Eggshell-type catalyst, modified carrier, and preparation method therefor and use thereof

Abstract

The present invention relates to an ultrathin eggshell-type high-dispersion selective hydrogenation catalyst, a modified carrier, and a preparation method therefor and the use thereof. The eggshell-type catalyst comprises a carrier and an active metal element, wherein by calculating the thickness from the outer surface, as the starting point, of the carrier to the center, the active metal element, which accounts for 95-99 wt% of the total weight of the active metal element, is distributed in the shell having a thickness within 60 μm of the carrier and is distributed in an eggshell type; and the dispersity of the active metal element is 50-80%. The active metal in the catalyst of the present invention is distributed in an extremely thin shell region on the surface of the carrier, is also in a highly dispersed state, and exhibits good performance in a selective hydrogenation catalytic reaction.

Description

Eggshell-type catalyst, modified carrier, preparation method and application thereof Technical Field

[0001] The present invention belongs to the field of catalysts, and in particular relates to an ultra-thin eggshell-type highly dispersed selective hydrogenation catalyst, a modified carrier, and a preparation method and application thereof. Background Art

[0002] Supported catalysts with metals as active components are widely used in the field of petrochemicals. Depending on the different locations where the active components are enriched, they can generally be divided into four forms: uniform, eggshell, yolk, and egg white. For noble metal supported catalysts, due to the scarcity and high price of noble metal resources, appropriate methods need to be adopted to enrich the noble metals on the surface of the carrier to form eggshell catalysts to improve the utilization rate of the noble metals. The thinner the shell, the more conducive it is to surface fast reaction and diffusion-controlled catalytic reactions. However, it is generally believed that during the preparation of eggshell catalysts, active metals are very prone to agglomeration or aggregation, resulting in a decrease in metal dispersion and utilization, and poor catalytic performance. Therefore, how to control the enrichment of active metals in the thin shell of the carrier while maintaining their uniform distribution under the premise of keeping the total amount of active metals unchanged is a current research hotspot and difficulty.

[0003] CN101730588A discloses a catalyst for selective hydrogenation of alkynes and a preparation method thereof. An active metal compound and a promoter metal compound are dissolved in a mixture of water and an organic solvent to obtain an impregnation solution, a carrier is then impregnated with the impregnation solution, and the impregnated carrier is finally calcined to obtain a catalyst in which at least 90% of the active components are present on a carrier with a thickness of up to 250 μm.

[0004] CN103769094A discloses an eggshell-type catalyst for selective hydrogenation reaction. The carrier is immersed 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 precious metal loading and low cost is obtained.

[0005] CN111229216A discloses an eggshell-shaped silver catalyst, its preparation method, and application. The eggshell-shaped silver catalyst is obtained by first impregnating an active precursor solution and then performing in-situ treatment using a chemical energy transfer-deposition method. The catalyst is suitable for oxidative dehydrogenation of alcohols to produce aldehydes and epoxidation reactions, especially for catalyzing the oxidative dehydrogenation of isopentenol to produce isopentenal.

[0006] Existing technical solutions (such as the aforementioned CN101730588A, CN103769094A, and CN111229216A) mostly employ traditional impregnation methods, which are subject to numerous and complex influencing factors (such as pH, metal ion concentration, viscosity, and drying process), making parameters such as catalyst shell thickness, active metal loading, and dispersion difficult to control. Furthermore, these methods often utilize various organic reducing agents, dispersants, and solvents, making them less environmentally friendly and difficult to scale up for production.

[0007] Summary of the Invention

[0008] To address the problems of the prior art, the present invention provides an eggshell-type catalyst, particularly an ultrathin eggshell-type highly dispersed catalyst, a modified support, and its preparation method and application. The modified support preparation method utilizes heat treatment, crystallization, and irradiation to treat a carbon-containing compound support precursor mixture by regulating the support's surface properties, thereby enriching and increasing the types and density of oxygen-containing groups on the support surface. The catalyst prepared from this modified support achieves a highly dispersed distribution of active metals within an extremely thin shell region on the support surface, exhibiting excellent performance in selective hydrogenation catalytic reactions.

[0009] The first aspect of the present invention is to provide an eggshell-shaped, particularly ultrathin eggshell-shaped, highly dispersed catalyst, comprising a carrier and an active metal element, wherein the active metal element, accounting for 95% to 99% by weight of the total weight of the active metal element, is distributed in an eggshell-shaped shell within a thickness of 60 μm of the carrier, as measured from the outer surface of the carrier toward the center.

[0010] The dispersion degree of the active metal elements is 50% to 80%.

[0011] In one embodiment of the present invention, the active metal element includes a main metal element and an optional auxiliary metal element.

[0012] In one embodiment of the present invention, 95% to 99% by weight of the active metal elements, accounting for 95% to 99% by weight of the total weight of the active metal elements, are distributed in a shell within 50 μm of the carrier, with the thickness calculated from the outer surface of the carrier toward the center; and / or

[0013] In one embodiment of the present invention, the dispersion of the active metal elements is 60% to 80%, preferably greater than 70%, more preferably 71-80%, such as 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%; and / or

[0014] In one embodiment of the present invention, the average particle size of the active metal is less than 4 nm, preferably 2-3.7 nm; and / or,

[0015] In one embodiment of the present invention, the specific surface area of ​​the catalyst is 20-150m 2 / g.

[0016] According to the present invention, the ratio of the weight 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 ratio of the weight of the main metal element to the weight of the carrier is (0.01-0.5):100, preferably (0.05-0.3):100, calculated based on the weight of the main metal element.

[0017] 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.

[0018] 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, calculated based on the weight of the auxiliary metal elements.

[0019] 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.

