A catalyst for liquid phase hydrogenation of nitrobenzene to aniline and a preparation method and application thereof

Abstract

The application belongs to the field of catalyst preparation, and particularly relates to a catalyst for preparing aniline by liquid-phase hydrogenation of nitrobenzene and a preparation method and application thereof. The catalyst has a core-shell structure of ZrO2@ Cu-containing framework molecular sieve. The molecular sieve structure is a modified molecular sieve doped with an active component Cu. The carrier content is 70-80% by mass percentage, the mass ratio of ZrO2 / molecular sieve is 1:1-1:4, and the active component CuO content is 20-30%. The prepared catalyst for preparing aniline by liquid-phase hydrogenation of nitrobenzene has a nitrobenzene conversion rate of 100%, aniline selectivity of 99.99%, excellent activity, selectivity and stability, and is conducive to industrial application and promotion.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a catalyst for preparing aniline from nitrobenzene in liquid phase, and a preparation method and application thereof. BACKGROUND

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

[0003] The industrial production methods of aniline include nitrobenzene iron powder reduction method, phenol direct ammoniation method and nitrobenzene catalytic hydrogenation method. The nitrobenzene iron powder reduction method and the phenol direct ammoniation method have the disadvantages of high preparation cost and non-compliance with green production, and the mainstream method for producing aniline at present is the nitrobenzene catalytic hydrogenation method. The nitrobenzene catalytic hydrogenation method is divided into liquid phase hydrogenation and gas phase hydrogenation. The nitrobenzene catalytic hydrogenation method is further divided into fixed bed gas phase catalytic hydrogenation, fluidized bed gas phase catalytic hydrogenation and slurry bed liquid phase catalytic hydrogenation. The gas phase hydrogenation reaction usually requires high reaction temperature and hydrogen pressure, has high requirements for equipment, large energy consumption and dangerous operation, while the liquid phase hydrogenation has the advantages of low reaction temperature, few side reactions, high catalytic load, large equipment production capacity, low total investment and gradually becomes a research hotspot.

[0004] The catalysts for preparing aniline from nitrobenzene in liquid phase mainly include noble metal catalysts such as Pt, Pd and Rh supported on alumina and activated carbon carriers, such as the catalyst in patent CN103316676A which supports active components Pt and one of La, Co, Cu and Cr in the alumina carrier by a step-by-step impregnation method; and supported nickel, copper, nano and ferrite alloy catalysts, such as the new method for preparing a nano catalyst disclosed in patent CN10259414A which uses a carrier loaded with an inducing agent as a precursor, induces hydrazine hydrate to reduce a nickel salt solution, and forms directional deposition of nano nickel grains on the surface of the carrier.

[0005] However, these catalysts have many problems such as high price, high reaction pressure, poor resistance to toxicity and complicated production steps. Therefore, there is an urgent need in the market for a catalyst with high catalytic activity and good selectivity, which can convert nitrobenzene into aniline at a low reaction temperature and normal pressure, and which also needs to take into account the production cost and be easy to industrialize and popularize. SUMMARY

[0006] The application aims to provide a catalyst for preparing aniline by liquid-phase hydrogenation of nitrobenzene and a preparation method and application thereof.

[0007] The main feature of the application is that ultrafine ZrO2 is used as a crystal nucleus, and Cu atom-doped molecular sieves are introduced in a hydrothermal crystallization form on the surface of the crystal nucleus, so as to form ZrO2@ Cu-containing framework molecular sieves with a core-shell structure. Cu is used as an active component and is dispersed in the molecular sieve framework in an embedded form, and the active component Cu is anchored, so as to avoid migration of the active component Cu and the consequence of copper grain growth in the use process. ZrO2 is used as a carrier matrix, so as to stabilize the carrier structure and make the pore structure suitable, which is conducive to improving the shape selection of the product and promoting heat dissipation, so as to improve the activity, selectivity and stability of the catalyst.

