Preparation method and application of Ru / ZnO catalyst

Abstract

The present invention provides a method for preparing a Ru / ZnO catalyst and its application, and provides a method for preparing a Ru / ZnO ruthenium-zinc enzyme-mimicking catalyst for low-temperature hydrogen production from formaldehyde and water. The catalyst can produce 2546 mol mol of hydrogen in the liquid-phase reforming of formaldehyde-water at atmospheric pressure and 25°C for 1 hour. Ru ‑1 At 5°C, the hydrogen production can reach 1452 mol mol Ru ‑1 . The preparation method comprises the following steps: a first step of loading the precious metal Ru by a traditional impregnation method, and a second step of reducing the catalyst under an inert atmosphere. The present invention prepares a catalyst having oxidase-like catalytic activity and achieves excellent catalytic activity of the catalyst in a formaldehyde-water system. Under mild reaction conditions, formaldehyde hydrogen production can be achieved using a small amount of catalyst. At the same time, the catalyst has the advantages of high catalytic activity, high product selectivity, and high stability, providing a novel and effective method for preparing an efficient formaldehyde hydrogen production catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and relates to a Ru / ZnO catalyst with oxidase-like activity, a preparation method thereof, and application of the catalyst in formaldehyde-water liquid phase reforming hydrogen production reaction. Background Art

[0002] As the total population grows, people's demand for fossil energy is also increasing. The development of new energy sources that can replace fossil energy is crucial to human survival and development.

[0003] Hydrogen is a clean, pollution-free, energy-dense, and sustainable secondary energy source, considered one of the most promising energy carriers. Currently, hydrogen production methods primarily involve pyrolysis of fossil fuels (grey hydrogen production) and natural gas reforming (blue hydrogen production). While hydrogen itself is clean, these production methods generate significant carbon emissions during the production process, hindering sustainable development. In contrast, combining renewable energy with reforming hydrogen production technology to produce "green hydrogen" can achieve zero carbon emissions.

[0004] The current utilization of hydrogen energy still faces the problem of high costs in hydrogen production, storage, and transportation. Using liquid chemicals as hydrogen carriers and then releasing hydrogen in situ through catalytic reactions to provide fuel for power equipment can simply and effectively solve the high storage and transportation costs. Formaldehyde, as a liquid organic compound with high hydrogen content and easy production, has unique advantages in storage and transportation. The reforming of formaldehyde and water to produce hydrogen can further increase hydrogen release and effectively solve the problem of hydrogen production, greatly promoting the utilization of hydrogen energy, especially its application in automotive fuel cells.

[0005] To achieve efficient utilization of the produced hydrogen, it is still urgent to develop a catalyst that can improve the activity and stability of the formaldehyde-water liquid phase reforming hydrogen production reaction under milder reaction conditions, while further reducing the particle size of the metal Ru particles in the catalyst to inhibit the formation of CO. Summary of the Invention

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0007] First, the present invention provides a method for preparing a Ru / ZnO catalyst, comprising the following steps:

[0008] S1. The noble metal Ru is loaded onto the ZnO carrier by an impregnation method to prepare a Ru / ZnO catalyst, wherein the loading amount of the noble metal Ru is 0.1 wt%.

[0009] Preferably, step S1 comprises: mixing a ruthenium chloride aqueous solution, a solvent ethanol and a ZnO carrier, removing the solvent from the obtained mixture and then calcining it to obtain a Ru / ZnO catalyst.

[0010] Preferably, the calcination treatment should be carried out in a 5% H2 / Ar mixed gas by heating the temperature to 350°C at a rate of 5°C / min and calcining for 2 hours.

[0011] In addition, the present invention also discloses a Ru / ZnO catalyst that exhibits a special oxidase-like catalytic activity in the hydrogen production process of formaldehyde-water liquid phase reforming. Under mild conditions of atmospheric pressure and 25°C for 1 h, the hydrogen production rate can reach 2546 mol mol Ru −1 .

[0012] Preferably, a Ru / ZnO catalyst has metal Ru nanoparticles with a size of 1-2 nm supported thereon. Compared with the prior art, nanoparticles of this size have high dispersion and better activity.

[0013] The technical solution of the present invention has the following beneficial effects:

[0014] 1. The preparation method of the present invention has simple steps and operations, mild conditions, readily available raw materials, and easy-to-control reaction conditions.

[0015] 2. The catalyst synthesized by the present invention has unique oxidase-like catalytic activity and has good formaldehyde reforming hydrogen production activity under normal pressure and low temperature conditions.

