Composite catalyst for hydrogen production by methanol steam reforming and preparation method thereof

Abstract

The invention relates to the technical field of hydrogen production, in particular to a composite catalyst for hydrogen production through methanol steam reforming and a preparation method thereof.The preparation method comprises the steps that S1, aluminum isopropoxide, copper nitrate, magnesium nitrate and zinc nitrate are added into a mortar, fully ground and evenly mixed; s2, uniformly mixed powder is transferred into a crucible, the crucible is placed in a muffle furnace to be calcined, the powder is rapidly taken out after calcination is finished, cooling is conducted, and the composite catalyst is obtained.The preparation method is simple in preparation process and free of waste water, in the preparation process, aluminum isopropoxide serves as an organic aluminum source, isopropanol is released in the calcination process to form a porous structure, and the composite catalyst is obtained. Meanwhile, the combination of aluminum isopropoxide, magnesium nitrate, copper nitrate and zinc nitrate can form a copper-zinc doped magnesium aluminate spinel structure under the condition of relatively low calcination temperature, so that the prepared composite catalyst has higher stability, has activity in a relatively low temperature range, keeps good activity and stability in a long-time test reaction, and is suitable for industrial production. Good application prospects are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production, and in particular to a composite catalyst for producing hydrogen through methanol steam reforming and a preparation method thereof. Background Art

[0002] Among the many hydrogen production processes, methanol steam reforming has gradually become a key development area due to its significant advantages, including easy storage and transportation of raw materials, low energy consumption, and high hydrogen production efficiency. The key to this process lies in the catalyst, whose performance directly determines the efficiency and quality of hydrogen production.

[0003] Currently, catalysts prepared using the liquid-phase method are widely used in methanol steam reforming to produce hydrogen due to their excellent low-temperature activity and mature preparation process. However, this method is not without its drawbacks. It inevitably generates wastewater pollution, and the high cost of wastewater treatment has, to a certain extent, hindered the further promotion and development of this process.

[0004] Notably, aluminum isopropoxide, as an organic aluminum source, can directly decompose to form Al2O3 (α-Al2O3 or γ-Al2O3) under high-temperature calcination conditions, making it an ideal catalyst support. Unlike the liquid-phase method, which generates Al2O3 through hydrolysis, the decomposition of aluminum isopropoxide in the solid-phase method is accompanied by the volatilization of isopropanol, forming a unique porous structure. This porous structure provides the catalyst with a larger specific surface area, which helps improve its activity and selectivity. Furthermore, aluminum isopropoxide, magnesium nitrate, copper nitrate, and zinc nitrate can form a copper-zinc-doped magnesium-aluminum spinel upon high-temperature calcination. This material possesses advantages such as high mechanical strength, excellent chemical and thermal stability, and a high heat transfer coefficient, making it a highly promising support material for the preparation of composite catalysts and promising new breakthroughs in the development of methanol steam reforming hydrogen production processes.

[0005] In view of this, the present application aims to develop a composite catalyst for methanol steam reforming to produce hydrogen and a preparation method thereof, so as to solve the problems of waste liquid pollution and complicated preparation process in liquid phase preparation. Summary of the Invention

[0006] To solve the above problems, the present invention provides a composite catalyst for methanol steam reforming to produce hydrogen and a preparation method thereof. The composite catalyst for methanol steam reforming to produce hydrogen is prepared by solid-phase grinding, wherein copper-zinc-doped magnesia-aluminum spinel loads active components CuO and ZnO. The catalyst prepared by this method has high activity for methanol steam reforming to produce hydrogen at low temperatures, and the preparation process is simple and no waste liquid is generated.

[0007] The technical solution adopted in the present invention is:

[0008] A method for preparing a composite catalyst for hydrogen production by methanol steam reforming comprises the following steps:

[0009] S1. Add aluminum isopropoxide, copper nitrate, magnesium nitrate, and zinc nitrate to a mortar, grind thoroughly, and mix well;

[0010] S2. Then, the uniformly mixed powder is transferred to a crucible, placed in a muffle furnace for calcination, and quickly taken out after calcination, and cooled to obtain a composite catalyst.

