A process for hydrogen production from alcohols based on microwave-induced induction

Abstract

This invention discloses a microwave-induced process for hydrogen production from alcohols, belonging to the field of hydrogen energy production technology. The method utilizes microwave radiation to induce activation of a metal oxide catalyst, generating localized high-temperature hotspots, while simultaneously employing electromagnetic heating to preheat the alcohol reactants. Once the catalyst and reactants reach the desired temperature, the alcohol reactants are mixed with water vapor in a specific ratio to form a homogeneous gaseous reactant, which is then injected into a microwave cavity reactor at a predetermined space velocity. Under the continuous action of the microwave field, the gaseous reactant undergoes a steam reforming reaction on the catalyst surface, generating a mixed gas primarily composed of hydrogen and carbon dioxide. Finally, high-purity hydrogen is obtained through pressure swing adsorption. This invention utilizes the selective heating and hotspot effect of microwave energy to improve hydrogen production efficiency and catalyst activity, enabling efficient hydrogen production from organic matter under mild conditions. It is applicable to various application scenarios, including internal combustion engines, external combustion engine combustion, and chemical raw materials.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production technology, specifically a process for producing hydrogen from alcohols based on microwave-induced oxidation. Background Technology

[0002] Hydrogen, as a clean and efficient energy carrier, has always been a key research focus in the field of new energy. Among the many hydrogen production routes, alcohol catalytic reforming has attracted much attention due to its high hydrogen content and safe storage and transportation. However, traditional alcohol reforming processes generally adopt external heating, and energy needs to penetrate the reactor wall through convection and conduction, which has inherent defects such as low thermal efficiency and slow response, resulting in high system energy consumption. At the same time, in order to maintain a sufficient reaction rate, the process often needs to operate under high temperature and high pressure, which places stringent requirements on the equipment. Moreover, the catalyst is prone to deactivation due to carbon deposition and sintering, which seriously affects the economic efficiency and continuity of operation.

[0003] Microwave heating technology offers a new approach to overcoming the bottlenecks of traditional heating methods due to its ability to heat substances in bulk, rapid temperature rise, and high energy efficiency. However, successfully applying microwave energy to hydrogen production from alcohols still faces a series of challenges: simple microwave heating without efficient coupling design between the catalyst and reactants makes it difficult to achieve selective energy input and precise control of the reaction path; in addition, a complete hydrogen production process not only requires an efficient reaction core, but also integrated units such as feed pretreatment and product purification matched with the reactor. However, existing technologies mostly improve only the reactor locally, lacking a complete process scheme that systematically integrates microwave induction, material preheating, uniform mixing, efficient reaction, and fine separation. This greatly limits the reliability of large-scale application of this technology in on-the-go scenarios such as vehicle-mounted and distributed systems.

[0004] Therefore, developing a microwave-induced alcohol-to-hydrogen process that can achieve efficient catalyst activation, precise control of the reaction process, and high system integration is of great significance for breaking through existing technological bottlenecks and promoting the widespread application of hydrogen energy. Summary of the Invention

[0005] The purpose of this invention is to overcome the technical shortcomings of existing alcohol-based hydrogen production processes, such as low energy utilization efficiency, high catalyst cost and easy deactivation, and complex product purification processes. This invention provides a microwave-induced alcohol-based hydrogen production process. The method integrates a microwave-sensitive composite catalyst system with the process, achieving a shift from traditional heat conduction heating to precise microwave field energy supply. This significantly improves energy utilization efficiency while reducing the precious metal loading of the catalyst and simplifying the subsequent purification process, providing a new technological pathway for green and low-carbon hydrogen production.

[0006] The objective of this invention can be achieved through the following technical solutions: This application provides a process for producing hydrogen from alcohols based on microwave-induced oxidation, comprising: Turn on the microwave power source to induce the catalyst metal oxide, and then preheat the reactants participating in the reaction using electromagnetic heating; Once the catalyst and reactants reach the temperature required for the reaction, the reactants are injected into the microwave cavity at a predetermined space velocity. After the reaction time is appropriate, hydrogen and other products will be generated. After purification by pressure swing adsorption, the required hydrogen can be obtained for combustion in internal or external combustion engines or as a chemical raw material.

[0007] Preferably, the step of turning on the microwave power source to induce the catalyst metal oxide specifically includes: The microwave electromagnetic energy generated by the microwave power source is coupled into the microwave cavity, so that the metal oxide catalyst selectively absorbs the microwave energy through its metal ions and directly converts the electromagnetic energy into its own internal energy. Under the condition that the overall temperature of the catalyst reaches 300-600℃, the basic induction of the catalyst is achieved. Through the instantaneous concentrated dissipation of energy within the catalyst particles during the selective absorption process, a local high-temperature region, namely a microwave hotspot, is formed on the catalyst surface under the condition of forming a temperature gradient of over 400°C, thereby achieving enhanced induction of local catalyst activity. When microwave power density reaches 100-1000 W / cm² 2 Under the influence of a strong microwave field, the catalyst surface is further induced to generate microwave plasma through electrodeless discharge, thereby achieving deep induction of the catalyst. Through the synergistic effect of the microwave hotspot and the extreme hotspot region, the final induction of the catalyst metal oxide is completed under the condition that the plasma discharge core temperature exceeds 1000℃, so that the catalyst metal oxide reaches the activated state and generates a stable local high temperature hotspot.

