A methanation reaction catalyst, a preparation method and application thereof

Abstract

The application discloses a methanation reaction catalyst and a preparation method and application thereof. The catalyst comprises an inorganic salt modified temperature-sensitive polymer modified full-silica zeolite S-1 carrier, a metal active component Ni supported on the carrier, and an auxiliary component Mo from a formaldehyde waste iron-molybdenum catalyst. The catalyst has the heat stability of the molecular sieve structure and the unique shape selectivity of the crystal pore, which helps to improve the low-temperature activity and the dispersion degree of the metal particles, and the catalyst has strong anti-poisoning capacity. The catalyst preparation method realizes the recycling of the effective components in the formaldehyde waste iron-molybdenum catalyst, improves the low-temperature activity of the methanation reaction catalyst, effectively inhibits the generation of nickel carbonyl, and the catalyst has good stability.

Description

Technical Field

[0001] This invention belongs to the field of chemical catalysis technology, specifically relating to a methanation reaction catalyst, its preparation method, and its application. Background Technology

[0002] The increasing concentration of CO2 in the atmosphere is exacerbating climate change problems, such as the greenhouse effect. Therefore, effectively utilizing CO2 is crucial for addressing both the greenhouse effect and environmental pollution. Furthermore, the crude hydrogen gas produced in ammonia synthesis plants inevitably contains CO and CO2 components, which can cause problems for downstream equipment; therefore, thorough purification is essential.

[0003] Methanation is a strongly exothermic reaction in which CO and CO2 are hydrogenated to produce methane and water under the action of a catalyst. Methanation not only reduces the concentration of CO and CO2 in crude hydrogen but also effectively addresses the problem of natural gas scarcity. Currently, methanation mainly uses nickel-based catalysts and noble metal catalysts such as Ru and Pd. Nickel-based catalysts have high catalytic activity and various preparation methods, but they typically exhibit low activity at low temperatures, poor resistance to poisoning, and are prone to deactivation due to sintering and carbon deposition. Patents CN110893347A and CN110893346A disclose a low-temperature, high-activity nickel-based Ni / Mo bimetallic methanation catalyst. This catalyst exhibits good activity above 200℃, but at lower temperatures, it cannot prevent the formation of nickel carbonyl and has poor resistance to poisoning. CN111097534A discloses a bimetallic methanation catalyst using a water-soluble polymer as an additive. While the water-soluble polymer improves catalyst dispersion, the lack of a good steric effect between the bimetals results in low conversion rates at low temperatures. CN106179484B discloses a Ni / Cu bimetallic methanation catalyst prepared by adding a water-soluble polymer to an all-silica zeolite S-1 molecular sieve support. This catalyst exhibits good stability and mechanical strength at high temperatures but lacks good low-temperature activity and resistance to poisoning. Patent CN108355668B discloses a nickel catalyst with added alkaline earth metals or rare earth metals. This catalyst improves its resistance to carbon deposition and catalytic activity to some extent, but the multiple metal components and their varying adsorption properties hinder mass production.

[0004] In summary, pure nickel-based methanation catalysts exhibit low catalytic activity and poor resistance to poisoning at low temperatures. Therefore, the development of methanation catalysts with better low-temperature activity, selectivity, and stability remains an urgent task. Summary of the Invention

[0005] The purpose of this invention is to provide a methanation reaction catalyst in which Ni does not readily react with CO to form nickel carbonyl at low temperatures, exhibits high methane selectivity, and also possesses advantages such as strong stability and resistance to poisoning.

[0006] Another object of the present invention is to provide a method for preparing such a methanation reaction catalyst.

[0007] Another object of the present invention is to provide the application of such a methanation catalyst in a methanation reaction.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A methanation catalyst comprises an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support, a metal active component Ni supported on the support, and an auxiliary component Mo.

[0010] In a preferred embodiment, the methanation catalyst contains, based on the total weight of the catalyst, 10-30 wt% Ni, preferably 15-25 wt%, of the active metal component supported on the support; and 1-15 wt% Mo, preferably 3-10 wt%.

[0011] In one specific embodiment, the catalyst has a specific surface area of ​​300-500 m². 2 / g, with a pore size of 5-40nm, and the active component Ni has a grain size of 1-5nm.

[0012] In one specific embodiment, the preparation method of the inorganic salt modified thermosensitive polymer-modified all-silica zeolite S-1 support includes the following steps: dispersing all-silica zeolite S-1 in an aqueous solution of N-vinylacrylamide, adding inorganic salt, stirring under inert gas protection, filtering, washing, and drying to obtain the inorganic salt modified thermosensitive polymer-modified all-silica zeolite S-1 support.

[0013] In one specific embodiment, the mass ratio of N-vinylacrylamide to all-silica zeolite S-1 is 0.1:1-2:1, preferably 0.2:1-1:1; the mass ratio of inorganic salt to all-silica zeolite S-1 is 0.1:1-2:1, preferably 0.5:1-1:1.

[0014] In one specific embodiment, the inorganic salt is selected from one or more of sodium sulfate, sodium chloride, and potassium chloride, preferably sodium sulfate.

