Carbon-coated nickel-palladium alloy nanoparticle composite material, preparation method and application thereof

Abstract

The present application relates to a carbon-coated nickel-palladium alloy nanoparticle composite material, a preparation method and applications thereof, wherein the composite material has a core-shell structure with a shell layer and a core, the shell layer is a graphitized carbon layer, and the core is a nickel-palladium alloy nanoparticle. The composite material has intrinsic safety, can avoid the problems of metal particle coalescence deactivation and loss, and exhibits higher catalytic activity than carbon-coated nickel nanoparticle composite materials in hydrogenation reactions.

Description

TECHNICAL FIELD

[0001] The present application relates to a composite material of carbon-coated nickel-palladium alloy nanoparticles and a preparation method and application thereof. BACKGROUND

[0002] Metallic particles have a long history as catalyst active components and are widely used. In the field of catalytic hydrogenation, palladium is generally more catalytically active than nickel, for example, in the hydrogenation dechlorination reaction, it is generally recognized that palladium has the highest catalytic activity.

[0003] Metal particle coalescence is one of the main reasons for catalyst deactivation. The smaller the particle size of the metal particles, the higher the catalytic activity, but the surface energy is greater and the coalescence deactivation is more likely. When the particle size is reduced to a certain extent, it may even cause safety hazards, such as nanoscale nickel and palladium can spontaneously ignite in air. Metal poisoning is another main reason for catalyst deactivation. Hydrogenation feedstocks such as hydrogen and reaction substrates may contain sulfur, and sulfur is a common poison for nickel and palladium, and palladium is more easily poisoned by sulfur than nickel.

[0004] There are many documents reporting composite materials with a core-shell structure of graphitized carbon-coated nickel nanoparticles. The core-shell structure is generally a nickel nanoparticle coated with a graphene layer with a thickness of less than 10 nm. When such a composite material is used for catalytic hydrogenation reaction, it has both the stability of carbon nanomaterials and the high activity of nickel nanoparticles. CN114425341 A discloses the sulfur poisoning resistance of graphene-coated nickel nanoparticles. The tight coating of the graphitized carbon layer is one of the key factors for its sulfur poisoning resistance. However, it is difficult to manufacture a composite material of graphitized carbon-coated palladium. Although the existing technology discloses a large number of graphitized carbon-coated nickel nanomaterials, there are relatively few documents on graphitized carbon-coated palladium. The existing technology still lacks a simple and effective method for manufacturing graphitized carbon-coated palladium. Therefore, how to take advantage of the high catalytic activity of palladium while overcoming its weaknesses of easy coalescence and poisoning deactivation is a technical problem that the existing technology has not yet solved well.

[0005] Methods for improving reaction selectivity can be roughly divided into two categories. One is to change the properties of the catalyst during the catalyst manufacturing process, and the other is to control the reaction conditions or add a selectivity regulator during the reaction process. A large number of documents on reaction selectivity are directed to metal or metal oxide catalyzed reactions, and there are few documents on adjusting the selectivity of carbon-coated metal material catalyzed reactions.

[0006] Haloarylamines are important organic intermediates, and catalytic hydrogenation of halo-nitroarenes is the most important method for their synthesis. Palladium and nickel are both metals commonly used in catalytic hydrogenation of halo-nitroarenes. The most important problem in catalytic hydrogenation of halo-nitroarenes is the easy occurrence of dehalogenation. The focus of the prior art is on the atomic economy of the reaction; however, even if only a small amount of dehalogenation occurs, the generated hydrogen halide can still cause halogen poisoning and metal loss of the catalyst, resulting in a decrease in the performance of the catalyst, so it is still necessary to improve.

[0007] Catalytic hydrogenation of halo-nitroarenes is a complex reaction process, and the reaction mechanism is different for different catalytic systems. One of the main ways to solve the dehalogenation problem in the prior art is to add a dehalogenation inhibitor during the reaction. The dehalogenation inhibitor is usually a compound containing nitrogen, sulfur, or phosphorus, which binds to the metal surface through these heteroatoms to block some of the high activity sites, thereby inhibiting the dehalogenation reaction. The disadvantage is that these heteroatoms interact strongly with the metal surface, and can easily form chemical adsorption bonds or directly react with the active center, so the type and amount of the dehalogenation inhibitor are very critical, and improper selection can cause a serious decrease in the performance of the catalyst, or even loss of catalytic ability. The prior art can usually only add a dechlorination inhibitor during the reaction, and these toxic compounds are often present in the reaction product components, making it difficult to completely remove them. SUMMARY

[0008] The first object of the present application is to provide a carbon-coated palladium metal catalyst material with higher catalytic hydrogenation activity, more stable performance, and stronger resistance to sulfur poisoning. The second object of the present application is to provide the use of the above-mentioned catalyst material when the hydrogenation raw material contains sulfur. The third object of the present application is to provide the use of the above-mentioned catalyst material in the hydrogenation of nitro compounds. The fourth object of the present application is to provide the use of the above-mentioned catalyst material in the selective hydrogenation of halo-nitroarenes. The fifth object of the present application is to overcome the disadvantage of mixing toxic additives into the hydrogenation product on the basis of the fourth object.

[0009] To achieve the above objects, the present application provides the following technical solutions.

[0010] 1. A composite material of carbon-coated nickel-palladium alloy nanoparticles, the composite material having a core-shell structure with a shell layer and a core, the shell layer being a graphitized carbon layer, and the core being a nickel-palladium alloy nanoparticle; in the composite material, the mass ratio of nickel to palladium is 3:1 to 100:1; and the total mass fraction of nickel and palladium, based on the mass of the composite material, is 1% to 80%.

[0011] 2. The composite material according to the preceding claim; wherein the mass ratio of nickel to palladium is 4:1 to 100:1.

[0012] 3. The composite material according to any one of the preceding; wherein the total mass fraction of nickel and palladium is 30% to 80%, preferably 50% to 78%, based on the composite material.

[0013] 4. The composite material according to any one of the preceding; wherein the composite material is a mesoporous and / or macroporous material, and the mesoporous and macroporous volume is more than 50% of the total pore volume.