[0008] Preferably, the preheating of the reactants using electromagnetic heating specifically includes: Turn on the electromagnetic heating device, which heats the flowing alcohol reactants through its built-in induction heating circuit; Under the action of an alternating magnetic field, the induction heating pipe generates eddy currents on its wall, which in turn generates heat, thereby indirectly heating the alcohol reactants in the pipe to a predetermined reaction temperature of 150-400°C. The output power of the electromagnetic heating device is controlled by the temperature sensor feedback to maintain the reactant temperature stable within a set value of ±10℃.

[0009] Preferably, the control of the output power of the electromagnetic heating device specifically includes: When the temperature sensor detects that the reactant temperature has reached the upper limit of the set value, the output power of the electromagnetic heating device is controlled to gradually decrease from 100% to 10%. When the temperature sensor detects that the temperature of the reactants is 10°C lower than the set lower limit, the output power of the electromagnetic heating device is controlled to gradually increase from 10% to 100%.

[0010] Preferably, when the temperature of the catalyst and reactants reaches the temperature required for the reaction, the reactants are injected into the microwave cavity at a predetermined space velocity, specifically including: The preheated alcohol reactants are mixed and homogenized with water vapor to form a homogeneous gaseous reactant, which is then injected into the microwave cavity. The mixing and homogenization process specifically includes: Preheated alcohol reactants at 150-400℃ and superheated steam at 180℃ are metered and controlled by flow meters and regulating valves, respectively, to ensure that the flow fluctuation of alcohol reactants does not exceed ±2.5% of the set value and the flow fluctuation of steam does not exceed ±2.5% of the set value, so that the molar flow rate is stabilized within the ratio range of (1.0-3.0):1. The metered alcohol reactants and water vapor are fed into a static mixer, which is equipped with multiple alternating left-handed and right-handed mixing units. As the gaseous reactants flow through the left-handed and right-handed mixing units, they are continuously cut, sheared, diverted, and recombine to achieve radial mixing and component homogenization at the microscale, forming a homogeneous gaseous reactant with uniform temperature distribution and component concentration fluctuations not exceeding ±5%. The homogeneous gaseous reactants are subjected to a reaction at a rate of 2000-10000 h. -1 The predetermined air velocity is injected into the reactor inside the microwave cavity.

[0011] Preferably, after a suitable reaction time, hydrogen gas and other products will be generated, specifically including: Under the continuous action of a microwave field, the gaseous reactants undergo a steam reforming reaction on the catalyst surface, with the reaction time controlled within the range of 10-120 minutes. When the reaction time reaches 10-120 minutes, the conversion rate of alcohol reactants reaches more than 95%, at which point the reaction is complete, producing a mixed gas mainly composed of hydrogen and carbon dioxide. When the alcohol reactant is methanol, the overall chemical reaction is: CH3OH + H3O → CO3 + 3H3; The steam reforming reaction is carried out under the conditions of catalyst bed temperature of 250-290℃ and operating pressure ≤2.5 MPa.

[0012] Preferably, the steam reforming reaction occurring on the catalyst surface specifically includes: Under the continuous action of the microwave field, alcohol molecules first undergo chemical adsorption at the metal active sites on the catalyst surface, and their CH and OH bonds break and dissociate under the high temperature of the microwave hot spot region. The intermediate species generated by dissociation react with water molecules adsorbed on the catalyst surface. Among them, the carbon-containing intermediate is oxidized to carbon monoxide, and hydrogen atoms are released at the same time. The generated carbon monoxide further reacts with surface hydroxyl species in a water-gas shift reaction, converting into carbon dioxide and producing additional hydrogen. Ultimately, the hydrogen atoms adsorbed on the catalyst surface combine to form hydrogen molecules and desorb from the active sites, completing the steam reforming reaction on the catalyst surface.

[0013] Preferably, the required hydrogen gas can be obtained through pressure swing adsorption purification, specifically including: The mixed gas generated by the reaction is first passed through a condensation and dehydration device. The gas temperature is reduced to 25-40℃ by circulating cooling water, so that the water vapor in the mixed gas condenses and precipitates out, thus lowering the gas dew point. The dehydrated mixed gas is pressurized to an operating pressure of 1.5-3.0 MPa by a compressor unit, and the pressure is maintained within the range of fluctuation not exceeding ±0.1 MPa. The pressurized mixed gas is passed into a pressure swing adsorption system consisting of 4-8 adsorption towers, each adsorption tower being filled with a multi-bed adsorbent composed of activated alumina, molecular sieves and activated carbon. The following cyclic steps are executed sequentially by the program control system in each adsorption tower: adsorption is carried out at a pressure of 1.5-3.0 MPa, where impurities such as carbon dioxide, carbon monoxide, and residual moisture are selectively adsorbed by the adsorbent; the pressure of the adsorption tower is reduced to 0.2-0.5 MPa for reverse venting to remove the adsorbed impurities; a portion of the product hydrogen is used to backwash the adsorption tower to further purify the adsorbent; finally, the pressure of the adsorption tower is restored to the working pressure using product hydrogen to complete the adsorbent regeneration. Through continuous cyclic operation of the pressure swing adsorption system, a hydrogen product with a purity of ≥99.5% is obtained, wherein the carbon dioxide content is ≤50 ppm, the carbon monoxide content is ≤10 ppm, and the oxygen content is ≤5 ppm.