[0015] In one specific embodiment, the auxiliary component Mo is derived from an ammonium molybdate solution; preferably, the method for preparing the ammonium molybdate solution includes the following steps:

[0016] The formaldehyde waste iron-molybdenum catalyst was roasted, crushed and ground, then mixed evenly with quicklime and ammonium carbonate, followed by hydrothermal reaction, and filtered to obtain ammonium molybdate solution.

[0017] In one specific implementation, the calcination temperature of the formaldehyde waste iron-molybdenum catalyst is 400-800℃, and the calcination time is 1-4h; preferably, the mass ratio of quicklime to formaldehyde waste iron-molybdenum catalyst is 0.5:1-5:1, more preferably 1:1-2:1; the mass ratio of ammonium carbonate to formaldehyde waste iron-molybdenum catalyst is 0.5:1-5:1, more preferably 1:1-2:1; preferably, the hydrothermal reaction temperature is 100-300℃, and the crystallization time is 5-10h.

[0018] On the other hand, a method for preparing the aforementioned catalyst includes the following steps: adding a solution of the active component nickel salt and the auxiliary component ammonium molybdate to an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support, followed by ultrasonic impregnation, drying, and calcination to obtain the catalyst.

[0019] In one specific embodiment, the nickel salt is selected from one or more of nickel nitrate, nickel carbonate, and nickel chloride, preferably nickel nitrate; preferably, the mass ratio of the nickel salt to the inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support is 0.5:1-2:1, more preferably 1:1-1.8:1; the mass ratio of the ammonium molybdate solution to the inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support is 0.02:1-0.5:1, more preferably 0.1:1-0.3:1.

[0020] On the other hand, the aforementioned catalysts or catalysts prepared by the aforementioned methods are used in methanation reactions.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1) This invention employs inorganic salt-modified thermosensitive polymers to modify the surface of the all-silica zeolite S-1 support. All-silica zeolite S-1 possesses a large number of hydroxyl pockets, enabling it to react with carbon deposits formed on the catalyst surface, thus improving the catalyst's resistance to carbon deposition and simultaneously protecting the active metal ligands. The well-developed micropores and unique shape-selective channels of the crystals significantly promote the uniform dispersion of metal oxides, increase the proportion of oxidized Ni, prevent the formation of nickel carbonyl from CO and Ni at low temperatures, improve anti-poisoning ability, and thereby enhance low-temperature activity. The thermosensitive polymers can modulate the chemical properties of the support surface; above a certain temperature, the catalyst surface becomes hydrophobic, facilitating the timely desorption of water molecules from the reaction products and increasing the methanation reaction rate. This allows for temperature control of the catalytic reaction rate. Simultaneously, the use of inorganic salt modifiers to modify the thermosensitive polymers regulates their dissolution response index, enabling them to form coordination bonds with Ni and Mo components in the catalyst, resulting in a strong alloying effect in the bimetallic components and improving catalyst stability and methane selectivity.

[0023] 2) In the process of preparing the catalyst using the ammonium molybdate solution as an auxiliary agent, the oxide of the auxiliary metal interacts with the metallic Ni, and electrons are transferred from the auxiliary agent to the metallic Ni, which enhances the electron cloud density around the Ni atoms. This is beneficial to the activation of CO / CO2 during the methanation reaction. At the same time, it can effectively inhibit the accumulation and growth of Ni grains during the reduction process, so that the catalyst can generate very small Ni grains after reduction, thereby improving the low-temperature activity during the methanation reaction.

[0024] 3) This invention uses formaldehyde-based waste iron-molybdenum catalyst to prepare ammonium molybdate solution as an auxiliary agent. The process is simple and easy to operate, and it realizes the resource recovery of the effective component Mo.

[0025] 4) The catalyst of the present invention is suitable for fixed-bed methanation reaction. The catalyst has high low-temperature activity and methane selectivity for methanation reaction and good stability in the temperature range of 150-300℃. Detailed Implementation

[0026] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other well-known modifications within the scope of the claims of the present invention.

[0027] A fixed-bed methanation catalyst comprises an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support, Ni supported on the support, and an auxiliary component Mo.

[0028] In the catalyst of the present invention, based on the total weight of the catalyst, the content of the active metal component Ni supported on the support is 10-30 wt%, for example, including but not limited to 15 wt%, 20 wt%, 25 wt%, preferably 15-25 wt%; the content of metal Mo is 1-15 wt%, for example, including but not limited to 5 wt%, 10 wt%, 12 wt%, preferably 3-10 wt%, and the balance is the mass of the support.

[0029] The catalyst of the present invention has a specific surface area of ​​300-500 m². 2 / g, for example, including but not limited to 350m 2 / g、400m 2 / g、450m 2 / g, with a pore size of 5-40nm, including but not limited to 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, and 45nm, and the active component Ni grain size of 1-5nm, including but not limited to 1nm, 2nm, 3nm, 4nm, and 5nm.

