PdNi bimetallic supported catalyst as well as preparation method and application thereof

Abstract

The invention discloses a PdNi bimetallic supported catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalytic hydrogenation. According to the preparation method, an ordered porous organic polymer framework material is prepared through aldehyde amine condensation polymerization, a mesoporous nitrogen-doped carbon carrier with a stable structure is prepared through subsequent roasting, the PdNi bimetallic supported catalyst is prepared through active component impregnation adsorption and roasting reduction, the preparation process is simple, conditions are mild, the cost is low, control is easy, and the preparation method is suitable for industrial production. And industrial application and large-scale production are facilitated. According to the prepared catalyst, due to the fact that PdNi bimetallic superfine nano-particles are formed between Ni and Pd, obvious lattice mismatch can be prevented from occurring in the process that nitrogen is doped into a carbon skeleton, and damage to a carbon material is reduced. The electron-rich N atoms can also modify the properties of the carbon material, the electron density of the metal can be adjusted through coordination with the N atoms, the catalytic performance is improved, the Pd active atom density is diluted by Ni atoms, and the selectivity of alkene preparation through alkyne hydrogenation is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic hydrogenation, and particularly relates to a PdNi bimetallic supported catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Olefins are widely used in fine chemical fields such as the synthesis of polymers, flavors, and pharmaceuticals. In addition, in the process of catalytic cracking of heavy oil to produce olefins, there will be a small amount of alkyne impurities. The highly selective hydrogenation removal of trace alkyne impurities in olefins is a key step in purifying olefins. Palladium-based catalysts are widely used in the selective catalytic hydrogenation of alkynes to prepare olefins. Palladium nanoparticles have excellent catalytic activity for the hydrogenation reaction of alkynes, but have low selectivity for the product olefins. Therefore, it is necessary to modify the Pd active sites to inhibit the over-hydrogenation of alkynes to form alkanes. The traditional Lindlar catalyst (Pd / CaCO3) appropriately poisons the catalytic activity of the catalyst by introducing lead acetate or quinoline, thereby improving its alkyne hydrogenation selectivity; however, the toxicity of lead salts and the pollution of products by quinoline additives limit the further application of this catalyst and also accelerate the development of alternative catalysts. At present, the hydrogenation selectivity of Pd active sites can be regulated by regulating the geometric structure and electronic state of Pd active sites, including introducing a second metal to form alloy active sites and forming strong metal-support interactions.

[0003] There is literature proving that by forming bimetallic or core-shell catalysts with a second metal such as Ag, Zn, Cu, or Ru, the alkyne hydrogenation selectivity on Pd-based catalysts can be effectively improved (ACS Catal., 10(2020)8567 - 8581; J.Am.Chem.S℃., 144(2022)573 - 581). The catalytic performance of bimetallic catalysts is mainly due to the change in the metal electron density caused by charge transfer and orbital hybridization, which can effectively regulate the adsorption kinetics of alkynes / olefins. In addition, the strong metal-support interaction obtained with a carrier having special chemical and structural properties can also significantly affect the electronic structure of the metal and improve the selectivity of the alkyne hydrogenation reaction. Mesoporous carbon materials have a high specific surface area, pore volume, and stability, and are important carriers for heterogeneous catalysis. In particular, introducing heteroatoms into the carbon structure can significantly improve the chemical and electrical properties of carbon materials. However, how to effectively prepare heteroatom-doped mesoporous carbon materials with a high specific surface area and highly stably anchor Pd-based bimetallic ultrafine nanoparticles for the highly selective catalytic hydrogenation of alkynes to prepare olefins remains challenging. Summary of the Invention

[0004] In view of the above problems, on the one hand, the present invention provides a preparation method of a PdNi bimetallic supported catalyst, and the preparation method includes the following steps:

[0005] Melamine and terephthalaldehyde are added into an organic solvent according to a specific mass ratio, and stirred and reacted in a first inert atmosphere. The precipitate obtained from the stirring reaction is filtered, washed, and dried to obtain a porous organic polymer material;

[0006] The porous organic polymer material is heated according to a first heating program and calcined at a high temperature in a second inert atmosphere to obtain a mesoporous nitrogen-doped carbon material;

[0007] The mesoporous nitrogen-doped carbon material is ultrasonically and uniformly dispersed in an aqueous solution, and then chloroplatinic acid and nickel chloride with a certain mass ratio are added and stirred to dissolve. The mesoporous nitrogen-doped carbon material adsorbs and impregnates the mixed solution of chloroplatinic acid and nickel chloride obtained after dissolution, and then the solvent in the dissolution solution is removed by rotary evaporation to obtain a solid;

[0008] The solid is heated to 200 - 400 °C and then calcined in a reducing atmosphere to obtain a PdNi bimetal-supported catalyst.

