Monolithic honeycomb ceramic catalyst for hydrogen production by reforming methanol steam as well as preparation method and application of monolithic honeycomb ceramic catalyst

Abstract

The invention relates to the technical field of solid oxide fuel cells, in particular to a monolithic honeycomb ceramic catalyst for hydrogen production through methanol steam reforming, a preparation method and application. Comprising a copper oxide, zinc oxide and lanthanum oxide, and further comprises aluminum oxide; in the composite active catalyst layer, the mass ratio of copper to zinc to lanthanum is (3-6): (2-4): (1-3), and the mesh number of the honeycomb ceramic carrier is 1000-2000. The micro-channel type integral honeycomb ceramic is used as the carrier, so that the specific surface area can be greatly increased, the uniform distribution of active substance sites in the composite active catalyst layer is facilitated, and the conversion rate and the reaction rate of a methanol-water reforming reaction are improved.

Description

Technical Field

[0001] This invention relates to the field of solid oxide fuel cell technology, and more specifically, to a monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen, its preparation method, and its application. Background Technology

[0002] Solid oxide fuel cells (SOFCs) are considered ideal power sources for distributed energy supply and on-board range extension systems due to their high efficiency, low emissions, and wide fuel adaptability. However, to enable SOFC stacks to output higher power within limited volume and mass, it is necessary to simultaneously improve fuel energy density, reforming reaction rate, and system thermal-mass-electric coupling efficiency. Methanol, with its high hydrogen content (12.6 wt%), safe storage and transportation in its liquid state at room temperature, and moderate reforming temperature (200–400℃), has become the preferred fuel for the SOFC-MSR (methanol steam reforming) route.

[0003] Existing technologies mostly use particulate or powdered catalysts (Cu / Zn / Al, Ni / Ce, etc.) to fill fixed beds, but their shortcomings are becoming increasingly apparent:

[0004] (1) Uneven distribution of active sites: Micron-sized particles cause local hot spots and cold zones to coexist, resulting in a large temperature gradient and rapid catalyst deactivation due to sintering.

[0005] (2) Significant mass transfer resistance: The tortuous channels formed between particles make the diffusion paths of methanol, water vapor and products long, reducing the effective diffusion coefficient by 1–2 orders of magnitude, and the reaction rate is controlled by internal diffusion.

[0006] (3) Limited conversion rate: Due to the dual limitations of heat transfer and mass transfer, the single-pass methanol conversion rate is usually <85%, which requires increasing the amount of catalyst or increasing the reactor volume to compensate, which violates the design goal of "high energy density / low mass-volume ratio".

[0007] (4) Low system integration: Traditional fixed-bed reactors require independent preheating, insulation layer and gas-liquid separator, accounting for more than 30% of the volume, making it difficult to directly thermally integrate with SOFC reactors.

[0008] Therefore, developing a novel catalytic structure that combines high activity, high mass transfer efficiency, low back pressure, and can be co-fired with SOFC stacks or coupled with microchannels is key to breaking through the power density bottleneck of SOFC-MSR systems. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide an integral honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen, its preparation method and its application.

[0010] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0011] This invention provides an integral honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen, comprising an alumina honeycomb ceramic support and a composite active catalyst layer coated on the pore walls of the alumina honeycomb ceramic support. The composite active catalyst layer comprises copper oxide, zinc oxide, and lanthanum oxide, and also includes alumina. In the composite active catalyst layer, the mass ratio of copper, zinc, and lanthanum is 3-6:2-4:1-3, and the mesh size of the honeycomb ceramic support is 1000-2000 mesh.

[0012] Based on the above technical solution, the present invention can be further improved as follows.

[0013] Furthermore, in the composite active catalyst layer, the mass ratio of copper, zinc, and lanthanum is 5:3:2.

[0014] Furthermore, the mass percentage of the alumina is 25-35% of the total mass of the composite active catalyst layer.

