A catalyst for preparing olefins by hydrogenation of co and its preparation method and application

Abstract

The application belongs to the technical field of hydrogenation catalysts, and discloses a catalyst for preparing olefins through CO hydrogenation, a preparation method and application of the catalyst, and the catalyst contains Ga2O3 modified Fe5C2 active centers and a MgO carrier. The catalyst can be prepared by a hydrotalcite precursor method or a loading method. The catalyst has high olefin selectivity in the process of preparing olefins through CO hydrogenation, and can maintain stability for a long time.

Description

Technical Field

[0001] This invention belongs to the field of hydrogenation catalyst technology, specifically relating to a catalyst for the hydrogenation of CO to olefins and its preparation method, as well as the application of the catalyst in the hydrogenation of CO to olefins. Background Technology

[0002] Syngas can be used to convert coal, oil, natural gas, and biomass into basic chemical products with high utilization value, such as oxygen-containing chemicals and olefins. Olefins are important basic chemical raw materials that can be used to produce polyolefins, rubber, plastics, etc.

[0003] Currently, the production of low-carbon olefins mainly adopts traditional petroleum-based processes, including naphtha steam cracking and catalytic cracking. In recent years, non-petroleum-based routes, represented by propane dehydrogenation, methanol-to-olefins (MTO), and syngas-to-olefins (STO) processes, have also developed rapidly, especially propane dehydrogenation and MTO, which have been industrialized.

[0004] In the 1930s, German chemists Hans Tropsch and Frans Fischer developed the Fischer-Tropsch synthesis reaction, using syngas (CO + H2) as a raw material and employing an iron-based catalyst under suitable reaction conditions to produce long-chain hydrocarbons, which are used as liquid fuels such as gasoline and diesel. Simultaneously, the reaction produces large quantities of olefins and oxygen-containing compounds as byproducts. Based on the abundance and tunability of the FT reaction products, using syngas as a platform molecule to convert coal, natural gas, and biomass resources into low-carbon olefins is one of the feasible routes for producing low-carbon olefins from non-petroleum resources. This route also achieves the efficient and clean utilization of coal resources.

[0005] Currently reported catalysts for olefin synthesis can be categorized into two process routes based on the reaction pathway: one is the FTO route, which directly prepares low-carbon olefins through Fischer-Tropsch synthesis using traditional Fe and Co-based catalysts to catalyze the direct hydrogenation of CO to low-carbon olefins via Fischer-Tropsch synthesis; the other is the OX-ZEO route, a bifunctional catalyst reaction coupling route where syngas is used to synthesize low-carbon olefins via intermediates such as methanol or ketene. Although the two routes have different mechanisms, both involve managing the competition between CO dissociation, hydrogenation of active hydrocarbon intermediates, and carbon chain growth / termination capabilities, as well as maintaining the stability of the catalyst's active phase at the reaction temperature and mitigating the effects of WGS and methanation reactions.

[0006] Despite decades of research, the conversion of syngas into olefins via Fischer-Tropsch synthesis has been extensively studied, but it still suffers from drawbacks such as low olefin selectivity and high selectivity for methane and carbon dioxide. Therefore, it is essential to develop inexpensive and efficient catalysts for the hydrogenation of carbon monoxide to olefins. Summary of the Invention

[0007] Based on the above, the purpose of this invention is to provide a catalyst for the hydrogenation of CO to prepare olefins, its preparation method and application, wherein the active center of the catalyst is Fe5C2 modified with Ga2O3, and it exhibits excellent olefin selectivity in the reaction of hydrogenation of CO to prepare olefins.

[0008] A first aspect of the present invention provides a catalyst for the hydrogenation of CO to prepare olefins, the catalyst containing a Ga2O3-modified Fe5C2 active center and an MgO support.

[0009] A second aspect of the present invention provides a method for preparing the catalyst for the hydrogenation of CO to olefins described above, wherein the preparation method is either method one or method two, wherein...

