Hydrogenation catalyst and preparation method and application thereof

Abstract

The invention discloses a hydrogenation catalyst as well as a preparation method and application thereof. The preparation method of the catalyst comprises the following steps: mixing, calcining and pickling a carbon source, a heteroatom source, transition metal salt and a metal oxide template agent to obtain a porous carbon carrier containing transition metal single atoms; the preparation method comprises the following steps: impregnating a porous carbon carrier containing transition metal monatomic by adopting a first solution containing noble metal, adding a reducing agent, and drying to obtain the transition metal monatomic synergistic noble metal nanoparticle hydrogenation catalyst; or mixing, calcining and pickling the carbon source, the heteroatom source and the metal oxide template agent to obtain the porous carbon carrier; and impregnating the porous carbon carrier with a second solution containing noble metal, and then performing drying, low-temperature calcination and high-temperature calcination to obtain the noble metal monatomic synergistic noble metal nanoparticle hydrogenation catalyst. The hydrogenation catalyst provided by the invention has high catalytic activity, selectivity and long service life in catalysis of hydrogenation reaction of nitrogen-containing heterocyclic compounds.

Description

Technical Field

[0001] The invention relates to a hydrogenation catalyst and a preparation method and application thereof, belonging to the technical field of hydrogenation catalysts. Background Art

[0002] Among organic compounds, heterocyclic compounds account for about one-third of the total. Nitrogen-containing heterocyclic compounds are an important branch of heterocyclic compounds. Nitrogen-containing heterocyclic compounds usually have unique biological activity and low toxicity, and are often used as structural units of medicines and pesticides. Among them, piperidine compounds are mainly produced in industry by catalytic hydrogenation of pyridine. Due to the abundant source of pyridine, the process route for synthesizing piperidine by catalytic hydrogenation of pyridine is simple, suitable for large-scale production, and low cost.

[0003] Hydrogenation catalysts for nitrogen-containing heterocyclic compounds can be divided into homogeneous catalysts and heterogeneous catalysts. Although homogeneous metal catalysts have been studied earlier due to their high atomic utilization and large contact area, their disadvantages of being difficult to separate and recycle have made heterogeneous metal catalysts gradually popular. In recent years, the development of highly dispersed and single-atom catalysts has also made the atomic utilization of heterogeneous catalysts comparable to that of homogeneous catalysts.

[0004] In addition, an important link in the development of heterogeneous catalysts is the selection of carriers. Early epoxy resins and oxide carriers had weak interactions with active components, which often led to active site leaching problems, thereby reducing catalyst activity or even deactivating it. The discovery and application of carbon material carriers gradually solved these problems because they have many advantages, such as large specific surface area and porosity, and easy modification and modification.

[0005] CN113101924A discloses a supported metal catalyst with single atoms and particles, and its preparation method and application. The metal in the catalyst is uniformly supported on the carrier in the form of single atoms and nanoparticles coexisting; the metal is at least one of Ir, Ru, Rh, Pd, Co and Pt; the pore size of the carrier is 0.5-10nm, and the specific surface area is 200-1500m 2 / g; the carrier is any one of mesoporous carbon, mesoporous molecular sieve and activated carbon. The supported metal catalyst with single atom and particle synergistically exhibits high activity and selectivity in the hydrogenation reaction of quinoline, aromatic nitro, aromatic aldehyde or carbonyl compounds.

[0006] CN115138359A discloses a supported single-atom synergistic nanoparticle bimetallic catalyst and its preparation method. The catalyst is composed of a main active component, an auxiliary agent and a carrier; the carrier is silicon oxide, aluminum oxide, titanium oxide, nano silica gel or molecular sieve; the main active component is a noble metal Rh or Pd, which exists in the form of a single atom; and the auxiliary agent is one of Fe, Co, Ni, Ru, Mn, Cu metal or metal oxide, which exists in the form of particles with a particle size of 2 to 8 nm. In the catalyst, the single-atom noble metal is in close contact with the auxiliary agent particles and is evenly dispersed on the carrier surface, showing a high ethanol selectivity in the CO hydrogenation reaction.

[0007] CN103394348A discloses a method for preparing a catalyst for hydrogenation of pyridine compounds, comprising the following steps: pretreatment of activated carbon or alumina; preparation of a precursor solution; impregnation of the precursor solution with activated carbon or alumina; and obtaining a catalyst through drying, reduction and other steps. The catalyst uses activated carbon or activated alumina as a carrier, and noble metal ruthenium and auxiliary metal elements are loaded and highly dispersed on the carrier, and the particle size of ruthenium metal particles in the catalyst is 30nm to 80nm. The catalyst is suitable for catalytic hydrogenation of pyridine compounds to synthesize piperidine compounds, and the conversion rate of the catalytic hydrogenation reaction is high, which reduces the production cost of piperidine compounds.

[0008] However, in the catalysts of the prior art, single atoms lack metal-metal bonds, and during the hydrogenation process, the barrier for H2 to dissociate on single atoms is higher than that for H2 to dissociate on nanoparticles, thus limiting the hydrogenation activity of metal single atoms. Metal nanoparticles are prone to sintering under high-temperature reaction conditions, causing the particles to grow, reducing the number of exposed active sites, and thus reducing the activity and stability of the catalyst; and, generally speaking, only the atoms on the surface of the nanoparticles can participate in the catalytic reaction, while the atoms inside cannot fully play their role, resulting in low metal utilization. In addition, the interaction between the carbon material carrier and the metal active component still needs to be further improved.

[0009] Therefore, developing a new hydrogenation catalyst and a preparation method thereof has become one of the problems to be solved urgently in this field. Summary of the invention

[0010] In order to solve the above technical problems, the purpose of the present invention is to provide a hydrogenation catalyst and its preparation method and application. The present invention can prepare a metal single atom (transition metal single atom or noble metal single atom) synergistic metal nanoparticle (noble metal nanoparticle) supported hydrogenation catalyst with porous carbon containing heteroatoms as a carrier, which has high catalytic activity, selectivity and life in the hydrogenation reaction of nitrogen-containing heterocyclic compounds.

[0011] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a hydrogenation catalyst, which comprises the following steps:

[0012] Preparation of transition metal single atom synergistic noble metal nanoparticle hydrogenation catalysts:

[0013] S101. Preparation of porous carbon supports containing single transition metal atoms

[0014] The carbon source, the heteroatom source, the transition metal salt and the metal oxide template are uniformly mixed to obtain a first solid mixture; the first solid mixture is calcined at 700 to 800° C. for 1 to 3 hours in an inert gas atmosphere to obtain a porous carbon precursor containing a transition metal; the porous carbon precursor containing a transition metal is subjected to a first acid wash, a first washing and a first drying to obtain a porous carbon carrier containing a transition metal single atom;

[0015] S201. Preparation of hydrogenation catalyst

[0016] The porous carbon support containing transition metal single atoms is impregnated with a first solution containing a precious metal, and then a reducing agent is added and reacted for a period of time, followed by a second washing and a second drying to obtain a transition metal single atom synergistic precious metal nanoparticle hydrogenation catalyst, namely the hydrogenation catalyst;

[0017] Or include the following steps:

[0018] Preparation of noble metal single atom-assisted noble metal nanoparticle hydrogenation catalysts:

[0019] S102. Preparation of porous carbon support

[0020] The carbon source, the heteroatom source and the metal oxide template are uniformly mixed to obtain a second solid mixture; the second solid mixture is calcined at 700 to 800° C. for 1 to 3 hours in an inert gas atmosphere to obtain a porous carbon precursor; the porous carbon precursor is subjected to a second acid wash, a third wash and a third drying to obtain a porous carbon carrier;

[0021] S202. Preparation of hydrogenation catalyst

[0022] The porous carbon support is impregnated with a second solution containing a precious metal, and then dried for a fourth time, and then calcined at 200-300°C for 1-3 hours in an inert gas atmosphere, and then calcined at 450-550°C for 1-3 hours in an inert gas atmosphere to obtain a precious metal single atom synergistic precious metal nanoparticle hydrogenation catalyst, which is the hydrogenation catalyst.

[0023] According to a specific embodiment of the present invention, preferably, in step S101 and step 102, the carbon source includes one or more of fossil fuel carbon sources and biomass carbon sources, etc. More preferably, the fossil fuel carbon source includes one or more of asphalt and petroleum coke, etc.; the biomass carbon source includes one or more of wood, crop straw, and fruit shells, etc.

