An ultrathin eggshell type high-dispersion catalyst, a preparation method and application thereof

Abstract

This invention belongs to the field of catalysts, specifically relating to an ultrathin eggshell-shaped highly dispersed selective hydrogenation catalyst, its preparation method, and its application. This eggshell-shaped catalyst comprises a support and active metal elements. The active metal elements, accounting for 95wt% to 99wt% of the total weight of the active metal elements, are distributed in an eggshell-shaped pattern within a shell less than 60μm thick on the support, with the dispersion of the active metal elements ranging from 50% to 80%. The active metal elements include a main metal element and optional auxiliary metal elements. The catalyst of this invention exhibits highly dispersed active metals within an extremely thin shell region on the support surface and demonstrates excellent performance in selective hydrogenation catalytic reactions.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to an ultrathin eggshell-type highly dispersed selective hydrogenation catalyst, its preparation method, and its application. Background Technology

[0002] Supported catalysts with metals as active components have wide applications in the petrochemical industry. Based on the different enrichment sites of the active components, they can generally be classified into four types: homogeneous, eggshell-shaped, yolk-shaped, and egg white-shaped. For noble metal supported catalysts, due to the scarcity and high cost of noble metals, appropriate methods are needed to enrich the noble metals on the support surface to form an eggshell-shaped catalyst, thereby improving the utilization rate of the noble metals. Furthermore, a thinner shell layer is more conducive to surface-based fast reactions and diffusion-controlled catalytic reactions. However, it is generally believed that active metals are very prone to agglomeration or aggregation during the preparation of eggshell-shaped catalysts, leading to decreased metal dispersion and utilization, and poor catalytic performance. Therefore, how to control the enrichment of active metals in the thin shell layer of the support while maintaining their uniform distribution, without changing the total amount of active metals, is currently a research hotspot and challenge.

[0003] CN101730588A discloses a catalyst for selective hydrogenation of alkynes and its preparation method. The method involves dissolving an active metal compound and a co-catalyst metal compound in a mixture of water and an organic solvent to obtain an impregnation solution, then impregnating a support with the impregnation solution, and finally calcining the impregnated support to obtain a catalyst in which at least 90% of the active component is present in a support with a thickness of up to 250 μm. The catalyst exhibits good performance in the selective hydrogenation of alkynes.

[0004] CN103769094A discloses an eggshell-type catalyst for selective hydrogenation reactions. The support is impregnated in aqueous solutions of a reducing agent, an auxiliary agent, and an active component, respectively. After drying, calcination, and reduction, an eggshell-type catalyst with low noble metal loading and low cost is obtained. It has the characteristics of high activity, good selectivity, and good stability in the selective hydrogenation reaction of C=C bonds in α,β-unsaturated carbonyl compounds.

[0005] CN111229216A discloses an eggshell-shaped silver catalyst, its preparation method, and its application. The catalyst is prepared by chemical energy migration-deposition, which involves impregnating an active precursor solution with the catalyst and then performing in-situ treatment to obtain an eggshell-shaped silver catalyst. The catalyst is suitable for the oxidative dehydrogenation of alcohols to aldehydes and epoxidation reactions, especially for catalyzing the oxidative dehydrogenation of isopentenol to isopentenaldehyde.

[0006] Existing technical solutions (such as CN101730588A, CN103769094A, and CN111229216A mentioned above) mostly employ the traditional impregnation method. The influencing factors (such as pH value, metal ion concentration, viscosity, and drying process) are numerous and complex, making it difficult to control parameters such as catalyst shell thickness, active metal loading, and dispersion. Furthermore, these methods often utilize various organic reducing agents, dispersants, and solvents, resulting in low environmental friendliness and making large-scale production difficult. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides an ultrathin eggshell-type highly dispersed catalyst, its preparation method, and its applications. This method starts by controlling the surface properties of the support, utilizing heat treatment, crystallization, irradiation, and other means to treat a mixture of carbon-containing alumina precursors, enriching and increasing the types and density of oxygen-containing groups on the alumina support surface. This allows the active metal to be distributed in a highly dispersed state within an extremely thin shell region on the support surface, and exhibits excellent performance in selective hydrogenation catalysis.

[0008] The first aspect of the present invention is to provide an eggshell-type catalyst, the catalyst comprising a support and an active metal element, wherein the thickness is calculated from the outer surface of the support towards the center, and the active metal element, accounting for 95wt% to 99wt% of the total weight of the active metal element, is distributed in a shell of the support with a thickness of less than 60μm and is distributed in an eggshell shape.

[0009] The dispersion of the active metal element is 50% to 80%;

[0010] The active metal element includes a main metal element and optional auxiliary metal elements.

[0011] In a preferred embodiment of the present invention, the thickness is calculated from the outer surface of the carrier towards the center, and 95wt% to 99wt% of the total weight of the active metal elements are distributed in a shell within a thickness of less than 50μm of the carrier; and / or,

[0012] In a preferred embodiment of the present invention, the dispersion of the active metal element is 60%–80%. In a preferred embodiment of the present invention, the average particle size of the active metal is less than 4 nm; and / or, in a preferred embodiment of the present invention, the specific surface area of ​​the catalyst is 20–150 m². 2 / g.

