Propane dehydrogenation method for regulating and controlling temperature of catalyst bed through heating material

Abstract

The invention discloses a propane dehydrogenation method for regulating and controlling the temperature of a catalyst bed through a heating material, and belongs to the technical field of chemical engineering and catalytic reaction. By combining a honeycomb matrix formed by compounding iron-silicon-aluminum alloy powder and silicon carbide powder with a partitioned electromagnetic induction heating technology, uniform temperature distribution, quick response and long-acting operation of a bed layer are realized. A gradient catalytic coating optimizes a mass transfer path, and pulse carbon elimination and regeneration treatment cooperate to prolong the service life of the catalyst. The industrial pilot plant test shows that the propylene selectivity is high, the conversion per pass is high, the continuous operation period is prolonged, and the energy consumption is obviously reduced. The invention provides an efficient, stable and economical technical path for the propane dehydrogenation process.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering and catalytic reaction technology, specifically a method for propane dehydrogenation by regulating the temperature of the catalyst bed through a heating material. Background Technology

[0002] Propane dehydrogenation (PDH) is a key process in propylene production, and its core lies in developing a reaction system that combines efficient temperature control with stable operation. Precise control of catalyst bed temperature directly affects reaction efficiency and selectivity; however, existing technologies still face challenges in terms of uniformity, rapid response, and long-term operation, which limits the overall performance and techno-economic viability of the process.

[0003] Patent CN102041048B discloses a method for regulating the temperature of a coal tar hydrogenation catalyst bed. This technology involves injecting cold oil or a mixture of cold oil and cold hydrogen into the catalyst bed to regulate the bed temperature, controlling the temperature difference between the outlet and inlet of each catalyst bed within the range of 5℃ to 20℃. However, this method relies on the injection of an external cold medium, which has certain limitations: First, the introduction of the cold medium may cause uneven local temperature distribution, affecting the overall consistency of the bed temperature; second, the amount of cold medium used is relatively large, and additional conveying and heating equipment is required, increasing energy consumption and operational complexity; third, under high-temperature conditions, this method has limited adaptability to rapid temperature changes, especially in strongly endothermic reactions such as propane dehydrogenation, making it difficult to fully meet the requirements for real-time temperature control.

[0004] Another patent, CN115990437B, discloses a method for controlling the feed temperature and temperature rise of each catalyst bed section in a reactor. This method maintains the inlet temperature variation of each catalyst bed section to no more than ±2% and the temperature rise variation to no more than ±10% through staged heat exchange and precise control of the feed rate. However, this technical solution also has certain problems: First, relying on heat exchange between the feed and product to regulate temperature may lead to a decrease in temperature control accuracy due to fluctuations in feed composition, especially in temperature-sensitive reactions such as propane dehydrogenation, where the risk is more significant. Second, this method requires a complex heat exchange system and flow control system, increasing equipment investment and maintenance costs. Third, due to the inherent hysteresis effect in the heat exchange process, adjustments may not be made in time during rapid temperature fluctuations, making it difficult to completely avoid local overheating or overcooling.

[0005] The aforementioned problems indicate that existing technologies still suffer from limitations in catalyst bed temperature control, including insufficient temperature distribution uniformity, limited rapid response capability, and high system complexity. These shortcomings create technical bottlenecks for the efficient and stable operation of propane dehydrogenation processes, necessitating an innovative solution to improve the accuracy, response speed, and operational stability of temperature control. Summary of the Invention

[0006] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide a propane dehydrogenation method that regulates the catalyst bed temperature through a heating material. This method utilizes a magnetic honeycomb reactor bed structure combined with zoned electromagnetic induction heating technology to achieve uniform temperature distribution, rapid response, and long-term operation of the bed, while simultaneously simplifying the system structure and reducing energy consumption.