[0020] The second aspect of the present invention is to provide a method for preparing the catalyst described in the first aspect, comprising:

[0021] The catalyst is obtained by impregnating a solution containing an active metal element source on a modified carrier for activation. The surface of the modified carrier has oxygen-containing groups with a density of 0.1-1.2 mmol / m 2 , preferably 0.1-0.9mmol / m 2 , more preferably 0.15-0.9mmol / m 2 , still more preferably 0.18-0.85 mmol / m 2 .

[0022] In one embodiment, the modified support is at least one of aluminum oxide, aluminum oxide, magnesium oxide, calcium oxide, magnesium aluminate carbonate, silicon oxide, titanium oxide, and cerium oxide, preferably aluminum oxide.

[0023] Preferably, the oxygen-containing group is at least one of a hydroxyl group, a carboxyl group and a lactone group, and more preferably, the oxygen-containing group is a hydroxyl group, a carboxyl group and a lactone group. Preferably, the content of the hydroxyl group, the carboxyl group and the lactone group is:

[0024] The content of the hydroxyl group is 4-40 mmol / g, preferably 6-30 mmol / g; and / or,

[0025] The carboxyl content is 2.5-30 mmol / g, preferably 6-20 mmol / g; and / or,

[0026] The content of the lactone group is 0.05-20 mmol / g, preferably 1.5-20 mmol / g.

[0027] In one embodiment, the specific surface area of ​​the modified support is 20-150 m 2 / g, preferably 30-130m 2 / g.

[0028] Here, the activation steps can be performed in any suitable order.

[0029] In one embodiment of the present invention, the active metal element source includes a main metal element source and an optional auxiliary metal element source.

[0030] 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 soluble compound containing a main metal element (e.g., a Group VIIIB metal element), preferably at least one water-soluble palladium compound, and more preferably at least one of palladium nitrate, palladium chloride, sodium chloropalladate, palladium oxalate, and palladium citrate.

[0031] Preferably, the weight ratio of the main metal element source (eg, palladium compound), calculated as the metal element, to the carrier is (0.01-0.5):100, preferably (0.02-0.45):100.

[0032] According to the present invention, the auxiliary metal element source can be selected from a wide range. In a preferred embodiment of the present invention, the auxiliary metal element source is selected from at least one of soluble compounds containing auxiliary metal elements (such as elements of Group IB, Group IIB, Group IIIA, Group IIIA and lanthanide metals), preferably a water-soluble auxiliary metal element salt compound. As an example, the auxiliary metal compound is at least one of soluble salt compounds of silver, indium, gallium, cerium and zinc. The content of the auxiliary metal element source (auxiliary metal compound), calculated as metal element, can be in a weight ratio of (0 to 5):100 to the carrier; preferably (0.02 to 4):100.

[0033] In one embodiment of the present invention, the activation method includes a calcination stage, or an irradiation stage, or a calcination stage and an irradiation stage performed in any order.

[0034] Preferably, the calcination conditions include:

[0035] Temperature 150~750℃, and / or

[0036] Time 2 to 20 hours, for example 4 to 20 hours, and / or,

[0037] The atmosphere is at least one of air, nitrogen, hydrogen, and argon.

[0038] The calcination conditions are more preferably a temperature of 180-725° C., preferably 400-650° C.; a time of 2-18 hours, preferably 6-18 hours; and an atmosphere of at least one of air, nitrogen, hydrogen and argon, preferably at least one of air, nitrogen and hydrogen.

[0039] In one embodiment of the present invention, the irradiation conditions include: the irradiation source is selected from gamma rays, and / or the irradiation dose is 1 to 20 kGy, preferably 4 to 18 kGy.

[0040] In one embodiment of the present invention, the impregnation solution used is an aqueous solution of a palladium compound or a promoter metal compound, or a mixture of aqueous solutions of the above two compounds.

[0041] According to the present invention, when there are two or more impregnation liquids, the impregnation can be performed in steps or simultaneously. When the impregnation is performed in steps, each impregnation needs to be dried before the next impregnation. The calcination and activation can be performed in steps, or they can be performed in one step after all components are loaded.

[0042] According to the present invention, the number of impregnations may be one or more times, and the activation is optionally performed before, after, or in the intervals between multiple impregnations; preferably, when the activation comprises multiple stages, some stages of the activation are optionally performed before, after, or in the intervals between multiple impregnations.

[0043] The third aspect of the present invention is to provide a modified carrier for eggshell-type catalysts, especially ultra-thin eggshell-type highly dispersed catalysts, wherein the surface of the modified carrier has oxygen-containing groups, and the density of the oxygen-containing groups is 0.1-1.2 mmol / m 2 , preferably 0.1-0.9mmol / m 2 , more preferably 0.15-0.9mmol / m 2 , still more preferably 0.18-0.85 mmol / m 2 .

[0044] In one embodiment, the modified support is at least one of aluminum oxide, aluminum oxide, magnesium oxide, calcium oxide, magnesium aluminate carbonate, silicon oxide, titanium oxide, and cerium oxide, preferably aluminum oxide.

[0045] Preferably, the oxygen-containing group is at least one of a hydroxyl group, a carboxyl group and a lactone group, and more preferably, the oxygen-containing group is a hydroxyl group, a carboxyl group and a lactone group. Preferably, the content of the hydroxyl group, the carboxyl group and the lactone group is:

[0046] The content of the hydroxyl group is 4-40 mmol / g, preferably 6-30 mmol / g; and / or,

[0047] The carboxyl content is 2.5-30 mmol / g, preferably 6-20 mmol / g; and / or,

[0048] The content of the lactone group is 0.05-20 mmol / g, preferably 1.5-20 mmol / g.

[0049] In one embodiment, the specific surface area of ​​the modified support is 20-150 m 2 / g, preferably 30-130m 2 / g.