[0014] More preferably, the multi-bed adsorbent packed in the pressure swing adsorption system specifically includes, according to the gas flow direction: The activated alumina layer is located at the inlet of the adsorption tower and is used to deeply remove residual moisture; the molecular sieve layer is located downstream of the activated alumina layer and is used to selectively adsorb carbon dioxide and carbon monoxide; the activated carbon layer is located at the end of the adsorption tower and is used to deeply remove other trace impurities.

[0015] The beneficial effects of this invention are as follows: This invention achieves a comprehensive improvement in energy consumption, efficiency, and product purity in the alcohol-to-hydrogen process by constructing a complete microwave-induced catalysis and process intensification system. First, a multi-stage microwave induction mechanism is employed to efficiently activate the catalyst under relatively mild conditions, forming stable local high-temperature hotspots and significantly enhancing the catalyst's activity and stability. Second, precise preheating of the alcohol reactants using an electromagnetic heating device, combined with an intelligent power regulation system, maintains the stability and uniformity of the reactant temperature, creating ideal feeding conditions for subsequent reactions. Third, an optimized material mixing system achieves precise proportioning and efficient homogenization of the reaction components, improving the mass transfer efficiency and reaction uniformity on the catalyst surface. During the reaction stage, the alcohol materials undergo a complete steam reforming path under the influence of the microwave field and on the catalyst surface, achieving efficient conversion of alcohol feedstocks and highly selective hydrogen production under relatively mild reaction conditions. Finally, through an optimized pressure swing adsorption purification system, deep removal of impurity gases was achieved, resulting in high-purity hydrogen products. The entire process organically combines microwave induction, electromagnetic preheating, efficient mixing, mild reaction conditions, and intelligent purification. While reducing system energy consumption, it simplifies the process flow, improves reaction efficiency, and achieves high standards of product purity, providing reliable technical support for the industrial application of hydrogen production from alcohols. Attached Figure Description

[0016] To better understand and implement this application, the technical solution is described in detail below with reference to the accompanying drawings.

[0017] Figure 1 This is an overall process flow diagram of a microwave-induced alcohol hydrogen production process according to Embodiment 1 of the present invention; Figure 2 This is a block diagram illustrating the working principle of the steam reforming reaction process in Embodiment 1 of the present invention; Figure 3 This is an overall process flow diagram of a microwave-induced alcohol hydrogen production process according to Embodiment 2 of the present invention. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, exemplary embodiments will be described in detail below, examples of which are illustrated in the accompanying drawings. In the following description relating to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of methods and systems consistent with some aspects of this application as detailed in the appended claims.

[0019] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0020] The following detailed description of the specific implementation methods, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided in detail.