[0007] The technical solution adopted by this invention to solve its technical problem is: a propane dehydrogenation method by regulating the temperature of the catalyst bed through a heating material, characterized by comprising the following steps: Zoned electromagnetic induction heating: A magnetic honeycomb reactor bed with an embedded catalyst coating is arranged axially in the inlet, main reaction, and outlet zones of the propane dehydrogenation reactor. Each zone has an independent induction coil installed outside the tower. During startup, the propane feedstock is preheated to 440℃~460℃ and introduced into the reactor. The induction coils in the three zones increase their power to control the temperature in the inlet zone to be maintained at 575℃~585℃, the main reaction zone at 615℃~625℃, and the outlet zone at 595℃~605℃. The space velocity is controlled at 900 h⁻¹. -1 ~1100h -1 The pressure is controlled at 0.09 MPa to 0.11 MPa to complete continuous propane dehydrogenation; Pulse decarbonization operation: Every 100-150 minutes, the set temperature of the outlet zone is raised to 618-623℃ and maintained for 150-200 seconds. After completion, it is restored to the reaction temperature. During the high-temperature pulse process, the carbon deposits are decomposed in situ into gaseous products in the outlet zone and discharged with the gas flow.

[0008] This invention constructs a highly efficient energy conversion system using a honeycomb matrix formed by combining iron-silicon-aluminum alloy powder and silicon carbide powder, combined with zoned electromagnetic induction heating technology. The hysteresis and eddy current loss characteristics of the iron-silicon-aluminum alloy powder enable it to generate heat efficiently in an alternating magnetic field, while the introduction of silicon carbide powder significantly improves the mechanical strength and thermal stability of the matrix. The gradient catalytic coating design further optimizes the mass transfer path of the reactants; the thicker coating in the inlet region provides sufficient active sites, while the thinner coating in the outlet region reduces diffusion resistance, thereby improving reaction efficiency.

[0009] Building upon this foundation, zoned electromagnetic induction heating combined with material temperature feedback achieves precise temperature control. Independent induction coils are installed in the inlet, main reaction, and outlet zones, allowing for dynamic adjustment of power output in each zone via cascaded PID control, ensuring an axial temperature difference of less than 20°C. This zoned heating method avoids the complexity of traditional cold medium injection or heat exchange systems, while significantly improving the uniformity of temperature distribution and rapid response capability.

[0010] Pulse decarburization effectively suppresses carbon buildup through periodic high-temperature treatment. The carbon deposits decompose into gaseous products at high temperatures and are discharged with the gas flow, thus extending the catalyst's operating cycle.

[0011] Specifically, the preparation method of the magnetic honeycomb reaction bed is as follows: (1) Mix the main materials: iron-silicon-aluminum alloy powder, silicon carbide powder and kaolin in a mass ratio of 62~68:23~27:7, and add 2.5%~3.2% of graphite as a pore-forming agent; after ball milling for 11h~13h, prepare a slurry, and vacuum extrude it to form a pore size of 55 pores / cm. 2 ~65 holes / cm 2 honeycomb preform; (2) After gradient drying, the organic matter is removed by pre-firing at 580℃~620℃ for 100min~150min, and then sintered in a hydrogen atmosphere at 1475℃~1485℃ for 220min~260min to form a honeycomb matrix. (3) After acid etching to activate the surface of the honeycomb substrate, impregnate it with an alumina slurry containing platinum and tin precursors for 500s~650s, control the platinum concentration to be 14g / L~16g / L, and the molar ratio of tin to platinum to be 0.45~0.55:1; (4) After being purged with compressed air, it is baked at 540℃~560℃ for 160min~200min to form a catalytic coating.

[0012] This invention utilizes a composite matrix design of iron-silicon-aluminum alloy powder and silicon carbide powder to simultaneously achieve magnetocaloric functionality and structural stability during high-temperature sintering in a hydrogen atmosphere, endowing the carrier with efficient electromagnetic response and resistance to thermal deformation. By combining acid etching activation and vacuum impregnation processes, a catalytic coating is constructed within the honeycomb channels. Optimizing the pore-forming agent ratio and the synergistic effect of stepped heat treatment ensures high bonding strength between the coating and the matrix, significantly improving the long-term stability of the catalyst under high-temperature pulsed carbon removal conditions. This method overcomes the compatibility bottleneck between magnetic carriers and catalytic coatings, providing core hardware support for electromagnetic induction temperature control technology.

