Coated catalyst as well as preparation method and application thereof

Abstract

The invention relates to a coated catalyst as well as a preparation method and application thereof. The catalyst comprises a core-layer catalyst and a SiO2 layer coated on the surface of the core-layer catalyst, the core-layer catalyst comprises an alumina carrier as well as an active component and an auxiliary component which are loaded on the alumina carrier; the auxiliary agent component comprises alkali metal and / or alkaline earth metal; the active component comprises at least one group VIB metal; the content of the group VIB metal is 8-25wt% in terms of oxide and on the basis of the total weight of the core-layer catalyst. According to the invention, tetracyclic aromatic hydrocarbon is limited from entering the core layer catalyst by using the screening function of the SiO2 layer, so that the retention rate of tetracyclic aromatic hydrocarbon is improved while the desulfurization activity is improved; meanwhile, the modification of the alkali metal and / or alkaline earth metal is beneficial to enhancing the interaction between the carrier and the active component, and the dispersity of the active component in the hydrogenation catalyst is improved, so that the hydrodesulfurization activity of the catalyst is further improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of petrochemical industry, and particularly relates to a coated catalyst and a preparation method and application thereof. BACKGROUND

[0002] Needle coke has the advantages of low thermal expansion coefficient, low porosity, low metal content, low ash content, high electrical conductivity and easy graphitization, and is widely used in industries such as electrodes, fuel cells and lithium ion batteries. With the structural adjustment and transformation and upgrading of the steel and automobile industries, the rapid development of electric arc furnace steelmaking and new energy vehicles has increased the demand for raw needle coke.

[0003] Catalytic cracking slurry is an important raw material for preparing needle coke, and the ideal component is catalytic slurry with sulfur content lower than 0.5 wt% and high content of three-ring and four-ring short side chain aromatics after hydroprocessing. However, the content of impurities such as sulfur in the catalytic slurry is relatively high, and the sulfur-containing compounds in the slurry mainly include C1-C3 short side chain alkyl-substituted benzothiophene, diphenylthiophene and naphthalene benzothiophene. In the process of hydrodesulfurization, these sulfur-containing compounds need to be saturated with aromatics and then desulfurized by hydrogenolysis. Since the reaction path of aromatic saturation of sulfur-containing compounds is similar to that of polycyclic aromatic hydrocarbons, and compared with the sulfur-containing compound molecules, polycyclic aromatic hydrocarbons are more easily adsorbed on the hydrogenation active sites of the catalyst, and have stronger competitive adsorption ability, thereby inhibiting the desulfurization reaction of the sulfur-containing compounds. The hydrogenation saturation of polycyclic aromatic hydrocarbons prior to the sulfur-containing compounds not only increases the difficulty of desulfurization, but also causes loss of ideal aromatic components.

[0004] In view of the problems existing in the process of oil slurry hydrodesulfurization, CN114984985A discloses a preparation method of a hydrodesulfurization catalyst, which uses a wetting agent and a pore-expanding agent to modify the carrier, thereby enhancing the adsorption capacity of the carrier to the solution; the hydrodesulfurization catalyst has a good pore structure and certain acidity, which can effectively remove complex thiophene-containing sulfur compounds in needle coke raw materials while retaining as much three-ring and four-ring aromatics in the needle coke raw materials as possible.

[0005] CN110628461A discloses a method for selectively hydrodesulfurizing and retaining aromatics of oil slurry, which uses ultrasonic-assisted centrifugal operation to remove the catalyst particles in the middle layer of the oil slurry, and the mechanical action of ultrasonic waves can effectively improve the removal effect of the catalyst particles; the catalyst particles, asphaltenes and resins remaining in the oil slurry are removed, and the extracted oil rich in aromatic hydrocarbons is retained; then selective hydrodesulfurization is performed on the extracted oil, and Fe-modified CoMo / γ-Al2O3 selective hydrodesulfurization catalyst is used for desulfurization; the desulfurization rate is improved, selective hydrogenation is realized, the content of aromatic components is retained, and the loss of aromatic hydrocarbons is reduced.

