Carbon quantum dots enhanced FexM / RGO catalyst, and preparation method and application thereof

Abstract

The application provides a carbon quantum dot enhanced Fe x The application relates to a catalyst and a carbon dioxide hydrogenation technology field, and relates to an M / RGO catalyst, a preparation method and application of the M / RGO catalyst. x The application provides a carbon quantum dot enhanced Fe x M / RGO catalyst, which comprises reduced graphene oxide, nitrogen-doped carbon quantum dots embedded on the surface of the reduced graphene oxide, and an active component Fe x M nanoparticles, wherein M is one or more of C, N and P, and x is 2-16. 16 The application is based on the synergistic effect among the components, and effectively improves the stability of the Fe-based catalyst and the selectivity of the product C8-C 16 The catalyst provided by the application has excellent performance, is used for catalyzing aviation kerosene prepared by CO2 hydrogenation, can promote the reaction, has high CO2 conversion rate, and has high component selectivity.

Description

Technical Field

[0001] This invention relates to the fields of catalysts and carbon dioxide hydrogenation technology, and particularly to a carbon quantum dot-enhanced Fe... x M / RGO catalysts, their preparation methods, and applications. Background Technology

[0002] Aviation kerosene, used as fuel for aircraft turbine engines, possesses advantages such as suitable density, high calorific value, good combustion performance, low carbon buildup, good low-temperature fluidity, good thermal and oxidation stability, high cleanliness, and minimal corrosion to engine parts. It is suitable for use in gas turbine engines and ramjet engines, and is widely used in both civil and military aircraft. Unlike other transportation vehicles, due to the specific energy density and weight requirements of aircraft engines, aviation kerosene cannot currently be replaced by new energy power sources. Aviation kerosene mainly consists of fuels with a carbon number of C8 to C99. 16 It is composed of hydrocarbon compounds, and its current source is mainly petroleum refining products, but it can also be obtained through coal liquefaction, natural gas liquefaction and biomass liquefaction.

[0003] Carbon dioxide (CO2) is a greenhouse gas. With industrial development and the large-scale use of fossil fuels such as coal, oil, and natural gas, CO2 emissions have increased year by year. The increase in CO2 emissions has accelerated global warming and caused significant damage to the Earth's ecological environment. Therefore, the reduction, storage, and utilization of CO2 emissions are common research topics faced by scientists around the world.

[0004] Utilizing CO2 resources is a crucial pathway to carbon reduction. Due to CO2's chemical inertness, it is difficult to convert it into compounds containing two or more carbon atoms through hydrogenation. The preparation of hydrocarbons from carbon dioxide via hydrogenation generally employs iron-based catalysts, using continuous catalytic reverse water-gas reactions and Fischer-Tropsch synthesis to generate long-chain hydrocarbons. However, iron-based catalysts are prone to particle breakage during the reaction, leading to reaction shutdown; furthermore, under high partial pressures of CO2 and H2O (a large amount of water is generated during the CO2 reaction), iron-based catalysts are easily oxidized, resulting in catalyst deactivation.

[0005] In summary, current catalysts for the synthesis of aviation kerosene via CO2 hydrogenation still face challenges such as low product selectivity and poor catalyst stability. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a carbon quantum dot-enhanced Fe x M / RGO catalysts, their preparation methods, and applications. This invention provides carbon quantum dot-enhanced Fe... x The M / RGO catalyst has good stability and can achieve highly selective synthesis of aviation kerosene through direct hydrogenation of CO2.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a carbon quantum dot-enhanced Fe x The M / RGO catalyst comprises reduced graphene oxide, nitrogen-doped carbon quantum dots embedded on the surface of the reduced graphene oxide, and an active component Fe anchored on the surface and in the bulk of the reduced graphene oxide. x M nanoparticles, the Fe x In M nanoparticles, M is one or more of C, N and P, and x is 2 to 16.

[0009] Preferably, the reduced graphene oxide, nitrogen-doped carbon quantum dots, and Fe... x The mass ratio of M nanoparticles is (15–90):(0.5–10):(3–90).

[0010] Preferably, the reduced graphene oxide is further anchored on the surface and in the bulk phase with alkali metal oxides, the alkali metal oxides including potassium oxide and / or sodium oxide, and the mass ratio of alkali metal element to reduced graphene oxide in the alkali metal oxide is (0.05-10):(15-90).

[0011] This invention provides the carbon quantum dot-enhanced Fe as described in the above technical solution. x The preparation method of M / RGO catalyst includes the following steps:

[0012] (1) A first hydrothermal reaction was carried out by mixing carbon source, nitrogen source and solvent to obtain nitrogen-doped carbon quantum dots;

[0013] (2) The nitrogen-doped carbon quantum dots, graphene oxide, water and iron salt are mixed, and the pH of the resulting mixture is adjusted to 8.0-12.0 before a second hydrothermal reaction is carried out to obtain the catalyst precursor.

[0014] (3) The catalyst precursor is heat-treated in the presence of a non-metallic source to obtain the carbon quantum dot-enhanced Fe. x M / RGO catalyst; the non-metallic source includes one or more of carbon, nitrogen and phosphorus sources.

[0015] Preferably, the carbon source in step (1) is one or more of glucose, citric acid, tartaric acid, malonic acid, lactose and lactic acid, and the nitrogen source is one or more of ethylenediamine, urea, ammonia, biuret, phenylenediamine, glycine, tryptophan and arginine; the mass ratio of the carbon source to the nitrogen source is 1:1 to 100:1.

