A short Fe-C bond Fe-based catalyst for catalytic CO2 hydrogenation, its preparation method and its application in the preparation of C 2+ Applications in high value-added products

Abstract

This invention discloses a short Fe-C bond Fe-based catalyst for catalytic CO2 hydrogenation, its preparation method, and its application in the preparation of C 2+ This invention relates to the application of high-value-added products, belonging to the field of CO2 capture, utilization, and storage technology. The catalyst is a carbon quantum dot-doped Fe-based catalyst, prepared by the following method: dissolving carbon quantum dots (CQDs) in an aqueous ethanol solution to obtain a CQDs dispersion; then adding cubic Fe2O3 nanoparticles, stirring the reaction, and drying to obtain a short Fe-C bond Fe-based catalyst. The short Fe-C bond Fe-based catalyst of this invention is simple to prepare, low in cost, and can achieve highly selective one-step catalytic hydrogenation of CO2 to C. 2+ The product is obtained by effectively reducing the selectivity of the main C1 byproducts CO and CH4. This invention opens up a new strategy for regulating the electronic structure of Fe-based catalysts for CO2 hydrogenation catalysis, providing a new approach for the rational design of catalysts with directed synthesis capabilities, and has good application prospects in the field of CO2 capture, utilization, and storage.

Description

Technical Field

[0001] This invention belongs to the field of CO2 capture, utilization, and storage technology, specifically relating to a short Fe-C bond Fe-based catalyst for catalytic CO2 hydrogenation, its preparation method, and its application in the preparation of C 2+ Applications in high value-added products. Background Technology

[0002] Global annual CO2 emissions have exceeded 35 billion tons, with an average concentration surpassing 420 ppm, leading to environmental disasters such as global warming and frequent extreme weather events. Besides being a major component of greenhouse gases, CO2 is also one of the most important large-scale resources available to humankind, following fossil and biomass resources. Artificially converting CO2 into high-value-added chemicals (olefins, aromatics, oxygen-containing compounds, etc.) through chemical means is crucial for developing strategic emerging industries and promoting sustainable economic and social development in the future.

[0003] Among numerous CO2 conversion pathways, thermocatalytic CO2 hydrogenation technology has become a cutting-edge research direction in the field of carbon resource recycling due to its excellent CO2 activation capability, precise product control characteristics, and scalable industrial adaptability. With the accelerated iteration of green hydrogen production technologies such as wind power and photovoltaics, the technical and economic advantages of CO2 thermocatalytic hydrogenation systems coupled with renewable energy in the synthesis of high-end chemicals are becoming increasingly prominent.

[0004] In thermocatalytic CO2 hydrogenation systems, high-value-added C 2+ The synthesis of products (olefins, aromatics, or oxygen-containing intermediates) mainly relies on two dominant reaction mechanisms: the methanol-mediated pathway and the modified Fischer-Tropsch pathway. The former utilizes reducing metal oxides (such as ZnO-ZrO2, In2O3-ZrO2, ZnGa2O4, etc.) to hydrogenate CO2 to methanol. Methanol molecules can then further generate multi-carbon compounds under the action of other functional catalytic components. Although the methanol-mediated route can overcome the Anderson-Schulz-Flory (ASF) distribution limitations of traditional Fischer-Tropsch synthesis and achieve selective control of specific products, its thermodynamic bottleneck limits the single-pass CO2 conversion efficiency and results in significantly higher CO selectivity, restricting the yield improvement of high-value-added chemicals. In the modified Fischer-Tropsch synthesis route, CO2 is converted to CO via reverse water-gas shift (RWGS: CO2 + H2 → CO + H2O), and then reacts with H2 in a Fischer-Tropsch (FTS) chain-growth reaction to generate high-value C. 2+ Products. The modified Fischer-Tropsch synthesis route exhibits high CO2 conversion and low CO selectivity, providing a feasible solution for the large-scale preparation of high-value chemicals.

