阅读说明：本技术 一种碳载钯基合金催化剂、其制备方法及催化制备苯乙烯的应用 (Carbon-supported palladium-based alloy catalyst, preparation method thereof and application of catalyst in preparation of styrene ) 是由 梁海伟 王正树 于 2019-11-28 设计创作，主要内容包括：本发明提供了一种碳载钯基合金催化剂的制备方法,包括：S1)将硫掺杂介孔碳材料、钯盐与第一过渡金属盐在第一溶剂中混合,除去第一溶剂后得到混合物；S2)将所述混合物在还原气氛中煅烧,得到碳载钯基合金催化剂。与现有技术相比,本发明利用浸渍后还原煅烧技术制备碳载钯基合金催化剂,可一步将合金纳米颗粒负载在硫掺杂介孔碳材料上,同时通过金属与硫掺杂介孔碳材料上的杂环子硫形成金属-硫配位键,及载体中丰富的孔道限域作用,使合金颗粒比较均匀地分散在硫掺杂介孔碳材料表面,再者介孔碳材料中掺杂的硫原子会进一步调节合金中钯原子的电子结构,从而实现苯乙炔高选择性加氢制备苯乙烯,具有较高的催化活性。(The invention provides a preparation method of a carbon-supported palladium-based alloy catalyst, which comprises the following steps: s1) mixing the sulfur-doped mesoporous carbon material, the palladium salt and the first transition metal salt in a first solvent, and removing the first solvent to obtain a mixture; s2) calcining the mixture in a reducing atmosphere to obtain the carbon-supported palladium-based alloy catalyst. Compared with the prior art, the carbon-supported palladium-based alloy catalyst is prepared by using a reduction calcination technology after impregnation, alloy nanoparticles can be further supported on the sulfur-doped mesoporous carbon material, metal-sulfur coordination bonds are formed by metal and heterocyclic sulfur on the sulfur-doped mesoporous carbon material, and rich pore confinement effects are achieved in the carrier, so that the alloy particles are uniformly dispersed on the surface of the sulfur-doped mesoporous carbon material, and the electronic structure of palladium atoms in the alloy can be further adjusted by sulfur atoms doped in the mesoporous carbon material, so that the styrene is prepared by high-selectivity hydrogenation of phenylacetylene, and the catalyst has high catalytic activity.)

1. A preparation method of a carbon-supported palladium-based alloy catalyst is characterized by comprising the following steps:

s1) mixing the sulfur-doped mesoporous carbon material, the palladium salt and the first transition metal salt in a first solvent, and removing the first solvent to obtain a mixture;

s2) calcining the mixture in a reducing atmosphere to obtain the carbon-supported palladium-based alloy catalyst.

2. The method according to claim 1, wherein the sulfur element content in the sulfur-doped mesoporous carbon material is 14 wt% or more; the specific surface area of the sulfur-doped mesoporous carbon material is larger than or equal to 1200m²/g。

3. The method according to claim 1, wherein the sulfur-doped mesoporous carbon material is prepared by:

A1) mixing sulfur-containing organic micromolecules, a pore-forming agent and a second transition metal salt in a second solvent, and removing the second solvent to obtain powder;

A2) calcining the powder in a protective atmosphere to obtain a carbon nano material;

A3) and etching the carbon nano material in an alkali solution and an acid solution in sequence to obtain the sulfur-doped mesoporous carbon material.

4. The method of claim 3, wherein the sulfur-containing small organic molecule is selected from the group consisting of 2,2' -bithiophene; the pore-foaming agent is selected from silicon dioxide aerogel; the second transition metal salt is selected from cobalt nitrate; the mass ratio of the sulfur-containing organic micromolecules to the pore-foaming agent to the metal in the second transition metal salt is 10: (8-12): (0.5 to 1.5).

5. The preparation method according to claim 3, wherein the temperature of the calcination in the step A2) is 600-1000 ℃; the calcining time is 1-3 h; the temperature rise rate of the calcination is 4-6 ℃/min.

