A gallium-lanthanum co-modified cobalt-iron bimetallic catalyst, its preparation method and application

Abstract

This invention discloses a gallium-lanthanum co-modified cobalt-iron bimetallic catalyst, its preparation method, and its application, comprising the following steps: S1. A mixed metal salt solution and a precipitant solution are added dropwise to a reactor in a co-current manner to react and obtain a solution containing a precipitate; the mixed metal salt solution contains soluble salts of cobalt, iron, gallium, and lanthanum; S2. The precipitate is aged, then separated, washed, dried, and finally calcined to obtain the gallium-lanthanum co-modified cobalt-iron bimetallic catalyst. This invention optimizes the electronic structure, surface adsorption sites, and oxygen vacancy concentration through Ga / La dual-auxiliary modification, increases CO non-dissociative adsorption sites, inhibits the formation of byproducts such as carbon dioxide and methane, strengthens C-C coupling and carbon chain growth, and significantly improves catalytic activity and C... 2+ Alcohol selectivity, higher alcohol yield, and catalytic stability.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology and is applied to the direct preparation of higher alcohols from syngas. In particular, it relates to a gallium and lanthanum co-modified cobalt-iron bimetallic catalyst, its preparation method, and its application. Background Technology

[0002] Energy, as an indispensable material foundation for socio-economic development and technological innovation, has a century-long history in syngas catalytic conversion technology, which is a core research direction in the field of C1 chemistry. Alcohols with a carbon chain length of 2-5 carbon atoms are generally defined as low-carbon alcohols, while those with 6 or more carbon atoms are classified as high-carbon alcohols. High-carbon alcohols have significant industrial application value. They can serve as key chemical intermediates in the preparation of surfactants, detergents, and other chemical products; they can also be used to prepare α-high-carbon olefins through dehydration reactions, showing great promise in the upgrading of the polyolefin industry and the synthesis of high-end lubricants.

[0003] Currently, the key to the direct conversion of syngas to higher alcohols lies in the performance of the catalyst. This reaction process requires the simultaneous realization of multiple steps, such as CO activation and dissociation, carbon chain growth, and hydrogenation to form hydroxyl groups. This places strict requirements on the bifunctional active sites of the catalyst, namely, the catalyst must have active sites that can dissociate CO and form surface alkyl species, as well as active sites that can catalyze the adsorption, insertion, and formation of alcohol hydroxyl groups from non-dissociated CO. The synergistic effect of the two is the key to improving the selectivity and yield of higher alcohols.

[0004] Existing catalyst systems for the production of higher alcohols from syngas are mainly classified into rhodium-based, molybdenum-based, modified Fischer-Tropsch synthesis catalysts, and bimetallic / multimetallic catalysts. While Rh-based catalysts exhibit high catalytic activity and selectivity for higher alcohols, the scarcity and high cost of Rh resources severely limit their large-scale industrial application. Mo-based catalysts demonstrate strong resistance to poisoning and coking, but exhibit weak carbon chain growth, producing primarily lower alcohols with low selectivity for higher alcohols. Single-metal catalysts (such as single-metal Co and Fe catalysts) suffer from limited active sites and insufficient synergistic effects. Single-metal Co catalysts have fewer active sites for non-dissociative CO adsorption, resulting in low selectivity for higher alcohols, while single-metal Fe catalysts are prone to excessive carburization, leading to excessively high selectivity for byproduct hydrocarbons, which fails to meet the catalytic performance requirements of industrial production.

