CN103657643B - Method for preparing nano palladium metal catalyst - Google Patents

Abstract

The invention relates to a method for preparing a nano palladium metal catalyst, which comprises the following steps: the method comprises the steps of functional grafting pretreatment of a carrier, dipping of a palladium salt solution, reduction to obtain nano metal particles, and finally, carrying out separation coating on the metal particles by using an embedding agent to obtain the final immobilized nano palladium metal catalyst. The invention is technically characterized in that the carrier is subjected to functional grafting and the nano metal catalyst is coated in a separating way, and the technical effects are that the grafting effect of the functional auxiliary agent is favorable for the formation and dispersion of nano palladium metal particles, and the embedding agent can enhance the stability of the catalyst and is favorable for the recovery of the catalyst in the use process of the palladium nano particle catalyst so as to be convenient for repeated use. The preparation method of the catalyst is simple and convenient, and the raw materials are cheap and easy to obtain, so that the catalyst is suitable for industrial production.

Description

A kind of method for preparing nanometer palladium metal catalyst

technical field

The present invention relates to a kind of method for preparing nanometer palladium metal catalyst, relate in particular to the method for preparing a kind of immobilized type nanometer palladium metal catalyst, which involves the addition of functional auxiliary agent which has coordination effect with metal, and functional auxiliary agent can be combined with The grafting effect of the carrier is beneficial to the formation and stability of the catalyst. At the same time, the embedding agent of nano-palladium metal is introduced, which can separate and cover the nano-palladium catalyst and prevent the aggregation and deactivation of the metal palladium particles during the reaction process.

Background technique

Nanoscale noble metal catalysts are gradually becoming a typical representative of high-efficiency catalysts and a hotspot in catalyst research. However, due to the large specific surface area of nanoparticles, it is very unstable and prone to agglomeration and deactivation. At the same time, in the catalytic reaction, due to various complex reaction conditions, the catalyst particles will also be agglomerated and deactivated with different degrees of loss. These problems severely limit the preparation and application of nanocatalysts, so it is particularly important to prepare stable (during reaction) nanocatalysts. Nanoparticles supported on solid supports are the most commonly used and most effective for preparing stable catalysts. Recently, people's research mainly focuses on nanoparticles immobilized on metal oxides. The main metals are silica, alumina, titania, zirconia and so on.

Nano-palladium metal catalysts have important application prospects in the fields of catalytic hydrogenation, oxidation, and CX coupling reactions. Copelin discloses a kind of Pd/SiO in European patent _EP0009802 Catalyst and anthraquinone method prepare the method for hydrogen peroxide, palladium catalyst is relatively stable in this process, probably because palladium catalyst generally all exists with the form of palladium oxide, effectively Catalyst deactivation is prevented. placed Pd nanoparticles in the core of block-copolymerized micelles of polyethylene oxide and polyvinylpyridine, and then supported the copolymer _{on Al2O3} . The catalyst has extremely high activity to the selective reduction of butynediol, and can be recycled and used many times. It can be seen that the catalyst is well protected in micelles (N.Semagina, et al Appl.Catal.A:Gen.2005 , 280, 141-147). Das et al. immobilized monodisperse Pd nanoparticles in MCM-41. The particles were reduced at room temperature, but they showed excellent stability. After the catalyst was sintered at 500°C, the nanoparticles only increased from 2.8nm to 3.4nm. The catalyst was used in the Suzuki reaction, and ICP test analysis showed that there was only 6ppb of Pd in the filtrate (DDDas, et al, J. Catal., 2007, 246, 60-65.33). The preparation methods of these nano-palladium catalysts can obtain highly active nano-metal catalysts, but most of them have complicated processes and are not conducive to large-scale production.

Contents of the invention

The purpose of the present invention is to provide a method for preparing nano-palladium metal catalysts supported by functionalized carriers in order to improve the deficiencies of the prior art.

The technical proposal of the present invention is: grafting the functional auxiliary agent and the carrier, and the auxiliary agent will coordinate with metal palladium, thereby facilitating the formation, dispersion and stability of transition metal particles. With the help of the functional auxiliary, the added metal palladium compound can be quickly captured by the carrier from the metal palladium compound solution and concentrated on the surface of the carrier. Subsequent addition of reducing agent sodium borohydride, hydrazine hydrate, or passing hydrogen gas at high temperature can reduce to obtain nanometer metal palladium particles. Finally, the metal palladium particles are separated and coated with an embedding agent, which is beneficial to the stability of the catalyst during the reaction and prevents the metal palladium particles from agglomerating and losing during the reaction.

