A method for producing hydrogen from methanol

Abstract

This invention relates to a method for producing hydrogen from methanol, and relates to the field of hydrogen production technology. The preparation steps of the methanol-to-hydrogen process include: raw material pretreatment, catalytic reaction, heat recovery and separation. This application utilizes the sensible heat of the high-temperature reaction products for the preheating and gasification of the raw materials, thereby achieving cascaded energy utilization, reducing the external heat source supply required to maintain the reaction temperature, improving overall thermal efficiency, and solving the problems of high energy consumption and low thermal energy utilization in traditional methanol-to-hydrogen processes. At the same time, it further improves the service life of the catalyst in the methanol-to-hydrogen process.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production technology, and in particular to a method for producing hydrogen from methanol. Background Technology

[0002] Hydrogen energy, as a clean and efficient secondary energy source, is a key direction for promoting the transformation of the energy structure. Methanol-to-hydrogen technology has become the mainstream hydrogen production technology route due to its advantages such as readily available raw materials, convenient storage and transportation, high hydrogen storage density, and mild reaction conditions. It is widely used in many fields such as distributed hydrogen supply, chemical production, and fuel power generation, and has the foundation and potential for large-scale industrial application.

[0003] However, the methanol-to-hydrogen method suffers from low methanol decomposition efficiency and slow process heating, which often leads to incomplete methanol decomposition, resulting in high methanol consumption or low hydrogen production.

[0004] Chinese invention patent application CN121063484A, published on December 5, 2025, proposes a methanol cracking hydrogen production process and system. By preheating, vaporizing, and catalytically cracking methanol, heat exchange is carried out between the high-temperature conversion gas and the raw methanol to ensure that the methanol is fully vaporized. The reactor temperature is controlled at the optimal temperature for direct methanol cracking. At the same time, under the catalysis of a copper-based catalyst with high activity and good selectivity, the direct methanol cracking reaction is complete and there are few side reactions.

[0005] However, the inventors discovered that the above technical solution relies only on a single heat exchange and fails to form an efficient waste heat gradient utilization and closed-loop recovery system, resulting in room for improvement in the overall thermal energy utilization rate of the process. Summary of the Invention

[0006] In order to improve the utilization rate of thermal energy and reduce the overall energy consumption, this invention provides a method for producing hydrogen from methanol.

[0007] This application provides a method for producing hydrogen from methanol, which adopts the following technical solution: A method for producing hydrogen from methanol includes the following steps: Raw material pretreatment: The methanol raw material is preheated and vaporized to obtain methanol vapor; Catalytic reaction: The methanol vapor is mixed with water vapor and then introduced into a reactor containing a copper-based catalyst bed. The catalytic reforming reaction is carried out under the heating of synthetic heat transfer oil to generate a high-temperature mixed gas containing hydrogen, carbon dioxide and unreacted methanol. Heat recovery and separation: The high-temperature mixed gas is cooled by passing it through a heat exchanger and exchanging heat with the methanol feedstock; then it enters a gas-liquid separator to separate the unreacted liquid methanol and recycle it back to the feedstock.

[0008] By adopting the above technical solution, synthetic heat transfer oil is used as the heating medium to heat the strongly endothermic methanol steam reforming reaction, providing a stable and uniform thermal field for the catalytic reforming reaction: CH3OH + H2O → CO2 + 3H2. This avoids the generation of local high-temperature hot spots in the reactor, thereby protecting the active structure of the copper-based catalyst and improving the single-pass conversion rate and thermal efficiency of the reaction. The waste heat of the reaction products is used to preheat and vaporize the methanol feedstock, replacing the input of external energy and reducing the energy consumption of the feedstock processing stage from the source. Subsequently, unreacted methanol is separated and recycled back to the feedstock end, which not only improves the methanol conversion rate and reduces feedstock waste, but also avoids the environmental pressure and resource consumption caused by the emission of unreacted methanol, indirectly reducing the overall energy consumption caused by feedstock replenishment. Overall, it achieves tiered energy utilization, reduces the external energy consumption required to maintain the reaction temperature, and solves the problem of low thermal energy utilization in traditional processes.

[0009] Optionally, in the catalytic reaction step, the synthesized heat transfer oil is a modified heat transfer oil; the preparation method of the modified heat transfer oil is as follows: The product is prepared by adding 0.5–1.0 wt% nano-copper powder and 0.3–0.5 wt% nano-silica to synthetic heat transfer oil as the base liquid, and then dispersing it ultrasonically for 30–40 min.

[0010] By adopting the above technical solution, the high thermal conductivity of nano-copper powder and the increase of specific heat capacity and suspension stability of the fluid by nano-silica are used. These two nanoparticles are ultrasonically dispersed in the heat transfer oil to form a nanofluid. By utilizing the Brownian motion and micro-convection effect of the nanoparticles, the overall thermal conductivity and heat storage capacity of the heat transfer oil are improved. Under the same heating power, the reactor can reach the set temperature faster and the internal temperature difference of the bed is smaller, thereby improving the efficiency of heat transfer from the heat source to the reaction center and directly reducing the operating energy consumption of the system.

