Titanium-induced interface engineering strategy for hydrogen production by reforming methanol steam

Abstract

The invention belongs to the technical field of catalyst preparation, relates to a titanium-induced interface engineering strategy for hydrogen production through methanol steam reforming, and particularly provides a preparation method of a Ti-doped Cu / CeO2 catalyst and application of the Ti-doped Cu / CeO2 catalyst in hydrogen production through methanol steam reforming. The method comprises the following steps: by taking a copper source, a cerium source and a titanium source as precursors, oxalic acid as a complex and ethanol as a reaction medium, reacting, aging, drying and roasting to prepare the Ti-doped Cu / CeO2 catalyst. The preparation method is simple, raw materials are easy to obtain, the cost is low, the preparation process is economical and efficient, and the prepared catalyst is high in activity and good in stability and can efficiently catalyze CH3OH to be oxidized into CO2 and H2 at the low temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and more specifically relates to a titanium-induced interfacial engineering strategy for hydrogen production by methanol steam reforming. Background Art

[0002] As a highly efficient and clean secondary energy form, at the current stage, industrial hydrogen production mainly relies on technical routes such as water electrolysis, hydrocarbon steam reforming, and methanol reforming. Among them, the methanol steam reforming (MSR) technology is recognized as an ideal technical choice for distributed hydrogen supply scenarios due to the significant advantages of methanol itself, such as a relatively high hydrogen storage density, relatively mild reaction conditions, and a theoretical hydrogen production efficiency of up to 75%. Compared with other hydrogen production technologies, the MSR technology not only has obvious advantages in equipment investment costs (the cost can be reduced by more than 40% compared with proton exchange membrane water electrolysis technology), but also does not produce corrosive by-products during the reaction process, and has a high system integration degree. These characteristics make it particularly suitable for small and medium-sized hydrogen production application scenarios, showing broad application prospects and high research and promotion value. However, the existing catalyst systems still have significant bottlenecks in terms of activity, stability, and product selectivity, restricting their large-scale application.

[0003] Currently, research mainly focuses on the development and optimization of noble metal (Pt / Pd) and Cu-based catalyst systems. Although noble metal-based catalysts (such as Pt, Pd) have high thermal stability and anti-coking ability, their high cost and resource scarcity limit industrial applications [J. Am. Chem. Soc. 2021, 143, 12074 - 12081; J. Am. Chem. Soc. 2023, 145, 905 - 918]. At the same time, the noble metal loading is positively correlated with CO selectivity. Although a high loading can improve activity, it exacerbates CO generation, forming an "activity-selectivity" trade-off dilemma [ACS Catal. 2022, 12, 2714 - 2721].

[0004] In contrast, copper-based catalysts (such as Cu / ZnO / Al2O3) have the advantage of low-temperature activity, but are easily deactivated due to copper particle sintering at high temperatures, and have insufficient anti-coking ability, resulting in a short catalyst life and frequent regeneration. In addition, copper-based catalysts are prone to induce the reverse water gas shift reaction (RWGS) during the reaction, leading to an increase in the concentration of by-product CO (usually >1%), and CO has a poisoning effect on fuel cell electrodes, requiring an additional purification device, increasing system complexity and cost. Summary of the Invention

[0005] The object of the present invention is to provide a titanium-induced interface engineering strategy for hydrogen production by methanol steam reforming. More specifically, it provides a preparation method of a Ti-doped Cu / CeO2 catalyst and its application in methanol steam reforming for hydrogen production. Titanium-based materials are regarded as ideal candidate carriers due to their excellent oxygen vacancy regulation ability and chemical stability. By optimizing the electronic structure and surface active site distribution of copper-based catalysts through titanium-induced interface engineering, the reaction path can be directionally regulated, side reactions can be inhibited, and the anti-sintering ability can be enhanced, thereby solving the problems existing in the above-mentioned copper-based catalysts.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention: provides a preparation method of a Ti-doped Cu / CeO2 catalyst, and the steps include:

[0008] Using copper source, cerium source and titanium source as precursors, oxalic acid as a complexing agent, and ethanol as a reaction medium, after reacting under vigorous stirring, aging, washing, drying and calcining, the Ti-doped Cu / CeO2 catalyst is obtained.

[0009] Further, the loading amount of Cu in the Ti-doped Cu / CeO2 catalyst is 20 wt.%.