[0014] 5. The composite material according to any one of the preceding; wherein the particle size of the nickel-palladium alloy nanoparticles is 1 nm to 50 nm, preferably 2 nm to 25 nm, more preferably 3 nm to 15 nm.

[0015] 6. The composite material according to any one of the preceding; wherein the thickness of the graphitized carbon layer is 0.5 nm to 10 nm, preferably 0.5 nm to 5 nm, more preferably 1 nm to 5 nm.

[0016] 7. The composite material according to any one of the preceding; wherein the XRD spectrum of the composite material has only one diffraction peak in the range of 40.1° to 44.5°.

[0017] 8. A preparation method of a composite material of carbon-coated nickel-palladium alloy nanoparticles, comprising:

[0018] S1 mixing a nickel source, a palladium source and a polybasic organic carboxylic acid in the presence of a first solvent to obtain a precursor solution, and then removing the first solvent to obtain a precursor;

[0019] S2 pyrolyzing the precursor in an inert gas.

[0020] 9. The preparation method according to the preceding; wherein the first solvent is water and / or ethanol, preferably water.

[0021] 10. The preparation method according to any one of the preceding; wherein the nickel source is one or more of nickel acetate, basic nickel carbonate and nickel carbonate.

[0022] 11. The preparation method according to any one of the preceding; wherein the palladium source is an acetic acid solution of palladium acetate.

[0023] 12. The preparation method according to any one of the preceding; wherein the organic polybasic carboxylic acid is one or more of citric acid, ascorbic acid, ethylenediaminetetraacetic acid, 2,5-pyridinedicarboxylic acid, malic acid, tartaric acid, benzoic acid and terephthalic acid.

[0024] 13. The preparation method according to any one of the preceding; wherein the mass ratio of the nickel source to the palladium source, calculated based on metal elements, is 3:1 to 100:1, preferably 4:1 to 100:1, more preferably 4:1 to 9:1.

[0025] 14. The production method according to any one of the preceding; wherein the molar ratio of the nickel source and the palladium source to the organic polycarboxylic acid is 0.1:1 to 3:1, preferably 0.3:1 to 1.5:1, wherein the nickel source and the palladium source are based on the total molar amount of the metal elements.

[0026] 15. The production method according to any one of the preceding; wherein in S2, the pyrolysis temperature is 550°C to 650°C.

[0027] 16. The production method according to any one of the preceding; wherein an acid treatment step is included after S2.

[0028] 17. A composite material of carbon-coated nickel-palladium alloy nanoparticles; wherein 1 the composite material and a sulfur-containing compound supported thereon are included.

[0029] 18. The composite material according to 17; wherein the sulfur-containing compound is thiourea.

[0030] 19. The composite material according to 17 or 18; wherein the mass fraction of sulfur element by elemental analysis is 0.5% to 5%.

[0031] 20. A production method of a composite material of carbon-coated nickel-palladium alloy nanoparticles, comprising: a step of supporting a sulfur-containing compound on 1 the composite material.

[0032] 21. The production method according to 20; wherein the sulfur-containing compound is thiourea.

[0033] 22. The production method according to 20 or 21; wherein the amount of the sulfur-containing compound in terms of sulfur element is 0.01 to 20 with respect to 1 mol of palladium element in 1 the composite material.

[0034] 23. The composite material produced by the production method according to any one of 8 to 16.

[0035] 24. The composite material produced by the production method according to any one of 20 to 22.

[0036] 25. Use of the composite material according to any one of the preceding as a hydrogenation catalyst in a catalytic hydrogenation system containing sulfur.

[0037] 26. The use according to 25; wherein the hydrogen and / or the hydrogenation substrate contains sulfur.

[0038] 27. Use of the composite material according to any one of the preceding for catalytic hydrogenation of a nitro group in an organic compound.

[0039] 28. A method for selectively hydrogenating nitro group in halonitroaromatics, comprising: under the condition of liquid phase catalytic hydrogenation, contacting hydrogen with halonitroaromatics and a catalyst in the presence of a sulfur-containing compound to carry out liquid phase catalytic hydrogenation reaction; the catalyst is any one of the composite materials described in 1-7 and 23; the sulfur-containing compound is thiocyanate and / or thiourea, and the mass ratio of the sulfur-containing compound to halonitroaromatics is 1:100-1:10000.

[0040] 29. The method according to 28, wherein the mass ratio of the sulfur-containing compound to halonitroaromatics is 1:100-1:150.

[0041] 30. A method for selectively hydrogenating nitro group in halonitroaromatics, comprising: under the condition of liquid phase catalytic hydrogenation, contacting hydrogen with halonitroaromatics and a catalyst to carry out liquid phase catalytic hydrogenation reaction; the catalyst is any one of the composite materials described in 17-19 and 24.

[0042] Compared with the prior art, the present application has the following beneficial technical effects.

[0043] The present application utilizes the promotion of carbon graphitization ability of nickel, combines the specific complexation and reduction ability of multi-element organic carboxylic acid, realizes the coating of palladium metal into carbon by a simple method, and the coating is relatively rigorous, thereby obtaining a composite material of carbon-coated nickel-palladium alloy nanoparticles. The composite material has the stability of nanocarbon material and the catalytic characteristics of palladium metal nanoparticles. Specifically, the composite material has intrinsic safety, and theoretically, there is no problem of metal particle coalescence deactivation and loss, and the catalytic activity is higher than that of carbon-coated nickel nanoparticle composite material in hydrogenation reaction.

[0044] The catalytic properties of the composite material can be conveniently adjusted, and the composite material is suitable for different uses, especially for selective hydrogenation of nitro groups in organic compounds. Specifically, whether the sulfur-containing compound is added during the reaction or the sulfur-containing compound is pre-loaded on the surface of the composite material, high selective hydrogenation of nitro groups in organic compounds can be realized.

[0045] Other features and advantages of the present application will be described in detail in the specific embodiment part. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 It is a spherical difference electron microscope picture of the composite material prepared according to Preparation Example 3.

[0047] Figure 2 It is an XRD spectrum of the composite material prepared according to Preparation Example 3.