[0011] Optionally, in the raw material pretreatment step, a pretreatment aid is added to the methanol raw material, the pretreatment aid including diethylene glycol dimethyl ether, wherein the amount of diethylene glycol dimethyl ether added accounts for 0.8 to 1.5 wt% of the mass of the methanol raw material.

[0012] By adopting the above technical solution, diethylene glycol dimethyl ether can form an azeotropic or miscible system with methanol and trace amounts of water in the methanol feedstock, playing a role in solubilization and anti-condensation. This not only improves the atomization effect of the feedstock and promotes the molecular-level uniform mixing of methanol vapor and water vapor, but also reduces the surface tension of the mixed vapor and improves the gasification efficiency. In addition, during the preheating and gasification process, it avoids local overheating and cracking of methanol, reduces the generation of by-products, thereby protecting the active sites of the copper-based catalyst, ensuring the catalytic reaction, avoiding increased energy consumption due to catalyst deactivation, and thus reducing energy waste caused by unstable feedstock conditions.

[0013] Optionally, the pretreatment aid further includes lanthanum oxide, wherein the mass ratio of lanthanum oxide to diethylene glycol dimethyl ether is 1:2.5 to 3.5.

[0014] By adopting the above technical solution, lanthanum oxide can neutralize trace acidic impurities that may exist in the raw materials, preventing catalyst acid poisoning. At the same time, its basic sites can promote the desorption of hydroxyl groups (-OH) in methanol molecules and the activation of water molecules. At the microscopic level, lanthanum oxide helps to regulate the electron cloud density on the surface of copper-based catalysts, enhances the adsorption and conversion capacity of the catalyst surface for reaction intermediates, such as methoxy groups, thereby reducing the reaction activation energy at the molecular level, further improving the catalytic activity at low temperatures, and reducing the extra energy consumption caused by excessively increasing the reaction temperature to achieve high conversion rates.

[0015] Optionally, in the catalytic reaction step, the temperature of the catalytic reforming reaction is 220–260 °C, and the reaction pressure is atmospheric pressure to 0.3 MPa.

[0016] By adopting the above technical solutions, the system's sensible heat loss and heating costs are reduced while ensuring a sufficient reaction rate. At the same time, low pressure reduces the mass transfer resistance of the reaction system, reduces the power consumption of the compressor, and reduces the occurrence of side reactions under high pressure, such as the generation of hydrocarbons like methane, thereby improving hydrogen selectivity.

[0017] Optionally, in the catalytic reaction step, a rare earth-based oxygen buffer layer is filled upstream of the copper-based catalyst bed; the rare earth-based oxygen buffer layer is a composite oxide, which includes a cerium-zirconium solid solution; the specific surface area of ​​the cerium-zirconium solid solution reaches 80–150 m². 2 / g.

[0018] By adopting the above technical solution, the cerium-zirconium solid solution can adsorb trace impurities in the feed gas and byproducts generated during the reaction, preventing them from entering the copper-based catalyst bed and causing catalyst poisoning, thus protecting catalyst activity, extending catalyst lifespan, and avoiding increased energy consumption due to catalyst deactivation. Using the cerium-zirconium solid solution as an oxygen buffer layer, when local oxygen concentration in the feed gas fluctuates or the reaction environment changes, the cerium-zirconium solid solution, through Ce... 4+ / Ce 3+ The redox cycle releases or absorbs lattice oxygen, stabilizing the gas entering the main catalyst bed; in addition, it can also act as a physical barrier to prevent impurities in the reaction gas flow from directly impacting the main catalyst, and absorb the local excess heat generated by the reaction, preventing the "runaway temperature" phenomenon in the main catalyst bed and extending the service life of the main catalyst.

[0019] Optionally, a porous quartz fiber pad with a thickness of 0.5 to 1 mm is provided between the rare earth-based oxygen buffer layer and the copper-based catalyst bed.

[0020] By adopting the above technical solution, the rare earth-based oxygen buffer layer with different particle sizes and densities is prone to interfacial mixing with the copper-based catalyst bed under long-term operation or airflow impact, resulting in increased bed pressure drop and uneven airflow distribution, which in turn produces channeling effect. Channeling causes some raw materials to flow out before fully reacting, reducing the conversion rate and increasing the energy consumption of subsequent separation and purification. The quartz fiber pad, as an inert and high-temperature resistant physical isolation layer, can not only ensure the smooth passage of gas and heat, but also effectively prevent the mutual doping of the two solid particles, ensuring the uniformity of airflow distribution in the reactor, so that each part of the catalyst can play a full role, avoiding the waste of raw materials and ineffective heat loss caused by airflow short circuit.

[0021] Optionally, in the catalytic reaction step, the copper-based catalyst is a ceramic-supported copper-zinc-aluminum catalyst; the preparation method of the ceramic-supported copper-zinc-aluminum catalyst is as follows: Carrier pretreatment: The ceramic carrier is immersed in a 5-8 wt% nitric acid solution for 2-3 hours, washed until the pH value is 6.9±0.1, dried, and then microwave treated to obtain the pretreated ceramic carrier; Active component impregnation: Prepare a copper-zinc-aluminum mixed impregnation solution, and immerse the pretreated ceramic carrier in the copper-zinc-aluminum mixed impregnation solution to obtain the impregnated ceramic carrier; Modification and doping: A rare earth doping solution is sprayed onto the surface of the impregnated ceramic support to obtain a doped ceramic support; the rare earth doping solution is a mixed solution of lanthanum oxide and yttrium oxide, wherein the mass ratio of lanthanum oxide to yttrium oxide is 1-3:1, and the rare earth doping solution accounts for 0.3-0.5 wt% of the mass of the impregnated ceramic support; Drying and calcination: The doped ceramic support is dried and calcined to obtain the ceramic-supported copper-zinc-aluminum catalyst.