[0010] Method 1 includes:

[0011] 1) Preparation of catalyst precursor: Hydrotalcite was prepared using the double-drop method, and the M of the hydrotalcite layers... 2+ Mg 2+ Fe 2+ M 3+ For Ga 3+ Or the M of the hydrotalcite layer 2+ Mg 2+ M 3+ For Ga 3+ Fe 3+ ;

[0012] 2) Catalyst preparation: The catalyst precursor is reduced in a hydrogen atmosphere, then oxidized in an oxygen atmosphere, and finally carburized in syngas to obtain the catalyst.

[0013] Method 2 includes:

[0014] 1) Preparation of catalyst precursor: Ga was prepared by the supported method. 3+ / Fe 3+ / MgO or Ga 3+ / Fe 2+ / MgO;

[0015] 2) Catalyst preparation: The catalyst precursor is reduced in a hydrogen atmosphere, then oxidized in an oxygen atmosphere, and finally carburized in syngas to obtain the catalyst.

[0016] The significant advantages of this invention are:

[0017] 1. The catalyst of the present invention achieves high olefin selectivity by modifying Fe5C2 with Ga2O3, while maintaining stability for a long time.

[0018] 2. The catalyst of the present invention can be prepared by the hydrotalcite precursor method or the loading method. When the hydrotalcite precursor method is used, the characteristic of the trivalent metal in hydrotalcite being dispersed at the atomic level in the divalent metal is taken advantage of. After heat treatment, a uniformly dispersed oxide is obtained and loaded on the surface structure of iron carbide, which achieves a good synergistic effect and can further improve the performance of the catalyst.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0020] Figure 1 XRD patterns of different catalyst precursors, where b is the catalyst precursor of Example 1, c is the catalyst precursor of Example 2, and a is the catalyst precursor of Comparative Example 2.

[0021] Figure 2 XRD patterns of different catalysts, where d is the catalyst of Example 1, f is the catalyst of Example 2, g is the catalyst of Comparative Example 1, and h is the catalyst of Comparative Example 2. Detailed Implementation

[0022] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0023] According to a first aspect of the present invention, the present invention provides a catalyst for the hydrogenation of CO to prepare olefins, the catalyst containing a Ga2O3-modified Fe5C2 active center and an MgO support.

[0024] In this invention, the particle size of Fe5C2 can be 10nm-20nm.

[0025] According to the present invention, based on the total weight of the catalyst, the loading of Fe5C2 is 5wt%-15wt% and the loading of Ga2O3 is 10wt%-20wt%.

[0026] According to a second aspect of the present invention, the present invention provides a method for preparing the above-described catalyst for the hydrogenation of CO to olefins, wherein the preparation method is method one or method two, wherein...

[0027] Method 1 includes:

[0028] 1) Preparation of catalyst precursor: Hydrotalcite was prepared using the double-drop method, and the M of the hydrotalcite layers... 2+ Mg 2+ Fe 2+ M 3+ For Ga 3+ Or the M of the hydrotalcite layer 2+ Mg 2+ M3+ For Ga 3+ Fe 3+ ;

[0029] 2) Catalyst preparation: The catalyst precursor is reduced in a hydrogen atmosphere, then oxidized in an oxygen atmosphere, and finally carburized in syngas to obtain the catalyst.

[0030] Method 2 includes:

[0031] 1) Preparation of catalyst precursor: Ga was prepared by the supported method. 3+ / Fe 3+ / MgO or Ga 3+ / Fe 2+ / MgO;

[0032] 2) Catalyst preparation: The catalyst precursor is reduced in a hydrogen atmosphere, then oxidized in an oxygen atmosphere, and finally carburized in syngas to obtain the catalyst.

[0033] According to the present invention, the catalyst precursor in Method 1 can be prepared using conventional methods in the prior art, and may specifically include the following steps:

[0034] (1) M, which makes up the hydrotalcite slab 2+ M 3+ Prepare a salt solution and prepare an alkaline solution from Na2CO3 and NaOH. Add the salt solution and alkaline solution dropwise to a reaction vessel with a stirring speed of 800-1200 r / min. Control the pH of the reaction solution to 10±0.2. After the salt solution is added, crystallize the reaction solution at a constant temperature of 60-80℃ for 8-15 h.

[0035] (2) The reaction product was filtered, washed with water until neutral, washed with ethanol, and dried to obtain the catalyst precursor.

