Iron-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses an iron-based catalyst as well as a preparation method and application thereof. The iron-based catalyst comprises Fe, Cu, Mn, Na and K, and the total weight of Na and K accounts for 1-3 wt% of the total weight of the iron-based catalyst; the weight ratio of Na to K is 1: (0.1-10). According to the invention, the total weight of Na and K and the weight ratio of Na and K are simultaneously controlled to be within the range, so that the iron-based catalyst has higher activity, higher carbon monoxide conversion rate and higher olefin selectivity, and can be used for carbon monoxide hydrogenation reaction. The iron-based catalyst provided by the invention has the advantages of short synthesis period, simple preparation process, cheap and easily available catalyst raw materials, lower catalyst synthesis cost, less waste generation in the whole preparation process, environmental friendliness and suitability for industrial production.

Description

Technical Field

[0001] This invention relates to iron-based catalysts, specifically to their preparation methods and applications. Background Technology

[0002] Olefins are fundamental petrochemical chemicals used as intermediates in the production of polymers, plastics, detergents, and solvents. Their applications are widespread, and the growing demand for plastics necessitates a sustainable supply of olefins. Olefins are typically produced via the steam cracking (SC) of naphtha. However, depleted fossil fuel reserves and rapidly increasing CO2 emissions have prompted the adoption of alternative non-petroleum feedstock routes, such as Fischer-Tropsch synthesis to olefins (FTSO). Catalysts are the most critical component for efficient, commercial-scale olefin production via FTS. Catalysts need to be tuned for olefin selectivity by altering chain growth and limiting secondary hydrogenation reactions.

[0003] Fischer-Tropsch synthesis using iron-based catalysts has been a research hotspot in recent decades, as iron-based catalysts are more suitable for high-temperature Fischer-Tropsch synthesis compared to other catalysts. However, iron-based catalysts prepared by co-precipitation methods suffer from poor thermal stability, short service life, and poor olefin selectivity.

[0004] Therefore, the research and preparation of iron-based catalysts with high activity and long service life has great social and economic significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor thermal stability and poor olefin selectivity in the prior art, and to provide an iron-based catalyst, its preparation method and application. The iron-based catalyst has high activity, high carbon monoxide conversion rate and high olefin selectivity.

[0006] To achieve the above objectives, the first aspect of the present invention provides an iron-based catalyst comprising Fe, Cu, Mn, Na and K, wherein the total weight of Na and K accounts for 1-3 wt% of the total weight of the iron-based catalyst; and the weight ratio of Na to K is 1:0.1-10.

[0007] A second aspect of the present invention provides a method for preparing an iron-based catalyst, the method comprising:

[0008] An alkali metal salt is co-precipitated with a metal precursor, followed by aging to obtain a precipitate; wherein the alkali metal salt includes soluble sodium salt and soluble potassium salt, and the metal precursor includes iron precursor, manganese precursor and copper precursor.

[0009] The precipitate is filtered, and the resulting filter cake is washed, then dried and calcined.

[0010] The washing process uses deionized water, and the volume ratio of filter cake to deionized water is 1:5-20.

[0011] The third aspect of the present invention provides the application of the iron-based catalyst as described in the first aspect above or the iron-based catalyst prepared by the preparation method described in the second aspect above in the preparation of olefins by hydrogenation of carbon monoxide.

[0012] A fourth aspect of the present invention provides a method for preparing olefins by hydrogenation of carbon monoxide, the method comprising:

[0013] In the presence of an iron-based catalyst, carbon monoxide is hydrogenated to obtain an olefin; wherein the iron-based catalyst is the iron-based catalyst described in the first aspect above or the iron-based catalyst prepared by the preparation method described in the second aspect above.

[0014] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0015] (1) The iron-based catalyst provided by the present invention, by simultaneously controlling the total weight of Na and K and the weight ratio of Na and K within the above range, enables the iron-based catalyst to have high activity, high carbon monoxide conversion rate and high olefin selectivity, and can be used for carbon monoxide hydrogenation reaction.