[0010] The copper source provides the active component Cu, and its loading amount directly affects the number of active sites of the catalyst. In the titanium-induced Cu / CeO2 catalyst interface engineering strategy (Ti-doped Cu / CeO2 catalyst) provided by the present invention, the loading amount of Cu is limited to 20 wt.%. When the Cu loading amount is too high, Cu particles may agglomerate, resulting in a decrease in its dispersion on the CeO2 support, thereby affecting the number and exposure degree of active sites of the catalyst. In addition, too high a Cu loading amount may cover the active sites on the surface of CeO2, inhibit the redox performance of CeO2 and the formation of oxygen vacancies, and thus weaken the overall catalytic performance of the catalyst. When it is too low, the number of active sites of the catalyst will be significantly reduced, resulting in a decrease in the efficiency of the catalytic reaction. At the same time, the synergistic effect between Cu and CeO2 will also be limited, and the enhanced effect on the redox performance of CeO2 after Ti doping cannot be fully exerted. In addition, a low loading amount of Cu may not effectively promote the adsorption and activation of reactants, thereby affecting the performance of the catalyst in practical applications.

[0011] Further, the molar ratio of titanium in the titanium source to cerium in the cerium source is 0.05 - 0.5.

[0012] The doping ratio of titanium in the present invention will affect the performance of the catalyst. When the doping ratio is too high (molar ratio > 0.5), it will damage the stability of the CeO2 lattice, resulting in lattice distortion, thus affecting the redox performance of the catalyst and possibly weakening the synergistic effect between copper and CeO2, leading to a reduction in catalytic active sites and a decline in catalytic performance. When the doping ratio is too low (molar ratio < 0.05), the modification effect of titanium on CeO2 is not obvious, and the synergistic effect between titanium and copper cannot be fully exerted, resulting in insufficient redox performance and oxygen vacancy formation ability of the catalyst.

[0013] Further, the copper source includes at least one of copper nitrate trihydrate, copper chloride, copper acetate, and copper hydroxide.

[0014] Further, the cerium source includes at least one of cerium nitrate hexahydrate, cerium chloride, cerium acetate, and cerium hydroxide.

[0015] Further, the titanium source includes at least one of tetrabutyl titanate, titanium tetrachloride, titanium carbide, and titanium boride.

[0016] In the present invention, ethanol is used as the reaction medium. Due to its low polarity, it can slow down the hydrolysis rate, provide a uniform environment for the reaction, reduce the phase separation problem during the reaction, and promote the full contact of reactants and the efficient progress of the reaction.

[0017] Further, the rotation speed of the vigorous stirring is 200 - 600 rpm, and the time is 50 min.

[0018] Further, the aging is precipitation for 2 - 12 h.

[0019] Further, the washing is carried out by washing with ethanol at least once.

[0020] Further, the drying temperature is 120 °C.

[0021] Further, the calcination temperature is 550 °C, the heating rate is 5 °C / min, and the time is 4 - 5 h.

[0022] Under the calcination temperature defined in the present invention, multiple optimization effects can be achieved during the calcination process: it can avoid the residual oxalic acid due to too low temperature, thus affecting the purity and performance of the catalyst, and prevent side reactions (such as carbon deposition, etc.) due to too high temperature, reducing the activity and stability of the catalyst. A reasonable calcination temperature can ensure that Ti atoms can uniformly enter the CeO2 lattice to form a stable solid solution structure, and can also effectively inhibit the excessive sintering of Cu particles and maintain their high dispersion, thereby ensuring that the catalyst has abundant active sites and excellent catalytic performance.

[0023] Further, a step of grinding and sieving is also included before the calcination.

[0024] Optionally, the grinding and sieving is through a 40-60 mesh sieve.

[0025] The second technical solution of the present invention: Provide a Ti-doped Cu / CeO2 catalyst, and the Ti-doped Cu / CeO2 catalyst is prepared by the above preparation method.

[0026] The third technical solution of the present invention: Provide an application of the above Ti-doped Cu / CeO2 catalyst in the production of hydrogen by methanol steam reforming.

[0027] The fourth technical solution of the present invention: Provide a method for producing hydrogen by methanol steam reforming, and the method uses the above Ti-doped Cu / CeO2 catalyst to catalyze the steam reforming of methanol to produce hydrogen.