[0048] Figure 3 It is an XPS wide spectrum of the composite material prepared according to Preparation Example 4. DETAILED DESCRIPTION

[0049] The present application is described in detail below with specific embodiments, but it should be noted that the scope of protection of the present application is not limited by these specific embodiments and the principle explanation, but is determined by the claims.

[0050] In the present application, any matter or item not mentioned, except for the explicitly mentioned content, is directly applicable to the content known in the art without any change. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solution or technical idea formed thereby is considered as part of the original disclosure or description of the present application, and should not be considered as new content not disclosed or anticipated herein, unless the combination is considered as obviously unreasonable by the person skilled in the art.

[0051] All the features disclosed in the present application can be combined arbitrarily, and these combinations should be understood as the disclosed or described content of the present application, and should be considered as specifically disclosed and described by the present application, unless the combination is considered as obviously unreasonable by the person skilled in the art. The numerical points disclosed in the present specification, unless specifically indicated, not only include the numerical points specifically disclosed in the embodiments, but also include the end points of the numerical ranges in the specification, and the ranges formed by the arbitrary combination of these numerical points should be considered as the disclosed or described range of the present application.

[0052] The technical and scientific terms in the present application are defined according to their definitions, and the terms not defined are understood according to the general meaning in the art.

[0053] The term "graphitized carbon layer" refers to the layered carbon structure that can be obviously observed under high-resolution transmission electron microscopy, rather than amorphous structure, and the interlayer spacing is about 0.34 nm.

[0054] The term "alloy" refers to the mixture of different metal elements.

[0055] The term "mesopore" is defined as the pore with a pore size in the range of 2 nm to 50 nm. The pore with a pore size less than 2 nm is defined as micropore, and the pore with a pore size greater than 50 nm is defined as macropore.

[0056] The term "acid treatment" refers to the operation of acid washing the product generated after the high-temperature pyrolysis step at a temperature close to the boiling temperature when preparing the composite material of carbon-coated nickel-palladium alloy nanoparticles.

[0057] The term "inert gas" is defined as the gas that does not constitute a perceptible effect on the catalytic hydrogenation performance of the composite material.

[0058] The term "soluble" refers to the solubility in the solvent used.

[0059] The symbol "PPMw" represents parts per million by weight.

[0060] The term "optionally" means that there can or can not be, e.g. A and optionally B means "A and not B" or "A and B".

[0061] The first aspect of the present application provides a carbon-coated nickel-palladium alloy nanoparticle composite material, which has a core-shell structure with a shell layer and a core, the shell layer being a graphitized carbon layer, and the core being a nickel-palladium alloy nanoparticle; in the composite material, the mass ratio of nickel to palladium is 3:1 to 100:1; and the total mass fraction of nickel and palladium is 1% to 80% based on the mass of the composite material.

[0062] The composite material according to the first aspect is composed of nickel, palladium, carbon and oxygen. It should be understood that the composite material of the present application is mainly composed of zero-valent nickel, palladium and carbon, and a small amount of oxygen is inevitably doped in the surface layer carbon of the composite material due to the oxygen-containing carbon source in the synthesis raw materials; a small amount or trace amount of nickel and palladium can exist in the form of oxides, and a small amount or trace amount of other elements can be caused by impurities in the synthesis raw materials, but these factors have no obvious effect on the performance of the composite material; the present application does not consider it necessary to specify these.

[0063] In the composite material according to the first aspect, the mass ratio of nickel to palladium is 3:1 to 100:1, preferably 4:1 to 100:1; if a relatively higher catalytic hydrogenation activity is required, the mass ratio of nickel to palladium can be further controlled to be between 4:1 and 9:1. Within the above ratio range, only the diffraction peaks of fcc NiPd alloy are present in the XRD pattern of the composite material; and when the palladium content is higher, characteristic peaks of elemental palladium appear, which are difficult to be tightly coated by carbon and do not have the ability to resist coalescence and poisoning deactivation.

[0064] In the composite material according to the first aspect, the total mass fraction of nickel and palladium is 1% to 80%, preferably 30% to 80%, and more preferably 50% to 78%, based on the composite material. It has been found by the present application that even if about 1% of palladium is doped in nickel, the catalytic hydrogenation ability of the composite material is significantly improved. In some preparation examples of the present application, even after acid treatment, the total mass fraction of nickel and palladium in the composite material can still reach about 75%.

[0065] The composite material according to the first aspect is composed of the core-shell structure and a small amount of carbon matrix.

[0066] The composite material according to the first aspect is a mesoporous and / or macroporous material, and the mesopore and macropore volume accounts for more than 50% of the total pore volume. In some preparation examples, the composite material has a mesoporous structure or a mesoporous and macroporous structure. It is well known in the art that the pore structure is a macroscopic property of a catalytic material.

[0067] The specific surface area of the composite material according to the first aspect is 50 m 2 / g to 500 m 2 / g, preferably 100 m 2 / g to 300 m 2 / g.

[0068] The particle size of the nickel-palladium alloy nanoparticles in the composite material according to the first aspect is 1 nm to 50 nm, generally between 2 nm and 25 nm, and preferably between 3 nm and 15 nm, under transmission electron microscope observation. In some examples, the particle size of the nickel-palladium alloy nanoparticles is relatively narrow, and is generally between 4 nm and 10 nm.

[0069] The thickness of the graphitized carbon layer in the composite material according to the first aspect is 0.5 nm to 10 nm, preferably 0.5 nm to 5 nm, and generally between 1 nm and 5 nm, under transmission electron microscope observation.

[0070] The core-shell structure in the composite material according to the first aspect is spherical or spheroidal.

[0071] In some examples of the composite material according to the first aspect, there is only one diffraction peak in the XRD spectrum within the range of 40.1° to 44.5°.

[0072] The second aspect of the present application provides another composite material of carbon-coated nickel-palladium alloy nanoparticles, which comprises the composite material according to the first aspect and a sulfur-containing compound supported thereon.

[0073] The composite material according to the second aspect is composed of the composite material according to the first aspect and a sulfur-containing compound supported thereon.

