A porous carbon nanosheet supported bimetallic phosphide catalyst and a preparation method thereof

Abstract

The application discloses a kind of porous carbon nanosheet supported bimetallic phosphide catalyst and preparation method thereof, the catalyst includes porous carbon nanosheet and the molybdenum phosphide / tungsten phosphide nano heterojunction supported thereon.Preparation method includes: ammonium heptamolybdate, ammonium metatungstate is made Mo / W precursor solution, mixed with porous carbon nanosheet / melamine dispersion, stirring, ultrasonic, join phosphorus source to make catalyst precursor powder, calcination, obtain porous carbon nanosheet supported bimetallic phosphide catalyst.The catalyst of the application has the advantages of strong catalytic activity, good stability, etc., when used for removing organic sulfur compounds in oil, it can realize effective degradation of organic sulfur compounds under the condition of less dosage, and can realize ultra-deep oxidation desulfurization, high use value and good application prospect.The preparation method of the application has the advantages of simple process, easy operation, low cost, green and pollution-free, etc., and can realize large-scale production, which is beneficial to industrial application.

Description

Technical Field

[0001] This invention belongs to the field of heterogeneous catalysis technology and petrochemical technology, and relates to a catalyst for oxidative desulfurization, specifically a porous carbon nanosheet supported bimetallic phosphide catalyst and its preparation method. Background Technology

[0002] The transportation industry remains heavily reliant on fossil fuels containing large amounts of organic sulfur compounds (such as dibenzothiophene (DBT) and dimethyldibenzothiophene (DMDBT)). The combustion of these sulfur-containing fuels causes serious environmental problems, leading to sulfur oxide emissions and acid rain. Hydrodesulfurization (HDS) is a traditional and common technique for removing sulfides; however, it is less efficient at removing polycyclic aromatic sulfides with high steric hindrance, such as dibenzothiophene. As an alternative, oxidative desulfurization (ODS) shows great promise, enabling the removal of difficult-to-remove aromatic sulfides under mild conditions (low temperature and reaction pressure) without the aid of H2, thus achieving deep desulfurization.

[0003] Currently, many homogeneous and heterogeneous catalysts, including organic peracids, ionic liquids, deep eutectic solvents, polymetallic oxides, metal oxides, carbon nanotubes, metal silicate zeolites, and metal-organic frameworks, have been applied to ODS technology. However, due to their low activity, poor recyclability, difficult regeneration, and high toxicity, and the occasional corrosion of equipment during catalyst preparation or reaction, most catalysts are not ideal for practical applications. To this end, the inventors of this application propose a molybdenum phosphide composite catalyst, comprising nitrogen and phosphorus co-doped carbon nanosheets and molybdenum phosphide nanoparticles supported thereon. By loading molybdenum phosphide particles onto nitrogen and phosphorus co-doped carbon nanosheets, the interaction between the metal and the support can be enhanced by regulating the interfacial charge. This can improve the catalytic activity of molybdenum phosphide while effectively inhibiting metal leaching and enhancing catalyst stability. Furthermore, the inventors of this application have found in actual research that: (1) by optimizing the thickness of the heterogeneous carbon nanosheets, it is beneficial to increase the specific surface area and active sites of the catalyst, thereby providing more sites for the attachment of active sites and the catalytic reaction, which is conducive to the formation of more unsaturated metal sites on the catalyst surface; (2) by optimizing the type of active sites, more unsaturated metal sites can be formed on the catalyst surface, which is beneficial to further improve the catalytic activity of the catalyst. In particular, by optimizing the combination of active sites, it is beneficial to promote the reconstruction of the electronic structure on the catalyst surface, which is beneficial to improve the oxidation resistance of the catalyst, thus making the active components on the catalyst surface less prone to oxidation during actual use and resulting in better structural stability. Furthermore, the inventors of this application have discovered that by optimizing the catalyst preparation method, it is beneficial to obtain a support material with a large specific surface area and numerous active sites. Simultaneously, the original morphology of the support material can be maintained while controlling the loading of the active component, which helps avoid deficiencies such as carbon nanosheet aggregation or encapsulation of active site particles, thereby improving the accessibility of surface active sites. Therefore, developing a catalyst with high activity, good reusability, and excellent regeneration performance is of great significance for achieving the effective conversion of sulfur-containing organic pollutants in petroleum products and improving the availability of petroleum products. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a porous carbon nanosheet supported bimetallic phosphide catalyst with high catalytic activity and good stability. It also provides a simple, low-cost, convenient, green and pollution-free method for preparing the porous carbon nanosheet supported bimetallic phosphide catalyst.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A porous carbon nanosheet-supported bimetallic phosphide catalyst comprises porous carbon nanosheets and a molybdenum phosphide / tungsten phosphide nanoheterostructure, wherein the molybdenum phosphide / tungsten phosphide nanoheterostructure is supported on the porous carbon nanosheets.

