Catalyst for hydrogen production by means of methanol reforming, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a catalyst for hydrogen production by means of methanol reforming, and a preparation method therefor and the use thereof. The catalyst is a metal-loaded porous two-dimensional molybdenum sulfide material, wherein the size of the two-dimensional molybdenum sulfide is 2-100 nm; and the metal is distributed at edge sites of the two-dimensional molybdenum sulfide in a monoatomic state. In the present invention, molybdenum sulfide is synthesized on a template by using a hard template method; the molybdenum sulfide has rich edge sites after the template is removed; after the molybdenum sulfide is further modified with a metal and subjected to a reduction gas treatment, the loaded metal is distributed in a monoatomic state; and the catalyst exhibits relatively good activity during a reaction of hydrogen production by means of methanol reforming. The present invention solves the problems of low activity and poor stability of the existing catalytic system, and achieves the balance of high activity and high stability; and the provided catalyst for hydrogen production by means of methanol reforming has the characteristics of a high mass specific activity, good stability, etc., and has good industrial application prospects and commercial values.

Description

A methanol reforming hydrogen production catalyst and its preparation method and application Technical Field

[0001] The invention relates to a methanol reforming hydrogen production catalyst and a preparation method and application thereof, belonging to the field of chemistry and chemical engineering. Background Art

[0002] Methanol is the simplest organic alcohol with the highest hydrogen-to-carbon ratio. It can be used as a hydrogen carrier for in-situ reforming to produce hydrogen. Furthermore, methanol reforming hydrogen production technology has the potential to overcome the difficulties of hydrogen storage and transportation, promoting the further development of hydrogen energy.

[0003] The most commonly used catalyst for methanol reforming to produce hydrogen is a Cu-based catalyst, namely Cu / ZnO / Al2O3 (Appl. Catal. A Gen. 278, 25-35, 2004; Appl. Catal. B 99, 43-57, 2010; Top. Catal. 49, 73-80, 2008). It has catalytic activity towards both water and methanol and is characterized by low cost and high activity. However, Cu-based catalysts have poor thermal stability, are prone to sintering, and produce a large amount of CO byproducts (Science 336, 893-897, 2012). In addition to Cu-based catalysts, precious metal catalysts such as Pt / MoC (Nature, 544, 80-83, 2017) and Pd / MoC (Appl. Catal. B 299, 120648, 2021) have also been widely reported for methanol reforming to produce hydrogen, but poor catalyst stability is one of the drawbacks of this type of catalytic system.

[0004] As a two-dimensional material, molybdenum disulfide has the characteristics of anti-sulfurization and good stability. Its edge sulfur vacancies have good dissociation ability for methanol (Nat Catal 4, 242-250, 2021). However, the molybdenum disulfide reported in the literature is generally large in size. After loading metal, it has poor activity and stability in the methanol reforming hydrogen production reaction. Summary of the Invention

[0005] The purpose of the present invention is to provide a methanol reforming hydrogen production catalyst and its preparation method and application. The two-dimensional molybdenum sulfide material synthesized by the hard template method of the present invention has the characteristics of small size, small number of layers, etc., and has abundant edge sulfur vacancies, which is conducive to activating methanol molecules and improving the catalytic activity of the methanol reforming hydrogen production reaction. The present invention loads the metal on the two-dimensional edge-rich molybdenum sulfide material and treats it with reducing gas. The metal is distributed in the edge position of the molybdenum sulfide in a single atomic state, which not only improves the catalyst's ability to dissociate the reactants, but also facilitates the diffusion of reaction intermediates, further improving its catalytic activity.

[0006] The present invention realizes the application of high-loaded single-atom (>2%) catalyst in methanol reforming hydrogen production reaction for the first time, thereby improving the utilization rate of precious metals and reducing catalyst costs.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] On one hand, the present invention provides a methanol reforming hydrogen production catalyst, which is a metal-loaded porous two-dimensional molybdenum sulfide material; the size of the two-dimensional molybdenum sulfide is 2-100nm; and the metal is distributed in a single-atom state at the edge of the two-dimensional molybdenum sulfide.