[0050] The fourth aspect of the present invention is to provide a method for preparing the modified carrier, which includes mixing dry materials including a carrier precursor, a forming pore-enlarging agent, and inorganic carbon with a liquid, and obtaining the modified carrier through kneading, granulation, and surface modification, wherein the surface modification is at least two of heat treatment, crystallization, and irradiation.

[0051] Preferably, the inorganic carbon is selected from at least one of charcoal, bamboo charcoal, coconut shell charcoal, graphene, graphyne and diamond.

[0052] The order of heat treatment, crystallization, and irradiation in the surface modification can be arbitrarily selected based on the actual reaction conditions. In one embodiment, the surface modification is crystallization and heat treatment, irradiation and heat treatment, or irradiation and crystallization, preferably crystallization and heat treatment, or irradiation and heat treatment. The order of operations can be arbitrarily selected based on the actual reaction conditions, for example, irradiation first and then heat treatment, or crystallization first and then heat treatment.

[0053] In one embodiment, the heat treatment conditions include treatment with a heat treatment atmosphere, the heat treatment atmosphere comprising a first atmosphere and a second atmosphere, wherein the first atmosphere is selected from at least one of air, nitrogen, carbon monoxide and carbon dioxide, and the second atmosphere is selected from water vapor, wherein the volume ratio of the first atmosphere to the second atmosphere is (1 to 10): 1, for example (5 to 9): 1 or (1 to 2): 1, the heat treatment temperature is 300-1200°C, and the heat treatment time is 1-24h, preferably 1-7h.

[0054] According to the present invention, the crystallization conditions can be selected within a wide range. In one embodiment of the present invention, the crystallization conditions include at least one of the following: a temperature of 150-300°C, for example, 150-250°C; a time of 2-24 hours, preferably 2-20 hours; a pressure of 0.2-10 MPa, preferably 2-5 MPa; a solvent of water; and a pH of the solution used for crystallization of 8-14, preferably 9-11.

[0055] In one embodiment of the present invention, the irradiation conditions include: the irradiation source is selected from gamma rays, and / or the irradiation dose is 1 to 20 kGy, preferably 8 to 18 kGy.

[0056] In one embodiment of the present invention, the amount of the inorganic carbon is 1-30 parts, preferably 3-20 parts, relative to 100 parts of the support (eg, alumina) precursor, in parts by mass.

[0057] According to the present invention, when the modified support is alumina, the alumina precursor can be selected from a wide range. In one embodiment of the present invention, the alumina precursor is selected from at least one of pseudo-boehmite, α-alumina, θ-alumina, γ-alumina, and amorphous alumina, for example, at least one of pseudo-boehmite, α-alumina, and γ-alumina.

[0058] According to the present invention, the forming pore-enlarging agent can be selected from a wide range. In one embodiment of the present invention, the forming pore-enlarging agent is at least one selected from polyethylene glycol cellulose, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose and starch, and at least one selected from polyvinyl alcohol, polyethylene glycol, polyacrylamide, polypropylene glycol and sesbania powder.

[0059] According to the present invention, the ratio of the mass of the forming pore-expanding agent to the total mass of the dry material can be selected within a wide range. In one embodiment of the present invention, the ratio of the mass of the forming pore-expanding agent to the total mass of the dry material is (0.5-25):100, preferably (5-13):100.

[0060] In one embodiment of the present invention, the liquid is an acidic solution. Preferably, the acidic solution is selected from at least one of aqueous solutions of acetic acid, oxalic acid, diacetic acid, maleic acid, citric acid, oxalic acid, formic acid, tartaric acid, nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid and hypochlorous acid, and / or the concentration of the acidic solution is 0.01 to 5 mol / L, preferably 0.2 to 4 mol / L.

[0061] The fifth 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, preferably in the preparation of ethylene by catalytic hydrogenation of acetylene.

[0062] The sixth aspect of the present invention is to provide a use of the modified carrier described in the third aspect or the modified carrier prepared by the preparation method described in the fourth aspect in the preparation of an eggshell catalyst.

[0063] Compared with the prior art, the advantages of the present invention are:

[0064] (1) The catalyst of the present invention has 95% to 99% by weight of the active metal elements distributed in a shell layer of the carrier with a thickness of less than 60 μm. Compared with conventional eggshell catalysts, the shell layer is thinner, which is more conducive to fast surface reaction and diffusion-controlled catalytic reaction.

[0065] (2) The catalyst of the present invention has a dispersion of active metal elements of 50% to 80%, 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 the catalyst.

[0066] (3) The present invention can prepare the catalyst by using a specific alumina carrier with a high content and density of oxygen-containing groups. Not only is the requirement for impregnation conditions low, but the rich oxygen-containing group types and high density on the surface of the alumina carrier can make the active metal distributed in an extremely thin shell area on the surface of the carrier while weakening its growth, agglomeration or aggregation tendency, thereby presenting a highly dispersed state, and the regulation of the catalyst is more precise and accurate.

[0067] (4) The catalyst of the present invention exhibits excellent performance in selective hydrogenation catalytic reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 shows the SEM results of the active metal palladium of catalyst X1 in Example 1.

[0069] Figure 2 shows the SEM results of active metal palladium of catalyst Y1 in Comparative Example 1. DETAILED DESCRIPTION

[0070] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0071] 1. Preparation Example

[0072] Example 1

[0073] Take 200g pseudo-boehmite powder (pore volume 0.6ml / g, specific surface area 208.5m 2 / g), 5g methylcellulose, 7g polypropylene glycol, and 8g graphene were mixed uniformly. 20ml of a mixed aqueous solution of 1mol / L nitric acid and 0.5mol / L citric acid was added to the mixed powder, which was then thoroughly kneaded, extruded, formed, and pelletized to obtain 3mm spherical particles. The particles were dried at 120°C for 4h, then heat-treated at 500°C for 2h in a mixed atmosphere of carbon monoxide and water vapor (volume ratio 5:1), and then crystallized in an aqueous solution at 200°C, 2MPa, and pH 9.8 for 2h to obtain carrier A1. 50g of A1 was then impregnated with 60ml of a palladium chloride solution containing 0.025g of palladium. The mixture was allowed to stand for 2h, then dried at 120°C for 4h, and calcined at 400°C in a flowing hydrogen atmosphere for 12h to obtain catalyst X1 with a palladium loading of 0.05wt%.