[0013] According to the present invention, the weight ratio of the main metal element to the weight of the carrier can be selected within a wide range. In a preferred embodiment of the present invention, the weight ratio of the main metal element to the weight of the carrier is (0.01 to 0.5):100.

[0014] According to the present invention, the main metal element can be selected from a wide range. In a preferred embodiment of the present invention, the main metal element is selected from at least one of the group VIIIB metal elements, preferably palladium.

[0015] According to the present invention, the ratio of the total weight of the auxiliary metal elements to the weight of the carrier can be selected within a wide range. In a preferred embodiment of the present invention, the ratio of the total weight of the auxiliary metal elements to the weight of the carrier is (0-5):100, based on the weight of the auxiliary metal elements.

[0016] According to the present invention, the auxiliary metal element can be selected from a wide range. In a preferred embodiment of the present invention, the auxiliary metal element is selected from at least one of Group IB, Group IIB, Group IIIA, Group IIIA and lanthanide metal elements, preferably at least one of silver, indium, gallium, cerium and zinc.

[0017] In a preferred embodiment of the present invention, the catalyst is prepared by impregnating the support with a solution containing an active metal element source and activating it in an optional sequence to obtain the catalyst.

[0018] The carrier is an alumina carrier, and the surface of the alumina carrier has oxygen-containing groups, the density of which is 0.1-0.9 mmol / m³. 2 Wherein, the oxygen-containing group is at least one of hydroxyl, carboxyl, and lactone groups; the specific surface area of ​​the alumina support is 20-150 m². 2 / g; Preferably:

[0019] The content of the hydroxyl groups is 4-40 mmol / g; and / or,

[0020] The content of the carboxyl groups is 2.5-30 mmol / g; and / or,

[0021] The content of the lactone group is 0.05-20 mmol / g.

[0022] In a preferred embodiment of the present invention, the carrier is prepared by the following method:

[0023] The dry materials, including alumina precursor, molding and pore-expanding agent, and inorganic carbon, are mixed with liquid, kneaded, granulated, and surface modified to obtain the alumina carrier; the inorganic carbon is selected from at least one of charcoal, bamboo charcoal, coconut shell charcoal, graphene, graphyne and diamond.

[0024] The surface modification method is: heat treatment; or heat treatment and crystallization; or heat treatment and irradiation; or irradiation and crystallization.

[0025] The heat treatment conditions include: the heat treatment atmosphere includes a first atmosphere and a second atmosphere, the first atmosphere is selected from at least one of air, nitrogen and carbon dioxide, the second atmosphere is selected from water vapor, the volume ratio of the first atmosphere and the second atmosphere is (1~2):1, the heat treatment temperature is 300-1200℃, and the heat treatment time is 1-24h.

[0026] According to the present invention, the crystallization conditions can be selected within a wide range. In a preferred embodiment of the present invention, the crystallization conditions include at least one of the following conditions: 150-250°C, 2-24h, 0.2-10 MPa, water as the solvent, and pH of the solution used for crystallization being 8-14.

[0027] In a preferred embodiment of the present invention, the irradiation conditions include: the radiation source being selected from gamma rays, and / or the irradiation dose being 1 to 20 kGy.

[0028] In a preferred embodiment of the present invention, the amount of inorganic carbon is 1-30 parts by weight relative to 100 parts of alumina precursor.

[0029] In a preferred embodiment of the present invention, when the inorganic carbon is charcoal, bamboo charcoal, or coconut shell charcoal, surface modification is performed by heat treatment and crystallization; when the inorganic carbon species is graphene, graphyne, or diamond, surface modification is performed by heat treatment and irradiation; or, surface modification is performed by irradiation and crystallization.

[0030] According to the present invention, the alumina precursor can be selected from a wide range. In a preferred embodiment of the present invention, the alumina precursor is selected from at least one of boehmite, α-alumina, θ-alumina, γ-alumina, and amorphous alumina, preferably at least one of boehmite, α-alumina, and γ-alumina.

[0031] According to the present invention, the molding and expanding agent can be selected from a wide range. In a preferred embodiment of the present invention, the molding and expanding agent is at least one of polyethylene glycol cellulose, methylcellulose, carboxymethyl cellulose, ethylcellulose, hydroxyethyl cellulose, and starch, and at least one of polyvinyl alcohol, polyethylene glycol, polyacrylamide, polypropylene glycol, and guar gum powder.

[0032] According to the present invention, the ratio of the mass of the molding pore expander to the total mass of the dry material can be selected within a wide range. In a preferred embodiment of the present invention, the ratio of the mass of the molding pore expander to the total mass of the dry material is (0.5 to 25):100.