[0013] Preferably, in the above-mentioned method for preparing the magnetic honeycomb reactor bed, the iron-silicon-aluminum alloy powder in step (1) has the following mass percentage composition: Fe 83wt%~87wt%, Si 8wt%~10wt%, and Al 5wt%~7wt%. This composition ratio, through the synergistic effect of the ferromagnetic phase and the highly stable compound, significantly improves the carrier durability while maintaining strong magnetothermal conversion capability: the iron element ensures that the material has excellent saturation magnetization characteristics, enabling it to generate heat efficiently in an alternating magnetic field; the silicon-aluminum component forms a stable intermetallic compound phase, significantly enhancing the material's resistance to deformation and oxidation under high-temperature conditions, and effectively suppressing magnetic property decay. The synergy of these three elements not only ensures the efficiency of electromagnetic induction heating but also overcomes the bottleneck problem of easy magnetic decay failure of traditional magnetic materials under high-temperature conditions.

[0014] Preferably, in the above-mentioned method for preparing the magnetic honeycomb reaction bed, the gradient drying conditions in step (2) are as follows: first, pre-drying at a negative pressure of 47 Pa to 53 Pa and a temperature of 38 °C to 44 °C for 10 h to 15 h, and then heating to 75 °C to 85 °C to complete dehydration. This gradient drying process avoids the collapse of the sol network structure, removes free water molecules at the low temperature stage, and removes bound water at the high temperature stage, thereby obtaining a through-pore structure with a concentrated pore size distribution.

[0015] Preferably, in the above-mentioned method for preparing the magnetic honeycomb reactor bed, the acid etching activation in step (3) specifically involves immersing the honeycomb substrate in a 0.45 mol / L to 0.55 mol / L nitric acid solution, ultrasonically dispersing it for 9 to 11 minutes, and then rinsing it with deionized water until neutral. Acid etching activation enhances the surface roughness of the substrate, providing more anchoring points for subsequent catalytic coating loading. The precise concentration control of the nitric acid solution and the synergistic effect of ultrasound form a uniform micron-level rough structure on the surface of the honeycomb substrate, significantly improving the physical bonding energy between the coating and the substrate; the surface active groups generated by chemical etching form strong chemical bonds with the alumina coating, greatly improving the adsorption strength of the active components, effectively avoiding coating peeling failure under high-temperature pulse carbon elimination conditions, and ensuring the long-term stable operation of the reactor.

[0016] Preferably, in the above-mentioned method for preparing the magnetic honeycomb reactor bed, the alumina slurry impregnated with platinum and tin precursors in step (3) specifically involves dissolving chloroplatinic acid and stannous chloride in ethanol, adding alumina powder and stirring evenly to obtain the slurry; the slurry is then impregnated after ultrasonic dispersion for 25 min to 35 min. Using ethanol to dissolve chloroplatinic acid and stannous chloride instead of the traditional aqueous solution system significantly improves the dispersion of the precursors: the ethanol medium simultaneously inhibits nitrate residues, avoiding acidic corrosion of the carrier surface; ultrasonic dispersion enables the platinum and tin active components to be uniformly anchored to the alumina framework with molecular-level precision, and the metal dispersion is greatly improved after calcination, effectively enhancing the catalyst's anti-sintering ability, maintaining the stability of active sites under high-temperature pulse and regeneration conditions, and ensuring the high efficiency and durability of the dehydrogenation reaction.

[0017] Preferably, in the above-mentioned method for preparing the magnetic honeycomb reactor bed, the thickness of the catalytic coating in step (4) is 40 μm to 60 μm. This thickness range ensures that the catalyst has both high active site density and efficient mass transfer, meeting the high reactivity requirements of the inlet region while optimizing the product diffusion path in the outlet region and reducing the risk of cracking and coking. Different concentrations and times of impregnation are used for the magnetic honeycomb reactor bed in the inlet region, main reaction region, and outlet region to achieve gradient control of the catalytic coating thickness in the three regions. More preferably, the catalytic coating thickness in the inlet region is 60 μm and the catalytic coating thickness in the outlet region is 40 μm. The gradient catalytic coating design can further optimize the mass transfer path of the reactants.

[0018] Preferably, the propane dehydrogenation method further includes a regeneration process: after cutting off the propane feed, nitrogen is introduced for purging for 9-12 minutes; then, a mixture of oxygen and nitrogen at a volume ratio of 2.5%-3.5% is introduced, and induction heating is used to maintain a constant temperature of 545℃-555℃ for coking; the carbon dioxide concentration in the tail gas is monitored in real time, and regeneration is stopped when the concentration is below 0.1%; finally, nitrogen is introduced to cool down to the reaction temperature. This regeneration process further removes deep-seated carbon deposits, and the induction heating and constant temperature coking avoid damage to the catalyst from localized overheating, while also reducing regeneration energy consumption. The controlled oxygen concentration combined with precise temperature control via induction heating efficiently oxidizes carbon deposits while avoiding the risk of localized overheating and thermal damage to the catalyst core support.

