Supported single-layer molybdenum disulfide catalyst precursor as well as preparation method and application thereof

Abstract

The invention provides a preparation method of a supported single-layer molybdenum disulfide catalyst precursor, which can be applied to the technical field of inferior oil hydrogenation. The preparation method comprises the following steps: S1, preparing a dilute alkali solution with the pH value of 8.0 to 10.0; s2, dissolving a molybdenum source and a sulfur source in the dilute alkali solution obtained in the step S1, and stirring and mixing to form a uniform solution; s3, adding a carrier into the uniform solution obtained in the step S2, and continuously stirring and mixing to obtain a solid-liquid mixture; s4, carrying out solid-liquid separation on the solid-liquid mixture obtained in the step S3, and collecting a solid product; and S5, drying the solid product obtained in the step S4 at 50-80 DEG C to obtain the supported single-layer molybdenum disulfide catalyst precursor. The invention also provides a supported single-layer molybdenum disulfide catalyst precursor and application thereof.

Description

Technical Field

[0001] This invention relates to the field of hydrogenation technology for inferior oils, and more specifically to a supported monolayer molybdenum disulfide catalyst precursor, its preparation method, and its application. Background Technology

[0002] In recent years, with the continued growth in global demand for chemicals, the increasing scarcity of crude oil reserves, and the tight supply of conventional light crude oil, unconventional heavy resources such as residual oil, coal tar, and wood tar have been widely used to produce high-value-added fuels and chemicals. Among these, catalytic hydroconversion is one of the most effective technological approaches to upgrade these inferior heavy oils into light fuel oils.

[0003] Currently, industrial hydrogenation processes mainly employ different types of reactors, such as fixed-bed, slurry-bed, or fluidized-bed reactors. Fixed-bed reactors, as typical gas-liquid-solid three-phase trickle-bed reactors, face the challenge of continuous catalyst replacement due to deactivation, resulting in cumbersome operation. While fluidized-bed reactors allow for online catalyst replenishment and removal, they still suffer from technical bottlenecks such as system pressure drop and mass transfer limitations. In contrast, slurry-bed reactors using dispersed catalysts effectively overcome these drawbacks; however, when processing low-quality oils, they still struggle to completely avoid the problem of coking (coking) inside the reactor due to the heavy feedstock and high impurity content.

[0004] Among various hydrogenation catalysts, molybdenum disulfide (MoS2) is widely favored due to its superior hydrogenation activity and coke suppression ability for coal tar rich in impurities and heavy components, even under harsh reaction conditions such as high temperature and high pressure. The theoretical research on the MoS2 "rim-edge" hydrogenation reaction model further demonstrates that monolayer MoS2, due to its higher proportion of exposed active "edge" sites, exhibits significantly higher catalytic hydrogenation activity than traditional multilayer stacked MoS2.

[0005] However, the preparation of highly active monolayer MoS2 catalysts in existing technologies typically relies on synthesis routes such as hydrothermal or solvothermal methods. These methods not only require high-temperature conditions of 150-200℃, but also generate large amounts of wastewater or organic waste solvents during the synthesis process, posing environmental pollution risks, high energy consumption, and complex processes, which seriously hinder the large-scale, green industrial production and application of monolayer MoS2 catalysts.

[0006] Therefore, developing a method for preparing monolayer MoS2 catalysts that can be carried out under mild conditions (especially at room temperature), is environmentally friendly, and is suitable for industrial scale-up has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address at least one of the aforementioned problems, this invention provides a supported monolayer molybdenum disulfide catalyst precursor, its preparation method, and its applications. By employing a specific weakly alkaline aqueous phase reaction system, the active component precursor is uniformly loaded and assembled at the molecular level on a support under ambient temperature conditions, successfully constructing a structural precursor that can be in situ converted into highly active monolayer molybdenum disulfide during hydrogenation reactions. This method not only features mild process conditions and low energy consumption but also achieves a completely green and environmentally friendly process with zero waste discharge through mother liquor recycling. Simultaneously, it solves the technical challenges of high synthesis temperature, significant pollution, and insufficient exposure of active sites in monolayer structures inherent in traditional methods.

[0009] (II) Technical Solution

[0010] To address the aforementioned technical problems, embodiments of the present invention propose a supported monolayer molybdenum disulfide catalyst precursor, its preparation method, and its application.

