Hydroprocessing of diesel and systems

Abstract

The present application relates to the field of oil refining and chemical industry, and discloses a diesel oil hydrogenation method and system. The diesel oil hydrogenation method comprises the following steps: (1) carrying out a gas phase desulfurization reaction on diesel oil in a gas phase hydrogenation reactor in the presence of hydrogen to obtain a gas phase desulfurization reaction product; (2) carrying out gas-liquid separation on the gas phase desulfurization reaction product to obtain a gas phase component and a liquid phase component; and (3) carrying out pressurization and hydrogen mixing on the liquid phase component, and then carrying out a liquid phase de-aromatics reaction on the liquid phase component in a liquid phase hydrogenation reactor to obtain a liquid phase de-aromatics reaction product. The method can achieve deep de-aromatics effect on the basis of desulfurization, and can also simplify the process flow, reduce the reaction severity, and reduce energy consumption and hydrogen consumption.

Description

Technical Field

[0001] This invention relates to the field of oil refining and chemical technology, and specifically to a method and system for hydrogenating diesel fuel. Background Technology

[0002] Currently, diesel hydrorefining generally employs a fixed-bed hydrotreating process. With increasingly stringent environmental regulations, in addition to requiring refined diesel to have a sulfur content ≤10 ppm, the 2019 China VI diesel quality standard requires polycyclic aromatic hydrocarbons (PAHs) to be ≤11%, and the 2023 China VIB standard requires PAHs to be ≤5%. However, from the reaction mechanisms of deep desulfurization and deep aromatics removal, the requirements for the reaction environment differ significantly. For desulfurization reactions, the removal of small-molecule sulfur mainly follows the direct desulfurization route, i.e., hydrodesulfurization. Large-molecule sulfides with lower reactivity mainly follow the hydrodesulfurization reaction route, i.e., first hydrogenation of the aromatic rings, then hydrodesulfurization. In the upper part of the reactor, the main processes are the hydrogenation of small-molecule sulfides and nitrides, as well as the conversion of some bicyclic aromatics (exothermic). In the lower part of the reactor, the accumulation of heat and hydrogen sulfide creates a high-temperature, low-hydrogen partial pressure reaction environment, which is unfavorable for the hydrodesulfurization pathway of large-molecule sulfur and for PAH saturation. Especially towards the end of the reaction, the catalyst activity decays. Raising the temperature can compensate for the loss of desulfurization activity, but it will further affect the dearomatization effect. In addition to the different requirements of the two for the reaction environment, the competitive adsorption of aromatics on the catalyst surface also inhibits deep desulfurization, making it difficult for traditional hydrogenation technology to meet the dual requirements of ultra-deep desulfurization and efficient aromatic saturation.

[0003] Meanwhile, existing hydrogenation technologies also suffer from problems such as unnecessary reactant hydrogenation and over-hydrogenation. While there are no limits on nitrogen oxides in diesel fuel, during deep desulfurization and dearomatization, nitrogen oxides are more readily adsorbed onto catalyst surfaces than sulfides and aromatics. Therefore, nitrogen oxides not only significantly inhibit desulfurization and dearomatization reactions but also waste hydrogen resources due to their preferential hydrogenation. Furthermore, diesel fuel only restricts the content of polycyclic aromatic hydrocarbons (PAHs), but during hydrogenation, some monocyclic aromatic hydrocarbons undergo hydrogenation saturation, further wasting hydrogen. Based on these two aspects, the necessity and urgency of upgrading diesel fuel to cleaner production technologies become even more apparent.

[0004] Existing technologies for achieving deep dearomatization employ a two-stage process. After conventional hydrogenation, the product oil is stripped to remove hydrogen sulfide before entering a precious metal hydrogenation reactor. This significantly increases catalyst costs and process complexity, and fails to address the hydrogen waste caused by over-hydrogenation. Alternatively, the feedstock can be divided into light and heavy components. The light component undergoes shallow hydrogenation to minimize monocyclic aromatic saturation, while the heavy component undergoes deep hydrogenation for desulfurization and dearomatization. However, shallow hydrogenation typically uses medium-pressure hydrogenation, increasing overall energy consumption and preventing industrial-scale application.

[0005] Patent application CN108085058A discloses a method for deep dearomatization of hydrocarbon oils. This method employs relatively mild temperature and pressure conditions, allowing feedstock oil and hydrogen to pass through a highly dispersed Pt-Pd / Al2O3 catalyst. The resulting gas phase is compressed and recycled, while the liquid phase is a low-aromatic product. However, the Pt-Pd / Al2O3 hydrogenation catalyst is mainly suitable for dearomatization of low-sulfur diesel feedstocks, and its effect on desulfurization and dearomatization of inferior diesel is not ideal.

