CN1226086C - Solid supported noble metal catalyst and its preparing method - Google Patents

Abstract

A supported noble metal catalyst, the active component is any one of Ru, Rh, Pd, Os, Ir, Pt, Au, Ag, Cu or Ni, and the carrier is activated carbon, graphite carbon, carbon nanotubes, Al ₂ O _3. Any one of SiO ₂ , molecular sieve, MgO or TiO ₂ , wherein the active component content is 0.1-90%, and the metal particle size of the catalyst is 0.5-6nm. The preparation process is as follows: the active component, the hydroxide or carbonate of alkali metal or alkaline earth metal and the carrier are respectively dispersed in the solvent, mixed in proportion, the solution is heated, and nitric acid, sulfuric acid, hydrochloric acid, oxalic acid or acetic acid are added as accelerators. Settling agent, drying. The catalyst is used as a fuel cell catalyst and outperforms cells using the same type of commercial catalyst. The method is environment-friendly, simple in process, short in process, less time-consuming, high in yield, and reduces catalyst production cost.

Description

A kind of supported metal catalyst and preparation method thereof

technical field

The invention relates to a supported metal catalyst and a preparation method of the catalyst.

Background technique

Supported noble metal catalysts have been widely used as fuel cell electrode catalysts, hydrogenation, dehydrogenation reactions and a few oxidation reaction catalysts. Due to the high price of platinum and the scarcity of resources. Therefore, appropriate preparation methods and process conditions must be adopted to reduce the particle size of platinum metal, increase the dispersion of platinum on carbon, and improve the activity and utilization of catalysts, especially for high-load supported noble metal catalysts.

In recent years, many researchers at home and abroad have tried various methods to prepare supported noble metal catalysts:

Document [1] (Henry G Petrow, US 3992331) introduces a method for preparing a highly dispersed activated carbon-supported platinum catalyst. In this method, chloroplatinic acid is firstly prepared into sodium platinum sulfite (Na ₆ [Pt(SO ₃ ) ₄ ]), and then the sodium ions in sodium platinum sulfite are exchanged for hydrogen ions through ion exchange, and heated and boiled in air , release excess sulfite ions, and finally dry at a certain temperature to obtain a black colloid of platinum, which can be dispersed in water or other solvents again, so that it can be easily loaded on various carriers. The method can be used to prepare a platinum catalyst of 1.5-2.5 nanometers, and at the same time, because the method uses sulfite to replace chloride ions, it can effectively avoid the reduction of catalytic activity caused by trace chloride ions in the catalyst. The disadvantage of this method is that the preparation cost is high, the technological process is complicated, and the process is not easy to control.

The method for preparing catalyst in document [2] (M.Watanabe, J.Electroanal.Chem.229 (1987) 395) is to make sodium chloroplatinate sodium platinum sulfite earlier, but what is different from document [1] is that this The method does not separate platinum sodium sulfite alone, but directly adds excess hydrogen peroxide to oxidize and decompose it to form a stable platinum oxide colloid, and then adds ruthenium compounds such as ruthenium trichloride dropwise to the colloid, quickly The excess hydrogen peroxide is decomposed, and the generated ruthenium oxide and platinum oxide are combined to form platinum ruthenium oxide clusters, which are deposited on activated carbon and other carriers through pH adjustment, and the platinum in them is reduced to a metal state by hydrogen. The catalyst prepared using this method is a metal cluster with ruthenium oxide as the core and platinum on the surface.

The method for preparing catalyst in document [3] (AKShukla, J.Appl.Electrochem.29 (1999) 129) is at first all the chlorides of platinum and ruthenium are converted into sulfurous acid complexes, i.e. sodium platinum sulfite and sulfurous acid Sodium ruthenium sulfate (Na ₆ [Ru(SO ₃ )] ₄ ), and separate it, then mix it, oxidize and decompose it into mixed oxide colloid with hydrogen peroxide, and then load it on activated carbon, or as described in literature [2] In the process, sodium platinum sulfite is first oxidized and decomposed with hydrogen peroxide, then sodium ruthenium sulfite is added to decompose excess hydrogen peroxide, and sodium ruthenium sulfite is transformed into ruthenium oxide at the same time, and the two oxides are co-precipitated on the activated carbon by adjusting the pH. Finally, it can be obtained by adding formic acid or introducing hydrogen for reduction.

