Low specific surface area heat generating material, and preparation method and application thereof

Abstract

The application provides a low specific surface area heat generating material and a preparation method and application thereof, characterized in that: the heat generating material has a core-shell structure, and a structure adjusting layer composed of a structure adjusting agent is further arranged between the core layer and the shell layer; the structure adjusting agent is an oxide of metal M, and the metal M is V, Nb, Mo or Sb; the core layer and the shell layer are both composed of an Al2O3-CaO carrier and an active component copper loaded on the carrier, and the atomic ratio of Cu / (Ca+Al) in the core layer is 0.1-0.3, and the atomic ratio of Cu / (Ca+Al) in the shell layer is 0.3-0.6; the heat generating material exhibits uniform heat generation characteristics and high heat conduction efficiency in an alkane dehydrogenation reaction, simultaneously reduces side reactions such as carbon deposition, improves reaction selectivity and energy efficiency, and can be recycled.

Description

Technical Field

[0001] This invention belongs to the field of alkane dehydrogenation technology, specifically relating to a low specific surface area copper-based heating material and its preparation method and application. Background Technology

[0002] Heating materials have wide applications in the chemical industry, energy sector, and daily life, such as alkane dehydrogenation reaction aids, electric heating elements, and chemical heat pumps. Existing heating materials mainly include metal alloys, carbon-based materials, and ceramic composites. In the chemical industry, especially in alkane dehydrogenation reactions, heating materials not only need to provide sufficient heat but also need to maintain structural stability and sustained activity under high-temperature reducing atmospheres.

[0003] In existing technologies, many heating materials employ high specific surface area carriers (such as γ-Al₂O₃) to load active components, thereby increasing the number of active sites. However, high specific surface area materials are prone to sintering under high-temperature conditions, leading to rapid activity decay and a limited service life. Furthermore, in reactions such as alkane dehydrogenation, high specific surface area carriers often promote side reactions, such as carbon deposition and cracking reactions, reducing the selectivity of the target product.

[0004] For example, CN113388376B discloses an alkane dehydrogenation exothermic agent composed of CaO, CuO, and Al2O3, which improves thermal stability through a specific phase structure. However, this patent does not address the control of carrier morphology and specific surface area, and its preparation method fails to effectively solve the problems of copper component migration and agglomeration at high temperatures.

[0005] Furthermore, in copper-based heating materials, the interaction between the copper component and the carrier is crucial to the material's stability and heating efficiency. In traditional preparation methods, copper is often distributed on the carrier surface in the form of oxides or metals. At high temperatures, it easily forms copper-aluminum spinel with alumina or undergoes sintering, leading to a decrease in activity.

[0006] The alumina-calcium oxide system has good thermal and chemical stability as a carrier, but conventional preparation methods are difficult to control its phase composition and pore structure, often resulting in materials with high specific surface area, which are not suitable for high-temperature reaction conditions. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a low specific surface area heating material, its preparation method, and its application. The heating material uses a certain proportion of alumina and calcium oxide to form a strip-shaped carrier and loads copper active components, forming a "core-shell" gradient structure. It has excellent thermal stability and anti-sintering properties and is suitable for alkane dehydrogenation reactions.

[0008] A low specific surface area heating material, wherein the heating material has a core-shell structure, and a structure regulating layer composed of a structure regulating agent is provided between the core layer and the shell layer; the structure regulating layer serves as a core-shell layering barrier. The structure modifier is an oxide of metal M, wherein metal M is V, Nb, Mo, or Sb; Both the core and shell layers are composed of an Al2O3-CaO support and copper, an active component loaded on the support. The atomic ratio of Cu / (Ca+Al) in the core layer is 0.1-0.3, and the atomic ratio of Cu / (Ca+Al) in the shell layer is 0.3-0.6. In the heating material, the amount of the active component copper is calculated as CuO, and the total amount of Al2O3, CaO and CuO is calculated as 100%. The content of each component is as follows: CaO 15-40%, Al2O3 50-70%, CuO 5-30%; The structure modifier accounts for 0.4-2.5% of the CuO mass.

[0009] Preferably, the heating material has a three-level pore structure consisting of macropores, mesopores, and micropores, with macropores having a porosity of 15-30%, mesopores having a porosity of 8-16%, and the remainder being micropores. In this invention, the macropores have a diameter >50 nm, the mesopores have a diameter of (2-50) nm, and the micropores have a diameter <2 nm.

[0010] Preferably, the specific surface area of ​​the heating material is 2-60 m². 2 / g. More preferably, the specific surface area of ​​the heating material is 5-25m². 2 / g.

[0011] Preferably, the thickness of the shell layer is 60-240 μm.

[0012] Preferably, the heating material has a cylindrical strip structure with a diameter of 2-4 mm, a length of 3-7.2 mm, and a bulk density of 0.8-1.5 g / cm³. 3 .

