Zinc-based composite oxide catalyst, preparation thereof and application of zinc-based composite oxide catalyst in methanol reforming hydrogen production

Abstract

The invention relates to the technical field of novel energy catalysis, in particular to a zinc-based composite oxide catalyst, preparation thereof and application of the zinc-based composite oxide catalyst in hydrogen production through methanol reforming. The zinc-based composite oxide catalyst provided by the invention is obtained by depositing and precipitating precursor salt of zinc and zirconium hydroxide and then roasting; the composition of the material is xZnO-yZrO2, and x / y is 0.01-1. The catalyst is relatively simple in preparation process, does not need to be subjected to pre-reduction treatment before being used, has relatively high methanol conversion rate, relatively high hydrogen production rate and relatively low CO selectivity in a methanol steam reforming hydrogen production reaction system, and can reach 100% conversion rate at a relatively low temperature; the method is suitable for industrial requirements, low in raw material price, free of precious metal and wide in application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of novel energy catalysis, and in particular to a zinc-based composite oxide catalyst, its preparation, and its application in methanol reforming to produce hydrogen. Background Art

[0002] The increasing consumption of fossil fuels has led to numerous environmental problems, necessitating the development of sustainable, clean energy sources. Hydrogen, with its high energy density and pollution-free combustion, is considered a promising alternative to fossil fuels. Hydrogen can be used in fuel cells to generate electricity. Polymer electrolyte membrane fuel cells (PEMFCs) are being widely researched due to their "zero emissions" advantages.

[0003] Compared to ethanol and methane, methanol offers two advantages in hydrogen production. First, methanol has only one carbon atom and lacks strong carbon-carbon bonds, making it the simplest of all alcohols. Second, methanol can be reformed to produce hydrogen at low temperatures (200-300°C), while methane reforming produces hydrogen at temperatures above 500°C and ethanol reforming produces hydrogen at around 400°C. Currently, several methods for producing hydrogen from methanol have been established, such as methanol steam reforming (MSR), methanol partial oxidation (POM), and methanol autothermal reforming (ATR). While all methods have achieved substantial progress, methanol steam reforming (MSR) offers some unique advantages over the other two methods, including low carbon monoxide selectivity and a high hydrogen-to-carbon ratio.

[0004] The catalyst is the core of the methanol steam reforming hydrogen production process. Currently, Cu-based catalysts are widely used in this process due to their good low-temperature activity and mature preparation process. However, the reactivity and stability of Cu-based catalysts still need to be improved.

[0005] Patent CN101612563A discloses a composite oxide catalyst for methanol steam reforming to produce hydrogen. The catalyst is composed of ZnO as the main active component, and includes composite oxides such as Cr2O3, ZrO2, and CeO2 as catalytic and thermal stabilizing additives and carriers to address the defects of low catalyst activity and poor stability in existing methanol steam reforming hydrogen production technology. However, the reforming hydrogen production using this catalyst has a relatively high conversion temperature of about 450°C and a CO selectivity of up to 10%.

[0006] Patent CN119034785A discloses a supported methanol steam reforming hydrogen production catalyst and its preparation method. The catalyst is prepared using a reverse coprecipitation method using boron nitride nanosheets (BNNSOH) with hydroxyl groups on their surfaces as a support. The catalyst consists of an active component and a support, the active components being CuO and ZnO. However, the preparation process is complex and involves the use of a high-pressure reactor, which is hazardous. Furthermore, copper is prone to sintering and deactivation.

[0007] ZnZr composite oxide catalysts exhibit high conversion, low CO selectivity, and good stability in MSR, making them a potential alternative to traditional Cu-based catalysts. Wang Y, Men Y, et al. used a Li-doped oxygen vacancy engineering strategy to prepare ZrO2 supports of different crystalline phases, and then prepared ZnO / ZrO2 catalysts using an isovolumetric impregnation method. Oxygen vacancy engineering in ZnO / ZrO2 composite catalysts for highly enhanced hydrogen production by methanol steam reforming[J].Colloids and Surfaces A:PHysicochemical and Engineering Aspects,2024,701134924-134924. At 375°C, S / C=1.4, and WHSV=14.6L / gcat·h, the catalyst ZnO / ZrO2-3Li achieved complete methanol conversion with a CO selectivity as low as 3.1%. However, the lithium element increases production complexity and cost, and the complex disposal of lithium-containing catalysts also increases the overall lifecycle cost.

