A method and catalyst suitable for the dehydrogenation of low carbon alcohols to aldehydes driven by alternating electromagnetic fields

Abstract

The application provides a method and a catalyst for preparing aldehydes by dehydrogenation of low-carbon alcohols driven by an alternating electromagnetic field. The catalyst is a metal active center loaded on a magnetic induction carrier. The preparation method comprises: loading metal ions on the carrier by impregnation; and finally gradient carbonization and synchronous in-situ reduction under an inert atmosphere. In application, the catalyst is placed in an alternating electromagnetic field, and under the conditions of normal pressure and 150-300 DEG C, the catalyst can catalyze the efficient dehydrogenation of ethanol, n-butanol, isobutanol and isopentanol to prepare aldehydes, and under the conditions of normal pressure and 450-500 DEG C, the catalyst can realize the dehydrogenation of methanol to prepare formaldehyde, and beneficial conversion rate and selectivity are obtained. The application realizes in-situ precise heating by using the magnetic heat effect, avoids the disadvantages of traditional external heating, realizes high conversion rate and nearly 100% selectivity at low temperature, and has excellent catalyst stability and low cost, and has good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of catalytic dehydrogenation technology, specifically to a method and catalyst suitable for the dehydrogenation of low alcohols to aldehydes driven by alternating electromagnetic fields. Background Technology

[0002] The catalytic dehydrogenation of low-carbon alcohols to produce low-carbon aldehydes is a crucial link in the chemical industry chain. Products such as formaldehyde are fundamental raw materials for the resin, plastics, and adhesives industries. Compared to traditional oxidation methods, its dehydrogenation route offers advantages such as high atom economy, hydrogen production as a byproduct, and no wastewater generation. Acetaldehyde, as an important intermediate in pharmaceuticals, pesticides, and fine chemicals, can be produced using biomass ethanol dehydrogenation, effectively reducing dependence on fossil resources. The dehydrogenation of n- / isobutanol to n-butyraldehyde is mainly used as a plasticizer raw material, through hydrogenation to n-butanol or condensation hydrogenation to 2-ethylhexanol, further producing phthalate plasticizers. Isobutyraldehyde is mainly used in the synthesis of fine chemicals, including hydrogenation to isobutanol, oxidation to isobutyric acid, or methacrylic acid. Isovaleraldehyde plays an important role in pharmaceutical synthesis. It can be used as a raw material for the synthesis of vitamin E. Currently, the mainstream technical route for the dehydrogenation of low-carbon alcohols to aldehydes is the gas-phase catalytic dehydrogenation process.

[0003] Alcohol dehydrogenation is a typical strongly endothermic process. Currently, the mainstream technology for the dehydrogenation of low-carbon alcohols to aldehydes is gas-phase thermocatalytic dehydrogenation. Studies have shown that, for example, the enthalpy change of isopropanol dehydrogenation can reach approximately 100.4 kJ / mol H2. Methanol dehydrogenation to formaldehyde is a strongly endothermic reaction, requiring operation at temperatures above 600℃ to achieve a high equilibrium conversion rate. However, under high temperatures, the main product, formaldehyde, is prone to deep decomposition to generate CO and H2, leading to a significant reduction in the selectivity of the target product. It is difficult to achieve both conversion rate and selectivity simultaneously, and the catalyst is prone to sintering and deactivation at high temperatures. Although ethanol dehydrogenation has a lower reaction temperature, it is limited by thermodynamic equilibrium, requiring the recycling of unreacted feedstock, increasing energy consumption. The high endothermic nature of the reaction dictates that it usually needs to be carried out at higher temperatures to obtain a considerable conversion rate, but this also poses challenges to reactor thermal management and catalyst lifetime.

[0004] Furthermore, in existing heating processes, heat is transferred layer by layer from the reactor wall to the catalyst bed, resulting in significant thermal hysteresis and temperature gradients. Localized overheating or undercooling zones easily appear within the catalyst bed. Localized overheating triggers side reactions such as alcohol cracking and deep decarbonization, while undercooling leads to insufficient reaction rates, severely impacting the yield and selectivity of the target product. In this context, magnetic induction offers the possibility of directly heating magnetic materials. By using the magnetic material as both the active center and the magnetic induction heating center in the catalytic process, in-situ heating of the catalyst bed is achieved, enabling efficient and rapid temperature rise, improving energy utilization, reducing energy consumption, and ensuring uniform temperature distribution within the catalyst bed. This effectively avoids side reactions caused by localized overheating. Moreover, the uniform and precisely controllable temperature of the catalyst bed avoids energy waste caused by temperature fluctuations, aligning with the development direction of green chemistry and energy conservation and emission reduction.

