A method for preparing a nickel-based catalyst for dry reforming of methane and its application.

Abstract

This invention discloses a method for preparing a nickel-based catalyst for dry reforming of methane and its application. The catalyst mainly comprises an active metal, an additive, and a support. The preparation method involves ball milling a mixture of nickel salt, magnesium acetate tetrahydrate, calcium acetate monohydrate, and ethylenediaminetetraacetic acid (EDTA) as raw materials. The ball-milled product is then mixed with melamine and calcined at high temperature to obtain the target catalyst with a Ni-NC structure. The active metal Ni in the catalyst prepared by this invention is highly dispersed, and the catalyst is less prone to carbon deposition during the reaction. Compared with traditional preparation methods, this invention is characterized by: inexpensive and readily available raw materials; a simple catalyst preparation process; suitability for large-scale production; and both high activity and high stability.

Description

Technical Field

[0001] This invention relates to a method for the large-scale preparation and application of a nickel-based catalyst for dry reforming of methane, belonging to the fields of catalyst manufacturing engineering technology and environmental protection technology. Background Technology

[0002] Carbon dioxide (CO2) is a greenhouse gas and a major contributor to the greenhouse effect. However, it is also a natural source of carbon, serving as a carbon source for the production of various useful fuels and chemicals, while simultaneously helping to reduce CO2 emissions. In recent years, due to the discovery of abundant shale gas reserves and the advancement of hydraulic fracturing technology, methane (CH4) has become the preferred energy source. Besides shale gas, biogas from anaerobic decomposition and landfill gas produce CO2 and CH4. These can be used as feedstock for dry methane reforming (DRM) to produce syngas, enabling the synthesis of other high-value-added chemicals while reducing carbon emissions. DRM can convert CO2 and CH4 into syngas (a mixture of H2 and CO), with an H2 / CO ratio close to 1.

[0003] Catalysts commonly used in methane dry reforming reactions are generally classified into noble metal catalysts and nickel-based catalysts. Compared with noble metal catalysts such as Pd, Pt, Ir, and Ru, nickel is much cheaper and exhibits high activity for methane conversion. However, Ni-based catalysts still face many problems in industrialization. On the one hand, the problems of easy sintering and carbon deposition of nickel-based catalysts are often not properly resolved, and the activity and stability of the catalyst cannot be guaranteed. On the other hand, the synthesis steps of most Ni-based catalysts are cumbersome, making mass production impossible and hindering industrialization.

[0004] Chinese invention patent CN 112717914A discloses a methane-carbon dioxide reforming catalyst. This invention organically combines pyrochlore oxide with a hydrotalcite-like semi-finished product to prepare a pyrochlore-magnesium aluminum spinel support. Then, active nickel is impregnated onto the composite support and calcined to obtain the target catalyst. Its key features are the strong interaction between the nickel particles and the support and the high stability of the support. This catalyst exhibits a high conversion rate for the dry reforming of methane and carbon dioxide to syngas, but its high stability is not demonstrated. Chinese invention patent CN113952956A relates to a mesoporous catalyst with a regular and ordered structure. Its key features are a large specific surface area and superior high-temperature stability; however, the catalyst synthesis involves too many steps, including evaporation, dissolution, and calcination, making large-scale mass production difficult.

[0005] Chinese invention patent CN 116078393A discloses a transition metal-supported high-entropy oxide low-temperature methane dry reforming catalyst, its preparation method, and its application. In the methane dry reforming reaction, the entropy stability of the high-entropy oxide support inhibits the migration of the transition metal, effectively extending the catalyst's lifetime and maintaining high catalytic activity.

[0006] Most patent reports have yielded catalysts with high catalytic conversion efficiency for dry methane reforming, but these catalysts still exhibit deactivation during long-term operation. Ensuring high catalyst activity and stability, and developing catalyst synthesis processes suitable for large-scale production, are key research areas in the field of dry methane reforming. Summary of the Invention

[0007] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention proposes a nickel-based catalyst prepared by ball milling and applied to the dry reforming reaction of methane. This method utilizes readily available raw materials, has a simple and easily implemented process, and is readily mass-produced. The catalyst exhibits highly dispersed active nickel metal, demonstrating strong resistance to carbon deposition and sintering.

[0008] A nickel-based catalyst for dry reforming of methane is prepared by using nickel as the active metal and MgO and CaO as promoters, and supporting it on a carbon film formed by calcining melamine, thereby preparing a nickel-based catalyst with strong metal-support interaction.