[0006] Patent application CN109926067A discloses a platinum-palladium-cobalt ternary metal hydrodearomatics catalyst and its preparation method. This method employs a stepwise impregnation process with active metal precursors, resulting in high utilization of the platinum and palladium noble metals in the prepared catalyst, strong synergistic catalytic activity, and enhanced aromatics hydrotreating performance of the non-noble metal cobalt due to the introduction of platinum and palladium. However, this catalyst is still designed for hydrocarbon oils where sulfur compounds have been largely removed, to avoid the influence of hydrogen sulfide on the deep dearomatics removal of noble metals, and cannot achieve desulfurization and dearomatics removal for low-quality diesel fuel. Summary of the Invention

[0007] The purpose of this invention is to overcome the technical problems of poor hydrodesulfurization and dearomatics removal effects of inferior diesel fuel in the prior art, and to provide a method and system for hydrotreating diesel fuel. This method can achieve deep dearomatic removal while realizing desulfurization, and at the same time, it simplifies the process flow, reduces the severity of the reaction, and reduces energy consumption and hydrogen consumption.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for hydrogenating diesel fuel, wherein the method includes the following steps:

[0009] (1) In the presence of hydrogen, diesel is subjected to gas phase desulfurization reaction in a gas phase hydrogenation reactor to obtain gas phase desulfurization reaction products;

[0010] (2) The gas phase desulfurization reaction products are subjected to gas-liquid separation to obtain gas phase components and liquid phase components;

[0011] (3) The liquid phase components are pressurized and mixed with hydrogen, and then the liquid phase dearomatic reaction is carried out in the liquid phase hydrogenation reactor to obtain the liquid phase dearomatic reaction product.

[0012] A second aspect of the present invention provides a diesel fuel hydrogenation system, wherein the system comprises a gas phase hydrogenation reactor, a gas-liquid separation unit, a pressurization and hydrogen mixing unit, and a liquid phase hydrogenation reactor connected in sequence; the liquid phase component outlet of the gas-liquid separation unit is connected to the inlet of the pressurization and hydrogen mixing unit.

[0013] The gas-phase hydrogenation reactor is used to perform a gas-phase desulfurization reaction on diesel and hydrogen to obtain gas-phase desulfurization reaction products.

[0014] The pressurization and hydrogen mixing unit is used to pressurize and mix the liquid phase components obtained by the gas-liquid separation unit to obtain a pressurized and hydrogen-mixed stream.

[0015] The liquid-phase hydrogenation reactor is used to carry out a liquid-phase dearomatization reaction on the pressurized and mixed hydrogen post-stream to obtain the liquid-phase dearomatization reaction product.

[0016] Compared with the prior art, the method and system of the present invention have the following advantages:

[0017] (1) The method of the present invention places the gas phase desulfurization reaction and the liquid phase dearomatic reaction in different reactors, thus avoiding the defects of placing deep desulfurization and dearomatic removal in the same reaction system and the incompatibility of reaction conditions.

[0018] (2) The inventors discovered that, under preferred conditions, by controlling the reaction conditions of the gas-phase hydrogenation reactor, only the hydrogenation removal reaction of sulfides occurs, thereby separating the desulfurization and dearomatization reactions. The reaction conditions of the gas-phase desulfurization reaction and the liquid-phase dearomatization reaction are controlled separately to improve their respective reaction efficiencies. Under preferred conditions, in the gas-phase hydrogenation reactor, only the low-hydrogen-consumption desulfurization reaction occurs under low-pressure and low-hydrogen-to-oil volume ratio conditions, reducing the hydrogen consumption of the reaction. Moreover, most of the gas-phase components in the effluent no longer undergo further hydrogenation denitrification and dearomatization reactions, further reducing the hydrogen consumption of the reaction. The liquid-phase components obtained after gas-liquid separation undergo a polycyclic aromatic hydrocarbon hydrogenation saturation reaction after pressurization and hydrogen dissolution.

[0019] (3) The method and system provided by the present invention can achieve deep desulfurization and dearomatization of diesel fuel under more moderate operating conditions and a simpler process flow. The entire reaction system does not require the hydrogen compressor in the fixed bed reaction system and the circulating oil pump in the liquid phase hydrogenation reaction system, which reduces investment costs, simplifies the process flow, improves reaction efficiency, and reduces the severity of the reaction.

[0020] (4) The system provided by the present invention replenishes the hydrogen consumed by the liquid phase hydrogenation reactor while pressurizing the pressurization and hydrogen mixing unit. The hydrogen can be used without recycling, eliminating the need for a circulating hydrogen compressor and significantly reducing the investment in equipment construction. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0022] Figure Labels

[0023] Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] The description of exemplary embodiments is intended to be read in conjunction with the accompanying drawings, which are considered an integral part of the entire written description. In this specification, relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “upward,” “downward,” “top,” and “bottom,” and their derivatives (e.g., “horizontally,” “downward,” “upward,” etc.) should be interpreted as referring to the orientation shown in the accompanying drawings as described at the time. These relative terms are for ease of description and do not require the device to be constructed or operated in a particular orientation. Unless otherwise stated, “connection” as used in this invention refers to a relationship in which structures are directly or indirectly fixed or connected to each other via an intermediate structure.