[0008] In order to improve the shortcomings of the catalyst in this system, it is crucial to prepare a methanol reforming catalyst that has good low-temperature reaction activity and high selectivity, is not easy to sinter at high temperatures, has a simple preparation process and is low in price. Summary of the Invention

[0009] In order to solve the above problems, the purpose of the present invention is to provide a zinc-based composite oxide catalyst, its preparation, and its application in methanol reforming to produce hydrogen. The zinc-based composite oxide catalyst provided by the present invention is obtained by calcining a zinc precursor salt and zirconium hydroxide through precipitation; its composition is xZnO-yZrO2, wherein x / y is 0.01 to 1. The preparation process of the catalyst is relatively simple, and no pre-reduction treatment is required before use. In the methanol steam reforming hydrogen production reaction system, the catalyst has a high methanol conversion rate and a high hydrogen production rate and a low CO selectivity. The catalyst can achieve a conversion rate of 100% at a relatively low temperature; it is suitable for industrial requirements, has low raw material prices, does not contain precious metals, and has broad application prospects.

[0010] The purpose of the present invention can be achieved by the following technical solutions:

[0011] The first object of the present invention is to provide a zinc-based composite oxide catalyst, which is prepared by a zinc precursor salt and zirconium hydroxide; its composition is xZnO-yZrO2, wherein x is the molar number of ZnO in the catalyst, y is the molar number of ZrO2 in the catalyst, and x / y is 0.01 to 1.

[0012] In one embodiment of the present invention, x / y is 0.01 to 0.5.

[0013] A second object of the present invention is to provide a method for preparing a zinc-based composite oxide catalyst, comprising the following steps:

[0014] The zinc precursor salt and zirconium hydroxide are mixed and dried, and then calcined to obtain a zinc-based composite oxide catalyst.

[0015] In one embodiment of the present invention, the zinc precursor salt is selected from one or more of zinc chloride, zinc acetate, zinc nitrate hexahydrate, and basic zinc carbonate;

[0016] Preferably, the zinc precursor salt is zinc nitrate hexahydrate.

[0017] In one embodiment of the present invention, the molar ratio of the zinc precursor salt to zirconium hydroxide is 0.01 to 1:1.

[0018] In one embodiment of the present invention, the mixing method is selected from one of the following methods:

[0019] Template method, hydrothermal method, deposition precipitation method, impregnation method, sol-gel method or mechanical mixing method;

[0020] Preferably, the mixing method is a sedimentation precipitation method.

[0021] In one embodiment of the present invention, the drying process is performed at a temperature of 60 to 120° C. and a time of 4 to 12 hours;

[0022] During the calcination process, the temperature is 300-600°C and the time is 2-8 hours;

[0023] Preferably, during the calcination process, the temperature is 300-450° C. and the time is 2-8 hours.

[0024] The third object of the present invention is to provide a zinc-based composite oxide catalyst for use in methanol reforming to produce hydrogen.

[0025] A fourth object of the present invention is to provide a method for producing hydrogen by reforming methanol, comprising the following steps:

[0026] The zinc-based composite oxide catalyst is screened and loaded into a fixed bed reactor to catalyze methanol steam reforming to produce hydrogen.

[0027] In one embodiment of the present invention, during the catalytic reaction, the pressure is 1 to 50 atmospheres and the temperature is 250 to 450°C; the preferred reaction temperature range is 280°C to 360°C.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) This invention proposes, for the first time, the use of zirconium hydroxide as a zirconium metal source in a system by optimizing the preparation methods of single oxide and composite oxide catalysts, as well as the composition of the composite oxides. Simultaneously, the ratio of Zn to Zr is adjusted to find a suitable zinc-zirconium ratio range with a relatively low zinc content, thereby achieving a more uniform dispersion of zinc on the zirconium surface and improving the dispersion of the active components to achieve high catalytic activity, low CO selectivity, high H2 selectivity, and high stability.

[0030] (2) The catalyst preparation process is relatively simple, requiring no pre-reduction treatment before use, and the calcination temperature is lower than that of catalysts in the same reaction system. In a methanol steam reforming hydrogen production reaction system, the catalyst exhibits high methanol conversion, high hydrogen production rate, and low CO selectivity. The catalyst can achieve 100% conversion at 340°C, which is approximately 40°C lower than the complete conversion temperature of catalysts in the same system. It is suitable for industrial applications, has low raw material prices, contains no precious metals, and has considerable potential for application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a graph showing the hydrogen generation rate when the catalysts prepared in Examples 1 to 4 catalyze methanol steam reforming to produce hydrogen;

[0032] Figure 2This is a graph showing the percentage of methanol conversion when the catalysts prepared in Examples 1 to 4 catalyze methanol steam reforming to produce hydrogen;

