Preparation method of supported monolayer molybdenum disulfide hydrotreating catalyst

Abstract

The invention discloses a preparation method of a supported monolayer molybdenum disulfide hydrogenation catalyst, and relates to the technical field of molybdenum disulfide catalyst. Under stirring, a molybdenum source and a sulfur source are dissolved in 300ml deionized water to form a uniform solution and stirred for 0.5h, a carrier is added, the solution is transferred to a hydrothermal kettle, reacted at 180-200°C for 12-36h, centrifuged, washed with water three times, washed with ethanol three times, and dried at 140-180°C in a vacuum drying oven for 2h to obtain a molybdenum precursor; 0.1g of the above-mentioned molybdenum precursor, 0.1g of sulfur element, and 50ml of solvent are added to an autoclave, washed with ethanol three times, the initial hydrogen pressure is controlled to 6-10Mpa, and the temperature is raised to 350-450°C at 5-10°C / min for 1-3h; the resultant is centrifuged, washed with ethanol three times, and dried at 120°C in a vacuum drying oven for 2h to obtain a supported monolayer molybdenum disulfide hydrogenation catalyst. A molybdenum precursor is synthesized by using a molybdenum source, a sulfur source, a carrier, etc., and a supported monolayer molybdenum disulfide with a lateral size of 5-9 nm is synthesized under high temperature, hydrogen and elemental sulfur conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of molybdenum disulfide catalysts, and specifically to a preparation method of a supported monolayer molybdenum disulfide hydrotreating catalyst. Background Art

[0002] In the past two years, due to the growing demand for more environmentally friendly light fuels, the shortage of crude oil reserves, and the decline of conventional oils, there has been an urgent need to develop heavy oil upgrading technologies. In the field of oil processing, research has mainly focused on the progress of refining technologies for low-value industrial by-products (such as vacuum residue, coal tar, etc.) and unconventional oils (such as extra-heavy oil, oil sands, etc.) regarded as alternative energy sources. Generally speaking, inferior oils such as heavy oil and coal tar exhibit similar properties, such as high molecular weight, high density, and low hydrogen content, and are extremely viscous in nature, with an API gravity between 10 and 20°. In addition, it contains high concentrations of heteroatoms (S, N, and O), transition metals (V, Ni, Fe, and Si), and complex molecules, which are the reasons for catalyst deactivation and coking during the upgrading of inferior oils such as heavy oil and coal tar. The ultimate goal of the hydroconversion of inferior oils such as heavy oil and coal tar is to reduce viscosity, boiling point, impurity concentration, and coking, and to increase the H / C ratio required for commercial products, while reducing hazards such as air pollution and acid rain during fuel consumption. Studying the efficient production of light dyes from inferior oil resources such as coal tar and heavy oil is of great significance.

[0003] In the hydrocatalytic conversion process of inferior oils, one of the core technologies is the catalyst, which has been widely studied at present. Among these catalysts, molybdenum disulfide (MoS2) is one of the representative catalysts. Molybdenum disulfide presents a hexagonal crystal structure, with a molybdenum atom layer sandwiched between two sulfur atom layers, formed by van der Waals interactions between the sulfur layers along the C-axis. According to the Rim-Edge model, the basal plane of molybdenum disulfide is inert, while the edges accommodate catalytic active centers. However, the exposed active edges of large-sized molybdenum disulfide used for catalytic reactions are very limited. Therefore, synthesizing molybdenum disulfide catalysts with more exposed active edges is an effective strategy to improve its catalytic activity.

[0004] The preparation methods of molybdenum disulfide are divided into "top-down" and "bottom-up". "Bottom-up" includes mechanical exfoliation, liquid-phase exfoliation, chemical exfoliation, electrochemical exfoliation, and sputtering methods. By breaking the van der Waals interactions between the molybdenum disulfide interlayers, the top-down exfoliation process is very effective in thinning large pieces of molybdenum disulfide into monolayer and thin-layer molybdenum disulfide nanosheets to enhance the exposure of the edges. Single sulfur atom vacancies are the main defects in the monolayer exfoliation of molybdenum disulfide. However, the top-down exfoliation process cannot break the chemical bonds in a single S-Mo-S atomic layer, so as to reduce the lateral size of molybdenum disulfide nanosheets to nanoscale molybdenum disulfide sheets, thereby further increasing the exposed edges.