[0030] The carrier described in this invention has a pore size of 5-40 nm, including but not limited to 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, and 40 nm, and a specific surface area of ​​400-600 m². 2 / g, for example, including but not limited to 400m 2 / g、450m 2 / g、500m 2 / g、550m 2 / g. The carrier of the present invention possesses the advantages of molecular sieve structural stability and a larger specific surface area, which facilitates the exposure of metal active centers and has strong resistance to poisoning.

[0031] The preparation method of the inorganic salt modified thermosensitive polymer-modified all-silica zeolite S-1 support of the present invention includes the following steps: dispersing all-silica zeolite S-1 in an aqueous solution of N-vinylacrylamide, adding inorganic salt, stirring under inert gas protection, filtering, washing and drying to obtain the inorganic salt modified thermosensitive polymer-modified all-silica zeolite S-1 support.

[0032] The all-silica zeolite S-1 can be purchased directly or synthesized. A synthesis method, for example, involves uniformly mixing a template agent, silica sol, and water, followed by isothermal crystallization, washing, drying, and calcination to obtain all-silica zeolite S-1. The template agent is selected from one or more of tetrapropylammonium hydroxide, tetraethylammonium bromide, and triethylamine, with tetrapropylammonium hydroxide being preferred. The silica sol has a SiO2 content of 10-30 wt%. The mass ratio of water to the template agent is 5:1-30:1, including but not limited to 5:1, 10:1, 15:1, 20:1, 25:1, and 30:1, preferably 15:1-20:1. The mass ratio of water to silica sol is 0.5:1-10:1, including but not limited to 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, and 10:1, preferably 1.5:1-5:1. The crystallization temperature is, for example, 100-300℃, including but not limited to 100℃, 150℃, 200℃, 250℃, and 300℃, and the crystallization time is 1-4 hours, including but not limited to 1.5 hours, 2 hours, 2.5 hours, 3 hours, and 3.5 hours. The roasting temperature is 500-700℃, including but not limited to 500℃, 550℃, 600℃, 650℃, and 700℃, and the roasting time is 6-8h, including but not limited to 6h, 6.5h, 7h, 7.5h, and 8h.

[0033] The mass ratio of N-vinylacrylamide to all-silica zeolite S-1 is 0.1:1-2:1, including but not limited to 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, and preferably 0.2:1-1:1. The mass ratio of inorganic salt to all-silica zeolite S-1 is 0.1:1-2:1, including but not limited to 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, and preferably 0.5:1-1:1.

[0034] The inorganic salt is selected from one or more of sodium sulfate, sodium chloride, and potassium chloride, preferably sodium sulfate.

[0035] In the catalyst of the present invention, the auxiliary component Mo is derived from an ammonium molybdate solution; wherein, the preparation method of the ammonium molybdate solution includes the following steps:

[0036] The formaldehyde waste iron-molybdenum catalyst was roasted, crushed and ground, then mixed evenly with water, quicklime and ammonium carbonate, and then subjected to hydrothermal reaction. The mixture was then filtered to obtain an ammonium molybdate solution.

[0037] The mass ratio of quicklime to formaldehyde waste iron-molybdenum catalyst is 0.5:1-5:1, for example, including but not limited to 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, preferably 1:1-2:1.

[0038] The mass ratio of ammonium carbonate to formaldehyde waste iron-molybdenum catalyst is 0.5:1-5:1, for example, including but not limited to 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, preferably 1:1-2:1.

[0039] The hydrothermal temperature of quicklime, ammonium carbonate and formaldehyde waste iron-molybdenum catalyst is 100-300℃, including but not limited to 100℃, 150℃, 200℃, 250℃ and 300℃, and the hydrothermal time is 5-10h, including but not limited to 6h, 6.5h, 7h, 7.5h, 8h, 9h and 10h.

[0040] This invention uses formaldehyde waste iron-molybdenum catalyst as molybdenum source. The waste catalyst is first roasted at a temperature of 400-800℃, including but not limited to 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, and 800℃, for a time of 1-4 hours, including but not limited to 1.5 hours, 2 hours, 2.5 hours, 3 hours, and 3.5 hours.

[0041] The present invention provides a method for preparing a catalyst for fixed-bed methanation reaction, comprising the following steps: adding an active component metal salt and an auxiliary agent ammonium molybdate solution to an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support in a proportion, followed by ultrasonic impregnation, drying, and calcination to obtain the catalyst.

[0042] The active component metal salt is selected from one or more of nickel nitrate, chloroplatinic acid, and nickel chloride, preferably nickel nitrate. The mass ratio of the active component metal salt (e.g., nickel nitrate) to the catalyst support (i.e., inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1) is 0.5:1-2:1, for example, including but not limited to 0.5:1, 1:1, 1.5:1, 2:1, preferably 1:1-1.8:1. The mass ratio of ammonium molybdate solution to the catalyst support is 0.02:1-0.5:1, for example, including but not limited to 0.04:1, 0.06:1, 0.08:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, preferably 0.1:1-0.3:1.