[0026] In this invention, the symbol “≯” indicates not greater than, and the symbol “≮” indicates not less than.

[0027] The first aspect of this invention provides a method for hydrogenating diesel fuel, wherein the method includes the following steps:

[0028] (1) In the presence of hydrogen, diesel is subjected to gas phase desulfurization reaction in a gas phase hydrogenation reactor to obtain gas phase desulfurization reaction products;

[0029] (2) The gas phase desulfurization reaction products are subjected to gas-liquid separation to obtain gas phase components and liquid phase components;

[0030] (3) The liquid phase components are pressurized and mixed with hydrogen, and then the liquid phase dearomatic reaction is carried out in the liquid phase hydrogenation reactor to obtain the liquid phase dearomatic reaction product.

[0031] The method provided by this invention involves a gas-phase desulfurization reaction of diesel fuel in a gas-phase hydrogenation reactor. The gas-phase desulfurization reaction mainly removes small-molecule sulfides. The liquid phase component obtained by gas-liquid separation of the gas-phase desulfurization reaction product is pressurized and mixed with hydrogen before entering the liquid-phase hydrogenation reactor to undergo a deep hydrogenation dearomatic reaction. The method provided by this invention is applicable to any situation where it is necessary to simultaneously remove small-molecule sulfides and large-molecule aromatics.

[0032] In this invention, the hydrogen gas mentioned in step (1) can be any hydrogen-containing gas capable of providing hydrogen, including fresh hydrogen, recycled hydrogen, and hydrogen-rich gas. Those skilled in the art, after understanding the technical solution of this invention, can clearly understand the hydrogen-containing gas described in this invention.

[0033] In this invention, the range of diesel fuel types is relatively wide. Preferably, in step (1), the diesel fuel is selected from at least one of straight-run diesel fuel, catalytic diesel fuel, coking diesel fuel, and fluidized bed residue hydrotreated diesel fuel.

[0034] The terms straight-run diesel, catalytic diesel, coking diesel, and fluidized bed residue hydrotreated diesel used in this invention have conventional meanings in the art, and this invention does not impose any particular limitations on them.

[0035] In this invention, the range of properties of diesel fuel is relatively wide. Preferably, in step (1), the initial boiling point of the diesel fuel is 140-200℃, the final boiling point is 300-400℃, the sulfur content is ≤20000μg / g, preferably ≤15000μg / g, the nitrogen content is ≤1000μg / g, preferably ≤800μg / g, and the polycyclic aromatic hydrocarbon content is ≤50wt%. For example, the sulfur content of the diesel fuel can be, but is not limited to: 8000μg / g, 9000μg / g, 10000μg / g, 11500μg / g, etc., the nitrogen content can be, but is not limited to: 500μg / g, 600μg / g, 700μg / g, etc., and the polycyclic aromatic hydrocarbon content can be, but is not limited to: 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, etc.

[0036] In this invention, the gas-phase desulfurization reactor is filled with a hydrogenation catalyst with desulfurization function. This invention does not specifically limit the type of hydrogenation desulfurization catalyst; those skilled in the art can select one according to actual needs. Preferably, in step (1), the gas-phase desulfurization reaction is carried out in the presence of a hydrogenation desulfurization catalyst, which includes a support and a hydrogenation component.

[0037] In this invention, the range of types of carriers is relatively wide. Preferably, the carrier is an inorganic refractory oxide, which is selected from at least one of alumina, amorphous aluminum silica, silicon dioxide, and titanium oxide, and more preferably alumina.

[0038] In this invention, the selection range of hydrogenation components is relatively wide. Preferably, the hydrogenation components include Group VIII metal components and / or Group VIB metal components. In this invention, the specific types of Group VIII and Group VIB metals are not limited, and those skilled in the art can select them according to actual needs.

[0039] In this invention, preferably, the hydrodesulfurization catalyst is a Mo-Co type hydrodesulfurization catalyst.

[0040] In this invention, preferably, based on the total amount of Mo-Co type hydrodesulfurization catalyst, the content of Mo, calculated as oxide, is 15-30 wt%, and the content of Co, calculated as oxide, is 2-6 wt%.

[0041] In this invention, preferably, the Mo-Co type hydrodesulfurization catalyst further includes an auxiliary component, which is selected from at least one of phosphorus, silicon, boron, magnesium, and fluorine. Preferably, the content of the auxiliary component, calculated as oxides, is 6 wt% or less.

[0042] In this invention, the source of the Mo-Co type hydrodesulfurization catalyst is not limited. For example, it can be prepared by any method conventionally defined in the art, or it can be obtained commercially, such as the FHUDS-5 and / or FHUDS-7 catalysts developed by the Sinopec Fushun Petrochemical Research Institute (FRIPP).

[0043] In this invention, preferably, in step (1), the sulfur content in the gas-phase desulfurization reaction product is 1-25 wt% of the diesel sulfur content, more preferably 5-15 wt%, and even more preferably 5-10 wt%. Under low-pressure conditions, the aromatic rings of large molecular sulfides cannot be hydrogenated, and only small molecular sulfur is removed. Therefore, the removal follows the hydrogen desulfurization pathway more often, reducing the hydrogen consumption of the chemical reaction and improving the hydrogenation selectivity. For sterically hindered 4,6-DMDBT-type large molecular sulfides, they are deeply removed in the subsequent hydrogenation reaction.