[0033] In a preferred embodiment of the present invention, the liquid is an acidic solution. Preferably, the acidic solution is selected from at least one aqueous solution of acetic acid, oxalic acid, diacetic acid, maleic acid, citric acid, oxalic acid, formic acid, tartaric acid, nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid, and / or the concentration of the acidic solution is 0.01 to 5 mol / L, preferably 0.2 to 4 mol / L.

[0034] A second aspect of the present invention is to provide a method for preparing the catalyst described in the first aspect, comprising:

[0035] The catalyst is obtained by impregnating the support with a solution containing an active metal element source and activating it in an optional sequence; the active metal element source includes a main metal element source and an optional auxiliary metal element source.

[0036] The carrier is an alumina carrier, and the surface of the alumina carrier has oxygen-containing groups, the density of which is 0.1-0.9 mmol / m³. 2 ;

[0037] Wherein, the oxygen-containing group is at least one selected from hydroxyl, carboxyl, and lactone groups; the specific surface area of ​​the alumina support is 20-150 m². 2 / g; Preferably:

[0038] The content of the hydroxyl groups is 4-40 mmol / g; and / or,

[0039] The content of the carboxyl groups is 2.5-30 mmol / g; and / or,

[0040] The content of the lactone group is 0.05-20 mmol / g.

[0041] The preferred preparation method of the carrier described in this invention is as described in the first aspect, and will not be repeated here.

[0042] According to the present invention, the main metal element source can be selected from a wide range. In a preferred embodiment of the present invention, the main metal element source is selected from at least one of soluble compounds containing a main metal element, preferably at least one of water-soluble palladium compounds; more preferably at least one of palladium nitrate, palladium chloride, sodium chloropalladium, palladium oxalate, and palladium citrate.

[0043] Preferably, the content of palladium compound, calculated as metal element, is in a weight ratio of (0.01-0.5):100 to the carrier, more preferably (0.02-0.45):100.

[0044] According to the present invention, the source of the auxiliary metal element can be selected from a wide range. In a preferred embodiment of the present invention, the source of the auxiliary metal element is selected from at least one of soluble compounds containing the auxiliary metal element, preferably a water-soluble salt compound of the auxiliary metal element. For example, the auxiliary metal compound is at least one of the soluble salt compounds of silver, indium, gallium, cerium, and zinc; the content of the auxiliary metal compound, calculated as metal element, is in a weight ratio of (0-5):100 to the carrier, preferably (0.02-4):100.

[0045] In a preferred embodiment of the present invention, the activation method includes a roasting stage, an irradiation stage, or an optional sequential roasting and irradiation stage. Preferably,

[0046] The calcination conditions include: 150–750°C, and / or, 4–20 h, and / or, an atmosphere of at least one selected from air, nitrogen, hydrogen, and argon. Preferably, the calcination conditions are 180–725°C for 6–18 h; the atmosphere is at least one selected from air, nitrogen, hydrogen, and argon, preferably at least one selected from air, nitrogen, and hydrogen.

[0047] In a preferred embodiment of the present invention, the irradiation conditions include: the radiation source being selected from gamma rays, and / or the irradiation dose being 1 to 20 kGy, preferably 4 to 18 kGy.

[0048] The impregnation solution used is an aqueous solution of a palladium compound, an auxiliary metal compound, or a mixture of the two.

[0049] According to the present invention, when there are two or more impregnation solutions, the impregnation can be stepwise impregnation or simultaneous impregnation; when stepwise impregnation is used, each impregnation needs to be dried before the next impregnation, and stepwise calcination and activation can be adopted, or calcination and activation can be carried out at one time after all components are loaded.

[0050] According to the present invention, the number of impregnations is one or more, and the activation is optionally performed before, after, or between multiple impregnations; preferably, when the activation comprises multiple stages, some stages of the activation are optionally performed before, after, or between multiple impregnations.

[0051] A third aspect of the present invention is to provide an application of the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect in the field of catalytic hydrogenation;

[0052] Preferred application in the catalytic hydrogenation of acetylene to produce ethylene.

[0053] Compared with the prior art, the advantages of the present invention are:

[0054] (1) The catalyst of the present invention: 95wt to 99wt% of the total weight of active metal elements are distributed in a shell layer with a thickness of less than 60μm on the support. Compared with conventional eggshell catalysts, it has a thinner shell layer, which is more conducive to fast surface reaction and diffusion-controlled catalytic reaction.

[0055] (2) The catalyst of the present invention has a dispersion of 50% to 80% of active metal elements, which is higher than that of conventional eggshell catalysts. The atomic utilization rate of active metals is higher, which can significantly reduce the cost of catalyst.

[0056] (3) The present invention uses a specific alumina support with a high content and density of oxygen-containing groups to prepare the catalyst. This not only reduces the requirements for impregnation conditions, but also allows the active metal to be distributed in the extremely thin shell area on the surface of the alumina support while weakening its growth, agglomeration or aggregation, thus exhibiting a highly dispersed state. The control of the catalyst is more precise and accurate.

