Preparation method of methane dry reforming cobalt-based bimetallic catalyst using modified spinel as carrier

Abstract

The invention belongs to the technical field of methane dry reforming catalysts, and particularly relates to a preparation method of a methane dry reforming cobalt-based bimetallic catalyst using modified spinel as a carrier. According to the preparation method disclosed by the invention, the cheap metal rare earth oxide with redox property, high oxygen storage capacity and rich oxygen defects on the surface of CeO2 is utilized, lattice oxygen is released through switching between Ce < 3 + > and Ce < 4 + >, the migration of oxygen is accelerated, the elimination of carbon on the surface is promoted, and the stability of the catalyst is improved; the catalyst prepared from the modified carrier by the simplest impregnation method can obtain a stable conversion rate at a low reaction temperature, and has a wide application prospect and potential.

Description

Technical Field

[0001] The present invention belongs to the technical field of methane dry reforming catalysts, and particularly relates to a preparation method of a cobalt-based bimetallic catalyst for methane dry reforming using modified spinel as a carrier. Background Art

[0002] The global warming potential or warming effect of methane is 84 times that of carbon dioxide at the 20-year level and 28 times that of carbon dioxide at the 100-year level. To effectively reduce the global greenhouse effect and reduce greenhouse gas emissions, many effective methods for utilizing carbon dioxide have been developed. The DRM reaction (methane dry reforming reaction) is a potential method for converting a large amount of carbon dioxide, stranded gas, and coke oven gas into syngas; theoretically, DRM is an effective method to achieve 100% utilization of carbon and hydrogen; on the other hand, the syngas produced by DRM has an ideal H2 / CO ratio, meeting the requirements of Fischer-Tropsch synthesis.

[0003] The main challenge in the current field of methane dry reforming is to reduce the sintering and carbon deposition of the catalyst under high-temperature reaction conditions. Moreover, the methane dry reforming reaction is a highly endothermic reaction, and the methane conversion rate is limited by the thermodynamics of the reforming reaction. The reaction temperature is high and the requirements for the reactor material are high; therefore, how to improve the carbon deposition resistance and low-temperature activity of the catalyst has become the key to the industrial application of methane dry reforming. Therefore, the development of highly active, highly selective, and highly stable methane dry reforming catalysts is still the key research in this field at present.

[0004] Chinese Patent CN113000059A discloses a nickel-based catalyst for methane carbon dioxide dry reforming, its preparation method and application; this patent uses metal oxide as a carrier, and prepares a boron nitride-coated nickel-based catalyst by impregnating boric acid and urea and calcining. This catalyst combines the advantages of boron nitride and metal oxide, has highly dispersed active metals, and has excellent anti-carbon deposition and anti-sintering properties. Chinese Patent CN114570372B discloses a nickel-based catalyst for methane carbon dioxide dry reforming, its preparation method and application; it creatively uses laser direct writing technology to rapidly prepare a nickel-based catalyst for methane carbon dioxide dry reforming, and has excellent catalytic activity and stability. Chinese Patent CN112403466B discloses a preparation method of a core-shell catalyst for methane carbon dioxide dry reforming; in this method, CaO and a cobalt source / iron source are dissolved in deionized water and reacted, and then the product Co(OH)2 nanosheets / Fe(OH)2 nanosheets are filtered and separated. The obtained nanosheets and metal source M are dispersed in deionized water and transferred to a hydrothermal kettle for reaction to obtain CoFe@M x O yA catalyst that enhances the interaction between the active metal and the support. Moreover, since the CoFe alloy active centers are encapsulated by the metal oxide support, it plays a certain confinement protection role. Therefore, it can effectively inhibit the growth of active metal particles during the high-temperature reforming reaction.

[0005] However, the preparation method proposed in the above patent is complex and time-consuming. Developing a catalyst with anti-coking and anti-sintering properties and a simple and effective preparation method is the focus of this patent research. Summary of the Invention

[0006] In view of the above technical problems, the present invention provides a preparation method of a cobalt-based bimetallic catalyst for dry reforming of methane using a modified spinel as a support. This preparation method utilizes CeO2, a cheap metal rare earth oxide with redox properties, high oxygen storage capacity, and abundant oxygen defects on the surface. By switching between Ce 3+ and Ce 4+ to release lattice oxygen, accelerate the migration of oxygen, promote the elimination of surface carbon deposition, and improve the stability of the catalyst.

