Synthesis gas to olefin catalyst, method for preparing the same, and use thereof

Abstract

The application discloses a synthesis gas to olefin catalyst as well as a preparation method and application thereof. The synthesis gas to olefin catalyst comprises a carrier, an active component and a modified component which are loaded on the carrier. The carrier is a biochar-clay-based composite carrier. The active component is iron. The modified component is gallium or indium. The catalyst is applied to a catalytic synthesis gas to olefin reaction, can significantly enhance the adsorption and activation capacity of CO molecules, has high CO conversion rate and excellent olefin selectivity, reduces the dependence on fossil energy, and has sustainable economic benefits.

Description

Technical Field

[0001] This invention relates to the field of catalytic conversion of syngas to olefins, and more particularly to a syngas-to-olefins catalyst, its preparation method, and its application. Background Technology

[0002] Against the backdrop of dual carbon emissions, due to the depletion of fossil fuels and ecological climate change, syngas-to-olefins (STO) has attracted increasing attention from industry and academia in recent years. Syngas (CO / H2) can be extracted from coal, natural gas, or biomass resources. Using syngas as a raw material, olefins are produced through Fischer-Tropsch synthesis (FTS) under the action of a catalyst. This is an important non-petroleum route for producing liquid fuels and various value-added chemicals, and it has good economic benefits.

[0003] Current research indicates that common FTS catalysts include iron, cobalt, and ruthenium. Iron-based catalysts have attracted significant attention in the FTS field due to their lower cost, superior activity, and high operational flexibility. Besides the role of the active metal, the support is also crucial to the performance of FTS catalysts. Commonly used supports include Al₂O₃, SiO₂, TiO₂, and carbon materials. Compared to oxide supports, carbon supports have a larger surface area, more porous structures, and richer surface chemistry, which is beneficial for dispersing the active metal. Furthermore, carbon materials have an inert structure and weaker interactions with metal precursors, making it easier to induce the reduction of iron oxides, thereby promoting the formation of the iron carbide active phase.

[0004] Biomass' rich carbon content, sustainability, and renewability make it an ideal raw material for producing renewable carbon materials. However, problems such as poor stability due to metal-support interactions, high cost, catalyst agglomeration, and sintering limit the use of carbon supports. Therefore, exploring novel carbon materials with tunable metal-support interactions and low cost is crucial to achieving better FTS performance. Summary of the Invention

[0005] The main objective of this invention is to provide a syngas-to-olefins catalyst with better catalytic effect, greener and lower cost, as well as its preparation method and application.

[0006] To achieve the above objectives, the present invention provides a syngas-to-olefins catalyst, comprising a support and an active component and a modified component supported on the support, wherein the support is a biochar-clay-based composite support, the active component is iron, and the modified component is gallium or indium.

[0007] Furthermore, the iron content is 1–15 wt.%, the gallium content is 1–3 wt.%, and the indium content is 1–3 wt.%.

[0008] Furthermore, some of the iron exists in the form of iron carbide, and the active phase is any one or a mixture of two or more of χ-Fe5C2, θ-Fe3C, and ε-Fe2C. Here, "some" has no limitation on content; it is sufficient that iron exists in the form of iron carbide.

[0009] Furthermore, the biochar raw material is any one or more of wheat straw, corn cobs, and rice husks mixed in any proportion, and the clay is attapulgite or sepiolite.

[0010] The present invention also provides a method for preparing the above-mentioned syngas-to-olefins catalyst, comprising the following steps:

[0011] (1) Preparation of the carrier

[0012] Biochar-clay-based composite carriers are synthesized by hydrothermal treatment of biological raw materials and clay, followed by pyrolysis treatment coupled with metal ion pore-expansion method.

[0013] (2) Component loading

[0014] Iron precursor salts, gallium or indium precursor salts are loaded onto a biochar-clay-based composite support using an impregnation method to obtain catalyst precursors;

[0015] (3) Calcination of precursors

[0016] The catalyst precursor was subjected to reduction-carburizing coupled high-temperature calcination to obtain the syngas-to-olefins catalyst.

[0017] Furthermore, the specific process of step (1) is as follows:

[0018] 1.1) Mix biomass powder and clay powder at a mass ratio of 1 to 5:1, dry at 100 to 120°C for 12 to 24 hours, add deionized water, transfer to a high-pressure reactor, purge with 1 MPa nitrogen, and hydrothermally heat at 160 to 180°C for 4 to 8 hours. After filtration and washing, obtain a hydrothermal mixture of biomass and clay.