[0016] (2) By adjusting the ratio of Na and K in the precipitant solution and the washing process conditions of the precipitate filter cake, the present invention can change the content and ratio of Na and K in the catalyst, so that the iron-based catalyst can be prepared in the fixed-bed Fischer-Tropsch synthesis reaction, while ensuring a high carbon monoxide conversion rate and a high olefin selectivity, and no deactivation phenomenon occurs during the reaction process of at least 500h, and the reaction stability is greatly improved.

[0017] (3) The iron-based catalyst provided by the present invention has a short synthesis cycle, simple manufacturing process, cheap and readily available catalyst raw materials, lower catalyst synthesis cost, and generates very little waste in the entire manufacturing process, making it more environmentally friendly and suitable for industrial production. Attached Figure Description

[0018] Figure 1 The graph shows the CO conversion rate of the catalysts prepared in Examples 1-2 and Comparative Examples 1-2 as a function of operating time. Detailed Implementation

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] The first aspect of the present invention provides an iron-based catalyst comprising Fe, Cu, Mn, Na and K, wherein the total weight of Na and K accounts for 1-3 wt% of the total weight of the iron-based catalyst; and the weight ratio of Na to K is 1:0.1-10.

[0021] According to the present invention, by simultaneously controlling the total weight of Na and K and the weight ratio of Na and K within the above-mentioned range, the iron-based catalyst can exhibit high activity, high carbon monoxide conversion rate, and high olefin selectivity.

[0022] According to a preferred embodiment of the present invention, the total weight of Na and K accounts for 1.5-2.5 wt% of the total weight of the iron-based catalyst.

[0023] According to a preferred embodiment of the present invention, the weight ratio of Na to K is 1:0.5-5.

[0024] According to the present invention, by simultaneously controlling the total weight of Na and K and the weight ratio of Na and K within the above-mentioned range, the activity and olefin selectivity of the iron-based catalyst can be further improved.

[0025] According to a preferred embodiment of the present invention, based on the total weight of the iron-based catalyst, the weight content of Fe is 88-97%, the weight content of Na is 0.1-2%, the weight content of K is 0.1-2%, the weight content of Mn is 4-8%, and the weight content of Cu is 0.5-1.5%.

[0026] According to a preferred embodiment of the present invention, based on the total weight of the iron-based catalyst, the weight content of Fe is 90-95%, the weight content of Na is 0.3-1.5%, the weight content of K is 0.3-1.5%, the weight content of Mn is 5-7%, and the weight content of Cu is 0.7-1.3%.

[0027] According to a preferred embodiment of the present invention, the D50 particle size of the iron-based catalyst is 2-6 nm, preferably 3-5 nm.

[0028] According to a preferred embodiment of the present invention, the iron-based catalyst has a specific surface area of ​​100-180 m². 2 / g, preferably 120-150m 2 / g.

[0029] According to a preferred embodiment of the present invention, the pore volume of the iron-based catalyst is 0.05-0.1 m³. 3 / g, preferably 0.06-0.08m 3 / g.

[0030] A second aspect of the present invention provides a method for preparing an iron-based catalyst, the method comprising:

[0031] An alkali metal salt is co-precipitated with a metal precursor, followed by aging to obtain a precipitate; wherein the alkali metal salt includes soluble sodium salt and soluble potassium salt, and the metal precursor includes iron precursor, manganese precursor and copper precursor.

[0032] The precipitate is filtered, and the resulting filter cake is washed, then dried and calcined.

[0033] The washing process uses deionized water, and the volume ratio of filter cake to deionized water is 1:5-20.

[0034] According to the present invention, the Na and K contents are controlled by washing the catalyst filter cake obtained by vacuum filtration. The purpose of washing is to remove excess K and Na ions from the catalyst using deionized water, so that the K / Na ratio reaches a specific value.

[0035] According to a preferred embodiment of the present invention, the soluble sodium salt is selected from at least one of sodium carbonate, sodium chloride, and sodium hydroxide.

[0036] According to a preferred embodiment of the present invention, the soluble potassium salt is selected from at least one of potassium carbonate, potassium chloride, and potassium hydroxide.

[0037] According to a preferred embodiment of the present invention, the iron precursor is selected from one or more of ferric nitrate, ferric carbonate, ferric bicarbonate and ferric chloride.