[0044] In this invention, the selection range of conditions for the gas-phase desulfurization reaction is relatively wide. Preferably, in step (1), the conditions for the gas-phase desulfurization reaction include: pressure of 0.1-2.8 MPa, preferably 0.5-2 MPa; temperature of 260-400℃, preferably 300-380℃, for example, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, and any value between any two groups; hydrogen-to-oil volume ratio of 50-500, preferably 50-300, for example, 50, 100, 150, 200, 250, 300, and any value between any two groups; and volume hourly space velocity of 0.5-3 h⁻¹. -1 Preferably 0.8-2h -1 In the method provided by this invention, the gas-phase hydrodesulfurization reaction is carried out under preferred conditions, such as within the preferred hydrogen-to-oil volume ratio range, which is more conducive to reducing the partial pressure of the feedstock diesel and achieving complete vaporization of the feedstock diesel. Furthermore, the gas-phase desulfurization reaction of this invention can be carried out at lower pressures, significantly saving energy consumption.

[0045] It should be noted that during the gas phase desulfurization reaction in step (1), not only will small molecule sulfur in the raw diesel oil be removed, but also some small molecule nitrogen compounds will be removed.

[0046] According to the method provided by this invention, by using a high-hydrogen desulfurization pathway catalyst in the gas-phase hydrogenation reactor, the desulfurization reaction is controlled to follow a low-hydrogen-consumption reaction path, reducing the chemical hydrogen consumption of the desulfurization reaction. Simultaneously, the hydrogen-to-oil volume ratio in the gas-phase hydrogenation reactor can be reduced, lowering the reaction severity. Furthermore, by controlling the optimized reaction conditions of the gas-phase hydrogenation reactor, not only is gas-phase desulfurization performed, but more importantly, it is better coordinated with the liquid-phase hydrogenation reactor, thus facilitating subsequent deep aromatic removal. Moreover, the optimized gas-phase desulfurization reaction conditions of this invention avoid hydrogen saturation of large molecular weight nitrides, reducing hydrogen consumption. Large molecular weight nitrides often have structures containing aromatic rings and nitrogen heterocycles, and CN-bond breakage only occurs after the aromatic and nitrogen heterocycles are completely hydrogenated. Under the reaction conditions of the gas-phase hydrogenation reactor, large molecular weight nitrides are difficult to hydrogenate and, through gas-liquid separation, largely enter the gas phase component without undergoing deep hydrogenation, thus reducing the hydrogen consumption of the chemical reaction.

[0047] In this invention, preferably, the method further includes cooling the gas-phase desulfurization reaction products by heat exchange before performing the gas-liquid separation. This invention does not impose particular limitations on the heat exchange conditions; preferably, conditions sufficient to ensure the liquefaction of large molecular weight heavy substances in the gas-phase desulfurization reaction products are met.

[0048] The present invention does not particularly limit the specific operation of the heat exchange, and any heat exchange medium conventionally used in the art can be used. The heat exchange can be carried out in a heat exchange unit, such as a heat exchanger. The present invention does not particularly limit the specific type of heat exchanger, for example, it can be a commercially available heat exchanger conventionally defined in the art, or it can be a tubular heat exchanger.

[0049] This invention achieves the desired feed conditions for the liquid-phase hydrogenation reactor by using a small amount of heat exchange at high temperature on the gas-phase desulfurization reaction products, thus saving energy while ensuring the liquefaction of macromolecules.

[0050] In this invention, preferably, the mass percentage of the liquid phase component is 1-50%, more preferably 10-30%, based on the total amount of the gas-phase desulfurization reaction products. This preferred embodiment is more conducive to precisely controlling the liquefaction ratio, selectively hydrogenating heavy components, and reducing chemical hydrogen consumption.

[0051] In this invention, the liquid-phase hydrogenation reactor is filled with a hydrogenation catalyst that has a dearomatics removal function. The range of types of hydrogenation dearomatics catalysts is relatively wide in this invention. Preferably, in step (3), the liquid-phase dearomatics removal reaction is carried out in the presence of a hydrogenation dearomatics catalyst, which is a non-precious metal catalyst and / or a precious metal catalyst. In this invention, the non-precious metal catalyst may include a support and a hydrogenation active metal, wherein the support is an inorganic refractory oxide, generally selected from at least one of alumina, amorphous aluminum silicate, silica, and titanium dioxide, preferably alumina; the hydrogenation active metal includes a Group VIB metal component and / or a Group VIII metal component. Preferably, in the hydrogenation dearomatics catalyst, the Group VIB metal component is preferably selected from tungsten and / or molybdenum, with a content of 5-30% by mass of oxide in the catalyst, preferably 15-30%, and the Group VIII metal component is preferably selected from nickel and / or cobalt, with a content of 1-6% by mass of oxide in the catalyst, preferably 2-5%. Preferably, the hydrodearomatization catalyst may also contain an auxiliary component, such as at least one of phosphorus, silicon, boron, magnesium, and fluorine, with a mass content generally below 6 wt%. The hydrodearomatization catalyst is preferably a Mo-Ni type catalyst.

