CN114289050A - Catalyst applied to continuous hydrogenation of aromatic nitro compound and preparation method - Google Patents
Catalyst applied to continuous hydrogenation of aromatic nitro compound and preparation method Download PDFInfo
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Abstract
The invention relates to the technical field of catalytic hydrogenation, and particularly discloses a catalyst for continuous hydrogenation of an aromatic nitro compound and a preparation method thereof. The catalyst of the invention takes urea and nickel nitrate as raw materials to generate Ni/g-C by a thermal polycondensation method3N4The composite carrier is used for loading active noble metal, namely the catalyst; wherein, the active noble metal is one or a combination of more of Pt and Pd, and the active metal accounts for 5-10% of the mass of the catalyst. The active metal nano particles are uniformly distributed on the composite carrier. The catalyst is applied to the micro packed bed for continuous hydrogenation reaction of aromatic nitro compounds, can further improve heat and mass transfer in the reaction process, realizes full-automatic reaction, and has the advantages of simple process, low energy consumption, low cost and high production efficiency.
Description
Technical Field
The invention relates to the technical field of catalytic hydrogenation, and particularly discloses a catalyst for continuous hydrogenation of an aromatic nitro compound and a preparation method thereof.
Background
Hydrogenated products of aromatic nitro compounds are widely used as chemical raw materials, are important organic synthesis intermediates, and are widely applied to synthesis of various fine chemical products in the fields of pesticides, medicines, dyes, pigments and the like.
The hydrogenation product of aromatic nitro compound is produced in batch kettle mode in industrial production, and has the disadvantages of large volume, difficult heat and mass transfer, complex operation, low production efficiency, etc. The micro packed bed reactor is a process strengthening innovation technology which is developed rapidly in recent years, is commonly used for continuous hydrogenation reaction, and has the characteristics of high heat and mass transfer rate, small volume, high automation degree and the like, but the continuous hydrogenation process technology has industrial use value and significance only by taking a high-efficiency catalyst with high stability and long service life as a premise. In addition, the activated carbon powder catalyst is used for a micro packed bed reactor, which often has larger pressure drop and is easy to cause blockage; the use of activated carbon particle catalysts in micro-packed bed reactors can lead to the breaking and powdering of the activated carbon particles under long-term flushing, resulting in increased pressure drop. Therefore, a catalyst which is simple, easy to obtain, green, safe, easy to form, long in anti-pulverization performance and long in catalytic life is urgently needed.
Graphite-like phase carbon nitride (g-C)3N4) Is a non-metal n-type semiconductor polymer with a layered stacking structure and a pi conjugated system. g-C3N4Due to the characteristics of unique electronic structure, high thermal stability and chemical stability, low preparation cost, simple preparation, no toxicity, no harm and the like. The application of g-C3N4 in the heterogeneous catalysis process is summarized in the literature (Green Chemistry, 2015,2, 715-736), wherein the catalytic activity and the application times of the catalyst obtained by taking g-C3N4 as a carrier to load active metal in hydrogenation are higher than those of the conventional active carbon carrier. But a single g-C3N4Still has small specific surface area and limited active sites, so that the catalytic activity is limited.
Disclosure of Invention
In view of the above problems in the prior art, the present invention provides a catalyst for continuous hydrogenation of aromatic nitro compounds and a method thereof.
In order to achieve the purpose, the invention adopts the technical scheme that:
a catalyst for the continuous hydrogenation of aromatic nitro compound is prepared from urea and nickel nitrate through thermal polycondensation to obtain Ni/g-C3N4The composite carrier is used for loading active noble metal, namely the catalyst; wherein, the active noble metal is one or a combination of more of Pt and Pd, and the active metal accounts for 5-10% of the mass of the catalyst.
The active metal nano particles are uniformly distributed on the composite carrier.
Mixing urea and nickel nitrate, adding a certain amount of pure water, grinding, and drying to obtain the composite solid. Placing the composite solid into a crucible, heating to 500-600 ℃ at the heating rate of 8-12 ℃/min under the helium atmosphere in a tubular furnace, calcining for 1-3h at the high temperature, then cooling to room temperature, and molding the prepared composite carrier, wherein the particle size is 0.4-0.6 mm; wherein the mass ratio of the urea to the nickel nitrate to the pure water is 10-20g, 3.1-6.2g and 2.5-5 g.