[0019] 1.2) The hydrothermal mixture was added to a CuCl2 solution with a concentration of 5-20%, stirred at room temperature for 5-10 h, then filtered and washed, and dried at 100-120℃ for 10-12 h to obtain biochar-clay precursor;

[0020] 1.3) The biochar-clay precursor was immersed in a 0.05-0.3M HCl solution and stirred at room temperature for 4-8 hours. Then it was washed with deionized water until the pH value reached 6-7, dried at 100-120℃ for 10-12 hours, and finally carbonized at 500-600℃ for 1-4 hours under a nitrogen atmosphere with a heating rate of 2-6℃ / min to obtain the carbonized body.

[0021] 1.4) The carbonized body is immersed in 0.5-2M NaOH solution, boiled for 1-2 hours, then washed with deionized water and ethanol in sequence until the pH value reaches 6-7, and dried at 100-120℃ for 10-12 hours to obtain the biochar-clay-based composite carrier.

[0022] Further, the specific process of step (2) is as follows: iron precursor salt and gallium or indium precursor salt are dissolved in deionized water, biochar-clay-based composite support is added, and the mixture is stirred at room temperature for 8 to 12 hours. Then, the water is evaporated at 80 to 120°C, dried at 105°C for 10 to 12 hours, and finally calcined at 350 to 450°C for 3 to 6 hours under a nitrogen atmosphere at a heating rate of 2 to 6°C / min to obtain the catalyst precursor.

[0023] Further, the specific process of step (3) is as follows: the catalyst precursor and inert silica are mixed at a mass ratio of 1:3 to 10, ground evenly, and then loaded into a reactor. First, the temperature is raised to 350 to 450°C for 4 to 8 hours under a 10 vol% H2 / N2 atmosphere at a heating rate of 1 to 5°C / min. Then, the temperature is adjusted to 280 to 320°C, and in-situ carbonization is carried out for 4 to 10 hours under a 20 to 40 mL / min atmosphere of 45% H2 / 45% CO / 10% N2 or 50% H2 / 25% CO / 25% N2 to obtain the syngas to olefins catalyst.

[0024] The present invention also provides the application of the above-mentioned syngas to olefins catalyst in the catalytic conversion of syngas to olefins.

[0025] This invention also provides a method for catalytic conversion of syngas to prepare olefins, using syngas as a raw material and adding the above-mentioned catalyst to carry out the reaction. The reaction conditions are: the molar ratio of H2 to CO in the syngas feed is 1-2, and the syngas feed space velocity is 12000-24000 mL·h. -1 ·g cat -1 The reaction temperature is 280–320℃.

[0026] Wheat straw, corn cobs, rice husks, and other biomass wastes are renewable resources with high carbon content, while clay is a low-cost, green, and natural mineral with good thermal stability and strong adsorption capacity. Using biomass wastes as a carbon source, biochar-clay-based composite carriers are synthesized under the action of metal chlorides and inorganic acids and bases. This process retains the porous structural stability of biomass wastes while optimizing the specific surface area and pore structure, which is beneficial for the high dispersion of iron, gallium, or indium metals and subsequent in-situ carburization to form a highly active iron carbide phase.

[0027] The beneficial effects of this invention are reflected in:

[0028] 1. The carrier raw materials used in this invention are biomass waste and clay, which are widely available and inexpensive. They are characterized by being green and economical, and having a stable porous structure. When applied to the catalytic conversion of syngas to olefins, the CO conversion rate exceeds 80% and the C2-C4 selectivity exceeds 20% in 100 hours of catalytic reaction. 5+ The selectivity exceeds 55%.

[0029] 2. The carrier used in this invention is a biochar-clay-based composite carrier prepared by hydrothermal treatment coupled with metal ion pore expansion method. It has abundant surface defects and high specific surface area, which is conducive to anchoring metal nanoparticles and promoting uniform dispersion of metal on the carrier. This facilitates CO adsorption and activation to synthesize highly dispersed iron carbide reactive sites during high-temperature carburizing.

[0030] 3. In the preparation of the carrier in this invention, the biomass and clay raw materials are first subjected to hydrothermal treatment to form a preliminary precursor, and then pore-expanding treatment is performed to increase the specific surface area and pore size of the precursor. Finally, the precursor structure is enhanced by calcination.