[0019] Preferably, the induction heating temperature control specifically involves heating at a rate of 4.5℃ / min to 5.5℃ / min; the nitrogen cooling rate is also 4.5℃ / min to 5.5℃ / min. This limited heating and cooling rate perfectly matches the thermal expansion coefficient of the magnetic honeycomb structure. During the heating phase, the internal thermal stress of the carrier is kept below the critical fracture threshold, while the cooling process avoids micro-cracks in the coating caused by rapid cooling. This rate also optimizes the oxidation and charring kinetics, ensuring efficient removal of carbon deposits and compressing the entire regeneration process to within 90 minutes, reducing energy consumption and achieving zero structural damage during the thermal cycling process.

[0020] This invention significantly improves the temperature control performance of the propane dehydrogenation process by combining a magnetic honeycomb reactor bed structure with partitioned electromagnetic induction heating technology. The honeycomb matrix formed by the composite of iron-silicon-aluminum alloy powder and silicon carbide powder possesses excellent thermal characteristics and mechanical strength. The gradient catalytic coating design optimizes the mass transfer path of the reactants. Partitioned electromagnetic induction heating combined with material temperature feedback achieves precise temperature control. Pulse decarbonization and regeneration processes synergistically extend the catalyst's operating cycle. Industrial pilot-scale data show that propylene selectivity reaches over 92.1%, single-pass conversion rate increases to over 42.5%, continuous operation is significantly extended, regeneration time is shortened, and overall energy consumption per ton of propylene is reduced.

[0021] Compared with existing technologies, the advantages of this invention are as follows: By employing a magnetic honeycomb reactor bed structure and zoned electromagnetic induction heating technology, it overcomes the shortcomings of traditional cold medium injection and heat exchange systems in terms of temperature uniformity, rapid response, and long-term operation. Zoned electromagnetic induction heating combined with material temperature feedback achieves dynamic temperature control within ±10℃; the gradient catalytic coating design and pulsed carbon elimination technology synergistically reduce the coking rate; and induction heating and constant-temperature coking avoid damage to the catalyst from localized overheating. This invention provides a highly efficient, stable, and economical technical path for propane dehydrogenation processes. Detailed Implementation

[0022] This invention relates to a propane dehydrogenation method that regulates the temperature of a catalyst bed using a heating material. The core of this method lies in the combination of a magnetic honeycomb reactor structure design and zoned electromagnetic induction heating technology. The specific embodiments of this invention are described in detail below.

[0023] In this invention, the magnetic honeycomb reactor bed is divided into an inlet zone, a main reaction zone, and an outlet zone along the reactor's axial direction. The inlet zone is located near the reactor's feed end, the outlet zone is located at the reactor's discharge end, and the main reaction zone is situated between the two. Each zone is equipped with an independent induction coil for zoned heating control. The induction coils are connected to a cascaded PID controller via wires, forming a closed-loop control system. Temperature feedback signals are collected from within each zone and transmitted to the cascaded PID controller, dynamically adjusting the power output of the induction coils in each zone. This zoned design ensures uniform temperature distribution and rapid response capability within the reactor.

[0024] The magnetic honeycomb matrix is ​​the core component of the reaction bed, and its preparation process is as follows: Ferro-silicon-aluminum alloy powder, silicon carbide powder, and kaolin are mixed in a specific mass ratio, with graphite added as a pore-forming agent. The mixture is ball-milled to form a slurry, which is then vacuum-extruded into a honeycomb preform. The preform is pretreated under gradient drying conditions, first by pre-drying to remove free water molecules, followed by heating to remove bound water. The dried preform is then pre-fired to remove organic matter, and subsequently sintered in a hydrogen atmosphere to form a honeycomb matrix with a Curie point of 720℃ and a thermal conductivity of 45 W / (m·K). The honeycomb matrix has a uniformly distributed, interconnected mesoporous structure with pore sizes concentrated at the micrometer level, providing excellent channels for gas flow.