[0028] The fifth technical solution of the present invention: Provide a method for improving the low-temperature catalytic performance of a Cu / CeO2 catalyst in the production of hydrogen by methanol steam reforming, and the method is to perform Ti doping on the Cu / CeO2 catalyst;

[0029] The molar ratio of Ti to Ce in the catalyst after Ti doping is 0.05-0.5, and the Cu loading is 20 wt.%.

[0030] The low temperature is 150-200 °C.

[0031] The present invention discloses the following technical effects:

[0032] The preparation method of the present invention is simple, the raw materials are easy to obtain, and the cost is low, making the preparation process economical and efficient. Moreover, the prepared catalyst has high activity and good stability, and can efficiently catalyze the oxidation of CH3OH to CO2 and H2 at low temperatures.

[0033] The conversion rate of the Ti-doped Cu / CeO2 catalyst prepared by the present invention still remains above 80% after 100 h of use, and the conversion rate of methanol is as high as 40% at a low temperature of about 150 °C.

[0034] The method for preparing the Ti-doped Cu / CeO2 catalyst of the present invention adopts a simple preparation process and successfully constructs a catalyst with a mesoporous structure. The mesoporous structure of the catalyst significantly increases its specific surface area, provides an efficient mass transfer channel for the adsorption of reactants and the desorption of products, and thus accelerates the kinetic process of the catalytic reaction. In addition, the mesoporous structure also enhances the thermal stability and anti-coking performance of the catalyst, enabling it to maintain excellent catalytic activity and stability under complex reaction conditions, and having broad application prospects, especially meeting the requirements for efficient and stable catalysts in industrial catalytic reactions. Description of the Drawings

[0035] The accompanying drawings, which form a part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0036] Figure 1 For the methanol conversion rate of the catalysts prepared in Example 1 and Comparative Examples 1-2 at 150-300 °C.

[0037] Figure 2 For the methanol stability of the catalysts prepared in Example 1 and Comparative Examples 1-2 at 250 °C.

[0038] Figure 3 For the XPS spectra of the catalysts prepared in Example 1 and Comparative Examples 1-2.

[0039] Figure 4 For the nitrogen adsorption-desorption isotherm curves of the catalysts prepared in Example 1 and Comparative Examples 1-2.

[0040] Figure 5 For the pore size distribution curves of the catalysts prepared in Example 1 and Comparative Examples 1-2. Detailed Description of the Invention

[0041] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation to the present invention, but rather as a more detailed description of certain aspects, characteristics, and embodiments of the present invention.

[0042] It should be understood that the terms used in the present invention are only for describing particular embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0043] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0044] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the specification of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0045] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0046] It should be noted that the operations not detailed in the present invention are all conventional operating means in the art and are not the focus of the present invention.

[0047] Unless otherwise specified, normal temperature and room temperature referred to in the specific embodiments of the present invention both refer to 20 - 30 °C.

[0048] The raw materials and reagents used in the specific embodiments of the present invention are all commercially available products, and the purchase channels do not affect the realization of the technical effects.

[0049] Example 1

[0050] Cu / Ti 0.1 The preparation steps of the CeO2 catalyst (the loading amount of Cu is 20 wt.%) include:

[0051] S1. Mix 60 mmol of copper nitrate trihydrate, 90 mmol of cerium nitrate hexahydrate, 10 mmol of tetrabutyl titanate and 1 mol of ethanol, and ultrasonically disperse and dissolve to obtain a mixed solution;

[0052] S2. Dissolve oxalic acid in ethanol to prepare an oxalic acid ethanol solution with a concentration of 0.6 M;

[0053] S3. Mix the mixed solution in step S1 with the oxalic acid ethanol solution in step S2 according to a volume ratio of 1:5, vigorously stir (400 rpm) at room temperature for 50 min, let it stand for precipitation for 2 h, and then centrifuge to obtain a solid reaction product;

[0054] S4. Wash the solid reaction product obtained in step S3 three times with ethanol, dry it overnight in an oven at 120 °C, grind it, pass it through a 60 - mesh sieve, and then calcine it in a muffle furnace at 550 °C (heating rate is 5 °C / min) in an air atmosphere for 5 h to obtain the Cu / Ti 0.1 CeO2 catalyst.