[0033] Figure 3 Graph showing percentage of CO selectivity when the catalysts prepared in Examples 1 to 4 and Example 1 are used to catalyze steam reforming of methanol to produce hydrogen;

[0034] Figure 4 This is a graph showing the hydrogen generation rate when the catalysts prepared in Examples 5 to 8 and Example 1 are used to catalyze methanol steam reforming to produce hydrogen;

[0035] Figure 5 A graph showing the percentage of methanol conversion when the catalysts prepared in Examples 5 to 8 and Example 1 are used to catalyze methanol steam reforming to produce hydrogen;

[0036] Figure 6 This is a graph showing the percentage of methanol conversion when the catalysts prepared in Example 1 and Comparative Example 1 are used to catalyze methanol steam reforming to produce hydrogen. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] In the following examples, unless otherwise specified, all reagents used are commercially available reagents, and all detection means and methods used are conventional detection means and methods in the art.

[0039] Example 1

[0040] This embodiment provides a preparation method of a zinc-based composite metal oxide (1ZnO-10ZrO2), which is as follows:

[0041] A mixture of 2g of zirconium hydroxide and 0.3735g of zinc nitrate was placed in a 300mL beaker, 200mL of deionized water was added, and the mixture was stirred at room temperature for 1.5h; then 4mL of ammonia water was added to adjust the pH to 10, followed by stirring at room temperature for 1h. After the stirring was completed, the mixture was allowed to stand for obvious stratification, centrifuged, and washed with water 3 times; then placed in an oven, dried at 80°C for 6h, and calcined at 500°C for 3h to prepare a zinc-based composite metal oxide: 1ZnO-10ZrO2 (marked as "S1").

[0042] Example 2

[0043] This embodiment provides a preparation method of a zinc-based composite metal oxide (1ZnO-10ZrO2), which is as follows:

[0044] A mixture of 2g of zirconium hydroxide and 0.17113g of zinc chloride was placed in a 300mL beaker, 200mL of deionized water was added, and the mixture was stirred at room temperature for 1.5h; then 2mL of ammonia water was added to adjust the pH to 10, followed by stirring at room temperature for 1h. After the stirring was completed, the mixture was allowed to stand for obvious stratification, centrifuged, and washed with water 3 times; then placed in an oven, dried at 80°C for 6h, and calcined at 500°C for 3h to prepare a zinc-based composite metal oxide: 1ZnO-10ZrO2 (marked as "S2").

[0045] Example 3

[0046] This embodiment provides a preparation method of a zinc-based composite metal oxide (1ZnO-10ZrO2), which is as follows:

[0047] A mixture of 2g of zirconium hydroxide and 0.1575g of zinc acetate was placed in a 300mL beaker, 200mL of deionized water was added, and the mixture was stirred at room temperature for 1.5h; then 2mL of ammonia water was added to adjust the pH to 10, followed by stirring at room temperature for 1h. After the stirring was completed, the mixture was allowed to stand for obvious stratification, centrifuged, and washed with water 3 times; then placed in an oven, dried at 80°C for 6h, and calcined at 500°C for 3h to prepare a zinc-based composite metal oxide: 1ZnO-10ZrO2 (marked as "S3").

[0048] Example 4

[0049] This embodiment provides a preparation method of a zinc-based composite metal oxide (1ZnO-10ZrO2), which is as follows:

[0050] A mixture of 2g of zirconium hydroxide and 0.6893g of basic zinc carbonate was placed in a 300mL beaker, 200mL of deionized water was added, and the mixture was stirred at room temperature for 1.5h; then 2mL of ammonia water was added to adjust the pH to 10, followed by stirring at room temperature for 1h. After the stirring was completed, the mixture was allowed to stand for obvious stratification, centrifuged, and washed with water 3 times; then placed in an oven, dried at 80°C for 6h, and calcined at 500°C for 3h to prepare a zinc-based composite metal oxide: 1ZnO-10ZrO2 (marked as "S4").

[0051] Example 5

[0052] This embodiment provides a preparation method of a zinc-based composite metal oxide (1ZnO-100ZrO2), which is as follows:

[0053] A mixture of 2g of zirconium hydroxide and 0.0374g of zinc nitrate was placed in a 300mL beaker, 200mL of deionized water was added, and the mixture was stirred at room temperature for 1.5h; then 2mL of ammonia water was added to adjust the pH to 10, followed by stirring at room temperature for 1h. After the stirring was completed, the mixture was allowed to stand for obvious stratification, centrifuged, and washed with water 3 times; then placed in an oven, dried at 80°C for 6h, and calcined at 500°C for 3h to prepare a zinc-based composite metal oxide: 1ZnO-100ZrO2 (marked as "S5").

