A preparation method of high-entropy metal oxide for carbon dioxide and methane dry reforming of carbonates to produce synthesis gas

Abstract

The application discloses a preparation method of a high-entropy metal oxide for carbon dioxide and methane dry reforming of carbonates to prepare synthesis gas, wherein the high-entropy composite metal oxide is obtained by nucleation of a mixed salt solution and an alkali source solution in a nucleation reactor, crystallization, washing, drying, grinding and high-temperature calcination. The high-entropy composite metal oxide prepared by the method is used for an ultrahigh-temperature coupling reaction of industrial tail gas CO2 and CH4 as raw materials in a carbonates pyrolysis process to prepare synthesis gas, and the synthesis gas is prepared efficiently, the waste heat of the carbonates pyrolysis process is fully utilized, and the resource conversion of CO2 is realized, which contributes to the development of an environment-friendly society and a circular economy; and the high-entropy composite metal oxide catalyst has excellent activity, selectivity and stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst preparation, and particularly relates to a preparation method of a high-entropy metal oxide for carbon dioxide and methane dry reforming to synthesize a synthesis gas through carbonates pyrolysis. BACKGROUND

[0002] Metal oxides produced by carbonate pyrolysis are important raw materials in process industries such as steel, cement, and refractory materials. However, the process of producing industrial raw materials from carbonate decomposition also produces and releases a large amount of CO2, causing serious greenhouse effect. The carbon emissions from related process industries account for more than 50% of the total national industrial carbon emissions, so it is imperative and urgent to utilize CO2 in the industrial tail gas of carbonate pyrolysis.

[0003] Methane dry reforming is an effective method to convert two greenhouse gases into synthesis gas (H2+CO), which is then used for downstream reactions such as Fischer-Tropsch synthesis to produce higher value chemicals. Synthesis gas is not only a basic raw material for the chemical industry, which can be used to produce chemicals such as methanol and synthetic ammonia, but also an important source of clean energy. However, the industrial application of DRM technology is limited by poor catalyst stability, easy carbon deposition, and harsh reaction conditions.

[0004] So far, the research on DRM has been very extensive, in which noble metals are used for the reaction, although the catalytic effect is significant, but the high cost limits its large-scale application. In contrast, non-noble metal catalysts, especially nickel-based catalysts, have become a research hotspot due to their cost advantage and good catalytic performance. In recent years, through the innovation of material science, new nickel-based catalysts with anti-carbon deposition performance have been developed. Among them, the emergence of high-entropy composite metal oxide catalysts not only effectively solves the problem of high-temperature stability of the catalyst, but also significantly improves the catalytic efficiency, opening up a new direction for the industrial application of DRM technology.

[0005] Existing high-entropy composite metal oxide catalysts face multiple challenges in catalyzing methane dry reforming: they often lack stability at high temperatures, are prone to sintering and structural damage, leading to rapid decline in catalytic activity; at the same time, carbon deposition on the surface of the catalyst not only reduces the catalytic efficiency, but also can cause blockage and failure of the catalyst. In addition, existing catalysts have poor adaptability to reaction conditions, requiring strict operating conditions to maintain their performance, which increases the complexity and cost of industrial application. More critically, many catalysts rely on expensive noble metals, which significantly increases production costs and limits the potential for large-scale application. SUMMARY

[0006] This invention is proposed to overcome the shortcomings of the prior art, and its purpose is to provide a method for preparing high-entropy metal oxides for dry reforming of carbon dioxide and methane from carbonate pyrolysis to produce syngas.

[0007] This invention is achieved through the following technical solution:

[0008] A method for preparing high-entropy metal oxides for dry reforming of carbon dioxide and methane from carbonate pyrolysis to produce syngas includes the following steps:

[0009] (I) Dissolve soluble nickel salt, soluble cobalt salt, soluble magnesium salt, soluble iron salt and soluble aluminum salt in deionized water, and disperse by ultrasonication to obtain a mixed salt solution;

[0010] (II) Preparation of alkaline source solution;

[0011] (III) The mixed salt solution and the alkali source solution were simultaneously and slowly added to a conventional colloid mill. The colloid mill was stirred at a high speed of 5000 rad / min for 5 min to obtain the initial product.