[0009] In the above technical solution, further, the metal is one or more of Pt, Ir, Au, Ru, Rh, Pd, Ag, Fe, Co, Ni, and Cu.

[0010] In the above technical solution, further, the number of layers of the two-dimensional molybdenum sulfide is 1-50 layers.

[0011] In the above technical solution, further, the loading amount of the metal is 0.1-10 wt%.

[0012] Another aspect of the present invention provides a method for preparing the above catalyst, the method comprising the following steps:

[0013] (1) depositing a molybdenum source onto a template to obtain a precursor;

[0014] (2) placing the precursor and the sulfur source in a high-pressure reactor under argon protection at a reaction temperature of 150-600°C;

[0015] (3) removing the template from the product obtained in step (2) using an acid or alkaline solution, and washing to obtain nanoporous molybdenum disulfide;

[0016] (4) loading a metal on the nanoporous molybdenum disulfide;

[0017] (5) treating the metal-loaded nanoporous molybdenum disulfide obtained in step (4) at 100-500° C. for 0.5-12 h using reducing gas to obtain the catalyst.

[0018] In the above technical solution, further, in step (1), the molybdenum source is one of ammonium molybdate, ammonium phosphomolybdate, sodium phosphomolybdate, and sodium molybdate; the template is one or more of SiO2 nanospheres, SiO2 nanowires, SBA-15, SAPO-34, KIT-6, MCM-41, and ZSM-5; the molar ratio of the silicon element in the template to the molybdenum element in the molybdenum source is 1-40:1, preferably 10-20:1.

[0019] In the above technical solution, further, in step (2), the sulfur source is one or more of sulfur, hydrogen sulfide, sodium sulfide, potassium sulfide, thiourea, carbon disulfide, thioacetamide, dimethyl sulfoxide, sulfur dioxide, cysteine, methionine, thiol, thiol, and thioether; and the molar ratio of the sulfur element in the sulfur source to the molybdenum element in the molybdenum source is 2-50:1, preferably 2-8:1.

[0020] In the above technical solution, further, in step (3), the acid is a hydrofluoric acid solution with a mass fraction of 10-50% or a mixture thereof with other inorganic acids;

[0021] The base is 1-10 mol / L hydroxide or a mixture thereof with ammonia water.

[0022] In the above technical solution, further, in step (4), the reducing gas includes one or more of hydrogen, carbon monoxide, and ammonia, or a mixture of at least one of hydrogen, carbon monoxide, and ammonia and an inert gas, or a mixture of at least one of hydrogen, carbon monoxide, and ammonia and carbon dioxide.

[0023] The present invention also provides an application of the above catalyst in a methanol reforming hydrogen production reaction, wherein the reaction is carried out in one or more of a fixed bed reactor and a tank reactor, the reaction temperature is 100-500°C, the molar percentage of methanol in the reaction liquid is 10-100%, and the mass ratio of the reaction liquid to the catalyst is 1-10000:1.

[0024] The beneficial effects of the present invention are:

[0025] (1) The two-dimensional molybdenum sulfide material synthesized by the hard template method provided by the present invention has the characteristics of small size, small number of layers, and abundant edge sulfur vacancies, which is conducive to activating methanol molecules and improving the catalytic activity of methanol reforming hydrogen production reaction.

[0026] (2) Electron microscopic characterization of the catalyst provided by the present invention revealed that most of the loaded metal is distributed in a single atomic state on the edge sites of the two-dimensional molybdenum sulfide. This facilitates the synergistic effect of the two active centers, which not only promotes the dissociation of the catalyst from the reactants but also facilitates the diffusion of reaction intermediates, further enhancing its catalytic activity. This also increases the utilization rate of the precious metal and reduces the cost for subsequent scale-up applications.

[0027] (3) The preparation method used in the present invention is simple and has a wide range of applications. The prepared metal-loaded nanoporous molybdenum disulfide material has potential application scenarios in the conversion of energy small molecules.