[0031] 4. Compared to other iron-based catalysts, the catalyst of this invention uses gallium or indium to modify the iron-based catalyst and constructs a biochar-clay-based composite support to enhance the interaction between the active component and the support; moreover, the support surface has abundant defects, which is conducive to the formation of highly dispersed active metal sites, enhancing the adsorption and activation of reactants. At the same time, the biochar-clay-based composite support has excellent electron accepting and donating capabilities, which is beneficial to the transfer of electrons between the support and the metal.

[0032] 5. When the catalyst described in this invention is applied to the catalytic synthesis gas to olefins reaction, it can significantly enhance the catalytic adsorption and activation ability of CO molecules, exhibit high CO conversion rate, excellent olefin selectivity, reduce dependence on fossil energy, and have sustainable economic benefits. Attached Figure Description

[0033] Figure 1 XRD pattern of biochar-clay-based composite carrier;

[0034] Figure 2 The N2 adsorption-desorption isotherm of the biochar-clay-based composite carrier;

[0035] Figure 3 This is a pore size distribution diagram of the biochar-clay-based composite carrier.

[0036] Figure 4 The FTIR spectrum of the biochar-clay-based composite support;

[0037] Figure 5SEM image of the biochar-clay-based composite carrier;

[0038] Figure 6 The XRD pattern of catalyst #2;

[0039] Figure 7 The carrier SEM image was obtained by omitting attapulgite. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, all raw materials used in the following embodiments are commercially available products known in the art.

[0041] Example 1

[0042] Preparation of catalysts for syngas to olefins

[0043] The syngas-to-olefins catalyst prepared in this embodiment has an iron content of 1 wt.%, a gallium content of 1 wt.%, and the balance is a biochar-clay-based composite support. The preparation method is as follows:

[0044] (1) Preparation of the carrier

[0045] 1.1) Mix wheat straw powder and attapulgite powder at a mass ratio of 3:1, dry them in an oven at 100℃ for 24h, then add 10 times the mass of deionized water, stir evenly, transfer to a high-pressure reactor, purge with 1MPa nitrogen, and hydrothermally heat at 160℃ for 8h. Afterwards, filter and wash with deionized water to obtain a hydrothermal mixture of biomass and clay.

[0046] 1.2) Take the hydrothermal mixture and add 5% CuCl2 solution at a ratio of 5 mL / g. Stir at room temperature for 10 h, then filter and wash with deionized water and ethanol in sequence, and dry in an oven at 100℃ for 12 h to obtain biochar-clay precursor.

[0047] 1.3) The biochar-clay precursor was immersed in 0.05M HCl solution and stirred at room temperature for 8 hours to remove residual chemical reagents. Then it was washed with deionized water until the pH value reached 6. It was dried in an oven at 100℃ for 12 hours. Finally, it was carbonized at 600℃ for 1 hour under a nitrogen atmosphere at a heating rate of 2℃ / min to obtain the carbonized body.

[0048] 1.4) The carbonized body was immersed in 0.5M NaOH solution and boiled for 2 hours. Then it was washed with deionized water and ethanol in sequence until the pH value reached 6. After drying in an oven at 100℃ for 12 hours, the biochar-clay-based composite carrier was obtained.

[0049] (2) Component loading

[0050] Weigh 0.0736 g of ferric nitrate nonahydrate and 0.0374 g of gallium nitrate hydrate (molecular weight: 255.74, the same below) and dissolve them in 100 mL of deionized water. After stirring at room temperature for 4 h, add 1 g of biochar-clay-based composite support and continue stirring for 8 h. Then evaporate the water at 90 °C and dry at 105 °C for 12 h. Finally, calcine at 400 °C for 4 h under a nitrogen atmosphere with a heating rate of 3 °C / min to obtain the catalyst precursor.

[0051] (3) Calcination of precursors

[0052] The catalyst precursor and inert silica were mixed at a mass ratio of 1:3, ground in the solid phase for 5 min, and then loaded into a vertical micro fixed-bed reactor. The reactor was first reduced to 450℃ at a heating rate of 2℃ / min for 4 h under a 10 vol% H2 / N2 atmosphere at a heating rate of 50 mL / min. Then the temperature of the reactor was adjusted to 320℃, and in-situ carburization was carried out for 10 h under a 50% H2 / 25% CO / 25% N2 atmosphere at a heating rate of 30 mL / min to obtain the syngas to olefins catalyst, designated as catalyst #2.

