Ni / Mo2C catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of methane dry reforming catalysts, and particularly relates to a Ni / Mo2C catalyst and a preparation method and application thereof. The preparation method comprises the following steps: by taking a nickel source and a molybdenum source as reactants and glucose as a carbon source, preparing a precursor through a mechanical grinding method; and carrying out roasting treatment on the precursor in an inert atmosphere, and then carrying out surface passivation treatment to obtain the Ni / Mo2C catalyst. According to the Ni / Mo2C catalyst prepared by taking glucose as a carbon source and combining with a mechanical grinding method, multiple functions of high specific surface area, excellent mass transfer, stable protection of an active phase and the like are simultaneously realized through a unique composite structure of embedding a high-dispersion active site into a high-carbon matrix. Compared with a traditional CH4 carbonization method, the catalyst shows more excellent catalytic activity, selectivity and long-term stability in the DRM reaction, the glucose-derived high-carbon-content matrix effectively prevents the active phase from being oxidized and sintered, and a new preparation strategy and theoretical basis are provided for developing an efficient, stable and environment-friendly DRM catalyst.

Description

Technical Field

[0001] This invention belongs to the field of methane dry reforming catalyst technology, and more specifically relates to a Ni / Mo2C catalyst, its preparation method and application. Background Technology

[0002] DRM (distilled methane reforming) technology, as an important pathway for efficiently converting greenhouse gases CH4 and CO2 into syngas (H2 and CO), has broad application prospects in realizing carbon resource recycling and clean energy production. However, this reaction process faces many technical challenges, among which the design and preparation of catalysts are key factors determining its industrial application.

[0003] While the traditional CH4 carbonization method for preparing Ni / Mo2C catalysts has been industrially applied, this process has significant limitations. This method typically involves preparing the precursor using impregnation or co-precipitation methods, followed by catalyst synthesis through temperature-programmed carbonization in a CH4-H2 mixed atmosphere. This process is not only cumbersome and energy-intensive, but also requires the use of flammable and explosive CH4 / H2 gases, posing safety hazards. Furthermore, high-temperature carbonization easily leads to sintering and agglomeration of active components, reducing the catalyst's specific surface area and active site density, thus affecting catalytic performance. More importantly, catalysts prepared by traditional methods have low carbon content, making it difficult to effectively protect the Mo2C active phase from oxidation during the DRM reaction, resulting in insufficient catalyst stability and a limited lifespan.

[0004] To address the above issues, researchers are actively exploring new catalyst preparation methods. How to provide a highly efficient, stable, and environmentally friendly DRM catalyst has become a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a Ni / Mo2C catalyst, its preparation method, and its application, in order to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of this invention: provides a method for preparing a Ni / Mo2C catalyst, comprising the following steps:

[0008] The precursor was prepared by mechanical grinding using nickel and molybdenum sources as reactants and glucose as a carbon source.

[0009] The precursor was calcined in an inert atmosphere and then surface passivated to obtain the Ni / Mo2C catalyst.

[0010] Furthermore, the nickel source includes nickel acetate and / or nickel nitrate.

[0011] Furthermore, the molybdenum source includes ammonium molybdate.

[0012] Furthermore, the molar ratio of Ni and Mo in the nickel source and the molybdenum source is 1:2.

[0013] Furthermore, the molar ratio of Ni to glucose in the nickel source is 1:8.

[0014] Furthermore, the grinding time for the mechanical grinding method is 30 minutes.

[0015] Furthermore, the inert atmosphere is provided by argon gas at a flow rate of 100 mL / min.

[0016] Furthermore, the heating rate of the calcination treatment is 10 ℃ / min, the temperature is 700-900 ℃, and the holding time is 1 h.

[0017] Furthermore, the surface passivation treatment involves introducing a 1% O2 / Ar mixed gas for 2 hours.

[0018] The second technical solution of the present invention provides a Ni / Mo2C catalyst, wherein the Ni / Mo2C catalyst is prepared by the above preparation method.

[0019] The third technical solution of the present invention provides an application of the above-mentioned Ni / Mo2C catalyst in the methane-carbon dioxide reforming reaction.

[0020] The present invention discloses the following technical effects:

[0021] This invention prepares a Ni / Mo2C catalyst using glucose as a carbon source. The method is simple to operate, combined with mechanical grinding, and the steps are straightforward, avoiding the complex process of traditional CH4-H2 programmed temperature carbonization. It is also environmentally friendly, avoiding the use of CH4 / H2 mixed gas, thus reducing potential greenhouse gas emissions and safety hazards. The synthesis process is more direct, potentially reducing the energy consumption requirements for high-temperature processing.

[0022] The Ni / Mo2C catalyst prepared by this invention has the characteristics of high dispersion, large specific surface area and abundant mesopores. Ni and Mo2C particles are highly dispersed and uniformly distributed in the carbon sheet region (conventional methods tend to agglomerate), exposing more active sites. The large specific surface area provides abundant active surfaces and sites for the reaction, and the well-developed pore structure is conducive to the mass transfer and diffusion of reactants / products, reducing carbon buildup and blockage.

[0023] The Ni / Mo2C catalyst prepared by this invention has an extremely high initial carbon content. During the reaction, the carbon generated continuously by the high carbon content and high methane dissociation rate can preferentially react with CO2, effectively protecting the active phase of Mo2C from being oxidized into deactivated MoO2, and further improving the stability of the catalyst.