[0025] The honeycomb substrate surface undergoes acid etching activation treatment to enhance roughness. Specifically, the substrate is immersed in a nitric acid solution, ultrasonically dispersed, and then rinsed with deionized water until neutral. After acid etching activation, numerous micropores and grooves form on the substrate surface, providing anchoring points for subsequent catalytic coating loading. The catalytic coating is prepared using a stepwise impregnation method. First, chloroplatinic acid and stannous chloride are dissolved in ethanol, and alumina powder is added and stirred until homogeneous. The slurry is then ultrasonically dispersed to ensure uniform dispersion of the precursor. The honeycomb substrate is sequentially impregnated with this slurry, followed by purging with compressed air to remove excess slurry, and then calcined to form a catalytic coating with controllable thickness. The coating thickness in the inlet region is preferably 60 μm, the coating thickness in the main reaction region 3 gradually decreases, and the coating thickness in the outlet region 4 is preferably 40 μm. This gradient design optimizes the mass transfer path of the reactants; the thicker coating in the inlet region provides sufficient active sites, while the thinner coating in the outlet region reduces diffusion resistance.

[0026] Induction coils are arranged around the outside of the reactor, corresponding to the inlet, main reaction, and outlet zones respectively. During startup, propane feedstock is preheated to approximately 450°C and introduced into the reactor. The power of the three induction coils is increased in a stepwise manner at a rate of 5% / min, reaching the operating temperature within 25 minutes. The preferred temperatures are set at 580°C for the inlet zone, 620°C for the main reaction zone, and 600°C for the outlet zone. Temperature feedback signals are acquired in real-time via thermocouples and transmitted to a cascaded PID controller to dynamically adjust the power output of the induction coils in each zone, ensuring an axial temperature difference of less than 20°C. The feedstock space velocity is controlled at 1000 h⁻¹. -1 The pressure is controlled at around 0.1 MPa. The current frequency of the induction coil is optimized based on the hysteresis loss and eddy current loss characteristics of the iron-silicon-aluminum alloy powder, and set in the range of 10kHz to 50kHz to achieve efficient energy conversion.

[0027] The pulse decarbonization operation is performed approximately every 2 hours. The power of the induction coil in the outlet zone is increased to about 120% of its rated value, maintained for about 3 minutes, and then returned to its original power. During the high-temperature pulse process, the carbon deposits are decomposed into CO and CO2 in the outlet zone and discharged with the gas flow. This periodic high-temperature treatment effectively inhibits carbon deposit formation and extends the catalyst's operating cycle. The regeneration process further removes deep-seated carbon deposits. The preferred steps include cutting off the propane feed and then purging with nitrogen, followed by the introduction of an oxygen-nitrogen mixture for induction heating and isothermal decarbonization. The carbon dioxide concentration in the tail gas is monitored in real time, and regeneration is stopped when the concentration falls below 0.1%. Finally, nitrogen is introduced to cool the gas to the reaction temperature.

[0028] The operation of the magnetic honeycomb reactor is as follows: Propane feedstock enters the reactor from the inlet zone and undergoes a dehydrogenation reaction catalyzed by the catalytic coating. Due to the low temperature in the inlet zone, the reaction starts gradually at this stage, avoiding localized overheating caused by intense exothermic reactions. As the reactants advance into the main reaction zone, the temperature rises to approximately 620°C, significantly accelerating the reaction rate while reducing diffusion resistance and improving reaction efficiency. The temperature in the outlet zone decreases to approximately 600°C, minimizing the occurrence of side reactions. The induction coil dynamically adjusts the power output through a cascaded PID controller to ensure that the temperature in each zone remains stable within the set range. Temperature feedback signals are acquired in real time and transmitted to the controller, achieving precise temperature control.

[0029] Table 1 shows a comparison of the parameters of the various propane dehydrogenation process embodiments.