[0005] The bottom-up synthesis method can effectively solve these problems. The "bottom-up" method includes physical vapor method, solvent thermal method, hydrothermal method, chemical vapor phase method and atomic layer method. Among them, the hydrothermal method can adjust more synthesis parameters to control the reaction rate, nucleation and crystallization process. The crystallinity, particle size and nanostructure can be precisely constructed through the bottom-up hydrothermal process, and molybdenum disulfide with 4-8 average stacking layers and 10-20nm lateral size can be constructed. However, the molybdenum disulfide synthesized by the hydrothermal method is usually still stacked more obviously, and the active sites of molybdenum disulfide are not exposed to the greatest extent, and the hydrogenation effect on heavy oil and coal tar is not ideal. Summary of the invention

[0006] To solve the above problems, that is, to solve the problems raised by the above background technology, the present invention proposes a method for preparing a supported monolayer molybdenum disulfide hydrogenation catalyst, and the specific technical solution is as follows:

[0007] A preparation method of a supported single-layer molybdenum disulfide hydrogenation catalyst comprises the following steps: dissolving a molybdenum source and a sulfur source in 300 ml of deionized water under stirring to form a uniform solution, stirring for 0.5 h, adding a carrier, transferring the solution to a hydrothermal autoclave, reacting at 180-200° C. for 12-36 h, centrifuging, washing three times with water, washing three times with ethanol, and drying in a vacuum drying oven at 140-180° C. for 2 h to obtain a molybdenum precursor; adding 0.1 g of the molybdenum precursor, 0.1 g of elemental sulfur, and 50 ml of a solvent to a high-pressure reactor, washing three times with ethanol, controlling the initial hydrogen pressure to 6-10 MPa, heating to 350-450° C. at 5-10° C. / min, reacting for 1-3 h; centrifuging the resultant, washing three times with ethanol, and drying in a vacuum drying oven at 120° C. for 2 h to obtain the supported single-layer molybdenum disulfide hydrogenation catalyst.

[0008] Furthermore, in the method, the molybdenum source is ammonium tetrathiomolybdate, ammonium heptamolybdate or sodium molybdate, the sulfur source is sodium sulfide or thiourea, the carrier is titanium dioxide, silicon dioxide or aluminum oxide, and the solvent is tetralin or toluene.

[0009] The beneficial technical effects of the present invention are: by utilizing a molybdenum source, a sulfur source, a carrier, etc. to synthesize a molybdenum precursor, and synthesizing a supported monolayer molybdenum disulfide with a lateral size of 5-9nm under high temperature, hydrogen and elemental sulfur conditions, it has good hydrogenation performance in the upgrading of inferior oil products such as coal tar and heavy oil; the Mo6+ and elemental Mo in the molybdenum precursor are successfully converted into Mo4+ with high hydrogenation activity by hydrogen and elemental sulfur, and the reaction system is more uniform under the stirring conditions of the reactor (no stirring in the hydrothermal reactor), so that a single-layer MoS2 catalyst can be synthesized. DETAILED DESCRIPTION

[0010] The preferred embodiments of the present invention will be described below with reference to the embodiments. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0011] Example 1

[0012] Under stirring, 0.5 g of ammonium heptamolybdate and 0.7 g of thiourea were dissolved in 300 ml of deionized water to form a homogeneous solution, which was stirred for 0.5 h, and then 3 g of titanium dioxide was added. The solution was transferred to a hydrothermal reactor and reacted at 200 °C for 12 h, centrifuged, washed three times with water, and three times with ethanol. It was dried in a vacuum drying oven at 140 °C for 2 h to obtain a molybdenum precursor. 0.1 g of the above molybdenum precursor, 0.1 g of sulfur, and 50 ml of the solvent tetralin were added to a high-pressure reactor, the initial hydrogen pressure was controlled at 8 Mpa, and it was heated to 400 °C at a rate of 10 °C / min and reacted for 1 h, centrifuged, washed three times with ethanol, and dried in a vacuum drying oven at 120 °C for 2 h to obtain monolayer molybdenum disulfide with a lateral size of 5 - 9 nm. When applied to coal tar hydrogenation, the yield of light fuel oil can be increased by 50 - 60%, and it has excellent recyclability.