[0007] To achieve the above object, the present invention adopts the following technical solutions.

[0008] A preparation method of a cobalt-based bimetallic catalyst for dry reforming of methane using a modified spinel as a support, specifically including the following steps: Step 1: Dissolve magnesium acetate, aluminum nitrate, cerium nitrate, and citric acid in deionized water and stir evenly to obtain a mixed solution. Step 2: Place the above mixed solution in an oil bath and heat and stir for a certain time to obtain a transparent solution. Step 3: Weigh a certain mass of ethylene glycol and slowly drop it into the transparent solution in Step 2 and stir evenly. Step 4: Slowly raise the temperature of the solution in Step 3 to a certain temperature, evaporate the water to form a gel, and place it at room temperature for room temperature aging. Step 5: Place the gel aged in Step 4 in a muffle furnace for calcination to obtain a modified spinel support. Step 6: Prepare cobalt nitrate solution and iridium chloride solution with a certain concentration, impregnate the modified spinel support by the impregnation method to obtain an impregnated sample, and place the sample still and then put it into an oven for drying. Step 7: Place the sample dried in Step 6 in a muffle furnace for calcination at a certain temperature to finally obtain a cobalt-based bimetallic catalyst for dry reforming of methane using a modified spinel as a support.

[0009] Further, in Step 1, the molar amount of magnesium acetate is 0.01 - 0.9; the molar amount of aluminum nitrate is 0.01 - 0.9; the molar amount of cerium nitrate is 0.01 - 0.9; the molar amount of citric acid is 0.01 - 0.9.

[0010] Further, in Step 2, the heating temperature is 10°C - 100°C.

[0011] Further, in Step 3, the mass of ethylene glycol is 10 wt% - 90 wt% of the mass of citric acid.

[0012] Further, in Step 4, the temperature is 100°C - 170°C.

[0013] Further, in Step 5, the calcination temperature is 500°C - 1000°C.

[0014] Further, in Step 6, the mass fraction of cobalt nitrate is 1 wt% - 20 wt%.

[0015] Further, in Step 6, the mass fraction of iridium chloride is 0.1 wt% - 5 wt%.

[0016] Further, in Step 7, the calcination temperature is 400°C - 700°C.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0018] The preparation method provided by the present invention has the advantages of simple process, rapidity, universality, etc., and is widely applicable to various supported metal catalysts. The catalyst prepared by the simplest impregnation method using the modified support can obtain a stable conversion rate at a lower reaction temperature, and has broad application prospects and potential. Description of the Drawings

[0019] Figure 1 Methane conversion rate and carbon dioxide conversion rate of Example 2, Comparative Examples 1, 2, and 3 (a, methane conversion rate; b, carbon dioxide conversion rate).

[0020] Figure 2 Methane conversion rate and carbon dioxide conversion rate after 30 h of each example and Comparative Examples 3 and 4 (a, methane conversion rate; b, carbon dioxide conversion rate). Detailed Embodiments

[0021] For the convenience of understanding the present invention, the technical solutions of the present invention will be comprehensively described below in conjunction with specific embodiments and the accompanying drawings. However, the following described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0022] A preparation method of a cobalt-based bimetallic catalyst for dry reforming of methane using modified spinel as a carrier specifically includes the following steps: Step 1: Dissolve magnesium acetate, aluminum nitrate, cerium nitrate, and citric acid in deionized water and stir evenly to obtain a mixed solution. Step 2: Place the above mixed solution in an oil bath and heat and stir for a certain time to obtain a transparent solution. Step 3: Weigh a certain mass of ethylene glycol and slowly drip it into the transparent solution in Step 2 and stir evenly. Step 4: Slowly raise the temperature of the solution in Step 3 to a certain temperature, evaporate the water to form a gel, and place it at room temperature for room temperature aging. Step 5: Place the gel aged in Step 4 in a muffle furnace for calcination to obtain a modified spinel carrier. Step 6: Prepare cobalt nitrate solution and iridium chloride solution with a certain concentration, impregnate the modified spinel carrier by the impregnation method to obtain the impregnated sample, and place the sample in an oven for drying after standing. Step 7: Place the dried sample in Step 6 in a muffle furnace for calcination at a certain temperature to finally obtain a cobalt-based bimetallic catalyst for dry reforming of methane using modified spinel as a carrier.

