Methanation catalyst as well as preparation method and application thereof
By using a methanation catalyst prepared with a highly water-absorbing alumina support and a specific crystal phase, the problem of low water absorption of the support was solved, achieving high catalyst activity and low energy consumption, reducing production costs and improving metal dispersion.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-11-18
- Publication Date
- 2026-05-19
AI Technical Summary
Existing methanation catalysts have low support water absorption rates, resulting in high reaction energy consumption. Multiple impregnation operations are cumbersome and costly. Active metal clusters are prone to agglomeration, leading to reduced catalytic activity.
The catalyst is prepared by using alumina with high water absorption as a support, with an average mesopore diameter greater than 20 nm and a water absorption rate of 180-300%. The crystal phase is θ and/or δ phase. The active components are selected from Ni, Fe and Co, and the additives are selected from alkaline earth metals, transition metals and rare earth metals. The catalyst is prepared by impregnation, drying and calcination.
It improves the activity and lifespan of the catalyst, lowers the reaction temperature, reduces the number of calcinations, reduces production costs, and achieves uniform dispersion of active metals, thereby improving metal utilization.
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Figure CN122057582A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst technology, specifically to a methanation catalyst, its preparation method, and its application. Background Technology
[0002] Methanation, the simplest reaction in the Fischer-Tropsch synthesis, is mainly used in the ethylene industry, ammonia synthesis, hydrogen purification, and coal gasification. Its purpose is to convert CO into methane or remove impurities like CO from the feed gas for purification. Natural gas, a fossil fuel, is primarily used in the chemical and fuel industries; its main component, methane, can be obtained through the catalytic conversion of syngas (COx and hydrogen). As the simplest Fischer-Tropsch synthesis reaction, methanation offers advantages such as high calorific value, high conversion rate, single product, and good economic benefits.
[0003] Currently, there is a wide variety of methanation catalysts on the market, which are basically composed of a support, promoters, and active components. Alumina supports are mostly formed by particle packing, with small specific surface area and pore size. To achieve high catalyst loading, multiple impregnations are usually required. This leads to losses due to catalyst breakage during multiple impregnations, and the multiple impregnation process is cumbersome and costly. Active metals are typically loaded onto the support surface using an impregnation method. The higher the water absorption rate of the support, the more active components can be loaded; therefore, improving the water absorption rate of the support is crucial. In addition, high-load catalysts tend to accumulate and agglomerate active metal clusters on the catalyst surface, leading to reduced catalyst activity. Therefore, it is essential to improve the dispersion of metal clusters on the catalyst surface.
[0004] Therefore, there is an urgent need for a carrier with high water absorption, which also has high research value in improving catalytic activity and reducing reaction temperature. Summary of the Invention
[0005] The purpose of this invention is to overcome the problems of low water absorption rate of the carrier and high reaction energy consumption in the prior art, and to provide a methanation catalyst, its preparation method and application.
[0006] To achieve the above objectives, a first aspect of the present invention provides a methanation catalyst comprising a support, an active component, and optional promoters, wherein the support is alumina with high water absorption, the alumina having an average mesopore diameter greater than or equal to 20 nm, a water absorption rate of 180-300%, a sulfur content of 0.01-0.2 wt%, and a crystalline phase of θ and / or δ; the active component is selected from at least one of Ni, Fe, and Co; the promoter is selected from at least one of alkaline earth metals, transition metals, and rare earth metals, and the metal dispersion of the catalyst is between 4-6%.
[0007] A second aspect of the present invention provides a method for preparing a methanation catalyst, the method comprising:
[0008] (1) The alumina support mentioned in the catalyst according to the first aspect of the present invention;
[0009] (2) The alumina is immersed in a mixed solution containing active components and additives, and then dried and calcined in sequence; the active components are selected from at least one of Ni, Fe and Co; the additives are selected from at least one of alkaline earth metals, transition metals and rare earth metals.
[0010] A third aspect of the present invention provides a methanation catalyst prepared by the above-described preparation method.
[0011] The fourth aspect of the present invention provides an application of the methanation catalyst described in any one of the first and third aspects of the present invention in the synthesis of methane from CO and H2.
[0012] The fifth aspect of the present invention provides a method for synthesizing methane, the method comprising: reacting CO with H2 in the presence of a methanation catalyst as described above.
