CN113600181A - Preparation method of nano palladium supported catalyst - Google Patents
Preparation method of nano palladium supported catalyst Download PDFInfo
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- CN113600181A CN113600181A CN202110745051.7A CN202110745051A CN113600181A CN 113600181 A CN113600181 A CN 113600181A CN 202110745051 A CN202110745051 A CN 202110745051A CN 113600181 A CN113600181 A CN 113600181A
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
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- C—CHEMISTRY; METALLURGY
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- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
- C07C209/30—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds
- C07C209/32—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups
- C07C209/36—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups by reduction of nitro groups bound to carbon atoms of six-membered aromatic rings in presence of hydrogen-containing gases and a catalyst
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Abstract
The invention discloses a preparation method of a nano palladium supported catalyst, belonging to the technical field of preparation of hydrogenation catalysts. The method comprises the steps of adding deionized water into a porous carrier for pretreatment, adding a palladium precursor solution for adsorption loading, adding a coordination agent capable of coordinating with palladium and a reducing agent for heating and reducing after separation and drying, and washing after filtration and separation to obtain the highly dispersed nano-palladium catalyst. The catalyst prepared by the method disclosed by the invention has the palladium content of 1-20%, the nano palladium particles are highly dispersed on the carrier, the catalyst is high in hydrogenation activity, mainly used for catalytic hydrogenation of unsaturated hydrocarbon or CO, and commonly used for selective hydrogenation of nitro, benzene ring, alkyne, ketone, aldehyde and the like.
Description
Technical Field
The invention belongs to the technical field of preparation of high-activity hydrogenation catalysts, and relates to a method for preparing a nano palladium supported catalyst with high dispersion and high activity by using a noble metal solution as an active precursor and activated carbon as a carrier.
Background
Catalytic hydrogenation is one of the most common reactions in chemical production, mainly catalytic hydrogenation of unsaturated hydrocarbons or CO, and is commonly used for selective hydrogenation of nitro, benzene ring, alkyne, ketone, aldehyde and the like; in the oxidation reaction, acetaldehyde, vinyl acetate and methyl methacrylate are produced by selective oxidation, and a noble metal supported catalyst is often used as a reaction catalyst, so that the method is widely applied to the hydrogenation reduction refining process of petrochemical industry, pharmaceutical industry, electronic industry, perfume industry, fuel industry and other fine chemical industries.
The palladium-carbon catalyst has the advantages of high hydrogenation reducibility, good selectivity, good stability, small feed ratio in use, repeated application, easy recovery and the like, and becomes a research hotspot
Palladium carbon (Pd/C) is an important catalyst prepared by loading a palladium compound on the surface of activated carbon, and the preparation methods of the traditional supported catalysts using activated carbon as a carrier mainly include an impregnation method, an impregnation precipitation method, an ion exchange method, an organic metal compound chemical vapor deposition method, an electrochemical vapor deposition method, and the impregnation method is most commonly used due to convenient operation, and different impregnation methods are adopted according to the type of the carrier and the precursor.
Zhang Zao light (catalyst preparation process technology) uses water-soluble palladium compound as precursor, firstly dissolves active component in solvent to prepare soluble salt or complex solution, adds it into carrier, after these salts are loaded on the surface of carrier, heats it to volatilize solvent, then activates catalyst by roasting or reducing agent, after the method is immersed, it directly heats it without separation to make palladium particles flow along with volatilization of solution in the solvent volatilization process to cause palladium aggregation.
The patent CN200510010606.4 takes a palladium compound which is easily dissolved in an organic solvent as a precursor, takes palladium acetate as an active component precursor compound, takes an organic solvent n-butylamine as a solvent, and obtains the high-activity palladium-carbon catalyst through hydrogen low-temperature wet reduction.
In patent CN200610047702.0, palladium colloid is used as a precursor, a supported nano Pd/C catalyst is prepared from a colloid solution, a nano palladium colloid solution which adopts a surfactant and a macromolecule as a stabilizer is prepared by chemically reducing palladium salt, and then a palladium colloid is prepared by adsorbing a proper carrier, so that a highly dispersed nano palladium catalyst is obtained. But the surfactant and the polymer stabilize the metal colloid and simultaneously have the inhibiting effect on the effective adsorption of reactants and the desorption of products. And the colloid is dispersed in the mixed liquid of the organic solvent and the water, so that a large amount of wastewater containing organic pollutants is generated.
Wangdawei (a process research for preparing high-activity palladium (II) tetraammine dichloride) has good water solubility and relatively stable solution chemical property3)4Cl2The catalyst is used for loading a precursor, and the phenomenon that palladium oxide particles generated by hydrolysis of palladium in an acid solution are agglomerated to generate large particles when activated carbon loading is carried out is reduced, so that the activity of the palladium-carbon catalyst is influenced. However, the activated carbon used in this method requires alkali treatment, which increases the complexity of the preparation process.
