performance is as follows Figure 5 (B) The results show that (Ni) :n (NB) = 1:1867 (lower catalyst dosage) after 5 cycles of reaction, the conversion rate of nitrobenzene remained at about 80.0%, and the product was mainly azoxybenzene (AOB), indicating that the 20 wt% (Ni1Al 87 O z ) / ZSM-5-50-500 catalyst has good cyclic stability for the catalytic reduction of nitrobenzene.

Claims

1. A catalyst for preparing azoxybenzene from nitrobenzene in one step, characterized in that: It is an amorphous composite oxide with the chemical formula of Ni x -Al y -O z , wherein x, y, and z are the number of Ni, Al, and O, respectively, x = 1-20, y = 80-99, and z = 2-3.

2. The catalyst for preparing azoxybenzene from nitrobenzene by one-step method according to claim 1, characterized in that: The amorphous composite oxide is loaded on a carrier, and the mass ratio of the amorphous composite oxide to the carrier is 1-30%, and the carrier is ZSM-5, MCM-41 or porous carbon.

3. A method for preparing a catalyst for preparing azoxybenzene from nitrobenzene in one step as claimed in claim 1, characterized in that The method is carried out in the following steps: dissolving nickel salt, aluminum salt and complexing agent in water, heating to 60-80°C, stirring for 3-6 hours, evaporating to dryness at 80-110°C, and roasting in air at 400-700°C for 3-5 hours; the molar ratio of the nickel salt to the aluminum salt is 1:4-99, and the molar ratio of the complexing agent to the metal ion is 1-4:

1.

4. The method for preparing a catalyst for preparing azoxybenzene from nitrobenzene in one step according to claim 3, characterized in that: The calcination temperature is 500°C.

5. The method for preparing a catalyst for preparing azoxybenzene from nitrobenzene in one step according to claim 3 or 4, characterized in that: The nickel salt and aluminum salt are nitrate, chloride or acetate.

6. The method for preparing a catalyst for preparing azoxybenzene from nitrobenzene in one step according to claim 5, characterized in that: The complexing agent is one or two of citric acid, glucose, ethylene glycol, and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

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