[0005] As one of the earliest and most thoroughly studied catalyst systems in the Fischer-Tropsch synthesis field, Fe-based catalysts exhibit unique advantages in CO2 hydrogenation due to their significant cost advantages, tunable electronic structure, and unique product distribution control dimensions. Fe-based catalysts possess both the reactive phase of RWGS (Fe3O4) and the reactive phase of FTS (primarily Fe5C2). The precise construction and synergistic control of these reactive phases, along with their inherent intrinsic reactivity and selectivity, are crucial for improving the CO2 hydrogenation performance of Fe-based catalysts, particularly enhancing CO2 conversion and high-value C content. 2+ It improves product selectivity and suppresses C1 product selectivity. However, when Fe is used alone as the active metal, its catalytic activity and stability may be limited, and it is difficult to meet the requirements for C1 product selectivity. 2+ The requirement for high product selectivity. Modifying Fe-based catalysts with electronic promoters can adjust their electronic structure and improve catalytic performance. Alkali metal promoters (such as Li, Na, K, and Cs) can significantly increase CO2 adsorption intensity, while also altering the Wulff configuration and enhancing the carburization process of Fe-based catalysts. Furthermore, due to their strong electron-donating effect, alkali metal promoters can significantly increase the electron density of active sites, promoting olefin desorption and inhibiting H2 adsorption, thereby improving the selectivity for high-value C atoms. 2+ Product selectivity. However, the active ratio of Fe3O4 / Fe5C2 induced by alkali metals is severely mismatched, and the Fischer-Tropsch activity of the in-situ generated Fe5C2 species is insufficient, resulting in limited ability to improve overall CO2 conversion and suppress CO selectivity, which severely limits the space-time yield of the target product.

[0006] Furthermore, the coordination environment of active sites, especially the bond length and electronic structure of the Fe-C bond, often has a decisive influence on the choice of reaction pathway and the final catalytic performance. In traditional iron-based catalytic systems, although alkali metal modification can improve the electronic structure of Fe species to some extent, the active sites it imparts usually exhibit a single electron-rich characteristic, and the regulatory space of the Fe-C bond length (1.92 Å) is limited, making it difficult to achieve fine optimization of the electronic structure of the active center. This limited electronic regulation capability leads to low CO bond activation efficiency and hindered CC coupling in the reaction, thereby reducing the catalytic efficiency of CO2 hydrogenation and C. 2+ Product selectivity still has significant room for improvement, making it difficult to meet the demands of efficient thermocatalytic conversion. Furthermore, the single type of active sites in existing iron-based catalysts is insufficient to accommodate various C4+ molecules. 2+ The product formation pathways (such as olefins, ethanol, and aromatics) limit the flexibility and precision of product distribution control. Furthermore, the H₂O generated during the reaction readily reacts with the iron carbide active phase, gradually oxidizing it to Fe₃O₄, leading to catalyst structural degradation and decreased long-term stability.

[0007] Therefore, it is necessary to develop an Fe-based catalyst with a shorter Fe-C bond to enhance its activity in Fischer-Tropsch synthesis. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a novel Fe-based catalyst that shortens the Fe-C bond by modulating the electronic structure. By introducing carbon quantum dots (CQDs) into the catalytic system, the electronic interaction between Fe and C is effectively enhanced, significantly shortening the Fe-C bond length from the traditional 1.92 Å to approximately 1.63 Å. This optimizes the electronic environment of the active site, promotes CO breaking and CC coupling steps in the CO2 hydrogenation process, and ultimately achieves highly efficient and stable C… 2+ Product synthesis.

[0009] This invention provides a short Fe-C bond Fe-based catalyst for catalytic CO2 hydrogenation, wherein the catalyst is a carbon quantum dot-doped Fe-based catalyst.

[0010] The preparation method of the above-mentioned short Fe-C bond Fe-based catalyst for catalytic CO2 hydrogenation includes the following steps: (1) Preparation of cubic Fe2O3 nanoparticles At 60~80℃, an iron salt solution is added dropwise to an alkaline solution to form Fe(OH)3 gel; the Fe(OH)3 gel is continuously stirred to form a suspension, and then hydrothermally reacted at 80~150℃ for 24~100h; after the reaction is completed, the product is centrifuged, washed, and dried to obtain cubic Fe2O3 nanoparticles.

[0011] (2) Preparation of carbon quantum dots (CQDs) The carbon source was placed in an air atmosphere and calcined to obtain black carbon material. The black carbon material was then dissolved in water, and an alkaline solution was added to promote dissolution. The material was ultrasonically dispersed for 15-60 min. The supernatant was then centrifuged and dialyzed. The dialysate was freeze-dried to obtain carbon quantum dots (CQDs).