The specific technical scheme of the present invention is: a kind of method for preparing nano palladium metal catalyst, it is characterized in that: carry out grafting reaction with carrier and functional auxiliary agent in organic solvent, then add palladium salt or the organic solution of palladium salt, make palladium The coordination reaction between the salt and the functional auxiliary agent is also captured by the carrier, and then the palladium salt is reduced to metal palladium nanoparticles by using a reducing agent, and then the embedding agent is added to carry out the separation coating reaction, and finally a stable immobilized type is obtained. nano-palladium metal catalyst.

Preferably, the carrier is silica, alumina or titania; wherein the specific surface of silica is 80m ² /g-850m ² /g; the specific surface of activated alumina is 50m ² /g-500m ² /g; The surface is 30m ² /g to 300m ² /g.

The basic chemical structural formula of the preferred above-mentioned functional auxiliary agent is:

in

Preferably, the grafting ratio of the functional auxiliary agent to the carrier is 0.1-1:1 by mass; the organic solvent for the grafting reaction of the functional auxiliary agent and the carrier is one of toluene, ethanol, methanol, tetrahydrofuran or dioxane. Use one of the solvents toluene, ethanol, methanol, tetrahydrofuran or dioxane to dissolve the additive, and then add the carrier. The amount of solvent added only needs to dissolve the additive. Preferably, the temperature of the grafting reaction is 25° C. to 80° C., and the time of the grafting reaction is 4 hours to 48 hours.

Preferably described palladium salt is a kind of in palladium chloride, palladium acetate or palladium nitrate; The concentration of the organic solution of palladium salt is 0.01g/mL～0.05g/mL; The used solvent of palladium salt organic solution is toluene, ethanol , methanol or dioxane.

Preferably, the mass ratio of the palladium salt to the total mass of the carrier and the functional aid in the coordination reaction is 0.005-0.05:1; the temperature of the coordination reaction is 25°C-80°C, and the reaction time is 3h-12h.

Preferably, the reducing agent is one of sodium borohydride, hydrazine hydrate or hydrogen. When the reducing agent is sodium borohydride or hydrazine hydrate, add the reducing agent directly to the reaction system, the molar ratio of reducing agent to palladium salt is 3-10:1, the reduction reaction temperature is 25°C-60°C, and the reduction reaction time is 5h ~16h; if hydrogen reduction is used, after the solid palladium-containing material is dried, it is reduced by passing hydrogen gas at 180°C to 300°C, and the reduction time is 2h to 6h.

Preferably, the embedding agent is one of tetraethyl orthosilicate, isopropanol aluminum acid or tetrabutyl titanate; the mass ratio of the embedding agent to the total mass of the carrier and the functional auxiliary agent is 0.05- 0.5:1; the temperature of the separation coating reaction is 25°C-80°C, and the reaction time is 5h-24h. Finally, filter and dry to obtain the supported nano-palladium catalyst.

Beneficial effect:

The used catalyst raw material is cheap and easy to obtain, the catalyst has high activity, good stability and is not easy to deactivate. The metal palladium particle size of the finally prepared catalyst is between 1nm and 10nm, which has the characteristics of high catalytic performance of the nano-catalyst, and is not easy to agglomerate under the reaction conditions. The catalyst is easy to recycle, and the metal component is not easy to lose, and has no pollution to the environment.

Detailed ways

Implementation case 1:

Under argon atmosphere, weigh 0.2g of functional additive A1 and dissolve in 4mL of toluene, stir for 30min, then add 0.8g of SiO ₂ (specific surface is 420m ² /g), stir at 80°C for 4h, then cool to room temperature , then add 1mL of Pd(OAc) ₂ toluene solution with a concentration of 0.02g/mL, stir at 80°C for 6h, filter, wash the filter cake with toluene, dry the filter cake in vacuum at room temperature, and reduce it under hydrogen atmosphere at 200°C for 3h, the obtained solid Add 4mL of toluene, then add 0.1g of tetraethyl orthosilicate, stir at 50°C for 10h, filter, wash the filter cake with toluene, and dry the filter cake in vacuum at 50°C for 20h to obtain the final catalyst C1.