[0038] According to a preferred embodiment of the present invention, the manganese precursor is selected from one or more of manganese nitrate, manganese carbonate, manganese bicarbonate and manganese chloride.

[0039] According to a preferred embodiment of the present invention, the copper precursor is selected from a variety of copper nitrate, copper carbonate, copper bicarbonate and copper chloride and their hydrates.

[0040] According to a preferred embodiment of the present invention, the conditions for the coprecipitation reaction include: a temperature of 50-70°C, a time of 2-5 hours, and a pH of 6-10.

[0041] According to the present invention, controlling the stirring rate to 650-680 r / min during the coprecipitation reaction can better achieve coprecipitation.

[0042] According to a preferred embodiment of the present invention, the aging conditions include: a temperature of 20-40°C and a time of 10-20 hours.

[0043] Preferably, the aging conditions include: a temperature of 25-30°C and a time of 12-14 hours, more preferably aging at room temperature for 12 hours.

[0044] According to a preferred embodiment of the present invention, the conditions for the filtration include: a temperature of 20-40°C, a pressure of 0.01-0.1 MPa, and a time of 3-5 hours.

[0045] Preferably, the filtration conditions include: a temperature of 25-30℃, a pressure of 0.05-0.09MPa, and a time of 3.5-4.5h.

[0046] According to a preferred embodiment of the present invention, the washing temperature is 50-70°C, preferably 60-65°C.

[0047] According to the present invention, qualitative filter paper with a pore size of 100-110 micrometers (preferably 102 micrometers) is used, and the filter is subjected to a filtration pressure of 0.01-0.1 MPa for 3-5 hours. Then, the content of Na and K is adjusted by washing the catalyst filter cake obtained by filtration so that the K / Na ratio reaches a specific value.

[0048] According to a preferred embodiment of the present invention, the calcination conditions include: a temperature of 300-500°C and a time of 1-4 hours.

[0049] Preferably, the roasting conditions include: a temperature of 340-400℃ and a time of 2-3 hours.

[0050] The third aspect of the present invention provides the application of the iron-based catalyst as described in the first aspect above or the iron-based catalyst prepared by the preparation method described in the second aspect above in the preparation of olefins by hydrogenation of carbon monoxide.

[0051] According to this invention, by adjusting the ratio of Na and K in the precipitant solution and the washing process conditions of the precipitate filter cake, the content and ratio of Na and K in the catalyst can be changed, so that the prepared iron-based catalyst can be used in fixed-bed Fischer-Tropsch synthesis reactions, even when using synthesis gas with an H / C ratio of 1.5-4.0. At an H / C ratio of 4, the CH4 selectivity (0.5-1 cmol%) is very low, while the CO2 selectivity (4-7 cmol%), low-carbon olefins (15-30 cmol%), and all α-olefins (C2-C30 terminal olefins) are also high. Selectivity (60-75 Cmol%); at H / C ratio of 1.5, CO2 selectivity (3-6 Cmol%) was obtained, CH4 selectivity (0.4-0.8 Cmol%), low-carbon olefin selectivity (15-25 Cmol%), and all-α-olefin (C2-C30 terminal olefin) selectivity (55-70 Cmol%). While ensuring a high carbon monoxide conversion rate, no deactivation was observed during the reaction process of at least 500 h, and the reaction stability was greatly improved.

[0052] A fourth aspect of the present invention provides a method for preparing olefins by hydrogenation of carbon monoxide, the method comprising:

[0053] In the presence of an iron-based catalyst, carbon monoxide is hydrogenated to obtain an olefin; wherein the iron-based catalyst is the iron-based catalyst described in the first aspect above or the iron-based catalyst prepared by the preparation method described in the second aspect above.

[0054] According to a preferred embodiment of the present invention, the space velocity of the syngas is 5000-14000 mL·g during the reaction with the iron-based catalyst. -1 ·h -1 .

[0055] According to a preferred embodiment of the present invention, the conditions for the hydrogenation reaction include: a temperature of 250-350°C and a pressure of 2-5 MPa.

[0056] Preferably, the conditions for the hydrogenation reaction include: a temperature of 275-325°C and a pressure of 3-4 MPa.

