Diesel hydrogenation method and system

Abstract

The invention relates to the field of oil refining and chemical engineering, and discloses a diesel hydrogenation method and system. The invention relates to a diesel hydrogenation method, which comprises: (1) carrying out a gas phase desulfurization reaction on diesel 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 dearomatization reaction in a liquid-phase hydrogenation reactor to obtain a liquid-phase dearomatization reaction product. According to the method, the deep dearomatization effect can be achieved on the basis of achieving desulfurization, meanwhile, the technological process is simplified on the whole, the reaction severity is reduced, and energy consumption and hydrogen consumption are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of oil refining and chemical engineering, and in particular to a diesel hydrogenation method and system. Background Art

[0002] At present, the hydrofining of diesel generally adopts a fixed bed hydrogenation process. With the increasingly stringent environmental regulations, in addition to requiring the sulfur content in refined diesel to be ≯10ppm, the National VI diesel quality standard proposed in 2019 requires polycyclic aromatic hydrocarbons ≯11%, and the National VIB standard implemented in 2023 requires polycyclic aromatic hydrocarbons ≯5%. However, from the perspective of the reaction mechanism of deep desulfurization and deep dearomatization, there are significant differences in the requirements for the reaction environment between the two. For the desulfurization reaction, the removal of small molecular sulfur mainly follows the direct desulfurization route, that is, hydrogenolysis. Large molecular sulfides with low reaction activity mainly follow the hydrodesulfurization reaction route, that is, first hydrogenation of aromatic rings and then hydrogenolysis. In the upper part of the reactor, the hydrogenation of small molecular sulfides and nitrides and the conversion of some dicyclic aromatic hydrocarbons (large amounts of heat release) mainly occur. In the lower part of the reactor, the accumulation of heat and hydrogen sulfide makes the reaction environment high temperature and low hydrogen partial pressure. This reaction environment is not conducive to the hydrodesulfurization path of large molecular sulfur and the saturation of polycyclic aromatic hydrocarbons. Especially at the end of the reaction, the catalyst activity decays. Raising the temperature can make up for the loss of the catalyst's desulfurization activity, but it will further affect the dearomatization effect. In addition to the different requirements 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 saturation of aromatics.

[0003] At the same time, existing hydrogenation technologies still have problems with hydrogenation of unnecessary reactants and over-hydrogenation. There is no index limit on nitrides in diesel, but during deep desulfurization and dearomatization, since nitrides are more easily adsorbed on the catalyst surface than sulfides and aromatics, nitrides not only greatly inhibit desulfurization and dearomatization reactions, but also cause waste of hydrogen resources due to their preferential hydrogenation. In addition, diesel only limits the content of polycyclic aromatic hydrocarbons, but during the hydrogenation reaction, a portion of monocyclic aromatic hydrocarbons will undergo hydrogenation saturation reaction, further causing waste of hydrogen consumption. Based on the above two aspects, the necessity and urgency of upgrading diesel cleaning technology have become more prominent.

[0004] The existing technology can use a two-stage process to achieve deep dearomatization. After conventional hydrogenation, the generated oil is stripped to remove hydrogen sulfide and then enters the precious metal hydrogenation reactor. This will greatly increase the cost of catalyst use and the complexity of the process, and cannot solve the waste of hydrogen consumption caused by excessive hydrogenation. The crude oil can also be cut into light and heavy components. The light component is shallowly hydrogenated to avoid saturation of monocyclic aromatics as much as possible, and the heavy component is deeply hydrogenated for desulfurization and dearomatization. However, shallow hydrogenation generally uses medium-pressure hydrogenation, which increases the energy consumption of the entire technology and has not been industrialized.

[0005] Patent application CN108085058A discloses a method for deep dearomatization of hydrocarbon oil. The method uses relatively mild temperature and pressure conditions to make the crude oil and hydrogen pass through a highly dispersed Pt-Pd / Al2O3 catalyst, and the gas phase after the reaction is compressed and recycled, and the liquid phase is a low-aromatic product. However, the Pt-Pd / Al2O3 hydrogenation catalyst is mainly suitable for dearomatization of low-sulfur diesel raw materials, and the effect of desulfurization and dearomatization on low-quality diesel is not ideal.

