A 1T-2H mixed phase molybdenum disulfide catalyst and its preparation method and application

Abstract

The present invention discloses a 1T-2H mixed phase molybdenum disulfide catalyst and its preparation method and application. The molybdenum disulfide catalyst morphology is a nanoflower cluster composed of multiple nanosheets, the nanosheet length is 1-9nm, and the size of the nanoflower cluster is 50-1000nm; the molybdenum disulfide catalyst basal surface presents two crystalline phases of 1T and 2H. The present invention adopts a hydrothermal method to prepare a molybdenum disulfide catalyst with a specific crystal form, and the morphology and crystallinity of molybdenum disulfide are regulated by changing the content of DMSO. The DMSO-modified molybdenum disulfide catalyst prepared by the present invention shows high activity and high selectivity for indirect desulfurization in the hydrodesulfurization reaction, the dibenzothiophene conversion rate can reach more than 98%, and the selectivity of the indirect desulfurization hydrogenation reaction pathway can reach 80%.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a 1T-2H mixed phase molybdenum disulfide catalyst and a preparation method and application thereof. Background Art

[0002] Many countries and regions have implemented a series of standards to limit the sulfur content in gasoline. Currently, the sulfur content of gasoline is limited to 10ppm, which puts forward stricter requirements for new desulfurization catalysts. Organic sulfur compounds in petroleum are difficult to remove by physical methods, and usually require hydrodesulfurization reaction to obtain ultra-low sulfur fuel.

[0003] Molybdenum disulfide catalysts have the advantages of high activity, low cost, and good stability, and have been widely used in industrial hydrodesulfurization reactions. Unsupported molybdenum disulfide catalysts have a high proportion of reactive components and have better catalytic activity than supported catalysts. Preparing molybdenum disulfide into poor crystals is an effective way to increase the active components and improve its hydrodesulfurization activity. Poorly crystallized molybdenum disulfide has a short-range ordered microstructure, and its crystal defects reduce the length of the nanosheets and expose more edges, thereby showing higher catalytic activity.

[0004] Hydrothermal method and solvothermal method are often used for the preparation of molybdenum disulfide catalysts. Compared with chemical vapor deposition, thermal decomposition, coprecipitation and intercalation stripping methods, the in-situ crystal growth conditions provided by the hydrothermal method make it easier to control the morphology and crystallinity of the crystal. CN109637838A discloses a method for preparing a hollow molybdenum disulfide material in the shape of a loofah by a hydrothermal method. CN115180650B discloses a method for synthesizing a molybdenum disulfide nanorod material assembled by a hydrothermal method. The above studies adjusted the morphology of the molybdenum disulfide material by different methods, but did not adjust the crystallinity of the molybdenum disulfide.

[0005] Therefore, developing a simple method for preparing stable molybdenum disulfide materials with adjustable crystallinity for use as high-performance hydrodesulfurization catalysts has important guiding significance for the design and application of hydrodesulfurization catalysts and nanocomposites.

[0006] In order to solve the above problems, the present invention is proposed. Summary of the invention

[0007] The present invention adopts a hydrothermal synthesis method, introduces DMSO to regulate the crystallization time and crystallinity of molybdenum disulfide, and synthesizes 1T-2H mixed phase molybdenum disulfide with a nanosheet length of several nanometers, thereby improving the hydrodesulfurization activity and indirect desulfurization selectivity of the molybdenum disulfide catalyst.

[0008] The purpose of the present invention is to provide a 1T-2H mixed phase molybdenum disulfide catalyst and its preparation method and application. The morphology of the molybdenum disulfide catalyst is a nanoflower cluster composed of multiple nanosheets, the length of the nanosheet is 1-9nm, and the size of the nanoflower cluster is 50-1000nm; the basal surface of the molybdenum disulfide catalyst presents two crystal phases, 1T and 2H. The present invention adopts a hydrothermal method to prepare a molybdenum disulfide catalyst with a specific crystal morphology, and the morphology and crystallinity of molybdenum disulfide are regulated by changing the content of DMSO. The DMSO-modified molybdenum disulfide catalyst prepared by the present invention shows high activity and high selectivity for indirect desulfurization in the hydrodesulfurization reaction, the dibenzothiophene conversion rate can reach more than 98%, and the selectivity of the indirect desulfurization hydrogenation reaction pathway can reach 80%.