[0013] The beneficial effects of the present invention include at least the following:
[0014] 1) The catalyst has high activity. Under the same reaction conditions, the CO removal temperature can reach 130℃, which significantly reduces the reaction temperature, extends the catalyst life, and also achieves the effect of energy saving and consumption reduction.
[0015] 2) Traditional catalyst supports require three or even four calcinations to achieve the desired loading, while the catalyst of this invention can achieve it in one step, effectively reducing the number of calcinations and lowering the production cost of the catalyst.
[0016] 3) The alumina support of the catalyst has a lamellar structure, which results in more highly active defect sites at the edges of the lamellar structure compared to particulate alumina supports, thus helping to anchor the active metal. Furthermore, the (110) interplanar spacing of the lamellar alumina matches the interplanar spacing of the active metal (such as Ni), and lattice matching occurs during the growth of the active metal on the support, achieving strong anchoring between the support and the metal. Even with high loading, a uniformly dispersed catalyst can still be obtained, with high active metal dispersion. The metal dispersion of traditional catalysts is 3.9%, while the metal dispersion of the catalyst of this invention can reach as high as 5.8%, which is higher than that of catalysts prepared by traditional methods.
[0017] (4) The crystal phase of the alumina support is different from that of the traditional alumina support. The alumina support with mixed θ and δ phases interacts with the active metal, which helps to improve the activity of the support. Attached Figure Description
[0018] Figure 1 This is a transmission electron microscope image of the catalyst prepared in Example 1.
[0019] Figure 2 This is the BET diagram of the alumina prepared in Example 1.
[0020] Figure 3 This is the XRD diffraction pattern of the alumina prepared in Example 1. Detailed Implementation
[0021] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0022] The first aspect of this invention provides a methanation catalyst, comprising a support, an active component, and optional promoters, wherein the support is alumina with high water absorption, the alumina having an average mesopore diameter greater than or equal to 20 nm, a water absorption rate of 180-300%, a sulfur content of 0.01-0.2 wt%, and a crystalline phase of θ and / or δ; the active component is selected from at least one of Ni, Fe, and Co; the promoter is selected from at least one of alkaline earth metals, transition metals, and rare earth metals, and the metal dispersion of the catalyst is between 4-6%.
[0023] In this invention, the alumina has an average mesopore diameter greater than or equal to 20 nm, a water absorption rate of 180-300%, a sulfur content of 0.01-0.2%, and a crystalline phase of θ and / or δ. The alumina support used in this invention has a high water absorption rate, which allows the active components and additives to be uniformly distributed on the support, thereby improving the catalytic activity of the catalyst.
[0024] According to the present invention, preferably, the average pore size of the alumina mesopores is 20-40 nm.
[0025] According to the present invention, preferably, the pore volume of the alumina is 0.6-1.5 cm. 3 / g.
[0026] According to the present invention, preferably, the alumina has a water absorption rate of 190-260%.
[0027] According to the present invention, preferably, the sulfur content of the alumina is 0.05-0.15 wt%.
[0028] According to the present invention, preferably, the metal dispersion of the catalyst is between 5 and 5.8%.
[0029] In this invention, when the average pore size and other parameters of the alumina meet the above-mentioned range, it is more conducive to the loading of active metals, controlling the reaction rate of the catalyst, and further improving the catalytic activity of the catalyst.
[0030] In this invention, the method for preparing alumina includes: preparing boehmite by the sulfuric acid method; and calcining the obtained boehmite at 900-1100℃.
[0031] According to the present invention, preferably, the method for preparing boehmite by the sulfuric acid method is as follows: (1) preparing a sodium aluminate solution by dissolving sodium hydroxide and sodium aluminate; (2) adding the sodium aluminate solution dropwise to an aluminum sulfate solution to make the pH of the mixed system 8-10 to obtain a boehmite precursor; (3) crystallizing the boehmite precursor to obtain boehmite.
[0032] According to the present invention, preferably, the amount of sodium hydroxide and sodium aluminate used is such that the concentration of aluminum in the sodium aluminate aqueous solution is 0.1-2 mol / L, more preferably 0.5-1.5 mol / L.
[0033] According to the present invention, preferably, the amount of sodium hydroxide and sodium aluminate is such that the molar ratio of Na to Al in the sodium aluminate aqueous solution is 3-6:1, more preferably 3.5-4.5:1.