[0013] The preparation method of the low specific surface area heating material includes the following steps: (1) Aluminum source, calcium source and water are mixed and ball-milled to form a uniform slurry. The slurry is then spray-dried to obtain calcium aluminate precursor powder. (2) Add the calcium aluminate precursor and molding aid together to a kneader and knead evenly under vacuum until it becomes a lump. Then extrude it to obtain a strip carrier with a porous structure. (3) The strip-shaped support is dried and then microwave-calcined in a stepwise manner to obtain an Al2O3-CaO support; (4) The active copper component and structure modifier are loaded by concentration gradient impregnation method, and the heating material is obtained by drying and temperature-controlled thermal reduction treatment.

[0014] Preferably, the aluminum source is boehmite, aluminum nitrate, or aluminum hydroxide; the calcium source is calcium carbonate, calcium hydroxide, or calcium nitrate; in step (1), the total mass ratio of the aluminum source and the calcium source to the mass of water is 1:(0.06-0.4); The molding aids include a binder, a plasticizer, a pore-forming agent, and a surface modifier; the binder is at least one selected from guar gum powder, methylcellulose, guar gum, locust bean gum, agar, sodium alginate, chitosan, and polyvinyl alcohol; the plasticizer is glycerol or polyethylene glycol; the pore-forming agent is kapok fiber, bamboo fiber, sucrose, glucose, or sodium bicarbonate; the surface modifier is at least one selected from ammonium bicarbonate, ammonium carbonate, and ammonium carbamate; the binder, plasticizer, pore-forming agent, and surface modifier account for 0.05-0.15%, 0.5-2%, 3-8%, and 0.04-0.2% of the mass of the calcium aluminate precursor, respectively.

[0015] Preferably, the microwave stepped calcination involves first holding at 400-550℃ for 0.5-2 hours to remove organic components, and then holding at 1050-1200℃ for 3-6 hours to form a crystal structure. The microwave power is 500-2000W. The concentration gradient impregnation method is as follows: First, the Al2O3-CaO support is impregnated with a 5-27wt% copper salt solution for 1-2 hours, while the salt corresponding to metal M is added, and then dried. Second, the support is impregnated with a 20-38% copper salt solution for 1-2 hours, and the concentration of the copper salt solution in the second impregnation is greater than that in the first impregnation.

[0016] More preferably, the copper salt is copper nitrate, copper acetate, or copper chloride; when the metal M is V, the corresponding vanadium salt is sodium metavanadate or ammonium metavanadate; when the metal M is Nb, the corresponding niobium salt is niobium oxalate or niobium chloride; when the metal M is Mo, the molybdenum salt is ammonium molybdate or sodium molybdate; when the metal M is Sb, the corresponding antimony salt is antimony nitrate or antimony chloride.

[0017] Preferably, the drying is a gradient staged drying process, first maintaining the temperature at 60-80℃ for 12-18 hours, and then maintaining the temperature at 105-120℃ for 18-24 hours.

[0018] Preferably, the programmed temperature-controlled thermal reduction treatment involves first reducing the temperature at 300-400℃ for 0.5-3 hours to weakly reduce and form seed crystals, then reducing the temperature at 500-700℃ for 0.5-3 hours to moderately reduce and construct a core-shell structure, and finally reducing the temperature at 750-900℃ for 3-6.5 hours to strongly reduce and stabilize the active phase.

[0019] Preferably, the ball milling time is 2-8 hours.

[0020] Preferably, the kneading temperature is controlled below 35°C, and the kneading time is 2-6.5 hours.

[0021] Preferably, the extrusion molding is performed using a twin-screw extruder, followed by pelletizing to the desired length; the extrusion temperature is 30-50℃ and the pressure is 2-6.5MPa; the die of the twin-screw extruder is designed with a porous honeycomb structure, and the pore size matches the diameter of the heating material.

[0022] Application of the heating material in alkane dehydrogenation reaction: The heating material is mixed evenly with the alkane dehydrogenation catalyst, packed into a fixed-bed reactor, and alkanes are introduced. The dehydrogenation reaction is carried out at 570-620℃ under normal pressure, with a mass hourly space velocity (WHSV) of 1-2 h⁻¹. -1 The mass ratio of the heating material to the alkane dehydrogenation catalyst is 1:2.

[0023] Preferably, after the dehydrogenation reaction has been carried out for a period of time, steam, air, and hydrogen are introduced respectively to regenerate and cycle the heating material and the catalyst.

[0024] More preferably, the operation time of one round of dehydrogenation reaction and regeneration cycle is 40 min, specifically: after 9 min of dehydrogenation reaction, steam is introduced for 1 min of purging, air is introduced for 15 min of regeneration, and hydrogen is introduced for activation for 15 min. The flow rates of the steam, air, and hydrogen are all in the ratio of (2-3.5) mL / min to the total mass of the heating material and catalyst.

[0025] The flow rates of the steam, air, and hydrogen may be the same or different.

[0026] The steam is water vapor.

