A catalyst for hydrodeoxygenation of coal tar at medium-low temperature to produce aromatic hydrocarbons, a preparation method and application thereof

Abstract

The present application relates to a kind of low-temperature coal tar hydrogenation catalyst for deoxygenation of aromatic hydrocarbon and its preparation method and application.The preparation method includes: the precursor of molybdenum, cationic surfactant, carrier are mixed, after drying, obtain dry product;The dry product is sulfided, to obtain the low-temperature coal tar hydrogenation catalyst for deoxygenation of aromatic hydrocarbon;Wherein, the molar ratio of cationic surfactant and molybdenum is 0.8-1.5;Mo in the catalyst, the mass fraction is 5-20 wt%.The present application also provides the catalyst prepared by the above method and the hydrogenation refining method of coal tar based on the catalyst.The catalyst has higher stacking number, improves the edge / rim site ratio, so that the selectivity of aromatic hydrocarbon in hydrogenation product is improved;Lamella length reduces, the proportion of Mo atom in edge site is higher, higher Mo atom utilization rate and the number of active sites make hydrogenation deoxygenation activity improve.

Description

Technical Field

[0001] This invention relates to a catalyst for the hydrodeoxygenation of coal tar to produce aromatics at medium and low temperatures, its preparation method, and its application, belonging to the field of coal chemical technology. Background Technology

[0002] The graded and graded utilization of low-rank coal, centered on low-temperature pyrolysis, is an important direction for the clean and efficient utilization of low-rank coal. Processing and upgrading low-temperature coal tar to produce high-quality fuels and chemicals is the main way to achieve its high-value utilization. However, the compositional characteristics of low-temperature coal tar differ significantly from those of petroleum. For example, the oxygen content of coal tar is much higher than the typically less than 1% oxygen content in petroleum; correspondingly, its oxygen-containing compounds account for more than 20%, mainly including phenols and furans. Currently, coal tar hydrogenation products are mainly naphthenic specialty oils such as gasoline, diesel, industrial white oil, and transformer oil. Although hydrogenation stabilization has been achieved, the inherent structural advantages of coal tar have not been fully utilized. In fact, the aromatic potential content of coal tar-based oils is higher than 70%, significantly higher than the 30%-50% of petroleum-based oils. If aromatic chemicals are targeted as products, the inherent structural characteristics of coal tar can be utilized, and the economic benefits of enterprises can be improved. Therefore, developing catalysts suitable for the hydrogenation and deoxygenation of low-temperature coal tar and the highly selective preparation of aromatics is of great significance.

[0003] In existing technologies, noble metal catalysts and transition metal phosphide catalysts have been extensively studied and reported for use in medium- and low-temperature coal tar hydrodeoxygenation reactions. However, noble metal catalysts (such as Pt and Pd) are not only expensive but also susceptible to poisoning and deactivation by sulfur components in coal tar, making it difficult to meet the durability and economic requirements for large-scale industrial applications. Although transition metal phosphide catalysts exhibit good catalytic activity in hydrodeoxygenation reactions, their synthesis processes are demanding, often involving high-temperature phosphating or the use of hazardous phosphorus sources, resulting in severe environmental pollution and high preparation costs, which also limit their large-scale application.

[0004] To address the aforementioned issues, several improved solutions have been proposed in existing patent literature. For example, CN107537477A discloses a Pt / TiO2 catalyst and its preparation method. This catalyst uses the precious metal Pt as the active component, resulting in a complex preparation process, high costs, and a susceptibility to sulfur poisoning in low- and medium-temperature coal tar containing sulfur, thus exhibiting poor industrial applicability. CN117797832A discloses a polymetallic sulfide catalyst and its preparation method. The raw materials for this preparation method involve metal sulfates, metal acid salt solutions, chloride ionic liquids, hydrogen peroxide, and sulfur powder, resulting in a lengthy preparation process, numerous raw material types, and high costs. Furthermore, the introduction of polymetallic components leads to a hydrodeoxygenation pathway that primarily involves hydrogenation followed by deoxygenation, resulting in low aromatic selectivity and difficulty in preserving the inherent aromatic structure of coal tar.

[0005] Non-patent literature also reports on this. Wu et al. (Kui Wu, Xinxin Li, Weiyan Wang, Yanping Huang, Qike Jiang, Wensong Li, Yuanqiu Chen, Yunquan Yang, Changzhi Li; Creating Edge Sites within the Basal Plane of a MoS2 Catalyst for Substantially Enhanced Hydrodeoxygenation Activity; ACS Catal., 2021, Vol 12 / Issue 1, 8-17) improved the hydrodeoxygenation activity of MoS2 for m-cresol by introducing Pt onto MoS2. However, the selectivity of cycloalkanes in the product exceeded 90%. If this strategy is applied to the hydrodeoxygenation of medium and low temperature coal tar, it still cannot effectively retain aromatic components. Moreover, the introduction of the precious metal Pt also brings cost and sulfur resistance issues.