[0008] To achieve the above-mentioned purpose, the application provides the following technical scheme:

[0009] In a first aspect, the application discloses a catalyst for preparing aniline by liquid-phase hydrogenation of nitrobenzene, which is ZrO2@ Cu-containing framework molecular sieves with a core-shell structure. The molecular sieve structure is a modified molecular sieve doped with an active component Cu. The carrier content is 70-80% by mass percentage, the mass ratio of ZrO2 to the molecular sieve is 1:1-1:4, and the active component CuO content is 20-30%.

[0010] The average pore diameter of the catalyst is 15-35 nm, and the pore volume is 0.21-0.45 cm3 / g.

[0011] In a second aspect, the application discloses a preparation method of a catalyst for preparing aniline by liquid-phase hydrogenation of nitrobenzene, which comprises the following steps:

[0012] 1) Zirconium salt is added to an alkali solution under the action of ultrasonic waves to prepare a suspension of ultrafine nanocrystal nuclei;

[0013] 2) Silica sol, inorganic aluminum salt, alkali solution and organic ammonium template agent are uniformly mixed, and then Cu salt is added under the action of ultrasonic waves to prepare a gel. The inorganic aluminum salt is one of aluminum sulfate, aluminum nitrate, aluminum chloride and aluminum hydroxide;

[0014] 3) The gel in step 2) is added to the suspension in step 1), and stirring is continued for 20-40 min to obtain a catalyst precursor solution;

[0015] 4) The catalyst precursor solution is subjected to hydrothermal crystallization treatment in a reaction kettle under temperature control;

[0016] 5) The product subjected to the hydrothermal crystallization treatment is washed, filtered, dried, granulated, calcined and formed to obtain the catalyst of ZrO2@ Cu-containing framework molecular sieves with a core-shell structure.

[0017] Further, the base of the alkali solution in the steps 1) and 2) is NaOH or KOH.

[0018] Further, the organic ammonium template agent in the step 2) is tetrabutylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium hydroxide or tetrapropylammonium hydroxide.

[0019] Further, the copper salt in the step 2) is one of copper nitrate, copper sulfate and copper chloride.

[0020] Further, the temperature of the temperature control condition in the step 4) is 140-240 DEG C, and the time of the hydrothermal crystallization treatment is 24-120h.

[0021] Further, the calcination temperature in the step 5) is 350-450 DEG C, and the calcination time is 4-8h.

[0022] In a third aspect, the application discloses application of the catalyst for preparing aniline by liquid-phase nitrobenzene hydrogenation in a reaction for preparing aniline by liquid-phase nitrobenzene hydrogenation.

[0023] Further, when the catalyst is used in the reaction for preparing aniline by liquid-phase nitrobenzene hydrogenation, the reaction conditions are as follows: the reaction temperature is 120-180 DEG C, the reaction pressure is normal pressure, the hydrogen flow is 250-400ml / min, the liquid hourly space velocity of nitrobenzene is 0.4-1.2h -1 .

[0024] According to the technical scheme, the application has the following beneficial effects:

[0025] The application provides the catalyst for preparing aniline by liquid-phase nitrobenzene hydrogenation and a preparation method and application thereof, and relates to the field of catalysts.

[0026] The technical scheme of the application can obtain a suitable pore structure of the catalyst, fully exert the shape selection of the molecular sieve, and make the active component more uniformly and firmly dispersed, so that the activity, selectivity and stability of the catalyst are ensured.

[0027] The application takes ZrO2 micro-particles as crystal nucleus, and improves the activity of the catalyst carrier by covering and growing molecular sieve on the surface of the ZrO2 micro-particles, promotes the dispersion of the active component, and improves the selectivity of aniline by the shape selection of the molecular sieve on the surface of the catalyst;

[0028] The application introduces Cu in the preparation process of the molecular sieve, forms a Cu-containing framework molecular sieve structure, promotes the dispersion of the active component, strengthens the action of the active component and the carrier, and inhibits the loss of the active component in the liquid phase reaction;

[0029] The technical method adopted by the application is simple, beneficial to industrial application and popularization, and has important social and economic significance.

