Core-shell structure copper-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to a copper-based catalyst with a core-shell structure as well as a preparation method and application of the copper-based catalyst. The core-shell structure copper-based catalyst contains an original core material, copper and an auxiliary agent, the specific surface area of the original core material is 50-400 m < 2 > / g, the pore volume of the original core material is 0.1-1.5 cm < 3 > / g, based on the total mass of the copper-based catalyst, the content of copper in terms of metal elements is 0.5-15% by mass, preferably 1.5-12% by mass, and more preferably 1.8-10% by mass, 72-95% by mass of copper is dispersed in a shell layer, and the auxiliary agent is an auxiliary agent. The thickness of the catalyst shell layer is 0.02-0.3 mm, and the content of the auxiliary agent is 1-15% by mass in terms of auxiliary agent elements. The preparation method has the advantages that the preparation method is simple, the cost is low, batch production is easy, and VOCs components can be removed through efficient catalytic oxidation under the condition of trace oxygen.

Description

Technical Field

[0001] The present invention relates to a core-shell copper-based catalyst. More specifically, the present invention relates to a core-shell copper-based catalytic material and a preparation method thereof. The present invention also relates to the use of the core-shell copper-based catalytic material in the catalytic oxidation treatment of volatile organic compounds under trace oxygen conditions. Background Art

[0002] In recent years, with the increasing requirements of the country for environmental protection, recovery technologies such as adsorption, catalytic oxidation, high temperature incineration, absorption, condensation and membrane separation have been widely used in the recovery / treatment of various waste gases containing volatile organic compounds (VOCs). 3 Exhaust gases are typically treated using catalytic oxidation. For example, the VOC-containing tail gas generated during the production of purified terephthalic acid is treated using an HPCCU (high-pressure catalytic combustion unit). Generally speaking, the catalytic oxidation reaction of VOC-containing exhaust gases is controlled by external diffusion. The goal of constructing catalysts with fully exposed active components or catalysts with active components fully confined to the shell is a goal pursued by both academia and industry.

[0003] Core-shell catalysts have been reported in many literatures. For example, patent CN119158598A discloses a core-shell catalyst comprising a core and an outer shell, wherein the core comprises a carrier and non-precious metals, co-metals, and additives loaded on the carrier, and the outer shell comprises an alumina coating layer and a precious metal active component loaded on the alumina coating layer, wherein the additives are S and / or P. The preparation process of this catalyst is relatively complicated, and the additives S and / or P are not conducive to the catalytic oxidation reaction of VOCs. CN119549163A designs a catalyst in which Pt is deposited on the surface of a carbon carrier by atomic layer deposition, and then deposits the metal oxide CuOx onto the surface of the metal Pt. Although this catalyst can control the size of the Pt particles at the atomic scale, its preparation process involves chemical deposition technology, which is cumbersome and costly. CN119608149A first prepared a competitive adsorption sol by a competitive adsorption method, and then prepared a high-efficiency anti-poisoning PTA waste gas oxidation catalyst by ball milling with an insoluble manganese precursor and an inert carrier. In general, the preparation process of the catalyst is relatively cumbersome, and whether the active components of the core-shell structure catalyst are fully exposed or distributed in the core-shell is not involved, and the stability of the catalyst is not reflected in the examples. In the WO2022127911A1 patent, a catalytic material with a core of spherical porous Mn2O3 and a shell of undoped or Cu-doped flaky MnO2 is prepared. The catalyst is nanoscale, and the application of 400-1500nm powder materials in the catalytic oxidation of VOCs is challenging. In the CN119771489A patent, a Cu-SSZ-13 molecular sieve with a low core silicon-aluminum ratio, a high copper loading, a high shell silicon-aluminum ratio, and a low copper loading is prepared. The active component copper is not fully enriched on the outer surface.

[0004] In summary, there is an urgent need in this field for a catalyst in which the active components are highly dispersed on the outer surface of the catalyst, and the carrier, auxiliary agent and active components have strong interactions. The catalyst can be manufactured at low cost and can be used for catalytic oxidation and purification of VOCs in the presence of trace oxygen, maintaining long-term performance. Summary of the Invention

[0005] In view of the technical problems in the prior art, the inventors conducted diligent research based on the existing technology and found that by using a core material as the original matrix and further combining it with appropriate copper components and auxiliary components, a core-shell structured copper-based catalyst can be prepared. The catalyst can complete the catalytic oxidation conversion of VOCs in the presence of trace amounts of oxygen, thus completing the present invention.

[0006] Specifically, the present invention provides a core-shell structure copper-based catalyst, comprising an original core material, copper and an additive, wherein the specific surface area of ​​the original core material is 50 to 400 m 2 / g, pore volume is 0.1~1.5cm 3 / g, the content of copper is 0.5-15 mass% in terms of metal elements based on the total mass of the copper-based catalyst, preferably 1.5-12 mass%, more preferably 1.8-10 mass%, wherein 72-95 mass% of the copper is dispersed in the shell layer, the thickness of the catalyst shell layer is 0.02-0.3 mm, and the content of the auxiliary agent is 1-15 mass% in terms of auxiliary agent elements.

[0007] According to the present application, the auxiliary agent is one or more than two combinations of titanium, vanadium, chromium, cobalt, nickel, gallium, molybdenum, antimony, manganese, tungsten, rhenium, bismuth, lanthanum, cerium, zinc and silver, preferably one or more than two combinations of titanium, vanadium, chromium, cobalt, zinc, antimony, bismuth, cerium and manganese, and further preferably one or more than two combinations of cobalt, antimony, cerium, manganese, titanium and vanadium.