[0054] Example 6

[0055] This embodiment provides a preparation method of a zinc-based composite metal oxide (5ZnO-100ZrO2), which is as follows:

[0056] A mixture of 2g of zirconium hydroxide and 0.0187g of zinc nitrate was placed in a 300mL beaker, 200mL of deionized water was added, and the mixture was stirred at room temperature for 1.5h; then 2mL of ammonia water was added to adjust the pH to 10, followed by stirring at room temperature for 1h. After the stirring was completed, the mixture was allowed to stand for obvious stratification, centrifuged, and washed with water 3 times; then placed in an oven, dried at 80°C for 6h, and calcined at 500°C for 3h to prepare a zinc-based composite metal oxide: 5ZnO-100ZrO2 (marked as "S6").

[0057] Example 7

[0058] This embodiment provides a preparation method of a zinc-based composite metal oxide (15ZnO-100ZrO2), which is as follows:

[0059] A mixture of 2g of zirconium hydroxide and 0.560g of zinc nitrate was placed in a 300mL beaker, 200mL of deionized water was added, and the mixture was stirred at room temperature for 1.5h; then 2mL of ammonia water was added to adjust the pH to 10, followed by stirring at room temperature for 1h. After the stirring was completed, the mixture was allowed to stand for obvious stratification, centrifuged, and washed with water 3 times; then placed in an oven, dried at 80°C for 6h, and calcined at 500°C for 3h to prepare a zinc-based composite metal oxide: 15ZnO-100ZrO2 (marked as "S7").

[0060] Example 8

[0061] This embodiment provides a preparation method of a zinc-based composite metal oxide (30ZnO-100ZrO2), which is as follows:

[0062] A mixture of 2g of zirconium hydroxide and 1.12g of zinc nitrate was placed in a 300mL beaker, 200mL of deionized water was added, and the mixture was stirred at room temperature for 1.5h; then 2mL of ammonia water was added to adjust the pH to 10, followed by stirring at room temperature for 1h. After the stirring was completed, the mixture was allowed to stand for obvious stratification, centrifuged, and washed with water 3 times; then placed in an oven, dried at 80°C for 6h, and calcined at 500°C for 3h to prepare a zinc-based composite metal oxide: 15ZnO-100ZrO2 (marked as "S8").

[0063] Comparative Example 1

[0064] This embodiment provides a preparation method of a zinc-based composite metal oxide (1ZnO-10ZrO2), which is as follows:

[0065] A mixture of 2 g of zirconium oxychloride hexahydrate and 0.1846 g of zinc nitrate was placed in a 300 mL beaker, 200 mL of deionized water was added, and the mixture was stirred at room temperature for 1.5 h; then 4 mL of ammonia water was added to adjust the pH to 10, followed by stirring at room temperature for 1 h. After stirring, the mixture was allowed to stand for obvious stratification, centrifuged, and washed with water 3 times; then placed in an oven, dried at 80 ° C for 6 h, and calcined at 500 ° C for 3 h to prepare a zinc-based composite metal oxide: 1ZnO-10ZrO2 (marked as "Comparative Example 1").

[0066] The catalysts prepared in Examples 1 to 8 and Comparative Example 1 were sieved to obtain 40-60 mesh particles, which were then loaded into a fixed reactor to catalyze methanol steam reforming to produce hydrogen. During the catalytic reaction, the temperature was 280-380°C, the water-to-methanol ratio was 1.4, and the gas phase space velocity was 23166h-1. -1 The performance comparison of the catalysts prepared in Examples 1 to 8 at 340°C is shown in Table 1. The hydrogen generation rate of the catalysts prepared in Examples 1 to 4 when catalyzing methanol steam reforming to produce hydrogen is shown in the figure below. Figure 1 As shown in the graph, the methanol conversion percentage of the catalysts prepared in Examples 1 to 4 when catalyzing methanol steam reforming to produce hydrogen is as follows: Figure 2 As shown in the graph, the CO selectivity percentage of the catalysts prepared in Examples 1 to 4 when catalyzing methanol steam reforming to produce hydrogen is shown in the graph. Figure 3 As shown in the graph, the hydrogen generation rate of the catalysts prepared in Examples 5 to 8 and Example 1 when catalyzing methanol steam reforming to produce hydrogen is as shown in the graph. Figure 4 As shown in the graph, the methanol conversion percentage of the catalysts prepared in Examples 5 to 8 and Example 1 when catalyzing methanol steam reforming to produce hydrogen is as follows: Figure 5 The methanol conversion percentage of the catalysts prepared in Example 1 and Comparative Example 1 in catalytic methanol steam reforming to produce hydrogen is shown in the figure below. Figure 6 shown.