[0012] (3) Preparation of Fe-based catalysts with short Fe-C bonds Carbon quantum dots (CQDs) were dissolved in an aqueous ethanol solution to obtain a CQDs dispersion. Then, cubic Fe2O3 nanoparticles were added, the mixture was stirred, and dried to obtain a CQDs-Fe catalyst, i.e., a short Fe-C bond Fe-based catalyst.

[0013] In the above preparation method, in step (1), the iron salt solution is one or more of FeCl3 solution, Fe(NO3)3 solution, and FeSO4 solution; the concentration is 0.5~3 mol / L.

[0014] In the above preparation method, in step (1), the alkaline solution is a NaOH solution or a KOH solution with a concentration of 3~6 mol / L.

[0015] In the above preparation method, in step (1), the volume ratio of the iron salt solution to the alkaline solution is 1:1.

[0016] In the above preparation method, in step (2), the carbon source is one or more of aspartic acid, citric acid, and glucose.

[0017] In the above preparation method, in step (2), the calcination conditions are: calcination at 100~400℃ for 24~120h.

[0018] In the above preparation method, in step (2), the alkaline solution is a NaOH solution or a KOH solution with pH > 12.

[0019] In the above preparation method, in step (3), the mass ratio of carbon quantum dots (CQDs) to cubic Fe2O3 nanoparticles is (3~20):100.

[0020] In the above preparation method, in step (3), the stirring reaction conditions are: stirring at 15~35℃ for 20~60 min.

[0021] In the above preparation method, in step (3), the concentration of the CQDs dispersion is 0.1~20 mg / mL; the concentration of the ethanol aqueous solution is 5~70 wt%.

[0022] This invention provides the above-mentioned short Fe-C bond Fe-based catalyst for catalytic CO2 hydrogenation in the preparation of C 2+ Applications in high-value-added products; in the above applications, short Fe-C bond Fe-based catalysts can directly catalyze the hydrogenation of CO2 to produce C 2+ The product can also be used to prepare aromatic products by coupling with acidic zeolite (H-ZSM-5) to catalyze the hydrogenation of CO2, and can also be used to prepare ethanol products by coupling with alkali metal modified CuZnAl (KCZA) to catalyze the hydrogenation of CO2.

[0023] This invention provides a method for preparing C by CO2 hydrogenation. 2+ The method for producing the product, the steps are as follows: A short Fe-C bond Fe-based catalyst was placed in a fixed-bed reactor and activated in a pure H2 atmosphere at 200–400 °C for 1–6 h. After cooling to room temperature, a reaction gas mixture was added to carry out the reaction, yielding C. 2+ product.

[0024] The above CO2 hydrogenation preparation of C 2+In the method for producing the product, the reaction gas mixture consists of CO2, H2 and an inert gas; the inert gas is preferably argon; the volume ratio of CO2 to H2 is 1:(2~5), preferably 1:3; the volume content of argon is 2~8%, preferably 5%.

[0025] The above CO2 hydrogenation preparation of C 2+ In the method for producing the product, the reaction conditions are: a reaction temperature of 300~400℃, a reaction pressure of 2~10MPa, and a reaction time of 12~48 h.

[0026] The beneficial effects of this invention are as follows: The short Fe-C bond Fe-based catalyst for catalytic CO2 hydrogenation provided by this invention can enhance the hydrogenation reaction process, improve CO2 conversion and target product selectivity, open up a new strategy for electronic structure regulation of Fe-based catalysts for CO2 hydrogenation catalysis, provide a new idea for the rational design of catalysts with directional synthesis function, and have good application prospects in the field of CO2 capture, utilization and storage.

[0027] This invention employs CQDs with tiny size and unique surface chemistry to modify Fe-based catalysts. The unique electronic properties and coordination environment formed at the interface between CQDs and Fe-based catalysts can enhance the activity of CO2 hydrogenation reaction and increase the high-value C 2+ Product selectivity. Novel, highly efficient Fe-C bonds were constructed through coordination between Fe atoms and C atoms in CQDs, enhancing the reactivity of the Fischer-Tropsch synthesis and significantly accelerating CO2 conversion and C production. 2+ Product formation. The CQDs modification strategy proposed in this invention has created a groundbreaking paradigm for the rational design of catalysts for CO2 hydrogenation and syngas conversion, and is expected to expand the research prospects of C1 molecular catalytic systems.