[0030] Table 1: Parameters of the Example Key parameters Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Zone temperature (°C) Entrance area 580 577 584 582 578 583 576 585 Main reaction zone 620 618 624 621 616 622 615 625 Export Zone 600 598 604 601 596 603 595 605 Pulse carbon removal Period (min) 150 140 100 120 130 110 145 90 Temperature (°C) 620 619 623 621 618 622 618 623 Duration (s) 180 170 150 180 160 190 200 155 Matrix ratio (mass ratio) Iron-silicon-aluminum alloy powder 65 62 68 66 63 67 64 66 silicon carbide powder 25 27 23 24 26 24 25 23 Kaolin 7 7 7 7 7 7 7 7 Graphite addition (wt%) 3.0 2.8 3.2 3.0 2.6 2.9 3.1 2.5 Alloy composition (wt%) Fe 85 84 87 86 83 85 84 87 Si 9 8 9 9 10 8 9 10 Al 6 8 4 5 7 7 7 3 Gradient drying Negative pressure (Pa) 50 48 53 50 47 49 52 45 Pre-drying temperature (°C) 40 39 43 41 38 42 44 37 Dehydration temperature (°C) 80 78 84 82 76 83 85 75 Acid etching activation Nitric acid concentration (mol / L) 0.50 0.48 0.53 0.50 0.46 0.52 0.54 0.45 Ultrasound time (min) 10 9.5 10.5 10 9 11 10.8 8.5 Impregnation process Platinum concentration (g / L) 15.0 14.5 15.5 15.0 14.2 15.8 16.0 14.0 Sn / Pt molar ratio 0.50 0.48 0.52 0.50 0.46 0.54 0.55 0.45 Ultrasonic dispersion (min) 30 28 33 30 26 32 35 25 Coating thickness (μm) 55 50 60 58 48 59 61 42 Regeneration parameters Nitrogen purging (min) 10 9.5 11 10 9 10.5 12 8.5 Oxygen concentration (v%) 3.0 2.8 3.4 3.0 2.6 3.3 3.5 2.5 Burning temperature (°C) 550 548 553 550 547 552 555 545 heating rate 5.0 4.8 5.3 5.0 4.6 5.2 5.5 4.5 cooling rate 5.0 4.8 5.3 5.0 4.6 5.2 5.5 4.5 Test methods and standards for performance testing of each embodiment: 1. Propylene selectivity / conversion: Product composition was analyzed by online gas chromatography (GC) (ASTM D6729).

[0031] 2. Energy consumption calculation: Comprehensive energy consumption per ton of propylene = (electricity + preheating fuel) / propylene production (standard coal equivalent).

[0032] 3. Carbon Deposits: Thermogravimetric analysis (TGA) was used to determine the mass of carbon deposits on the catalyst coating before and after pulse decarburization. Residual carbon deposits after pulse decarburization (wt%) = W 终 / W 初 ×100%; W 初 Carbon deposit quality before pulse decarbonization W 终 Carbon deposit quality after pulse decarbonization 4. Temperature uniformity: Five thermocouples are arranged axially, and the maximum temperature difference is calculated.

[0033] The performance test results are shown in Table 2.

[0034] Table 2 Performance test results of the embodiment Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Propylene selectivity (%) 91.2 90.5 91.8 93.0 89.3 91.5 88.6 92.1 One-way conversion rate (%) 41.0 39.8 41.5 43.2 38.7 40.8 37.9 41.9 Maximum axial temperature difference (°C) 18.5 22.1 16.3 13.5 24.7 17.2 26.3 15.8 Residual carbon deposits after decarbonization (wt%) 0.32 0.41 0.29 0.21 0.48 0.31 0.52 0.27 Energy consumption per ton of propylene (tons of standard coal) 1.86 1.93 1.82 1.78 1.98 1.84 2.05 1.81 Continuous operating cycle (h) 225 195 235 270 180 220 170 240 Pulse carbon removal efficiency (%) 94.5 92.1 95.3 98.1 90.6 94.8 89.2 95.7 Comparative Example An induction coil was installed only in the main reaction zone of the reactor (the inlet / outlet separation was eliminated), and the temperature was uniformly controlled at 620℃. Other parameters were the same as in Example 4.