[0023] Further, in Step 1, the molar amount of magnesium acetate is 0.01 - 0.9, preferably 0.01 - 0.5, and more preferably 0.01 - 0.09.

[0024] Further, in Step 1, the molar amount of aluminum nitrate is 0.01 - 0.9, preferably 0.01 - 0.5, and more preferably 0.01 - 0.09.

[0025] Further, in Step 1, the molar amount of cerium nitrate is 0.01 - 0.9, preferably 0.01 - 0.5, and more preferably 0.01 - 0.09.

[0026] Further, in Step 1, the molar amount of citric acid is 0.01 - 0.9, preferably 0.1 - 0.9, and more preferably 0.1 - 0.5.

[0027] Further, in Step 2, the heating temperature is 10°C - 100°C, preferably 50°C - 100°C, more preferably 50°C - 80°C.

[0028] Further, in Step 3, the mass of ethylene glycol is 10 wt% - 90 wt% of the mass of citric acid, preferably 30 wt% - 90 wt%, more preferably 40 wt% - 70 wt%.

[0029] Further, in Step 4, the temperature is 100°C - 170°C, preferably 100°C - 150°C, more preferably 110°C - 130°C; the aging time is 48 h.

[0030] Further, in Step 5, the calcination temperature is 500°C - 1000°C, preferably 500°C - 900°C, more preferably 550°C - 850°C.

[0031] Further, in Step 6, the mass fraction of cobalt nitrate is 1 - 20 wt%, preferably 1 wt% - 15 wt%, more preferably 6 - 12 wt%.

[0032] Further, in Step 6, doping a small amount of iridium chloride further improves the catalytic stability. The selected mass fraction of iridium chloride is 0.1 wt% - 5 wt%, preferably 0.1 wt% - 1 wt%, more preferably 0.1 wt% - 0.5 wt%.

[0033] Further, in Step 7, the calcination temperature is 400°C - 700°C, preferably 400°C - 600°C, more preferably 400°C - 500°C.

[0034] Example 1.

[0035] Weigh 2.8478 g of magnesium acetate, 8.52 g of aluminum nitrate, 4.3422 g of cerium nitrate, and 96 g of citric acid, dissolve them in 500 ml of deionized water, place them in an oil bath, stir evenly for 3 h, and heat up to 70°C at a rate of 2°C / min; measure 52 ml of ethylene glycol, slowly add it, stir evenly, and keep warm for 30 min; heat up to 120°C at a rate of 2°C / min to evaporate the water until a gel is formed, and age at room temperature for 48 h; after aging, place the sample in a muffle furnace, heat up to 550°C at a rate of 3°C / min and calcine for 2 h to remove organic substances, and then heat up to 850°C at the same heating rate and calcine for 6 h to obtain MA-Ce.

[0036] Weigh 0.395 g of cobalt nitrate and 0.0082 g of iridium chloride, place them in a beaker, add an appropriate amount of deionized water, stir to dissolve, place in an oven at 70 °C for 20 min of heat preservation. Weigh 0.9 g of MA-Ce, pour it into the beaker, stir evenly, place at room temperature for 12 h, dry the sample in an oven at 80 °C, and then place it in a muffle furnace at 400 °C for 3 h of calcination to obtain the methane dry reforming cobalt-based bimetallic catalyst 8Co-0.5Ir / MA-Ce using the modified spinel as the carrier.

[0037] Example 2.

[0038] The preparation of the modified carrier is the same as that in Example 1 and will not be elaborated here.

[0039] Weigh 0.395 g of cobalt nitrate and 0.0082 g of iridium chloride, place them in a beaker, add an appropriate amount of deionized water, stir to dissolve, place in an oven at 70 °C for 20 min of heat preservation. Weigh 0.9 g of MA-Ce, pour it into the beaker, stir evenly, place at room temperature for 12 h, dry the sample in an oven at 80 °C, and then place it in a muffle furnace at 600 °C for 3 h of calcination to obtain the bimetallic catalyst 8Co-0.5Ir / MA-Ce.

[0040] Comparative Example 1.