[0006] Transition metal sulfide catalysts have become a research hotspot due to their combination of good hydrodeoxygenation activity, resistance to sulfur poisoning, and relatively low cost. Industrially, ammonium molybdate hydrate is typically used as the molybdenum source, with γ-Al₂O₃ as the support (due to its suitable acidity, pore size, and large specific surface area). Supported metal sulfide catalysts are prepared through co-impregnation or sequential impregnation, calcination, and sulfidation. However, this system has the following inherent drawbacks: A strong interaction exists between molybdenum oxide and the γ-Al₂O₃ support, leading to the formation of a sulfide active phase with long lamellar lengths and low stacking layers during sulfidation. This significantly reduces the proportion of Mo edge active sites, resulting in insufficient hydrodeoxygenation activity of the catalyst. Simultaneously, the low stacking layer active phase promotes the reaction along a hydrogenation-deoxygenation pathway, which not only fails to preserve the aromatic structure of coal tar but also increases hydrogen consumption.

[0007] Therefore, how to improve the hydrodeoxygenation activity and achieve high aromatic selectivity by structurally regulating and modifying supported molybdenum sulfide catalysts while maintaining their advantages of low cost and easy preparation remains a technical challenge that urgently needs to be overcome in the field of high-value utilization of coal tar. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a catalyst for the hydrodeoxygenation of coal tar to produce aromatics at medium and low temperatures, as well as its preparation method and application. This catalyst exhibits high hydrodeoxygenation activity and aromatic selectivity.

[0009] To achieve the above objectives, the present invention provides a method for preparing a catalyst for the hydrodeoxygenation of coal tar to produce aromatics at medium and low temperatures, comprising the following steps: Step 1: Mix the molybdenum precursor, cationic surfactant, and carrier, and then dry the mixture to obtain the dried product. Step 2: Sulfide the dried product to obtain the catalyst for medium-low temperature coal tar hydrodeoxygenation to produce aromatics; The molar ratio of the cationic surfactant to molybdenum is 0.8-1.5. The catalyst contains 5-20 wt% Mo.

[0010] According to a specific embodiment of the present invention, preferably, in the above preparation method, the molybdenum precursor includes one or more of ammonium molybdate tetrahydrate, sodium molybdate hydrate, ammonium dimolybdate, and ammonium tetramolybdate dihydrate.

[0011] According to a specific embodiment of the present invention, preferably, in the above preparation method, the cationic surfactant includes one or more of trimethylhexadecylammonium bromide, trimethyltetradecylammonium bromide, and trimethyldodecylammonium bromide, more preferably trimethylhexadecylammonium bromide and / or trimethyltetradecylammonium bromide.

[0012] According to a specific embodiment of the present invention, preferably, in the above preparation method, the support includes one or more of γ-Al2O3, α-Al2O3, molecular sieve, and magnesium-aluminum composite oxide.

[0013] According to a specific embodiment of the present invention, preferably, in the above preparation method, step 1 includes: A solution containing a molybdenum precursor is mixed with a cationic surfactant, added to a carrier for impregnation, and then dried to obtain a dried product. A carrier is added to a solution containing a cationic surfactant for impregnation, followed by the addition of a solution containing a molybdenum precursor, and then the mixture is dried to obtain a dried product.

[0014] According to a specific embodiment of the present invention, preferably, in the above preparation method, step 2 involves granulating the dried product into 60-80 mesh and then subjecting it to sulfidation.

[0015] According to a specific embodiment of the present invention, preferably, in the above preparation method, the vulcanization includes: placing the dried product in a vulcanizing atmosphere and heating it to 350-400°C for vulcanization. This vulcanization process can be carried out according to the following specific steps: placing the dried product in the center of the vulcanizing furnace, introducing a vulcanizing atmosphere (e.g., H2S / H2, 10 vol.% (H2S content is 10 vol.%, H2 content is 90 vol.%), with a flow rate controlled at 60-100 mL / min), heating to 350-400°C at a rate of 5-10 °C / min for vulcanization, and controlling the vulcanization time to 4-6 h. When granulation is performed first, followed by vulcanization, the granulated product can be placed in the center of the vulcanizing furnace first, N2 can be introduced (flow rate controlled at 60-100 mL / min), and then heated for drying (e.g., heating to 150 °C at a rate of 5-10 °C / min for 2 h), and then introducing a vulcanizing atmosphere for vulcanization.