[0009] A method for preparing a nickel-based catalyst for dry reforming of methane specifically includes the following steps:

[0010] (1) Nickel salt, magnesium acetate tetrahydrate, calcium acetate monohydrate and EDTA were mixed and ball-milled to obtain the precursor;

[0011] (2) After the precursor obtained in step (1) and melamine are mixed evenly in a certain proportion, they are calcined in a tube furnace to obtain the methane dry reforming catalyst Ni-NC.

[0012] Preferably, the nickel salt in step (1) is one of nickel acetate, nickel carbonate, nickel chloride, and nickel nitrate.

[0013] Preferably, the mass ratio of magnesium acetate tetrahydrate, calcium acetate monohydrate, nickel salt, and EDTA in step (1) is 1:2-5:3-18:100-150.

[0014] Preferably, the ball milling frequency in step (1) is 20-50Hz and the ball milling time is 20-60min.

[0015] Preferably, the mass ratio of the precursor to melamine in step (2) is 1:3-8.

[0016] Preferably, the calcination atmosphere in step (2) is nitrogen or argon.

[0017] Preferably, the calcination temperature rate in step (2) is 2-10℃ / min, the calcination temperature is 600-1000℃, and the calcination time is 2-4h.

[0018] Preferably, the nickel-based methane dry reforming catalyst prepared by the method has a Ni mass fraction of 2-12%.

[0019] On the other hand, the present invention provides the application of the nickel-based catalyst prepared by the aforementioned method in gas conditions such as carbon dioxide-rich flue gas and methane-rich flue gas. Syngas is prepared using methane and carbon dioxide as raw materials under the catalytic action of the aforementioned methane dry reforming nickel-based catalyst.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) The nickel-based catalyst for dry reforming of methane prepared in this invention uses nickel as the active metal and MgO and CaO as promoters, and is supported on a carbon film formed by calcination of melamine. It has strong metal-support interaction, which significantly improves the thermal stability and carbon deposition removal ability of the catalyst in the dry reforming reaction.

[0022] (2) The nickel-based catalyst prepared in this invention is applied to the synthesis gas produced in the dry reforming reaction of methane with a hydrogen to carbon monoxide ratio close to 1, and no deactivation trend is observed after 1000 hours of continuous reaction.

[0023] (3) The preparation method of this invention is simple, the raw materials are widely available, and the preparation conditions are easy to control accurately. It is expected to significantly reduce the production cost of this type of catalyst in actual production and is suitable for large-scale industrial production. Attached Figure Description

[0024] Figure 1 The image shows a SEM image of the nickel-based catalyst prepared in Example 1.

[0025] Figure 2 The image shows the EDX curve of the nickel-based catalyst prepared in Example 1.

[0026] Figure 3 The graph shows the stability test results of the nickel-based catalyst prepared in Example 1 during methane reforming. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to embodiments, but the scope of protection of the present invention is not limited thereto.

[0028] Example 1: A nickel-based catalyst for dry reforming of methane

[0029] The preparation of Ni-NC using a mechanical mixing method includes the following steps:

[0030] (1) Nickel salt, magnesium acetate tetrahydrate, calcium acetate monohydrate and EDTA were mixed and ball-milled to obtain the precursor;

[0031] (2) After the precursor obtained in step (1) and melamine are mixed evenly in a certain proportion, they are calcined in a tube furnace to obtain methane dry reforming catalyst Ni-NC, denoted as C1, with a Ni mass fraction of 6%.

[0032] In step (1), the nickel salt is nickel acetate tetrahydrate.

[0033] The mass ratio of magnesium acetate tetrahydrate, calcium acetate monohydrate, nickel salt, and EDTA in step (1) is 1:3.6:3.0:122.1.

[0034] In step (1), the ball mill frequency is 30Hz and the ball milling time is 30min.

[0035] The mass ratio of the precursor to melamine in step (2) is 1:5.

[0036] The calcination atmosphere in the tubular furnace in step (2) is nitrogen.

[0037] In step (2), the heating rate of calcination is 5℃ / min, the calcination temperature is 800℃, and the calcination time is 2h.

[0038] Example 2: A nickel-based catalyst for dry reforming of methane

[0039] Its preparation method is basically the same as in Example 1, except that:

[0040] The nickel salt in step (1) is nickel nitrate hexahydrate.

[0041] In step (1), the mass ratio of magnesium acetate tetrahydrate, calcium acetate monohydrate, nickel salt, and EDTA is 1:3.6:3.5:122.1. The prepared nickel-based catalyst is denoted as C2, and the mass fraction of Ni is 6%.