The total nitrogen content in the urea is 46.5%; the initial temperature of the calcination is 40-60 ℃.
Adding the carrier particles into water, heating the carrier particles in a water bath for 1 to 2 hours at the temperature of between 70 and 90 ℃, adding an active noble metal salt solution, stirring the solution for 1 to 2 hours, then adjusting the pH of the system to be alkaline, continuing stirring the solution for 1 to 2 hours, cooling the solution to room temperature after stirring, adding NaBH (sodium borohydride)4Reducing the water solution at 20-25 deg.c and stirring for 1-2 hr, filtering, and vacuum drying at 60 deg.c for 4 hr to obtain the catalyst with supported active noble metal.
The composite carrier, water, active noble metal salt (calculated by metal dosage), NaBH4Aqueous solution (with NaBH)4Mass meter) mass-to-volume ratio of 1 g: 200 g: 0.05-0.10g, 0.019g-0.378 g.
The active metal salt is a salt containing one or more metal elements of Pt and Pd.
Wherein, the salt containing Pt is one or more of chloroplatinic acid, potassium chloroplatinate and ammonium chloroplatinate.
The Pd-containing salt is one or more of palladium nitrate, palladium chloride and palladium chloride acid.
A process for preparing catalyst from urea and nickel nitrate by thermal polycondensation method to obtain Ni/g-C3N4The composite carrier is prepared by loading active metal on the surface of the carrier, namely the catalyst; wherein, the active metal is one or a combination of more of Pt and Pd, and the active metal accounts for 5-10% of the mass of the catalyst.
Further, urea and nickel nitrate are mixed, a certain amount of pure water is added, and the mixture is ground and dried to obtain a composite solid. Composite solid packagePutting the mixture into a ceramic crucible, and heating the mixture to a calcining temperature at a slow heating rate for calcining. After calcining and sintering, naturally cooling to room temperature, molding the obtained composite carrier, wherein the particle size is 0.4-0.6 mm. Adding the composite carrier prepared in the above into pure water, and stirring. Heating in water bath, adding active metal salt solution, stirring, adjusting pH to 8.0, stirring, and cooling to room temperature. Adding NaBH4The aqueous solution was stirred for 1 hour. Filtering to obtain a catalyst, washing the catalyst with a solvent, and drying the catalyst in a vacuum drying oven at 60 ℃ for 4 hours to obtain catalyst particles.
The mass of the composite solid powder and the volume ratio of the crucible are 10g: 50 ml.
The pH is adjusted by Na2CO3The concentration of the solution is 0.25 mol/L.
The NaBH4The concentration of the aqueous solution is 0.1mol/L-0.2 mol/L.
The application of the catalyst in the catalytic reaction of continuous hydrogenation of aromatic nitro-compounds.
And the hydrogenation reaction of the aromatic nitro compound is carried out through a micro packed bed reactor to carry out continuous hydrogenation reaction.
The specific experimental steps are as follows:
filling catalyst particles into a micro packed bed reactor, and plugging quartz wool at two ends. The aromatic nitro-compound reaction liquid and hydrogen are continuously introduced into a micro mixer at the same time to be mixed and then are introduced into a micro packed bed reactor to contact with a catalyst to carry out gas-liquid-solid three-phase hydrogenation reduction reaction, the reacted materials enter a gas-liquid separator to be separated, and liquid phase products are collected and analyzed.
The reaction system of the micro packed bed comprises a micro mixer, a micro packed bed reactor and a gas-liquid separator.
The technical scheme is that the micro mixer is a T-shaped mixer.
The technical scheme is that the micro packed bed reactor is a stainless steel tube with the length of 200mm and the inner diameter of 6 mm.
The technical scheme is that the filling mode of the micro packed bed reactor is as follows: filling quartz wool, quartz sand and a catalyst at the bottom of the micro packed bed reactor, filling the quartz sand to the top end of the micro packed bed reactor, and filling the quartz wool at the top end of the micro packed bed reactor to ensure that the catalyst is positioned in the middle of the micro packed bed reactor.
The further technical scheme is that the aromatic nitro compound is an aromatic compound containing nitro substitution, such as sodium p-sulfanilate, nitrobenzene, p-trifluoromethyl nitrobenzene and the like.