[0024] According to a specific embodiment of the present invention, preferably, in step S101 and step 102, the heteroatom source includes a nitrogen source and / or a phosphorus source. More preferably, the heteroatom source includes a nitrogen source and a phosphorus source, and the mass ratio of the nitrogen source to the phosphorus source is 1:2 to 2:1.

[0025] According to a specific embodiment of the present invention, preferably, in step S101 and step 102, the nitrogen source includes one or more of 1,10-phenanthroline, urea, melamine, and the like.

[0026] According to a specific embodiment of the present invention, preferably, in step S101 and step 102, the phosphorus source includes one or two of triphenylphosphine and phosphoric acid.

[0027] According to a specific embodiment of the present invention, preferably, in step S101, the mass ratio of the carbon source, the heteroatom source and the metal oxide template is 1:1:3 to 1:3:5, and the mass ratio of the transition metal salt to the heteroatom source is 1:2 to 2:1.

[0028] According to a specific embodiment of the present invention, preferably, in step S102, the mass ratio of the carbon source, the heteroatom source and the metal oxide template is 1:1:3 to 1:3:5.

[0029] According to a specific embodiment of the present invention, preferably, in step S101 and step 102, the metal oxide template includes magnesium oxide or the like.

[0030] According to a specific embodiment of the present invention, preferably, in step S101 and step 102, the first solid mixture and the second solid mixture further include an activator, and the mass ratio of the carbon source, the heteroatom source, the metal oxide template and the activator is 1:1:3:2 to 1:3:5:2. More preferably, the activator includes one or more of potassium hydroxide, zinc chloride and sodium hydroxide.

[0031] According to a specific embodiment of the present invention, preferably, in step S101, the transition metal in the transition metal salt includes one or more of Mn, Fe, Co, Ni and Cu, etc. More preferably, the transition metal salt includes one or more of nitrates, chlorides, sulfates, acetates and acetylacetonates of transition metals, etc. Specifically, the transition metal salt may include one or more of MnCl2, FeCl3, CoCl2, NiCl2 and CuCl2, etc.

[0032] According to a specific embodiment of the present invention, preferably, in step S101 and step 102, the first solid mixture and the second solid mixture can be obtained by solid phase mixing, or by liquid phase mixing and then drying. The specific method of the solid phase mixing can be conventionally selected by those skilled in the art, such as ball milling or mechanical stirring. The specific method of the liquid phase mixing can also be conventionally selected by those skilled in the art, such as stirring and mixing the carbon source, heteroatom source, transition metal salt, metal oxide template and selectively added activator in a suitable solvent (such as water and / or ethanol, etc.) and then drying to obtain the first solid mixture. The second solid mixture can also be mixed in the same way, which will not be repeated here. When liquid phase mixing is adopted, the drying temperature can be 60 to 80°C, and the time is until the solvent is evaporated.

[0033] According to a specific embodiment of the present invention, preferably, in step S101 and step 102, the inert gas atmosphere of the calcination may include, for example, argon, etc. The heating rate of the calcination may be 1-5°C / min.

[0034] According to a specific embodiment of the present invention, preferably, in step S101, the first pickling is carried out by sequentially using a 2-4 mol / L hydrochloric acid solution and a 4-6 mol / L sulfuric acid solution. The transition metal particles (and impurities) can be washed away by the first pickling, and the transition metal single atoms loaded on the carrier are retained. The ratio of the hydrochloric acid solution, the sulfuric acid solution and the porous carbon precursor containing transition metals can be conventionally adjusted by a person skilled in the art. The first washing can be rinsed several times with deionized water and ethanol. The temperature of the first drying can be 70-100°C, and the time can be 8-12 hours.

[0035] According to a specific embodiment of the present invention, preferably, in step S102, the second pickling is carried out by pickling with a 2-4 mol / L hydrochloric acid solution. The ratio of the hydrochloric acid solution to the porous carbon precursor can be conventionally adjusted by a person skilled in the art. The third washing can be rinsed several times with deionized water and ethanol. The temperature of the third drying can be 70-100°C and the time can be 8-12 hours.

[0036] In the present invention, a porous carbon carrier is prepared by a hard template method, and preferably combined with a chemical activation method, so that the porous carbon carrier containing transition metal single atoms and the porous carbon carrier of the present invention have abundant micropores and mesoporous structures and a high specific surface area, and a heteroatom source is introduced at the same time, so that the carrier contains N and / or P, and further preferably a nitrogen source and a phosphorus source are simultaneously doped, so that the carrier contains N and P at the same time. Therefore, the present invention obtains a micro-mesoporous high specific surface area carrier containing heteroatoms.

[0037] The present invention introduces a strongly coordinated heteroatom source, which can be used as a metal chelating agent. In the process of preparing a transition metal single atom and a noble metal nanoparticle hydrogenation catalyst, the introduction of the heteroatom source forms a chemical bond such as a coordination bond with the transition metal. This chemical bonding allows the transition metal to be firmly anchored on the carrier during the formation of the carrier, and improves the dispersity of the transition metal, while preventing the transition metal from agglomerating or falling off during use. In addition, the present invention carries out the loading of the transition metal and the preparation of the porous carbon carrier simultaneously, rather than the conventional method of first preparing the carrier and then loading the transition metal, which can improve the dispersity of the transition metal and is conducive to the formation of transition metal single atoms. In addition, after the carrier containing heteroatoms is prepared, the heteroatoms can also form chemical bonds with the noble metal in the subsequent loading process, further preventing the noble metal from excessively agglomerating. At the same time, after doping N and / or P, the surface properties of the porous carbon carrier change, generating more defects and active sites, thereby providing more adsorption centers for the subsequent loading of the noble metal, making it easier for the metal to be evenly dispersed on the carrier, forming highly dispersed metal single atoms and metal nanoparticles, increasing the number of active sites of the metal, and improving the catalytic activity. Moreover, the presence of N and / or P heteroatoms will form a certain steric hindrance on the surface of the porous carbon support, further limiting the agglomeration of the metal, and promoting the uniform distribution of the metal on the support in the form of nanoparticles or single atoms, further improving the dispersion and utilization of the metal. Therefore, the introduction of heteroatoms N and / or P of the present invention enhances the interaction between the supported metal and the support, and improves the dispersion of the metal, and preferably adopts N and P doping at the same time, which can further enhance this interaction and improve the dispersion of the metal, thereby improving the activity and life of the catalyst.

[0038] At the same time, due to the preparation steps of the porous carbon carrier of the present invention, a micro-mesoporous stepped pore structure and a higher specific surface area are constructed; the microporous structure can improve hydrogen adsorption, and the mesoporous structure can provide a reaction channel. The micro-mesoporous stepped pore structure of the present invention can provide more reaction sites and optimize the mass transfer process in the hydrogenation reaction of nitrogen-containing heterocyclic compounds; the high surface area can increase the loading amount and dispersion of the metal, and provide stronger adsorption for the reactants in the hydrogenation reaction of nitrogen-containing heterocyclic compounds, and is beneficial to the transmission and transfer of electrons in the catalytic process, thereby promoting the reaction.

[0039] Through the introduction of heteroatoms in the porous carbon carrier of the present invention, the simultaneous loading of transition metals and preparation of the porous carbon carrier, and the synergistic effect between the micro-mesoporous ladder channel structure and the higher specific surface area, the catalyst of the present invention is particularly suitable for catalyzing the hydrogenation of nitrogen-containing heterocyclic compounds, can achieve efficient catalytic hydrogenation of nitrogen-containing heterocyclic compounds, and make the catalyst have a longer life.

[0040] According to a specific embodiment of the present invention, preferably, in step S201 and step 202, the precious metals in the first precious metal-containing solution and the second precious metal-containing solution respectively include one or more of Pd, Pt, Ru and the like.