[0015] Furthermore, the mass percentage of the alumina is 30% of the total mass of the composite active catalyst layer.

[0016] The present invention also provides a method for preparing the monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen as described above, comprising the following steps:

[0017] S1. Prepare the alumina honeycomb ceramic carrier from the raw material of the honeycomb ceramic carrier;

[0018] S2. Dissolve copper, zinc, and lanthanum metals in water in the form of nitrates according to the mass ratio, add aluminum oxide, and stir until homogeneous to obtain a mixed solution;

[0019] S3. The mixed solution is coated onto the pore walls of the alumina honeycomb ceramic carrier using a vacuum coating method;

[0020] S4. Dry and calcine to obtain the monolithic honeycomb ceramic catalyst.

[0021] Furthermore, the raw materials of the cellular ceramic carrier include inorganic solid components, organic components, and water. The inorganic solid components include kaolin, spherical alumina, and talc, and the organic components include methylcellulose and polyethyleneimine.

[0022] Furthermore, in the inorganic solid component, the mass percentage of kaolin is 31%, the mass percentage of spherical alumina is 27%, and the mass percentage of talc is 42%; the average particle size of the spherical alumina is less than 1 μm.

[0023] Furthermore, in step S2, aluminum sol is added to the mixed solution, wherein the mass percentage of the aluminum sol is 3-6% of the total mass of the mixed solution.

[0024] Further, in step S3, the vacuum coating method involves spraying the mixed solution onto one end face of the alumina honeycomb ceramic carrier and then suctioning it from the other end face of the alumina honeycomb ceramic carrier using compressed air.

[0025] This invention also provides the application of the monolithic honeycomb ceramic catalyst described above in the methanol steam reforming hydrogen production reaction in SOFC, under atmospheric pressure, with a water-to-methanol molar ratio of 0.8 and a liquid hourly space velocity of 1 h⁻¹. -1 Under the condition of reaction temperature of 230-300℃, the monolithic honeycomb ceramic catalyst is used to catalyze the reaction of a mixture of methanol and water vapor.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) The methanol steam reforming hydrogen production monolithic honeycomb ceramic catalyst of the present invention uses microchannel monolithic honeycomb ceramic as a carrier, which can significantly increase the specific surface area, which is conducive to the uniform distribution of active material sites in the composite active catalyst layer, and improves the conversion rate and reaction rate of methanol water reforming reaction.

[0028] (2) The integral honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen of the present invention uses copper oxide as the active component in the composite active catalyst layer, which has the advantages of high activity at low temperature and low cost. Modification with zinc oxide and lanthanum oxide can effectively improve the catalyst stability and anti-sintering ability. At the same time, the addition of Al2O3 can improve the dispersion and loading of the active component.

[0029] (3) The monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen of the present invention optimizes the thermal matching between the active components of the catalyst and SOFC, effectively reduces the system volume, increases the specific surface area of ​​the catalyst, and improves the efficiency, stability and hydrogen purity of the methanol reforming to produce hydrogen reaction.

[0030] (4) The method for preparing the monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen in this invention involves directly and uniformly coating the mixed solution of catalyst slurry onto an alumina honeycomb ceramic carrier using a vacuum coating method. After coating, drying and heat treatment are performed to obtain the finished monolithic honeycomb ceramic catalyst. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the process of using the monolithic honeycomb ceramic catalyst of the present invention for catalytic methanol steam reforming to produce hydrogen. Detailed Implementation

[0032] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0033] The methanol steam reforming hydrogen production monolithic honeycomb ceramic catalyst of the present invention includes an alumina honeycomb ceramic support and a composite active catalyst layer coated on the pore walls of the alumina honeycomb ceramic support. The composite active catalyst layer includes copper oxide, zinc oxide and lanthanum oxide, and also includes alumina. In the composite active catalyst layer, the mass ratio of copper, zinc and lanthanum is 3-6:2-4:1-3, and the mesh size of the honeycomb ceramic support is 1000-2000 mesh.