[0036] Preferably, in the salt solution, M 2+ :M 3+ The molar ratio is 2-8:1, M 2+ and M 3+ The total molar concentration is 0.1-0.5 mol / L;

[0037] In the alkaline solution, the molar concentration of Na2CO3 is 0.05-0.5 mol / L and the molar concentration of NaOH is 0.1-0.8 mol / L.

[0038] According to the present invention, in method two, the preparation of the catalyst precursor includes: preparing a Ga-containing catalyst precursor. 3+ Salt solutions containing Fe 3+ or Fe 2+The salt solutions were impregnated and loaded onto the MgO support in steps, and each impregnation and loading step of the salt solution included impregnation and drying operations.

[0039] Contains Ga 3+ The molar concentration of the salt solution is 1.5-2.0 mol / L;

[0040] Contains Fe 3+ or Fe 2+ The molar concentration of the salt solution is 1.0-1.5 mol / L.

[0041] In both Method 1 and Method 2, the reduction conditions include: a reduction temperature of 650-800℃, a heating rate of 2-5℃ / min, and immediate cooling after reaching the reduction temperature.

[0042] The conditions for oxidation treatment include: an oxygen atmosphere of 1% O2 / N2, a heat treatment temperature of 300-400℃, a heating rate of 2-5℃ / min, and immediate cooling after reaching the heat treatment temperature.

[0043] The conditions for carburizing treatment include: a molar ratio of CO:H2 = 1:1 in the synthesis gas, a carburizing temperature of 250-350℃, a heating rate of 2-5℃ / min, and a carburizing time of 2-5h after isothermal treatment.

[0044] According to a third aspect of the present invention, the present invention provides the application of the above-described catalyst and the catalyst prepared by the above-described method in the hydrogenation of CO to prepare olefins.

[0045] In this invention, the reaction conditions for the preparation of olefins by CO hydrogenation include: a reaction temperature of 250-350℃; a reaction pressure of 1.5-2.5 MPa; a feed composition of CO:H2:Ar in a molar ratio of 47.5%:47.5%:5%; and a mass hourly space velocity of 3000 h⁻¹. -1 The catalyst dosage is 0.50-2.0g.

[0046] The substances and parameters not limited in this invention can be selected according to existing technology, which is a conventional technical means in this field.

[0047] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0048] Example 1

[0049] Step A: Weigh out 8.55g Mg(NO3)2·6H2O, 2.32g FeSO4·7H2O, and 2.13g Ga(NO3)3·xH2O (molar ratio M... 2+ / M 3+=5:1) Dissolve in 150mL of deoxygenated water, stir rapidly and sonicate until completely dissolved to obtain a clear and transparent salt solution; weigh 3.53g Na2CO3 and 4.00g NaOH and dissolve in 150mL of deoxygenated water to prepare an alkaline solution; add 200mL of deoxygenated water to a 1000mL four-necked flask, stir at 1000r / min at room temperature, and rapidly add the salt solution and alkaline solution dropwise to the four-necked flask under N2 protection, controlling the pH = 10±0.2. After the solution has been completely added, the reaction solution is crystallized at 65℃ in an oil bath for 12h. The reaction product is filtered, washed with deoxygenated water until neutral, washed twice with ethanol, and then dried in a vacuum oven at 60℃ for 12h, and ground to obtain Mg8Fe(II)2Ga2-CO3. 2- -LDHs powder, dry and store.

[0050] Step B: Weigh the Mg8Fe(II)2Ga2-CO3 prepared above. 2- 1.50 g of -LDHs was placed in a porcelain boat and heated from room temperature to 700 °C under hydrogen atmosphere at a rate of 2 °C / min. After reaching 700 °C, the temperature was immediately lowered. Upon reaching room temperature, 1% O2 / N2 was introduced for oxidation treatment. The oxidation treatment conditions were: heating from room temperature to 400 °C at a rate of 5 °C / min, followed by immediate cooling to 400 °C, yielding Ga2O3-Fe2O3 / MgO-Fe II .