[0005] Cobalt-iron bimetallic catalysts have become a research hotspot due to their abundant reserves, low cost, and moderate carbon chain growth capability. Cobalt can promote CO dissociation and CC coupling, while iron can enhance CO adsorption activation and chain growth; the synergy between the two can effectively improve alcohol selectivity. However, cobalt-iron bimetallic catalysts still suffer from problems such as high methane selectivity, insufficient yield of higher alcohols, and unstable active phase structure. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a gallium and lanthanum co-modified cobalt-iron bimetallic catalyst, its preparation method and application, so as to improve catalytic performance.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0008] A method for preparing a gallium and lanthanum co-modified cobalt-iron bimetallic catalyst includes the following steps:

[0009] S1. The mixed metal salt solution and the precipitant solution are added dropwise to the reactor in a parallel flow manner to carry out the reaction, and a solution containing the precipitate is obtained;

[0010] The mixed metal salt solution contains soluble salts of cobalt, iron, gallium, and lanthanum, wherein the molar ratio of Co, Fe, Ga, and La is 1:(1.2~1.8):(0.1~1):(0.001~0.1).

[0011] The precipitant solution is a sodium carbonate solution;

[0012] S2. The precipitate is aged, then separated, washed, dried, and finally calcined to obtain the gallium and lanthanum co-modified cobalt-iron bimetallic catalyst;

[0013] The calcination is carried out in an air atmosphere at a temperature of 400-600℃.

[0014] Furthermore, the concentration of Ga in the mixed metal salt solution described in S1 is 0.004 mol / L to 0.06 mol / L; the concentration of the precipitant solution is 0.2 mol / L to 0.4 mol / L, and the total molar amount of the precipitant is 2 to 6 times the total molar amount of cobalt, iron, gallium, and lanthanum.

[0015] Furthermore, the temperature of the parallel-flow dripping process described in S1 is controlled at 55~65℃.

[0016] Furthermore, in S1, the parallel droplet addition is controlled so that the dropping rate of both solutions is 1.5 ml / min-2.0 ml / min.

[0017] Furthermore, the aging temperature described in S2 is 55~65℃, and the time is 2~4h.

[0018] Furthermore, the washing described in S2 controls the sodium residue to remain stable at 0.05 wt%–0.2 wt% by controlling the amount of washing water.

[0019] The present invention also provides a gallium and lanthanum co-modified cobalt-iron bimetallic catalyst, which is prepared by the aforementioned preparation method.

[0020] The present invention also provides an application of the gallium and lanthanum co-modified cobalt-iron bimetallic catalyst, which is used for the catalytic conversion of syngas to directly produce higher alcohols.

[0021] Furthermore, the catalyst is first reduced in situ in a hydrogen atmosphere before application.

[0022] Furthermore, the reduction temperature is 350~450℃.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention utilizes Ga / La dual-catalyst synergistic modification to optimize electronic structure, surface adsorption sites, and oxygen vacancy concentration, increasing non-dissociative CO adsorption sites, inhibiting the formation of byproducts such as carbon dioxide and methane, enhancing CC coupling and carbon chain growth, and significantly improving catalytic activity and C. 2+ Alcohol selectivity, higher alcohol yield, and catalytic stability.

[0025] This invention employs a co-precipitation method, which ensures uniform mixing and high dispersion of the metal components, resulting in a catalyst with a uniform structure and good reproducibility. The preparation process of this invention is simple and the conditions are mild, making it suitable for industrial applications. Attached Figure Description

[0026] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 These are the XRD characterization patterns of the examples and comparative examples;

[0028] Figure 2 These are magnified XRD characterization maps of the embodiments and comparative examples;

[0029] Figure 3 This is a comparison chart of the performance of syngas synthesis of higher alcohols in the examples and comparative examples. Detailed Implementation

[0030] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0031] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0032] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0033] In some specific embodiments, the preparation method of the gallium and lanthanum co-modified cobalt-iron bimetallic catalyst of the present invention includes the following steps:

[0034] (1) Dissolve the soluble salts of cobalt, iron, gallium and lanthanum in water to obtain a mixed metal salt solution.

[0035] In some embodiments, the molar ratio of Co:Fe:Ga:La is 1:(1.2~1.8):(0.1~1):(0.001~0.1), preferably 1:(1.2~1.8):(0.1~0.3):(0.01~0.08).