The further technical scheme is that the nitro-compound reaction solution is prepared by dissolving an aromatic nitro-compound in a solvent, wherein the concentration of the reaction solution is 0.2-1 mol/L. The solvent is typically pure water, methanol, ethanol, etc.
The further technical scheme is that the gas-liquid flow ratio is 50-200.
The further technical scheme is that the reaction pressure and the reaction temperature range are respectively 0.5-2MPa and 80-120 ℃.
The invention has the following advantages
1. The invention uses cheap urea and nickel nitrate as raw materials to generate Ni/g-C by a thermal polycondensation method3N4The carrier has a loose structure, a high specific surface area, good cohesiveness, easy forming, and strong erosion and pulverization resistance.
2. Production of Ni/g-C by the invention3N4The composite carrier is loaded with active noble metal Pd and Pt nano particles suitable for nitro hydrogenation to obtain the catalyst, and the composite carrier contains C3N4The structure has a cavity surrounded by pyridine type nitrogen-containing groups, so that Pd and Pt nano particles are uniformly loaded on g-C3N4The surface of the composite carrier can effectively stabilize Pd and Pt nanoparticles, avoid activity reduction caused by aggregation of the Pd and Pt nanoparticles, and simultaneously the Ni in the composite carrier endows C with Ni3N4The new active site can provide active hydrogen during reaction, thereby obviously enhancing the catalytic activity and stability of the catalyst in the continuous flow catalytic hydrogenation process.
3. The catalyst obtained by the invention is applied to a micro packed bed adopted for carrying out continuous hydrogenation reaction of aromatic nitro-compounds, can further improve heat and mass transfer in the reaction process, realizes full-automatic reaction, and has the advantages of simple process, low energy consumption, low cost and high production efficiency.
4. The catalyst prepared by the method has good catalytic activity and stability, the selectivity of a hydrogenation product is good, byproducts are few, and the atom economy is high; meanwhile, the catalyst carrier is not lost, the service life is long, and the catalyst is not inactivated after continuously running for 500 hours.
5. The continuous hydrogenation method of the aromatic nitro compound is suitable for various aromatic nitro compounds and derivatives thereof, and has unique advantages in continuous flow synthesis of fine chemical intermediates.
Drawings
Fig. 1 is a schematic view of a continuous hydrogenation process for an aromatic nitro compound according to an embodiment of the present invention, in which a hydrogenation system includes a micro mixer, a micro packed bed reactor, a gas-liquid separator, and a pressure gauge.
Detailed Description
The technical solutions in the examples will be clearly and completely described below. It is apparent that the embodiments to be described below are only a part of the embodiments of the present invention, not all of the embodiments, and the present invention is not limited to the following embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention adopts a specific method to prepare Ni/g-C3N4As a carrier of active metal, the carrier has stable structure, and the unique structure can ensure that the active metal is stably and uniformly distributed on the carrier, thereby improving the catalytic activity and stability.
The preparation of the catalyst of the invention is that urea and nickel nitrate composite solid are thermally shrunk at high temperature to obtain a carrier, active metal is loaded by an impregnation method, and NaBH is then used4Reducing to prepare the catalyst. The catalyst shows high-efficiency catalytic activity for hydrogenation of aromatic nitro compounds in a micro packed bed reactor, has long catalyst life and has excellent applicability in the continuous hydrogenation process.
Example 1Pt/Ni/g-C3N4Catalyst preparation
20g of urea powder and 6.2g of nickel nitrate were mixed, 5g of pure water was added, and the mixture was ground and dried to obtain a composite solid. 10g of the composite solid was charged into a 50ml crucible and heated to a calcination temperature of 550 ℃ in a tube furnace under a helium purge at a heating rate of 10 ℃ per minute for 2 hours. Naturally cooling to room temperature, naturally cooling to room temperature after calcining, and molding the obtained composite carrier with particle size of 0.4-0.6 mm. 1.0g of the composite carrier was added to 200g of pure water and stirred. Heating the water bath at 80 ℃, and adding a certain amount of chloroplatinic acid (active metal Pt accounts for 5 percent of the mass of the catalyst). Stirring for 1 hour, adding Na2CO3The pH of the solution is adjusted to 8.0, the solution is continuously stirred for 1 hour, and the temperature is reduced to room temperature. 0.15g NaBH4Dissolving in 50ml of pure water, and dropwise adding NaBH4The aqueous solution was stirred for 1 hour. And filtering to obtain the catalyst. Washing with pure water, and drying in a vacuum drying oven at 60 ℃ for 4h to obtain catalyst particles. The resulting catalyst was designated Pt/NiCN.