[0016] According to a specific embodiment of the present invention, the preparation method of the catalyst for the hydrodeoxygenation of medium- and low-temperature coal tar to produce aromatics does not involve calcination, thereby ensuring the integrity of the cationic surfactant and its regulatory effect on the molybdenum sulfide active phase during sulfidation. If calcination is performed, the regulation of the molybdenum sulfide active phase cannot be achieved, and thus the high selectivity of aromatics production cannot be achieved.

[0017] According to a specific embodiment of the present invention, preferably, the preparation method of the above-mentioned catalyst for the hydrodeoxygenation of coal tar to produce aromatics at medium and low temperatures includes the following specific steps: (1) Dissolution of molybdenum precursor: At a temperature of 25-40 °C, take an appropriate amount of molybdenum precursor and dissolve it in an appropriate amount of deionized water and stir (stirring time is generally not less than 1 h) to ensure complete dissolution; (2) Reaction of cationic surfactant with molybdenum precursor: Under uniform stirring, take an appropriate amount of cationic surfactant and slowly add it to the solution obtained in step (1) and stir (the stirring time is generally not less than 6 h); the molar ratio of cationic surfactant to molybdenum is 0.8-1.5; (3) Introduction of carrier: Under uniform stirring, an appropriate amount of carrier is slowly added to the solution obtained in step (2) for impregnation, wherein the impregnation time is generally not less than 24 h; preferably the sample is stirred at room temperature until dry; (4) Solvent removal: The sample obtained in step (3) is dried in an oven (e.g., at 120 °C for 12 h); no calcination is performed in this process, so as to ensure the integrity of the cationic surfactant and its regulatory effect on the active phase of molybdenum sulfide during the sulfidation process. (5) Catalyst sulfidation: The dried sample is granulated to 60-80 mesh and placed in the center of the sulfidation furnace. N2 is introduced (flow rate of 60-100 mL / min). The sample is then dried at room temperature at a rate of 5-10 °C / min (e.g., drying at 150 °C for 2 h). Then, a sulfidation atmosphere (e.g., H2S / H2 10 vol.%, flow rate of 60-100 mL / min) is introduced, and the temperature is increased to 350-400 °C at a rate of 5-10 °C / min for sulfidation for 4-6 h to obtain a supported molybdenum sulfide catalyst induced by cationic surfactant, wherein the mass fraction of Mo in the catalyst is 5-20 wt%.

[0018] The present invention also provides a catalyst for the hydrodeoxygenation of coal tar to produce aromatics at medium and low temperatures, which is prepared by the above-described preparation method.

[0019] According to a specific embodiment of the present invention, preferably, the catalyst has 3-6 stacked layers, more preferably 4-6 layers.

[0020] According to a specific embodiment of the present invention, preferably, the average lamellar length of the catalyst is 3.0-4.5 nm, more preferably 3.0 nm-3.8 nm.

[0021] According to a specific embodiment of the present invention, preferably, the ratio of edge / rim sites of the catalyst is 0.4-2.0, more preferably 0.5-2.0, and even more preferably 0.4-1.0.

[0022] According to a specific embodiment of the present invention, preferably, the Mo dispersion of the catalyst is 28-35%.

[0023] The catalyst and its preparation method for the medium- and low-temperature coal tar hydrodeoxygenation to produce aromatics in this invention address the shortcomings of the traditional impregnation method for preparing supported metal sulfide catalysts. This preparation method can improve the atomic utilization of molybdenum, regulate the type of sterically hindered active sites, enhance the hydrodeoxygenation activity of the catalyst, and improve the selectivity of aromatics in the product.

[0024] This invention introduces a cationic surfactant during the impregnation process, based on the cationic surfactant and molybdate (e.g., Mo7O) 24 6- MoO4 2- Mo2O7 2- Mo4O 13 2- The strong electrostatic interaction between the cationic surfactant and the active phase MoS2 induces the formation of the molybdenum sulfide catalyst, thereby obtaining a supported molybdenum sulfide catalyst induced by the cationic surfactant. The catalyst prepared in this invention can be represented as MoS2- x / γ-Al2O3, where x It is a cationic surfactant. x The content of [Mo] is 0.8-1.5 times the mass of the active metal. In this catalyst, the content of Mo is 5-20 wt%, with the balance being an alumina support.

[0025] According to a specific embodiment of the present invention, preferably, the content of Mo in the catalyst is 8-12 wt%, with the balance being an alumina support.

[0026] The present invention also provides a method for hydrorefining coal tar, which involves contacting coal tar with a catalyst to carry out a hydrodeoxygenation reaction. The catalyst is the medium-low temperature coal tar hydrodeoxygenation catalyst for producing aromatics provided by the present invention.