[0006] Patent application CN109926067A discloses a platinum-palladium-cobalt ternary metal hydrogenation dearomatization catalyst and its preparation method. The method adopts a step-by-step impregnation method of active metal precursors, so that the utilization rate of the prepared catalyst platinum palladium precious metal is high, the synergistic catalytic ability is strong, and the introduction of platinum palladium leads to the enhancement of the aromatic hydrogenation performance of non-precious metal cobalt. However, the catalyst is still aimed at hydrocarbon oil after the sulfur-containing compounds have been basically removed to avoid the influence of hydrogen sulfide on the deep dearomatization of precious metals, and cannot achieve the desulfurization and dearomatization of inferior diesel. Summary of the invention

[0007] The purpose of the present invention is to overcome the technical problem of poor hydrodesulfurization and dearomatization effects of inferior diesel in the prior art, and to provide a diesel hydrogenation method and system, which can have a deep dearomatization effect on the basis of achieving desulfurization, while also simplifying the process flow as a whole, reducing the severity of the reaction, and reducing energy consumption and hydrogen consumption.

[0008] In order to achieve the above object, the present invention provides a diesel hydrogenation method in a first aspect, wherein the method comprises the following steps: (1) In the presence of hydrogen, diesel is subjected to a gas-phase desulfurization reaction in a gas-phase hydrogenation reactor to obtain a gas-phase desulfurization reaction product; (2) separating the gas-phase desulfurization reaction product into gas-liquid components to obtain a gas-phase component and a liquid-phase component; (3) The liquid phase components are pressurized and mixed with hydrogen, and then a liquid phase dearomatization reaction is carried out in a liquid phase hydrogenation reactor to obtain a liquid phase dearomatization reaction product.

[0009] The second aspect of the present invention provides a diesel 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 which are 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; The gas phase hydrogenation reactor is used to carry out a gas phase desulfurization reaction on diesel and hydrogen to obtain a gas phase desulfurization reaction product; The pressurization and hydrogen mixing unit is used to pressurize and hydrogen mix the liquid phase component obtained by the gas-liquid separation unit to obtain a pressurized and hydrogen mixed logistics; The liquid phase hydrogenation reactor is used to carry out liquid phase dearomatization reaction on the pressurized and hydrogenated logistics to obtain a liquid phase dearomatization reaction product.

[0010] Compared with the prior art, the method and system of the present invention have the following advantages: (1) The method of the present invention places the gas phase desulfurization reaction and the liquid phase dearomatization reaction in different reactors, thereby avoiding the defect that the deep desulfurization and dearomatization are placed in the same reaction system and the reaction conditions are difficult to be compatible.

[0011] (2) The inventors have found that, preferably, 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, and controlling the reaction conditions of the gas-phase desulfurization reaction and the liquid-phase dearomatization reaction respectively, thereby improving the efficiency of each reaction. Preferably, 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, and most of the gas-phase components in the effluent no longer undergo further hydrogenation denitrogenation and dearomatization reactions, reducing the hydrogen consumption of the reaction. The liquid-phase components obtained by gas-liquid separation undergo a polycyclic aromatic hydrocarbon hydrogenation saturation reaction after pressurization and hydrogen dissolution.

[0012] (3) The method and system provided by the present invention can achieve deep desulfurization and dearomatization of diesel as raw material under milder operating conditions and a more simplified process flow. The entire reaction system does not require a hydrogen compressor in a fixed bed reaction system and a circulating oil pump in a liquid phase hydrogenation reaction system, which reduces investment costs, simplifies the process flow, improves reaction efficiency, and reduces the severity of the reaction.

[0013] (4) In the system provided by the present invention, the boosting and hydrogen mixing units can simultaneously boost the pressure and replenish the hydrogen consumed by the liquid phase hydrogenation reactor. The hydrogen does not need to be recycled, thus eliminating the need for a circulating hydrogen compressor and significantly reducing the investment in device construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the process flow of the present invention.