[0034] In this invention, the alkaline sodium aluminate aqueous solution can be controlled by an alkali metal hydroxide (such as sodium hydroxide). According to one embodiment of the invention, the alkaline sodium aluminate solution is prepared by mixing sodium hydroxide and sodium aluminate with a solvent. The amount of solvent is sufficient to completely dissolve the sodium aluminate. The solvent is not specifically required and can be water or a lower alcohol, preferably at least one of deionized water and ethanol.
[0035] According to the present invention, preferably, the concentration of aluminum sulfate in the aluminum sulfate solution is 0.1-1 mol / L, more preferably 0.3-0.6 mol / L.
[0036] In this invention, the specific conditions for reacting the alkaline sodium aluminate aqueous solution and the aluminum sulfate aqueous solution are not limited and can be conventional methods used in the art. Preferably, the reaction method involves adding the alkaline sodium aluminate aqueous solution dropwise to the aluminum sulfate aqueous solution at room temperature.
[0037] According to the present invention, preferably, the sulfur content of boehmite prepared by the sulfuric acid method is 1-5 wt%, more preferably 2-3 wt%. This preferred embodiment eliminates the need for multiple washings of the boehmite, allowing for calcination at higher sulfur content, which is more conducive to obtaining alumina with a mesoporous average pore size and high water absorption rate.
[0038] According to the present invention, preferably, the crystallization temperature in the preparation of boehmite by the sulfuric acid method is 50-120°C and the time is 2-24h; more preferably, the crystallization temperature is 70-100°C and the time is 5-20h.
[0039] In this invention, the preparation of boehmite by the sulfuric acid method can also be carried out by drying after crystallization. Preferably, the drying temperature is 80-120℃ and the time is 2-5h.
[0040] In this invention, the method for preparing boehmite using the sulfuric acid process may further include a forming step to obtain alumina of a specific shape. There is no particular limitation on the shape of the prepared alumina carrier; any shape conventionally prepared in the art can be used. Preferably, the carrier shape is at least one of cylindrical, spherical, or trilobal, with a cylindrical shape being the most preferred.
[0041] In this invention, the molding method is not particularly limited and can be any method commonly used in the art, such as tableting.
[0042] According to the present invention, preferably, the calcination temperature in the alumina preparation method is 1000-1100℃ and the time is 4-10h.
[0043] In this invention, the roasting atmosphere is not particularly limited and can be any gas commonly used in the art. Preferably, the gas is at least one of nitrogen, oxygen, argon, or air, with air being the most preferred.
[0044] According to the present invention, preferably, the alkaline earth metal is selected from at least one of Be, Mg, Ca, Sr and Ba, more preferably Mg and / or Ca.
[0045] According to the present invention, preferably, the transition metal is selected from at least one of Sc, Ti, V, Cr, Mn, Mo, Cu, Zn, Ag, Cd, Au and Pt, more preferably from at least one of Ti, Mn, Mo, Cu, Zn and Ag.
[0046] According to the present invention, preferably, the rare earth metal is selected from at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, more preferably at least one of La, Ce, Pr and Sm.
[0047] In this invention, when the additive meets the above-mentioned range of alkaline earth metals, transition metals and rare earth metals, it can enhance the stability and selectivity of the catalyst, thereby further improving the catalytic activity of the catalyst.
[0048] According to the present invention, preferably, based on the total mass of the methanation catalyst, the content of the active component in the methanation catalyst is 30-60 wt%, the content of the promoter is 0-5 wt%, and the content of the support is 35-70 wt%. More preferably, based on the total mass of the methanation catalyst, the content of the active component in the methanation catalyst is 41-55 wt%, the content of the promoter is 0-4 wt%, and the content of the support is 41-55 wt%. The content of the active component or promoter is calculated as metal oxide.
[0049] In this invention, when the contents of the active component, promoter, and support meet the above-mentioned range based on the total mass of the methanation catalyst, the prepared catalyst can have high metal dispersion, high metal utilization, and improved catalytic activity.
[0050] A second aspect of the present invention provides a method for preparing a methanation catalyst, the method comprising:
[0051] (1) The alumina support mentioned in the catalyst according to the first aspect of the present invention;
[0052] (2) The alumina is immersed in a mixed solution containing active components and additives, and then dried and calcined in sequence; the active components are selected from at least one of Ni, Fe and Co; the additives are selected from at least one of alkaline earth metals, transition metals and rare earth metals.
