Preparation process and application of red-mud-based Ni-Co-Cu multi-metal bifunctional catalyst

Abstract

The invention belongs to the technical field of solid waste recycling and catalysts, and particularly relates to a preparation process and application of a red mud-based Ni-Co-Cu multi-metal bifunctional catalyst, and the preparation process comprises the following steps: (1) modifying a red mud carrier; (2) multi-metal loading; (3) adding composite powder; (4) a CVD protection layer; according to the application of the prepared catalyst in CO + H20 methanation reaction and thermochemical steam hydrogen production, the red mud is used as a carrier, solid waste high value is achieved, compared with a traditional carrier, the cost is reduced by 60% or above, a four-layer structure is formed from outside to inside through carrier modification, metal loading and final passivation forming, and the catalyst can be applied to CO + H20 methanation reaction and thermochemical steam hydrogen production. The three components are respectively a SiO2 nano film, Ni-Co alloy particles, a Cu-Fe2O3 electron bridge and Fe-coated (Fe, Co) Fe2O4, and the problems of carbon deposition (rate of 87%), sintering (grain lt; 10 nm), the catalyst activity attenuation loss lt after 50 cycles; and 5%.

Description

Technical Field

[0001] This invention relates to the fields of solid waste resource utilization and catalyst technology, specifically a preparation process and application of a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst. Background Technology

[0002] Most CO methanation catalysts are nickel (Ni) based catalysts, typically formed by combining them with supports such as Al2O or Fe2O3.

[0003] However, existing technologies have several problems: high cost; and controlling the activity loss of catalysts during recycling is one of the core challenges for industrial applications. The main factors affecting catalyst activity are as follows: high temperature: Ni-based catalysts require temperatures above 220℃ to achieve complete CO conversion (>99%), and have poor activity at low temperatures; severe deactivation due to carbon deposition: when the H2 / CO ratio is <3, the carbon deposition rate is >5 mgC / g·h, resulting in a lifespan of less than 8000 hours; therefore, catalysts in existing technologies often experience an activity intensity decrease of >20% after 50 cycles of use.

[0004] Currently, the preparation of CO methanation catalysts relies on limited natural resources, which not only increases the production cost of the catalysts but also limits their large-scale application. Furthermore, the preparation process of some catalysts is complex, requiring multiple reaction steps and complex process conditions, resulting in high energy consumption, low production efficiency, and the potential generation of new waste, causing secondary pollution to the environment.

[0005] Red mud (RM), also known as bauxite slag, is a waste product generated during the aluminum industry. It is composed of catalytically active metal oxides. In 2023, my country produced 107 million tons of red mud, while the global production was approximately 180 million tons, with a utilization rate of only 7.2%, at approximately 13 million tons. In 2024, my country's red mud utilization is projected to exceed 13 million tons. Red mud, used as a catalyst, has advantages such as low cost, rich chemical composition (Fe2O3, Al2O3, Na2O, SiO2, TiO2), and abundant reserves.

[0006] Due to the aforementioned problems, red mud presents the following application obstacles in existing technologies: alkali metal migration (Na₂O content reaches 3-10%, leading to catalyst poisoning); and pore structure deterioration (specific surface area <15m²). 2 / g, requires pore-forming modification; unstable phase composition: Fe2O3 undergoes uncontrollable phase transformation in a reducing atmosphere.

[0007] Therefore, the challenge lies in how to achieve efficient coupling of low-temperature CO methanation and medium-temperature chemical chaining hydrogen production on a single catalyst through red mud functionalization and multi-metal modification, while simultaneously solving the problems of carbon deposition, sintering, and poor cycle stability.

[0008] Therefore, based on the above technical problems, a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst and its application were designed. Summary of the Invention

[0009] To address the problems of existing technologies, this invention proposes a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst and its applications.