[0057] According to a particularly preferred embodiment of the present invention, the preparation method of potassium and sodium modified iron-based catalyst (1.5% K-0.5% Na-Mn-Cu-Fe) specifically includes the following steps:

[0058] (1) Weigh out Fe(NO)3·9H2O, Mn(NO)3·solution and Cu(NO)2·3H2O according to the proportion and dissolve them in deionized water. Stir magnetically to make them completely dissolved. This is called the precipitate.

[0059] (2) Dissolve Na2CO3 and K2CO3 in deionized water and stir magnetically to completely dissolve them to obtain a precipitant;

[0060] (3) Place the above-mentioned precipitate and precipitant into titration bottles, fix them on an iron stand, and introduce the lower end into a beaker (placed in a water bath, pre-filled with deionized water). Control the titration temperature, pH and stirrer speed to 650-680 r / min. Start with a slightly lower speed. After the precipitate salt has completely precipitated, continue stirring for half an hour to make the precipitation uniform. Finally, age the precipitate at room temperature.

[0061] (4) Transfer the aged precipitate to a Buchner funnel for filtration, then wash the filter cake with deionized water; dry the obtained filter cake under set conditions.

[0062] (5) The dried catalyst is ground and then calcined to obtain Na-K-Fe-Mn-Cu catalyst.

[0063] The present invention will be described in detail below through examples. Unless otherwise specified in the following examples and comparative examples, conditions were performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0064] CO conversion rate and CO2 selectivity were obtained by detection and calculation using a thermal conductivity detector (TCD) with a Carboxen column.

[0065] CH4 selectivity and all-olefin selectivity were determined by detection and calculation using a flame ionization detector (FID) equipped with an alumina S-column.

[0066] Stability of iron-based catalysts: CO conversion rate remains stable within the ideal range for a long period of time.

[0067] Example 1

[0068] The preparation method of potassium and sodium modified iron-based catalyst (1.5% K-0.5% Na-Mn-Cu-Fe) includes the following steps:

[0069] ① Weigh out 0.06 mol Fe(NO)3·9H2O (24.24 g, Macklin), 0.0054 mol Mn(NO)3·solution (1.9326 g 50 wt%, AR 1.24 mL) and 0.0006 mol Cu(NO)2·3H2O (0.1450 g) according to the proportions and dissolve them in 540 mL of deionized water. Stir magnetically for 10 min until completely dissolved. This solution is called the precipitate.

[0070] ② Weigh 7.670g Na2CO3 and 10g K2CO3 and dissolve them in 240mL deionized water. Stir magnetically for 10min until completely dissolved to obtain a precipitant.

[0071] ③ Place the above-mentioned precipitate and precipitant into separate titration bottles, fix them on an iron stand, and introduce the lower end into a beaker (placed in a water bath, pre-filled with 540ml of deionized water). Control the titration temperature at 60℃, pH at 8.0, and the stirrer speed at 650-680r / min. Start with a slightly lower speed and continue stirring for half an hour after the precipitate salt has completely precipitated to ensure uniform precipitation. Finally, age the precipitate at room temperature for 12 hours.

[0072] ④ Transfer the aged precipitate to a Buchner funnel for filtration, then wash the filter cake with 400 mL of deionized water at 60°C; dry the obtained filter cake under the set conditions (120°C, 12 h).

[0073] ⑤ Grind the dried material from step ④ into powder and calcine it at 350℃ for 2 hours to obtain a 1.5% K-0.5% Na-Mn-Cu-Fe catalyst.

[0074] Based on the total weight of the iron-based catalyst, the analysis revealed that the Fe content was 91.1%, the Na content was 0.5%, the K content was 1.5%, the Mn content was 6.2%, and the Cu content was 0.7%.

[0075] Example 2

[0076] ① Weigh out 0.06 mol Fe(NO)3·9H2O (24.24 g, Macklin), 0.0054 mol Mn(NO)3·solution (1.9326 g 50 wt%, AR 1.24 mL) and 0.0006 mol Cu(NO)2·3H2O (0.1450 g) according to the proportions and dissolve them in 540 mL of deionized water. Stir magnetically for 10 min until completely dissolved. This solution is called the precipitate.