[0024] The Ni / Mo2C catalyst prepared by this invention has the characteristics of high activity, high stability, and high H2 / CO ratio. In the DRM reaction, it exhibits excellent initial activity and outstanding long-term stability, as well as a higher H2 / CO molar ratio.

[0025] The Ni / Mo2C catalyst prepared by this invention has excellent structural stability, strong antioxidant capacity, and excellent methane dissociation and carbon removal capabilities.

[0026] This invention presents a Ni / Mo2C catalyst prepared using glucose as a carbon source and mechanical milling. Through its unique composite structure of "highly dispersed active sites embedded in a high-carbon matrix," it simultaneously achieves multiple functions including high specific surface area, excellent mass transfer, and stable protection of the active phase. Compared to the traditional CH4 carbonization method, this catalyst exhibits superior catalytic activity, selectivity, and long-term stability in the DRM reaction. Its core advantage lies in the fact that the glucose-derived high-carbon matrix effectively prevents oxidation and sintering of the active phase, providing a new preparation strategy and theoretical basis for developing efficient, stable, and environmentally friendly DRM catalysts. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1 The XRD patterns of the catalysts prepared in Comparative Example 1 and Comparative Example 2 are shown.

[0029] Figure 2 The XRD patterns of the catalysts prepared in Examples 1-3 and Comparative Examples 3-4 at different calcination temperatures are shown.

[0030] Figure 3 The images are TEM images of Ni / Mo2C-CH4-700, where (a) is a low-magnification TEM image, and (b) and (c) are high-magnification TEM images.

[0031] Figure 4 EDX elemental analysis of Ni / Mo2C-CH4-700, where (a) is the TEM image and (b)-(e) are elemental mapping maps.

[0032] Figure 5The images are TEM images of Ni / Mo2C-CH4-900, where (a) is a low-magnification TEM image, and (b) and (c) are high-magnification TEM images.

[0033] Figure 6 EDX elemental analysis of Ni / Mo2C-CH4-900, where (a) is a TEM image and (b)-(e) are elemental mapping maps.

[0034] Figure 7 The images are TEM images of Ni / Mo2C-Glu-900, where (a) and (b) are low-magnification TEM images, and (c) and (d) are high-magnification TEM images.

[0035] Figure 8 EDX elemental analysis of Ni / Mo2C-Glu-900, where (a) is a TEM image and (b)-(e) are elemental mapping maps.

[0036] Figure 9 The methane dissociation curves for Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900 are shown.

[0037] Figure 10 The methane conversion rates of Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900 in the DRM reaction are given.

[0038] Figure 11 The carbon dioxide conversion rates of Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900 in the DRM reaction are given.

[0039] Figure 12 H2 / CO in the DRM reaction of Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900 and Ni / Mo2C-Glu-900.

[0040] Figure 13 The XRD patterns are those of Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900 after reacting for 10 hours.

[0041] Figure 14 The TEM microstructure and structural features of Ni / Mo2C-CH4-700 after the reaction are shown, where (a) is a low-magnification TEM image and (b)-(d) are high-magnification TEM images.

[0042] Figure 15The TEM microstructure and structural features of Ni / Mo2C-CH4-900 after the reaction are shown in (a) low magnification TEM, and (b) and (c) high magnification TEM.

[0043] Figure 16 The TEM microstructure and structural features of Ni / Mo2C-Glu-900 after the reaction are shown in (a) and (b) at low magnification, and (c) and (d) at high magnification.

[0044] Figure 17 The carbon content and thermogravimetric curves of the samples before and after the Ni / Mo2C-CH4-700 reaction were determined.

[0045] Figure 18 The carbon content and thermogravimetric curves of the samples before and after the Ni / Mo2C-CH4-900 reaction were determined.

[0046] Figure 19 The carbon content and thermogravimetric curves of the samples before and after the Ni / Mo2C-Glu-900 reaction were determined. Detailed Implementation

[0047] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0048] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0049] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0050] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0051] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0052] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.

[0053] Unless otherwise specified, room temperature and normal temperature in the specific embodiments of this invention refer to 20-30℃.

[0054] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0055] Example 1

[0056] The steps for preparing Ni / Mo2C catalysts using glucose as a carbon source include:

[0057] S1, with glucose (Glu, C6H) 12 The precursor for the catalyst was prepared using Ni(CH3COO)2·4H2O as the carbon source, with an elemental molar ratio of Ni:Mo:Glu = 1:2:8. Based on a glucose mass of 4g, the required nickel acetate (Ni(CH3COO)2·4H2O) and ammonium molybdate ((NH4)6Mo7O) were calculated. 24 To obtain the precursor, nickel acetate, ammonium molybdate, and glucose were mixed evenly in a mortar and mechanically ground for 30 minutes.

[0058] S2. Place the precursor in a quartz tube and rapidly heat it from room temperature to the target temperature of 900 ℃ (heating rate of 10 ℃ / min) under an argon atmosphere (100 mL / min). Hold it for one hour, cool it to room temperature, and then introduce a 1% O2 / Ar mixed gas and hold it for two hours to passivate the catalyst surface, thus obtaining the Ni / Mo2C catalyst, denoted as Ni / Mo2C-Glu-900.

[0059] Example 2

[0060] The only difference from Example 1 is that the calcination temperature in step S2 is 800 °C, and the product is denoted as Ni / Mo2C-Glu-800.

[0061] Example 3

[0062] The only difference from Example 1 is that the calcination temperature in step S2 is 700 °C, and the product is denoted as Ni / Mo2C-Glu-700.