Implementation case 2:

Under argon atmosphere, weigh 0.3g of functional additive A1 and dissolve in 4mL of toluene, stir for 30min, then add 0.7g of SiO ₂ (specific surface is 420m ² /g), stir at 80°C for 4h, then cool to room temperature , then add 0.5mL of Pd(OAc) ₂ toluene solution with a concentration of 0.02g/mL, stir at 50°C for 6h, filter, wash the filter cake with toluene, dry the filter cake in vacuum at room temperature, reduce it under hydrogen atmosphere at 200°C for 3h, and obtain the above Add 4 mL of toluene to the solid, then add 0.1 g of tetraethyl orthosilicate, stir at 50°C for 8 hours, filter, wash the filter cake with toluene, and dry the filter cake under vacuum at 50°C for 20 hours to obtain the final catalyst C2.

Implementation case 3:

Under an argon atmosphere, weigh 0.1g of functional aid A2 and dissolve it in 4mL of methanol, stir for 30min, then add 0.9g of treated SiO ₂ (specific surface is 420m ² /g), stir at 25°C for 48h, Add 0.5mL of Pd(OAc) ₂ methanol solution with a concentration of 0.01g/mL, stir at 25°C for 8h, filter, wash the filter cake with methanol, dry the filter cake under vacuum at room temperature, and reduce it under hydrogen for 6h at 180°C. Add 4 mL of methanol to the catalyst, then add 0.1 g of tetraethyl orthosilicate, stir at 25°C for 16 hours, filter, wash the filter cake with methanol, and dry it in vacuum at 50°C for 12 hours to obtain the final catalyst C3.

Implementation case 4:

Under an argon atmosphere, weigh 0.25g of functional additive A3 and dissolve in 4mL of toluene, stir for 30min, then add 0.75g of treated SiO ₂ (specific surface is 850m ² /g), stir at 80°C for 4h, Cool to room temperature, then add 0.2 mL of Pd(OAc) ₂ toluene solution with a concentration of 0.05 g/mL, stir at 80 °C for 3 h, filter, wash the filter cake with toluene, dry the filter cake in vacuum at room temperature, and reduce under hydrogen at 200 °C 4h, add 4mL toluene to the reduced product, then add 0.15g tetraethyl orthosilicate, stir at 50°C for another 10h, filter, wash the filter cake with toluene, and vacuum dry at 50°C for 12h to obtain the final catalyst C4.

Implementation case 5:

Under an argon atmosphere, weigh 0.3g of functional additive A4 and dissolve in 4mL of toluene, stir for 30min, then add 0.7g of treated SiO ₂ (specific surface is 80m ² /g), stir at 80°C for 16h, After cooling to room temperature, 1 mL of Pd(OAc) ₂ toluene solution with a concentration of 0.05 g/mL was added, and stirred at 25° C. for 12 h. Slowly add 45 mg (5 times the molar amount of Pd(OAc) ₂ ) 50% hydrazine hydrate solution, stir at 40°C for 10 h, filter, wash the filter cake with distilled water, dry the filter cake under vacuum at room temperature, add 4 mL of toluene to the solid obtained above, and then Add 0.1 g of tetraethyl orthosilicate, stir at 50°C for another 10 h, filter, wash the filter cake with toluene, and vacuum-dry the filter cake at 50°C to obtain the final catalyst C5.

Implementation case 6:

Under argon atmosphere, weigh 0.25g of functional additive A1 and dissolve in 4mL of toluene, stir for 30min, then add 0.75g of treated Al ₂ O ₃ (specific surface is 270m ² /g), stir at 80°C for 10h After cooling to room temperature, add 1 mL of Pd(OAc) ₂ toluene solution with a concentration of 0.02 g/mL, stir at 25°C for 8 h, filter, wash the filter cake with toluene, and dry it in vacuum. , reduced at 220°C for 3h, added 4mL to the reduced product, then added 0.5g of aluminum isopropoxide, stirred at 50°C for 14h, filtered, washed the filter cake with toluene, and vacuum dried the filter cake at 50°C to obtain the final catalyst C6.