[0027] Advantages of this invention: (1) Innovation in carrier composition and structure: The active component copper and the structure regulator are loaded by the concentration gradient impregnation method. Although both the core layer and the shell layer are composed of Al2O3-CaO carrier and active component copper loaded on the carrier, the shell layer is an alumina-calcium oxide outer framework rich in high concentration of copper active component, and the core layer is an alumina-calcium oxide central framework containing low concentration of active component copper, forming a "core-shell" gradient structure. This avoids the presence of free alumina, thereby preventing CuO from forming aluminum copper spinel with alumina and improving the dispersion and stability of copper component. (2) Advantages of low specific surface area: The carrier prepared by biomimetic multi-level channel design and microwave-assisted heat treatment process has low specific surface area, which reduces the sintering phenomenon driven by surface energy at high temperature and improves the service life of the material under high temperature conditions. (3) Innovative preparation process: The preparation sequence of first forming and then loading is adopted, combined with a specific heat treatment process, so that copper element mainly exists in the form of CaCu2O3 and Ca2CuO3. These composite oxides have excellent structural stability and heat dissipation performance at high temperature. (4) Advantages in heating performance: It exhibits uniform heating characteristics and high thermal conductivity in the dehydrogenation reaction of alkane, while reducing side reactions such as carbon deposition, improving reaction selectivity and energy efficiency, and can be recycled. Detailed Implementation

[0028] Example 1 1. A low specific surface area heating material, having a cylindrical strip structure with a diameter of 3 mm, a length of 5 mm, and a bulk density of 1.0 g / cm³. 3 The heating material has a core-shell structure, the shell layer is 120 μm thick, and there is a structure regulating layer composed of a structure regulating agent between the core layer and the shell layer, the structure regulating layer serving as a core-shell layering barrier. The structure modifier is an oxide of metal V, V₂O₃; Both the core and shell layers are composed of an Al2O3-CaO support and copper, an active component loaded on the support. The atomic ratio of Cu / (Ca+Al) in the core layer is 0.2, and the atomic ratio of Cu / (Ca+Al) in the shell layer is 0.4. In the heating material, the amount of the active component copper is calculated as CuO, and the contents of Al2O3, CaO, and CuO are as follows: CaO 30%, Al2O3 60%, CuO 10%; the structure modifier accounts for 1.5% of the mass of CuO. 2. The preparation method of the heating material: (1) Weigh 60g of boehmite, 53.6g of calcium carbonate and 30g of water, mix them, and ball mill for 4 hours to form a uniform slurry. The slurry is then spray-dried to obtain calcium aluminate precursor powder. (2) Weigh 100g of calcium aluminate precursor powder and add molding aids, including 0.1g of guar gum powder, 1g of glycerol, 5g of kapok fiber and 0.08g of ammonium bicarbonate. Add the mixture to a kneader and knead it for 4 hours under vacuum at 35°C to form a lumpy mass. Then, extrude it into a strip with a diameter of 3mm in a twin-screw extruder (temperature 40°C, pressure 4MPa). Cut it into strips with a length of 5mm to obtain a strip carrier with a porous structure. (3) The strip-shaped carrier is dried in segments. First, it is kept at 70°C for 16 hours, then the temperature is raised to 110°C and kept for 20 hours. Then, microwave step-calcination is used. First, it is kept at 500°C for 1 hour, then kept at 1100°C for 4 hours. The microwave power is 1000W to obtain Al2O3-CaO carrier. (4) Weigh 15.2g of copper nitrate trihydrate to prepare a 10% copper salt solution, and add 0.35g of ammonium metavanadate to impregnate the Al2O3-CaO support for 1h. After impregnation, keep it at 70℃ for 16h, then raise the temperature to 110℃ and keep it for 20h. Then take 15g of copper nitrate trihydrate to prepare a 25% copper salt solution and impregnate it for the second time for 1h. Then keep it at 70℃ for 16h, then raise the temperature to 110℃ and keep it for 20h. Use programmed temperature-controlled thermal reduction treatment: first weakly reduce at 350℃ for 2h to form seed crystals, then moderately reduce at 600℃ for 1h to construct a core-shell structure, and finally strongly reduce at 800℃ for 4h to stabilize the active phase. The resulting heating material is denoted as S1.