[0063] Comparative Example 1

[0064] The steps for preparing Ni / Mo2C catalysts using the traditional CH4 carbonization method include:

[0065] S1. The oxidation precursor of the catalyst is prepared by solution mixing with an elemental molar ratio of Ni:Mo = 1:2. Based on a calculation baseline of 2g of nickel acetate (Ni(CH3COO)2·4H2O), calculate the required amount of ammonium molybdate ((NH4)6Mo7O). 24 The mass of nickel acetate and ammonium molybdate (·4H2O) was determined by stirring and dissolving them separately in 20 mL of deionized water. The two were then mixed and stirred for 20 minutes to ensure thorough mixing. The mixture was then placed in a forced-air drying oven and dried at 110 °C for 12 h. After drying, the mixture was placed in a muffle furnace and calcined at 500 °C for 3 h to prepare the precursor.

[0066] S2. Place the precursor in a quartz tube and heat it from room temperature to 700 °C (heating rate of 10 °C / min) under an atmosphere of hydrogen (60 mL / min) and methane (260 mL / min). Hold the temperature for one hour, then cool it to room temperature and passivate the catalyst surface by introducing a 1% O2 / Ar mixed gas for 2 hours to obtain the Ni / Mo2C catalyst, denoted as Ni / Mo2C-CH4-700.

[0067] Comparative Example 2

[0068] Compared with Comparative Example 1, the only difference is that the calcination temperature in step S2 is 900 °C, and the product is denoted as Ni / Mo2C-CH4-900.

[0069] Comparative Example 3

[0070] The only difference from Example 1 is that the calcination temperature in step S2 is 600 °C, and the product is denoted as Ni / Mo2C-Glu-600.

[0071] Comparative Example 4

[0072] The only difference from Example 1 is that the calcination temperature in step S2 is 500 °C, and the product is denoted as Ni / Mo2C-Glu-500.

[0073] Test case

[0074] Figure 1The XRD patterns of the catalysts prepared for Comparative Example 1 and Comparative Example 2 are shown in the figure. The figure shows the XRD analysis results of Ni / Mo2C catalysts prepared by conventional CH4 carbonization at different temperatures (700 ℃ and 900 ℃). The XRD patterns show that both catalysts have obvious Mo2C characteristic diffraction peaks at 2θ=34.4°, 37.9°, 39.4°, 52.1°, 61.5°, 69.5°, 74.6° and 75.5°, which correspond to the (021), (200), (121), (221), (040), (321), (240) and (142) crystal planes of β-Mo2C (PDF 72-1683), respectively. Meanwhile, the characteristic peaks observed at 2θ = 44.4° and 51.4° can be attributed to the (111) and (200) crystal planes of metallic Ni (PDF 87-0712), confirming the successful loading of the Ni active component in the catalyst. Notably, a diffraction peak at 2θ = 26.1° was detected only in the sample synthesized at 900 °C, corresponding to the (002) crystal plane of graphitic carbon (PDF 75-0444). This phenomenon suggests that the higher synthesis temperature promotes deep cracking of methane, leading to the formation of graphitic carbon species. The presence of graphitic carbon may affect the catalyst performance by acting as a protective layer to prevent the oxidation of the active component.

[0075] Figure 2The XRD patterns of the catalysts prepared in Examples 1-3 and Comparative Examples 3-4 at different calcination temperatures are shown. From the XRD patterns, it can be observed that the catalysts synthesized at 500 °C and 600 °C only exhibit characteristic peaks of MoO2 (PDF 73-1249) (2θ=25.9°(011), 36.9°(211), 53.4°(311)) and characteristic peaks of metallic Ni (PDF 87-0712) (2θ=44.4°(111) and 51.4°(200)), indicating that Ni can be reduced at 500 °C, but the Mo2C phase has not yet formed. As the temperature increases, the MoO2 diffraction peaks gradually weaken, while a diffraction peak for carbon species produced by glucose decomposition appears at 2θ=26.1°. When the temperature rises to 700 °C, the characteristic peak of Mo2C first appears at 2θ=39.4°, indicating that Mo2C begins to form. At 800 ℃, the Mo2C diffraction peaks (2θ = 34.4°, 37.9°, 39.4°, 52.1°, 61.5°, 69.5°, 72.3°, 74.6°, and 75.5°) were still relatively weak, while at 900 ℃ these diffraction peaks were significantly enhanced, with smaller half-widths and sharper peak heights, indicating a significant increase in the crystallinity and content of Mo2C, and a more complete catalyst structure. These results fully demonstrate that the synthesis temperature has a decisive influence on the formation of the Mo2C crystal phase, and 900 ℃ is the optimal synthesis temperature, yielding a Ni / Mo2C catalyst with a complete structure and the highest activity.

[0076] Figure 3 The images are TEM images of Ni / Mo2C-CH4-700, where (a) is a low-magnification TEM image, and (b) and (c) are high-magnification TEM images.

[0077] Figure 4 EDX elemental analysis of Ni / Mo2C-CH4-700, where (a) is the TEM image and (b)-(e) are elemental mapping maps.

[0078] Figure 3 and Figure 4 The TEM and EDX characterization results of the Ni / Mo2C catalyst prepared by the conventional CH4 carbonization method at 700 °C are shown. Low-magnification TEM image ( Figure 3 (a) shows that Ni and Mo2C components exhibit significant aggregation; high-resolution TEM analysis ( Figure 3 In (b) and (c), the interplanar spacing of adjacent lattice fringes in β-Mo2C was measured to be 0.228 nm, which is consistent with the interplanar spacing of the (121) crystal plane of β-Mo2C. The interplanar spacing of adjacent lattice fringes in Ni was 0.204 nm, which is consistent with the interplanar spacing of the (111) crystal plane of Ni. EDX element mapping ( Figure 4Further confirmation revealed the presence of uniformly distributed Ni, Mo, C, and O elements in the catalyst. The strong signals from Ni and Mo indicate they are the main components of the catalyst, while the widespread distribution of C and O reveals the presence of carbon species and oxides on the catalyst surface. These results collectively validate the successful preparation of the Ni / Mo₂C catalyst and its microstructural characteristics.

