Platinum-based catalyst for hydrogen production by methanol water phase reforming and preparation method and application thereof

Abstract

The invention relates to a platinum-based catalyst for hydrogen production by methanol water phase reforming and a preparation method and application thereof. The catalyst comprises an active component and a carrier, the active component is Pt, and the carrier is gamma-Mo2N; a gamma-Mo2N carrier is synthesized in a temperature programming calcination mode, and then a platinum solution serves as a precursor and is reduced in a hydrogen atmosphere through an equivalent-volume impregnation method to obtain the Pt / gamma-Mo2N catalyst. Compared with a platinum-based catalyst synthesized through other carriers, the catalyst has excellent catalytic activity. The preparation process mainly comprises the following steps: a) synthesizing MoO3; b) in an ammonia gas atmosphere, carrying out temperature programming calcination to obtain a gamma-Mo2N carrier; and c) dipping in a platinum solution by an equivalent-volume dipping method, and then reducing to obtain the Pt / gamma-Mo2N catalyst. The metal catalyst provided by the invention has the characteristics of high dispersity and good activity, has excellent catalyst activity at different temperature sections when being applied to a methanol aqueous phase reforming process, shows a higher conversion rate than a supported catalyst of a traditional oxide carrier, is suitable for industrial production, and has a good application prospect.

Description

Technical Field

[0001] The invention relates to the field of hydrogen production by aqueous phase reforming of methanol, and in particular to a platinum-based catalyst and a preparation method and application thereof. Background Art

[0002] Energy is the most basic driving force for the development and economic growth of the entire world, and it is the foundation for human survival. With the rapid consumption of fossil energy represented by coal, oil, and natural gas, and the increasingly serious environmental problems caused by the use of fossil energy, it has become urgent to find and develop clean energy. Hydrogen energy, as a clean and environmentally friendly renewable energy, has attracted worldwide attention. However, due to the flammable and explosive characteristics of hydrogen, traditional storage and transportation methods are difficult to meet its large-scale and low-cost transportation requirements, and the transportation materials will also be embrittled during transportation. Based on this, organic hydrogen storage materials can be used as new hydrogen storage containers, and they also have the potential to produce hydrogen in situ and be used in fuel cell vehicles. Among them, methanol has many advantages such as high hydrogen storage capacity per unit volume, low activation temperature, few by-products, and low price and easy availability. It is an ideal liquid hydrogen storage platform molecule. Nobel Prize winner George Andrew Olah also proposed the concept of "methanol economy". In summary, the use of methanol in situ hydrogen production as an energy source for fuel cell vehicles is very feasible, and related research has also received increasing attention from academia and industry. Studies have shown that methanol aqueous phase reforming to produce hydrogen is generally carried out at a low temperature of 150 to 250 ° C, with a high hydrogen yield and a low yield of byproduct CO. . At present, the main research and application are mainly based on supported metal catalysts, among which platinum-based catalysts have better activity. Usually, the structure of the catalyst uses Al2O3, ZnO, and ZrO2 as carriers, and nanoparticles of platinum are dispersed on the surface as active metals. Among them, the carrier is the main component of the catalyst, and a small part is active metal platinum. However, the activity of traditional methanol aqueous phase reforming catalysts using metal oxides as carriers is relatively limited, and it is difficult to meet the use requirements of fuel cells. In response to the above problems, metal nitrides are used as carriers. Studies have shown that when metal nitrides are used as carriers, platinum-based catalysts can show better activity and stability. Therefore, this field urgently needs to expand the design and optimization of platinum-based catalyst structures on the basis of maintaining activity. Summary of the invention

[0003] The purpose of the present invention is to overcome the activity limitations of the above-mentioned existing methanol hydrogen production catalysts and to provide a platinum-based catalyst for methanol aqueous phase hydrogen production and its preparation method and application. This application adopts (NH4)6Mo7O 24·4H2O was calcined to obtain a MoO3 precursor, which was then calcined by programmed temperature in an ammonia atmosphere to obtain a γ-Mo2N carrier, and a methanol aqueous phase reforming hydrogen production catalyst was prepared by loading platinum salt on the surface of γ-Mo2N by impregnation. A new catalyst structure was synthesized by dispersing Pt on the surface of the γ-Mo2N carrier, which improved the activity of the original supported copper-based catalyst.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] A platinum-based catalyst, a preparation method and its application in methanol aqueous phase reforming to produce hydrogen. The catalyst composition is Pt / γ-Mo2N, and the Pt content is 0.1wt% to 10wt%.

[0006] Based on the above technical scheme, the synthesis method of γ-Mo2N is preferred. The catalyst preparation method comprises the following steps:

[0007] (1) obtaining a MoO3 precursor by calcining a Mo salt precursor;

[0008] (2) calcining the MoO3 precursor obtained in step (1) under an ammonia atmosphere to obtain a γ-Mo2N carrier;

[0009] (3) dissolving a platinum metal salt in water to obtain a solution A;

[0010] (4) adding γ-Mo2N to solution A, mixing evenly, ultrasonicating, and drying to obtain precursor B;

[0011] (5) The precursor B is ground into powder and then reduced in a hydrogen and argon atmosphere to obtain a finished catalyst.