[0028] (4) The present invention solves the problem of catalyst deactivation at high temperatures, achieves a balance between catalytic activity and stability, achieves high reaction activity and excellent stability, and has the potential for further expansion of applications.

[0029] In summary, the methanol reforming hydrogen production catalyst provided by the present invention can achieve high activity and selectivity, and has excellent stability, and is expected to be further expanded in application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a TEM image of Cat1 in Example 1;

[0031] FIG2 is a STEM image and EDS element distribution diagram of Cat1 in Example 1;

[0032] FIG3 is a TEM image of Cat8 in Comparative Example 1;

[0033] FIG4 is a graph showing the cyclic stability test of Cat1 in Example 1;

[0034] FIG5 is an EXAFS spectrum of Cat1 in Example 1. DETAILED DESCRIPTION

[0035] The following examples illustrate the preparation method and reaction performance of the methanol reforming hydrogen production catalyst provided by the present invention, but the present invention is not limited thereto.

[0036] Unless otherwise specified, the materials used in the examples of the present invention can be obtained from commercial sources or prepared according to conventional methods well known to those skilled in the art.

[0037] Example 1

[0038] 0.8g of ammonium molybdate was dissolved in water and placed in a beaker, 2.5g of SBA-15 was added, and after ultrasonic dispersion for 24h, it was stirred to dryness at room temperature and then dried in an oven at 80℃ for 12h; then the precursor was placed in a high-pressure reactor under argon protection, and 20mL of carbon disulfide was added; the high-pressure reactor was sealed and heated to 400℃ for 4 hours; after the reaction was complete, the crude product was taken out, the template was removed with 40% hydrofluoric acid by mass, and the crude product was washed alternately with ethanol and water until the filtrate was neutral, and MoS2-1 was obtained after drying; 0.016g of chloroplatinic acid was dissolved in water, and 0.2g MoS2-1 was ultrasonically dispersed for 1 h, stirred to dryness at room temperature, and then dried in an oven at 100°C for 12 h to obtain Pt / MoS2-1. Pt / MoS2-1 was placed in a tube furnace and a mixed gas flow of 10% H2 and 90% N2 was introduced at a pressure of 1 bar and a space velocity of 9000 mL h -1 g -1 Under the conditions of , the temperature was raised to 300℃ for heat treatment, and the heat treatment time was 2h to obtain Cat1.

[0039] Example 2

[0040] 0.8g of ammonium molybdate was dissolved in water and placed in a beaker, 2.5g of KIT-6 was added as a template, and after ultrasonic dispersion for 24h, it was stirred to dryness at room temperature and then dried in an oven at 80℃ for 12h to obtain a precursor; then the precursor was placed in a high-pressure reactor under argon protection, and 20mL of carbon disulfide was added; the high-pressure reactor was sealed and heated to 400℃ for a high-temperature reaction for 4 hours; after the reaction was complete, the crude product was taken out, the template was removed with 40% hydrofluoric acid by mass, and the crude product was washed alternately with ethanol and water until the filtrate was neutral, and MoS2-2 was obtained after drying; an appropriate amount of 0.016g of chloroplatinic acid was dissolved in water, and 0.2g MoS2-2 was ultrasonically dispersed for 1 h, stirred to dryness at room temperature, and then dried in an oven at 100°C for 12 h to obtain Pt / MoS2-2. Pt / MoS2-2 was weighed and placed in a tube furnace. A mixed gas flow of 10% H2 and 90% N2 with a volume fraction of 10% was introduced at a pressure of 1 bar and a space velocity of 9000 mL h -1 g -1 Under the conditions of , the temperature was raised to 300℃ for heat treatment for 2h to obtain Cat2.