[0009] Furthermore, the mass ratio of melamine, terephthalaldehyde and the organic solvent is 8 - 10:10 - 20:500 - 600.

[0010] Furthermore, the organic solvent is dimethyl sulfoxide, and the mass ratio of melamine, terephthalaldehyde and dimethyl sulfoxide is: 9.3:15:550;

[0011] The first inert atmosphere is nitrogen or argon.

[0012] Furthermore, the conditions of the stirring reaction are specifically that the stirring time is 72 h and the stirring temperature is 150 °C - 200 °C.

[0013] Furthermore, the first heating program is to heat at a heating rate of 5 °C / min from room temperature to 600 - 900 °C;

[0014] The high-temperature calcination is specifically calcined for 1 - 3 h in a second inert atmosphere, and the second inert atmosphere is argon.

[0015] Furthermore, the chloroplatinic acid, nickel chloride and the mesoporous nitrogen-doped carbon material are fed according to the mass ratio of Pd:Ni:m-NC = 0.001 - 0.03:0.001 - 0.01:1.

[0016] Furthermore, the reducing atmosphere is a mixed gas of hydrogen and argon with a volume ratio of 2:3, and the gas flow rate is 200 mL / min;

[0017] The calcination time in the reducing atmosphere is 2 - 5 hours, and the calcination temperature is 200 - 400 °C.

[0018] In a second aspect, the present invention also provides a PdNi bimetallic supported catalyst prepared by the described preparation method.

[0019] In a third aspect, the present invention also provides the application of the described PdNi bimetallic supported catalyst in the selective hydrogenation of alkynes to prepare alkenes.

[0020] Further, the application specifically is:

[0021] Add the PdNi bimetallic supported catalyst and the alkyne into a reactor containing an ethanol solvent, and charge normal-pressure hydrogen into the reactor, and carry out catalytic hydrogenation reaction at room temperature to synthesize alkenes;

[0022] Wherein, the input ratio of the PdNi bimetallic supported catalyst to the alkyne is to add 10 mg of the PdNi bimetallic supported catalyst per 1 mmol of the alkyne.

[0023] Advantages of the present invention:

[0024] The present invention first prepares an ordered porous organic polymer framework material by aldehyde-amine polycondensation, and then obtains a mesoporous nitrogen-doped carbon support with stable structure by calcination, and obtains a PdNi bimetallic supported catalyst PdNi / m-NC through impregnation and adsorption of active components and calcination reduction. The whole preparation process is simple, with mild conditions, low cost, easy to control, and is easy for industrial application and scale-up production.

[0025] For the PdNi / m-NC catalyst prepared by the present invention, PdNi bimetallic ultrafine nanoparticles are formed between Ni and Pd. The atomic radii of N atoms and C atoms are similar, which can prevent obvious lattice mismatch during the nitrogen doping into the carbon skeleton and reduce the damage to the carbon material. The electron-rich N atoms can also modify the properties of the carbon material. Coordination with N atoms can adjust the electron density of the metal and improve the catalytic performance. In addition, nitrogen-doped carbon can evenly disperse and stably anchor metal nanoparticles, improving the stability of the PdNi / m-NC catalyst. The Ni atoms dilute the density of Pd active atoms, which can effectively adjust the catalytic activity and further improve the selectivity of alkyne hydrogenation to prepare alkenes.

