Preparation method and application of a methane dry reforming Ni-Co bimetallic catalyst

Abstract

The application belongs to the technical field of catalytic material synthesis, and discloses a preparation method of a Ni-Co bimetallic catalyst for dry reforming of methane and application thereof; the Ni-Co bimetallic catalyst is prepared by using Ni and Co as active components of a dry reforming of methane catalyst and an alkali earth metal as a carbon dioxide adsorbent by an impregnation method; the catalyst prepared by the application not only effectively overcomes the problem of poor stability of a Ni-based catalyst, but also promotes carbon dioxide adsorption and improves the efficiency of dry reforming of methane; and the method for preparing the Ni-Co bimetallic catalyst is simple and low in cost, and the catalyst exhibits excellent catalytic performance and stability in a dry reforming of methane reaction.

Description

Technical Field

[0001] This invention belongs to the field of catalytic material preparation technology. Specifically, it relates to a method for preparing a Ni-Co bimetallic catalyst for methane dry reforming and its application. Background Technology

[0002] Coal, oil, and natural gas are the main fossil fuels upon which humanity depends for survival today. The large-scale use of high-carbon energy like coal leads to massive emissions of carbon dioxide (CO2). The depletion of oil resources and their volatile prices, coupled with the fact that new energy sources (such as wind and solar power) cannot replace fossil fuels on a large scale in the short term, have made clean and environmentally friendly natural gas resources a focus of attention for many countries. Over-reliance on fossil fuels brings convenience to human life but also emits large amounts of CO2. The continuous increase in atmospheric CO2 levels exacerbates the global greenhouse effect, leading to numerous environmental problems such as rising global average temperatures, slowly rising sea levels, melting polar ice caps, and frequent extreme weather events.

[0003] In industrial sectors, such as fossil fuel power plants and energy-intensive industries, captured or separated CO2 is stored in geological reservoirs. Given the high costs of CO2 purification and compression, a more practical strategy for addressing the CO2 challenge is gaining attention: using CO2 as a carbon feedstock for value-added fuel and chemical production, rather than viewing it as a pollutant—namely, CO2 capture and conversion.

[0004] In the field of CO2 conversion, dry reforming of methane has attracted widespread attention. However, low reforming efficiency and poor catalyst stability are pressing problems that need to be solved in the CO2 dry reforming of methane. Among numerous catalyst synthesis methods, the material preparation strategy of combining adsorbent and catalyst into a single particle has become a promising process. This bifunctional catalyst utilizes the adsorbent to capture CO2 generated during the reforming process in situ, while simultaneously promoting the forward shift of the reforming reaction and the water-gas shift reaction, reducing the concentration of other byproducts, and improving the conversion rate of the reactants. However, most bifunctional catalysts currently prepared typically lack a porous structure, have a small specific surface area, and exhibit significantly reduced stability after multiple cycles, greatly affecting the application of bifunctional catalysts.

[0005] Bifunctional reforming catalysts can be classified into noble metal-based catalysts (such as Rh, Ru, Pt, and Pd) and non-noble metal-based catalysts (Ni and Co) based on the active metal. Noble metal catalysts exhibit high activity and good stability; however, due to the scarcity of noble metal resources and their high cost, they are not suitable for large-scale industrial production. Among non-noble metal catalysts, Ni-based catalysts show the best activity. However, Ni-based catalysts suffer from sintering of the active component Ni and the formation of carbon deposits during the reaction process, resulting in a short catalyst lifespan. Sintering of the active component Ni reduces the number of active sites, thereby decreasing the reaction activity; while the generated carbon deposits cover the active sites and block the catalyst pores, thus affecting the diffusion of reactants and products. This invention provides a method for preparing a Ni-Co bimetallic catalyst, producing a porous catalyst with a high specific surface area, successfully solving the problems of catalyst sintering and carbon deposition, and greatly improving the catalyst activity and stability. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a Ni-Co bimetallic catalyst for methane dry reforming, which exhibits high conversion efficiency and stable catalytic performance in methane dry reforming.