The reduction method for preparing the high-dispersion nano noble metal load comprises LiAlH4、NaBH4、N2H4The preparation processes of the formaldehyde method, the room-temperature chemical reduction loading method and the photoreduction method are complicated and expensive, the reduction process is carried out in solution, and palladium particles are easy to move and gather.
In patent CN200510200435.1, stoichiometric active metals such as Zn, Al, Fe and the like are added into a noble metal salt solution for chemical displacement reaction, or reducing agents such as methanol, formaldehyde, hydrazine hydrate sodium borohydride and the like are used for preparing a highly dispersed nano noble metal colloid, and activated carbon is added for adsorption to generate an activated carbon-supported palladium catalyst. The reduction method has the advantages that the colloid is easy to agglomerate, and metal impurities are introduced to influence the activity of the catalyst.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a preparation method of a nano palladium supported catalyst with high dispersion and high activity, the method is simple, convenient and quick, and the prepared catalyst has high hydrogenation reaction activity.
The method is realized by the following technical scheme.
The invention provides a preparation method of a nano palladium supported catalyst, which comprises the following steps:
1) weighing a porous active carrier, adding deionized water, uniformly mixing, and standing to wet the porous active carrier;
2) dissolving palladium salt in sufficient deionized water to prepare a palladium active precursor solution;
3) dripping the prepared palladium active precursor solution into the wetted porous active carrier, stirring overnight, and filtering under reduced pressure to obtain a palladium-containing wet filter cake;
4) vacuum drying the wet filter cake containing palladium to constant weight to obtain a dry base containing palladium;
5) transferring the palladium-containing dry base to a reduction reaction kettle, continuously dropwise adding a reduction solution, stirring, heating and reducing; the reducing solution is a compound solution of a reducing agent and a complexing agent; the mass ratio of the reducing agent to the complexing agent is 10-1; total volume of reducing solution (V/ml): the dry carrier (wt/g) is 20-5;
6) and filtering, washing with deionized water until no chloride ion exists in the filtrate, and pumping to obtain the palladium-carbon catalyst product.
In the technical proposal, the device comprises a base,
the porous active carrier is preferably alumina, molecular sieve or active carbon.
Step 1), deionized water for wetting the porous active carrier is added, wherein the mass ratio of the deionized water to the porous active carrier is 1-10.
The palladium salt is preferably sodium chloropalladate, potassium chloropalladate or a mixture of the two.
The reducing agent is aldehyde group and hydroxyl compound with reducibility. Preferably, the reducing agent is one or more of formaldehyde, acetaldehyde, methanol and ethanol.
The coordination agent in the step 5) is an N, P, S-containing organic reagent with palladium coordination capacity, and is preferably one or more of acetonitrile, triphenylphosphine, thiourea and dimethylglyoxime.
And 5) adding the reducing solution into the palladium-loaded dry base and heating to reflux.
The invention also provides the nano palladium supported catalyst prepared by the preparation method.
The water content of the palladium-carbon catalyst product is 0-80%.
The invention has the beneficial effects that:
1) the palladium salt which is easy to dissolve in water is used as an active precursor compound, so that the particle growth caused by palladium agglomeration due to hydrolysis of palladium in an acid solution is reduced; meanwhile, after loading, the precursor mother liquor is filtered, separated and removed, and vacuum drying is carried out, so that the aggregation and growth of palladium particles caused by palladium flow can be effectively reduced.
2) The reduction solution is an organic solvent, and the growth of palladium particles caused by the dissolution and migration of reduced palladium ions in an aqueous solution after palladium loading is further avoided; preferably, a reduction-coordination mixed system is used, and a coordination agent and palladium are subjected to a reduction reaction while being coordinated, so that the effect of fixing palladium particles is achieved, the palladium migration is reduced, the aggregation and growth of the palladium particles in the traditional reduction process of aldehyde, hydrazine and boron aqueous solutions are avoided, the dispersion degree of metal particles can be effectively increased, the particle size of active metal is reduced, the nano metal particles are highly dispersed on a carrier, and the hydrogenation activity of the catalyst is improved;
3) by using the palladium salt which is easy to dissolve in water as an active precursor compound, the acidity of the negative carrier liquid can be reduced, the primary loading rate of palladium is improved, and the prepared catalyst has wide palladium content distribution (0.5-20%);
4) the catalyst has the advantages of simple preparation method, good palladium dispersion, nano-particles of palladium particles, high hydrogenation activity and no introduction of harmful impurities.