[0074] Example 2

[0075] Take 100g of α-alumina (pore volume 1.7ml / g, specific surface area 79.5m 2 / g) and 50g of amorphous alumina (pore volume 1.1ml / g, specific surface area 86.2m 2 / g), 5g methylcellulose, 7g polyethylene glycol, 8g coconut shell charcoal, 5.3g indium nitrate, and 4g zinc nitrate were mixed uniformly. 40ml of a mixed aqueous solution of 2mol / L oxalic acid and 1mol / L acetic acid was added to the mixed powder, which was then thoroughly kneaded, extruded, shaped, and pelletized to obtain cylindrical particles with a diameter of 4mm. The particles were dried at 150°C for 2h, irradiated with 10kGy of gamma rays, and crystallized in an aqueous solution at 240°C, 2MPa, and pH 11 for 2h to obtain carrier A2. 50g of A2 was then impregnated with 50ml of a palladium chloride solution containing 0.025g of palladium. The mixture was allowed to stand for 1h, dried at 150°C for 6h, and calcined at 550°C in a flowing nitrogen and argon atmosphere for 6h to obtain catalyst X2 with a palladium loading of 0.05wt%.

[0076] Example 3

[0077] Take 100g of α-alumina (pore volume 0.9ml / g, specific surface area 48.2m 2 / g) and 50g of θ-alumina (pore volume 1.8ml / g, specific surface area 106.3m 2 / g), 5g methylcellulose, 5g starch, 5g polypropylene glycol, 5g sesbania powder, 5g bamboo charcoal, and 5g coconut shell charcoal were mixed uniformly. 45ml of a 1.5mol / L sulfuric acid solution was added to the mixed powder, which was then thoroughly kneaded, extruded, shaped, and pelletized to produce 3mm spherical particles. The particles were dried at 120°C for 4h, heat treated at 850°C for 6h in a mixture of carbon dioxide and water vapor (9:1 by volume), and irradiated with gamma rays for 8kGy to obtain carrier A3. 50g of A3 was then loaded with 35ml of a palladium nitrate solution containing 0.05g of palladium. The mixture was allowed to stand for 5h, dried at 120°C for 2h, and calcined at 450°C in a flowing air mixture for 2h to obtain catalyst X3 with a palladium loading of 0.1wt%.

[0078] Example 4

[0079] Take 100g of α-alumina (pore volume 0.9ml / g, specific surface area 48.2m 2 / g) and 50g of γ-alumina (pore volume 1.5ml / g, specific surface area 92.7m 2 / g), 5g carboxymethyl cellulose, 5g hydroxyethyl cellulose, 5g sesbania powder, 5g diamond, and 5g graphyne were mixed uniformly. 30mL of a mixed aqueous solution of 0.5mol / L hydrochloric acid and 0.2mol / L hypochlorous acid was added to the mixed powders, which were then thoroughly kneaded, extruded, shaped, and pelletized to obtain 3mm spherical particles. The particles were dried at 110°C for 4h, crystallized in an aqueous solution at 245°C, 5MPa, and pH 10 for 20h, and dried at 130°C for 4h. After irradiation with gamma rays for 8kGy, the particles were heat-treated at 350°C for 6h in a mixed atmosphere of carbon monoxide, carbon dioxide, and water vapor (volume ratio 6:2:1). Carrier A4 was then loaded with 25ml of a palladium nitrate solution containing 0.15g of palladium on 50g of A4 and irradiated with gamma rays for 5kGy to obtain catalyst X4 with a palladium loading of 0.3wt%.

[0080] Example 5

[0081] Take 80g of amorphous alumina (pore volume 1.1ml / g, specific surface area 86.2m 2 / g) and 40g of pseudo-boehmite (pore volume 0.6ml / g, specific surface area 208.5m 2 / g), 10g starch, 10g sesbania powder, 6g bamboo charcoal, 6g charcoal, and 6g coconut shell charcoal were mixed uniformly. A mixed aqueous solution of 1.5mol / L formic acid, 1.5mol maleic acid, and 0.5mol / L diacetic acid was added to the mixed powders, which were then thoroughly kneaded, extruded, formed, and pelletized to obtain 3mm spherical particles. The particles were dried at 110°C for 4h, irradiated with 18kGy of gamma rays, and then heat-treated at 950°C for 1.5h in a mixed atmosphere of nitrogen, carbon dioxide, and water vapor (4:5:1 by volume) to obtain carrier A5. 30ml of a mixed aqueous solution containing 0.04g palladium in palladium nitrate and 0.04g silver in silver nitrate was then loaded onto 50g of A5, allowed to stand for 4h, and calcined at 650°C in a flowing air atmosphere for 8h to obtain catalyst X5 with a palladium loading of 0.08wt%.

