Oil product hydrotreating catalyst grading method and hydrotreating method

Abstract

The application provides a method for grading oil product hydrogenation treatment catalysts and a hydrogenation treatment method, and the grading method comprises the following steps: sequentially loading a protective layer and a catalyst layer in a hydrogenation reactor along the material flow direction in the hydrogenation reactor; the protective layer comprises a protective agent, and the pore volume of the protective agent in the protective layer presents a decreasing trend along the material flow direction in the hydrogenation reactor; the catalyst layer comprises a catalyst, and the total acid amount of the catalyst in the catalyst layer presents a trend of first increasing and then decreasing along the material flow direction in the hydrogenation reactor; the catalyst comprises a second active metal, and the mass percentage of the second active metal of the catalyst in the catalyst layer presents an increasing trend along the material flow direction in the hydrogenation reactor. The application can improve the desulfurization, denitrification, de-residual carbon and demetallization efficiency of the oil product to be treated, and also improves the liquid yield.

Description

Technical Field

[0001] This invention relates to a method for grading a catalyst for oil hydrotreating and a hydrotreating method, belonging to the field of oil hydrotreating technology. Background Technology

[0002] On the one hand, the degree of heavy and inferior quality of crude oil and other petroleum resources is increasing. On the other hand, with the improvement of clean oil standards, the requirements for high-quality and clean petroleum fuel products are becoming increasingly stringent. Therefore, it is urgent to lighten heavy crude oil and other petroleum products and efficiently convert them into clean oil products.

[0003] Hydrocracking and catalytic cracking are important technologies for reducing heavy oil to lighter grades. However, components such as nitrogen oxides, sulfides, metals, and residual carbon in the feedstock have a significant negative impact on the cracking process. Taking wax oil as an example, in recent years, the proportion of straight-run wax oil in hydrocracking and catalytic cracking feedstocks has gradually decreased, while the proportion of inferior components such as high-sulfur and high-nitrogen wax oil, vacuum-pressed wax oil, coking wax oil, and deasphalted oil has been increasing, leading to a decline in feedstock quality. Nitrogen oxides and other components in these feedstocks have a significant negative effect on the catalyst activity and product quality of the cracking process, thus forcing refining enterprises to conduct deep hydrotreating of hydrocracking and catalytic cracking wax oil feedstocks. Therefore, hydrotreating (or hydrotreatment) has a significant impact on the overall efficiency of hydrocracking and catalytic cracking processes and has become one of the key core technologies in hydrocracking and catalytic cracking.

[0004] The key to hydrotreating technology lies in catalyst development. Related technologies primarily focus on catalyst particle internal structure and catalyst preparation processes. For example, patent document CN100469443C discloses a hydrotreating catalyst using alumina-silica as a support, introducing phosphorus during catalyst preparation to increase catalyst acidity and improve performance; patent document CN100556994C discloses a hydrotreating catalyst using a titanium dioxide and silica composite oxide and HY molecular sieve or acid-modified HY molecular sieve as a support to load active components; patent document CN1769384A discloses a method for preparing a heavy oil hydrotreating catalyst, using a certain amount of Beta molecular sieve and alumina as a support, impregnating active components to prepare the catalyst; and patent document CN102019201A discloses a method for preparing a heavy distillate oil hydrorefining catalyst containing molecular sieves, using alumina and phosphorus aluminum molecular sieve AlPO4- 5. ETS-10, a titanium-silicon molecular sieve, is used together as a support. Through the synergistic effect of the two molecular sieves, the hydrorefining performance of the catalyst is improved. Patent document CNCN109701452B discloses a paraffin-based residue oil hydrotreating catalyst. Along the flow direction, the total acid content of the catalyst gradually decreases, while the proportion of Lewis acid gradually increases. This gradation method results in high initial cracking activity, easily forming coke deposits, affecting long-term operation. Patent document CN101332430A discloses a heavy oil hydrotreating catalyst and its preparation method. The catalyst is prepared by adding boron to an alumina support to control the acid content and type of acid. Patent document CN101928593A discloses a gradation combination for a heavy oil hydrotreating catalyst. From the center to the surface of the catalyst particles, the concentration of active metal components and acidic additives in the demetallization catalyst gradually decreases, while the concentration of active metal components and acidic additives in the denitrification catalyst gradually increases, and the concentration of active metal components and acidic additives in the desulfurization catalyst is uniformly distributed.

[0005] Although there are existing studies and reports on hydrotreating catalysts, existing hydrotreating catalysts generally suffer from poor performance in desulfurization, denitrification, residual carbon removal, and demetallization, as well as low liquid yield, which urgently need to be addressed. Summary of the Invention

[0006] This invention provides a method for grading a catalyst for oil hydrotreating and a hydrotreating method. By using specific protective agents and catalyst grading methods, the desulfurization, denitrification, carbon residue removal, and metal removal performance of the overall catalytic system can be improved, while also increasing the liquid yield of the hydrotreating process, effectively overcoming the defects of the existing technology.

[0007] In one aspect, the present invention provides a method for grading a catalyst for oil hydrotreating, comprising: sequentially loading a protective layer and a catalyst layer into a hydrotreating reactor along the material flow direction within the reactor; the protective layer comprising a protective agent, wherein the pore volume of the protective agent in the protective layer decreases along the material flow direction within the hydrotreating reactor; the catalyst layer comprising a catalyst, wherein the total acid content of the catalyst in the catalyst layer first increases and then decreases along the material flow direction within the hydrotreating reactor; and the catalyst comprising a second active metal, wherein the mass percentage content of the second active metal in the catalyst in the catalyst layer increases along the material flow direction within the hydrotreating reactor.

[0008] According to one embodiment of the present invention, the decreasing trend includes a gradual decrease or a gradient decrease.

[0009] According to one embodiment of the present invention, the specific surface area of ​​the protective agent in the protective layer increases along the material flow direction in the hydrogenation reactor. Preferably, the increasing trend includes a gradual increase or a gradient increase.

[0010] According to one embodiment of the present invention, the pore volume of the protective agent is not less than 0.4 ml / g.

[0011] According to one embodiment of the present invention, the protective agent comprises a first carrier and a first active metal, wherein the mass percentage of the first active metal in the protective agent is 0-10%; and / or, the first active metal comprises one or more of nickel, cobalt, molybdenum, and tungsten; and / or, the first carrier comprises inorganic materials and / or molecular sieves, preferably, the inorganic materials comprise alumina, amorphous aluminum silicate, titanium dioxide, zirconium dioxide, silicon dioxide, Al2O3-SiO2 composite oxide, Al2O3-TiO2 composite oxide, Al2O One or more of 3-ZrO2 composite oxide, ZrO2-TiO2 composite oxide, and TiO2-SiO2 composite oxide; the molecular sieve includes one or more of Y molecular sieve, ZSM-5, ZSM-22, ZSM-23, ZSM-35, Beta, and ZSM-48; and / or, the mass percentage content of the first active metal of the protective agent in the protective layer remains unchanged or increases along the material flow direction in the hydrogenation reactor, preferably, the increasing trend includes gradual increase or gradient increase.