6. The preparation method according to claim 1, wherein the total mass of the palladium ions in the palladium salt and the transition metal ions in the first transition metal salt in the step S1) is 10-30% of the mass of the sulfur-doped mesoporous carbon; the molar ratio of palladium ions in the palladium salt to transition metal ions in the first transition metal salt is 1: 3-3: 1; the first transition metal salt is selected from one or more of cobalt nitrate, ferric nitrate, gallium nitrate, copper nitrate, cobalt chloride, nickel chloride, copper chloride and ferric chloride.

7. The method according to claim 1, wherein the reducing atmosphere in step S2) comprises hydrogen and a protective gas; the volume content of hydrogen in the reducing atmosphere is 3-10%; the calcining temperature in the step S2) is 400-600 ℃; the calcining time is 1-3 h; the temperature rise rate of the calcination is 4-6 ℃/min.

8. The carbon-supported palladium-based alloy catalyst prepared according to any one of claims 1 to 7, wherein the carbon-supported palladium-based alloy catalyst uses sulfur-doped mesoporous carbon as a carrier; the carrier is loaded with palladium-based alloy; the palladium-based alloy is formed from metallic palladium and a first transition metal.

9. Use of the palladium-on-carbon-based alloy catalyst prepared according to any one of claims 1 to 7 as a hydrogenation catalyst.

10. A method for preparing styrene, which is characterized by comprising the following steps:

mixing and dispersing the carbon-supported palladium-based alloy catalyst prepared according to any one of claims 1 to 7 and phenylacetylene in an organic solvent, introducing hydrogen, and reacting to obtain styrene.

Technical Field

The invention belongs to the technical field of selective hydrogenation catalysts, and particularly relates to a carbon-supported palladium-based alloy catalyst, a preparation method thereof and application of the catalyst in preparation of styrene.

Background

The selective hydrogenation of phenylacetylene to styrene is of great significance in the field of fine chemical engineering. In the production process of polystyrene, a small amount of phenylacetylene impurities mixed in a styrene raw material can cause the polystyrene product to discolor, degrade and release odor and the like, thereby affecting the quality of the product, and on the other hand, the phenylacetylene is easy to generate poisoning effect on a polymerization reaction catalyst until the catalyst is inactivated. Therefore, it is necessary to control the phenylacetylene impurity in the styrene raw material to ppm level, and the catalytic selective hydrogenation is an effective means for removing the phenylacetylene.

Currently, a highly optimized Pd-based catalyst is generally used for the phenylacetylene selective hydrogenation reaction, and has excellent activity and selectivity, but when the conversion rate of the phenylacetylene is high, the selectivity is sharply reduced. The indiscriminate desorption and hydrogenation energy barriers of olefins at Pd sites are believed to be the main cause of selectivity decline. Researchers dope a second transition metal, such as Ag, Au, Fe, Zn, Ga and the like, in Pd lattices, and the stability of olefin adsorption on the surface of the catalyst is weakened by an electronic effect generated by metal-metal interaction, so that the selectivity is improved, and the cost of the catalyst can be reduced; zhao et al report that S doped into the lattice of Pd also has a similar transition metal doping effect, thiol-modified ultrathin Pd nanosheets are used to catalyze 1-phenyl-1-propyne for hydrogenation to generate 1-phenyl-1-propene, the selectivity reaches 98.1% at 100% alkyne conversion rate, and DFT calculation shows that the electron transfer between Pd and S greatly improves the reaction energy barrier in the olefin semi-hydrogenation process, thereby improving the selectivity. However, in this method, the used additives are toxic when the surface of the metal particles is modified, and the synthesis method of the catalyst is complicated. There are also reports of introducing S species by carriers, but the introduction is often limited by too low S content and poor effect, and carriers with high S content are rarely reported.

Disclosure of Invention

In view of the above, the technical problem to be solved by the present invention is to provide a carbon-supported palladium-based alloy catalyst, a preparation method thereof, and an application of the catalyst in preparing styrene; the carbon-supported palladium-based alloy catalyst prepared by the method has high sulfur content, and can be used for preparing styrene by catalyzing phenylacetylene hydrogenation with high selectivity.