[0041] Example 3

[0042] 0.8 g of ammonium molybdate was dissolved in water and placed in a beaker, 2.5 g of ZSM-5 was added as a template, and after ultrasonic dispersion for 24 h, it was stirred to dryness at room temperature and then dried in an oven at 80 ° C for 12 h to obtain a precursor; the precursor was then placed in a high-pressure reactor under argon protection, and 20 mL of carbon disulfide was added; the high-pressure reactor was sealed and heated to 400 ° C for 4 hours; after the reaction was complete, the crude product was taken out, the template was removed with 40% hydrofluoric acid by mass, and the crude product was washed alternately with ethanol and water until the filtrate was neutral, and MoS2-3 was obtained after drying; 0.016 g of chloroplatinic acid was dissolved in water, 0.2 g of MoS2-3 was ultrasonically dispersed for 1 h, stirred to dryness at room temperature, and dried in an oven at 100 °C for 12 h to obtain Pt / MoS2-3; Pt / MoS2-3 was weighed and placed in a tube furnace, and a mixed gas flow of 10% H2 and 90% N2 with a volume fraction of 10% was introduced at a pressure of 1 bar and a space velocity of 9000 mL h -1 g -1 Under the conditions of , the temperature was raised to 300℃ for heat treatment for 2h to obtain Cat3.

[0043] Example 4

[0044] 0.8g of ammonium molybdate was dissolved in water and placed in a beaker, 2.5g of SiO2 nanospheres were added as a template, and after ultrasonic dispersion for 24h, the mixture was stirred to dryness at room temperature and then dried in an oven at 80℃ for 12h to obtain a precursor; the precursor was then placed in a high-pressure reactor under argon protection, and 20mL of carbon disulfide was added; the high-pressure reactor was sealed and heated to 400℃ for a high-temperature reaction for 4 hours; after the reaction was complete, the crude product was taken out, the template was removed with 40% hydrofluoric acid by mass, and the crude product was washed alternately with ethanol and water until the filtrate was neutral, and MoS2-4 was obtained after drying; 0.016g of chloroplatinic acid was dissolved in water, 0.2g MoS2-4 was ultrasonically dispersed for 1 h, stirred to dryness at room temperature, and dried in an oven at 100°C for 12 h to obtain Pt / MoS2-4. Pt / MoS2-4 was weighed and placed in a tube furnace. A mixed gas flow of 10% H2 and 90% N2 with a volume fraction of 10% was introduced at a pressure of 1 bar and a space velocity of 9000 mL h -1 g -1 Under the conditions of , the temperature was raised to 300℃ for heat treatment for 2h to obtain Cat4.

[0045] Example 5

[0046] 0.8 g of ammonium molybdate was dissolved in water and placed in a beaker, 2.5 g of MCM-41 was added as a template, and after ultrasonic dispersion for 24 h, the mixture was stirred to dryness at room temperature and then dried in an oven at 80 ° C for 12 h to obtain a precursor; the precursor was then placed in a high-pressure reactor under argon protection, and 20 mL of carbon disulfide was added; the high-pressure reactor was sealed and heated to 400 ° C for a high-temperature reaction for 4 hours; after the reaction was complete, the crude product was taken out, the template was removed with 40% hydrofluoric acid by mass, and the crude product was washed alternately with ethanol and water until the filtrate was neutral, and MoS2-5 was obtained after drying; 0.016 g of chloroplatinic acid was dissolved in water, 0.2 g of MoS2-5 was ultrasonically dispersed for 1 h, stirred to dryness at room temperature, and then dried in an oven at 100°C for 12 h to obtain Pt / MoS2-5. Pt / MoS2-5 was weighed and loaded into a tube furnace, and a mixed gas flow of 10% H2 and 90% N2 with a volume fraction of 10% was introduced at a pressure of 1 bar and a space velocity of 9000 mL h -1 g -1 Under the conditions of , the temperature was raised to 300℃ for heat treatment for 2h to obtain Cat5.