[0053] Example 2

[0054] Preparation of catalysts for syngas to olefins

[0055] The syngas-to-olefins catalyst prepared in this embodiment has an iron content of 5 wt.%, a gallium content of 2 wt.%, and the balance being a biochar-clay-based composite support. The preparation method is as follows:

[0056] (1) Preparation of the carrier

[0057] 1.1) Mix wheat straw powder and attapulgite powder at a mass ratio of 1:1, dry them in an oven at 105℃ for 18h, then add 10 times the mass of deionized water, stir evenly, transfer to a high-pressure reactor, purge with 1MPa nitrogen, and hydrothermally heat at 170℃ for 6h. Afterwards, filter and wash with deionized water to obtain a hydrothermal mixture of biomass and clay.

[0058] 1.2) Take the hydrothermal mixture and add 10% CuCl2 solution at a ratio of 5 mL / g. Stir at room temperature for 8 h, then filter and wash with deionized water and ethanol in sequence, and dry in an oven at 105℃ for 12 h to obtain biochar-clay precursor.

[0059] 1.3) The biochar-clay precursor was immersed in 0.1M HCl solution and stirred at room temperature for 5 hours to remove residual chemical reagents. Then it was washed with deionized water until the pH value reached 7. It was dried in an oven at 105℃ for 12 hours. Finally, it was carbonized at 600℃ for 2 hours under a nitrogen atmosphere at a heating rate of 5℃ / min to obtain the carbonized body.

[0060] 1.4) The carbonized body was immersed in 1M NaOH solution and boiled for 1 hour. Then it was washed with deionized water and ethanol in sequence until the pH value reached 7. After drying in an oven at 105℃ for 12 hours, the biochar-clay-based composite carrier was obtained.

[0061] (2) Component loading

[0062] Weigh 0.3879 g of ferric nitrate nonahydrate and 0.0789 g of gallium nitrate hydrate and dissolve them in 100 mL of deionized water. Stir at room temperature for 4 h and then add 1 g of biochar-clay-based composite support. Continue stirring for 8 h, then evaporate the water at 90 °C and dry at 105 °C for 12 h. Finally, calcine at 400 °C for 4 h under a nitrogen atmosphere at a heating rate of 3 °C / min to obtain the catalyst precursor.

[0063] (3) Calcination of precursors

[0064] The catalyst precursor and inert silica were mixed at a mass ratio of 1:4, ground in the solid phase for 5 min, and then loaded into a vertical micro fixed-bed reactor. The reactor was first reduced to 400℃ at a heating rate of 5℃ / min for 6 h under a 10 vol% H2 / N2 atmosphere at a heating rate of 40 mL / min. Then the temperature of the reactor was adjusted to 300℃, and in-situ carburization was carried out for 8 h under a 50% H2 / 25% CO / 25% N2 atmosphere at a heating rate of 20 mL / min to obtain the syngas to olefins catalyst, designated as catalyst #1.

[0065] Example 3

[0066] Preparation of catalysts for syngas to olefins

[0067] The syngas-to-olefins catalyst prepared in this embodiment has an iron content of 10 wt.%, a gallium content of 3 wt.%, and the balance being a biochar-clay-based composite support. The preparation method is as follows:

[0068] (1) Preparation of the carrier

[0069] 1.1) Mix wheat straw powder and attapulgite powder at a mass ratio of 5:1, dry them in an oven at 120℃ for 12h, then add 10 times the mass of deionized water, stir evenly, transfer to a high-pressure reactor, purge with 1MPa nitrogen, and hydrothermally heat at 180℃ for 4h. Afterwards, filter and wash with deionized water to obtain a hydrothermal mixture of biomass and clay.

[0070] 1.2) Take the hydrothermal mixture and add 20% CuCl2 solution at a ratio of 5 mL / g. Stir at room temperature for 5 h, then filter and wash with deionized water and ethanol in sequence, and dry in an oven at 120℃ for 10 h to obtain biochar-clay precursor.

[0071] 1.3) The biochar-clay precursor was immersed in 0.3M HCl solution and stirred at room temperature for 4 hours to remove residual chemical reagents. Then it was washed with deionized water until the pH value reached 7. It was dried in an oven at 120℃ for 10 hours. Finally, it was carbonized at 500℃ for 4 hours under a nitrogen atmosphere at a heating rate of 6℃ / min to obtain the carbonized body.