[0005] Currently, the main types of catalysts used in the dehydrogenation of low-carbon alcohols to aldehydes include: noble metal catalysts (Pt, Pd, Ru, Au, etc.) and non-noble metal and oxide catalysts (Cu, Mo, etc.). However, highly active catalysts mostly rely on noble metals such as Pt and Ru, which suffer from high cost and scarcity, hindering their large-scale industrial application. Non-metallic catalysts have attracted attention due to their low price and abundant resources, but they still suffer from carbon buildup and deactivation during reactions, and their lifespan is insufficient to meet the requirements of long-term industrial operation.

[0006] In conclusion, achieving efficient and highly selective conversion of low-carbon alcohols to low-carbon aldehydes in an exothermic reaction system under mild conditions remains a significant challenge. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of the prior art and provide a catalyst, its preparation method and application, that can achieve efficient and selective conversion of low-carbon alcohols to low-carbon aldehydes under mild conditions of low temperature and normal pressure.

[0008] This invention, for the first time, utilizes a magnetic catalyst under an alternating electromagnetic field to perform magnetic induction catalysis of the dehydrogenation reaction of low-carbon alcohols (methanol, ethanol, n / isobutanol, and isoamyl alcohol) to produce low-carbon aldehydes, and prepares the magnetic catalyst. Under normal pressure and without external heating, by applying a magnetic field to a ferromagnetic or highly conductive magnetic catalyst, the "charge-spin" synergistic catalysis of the low-carbon alcohol conversion process is achieved. Since the dehydrogenation reaction of low-carbon alcohols is an endothermic process requiring a high reaction temperature, the magnetic catalyst used in the magnetic induction low-carbon alcohol dehydrogenation system simultaneously possesses both heating and catalytic effects, achieving superior performance. Furthermore, it avoids the problems of high energy consumption, low energy utilization, and uneven heating associated with traditional catalytic reactions.

[0009] This invention provides a catalyst for the above-mentioned dehydrogenation of lower alcohols to aldehydes driven by alternating electromagnetic fields, wherein the catalyst is a metal supported on a magnetic carrier: Magnetic carrier: one of the following: copper foam, nickel foam, carbon felt, porous carbon materials, and silicon carbide.

[0010] Metal active center: at least one of Cu, Ni, Fe, Zn, Ag, and Pt.

[0011] The present invention also provides a method for preparing the above-mentioned catalyst, comprising the following steps: Step S1: Pre-treat the carrier, which is one of copper foam, nickel foam, carbon felt, porous carbon material or silicon carbide; the pre-treatment is carried out by cleaning with dilute hydrochloric acid, deionized water and ethanol in sequence to remove surface oxides and impurities. Step S2: The support pretreated in step S1 is impregnated and dispersed in a solution containing at least one metal active center, wherein the metal active center is selected from nitrates, chlorides or acetylacetonates of Cu, Ni, Fe, Zn, Ag, and Pt; after impregnation overnight, it is vacuum dried or freeze-dried to obtain a catalyst precursor supported on a metal precursor. Step S3: Place the catalyst precursor obtained in step S2 in a tube furnace and heat it from room temperature to 300-500℃ at a rate of 1-5℃ / min under a nitrogen atmosphere, and hold it at that temperature for 2-4 hours. After calcination, allow it to cool naturally to room temperature under the same atmosphere to obtain a metal oxide supported precursor.

[0012] Step S4: The precursor obtained in step S4.4 is placed in a quartz boat and then placed in a tubular furnace quartz tube. It is reduced at 200-600℃ for 1-4 hours in a reducing atmosphere. After natural cooling, the catalyst is obtained.

[0013] In some embodiments, step S1 specifically includes the following steps: Step S1.1: The carrier is one of the following: copper foam, nickel foam, carbon felt, porous carbon material, or silicon carbide; the pore size of copper foam and nickel foam is 10-100 ppi, the thickness of carbon felt is 1-5 mm, and the specific surface area of ​​porous carbon material is 500-1500 m². 2 / g, the particle size of silicon carbide is 0.1-1mm.