[0035] Failure symptoms: The temperature in the export zone reached 645±25℃ (far exceeding the upper limit of 605℃), triggering excessive dehydrogenation: methane byproducts increased by 2.3 times; The axial temperature difference was 36.2℃, due to insufficient heating in the inlet zone (548℃) and overheating in the outlet zone; the platinum particles were sintered to 12nm, and the catalyst life was shortened to 200h.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for propane dehydrogenation by regulating the catalyst bed temperature through a heating material, characterized in that, Includes the following steps: Zoned electromagnetic induction heating: A magnetic honeycomb reactor bed with an embedded catalyst coating is arranged axially in the inlet, main reaction, and outlet zones of the propane dehydrogenation reactor. Each zone has an independent induction coil installed outside the tower. During startup, the propane feedstock is preheated to 440℃~460℃ and introduced into the reactor. The induction coils in the three zones increase their power to control the temperature in the inlet zone to be maintained at 575℃~585℃, the main reaction zone at 615℃~625℃, and the outlet zone at 595℃~605℃. The space velocity is controlled at 900 h⁻¹. -1 ~1100h -1 The pressure is controlled at 0.09 MPa to 0.11 MPa to complete continuous propane dehydrogenation; Pulse decarbonization operation: Every 100-150 minutes, the set temperature of the outlet zone is raised to 618-623℃ and maintained for 150-200 seconds. After completion, it is restored to the reaction temperature. During the high-temperature pulse process, the carbon deposits are decomposed in situ into gaseous products in the outlet zone and discharged with the gas flow.

2. The propane dehydrogenation method according to claim 1, characterized in that, The method for preparing the magnetic honeycomb reaction bed is as follows: (1) Mix the main materials: iron-silicon-aluminum alloy powder, silicon carbide powder and kaolin in a mass ratio of 62~68:23~27:7, and add 2.5%~3.2% of graphite as a pore-forming agent; after ball milling for 11h~13h, prepare a slurry, and vacuum extrude it to form a pore size of 55 pores / cm. 2 ~65 holes / cm 2 honeycomb preform; (2) After gradient drying, the organic matter is removed by pre-firing at 580℃~620℃ for 100min~150min, and then sintered in a hydrogen atmosphere at 1475℃~1485℃ for 220min~260min to form a honeycomb matrix. (3) After acid etching to activate the surface of the honeycomb substrate, impregnate it with an alumina slurry containing platinum and tin precursors for 500s~650s, control the platinum concentration to be 14g / L~16g / L, and the molar ratio of tin to platinum to be 0.45~0.55:1; (4) After being purged with compressed air, it is baked at 540℃~560℃ for 160min~200min to form a catalytic coating.

3. The propane dehydrogenation method according to claim 2, characterized in that: The iron-silicon-aluminum alloy powder in step (1) has the following mass percentage composition: Fe 83wt%~87wt%, Si 8wt%~10wt%, and Al 5wt%~7wt%.

4. The propane dehydrogenation method according to claim 2, characterized in that: The gradient drying conditions described in step (2) are as follows: first, pre-dry at a negative pressure of 47Pa~53Pa and a temperature of 38℃~44℃ for 10h~15h, and then raise the temperature to 75℃~85℃ to complete the dehydration.

5. The propane dehydrogenation method according to claim 2, characterized in that: The acid etching activation in step (3) specifically involves immersing the honeycomb substrate in a 0.45 mol / L to 0.55 mol / L nitric acid solution, ultrasonically dispersing it for 9 min to 11 min, and then rinsing it with deionized water until it is neutral.

6. The propane dehydrogenation method according to claim 2, characterized in that: The alumina slurry impregnated with platinum and tin precursors in step (3) is specifically prepared by dissolving chloroplatinic acid and stannous chloride in ethanol, adding alumina powder and stirring evenly to obtain the slurry; the slurry is then ultrasonically dispersed for 25 min to 35 min before impregnation.

7. The propane dehydrogenation method according to claim 2, characterized in that: The thickness of the catalytic coating mentioned in step (4) is 40 μm to 60 μm.

8. The propane dehydrogenation method according to claim 1, characterized in that: It also includes regeneration treatment: after cutting off the propane feed, nitrogen is introduced to purge for 9 to 12 minutes; then a mixture of oxygen and nitrogen with a volume ratio of 2.5% to 3.5% is introduced, and constant temperature coking is carried out by induction heating at 545℃ to 555℃; the carbon dioxide concentration in the tail gas is monitored in real time, and regeneration is stopped when the concentration is lower than 0.1%; finally, nitrogen is introduced to cool down to the reaction temperature.

9. A propane dehydrogenation method according to claim 8, characterized in that: The induction heating temperature control specifically involves heating at a rate of 4.5℃ / min to 5.5℃ / min; the nitrogen cooling rate is also 4.5℃ / min to 5.5℃ / min.