The invention provides a preparation method of a carbon-supported palladium-based alloy catalyst, which comprises the following steps:

s1) mixing the sulfur-doped mesoporous carbon material, the palladium salt and the first transition metal salt in a first solvent, and removing the first solvent to obtain a mixture;

s2) calcining the mixture in a reducing atmosphere to obtain the carbon-supported palladium-based alloy catalyst.

Preferably, the content of sulfur element in the sulfur-doped mesoporous carbon material is greater than or equal to 14 wt%; the specific surface area of the sulfur-doped mesoporous carbon material is larger than or equal to 1200m²/g。

Preferably, the sulfur-doped mesoporous carbon material is prepared by the following method:

A1) mixing sulfur-containing organic micromolecules, a pore-forming agent and a second transition metal salt in a second solvent, and removing the second solvent to obtain powder;

A2) calcining the powder in a protective atmosphere to obtain a carbon nano material;

A3) and etching the carbon nano material in an alkali solution and an acid solution in sequence to obtain the sulfur-doped mesoporous carbon material.

Preferably, the sulfur-containing organic small molecule is selected from 2,2' -bithiophene; the pore-foaming agent is selected from silicon dioxide aerogel; the second transition metal salt is selected from cobalt nitrate; the mass ratio of the sulfur-containing organic micromolecules to the pore-foaming agent to the metal in the second transition metal salt is 10: (8-12): (0.5 to 1.5).

Preferably, the calcining temperature in the step A2) is 600-1000 ℃; the calcining time is 1-3 h; the temperature rise rate of the calcination is 4-6 ℃/min.

Preferably, the total mass of the palladium ions in the palladium salt and the transition metal ions in the first transition metal salt in the step S1) is 10-30% of the mass of the sulfur-doped mesoporous carbon; the molar ratio of palladium ions in the palladium salt to transition metal ions in the first transition metal salt is 1: 3-3: 1; the first transition metal salt is selected from one or more of cobalt nitrate, ferric nitrate, gallium nitrate, copper nitrate, cobalt chloride, nickel chloride, copper chloride and ferric chloride.

Preferably, the reducing atmosphere in step S2) comprises hydrogen and a protective gas; the volume content of hydrogen in the reducing atmosphere is 3-10%; the calcining temperature in the step S2) is 400-600 ℃; the calcining time is 1-3 h; the temperature rise rate of the calcination is 4-6 ℃/min.

The invention also provides a carbon-supported palladium-based alloy catalyst prepared by the method, wherein the carbon-supported palladium-based alloy catalyst takes sulfur-doped mesoporous carbon as a carrier; the carrier is loaded with palladium-based alloy; the palladium-based alloy is formed from metallic palladium and a first transition metal.

The invention also provides application of the prepared carbon-supported palladium-based alloy catalyst as a hydrogenation catalyst.

The invention also provides a preparation method of styrene, which comprises the following steps:

and mixing and dispersing the prepared carbon-supported palladium-based alloy catalyst and phenylacetylene in an organic solvent, introducing hydrogen, and reacting to obtain styrene.

The invention provides a preparation method of a carbon-supported palladium-based alloy catalyst, which comprises the following steps: s1) mixing the sulfur-doped mesoporous carbon material, the palladium salt and the first transition metal salt in a first solvent, and removing the first solvent to obtain a mixture; s2) calcining the mixture in a reducing atmosphere to obtain the carbon-supported palladium-based alloy catalyst. Compared with the prior art, the carbon-supported palladium-based alloy catalyst is prepared by using a reduction calcination technology after impregnation, alloy nanoparticles can be further supported on the sulfur-doped mesoporous carbon material, metal-sulfur coordination bonds are formed by metal and heterocyclic sulfur on the sulfur-doped mesoporous carbon material, and rich pore confinement effects are realized in a carrier, so that the alloy particles are uniformly dispersed on the surface of the sulfur-doped mesoporous carbon material, the alloy particles are high in dispersity, uniform in size and high in sulfur content, any reducing agent which is not friendly to the environment is not needed, the preparation is simple and convenient, the catalyst is suitable for large-scale production, the electronic structure of palladium atoms in the alloy can be further adjusted by sulfur atoms doped in the mesoporous carbon material, and the styrene is prepared by high-selectivity hydrogenation of phenylacetylene and has high catalytic activity.