[0051] Step C: The Ga2O3-Fe2O3 / MgO-Fe prepared above... II After granulation, 1.0 g of 20-40 mesh sample was subjected to in-situ carburizing treatment in a fixed-bed reactor. Specifically, the sample was heated from room temperature to 280℃ under syngas (CO:H2 = 1:1) at a heating rate of 2℃ / min, and then held at 280℃ for 3 hours for carburizing treatment, yielding the catalyst Ga2O3-Fe5C2 / MgO-Fe. II The active center structure of this sample is characterized by uniformly distributed and highly dispersed Ga2O3-modified Fe5C2.

[0052] Example 2

[0053] Step A: Weigh out 8.55g Mg(NO3)2·6H2O, 3.36g Fe(NO3)3·9H2O, and 2.13g Ga(NO3)3·xH2O (molar ratio M). 2+ / M 3+Dissolve Mg8Fe(III)2Ga2-CO3 in 150 mL of deionized water, stir rapidly and sonicate until completely dissolved to prepare a clear and transparent salt solution; weigh 3.63 g Na2CO3 and 4.00 g NaOH and dissolve them in 150 mL of deionized water to prepare an alkaline solution; add 200 mL of deionized water to a 1000 mL four-necked flask, and stir at 1000 r / min at room temperature. Add the salt solution and alkaline solution dropwise to the four-necked flask, controlling the pH to 10 ± 0.2. After the solution has been completely added, crystallize at 65 °C in an oil bath for 12 h. Wash with deionized water until neutral, and finally wash twice with ethanol. Dry in an oven at 60 °C for 12 h, and grind to obtain Mg8Fe(III)2Ga2-CO3. 2- -LDHs powder, dry and store.

[0054] Step B: Weigh the Mg8Fe(III)2Ga2-CO3 prepared above. 2- 1.50 g of -LDHs was placed in a porcelain boat and heated from room temperature to 700 °C under hydrogen atmosphere at a rate of 2 °C / min. After reaching 700 °C, the temperature was immediately lowered. Upon reaching room temperature, 1% O2 / N2 was introduced for oxidation treatment. The oxidation treatment conditions were: heating from room temperature to 400 °C at a rate of 5 °C / min, followed by immediate cooling to 400 °C, yielding Ga2O3-Fe2O3 / MgO-Fe III .

[0055] Step C: The Ga2O3-Fe2O3 / MgO-Fe prepared above... III After granulation, 1.0 g of 20-40 mesh sample was subjected to in-situ carburizing treatment in a fixed-bed reactor. Specifically, the sample was heated from room temperature to 280℃ under syngas (CO:H2 = 1:1) at a heating rate of 2℃ / min, and then held at 280℃ for 3 hours for carburizing treatment, yielding the catalyst Ga2O3-Fe5C2 / MgO-Fe. III .

[0056] Example 3

[0057] Step A: Weigh 2.0 g MgO and place it in a 15 mL round-bottom flask. Weigh 1.88 g Fe(NO3)3·9H2O and dissolve it in 3.5 mL deionized water. Sonicate until the salt is completely dissolved to obtain a clear and transparent solution A. Pour solution A into a round-bottom flask containing MgO, shake at room temperature for 2 hours, and dry in an oven at 120 °C overnight to obtain Fe. 3+ / MgO sample. Using a similar method, 2 mL of deionized water containing 0.88 g Ga(NO3)2·xH2O was poured into a container containing 1.50 g Fe. 3+ The MgO sample was placed in a round-bottom flask, shaken at room temperature for 2 hours, and then dried overnight in an oven at 120°C to obtain Ga. 3+ / Fe 3+ / MgO sample.

[0058] Step B: Weigh the Ga prepared above. 3+ / Fe 3+ 1.50g of MgO was placed in a porcelain boat and heated from room temperature to 700℃ under hydrogen atmosphere at a rate of 2℃ / min. After reaching 700℃, the temperature was immediately lowered. After cooling to room temperature, 1% O2 / N2 was introduced for oxidation treatment. The oxidation treatment conditions were: heating from room temperature to 400℃ at a rate of 5℃ / min, and then immediately cooling after reaching 400℃, to obtain Ga2O3 / Fe2O3 / MgO.