[0077] ② Weigh 7.670g Na2CO3 and 10g K2CO3 and dissolve them in 240mL deionized water. Stir magnetically for 10min until completely dissolved to obtain a precipitant.

[0078] ③ Place the above-mentioned precipitate and precipitant into separate titration bottles, fix them on an iron stand, and introduce the lower end into a beaker (placed in a water bath, pre-filled with 540ml of deionized water). Control the titration temperature at 65℃, the pH at 8.5, and the stirrer speed at 650-680r / min. Start with a slightly lower speed, and continue stirring for half an hour after the precipitate salt has completely precipitated to ensure uniform precipitation. Finally, age the precipitate at room temperature for 13 hours.

[0079] ④ Transfer the aged precipitate to a Buchner funnel for filtration, then wash the filter cake with 450 mL of deionized water at 60°C; dry the obtained filter cake under the set conditions (120°C, 12 h).

[0080] ⑤ Grind the dried material from step ④ into powder and calcine it at 350℃ for 2 hours to obtain a 1.2% K-0.7% Na-Mn-Cu-Fe catalyst.

[0081] Based on the total weight of the iron-based catalyst, the analysis revealed that the Fe content was 91.3%, the Na content was 0.7%, the K content was 1.2%, the Mn content was 5.8%, and the Cu content was 1%.

[0082] Example 3

[0083] The method is the same as in Example 1, except that: ④ the aged precipitate is transferred to a Buchner funnel for filtration, and then the filter cake is washed with 300 mL of deionized water at 60°C; the obtained filter cake is dried under set conditions (120°C, 12 h).

[0084] ⑤ Grind the dried material from step ④ into powder and calcine it at 350℃ for 2 hours. A 1.8% K-0.7% Na-Mn-Cu-Fe catalyst is obtained.

[0085] Based on the total weight of the iron-based catalyst, the analysis revealed that the Fe content was 91%, the Na content was 0.7%, the K content was 1.8%, the Mn content was 5.5%, and the Cu content was 1%.

[0086] Example 4

[0087] Following the method of Example 1, except that 10.226 g of Na2CO3 and 6.667 g of K2CO3 were weighed, while the other steps were the same, to obtain a 0.7% K-2.1% Na-Mn-Cu-Fe catalyst.

[0088] Based on the total weight of the iron-based catalyst, the analysis revealed that the Fe content was 89.5%, the Na content was 2.1%, the K content was 0.7%, the Mn content was 6.5%, and the Cu content was 1.2%.

[0089] Example 5

[0090] Following the method of Example 1, except that 5.113g of Na2CO3 and 13.333g of K2CO3 were weighed, while the other steps were the same, to obtain a 0.8%K-0.4%Na-Mn-Cu-Fe catalyst.

[0091] Based on the total weight of the iron-based catalyst, the analysis revealed that the Fe content was 90%, the Na content was 0.4%, the K content was 0.8%, the Mn content was 7.3%, and the Cu content was 1.5%.

[0092] Example 6

[0093] The method of Example 4 was followed, except that the filter cake was washed with 500 mL of deionized water, while the other steps were the same, to obtain a 1.2% K-0.4% Na-Mn-Cu-Fe catalyst.

[0094] Based on the total weight of the iron-based catalyst, the analysis revealed that the Fe content was 92.4%, the Na content was 0.4%, the K content was 1.0%, the Mn content was 4.8%, and the Cu content was 1.4%.

[0095] Comparative Example 1

[0096] ① Weigh out 0.06 mol Fe(NO)3·9H2O (24.24 g, Macklin), 0.0054 mol Mn(NO)3·solution (1.9326 g 50 wt%, AR 1.24 mL) and 0.0006 mol Cu(NO)2·3H2O (0.1450 g) according to the proportions and dissolve them in 540 mL of deionized water. Stir magnetically for 10 min until completely dissolved. This solution is called the precipitate.

[0097] ② Weigh 17.670g of K2CO3 and dissolve it in 240mL of deionized water. Stir magnetically for 10min until it is completely dissolved to obtain a precipitant.