[0013] Example 2

[0014] Under stirring, 0.5 g of sodium molybdate and 0.7 g of thiourea were dissolved in 300 ml of deionized water to form a homogeneous solution, which was stirred for 0.5 h, and then 3 g of silica was added. The solution was transferred to a hydrothermal reactor and reacted at 190 °C for 24 h, centrifuged, washed three times with water, and three times with ethanol. It was dried in a vacuum drying oven at 160 °C for 2 h to obtain a molybdenum precursor. 0.1 g of the above molybdenum precursor, 0.1 g of sulfur, and 50 ml of toluene were added to a high-pressure reactor, the initial hydrogen pressure was controlled at 6 Mpa, and it was heated to 350 °C at a rate of 5 °C / min and reacted for 2 h, centrifuged, washed three times with ethanol, and dried in a vacuum drying oven at 120 °C for 2 h to obtain monolayer molybdenum disulfide with a lateral size of 4 - 8 nm. When applied to vacuum residue hydrogenation, the yield of light fuel oil can be increased by 55 - 60%, and it has excellent recyclability.

[0015] Example 3

[0016] Under stirring, 0.5 g of ammonium heptamolybdate and 0.7 g of sodium sulfide are dissolved in 300 ml of deionized water to form a homogeneous solution, which is stirred for 0.5 h, and then 3 g of aluminum oxide is added. The solution is transferred to a hydrothermal reactor and reacted at 280 °C for 36 h, centrifuged, washed three times with water and three times with ethanol. It is dried in a vacuum drying oven at 180 °C for 2 h to obtain a molybdenum precursor. 0.1 g of the above-mentioned molybdenum precursor, 0.1 g of sulfur and 50 ml of tetralin are added to a high-pressure reactor, the initial pressure of hydrogen is controlled to be 10 Mpa, heated to 450 °C at 7 °C / min and reacted for 3 h, centrifuged, washed three times with ethanol, and dried in a vacuum drying oven at 120 °C for 2 h to obtain molybdenum disulfide with a supported single layer and a lateral size of 4-8 nm. When applied to the hydrotreating of coker residue oil, it can increase the yield of light fuel oil by 50-60% and has excellent recyclability.

[0017] Although the present invention has been described with reference to the preferred embodiments, various modifications can be made thereto and components thereof can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0018] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. A preparation method of a supported monolayer molybdenum disulfide hydrotreating catalyst, characterized in that: The method comprises the following steps: dissolving a molybdenum source and a sulfur source in 300 mL of deionized water under stirring to form a uniform solution, stirring for 0.5 h, adding a carrier, transferring the solution to a hydrothermal autoclave, reacting at 180-200° C. for 12-36 h, centrifuging, washing three times with water, washing three times with ethanol, and drying in a vacuum drying oven at 140-180° C. for 2 h to obtain a molybdenum precursor; adding 0.1 g of the molybdenum precursor, 0.1 g of elemental sulfur, and 50 mL of solvent to a high-pressure reactor, washing three times with ethanol, controlling the initial hydrogen pressure to be 6-10 MPa, heating to 350-450° C. at a rate of 5-10° C. / min, and reacting for 1-3 h; centrifuging the resultant, washing three times with ethanol, and drying in a vacuum drying oven at 120° C. for 2 h to obtain a supported single-layer molybdenum disulfide hydrogenation catalyst.

2. The preparation method of a supported monolayer molybdenum disulfide hydrotreating catalyst according to claim 1, characterized in that: In the method, the molybdenum source is ammonium tetrathiomolybdate, ammonium heptamolybdate or sodium molybdate, the sulfur source is sodium sulfide or thiourea, the carrier is titanium dioxide, silicon dioxide or aluminum oxide, and the solvent is tetralin or toluene.