[0030] The catalyst prepared by the application is applied to the reaction of preparing aniline by liquid phase hydrogenation of nitrobenzene, the conversion rate of nitrobenzene reaches 100%, the selectivity of aniline reaches 99.99%, and the prepared catalyst has excellent activity, selectivity and stability.

[0031] It should be understood that all combinations of the aforementioned concepts and additional concepts described in greater detail below can be seen as part of the subject matter of the present disclosure as long as such concepts are not mutually contradictory. Embodiments

[0032] The silicon-based hydrogenation catalyst, the preparation method and the application thereof disclosed by the application are further specifically introduced below in combination with specific examples. Example 1

[0033] Step 1) 152.7 g of zirconium nitrate nonahydrate and 48.8 g of NaOH are respectively weighed and dissolved in 500 ml of deionized water to prepare a zirconium nitrate solution and a lye, and the zirconium nitrate solution is added to the lye under the action of ultrasonic waves to obtain a suspension of ultra-fine Zr(OH)4 precipitate;

[0034] Step 2) 92.2 g of silica sol (40%wt), 4.6 g of aluminum nitrate nonahydrate, 11.4 g of tetrapropylammonium bromide and 40 g of NaOH are uniformly mixed to obtain a molecular sieve precursor, and 58.4 g of copper nitrate is weighed and prepared into a 200 ml solution, and the copper nitrate solution is added to the molecular sieve precursor under the action of ultrasonic waves, and the mixture is uniformly mixed to obtain a gel;

[0035] Step 3) the obtained gel is added to the suspension in step 1), and stirring is continued for 20 min to obtain a catalyst precursor;

[0036] Step 4) the obtained catalyst carrier precursor is placed in a reaction kettle, and hydrothermal crystallization treatment is carried out at 160℃ for 48 h;

[0037] Step 5) The product is poured out, washed, filtered, dried, granulated, calcined at 400°C for 4h, and finally extruded into strips with water and a binder to obtain catalyst C1. Example 2

[0038] Step 1) Zirconium nitrate 108.6g and NaOH 34.7g were weighed into 500ml deionized water respectively to prepare a zirconium nitrate solution and a lye, and under the action of ultrasonic waves, the zirconium nitrate solution was added to the lye to obtain a suspension of ultra-fine Zr(OH)4precipitate;

[0039] Step 2) Silica sol (40%wt) 206.9g, aluminum hydroxide 1.36g, tetrabutylammonium bromide 9.66g, and NaOH 30g were mixed uniformly to obtain a molecular sieve precursor, and copper nitrate 46.7g was weighed into 200ml solution, under the action of ultrasonic waves, the copper nitrate solution was added to the molecular sieve precursor, and after mixing uniformly, a gel was obtained;

[0040] Step 3) The obtained gel was added to the suspension in step 1), and stirring was continued for 30min to obtain a catalyst precursor;

[0041] Step 4) The obtained catalyst carrier precursor was placed in a reaction kettle, and hydrothermal crystallization treatment was carried out at 180°C for 72h;

[0042] Step 5) The product was poured out, washed, filtered, dried, granulated, calcined at 420°C for 4h, and finally extruded into strips with water and a binder to obtain catalyst C2. Example 3

[0043] Step 1) Zirconium nitrate 71.3g and KOH 31.9g were weighed into 500ml deionized water respectively to prepare a zirconium nitrate solution and a lye, and under the action of ultrasonic waves, the zirconium nitrate solution was added to the lye to obtain a suspension of ultra-fine Zr(OH)4precipitate;