[0022] By adopting the above technical solution, the mechanical strength and regular channels of the ceramic support are utilized, combined with nitric acid immersion and microwave treatment, to increase the surface roughness and number of active sites of the support, thereby enhancing the adhesion of the active components. Lanthanum oxide and yttrium oxide are added for rare earth doping, and rare earth elements are used to inhibit the migration and growth of copper microcrystals at high temperatures, thereby improving the dispersion of copper. The catalyst with this structure not only reduces the bed pressure drop, but also significantly improves the long-term stability of the catalyst in the high-temperature heat transfer oil environment.

[0023] Optionally, in the copper-zinc-aluminum mixed impregnation solution, the molar ratio of copper, zinc, and aluminum is 2-4:1-3:1.

[0024] By adopting the above technical solution, copper is the main active center in the copper-based catalyst, responsible for the dehydrogenation of methanol; zinc not only acts as a structural aid to disperse copper, but also forms copper-zinc interfacial active sites with copper, promoting the adsorption and activation of water; aluminum plays a role in stabilizing the crystal structure; thus maximizing the promotion of methanol dehydrogenation to methoxy and the subsequent water-gas shift reaction, thereby achieving a high methanol conversion rate at a lower temperature.

[0025] Optionally, in the heat recovery and separation step, the gaseous product separated by the gas-liquid separator enters the purification unit; the purification unit uses polyethylene glycol dimethyl ether as the absorbent for low-temperature washing, and the injection temperature is 0-10℃.

[0026] By adopting the above technical solution, polyethylene glycol dimethyl ether has a much higher solubility for acidic gases, such as CO2 and organic vapors (such as unreacted methanol) than for hydrogen, and the solubility increases significantly as the temperature decreases. Under low temperature conditions of 0-10℃, the absorbent can selectively remove CO2 and methanol vapors from the mixed gas. At the same time, this low-temperature washing process has simple equipment, high operational flexibility, and can obtain high-purity hydrogen with low power consumption and cooling consumption, thus expanding the application range of the product.

[0027] In summary, this application includes at least one of the following beneficial technical effects: 1. By adopting a closed-loop thermal cycle system that uses synthetic heat transfer oil for heating and product waste heat recovery, the synthetic heat transfer oil provides a thermal environment for the methanol steam reforming reaction. The sensible heat of the high-temperature reaction products is used for the preheating and vaporization of the raw materials through a heat exchanger, realizing the cascade utilization of energy, reducing the external heat source supply required to maintain the reaction temperature, improving the overall thermal efficiency, and solving the problems of high energy consumption and low thermal energy utilization in the traditional methanol-to-hydrogen process.

[0028] 2. By using diethylene glycol dimethyl ether to improve the uniformity and mixing of the gasification of the raw materials, lanthanum oxide not only neutralizes acidic impurities, but also promotes the activation of water molecules and the dehydrogenation of methanol through electronic effects, effectively reducing the activation energy of the reaction, so that the reforming reaction can still maintain high activity at a lower temperature of 220-260℃.

[0029] 3. By setting a rare earth-based oxygen buffer layer and a porous quartz fiber isolation layer, the cerium-zirconium solid solution oxygen buffer layer dynamically stabilizes the reaction atmosphere and prevents catalyst oxidation and sintering caused by feed fluctuations. The porous quartz fiber pad physically blocks particle mixing between the bed layers, ensuring the uniformity of fluid distribution. At the same time, the ceramic-loaded copper-zinc-aluminum catalyst improves the mechanical strength and anti-sintering ability of the catalyst, and extends the service life of the catalyst.

[0030] 4. Energy conversion and material separation are achieved by using modified heat transfer oil and low-temperature physical absorption purification. On the one hand, the modified heat transfer oil with added nano copper powder and nano silica improves thermal conductivity and accelerates heat transfer. On the other hand, low-temperature washing is performed using polyethylene glycol dimethyl ether, which is simple to use and has a high hydrogen recovery rate. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the methanol-to-hydrogen process in Example 1 of this application. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the embodiments.

[0033] Unless otherwise specified, the experimental methods used in the embodiments of this application are conventional methods, and the materials used are commercially available unless otherwise specified.

[0034] Example 1: This example discloses a method for producing hydrogen from methanol.