[0016] Preferably, in step (2), the pH value is adjusted by adding an inorganic alkali, which includes one or more of ammonia, sodium inorganic alkali, and potassium inorganic alkali.

[0017] Preferably, the carbon source in step (3) includes one or more of CO, CO2, C2H2, CH4 and C2H4, the nitrogen source includes N2 and / or NH3, and the phosphorus source includes one or more of white phosphorus, red phosphorus, PH3 and sodium hypophosphite.

[0018] Preferably, the temperature of the first hydrothermal reaction is 100–230°C and the time is 6–48 h; the temperature of the second hydrothermal treatment is 120–240°C and the time is 4–48 h; and the temperature of the heat treatment is 200–900°C and the time is 4–24 h.

[0019] This invention provides the carbon quantum dot-enhanced Fe as described in the above technical solution. x The carbon quantum dot-enhanced Fe2O3 catalyst prepared by the preparation method described in the above technical solutions or the M / RGO catalyst is an example of a carbon quantum dot-enhanced Fe2O3 catalyst. x Application of M / RGO catalyst in CO2 hydrogenation to aviation kerosene.

[0020] Preferably, the feed gas for CO2 hydrogenation to produce aviation kerosene comprises CO2 and H2, wherein the molar ratio of CO2 to H2 in the feed gas is 1.0–5.0:1, and the space velocity of the feed gas is 3–50 L / g. cat The reaction rate is 1 / h, the reaction temperature is 250-350℃, and the reaction pressure is 1-6MPa.

[0021] This invention provides a carbon quantum dot-enhanced Fe x The M / RGO catalyst comprises reduced graphene oxide, nitrogen-doped carbon quantum dots embedded on the surface of the reduced graphene oxide, and an active component Fe anchored on the surface and in the bulk of the reduced graphene oxide. x M nanoparticles, the Fe x In the M nanoparticles, M is one or more of C, N, and P, and x is 2–16. This invention utilizes nitrogen-doped carbon quantum dots to modulate the electronic structure of the active metal Fe, thereby improving the performance of Fe-based catalysts on C8–C8 middle distillate fractions. 16 The selective nature of reduced graphene oxide effectively inhibits the agglomeration, growth, and breakage of iron-based catalysts. The synergistic effect of these two components effectively suppresses the oxidation of iron catalysts by CO2 and H2O. Simultaneously, the abundant organic functional groups on the surface of reduced graphene oxide and nitrogen-doped carbon quantum dots provide excellent anchoring sites, facilitating the anchoring of metal ions and promoting the uniform dispersion of active metal Fe atoms. This further prevents Fe agglomeration and growth. The synergistic effect among these components effectively improves the stability of Fe-based catalysts and their ability to target C8–C4 products. 16 Product selectivity.

[0022] Furthermore, the introduction of nitrogen-doped carbon quantum dots into the catalyst can also synergistically work with K and Na elements in alkali metal oxides to improve the alkalinity of the catalyst surface and promote the adsorption and reaction of CO2.

[0023] This invention provides the carbon quantum dot-enhanced Fe as described in the above technical solution. x Application of M / RGO catalyst in CO2 hydrogenation to aviation kerosene. The catalyst provided by this invention has excellent performance and is used to catalyze the CO2 hydrogenation to aviation kerosene. It can promote the reaction, achieve high CO2 conversion, and produce the target product C8-C9. 16 High component selectivity. Example results show that when the catalyst is used in the catalytic hydrogenation of CO2 to aviation kerosene, the CO2 conversion rate can reach 53.46%, and the C8-C9 ratio is [not specified]. 16 The fraction selectivity exceeded 41%, and the catalyst was used at a reaction temperature of 290℃, an H2 / CO2 ratio of 3 (molar ratio), a reaction pressure of 3.5 MPa, and a reaction space velocity of 3 L / g. cat It can run continuously for 4000 hours under the condition of / h. Attached Figure Description

[0024] Figure 1 XRD patterns of the catalysts prepared in Examples 1, 2 and 4;

[0025] Figure 2 SEM image of the catalyst prepared in Example 1;

[0026] Figure 3 TEM image of the catalyst prepared in Example 1;

[0027] Figure 4 The results are from the stability test of the catalyst prepared in Example 1. Detailed Implementation

[0028] This invention provides a carbon quantum dot-enhanced Fe x The M / RGO catalyst comprises reduced graphene oxide, nitrogen-doped carbon quantum dots embedded on the surface of the reduced graphene oxide, and an active component Fe anchored on the surface and in the bulk of the reduced graphene oxide. x M nanoparticles, the Fe x In M nanoparticles, M is one or more of C, N and P, and x is 2 to 16.

[0029] In this invention, the nitrogen-doped carbon quantum dots are embedded in the surface of reduced graphene oxide via CN covalent bonds to form new functional sites, and there is a π-π interaction between the nitrogen-doped carbon quantum dots and the reduced graphene oxide.

[0030] In this invention, the Fex M nanoparticles are preferably iron carbide, iron nitride, iron phosphide, or iron carbonitride, and x is preferably 2 to 4.

[0031] In this invention, the reduced graphene oxide, nitrogen-doped carbon quantum dots, and Fe... x The preferred mass ratio of M nanoparticles is (15-90):(0.5-10):(3-90), and more preferably (25-40):(1.5-5):(10-40).