[0009] The first aspect of the present invention provides a 1T-2H mixed phase molybdenum disulfide catalyst, the morphology of the molybdenum disulfide catalyst is a nanoflower cluster composed of multiple nanosheets, the length of the nanosheet is 1-9nm, the size of the nanoflower cluster is 50-1000nm, and the basal surface of the molybdenum disulfide catalyst presents two crystal phases, 1T and 2H.

[0010] Preferably, the nanosheet is curved, and the bending angle is 0-90°; multiple layers of the nanosheet are stacked together, and the number of stacked layers is 1-6.

[0011] The second aspect of the present invention provides a method for preparing the molybdenum disulfide catalyst described in the first aspect of the present invention, which is synthesized based on a hydrothermal method and prepared by adding dimethyl sulfoxide (DMSO).

[0012] Preferably, the preparation method of the molybdenum disulfide catalyst comprises the following steps:

[0013] (1) adding water, a molybdenum source and a sulfur source into the inner lining of a hydrothermal reactor and stirring until fully dissolved to obtain a first mixture;

[0014] (2) adding DMSO to the first mixture obtained in step (1), sealing and performing ultrasonic treatment to obtain a second mixture;

[0015] (3) transferring the second mixture obtained in step (2) into a hydrothermal reactor and sealing it, followed by crystallization to obtain a third mixture;

[0016] (4) performing solid-liquid separation on the third mixture to obtain a first solid, then washing the first solid with a first solvent, followed by filtering and drying to obtain the molybdenum disulfide catalyst.

[0017] Preferably, in step (1), the molybdenum source is a soluble Mo-containing compound selected from one or more of sodium molybdate, ammonium molybdate, potassium molybdate, molybdenum acetate, molybdenum nitrate, and molybdenum chloride, and the S source is a soluble sulfur-containing compound selected from one or more of carbon disulfide, sodium sulfide, potassium sulfide, ammonium sulfide, thiourea, ammonium thiosulfate, thioacetamide, L-cysteine, and cystine.

[0018] Preferably, in step (1), the concentration of molybdenum in the first mixture is 1 mg / ml-20 mg / ml, more preferably 5 mg / ml-15 mg / ml.

[0019] Preferably, in step (1), the concentration of sulfur in the first mixture is 1 mg / ml-20 mg / ml, more preferably 5 mg / ml-15 mg / ml.

[0020] Preferably, in step (1), the stirring time is 1-10 min.

[0021] Preferably, in step (2), the mass percentage of the added amount of DMSO is 0wt%-80wt% and is not 0, more preferably 0wt%-75wt%.

[0022] In step (2), the ultrasonic time is 1-90 min, more preferably, the ultrasonic time is 30 min. The Teflon liner (hydrothermal reactor liner) can be placed in an ultrasonic cleaning machine for ultrasonic treatment for 1-90 min.

[0023] Preferably, in step (3), the crystallization temperature is 100-350° C., more preferably 140-220° C., and the crystallization time is 1-48 hours, more preferably 8-36 hours. The hydrothermal autoclave can be placed in a blast oven for crystallization.

[0024] Preferably, in step (4), the first solvent is selected from dichloromethane, ethanol or water; the drying temperature is 40-150° C., and the drying time is 8-24 h.

[0025] Preferably, the solid separation process in step (4) is filtration. The washing process is: washing with ethanol or dichloromethane and deionized water alternately for 4 times, and drying at 40-100° C. under vacuum conditions for 8-24 hours.

