Catalyst for hydrogenating nitrobenzene to produce aniline, preparation method and application thereof

Abstract

The present invention belongs to the field of catalyst preparation, and specifically relates to a catalyst for preparing aniline by hydrogenating nitrobenzene, and a preparation method and application thereof. The catalyst comprises an active component Cu after copper-ammine complexation, a carrier SiO2 treated with a polycarboxylic acid, and an auxiliary agent Ni or K, wherein the Cu:Si molar ratio is 1:2-4, and the content of the auxiliary agent is 1%-5% by mass percentage of the catalyst. The catalyst for preparing aniline by hydrogenating nitrobenzene prepared by the present invention can shorten the reaction induction period to 3.5h during use, has excellent activity, selectivity and stability, and is conducive to the promotion of industrial application.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and specifically relates to a catalyst for preparing aniline by hydrogenating nitrobenzene, and a preparation method and application thereof. Background Art

[0002] Aniline (English name Aniline, molecular formula C6H7N) is characterized by a colorless, slightly yellow oily liquid. When aniline is exposed to air or sunlight, it appears brown. It has a strong odor. Aniline is slightly soluble in water, but it is miscible with organic solvents such as ethanol, ether and benzene. Aniline is alkaline and can react with hydrochloric acid and sulfuric acid to form hydrochloride and sulfate. It can also undergo reduction, oxidation, halogenation and other reactions. Aniline is one of the most important amine substances and an important organic chemical raw material intermediate. It is mainly used in the production of polyurethane raw material diphenylmethane diisocyanate (MDI), and in the chemical industry fields such as dyes, pesticides, medicines, special fibers, rubber additives and organic intermediates.

[0003] Industrial methods for producing aniline include: nitrobenzene iron powder reduction method, phenol direct amination method and nitrobenzene catalytic hydrogenation method. Nitrobenzene iron powder reduction method and phenol direct amination method have the disadvantages of high preparation cost and not meeting the requirements of green production. At present, the mainstream method for aniline production is nitrobenzene catalytic hydrogenation method. Nitrobenzene catalytic hydrogenation method is divided into liquid phase hydrogenation and gas phase hydrogenation. The nitrobenzene liquid phase catalytic hydrogenation process mainly uses precious metal catalysts under anhydrous conditions. The advantages of this process are low reaction temperature, high catalyst load, long life and large equipment production capacity. The disadvantages are high pressure required for the reaction, the reactants, catalysts and solvents must be separated, the equipment operation cost is high, the catalyst is expensive, and the catalyst activity is too high, resulting in more by-products. The fluidized bed gas-phase catalytic hydrogenation method is that the raw material nitrobenzene is heated and vaporized and mixed with hydrogen, and then enters a fluidized bed reactor equipped with a catalyst for reaction, which improves the heat transfer condition and avoids local overheating. The disadvantage is that it is found in industrial applications that during a period of time at the beginning of start-up, the content of low-boiling substances in the hydrogenation crude product is relatively high, and the base catalyst has an induction period, which has an adverse effect on the quality of the aniline product. Therefore, it is particularly important to develop a nitrobenzene gas-phase hydrogenation catalyst that shortens the reaction induction period. Summary of the invention

[0004] The purpose of the present invention is to provide a catalyst for preparing aniline by hydrogenating nitrobenzene, and a preparation method and application thereof.

[0005] The main features of the present invention are that the macroporous silica gel is treated with polycarboxylic acid, and excess ammonia gas is used to form a copper-ammonia complex with copper nitrate to promote the uniform distribution of the active component copper in the macroporous silica gel. The decomposition of the polycarboxylic acid during the roasting process is used to pre-reduce the active components of the catalyst. Therefore, when the catalyst is applied to the nitrobenzene hydrogenation reaction, the catalyst does not need to be reduced and activated, and the reaction can reach reaction equilibrium in a very short time, thereby greatly shortening the induction period of the catalyst.