[0041] According to a specific embodiment of the present invention, preferably, in step S201, the first solution containing a noble metal includes a solution of a noble metal salt, and the mass of the noble metal in the noble metal salt is 1 to 10% of the mass of the porous carbon support containing transition metal single atoms. More preferably, the noble metal salt includes one or more of nitrates, chlorides, sulfates, acetates and acetylacetonates of noble metals. Specifically, the noble metal salt may include one or more of Na2PdCl4, H2PtCl6 and RuCl3. The concentration of the solution of the noble metal salt can be conventionally adjusted by a person skilled in the art, as long as the noble metal in the noble metal salt satisfies the above-mentioned proportional relationship with the porous carbon support containing transition metal single atoms, and the reaction proceeds smoothly. More preferably, the solvent in the solution of the noble metal salt includes water and / or ethanol. Further preferably, in order to improve the solubility of the noble metal salt, the solution of the noble metal salt may contain an appropriate concentration of hydrochloric acid. More preferably, the use of the first solution containing a noble metal to impregnate the porous carbon support containing transition metal single atoms is an equal volume impregnation. More preferably, the time for impregnating the porous carbon support containing transition metal single atoms with the first solution containing a precious metal is 1 to 3 hours. The temperature of the impregnation may be room temperature. Moreover, the impregnation may be carried out under stirring. More preferably, the reducing agent comprises one or more of sodium borohydride, potassium borohydride and hydrazine hydrate, and the mass ratio of the reducing agent to the precious metal salt in the first solution containing a precious metal is (4 to 6): 1, and the time for adding the reducing agent and reacting is 1 to 3 hours. The temperature of the reaction may be room temperature. In addition, the reaction may be carried out under stirring. The second washing may be rinsed several times with deionized water and ethanol. The temperature of the second drying may be 70 to 100°C, and the time may be 8 to 12 hours.

[0042] In the present invention, in the preparation step of the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, a porous carbon carrier containing transition metal single atoms is first prepared, wherein the transition metal single atoms can provide loading sites for the loading of noble metal nanoparticles, and can better anchor the noble metal on the carrier surface. Then, the present invention uses a first solution containing a noble metal to load the noble metal, and then reduces the loaded noble metal to nanoparticles by a chemical reduction method, thereby preparing a transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst. The inventor has found through research that by adopting a chemical reduction method, the loaded noble metal can be reduced to nanoparticles with a suitable particle size, while not destroying the transition metal single atom formed in the previous step, so that the catalyst contains a suitable content of transition metal single atoms and noble metal nanoparticles at the same time. If the calcination reduction method is adopted, then if a lower temperature is used for calcination, the noble metal nanoparticles cannot be effectively formed, and if a higher temperature is used for calcination, the transition metal single atoms formed in the previous step may aggregate to form transition metal nanoparticles, thereby making it difficult to prepare a transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst.

[0043] According to a specific embodiment of the present invention, preferably, in step S202, the second solution containing a precious metal includes a solution of a precious metal salt, and the mass of the precious metal in the precious metal salt is 0.5 to 10% of the mass of the porous carbon support. More preferably, the precious metal salt includes one or more of nitrates, chlorides, sulfates, acetates and acetylacetonates of precious metals. Specifically, the precious metal salt may include one or more of Na2PdCl4, H2PtCl6 and RuCl3. The concentration of the solution of the precious metal salt can be conventionally adjusted by a person skilled in the art, as long as the precious metal in the precious metal salt satisfies the above-mentioned proportional relationship with the porous carbon support and the reaction proceeds smoothly. More preferably, the solvent in the solution of the precious metal salt includes water and / or ethanol. Further preferably, in order to improve the solubility of the precious metal salt, the solution of the precious metal salt may contain an appropriate concentration of hydrochloric acid. More preferably, the second solution containing a precious metal is used to impregnate the porous carbon support as an equal volume impregnation. More preferably, the porous carbon carrier is impregnated with the second solution containing a precious metal for 1 to 3 hours. The impregnation temperature may be room temperature. Furthermore, the impregnation may be performed under stirring. The fourth drying temperature may be 60 to 80°C, and the time may be until the solvent evaporates. More preferably, the inert gas atmosphere of the calcination may include, for example, argon gas, etc. The heating rate of the calcination may be 1 to 5°C / min.

[0044] In the present invention, in the preparation step of the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, a second solution containing the noble metal is first used to load the noble metal on the porous carbon carrier; then a two-step calcination method is adopted, the first step of calcination is a low-temperature calcination at 200-300°C, in which noble metal single atoms are produced; the second step of calcination is a high-temperature calcination at 450-550°C, in which noble metal nanoparticles are produced, thereby preparing the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst.

[0045] Specifically, in the first calcination process, the present invention controls the calcination temperature and time within the above range, so that the migration ability of the noble metal atoms is weak and it is not easy to aggregate into particles, thereby forming noble metal single atoms. If the temperature and time of the first calcination are lower than the range of the present invention, the noble metal salt cannot be fully decomposed, and it is difficult to reduce the noble metal ions to single atoms, and it is not conducive to the formation of a strong chemical bond or physical adsorption between the noble metal single atoms and the carrier; if the temperature and time of the first calcination are higher than the range of the present invention, the noble metal single atoms will aggregate into nanoparticles, resulting in insufficient content of noble metal single atoms in the catalyst.

[0046] During the second step of calcination, the present invention controls the calcination temperature and time within the above ranges, so that adjacent noble metal atoms migrate and aggregate to form nanoparticles. If the temperature and time of the second step of calcination are lower than the range of the present invention, it is insufficient to effectively aggregate the noble metal atoms, so that the dispersion of the formed nanoparticles is poor. If the temperature and time of the second step of calcination are higher than the range of the present invention, the noble metal nanoparticles will grow excessively to form oversized particles, resulting in reduced catalytic activity, and the structure of the porous carbon carrier may be destroyed, thereby affecting the catalyst performance.

[0047] The present invention controls the temperature and time of the two-step calcination within the above range, so that the content of the noble metal single atom and the nanoparticle in the catalyst is appropriate, thereby having higher catalytic activity, selectivity and lifespan.

[0048] The second aspect of the present invention provides a hydrogenation catalyst, which is prepared by the above-mentioned method for preparing the hydrogenation catalyst.

[0049] According to a specific embodiment of the present invention, preferably, the hydrogenation catalyst is a transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, or a noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst;

[0050] The transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst comprises: a porous carbon carrier containing transition metal single atoms, and noble metal nanoparticles supported on the porous carbon carrier containing transition metal single atoms;

[0051] The noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst comprises: a porous carbon carrier, and noble metal single atoms and noble metal nanoparticles supported on the porous carbon carrier.

[0052] According to a specific embodiment of the present invention, preferably, in the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the porous carbon support containing the transition metal single atom includes micropores and mesopores, and the total pore volume of the porous carbon support containing the transition metal single atom is 1.7 to 2.2 cm 3 / g, micropore volume is 0.6~1.0cm 3 / g, mesopore volume is 0.9~1.4cm 3 / g, specific surface area is 1250~1500m 2 / g. It can be understood by those skilled in the art that pores with a pore size of less than 2 nm are micropores, and pores with a pore size of 2 to 50 nm are mesopores. More preferably, the ratio of the micropore volume to the mesopore volume of the porous carbon support containing transition metal single atoms is (0.4 to 0.9):1.

[0053] According to a specific embodiment of the present invention, in the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the porous carbon support containing the transition metal single atom contains heteroatoms, and the heteroatoms include N and / or P. Based on the mass of the porous carbon support containing the transition metal single atom as 100%, the heteroatom content in the hydrogenation catalyst is 3-5%; more preferably, the heteroatoms include N and P, and based on the mass of the porous carbon support containing the transition metal single atom as 100%, the N content in the hydrogenation catalyst is 1.0-3.5%, and the P content is 1.0-3.5%.

[0054] According to a specific embodiment of the present invention, preferably, in the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, based on the mass of the porous carbon support containing the transition metal single atom as 100%, the content of the transition metal single atom is 1.5-10%, and the content of the noble metal nanoparticles is 0.9-10%.

[0055] According to a specific embodiment of the present invention, preferably, in the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the average particle size of the noble metal nanoparticles is 2 to 5 nm.

[0056] According to a specific embodiment of the present invention, preferably, in the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the porous carbon support comprises micropores and mesopores, and the total pore volume of the porous carbon support is 1.7 to 2.2 cm 3 / g, micropore volume is 0.6~1.0cm 3 / g, mesopore volume is 0.9~1.4cm 3 / g, specific surface area is 1250~1500m 2 More preferably, the ratio of the micropore volume to the mesopore volume of the porous carbon carrier is (0.4-0.9):1.

[0057] According to a specific embodiment of the present invention, preferably, in the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the porous carbon support contains heteroatoms, the heteroatoms include N and / or P, and the heteroatom content in the hydrogenation catalyst is 3-5% based on the mass of the porous carbon support as 100%; more preferably, the heteroatoms include N and P, and the N content in the hydrogenation catalyst is 1.0-3.5%, and the P content is 1.0-3.5% based on the mass of the porous carbon support as 100%.