[0072] 1.4) The carbonized body was immersed in 2M NaOH solution and boiled for 1 hour. Then it was washed with deionized water and ethanol in sequence until the pH value reached 7. After drying in an oven at 120℃ for 10 hours, the biochar-clay-based composite carrier was obtained.

[0073] (2) Component loading

[0074] Weigh 0.8293 g of ferric nitrate nonahydrate and 0.1265 g of gallium nitrate hydrate and dissolve them in 100 mL of deionized water. Stir at room temperature for 4 h and then add 1 g of biochar-clay-based composite support. Continue stirring for 8 h, then evaporate the water at 90 °C and dry at 105 °C for 12 h. Finally, calcine at 400 °C for 4 h under a nitrogen atmosphere at a heating rate of 3 °C / min to obtain the catalyst precursor.

[0075] (3) Calcination of precursors

[0076] The catalyst precursor and inert silica were mixed at a mass ratio of 1:10, ground in the solid phase for 5 min, and then loaded into a vertical micro fixed-bed reactor. The reactor was first reduced to 350℃ at a heating rate of 3℃ / min for 8 h under a 10 vol% H2 / N2 atmosphere at a heating rate of 60 mL / min. Then, the reactor temperature was adjusted to 280℃, and in-situ carburization was carried out for 4 h under a 50% H2 / 25% CO / 25% N2 atmosphere at a heating rate of 40 mL / min to obtain the syngas to olefins catalyst, designated as catalyst #3.

[0077] Example 4

[0078] Preparation of catalysts for syngas to olefins

[0079] The preparation process of this embodiment is the same as that of embodiment 2, except that the content of the components is different. Specifically, the iron content is 1 wt.%, the indium content is 1 wt.%, and the balance is biochar-clay-based composite carrier; the raw material amount in step (2) is 0.0736 g of ferric nitrate nonahydrate, 0.0267 g of indium nitrate hydrate (molecular weight: 300.83, the same below) and 1 g of biochar-clay-based composite carrier. The catalyst obtained in this embodiment is catalyst number 4#.

[0080] Example 5

[0081] Preparation of catalysts for syngas to olefins

[0082] The preparation process of this embodiment is the same as that of embodiment 2, except that the content of the components is different. Specifically, the iron content is 5 wt.%, the indium content is 2 wt.%, and the balance is biochar-clay-based composite carrier; the amount of raw materials used in step (2) is 0.3879 g of ferric nitrate nonahydrate, 0.0562 g of indium nitrate hydrate and 1 g of biochar-clay-based composite carrier. The catalyst obtained in this embodiment is catalyst number 5#.

[0083] Example 6

[0084] Preparation of catalysts for syngas to olefins

[0085] The preparation process of this embodiment is the same as that of embodiment 2, except that the content of the components is different. Specifically, the iron content is 10 wt.%, the indium content is 3 wt.%, and the balance is biochar-clay-based composite carrier; the amount of raw materials used in step (2) is 0.8293 g of ferric nitrate nonahydrate, 0.0902 g of indium nitrate hydrate and 1 g of biochar-clay-based composite carrier. The catalyst obtained in this embodiment is catalyst number 6#.

[0086] Comparative Example 1

[0087] Preparation of catalysts for syngas to olefins

[0088] The preparation process of this comparative example is the same as that of Example 2, except that the gallium component is omitted. The catalyst obtained in this comparative example is numbered 1& catalyst.

[0089] Structural determination of syngas to olefins catalyst

[0090] Structural analysis was performed on the biochar-clay-based composite support and catalyst #2 prepared in Example 2, and the results are as follows: Figures 1 to 6 As shown.

[0091] See Figure 1Characteristic diffraction peaks corresponding to the carbon structure were detected at 2θ = 20.86°, 26.73°, 36.36°, 43.73°, 50.04° and 68.10° in the XRD pattern of the biochar-clay-based composite carrier, proving that carbon carriers can be successfully prepared using wheat straw, a biomass waste, as a carbon source.

[0092] See Figure 2 According to the IUPAC classification, the biochar-clay-based composite support exhibits a combination of Type I and Type II isotherms, accompanied by an H4-type hysteresis loop. This indicates that the synthesized biochar-clay-based composite support possesses a composite pore structure composed of ordered micropores and mesopores.

