Metal carbide / nitrogen-doped carbon heterojunction catalyst as well as preparation method and application thereof
By using metal carbide/nitrogen doped carbon heterojunction catalyst in the oxidation desulfurization catalyst, and using the constraint effect and donor effect of nitrogen doped carbon support, the limited mass transfer and post-treatment complexity of existing catalysts when removing low concentrations of sulfides and treating oxidation products is solved, achieving efficient and stable sulfide removal and good recovery performance.
Patent Information
- Application Number
- CN202510341051.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-21
- Publication Date
- 2025-06-24
AI Technical Summary
The existing oxidation and desulfurization catalysts have problems of limited mass transfer and complexity in the removal of low concentrations of sulfides and treating oxidized products, and there are problems of insufficient stability and recyclability in industrial applications.
Using metal carbide/nitrogen doped carbon heterojunction catalysts, highly dispersed heterojunction carbide nanoparticles are formed through the constraint effect and donor effect of nitrogen doped carbon support, improving structural stability and promoting electron concentration, thereby enhancing catalytic activity.
It is achieved efficient removal of sulfides in fuel oil at relatively mild temperatures, especially for difficult-to-treat thiophene sulfides with excellent catalytic activity and good recovery stability.
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Figure CN120189960A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of oxidative desulfurization catalysts, and specifically relates to a metal carbide / nitrogen-doped carbon heterojunction catalyst and a preparation method and application thereof. Background Art
[0002] Against the backdrop of sustained global economic growth and a strong upswing in the renewable energy industry, oil remains a core part of the current energy landscape, accounting for more than 30% of the global energy structure. However, due to the over-exploitation and use of crude oil, crude oil reserves have been greatly reduced. In order to meet market demand, people have developed and used low-quality fossil fuels containing impurities (S, N, etc.). However, the combustion of a large amount of sulfur-containing substances in these fuels will lead to the production of SOx compounds, which will bring many environmental problems. Therefore, the production of sulfur-free fuels by desulfurizing crude oil is crucial to solving environmental problems and protecting public health. The main desulfurization technology currently used in the industry is hydrodesulfurization (HDS), which converts sulfur in oil products into H2S gas, directly reducing the sulfur content in oil products. Although HDS can effectively remove small molecular sulfides, the catalytic removal of thiophene sulfides (such as dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT) and benzothiophene (BT)) requires high temperature, high pressure and a large amount of H2, and the removal efficiency is limited. Considering these limitations, non-hydrodesulfurization technologies have received increasing attention, including oxidative desulfurization (ODS), adsorption desulfurization, extractive desulfurization, photocatalytic desulfurization, and biological desulfurization. Among them, ODS has attracted widespread attention due to its mild reaction conditions, low equipment cost, and strong ability to remove thiophene. ODS can oxidize difficult-to-treat sulfur compounds into highly polar sulfur oxides and / or sulfones, and can be easily separated and recovered by adsorption, extraction, distillation, and crystallization. However, to ensure the efficiency of ODS, highly active catalysts are essential. So far, with people's unremitting efforts, various transition metal oxides (such as WO3, MoO3, and MoOx), nitrides (such as WxN), and carbides (including MxC, where M=W or Mo) have been studied as potential ODS catalysts and show great development potential. In particular, transition metal carbides have been widely developed and utilized in the field of catalysis in recent years due to their stable nanostructure and excellent catalytic performance. However, they still face challenges as industrial ODS catalysts in reaction systems, including limited mass transfer of sulfides at low concentrations and the complexity of post-treatment of oxidation products. Therefore, developing an ODS catalyst with simple preparation method, low price and excellent performance is a technical problem that needs to be solved urgently. Summary of the invention
[0003] The object of the present invention is to provide a metal carbide / nitrogen-doped carbon heterojunction catalyst, a preparation method and an application thereof, aiming at the above deficiencies of the prior art. The catalyst makes full use of the confinement effect of the nitrogen-doped carbon support, enabling the heterojunction carbide nanoparticles to be highly dispersed and firmly combined with the carbon matrix, thereby improving the structural stability of the composite material. In addition, the donor effect of the nitrogen-doped carbon support and the synergistic effect between the heterojunction carbide effectively promote the concentration of electrons towards the active sites, thus greatly enhancing the ODS catalytic activity of the active centers.