Drawings

FIG. 1 is a TEM image of a sulfur-doped mesoporous carbon material obtained in example 1 of the present invention;

FIG. 2 is an HAADF-STEM electron micrograph of a palladium-on-carbon-based alloy material obtained in example 2 of the present invention;

FIG. 3 is an EDS mapping chart of the carbon-supported palladium-based alloy material obtained in example 2 of the present invention;

FIG. 4 shows Pd obtained in example 3 of the present invention₂HAADF-STEM Electron micrograph of Co/meso _ S-C;

FIG. 5 shows Pd obtained in example 3 of the present invention₂EDS line scan of Co/meso _ S-C;

FIG. 6 shows Pd obtained in example 4 of the present invention₂HAADF-STEM Electron micrograph of Ni/meso _ S-C;

FIG. 7 shows Pd obtained in example 4 of the present invention₂EDS line scan of Ni/meso _ S-C;

FIG. 8 shows Pd obtained in example 5 of the present invention₃HAADF-STEM Electron micrograph of Cu/meso _ S-C;

FIG. 9 shows Pd obtained in example 5 of the present invention₃EDS line scan of Cu/meso _ S-C;

FIG. 10 shows Pd obtained in example 6 of the present invention₃HAADF-STEM Electron micrograph of Ga/meso _ S-C;

FIG. 11 shows Pd obtained in example 6 of the present invention₃EDS line scan of Ga/meso _ S-C;

FIG. 12 is an X-ray diffraction chart of Pd/meso-S-C obtained in comparative example 1 of the present invention;

FIG. 13 is a graph showing activity and selectivity data of Pd/meso _ S-C in the selective hydrogenation of phenylacetylene to styrene obtained in comparative example 1 of the present invention;

FIG. 14 is a TEM image of a commercial Pd-based alloy material loaded on a carbon material obtained in comparative examples 2 to 6 of the present invention;

FIG. 15 shows Pd as a palladium-on-carbon-based alloy material obtained in examples 2 to 5 of the present invention and comparative examples 2 to 6₃Data graphs of activity and selectivity of the preparation of styrene by selective hydrogenation of phenylacetylene catalyzed by Fe/meso _ S-C;

FIG. 16 is a data diagram of activity and selectivity of the carbon-supported palladium-based alloy material obtained in examples 2 to 14 of the present invention in the preparation of styrene by the selective hydrogenation of phenylacetylene;

fig. 17 is a cycle performance test chart of the carbon-supported palladium-based alloy material obtained in example 2 of the present invention in a reaction for preparing styrene through selective hydrogenation of phenylacetylene.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the 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 provides a preparation method of a carbon-supported palladium-based alloy catalyst, which comprises the following steps: s1) mixing the sulfur-doped mesoporous carbon material, the palladium salt and the first transition metal salt in a first solvent, and removing the first solvent to obtain a mixture; s2) calcining the mixture in a reducing atmosphere to obtain the carbon-supported palladium-based alloy catalyst.

In the present invention, the sources of all raw materials are not particularly limited, and the raw materials may be commercially available or self-made.

The content of sulfur element in the sulfur-doped mesoporous carbon material is preferably greater than or equal to 14 wt%; the specific surface area of the sulfur-doped mesoporous carbon material is preferably 1200m or more²(ii) in terms of/g. In the present invention, the sulfur-doped mesoporous carbon material is preferably prepared by the following steps: A1) mixing sulfur-containing organic micromolecules, a pore-forming agent and a second transition metal salt in a second solvent, and removing the second solvent to obtain powder; A2) calcining the powder in a protective atmosphere to obtain a carbon nano material; A3) and etching the carbon nano material in an alkali solution and an acid solution in sequence to obtain the sulfur-doped mesoporous carbon material.