[0059] Step C: After granulating the Ga2O3 / Fe2O3 / MgO obtained above, take 1.0g of 20-40 mesh sample and perform in-situ carburizing treatment in a fixed bed reactor. Specifically, the sample is heated from room temperature to 280℃ under syngas (CO:H2=1:1) conditions at a heating rate of 2℃ / min, and then held at 280℃ for 3h for carburizing treatment to obtain the catalyst Ga2O3 / Fe5C2 / MgO.

[0060] Comparative Example 1

[0061] Step A: Weigh out 8.55g Mg(NO3)2·6H2O, 2.32g FeSO4·7H2O, and 2.13g Ga(NO3)3·xH2O (molar ratio M... 2+ / M 3+ =5:1) Dissolve in 150mL of deoxygenated water, stir rapidly and sonicate until completely dissolved to obtain a clear and transparent salt solution; weigh 3.53g Na2CO3 and 4.00g NaOH and dissolve in 150mL of deoxygenated water to prepare an alkaline solution; add 200mL of deoxygenated water to a 1000mL four-necked flask, stir at 1000r / min at room temperature, and rapidly add the salt solution and alkaline solution dropwise to the four-necked flask under N2 protection, controlling the pH = 10±0.2. After the solution has been completely added, the reaction solution is crystallized at 65℃ in an oil bath for 12h. The reaction product is filtered, washed with deoxygenated water until neutral, washed twice with ethanol, and then dried in a vacuum oven at 60℃ for 12h, and ground to obtain Mg8Fe(II)2Ga2-CO3. 2- -LDHs powder, dry and store.

[0062] Step B: Weigh the Mg8Fe(II)2Ga2-CO3 prepared above. 2-1.50 g of -LDHs was placed in a porcelain boat and heated from room temperature to 600 °C under hydrogen atmosphere at a rate of 2 °C / min. After reaching 600 °C, the temperature was immediately lowered. Upon reaching room temperature, 1% O2 / N2 was introduced for oxidation treatment. The oxidation conditions were: heating from room temperature to 400 °C at a rate of 5 °C / min, followed by immediate cooling to 400 °C, yielding Fe2O3 / Mg(Ga)O-Fe. II .

[0063] Step C: The Fe2O3 / Mg(Ga)O-Fe obtained above II After granulation, 1.0 g of 20-40 mesh sample was subjected to in-situ carburizing treatment in a fixed-bed reactor. Specifically, the sample was heated from room temperature to 280℃ under syngas (CO:H2 = 1:1) conditions at a heating rate of 2℃ / min, and then held at 280℃ for 3 hours for carburizing treatment, yielding the catalyst Fe5C2 / Mg(Ga)O-Fe. II .

[0064] Comparative Example 2

[0065] Step A: Weigh 8.55g Mg(NO3)2·6H2O and 3.36g Fe(NO3)3·9H2O (molar ratio M) 2+ / M 3+ Dissolve 4:1 Na₂CO₃ in 150 mL of deionized water, stir rapidly and sonicate until completely dissolved to prepare a clear and transparent salt solution; weigh 3.53 g Na₂CO₃ and 4.00 g NaOH and dissolve them in 150 mL of deionized water to prepare an alkaline solution; add 200 mL of deionized water to a 1000 mL four-necked flask, and stir at 1000 r / min at room temperature. Add the salt and alkaline solutions dropwise to the four-necked flask, controlling the pH to 10 ± 0.2. After the solution has been completely added, crystallize at 65 °C in an oil bath for 12 h. Filter the reaction product, wash with deionized water until neutral, wash twice with ethanol, dry in an oven at 60 °C for 12 h, and grind to obtain Mg₈Fe(III)₂-CO₃. 2- -LDHs powder, dry and store.

[0066] Step B: Weigh the Mg8Fe(III)2-CO3 prepared above. 2- 1.50g of -LDHs was placed in a porcelain boat and heated from room temperature to 700℃ under hydrogen atmosphere at a rate of 2℃ / min. After reaching 700℃, the temperature was immediately lowered. Upon reaching room temperature, 1% O2 / N2 was introduced for oxidation treatment. The oxidation treatment conditions were: heating from room temperature to 400℃ at a rate of 5℃ / min, followed by immediate cooling to 400℃, yielding Fe2O3 / MgO-Fe. III .