[0058] According to a specific embodiment of the present invention, preferably, in the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, based on the mass of the porous carbon carrier being 100%, the total content of the noble metal single atom and the noble metal nanoparticle is 0.4-10%.

[0059] According to a specific embodiment of the present invention, preferably, in the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the average particle size of the noble metal nanoparticles is 2 to 5 nm.

[0060] The hydrogenation catalyst of the present invention is a metal single atom (transition metal single atom or noble metal single atom) synergistic metal nanoparticle (noble metal nanoparticle) supported catalyst with porous carbon containing heteroatoms as a carrier. As described above, the introduction of heteroatoms in the porous carbon carrier of the present invention, the simultaneous loading of transition metals and the preparation of the porous carbon carrier, the synergistic effect between the micro-mesoporous stepped pore structure and the high specific surface area enhance the interaction between the metal and the carrier, and improve the dispersion of the metal. At the same time, in the prior art, metal single atoms lack metal-metal bonds, and the potential barrier for H2 to dissociate on single atoms is higher than that for H2 to dissociate on nanoparticles, thereby limiting the hydrogenation activity of single atoms; in the present invention, due to the synergistic effect between metal single atoms and nanoparticles, molecular hydrogen is easily dissociated on noble metal nanoparticles, and the activated hydrogen reaches the hydrogenation site-single atom through H overflow, combined with the high catalytic activity of single atoms, the two complement each other. At the same time, the electronic interaction between the single atom and the nanoparticle can change the electronic structure of the catalyst, so that it has a more suitable energy level distribution, especially for the hydrogenation of catalytic nitrogen-containing heterocyclic compounds, it is conducive to the adsorption and activation of reactants, reduces the energy barrier of the reaction, and improves the rate and efficiency of the catalytic reaction. Therefore, the synergistic effect between the metal single atom of the present invention and the nanoparticle can increase the active sites of the hydrogenation reaction of the nitrogen-containing heterocyclic compound and improve the activity of the catalyst. In addition, in the hydrogenation reaction of the catalytic nitrogen-containing heterocyclic compound, the specific coordination environment and electronic structure of the single atom can selectively adsorb and activate the reactant, and the nanoparticle can further transform the reaction intermediate, so the synergistic effect between the metal single atom of the present invention and the nanoparticle can improve the selectivity of the catalytic hydrogenation product of the nitrogen-containing heterocyclic compound. In addition, the strong interaction between the single atom and the carrier can also limit the movement and aggregation of the nanoparticles during use, thereby improving the stability of the nanoparticles, reducing the occurrence of sintering, and thus improving the overall stability of the catalyst. In addition, the present invention constructs a micro-mesoporous stepped pore structure and a high specific surface area. By controlling the micropore volume, mesopore volume and specific surface area within the above range, and by further controlling the ratio of the micropore volume to the mesopore volume within the above range, the catalyst of the present invention is particularly suitable for catalyzing the hydrogenation reaction of nitrogen-containing heterocyclic compounds, and can provide more sufficient reaction sites, optimized mass transfer processes and more active sites in the reaction, and promote electron transfer, thereby promoting the hydrogenation reaction of nitrogen-containing heterocyclic compounds and improving catalytic activity and selectivity. At least due to the above factors, the catalyst of the present invention can achieve efficient catalytic hydrogenation of nitrogen-containing heterocyclic compounds, and the catalyst has a higher life and selectivity.

[0061] The third aspect of the present invention provides the use of the above hydrogenation catalyst in catalyzing the hydrogenation reaction of nitrogen-containing heterocyclic compounds.

[0062] According to a specific embodiment of the present invention, preferably, the nitrogen-containing heterocyclic compound includes one or more of pyridine compounds and quinoline compounds.

[0063] According to a specific embodiment of the present invention, preferably, the conditions of the hydrogenation reaction include: the reaction temperature is room temperature (25±5°C), the reaction pressure is normal pressure (0.1013MPa) to 1MPa; based on 1mmol of the nitrogen-containing heterocyclic compound, the amount of the hydrogenation catalyst is 4 to 10mg. More preferably, the hydrogenation reaction is carried out in a solvent. Specifically, the solvent may include one or more of tetrahydrofuran, methanol, ethanol, toluene, acetonitrile and water. Based on 1mmol of the nitrogen-containing heterocyclic compound, the amount of the solvent may be 0.5 to 2mL. In addition, the hydrogenation reaction may be provided with a hydrogen source by a hydrogen balloon and a reaction pressure. Moreover, the hydrogenation reaction may be carried out under stirring conditions, and the time of the hydrogenation reaction may be conventionally adjusted by a person skilled in the art, for example, 10 to 20 hours.

[0064] The hydrogenation catalyst of the present invention is suitable for catalyzing the hydrogenation of nitrogen-containing heterocyclic compounds, especially in the reaction process of pyridine hydrogenation catalytic preparation of piperidine, conventional hydrogenation catalysts usually require relatively harsh catalyst conditions such as high temperature and high pressure, and the reaction activity under normal temperature and pressure conditions is low, the stability is poor, and it is difficult to ensure the complete conversion of pyridine compounds. However, due to the introduction of heteroatoms in the porous carbon carrier, the micro-mesoporous ladder channel structure and the high specific surface area, and the metal single atom (transition metal single atom or noble metal single atom) and the metal nanoparticles (noble metal nanoparticles), the catalyst of the present invention still has high catalytic activity, selectivity and life in the catalytic hydrogenation reaction of nitrogen-containing heterocyclic compounds, especially in the reaction of pyridine hydrogenation catalytic preparation of piperidine under normal temperature and pressure conditions.

[0065] The present invention achieves at least the following beneficial effects:

[0066] The present invention prepares a metal single atom (transition metal single atom or noble metal single atom) synergistic metal nanoparticle (noble metal nanoparticle) supported hydrogenation catalyst using porous carbon containing heteroatoms as a carrier. Due to the introduction of heteroatoms in the porous carbon carrier, the micro-mesoporous ladder channel structure and the high specific surface area, as well as the metal single atom (transition metal single atom or noble metal single atom) synergistic metal nanoparticle (noble metal nanoparticle) and other multi-faceted effects, the hydrogenation catalyst of the present invention has high catalytic activity, selectivity and life in the hydrogenation reaction of catalyzing nitrogen-containing heterocyclic compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1N2 adsorption-desorption curve and pore size distribution diagram of the porous carbon support containing transition metal single atoms prepared in Example 1.

[0068] Figure 2 This is the SEM image of the porous carbon support containing transition metal single atoms prepared in Example 1.

[0069] Figure 3 This is the TEM image of the hydrogenation catalyst prepared in Example 1.

[0070] Figure 4 This is the cycle performance diagram of the hydrogenation catalyst prepared in Example 1.

[0071] Figure 5 This is the HDDAF-STEM image of the hydrogenation catalyst prepared in Example 1.

[0072] Figure 6 This is the HDDAF-STEM image of the hydrogenation catalyst prepared in Example 5. DETAILED DESCRIPTION

[0073] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the present invention is now described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0074] It should be noted that, unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0075] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0076] It should be understood that the terms "comprises," "comprising," and / or "containing" when used herein specify the presence of stated features, integers, steps, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

[0077] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0078] Test method:

[0079] Total pore volume, micropore volume, mesopore volume, specific surface area and pore size distribution of porous carbon supports containing single transition metal atoms or porous carbon supports: The pore volume, specific surface area and pore size distribution were analyzed using a Micromeritics (ASAP 2020) fully automatic physical adsorption instrument. The specific surface area was calculated using the Brunauer-Emmett-Teller (BET) method. The total pore volume, micropore volume and mesopore volume were calculated using the Barrett-Joyner-Halenda (BJH) method. The pore size distribution was calculated using the nonlocal density functional theory (NLDFT) method for micropores and the Barrett-Joyner-Halenda method for mesopores based on the corresponding adsorption branches of the N2 isotherm.

[0080] Heteroatom content in the catalyst: The heteroatom content in the catalyst was determined using X-ray energy dispersive spectroscopy (EDS) at an accelerating voltage of 200 kV.

[0081] The content of transition metal single atoms and the content of noble metal nanoparticles in the transition metal single atom synergistically with noble metal nanoparticles hydrogenation catalyst: The metal content in the catalyst was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES, Optima 7300V).