[0053] According to the present invention, the active component and the auxiliary agent can be introduced in the form of their corresponding soluble salts. The soluble salts can be of various common types, preferably selected from at least one of nitrates and carbonates, with nitrates being more preferred. The specific selection of the active component and the auxiliary agent is as described above, and those skilled in the art can select the corresponding soluble salts based on the aforementioned types; further details will not be elaborated here. Similarly, the amounts of the active component, the auxiliary agent, and alumina are such that their content in the catalyst meets the aforementioned range.
[0054] According to the present invention, the amount of solvent in the mixed solution is sufficient to completely dissolve the soluble salts corresponding to the active components and the adjuvants. There are no specific requirements for the type of solvent, which can be water or a lower alcohol, preferably at least one of ethanol and deionized water.
[0055] In this invention, preferably, the concentration of the active component (calculated as metal element) in the mixed solution is 2-8 mol / L, more preferably 2.5-6 mol / L;
[0056] In this invention, preferably, the concentration of the auxiliary agent in the mixed solution is 0.2-1.2 mol / L, more preferably 0.3-0.9 mol / L.
[0057] According to the present invention, preferably, the drying conditions in step (2) include: a temperature of 60-140°C and a time of 2-10 hours.
[0058] According to the present invention, preferably, the calcination conditions in step (2) include: a temperature of 300-450°C and a time of 2-6 hours.
[0059] In this invention, in step (2), the roasting atmosphere is not particularly limited and can be any gas commonly used in the art. Preferably, the gas is at least one of nitrogen, oxygen, argon or air, and more preferably nitrogen.
[0060] A third aspect of the present invention provides a methanation catalyst prepared by the above-described preparation method.
[0061] The fourth aspect of the present invention provides an application of the methanation catalyst described in any one of the first and third aspects of the present invention in the synthesis of methane from CO and H2.
[0062] The methanation catalyst of this invention can catalyze the conversion of CO to CH4 and has high catalytic activity.
[0063] The fifth aspect of the present invention provides a method for synthesizing methane, the method comprising: reacting CO with H2 in the presence of a methanation catalyst as described above.
[0064] According to the present invention, the volume ratio of CO to H2 can be 1:200-300.
[0065] According to a preferred embodiment of the present invention, the reaction conditions include: a temperature of 130-250°C, a reaction pressure of 1-5 MPa, a reaction time of 90-150 h, and a total volume hourly space velocity (VHSV) of CO and H2 of 1000-10000 h⁻¹. -1 .
[0066] The present invention will be described in detail below through examples. In the following examples and comparative examples, the glucose solution was commercially available from Sinopharm Corporation and was an analytical grade product. The elemental content was detected by X-ray fluorescence spectrometry (XRF).
[0067] Example 1
[0068] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml deionized water for later use.
[0069] (2) Weigh 88.4g of aluminum sulfate into 500ml of deionized water, add the sodium aluminate solution prepared in step (1) dropwise into the aluminum sulfate solution with a concentration of 0.5mol / L until the pH is 9, stir at room temperature for 60min to obtain boehmite precursor.
[0070] (3) Continue crystallization at 80℃ for 10 hours, and then dry at 120℃ for 2 hours to obtain boehmite with a large specific surface area (specific surface area of 456 cm²). 2 / g, sulfur content is 2.8wt%.
[0071] (4) Use a tablet press to press boehmite into cylindrical particles of 5mm*3mm, and calcine them at 1100℃ for 6 hours in air atmosphere to obtain alumina with a water absorption rate of 220% and a carrier sulfur content of 0.08wt%.
[0072] (5) Dissolve 20g of nickel nitrate hexahydrate in 12mL of deionized water and stir evenly. Load the product onto 6g of alumina support using the equal volume impregnation method. Place the impregnated product in an oven and dry at 120°C for 2 hours. Place the dried product in a tube furnace and calcine at 400°C for 3 hours under a nitrogen atmosphere to obtain a catalyst with a nickel oxide content of 46wt%.
[0073] Figure 1 This is a transmission electron microscope (TEM) image of the catalyst prepared in Example 1. (The image is from...) Figure 1 The interaction between the metal and the support can be observed, and the aggregation of metal clusters with large loads is not obvious; nickel nitrate particles (deep contrast) grow on a lamellar alumina support (low contrast), and the alumina support exhibits a lamellar structure.
[0074] Figure 2 This is the BET plot of the alumina prepared in Example 1. (From...) Figure 2 It can be seen that, compared with traditional alumina carriers, the prepared alumina has a larger average mesopore size distribution.