[0016] 3. After the catalyst is added to the formaldehyde-water solution, hydrogen is released instantly, and the catalyst does not produce CO gas that poisons the catalyst in the formaldehyde-water system.

[0017] 4. The catalyst has good stability, is easy to recycle, the product is easy to purify, is environmentally friendly and energy-saving, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Transmission electron micrographs (a) and (b) provided for Example 1;

[0019] Figure 2 Schematic diagram of the catalyst cycle stability test results in Example 3. DETAILED DESCRIPTION

[0020] The present invention discloses a method for loading precious metal Ru onto a ZnO catalyst material by an impregnation method and its application in hydrogen production in a formaldehyde-water liquid phase system. The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments.

[0021] Embodiment 1:

[0022] Preparation of Ru / ZnO catalyst

[0023] At room temperature, 300 mg of ZnO was uniformly dispersed in 30 mL of ethanol. After stirring for 0.5 h, 60 μL of a 5 mg / mL aqueous solution of ruthenium chloride was added dropwise to the suspension. Stirring was continued for 2 h, and the mixture was heated to 80°C and maintained at this temperature until the ethanol was completely evaporated to obtain a light gray powder. The mixture was then heated to 350°C in a 5% H2 / Ar mixture at a rate of 5°C / min and calcined for 2 h. The precious metal loading was then 0.1 wt%.

[0024] like Figure 1 (a) and Figure 1 As shown in (b), Figure 1 The lattice fringe spacing of the small bright spot particles on the surface of the larger particles in (a) is 0.23 nm, corresponding to the (111) crystal plane of Ru nanoparticles, indicating that Figure 1 The small bright spots on the surface of the larger particles in (a) are metal Ru nanoparticles, which are successfully loaded onto ZnO. The particle size distribution of the small particles in the figure shows that the size of the metal Ru nanoparticles is 1-2nm. Compared with the existing technology, this size has high dispersion and better activity.

[0025] Experimental Example 1: Hydrogen production using Ru / ZnO catalyst formaldehyde-water liquid phase system

[0026] (1) Pour 20 mL of 18.5 mL of H2O and 1.5 mL of HCHO into a 100 mL flask, and then add 1.0 mol / L NaOH (molar concentration based on the total HCHO / H2O volume) to form a mixed solution;

[0027] (2) Weigh 5 mg of the catalyst and evenly disperse it in the mixture (1) above and seal the flask with a rubber stopper. Place the flask on a magnetic stirring furnace that has been heated to 25°C and stir.

[0028] (3) The gas composition was quantitatively analyzed and recorded using a gas chromatograph. The hydrogen yield on the Ru / ZnO catalyst was 2456 mol mol after 1 h of reaction. Ru -1 .

[0029] Experimental Example 2:

[0030] The difference from Experimental Example 1 is that in step (2), 5 mg of the catalyst was weighed and uniformly dispersed in the mixed solution (1) and sealed with a rubber stopper. The flask was placed on a magnetic stirring furnace that was previously controlled to 5°C and stirred.

[0031] (3) The gas composition was quantitatively analyzed and recorded using a gas chromatograph. The hydrogen yield on the Ru / ZnO catalyst was 1452 mol mol after 1 h of reaction. Ru -1 As can be seen, even at relatively low temperatures, the hydrogen production rate remains high. Therefore, this catalyst can be used to continuously supply high-calorific-value clean energy at low temperatures, greatly promoting the utilization of hydrogen energy, especially in automotive fuel cells, which is crucial for alleviating the global energy and environmental crisis.

[0032] Experimental Example 3: Catalyst Cycling Stability Test

[0033] Catalyst stability is also an important factor in evaluating catalytic performance. Weigh 5 mg of catalyst and evenly disperse it in a solution of 18.5 mL of H₂O and 1.5 mL of HCHO. Then, add a 1 mol / L NaOH solution (the molar concentration is based on the total HCHO / H₂O volume). The mixture is sealed with a rubber stopper and the reaction is carried out at 25°C. One reaction cycle lasts approximately 1 hour. The catalyst can be separated by centrifugation and recycled without treatment. Five cycles were tested.

[0034] Figure 2 The test results of hydrogen production at different reaction cycles and different times on Ru / ZnO catalyst are shown in Figure 2. The results show that the H2 production of Ru / ZnO catalyst is 2891 mol mol in the initial reaction of 1 h. Ru −1 After 5 h of reaction, the H2 production can still reach 2456 mol mol Ru −1 The Ru / ZnO catalyst maintained strong hydrogen production activity even after 5 hours of reaction, demonstrating excellent catalytic stability. Furthermore, no byproduct CO was detected by chromatography during the reaction, demonstrating the Ru / ZnO catalyst's excellent selectivity. Therefore, the Ru / ZnO catalyst exhibited excellent catalytic activity, selectivity, and stability in the low-temperature formaldehyde-water liquid phase reaction.