[0052] In this invention, the source of the hydrodearomatic catalyst is not particularly limited. For example, it can be prepared by any method or obtained commercially. For example, it can be at least one of FHUDS-10, FHUDS-6 and FHUDS-8 developed by Sinopec Fushun Petrochemical Research Institute (FRIPP).

[0053] In this invention, the precious metal catalyst preferably uses Pt, Pd, etc. as the active metal. It can be prepared by any method or it can be a commercially available catalyst, such as the FHDA-10 catalyst developed by the Sinopec Fushun Petrochemical Research Institute (FRIPP).

[0054] In this invention, the selection range of conditions for the liquid-phase dearomatization reaction is relatively wide. Preferably, in step (3), the conditions for the liquid-phase dearomatization reaction include: a pressure of 2-10 MPa, preferably 3-7 MPa; a temperature of 200-400℃, preferably 260-360℃, for example, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, and any values ​​between any two groups; and a volume hourly space velocity of 0.1-5 h⁻¹. -1 Preferably, it is 0.1-0.45h. -1 .

[0055] According to the present invention, in step (3), the specific operation and conditions for pressurizing and mixing the liquid phase component are within a wide range. The pressurization and mixing are used to supplement the hydrogen required for the reaction based on the pressurization of the liquid phase component. Preferably, the pressurization and mixing are performed to meet the reaction conditions and hydrogen consumption requirements in the liquid phase hydrogenation reactor. In the present invention, there are no particular limitations on the specific operation of pressurization and mixing. A specific process can be that the liquid phase component is first pressurized by a pressurization unit, and then enters the mixing unit. Hydrogen is pressurized by a compressor (pressurization unit) to a pressure slightly higher than that of the liquid phase component (0.05-0.1 MPa higher), and also enters the mixing unit. The material flowing out of the mixing unit is the liquid phase component with dissolved hydrogen.

[0056] In this invention, the pressurization and hydrogen mixing in step (3) can be carried out in any unit that can achieve pressurization and hydrogen mixing. For example, pressurization and hydrogen mixing can be carried out in a pressurization unit and a hydrogen mixing unit, respectively. There is no particular limitation on the type of pressurization unit and hydrogen mixing unit, as long as the pressurization and hydrogen mixing of the liquid phase components can be achieved.

[0057] In this invention, preferably, the pressurization unit is a gas-phase pressurizer.

[0058] In this invention, preferably, the hydrogen mixing unit is selected from at least one of membrane tube hydrogen dissolving components, hydrogen mixers (e.g., high-efficiency hydrogen mixers), microbubble generators, and bubble fractors. For example, a hydrogen mixer with strong convection backmixing or a hydrogen mixer that generates microbubbles through microchannels is used to increase solubility. Preferably, the hydrogen mixer is provided with a support disk with uniformly distributed pores and downcomers to improve gas phase dispersion.

[0059] In this invention, preferably, in step (3) during the hydrogen mixing process, relative to 1m 3 The liquid phase component has a hydrogen replenishment amount of 10-40 Nm. 3 .

[0060] In this invention, preferably, the pressure of the liquid-phase dearomatic reaction is at least 1 MPa higher than the pressure of the gas-phase desulfurization reaction, and more preferably 2-6 MPa higher. The method provided by this invention can be carried out under medium to low pressure, which greatly reduces the harshness of the reaction and saves energy.

[0061] In this invention, preferably, the temperature of the liquid-phase dearomatic reaction is at least 15°C lower than the temperature of the gas-phase desulfurization reaction, and more preferably 15-40°C lower. This preferred embodiment is more advantageous for liquefying large molecules that require further reaction while retaining the heat of reaction.

[0062] In this invention, there are no particular limitations on the application of the gaseous component (also known as the hydrogenated light component) and the liquid-phase hydrogenation reaction product obtained by gas-liquid separation, and the application can be adapted according to the specific needs of the product. Preferably, the method further includes mixing the gaseous component and the liquid-phase dearomatic reaction product obtained in step (2) and then performing desulfurization treatment. The gaseous component and the liquid-phase dearomatic reaction product can be processed separately or together, preferably together. According to a preferred embodiment of the invention, the method further includes mixing the gaseous component and the liquid-phase dearomatic reaction product and then performing desulfurization treatment to obtain refined diesel product. This invention does not particularly limit the specific operation and conditions of the desulfurization treatment, and it can be carried out according to conventional techniques in the art, preferably by stripping. The stripping can be carried out in a stripping unit, such as a stripping tower. In this invention, preferably, the polycyclic aromatic hydrocarbon content in the refined diesel product is less than 6 wt%, and the sulfur content is less than 11 μg / g.