[0075] Figure 3 This is the XRD diffraction pattern of the alumina obtained in Example 1. Figure 3 It can be seen that the alumina support obtained at 1100℃ is a mixed phase of δ and θ.
[0076] Example 2
[0077] (1)-(3) are the same as in Example 1.
[0078] (4) The boehmite was pressed into cylindrical particles of 5mm*3mm using a tablet press. The particles were then calcined at 1000℃ for 6 hours in air to obtain alumina with a water absorption rate of 240% and a carrier sulfur content of 0.15wt%.
[0079] (5) Dissolve 20g of nickel nitrate hexahydrate and 1.5g of magnesium nitrate in 12mL of deionized water and stir evenly. Load the product onto 6g of alumina support using the equal volume impregnation method. Place the impregnated product in an oven and dry it at 120℃ for 2 hours. Then place the dried product in a tube furnace and calcine it at 400℃ for 3 hours under a nitrogen atmosphere to obtain a catalyst with a NiO content of 45wt% and a MgO content of 3.5wt%.
[0080] Example 3
[0081] (1)-(3) are the same as in Experiment 1.
[0082] (4) The boehmite was pressed into cylindrical particles of 5mm*3mm using a tablet press. The particles were then calcined at 1050℃ for 6 hours in air to obtain alumina with a water absorption rate of 190% and a carrier sulfur content of 0.09wt%.
[0083] (5) Dissolve 25g of nickel nitrate hexahydrate and 2g of magnesium nitrate in 17mL of deionized water and stir until homogeneous. Mix the two solutions and stir until homogeneous. Load the mixture onto 9g of alumina support using the equal volume impregnation method. Place the impregnated product in an oven and dry at 120°C for 2 hours. Then place the dried product in a tube furnace and calcine at 400°C for 3 hours under a nitrogen atmosphere to obtain a catalyst with a NiO content of 41wt% and a MgO content of 3.4wt%.
[0084] Example 4
[0085] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml deionized water for later use.
[0086] (2) Weigh 88.4g of aluminum sulfate into 500ml of deionized water, add the sodium aluminate solution prepared in step (1) dropwise into the aluminum sulfate solution with a concentration of 0.5mol / L until the pH is 9.5, stir at room temperature for 60min to obtain boehmite precursor.
[0087] (3) Continue crystallization at 80℃ for 10h, and dry at 120℃ for 2h to obtain boehmite (sulfur content of 2.6wt%).
[0088] (4) Use a tablet press to press boehmite into cylindrical particles of 5mm*3mm, and calcine them at 1100℃ for 6 hours in air atmosphere to obtain alumina with a water absorption rate of 200% and a carrier sulfur content of 0.08wt%.
[0089] (5) Dissolve 20g of nickel nitrate hexahydrate in 14mL of deionized water and stir evenly. Load it onto 7g of alumina using the equal volume impregnation method. Place the impregnated product in an oven and dry it at 120℃ for 2 hours. Then place the dried product in a tube furnace and calcine it at 400℃ for 3 hours under a nitrogen atmosphere to obtain a catalyst with a NiO content of 42wt%.
[0090] Comparative Example 1
[0091] The catalyst was prepared according to step (5) of Example 1, except that alumina was replaced with an alumina support (commercially available alumina industrial support particles, purchased from Shandong Taiguang Company, calcination temperature 600℃, specific surface area 230m²). 2 / g, pore volume 1cm 3 / g, carrier water absorption rate 100%).
[0092] 20g of nickel nitrate hexahydrate was dissolved in 10mL of deionized water and stirred until homogeneous. The two solutions were then mixed and stirred until homogeneous, and the mixture was impregnated onto 10g of alumina support. The impregnated product was filtered and then placed in an oven at 100℃ for 10 hours to dry. The dried product was then placed in a tube furnace and calcined at 400℃ for 3 hours under a nitrogen atmosphere to obtain the catalyst product. The above operation was repeated 3 times to obtain a comparative catalyst with a NiO loading of 44wt%.
[0093] Comparative Example 2
[0094] (1) A commercially available alumina support was calcined at 1000℃ for 6 hours in air to obtain an alumina support with a mixed δ and θ crystalline phase. BET characterization showed that the specific surface area of the calcined alumina support was 104 m². 2 / g, pore volume 0.6cm 3 / g, carrier water absorption rate 90%.