[0007] On the one hand, this invention provides a method for preparing a Ni-Co bimetallic catalyst for methane dry reforming that exhibits strong resistance to sintering and carbon deposition, high activity, and high stability, specifically including the following steps:

[0008] (1) Alkali earth metals and tannins are mixed by ball milling and then calcined to obtain the auxiliary agent MO. x ;

[0009] (2) After mixing nickel salt, cobalt salt, EDTA and water, ammonia water is added dropwise to make it a homogeneous solution, and then a certain amount of the auxiliary agent MO obtained in step (1) is added. x A mixed solution is obtained;

[0010] (3) The mixed solution obtained in step (2) is dispersed by ultrasonication and then dried by rotary evaporation to obtain the precursor;

[0011] (4) After grinding the precursor and anchoring agent melamine obtained in step (3) into uniform form in a certain proportion, they are calcined under an inert atmosphere to obtain the Ni-Co bimetallic catalyst for methane dry reforming.

[0012] Preferably, the total mass fraction of Ni and Co in the Ni-Co bimetallic catalyst is 2-12%.

[0013] Preferably, the mass ratio of alkaline earth metal salt to tannin in step (1) is 1:2.5-9; the alkaline earth metal is a calcium salt or a magnesium salt.

[0014] Preferably, the mass ratio of nickel salt, cobalt salt, EDTA, water, ammonia and MOx in step (2) is 1:1-3:8-12:10-15:16-25:0.1-1.

[0015] Preferably, the ultrasonic time in step (3) is 30 min, the rotary evaporation temperature is 50-90℃, and the rotary evaporation time is 0.5-2 h.

[0016] Preferably, the mass ratio of the precursor to the anchoring agent melamine in step (4) is 1:2-10.

[0017] Preferably, the calcination temperature rate in step (1) is 1-5℃ / min, the calcination temperature is 400-800℃, and the calcination time is 3-6h.

[0018] Preferably, the calcination temperature rate in step (4) is 1-5℃ / min, the calcination temperature is 500-1000℃, and the calcination time is 1-5h.

[0019] On the other hand, the present invention provides the application of the Ni-Co bimetallic catalyst prepared by the above preparation method in CO2 methane dry reforming.

[0020] Compared with existing technologies, the catalyst prepared by this invention has the following advantages:

[0021] (1) The raw materials of this invention are widely available, the preparation process is simple, the preparation conditions are easy to control accurately, and the resulting catalyst has good reproducibility;

[0022] (2) In this invention, under the reaction conditions, MO x The surface can adsorb CO2 and generate carbonic acid compounds, and can decompose and release CO2 at high temperatures, which helps to promote the contact between the reactant gas and the catalyst, thereby improving the conversion and reaction activity. In addition, due to the doping of alkaline earth metals, Ni particles are fixed, which can prevent Ni sintering. On the other hand, due to the doping of alkaline earth metals, the formation of carbon deposits is also inhibited, thereby improving the stability of the catalyst.

[0023] (3) The present invention can change the composition of the precursor salt in the preparation of catalysts to prepare catalysts with different active centers with coated structures, which can be widely used in other catalytic systems and have good universality.

[0024] (4) The catalyst prepared by this invention exhibits high efficiency and stable catalytic performance, has good environmental friendliness, and has good application prospects in the treatment of gases such as CO2 and CH4. Attached Figure Description

[0025] Figure 1This is a TEM image of the Ni-Co catalyst.

[0026] Figure 2 Here is the EDX image of the Ni-Co catalyst.

[0027] Figure 3 This is a stability test diagram of Ni-Co catalyst used in methane reforming. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally operated under conventional conditions. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as familiar to those skilled in the art.

[0029] Example 1: A Ni-Co bimetallic catalyst for dry reforming of methane

[0030] Its preparation method specifically includes the following steps:

[0031] (1) Alkali earth metal salts and tannins are mixed by ball milling and then calcined to obtain the auxiliary agent MO. x ;

[0032] (2) After mixing nickel salt, cobalt salt, EDTA and water, ammonia water is added dropwise to make it a homogeneous solution, and then a certain amount of the auxiliary agent MO obtained in step (1) is added. x A mixed solution is obtained;

[0033] (3) The mixed solution obtained in step (2) is dispersed by ultrasonication, and then subjected to rotary evaporation and drying to obtain the precursor;

[0034] (4) Grind the precursor and anchoring agent melamine obtained in step (3) in a certain proportion until homogeneous, and then calcine them in nitrogen to obtain the Ni-Co bimetallic catalyst for methane dry reforming, denoted as Ni-Co-MO. x .

[0035] The alkaline earth metal salt in step (1) is calcium acetate monohydrate.

[0036] The mass ratio of alkaline earth metals to tannins in step (1) is 1:2.5.