[0032] In this invention, the reduced graphene oxide surface and bulk phase are preferably anchored with alkali metal oxides, which preferably include potassium oxide and / or sodium oxide, and the mass ratio of the metal element to the reduced graphene oxide in the alkali metal oxide is preferably (0.05-10):(15-90).

[0033] In this invention, reduced-redox graphene serves as a support, exhibiting excellent water resistance. The iron carbides, nitrides, carbonitrides, and phosphides on the reduced-redox graphene support alter the electronic environment of iron due to the electronic effects of graphene and carbon quantum dots, thus promoting the stability of the iron phase and improving the performance of the Fe-based catalyst on C8-C4 phases. 16 Product selectivity. Furthermore, the presence of small amounts of alkali metals K and Na also favors Fe. x The retention of the M phase is achieved. In this invention, the synergistic effect between the components effectively solves the problem of Fe-based catalysts affecting the target product C8-C8. 16 The product selection is limited, and the stability is poor.

[0034] This invention provides the carbon quantum dot-enhanced Fe as described in the above technical solution. x The preparation method of M / RGO catalyst includes the following steps:

[0035] (1) A first hydrothermal reaction was carried out by mixing carbon source, nitrogen source and solvent to obtain nitrogen-doped carbon quantum dots;

[0036] (2) The nitrogen-doped carbon quantum dots, graphene oxide, water and iron salt are mixed, and the pH of the resulting mixture is adjusted to 8.0-12.0 before a second hydrothermal reaction is carried out to obtain the catalyst precursor.

[0037] (3) The catalyst precursor is heat-treated in the presence of a non-metallic source to obtain the carbon quantum dot-enhanced Fe. x M / RGO catalyst; the non-metallic source includes one or more of carbon, nitrogen and phosphorus sources.

[0038] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known to those skilled in the art.

[0039] This invention involves mixing a carbon source, a nitrogen source, and a solvent to perform a first hydrothermal reaction, thereby obtaining nitrogen-doped carbon quantum dots.

[0040] In this invention, the carbon source is preferably one or more of glucose, citric acid, tartaric acid, malonic acid, lactose, and lactic acid; the nitrogen source is preferably one or more of ethylenediamine, urea, ammonia, biuret, phenylenediamine, glycine, tryptophan, and arginine. The mass ratio of the carbon source to the nitrogen source is preferably 1:1 to 100:1, more preferably 1:1 to 10:1, and even more preferably 1.5:1 to 5:1. In this invention, the solvent is preferably water. This invention does not have particular requirements on the amount of solvent used, as long as it is sufficient to fully disperse the carbon source and nitrogen source. In this invention, the method of mixing the carbon source, nitrogen source, and solvent is preferably stirring, wherein the stirring is sufficient to fully dissolve or disperse the carbon source and nitrogen source in the solvent.

[0041] In this invention, the temperature of the first hydrothermal reaction is preferably 100–230°C, more preferably 180–220°C, and even more preferably 190–210°C; the time is preferably 6–48 h, more preferably 10–36 h, and even more preferably 12–16 h. During the first hydrothermal reaction, the carbon source and nitrogen source undergo a polymerization reaction to generate nitrogen-doped carbon quantum dots.

[0042] After the first hydrothermal reaction is completed, the present invention preferably subjectes the resulting reaction solution to sequential dialysis purification, rotary evaporation concentration, and drying to obtain the nitrogen-doped carbon quantum dots. In the present invention, the molecular weight cutoff of the dialysis bag used for dialysis purification is preferably 500 Da, and the dialysis solution used is preferably deionized water. The present invention removes metal heteroatoms and polymers with too low a degree of polymerization through dialysis purification. In the present invention, the drying is preferably freeze-drying.

[0043] In this invention, nitrogen-doped carbon quantum dots, graphene oxide, water, and iron salt are mixed, and the pH of the resulting mixture is adjusted to 8.0–12.0 before a second hydrothermal reaction is carried out to obtain a catalyst precursor.

[0044] This invention does not have any particular requirements for the graphene oxide used; any graphene oxide well-known to those skilled in the art can be used. In this embodiment, it is prepared using flake graphite as raw material via a modified Hummer method. In this invention, the iron salt is preferably one or more of ferric nitrate, ferric sulfate, ferric chloride, ferrous nitrate, ferrous sulfate, ferrous chloride, ferric oxalate, ferric acetylacetone, ferric acetate, ferric oleate, and ferric citrate; more preferably, it is one or more of ferric nitrate, ferrous nitrate, ferric sulfate, ferrous sulfate, ferric chloride, ferric citrate, ferrous chloride, and ferric acetylacetone. In this invention, the iron salt is preferably added in the form of an aqueous solution of the iron salt, and the concentration of the aqueous solution is preferably 0.15–0.2 mol / L.

[0045] In this invention, the amounts of nitrogen-doped carbon quantum dots, graphene oxide, and iron salt are adjusted to satisfy the above-mentioned reduced graphene oxide, nitrogen-doped carbon quantum dots, and Fe... x The mass ratio of M particles is the standard. This invention does not have special requirements for the amount of water added, as long as it can ensure that all components are fully dispersed.