[0093] See Figure 3 The biochar-clay-based composite support exhibits a pore size distribution concentrated at 0.3 nm and 4.5 nm, further proving the existence of this microporous-mesoporous composite channel structure, which is beneficial for promoting the dispersion of active metals on the surface of the support and promoting reaction mass transfer.

[0094] See Figure 4 FTIR spectrum of biochar-clay-based composite support. Approximately 3430 cm⁻¹ -1 The adsorption bands detected at 803, 1108, and 1600 cm⁻¹ correspond to the tensile vibrations of surface hydroxyl substances, while at 803, 1108, and 1600 cm⁻¹... -1 The characteristic bands appearing at these sites correspond to the vibrations of CH, CO, and C=O bonds. These functional groups facilitate the uniform adsorption and dispersion of metal ions and help suppress the aggregation of nanoparticles during pyrolysis.

[0095] See Figure 5 The SEM image of the biochar-clay-based composite carrier shown reveals a honeycomb-like porous structure in the cross-section, with numerous small pores and pits on the side. This result further demonstrates that the prepared biochar-clay-based composite carrier possesses a microporous-mesoporous-macroporous composite porous structure.

[0096] See Figure 6 The XRD pattern of catalyst #2 shown shows that the peaks at 41.4°, 43.7°, 45.3° and 58.5° are characteristic of χ-Fe5C2, while the peaks at 37.7°, 43.5° and 67.8° correspond to the characteristics of ε-Fe2C. This result proves that the syngas to olefins catalyst was successfully prepared.

[0097] The pore size and other properties of the biochar-clay-based composite carriers prepared in Examples 1 to 3 were measured, and the results are shown in Table 1:

[0098] Table 1

[0099] carrier <![CDATA[Specific surface area (m 2 / g)]]> Aperture (nm) Example 1 741.8 7.15 Example 2 734.1 7.11 Example 3 725.6 6.98

[0100] Performance testing of syngas-to-olefins catalyst for catalytic conversion of syngas to olefins

[0101] The catalysts of the above examples and comparative examples were tested for their syngas-to-olefins performance using a micro fixed-bed reactor. The reaction conditions were as follows: the molar ratio of H2 to CO in the syngas was 1, the syngas feed space velocity was 12000–24000 mL·h⁻¹·gcat⁻¹, and the reaction temperature was 280–320 °C. The specific reaction conditions and results are shown in Table 2.

[0102] Table 2

[0103]

[0104] The influence of clay on carrier performance

[0105] Following the method of Example 2, omitting the attapulgite powder raw material, the prepared carrier was measured, and its SEM image is shown below. Figure 7 As shown, without the use of attapulgite, the porous structure of the carrier is disrupted, forming an amorphous structure. Its pore size was measured to be 4.04 nm, and its specific surface area was 364.5 m². 2 / g, the performance of syngas to olefins was tested according to the test conditions of catalyst #2. The result was that the CO conversion rate was 28.7%, which was far worse than the performance of Example 2.

[0106] The possible reason is that biochar made solely from biomass waste has an unstable structure. After pore expansion, the material structure becomes more fragile and therefore difficult to shape. However, by adding clay, the structure of biochar can be enhanced, thereby achieving stable and effective pore expansion in the material.

[0107] To verify this, based on the above-mentioned omission of attapulgite powder raw material testing, the amount of CuCl2 solution used as the pore-expanding agent was gradually reduced, and the properties of the resulting support were measured. The results showed that when the dosage was reduced to 3 mL / g, the material could be stabilized, but the pore size was only 2.95 nm, and the specific surface area was only 325.3 m². 2 / g.