[0036] In some embodiments, the soluble salt of cobalt includes one or both of cobalt nitrate hexahydrate and cobalt chloride; the soluble salt of iron includes one or both of ferric nitrate nonahydrate and ferric chloride; the soluble salt of gallium includes gallium nitrate hydrate; and the soluble salt of lanthanum includes one or both of lanthanum nitrate hexahydrate and lanthanum chloride.

[0037] In some embodiments, the concentration of gallium in the mixed metal salt solution is 0.004 mol / L to 0.06 mol / L.

[0038] In this invention, the synergistic effect of Ga and La as dual promoters significantly improves catalyst performance: Ga increases non-dissociative CO adsorption sites and promotes alcohol formation; La provides oxygen vacancies, stabilizes the active phase, inhibits coking and metal sintering, and further optimizes carbon chain growth. The synergistic effect of these two promoters significantly improves the selectivity and yield of higher alcohols.

[0039] (2) Dissolve anhydrous sodium carbonate in water to obtain a precipitant solution.

[0040] In some embodiments, the concentration of the precipitant solution is 0.2 mol / L-0.4 mol / L, and the total molar amount of the precipitant is 2-6 times, preferably 3-4 times, the total molar amount of cobalt, iron, gallium, and lanthanum.

[0041] In some embodiments, the mixed metal salt solution and precipitant solution from steps (1) and (2) are stirred on a magnetic stirrer at 30°C for 30 minutes to ensure complete dissolution.

[0042] (3) The mixed metal salt solution and the precipitant solution are added to the reactor in a parallel-flow dropping manner (i.e., the two solutions are added dropwise at the same time) to obtain a solution containing precipitate.

[0043] In some embodiments, the temperature is controlled at 55~65℃ during the dropwise addition; the dropping rate of both solutions is controlled at 1.5ml / min-2.0ml / min to ensure that the pH of the solution is 7-10 during the precipitation process.

[0044] This invention uses a co-precipitation method to prepare the catalyst, which ensures that Co, Fe, Ga, and La are highly uniformly dispersed, avoiding component segregation caused by local pH fluctuations.

[0045] (4) Aging the precipitate.

[0046] In some embodiments, the solution containing the precipitate is aged at 55-65°C for 2-4 hours. The purpose of aging is to make the catalyst particle size uniform, optimize the metal dispersion, and construct the active precursor phase.

[0047] (5) The precipitate was separated, washed with water, dried, and then calcined to obtain a gallium and lanthanum co-modified cobalt-iron bimetallic catalyst.

[0048] In some embodiments, the water-to-solid ratio (total water volume to solid precipitate mass) is 667–833 mL / g (based on wet precipitate mass). In the following embodiments, the water volume used during the washing process is controlled to be between 2000–2500 ml, and the sodium residue is controlled to be stable at 0.05 wt%–0.2 wt%. After washing, the precipitate is obtained by centrifugation. The centrifugation speed is 7000–8000 r / min, and the time is 1–2 min.

[0049] By precisely controlling the amount of water used for washing, the sodium content of the catalyst can be kept stable and controllable, eliminating the interference of alkali metal differences on catalytic performance, and the comparison results of catalytic performance are reliable.

[0050] In some embodiments, the drying temperature is 75~85°C.

[0051] In some embodiments, the calcination is carried out in an air atmosphere at a temperature of 400-600°C for 3-6 hours. During calcination, the metal carbonate is transformed into metal oxides: iron oxide and cobalt oxide, then forming CoFe₂O₄ spinel, and Ga is incorporated into the CoFe lattice to form Ga₂O₄. x Co y Fe 3-x-y O4, trace amounts of La form La2O3.

[0052] The gallium and lanthanum co-modified cobalt-iron bimetallic catalyst of the present invention can be applied to the direct preparation of higher alcohols by catalytic conversion of syngas. The application methods include:

[0053] (1) The catalyst is reduced in situ in a hydrogen atmosphere.

[0054] In some embodiments, the catalyst after being sieved through a 40-60 mesh is diluted with quartz sand, and then H2 is introduced for in-situ reduction. The reducing gas flow rate is 30-50 ml / min, the reduction temperature is 350-450℃, and the reduction time is 4-8 h.