[0006] However, the hydrogenation desulfurization catalyst in the prior art still has the problem of excessive loss of tetranuclear aromatic hydrocarbons in the process of removing needle coke raw materials. SUMMARY

[0007] The present application aims to further improve the desulfurization rate and the retention rate of tetranuclear aromatic hydrocarbons in the process of hydrogenation desulfurization treatment of needle coke raw materials.

[0008] To achieve the above-mentioned purpose, the first aspect of the present application provides a coated catalyst, which comprises a core layer catalyst and a SiO2 layer coated on the surface of the core layer catalyst; the core layer catalyst comprises an alumina carrier and an active component and an auxiliary component loaded on the alumina carrier; the auxiliary component comprises an alkali metal and / or an alkaline earth metal; the active component comprises at least one Group VIB metal; the content of the Group VIB metal is 8-25% by weight based on the total weight of the core layer catalyst in terms of oxide.

[0009] Optionally, the thickness of the SiO2 layer is 1 nm-30 µm, preferably 20 nm-20 µm; the SiO2 layer has a porous structure with a pore size of 0.5-3 nm, preferably 1-2 nm.

[0010] Optionally, the alkali metal is selected from one or more of lithium, sodium, potassium, rubidium and cesium; the alkaline earth metal is selected from one or more of beryllium, magnesium, calcium, strontium and barium; the content of the auxiliary component is 0.1-10% by weight based on the weight of the core layer catalyst in terms of oxide, preferably 0.5-5% by weight.

[0011] Optionally, the active component further comprises at least one Group VIII metal; the content of the Group VIB metal is 10-20% by weight based on the total weight of the core layer catalyst in terms of oxide, preferably 12-20% by weight; the content of the Group VIII metal is 0.5-15% by weight, preferably 2-15% by weight, more preferably 2-8% by weight; preferably, the Group VIB metal is molybdenum and / or tungsten, more preferably molybdenum; the Group VIII metal is cobalt and / or nickel, more preferably cobalt.

[0012] The second aspect of the present application provides a preparation method of a coated catalyst, which comprises the following steps: mixing an alumina dispersion liquid and a template agent to obtain a mixture; the alumina dispersion liquid comprises an alumina carrier and an alcohol solution; the alumina carrier is loaded with an auxiliary component; the auxiliary component comprises an alkali metal and / or an alkaline earth metal; mixing the mixture and an organic silicon source under alkaline conditions to coat the alumina carrier, and solid-liquid separation to obtain a first carrier coated with a silicon-containing compound on the surface; removing the template agent in the first carrier to obtain a second carrier; and immersing a solution containing a precursor of an active component into the second carrier to obtain an immersed second carrier; carrying out first drying and first calcination on the immersed second carrier to obtain the coated catalyst; the active component comprises at least one Group VIB metal, and the mass ratio of the Group VIB metal in oxide to the alumina carrier is 0.1-0.3:1.

[0013] Optionally, the volume fraction of the alcohol in the alcohol solution is 10%-95%, preferably 50%-90%; the mass ratio of the alumina carrier to the template agent is 1:0.05-1; the content of the auxiliary component is 0.1-10% by weight, preferably 0.5-5% by weight, based on the total weight of the alumina carrier in oxide; preferably, the template agent is selected from one or more of octadecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and dodecyltrimethylammonium chloride; preferably, the alkali metal is selected from one or more of lithium, sodium, potassium, rubidium, and cesium; preferably, the alkaline earth metal is selected from one or more of beryllium, magnesium, calcium, strontium, and barium.

[0014] Optionally, the coating method comprises adding an alkaline reagent to the mixture to adjust the pH value of the mixture, and then adding the organosilicon source, so that the organosilicon source is hydrolyzed and coated on the surface of the alumina carrier; wherein, after adding the alkaline reagent, the pH value of the mixture is 8-10; the mass ratio of the organosilicon source to the hydrogenation catalyst is 0.03-0.8:1, calculated as SiO2; preferably, the alkaline reagent is selected from one or more of aqueous ammonia, sodium hydroxide, potassium hydroxide, and triethanolamine, preferably aqueous ammonia and sodium hydroxide; preferably, the organosilicon source is selected from at least one of dimethyldiethylsiloxane, methyl orthosilicate, and ethyl orthosilicate.