[0043] The ultrasonic impregnation time is 2-6 hours, and the ultrasonic frequency is not particularly limited, for example, 30 kHz. The drying temperature and time are not particularly limited; any conventional drying method that achieves catalyst drying is acceptable, such as drying at 100°C for 8 hours. The calcination temperature is 300-500°C, for example, including but not limited to 350°C, 400°C, 450°C, and 500°C, and the calcination time is 6-10 hours, for example, including but not limited to 7 hours, 8 hours, 9 hours, and 10 hours.

[0044] The methanation catalyst described in this invention can be used in CO / CO2 methanation reactions. Specifically, the methanation catalyst, after reduction, exhibits catalytic activity, comprising the following steps: loading the catalyst into a fixed-bed reactor at a pressure of 0.1-30 MPa, using pure hydrogen as the reducing gas, and a volume hourly space velocity (VHSV) of 1000-10000 h⁻¹. -1 The catalyst was reduced at a temperature of 250-500℃ for 2-8 hours.

[0045] The evaluation of the methanation activity of the catalyst includes the following steps: placing the catalyst of the present invention in the isothermal section of a fixed-bed reactor, with the upper and lower layers filled with ceramic balls, the reaction pressure being 0.1-30 MPa, the reaction temperature being 150-300℃, and the CO+CO2 content being 0.1-5%.

[0046] The present invention will now be described in more detail with reference to more specific embodiments, but this does not constitute any limitation.

[0047] In the examples, all chemical reagents were from Sinopharm Chemical Reagent Co., Ltd., and were of analytical grade; the purity of the raw materials hydrogen and CO were both ≥99%, and they were commercially available.

[0048] In this embodiment, an Agilent Technologies 7890A gas chromatograph was used to quantitatively analyze the methane composition of the product. An FID detector and a DB-5 column were used, with an injection port temperature of 280°C, a detector temperature of 280°C, a carrier gas (nitrogen) flow rate of 3 ml / min, an air flow rate of 400 ml / min, and a hydrogen flow rate of 40 ml / min.

[0049] Catalyst characterization: Pore structure properties were analyzed using a Tristar 3020 mesoporous physical adsorption analyzer (McClone Technik, Inc.). The measurement was performed on the entire pore structure. Samples underwent drying, degassing under vacuum at 300℃ for 8 hours, liquid nitrogen adsorption, and desorption before measurement. The specific surface area of ​​the catalyst was obtained using the BET method, and the pore size distribution was calculated using the BJH method.

[0050] The particle size of the active component was determined using a JEM-2100UHR transmission electron microscope manufactured by Nippon Electron Ltd., which was used to measure the size and distribution of Ni crystal grains in the catalyst.

[0051] The formaldehyde waste iron-molybdenum catalyst comes from the reactor of the formaldehyde unit in Wanhua Chemical Yantai Industrial Park. The Mo content in the formaldehyde waste iron-molybdenum catalyst is 5-30 wt%.

[0052] This invention uses a tubular fixed-bed reactor for catalyst activity evaluation.

[0053] Example 1

[0054] 1.0 g of tetrapropylammonium hydroxide and 3 g of silica sol (SiO2 content 20 wt%) were weighed and added to 30 g of deionized water and stirred until a homogeneous colloidal state was formed. The mixture was then placed in a reaction vessel and crystallized at 200 °C for 3 h. After removal, it was washed, dried, and calcined at 600 °C for 7 h to obtain all-silica zeolite S-1. 4 g of N-vinylacrylamide was dissolved in water, and 40 g of the prepared all-silica zeolite S-1 was dispersed in it. 4 g of sodium sulfate was added, and the mixture was stirred under argon protection. After filtration, washing, and vacuum drying at 100 °C for 8 h, an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support was obtained. The specific surface area was determined to be 482 m² / g and the average pore size was 35 nm by the BET method.

[0055] Weigh 20g of formaldehyde waste iron-molybdenum catalyst, calcine it at 600℃ for 2h, then add it to deionized water, gradually add 100g of quicklime and 100g of ammonium carbonate and mix evenly, hydrothermally at 120℃ for 8h, filter, and obtain ammonium molybdate solution.

[0056] 27g of nickel nitrate was dissolved in deionized water, and 4g of ammonium molybdate solution was added and mixed thoroughly. Then, 20g of the prepared inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support was added. After ultrasonic treatment and impregnation for 4 hours, the mixture was dried and calcined at 400℃ for 8 hours to obtain catalyst #1. Its specific surface area was determined to be 454 m² / g by the BET method. 2 / g, with an average pore size of 30nm. TEM testing showed that the average particle size of the active component Ni in the catalyst was 4nm.

[0057] Comparative Example 1

[0058] 1.0 g of tetrapropylammonium hydroxide and 3 g of silica sol (SiO2 content 20 wt%) were weighed and added to 30 g of deionized water and stirred until a homogeneous colloidal state was formed. The mixture was then placed in a reaction vessel and crystallized at 200 °C for 3 h. After removal, it was washed, dried, and calcined at 600 °C for 7 h to obtain all-silica zeolite S-1. 4 g of N-vinylacrylamide was dissolved in water, and 40 g of the prepared all-silica zeolite S-1 was dispersed in it. 4 g of sodium sulfate was added, and the mixture was stirred under argon protection. After filtration, washing, and vacuum drying, an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support was obtained. The specific surface area was determined to be 404 m² / g and the average pore size was 34 nm by the BET method.