[0057] (4) The catalyst of the present invention exhibits excellent performance in selective hydrogenation catalysis. Attached Figure Description

[0058] Figure 1 SEM results of the active palladium metal of catalyst C1 in Example 1.

[0059] Figure 2 SEM results of the active palladium metal in catalyst D1 in Comparative Example 1. Detailed Implementation

[0060] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0061] Example 1

[0062] Take 200g of boehmite powder, 6g of methylcellulose, 6g of polypropylene glycol, and 5g of charcoal, and mix them evenly. Add 20ml of a mixed solution of 0.8mol / L nitric acid and 0.5mol / L citric acid to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, and then heat-treat at 1080℃ for 2h in air and water vapor (volume ratio 1.5:1) to obtain alumina support A1. Then, take 50g of A1 and impregnate it in 60ml of a solution containing 0.034g of palladium chloride for 3h, dry at 110℃ for 4h, and calcine at 400℃ in a hydrogen atmosphere for 12h to obtain catalyst C1.

[0063] Example 2

[0064] Take 100g of α-alumina, 50g of amorphous alumina, 6g of methylcellulose, 6g of polypropylene glycol, and 7g of diamond, and mix them evenly. Add 40ml of a mixed solution of 2mol / L oxalic acid and 1mol / L acetic acid to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, then heat-treat at 350℃ for 12h with nitrogen, carbon dioxide, and water vapor (volume ratio 1:1:1), and then crystallize in an aqueous solution at 340℃, 9MPa, and pH 13 for 3h to obtain alumina support A2. Then, take 50g of A2 and impregnate it in 60ml of a solution containing 0.034g of palladium chloride for 3h, dry at 110℃ for 4h, and calcine at 700℃ in air atmosphere for 5h to obtain catalyst C2.

[0065] Example 3

[0066] Take 100g of α-alumina, 50g of θ-alumina, 5g of methylcellulose, 5g of starch, 5g of polypropylene glycol, 5g of guar gum powder, 5g of bamboo charcoal, and 5g of coconut shell charcoal, and mix them evenly. Add 45ml of 1.5mol / L sulfuric acid solution to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, crystallize in an aqueous solution at 150℃, 0.3MPa, and pH 8 for 12h, and then heat-treat with carbon dioxide and water vapor (volume ratio 1:1) at 350℃ for 12h to obtain alumina support A3. Then, take 50g of A3 and impregnate it in 60ml of a solution containing 0.037g of palladium oxalate for 3h, dry at 110℃ for 4h, calcine at 150℃ in air atmosphere for 23h, and irradiate with 10kGy of γ-rays to obtain catalyst C3.

[0067] Example 4

[0068] Take 100g of α-alumina, 50g of θ-alumina, 5g of methylcellulose, 5g of starch, 5g of polypropylene glycol, 5g of guar gum powder, 3g of graphene, and 3g of graphyne, and mix them thoroughly. Add 30mL of a mixed solution of 0.5mol / L hydrochloric acid and 0.2mol / L hypochlorous acid to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, then crystallize in an aqueous solution at 245℃, 5MPa, and pH 12 for 22h, and then irradiate with γ-rays for 3kGy to obtain alumina support A4. Then, take 50g of A4 and impregnate it in 60ml of a solution containing 0.037g of palladium oxalate for 3h, and irradiate with γ-rays for 5kGy to obtain catalyst C4.

[0069] Example 5

[0070] Take 80g of amorphous alumina, 40g of boehmite, 10g of starch, 10g of guar gum powder, and 15g of diamond, and mix them thoroughly. Add 25mL of 0.5mol / L nitric acid solution to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, irradiate with 18kGy of gamma rays, and then heat-treat at 650℃ for 6h with air, carbon dioxide, and water vapor (volume ratio 1:1:1) to obtain alumina support A5. Then, take 50g of A5 and impregnate it in 60ml of a mixed solution containing 0.108g of palladium nitrate and 0.039g of silver nitrate for 3h, and irradiate with 5kGy of gamma rays to obtain catalyst C5.

[0071] Example 6

[0072] Take 80g of amorphous alumina, 40g of boehmite, 10g of starch, 10g of guar gum powder, and 15g of diamond, and mix them thoroughly. Add 50mL of 3.5mol / L phosphoric acid solution to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, then heat-treat with air and water vapor (volume ratio 1:1) at 650℃ for 6h to obtain alumina support A6. Take 50g of A6 and impregnate it in 60ml of solution containing 0.108g of palladium nitrate for 3h, dry at 110℃ for 4h, then impregnate it in 0.039g of silver nitrate solution for 3h, and irradiate with 2kGy of gamma rays to obtain catalyst C6.