[0008] According to the present application, the specific surface area of copper measured by N2O titration is 30-93 m 2 / g.

[0009] According to the present application, the inner core material is selected from at least one of (a), (b) and (c);

[0010] (a) alumina, titania, zirconia, silica, ceria, zinc oxide, magnesium oxide, silica-alumina, silica-magnesia, chromia-alumina and silica-zirconia;

[0011] (b) molecular sieve: specifically including at least one of ZSM, X, Y, beta, mordenite;

[0012] (c) spinel with the general formula MO-Al2O3, wherein M is a divalent metal, forming compounds such as MgAl2O4, FeAl2O4, ZnAl2O4, CaAl2O4 and other similar compounds.

[0013] According to the present application, the original inner core material has a certain macro shape, and the length of a certain direction of the corner edge or diameter is greater than 2 mm, and the shape is spherical, Laxi ring, strip, three-leaf clover, four-leaf clover or irregular granular.

[0014] The present application also provides a preparation method of the core-shell structure copper-based catalyst, comprising the following steps:

[0015] (1) contacting the original inner core material, auxiliary agent element precursor, additive and solvent to form a mixed contact body; wherein the amount of the additive is 0-30 mass% of the original inner core material, the amount of the solvent is 0.5-170 mass% of the original inner core material, and the auxiliary agent element precursor and the original inner core material meet the aforementioned provisions of the present application after calcination;

[0016] (2) contacting the mixed contact body with a copper precursor in a predetermined ratio to obtain a composite system;

[0017] (3) calcining the composite system to obtain the core-shell structure copper-based catalyst.

[0018] According to the present invention, the predetermined ratio is such that the composition of the core-shell structure copper-based catalyst finally obtained after the calcination step complies with the aforementioned provisions of the present invention.

[0019] According to the present invention, the auxiliary element precursor in step (1) refers to a substance that can generate the auxiliary element described herein after calcination in step (3), such as a soluble salt of the auxiliary element, more preferably, at least one selected from the group consisting of acetate, ammonium salt, sulfate, phosphate, nitrate, and halide salt of the auxiliary element, and even more preferably, at least one selected from the group consisting of acetate, nitrate, and chloride salt of the auxiliary element. For example, cobalt nitrate, cobalt acetate, cerium nitrate, zinc nitrate, lanthanum nitrate, antimony acetate, etc. can be cited.

[0020] According to the present invention, the copper precursor in step (2) refers to a substance that can generate the copper mentioned above in this article after being calcined in step (3), preferably a soluble salt of copper, more preferably a water-soluble salt of copper, and even more preferably, at least one selected from the group consisting of copper nitrates, sulfates, sulfites, phosphates, halides, hydrogen phosphates, carbonates, hydrogen carbonates, and ammonium salts.

[0021] According to the present invention, in the contacting step (1), there is no particular limitation on the order in which the components (i.e., the original core material, the auxiliary element precursor, the additive, and the solvent) are contacted. Furthermore, according to the present invention, there is no particular limitation on the manner in which the contacting step is performed, as long as sufficient contact between the components is achieved and a uniform mixed contact body is formed. For example, the components may be mixed (with auxiliary stirring, if necessary) until uniformity is achieved in any manner known in the art.

[0022] According to the present invention, in the contacting step (2), the mixed contact body and the copper precursor are contacted in a predetermined ratio. There is no particular limitation on the manner in which the contacting step is carried out, as long as sufficient contact between the raw material components is achieved and a uniform composite system is formed. For example, mixing (with auxiliary stirring if necessary) until uniformity is achieved can be performed in any manner known in the art.

[0023] If necessary, in order to make the contact more uniform and sufficient, or to facilitate the contact, the contact step can also be carried out in the presence of a dispersion medium (such as water). The contact product obtained at this time may be in the form of a mixture with an impregnation liquid, a slurry or a paste liquid.

[0024] The contacting steps of step (1) and step (2) can be carried out at any temperature between 0°C and 150°C, for example, at room temperature. When the temperature is higher than the boiling point of the solvent, the reaction can be carried out in a pressure vessel so that the boiling point corresponding to the pressure is higher than the temperature. From the perspective of convenience, room temperature is preferred, but this is not always limited to this. The contact time is based on obtaining a uniform contact product and is generally 0.5 to 5 hours, but this is not always limited to this.

[0025] According to the present invention, in the contacting step (2), after the mixed product is prepared, especially when the mixed product is a slurry, it can sometimes be dried by any means known in the art, such as oven drying (e.g., at 60-150° C., preferably 70-120° C.), air drying, or air drying, to remove any dispersion medium (e.g., water) that may have been introduced during its preparation. According to the present invention, the dried mixed product is also simply referred to as a mixed product.

[0026] According to the present invention, the additive used in step (1) is at least one of protein, urea, chitosan, cellulose, cyanamide, dicyandiamide, melamine, methylguanamine and polydopamine.

[0027] According to the present invention, in step (1), the cellulose used may be those known in the art, such as methyl cellulose, hydroxymethyl cellulose, and the like.