[0067] Step C: The Fe2O3 / MgO-Fe obtained above III After granulation, 1.0 g of 20-40 mesh sample was subjected to in-situ carburizing treatment in a fixed-bed reactor. Specifically, the sample was heated from room temperature to 280℃ under syngas (CO:H2 = 1:1) at a heating rate of 2℃ / min, and then held at 280℃ for 3 hours for carburizing treatment, yielding the catalyst Fe5C2 / MgO-Fe. III .

[0068] Comparative Example 3

[0069] Step A: Weigh out 8.55g Mg(NO3)2·6H2O, 2.32g FeSO4·7H2O, and 2.13g Ga(NO3)3·xH2O (molar ratio M... 2+ / M 3+ =5:1) Dissolve in 150mL of deoxygenated water, stir rapidly and sonicate until completely dissolved to obtain a clear and transparent salt solution; weigh 3.53g Na2CO3 and 4.00g NaOH and dissolve in 150mL of deoxygenated water to prepare an alkaline solution; add 200mL of deoxygenated water to a 1000mL four-necked flask, stir at 1000r / min at room temperature, and rapidly add the salt solution and alkaline solution dropwise to the four-necked flask under N2 protection, controlling the pH = 10±0.2. After the solution has been completely added, the reaction solution is crystallized at 65℃ in an oil bath for 12h. The reaction product is filtered, washed with deoxygenated water until neutral, washed twice with ethanol, and then dried in a vacuum oven at 60℃ for 12h, and ground to obtain Mg8Fe(II)2Ga2-CO3. 2- -LDHs powder, dry and store.

[0070] Step B: Weigh the Mg8Fe(II)2Ga2-CO3 prepared above. 2- 1.50 g of -LDHs was placed in a porcelain boat and heated from room temperature to 700 °C under hydrogen atmosphere at a rate of 2 °C / min. After reaching 700 °C, the temperature was immediately lowered. Upon reaching room temperature, 1% O2 / N2 was introduced for oxidation treatment. The oxidation treatment conditions were: heating from room temperature to 400 °C at a rate of 5 °C / min, followed by immediate cooling. This yielded the catalyst Ga2O3-Fe2O3 / MgO-Fe II .

[0071] Comparative Example 4

[0072] Step A: Weigh out 8.55g Mg(NO3)2·6H2O, 2.32g FeSO4·7H2O, and 2.13g Ga(NO3)3·xH2O (molar ratio M... 2+ / M 3+=5:1) Dissolve in 150mL of deoxygenated water, stir rapidly and sonicate until completely dissolved to obtain a clear and transparent salt solution; weigh 3.53g Na2CO3 and 4.00g NaOH and dissolve in 150mL of deoxygenated water to prepare an alkaline solution; add 200mL of deoxygenated water to a 1000mL four-necked flask, stir at 1000r / min at room temperature, and rapidly add the salt solution and alkaline solution dropwise to the four-necked flask under N2 protection, controlling the pH = 10±0.2. After the solution has been completely added, the reaction solution is crystallized at 65℃ in an oil bath for 12h. The reaction product is filtered, washed with deoxygenated water until neutral, washed twice with ethanol, and then dried in a vacuum oven at 60℃ for 12h, and ground to obtain Mg8Fe(II)2Ga2-CO3. 2- -LDHs powder, dry and store.

[0073] Step B: Weigh the Mg8Fe(II)2Ga2-CO3 prepared above. 2- 1.50 g of -LDHs were placed in a porcelain boat and heated from room temperature to 700 °C under hydrogen atmosphere at a rate of 2 °C / min. After reaching 700 °C, the temperature was immediately lowered. Once cooled to room temperature, 1% O2 / N2 was introduced for passivation treatment, yielding FeGa / MgO-Fe. II After granulation, 1.0g of a 20-40 mesh sample was taken as a catalyst for performance testing.