[0012] According to one embodiment of the present invention, the second active metal includes one or more of Co, Mo, Ni and W; and / or, the mass percentage of the second active metal in the catalyst is 10-40%.

[0013] According to one embodiment of the present invention, the catalyst further includes a second support, the second support comprising an inorganic material and / or a molecular sieve. Preferably, the inorganic material comprises one or more of alumina, amorphous aluminum silicate, titanium dioxide, zirconium dioxide, silicon dioxide, Al2O3-SiO2, Al2O3-TiO2 composite oxide, Al2O3-ZrO2 composite oxide, ZrO2-TiO2 composite oxide, and TiO2-SiO2 composite oxide; the molecular sieve comprises one or more of Y molecular sieve, ZSM-5, ZSM-22, ZSM-23, ZSM-35, Beta, and ZSM-48; preferably, the mass percentage of the inorganic material in the catalyst is 50-90%, and the mass percentage of the molecular sieve in the catalyst is 0-10%.

[0014] According to one embodiment of the present invention, the catalyst further includes an acidic auxiliary agent, wherein the mass percentage of the acidic auxiliary agent in the catalyst is 0.5-3%, and / or the acidic auxiliary agent comprises one or more of phosphoric acid, boric acid, hydrofluoric acid, nitric acid, citric acid, tartaric acid, and malic acid.

[0015] According to one embodiment of the present invention, the trend of first increasing and then decreasing includes first gradually increasing and then gradually decreasing, first gradually increasing and then gradually decreasing, first gradually increasing and then gradually decreasing, or first gradually increasing and then gradually decreasing; and / or, the increasing trend includes gradually increasing or gradually increasing.

[0016] According to one embodiment of the present invention, the total acid content of the catalyst is 0.2 to 20 μmol / g; and / or, the weak acid content of the catalyst is 0.1 to 15 μmol / g; and / or, the weak acid content of the catalyst in the catalyst layer shows a trend of first increasing and then decreasing along the material flow direction in the hydrogenation reactor; and / or, the pore volume of the catalyst is 0.2 to 0.6 ml / g.

[0017] According to one embodiment of the present invention, the volume of the protective layer accounts for 2 to 20% of the sum of the volume of the protective layer and the volume of the catalyst layer, and / or the volume of the catalyst layer accounts for 80 to 98% of the sum of the volume of the protective layer and the volume of the catalyst layer.

[0018] In another aspect, the present invention provides a method for hydrotreating oil, comprising: introducing the oil to be treated into a hydrotreating reactor and contacting it with a protective agent and a catalyst for hydrotreating, wherein the protective agent and the catalyst in the hydrotreating reactor are loaded according to the gradation method of any one of claims 1-8, and the flow direction of the oil to be treated in the hydrotreating reactor is the same as the material flow direction in the hydrotreating reactor.

[0019] According to one embodiment of the present invention, the conditions for the hydrogenation treatment are: a reaction pressure of 6–15 MPa, a reaction temperature of 300–400 °C, and a volume hourly space velocity of 0.5–2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (100-1000):1; and / or the oil to be treated includes one or more of coking wax oil (CGO), vacuum wax oil (VGO), coking diesel oil, and under-wax oil; and / or the sulfur content in the oil to be treated is 0.3-2% by mass; and / or the nitrogen content in the oil to be treated is 0.1-1% by mass.

[0020] In this invention, from the perspective of the catalytic system loading in the hydrogenation reactor, a protective agent (protective layer) and a catalyst (catalyst layer) are sequentially loaded along the material flow direction of the hydrogenation reactor. The pore volume of the protective agent decreases along the material flow direction, the total acid content of the catalyst first increases and then decreases along the material flow direction, and the content of the second active metal in the catalyst increases along the material flow direction. Through this gradation method, the desulfurization, denitrification, residual carbon removal, and demetallization performance of the overall catalytic system formed by the protective layer and the catalyst layer in the hydrogenation reactor can be improved. It can also improve the liquid yield (i.e., liquid recovery rate) of the hydrogenation process and extend the overall operating cycle of the hydrogenation reactor / unit. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In the description of this invention, terms such as "first" and "second" are used for descriptive purposes only, such as to distinguish between components to more clearly illustrate / explain the technical solution, and should not be construed as indicating or implying the number of technical features indicated or the order of features with substantial significance.

[0023] Hydrotreating (or hydrotreatment) has a significant impact on the overall efficiency of hydrocracking and catalytic cracking processes, and it has become one of the key core technologies for hydrocracking and catalytic cracking. The focus of hydrotreating technology lies in the development of catalysts.

[0024] Taking wax oil as an example, the key to wax oil hydrocracking pretreatment technology lies in the development of catalysts. The hydrocracking pretreatment catalyst is mainly composed of a support and an active metal. The active metal can be a group VIB or group VIII metal, specifically a metal oxide or a metal sulfide, etc. The support is generally alumina. Due to the limitations of alumina pore size and surface acidity, catalysts using alumina as the support alone cannot achieve deep polycyclic aromatic hydrocarbon saturation and removal of heterocyclic nitrogen compounds.

[0025] Therefore, according to the inventors' research, further development of catalysts requires not only improving the pore structure of the support and adjusting the interaction forces between the support and the metal, but also optimizing the surface acidic structure of the hydrogenation catalyst. Increasing the catalyst's acidity is beneficial for the ring-opening and removal of heterocyclic nitrides, but excessive acidity can also lead to increased catalyst cracking activity, decreased liquid yield, and an increased tendency for catalyst coking, thus affecting the long-term stable operation of the catalyst. Depending on the preparation process, the hydrogenation catalyst may have two types of acid centers, namely... The total acidity of the catalyst is due to the presence of both acid centers and Lewis acid centers. The sum of the acidity of the acid and Lewis acid is that the Bronsted acid center can donate protons, while the Lewis acid center can accept unpaired electrons. Existing technologies mainly optimize acidity at the catalyst particle scale, and generally suffer from poor performance in desulfurization, denitrification, residual carbon removal, and demetallization, as well as low liquid yield. There are few technologies that use gradation processes to synergize the acidity and other characteristics of the catalyst to improve the hydrogenation treatment effect.

[0026] In view of this, embodiments of the present invention provide a method for grading a catalyst for oil hydrotreating, comprising: sequentially loading a protective layer and a catalyst layer into a hydrotreating reactor along the material flow direction within the reactor; the protective layer comprising a protective agent, wherein the pore volume of the protective agent in the protective layer decreases along the material flow direction within the hydrotreating reactor; the catalyst layer comprising a catalyst, wherein the total acid content of the catalyst in the catalyst layer first increases and then decreases along the material flow direction within the hydrotreating reactor; and the catalyst comprising a second active metal, wherein the mass percentage content of the second active metal in the catalyst in the catalyst layer increases along the material flow direction within the hydrotreating reactor.