[0004] To achieve the above object, the present invention adopts the following technical solutions:
[0005] The first aspect of the present invention is to provide a preparation method of a metal carbide / nitrogen-doped carbon heterojunction catalyst, comprising the following steps:
[0006] S1. Dissolve aniline in a hydrochloric acid solution to form solution A; dissolve a certain amount of heteropolyacid in ice water to form solution B; then, under the stirring condition of an ice-water bath, dropwise add solution A into solution B and react for a preset time to form solution C; the heteropolyacid-loaded polyaniline precursor is any one of phosphotungstic acid, silicotungstic acid and phosphomolybdic acid;
[0007] S2. Add an aqueous ammonium persulfate solution, and then dropwise add it into solution C, continue to react under ice bath conditions, then centrifuge to obtain a solid product, wash the solid product with water and dry it to obtain the heteropolyacid-loaded polyaniline precursor;
[0008] S3. Pyrolyze the heteropolyacid-loaded polyaniline precursor at high temperature under a nitrogen atmosphere to obtain the metal carbide / nitrogen-doped carbon heterojunction catalyst; the high-temperature pyrolysis specifically is: heat up to 500-1000 °C at a rate of 4-5 °C / min and keep it warm for 2-3 h.
[0009] Further, in step S1, the molar concentration of hydrochloric acid is 2-2.5 M, and the volume ratio of aniline to hydrochloric acid is (0.6-0.7):20.
[0010] Further, the mass concentration of the heteropolyacid in solution B is 5-50 mg / mL, and the reaction time for dropwise adding solution A into solution B is 30-35 min.
[0011] Further, in step S2, the mass concentration of the aqueous ammonium persulfate solution is 0.125-0.15 g / mL.
[0012] The second aspect of the present invention is to provide a metal carbide / nitrogen-doped carbon heterojunction catalyst prepared by the above preparation method.
[0013] The third aspect of the present invention is to provide the application of metal carbide / nitrogen-doped carbon heterojunction catalysts in the deep oxidative desulfurization of fuel oil.
[0014] Furthermore, the sulfides removed during the oxidative desulfurization process include any one of dibenzothiophene, benzothiophene, and 4,6-dimethyldibenzothiophene.
[0015] The fourth aspect of the present invention is to provide a method for the deep oxidative desulfurization of fuel oil. The above-mentioned metal carbide / nitrogen-doped carbon heterojunction catalyst is added to fuel oil containing sulfides, and then acetonitrile and an aqueous H2O2 solution are added, and the reaction is carried out at 30 - 70 °C for 2 - 40 min.
[0016] Furthermore, every 20 mL of fuel oil contains 4000 - 5000 ppm of sulfides, and the added metal carbide / nitrogen-doped carbon heterojunction catalyst is 0.005 - 0.1 g, acetonitrile is 20 - 25 mL, and a 30% aqueous H2O2 solution is 128 - 510 μL.
[0017] The fifth aspect of the present invention is to provide a desulfurizer containing the above-mentioned metal carbide / nitrogen-doped carbon heterojunction catalyst.
[0018] Compared with the prior art, the beneficial effects brought by the technical solution provided by the present invention are as follows:
[0019] (1) The present invention synthesizes a heterojunction composite catalyst through a one-step simple polymerization reaction and a one-step pyrolysis process, simplifies the synthesis process, reduces the industrialization difficulty, and reduces the possible environmental pollution during the production process;
[0020] (2) The in-situ synthesized porous nitrogen-doped carbon of the present invention enhances the mass transfer process. The coating effect of the carbon layer effectively improves the stability and recyclability of the catalyst. In addition, the strong electron-donating ability of nitrogen elements in the carbon layer increases the electron density around the active center and improves its catalytic activity;
[0021] (3) The heterojunction interface of the active center of the heterojunction prepared by the present invention exposes rich active sites, which is conducive to electron transfer;
[0022] (4) The WC / W2C@NC, W / W2C@NC, and MoC / Mo2C@NC heterojunction composite catalysts provided by the present invention can completely remove 4000 ppm of DBT sulfides in n-octane simulated oil within 10 - 20 min at a relatively mild temperature (60 °C), and have excellent ODS catalytic activity and recycling stability. Description of the Drawings
[0023] Figure 1 Polyaniline precursor PW loaded with heteropolyacid prepared for Example 1 12Infrared spectrum comparison diagram of / PANI and each raw material;
[0024] Figure 2 PW obtained in Example 1 12 XRD patterns of the / PANI precursor after calcination at different temperatures in a nitrogen atmosphere;
[0025] Figure 3a SEM image of the WC / W2C@NC catalyst obtained after calcination at 900 °C in Example 1;
[0026] Figure 3b TEM image of the WC / W2C@NC catalyst obtained after calcination at 900 °C in Example 1;
[0027] Figure 3c and Figure 3d Both are HRTEM images of the WC / W2C@NC catalyst obtained after calcination at 900 °C in Example 1;
[0028] Figure 3e EDX elemental mapping of the WC / W2C@NC catalyst obtained after calcination at 900 °C in Example 1; It can be clearly observed from the figure that there is a thin carbon layer on the surface of the nanoparticles, which can effectively prevent particle aggregation and corrosion, while increasing electron transport and providing additional catalytic active sites;
[0029] Figure 4 Removal effect curve diagrams of different sulfides DBT, BT, and 4,6-DMDBT using the WC / W2C@NC catalyst prepared in Example 1;
[0030] Figure 5 Performance graph of the WC / W2C@NC catalyst prepared in Example 1 after 8 cycles. Detailed implementation manners
[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes in detail the specific implementation manners of the present invention in combination with specific examples and drawings. For those not specified in the examples regarding specific test methods, instrument equipment, or conditions, they are all carried out according to the techniques or conditions described in the literature in this field or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.