[0041] Weigh 2.8478 g of magnesium acetate, 8.52 g of aluminum nitrate, 8.6844 g of cerium nitrate, and 96 g of citric acid, dissolve them in 500 ml of deionized water, place in an oil bath and stir evenly for 3 h; heat up to 70 °C at a rate of 2 °C / min, measure 52 ml of ethylene glycol and slowly add it, and keep warm for 30 min, then heat up to 120 °C at a rate of 2 °C / min to evaporate the water until a gel is formed, and age at room temperature for 48 h; after aging, place the sample in a muffle furnace, heat up to 550 °C at a rate of 3 °C / min for 2 h of calcination to remove organic substances, and then heat up to 850 °C at the same heating rate for 6 h of calcination to obtain MA-2Ce.

[0042] Weigh 0.395 g of cobalt nitrate and 0.0082 g of iridium chloride, place them in a beaker, add an appropriate amount of deionized water, stir to dissolve, place in an oven at 70 °C for 20 min of heat preservation. Weigh 0.9 g of MA-2Ce, pour it into the beaker, stir evenly, place at room temperature for 12 h, dry the sample in an oven at 80 °C, and then place it in a muffle furnace at 600 °C for 3 h of calcination to obtain the methane dry reforming cobalt-based bimetallic catalyst 8Co-0.5Ir / MA-2Ce using the modified spinel as the carrier.

[0043] Comparative Example 2.

[0044] Weigh 2.8478 g of magnesium acetate, 8.52 g of aluminum nitrate, 17.3688 g of cerium nitrate, and 96 g of citric acid, dissolve them in 500 ml of deionized water, and place them in an oil bath and stir evenly for 3 h. Heat it up to 70 °C at a rate of 2 °C / min, measure 52 ml of ethylene glycol and slowly add it, and keep it warm for 30 min. Then heat it up to 120 °C at a rate of 2 °C / min to evaporate the water until a gel is formed, and age it at room temperature for 48 h. After aging, place the sample in a muffle furnace and heat it up to 550 °C at a rate of 3 °C / min and calcine it for 2 h to remove the organic matter. Then heat it up to 850 °C at the same heating rate and calcine it for 6 h to obtain MA-4Ce.

[0045] The preparation of the catalyst by impregnation is the same as that in Comparative Example 1 and will not be elaborated here. The bimetallic catalyst 8Co-0.5Ir / MA-4Ce is obtained.

[0046] Comparative Example 3.

[0047] Weigh 0.395 g of cobalt nitrate and 0.0082 g of iridium chloride, place them in a beaker, add an appropriate amount of deionized water and stir to dissolve. Place it in an oven at 70 °C and keep it warm for 20 min. Weigh 0.9 g of MA, pour it into the beaker and stir evenly. Place it at room temperature for 12 h, dry the sample in an oven at 80 °C, and place it in a muffle furnace at 600 °C and calcine it for 3 h to obtain 8Co-0.5Ir / MA.

[0048] Comparative Example 4.

[0049] Weigh 0.395 g of cobalt nitrate and 0.0082 g of iridium chloride, place them in a beaker, add an appropriate amount of deionized water and stir to dissolve. Place it in an oven at 70 °C and keep it warm for 20 min. Weigh 0.9 g of MA-Ce, pour it into the beaker and stir evenly. Place it at room temperature for 12 h, dry the sample in an oven at 80 °C, and place it in a muffle furnace at 800 °C and calcine it for 3 h to obtain the bimetallic catalyst 8Co-0.5Ir / MA-Ce.

[0050] MA doped with different Ce ratios is used as a carrier to prepare cobalt-based bimetallic catalysts, such as Figure 1 It can be seen that for the catalyst prepared in Example 2, whether it is the methane conversion rate or the carbon dioxide conversion rate, it always remains in a stable state and is higher than that of the other catalysts, indicating that after doping a certain proportion of Ce, the migration of oxygen is accelerated, the elimination of surface carbon deposition on the catalyst is promoted, and the stability of the catalyst is improved.

[0051] Such as Figure 2 As shown, in the 30-h catalyst stability test of the catalyst prepared by the method of Example 1, it always remained at a stable level. After reacting for 30 h, the conversion rates of CH4 and CO2 were 81% and 86% respectively. Compared with the catalyst in Comparative Example 3, the conversion rates of CH4 and CO2 increased by 8% and 6% respectively.

[0052] The present invention provides an application of a catalyst in the dry reforming reaction of methane and carbon dioxide, and the catalyst is the cobalt-based bimetallic catalyst for dry reforming of methane and carbon dioxide described in the above technical solution.

