Ruthenium-based reforming hydrogen production catalyst and preparation method thereof

Abstract

The invention discloses a ruthenium-based reforming hydrogen production catalyst and a preparation method thereof, porous alumina is adopted as a catalyst carrier, loading of a ruthenium nano-catalyst is realized through a multi-step method, a ruthenium-based alumina composite catalyst is prepared, and a vacuum-assisted impregnation method is adopted to ensure that a precursor is fully impregnated in a carrier pore channel; through two-step roasting, metal active sites are uniformly dispersed on the surface of the carrier and are reduced into active metal. The ruthenium-based aluminum oxide catalyst has good catalytic activity and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil reforming hydrogen production, in particular to a ruthenium-based reforming hydrogen production catalyst and a preparation method thereof. BACKGROUND

[0002] Under the background of the global energy structure accelerating transformation towards low carbonization and cleanization, hydrogen energy has become a key link between traditional energy and renewable energy due to its core characteristics of clean and efficient, such as only water as combustion product, high energy conversion efficiency, and cross-seasonal storage. As an important product of petroleum refining, diesel is one of the most widely used fossil fuels in the world, with the outstanding advantage of high energy density. Relying on the hundred-year petroleum industry, it has formed a perfect storage and transportation infrastructure network covering exploration, refining, storage and transportation. Without large-scale new construction facilities, it can quickly adapt to the demand of hydrogen production. Compared with other hydrogen production raw materials such as methanol and ethanol, diesel has significant comprehensive advantages in raw material availability, energy density and storage and transportation cost, making it an important raw material for large-scale hydrogen production at the present stage, especially in the scenes of on-board mobile hydrogen production and distributed energy supply, which has irreplaceable application value. Diesel reforming hydrogen production technology converts complex hydrocarbons in diesel into synthesis gas mainly composed of hydrogen and carbon monoxide through the action of catalysts, and then improves the purity of hydrogen through water gas shift reaction, so as to obtain high-purity hydrogen product. It is one of the key technical approaches for current hydrogen production. However, the long-chain hydrocarbon molecules in diesel have complex molecular structures and are easy to crack and polymerize under high-temperature reaction conditions. The generated carbon deposits will cover the active sites of the catalyst and block the micropores of the carrier, resulting in rapid deactivation of the catalyst. At the same time, the sulfur elements in the reaction system will form stable sulfides with the metal active components, causing permanent poisoning of the catalyst. Therefore, how to efficiently convert complex hydrocarbons in diesel through catalytic reforming process while effectively inhibiting the generation of carbon deposition, sulfur poisoning and other side reactions to achieve high conversion rate has become the core bottleneck of the development of this technology. SUMMARY

[0003] The present application aims to provide a ruthenium-based reforming hydrogen production catalyst and a preparation method thereof, to solve the problems of low efficiency, low hydrogen content and catalyst carbon deposition of current diesel reforming catalysts.

[0004] In order to achieve the above requirements, the present application adopts the following technical scheme: a preparation method of a ruthenium-based reforming hydrogen production catalyst, which uses porous alumina as a catalyst carrier and realizes the loading of ruthenium nanocatalyst through a multi-step method to prepare a ruthenium-based alumina composite catalyst, including the following steps: S1, heat and calcine the high-purity spherical alumina carrier to remove water, organic impurities and volatile components in the micropores on the surface of the carrier; S2, the active metal source containing ruthenium is weighed and dissolved in deionized water to form a uniform transparent solution, the pH value is adjusted to 3.0-5.0, and the volume is made up to obtain an acidic precursor solution; S3, the active component is loaded by using an equal volume impregnation method, the alumina carrier is placed in a vacuum impregnation tank, and a vacuum state is maintained to remove air in the micropores of the carrier, and the acidic precursor solution of the active metal is added dropwise into the carrier, and the precursor solution is fully infiltrated and uniformly adsorbed on the surface and micropores of the carrier, and then dried; S4, the dried carrier-precursor composite is placed in a tube furnace, and calcination is performed to decompose the metal source on the surface of the carrier and further remove residual impurities; the calcination atmosphere is switched to high-purity hydrogen to reduce the oxidized metal species to a metallic state, and finally form highly dispersed metal-based active sites on the surface of the alumina carrier to obtain a ruthenium-based hydrogen reforming catalyst. Further, in the ruthenium-based hydrogen reforming catalyst, the mass fraction of RuO2 is 0.01%-1%.