[0034] The monolithic honeycomb ceramic catalyst for methanol steam reforming to hydrogen production of the present invention uses microchannel monolithic honeycomb ceramic as a support, which can significantly increase the specific surface area, which is beneficial to the uniform distribution of active material sites in the composite active catalyst layer, thereby improving the conversion rate and reaction rate of methanol-water reforming reaction.

[0035] In the composite active catalyst layer, copper oxide is used as the active component, which has the advantages of high activity at low temperatures and low cost. Modification with zinc oxide and lanthanum oxide can effectively improve the catalyst's stability and anti-sintering ability. ZnO and La2O3 can improve the adhesion of the coating slurry, ensuring that the active component is uniformly loaded on the surface of the ceramic channel. In addition, the Zn / La modified catalyst can balance activity and selectivity, avoiding the problem of by-product blockage in the honeycomb channel. At the same time, the addition of Al2O3 improves the dispersion and loading of the active component.

[0036] The present invention specifically defines the mesh number of the honeycomb ceramic carrier. When the mesh number is too low or too high, the specific surface area of ​​the honeycomb ceramic carrier is small, the loading of the catalyst active component is reduced, and the conversion rate of the monolithic catalyst is low.

[0037] The monolithic honeycomb ceramic catalyst of this invention optimizes the thermal matching between the active components of the catalyst and SOFC, effectively reduces the system volume, increases the specific surface area of ​​the catalyst, and improves the efficiency, stability and hydrogen purity of the methanol reforming hydrogen production reaction.

[0038] Preferably, in the composite active catalyst layer, the mass ratio of copper, zinc, and lanthanum is 10:9:1; at this ratio, ZnO and Cu can form a Cu-ZnO interface, which promotes the dispersion of Cu and prevents sintering; La can significantly improve the low-temperature activity and stability of the catalyst.

[0039] Preferably, the mass percentage of alumina is 25-35% of the total mass of the composite active catalyst layer; more preferably, the mass percentage of alumina is 30% of the total mass of the composite active catalyst layer.

[0040] The present invention provides a method for preparing a monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen in SOFCs, comprising the following steps:

[0041] S1. Prepare alumina honeycomb ceramic carrier from the raw material of the honeycomb ceramic carrier.

[0042] Preferably, the raw materials of the cellular ceramic carrier include inorganic solid components, organic components and water. The inorganic solid components include kaolin, spherical alumina and talc, and the organic components include methylcellulose and polyethyleneimine.

[0043] Of the aforementioned inorganic solid components, kaolin accounts for 31% by mass, spherical alumina for 27% by mass, and talc for 42% by mass; the average particle size of the spherical alumina is less than 1 μm; nano-sized spherical alumina (less than 1 μm) has a higher specific surface area (typically greater than 200 m²). 2 ( / g) can provide more loading sites for Cu / Zn active components, significantly improve the dispersion of active metals, and reduce agglomeration.

[0044] Specifically, in one embodiment of the present invention, kaolin, spherical alumina and talc are first thoroughly mixed evenly using a mixing device, and then water, methylcellulose and polyethyleneimine are added and thoroughly mixed to form mud segments with suitable softness and hardness. After aging for 12 hours, the mud segments are extruded into a honeycomb structure, microwave dried and then fired in a shuttle automatic kiln.

[0045] S2. Copper, zinc, and lanthanum metals are dissolved in water in the form of nitrates according to the mass ratio. Alumina and aluminum sol are added, and the mixture is stirred evenly to obtain a mixed solution. By adding aluminum sol, the raw materials can be kept stable during the preparation process.

[0046] The aluminum sol used in this invention is a colloidal solution formed by uniformly dispersing nano-sized alumina hydrate particles in water. Its core component is Al2O3·nH2O, and its appearance is a semi-transparent colorless liquid.