[0098] ③ Place the above-mentioned precipitate and precipitant into separate titration bottles, fix them on an iron stand, and introduce the lower end into a beaker (placed in a water bath, pre-filled with 540ml of deionized water). Control the titration temperature at 60℃, pH at 8.0, and the stirrer speed at 650-680r / min. Start with a slightly lower speed and continue stirring for half an hour after the precipitate salt has completely precipitated to ensure uniform precipitation. Finally, age the precipitate at room temperature for 12 hours.

[0099] ④ Transfer the aged precipitate to a Buchner funnel for filtration, then wash the filter cake with 400 mL of deionized water at 60°C; dry the obtained filter cake under the set conditions (120°C, 12 h).

[0100] ⑤ Grind the dried material from step ④ and calcine it at 350℃ for 2 hours. A 2% K-Mn-Cu-Fe catalyst is obtained.

[0101] Based on the total weight of the iron-based catalyst, the analysis revealed that the Fe content was 91.1%, the K content was 2%, the Mn content was 6.2%, and the Cu content was 0.7%.

[0102] Comparative Example 2

[0103] ① Weigh out 0.06 mol Fe(NO)3·9H2O (24.24 g, Macklin), 0.0054 mol Mn(NO)3·solution (1.9326 g 50 wt%, AR 1.24 mL) and 0.0006 mol Cu(NO)2·3H2O (0.1450 g) according to the proportions and dissolve them in 540 mL of deionized water. Stir magnetically for 10 min until completely dissolved. This solution is called the precipitate.

[0104] ② Weigh 17.670g of Na2CO3 and dissolve it in 240mL of deionized water. Stir magnetically for 10min until it is completely dissolved to obtain a precipitant.

[0105] ③ Place the above-mentioned precipitate and precipitant into separate titration bottles, fix them on an iron stand, and introduce the lower end into a beaker (placed in a water bath, pre-filled with 540ml of deionized water). Control the titration temperature at 60℃, pH at 8.0, and the stirrer speed at 650-680r / min. Start with a slightly lower speed and continue stirring for half an hour after the precipitate salt has completely precipitated to ensure uniform precipitation. Finally, age the precipitate at room temperature for 12 hours.

[0106] ④ The aged precipitate was transferred to a Buchner funnel and filtered, then the filter cake was washed with 400 mL of deionized water at 60 °C; the obtained filter cake was dried under set conditions (120 °C, 12 h). ⑤ The dried material from step ④ was ground into powder and calcined at 350 °C for 2 h to obtain a 2% Na-Mn-Cu-Fe catalyst.

[0107] Based on the total weight of the iron-based catalyst, the analysis revealed that the Fe content was 91.1%, the Na content was 2%, the Mn content was 6.2%, and the Cu content was 0.7%.

[0108] Comparative Example 3

[0109] ① Weigh out 0.06 mol Fe(NO)3·9H2O (24.24 g, Macklin), 0.0054 mol Mn(NO)3·solution (1.9326 g 50 wt%, AR 1.24 mL) and 0.0006 mol Cu(NO)2·3H2O (0.1450 g) according to the proportions and dissolve them in 540 mL of deionized water. Stir magnetically for 10 min until completely dissolved. This solution is called the precipitate.

[0110] ② Weigh 7.670g Na2CO3 and 10g K2CO3 and dissolve them in 240mL deionized water. Stir magnetically for 10min until completely dissolved to obtain a precipitant.

[0111] ③ Place the above-mentioned precipitate and precipitant into separate titration bottles, fix them on an iron stand, and introduce the lower end into a beaker (placed in a water bath, pre-filled with 540ml of deionized water). Control the titration temperature at 60℃, pH at 8.0, and the stirrer speed at 650-680r / min. Start with a slightly lower speed and continue stirring for half an hour after the precipitate salt has completely precipitated to ensure uniform precipitation. Finally, age the precipitate at room temperature for 12 hours.

[0112] ④ Transfer the aged precipitate to a Buchner funnel for filtration, and dry the resulting filter cake under set conditions (120℃, 12h).

[0113] ⑤ Grind the dried material from step ④ into powder and calcine it at 350℃ for 2 hours. A 14% K-6% Na-Mn-Cu-Fe catalyst is obtained.

[0114] Based on the total weight of the iron-based catalyst, the analysis revealed that the Fe content was 67%, the Na content was 6%, the K content was 14%, the Mn content was 8%, and the Cu content was 5%.