[0028] This invention shortens the Fe-C bond length from 1.92 Å in the traditional Fe5C2 to 1.63 Å through the strong electronic interaction between CQDs and Fe2O3 (Fe→CQDs electron transfer), significantly reducing the C-C coupling energy barrier and providing a new paradigm for the electronic structure regulation of Fe-based catalysts.

[0029] This invention introduces carbon quantum dots (CQDs) onto the surface of Fe2O3, inducing enhanced electron transfer between Fe and C, thereby generating novel active sites with short Fe-C bonds. This is used for the efficient and highly selective preparation of C via CO2 hydrogenation. 2+ Products (including olefins, alcohols, aromatics, etc.).

[0030] The catalyst described in this invention is simple to prepare, requiring no high-temperature calcination or complex in-situ carbonization. CQDs can be supported simply by equal-volume impregnation, resulting in low cost and easy industrial scale-up. It can achieve highly selective one-step catalytic hydrogenation of CO2 to C60. 2+ The product is obtained by effectively reducing the selectivity of the main C1 byproducts CO and CH4. The technical solution provided by this invention opens up a new strategy for regulating the electronic structure of Fe-based catalysts in CO2 hydrogenation catalysis, offering new insights for the rational design of catalysts with directed synthesis capabilities.

[0031] This invention enables multi-path conversion of CO2 hydrogenation—both direct synthesis of C and... 2+ The products (olefins / alkanes) can also be used to prepare aromatics by coupling with acidic zeolite (H-ZSM-5) and to prepare ethanol by coupling with alkali metal modified CuZnAl (KCZA), which can meet the needs of a variety of high-value chemicals.

[0032] This invention can achieve "C" 2+ The multi-path conversion of hydrocarbons (olefins / alkanes) / ethanol / aromatics covers three major fields: fuels (olefins), basic chemicals (ethanol), and high-end material precursors (aromatics), and is suitable for multiple scenarios such as petrochemicals and pharmaceutical intermediates; the product direction is adjustable: by changing the coupling components (KCZA / H-ZSM-5) and reaction parameters, the selectivity of the target product can be precisely controlled (such as ethanol selectivity of 26.8% and aromatic selectivity of 37.3%), which is far more flexible than existing technologies.

[0033] This invention utilizes the strong interfacial electronic interactions between CQDs and Fe2O3 to systematically construct and stabilize novel active sites with high-density "short Fe-C bonds," thereby significantly reducing the energy barrier for CO* hydrogenation and CC binding, and increasing the FTS step rate and C... 2+ Product selectivity. Attached Figure Description

[0034] Figure 1 Transmission electron microscope (TEM) image (a), high-angle annular dark-field scanning TEM image (b), and elemental distribution diagram of Fe (b-1), O (b-2), and C (b-3) in CQDs-Fe catalyst are shown. Detailed Implementation

[0035] Other materials used in this invention, unless otherwise stated, are commercially available. Other terms used in this invention, unless otherwise specified, generally have the meanings commonly understood by those skilled in the art. The invention is further described in detail below with reference to specific embodiments and data. The following embodiments are merely illustrative and not intended to limit the scope of the invention in any way.

[0036] Example 1 The steps for preparing a short Fe-C bond Fe-based catalyst for catalytic CO2 hydrogenation are as follows: (1) Preparation of cubic Fe2O3 nanoparticles Prepare a NaOH solution (5.4 mol / L) and a FeCl3 aqueous solution (2 mol / L), and heat both solutions in a 75 ℃ oil bath until the temperature stabilizes at 75 ℃.

[0037] At 75 °C and with the magnetic stirrer maintaining a stirring speed of 800 r / min, 50 mL of FeCl3 aqueous solution (2 M) was added dropwise to 50 mL of NaOH solution (5.4 M) at a uniform rate, with the addition time controlled at 5 min, to form Fe(OH)3 gel.

[0038] The Fe(OH)3 gel was continuously stirred for 5 min to form a suspension; then it was poured into a stainless steel reactor with a polytetrafluoroethylene liner, and after being strictly sealed to ensure no leakage, it was hydrothermally reacted at 100 ℃ in a forced-air drying oven for 4 days.