[0082] Noble Metal Single Atom Synergistically with Noble Metal Nanoparticles The content of noble metal single atoms and the content of noble metal nanoparticles in the hydrogenation catalyst: The metal content in the catalyst was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES, Optima 7300V).

[0083] Average particle size of precious metal nanoparticles: The morphology and particle size distribution of the nanoparticles in the catalyst were measured using a scanning electron microscope (SEM, Hitachi, SU8010) and a transmission electron microscope (TEM, Tecnai G2, F20), and the average particle size was obtained by statistics.

[0084] Example 1

[0085] This embodiment provides a transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, and the preparation method thereof comprises the following steps:

[0086] S101. Preparation of porous carbon supports containing single transition metal atoms

[0087] Asphalt, heteroatom source, nickel chloride (NiCl2), magnesium oxide and potassium hydroxide are mixed in the solid phase by a mechanical stirrer to make them uniformly mixed, wherein the mass ratio of asphalt, heteroatom source, magnesium oxide and potassium hydroxide is 1:1:3:2, the mass ratio of nickel chloride and heteroatom source is 1:1, and the heteroatom source is urea and triphenylphosphine with a mass ratio of 1:1, and then the obtained mixture is put into a porcelain boat and placed in a tube furnace, and the temperature is increased to 800°C at a heating rate of 5°C / min in an argon atmosphere, and calcined at 800°C for 2 hours to obtain a porous carbon precursor containing transition metals; the porous carbon precursor containing transition metals is acid-washed with 3 mol / L hydrochloric acid solution and 5 mol / L sulfuric acid solution in turn, and the volume mass ratio of the hydrochloric acid solution and the sulfuric acid solution to the precursor is 10 mL:1 g, respectively; and then rinsed with deionized water and ethanol several times; and then placed in an oven at 80°C for 8 hours to obtain a porous carbon carrier containing Ni single atoms;

[0088] S201. Preparation of hydrogenation catalyst

[0089] A porous carbon support containing a single Ni atom is impregnated with an equal volume of a hydrochloric acid solution of sodium chloropalladate (Na2PdCl4), wherein the mass of palladium is 10% of the mass of the porous carbon support containing a single Ni atom. The hydrochloric acid solution of sodium chloropalladate is prepared by dissolving sodium chloropalladate in a 2 mol / L hydrochloric acid solution. The impregnation is carried out under stirring conditions for 2 hours at room temperature. Then, sodium borohydride is added and reacted at room temperature for 2 hours under stirring conditions. The amount of sodium borohydride used is 5 times the mass of sodium chloropalladate in the hydrochloric acid solution of sodium chloropalladate (Na2PdCl4). Thereafter, the catalyst is rinsed several times with deionized water and ethanol. The catalyst is then dried in an oven at 80°C for 8 hours to obtain a transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst.

[0090] After testing with the above method, Figure 1 N2 adsorption-desorption curve and pore size distribution diagram of the porous carbon support containing Ni single atoms prepared in this example, Figure 2 This is a SEM image of the porous carbon support containing Ni single atoms prepared in this example. Figure 3 This is a TEM image of the hydrogenation catalyst prepared in this example. The transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst of this example comprises: a porous carbon support containing a Ni single atom, and Pd nanoparticles supported on the porous carbon support containing a Ni single atom. Figure 5 The HDDAF-STEM image of the hydrogenation catalyst shows that the Ni single atom and the Pd nanoparticles exist synergistically. The porous carbon support containing the Ni single atom includes micropores and mesopores. The total pore volume of the porous carbon support containing the Ni single atom is 1.87 cm 3 / g, micropore volume is 0.62cm3 / g, and the mesopore volume is 1.25cm 3 / g, specific surface area is 1338m 2 / g. The porous carbon carrier containing Ni single atoms contains N and P heteroatoms. Taking the mass of the porous carbon carrier containing Ni single atoms as 100%, the N content in the hydrogenation catalyst is 1.9%, and the P content is 2.2%. Taking the mass of the porous carbon carrier containing Ni single atoms as 100%, the Ni single atom content in the hydrogenation catalyst is 4.5%, and the Pd nanoparticle content is 8.6%. The average particle size of the Pd nanoparticles is 3.7nm.

[0091] Example 2

[0092] This embodiment is basically the same as the embodiment 1, except that: in step S101, the heteroatom source is urea instead of triphenylphosphine; the mass ratio of asphalt, heteroatom source, magnesium oxide and potassium hydroxide is the same as that in the embodiment 1. The remaining steps are the same as those in the embodiment 1.

[0093] The above method was used to test that the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst includes: a porous carbon support containing a Ni single atom, and Pd nanoparticles supported on the porous carbon support containing a Ni single atom. The porous carbon support containing a Ni single atom includes micropores and mesopores, and the total pore volume of the porous carbon support containing a Ni single atom is 1.93 cm 3 / g, micropore volume is 0.87cm 3 / g, and the mesopore volume is 1.06cm 3 / g, specific surface area is 1352m 2 / g. The porous carbon support containing Ni single atoms contains N heteroatoms. Taking the mass of the porous carbon support containing Ni single atoms as 100%, the N content in the hydrogenation catalyst is 3.1%. Taking the mass of the porous carbon support containing Ni single atoms as 100%, the content of Ni single atoms in the hydrogenation catalyst is 4.2%, and the content of Pd nanoparticles is 8.2%. The average particle size of the Pd nanoparticles is 3.8nm.

[0094] Example 3

[0095] This embodiment is basically the same as the embodiment 1, except that: in step S101, the heteroatom source is triphenylphosphine instead of urea; the mass ratio of asphalt, heteroatom source, magnesium oxide and potassium hydroxide is the same as that in the embodiment 1. The remaining steps are the same as those in the embodiment 1.

[0096] The above method was used to test that the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst includes: a porous carbon support containing a Ni single atom, and Pd nanoparticles supported on the porous carbon support containing a Ni single atom. The porous carbon support containing a Ni single atom includes micropores and mesopores, and the total pore volume of the porous carbon support containing a Ni single atom is 1.74 cm 3 / g, micropore volume is 0.63cm 3 / g, and the mesopore volume is 1.11cm 3 / g, specific surface area is 1298m 2 / g. The porous carbon carrier containing Ni single atoms contains P heteroatoms. Taking the mass of the porous carbon carrier containing Ni single atoms as 100%, the P content in the hydrogenation catalyst is 4.1%. Taking the mass of the porous carbon carrier containing Ni single atoms as 100%, the content of Ni single atoms in the hydrogenation catalyst is 4.5%, and the content of Pd nanoparticles is 8.1%. The average particle size of the Pd nanoparticles is 4.0nm.

[0097] Example 4

[0098] This embodiment is basically the same as the embodiment 1, except that in step S201, cobalt chloride (CoCl2) is used to replace nickel chloride (NiCl2), and the amount used remains unchanged. The remaining steps are the same as the embodiment 1.

[0099] The above method was used to test that the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst includes: a porous carbon support containing a Co single atom, and Pd nanoparticles supported on the porous carbon support containing a Co single atom. The porous carbon support containing a Co single atom includes micropores and mesopores, and the total pore volume of the porous carbon support containing a Co single atom is 1.91 cm 3 / g, micropore volume is 0.81cm 3 / g, and the mesopore volume is 1.10cm 3 / g, specific surface area is 1377m 2 / g. The porous carbon carrier containing Co single atoms contains N and P heteroatoms. Taking the mass of the porous carbon carrier containing Co single atoms as 100%, the N content in the hydrogenation catalyst is 2.0%, and the P content is 2.2%. Taking the mass of the porous carbon carrier containing Co single atoms as 100%, the content of Co single atoms in the hydrogenation catalyst is 4.5%, and the content of Pd nanoparticles is 8.0%. The average particle size of the Pd nanoparticles is 3.9nm.

