Preparation method of MoS < 2 >-SnS < 2 >-SnO < 2 > nano material with core-shell structure

Abstract

The invention discloses a preparation method of a MoS < 2 > (at) SnS < 2 > (at) SnO < 2 > nano material with a core-shell structure. The method comprises the following steps: 1, ultrasonically dispersing a SnO2 nano material with an exposed high-energy surface in water or a low-carbon alcohol or alcohol amine solvent; 2, a sulfur source precursor, a tin source precursor and a molybdenum source precursor are sequentially added into the solvent, the types of precursor raw materials are regulated and controlled, and turbid liquid is formed; and 3, regulating and controlling the substance proportion in the solvent. And 4, transferring the obtained turbid liquid into a closed system, and crystallizing by microwave heating or electric heating. And 5, after the crystallization is finished, separating a solid product, washing and drying to obtain the MoS < 2 >-SnS < 2 >-SnO < 2 > nano material which takes SnO < 2 > as a core and is sequentially coated with SnS < 2 > and MoS < 2 > shell layers from inside to outside. The synthesis method disclosed by the invention has the advantages of mild conditions, simplicity in operation, high yield and the like; and the prepared MoS < 2 >-SnS < 2 >-SnO < 2 > nano material with the core-shell structure has the characteristics of high hydrogenation active site exposure and good high-temperature and high-pressure stability.

Description

Technical Field

[0001] This invention relates to a method for preparing core-shell structured MoS2@SnS2@SnO2 nanomaterials, belonging to the field of controllable preparation of novel structurally efficient nanocatalysts. Background Technology

[0002] Transition metal sulfide MoS2 has a typical layered structure, with layers bonded by weak van der Waals forces, making it easy to peel off. Each molybdenum atom in a single atomic layer is surrounded by six sulfur atoms, forming a triangular prism shape, exposing many Mo-S facets that can serve as catalytic active centers. (See Chianelli, R.R. Catal. Rev. 2006, 48(1), 1-41) Due to the increasing interest in layered MoS2 materials, and because of its high hydrogenation activity and good resistance to poisoning, MoS2 catalysts have become a research hotspot in recent years for the hydrogenation of heavy oil to lighter materials. (Al-Attas T.A. Energy Fuels 2019, 33, 7917-7949) The catalytic hydrogenation activity of MoS2 materials is closely related to its structural characteristics. Since the catalytic hydrogenation active centers of MoS2 are mainly located on the facets, the surface energy is high, at 0.7 J / m². 2 MoS2 has a reactive and unstable surface, providing active sites for heterogeneous catalytic hydrogenation reactions. Reducing the catalyst size and the number of stacked layers can effectively increase the exposure of active sites for MoS2 hydrogenation, thereby obtaining a highly active hydrogenation catalyst.

[0003] To date, various methods have been developed for preparing nano-MoS2, resulting in a variety of product morphologies. CN 103086436 discloses a method for preparing flower-like and rod-shaped nano-MoS2 in a reaction system, which requires the addition of inorganic salts for auxiliary control in the preparation of flower-like and rod-shaped nano-MoS2. CN201410436988.6 discloses a method for hydrothermal synthesis of uniform MoS2 nanospheres using citric acid as a complexing agent. CN2015108639802 discloses a method for hydrothermal synthesis of polyhedral hollow MoS2 particles assisted by ionic liquids. CN201410758657.4 discloses a method for preparing MoS2 microspheres in a reverse microemulsion system. The aforementioned wet chemical synthesis of MoS2 materials mostly involves the assembly of nanosheets with sizes ranging from hundreds of nanometers to micrometers, and the large number of nanosheet layers is detrimental to the exposure of active sites. However, due to the extremely high surface energy of MoS2 nanosheets produced during wet synthesis, they often aggregate into micro / nanospheres, nanoflowers, hollow cages, and other morphologies during crystallization to reduce surface energy. This undoubtedly leads to the embedding and covering of many catalytically active sites. Furthermore, the stability of this self-aggregated MoS2 material in high-temperature, high-pressure heavy oil slurry bed hydrogenation systems needs to be improved.

[0004] One improvement to address the aforementioned problem is to chemically anchor MoS2 nanosheets to the surface of the nanomaterial, thereby reducing surface energy and preventing self-aggregation of the MoS2 nanosheets. This chemical anchoring method enables the preparation of highly active MoS2 catalysts, maximizing the exposure of active sites while ensuring high stability of the catalyst in high-temperature, high-pressure systems. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems by providing a method for preparing core-shell structured MoS2@SnS2@SnO2 nanomaterials.