[0007] In the above-mentioned porous carbon nanosheet-supported bimetallic phosphide catalyst, the mass ratio of the molybdenum phosphide / tungsten phosphide nanoheterojunction to the porous carbon nanosheet is further improved to be 0.1 to 0.8:1.

[0008] The above-mentioned porous carbon nanosheet-supported bimetallic phosphide catalyst is further improved by having uniformly distributed nanoscale pores on the porous carbon nanosheets.

[0009] The above-mentioned porous carbon nanosheet-supported bimetallic phosphide catalyst is further improved in that the molybdenum phosphide / tungsten phosphide nanoheterostructure has a molybdenum phosphide mass content of 20% to 60% and an average particle size of 20 nm to 60 nm.

[0010] As a general technical concept, the present invention also provides a method for preparing a porous carbon nanosheet-supported bimetallic phosphide catalyst, comprising the following steps:

[0011] S1. Prepare a Mo / W precursor solution by mixing ammonium heptamolybdate and ammonium metatungstate.

[0012] S2. Mix the Mo / W precursor solution obtained in step S1 and the porous carbon nanosheet / melamine dispersion, stir, and sonicate to obtain the precursor dispersion.

[0013] S3. Add the phosphorus source to the precursor dispersion obtained in step S2, stir, filter, and dry to obtain catalyst precursor powder.

[0014] S4. The catalyst precursor powder obtained in step S3 is calcined to obtain a porous carbon nanosheet supported bimetallic phosphide catalyst.

[0015] In a further improvement to the above-described method for preparing a porous carbon nanosheet-supported bimetallic phosphide catalyst, in step S2, the volume ratio of the Mo / W precursor solution to the porous carbon nanosheet / melamine dispersion is 0.5–1:1; the sum of the concentrations of ammonium heptamolybdate and ammonium metatungstate in the Mo / W precursor solution is 0.01 mol / L–0.06 mol / L; the molar ratio of ammonium heptamolybdate to ammonium metatungstate in the Mo / W precursor solution is 0.4–7:1; the porous carbon nanosheet / melamine dispersion is prepared by mixing melamine, porous carbon nanosheets, and water; the sum of the concentrations of melamine and porous carbon nanosheets in the porous carbon nanosheet / melamine dispersion is 50 g / L–80 g / L; and the mass ratio of melamine to porous carbon nanosheets in the porous carbon nanosheet / melamine dispersion is 4–6:1.

[0016] In a further improvement to the above-mentioned method for preparing a porous carbon nanosheet-supported bimetallic phosphide catalyst, in step S3, the phosphorus source is an H3PO4 solution and / or a phytic acid solution; the mass concentration of the H3PO4 solution and the phytic acid solution is 85%; and the volume ratio of the precursor dispersion to the phosphorus source is 18-24:1.

[0017] The above-mentioned method for preparing porous carbon nanosheets-supported bimetallic phosphide catalysts is further improved by comprising the following steps:

[0018] (1) Sodium citrate was calcined under an inert atmosphere to obtain porous carbon nanosheet precursor material;

[0019] (2) The porous carbon nanosheet precursor material obtained in step (1) is added to hydrochloric acid solution for reaction, washed, and dried to obtain porous carbon nanosheets.

[0020] The above-mentioned method for preparing a porous carbon nanosheet-supported bimetallic phosphide catalyst is further improved in that, in step (1), the calcination is carried out at a temperature of 750℃~800℃; the calcination time is 60min~180min; and the inert atmosphere is a nitrogen or argon atmosphere.

[0021] The above-mentioned method for preparing a bimetallic phosphide catalyst supported on porous carbon nanosheets is further improved in step (2) by wherein the mass ratio of the hydrochloric acid solution to the porous carbon nanosheet precursor material is 20-30:1; the concentration of the hydrochloric acid solution is 1.5 mol / L-2.5 mol / L; and the reaction time is 24-48 h.