[0015] Optionally, the method further comprises: impregnating the alumina carrier with a solution containing the promoter component precursor to obtain an alumina carrier impregnated with the promoter component; subjecting the alumina carrier impregnated with the promoter component to a second drying and a second calcination; the mass ratio of the alumina carrier to the promoter component precursor is 1:0.01-0.3; the promoter component precursor is selected from at least one of nitrate, sulfate and hydrochloride of the promoter component; the conditions of the second drying comprise: a temperature of 100-200 ℃; a time of 1-4 h; the conditions of the second calcination comprise: a temperature of 200-600 ℃; a time of 1-4 h; preferably, the solution containing the active component precursor further comprises a Group VIII metal; in the solution containing the active component precursor, the mass ratio of the Group VIB metal in terms of oxide to the alumina carrier is 0.1-0.3:1; the mass ratio of the Group VIII metal in terms of oxide to the alumina carrier is 0.005-0.1:1, preferably 0.01-0.05:1; preferably, the Group VIB metal is molybdenum and / or tungsten, preferably molybdenum; the Group VIII metal is cobalt and / or nickel, preferably cobalt.

[0016] Optionally, the template in the first carrier is removed by calcination; the conditions of the calcination comprise: a temperature of 200-600 ℃; a time of 2-10 h; preferably, the calcination comprises a third calcination and a fourth calcination performed in sequence; the conditions of the third calcination comprise: a temperature of 200-300 ℃; a time of 1-3 h; the conditions of the fourth calcination comprise: a temperature of 400-500 ℃; a time of 3-5 h; a temperature rising rate of 0.5 ℃ / min-10 ℃ / min, preferably 1 ℃ / min-3 ℃ / min.

[0017] The third aspect of the present application provides a method for hydroprocessing of oil slurry, which comprises: contacting an oil slurry feedstock with any of the coated catalysts provided in the first aspect of the present application or the coated catalyst prepared by any of the methods provided in the second aspect of the present application under hydroprocessing conditions.

[0018] By the above technical solution, the porous SiO2 shell layer is coated on the surface of the traditional hydrodesulfurization catalyst, the sieve function of the SiO2 shell layer is utilized to limit the tetralin from entering the core layer catalyst, the desulfurization activity is improved, and the retention rate of tetralin is improved; at the same time, the modification of the alkali metal and / or the alkaline earth metal helps to enhance the interaction between the carrier and the active component, improve the dispersion of the active component in the hydroprocessing catalyst, and further improve the hydrodesulfurization activity of the catalyst.

[0019] Other features and advantages of the present application will be described in detail in the following specific embodiments. DETAILED DESCRIPTION

[0020] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and explanatory in nature and are not intended to limit the application.

[0021] The first aspect of the present application provides a coated catalyst, which comprises a core layer catalyst and a SiO2 layer coated on the surface of the core layer catalyst; the core layer catalyst comprises an alumina carrier and an active component and an auxiliary component supported on the alumina carrier; the auxiliary component comprises an alkali metal and / or an alkaline earth metal; the active component comprises at least one Group VIB metal; the content of the Group VIB metal is 8-25 wt% based on the total weight of the core layer catalyst in terms of oxide.

[0022] The present application coats a porous SiO2 shell layer on the surface of a conventional hydrodesulfurization catalyst, uses the sieving function of the SiO2 shell layer to limit the entry of tetralophatic arenes into the core layer catalyst, improves the desulfurization activity and the retention rate of tetralophatic arenes; at the same time, the modification of the alkali metal and / or the alkaline earth metal helps to enhance the interaction between the carrier and the active component, improve the dispersity of the active component in the core layer catalyst, and further improve the hydrodesulfurization activity of the coated catalyst.

[0023] In some embodiments of the present application, the thickness of the SiO2 layer is 1 nm-30 µm, preferably 20 nm-20 µm.

[0024] In some embodiments of the present application, the SiO2 layer is of a porous structure, and the pore size is 0.5-3 nm, preferably 1-2 nm.