[0012] Based on the above technical solution, preferably, the Mo salt precursor in step (1) is (NH4)6Mo7O 24 ·4H2O, and the calcination temperature in air atmosphere is 300-800°C, preferably 500-600°C; the heating rate is 5-10°C / min.

[0013] Based on the above technical scheme, preferably, in step (2), the calcination temperature of the MoO3 precursor in an ammonia atmosphere is 600-800°C, preferably 700-800°C; the calcination time is 6-10h, preferably 8h; and the heating rate is 5°C / min.

[0014] Based on the above technical solution, preferably, the platinum metal salt in step (3) can be a nitrate or a chloride.

[0015] Based on the above technical solution, preferably, step (4) is performed by stirring for 5 to 10 minutes under normal temperature ultrasound. After drying at 80 to 100° C. for 12 hours, excess water is removed to obtain a powdered catalyst precursor.

[0016] Based on the above technical solution, preferably, the reducing gas in step (5) is a hydrogen-argon mixture, the reduction temperature is 300-500°C, preferably 400°C; the reduction time is 2-4h, preferably 3h, and the heating rate is 5-10°C / min.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The platinum-based catalyst synthesized in the present invention has a higher dispersion of platinum on the carrier surface after being loaded with platinum (0.2-10wt%), so that the methanol reforming rate of the Pt / γ-Mo2N catalyst is higher than that when the traditional oxide is used as a carrier at the same temperature, thus overcoming the bottleneck of the activity of the supported oxide in the existing catalytic system.

[0019] The present invention utilizes specific metal nitrides dispersed in platinum particles to greatly improve the activity of supported platinum-based catalysts, breaking through the limitations of traditional catalyst design and preparation structure. The programmed temperature calcination method in the present invention completes the preparation of the γ-Mo2N carrier, and then the platinum is loaded onto the surface of the γ-Mo2N carrier by the impregnation method. The method is simple and has strong applicability. Under the condition of a specific loading amount, the optimal microscopic configuration effect can be achieved. The overall synthesis steps are simple, the conditions are mild, and the controllability is strong, and it can be applied to large-scale industrial production. DETAILED DESCRIPTION

[0020] Embodiment 1:

[0021] First, by calcining (NH4)6Mo7O 24 ·4H2O was used to prepare MoO3 precursor, and then γ-Mo2N was obtained by programmed temperature calcination in an ammonia atmosphere. Then, Pt was loaded onto the surface of γ-Mo2N by impregnation to prepare Pt / γ-Mo2N catalyst. The activity of the supported platinum-based catalyst was improved by dispersing Pt on the surface of the γ-Mo2N carrier.

[0022] This example is the preparation of 1Pt / γ-Mo2N catalyst, the mass content of Pt is 1wt%. Preparation process:

[0023] (1) 4g (NH4)6Mo7O 24 4H2O was calcined at 500℃ for 4h to obtain MoO3;

[0024] (2) MoO3 was calcined at 750°C for 8 h in an ammonia atmosphere in a tube furnace to obtain γ-Mo2N;

[0025] (3) 0.6 g of the γ-Mo2N obtained in step (2) was added to a H2PtCl6 or Pt(NO3)2 solution;

[0026] (4) subjecting the solid in step (3) to ultrasonic treatment for 10 min, and then placing it in an oven for 12 h at a temperature set at 100 °C;

[0027] (5) Grinding the solid obtained in step (4) into powder, and reducing it in a tube furnace at 300° C. in a hydrogen-argon atmosphere for 3 h to obtain the final product.

[0028] Testing process:

[0029] Catalyst evaluation process:

[0030] (1) The prepared catalyst was placed in a high-pressure reactor, methanol and aqueous solution were added, and then 3 MPa of inert gas N2 was introduced at room temperature. The test was performed at 220°C. After the reaction was completed, the gas was collected through an air bag and analyzed by gas chromatography.

[0031] The performance test of the catalyst in this experiment was carried out in a high-pressure reactor. The application process of the catalyst for methanol aqueous phase hydrogen production process was as follows: 50 mg of catalyst was weighed, 15 g of methanol aqueous solution was added, wherein the molar ratio of methanol to water in the methanol aqueous solution was 1:1, 3 MPa of inert gas N2 was introduced at room temperature, the reaction temperature was 210 °C, and the reaction results are shown in Table 1.

[0032] Embodiment 2-6:

[0033] The preparation process of the above embodiment is the same as that of embodiment 1, except that the Pt contents are 0.2wt%, 0.5wt%, 2wt%, 5wt% and 10wt% respectively.

[0034] The test results show that when the Pt content is 2wt%, the catalyst exhibits the best activity, and the methanol reforming efficiency is the highest under this test condition. As the Pt content increases, the activity does not decrease significantly, indicating that the reforming efficiency of the catalyst Pt is the highest at 2wt%.

[0035] Embodiment 7-11:

[0036] The preparation process of the above embodiment is the same as that of embodiment 1, except that the Pt content is 2 wt%, and the reaction temperatures are 170° C., 180° C., 190° C., 200° C., and 220° C. respectively. The reaction results are shown in Table 2.