[0029] Example 2 1. A low specific surface area heating material, having a cylindrical strip structure with a diameter of 2.5 mm, a length of 4.5 mm, and a bulk density of 1.2 g / cm³. 3 The heating material has a core-shell structure, the shell layer is 200 μm thick, and there is a structure regulating layer composed of a structure regulating agent between the core layer and the shell layer, the structure regulating layer serving as a core-shell layering barrier. The structure modifier is NbO, an oxide of metallic Nb; Both the core and shell layers are composed of an Al2O3-CaO support and copper, an active component loaded on the support. The atomic ratio of Cu / (Ca+Al) in the core layer is 0.25, and the atomic ratio of Cu / (Ca+Al) in the shell layer is 0.5. In the heating material, the amount of the active component copper is calculated as CuO, and the contents of Al2O3, CaO, and CuO are as follows: CaO 35%, Al2O3 55%, CuO 10%; the structure modifier accounts for 2% of the mass of CuO. 2. The preparation method of the heating material: (1) Weigh 229.7g aluminum nitrate, 46.25g calcium hydroxide and 25g water, mix them, ball mill for 6 hours to form a uniform slurry, take the slurry and spray dry it to obtain calcium aluminate precursor powder; (2) Weigh 100g of calcium aluminate precursor powder and add molding aids, including 0.08g of methylcellulose, 1.5g of polyethylene glycol, 6g of bamboo fiber and 0.15g of ammonium carbonate. Add the mixture to a kneader and knead it for 6 hours under vacuum at 35°C to form a lumpy mass. Then, extrude it into a strip with a diameter of 2.5mm in a twin-screw extruder (temperature 35°C, pressure 3MPa). Cut it into strips with a length of 4.5mm to obtain a strip carrier with a porous structure. (3) The strip-shaped carrier is dried in segments. First, it is kept at 65°C for 14 hours, then the temperature is raised to 108°C and kept for 22 hours. Then, microwave step-calcination is used. First, it is kept at 480°C for 1.5 hours, then kept at 1150°C for 4.5 hours. The microwave power is 800W to obtain Al2O3-CaO carrier. (4) Weigh 10.96g of copper acetate to prepare an 8% copper salt solution, and add 1.16g of niobium oxalate to impregnate the Al2O3-CaO support for 1h. After impregnation, keep it at 65℃ for 14h, then raise the temperature to 108℃ and keep it for 22h. Then take 14g of copper nitrate trihydrate to prepare a 30% copper salt solution and impregnate it for the second time for 1h. Then perform segmented drying, keep it at 65℃ for 14h, then raise the temperature to 108℃ and keep it for 22h. Use programmed temperature-controlled thermal reduction treatment: first weakly reduce at 380℃ for 1.5h to form seed crystals, then moderately reduce at 550℃ for 2h to construct a core-shell structure, and finally strongly reduce at 850℃ for 5h to stabilize the active phase. The resulting heating material is denoted as S2.

[0030] Example 3 1. A low specific surface area heating material, having a cylindrical strip structure with a diameter of 3.5 mm, a length of 3.5 mm, and a bulk density of 0.8 g / cm³. 3 The heating material has a core-shell structure, the shell layer is 180 μm thick, and there is a structure regulating layer composed of a structure regulating agent between the core layer and the shell layer, the structure regulating layer serving as a core-shell layering barrier. The structure modifier is MoO2, an oxide of metallic Mo; Both the core and shell layers are composed of an Al2O3-CaO support and copper, an active component loaded on the support. The atomic ratio of Cu / (Ca+Al) in the core layer is 0.15, and the atomic ratio of Cu / (Ca+Al) in the shell layer is 0.45. In the heating material, the amount of the active component copper is calculated as CuO, and the contents of Al2O3, CaO, and CuO are as follows: CaO 25%, Al2O3 50%, CuO 25%; the structure modifier accounts for 0.8% of the mass of CuO. 2. The preparation method of the heating material: (1) Weigh 76.47g of aluminum hydroxide, 25g of calcium nitrate and 28g of water and mix them. Ball mill for 3 hours to form a uniform slurry. The slurry is spray dried to obtain calcium aluminate precursor powder. (2) Weigh 100g of calcium aluminate precursor powder and add molding aids, including 0.05g of guar gum, 0.8g of glycerol, 7g of sucrose and 0.05g of ammonium carbamate. Add the mixture to a kneader and knead it for 5 hours under vacuum at 35°C to form a lumpy mass. Then, extrude it into a strip with a diameter of 3.5mm in a twin-screw extruder (temperature 35°C, pressure 2.5MPa). Cut it into strips with a length of 3.5mm to obtain a strip carrier with a porous structure. (3) The strip-shaped carrier is dried in segments. First, it is kept at 60°C for 18 hours, then the temperature is raised to 105°C and kept for 24 hours. Then, microwave step-calcination is used. First, it is kept at 420°C for 1.8 hours, then kept at 1080°C for 5 hours. The microwave power is 1500W to obtain Al2O3-CaO carrier. (4) Weigh 18g of copper chloride to prepare a 27% copper salt solution, and add 0.41g of ammonium molybdate to impregnate the Al2O3-CaO support for 1h. After impregnation, keep it at 60℃ for 18h, then raise the temperature to 105℃ and keep it for 24h. Then take 24g of copper chloride to prepare a 30% copper salt solution and impregnate it for the second time for 1h. Then perform segmented drying, keep it at 60℃ for 18h, then raise the temperature to 105℃ and keep it for 24h. Use programmed temperature-controlled thermal reduction treatment: first weakly reduce at 330℃ for 1h to form seed crystals, then moderately reduce at 560℃ for 0.8h to construct the core-shell structure, and finally strongly reduce at 820℃ for 4.6h to stabilize the active phase. The resulting heating material is called S3.