[0067] Table 1 Performance comparison of catalysts from Examples 1 to 8 and Comparative Example 1 at 340°C

[0068]

[0069] It can be seen from Table 1 that Example 1 has excellent catalytic activity. In the zinc-zirconium system, complete conversion can be achieved at a temperature of 340°C, and the CO selectivity is as low as 1.68%, which meets the CO selectivity requirements of the composite fuel cell and has a high hydrogen production rate.

[0070] At 340℃, Figure 1 The hydrogen generation rate follows the rule of S1>S4>S2>S3, among which the hydrogen generation rate of S1 catalyst at 280-380℃ is much higher than that of other catalysts; at 340℃, Figure 4 The hydrogen generation rate follows S1>S7>S8>S6>S5. At 340℃, Figure 6 The hydrogen generation rate in the S1 catalyst is much higher than that of the other catalysts at 280-380°C. The hydrogen generation rate reaches 2995 mmol.g -1 cat.h -1 .

[0071] pass Figure 2 and Figure 5 It can be seen that different metal zirconium salt catalysts have different effects on methanol conversion. Temperature has a significant impact on the methanol conversion of the four catalysts. The methanol conversion rate increases continuously with increasing temperature. The catalyst prepared in Example 1 is significantly more active at low temperatures than the other catalysts, and the catalyst prepared in Example 1 can achieve complete conversion at 340°C. At every temperature point in the figure, the methanol conversion rate of the catalyst prepared in Example 1 is significantly higher than that of the other catalysts, demonstrating its excellent activity.

[0072] pass Figure 3 It can be found that the CO selectivity of Example 1 maintains low CO selectivity from the beginning to complete conversion, and the CO selectivity does not exceed 3% until complete conversion, which meets the requirements of the fuel cell for CO selectivity.

[0073] Compared with Comparative Example 1, Example 1 found that using zirconium hydroxide as the zirconium metal source can make zinc more evenly dispersed on the surface of zirconium, thereby greatly improving the activity.

[0074] In general, the catalyst provided by the present invention plays an especially important role in the catalysis of methanol steam reforming to produce hydrogen.

[0075] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the explanations of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A zinc-based composite oxide catalyst, characterized in that The catalyst is prepared from a zinc precursor salt and zirconium hydroxide; its composition is xZnO-yZrO2, wherein x is the molar number of ZnO in the catalyst, y is the molar number of ZrO2 in the catalyst, and x / y is 0.01-1.

2. A zinc-based composite oxide catalyst according to claim 1, characterized in that: x / y is 0.01~0.

5.

3. A method for preparing a zinc-based composite oxide catalyst according to any one of claims 1 to 2, characterized in that: The following steps are involved: The zinc precursor salt and zirconium hydroxide are mixed and dried, and then calcined to obtain a zinc-based composite oxide catalyst.

4. The method for preparing a zinc-based composite oxide catalyst according to claim 3, wherein: The zinc precursor salt includes zinc chloride, zinc acetate, zinc nitrate hexahydrate or basic zinc carbonate.

5. The method for preparing a zinc-based composite oxide catalyst according to claim 3, wherein: The molar ratio of the zinc precursor salt to zirconium hydroxide is 0.01 to 1:

1.

6. The method for preparing a zinc-based composite oxide catalyst according to claim 3, characterized in that: During the drying process, the temperature is 60-120°C and the time is 4-12 hours; During the calcination process, the temperature is 300-600° C. and the calcination time is 2-8 hours.

7. Use of the zinc-based composite oxide catalyst according to any one of claims 1 to 2 in methanol reforming to produce hydrogen.

8. A method for producing hydrogen by reforming methanol, characterized in that: The following steps are involved: The zinc-based composite oxide catalyst according to any one of claims 1 to 2 is sieved and loaded into a fixed bed reactor to catalyze methanol steam reforming to produce hydrogen.

9. The method for producing hydrogen by methanol reforming according to claim 8, characterized in that: During the catalytic reaction, the temperature is 250-450°C.

10. The method for producing hydrogen by methanol reforming according to claim 8, characterized in that: During the catalytic reaction, the preferred reaction temperature range is 280°C to 360°C.

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