[0046] In this invention, the pH value is preferably adjusted by adding an inorganic base. The inorganic base preferably includes one or more of ammonia, sodium inorganic bases, and potassium inorganic bases, more preferably sodium inorganic bases and / or potassium inorganic bases. The sodium inorganic base is preferably one or more of NaOH, Na₂CO₃, and NaHCO₃, more preferably NaOH. The potassium inorganic base is preferably one or more of KOH, K₂CO₃, and KHCO₃, more preferably KOH. In this invention, the inorganic base is preferably added in the form of an aqueous solution of the inorganic base, and the concentration of the aqueous solution is preferably 0.5–1 mol / L. When sodium inorganic bases and / or potassium inorganic bases are used, the pH value is adjusted while simultaneously introducing K and / or Na elements into the catalyst.

[0047] In this invention, the nitrogen-doped carbon quantum dots and graphene oxide are preferably dispersed in water, and then iron salt is slowly added. After stirring evenly, an inorganic alkali is added to adjust the pH of the mixture to 8.0-12.0.

[0048] In this invention, after the addition of iron salt, iron ions are anchored on graphene oxide. Subsequently, the addition of inorganic base transforms the iron ions into iron oxides or hydroxyl oxides, which are then anchored on the graphene oxide carrier.

[0049] In this invention, the temperature of the second hydrothermal reaction is preferably 120–240°C, more preferably 180–230°C, and even more preferably 190–210°C; the time is preferably 4–48 h, more preferably 8–30 h, and even more preferably 18–24 h. During the second hydrothermal reaction, the degree of crystallization of iron oxides or hydroxyoxides further increases, and the morphology gradually becomes more perfect.

[0050] After the second hydrothermal reaction is completed, the resulting reaction solution is preferably cooled and then washed, centrifuged, and dried sequentially to obtain the catalyst precursor. In this invention, the washing solution is preferably an ethanol-water solution, wherein the volume fraction of ethanol in the ethanol-water solution is preferably 50-70%, and the washing is preferably performed 3-5 times. The purpose of washing is to remove excess inorganic alkali. In this invention, the drying temperature is preferably 90°C, and the drying time is preferably 6 hours.

[0051] After obtaining the catalyst precursor, the present invention heat-treats the catalyst precursor in the presence of a non-metallic source to obtain the carbon quantum dot-enhanced Fe. x M / RGO catalyst.

[0052] In this invention, the catalyst precursor is preferably crushed and sieved before the heat treatment. In this invention, the non-metallic source includes one or more of a carbon source, a nitrogen source, and a phosphorus source. The carbon source preferably includes one or more of CO, CO2, C2H2, CH4, and C2H4; the nitrogen source preferably includes N2 and / or NH3; and the phosphorus source preferably includes one or more of white phosphorus, red phosphorus, PH3, and sodium hypophosphite. In this invention, the type and amount of the non-metallic source are determined to satisfy the formation of Fe. x The standard is M nanoparticles (M is one or more of C, N and P, and x is 2 to 16).

[0053] In this invention, the heat treatment temperature is preferably 200–900°C, more preferably 300–700°C, and even more preferably 350–400°C; the heat treatment time is preferably 4–24 h, more preferably 8–20 h. In this invention, the heat treatment atmosphere preferably includes one or more of N2, He, and Ar. During the heat treatment process, iron undergoes a phase transformation into iron carbides, nitrides, carbonitrides, or phosphides, and graphene oxide is reduced to reduced graphene oxide.

[0054] This invention provides the carbon quantum dot-enhanced Fe as described in the above technical solution. x The carbon quantum dot-enhanced Fe2O3 catalyst prepared by the preparation method described in the above technical solutions or the M / RGO catalyst is an example of a carbon quantum dot-enhanced Fe2O3 catalyst. xApplication of M / RGO catalyst in CO2 hydrogenation to aviation kerosene.

[0055] In this invention, the feed gas for CO2 hydrogenation to produce aviation kerosene comprises CO2 and H2, wherein the molar ratio of CO2 to H2 in the feed gas is preferably 1 to 5:1, more preferably 2 to 4:1; and the space velocity of the feed gas is preferably 3 to 50 L / g. cat The reaction rate is 1-6 MPa, and the reaction temperature is preferably 250-350℃, more preferably 260-300℃, and the reaction pressure is preferably 3-5 MPa.

[0056] The carbon quantum dot-enhanced Fe provided by this invention x M / RGO catalysts are used for the catalytic hydrogenation of CO2 to aviation kerosene, exhibiting excellent performance, high CO2 conversion, and targeting C8-C6 products. 16 High component selectivity.

[0057] To further illustrate the present invention, the following examples demonstrate the carbon quantum dot-enhanced Fe provided by the present invention. x The M / RGO catalyst, its preparation method, and its applications are described in detail, but they should not be construed as limiting the scope of protection of this invention.

[0058] Example 1

[0059] Graphene oxide was prepared using a modified Hummer method. After washing, sonication, rotary evaporation concentration, and freeze-drying, dark brown graphene oxide powder was obtained. 2g of glucose and 1g of tryptophan were dispersed in deionized water and, after complete dissolution, transferred to a hydrothermal reactor. The reactor was reacted at 200℃ for 10 hours. After cooling, the reactor was removed, yielding a brown liquid. This brown liquid was dialyzed in a dialysis bag (MWCO = 500 Da), and after several changes of deionized water, it was concentrated by rotary evaporation and freeze-dried to obtain nitrogen-doped carbon quantum dot powder.