Example 2Pd/Ni/g-C3N4Catalyst preparation
The catalyst of this example was prepared in the same manner as in example 1. Except that the active metal used was Pd (active metal Pd makes up 5% of the mass of the catalyst) and the resulting catalyst was reported as Pd/NiCN.
Example 3Pt-Pd/Ni/g-C3N4Catalyst preparation
The catalyst of this example was prepared in the same manner as in example 1. Except that the active metals used were Pt and Pd (active metal Pt accounted for 2.5% of the mass of the catalyst and active metal Pd accounted for 2.5% of the mass of the catalyst), and the resulting catalyst was noted as Pt-Pd/NiCN.
Comparative example 1Pt/C catalyst preparation
Tabletting activated carbon powder, crushing and sieving, wherein the particle size is 0.4-0.6 mm. 1.0g of the activated carbon carrier was added to 200ml of pure water and stirred. Heating the carrier in water bath at 80 ℃, and adding a certain amount of chloroplatinic acid (active metal Pt accounts for 5 percent of the mass of the carrier). Stirring was continued for 1 hour, pH was adjusted to 8.0 and stirring was continued for 1 hour. Cooling to room temperature, adding NaBH4Reducing, stirring for 1 hour, and filtering to obtain the catalyst. Washing with pure water, and drying in a vacuum drying oven at 60 ℃ for 4h to obtain catalyst particles. Obtained byThe catalyst was noted as Pt/C.
Comparative example 2
20g of melamine powder and 6.2g of nickel nitrate were mixed, 5g of pure water was added, and the mixture was ground and dried to obtain a composite solid. 10g of the composite solid was charged into a 50ml crucible and heated to a calcination temperature of 500 ℃ in a tube furnace under a helium purge at a rate of 5 ℃ per minute for 2 hours. Naturally cooling to room temperature, naturally cooling to room temperature after calcining, and molding the obtained composite carrier with particle size of 0.4-0.6 mm. 1.0g of the composite carrier was added to 200g of pure water and stirred. Heating the water bath at 80 ℃, and adding a certain amount of chloroplatinic acid (active metal Pt accounts for 5 percent of the mass of the catalyst). Stirring for 1 hour, adding Na2CO3The pH of the solution is adjusted to 8.0, the solution is continuously stirred for 1 hour, and the temperature is reduced to room temperature. 0.15g NaBH4Dissolving in 50ml of pure water, and dropwise adding NaBH4The aqueous solution was stirred for 1 hour. And filtering to obtain the catalyst. Washing with pure water, and drying in a vacuum drying oven at 60 ℃ for 4h to obtain catalyst particles. The resulting catalyst was designated Pt/NiCN-2.
Examples 4-8 catalysts prepared in examples 1-3 and comparative examples 1-2 catalyze the hydrogenation of sodium m-nitrobenzenesulfonate
Examples 4 to 8 were prepared by sequentially filling a micro packed bed reactor (see fig. 1) with pure water using the catalysts described in examples 1 to 5 and comparative examples 1 to 2, respectively. Sodium m-nitrobenzenesulfonate is used as a raw material, pure water is used as a solvent, and a raw material reaction solution with the concentration of 1mol/L is prepared. Under the conditions that the temperature is 90 ℃, the pressure is 1.5MPa and the gas-liquid flow ratio is 200, the raw material reaction liquid and high-purity hydrogen are introduced into a micro mixer for dispersion and mixing, then a gas-liquid mixture enters a micro packed bed to contact with a catalyst for reaction, the reacted material enters a gas-liquid separator for separation, a liquid phase product is collected for analysis, and the addition amount of the catalyst is 0.6 g. The reaction results are shown in Table 1.