[0010] The technical solution adopted by this invention to solve its technical problem is: a preparation process for a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst, comprising the following steps:

[0011] (1) Dealkali treatment: Mix red mud with 3-10 wt% weak acid at a solid-liquid ratio of 1:3-10, stir at 60-90℃ for 2-6 hours, and wash until the conductivity of the filtrate is <100μS / cm;

[0012] (2) Pore structure optimization: The dealkalized red mud obtained after the above treatment is mixed with a pore-forming agent and a binder, and then kneaded with water to form a shape. After drying, it is calcined at 600-800℃ for 2-6 hours. The calcination conditions are a temperature increase of 2-5℃ / min. The red mud, pore-forming agent and binder are in the following mass percentage ratios: 45-65wt%, 5-30wt%, and 5-25wt%.

[0013] (3) Acid activation: The above-mentioned calcined red mud particles are treated with 0.1-2 mol / L H2SO4 for 1-5 h, wherein the solid-liquid ratio of H2SO4 to the above-mentioned calcined red mud particles is 3:1-8:1;

[0014] (4) Loaded metal solution: Dissolve Cu-Co solution in water at a mass ratio of copper salt to cobalt salt of 1:0.5-2, the concentration of the loaded Cu-Co solution is 0.5 mol / L, and 1-5% CeO2 is added to the Cu-Co solution by mass ratio. The acid-activated red mud particles are impregnated in the loaded Cu-Co solution with added CeO2 by equal volume for loading, and allowed to stand for 2-12 hours; Loaded Ni solution: Dissolve nickel salt and structural stabilizer in ethanol-water mixed solvent, and ultrasonically impregnate the above loaded Cu-Co solution in Ni solution for 0.5-3 hours, the structural stabilizer is added by mass ratio of 0.5-10 wt%;

[0015] (5) Reduction atmosphere treatment: The red mud particles after ultrasonic assisted impregnation in Ni solution in the above steps are reduced at 200-400℃ for 1-5 hours in an atmosphere of H2 / N2 = 1:9-3:7;

[0016] (6) Add composite powder: The red mud carrier obtained in step (5) after impregnation is mixed with composite powder at a mass ratio of 2wt%-5wt% and then pressed into tablets. The preparation method of the composite powder is as follows: FeF2 nanopowder and LaPO4 sol are added at a mass ratio of 1:2-4, ball milled for 4-6 hours, and calcined at 500-600℃ for 1-3 hours.

[0017] (7) CVD protective layer: Tetraethoxysilane (TEOS) vapor is introduced and deposited at 150-250℃ for 0.5-3 hours to form SiO2 nanofilm;

[0018] (8) High-strength molding: Add 1-5wt% binder by mass ratio, add water and press to form, and cure at 60-100℃ for 12-48 hours.

[0019] Preparation principle: This application first modifies red mud, and then constructs a three-level pore system through a pore-forming agent, a binder, and an acid-wash-alkali reconstruction coupling process. Specifically, the three-level pore system consists of: micropores (2-5 nm), mesopores (20-50 nm), and macropores (>100 nm). The functions of these three levels of pores are as follows: the micropores (2-5 nm) increase the specific surface area to 110-150 nm. 2 / g; Mesopores (20-50nm) promote reactant diffusion; Macropores (>100nm) inhibit carbon deposition. A two-stage acid washing method was used during the modification of red mud, first using a weak acid to complex free Na. + Then, the sodium silicate framework is dissolved in 0.1-1 mol / L H2SO4 to ensure that the residual Na2O content is <1.5%. Following this, metal loading is performed, resulting in a Ni-Co-Cu ternary alloy structure: Ni provides CO dissociation and adsorption sites; Co promotes lattice oxygen migration and reduces the carbon deposition rate; Cu accelerates Fe... 3+ / Fe 2+ Cycling to lower the reduction temperature; interfacial electronic effects: by controlling the atomic ratios of Co / Ni = 0.05-0.3 and Cu / Fe = 0.01-0.2, Ni transfers electrons to Co to enhance CO adsorption, and Cu transfers electrons to Fe2O3 to lower the oxygen vacancy formation energy; and the catalyst prepared in this application forms a four-layer structure from the outside to the inside, namely: SiO2 nanofilm (1-5nm): CVD deposition anti-burning; Ni-Co alloy particles (5-10nm): CO methanation active sites; Cu-Fe2O3 electron bridge: reducing Fe 3+ Reduction barrier (activation energy ↓ 28%); Fe@(Fe,Co)Fe2O4: chemically chained hydrogen-oxygen storage medium;

[0020] At the same time, CeO2 provides lattice oxygen to remove surface carbon, further preventing carbon buildup and thus improving its service life.