[0039] After the hydrothermal process is completed and the reactor temperature has completely cooled to room temperature, the product is removed from the liner, centrifuged at 8000 rpm for 10 min, and washed with deionized water and ethanol. After washing three times, the resulting red product is transferred to a forced-air drying oven and dried at 60 ℃ for 12 h to obtain a dry red powder, which is cubic Fe2O3 nanoparticles with an average particle size of 200 nm.

[0040] (2) Preparation of carbon quantum dots (CQDs) 10 g of aspartic acid was placed in a muffle furnace and calcined at 320 °C for 100 h under air atmosphere at a rate of 5 °C / min. The pyrolyzed carbon material (calcined product) was then ground in an agate mortar and dissolved in 100 mL of deionized water, with 1 mL of NaOH solution (5 mol / L) added to promote dissolution.

[0041] After sonicating the solution for 30 min, centrifuge it at 8000 r / min for 10 min and collect the supernatant. Then, place the supernatant into a 1000 Da dialysis membrane and dialyze for 7 days, changing the deionized water every 12 h. Freeze-dry the dialysate to obtain a brown powder, namely carbon quantum dots (CQDs).

[0042] (3) Preparation of Fe-based catalysts with short Fe-C bonds 0.15 g of CQDs was dissolved in 10 mL of ethanol aqueous solution (containing 2 mL of ethanol) to obtain CQDs dispersion; 1 g of cubic Fe2O3 nanoparticles were added, the mixture was stirred at room temperature for 30 min, dried at 60 ℃ for 24 h, and crushed and sieved to 20~40 mesh to obtain CQDs-Fe catalyst.

[0043] The Fe-C bond length in the above CQDs-Fe catalyst was determined by X-ray absorption fine structure characterization (XAFS) combined with density functional theory calculation (DFT), and the result was 1.63 Å, which is significantly lower than the 1.92 Å of the conventional Fe5C2 catalyst (this value was obtained by DFT calculation and is the intrinsic value of the Fe5C2 unit cell).

[0044] This invention breaks through the traditional iron-carbide bond length limitation (1.92 Å). DFT calculations show that this bond length can reduce the CO* hydrogenation energy barrier (0.62 eV) and the CC coupling energy barrier (0.45 eV), fundamentally improving FTS activity.

[0045] Transmission electron microscopy (TEM) image (a) of CQDs-Fe catalyst, high-angle annular dark-field scanning TEM image (b), and elemental distribution of Fe(b-1), O(b-2), and C(b-3) in CQDs-Fe catalyst, as shown in the image. Figure 1 As shown in the transmission electron microscope image of the CQDs-Fe catalyst, a light-colored and nearly transparent layer was detected on the outer surface of the CQDs-Fe catalyst, which can be attributed to CQDs modification. Furthermore, the carbon elements introduced by CQDs are uniformly distributed on the surface of the CQDs-Fe catalyst, further demonstrating that CQDs were successfully anchored on the surface of Fe2O3 nanocubes.

[0046] I. Catalytic CO2 hydrogenation to C 2+ product The CQDs-Fe catalyst was tableted at 10 MPa, then crushed, sieved, and granulated to a particle size of 20–40 mesh. 0.3 g of the granulated CQDs-Fe catalyst was uniformly mixed with 1 g of quartz sand particles and then packed into a fixed-bed reactor (reaction tube inner diameter 6 mm). 2.0 g of quartz sand was added to the top of the catalyst bed to promote fluid agitation, and appropriate amounts of quartz wool were filled at the top and bottom of the reactor to seal and support the catalyst bed, preventing catalyst particles from falling off. The catalyst was first pretreated by reduction in an H2 atmosphere at 400 °C for 4 h at a flow rate of 60 mL / min. The active catalyst was placed in the reaction tube, and a mixed gas (containing 5% Ar, 23.7% CO2, and 71.3% H2) was introduced at a flow rate of 15 mL / min. The reaction was carried out at 320 °C and 3.0 MPa for 24 h. The products were analyzed by gas chromatography. Cubic Fe2O3 nanoparticles and Na-doped Fe2O3 nanocubes (Na-Fe) were used as catalysts as controls.

[0047] The Na-Fe catalyst was prepared by the following method: 0.069 g of Na2CO3 was dissolved in 1 g of ethanol aqueous solution (containing 0.2 g of ethanol), and 1 g of cubic Fe2O3 nanoparticles were impregnated with the solution. After drying in a forced-air drying oven at 60 ℃ for 24 h, an alkali metal Na-doped Fe-based catalyst (Na-Fe) was obtained, wherein the loading of alkali metal Na was 3 wt%.