[0047] Preferably, the solid particles in the aluminum sol have a particle size of less than 20 nm and a zeta potential of greater than 30 mV, exhibiting high stability; more preferably, the aluminum sol is of type LA-10 or LA-20.

[0048] Preferably, the mass percentage of aluminum sol is 3-6% of the total mass of the mixed solution; more preferably, the mass percentage of aluminum sol is 5% of the total mass of the mixed solution.

[0049] Preferably, the solid content of the mixed solution is 40%.

[0050] S3. The mixed solution is coated onto the pore walls of the alumina honeycomb ceramic carrier using a vacuum coating method.

[0051] Preferably, the vacuum coating method involves spraying a mixed solution onto one end face of the alumina honeycomb ceramic carrier and then suctioning it from the other end face using compressed air.

[0052] The catalyst slurry mixture is directly and uniformly coated onto an alumina honeycomb ceramic carrier using a vacuum coating method. After coating, drying and heat treatment are performed to obtain the finished monolithic honeycomb ceramic catalyst.

[0053] During compressed air suction, after coating is completed, excess mixed solution can also be removed to prevent clogging of the pores in the honeycomb ceramic.

[0054] Preferably, the suction pressure is 20 MPa.

[0055] After drying at 120℃ for 5 hours, the catalyst was calcined in a muffle furnace at 450℃ for 4 hours to obtain an integral honeycomb ceramic catalyst.

[0056] The monolithic honeycomb ceramic catalyst of this invention can be used in the methanol reforming hydrogen production reaction of SOFC. Specifically, it can be used at atmospheric pressure, with a water-to-methanol molar ratio of 0.8 and a liquid hourly space velocity of 1 h⁻¹. -1 At a reaction temperature of 230-300℃, an integral honeycomb ceramic catalyst is used to catalyze the reaction of a mixture of methanol and water vapor.

[0057] After methanol and water vapor react in a mixer, they enter an integral honeycomb ceramic catalyst and undergo the following reaction:

[0058] CH3OH + H2O → CO2 + 3H2

[0059] CO + H₂O → CO₂ + H₂

[0060] The products after the reaction are passed through a condenser and a dryer in sequence to obtain hydrogen, carbon dioxide and carbon monoxide.

[0061] The monolithic honeycomb ceramic catalyst of this invention significantly increases the specific surface area of ​​the catalyst and improves the utilization rate of active sites through microchannel design. At 230-300℃, the methanol conversion rate is ≥85%, and the output power density reaches 0.67 W / cm² under optimal conditions. 2 ;

[0062] The monolithic structure of the integral honeycomb ceramic catalyst of the present invention facilitates installation and integration, reduces system complexity and cost, and improves system reliability and stability; it can also effectively inhibit carbon deposition and extend the service life of the catalyst.

[0063] The present invention will be illustrated by specific embodiments below.

[0064] Example 1

[0065] This embodiment uses a 1000-mesh monolithic honeycomb ceramic catalyst, under normal pressure and at a temperature of 230°C, with a liquid hourly space velocity of 1 h⁻¹. -1SOFC integration experiments were conducted under operating conditions with a water-to-alcohol molar ratio of 0.8, and the catalyst conversion rate was tested after stable operation.

[0066] Examples 2-4 are all based on Example 1, the difference being the reaction temperature during the SOFC integration performance test. The test parameters and performance evaluation indicators for Examples 1-4 are shown in Table 1.

[0067] Table 1. Test parameters and performance evaluation indicators for Examples 1-4

[0068]

[0069] Examples 5-8 are all based on Examples 1-4, the difference being that the monolithic honeycomb ceramic catalyst used in the SOFC experiments was 1500 mesh. The test parameters and performance evaluation indicators for Examples 5-8 are shown in Table 2.

[0070] Table 2 Test parameters and performance evaluation indicators for Examples 5-8

[0071]

[0072] Examples 9-12 are all based on Examples 1-4, the difference being that the monolithic honeycomb ceramic catalyst used in the SOFC experiments was 2000 mesh. The test parameters and performance indicators of Examples 9-12 are shown in Table 3.