[0032] Example 1
[0033] This example provides a preparation method of a metal carbide / nitrogen-doped carbon heterojunction catalyst.
[0034] Preparation of Porous Carbon-Supported WC / W2C Heterojunction Composite Catalyst (WC / W2C@NC): Dissolve 0.6 mL of aniline in 20 mL of 2 M hydrochloric acid solution to form Solution A; dissolve 0.6 g of PW 12 in 40 mL of ice water to form Solution B; then, under stirring in an ice-water bath, add Solution A dropwise to Solution B and react for 30 min to form Solution C; weigh 1 g of ammonium persulfate and dissolve it in 8 mL of water, then add it dropwise to the above Solution C and continue to react for 24 h under ice-bath conditions. After the reaction, centrifuge at 9000 rpm for 5 min to obtain a solid product, wash it with water multiple times, and dry it in an oven at 60 °C for 6 h to obtain the PW 12 -loaded polyaniline precursor (PW 12 / PANI). Finally, pyrolyze the PW 12 / PANI precursor at 900 °C in a nitrogen atmosphere for 2 h to obtain the WC / W2C@NC composite catalyst.
[0035] Example 2
[0036] This example provides a method for preparing a metal carbide / nitrogen-doped carbon heterojunction catalyst.
[0037] Basically the same as Example 1, the difference is: Pyrolyze at 800 °C for 2 h to prepare the W / W2N@NC composite catalyst.
[0038] Example 3
[0039] This example provides a method for preparing a metal carbide / nitrogen-doped carbon heterojunction catalyst.
[0040] Basically the same as Example 1, the difference is: Pyrolyze at 700 °C for 2 h to prepare the WO3@NC composite catalyst.
[0041] Example 4
[0042] This example provides a method for preparing a metal carbide / nitrogen-doped carbon heterojunction catalyst.
[0043] Basically the same as Example 1, the difference is: Pyrolyze at 500 °C for 2 h to prepare the PW 12 @NC composite catalyst.
[0044] Example 5
[0045] Preparation of Porous Carbon-Supported W / W2C Heterojunction Composite Catalyst (W / W2C@NC): Dissolve 0.6 mL of aniline in 20 mL of 2 M hydrochloric acid solution to form Solution A; dissolve 0.8 g of SiW 12Dissolve it in 40 mL of ice water to form Solution B; subsequently, under the stirring condition of an ice-water bath, slowly add Solution A dropwise to Solution B and react for 30 min to form Solution C; weigh 0.6 g of ammonium persulfate, dissolve it in 8 mL of water, and then slowly add it dropwise to the above-mentioned Solution C. Continue the reaction for 24 h under ice-bath conditions. After the reaction is completed, centrifuge at a speed of 9000 rpm for 5 min to obtain a solid product. Wash it with water multiple times and dry it in an oven at 60 °C for 6 h to obtain SiW 12 supported polyaniline precursor (SiW 12 / PANI). Finally, pyrolyze the SiW 12 / PANI precursor at 800 °C for 2 h under a nitrogen atmosphere to obtain the W / W2C@NC composite catalyst.