[0021] Example 1 Please see Figures 1-2 This embodiment provides a process for producing hydrogen from alcohols based on microwave-induced oxidation, comprising the following steps: S1. Turn on the microwave power source to induce the catalyst metal oxide, and then preheat the reactants participating in the reaction using electromagnetic heating. First, microwave-induced activation of the catalyst is performed. A pre-formed and packed metal oxide catalyst is placed in a microwave reaction chamber, and an industrial microwave generator is activated to couple 2.45 GHz microwave electromagnetic energy into the chamber. The metal oxide catalyst is activated through its specific metal ions (such as Fe). 3+ Ni 2+ Selective absorption of microwave energy (etc.) directly converts electromagnetic energy into molecular kinetic energy and internal energy, causing the overall temperature of the catalyst to rise rapidly to the range of 300-600℃ within 3-5 minutes, thus completing the basic induction of the catalyst. The reason why it can selectively absorb microwave energy lies in the significant differences in the dielectric loss characteristics of different components of the catalyst in a microwave electromagnetic field, specifically including: First, there are the polarization and loss mechanisms at the molecular level. Microwaves are a high-frequency alternating electromagnetic field (this system uses 2.45 GHz). The metal oxide components in the catalyst (such as Co3O4, NiO, etc.) contain unpaired d electrons in their crystal structure, resulting in transition metal ions (such as Co...). 2+ Ni 2+ These ions undergo electronic and ionic polarization under the action of an alternating electric field. The change in polarization direction attempts to keep up with the rapid change in the direction of the electric field, but due to factors such as lattice resistance, a strong relaxation effect is generated, leading to molecular-level friction, thereby efficiently converting the electromagnetic energy of microwaves into molecular vibrational energy. This process is called dielectric loss, which is the fundamental reason for the self-heating of the catalyst. Secondly, there is the hotspot formation mechanism at the microscale. Catalysts are not homogeneous materials; they consist of active components, additives, and supports. Commonly used supports (such as γ-Al2O3 and SiO2) may be microwave-transparent or weakly absorbent. Metal oxides (such as Co3O4, NiO, or silicon carbide SiC mentioned above) that serve as active components or microwave sensitizers are high dielectric loss materials. When irradiated with microwaves, energy is preferentially absorbed by these high-loss components, causing them to heat up instantly, while the surrounding support material mainly obtains heat from these points through thermal conduction. This difference in energy absorption due to the different dielectric properties of the materials themselves is the core of selective absorption. Furthermore, there is the macroscopic bulk heating effect. Because microwaves are penetrating, they can act on the entire catalyst bed simultaneously, causing all the highly destructive components inside the catalyst particles to generate heat synchronously and rapidly. This achieves bulk heating from the inside of the material, overturning the traditional external heating method that relies on heat conduction and slow heating from the surface to the inside, thus achieving ultra-fast overall heating of the catalyst within seconds to minutes. With the continuous input of microwave energy, due to the difference in dielectric loss characteristics of the components inside the catalyst particles, the energy is instantaneously concentrated and dissipated inside the particles, forming a significant temperature gradient of over 400°C. This process rapidly forms a large number of local high-temperature regions, namely microwave hot spots, on the catalyst surface and in the pores, thereby enhancing the induction of active sites on the catalyst surface and improving its local catalytic activity. When the system increases the microwave power, the average power density inside the cavity reaches 100-1000 W / cm². 2 Under strong field conditions, the electric field is highly concentrated at the microscopic tips and defects on the catalyst surface, which further induces electrodeless discharge and generates microwave plasma. This process achieves deep induction of the surface lattice and electronic structure of the catalyst, effectively removes the surface passivation layer and creates a large number of highly active sites. Finally, through the synergistic effect of the stable microwave hotspot formed above and the extreme plasma discharge core region with an instantaneous temperature exceeding 1000℃, the final induction of the catalyst metal oxide was completed; at this point, the catalyst reached a fully activated state and established a stable local high-temperature reaction microenvironment, providing a crucial highly active catalytic interface for the subsequent reforming reaction. Simultaneously, the reactants are preheated. The electromagnetic heating device is turned on, and an alcohol-water mixture solution, precisely prepared by mixing alcohol raw materials (such as methanol) and deionized water in a molar ratio of 1:1 to 1:3, is introduced into the induction heating pipeline built into the device at a constant flow rate of 0.5-2.0 L / min. Under the action of an alternating magnetic field, the tube wall of the induction heating pipeline heats up rapidly due to the eddy current effect, thereby efficiently and uniformly indirectly heating the flowing alcohol-water mixture solution to a predetermined vaporization temperature of 150-400℃. The reactant temperature is monitored in real time by a Pt100 temperature sensor attached to the pipeline outlet, and the signal is fed back to the PLC control system. The PLC control system uses a fuzzy PID algorithm to dynamically adjust the output power of the electromagnetic heating device: when the temperature reaches the upper limit of the set value, the power is automatically and smoothly reduced from 100% to 10% to maintain the temperature; when the temperature is more than 10°C below the lower limit of the set value, the power is rapidly increased from 10% to 100% to compensate. Through this closed-loop control logic, the reactant outlet temperature is accurately stabilized within ±10°C of the set value, so that the temperature of the material entering the reactor remains uniform and stable, laying a solid foundation for the smooth progress of the subsequent reaction. This step involves multi-stage induced activation of the catalyst using microwaves, constructing a highly efficient catalytic interface with high activity and stable local hot spots. Simultaneously, electromagnetic heating and precise temperature control provide the reaction system with preheated feedstock that is temperature-uniform and stable. This step lays a highly efficient catalytic foundation and ideal initial reactant conditions for the entire hydrogen production process, and is a key prerequisite for achieving subsequent efficient conversion.