[0060] 0.5 g of graphene oxide and 50 mg of nitrogen-doped carbon quantum dot powder were ultrasonically dispersed in 500 mL of deionized water. Then, 30 mL of a 0.15 mol / L Fe(NO3)3 solution was slowly added. After stirring until homogeneous, 15 mL of a 1 mol / L NaOH aqueous solution was added. The mixture was stirred for 30 minutes, then transferred to a hydrothermal reactor and hydrothermally heated at 190 °C for 8 hours. After cooling, the resulting black precipitate was washed three times with an ethanol-water solution (50% ethanol by volume). Finally, the precipitate was dried in an oven at 90 °C for 6 hours to obtain a black solid.

[0061] The resulting black solid was crushed and sieved, and then heat-treated at 350°C for 12 hours in a 10% CO + 90% He atmosphere to obtain a carbon quantum dot-enhanced Fe3C / RGO catalyst.

[0062] Example 2

[0063] Graphene oxide was prepared using a modified Hummer method. After washing, sonication, rotary evaporation concentration, and freeze-drying, a dark brown graphene oxide powder was obtained. 2.3 g of citric acid and 0.8 g of ethylenediamine were dispersed in deionized water. After complete dissolution, the solution was transferred to a hydrothermal reactor and reacted at 180°C for 16 hours. After cooling, the reactor was removed, yielding a brown liquid. This brown liquid was dialyzed in a dialysis bag (MWCO = 500 Da). After several changes of deionized water, the solution was concentrated by rotary evaporation and freeze-dried to obtain nitrogen-doped carbon quantum dot powder.

[0064] 0.5 g of graphene oxide and 30 mg of nitrogen-doped carbon quantum dot powder were ultrasonically dispersed in 500 mL of deionized water. Then, 30 mL of a 0.2 mol / L FeSO4 solution was slowly added, and after stirring until homogeneous, 20 mL of a 1 mol / L NaOH solution was added. The mixture was stirred for 30 minutes, then transferred to a hydrothermal reactor and hydrothermally heated at 200 °C for 8 hours. After the reactor cooled, the resulting black precipitate was washed three times with an ethanol-water solution (50% ethanol by volume), and then dried in an oven at 90 °C for 6 hours to obtain a black solid.

[0065] The resulting black solid was crushed and sieved, and then heat-treated at 300°C for 20 hours in a 5% NH3 + 95% He atmosphere to obtain a carbon quantum dot-enhanced Fe2N / RGO catalyst.

[0066] Example 3

[0067] Graphene oxide was prepared using a modified Hummer method. After washing, sonication, rotary evaporation concentration, and freeze-drying, a dark brown graphene oxide powder was obtained. 1.7 g of tartaric acid and 0.65 g of biuret were dispersed in deionized water. After complete dissolution, the solution was transferred to a hydrothermal reactor and reacted at 190 °C for 12 hours. After cooling, the reactor was removed, yielding a brown liquid. This brown liquid was dialyzed in a dialysis bag (MWCO = 500 Da). After several changes of deionized water, the solution was concentrated by rotary evaporation and freeze-dried to obtain nitrogen-doped carbon quantum dot powder.

[0068] 0.5 g of graphene oxide and 100 mg of nitrogen-doped carbon quantum dot powder were ultrasonically dispersed in 500 mL of deionized water. Then, 30 mL of a 0.2 mol / L FeCl2 solution was slowly added, and after stirring until homogeneous, 15 mL of a 1 mol / L K2CO3 solution was added. The mixture was stirred for 30 minutes, then transferred to a hydrothermal reactor and hydrothermally heated at 200 °C for 12 hours. After the reactor cooled, the resulting black precipitate was washed five times with an ethanol-water solution (50% ethanol by volume), and then dried in an oven at 90 °C for 6 hours to obtain a black solid.

[0069] The resulting black solid was crushed and sieved, and then heat-treated at 220°C for 24 hours in a 70% He + 20% CO + 10% CO2 atmosphere to obtain carbon quantum dot-reinforced Fe. 2.2 C / RGO catalyst.

[0070] Example 4

[0071] Graphene oxide was prepared using a modified Hummer method. After washing, sonication, rotary evaporation concentration, and freeze-drying, dark brown graphene oxide powder was obtained. 2.3 g of glucose, 0.6 g of arginine, and 0.7 g of tryptophan were dispersed in deionized water. After complete dissolution, the solution was transferred to a hydrothermal reactor and reacted at 180°C for 16 hours. After cooling, the reactor was removed, yielding a brown liquid. This brown liquid was dialyzed in a dialysis bag (MWCO = 500 Da). After several changes of deionized water, the solution was concentrated by rotary evaporation and freeze-dried to obtain nitrogen-doped carbon quantum dot powder.

[0072] 0.5 g of graphene oxide and 65 mg of nitrogen-doped carbon quantum dot powder were ultrasonically dispersed in 500 mL of deionized water. Then, 70 mL of a 0.2 mol / L FeCl3 solution was slowly added, and after stirring until homogeneous, 30 mL of a 1 mol / L Na2CO3 aqueous solution was added. The mixture was stirred for 30 minutes, then transferred to a hydrothermal reactor and hydrothermally heated at 200 °C for 18 hours. After the reactor cooled, the resulting black precipitate was washed five times with an ethanol-water solution (50% ethanol by volume), and then dried in an oven at 90 °C for 6 hours to obtain a black solid.