[0026] Other features and advantages of the present invention will be described in the subsequent specification, and part of them will be obvious from the specification or understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures pointed out in the specification and the drawings. Description of the Drawings

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 The flowchart of the preparation method of the PdNi bimetallic ultrafine nanoparticle-supported catalyst proposed in the embodiment of the present invention is shown;

[0029] Figure 2 The transmission electron microscopy image of the m-NC support prepared in Example 1 of the present invention is shown;

[0030] Figure 3 The transmission electron microscopy image of the Pd(0.3%)Ni(0.6%) / m-NC catalyst prepared in Example 1 of the present invention is shown. Detailed implementation manners

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] In view of the defects of the existing Pd-based catalysts for selective catalytic hydrogenation of alkynes with poor selectivity and stability, the present invention provides a PdNi bimetallic supported catalyst, its preparation method, and application, which can catalytically hydrogenate alkynes with higher selectivity and better catalyst stability to prepare olefins.

[0033] The preparation method of the PdNi bimetallic supported catalyst proposed by the present invention uses melamine and terephthalaldehyde as raw materials, heats in a dimethyl sulfoxide liquid phase system to carry out aldehyde-amine polycondensation to obtain a porous organic polymer, and calcines at high temperature in an inert atmosphere to obtain a mesoporous nitrogen-doped carbon material (m-NC); then, the m-NC is impregnated in an aqueous solution of chloroplatinic acid and nickel chloride prepared according to a certain mass ratio, fully adsorbed and impregnated, and after evaporating the solvent water, the solid powder is placed in a closed tube furnace and the temperature is programmed to rise to 200-400 °C, and then a normal pressure reducing atmosphere is introduced to reduce for 2-5 hours to obtain the PdNi / m-NC catalyst.

[0034] The specific process is as Figure 1 shown, and includes the following steps:

[0035] S1: Prepare the catalyst support mesoporous nitrogen-doped carbon material m-NC using melamine and terephthalaldehyde as raw materials. Specifically:

[0036] Add melamine, terephthalaldehyde, and dimethyl sulfoxide to the reactor in a mass ratio of 8 - 10:10 - 20:500 - 600, stir and react in the first inert atmosphere, filter, wash, and dry the precipitate obtained from the stirring reaction to obtain a porous organic polymer material. The first inert gas is argon or nitrogen; the stirring time is 72 h, and the stirring temperature is 150 - 200 °C.

[0037] In some exemplary embodiments of the present invention, the masses of melamine and terephthalaldehyde are 9.3 g and 15 g respectively, and the added mass of dimethyl sulfoxide is 550 g; it can also be that the masses of melamine and terephthalaldehyde are 8 g and 20 g respectively, and the added mass of dimethyl sulfoxide is 600 g, or the masses of melamine and terephthalaldehyde are 10 g and 10 g respectively, and the added mass of dimethyl sulfoxide is 600 g, etc.

[0038] Heat the porous organic polymer material according to the first heating program and perform high-temperature calcination for 1 - 3 h in the second inert atmosphere to obtain the m-NC support. Among them, the first heating program is to heat from room temperature to 600 - 900 °C at a rate of 5 °C / min.

[0039] S2: Use the mesoporous nitrogen-doped carbon material m-NC as the support, and add a compound containing metal Pd and a compound containing metal Ni to prepare the PdNi bimetal-loaded catalyst PdNi / m-NC. Specifically:

[0040] Disperse m-NC ultrasonically and uniformly in an aqueous solution, then add chloroplatinic acid and nickel chloride with a certain mass ratio and stir to dissolve. m-NC adsorbs and impregnates the mixed solution of chloroplatinic acid and nickel chloride obtained after dissolution, and then rotates and evaporates to remove the solvent in the solution to obtain a solid.

[0041] Place the solid in a tube furnace and heat it from room temperature to 200 - 400 °C in a reduction atmosphere with a flow rate of 200 mL / min and a V(H2):V(Ar) = 2:3 for 2 - 5 hours to obtain the PdNi / m-NC catalyst.

[0042] In step S2, the mass ratio of chloroplatinic acid, nickel chloride to the mesoporous nitrogen-doped carbon material m-NC in the PdNi / m-NC catalyst is Pd:Ni:m-NC = 0.001 - 0.03:0.001 - 0.01:1.