[0021] The specific reaction equation is as follows:

[0022] Methanation stage (200-400℃):

[0023] CO+3H2→CH4+H2OΔH=-206kJ / mol;

[0024] Ni-Co alloy catalyzes CO hydrogenation;

[0025] Thermochemical hydrogen production stage (500-700℃):

[0026] 3FeO+H2O→Fe3O4+H2ΔH=-150kJ / mol.

[0027] Cu promotes the FeO→Fe3O4 conversion, while Co inhibits the dissolution of Fe, thus improving the cycle stability to >50 cycles. Then, during the preparation and molding process, 5-15 wt% metakaolin is added, which generates an aluminosilicate network through a geological polymerization reaction, inhibiting the Fe2O3 phase transition.

[0028] Furthermore, the pore-forming agent includes calcium carbonate, ammonium carbonate, starch, and polyethylene glycol.

[0029] Furthermore, the binder includes sodium silicate, metakaolin, and alumina sol.

[0030] Furthermore, the structural stabilizer includes La2O3, ZrO2, and TiO2.

[0031] Furthermore, the nickel salt includes nickel nitrate, nickel acetate, nickel chloride, and nickel acetylacetonate; the cobalt salt includes cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt oxalate, and potassium cobalt cyanide; and the copper salt includes copper nitrate, copper sulfate, copper acetate, and copper chloride.

[0032] Furthermore, the raw material red mud is one of the Bayer process or sintering process red mud, and the raw material red mud contains: Fe2O3 30-60wt%, Al2O3 10-25wt%, CaO 2-20wt%, and Na2O <3wt% after dealkali treatment.

[0033] Furthermore, the weak acid includes oxalic acid and citric acid.

[0034] Furthermore, the application of the red mud-based Ni-Co-Cu bimetallic bifunctional catalyst in the CO+H2O methanation reaction and thermochemical steam hydrogen production.

[0035] The advantages of this invention are:

[0036] 1. This invention uses red mud as a carrier to realize the high value of solid waste, reducing costs by more than 60% compared to traditional carriers.

[0037] 2. In this invention, a four-layer structure is formed from the outside to the inside through modification of the support, loading of metal, and final passivation molding. The structure consists of SiO2 nanofilm, Ni-Co alloy particles, Cu-Fe2O3 electron bridge, and Fe@(Fe,Co)Fe2O4. This simultaneously solves the problems of carbon deposition (rate ↓87%) and sintering (grain size <10nm), resulting in a CO conversion rate decrease of <0.5% after 50 cycles of use of the catalyst prepared in this application. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a process flow diagram of the present invention;

[0040] Figure 2 The graph shows the CO conversion rate (%) of the catalyst in 50 cycles of testing.

[0041] Figure 3 The graph shows the change in H2 yield (mmol / g·min) of the catalyst during 50 cycles of testing.

[0042] Figure 4 This is a schematic diagram of the structure of the catalyst prepared in this invention.