[0011] Furthermore, in step S1, the mass ratio of aluminum isopropoxide, copper nitrate, zinc nitrate and magnesium nitrate is 36-60:12-31:15-26:7-13.

[0012] Furthermore, in step S2, the calcination temperature of the muffle furnace is 400-600° C., and the calcination time is 6-10 hours.

[0013] Furthermore, in step S2, the muffle furnace needs to be heated to 400-600°C in advance.

[0014] Based on the same inventive concept, the present application also provides a composite catalyst for hydrogen production by steam reforming of methanol, which is prepared using the above-mentioned preparation method.

[0015] Furthermore, the composite catalyst is composed of active components and a carrier, wherein the active components are CuO and ZnO, and the carrier is Cu 0.33 Zn 0.33 Mg 0.34 Al2O4.

[0016] Furthermore, in terms of mass percentage, in the composite catalyst, the mass percentage of CuO is no more than 34%, the mass percentage of ZnO is no more than 17%, and the mass percentage of Cu 0.33 Zn 0.33 Mg 0.34 The mass percentage of Al2O4 is not less than 54%.

[0017] The beneficial effects of the present invention are as follows:

[0018] The preparation method provided by the present invention has a simple and efficient preparation process, and no wastewater is discharged in the entire production process, which is in line with the green and environmentally friendly production concept; in the preparation process, aluminum isopropoxide is selected as a key organic aluminum source, and when calcined, the aluminum isopropoxide decomposes and releases isopropanol gas, which forms unique channels inside the material, thereby constructing a porous structure, effectively improving the specific surface area and porosity of the material, and providing more active sites for the catalytic reaction; at the same time, in the preparation process, there is an ingenious synergistic effect between aluminum isopropoxide and magnesium nitrate, copper nitrate and zinc nitrate, and by precisely controlling the ratio of each raw material and the calcination conditions, they can be calcined at a relatively low calcination temperature. The chemical reaction took place at a temperature of 1000 ℃ and a copper-zinc-doped magnesium-aluminum spinel structure was successfully constructed. This special crystal structure not only gives the composite catalyst higher stability, enabling it to resist the influence of various adverse factors in a complex reaction environment and maintain structural integrity, but also enables the catalyst to exhibit excellent catalytic activity within a lower temperature range, greatly reducing energy consumption and reaction costs. After a long period of test reaction verification, the composite catalyst showed excellent activity and stability. During continuous operation, its catalytic performance always remained at a high level without any obvious attenuation. This feature gives the composite catalyst broad application prospects in many industrial catalysis fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The XRD spectra of the catalysts in Examples 1, 3 and 4 of the present invention in the unreduced activated state are shown;

[0020] Figure 2 Activity test diagram of the catalysts in Examples 1-6 of the present invention and Comparative Examples 1-2;

[0021] Figure 3 Graph showing the CO selectivity of the catalysts in Examples 1-6 and Comparative Examples 1-2 of the present invention;

[0022] Figure 4 This is a SEM image of the catalyst in Example 3 of the present invention in a state where no reduction activation is performed;

[0023] Figure 5 This is a TEM image of the catalyst in Example 3 of the present invention in a state where no reduction activation is performed. DETAILED DESCRIPTION

[0024] To facilitate understanding of the present invention, the present invention will be described more fully below through examples, with preferred embodiments of the present invention provided below. However, the present invention can be implemented in a variety of different forms and is not limited to the embodiments described herein. Any other embodiments obtained by modifying or equivalently replacing the technical solution of the present invention without inventive results are within the scope of protection of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0026] The numerical values ​​disclosed in the embodiments of the present invention are approximate values, not definite values. Where errors or experimental conditions permit, all values ​​within the error range may be included without being limited to the specific numerical values ​​disclosed in the embodiments of the present invention.

[0027] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0028] Example 1

[0029] This embodiment provides a method for preparing a composite catalyst for hydrogen production by methanol steam reforming, comprising the following steps:

[0030] S1: Weigh 1.225 g of aluminum isopropoxide, 0.26 g of magnesium nitrate, 0.24 g of copper nitrate, and 0.3 g of zinc nitrate into a mortar, grind thoroughly, and mix well.

