Method for one-step production of ethylbenzene from ethane and benzene by alternating electromagnetic field and catalyst thereof

Abstract

The application provides a method for preparing ethylbenzene from ethane and benzene by an alternating electromagnetic field and a catalyst thereof. The method comprises the following steps: introducing a reaction gas containing ethane and benzene into a reactor filled with a metal-molecular sieve bifunctional catalyst, and applying an alternating electromagnetic field. The magnetic heating effect of the magnetic metal component (such as Fe, Co and Ni) in the catalyst is utilized to realize directional heating, drive the cooperative reaction of ethane dehydrogenation and benzene alkylation, and generate ethylbenzene in one step. The catalyst is composed of magnetic metal nanoparticles and a molecular sieve (such as ZSM-5). The application solves the problem that the reaction temperatures of the endothermic dehydrogenation and the exothermic alkylation are not matched in the prior art, simultaneously utilizes the non-thermal effect induced by the magnetic field to enhance hydrogen overflow and inhibit carbon deposition, realizes the cooperative improvement of the benzene conversion rate and the ethylbenzene selectivity, and has the advantages of a short process, high energy efficiency and good catalyst stability.

Description

Technical Field

[0001] This invention relates to the field of energy and chemical catalysis technology, specifically to a method for one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field, and its catalyst. Background Technology

[0002] Ethylbenzene is a key precursor in the production of styrene, which is an important monomer for the synthesis of polymers such as polystyrene. Currently, the industrial production of ethylbenzene mainly employs a two-step process: first, ethane is steam-cracked at ultra-high temperatures (typically >800℃) to produce ethylene; subsequently, the separated ethylene undergoes an alkylation reaction with benzene at a lower temperature. This process suffers from problems such as drastic temperature transitions between high and low temperatures, a long process flow, and high energy consumption.

[0003] To overcome the drawbacks of the two-step process, researchers have developed a novel one-step alkylation process for ethane and benzene to produce ethylbenzene in a single reactor. The core of this technology lies in designing a bifunctional catalyst that combines ethane dehydrogenation activity with benzene alkylation activity. For example, (Fuel, 2023, 342, 127764) reported achieving approximately 10% benzene conversion and 92% ethylbenzene selectivity under optimized conditions using a Pt / ZSM-5 nanosheet catalyst; and (Ind. Eng. Chem. Res., 2024, 62, 15834-15843) reported achieving 17% benzene conversion and 95% ethylbenzene selectivity using a PtZnPr / ZSM-5 catalyst.

[0004] However, the aforementioned one-step process suffers from a fundamental technical contradiction: ethane dehydrogenation is a strongly endothermic reaction, requiring high temperatures (typically >650℃) to achieve a considerable conversion rate; while benzene alkylation is an exothermic reaction, which is more favorable for improving ethylbenzene selectivity and suppressing side reactions such as isomerization and cracking at lower temperatures (<450℃). Because traditional fixed-bed reactors operate in a single temperature zone, they cannot simultaneously provide optimal temperature environments for both dehydrogenation and alkylation steps within the same reaction system, resulting in a seesaw relationship between benzene conversion and ethylbenzene selectivity. Although introducing external catalytic fields such as plasma and light fields can lower the ethane activation energy, these methods generally suffer from low energy utilization efficiency and difficulty in precisely controlling the reaction pathway. Summary of the Invention

[0005] This invention provides a catalyst for the one-step production of ethylbenzene from ethane and benzene driven by the above-mentioned alternating electromagnetic field. The catalyst is a metal-molecular sieve bifunctional catalyst, comprising: 1. Magnetic metal component: The magnetic metal component is selected from at least one of Fe, Co, and Ni, or from at least one of FeCo alloy, NiCo alloy, and FeNi alloy, and exists in the form of nanoparticles with a particle size of 2-50 nm; the mass fraction of the magnetic metal component in the catalyst is 1%-20%. The magnetic metal component can generate heat through hysteresis loss and / or eddy current loss in an alternating electromagnetic field, and at the same time provide active sites for ethane dehydrogenation.