[0042] Example 3: A nickel-based catalyst for dry reforming of methane

[0043] Its preparation method is basically the same as in Example 1, except that:

[0044] The nickel salt in step (1) is basic nickel carbonate.

[0045] In step (1), the mass ratio of magnesium acetate tetrahydrate, calcium acetate monohydrate, nickel salt, and EDTA is 1:5:3:100.

[0046] In step (1), the ball mill frequency is 20Hz and the ball milling time is 60min.

[0047] In step (2), the mass ratio of the precursor to melamine is 1:8.

[0048] The calcination atmosphere in the tubular furnace in step (2) is nitrogen.

[0049] In step (2), the heating rate of calcination is 2℃ / min, the calcination temperature is 600℃, and the calcination time is 4h.

[0050] The prepared nickel-based catalyst is designated C3, with a Ni mass fraction of 3.75%.

[0051] Example 4: A nickel-based catalyst for dry reforming of methane

[0052] Its preparation method is basically the same as in Example 1, except that:

[0053] The nickel salt in step (1) is nickel chloride.

[0054] The mass ratio of magnesium acetate tetrahydrate, calcium acetate monohydrate, nickel salt, and EDTA in step (1) is 1:2:18:150.

[0055] In step (1), the ball mill frequency is 50Hz and the ball milling time is 20min.

[0056] The mass ratio of the precursor to melamine in step (2) is 1:3.

[0057] The calcination atmosphere in the tubular furnace in step (2) is argon.

[0058] In step (2), the heating rate of calcination is 10℃ / min, the calcination temperature is 1000℃, and the calcination time is 4h.

[0059] The prepared nickel-based catalyst is designated C4, with a Ni mass fraction of 10%.

[0060] Comparative Example 1: A nickel-based catalyst for dry reforming of methane

[0061] Ni-NC was prepared using a mechanical mixing method, and the specific preparation method is as follows:

[0062] (1) 0.0481g magnesium acetate tetrahydrate, 0.1714g calcium acetate monohydrate and 1.5816g tannin were placed in a ball mill jar and ball milled at a frequency of 30Hz for 30min to mix them evenly. The mixture was then taken out and placed in a crucible and placed in a muffle furnace. The temperature was increased to 800℃ at a rate of 5℃ / min and calcined for 4h to obtain the auxiliary agent MgCaO.

[0063] (2) 0.1435g nickel acetate tetrahydrate, 0.06g MgCaO and 5.874g EDTA were placed in a ball mill jar and milled at a frequency of 30Hz for 30min to obtain the catalyst precursor.

[0064] (3) The catalyst precursor and melamine (1:5 mass ratio) were mixed and ground evenly, placed in a boat, and calcined in a tube furnace under a nitrogen atmosphere at a rate of 5℃ / min to 800℃ for 2h. The resulting methane dry reforming catalyst Ni-NC, denoted as D1, had a Ni mass fraction of 6%.

[0065] Comparative Example 2: A nickel-based catalyst for dry reforming of methane

[0066] Its preparation method is basically the same as in Example 1, except that:

[0067] The mass ratio of magnesium acetate tetrahydrate, calcium acetate monohydrate, nickel salt, and EDTA in step (1) is 1:3.6:1.5:61.1.

[0068] Ni-NC(2MO) methane dry reforming catalyst was obtained x ), denoted as D2, with a Ni mass fraction of 6%.

[0069] Comparative Example 3: A nickel-based catalyst for dry reforming of methane

[0070] Its preparation method is basically the same as in Example 1, except that:

[0071] The mass ratio of magnesium acetate tetrahydrate, calcium acetate monohydrate, nickel salt, and EDTA in step (1) is 1:3.6:0.6:24.4.

[0072] The methane dry reforming catalyst Ni-NC(5MOx) was obtained, denoted as D3, with a Ni mass fraction of 6%.

[0073] Comparative Example 4: A nickel-based catalyst for dry reforming of methane

[0074] Its preparation method is basically the same as in Example 1, except that:

[0075] The mass ratio of magnesium acetate tetrahydrate, calcium acetate monohydrate, nickel salt, and EDTA in step (1) is 1:3.6:3.0:61.1.

[0076] The methane dry reforming catalyst Ni-NC-1 / 2EDTA, denoted as D4, was obtained, with a Ni mass fraction of 12%.