[0043] In the figure: 1. SiO2 nanofilm; 2. Ni-Co alloy particles; 3. Cu-Fe2O3 electron bridge; 4. Fe@(Fe,Co)Fe2O4. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to tables and other data. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Raw materials: Red mud, Bayer process red mud (produced in Guangxi), with oxide composition by mass ratio of 50% Fe2O3, 15% Al2O3, 15% SiO2, 5% CaO, 8% Na2O, and 2% other components;

[0046] Nickel nitrate (Ni(NO3)2·6H2O, purity ≥99%);

[0047] Cobalt nitrate (Co(NO3)2·6H2O, purity ≥98.5%);

[0048] Copper nitrate (Cu(NO3)2·3H2O, purity ≥99%);

[0049] Copper acetate (Cu(CH3COO)·H2O, purity ≥99%)

[0050] Cobalt acetate (Co(CH3COO)2·4H2O, purity ≥99%)

[0051] Nickel acetate (Ni(CH3COO)2·4H2O, purity ≥99%)

[0052] Oxalic acid: (H2C2O4·2H2O, purity ≥99%)

[0053] Nano-sized calcium carbonate (CaCO3, 50nm);

[0054] Sodium silicate (Na2SiO3, modulus 3.2, industrial grade);

[0055] Metakaolin: Shanxi Xinjingtai Technology Co., Ltd.;

[0056] Tetraethoxysilane (TEOS) vapor: Jiangxi Chenguang New Materials Co., Ltd.: Model CG-502;

[0057] FeF2 nanoparticles: 50-100nm

[0058] LaPO4 sol: Hubei Guangao Biotechnology Co., Ltd.

[0059] Equipment list:

[0060] Spray dryer: Shanghai Qiaofeng Industrial Co., Ltd., QFN-8000S;

[0061] Tubular reduction furnace: Yixing Bangshida Furnace Industry Co., Ltd., BJXG-14-10;

[0062] High-speed shear emulsifier: Hangzhou Qiwei Instrument Co., Ltd., JRH-400S;

[0063] Example 1:

[0064] A process for preparing a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst includes the following steps:

[0065] (1) Dealkali treatment: Red mud and 3wt% oxalic acid were mixed at a solid-liquid ratio of 1:3 and stirred at 60°C for 2 hours. The mixture was washed until the conductivity of the filtrate was <100μS / cm and the residual Na2O was ≤1.5%.

[0066] (2) Pore structure optimization: The dealkalized red mud obtained after the above treatment is mixed with a pore-forming agent and a binder, kneaded with water to form a shape, dried, and then calcined at 600℃ for 2 hours. The calcination conditions are a temperature increase of 2℃ / min. The red mud, calcium carbonate, and sodium silicate are in the following mass percentage ratios: 45wt%, 30wt%, and 25wt%, respectively. The specific surface area is ≥120m². 2 / g, pore volume ≥0.35cm 3 / g;

[0067] (3) Acid activation: The above-mentioned calcined red mud particles were treated with 0.5 mol / L H2SO4 for 1 h, and the solid-liquid ratio of H2SO4 to the above-mentioned calcined red mud particles was 3:1.

[0068] (4) Loaded metal solution: Dissolve Cu-Co solution in water at a mass ratio of copper nitrate to cobalt nitrate of 1:0.5. The concentration of the loaded Cu-Co solution is 0.5 mol / L. Add 1% CeO2 to the Cu-Co solution by mass ratio. Immerse the acid-activated red mud particles in the loaded Cu-Co solution with added CeO2 by equal volume and let stand for 2 hours.

[0069] (5) Ni-loaded solution: Nickel nitrate and La2O3 are dissolved in an ethanol-water mixed solvent, and the red mud particles loaded with the above Cu-Co solution are ultrasonically impregnated in the Ni solution for 0.5 hours, with the La2O3 added at a mass ratio of 0.5 wt%.

[0070] (6) Reduction atmosphere treatment: The red mud particles that have been ultrasonically impregnated in Ni solution in the above steps are reduced at 200°C for 1.5 hours in an atmosphere of H2 / N2 = 1:9;

[0071] (7) The impregnated red mud carrier obtained in the previous step is mixed with composite powder at a mass ratio of 2wt% and then pressed into tablets. The composite powder is prepared by adding FeF2 nanoparticles and LaPO4 sol at a mass ratio of 1:2, ball milling for 4 hours, and calcining at 500℃ for 1 hour.