[0055] The catalyst is activated through reduction, forming active centers. The oxide is reduced by hydrogen gas: CoFe₂O₄ + 4H₂ → CoFe₂ + 4H₂O. This reduction process converts the metal oxide into an alloy phase, forming an alloy and a metallic element. Specifically, the composition mainly consists of a CoFe₂ alloy and CoFe₂O₄. 2-x Ga x It contains small amounts of elemental metals and La2O3.

[0056] The gallium and lanthanum co-modified cobalt-iron bimetallic catalyst of the present invention comprises an additive and an active phase. The active phase is a cobalt-iron bimetallic compound or cobalt / cobalt carbide, and the additive is lanthanum oxide or gallium oxide. The catalyst forms a cobalt-iron bimetallic alloy carbide active phase during the reaction.

[0057] (2) Syngas catalytic conversion directly produces higher alcohols.

[0058] In some embodiments, the molar ratio of H2 to CO in the synthesis gas is (0.5-5):1, the reaction temperature is 220-260℃, the reaction pressure is 2-5 MPa, and the reaction space velocity is 3000-6000 h⁻¹. -1 .

[0059] Example 1

[0060] (1) Weigh 4.6565g of cobalt nitrate hexahydrate, 9.696g of ferric nitrate nonahydrate, 0.8184g of gallium nitrate hydrate and 0.4330g of lanthanum nitrate hexahydrate and dissolve them in 300ml of water and stir until homogeneous to form solution A. The molar ratio of cobalt to iron to gallium to lanthanum is 1:1.5:0.2:0.07, the concentration of gallium is 0.01mol / L, and the molar amount of La is 1mmol.

[0061] (2) Weigh 14.0556g of anhydrous sodium carbonate and dissolve it in 442ml of water and stir until homogeneous to form solution B, in which the concentration of alkali solution is 0.3mol / L.

[0062] (3) Add the solutions from steps (1) and (2) in parallel dropwise to a beaker, control the temperature of the whole process at 60℃, the titration rate at 2ml / min, and the pH of the solution at 10.

[0063] (4) The precipitate after titration in step (3) is aged at the same temperature for 2 hours.

[0064] (5) The precipitate after aging in step (4) is separated by centrifugation, then washed and centrifuged. The washing volume is controlled at 2000 ml, the centrifugation speed is 7000 r / min, and the centrifugation time is 1 min. The centrifuged precipitate is then dried in an 80℃ forced-air drying oven for 16 h. Finally, it is calcined in a muffle furnace at 400℃ in air atmosphere for 3 h to obtain Co1Fe. 1.5 Ga 0.2 La 0.07 catalyst.

[0065] Before the direct synthesis of higher alcohols from syngas, the catalyst is first pressed into tablets and sieved to 40-60 mesh. 0.5g of the sieved catalyst is weighed and mixed with 2.0g of quartz sand. After mixing, the mixture is loaded into a reaction quartz tube for in-situ reduction. The reducing gas is hydrogen, the reduction temperature is 350℃, the reduction time is 4h, and the reducing gas flow rate is 30ml / min.

[0066] After reduction, the gas was switched to syngas and pressurized to 3 MPa for the reaction, with a molar ratio of H2 / CO of 2. The reaction temperature was 220℃ and the reaction space velocity was 3600 h⁻¹. -1 After the reaction was completed, the corresponding CO conversion rate and product selectivity were calculated. The detailed results are shown in Table 1.

[0067] Example 2

[0068] (1) Weigh 4.6565g of cobalt nitrate hexahydrate, 6.4872g of ferric chloride nonahydrate, 2.4551g of gallium nitrate hydrate and 0.4330g of lanthanum nitrate hexahydrate and dissolve them in 300ml of water and stir well to form solution A. The molar ratio of cobalt to iron to gallium to lanthanum is 1:1.5:0.6:0.07, the concentration of gallium is 0.032mol / L, and the molar amount of La is 1mmol.