[0031] S2: The uniformly mixed powder is then transferred to a crucible, placed in a muffle furnace at 600°C and calcined for 6 hours, and then quickly taken out and cooled to obtain a methanol reforming hydrogen production composite catalyst.

[0032] The catalyst prepared in this example is labeled as catalyst 1 (mass percentage: CuO: ZnO: Cu 0.33 Zn 0.33 Mg 0.34 Al2O4=0:0:100).

[0033] Example 2

[0034] This embodiment provides a method for preparing a composite catalyst for hydrogen production by methanol steam reforming, which differs from Example 1 in that:

[0035] In step S1, 1.225 g of aluminum isopropoxide, 0.26 g of magnesium nitrate, 1.06 g of copper nitrate, and 0.6 g of zinc nitrate were weighed and added to a mortar, and the mixture was thoroughly ground.

[0036] The catalyst prepared in this example is labeled as catalyst 2 (mass percentage: CuO: ZnO: Cu 0.33 Zn 0.33 Mg 0.34 Al2O4=31:10:59).

[0037] Example 3

[0038] This embodiment provides a method for preparing a composite catalyst for hydrogen production by methanol steam reforming, which differs from Example 1 in that:

[0039] In step S1, 1.225 g of aluminum isopropoxide, 0.26 g of magnesium nitrate, 1.06 g of copper nitrate, and 0.9 g of zinc nitrate were weighed and added to a mortar and ground thoroughly.

[0040] The catalyst prepared in this example is labeled as catalyst 3 (mass percentage: CuO: ZnO: Cu 0.33 Zn 0.33 Mg 0.34 Al2O4=29:17:54).

[0041] Example 4

[0042] This embodiment provides a method for preparing a composite catalyst for hydrogen production by methanol steam reforming, which differs from Example 1 in that:

[0043] In step S1, 1.225 g of aluminum isopropoxide, 0.26 g of magnesium nitrate, 1.06 g of copper nitrate, and 0.39 g of zinc nitrate were weighed and added to a mortar and ground thoroughly.

[0044] The catalyst prepared in this example is labeled as catalyst 4 (mass percentage: CuO: ZnO: Cu 0.33 Zn 0.33 Mg 0.34 Al2O4=34:3:63).

[0045] Example 5

[0046] This embodiment provides a method for preparing a composite catalyst for hydrogen production by methanol steam reforming, which differs from Example 3 in that:

[0047] The calcination temperature in the muffle furnace in step S2 is 400°C

[0048] The catalyst prepared in this example is labeled as catalyst 5 (mass percentage: CuO: ZnO: Cu 0.33 Zn 0.33 Mg 0.34 Al2O4=29:17:54).

[0049] Example 6

[0050] This embodiment provides a method for preparing a composite catalyst for hydrogen production by methanol steam reforming, which differs from Example 3 in that:

[0051] The calcination time in step S2 is 10 hours.

[0052] The catalyst prepared in this example is labeled as catalyst 6 (mass percentage: CuO: ZnO: Cu 0.33 Zn 0.33 Mg 0.34 Al2O4=29:17:54).

[0053] Comparative Example 1

[0054] This comparative example provides a method for preparing a composite catalyst for hydrogen production by methanol steam reforming, which differs from Example 3 in that:

[0055] In step S1, 1.225 g of aluminum isopropoxide, 0.78 g of magnesium nitrate, 1.08 g of copper nitrate, and 0.46 g of zinc nitrate were weighed and added to a mortar and ground thoroughly.

[0056] The catalyst prepared in this comparative example is marked as comparative example 1 (mass percentage: CuO:ZnO:MgAl2O4=40:13:47).

[0057] Comparative Example 2

[0058] This comparative example provides a method for preparing a composite catalyst for hydrogen production by methanol steam reforming, which differs from Example 3 in that:

[0059] In step S1, 2.25 g of aluminum nitrate, 0.26 g of magnesium nitrate, 1.06 g of copper nitrate, and 0.9 g of zinc nitrate were weighed and added to a mortar and ground thoroughly.