[0073] Example 7

[0074] Take 80g of amorphous alumina, 40g of boehmite, 10g of starch, 10g of guar gum powder, 4g of coconut shell charcoal, and 6g of bamboo charcoal, and mix them evenly. Add 50mL of a mixed solution of 1.5mol / L formic acid, 1.5mol maleic acid, and 0.5mol / L diacetic acid to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, irradiate with 10kGy for 4h, and then crystallize in an aqueous solution at 190℃, 2MPa, and pH 10 for 4h to obtain alumina carrier A7. Another 50g of A7 was impregnated in 60ml of a solution containing 4.34g of zinc nitrate for 3h, dried at 110℃ for 4h, then impregnated in a solution containing 0.344g of sodium chloropalladium for 3h, dried at 110℃ for 4h, calcined at 500℃ in a hydrogen atmosphere for 8h, and then impregnated in a solution containing 1.55g of cerium nitrate. After irradiation with 10kGy of γ-rays, catalyst C7 was obtained.

[0075] Example 8

[0076] Take 80g of amorphous alumina, 40g of boehmite, 10g of starch, 10g of guar gum powder, 4g of graphene, and 6g of diamond, and mix them evenly. Add 50mL of a mixed solution of 1.0mol / L oxalic acid and 0.5mol / L nitric acid to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Irradiate with 15kGy of gamma rays, and then heat-treat at 650℃ for 8h in carbon dioxide and water vapor (volume ratio 1:1) to obtain alumina support A8. Take 50g of A8, impregnate it in 60ml of a solution containing 6.75g of zinc sulfate for 3h, dry it at 110℃ for 4h, calcine it in air and nitrogen (volume ratio 1:1) at 400℃ for 4h, and then impregnate it in a solution containing 0.344g of sodium chloropalladium for 3h, and calcine it in a hydrogen atmosphere at 500℃ for 6h to obtain catalyst C8.

[0077] Comparative Example 1

[0078] Take 200g of boehmite powder, 6g of methylcellulose, 6g of polypropylene glycol, 3g of charcoal, 3g of bamboo charcoal, 3g of coconut shell charcoal, 3g of graphene, 3g of graphyne, and 3g of diamond, and mix them evenly. Add 20ml of a mixed solution of 0.8mol / L nitric acid and 0.5mol / L citric acid to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, and then heat-treat in air at 1080℃ for 2h to obtain alumina support B1. Then, take 50g of B1 and impregnate it in 60ml of a solution containing 0.034g of palladium chloride for 3h, dry at 110℃ for 4h, and calcine at 400℃ in a hydrogen atmosphere for 12h to obtain catalyst D1.

[0079] Comparative Example 2

[0080] Take 100g of α-alumina, 50g of amorphous alumina, 6g of methylcellulose, and 6g of polypropylene glycol, and mix them thoroughly. Add 40ml of a mixed solution of 2mol / L oxalic acid and 1mol / L acetic acid to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, then heat-treat at 350℃ for 12h with nitrogen, carbon dioxide, and water vapor (volume ratio 1:1:1), and then crystallize in an aqueous solution at 340℃, 9MPa, and pH 13 for 3h to obtain alumina support B2. Then, take 50g of B2 and impregnate it in 60ml of a solution containing 0.034g of palladium chloride for 3h, dry at 110℃ for 4h, and calcine at 700℃ in air atmosphere for 5h to obtain catalyst D2.

[0081] Comparative Example 3

[0082] Take 100g of α-alumina, 50g of θ-alumina, 5g of methylcellulose, 5g of starch, 5g of polypropylene glycol, and 5g of guar gum powder, and mix them evenly. Add 30mL of a mixed solution of 0.5mol / L hydrochloric acid and 0.2mol / L hypochlorous acid to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, then crystallize in an aqueous solution at 245℃, 5MPa, and pH 12 for 22h, and then irradiate with γ-rays for 3kGy to obtain alumina support B3. Then, take 50g of B3 and impregnate it in 60ml of a solution containing 0.037g of palladium oxalate for 3h, and irradiate with γ-rays for 5kGy to obtain catalyst D3.

[0083] Comparative Example 4

[0084] Take 80g of amorphous alumina, 40g of boehmite, 10g of starch, and 10g of guar gum powder, and mix them evenly. Add 25mL of 0.5mol / L nitric acid solution to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a diameter of 3mm. Dry at 110℃ for 4h, irradiate with 18kGy of gamma rays, and then heat-treat at 650℃ for 6h with air, carbon dioxide, and water vapor (volume ratio 1:1:1) to obtain alumina support B4. Then, take 50g of B4 and impregnate it in 60ml of a mixed solution containing 0.108g of palladium nitrate and 0.039g of silver nitrate for 3h, and irradiate with 5kGy of gamma rays to obtain catalyst D4.

[0085] Comparative Example 5

[0086] Take 80g of amorphous alumina, 40g of boehmite, 10g of starch, and 10g of guar gum powder, and mix them evenly. Add 50mL of 3.5mol / L phosphoric acid solution to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, then heat-treat with air and water vapor (volume ratio 1:1) at 650℃ for 6h to obtain alumina support B5. Take 50g of B5 and impregnate it in 60ml of solution containing 0.108g of palladium nitrate for 3h, dry it at 110℃ for 4h, then impregnate it in solution containing 0.039g of silver nitrate for 3h, and irradiate with 2kGy of gamma rays to obtain catalyst D5.