[0035] A method for producing hydrogen from methanol, referring to Figure 1 This includes the following steps: (1) Raw material pretreatment: First, the methanol raw material is sent to the gas-liquid separator for preheating to 60±1℃. The preheated methanol enters the heat exchanger and continues to cool the high-temperature hydrogen with methanol. At the same time, the methanol itself is further preheated. After two stages of preheating, the methanol is sent to the vaporization tank and heated. When the temperature in the vaporization tank reaches about 80℃, the methanol begins to boil and vaporize. The methanol material is sent to the superheater tank to obtain methanol vapor. (2) Catalytic reaction: The methanol vapor and water vapor prepared from deionized water were mixed at a volume ratio of 1:1.8 to obtain a mixed feed gas. The mixed feed gas was then introduced into a reactor containing a copper-based catalyst bed. The height of the copper-based catalyst bed was 400 mm, and the bulk density of the copper-based catalyst bed was 1.2 g / cm³. 3 The reactor was heated using synthetic heat transfer oil (L-QB300) to achieve a catalytic reforming reaction temperature of 240℃, a reaction pressure of 0.15MPa, and a mixed feed gas space velocity of 3000 h⁻¹. -1 The process generates a high-temperature mixed gas containing hydrogen, carbon dioxide, and unreacted methanol; the heating temperature of the synthesized heat transfer oil is 270±10℃. In other embodiments, the heat of the reaction products can also be used to preheat the heat transfer oil through a heat exchanger, thereby reducing the energy consumption of external electric heating to synthesize the heat transfer oil. (3) Heat recovery and separation: ① First-stage cooling: The high-temperature mixed gas is first cooled by passing it through a heat exchanger and exchanged with the methanol raw material to be preheated. The methanol absorbs the heat from the hydrogen and continues to heat up, while the temperature of the hydrogen is initially reduced to about 110°C; ② Second-stage cooling: The mixed gas after the first-stage cooling is sent to a gas-liquid separator. In the gas-liquid separator, the hydrogen is further cooled and condensed, and gas-liquid separation is achieved at the same time. The trace amount of condensate in the hydrogen, mainly unreacted methanol, is separated out. The temperature of the hydrogen is finally reduced to about 50°C, which meets the qualified outlet temperature requirements. The unreacted methanol in liquid is separated and recycled back to the raw material end. The gaseous products separated by the gas-liquid separator (mainly hydrogen and carbon dioxide, with a small amount of impurities) enter the purification unit. The purification unit uses a packed tower with an inner diameter of 80 mm and a height of 1200 mm. Polyethylene glycol dimethyl ether (molecular weight 200) is used as the absorbent for low-temperature washing. The injection temperature of the absorbent is 5°C, and the flow rate of the absorbent is 1.2 m / s². 3 / h, washing pressure is 0.1MPa.

[0036] The methanol feedstock can be any one of industrial grade methanol (purity ≥ 99.5 wt%), reagent grade methanol, or anhydrous methanol. In this embodiment, industrial grade methanol is selected. In this embodiment, a copper-zinc-aluminum catalyst was selected as the copper-based catalyst.

[0037] The following indicators were tested on the methanol-to-hydrogen method of this embodiment: methanol single-pass conversion rate, hydrogen selectivity, overall system energy consumption, and catalyst stable operation time. ① Methanol Single-Pass Conversion Rate (%): Characterizes the degree of methanol conversion in a single pass through the catalyst bed in the reactor, reflecting the catalytic reaction efficiency; the higher the conversion rate, the higher the feed utilization rate and the lower the feed loss; the testing standard is: GB / T34540-2017 "Technical Requirements for Methanol Conversion Pressure Swing Adsorption Hydrogen Production System"; ISO 19758 (General Rules for Testing the Activity of Chemical Catalysts); the testing method is: continuous operation for ≥24 hours, and the methanol flow rate F at the reactor inlet is measured using a flow meter. in Unreacted methanol flow rate F at the outlet out (Liquid phase after condensation and separation), calculated according to material balance: X MeOH =(F in -F out ) / F in ×100%; ② Hydrogen selectivity (%): Characterizes the proportion of hydrogen gas, the target product, generated in the reaction system, and evaluates the side reaction inhibition effect; the higher the selectivity, the fewer ineffective byproducts and the lower the purification load; the detection standard is GB / T 3634.2 (hydrogen purity analysis); the detection method is as follows: after cooling and gas-liquid separation, the dry gas composition of the reactor outlet mixed gas is analyzed by gas chromatography, and the normalized calculation is based on carbon-containing products: S(H2) = n(H2) / 3n MeOH，conv ×100%, where n MeOH，conv The molar number of methanol converted is given. According to the stoichiometric ratio, 1 mol of methanol theoretically produces 3 mol of H2. ③System comprehensive energy consumption (MJ / Nm³) 3 H2): Reflects the total electricity and heat consumption of a hydrogen production unit; the test is based on GB / T 2589-2020 "General Rules for Calculation of Comprehensive Energy Consumption"; the test method involves installing an electricity meter, steam / heat transfer oil heat meter, and raw material / product flow meter, continuously measuring for ≥72 hours, and statistically analyzing various energy consumption items: Electricity consumption: E 电 (kWh); Heat consumption: Q 热 (MJ, heat transfer oil / steam heating); Raw material energy consumption: Calculate the lower heating value of methanol according to GB / T 2589; Calculate the volume of hydrogen V (H2) under standard conditions (Nm³). 3 System overall energy consumption E 综合 = (3.6 × E) 电 +Q 热 ) / V(H2); ④ Stable operating time of catalyst (h): This reflects the catalyst's ability to resist impurity poisoning, sintering, and bed particle mixing. The longer the operating time, the lower the replacement frequency and the lower the maintenance cost. The testing standard is ISO 19759 (catalyst life test). The testing method is as follows: Under continuous operation, samples are taken and analyzed every 24 hours: methanol single-pass conversion rate and hydrogen selectivity. The deactivation judgment point is defined as the methanol single-pass conversion rate dropping to 95% of the initial value. The cumulative continuous operating time from start-up to the deactivation judgment point is recorded, which is the stable operating time.