[0095] (2) Dissolve 20g of nickel nitrate hexahydrate and 0.6g of magnesium nitrate in 9mL of deionized water and stir until homogeneous. Mix the two solutions together and stir until homogeneous. Impregnate the 10g alumina support using the impregnation method. Filter the impregnated product and then place it in an oven at 100℃ for 10 hours. Place the dried product in a tube furnace and calcine it at 400℃ for 3 hours under a nitrogen atmosphere to obtain the catalyst product. Repeat the above operation 3 times to obtain a comparative catalyst with a NiO loading of 42wt% and an MgO content of 3.2wt%.
[0096] Comparative Example 3
[0097] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml deionized water for later use.
[0098] (2) Weigh 88.4g of aluminum sulfate into 500ml of deionized water, add the sodium aluminate solution prepared in step (1) dropwise into the aluminum sulfate solution with a concentration of 0.5mol / L until the pH is 9, stir at room temperature for 60min to obtain boehmite precursor.
[0099] (3) Continue crystallization at 80℃ for 10h to obtain boehmite with a large specific surface area.
[0100] (4) Use a tablet press to press the alumina carrier into cylindrical particles of 5mm*3mm.
[0101] (5) The cylindrical particle carrier was immersed in a 5 wt% glucose solution (1 g of glucose was used), then transferred to a hydrothermal reactor and reacted at 100 °C for 10 h. After cooling and filtration, it was dried at 80 °C for 4 h, and then placed in a nitrogen atmosphere and calcined at 600 °C for 10 h to obtain a carrier (carbon-doped γ-alumina) with a water absorption rate of 120% and no sulfur content was detected.
[0102] (6) Dissolve 20g of nickel nitrate hexahydrate in 15mL of deionized water and stir evenly. Impregnate the product onto 12g of carbon-doped alumina support using the impregnation method. Filter the impregnated product and then dry it in an oven at 120℃ for 2 hours. Then, place the dried product into a muffle furnace and calcine it at 400℃ for 3 hours. Repeat the above operation 3 times to obtain a comparative catalyst with a NiO content of 45wt%.
[0103] Comparative Example 4
[0104] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml deionized water for later use.
[0105] (2) Weigh 88.4g of aluminum sulfate into 500ml of deionized water, add the sodium aluminate solution prepared in step (1) dropwise into the aluminum sulfate solution with a concentration of 0.5mol / L until the pH is 9, stir at room temperature for 60min to obtain boehmite precursor.
[0106] (3) Continue crystallization at 80℃ for 10h to obtain boehmite with a large specific surface area (sulfur content of 2.8wt%).
[0107] (4) Use a tablet press to press the alumina carrier into cylindrical particles of 5mm*3mm.
[0108] (5) The obtained boehmite with a large specific surface area was calcined at 600°C for 6 hours in air to obtain macroporous γ-alumina. The water absorption rate was 260%, and the sulfur content of the carrier was 2.1 wt%.
[0109] (6) Dissolve 54g of nickel nitrate hexahydrate in 32mL of deionized water and stir evenly. Impregnate the product onto 12g of alumina support using the impregnation method. Place the impregnated product in an oven at 120℃ and dry for 2 hours. Place the dried product in a tube furnace and calcine at 400℃ for 3 hours under a nitrogen atmosphere to obtain a comparative catalyst with a NiO content of 53wt%.
[0110] Comparative Example 5
[0111] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml deionized water for later use.
[0112] (2) Weigh 88.4g of aluminum sulfate into 500ml of deionized water, add the sodium aluminate solution prepared in step (1) dropwise into the aluminum sulfate solution with a concentration of 0.5mol / L until the pH is 9, stir at room temperature for 60min to obtain boehmite precursor.
[0113] (3) Continue crystallization at 80℃ for 10h, filter, wash five times with deionized water, and dry at 120℃ for 2h to obtain boehmite with a large specific surface area (sulfur content of 1.2wt%).
[0114] (4) Use a tablet press to press boehmite into cylindrical particles of 5mm*3mm, and calcine them at 1100℃ for 6 hours in air atmosphere to obtain alumina with a water absorption rate of 90% and a carrier sulfur content of 0.05wt%.