[0087] Comparative Example 6

[0088] Take 80g of amorphous alumina, 40g of boehmite, 10g of starch, and 10g of guar gum powder, and mix them evenly. Add 50mL of a mixed solution of 1.5mol / L formic acid, 1.5mol maleic acid, and 0.5mol / L diacetic acid to the mixed powder, then knead, extrude, shape, and granulate to obtain spherical particles with a particle size of 3mm. Dry at 110℃ for 4h, irradiate with 10kGy for 4h, and then crystallize in an aqueous solution at 190℃, 2MPa, and pH 10 for 4h to obtain alumina support B6. Another 50g of B6 was impregnated in 60ml of a solution containing 4.34g of zinc nitrate for 3h, dried at 110℃ for 4h, then impregnated in a solution containing 0.344g of sodium chloropalladium for 3h, dried at 110℃ for 4h, calcined at 500℃ in a hydrogen atmosphere for 8h, and then impregnated in a solution containing 1.55g of cerium nitrate. After irradiation with 10kGy of γ-rays, catalyst D6 was obtained.

[0089] Detection example

[0090] Carrier physical property specific surface area determination: measured by nitrogen physical adsorption BET method.

[0091] Determination of oxygen-containing group density on the carrier: The properties and quantity of oxygen-containing groups on the carrier were determined using the Boehm chemical method. Three 1g portions of carrier samples were weighed and soaked in 50ml of 0.05mol / L NaHCO3, Na2CO3, and NaOH solutions, respectively, for 24h. 10ml of the soaking solution was titrated with 0.06mol / L hydrochloric acid. Each sample was titrated three times, and the arithmetic mean was taken. The quantity of each type of oxygen-containing group on the carrier surface was calculated based on the amount of alkali consumed. The oxygen-containing group density was then obtained by combining this with the carrier specific surface area data.

[0092] Determination of active metal distribution on catalyst surface: The catalyst sample particles were cut in half, and the distribution of active elements on the cross-section was analyzed using a JSM-7900F scanning electron microscope equipped with an EDX elemental analysis attachment. The shell thickness L corresponding to an active metal content exceeding 95% in the shell region (where the active metal content is less than 0.01% from the outside to the inside) was calculated (measurements were taken at three different locations for each cross-section, and the average value was taken).

[0093] Palladium content determination in catalyst: The palladium metal content in the catalyst was determined by conventional ICP-MS method.

[0094] Determination of the dispersion of active metals in the catalyst: Using a Chemisorb 2920 chemical adsorption instrument, 0.1 g of catalyst sample was weighed, reduced with hydrogen at 160℃ for 30 min, purged with nitrogen for 10 min, and then cooled to 40℃ for CO pulse adsorption until adsorption saturation. The dispersion of active metals was calculated by measuring the adsorption amount and palladium content.

[0095] Determination of active metal particle size distribution in catalysts: Catalyst sample particles were cut to approximately 0.5 mm from their surface, ground, and reduced with hydrogen at 160℃ for 1 h. The powdered sample was then added to a solution of water and ethanol (volume ratio 4:1), ultrasonically dispersed, and 4–6 drops of the dispersion were dropped onto a copper mesh using a dropper. After drying under an infrared lamp for 15 min, the mesh was directly transferred to an electron microscope. Four images were acquired for each sample, and the particle size of at least 200 particles was calculated.

[0096] Catalytic performance test: 10 ml of catalyst was loaded into a tubular reactor, purged with nitrogen, and then reduced with hydrogen at 160 °C for 3 h; after natural cooling to room temperature, nitrogen was purged and replaced, and the catalyst was subjected to a space velocity of 20,000 h⁻¹. -1 The performance was tested in the C2 reactant (material 1) under a pressure of 2 MPa (Test 1); the above steps and conditions were repeated to test the performance in the C2 reactant (material 2) (Test 2).

[0097] Material 1 composition: 1000ppm acetylene, 800ppm carbon monoxide, 13% hydrogen, 12% ethane, 1% methane, 20% propylene, 0.3% propadiene, 0.2% propyne, 0.9% propane, with the remainder being ethylene.

[0098] Material 2 composition: 1000ppm acetylene, 900ppm carbon monoxide, 26% hydrogen, 14% ethane, 3% methane, and the remainder is ethylene.

[0099] The lowest temperature corresponding to an acetylene concentration of 0 ppm in the outlet gas and the ethylene selectivity were investigated.

[0100] The formula for calculating ethylene selectivity is as follows:

[0101] Ethylene selectivity = [(Outlet ethylene content - Inlet ethylene content) / (Inlet acetylene content)] × 100%

[0102] Table 1. Measurement results of oxygen-containing groups on alumina supports in examples and comparative examples

[0103]

[0104]

[0105] Table 2. Physicochemical property characterization results of the catalysts in the examples and comparative examples.