[0027] By using the above-mentioned gradation method, the desulfurization, denitrification, residual carbon removal, and demetallization performance of the overall catalytic system formed by the protective layer and catalyst layer in the hydrogenation reactor can be improved, and the liquid yield of the hydrogenation process can be increased, thereby extending the overall operating cycle of the hydrogenation reactor / unit.

[0028] The inventors, through research and analysis, believe that in the above-mentioned gradation method, reasonable gradation and filling are carried out based on the functions of the protective agent and the catalyst. The protective agent can be used to perform preliminary impurity removal on the materials entering the hydrotreating reactor (such as oil to be processed), such as removing mechanical impurities and at least some metals. The catalyst layer further performs deep hydrotreating on the materials. Among them, the second active metal in the catalyst tends to increase along the material flow direction, so that the hydrogenation activity of the catalyst tends to increase along the material flow direction. This can relatively slowly improve the desulfurization, denitrification and demetallization activities, and control the temperature rise of the bed in the hydrotreating reactor, which is conducive to the hydrogenation reaction. At the same time, the total acidity of the catalyst layer tends to increase and then decrease along the material flow direction, so that the catalyst cracking activity increases slowly, ensuring a moderate ring-opening cracking activity, which is conducive to further desulfurization, denitrification and demetallization. After desulfurization, denitrification and demetallization reach a certain depth, it is not necessary to strengthen the ring-opening cracking activity. As a result, the acidity decreases, which can effectively ensure the overall liquid yield. Therefore, by using the above-mentioned gradation method, the overall catalytic performance of the catalytic system formed by the protective agent and the catalyst can be brought into play, improving the desulfurization, denitrification, residual carbon removal and demetallization activity of the catalytic system, while also improving the liquid yield of the hydrogenation process.

[0029] Specifically, the hydrogenation reactor can be placed vertically, and the material flow direction inside the hydrogenation reactor can be from top to bottom (i.e., from the top / top of the hydrogenation reactor to the bottom / side of the hydrogenation reactor).

[0030] The decreasing trend described above can include gradual or gradient decreasing (or stepwise decreasing), that is, the pore volume of the protective agent in the protective layer can gradually or gradient decrease along the material flow direction in the hydrogenation reactor.

[0031] Specifically, the protective layer may include at least two protective sub-layers sequentially distributed along the material flow direction within the hydrogenation reactor. The pore volume of the protective agent in each protective sub-layer may remain constant or decrease along the material flow direction. In some specific embodiments, in two adjacent protective sub-layers, the pore volume of the protective agent in the upstream sub-layer is greater than that in the downstream sub-layer. The upstream to downstream direction is the material flow direction within the hydrogenation reactor; that is, the pore volume of the protective agent in the sub-layer closer to the catalyst layer is smaller, thereby causing the pore volume of the protective agent in the protective layer to gradually decrease along the material flow direction within the hydrogenation reactor.

[0032] In some specific embodiments, the above-mentioned protective layer includes two protective sub-layers, namely a first protective sub-layer and a second protective sub-layer, which are distributed sequentially along the material flow direction of the hydrogenation reactor. That is, the first protective sub-layer, the second protective sub-layer, and the catalyst layer are distributed sequentially along the material flow direction in the hydrogenation reactor. The pore volume of the protective agent in the first protective sub-layer is greater than the pore volume of the protective agent in the second protective sub-layer.

[0033] Specifically, the pore volume of the aforementioned protective agent may be not less than 0.4 ml / g, and more particularly, not less than 0.5 ml / g. For example, the pore volume of the aforementioned protective agent may be, for example, a range consisting of 0.4 ml / g, 0.5 ml / g, 0.6 ml / g, 0.7 ml / g, 0.8 ml / g, 0.9 ml / g, 1 ml / g, or any combination thereof.

[0034] It is understood that when the protective layer includes at least two protective sublayers (such as a first protective sublayer and a second protective sublayer), the pore volume of the protective agent in each sublayer is not less than 0.4 ml / g, and may be not less than 0.5 ml / g.

[0035] Specifically, the difference in pore volume of the protective agent in two adjacent protective sublayers (such as the difference in pore volume between the protective agent in the first protective sublayer and the protective agent in the second protective sublayer) can be, for example, 0.1 to 0.5 ml / g, such as 0.1 ml / g, 0.2 ml / g, 0.3 ml / g, 0.4 ml / g, 0.5 ml / g, or any combination thereof, but is not limited thereto.

[0036] For example, the pore volume of the first protective sublayer is greater than 0.6 ml / g, for example, 0.65 ml / g to 0.9 ml / g, and the pore volume of the second protective sublayer is less than 0.6 ml / g, for example, 0.4 ml / g to 0.58 ml / g.

[0037] Generally, the specific surface area of ​​the protective agent in the protective layer tends to increase along the material flow direction in the hydrogenation reactor. This increasing trend can include gradual increase or gradient increase (or stepwise increase, stepwise increase), that is, the specific surface area of ​​the protective agent in the protective layer can gradually increase or gradient increase along the material flow direction in the hydrogenation reactor.

[0038] In the aforementioned at least two protective sublayers, the specific surface area of ​​the protective agent in each sublayer may remain constant or increase along the material flow direction. In some specific embodiments, in two adjacent protective sublayers, the specific surface area of ​​the protective agent in the upstream sublayer is smaller than that in the downstream sublayer; that is, the specific surface area of ​​the protective agent in the sublayer closer to the catalyst layer is larger, thereby causing the specific surface area of ​​the protective agent in the protective layer to gradually increase along the material flow direction within the hydrogenation reactor.

[0039] For example, the specific surface area of ​​the protective agent in the first protective sublayer is smaller than that of the protective agent in the second protective sublayer.

[0040] Specifically, the specific surface area of ​​the aforementioned protective agent can be 50–100 m². 2 / g, for example 50m 2 / g、55m 2 / g、60m 2 / g、65m 2 / g、70m 2 / g、75m 2 / g、80m 2 / g、85m 2 / g、90m 2 / g、95m 2 / g, 100m 2 / g or a range consisting of any two of them.

[0041] It is understandable that when the protective layer includes at least two protective sublayers (such as a first protective sublayer and a second protective sublayer), the specific surface area of ​​the protective agent in each sublayer can be 50–100 m². 2 / g.