Implementation case 7:

Under argon atmosphere, weigh 0.5g of functional additive A2 and dissolve in 6mL of tetrahydrofuran, stir for 30min, then add 0.5g of treated Al ₂ O ₃ (specific surface is 500m ² /g), stir at 25°C for 48h After that, add 0.02g of PdCl ₂ , sonicate at 45°C for 20min, stir at 45°C for 6h, slowly add 0.0128g (3 times the molar amount of PdCl ₂ ) NaBH ₄ , filter, react at 60°C for 5h, filter, and wash with distilled water The filter cake was vacuum-dried at room temperature. After drying, 5 mL of tetrahydrofuran was added, followed by 0.2 g of aluminum isopropoxide, reacted at 25°C for 24 hours, filtered, washed with distilled water, and vacuum-dried at 50°C to obtain the final catalyst C7.

Implementation case 8:

Under argon atmosphere, weigh 0.25g of functional additive A2 and dissolve in 6mL of dioxane, stir for 30min, then add 0.75g of treated TiO ₂ (specific surface is 82m ² /g), stir at 25°C After 20h, add 0.02g Pd(NO ₃ ) ₂ ·2H ₂ O to 2mL of 0.1mol/L nitric acid solution, stir at 25°C for 8h, filter, wash the filter cake with dioxane and water, and dry in vacuo. Add 4mL of dioxane to the solid obtained above, then add 0.0284g (10 times the molar weight of Pd(NO ₃ ) ₂ 2H ₂ O) NaBH ₄ , stir at 25°C for 16h, filter, and wash the filter cake with water , vacuum-dry, add 4mL of dioxane to the obtained solid, add 0.15g of tetrabutyl titanate, stir at 80°C for 5h, filter, wash the filter cake with dioxane, and vacuum-dry at 50°C to obtain the final Catalyst C8.

Implementation case 9:

Under argon atmosphere, weigh 0.1g of functional additive A3 and dissolve in 4mL of toluene, stir for 30min, then add 0.9g of treated Al ₂ O ₃ (specific surface is 50m ² /g), stir at 80°C for 8h After cooling to room temperature, add 0.5 mL of Pd(OAc) ₂ toluene solution with a concentration of 0.02 g/mL, stir at 25 °C for 10 h, filter, and vacuum-dry the filter cake at room temperature, reduce it under _H2 atmosphere at 300 °C for 2 h, and Add 4 mL of toluene to the reduced product, then add 0.2 g of aluminum isopropoxide, stir at 25 °C for 15 h, filter, wash the filter cake with toluene, and dry it in vacuum at 50 °C to obtain the final catalyst C9.

Implementation Case 10:

Under argon atmosphere, weigh 0.3g of functional additive A3 and dissolve in 4mL of ethanol, stir for 30min, then add 0.7g of treated TiO ₂ (specific surface is 30m ² /g), stir at 50°C for 16h, Cool to room temperature, then add 1 mL of Pd(OAc) ₂ ethanol solution with a concentration of 0.02 g/mL, stir at 25°C for 5 h, slowly add 45 mg (5 times the molar amount of Pd(OAc) ₂ ) 50% hydrazine hydrate solution, 50 Stir at ℃ for 10 h, filter, and dry the filter cake in vacuum at room temperature. Add 4 mL of ethanol to the solid obtained above, then add 0.05 g of tetrabutyl titanate, stir at 50 ° C for 10 h, filter, wash the filter cake with ethanol, and °C and dried under vacuum to obtain the final catalyst C10.

Implementation Case 11:

Under an argon atmosphere, weigh 0.25g of functional aid A4 and dissolve it in 4mL of methanol, stir for 30min, then add 0.75g of treated TiO ₂ (specific surface is 300m ² /g), stir at 25°C for 12h, Then add 1mL of Pd(OAc) ₂ methanol solution with a concentration of 0.02g/mL, stir at ₂₅ °C for 6h, filter, wash the filter cake with methanol, and dry the filter cake under vacuum at room temperature. After reducing for 2 hours, add 4 mL of methanol to the solid obtained above, then add 0.2 g of tetrabutyl titanate, stir at 80°C for another 5 hours, filter, wash the filter cake with methanol, and dry the filter cake under vacuum at room temperature to obtain the final catalyst C11 .

Implementation Case 12:

Under argon atmosphere, weigh 0.3g of functional aid A4 and dissolve in 4mL of methanol, stir for 30min, then add 0.7g of treated Al ₂ O ₃ (specific surface is 420m ² /g), stir at 25°C for 20h After that, add 0.02g Pd(NO ₃ ) ₂ ·2H ₂ O to 2mL of 0.1mol/L nitric acid solution, stir at 25°C for 10h, slowly add 38mg (Pd(NO ₃ ) ₂ ·°CH ₂ O molar amount of 5 times) 50% hydrazine hydrate solution, stirred at 50°C for 10h, filtered, washed the filter cake with methanol, dried in vacuum at room temperature, added 4mL of methanol to the above solid, then added 0.1g of aluminum isopropoxide, stirred at 50°C for 10h, filtered, The filter cake was washed with methanol, and the filter cake was vacuum-dried at 50°C to obtain the final catalyst C12.