[0073] The resulting black solid was crushed and sieved, and then heat-treated at 300°C for 18 hours in an atmosphere of 5% NH3 + 85% He + 10% CO to obtain a carbon quantum dot-enhanced Fe2C-Fe4N / RGO catalyst.

[0074] Example 5

[0075] Graphene oxide was prepared using a modified Hummer method. After washing, sonication, rotary evaporation concentration, and freeze-drying, dark brown graphene oxide powder was obtained. 2.5 g of glucose and 1.3 g of arginine were dispersed in deionized water and, after complete dissolution, transferred to a hydrothermal reactor. The reaction was carried out at 210 °C for 6 hours. After cooling, the reactor was removed, yielding a brown liquid. This brown liquid was dialyzed in a dialysis bag (MWCO = 500 Da), and after several changes of deionized water, it was concentrated by rotary evaporation and freeze-dried to obtain nitrogen-doped carbon quantum dot powder.

[0076] 0.65 g of graphene oxide and 50 mg of nitrogen-doped carbon quantum dot powder were ultrasonically dispersed in 650 mL of deionized water. Then, 35 mL of a 0.15 mol / L Fe(NO3)2 solution was slowly added. After stirring until homogeneous, 17 mL of a 1 mol / L KOH aqueous solution was added. The mixture was stirred for 30 minutes, then transferred to a hydrothermal reactor and hydrothermally heated at 210 °C for 6 hours. After cooling, the resulting black precipitate was washed three times with an ethanol-water solution (50% ethanol by volume). Finally, the precipitate was dried in an oven at 90 °C for 6 hours to obtain a black solid.

[0077] The resulting black solid was crushed and sieved, then heat-treated at 400℃ for 8 hours in an atmosphere of 10% NH3 + 90% He. The atmosphere was then switched to 20% CO + 70% He + 10% CO2 and heat-treated at 330℃ for 6 hours. After cooling, carbon quantum dot-reinforced Fe was obtained. 2.5 CN / RGO catalyst.

[0078] Example 6

[0079] Graphene oxide was prepared using a modified Hummer method. After washing, sonication, rotary evaporation concentration, and freeze-drying, dark brown graphene oxide powder was obtained. 2.0 g of glucose and 1.7 g of glycine were dispersed in deionized water and, after complete dissolution, transferred to a hydrothermal reactor. The reaction was carried out at 210 °C for 6 hours. After cooling, the reactor was removed, yielding a brown liquid. This brown liquid was dialyzed in a dialysis bag (MWCO = 500 Da), and after several changes of deionized water, it was concentrated by rotary evaporation and freeze-dried to obtain nitrogen-doped carbon quantum dot powder.

[0080] 0.75 g of graphene oxide and 50 mg of nitrogen-doped carbon quantum dot powder were ultrasonically dispersed in 800 mL of deionized water. Then, 35 mL of a 0.15 mol / L ferric citrate solution was slowly added. After stirring until homogeneous, 20 mL of a 0.5 mol / L K₂CO₃ aqueous solution was added. The mixture was stirred for 30 minutes, then transferred to a hydrothermal reactor and hydrothermally heated at 180 °C for 24 hours. After cooling, the resulting black precipitate was washed three times with an ethanol-water solution (50% ethanol by volume). Finally, it was dried in an oven at 90 °C for 6 hours to obtain a black solid.

[0081] The obtained black solid was crushed and sieved. 0.5g of solid particles were mixed with 0.08g of red phosphorus and heat-treated at 350℃ for 6 hours in N2 atmosphere. Then the mixture was cooled to obtain a carbon quantum dot-enhanced Fe3P / RGO catalyst.

[0082] Comparative Example 1

[0083] 30 mL of a 0.15 mol / L Fe(NO3)3 solution was slowly mixed with 15 mL of a 1 mol / L NaOH aqueous solution under stirring. After the mixture was homogeneous, stirring was continued for another 30 minutes. The mixture was then transferred to a hydrothermal reactor and hydrothermally heated at 190 °C for 8 hours. After the reactor cooled, the resulting black precipitate was washed three times with an ethanol-water solution (50% ethanol by volume). The precipitate was then dried in an oven at 90 °C for 6 hours to obtain a black solid. The black solid was crushed, sieved, and heat-treated at 350 °C for 12 hours in a 10% CO + 90% He atmosphere to obtain the Fe3C catalyst.

[0084] Comparative Example 2

[0085] Graphene oxide was prepared using a modified Hummer method. After washing, sonication, rotary evaporation concentration, and freeze-drying, a dark brown graphene oxide powder was obtained. 0.5 g of the graphene oxide powder was ultrasonically dispersed in 500 mL of deionized water, followed by the slow addition of 30 mL of a 0.2 mol / L FeSO4 solution. After stirring until homogeneous, 20 mL of a 1 mol / L NaOH aqueous solution was added. The mixture was stirred for 30 minutes, then transferred to a hydrothermal reactor and hydrothermally heated at 200 °C for 8 hours. After cooling, the resulting black precipitate was washed three times with an ethanol-water solution (50% ethanol by volume), and then dried in an oven at 90 °C for 6 hours to obtain a black solid.

[0086] The resulting black solid was crushed and sieved, and then heat-treated at 300°C for 20 hours in a 5% NH3 + 95% He atmosphere to obtain the Fe2N / RGO catalyst.