[0038] Example 2: This example discloses a method for producing hydrogen from methanol.

[0039] In this embodiment, in the catalytic reaction step, the synthesized heat transfer oil is a modified heat transfer oil; the preparation method of the modified heat transfer oil is as follows: Using synthetic heat transfer oil as the base liquid, 0.8 wt% of nano copper powder and 0.4 wt% of nano silica were added to the base liquid. The mixture was placed in an ultrasonic disperser and ultrasonically dispersed for 35 min at 300 W and 40 kHz to obtain modified heat transfer oil. The nano-copper powder can be selected from one or a mixture of several with particle sizes of 30nm, 50nm, and 80nm. In this embodiment, the nano-copper powder with a particle size of 50nm is selected. The nano-silica can be selected from one or a mixture of several with particle sizes of 20nm, 30nm, and 50nm. In this embodiment, the nano-silica with a particle size of 30nm is selected. Everything else is the same as in Example 1.

[0040] Example 3: This example discloses a method for producing hydrogen from methanol.

[0041] In this embodiment, in the raw material pretreatment step, a pretreatment aid, namely diethylene glycol dimethyl ether, is first added to the methanol raw material, wherein the amount of diethylene glycol dimethyl ether added accounts for 1.2 wt% of the mass of the methanol raw material; The methanol feedstock with added pretreatment additives was thoroughly stirred and then the subsequent operations were carried out according to the conditions of Example 1. Everything else is the same as in Example 2.

[0042] Example 4: This example discloses a method for producing hydrogen from methanol.

[0043] In this embodiment, in the raw material pretreatment step, the pretreatment aid includes diethylene glycol dimethyl ether and lanthanum oxide, wherein the mass ratio of lanthanum oxide to diethylene glycol dimethyl ether is 1:3.0. The specific addition method is as follows: first, lanthanum oxide is pulverized to a particle size ≤10μm, added to diethylene glycol dimethyl ether, and stirred to obtain a pretreatment additive mixture; then, the mixture is added to the methanol raw material and stirred evenly. Everything else is the same as in Example 3.

[0044] Example 5: This example discloses a method for producing hydrogen from methanol.

[0045] In this embodiment, during the catalytic reaction step, a rare earth-based oxygen buffer layer is filled upstream of the copper-based catalyst bed in the reactor. This rare earth-based oxygen buffer layer is a composite oxide, which is a cerium-zirconium solid solution, wherein the molar ratio of cerium to zirconium in the cerium-zirconium solid solution is 3:1; the specific surface area of ​​the cerium-zirconium solid solution reaches 123 m². 2 / g; The cerium-zirconium solid solution was prepared by a co-precipitation method, as follows: ① Raw material preparation: Take cerium nitrate (Ce(NO3)3·6H2O) and zirconium nitrate (Zr(NO3)4·5H2O), add them to deionized water to prepare a mixed salt solution. The total concentration of cerium ions and zirconium ions in the mixed salt solution is 0.8 mol / L. Stir at 300 r / min for 15 min to obtain a homogeneous mixed salt solution. At the same time, prepare a 1.0 mol / L sodium carbonate solution as a precipitant for later use. ② Coprecipitation reaction: The mixed salt solution was placed in a 60℃ constant temperature water bath, and the precipitant was added dropwise while stirring at 400r / min to stabilize the pH value of the reaction system at 9.0±0.2. After the addition was completed, stirring was continued for 30min, and then the mixture was allowed to stand for 2h to form cerium zirconium hydroxide precipitate. ③ Washing and drying: The aged precipitate was repeatedly washed with deionized water until the pH of the washing solution was 7.0±0.1. After washing, the precipitate was placed in an oven and dried at 110℃ for 6 hours to obtain dried cerium zirconium hydroxide. ④ Calcination and molding: The dried cerium-zirconium hydroxide was placed in a muffle furnace for calcination. The calcination heating rate was controlled at 5℃ / min, and the temperature was raised from room temperature to 600℃. The temperature was kept constant for 4 hours. After calcination, the mixture was naturally cooled to room temperature to obtain cerium-zirconium solid solution powder. A small amount of deionized water was added to the powder, and after stirring evenly, it was pressed into shape at a molding pressure of 15MPa. Then, it was placed in an oven at 110℃ for 2 hours to dry to obtain cerium-zirconium solid solution composite oxide. The rare earth-based oxygen buffer layer has a filling height of 80 mm and a bulk density of 1.1 g / cm³. 3 It is in close contact with the copper-based catalyst bed. The mixed feed gas first passes through the rare earth-based oxygen buffer layer and then enters the copper-based catalyst bed for catalytic reforming reaction. Everything else is the same as in Example 4.

[0046] Example 6: This example discloses a method for producing hydrogen from methanol.