The above two methods are not obtained by first preparing the metal colloid and then dispersing, but first oxidizing sodium platinum sulfite with high-cost hydrogen peroxide and then reducing platinum oxide with hydrogen or irritating formic acid. Not only the process is complicated, but the cost is high , to some extent also cause environmental pollution.

Literature [4] (HBnnemann, Angew.Chem.Int.Ed.Engl.30 (1991) 1312) and literature [5] (HBnnemann, US 5641723) use NR ₄ BR ₃ H in tetrahydrofuran (THF) By reducing metal salts, various nano-scale metal colloids with narrow particle size distribution protected by quaternary ammonium salts were prepared. Wherein the preparation of the Rh colloid is carried out as follows: 2.79 grams of RhCl ₃ are dissolved in 500 milliliters of tetrahydrofuran, added to 100 milliliters of 0.4mol/LN(C ₈ H ₁₇ ) ₄ BEt ₃ H tetrahydrofuran solution, after the dissolution is complete, at room temperature Pass inert gas and stir for 15 hours, dry at 40°C and 10-3 mbar to obtain Rh colloid, then dissolve the prepared Rh colloid in tetrahydrofuran and slowly add it to titanium-containing activated carbon dispersed in tetrahydrofuran, and finally prepare A catalyst containing 0.2 wt% of titanium and 10 wt% of Rh was obtained.

The above two methods operate under anhydrous and oxygen-free conditions, use a large amount of toxic organic solvents, and generate a large amount of by-product waste, which is not an environmentally friendly process.

Document [6] (H.E.Van Dam, J.Catal., 131 (1991) 335) introduced the preparation of carbon-supported platinum catalyst by formaldehyde reduction method. Add chloroplatinic acid aqueous solution to NoritROX 0.8 activated carbon pretreated by different methods, stir slowly at room temperature, soak for 5 days until adsorption equilibrium, filter off the solution, hydrothermally treat in a closed container at 95°C, and finally add formaldehyde to reduce Platinum 5wt% carbon-supported platinum catalyst, its dispersion is about 60%. The disadvantage of this method is that formaldehyde needs to be used as a reducing agent, and formaldehyde is very harmful to the human body.

Contents of the invention

The object of the present invention is to provide a supported metal catalyst, which has a small particle size and uniform distribution, and has a good degree of dispersion.

Another object of the present invention is to provide a method for preparing a supported noble metal catalyst, which is low in cost, environmentally friendly, simple in process flow and easy to control.

In order to achieve the above object, the active component of a supported noble metal catalyst provided by the present invention is Ru, Rh, Pd, Os, Ir, Pt, Au, Ag, Cu or Ni, and the carrier is activated carbon, graphite carbon, carbon nanotube , Al ₂ O ₃ , SiO ₂ , molecular sieve, MgO or TiO ₂ , the metal particle size of the catalyst is 0.5-6nm. Wherein the content of active components is 5-90%, preferably 10-60%.

A kind of method for preparing supported noble metal catalyst provided by the invention, its preparation process is as follows:

(1) The active component, the hydroxide or carbonate of the alkali metal or alkaline earth metal and the carrier are respectively dispersed in the solvent, and the concentrations of the three solutions are respectively:

The concentration of the noble metal salt solution is 0.1-100mg/ml;

The concentration of alkali metal or alkaline earth metal hydroxide or carbonate solution is 0.1-10mol/L;

Carrier suspension concentration 0.1-1000g/L;

(2) These three kinds of solutions are mixed again by 1: 0.01-1: 0.5-3 volume ratio, and the pH of solution is 6-14;

(3) Heating the solution prepared in step (2), keeping the temperature at 60-250°C for 15-600 minutes;

(4) Add nitric acid, sulfuric acid, hydrochloric acid, oxalic acid or acetic acid with a concentration of 0.1-10mol/L to the above mixed solution as a settling agent, so that the pH of the mixed solution system is 1-8, stir for 30 minutes, filter, and use deionized Wash with water repeatedly until there is no Cl ^- , dry, and keep the temperature at 40-200°C for 30-1800 minutes;

The active component is one of nitrates and halides of Ru, Rh, Pd, Os, Ir, Pt, Au, Ag, Cu, Ni,

The dispersant is one of C ₂ -C ₈ monohydric alcohols, dihydric alcohols, and trihydric alcohols, or a mixed solution or a solvent mixed with water.