[0006] 2. Molecular sieve component: The molecular sieve component is selected from at least one of ZSM-5, ZSM-11, ZSM-12, Beta, MCM-22, and SAPO-34; the silica-alumina molar ratio of the molecular sieve is 10-300; the molecular sieve component has acidic sites, providing active centers for benzene alkylation.

[0007] 3. Structural features: The integration method of the magnetic metal component and the molecular sieve component is selected from one of the following: physical mixing, impregnation loading, in-situ encapsulation, or core-shell structure, preferably a metal@molecular sieve core-shell structure; In the core-shell structure, the magnetic metal nanoparticles serve as the core and are partially and completely encapsulated by the molecular sieve shell layer. This not only restricts the migration and aggregation of metal particles at high temperatures, but also creates a large number of tight metal-acid center interfaces to enhance the synergistic effect of the two reaction steps of ethane dehydrogenation and benzene alkylation.

[0008] In some embodiments, the magnetic metal component further includes a noble metal additive selected from at least one of Pt, Pd, Ru, and Rh, with a mass fraction of 0.1%-1% of the total mass of the magnetic metal component, used to regulate the electronic structure of the metal active sites and the ethane dehydrogenation activity.

[0009] In some embodiments, the molecular sieve components may also be treated with alkali (e.g., NaOH solution), acid, or ion exchange (e.g., Zn). 2+ Ga 3+ Pr 3+ The molecular sieve is modified by exchange to control the type of acid (the ratio of Brønsted acid to Lewis acid), acid strength and acid density, thereby optimizing the activity and selectivity of the benzene alkylation reaction.

[0010] The present invention also discloses a method for preparing the above-mentioned catalyst, comprising: (a) The magnetic metal nanoparticles are prepared by one of the following methods: solvothermal method, coprecipitation method, thermal decomposition method or polyol reduction method; (b) Molecular sieves were prepared by hydrothermal synthesis. (c) Integrating magnetic metal nanoparticles with molecular sieves through physical mixing, impregnation loading, or in-situ encapsulation.

[0011] In some embodiments, when magnetic metal nanoparticles are prepared using a solvothermal method, a metal precursor (such as iron acetylacetonate, cobalt acetylacetonate, nickel acetylacetonate, etc.) is dissolved in an organic solvent (such as benzyl ether, octadecene, etc.), and reacted at 180-300°C for 0.5-5 hours in the presence of a surfactant (such as oleic acid, oleylamine, etc.) to obtain magnetic metal nanoparticles. By controlling the type and ratio of the metal precursor, the amount of surfactant, the reaction temperature, and the time, the size of the metal particles can be controlled to be 2-50 nm, and the morphology to be spherical, cubic, or polyhedral. When preparing alloy nanoparticles (such as FeCo, NiCo), two metal precursors are simultaneously added to the reaction system at a target molar ratio for co-reduction. After the magnetic metal nanoparticles are prepared, they undergo magnetic separation, washing, and drying.

[0012] In some embodiments, the hydrothermal synthesis method for preparing molecular sieves is as follows: Taking ZSM-5 as an example, a silicon source (such as tetraethyl orthosilicate or silica sol), an aluminum source (such as sodium aluminate or aluminum isopropoxide), a template agent (tetrapropylammonium hydroxide), and deionized water are mixed in a certain ratio and crystallized at 150-180℃ for 24-96 hours. After washing, drying, and calcination at 550℃ to remove the template agent, ZSM-5 molecular sieve is obtained. By adjusting the silicon-aluminum molar ratio (30-300), the amount of template agent, and the crystallization conditions, the crystallite size of the molecular sieve is controlled to be 50nm-5μm, and the pore structure is a microporous or micro-mesoporous composite structure. Further selective desilication is achieved through alkali treatment (NaOH solution, 0.1-1.0 mol / L, 50-80℃ for 0.5-2 hours), introducing mesopores and forming a hierarchical pore structure; metal cations are introduced through ion exchange (such as Zn(NO3)2, Ga(NO3)3 solution), thereby controlling the type, amount, and strength of the molecular sieve acid. In some embodiments, when magnetic metal nanoparticles and molecular sieves are physically mixed, the magnetic metal nanoparticles prepared in step (a) and the molecular sieves prepared in step (b) are ground or ball-milled at a mass ratio of 1:(2-50) to obtain a metal-molecular sieve mixed catalyst.