[0063] In this invention, there is no particular limitation on the types of gas-phase hydrogenation reactors and liquid-phase hydrogenation reactors. Preferably, the gas-phase hydrogenation reactor and the liquid-phase hydrogenation reactor are each independently a fixed-bed reactor.

[0064] A second aspect of the present invention provides a diesel fuel hydrogenation system, wherein the system comprises a gas phase hydrogenation reactor, a gas-liquid separation unit, a pressurization and hydrogen mixing unit, and a liquid phase hydrogenation reactor connected in sequence.

[0065] The liquid phase component outlet of the gas-liquid separation unit is connected to the inlet of the pressurization and hydrogen mixing unit.

[0066] The gas-phase hydrogenation reactor is used to perform a gas-phase desulfurization reaction on diesel and hydrogen to obtain gas-phase desulfurization reaction products.

[0067] The pressurization and hydrogen mixing unit is used to pressurize the liquid phase component obtained by the gas-liquid separation unit to obtain a pressurized and hydrogen-mixed stream.

[0068] The liquid-phase hydrogenation reactor is used to carry out a liquid-phase dearomatization reaction on the pressurized and mixed hydrogen post-stream to obtain the liquid-phase dearomatization reaction product.

[0069] In this invention, preferably, the gas-phase hydrogenation reactor is filled with a hydrodesulfurization catalyst, and the liquid-phase hydrogenation reactor is filled with a hydrodearomatics removal catalyst. By matching appropriate catalysts in different reactors, various hydrodesulfurization and hydrodearomatics removal reactions can be achieved.

[0070] In this invention, the types of gas-phase hydrogenation reactors and liquid-phase hydrogenation reactors have been described in the first aspect and will not be repeated here.

[0071] In this invention, preferably, the gas-liquid separation unit is provided with a gas phase component outlet at the top and a liquid phase component outlet at the bottom.

[0072] In this invention, preferably, the bottom of the liquid-phase hydrogenation reactor is provided with a liquid-phase hydrogenation reaction product outlet.

[0073] Preferably, in this invention, the system further includes a stripping unit, the inlet of which is connected to the outlet of the liquid-phase dearomatics reaction product of the liquid-phase hydrogenation reactor and / or to the outlet of the gas-phase component of the gas-liquid separation unit. The stripping unit is used to treat the liquid-phase hydrogenation reaction product and / or the gas-phase component obtained from the gas-liquid separation unit to remove hydrogen sulfide.

[0074] In this invention, preferably, the system further includes a heat exchange unit disposed between the gas-phase hydrogenation reactor and the gas-liquid separation unit. The heat exchange unit is used to exchange heat with the gas-phase desulfurization reaction products before gas-liquid separation. This invention does not impose any particular limitation on the heat exchange unit; any conventional choice in the art, such as a heat exchanger, can be used.

[0075] In this invention, there is no particular limitation on the gas-liquid separation unit, and it can be any conventional choice in the art, such as a gas-liquid separator.

[0076] In this invention, preferably, the pressurization and hydrogen mixing unit is used to supplement the required hydrogen gas for the reaction by pressurizing the liquid phase components, and more preferably, pressurizing and mixing the hydrogen to meet the reaction conditions and hydrogen consumption requirements in the liquid phase hydrogenation reactor. The types of pressurization and hydrogen mixing units have been described in the first aspect and will not be repeated here.

[0077] The present invention will be described in detail below through embodiments.

[0078] In this invention, unless otherwise explicitly stated, percentages and percentage contents are all expressed by mass.

[0079] The following is combined with Figure 1 The method and system of the present invention are described in detail below. Diesel feedstock and hydrogen 1 enter a gas-phase hydrogenation reactor 2, where a gas-phase desulfurization reaction occurs to obtain a gas-phase desulfurization product 3. This product then enters a heat exchange unit 4 (heat exchanger), where it is cooled before entering a gas-liquid separation unit 5 (gas-liquid separator) to obtain a liquid phase component 6 and a gas phase component 7. Gas phase component 7 is discharged upwards from the gas-liquid separator, while liquid phase component 6 is discharged downwards. After passing through a pressurization and hydrogen mixing unit 8, the product enters a liquid-phase hydrogenation reactor 9 for a liquid-phase hydrogenation reaction to obtain a hydrogenated heavy component 10. Gas phase component 7 and hydrogenated heavy component 10 are mixed and then enter a stripping unit 11 (stripping tower) to finally obtain refined diesel product 12.

[0080] In the following examples and comparative examples, chemical hydrogen consumption refers to the percentage of hydrogen mass consumed per unit mass of raw material.