[0048] The reaction results are shown in Table 1.

[0049] Table 1 Results of catalytic CO2 hydrogenation reaction Note: In Table 1, C2 0 -C4 0 This refers to C2-C4 products of alkanes, C 5+ 0 C represents alkanes 5+ Products, C2-C4 = Represents C2-C4 products of alkenes, C 5+ = C represents the olefin 5+ product.

[0050] The pure Fe2O3 catalyst exhibited poor catalytic performance, with a CO2 conversion rate of only 19.0%, and the products mainly concentrated in methane (40.6%) and light alkanes (C2O3). 0 -C4 0 The CO2 conversion rate of the CQDs-Fe catalyst was significantly improved to 38.5%, while the carbon monoxide selectivity was only 8.8%, and the C...2+ The product selectivity increased to 81.3%. The overall selectivity of olefin products reached a maximum of 51.1%, of which light olefins (C2... = -C4 = ) accounted for 29.5%, and heavy olefins (C 5+ = (21.6%). Compared with pure Fe2O3, the introduction of Na and CQDs significantly increased C. 2+ Product selectivity. Furthermore, the CO selectivity of the CQDs-Fe catalyst (8.8%) is much lower than that of the Na-Fe catalyst (23.8%). Its higher CO* intermediate conversion efficiency is beneficial to promoting the overall reaction and improving the overall CO2 conversion rate.

[0051] II. Ethanol production via CQDs-Fe coupling with KCZA Bifunctional system: 0.1g CQDs-Fe + 0.1g KCZA. The above catalyst was packed into a fixed-bed reactor; pretreatment: 400℃, H2 reduction for 4h; heating to 320℃, introducing feed gas (CO2:H2:Ar = 23.7:71.3:5); adjusting the pressure to 5MPa, space velocity to 4500 mL g / L. Fe -1 h -1 The reaction was carried out for 24 h. Fe2O3&KCZA and Na-Fe&KCZ were used as controls.

[0052] The KCZA is a potassium copper zinc aluminum catalyst, prepared by the following method: 26.81 g of copper nitrate trihydrate, 13.38 g of zinc nitrate hexahydrate, 11.25 g of aluminum nitrate nonahydrate, and 48.29 g of urea were dissolved in 750 mL of deionized water to form a homogeneous solution. This solution was placed in an oil bath and heated to 95 °C with stirring for 2 h. Subsequently, it was subjected to a sedimentation aging treatment at 95 °C for 24 h. The blackish-gray product was separated and collected by centrifugation, washed four times with deionized water, and then dried overnight in an oven at 70 °C. Next, the blackish-gray product was calcined at 350 °C for 3 h under air atmosphere at a heating rate of 5 °C / min to obtain a copper-zinc-aluminum catalyst. The catalyst was then impregnated with a potassium nitrate solution (0.40 mol / L) for a 5% potassium impregnation treatment, followed by drying overnight in an oven at 70 °C to obtain a potassium-copper-zinc-aluminum catalyst, named KCZA.

[0053] The test results are shown in Table 2.

[0054] Table 2 Results of catalytic CO2 hydrogenation reaction Thanks to the oxygen-containing intermediate provided by the KCZA component, CQDs-Fe&KCZA exhibits a C content of 31.3%. 2+ The alcohol selectivity surpasses that of Fe2O3&KCZA (16.4%) and Na-Fe&KCZA (26.4%). In terms of ethanol synthesis performance, CQDs-Fe&KCZA achieves an excellent ethanol selectivity of 26.8%, compared to Fe2O3&KCZA (13.6%) and Na-Fe&KCZA (21.9%).

[0055] III. Production of Aromatic Hydrocarbons via CQDs-Fe Coupling with H-ZSM-5 Bifunctional system: 0.2g CQDs-Fe + 0.6g H-ZSM-5 (Si / Al=25), packed in a fixed-bed reactor; pretreatment: 400℃, H2 reduction for 4 h; heating to 320℃, introducing feed gas (CO2:H2:Ar=23.7:71.3:5); adjusting pressure to 3MPa, space velocity to 3000 mL g / L. Fe -1 h -1 The reaction was carried out for 24 h. Fe2O3-Z5 and Na-Fe-Z5 were used as catalysts as controls.