[0005] Further, the active metal source also contains a Ni source.

[0006] Further, in S1, the high-purity spherical alumina carrier is placed in a muffle furnace, and programmed temperature calcination is performed at a heating rate of 5℃ / min, and the temperature is raised to 800℃ and held for 2h. Further, in S2, the active metal source is a chloride salt of the active metal.

[0007] Further, in S3, the following steps are included: S31. The total pore volume of the alumina carrier treated in S1 is determined, and an equal volume of the active metal precursor solution obtained in S2 is accurately measured according to the total pore volume data; S32. The alumina carrier is placed in a vacuum impregnation tank, the tank door is closed, and the vacuum is drawn to a vacuum degree of ≤-0.095MPa, and the vacuum state is maintained for 30min to remove air in the micropores of the carrier; S33. Under the condition of maintaining the vacuum, the active metal precursor solution is added dropwise into the carrier at a rate of 5mL / min, and the vacuum state is maintained for 60min after the addition is completed to ensure that the precursor solution is fully infiltrated and uniformly adsorbed on the surface and micropores of the carrier; S34. The impregnated carrier is transferred to a forced air drying oven and dried at a temperature of 110℃±5℃ for 12h to complete the drying process. Further, in S4, the carrier-precursor composite after drying in S3 is placed in a tube furnace, and calcination and reduction treatment are sequentially performed, including the following steps S41. Calcination treatment: air with a flow rate of 200 mL / min is introduced into the tube furnace as a calcination atmosphere, and a programmed temperature is adopted, with a temperature increasing rate of 5 DEG C / min, and when the temperature is increased to 500 DEG C, the temperature is kept for 3h, so that the ruthenium source on the surface of the carrier is decomposed into ruthenium oxide species, and further residual impurities are removed; S42. Reduction treatment: when the temperature in the tube furnace is reduced to 200 DEG C, the calcination atmosphere is switched to high-purity hydrogen, and the hydrogen flow rate is controlled to be 100 mL / min; a programmed temperature is continuously adopted, with a temperature increasing rate of 3 DEG C / min, and after the temperature is increased to 350 DEG C, the temperature is kept for 4h, so that the ruthenium oxide species is reduced to metallic ruthenium, and finally highly dispersed metal Ru-based active sites are formed on the surface of the alumina carrier, and the target ruthenium-based hydrogen reforming catalyst is obtained. Further, two active metals of Ni and Ru are adopted, and the molar ratio of Ni:Ru is 10:1.

[0008] Further, the concentration of NiCl2 in the mixed solution is 0.1 mol / L, the concentration of RuCl3 is 0.01 mol / L, and the pH is 3-5.

[0009] The ruthenium-based hydrogen reforming catalyst prepared by the preparation method.

[0010] Compared with the prior art, the beneficial effects of the present application are as follows: the vacuum-assisted impregnation method adopted in the present application ensures that the precursor is fully impregnated in the pore channel of the carrier, and through two-step calcination, the metal active sites are uniformly dispersed on the surface of the carrier and are reduced to active metals. The ruthenium-based alumina catalyst has good catalytic activity and stability. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 It is a catalytic reforming performance evaluation graph of Example 1; Figure 2 It is a full spectrum graph of X-ray photoelectron spectroscopy of the catalyst; Figure 3 It is an O1s fitting curve graph of the catalyst before and after the reforming reaction; Figure 4 It is a scanning electron microscope graph of the catalyst before the reforming reaction; Figure 5 It is a scanning electron microscope graph of the catalyst after the reforming reaction; Figure 6 It is a transmission electron microscope graph of the catalyst before and after the reforming reaction ((a) before the reaction, (b) after the reaction); Figure 7 It is a sample XRD spectrum; Figure 8 It is a SEM morphology graph of the catalysts of Examples 1-3 (a) 10Ni, b) 10Ni1Ru, c) 1Ru); Figure 9 It is a catalytic reforming performance evaluation graph of Example 2 Figure 10 Figure 3 is a graph for evaluating the catalytic reforming performance of Example 3. DETAILED DESCRIPTION