[0055] Comparative Example 1

[0056] The preparation steps of the Cu / TiO2 catalyst (the loading amount of Cu is 20 wt.%) include:

[0057] S1. Mix 2.5 mmol of copper nitrate trihydrate, 10 mmol of tetrabutyl titanate and 1 mol of ethanol, and disperse and dissolve them by ultrasonic wave to obtain a mixed solution;

[0058] S2. Dissolve oxalic acid in ethanol to prepare an ethanolic oxalic acid solution with a concentration of 0.6 M;

[0059] S3. Mix the mixed solution in step S1 with the ethanolic oxalic acid solution in step S2 according to a volume ratio of 1:5, stir vigorously (400 rpm) at room temperature for 50 min, let it stand and precipitate for 2 h, and then centrifuge to obtain a solid reaction product;

[0060] S4. Wash the solid reaction product obtained in step S3 three times with ethanol, dry it overnight in an oven at 120 °C, grind it and pass it through a 60-mesh sieve, and then calcine it in a muffle furnace at 550 °C (heating rate: 5 °C / min) in an air atmosphere for 5 h to obtain a Cu / TiO2 catalyst.

[0061] Comparative Example 2

[0062] The preparation steps of the Cu / CeO2 (Cu loading is 20 wt.%) catalyst include:

[0063] S1. Mix 0.3146 mol of copper nitrate trihydrate, 10 mol of cerium nitrate hexahydrate and 1 mol of ethanol, and disperse and dissolve them by ultrasonic wave to obtain a mixed solution;

[0064] S2. Dissolve oxalic acid in ethanol to prepare an ethanolic oxalic acid solution with a concentration of 0.6 M;

[0065] S3. Mix the mixed solution in step S1 with the ethanolic oxalic acid solution in step S2 according to a volume ratio of 1:5, stir vigorously (400 rpm) at room temperature for 50 min, let it stand and precipitate for 2 h, and then centrifuge to obtain a solid reaction product;

[0066] S4. Wash the solid reaction product obtained in step S3 three times with ethanol, dry it overnight in an oven at 120 °C, grind it and pass it through a 60-mesh sieve, and then calcine it in a muffle furnace at 550 °C (heating rate: 5 °C / min) in an air atmosphere for 5 h to obtain a Cu / CeO2 catalyst.

[0067] Test Example

[0068] Respectively take 0.2 g of the catalysts prepared in Example 1 and Comparative Examples 1-2 and load them into a tubular furnace reactor. Pass a mixed gas of N2, methanol and water into the tubular furnace reactor equipped with the catalyst, and pretreat it at normal pressure and 350 °C for 2 h;

[0069] The reaction gas was switched to a CH3OH / H2O / N2 mixed gas (the feed space velocity of N2 was 40.8 mL / min, the feed space velocity of CH3OH / H2O was 0.01 mL / min, and the molar ratio of CH3OH / H2O was 1:1.3), and the reaction was carried out at a reaction temperature of 150 - 300 °C under atmospheric pressure.

[0070] Figure 1 For the catalysts prepared in Example 1 and Comparative Examples 1 - 2, the methanol conversion rate at 150 - 300 °C.

[0071] Figure 2 For the catalysts prepared in Example 1 and Comparative Examples 1 - 2, the methanol stability at 250 °C.

[0072] From Figure 1 - Figure 2 It can be seen that the Cu / Ti 0.1 CeO2 catalyst provided in Example 1 of the present invention had a conversion rate of 100% for CH3OH at a reaction temperature of 250 °C under atmospheric pressure. At a reaction temperature of 250 °C under atmospheric pressure, the conversion rate of the Cu / TiO2 catalyst for CH3OH was 93%. At a reaction temperature of 250 °C under atmospheric pressure, the conversion rate of the Cu / CeO2 catalyst for CH3OH was 99.7%. The conversion rate of the catalyst prepared in Example 1 remained above 80% after 100 h of use, and the conversion rate of methanol was as high as 40% at a low temperature of about 150 °C. It can be seen that the catalyst prepared by the present invention has a good low-temperature methanol activation effect.

[0073] Figure 3 XPS diagrams of the catalysts prepared in Example 1 and Comparative Examples 1 - 2.

[0074] Figure 4 N2 adsorption and desorption curve diagrams of the catalysts prepared in Example 1 and Comparative Examples 1 - 2.