[0079] Figure 5 The images are TEM images of Ni / Mo2C-CH4-900, where (a) is a low-magnification TEM image, and (b) and (c) are high-magnification TEM images.

[0080] Figure 6 EDX elemental analysis of Ni / Mo2C-CH4-900, where (a) is a TEM image and (b)-(e) are elemental mapping maps.

[0081] Figure 5 and Figure 6 The microstructure characteristics of the Ni / Mo2C catalyst prepared by the conventional CH4 carbonization method at 900 °C are shown: TEM analysis ( Figure 5 (a) shows a comparison with 700 o Sample prepared by C ( Figure 3 In (a) of the image, the Ni and Mo2C components exhibit more significant agglomeration, indicating that the active components of the catalyst synthesized at high temperatures are more aggregated. High-resolution TEM image ( Figure 5 (b) and (c) show clear lattice fringes. The interplanar spacing of Mo2C(121) was measured to be 0.229 nm, and that of Ni(111) was 0.203 nm, both consistent with the standard interplanar spacings. EDX elemental distribution diagram ( Figure 6 The study showed that there were obvious Ni and Mo aggregation regions in the catalyst, and a small amount of O and uniformly dispersed C species were also observed.

[0082] Figure 7 The images are TEM images of Ni / Mo2C-Glu-900, where (a) and (b) are low-magnification TEM images, and (c) and (d) are high-magnification TEM images.

[0083] Figure 8 EDX elemental analysis of Ni / Mo2C-Glu-900, where (a) is a TEM image and (b)-(e) are elemental mapping maps.

[0084] Figure 7 and Figure 8 The microstructure characteristics of Ni / Mo2C-Glu-900 prepared using glucose as a carbon source are shown: TEM analysis ( Figure 7(a) shows that although there is localized agglomeration of Ni and Mo2C, which may be due to uneven mechanical mixing, in the carbon sheet region ( Figure 7 In (b) of the study, highly dispersed and uniformly distributed Ni and Mo2C active components were observed, and this good dispersion is beneficial to the enhancement of catalytic activity. HRTEM characterization ( Figure 7 (c) and (d) show clear lattice fringes. The interplanar spacing of Mo2C(121) was measured to be 0.228 nm, and that of Ni(111) was 0.202 nm, which are in perfect agreement with the standard values. EDX elemental analysis ( Figure 8 The study confirmed the presence of four elements: Ni, Mo, O, and C in the catalyst. Ni and Mo showed relatively weak signals, while C and O exhibited high intensity and uniform distribution, indicating that the catalyst prepared using glucose as a carbon source successfully achieved effective dispersion and stable existence of carbon species in the catalyst.

[0085] Figures 3-8 In this study, a systematic comparison of TEM and EDX characterization results of catalysts prepared by different methods revealed that the Ni / Mo2C catalyst prepared using glucose as a carbon source exhibits superior microstructural characteristics compared to samples prepared by the traditional CH4 carbonization method (700 ℃ and 900 ℃). Specifically, the active components (Ni and Mo2C) show higher dispersion and a more uniform distribution. EDX analysis showed a significant increase in carbon content and uniform distribution. These structural advantages may lead to higher catalytic activity and stability of the glucose-based catalyst in the dry reforming reaction of methane.

[0086] In the reforming reaction of methane and carbon dioxide, the activity of Ni / Mo2C catalysts is affected by the methane dissociation rate. A higher dissociation rate indicates more active sites on the catalyst and stronger catalytic activity. The methane dissociation of Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900 catalysts was analyzed in detail to investigate their performance differences in the catalytic reforming of methane and carbon dioxide.

[0087] The experiment used a fixed-bed reactor to test the activity of the methane-carbon dioxide reforming reaction. The catalyst dosage was 0.1 g, and the reaction pressure was maintained at 0.3 MPa. Specifically:

[0088] The catalyst activity was tested at 800 °C. First, 0.1 g of the prepared catalyst was loaded into a quartz reaction tube, followed by an appropriate amount of quartz sand. A fixed-bed reactor was assembled, and the air inside the tube was replaced with reaction gas. After airtightness testing, quartz wool was filled at both ends of the reaction tube, and the reaction chamber was sealed. Gas chromatography was then used to obtain baseline signals of each component before the reaction. Subsequently, activation pretreatment was performed in Ni / Mo2C-CH4-700 and Ni / Mo2C-CH4-900 systems using 40 mL / min H2, while in the Ni / Mo2C-Glu-900 system, Ar was used instead of H2 for activation pretreatment. After activation, the H2 pretreated system was purged with pure Ar to remove residual H2. After system purification, a CH4 / CO2 reaction mixture was introduced to begin catalytic activity testing, with gas chromatography data collected hourly to monitor product composition. At the end of the reaction, Ar protective gas was switched to, heating was stopped, and the system was allowed to cool naturally to room temperature. Finally, the catalyst sample was sealed and stored for subsequent characterization and analysis.

[0089] The gaseous components generated during the reaction were analyzed using a GC7900 gas chromatograph.