[0069] (2) Weigh 16.0908g of anhydrous sodium carbonate and dissolve it in 506ml of water and stir until homogeneous to form solution B, in which the concentration of alkali solution is 0.3mol / L.

[0070] (3) Add the solutions from steps (1) and (2) in parallel dropwise to a beaker, control the temperature of the whole process at 60℃, the titration rate at 2ml / min, and the pH of the solution at 10.

[0071] (4) The precipitate after titration in step (3) is aged at the same temperature for 2 hours.

[0072] (5) Separate the precipitate after aging in step (4) by centrifugation, then wash and centrifuge, controlling the water washing volume to 2000 ml, the centrifugation speed to 7000 r / min, and the centrifugation time to 1 min. Then, let the centrifuged precipitate stand and dry in an 80℃ forced-air drying oven for 14 h. Finally, calcine it in a muffle furnace at 400℃ for 3 h in an air atmosphere to obtain Co1Fe. 1.5 Ga 0.6 La 0.07 catalyst.

[0073] Before the direct synthesis of higher alcohols from syngas, the catalyst is first pressed into tablets and sieved to 40-60 mesh. 0.5g of the sieved catalyst is weighed and mixed with 2.0g of quartz sand. After mixing, the mixture is loaded into a reaction quartz tube for in-situ reduction. The reducing gas is hydrogen, the reduction temperature is 350℃, the reduction time is 4h, and the reducing gas flow rate is 30ml / min.

[0074] After reduction, the gas was switched to syngas and pressurized to 3 MPa for the reaction, with a molar ratio of H2 / CO of 2. The reaction temperature was 220℃ and the reaction space velocity was 3600 h⁻¹. -1 After the reaction was completed, the corresponding CO conversion rate and product selectivity were calculated. The detailed results are shown in Table 1.

[0075] Example 3

[0076] (1) Weigh 3.8069g of cobalt chloride hexahydrate, 6.4872g of ferric chloride nonahydrate, 3.6827g of gallium nitrate hydrate and 0.4330g of lanthanum nitrate hexahydrate and dissolve them in 300ml of water and stir until homogeneous to form solution A. The molar ratio of cobalt to iron to gallium to lanthanum is 1:1.5:0.9:0.07, the concentration of gallium is 0.048mol / L, and the molar amount of La is 1mmol.

[0077] (2) Weigh 17.6172g of anhydrous sodium carbonate and dissolve it in 554ml of water and stir until homogeneous to form solution B, in which the concentration of alkali solution is 0.3mol / L.

[0078] (3) Add the solutions from steps (1) and (2) in parallel flow to a beaker, control the temperature of the whole process at 60℃, the titration rate at 1.9 ml / min, and the pH of the solution at 10.

[0079] (4) The precipitate after titration in step (3) is aged at the same temperature for 2 hours.

[0080] (5) Separate the precipitate after aging in step (4) by centrifugation, then wash and centrifuge, controlling the water washing volume to 2000 ml, the centrifugation speed to 7000 r / min, and the centrifugation time to 1 min. Then, let the centrifuged precipitate stand and dry in an 80℃ forced-air drying oven for 14 h. Finally, calcine it in a muffle furnace at 400℃ for 3 h in an air atmosphere to obtain Co1Fe. 1.5 Ga 0.9 La 0.07 catalyst.

[0081] Before the direct synthesis of higher alcohols from syngas, the catalyst is first pressed into tablets and sieved to 40-60 mesh. 0.5g of the sieved catalyst is weighed and mixed with 2.0g of quartz sand. After mixing, the mixture is loaded into a reaction quartz tube for in-situ reduction. The reducing gas is hydrogen, the reduction temperature is 350℃, the reduction time is 4h, and the reducing gas flow rate is 30ml / min.

[0082] After reduction, the gas was switched to syngas and pressurized to 3 MPa for the reaction, with a molar ratio of H2 / CO of 2. The reaction temperature was 220℃ and the reaction space velocity was 3600 h⁻¹. -1 After the reaction was completed, the corresponding CO conversion rate and product selectivity were calculated. The detailed results are shown in Table 1.