The micro packed bed reactor adopts the device flow recorded in fig. 1, and specifically, catalyst particles are filled in the micro packed bed reactor, and quartz wool is plugged at two ends of the micro packed bed reactor. The aromatic nitro-compound reaction liquid and hydrogen are continuously introduced into a micro mixer at the same time to be mixed and then are introduced into a micro packed bed reactor to contact with a catalyst to carry out gas-liquid-solid three-phase hydrogenation reduction reaction, the reacted materials enter a gas-liquid separator to be separated, and liquid phase products are collected and analyzed.
TABLE 1
As can be seen from Table 1, examples 4, 7, the catalytic activity of the Pt/NiCN catalyst is significantly higher than that of the Pt/C catalyst, since Ni/g-C3N4The distribution of the metal nano particles on the composite carrier is more dispersed and more stable, the particle size is smaller, in addition, the Pt/C catalyst is eroded in long-time operation, partial catalyst powder falls off, the pressure drop of the reactor is increased, and the reaction is stopped due to overhigh pressure drop after the operation for more than 200 hours. As can be seen from examples 4 and 8, Pt/NiCN has higher catalytic activity and longer catalyst life than Pt/NiCN-2, and on the one hand, the catalyst is derived from g-C prepared by taking urea as a precursor3N4The carrier has more pore channel structures; on the other hand, higher calcination temperature and fast temperature rise rate allow g-C3N4The pore channel structure is further increased, and the specific surface area of the carrier is high. In addition, Pt-Pd bimetallic catalysts were found to have the best catalytic performance and catalytic life in comparison of the various active metals.
Example 9
The catalyst prepared in example 3 was used and packed into a micro packed bed reactor. Nitrobenzene is selected as a raw material, methanol is selected as a solvent, and a raw material reaction solution with the concentration of 0.5mol/L is prepared.
And (2) simultaneously introducing the raw material reaction liquid and high-purity hydrogen into a micro mixer for dispersion and mixing at the temperature of 80 ℃ and the pressure of 0.5MPa, wherein the gas-liquid flow ratio is 100, then introducing the gas-liquid mixture into a micro packed bed to contact with a catalyst for reaction, introducing the reacted material into a gas-liquid separator for separation, and collecting and analyzing a liquid-phase product. The addition amount of the catalyst is 0.6 g; the operation is continued for 500h, and the reaction results are shown in Table 2: the conversion rate of nitrobenzene is 99.4-100%, and the selectivity of the product is 99.2-99.8%.
TABLE 2
| Reaction time h | Conversion rate% | Selectivity% |
| 100 | 100 | 99.8 |
| 200 | 100 | 99.7 |
| 300 | 99.8 | 99.5 |
| 400 | 99.6 | 99.4 |
| 500 | 99.4 | 99.2 |
Example 10
The catalyst prepared in example 3 was used and packed into a micro packed bed reactor. M-chloronitrobenzene is selected as a raw material, methanol is selected as a solvent, and a raw material reaction solution with the concentration of 1.0mol/L is prepared.
And (2) simultaneously introducing the raw material reaction liquid and high-purity hydrogen into a micro mixer for dispersing and mixing under the conditions that the temperature is 90 ℃ and the pressure is 1.5MPa, wherein the gas-liquid flow ratio is 150, then introducing the gas-liquid mixture into a micro packed bed to contact with a catalyst for reaction, introducing the reacted material into a gas-liquid separator for separation, and collecting and analyzing a liquid-phase product. The addition amount of the catalyst is 0.6 g; the operation is continued for 500h, and the reaction results are shown in Table 3: the conversion rate of m-chloronitrobenzene is 99.6-100%, and the selectivity of the product is 99.1-99.7%.
TABLE 3
| Reaction time h | Conversion rate% | Selectivity% |
| 100 | 100 | 99.7 |
| 200 | 100 | 99.5 |
| 300 | 99.9 | 99.5 |
| 400 | 99.7 | 99.3 |
| 500 | 99.6 | 99.1 |
Example 11
The catalyst prepared in example 3 was used and packed into a micro packed bed reactor. M-dinitrobenzene is selected as a raw material, methanol is selected as a solvent, and a raw material reaction solution with the concentration of 0.4mol/L is prepared.