[0012] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application but not all the embodiments of the present application; the technical features designed in different embodiments of the present application can be combined with each other as long as they do not conflict with each other; all other embodiments obtained by a person of ordinary skill in the art without creative labor based on the embodiments of the present application are within the protection scope of the present application.

[0013] In the description of the present application, it should be noted that all the terms (including technical terms and scientific terms) used in the present application have the same meanings as those generally understood by a person of ordinary skill in the art to which the present application belongs, and should not be understood as a limitation on the present application; it should be further understood that the terms used in the present application should be understood as having meanings consistent with the meanings of these terms in the context of the present specification and the related art, and should not be understood in an idealized or overly formal sense, except as expressly defined in the present application.

[0014] Example 1 Step one: high-purity spherical alumina carrier is placed in a muffle furnace for programmed temperature calcination; the temperature rising rate is controlled at 5℃ / min, and the temperature is raised to 800℃ and kept for 2h; the calcination process removes the water, organic impurities and volatile components in the micropores on the surface of the carrier, providing a suitable surface structure for subsequent active component loading. Step two: RuCl3·3H2O is used as the ruthenium source, 2.074g of the ruthenium source is accurately weighed and dissolved in 900mL of deionized water; during the dissolution process, the stirring rate is controlled at 300rpm, and the stirring time is 30min, until a uniform transparent solution is formed; then the pH value of the solution is adjusted to 3.0-5.0 using a hydrochloric acid solution with a concentration of 1mol / L, poured into a volumetric flask and diluted to 1000mL to obtain a 0.01mol / L acidic ruthenium chloride solution. Step three: active component loading is carried out by equal volume impregnation, the specific operation is as follows: (1) first determine the total pore volume of the alumina carrier treated in step one, and accurately take an equal volume of the active metal precursor solution obtained in step two according to the pore volume data; (2) the alumina carrier is placed in a vacuum impregnation tank, the tank door is closed, vacuum is drawn to a vacuum degree of ≤-0.095MPa, and the vacuum state is maintained for 30min to remove the air in the micropores of the carrier; (3) Under the condition of maintaining vacuum, the active metal precursor solution is added to the carrier at a rate of 5 mL / min through a dripping device, and after the dripping is completed, the vacuum state is maintained for 60 min to ensure that the precursor solution is fully infiltrated and uniformly adsorbed on the surface of the carrier and in the micropores; (4) The impregnated carrier is transferred to a blast drying oven and dried at a temperature of 110℃±5℃ for 12 h to complete the drying process. Step four: The carrier-precursor composite dried in step three is placed in a tube furnace for calcination and reduction treatment in sequence, as follows: (1) Calcination treatment: Air with a flow rate of 200 mL / min is introduced into the tube furnace as a calcination atmosphere, and a programmed temperature rise is adopted with a heating rate of 5℃ / min. When the temperature rises to 500℃, the temperature is maintained for 3 h to decompose the ruthenium source on the surface of the carrier into ruthenium oxide species (mainly RuO2) and further remove residual impurities. (2) Reduction treatment: When the temperature in the tube furnace drops to 200℃, the calcination atmosphere is switched to high-purity hydrogen, and the hydrogen flow rate is controlled at 100 mL / min. A programmed temperature rise is continued with a heating rate of 3℃ / min. When the temperature rises to 350℃, the temperature is maintained for 4 h to reduce the ruthenium oxide species to metallic ruthenium, and finally form highly dispersed metal Ru-based active sites on the surface of the alumina carrier to obtain the target hydrogen reforming catalyst, which is named as 1Ru catalyst. 5 g of the hydrogen reforming catalyst is filled into a reaction tube with a diameter of 10 mm to form a catalyst bed, and quartz sand is added as a support layer. The reaction tube temperature is maintained at 750℃ by heating and maintaining the reaction tube in a reaction furnace. A metering pump is used to add diesel and water into the reaction tube, with a diesel flow rate of 1 mL / min and a water flow rate of 5 mL / min. The products are condensed and analyzed by gas chromatography, and the reforming performance results of Example 1 are shown in Table 1. Figure 1 The hydrogen content in the reforming gas is greater than 70%, indicating that the catalyst has good catalytic activity. As the reaction time increases, the hydrogen content in the reforming gas decreases, and the carbon dioxide content increases, indicating that the catalyst activity decreases.