[0011] According to a first aspect of the present invention, a method for preparing a supported monolayer molybdenum disulfide catalyst precursor is provided, comprising: step S1, preparing a dilute alkaline solution with a pH value of 8.0 to 10.0; step S2, dissolving a molybdenum source and a sulfur source in the dilute alkaline solution obtained in step S1, stirring and mixing to form a homogeneous solution; step S3, adding a support to the homogeneous solution obtained in step S2, continuing to stir and mix to obtain a solid-liquid mixture; step S4, performing solid-liquid separation on the solid-liquid mixture obtained in step S3, and collecting the solid product; step S5, drying the solid product obtained in step S4 at 50°C to 80°C to obtain the supported monolayer molybdenum disulfide catalyst precursor.

[0012] In some exemplary embodiments, in step S1, the strong base used to prepare the dilute alkaline solution includes either sodium hydroxide or potassium hydroxide.

[0013] In some exemplary embodiments, in step S2, the molybdenum source includes one of ammonium heptamolybdate or sodium molybdate; the sulfur source includes one of thioacetamide or thiourea.

[0014] In some exemplary embodiments, in step S2, the molar ratio of molybdenum in the molybdenum source to sulfur in the sulfur source is 1:2-1:6.

[0015] In some exemplary embodiments, in step S3, the carrier includes one of silicon dioxide, aluminum oxide or titanium dioxide; the mass percentage of molybdenum in the molybdenum source is 1%-20% of the mass of the carrier.

[0016] In some exemplary embodiments, in step S2, the stirring time for mixing is 2 to 10 hours; in step S3, the stirring time for continuing mixing is 3 to 12 hours.

[0017] In some exemplary embodiments, the drying time in step S5 is 1 to 3 hours.

[0018] In some exemplary embodiments, after solid-liquid separation is completed in step S4, the remaining mother liquor is collected, and the composition of the mother liquor is adjusted by adding strong alkali, molybdenum source and sulfur source. The adjusted mother liquor is then reused in the preparation of dilute alkali solution in step S1 for the preparation of the next batch of catalyst precursor.

[0019] According to a second aspect of the present invention, a supported monolayer molybdenum disulfide catalyst precursor prepared by any of the above methods is provided.

[0020] According to a third aspect of the present invention, an application is provided of the above-mentioned supported monolayer molybdenum disulfide catalyst precursor in the hydrogenation reaction of inferior oil, including coal tar, residue oil or wood tar; the precursor is converted in situ into catalytically active monolayer molybdenum disulfide during the hydrogenation reaction.

[0021] (III) Beneficial Effects

[0022] As can be seen from the above technical solutions, the supported monolayer molybdenum disulfide catalyst precursor, its preparation method, and its application provided by the embodiments of the present invention have at least the following beneficial effects:

[0023] (1) The main preparation process of this invention, including reaction and loading, is completed at room temperature, requiring only simple product drying at 50-80℃. This completely eliminates the need for the high temperature and high pressure reaction conditions of 150-200℃ required by the traditional hydrothermal / solvothermal method, greatly reducing energy consumption and equipment requirements, and making large-scale industrial production possible.

[0024] (2) The preparation process of this invention uses water as a solvent, and the key is that the mother liquor remaining after solid-liquid separation can be recycled to replenish the effective components and used for the preparation of the next batch of precursors. The entire process forms a closed loop, with no wastewater or organic waste solvents generated, which conforms to the principles of green chemistry, is environmentally friendly, and has no subsequent environmental protection pressure.

[0025] (3) This precursor can generate highly catalytically active monolayer MoS2 in situ during the hydrogenation reaction of inferior oil. According to the data from the examples, compared with the monolayer MoS2 catalyst prepared by the conventional hydrothermal method, it can increase the yield of light oil (<360°C) by 15% to 20% in the hydrogenation reaction of coal tar, and has excellent hydrogenation conversion efficiency.

[0026] (4) The examples show that the catalyst precursor can maintain high catalytic activity after multiple regenerations, exhibiting good cycle stability and lifespan, reducing the catalyst replacement cost in industrial plants, and has good economic benefits and industrial application prospects.

[0027] (5) This invention ingeniously combines the “formation” step of monolayer MoS2 with the “hydrogenation reaction” step. The precursor is converted into the active phase in situ at the hydrogenation reaction site, which not only simplifies the process flow, but also may generate catalytic active centers with more active sites and stronger binding to the support, thereby simultaneously achieving high activity and high stability. Attached Figure Description

[0028] The above-described features, other objects, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0029] Figure 1 A flowchart illustrating a method for preparing a supported monolayer molybdenum disulfide catalyst precursor according to an embodiment of the present invention is shown. Detailed Implementation

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

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0032] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0033] Figure 1 A flowchart illustrating a method for preparing a supported monolayer molybdenum disulfide catalyst precursor according to an embodiment of the present invention is shown.