[0072] (8) CVD protective layer: Tetraethoxysilane (TEOS) vapor is introduced and deposited at 150°C for 0.5 hours to form a SiO2 nanofilm;

[0073] (9) High-strength molding: Add 1wt% metakaolin by mass ratio, add water and press into shape, and cure at 60℃ for 12 hours.

[0074] Example 2:

[0075] A process for preparing a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst includes the following steps:

[0076] (1) Dealkali treatment: Red mud and 5wt% oxalic acid were mixed at a solid-liquid ratio of 1:5 and stirred at 70°C for 3 hours. The mixture was washed until the conductivity of the filtrate was <100μS / cm and the residual Na2O was ≤1.5%.

[0077] (2) Pore structure optimization: The dealkalized red mud obtained after the above treatment is mixed with starch and metakaolin, kneaded with water to form a shape, dried, and then calcined at 700℃ for 3 hours. The calcination conditions are a temperature increase of 3℃ / min. The red mud, starch, and metakaolin are in the following mass percentage ratios: 50wt%, 28wt%, and 22wt%, respectively. The specific surface area is ≥120m². 2 / g, pore volume ≥0.35cm 3 / g;

[0078] (3) Acid activation: The above-mentioned calcined red mud particles were treated with 0.5 mol / L H2SO4 for 2 h, and the solid-liquid ratio of H2SO4 to the above-mentioned calcined red mud particles was 5:1.

[0079] (4) Loaded metal solution: Dissolve Cu-Co solution in water at a mass ratio of 1:1 for copper acetate and cobalt acetate. The concentration of the loaded Cu-Co solution is 0.5 mol / L. Add 2% CeO2 to the Cu-Co solution at a mass ratio. Immerse the acid-activated red mud particles in the loaded Cu-Co solution with added CeO2 in an equal volume and let stand for 5 hours.

[0080] (5) Ni-loaded solution: Nickel acetate and ZrO2 are dissolved in an ethanol-water mixed solvent, and the red mud particles loaded with the above Cu-Co solution are ultrasonically impregnated in the Ni solution for 0.5-3 hours, with ZrO2 added at a mass ratio of 5wt%.

[0081] (6) Reduction atmosphere treatment: The red mud particles after ultrasonic assisted impregnation in Ni solution in the above steps are reduced at 300°C for 3 hours in an atmosphere of H2 / N2 = 2:8;

[0082] (7) The impregnated red mud carrier obtained in the previous step is mixed with composite powder at a mass ratio of 3 wt% and then pressed into tablets. The composite powder is prepared by adding FeF2 nanoparticles and LaPO4 sol at a mass ratio of 1:3, ball milling for 5 h, and calcining at 550℃ for 2 h.

[0083] (8) CVD protective layer: Tetraethoxysilane (TEOS) vapor is introduced and deposited at 200°C for 1.5 hours to form a SiO2 nanofilm;

[0084] (9) High-strength molding: Add 3wt% aluminum sol by mass ratio, add water and press into shape, and cure at 80℃ for 24 hours.

[0085] Example 3

[0086] A process for preparing a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst includes the following steps:

[0087] (1) Dealkali treatment: Red mud and 10wt% citric acid were mixed at a solid-liquid ratio of 1:3, stirred at 60℃ for 2 hours, and washed until the conductivity of the filtrate was <100μS / cm;

[0088] (2) Pore structure optimization: The red mud obtained after the above treatment and dealkalization is kneaded with calcium carbonate and sodium silicate, dried, and then roasted at 800℃ for 6 hours. The roasting conditions are 5℃ / min heating. The red mud, calcium carbonate and sodium silicate are in the following mass percentage ratios: 65wt%, 30wt%, and 5wt%.

[0089] (3) Acid activation: The above-mentioned roasted red mud particles were treated with 2 mol / L H2SO4 for 5 h, and the solid-liquid ratio of H2SO4 to the above-mentioned roasted red mud particles was 8:1.