[0087] Comparative Example 3

[0088] Disperse 3.4 g of tartaric acid and 1.3 g of biuret in deionized water. After complete dissolution, transfer the solution to a hydrothermal reactor and react at 190 °C for 12 hours. After cooling, remove the reactor to obtain a brown liquid. Dialyze the brown liquid in a dialysis bag (MWCO = 500 Da). After changing the deionized water several times, concentrate the solution by rotary evaporation and freeze-dry to obtain nitrogen-doped carbon quantum dot powder.

[0089] 100 mg of nitrogen-doped carbon quantum dot powder was ultrasonically dispersed in 500 mL of deionized water. Then, 30 mL of a 0.2 mol / L FeCl2 solution was slowly added, and after stirring until homogeneous, 15 mL of a 1 mol / L K2CO3 solution was added. The mixture was stirred for 30 minutes, then transferred to a hydrothermal reactor and hydrothermally heated at 200 °C for 12 hours. After the reactor cooled, the resulting black precipitate was washed five times with an ethanol-water solution (50% ethanol by volume), and then dried in an oven at 90 °C for 6 hours to obtain a black solid.

[0090] The resulting black solid was crushed and sieved, and then heat-treated at 220°C for 24 hours in a 70% He + 20% CO + 10% CO2 atmosphere to obtain carbon quantum dot-reinforced Fe. 2.2 C catalyst.

[0091] Comparative Example 4

[0092] Graphene oxide was prepared using a modified Hummer method. After washing, sonication, rotary evaporation concentration, and freeze-drying, dark brown graphene oxide powder was obtained. 2.3 g of glucose, 0.6 g of arginine, and 0.7 g of tryptophan were dispersed in deionized water. After complete dissolution, the solution was transferred to a hydrothermal reactor and reacted at 180°C for 16 hours. After cooling, the reactor was removed, yielding a brown liquid. This brown liquid was dialyzed in a dialysis bag (MWCO = 500 Da). After several changes of deionized water, the solution was concentrated by rotary evaporation and freeze-dried to obtain nitrogen-doped carbon quantum dot powder.

[0093] 0.5 g of graphene oxide and 65 mg of nitrogen-doped carbon quantum dot powder were ultrasonically dispersed in 500 mL of deionized water. Then, 70 mL of a 0.2 mol / L FeCl3 solution was slowly added, and after stirring until homogeneous, 30 mL of a 1 mol / L Na2CO3 aqueous solution was added. The mixture was stirred for 30 minutes, then transferred to a hydrothermal reactor and hydrothermally heated at 200 °C for 18 hours. After cooling, the resulting black precipitate was washed five times with an ethanol-water solution (50% ethanol by volume), and then dried in an oven at 90 °C for 6 hours to obtain the carbon quantum dot-enhanced Fe2O3 / RGO catalyst.

[0094] Comparative Example 5

[0095] Graphene oxide was prepared using a modified Hummer method. After washing, sonication, rotary evaporation concentration, and freeze-drying, a dark brown graphene oxide powder was obtained. 1.7 g of tartaric acid and 0.65 g of biuret were dispersed in deionized water. After complete dissolution, the solution was transferred to a hydrothermal reactor and reacted at 190 °C for 12 hours. After cooling, the reactor was removed, yielding a brown liquid. This brown liquid was dialyzed in a dialysis bag (MWCO = 500 Da). After several changes of deionized water, the solution was concentrated by rotary evaporation and freeze-dried to obtain nitrogen-doped carbon quantum dot powder.

[0096] 0.5 g of graphene oxide and 100 mg of nitrogen-doped carbon quantum dot powder were ultrasonically dispersed in 500 mL of deionized water. Then, 30 mL of a 0.2 mol / L FeCl2 solution was slowly added, and after stirring until homogeneous, 15 mL of a 1 mol / L K2CO3 solution was added. The mixture was stirred for 30 minutes, then transferred to a hydrothermal reactor and hydrothermally heated at 200 °C for 12 hours. After cooling, the resulting black precipitate was washed five times with an ethanol-water solution (50% ethanol by volume), and then dried in an oven at 90 °C for 6 hours to obtain a black solid. The black solid was crushed and sieved to obtain the carbon quantum dot-enhanced Fe3O4 / RGO catalyst.

[0097] Figure 1 XRD patterns of the catalysts prepared in Examples 1, 2, and 4. From... Figure 1 It can be seen that: in the catalyst prepared in Example 1, Fe exists in the form of Fe3C; in the catalyst prepared in Example 2, Fe exists in the form of Fe2N; and in the catalyst prepared in Example 4, Fe exists in the forms of Fe4N and Fe2C.

[0098] Figure 2 This is a SEM image of the catalyst prepared in Example 1. Figure 2 As can be seen from the above, the Fe in the catalyst prepared in Example 1 has an octahedral morphology with a size ranging from 100 to 600 nm.

[0099] Figure 3 TEM image of the catalyst prepared in Example 1. Figure 3 As can be seen from the figure, the Fe in the catalyst in Example 1 has an octahedral morphology, and the size of the particles seen in the figure is about 300 nm.

[0100] The catalysts prepared in Examples 1-6 and Comparative Examples 1-5 were used for the catalytic hydrogenation of CO2 to produce aviation kerosene. The reaction conditions were: CO2:H2 = 3 (molar ratio), reaction pressure 3.5 MPa, and reaction space velocity 3 L / g. catThe reaction was carried out at a rate of 1 / h, a reaction temperature of 290℃, and a reaction time of 120h. The reaction results for each catalyst are shown in Table 1 (C in Table 1...). 5+ Hydrocarbons with 5 or more carbon atoms:

[0101] Table 1. Results of CO2 hydrogenation synthesis of aviation kerosene using iron-based catalysts.