[0106]

[0107]

[0108] Table 3. Catalytic performance evaluation results of the catalysts in the examples and comparative examples.

[0109]

[0110] As shown in Table 1, the carrier modification method described in this invention can significantly increase the content and density of various oxygen-containing groups on the surface of the alumina carrier. Furthermore, through… Figure 1 and Figure 2 As can be seen from the comparison and Table 2, the catalysts in the examples are significantly different from the comparative catalysts. The active metals of the catalysts in the examples are all enriched in an extremely thin shell (less than 60 μm) and the dispersion is more than 55%, with an average particle size of less than 4 nm. This is mainly due to the high density and variety of oxygen-containing groups on the surface of the support in the examples.

[0111] The results in Table 3 show that, under the same condition of achieving an acetylene outlet concentration of 0 ppm (i.e., an acetylene conversion rate of 100%), the temperature required for the catalyst in the examples is lower than that for the corresponding comparative catalyst, indicating that the catalyst in the examples has better activity. Furthermore, when the acetylene conversion rate is 100%, the selectivity of the catalyst in the examples is also superior to that of the corresponding comparative catalyst. Therefore, the performance of the catalyst in the examples is superior to that of the comparative catalyst, achieving unexpected technical effects.

[0112] In two typical C2 selective hydrogenation reactions (Table 3), the catalysts in the examples showed significantly better activity and selectivity than the comparative catalysts. This can be attributed to the fact that C2 selective hydrogenation is a surface-fast and diffusion-controlled catalytic reaction. The more concentrated and dispersed the active metal distribution on the outer layer of the catalyst (atomic utilization), the better its activity. Furthermore, ethylene desorption is easier, the diffusion path from the catalyst surface to the gas phase is shorter, and the probability of over-hydrogenation is lower, thus resulting in higher catalyst selectivity.

[0113] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[0114] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0115] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0116] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0117] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0118] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be obviously unreasonable.

Claims

1. An eggshell-shaped catalyst, the catalyst comprising a support and an active metal element, wherein the thickness of the active metal element is calculated from the outer surface of the support towards the center, and the active metal element, accounting for 95wt% to 99wt% of the total weight of the active metal element, is distributed in a shell of the support with a thickness of less than 60μm and is distributed in an eggshell shape. The dispersion of the active metal element is 50%~80%; The active metal element includes a main metal element and an auxiliary metal element, or the active metal element contains only the main metal element; The carrier is an alumina carrier, and the surface of the alumina carrier has oxygen-containing groups, the density of which is 0.1-0.9 mmol / m³. 2 ; The alumina precursor is surface modified by dry materials including inorganic carbon, wherein the surface modification method is: heat treatment; or heat treatment and crystallization; or heat treatment and irradiation; or irradiation and crystallization.

2. The catalyst according to claim 1, characterized in that: Calculating the thickness from the outer surface of the carrier towards the center, 95wt% to 99wt% of the total weight of the active metal elements are distributed within a shell of less than 50μm in thickness within the carrier; and / or, The dispersion of the active metal element is 60%~80%; and / or, The average particle size of the active metal is less than 4 nm; and / or, The catalyst has a specific surface area of ​​20-150 m². 2 / g.

3. The catalyst according to claim 1, characterized in that: The weight ratio of the main metallic element to the carrier is 0.01~0.5:100, based on the weight of the main metallic element; and / or, The main metallic element is selected from at least one of Group VIIIB metallic elements; and / or, Based on the weight of the auxiliary metal elements, the ratio of the total weight of the auxiliary metal elements to the weight of the carrier is 0~5:100; and / or, The auxiliary metal element is selected from at least one of Group IB, Group IIB, Group IIIA, Group IIIA, and lanthanide metal elements.

4. The catalyst according to claim 1, characterized in that: The main metallic element is selected as palladium; and / or, The auxiliary metal element is selected from at least one of silver, indium, gallium, cerium, and zinc.

5. The catalyst according to any one of claims 1-4, characterized in that: The catalyst is prepared by impregnating the support with a solution containing an active metal element source and activating it to obtain the catalyst. Wherein, the oxygen-containing group is at least one selected from hydroxyl, carboxyl, and lactone groups; the specific surface area of ​​the alumina support is 20-150 m². 2 / g.

6. The catalyst according to claim 5, characterized in that: The content of the hydroxyl groups is 4-40 mmol / g; and / or, The content of the carboxyl groups is 2.5-30 mmol / g; and / or, The content of the lactone group is 0.05-20 mmol / g.

7. The catalyst according to claim 5, characterized in that, The carrier was prepared by the following method: The dry materials, including alumina precursor, molding and pore-expanding agent, and inorganic carbon, are mixed with liquid, kneaded, granulated, and surface modified to obtain the alumina carrier; the inorganic carbon is selected from at least one of charcoal, bamboo charcoal, coconut shell charcoal, graphene, graphyne, and diamond. The heat treatment conditions include: the heat treatment atmosphere includes a first atmosphere and a second atmosphere, the first atmosphere is selected from at least one of air, nitrogen and carbon dioxide, the second atmosphere is selected from water vapor, the volume ratio of the first atmosphere and the second atmosphere is 1~2:1, the heat treatment temperature is 300-1200℃, and the heat treatment time is 1-24h.