[0022] In a further improvement to the above-mentioned method for preparing a porous carbon nanosheet-supported bimetallic phosphide catalyst, in step S2, the stirring time is 0.5 h to 2 h; and the ultrasonication time is 30 min to 60 min.

[0023] In a further improvement to the above-mentioned method for preparing a porous carbon nanosheet-supported bimetallic phosphide catalyst, in step S3, the stirring is carried out at a temperature of 60℃~80℃; the stirring time is 12h~16h; the drying process is carried out under vacuum conditions; the drying temperature is 60℃~80℃; and the drying time is 2h~12h.

[0024] The above-mentioned method for preparing a porous carbon nanosheet-supported bimetallic phosphide catalyst is further improved in that, in step S4, the calcination is carried out under an argon atmosphere; the gas flow rate is controlled at 20 mL / min during the calcination process; the heating rate during the calcination process is 5 °C / min; the calcination temperature is 800 °C to 900 °C; and the calcination time is 2 h to 3 h.

[0025] In a further improvement to the above-described method for preparing a porous carbon nanosheet-supported bimetallic phosphide catalyst, in step S4, the porous carbon nanosheet-supported bimetallic phosphide catalyst comprises porous carbon nanosheets and molybdenum phosphide / tungsten phosphide nanoheterojunctions, wherein the molybdenum phosphide / tungsten phosphide nanoheterojunctions are supported on the porous carbon nanosheets; the mass ratio of the molybdenum phosphide / tungsten phosphide nanoheterojunctions to the porous carbon nanosheets is 0.1–0.8:1; the porous carbon nanosheets have uniformly distributed nanoscale pores; the mass content of molybdenum phosphide in the molybdenum phosphide / tungsten phosphide nanoheterojunctions is 20%–60%; and the average particle size of the molybdenum phosphide / tungsten phosphide nanoheterojunctions is 20 nm–60 nm.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] (1) In view of the shortcomings of existing molybdenum phosphide composite catalysts, such as poor catalytic activity and poor stability, the present invention creatively provides a porous carbon nanosheet supported bimetallic phosphide catalyst, including porous carbon nanosheets and molybdenum phosphide / tungsten phosphide nanoheterostructures, wherein the molybdenum phosphide / tungsten phosphide nanoheterostructures are supported on porous carbon nanosheets. On the one hand, compared with conventional nitrogen and phosphorus co-doped carbon nanosheets, the porous carbon nanosheets used in this invention have a two-dimensional layered structure and uniformly distributed pores on the surface, thus having a larger specific surface area. This not only provides more surface area for the attachment of active sites but also provides more sites for catalytic reactions. On the other hand, compared with single molybdenum phosphide nanoparticles, the molybdenum phosphide / tungsten phosphide nanoheterojunction used in this invention as the active site has a richer and more tunable electronic structure and exposes more unsaturated metal sites on the surface, thus exhibiting stronger catalytic activity. In particular, electron transfer between the molybdenum phosphide / tungsten phosphide heterojunction interface can lead to the reconstruction of the electronic structure on the catalyst surface. While further improving the catalytic activity of molybdenum phosphide, it can also effectively improve the antioxidant properties of the active sites, thereby effectively preventing the decomposition and failure of the active sites. This significantly enhances the stability of the catalyst and exhibits better reusability. Therefore, the porous carbon nanosheet-supported bimetallic phosphide catalyst of this invention has the advantages of strong catalytic activity and good stability. It is a novel and efficient oxidative desulfurization catalyst with excellent performance and wide applicability. When used to remove organic sulfur compounds in oil, it can achieve effective degradation of organic sulfur compounds with less dosage. At the same time, it can achieve rapid and selective removal of sulfur-containing organic compounds in oil and realize ultra-deep oxidative desulfurization. It has high application value and good application prospects.

[0028] (2) In the porous carbon nanosheet-supported bimetallic phosphide catalyst of the present invention, by optimizing the mass ratio of molybdenum phosphide / tungsten phosphide nanoheterostructure to porous carbon nanosheets to 0.1–0.8:1, a sufficient number of active sites on the catalyst surface can be ensured, thereby exhibiting superior catalytic activity and stability. Furthermore, by optimizing the content of molybdenum phosphide and tungsten phosphide in the molybdenum phosphide / tungsten phosphide nanoheterostructure, a catalyst with excellent catalytic activity and stability can also be obtained. This is because the ratio of tungsten phosphide to molybdenum phosphide in the molybdenum phosphide / tungsten phosphide nanoheterostructure has a significant impact on the electronic structure of the active sites on the catalyst surface, thereby affecting the catalyst activity.