[0090] Figure 9 The figures show the methane dissociation curves for Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900. As can be seen from the figures, the methane dissociation rates of all three catalysts are relatively low from 250 °C to 450 °C. However, with increasing temperature, specifically from 450 °C to 900 °C, the methane dissociation rates of Ni / Mo2C-CH4-700 and Ni / Mo2C-CH4-900 show no significant difference, increasing from 0.12 to 1.32 and from 0.20 to 1.54, respectively. In contrast, the CH4 dissociation rate of Ni / Mo2C-Glu-900 shows a sharp increasing trend, with the methane dissociation rate increasing from 0.32 to 5.00. Data analysis of the methane dissociation rates of the three catalysts showed that Ni / Mo2C-Glu-900 significantly outperformed Ni / Mo2C-CH4-700 and Ni / Mo2C-CH4-900 in methane dissociation. This is because the catalyst prepared using glucose as a carbon source has smaller Ni and Mo2C crystal particles, resulting in a stronger methane dissociation intensity. Characterization analysis using TEM further confirmed this. Figure 7 ) and the determination of carbon content ( Figure 19 This result is also confirmed. Ni / Mo2C-Glu-900 generates a large amount of carbon through the dissociation of methane, which protects the catalyst from oxidation and thus enables the Ni / Mo2C catalyst to have higher catalytic stability.

[0091] To investigate the methane-carbon dioxide reforming performance of Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900 catalysts, and to compare their catalytic activity and long-term catalytic performance in the methane-carbon dioxide reforming reaction, stability tests were conducted on the three Ni / Mo2C catalysts. The stability test temperature was 800 ℃, and the test duration was 10 h. First, 0.1 g of catalyst was weighed and placed in a reaction tube, and then activated. After activation, a mixed gas (CH4:CO2 = 1:1, 20 mL / min) was introduced into the reaction tube to carry out the methane-carbon dioxide reforming reaction. The reacted gas was then passed through a gas chromatograph to obtain a spectrum. The gas composition was then quantitatively analyzed based on the chromatogram. Injection began 1 h after the reaction, and then every 1 h thereafter. The catalytic performance and stability of the catalysts were systematically evaluated by analyzing the methane conversion efficiency, carbon dioxide conversion efficiency, and the molar ratio of hydrogen to carbon monoxide. The results are as follows: Figures 11-12 As shown.

[0092] Conditions: T = 800 ℃, P = 1 atm, CH4 / CO2 = 1, WHSV = 15000 mL·g -1 ·h -1 .

[0093] Figure 10 The methane conversion rates of Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900 in the DRM reaction are given.

[0094] Figure 11 The carbon dioxide conversion rates of Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900 in the DRM reaction are given.

[0095] Figures 10-11The results showed that Ni / Mo2C-CH4-700 exhibited the lowest catalytic performance, with initial conversions of methane and carbon dioxide of 68.86% and 73.11%, respectively. Ni / Mo2C-CH4-900 showed slightly better catalytic activity, with initial conversions of methane and carbon dioxide of 70.96% and 76.63%, respectively. Ni / Mo2C-Glu-900 demonstrated the best catalytic performance in the initial stage of the reaction, with initial conversions of methane and carbon dioxide of 74.66% and 79.54%, respectively. This is because the catalyst synthesized using glucose as a carbon source has highly dispersed Ni molecules and Mo2C, and also has a much larger specific surface area than catalysts prepared by the traditional CH4 carbonization method, thus significantly improving catalytic activity. With the extension of reaction time, the activity of all three catalysts showed a decreasing trend. Ni / Mo2C-CH4-700 essentially lost its activity after six hours of reaction, with methane and carbon dioxide conversions decreasing to 10.83% and 29.83%, respectively. This activity decay is mainly due to the varying degrees of oxidation of Mo2C. Mo2C reacts with CO2 to produce MoO2 and CO, reducing the catalyst's activity. After 10 hours of reaction, the methane and carbon dioxide conversion rates of Ni / Mo2C-CH4-900 decreased significantly, by 17.83% and 8.20%, respectively. The methane and carbon dioxide conversion rates of Ni / Mo2C-Glu-900 only decreased slightly, by 3.32% and 2.25%, respectively, demonstrating its excellent catalytic stability. Measurement of the catalyst's carbon content showed that the catalyst prepared by the CH4 carbonization method at 700 °C had the lowest carbon content and could not effectively protect Mo2C during the long reaction period, resulting in near-deactivation of the catalyst after six hours. The catalyst prepared by the traditional CH4 carbonization method at 900 °C contains a small amount of carbon because the high-temperature synthesis process promotes methane dissociation, which can protect Mo2C to some extent during the reaction, reducing its oxidation and enhancing its stability. The catalyst prepared using glucose as a carbon source has the highest carbon content and the strongest methane dissociation ability. The generated C first reacts with CO2 to form CO, protecting Mo2C from oxidation. Therefore, it exhibits excellent catalytic activity and stability in long-term DRM reactions.

[0096] Figure 12The figure shows the H2 / CO ratios of Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900 in the DRM reaction. The initial H2 / CO molar ratios of Ni / Mo2C-CH4-700 and Ni / Mo2C-CH4-900 are low, at 0.679 and 0.646, respectively. In contrast, Ni / Mo2C-Glu-900 consistently exhibits a higher H2 / CO ratio, reaching an initial H2 / CO molar ratio of 0.745. With increasing reaction time, the H2 / CO molar ratios of Ni / Mo2C-CH4-700 and Ni / Mo2C-CH4-900 decreased to 0.561 and 0.107, respectively, after the reaction. However, Ni / Mo2C-Glu-900 maintained a relatively high H2 / CO molar ratio (0.736) even after 10 hours. This is because the smaller grain size of Ni and Mo2C molecules in the catalyst prepared using glucose as a carbon source promotes the dissociation of methane, thereby producing more hydrogen.