[0022] S2. Once the catalyst and reactants reach the temperature required for the reaction, inject the reactants into the microwave cavity at a predetermined space velocity. First, the mixing and feeding of reactants are controlled. When the system detects that the catalyst bed temperature is stable at 450-550℃ and the preheating temperature of the alcohol-water mixture reaches the set range of 150-400℃, the feeding program is started. The alcohol reactants (taking methanol as an example) preheated to this temperature range and the superheated steam at a temperature not lower than 180℃ are independently metered and controlled by a high-precision Coriolis mass flow meter and a pneumatic regulating valve, respectively. Through the PLC control system, the instantaneous flow fluctuation of the alcohol reactants is kept within ±2.5% of the set value, and the flow fluctuation of the steam is also controlled within ±2.5% of the set value, so that the molar flow ratio of alcohol to steam is accurately stabilized within the process requirement range of (1.0-3.0):1. Subsequently, the two precisely metered streams of material are introduced into a specially designed static mixer. The static mixer is equipped with multiple alternating left-handed and right-handed spiral mixing units. When the mixed gas of alcohol vapor and water vapor flows through these mixing units, it is continuously cut, sheared, split, and recombine, forming strong radial turbulence inside the flow channel, thereby achieving ultimate mixing and component homogenization at the microscale. After this treatment, a homogeneous gaseous reactive material with uniform temperature distribution and component concentration fluctuations not exceeding ±5% is formed. Finally, the homogeneous gaseous reactants that have been mixed uniformly are passed through an insulated pipeline at a rate of 2000-10000 h. -1The catalyst is injected stably into the fixed-bed reactor within the microwave reaction chamber at a predetermined high air velocity, making full contact with the activated catalyst bed and initiating the subsequent reforming hydrogen production reaction. This step ensures the homogeneity of reactants at the molecular scale through precise flow control and efficient static mixing; and by feeding the homogeneous material into the reactor at an optimized high space velocity, uniform distribution of reactants and efficient mass transfer in the catalyst bed are achieved. This step serves as a bridge connecting the pretreatment and the core reaction unit, providing a fundamental guarantee for high-speed and uniform catalytic reforming reactions.

[0023] S3. After the reaction time is appropriate, hydrogen and other products will be generated. After purification by pressure swing adsorption, the required hydrogen can be obtained for combustion in internal combustion engines or as a chemical raw material. First, an alcohol steam reforming reaction is carried out. When the homogeneous gaseous reactants enter the microwave reaction chamber at high space velocity, they undergo a complete steam reforming process under the continuous action of the microwave field and on the catalyst surface. Specifically, under the special effect of the microwave field, alcohol molecules (taking methanol as an example) first undergo chemical adsorption on the metal active sites on the catalyst surface. Their CH and OH bonds break and dissociate under the high temperature environment of the microwave hotspot region. The intermediate species generated by dissociation then react with water molecules adsorbed on the catalyst surface. The carbon-containing intermediate is oxidized to generate carbon monoxide and releases hydrogen atoms. The generated carbon monoxide further reacts with surface hydroxyl species in a water-gas shift reaction, converting into carbon dioxide and generating additional hydrogen gas. Finally, the hydrogen atoms adsorbed on the catalyst surface combine to form hydrogen molecules and desorb from the active sites. The entire steam reforming reaction is carried out under the conditions of a catalyst bed temperature of 250-290℃ and a system operating pressure ≤2.5 MPa, with the reaction time controlled at 10-120 minutes. Under these optimized conditions, the methanol conversion rate reaches over 95%, and the overall chemical reaction follows the sequence: CH3OH + H3O→CO3+3H3, ultimately producing a mixed gas mainly composed of hydrogen and carbon dioxide, with a small amount of unreacted water vapor, trace amounts of carbon monoxide, and inert components. Subsequently, the reaction products are purified, and the above mixed gas is introduced into a condensation and dehydration unit. The gas temperature is reduced to 25-40℃ by circulating cooling water, causing most of the water vapor to condense and precipitate, significantly reducing the gas dew point. The dehydrated mixed gas is then pressurized to an operating pressure of 1.5-3.0 MPa by a compressor unit, and the pressure fluctuation is maintained within ±0.1 MPa by pressure stabilization control. The pressurized gas is then passed into a pressure swing adsorption system consisting of six adsorption towers connected in parallel. This system is the core unit for achieving fine hydrogen separation. Each adsorption tower is filled sequentially in the gas flow direction with: an activated alumina layer at the inlet for deep removal of residual moisture; a molecular sieve layer in the middle for selective adsorption of carbon dioxide and carbon monoxide; and an activated carbon layer at the end for deep removal of other trace impurities, forming a multi-bed adsorption system with clearly defined functions. The programmable control system controls six adsorption towers to sequentially execute cyclic steps of adsorption, reverse evaporation, rinsing, pressure equalization, and pressurization. Specifically, adsorption occurs at a pressure of 1.5-3.0 MPa, where impurities such as carbon dioxide, carbon monoxide, and residual moisture are selectively captured by the corresponding adsorbents. Subsequently, the pressure of the adsorption tower is reduced to 0.2-0.5 MPa for reverse evaporation to remove the adsorbed impurities. Then, a portion of the product hydrogen is used to reverse-flush the adsorption towers to further purify the adsorbent bed. Finally, product hydrogen is used to restore the pressure of the adsorption towers to the working pressure, completing adsorbent regeneration and preparing for the next adsorption cycle. Through continuous and cyclic operation of the pressure swing adsorption system, a high-purity hydrogen product with a purity of ≥99.5% is stably obtained at the product end, wherein the content of key impurities meets the following requirements: carbon dioxide ≤50 ppm, carbon monoxide ≤10 ppm, and oxygen ≤5 ppm. After the high-purity hydrogen product passes the test, it can be transported to the hydrogen storage system or directly applied at the application end for use as fuel for internal combustion engines or external combustion engines, or as a high-quality chemical raw material. This step first achieves efficient conversion and highly selective hydrogen production from alcohol feedstock under mild conditions, completing the transformation from feedstock to hydrogen-rich gas. Subsequently, through gradient condensation and multi-bed pressure swing adsorption technology, various impurities are deeply removed, ultimately obtaining a high-purity hydrogen product that meets the requirements of high-end applications. This step is the value realization link of the entire process, directly determining the hydrogen yield, purity, and the technical and economic efficiency of the entire process.