[0082] Example 6

[0083] Take 80g of amorphous alumina (pore volume 1.1ml / g, specific surface area 86.2m 2 / g) and 40g of pseudo-boehmite (pore volume 0.6ml / g, specific surface area 208.5m 2 / g), 5g starch, 5g carboxymethyl cellulose, 5g sesbania powder, 6g polyvinyl alcohol, 10g charcoal, and 12g graphene were mixed uniformly. 50mL of 3.5mol / L phosphoric acid solution was added to the mixed powder, which was then thoroughly kneaded, extruded, formed, and pelletized to obtain 3mm spherical particles. The particles were dried at 110°C for 4h, then crystallized in an aqueous solution at 280°C, 0.8MPa, and pH 10 for 2h. The carrier A6 was then heat-treated at 1050°C for 6h in a mixed atmosphere of air, carbon monoxide, and water vapor (volume ratio 0.25:8:1). 50g of A6 was then loaded with 30ml of a mixed aqueous solution of palladium oxalate containing 0.03g of palladium, allowed to stand for 4h, and calcined at 400°C in a flowing nitrogen atmosphere for 8h to obtain catalyst X6 with a palladium loading of 0.04wt%.

[0084] Comparative Example 1

[0085] Take 200g pseudo-boehmite powder (pore volume 0.6ml / g, specific surface area 208m 2 / g), 5g methylcellulose, and 7g polypropylene glycol were mixed evenly. 20ml of a mixed aqueous solution of 1mol / L nitric acid and 0.5mol / L citric acid was added to the mixed powder, which was then thoroughly kneaded, extruded, formed, and pelletized to obtain 3mm spherical particles. The particles were dried at 120°C for 4h, then heat-treated at 500°C for 2h in a mixed atmosphere of carbon monoxide and water vapor (volume ratio 5:1), and then crystallized in an aqueous solution at 200°C, 2MPa, and pH 9.8 for 2h to obtain carrier B1. 50g of B1 was then impregnated with 60ml of a palladium chloride solution containing 0.025g of palladium. The mixture was allowed to stand for 2h, then dried at 120°C for 4h, and calcined at 400°C in a flowing hydrogen atmosphere for 12h to obtain catalyst Y1 with a palladium loading of 0.05wt%.

[0086] Comparative Example 2

[0087] Take 200g pseudo-boehmite powder (pore volume 0.6ml / g, specific surface area 208m 2 / g), 5g methylcellulose, 7g polypropylene glycol, and 8g graphene were mixed uniformly. 20ml of a mixed aqueous solution of 1mol / L nitric acid and 0.5mol / L citric acid was added to the mixed powders, which were then thoroughly kneaded, extruded, shaped, and pelletized to obtain 3mm spherical particles. The particles were dried at 120°C for 4h and then calcined at 500°C in air for 2h to obtain carrier B2. 50g of B2 was then impregnated with 60ml of a palladium chloride solution containing 0.025g of palladium. The mixture was allowed to stand for 2h, then dried at 120°C for 4h and calcined at 400°C in a flowing hydrogen atmosphere for 12h to obtain catalyst Y2 with a palladium loading of 0.05wt%.

[0088] Comparative Example 3

[0089] Take 100g of α-alumina (pore volume 1.7ml / g, specific surface area 79.5m 2 / g) and 50g of amorphous alumina (pore volume 1.1ml / g, specific surface area 86.2m 2 / g), 5g methylcellulose, 7g polyethylene glycol, 8g coconut shell charcoal, 5.3g indium nitrate, and 4g zinc nitrate were mixed uniformly. 40ml of a mixed aqueous solution of 2mol / L oxalic acid and 1mol / L acetic acid was added to the mixed powder, which was then thoroughly kneaded, extruded, shaped, and pelletized to produce cylindrical particles with a diameter of 4mm. The particles were dried at 150°C for 2h and then irradiated with 10kGy of gamma rays to obtain carrier B3. 50g of B3 was then impregnated with 50ml of a palladium chloride solution containing 0.025g of palladium. The mixture was allowed to stand for 1h, dried at 150°C for 6h, and calcined at 550°C in a flowing nitrogen and argon atmosphere for 6h to obtain catalyst Y3 with a palladium loading of 0.05wt%.

[0090] Comparative Example 4

[0091] Take 100g of α-alumina (pore volume 0.9ml / g, specific surface area 48.2m 2 / g) and 50g of γ-alumina (pore volume 1.5ml / g, specific surface area 92.7m 2 / g), 5g carboxymethyl cellulose, 5g hydroxyethyl cellulose, 5g sesbania powder, 5g diamond, and 5g graphyne were mixed uniformly. 30mL of a mixed aqueous solution of 0.5mol / L hydrochloric acid and 0.2mol / L hypochlorous acid was added to the mixed powders, which were then thoroughly kneaded, extruded, shaped, and pelletized to obtain 3mm spherical particles. The particles were dried at 110°C for 4h, crystallized in an aqueous solution at 245°C, 5MPa, and pH 10 for 20h, and dried at 130°C for 4h to obtain carrier B4. 25mL of a palladium nitrate solution containing 0.15g palladium was then loaded onto 50g of B4 and irradiated with γ-rays for 5kGy to obtain catalyst Y4 with a palladium loading of 0.3wt%.

[0092] Comparative Example 5

[0093] Take 80g of amorphous alumina (pore volume 1.1ml / g, specific surface area 86.2m 2 / g) and 40g of pseudo-boehmite (pore volume 0.6ml / g, specific surface area 208.5m 2 / g), 10g starch, 10g sesbania powder, 6g bamboo charcoal, 6g wood charcoal, and 6g coconut shell charcoal were mixed uniformly. A mixed aqueous solution of 1.5mol / L formic acid, 1.5mol maleic acid, and 0.5mol / L diacetic acid was added to the mixed powders, which were then thoroughly kneaded, extruded, shaped, and pelletized to produce 3mm spherical particles. The particles were dried at 110°C for 4 hours and then heat-treated at 950°C for 1.5 hours in a mixed atmosphere of nitrogen, carbon dioxide, and water vapor (4:5:1 by volume) to obtain carrier B5. 50g of B5 was then loaded with 30ml of a mixed aqueous solution of palladium nitrate containing 0.04g palladium and silver nitrate containing 0.04g silver. The mixture was allowed to stand for 4 hours and then calcined at 650°C in a flowing air atmosphere for 8 hours to obtain catalyst Y5 with a palladium loading of 0.08wt%.