[0097] By comparing the performance of the three catalysts in the catalytic reforming reaction of methane and carbon dioxide, it can be seen that using glucose as a carbon source significantly improves the initial activity and stability of the catalyst under the same synthesis temperature, exhibiting higher methane and carbon dioxide conversion rates and a higher hydrogen-to-carbon monoxide ratio. This is attributed to the smaller Ni and Mo2C molecule crystal sizes and higher carbon content in the Ni / Mo2C catalyst prepared with glucose as the carbon source, which greatly protects Mo2C from oxidation, thus demonstrating superior catalytic performance and stability. Simultaneously, the uniform dispersion of Ni and Mo2C molecules in the Ni / Mo2C catalyst prepared with glucose as the carbon source significantly increases the specific surface area and active site density of the catalyst, thereby improving catalytic efficiency. Over time, during long-term reactions, the activity of all three catalysts shows a decreasing trend, possibly due to carbon deposition on the catalyst; the decline in catalytic activity is still inevitable. However, compared with the Ni / Mo2C catalyst prepared by the conventional CH4 method, the stability of the Ni / Mo2C catalyst prepared with glucose as the carbon source is significantly improved.

[0098] Figure 13The XRD patterns of Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900 after 10 hours of reaction are shown. From the XRD patterns, characteristic diffraction peaks of Mo2C appear at 2θ = 34.4°, 37.9°, 39.4°, 52.1°, 61.5°, 69.5°, 72.3°, 74.6°, and 75.5°, respectively, belonging to their (021), (200), (121), (221), (040), (321), (240), and (142) crystal planes (PDF 72-1683). This result indicates that all three catalysts retain the Mo2C crystal phase structure after 10 hours of reaction. The XRD patterns are compared with those before the reaction. Figure 1 In contrast, Ni / Mo2C-CH4-700 exhibits significant characteristic diffraction peaks of MoO2 at 2θ = 26.0°, 36.9°, and 53.5°, attributed to its (011), (211), and (220) crystal planes (PDF 73-1249). Weak characteristic diffraction peaks of MoO2 are also observed at 60.2° and 66.6°. This is because the catalyst has a low carbon content, which fails to protect Mo2C from CO2 oxidation, resulting in a large amount of Mo2C being oxidized to MoO2 during the reaction. After the reaction, the characteristic diffraction peak of carbon (011) at 2θ = 26.1° disappears in Ni / Mo2C-CH4-900, indicating that carbon is consumed during the reaction (reacting with oxygen to generate CO or CO2 escaping). However, no significant characteristic diffraction peak of MoO2 is detected. This is because the higher preparation temperature helps methane dissociate to generate a certain amount of carbon, protecting Mo2C from oxidation. The intensity of carbon diffraction peaks remained essentially unchanged before and after the Ni / Mo2C-Glu-900 reaction, and no characteristic peaks of MoO2 were observed, indicating that the glucose-derived carbon layer effectively inhibited the oxidation of Mo2C. Furthermore, TEM (… Figure 7 Analysis shows that the catalyst has small Ni and Mo2C crystallite sizes, which can significantly improve the methane dissociation rate. Figure 10 The catalyst generates protective carbon species, thus maintaining its stability. Notably, the catalyst prepared using glucose as the carbon source did not exhibit any new diffraction peaks after the reaction, and the positions and intensities of the diffraction peaks for Ni and Mo₂C remained essentially unchanged, indicating that its crystal structure was highly stable during the reaction, without significant phase transitions or loss of active components. Furthermore, this result is consistent with TEM (… Figure 7 The observed good dispersibility further confirms that the catalyst prepared with glucose as the carbon source has excellent structural stability and anti-sintering ability.

[0099] Overall, due to its lower carbonization temperature, Ni / Mo2C-CH4-700 exhibits the most severe oxidation of the Mo2C active phase after 10 hours of reaction. The Mo2C crystal structure is more easily oxidized to MoO2 by CO2 under the reaction conditions, leading to a significant decrease in catalyst activity. This structural change may severely affect the catalyst's activity and stability in long-term reactions. To examine the impact of carbon content, the temperature of the traditional carbonization method was increased to 900 ℃ compared to 700 ℃. Ni / Mo2C-CH4-900, due to its higher preparation temperature, promotes methane dissociation, generating a certain amount of graphite carbon, which to some extent protects Mo2C from oxidation. However, with carbon consumption, the catalyst cannot maintain its catalytic performance for an extended period. Ni / Mo2C-Glu-900 demonstrates excellent structural stability before and after the reaction; its Mo2C crystal structure remains stable during the reaction, without significant phase transitions, new phase formation, or loss of active components. Its high methane dissociation rate continuously generates graphite carbon, protecting Mo2C from oxidation and enabling it to maintain excellent and stable catalytic performance in long-term DRM reactions.