[0028] According to the present invention, the solvent used in step (1) is at least one of water, alcohol, acid, ether and ester. The acid includes inorganic acid and organic acid. As the inorganic acid, at least one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and perchloric acid can be selected. As the organic acid, polycarboxylic acid can be selected, for example, C with 2 to 10 (preferably 3 to 6) carboxyl groups can be cited. 2-20 Examples of alkanes include oxalic acid, succinic acid, adipic acid, and the like. Examples of polycarboxylic acids include C 2-10 (preferably 3-6) carboxyl groups and one or more hydroxyl groups. 2-20 Examples of alkanes include malic acid, tartaric acid, and citric acid.

[0029] According to the present invention, in step (1), alcohol, ether, ester further refers to alcohol, ether, ester having more than 2 carbon atoms, such as ethanol, propanol, butanol, butyl ether, ethyl acetate, ethylene glycol, glycerol, polymethyl methacrylate, etc., and also includes fatty alcohol polyoxyethylene ether with a molecular formula of RO(CH2CH2O)5H, R is C7-C9; alkylphenol polyoxyethylene ether with a molecular formula of RC6H4O(CH2CH2O)nH, R is C9-C12, n is 9-12; octanol polyoxyethylene ether with a molecular formula of C8H 17 (CH2CH2O)nH, n is 1 to 6.

[0030] According to the present invention, the dispersion medium in step (2) is at least one of water, alcohol, acid and ester. The acid includes inorganic acid and organic acid. As the inorganic acid, at least one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and perchloric acid can be selected. As the organic acid, polycarboxylic acid can be selected, for example, C with 2 to 10 (preferably 3 to 6) carboxyl groups can be cited. 2-20 Examples of alkanes include oxalic acid, succinic acid, adipic acid, and the like. Examples of polycarboxylic acids include C 2-10 (preferably 3-6) carboxyl groups and one or more hydroxyl groups. 2-20 Examples of alkanes include malic acid, tartaric acid, and citric acid.

[0031] According to the present invention, the alcohol, ether and ester in the dispersion medium in step (2) further refers to alcohols, ethers and esters having a carbon number greater than 2, such as ethanol, propanol, butanol, butyl ether, ethyl acetate, ethylene glycol, glycerol, polymethyl methacrylate, etc., and also includes fatty alcohol polyoxyethylene ethers having a molecular formula of RO(CH2CH2O)5H, R is C7-C9; alkylphenol polyoxyethylene ethers having a molecular formula of RC6H4O(CH2CH2O)nH, R is C9-C12, and n is 9-12; and octanol polyoxyethylene ethers having a molecular formula of C8H 17 (CH2CH2O)nH, n is 1 to 6.

[0032] According to the present invention, the calcination temperature of the composite system in step (3) is 400-650° C., the calcination time is 1-10 hours, and the calcination atmosphere conditions are air, nitrogen, hydrogen, nitrogen-hydrogen mixture, nitrogen-carbon monoxide mixture, air-carbon monoxide mixture, helium, argon, helium-hydrogen mixture, helium-carbon monoxide mixture, argon-hydrogen mixture or helium-carbon monoxide mixture.

[0033] The present invention also provides an application of a core-shell structured copper-based catalyst in the catalytic oxidation treatment of volatile organic compounds in the presence of trace amounts of oxygen.

[0034] According to the present invention, the catalytic oxidation reaction conditions are as follows: a core-shell structure copper-based catalyst is loaded into a reactor, and a stream containing trace oxygen (300-3000 ppm oxygen) and volatile organic compounds (non-methane total hydrocarbons at 400-1800 mg / m 3 ) gas (the remaining balance gas is mainly nitrogen) VOCs gas, the gas space velocity is 1000~10000h -1 , the reaction temperature is 220-400℃.

[0035] In the application of the present invention, the volatile organic compound is one or a combination of two or more of formaldehyde, methanol, dimethyl ether, ethanol, acetaldehyde, acetic acid, ethylene glycol, glycerol, aromatic hydrocarbons, substituted aromatic hydrocarbons, substituted methane, C2-C10 alkanes, C6-C16 aromatic hydrocarbons, and C4-C16 cycloalkanes.

[0036] Beneficial effects of the present invention:

[0037] The core-shell copper-based catalyst provided by the present invention has a simple and feasible preparation method, with a relatively large proportion of the copper component dispersed in the shell. Compared with existing core-shell copper-based catalysts, the copper component in the catalyst provided by the present invention is highly dispersed in the shell, resulting in a high specific surface area. Strong interactions exist between the copper, the support, and the additives, making the active component less likely to fall off and the grains less likely to grow. Furthermore, the catalyst exhibits excellent resistance to carbon deposition during the catalytic oxidation of VOCs pollutant molecules in trace oxygen conditions, thereby extending the catalyst's lifespan. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the SEM image of Example 1. DETAILED DESCRIPTION

[0039] The embodiments of the present invention will be described in more detail below with reference to specific embodiments. However, those skilled in the art will understand that the specific embodiments described below are only for illustrating the present invention and should not be regarded as limiting the scope of protection of the present invention. On the contrary, the present invention is intended to cover all alternatives, modifications and equivalents that may be included within the scope of the present invention as defined by the claims.

[0040] Unless otherwise specified, the various embodiments of the present invention may be combined in any manner, and the conversion, deformation, and change of the technical solutions obtained thereby are also included in the scope of the present invention and do not exceed the scope of the present invention.

[0041] The present invention is further described in detail below with reference to examples, but the present invention is not limited to these examples.