[0035] The above experimental results show that the catalyst Ru / ZnO has high recycling properties in the formaldehyde-water liquid phase system.

[0036] Comparative Example 1: Preparation of Ru / Al2O3 Catalyst

[0037] Ru / Al2O3 was prepared using a traditional impregnation method. At room temperature, 300 mg of Al2O3 was uniformly dispersed in 30 mL of ethanol. After stirring for 2 hours, 60 μL of a 5 mg / mL aqueous ruthenium chloride solution was added dropwise to the suspension. Stirring was continued for another 2 hours, and the mixture was heated to 80°C and maintained at this temperature until the ethanol was completely evaporated. Finally, the Ru / Al2O3 catalyst was calcined at 350°C in a 5% H2 / Ar atmosphere for 2 hours to obtain the catalyst. The noble metal loading was 0.1 wt%.

[0038] Hydrogen production from formaldehyde-water liquid phase system using Ru / Al2O3 catalyst

[0039] (1) Pour 20 mL of 18.5 mL of H2O and 1.5 mL of HCHO into a 100 mL flask, and then add 1.0 mol / L NaOH (molar concentration based on the total HCHO / H2O volume) to form a mixed solution;

[0040] (2) Weigh 5 mg of the catalyst and evenly disperse it in the mixture (1) above and seal the flask with a rubber stopper. Place the flask on a magnetic stirring furnace that has been heated to 25°C and stir.

[0041] (3) The gas composition was quantitatively analyzed and recorded using a gas chromatograph. The hydrogen yield on the Ru / Al2O3 catalyst was 402 mol mol after 1 h of reaction. Ru -1 , much lower than that of catalyst Ru / ZnO.

[0042] Comparative Example 2: Preparation of Ru / TiO2 Catalyst

[0043] Ru / TiO2 was prepared using a traditional impregnation method. At room temperature, 300 mg of TiO2 was uniformly dispersed in 30 mL of ethanol. After stirring for 2 hours, 60 μL of a 5 mg / mL aqueous ruthenium chloride solution was added dropwise to the suspension. Stirring was continued for another 2 hours, and the mixture was heated to 80°C and maintained at this temperature until the ethanol was completely evaporated. Finally, the Ru / Al2O3 catalyst was calcined at 350°C in a 5% H2 / Ar atmosphere for 2 hours to obtain the catalyst. The precious metal loading was 0.1 wt%.

[0044] Hydrogen production from formaldehyde-water liquid phase system using Ru / TiO2 catalyst

[0045] (1) Pour 20 mL of 18.5 mL of H2O and 1.5 mL of HCHO into a 100 mL flask, and then add 1.0 mol / L NaOH (molar concentration based on the total HCHO / H2O volume) to form a mixed solution;

[0046] (2) Weigh 5 mg of the catalyst and evenly disperse it in the mixture (1) above and seal the flask with a rubber stopper. Place the flask on a magnetic stirring furnace that has been heated to 25°C and stir.

[0047] (3) The gas composition was quantitatively analyzed and recorded using a gas chromatograph. The hydrogen yield on the Ru / TiO2 catalyst was 947 mol mol after 1 h of reaction. Ru -1 , much lower than that of catalyst Ru / ZnO.

[0048] Comparative Example 3: Preparation of Ru / ZnO Catalyst

[0049] Ru / ZnO was prepared using a traditional impregnation method. At room temperature, 300 mg of ZnO was uniformly dispersed in 30 mL of ethanol. After stirring for 2 hours, 120 μL of a 5 mg / mL ruthenium chloride aqueous solution was added dropwise to the suspension. Stirring was continued for another 2 hours, and the mixture was heated to 80°C and maintained at this temperature until the ethanol was completely evaporated. Finally, the Ru / ZnO catalyst was calcined at 350°C in a 5% H2 / Ar atmosphere for 2 hours to obtain the catalyst. The noble metal loading was 0.2 wt%.

[0050] Hydrogen production from formaldehyde-water liquid phase system using Ru / ZnO catalyst

[0051] (1) Pour 20 mL of 18.5 mL of H2O and 1.5 mL of HCHO into a 100 mL flask, and then add 1.0 mol / L NaOH (molar concentration based on the total HCHO / H2O volume) to form a mixed solution;

[0052] (2) Weigh 5 mg of the catalyst and evenly disperse it in the mixture (1) above and seal the flask with a rubber stopper. Place the flask on a magnetic stirring furnace that has been heated to 25°C and stir.