[0075] Figure 5 Pore size distribution diagrams of the catalysts prepared in Example 1 and Comparative Examples 1 - 2.

[0076] From Figure 4 - Figure 5 It can be seen that the catalyst prepared by the present invention has a mesoporous structure.

[0077] Example 2

[0078] Cu / Ti 0.3 The preparation steps of the CeO2 (the Cu loading was 20 wt.%) catalyst included:

[0079] S1. 0.3146 mol of copper nitrate trihydrate, 70 mmol of cerium nitrate hexahydrate, 30 mmol of tetrabutyl titanate, and 1 mol of ethanol were mixed and ultrasonically dispersed and dissolved to obtain a mixed solution;

[0080] S2 - S4 are the same as those in Example 1, and the obtained product is Cu / Ti 0.3 CeO2 catalyst.

[0081] The reaction temperature is 250 °C, and under atmospheric pressure, the Cu / Ti 0.3 CeO2 catalyst has a conversion rate of 100% for CH3OH.

[0082] Example 3

[0083] Cu / Ti 0.5 The preparation steps of the CeO2 (the Cu loading is 20 wt.%) catalyst include:

[0084] S1. Mix 0.3146 mol of copper nitrate trihydrate, 50 mmol of cerium nitrate hexahydrate, 50 mmol of tetrabutyl titanate and ethanol mol, and ultrasonically disperse and dissolve them to obtain a mixed solution;

[0085] S2 - S4 are the same as those in Example 1, and the obtained product is Cu / Ti 0.5 CeO2 catalyst.

[0086] The reaction temperature is 250 °C, and under atmospheric pressure, the Cu / Ti 0.5 CeO2 catalyst has a conversion rate of 100% for CH3OH.

[0087] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same and similar parts among the embodiments, reference can be made to each other.

[0088] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a Ti-doped Cu / CeO2 catalyst, characterized in that the steps Comprising: Using a copper source, a cerium source, and a titanium source as precursors, oxalic acid as a complexing agent, and ethanol as a reaction medium. After the reaction, through aging, drying, and calcination, the Ti-doped Cu / CeO2 catalyst is obtained.

2. The preparation method according to claim 1, characterized in that, The loading amount of Cu in the Ti-doped Cu / CeO2 catalyst is 20 wt.%; and / or, the molar ratio of titanium in the titanium source to cerium in the cerium source is 0.05 - 0.

5.

3. The preparation method according to claim 1, wherein The copper source includes at least one of copper nitrate trihydrate, copper chloride, copper acetate, and copper hydroxide; and / or, the cerium source includes at least one of cerium nitrate hexahydrate, cerium chloride, cerium acetate, and cerium hydroxide; and / or, the titanium source includes at least one of tetrabutyl titanate, titanium tetrachloride, titanium carbide, and titanium boride.

4. The preparation method according to claim 1, characterized in that, The reaction is carried out under stirring conditions, the stirring speed is 200 - 600 rpm, and the stirring time is 50 min; and / or, the aging is precipitation for 2 - 12 h.

5. The preparation method according to claim 1, characterized in that, The drying temperature is 120 °C; and / or, the calcination temperature is 550 °C, the heating rate is 5 °C / min, and the time is 4 - 5 h; and / or, before the calcination, there is also a step of grinding and sieving.

6. The preparation method according to claim 5, characterized in that, The grinding and sieving is through a 40 - 60 mesh sieve.

7. A Ti-doped Cu / CeO2 catalyst, characterized in that, The Ti-doped Cu / CeO2 catalyst is prepared by the preparation method according to any one of claims 1 - 6.

8. An application of the Ti-doped Cu / CeO2 catalyst according to claim 7 in the production of hydrogen by methanol steam reforming.

9. A method for producing hydrogen by steam reforming of methanol and water, characterized in that, The method uses the Ti-doped Cu / CeO2 catalyst according to claim 7 to catalyze the production of hydrogen by methanol steam reforming.

10. A method for improving the low-temperature catalytic performance of a Cu / CeO2 catalyst in methanol steam reforming for hydrogen production, characterized in that, The method is to perform Ti doping on the Cu / CeO2 catalyst; After the Ti doping, the molar ratio of Ti to Ce in the catalyst is 0.05 - 0.5, and the loading amount of Cu is 20 wt.%; The low temperature is 150 - 200 °C.

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