[0025] In the formula, the alkali metal is selected from one or more of lithium, sodium, potassium, rubidium and cesium; the alkaline earth metal is selected from one or more of beryllium, magnesium, calcium, strontium and barium; the content of the auxiliary component is 0.1-10 wt%, preferably 0.5-5 wt% based on the weight of the core layer catalyst in terms of oxide.

[0026] In the formula, the active component further comprises at least one Group VIII metal; in some embodiments of the present application, the content of the Group VIB metal is 10-20 wt%, preferably 12-20 wt% based on the total weight of the core layer catalyst in terms of oxide; the content of the Group VIII metal is 0.5-15 wt%, preferably 2-15 wt%, more preferably 2-8 wt%; preferably, the Group VIB metal is molybdenum and / or tungsten, more preferably molybdenum; the Group VIII metal is cobalt and / or nickel, more preferably cobalt.

[0027] The second aspect of the present application provides a preparation method of a coated catalyst, comprising the following steps: mixing the alumina dispersion liquid and the template agent to obtain a mixture; the alumina dispersion liquid comprises an alumina carrier and an alcohol solution; the alumina carrier is loaded with an auxiliary component; the auxiliary component comprises an alkali metal and / or an alkaline earth metal; mixing the mixture and an organic silicon source under alkaline conditions to coat the alumina carrier, and performing solid-liquid separation to obtain a first carrier coated with a silicon-containing compound on the surface; removing the template agent in the first carrier to obtain a second carrier; and immersing a solution containing a precursor of an active component into the second carrier to obtain an immersed second carrier; performing first drying and first calcination on the immersed second carrier to obtain the coated catalyst; the active component comprises at least one Group VIB metal, and the mass ratio of the Group VIB metal in oxide to the alumina carrier is 0.1-0.3:1.

[0028] In some embodiments of the present application, the volume fraction of alcohol in the alcohol solution is 10%-95%, preferably 50%-90%; and the mass ratio of the alumina carrier to the template agent is 1:0.05-1. Specifically, the alcohol solution is an ethanol solution, and the volume fraction of ethanol is above 50%.

[0029] During the coating treatment, the concentration of the template agent in the system is 1-50 mmol / L, preferably 5-30 mmol / L, so as to form a continuous and complete coating on the surface of the core layer catalyst. The pore size of the pores on the SiO2 layer can be controlled by selecting a suitable template agent. Preferably, the template agent is selected from one or more of octadecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and dodecyltrimethylammonium chloride.

[0030] In some embodiments of the present application, the content of the auxiliary component is 0.1-10 wt%, preferably 0.5-5 wt%, based on the total weight of the alumina carrier in oxide.

[0031] Preferably, the template agent is selected from one or more of octadecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and dodecyltrimethylammonium chloride; preferably, the alkali metal is selected from one or more of lithium, sodium, potassium, rubidium and cesium; and preferably, the alkaline earth metal is selected from one or more of beryllium, magnesium, calcium, strontium and barium.

[0032] The coating method comprises: adding an alkaline reagent to the mixture to adjust the pH value of the mixture, and then adding the organosilicon source, so that the organosilicon source is hydrolyzed and coated on the surface of the alumina carrier; wherein, after adding the alkaline reagent, the pH value of the mixture is 8-10.

[0033] The mass ratio of the organosilicon source to the hydrogenation catalyst is 0.03-0.8:1, calculated based on SiO2. Specifically, the concentration of the organosilicon source in the system during the coating treatment is 1-50 mmol / L, preferably 5-30 mmol / L.

[0034] Preferably, the organosilicon source is selected from at least one of dimethyldiethylsiloxane, methyl orthosilicate and ethyl orthosilicate.

[0035] Preferably, the alkaline reagent is selected from one or more of ammonia, sodium hydroxide, potassium hydroxide and triethanolamine, preferably ammonia and sodium hydroxide.