[0073] Table 3 Test parameters and performance indicators for Examples 9-12

[0074]

[0075] Comparative Example 1

[0076] Referring to Example 1, the difference is that the active component of the catalyst used in the SOFC experiment is Cu.

[0077] Comparative Example 2

[0078] Referring to Example 1, the difference is that the mass ratio of the active components of the catalyst used in the SOFC experiment is Cu:Zn:La = 5:8:4.

[0079] Comparative Example 3

[0080] Referring to Example 1, the difference is that the mass ratio of the active components of the catalyst used in the SOFC experiment is Cu:Zn:La = 6:3:2.

[0081] Comparative Example 4

[0082] Referring to Example 1, the difference is that the monolithic honeycomb ceramic catalyst used in the SOFC experiment was 400 mesh.

[0083] Comparative Example 5

[0084] Referring to Example 1, the difference is that the monolithic honeycomb ceramic catalyst used in the SOFC experiment is 5000 mesh.

[0085] Comparative Example 6

[0086] Referring to Example 1, the difference is that the monolithic honeycomb ceramic catalyst used in the SOFC experiment was prepared by impregnation, resulting in a lower loading and uneven coating.

[0087] In addition, the highest mesh count of silicon carbide honeycomb ceramics is currently 600 cpsi. High mesh count carriers cannot use silicon carbide honeycomb ceramics, making comparative experiments impossible.

[0088] The test parameters and performance indicators of Comparative Examples 1-6 are shown in Table 4.

[0089] Table 4 shows the test parameters and performance indicators for Comparative Examples 1-6.

[0090]

[0091]

[0092] Examples 1-12 generally show a trend where the methanol conversion rate and output power density increase synchronously with the temperature increasing from 230℃ to 300℃, and the increase is more significant with higher pore density: the conversion rate of the 1000-mesh system (Examples 1-4) increases from 92.3% to 96.8%, and the power density increases from 0.43 W / cm². 2 Increased to 0.63 W / cm 2 The conversion rate of the 1500-mesh system (Examples 5-8) increased from 92.5% to 97.2%, and the power density increased from 0.47 W / cm³. 2 Increased to 0.67 W / cm 2 The conversion rate of the 2000-mesh system (Examples 9-12) increased from 93.2% to 96.4%, and the power density increased from 0.45 W / cm³. 2 Increased to 0.59 W / cm 2 This indicates that in the lower temperature range (230-250℃), 1500 mesh can provide better activity and output than 1000 mesh. However, when the temperature is further increased, 2000 mesh is slightly lower than 1500 mesh due to diffusion resistance, suggesting that there is an optimal window for pore density.

[0093] Comparative Examples 1-3 reveal the crucial role of the active component: the single Cu catalyst (Comparative Example 1) only yielded a conversion of 73.5% and 0.32 W / cm². 2The conversion rate was significantly lower than that in Example 1; in the Cu-Zn-La multi-component system, the 5:8:4 ratio (Comparative Example 2) achieved a conversion rate of 86.2% and a concentration of 0.38 W / cm³. 2 The conversion rate was 83.7% and 0.35 W / cm³, which was better than the 6:3:2 ratio (Comparative Example 3). 2 This indicates that the Zn and La ratio needs to be precisely balanced to coordinate the dehydrogenation and oxygen vacancy supply functions of Cu.

[0094] Comparative Examples 4-5 further illustrate the traps at both ends of pore density: 400 mesh (Comparative Example 4) suffers from insufficient geometric area, resulting in a conversion rate of 89.3% and a density of 0.41 W / cm². 2 Although higher than that of single Cu, it is still lower than the 1000 mesh benchmark; at 5000 mesh (Comparative Example 5), the conversion rate drops to 84.8% and the power density is only 0.37 W / cm³ due to excessively high mesh count causing channel blockage and increased pressure drop. 2 This proves that a higher mesh size is not necessarily better, and that the 1500-2000 mesh range is suitable for use at 230℃ for 1 hour. -2 The optimal conditions are 0.8% water and alcohol.