[0027] According to a specific embodiment of the present invention, preferably, in the above-described hydrorefining method, the reaction conditions for the hydrodeoxygenation reaction include: The reaction temperature is 200-360 °C; The reaction pressure is 0.1-8 MPa; The volume ratio of hydrogen to oil is 200-600; The heavy hourly space velocity is 0.5-5 h. -1 .

[0028] According to a specific embodiment of the present invention, preferably, in the above-mentioned hydrorefining method, the raw material for the hydrodeoxygenation reaction is a light component below 360 °C in medium- and low-temperature coal tar, that is, a light component below 360 °C obtained by fractionation of medium- and low-temperature coal tar.

[0029] This invention proposes a catalyst for the hydrodeoxygenation of coal tar to produce aromatics at medium and low temperatures, as well as its preparation and application methods. Compared with catalysts prepared by the traditional impregnation method, the prepared catalyst has high hydrodeoxygenation activity and significantly improved selectivity of aromatics in the product. Moreover, the preparation method of this catalyst is simple, has a short cycle, and is highly controllable, making it suitable for large-scale industrial applications.

[0030] The technical solution of the present invention has the following technical effects: (1) The catalyst prepared by the present invention has a high number of stacking layers, which increases the edge / rim site ratio and improves the selectivity of aromatics in the hydrogenation product; the lamella length is reduced and the proportion of Mo atoms at the edge sites is high. The high utilization rate of Mo atoms and the number of active sites improve the hydrodeoxygenation activity.

[0031] (2) The preparation method provided by the present invention can control the number of stacking layers of the active phase of the catalyst, realize the control of the edge / rim ratio, increase the proportion of edge sites, improve the selectivity of the hydrodeoxygenation reaction along the direct deoxygenation path, and thus obtain a higher proportion of aromatics. Attached Figure Description

[0032] Figure 1 The flowcharts show the preparation processes of the catalysts in Examples 1 and 2 and Comparative Examples 1 and 2.

[0033] Figure 2 TEM images of the catalysts prepared in Examples 1, 2, 3 and Comparative Example 1.

[0034] Figure 3 The results show the Mo dispersion and edge / rim site ratio in the catalysts prepared in Example 1 and Comparative Example 1.

[0035] Figure 4 The results show the catalytic performance evaluation of the catalysts prepared in Examples 1 and 2 and Comparative Examples 1 and 2 for the hydrodeoxygenation of dibenzofuran.

[0036] Figure 5 The results show the catalytic performance evaluation of the catalysts prepared in Example 1 and Comparative Example 1 for the hydrogenation and deoxygenation of m-cresol. Detailed Implementation

[0037] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0038] Example 1

[0039] This embodiment provides a method for preparing a supported molybdenum sulfide catalyst, the preparation process of which is as follows: Figure 1 As shown, it includes the following steps: (1) Under constant temperature of 35 °C, 0.7532 g of ammonium heptamolybdate tetrahydrate was dissolved in 20 mL of deionized water and stirred continuously for 1 h. (2) Under rapid stirring, add 1.5331 g of trimethylhexadecylammonium bromide to the solution obtained in step (1), seal with a PE membrane and continue stirring for 6 h to form a homogeneous solution; (3) After stirring for 6 h, 3 g of γ-Al2O3 powder (with a specific surface area of ​​136.1 m²) was added to the solution obtained in step (2) under continuous stirring. 2 / g, pore volume 0.65 cm³ 3 / g), and stir at room temperature until the sample is dry; (4) Place the sample obtained in step (3) in an oven and dry it at 120 °C for 12 h to obtain a completely dried sample; (5) The completely dried sample obtained in step (4) is granulated to 60-80 mesh, placed in the center of the sulfurization furnace, and N2 (60 mL / min) is introduced. Then, the sample is heated to 150 °C at a rate of 5 °C / min and dried for 2 h at room temperature to remove water and other substances that may be absorbed in the sample. Then, H2S / H2 10 vol.% (flow rate of 60 mL / min; H2S content of 10 vol.% and H2 content of 90 vol.%) is introduced, and the sample is heated to 400 °C at a rate of 5 °C / min and sulfurized for 4 h to obtain a supported molybdenum sulfide catalyst formed by cationic surfactant-induced assisted impregnation. The sample is named MoS2-CTAB / γ-Al2O3.