[0014] Step S1.2: The carrier is immersed in 1 mol / L dilute hydrochloric acid and ultrasonically treated for 10 min to remove surface oxides and metal impurities. The acid-washed carrier is ultrasonically treated with deionized water and ethanol for 10 min respectively to remove surface organic residues.

[0015] Step S1.3: Place the carrier in a freeze dryer, cold trap temperature -50℃, vacuum degree 1Mpa, dry for 24h, and set aside for later use.

[0016] In some embodiments, step S2 specifically includes the following steps: Step S2.1: Weigh at least one precursor salt with a metal active center, wherein the metal active center is selected from the nitrate, chloride or acetylacetone salt of Cu, Ni, Fe, Zn, Ag or Pt; dissolve the precursor salt in deionized water or anhydrous ethanol.

[0017] Step S2.2: Immerse the dried support from step S1.5 into the metal precursor solution prepared in step S2.1, ensuring that the support is completely submerged; allow it to stand overnight at room temperature, during which slow stirring can be used to promote uniform adsorption.

[0018] Step S2.3: When using wet impregnation, place the sample in a water bath to evaporate it to ensure that the specific catalyst loading is obtained.

[0019] Step S2.4: Place the drained support in a vacuum drying oven and dry it for 12-24 hours at 40-60℃ and a vacuum degree below -0.09MPa; or place it in a freeze dryer and freeze dry it for 24-48 hours at -50℃ to -40℃ and a vacuum degree below 10Pa to obtain the catalyst precursor supported on the metal precursor.

[0020] In some embodiments, step S3 specifically includes the following steps: Step S3.1: Place the catalyst precursor obtained in step S2.4 in a quartz boat or corundum boat and put it into the quartz tube of a tube furnace; Step S3.2: Pour argon or nitrogen into the tube furnace at a flow rate of 50-200 mL / min for 15-30 minutes to replace the original gas in the tube. Step S3.3: Increase the temperature from room temperature to 300-500℃ at a rate of 1-5℃ / min, and hold at that temperature for 2-4 hours; Step S3.4: After calcination, the metal oxide supported precursor is naturally cooled to room temperature under the same atmosphere to obtain the precursor.

[0021] In some embodiments, step S4 specifically includes the following steps: Step S4.1: Place the precursor obtained in step S4 in a tube furnace and introduce a reducing atmosphere at a gas flow rate of 50-200 mL / min.

[0022] Step S4.2: Increase the temperature from room temperature to the reduction temperature of 200-600℃ at a heating rate of 1-10℃ / min, and hold for 1-4 hours to reduce the metal oxide in situ into highly dispersed metal nanoparticles.

[0023] Step S4.3: After the reduction is completed, the catalyst is naturally cooled to below 80°C under a reducing atmosphere, then switched to an inert atmosphere for purging for 15-30 minutes. After that, the catalyst is removed and sealed for storage under the protection of an inert atmosphere.

[0024] The present invention also provides a method for using the above-mentioned catalyst to dehydrogenate low-carbon alcohols to low-carbon aldehydes, comprising the following steps: Place any of the aforementioned catalysts in the induction coil area of ​​the alternating electromagnetic field heating device; Low-carbon alcohol feedstock is introduced into the reactor to react and obtain low-carbon aldehyde; The low-carbon alcohol is selected from at least one of methanol, ethanol, n / isobutanol and isoamyl alcohol; the low-carbon alcohol is fed in gas phase form and vaporized in a preheater before feeding, with a preheating temperature of 150-250℃. The reaction conditions are as follows: except for methanol, which reacts at 450-500℃, other alcohols react at 150-300℃, under normal pressure, and the liquid hourly space velocity (LHSV) for lower alcohols is 0.5-5 h⁻¹. -1 At the same time, nitrogen gas is introduced as a carrier gas, and the volume ratio of carrier gas to low-carbon alcohol vapor is (10-100):1. In some embodiments, the lower alcohol is one of methanol, ethanol, n / isobutanol and isoamyl alcohol, and the carrier gas is nitrogen.

[0025] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes the in-situ magnetocaloric effect of magnetic materials under an alternating electromagnetic field to directly heat the catalytic active center. The temperature distribution is uniform and the system has high heat transfer efficiency, achieving precise energy transport. No external high-temperature heating is required, the system has a low apparent temperature, significantly reducing energy consumption. The system equipment is simple and the process is safe and controllable.