[0006] The method used in this invention is as follows:

[0007] 1. Solution preparation: Disperse SnO2 nanomaterials in water, low-carbon alcohol or alkanolamine solvent, and dissolve sulfur source, tin source and molybdenum source in solvent in sequence to form a homogeneous suspension.

[0008] 2. Crystallization reaction: Transfer the suspension to a closed crystallization system and crystallize at 0.01-5.0 MPa and 120-220℃ for 3-72 hours. Microwave or electric heating or hydrothermal or solvothermal methods are used to complete the crystallization.

[0009] 3. Separation of products: Using conventional separation methods, such as vacuum filtration and centrifugation, the precipitate was washed with deionized water and anhydrous ethanol, and then vacuum or freeze-dried to obtain black MoS2@SnS2@SnO2 nanomaterials with SnO2 core and SnS2 and MoS2 shells sequentially coated.

[0010] The SnO2 nanomaterials used above are one or a mixture of two or more of the following: self-made or commercially available (111) high-energy surface exposed SnO2 nanomaterials with particle sizes of 50-300 nm; the sulfur source used is one or a mixture of two or more of the following soluble sulfur sources: sodium sulfide, potassium sulfide, ammonium sulfide, ammonium thiocyanate, thiourea, thioacetamide, L-cysteine, glutathione, etc.; the tin source used is one or a mixture of two or more of the following: tin dichloride, stannous nitrate, tin tetrachloride, or tin nitrate; the molybdenum source used is one or a mixture of two or more of the following: ammonium heptamolybdate, sodium molybdate, ammonium molybdate, phosphomolybdic acid, or ammonium tetrathiomolybdate; and the solvent used is one or a mixture of two or more of the following: water, monohydric, dihydric, or trihydric alcohols or alkanolamines of C1-C4. The molar concentration of Sn in the solvent is 0.001M to 0.1M, the molar concentration of Mo is 0.001M to 0.1M, the molar ratio of S / (Mo+Sn) is 1.0 to 4.0, the molar ratio of Sn / Mo is 0.1 to 10.0, and the molar ratio of metallic Mo to SnO2 nanomaterials with exposed high-energy surfaces is 0.1 to 10.0.

[0011] As attached Figure 1 and 2As shown, (111) octahedral SnO2 nanoparticles with exposed high-energy surfaces serve as the composite material for MoS2, becoming a core-shell structure precursor. They are dispersed in a solvent, and a sulfur source is added. The sulfur source adsorbs onto the high-energy surface of SnO2 to reduce its surface energy and improve stability. After adding the Sn source precursor, the S source forms a SnS2 shell on the high-energy surface of SnO2. Based on the similarity of the 2H crystal phase structure of SnS2 and MoS2, a Mo source is further added to the above system, and Mo adsorbs onto the surface of the SnS2 shell to form a MoS2 shell. After crystallization, a core-shell structure MoS2@SnS2@SnO2 nanomaterial is obtained. (See attached image) Figure 3 The XRD pattern of the MoS2@SnS2@SnO2 nanomaterials mainly showed SnO2 diffraction peaks, and the relative peak intensities of these peaks changed compared to before recombination. No diffraction peaks of MoS2 and SnS2 were observed in the XRD pattern of the MoS2@SnS2@SnO2 nanomaterials, indicating that both the SnS2 and MoS2 shells are thin and uniformly distributed, without self-aggregation. (See attached image) Figure 4 HRTEM (High Resolution Transmission Electron Microscopy) elemental mapping results confirmed that the outer shell is indeed a MoS2 layer. The Sn in SnS2 is bonded to the SnO2 core, therefore a separate SnS2 shell is not visible. Figure 5 HRTEM images show that the prepared core-shell MoS2@SnS2@SnO2 material consists of 1–3 stacked MoS2 nanosheets with a sheet length of 5–15 nm, achieving small-size, low-density MoS2 loading and maximizing the exposure of its catalytically active edges. The construction of the core-shell MoS2@SnS2@SnO2 structure in this invention can greatly avoid the aggregation of MoS2 nanosheets, effectively preventing the embedding and covering of catalytically active edges caused by the aggregation process (see [link to relevant documentation]). Figure 6 This improves the stability of the MoS2 catalyst.

[0012] Compared with the prior art, the present invention has the following advantages and effects:

[0013] The preparation method developed in this invention fully utilizes the characteristic of SnO2 nanoparticles exposing high-energy surfaces to achieve S source adsorption, and adds Sn source to form a fresh SnS2 shell as an intermediate link. Based on the similarity of the crystal phase structure of SnS2 and MoS2, MoS2 is further composited to form a shell, resulting in a core-shell structured MoS2@SnS2@SnO2 nanomaterial.