[0037] In step (2), cobalt nitrate is Co(NO3)2·6H2O and nickel nitrate is Ni(NO3)2·6H2O.

[0038] The mass ratio of nickel salt, cobalt salt, EDTA, water, ammonia and MOx in step (2) is 1:1:8:12:18:0.15.

[0039] In step (3), the ultrasonic time is 30 min, the rotary evaporation temperature is 80℃, and the rotary evaporation time is 1 h.

[0040] The mass ratio of the precursor to melamine in step (4) is 1:5.

[0041] The heating rate of calcination in step (1) is 5℃ / min, the calcination temperature is 800℃, and the calcination time is 4h.

[0042] The calcination temperature rate in step (4) is 5℃ / min, the calcination temperature is 800℃, and the calcination time is 2h.

[0043] The catalyst prepared is denoted as Ni-Co-MOx, wherein the mass fraction of Ni is 3% and the mass fraction of Co is 3%.

[0044] Example 2: A Ni-Co bimetallic catalyst for methane dry reforming

[0045] Its preparation method is basically the same as in Example 1, except that:

[0046] The alkaline earth metal in step (1) is magnesium carbonate pentahydrate.

[0047] The mass ratio of alkaline earth metals to tannins in step (1) is 1:3.

[0048] The mass ratio of nickel salt, cobalt salt, EDTA, water, ammonia and MOx in step (2) is 1:3:8:15:16:1.

[0049] In step (3), the rotary evaporation temperature is 50℃ and the rotary evaporation time is 2 hours.

[0050] In step (4), the mass ratio of the precursor to melamine is 1:10.

[0051] The heating rate of calcination in step (1) is 1℃ / min, the calcination temperature is 400℃, and the calcination time is 3h.

[0052] The calcination temperature rate in step (4) is 1℃ / min, the calcination temperature is 1000℃, and the calcination time is 5h.

[0053] The catalyst prepared is designated as Ni-Co-MOx-1, wherein the mass fraction of Ni is 3% and the mass fraction of Co is 9%.

[0054] Example 3: A Ni-Co bimetallic catalyst for methane dry reforming

[0055] Its preparation method is basically the same as in Example 1, except that:

[0056] The mass ratio of alkaline earth metals to tannins in step (1) is 1:9.

[0057] The mass ratio of nickel salt, cobalt salt, EDTA, water, ammonia and MOx in step (2) is 1:2:12:10:25:0.1.

[0058] In step (3), the rotary evaporation temperature is 90℃ and the rotary evaporation time is 0.5h.

[0059] In step (4), the mass ratio of the precursor to melamine is 1:2.

[0060] The heating rate of calcination in step (1) is 3℃ / min, the calcination temperature is 800℃, and the calcination time is 6h.

[0061] The calcination temperature rate in step (4) is 4℃ / min, the calcination temperature is 500℃, and the calcination time is 1h.

[0062] The catalyst prepared is denoted as Ni-Co-MOx-2, wherein the mass fraction of Ni is 3% and the mass fraction of Co is 6%.

[0063] Comparative Example 1: A catalyst for dry reforming of methane

[0064] Its preparation method is basically the same as in Example 1, except that:

[0065] Cobalt nitrate is not added in step (2).

[0066] The catalyst prepared is designated as Ni-MO X The mass fraction of Ni is 3%.

[0067] Comparative Example 2: A catalyst for dry reforming of methane

[0068] Its preparation method is basically the same as in Example 1, except that:

[0069] In step (2), without adding cobalt nitrate and nickel nitrate, the resulting catalyst is denoted as MOx.

[0070] Comparative Example 3: A Ni-Co catalyst for dry reforming of methane

[0071] Its preparation method is basically the same as in Example 1, except that:

[0072] The mass ratio of nickel salt, cobalt salt, EDTA, water, ammonia and MOx in step (2) is 1:1:8:12:18:0.75.

[0073] The catalyst prepared is denoted as Ni-Co-5MOx, wherein the mass fraction of Ni is 3% and the mass fraction of Co is 3%.

[0074] Comparative Example 4: A Ni-Co catalyst for dry reforming of methane

[0075] Its preparation method is basically the same as in Example 1, except that:

[0076] The mass ratio of nickel salt, cobalt salt, EDTA, water, ammonia and MOx in step (2) is 1:1:8:12:18:1.5.

[0077] The catalyst prepared is designated as Ni-Co-10MOx, wherein the mass fraction of Ni is 3% and the mass fraction of Co is 3%.