[0034] like Figure 1 As shown, the preparation method of the supported monolayer molybdenum disulfide catalyst precursor according to an embodiment of the present invention includes steps S1 to S5.

[0035] In step S1, a dilute alkaline solution with a pH value of 8.0 to 10.0 is prepared.

[0036] This step creates a stable, weakly alkaline reaction environment. This pH range ensures that the molybdenum source species fully dissolve and form suitable molybdate ions, laying the foundation for subsequent molecular-level reactions with the sulfur source, while effectively preventing the sulfur source from decomposing too quickly under acidic or strongly alkaline conditions to produce hydrogen sulfide gas, thus guaranteeing the controllability and safety of the reaction process.

[0037] In embodiments of the present invention, the strong base used to prepare the dilute alkaline solution includes either sodium hydroxide or potassium hydroxide. The selection of these two strong bases allows for the rapid and stable achievement and maintenance of the desired pH window, and the introduction of alkali metal ions (Na+, Na+, and potassium hydroxide)... + or K + These impurities are easily removed by water washing during post-treatment, avoiding the potential negative impact of impurity ions on the final activity of the catalyst.

[0038] In step S2, the molybdenum source and the sulfur source are dissolved in the dilute alkaline solution obtained in step S1, and stirred to form a homogeneous solution.

[0039] This step is crucial for achieving molecular-level homogeneous mixing of the active component precursor in solution. Through sufficient reaction in the liquid phase, molybdenum and sulfur species are pre-combined to form the basic structural unit subsequently loaded onto the support, which is a prerequisite for ultimately obtaining a monolayer molybdenum disulfide structure.

[0040] In embodiments of the present invention, in step S2, the molybdenum source includes either ammonium heptamolybdate or sodium molybdate. In step S2, the sulfur source includes either thioacetamide or thiourea. Preferably, the molar ratio of molybdenum in the molybdenum source to sulfur in the sulfur source is 1:2 to 1:6. The selected molybdenum and sulfur sources exhibit moderate reactivity under weakly alkaline conditions. They can slowly and controllably release molybdate ions and sulfur ions at room temperature, thereby facilitating the formation of precursor compounds with uniform size and regular structure, rather than rapidly precipitating to form amorphous or poorly crystallized polysulfides.

[0041] In an embodiment of the invention, the stirring time in step S2 is 2 to 10 hours. This time range is set to ensure that the reaction proceeds fully and reaches equilibrium. Too short a time may lead to incomplete reaction; too long a time will reduce production efficiency. This optimized time window ensures both precursor quality and process efficiency.

[0042] In step S3, a carrier is added to the homogeneous solution obtained in step S2, and the mixture is stirred and mixed to obtain a solid-liquid mixture.

[0043] This step enables the effective loading of the active component precursor from the solution phase to the support surface. The mass transfer kinetics provided by stirring allow the precursor molecules in the solution to come into full contact with the support surface and be uniformly anchored on the support by physicochemical forces (such as electrostatic adsorption).

[0044] In an embodiment of the present invention, in step S3, the support comprises one of silicon dioxide, aluminum oxide, or titanium dioxide; the molybdenum element in the molybdenum source accounts for 1%-20% of the mass percentage of the support. These support materials have high specific surface area and abundant surface functional groups, which can provide a large number of attachment sites for the active component precursor, which is beneficial to the formation of a highly dispersed catalyst. At the same time, they are stable in the hydrogenation reaction and will not interact adversely with the active component.

[0045] In an embodiment of the present invention, in step S3, the stirring time for continued mixing is 3 to 12 hours. This stirring time ensures the sufficiency and balance of the loading process, ensuring that the precursor molecules have sufficient time to diffuse into the pores of the support and reach adsorption equilibrium, thereby achieving deep and uniform loading and avoiding a "shell" distribution that only remains on the outer surface of the support.

[0046] In step S4, the solid-liquid mixture obtained in step S3 is subjected to solid-liquid separation, and the solid product is collected.

[0047] This step separates the loaded solid catalyst precursor from the remaining mother liquor. The operation is simple and easy to implement industrially. The collected solid product is the wet product of the target catalyst precursor.

[0048] In some exemplary embodiments, after solid-liquid separation is completed in step S4, the remaining mother liquor is collected. The composition of the mother liquor is adjusted by adding a strong alkali, a molybdenum source, and a sulfur source. The adjusted mother liquor is then reused in the preparation of the dilute alkali solution in step S1 for the next batch of catalyst precursor. This step is one of the core aspects of this invention's green environmental protection and cost reduction. By recycling the mother liquor, zero wastewater discharge is achieved, completely solving the environmental pollution problems of traditional methods. Furthermore, the unused raw materials in the mother liquor are recovered, significantly reducing material consumption and production costs, which conforms to the principle of atom economy.