[0031] Example 4 1. A low specific surface area heating material, having a cylindrical strip structure with a diameter of 2.2 mm, a length of 3 mm, and a bulk density of 1.5 g / cm³. 3 The heating material has a core-shell structure, the shell layer is 100 μm thick, and there is a structure regulating layer composed of a structure regulating agent between the core layer and the shell layer, the structure regulating layer serving as a core-shell layering barrier. The structure modifier is Sb2O3, an oxide of metallic Sb. Both the core and shell layers are composed of an Al2O3-CaO support and copper, an active component loaded on the support. The atomic ratio of Cu / (Ca+Al) in the core layer is 0.24, and the atomic ratio of Cu / (Ca+Al) in the shell layer is 0.35. In the heating material, the amount of the active component copper is calculated as CuO, and the contents of Al2O3, CaO, and CuO are as follows: CaO 22.5%, Al2O3 58%, CuO 19.5%; the structure modifier accounts for 1% of the mass of CuO. 2. The preparation method of the heating material: (1) Weigh 58g of boehmite, 40.18g of calcium carbonate and 35g of water, mix them, and ball mill for 5h to form a uniform slurry. The slurry is then spray-dried to obtain calcium aluminate precursor powder. (2) Weigh 100g of calcium aluminate precursor powder and add molding aids, including a mixture of 0.06g sodium alginate, 0.5g polyethylene glycol, 4g glucose, 0.06g ammonium carbonate and ammonium bicarbonate. Add the mixture to a kneader and knead it for 5.5h under vacuum at 35°C to form a colloid. Then, extrude it into a strip with a diameter of 2.2mm in a twin-screw extruder (temperature 30°C, pressure 2MPa). Cut it into strips with a length of 3mm to obtain a strip carrier with a porous structure. (3) The strip-shaped carrier is dried in segments. First, it is kept at 80°C for 12 hours, then the temperature is raised to 120°C and kept for 18 hours. Then, microwave step-calcination is used. First, it is kept at 400°C for 2 hours, then kept at 1050°C for 6 hours. The microwave power is 1800W to obtain Al2O3-CaO carrier. (4) Weigh 28.89g of copper nitrate trihydrate to prepare an 8.5% copper salt solution, add 0.49g of antimony nitrate, and impregnate the Al2O3-CaO support for 1h. After impregnation, keep it at 80℃ for 12h, then raise the temperature to 120℃ and keep it for 18h. Then take 30g of copper nitrate trihydrate to prepare a 32% copper salt solution and impregnate it for the second time for 1h. Then perform segmented drying, keep it at 80℃ for 12h, then raise the temperature to 120℃ and keep it for 18h. Use programmed temperature-controlled thermal reduction treatment: first weakly reduce at 360℃ for 2.5h to form seed crystals, then moderately reduce at 610℃ for 1.5h to construct the core-shell structure, and finally strongly reduce at 880℃ for 3.5h to stabilize the active phase. The resulting heating material is denoted as S4.

[0032] Example 5 1. A low specific surface area heating material, having a cylindrical strip structure with a diameter of 2 mm, a length of 5.2 mm, and a bulk density of 1.2 g / cm³. 3 The heating material has a core-shell structure, the shell layer is 60 μm thick, and there is a structure regulating layer composed of a structure regulating agent between the core layer and the shell layer, the structure regulating layer serving as a core-shell layering barrier. The structure modifier is an oxide of metal V, VO; Both the core and shell layers are composed of an Al2O3-CaO support and copper, an active component loaded on the support. The atomic ratio of Cu / (Ca+Al) in the core layer is 0.1, and the atomic ratio of Cu / (Ca+Al) in the shell layer is 0.3. In the heating material, the amount of the active component copper is calculated as CuO, and the contents of Al2O3, CaO, and CuO are as follows: CaO 15%, Al2O3 70%, CuO 15%; the structure modifier accounts for 0.6% of the mass of CuO. 2. The preparation method of the heating material: (1) Weigh 70g of boehmite, 19.82g of calcium hydroxide and 36g of water, mix them, and ball mill for 7h to form a uniform slurry. The slurry is then spray-dried to obtain calcium aluminate precursor powder. (2) Weigh 100g of calcium aluminate precursor powder and add molding aids, including a mixture of 0.07g chitosan and agar, 1.8g polyethylene glycol, 3g kapok fiber, and a mixture of 0.18g ammonium bicarbonate, ammonium carbonate, and ammonium carbamate. Add the mixture to a kneader and knead it for 7 hours under vacuum at 35°C to form a colloid. Then, extrude it into a strip with a diameter of 2mm in a twin-screw extruder (temperature 38°C, pressure 3.8MPa). Cut it into strips with a length of 5.2mm to obtain a strip carrier with a porous structure. (3) The strip-shaped carrier is dried in segments. First, it is kept at 75°C for 15 hours, then the temperature is raised to 115°C and kept for 20 hours. Then, microwave step-calcination is used. First, it is kept at 550°C for 0.5 hours, then kept at 1200°C for 3 hours. The microwave power is 500W to obtain Al2O3-CaO carrier. (4) Weigh 18.5g of copper acetate to prepare a 9% copper salt solution, and add 0.21g of ammonium metavanadate to impregnate the Al2O3-CaO support for 1h. After impregnation, keep it at 75℃ for 15h, then raise the temperature to 120℃ and keep it for 18h. Then take 18.93g of copper acetate to prepare a 20% copper salt solution and impregnate it for the second time for 1h. Then perform segmented drying, keep it at 75℃ for 15h, then raise the temperature to 120℃ and keep it for 18h. Use programmed temperature-controlled thermal reduction treatment: first weakly reduce at 300℃ for 0.5h to form seed crystals, then moderately reduce at 500℃ for 0.5h to construct the core-shell structure, and finally strongly reduce at 750℃ for 3h to stabilize the active phase. The resulting heating material is called S5.