[0059] 27g of nickel nitrate was dissolved in deionized water and added to 20g of the prepared inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support. The mixture was ultrasonically treated for 4 hours, dried, and calcined at 400℃ for 8 hours to obtain catalyst 1#-1. Its specific surface area was determined to be 380 m² / g by the BET method. 2 / g, with an average pore size of 28nm. TEM testing showed that the average particle size of the active component Ni in the catalyst was 3nm.

[0060] Example 2

[0061] 2.0 g of tetrapropylammonium hydroxide and 14.4 g of silica sol (SiO2 content 20 wt%) were weighed and added to 36 g of deionized water and stirred until a homogeneous colloidal state was formed. The mixture was then placed in a reaction vessel and crystallized at 200 °C for 3 h. After removal, it was washed, dried, and calcined at 600 °C for 7 h to obtain all-silica zeolite S-1. 20 g of N-vinylacrylamide was dissolved in water, and 40 g of the prepared all-silica zeolite S-1 was dispersed in it. 32 g of sodium sulfate was added, and the mixture was stirred under argon protection. After filtration, washing, and vacuum drying at 100 °C for 8 h, an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support was obtained. Its specific surface area was determined to be 513 m² / g by the BET method. 2 / g, average pore size 37nm.

[0062] Weigh 20g of formaldehyde waste iron-molybdenum catalyst, calcine it at 600℃ for 2h, then add it to deionized water, gradually add 30g of quicklime and 30g of ammonium carbonate and mix evenly, hydrothermally heat at 120℃ for 8h, filter, and obtain ammonium molybdate solution.

[0063] 27g of nickel nitrate was dissolved in deionized water, and 4g of ammonium molybdate solution was added and mixed thoroughly. Then, 20g of the prepared inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support was added. After ultrasonic impregnation for 4 hours, drying, and calcination at 400℃ for 8 hours, catalyst #2 was obtained. Its specific surface area was determined to be 482 m² / g by the BET method. 2 / g, with an average pore size of 33nm. TEM testing showed that the average particle size of the active component Ni in the catalyst was 3nm.

[0064] Comparative Example 2

[0065] 2.0 g of tetrapropylammonium hydroxide and 14.4 g of silica sol (SiO2 content 20 wt%) were weighed and added to 36 g of deionized water and stirred until a homogeneous colloidal state was formed. The mixture was then placed in a reaction vessel and crystallized at 200 °C for 3 h. After removal, it was washed, dried, and calcined at 600 °C for 7 h to obtain all-silica zeolite S-1. Its specific surface area was determined to be 445 m² / g by the BET method. 2 / g, average pore size 29nm.

[0066] Weigh 20g of formaldehyde waste iron-molybdenum catalyst, calcine it at 600℃ for 2h, then add it to deionized water, gradually add 30g of quicklime and 30g of ammonium carbonate and mix evenly, hydrothermally heat at 120℃ for 8h, filter, and obtain ammonium molybdate solution.

[0067] 27g of nickel nitrate was dissolved in deionized water, and 4g of ammonium molybdate solution was added and mixed thoroughly. This mixture was then added to 20g of all-silica zeolite S-1 support, and the mixture was ultrasonically treated for 4 hours, dried, and calcined at 400℃ for 8 hours to obtain catalyst 2#-1. Its specific surface area was determined to be 415 m² / g by the BET method. 2 / g, with an average pore size of 27nm. TEM testing showed that the average particle size of the active component Ni in the catalyst was 4nm.

[0068] Comparative Example 3

[0069] 2.0 g of tetrapropylammonium hydroxide and 14.4 g of silica sol (SiO2 content 20 wt%) were weighed and added to 36 g of deionized water and stirred until a homogeneous colloidal state was formed. The mixture was then placed in a reaction vessel and crystallized at 200 °C for 3 h. After removal, it was washed, dried, and calcined at 600 °C for 7 h to obtain all-silica zeolite S-1. 40 g of the prepared all-silica zeolite S-1 was dispersed in water, and 32 g of sodium sulfate was added. The mixture was stirred under argon protection, filtered, washed, and vacuum dried at 100 °C for 8 h to obtain an inorganic salt-modified all-silica zeolite S-1 support. Its specific surface area was determined to be 476 m² / g by the BET method. 2 / g, average pore size 30nm.

[0070] Weigh 20g of formaldehyde waste iron-molybdenum catalyst, calcine it at 600℃ for 2h, then add it to deionized water, gradually add 30g of quicklime and 30g of ammonium carbonate and mix evenly, hydrothermally heat at 120℃ for 8h, filter, and obtain ammonium molybdate solution.

[0071] 27g of nickel nitrate was dissolved in deionized water, and 4g of ammonium molybdate solution was added and mixed thoroughly. This mixture was then added to 20g of the prepared inorganic salt-modified all-silica zeolite S-1 support. The mixture was ultrasonically treated for 4 hours, dried, and calcined at 400℃ for 8 hours to obtain catalyst 2#-2. Its specific surface area was determined to be 450 m² / g by the BET method. 2 / g, with an average pore size of 29nm. TEM testing showed that the average particle size of the active component Ni in the catalyst was 3nm.