[0046] Example 6
[0047] Preparation of porous carbon-supported MoC / Mo2C heterojunction composite catalyst (MoC / Mo2C@NC): Dissolve 0.6 mL of aniline in 20 mL of hydrochloric acid solution with a concentration of 2 M to form Solution A; dissolve 1.6 g of PMo 12 in 40 mL of ice water to form Solution B; subsequently, under the stirring condition of an ice-water bath, slowly add Solution A dropwise to Solution B and react for 30 minutes to form Solution C; weigh 1.2 g of ammonium persulfate, dissolve it in 8 mL of water, and then slowly add it dropwise to the above-mentioned Solution C. Continue the reaction for 24 h under ice-bath conditions. After the reaction is completed, centrifuge at a speed of 9000 rpm for 5 min to obtain a solid product. Wash it with water multiple times and dry it in an oven at 60 °C for 6 h to obtain PMo 12 supported polyaniline precursor (PMo 12 / PANI). Finally, pyrolyze the PMo 12 / PANI precursor at 1000 °C for 2 h under a nitrogen atmosphere to obtain the MoC / Mo2C@NC composite catalyst.
[0048] Example 7
[0049] ODS application of porous carbon-supported heterojunction carbide composite catalyst: Taking Example 1 as an example, for the prepared composite catalyst WC / W2C@NC at 60 °C, using n-octane as the simulated oil and acetonitrile phase as the extractant, test the desulfurization effect of WC / W2C@NC on 4000 ppm sulfide and draw a desulfurization curve. As Figure 4 shown, the desulfurization efficiency of the catalyst for different sulfides is in the order of DBT > 4,6-DMDBT > BT. Especially for DBT, complete removal can be achieved within 15 min. In addition, through the re-desulfurization experiment on the catalyst after the desulfurization is completed, it is found that the catalyst exhibits good recyclability and stability.
[0050] ReferenceFigure 1 The polyoxometalate-loaded polyaniline precursor PW 12 / PANI prepared during the implementation of Example 1 in the present invention and the infrared spectra of each raw material have verified that aniline monomers have been successfully polymerized into polyaniline and simultaneously electrostatically adsorbed with polyoxometalate PW 12 From Figure 1 it can be seen that in the spectrum of the PW 12 / PANI precursor, in addition to the main characteristic absorption peaks at 1567 / 1485 and 1300 cm -1 (corresponding to C═C and C-N bonds in PANI), other peaks at 969, 875, and 781 cm -1 are also found, corresponding to the stretching vibrations of W═Od, W-Ob-W, and W-Oc-W bonds respectively. These results indicate the successful assembly of the PW 12 / PANI composite material.
[0051] Refer to Figure 2 for the XRD pattern changes of the PW 12 / PANI precursor obtained in Example 1 after calcination at 500-1000 °C in a nitrogen atmosphere. From Figure 2 it can be seen that as the calcination temperature increases, the XRD pattern of the product also changes accordingly. When the temperature rises to 700 °C, the characteristic diffraction peaks of WO3 gradually appear in the product. Further increasing to 800 °C, diffraction peaks of W and W2N appear simultaneously in the pattern, indicating the formation of a W / W2N heterojunction at this temperature. The XRD pattern at 900 °C shows the characteristic diffraction peaks of WC and W2C, indicating that as the temperature increases, the carburization effect gradually strengthens, and finally a WC / W2C heterojunction is formed. At a further 1000 °C, only the characteristic diffraction peaks of WC and W2C are observed to become sharp, indicating that excessive grain growth and agglomeration occur at high temperatures.
[0052] Refer to Figure 3a for the SEM image of the WC / W2C@NC catalyst obtained after calcination at 900 °C in Example 1. The figure shows the unique three-dimensional porous structure of the catalyst.
[0053] Refer to Figure 3b for the TEM image of the WC / W2C@NC catalyst obtained after calcination at 900 °C in Example 1. The figure shows that a large number of black nanoparticles are densely and evenly distributed in the polymer-derived carbon material.
[0054] Refer to Figure 3c and Figure 3d, which is the HRTEM image of the WC / W2C@NC catalyst obtained after calcination at 900 °C in Example 1. The figure shows that the lattice spacings of 0.24 and 0.25 nm are visible on the surface of these black nanoparticles, corresponding to the (100) crystal plane of WC and the (002) crystal plane of WC, respectively, which is consistent with the XRD results. From Figure 3d it can be clearly observed that there is a thin carbon layer on the surface of the nanoparticles. This carbon layer can effectively prevent particle aggregation and corrosion, while increasing electron transport and providing additional catalytic active sites.