[0044] Step 2) Silica sol (40%wt) 203.7g, aluminum chloride 2.29g, tetrabutylammonium bromide 11.10g, and KOH 50g were mixed uniformly to obtain a molecular sieve precursor, and copper nitrate 58.4g was weighed into 200ml solution, under the action of ultrasonic waves, the copper nitrate solution was added to the molecular sieve precursor, and after mixing uniformly, a gel was obtained;

[0045] Step 3) The obtained gel was added to the suspension in step 1), and stirring was continued for 40min to obtain a catalyst precursor;

[0046] Step 4) The obtained catalyst carrier precursor was placed in a reaction kettle, and hydrothermal crystallization treatment was carried out at 240°C for 24h;

[0047] Step 5) The product was poured out, washed, filtered, dried, granulated, calcined at 450°C for 4h, and finally extruded into strips with water and a binder to obtain catalyst C3. Example 4

[0048] Step 1) Zirconium nitrate 61.1 g and KOH 27.3 g were weighed out respectively and dissolved in 500 ml of deionized water to prepare a zirconium nitrate solution and a lye, respectively. Under the action of ultrasonic waves, the zirconium nitrate solution was added to the lye to obtain a suspension of ultra-fine Zr(OH)4precipitate;

[0049] Step 2) Silica sol (40%wt) 232.8 g, aluminum sulfate 3.36 g, tetrabutylammonium hydroxide 9.72 g, and KOH 45 g were mixed uniformly to obtain a molecular sieve precursor. Copper nitrate 58.4 g was weighed out to prepare a 200 ml solution. Under the action of ultrasonic waves, the copper nitrate solution was added to the molecular sieve precursor, and after being mixed uniformly, a gel was obtained;

[0050] Step 3) The obtained gel was added to the suspension in step 1), and stirring was continued for 25 min to obtain a catalyst precursor;

[0051] Step 4) The obtained catalyst carrier precursor was placed in a reaction kettle and hydrothermally crystallized at 140°C for 120 h;

[0052] Step 5) The product was poured out, washed, filtered, dried, granulated, calcined at 350°C for 8h, and finally extruded into strips with water and a binder to obtain catalyst C4. Example 5

[0053] Step 1) Zirconium nitrate 152.7 g and NaOH 48.8 g were weighed out respectively and dissolved in 500 ml of deionized water to prepare a zirconium nitrate solution and a lye, respectively. Under the action of ultrasonic waves, the zirconium nitrate solution was added to the lye to obtain a suspension of ultra-fine Zr(OH)4precipitate;

[0054] Step 2) Silica sol (40%wt) 92.8 g, aluminum nitrate 2.9 g, tetrabutylammonium hydroxide 11.4 g, and NaOH 40 g were mixed uniformly to obtain a molecular sieve precursor. Copper nitrate 58.4 g was weighed out to prepare a 200 ml solution. Under the action of ultrasonic waves, the copper nitrate solution was added to the molecular sieve precursor, and after being mixed uniformly, a gel was obtained;

[0055] Step 3) The obtained gel was added to the suspension in step 1), and stirring was continued for 25 min to obtain a catalyst precursor;

[0056] Step 4) The obtained catalyst carrier precursor was placed in a reaction kettle and hydrothermally crystallized at 200°C for 60 h;

[0057] Step 5) The product was poured out, washed, filtered, dried, granulated, calcined at 380°C for 74h, and finally extruded into strips with water and a binder to obtain catalyst C5. Example 6

[0058] Step 1) Zirconium nitrate 152.7g and NaOH 48.8g were weighed out separately and dissolved in 500ml of deionized water to prepare a zirconium nitrate solution and a lye, respectively. Under the action of ultrasonic waves, the zirconium nitrate solution was added to the lye to obtain a suspension of ultra-fine Zr(OH)4precipitate;

[0059] Step 2) Silica sol (40%wt) 92.2g, aluminum nitrate 4.6g, tetrapropylammonium bromide 11.4g, and NaOH 40g were mixed uniformly to obtain a molecular sieve precursor. Copper nitrate 58.4g was weighed out and dissolved in 200ml of solution. Under the action of ultrasonic waves, the copper nitrate solution was added to the molecular sieve precursor, and the mixture was mixed uniformly to obtain a gel;