And (2) simultaneously introducing the raw material reaction liquid and high-purity hydrogen into a micro mixer for dispersion and mixing at the temperature of 100 ℃ and the pressure of 1.0MPa, wherein the gas-liquid flow ratio is 200, then introducing the gas-liquid mixture into a micro packed bed to contact with a catalyst for reaction, introducing the reacted material into a gas-liquid separator for separation, and collecting and analyzing a liquid-phase product. The addition amount of the catalyst is 0.6 g; the operation is continued for 500h, and the reaction results are shown in Table 4: the conversion rate of m-dinitrobenzene is 99.8-100%, and the selectivity of the product is 99.3-99.9%.
TABLE 4
| Reaction time h | Conversion rate% | Selectivity% |
| 100 | 100 | 99.9 |
| 200 | 100 | 99.7 |
| 300 | 100 | 99.5 |
| 400 | 99.9 | 99.5 |
| 500 | 99.8 | 99.3 |
Example 12
The catalyst prepared in example 3 was used and packed into a micro packed bed reactor. P-trifluoromethyl nitrobenzene is selected as a raw material, methanol is selected as a solvent, and a raw material reaction solution with the concentration of 0.8mol/L is prepared.
And (2) simultaneously introducing the raw material reaction liquid and high-purity hydrogen into a micro mixer for dispersing and mixing under the conditions that the temperature is 120 ℃ and the pressure is 1.5MPa, wherein the gas-liquid flow ratio is 150, then introducing the gas-liquid mixture into a micro packed bed to contact with a catalyst for reaction, introducing the reacted material into a gas-liquid separator for separation, and collecting and analyzing a liquid-phase product. The addition amount of the catalyst is 0.6 g; the operation is continued for 500h, and the reaction results are shown in Table 5: the conversion rate of the trifluoromethyl nitrobenzene is 99.7 to 100 percent, and the selectivity of the product is 99.5 to 99.8 percent.
TABLE 5
| Reaction time h | Conversion rate% | Selectivity% |
| 100 | 100 | 99.8 |
| 200 | 100 | 99.8 |
| 300 | 99.8 | 99.7 |
| 400 | 99.7 | 99.5 |
| 500 | 99.7 | 99.5 |
Example 13
The catalyst prepared in example 3 was used and packed into a micro packed bed reactor. 4-methoxy-3-nitrotoluene is selected as a raw material, methanol is selected as a solvent, and a raw material reaction solution with the concentration of 0.2mol/L is prepared.
And (2) simultaneously introducing the raw material reaction liquid and high-purity hydrogen into a micro mixer for dispersion and mixing at the temperature of 110 ℃ and the pressure of 2MPa, wherein the gas-liquid flow ratio is 100, then introducing the gas-liquid mixture into a micro packed bed to contact with a catalyst for reaction, introducing the reacted material into a gas-liquid separator for separation, and collecting and analyzing a liquid-phase product. The addition amount of the catalyst is 0.6 g; the operation is continued for 500h, and the reaction results are shown in Table 6: the conversion rate of the 4-methoxy-3-nitrotoluene is 99.4-100%, and the selectivity of the product is 99.2-99.7%.
TABLE 6
| Reaction time h | Conversion rate% | Selectivity% |
| 100 | 100 | 99.7 |
| 200 | 99.9 | 99.6 |
| 300 | 99.7 | 99.6 |
| 400 | 99.5 | 99.4 |
| 500 | 99.4 | 99.2 |
In conclusion, the invention uses cheap urea and nickel nitrate as raw materials to generate Ni/g-C by a thermal polycondensation method3N4The carrier has loose structure, high specific surface area, high adhesion, easy forming, high erosion and powdering resistance, and the Ni/g-C produced by the method3N4The composite carrier is loaded on active noble metal Pd and Pt nano particles with advantages of nitro hydrogenation to obtain the catalyst, and the active metal particles are uniformly loaded on g-C due to the carrier having a cavity surrounded by pyridine type nitrogen-containing groups3N4The surface of the catalyst can effectively stabilize the metal nanoparticles, avoid the aggregation of the metal nanoparticles and further remarkably enhance the stability of the catalyst in the continuous flow catalytic hydrogenation process; the catalyst obtained by the invention is applied to the adopted micro packed bed for continuous productionThe aromatic nitro-compound hydrogenation reaction can further improve the heat and mass transfer in the reaction process, realize full-automatic reaction, and has the advantages of simple process, low energy consumption, low cost and high production efficiency; the catalyst prepared by the method has good catalytic activity and stability, the selectivity of a hydrogenation product is good, byproducts are few, and the atom economy is high; meanwhile, the catalyst carrier is not lost, the service life is long, and the catalyst is not inactivated after continuously running for 500 hours; the continuous hydrogenation method of the aromatic nitro compound is suitable for various aromatic nitro compounds and derivatives thereof, and has unique advantages in continuous flow synthesis of fine chemical intermediates.