[0053] (3) The gas composition was quantitatively analyzed and recorded using a gas chromatograph. The hydrogen yield on the Ru / ZnO catalyst was 1435 mol mol after 1 h of reaction. Ru -1 , which is significantly lower than that of the Ru / ZnO catalyst with a noble metal loading of 0.1 wt%.

[0054] Comparative Example 4: Preparation of Ru / ZnO Catalyst

[0055] Ru / ZnO was prepared using a traditional impregnation method. At room temperature, 300 mg of ZnO was uniformly dispersed in 30 mL of ethanol. After stirring for 2 hours, 300 μL of a 5 mg / mL aqueous ruthenium chloride solution was added dropwise to the suspension. Stirring was continued for another 2 hours, and the mixture was heated to 80°C and maintained at this temperature until the ethanol was completely evaporated. Finally, the Ru / ZnO catalyst was calcined at 350°C in a 5% H2 / Ar atmosphere for 2 hours to obtain the catalyst. The noble metal loading was 0.5 wt%.

[0056] Hydrogen production from formaldehyde-water liquid phase system using Ru / ZnO catalyst

[0057] (1) Pour 20 mL of 18.5 mL of H2O and 1.5 mL of HCHO into a 100 mL flask, and then add 1.0 mol / L NaOH (molar concentration based on the total HCHO / H2O volume) to form a mixed solution;

[0058] (2) Weigh 5 mg of the catalyst and evenly disperse it in the mixture (1) above and seal the flask with a rubber stopper. Place the flask on a magnetic stirring furnace that has been heated to 25°C and stir.

[0059] (3) The gas composition was quantitatively analyzed and recorded using a gas chromatograph. The hydrogen yield on the Ru / ZnO catalyst was 667 mol mol after 1 h of reaction. Ru -1 , which is significantly lower than that of the Ru / ZnO catalyst with a noble metal loading of 0.2 wt%.

[0060] Comparative Example 5: Preparation of Ru / ZnO Catalyst

[0061] Ru / ZnO was prepared using a traditional impregnation method. At room temperature, 300 mg of ZnO was uniformly dispersed in 30 mL of ethanol. After stirring for 2 hours, 600 μL of a 5 mg / mL aqueous ruthenium chloride solution was added dropwise to the suspension. Stirring was continued for another 2 hours, and the mixture was heated to 80°C and maintained at this temperature until the ethanol was completely evaporated. Finally, the Ru / ZnO catalyst was calcined at 350°C in a 5% H2 / Ar atmosphere for 2 hours to obtain the catalyst. The noble metal loading was 1.0 wt%.

[0062] Hydrogen production from formaldehyde-water liquid phase system using Ru / ZnO catalyst

[0063] (1) Pour 20 mL of 18.5 mL of H2O and 1.5 mL of HCHO into a 100 mL flask, and then add 1.0 mol / L NaOH (molar concentration based on the total HCHO / H2O volume) to form a mixed solution;

[0064] (2) Weigh 5 mg of the catalyst and evenly disperse it in the mixture (1) above and seal the flask with a rubber stopper. Place the flask on a magnetic stirring furnace that has been heated to 25°C and stir.

[0065] (3) The gas composition was quantitatively analyzed and recorded using a gas chromatograph. The hydrogen yield on the Ru / ZnO catalyst was 374 mol mol after 1 h of reaction. Ru -1 , which is significantly lower than that of the Ru / ZnO catalyst with a noble metal loading of 0.5wt%.

[0066] The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For ordinary researchers in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. Application of a Ru / ZnO catalyst in the liquid phase reforming of formaldehyde-water to produce hydrogen at normal pressure and low temperature, characterized in that: The preparation method of the Ru / ZnO catalyst is: The noble metal Ru was loaded onto the ZnO carrier by an impregnation method to prepare a Ru / ZnO catalyst, wherein the noble metal Ru loading amount was 0.1 wt % and the low temperature was 25°C.

2. The use according to claim 1, characterized in that: The specific steps are as follows: A ruthenium chloride aqueous solution, a solvent ethanol and the ZnO carrier are mixed, and the obtained mixture is subjected to calcination after the solvent ethanol is removed to obtain a Ru / ZnO catalyst.

3. The use according to claim 2, characterized in that The size of the metal Ru nanoparticles supported by the catalyst is 1-2 nm.

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