[0094] Comparative Example 6

[0095] Take 80g, pore volume 1.2ml / g, specific surface area 180m 2 / g, 4mm long trilobate extrudates of alumina were used as support B6. About 7mL of sodium hydroxide was added to a palladium nitrate solution (obtained by diluting 1g of a palladium nitrate solution containing 8.0% by weight of palladium with 45mL of demineralized water) at 25°C with stirring to obtain a pH of 2.4 to prepare a colloidal suspension of palladium oxide. The suspension was then diluted with demineralized water to a volume corresponding to the pore volume of support B6. The solution was then impregnated onto the selected alumina support. The impregnated support was aged for 20 hours in air in a closed humid medium. It was dried in air at 120°C for 2 hours and calcined at 450°C in a flowing air atmosphere for 2 hours to obtain catalyst Y6 with a palladium loading of 0.1% by weight.

[0096] Comparative Example 7

[0097] Take 80g, pore volume 1.2ml / g, specific surface area 180m 2 / g, 4mm long trilobate extrudates of alumina were used as support B7. About 7mL of sodium hydroxide was added to a palladium nitrate solution (prepared by diluting 0.1g of a palladium nitrate solution containing 8.0% by weight of palladium with 45mL of demineralized water) at 25°C with stirring to obtain a pH of 2.4 to prepare a colloidal suspension of palladium oxide. The suspension was then diluted with demineralized water to a volume corresponding to the pore volume of support B7. The solution was then impregnated onto the selected alumina support. The impregnated support was aged for 20 hours in air in a closed humid medium. It was then dried in air at 120°C for 2 hours and calcined at 450°C in a flowing air atmosphere for 2 hours to obtain catalyst Y7 with a palladium loading of 0.01% by weight.

[0098] 2. Test Examples

[0099] Determination of specific surface area of ​​carrier physical properties: nitrogen physical adsorption BET method was used for measurement.

[0100] Determination of Support Oxygen Group Density: The nature and quantity of oxygen-containing groups on the support were determined using the Boehm method (see HP Boehm, "Some Aspects of the Surface Chemistry of Carbon Blacks and Other Carbons," Carbon, 1994). Three 1g support samples were weighed and soaked in 50ml of 0.05mol / L NaHCO3, Na2CO3, and NaOH solutions for 24 hours. 10ml of the soaked solution was titrated with 0.06mol / L hydrochloric acid. Each sample was titrated three times, and the arithmetic mean was taken. The number of each oxygen-containing group on the support surface was calculated based on the base consumption. Combined with the support specific surface area data, the oxygen-containing group density was calculated.

[0101] Determination of active metal distribution on the catalyst surface: 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 accessory. The shell thickness (L) corresponding to the active metal content exceeding 95% within the shell region where the active metal content is less than 0.01% was calculated (measurements were taken at three different locations on each cross-section and the average value was taken).

[0102] Determination of palladium content in the catalyst: The conventional ICP-MS method was used to detect the content of palladium metal in the catalyst.

[0103] Determination of the dispersion of active metals in the catalyst: Using a Chemisorb 2920 chemical adsorption instrument, weigh 0.1 g of the catalyst sample, reduce it with hydrogen at 160°C for 30 minutes, purge it with nitrogen for 10 minutes, then cool it to 40°C. Pulse adsorption of CO2 was performed until adsorption was saturated. The dispersion of the active metals was calculated based on the adsorption amount and the palladium content.

[0104] Determination of Catalyst Active Metal Particle Size Distribution: Catalyst sample particles were cut approximately 0.5 mm from the surface, ground, and then reduced in hydrogen at 160°C for 1 hour. The powdered sample was then added to a solution of water and ethanol in a 4:1 volume ratio and ultrasonically dispersed. Four to six drops of the dispersion solution were then pipetted onto a copper mesh. After drying under an infrared lamp for 15 minutes, the sample was directly transferred to an electron microscope. Four images were collected for each sample, and the particle sizes of at least 200 particles were calculated.

[0105] Catalytic performance test: 10 ml of catalyst was loaded into a tubular reactor, and hydrogen was introduced after nitrogen replacement at 160 ° C for 3 h; after cooling naturally to room temperature, nitrogen was purged and replaced, and the reaction was carried out at a space velocity of 20000 h -1 and a carbon two reaction material (material 1) under a pressure of 2 MPa to perform a performance test (test 1); repeat the above steps and conditions to perform a performance test (test 2) in a carbon two reaction material (material 2)

[0106] Material 1 consists of the following components: 1000 ppm acetylene, 800 ppm carbon monoxide, 13% hydrogen, 12% ethane, 1% methane, 20% propylene, 0.3% propadiene, 0.2% propyne, 0.9% propane, and the remainder is ethylene.

[0107] Material 2 consists of 1000 ppm acetylene, 900 ppm carbon monoxide, 26% hydrogen, 14% ethane, 3% methane, and the remainder is ethylene.

[0108] The lowest temperature and ethylene selectivity corresponding to the acetylene concentration of 0 ppm in the outlet gas were investigated.

[0109] The formula for calculating ethylene selectivity is as follows:

[0110] Ethylene selectivity = [(ethylene content at outlet - ethylene content at inlet) / (acetylene content at inlet)] × 100%

[0111] Table 1. Measurement results of oxygen-containing groups on alumina supports of Examples and Comparative Examples

[0112] Table 2 Physical and chemical properties characterization test results of the catalysts of the examples and comparative examples

[0113] As can be seen from Table 1, the support modification method described herein significantly increases the number and density of oxygen-containing groups on the surface of the alumina support. Furthermore, Table 2 shows that, compared to the comparative catalyst, the active metal in the catalyst prepared by the method described herein can simultaneously meet the requirements of an extremely thin shell (less than 60 μm), a dispersion greater than 55%, and an average particle size less than 4 nm. See also the comparison of Figures 1 and 2.