[0081]

[0082] Examples 1-3

[0083] Adopting such Figure 1 The process flow diagram is shown below. Two 100mL fixed-bed hydrogenation reactors are connected in series, serving as a gas-phase hydrogenation reactor and a liquid-phase hydrogenation reactor, respectively. A heat exchanger, gas-liquid separator, booster, and hydrogen mixer are installed between the reactors. The gas-phase hydrogenation reactor is loaded with 50mL of Mo-Co type diesel hydrogenation catalyst A, and the liquid-phase hydrogenation reactor is loaded with 50mL of Mo-Ni type diesel hydrogenation catalyst B. A gas phase component outlet is located above the gas-liquid separator, which is connected to the bottom effluent of the liquid-phase hydrogenation reactor, and both flow into a stripping tower to obtain refined diesel product.

[0084] A mixture of straight-run diesel, coking diesel, and catalytic diesel was used as feedstock. Catalyst properties are shown in Table 1, feedstock properties in Table 2, and reaction process conditions and results in Table 3.

[0085] Example 4

[0086] The same process flow as in Examples 1-3 was used, except that the hydrogen-to-oil volume ratio at the inlet of the gas-phase reactor was increased. Catalyst properties are shown in Table 1, feedstock properties in Table 2, and reaction process conditions and results in Table 3.

[0087] Example 5

[0088] The same process flow as in Examples 1-3 was used, except that the gas-liquid separation conditions were changed. Catalyst properties are shown in Table 1, feedstock properties are shown in Table 2, and reaction process conditions and results are shown in Table 3.

[0089] Comparative Example 1

[0090] A conventional fixed-bed diesel hydrotreating process was adopted, with two hydrotreating reactors connected in series: a gas-phase hydrotreating reactor and a liquid-phase hydrotreating reactor. A stripping tower was installed between the two reactors to remove hydrogen sulfide. The gas-phase hydrotreating reactor was loaded with 50 mL of Mo-Co type diesel hydrotreating catalyst A, and the liquid-phase hydrotreating reactor was loaded with 50 mL of Mo-Ni type diesel hydrotreating catalyst B. After the reactors, conventional processes such as high-precision separation, low-precision separation, and stripping were followed to obtain refined diesel product. Hydrogen, after hydrogen sulfide removal, was pressurized and recycled using a circulating hydrogen compressor. The properties of the raw materials and catalysts were the same as in Examples 1-3, and the reaction process conditions and results are shown in Table 3.

[0091] Comparative Example 2

[0092] The same process flow as in Examples 1-3 was adopted, with the only difference being the increased hydrogen-to-oil volume ratio at the inlet of the gas-phase reactor and the replacement of the hydrogen mixer before the liquid-phase hydrogenation reactor with a liquid-phase booster pump. The gas-phase hydrogenation reactor was loaded with 50 mL of Mo-Co type diesel hydrogenation catalyst A, and the liquid-phase hydrogenation reactor was loaded with 50 mL of Mo-Ni type diesel hydrogenation catalyst B. The properties of the raw materials and catalysts were the same as in Examples 1-3, and the reaction process conditions and results are shown in Table 3.

[0093] Table 1

[0094]

[0095] Table 2

[0096]

[0097] Table 3

[0098]

[0099] Note: In Table 3, the hydrogen replenishment amount refers to the amount relative to 1m. 3 The amount of hydrogen required to supplement the liquid phase components.

[0100] As can be seen from the table above, in Example 4, due to the excessively large hydrogen-to-oil volume ratio at the inlet of the gas phase reactor, the oil partial pressure was low and liquefaction was difficult during the heat exchange process, resulting in a decrease in the liquefaction ratio (content of liquid phase components). Some polycyclic aromatic hydrocarbons and macromolecular sulfides entered the gas phase components and could not undergo further hydrogenation reactions, leading to a poorer saturated desulfurization effect of polycyclic aromatic hydrocarbons.

[0101] In Example 5, due to the high liquefaction ratio (liquid phase component content) after heat exchange, the liquid phase temperature did not meet the feed reaction temperature, requiring reheating and increasing energy consumption. Furthermore, the unnecessary reaction of nitrides and monocyclic aromatic hydrocarbons into the liquid phase component increased hydrogen consumption in the chemical reaction.

[0102] Comparative Example 1 employs conventional fixed-bed hydrogenation technology and a traditional catalyst loading system. The high pressure in the gas-phase hydrogenation reactor 1 leads to simultaneous and mutually influential desulfurization, denitrification, and dearomatization. The reaction conditions in both reactors cannot be optimized for any single reaction, resulting in poor reaction efficiency, high hydrogen consumption, hydrogen recycling, and high energy consumption. In contrast, the reaction system of this invention, with a significantly reduced pressure in the gas-phase hydrogenation reactor, separates desulfurization and dearomatization into two reaction systems, allowing for targeted optimization of reaction conditions. This results in better dearomatization and better preservation of nitrogen compounds that do not require hydrogenation, avoiding the limitation of nitrogen compounds on the hydrogenation reaction and improving reaction efficiency. Sulfides are removed via hydrogenolysis, and nitrogen compounds are hydrogenated in small amounts, reducing hydrogen consumption. Furthermore, hydrogen does not need to be recycled, further reducing energy consumption.