[0026] The third aspect of the present invention provides an application of the molybdenum disulfide catalyst described in the first aspect of the present invention, which is used as a catalyst for a hydrodesulfurization reaction to improve the reaction activity and the selectivity of the hydrogenation reaction pathway. The sulfur-containing compounds in the hydrodesulfurization reaction include one or more of mercaptans, thiophene, benzothiophene, dibenzothiophene or 4,6-dimethyldibenzothiophene.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention prepares a molybdenum disulfide catalyst with a special morphology, wherein the molybdenum disulfide catalyst has a nanoflower cluster composed of multiple nanosheets, the length of the nanosheet is 1-9nm, and the size of the nanoflower cluster is 50-1000nm. The basal surface of the molybdenum disulfide catalyst of the present invention presents two crystal phases, 1T and 2H.

[0029] 2. The preparation method of the present invention is simple. A 1T-2H mixed phase molybdenum disulfide catalyst with a nanosheet length of several nanometers is prepared by a hydrothermal method only by adding DMSO. Furthermore, the present invention can adjust the morphology and crystallinity of the molybdenum disulfide catalyst by adjusting the amount of DMSO added.

[0030] 3. The molybdenum disulfide catalyst prepared by the present invention has high hydrodesulfurization activity, high stability and high indirect desulfurization selectivity in the catalytic hydrodesulfurization reaction. Compared with the molybdenum disulfide directly hydrothermally synthesized without adding DMSO, the molybdenum disulfide synthesized under the condition of adding 3 ml of DMSO has the best hydrodesulfurization performance. It not only has high catalytic activity and high indirect desulfurization selectivity, but also has a dibenzothiophene conversion rate of up to 98% and an indirect desulfurization selectivity (HYD) of up to 80%.

[0031] 4. The preparation method of the 1T-2H mixed phase molybdenum disulfide catalyst with a nanosheet length of several nanometers described in the present invention is simple and easy, the conditions are easy to control, and cumbersome processes such as secondary hydrothermal and high-temperature calcination are avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 : Schematic diagram of the reaction pathway for dibenzothiophene hydrodesulfurization;

[0033] Figure 2 : XRD patterns of molybdenum disulfide catalysts prepared in different embodiments of the present invention;

[0034] Figure 3 : Scanning electron microscope image of the molybdenum disulfide catalyst prepared in Example 3;

[0035] Figure 4 : Scanning electron microscope image of the molybdenum disulfide catalyst prepared in Example 8;

[0036] Figure 5 : Transmission electron microscopy image of the molybdenum disulfide catalyst prepared in Example 8 and the statistical results of the length of the nanosheets and the number of stacked layers;

[0037] Figure 6 : Raman spectra of molybdenum disulfide catalysts prepared in Examples 1, 2, and 8;

[0038] Figure 7: External standard curve of dibenzothiophene hydrodesulfurization reaction, the solvent is n-dodecane. DETAILED DESCRIPTION

[0039] The present invention is further described below by way of examples, which are not limited to the examples. Experimental methods without specific conditions specified in the examples are generally carried out under conventional conditions and conditions described in the manual, or under conditions recommended by the manufacturer. The general equipment, materials, reagents, etc. used are all commercially available unless otherwise specified.

[0040] The present invention will be described in detail below with reference to the embodiments and the accompanying drawings.

[0041] Example 1

[0042] Take thiourea (1.827g) and tetrahydrated ammonium heptamolybdate (0.706g) and dissolve them in 80ml of ultrapure water, stir until dissolved to obtain a first mixture, wherein the concentration of molybdenum is 0.3mol / L, and the molar ratio of sulfur to molybdenum is 6:1. Ultrasonicate for 30min at room temperature to obtain a second mixture. Then move it into a crystallization kettle for crystallization, the crystallization temperature is 200℃, and the crystallization time is 12h. After the crystallization is completed, filter and remove the supernatant, wash it alternately with deionized water and ethanol 4 times, and fully dry the precipitate at 80℃ under vacuum conditions for 12h to obtain a molybdenum disulfide catalyst.