[0115] Application Example 1

[0116] Weigh 0.5g of the catalysts prepared in Examples 1-6 and Comparative Examples 1-3 respectively, and press them at 5-20MPa for 10-30min; then crush and sieve to obtain 20-40 mesh catalyst particles, and mechanically mix them with 1.0g of quartz sand particles pretreated by calcination at 400℃ for 2h and sieved to 20-40 mesh, and then load them into a fixed-bed reactor; introduce pure hydrogen gas at a flow rate of 40mL / min and feed gas (H2 / CO molar ratio of 3, containing 5% argon as a raw material) at a flow rate of 10mL / min. The catalyst was heated to 275°C (internal standard) at a heating rate of 2°C / min and reduced in situ for 10 h. After reduction, it was cooled to room temperature under a N2 atmosphere at a heating rate of 20 mL / min. Before the carbon monoxide hydrogenation reaction, the feed gas was switched to (H2 / CO molar ratio of 3, containing 5% argon as an internal standard), and the reactor pressure was adjusted to 3 MPa. Then, the temperature of the reaction tube was raised to 275°C at a heating rate of 10°C / min, and the carbon dioxide hydrogenation performance of the catalyst was tested. The reaction space velocity (GHSV) was 6500 mL·h. -1 ·g -1The test was performed from the start of the reaction, and then every hour thereafter. The reaction ran for 50 hours. After removing the first hour, the average value of the entire reaction was taken as the test result of the catalyst, as shown in Table 1.

[0117] Table 1

[0118]

[0119] As can be seen from the results in Table 1, the catalysts obtained using Examples 1-6 and Comparative Examples 1-3 have higher all-olefin selectivity and CO conversion than those using Comparative Examples 1-3. Furthermore, the catalysts prepared using the present invention have lower CO2 selectivity and CH4 selectivity, higher CO conversion, and stronger stability over long-term reactions.

[0120] Based on the test results of Examples 1-2 and Comparative Examples 1-2 after running for 50 hours, the following results were obtained: Figure 1 The graph shown illustrates the change in CO conversion rate of the catalyst over operating time. Figure 1 It can be seen that the CO conversion rate of the catalysts obtained in Examples 1 and 2 did not change much with the reaction time during the 50-hour reaction process. The conversion rate was almost unaffected and even improved during the 50-hour reaction process, indicating good stability.

[0121] Application Example 2

[0122] Weigh 0.5g of the catalyst prepared in Example 1 above and press it at 10MPa for 20min; then crush and sieve to obtain 30-mesh catalyst particles, and mechanically mix them with 1.0g of quartz sand particles that have been pretreated by calcination at 400℃ for 2h and sieved to 30-mesh. The mixture is then loaded into a fixed-bed reactor. Pure hydrogen is introduced at a flow rate of 40mL / min, and feed gas (H2 / CO molar ratio of 3, containing 5% argon as an internal standard) is introduced at a flow rate of 10mL / min, while the flow rate is 2℃ / min. The heating rate of n was increased to 275℃ for in-situ reduction for 10 h; after reduction, it was cooled to room temperature under a N2 atmosphere at a rate of 20 mL / min; before the carbon monoxide hydrogenation reaction, the feed gas was switched to (H2 / CO molar ratio of 2, containing 5% argon as an internal standard), and the reactor pressure was adjusted to 3 MPa; then, the temperature of the reaction tube was increased to 275℃ at a heating rate of 10℃ / min, and the carbon dioxide hydrogenation performance of the catalyst was tested, with a reaction space velocity (GHSV) of 13000 mL·h. -1 ·g -1 The test was conducted from the start of the reaction, and then every hour thereafter. The reaction ran for 50 hours. After removing the first hour, the average value of the entire reaction was taken as the test result of the catalyst, as shown in Table 2.

[0123] Table 2

[0124]

[0125] With an H2 / CO molar ratio of 2 and a reaction space velocity (GHSV) of 13000 mL·h, -1 ·g -1 Under the reaction conditions described in Example 1, the all-olefin selectivity of the catalyst was further enhanced, and the average conversion rate remained stable at over 60%.