[0049] In step S5, the solid product obtained in step S4 is dried at 50°C to 80°C to obtain a supported monolayer molybdenum disulfide catalyst precursor. This low-temperature drying condition aims to gently remove physically adsorbed water from the solid product while avoiding structural collapse, aggregation, or crystal transformation of the precursor. This step effectively preserves the unstable precursor structure built on the support, which is easily converted into monolayer molybdenum disulfide.

[0050] In an embodiment of the present invention, in step S5, the drying time is 1 to 3 hours.

[0051] This drying time, matched with low-temperature conditions, ensures effective removal of moisture to obtain a free-flowing solid powder, while preventing energy waste or potential local structural changes due to excessive drying time, thus achieving a balance between efficiency and product quality.

[0052] The supported monolayer molybdenum disulfide catalyst precursor according to embodiments of the present invention can be used in the hydrogenation reaction of inferior oils, including coal tar, residue oil or wood tar; the precursor is converted in situ into catalytically active monolayer molybdenum disulfide during the hydrogenation reaction.

[0053] In the initial stage of the hydrogenation reaction, the precursor in the reaction environment is in-situ sulfided and activated under high temperature, high pressure, and a reducing atmosphere. During this process, the stable interaction between the ordered molybdenum-sulfur structure in the precursor and the support guides its directional transformation into highly dispersed monolayer molybdenum disulfide nanosheets with a large number of exposed active edge sites. Compared with pre-synthesized and subsequently supported catalysts, this in-situ generated monolayer structure exhibits a more robust bond between the active phase and the support, and a significantly improved utilization rate of active sites.

[0054] When this precursor is applied to the hydrotreating of low-quality oils such as coal tar, residual oil, or wood tar, it exhibits the following significant advantages:

[0055] High hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activity: The large number of monolayer molybdenum disulfide active edge sites generated in situ can efficiently break the CS and CN bonds of complex heteroatom compounds such as sulfides and nitrides in inferior oils, thereby achieving deep desulfurization and denitrification.

[0056] Excellent coking performance: The highly dispersed monolayer molybdenum disulfide active centers can rapidly adsorb and saturate unstable intermediates and polycyclic aromatic hydrocarbons generated in the hydrogenation reaction, effectively inhibiting the occurrence of condensation coking reaction and ensuring the long-term stable operation of the reactor.

[0057] Significantly improves light oil yield: Due to its excellent hydrogenation activity and coking ability, it can efficiently crack and hydrogenate heavy components (such as asphaltenes and gums) into light fractions, thereby significantly improving the yield of light oil at <360℃.

[0058] Excellent stability and regeneration performance: Thanks to the strong interaction between the active phase and the support, this catalyst is not prone to sintering, loss, or active phase stripping under harsh reaction conditions, exhibiting excellent stability. Even after multiple regeneration cycles, its active centers can still be well recovered and maintained.

[0059] In summary, the supported monolayer molybdenum disulfide catalyst precursor provided by this invention is not only green and economical in its preparation process, but also exhibits comprehensive advantages such as high catalytic activity, good stability, and high yield of light oil in practical applications. It provides a catalytic material with great industrial application prospects for the efficient and clean conversion of inferior oil.

[0060] Implementation Case 1

[0061] (1) Prepare 300 ml of a dilute alkaline solution with pH=8.0 using sodium hydroxide and deionized water. (2) Dissolve 0.5 g of ammonium heptamolybdate and 0.4 g of thioacetamide in the dilute alkaline solution while stirring to form a homogeneous solution and stir for 2 h. (3) Add 9.1 g of silica support and continue stirring for 5 h. (4) After stirring, filter the solid product and dry it at 80 °C for 1 h to obtain the supported monolayer MoS2 catalyst precursor.

[0062] Testing revealed that this precursor exhibited excellent catalytic performance while simultaneously generating monolayer MoS2 in the coal tar hydrogenation reaction, resulting in an 18% increase in light oil (<360℃) yield compared to conventional hydrothermal-prepared monolayer MoS2 catalysts. Furthermore, the catalyst demonstrated good cyclic stability, maintaining high activity even after multiple regenerations, indicating promising prospects for industrial applications.