[0056] H-ZSM-5 zeolite is prepared by the following method: 91.50 g of deionized water was added to a 200 mL polytetrafluoroethylene (PTFE) bottle. Then, while stirring, 0.48 g of sodium aluminate, 1.83 g of tetrapropylammonium bromide, and 3.92 g of n-butylamine were added, and the mixture was magnetically stirred for 15 min to ensure complete dissolution. Next, 22.53 g of silica sol was slowly added dropwise, and stirring was continued for 30 min. The resulting solution was evenly poured into two stainless steel reactors lined with PTFE. After being tightly sealed to ensure no leakage, the reactors were transferred to a rotary drying oven and fixed on a rotating support. The temperature was increased to 180 °C at a rate of 10 °C / min, controlled at 5.6 rpm, and maintained for 48 h. After the hydrothermal treatment ended and the reactor temperature naturally cooled to room temperature, the resulting emulsion was washed three times with deionized water by centrifugation and then dried overnight in a 60 °C rotary drying oven to obtain the HZSM-5 precursor. The HZSM-5 precursor was appropriately ground in an agate mortar and heated to 550 °C in an air atmosphere in a muffle furnace at a heating rate of 5 °C / min, held for 6 h, and calcined to remove the organic template agent, thus obtaining H-ZSM-5 zeolite.

[0057] The test results are shown in Table 3.

[0058] Table 3 Results of catalytic CO2 hydrogenation reaction Combining CQDs-Fe catalysts with Z5 zeolite enables efficient aromatic synthesis. The CQDs-Fe-Z5 catalyst achieves an aromatic selectivity of 37.3%, superior to the Na-Fe-Z5 catalyst (30.0%). In contrast, the Fe2O3-Z5 catalyst exhibits an aromatic selectivity of only 4.2%, which can be attributed to the poor olefin synthesis ability of the Fe2O3 component.

[0059] Based on the above results, the CQDs modification strategy also demonstrates considerable universality and can be used to rationally design iron-based catalysts to promote the synthesis of a variety of high-value-added chemicals by CO2 hydrogenation.

[0060] This invention also provides other feasible implementation examples, as follows: Example 2 Preparation of short Fe-C bond Fe-based catalysts for catalytic CO2 hydrogenation 0.03 g of CQDs was dissolved in 10 mL of deionized water (containing 2 mL of ethanol) to obtain a CQDs dispersion; 1 g of cubic Fe2O3 nanoparticles were added, the mixture was stirred at room temperature for 30 min, dried at 60 ℃ for 24 h, and then crushed and sieved to 20~40 mesh to obtain the CQDs-Fe catalyst.

[0061] Example 3 Preparation of short Fe-C bond Fe-based catalysts for catalytic CO2 hydrogenation 0.05 g of CQDs was dissolved in 10 mL of deionized water (containing 2 mL of ethanol) to obtain a CQDs dispersion; 1 g of cubic Fe2O3 nanoparticles were added, and the mixture was stirred at room temperature for 30 min, dried at 60 ℃ for 24 h, and crushed and sieved to 20~40 mesh to obtain the CQDs-Fe catalyst.

[0062] Example 4 Preparation of short Fe-C bond Fe-based catalysts for catalytic CO2 hydrogenation 0.1 g of CQDs was dissolved in 10 mL of deionized water (containing 2 mL of ethanol) to obtain a CQDs dispersion; 1 g of cubic Fe2O3 nanoparticles were added, and the mixture was stirred at room temperature for 30 min, dried at 60 ℃ for 24 h, and crushed and sieved to 20~40 mesh to obtain the CQDs-Fe catalyst.