Above-mentioned steps (1) and step (2) are carried out as follows:

Dissolving the active ingredient in the dispersant;

Adjust the pH to 6-14 with alkali metal or alkaline earth metal hydroxide or carbonate solution, and add the carrier;

Then proceed to steps (3) and (4).

The present invention has following effect:

1. Change the composition of the solvent in the dispersion system, without using any surfactant, make the particle size of the carbon-supported noble metal catalyst with a higher loading amount as small as 0.5-6nm and evenly distribute, and improve the utilization rate of the noble metal.

2. The use of mild and environmentally friendly reducing agents to reduce noble metal ions avoids the adverse effects on the environment caused by the use of commonly used reducing agents.

3. Through the treatment of the surface carrier of activated carbon, the interaction between the metal and the carrier is strengthened, and the particle size growth during the use of the catalyst is avoided.

4. By changing the composition of the solvent in the dispersion system, the weaker hydrophilic carrier can be well infiltrated.

5. Using the method to prepare supported noble metal catalysts has simple process, short process, less time-consuming, high recovery rate, and greatly reduces the production cost of the catalyst.

6. The catalyst prepared by the method is used as a fuel cell catalyst, and its performance is better than that of a battery using the same type of commercial catalyst.

Description of drawings

Below by embodiment and in conjunction with accompanying drawing the present invention is described in detail, wherein:

Fig. 1 is the transmission electron micrograph of the carbon-supported platinum catalyst of the present invention containing 20wt% platinum;

Fig. 2 is the transmission electron micrograph of the carbon-supported platinum catalyst containing 40wt% platinum in the present invention;

Fig. 3 is the transmission electron micrograph of the present invention containing ruthenium content 10wt% carbon-loaded ruthenium catalyst;

Fig. 4 is a transmission electron microscope image of a carbon nanotube-supported platinum catalyst with a platinum content of 10 wt% in the present invention.

Detailed ways

Embodiment 1: 1 gram of chloroplatinic acid hexahydrate is dissolved in the mixed solvent that 100 milliliters of ethanol, 300 milliliters of ethylene glycol and 100 milliliters of water form, stir well, add 0.25mol/L NaOH aqueous solution 50 milliliters, Heated to 250°C under a protective atmosphere, kept for 30 minutes, added 3.4 grams of Black Pearls carbon dispersed in water, and after cooling down to room temperature, added a settling accelerator, stirred for 30 minutes, filtered, washed with water, and dried at 80°C for 6 hours to obtain 3.8 grams of carbon-supported platinum catalyst with a platinum content of 10%.

Example 2: Dissolve 1 gram of ruthenium trichloride trihydrate in a mixed solvent composed of 100 milliliters of ethanol, 300 milliliters of ethylene glycol and 100 milliliters of water, stir evenly, then add 50 milliliters of 0.25mol/L NaOH aqueous solution liter, then heated to 180°C in a protective atmosphere, kept for 30 minutes, added 3.4 grams of XC-72R carbon dispersed in water, after cooling down to room temperature, added a settling accelerator, stirred for 30 minutes, filtered, washed with water, and dried at 80°C After 6 hours, 3.7 g of a carbon-supported ruthenium catalyst containing 10% ruthenium was obtained.