[0036] Specifically, the concentration of the alkaline reagent is 0.05-2 mol / L, preferably 0.1-0.5 mol / L. The appropriate amount of alkaline reagent is conducive to the hydrolysis of the organosilicon source and the coating on the surface of the core layer catalyst. Too little (too low concentration) or too much (too high concentration) of the alkaline reagent is not conducive to the formation of a continuous shell layer, or it cannot be coated on the surface of the core layer catalyst.

[0037] The method further comprises: impregnating the alumina carrier with a solution containing the precursor of the auxiliary component to obtain an alumina carrier impregnated with the auxiliary component; and performing second drying and second calcination on the alumina carrier impregnated with the auxiliary component.

[0038] The mass ratio of the alumina carrier to the precursor of the auxiliary component is 1:0.01-0.3; the precursor of the auxiliary component is selected from at least one of a nitrate, a sulfate and a hydrochloride of the auxiliary component; the conditions of the second drying include: a temperature of 100-200 ℃; a time of 1-4 h; the conditions of the second calcination include: a temperature of 200-600 ℃; a time of 1-4 h.

[0039] In the solution containing the precursor of the active component, the mass ratio of the Group VIB metal, calculated as an oxide, to the alumina carrier is 0.1-0.3:1; preferably, the solution containing the precursor of the active component further comprises a Group VIII metal; the mass ratio of the Group VIII metal, calculated as an oxide, to the alumina carrier is 0.005-0.1:1, preferably 0.01-0.05:1.

[0040] Preferably, the Group VIB metal is molybdenum and / or tungsten, preferably molybdenum; and the Group VIII metal is cobalt and / or nickel, preferably cobalt.

[0041] The template in the first carrier is removed by calcination, and the conditions of the calcination include a temperature of 200-600 ℃ and a time of 2-10 h.

[0042] Preferably, the calcination includes third calcination and fourth calcination performed in sequence, the conditions of the third calcination include a temperature of 200-300 ℃ and a time of 1-3 h, and the conditions of the fourth calcination include a temperature of 400-500 ℃ and a time of 3-5 h. Preferably, a gradient temperature rise is adopted, i.e., first rising from room temperature to 200-300 ℃ and maintaining for 1-3 h, and then rising to 400-500 ℃ and maintaining for 3-5 h, with a rising rate of 0.5 ℃ / min-10 ℃ / min, preferably 1 ℃ / min-3 ℃ / min.

[0043] A third aspect of the present application provides a method for hydroprocessing of oil slurry, which comprises contacting an oil slurry feedstock with any of the coated catalysts provided in the first aspect of the present application under hydroprocessing reaction conditions.

[0044] The present application is further illustrated in detail by the following examples, but the present application is not limited to the following examples.

[0045] The raw materials used in the examples can be obtained by commercial channels. Among them, dodecyltrimethylammonium chloride (DTAC) has a purity of ≥99.0%; Anhydrous ethanol, 99.5 wt%; Ammonia water, ammonia mass fraction of 26-28 wt%; Tetraethyl orthosilicate (TEOS), purity ≥99.0%; Alumina carrier, specific surface area of 268 m 2 / g, average pore size of 13.52 nm, and total pore volume of 0.9 cm 3 / g.

[0046] The properties of the raw oil in the examples and comparative examples of the present application are shown in Table 1.

[0047] Table 1

[0048] Preparation Example 1 100 g of the alumina carrier was weighed, and a solution containing 19.4 g of magnesium nitrate was used to impregnate the alumina carrier for 1 hour; the impregnated alumina carrier was dried and calcined, dried at 120 ℃ for 3 hours, and then calcined at 300 ℃ for 3 hours to obtain the magnesium oxide modified alumina carrier S1. wherein the drying temperature is 120 °C, the drying time is 3 h; the calcination temperature is 400 °C, and the calcination time is 3 h.

[0049] Preparation Example 2 This preparation example refers to the method of Preparation Example 1 to prepare the magnesium oxide modified alumina carrier, which is different from Preparation Example 1 in that 100 g of the alumina carrier is impregnated with a magnesium nitrate solution containing 3.88 g of magnesium nitrate. The obtained alumina carrier is denoted as S2.