Mixing sulfur-containing organic micromolecules, a pore-foaming agent and a second transition metal salt in a second solvent; wherein, the sulfur-containing organic small molecule is preferably 2,2' -bithiophene; the pore-foaming agent is selected from silicon dioxide aerogel; the second transition metal salt is preferably a cobalt salt, more preferably cobalt nitrate; the mass ratio of the sulfur-containing organic micromolecules to the pore-foaming agent to the metal in the second transition metal salt is preferably 10: (8-12): (0.5 to 1.5), more preferably 10: (9-11): (0.8 to 1.2), preferably 10: 10: 1; the second solvent is not particularly limited as long as it is an organic solvent well known to those skilled in the art, and tetrahydrofuran is preferable in the present invention; after mixing, the second solvent is removed, preferably by rotary evaporation in the present invention; the second solvent is removed and preferably milled to obtain a powder.

Calcining the powder in a protective atmosphere; the protective atmosphere is preferably nitrogen; the calcination temperature is preferably 600-1000 ℃, more preferably 700-900 ℃, and further preferably 800 ℃; the calcination time is preferably 1-3 h; the heating rate of the calcination is preferably 4-6 ℃/min, and more preferably 5 ℃/min; preferably cooling to room temperature after calcination to obtain the carbon nano material; the cooling rate is preferably 4-6 ℃/min, and more preferably 5 ℃/min.

Etching the carbon nano material in an alkali solution; the alkali solution is preferably an aqueous alkali metal hydroxide solution, more preferably an aqueous sodium hydroxide solution; the concentration of alkali in the alkali solution is preferably 1-3 mol/L, more preferably 2-3 mol/L, and further preferably 2 mol/L; the etching time is preferably 20-60 h, more preferably 36-54 h, and further preferably 48 h; etching the carbon nano material by using an alkali solution to form a mesopore; and after etching, centrifuging to remove the supernatant to obtain the etched carbon nano material.

In order to improve the porosity of the carbon material, the etched carbon nano material is preferably subjected to secondary etching in an alkaline solution; the alkali solution is preferably an aqueous alkali metal hydroxide solution, more preferably an aqueous sodium hydroxide solution; the concentration of alkali in the alkali solution is preferably 1-3 mol/L, more preferably 2-3 mol/L, and further preferably 2 mol/L; the etching time is preferably 20-40 h, more preferably 20-30 h, and further preferably 24-26 h; after etching, preferably centrifugally washing to neutrality, and drying to obtain a carbon nano material after secondary etching;

etching the carbon nano material subjected to the secondary etching in an acid solution; etching away the residual metal by acid; the acid solution is preferably a sulfuric acid solution; the concentration of the acid in the acid solution is preferably 0.3-1 mol/L, more preferably 0.5-0.8 mol/L, and still more preferably 0.5 mol/L; the etching time is preferably 6-10 h; the etching temperature is preferably 60-80 ℃; and after the etching is finished, preferably centrifugally washing to neutrality, and drying to obtain the sulfur-doped mesoporous carbon material.

Mixing a sulfur-doped mesoporous carbon material, a palladium salt and a first transition metal salt in a first solvent; the palladium salt is preferably an inorganic palladium salt, more preferably palladium chloride and/or palladium nitrate; the first transition metal salt is preferably one or more of inorganic cobalt salt, inorganic iron salt, inorganic gallium salt and inorganic copper salt, and more preferably one or more of cobalt nitrate, ferric nitrate, gallium nitrate, copper nitrate, cobalt chloride, nickel chloride, copper chloride and ferric chloride; the total mass of the palladium ions in the palladium salt and the transition metal ions in the first transition metal salt is 10-30%, more preferably 15-25% and still more preferably 20% of the mass of the sulfur-doped mesoporous carbon; the molar ratio of palladium ions in the palladium salt to transition metal ions in the first transition metal salt is preferably 1: 3-3: 1, more preferably 2: 3-3: 1, more preferably 3: 3-3: 1, more preferably 3: 2-3: 1, most preferably 3: 1; the first solvent is preferably water; the mass-volume ratio of the sulfur-doped mesoporous carbon material to water is preferably 5 mg: (3-10) ml, more preferably 5 mg: (3-7) ml, more preferably 5 mg: (3-5) ml, most preferably 5 mg: 4 ml; the mixing method is preferably ultrasonic, and then stirring is carried out to fully and uniformly mix the palladium salt, the first transition metal salt and the sulfur-doped mesoporous carbon material; the ultrasonic time is preferably 0.5-1.5 h, and more preferably 1 h; the stirring time is preferably 10-14 h, and more preferably 12 h.