[0074] The molecular weight of the sulfur-containing compound in the composite material according to the second aspect is generally less than 200. The sulfur-containing compound can be an organic sulfur compound or an inorganic sulfur compound; in the organic sulfur compound, the carbon-sulfur bond can be a double bond or a single bond. The sulfur-containing compound is preferably thiourea.

[0075] The mass fraction of sulfur in the composite material according to the second aspect can be 0.1% to 10%, preferably 0.5% to 5%, and more preferably 0.8% to 1.8%.

[0076] The third aspect of the present application provides a preparation method of the composite material according to the first aspect, which comprises:

[0077] S1 mixing a nickel source, a palladium source and a polybasic organic carboxylic acid in the presence of a first solvent to obtain a precursor solution, and then removing the first solvent to obtain a precursor;

[0078] S2 pyrolyzing the precursor in an inert gas.

[0079] According to the preparation method of the third aspect, the first solvent is water and / or ethanol, preferably water.

[0080] According to the preparation method of the third aspect, the nickel source is a soluble nickel salt, which can be one or more of nickel acetate, basic nickel carbonate and nickel carbonate.

[0081] According to the preparation method of the third aspect, the palladium source is preferably a solution containing palladium, which can be a solution of palladium acetate, preferably a solution of palladium acetate in glacial acetic acid.

[0082] According to the preparation method of the third aspect, the organic polycarboxylic acid is preferably a polybasic organic carboxylic acid containing hydroxyl groups in the molecule. The organic polycarboxylic acid can be one or more of citric acid, ascorbic acid, ethylenediaminetetraacetic acid, 2,5-pyridinedicarboxylic acid, tartaric acid, benzoic acid or terephthalic acid, preferably citric acid.

[0083] According to the preparation method of the third aspect, the mass ratio of the nickel source to the palladium source, in terms of metal elements, is 3:1 to 100:1, preferably 4:1 to 100:1, and more preferably 4:1 to 9:1.

[0084] According to the preparation method of the third aspect, in S1, the molar ratio of the nickel source and the palladium source to the organic polycarboxylic acid is 0.1:1 to 3:1, preferably 0.3:1 to 1.5:1, wherein the nickel source and the palladium source are in terms of the total molar amount of metal elements.

[0085] According to the preparation method of the third aspect, in S1, the precursor solution can be prepared by adding the nickel source, the palladium source and the carbon source into water and / or alcohol, stirring at 40°C to 100°C for 8h to 16h, preferably stirring at 50°C to 90°C for 10h to 12h; wherein the palladium source is provided by dissolving 0.5g to 1.1g of palladium acetate containing 0.5g to 1.1g of palladium in 100mL of glacial acetic acid, and the nickel source is provided in the form of nickel acetate (which can or can not contain crystal water).

[0086] According to the preparation method of the third aspect, in S1, the first solvent in the precursor solution is preferably removed by direct evaporation, for example, the first solvent in the precursor solution can be evaporated to dryness on a rotary evaporator and / or dried in an oven.

[0087] According to the preparation method of the third aspect, in S2, the pyrolysis temperature is 500°C to 800°C, preferably 500°C to 700°C, and more preferably 550°C to 650°C; and / or, the pyrolysis time is 1h to 4h, preferably 1.5h to 3h; and / or, the heating rate is 1°C / min to 10°C / min, preferably 2°C / min to 5°C / min.

[0088] According to the preparation method of the third aspect, in S2, the inert gas can be nitrogen, argon or helium.

[0089] According to the preparation method of the third aspect, it further comprises an optional acid treatment step after S2. The present application does not limit the type, amount and treatment time of the acid used in the acid treatment, which can be selected by those skilled in the art according to the existing knowledge and / or simple experiments. Generally, a non-oxidizing strong acid is used for acid treatment, such as hydrochloric acid or sulfuric acid. In some preparation examples of the present application, hydrochloric acid is used, the concentration is generally 0.5 mol / L to 2 mol / L, the temperature can be 60°C to 100°C, generally close to boiling, and the time can be 3h to 24h, generally 3h to 10h.

[0090] According to the preparation method of the third aspect, it further comprises a post-treatment step of the product, such as filtration, washing, drying, etc.

[0091] The fourth aspect of the present application provides a preparation method of the composite material of the second aspect, comprising a step of loading a sulfur-containing compound on the composite material of the first aspect.

[0092] According to the preparation method of the fourth aspect, the loading method of the sulfur-containing compound is not particularly limited, and those skilled in the art can use any known method to load the sulfur-containing compound on the composite material of the first aspect. One preferred method is to first disperse the composite material of the first aspect in a second solvent, dissolve the sulfur-containing compound in a third solvent to form a solution; then mix the two liquids; in order to make the contact between the two sufficient and uniform, mechanical stirring mixing can be used, ultrasonic mixing can be used, or the two can be combined, first ultrasonic mixing, and then mechanical stirring mixing. Generally, the loading time is 12h to 24h. In some preparation examples, the sulfur-containing compound is thiourea, and at this time the solvent is preferably water. In some preparation examples, the ultrasonic time is 0.5h to 3h, the mechanical stirring time is 2h to 24h, and the loading temperature is 25°C to 90°C.

[0093] According to the preparation method of the fourth aspect, the type and amount of the sulfur-containing compound can vary within a wide range. The present application has found that after treating the composite material of the first aspect with a sulfur-containing compound, the selectivity in the catalytic hydrogenation reaction can be significantly affected, and those skilled in the art can select the appropriate sulfur-containing compound and determine its amount by trial according to the actual needs. However, different small-molecule sulfur-containing compounds have different effects on the composite material, for example, when thiourea is selected, the selectivity in the catalytic hydrogenation reaction of halogenated nitrobenzene can reach 100%.

[0094] According to the preparation method of the fourth aspect, the sulfur-containing compound can be loaded by impregnation. In order to have higher selectivity, the amount of the sulfur-containing compound in terms of sulfur element can be 0.01 to 20, preferably 0.3 to 5, relative to 1 mol of palladium element in the composite material of the first aspect.

[0095] According to the preparation method of the fourth aspect, the second solvent is water and / or an alcohol solvent, preferably water.

[0096] According to the preparation method of the fourth aspect, the third solvent is water and / or an alcohol solvent, preferably water.