[0050] Preparation Example 3 This preparation example refers to the method of Preparation Example 1 to prepare the calcium oxide modified alumina carrier, which is different from Preparation Example 1 in that 100 g of the alumina carrier is impregnated with a calcium nitrate solution containing 21.49 g of calcium nitrate. The obtained alumina carrier is denoted as S3.

[0051] Example 1 This example is used to illustrate the preparation method of the alkaline earth metal-containing coated catalyst according to the present application, which comprises the following steps: S1, 360 mL of anhydrous ethanol and 40 mL of deionized water are mixed to obtain an ethanol solution, and 100 g of the magnesium oxide modified alumina carrier S1 obtained in Preparation Example 1 is dispersed in the ethanol solution to obtain an alumina dispersion; S2, 1 g of a template DTAC is added to the alumina dispersion, and ultrasonic treatment is performed for 30 min to obtain a first mixed material; 5 mL of ammonia water is added dropwise to the first mixed material under stirring, and reaction is performed for 30 min to obtain a second mixed material; S3, 1 mL of TEOS is slowly added dropwise to the second mixed material under stirring, and reaction is performed for 6 h, followed by filtration to obtain a first carrier; the first carrier is washed, dried and calcined to obtain an Al2O3-MgO@SiO2 carrier; S4, 100 g of the Al2O3-MgO@SiO2 carrier is weighed, and the Al2O3-MgO@SiO2 carrier is impregnated with 85 mL of an impregnating solution for 1 hour; then the impregnated solid is dried and calcined to obtain a core-shell type hydrogenation catalyst C1; wherein the impregnating solution is prepared from molybdenum trioxide, basic cobalt carbonate and phosphoric acid, and the content of the molybdenum compound in the impregnating solution is 268.9 g / L in terms of MoO3, and the content of the cobalt compound in the impregnating solution is 63.0 g / L in terms of CoO; the drying temperature is 120 °C, the drying time is 3 h; the calcination temperature is 400 °C, and the calcination time is 3 h.

[0052] The properties of the catalyst C1 are shown in Table 2.

[0053] Example 2 The method for preparing the coated catalyst in this example was performed according to Example 1, with the difference that: The modified alumina carrier used in step S1 was the magnesium oxide modified alumina carrier S2. The obtained coated catalyst was recorded as C2, and its properties are shown in Table 2.

[0054] Example 3 The method for preparing the coated catalyst in this example was performed according to Example 1, with the difference that: The modified alumina carrier used in step S1 was the calcium oxide modified alumina carrier S3. The obtained coated catalyst was recorded as C3, and its properties are shown in Table 2.

[0055] Example 4 The method for preparing the coated catalyst in this example was performed according to Example 1, with the difference that: The amount of anhydrous ethanol used in step S1 was 280 mL, and the amount of deionized water used was 120 mL. The obtained coated catalyst was recorded as C4, and its properties are shown in Table 2.

[0056] Example 5 The method for preparing the coated catalyst in this example was performed according to Example 1, with the difference that: The amount of anhydrous ethanol used in step S1 was 200 mL, and the amount of deionized water used was 200 mL. The obtained coated catalyst was recorded as C5, and its properties are shown in Table 2.

[0057] Example 6 The method for preparing the coated catalyst in this example was performed according to Example 1, with the difference that: The amount of ammonia used in step S2 was 2 mL; the obtained coated catalyst was recorded as C6, and its properties are shown in Table 2.

[0058] Comparative Example 1 The method for preparing the coated catalyst in this example was performed according to Example 1, with the difference that: The carrier used in step S1 was an unmodified alumina carrier, and the obtained coated catalyst was recorded as D1, and its properties are shown in Table 2.

[0059] Comparative Example 2 100 g of the modified alumina carrier S1 was weighed, and the magnesium oxide modified alumina carrier was impregnated with 85 mL of the impregnation solution for 1 hour; then the impregnated solid was dried and calcined to obtain the hydrogenation catalyst D2, and its properties are shown in Table 2. The impregnation solution is prepared from molybdenum trioxide, basic cobalt carbonate and phosphoric acid, and the content of molybdenum compound in the impregnation solution is 268.9 g / L calculated as MoO3, and the content of cobalt compound is 63.0 g / L calculated as CoO; the drying temperature is 120 ℃, and the drying time is 3 h; the calcination temperature is 400 ℃, and the calcination time is 3 h.