[0033] Example 6 1. A low specific surface area heating material, having a cylindrical strip structure with a diameter of 3.8 mm, a length of 6 mm, and a bulk density of 0.9 g / cm³. 3 The heating material has a core-shell structure, the shell layer is 240 μm thick, and there is a structure regulating layer composed of a structure regulating agent between the core layer and the shell layer, the structure regulating layer serving as a core-shell layering barrier. The structure modifier is MoO2, an oxide of metallic Mo; Both the core and shell layers are composed of an Al2O3-CaO support and copper, an active component loaded on the support. The atomic ratio of Cu / (Ca+Al) in the core layer is 0.3, and the atomic ratio of Cu / (Ca+Al) in the shell layer is 0.6. In the heating material, the amount of the active component copper is calculated as CuO, and the contents of Al2O3, CaO, and CuO are as follows: CaO 34%, Al2O3 61%, CuO 5%; the structure modifier accounts for 0.4% of the mass of CuO. 2. The preparation method of the heating material: (1) Weigh 254.76g of aluminum nitrate, 97.14g of calcium nitrate and 24g of water, mix them, and ball mill for 8 hours to form a uniform slurry. The slurry is then spray-dried to obtain calcium aluminate precursor powder. (2) Weigh 100g of calcium aluminate precursor powder and add molding aids, including a mixture of 0.09g of polyvinyl alcohol, chitosan and guar gum powder, 0.65g of glycerol, 6.5g of sucrose and 0.16g of ammonium carbonate, add to a kneader, knead for 3h at 35℃ under vacuum to form a colloid, and then extrude it into a strip with a diameter of 3.8mm in a twin-screw extruder (temperature 48℃, pressure 2.4MPa), cut it into 6mm lengths to obtain a strip carrier with a porous structure; (3) The strip-shaped carrier is dried in segments. First, it is kept at 60°C for 15 hours, then the temperature is raised to 110°C and kept for 22 hours. Then, microwave step-calcination is used. First, it is kept at 430°C for 1.8 hours, then kept at 1060°C for 5.5 hours. The microwave power is 750W to obtain Al2O3-CaO carrier. (4) Weigh 2.4g of copper chloride to prepare a 5% copper salt solution, add 0.04g of sodium molybdate, and impregnate the Al2O3-CaO support for 1h. After impregnation, keep it at 60℃ for 15h, then raise the temperature to 120℃ and keep it for 18h. Then take 6g of copper chloride to prepare a 24% copper salt solution and impregnate it for the second time for 1h. Then perform segmented drying, keep it at 60℃ for 15h, then raise the temperature to 120℃ and keep it for 18h. Use programmed temperature-controlled thermal reduction treatment: first weakly reduce at 400℃ for 3h to form seed crystals, then moderately reduce at 700℃ for 3h to construct the core-shell structure, and finally strongly reduce at 900℃ for 6.5h to stabilize the active phase. The resulting heating material is called S6.

[0034] Example 7 1. A low specific surface area heating material, having a cylindrical strip structure with a diameter of 2.5 mm, a length of 3.8 mm, and a bulk density of 1.3 g / cm³. 3The heating material has a core-shell structure, the shell layer is 230 μm thick, and there is a structure regulating layer composed of a structure regulating agent between the core layer and the shell layer, the structure regulating layer serving as a core-shell layering barrier. The structure modifier is SbO, an oxide of metallic Sb. Both the core and shell layers are composed of an Al2O3-CaO support and copper, an active component loaded on the support. The atomic ratio of Cu / (Ca+Al) in the core layer is 0.21, and the atomic ratio of Cu / (Ca+Al) in the shell layer is 0.36. In the heating material, the amount of the active component copper is calculated as CuO, and the contents of Al2O3, CaO, and CuO are as follows: CaO 20%, Al2O3 50%, CuO 30%; the structure modifier accounts for 1.8% of the mass of CuO. 2. The preparation method of the heating material: (1) Weigh 50g of boehmite, 57.14g of calcium nitrate and 40g of water, mix them, and ball mill for 2 hours to form a uniform slurry. The slurry is then spray-dried to obtain calcium aluminate precursor powder. (2) Weigh 100g of calcium aluminate precursor powder and add molding aids, including 0.13g of locust bean gum, 1.2g of polyethylene glycol, 4.4g of bamboo fiber and 0.04g of ammonium bicarbonate. Add the mixture to a kneader and knead it for 2 hours under vacuum at 35°C to form a lumpy mass. Then, extrude it into a strip with a diameter of 2.5mm in a twin-screw extruder (temperature 40°C, pressure 4MPa). Cut it into strips with a length of 3.8mm to obtain a strip carrier with a porous structure. (3) The strip-shaped carrier is dried in segments. First, it is kept at 68°C for 17 hours, then the temperature is raised to 106°C and kept for 23 hours. Then, microwave step-calcination is used. First, it is kept at 500°C for 1.2 hours, then kept at 1100°C for 4.5 hours. The microwave power is 2000W to obtain Al2O3-CaO carrier. (4) Weigh 42.6g of copper nitrate trihydrate to prepare a 15% copper salt solution, and add 1.01g of antimony chloride. Impregnate the Al2O3-CaO support for 1h. After impregnation, keep it at 68℃ for 17h, then raise the temperature to 120℃ and keep it for 18h. Then take 48g of copper nitrate trihydrate to prepare a 38% copper salt solution and impregnate it for the second time for 1h. Then perform segmented drying. Keep it at 68℃ for 17h, then raise the temperature to 120℃ and keep it for 18h. Use programmed temperature-controlled thermal reduction treatment: first weakly reduce at 345℃ for 0.8h to form seed crystals, then moderately reduce at 578℃ for 2.7h to construct the core-shell structure, and finally strongly reduce at 856℃ for 5.6h to stabilize the active phase. The resulting heating material is called S7.