[0042] Specifically, the difference in specific surface area of ​​the protective agent in two adjacent protective sublayers (such as the difference in specific surface area between the protective agent in the first protective sublayer and the protective agent in the second protective sublayer) can, for example, be 10–25 m². 2 / g, such as 10m 2 / g、12m 2 / g, 15m 2 / g、18m 2 / g、20m 2 / g、22m 2 / g、25m 2 / g or a range consisting of any two of them, but not limited to this.

[0043] For example, the specific surface area of ​​the first protective sublayer is no greater than 74 m². 2 / g, for example, 55-74m 2 / g, the specific surface area of ​​the second protective sublayer is greater than 74m² 2 / g, for example, 75-100m 2 / g.

[0044] Specifically, the aforementioned protective agent may include a first carrier and a first active metal, wherein the first active metal may include one or more of nickel, cobalt, molybdenum, and tungsten, and the first carrier may include inorganic materials and / or molecular sieves, wherein the inorganic material may specifically be an amorphous inorganic porous material.

[0045] In some embodiments, the inorganic material may include one or more of alumina, amorphous aluminum silicate (ASA), titanium dioxide, zirconium dioxide, silicon dioxide, Al2O3-SiO2 composite oxide, Al2O3-TiO2 composite oxide, Al2O3-ZrO2 composite oxide, ZrO2-TiO2 composite oxide, and TiO2-SiO2 composite oxide; the molecular sieve may include one or more of Y molecular sieve, ZSM-5, ZSM-22, ZSM-23, ZSM-35, Beta, and ZSM-48.

[0046] Specifically, the mass percentage of the first active metal in the protective agent is 0 to 10%, for example, 0% (i.e., the protective agent does not contain the first active metal), 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination thereof.

[0047] Generally, when the protective agent contains a first active metal (i.e., the mass percentage of the first active metal is not 0), the protective layer also has certain desulfurization and denitrification functions, which is beneficial to further improve the efficiency of hydrogenation treatment.

[0048] When the protective layer includes at least two protective sublayers, the type of the first carrier, the type of the first active metal, and the mass percentage of the first active metal in these protective sublayers may be the same or different.

[0049] In some embodiments, the mass percentage of the first active metal of the protective agent in the protective layer remains constant or increases along the material flow direction in the hydrogenation reactor. The increasing trend may include a gradual increase or a gradient increase, that is, the mass percentage of the first active metal of the protective agent in the protective layer may remain constant, gradually increase, or increase gradient along the material flow direction in the hydrogenation reactor.

[0050] Specifically, when the protective layer includes at least two protective sublayers, the mass percentage of the first active metal in each protective sublayer can remain unchanged or increase along the material flow direction.

[0051] For example, the mass percentage of the first active metal in each protective sublayer is substantially the same (i.e., constant) along the material flow direction, and the mass percentage of the first active metal in any two adjacent protective sublayers is substantially the same, thereby ensuring that the mass percentage of the first active metal of the protective agent in the protective layer remains constant along the material flow direction in the hydrogenation reactor; or, in these protective sublayers, the mass percentage of the first active metal is higher in the protective sublayer closer to the catalyst layer, thereby causing the mass percentage of the first active metal of the protective agent in the protective layer to show an increasing trend.

[0052] For example, the protective agent in the first protective sublayer does not contain the first active metal (i.e., the mass percentage of the first active metal therein is 0), and the mass percentage of the second active metal in the protective agent in the second protective sublayer is 0 or greater than 0, for example, 5 to 10%, but is not limited thereto.

[0053] In the above-mentioned gradation method, the total acid content of the catalyst in the catalyst layer shows a trend of first increasing and then decreasing along the material flow direction in the hydrogenation reactor. The increase in the trend of first increasing and then decreasing can be a gradual increase or a gradient increase, and the decrease can be a gradual decrease or a gradient decrease. That is, the trend of first increasing and then decreasing can specifically include first gradually increasing and then gradually decreasing, first gradually increasing and then gradually decreasing, first gradient increasing and then gradually decreasing, or first gradient increasing and then gradient decreasing.

[0054] Specifically, the catalyst layer may include at least two catalyst sublayers distributed sequentially along the material flow direction in the hydrogenation reactor. The total acid content of the catalyst in each catalyst sublayer may remain unchanged, increase, decrease, or increase first and then decrease, etc., and the distribution of the total acid content of the catalyst in these catalyst sublayers satisfies the condition that the total acid content of the catalyst in the catalyst layer increases first and then decreases along the material flow direction in the hydrogenation reactor.

[0055] For example, the catalyst layer mentioned above includes three catalyst sublayers, namely the first catalyst sublayer, the second catalyst sublayer, and the third catalyst sublayer. The protective layer, the first catalyst sublayer, the second catalyst sublayer, and the third catalyst sublayer are distributed sequentially along the material flow direction. The total acid content of the catalyst in the first catalyst sublayer is lower than that in the second catalyst sublayer, and the total acid content of the catalyst in the second catalyst sublayer is higher than that in the third catalyst sublayer. As a result, the total acid content of the catalyst in the catalyst layer shows a trend of first increasing and then decreasing along the material flow direction.

[0056] The types of acids in catalysts are divided into According to the inventors' research, by appropriately adjusting the number and strength of acid centers in the catalyst, the desulfurization and denitrification activities of the catalyst can be further adjusted. However, the amount of acid in the catalyst also affects the liquid yield. Excessive acid in the catalyst and excessive acidity will intensify the cracking reaction and lead to a decrease in liquid yield. Insufficient acid in the catalyst will result in low conversion rate of raw materials and high sulfur and nitrogen content in the liquid product. Taking all these factors into consideration, in order to simultaneously improve the liquid yield and the desulfurization and denitrification effects of the liquid product, in some preferred embodiments, the total acid content of the catalyst can be controlled to be 0.2–20 μmol / g, for example, 0.2 μmol / g, 0.3 μmol / g, 0.5 μmol / g, 0.8 μmol / g, 1 μmol / g, 1.5 μmol / g, 2 μmol / g, 2.5 μmol / g, 3 μmol / g, 4 μmol / g, 5 μmol / g, 6 μmol / g, 7 μmol / g, 8 μmol / g, 9 μmol / g, 10 μmol / g, 11 μmol / g, 12 μmol / g, 13 μmol / g, 14 μmol / g, 15 μmol / g, 16 μmol / g, 17 μmol / g, 18 μmol / g, 19 μmol / g, 20 μmol / g, or any combination thereof.

[0057] It is understandable that when the catalyst layer includes at least two catalyst sublayers (such as the first, second, and third catalyst sublayers mentioned above), the total acid content of the catalyst in each catalyst sublayer is 0.2–20 μmol / g, and the total acid content of the catalyst in the catalyst layer shows a trend of first increasing and then decreasing along the material flow direction in the hydrogenation reactor.

