CN112675839B - High-performance palladium-carbon catalyst and preparation method thereof - Google Patents
High-performance palladium-carbon catalyst and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the field of nitroaniline synthesis, and particularly relates to a high-performance palladium-carbon catalyst and a preparation method thereof. The invention solves the problem of low dispersity of the palladium-carbon catalyst, and utilizes the modification of the porous activated carbon to form amino traction on the surface, thereby being beneficial to the solidification of palladium ions and preventing the palladium ions from agglomerating, thereby realizing the improvement of the dispersity.
Description
Technical Field
The invention belongs to the field of nitroaniline synthesis, and particularly relates to a high-performance palladium-carbon catalyst and a preparation method thereof.
Background
Nitroaniline includes o-nitroaniline, m-nitroaniline and p-nitroaniline, which are artificially synthesized chemical substances widely applied to the dye-burning industry and are mainly used as intermediates for dye synthesis and intermediates for pharmaceutical chemicals.
Nitro-chlorobenzene ammonolysis is commonly used industrially to prepare nitroaniline directly from nitrochlorobenzene by ammonolysis under high pressure. The nitroaniline prepared by the process has high selectivity and high product purity, but the process has low production efficiency, generates a large amount of chlorine-containing wastewater in the process and is not environment-friendly. With the continuous development of catalytic hydrogenation reduction technology, more and more catalytic hydrogenation technology is used for the catalytic reduction of nitrobenzene compounds. Pd/C as catalyst, H 2 The catalytic reduction technology which is a reducing agent can make the catalyst show excellent performance in terms of both reactivity and selectivity by controlling the preparation conditions of the catalyst preparation process. However, the surface inertness and surface unevenness of the carbon material make it difficult to highly disperse the supported palladium nanoparticles.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a high-performance palladium-carbon catalyst, which solves the problem of low dispersity of the palladium-carbon catalyst, and utilizes the modification of porous activated carbon to form amino traction on the surface, thereby being beneficial to the solidification of palladium ions and preventing the agglomeration of the palladium ions, and further realizing the improvement of the dispersity.
In order to realize the technical purpose, the technical scheme of the invention is as follows:
a high-performance palladium-carbon catalyst is prepared from porous activated carbon structure and palladium particles as catalytic activity.
The porosity of the porous activated carbon is 200-500ppi; the palladium particles are nano palladium and have the particle size of 20-100nm.
The preparation method of the high-performance palladium-carbon catalyst comprises the following steps:
step 1, adding activated carbon into distilled water, uniformly stirring to form a suspension, then adding methylcellulose and sodium chloride, performing low-temperature ultrasonic treatment to completely disperse, stirring at a constant temperature, and standing to form gel, wherein the concentration of the activated carbon in the water is 30-80g/L, and the stirring speed for uniform stirring is 1000-2000r/min; the addition amount of the methyl cellulose is 20-30% of the mass of the activated carbon, the addition amount of the sodium chloride is 40-60% of the mass of the activated carbon, the low-temperature ultrasonic temperature is 2-6 ℃, the ultrasonic frequency is 60-80kHz, the constant-temperature stirring temperature is 80-100 ℃, and the stirring speed is 100-200r/min;
step 2, putting the gel into a die, extruding at constant temperature to form particles, sealing and carbonizing to obtain a prefabricated carrier, putting the prefabricated carrier into distilled water for microwave reaction for 10-20in, and drying to obtain porous activated carbon; the temperature of the constant-temperature extrusion is 100-120 ℃, and the pressure is 80-90% of the standard atmospheric pressure; the carbonization temperature is 300-700 ℃, the filtration of the microwave reaction is 100-200W, the temperature is 80-90 ℃, and the drying temperature is 100-110 ℃;
step 3, dissolving palladium chloride in absolute ethyl alcohol, and uniformly stirring to form palladium alcohol solution, wherein the concentration of the palladium chloride is 10-20g/L;
step 4, placing the porous activated carbon into an ammonia reaction kettle to stand still for 10-20min to form modification treatment; adding the modified porous activated carbon into the palladium alcohol solution, performing ultrasonic treatment for 20-40min, taking out, and drying to obtain coated porous activated carbon; the ammonia reaction kettle contains water vapor with volume concentration of 5-10%, the standing temperature is 70-80 ℃, the pressure is 0.2-0.3MPa, the ultrasonic frequency of the ultrasonic is 40-50kHz, the temperature is 10-20 ℃, and the drying temperature is 100-110 ℃;
and 5, standing the coated porous activated carbon in a reaction kettle for reaction for 10-20min, taking out and drying, and then carrying out reduction reaction to obtain the palladium-carbon catalyst, wherein the volume content of water vapor in the reaction kettle is 30-40%, the standing temperature is 80-100 ℃, and the reducing agent of the reduction reaction adopts hydrogen, and the reduction temperature is 80-90 ℃.