[0060] Step 3) The obtained gel was added to the suspension in step 1) and stirred for 40min to obtain a catalyst precursor;

[0061] Step 4) The obtained catalyst carrier precursor was placed in a reaction kettle and hydrothermally crystallized at 220°C for 80h;

[0062] Step 5) The product was poured out, washed, filtered, dried, granulated, calcined at 420°C for 4h, and finally extruded into strips with water and a binder to obtain catalyst C6. Example 7

[0063] Step 1) Zirconium nitrate 152.7g and NaOH 48.8g were weighed out separately and dissolved in 500ml of deionized water to prepare a zirconium nitrate solution and a lye, respectively. Under the action of ultrasonic waves, the zirconium nitrate solution was added to the lye to obtain a suspension of ultra-fine Zr(OH)4precipitate;

[0064] Step 2) Silica sol (40%wt) 92.2g, aluminum nitrate 4.6g, tetrapropylammonium bromide 11.4g, and NaOH 40g were mixed uniformly to obtain a molecular sieve precursor. Copper nitrate 58.4g was weighed out and dissolved in 200ml of solution. Under the action of ultrasonic waves, the copper nitrate solution was added to the molecular sieve precursor, and the mixture was mixed uniformly to obtain a gel;

[0065] Step 3) The obtained gel was added to the suspension in step 1) and stirred for 20min to obtain a catalyst precursor;

[0066] Step 4) The obtained catalyst carrier precursor was placed in a reaction kettle and hydrothermally crystallized at 240°C for 96h;

[0067] Step 5) The product is poured out, washed, filtered, dried, granulated, and extruded into a strip after adding water and a binder, and then calcined at 400°C for 8h to obtain catalyst C7. Example 8

[0068] The catalyst is applied to the liquid phase hydrogenation of nitrobenzene to aniline.

[0069] C1-C7 catalyst is taken and crushed to 20-40 mesh, 10ml of the catalyst is loaded into a fixed bed reactor, and the catalyst is reduced in a nitrogen-hydrogen gas atmosphere with a hydrogen concentration of 5% at 180°C and 0.2MPa for 12h before the reaction, the temperature is lowered to 160°C, the reaction pressure is normal pressure, the nitrobenzene feed amount is 0.6h -1 , the H2 flow is 250ml / min, and the results are shown in Table 1.

[0070] Table 1 Results of activity evaluation

[0071]

[0072] As can be seen from the data in Table 1, the catalyst designed according to the technical scheme of the present application is applied to the liquid phase hydrogenation of nitrobenzene to aniline, the conversion rate of nitrobenzene reaches 100%, the selectivity of aniline reaches more than 99%, and the catalyst has good performance. Example 9

[0073] C1 catalyst is taken and crushed to 20-40 mesh, 10ml of the catalyst is loaded into a fixed bed reactor, and the catalyst is reduced in a nitrogen-hydrogen gas atmosphere with a hydrogen concentration of 5% at 180°C and 0.2MPa for 12h before the reaction, the temperature is lowered to 120°C, the reaction pressure is normal pressure, the nitrobenzene feed amount is 0.8h -1 , the H2 flow is 400ml / min, and the results are shown in Table 2. Example 10

[0074] C1 catalyst is taken and crushed to 20-40 mesh, 50ml of the catalyst is loaded into a fixed bed reactor, and the catalyst is reduced in a nitrogen-hydrogen gas atmosphere with a hydrogen concentration of 5% at 180°C and 0.2MPa for 12h before the reaction, the temperature is lowered to 140°C, the reaction pressure is normal pressure, the nitrobenzene feed amount is 1.2h -1 , the H2 flow is 300ml / min, and the results are shown in Table 2. Example 11

[0075] C1 catalyst is taken and crushed to 20-40 mesh, 50ml of the catalyst is loaded into a fixed bed reactor, and the catalyst is reduced in a nitrogen-hydrogen gas atmosphere with a hydrogen concentration of 5% at 180°C and 0.2MPa for 12h before the reaction, the temperature is lowered to 140°C, the reaction pressure is normal pressure, the nitrobenzene feed amount is 1.2h -1 , the H2 flow is 300ml / min, and the results are shown in Table 2.