[0060] Table 2

[0061] Catalytic performance evaluation The catalysts prepared in Examples 1-6 and Comparative Examples 1-2 were subjected to catalytic performance evaluation with catalytic oil slurry (properties as shown in Table 1) as raw material. The catalytic oil slurry was fed into a 100 mL small fixed bed reactor to contact with the hydrogenation catalyst (catalyst loading amount was 100 mL, and particle size was 0.8-1.2 mm) packed therein to perform catalytic hydrogenation reaction. The catalytic hydrogenation reaction conditions included: reaction temperature was 320 ℃, hydrogen partial pressure was 4 MPa, liquid hourly space velocity was 0.5 h -1 , and hydrogen / oil volume ratio was 600.

[0062] The sulfur content and tetranuclear aromatic hydrocarbon content in the generated oil were determined, and the desulfurization rate and tetranuclear aromatic hydrocarbon retention rate were calculated, and the results are shown in Table 3.

[0063] The calculation formulae of the desulfurization rate and aromatic hydrocarbon retention rate are as follows: ; Tetranuclear aromatic hydrocarbon retention rate = (tetranuclear aromatic hydrocarbon content in generated oil / tetranuclear aromatic hydrocarbon content in raw material) x 100%.

[0064] The catalyst was pre-sulfided before reaction, and the pre-sulfiding conditions included: temperature was 360 ℃, and time was 3 hours; hydrogen partial pressure was 4.0 MPa, hydrogen / oil volume ratio was 600, and liquid hourly space volume speed of sulfidation oil (5 wt% CS2+95 wt% cyclohexane) was 1.2 h -1 .

[0065] Table 3

[0066] From the data in the above table, it can be found that, compared with the conventional catalyst containing alkali earth metal without SiO2 coating, the catalyst provided by the application can significantly improve the retention rate of tetranuclear aromatic hydrocarbons in the raw material; compared with the coated catalyst without alkali earth element, the catalyst provided by the application can further improve the desulfurization performance of the catalyst under the condition of the same content of active component.

[0067] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the specific details of the above-described embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0068] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, various possible combinations are not described again by the present application.

[0069] In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the idea of the present application, and it should also be considered as disclosed by the present application.

Claims

1. A coated catalyst characterized by, The catalyst comprises a core layer catalyst and a SiO2 layer coated on the surface of the core layer catalyst; the core layer catalyst comprises an alumina carrier and an active component and an auxiliary component supported on the alumina carrier; the auxiliary component comprises an alkali metal and / or an alkaline earth metal; the active component comprises at least one Group VIB metal; the content of the Group VIB metal is 8-25% by weight based on the total weight of the core layer catalyst.

2. The catalyst of claim 1, wherein, The thickness of the SiO2 layer is 1 nm-30 µm, preferably 20 nm-20 µm; the SiO2 layer is a porous structure with a pore size of 0.5-3 nm, preferably 1-2 nm.

3. The catalyst of claim 1, wherein, The alkali metal is selected from one or more of lithium, sodium, potassium, rubidium and cesium; The alkaline earth metal is selected from one or more of beryllium, magnesium, calcium, strontium and barium; The content of the auxiliary component is 0.1-10% by weight based on the weight of the core layer catalyst, preferably 0.5-5% by weight based on the weight of the core layer catalyst.

4. The catalyst of claim 1, wherein, The active component further comprises at least one Group VIII metal; The content of the Group VIB metal is 10-20% by weight based on the total weight of the core layer catalyst, preferably 12-20% by weight based on the total weight of the core layer catalyst; the content of the Group VIII metal is 0.5-15% by weight, preferably 2-15% by weight, more preferably 2-8% by weight; Preferably, the Group VIB metal is molybdenum and / or tungsten, more preferably molybdenum; the Group VIII metal is cobalt and / or nickel, more preferably cobalt.