[0097] According to the preparation method of the fourth aspect, the preparation method further comprises a post-treatment step of the product, such as filtration, washing, drying, etc.

[0098] The fifth aspect of the present application provides a composite material of carbon-coated nickel-palladium alloy nanoparticles prepared by the preparation method of any one of the preceding aspects.

[0099] The sixth aspect of the present application provides an application of the composite material of any one of the preceding aspects as a hydrogenation catalyst in a catalytic hydrogenation system containing sulfur.

[0100] According to the application of the sixth aspect, the hydrogen and / or the hydrogenation substrate contain sulfur. Fossil fuels are the main way to obtain industrial hydrogen in the field of petroleum chemical industry, and such raw materials will inevitably produce sulfur compounds during hydrogen production. Although pressure swing adsorption (PSA) technology can make the purity of hydrogen reach more than 99.9%, there are still sulfur compounds in hydrogen. Some reaction substrates themselves contain sulfur, such as thionitroarene, etc. There may also be sulfur-containing impurities in the reaction substrate. The influence of these sulfur compounds on the hydrogenation catalyst cannot be ignored. The present application has found that even if the composite material is treated with thiocyanate with very high concentration and high toxicity, it still has very high catalytic hydrogenation activity, so it has unique advantages when used as a hydrogenation catalyst in these catalytic hydrogenation systems containing sulfur.

[0101] According to the application of the sixth aspect, the hydrogenation substrate contains one or more functional groups such as nitro group, carbon-carbon double bond, carbon-carbon triple bond, ketone group, aldehyde group and aromatic ring. The prior art has realized the hydrogenation of the above-mentioned functional groups by using carbon-coated nickel nanoparticle composite material, and the catalytic hydrogenation activity of the composite material of the present application is higher than that of the carbon-coated nickel nanoparticle composite material, so it can also catalytically hydrogenate the above-mentioned functional groups contained in organic compounds.

[0102] The seventh aspect of the present application provides an application of the composite material of the first, second or fifth aspect in catalytically hydrogenating nitro group in organic compounds.

[0103] According to the application of the seventh aspect, the organic compound is thionitroarene.

[0104] According to the application of the seventh aspect, the thionitroarene has a structure as shown in formula (I):

[0105]

[0106] wherein X is selected from one or more of sulfur, sulfone group, R1 is selected from one or more of hydrogen, C1-C6 alkyl, C1-C3 haloalkyl, C1-C3 hydroxyalkyl, mercapto, aryl and arylthio, R2 is selected from one or more of hydrogen, C1-C6 alkyl, hydroxy, carboxyl, halogen, amino, mercapto, aryl, arylthio and nitro, the aryl being unsubstituted or substituted by one or more of nitro, C1-C6 alkyl, hydroxy, carboxyl, halogen, amino or amino. Common thionitroarenes are 4-nitrothioanisole, 2-nitrothiophenyl sulfide, 4-nitrothiophenol, 3,3'-dinitrothiobisphenyl sulfone and 4,4'-dinitrothiobisphenyl sulfone. The prior art has realized the hydrogenation of the above compounds using carbon-coated nickel nanoparticle composite materials. The composite material of the present application has higher catalytic hydrogenation activity than the carbon-coated nickel nanoparticle composite material, and thus can also catalyze the hydrogenation of the above organic compounds.

[0107] The eighth aspect of the present application provides a method for selectively hydrogenating nitro groups in halogenated nitroarenes, comprising: contacting hydrogen gas with halogenated nitroarenes and a catalyst in the presence of a sulfur-containing compound under conditions of liquid-phase catalytic hydrogenation to perform a liquid-phase catalytic hydrogenation reaction; the catalyst being the composite material of the first aspect of the present application; the sulfur-containing compound being thiocyanate and / or thiourea, and the mass ratio of the sulfur-containing compound to the halogenated nitroarenes being 1:100-1:10000.

[0108] It has been found that the addition of a sulfur-containing compound can significantly affect the selectivity during catalytic hydrogenation. Those skilled in the art can select appropriate sulfur-containing compounds and determine their amounts by experiments according to actual needs. According to the method of the eighth aspect, the molecular weight of the sulfur-containing compound is generally below 200, which is more convenient for operation; and the amount range is relatively wide, which makes control easier. However, different small-molecule sulfur-containing compounds have different effects on the selectivity of the reaction. For example, the selectivity of sodium sulfide is only 70% to 80% for the selective hydrogenation of chloronitrobenzene to produce chloroaniline, the selectivity of thiocyanate is above 98%, and the selectivity of thiourea can reach 100%.

[0109] According to the method of the eighth aspect, the thiocyanate is generally potassium thiocyanate and / or sodium thiocyanate.

[0110] According to the method of the eighth aspect, the mass ratio of the sulfur-containing compound to the halogenated nitroarenes is preferably 1:100-1:150.

[0111] According to the method of the eighth aspect, the mass ratio of the catalyst to the halogenated nitroarenes is 1:1-1:15, preferably 1:1-1:7.

[0112] According to the method of the eighth aspect, the liquid phase catalytic hydrogenation is carried out at a temperature of 20-100°C, preferably 40-60°C, and / or at a hydrogen pressure of 0.5-4 MPa, preferably 0.8-2 MPa.

[0113] According to the method of the eighth aspect, the liquid phase hydrogenation reaction uses a solvent selected from one or more of isopropyl alcohol, ethanol, acetone and water, preferably isopropyl alcohol and / or water, more preferably a mixed solvent of isopropyl alcohol and water in a volume ratio of 10:1-5:1.

[0114] According to the method of the eighth aspect, the halogenated nitroarene is chloronitrobenzene, preferably m-chloronitrobenzene or p-chloronitrobenzene.

[0115] The ninth aspect of the present application provides another method for selectively hydrogenating nitro groups in halogenated nitroarenes, comprising: contacting hydrogen with halogenated nitroarenes and a catalyst under conditions for liquid phase catalytic hydrogenation to carry out liquid phase catalytic hydrogenation reaction; the catalyst is the composite material of the second aspect of the present application.