The catalyst is used for a catalytic hydrogenation process for preparing nitroaniline from dinitrobenzene.
As can be seen from the above description, the present invention has the following advantages:
1. the invention solves the problem of low dispersity of the palladium-carbon catalyst, and utilizes the modification of the porous activated carbon to form amino traction on the surface, thereby being beneficial to the solidification of palladium ions and preventing the agglomeration of the palladium ions, and further realizing the improvement of the dispersity.
2. The invention uses a solid-gas reaction system to promote the full modification of the active carbon, and simultaneously uses a fixed bed system to form gaseous hydrolysis conversion to form an in-situ reaction system.
Detailed Description
The present invention is described in detail with reference to examples, but the present invention is not limited to the claims.
Example 1
A high-performance palladium-carbon catalyst is prepared from porous activated carbon structure and palladium particles as catalytic activity.
The preparation method of the high-performance palladium-carbon catalyst comprises the following steps:
step 1, adding activated carbon into 1L of distilled water, uniformly stirring to form a suspension, then adding methyl cellulose and sodium chloride, performing low-temperature ultrasonic treatment until the mixture is completely dispersed, stirring at a constant temperature, and standing to form gel, wherein the concentration of the activated carbon in the water is 80g/L, and the stirring speed for uniform stirring is 2000r/min; the adding amount of the methyl cellulose is 30 percent of the mass of the activated carbon, the adding amount of the sodium chloride is 60 percent of the mass of the activated carbon, the low-temperature ultrasonic temperature is 6 ℃, the ultrasonic frequency is 80kHz, the constant-temperature stirring temperature is 100 ℃, and the stirring speed is 200r/min;
step 2, putting the gel into a mold, extruding at constant temperature to form particles, sealing and carbonizing to obtain a prefabricated carrier, putting the prefabricated carrier into distilled water for microwave reaction for 20in, and drying to obtain porous activated carbon; the temperature of the constant-temperature extrusion is 120 ℃, and the pressure is 90% of the standard atmospheric pressure; the carbonization temperature is 700 ℃, the filtration of the microwave reaction is 200W, the temperature is 90 ℃, and the drying temperature is 110 ℃;
step 3, dissolving palladium chloride in 1L of absolute ethyl alcohol, and uniformly stirring to form palladium alcohol solution, wherein the concentration of the palladium chloride is 20g/L;
step 4, placing the porous activated carbon into an ammonia reaction kettle to stand for 20min to form modification treatment; adding the modified porous activated carbon into a palladium alcohol solution, performing ultrasonic treatment for 40min, taking out, and drying to obtain coated porous activated carbon; the ammonia reaction kettle contains water vapor with the volume concentration of 10%, the standing temperature is 80 ℃, the pressure is 0.3MPa, the ultrasonic frequency of the ultrasonic is 50kHz, the temperature is 20 ℃, and the drying temperature is 110 ℃;
and 5, standing the coated porous activated carbon in a reaction kettle for reaction for 20min, taking out and drying the coated porous activated carbon, and performing reduction reaction to obtain a palladium-carbon catalyst, wherein the volume content of water vapor in the reaction kettle is 40%, the standing temperature is 100 ℃, and a reducing agent of the reduction reaction adopts hydrogen, and the reduction temperature is 90 ℃.
The palladium on carbon catalyst of this example had a porosity of 500ppi; the palladium particles are nano palladium and have the particle size of 100nm.
Example 2
A high-performance palladium-carbon catalyst is prepared from porous activated carbon structure and palladium particles as catalytic activity.