[0006] The present invention discloses a catalyst for preparing aniline by hydrogenating nitrobenzene, and a preparation method and application thereof, which are achieved by the following technical scheme:

[0007] A catalyst for preparing aniline by hydrogenating nitrobenzene comprises an active component Cu, a carrier SiO2 and an auxiliary agent selected from Ni and K, wherein the molar ratio of Cu:Si is 1:2-4 and the content of the auxiliary agent is 1%-5% based on the mass percentage of the catalyst.

[0008] The carrier SiO2 is a coarse-porous silica gel treated with citric acid, tartaric acid or oxalic acid.

[0009] The treated macroporous silica gel has a diameter of 1-2 mm and a specific surface area of ​​300-500 m 2 / ml, pore size 10-30nm.

[0010] The active component Cu is [Cu(NH3)4](NO3)2 or [Cu(NH3)4]NO3 after being complexed with ammonia water.

[0011] The present invention also relates to a method for preparing the catalyst, comprising the following steps:

[0012] 1) Firstly, the coarse-porous silica gel is treated with polycarboxylic acid, and then filtered and dried;

[0013] 2) passing excess ammonia into the Cu(NO3)2 solution to form a copper-ammine complex;

[0014] 3) placing the macroporous silica gel treated in step 1) into the copper ammonia complex obtained in step 2) and subjecting the treatment to temperature control;

[0015] 4) pouring out the product in step 3) and drying;

[0016] 5) impregnating the catalyst precursor obtained in step 4) with a solution of the auxiliary agent, drying and calcining, and finally obtaining a catalyst for hydrogenating nitrobenzene to produce aniline.

[0017] Generally, the treatment temperature of the polycarboxylic acid is 50-70°C, and the treatment time is 30-60 minutes.

[0018] The temperature of the temperature control treatment is 50-70°C and the time is 20-40 minutes.

[0019] The calcination temperature is 360° C.-400° C., and the calcination time is 2-4 hours.

[0020] The invention also relates to the application of the catalyst, which can be used for the reaction of hydrogenating nitrobenzene to prepare aniline.

[0021] When the catalyst is used for the hydrogenation of nitrobenzene to produce aniline, the reaction does not require reduction, the reaction pressure is 01-0.3 MPa, and the reaction temperature is 140° C.-180° C.

[0022] Beneficial effects:

[0023] (1) The present invention uses polycarboxylic acid to treat the catalyst carrier macroporous silica gel, and at the same time, the pores are expanded. During the calcination of the catalyst, the active components of the catalyst are pre-reduced by thermal decomposition of the polycarboxylic acid, thereby eliminating the step of reducing and activating the catalyst during use;

[0024] (2) The present invention utilizes excess ammonia water to react with copper nitrate to generate a copper-ammonia complex, thereby promoting the dispersion of active components in the carrier, thereby improving the activity and stability of the catalyst;

[0025] (3) The technical method adopted by the present invention is simple, conducive to industrial application and promotion, and has important social and economic significance. DETAILED DESCRIPTION

[0026] The following examples are only used to further explain the content and effects of the present invention, rather than to limit the present invention.

[0027] Example 1

[0028] Cu:SiO2 has a molar ratio of 1:3. Weigh 187.56g of Cu(NO3)2 and 180g of coarse-porous silica gel. Add the coarse-porous silica gel into 500ml of 1mol / l citric acid solution at 60°C, stir for 40min, filter and dry. Determine the water absorption of the coarse-porous silica gel, prepare an equal volume of Cu(NO3)2 solution, pass excess ammonia to obtain a copper-ammine complex, add the dried coarse-porous silica gel, treat at 60°C for 30min, dry, weigh 2% by mass of nickel nitrate and impregnate it with an equal volume, then dry and calcine at 380°C for 2h to obtain catalyst C1.