[0043] Another object of the present invention is to propose the application of PdNi bimetallic supported catalyst in the selective hydrogenation of alkynes to prepare olefins. Specifically, a certain mass of PdNi / m-NC catalyst and alkyne are added to a reactor, and normal-pressure hydrogen is filled into the reactor, and catalytic hydrogenation reaction is carried out at room temperature to synthesize olefins. In some embodiments of the present invention, the input ratio of the PdNi bimetallic supported catalyst to the alkyne is to add 10 mg of the PdNi bimetallic supported catalyst per 1 mmol of alkyne.

[0044] The preparation process and application effect of the PdNi / m-NC catalyst are exemplarily described below in combination with specific examples.

[0045] Example 1 A method for preparing a PdNi bimetallic supported catalyst is as follows:

[0046] 9.3 g of melamine and 15 g of terephthalaldehyde are added to 500 mL of dimethyl sulfoxide, and stirred and reacted at 180 °C for 72 h under a nitrogen atmosphere. The precipitate is obtained by filtration, washing and drying to obtain a porous organic polymer material; the porous organic polymer material is heated to 800 °C at a rate of 5 °C / min, and calcined at a high temperature for 2 h under an argon atmosphere to obtain an m-NC support. The transmission electron micrograph of the m-NC support is as Figure 2 shown.

[0047] 1 g of the m-NC support is ultrasonically and uniformly dispersed in an aqueous solution, and then chloroplatinic acid and nickel chloride with a certain mass ratio are added, dissolved and fully adsorbed and impregnated under stirring; the solvent is removed by rotary evaporation, and the obtained solid is then placed in a tubular furnace and heated to 300 °C at a programmed temperature, and calcined for 2 hours in a reducing atmosphere with V(H2):V(Ar)=2:3 and a flow rate of 200 mL / min to obtain a PdNi / m-NC catalyst, specifically a Pd(0.3%)Ni(0.6%) / m-NC catalyst. The transmission electron micrograph of the Pd(0.3%)Ni(0.6%) / m-NC catalyst is as Figure 3 shown.

[0048] In this example, the mass ratio of chloroplatinic acid, nickel chloride to the m-NC support in the PdNi / m-NC catalyst is Pd:Ni:m-NC = 0.001-0.03:0.001-0.01:1.

[0049] Example 2 Application of PdNi bimetallic supported catalyst in the selective hydrogenation of phenylacetylene to prepare olefins.

[0050] 10 mg of the Pd(0.3%)Ni(0.6%) / m-NC catalyst prepared in Example 1 and 1 mmol of phenylacetylene were added to a reactor containing 10 mL of ethanol solvent. The reactor was filled with hydrogen at atmospheric pressure, and the catalytic hydrogenation reaction was carried out at room temperature for 60 minutes. The conversion rate of phenylacetylene was 96%, and the selectivity of the product styrene was 98%.

[0051] In Examples 3 - 12, the PdNi / m-NC catalyst prepared in Example 1 was used to catalyze the selective hydrogenation of various alkynes to olefins. The specific method was as follows:

[0052] 1 mmol of alkyne, 10 mL of ethanol, and 10 mg of Pd(0.3%)Ni(0.6%) / m-NC catalyst were added to the reactor. Hydrogen was filled at atmospheric pressure, and magnetic stirring was carried out for 50 - 100 min. The catalytic hydrogenation reaction was carried out at room temperature, and the reaction situation was analyzed and detected by a gas chromatograph. The specific reaction results are shown in Table 1.

[0053] Table 1. Results of chemoselective hydrogenation of various alkynes catalyzed by PdNi / m-NC catalyst

[0054]

[0055]

[0056] As can be seen from Table 1, using the PdNi / m-NC catalyst prepared by the present invention, the conversion rate of various types of alkynes can reach more than 95%, and even up to 98.6%.

[0057] Example 13 The repeated application of a PdNi bimetal-supported catalyst, the specific method was as follows:

[0058] 10 mg of the Pd(0.3%)Ni(0.6%) / m-NC catalyst prepared in Example 1 and 1 mmol of phenylacetylene were added to a reactor containing 10 mL of ethanol solvent. The reactor was filled with hydrogen at atmospheric pressure, and the catalytic hydrogenation reaction was carried out at room temperature for 60 minutes; the catalyst was separated and recovered, and the conversion rate of phenylacetylene and the yield of styrene in the reaction solution were analyzed and detected; the recovered catalyst was reused in this reaction, and the catalyst could be reused at least 15 times, still maintaining a phenylacetylene conversion rate higher than 95% and a styrene selectivity higher than 96%.