[0100] Example 5

[0101] This embodiment provides a noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, and the preparation method thereof comprises the following steps:

[0102] S102. Preparation of porous carbon support

[0103] Asphalt, heteroatom source, magnesium oxide and potassium hydroxide are mixed in a solid phase with a mechanical stirrer in a mass ratio of 1:1:3:2 to make them uniformly mixed, wherein the heteroatom source is urea and triphenylphosphine in a mass ratio of 1:1, and then the obtained mixture is placed in a porcelain boat and placed in a tube furnace, and heated to 800°C at a heating rate of 5°C / min in an argon atmosphere, and calcined at 800°C for 2 hours to obtain a porous carbon precursor; the porous carbon precursor is pickled with a 3 mol / L hydrochloric acid solution, and the volume mass ratio of the hydrochloric acid solution to the porous carbon precursor is 10 mL:1 g; then rinsed with deionized water and ethanol several times; and then placed in an oven at 80°C for 8 hours to obtain a porous carbon carrier;

[0104] S202. Preparation of hydrogenation catalyst

[0105] A porous carbon support is impregnated with an equal volume of a hydrochloric acid solution of sodium chloropalladate (Na2PdCl4), wherein the mass of palladium is 5% of the mass of the porous carbon support. The hydrochloric acid solution of sodium chloropalladate is prepared by dissolving sodium chloropalladate in a 2 mol / L hydrochloric acid solution. The impregnation is carried out under stirring conditions for 2 hours at room temperature. A rotary evaporator is then used to evaporate the solvent at 60°C. The mixture is then placed in a porcelain boat and placed in a tubular furnace. The mixture is heated to 300°C at a heating rate of 5°C / min in an argon atmosphere, calcined at 300°C for 2 hours, and then heated to 550°C at a heating rate of 5°C / min in an argon atmosphere, calcined at 550°C for 2 hours, to obtain a noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst.

[0106] Through testing by the above method, the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst includes: a porous carbon support, and Pd single atoms and Pd nanoparticles supported on the porous carbon support. Figure 6 The HDDAF-STEM image of the hydrogenation catalyst shows that Pd single atoms and Pd nanoparticles exist synergistically. The porous carbon support includes micropores and mesopores, and the total pore volume of the porous carbon support is 2.02 cm 3 / g, micropore volume is 0.92cm 3 / g, and the mesopore volume is 1.09cm 3 / g, specific surface area is 1493m 2 / g. The porous carbon carrier contains N and P heteroatoms. Based on the mass of the porous carbon carrier being 100%, the N content in the hydrogenation catalyst is 2.7%, and the P content is 2.1%. Based on the mass of the porous carbon carrier being 100%, the Pd metal (including single atoms and nanoparticles) content in the hydrogenation catalyst is 4.3%. The average particle size of the Pd nanoparticles is 2.9 nm.

[0107] Example 6

[0108] This embodiment is substantially the same as Embodiment 5, except that: in step S102, the heteroatom source is melamine and phosphoric acid in a mass ratio of 1:2; the mass ratio of asphalt, heteroatom source, magnesium oxide and potassium hydroxide is the same as that in Embodiment 5. The remaining steps are the same as those in Embodiment 5.

[0109] The above method was used to test that the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst includes: a porous carbon support, and Pd single atoms and Pd nanoparticles supported on the porous carbon support. The porous carbon support includes micropores and mesopores, and the total pore volume of the porous carbon support is 1.73 cm 3 / g, micropore volume is 0.81cm 3 / g, and the mesopore volume is 0.92cm 3 / g, specific surface area is 1356m 2 / g. The porous carbon carrier contains N and P heteroatoms. Based on the mass of the porous carbon carrier being 100%, the N content in the hydrogenation catalyst is 2.1%, and the P content is 2.0%. Based on the mass of the porous carbon carrier being 100%, the Pd metal (including single atoms and nanoparticles) content in the hydrogenation catalyst is 4.3%. The average particle size of the Pd nanoparticles is 3.1 nm.

[0110] Example 7

[0111] This embodiment is substantially the same as Embodiment 5, except that: in step S102, the heteroatom source is melamine and phosphoric acid in a mass ratio of 2:1; the mass ratio of asphalt, heteroatom source, magnesium oxide and potassium hydroxide is the same as that in Embodiment 5. The remaining steps are the same as those in Embodiment 5.

[0112] The above method was used to test that the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst includes: a porous carbon support, and Pd single atoms and Pd nanoparticles supported on the porous carbon support. The porous carbon support includes micropores and mesopores, and the total pore volume of the porous carbon support is 2.03 cm 3 / g, micropore volume is 0.71cm 3 / g, and the mesopore volume is 1.32cm 3 / g, specific surface area is 1273m 2 / g. The porous carbon carrier contains N and P heteroatoms. Based on the mass of the porous carbon carrier being 100%, the N content in the hydrogenation catalyst is 3.1%, and the P content is 1.1%. Based on the mass of the porous carbon carrier being 100%, the Pd metal (including single atoms and nanoparticles) content in the hydrogenation catalyst is 4.2%. The average particle size of the Pd nanoparticles is 2.8 nm.

[0113] Example 8

[0114] This embodiment is substantially the same as Embodiment 5, except that: in step S202, a hydrochloric acid solution of sodium chloropalladate (Na2PdCl4) and ruthenium trichloride (RuCl3) is used to impregnate the porous carbon support in equal volumes, wherein the mass of palladium is 2.5% of the mass of the porous carbon support, and the mass of ruthenium is 2.5% of the mass of the porous carbon support, and the solution is prepared by dissolving sodium chloropalladate and ruthenium trichloride in a 2 mol / L hydrochloric acid solution, and the impregnation is carried out under stirring, the impregnation time is 2 hours, and the impregnation temperature is room temperature. The remaining steps are the same as in Embodiment 5.

[0115] The above method was used to test that the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst includes: a porous carbon support, and Pd single atoms, Ru single atoms, Pd nanoparticles and Ru nanoparticles supported on the porous carbon support. The porous carbon support includes micropores and mesopores, and the total pore volume of the porous carbon support is 2.00 cm 3 / g, micropore volume is 0.89cm 3 / g, and the mesopore volume is 1.11cm 3 / g, specific surface area is 1432m 2 / g. The porous carbon carrier contains N and P heteroatoms. Based on the mass of the porous carbon carrier being 100%, the N content in the hydrogenation catalyst is 2.7%, and the P content is 2.0%. Based on the mass of the porous carbon carrier being 100%, the Pd metal (including single atoms and nanoparticles) content in the hydrogenation catalyst is 2.1%, and the Ru metal (including single atoms and nanoparticles) content is 2.0%. The average particle size of the Pd nanoparticles and the Ru nanoparticles is 2.1 nm.

[0116] Comparative Example 1

[0117] This comparative example is substantially the same as Example 1, except that: in step S101, magnesium oxide is not used, and asphalt, heteroatom source, nickel chloride and potassium hydroxide are solid-phase mixed by a mechanical stirrer at a mass ratio of 1:1:1:2. The remaining steps are the same as Example 1.

[0118] The porous carbon support containing Ni atoms prepared in this comparative example includes micropores and mesopores, and the total pore volume of the porous carbon support containing Ni atoms is 0.97 cm 3 / g, micropore volume is 0.80cm 3 / g, and the mesopore volume is 0.17cm 3 / g, specific surface area is 2250m 2 The porous carbon carrier containing Ni single atoms contains N and P heteroatoms. Based on the mass of the porous carbon carrier containing Ni single atoms as 100%, the N content in the hydrogenation catalyst is 2.3% and the P content is 1.9%.

[0119] Comparative Example 2

[0120] This comparative example is substantially the same as Example 1, except that: in step S101, potassium hydroxide is not used, and asphalt, heteroatom source, nickel chloride and magnesium oxide are solid-phase mixed in a mass ratio of 1:1:1:3 using a mechanical stirrer. The remaining steps are the same as Example 1.

[0121] The porous carbon support containing Ni single atoms prepared in this comparative example includes micropores and mesopores, and the total pore volume of the porous carbon support containing Ni single atoms is 1.96 cm 3 / g, micropore volume is 0.27cm 3 / g, and the mesopore volume is 1.69 cm 3 / g, specific surface area is 678m 2 The porous carbon support containing a single Ni atom contains N and P heteroatoms. Taking the mass of the porous carbon support containing a single Ni atom as 100%, the N content in the hydrogenation catalyst is 2.3% and the P content is 2.1%.

[0122] By comparing Comparative Examples 1 and 2 with Example 1, it can be seen that the embodiment of the present invention adopts a chemical activation method combined with a hard template method to prepare a porous carbon carrier, so that the porous carbon carrier containing a single transition metal atom has a rich micropore and mesoporous structure and a high specific surface area. Comparative Examples 1 and 2 omit magnesium oxide and potassium hydroxide, respectively, so that the micropore volume and / or mesopore volume and / or specific surface area of ​​the porous carbon carrier containing a single transition metal atom decrease.