[0072] Comparative Example 4

[0073] 2.0 g of tetrapropylammonium hydroxide and 14.4 g of silica sol (SiO2 content 20 wt%) were weighed and added to 36 g of deionized water and stirred until a homogeneous colloidal state was formed. The mixture was then placed in a reaction vessel and crystallized at 200 °C for 3 h. After removal, it was washed, dried, and calcined at 600 °C for 7 h to obtain all-silica zeolite S-1. 20 g of N-vinylacrylamide was dissolved in water, and 40 g of the prepared all-silica zeolite S-1 was dispersed in it. The mixture was stirred under argon protection, filtered, washed, and vacuum dried at 100 °C for 8 h to obtain a thermosensitive polymer-modified all-silica zeolite S-1 support. Its specific surface area was determined to be 516 m² / g by the BET method. 2 / g, average pore size 33nm.

[0074] Weigh 20g of formaldehyde waste iron-molybdenum catalyst, calcine it at 600℃ for 2h, then add it to deionized water, gradually add 30g of quicklime and 30g of ammonium carbonate and mix evenly, hydrothermally heat at 120℃ for 8h, filter, and obtain ammonium molybdate solution.

[0075] 10g of nickel nitrate was dissolved in deionized water, and 0.4g of ammonium molybdate solution was added and mixed thoroughly. This mixture was then added to 20g of the prepared thermosensitive polymer-modified all-silica zeolite S-1 support. The mixture was ultrasonically treated for 4 hours, dried, and calcined at 400℃ for 8 hours to obtain catalyst 2#-3. Its specific surface area was determined to be 474 m² / g by the BET method. 2 / g, with an average pore size of 32nm. TEM testing showed that the average particle size of the active component Ni in the catalyst was 2nm.

[0076] Example 5

[0077] 4.0 g of tetrapropylammonium hydroxide and 40 g of silica sol (SiO2 content 20 wt%) were weighed and added to 60 g of deionized water and stirred until a homogeneous colloidal state was formed. The mixture was then placed in a reaction vessel and crystallized at 200 °C for 3 h. After removal, it was washed, dried, and calcined at 600 °C for 7 h to obtain all-silica zeolite S-1. 40 g of N-vinylacrylamide was dissolved in water, and 40 g of the prepared all-silica zeolite S-1 was dispersed in it. 40 g of sodium sulfate was added, and the mixture was stirred under argon protection. After filtration, washing, and vacuum drying at 100 °C for 8 h, an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support was obtained. Its specific surface area was determined to be 520 m² / g by the BET method. 2 / g, average pore size 37nm.

[0078] Weigh 20g of formaldehyde waste iron-molybdenum catalyst, calcine it at 600℃ for 2h, then add it to deionized water, gradually add 20g of quicklime and 20g of ammonium carbonate and mix evenly, hydrothermally heat at 120℃ for 8h, filter to obtain ammonium molybdate solution.

[0079] 36g of nickel nitrate was dissolved in deionized water, and 6g of ammonium molybdate solution was added and mixed thoroughly. This mixture was then added to 20g of the prepared inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support. The mixture was ultrasonically impregnated for 4 hours, dried, and calcined at 400℃ for 8 hours to obtain catalyst #3. Its specific surface area was determined to be 495 m² / g by the BET method. 2 / g, with an average pore size of 32nm. TEM testing showed that the average particle size of the active component Ni in the catalyst was 3nm.

[0080] Example 6

[0081] 4.0 g of tetrapropylammonium hydroxide and 40 g of silica sol (SiO2 content 20 wt%) were weighed and added to 60 g of deionized water and stirred until a homogeneous colloidal state was formed. The mixture was then placed in a reaction vessel and crystallized at 200 °C for 3 h. After removal, it was washed, dried, and calcined at 600 °C for 7 h to obtain all-silica zeolite S-1. 4 g of N-vinylacrylamide was dissolved in water, and 40 g of the prepared all-silica zeolite S-1 was dispersed in it. 40 g of sodium sulfate was added, and the mixture was stirred under argon protection. After filtration, washing, and vacuum drying at 100 °C for 8 h, an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support was obtained. Its specific surface area was determined to be 471 m² by the BET method. 2 / g, average pore size 38nm.

[0082] Weigh 20g of formaldehyde waste iron-molybdenum catalyst, calcine it at 600℃ for 2h, then add it to deionized water, gradually add 20g of quicklime and 20g of ammonium carbonate and mix evenly, hydrothermally heat at 120℃ for 8h, filter to obtain ammonium molybdate solution.

[0083] 36g of nickel nitrate was dissolved in deionized water, and 6g of ammonium molybdate solution was added and mixed thoroughly. This mixture was then added to 20g of the prepared inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support. After ultrasonic impregnation for 4 hours, drying, and calcination at 400℃ for 8 hours, catalyst #4 was obtained. Its specific surface area was determined to be 442 m² / g by the BET method. 2 / g, with an average pore size of 31nm. TEM testing showed that the average particle size of the active component Ni in the catalyst was 3nm.