[0014] The preparation process developed in this invention can effectively solve the problem of MoS2 nanosheets agglomerating into large micron-sized particles in the synthesis system in order to reduce surface energy. Furthermore, the presence of the SnS2 intermediate layer in the core-shell structure provides a substrate for the growth of MoS2, effectively reducing the surface energy of MoS2 nanosheets, inhibiting their self-agglomeration, and improving the stability of MoS2 materials.

[0015] This invention provides a method for effectively improving the activity and stability of catalysts. Specifically, a SnS2 intermediate shell is formed by the interaction of high-energy-surface-exposed nanomaterials with a sulfur source and a Sn source. Subsequent interaction with a Mo source generates a low-density, small-sized MoS2 nanosheet shell. Furthermore, this core-shell structure allows for adjustment of the shell thickness by regulating the type of precursor and its ratio with SnO2, thereby altering the density and sheet size of the final product. This method can be applied to the structural control of similar materials.

[0016] The product prepared by this invention is a core-shell structured MoS2@SnS2@SnO2 nanomaterial with 1 to 3 layers and a sheet length of 5 to 15 nm. Compared with conventional methods for preparing MoS2 catalysts, the method used in this invention effectively reduces MoS2 agglomeration, increases the exposure of catalytic active sites, and ensures catalyst stability. The MoS2@SnS2@SnO2 nanomaterial prepared by this invention consists of small-sized MoS2 nanosheets with low packing density uniformly loaded on the SnS2@SnO2 surface, resulting in numerous exposed catalytic active sites and high stability.

[0017] The core-shell structured MoS2@SnS2@SnO2 nanomaterials synthesized in this invention have wide applications in electrochemistry, electrode materials, and catalytic hydrogenation. In particular, the core-shell structured MoS2@SnS2@SnO2 nanomaterials exhibit high activity at exposed edges and high stability, making them suitable for high-temperature and high-pressure hydrogenation reactions in fixed-bed, fluidized-bed / boiling-bed, and slurry-bed reactors.

[0018] The synthesis method of this invention has the advantages of mild conditions, simple operation, and high yield. The core-shell structured MoS2@SnS2@SnO2 nanomaterials prepared by this invention exhibit high exposure of hydrogenation active sites and good stability under high temperature and pressure. The core-shell structured MoS2@SnS2@SnO2 nanomaterials synthesized by the method of this invention can be used in the field of catalytic hydrogenation of oil products, and are expected to have excellent catalytic hydrogenation activity and stability. Attached Figure Description

[0019] Figure 1 SEM images of SnO2 nanoparticles exposed at high energy surfaces. (a) is an elongated octahedral SnO2-1 nanocrystal exposed at the high energy surface (111) of Example 1, and (b) is an octahedral SnO2-2 nanocrystal exposed at the high energy surface (111) of Example 2.

[0020] Figure 2 The XRD patterns are of SnO2-1 sample from Example 1 and SnO2-2 sample from Example 2.

[0021] Figure 3TEM images of SnO2 nanoparticles exposed at high energy surfaces. (a) is an elongated octahedral SnO2-1 nanocrystal exposed at the high energy surface (111) of Example 1, and (b) is an octahedral SnO2-2 nanocrystal exposed at the high energy surface (111) of Example 2.

[0022] Figure 4 The XRD spectra of the MoS2 sample of Comparative Example 1, the SnS2 sample of Comparative Example 2, and the core-shell structured MoS2@SnS2@SnO2 nanomaterials of Examples 1 and 2 are shown.

[0023] Figure 5 The image shows the SEM and elemental distribution images of the core-shell structured MoS2@SnS2@SnO2 nanomaterials from Example 2.

[0024] Figure 6 TEM image of the core-shell structured MoS2@SnS2@SnO2 nanomaterial from Example 2.

[0025] Figure 7 TEM image of the core-shell structured MoS2@SnS2@SnO2 nanomaterial of Example 1.

[0026] Figure 8 This is an image showing the elemental distribution of the core-shell structured MoS2@SnS2@SnO2 nanomaterial from Example 2.

[0027] Figure 9 SEM and TEM images of MoS2 sample 1 (Comparative Example 1).

[0028] Figure 10 SEM and TEM images of sample SnS2 in Comparative Example 2. Detailed Implementation

[0029] The invention will now be described in further detail with reference to specific experimental examples.