[0013] In some embodiments, when magnetic metal nanoparticles and molecular sieves are physically mixed using an impregnation loading method, a metal precursor solution is impregnated onto the molecular sieve, followed by drying, calcination (300-500°C, 2-5 hours), and reduction (H2 atmosphere, 400-600°C, 1-4 hours) to obtain a supported metal / molecular sieve catalyst.

[0014] In some embodiments, the in-situ encapsulation of magnetic metal nanoparticles and molecular sieves includes: dispersing the prepared magnetic metal nanoparticles in a molecular sieve synthesis precursor gel during the hydrothermal synthesis of molecular sieves, and obtaining a magnetic metal@molecular sieve core-shell structure catalyst by crystallization.

[0015] In some embodiments, the method further includes regenerating the catalyst by introducing an oxygen-containing atmosphere (such as air or an O2 / N2 mixture with an O2 volume fraction of 1%-21%) into the reactor under the action of an alternating electromagnetic field, adjusting the catalyst bed temperature to 350-500°C, and treating for 1-6 hours to burn off the carbon deposits on the catalyst surface and restore catalytic activity.

[0016] This invention also provides a method for one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field, comprising the following steps: Step S1: The catalyst is loaded into a fixed-bed reactor, which is a quartz tube or stainless steel tube with an inner diameter of 4-40 mm and a catalyst loading amount of 0.1-500 g. An alternating electromagnetic field generator is installed outside the reactor. The alternating electromagnetic field generator includes an induction coil and a high-frequency power supply. The induction coil is wound around the outer wall of the reactor with 3-10 turns and an inner diameter of 10-100 mm.

[0017] Step S2: Introduce a reaction gas into the reactor. The reaction gas contains ethane and benzene, with a molar ratio of ethane to benzene of 1:1 to 10:1. The reaction gas may also selectively contain a dilution gas, which is selected from at least one of N2, Ar, and He, and has a volume fraction of 0-90%. The total mass hourly space velocity (WHSV, based on the total mass of ethane and benzene) of the reaction gas is 0.1-10 h⁻¹. The pressure of the reaction system is atmospheric pressure.

[0018] Step S3: Turn on the alternating electromagnetic field generator, setting the frequency of the alternating electromagnetic field to 1-90kHz and the magnetic field strength (measured by the magnetic field strength at the center of the coil) to 1-20mT. By adjusting the frequency and magnetic field strength of the alternating electromagnetic field, the magnetic metal components are induced to generate heat, maintaining the macroscopic temperature of the catalyst bed in the reactor at 300-700℃. The macroscopic temperature of the catalyst bed is monitored in real time using an infrared thermal imager or thermocouples. The power of the alternating electromagnetic field is dynamically adjusted according to the target temperature of the catalyst bed, with an input power density of 1-100W / g catalyst. Once the reaction system reaches the target temperature, the parameters of the alternating electromagnetic field are kept stable, and the reaction continues.

[0019] Step S4: Under the above reaction conditions, ethane undergoes CH bond cleavage at the active sites of the magnetic metal, generating alkylating active species such as ethylene or adsorbed ethyl groups. These active species migrate to adjacent acidic sites of the molecular sieve via diffusion, where they undergo alkylation reactions with adsorbed benzene to generate the target product, ethylbenzene. During this process, the directional induction heating of the magnetic metal by the alternating electromagnetic field rapidly raises the metal sites to the temperature required for ethane activation. Simultaneously, the localized induced electric field generated by the alternating electromagnetic field promotes electron transfer at the metal-molecular sieve interface, lowers the ethane CH bond activation barrier, and accelerates the migration of active hydrogen species on the catalyst surface (hydrogen spillover effect), inhibiting the formation of carbon precursors and improving the catalyst's reaction stability.