[0024] Example 2 Please see Figure 3 This embodiment mainly describes a process for producing hydrogen from alcohols based on microwave-induced oxidation. The difference from Embodiment 1 is that a specific microwave-sensitive composite catalyst system is used, and the subsequent purification process is optimized. A hydrogen separation membrane is used instead of pressure swing adsorption for hydrogen purification, while the carbon monoxide in the tail gas is recycled. S1. Prepare a microwave-sensitive composite catalyst and fill it into a fixed-bed reactor; First, the microwave-sensitive composite catalyst was prepared and loaded. Chloroplatinic acid solution was weighed as the precursor for the noble metal active component, nano-silicon carbide powder as the microwave-sensitizing component, and γ-alumina as the support. The materials were precisely prepared according to the following ratio: active component loading 2 wt% (based on platinum), microwave-sensitizing component content 15 wt%, and γ-alumina support to be supplemented to 100%. The above components and an appropriate amount of deionized water were placed in a planetary ball mill and milled at 350 rpm for 6 hours to obtain a uniformly distributed slurry. The slurry was then transferred to a spray drying tower for spray granulation, with the inlet temperature set at 200℃ and the outlet temperature at 90℃ to obtain a well-flowing mixed powder. The obtained powder was then pressed into a cylindrical catalyst precursor with a diameter of 4 mm and a height of 3 mm under a pressure of 15 MPa. The shaped catalyst precursor was placed in a tubular heat treatment furnace, and high-purity nitrogen was introduced as a protective atmosphere. Then, a programmed temperature-controlled segmented heat treatment was performed: first, the temperature was increased from room temperature to 250°C at a rate of 2°C / min and held at this temperature for 120 minutes to complete preheating and dehumidification; then, the heating rate was increased to 5°C / min, and the temperature was further increased to 550°C and held at this temperature for 180 minutes to enter the crystallization construction stage, allowing the platinum species to form a strong interaction with the alumina support, while silicon carbide completes its crystal transformation; finally, the temperature was slowly cooled to room temperature at a rate of 1°C / min to complete the slow cooling and stabilization stage, ultimately obtaining a microwave-sensitive composite catalyst with a stable structure and well-developed mesoporous structure; the prepared catalyst particles were then packed into the isothermal zone of a fixed-bed reactor to form a catalyst bed. This step, through precise material design and controllable preparation process, constructs a composite catalyst that combines high catalytic activity with excellent microwave response characteristics, providing a core material basis for subsequent efficient microwave-induced reforming reactions.

[0025] S2, Preparation and delivery of alcohol-water mixed solutions; Analytical grade methanol and deionized water were added to a mixing tank equipped with a jacketed temperature control unit and a mechanical stirrer at a molar ratio of 1:2. The mixing tank was started, and the mechanical stirrer was controlled to stir at a speed of 400 rpm. At the same time, the mixing system was kept at a constant temperature of 25±2℃ by a constant temperature water bath circulating in the jacket. Stirring was continued for 40 minutes to form a homogeneous and stable alcohol-water mixture. Subsequently, the prepared alcohol-water mixture was pumped to the inlet of the fixed bed reactor loaded with catalyst at a flow rate of 1.0 L / min using a corrosion-resistant diaphragm pump. This step, through constant temperature and speed stirring control, prepares reaction raw materials with uniform composition and stable properties, and provides reliable feeding guarantee for continuous reaction through a stable conveying system.

[0026] S3, microwave-induced catalytic reforming reaction; A 2.45 GHz microwave generator coupled to the fixed-bed reactor was activated, and an initial microwave power of 1.5 kW was applied to rapidly generate localized high-temperature hot spots in the catalyst bed under the action of the silicon carbide microwave-sensitized component. The bed temperature was fed back in real time through a distributed thermocouple temperature monitoring system, and the microwave power output was dynamically adjusted based on a fuzzy PID control algorithm to precisely control the catalyst bed temperature within the range of 500±10℃. This activation temperature was maintained for 40 minutes to complete the lattice activation and surface reconstruction of the catalyst. After catalyst activation, the pretreated alcohol-water mixture is introduced into the reactor. Under the continuous action of a microwave field, the solution rapidly vaporizes and undergoes a reforming reaction within the catalyst bed: methanol molecules first dehydrogenate at platinum active sites to form formaldehyde intermediates, and then, under the influence of acidic sites on the support, C-C bonds break, decomposing into carbon monoxide and hydrogen. The generated carbon monoxide further reacts with water vapor in the system in a water-gas shift reaction, producing carbon dioxide and additional hydrogen. The final product is a mixed gas primarily composed of hydrogen and carbon dioxide, containing small amounts of unreacted water vapor and trace amounts of carbon monoxide. Online analysis shows that the methanol conversion rate is greater than 98%, and the hydrogen selectivity is higher than 96%. This step utilizes microwave energy to achieve rapid catalyst activation and efficient, uniform heating of the reaction system, enabling alcohol molecules to complete stepwise catalytic conversion under optimized conditions, thus achieving a hydrogen production process with high conversion rate and high selectivity.