[0029] Example 2

[0030] Cu:SiO2 has a molar ratio of 1:2. Weigh 187.56g of Cu(NO3)2 and 120g of coarse-porous silica gel. Add the coarse-porous silica gel into 333ml of 1mol / l tartaric acid solution at 70°C, stir for 30min, filter and dry. Determine the water absorption of the coarse-porous silica gel, prepare an equal volume of Cu(NO3)2 solution, pass excess ammonia to obtain a copper-ammine complex, add the dried coarse-porous silica gel, treat at 70°C for 20min, and after drying, weigh 3% by mass of potassium carbonate for impregnation of an equal volume. Finally, dry and calcine at 400°C for 2h to obtain catalyst C2.

[0031] Example 3

[0032] Cu:SiO2 has a molar ratio of 1:4. Weigh 187.56g of Cu(NO3)2 and 240g of coarse-porous silica gel. Add the coarse-porous silica gel into 667ml of 1mol / l oxalic acid solution at 50°C, stir for 60min, filter and dry. Determine the water absorption of the coarse-porous silica gel, prepare an equal volume of Cu(NO3)2 solution, pass excess ammonia to obtain a copper-ammine complex, add the dried coarse-porous silica gel, treat at 50°C for 40min, and after drying, weigh 5% by mass of nickel nitrate for impregnation of an equal volume. Finally, dry and calcine at 360°C for 4h to obtain catalyst C3.

[0033] Example 4

[0034] Cu:SiO2 has a molar ratio of 1:3. Weigh 187.56g of Cu(NO3)2 and 180g of coarse-porous silica gel. Add the coarse-porous silica gel into 500ml of 1mol / l citric acid solution at 60°C, stir for 60min, filter and dry. Determine the water absorption of the coarse-porous silica gel, prepare an equal volume of Cu(NO3)2 solution, pass excess ammonia to obtain a copper-ammine complex, add the dried coarse-porous silica gel, treat at 60°C for 40min, and after drying, weigh 5% by mass of potassium carbonate for impregnation of an equal volume. Finally, dry and calcine at 380°C for 2h to obtain catalyst C4.

[0035] Example 5

[0036] Cu:SiO2 has a molar ratio of 1:4. Weigh 187.56g of Cu(NO3)2 and 240g of coarse-porous silica gel. Add the coarse-porous silica gel into 667ml of 1mol / l citric acid solution at 70°C, stir for 60min, filter and dry. Determine the water absorption of the coarse-porous silica gel, prepare an equal volume of Cu(NO3)2 solution, pass excess ammonia to obtain a copper-ammine complex, add the dried coarse-porous silica gel, treat at 70°C for 20min, dry, weigh 1% by mass of nickel nitrate and impregnate it with an equal volume, dry it and calcine it at 360°C for 4h to obtain catalyst C5.

[0037] Example 6

[0038] The catalyst was applied to the hydrogenation of nitrobenzene to produce aniline.

[0039] Take 10 ml of C1-C5 catalyst and load it into a fixed bed reactor with a pressure of 0.2 MPa, an inlet temperature of 160°C, a nitrobenzene flow rate of 0.25 mL / min, and a hydrogen tail gas reading of 300 mL / min. The results are shown in Table 1-5.

[0040] Table 1 C1 activity evaluation results

[0041] Reaction time, h aniline,% Nitrobenzene, % phenol,% Cyclohexanol, % Cyclohexylamine, % 1 92.1393 5.7048 0.0336 0.0110 Not detected 2 98.2676 0.5402 0.1331 0.0492 Not detected 3.5 99.2600 0.1226 0.0099 0.0019 Not detected 4.5 99.5980 0.2681 0.0092 Not detected Not detected 5.5 99.8896 0.0215 0.0041 Not detected Not detected 6.5 99.8818 0.0257 0.0068 Not detected Not detected 7.5 99.7893 0.0588 0.0065 Not detected Not detected 8.5 99.8712 0.0190 0.0063 Not detected Not detected 9.5 99.8920 0.0326 0.0061 Not detected Not detected