[0029] (3) To address the shortcomings of existing molybdenum phosphide composite catalyst preparation methods, such as difficulty in controlling the number of active sites and the morphology of the support material, and the resulting poor catalytic activity and stability, this invention creatively provides a method for preparing a porous carbon nanosheet-supported bimetallic phosphide catalyst. Using ammonium heptamolybdate and ammonium metatungstate as molybdenum and tungsten sources, respectively, melamine as a crosslinking agent, phosphoric acid as a phosphorus source, and porous carbon nanosheets as the support, ammonium heptamolybdate and ammonium metatungstate are first prepared into a Mo / W precursor solution, and then combined with porous carbon nanosheets... A mixture of carbon nanosheets and melamine dispersion is stirred, and the cross-linking effect of melamine induces strong coordination between molybdenum and tungsten ions, anchoring them onto porous carbon nanosheets. Then, H3PO4 solution is added, and through stirring and the cross-linking effect of melamine, the phosphorus source is anchored onto the porous carbon nanosheets. Finally, a simple one-step pyrolysis process forms molybdenum phosphide / tungsten phosphide nanoheterojunctions, which are then anchored onto the porous carbon nanosheets. This yields a porous carbon nanosheet-supported bimetallic phosphide catalyst with strong catalytic activity and good stability. The preparation method of this invention allows for easy optimization of catalyst performance by adjusting the amount of molybdenum / tungsten precursors during synthesis. It has advantages such as simple process, convenient operation, low cost, and environmental friendliness. Furthermore, it does not use flammable phosphorus or highly toxic phosphine as phosphating agents, has low equipment requirements, high repeatability, and can achieve large-scale production, which is beneficial for industrial applications. Attached Figure Description

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0031] Figure 1 This is a flowchart illustrating the preparation process of the porous carbon nanosheet-supported bimetallic phosphide catalyst in Example 1 of the present invention.

[0032] Figure 2 This is a scanning electron microscope image of the porous carbon nanosheets (PCNS) prepared in Example 1 of the present invention.

[0033] Figure 3 This is a scanning electron microscope image of the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1 of the present invention.

[0034] Figure 4 This is a high-resolution transmission electron microscope image of the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1 of the present invention.

[0035] Figure 5The X-ray diffraction patterns are those of the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1, the porous carbon nanosheet-supported tungsten phosphide catalyst (WP / PCNS) prepared in Comparative Example 1, and the porous carbon nanosheet-supported molybdenum phosphide catalyst (MoP / PCNS) prepared in Comparative Example 2.

[0036] Figure 6 The nitrogen adsorption-desorption curves are shown for the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1 of this invention.

[0037] Figure 7 XPS image of the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1 of this invention.

[0038] Figure 8 This is a high-resolution transmission electron microscope image of the porous carbon nanosheet-supported tungsten phosphide catalyst (WP / PCNS) prepared in Comparative Example 1.

[0039] Figure 9 This is a high-resolution transmission electron microscope image of the porous carbon nanosheet-supported molybdenum phosphide catalyst (MoP / PCNS) prepared in Comparative Example 2.

[0040] Figure 10 This is a comparison chart of the removal effects of porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS), porous carbon nanosheet-supported tungsten phosphide catalyst (WP / PCNS), and porous carbon nanosheet-supported molybdenum phosphide catalyst (MoP / PCNS) on dibenzothiophene sulfur in fuel oil in Example 2 of the present invention.

[0041] Figure 11 This is a diagram showing the repeated cyclic removal effect of the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) on dibenzothiophene sulfur in fuel oil in Example 3 of the present invention. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0043] The materials and instruments used in the following examples are all commercially available.

[0044] Example 1

[0045] A porous carbon nanosheet-supported bimetallic phosphide catalyst comprises porous carbon nanosheets on which molybdenum phosphide / tungsten phosphide nanoheterojunctions are supported, wherein the mass contents of molybdenum and tungsten are 10% and 20%, respectively.

[0046] In this embodiment, the mass ratio of molybdenum phosphide / tungsten phosphide nanoheterojunction to porous carbon nanosheets is 0.58:1.

[0047] In this embodiment, the porous carbon nanosheets have uniformly distributed nanoscale pores.

[0048] In this embodiment, the molybdenum phosphide content in the molybdenum phosphide / tungsten phosphide nanoheterojunction is 37% by mass.