[0100] Figure 14 The TEM microstructure and structural features of Ni / Mo2C-CH4-700 after the reaction are shown in the figures. (a) is a low-magnification TEM image, and (b)-(d) are high-magnification TEM images. As can be seen from the figures, by comparing the microstructure before and after the reaction... Figure 3 The morphology of (a) shows that after the DRM reaction, the Ni and Mo2C active components in the catalyst underwent significant sintering, forming large agglomerates. This structural change may lead to a reduction in the active sites of the catalyst. High-resolution transmission electron microscopy (HRTEM) analysis further revealed the phase transition behavior of the catalyst during the reaction process: Figure 14 As shown in (b), lattice fringes with a spacing of 0.341 nm can be clearly observed, which matches the (011) crystal plane of MoO2, confirming that the active phase of Mo2C is oxidized to MoO2 under the reaction conditions. Meanwhile, in Figure 14 A lattice spacing of 0.225 nm can still be detected in (c), corresponding to the (121) crystal plane of Mo2C, indicating that part of the Mo2C phase is retained. Furthermore, Figure 14 The 0.201 nm lattice spacing shown in (d) corresponds to the (111) crystal plane of metallic Ni, indicating the presence of metallic Ni after the reaction. These structural characterization results clearly show that the catalyst underwent partial oxidation and sintering during the reaction, which may be an important reason for the decline in its catalytic performance.

[0101] Figure 15The TEM microstructure and structural features of Ni / Mo2C-CH4-900 after the reaction are shown in Figures (a) (low magnification TEM) and (b) and (c) (high magnification TEM). As can be seen from the figures, in Figure (a), Ni and Mo2C molecules also exhibit aggregation due to sintering, although to a lesser degree than Ni / Mo2C-CH4-700 prepared at 700 °C. However, this still leads to a reduction in the number of active sites on the catalyst, resulting in a decrease in catalytic activity. Nevertheless, relatively clear lattice fringes can still be seen in the high-resolution transmission electron microscopy (TEM) images. Figure 15 In (b), we can see that the lattice spacing of Mo2C is 0.226 nm, which corresponds to the (121) crystal plane of Mo2C. Figure 15 In (c), we can see that the lattice spacing of Ni is 0.203 nm, which corresponds to the (111) crystal plane of metallic Ni.

[0102] Figure 16 The images show the TEM microstructure and structural features of Ni / Mo2C-Glu-900 after the reaction, with (a) and (b) being low-magnification TEM images and (c) and (d) being high-magnification TEM images. It can be observed from the figures that the catalyst maintains good structural stability after the reaction. (From the low-magnification TEM images...) Figure 16 As can be seen from (a), although the active components showed slight aggregation during the reaction, the change was not significant compared to before the reaction. Figure 16 (b) further shows that although some Ni and Mo2C particles sintered, the overall structure remained highly dispersed with a uniform particle size distribution and a large number of nanoscale active particles. This excellent dispersion indicates that the catalyst has outstanding anti-sintering ability. High-resolution transmission electron microscopy (HRTEM) analysis results ( Figure 16 (c) and (d) further confirm the catalyst's stability: clear 0.227 nm lattice fringes are observed, corresponding to the (121) crystal plane of Mo2C. A lattice spacing of 0.202 nm is also detected, perfectly matching the (111) crystal plane of metallic Ni. These characterization results fully demonstrate that Ni / Mo2C-Glu-900 can effectively maintain its active phase structure under reaction conditions, exhibiting excellent thermal and structural stability, which provides a structural basis for its sustained catalytic performance in high-temperature reactions.

[0103] By comparing the TEM images of the samples before and after the reaction, it can be seen that the morphology and internal structure of Ni / Mo2C-Glu-900 remained basically unchanged compared with Ni / Mo2C-CH4-700 and Ni / Mo2C-CH4-900. The Ni and Mo2C molecules still exhibited high dispersion and relatively uniform distribution. This indicates that Ni / Mo2C-Glu-900 possesses good thermal stability and can still demonstrate high catalytic activity at high temperatures. Compared with before the reaction, the particle size of Ni and Mo2C in each catalyst increased after the reaction, indicating that the active components of each catalyst underwent varying degrees of sintering and growth during the methane-carbon dioxide reforming reaction. Ni / Mo2C-CH4-700 exhibited the largest particle size and the highest degree of sintering and agglomeration after the reaction. Ni / Mo2C-Glu-900 exhibited the smallest particle size and the lowest degree of sintering and agglomeration after the reaction.

[0104] To further investigate the reasons for the performance differences among Ni / Mo2C-CH4-700, Ni / Mo2C-CH4-900, and Ni / Mo2C-Glu-900, thermogravimetric (TG) analysis was performed on samples before and after the reaction. Figures 17-19 ) and carbon content ( Figures 17-19 The determination of (illustration)

[0105] Figure 17 The carbon content and thermogravimetric curves of the Ni / Mo2C-CH4-700 samples before and after the reaction are shown in the figure. The figure reveals the compositional changes of Ni / Mo2C-CH4-700 before and after the reaction. Carbon content analysis shows that the initial carbon content of the catalyst was only 8.6%, which further decreased to 2.3% after the reaction. This is mainly due to the consumption of carbon components with oxygen during the reaction. TG curve analysis shows that the samples before and after the reaction exhibit a significant increase in mass below 750 °C. This phenomenon originates from the oxidation reaction that occurs during the thermal analysis: Mo2C reacts with oxygen to generate MoO2 and CO, while Ni is oxidized to NiO. It is noteworthy that although the formation of CO leads to mass loss, the mass increase effect from the formation of MoO2 and NiO is dominant. Comparing the TG curves before and after the reaction reveals two important characteristics: First, the oxidation initiation temperature of the sample after the reaction is significantly lower, which is attributed to the reduced carbon content of the catalyst after the reaction, making Mo2C more easily oxidized. Secondly, the increase in sample mass after the reaction was significantly reduced. This is because the catalyst was partially oxidized during the reaction, generating a large amount of MoO2, which reduced the content of Mo2C that could be further oxidized during thermogravimetric analysis. These results indicate that under the reaction conditions, the carbon protective layer of the catalyst is gradually consumed, making the active components more susceptible to oxidation, which is closely related to the decline in its catalytic performance.