[0115] (5) Dissolve 20g of nickel nitrate hexahydrate in 10mL of deionized water and stir evenly. Load the product onto 10g of alumina support using the impregnation method. Filter the impregnated product and dry it in an oven at 120℃ for 2 hours. Then place the dried product in a tube furnace and calcine it at 400℃ for 3 hours under a nitrogen atmosphere. Repeat the impregnation process three times to obtain a comparative catalyst with a NiO content of 42wt%.
[0116] Comparative Example 6
[0117] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml deionized water for later use.
[0118] (2) Weigh 88.4g of aluminum sulfate into 500ml of deionized water, add the sodium aluminate solution prepared in step (1) dropwise into the aluminum sulfate solution with a concentration of 0.5mol / L until the pH is 9, stir at room temperature for 60min to obtain boehmite precursor.
[0119] (3) Continue crystallization at 80℃ for 10h, and dry at 120℃ for 2h to obtain boehmite (sulfur content of 2.8wt%).
[0120] (4) Boehmite was pressed into cylindrical particles of 5mm*3mm using a tablet press and then calcined at 1200℃ for 6 hours in air to obtain alumina with a water absorption rate of 80% and no detectable sulfur content in the carrier.
[0121] (5) Dissolve 20g of nickel nitrate hexahydrate in 10mL of deionized water and stir evenly. Load the product onto 10g of alumina support using the impregnation method. Filter the impregnated product and dry it in an oven at 120℃ for 2 hours. Then place the dried product in a tube furnace and calcine it at 400℃ for 3 hours under a nitrogen atmosphere. Repeat the impregnation process three times to obtain a comparative catalyst with a NiO content of 35wt%.
[0122] Test Example 1
[0123] The alumina (support) and catalyst obtained in the above examples and comparative examples were analyzed as follows:
[0124] The metal dispersion (%) of the catalyst was measured using a chemisorption analyzer; the content of active components and auxiliary agents (wt%) was measured using X-ray fluorescence spectroscopy (XRF); the water absorption rate (%) was tested by weighing 10g of the support into 100mL of deionized water, weighing the support after 10 minutes, and calculating the water absorption rate; the average pore size distribution (nm) and specific surface area (m²) of the mesopores were also measured. 2 The pore volume (g) and pore volume were measured using a physical adsorption analyzer (BET) via nitrogen adsorption. The results are shown in Table 1.
[0125] Furthermore, the XRD diffraction patterns of the alumina obtained in other embodiments are similar to those in Example 1, exhibiting a mixed δ and / or θ phase structure.
[0126] Table 1
[0127]
[0128] Test Example 2
[0129] Methanation reaction performance test
[0130] 5 mL of the catalyst prepared in the above examples and comparative examples was loaded into a stainless steel fixed-bed reactor. High-purity nitrogen gas was introduced at a flow rate of 300 mL / min, and the temperature was raised to 120 °C. The high-purity nitrogen gas was then switched to hydrogen gas at a flow rate of 200 mL / min, and the temperature was raised to 400 °C and maintained for 4 h. Then, the hydrogen gas was switched to the feed gas (composition: CO 0.35%, H2 99.65%, by volume fraction), and the catalyst was tested at different space velocities (the volume hourly space velocity of the feed gas was 3000 h⁻¹). -1 5000h -1 and 10000h -1The reaction was carried out at a temperature (130-250℃) and a reaction pressure of 3 MPa. After 100 h of reaction, the gas composition of the reaction products was analyzed by an Agilent 7890 gas chromatograph. Table 2 shows the space velocity and CO removal temperature at which both CO conversion and CH4 yield reached 100% after 100 h of reaction.
[0131] Table 2
[0132]
[0133]
[0134] As can be seen from the results in Table 2, under the same conditions, the catalyst in the embodiments of the present invention has a lower conversion temperature of CO in the methanation reaction than the comparative example, indicating that the catalyst has high activity and the catalyst in the embodiments has higher dispersion.
[0135] Therefore, the methanation catalyst prepared by the method of the present invention uses alumina as a support, which has a greater water absorption rate, so that the active components and promoters are evenly distributed on the support. This can effectively improve the utilization rate of active metals and the catalytic activity of the catalyst, while reducing the reaction temperature and achieving the effect of saving costs.
[0136] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A methanation catalyst, characterized in that, The catalyst comprises a support, an active component, and optional promoters, wherein the support is alumina with high water absorption, the mesopore average pore size being greater than or equal to 20 nm, the water absorption rate being 180-300%, the sulfur content being 0.01-0.2 wt%, and the crystal phase being θ and / or δ phase; the active component is selected from at least one of Ni, Fe, and Co; the promoters are selected from at least one of alkaline earth metals, transition metals, and rare earth metals; and the metal dispersion of the catalyst is between 4-6%.