[0040] Example 2

[0041] This embodiment provides a method for preparing a supported molybdenum sulfide catalyst, the preparation process of which is as follows: Figure 1 As shown, it includes the following steps: (1) Under constant temperature of 35 °C, 1.5331 g of trimethylhexadecylammonium bromide was dissolved in 20 mL of deionized water, sealed with PE film and stirred continuously for 1 h to form a homogeneous solution. (2) After stirring for 1 h, 3 g of γ-Al2O3 powder was added to the solution obtained in step (1) under continuous stirring, and stirred at room temperature until the sample was dry. (3) Place the sample obtained in step (2) in an oven and dry it at 120 °C for 12 h to obtain a completely dried sample, denoted as γ-Al2O3-CTAB; (4) Dissolve 0.7532 g of ammonium heptamolybdate tetrahydrate in 20 mL of deionized water and stir continuously for 1 h; (5) After stirring for 1 h, under continuous stirring, the sample obtained in step (3) is slowly added to the solution obtained in step (4), and stirred at room temperature until the sample is dry. (6) The sample obtained from drying in step (5) was granulated to 60-80 mesh, placed in the center of the sulfurization furnace, and N2 (60 mL / min) was introduced. Then the sample was heated to 150 °C at a rate of 5 °C / min and dried for 2 h. Then H2S / H210 vol.% (60 mL / min) was introduced and the temperature was raised to 400 °C at a rate of 5 °C / min for 4 h to obtain a supported molybdenum sulfide catalyst formed by cationic surfactant-induced assisted impregnation. The sample was named MoS2 / γ-Al2O3-CTAB.

[0042] Example 3

[0043] This embodiment provides a method for preparing a supported molybdenum sulfide catalyst, which includes the following steps: (1) Under constant temperature of 35 °C, 0.7532 g of ammonium heptamolybdate tetrahydrate was dissolved in 20 mL of deionized water and stirred continuously for 1 h. (2) Under rapid stirring, add 1.3560 g of tetrabutylammonium bromide to the solution obtained in step (1), seal with a PE film and continue stirring for 6 h to form a homogeneous solution; (3) After stirring for 6 h, add 3 g of γ-Al2O3 powder to the solution obtained in step (2) under continuous stirring, and stir at room temperature until the sample is dry; (4) Place the sample obtained in step (3) in an oven and dry it at 120 °C for 12 h to obtain a completely dried sample; (5) The completely dried sample obtained in step (4) was granulated to 60-80 mesh, placed in the center of the sulfurization furnace, and N2 (60 mL / min) was introduced. Then the sample was heated to 150 °C at room temperature at a rate of 5 °C / min and dried for 2 h. Then H2S / H2 10 vol.% (60 mL / min) was introduced and the temperature was raised to 400 °C at a rate of 5 °C / min for 4 h to obtain a supported molybdenum sulfide catalyst formed by cationic surfactant-induced assisted impregnation. The sample was named MoS2-TBAB / γ-Al2O3.

[0044] Comparative Example 1

[0045] This comparative example provides a method for preparing a supported molybdenum sulfide catalyst, the preparation process of which is as follows: Figure 1 As shown, it includes the following steps: (1) Under constant temperature of 35 °C, 0.7532 g of ammonium heptamolybdate tetrahydrate was dissolved in 20 mL of deionized water and stirred continuously for 1 h. (2) After stirring for 1 h, 3 g of γ-Al2O3 powder was added to the solution obtained in step (1) under continuous stirring, and stirred at room temperature until the sample was dry. (3) Place the sample obtained in step (2) in an oven and dry it at 120 °C for 12 h to obtain a completely dried sample; (4) The completely dried sample obtained in step (3) is granulated to 60-80 mesh, placed in the center of the sulfurization furnace, and N2 (60 mL / min) is introduced. Then the sample is heated to 150 °C at room temperature at a rate of 5 °C / min and dried for 2 h. Then H2S / H2 10 vol.% (60 mL / min) is introduced and the temperature is raised to 400 °C at a rate of 5 °C / min for 4 h to obtain the supported molybdenum sulfide catalyst prepared by the traditional impregnation method. The sample is denoted as MoS2 / γ-Al2O3.

[0046] Comparative Example 2

[0047] This comparative example provides a method for preparing a supported molybdenum sulfide catalyst, the preparation process of which is as follows: Figure 1 As shown, it includes the following steps: (1) Under constant temperature of 35 °C, 1.5331 g of trimethylhexadecylammonium bromide was dissolved in 20 mL of deionized water, sealed with a PE membrane and stirred continuously for 1 h to form a homogeneous solution. (2) After stirring for 1 h, 3 g of γ-Al2O3 powder was added to the solution obtained in step (1) under continuous stirring, and stirred at room temperature until the sample was dry. (3) Place the sample obtained in step (2) in an oven and dry it at 120 °C for 12 h to obtain a completely dried sample, denoted as γ-Al2O3-CTAB; (4) Place the sample obtained in step (3) in the center of the tube furnace, introduce nitrogen to remove the air in the tube (60 mL / min), and then heat it to 400 °C for 4 h at a rate of 5 °C / min under a flowing nitrogen atmosphere (60 mL / min) to pyrolyze CTAB to form carbon and form a carbon layer on the surface of γ-Al2O3. The obtained sample is recorded as γ-Al2O3-C. (5) Dissolve 0.7532 g of ammonium heptamolybdate tetrahydrate in 20 mL of deionized water and stir continuously for 1 h; (6) Under continuous stirring, the γ-Al2O3-C sample obtained in step (4) is slowly added to the solution obtained in step (5), and stirred at room temperature until the sample is dry; (7) The dried sample was granulated to 60-80 mesh and placed in the center of the sulfurization furnace. N2 (60 mL / min) was introduced and the sample was then heated to 150 °C at a rate of 5 °C / min for 2 h at room temperature. Then, 10 vol.% H2S / H2 (60 mL / min) was introduced and the sample was heated to 400 °C at a rate of 5 °C / min for 4 h to sulfurize. The obtained supported molybdenum sulfide catalyst was named MoS2 / γ-Al2O3-C.