8. The catalyst according to claim 7, characterized in that: The crystallization conditions include at least one of the following: 150~250℃, 2~24h, 0.2~10MPa, water as solvent, and pH of the solution used for crystallization being 8~14; And / or, The irradiation conditions include: the radiation source being selected from gamma rays, and / or the irradiation dose being 1~20 kGy.

9. The catalyst according to claim 7, characterized in that: The amount of inorganic carbon used is 1-30 parts by weight relative to 100 parts of alumina precursor; and / or, When the inorganic carbon is wood charcoal, bamboo charcoal, or coconut shell charcoal, surface modification is carried out by heat treatment and crystallization; when the inorganic carbon species is graphene, graphyne, or diamond, surface modification is carried out by heat treatment and irradiation; or, surface modification is carried out by irradiation and crystallization.

10. The catalyst according to claim 7, characterized in that: The alumina precursor is selected from at least one of boehmite, α-alumina, θ-alumina, γ-alumina, and amorphous alumina; and / or, The molding and expanding agent is at least one of polyethylene glycol cellulose, methylcellulose, carboxymethyl cellulose, ethylcellulose, hydroxyethyl cellulose, and starch, and at least one of polyvinyl alcohol, polyethylene glycol, polyacrylamide, polypropylene glycol, and guar gum powder; and / or, The mass ratio of the molding pore-expanding agent to the total mass of the dry material is 0.5~25:

100.

11. The catalyst according to claim 7, characterized in that: The liquid is an acidic solution.

12. The catalyst according to claim 11, characterized in that: The acidic solution is selected from at least one of aqueous solutions of acetic acid, oxalic acid, maleic acid, citric acid, oxalic acid, formic acid, tartaric acid, nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid, and / or the concentration of the acidic solution is 0.01~5 mol / L.

13. A method for preparing a catalyst according to any one of claims 1-12, comprising: The catalyst is obtained by immersing the support in a solution containing an active metal element source and activating it. The active metal element source includes a main metal element source and an optional auxiliary metal element source; The carrier is an alumina carrier, and the surface of the alumina carrier has oxygen-containing groups, the density of which is 0.1-0.9 mmol / m³. 2 ; Wherein, the oxygen-containing group is at least one selected from hydroxyl, carboxyl, and lactone groups; the specific surface area of ​​the alumina support is 20-150 m². 2 / g.

14. The preparation method according to claim 13, characterized in that: The content of the hydroxyl groups is 4-40 mmol / g; and / or, The content of the carboxyl groups is 2.5-30 mmol / g; and / or, The content of the lactone group is 0.05-20 mmol / g.

15. The preparation method according to claim 13, characterized in that: The main metal element source is selected from at least one soluble compound containing a main metal element, and / or, the content of the palladium compound, calculated as metal element, is in a weight ratio of 0.01~0.5:100 to the carrier; and / or, The auxiliary metal element source is selected from at least one of soluble compounds containing the auxiliary metal element; and / or, Compounds containing auxiliary metal elements, with a weight ratio of metal element to carrier of 0~5:

100.

16. The preparation method according to claim 13, characterized in that: The main metal element source is selected from at least one water-soluble palladium compound; and / or, The source of the auxiliary metal element is selected from water-soluble auxiliary metal element salt compounds.

17. The preparation method according to claim 13, characterized in that: The main metal element source is selected from at least one of water-soluble palladium compounds; the palladium compound is at least one of palladium nitrate, palladium chloride, sodium chloropalladium, palladium oxalate, and palladium citrate.

18. The preparation method according to any one of claims 13-17, characterized in that: The activation method includes a roasting stage, an irradiation stage, or a roasting stage and an irradiation stage performed in any order; And / or, The irradiation conditions include: the radiation source being selected from gamma rays, and / or the irradiation dose being 1~20 kGy.

19. The preparation method according to any one of claims 13-17, characterized in that: The activation method includes a roasting stage, or an irradiation stage, or a roasting stage and an irradiation stage. The roasting conditions include: 150~750℃, and / or 4~20h, and / or an atmosphere of at least one of air, nitrogen, hydrogen, and argon.

20. The preparation method according to any one of claims 13-17, characterized in that: The immersion is performed once or multiple times, and the activation is performed before, after, or between multiple immersions.

21. The preparation method according to claim 20, characterized in that: When the activation comprises multiple stages, some of the activation stages are performed before impregnation, after impregnation, or in the intervals between multiple impregnations.

22. The application of a catalyst according to any one of claims 1-12 or a catalyst prepared by any one of claims 13-21 in the field of catalytic hydrogenation.

23. The application according to claim 22, characterized in that: The application is in the catalytic hydrogenation of acetylene to produce ethylene.

Images