[0074] Comparative Example 5

[0075] Step A: Weigh 2.0 g MgO and place it in a 15 mL round-bottom flask. Weigh 1.88 g Fe(NO3)3·9H2O and dissolve it in 3.5 mL deionized water. Sonicate until the salt is completely dissolved to obtain a clear and transparent solution A. Pour solution A into a round-bottom flask containing MgO, shake at room temperature for 2 hours, and dry in an oven at 120 °C overnight to obtain Fe. 3+ / MgO sample.

[0076] Step B: Weigh the Fe prepared above. 3+ 1.50g of Fe2O3 / MgO was placed in a porcelain boat and heated from room temperature to 700℃ under hydrogen atmosphere at a rate of 2℃ / min. After reaching 700℃, the temperature was immediately lowered. After cooling to room temperature, 1% O2 / N2 was introduced for oxidation treatment. The oxidation treatment conditions were: heating from room temperature to 400℃ at a rate of 5℃ / min, and then immediately cooling after reaching 400℃, to obtain Fe2O3 / MgO.

[0077] Step C: After granulating the Fe2O3 / MgO obtained above, take 1.0g of 20-40 mesh sample and perform in-situ carburizing treatment in a fixed bed reactor. Specifically, the sample is heated from room temperature to 280℃ under syngas (CO:H2=1:1) conditions at a heating rate of 2℃ / min, and then held at 280℃ for 3h for carburizing treatment to obtain Fe5C2 / MgO.

[0078] The catalysts prepared in the various examples and comparative examples were used for the hydrogenation of CO to prepare olefins. The reaction temperature was 280°C, the reaction pressure was 2.0 MPa, the feed composition was CO:H2:Ar = 47.5%:47.5%:5% (molar ratio), and the mass hourly space velocity was 3000 h⁻¹. -1 The catalyst dosage was 1.0 g. Performance data are shown in Table 1.

[0079] Table 1

[0080]

[0081] Table 1 shows that the catalyst used in this application exhibits high olefin selectivity, approaching the maximum allowable value for ASF distribution. Compared to samples with Ga in the support and samples without Ga, the olefin selectivity of the Ga2O3-modified Fe5C2 structure catalyst in this application is significantly improved, even reaching 2 times, indicating a synergistic effect between Ga2O3 and Fe5C2. Compared to the uncarburized sample Ga2O3-Fe2O3 / MgO-Fe... II In comparison, the activity and selectivity of the sample in the examples are significantly improved. Compared with the FeGa alloy sample, the catalyst activity of this application is similar, while the olefin selectivity is significantly improved. Compared with the Fe5C2 / MgO sample obtained by impregnation, the catalyst activity of this application is slightly decreased, while the olefin selectivity is increased by two times. In addition, the catalyst of the examples in this application still maintains the conversion rate and selectivity shown in Table 1 after 100 hours of operation in a fixed-bed reactor, indicating good stability.

[0082] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A catalyst for the production of olefins by hydrogenation of CO, characterized in that, The catalyst contains Ga2O3 modified Fe5C2 active center and MgO carrier; The loading amount of Fe5C2 is 5wt%-15wt% and the loading amount of Ga2O3 is 10wt%-20wt% based on the total weight of the catalyst; The preparation method of the catalyst is method one or method two, wherein, Method one comprises: 1) Preparation of the catalyst precursor: hydrotalcite is prepared by double- drop method, the M 2+ of the hydrotalcite lamellas is Mg 2+ , Fe 2+ , M 3+ is Ga 3+ or the M 2+ of the hydrotalcite lamellas is Mg 2+ , M 3+ is Ga 3+ , Fe 3+ ; 2) Preparation of the catalyst: reducing the catalyst precursor under hydrogen atmosphere, then treating it under oxygen atmosphere, and finally carburizing it under synthesis gas to obtain the catalyst; Method two comprises: 1) Preparation of catalyst precursor: Ga 3+ / Fe 3+ / MgO or Ga 3+ / Fe 2+ / MgO; 2) Preparation of the catalyst: reducing the catalyst precursor under hydrogen atmosphere, then treating it under oxygen atmosphere, and finally carburizing it under synthesis gas to obtain the catalyst.

2. The catalyst for the production of olefins by CO hydrogenation according to claim 1, wherein, The particle size of the Fe5C2 is 10nm-20nm.