[0090] (4) Loaded metal solution: Dissolve Cu-Co solution in water at a mass ratio of copper nitrate to cobalt nitrate of 1:2. The concentration of the loaded Cu-Co solution is 0.5 mol / L. Add 5% CeO2 to the Cu-Co solution at a mass ratio. Immerse the acid-activated red mud particles in the loaded Cu-Co solution with added CeO2 in an equal volume and let stand for 12 hours.

[0091] (5) Loaded Ni solution: Nickel nitrate and structural stabilizer are dissolved in ethanol-water mixed solvent, and the red mud particles loaded with Cu-Co solution are ultrasonically impregnated in Ni solution for 3 hours. The structural stabilizer is added at a mass ratio of 10wt%.

[0092] (6) Reduction atmosphere treatment: The red mud particles after ultrasonic assisted impregnation in Ni solution in the above steps are reduced at 400°C for 5 hours in an atmosphere of H2 / N2 = 3:7;

[0093] (7) The impregnated red mud carrier obtained in the previous step is mixed with composite powder at a mass ratio of 5 wt% and then pressed into tablets. The composite powder is prepared by adding FeF2 nanoparticles and LaPO4 sol at a mass ratio of 1:4, ball milling for 6 h, and calcining at 600℃ for 3 h.

[0094] (8) CVD protective layer: Tetraethoxysilane (TEOS) vapor is introduced and deposited at 250°C for 3 hours to form SiO2 nanofilm;

[0095] (9) High-strength molding: Add 5wt% metakaolin by mass ratio, add water and press into shape, and cure at 100℃ for 48 hours.

[0096] The following are several comparative examples:

[0097] Comparative Example 1: Methanation catalyst, DZC-JWH42: produced by Shandong Dengzhuo Chemical Co., Ltd., priced at US$45-70 / kg;

[0098] Comparative Example 2: Methanation catalyst, KJ-1: produced by Huahai factory, priced at US$100,000-200,000 / ton;

[0099] Comparative Example 3:

[0100] A process for preparing a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst includes the following steps:

[0101] (1) Dealkali treatment: Red mud and 3wt% oxalic acid were mixed at a solid-liquid ratio of 1:3, stirred at 60℃ for 2 hours, and washed until the conductivity of the filtrate was <100μS / cm.

[0102] (2) Pore structure optimization: The red mud obtained after the above treatment and dealkalization is mixed with pore-forming agent and binder, and kneaded with water to form a shape. After drying, it is calcined at 600℃ for 2h. The calcination conditions are 2℃ / min heating. The red mud, calcium carbonate and sodium silicate are in the following mass percentage ratios: 45wt%, 30wt%, and 25wt%.

[0103] (3) Acid activation: The above-mentioned calcined red mud particles were treated with 0.5 mol / L H2SO4 for 1 h, and the solid-liquid ratio of H2SO4 to the above-mentioned calcined red mud particles was 3:1.

[0104] (4) Ni-loaded solution: Nickel nitrate and La2O3 are dissolved in an ethanol-water mixed solvent, and the red mud particles loaded with the above Cu-Co solution are ultrasonically impregnated in the Ni solution for 0.5 hours. The La2O3 is added at a mass ratio of 0.5 wt%.

[0105] (5) Reduction atmosphere treatment: The red mud particles that have been ultrasonically impregnated in Ni solution in the above steps are reduced at 200°C for 1.5 hours in an atmosphere of H2 / N2 = 1:9;

[0106] (6) CVD protective layer: Tetraethoxysilane (TEOS) vapor is introduced and deposited at 150°C for 0.5 hours to form a SiO2 nanofilm;

[0107] (7) High-strength molding: Add 1wt% metakaolin by mass ratio, add water and press into shape, and cure at 60℃ for 12 hours.

[0108] Table 1: Changes in CO conversion (%) of the catalyst during 50 cycles of testing

[0109] Loop count Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 2 0 99.8 99.8 99.8 99.8 10 99.7 99.6 99.5 99.5 20 99.6 98.5 97.5 98.5 30 99.5 95.1 94.1 95.1 40 99.4 92.5 90.4 92.5 50 99.3 88.1 86.4 90

[0110] Table 2: Changes in H2 yield (mmol / g·min) of the catalyst during 50 cycles.