[0042] In the present invention, the surface area of ​​the original core material is measured by the BET specific surface area measurement method, and the pore volume is measured by the BJH (Barrett-Joyner-Halenda) method.

[0043] In the present invention, the copper and auxiliary element contents of the core-shell structure catalyst are determined by X-ray fluorescence spectrometer according to ASTM D7085-2004.

[0044] The specific surface area of ​​copper was determined by the method described by Antonella Gervasini et al. in "Dispersion and surface states of copper catalysts by temperature-programmed-reduction of oxidized surfaces (s-TPR)" in Applied Catalysis A: General, 2005, Vol. 281 (Issue 1-2), pp. 199-205, wherein the copper catalyst was pre-reduced, then oxidized with N2O, and then temperature-programmed reduced with H2. The specific surface area of ​​copper was calculated using MSA (m 2 g -1 Cu )=MolH2SF.A / 10 4 C M W Cu calculate.

[0045] In the present invention, the thickness of the noble metal on the catalyst surface is measured using SEM with mapping.

[0046] In the present invention, the carbon deposition of the catalyst is tested by thermogravimetric analysis under air conditions at a heating rate of 10° C. / min.

[0047] Example 1

[0048] Spherical alumina (diameter 3.2-3.6 mm, specific surface area 261 m 2 / g, pore volume is 0.41cm 3 / g), manganese nitrate, hydroxymethyl cellulose and water in a mass ratio of 1:0.3:0.2:1.8, a mixed contact body is prepared at 40°C, and the mixed contact body is contacted again with an aqueous solution with a mass concentration of copper nitrate of 20% to obtain a composite system, the contact temperature is 50°C, wherein the mass ratio of aluminum oxide to copper element in the composite system is 50:3, and the composite system is calcined in air at 500°C for 5 hours to obtain a core-shell structure copper-based catalyst A, wherein the mass percentage of copper is 5.2%, the mass percentage of manganese is 7.9%, the copper content within 0.2 mm of the shell layer of the spherical alumina reaches 91% of the total copper content, and the specific surface area of ​​copper is 69 m 2 / g.

[0049] SEM images of core-shell structure copper-based catalyst A Figure 1 ,from Figure 1 It can be seen that copper is highly dispersed in the catalyst shell.

[0050] Example 2

[0051] Spherical alumina (diameter 3.2-3.6 mm, specific surface area 261 m 2 / g, pore volume is 0.41cm 3 / g), cobalt nitrate, hydroxymethyl propyl cellulose and water are contacted in a mass ratio of 1:0.1:0.3:1.2 to prepare a mixed contact body at 50°C, and the mixed contact body is contacted again with an aqueous solution with a mass concentration of copper chloride of 15% to obtain a composite system, the contact temperature is 60°C, wherein the mass ratio of aluminum oxide to copper element in the composite system is 50:4, and the composite system is calcined under nitrogen at 520°C for 3 hours to obtain a core-shell structure copper-based catalyst B, wherein the mass percentage of copper is 6.8%, the mass percentage of cobalt is 5.3%, the copper content within 0.2mm of the shell layer of the spherical alumina reaches 87% of the total copper content, and the specific surface area of ​​copper is 60m 2 / g.

[0052] Example 3

[0053] Spherical silicon oxide (diameter 3.2-3.6 mm, specific surface area 327 m 2 / g, pore volume is 0.49cm 3 / g), lanthanum nitrate hexahydrate, polyethylene glycol-1000 and ethanol in a mass ratio of 1:0.1:0.3:0.9, and a mixed contact body is prepared at 50°C. The mixed contact body is contacted again with an aqueous solution with a copper acetate mass concentration of 15% and an aqueous nitric acid solution with a pH value of 0.05 times the mass of the copper acetate to obtain a composite system. The contact temperature is 60°C, wherein the mass ratio of alumina to copper in the composite system is 50:4. The composite system is calcined in air at 450°C for 4 hours to obtain a core-shell structure copper-based catalyst C, wherein the mass percentage of copper is 7.0%, the mass percentage of lanthanum is 3.9%, the copper content within 0.3 mm of the shell layer of the spherical alumina reaches 82% of the total copper content, and the specific surface area of ​​copper is 48 m 2 / g.

[0054] Example 4

[0055] Spherical molecular sieve (ZSM-5, diameter 2.2-2.8 mm, specific surface area 351 m 2 / g, pore volume is 0.47cm 3 / g), vanadyl oxalate pentahydrate, melamine and ethanol are contacted in a mass ratio of 1:0.3:0.3:0.9 to prepare a mixed contact body at 50°C, and the mixed contact body is contacted again with a copper sulfate aqueous solution with a mass concentration of 5% to obtain a composite system, the contact temperature is 50°C, wherein the mass ratio of spherical molecular sieve to copper element in the composite system is 50:5, and the composite system is calcined under a hydrogen-nitrogen mixed gas (wherein the hydrogen gas volume fraction is 15%) at 500°C for 3 hours to obtain a core-shell structure copper-based catalyst D, wherein the mass percentage of copper is 10.1%, the mass percentage of vanadium is 5.0%, the copper content within 0.3 mm of the shell layer of the spherical alumina reaches 80% of the total copper content, and the specific surface area of ​​copper is 47 m 2 / g.