3. The process for producing a catalyst for the production of olefins by CO hydrogenation as claimed in claim 1 or 2, characterized in that, The preparation method is method one or method two, wherein, Method one comprises: 1) Preparation of catalyst precursor: Hydrotalcite was prepared using the double-drop method, and the M of the hydrotalcite layers... 2+ Mg 2+ Fe 2+ M 3+ For Ga 3+ Or the M of the hydrotalcite layer 2+ Mg 2+ M 3+ For Ga 3+ Fe 3+ ; 2) Preparation of the catalyst: reducing the catalyst precursor under hydrogen atmosphere, then treating it under oxygen atmosphere, and finally carburizing it under synthesis gas to obtain the catalyst; Method two comprises: 1) Preparation of catalyst precursor: Ga 3+ / Fe 3+ / MgO or Ga 3+ / Fe 2+ / MgO; 2) Preparation of the catalyst: reducing the catalyst precursor under hydrogen atmosphere, then treating it under oxygen atmosphere, and finally carburizing it under synthesis gas to obtain the catalyst.

4. The process for preparing a catalyst for the production of olefins by CO hydrogenation according to claim 3, wherein, The preparation method of the catalyst precursor in method one comprises the following steps: (1) M 2+ , M 3+ gypsum is made into a salt solution, Na2CO3, NaOH is made into an alkali solution, the salt solution and the alkali solution are added dropwise into a reaction container with a stirring speed of 800-1200 r / min, the pH of the reaction solution is controlled to be 10±0.2, after the salt solution is added dropwise completely, the reaction solution is crystallized at a constant temperature of 60-80℃ for 8-15h; (2) The reaction product is suction filtered, washed with water until neutral, then washed with ethanol, and dried to obtain the catalyst precursor.

5. The process for preparing a catalyst for the production of olefins by CO hydrogenation according to claim 4, wherein, M 2+ : the molar ratio of M 3+ : the total molar concentration of M 2+ and M 3+ is 0.1-0.5 mol / L. In the alkaline solution, the molar concentration of Na2CO3 is 0.05-0.5mol / L and the molar concentration of NaOH is 0.1-0.8mol / L.

6. The process for preparing a catalyst for the production of olefins by CO hydrogenation according to claim 3, wherein, In the second method, the preparation of the catalyst precursor includes: stepwise impregnating a Ga 3+ containing salt solution, an Fe 3+ containing salt solution or an Fe 2+ containing salt solution on a MgO carrier, each of the impregnation steps of the salt solutions comprises an impregnation and a drying operation; Ga-containing 3+ The molar concentration of the salt solution containing Ga is 1.5-2.0 mol / L. Fe 3+ or Fe 2+ The molar concentration of the salt solution is 1.0-1.5 mol / L.

7. The process for preparing a catalyst for the production of olefins by CO hydrogenation according to claim 3, wherein, In method one and method two, the reduction conditions comprise: the reduction temperature is 650-800℃, the heating rate is 2-5℃ / min, and the temperature is immediately lowered after being heated to the reduction temperature; The oxidation treatment conditions comprise: the oxygen atmosphere is 1%O2 / N2, the heat treatment temperature is 300-400℃, the heating rate is 2-5℃ / min, and the temperature is immediately lowered after being heated to the heat treatment temperature; The carburizing treatment conditions comprise: in terms of molar ratio, CO:H2 in the synthesis gas is 1:1, the carburizing treatment temperature is 250-350℃, the heating rate is 2-5℃ / min, and the carburizing treatment time is 2-5h after constant temperature.

8. The use of the catalyst of claim 1 or 2 or the catalyst prepared by the preparation method of any one of claims 3-7 in the preparation of olefins by CO hydrogenation.

9. Use according to claim 8, wherein, The reaction conditions for preparing olefins by hydrogenation of CO include: reaction temperature of 250-350℃; reaction pressure of 1.5-2.5MPa; reaction feed composition of CO:H2:Ar = 47.5%:47.5%:5% in terms of molar ratio; mass space velocity of 3000h -1 , and catalyst dosage of 0.50-2.0g.

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