[0055] Reference Figure 3e , which is the EDX elemental mapping of the WC / W2C@NC catalyst obtained after calcination at 900 °C in Example 1. The figure shows that WC / W2C@NC is composed of C, P, N, W, and O elements evenly distributed on the surface of the material.
[0056] Reference Figure 4 is the desulfurization efficiency curve of the catalyst WC / W2C@NC prepared in Example 1 at a reaction temperature of 60 °C, with n-octane as the simulated oil, for different sulfides DBT, BT, and 4,6-DMDBT at 4000 ppm. From Figure 4 it can be seen that the desulfurization efficiency of the catalyst for different sulfides is in the order of DBT > 4,6-DMDBT > BT. Especially for DBT, complete removal can be achieved within 15 min. Due to steric hindrance and the distribution of S electron concentration in the sulfides, 4,6-DMDBT requires 20 min to be completely removed, while BT has the lowest electron cloud density of S atoms in the molecule, resulting in a longer desulfurization time and incomplete removal.
[0057] Reference Figure 5 , which is the performance graph of the catalyst WC / W2C@NC prepared in Example 1 after 8 cycles. The figure shows that the cyclic performance is very stable.
[0058] Without conflict, the above embodiments and the features in the embodiments in this article can be combined with each other.
[0059] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A method for preparing a metal carbide / nitrogen-doped carbon heterojunction catalyst, characterized in that: The preparation method comprises the following steps: S1, dissolving aniline in a hydrochloric acid solution to form a solution A; dissolving a certain amount of heteropoly acid in ice water to form a solution B; then, under stirring conditions in an ice water bath, adding the solution A dropwise into the solution B, reacting for a preset time, to form a solution C; the heteropoly acid is any one of phosphotungstic acid, silicotungstic acid and phosphomolybdic acid; S2, adding the ammonium persulfate aqueous solution dropwise to the C solution, continuing the reaction under ice bath conditions, centrifuging to obtain a solid product, washing the solid product with water, and drying it to obtain a heteropolyacid-supported polyaniline precursor; S3. The polyaniline precursor supported by the heteropolyacid is pyrolyzed at high temperature in a nitrogen atmosphere to obtain a metal carbide / nitrogen-doped carbon heterojunction catalyst; wherein the high temperature pyrolysis mechanism is: heating to 500-1000° C. at a rate of 4-5° C. / min and keeping warm for 2-3 hours.
2. The preparation method according to claim 1, characterized in that In step S1, the molar concentration of hydrochloric acid is 2-2.5M, and the volume ratio of aniline to hydrochloric acid is (0.6-0.7):
20.
3. The preparation method according to claim 2, characterized in that: The mass concentration of the heteropoly acid in the B solution is 5-50 mg / mL, and the A solution is added dropwise into the B solution for a reaction time of 30-35 minutes.
4. The preparation method according to claim 3, characterized in that: In step S2, the mass concentration of the ammonium persulfate aqueous solution is 0.125-0.15 g / mL.
5. A metal carbide / nitrogen-doped carbon heterojunction catalyst prepared by the preparation method according to any one of claims 1 to 4.
6. Use of the metal carbide / nitrogen-doped carbon heterojunction catalyst as claimed in claim 5 in deep oxidation desulfurization of fuel oil.
7. The use according to claim 6, characterized in that The sulfide removed during the oxidative desulfurization process includes any one of dibenzothiophene, benzothiophene, and 4,6-dimethyldibenzothiophene.
8. A method for deep oxidation desulfurization of fuel oil, characterized in that: The metal carbide / nitrogen-doped carbon heterojunction catalyst as claimed in claim 5 is added to the fuel containing sulfide, and then acetonitrile and H2O2 aqueous solution are added to react at 30-70°C for 2-40 minutes.
9. The method according to claim 8, characterized in that Every 20 mL of fuel contains 4000-5000 ppm of sulfide, and the added metal carbide / nitrogen-doped carbon heterojunction catalyst is 0.005-0.1 g, acetonitrile is 20-25 mL, and 30% H2O2 aqueous solution is 128-510 μL.
10. A desulfurizing agent, characterized in that: It comprises the metal carbide / nitrogen-doped carbon heterojunction catalyst as claimed in claim 5.