[0047] In this embodiment, during the catalytic reaction step, a porous quartz fiber pad is provided between the rare earth-based oxygen buffer layer and the copper-based catalyst bed. The porous quartz fiber pad has a thickness of 0.8 mm and a porosity of 85%. During the laying process, it is ensured that the porous quartz fiber pad is in close contact with the rare earth-based oxygen buffer layer and the copper-based catalyst bed. Everything else is the same as in Example 5.

[0048] Example 7: This example discloses a method for producing hydrogen from methanol.

[0049] In this embodiment, in the catalytic reaction step, the copper-based catalyst is a ceramic-supported copper-zinc-aluminum catalyst; the preparation method of the ceramic-supported copper-zinc-aluminum catalyst is as follows: ① Carrier pretreatment: The ceramic carrier was immersed in a 6.5wt% nitric acid solution for 2.5h, and stirred every 30min during the period. After immersion, the carrier surface was repeatedly washed with deionized water until the pH of the washing solution was 6.9±0.1. The washed carrier was placed in an oven and dried at 120℃ for 4h. Then, it was microwaved for 15min under microwave power of 500W and microwave frequency of 2.45GHz to obtain the pretreated ceramic carrier. ②Impregnation of active components: Add copper nitrate (Cu(NO3)2·3H2O), zinc nitrate (Zn(NO3)2·6H2O), and aluminum nitrate (Al(NO3)3·9H2O) to deionized water to prepare a copper-zinc-aluminum mixed impregnation solution, wherein the molar ratio of copper, zinc, and aluminum is 3:2:1, and the concentration of the mixed impregnation solution is 1.5 mol / L; The pretreated ceramic carrier was immersed in the above copper-zinc-aluminum mixed impregnation solution. The equal volume impregnation method was used, and the carrier was impregnated at an impregnation temperature of 60°C for 4 hours. The carrier was turned over every hour during the impregnation. After the impregnation was completed, the carrier was removed and the excess impregnation solution on the surface was drained to obtain the impregnated ceramic carrier. ③ Modification and doping: Preparation of rare earth doping solution: Take lanthanum oxide (La2O3) and yttrium oxide (Y2O3), add them to nitric acid solvent, and stir to obtain rare earth doping solution, wherein the mass ratio of lanthanum oxide to yttrium oxide is 2:1, and the concentration of rare earth doping solution is 0.1 mol / L; Rare earth doping solution was sprayed onto the surface of the impregnated ceramic carrier using a spraying method. The amount of sprayed solution was 0.4 wt% of the mass of the impregnated ceramic carrier. After spraying, the carrier was left to stand for 30 minutes to allow the rare earth doping solution to fully penetrate into the interior of the carrier, thus obtaining the doped ceramic carrier. ④ Drying and calcination: The doped ceramic support is placed in an oven and dried at 110℃ for 3 hours. Then it is placed in a muffle furnace for calcination at 500℃ for 4 hours. During the calcination process, the heating rate is controlled at 5℃ / min, from room temperature to the calcination temperature. After calcination, it is naturally cooled to room temperature to obtain the ceramic-supported copper-zinc-aluminum catalyst. The ceramic carrier can be either an alumina ceramic carrier or a silicon carbide ceramic carrier; in this embodiment, an alumina ceramic carrier is selected. Everything else is the same as in Example 6.

[0050] Comparative Example 1: This comparative example discloses a method for producing hydrogen from methanol.

[0051] In this comparative example, during the catalytic reaction step, methanol vapor was not mixed with water vapor and was directly introduced into the reactor containing a copper-based catalyst bed; everything else was the same as in Example 1.

[0052] Comparative Example 2: This comparative example discloses a method for producing hydrogen from methanol.

[0053] In this comparative example, the heating of the synthetic heat transfer oil in the catalytic reaction step was changed to electric heating; everything else was the same as in Example 1.

[0054] Comparative Example 3: This comparative example discloses a method for producing hydrogen from methanol.

[0055] In this comparative example, the methanol preheating step in the raw material pretreatment step is omitted, and the methanol raw material enters the gasifier directly for gasification without preheating; everything else is the same as in Example 1.

[0056] The following indicators were tested on the methanol-to-hydrogen methods in Examples 1-7 and Comparative Examples 1-3, and the test data are shown in Table 1: Table 1. Detection results of Examples 1-7 and Comparative Examples 1-3: Example 1 88.3 98.2 9.33 1280 Example 2 91.7 98.4 8.80 1320 Example 3 93.5 98.7 8.47 1380 Example 4 95.5 99.1 8.04 1460 Example 5 95.8 99.1 7.93 1650 Example 6 97.9 99.3 7.82 1780 Example 7 98.2 99.5 7.56 2100 Comparative Example 1 74.6 94.5 11.04 1050 Comparative Example 2 87.9 97.9 11.46 1260 Comparative Example 3 85.5 96.8 10.33 1250 As can be seen from Example 1, this process can realize continuous production of methanol to hydrogen, with high methanol feedstock conversion efficiency and hydrogen selectivity. At the same time, the use of waste heat recovery realizes the cascade utilization of energy, and the catalyst also has good operational stability.