[0012] (IV) The primary product is loaded into a reaction vessel for crystallization to obtain the intermediate product;

[0013] (V) The intermediate product was washed, dried and ground to obtain a high-entropy composite metal oxide catalyst precursor;

[0014] (VI) The high-entropy composite metal oxide catalyst precursor was calcined at high temperature to obtain the high-entropy composite metal oxide catalyst.

[0015] In the above technical solution, the soluble nickel salt is any one or more of nickel nitrate or nickel chloride; the soluble cobalt salt is any one or more of cobalt nitrate or cobalt chloride; the soluble magnesium salt is any one or more of magnesium nitrate or magnesium chloride; the soluble iron salt is any one or more of ferric nitrate or ferric chloride; and the soluble aluminum salt is any one or more of aluminum nitrate or aluminum chloride.

[0016] In the above technical solution, the molar ratio of soluble nickel salt, soluble cobalt salt, soluble magnesium salt, soluble iron salt and soluble aluminum salt in step (Ⅰ) is (0.1~1):(0.1~1):1:1:1; preferably 1:1:1:1:1, 0.5:0.5:1:1:1, 0.25:0.25:1:1:1 or 0.1:0.1:1:1:1.

[0017] In the above technical solution, the ultrasonic dispersion time in step (I) is 5 min to 30 min.

[0018] In the technical scheme, the alkali source solution is a mixed aqueous solution of sodium hydroxide and sodium carbonate, the molar amount of sodium carbonate is 2 times the total molar amount of trivalent cations in the mixed salt solution, and the molar amount of sodium hydroxide is 1.6 times the total molar amount of cations in the mixed salt solution.

[0019] In the technical scheme, the rotating speed of the nucleation stirring in step (III) is 3000 rpm, and the nucleation stirring time is 5 min.

[0020] In the technical scheme, the crystallization condition in step (IV) is crystallization at 120 DEG C for 24 h.

[0021] In the technical scheme, the drying condition in step (V) is drying at 80 DEG C for 24 h.

[0022] In the technical scheme, the high-temperature calcination condition in step (VI) is calcination at 900 DEG C for 4 h in an air atmosphere.

[0023] A high-entropy composite metal oxide prepared by the above method, the high-entropy composite metal oxide has the characteristics of multiple elements and different element ratios, and the chemical formula of the high-entropy composite metal oxide is Ni x Co y Mg1Fe1Al1-LDOs, wherein: x = 0.1-1; y = 0.1-1; the high-entropy composite metal oxide catalyst has the characteristics of multiple elements and different element ratios, and the chemical formula of the high-entropy composite metal oxide catalyst is Ni x Co y Mg1Fe1Al1-LDOs, wherein: x = 0.1-1; y = 0.1-1; preferably, the chemical formula of the high-entropy composite metal oxide catalyst is Ni 0.5 Co 0.5 Mg1Fe1Al1-LD, Ni 0.25 Co 0.25 Mg1Fe1Al1-LDO or Ni 0.1 Co 0.1 Mg1Fe1Al1-LDO; by giving flexible adjustment space on the content of Ni and Co (x = 0.1-1; y = 0.1-1), while keeping the constant ratio of Mg, Fe and Al, the catalyst ingeniously combines the core characteristics of high-entropy materials. This composition design not only promotes the formation of solid solution structure, enhances the uniformity and stability of the material, but also optimizes the surface properties and active site distribution of the catalyst through complex electronic and geometric effects. In addition, the thermodynamic and kinetic stability brought by the high-entropy effect enables the catalyst to maintain high efficiency and stability under harsh reaction conditions.