[0047] Example 6

[0048] 0.8 g of ammonium molybdate was dissolved in water and placed in a beaker, 2.5 g of SBA-15 was added as a template, and after ultrasonic dispersion for 24 h, it was stirred to dryness at room temperature and then dried in an oven at 80 ° C for 12 h to obtain a precursor; the precursor was then placed in a high-pressure reactor under argon protection, and 20 mL of carbon disulfide was added; the high-pressure reactor was sealed and heated to 400 ° C for 4 hours; after the reaction was complete, the crude product was taken out, the template was removed with 40% hydrofluoric acid by mass, and the crude product was washed alternately with ethanol and water until the filtrate was neutral, and MoS2-6 was obtained after drying; 0.015 g of rhodium chloride was dissolved in water, 0.2 g of rhodium chloride was added, and the reaction mixture was stirred for 24 h. MoS2-6 was ultrasonically dispersed for 1 h, stirred to dryness at room temperature, and then dried in an oven at 100°C for 12 h to obtain Rh / MoS2-6. Rh / MoS2-6 was weighed and loaded into a tube furnace, and a mixed gas flow of 10% H2 and 90% N2 with a volume fraction of 10% was introduced at a pressure of 1 bar and a space velocity of 9000 mL h -1 g -1 Under the conditions of , the temperature is raised to 300 ℃ for heat treatment for 2 hours to obtain Cat6.

[0049] Example 7

[0050] 0.8 g of ammonium molybdate was dissolved in water and placed in a beaker, 2.5 g of SBA-15 was added as a template, and after ultrasonic dispersion for 24 h, the mixture was stirred to dryness at room temperature and then dried in an oven at 80 ° C for 12 h to obtain a precursor; the precursor and 3.949 g of thiourea were then placed in an autoclave under argon protection; the autoclave was sealed and heated to 400 ° C for 4 hours; after the reaction was complete, the crude product was taken out, the template was removed with 40% hydrofluoric acid by mass, and the crude product was washed alternately with ethanol and water until the filtrate was neutral, and MoS2-7 was obtained after drying; 0.016 g of chloroplatinic acid was dissolved in water, 0.2 g of chloroplatinic acid was added, and the mixture was dried. MoS2-7 was ultrasonically dispersed for 1 h, stirred to dryness at room temperature, and dried in an oven at 100°C for 12 h to obtain Pt / MoS2-7. Pt / MoS2-7 was weighed and placed in a tube furnace, and a mixed gas flow of 10% H2 and 90% N2 with a volume fraction of 10% was introduced at a pressure of 1 bar and a space velocity of 9000 mL h -1 g -1 Under the conditions of , the temperature was raised to 300℃ for heat treatment for 2h to obtain Cat7.

[0051] Comparative Example 1

[0052] 0.016 g of chloroplatinic acid was dissolved in water, 0.2 g of commercial molybdenum sulfide (Zhongnuo New Materials, YJ05122) was added, and the mixture was ultrasonically dispersed for 1 h. After being stirred to dryness at room temperature, the mixture was dried in an oven at 100 °C for 12 h to obtain metal-supported molybdenum sulfide. The metal-supported molybdenum sulfide was weighed and loaded into a tube furnace. A mixed gas flow of 10% by volume of H2 and 90% by volume of N2 was introduced. The mixture was heated at a pressure of 1 bar and a space velocity of 9000 mL h -1 g -1 Under the conditions of , the temperature was raised to 300 ℃ and the catalyst was heat treated for 2 hours to obtain Cat8.

[0053] Application Example 1

[0054] Under inert gas, 0.1 g of the catalysts prepared in Examples 1-7 and Comparative Example 1 was placed in a reaction kettle, 50 ml of aqueous methanol was added, and the reaction was sealed and initiated at a temperature of 240°C for 2 hours. The reaction products were analyzed online using a gas chromatograph, with TCD and FID detectors used for qualitative and quantitative analysis, respectively. Specific reaction performance is listed in Table 1.