Embodiment 3: 1 gram of rhodium trichloride trihydrate is dissolved in a mixed solvent of 250 milliliters of ethylene glycol and 250 milliliters of water, stir well, add 25 milliliters of 0.25mol/L NaOH aqueous solution, and then protect Heating to 120°C under a neutral atmosphere, keeping it for 30 minutes, adding 3.6 grams of coconut shell carbon dispersed in water, after cooling down to room temperature, adding a settling agent, stirring for 30 minutes, filtering, washing with water, and drying at 80°C for 6 hours to obtain rhodium-containing The amount is 3.9 grams of 10% carbon-supported rhodium catalyst.

Embodiment 4: 1 gram of palladium dichloride is dissolved in the mixed solvent that 100 milliliters of glycerol, 300 milliliters of ethylene glycol and 100 milliliters of water form, stir well, add 0.25mol/L NaOH aqueous solution 10 milliliters , heated to 200°C in a protective atmosphere, kept for 30 minutes, added 5.6 grams of almond charcoal dispersed in water, and after cooling down to room temperature, added a settling accelerator, stirred for 30 minutes, filtered, washed with water, and dried at 80°C for 6 hours to obtain 5.9 grams of carbon-supported palladium catalyst containing 10% palladium.

Embodiment 5: 1 gram of chloroiridic acid is dissolved in a mixed solvent of 100 milliliters of glycerol and 900 milliliters of water, stir well, add 20 milliliters of 1mol/L NaOH ethylene glycol solution, add 370 grams of ZSM-5 Molecular sieves, heated to 60°C in a protective atmosphere, kept under stirring for 10 hours, cooled to room temperature, filtered, washed with water, and dried at 120°C for 6 hours to obtain a ZSM-5 supported Ir catalyst 363.1 with an iridium content of 0.1%. gram.

Embodiment 6: 0.5 gram of osmium tetroxide is dissolved in the mixed solvent that 50 milliliters of glycerol and 450 milliliters of water form, stir well, add 20 milliliters of 1mol/L NaOH ethylene glycol solution, add the active carbon fiber of 7.1 grams, Heated to 80° C. under protective atmosphere, kept under stirring for 10 hours, cooled to room temperature, filtered, washed with water, and dried at 120° C. for 6 hours to obtain 7.2 grams of osmium catalyst supported on activated carbon fibers containing 0.1% osmium.

Embodiment 7: 1 gram of chloroauric acid is dissolved in a mixed solvent of 100 milliliters of tert-butyl alcohol and 400 milliliters of water, stir well, add 5 milliliters of 0.5mol/L NaOH aqueous solution, add 9.1 grams of titanium dioxide (anatase) , in a protective atmosphere, heated to 250°C for 30 minutes, then lowered to 120°C for 3 hours, after cooling down to room temperature, filtered, washed with water, and dried at 120°C for 6 hours to obtain 9.1 grams of titanium dioxide-supported gold catalyst with a gold content of 5%. .

Embodiment 8: In the silver nitrate aqueous solution of 20 milliliters 0.5mol/L, add the isooctyl alcohol of 5 milliliters, stir evenly, add 1 milliliter of 0.25mol/L NaOH aqueous solution, add the silicon dioxide of 12.4 grams, in protective atmosphere Heated to 250° C. for 15 minutes, then rapidly cooled to room temperature, filtered, washed with water, and dried at 120° C. for 6 hours to obtain 12.3 grams of silica-supported silver catalyst with a silver content of 8%.

Embodiment 9: In the copper nitrate aqueous solution of 50 milliliters 1mol/L, add the Virahol of 30 milliliters, stir well, add 2 milliliters of 0.25mol/L NaOH aqueous solution, add the magnesium oxide of 23.3 grams, under protective atmosphere, Heated to 250° C. for 30 minutes, then lowered to 120° C. for 3 hours, and then cooled to room temperature, filtered, washed with water, and dried at 120° C. for 6 hours to obtain 26.0 grams of magnesia-supported copper catalyst with a copper content of 12%.

Example 10: In 50 milliliters of 1mol/L nickel nitrate aqueous solution, add 20 milliliters of glycerol, stir evenly, add 2 milliliters of 0.25 mol/L NaOH aqueous solution, add 21.5 grams of γ-Al ₂ O ₃ , in Under a protective atmosphere, heat to 250°C for 30 minutes, then drop to 120°C for 3 hours, after cooling down to room temperature, filter, wash with water, and dry at 120°C for 6 hours to obtain an alumina-supported nickel catalyst 23.9 with a nickel content of 12%. gram.