[0123] Comparative Example 3

[0124] This comparative example is substantially the same as Example 1, except that: in step S101, no heteroatom source is used, and asphalt, nickel chloride, magnesium oxide and potassium hydroxide are solid-phase mixed in a mass ratio of 1:1:3:2 using a mechanical stirrer. The remaining steps are the same as Example 1.

[0125] The porous carbon support containing Ni single atoms prepared in this comparative example includes micropores and mesopores, and the total pore volume of the porous carbon support containing Ni single atoms is 2.01 cm 3 / g, micropore volume is 0.68cm 3 / g, and the mesopore volume is 1.42cm 3 / g, specific surface area is 1756m 2 / g.

[0126] Comparative Example 4

[0127] This comparative example is substantially the same as Example 1, except that in step S101, nickel chloride is not used, and asphalt, heteroatom source, magnesium oxide and potassium hydroxide are solid-phase mixed in a mass ratio of 1:1:3:2 using a mechanical stirrer. The remaining steps are the same as Example 1.

[0128] The comparative example obtained a noble metal nanoparticle hydrogenation catalyst by testing with the above method, which includes: a porous carbon support, and Pd nanoparticles supported on the porous carbon support. Based on the mass of the porous carbon support as 100%, the content of the Pd nanoparticles in the hydrogenation catalyst is 7.5%. The average particle size of the Pd nanoparticles is 4.1 nm.

[0129] Comparative Example 5

[0130] This comparative example is substantially the same as Example 1, except that step S201 is not performed. The remaining steps are the same as Example 1.

[0131] Through the above method, a transition metal single atom hydrogenation catalyst was prepared in this comparative example, which includes a porous carbon support and a Ni single atom supported on the porous carbon support. Based on the mass of the hydrogenation catalyst being 100%, the content of the Ni single atom in the hydrogenation catalyst is 4.5%.

[0132] Comparative Example 6

[0133] This comparative example is basically the same as Example 5, except that: in step S202, after the solvent is evaporated to dryness, it is placed in a porcelain boat and placed in a tube furnace, and the temperature is increased to 300° C. at a heating rate of 5° C. / min in an argon atmosphere, and calcined at 300° C. for 2 hours to obtain a noble metal single-atom hydrogenation catalyst. That is, high-temperature calcination is not performed, and the remaining steps are the same as Example 5.

[0134] According to the test by the above method, the noble metal single atom hydrogenation catalyst of this comparative example comprises: a porous carbon support and Pd single atoms supported on the porous carbon support. Based on the mass of the porous carbon support being 100%, the content of Pd single atoms in the hydrogenation catalyst is 4.1%.

[0135] Comparative Example 7

[0136] This comparative example is basically the same as Example 5, except that: in step S202, after the solvent is evaporated to dryness, it is placed in a porcelain boat and placed in a tube furnace, and the temperature is increased to 550° C. at a heating rate of 5° C. / min in an argon atmosphere, and calcined at 550° C. for 2 hours to obtain a noble metal nanoparticle hydrogenation catalyst. That is, low-temperature calcination is not performed, and the remaining steps are the same as Example 5.

[0137] The noble metal nanoparticle hydrogenation catalyst of this comparative example comprises: a porous carbon support and Pd nanoparticles supported on the porous carbon support. Based on the mass of the porous carbon support being 100%, the content of the Pd nanoparticles in the hydrogenation catalyst is 3.9%. The average particle size of the Pd nanoparticles is 4.2 nm.

[0138] Comparative Example 8

[0139] This comparative example is basically the same as Example 5, except that: in step S202, after the solvent is evaporated, it is placed in a porcelain boat and placed in a tubular furnace, and the temperature is increased to 400°C at a heating rate of 5°C / min in an argon atmosphere, and calcined at 400°C for 2 hours, and then the temperature is increased to 600°C at a heating rate of 5°C / min in an argon atmosphere, and calcined at 600°C for 2 hours to obtain a noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst.

[0140] The method was used to test the noble metal single atom and noble metal nanoparticle hydrogenation catalyst, which includes a porous carbon carrier, and Pd single atoms and Pd nanoparticles supported on the porous carbon carrier. The content of Pd metal (including single atoms and nanoparticles) in the hydrogenation catalyst is 4.0%, based on the mass of the porous carbon carrier as 100%. The average particle size of the Pd nanoparticles is 3.7 nm.

[0141] Comparative Example 9

[0142] This comparative example is basically the same as Example 5, except that: in step S202, after the solvent is evaporated, it is placed in a porcelain boat and placed in a tubular furnace, and the temperature is increased to 150°C at a heating rate of 5°C / min in an argon atmosphere, and calcined at 150°C for 2 hours, and then the temperature is increased to 900°C at a heating rate of 5°C / min in an argon atmosphere, and calcined at 900°C for 2 hours to obtain a noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst.

[0143] The method was used to test the noble metal single atom and noble metal nanoparticle hydrogenation catalyst, which includes a porous carbon carrier, and Pd single atoms and Pd nanoparticles supported on the porous carbon carrier. The content of Pd metal (including single atoms and nanoparticles) in the hydrogenation catalyst is 4.1%, based on the mass of the porous carbon carrier as 100%. The average particle size of the Pd nanoparticles is 4.1 nm.

[0144] Test Case

[0145] The catalyst prepared by the above-mentioned embodiment and comparative example was used to carry out the catalytic hydrogenation test of pyridine. Specifically, a Schlenk tube was used for catalytic hydrogenation reaction to simulate a fixed bed catalytic hydrogenation reaction; a hydrogen balloon was used as a hydrogen source to react at room temperature; a catalyst (amount as shown in Table 1 below), 3mmol pyridine and 3mL methanol were added to the Schlenk tube at the same time, and the reaction was stirred for 15 hours at room temperature (about 25°C) and a hydrogen balloon pressure (about 0.1MPa), and the reaction product was filtered and analyzed by GC-MS. In addition, each catalyst was reacted five times (i.e., cycled five times) using the above steps, and the reaction product was filtered and analyzed by GC-MS.

[0146] The results are shown in Table 1. The cycle performance of the hydrogenation catalyst prepared in Example 1 is shown in Table 1. Figure 4 shown.

[0147] Table 1

[0148]

[0149] Wherein, conversion rate (%) = (molar amount of raw material pyridine - molar amount of pyridine in the product) ÷ molar amount of raw material pyridine × 100%. The molar amount of pyridine in the product is obtained by GC-MS detection.

[0150] Yield (%) = actual yield of piperidine / theoretical yield of piperidine calculated based on the molar amount of raw material pyridine × 100%. The actual yield of piperidine is the molar amount of piperidine in the product, which is obtained by GC-MS detection.

[0151] Selectivity (%) = molar amount of piperidine in the product / molar amount of converted raw material pyridine × 100%. The molar amount of piperidine in the product is obtained by GC-MS detection. The molar amount of converted raw material pyridine = molar amount of raw material pyridine - molar amount of pyridine in the product.

[0152] It can be seen from the above results that, compared with the catalysts of the comparative examples, the hydrogenation catalyst of the embodiment of the present invention has higher catalytic activity and selectivity, and still has higher selectivity after being recycled for 5 times, which proves that the hydrogenation catalyst of the embodiment of the present invention has a longer life.

Claims

1. A method for preparing a hydrogenation catalyst, comprising the following steps: Preparation of transition metal single atom synergistic noble metal nanoparticle hydrogenation catalysts: S101. Preparation of porous carbon supports containing single transition metal atoms The carbon source, the heteroatom source, the transition metal salt and the metal oxide template are uniformly mixed to obtain a first solid mixture; the first solid mixture is calcined at 700 to 800° C. for 1 to 3 hours in an inert gas atmosphere to obtain a porous carbon precursor containing a transition metal; the porous carbon precursor containing a transition metal is subjected to a first acid wash, a first washing and a first drying to obtain a porous carbon carrier containing a transition metal single atom; S201. Preparation of hydrogenation catalyst The porous carbon support containing transition metal single atoms is impregnated with a first solution containing a precious metal, and then a reducing agent is added and reacted for a period of time, followed by a second washing and a second drying to obtain a transition metal single atom synergistic precious metal nanoparticle hydrogenation catalyst, namely the hydrogenation catalyst; Or include the following steps: Preparation of noble metal single atom-assisted noble metal nanoparticle hydrogenation catalysts: S102. Preparation of porous carbon support The carbon source, the heteroatom source and the metal oxide template are uniformly mixed to obtain a second solid mixture; the second solid mixture is calcined at 700 to 800° C. for 1 to 3 hours in an inert gas atmosphere to obtain a porous carbon precursor; the porous carbon precursor is subjected to a second acid wash, a third wash and a third drying to obtain a porous carbon carrier; S202. Preparation of hydrogenation catalyst The porous carbon support is impregnated with a second solution containing a precious metal, and then dried for a fourth time, and then calcined at 200-300°C for 1-3 hours in an inert gas atmosphere, and then calcined at 450-550°C for 1-3 hours in an inert gas atmosphere to obtain a precious metal single atom synergistic precious metal nanoparticle hydrogenation catalyst, which is the hydrogenation catalyst.