[0024] The application relates to a method for preparing synthesis gas by coupling carbon dioxide and methane dry reforming of carbonate pyrolysis, and specifically relates to the following steps: under normal pressure, a high-entropy composite metal oxide prepared by the method in any one of claims 1 to 7 is filled in a continuous fixed bed reactor, a mixed gas of methane and carbon dioxide is introduced into the reactor at a volume ratio of 1:1, the reaction temperature is 500 DEG C to 900 DEG C, the space velocity is 60000 ml.g -1 ·h -1 ~3000000 ml.g -1 ·h -1 , and H2 and CO are generated.

[0025] The application has the following beneficial effects:

[0026] The application provides a preparation method of a high-entropy metal oxide for coupling reaction of synthesis gas prepared by coupling carbon dioxide and methane dry reforming of carbonate pyrolysis industrial tail gas, realizes efficient preparation of synthesis gas, realizes full utilization of waste heat of the carbonate pyrolysis process and resource conversion of CO2, and contributes to the development of an environment-friendly society and a circular economy; the high-entropy composite metal oxide catalyst has excellent activity, selectivity and stability.

[0027] The high-entropy composite metal oxide has excellent high-temperature stability, can maintain structural integrity and activity stability under extreme conditions, and effectively inhibits sintering; meanwhile, the high-entropy composite metal oxide has excellent carbon deposition resistance, ensures long-time stable operation and efficient catalytic conversion. In addition, the high-entropy composite metal oxide has wide adaptability to reaction conditions, can work efficiently in a wide temperature and space velocity range, and simplifies the industrial operation process. By using non-noble metal components with higher cost-effectiveness, the high-entropy composite metal oxide greatly reduces production cost, and provides strong support for economic feasibility and environmental sustainability of the methane dry reforming technology. DETAILED DESCRIPTION

[0028] Figure 1 Fig. 1 is a scanning electron microscope photo of the high-entropy composite metal oxide prepared in Example 1 of the application;

[0029] Figure 2 Fig. 4 is a performance graph of the high-entropy composite metal oxide prepared in Example 1 of the application under different space velocities;

[0030] Figure 3 Fig. 5 is a stability performance graph of the high-entropy composite metal oxide prepared in Example 1 of the application;

[0031] Figure 4 Fig. 6 is a performance comparison graph of the high-entropy composite metal oxides prepared in Examples 1 to 4 of the application.

[0032] Other related drawings can be obtained by those of ordinary skill in the art without creative effort based on the above drawings. DETAILED DESCRIPTION

[0033] In order for those skilled in the art to better understand the technical solutions of the present application, the technical solutions of the present application will be further described below in combination with the drawings of the specification and through specific embodiments.

[0034] Example 1

[0035] A preparation method of a Ni1Co1Mg1Fe1Al1-LDO catalyst, the specific steps are as follows:

[0036] First, a mixed solution of 0.01 mol / L nickel nitrate, 0.01 mol / L cobalt nitrate, 0.01 mol / L magnesium nitrate, 0.01 mol / L iron nitrate and 0.01 mol / L aluminum nitrate is prepared with deionized water, and a mixed solution of 1.6 times the total molar amount of cations of sodium hydroxide and 2 times the molar amount of trivalent cations of sodium carbonate is prepared with deionized water; the two mixed solutions are transferred to a nucleation reactor and stirred for 5 min; the mixed solution is loaded into a reaction kettle, crystallized at 120℃ for 24h to obtain a Ni1Co1Mg1Fe1Al1-LDH catalyst precursor; the product is washed, dried, ground, and then heated to 900℃ at a rate of 5℃ / min in a muffle furnace, and then cooled to room temperature at a rate of 10℃ / min after calcination for 4h.