[0042] Table 2 C2 activity evaluation results

[0043] Reaction time, h aniline,% Nitrobenzene, % phenol,% Cyclohexanol, % Cyclohexylamine, % 1 88.0253 1.5181 0.0121 0.0487 Not detected 2 96.0382 0.4317 0.0104 0.0197 Not detected 3 99.0846 0.0761 0.0122 0.0066 Not detected 4 99.7558 0.0214 0.0089 0.0048 Not detected 5 99.8692 0.0109 0.0080 0.0006 Not detected 6 99.8891 0.0112 0.0071 0.0004 Not detected 7 99.8988 0.0082 0.0058 0.0003 Not detected 8 99.9063 0.0067 0.0052 Not detected Not detected

[0044] Table 3 C3 activity evaluation results

[0045] Reaction time, h aniline,% Nitrobenzene, % phenol,% Cyclohexanol, % Cyclohexylamine, % 1 98.0000 1.7700 0.0295 0.0012 Not detected 2 99.3308 0.3087 0.0374 0.0031 Not detected 3 99.7789 0.0424 0.0212 0.0010 Not detected 4 99.8796 0.0117 0.0099 0.0004 Not detected 5 99.8849 0.0078 0.0090 0.0002 Not detected 6 99.8976 0.0056 0.0089 Not detected Not detected 7 99.9060 Not detected 0.0088 Not detected Not detected 8 99.9414 Not detected 0.0070 Not detected Not detected 9 99.9193 Not detected 0.0061 Not detected Not detected 10 99.9642 Not detected 0.0049 Not detected Not detected

[0046] Table 4 C4 activity evaluation results

[0047] Reaction time, h aniline,% Nitrobenzene, % phenol,% Cyclohexanol, % Cyclohexylamine, % 1 97.6425 1.9700 0.0305 0.0012 Not detected 2 99.2708 0.3887 0.0404 0.0032 Not detected 3 99.7249 0.0464 0.0232 0.0021 Not detected 4 99.8425 0.0137 0.0136 0.0018 Not detected 5 99.8649 0.0098 0.0098 0.0004 Not detected 6 99.8843 0.0076 0.0091 0.0002 Not detected 7 99.8924 0.0052 0.0088 Not detected Not detected 8 99.9214 Not detected 0.0074 Not detected Not detected 9 99.9193 Not detected 0.0062 Not detected Not detected 10 99.9442 Not detected 0.0053 Not detected Not detected

[0048] Table 5 C5 activity evaluation results

[0049] Reaction time, h aniline,% Nitrobenzene, % phenol,% Cyclohexanol, % Cyclohexylamine, % 1 97.4415 2.2559 0.0311 0.0011 Not detected 2 99.1745 0.4211 0.0425 0.0039 Not detected 3 99.6532 0.0692 0.0256 0.0107 Not detected 4 99.8085 0.0198 0.0132 0.0084 Not detected 5 99.8146 0.0177 0.0096 0.0003 Not detected 6 99.8549 0.0205 0.0094 0.0002 Not detected 7 99.8980 0.0204 0.0087 Not detected Not detected 8 99.9352 0.0141 0.0076 Not detected Not detected 9 99.94 0.0106 0.0080 Not detected Not detected

[0050] From the data in Table 1-5, we can see that nitrobenzene, phenol, cyclohexanol and cyclohexylamine are impurities in aniline products. We use impurities below 100ppm as the standard for qualified products. The induction period of C1-C5 catalysts is shortened to 4-5h, and the induction period of C1 catalyst is only 3.5h.

[0051] Comparative Example 1

[0052] A commercially available Cu-Si catalyst was used for the test. 10 ml of the catalyst was loaded into a fixed bed reactor with a pressure of 0.2 MPa, an inlet temperature of 160°C, a nitrobenzene flow rate of 0.25 mL / min, and a hydrogen tail gas reading of 300 mL / min. The results are shown in Table 6.