[0084] Example 7

[0085] 2.0 g of tetrapropylammonium hydroxide and 40 g of silica sol (SiO2 content 20 wt%) were weighed and added to 20 g of deionized water and stirred until a homogeneous colloidal state was formed. The mixture was then placed in a reaction vessel and crystallized at 200 °C for 3 h. After removal, it was washed, dried, and calcined at 600 °C for 7 h to obtain all-silica zeolite S-1. 80 g of N-vinylacrylamide was dissolved in water, and 40 g of the prepared all-silica zeolite S-1 was dispersed in it. 80 g of sodium sulfate was added, and the mixture was stirred under argon protection. After filtration, washing, and vacuum drying at 100 °C for 8 h, an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support was obtained. Its specific surface area was determined to be 512 m² / g by the BET method. 2 / g, average pore size 34nm.

[0086] Weigh 20g of formaldehyde waste iron-molybdenum catalyst, calcine it at 600℃ for 2h, then add it to deionized water, gradually add 60g of quicklime and 10g of ammonium carbonate and mix evenly, hydrothermally at 120℃ for 8h, filter, and obtain ammonium molybdate solution.

[0087] 40g of nickel nitrate was dissolved in deionized water, and 10g of ammonium molybdate solution was added and mixed thoroughly. This mixture was then added to 20g of the prepared inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support. The mixture was ultrasonically treated for 4 hours, dried, and calcined at 400℃ for 8 hours to obtain catalyst #5. Its specific surface area was determined to be 476 m² / g by the BET method. 2 / g, with an average pore size of 30nm. TEM testing showed that the average particle size of the active component Ni in the catalyst was 2nm.

[0088] Comparative Example 5

[0089] Compared with Example 7, the difference is that the inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support was replaced with the same mass of ZSM-5 molecular sieve, resulting in catalyst 5#-1, whose specific surface area was determined to be 389 m² by the BET method. 2 / g, with an average pore size of 25nm. TEM testing showed that the average particle size of the active component Ni in the catalyst was 2nm.

[0090] Comparative Example 6

[0091] Compared with Example 7, the difference lies in replacing the inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support with the same mass of γ-Al2O3 molecular sieve, resulting in catalyst 5#-2, whose specific surface area was determined to be 395 m² by the BET method. 2 / g, with an average pore size of 27nm. TEM testing showed that the average particle size of the active Ni component in the catalyst was 2nm.

[0092] The methanation performance of the catalysts prepared in the above examples and comparative examples was tested using a tubular fixed-bed reactor. The test conditions were as follows: high-purity H2 was introduced at a flow rate of 100 mL / min, the temperature was increased from room temperature to 400-500℃ at a heating rate of 4-6℃ / min and held for 5 h, and then the temperature was reduced to the reaction temperature (150-300℃). At the same time, the H2 was switched to the feed gas (a mixture of 3% CO and 97% H2). The reaction pressure was 3.0 MPa at different reaction temperatures of 150-250℃.

[0093] The reaction products were analyzed, and the results are shown in Table 1 below:

[0094] Table 1. Reaction products of comparative examples.

[0095]

[0096]

[0097] As can be seen from the table, the addition of formaldehyde to the recovered metallic Mo active component from the waste iron-molybdenum catalyst enhances the electron cloud density around Ni atoms, increases the number of active centers on the support surface and in the bulk phase, effectively inhibits the accumulation and growth of Ni grains during reduction, and is beneficial to improving the low-temperature activity in the methanation reaction. In the experiment with catalyst 1#-1 without the addition of additives, the CO conversion rate at low temperature was approximately 86%, and its methanation activity and selectivity were relatively low.

[0098] Compared to the experiment with catalyst #2, catalyst #2 (with only inorganic salt-modified support) showed lower CO conversion and CH4 selectivity at low temperatures. However, catalyst #2 (modified with inorganic salts to the thermosensitive polymer) achieved a CO conversion of over 99%. The thermosensitive polymer modulates the surface chemical properties of the support; at low temperatures, the catalyst surface becomes hydrophobic, facilitating the timely desorption of water molecules from the reaction products and increasing the methanation rate. Simultaneously, inorganic salts can regulate the solubility response index of the thermosensitive polymer and form coordination bonds with Ni and Mo components in the catalyst, resulting in a strong alloying effect of the bimetallic components, thus improving catalyst stability and methane selectivity. In the experiment with catalyst #2 (without inorganic salt modification to the thermosensitive polymer), both CO conversion and methane selectivity decreased. Furthermore, catalyst #2 (without modified silica zeolite S-1 support) exhibited even lower CO conversion and methane selectivity.

[0099] Amides can attach basic groups to the support, thereby increasing the rate of methanation reaction. Compared with the experiment with catalyst #3, the CO conversion rate and methane selectivity were reduced in the experiment with catalyst #4, which had a small amount of N-vinylacrylamide added.