[0095] Comparative Example 6, using the impregnation method, achieved only an 80.6% conversion rate and 0.33 W / cm³ due to low and uneven loading. 2 This is significantly lower than in Example 1 with vacuum coating, highlighting the decisive influence of uniform coating on the utilization rate of the active layer.

[0096] In summary, the 1500-mesh honeycomb ceramic carrier coupled with an optimized Cu-Zn-La ratio and formed by vacuum coating can achieve the best balance between methanol conversion and power generation performance under normal pressure, 230-300℃, and low water-to-methanol ratio conditions. It breaks through the traditional silicon carbide mesh limit of 600cpsi while avoiding diffusion inhibition caused by excessively high pore density, providing a technical path with both high activity and high output for SOFC-methanol reforming integrated systems.

[0097] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen, characterized in that, The invention comprises an alumina honeycomb ceramic carrier and a composite active catalytic layer coated on the pore walls of the alumina honeycomb ceramic carrier. The composite active catalytic layer comprises copper oxide, zinc oxide, and lanthanum oxide, and also includes alumina. In the composite active catalytic layer, the mass ratio of copper, zinc, and lanthanum is 3-6:2-4:1-3, and the mesh size of the honeycomb ceramic carrier is 1000-2000 mesh.

2. The monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen according to claim 1, characterized in that, In the composite active catalyst layer, the mass ratio of copper, zinc, and lanthanum is 5:3:

2.

3. The monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen according to claim 1, characterized in that, The mass percentage of alumina is 25-35% of the total mass of the composite active catalyst layer.

4. The monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen according to claim 3, characterized in that, The mass percentage of alumina is 30% of the total mass of the composite active catalyst layer.

5. A method for preparing an integral honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Prepare the alumina honeycomb ceramic carrier from the raw material of the honeycomb ceramic carrier; S2. Dissolve copper, zinc, and lanthanum metals in water in the form of nitrates according to the mass ratio, add aluminum oxide, and stir until homogeneous to obtain a mixed solution; S3. The mixed solution is coated onto the pore walls of the alumina honeycomb ceramic carrier using a vacuum coating method; S4. Dry and calcine to obtain the monolithic honeycomb ceramic catalyst.

6. The method for preparing a monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen according to claim 5, characterized in that, The raw materials of the cellular ceramic carrier include inorganic solid components, organic components and water. The inorganic solid components include kaolin, spherical alumina and talc, and the organic components include methylcellulose and polyethyleneimine.

7. The method for preparing a monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen according to claim 6, characterized in that, The inorganic solid components comprise 31% kaolin by mass, 27% spherical alumina by mass, and 42% talc by mass; the average particle size of the spherical alumina is less than 1 μm.

8. The method for preparing a monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen according to claim 5, characterized in that, In step S2, aluminum sol is also added to the mixed solution, and the mass percentage of the aluminum sol is 3-6% of the total mass of the mixed solution.

9. The method for preparing a monolithic honeycomb ceramic catalyst for methanol steam reforming to produce hydrogen according to claim 5, characterized in that, In step S3, the vacuum coating method involves spraying the mixed solution onto one end face of the alumina honeycomb ceramic carrier and then suctioning it from the other end face of the alumina honeycomb ceramic carrier using compressed air.

10. The application of a monolithic honeycomb ceramic catalyst as described in any one of claims 1-4 in the methanol steam reforming reaction for hydrogen production in SOFC, characterized in that, At normal pressure, with a water-to-alcohol molar ratio of 0.8 and a liquid hourly space velocity of 1 h⁻¹ -1 Under the condition of reaction temperature of 230-300℃, the monolithic honeycomb ceramic catalyst is used to catalyze the reaction of a mixture of methanol and water vapor.

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