Implementation Case 13:

Under an argon atmosphere, add 310 μL (3 mmol) of benzyl alcohol and 273 μL (3 mmol) of aniline to the reactor, add 5 mL of xylene, add a catalyst (the system contains 1.0 mol% Pd catalyst), and react at 160 ° C for 6 h.

catalyst Conversion rate selectivity C6 98% 91% C7 56% 84% C9 47% 77% C12 63% 73%

Implementation Case 14:

Add 1.02g (10mmol) of phenylacetylene into the reactor, add a hydrogen balloon (1atm), add a catalyst (the system contains 0.01mol% Pd catalyst) and add 10mL of ethanol.

catalyst Reaction temperature/℃ Reaction time/h Conversion rate selectivity C1 30 10 97% 96% C2 30 10 95% 94% C3 30 10 97% 98% C4 30 10 99% 98% C5 30 10 97% 94% C8 30 8 96% 95% C10 30 8 93% 98% C11 30 8 98% 95%

Recovery of catalyst C4:

Recycling times Conversion rate selectivity 1 99% 98% 2 98% 98% 3 98% 97% 4 96% 97% 5 97% 97%

Claims (8)

1. prepare the method for nano palladium metal catalyst for one kind, it is characterized in that: carrier and function additive are carried out graft reaction in organic solvent, add the organic solution of palladium salt or palladium salt again, while making palladium salt and function additive generation complexation reaction, also loaded body caught, re-use reducing agent and palladium salt is reduced into Metal Palladium nano particle, then add embedding medium, carry out separation coating reaction, finally obtain the nano palladium metal catalyst of stable solid-carrying type; The basic chemical structure formula of wherein said function additive is:

described embedding medium is the one in tetraethyl orthosilicate, aluminium isopropoxide or butyl titanate; The mass ratio of embedding medium and carrier and function additive gross mass is 0.05 ~ 0.5:1; The temperature separating coating reaction is 25 DEG C ~ 80 DEG C, and the reaction time is 5h ~ 24h.

2. method according to claim 1, is characterized in that described carrier is silica, aluminium oxide or titanium dioxide; Wherein silica specific surface is 80m ²/ g ~ 850m ²/ g; Activated alumina specific surface is 50m ²/ g ~ 500m ²/ g; Titanium dioxide specific surface is 30m ²/ g ~ 300m ²/ g.

3. method according to claim 1, is characterized in that the graft ratio of function additive and carrier is mass ratio 0.1 ~ 1:1; The organic solvent that function additive and carrier carry out the reaction of grafting is the one in toluene, ethanol, methyl alcohol, oxolane or dioxane.

4. method according to claim 1, it is characterized in that the temperature of graft reaction is 25 DEG C ~ 80 DEG C, the time of graft reaction is 4h ~ 48h.

5. method according to claim 1, is characterized in that described palladium salt is the one in palladium bichloride, acid chloride or palladium nitrate; The concentration of the organic solution of palladium salt is 0.01g/mL ~ 0.05g/mL; Palladium salt organic solution solvent used is the one in toluene, ethanol, methyl alcohol or dioxane.

6. method according to claim 1, is characterized in that palladium salt in complexation reaction is 0.005 ~ 0.05:1 with the mass ratio of carrier and function additive gross mass; The temperature of complexation reaction is 25 DEG C ~ 80 DEG C, and the reaction time is 3h ~ 12h.

7. method according to claim 1, is characterized in that described reducing agent is that sodium borohydride, hydrazine hydrate or hydrogen are wherein a kind of.

8. method according to claim 7, it is characterized in that reducing agent be sodium borohydride or hydrazine hydrate time, the mol ratio of reducing agent and palladium salt is 3 ~ 10:1, and reduction reaction temperature is 25 DEG C ~ 60 DEG C, and the reduction reaction time is 5h ~ 16h; When reducing agent is hydrogen, reduction reaction temperature is 180 DEG C ~ 300 DEG C, and the reduction reaction time is 2h ~ 6h.