[0100] Inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support can improve the catalyst's resistance to carbon deposition and protect the active metal ligands. Its unique structure can significantly promote the uniform dispersion of metal oxides, increase the proportion of oxidized Ni, prevent the formation of nickel carbonyl from CO and Ni at low temperatures, improve anti-poisoning ability, and enhance low-temperature activity during methanation. Compared with the No. 5 catalyst experiment, the CO conversion rate and methane selectivity of ZSM-5 molecular sieve catalyst No. 5#-1 and γ-Al2O3 molecular sieve catalyst No. 5#-2 decreased, indicating lower low-temperature activity.

[0101] It can be seen that catalyst #3 has the highest loading of active components and additives, the most complete CO conversion, the highest methane selectivity, and the highest low-temperature activity.

[0102] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A methanation reaction catalyst, characterized in that, The catalyst comprises an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support, a metal active component Ni supported on the support, and an auxiliary component Mo; based on the total weight of the catalyst, the content of the metal active component Ni supported on the support is 10-30 wt%; the content of metal Mo is 1-15 wt%. The preparation method of the inorganic salt modified thermosensitive polymer-modified all-silica zeolite S-1 support includes the following steps: dispersing all-silica zeolite S-1 in an aqueous solution of N-vinylacrylamide, adding inorganic salt, stirring under inert gas protection, filtering, washing, and drying to obtain the inorganic salt modified thermosensitive polymer-modified all-silica zeolite S-1 support. The inorganic salt is selected from one or more of sodium sulfate, sodium chloride, and potassium chloride.

2. The catalyst according to claim 1, characterized in that, Based on the total weight of the catalyst, the content of the active metal component Ni supported on the support is 15-25 wt%; the content of the metal Mo is 3-10 wt%.

3. The catalyst according to claim 1 or 2, characterized in that, The catalyst has a specific surface area of ​​300-500 m². 2 / g, with a pore size of 5-40nm, and the active component Ni has a grain size of 1-5nm.

4. The catalyst according to claim 1, characterized in that, The mass ratio of N-vinylacrylamide to all-silica zeolite S-1 is 0.1:1-2:1; the mass ratio of inorganic salt to all-silica zeolite S-1 is 0.1:1-2:

1.

5. The catalyst according to claim 1, characterized in that, The mass ratio of N-vinylacrylamide to all-silica zeolite S-1 is 0.2:1-1:1; the mass ratio of inorganic salt to all-silica zeolite S-1 is 0.5:1-1:

1.

6. The catalyst according to claim 4, characterized in that, The inorganic salt is sodium sulfate.

7. The catalyst according to claim 1, characterized in that, The auxiliary component Mo is derived from an ammonium molybdate solution.

8. The catalyst according to claim 7, characterized in that, The method for preparing the ammonium molybdate solution includes the following steps: The formaldehyde waste iron-molybdenum catalyst was roasted, crushed and ground, then mixed evenly with quicklime and ammonium carbonate, followed by hydrothermal reaction, and filtered to obtain ammonium molybdate solution.

9. The catalyst according to claim 8, characterized in that, The calcination temperature of the formaldehyde waste iron-molybdenum catalyst is 400-800℃, and the calcination time is 1-4h.

10. The catalyst according to claim 8, characterized in that, The mass ratio of quicklime to formaldehyde waste iron-molybdenum catalyst is 0.5:1-5:1; the mass ratio of ammonium carbonate to formaldehyde waste iron-molybdenum catalyst is 0.5:1-5:

1.

11. The catalyst according to claim 10, characterized in that, The mass ratio of quicklime to formaldehyde waste iron-molybdenum catalyst is 1:1-2:1; the mass ratio of ammonium carbonate to formaldehyde waste iron-molybdenum catalyst is 1:1-2:

1.

12. The catalyst according to claim 8, characterized in that, The hydrothermal reaction is carried out at a temperature of 100-300℃ and a crystallization time of 5-10h.

13. A method for preparing the catalyst according to any one of claims 1-12, characterized in that, The process includes the following steps: adding a solution of the active component nickel salt and the auxiliary component ammonium molybdate to an inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support, followed by ultrasonic impregnation, drying, and calcination to obtain the catalyst.

14. The preparation method according to claim 13, characterized in that, The nickel salt is selected from one or more of nickel nitrate, nickel carbonate, and nickel chloride.

15. The preparation method according to claim 14, characterized in that, The nickel salt is nickel nitrate.

16. The preparation method according to claim 13, characterized in that, The mass ratio of nickel salt to inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support is 0.5:1-2:1; the mass ratio of ammonium molybdate solution to inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support is 0.02:1-0.5:

1.

17. The preparation method according to claim 16, characterized in that, The mass ratio of nickel salt to inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support is 1:1-1.8:1; the mass ratio of ammonium molybdate solution to inorganic salt-modified thermosensitive polymer-modified all-silica zeolite S-1 support is 0.1:1-0.3:

1.

18. The use of the catalyst according to any one of claims 1-12 or the catalyst prepared by the method according to any one of claims 13-17 in a methanation reaction.

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