[0043] Example 2

[0044] Take thiourea (1.827g) and tetrahydrated ammonium heptamolybdate (0.706g) and dissolve them in 80ml of ultrapure water, stir until dissolved to obtain a first mixture, wherein the concentration of molybdenum is 0.3mol / L, and the molar ratio of sulfur to molybdenum is 6:1. Add 3ml of DMSO and ultrasonicate for 30min at room temperature to obtain a second mixture. Then move it into a crystallization kettle for crystallization, the crystallization temperature is 200℃, and the crystallization time is 12h. After the crystallization is completed, filter and remove the supernatant, wash it alternately with deionized water and ethanol 4 times, and fully dry the precipitate at 80℃ under vacuum conditions for 12h to obtain a molybdenum disulfide catalyst.

[0045] Example 3

[0046] Take carbon disulfide (0.730ml) and tetrahydrate heptamolybdate ammonium (0.706g) and dissolve them in 80ml of ultrapure water, stir until dissolved to obtain a first mixture, wherein the concentration of molybdenum is 0.3mol / L, and the molar ratio of sulfur to molybdenum is 6:1. Ultrasonicate for 30min at room temperature to obtain a second mixture. Then move it into a crystallization kettle for crystallization, the crystallization temperature is 200℃, and the crystallization time is 12h. After the crystallization is completed, filter and remove the supernatant, wash it alternately with deionized water and ethanol 4 times, and fully dry the precipitate at 80℃ under vacuum conditions for 12h to obtain a molybdenum disulfide catalyst.

[0047] Example 4

[0048] Take carbon disulfide (0.730ml) and tetrahydrate heptamolybdate ammonium (0.706g) and dissolve them in 80ml of ultrapure water, stir until dissolved to obtain a first mixture, wherein the concentration of molybdenum is 0.3mol / L, and the molar ratio of sulfur to molybdenum is 6:1. Add DMSO1ml and ultrasonicate for 30min at room temperature to obtain a second mixture. Then move it into a crystallization kettle for crystallization, the crystallization temperature is 200℃, and the crystallization time is 12h. After the crystallization is completed, filter and remove the supernatant, wash it alternately with deionized water and ethanol 4 times, and fully dry the precipitate at 80℃ under vacuum conditions for 12h to obtain a molybdenum disulfide catalyst.

[0049] Example 5

[0050] Based on Example 4, the amount of DMSO added was 1.5 ml, and the remaining preparation steps were the same as Example 4.

[0051] Example 6

[0052] Based on Example 4, the amount of DMSO added was 2 ml, and the remaining preparation steps were the same as Example 4.

[0053] Example 7

[0054] Based on Example 4, the amount of DMSO added was 2.5 ml, and the remaining preparation steps were the same as Example 4.

[0055] Example 8

[0056] Based on Example 4, the amount of DMSO added was 3 ml, and the remaining preparation steps were the same as Example 4.

[0057] Figure 2 XRD diagrams of molybdenum disulfide catalysts prepared in different embodiments of the present invention. In the figure, (002), (100), and (110) correspond to characteristic peaks of molybdenum disulfide (JCPDS-37-1492), proving that the above embodiments have successfully synthesized molybdenum disulfide catalysts. It can be seen that under the regulation of DMSO, the crystallinity of Example 8 in the left figure is relatively enhanced relative to that of Example 3, while the crystallinity of Example 2 is relatively weakened relative to that of Example 1; with the addition of DMSO, the crystallinity of Examples 4-8 in the right figure gradually decreases. This shows that DMSO has the ability to regulate the crystallinity of molybdenum disulfide.

[0058] Figure 3 and Figure 4The scanning electron microscope images of the molybdenum disulfide catalysts prepared in Examples 3 and 8 are shown respectively. It can be seen from the electron microscope image that the addition of DMSO changes the irregular block morphology of Example 3 and forms a uniform nanoflower cluster composed of multiple nanosheets. The molybdenum disulfide prepared in Example 8 is a nanoflower cluster structure, and the size of the nanoflower cluster is 50-1000nm, and most (more than 90%) are around 500nm.