[0116] According to the method of the ninth aspect, the mass ratio of the catalyst to halogenated nitroarenes is 1:1-1:15, preferably 1:1-1:7.

[0117] According to the method of the ninth aspect, the liquid phase catalytic hydrogenation is carried out at a temperature of 20-100°C, preferably 40-60°C, and / or at a hydrogen pressure of 0.5-4 MPa, preferably 0.8-2 MPa.

[0118] According to the method of the ninth aspect, the liquid phase hydrogenation reaction uses a solvent selected from one or more of isopropyl alcohol, ethanol, acetone and water, preferably isopropyl alcohol and / or water.

[0119] According to the method of the ninth aspect, the halogenated nitroarene is chloronitrobenzene, preferably m-chloronitrobenzene or p-chloronitrobenzene.

[0120] Analysis and characterization

[0121] The distribution of each element in the material is characterized by a spherical aberration electron microscope (STEM). The model of the spherical aberration electron microscope used is JEM-ARM200F (Japan Electron Corporation), and the test conditions are: an acceleration voltage of 200 kV.

[0122] The composition of the material, the structure or morphology of atoms or molecules inside the material, and other information are obtained by XRD. The XRD diffractometer used is an X-ray diffractometer of model X’Pert Pro purchased from the Netherlands PANalytical, and the test conditions are: Cu target, Kα ray, tube voltage of 40 kV, tube current of 40 mA, and 2θ scanning range of 5° to 80°.

[0123] The elements on the surface of the material were detected by an X-ray photoelectron spectrometer (XPS). The X-ray photoelectron spectrometer used was an ESCALab220i-XL produced by VG Scientifc Company and equipped with Avantage V5.926 software. The X-ray photoelectron spectrometry test conditions were as follows: the excitation source was monochromatic Al Kα X-ray, the power was 330 W, and the base vacuum during the analysis test was 3x10-9 mbar.

[0124] The specific surface area and pore size distribution of the material were determined by the Brunauer-Emmett-Taller method (BET, Quantachrome AS-6B analyzer).

[0125] The content of carbon, hydrogen, oxygen, nitrogen and sulfur elements was tested on an Elementar Vario EL Cube elemental analyzer. The specific operation method was as follows: about 5 mg of sample was weighed in a tin cup, placed in an automatic sample tray, and introduced into a combustion tube through a ball valve for combustion at a combustion temperature of 1000℃ (helium was used for purging to eliminate atmospheric interference during sampling). C, H, N and S in the sample were converted into carbon dioxide, water, nitrogen and sulfur dioxide, respectively. The mixed gas was separated by a chromatographic column and finally detected by a thermal conductivity cell. When the oxygen element was determined, the sample was cracked in a high-temperature cracking tube containing carbon powder. The oxygen in the sample was converted into carbon monoxide. The carrier gas carried the cracking products into a series of scrubbers to remove acid gas and water vapor, and finally into an infrared detector for detection.

[0126] The content of nickel and palladium elements was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The specific method was as follows: (1) nitration: 10 mg of catalyst sample was placed in a flask, 16 mL of freshly prepared aqua regia was added, a magnetic stirrer was added, the flask was placed in an oil bath, and the condensation reflux was carried out at 120℃ for 12 h. After cooling to room temperature, the solution was aspirated by a glass syringe, filtered by a disposable filter head with a pore size of 0.22 μm, and the filtrate was added to a 500 mL volumetric flask and diluted to volume with ultrapure water. (2) content test: 10 mL of the nitration and dilution solution was taken, and the metal content was tested by using the instrument Agilent 5110.

[0127] Unless otherwise specified, the reagents used in the present application are analytical pure, and the reagents used are commercially available.

[0128] Preparation Examples 1-4 were used to illustrate the composite material and the preparation method thereof of the present application

[0129] Preparation Example 1

[0130] 1) Take 0.040 g of palladium acetate and measure 3 mL of glacial acetic acid. Add to 170 mL of deionized water, and stir to dissolve at 50°C. According to the mass ratio of nickel source to palladium source of 100:1 (calculated as metal elements), the molar ratio of total nickel and palladium to complexing agent is 1:1, take citric acid monohydrate and nickel acetate tetrahydrate and add to the above solution, and stir to obtain a homogeneous solution at 70°C, and continue to heat and evaporate to dryness, grind the solid to obtain the precursor.

[0131] 2) Put the precursor obtained in step 1) into a porcelain boat, then place the porcelain boat in the constant temperature zone of the tube furnace, introduce nitrogen gas at a flow rate of 150 mL / min, and heat to 600°C at a rate of 2.5°C / min, stop heating after constant temperature for 2 h, and cool to room temperature under nitrogen atmosphere to obtain the pyrolysis product.

[0132] 3) Add the pyrolysis product obtained in step 2) to 200 mL of 1 mol / L HCl solution, stir and reflux at 90°C for 4 h, then perform suction filtration on the solution, wash with deionized water until neutral, and then place the powder in a 100°C oven to dry for 2 h to obtain the carbon-coated nickel-palladium nanocomposite.

[0133] Preparation Example 2

[0134] According to the method of Preparation Example 1, except that in step 1), take 0.040 g of palladium acetate and measure 3 mL of glacial acetic acid. Add to 170 mL of deionized water, and stir to dissolve at 50°C. According to the mass ratio of nickel source to palladium source of 100:1 (calculated as metal elements), the molar ratio of total nickel and palladium to complexing agent is 1:1, take citric acid monohydrate and nickel acetate tetrahydrate and add to the above solution, and stir to obtain a homogeneous solution at 70°C, and continue to heat and evaporate to dryness, grind the solid to obtain the precursor, and the rest is the same as Preparation Example 1, to obtain the carbon-coated nickel-palladium nanocomposite.

[0135] Preparation Example 3

[0136] According to the method of Preparation Example 1, except that in step 1), take 0.040 g of palladium acetate and measure 3 mL of glacial acetic acid. Add to 170 mL of deionized water, and stir to dissolve at 50°C. According to the mass ratio of nickel source to palladium source of 100:1 (calculated as metal elements), the molar ratio of total nickel and palladium to complexing agent is 1:1, take citric acid monohydrate and nickel acetate tetrahydrate and add to the above solution, and stir to obtain a homogeneous solution at 70°C, and continue to heat and evaporate to dryness, grind the solid to obtain the precursor, and the rest is the same as Preparation Example 1, to obtain the carbon-coated nickel-palladium nanocomposite.