[0026] This invention benefits from precise in-situ heat supply and uniform temperature distribution, effectively avoiding side reactions caused by local overheating and achieving high activity at low temperatures.

[0027] In this invention, an active metal (at least one of Cu, Ni, Fe, Zn, Ag, and Pt) forms highly dispersed nanoparticles on the surface of a support. The abundant active sites significantly improve the reaction rate and selectivity of dehydrogenation of low-carbon alcohols to aldehydes.

[0028] The carriers of this invention (foamed copper, foamed nickel, carbon felt, porous carbon materials, silicon carbide) have high melting points and excellent thermal conductivity, maintaining structural integrity during gradient high-temperature treatment and reaction processes; a stable anchoring structure is formed between the active metal and the carrier, effectively inhibiting the agglomeration and sintering of metal particles at high temperatures; the catalyst exhibits excellent long-term stability, with a catalyst life exceeding 500 hours.

[0029] The copper foam, nickel foam, carbon felt, porous carbon material, and silicon carbide used in this invention are all commercially available materials with wide sources. Low-cost or high-performance supports can be selected according to the actual application scenario, taking into account both catalytic performance and economy. Attached Figure Description

[0030] Figure 1 The graph shows the catalytic performance of the catalyst in Example 2 of this invention for the dehydrogenation of ethanol to acetaldehyde at different liquid space velocities. Figure 2 This is a morphology diagram of the catalyst in Example 1 of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0032] Example 1: Formaldehyde production from methanol dehydrogenation – Cu-Pt / carbon felt 1. Catalyst preparation: (1) Carrier pretreatment: The carbon felt was placed in 1M hydrochloric acid and ultrasonically cleaned for 10 minutes; then placed in deionized water and ultrasonically cleaned for 10 minutes; finally placed in anhydrous ethanol and ultrasonically cleaned for 15 minutes. The cleaned carbon felt was dried in a vacuum drying oven at 80℃ for 12 hours for later use.

[0033] (2) Using 0.5 g of carbon felt as a support, the target loading was 5 wt% Cu and 0.5 wt% Pt. Calculate and weigh 0.095 g Cu(NO3)2·3H2O and 0.0066 g H2PtCl6·6H2O, dissolve them in 15 mL of deionized water, and stir for 15 minutes until completely dissolved. Immerse the pretreated carbon felt in the above solution, ultrasonically disperse for 30 minutes, and then age it at room temperature for 12 hours. After aging, vacuum dry at 80 °C for 12 hours to obtain the catalyst precursor supported on the metal precursor.

[0034] (3) The catalyst precursor obtained in step 2 was placed in a tube furnace and heated from room temperature to 450°C at a heating rate of 2°C / min under a nitrogen atmosphere, and held at that temperature for 2 hours. After calcination, it was naturally cooled to room temperature under the same atmosphere to obtain a metal oxide supported precursor.

[0035] (4) The precursor obtained in step S3 was placed in a tube furnace and heated to 350°C at a heating rate of 5°C / min in a reducing atmosphere of 10% H2 / N2 (volume ratio) for 3 hours. After natural cooling, the catalyst was obtained and denoted as Cu-Pt / carbon felt catalyst.

[0036] 2. Catalyst Evaluation: The catalyst was filled into a quartz tube and placed in the induction coil area of ​​an induction heating device. The catalyst loading was 0.5 g. The alternating electromagnetic field frequency was 1-90 kHz, the reaction temperature was 500℃ (the temperature of the system generated by the magnetic catalyst itself), and the methanol liquid hourly space velocity was 1.5 h⁻¹. -1 The preheater temperature is 180℃. The low-carbon alcohol raw material methanol is vaporized and, under the action of carrier gas, the volume ratio of carrier gas to methanol vapor is 50:1. It enters a quartz tube containing catalyst to carry out a dehydrogenation reaction to produce formaldehyde.

[0037] 3. Application results: Methanol conversion rate 62.1%, selectivity 99.50%, conversion rate 57.3% after 500h.

[0038] Example 2: Ethanol dehydrogenation to acetaldehyde – Cu-Fe / nitrogen-doped porous carbon 1. Catalyst preparation: (1) Support pretreatment: Nitrogen-doped porous carbon was selected as the support, with a specific surface area of ​​1000 square meters per gram and an average pore size of 5 nanometers. 0.5 grams of nitrogen-doped porous carbon support was weighed, and the specific operation method was as described in step (1) of Example 1.