[0015] Reference numerals DETAILED DESCRIPTION The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0016] The description of the exemplary embodiments is intended to be read in conjunction with the accompanying drawings, which are considered a part of the entire written description. In the specification, relative terms such as "lower", "upper", "horizontal", "vertical", "above", "below", "upward", "downward", "top" and "bottom" and their derivatives (for example, "horizontally", "downwardly", "upwardly", etc.) should be interpreted as the directions shown in the drawings being described at the time. These relative terms are for convenience of description and do not require that the device be constructed or operated in a particular orientation. Unless otherwise specified, "connected" as used herein refers to a relationship whereby structures are directly or indirectly fixed or connected to each other through intermediate structures.

[0017] In the present invention, the symbol “≯” indicates not greater than, and the symbol “≮” indicates not less than.

[0018] The first aspect of the present invention provides a method for hydrogenating diesel, wherein the method comprises the following steps: (1) In the presence of hydrogen, diesel is subjected to a gas-phase desulfurization reaction in a gas-phase hydrogenation reactor to obtain a gas-phase desulfurization reaction product; (2) separating the gas-phase desulfurization reaction product into gas-liquid components to obtain a gas-phase component and a liquid-phase component; (3) The liquid phase components are pressurized and mixed with hydrogen, and then a liquid phase dearomatization reaction is carried out in a liquid phase hydrogenation reactor to obtain a liquid phase dearomatization reaction product.

[0019] The method provided by the present invention is that the raw diesel undergoes a gas-phase desulfurization reaction in a gas-phase hydrogenation reactor, the gas-phase desulfurization reaction mainly removes small molecular sulfides, and the liquid phase component obtained by gas-liquid separation of the gas-phase desulfurization reaction product enters a liquid phase hydrogenation reactor after pressurization and hydrogen mixing, and undergoes a deep hydrogenation dearomatization reaction. The method provided by the present invention is applicable to any substance that needs to remove small molecular sulfides and large molecular aromatics at the same time.

[0020] In the present invention, the hydrogen in step (1) can be any hydrogen-containing gas that can provide hydrogen, which can be fresh hydrogen, recycled hydrogen, or hydrogen-rich gas. Those skilled in the art can clearly understand the hydrogen-containing gas described in the present invention after understanding the technical solution of the present invention.

[0021] In the present invention, the diesel type can be selected in a wide range. Preferably, in step (1), the diesel is selected from at least one of straight-run diesel, catalytic diesel, coker diesel and ebullated bed residue hydrogenated diesel.

[0022] The straight-run diesel, catalytic diesel, coker diesel and ebullated-bed residue hydrogenated diesel mentioned in the present invention have conventional definitions in the art, and the present invention has no particular limitation thereto.

[0023] In the present invention, the range of diesel properties is relatively wide. Preferably, in step (1), the initial boiling point of the diesel is 140-200°C, the final boiling point is 300-400°C, the S content is ≯20000μg / g, preferably ≯15000μg / g, the N content is ≯1000μg / g, preferably ≯800μg / g, and the polycyclic aromatic hydrocarbon content is ≯50wt%. For example, the S content of the diesel can be exemplified but not limited to: 8000μg / g, 9000μg / g, 10000μg / g, 11500μg / g, etc., the N content can be exemplified but not limited to: 500μg / g, 600μg / g, 700μg / g, etc., and the polycyclic aromatic hydrocarbon content can be exemplified but not limited to: 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, etc.

[0024] In the present invention, a hydrogenation catalyst having a desulfurization function is loaded in the gas phase desulfurization reactor. The present invention does not particularly limit the type of the hydrodesulfurization catalyst, and those skilled in the art can select it according to actual needs. Preferably, in step (1), the gas phase desulfurization reaction is carried out in the presence of a hydrodesulfurization catalyst, and the hydrodesulfurization catalyst includes a carrier and a hydrogenation component.

[0025] In the present invention, the carrier has a wide range of choices. Preferably, the carrier is an inorganic refractory oxide, and the inorganic refractory oxide is selected from at least one of alumina, amorphous silica-alumina, silicon dioxide and titanium oxide, and more preferably alumina.

[0026] In the present invention, the selection range of the hydrogenation component is relatively wide. Preferably, the hydrogenation component includes a Group VIII metal component and / or a Group VIB metal component. In the present invention, the specific types of the Group VIII metal and the Group VIB metal are not limited, and those skilled in the art can select according to actual needs.