[0030] Example 1:

[0031] Weigh 1.0518 g of SnCl4·5H2O and dissolve it in a mixed solution of 9 ml anhydrous ethanol and 9 ml deionized water to obtain a colorless and transparent solution. Measure 42 ml of 1 M TMAH solution and add it dropwise to the above colorless and transparent solution while stirring. After the addition is complete, continue stirring for 1 h, and the solution remains colorless and transparent. Transfer the solution to a hydrothermal reactor, seal it, and place it in an oven to heat to 200 °C for 12 h. After crystallization, remove the hydrothermal reactor from the oven and allow it to cool naturally to room temperature. Open the reactor, centrifuge to separate the sample, and wash the sample three times each with deionized water and anhydrous ethanol to obtain a solid product. Then dry it at 60 °C for 12 h, grind and collect the white solid product, named SnO2-1. Figure 1 -a、 Figure 2and Figure 3 -a are SEM images, XRD patterns, and TEM images of the SnO2-1 sample, respectively. Analysis shows that the synthesized SnO2 sample size ranges from 100 to 300 nm. The morphology of nanocrystals is usually related to their exposed crystal faces. The TEM image shows that the SnO2-1 sample is hexagonal, with this morphology exposing both the {111} high-energy surface and the {110} low-energy surface. Therefore, elongated octahedral SnO2 nanocrystals with exposed {111} high-energy surfaces were synthesized. 0.2056 g of self-made SnO2-1 with high-energy (111) surface exposure (100-300 nm particle size) was dispersed in 60 ml of deionized water; then 0.2648 g of (NH4)6Mo7O was added sequentially. 24 0.6769 g SnCl2·2H2O and 0.6851 g NH4SCN were used as molybdenum, tin, and sulfur sources, respectively, and stirred for 30 min to form a suspension. This suspension was then transferred to a 100 ml hydrothermal reactor, sealed, and heated to 180 °C in an oven for 18 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was then opened, and the sample was separated by filtration. The sample was washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product. This product was then vacuum dried at 70 °C for 12 h, and the resulting MoS2@SnS2@SnO2 nanomaterials were collected by grinding.

[0032] Figure 4 The figure shows the XRD pattern of MoS2@SnS2@SnO2 nanomaterials. As can be seen from the figure, the XRD diffraction peaks of the MoS2@SnS2@SnO2 sample are consistent with the diffraction peaks of SnO2, and no diffraction peaks of MoS2 or SnS2 are observed. This indicates that the crystallinity of MoS2 and SnS2 in the MoS2@SnS2@SnO2 sample is poor or highly dispersed. Figure 7 and Figure 8 The images show STEM and elemental distribution images of the MoS2@SnS2@SnO2 nanomaterials. As can be seen from the images, 0.56 nm lattice fringes can be observed on the surface of the SnO2 nanomaterials, belonging to the (001) crystal plane of SnS2. Therefore, the inner layer can be identified as a SnS2 layer, with 1-2 stacked layers. Further outer layers show 0.62 nm lattice fringes, belonging to the (002) crystal plane of MoS2. Therefore, the outer layer can be identified as a MoS2 layer, with 3-4 stacked layers. The MoS2 layer, SnS2 layer, and SnO2 particles are tightly bonded, with relatively few SnS2 and MoS2 stacked layers. Therefore, the entire catalyst is a MoS2@SnS2@SnO2 core-shell structure, with SnO2 as the core and SnS2 and MoS2 shells sequentially covering it from the inside out.

[0033] Example 2:

[0034] Weigh 1.0518 g of SnCl4·5H2O and dissolve it in 9 ml of anhydrous ethanol to obtain a colorless and transparent solution. Measure 51 ml of 1 M TMAH solution and add it dropwise to the above colorless and transparent solution while stirring. After the addition is complete, continue stirring for 1 h, and the solution remains colorless and transparent. Transfer the solution to a hydrothermal reactor, seal it, and place it in an oven to heat to 200 °C for 12 h. After crystallization, remove the hydrothermal reactor from the oven and allow it to cool naturally to room temperature. Open the reactor, centrifuge the sample, wash the sample three times with deionized water and anhydrous ethanol respectively to obtain a solid product, then dry it at 60 °C for 12 h, grind and collect the white solid product, named SnO2-2. Figure 1 -b、 Figure 2 and Figure 3 -b are SEM images, XRD patterns, and TEM images of the SnO2-2 sample, respectively. The analysis results show that the size range of the synthesized SnO2-2 sample is 50-300 nm. The TEM image shows that the SnO2-2 sample is rectangular, and the SnO2 with this morphology exposes the {111} high-energy surface. Therefore, SnO2 with the {111} high-energy surface exposed was synthesized.