[0059] Figure 5 This is a transmission electron micrograph of the molybdenum disulfide catalyst prepared in Example 8. It can be seen from the transmission electron micrograph that the length of the prepared molybdenum disulfide nanosheets is 1-9nm, the average nanosheet length is about 5nm, and multiple layers of the nanosheets are stacked together, the number of stacked layers is 1-6 layers, and the average number of stacked layers is 3.6 layers, further confirming that the catalyst has extremely low crystallinity; in addition, the nanosheets have varying degrees of bending, with bending angles ranging from 0-90°, and most (more than 90%) are less than 30°.

[0060] Figure 6 The Raman spectra of molybdenum disulfide catalysts prepared in Examples 1, 2 and 8. It can be seen from the figure that the catalyst without DMSO addition has only and A 1g peak, indicating that it is a pure 2H phase structure. and A 1g The peak also has J1, J2, and J3 peaks, and J1, J2, and J3 peaks are unique peaks of molybdenum disulfide with a 1T phase structure, so it is explained that the molybdenum disulfide catalyst prepared in the embodiment of the present invention is a 1T-2H mixed phase structure.

[0061] Catalytic hydrodesulfurization reaction of the catalyst:

[0062] The hydrodesulfurization reaction of sulfur-containing compounds such as dibenzothiophene is carried out in a kettle reactor. The solvent is n-dodecane, and the sulfur content is 100-1000ppm. Take 30mL of dibenzothiophene / n-dodecane solution and place it in the hydrogenation kettle, add 100mg of catalyst and seal it. Pass 0.2MPa nitrogen and replace the air three times. Pass 4MPa hydrogen and use a hydrogen detector to check for leaks. After the seal is inspected and qualified, the hydrogen is evacuated and replaced with 0.2MPa nitrogen 5 times. Evacuate the nitrogen and start heating. After reaching the preset temperature of 300℃, pass 4MPa hydrogen and start timing. After 4h of reaction, the hydrogenation is completed and the temperature begins to drop. After cooling to room temperature, take out the reacted material, filter it with a 0.22μm oily filter membrane, and wait for testing.

[0063] Catalytic hydrodesulfurization product detection:

[0064] The quantitative analysis of hydrogenation products of sulfur-containing compounds such as dibenzothiophene was carried out using gas chromatography. Chromatographic column: SH-Rtx-5MS capillary column; chromatographic column heating program: starting temperature 80°C, heating rate 20°C / min, rising to 280°C, maintaining for 5 minutes; detector is hydrogen flame ionization detector, detector temperature 280°C; single injection 0.2μL; carrier gas is high-purity nitrogen. The conversion rate of dibenzothiophene was quantitatively analyzed and calculated using the external standard method, and the external standard curve is shown in Figure 7 .

[0065] Hydrodesulfurization is divided into two reaction pathways, direct desulfurization (DDS) and indirect desulfurization (HYD). Taking dibenzothiophene as an example, see Figure 1 The product of direct desulfurization is biphenyl (BP), and the product of indirect desulfurization is tetrahydrodibenzothiophene (THDBT). Tetrahydrodibenzothiophene is further hydrogenated to cyclohexylbenzene (CHB), and the product of cyclohexylbenzene is further hydrogenated to dicyclohexane (BC).

[0066] The results of the hydrodesulfurization reaction of dibenzothiophene catalyzed by the molybdenum disulfide catalyst prepared by the present invention are shown in Table 1. Including dibenzothiophene conversion rate, indirect desulfurization selectivity (HYD), direct desulfurization selectivity (DDS) and the ratio of HYD to DDS:

[0067] Table 1 Hydrodesulfurization performance of dibenzothiophene catalyzed by different molybdenum disulfide catalysts

[0068] Example No. Conversion rate (%) HYD(%) DDS(%) HYD / DDS 1 19 55 45 1.2 2 38 60 40 1.5 3 81 90 10 9.0 4 89 83 17 4.9 5 94 84 16 5.3 6 95 83 17 4.9 7 97 82 18 4.6 8 98 80 20 4.0

[0069] It can be seen from the experimental results in Table 1 that the addition of DMSO to the molybdenum disulfide catalyst prepared by the present invention has a significant effect on promoting the hydrodesulfurization reaction activity. In particular, the conversion rate of dibenzothiophene hydrodesulfurization catalyzed by the catalyst prepared in Example 8 can reach up to 98%, and the HYD selectivity can reach 80%.