Example 11: According to the preparation method of Example 1, 3.0 grams of Norit ROX 0.8 carbon was used as a carrier, and 2 grams of chloroplatinic acid hexahydrate was used as a raw material to prepare 3.7 grams of a carbon-supported platinum catalyst containing 20 wt% of platinum.

Embodiment 12: According to the preparation method of Example 1, 3.0 grams of almond charcoal are used as a carrier, and 2 grams of platinum metal are dissolved in aqua regia to obtain chloroplatinic acid as a raw material to obtain 4.9 grams of a platinum-containing 40wt% carbon-supported platinum catalyst.

Embodiment 13: according to the preparation method of example 1, use graphite carbon 2.0 grams as carrier, 3 grams of metal platinum is dissolved in aqua regia and make chloroplatinic acid as raw material, make 4.9 grams of platinum-containing 60wt% charcoal-supported platinum catalysts.

Embodiment 14: According to the preparation method of Example 1, 0.5 grams of petroleum colloid is used as a carrier, and 4.5 grams of metal platinum is dissolved in aqua regia to obtain chloroplatinic acid as a raw material, and 4.9 grams of platinum-containing 90% carbon-supported platinum catalysts are obtained. .

Example 15: According to the preparation method of Example 1, using 180 mg of carbon nanotubes as a carrier and 54 mg of chloroplatinic acid hexahydrate as a raw material, 195 mg of a platinum catalyst with a platinum content of 10 wt% was prepared on carbon nanotubes.

Claims (5)

1, a kind of solid supported noble metal catalyst, active constituent are any one of Ru, Rh, Pd, Os, Ir, Pt, Au, Ag, Cu or Ni, and carrier is active carbon, graphite charcoal, nano carbon tube, Al ₂O ₃, SiO ₂, molecular sieve, MgO or TiO ₂Any one, wherein the content of active constituent is 5-90%, it is characterized in that, the metal particle diameter of this catalyst is 0.5-6nm.

2, solid supported noble metal catalyst as claimed in claim 1 is characterized in that, the content of active constituent is 10-60%.

3, a kind of method for preparing the described solid supported noble metal catalyst of claim 1, its preparation process is as follows:

(1) hydroxide of active constituent, alkali metal or alkaline-earth metal or carbonate and carrier are scattered in respectively in the solvent, the concentration of its three kinds of solution is respectively:

Precious metal salt solution concentration is 0.1-100mg/ml;

The hydroxide of alkali metal or alkaline-earth metal or carbonate solution concentration are 0.1-10mol/L;

Carrier suspension concentration 0.1-1000g/L;

(2) with these three kinds of solution by 1: 0.01-1: the 0.5-3 volume ratio is mixed, and to make pH be 6-14;

(3) solution of heating steps (2) preparation keeps 60-250 ℃ of temperature, time 15-600 minute;

(4) adding concentration is that setting accelerator is made in the acid of 0.1-10mol/L, and making mixed solution system pH is 1-8, stirs 30 minutes, and filtration is washed till no Cl repeatedly with deionized water ^-, oven dry maintains the temperature at 40-200 ℃, retention time 30-1800 minute;

Described dispersant is C ₂-C ₈A kind of or mixed solution in monohydric alcohol, dihydroxylic alcohols, the trihydroxylic alcohol or mix the solvent of forming with water.

4, preparation method as claimed in claim 3 is characterized in that, carry out according to the following steps step (1) and (2):

Active constituent is dissolved in the dispersant;

Hydroxide or carbonate solution with alkali metal or alkaline-earth metal transfer to 6-14 with its pH, add carrier;

And then carry out step (3) and (4).

5, preparation method as claimed in claim 3 is characterized in that, described acid is nitric acid, sulfuric acid, hydrochloric acid, oxalic acid or acetic acid.

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