Drawings
FIG. 1 is an XRD diffraction pattern of the nano-palladium supported catalysts prepared in examples 1-3.
FIG. 2 is an SEM image of the nano-palladium supported catalyst prepared in examples 1-3.
FIG. 3 is a TEM image of the nano-palladium supported catalyst prepared in examples 1-3.
Detailed Description
The technical solution of the present invention is further illustrated by the following specific examples. The water referred to in the examples was deionized water.
Example 1
Weighing sodium chloropalladate containing 100g of palladium, adding 5000ml of water, and performing ultrasonic wave to completely dissolve the sodium chloropalladate to obtain a sodium chloropalladate solution; weighing 900g of activated carbon powder (the specific surface area is 500-2000 m)2(per gram, granularity is 100-200 meshes), adding 1800 grams of water and uniformly stirring; dropwise adding the prepared sodium chloropalladate solution into the wet carbon powder, and continuously stirring for 8 hours after the dropwise adding is finished; filtering, vacuum drying the wet filter cake at 70 ℃ to constant weight, and cooling; transferring the carbon powder loaded with palladium into a 20-liter kettle, adding 10 liters of ethanol and acetonitrile mixed solution (the mass ratio of ethanol to acetonitrile is 9), heating and refluxing for 2h, and cooling; and (4) filtering the palladium-carbon slurry under reduced pressure, washing with water until no chloride ion exists, and vacuumizing for storage. For evaluation of nitrobenzene hydrogenation, 100% conversion of nitrobenzene to aniline was achieved.
Example 2
Weighing 50g of potassium chloropalladate containing palladium, adding 2500ml of water, and performing ultrasonic wave to completely dissolve the potassium chloropalladate to obtain a potassium chloropalladate solution; weighing 950g of activated carbon powder, adding 950g of water and stirring uniformly; dropwise adding the prepared potassium chloropalladate solution into the wet carbon powder, and continuously stirring for 10 hours after the dropwise adding is finished; filtering, vacuum drying the wet filter cake at 70 ℃ to constant weight, and cooling; transferring the carbon powder loaded with palladium into a 20L kettle, adding 3L of formaldehyde and triphenylphosphine mixed solution (the mass ratio of formaldehyde to triphenylphosphine is 5), heating and refluxing for 4h, and cooling; and (4) filtering the palladium-carbon slurry under reduced pressure, washing with water until no chloride ion exists, and vacuumizing for storage. For evaluation of nitrobenzene hydrogenation, 100% conversion of nitrobenzene to aniline was achieved.
Example 3
Weighing 75g of sodium chloropalladate containing palladium, adding 5000ml of water, and performing ultrasonic wave to completely dissolve the sodium chloropalladate to obtain a sodium chloropalladate solution; 925g of active carbon powder is weighed, 180g of water is added, and the active carbon powder and the water are uniformly stirred; dripping the prepared chloropalladate solution into the wet carbon powder, and continuing stirring for 12 hours after the dripping is finished; filtering, vacuum drying the wet filter cake at 70 ℃ to constant weight, and cooling; transferring the carbon powder loaded with palladium into a 5-liter kettle, adding 5 liters of a mixed solution of methanol and dimethylglyoxime (the mass ratio of the methanol to the dimethylglyoxime is 3), heating and refluxing for 12 hours, and cooling; and (4) filtering the palladium-carbon slurry under reduced pressure, washing with water until no chloride ion exists, and vacuumizing for storage. For evaluation of nitrobenzene hydrogenation, 100% conversion of nitrobenzene to aniline was achieved.
And (3) performance effect characterization:
1) evaluation of hydrogenation Activity
30mg of the catalyst was weighed out. And (2) taking 7ml of nitrobenzene and 56ml of ethanol, sequentially pouring the mixture into a 100ml reaction kettle, sealing, replacing for 5 times by using nitrogen, emptying, setting the temperature to be 80 ℃ after the device is connected with hydrogen, and stirring for 400 r/min. And introducing hydrogen of 0.5Mpa after the temperature reaches 80 ℃, reacting for 30 minutes, stopping gas inlet, closing heating, closing stirring, taking out the reaction kettle, rapidly cooling the reaction kettle in an ice water bath, cooling the reaction kettle to room temperature, and sampling to analyze the content of nitrobenzene and aniline.
2) XRD test results
As seen from the XRD diffraction pattern of the reduction catalyst in figure 1, the diffraction peak 2 theta 23 degrees is an activated carbon peak, the diffraction peaks 2 theta are respectively 40.1, 46.6 and 68.1 degrees which are diffraction peaks of Pd crystal face characteristics, and the palladium supported catalyst is composed of cubic face-centered Pd and carbon after reduction.