[0059] As can be seen from the above examples, using the PdNi / m-NC catalyst prepared by the present invention, the selective catalytic hydrogenation reaction of alkynes can be carried out under the reaction conditions of atmospheric pressure hydrogen and room temperature; and the alkyne conversion rate is greater than 95%, and the olefin selectivity is greater than 96%. The selective catalytic hydrogenation reaction of alkynes is carried out in a batch reaction process, and the catalyst can be reused 15 times, and the activity is still maintained.

[0060] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of a PdNi bimetallic supported catalyst, characterized in that, It includes the following steps: Melamine and terephthalaldehyde are added into an organic solvent according to a specific mass ratio, and stirred and reacted in a first inert atmosphere. The precipitate obtained from the stirring reaction is filtered, washed, and dried to obtain a porous organic polymer material; The porous organic polymer material is heated according to a first heating program and calcined at a high temperature in a second inert atmosphere to obtain a mesoporous nitrogen-doped carbon material; The mesoporous nitrogen-doped carbon material is ultrasonically and uniformly dispersed in an aqueous solution, and then chloropalladic acid and nickel chloride with a certain mass ratio are added and stirred to dissolve. The mesoporous nitrogen-doped carbon material adsorbs and impregnates the mixed solution of chloropalladic acid and nickel chloride obtained after dissolution, and then the solvent in the dissolved solution is removed by rotary evaporation to obtain a solid; The solid is heated to 200 - 400 °C and then calcined in a reducing atmosphere to obtain a PdNi bimetal-loaded catalyst.

2. The preparation method of the PdNi bimetal-loaded catalyst according to claim 1, wherein The mass ratio of melamine, terephthalaldehyde and the organic solvent is 8 - 10:10 - 20:500 - 600.

3. The preparation method of the PdNi bimetal-loaded catalyst according to claim 1, wherein The organic solvent is dimethyl sulfoxide, and the mass ratio of melamine, terephthalaldehyde and dimethyl sulfoxide is: 9.3:15:550; The first inert atmosphere is nitrogen or argon.

4. The preparation method of the PdNi bimetal-loaded catalyst according to claim 1, wherein The conditions of the stirring reaction are specifically that the stirring time is 72 h and the stirring temperature is 150 °C - 200 °C.

5. The preparation method of the PdNi bimetal-loaded catalyst according to claim 1, wherein The first heating program is to heat at a heating rate of 5 °C / min, from room temperature to 600 - 900 °C; The high-temperature calcination is specifically to calcine for 1 - 3 h in the second inert atmosphere, and the second inert atmosphere is argon.

6. The preparation method of the PdNi bimetal-loaded catalyst according to claim 1, wherein The chloropalladic acid, nickel chloride and the mesoporous nitrogen-doped carbon material are fed according to the mass ratio of Pd:Ni:m-NC = 0.001 - 0.03:0.001 - 0.01:

1.

7. The preparation method of the PdNi bimetal-loaded catalyst according to claim 1, wherein The reducing atmosphere is a mixed gas of hydrogen and argon with a volume ratio of 2:3, and the gas flow rate is 200 mL / min; The calcination time in the reducing atmosphere is 2 - 5 hours, and the calcination temperature is 200 - 400 °C.

8. A PdNi bimetallic supported catalyst, characterized in that, It is prepared by the method described in any one of claims 1 - 7.

9. Use of a PdNi bimetallic supported catalyst in the selective hydrogenation of alkynes to prepare alkenes, characterized in that, The PdNi bimetal-loaded catalyst is prepared by the method described in any one of claims 1 - 7.

10. The application according to claim 9, characterized in that, The specific application is as follows: The PdNi bimetal-loaded catalyst and an alkyne are added into a reactor containing an ethanol solvent, and normal-pressure hydrogen is charged into the reactor, and a catalytic hydrogenation reaction is carried out at room temperature to synthesize an alkene; Among them, the input ratio of the PdNi bimetal supported catalyst to the alkyne is that 10 mg of the PdNi bimetal supported catalyst is added to every 1 mmol of the alkyne.

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