[0015] Example 1 is tested by X-ray photoelectron spectroscopy, as shown in Table 2. Figure 2The d-band center of Ru is located at -1.2 eV, which is in good match with C-H bond (HOMO energy -9.8 eV), and the C-H bond can be weakened by d-electron back-donation (bond energy from 413 kJ / mol to 380 kJ / mol), which promotes the dissociation of alkanes. At the same time, the adsorption energy of O2 and H2O on Ru is moderate (-45 kJ / mol and -52 kJ / mol, respectively), which can activate the oxidant and avoid excessive oxidation (such as CO→CO2). X-ray photoelectron spectroscopy (XPS) studies show that there are Ru 0 species on the surface of the catalyst, and the binding energy of 4f 7 / 2 is located at 280.1 eV, and the strong interaction with the carrier can inhibit the sintering of particles. The binding energy of 4f 7 / 2 electrons is located at 280.0-280.2 eV, which can weaken the C-C and C-H bonds through d-electron back-donation, significantly reducing the activation energy of cracking and reforming reactions. The XPS full spectrum of the fresh reforming catalyst and the catalyst sample after the reforming reaction is shown in Figure 2 . The elements contained in the catalyst are Ru, Al, O, and C, which are consistent with the test results of XRF and elemental analysis. The position of the photoelectron spectrum of the elements does not change before and after the reforming reaction.

[0016] The O1s X-ray photoelectron spectroscopy of the fresh catalyst was tested and peak fitting was performed, as shown in Figure 3 . The peaks at 530.9 eV and 531.8 eV in the photoelectron spectrum of the catalyst before the reaction are lattice oxygen and oxygen adsorbed by oxygen vacancies, respectively, and the peak area ratio is 1.63 ( Figure 3 a). The position of the peak after peak fitting of the catalyst O1s after the reforming reaction does not change significantly, and the ratio of lattice oxygen and oxygen adsorbed by oxygen vacancies is 1.49 ( Figure 3 b), and the lattice oxygen is significantly reduced.

[0017] The scanning electron microscopy and transmission electron microscopy images of the ruthenium-based noble metal catalyst before and after participating in the oil reforming reaction are shown in Figure 4 、 Figure 5 and Figure 6 : The catalyst sample was characterized for its morphology and structure after the reforming reaction at a temperature above 750°C. Electron microscopy characterization shows that the Ru-based active particles are uniformly dispersed on the surface of Al2O3 (particle size 3-5 nm). From the comparison of Figure 4 and Figure 5 , it can be found that the Ru-based catalyst after the reaction has little change in micro-morphology compared with the original one, and there is no sintering phenomenon, and no obvious carbon deposition is observed, which shows that the catalyst is suitable for diesel steam reforming.

[0018] The types and contents of trace elements in the substance were determined by X-ray fluorescence analysis (XRF), and the substance composition analysis and chemical state research were carried out. The results are shown in Table 1. The main element components are Al and Ru. The content of RuO2 in the catalyst before the reaction is 0.21%.

[0019] Table 1: XRF element analysis results

[0020] The crystal structure of the sample was determined and analyzed by an X-ray diffractometer (XRD). According to the XRD analysis results, 35.3°, 57.7° and 66.4° are the XRD characteristic peaks of RuO2 (PDF: 97-001-5071), and 25.5°, 37.7°, 43.2°, 52.5° and 68.2° are the XRD characteristic peaks of aluminum oxide (PDF: 97-016-5594).