[0053] The obtained calcined catalyst sample is first preliminarily ground in a mortar. Weigh 0.1 g of the catalyst, mix it with 2-3 times the volume of 20-40 mesh quartz sand, and load it into a reaction tube with an inner diameter of 8 mm. The atmospheric pressure micro fixed bed reactor is used to evaluate the performance of the catalyst.

[0054] Before the reaction starts, first test the airtightness of the device under a nitrogen atmosphere. After stabilization, preferably heat it to 700 °C at a heating rate of 5 °C / min under a hydrogen atmosphere, and reduce the metal oxides in the catalyst by reducing for 2 h after reaching the target temperature. Then switch to a nitrogen atmosphere and purge for 10 min. After that, switch to a raw material gas of 47.5% methane, 47.5% carbon dioxide, and 5% argon for catalytic performance testing. GHSV = 18000 ml·g -1 ·h -1 , and then analyze the tail gas by a gas chromatograph, and detect the gas by using a thermal conductivity detector (TCD) equipped to obtain the methane conversion rate and the carbon dioxide conversion rate, so as to evaluate the catalytic performance of the catalyst.

Claims

1. A method for preparing a cobalt-based bimetallic catalyst for methane dry reforming using modified spinel as a carrier, characterized in that: The specific steps include: Step 1, dissolving magnesium acetate, aluminum nitrate, cerium nitrate and citric acid in deionized water, stirring evenly to obtain a mixed solution; Step 2, placing the mixed solution in an oil bath, heating and stirring for a certain period of time to obtain a transparent solution; Step 3, weigh a certain amount of ethylene glycol and slowly add it dropwise to the transparent solution in step 2, and stir evenly; Step 4, slowly raising the temperature of the solution in step 3 to a certain level, evaporating water to form a gel, and placing the gel at room temperature for aging; Step 5, placing the aged gel in step 4 in a muffle furnace for calcination to obtain a modified spinel carrier; Step 6: preparing a cobalt nitrate solution and an iridium chloride solution of a certain concentration, and impregnating the modified spinel carrier by an impregnation method to obtain an impregnated sample, and placing the sample in an oven for drying after standing; Step 7: Place the dried sample in step 6 in a muffle furnace and calcine it at a certain temperature to finally obtain a cobalt-based bimetallic catalyst for dry reforming of methane using modified spinel as a carrier.

2. The method for preparing a cobalt-based bimetallic catalyst for dry reforming of methane using modified spinel as a carrier according to claim 1, characterized in that: In the step 1, the molar amount of magnesium acetate is 0.01-0.9; the molar amount of aluminum nitrate is 0.01-0.9; the molar amount of cerium nitrate is 0.01-0.9; and the molar amount of citric acid is 0.01-0.

9.

3. The method for preparing a cobalt-based bimetallic catalyst for dry reforming of methane using modified spinel as a carrier according to claim 1, characterized in that: In the step 2, the heating temperature is 10°C-100°C.

4. The method for preparing a cobalt-based bimetallic catalyst for dry reforming of methane using modified spinel as a carrier according to claim 1, characterized in that: In step 3, the mass of ethylene glycol is 10 wt%-90 wt% of the mass of citric acid.

5. The method for preparing a cobalt-based bimetallic catalyst for dry reforming of methane using modified spinel as a carrier according to claim 1, characterized in that: In step 4, the temperature is 100°C-170°C.

6. The method for preparing a cobalt-based bimetallic catalyst for dry reforming of methane using modified spinel as a carrier according to claim 1, characterized in that: In the step 5, the calcination temperature is 500°C-1000°C.

7. The method for preparing a cobalt-based bimetallic catalyst for dry reforming of methane using modified spinel as a carrier according to claim 1, characterized in that: In step 6, the mass fraction of cobalt nitrate is 1wt%-20wt%.

8. The method for preparing a cobalt-based bimetallic catalyst for dry reforming of methane using modified spinel as a carrier according to claim 1, characterized in that: In step 6, the mass fraction of iridium chloride is 0.1 wt%-5wt%.

9. The method for preparing a cobalt-based bimetallic catalyst for dry reforming of methane using modified spinel as a carrier according to claim 1, characterized in that: In the step 7, the calcination temperature is 400°C-700°C.

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