[0114] Table 3 Catalytic performance evaluation results of the catalysts of the examples and comparative examples

[0115] The results in Table 3 show that, under the same conditions of achieving an acetylene outlet concentration of 0 ppm, i.e., an acetylene conversion of 100%, the Example catalysts require lower temperatures than the corresponding Comparative Example catalysts, demonstrating superior activity. Furthermore, at 100% acetylene conversion, the Example catalysts also exhibited superior selectivity to the Comparative Example catalysts. Therefore, the Example catalysts outperformed the Comparative Example catalysts, achieving unexpected technical benefits.

[0116] In two typical C2 selective hydrogenation reactions (Table 3), the example catalysts exhibited significantly better activity and selectivity than the comparative catalysts. This can be attributed to the fact that C2 selective hydrogenation is a surface-fast, diffusion-controlled catalytic reaction. The more concentrated the active metals are in the catalyst's outer layer and the higher the degree of dispersion (atomic utilization), the better the activity. Furthermore, ethylene desorption is facilitated, the diffusion path from the catalyst surface to the gas phase is shortened, and the probability of overhydrogenation is reduced, resulting in a higher catalyst selectivity.

[0117] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of 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 words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

[0118] 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 conventionally understood by those skilled in the art. In the event of conflict, the definitions in this specification shall prevail.

[0119] When this specification uses the prefix "well known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, the objects introduced by the prefix include those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become generally recognized in the art to be suitable for similar purposes.

[0120] The endpoints and any values ​​of the ranges disclosed in this application document are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and a separate point value, and the separate point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0121] In the context of this specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0122] Moreover, any embodiment described herein may be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas thus formed shall be deemed as part of the original disclosure or original record of the present invention, and shall not be regarded as new content that has not been disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. An eggshell-shaped catalyst, comprising a carrier and an active metal element, wherein the active metal element, which accounts for 95% to 99% by weight of the total weight of the active metal element, is distributed in a shell of the carrier within 60 μm in thickness and is distributed in an eggshell-shaped manner, with the thickness calculated from the outer surface of the carrier to the center; The dispersion degree of the active metal elements is 50% to 80%.

2. The eggshell-type catalyst of claim 1, wherein The active metal element comprises a main metal element and an optional auxiliary metal element; and / or 95 wt % to 99 wt % of the total weight of the active metal elements are distributed in a shell within 50 μm of the carrier in thickness calculated from the outer surface of the carrier toward the center; and / or, The dispersion of the active metal element is 60% to 80%, preferably greater than 70%, more preferably 71-80%; and / or The average particle size of the active metal is less than 4 nm, preferably 2-3.7 nm; and / or The specific surface area of ​​the catalyst is 20-150m 2 / g.

3. The eggshell-type catalyst of claim 2, wherein Based on the weight of the main metal element, the ratio of the weight of the main metal element to the weight of the carrier is (0.01-0.5):100, preferably (0.05-0.3):100; and / or The main metal element is selected from at least one of the metal elements of Group VIIIB, preferably palladium; 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 IIIB and Lanthanide metal elements, preferably at least one of silver, indium, gallium, cerium and zinc.

4. A method for preparing a catalyst according to any one of claims 1 to 3, comprising: The solution containing the active metal element source is impregnated on the modified carrier to activate the catalyst, wherein the surface of the modified carrier has oxygen-containing groups, and the density of the oxygen-containing groups is 0.1-1.2 mmol / m 2 , preferably 0.1-0.9mmol / m 2 , more preferably 0.15-0.9mmol / m 2 , still more preferably 0.18-0.85 mmol / m 2 .

5. The preparation method according to claim 4, wherein The oxygen-containing group is at least one of a hydroxyl group, a carboxyl group and a lactone group. Preferably, the oxygen-containing group is a hydroxyl group, a carboxyl group and a lactone group. More preferably, the contents of hydroxyl, carboxyl and lactone groups are: The content of the hydroxyl group is 4-40 mmol / g, preferably 6-30 mmol / g; and / or, The carboxyl content is 2.5-30 mmol / g, preferably 6-20 mmol / g; and / or, The content of the lactone group is 0.05-20 mmol / g, preferably 1.5-20 mmol / g.

6. The preparation method according to claim 4 or 5, wherein The active metal element source includes a main metal element source and an optional auxiliary metal element source, Preferably, the main metal element source is selected from at least one of soluble compounds containing the main metal element (e.g., Group VIIIB metal element), preferably at least one of water-soluble palladium compounds, more preferably at least one of palladium nitrate, palladium chloride, sodium chloropalladate, palladium oxalate, and palladium citrate, and the weight ratio of the main metal element source (e.g., palladium compound) to the carrier, calculated as the metal element, is (0.01-0.5):100, preferably (0.02-0.45):100; and / or Preferably, the auxiliary metal element source is selected from at least one of soluble compounds containing auxiliary metal elements (such as elements of Group IB, Group IIB, Group IIIA, Group IIIA and lanthanide metals), preferably a water-soluble auxiliary metal element salt compound, for example, the auxiliary metal compound is at least one of soluble salt compounds of silver, indium, gallium, cerium and zinc, and the content of the auxiliary metal element source (auxiliary metal compound), calculated as metal element, can be in a weight ratio of (0 to 5):100 to the carrier; preferably (0.02 to 4):

100.