[0048] Comparative Example 3

[0049] This comparative example provides a method for preparing a supported molybdenum sulfide catalyst, comprising the following steps: (1) Under constant temperature of 35 °C, 0.7532 g of ammonium heptamolybdate tetrahydrate was dissolved in 20 mL of deionized water and stirred continuously for 1 h. (2) Under rapid stirring, add 0.8840 g of tetraethylammonium bromide to the solution obtained in step (1), seal with a PE film and continue stirring for 6 h to form a homogeneous solution; (3) After stirring for 6 h, add 3 g of γ-Al2O3 powder to the solution obtained in step (2) under continuous stirring, and stir at room temperature until the sample is dry; (4) Place the sample obtained in step (3) in an oven and dry it at 120 °C for 12 h to obtain a completely dried sample; (5) The completely dried sample obtained in step (4) was granulated to 60-80 mesh, placed in the center of the sulfurization furnace, and N2 (60 mL / min) was introduced. Then the sample was heated to 150 °C at room temperature at a rate of 5 °C / min and dried for 2 h. Then H2S / H2 10 vol.% (60 mL / min) was introduced and the temperature was raised to 400 °C at a rate of 5 °C / min for 4 h to obtain a supported molybdenum sulfide catalyst formed by cationic surfactant-induced assisted impregnation. The sample was named MoS2-TEAB / γ-Al2O3.

[0050] Comparative Example 4

[0051] This comparative example provides a method for preparing a supported molybdenum sulfide catalyst, comprising the following steps: (1) Under constant temperature of 35 °C, 0.7532 g of ammonium heptamolybdate tetrahydrate was dissolved in 20 mL of deionized water and stirred continuously for 1 h. (2) After stirring for 1 h, 3 g of α-Al2O3 powder was added to the solution obtained in step (1) under continuous stirring, and stirred at room temperature until the sample was dry. (3) Place the sample obtained in step (2) in an oven and dry it at 120 °C for 12 h to obtain a completely dried sample; (4) The completely dried sample obtained in step (3) was granulated to 60-80 mesh, placed in the center of the sulfurization furnace, and N2 (60 mL / min) was introduced. Then the sample was heated to 150 °C at a rate of 5 °C / min and dried for 2 h at room temperature. Then H2S / H2 10 vol.% (60 mL / min) was introduced and the temperature was raised to 400 °C at a rate of 5 °C / min for 4 h to obtain the supported molybdenum sulfide catalyst prepared by the conventional impregnation method. The sample was named MoS2 / α-Al2O3.

[0052] The reaction performance of the catalyst was evaluated using a high-pressure fixed-bed apparatus, specifically as follows: A certain amount of catalyst (60-80 mesh) was diluted with inert silica of the same mesh size as the catalyst to maintain a bed height of 50 mm and a weight hourly space velocity (WHSV) of 0.73-2.6 h⁻¹. -1 .

[0053] After the reaction tube is connected and sealed, nitrogen is introduced to the reaction pressure and a pressure holding test is performed for 12 hours. If the pressure does not decrease, it indicates that the seal is good. The catalyst sample was then subjected to in-situ sulfidation by introducing N2 (60 mL / min) and then drying at room temperature to 150 °C for 2 h at a rate of 5 °C / min. Next, 10 vol.% H2S / H2 (60 mL / min) was introduced, and the temperature was increased to 400 °C for sulfidation at a rate of 5 °C / min for 4 h. The temperature was then lowered to the reaction temperature of 340 °C under a hydrogen atmosphere, and the pressure was increased to 4 MPa. m-Cresol or dibenzofuran was introduced via a feed pump at a rate of 10 mL / h. Samples were taken every 1 h and analyzed by offline gas chromatography-mass spectrometry (GC-MS). The test results are shown in Table 1.