[0035] Example 8 1. A low specific surface area heating material, having a cylindrical strip structure with a diameter of 4 mm, a length of 7.2 mm, and a bulk density of 1.4 g / cm³. 3 The heating material has a core-shell structure, the shell layer is 75 μm thick, and there is a structure regulating layer composed of a structure regulating agent between the core layer and the shell layer, the structure regulating layer serving as a core-shell layering barrier. The structure modifier is NbO, an oxide of metallic Nb; Both the core and shell layers are composed of an Al2O3-CaO support and copper, an active component loaded on the support. The atomic ratio of Cu / (Ca+Al) in the core layer is 0.27, and the atomic ratio of Cu / (Ca+Al) in the shell layer is 0.55. In the heating material, the amount of the active component copper is calculated as CuO, and the contents of Al2O3, CaO, and CuO are as follows: CaO 40%, Al2O3 52.5%, CuO 7.5%; the structure modifier accounts for 2.5% of the mass of CuO. 2. The preparation method of the heating material: (1) Weigh 80.29g of aluminum hydroxide, 71.43g of calcium carbonate and 30g of water, mix them, and ball mill for 5.5h to form a uniform slurry. The slurry is then spray-dried to obtain calcium aluminate precursor powder. (2) Weigh 100g of calcium aluminate precursor powder and add molding aids, including 0.15g of methylcellulose, 2g of glycerol, 8g of glucose and 0.2g of ammonium carbamate. Add the mixture to a kneader and knead it for 8 hours under vacuum at 35°C to form a lumpy mass. Then, extrude it into a strip with a diameter of 4mm in a twin-screw extruder (temperature 50°C, pressure 6.5MPa). Cut it into strips with a length of 7.2mm to obtain a strip carrier with a porous structure. (3) The strip-shaped carrier is dried in segments. First, it is kept at 75°C for 18 hours, then the temperature is raised to 106°C and kept for 22 hours. Then, microwave step-calcination is used. First, it is kept at 520°C for 1.8 hours, then kept at 1175°C for 4.4 hours. The microwave power is 1650W to obtain Al2O3-CaO carrier. (4) Weigh 6g of copper chloride to prepare a 6% copper salt solution, add 0.47g of niobium tetrachloride, impregnate the Al2O3-CaO support for 1h, after impregnation, keep it at 68℃ for 17h, then raise the temperature to 120℃ and keep it for 18h, then take 6.2g of copper chloride to prepare a 35% copper salt solution, impregnate for the second time for 1h; then perform segmented drying, keep it at 68℃ for 17h, then raise the temperature to 120℃ and keep it for 18h; use programmed temperature-controlled thermal reduction treatment: first weak reduction at 350℃ for 1.2h to form seed crystals, then moderate reduction at 640℃ for 2.4h to construct the core-shell structure, and finally strong reduction at 860℃ for 3.5h to stabilize the active phase. The resulting heating material is denoted as S8.

[0036] Performance testing 1. Specific surface area distribution data of each heating material at different pore sizes. ; 2. Evaluation of propane dehydrogenation performance To investigate the promoting effect of the aforementioned heating material on the propane dehydrogenation to propylene reaction, the heating material was used in the propane dehydrogenation to propylene reaction, specifically as follows: 30g of the heating material was mixed evenly with 60g of a chromium-based propane dehydrogenation catalyst, and the mixture was packed into a stainless steel reaction tube of a fixed-bed reactor. Propane was introduced, and the dehydrogenation reaction was carried out at 580℃ under normal pressure, with a propane mass hourly space velocity of 1.2 h⁻¹. -1 The propane dehydrogenation chromium-based catalyst used is the catalyst disclosed in Example 1 of patent CN 120984265 A. After a certain period of dehydrogenation reaction, a regeneration cycle is performed. The operation time of one round of dehydrogenation reaction and regeneration cycle is 40 min, specifically: after 9 min of dehydrogenation reaction, steam purging for 1 min, air regeneration for 15 min, and hydrogen activation for 15 min. The flow rate of each gas and the total mass ratio of heating material and catalyst are 3.5 mL / min: 1 g. The product is analyzed by online gas phase detection to determine the yield of propylene. The regeneration cycle is repeated 200 times. The reaction results are shown in Table 2. The reaction without heating material is used as a blank control. The reaction using commercially available Clariant HGM heating material instead of the heating material described in this invention is used as a comparative example.