The preparation method of the high-performance palladium-carbon catalyst comprises the following steps:
step 1, adding activated carbon into 1L of distilled water, uniformly stirring to form a suspension, then adding methylcellulose and sodium chloride, performing low-temperature ultrasonic treatment to completely disperse, stirring at a constant temperature, and standing to form gel, wherein the concentration of the activated carbon in the water is 30g/L, and the stirring speed for uniform stirring is 1000r/min; the adding amount of the methyl cellulose is 20% of the mass of the activated carbon, the adding amount of the sodium chloride is 40% of the mass of the activated carbon, the low-temperature ultrasonic temperature is 2 ℃, the ultrasonic frequency is 60kHz, the constant-temperature stirring temperature is 80 ℃, and the stirring speed is 100-200r/min;
step 2, putting the gel into a mold, extruding at constant temperature to form particles, sealing and carbonizing to obtain a prefabricated carrier, putting the prefabricated carrier into distilled water for microwave reaction for 10 inches, and drying to obtain porous activated carbon; the temperature of the constant-temperature extrusion is 100 ℃, and the pressure is 80% of the standard atmospheric pressure; the carbonization temperature is 300 ℃, the filtration of the microwave reaction is 100W, the temperature is 80 ℃, and the drying temperature is 100 ℃;
step 3, dissolving palladium chloride in 1L of absolute ethyl alcohol, and uniformly stirring to form palladium alcohol solution, wherein the concentration of the palladium chloride is 10g/L;
step 4, placing the porous activated carbon into an ammonia reaction kettle to stand for 10min to form modification treatment; adding the modified porous activated carbon into the palladium alcohol solution, performing ultrasonic treatment for 20min, taking out, and drying to obtain coated porous activated carbon; the ammonia reaction kettle contains water vapor with volume concentration of 5%, the standing temperature is 70 ℃, the pressure is 0.2MPa, the ultrasonic frequency of the ultrasonic is 40kHz, the temperature is 10 ℃, and the drying temperature is 100 ℃;
and 5, standing the coated porous activated carbon in a reaction kettle for standing reaction for 10min, taking out and drying the coated porous activated carbon, and performing reduction reaction to obtain a palladium-carbon catalyst, wherein the volume content of water vapor in the reaction kettle is 30%, the standing temperature is 80 ℃, and a reducing agent of the reduction reaction adopts hydrogen, and the reduction temperature is 80 ℃.
The palladium on carbon catalyst of this example had a porosity of 200ppi; the palladium particles are nano palladium and have the particle size of 20nm.
Example 3
A high-performance palladium-carbon catalyst is prepared from porous activated carbon structure and palladium particles as catalytic activity.
The preparation method of the high-performance palladium-carbon catalyst comprises the following steps:
step 1, adding activated carbon into 1L of distilled water, uniformly stirring to form a suspension, then adding methylcellulose and sodium chloride, performing low-temperature ultrasonic treatment to completely disperse, stirring at a constant temperature, and standing to form gel, wherein the concentration of the activated carbon in the water is 60g/L, and the stirring speed for uniform stirring is 1500r/min; the adding amount of the methyl cellulose is 25% of the mass of the activated carbon, the adding amount of the sodium chloride is 50% of the mass of the activated carbon, the low-temperature ultrasonic temperature is 4 ℃, the ultrasonic frequency is 70kHz, the constant-temperature stirring temperature is 90 ℃, and the stirring speed is 150r/min;
step 2, putting the gel into a mold, extruding at constant temperature to form particles, sealing and carbonizing to obtain a prefabricated carrier, putting the prefabricated carrier into distilled water for microwave reaction for 15in, and drying to obtain porous activated carbon; the temperature of the constant-temperature extrusion is 110 ℃, and the pressure is 85% of the standard atmospheric pressure; the carbonization temperature is 500 ℃, the filtration of the microwave reaction is 150W, the temperature is 85 ℃, and the drying temperature is 105 ℃;
step 3, dissolving palladium chloride in 1L of absolute ethyl alcohol, and uniformly stirring to form palladium alcohol solution, wherein the concentration of the palladium chloride is 15g/L;
step 4, placing the porous activated carbon into an ammonia reaction kettle to stand for 15min to form modification treatment; adding the modified porous activated carbon into a palladium alcohol solution, performing ultrasonic treatment for 30min, taking out, and drying to obtain coated porous activated carbon; the ammonia reaction kettle contains 8% of water vapor by volume concentration, the standing temperature is 75 ℃, the pressure is 0.2MPa, the ultrasonic frequency of the ultrasonic is 45kHz, the temperature is 15 ℃, and the drying temperature is 105 ℃;
and 5, standing the coated porous activated carbon in a reaction kettle for reaction for 15min, taking out the coated porous activated carbon, drying the coated porous activated carbon, and performing reduction reaction to obtain a palladium-carbon catalyst, wherein the volume content of water vapor in the reaction kettle is 35%, the standing temperature is 85 ℃, and a reducing agent of the reduction reaction adopts hydrogen, and the reduction temperature is 85 ℃.
The palladium on carbon catalyst of this example had a porosity of 400ppi; the palladium particles are nano palladium and have a particle size of 70nm.
Examples of the invention
The catalyst of example 3 was used for the hydrogenation reaction as follows:
150g of p-dinitrobenzene, 200g of methanol and 2.2g of the catalyst are added into a 500mL high-pressure reaction kettle, nitrogen is replaced for 3 times under 1MPa, then hydrogen with 1MPa is used for replacing for 3 times, the temperature is raised to 150 ℃, the reaction pressure is controlled to be 2MPa, and the reaction is continued for 1.5 hours. And (3) cooling, distilling and recovering the methanol under the protection of nitrogen at normal pressure, and separating to obtain a p-nitroaniline crude product. The product was analyzed for its composition by gas chromatography, with a conversion of 99.8% for dinitrobenzene, a selectivity of 99.5% for p-nitroaniline and a yield of 99.1% for p-nitroaniline.