[0049] A method for preparing the porous carbon nanosheet-supported bimetallic phosphide catalyst in Example 1 of the present invention is shown in the following process flow diagram. Figure 1 As shown, it includes the following steps:

[0050] (1) Weigh 10.0g of sodium dihydrogen citrate and place it in a quartz boat. Place the boat in a tube furnace and heat it to 780℃ under a nitrogen atmosphere for 2h. Then cool it naturally to room temperature to obtain a porous carbon nanosheet precursor. Add 60mL of hydrochloric acid solution (2M) to the above 3g porous carbon nanosheet precursor and react at room temperature for 24h. Collect the black product by filtration and wash it several times with deionized water and ethanol. Dry it at 70℃ for 2h to obtain porous carbon nanosheets, denoted as PCNS.

[0051] (2) Weigh 0.2g of the porous carbon nanosheets obtained in step (1) and 1g of melamine, disperse them in 20mL of ultrapure water to prepare a porous carbon nanosheet / melamine dispersion.

[0052] (3) Weigh 0.074g of ammonium metatungstate and 0.053g of ammonium heptamolybdate, dissolve them in 18mL of ultrapure water to prepare a molybdenum / tungsten precursor solution.

[0053] (4) The porous carbon nanosheets / melamine dispersion obtained in step (2) and the molybdenum / tungsten precursor solution obtained in step (3) are slowly mixed, stirred for 30 min, sonicated for 30 min, and then 2 mL of phosphoric acid solution with a mass concentration of 85% is slowly added. The mixture is transferred to 80 °C for reaction (solvent-thermal reaction) for 12 h. The reaction product is filtered and recovered, and dried at 80 °C for 12 h to obtain catalyst precursor powder.

[0054] (5) The catalyst precursor powder obtained in step (4) is placed in a quartz boat and transferred to a tube furnace. Under an argon atmosphere, the temperature is increased to 900℃ for 2h at a heating rate of 5℃ / min. During the calcination process, the gas flow rate is controlled at 20mL / min. After the calcination is completed, the mixture is naturally cooled to room temperature to obtain a porous carbon nanosheet supported bimetallic phosphide catalyst, denoted as MoWP2 / PCNS.

[0055] Comparative Example 1

[0056] A porous carbon nanosheet supported tungsten phosphide catalyst differs from Example 1 in that the mass contents of molybdenum and tungsten in the porous carbon nanosheet supported tungsten phosphide catalyst in Comparative Example 1 are 0% and 30%, respectively.

[0057] A method for preparing a porous carbon nanosheet supported tungsten phosphide catalyst is basically the same as that in Example 1, except that the amount of ammonium metatungstate and ammonium heptamolybdate added in step (3) of Comparative Example 1 is 0.149 g and 0 g, respectively.

[0058] The porous carbon nanosheet-supported tungsten phosphide catalyst prepared in Comparative Example 1 is denoted as WP / PCNS.

[0059] Comparative Example 2

[0060] A method for preparing a porous carbon nanosheet-supported molybdenum phosphide catalyst is basically the same as that in Example 1, except that the mass contents of molybdenum and tungsten in the porous carbon nanosheet-supported molybdenum phosphide in Comparative Example 2 are 15% and 0%, respectively.

[0061] A method for preparing a porous carbon nanosheet supported molybdenum phosphide catalyst is basically the same as that in Example 1, except that the amount of ammonium metatungstate and ammonium heptamolybdate added in step (3) of Comparative Example 2 is 0 g and 0.106 g, respectively.

[0062] The porous carbon nanosheet-supported molybdenum phosphide catalyst prepared in Comparative Example 2 is denoted as MoP / PCNS.

[0063] Figure 2 This is a scanning electron microscope image of the porous carbon nanosheets (PCNS) prepared in Example 1 of the present invention. Figure 2 In the image, a and b are scanning electron microscope (SEM) images magnified 20.0K and 100.0K by PCNS, respectively. Figure 2 It can be observed that PCNS exhibits a vertically arranged two-dimensional sheet-like structure, forming a highly porous structure that is completely interconnected.