[0037] Table 2 Results of the propane dehydrogenation to propylene reaction

Claims

1. A low specific surface area heating material, characterized in that: The heating material has a core-shell structure, and there is a structure regulating layer composed of a structure regulating agent between the core layer and the shell layer; The structure modifier is an oxide of metal M, wherein metal M is V, Nb, Mo, or Sb; Both the core and shell layers are composed of an Al2O3-CaO support and copper, an active component loaded on the support. The atomic ratio of Cu / (Ca+Al) in the core layer is 0.1-0.3, and the atomic ratio of Cu / (Ca+Al) in the shell layer is 0.3-0.

6. In the heating material, the amount of active component copper is calculated as CuO, and the total amount of Al2O3, CaO and CuO is calculated as 100%. The content of each component is as follows: CaO 15-40%, Al2O3 50-70%, CuO 5-30%; the structure modifier accounts for 0.4-2.5% of the mass of CuO.

2. The low specific surface area heating material according to claim 1, characterized in that: The heating material has a three-level pore structure consisting of macropores, mesopores, and micropores, with a macropore porosity of 15-30%, a mesopore porosity of 8-16%, and the remainder being micropores; the specific surface area of ​​the heating material is 2-60 m². 2 / g.

3. The low specific surface area heating material according to claim 1, characterized in that: The thickness of the shell is 60-240 μm.

4. The low specific surface area heating material according to claim 1, characterized in that, The heating material has a cylindrical strip structure with a diameter of 2-4 mm, a length of 3-7.2 mm, and a bulk density of 0.8-1.5 g / cm³. 3 .

5. The method for preparing a low specific surface area heating material according to claim 1, characterized in that: Includes the following steps: (1) Aluminum source, calcium source and water are mixed and ball-milled to form a uniform slurry. The slurry is then spray-dried to obtain calcium aluminate precursor powder. (2) Add the calcium aluminate precursor and molding aid together to a kneader and knead evenly under vacuum until it becomes a lump. Then extrude it to obtain a strip carrier with a porous structure. (3) The strip-shaped support is dried and then microwave-calcined in a stepwise manner to obtain an Al2O3-CaO support; (4) The active copper component and structure modifier are loaded by concentration gradient impregnation method, and the heating material is obtained by drying and temperature-controlled thermal reduction treatment.

6. The method for preparing a low specific surface area heating material according to claim 5, characterized in that: The aluminum source is boehmite, aluminum nitrate, or aluminum hydroxide; the calcium source is calcium carbonate, calcium hydroxide, or calcium nitrate; in step (1), the total mass of the aluminum source and calcium source is in the mass ratio of water to 1:(0.06-0.4); The molding aids include a binder, a plasticizer, a pore-forming agent, and a surface modifier; the binder is at least one selected from guar gum powder, methylcellulose, guar gum, locust bean gum, agar, sodium alginate, chitosan, and polyvinyl alcohol; the plasticizer is glycerol or polyethylene glycol; the pore-forming agent is kapok fiber, bamboo fiber, sucrose, glucose, or sodium bicarbonate; the surface modifier is at least one selected from ammonium bicarbonate, ammonium carbonate, and ammonium carbamate; the binder, plasticizer, pore-forming agent, and surface modifier account for 0.05-0.15%, 0.5-2%, 3-8%, and 0.04-0.2% of the mass of the calcium aluminate precursor, respectively.

7. The method for preparing a low specific surface area heating material according to claim 5, characterized in that: The microwave stepped calcination involves first holding the temperature at 400-550℃ for 0.5-2 hours, and then holding it at 1050-1200℃ for 3-6 hours. The power of the microwave is 500-2000W. The concentration gradient impregnation method is as follows: First, the Al2O3-CaO support is impregnated with a 5-27wt% copper salt solution for 1-2 hours, while the salt corresponding to metal M is added, and then dried. Second, the support is impregnated with a 20-38% copper salt solution for 1-2 hours, and the concentration of the copper salt solution in the second impregnation is greater than that in the first impregnation.

8. The method for preparing a low specific surface area heating material according to claim 5 or 7, characterized in that: The drying process is a gradient-segmented drying, first maintaining the temperature at 60-80℃ for 12-18 hours, and then maintaining the temperature at 105-120℃ for 18-24 hours. The programmed temperature-controlled thermal reduction treatment involves first reducing the temperature at 300-400℃ for 0.5-3 hours, then reducing the temperature at 500-700℃ for 0.5-3 hours, and finally reducing the temperature at 750-900℃ for 3-6.5 hours.

9. The application of the heating material according to claim 1 in the dehydrogenation reaction of alkane, characterized in that: The application involves uniformly mixing the heating material with an alkane dehydrogenation catalyst, loading the mixture into a fixed-bed reactor, introducing alkanes, and carrying out a dehydrogenation reaction at 570-620°C under normal pressure, with a mass hourly space velocity (WHSV) of 1-2 h⁻¹ for the alkane. -1 The mass ratio of the heating material to the alkane dehydrogenation catalyst is 1:

2.

10. The application of the heating material according to claim 9 in the dehydrogenation reaction of alkane, characterized in that: After the dehydrogenation reaction has been going on for a period of time, steam, air, and hydrogen are introduced respectively to regenerate and cycle the heating material and catalyst.

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