[0070] By comparing the results of Example 1 and Example 2, and Example 3 and Example 8, it can be seen that by adding DMSO during the preparation of molybdenum disulfide, 1T-2H mixed phase molybdenum disulfide with a nanosheet length of a few nanometers and low crystallinity can be prepared, and the reaction activity is significantly improved. By comparing Examples 3-8, it can be found that gradually increasing the amount of DMSO added can further improve the reaction activity. The molybdenum disulfide synthesized under the action of an appropriate amount of DMSO has the best hydrodesulfurization performance, not only has high catalytic activity but also has high indirect desulfurization selectivity.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a 1T-2H mixed phase molybdenum disulfide catalyst for hydrodesulfurization reaction, characterized in that: The molybdenum disulfide catalyst has a morphology of a nanoflower cluster composed of multiple nanosheets, the length of the nanosheet is 1-9 nm, and the size of the nanoflower cluster is 50-1000 nm; the basal surface of the molybdenum disulfide catalyst presents two crystal phases, 1T and 2H; The preparation method is based on hydrothermal synthesis, and the molybdenum disulfide catalyst is prepared by adding dimethyl sulfoxide (DMSO); The preparation method comprises the following steps: (1) adding water, a molybdenum source and a sulfur source into the inner lining of a hydrothermal reactor and stirring until dissolved to obtain a first mixture; (2) adding DMSO to the first mixture obtained in step (1), sealing and performing ultrasonic treatment to obtain a second mixture; (3) transferring the second mixture obtained in step (2) into a hydrothermal reactor and sealing it, followed by crystallization to obtain a third mixture; (4) performing solid-liquid separation on the third mixture to obtain a first solid, and then washing the first solid with a first solvent, followed by filtering and drying to obtain the molybdenum disulfide catalyst.

2. The preparation method according to claim 1, characterized in that: The nanosheet is curved, and the bending angle is 0-90 degrees; multiple layers of the nanosheet are stacked together, and the number of stacked layers is 1-6.

3. The preparation method according to claim 1, characterized in that: In step (1), the molybdenum source is a soluble Mo-containing compound selected from one or more of sodium molybdate, ammonium molybdate, potassium molybdate, molybdenum acetate, molybdenum nitrate, and molybdenum chloride; the sulfur source is a soluble sulfur-containing compound selected from one or more of carbon disulfide, sodium sulfide, potassium sulfide, ammonium sulfide, thiourea, ammonium thiosulfate, thioacetamide, L-cysteine, and cystine.

4. The preparation method according to claim 1, characterized in that: In step (1), the concentration of molybdenum in the first mixture is 1 mg / mL-20 mg / mL; the concentration of sulfur in the first mixture is 1 mg / mL-20 mg / mL; and the stirring time is 1-10 min.

5. The preparation method according to claim 1, characterized in that: In step (2), the mass percentage of the DMSO added is 0wt%-80wt%, and is not 0; and the ultrasonic time is 1-90min.

6. The preparation method according to claim 1, characterized in that: In step (3), the crystallization temperature is 100-350 o C, crystallization time is 1-48 h.

7. The preparation method according to claim 1, characterized in that: In step (4), the first solvent is selected from dichloromethane, ethanol or water; the drying temperature is 40-150 o C, drying time is 8-24h.

8. An application of the molybdenum disulfide catalyst prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The molybdenum disulfide catalyst is used as a catalyst for the hydrodesulfurization reaction to improve the reaction activity and the selectivity of the hydrogenation reaction pathway. The sulfur-containing compounds in the hydrodesulfurization reaction include one or more of mercaptans, thiophene, benzothiophene, dibenzothiophene or 4,6-dimethyldibenzothiophene.

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