[0037] The test results show that the 2Pt / γ-Mo2N catalyst can exhibit good activity at different temperature ranges, making it possible for use in fuel cells.

[0038] Comparative Example 1:

[0039] This comparative example is the preparation of 2Pt / γ-Al2O3 catalyst, the mass content of Pt is 2wt% Preparation process

[0040] (1) Add 1 g of commercial γ-Al2O3 to H2PtCl6 or Pt(NO3)2 solution;

[0041] (2) subjecting the solid in step (1) to ultrasonic treatment for 10 min, and then placing it in an oven for 12 h at a temperature set at 100° C.;

[0042] (3) Grinding the solid obtained in step (2) into powder, and reducing it in a tube furnace at 300° C. in a hydrogen and argon atmosphere for 3 h to obtain the final product.

[0043] Testing process:

[0044] The performance test of the catalyst in this experiment was carried out in a high-pressure reactor. The application process of the catalyst for methanol aqueous phase hydrogen production process was as follows: 50 mg of catalyst was weighed, 15 g of methanol aqueous solution was added, wherein the molar ratio of methanol to water in the methanol aqueous solution was 1:1, 3 MPa of inert gas N2 was introduced at room temperature, the reaction temperature was 210 °C, and the reaction results are shown in Table 3.

[0045] Comparative Examples 2-5:

[0046] The preparation process of the above comparative example is the same as that of comparative example 1, except that the oxides therein correspond to NiAl2O4, ZnO, CeO2, and ZrO2, respectively.

[0047] The test results show that the traditional supported catalysts prepared with oxides as carriers all show poor methanol reforming rates, while the platinum-based catalysts with metal nitrides as carriers show higher methanol conversion rates, confirming the special role of metal nitride carriers in methanol applications.

[0048] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

[0049] Table 1 Catalyst performance data in each example under the above catalyst evaluation conditions

[0050]

[0051] Table 2 Catalyst performance data in each example under the above catalyst evaluation conditions

[0052]

[0053] Table 3 Catalyst performance data of each embodiment and comparative example under the above catalyst evaluation conditions

[0054]

Claims

1. A platinum-based catalyst for producing hydrogen from methanol aqueous phase reforming, characterized in that The active component of the catalyst is metal Pt, and the carrier is gamma-Mo2N; in terms of mass percentage, the content of metal Pt is 0.1-10wt%.

2. A platinum-based catalyst for producing hydrogen by aqueous phase reforming of methanol according to claim 1, wherein the preparation method thereof is characterized in that the nitride γ-Mo2N is used as a carrier.

3. The method for preparing the catalyst according to claim 2, comprising the following steps: (1) calcining a Mo salt precursor at 300-800°C for 4-6h to obtain a MoO3 precursor; the Mo salt precursor may be: (NH4)6Mo7O 24 4H2O or Na2MoO4; (2) calcining the MoO3 precursor obtained in step (1) at 600-800°C in an ammonia atmosphere for 6-10 hours to obtain a γ-Mo2N carrier; (3) dissolving a platinum metal salt in water to obtain a solution A; (4) adding γ-Mo2N to solution A, mixing evenly, ultrasonicating, and drying to obtain precursor B; (5) After the precursor B is ground into powder, it is calcined at 300-500°C for 2-4 hours to obtain a finished catalyst.

4. The method for preparing a platinum-based catalyst according to claim 3, characterized in that: The loading amount of platinum is adjusted to 0.2wt% to 10wt%.

5. The method for preparing a platinum-based catalyst according to claim 3, characterized in that: In step (1), the calcination temperature of the Mo salt precursor in the air atmosphere is 300-800°C, preferably 500-600°C; the heating rate is 5-10°C.

6. The method for preparing a platinum-based catalyst according to claim 3, characterized in that: In step (2), the MoO3 precursor is calcined in an ammonia atmosphere at a temperature of 600-800°C, preferably 700-800°C; the calcination time is 6-10h, preferably 8h; and the heating rate is 5°C / min.

7. The method for preparing a platinum-based catalyst according to claim 3, wherein the platinum metal salt in (3) is a nitrate or a chloride.

8. The method for preparing a platinum-based catalyst according to claim 3, characterized in that: Step (4) is to stir for 5 to 10 minutes under normal temperature and ultrasound. After drying at 80 to 100° C. for 12 hours, excess water is removed to obtain a powdered catalyst precursor.

9. The method for preparing a platinum-based catalyst according to claim 3, characterized in that: The reducing gas in step (5) is a hydrogen-argon mixed gas, the reducing temperature is 300-500°C, preferably 400°C; the reducing time is 2-4h, preferably 3h, and the heating rate is 5-10°C / min.

10. The use of a platinum-based reverse phase catalyst in methanol aqueous phase hydrogen production as claimed in claim 1, characterized in that: The reaction is carried out in a reactor, at a reaction temperature of 150-250°C, a reaction pressure of 3MPa at room temperature, 15g of methanol aqueous solution, and a molar ratio of methanol to water in the solution of 1:1, and a platinum-based catalyst is used to catalytically convert the reaction gas into hydrogen.

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