2. The method for preparing a hydrogenation catalyst according to claim 1, wherein: In step S101 and step 102, the carbon source includes one or more of a fossil fuel carbon source and a biomass carbon source; Preferably, in step S101 and step 102, the fossil fuel carbon source includes one or two of asphalt and petroleum coke; the biomass carbon source includes one or more of wood, crop straw and fruit shell.

3. The method for preparing a hydrogenation catalyst according to claim 1, wherein: In step S101 and step 102, the heteroatom source includes a nitrogen source and / or a phosphorus source; Preferably, in step S101 and step 102, the heteroatom source includes a nitrogen source and a phosphorus source, and the mass ratio of the nitrogen source to the phosphorus source is 1:2 to 2:1; Preferably, in step S101 and step 102, the nitrogen source includes one or more of 1,10-phenanthroline, urea and melamine; Preferably, in step S101 and step 102, the phosphorus source includes one or both of triphenylphosphine and phosphoric acid; Preferably, in step S101, the mass ratio of the carbon source, the heteroatom source and the metal oxide template is 1:1:3 to 1:3:5, and the mass ratio of the transition metal salt to the heteroatom source is 1:2 to 2:1; Preferably, in step S102, the mass ratio of the carbon source, the heteroatom source and the metal oxide template is 1:1:3 to 1:3:5; Preferably, in step S101 and step 102, the metal oxide template comprises magnesium oxide; Preferably, in step S101 and step 102, the first solid mixture and the second solid mixture further include an activator, and the mass ratio of the carbon source, the heteroatom source, the metal oxide template and the activator is 1:1:3:2 to 1:3:5:2; Preferably, in step S101 and step 102, the activator includes one or more of potassium hydroxide, zinc chloride and sodium hydroxide.

4. The method for preparing a hydrogenation catalyst according to claim 1, wherein: In step S101, the transition metal in the transition metal salt includes one or more of Mn, Fe, Co, Ni and Cu; Preferably, in step S101, the transition metal salt includes one or more of nitrates, chlorides, sulfates, acetates and acetylacetonates of transition metals.

5. The method for preparing a hydrogenation catalyst according to claim 1, wherein: In step S101, the first pickling is performed by sequentially using a 2-4 mol / L hydrochloric acid solution and a 4-6 mol / L sulfuric acid solution; Preferably, in step S102, the second pickling is performed using a 2-4 mol / L hydrochloric acid solution.

6. The method for preparing a hydrogenation catalyst according to claim 1, wherein: In step S201 and step S202 , the precious metals in the first precious metal-containing solution and the second precious metal-containing solution respectively include one or more of Pd, Pt and Ru.

7. The method for preparing a hydrogenation catalyst according to claim 1, wherein: In step S201, the first solution containing a noble metal includes a solution of a noble metal salt, and the mass of the noble metal in the noble metal salt is 1 to 10% of the mass of the porous carbon support containing transition metal single atoms; Preferably, in step S201, the noble metal salt includes one or more of nitrate, chloride, sulfate, acetate and acetylacetonate of the noble metal; Preferably, in step S201, the first solution containing a noble metal is used to impregnate the porous carbon support containing transition metal single atoms by equal volume impregnation; Preferably, in step S201, the time for impregnating the porous carbon support containing transition metal single atoms with the first solution containing a noble metal is 1 to 3 hours; Preferably, in step S201, the reducing agent includes one or more of sodium borohydride, potassium borohydride and hydrazine hydrate, the mass ratio of the reducing agent to the noble metal salt in the first solution containing the noble metal is (4-6):1, and the time for adding the reducing agent and reacting is 1-3 hours.

8. The method for preparing a hydrogenation catalyst according to claim 1, wherein: In step S202, the second solution containing a noble metal comprises a solution of a noble metal salt, and the mass of the noble metal in the noble metal salt is 0.5-10% of the mass of the porous carbon support; Preferably, in step S202, the noble metal salt includes one or more of nitrate, chloride, sulfate, acetate and acetylacetonate of the noble metal; Preferably, in step S202, the porous carbon carrier is impregnated with the second solution containing a precious metal in an equal volume manner; Preferably, in step S202, the porous carbon support is impregnated with the second solution containing a precious metal for 1 to 3 hours.

9. A hydrogenation catalyst, which is prepared by the method for preparing the hydrogenation catalyst according to any one of claims 1 to 8; Preferably, the hydrogenation catalyst is a transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, or a noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst; the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst comprises: A porous carbon carrier containing transition metal single atoms, and noble metal nanoparticles supported on the porous carbon carrier containing transition metal single atoms; The noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst comprises: a porous carbon support, and noble metal single atoms and noble metal nanoparticles supported on the porous carbon support; Preferably, in the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the porous carbon support containing the transition metal single atom comprises micropores and mesopores, and the total pore volume of the porous carbon support containing the transition metal single atom is 1.7 to 2.2 cm 3 / g, micropore volume is 0.6~1.0cm 3 / g, mesopore volume is 0.9~1.4cm 3 / g, specific surface area is 1250~1500m 2 / g; More preferably, the ratio of the micropore volume to the mesopore volume of the porous carbon carrier containing transition metal single atoms is (0.4-0.9):1; Preferably, in the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the porous carbon support containing the transition metal single atom contains heteroatoms, the heteroatoms include N and / or P, and the heteroatom content in the hydrogenation catalyst is 3-5% based on the mass of the porous carbon support containing the transition metal single atom as 100%; More preferably, the heteroatoms include N and P, and the N content in the hydrogenation catalyst is 1.0-3.5%, and the P content is 1.0-3.5% based on the mass of the porous carbon support containing the transition metal single atom as 100%; Preferably, in the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, based on the mass of the porous carbon support containing the transition metal single atom as 100%, the content of the transition metal single atom is 1.5-10%, and the content of the noble metal nanoparticle is 0.9-10%; Preferably, in the transition metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the average particle size of the noble metal nanoparticles is 2 to 5 nm; Preferably, in the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the porous carbon support comprises micropores and mesopores, and the total pore volume of the porous carbon support is 1.7 to 2.2 cm 3 / g, micropore volume is 0.6~1.0cm 3 / g, mesopore volume is 0.9~1.4cm 3 / g, specific surface area is 1250~1500m 2 / g; More preferably, the ratio of the micropore volume to the mesopore volume of the porous carbon carrier is (0.4-0.9):1; Preferably, in the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the porous carbon support contains heteroatoms, the heteroatoms include N and / or P, and the heteroatom content in the hydrogenation catalyst is 3-5% based on the mass of the porous carbon support as 100%; More preferably, the heteroatoms include N and P, and the N content in the hydrogenation catalyst is 1.0-3.5%, and the P content is 1.0-3.5% based on the mass of the porous carbon support as 100%; Preferably, in the noble metal single atom-coordinated noble metal nanoparticle hydrogenation catalyst, based on the mass of the porous carbon carrier being 100%, the total content of the noble metal single atom and the noble metal nanoparticle is 0.4-10%; Preferably, in the noble metal single atom synergistic noble metal nanoparticle hydrogenation catalyst, the average particle size of the noble metal nanoparticles is 2 to 5 nm.

10. Use of the hydrogenation catalyst according to claim 9 in catalyzing the hydrogenation reaction of nitrogen-containing heterocyclic compounds; Preferably, the nitrogen-containing heterocyclic compound includes one or more of pyridine compounds and quinoline compounds; Preferably, the conditions of the hydrogenation reaction include: The reaction temperature is room temperature, and the reaction pressure is normal pressure ~ 1MPa; Based on 1 mmol of the nitrogen-containing heterocyclic compound, the amount of the hydrogenation catalyst used is 4 to 10 mg.

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