[0064] Figure 3 This is a scanning electron microscope image of the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1 of the present invention. Figure 3In the images, a and b represent scanning electron microscope (SEM) images at different magnifications. The results show that the loading of molybdenum phosphide / tungsten phosphide nanoheterostructures does not change the main morphology of the porous carbon nanosheets; it only further etches some uniform pores onto the porous carbon nanosheets. This may be because: the addition of the metal complexes more melamine and phosphoric acid, so the large amount of complexes decomposes at high temperature, etching the carbon nanosheets and forming pores; when no metal is added, only a small amount of melamine and phosphoric acid bind, so during calcination, due to the small amount of complexes, no pores are etched; simultaneously, the uniform pores formed on the porous carbon nanosheets are beneficial to the mass transfer process of the catalytic reaction.

[0065] Figure 4 This is a high-resolution transmission electron microscope image of the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1 of the present invention. Figure 4 In the image, a and b represent transmission electron microscopy (TEM) images at different magnifications. Figure 4 It can be seen that the average particle size of the molybdenum phosphide / tungsten phosphide nanoheterostructure in the prepared MoWP2 / PCNS is 42.9 nm. Two distinct lattice fringes can be observed on high-resolution transmission electron microscopy, with lattice spacings of 0.32 nm and 0.29 nm, respectively. These are attributed to the (001) crystal plane of molybdenum phosphide and the (011) crystal plane of tungsten phosphide, respectively. This also indicates that the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) has been successfully synthesized.

[0066] Figure 5 The images show the X-ray diffraction patterns of the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1, the porous carbon nanosheet-supported tungsten phosphide catalyst (WP / PCNS) prepared in Comparative Example 1, and the porous carbon nanosheet-supported molybdenum phosphide catalyst (MoP / PCNS) prepared in Comparative Example 2. Figure 5 It can be seen that the diffraction peaks of WP / PCNS and MoP / PCNS can be perfectly summarized as typical characteristic peaks of tungsten phosphide and molybdenum phosphide, while the diffraction peaks of MoWP2 / PCNS are composed of characteristic peaks of tungsten phosphide and molybdenum phosphide.

[0067] Figure 6 This is a nitrogen adsorption-desorption curve of the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1 of this invention. Figure 6 It can be seen that the specific surface area of ​​MoWP2 / PCNS is as high as 289.83 m². 2 / g, such a high specific surface area is mainly attributed to the unique two-dimensional sheet structure of porous carbon nanosheets, which form a highly porous structure that is completely interconnected.

[0068] Figure 7This is an XPS image of the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1 of this invention. Figure 7 It can be seen that the porous carbon nanosheet-supported bimetallic phosphide catalyst is composed of Mo, W, P, C, N and O elements.

[0069] Figure 8 The image shows a high-resolution transmission electron microscope (HRTEM) image of the porous carbon nanosheet-supported tungsten phosphide catalyst (WP / PCNS) prepared in Comparative Example 1. Clearly visible lattice fringes with a lattice spacing of 0.29 nm can be observed on the HRTEM, which are attributed to the (011) crystal plane of tungsten phosphide, indicating that the porous carbon nanosheet-supported tungsten phosphide catalyst (WP / PCNS) was successfully synthesized.

[0070] Figure 9 The image shows a high-resolution transmission electron microscope (HRTEM) image of the porous carbon nanosheet-supported molybdenum phosphide catalyst (MoP / PCNS) prepared in Comparative Example 2. Clearly visible lattice fringes with a lattice spacing of 0.27 nm can be observed on the HRTEM, which are attributed to the (100) crystal plane of molybdenum phosphide, indicating that the porous carbon nanosheet-supported molybdenum phosphide catalyst (MoP / PCNS) was successfully synthesized.

[0071] Example 2

[0072] The catalytic oxidative desulfurization activity of the porous carbon nanosheet-supported bimetallic phosphide catalyst of the present invention was investigated. Specifically, the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1, the porous carbon nanosheet-supported tungsten phosphide catalyst (WP / PCNS) prepared in Comparative Example 1, and the porous carbon nanosheet-supported molybdenum phosphide catalyst (MoP / PCNS) prepared in Comparative Example 2 were used to remove dibenzothiophene from oil products, including the following steps:

[0073] Accurately weigh 3.0 mg of the MoWP2 / PCNS, WP / PCNS, and MoP / PCNS catalysts prepared in Examples 1 and Comparative Examples 1-2, respectively, and add them to 10 mL of a dibenzothiophene (DBT)-dodecane solution with a sulfur concentration of 500 ppm (i.e., simulated petroleum containing dibenzothiophene). Then add 2 mL of acetonitrile solution with a mass fraction of 99%, and stir for 10 min to reach extraction equilibrium. Next, add 48 μL of hydrogen peroxide solution with a mass fraction of 30% (oxidant, O / S molar ratio of 4), and carry out a catalytic oxidation reaction for 60 min at a temperature of 60 °C and with magnetic stirring (rotation speed of 800 r / min). The catalytic oxidation reaction is carried out in acetonitrile, where dibenzothiophene is converted to dibenzothiophene sulfone and retained in acetonitrile, thus completing the removal of dibenzothiophene from the oil. After the reaction is completed, separate the acetonitrile phase (lower layer) from the oil phase (upper layer) to obtain clean fuel.