[0056] Example 5

[0057] MgAl2O4 with a spinel structure was synthesized according to the literature (Low-temperature synthesis of mesoporous nanocrystalline magnesium aluminate (MgAl2O4) spinel with high surface area using a novel modified sol-gel method, Advanced Powder Technology, 2017, 28 (4): 1249-1257) and MgAl2O4 was formed into cylinders (diameter 4 mm, height 8 mm, specific surface area 263 m 2 / g, pore volume is 0.41cm 3 / g), the cylinder, titanium sulfate, protein powder and isopropanol were contacted in a mass ratio of 1:0.1:0.2:1 to prepare a mixed contact body at 50°C, and the mixed contact body was contacted again with an ammonia aqueous solution (pH 13) with a copper phosphate mass concentration of 10% to obtain a composite system, the contact temperature was 60°C, wherein the mass ratio of MgAl2O4:copper element in the composite system was 50:7, and the composite system was calcined under hydrogen conditions at 500°C for 5 hours to obtain a core-shell structure copper-based catalyst E, wherein the mass percentage of copper was 11.7%, the mass percentage of titanium was 3.0%, the copper content within 0.3 mm of the shell layer of MgAl2O4 reached 79% of the total copper content, and the specific surface area of ​​copper was 41 m 2 / g.

[0058] Example 6

[0059] TiO2 nanotubes were synthesized according to the literature (TiO2 nanotubes supported V2O5 for the selective oxidation of methanol to dimethoxymethane, Microporous and Mesoporous Materials, 2008, 116(1-3): 614-621) and were formed into cylinders (with a diameter of 4 mm, a height of 8 mm, and a specific surface area of ​​257 m 2 / g, pore volume is 0.79cm 3 / g), the cylinder, antimony acetate, cerium nitrate, protein powder and isopropyl alcohol are contacted in a mass ratio of 1:0.1:0.1:0.2:1 to prepare a mixed contact body at 50°C, and the mixed contact body is contacted again with a 15% aqueous solution of copper nitrate to obtain a composite system, the contact temperature is 60°C, wherein the mass ratio of TiO2 nanotubes:copper element in the composite system is 50:2.9, and the composite system is calcined in air at 430°C for 4 hours to obtain a core-shell structure copper-based catalyst F, wherein the mass percentage of copper is 5.1%, the mass percentage of antimony is 3.5%, and the mass percentage of cerium is 3.3%. The copper content within 0.3mm of the shell layer of the TiO2 nanotube cylinder reaches 92% of the total copper content, and the specific surface area of ​​copper is 81m 2 / g.

[0060] Example 7

[0061] The cylindrical magnesium oxide (diameter 3mm, height 8mm, specific surface area 79m 2 / g, pore volume is 0.11cm 3 / g), zinc nitrate, hydroxymethyl cellulose and water in a mass ratio of 1:0.1:0.5:1.4, to prepare a mixed contact body at 40°C, and the mixed contact body was contacted again with an aqueous solution with a copper nitrate mass concentration of 20% and n-butanol with a mass fraction of 1 / 20 of copper nitrate to obtain a composite system, the contact temperature was 50°C, wherein the mass ratio of magnesium oxide to copper element in the composite system was 50:2.7, and the composite system was calcined under hydrogen conditions at 500°C for 4 hours to obtain a core-shell structure copper-based catalyst G, wherein the mass percentage of copper was 4.8%, the mass percentage of zinc was 3.2%, the copper content within 0.3mm of the shell layer of the cylindrical magnesium oxide reached 85% of the total copper content, and the specific surface area of ​​copper was 72m 2 / g.

[0062] Example 8

[0063] The cylindrical zinc oxide (diameter 3mm, height 8mm, specific surface area 59m 2 / g, pore volume is 0.08cm 3 / g), zinc nitrate, hydroxymethyl cellulose and water in a mass ratio of 1:0.15:0.5:1.3, to prepare a mixed contact body at 40°C, and the mixed contact body was contacted again with an aqueous solution with a mass concentration of 20% copper nitrate and n-butanol with a mass fraction of 1 / 20 of copper nitrate to obtain a composite system, the contact temperature was 50°C, wherein the mass ratio of zinc oxide to copper element in the composite system was 50:2.2, and the composite system was calcined under hydrogen conditions at 510°C for 3 hours to obtain a core-shell structure copper-based catalyst H, wherein the mass percentage of copper was 3.9%, the mass percentage of zinc was 4.6%, the copper content within 0.3mm of the shell of the cylindrical zinc oxide reached 92% of the total copper content, and the specific surface area of ​​copper was 76m 2 / g.

[0064] Example 9

[0065] The cylindrical silica-alumina composite carrier (3 mm in diameter, 6 mm in height, and a specific surface area of ​​211 m 2 / g, pore volume is 0.32cm 3 / g), antimony acetate, hydroxymethyl propyl cellulose and ethylene glycol in a mass ratio of 1:0.15:0.5:1.1 to prepare a mixed contact body at 40°C, and the mixed contact body is contacted again with an aqueous solution with a mass concentration of 20% copper nitrate and n-butanol with a mass fraction of 1 / 20 of the copper nitrate to obtain a composite system, the contact temperature is 50°C, wherein the mass ratio of silicon oxide-alumina to copper element in the composite system is 50:3.1, and the composite system is calcined under hydrogen-nitrogen conditions (hydrogen gas volume fraction is 15%) at 450°C for 4 hours to obtain a core-shell structure copper-based catalyst I, wherein the mass percentage of copper is 5.4%, the mass percentage of antimony is 5.3%, the copper content within 0.3mm of the shell layer of the cylindrical silicon oxide-alumina reaches 92% of the total copper content, and the specific surface area of ​​copper is 87m 2 / g.