2. The catalyst according to claim 1, wherein, The average pore size of the mesopores in the alumina is 20-40 nm; And / or, the specific surface area of the alumina is 90-200 cm². 2 / g; And / or, the pore volume of the alumina is 0.6-1.5 cm³. 3 / g; And / or, the water absorption rate of the alumina is 190-260%; And / or, the sulfur content of the alumina is 0.05-0.15 wt%; And / or, the metal dispersion of the catalyst is between 5 and 5.8%.
3. The catalyst according to claim 1 or 2, wherein, The method for preparing the alumina includes: preparing boehmite by the sulfuric acid method; and calcining the obtained boehmite at 900-1100℃.
4. The catalyst according to claim 3, wherein, The method for preparing boehmite using the sulfuric acid process is as follows: (1) Prepare a sodium aluminate solution by mixing sodium hydroxide and sodium aluminate; (2) Add sodium aluminate solution dropwise to aluminum sulfate solution to make the pH of the mixed system 8-10 to obtain boehmite precursor; (3) Boehmite is obtained by crystallizing the boehmite precursor.
5. The catalyst according to claim 4, wherein, The amounts of sodium hydroxide and sodium aluminate are such that the concentration of aluminum in the sodium aluminate solution is 0.1-2 mol / L, and the molar ratio of Na to Al is 3-6:1; preferably, the concentration of aluminum in the sodium aluminate solution is 0.5-1.5 mol / L, and the molar ratio of Na to Al is 3.5-4.5:
1. And / or, the concentration of aluminum sulfate in the aluminum sulfate solution is 0.1-1 mol / L, preferably 0.3-0.6 mol / L.
6. The catalyst according to claim 4 or 5, wherein, The crystallization temperature is 50-120℃ and the time is 2-24h. Preferably, the crystallization temperature is 70-100℃ and the time is 5-20h.
7. The method according to claim 3, wherein the calcination temperature is 1000-1100℃ and the time is 4-10h; And / or, the sulfur content of the boehmite is 1-5 wt%.
8. The catalyst according to claim 1, wherein, The alkaline earth metal is selected from at least one of Be, Mg, Ca, Sr and Ba, preferably Mg and / or Ca; And / or, the transition metal is selected from at least one of Sc, Ti, V, Cr, Mn, Mo, Cu, Zn, Ag, Cd, Au and Pt, preferably at least one of Ti, Mn, Mo, Cu, Zn and Ag; And / or, the rare earth metal is selected from at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, preferably at least one of La, Ce, Pr and Sm.
9. The catalyst according to claim 1 or 8, wherein, Based on the total mass of the catalyst, the content of the active component is 30-60 wt%, the content of the auxiliary agent is 0-5 wt%, and the content of the support is 35-70 wt%. Preferably, the content of the active component is 41-55 wt%, the content of the auxiliary agent is 0-4 wt%, and the content of the carrier is 41-55 wt%.
10. A method for preparing a methanation catalyst, characterized in that, The method includes: (1) Alumina is prepared by the method for preparing alumina in the catalyst according to any one of claims 3-7; (2) The alumina is immersed in a mixed solution containing an active component and optional additives, and then dried and calcined in sequence; the active component is selected from at least one of Ni, Fe and Co; the additives are selected from at least one of alkaline earth metals, transition metals and rare earth metals.
11. The preparation method according to claim 10, wherein, In step (2), the roasting temperature is 300-450℃ and the time is 2-6h.
12. The methanation catalyst prepared by the preparation method according to claim 10 or 11.
13. The use of the methanation catalyst according to any one of claims 1-9 and 12 in the synthesis of methane from CO and H2.
14. A method for synthesizing methane, characterized in that, The method comprises reacting CO with H2 in the presence of the methanation catalyst according to any one of claims 1-9 and 12.
15. The method according to claim 14, wherein, The volume ratio of CO to H2 is 1:200-300; And / or, the reaction conditions include: a temperature of 130-250℃, a reaction pressure of 1-5 MPa, a reaction time of 90-150 h, and a total volume hourly space velocity (VHSV) of CO and H2 of 1000-10000 h⁻¹. -1 .