[0037] 0.03g of the catalyst prepared in this example was used for the dry reforming of carbon dioxide and methane to prepare syngas, 0.03g of the catalyst was loaded into a continuous fixed bed reactor under normal pressure, and a mixture of methane and carbon dioxide was introduced at a volume ratio of 1:1 to generate H2 and CO, respectively, at space velocities of 60000ml·g -1 ·h -1 , 120000ml·g -1 ·h -1 and 3000000ml·g -1 ·h -1 , and the catalytic performance at reaction temperatures of 650℃, 700℃, 750℃, 800℃, 850℃ and 900℃ was tested, each temperature was reacted for 1h, and the test results are shown in Figure 4 .

[0038] The SEM image of the Ni1Co1Mg1Fe1Al1-LDO catalyst prepared in this example is shown in Figure 1 , and it can be seen from Figure 1 that the morphology of the hydrotalcite nanosheet is stably present.

[0039] From Figure 2 andFigure 3 It can be seen that the Ni1Co1Mg1Fe1Al1-LDO catalyst prepared in the embodiment has good catalytic activity and stability.

[0040] Example 2

[0041] A Ni 0.5 Co 0.5 Mg1Fe1Al1-LDO catalyst was prepared by the following steps:

[0042] First, a mixed solution of 0.01 mol / L nickel nitrate, 0.01 mol / L cobalt nitrate, 0.01 mol / L magnesium nitrate, 0.01 mol / L iron nitrate and 0.01 mol / L aluminum nitrate was prepared with deionized water, and a mixed solution of 1.6 times the total molar amount of cations of sodium hydroxide and 2 times the molar amount of trivalent cations of sodium carbonate was prepared with deionized water; the two mixed solutions were transferred to a nucleation reactor and stirred for 5 min; the mixed solution was loaded into a reaction kettle, crystallized at 120℃ for 24 h to obtain a Ni 0.5 Co 0.5 Mg1Fe1Al1-LDH catalyst precursor; the obtained product was washed, dried and ground, and then heated to 900℃ at a rate of 5℃ / min in a muffle furnace, and then cooled to room temperature at a rate of 10℃ / min after calcination for 4h.

[0043] 0.03g of the catalyst prepared in the embodiment was used for the dry reforming of carbonates to prepare synthesis gas by coupling CO2 and methane, 0.03g of the catalyst was loaded into a continuous fixed bed reactor under normal pressure, and a mixture of methane and carbon dioxide was introduced at a volume ratio of 1:1 to generate H2 and CO, and the catalytic performance was tested at space velocities of 60000ml·g -1 ·h -1 , 120000ml·g -1 ·h -1 and 3000000ml·g -1 ·h -1 , respectively, at reaction temperatures of 650℃, 700℃, 750℃, 800℃, 850℃ and 900℃, and each temperature was reacted for 1h, and the test results are shown in Figure 4 .

[0044] Example 3

[0045] A Ni 0.25 Co 0.25 Mg1Fe1Al1-LDO catalyst was prepared by the following steps:

[0046] Firstly, a mixed solution of 0.01 mol / L nickel nitrate, 0.01 mol / L cobalt nitrate, 0.01 mol / L magnesium nitrate, 0.01 mol / L iron nitrate and 0.01 mol / L aluminum nitrate is prepared with deionized water, and a mixed solution of 1.6 times the total molar amount of cations of sodium hydroxide and 2 times the molar amount of trivalent cations of sodium carbonate is prepared with deionized water; the two mixed solutions are transferred to a nucleation reactor and stirred for 5 min; the mixed solution is loaded into a reaction kettle, crystallized at 120℃ for 24 h to obtain Ni 0.25 Co 0.25 Mg1Fe1Al1-LDH catalyst precursor; the obtained product is washed, dried and ground, and then heated to 900℃ at a rate of 5℃ / min in a muffle furnace, and then cooled to room temperature at a rate of 10℃ / min after calcination for 4 h.