[0066] Example 10

[0067] The cylindrical silica-alumina composite carrier (3 mm in diameter, 6 mm in height, and a specific surface area of ​​211 m 2 / g, pore volume is 0.32cm 3 / g), ammonium molybdate, hydroxymethylpropyl cellulose and ethylene glycol were contacted at a mass ratio of 1:0.14:0:1.1 to prepare a mixed contact body at 45°C, and the mixed contact body was contacted again with an aqueous solution with a mass concentration of 20% copper nitrate to obtain a composite system, the contact temperature was 50°C, wherein the mass ratio of silicon oxide-alumina:copper in the composite system was 50:4.1, and the composite system was calcined under hydrogen-nitrogen conditions (hydrogen gas volume fraction was 15%) at 480°C for 4 hours to obtain a core-shell structure copper-based catalyst J, wherein the mass percentage of copper was 7.0%, the mass percentage of molybdenum was 6.3%, the copper content within 0.3mm of the shell layer of the cylindrical silicon oxide-alumina reached 75% of the total copper content, and the specific surface area of ​​copper was 39m 2 / g.

[0068] Example 11

[0069] The cylindrical chromium oxide-aluminum oxide composite support (3 mm in diameter, 6 mm in height, and a specific surface area of ​​189 m 2 / g, pore volume is 0.23cm 3 / g), gallium nitrate nonahydrate, protein powder and ethylene glycol in a mass ratio of 1:0.12:0.33:1.1, a mixed contact body is prepared at 40°C, and the mixed contact body is contacted again with an aqueous solution with a mass concentration of copper nitrate of 20% to obtain a composite system, the contact temperature is 60°C, wherein the mass ratio of chromium oxide-aluminum oxide: copper element in the composite system is 50:4.2, and the composite system is calcined under hydrogen-nitrogen conditions (hydrogen gas volume fraction is 15%) at 500°C for 4 hours to obtain a core-shell structure copper-based catalyst K, wherein the mass percentage of copper is 7.8%, the mass percentage of gallium is 2.7%, the copper content within 0.3mm of the shell layer of the cylindrical chromium oxide-aluminum oxide reaches 78% of the total copper content, and the specific surface area of ​​copper is 38m 2 / g.

[0070] Example 12

[0071] The cylindrical chromium oxide-aluminum oxide composite support (3 mm in diameter, 6 mm in height, and a specific surface area of ​​189 m 2 / g, pore volume is 0.23cm 3 / g), ammonium perrhenate, hydroxymethylpropyl cellulose, ethylene glycol and water in a mass ratio of 1:0.18:0.33:1.1:1 were contacted at 60°C to prepare a mixed contact body, which was contacted again with an aqueous solution having a mass concentration of 20% copper chloride to obtain a composite system, the contact temperature being 50°C, wherein the mass ratio of chromium oxide-aluminum oxide to copper element in the composite system was 50:3.7, and the composite system was calcined under hydrogen-nitrogen (hydrogen gas volume fraction being 15%) at 480°C for 4 hours to obtain a core-shell structured copper-based catalyst L, wherein the mass percentage of copper was 6.1%, the mass percentage of rhenium was 9.9%, the copper content within 0.3 mm of the shell layer of the cylindrical chromium oxide-aluminum oxide reached 78% of the total copper content, and the specific surface area of ​​copper was 51 m 2 / g.

[0072] Example 13

[0073] The cylindrical chromium oxide-aluminum oxide composite support (3 mm in diameter, 6 mm in height, and a specific surface area of ​​189 m 2 / g, pore volume is 0.23cm 3 / g), bismuth nitrate, hydroxymethyl propyl cellulose and ethanol are contacted in a mass ratio of 1:0.18:0.33:1.1 to prepare a mixed contact body at 55°C, and the mixed contact body is contacted again with an aqueous solution with a mass concentration of copper nitrate of 20% to obtain a composite system, the contact temperature is 50°C, wherein the mass ratio of chromium oxide-aluminum oxide to copper element in the composite system is 50:3.6, and the composite system is calcined under hydrogen-nitrogen conditions (hydrogen gas volume fraction is 15%) at 460°C for 4 hours to obtain a core-shell structure copper-based catalyst M, wherein the mass percentage of copper is 6.1%, the mass percentage of bismuth is 8.1%, the copper content within 0.3mm of the shell layer of the cylindrical chromium oxide-aluminum oxide reaches 78% of the total copper content, and the specific surface area of ​​copper is 63m 2 / g.

[0074] Example 14

[0075] The clover alumina carrier (specific surface area 198m 2 / g, pore volume is 0.26cm 3 / g), silver nitrate, urea and water are contacted in a mass ratio of 1:0.15:0.35:1.2 to prepare a mixed contact body at 70°C, and the mixed contact body is contacted again with an aqueous solution with a mass concentration of copper nitrate of 25% to obtain a composite system, the contact temperature is 50°C, wherein the mass ratio of alumina:copper element in the composite system is 50:8, and the composite system is calcined under hydrogen-nitrogen conditions (hydrogen gas volume fraction is 15%) at 530°C for 4 hours to obtain a core-shell structure copper-based catalyst N, wherein the mass percentage of copper is 12.6%, the mass percentage of silver is 7.3%, the copper content within 0.3mm of the shell layer of clover alumina reaches 78% of the total copper content, and the specific surface area of ​​copper is 32m 2 / g.