[0035] 0.2056 g of self-made (111) high-energy surface exposed nanomaterial SnO2-2 was dispersed in 60 ml of methanol; then 0.2648 g of (NH4)6Mo7O was added to the methanol. 24 ·4H2O, 1.0518g SnCl4·5H2O, and 0.6851g NH4SCN were used as molybdenum, tin, and sulfur sources, respectively, and stirred for 30 min to form a suspension. This suspension was then transferred to a 100ml microwave-safe reactor liner, sealed, and heated to 180℃ in a microwave synthesizer for 18 h. After crystallization, the mixture was allowed to cool naturally to room temperature, and the reactor liner was removed from the microwave synthesizer. The sample was separated by high-speed centrifugation, washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product. This product was then vacuum-dried at 70℃ for 12 h, ground, and collected to obtain MoS2@SnS2@SnO2 nanomaterials.

[0036] Figure 4 The figure shows the XRD pattern of MoS2@SnS2@SnO2 nanomaterials. As can be seen from the figure, the XRD diffraction peaks of the MoS2@SnS2@SnO2 sample are consistent with the diffraction peaks of SnO2, and no diffraction peaks of MoS2 or SnS2 are observed. This indicates that the crystallinity of MoS2 and SnS2 in the MoS2@SnS2@SnO2 sample is poor or highly dispersed. Figure 5 SEM images and elemental distribution images of MoS2@SnS2@SnO2 nanomaterials. Figure 6The HRTEM interlayer spacing of 0.66 nm indicates that the outer layer is a MoS2 layer with a thickness of approximately 2.5 nm; the interlayer spacing of 0.56 nm indicates that the inner layer is a SnS2 layer with a thickness of approximately 1.5 nm. In summary, the MoS2@SnS2@SnO2 nanomaterials exhibit a SnO2 core, a SnS2 shell, and a MoS2 shell, arranged from the inside out, with uniform distribution and no self-aggregation. This is consistent with... Figure 3 The XRD results are consistent.

[0037] Example 3:

[0038] 0.2261 g of self-made high-energy surface (111) exposed SnO2-1 (prepared by the same method as in Example 1) was dispersed in 60 ml of ethylene glycol; then 0.7808 g of (NH4)2MoS4 and 0.3384 g of SnCl2·2H2O were added sequentially as molybdenum, sulfur, and tin sources, respectively, and stirred for 30 min to form a suspension; then the suspension was transferred to a 100 ml hydrothermal reactor, sealed, and placed in an oven to be heated to 140 °C for 36 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was opened, the sample was separated by vacuum filtration, and the sample was washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product, which was then vacuum dried at 70 °C for 12 h, and ground to collect the MoS2@SnS2@SnO2 nanomaterials.

[0039] Example 4:

[0040] 0.2261 g of self-made high-energy surface (111) exposed SnO2-2 (prepared by the same method as in Example 2) was dispersed in 60 ml of ethylene glycol; then 0.7808 g of (NH4)2MoS4 and 0.5259 g of SnCl4·5H2O were added sequentially as molybdenum, sulfur, and tin sources, respectively, and stirred for 30 min to form a suspension; then the suspension was transferred to a 100 ml hydrothermal reactor, sealed, and placed in an oven to be heated to 140 °C for 36 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was opened, and the sample was separated by high-speed centrifugation. The sample was washed three times with deionized water and anhydrous ethanol to obtain a black solid product, which was then vacuum dried at 70 °C for 12 h, and ground to collect the MoS2@SnS2@SnO2 nanomaterials.

[0041] Example 5:

[0042] 0.0904 g of self-made high-energy surface (111) exposed SnO2-1 (preparation method of SnO2-1 is the same as in Example 1) was dispersed in 60 ml of glycerol; then 0.9126 g of H3Mo was added sequentially. 12 O 40P·xH2O, 1.3538g SnCl2·2H2O, and 0.9016g C2H5NS were used as molybdenum, tin, and sulfur sources, respectively, and stirred for 30 min to form a suspension. This suspension was then transferred to a 100ml hydrothermal reactor, sealed, and heated to 160℃ in an oven for 27 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was then opened, and the sample was separated by filtration. The sample was washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product. This product was then vacuum dried at 70℃ for 12 h, and the resulting MoS2@SnS2@SnO2 nanomaterials were collected by grinding.