[0111] Loop count Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 2 0 8.5 5.0 6 7 10 8.4 4.7 5.5 6.8 20 8.4 4.5 5.4 6.7 30 8.3 4.1 5.1 6.6 40 8.3 4.0 4.9 6.3 50 8.2 3.9 4.8 6.1

[0112] Table 3: Activity decay rate of catalyst during 50 cycles of testing

[0113]

[0114]

[0115] Table 4: Cost Calculation Table of the Catalyst Prepared in this Application

[0116] Cost items Raw material specifications unit price Cost (USD / kg catalyst) Red mud carrier <![CDATA[Bayer red mud (Fe2O3 ≥ 45%)]]> 0.08 / kg 0.04 oxalic acid 3wt% 0.06 / kg 0.04 Nickel nitrate (Ni source) <![CDATA[Ni(NO3)2·6H2O,≥98.5%]]> 12.5 / kg 1.50 Cobalt nitrate (Co source) <![CDATA[Co(NO3)2·6H2O,≥99%]]> 25.0 / kg 0.38 Copper nitrate (Cu source) <![CDATA[Cu(NO3)2·3H2O,≥99%]]> 18.0 / kg 0.27 <![CDATA[Iron(II) fluoride (FeF2)]]> <![CDATA[FeF2, nanoscale (50 - 100nm)]]> 45.0 / kg 0.90 <![CDATA[Lanthanum phosphate (LaPO4)]]> <![CDATA[LaPO4·xH2O,≥99.9%]]> 120.0 / kg 1.20 CeO2 High-purity cerium oxide 28.25 / kg 0.02 <![CDATA[Pore-forming agent (CaCO3)]]> Nano calcium carbonate, 50nm 0.50 / kg 0.10 Adhesive (sodium silicate) Modulus 3.2, industrial grade 0.80 / kg 0.02 Energy consumption Electricity + Natural Gas (Roasting / Reduction) - 0.85 Labor and equipment depreciation Annual production scale of 100 tons - 1.50 Environmental protection treatment Wastewater / Exhaust Gas Treatment - 0.30 total - - 7.12

[0117] Figure 1 This is a flowchart of the preparation process for this application. Figure 4 The diagram shows the structure of the catalyst prepared in this application. The metal loading and final passivation process create a four-layer structure from the outside in: SiO2 nanofilm, Ni-Co alloy particles, Cu-Fe2O3 electron bridge, and Fe@(Fe,Co)Fe2O4. This simultaneously addresses the problems of carbon deposition (rate ↓87%) and sintering (grain size <10nm). Furthermore, the catalyst prepared in this application exhibits a CO conversion rate decrease of <0.5% after 50 cycles and an H2 yield decrease of <0.5% after 50 cycles. Comparative Examples 1 and 2 are compared to the catalyst prepared in Example 1 and Comparative Examples 1-3. Comparative Examples 1 and 2 are commercially available methanation catalysts. Comparative Example 3 is a catalyst prepared based on Example 1 without the loaded Cu-Co solution and without the addition of composite powder. Specific results are as follows... Figures 2-3 , Figure 1 This is a graph showing the change in CO conversion rate (%) during 50 cycles of testing in Example 1 and the three comparative examples. Figure 2 The graph shows the H2 yield (mmol / g·min) change curves in 50 cycles of testing for Example 1 and the three comparative examples. It can be clearly seen from the graph that the CO conversion rate decline and H2 yield decline of the comparative examples are significantly higher than those of the catalyst produced in the examples. Table 3 clearly shows that the catalyst produced in Example 1 is significantly better than the three comparative examples in 50 cycles of testing.

[0118] As shown in Table 4, the total cost of the catalyst in this application is US$7.12 / kg, which is much lower than the price of Comparative Example 1 and Comparative Example 2 on the market, and has a great advantage in economic value.