[0076] Example 15

[0077] The cylindrical chromium oxide-aluminum oxide composite support (3 mm in diameter, 6 mm in height, and a specific surface area of ​​189 m 2 / g, pore volume is 0.23cm 3 / g), cobalt nitrate hexahydrate, cerium nitrate hexahydrate, urea and water are contacted in a mass ratio of 1:0.22:0.12:0.35:1 to prepare a mixed contact body at 45°C, and the mixed contact body is contacted again with an aqueous solution with a mass concentration of copper nitrate of 20% to obtain a composite system, the contact temperature is 70°C, wherein the mass ratio of chromium oxide-aluminum oxide to copper element in the composite system is 50:3, and the composite system is calcined under hydrogen-nitrogen (hydrogen gas volume fraction is 15%) at 450°C for 4 hours to obtain a core-shell structure copper-based catalyst O, wherein the mass percentage of copper is 5.2%, the mass percentage of cobalt is 3.3%, and the mass percentage of cerium is 3.8%. The copper content within 0.3 mm of the chromium oxide-aluminum oxide shell layer reaches 86% of the total copper content, and the specific surface area of ​​copper is 81 m 2 / g.

[0078] Comparative Example 1

[0079] Comparing with Example 15, the copper content was increased. A cylindrical chromium oxide-aluminum oxide composite support (3 mm in diameter, 6 mm in height, and a specific surface area of ​​189 m 2 / g, pore volume is 0.23cm 3 / g), cobalt nitrate hexahydrate, cerium nitrate hexahydrate, urea and water are contacted in a mass ratio of 1:0.22:0.12:0.35:1 to prepare a mixed contact body at 45°C, and the mixed contact body is contacted again with an aqueous solution with a mass concentration of copper nitrate of 20% to obtain a composite system, and the contact temperature is 70°C, wherein the mass ratio of chromium oxide-aluminum oxide to copper element in the composite system is 50:11, and the composite system is calcined under hydrogen-nitrogen conditions (hydrogen gas volume fraction is 15%) at 450°C for 4 hours to obtain a copper-based catalyst O-1, wherein the mass percentage of copper is 16.3%, the mass percentage of cobalt is 2.8%, and the mass percentage of cerium is 3.2%. The copper content within 0.3 mm of the shell layer of chromium oxide-aluminum oxide reaches 50% of the total copper content, and the specific surface area of ​​copper is 13 m 2 / g.

[0080] Comparative Example 2

[0081] Comparing with Example 15, the mass percentage of the auxiliary agent was increased. A cylindrical chromium oxide-aluminum oxide composite carrier (3 mm in diameter, 6 mm in height, and a specific surface area of ​​189 m 2 / g, pore volume is 0.23cm 3 / g), cobalt nitrate hexahydrate, cerium nitrate hexahydrate, urea and water are contacted in a mass ratio of 1:0.3:0.5:0.35:1 to prepare a mixed contact body at 45°C, and the mixed contact body is contacted again with an aqueous solution with a mass concentration of copper nitrate of 20% to obtain a composite system, and the contact temperature is 70°C, wherein the mass ratio of chromium oxide-aluminum oxide to copper element in the composite system is 50:3, and the composite system is calcined under hydrogen-nitrogen conditions (hydrogen gas volume fraction is 15%) at 450°C for 4 hours to obtain a copper-based catalyst O-2, wherein the mass percentage of copper is 4.6%, the mass percentage of cobalt is 5.1%, and the mass percentage of cerium is 12.3%. The copper content within 0.3mm of the shell layer of chromium oxide-aluminum oxide reaches 83% of the total copper content, and the specific surface area of ​​copper is 37m 2 / g.

[0082] Comparative Example 3

[0083] The cylindrical chromium oxide-aluminum oxide composite support (3 mm in diameter, 6 mm in height, and a specific surface area of ​​189 m 2 / g, pore volume is 0.23cm 3 / g), cobalt nitrate hexahydrate, cerium nitrate hexahydrate and a 20% aqueous solution of copper nitrate in a mass ratio of 1:0.3:0.5:0.88, a mixed contact body was prepared at 45°C, and the composite system was calcined at 450°C under hydrogen-nitrogen (hydrogen gas volume fraction of 15%) for 4 hours to obtain a copper-based catalyst O-3, wherein the mass percentage of copper is 4.6%, the mass percentage of cobalt is 5.1%, and the mass percentage of cerium is 12.3%. The copper content within 0.3mm of the chromium oxide-aluminum oxide shell reaches 33% of the total copper content, and the specific surface area of ​​copper is 24m 2 / g.

[0084] Application Examples

[0085] The core-shell structure copper-based catalysts in Examples 1-15 and the copper-based catalysts in Comparative Examples 1-3 were respectively loaded into a fixed bed, and 500 mg / m 3 Acetaldehyde, 100 mg / m 3 Toluene, 50 mg / m 3 Ethanol and 50 mg / m 3 Ethylene glycol, 1800ppm oxygen, balance nitrogen, at a space velocity of 2000h -1 The performance of the catalyst was investigated for 1000 hours at a reaction temperature of 320°C. The conversion of total non-methane hydrocarbons is shown in Table 1.