In summary, the invention has the following advantages:
1. the invention solves the problem of low dispersity of the palladium-carbon catalyst, and utilizes the modification of the porous activated carbon to form amino traction on the surface, thereby being beneficial to the solidification of palladium ions and preventing the palladium ions from agglomerating, thereby realizing the improvement of the dispersity.
2. The invention uses a solid-gas reaction system to promote the full modification of the active carbon, and simultaneously uses a fixed bed system to form gaseous hydrolysis conversion to form an in-situ reaction system.
It should be understood that the detailed description of the invention is merely illustrative of the invention and is not intended to limit the invention to the specific embodiments described. It will be understood by those skilled in the art that the present invention may be modified and equivalents substituted for elements thereof to achieve the same technical result; and are within the scope of the present invention as long as the requirements of use are met.
Claims (8)
1. A high-performance palladium carbon catalyst is characterized in that: forming a porous palladium carbon catalyst by using a porous activated carbon structure and palladium particles as catalytic activity;
the preparation method of the high-performance palladium-carbon catalyst comprises the following steps:
step 1, adding activated carbon into distilled water, uniformly stirring to form a suspension, then adding methylcellulose and sodium chloride, performing low-temperature ultrasonic treatment to completely disperse, stirring at constant temperature, and standing to form gel;
step 2, putting the gel into a mold, extruding at constant temperature to form particles, sealing and carbonizing to obtain a prefabricated carrier, putting the prefabricated carrier into distilled water, performing microwave reaction for 10-20m in, and drying to obtain porous activated carbon;
step 3, dissolving palladium chloride in absolute ethyl alcohol, and uniformly stirring to form palladium alcohol solution;
step 4, placing the porous activated carbon into an ammonia reaction kettle to stand still for 10-20min to form modification treatment; adding the modified porous activated carbon into a palladium alcohol solution, performing ultrasonic treatment for 20-40min, taking out, and drying to obtain coated porous activated carbon;
and 5, standing the coated porous activated carbon in a reaction kettle for reaction for 10-20min, taking out and drying the coated porous activated carbon, and then carrying out reduction reaction to obtain the palladium-carbon catalyst.
2. The high performance palladium on carbon catalyst as claimed in claim 1, wherein: the porosity of the porous activated carbon is 200-500ppi; the palladium particles are nano palladium and have the particle size of 20-100nm.
3. The high-performance palladium-on-carbon catalyst according to claim 1, wherein: the concentration of the activated carbon in the step 1 in water is 30-80g/L, and the stirring speed for uniformly stirring is 1000-2000r/min; the addition amount of the methyl cellulose is 20-30% of the mass of the activated carbon, the addition amount of the sodium chloride is 40-60% of the mass of the activated carbon, the low-temperature ultrasonic temperature is 2-6 ℃, the ultrasonic frequency is 60-80kHz, the constant-temperature stirring temperature is 80-100 ℃, and the stirring speed is 100-200r/min.
4. The high performance palladium on carbon catalyst as claimed in claim 1, wherein: the temperature of the constant-temperature extrusion in the step 2 is 100-120 ℃, and the pressure is 80-90% of the standard atmospheric pressure; the carbonization temperature is 300-700 ℃, the power of the microwave reaction is 100-200W, the temperature is 80-90 ℃, and the drying temperature is 100-110 ℃.
5. The high performance palladium on carbon catalyst as claimed in claim 1, wherein: the concentration of the palladium chloride in the step 3 is 10-20g/L.
6. The high performance palladium on carbon catalyst as claimed in claim 1, wherein: the ammonia reaction kettle in the step 4 contains 5-10% of water vapor by volume concentration, the standing temperature is 70-80 ℃, the pressure is 0.2-0.3MPa, the ultrasonic frequency of the ultrasonic is 40-50kHz, the temperature is 10-20 ℃, and the drying temperature is 100-110 ℃.
7. The high-performance palladium-on-carbon catalyst according to claim 1, wherein: the volume content of the water vapor in the reaction kettle in the step 5 is 30-40%, the standing temperature is 80-100 ℃, the reducing agent for the reduction reaction adopts hydrogen, and the reduction temperature is 80-90 ℃.
8. The high performance palladium on carbon catalyst as claimed in claim 1, wherein: the catalyst is used for a catalytic hydrogenation process for preparing nitroaniline from dinitrobenzene.
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