[0119] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

Claims

1. A process for preparing a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst, characterized in that, Includes the following steps: (1) Red mud carrier modification: Red mud is mixed with a weak acid and washed until the conductivity of the filtrate is <100μS / cm. After washing, the filtrate is mixed with a pore-forming agent and a binder, and water is added to knead and shape it. After drying, it is calcined. The red mud particles formed after calcination are mixed with 0.1-2mol / L H2SO4 to form a red mud carrier. (2) Multimetallic loading: The red mud support obtained in step (1) is first loaded with Cu-Co solution, and then loaded with Ni solution. 1-5% CeO2 is added to the Cu-Co solution by mass ratio. A structural stabilizer is added when loading the Ni solution. The catalyst is formed by reduction at 200-400℃ for 1-5 hours in an atmosphere with a H2 / N2 mixing ratio of 1:9 to 3:

7. (3) The catalyst obtained in step (2) is mixed with composite powder at a mass ratio of 2wt%-5wt% and then pressed into tablets. The preparation method of the composite powder is as follows: FeF2 nanopowder and LaPO4 sol are added at a mass ratio of 1:2-4, ball milled for 4-6 hours, and calcined at 500-600℃ for 1-3 hours. (4) CVD protective layer: After the catalyst in step (3) is calcined, a passivating agent is passed through it to form a SiO2 nanofilm, and then a binder and water are added to press it into shape.

2. The preparation process of a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst according to claim 1, characterized in that: In step (1), the mixing and washing involves mixing red mud and a weak acid solution at a solid-liquid ratio of 1:3 to 1:10, with the concentration of the weak acid being 3-10 wt%. After mixing, the mixture is stirred at 60-90℃ for 2-6 hours. The drying temperature is 60-120℃, followed by calcination at 600-800℃ for 2-6 hours. The calcination conditions involve heating at 2-5℃ / min. The solid-liquid ratio of the calcined red mud particles to H2SO4 is 3:1-8:1, and the treatment time is 1-5 hours.

3. The preparation process of a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst according to claim 1, characterized in that: The red mud, pore-forming agent, and binder in step (1) are in the following mass percentage ratios: 45-65wt%, 5-30wt%, and 5-25wt%, respectively. The structural stabilizer in step (2) is added at a mass ratio of 0.5-10wt%, and the binder in step (4) is added at a mass ratio of 1-5wt%.

4. The preparation process of a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst according to claim 1, characterized in that: In step (2), the Cu-Co solution is dissolved in water at a mass ratio of copper salt to cobalt salt of 1:0.5 to 1:2, and the modified red mud carrier from step (1) is impregnated in an equal volume and left to stand for 2-12 hours.

5. The preparation process of a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst according to claim 1, characterized in that: The binder includes sodium silicate, metakaolin, and alumina sol; the pore-forming agent includes calcium carbonate, ammonium carbonate, starch, and polyethylene glycol; the structural stabilizer includes La2O3, ZrO2, and TiO2; and the weak acid includes oxalic acid or citric acid.

6. The preparation process of a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst according to claim 1, characterized in that: The nickel salts include nickel nitrate, nickel acetate, nickel chloride, and nickel acetylacetonate; the cobalt salts include cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt oxalate, and potassium cobalt cyanide; and the copper salts include copper nitrate, copper sulfate, copper acetate, and copper chloride.

7. The preparation process of a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst according to claim 1, characterized in that: The raw material red mud is one of the Bayer process or sintering process red mud, and the raw material red mud contains: Fe2O3 30-60wt%, Al2O3 10-25wt%, CaO 2-20wt%, and Na2O <3wt% after dealkali treatment.

8. The preparation process of a red mud-based Ni-Co-Cu multimetallic bifunctional catalyst according to claim 1, characterized in that: The passivating agent includes tetraethoxysilane (TEOS).

9. The application of the red mud-based Ni-Co-Cu multimetallic bifunctional catalyst according to any one of claims 1-8 in the CO+H2O methanation reaction and thermochemical steam hydrogen production.

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