[0020] Step S5: The product gas after the reaction is discharged from the reactor outlet and cooled to 5-40℃ by the condenser, so that ethylbenzene, unreacted benzene and other heavy components are liquefied and separated from the uncondensed light component gas (unreacted ethane, ethylene, dilution gas, etc.). After separation, the liquid phase product is obtained as ethylbenzene and recovered benzene (the recovered benzene can be recycled). The uncondensed light component gas can be partially or completely recycled back to the reactor inlet to continue to participate in the reaction.

[0021] In some embodiments, the method is a continuous operation mode for not less than 200 hours; under this condition, the single-pass conversion rate of benzene is not less than 15%; and the selectivity of ethylbenzene is not less than 95%.

[0022] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes an alternating electromagnetic field to directionally heat a magnetic metal component, causing the dehydrogenation active center to reach a locally high temperature while the surrounding molecular sieve and reactant gas mass remain at a relatively low temperature. The magnetic field-induced electric field and electron transfer effect directly reduce the activation energy of the ethane CH bond, accelerating reactant activation. This invention simultaneously satisfies the different temperature requirements of endothermic dehydrogenation and exothermic alkylation, achieving a synergistic improvement in benzene conversion and ethylbenzene selectivity.

[0023] The non-thermal effects induced by the alternating electromagnetic field of this invention, such as the enhanced hydrogen spillover effect, help to remove active hydrogen species on the metal center in a timely manner, inhibit the formation of deep dehydrogenation and carbon deposition precursors, thereby significantly improving catalyst stability, single-pass lifetime and ethylbenzene selectivity.

[0024] In this invention, the alternating electromagnetic field energy acts directly on the magnetic metal, resulting in rapid and precise heating. This avoids the huge energy waste caused by the need to heat the entire reactor and surrounding environment in traditional tube furnace heating, thus making the system more energy efficient.

[0025] This invention also highly integrates the traditional two-step process into a single reaction unit, resulting in a shorter process, lower equipment investment, lower operational complexity, and the ability to achieve online in-situ catalyst regeneration, further improving economic efficiency.

[0026] Through the verification of examples, it is found that using the catalyst and method of the present invention, under optimized conditions, a benzene conversion rate of >30% and an ethylbenzene selectivity of >95% can be achieved, and the catalyst stability is significantly better than that of the traditional thermocatalytic system. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall apparatus for the one-step production of ethylbenzene from ethane and benzene according to the present invention; Figure 2 This is a schematic diagram of the fixed-bed reactor driven by alternating electromagnetic field induction according to the present invention. Detailed Implementation

[0028] 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.

[0029] Reference Figure 1 Ethane, hydrogen, and oxygen are supplied from high-pressure gas cylinders. Gas filters are used to prevent impurities from clogging the flow meters. A gas mass flow meter is used to precisely control and measure the gas feed rate. The three gases are mixed before contacting liquid benzene. A liquid flow pump is used to control and measure the benzene feed rate. After contact, the gas and liquid benzene enter the gasification furnace together, where the benzene is vaporized. Then, all the raw material mixture enters the reactor. The reaction takes place on the catalyst bed in the reaction tubes within the reactor. After the reaction, the gas is connected to an online chromatograph for product analysis. The tail gas passes through a condenser, where the liquid products are condensed; non-condensable gases are discharged with the tail gas.

[0030] Reference Figure 2 The reaction tube is placed inside an alternating electromagnetic induction coil, ensuring the catalyst bed is completely within the coil's range. The catalyst inside the reaction tube is packed in a fixed bed. The alternating electromagnetic induction device allows adjustment of the magnetic field strength by regulating the current.

[0031] The following are specific embodiments and comparative examples of the present invention.