[0077] Comparative Example 5: A nickel-based catalyst for methane dry reforming

[0078] Ni-NC-2EDTA was prepared by mechanical mixing, and the preparation method was basically the same as in Example 1, except that:

[0079] The mass ratio of magnesium acetate tetrahydrate, calcium acetate monohydrate, nickel salt, and EDTA in step (1) is 1:3.6:3.0:244.2.

[0080] The methane dry reforming catalyst Ni-NC-2EDTA, denoted as D5, was obtained, with a Ni mass fraction of 3%.

[0081] Comparative Example 6: A nickel-based catalyst for methane dry reforming

[0082] Its preparation method is basically the same as in Example 1, except that:

[0083] The mass ratio of the precursor to melamine in step (2) is 1:2.5.

[0084] The methane dry reforming catalyst Ni-NC (1 / 2 melamine), denoted as D5, was obtained, with a Ni mass fraction of 12%.

[0085] Comparative Example 7: A nickel-based catalyst for methane dry reforming

[0086] Its specific preparation is basically the same as in Example 1, except that:

[0087] In step (2), the mass ratio of the precursor to melamine is 1:10.

[0088] The methane dry reforming catalyst Ni-NC(2-melamine) was obtained, denoted as D7, with a Ni mass fraction of 3%.

[0089] Experimental Example 1

[0090] Catalyst reaction performance evaluation:

[0091] The reactivity of the catalyst samples prepared in all examples and comparative examples was investigated. The reactions were carried out in a continuous flow fixed-bed reactor with 0.05 g of catalyst packed in a small-diameter quartz tube. The reaction conditions were 750 °C, CO2:CH4:N2 = 1:1:8 (V:V:V), atmospheric pressure, and a space velocity of 14400 mL·g. -1 ·h -1 The products were analyzed online by gas chromatography, and the reaction results are listed in Table 1.

[0092] Table 1 Comparison of methane reforming activity of Ni catalysts

[0093]

[0094]

[0095] The results above show that the catalysts prepared using the methods provided in Examples 1-4 of this invention have high reactivity.

[0096] Even after reacting the nickel-based catalysts obtained in Examples 1-2 of this invention for 1000 hours, they still exhibited high reactivity. Figure 3 As shown, after 1000 hours of operation, the CO2 conversion rate of the C1 catalyst reached 77.9% and the CH4 conversion rate reached 92.1%. The catalyst prepared by this invention can operate continuously, efficiently and stably for more than 1000 hours without deactivation.

[0097] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications and combinations can be made to the technical solutions of the present invention, and these simple modifications and combinations are all included within the protection scope of the present invention.

Claims

1. The application of a nickel-based catalyst for dry reforming of methane in the preparation of syngas, characterized in that: The preparation method of the methane dry reforming nickel-based catalyst includes the following steps: (1) Mix nickel salt, magnesium acetate tetrahydrate, calcium acetate monohydrate and EDTA and then ball mill to obtain the precursor; the mass ratio of magnesium acetate tetrahydrate, calcium acetate monohydrate, nickel salt and EDTA is 1:2-5:3-18:100-150. (2) After the precursor obtained in step (1) and melamine are mixed evenly in a certain proportion, they are calcined in an inert atmosphere to obtain the methane dry reforming catalyst Ni-NC; The ball milling frequency in step (1) is 20-50 Hz, and the ball milling time is 20-60 min; In step (2), the heating rate of calcination is 2-10℃ / min, the calcination temperature is 600-1000℃, and the calcination time is 2-4 h; Syngas was prepared using methane and carbon dioxide as raw materials under the catalysis of a nickel-based dry reforming catalyst for methane dry reforming; the volume ratio of carbon dioxide to methane was 0.8–1.2, the reaction temperature was 650–850 °C, the reaction pressure was atmospheric pressure to 2 MPa, and the gas hourly space velocity (GHSV) of the reactants was 3000–60000 mL·g. -1 ·h -1 .

2. The application of the nickel-based methane dry reforming catalyst according to claim 1 in the preparation of syngas, characterized in that: The nickel salt is one of nickel acetate, nickel carbonate, nickel chloride, and nickel nitrate.

3. The application of the nickel-based methane dry reforming catalyst according to claim 1 in the preparation of syngas, characterized in that, The mass ratio of the precursor to melamine in step (2) is 1:3-8.

4. The application of the nickel-based methane dry reforming catalyst according to claim 1 in the preparation of syngas, characterized in that, The calcination atmosphere in step (2) is nitrogen or argon.

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