[0083] In addition to the above embodiments, the catalyst of the present invention may further introduce a second metal M to further enhance its catalytic performance. M is selected from Ce, Mn, Zr, and La. The introduction method is as follows: in the mixed metal salt solutions of Examples 1-3, a soluble salt of the corresponding M is added in a designed proportion, while the remaining preparation steps, reduction conditions, and reaction evaluation conditions remain unchanged.

[0084] Comparative Example 1

[0085] (1) Weigh 3.8069g of cobalt chloride hexahydrate and 6.4872g of ferric chloride nonahydrate and dissolve them in 300ml of water and stir until homogeneous to form solution A, wherein the molar ratio of cobalt to iron is 1:1.5 and the concentration of cobalt is 0.053mol / L.

[0086] (2) Weigh 12.72g of anhydrous sodium carbonate and dissolve it in 400ml of water and stir until homogeneous to form solution B, in which the concentration of alkali solution is 0.3mol / L.

[0087] (3) Add the solutions from steps (1) and (2) in parallel flow to a beaker, control the temperature of the whole process at 60℃, the titration rate at 1.9 ml / min, and the pH of the solution at 10.

[0088] (4) The precipitate after titration in step (3) is aged at the same temperature for 2 hours.

[0089] (5) Separate the precipitate after aging in step (4) by centrifugation, then wash and centrifuge, controlling the water washing volume to 2000 ml, the centrifugation speed to 7000 r / min, and the centrifugation time to 1 min. Then, let the centrifuged precipitate stand and dry in an 80℃ forced-air drying oven for 14 h. Finally, calcine it in a muffle furnace at 400℃ for 3 h in an air atmosphere to obtain Co1Fe. 1.5 catalyst.

[0090] Before the direct synthesis of higher alcohols from syngas, the catalyst is first pressed into tablets and sieved to 40-60 mesh. 0.5g of the sieved catalyst is weighed and mixed with 2.0g of quartz sand. After mixing, the mixture is loaded into a reaction quartz tube for in-situ reduction. The reducing gas is hydrogen, the reduction temperature is 350℃, the reduction time is 4h, and the reducing gas flow rate is 30ml / min.

[0091] After reduction, the gas was switched to syngas and pressurized to 3 MPa for the reaction, with a molar ratio of H2 / CO of 2. The reaction temperature was 220℃ and the reaction space velocity was 3600 h⁻¹. -1 After the reaction was completed, the corresponding CO conversion rate and product selectivity were calculated. The detailed results are shown in Table 1.

[0092] Comparative Example 2

[0093] (1) Weigh 4.6565g of cobalt nitrate hexahydrate, 6.4872g of ferric chloride nonahydrate and 0.8184g of gallium nitrate hydrate and dissolve them in 300ml of water and stir until homogeneous to form solution A, wherein the molar ratio of cobalt to iron to Ga is 1:1.5:0.2 and the concentration of cobalt is 0.053mol / L.

[0094] (2) Weigh 13.7376g of anhydrous sodium carbonate and dissolve it in 432ml of water and stir until homogeneous to form solution B, in which the concentration of alkali solution is 0.3mol / L.

[0095] (3) Add the solutions from steps (1) and (2) in parallel flow to a beaker, control the temperature of the whole process at 60℃, the titration rate at 1.9 ml / min, and the pH of the solution at 10.

[0096] (4) The precipitate after titration in step (3) is aged at the same temperature for 2 hours.

[0097] (5) Separate the precipitate after aging in step (4) by centrifugation, then wash and centrifuge, controlling the water washing volume to 2000 ml, the centrifugation speed to 7000 r / min, and the centrifugation time to 1 min. Then, let the centrifuged precipitate stand and dry in an 80℃ forced-air drying oven for 14 h. Finally, calcine it in a muffle furnace at 400℃ for 3 h in an air atmosphere to obtain Co1Fe. 1.5 Ga0.2 catalyst.