[0032] Example 1: Preparation and performance of Fe@ZSM-5 core-shell catalyst 1. Catalyst preparation: 1) ZSM-5 molecular sieve (silicon-to-aluminum ratio = 50) was synthesized by hydrothermal method and mesoporous sieve was obtained by alkali treatment.

[0033] 2) Fe3O4 nanoparticles (average size 10 nm) were prepared by solvothermal method.

[0034] 3) Fe3O4 nanoparticles were dispersed in ZSM-5 precursor gel, and a ZSM-5 shell was grown on the surface of Fe3O4 by secondary crystallization to form a Fe3O4@ZSM-5 core-shell structure.

[0035] The Fe@ZSM-5 catalyst was obtained by reduction at 500℃ for 2 hours in an H2 atmosphere.

[0036] 2. Reaction Evaluation: 1) 1.0g of catalyst was packed into a quartz tube fixed bed reactor, and an induction coil was wound around the outside of the reactor.

[0037] 2) The composition of the reaction gas is: ethane: benzene: N2 = 3:1:6 (volume ratio), and the total gas velocity is 30 mL / min.

[0038] 3) Turn on the alternating electromagnetic field (frequency 50kHz, magnetic field strength 8mT), and the catalyst bed temperature is about 550℃ as monitored by thermocouples.

[0039] 4) Online gas chromatography analysis of the reaction products. Results: Benzene conversion rate 32%, ethylbenzene selectivity 98%, and no significant performance degradation after 100 hours of continuous reaction.

[0040] Example 2: Preparation and performance of CoNi / ZSM-5 catalyst 1. Catalyst preparation: 1) CoNi alloy nanoparticles (Co:Ni=1:1, average size 15nm) were prepared by coprecipitation method.

[0041] 2) CoNi alloy was loaded onto commercial HZSM-5 (silicon-to-aluminum ratio = 80) using an impregnation method, with a loading of 5 wt.%.

[0042] 3) Reduced in H2 at 450℃ for 3 hours to obtain CoNi / ZSM-5 catalyst.

[0043] 2. Reaction Evaluation: The reaction conditions were the same as in Example 1, with an alternating electromagnetic field frequency of 90 kHz and a magnetic field strength of 12 mT. The catalyst bed temperature was approximately 580 °C.

[0044] Results: Benzene conversion rate was 35%, ethylbenzene selectivity was 97.5%, and performance did not decrease significantly after 100 hours of continuous reaction.

[0045] Example 3: Preparation and performance of PtFe@ZSM-5 catalyst 1. Catalyst preparation: 1) PtFe alloy nanoparticles (Pt:Fe=1:9, size 5nm) were prepared by thermal decomposition.

[0046] 2) PtFe precursor was introduced into the ZSM-5 synthesis process by in-situ encapsulation to obtain PtFe@ZSM-5 core-shell catalyst.

[0047] 3) Use after H2 reduction.

[0048] 2. Reaction Evaluation: The reaction conditions were the same as in Example 1, with an alternating electromagnetic field frequency of 70 kHz and a magnetic field strength of 10 mT. The catalyst bed temperature was approximately 540 °C.

[0049] Results: Benzene conversion rate was 30.8%, ethylbenzene selectivity was 96.2%, and performance did not decrease significantly after 100 hours of continuous reaction.

[0050] Comparative Example 1: Traditional thermocatalysis (without alternating electromagnetic field) Using the Fe@ZSM-5 catalyst from Example 1, the reaction was carried out in a conventional tube furnace with the bed temperature controlled at 500°C. All other reaction conditions remained the same. Results: Benzene conversion was 13%, ethylbenzene selectivity was 88.3%, and the benzene conversion decreased to below 5% after 20 hours of reaction.

[0051] Comparative Example 2: Physically Mixed Catalysts (No Core-Shell Structure) Fe nanoparticles were physically mixed with ZSM-5 molecular sieves (mass ratio 1:9), and other procedures were the same as in Example 1. Results: Benzene conversion rate was 28%, ethylbenzene selectivity was 92%, the synergistic effect of the reaction was weak, and the benzene conversion rate dropped below 10% after 20 hours of reaction.