[0043] Example 6:

[0044] 0.0904 g of self-made high-energy surface (111) exposed SnO2-2 (preparation method of SnO2-2 is the same as in Example 2) was dispersed in 60 ml of isopropanol; then 0.9126 g of H3Mo was added sequentially. 12 O 40 P·xH2O, 2.1035g SnCl4·5H2O, and 0.9016g C2H5NS were used as molybdenum, tin, and sulfur sources, respectively, and stirred for 30 min to form a suspension. This suspension was then transferred to a 100ml hydrothermal reactor, sealed, and heated to 160℃ in an oven for 27 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was then opened, and the sample was separated by high-speed centrifugation. The sample was washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product. This product was then freeze-dried at 70℃ for 12 h, ground, and collected to obtain MoS2@SnS2@SnO2 nanomaterials.

[0045] Example 7:

[0046] 0.4521 g of self-made high-energy surface (111) exposed SnO2-1 (prepared by the same method as in Example 1) was dispersed in 60 ml of butanol to form a suspension. 0.1452 g of Na2MoO4·2H2O, 0.0135 g of SnCl2·2H2O, and 0.32 g of L-cysteine ​​were added sequentially to the suspension as molybdenum, tin, and sulfur sources, respectively. The mixture was stirred for 30 min to form a suspension, which was then transferred to a 100 ml hydrothermal reactor. After sealing, the reactor was placed in an oven and heated to 120 °C for 72 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was opened, and the sample was separated by filtration. The sample was washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product. This product was then vacuum dried at 70 °C for 12 h, and the MoS2@SnS2@SnO2 nanomaterials were collected by grinding.

[0047] Example 8:

[0048] 0.4521 g of self-made high-energy surface (111) exposed SnO2-2 (prepared by the same method as in Example 2) was dispersed in 60 ml of deionized water to form a suspension. 0.1452 g of Na2MoO4·2H2O, 0.0211 g of SnCl4·5H2O, and 0.32 g of L-cysteine ​​were added sequentially to the suspension as molybdenum, tin, and sulfur sources, respectively. The mixture was stirred for 30 min to form a suspension, which was then transferred to a 100 ml hydrothermal reactor. After sealing, the reactor was placed in an oven and heated to 120 °C for 72 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was then opened, and the sample was separated by high-speed centrifugation. The sample was washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product. This product was then freeze-dried at 70 °C for 12 h, ground, and collected to obtain MoS2@SnS2@SnO2 nanomaterials.

[0049] Example 9:

[0050] 0.0904 g of self-made high-energy surface (111) exposed SnO2-1 (prepared by the same method as in Example 1) was dispersed in 60 ml of ethylene glycol; then 0.0156 g of (NH4)2MoS4 and 0.2104 g of SnCl4·5H2O were added sequentially as molybdenum, sulfur, and tin sources, respectively, and stirred for 30 min to form a suspension; then the suspension was transferred to a 100 ml hydrothermal reactor, sealed, and placed in an oven to be heated to 220 °C for 3 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was opened, the sample was separated by vacuum filtration, and the sample was washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product, which was then vacuum dried at 70 °C for 12 h, and ground to collect the MoS2@SnS2@SnO2 nanomaterials.

[0051] Example 10:

[0052] 0.0904 g of self-made high-energy surface (111) exposed SnO2-2 (preparation method of SnO2-2 is the same as in Example 2) was dispersed in 60 ml of ethanol; then 0.0106 g of (NH4)6Mo7O was added to it sequentially. 24 0.2104 g SnCl4·5H2O, 0.1256 g NH4SCN were used as molybdenum, tin, and sulfur sources, respectively, and stirred for 30 min to form a suspension. This suspension was then transferred to a 100 ml hydrothermal reactor, sealed, and heated to 220 °C in an oven for 3 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was then opened, and the sample was separated by high-speed centrifugation. The sample was washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product. This product was then freeze-dried at 70 °C for 12 h, ground, and collected to obtain MoS2@SnS2@SnO2 nanomaterials.

[0053] Comparative Example 1:

[0054] 0.2648 g of (NH4)6Mo7O24·4H2O and 0.6851 g of NH4SCN were added sequentially to 60 ml of deionized water as molybdenum and sulfur sources, respectively, and stirred for 30 min to form a suspension. This suspension was then transferred to a 100 ml hydrothermal reactor, sealed, and heated to 180 °C in an oven for 18 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was then opened, and the sample was separated by filtration. The sample was washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product. This product was then vacuum dried at 70 °C for 12 h, and the resulting MoS2 microspheres were collected by grinding.