[0054] Table 1

[0055] To determine the impact of changes in the molybdenum disulfide active phase structure on active sites in the catalyst, at least 10 TEM images were selected for each catalyst, and at least 500 molybdenum disulfide lamellars in different regions of the images were statistically analyzed. This allowed for the statistical calculation of the average lamellar length of molybdenum disulfide and the dispersion of Mo. To ensure representative comparisons, the number of molybdenum disulfide nanosheets on different catalysts was statistically calculated. The number of layers of 250–300 independent molybdenum disulfide stacks was measured in different regions of at least 15 TEM images, and the statistical calculation was based on the following formulas: the number of molybdenum disulfide stack layers and the ratio of different types of sterically hindered active sites (Edge / rim ratio). The calculation methods are shown in equations (1)–(5), and the test results are shown in Table 2. Average lamellar length: (1) Average number of stacking layers: (2) Dispersion of Mo: (3) Edge / rim ratio: (4) Number of Mo atoms on a single edge of a lamellar crystal: (5) in, m i Indicates having N i Number of stacking layers; l i For wafer crystal i The length, in nm, is determined by TEM images; n The total number of lamellar crystals is the number of lamellar crystals recorded in the TEM image. n i The number of molybdenum atoms on a single side of a molybdenum disulfide crystal is calculated using Formula 5. L i The diameter of the molybdenum disulfide crystal (molybdenum-molybdenum atomic spacing is 0.32 nm) is in nm. k represents the number of monolayer molybdenum disulfide, which is obtained by statistical analysis of TEM images; t The total number of molybdenum disulfide nanosheets counted in the transmission electron microscopy images; f This represents the maximum number of stacking layers. Edge represents the edge position of the molybdenum disulfide stack sandwiched between the topmost and bottommost lamellar crystals and the middle lamellar crystals; rim represents the edge sites of the top and bottom lamellar crystals of the molybdenum disulfide stack.

[0056] Table 2

[0057] Figure 2 These are TEM images of the catalysts prepared in Example 1(b) and Comparative Example 1(a), from... Figure 2As can be seen, the MoS2 / γ-Al2O3 catalyst obtained by the conventional impregnation method in Comparative Example 1 has a low number of stacking layers, mainly consisting of single layers with relatively long lamellar lengths. In contrast, the MoS2-CTAB / γ-Al2O3 catalyst prepared by the induced assisted impregnation method in Example 1 by introducing a cationic surfactant significantly increases the number of stacking layers and reduces the lamellar length. The average number of stacking layers increases from 1.2 layers in MoS2 / γ-Al2O3 in Comparative Example 1 to 4.3 layers in MoS2-CTAB / γ-Al2O3, while the average lamellar length decreases from 4.90±0.17 nm in MoS2 / γ-Al2O3 to 3.50±0.07 nm in MoS2-CTAB / γ-Al2O3.

[0058] The dispersion of Mo atoms (the proportion of edge Mo atoms to the total number of Mo atoms) was calculated using statistical methods, and the results are as follows: Figure 3 As shown, the dispersion of Mo increased from 21.9% in Comparative Example 1 (MoS2 / γ-Al2O3) to 28.9% in Example 1 (MoS2-CTAB / γ-Al2O3), and the ratio of edge / rim sites increased from 0.17 in Comparative Example 1 (MoS2 / γ-Al2O3) to 0.84 in Example 1 (MoS2-CTAB / γ-Al2O3).

[0059] The catalyst performance was evaluated using dibenzofuran (DBF) and cresol, the main oxygen-containing compounds in coal tar, as model compounds. The prepared catalyst samples underwent in-situ sulfidation treatment, with N2 (60 mL / min) introduced, followed by heating at room temperature to 150 °C for 2 h at a rate of 5 °C / min. Then, H2S / H2 10 vol.% (60 mL / min) was introduced, and the temperature was increased to 400 °C for 4 h at a rate of 5 °C / min. The temperature was then lowered to the reaction temperature of 340 °C under a hydrogen atmosphere, and the reaction pressure was increased to 4 MPa. m-Cresol or dibenzofuran was introduced via a feed pump at a rate of 10 mL / h. Samples were taken every 1 h and analyzed by offline gas chromatography-mass spectrometry (GC-MS). The weight hourly space velocities (WHSVs) for the reactions of cresol and dibenzofuran were 2.6 h⁻¹. -1 and 0.73 h -1 The evaluation results are as follows Figure 4 and Figure 5 As shown. By Figure 4 , Figure 5It can be seen that the selectivity for the formation of biphenyl from dibenzofuran via the direct deoxygenation pathway increased from 11.2% in Comparative Example 1 (MoS2 / γ-Al2O3) to 36.2% in Example 1 (MoS2-CTAB / γ-Al2O3), an increase of 3.2 times. The selectivity for the formation of cresol from m-cresol via the direct deoxygenation pathway increased from 36.1% in Comparative Example 1 (MoS2 / γ-Al2O3) to 88.5% in Example 1 (MoS2-CTAB / γ-Al2O3), an increase of 2.5 times.