[0052] The specific comparison of the above experimental data is shown in Table 1:

[0053] The above embodiments and comparative examples demonstrate that the present invention, driven by an alternating electromagnetic field, utilizes the induction heating and non-thermal effects of magnetic metals to simultaneously achieve high benzene conversion rate and ethylbenzene selectivity, while exhibiting good stability. In contrast, the comparative examples, lacking an effective magnetic field drive or synergistic structure, show a significant performance degradation.

[0054] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A catalyst for the one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field, characterized in that, The catalyst is a metal-molecular sieve bifunctional catalyst, comprising at least one magnetic metal component and at least one molecular sieve component. The integration method of the magnetic metal component and the molecular sieve component is selected from one of physical mixing, impregnation loading, in-situ encapsulation, or core-shell structure.

2. The catalyst for the one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field as described in claim 1, characterized in that, The core-shell structure uses the magnetic metal component as the core and the molecular sieve component as the shell.

3. The catalyst for the one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field according to claim 1, characterized in that, The magnetic metal component is selected from at least one element of iron, cobalt, and nickel, or from at least one alloy of iron-cobalt alloy, nickel-cobalt alloy, and iron-nickel alloy; the molecular sieve component is selected from at least one of ZSM-5, ZSM-11, ZSM-12, Beta, MCM-22, and SAPO-34.

4. The catalyst for one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field according to claim 3, characterized in that, The magnetic metal component has a particle size of 2 nm to 50 nm and a mass fraction of 1% to 20% in the catalyst; the molecular sieve component has a silicon-to-aluminum molar ratio of 10 to 300.

5. The catalyst for one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field according to claim 1, characterized in that, The magnetic metal component further includes a noble metal additive selected from at least one of platinum, palladium, ruthenium, and rhodium, wherein the mass of the noble metal additive is 0.1% to 1% of the total mass of the magnetic metal component.

6. A method for preparing a catalyst for the one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field as described in any one of claims 1-5, characterized in that, Includes the following steps: Magnetic metal nanoparticles are prepared by one of the following methods: solvothermal method, coprecipitation method, thermal decomposition method, or polyol reduction method. Molecular sieves were prepared by hydrothermal synthesis. Magnetic metal nanoparticles are integrated with molecular sieves through physical mixing, impregnation loading, or in-situ encapsulation.

7. A method for one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field, characterized in that, Includes the following steps: A reaction gas containing ethane and benzene is introduced into a reactor packed with a catalyst as described in any one of claims 1-5; an alternating electromagnetic field is applied to the reactor to induce heat in the magnetic metal component of the catalyst to drive the reaction, thereby producing ethylbenzene.

8. The method for one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field according to claim 7, characterized in that, The frequency of the alternating electromagnetic field is from 1 kHz to 90 kHz, and the magnetic field strength is from 1 mT to 20 mT, measured by the magnetic field strength at the center of the coil. After the alternating electromagnetic field is applied, the macroscopic temperature of the catalyst bed in the reactor is maintained at 300°C to 700°C.

9. The method for one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field according to claim 7, characterized in that, In the reaction gas, the molar ratio of ethane to benzene is from 1:1 to 10:1; the total mass hourly space velocity (GHSV) of the reaction gas, based on the total mass of ethane and benzene, is 0.1 h⁻¹. -1 Up to 10h -1 .

10. The method for one-step production of ethylbenzene from ethane and benzene driven by an alternating electromagnetic field according to claim 7, characterized in that, It also includes in-situ regeneration of the deactivated catalyst: while continuing to apply the alternating electromagnetic field, the gas introduced into the reactor is switched to an oxygen-containing atmosphere, which is air or an O2 / N2 mixture with an O2 volume fraction of 1%-21%, and the catalyst bed temperature is adjusted to 350°C to 500°C for a processing time of 1 hour to 6 hours.

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