[0137] Preparation Example 4

[0138] This preparation example is used to illustrate a carbon-coated nickel-palladium nanocomposite containing sulfur.

[0139] Take 0.5 g of the composite material obtained according to the method of Preparation Example 3, add it to 10 mL of deionized water, and ultrasonically disperse the nanomaterial for 1 h; take 0.036 g of thiourea, add it to 10 mL of deionized water, and ultrasonically disperse the thiourea for 1 h; mix the two liquids, ultrasonically disperse them for 1 h, then mechanically stir them for 12 h at a speed of 800 rpm, filter them, wash them with deionized water 5 times, and freeze-dry them to obtain a carbon-coated nickel-palladium nanocomposite material containing sulfur, elemental analysis showing that the mass percentage of sulfur is 1.67%, and BET showing that the specific surface area of the material is 145.0 m 2 / g.

[0140] Examples 1-3 are used to illustrate the method for synthesizing p-chloroaniline by selectively hydrogenating p-chloronitrobenzene using the composite material of the present application as a catalyst

[0141] Take 100 mg of the carbon-coated nickel-palladium nanocatalytic material prepared according to the method of Preparation Examples 1-3, 315 mg of p-chloronitrobenzene, 2.4 mg of thiourea, 27 mL of isopropyl alcohol, and 3 mL of water, and add them to a reaction kettle, replace the reaction kettle with H2 four times, stir it at low pressure while heating it, heat it to a predetermined reaction temperature of 60°C, replace the reaction kettle with H2 again to make the pressure in the reaction kettle 1.0 MPa, continue the reaction until the pressure does not change for 10 minutes, cool it to room temperature, release the pressure, open the reaction kettle, and take out the product for chromatographic analysis. Calculate the conversion rate of the reactant and the selectivity of the target product by the following formulas:

[0142] Conversion rate = mass of reacted reactant / mass of added reactant x 100%

[0143] Selectivity = mass of target product / mass of reaction product x 100%

[0144] The time for which the reaction does not change for 10 minutes in Example 1 is 180 minutes, and after analyzing the product, the conversion rate of p-chloronitrobenzene is 100% and the selectivity of p-chloroaniline is 100%.

[0145] The time for which the reaction does not change for 10 minutes in Example 2 is 77 minutes, and after analyzing the product, the conversion rate of p-chloronitrobenzene is 100% and the selectivity of p-chloroaniline is 100%.

[0146] The time for which the reaction does not change for 10 minutes in Example 3 is 50 minutes, and after analyzing the product, the conversion rate of p-chloronitrobenzene is 100% and the selectivity of p-chloroaniline is 100%.

[0147] Example 4

[0148] According to the method of Example 3, except that the thiourea is replaced by potassium thiocyanate, and the rest is the same as Example 3, under the same conditions, the p-chloronitrobenzene hydrogenation reaction is catalyzed, the conversion rate of p-chloronitrobenzene is 100%, and the selectivity of p-chloroaniline is 98.84%.

[0149] Example 5

[0150] The method of Example 1 was followed, except that no thiourea was added, and the rest was the same as Example 1, and the hydrogenation reaction of p-chloronitrobenzene was catalyzed under the same conditions. The conversion rate of p-chloronitrobenzene was 100%, the selectivity of p-chloroaniline was 65.5%, and the rest was aniline.

[0151] Example 6

[0152] The method of Example 3 was followed, except that the catalyst was the composite material of Preparation Example 4, the amount was 100 mg, no thiourea was added, and p-nitrochlorobenzene was 157.5 mg, and the rest was the same as Example 3, and the hydrogenation reaction of p-chloronitrobenzene was catalyzed under the same conditions. The conversion rate of p-chloronitrobenzene was 100%, and the selectivity of p-chloroaniline was 100%.

[0153] Comparative Example 1

[0154] The method of Example 1 was followed, except that the catalyst was replaced by a commercial palladium-carbon catalyst (10wt% Pd, containing water 55%), and the rest was the same as Example 1, and the hydrogenation reaction was carried out under the same conditions. The conversion rate of p-chloronitrobenzene was 0%. It can be seen that the traditional supported Pd catalyst completely loses catalytic activity in the presence of sulfur poison and does not have the ability to resist sulfur poisoning.

[0155] Comparative Example 2

[0156] The method of Example 1 was followed, except that the catalyst was replaced by a commercial palladium-carbon catalyst (10wt% Pd, containing water 55%) and no thiourea was added, and the rest was the same as Example 1, and the hydrogenation reaction of p-chloronitrobenzene was catalyzed under the same conditions. The conversion rate of p-chloronitrobenzene was 100%, and the content of p-chloroaniline in the product was approximately 0. It can be seen that the traditional supported Pd catalyst has poor selectivity for p-chloroaniline.

[0157] Table 1 Mass fraction of nickel and palladium in the composite material of the application and mass ratio of nickel to palladium

[0158]

[0159] As can be seen from Table 1, although the acid pickling is performed and the mass ratio of nickel to palladium changes in a large range, the metal content in the composite materials of Preparation Examples 1-3 is about 75%, that is, the metal content in the composite material of the application is very high.

[0160] From the above, it can be seen that the composite material of the application has the following advantages: Figure 1As can be seen from the aberration-corrected electron microscopy images, in the composite material prepared according to Preparation Example 3, the metal nanoparticles are a mixture of nickel and palladium. Other preparation examples of the present invention also share this characteristic, namely, the metal nanoparticles in the composite material of the present invention are a nickel-palladium alloy. Figure 1 As can be seen in the image in the upper left corner, the particle size of the metal nanoparticles is between 2nm and 25nm, the thickness of the graphitized carbon layer is between 1nm and 5nm, and the core-shell structure of the carbon-coated nickel-palladium nanoparticles is spherical or near-spherical; other preparation examples of the present invention also have the same characteristics.