[0060] Comparative Example 2 was calcined after the addition of a cationic surfactant, which made it impossible to control the active phase and thus impossible to change the ratio of different active site types. The Edge / rim ratio of Comparative Example 2 was only 0.16, which was significantly lower than the Edge / rim ratio of the Example.

[0061] The catalyst in Comparative Example 3 achieved a dibenzofuran conversion of 30.1 μmol. -1 The selectivity for direct deoxygenation products was 21.6% at mmol-1 Mo, indicating that the carbon chain length of the cationic surfactant also plays an important role in regulating the active phase of molybdenum sulfide.

[0062] It should be noted that the above embodiments are only a part of the many embodiments of the present invention, and are intended to enable those skilled in the art to better understand the concept of the present invention, and should not be regarded as a limitation of the present invention. The scope of protection of the present invention is not limited to the above embodiments, but is defined by the claims of the present invention.

Claims

1. A method for preparing a catalyst for the hydrodeoxygenation of coal tar to produce aromatics at medium and low temperatures, comprising the following steps: Step 1: Mix the molybdenum precursor, cationic surfactant, and carrier, and then dry the mixture to obtain the dried product. Step 2: Sulfide the dried product to obtain the catalyst for medium-low temperature coal tar hydrodeoxygenation to produce aromatics; The molar ratio of the cationic surfactant to molybdenum is 0.8-1.

5. The catalyst contains 5-20 wt% Mo.

2. The preparation method according to claim 1, wherein, The molybdenum precursor includes one or more of the following: ammonium heptamolybdate tetrahydrate, sodium molybdate hydrate, ammonium dimolybdate, and ammonium tetramolybdate dihydrate.

3. The preparation method according to claim 1, wherein, The cationic surfactant includes one or a combination of two or more of trimethylhexadecylammonium bromide, trimethyltetradecylammonium bromide, and trimethyldodecylammonium bromide.

4. The preparation method according to claim 1, wherein, The carrier includes one or more of γ-Al2O3, α-Al2O3, molecular sieves, and magnesium-aluminum composite oxides.

5. The preparation method according to claim 1, wherein, Step 1 includes: A solution containing a molybdenum precursor is mixed with a cationic surfactant, a carrier is added for impregnation, and then dried to obtain a dried product. Alternatively, a carrier is added to a solution containing a cationic surfactant for impregnation, a solution containing a molybdenum precursor is added, and then dried to obtain a dried product.

6. The preparation method according to claim 1, wherein, Step 2 involves granulating the dried product into 60-80 mesh particles, followed by sulfidation.

7. The preparation method according to claim 1, wherein, The vulcanization includes: The dried product is placed in a sulfurizing atmosphere and heated to 350-400℃ for sulfurization.

8. A catalyst for the hydrodeoxygenation of coal tar to produce aromatics at medium and low temperatures, which is prepared by the preparation method according to any one of claims 1-7.

9. The catalyst according to claim 8, wherein, The catalyst has 3-6 stacked layers.

10. The catalyst according to claim 8, wherein, The catalyst has an average lamellar length of 3.0-4.5 nm.

11. The catalyst according to claim 8, wherein, The ratio of edge to rim sites in the catalyst is 0.4-2.

0.

12. The catalyst according to claim 11, wherein, The ratio of edge to rim sites in the catalyst is 0.4-1.

0.

13. The catalyst according to claim 8, wherein, The catalyst has a Mo dispersion of 28-35%.

14. The catalyst according to claim 8, wherein, In the catalyst, the mass fraction of Mo is 8-12 wt%.

15. A method for hydrorefining coal tar, wherein the coal tar is contacted with a catalyst to carry out a hydrodeoxygenation reaction; in, The catalyst is the catalyst for producing aromatics by hydrodeoxygenation of coal tar at medium and low temperatures prepared by the preparation method according to any one of claims 1-7, or the catalyst for producing aromatics by hydrodeoxygenation of coal tar at medium and low temperatures according to any one of claims 8-14.

16. The hydrorefining method according to claim 15, wherein, The reaction conditions for the hydrodeoxygenation reaction include: The reaction temperature is 200-360 °C; The reaction pressure is 0.1-8 MPa; The volume ratio of hydrogen to oil is 200-600; The heavy hourly space velocity is 0.5-5 h. -1 .

17. The hydrorefining method according to claim 15 or 16, wherein, The raw material for the hydrodeoxygenation reaction is a light component below 360 °C in medium- and low-temperature coal tar.

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