[0055] Table 1 Catalyst performance evaluation results

[0056] As can be seen from the above table, the catalyst provided by the present invention has high activity in the methanol reforming hydrogen production reaction. This is because the supported metal of Cat1 does not have a Pt-Pt bond (Figure 5) and is distributed in a single atom (Figure 2), so it has a higher unit mass activity than the nanoparticle distribution of Cat8 (Figure 3). The average size of Cat1 (Figure 1) is 10nm. Compared with Cat8, Cat1 has a smaller lateral size and exposes more edge sulfur vacancies, which is conducive to the dissociation of reactants and improves the activity of the catalyst. Therefore, Cat1 has a higher unit mass activity and exhibits excellent stability in further stability tests (Figure 4).

[0057] In addition, ICP-OES test results showed that the actual metal loading of Cat1 was 2.96%, which significantly exceeded the single-atom catalysts currently reported in methanol reforming hydrogen production reactions.

[0058] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Other variations or modifications may be made based on the above description. Obvious variations or modifications derived therefrom shall remain within the scope of protection of the present invention.

Claims

1. A methanol reforming hydrogen production catalyst, characterized in that: The catalyst is a metal-loaded porous two-dimensional molybdenum sulfide material; the size of the two-dimensional molybdenum sulfide is 2-100nm; the metal is distributed in a single-atom state at the edge of the two-dimensional molybdenum sulfide.

2. The catalyst according to claim 1, characterized in that: The metal is one or more of Pt, Ir, Au, Ru, Rh, Pd, Ag, Fe, Co, Ni, and Cu.

3. The catalyst according to claim 1, characterized in that: The number of layers of the two-dimensional molybdenum sulfide is 1-50.

4. The catalyst according to claim 1, characterized in that: The metal loading is 0.1-10 wt%.

5. A method for preparing the catalyst according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: (1) depositing a molybdenum source onto a template to obtain a precursor; (2) placing the precursor and the sulfur source in a high-pressure reactor under argon protection at a reaction temperature of 150-600° C.; (3) removing the template from the product obtained in step (2) using an acid or alkaline solution, and washing to obtain nanoporous molybdenum disulfide; (4) loading a metal on the nanoporous molybdenum disulfide; (5) The metal-loaded nanoporous molybdenum disulfide obtained in step (4) is treated with reducing gas at 100-500° C. for 0.5-12 h to obtain the catalyst.

6. The preparation method according to claim 1, characterized in that: In step (1), the molybdenum source is one of ammonium molybdate, ammonium phosphomolybdate, sodium phosphomolybdate, and sodium molybdate; The template is one or more of SiO2 nanospheres, SiO2 nanowires, SBA-15, SAPO-34, KIT-6, MCM-41, and ZSM-5; The molar ratio of the silicon element in the template to the molybdenum element in the molybdenum source is 1-40:1, preferably 10-20:

1.

7. The preparation method according to claim 1, characterized in that: In step (2), the sulfur source is one or more of sulfur, hydrogen sulfide, sodium sulfide, potassium sulfide, thiourea, carbon disulfide, thioacetamide, dimethyl sulfoxide, sulfur dioxide, cysteine, methionine, thiol, thiophenol, and thioether; The molar ratio of sulfur in the sulfur source to molybdenum in the molybdenum source is 2-50:1, preferably 2-8:

1.

8. The preparation method according to claim 1, characterized in that: In step (3), the acid is a hydrofluoric acid solution with a mass fraction of 10-50% or a mixture thereof with other inorganic acids; The alkali is 1-10 mol / L hydroxide or a mixture thereof with ammonia water.

9. The preparation method according to claim 1, characterized in that: In step (4), the reducing gas includes one or more of hydrogen, carbon monoxide, and ammonia, or a mixture of at least one of hydrogen, carbon monoxide, and ammonia and an inert gas, or a mixture of at least one of hydrogen, carbon monoxide, and ammonia and carbon dioxide.

10. Use of the catalyst according to any one of claims 1 to 4 in a methanol reforming hydrogen production reaction, characterized in that: The reaction is carried out in one or more of a fixed bed reactor and a tank reactor, the reaction temperature is 100-500°C, the molar percentage of methanol in the reaction liquid is 10-100%, and the mass ratio of the reaction liquid to the catalyst is 1-10000:1.

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