[0053] Table 6 Comparative example activity evaluation results

[0054] Reaction time, h aniline,% Nitrobenzene, % phenol,% Cyclohexanol, % Cyclohexylamine, % 2.5 74.6315 1.1390 0.0217 0.0839 Not detected 3.5 96.7888 0.2386 0.0262 0.01270 Not detected 4.5 99.3445 0.1504 0.0265 Not detected Not detected 5.5 99.4738 0.2998 0.0225 Not detected Not detected 6.5 99.8674 Not detected 0.0132 Not detected Not detected 7.5 99.8924 Not detected 0.0114 Not detected Not detected 8.5 99.8928 0.0210 0.0089 Not detected Not detected 9.5 99.8926 Not detected Not detected Not detected Not detected

[0055] From the data in Table 6, we can see that the commonly used Cu-Si aniline catalyst purchased on the market has a long induction period during use. In laboratory tests, the product is qualified only after 8.5 hours. The application in industrial equipment will have a greater impact.

[0056] Example 7

[0057] 10 ml of C1 catalyst was loaded into a fixed bed reactor with a nitrobenzene flow rate of 0.25 mL / min and a hydrogen tail gas reading of 300 mL / min. The influence of the reaction conditions was investigated. The results are shown in Table 7.

[0058] Table 7 Effect of reaction conditions

[0059] Reaction pressure / MPa Reaction temperature / ℃ Qualified time / h 0.1 150 5 0.2 140 4.5 0.3 160 3 0.2 160 3.5 0.3 180 4

[0060] It can be seen from Table 7 that at a reaction temperature of 140-180°C and a reaction pressure of 0.1-0.3 MPa, the catalysts all exhibited excellent catalytic effects, with a short induction period, which is suitable for industrial reaction conditions and is conducive to industrial promotion.

Claims

1. Application of a nitrobenzene hydrogenation to aniline catalyst in the nitrobenzene hydrogenation to aniline reaction, characterized in that: The reaction does not require reduction, the reaction pressure is 0.1-0.3MPa, and the reaction temperature is 140°C-180°C; the catalyst comprises an active component Cu, a carrier SiO2 and an auxiliary agent of Ni and K, the molar ratio of Cu:Si is 1:2-4, and the content of the auxiliary agent is 1%-5% by mass percentage of the catalyst; wherein the carrier SiO2 is a coarse-porous silica gel treated with one of citric acid, tartaric acid or oxalic acid, and the pore size of the treated coarse-porous silica gel is 10-30nm; the preparation method of the catalyst comprises the following steps: 1) Firstly, the coarse-porous silica gel is treated with one of citric acid, tartaric acid or oxalic acid, and then filtered and dried; 2) passing excess ammonia into the Cu(NO3)2 solution to form a copper-ammine complex; 3) adding the macroporous silica gel treated in step 1) to the copper ammonia complex obtained in step 2) and subjecting the mixture to temperature control treatment; 4) pouring out the product in step 3) and drying; 5) impregnating the catalyst precursor obtained in step 4) with a solution of the auxiliary agent, drying and calcining, and finally obtaining a catalyst for hydrogenating nitrobenzene to produce aniline.

2. The use according to claim 1, characterized in that: The macroporous silica gel treated with the catalyst has a diameter of 1-2 mm and a specific surface area of ​​300-500 m 2 / ml.

3. The use according to claim 1, characterized in that: The active component Cu of the catalyst is [Cu(NH3)4](NO3)2 or [Cu(NH3)4]NO3 after being complexed with ammonia water.

4. The use according to claim 1, characterized in that: In step 1), the acid treatment temperature is 50-70°C and the treatment time is 30-60 min.

5. The use according to claim 1, characterized in that: In step 3), the temperature of the temperature control treatment is 50-70°C, and the treatment time is 20-40 min.

6. The use according to claim 1, characterized in that: In step 5), the calcination temperature is 360°C-400°C and the calcination time is 2-4 h.