5. A method for producing a coated catalyst, characterized by, The method comprises the following steps: Mixing an alumina dispersion liquid and a template agent to obtain a mixture; the alumina dispersion liquid comprises an alumina carrier and an alcohol solution; the alumina carrier is loaded with an auxiliary component; the auxiliary component comprises an alkali metal and / or an alkaline earth metal; Mixing the mixture and an organic silicon source under alkaline conditions to coat the alumina carrier, and performing solid-liquid separation to obtain a first carrier coated with a silicon-containing compound on the surface; Removing the template agent in the first carrier to obtain a second carrier; and Impregnating a solution containing an active component precursor into the second carrier to obtain an impregnated second carrier; Performing first drying and first calcination on the impregnated second carrier to obtain the coated catalyst; the active component comprises at least one Group VIB metal, and the mass ratio of the Group VIB metal to the alumina carrier is 0.1-0.3:1 based on the oxide.

6. The method of claim 5, wherein, The volume fraction of alcohol in the alcohol solution is 10%-95%, preferably 50%-90%; The mass ratio of the alumina carrier to the template agent is 1:0.05-1; The content of the auxiliary component is 0.1-10% by weight based on the total weight of the alumina carrier, preferably 0.5-5% by weight based on the total weight of the alumina carrier; Preferably, the template agent is selected from one or more of octadecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide and dodecyl trimethyl ammonium chloride; Preferably, the alkali metal is selected from one or more of lithium, sodium, potassium, rubidium and cesium; Preferably, the alkaline earth metal is selected from one or more of beryllium, magnesium, calcium, strontium and barium.

7. The method of claim 5, wherein, The coating method comprises: adding an alkaline reagent to the mixture to adjust the pH value of the mixture, and then adding the organosilicon source, so that the organosilicon source is hydrolyzed and coated on the surface of the alumina carrier; Preferably, the alkaline reagent is selected from one or more of ammonia, sodium hydroxide, potassium hydroxide and triethanolamine, preferably ammonia and sodium hydroxide. Preferably, the organosilicon source is selected from at least one of dimethyldiethylsiloxane, methyl orthosilicate and ethyl orthosilicate. The method further comprises:

8. The method of claim 5, wherein, impregnating the alumina carrier with a solution containing the adjuvant component precursor to obtain an alumina carrier impregnated with the adjuvant component; and performing second drying and second calcination on the alumina carrier impregnated with the adjuvant component; The mass ratio of the alumina carrier to the adjuvant component precursor is 1:0.01-0.3; The adjuvant component precursor is selected from at least one of nitrate, sulfate and hydrochloride of the adjuvant component; The conditions of the second drying include: a temperature of 100-200 ℃; and a time of 1-4 h; The conditions of the second calcination include: a temperature of 200-600 ℃; and a time of 1-4 h; Preferably, the solution containing the active component precursor further comprises a Group VIII metal; the mass ratio of the Group VIB metal in the form of an oxide to the alumina carrier in the solution containing the active component precursor is 0.1-0.3:1; and the mass ratio of the Group VIII metal in the form of an oxide to the alumina carrier in the solution containing the active component precursor is 0.005-0.1:1, preferably 0.01-0.05:

1. Preferably, the Group VIB metal is molybdenum and / or tungsten, preferably molybdenum; and the Group VIII metal is cobalt and / or nickel, preferably cobalt. The template in the first carrier is removed by calcination; the conditions of the calcination include: a temperature of 200-600 ℃; and a time of 2-10 h; 9. The method of claim 5, wherein, Preferably, the calcination comprises third calcination and fourth calcination performed in sequence; the conditions of the third calcination include: a temperature of 200-300 ℃; and a time of 1-3 h; the conditions of the fourth calcination include: a temperature of 400-500 ℃; a time of 3-5 h of calcination; and a temperature rising rate of 0.5 ℃ / min-10 ℃ / min, preferably 1 ℃ / min-3 ℃ / min. The method comprises: contacting an oil slurry raw material and the coated catalyst of any one of claims 1-4 or the coated catalyst prepared by the method of any one of claims 5-9 under hydrogenation reaction conditions.

10. A method for hydroprocessing of oil slurry, characterized by, ​

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