[0027] S4. The product is dried by condensation and purified by membrane separation. The mixed gas generated by the reforming reaction is introduced into a three-stage gradient condensation and separation device. By gradually cooling it to 10°C, the unreacted methanol, water vapor and by-products (such as formic acid) are condensed into liquid and separated efficiently. The gas is then passed into an adsorption drying tower filled with 4A molecular sieves to further remove residual moisture and organic impurities, and obtain crude product gas with a dew point below -40°C. The crude product gas is fed into the purification unit, where it first passes through a pretreatment tower containing special activated carbon to remove trace amounts of alcohol impurities. Then, under an operating pressure of 2.0 MPa and an operating temperature of 40°C, it is passed through a polyimide hollow fiber hydrogen separation membrane. Due to the high permeation rate of hydrogen molecules, they preferentially permeate through the membrane wall as fast gas, resulting in a high-purity hydrogen product with a purity higher than 99.5%, which is collected in a product gas buffer tank. A portion (approximately 30%) of the impurity-rich tail gas (rich in CO and CO2) retained by the membrane is returned to the inlet of the fixed-bed reactor via a circulating compressor, allowing the carbon monoxide in it to participate in the water-gas shift reaction again, thereby increasing the overall hydrogen yield and reducing pollutant emissions. This step combines condensation drying and membrane separation technologies to achieve efficient purification of the mixed gas and fine purification of hydrogen. At the same time, the tail gas recirculation strategy improves the atom economy of the raw materials, reflecting the green and low-carbon process concept.

[0028] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations 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 scope of the present invention.

Claims

1. A process for producing hydrogen from alcohols based on microwave-induced oxidation, characterized in that, Includes the following steps: Turn on the microwave power source to induce the catalyst metal oxide, and then preheat the reactants participating in the reaction using electromagnetic heating; Once the catalyst and reactants reach the temperature required for the reaction, the reactants are injected into the microwave cavity at a predetermined space velocity. After the reaction time is appropriate, hydrogen and other products will be generated. After purification by pressure swing adsorption, the required hydrogen can be obtained for combustion in internal or external combustion engines or as a chemical raw material.

2. The process for producing hydrogen from alcohols based on microwave-induced oxidation according to claim 1, characterized in that, The step of turning on the microwave power source to induce the catalyst metal oxide specifically includes: The microwave electromagnetic energy generated by the microwave power source is coupled into the microwave cavity, so that the metal oxide catalyst selectively absorbs the microwave energy through its metal ions and directly converts the electromagnetic energy into its own internal energy. Under the condition that the overall temperature of the catalyst reaches 300-600℃, the basic induction of the catalyst is achieved. Through the instantaneous concentrated dissipation of energy within the catalyst particles during the selective absorption process, a local high-temperature region, namely a microwave hotspot, is formed on the catalyst surface under the condition of forming a temperature gradient of over 400°C, thereby achieving enhanced induction of local catalyst activity. When microwave power density reaches 100-1000 W / cm² 2 Under the influence of a strong microwave field, the catalyst surface is further induced to generate microwave plasma through electrodeless discharge, thereby achieving deep induction of the catalyst. Through the synergistic effect of the microwave hotspot and the extreme hotspot region, the final induction of the catalyst metal oxide is completed under the condition that the plasma discharge core temperature exceeds 1000℃, so that the catalyst metal oxide reaches the activated state and generates a stable local high temperature hotspot.

3. The process for producing hydrogen from alcohols based on microwave-induced oxidation according to claim 1, characterized in that, The preheating of the reactants using electromagnetic heating specifically includes: Turn on the electromagnetic heating device, which heats the flowing alcohol reactants through its built-in induction heating circuit; Under the action of an alternating magnetic field, the induction heating pipe generates eddy currents on its wall, which in turn generates heat, thereby indirectly heating the alcohol reactants in the pipe to a predetermined reaction temperature of 150-400°C. The output power of the electromagnetic heating device is controlled by the temperature sensor feedback to maintain the reactant temperature stable within a set value of ±10℃.

4. The process for producing hydrogen from alcohols based on microwave-induced oxidation according to claim 3, characterized in that, The control of the output power of the electromagnetic heating device specifically includes: When the temperature sensor detects that the reactant temperature has reached the upper limit of the set value, the output power of the electromagnetic heating device is controlled to gradually decrease from 100% to 10%. When the temperature sensor detects that the temperature of the reactants is 10°C lower than the set lower limit, the output power of the electromagnetic heating device is controlled to gradually increase from 10% to 100%.