[0021] Example 2 Compared with Example 1, the preparation process of the precursor solution in Step 2 is as follows. The other process operations are the same as those in Example 1. The final catalyst is named as 10Ni catalyst.

[0022] Taking NiCl2·6H2O as the nickel source, 23.769 g of the ruthenium source was accurately weighed and dissolved in 900 mL of deionized water. During the dissolution process, the stirring rate was controlled at 300 rpm, and the stirring time was 30 min, until a uniform transparent solution was formed. Then the pH value of the solution was adjusted to 3.0-5.0 using a hydrochloric acid solution with a concentration of 1 mol / L, poured into a volumetric flask and diluted to 1000 mL, to obtain a 0.1 mol / L acidic nickel chloride solution.

[0023] Example 3 Compared with Example 1, the preparation process of the precursor solution in Step 2 is as follows. The other process operations are the same as those in Example 1. The final catalyst obtained is named as 10Ni1Ru catalyst.

[0024] 2.074 g of RuCl3·3H2O and 23.769 g of NiCl2·6H2O were accurately weighed and dissolved in 900 mL of deionized water. During the dissolution process, the stirring rate was controlled at 300 rpm, and the stirring time was 30 min, until a uniform transparent solution was formed. Then the pH value of the solution was adjusted to 3.0-5.0 using a hydrochloric acid solution with a concentration of 1 mol / L, poured into a volumetric flask and diluted to 1000 mL, to obtain a 0.01 mol / L ruthenium chloride and 0.1 mol / L nickel chloride acidic mixed solution.

[0025] The obtained catalyst samples of Examples 1-3 were tested by scanning electron microscopy, and the results are shown in Figure 8As shown, for the NiRu bimetallic Al2O3 support system, the addition of Ru can reduce the surface carbon deposition compared to the Ni-based catalyst.

[0026] The obtained example 2 and example 3 were subjected to reforming hydrogen production catalytic effect evaluation, the process was the same as example 1, and the results were respectively as shown in Figure 9 and Figure 10 Compared with example 1, the activity of the 10Ni catalyst in example 2 decreased, the hydrogen content was lower than that in example 1, and the carbon dioxide content exceeded that in example 1; the initial activity of the 10Ni1Ru catalyst in example 3 was equivalent to that in example 1, and the hydrogen content remained good with the extension of the reaction time, which was higher than that in example 1, indicating that the bimetallic catalyst in example 3 had better stability.

[0027] In summary, the Ru-based Al2O3 catalyst for efficient reforming hydrogen production provided by the present application has a relatively simple and efficient preparation process, the morphology and structure thereof are characterized in detail, the structure size thereof is nanoscale, and the active metal sites are well dispersed on the support. The performance of the catalyst for diesel reforming hydrogen production was evaluated and compared with the Ni-based catalyst and the NiRu bimetallic catalyst, the addition of single Ru enables the catalyst to have higher activity, but the activity decreases with the extension of the reaction time, and the NiRu bimetallic catalyst has good catalytic activity and stability.

[0028] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing a ruthenium-based reforming catalyst for hydrogen production, characterized by, A porous alumina is used as a catalyst carrier, and a ruthenium nano-catalyst is loaded by a multi-step method to prepare a ruthenium-based alumina composite catalyst, including the following steps: S1. High-purity spherical alumina carrier is heated and calcined to remove water, organic impurities and volatile components in the micropores on the surface of the carrier; S2. An active metal source containing ruthenium is weighed and dissolved in deionized water to form a uniform transparent solution, the pH value is adjusted to 3.0-5.0, and the volume is fixed to obtain an acidic precursor solution; S3. An equal-volume impregnation method is used to load the active component, the alumina carrier is placed in a vacuum impregnation tank, and the vacuum state is maintained to remove air in the micropores of the carrier, and the acidic precursor solution of the active metal is added dropwise to the carrier to ensure that the precursor solution is fully infiltrated and uniformly adsorbed on the surface and in the micropores of the carrier, and then dried; S4. The dried carrier-precursor composite is placed in a tube furnace for calcination to decompose the metal source on the surface of the carrier and further remove residual impurities; the calcination atmosphere is switched to high-purity hydrogen to reduce the oxidized metal species to a metallic state, and finally form highly dispersed metal-based active sites on the surface of the alumina carrier to obtain a ruthenium-based reforming hydrogen catalyst.