[0106] Figure 18 The carbon content and thermogravimetric curves of the Ni / Mo2C-CH4-900 samples before and after the reaction are shown in the figure. The compositional evolution of Ni / Mo2C-CH4-900 before and after the reaction is systematically compared. Carbon content analysis shows that the initial carbon content of the catalyst was as high as 19.9%, which significantly decreased to 6.3% after the reaction, indicating significant carbon consumption during the methane-carbon dioxide reforming reaction. TG curve analysis shows that both the samples before and after the reaction exhibited significant mass increases below 600 °C, mainly attributed to the synergistic effect of Mo2C conversion to MoO2 and Ni oxidation to NiO during the oxidation process. Notably, the mass increase of the sample before the reaction was significantly smaller than that of the sample after the reaction. This is mainly because the catalyst before the reaction contained abundant carbon components (19.9%), which reacted with oxygen during thermogravimetric analysis to generate CO2 and CO, partially offsetting the mass increase effect caused by oxide formation. Comparative analysis also revealed that the oxidation onset temperature of the sample after the reaction was significantly earlier, mainly due to two factors: firstly, a large amount of carbon was consumed during the reaction, resulting in a significant reduction in the carbon protective layer. On the other hand, the residual carbon content (6.3%) was insufficient to effectively protect the Mo2C active phase, causing it to begin oxidizing to MoO2 at a lower temperature, thus exhibiting an earlier increase in mass. These results clearly demonstrate that although the catalyst prepared at a higher temperature (900 °C) has a higher initial carbon content, the continuous consumption of the carbon protective layer during the reaction still leads to a decrease in catalyst stability.

[0107] Figure 19 The carbon content and thermogravimetric curves of Ni / Mo2C-Glu-900 samples before and after the reaction are shown in the figure. Compared with Ni / Mo2C-CH4-700 and Ni / Mo2C-CH4-900, Ni / Mo2C-Glu-900 exhibits significantly different carbon behavior characteristics. Carbon content analysis shows that the carbon content remains highly stable before and after the reaction, decreasing only slightly from 47.9% to 46.5%. This excellent carbon retention ability stems from two mutually balanced processes: on the one hand, some carbon is consumed during the reaction to protect the Mo2C active phase from oxidation; on the other hand, thanks to the smaller Ni and Mo2C grain sizes of the catalyst prepared using glucose as a carbon source, it exhibits stronger methane dissociation ability and can continuously replenish carbon species. TG analysis results show that the catalyst as a whole exhibits a weight loss trend, but the pre-reaction sample begins to lose significant weight at 400℃, while the significant weight loss in the post-reaction sample increases to 500℃. This difference indicates that the carbon oxidation activity of the catalyst is reduced after the reaction (C+O2→CO / CO2). TEM ( Figure 16Observations confirmed that the aggregation of active components after the reaction is likely the main reason for the decrease in catalytic activity. Notably, the TG curve showed localized weight gain near 550 °C and 700 °C, corresponding to the partial oxidation of Mo2C to MoO2 and CO, and the oxidation of Ni to NiO. However, due to the extremely high initial carbon content (47.9%) of the catalyst, a large number of carbon species reacted with oxygen during oxidation to generate gaseous products (CO2 / CO), resulting in the release of these products. This dominant weight loss process caused the overall TG curve to show a downward trend. These results indicate that the catalyst prepared from glucose as a carbon source has excellent carbon retention capabilities, which provides an important guarantee for maintaining its long-term stability during the reaction.

[0108] The above fully demonstrates that the Ni / Mo2C catalyst prepared with glucose as the carbon source exhibits significantly superior catalytic activity and stability in the methane-carbon dioxide reforming reaction due to its excellent structural characteristics and chemical properties.

[0109] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a Ni / Mo2C catalyst, characterized in that the steps include... include: The precursor was prepared by mechanical grinding using nickel and molybdenum sources as reactants and glucose as a carbon source. The precursor was calcined in an inert atmosphere and then surface passivated to obtain the Ni / Mo2C catalyst.

2. The preparation method according to claim 1, characterized in that, The nickel source includes nickel acetate and / or nickel nitrate.

3. The preparation method according to claim 1, characterized in that, The molybdenum source includes ammonium molybdate.

4. The preparation method according to claim 1, characterized in that, The molar ratio of Ni and Mo in the nickel source and the molybdenum source is 1:

2.

5. The preparation method according to claim 1, characterized in that, The molar ratio of Ni to glucose in the nickel source is 1:

8.

6. The preparation method according to claim 1, characterized in that, The grinding time for the mechanical grinding method is 30 minutes.

7. The preparation method according to claim 1, characterized in that, The heating rate of the calcination process is 10 °C / min, the temperature is 700-900 °C, and the holding time is 1 h.

8. The preparation method according to claim 1, characterized in that, The surface passivation treatment involves introducing a 1% O2 / Ar mixed gas for 2 hours.

9. A Ni / Mo2C catalyst, characterized in that, The Ni / Mo2C catalyst is prepared by the preparation method according to any one of claims 1-8.

10. The application of the Ni / Mo2C catalyst according to claim 9 in the methane-carbon dioxide reforming reaction.

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