After mixing, removing the first solvent to obtain a mixture; the method for removing the first solvent is preferably rotary evaporation.

Calcining the mixture in a reducing atmosphere; the reducing atmosphere preferably comprises hydrogen and a protective gas; the protective gas is preferably nitrogen and/or argon; the volume content of hydrogen in the reducing atmosphere is preferably 3-10%, more preferably 3-8%, still more preferably 4-6%, and most preferably 5%; the calcination temperature is preferably 400-600 ℃, more preferably 400-500 ℃, and further preferably 400 ℃; the calcination time is preferably 1-3 h, and more preferably 2 h; the heating rate of the calcination is preferably 4-6 ℃/min, and more preferably 5 ℃/min.

After calcination, the temperature is preferably naturally reduced to room temperature, and the carbon-supported palladium-based alloy catalyst is obtained.

The invention utilizes reduction calcination technology after dipping to prepare the carbon-supported palladium-based alloy catalyst, can further load alloy nano particles on the sulfur-doped mesoporous carbon material, simultaneously forms metal-sulfur coordination bonds through metal and heterocyclic sulfur on the sulfur-doped mesoporous carbon material, and has rich pore confinement effect in a carrier, so that the alloy particles are uniformly dispersed on the surface of the sulfur-doped mesoporous carbon material, the alloy particles have high dispersity, uniform size and high sulfur content, no reducing agent which is not friendly to the environment is needed, the preparation is simple and convenient, the catalyst is suitable for large-scale production, and the sulfur atoms doped in the mesoporous carbon material can further adjust the electronic structure of palladium atoms in the alloy, thereby realizing the preparation of styrene by phenylacetylene through high-selectivity hydrogenation, and the catalyst has higher catalytic activity.

The invention also provides a carbon-supported palladium-based alloy catalyst prepared by the method, wherein the carbon-supported palladium-based alloy catalyst takes sulfur-doped mesoporous carbon as a carrier; the carrier is loaded with palladium-based alloy; the palladium-based alloy is formed from metallic palladium and a first transition metal.

The sulfur-doped mesoporous carbon and the first transition metal are the same as described above, and are not described herein again.

The invention also provides an application of the carbon-supported palladium-based alloy catalyst prepared by the method as a hydrogenation catalyst.

The invention also provides a preparation method of styrene, which comprises the following steps: the carbon-supported palladium-based alloy catalyst prepared by the method is mixed with phenylacetylene and dispersed in an organic solvent, and hydrogen is introduced for reaction to obtain styrene.

The carbon-supported palladium-based alloy catalyst is the same as the above, and is not described again; the organic solvent is preferably an alcohol solvent, more preferably ethanol; the ratio of the carbon-supported palladium-based alloy catalyst to styrene is preferably 3 mg: (4-10) mmol, more preferably 3 mg: (4-8) mmol, more preferably 3 mg: (6-7) mmol, most preferably 3 mg: 6.83 mmol; the pressure of the reaction is preferably 4-8 bar, more preferably 5-7 bar, and still more preferably 6 bar; the reaction temperature is preferably 20-30 ℃, and more preferably 25 ℃; the reaction time is preferably 15-30 min, and more preferably 20-25 min.

In order to further illustrate the present invention, the following will describe in detail a carbon-supported palladium-based alloy catalyst, its preparation method and its application in the catalytic preparation of styrene, in conjunction with the following examples.

The reagents used in the following examples are all commercially available.