[0126] As can be seen from the above, the catalyst prepared by the method of the present invention can not only be applied to the conventional carbon monoxide hydrogenation reaction, but also adapt to high space velocity reaction processes.

[0127] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An iron-based catalyst, characterized in that, The iron-based catalyst comprises Fe, Cu, Mn, Na and K, wherein the total weight of Na and K accounts for 1-3 wt% of the total weight of the iron-based catalyst; the weight ratio of Na to K is 1:0.1-10.

2. The iron-based catalyst according to claim 1, wherein, The total weight of Na and K accounts for 1.5-2.5 wt% of the total weight of the iron-based catalyst; And / or, the weight ratio of Na to K is 1:0.5-5.

3. The iron-based catalyst according to claim 1 or 2, wherein, Based on the total weight of the iron-based catalyst, the weight content of Fe is 88-97%, the weight content of Na is 0.1-2%, the weight content of K is 0.1-2%, the weight content of Mn is 4-8%, and the weight content of Cu is 0.5-1.5%. Preferably, based on the total weight of the iron-based catalyst, the weight content of Fe is 90-95%, the weight content of Na is 0.3-1.5%, the weight content of K is 0.3-1.5%, the weight content of Mn is 5-7%, and the weight content of Cu is 0.7-1.3%.

4. The iron-based catalyst according to any one of claims 1-3, wherein, The D50 particle size of the iron-based catalyst is 2-6 nm, preferably 3-5 nm; And / or, the specific surface area of ​​the iron-based catalyst is 100-180 m². 2 / g, preferably 120-150m 2 / g; And / or, the pore volume of the iron-based catalyst is 0.05-0.1 m³. 3 / g, preferably 0.06-0.08m 3 / g.

5. A method for preparing an iron-based catalyst, characterized in that, The preparation method includes: An alkali metal salt is co-precipitated with a metal precursor, followed by aging to obtain a precipitate; wherein the alkali metal salt includes soluble sodium salt and soluble potassium salt, and the metal precursor includes iron precursor, manganese precursor and copper precursor. The precipitate is filtered, and the resulting filter cake is washed, then dried and calcined. The washing process uses deionized water, and the volume ratio of filter cake to deionized water is 1:5-20.

6. The preparation method according to claim 5, wherein, The soluble sodium salt is selected from at least one of sodium carbonate, sodium chloride, and sodium hydroxide; And / or, the soluble potassium salt is selected from at least one of potassium carbonate, potassium chloride, and potassium hydroxide; And / or, the iron precursor is selected from one or more of ferric nitrate, ferric carbonate, ferric bicarbonate and ferric chloride; And / or, the manganese precursor is selected from one or more of manganese nitrate, manganese carbonate, manganese bicarbonate and manganese chloride; And / or, the copper precursor is selected from a plurality of copper nitrate, copper carbonate, copper bicarbonate and copper chloride.

7. The preparation method according to claim 5 or 6, wherein, The conditions for the coprecipitation reaction include: a temperature of 50-70℃, a time of 2-5 hours, and a pH of 6-10. And / or, the aging conditions include: a temperature of 20-40°C; and a time of 10-20 hours; And / or, the filtration conditions include: a temperature of 20-40℃, a pressure of 0.01-0.1MPa, and a time of 3-5h; And / or, the washing temperature is 50-70°C; And / or, the calcination conditions include: a temperature of 300-500℃; and a time of 1-4h.

8. The use of the iron-based catalyst according to any one of claims 1-4 or the iron-based catalyst prepared by the preparation method according to any one of claims 5-7 in the preparation of olefins by hydrogenation of carbon monoxide.

9. A method for preparing olefins by hydrogenation of carbon monoxide, characterized in that, The method includes: In the presence of an iron-based catalyst, carbon monoxide is hydrogenated to obtain an olefin; wherein the iron-based catalyst is the iron-based catalyst according to any one of claims 1-4 or the iron-based catalyst prepared by the preparation method according to any one of claims 5-7.

10. The method according to claim 9, wherein, During the reaction with the iron-based catalyst, the space velocity of the syngas is 5000-14000 mL·g. -1 ·h -1 ; And / or, the conditions for the hydrogenation reaction include: a temperature of 250-350°C; and a pressure of 2-5 MPa.

Images