[0039] (2) Using 0.5 g of nitrogen-doped porous carbon as a support, the target loading was 8 wt% Cu and 2 wt% Fe. 0.152 g Cu(NO3)2·3H2O and 0.072 g Fe(NO3)3·9H2O were dissolved in 15 mL of deionized water and magnetically stirred for 15 min until completely dissolved. The pretreated 0.5 g nitrogen-doped porous carbon support was immersed in the above solution and ultrasonically dispersed for 30 min. It was then aged at room temperature for 12 h. After aging, it was vacuum dried at 80 °C for 12 h to obtain the catalyst precursor supported on the copper-iron metal precursor.

[0040] (3) The subsequent steps are the same as steps (3)-(4) in Example 1, and are referred to as Cu-Fe / nitrogen-doped porous carbon catalyst.

[0041] 2. Catalyst Evaluation: The catalyst was filled into a quartz tube and placed in the induction coil area of ​​an induction heating device. The reaction pressure was atmospheric pressure, the reaction temperature was 250℃ (the system temperature generated by the magnetic catalyst itself), the alternating frequency was 1-90kHz, and the ethanol liquid hourly space velocity was 0.85h⁻¹. -1 The ethanol feedstock is vaporized and, under the action of a carrier gas, the volume ratio of the carrier gas to the low-carbon alcohol vapor is 80:1. It then enters a quartz tube containing a magnetic catalyst to carry out a dehydrogenation reaction and produce acetaldehyde.

[0042] 3. Application results: The ethanol conversion rate was 75.6%, the selectivity was 99.99%, and the conversion rate was 70.9% after 500 h.

[0043] Example 3: Dehydrogenation of n-butanol to n-butyraldehyde – Cu-Ni / SiC 1. Catalyst preparation: (1) Carrier pretreatment: Same as step (1) in Example 1.

[0044] (2) Using 0.5g SiC as a support, the target loading is 8wt% Cu and 5wt% Ni. Weigh 0.152g Cu(NO3)2·3H2O and 0.124g Ni(NO3)2·6H2O. The specific impregnation and drying steps are the same as step (2) in Example 1 to obtain the catalyst precursor supported on the copper-nickel metal precursor.

[0045] (3) Calcination: Same as step (3) in Example 1, to obtain copper-nickel oxide supported precursor.

[0046] (4) Reduction: Same as step (4) in Example 1, but the heating program is to raise the temperature from room temperature to 380°C at a heating rate of 5°C / min and hold for 3 hours. This is referred to as Cu-Ni / SiC catalyst.

[0047] 2. Catalyst Evaluation: Magnetic catalyst was filled into a quartz tube and placed in the induction coil area of ​​an induction heating device. The catalyst loading was 0.5g, the alternating electromagnetic field frequency was 1-90kHz, the reaction temperature was 280℃, the n-butanol liquid hourly space velocity was 1.0h-1, the preheater temperature was 180℃, the volume ratio of carrier gas N2 to n-butanol vapor was 80:1, and the reaction was carried out at atmospheric pressure.

[0048] 3. Application results: The conversion rate of n-butanol was 96.2%, the selectivity was 99.85%, and the conversion rate was 91.3% after 500 hours.

[0049] Example 4: Dehydrogenation of isobutanol to isobutyraldehyde – Cu-Ag / copper foam 1. Catalyst preparation: (1) Carrier pretreatment: Same as step (1) in Example 1.

[0050] (2) 0.5g copper foam, target loading of 6wt% Cu, 3wt% Ag. Dissolve 0.114g Cu(NO3)2·3H2O and 0.024g AgNO3 in 15mL deionized water. The specific impregnation and drying steps are the same as step (2) in Example 1 to obtain the catalyst precursor loaded with copper and silver metal precursors.

[0051] (3) Calcination: The obtained catalyst precursor was placed in a quartz boat and then placed inside the quartz tube of a tube furnace. High-purity N2 was introduced at a flow rate of 50 mL / min and continuously purged for 30 min to remove air from the tube. Under the N2 atmosphere, the temperature was increased from room temperature to 400℃ at a rate of 2℃ / min and held for 2 h to decompose the metal precursor into CuO and Ag2O. After calcination, the precursor was naturally cooled to room temperature under the N2 atmosphere to obtain a copper-silver oxide supported precursor.