[0058] Specifically, the difference in the total acidity of the catalyst in two adjacent catalytic sublayers can be 5 to 20 μmol / g, for example, 5 μmol / g, 8 μmol / g, 10 μmol / g, 12 μmol / g, 15 μmol / g, 18 μmol / g, 20 μmol / g, or any combination thereof.

[0059] The difference between the total acid content of the catalyst in the first catalyst layer and the total acid content of the catalyst in the second catalyst layer can be greater than, equal to, or less than the difference between the total acid content of the catalyst in the second catalyst layer and the total acid content of the catalyst in the third catalyst layer.

[0060] For example, the difference between the total acidity of the catalyst in the first catalyst sublayer and the total acidity of the catalyst in the second catalyst sublayer can be 9 to 20 mmol / g, and the difference between the total acidity of the catalyst in the second catalyst sublayer and the total acidity of the catalyst in the third catalyst sublayer can be 5 to 8 μmol / g.

[0061] Further research revealed that the amount of weak acid in the catalyst layer exhibits a trend of first increasing and then decreasing along the material flow direction within the hydrogenation reactor. Specifically, the increase can be a gradual increase or a gradient increase, and the decrease can be a gradual decrease or a gradient decrease. In other words, the trend of first increasing and then decreasing can specifically include first gradually increasing and then gradually decreasing, first gradually increasing and then gradually decreasing, first gradient increasing and then gradually decreasing, or first gradient increasing and then gradually decreasing.

[0062] In some preferred embodiments, the amount of weak acid in the catalyst can be 0.1 to 15 μmol / g, for example, 0.1 μmol / g, 0.2 μmol / g, 0.5 μmol / g, 0.8 μmol / g, 1 μmol / g, 1.5 μmol / g, 2 μmol / g, 2.5 μmol / g, 3 μmol / g, 4 μmol / g, 5 μmol / g, 6 μmol / g, 7 μmol / g, 8 μmol / g, 9 μmol / g, 10 μmol / g, 11 μmol / g, 12 μmol / g, 13 μmol / g, 14 μmol / g, 15 μmol / g, or any combination thereof.

[0063] It is understandable that when the catalyst layer includes at least two catalyst sublayers (such as the first catalyst sublayer, the second catalyst sublayer, and the third catalyst sublayer mentioned above), the amount of weak acid in the catalyst in each catalyst sublayer is 0.1 to 15 μmol / g, and the amount of weak acid in the catalyst in the catalyst layer shows a trend of first increasing and then decreasing along the material flow direction in the hydrogenation reactor.

[0064] Specifically, the difference in the amount of weak acid in the catalyst in two adjacent catalytic sublayers can be 4 to 10, for example, 4 μmol / g, 5 μmol / g, 6 μmol / g, 7 μmol / g, 8 μmol / g, 9 μmol / g, 10 μmol / g or any combination thereof.

[0065] For example, the difference between the total acidity of the catalyst in the first catalyst layer and the total acidity of the catalyst in the second catalyst layer can be 6 to 10 mmol / g, and the difference between the total acidity of the catalyst in the second catalyst layer and the total acidity of the catalyst in the third catalyst layer can be 4 to 5 μmol / g.

[0066] The difference between the amount of weak acid in the catalyst in the first catalyst layer and the amount of weak acid in the catalyst in the second catalyst layer can be greater than, equal to, or less than the difference between the amount of weak acid in the catalyst in the second catalyst layer and the amount of weak acid in the catalyst in the third catalyst layer.

[0067] Specifically, the acids in a catalyst can be classified into weak acids, moderately strong acids, and strong acids according to their acid strength. The amount of weak acid in the catalyst is the amount of weak acid, and the total amount of acid in the catalyst is the sum of the amounts of weak acid, moderately strong acid, and strong acid in the catalyst. This invention allows for the determination of the acid content and acid strength of catalysts using conventional methods in the art. For example, the acid content and acid strength of catalysts can be determined using the ammonia-programmed temperature desorption (NH3-TPD) characterization method. On the NH3-TPD desorption chart, the amount of ammonia desorbed between 100°C and 230°C corresponds to the amount of weak acid, the amount of ammonia desorbed between 230°C and 370°C corresponds to the amount of medium-strong acid, and the amount of ammonia desorbed above 370°C corresponds to the amount of strong acid. Specific operating methods generally include: purging the catalyst sample with helium at 500°C for 1 hour, then cooling to 60°C, introducing saturated ammonia vapor, and performing pulse adsorption five times to reach equilibrium; heating to 100°C and purging for 2 hours, then performing ammonia desorption by programmed temperature increase at a rate of 10°C / min, until reaching 650°C; absorbing the desorbed ammonia with hydrochloric acid solution, and then titrating the excess hydrochloric acid with sodium hydroxide solution. The amount of hydrochloric acid consumed in absorbing ammonia is used to define the amounts of weak acid, medium-strong acid, strong acid, and total acid in the catalyst.

[0068] Furthermore, the mass percentage of the second active metal in the catalyst layer increases along the material flow direction within the hydrogenation reactor. This increasing trend can specifically include a gradual increase or a gradient increase, meaning that the mass percentage of the second active metal in the catalyst layer can gradually increase or a gradient increase along the material flow direction within the hydrogenation reactor.

[0069] When the catalyst layer comprises at least two catalyst sublayers, the mass percentage of the second active metal in each catalyst sublayer can remain constant or increase along the material flow direction. In some specific embodiments, in two adjacent catalyst sublayers, the mass percentage of the second active metal in the upstream sublayer is less than that in the downstream sublayer. That is, the mass percentage of the second active metal in the catalyst sublayer further away from the protective layer is greater, thereby causing the mass percentage of the second active metal in the catalyst layer to increase gradually along the material flow direction within the hydrogenation reactor.

[0070] For example, the mass percentage of the second active metal in the catalyst in the first catalyst layer is less than that in the second catalyst layer, and the mass percentage of the second active metal in the catalyst in the second catalyst layer is less than that in the third catalyst layer, thereby causing the mass percentage of the second active metal in the catalyst layer to increase gradually along the material flow direction.

[0071] Specifically, the mass percentage of the second active metal in the catalyst can be 10-40% (i.e., the mass of the second active metal accounts for 10-40% of the total mass of the catalyst), for example, a range of 10%, 15%, 20%, 25%, 30%, 35%, 40% or any two of these. The second active metal may include one or more of Co, Mo, Ni and W.

[0072] It is understandable that when the catalyst layer includes at least two catalyst sublayers (such as the first catalyst sublayer, the second catalyst sublayer, and the third catalyst sublayer mentioned above), the mass percentage of the second active metal of the catalyst in each catalyst sublayer is 10% to 40%, and the mass percentage of the second active metal of the catalyst in the catalyst layer first increases along the material flow direction in the hydrogenation reactor.