5. The process for producing hydrogen from alcohols based on microwave-induced oxidation according to claim 1, characterized in that, When the temperature of the catalyst and reactants reaches the temperature required for the reaction, the reactants are injected into the microwave cavity at a predetermined space velocity, specifically including: The preheated alcohol reactants are mixed and homogenized with water vapor to form a homogeneous gaseous reactant, which is then injected into the microwave cavity. The mixing and homogenization process specifically includes: Preheated alcohol reactants at 150-400℃ and superheated steam at 180℃ are metered and controlled by flow meters and regulating valves, respectively, to ensure that the flow fluctuation of alcohol reactants does not exceed ±2.5% of the set value and the flow fluctuation of steam does not exceed ±2.5% of the set value, so that the molar flow rate is stabilized within the ratio range of (1.0-3.0):

1. The metered alcohol reactants and water vapor are fed into a static mixer, which is equipped with multiple alternating left-handed and right-handed mixing units. As the gaseous reactants flow through the left-handed and right-handed mixing units, they are continuously cut, sheared, diverted, and recombine to achieve radial mixing and component homogenization at the microscale, forming a homogeneous gaseous reactant with uniform temperature distribution and component concentration fluctuations not exceeding ±5%. The homogeneous gaseous reactants are subjected to a reaction at a rate of 2000-10000 h. -1 The predetermined air velocity is injected into the reactor inside the microwave cavity.

6. The process for producing hydrogen from alcohols based on microwave-induced oxidation according to claim 1, characterized in that, After a suitable reaction time, hydrogen gas and other products will be generated, including: Under the continuous action of a microwave field, the gaseous reactants undergo a steam reforming reaction on the catalyst surface, with the reaction time controlled within the range of 10-120 minutes. When the reaction time reaches 10-120 minutes, the conversion rate of alcohol reactants reaches more than 95%, at which point the reaction is complete, producing a mixed gas mainly composed of hydrogen and carbon dioxide. When the alcohol reactant is methanol, the overall chemical reaction is: CH3OH + H2O → CO2 + 3H2; The steam reforming reaction is carried out under the conditions of catalyst bed temperature of 250-290℃ and operating pressure ≤2.5 MPa.

7. The process for producing hydrogen from alcohols based on microwave-induced oxidation according to claim 6, characterized in that, The steam reforming reaction occurring on the catalyst surface specifically includes: Under the continuous action of the microwave field, alcohol molecules first undergo chemical adsorption at the metal active sites on the catalyst surface, and their CH and OH bonds break and dissociate under the high temperature of the microwave hot spot region. The intermediate species generated by dissociation react with water molecules adsorbed on the catalyst surface. Among them, the carbon-containing intermediate is oxidized to carbon monoxide, and hydrogen atoms are released at the same time. The generated carbon monoxide further reacts with surface hydroxyl species in a water-gas shift reaction, converting into carbon dioxide and producing additional hydrogen. Ultimately, the hydrogen atoms adsorbed on the catalyst surface combine to form hydrogen molecules and desorb from the active sites, completing the steam reforming reaction on the catalyst surface.

8. The process for producing hydrogen from alcohols based on microwave-induced oxidation according to claim 1, characterized in that, The required hydrogen gas can be obtained through pressure swing adsorption purification, specifically including: The mixed gas generated by the reaction is first passed through a condensation and dehydration device. The gas temperature is reduced to 25-40℃ by circulating cooling water, so that the water vapor in the mixed gas condenses and precipitates out, thus lowering the gas dew point. The dehydrated mixed gas is pressurized to an operating pressure of 1.5-3.0 MPa by a compressor unit, and the pressure is maintained within the range of fluctuation not exceeding ±0.1 MPa. The pressurized mixed gas is passed into a pressure swing adsorption system consisting of 4-8 adsorption towers, each adsorption tower being filled with a multi-bed adsorbent composed of activated alumina, molecular sieves and activated carbon. The following cyclic steps are executed sequentially by the program control system in each adsorption tower: adsorption is carried out at a pressure of 1.5-3.0 MPa, where impurities such as carbon dioxide, carbon monoxide, and residual moisture are selectively adsorbed by the adsorbent; the pressure of the adsorption tower is reduced to 0.2-0.5 MPa for reverse venting to remove the adsorbed impurities; a portion of the product hydrogen is used to backwash the adsorption tower to further purify the adsorbent; finally, the pressure of the adsorption tower is restored to the working pressure using product hydrogen to complete the regeneration of the adsorbent. Through continuous cyclic operation of the pressure swing adsorption system, a hydrogen product with a purity of ≥99.5% is obtained, wherein the carbon dioxide content is ≤50ppm, the carbon monoxide content is ≤10ppm, and the oxygen content is ≤5ppm.

9. The process for producing hydrogen from alcohols based on microwave-induced oxidation according to claim 8, characterized in that, The multi-bed adsorbent packed in the pressure swing adsorption system, arranged according to the gas flow direction, specifically includes: The activated alumina layer is located at the inlet of the adsorption tower and is used to deeply remove residual moisture; the molecular sieve layer is located downstream of the activated alumina layer and is used to selectively adsorb carbon dioxide and carbon monoxide; the activated carbon layer is located at the end of the adsorption tower and is used to deeply remove other trace impurities.

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