[0052] (4) Reduction: In a reducing atmosphere, the temperature is increased from room temperature to 300℃ at a rate of 5℃ / min and held for 2h to reduce CuO and Ag2O to metallic Cu. 0 and Ag 0 After reduction, the catalyst was naturally cooled to room temperature under a 10% H2 / N2 atmosphere and designated as Cu-Ag / foamed copper catalyst. 2. Catalyst Evaluation: Magnetic catalyst was filled into a quartz tube, which was then placed in the induction coil area of ​​an induction heating device. The reaction pressure was atmospheric pressure, and the reaction temperature was 270℃. The system temperature generated by the magnetic catalyst itself was measured. The alternating frequency was 1-90 kHz. Isobutanol was vaporized under the action of a carrier gas, with a carrier gas to lower alcohol vapor volume ratio of 90:1 and an isobutanol liquid hourly space velocity of 1.2 h⁻¹. -1 It enters a quartz tube containing a magnetic catalyst to carry out a dehydrogenation reaction.

[0053] 3. Application results: Isobutanol conversion rate was 98.9%, selectivity was 99.62%, and conversion rate was 95.6% after 500 hours.

[0054] Example 5: Dehydrogenation of isoamyl alcohol to isovaleraldehyde – Cu-Zn / nickel foam catalyst 1. Catalyst preparation: (1) Carrier pretreatment: Same as step (1) in Example 1.

[0055] (2) Using 0.5g of nickel foam as a carrier, the target loading is Cu 7 wt% and Zn 3 wt%. Dissolve 0.133g Cu(NO3)2·3H2O and 0.067g Zn(NO3)2·6H2O in 10mL of deionized water. The specific impregnation and drying steps are the same as step (2) in Example 1 to obtain the catalyst precursor loaded with copper and silver metal precursors.

[0056] (3) Calcination: Same as step (3) in Example 1, to obtain copper-zinc oxide supported precursor.

[0057] (4) Reduction: Same as step (4) in Example 1, referred to as Cu-Zn / foam nickel catalyst.

[0058] Catalyst evaluation: Magnetic catalyst was filled into a quartz tube and placed in the induction coil area of ​​an induction heating device. The reaction pressure was atmospheric pressure, the reaction temperature was 250℃, and the system temperature generated by the magnetic catalyst itself was measured. The alternating frequency was 1-90KHz, and the liquid hourly space velocity of isoamyl alcohol was 0.8h-1. Isoamyl alcohol was vaporized and, under the action of a carrier gas, the volume ratio of carrier gas to low-carbon alcohol vapor was 90:1. It then entered the quartz tube containing the magnetic catalyst to carry out the dehydrogenation reaction.

[0059] Application results: Isoamyl alcohol conversion rate 99.2%, selectivity 99.58%, and conversion rate 98.6% after 500 hours.

[0060] Comparative Example 1: Heating with a Traditional Electric Furnace Catalyst preparation method: Same as the catalyst preparation method in Examples 1-5.

[0061] Catalyst evaluation method: The reaction pressure was atmospheric pressure. 0.5g of catalyst was loaded, the preheater temperature was 180℃, and the heating method was changed to a traditional electric furnace.

[0062] Methanol is vaporized under the action of a carrier gas, with a carrier gas to methanol vapor volume ratio of 50:1, a reaction temperature of 500℃ (the system temperature generated by the magnetic catalyst itself), and a methanol liquid hourly space velocity of 1.5 h⁻¹.

[0063] The ethanol liquid hourly space velocity was 0.85 h⁻¹, the volume ratio of carrier gas to ethanol vapor was 80:1, and the reaction temperature was 250 °C.

[0064] The reaction temperature of n-butanol was 280℃, the liquid hourly space velocity was 1.0 h⁻¹, and the volume ratio of carrier gas N₂ to n-butanol vapor was 80:1.

[0065] The isobutanol reaction temperature was 270℃, the isobutanol liquid hourly space velocity was 1.0 h⁻¹, and the volume ratio of carrier gas N₂ to n-butanol vapor was 80:1.