[0073] Specifically, the difference in the mass percentage of the second active metal of the catalyst in two adjacent catalyst sublayers (such as the first catalyst sublayer and the second catalyst sublayer, or the second catalyst sublayer and the third catalyst sublayer, etc.) can be 5% to 28%, for example, 5%, 7%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, or any combination thereof.

[0074] The difference in the mass percentage of the second active metal in the catalyst between the first and second catalyst layers can be greater than, equal to, or less than the difference in the mass percentage of the second active metal in the catalyst between the second and third catalyst layers.

[0075] Furthermore, the pore volume of the catalyst can be 0.2 to 0.6 ml / g, for example, 0.2 ml / g, 0.3 ml / g, 0.4 ml / g, 0.5 ml / g, 0.6 ml / g, or any combination thereof.

[0076] It is understood that when the catalyst layer includes at least two catalyst sublayers (such as the first catalyst sublayer, the second catalyst sublayer, and the third catalyst sublayer mentioned above), the pore volume of the catalyst in each catalyst sublayer can be 0.2 to 0.6 ml / g, and the pore volumes of the catalyst in these catalyst sublayers can be the same or different.

[0077] Generally, the pore volume of the catalyst in the catalyst layer decreases along the material flow direction in the hydrogenation reactor, which can be gradually or gradually reduced.

[0078] When the catalyst layer includes at least two catalyst sublayers (such as the first catalyst sublayer, the second catalyst sublayer, and the third catalyst sublayer mentioned above), the pore volume of the catalyst in each catalyst sublayer can remain unchanged or decrease along the material flow direction.

[0079] In some specific embodiments, in two adjacent catalyst sublayers, the pore volume of the catalyst in the upstream sublayer is greater than that in the downstream sublayer. That is, the pore volume of the catalyst in the catalyst sublayer further away from the protective layer is smaller, thereby causing the pore volume of the catalyst in the catalyst layer to decrease gradually along the material flow direction in the hydrogenation reactor.

[0080] For example, the pore volume of the catalyst in the first catalyst layer is greater than that in the second catalyst layer, and the pore volume of the catalyst in the second catalyst layer is greater than that in the third catalyst layer, thereby causing the pore volume of the catalyst in the catalyst layer to decrease gradually along the material flow direction.

[0081] Specifically, the difference in pore volume of the catalyst in two adjacent catalyst sublayers (such as the first catalyst sublayer and the second catalyst sublayer, or the second catalyst sublayer and the third catalyst sublayer, etc.) can be 0.05% to 0.25%, for example, 0.05%, 0.07%, 0.1%, 0.12%, 0.15%, 0.18%, 0.22%, 0.25%, or any combination thereof.

[0082] The difference between the pore volume of the catalyst in the first catalyst layer and the pore volume of the catalyst in the second catalyst layer can be greater than, equal to or less than the difference between the pore volume of the catalyst in the second catalyst layer and the pore volume of the catalyst in the third catalyst layer.

[0083] In addition, the catalyst also includes a second support, which may include inorganic materials and / or molecular sieves, specifically amorphous inorganic porous materials.

[0084] In some embodiments, the inorganic material may include one or more of alumina, amorphous aluminum silicate (ASA), titanium dioxide, zirconium dioxide, silicon dioxide, Al2O3-SiO2, Al2O3-TiO2 composite oxide, Al2O3-ZrO2 composite oxide, ZrO2-TiO2 composite oxide, and TiO2-SiO2 composite oxide; the molecular sieve may include one or more of Y molecular sieve, ZSM-5, ZSM-22, ZSM-23, ZSM-35, Beta, and ZSM-48.

[0085] Furthermore, the mass percentage of inorganic materials in the catalyst can be 50% to 90% (i.e., the mass of inorganic materials accounts for 50% to 90% of the total mass of the catalyst), for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any combination thereof; and the mass percentage of molecular sieves in the catalyst can be 0% to 10% (i.e., the mass of molecular sieves accounts for 0% to 10% of the total mass of the catalyst), for example, 0% (i.e., the catalyst does not contain molecular sieves), 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination thereof.

[0086] In addition, the catalyst may also include an acidic promoter, and the mass percentage of the acidic promoter in the catalyst may be 0.5% to 3% (i.e., the mass of the acidic promoter accounts for 0.5% to 3% of the total mass of the catalyst), for example, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, or any combination thereof.

[0087] Specifically, acidic additives may include one or more of phosphoric acid, boric acid, hydrofluoric acid, nitric acid, citric acid, tartaric acid, and malic acid.

[0088] When the catalyst layer includes at least two catalyst sublayers, the composition of the second active metal, the mass percentage of the second active metal, the type of the second support (inorganic material / molecular sieve), the mass percentage of the second support (inorganic material / molecular sieve), the type of acidic additive, and the mass percentage of the acidic additive in these catalyst sublayers can be the same or different.

[0089] Furthermore, the volume of the aforementioned protective layer can account for 2% to 20% of the sum of the volumes of the protective layer and the catalyst layer, for example, 2%, 5%, 7%, 10%, 12%, 15%, 18%, 20%, or any combination thereof, and the volume of the catalyst layer can account for 80% to 98% of the sum of the volumes of the protective layer and the catalyst layer, for example, 80%, 82%, 85%, 88%, 90%, 93%, 95%, 98%, or any combination thereof.

[0090] Generally, in the aforementioned protective layer and catalyst layer, the volume ratio of the protective layer is approximately equal to its length (or thickness) ratio in the material flow direction, and the volume ratio of the catalyst layer is approximately equal to its length (or thickness) ratio in the material flow direction. That is, the length (thickness) of the protective layer in the material flow direction is L1, and the length (thickness) of the catalyst layer in the material flow direction is L2. L1 / (L1+L2) is equal to the ratio of the volume of the protective layer to the sum of the volumes of the protective layer and the catalyst layer, i.e., L1 / (L1+L2) is 2-20%, and L2 / (L1+L2) is equal to the ratio of the volume of the catalyst layer to the sum of the volumes of the protective layer and the catalyst layer, i.e., L2 / (L1+L2) is 80-98%.

[0091] When the protective layer includes at least two protective sublayers, the volume of the protective layer refers to the sum of the volumes of these protective sublayers, and the length (thickness) of the protective layer refers to the sum of the lengths (thicknesses) of these protective sublayers; when the catalyst layer includes at least two catalyst sublayers, the volume of the catalyst layer refers to the sum of the volumes of these catalyst sublayers, and the length (thickness) of the catalyst layer refers to the sum of the lengths (thicknesses) of these catalyst sublayers.

[0092] When the protective layer comprises at least two protective sublayers, the proportion of the volume of each of these protective sublayers to the sum of the volumes of the protective layer and the catalyst layer may be the same or different. For example, when the protective layer comprises a first protective sublayer and a second protective sublayer, the proportion of the volume of the first protective sublayer to the sum of the volumes of the protective layer and the catalyst layer is a1, and the proportion of the volume of the second protective sublayer to the sum of the volumes of the protective layer and the catalyst layer is a2. a1 may be greater than, equal to, or less than a2. For example, a1 and a2 may each be 2% to 15%, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any combination thereof.