[0063] Implementation Case 2

[0064] (1) Prepare 300 ml of a dilute alkaline solution with pH=9.0 using potassium hydroxide and deionized water. (2) Dissolve 0.5 g of ammonium heptamolybdate and 0.9 g of thiourea in the dilute alkaline solution while stirring to form a homogeneous solution and stir for 10 h. (3) Add 18.2 g of titanium dioxide support and continue stirring for 3 h. (4) After stirring, filter and collect the solid product. Dry it at 60 °C for 3 h to obtain the supported monolayer MoS2 catalyst precursor.

[0065] Testing revealed that this precursor exhibited excellent catalytic performance while simultaneously generating monolayer MoS2 in the coal tar hydrogenation reaction, resulting in a 20% increase in light oil (<360℃) yield compared to conventional hydrothermal-prepared monolayer MoS2 catalysts. Furthermore, the catalyst demonstrated good cyclic stability, maintaining high activity even after multiple regenerations, indicating promising prospects for industrial applications.

[0066] Implementation Case 3

[0067] (1) Prepare 300 ml of a dilute alkaline solution with pH=10.0 using sodium hydroxide and deionized water. (2) Dissolve 0.6 g of sodium molybdate and 1.1 g of thiourea in the dilute alkaline solution while stirring to form a homogeneous solution and stir for 8 h. (3) Add 5.4 g of alumina support and continue stirring for 12 h. (4) After stirring, filter the solid product and dry it at 50 °C for 3 h to obtain the supported monolayer MoS2 catalyst precursor.

[0068] Testing revealed that this precursor exhibited excellent catalytic performance while simultaneously generating monolayer MoS2 in the coal tar hydrogenation reaction, resulting in a 15% increase in light oil (<360℃) yield compared to conventional hydrothermal-prepared monolayer MoS2 catalysts. Furthermore, the catalyst demonstrated good cyclic stability, maintaining high activity even after multiple regenerations, indicating promising prospects for industrial applications.

[0069] Those skilled in the art will understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention can be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

Claims

1. A method for preparing a supported monolayer molybdenum disulfide catalyst precursor, characterized by, The method comprises: Step S1, preparing a dilute alkali solution with a pH value of 8.0-10.0; Step S2, dissolving a molybdenum source and a sulfur source in the dilute alkali solution obtained in Step S1, stirring and mixing to form a uniform solution; Step S3, adding a carrier to the uniform solution obtained in Step S2, continuing to stir and mix to obtain a solid-liquid mixture; Step S4, performing solid-liquid separation on the solid-liquid mixture obtained in Step S3, and collecting a solid product; Step S5, drying the solid product obtained in Step S4 at 50-80°C to obtain the supported monolayer molybdenum disulfide catalyst precursor.

2. The production method according to claim 1, characterized by, In Step S1, the strong alkali used to prepare the dilute alkali solution includes one of sodium hydroxide or potassium hydroxide.

3. The preparation method according to claim 1, characterized in that, In Step S2, the molybdenum source includes one of ammonium heptamolybdate or sodium molybdate; and the sulfur source includes one of thioacetamide or thiourea.

4. The method of claim 1, wherein, In Step S2, the molar ratio of molybdenum in the molybdenum source to sulfur in the sulfur source is 1:2-1:

6.

5. The preparation method according to claim 1, in Step S3, the carrier includes one of silicon dioxide, aluminum trioxide or titanium dioxide; The mass percentage of molybdenum in the molybdenum source in the carrier is 1%-20%.

6. The method of claim 1, wherein, In Step S2, the stirring time for stirring and mixing is 2-10 hours; In Step S3, the stirring time for continuing to stir and mix is 3-12 hours.

7. The preparation method according to claim 1, characterized in that, In Step S5, the drying time is 1-3 hours.

8. The production method according to any one of claims 1 to 7, characterized by, After completing the solid-liquid separation in Step S4, the remaining mother liquor is collected, the composition of the mother liquor is adjusted by supplementing a strong alkali, a molybdenum source and a sulfur source into the mother liquor, and the adjusted mother liquor is used for the preparation of the dilute alkali solution in Step S1 for the preparation of the catalyst precursor in the next batch.

9. A supported monolayer molybdenum disulfide catalyst precursor prepared by the preparation method according to any one of claims 1-8.

10. Use of the supported monolayer molybdenum disulfide catalyst precursor according to claim 9 in a hydroprocessing reaction of a poor quality oil, characterized in that, The poor-quality oil includes coal tar, residual oil or wood tar; and the precursor is converted into a catalytically active monolayer molybdenum disulfide in situ during a hydrogenation reaction.

Images