[0066] The reaction temperature of isoamyl alcohol is 250℃ and the liquid hourly space velocity is 0.8 h⁻¹. Isoamyl alcohol is vaporized under the action of a carrier gas, and the volume ratio of the carrier gas to the lower alcohol vapor is 90:1.

[0067] 3. Application Effects: The methanol conversion rate was 50.6%, the selectivity was 91.11%, and the conversion rate was 47.2% after 500 hours.

[0068] The ethanol conversion rate was 64.4%, the selectivity was 93.18%, and the conversion rate was 58.6% after 500 h.

[0069] The conversion rate of n-butanol was 91.5%, the selectivity was 96.64%, and the conversion rate was 89.7% after 500 h.

[0070] The isobutanol conversion rate was 92.0%, the selectivity was 97.14%, and the conversion rate was 90.6% after 500 h.

[0071] The conversion rate of isoamyl alcohol was 95.9%, the selectivity was 98.33%, and the conversion rate was 93.5% after 500 h.

[0072] Comparative Example 2: Non-magnetic thermal carrier 1. Catalyst preparation: (1) Prepare Stober SiO2 spheres with a particle size of about 200 nm.

[0073] (2) Following steps (2) to (4) of Examples 1, 2, 3, 4 and 5, Cu-Pt / SiO2, Cu-Fe / SiO2, Cu-Ni / SiO2, Cu-Ag / SiO2 and Cu-Zn / SiO2 catalysts were obtained.

[0074] 2. The catalyst evaluation method is the same as that used in Comparative Example 1.

[0075] 3. Application Effects: The methanol conversion rate was 23.6%, the selectivity was 72.11%, and the conversion rate after 500 hours was 18.2%.

[0076] The ethanol conversion rate was 32.8%, the acetaldehyde selectivity was 88.2%, and the conversion rate was 25.5% after 500 hours.

[0077] The conversion rate of n-butanol was 38.5%, the selectivity was 85.61%, and the conversion rate was 30.7% after 500 h.

[0078] The isobutanol conversion rate was 35.0%, the selectivity was 83.14%, and the conversion rate was 28.6% after 500 h.

[0079] The conversion rate of isoamyl alcohol was 30.9%, the selectivity was 80.33%, and the conversion rate was 22.5% after 500 h.

[0080] Comparative Example 3: Pure Carrier 1. Catalyst preparation: Refer to step (1) of Examples 1-5.

[0081] 2. The catalyst evaluation methods are the same as those used in Comparative Example 1.

[0082] 3. Application Effects: The methanol was not converted.

[0083] The ethanol conversion rate was 8.8%, the acetaldehyde selectivity was 58.2%, and the conversion rate was 5.5% after 500 hours.

[0084] There was no conversion of n-butanol.

[0085] The isobutanol conversion rate was 15.0%, the selectivity was 65.14%, and the conversion rate was 8.6% after 500 h.

[0086] The conversion rate of isoamyl alcohol was 3.9%, the selectivity was 50.33%, and the conversion rate after 500 h was 2.5%.

[0087] Comparative Example 4: Optimal Formulation of Non-Bimetallic Compounds n-Butanol dehydrogenation to n-Butyraldehyde — Cu-Ni / SiC 1. Catalyst preparation: (1) Same as step (1) in Example 3.

[0088] (2) Set the Cu:Ni molar ratio to 10:1, dissolve 0.226g Cu(NO3)2·3H2O and 0.027g Ni(NO3)2·6H2O in 10mL of deionized water, and then impregnate and dry as in step (2) of Example 3.

[0089] (3) The subsequent steps are the same as steps (3) and (4) in Example 3, to obtain the Cu-Ni / SiC catalyst.

[0090] 2. The catalyst evaluation method is the same as that in Example 3.

[0091] 3. Application results: n-Butanol conversion rate 85.1%, selectivity 95.43%, and conversion rate 83.2% after 500 hours.

[0092] The specific comparative data between the examples and the comparative examples are shown in Table 1:

[0093] As can be seen, the magnetic carrier, strong carrier-metal interaction, optimized metal loading and ratio are key features for achieving high conversion rate, ultra-high selectivity (>99.9%) and excellent stability (attenuation <5% after 500h).

[0094] Magnetic supports (copper foam, nickel foam, carbon felt, porous carbon, SiC) generate eddy currents and hysteresis losses in an alternating electromagnetic field, enabling in-situ, uniform, and rapid heating of the catalyst bed and completely eliminating the temperature gradient problem of traditional electric furnace heating. The functional groups on the support surface interact strongly with metal ions, anchoring metal nanoparticles and preventing migration and aggregation.