[0098] Before the direct synthesis of higher alcohols from syngas, the catalyst is first pressed into tablets and sieved to 40-60 mesh. 0.5g of the sieved catalyst is weighed and mixed with 2.0g of quartz sand. After mixing, the mixture is loaded into a reaction quartz tube for in-situ reduction. The reducing gas is hydrogen, the reduction temperature is 350℃, the reduction time is 4h, and the reducing gas flow rate is 30ml / min.

[0099] After reduction, the gas was switched to syngas and pressurized to 3 MPa for the reaction, with a molar ratio of H2 / CO of 2. The reaction temperature was 220℃ and the reaction space velocity was 3600 h⁻¹. -1 After the reaction was completed, the corresponding CO conversion rate and product selectivity were calculated. The detailed results are shown in Table 1.

[0100] Comparative Example 3

[0101] (1) Weigh 3.8069g of cobalt chloride hexahydrate, 9.696g of ferric nitrate nonahydrate and 0.4330g of lanthanum nitrate hexahydrate and dissolve them in 300ml of water and stir until homogeneous to form solution A, wherein the molar ratio of cobalt to iron to lanthanum is 1:1.5:0.07 and the concentration of cobalt is 0.053mol / L.

[0102] (2) Weigh 13.038g of anhydrous sodium carbonate and dissolve it in 410ml of water and stir until homogeneous to form solution B, in which the concentration of alkali solution is 0.3mol / L.

[0103] (3) Add the solutions from steps (1) and (2) in parallel flow to a beaker, control the temperature of the whole process at 60℃, the titration rate at 1.9 ml / min, and the pH of the solution at 10.

[0104] (4) The precipitate after titration in step (3) is aged at the same temperature for 2 hours.

[0105] (5) Separate the precipitate after aging in step (4) by centrifugation, then wash and centrifuge, controlling the water washing volume to 2000 ml, the centrifugation speed to 7000 r / min, and the centrifugation time to 1 min. Then, let the centrifuged precipitate stand and dry in an 80℃ forced-air drying oven for 14 h. Finally, calcine it in a muffle furnace at 400℃ for 3 h in an air atmosphere to obtain Co1Fe. 1.5 La 0.07 catalyst.

[0106] Before the direct synthesis of higher alcohols from syngas, the catalyst is first pressed into tablets and sieved to 40-60 mesh. 0.5g of the sieved catalyst is weighed and mixed with 2.0g of quartz sand. After mixing, the mixture is loaded into a reaction quartz tube for in-situ reduction. The reducing gas is hydrogen, the reduction temperature is 350℃, the reduction time is 4h, and the reducing gas flow rate is 30ml / min.

[0107] After reduction, the gas was switched to syngas and pressurized to 3 MPa for the reaction, with a molar ratio of H2 / CO of 2. The reaction temperature was 220℃ and the reaction space velocity was 3600 h⁻¹. -1 After the reaction was completed, the corresponding CO conversion rate and product selectivity were calculated. The detailed results are shown in Table 1.

[0108] The reaction results of the catalysts in the above embodiments and comparative examples were obtained through the following calculations:

[0109] (1) During the reaction, the tail gas passes through the heat trap (120℃) and the cold trap (2℃) and then enters the chromatograph for direct online detection. The heat trap and the cold trap collect the reaction liquid at regular intervals.

[0110] (2) The liquid products collected from the reaction were analyzed offline using Shimadzu GC-2030 and Shimadzu GC-2014.

[0111] (3) The reaction results were calculated using N2 as an internal standard. The formulas for calculating CO conversion, CO2 selectivity, and selectivity of alcohol and hydrocarbon products are as follows:

[0112] CO conversion rate: ;

[0113] CO2 selectivity: ;

[0114] Selectivity between alcohol and hydrocarbon products: ;

[0115] CO in and CO out These represent the number of moles of CO molecules in the feed gas and the exhaust gas, respectively; CO 2 out C represents the number of moles of CO2 molecules in the exhaust gas. i Let n be the mole fraction of product i. i Let i be the number of carbon atoms in product i.