[0047] 0.03 g of the catalyst prepared in the example is used for the dry reforming of carbon dioxide and methane to prepare synthesis gas, 0.03 g of the catalyst is loaded into a continuous fixed bed reactor, and a mixed gas of methane and carbon dioxide is introduced at a volume ratio of 1:1 to generate H2 and CO, and the catalytic performance at a space velocity of 60000 ml·g -1 ·h -1 , 120000 ml·g -1 ·h -1 and 3000000 ml·g -1 ·h -1 is tested at a reaction temperature of 650℃, 700℃, 750℃, 800℃, 850℃ and 900℃, and each temperature is reacted for 1 h, and the test results are shown in Figure 4 .

[0048] Example 4

[0049] A Ni 0.1 Co 0.1 Mg1Fe1Al1-LDO catalyst is prepared by the following specific steps:

[0050] Firstly, a mixed solution of 0.01 mol / L nickel nitrate, 0.01 mol / L cobalt nitrate, 0.01 mol / L magnesium nitrate, 0.01 mol / L iron nitrate and 0.01 mol / L aluminum nitrate is prepared with deionized water, and a mixed solution of 1.6 times the total molar amount of cations of sodium hydroxide and 2 times the molar amount of trivalent cations of sodium carbonate is prepared with deionized water; the two mixed solutions are transferred to a nucleation reactor and stirred for 5 min; the mixed solution is loaded into a reaction kettle, crystallized at 120℃ for 24 h to obtain Ni 0.1 Co 0.1Mg1Fe1Al1-LDH catalyst precursor; the obtained product is washed, dried, ground, and then heated to 900 DEG C at a rate of 5 DEG C / min in a muffle furnace, and then cooled to room temperature at a rate of 10 DEG C / min after calcination for 4 h.

[0051] 0.03 g of the catalyst prepared in the embodiment is weighed for the preparation of synthesis gas by coupling carbonated thermal decomposition with dry reforming of CO2 and methane, 0.03 g of the catalyst is loaded in a continuous fixed bed reactor under normal pressure, and a mixed gas of methane and carbon dioxide is introduced at a volume ratio of 1:1 to generate H2 and CO, and the space velocity is 60000 ml·g-1·h-1, 120000 ml·g-1·h-1, 3000000 ml·g-1·h-1, respectively, and the reaction temperature is 650 DEG C, 700 DEG C, 750 DEG C, 800 DEG C, 850 DEG C and 900 DEG C, respectively, and each temperature is reacted for 1 h, and the test results are shown in Table 1. -1 ·h -1 -1 ·h -1 ·h -1 ·h -1 Figure 4 .

[0052] Figure 4 is a performance comparison diagram of the catalysts prepared in embodiments 1-4 in the preparation of synthesis gas by coupling carbonated thermal decomposition with dry reforming of CO2 and methane, and from the diagram, it can be seen that the Ni1Co1Mg1Fe1Al1-LDO, Ni 0.5 Co 0.5 Mg1Fe1Al1-LDO, Ni 0.25 Co 0.25 Mg1Fe1Al1-LDO, Ni 0.1 Co 0.1 Mg1Fe1Al1-LDO has good catalytic performance, and the Ni1Co1Mg1Fe1Al1-LDO catalyst has the best catalytic activity.

[0053] The high-entropy composite metal oxide prepared by the application has a synergistic catalytic effect with MgFeAlO4 by regulating a lower content of NiCo, and the high dispersion of NiCo is conducive to inhibiting the defect sites on the surface of NiCo particles, MgFeAlO4 promotes the adsorption of carbon dioxide, improves the conversion rate of carbon dioxide, and realizes the efficient use of a plurality of metal elements.

[0054] ​​The high-entropy composite metal oxide prepared by the application has good catalytic performance in dry reforming reaction, and the conversion rate of CO2 can reach 98.6% at 900 DEG C. The high-entropy composite metal oxide has good stability in the reaction. Compared with the catalysts in the prior art, the high-entropy composite metal oxide has strong high-temperature sintering resistance, and has the advantages of simple preparation method and low production cost. Meanwhile, the application of the high-entropy composite metal oxide in the application of the application couples the CO2 pyrolysis of carbonate and the dry reforming reaction of methane, fully utilizes the high-calorific-value CO2 in the industrial tail gas of carbonate pyrolysis, and utilizes the excellent catalytic performance of the high-entropy composite metal oxide, so that the high-temperature waste heat generated in the carbonate pyrolysis process can be efficiently converted into chemical reaction energy, and the carbon source in the carbonate can be converted into a reaction raw material to replace part of CO2 gas, and the coupling reaction with methane can generate high-value products such as H2 and CO, so that the production steps can be further simplified, and the energy consumption and production cost can be reduced.