[0103] In Comparative Example 2, no hydrogen mixer was installed before the liquid-phase hydrogenation reactor. Sufficient hydrogen was provided by increasing the hydrogen-to-oil volume ratio at the inlet of the gas-phase hydrogenation reactor. However, the high hydrogen-to-oil volume ratio at the inlet of the gas-phase hydrogenation reactor resulted in low oil phase partial pressure within the separator, leading to insufficient liquefaction. This meant that polycyclic aromatic hydrocarbons (PAHs) could not fully enter the liquid phase for liquid-phase hydrogenation, resulting in a higher PAH content in the refined diesel product. Furthermore, the hydrogen recirculation required a compressor, and the energy consumption was still higher than in the example.

[0104] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for hydrogenating diesel fuel, characterized in that, The method includes the following steps: (1) In the presence of hydrogen, diesel is subjected to gas phase desulfurization reaction in a gas phase hydrogenation reactor to obtain gas phase desulfurization reaction products; (2) The gas phase desulfurization reaction products are subjected to gas-liquid separation to obtain gas phase components and liquid phase components; (3) The liquid phase components are pressurized and mixed with hydrogen, and then the liquid phase dearomatic reaction is carried out in a liquid phase hydrogenation reactor to obtain the liquid phase dearomatic reaction product; In step (1), the conditions for the gas-phase desulfurization reaction include: a pressure of 0.5-1 MPa, a temperature of 300-380℃, a hydrogen-to-oil volume ratio of 50-300, and a volume hourly space velocity of 0.8-2 h⁻¹. -1 ; In step (3), the conditions for the liquid-phase dearomatic reaction include: a pressure of 3-6 MPa, a temperature of 260-360 °C, and a volume hourly space velocity of 0.1-0.45 h⁻¹. -1 ; In step (1), the diesel fuel has an initial boiling point of 140-200℃, a final boiling point of 300-400℃, a sulfur content of ≤20000μg / g, a nitrogen content of ≤1000μg / g, and a polycyclic aromatic hydrocarbon content of ≤50wt%. In step (1), the sulfur content in the gas-phase desulfurization reaction products is 1-25 wt% of the sulfur content in diesel fuel; The method also includes cooling the gas-phase desulfurization reaction products by heat exchange before performing the gas-liquid separation; Based on the total amount of the gas-phase desulfurization reaction products, the mass percentage of the liquid phase component is 10-30%; The temperature of the liquid-phase dearomatization reaction is at least 15°C lower than the temperature of the gas-phase desulfurization reaction. The method further includes mixing the gas phase component described in step (2) with the liquid phase dearomatic reaction product and then performing desulfurization treatment to obtain refined diesel product.

2. The method according to claim 1, wherein, In step (1), the diesel fuel is selected from at least one of straight-run diesel fuel, catalytic diesel fuel, coking diesel fuel, and fluidized bed residue hydrotreated diesel fuel.

3. The method according to claim 1 or 2, wherein, The diesel fuel has an S content of ≤15000μg / g and an N content of ≤800μg / g.

4. The method according to claim 1 or 2, wherein, In step (1), the gas-phase desulfurization reaction is carried out in the presence of a hydrodesulfurization catalyst, which includes a support and a hydrogenation component.

5. The method according to claim 4, wherein, The carrier is an inorganic refractory oxide, which is selected from at least one of alumina, amorphous aluminum silica, silicon dioxide, and titanium dioxide.

6. The method according to claim 4, wherein, The hydrogenated component includes a Group VIII metal component and / or a Group VIIB metal component.

7. The method according to claim 6, wherein, The hydrodesulfurization catalyst is a Mo-Co type hydrodesulfurization catalyst.

8. The method according to claim 7, wherein, Based on the total amount of Mo-Co type hydrodesulfurization catalyst, the content of Mo in oxides is 15-30 wt%, and the content of Co in oxides is 2-6 wt%.

9. The method according to claim 1 or 2, wherein, In step (1), the sulfur content in the gas phase desulfurization reaction product is 5-15 wt% of the sulfur content in diesel fuel.

10. The method according to claim 9, wherein, In step (1), the sulfur content in the gas phase desulfurization reaction product is 5-10 wt% of the sulfur content in diesel fuel.

11. The method according to claim 1 or 2, wherein, In step (3), the liquid-phase dearomatization reaction is carried out in the presence of a hydrodearomatization catalyst, which is a non-precious metal catalyst and / or a precious metal catalyst.

12. The method according to claim 1 or 2, wherein, In step (3) during hydrogen mixing, relative to 1m 3 The liquid phase component has a hydrogen replenishment amount of 10-40 Nm. 3 .

13. The method according to claim 1 or 2, wherein, The temperature of the liquid-phase dearomatic reaction is 15-40℃ lower than that of the gas-phase desulfurization reaction.

14. The method according to claim 1 or 2, wherein, The refined diesel product contains less than 6 wt% polycyclic aromatic hydrocarbons and less than 11 μg / g sulfur.

15. The method according to claim 1 or 2, wherein, The gas-phase hydrogenation reactor and the liquid-phase hydrogenation reactor are each independently a fixed-bed reactor.

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