[0074] In this embodiment, after the reaction was completed, the sulfur content in the dibenzothiophene in the resulting product solution was determined by gas chromatography, and the conversion rate of sulfur in dibenzothiophene was calculated. The results are as follows: Figure 10 As shown.

[0075] Figure 10 This is a comparison chart showing the removal efficiency of three porous carbon nanosheet-supported catalysts (MoWP2 / PCNS, WP / PCNS, and MoP / PCNS) on dibenzothiophene sulfur in fuel oil, as described in Example 2 of this invention. Figure 10 It can be seen that, compared with WP / PCNS and MoP / PCNS, MoWP2 / PCNS can effectively catalyze the oxidation and removal of dibenzothiophene from fuel oil, and MoWP2 / PCNS can remove 100% of dibenzothiophene from simulated petroleum within 60 min. These results indicate that the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in this invention has better catalytic oxidation performance.

[0076] Furthermore, the total sulfur content in the oil treated with the porous carbon nanosheet-supported bimetallic phosphide catalyst prepared in this invention is <10 ppm, meeting Euro VI fuel standards, and the total desulfurization rate is as high as 100%. In particular, the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) exhibits excellent dibenzothiophene catalytic oxidation effect under conditions of extremely low catalyst (0.3 g / L) and oxidant (O:S = 4) dosages, demonstrating good economic benefits and promising industrial application prospects.

[0077] Example 3

[0078] The reusability of the porous carbon nanosheet-supported bimetallic phosphide catalyst of the present invention was investigated. The porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) prepared in Example 1 was used for the catalytic oxidation removal of dibenzothiophene from oil products, including the following steps:

[0079] 3 mg of porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) was weighed and added to 10 mL of a dibenzothiophene (DBT)-dodecane solution with a sulfur concentration of 500 ppm (i.e., simulated petroleum containing dibenzothiophene). Then, 2 mL of 99% acetonitrile solution was added, and the mixture was stirred for 10 min to reach extraction equilibrium. Next, 48 μL of 30% hydrogen peroxide solution (oxidant, O / S molar ratio of 4) was added, and the reaction was carried out at 60 °C with magnetic stirring (800 r / min) for 60 min. The catalytic oxidation reaction was conducted in acetonitrile, where dibenzothiophene was converted to dibenzothiophene sulfone and retained in acetonitrile, thus removing dibenzothiophene from the oil. After the reaction was complete, the upper oil phase was extracted. The catalytic apparatus containing the catalyst, acetonitrile, oxidant, sulfone product, and water was then dried at 80 °C for 3 h to completely remove acetonitrile, oxidant, and water. After the reactor cooled to room temperature, 10 mL of a 500 ppm sulfur solution of dibenzothiophene (DBT)-dodecane, 2 mL of a 99% acetonitrile solution, and 48 μL of a 30% hydrogen peroxide solution were added again to initiate a new round of catalytic reaction without changing the reaction conditions. This cycle was repeated 12 times, and the results are as follows: Figure 11 As shown.

[0080] Figure 11 This image shows the effect of the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) on the repeated cycle removal of dibenzothiophene sulfur from fuel oil in Example 3 of this invention. Figure 11 It is evident that the porous carbon nanosheet-supported bimetallic phosphide catalyst (MoWP2 / PCNS) of this invention can still achieve a 100% dibenzothiophene removal rate after being reused 9 times. Even after the 12th use, the removal rate of dibenzothiophene did not decrease significantly. It can still maintain excellent catalytic performance after multiple cycles, which indicates that the porous carbon nanosheet-supported bimetallic phosphide catalyst of this invention has very good reusability and stability.