[0108] The effect of pyrolysis method on carrier performance

[0109] Using the same amounts of wheat straw powder, attapulgite powder, and CuCl2 powder as in Example 2, the mixture was directly pyrolyzed to obtain the corresponding carrier. Its pore size was measured to be 2.73 nm, and its specific surface area was 289.2 m². 2 / g, which is significantly lower than that in Example 2.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A synthesis gas to olefins catalyst characterized in that, The catalyst comprises a carrier, an active component and a modified component supported on the carrier, the carrier is a biochar-clay-based composite carrier, the active component is iron, and the modified component is gallium or indium. The preparation method of the catalyst for preparing olefins from synthesis gas comprises the following steps: (1) preparation of a carrier The biochar-clay-based composite carrier is synthesized by hydrothermal treatment of a biological raw material and clay, pyrolysis treatment and metal ion pore expansion; The specific process of step (1) is as follows: 1.1) The biological raw material powder and the clay powder are mixed at a mass ratio of 1-5:1, dried at a temperature of 100-120 DEG C for 12-24 h, deionized water is added, and then transferred to a high-pressure reaction kettle, 1 MPa of nitrogen is filled, and hydrothermal treatment is carried out at a temperature of 160-180 DEG C for 4-8 h, and then filtered and washed to obtain a hydrothermal mixture of the biological raw material and the clay; 1.2) The hydrothermal mixture is added to a CuCl2 solution with a concentration of 5-20%, stirred at room temperature for 5-10 h, and then filtered and washed, and dried at a temperature of 100-120 DEG C for 10-12 h to obtain a biochar-clay precursor; 1.3) The biochar-clay precursor is immersed in a 0.05-0.3 M HCl solution, stirred at room temperature for 4-8 h, then washed with deionized water until the pH value reaches 6-7, dried at a temperature of 100-120 DEG C for 10-12 h, and finally carbonized at a temperature of 500-600 DEG C under a nitrogen atmosphere at a temperature rising rate of 2-6 DEG C / min for 1-4 h to obtain a carbonized body; 1.4) The carbonized body is immersed in a 0.5-2 M NaOH solution, boiled for 1-2 h, then sequentially washed with deionized water and ethanol until the pH value reaches 6-7, and dried at a temperature of 100-120 DEG C for 10-12 h to obtain the biochar-clay-based composite carrier; (2) loading of components The precursor salt of iron, the precursor salt of gallium or indium is loaded on the biochar-clay-based composite carrier by impregnation to obtain a catalyst precursor; (3) calcination of the precursor The catalyst precursor is subjected to reduction-carburization coupling high-temperature calcination treatment to obtain the catalyst for preparing olefins from synthesis gas.

2. The synthesis gas to olefins catalyst of claim 1, wherein, The content of iron is 1-15 wt.%, the content of gallium is 1-3 wt.%, and the content of indium is 1-3 wt.%.

3. The synthesis gas to olefins catalyst of claim 1 or 2, wherein, Part of the iron exists in the form of carburized iron, and the active phase is any one or a mixture of two or more of χ-Fe5C2, θ-Fe3C and ε-Fe2C.

4. The synthesis gas to olefins catalyst of claim 1 or 2, wherein, The biological raw material of the biochar is any one or a mixture of two or more of wheat straw, corn cob and rice husk in any proportion, and the clay is attapulgite or sepiolite.

5. The synthesis gas to olefins catalyst of claim 1 or 2, wherein, The specific process of step (2) is as follows: The precursor salt of iron and the precursor salt of gallium or indium are dissolved in deionized water, the biochar-clay-based composite carrier is added, stirred at room temperature for 8-12 h, then evaporated at a temperature of 80-120 DEG C, dried at a temperature of 105 DEG C for 10-12 h, and finally calcined at a temperature of 350-450 DEG C under a nitrogen atmosphere at a temperature rising rate of 2-6 DEG C / min for 3-6 h to obtain the catalyst precursor.

6. The synthesis gas to olefins catalyst of claim 1 or 2, wherein, The specific process of step (3) is as follows: The catalyst precursor is mixed with inert silica in a mass ratio of 1:3-10, ground uniformly, and then loaded into a reactor. First, the temperature is raised to 350-450°C at a temperature rising rate of 1-5°C / min under an atmosphere of 40-60 mL / min, 10 vol% H2 / N2, and reduction is carried out for 4-8 h. Then, the temperature is adjusted to 280-320°C, and in-situ carburization is carried out under an atmosphere of 20-40 mL / min, 45% H2 / 45% CO / 10% N2 or 50% H2 / 25% CO / 25% N2 for 4-10 h, to obtain the synthesis gas to olefin catalyst.

7. Use of the synthesis gas to olefin catalyst according to any one of claims 1 to 4 in the catalytic conversion of synthesis gas to prepare olefins.

8. A process for the catalytic conversion of synthesis gas to olefins, characterized in that: The reaction is carried out with a catalyst as claimed in any one of claims 1 to 4, using synthesis gas as raw material, under the following reaction conditions: molar ratio of H2 to CO in the synthesis gas feed is 1 to 2, space velocity of the synthesis gas feed is 12000 to 24000 mL·h -1 ·g cat -1 , and reaction temperature is 280 to 320℃.

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