[0078] Comparative Example 5: A Ni-Co catalyst for dry reforming of methane

[0079] Its preparation method is basically the same as in Example 1, except that:

[0080] The mass ratio of nickel salt, cobalt salt, EDTA, water, ammonia and MOx in step (2) is 1:1:4:12:18:0.75.

[0081] The catalyst prepared is designated as Ni-Co-MO x -1 / 2EDTA, wherein the mass fraction of Ni is 6% and the mass fraction of Co is 6%.

[0082] Comparative Example 6: A Ni-Co catalyst for dry reforming of methane

[0083] Its preparation method is basically the same as in Example 1, except that:

[0084] The mass ratio of nickel salt, cobalt salt, EDTA, water, ammonia and MOx in step (2) is 1:1:2:12:18:0.75.

[0085] The catalyst prepared is designated as Ni-Co-MO x -1 / 4 EDTA, wherein the mass fraction of Ni is 12% and the mass fraction of Co is 12%.

[0086] Experimental Example 1

[0087] The reaction performance of the catalyst samples prepared in all examples and comparative examples was investigated. The reaction was carried out in a fixed-bed reactor with continuous gas flow. 0.05 g of catalyst was packed in a quartz tube with a small diameter ratio. The reaction conditions were 750 °C, CO2:CH4:N2 = 1:1:8 (V:V:V), atmospheric pressure, and space velocity 14400 mL·g. -1 ·h-1 The products were analyzed online by gas chromatography, and the reaction results are listed in Table 1.

[0088] Table 1 Comparison of Methane Reforming Activities

[0089]

[0090]

[0091] As can be seen from Table 1, the Ni-based catalyst for methane dry reforming prepared by the method provided in Examples 1-3 of this invention exhibits high reactivity in the reaction of methane dry reforming to syngas, significantly higher than that of Comparative Examples 1-6. Figure 3 It can be seen that the catalyst has good activity and stability, and does not deactivate after 100 hours of operation.

[0092] The above description is only a preferred embodiment of the present invention. Any improvements and modifications to the technical solution of the invention without departing from the principle of the invention shall be regarded as the contents disclosed in the present invention and shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a Ni-Co bimetallic catalyst for dry reforming of methane, characterized in that: Specifically, the following steps are included: (1) Alkali earth metals and tannins are ball-milled and then calcined to obtain the auxiliary agent MO. x ; (2) After mixing nickel salt, cobalt salt, EDTA and water, ammonia water is added dropwise to make it a homogeneous solution, and then a certain amount of the auxiliary agent MO obtained in step (1) is added. x A mixed solution is obtained; (3) The mixed solution obtained in step (2) is dispersed by ultrasonication and then dried by rotary evaporation to obtain the precursor; (4) After grinding the precursor and anchoring agent melamine obtained in step (3) into uniform form in a certain proportion, calcining them under an inert atmosphere to obtain the Ni-Co bimetallic catalyst for methane dry reforming. The mass ratio of alkaline earth metal salt to tannin in step (1) is 1:2.5-9; The alkaline earth metal is a calcium salt or a magnesium salt; The calcination temperature rate in step (1) is 1-5℃ / min, the calcination temperature is 400-800℃, and the calcination time is 3-6 h; the calcination temperature rate in step (4) is 1-5℃ / min, the calcination temperature is 500-1000℃, and the calcination time is 1-5 h.

2. The method for preparing the Ni-Co bimetallic catalyst for dry reforming of methane as described in claim 1, characterized in that: The mass ratio of nickel salt, cobalt salt, EDTA, water, ammonia and MOx in step (2) is 1:1-3:8-12:10-15:16-25:0.1-1.

3. The method for preparing the Ni-Co bimetallic catalyst for dry reforming of methane as described in claim 1, characterized in that: The mass ratio of the precursor to the anchoring agent melamine in step (4) is 1:2-10.

4. The method for preparing the Ni-Co bimetallic catalyst for dry reforming of methane as described in claim 1, characterized in that: The total mass fraction of Ni and Co in the Ni-Co bimetallic catalyst is 2-12%.

5. The method for preparing the Ni-Co bimetallic catalyst for dry reforming of methane as described in claim 1, characterized in that: The rotary evaporation temperature in step (3) is 50-90℃, and the rotary evaporation time is 0.5-2 h.

6. The Ni-Co bimetallic catalyst for methane dry reforming prepared by the preparation method according to any one of claims 1-5.

Images