[0060] The catalyst prepared in this comparative example is marked as comparative example 2 (mass percentage ratio: CuO: ZnO: Cu 0.33 Zn 0.33 Mg 0.34 Al2O4=29:17:54).

[0061] See also Figure 1It can be seen from the XRD spectrum that the characteristic diffraction peak intensity of the copper-zinc doped magnesium-aluminum spinel in Example 3 is significantly different from that in Example 1 and Example 4. Specifically, compared with Example 1 and Example 4, the characteristic diffraction peak of the copper-zinc doped magnesium-aluminum spinel in Example 3 is sharper. This shows that the catalysts prepared with different mass fractions of copper, zinc, magnesium, and aluminum have an impact on the crystal phase structure of the copper-zinc doped magnesium-aluminum spinel. When the mass fraction ratio of each element is appropriate, the copper-zinc doped magnesium-aluminum spinel crystal phase formed is more stable, and a more stable crystal phase structure is beneficial to improving the activity of the catalyst. It can be inferred that the catalyst prepared in Example 3 has a catalytic activity higher than that of Example 1 and Example 4.

[0062] See also Figure 2 and Figure 3 The catalytic activity test curves show that the catalytic activities of Examples 5 and 6 are significantly lower than those of Example 3. Comparison of the preparation processes reveals that the only variable among the three groups of samples is the calcination conditions: Example 3 was calcined at 600°C for 6 hours, Example 5 was calcined at 400°C for 6 hours, and Example 6 was calcined at 600°C for 10 hours.

[0063] It can be seen that the calcination temperature and time directly affect the crystal phase transformation of the catalyst precursor, the dispersion of the active components and the pore structure of the carrier: when calcined at 400 ° C (Example 5), the precursor is not fully thermally decomposed, the copper-zinc-doped magnesium-aluminum spinel crystal phase is not completely formed, and the active component Cu / Zn species still partially remain in the form of hydroxides, resulting in an insufficient number of catalytic active sites; and calcined at 600 ° C for 10 hours (Example 6), although the temperature is suitable, the time is too long, which triggers the agglomeration of active components and the collapse of the carrier pores, resulting in a reduction in the effective reaction interface. In contrast, the 600 ° C calcination for 6 hours in Example 3 not only ensures that the precursor is fully thermally decomposed to form a stable spinel crystal phase, but also avoids structural degradation caused by excessive sintering, so that the catalyst has both suitable active site distribution and mass transfer channels.

[0064] In summary, the process parameters of calcination at 600°C for 6 hours adopted in Example 3 can achieve an optimized balance between catalyst activity and structural stability by regulating the thermochemical conversion path in the solid-phase preparation process. Therefore, this calcination condition is more suitable for the preparation process of the composite catalyst described in this application.

[0065] See also Figure 4 The following is a scanning electron microscope (SEM) image of the catalyst prepared in Example 3. It shows that the isopropyl alcohol gas generated by the decomposition of aluminum isopropylate during high-temperature calcination promotes the formation of a coral-like porous structure with multi-level pores. This unique morphology significantly increases the material's apparent roughness and three-dimensional through-porosity compared to catalysts prepared by traditional solid-phase methods, providing a larger effective specific surface area for catalytic reactions.

[0066] See also Figure 5 The figure shows a transmission electron microscope (TEM) image of the catalyst prepared in Example 3, in which copper oxide (CuO) and zinc oxide (ZnO) nanoparticles are highly uniformly dispersed on the surface of the carrier, with a particle size distribution concentrated in the range of 10-15 nm and no obvious agglomeration. 0.33 Zn 0.33 Mg 0.34 The high specific surface area of ​​the Al2O4 support effectively inhibits the sintering and agglomeration of active metal nanoparticles by providing abundant surface active sites and anchoring, maintaining good dispersion within the catalyst. This structural advantage not only provides more adsorption sites for reactant molecules, enhancing surface reactivity at low temperatures, but also significantly improves the long-term stability of the catalyst by stabilizing the nanoscale distribution of active components.