[0055] The application realizes full utilization of the high-temperature waste heat generated in the carbonate pyrolysis, promotes secondary utilization of the carbon source in the carbonate, effectively reduces CO2 emission, promotes efficient production of synthesis gas, opens up a new way for carbon cycle and sustainable utilization of resources, and has remarkable environmental and economic benefits.

[0056] It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict.

[0057] The applicant declares that the above description is only a specific embodiment of the application, but the protection scope of the application is not limited to this. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the application.

Claims

1. Use of a high-entropy complex metal oxide in the dry reforming of carbon dioxide and methane to produce syngas by carbonates pyrolysis, characterized in that: The application relates to a preparation method of a high-entropy metal oxide, which comprises the following steps: (I) dissolving soluble nickel salt, soluble cobalt salt, soluble magnesium salt, soluble iron salt and soluble aluminum salt in deionized water, and performing ultrasonic dispersion to obtain a mixed salt solution; (II) preparing an alkali source solution; (III) synchronously and slowly adding the mixed salt solution and the alkali source solution into a colloid mill, and performing high-speed stirring to obtain an initial product; (IV) loading the initial product into a reaction kettle for crystallization to obtain an intermediate product; (V) washing, drying and grinding the intermediate product to obtain a high-entropy composite metal oxide catalyst precursor; (VI) high-temperature calcining the high-entropy composite metal oxide catalyst precursor to obtain a high-entropy composite metal oxide catalyst. The high-entropy composite metal oxide has a chemical formula of Ni x Co y Mg1Fe1Al1-LDOs, wherein: x = 0.1-1; y = 0.1-1.

2. Use according to claim 1, characterized in that: The soluble nickel salt is any one or both of nickel nitrate and nickel chloride; the soluble cobalt salt is any one or both of cobalt nitrate and cobalt chloride; the soluble magnesium salt is any one or both of magnesium nitrate and magnesium chloride; the soluble iron salt is any one or both of iron nitrate and iron chloride; and the soluble aluminum salt is any one or both of aluminum nitrate and aluminum chloride.

3. Use according to claim 1, characterized in that: The ultrasonic dispersion time in the step (I) is 5 min to 30 min.

4. Use according to claim 1, characterized in that: The alkali source solution is a mixed aqueous solution of sodium hydroxide and sodium carbonate, the molar amount of sodium carbonate is 2 times the total molar amount of trivalent cations in the mixed salt solution, and the molar amount of sodium hydroxide is 1.6 times the total molar amount of cations in the mixed salt solution.

5. The use according to claim 1, characterized in that: The rotating speed of the colloid mill in the step (III) is 5000 rad / min, and the stirring time of the colloid mill is 5 min; and the crystallization condition in the step (IV) is crystallization at 120 DEG C for 24 h.

6. Use according to claim 1, characterized in that: The drying condition in the step (V) is drying at 80 DEG C for 24 h; and the high-temperature calcining condition in the step (VI) is calcining at 900 DEG C for 4 h in an air atmosphere.

7. The use according to claim 1, characterized in that: Under normal pressure, the high-entropy composite metal oxide is filled in a continuous fixed bed reactor, and a mixed gas of methane and carbon dioxide is introduced at a volume ratio of 1:1 for reaction, the reaction temperature is 500 ℃-900 ℃, the space velocity is 60000 ml·g -1 ·h -1 ~3000000 ml·g -1 ·h -1 , H2 and CO are generated.

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