[0102]

[0103]

[0104] As can be seen from Table 1, the carbon quantum dot-enhanced Fe prepared in the embodiments of the present invention... x M / RGO catalysts are used for the catalytic hydrogenation of CO2 to aviation kerosene, exhibiting excellent performance, high CO2 conversion, and targeting C8-C6 products. 16 High component selectivity.

[0105] Figure 4 The stability test results of the catalyst prepared in Example 1 for the catalytic hydrogenation of CO2 to synthesize aviation kerosene under the above reaction conditions are presented. Figure 4 It can be seen that the activity of the catalyst decreased slightly during the 4000h reaction operation period, C8~C 16 The selectivity of jet fuel fractions decreased with increasing reaction time, but the selectivity of CH4 remained essentially unchanged.

[0106] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A carbon quantum dot-enhanced Fe x The M / RGO catalyst comprises reduced graphene oxide, nitrogen-doped carbon quantum dots embedded on the surface of the reduced graphene oxide, and an active component Fe anchored on the surface and in the bulk of the reduced graphene oxide. x M nanoparticles, the Fe x In M nanoparticles, M is one or more of C, N and P, and x is 2 to 16. The carbon quantum dot-enhanced Fe x The preparation method of M / RGO catalyst includes the following steps: (1) A first hydrothermal reaction was carried out by mixing carbon source, nitrogen source and solvent to obtain nitrogen-doped carbon quantum dots; (2) The nitrogen-doped carbon quantum dots, graphene oxide, water and iron salt are mixed, and the pH of the resulting mixture is adjusted to 8.0~12.0 before a second hydrothermal reaction is carried out to obtain the catalyst precursor. (3) The catalyst precursor is heat-treated in the presence of a non-metallic source to obtain the carbon quantum dot-enhanced Fe. x M / RGO catalyst; the non-metallic source includes one or more of carbon, nitrogen and phosphorus sources.

2. The carbon quantum dot-enhanced Fe according to claim 1 x M / RGO catalyst, characterized in that The reduced graphene oxide, nitrogen-doped carbon quantum dots and Fe x The mass ratio of M nanoparticles is (15~90):(0.5~10):(3~90).

3. The carbon quantum dot-enhanced Fe according to claim 1 or 2 x M / RGO catalyst, characterized in that The reduced graphene oxide is also anchored on the surface and in the bulk phase with alkali metal oxides, including potassium oxide and / or sodium oxide, and the mass ratio of alkali metal element to reduced graphene oxide in the alkali metal oxide is (0.05~10):(15~90).

4. The carbon quantum dot-enhanced Fe according to any one of claims 1 to 2 x The method for preparing M / RGO catalyst is characterized by, Includes the following steps: (1) A first hydrothermal reaction was carried out by mixing carbon source, nitrogen source and solvent to obtain nitrogen-doped carbon quantum dots; (2) The nitrogen-doped carbon quantum dots, graphene oxide, water and iron salt are mixed, and the pH of the resulting mixture is adjusted to 8.0~12.0 before a second hydrothermal reaction is carried out to obtain the catalyst precursor. (3) The catalyst precursor is heat-treated in the presence of a non-metallic source to obtain the carbon quantum dot-enhanced Fe. x M / RGO catalyst; the non-metallic source includes one or more of carbon, nitrogen and phosphorus sources.

5. The preparation method according to claim 4, characterized in that, The carbon source in step (1) is one or more of glucose, citric acid, tartaric acid, malonic acid, lactose and lactic acid, and the nitrogen source is one or more of ethylenediamine, urea, ammonia, biuret, phenylenediamine, glycine, tryptophan and arginine; the mass ratio of the carbon source to the nitrogen source is 1:1 to 100:

1.

6. The preparation method according to claim 4, characterized in that, In step (2), the pH value is adjusted by adding an inorganic alkali, which includes one or more of ammonia, sodium inorganic alkali, and potassium inorganic alkali.

7. The preparation method according to claim 4, characterized in that, The carbon source in step (3) includes one or more of CO, CO2, C2H2, CH4 and C2H4, the nitrogen source includes NH3, and the phosphorus source includes one or more of white phosphorus, red phosphorus, PH3 and sodium hypophosphite.

8. The preparation method according to claim 4, characterized in that, The temperature of the first hydrothermal reaction is 100~230℃ and the time is 6~48h; the temperature of the second hydrothermal treatment is 120~240℃ and the time is 4~48h; the temperature of the heat treatment is 200~900℃ and the time is 4~24h.

9. The carbon quantum dot-enhanced Fe according to any one of claims 1 to 3 x M / RGO catalyst or carbon quantum dot-enhanced Fe prepared by the preparation method according to any one of claims 4 to 8 x Application of M / RGO catalyst in CO2 hydrogenation to aviation kerosene.

10. The application according to claim 9, characterized in that, The feed gas for the CO2 hydrogenation to aviation kerosene production comprises CO2 and H2, wherein the molar ratio of CO2 to H2 in the feed gas is 1.0~5.0:1, and the space velocity of the feed gas is 3~50 L / g. cat The reaction rate is 1 / h, the reaction temperature is 250~350℃, and the reaction pressure is 1~6MPa.

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