7. The preparation method according to any one of claims 4 to 6, wherein The modified carrier is at least one of aluminum oxide, magnesium oxide, calcium oxide, magnesium aluminate carbonate, silicon oxide, titanium oxide, and cerium oxide, preferably aluminum oxide, and / or The specific surface area of ​​the modified carrier is 20-150m 2 / g, preferably 30-130m 2 / g, and / or. The impregnation liquid used is an aqueous solution of a palladium compound or an auxiliary metal compound, or a mixture of aqueous solutions of the above two compounds; and / or The number of times of impregnation is one or more, and the activation is optionally performed before, after, or in the interval between multiple impregnations; preferably, when the activation comprises multiple stages, some stages of the activation are optionally performed before, after, or in the interval between multiple impregnations; and / or The activation steps may be performed in any suitable order; and / or The activation method includes a calcination stage, an irradiation stage, or any sequence thereof. The roasting stage and the irradiation stage are carried out, wherein the roasting conditions preferably include: Temperature 150~750℃, and / or Time 2 to 20 hours, for example 4 to 20 hours, and / or, The atmosphere is at least one of air, nitrogen, hydrogen and argon; and / or Preferably, the irradiation conditions in the irradiation stage include: the irradiation source is selected from gamma rays, and / or the irradiation dose is 1 to 20 kGy, preferably 4 to 18 kGy.

8. A modified carrier for an eggshell catalyst, wherein the surface of the modified carrier has oxygen-containing groups, and the density of the oxygen-containing groups is 0.1-1.2 mmol / m 2 , preferably 0.1-0.9mmol / m 2 , more preferably 0.15-0.9mmol / m 2 , still more preferably 0.18-0.85 mmol / m 2 .

9. The modified carrier according to claim 8, wherein The oxygen-containing group is at least one of a hydroxyl group, a carboxyl group and a lactone group. Preferably, the oxygen-containing group is a hydroxyl group, a carboxyl group and a lactone group. More preferably, the contents of hydroxyl, carboxyl and lactone groups are: The content of the hydroxyl group is 4-40 mmol / g, preferably 6-30 mmol / g; and / or, The carboxyl content is 2.5-30 mmol / g, preferably 6-20 mmol / g; and / or, The content of the lactone group is 0.05-20 mmol / g, preferably 1.5-20 mmol / g.

10. The modified carrier according to claim 8 or 9, wherein The modified carrier is at least one of aluminum oxide, aluminum oxide, magnesium oxide, calcium oxide, magnesium aluminate carbonate, silicon oxide, titanium oxide, and cerium oxide, preferably aluminum oxide, and / or The specific surface area of ​​the modified carrier is 20-150m 2 / g, preferably 30-130m 2 / g.

11. A method for preparing a modified carrier according to any one of claims 8 to 10, comprising mixing dry materials including a carrier precursor, a forming pore-enlarging agent, and inorganic carbon with a liquid, and obtaining the modified carrier through kneading, granulation, and surface modification, wherein the surface modification is at least two of heat treatment, crystallization, and irradiation.

12. The preparation method according to claim 11, wherein The inorganic carbon is selected from at least one of charcoal, bamboo charcoal, coconut shell charcoal, graphene, graphyne and diamond; and / or In parts by mass, the amount of the inorganic carbon is 1-30 parts, preferably 3-20 parts, relative to 100 parts of the carrier precursor; and / or The surface modification is crystallization and heat treatment, irradiation and heat treatment, or irradiation and crystallization, preferably crystallization and heat treatment, irradiation and heat treatment; and / or The heat treatment conditions include using a heat treatment atmosphere to treat, the heat treatment atmosphere includes Containing a first atmosphere and a second atmosphere, wherein the first atmosphere is selected from at least one of air, nitrogen, carbon monoxide and carbon dioxide, and the second atmosphere is selected from water vapor, wherein the volume ratio of the first atmosphere to the second atmosphere is (1-10):1, for example (5-9):1 or (1-2):1, the heat treatment temperature is 300-1200° C., the heat treatment time is 1-24 h, preferably 1-7 h; and / or The crystallization conditions include at least one of the following conditions: temperature 150-300°C, for example 150-250°C; time 2-24h, preferably 2-20h; 0.2-10Mpa, preferably 2-5Mpa; solvent is water; pH of the solution used for crystallization is 8-14, preferably 9-11; and / or The irradiation conditions include: The radiation source is selected from gamma rays, and / or the irradiation dose is 1 to 20 kGy, preferably 8 to 18 kGy.

13. The preparation method according to claim 11 or 12, wherein When the modified support is alumina, the alumina precursor is selected from at least one of pseudo-boehmite, α-alumina, θ-alumina, γ-alumina, and amorphous alumina; and / or The forming pore-enlarging agent is at least one selected from polyethylene glycol cellulose, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose and starch and at least one selected from polyvinyl alcohol, polyethylene glycol, polyacrylamide, polypropylene glycol and sesbania powder; and / or The ratio of the mass of the forming pore-enlarging agent to the total mass of the dry material is (0.5-25):100, preferably (5-13):100; and / or The liquid is an acidic solution. Preferably, the acidic solution is selected from at least one of aqueous solutions of acetic acid, oxalic acid, diacetic acid, maleic acid, citric acid, oxalic acid, formic acid, tartaric acid, nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid and hypochlorous acid, and / or the concentration of the acidic solution is 0.01 to 5 mol / L, preferably 0.2 to 4 mol / L.

14. Use of the catalyst according to any one of claims 1 to 3 or the catalyst prepared by the preparation method according to any one of claims 4 to 7 in the field of catalytic hydrogenation, preferably in the preparation of ethylene by catalytic hydrogenation of acetylene.

15. Use of the modified carrier according to any one of claims 8 to 10 or the modified carrier prepared by the preparation method according to any one of claims 11 to 13 in the preparation of eggshell catalysts, especially ultra-thin eggshell type highly dispersed catalysts.

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