[0055] Figure 4 The XRD pattern of the MoS2 microspheres shown indicates that a MoS2 sample with expanded interlayer spacing was synthesized. Figure 9 The MoS2 microspheres shown have a particle size range of 1.0-2.5 μm. These microspheres are self-assembled from MoS2 nanosheets, with each individual MoS2 nanosheet having 3-7 stacked layers and a layer size of 20-50 nm.

[0056] Comparative Example 2:

[0057] 2.1035 g of SnCl4·5H2O and 0.9016 g of C2H5NS were added sequentially to 60 ml of ethanol as tin and sulfur sources, respectively, and stirred for 30 min to form a suspension. This suspension was then transferred to a 100 ml hydrothermal reactor, sealed, and heated to 160 °C in an oven for 27 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was then opened, and the sample was separated by high-speed centrifugation. The sample was washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product. This product was then vacuum dried at 70 °C for 12 h, and the SnS2 nanomaterials were collected by grinding.

[0058] Figure 4 The XRD pattern of the SnS2 nanosheets shown indicates that SnS2 samples with expanded interlayer spacing were synthesized. Figure 10 The surface of the SnS2 nanomaterials shown exhibits lattice fringes of 0.63 nm, attributed to the (100) crystal plane of SnS2; and lattice fringes of 0.27 nm, attributed to the (101) crystal plane of SnS2. Therefore, SnS2 sheet-like materials were synthesized. Analysis using XRD patterns, SEM, and HRTEM revealed that the synthesized SnS2 samples had particle sizes ranging from 100 to 800 nm, with SnS2 sheet lengths greater than 60 nm and more than 6 stacked layers.

[0059] Comparative Example 3:

[0060] Disperse 0.0904g of commercial SnO2 in 60ml of ethanol; then add 0.0106g of (NH4)6Mo7O2 sequentially. 24 0.2104 g SnCl4·5H2O, 0.1256 g NH4SCN were used as molybdenum, tin, and sulfur sources, respectively, and stirred for 30 min to form a suspension. This suspension was then transferred to a 100 ml hydrothermal reactor, sealed, and heated to 220 °C in an oven for 3 h. After crystallization, the hydrothermal reactor was removed from the oven and allowed to cool naturally to room temperature. The reactor was then opened, and the sample was separated by high-speed centrifugation. The sample was washed three times with deionized water and anhydrous ethanol, respectively, to obtain a black solid product. This product was then freeze-dried at 70 °C for 12 h, ground, and collected to obtain MoS2@SnS2@SnO2 nanomaterials.

[0061] Application examples

[0062] The products prepared in the examples and comparative examples were subjected to phenanthrene-catalyzed hydrogenation in a 100 ml high-pressure reactor equipped with a stirrer. The specific procedures were as follows: 30.0 g of tridecane solvent, 3.0 g of phenanthrene, and 0.1 g of catalyst were added to the reactor. After sealing the reactor, the air inside was purged with nitrogen three times at room temperature, followed by purging with hydrogen three times, and then the pressure was increased to 8.0 MPa. Cooling water and stirring were turned on, with the stirring rate adjusted to 300 rpm. The temperature was increased to 350 °C at a rate of 10 °C / min and reacted at this temperature for 4 hours. After the reaction was completed, the liquid product from the phenanthrene hydrogenation reaction was removed after the reactor temperature had cooled to room temperature for analysis.

[0063] Gas chromatography-mass spectrometry analysis of the products showed that the hydrogenation products (PHx) of phenanthrene (PH) mainly consist of dihydrophenanthrene (PH2), tetrahydrophenanthrene and its isomer tetrahydroanthracene (PH4), octahydrophenanthrene and its isomer octahydroanthracene (PH8), and a small amount of tetradecahydrophenanthrene and its isomer tetradecahydroanthracene (PH14). The hydrogenation reaction pathway of phenanthrene on MoS2 catalyst is shown below.

[0064]

[0065] The selectivity, conversion, and hydrogenation rate of the phenanthrene hydrogenation products were calculated using the carbon balance method.

[0066] Selectivity of phenanthrene hydrogenation products (Sel) .(PHx) The calculation is as follows:

[0067]

[0068] AT(PHx) refers to the chromatographic peak area of ​​a certain hydrogenation product.

[0069] The hydrogen conversion rate (Conv.) of phenanthrene is calculated as follows:

[0070]

[0071] [pH]0 refers to the amount of phenanthrene before the reaction, and [pH] refers to the amount of phenanthrene after the reaction.