[0063] Example 5 Preparation of short Fe-C bond Fe-based catalysts for catalytic CO2 hydrogenation 0.2 g of CQDs was dissolved in 10 mL of deionized water (containing 2 mL of ethanol) to obtain a CQDs dispersion; 1 g of cubic Fe2O3 nanoparticles were added, and the mixture was stirred at room temperature for 30 min, dried at 60 ℃ for 24 h, and crushed and sieved to 20~40 mesh to obtain the CQDs-Fe catalyst.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. Use of short Fe-C bond Fe-based catalysts in the catalytic production of C 2+ high value-added products from CO2 hydrogenation. The short Fe-C bond Fe-based catalyst is prepared by the following method: (1) Preparation of cubic Fe2O3 nanoparticles At 60~80℃, an iron salt solution is dropped into an alkaline solution to form Fe(OH)3 gel; the Fe(OH)3 gel is continuously stirred to form a suspension, and then hydrothermally reacted at 80~150℃ for 24~100h; after the reaction is completed, the product is centrifuged, washed, and dried to obtain cubic Fe2O3 nanoparticles. (2) Preparation of carbon quantum dots (CQDs) The carbon source was placed in an air atmosphere and calcined to obtain black carbon material; then the black carbon material was dissolved in water and an alkaline solution was added to promote dissolution; ultrasonic dispersion was performed for 15-60 min; then centrifugation was carried out, the supernatant was collected and dialyzed; the dialysate was freeze-dried to obtain carbon quantum dots (CQDs). (3) Preparation of Fe-based catalysts with short Fe-C bonds Carbon quantum dots (CQDs) were dissolved in an aqueous ethanol solution to obtain a CQDs dispersion; then cubic Fe2O3 nanoparticles were added, the reaction was stirred, and the mixture was dried to obtain a CQDs-Fe catalyst, i.e., a short Fe-C bond Fe-based catalyst. in, In step (1), the iron salt solution is one or more of FeCl3 solution and Fe(NO3)3 solution, and the alkaline solution is NaOH solution or KOH solution; in step (2), the carbon source is one or more of aspartic acid, citric acid and glucose; in step (2), the calcination conditions are: calcination at 100~400℃ for 24~120h; in step (3), the mass ratio of carbon quantum dots (CQDs) to cubic Fe2O3 nanoparticles is (3~20):

100.

2. A method for preparing C by CO2 hydrogenation 2+ The method for producing the product is characterized by, The steps are as follows: A short Fe-C bond Fe-based catalyst was placed in a fixed-bed reactor and activated in a pure H2 atmosphere at 200–400 °C for 1–6 h. After cooling to room temperature, a reaction gas mixture was added to carry out the reaction, yielding C. 2+ product; The short Fe-C bond Fe-based catalyst is prepared by the following method: (1) Preparation of cubic Fe2O3 nanoparticles At 60~80℃, an iron salt solution is dropped into an alkaline solution to form Fe(OH)3 gel; the Fe(OH)3 gel is continuously stirred to form a suspension, and then hydrothermally reacted at 80~150℃ for 24~100h; after the reaction is completed, the product is centrifuged, washed, and dried to obtain cubic Fe2O3 nanoparticles. (2) Preparation of carbon quantum dots (CQDs) The carbon source was placed in an air atmosphere and calcined to obtain black carbon material; then the black carbon material was dissolved in water and an alkaline solution was added to promote dissolution; ultrasonic dispersion was performed for 15-60 min; then centrifugation was carried out, the supernatant was collected and dialyzed; the dialysate was freeze-dried to obtain carbon quantum dots (CQDs). (3) Preparation of Fe-based catalysts with short Fe-C bonds Carbon quantum dots (CQDs) were dissolved in an aqueous ethanol solution to obtain a CQDs dispersion; then cubic Fe2O3 nanoparticles were added, the reaction was stirred, and the mixture was dried to obtain a CQDs-Fe catalyst, i.e., a short Fe-C bond Fe-based catalyst. In step (1), the iron salt solution is one or more of FeCl3 solution and Fe(NO3)3 solution, and the alkaline solution is NaOH solution or KOH solution; in step (2), the carbon source is one or more of aspartic acid, citric acid, and glucose; in step (2), the calcination conditions are: calcination at 100~400℃ for 24~120h; in step (3), the mass ratio of carbon quantum dots (CQDs) to cubic Fe2O3 nanoparticles is (3~20):

100.

3. The CO2 hydrogenation preparation of C according to claim 2 2+ The method for producing the product is characterized by, The reaction gas mixture consists of CO2, H2 and an inert gas; the volume ratio of CO2 to H2 is 1:(2~5); and the volume content of the inert gas is 2~8%.

4. The CO2 hydrogenation preparation of C according to claim 2 2+ The method for producing the product is characterized by, The reaction conditions are: reaction temperature of 300~400℃, reaction pressure of 2~10MPa, and reaction time of 12~48 h.

Images