[0095] In-situ precise heating ensures uniform temperature distribution in the bed, eliminating the risk of side reactions such as alcohol cracking and deep decarbonization caused by localized overheating. At the same time, the lower apparent reaction temperature inhibits secondary cracking of the product.

[0096] Optimized metal loading and ratio are prerequisites for achieving synergistic effects; too little metal will result in insufficient synergy, while too much will cover active sites.

[0097] It should be understood that the above embodiments are merely exemplary. Those skilled in the art can make various non-substantial improvements and substitutions based on the technical concept of this invention, and all such improvements and substitutions should be considered to fall within the protection scope of this application.

Claims

1. A catalyst suitable for the dehydrogenation of lower alcohols to aldehydes driven by alternating electromagnetic fields, characterized in that, include: A magnetothermal carrier, and a metal active center loaded on the magnetothermal carrier; wherein the magnetothermal carrier is a material that can be inductively heated in an alternating electromagnetic field.

2. The catalyst according to claim 1, suitable for the dehydrogenation of lower alcohols to aldehydes driven by alternating electromagnetic fields, is characterized in that, The magnetothermal carrier is selected from one or more of copper foam, nickel foam, carbon felt, porous carbon materials, or silicon carbide.

3. The catalyst according to claim 1, suitable for the dehydrogenation of lower alcohols to aldehydes driven by alternating electromagnetic fields, is characterized in that, The metal active center is selected from at least one metal selected from Cu, Ni, Fe, Zn, Ag, and Pt.

4. The catalyst for the dehydrogenation of low alcohols to aldehydes driven by alternating electromagnetic fields according to claim 1, wherein the loading of the metal active center is 0.1wt%-20wt%.

5. A method for preparing a catalyst, used to prepare the catalyst as described in any one of claims 1-4, suitable for alternating electromagnetic field-driven dehydrogenation of lower alcohols to aldehydes, characterized in that, Includes the following steps: Step S1: Pre-treat the vector; Step S2: The support pretreated in step S1 is impregnated and dispersed in a solution containing at least one metal active center, and then dried to obtain a catalyst precursor supported on a metal precursor. Step S3: Calcine the catalyst precursor obtained in step S2 under an inert atmosphere to obtain a metal oxide supported precursor; Step S4: The metal oxide supported precursor obtained in step S3 is reduced and activated in a reducing atmosphere to obtain the catalyst.

6. The catalyst preparation method according to claim 5, characterized in that, In step S2, the impregnation is either equal-volume impregnation or wet impregnation; the drying is either vacuum drying or freeze drying.

7. The catalyst preparation method according to claim 5, characterized in that, In step S3, the calcination temperature is 300-500℃ and the holding time is 2-4 hours; in step S4, the reduction and activation temperature is 200-600℃ and the holding time is 1-4 hours.

8. The catalyst preparation method according to claim 7, characterized in that, Step S3: The temperature is increased from room temperature to 300-500°C at a heating rate of 1-5°C / min, and the inert atmosphere is nitrogen or argon.

9. A method for producing aldehydes from low-carbon alcohols via alternating electromagnetic field-driven dehydrogenation, characterized in that, Includes the following steps: The catalyst according to any one of claims 1-4 is placed in the induction coil area of ​​the alternating electromagnetic field heating device; Vaporized low-carbon alcohol feedstock and carrier gas are introduced into the reactor, and a dehydrogenation reaction is carried out under the drive of the alternating electromagnetic field. The lower alcohol is selected from at least one of methanol, ethanol, n-butanol, isobutanol, and isoamyl alcohol, and the reaction conditions are: atmospheric pressure, and the liquid hourly space velocity of the lower alcohol is 0.5-5 h⁻¹. -1 The volume ratio of carrier gas to low-carbon alcohol vapor is (10-100):1, and the frequency of the alternating electromagnetic field is 1-90kHz.

10. The method for producing aldehydes from low-carbon alcohols driven by alternating electromagnetic fields according to claim 9, characterized in that, When the lower alcohol is methanol, the reaction temperature is 450-500℃; when the lower alcohol is ethanol, n-butanol, isobutanol or isoamyl alcohol, the reaction temperature is 150-300℃.

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