[0072] The hydrogenation rate (HP) of the phenanthrene hydrogenation reaction is calculated as follows:

[0073]

[0074] The activity evaluation results are shown in Table 1, and the stability evaluation results are shown in Table 2. The results show that the core-shell structured MoS2@SnS2@SnO2 catalyst prepared in this invention has significantly better activity and stability than the comparative catalysts. The hydrogenation activity of the core-shell materials in the examples of this invention is more than twice that of the comparative examples, more than 20 times that of comparative example 2, and more than 1.5 times that of comparative example 3. Stability results show that the catalyst of Example 1 retains 96% of its initial activity after 5 cycles, while the catalyst of comparative example 1 retains only 46% of its initial activity after 5 cycles, and the catalyst of comparative example 3 retains only 74% of its initial activity after 5 cycles. The nanomaterials of this invention exhibit better high-temperature and high-pressure reaction stability.

[0075] Table 1 shows the hydrogenation activity of the catalysts prepared in the examples and comparative examples.

[0076]

[0077] Table 2 shows the phenanthrene conversion rates of Example 1 and Comparative Example 1 for recycling.

[0078]

Claims

1. A method for preparing MoS2@SnS2@SnO2 nanomaterials, characterized in that, The process includes the following steps: SnO2 nanomaterials are first dispersed in a solvent, and sulfur source, tin source and molybdenum source are added to the solvent to form a suspension; the resulting suspension is transferred to a closed system or container and heated for crystallization; after crystallization, the solid product is separated to obtain MoS2@SnS2@SnO2 nanomaterials with SnO2 as the core and SnS2 and MoS2 shells successively coated from the inside to the outside.

2. The method for preparing MoS2@SnS2@SnO2 nanomaterials according to claim 1, characterized in that: The SnO2 nanomaterials used are one or a mixture of two or more of the (111) high-energy surface exposed SnO2 nanomaterials with a particle size of 50-300 nm.

3. The method for preparing MoS2@SnS2@SnO2 nanomaterials according to claim 1, characterized in that: The sulfur source used is one or a mixture of two or more soluble sulfur sources such as sodium sulfide, potassium sulfide, ammonium sulfide, ammonium thiocyanate, thiourea, thioacetamide, L-cysteine, and glutathione.

4. The method for preparing MoS2@SnS2@SnO2 nanomaterials according to claim 1, characterized in that: The tin source used is one or a mixture of two or more of tin dichloride, tin nitrate, tin tetrachloride, or tin nitrate; the molar concentration of Sn in the solvent is 0.001M to 0.1M, preferably 0.01M to 0.05M.

5. The method for preparing MoS2@SnS2@SnO2 nanomaterials according to claim 1, characterized in that: The molybdenum source is one or a mixture of two or more of ammonium heptamolybdate, sodium molybdate, ammonium molybdate, phosphomolybdic acid, and ammonium tetrathiomolybdate; the molar concentration of Mo in the solvent is 0.001M to 0.1M, preferably 0.01M to 0.05M.

6. The method for preparing MoS2@SnS2@SnO2 nanomaterials according to claim 1, characterized in that: The solvent is water, a mono-, di-, or tri-ol of C1-C4, or a mixture of two or more of diethanolamine, diisopropanolamine, and triethanolamine.

7. The method for preparing MoS2@SnS2@SnO2 nanomaterials according to any one of claims 1-6, characterized in that: The molar ratio of S / (Mo+Sn) in the solvent is 1.0 to 4.0, preferably 1.5 to 2.5; the molar ratio of Sn / Mo in the solvent is 0.1 to 10.0, preferably 0.5 to 2.0; and the molar ratio of metallic Mo to SnO2 is 0.1 to 10.0, preferably 0.2 to 2.

0.

8. The method for preparing MoS2@SnS2@SnO2 nanomaterials according to claim 1, characterized in that: The crystallization method adopted is a hydrothermal or solvothermal process in a closed system; the heating method is microwave heating or electric heating; the crystallization temperature is 120-220℃, preferably 140-180℃; the crystallization time is 3-72h, preferably 18-36h; and the crystallization pressure is 0.01-5.0MPa, preferably 0.04-0.5MPa.

9. The method for preparing MoS2@SnS2@SnO2 nanomaterials according to claim 1, characterized in that: The process of separating solid products includes filtration or centrifugation, followed by washing with deionized water and anhydrous ethanol, vacuum drying or freeze drying, to obtain MoS2@SnS2@SnO2 nanomaterials with SnO2 core and SnS2 and MoS2 shells.

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