3) Analysis of SEM test results:
it can be seen from FIG. 2 that the palladium is dispersed on the surface of the catalyst without agglomeration.
4) TEM test results
The TEM images of examples 1-3 in FIG. 3 show that the palladium particles are in a nano-distribution.
Claims (10)
1. A preparation method of a nano palladium supported catalyst is characterized by comprising the following steps:
1) weighing a porous active carrier, adding deionized water, uniformly mixing, and standing to wet the porous active carrier;
2) dissolving palladium salt in sufficient deionized water to prepare a palladium active precursor solution;
3) dripping the prepared palladium active precursor solution into the wetted porous active carrier, stirring overnight, and filtering under reduced pressure to obtain a palladium-containing wet filter cake;
4) vacuum drying the wet filter cake containing palladium to constant weight to obtain a dry base containing palladium;
5) transferring the palladium-containing dry base to a reduction reaction kettle, continuously dropwise adding a reduction solution, stirring, heating and reducing; the reducing solution is a compound solution of a reducing agent and a complexing agent; the mass ratio of the reducing agent to the complexing agent is 10-1; total volume of reducing solution (V/ml): the dry carrier (wt/g) is 20-5;
6) and filtering, washing with deionized water until no chloride ion exists in the filtrate, and pumping to obtain the palladium-carbon catalyst product.
2. The method for preparing a nano-palladium supported catalyst according to claim 1, wherein the porous active carrier is alumina, molecular sieve or activated carbon.
3. The preparation method of the nano palladium supported catalyst according to claim 1, wherein the mass ratio of deionized water used for wetting the porous active carrier in the step 1) to the porous active carrier is 1-10.
4. The method for preparing a nano-palladium supported catalyst according to claim 1, wherein the palladium salt is sodium chloropalladate, potassium chloropalladate or a mixture of the two.
5. The method for preparing a nano-palladium supported catalyst according to claim 1, wherein the reducing agent is a reducing aldehyde or hydroxyl compound.
6. The preparation method of the nano-palladium supported catalyst according to claim 5, wherein the reducing agent is one or more of formaldehyde, acetaldehyde, methanol and ethanol.
7. The method of claim 1, wherein the complexing agent is N, P, S-containing organic agent having palladium complexing ability.
8. The preparation method of the nano-palladium supported catalyst according to claim 7, wherein the complexing agent is one or more of acetonitrile, triphenylphosphine, thiourea and dimethylglyoxime.
9. The method for preparing a nano-palladium supported catalyst according to claim 1, wherein the reducing solution in the step 5) is added to the palladium supported dry base and heated to reflux.
10. The preparation method of the nano palladium supported catalyst according to claim 1 to 9.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114937782A (en) * | 2022-04-24 | 2022-08-23 | 中国科学院长春应用化学研究所 | Supported metal-based catalyst and preparation method thereof |
| CN115020719A (en) * | 2022-06-21 | 2022-09-06 | 北京化工大学 | Preparation method of dual-site catalyst for direct formate fuel cell anode |
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| CN1709570A (en) * | 2004-06-18 | 2005-12-21 | 中国石油化工股份有限公司 | Method for preparing catalyst for refining of crude terephthalic acid |
| CN101502800A (en) * | 2008-12-30 | 2009-08-12 | 西安凯立化工有限公司 | Catalyst for one-step synthesis of alkyl cyclohexanone from alkylphenol and preparation method thereof |
| CN112237913A (en) * | 2019-07-18 | 2021-01-19 | 中国石油化工股份有限公司 | Preparation method of palladium-based supported hydrogenation catalyst and catalyst thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1709570A (en) * | 2004-06-18 | 2005-12-21 | 中国石油化工股份有限公司 | Method for preparing catalyst for refining of crude terephthalic acid |
| CN101502800A (en) * | 2008-12-30 | 2009-08-12 | 西安凯立化工有限公司 | Catalyst for one-step synthesis of alkyl cyclohexanone from alkylphenol and preparation method thereof |
| CN112237913A (en) * | 2019-07-18 | 2021-01-19 | 中国石油化工股份有限公司 | Preparation method of palladium-based supported hydrogenation catalyst and catalyst thereof |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114937782A (en) * | 2022-04-24 | 2022-08-23 | 中国科学院长春应用化学研究所 | Supported metal-based catalyst and preparation method thereof |
| CN114937782B (en) * | 2022-04-24 | 2024-03-08 | 中国科学院长春应用化学研究所 | Supported metal-based catalyst and preparation method thereof |
| CN115020719A (en) * | 2022-06-21 | 2022-09-06 | 北京化工大学 | Preparation method of dual-site catalyst for direct formate fuel cell anode |
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