[0093] When the protective layer comprises at least two catalyst sublayers, the proportion of the volume of each of these catalyst sublayers to the sum of the volumes of the protective layer and the catalyst layer can be the same or different. For example, when the catalyst layer comprises a first catalyst sublayer, a second catalyst sublayer, and a third catalyst sublayer, the proportion of the volume of the first catalyst sublayer to the sum of the volumes of the protective layer and the catalyst layer is b1, the proportion of the volume of the second catalyst sublayer to the sum of the volumes of the protective layer and the catalyst layer is b2, and the proportion of the volume of the third catalyst sublayer to the sum of the volumes of the protective layer and the catalyst layer is b3. b1 can be greater than, equal to, or less than b2, b2 can be greater than, equal to, or less than b3, and b1 can be greater than, equal to, or less than b3. For example, b1, b2, and b3 can each be 15% to 45%, for example, a range of 15%, 20%, 25%, 30%, 35%, 40%, 45%, or any combination thereof.

[0094] The hydrogenation reactor of this invention can be a conventional structure in the art, wherein each protective sublayer and each catalyst sublayer is a bed of the hydrogenation reactor. That is, the hydrogenation reactor can have a multi-layer bed composed of at least two protective sublayers and at least two catalyst sublayers. Any two adjacent beds can be separated by structures such as trays or distribution plates for distributing packing materials (such as protective agents or catalysts) into the hydrogenation reactor to form a bed.

[0095] The oil hydrotreating method provided in this embodiment of the invention includes: introducing the oil to be treated into a hydrotreating reactor and contacting it with a protective agent and a catalyst for hydrotreating, wherein the protective agent and catalyst in the hydrotreating reactor are loaded according to the above-mentioned gradation method, and the flow direction of the oil to be treated in the hydrotreating reactor is the same as the material flow direction in the hydrotreating reactor, that is, after the oil to be treated enters the hydrotreating reactor, it first flows through the protective layer and then flows through the catalyst layer.

[0096] Generally, the above-mentioned hydrotreating is carried out in the presence of hydrogen. Specifically, the oil to be treated can be mixed with hydrogen before entering the hydrotreating reactor, where it will come into contact with the protective agent and catalyst in sequence for hydrotreating. During the hydrotreating process, desulfurization, denitrification, and aromatic saturation ring opening reactions will occur, thereby achieving the lightening of the oil to be treated, as well as desulfurization, denitrification, removal of residual carbon and metals, and improving the liquid yield.

[0097] In some embodiments, the conditions for the above-mentioned hydrogenation treatment can be: a reaction pressure of 6–15 MPa, for example, a range of 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, or any combination thereof; a reaction temperature of 300–400 °C, for example, a range of 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 370 °C, 380 °C, 390 °C, 400 °C, or any combination thereof; and a volume hourly space velocity of 0.5–2.0 h⁻¹. -1 For example, 0.5h -1 0.8h -1 1h -1 1.2h -1 1.5h -1 1.8h -1 2h -1 or a range consisting of any two of them, with a hydrogen-to-oil volume ratio of (100 to 1000):1, for example 100:1, 200:1, 300:1, 400:1, 500:1, 600:1, 700:1, 800:1, 900:1, 1000:1 or a range consisting of any two of them.

[0098] In some embodiments, the sulfur mass percentage in the oil to be treated is 0.3% to 2%, for example, a range consisting of 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, or any two of these. The nitrogen mass percentage in the oil to be treated can be 0.1% to 1%, for example, a range consisting of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any two of these.

[0099] The oil products to be treated may include wax oil, specifically one or more of coking wax oil (CGO), vacuum wax oil (VGO), coking diesel oil, and under-wax oil. The hydrotreating method of this embodiment can improve the desulfurization, denitrification, residual carbon removal, and demetallization efficiency of these oil products to be treated, and increase the liquid yield.

[0100] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0101] In Examples 1 to 3 and Comparative Examples 1 to 3 below, a feedstock oil (oil to be treated) was prepared by mixing CGO and VGO in a volume ratio of 1:1. After being mixed with hydrogen, the feedstock oil entered the hydrogenation reactor and flowed sequentially through the protective layer and the catalyst layer for hydrogenation reaction treatment. The properties of the feedstock oil are shown in Table 1.

[0102] Table 1 Properties of Crude Oil

[0103]

[0104] In Examples 1 to 3 and Comparative Examples 1 to 3 below, the feedstock oil flows from top to bottom in the hydrotreating reactor (i.e., the material flow direction in the hydrotreating reactor is from top to bottom); in the hydrotreating reactor, the protective layer includes a first protective sub-layer (upper protective layer) and a second protective sub-layer (lower protective layer), and the catalyst layer includes a first catalyst sub-layer (upper catalyst layer), a second catalyst sub-layer (middle catalyst layer), and a third catalyst sub-layer (lower catalyst layer), and the upper protective layer, lower protective layer, upper catalyst layer, middle catalyst layer, and lower catalyst layer are distributed sequentially along the material flow direction;

[0105] The pore volume, specific surface area, first carrier, type and content of first active metal, and filling ratio (the ratio of the volume of each protective sublayer to the sum of the volumes of the protective layer and the catalyst layer) of each embodiment and comparative example are shown in Table 2. Additionally, the type and content of second active metal, type and content of inorganic material, type and content of molecular sieve, acidic additive and its content, total acid content, weak acid content, pore volume, and filling ratio (the ratio of the volume of each catalyst sublayer to the sum of the volumes of the protective layer and the catalyst layer) of each catalyst sublayer are also shown in Table 2. All contents are mass percentages.

[0106] In Comparative Example 1, a single protective agent was used (i.e., the same protective agent was used in the upper and lower protective layers), and the total acid content of the catalyst layer remained unchanged along the material flow direction (i.e., the total acid content of the catalyst in the upper, middle, and lower catalyst layers was the same).

[0107] In Comparative Example 2, a single protective agent was used (i.e., the same protective agent was used in the upper and lower protective layers), and the total acid content of the catalyst layer increased along the material flow direction (i.e., the total acid content of the catalyst in the upper, middle and lower catalyst layers increased sequentially).

[0108] In Comparative Example 3, a single protective agent was used (i.e., the same protective agent was used in both the upper and lower protective layers), and the total acid content of the catalyst layer decreased along the material flow direction (i.e., the total acid content of the catalyst in the upper, middle, and lower catalyst layers decreased sequentially).

[0109] Furthermore, the hydrogenation conditions in the hydrogenation reactors of all embodiments and comparative examples are the same, specifically: a reaction temperature of 370°C, a reaction pressure of 12 MPa, and a liquid hourly space velocity of 1.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 600:1.