[0057] By comparing Example 2 with Example 1, it can be seen that after replacing the conventional synthetic heat transfer oil with the modified heat transfer oil containing nano-copper powder and nano-silica, the modified heat transfer oil enhances the heat transfer efficiency of the methanol reforming reaction, improves the methanol conversion depth, suppresses side reactions caused by local overheating, and slightly improves hydrogen selectivity. The uniform and mild thermal field effectively protects the active structure of the copper-based catalyst, reduces the risk of thermal sintering, and moderately extends the service life of the catalyst while reducing external heating energy consumption.

[0058] Comparing Example 3 with Example 2, it can be seen that adding diethylene glycol dimethyl ether (DME) pretreatment aid to methanol feedstock allows DME to form a miscible azeotropic system with methanol and trace amounts of moisture in the feedstock. This improves the methanol atomization and gasification effect, promotes uniform mixing of methanol vapor and water vapor at the molecular level, reduces the surface tension of the mixed vapor, and enhances gasification efficiency. Simultaneously, it avoids localized overheating and abnormal cracking during the methanol preheating and gasification stage, reducing the generation of byproducts such as carbon deposits. This reduces energy consumption in the feedstock gasification process, improves methanol reaction conversion rate and hydrogen selectivity, and prevents byproducts from covering the catalyst active sites, slowing down the catalyst activity decay rate and extending the stable operation cycle.

[0059] Comparing Example 4 with Example 3, it can be seen that adding lanthanum oxide to the pretreatment aid neutralizes trace acidic impurities in the methanol feedstock, preventing acid poisoning and deactivation of the copper-based catalyst. Simultaneously, its surface alkaline sites can activate water molecules, promote the desorption of methanol hydroxyl groups, and regulate the electron cloud density on the surface of the copper-based catalyst, reducing the activation energy of the methanol reforming reaction, enhancing the low-temperature catalytic activity, and reducing heat consumption. Furthermore, lanthanum oxide strengthens the catalyst's adsorption and conversion capacity for reaction intermediates such as methoxy groups, inhibits side reactions, further improves hydrogen selectivity, reduces the probability of catalyst poisoning and deactivation from the source, and extends the catalyst's lifespan.

[0060] A comparison of Example 5 and Example 4 shows that adding a cerium-zirconium solid solution rare earth-based oxygen buffer layer upstream of the copper-based catalyst bed, with the cerium-zirconium solid solution having a high specific surface area, can adsorb trace impurities and reaction byproducts in the feed steam, preventing harmful substances from entering the main catalyst bed and avoiding catalyst poisoning; simultaneously relying on Ce... 4+ / Ce 3+ The reversible redox cycle enables the release and storage of lattice oxygen, stabilizes the reforming reaction atmosphere, and inhibits the oxidation and sintering of copper-based catalysts. It can also absorb excess heat in the local bed, prevent the catalyst bed from overheating, and delay the decay of catalyst activity.

[0061] A comparison of Example 6 and Example 5 shows that after setting a porous quartz fiber pad between the rare earth-based oxygen buffer layer and the copper-based catalyst bed, the particle size and packing density of the rare earth buffer layer and the copper-based catalyst particles differ. Long-term airflow impact can easily lead to particle doping and mixing, resulting in increased bed pressure drop, uneven airflow distribution, and channeling effect. This causes some methanol feedstock to flow out before fully reacting, reducing conversion efficiency and wasting heat energy. The porous quartz fiber pad has the characteristics of high temperature resistance, chemical inertness, and air permeability without particle permeability. It can act as a physical isolation layer to effectively prevent the particles of the two layers from doping each other, ensuring uniform airflow distribution in the reactor, eliminating channeling and airflow short-circuiting phenomena, and enabling all areas of the catalyst bed to fully participate in the catalytic reaction, improving methanol conversion rate and hydrogen purity, reducing feedstock waste and ineffective heat energy loss, and stabilizing bed operation.

[0062] By comparing Example 7 with Example 6, it can be seen that after using nitric acid modification, microwave pretreatment of the ceramic support, and lanthanum-yttrium rare earth doping modification to prepare ceramic-supported copper-zinc-aluminum catalyst, lanthanum-yttrium rare earth doping can inhibit the migration and growth of copper microcrystals at high temperature, improve the dispersion of active components and anti-sintering ability, thereby improving the low-temperature activity, thermal stability and structural stability of the catalyst. While improving methanol conversion rate and hydrogen selectivity, it reduces system heating and separation energy consumption, and reduces catalyst replacement frequency and maintenance costs.

[0063] By comparing Comparative Example 1 with Example 1, it can be seen that by eliminating the mixed feed of steam and methanol steam and using pure methanol feedstock for direct cracking to produce hydrogen, the methanol steam reforming becomes a mild and controllable main reaction. However, it easily generates byproducts such as methane and carbon deposits, which reduces methanol conversion efficiency and hydrogen selectivity. Furthermore, carbon deposits cover the active sites of the catalyst and block the pores, causing rapid catalyst deactivation. At the same time, the side reactions increase the system's energy load, reduce feedstock utilization, further increase the overall energy consumption per unit of hydrogen, and shorten the catalyst's lifespan.

[0064] By comparing Comparative Example 2 with Example 1, it can be seen that replacing the synthetic heat transfer oil heating with electric heating results in localized point heating, which is prone to generating localized high-temperature hot spots. Although it has little impact on the instantaneous conversion rate of methanol and the selectivity of hydrogen, the thermal energy utilization rate of electric heating is low, and the overall heating energy consumption is much higher than that of the synthetic heat transfer oil closed-loop heating system. At the same time, localized high temperatures can easily induce slight sintering and thermal stress aging of copper-based catalysts, resulting in a slight decrease in catalyst life.