[0081] The results above show that the porous carbon nanosheet-supported bimetallic phosphide catalyst of the present invention has the advantages of strong catalytic activity and good stability. It is a novel and efficient oxidative desulfurization catalyst with excellent performance and wide applicability. When used to remove organic sulfur compounds in oil, it can achieve effective degradation of organic sulfur compounds with less dosage. At the same time, it can achieve rapid and selective removal of sulfur-containing organic compounds in oil and realize ultra-deep oxidative desulfurization. It has high application value and good application prospects.

[0082] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a porous carbon nanosheet-supported bimetallic phosphide catalyst, characterized in that, Includes the following steps: S1. Prepare a Mo / W precursor solution by mixing ammonium heptamolybdate and ammonium metatungstate. S2. The Mo / W precursor solution and porous carbon nanosheet / melamine dispersion obtained in step S1 are mixed, stirred, and sonicated to obtain a precursor dispersion; the volume ratio of the Mo / W precursor solution to the porous carbon nanosheet / melamine dispersion is 0.5 to 1:1; the sum of the concentrations of ammonium heptamolybdate and ammonium metatungstate in the Mo / W precursor solution is 0.01 mol / L to 0.06 mol / L; the molar ratio of ammonium heptamolybdate to ammonium metatungstate in the Mo / W precursor solution is 0.4 to 7:1; the porous carbon nanosheet / melamine dispersion is prepared by mixing melamine, porous carbon nanosheets, and water; the sum of the concentrations of melamine and porous carbon nanosheets in the porous carbon nanosheet / melamine dispersion is 50 g / L to 80 g / L; the mass ratio of melamine to porous carbon nanosheets in the porous carbon nanosheet / melamine dispersion is 4 to 6:1; S3. Add the phosphorus source to the precursor dispersion obtained in step S2, stir, filter, and dry to obtain catalyst precursor powder; the phosphorus source is H3PO4 solution and / or phytic acid solution; the stirring is carried out at a temperature of 60℃~80℃; the stirring time is 12 h~16 h. S4. The catalyst precursor powder obtained in step S3 is calcined to obtain a porous carbon nanosheet-supported bimetallic phosphide catalyst; the porous carbon nanosheet-supported bimetallic phosphide catalyst includes porous carbon nanosheets and molybdenum phosphide / tungsten phosphide nanoheterostructures, wherein the molybdenum phosphide / tungsten phosphide nanoheterostructures are supported on the porous carbon nanosheets.

2. The preparation method according to claim 1, characterized in that, In step S3, the mass concentration of the H3PO4 solution and phytic acid solution is 85%; the volume ratio of the precursor dispersion to the phosphorus source is 18-24:

1.

3. The preparation method according to claim 2, characterized in that, The method for preparing the porous carbon nanosheets includes the following steps: (1) Sodium dihydrogen citrate was calcined under an inert atmosphere to obtain porous carbon nanosheet precursor material; (2) The porous carbon nanosheet precursor material obtained in step (1) is added to hydrochloric acid solution for reaction, washed, and dried to obtain porous carbon nanosheets.

4. The preparation method according to claim 3, characterized in that, In step (1), the calcination is carried out at a temperature of 750℃~800℃; the calcination time is 60 min~180 min; and the inert atmosphere is a nitrogen or argon atmosphere. In step (2), the mass ratio of the hydrochloric acid solution to the porous carbon nanosheet precursor material is 20-30:1; the concentration of the hydrochloric acid solution is 1.5 mol / L-2.5 mol / L; and the reaction time is 24 h-48 h.

5. The preparation method according to any one of claims 1 to 4, characterized in that, In step S2, the stirring time is 0.5 h to 2 h; the ultrasonication time is 30 min to 60 min. In step S3, the drying process is carried out under vacuum conditions; the drying temperature is 60℃~80℃; and the drying time is 2 h~12 h. In step S4, the calcination is carried out under an argon atmosphere; the gas flow rate is controlled at 20 mL / min during the calcination process; the heating rate during the calcination process is 5℃ / min; the calcination temperature is 800℃~900℃; and the calcination time is 2 h~3 h.

6. The preparation method according to claim 5, characterized in that, In step S4, the mass ratio of the molybdenum phosphide / tungsten phosphide nanoheterostructure to the porous carbon nanosheets is 0.1 to 0.8:1; the porous carbon nanosheets have uniformly distributed nanoscale pores; the mass content of molybdenum phosphide in the molybdenum phosphide / tungsten phosphide nanoheterostructure is 20% to 60%; and the average particle size of the molybdenum phosphide / tungsten phosphide nanoheterostructure is 20 nm to 60 nm.

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