[0161] Depend on Figure 2 As can be seen from the XRD pattern, the composite material prepared according to Preparation Example 3 only has the diffraction peak of fcc NiPd alloy, and there are no diffraction peaks of elemental nickel and elemental palladium. Other preparation examples of the present invention also have the same characteristics, that is, the metal nanoparticles in the composite material of the present invention are nickel-palladium alloy.

[0162] Depend on Figure 3 As can be seen, the surface layer of the composite material prepared according to Preparation Example 4 contains carbon, oxygen, nickel, palladium, sulfur and nitrogen elements.

[0163] As shown in Example 5, although a small amount of palladium was incorporated into the metal nanoparticles, about 35% of the chlorine could be removed, indicating that the catalytic hydrogenation ability of the composite material was significantly increased, while the metal nanoparticles, when they were only elemental nickel, had virtually no hydrogenation and dechlorination ability.

[0164] Comparative Example 2 shows that the commercial palladium-on-carbon catalyst has high hydrogenation activity, almost completely removing chlorine during the hydrogenation of p-chloronitrobenzene. Comparative Example 1 shows that the commercial palladium-on-carbon catalyst lacks resistance to sulfur poisoning; adding approximately 80 PPMw of sulfide can completely deactivate it.

[0165] As can be seen from Examples 1 to 4, when a trace amount of sulfide is added to the reaction system, the composite material of the present invention exhibits good resistance to sulfur poisoning, maintains high catalytic activity when catalyzing the hydrogenation of p-chloronitrobenzene, and also has high selective catalytic hydrogenation ability; that is, the composite material of the present invention can catalyze the hydrogenation of halonitroaromatic hydrocarbons to produce haloaromatic amines with high activity and high selectivity.

[0166] As shown in Example 6, even when treated with high concentrations of sulfides during the manufacturing process of the composite material, the composite material of the present invention still possesses high catalytic hydrogenation activity, indicating that the composite material of the present invention has extremely strong resistance to sulfur poisoning. Furthermore, the treated composite material does not require the addition of sulfides to the reaction system to selectively catalyze the hydrogenation of p-chloronitrobenzene to produce p-chloroaniline with high selectivity. That is, the composite material treated with sulfides of the present invention can directly and highly selectively catalyze the hydrogenation of halonitroaromatic hydrocarbons to produce haloaromatic amines with high activity, avoiding the mixing of toxic substances into the hydrogenation product.

Claims

1. A carbon-coated nickel-palladium alloy nanoparticle composite material, the composite material containing a core-shell structure having a shell and a core, wherein the shell is a graphitized carbon layer and the core is nickel-palladium alloy nanoparticles; wherein the mass ratio of nickel to palladium in the composite material is 3:1 to 100:1; and the total mass fraction of nickel and palladium, based on the mass of the composite material, is 30% to 80%; the composite material is composed of the core-shell structure and a carbon matrix.

2. The composite material according to claim 1, characterized in that, In the composite material, the mass ratio of nickel to palladium is 4:1 to 100:1; based on the mass of the composite material, the total mass fraction of nickel and palladium is 50% to 78%.

3. The composite material according to claim 1, characterized in that, The nickel-palladium alloy nanoparticles have a particle size of 1 nm to 50 nm.

4. The composite material according to claim 3, characterized in that, The nickel-palladium alloy nanoparticles have a particle size of 2 nm to 25 nm.

5. The composite material according to claim 1, characterized in that, The thickness of the graphitized carbon layer is 0.5 nm to 5 nm.

6. A method for preparing the composite material according to claim 1, comprising: S1 In the presence of a first solvent, a nickel source, a palladium source and a poly-organic carboxylic acid are mixed to obtain a precursor solution, and then the first solvent is removed to obtain the precursor. S2 The precursor is pyrolyzed in an inert gas.

7. The preparation method according to claim 6, characterized in that, The first solvent is water and / or ethanol.

8. The preparation method according to claim 6, characterized in that, The palladium source is a glacial acetic acid solution of palladium acetate.

9. The preparation method according to claim 6, characterized in that, The mass ratio of the nickel source to the palladium source is 3:1 to 100:1, calculated by metal element.

10. The preparation method according to claim 6, characterized in that, In S2, the pyrolysis temperature is 550℃~650℃.

11. The preparation method according to claim 6, characterized in that, This includes the acid treatment step following S2.

12. A composite material of carbon-coated nickel-palladium alloy nanoparticles, characterized in that, Includes the composite material as described in claim 1 and thiourea loaded thereon.

13. The composite material according to claim 12, characterized in that, The mass fraction of sulfur in the elemental analysis is 0.5% to 5%.

14. A method for preparing a composite material of carbon-coated nickel-palladium alloy nanoparticles, comprising: The step of loading thiourea onto the composite material as described in claim 1.

15. The preparation method according to claim 14, characterized in that, The amount of thiourea, calculated as sulfur, is 0.01 to 20 mol relative to 1 mol of palladium in the composite material of claim 1.

16. The application of the composite material of claim 1 or 12 as a hydrogenation catalyst in a sulfur-containing catalytic hydrogenation system.

17. The application of the composite material of claim 1 or 12 in nitro groups of catalytically hydrogenated organic compounds.

18. A method for selectively hydrogenating a nitro group in a halonitroaromatic hydrocarbon, comprising: Under liquid-phase catalytic hydrogenation conditions, in the presence of sulfur-containing compounds, hydrogen gas and halonitroaromatic hydrocarbons are contacted with a catalyst to carry out a liquid-phase catalytic hydrogenation reaction; the catalyst is the composite material described in claim 1; the sulfur-containing compound is thiocyanate and / or thiourea, and the mass ratio of the sulfur-containing compound to the halonitroaromatic hydrocarbon is 1:100 to 1:10000.

19. A method for selectively hydrogenating a nitro group in a halonitroaromatic hydrocarbon, comprising: Under liquid-phase catalytic hydrogenation conditions, hydrogen gas and halonitroaromatic hydrocarbons are contacted with a catalyst to carry out a liquid-phase catalytic hydrogenation reaction; the catalyst is the composite material described in claim 12.

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