[0065] By comparing Comparative Example 3 with Example 1, it can be seen that eliminating the methanol feedstock preheating step and directly feeding cold methanol into the gasification unit requires a large amount of additional heat energy to complete the heating and gasification, which disrupts the closed loop of energy cascade utilization in the process and increases the overall energy consumption of the system. At the same time, the cold feedstock has a slow gasification rate and poor gasification uniformity, which easily leads to droplet entrainment and local incomplete gasification, reducing the methanol reforming conversion efficiency and hydrogen selectivity. The unstable feedstock state is prone to local side reactions that generate trace impurities, slightly aggravate the catalyst activity decay, and shorten the stable operation time.

[0066] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for producing hydrogen from methanol, characterized in that, Includes the following steps: Raw material pretreatment: The methanol raw material is preheated and vaporized to obtain methanol vapor; Catalytic reaction: The methanol vapor is mixed with water vapor and then introduced into a reactor containing a copper-based catalyst bed. The catalytic reforming reaction is carried out under the heating of synthetic heat transfer oil to generate a high-temperature mixed gas containing hydrogen, carbon dioxide and unreacted methanol. Heat recovery and separation: The high-temperature mixed gas is cooled by passing it through a heat exchanger and exchanging heat with the methanol feedstock; then it enters a gas-liquid separator to separate the unreacted liquid methanol and recycle it back to the feedstock.

2. The method for producing hydrogen from methanol according to claim 1, characterized in that, In the catalytic reaction step, the synthesized heat transfer oil is a modified heat transfer oil; the preparation method of the modified heat transfer oil is as follows: The product is prepared by adding 0.5–1.0 wt% nano-copper powder and 0.3–0.5 wt% nano-silica to synthetic heat transfer oil as the base liquid, and then dispersing it ultrasonically for 30–40 min.

3. The method for producing hydrogen from methanol according to claim 1, characterized in that, In the raw material pretreatment step, a pretreatment aid is added to the methanol raw material, the pretreatment aid including diethylene glycol dimethyl ether, wherein the amount of diethylene glycol dimethyl ether added accounts for 0.8 to 1.5 wt% of the mass of the methanol raw material.

4. The method for producing hydrogen from methanol according to claim 3, characterized in that, The pretreatment aid also includes lanthanum oxide, wherein the mass ratio of lanthanum oxide to diethylene glycol dimethyl ether is 1:2.5 to 3.

5.

5. The method for producing hydrogen from methanol according to claim 1, characterized in that, In the catalytic reaction step, the temperature of the catalytic reforming reaction is 220–260 °C, and the reaction pressure is atmospheric pressure to 0.3 MPa.

6. The method for producing hydrogen from methanol according to claim 1, characterized in that, In the catalytic reaction step, a rare earth-based oxygen buffer layer is filled upstream of the copper-based catalyst bed; the rare earth-based oxygen buffer layer is a composite oxide, which includes a cerium-zirconium solid solution; the specific surface area of ​​the cerium-zirconium solid solution reaches 80-150 m² / g. 2 / g.

7. The method for producing hydrogen from methanol according to claim 6, characterized in that, A porous quartz fiber pad with a thickness of 0.5 to 1 mm is disposed between the rare earth-based oxygen buffer layer and the copper-based catalyst bed.

8. The method for producing hydrogen from methanol according to claim 7, characterized in that, In the catalytic reaction step, the copper-based catalyst is a ceramic-supported copper-zinc-aluminum catalyst; the preparation method of the ceramic-supported copper-zinc-aluminum catalyst is as follows: Carrier pretreatment: The ceramic carrier is immersed in a 5-8 wt% nitric acid solution for 2-3 hours, washed until the pH value is 6.9±0.1, dried, and then microwave treated to obtain the pretreated ceramic carrier; Active component impregnation: Prepare a copper-zinc-aluminum mixed impregnation solution, and immerse the pretreated ceramic carrier in the copper-zinc-aluminum mixed impregnation solution to obtain the impregnated ceramic carrier; Modification and doping: A rare earth doping solution is sprayed onto the surface of the impregnated ceramic support to obtain a doped ceramic support; the rare earth doping solution is a mixed solution of lanthanum oxide and yttrium oxide, wherein the mass ratio of lanthanum oxide to yttrium oxide is 1-3:1, and the rare earth doping solution accounts for 0.3-0.5 wt% of the mass of the impregnated ceramic support; Drying and calcination: The doped ceramic support is dried and calcined to obtain the ceramic-supported copper-zinc-aluminum catalyst.

9. The method for producing hydrogen from methanol according to claim 8, characterized in that, In the copper-zinc-aluminum mixed impregnation solution, the molar ratio of copper, zinc, and aluminum is 2-4:1-3:

1.

10. The method for producing hydrogen from methanol according to claim 1, characterized in that, In the heat recovery and separation step, the gaseous products separated by the gas-liquid separator enter the purification unit; the purification unit uses polyethylene glycol dimethyl ether as the absorbent for low-temperature washing, and the injection temperature is 0-10℃.

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