Claims (10)
1. A catalyst applied to the continuous hydrogenation of aromatic nitro-compounds is characterized in that: using urea and nickel nitrate as raw materials to generate Ni/g-C by a thermal polycondensation method3N4The carrier is used for loading active noble metal, namely the catalyst; wherein the active noble metal is Pt and/or Pd, and the active metal accounts for 5-10% of the mass of the carrier.
2. The catalyst for the continuous hydrogenation of aromatic nitro compounds according to claim 1, wherein: mixing urea and nickel nitrate, heating to 500-600 ℃ at the heating rate of 8-12 ℃/min, calcining for 1-3h, and then cooling to room temperature to obtain Ni/g-C3N4A carrier; the mass ratio of the urea to the nickel nitrate is 10-20: 3.1-6.2.
3. The catalyst for the continuous hydrogenation of aromatic nitro compounds according to claim 2, wherein: the total nitrogen content in the urea is 46.5%; the initial temperature of the calcination is 40-60 ℃.
4. The catalyst for the continuous hydrogenation of aromatic nitro compounds according to claim 2, wherein: adding the carrier particles into water for uniform dispersion, heating the carrier particles in a water bath at 70-90 ℃ for 1-2h after uniform dispersion, adding an active noble metal salt solution, stirring for 1-2h, then adjusting the pH of the system to be alkaline, continuing stirring for 1-2h, cooling to room temperature after stirring, adding NaBH4Reducing the water solution at 20-25 ℃ under stirring condition 1And filtering for-2 hours to obtain the catalyst loaded with the active noble metal.
5. The catalyst for the continuous hydrogenation of aromatic nitro compounds according to claim 4, wherein: the carrier, water, active noble metal salt (calculated by metal dosage), NaBH4Aqueous solution (with NaBH)4Mass meter) mass-to-volume ratio of 1 g: 200 ml: 0.05-0.10g, 0.019g-0.378 g.
6. The catalyst for the continuous hydrogenation of aromatic nitro compounds according to claim 4, wherein: the active noble metal salt is a salt of one or more metal elements containing Pt and/or Pd.
7. The catalyst for the continuous hydrogenation of aromatic nitro compounds according to claim 4, wherein: and cleaning the solid obtained after filtering with pure water, drying for 4 hours in a vacuum drying oven at 60 ℃, tabletting the obtained catalyst, and crushing and sieving with a 30-mesh sieve to obtain catalyst particles.
8. A method of preparing the catalyst of claim 1, wherein: using urea and nickel nitrate as raw materials to generate Ni/g-C by a thermal polycondensation method3N4The carrier is prepared by loading active noble metal on the surface of the carrier by a deposition-precipitation method; wherein the active metal is one or a combination of more of Pt, Pd, Ni and Co, and accounts for 5-10% of the mass of the carrier.
9. Use of a catalyst according to claim 1, wherein: the catalyst is applied to the catalytic reaction of the continuous hydrogenation of the aromatic nitro compound.
10. Use according to claim 9, characterized in that: and the hydrogenation reaction of the aromatic nitro compound is carried out through a micro packed bed reactor to carry out continuous hydrogenation reaction.
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| CN112495418A (en) * | 2020-12-03 | 2021-03-16 | 山东科技大学 | Preparation method of nitrogen-doped carbon-supported non-noble metal catalyst and application of nitrogen-doped carbon-supported non-noble metal catalyst in reduction of nitro compounds |
| CN113019414A (en) * | 2021-03-01 | 2021-06-25 | 中国科学院过程工程研究所 | Hydrogenation catalyst, preparation method and application thereof |
| CN113070087A (en) * | 2021-04-02 | 2021-07-06 | 绍兴绿奕化工有限公司 | Non-noble metal catalyst and preparation method and application thereof |
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