[0086] Table 1 Evaluation results of catalyst catalytic oxidation of VOCs

[0087]

[0088]

[0089] As can be seen from Table 1, the core-shell structured copper-based polymer obtained by the preparation method of the present invention has the characteristics of strong resistance to carbon deposition and stable activity in the presence of trace oxygen.

[0090] Compared with the present invention, the copper-based catalyst O-1 obtained in Comparative Example 1 has a lower copper content in the shell layer and a lower specific surface area of ​​copper, and its anti-carbon deposition ability and activity are both poor.

[0091] Compared with the present invention, the copper-based catalyst O-2 obtained in Comparative Example 2 has a higher content of additives, and its anti-carbon deposition ability and activity are relatively poor.

[0092] Compared with the present invention, the copper-based catalyst O-3 obtained in Comparative Example 3 has a higher content of additives and a lower content of copper in the shell layer, and its anti-carbon deposition ability and activity are both poor.

[0093] Although the present invention has been described in detail herein with reference to exemplary embodiments, it should be understood that the invention is not limited to the embodiments described. Those having ordinary skill in the art and having access to the teachings herein will recognize other variations, modifications, and embodiments within the scope of the invention. Therefore, the present invention should be broadly construed in accordance with the claims set forth below.

Claims

1. A core-shell structure copper-based catalyst, characterized in that Contains original core material, copper and additives, the specific surface area of ​​the original core material is 50 to 400m 2 / g, pore volume is 0.1~1.5cm 3 / g, based on the total mass of the copper-based catalyst, the content of copper is 0.5-15% by mass, preferably 1.5-12% by mass, more preferably 1.8-10% by mass, calculated as a metal element, wherein 72-95% by mass of the copper is dispersed in the shell layer, the thickness of the catalyst shell layer is 0.02-0.3 mm, and the content of the additive is 1-15% by mass, calculated as the additive element.

2. A core-shell structure copper-based catalyst according to claim 1, characterized in that: The additive is at least one of titanium, vanadium, chromium, cobalt, nickel, gallium, molybdenum, antimony, manganese, tungsten, rhenium, bismuth, lanthanum, cerium, zinc and silver, preferably at least one of titanium, vanadium, chromium, cobalt, zinc, antimony, bismuth, cerium and manganese, more preferably at least one of cobalt, antimony, cerium, manganese, titanium and vanadium.

3. A core-shell structure copper-based catalyst according to claim 1, characterized in that: The specific surface area of ​​copper measured by N2O titration is 30~93m 2 / g.

4. A core-shell copper-based catalyst according to claim 1, characterized in that: The original core material is selected from at least one of (a), (b) and (c): (a) alumina, titania, zirconia, silica, cerium oxide, zinc oxide, magnesium oxide, silica-alumina, silica-magnesia, chromia-alumina, and silica-zirconia; (b) Molecular sieve: specifically comprising at least one of ZSM, X, Y, β, and mordenite; (c) Spinels with the general formula MO-Al2O3, where M is a divalent metal, form compounds such as MgAl2O4, FeAl2O4, ZnAl2O4, CaAl2O4 and others.

5. The core-shell copper-based catalyst according to claim 1, characterized in that: The original core material has a certain macroscopic shape, the length of its edges or diameters in a certain direction is greater than 2 mm, and the shape is spherical, Raschig ring, strip, clover, four-leaf clover or irregular particles.

6. A method for preparing a core-shell structure copper-based catalyst, characterized in that: The following steps are involved: (1) contacting an original core material, an auxiliary element precursor, an additive, and a solvent to form a mixed contact body; wherein, relative to the original core material, the amount of the additive is 0 to 50% by mass of the original core material, the amount of the solvent is 0.5 to 170% by mass of the original core material, and the composition of the auxiliary element precursor and the original core material after calcination conforms to the aforementioned provisions of the present invention; (2) contacting the mixed contact body with a copper precursor in a predetermined ratio to obtain a composite system; (3) calcining the composite system to obtain the core-shell structure copper-based catalyst.

7. The preparation method according to claim 6, wherein the additive used in step (1) is at least one of protein, urea, chitosan, cellulose, cyanamide, dicyandiamide, melamine, methylguanamine and polydopamine.

8. The preparation method according to claim 6, wherein the solvent used in step (1) is at least one of water, alcohol, acid, ether and ester.

9. The preparation method according to claim 6, wherein the dispersion medium in step (2) is at least one of water, alcohol, acid and ester.

10. The preparation method according to claim 6, wherein the calcination temperature of the composite system in step (3) is 400-650° C., the calcination time is 1-10 hours, and the calcination atmosphere is air, nitrogen, hydrogen, nitrogen-hydrogen mixture, nitrogen-carbon monoxide mixture, air-carbon monoxide mixture, helium, argon, helium-hydrogen mixture, helium-carbon monoxide mixture, argon-hydrogen mixture or helium-carbon monoxide mixture.

11. Use of the core-shell copper-based catalyst according to claim 1 or the core-shell copper-based catalyst prepared according to the preparation method according to any one of claims 6 to 10 in catalytic oxidation treatment of volatile organic compounds in the presence of trace oxygen.

12. The use according to claim 11, characterized in that The catalytic oxidation reaction conditions are as follows: a core-shell copper-based catalyst is loaded into the reactor, and a VOCs gas containing trace oxygen is introduced at a gas space velocity of 1000 to 10000 h -1 , the reaction temperature is 220-400℃.

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