[0110] In addition, the hydrogenation treatment results of each embodiment and comparative example are shown in Table 3 (including the density, sulfur content, nitrogen content, residual carbon content, metal (mainly Fe, Ni, V) content and liquid yield of the liquid product).

[0111] Table 2 Catalyst gradation in the hydrogenation reactor

[0112]

[0113] Table 3 Results of Hydrogenation Treatment

[0114]

[0115] As can be seen, compared with Comparative Examples 1-3, Examples 1-3 can significantly improve the efficiency of desulfurization, denitrification, residual carbon removal and metal removal, while also improving the liquid yield.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for grading a catalyst for oil hydrotreating, characterized in that, include: Along the material flow direction inside the hydrogenation reactor, a protective layer and a catalyst layer are sequentially packed inside the hydrogenation reactor. The protective layer includes a protective agent, and the pore volume of the protective agent in the protective layer decreases along the material flow direction within the hydrogenation reactor. The catalyst layer includes a catalyst, and the total acid content of the catalyst in the catalyst layer shows a trend of first increasing and then decreasing along the material flow direction in the hydrogenation reactor. The catalyst includes a second active metal, and the mass percentage of the second active metal in the catalyst layer increases along the material flow direction in the hydrogenation reactor. The total acid content of the catalyst is 0.2~20 μmol / g; The catalyst has a weak acid content of 0.1~15 μmol / g; The amount of weak acid in the catalyst in the catalyst layer shows a trend of first increasing and then decreasing along the material flow direction in the hydrogenation reactor. The catalyst has a pore volume of 0.2~0.6 ml / g.

2. The method for grading the catalyst for oil hydrotreating according to claim 1, characterized in that, The reduction trend described in the protective layer includes gradual reduction or gradient reduction; And / or, the specific surface area of ​​the protective agent in the protective layer tends to increase along the material flow direction within the hydrogenation reactor.

3. The method for grading the catalyst for oil hydrotreating according to claim 2, characterized in that, The increasing trend of the specific surface area of ​​the protective agent in the protective layer includes a gradual increase or a gradient increase.

4. The method for grading the catalyst for oil hydrotreating according to claim 1 or 2, characterized in that, The pore volume of the protective agent is not less than 0.4 ml / g.

5. The method for grading the catalyst for oil hydrotreating according to claim 1, characterized in that, The protective agent comprises a first carrier and a first active metal, wherein, The mass percentage of the first active metal in the protective agent is 0-10%; The first active metal includes one or more of nickel, cobalt, molybdenum, and tungsten; The first carrier includes inorganic materials and / or molecular sieves; The mass percentage of the first active metal in the protective agent in the protective layer remains unchanged or increases along the material flow direction in the hydrogenation reactor.

6. The method for grading the catalyst for oil hydrotreating according to claim 5, characterized in that, The inorganic material includes one or more of the following: alumina, amorphous aluminum silica, titanium dioxide, zirconium dioxide, silicon dioxide, Al2O3-SiO2 composite oxide, Al2O3-TiO2 composite oxide, Al2O3-ZrO2 composite oxide, ZrO2-TiO2 composite oxide, and TiO2-SiO2 composite oxide; the molecular sieve includes one or more of the following: Y molecular sieve, ZSM-5, ZSM-22, ZSM-23, ZSM-35, Beta, and ZSM-48.

7. The method for grading the catalyst for oil hydrotreating according to claim 5, characterized in that, The increasing trend of the mass percentage of the first active metal in the protective agent in the protective layer includes a gradual increase or a gradient increase.

8. The method for grading the catalyst for oil hydrotreating according to claim 1, characterized in that, The second active metal includes one or more of Co, Mo, Ni, and W; And / or, the mass percentage of the second active metal in the catalyst is 10-40%; And / or, the catalyst further includes a second support, the second support comprising an inorganic material and / or a molecular sieve. And / or, the catalyst further includes an acidic auxiliary agent, wherein the mass percentage of the acidic auxiliary agent in the catalyst is 0.5-3%, and / or, the acidic auxiliary agent comprises one or more of phosphoric acid, boric acid, hydrofluoric acid, nitric acid, citric acid, tartaric acid, and malic acid.

9. The method for grading the catalyst for oil hydrotreating according to claim 8, characterized in that, The inorganic material includes one or more of the following: alumina, amorphous aluminum silica, titanium dioxide, zirconium dioxide, silicon dioxide, Al2O3-SiO2, Al2O3-TiO2 composite oxide, Al2O3-ZrO2 composite oxide, ZrO2-TiO2 composite oxide, and TiO2-SiO2 composite oxide; the molecular sieve includes one or more of the following: Y molecular sieve, ZSM-5, ZSM-22, ZSM-23, ZSM-35, Beta, and ZSM-48.

10. The method for grading the catalyst for oil hydrotreating according to claim 8, characterized in that, The inorganic material in the catalyst has a mass percentage of 50-90%, and the molecular sieve in the catalyst has a mass percentage of 0-10%; the sum of all components in the catalyst is 100%.

11. The method for grading the catalyst for oil hydrotreating according to claim 1, characterized in that, The trend of first increasing and then decreasing in the total acid content of the catalyst in the catalyst layer includes first gradually increasing and then gradually decreasing, first gradually increasing and then gradually decreasing, first gradually increasing and then gradually decreasing, or first gradually increasing and then gradually decreasing. The increasing trend of the mass percentage of the second active metal in the catalyst in the catalyst layer includes a gradual increase or a gradient increase.

12. The method for grading the catalyst for oil hydrotreating according to claim 1, characterized in that, The volume of the protective layer accounts for 2-20% of the sum of the volumes of the protective layer and the catalyst layer, and / or the volume of the catalyst layer accounts for 80-98% of the sum of the volumes of the protective layer and the catalyst layer.

13. A method for hydrotreating oil, characterized in that, include: The oil to be treated is introduced into a hydrotreating reactor to contact with a protective agent and a catalyst for hydrotreating. The protective agent and the catalyst in the hydrotreating reactor are loaded according to the gradation method described in any one of claims 1-12, and the flow direction of the oil to be treated in the hydrotreating reactor is the same as the material flow direction in the hydrotreating reactor.

14. The method for hydrotreating oil products according to claim 13, characterized in that, The conditions for the hydrogenation treatment are: reaction pressure of 6-15 MPa, reaction temperature of 300-400 °C, and volume hourly space velocity of 0.5-2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (100~1000):1; And / or, the oil to be processed includes one or more of coking wax oil (CGO), vacuum wax oil (VGO), coking diesel oil and under-wax oil; And / or, the sulfur content in the oil to be treated is 0.3-2% by mass; and / or, the nitrogen content in the oil to be treated is 0.1-1% by mass.

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