[0076] Table 2 Influence of reaction conditions on evaluation results of activity

[0077]

[0078] From Table 2, it can be seen that at a reaction temperature of 140-180°C, a reaction pressure of normal pressure, a nitrobenzene feed amount of 0.4-1.2 h -1 , the catalysts all exhibit excellent catalytic effects, the catalysts have excellent stability, are suitable for industrial reaction conditions, and are conducive to industrial promotion.

Claims

1. A catalyst for liquid phase hydrogenation of nitrobenzene to aniline, characterized in that, The catalyst has a core-shell structure of ZrO2@Cu-containing framework molecular sieve, wherein the molecular sieve structure is a modified molecular sieve doped with an active component Cu, the carrier content is 70-80% by mass percentage, the mass ratio of ZrO2 / molecular sieve is 1:1-1:4, and the active component CuO content is 20-30%; The preparation method of the catalyst for preparing aniline by liquid-phase hydrogenation of nitrobenzene comprises the following steps: 1) zirconium salt is added into an alkali solution under the action of ultrasonic waves to prepare a suspension of ultra-fine nanocrystal cores; 2) silica sol, inorganic aluminum salt, alkali solution and organic ammonium template are uniformly mixed, and then Cu salt is added under the action of ultrasonic waves to prepare a gel; the inorganic aluminum salt is one of aluminum sulfate, aluminum nitrate, aluminum chloride and aluminum hydroxide; 3) the gel in step 2) is added into the suspension in step 1), and stirring is continued for 20-40 min to obtain a catalyst precursor solution; 4) under temperature control, the catalyst precursor solution is subjected to hydrothermal crystallization treatment in a reaction kettle; 5) the product of hydrothermal crystallization treatment is washed, filtered, dried, granulated, calcined and molded to obtain the catalyst of core-shell structure ZrO2@Cu-containing framework molecular sieve.

2. The catalyst for liquid phase hydrogenation of nitrobenzene to aniline according to claim 1, wherein the catalyst is prepared by the method according to claim 1. The average pore diameter of the catalyst is 15-35 nm, the pore volume is 0.21-0.45 cm 3 / g.

3. The catalyst of claim 1, wherein The alkali in steps 1) and 2) is NaOH or KOH.

4. The catalyst of claim 1, wherein The organic ammonium template in step 2) is tetrabutylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium hydroxide or tetrapropylammonium hydroxide.

5. The catalyst of claim 1, wherein The Cu salt in step 2) is one of copper nitrate, copper sulfate and copper chloride.

6. The catalyst of claim 1, wherein The temperature of the temperature control condition in step 4) is 140-240 DEG C, and the hydrothermal crystallization treatment time is 24-120 h.

7. The catalyst of claim 1, wherein The calcination temperature in step 5) is 350-450 DEG C, and the calcination time is 4-8 h.

8. Application of the catalyst for preparing aniline by liquid-phase hydrogenation of nitrobenzene in a reaction of preparing aniline by liquid-phase hydrogenation of nitrobenzene.

9. Use of a catalyst according to claim 8 for the liquid phase hydrogenation of nitrobenzene to aniline, characterised in that, When the catalyst is used in the reaction of liquid phase hydrogenation of nitrobenzene to aniline, the reaction conditions are as follows: reaction temperature 120-180℃, reaction pressure normal pressure, hydrogen flow rate 250-400ml / min, liquid space velocity of nitrobenzene 0.4-1.2h -1 .

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