[0067] In summary, the porous morphology observed in the SEM image and the nanoparticle dispersion revealed by TEM jointly indicate that the special structural design of the copper-zinc-doped magnesium-aluminum spinel support achieves the synergistic optimization of the specific surface area of ​​the catalytic material and the dispersion of the active components by regulating the pore-forming effect of volatile products during high-temperature calcination, providing key support for improving the low-temperature catalytic performance and structural stability of the catalyst.

[0068] In summary, the preparation method provided by the present invention constructs copper-zinc-doped magnesium-aluminum spinel (Cu 0.33 Zn 0.33 Mg 0.34 A composite catalyst system for methanol steam reforming hydrogen production based on an Al2O4 (Al2O4)-supported catalyst. This preparation process, based on a solvent-free synthesis strategy, achieves an integrated precursor preparation and calcination process, eliminating the waste liquid pollution associated with traditional liquid-phase methods and establishing an environmentally friendly green synthesis route.

[0069] The copper-based composite catalyst prepared by the present invention exhibits excellent catalytic activity in the low-temperature range of 240-280°C, thanks to the high crystallinity of the cubic spinel structure and unique coral-like porous morphology of the copper-zinc-doped magnesium-aluminum spinel support. This performance advantage stems from the multiple synergistic effects provided by the support: on the one hand, the multi-level pore structure (constructed by the pore-inducing effect of the thermal decomposition of aluminum isopropoxide) significantly increases the specific surface area, providing uniformly dispersed nanoscale anchoring sites for the Cu / Zn active components; on the other hand, the strong metal-support interaction (SMSI) of the spinel lattice effectively suppresses the high-temperature agglomeration of active sites while optimizing the adsorption and activation pathway of the reactant molecules.

[0070] Compared to traditional solid-phase catalysts, the composite catalyst prepared in this application achieves synergistic optimization of the carrier's crystalline integrity, active component dispersion, and pore structure stability by precisely controlling the calcination process parameters (600°C x 6h), enabling the catalyst to possess both low-temperature catalytic activity and long-term operational stability. These technical features give the catalyst significant technical advantages in scenarios such as distributed hydrogen production equipment and fuel cell vehicle hydrogen supply systems, demonstrating excellent potential for industrial application.

[0071] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a composite catalyst for hydrogen production by methanol steam reforming, characterized in that: The steps include: S1. Add aluminum isopropoxide, copper nitrate, magnesium nitrate, and zinc nitrate to a mortar, grind thoroughly, and mix well; S2. Then, the uniformly mixed powder is transferred to a crucible, placed in a muffle furnace for calcination, and quickly taken out after calcination, and cooled to obtain a composite catalyst.

2. The method for preparing a composite catalyst for hydrogen production by methanol steam reforming according to claim 1, wherein: In step S1, the mass ratio of aluminum isopropoxide, copper nitrate, zinc nitrate and magnesium nitrate is 36-60:12-31:15-26:7-13.

3. The method for preparing a composite catalyst for hydrogen production by methanol steam reforming according to claim 1, wherein: In step S2, the calcination temperature of the muffle furnace is 400-600° C., and the calcination time is 6-10 hours.

4. The method for preparing a composite catalyst for hydrogen production by methanol steam reforming according to claim 1, wherein: In step S2, the muffle furnace needs to be heated to 400-600°C in advance.

5. A composite catalyst for hydrogen production by steam reforming of methanol, prepared by the preparation method according to any one of claims 1 to 4.

6. The composite catalyst for hydrogen production by methanol steam reforming according to claim 5, characterized in that The composite catalyst is composed of active components and a carrier, wherein the active components are CuO and ZnO, and the carrier is Cu 0.33 Zn 0.33 Mg 0.34 Al2O4.

7. The composite catalyst for producing hydrogen through methanol steam reforming according to claim 5, characterized in that: In terms of mass percentage, the mass percentage of CuO in the composite catalyst is no more than 34%, the mass percentage of ZnO is no more than 17%, and the mass percentage of Cu is no more than 10%. 0.33 Zn 0.33 Mg 0.34 The mass percentage of Al2O4 is not less than 54%.

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