[0116] Table 1. Catalyst performance data for the direct synthesis of higher alcohols from syngas.

[0117] ;

[0118] The comparative analysis of the examples and comparative examples in Table 1 shows that: the pure CoFe catalyst (Comparative Example 1) has the worst performance, with low yields of total alcohols and higher alcohols and a large number of byproducts; the performance of the single Ga modification (CoFeGa, Comparative Example 2) is improved, as Ga increases the non-dissociative adsorption sites of CO, promotes alcohol formation, and the yield of higher alcohols is significantly higher than that of pure CoFe; the performance of the single La modification (CoFeLa, Comparative Example 3) is improved, as La provides oxygen vacancies, stabilizes the active phase, and inhibits carbon deposition, and the yield of higher alcohols is also higher than that of pure CoFe; the performance of the Ga and La co-modification (CoFeGaLa, Examples 1-3) is the best, as Ga regulates the electronic structure and promotes CO insertion; La stabilizes the active phase and inhibits sintering; the synergistic effect of the two achieves a highly efficient matching of the three-step reaction of CO activation, carbon chain growth, and alcohol hydroxyl generation, significantly reducing the selectivity of byproducts such as carbon dioxide and methane, while greatly increasing the yield of higher alcohols, proving that the synergistic effect of the two promoters has a significant promoting effect on catalytic performance.

[0119] Under optimal conditions (Example 1), the catalyst exhibits higher catalytic activity, better selectivity for higher alcohols, and better structural stability (due to...). Figure 1-2 The results demonstrate that the synergistic effect of Ga and La significantly promotes the direct preparation of higher alcohols from syngas. In Examples 2 and 3, the Ga content is increased compared to Example 1; excessive Ga can cover active sites, leading to decreased activity.

[0120] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for preparing a gallium and lanthanum co-modified cobalt-iron bimetallic catalyst, characterized in that, Includes the following steps: S1. The mixed metal salt solution and the precipitant solution are added dropwise to the reactor in a parallel flow manner to carry out the reaction, and a solution containing the precipitate is obtained; The mixed metal salt solution contains soluble salts of cobalt, iron, gallium, and lanthanum, wherein the molar ratio of Co, Fe, Ga, and La is 1:(1.2~1.8):(0.1~1):(0.001~0.1). The precipitant solution is a sodium carbonate solution; S2. The precipitate is aged, then separated, washed, dried, and finally calcined to obtain the gallium and lanthanum co-modified cobalt-iron bimetallic catalyst; The calcination is carried out in an air atmosphere at a temperature of 400-600℃.

2. The preparation method according to claim 1, characterized in that, The concentration of Ga in the mixed metal salt solution S1 is 0.004 mol / L to 0.06 mol / L; the concentration of the precipitant solution is 0.2 mol / L to 0.4 mol / L, and the total molar amount of the precipitant is 2 to 6 times the total molar amount of cobalt, iron, gallium, and lanthanum.

3. The preparation method according to claim 1, characterized in that, The temperature of the parallel dripping process described in S1 is controlled at 55~65℃.

4. The preparation method according to claim 1 or 3, characterized in that, The parallel dripping of the two solutions described in S1 is controlled at a dripping rate of 1.5 ml / min to 2.0 ml / min.

5. The preparation method according to claim 1, characterized in that, The aging temperature described in S2 is 55~65℃, and the time is 2~4h.

6. The preparation method according to claim 1, characterized in that, The washing process described in S2 controls the sodium residue to remain stable at 0.05 wt%–0.2 wt% by controlling the amount of washing water.

7. A gallium- and lanthanum co-modified cobalt-iron bimetallic catalyst, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.

8. The application of the gallium and lanthanum co-modified cobalt-iron bimetallic catalyst of claim 7, characterized in that, It is used in the catalytic conversion of syngas to directly produce higher alcohols.

9. The application according to claim 8, characterized in that, Before application, the catalyst is reduced in situ in a hydrogen atmosphere.

10. The application according to claim 9, characterized in that, The reduction temperature is 350~450℃.

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