2. The method for preparing the ruthenium-based reforming hydrogen production catalyst according to claim 1, characterized in that, In the ruthenium-based reforming hydrogen catalyst, the mass fraction of RuO2 is 0.01%-1%.

3. The method for preparing the ruthenium-based reforming hydrogen production catalyst according to claim 1, characterized in that, The active metal source also contains a Ni source.

4. The method for preparing the ruthenium-based reforming hydrogen production catalyst according to claim 1, characterized in that, In S1, the high-purity spherical alumina carrier is placed in a muffle furnace and subjected to programmed temperature calcination at a heating rate of 5℃ / min, and then heated to 800℃ for 2h.

5. The method for preparing the ruthenium-based reforming hydrogen production catalyst according to claim 1, characterized in that, In S2, the active metal source is a chloride salt of an active metal.

6. The method for preparing the ruthenium-based reforming hydrogen production catalyst according to claim 1, characterized in that, S3 includes the following steps: S31. The total pore volume of the alumina carrier treated in S1 is determined, and an equal volume of the active metal precursor solution obtained in S2 is accurately measured according to the total pore volume data; S32. The alumina carrier is placed in a vacuum impregnation tank, the tank door is closed, and the vacuum degree is ≤-0.095MPa, and the vacuum state is maintained for 30min to remove air in the micropores of the carrier; S33. Under the condition of maintaining the vacuum, the active metal precursor solution is added dropwise to the carrier at a rate of 5mL / min, and the vacuum state is maintained for 60min after the addition is completed to ensure that the precursor solution is fully infiltrated and uniformly adsorbed on the surface and in the micropores of the carrier; S34. The impregnated carrier is transferred to a forced air drying oven and statically dried at a temperature of 110℃±5℃ for 12h to complete the drying process.

7. The method for preparing the ruthenium-based reforming hydrogen production catalyst according to claim 1, characterized in that, In S4, the carrier-precursor composite after drying in S3 is placed in a tube furnace for calcination and reduction treatment, including the following steps: S41. Calcination treatment: air with a flow rate of 200mL / min is introduced into the tube furnace as a calcination atmosphere, and programmed temperature heating is adopted at a heating rate of 5℃ / min, and when the temperature rises to 500℃, the temperature is maintained for 3h to decompose the ruthenium source on the surface of the carrier into an oxidized ruthenium species and further remove residual impurities; S42. Reduction treatment: when the temperature in the tube furnace is reduced to 200℃, the roasting atmosphere is switched to high-purity hydrogen, the hydrogen flow is controlled to be 100 mL / min; continue to use programmed heating, the heating rate is 3℃ / min, heat to 350℃ and keep for 4h, so that the ruthenium species in oxidation state is reduced to metallic ruthenium, and finally the highly dispersed metal Ru-based active sites are formed on the surface of the alumina carrier, and the target ruthenium-based hydrogen reforming catalyst is obtained.

8. The method for preparing the ruthenium-based reforming hydrogen production catalyst according to claim 3, characterized in that, Two active metals, Ni and Ru, are used, and the molar ratio of Ni:Ru is 10:

1.

9. The method for preparing the ruthenium-based reforming hydrogen production catalyst according to claim 8, characterized in that, The concentration of NiCl2 in the mixed solution is 0.1 mol / L, the concentration of RuCl3 is 0.01 mol / L, and the pH is 3-5.

10. The ruthenium-based hydrogen reforming catalyst prepared by the preparation method according to any one of claims 1-9.

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