[0027] In the present invention, preferably, the hydrodesulfurization catalyst is a Mo-Co type hydrodesulfurization catalyst.

[0028] In the present invention, preferably, based on the total amount of the Mo-Co type hydrodesulfurization catalyst, the content of Mo calculated as oxide is 15-30wt%, and the content of Co calculated as oxide is 2-6wt%.

[0029] In the present invention, preferably, the Mo-Co type hydrodesulfurization catalyst further comprises an auxiliary component, and the auxiliary component is selected from at least one of phosphorus, silicon, boron, magnesium and fluorine. Preferably, the content of the auxiliary component calculated as oxide is 6wt% or less.

[0030] In the present invention, there is no limitation on the source of the Mo-Co type hydrodesulfurization catalyst, for example, it can be prepared by any conventional method in the art, or it can be commercially available, for example, it can be the FHUDS-5 and / or FHUDS-7 catalyst developed by Fushun Research Institute of Petrochemical Industry (FRIPP) of Sinopec.

[0031] In the present invention, preferably, in step (1), the sulfur content in the gas phase desulfurization reaction product is 1-25wt% of the sulfur content of diesel, more preferably 5-15wt%, and even more preferably 5-10wt%. Under low pressure conditions, the aromatic rings of macromolecular sulfides cannot be hydrogenated, and only small molecular sulfur is removed. Therefore, more hydrogenation desulfurization is followed to remove, reducing hydrogen consumption in chemical reactions and improving hydrogenation selectivity. For macromolecular sulfides of the sterically hindered 4,6-DMDBT type, they are deeply removed in the subsequent hydrogenation reaction.

[0032] In the present invention, the conditions for the gas phase desulfurization reaction are selected in a wide range. Preferably, in step (1), the conditions for the gas phase desulfurization reaction include: a pressure of 0.1-2.8 MPa, preferably 0.5-2 MPa, a temperature of 260-400°C, preferably 300-380°C, for example, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C and values ​​between any two groups, a hydrogen-to-oil volume ratio of 50-500, preferably 50-300, for example, 50, 100, 150, 200, 250, 300 and values ​​between any two groups, and a volume space velocity of 0.5-3h -1 , preferably 0.8-2h -1 In the method provided by the present invention, the gas phase hydrodesulfurization reaction is carried out under the preferred conditions, for example, within the preferred hydrogen-to-oil volume ratio range, which is more conducive to reducing the partial pressure of the raw diesel and achieving complete vaporization of the raw diesel. In addition, the gas phase desulfurization reaction of the present invention can be carried out at a relatively low pressure, which greatly saves energy consumption.

[0033] It should be noted that during the gas phase desulfurization reaction in step (1), not only the small molecular sulfur in the raw diesel will be removed, but also some small molecular nitrogen compounds therein will be removed.

[0034] According to the method provided by the present invention, by matching the use of high hydrogenation desulfurization path catalyst in the gas phase hydrogenation reactor, the desulfurization reaction is controlled to follow the reaction path of low hydrogen consumption more, the chemical hydrogen consumption of the desulfurization reaction is reduced, and the hydrogen-oil volume ratio of the gas phase hydrogenation reactor can also be reduced, reducing the severity of the reaction. At the same time, by controlling the reaction conditions of the preferred gas phase hydrogenation reactor, it is not only for gas phase desulfurization, but also mainly for better coordination with the liquid phase hydrogenation reactor, so as to be more conducive to subsequent deep dearomatization. And the preferred gas phase desulfurization reaction conditions of the present invention avoid the hydrogenation saturation of macromolecular nitrides and reduce hydrogen consumption. Macromolecular nitrides are mostly structures containing aromatic rings and nitrogen heterocycles, and the breaking of CN bonds can only occur after the aromatic rings and nitrogen heterocycles are completely hydrogenated and saturated, and under the reaction conditions of the gas phase hydrogenation reactor, macromolecular nitrides are difficult to undergo hydrogenation reactions, and enter the gas phase components in large quantities through gas-liquid separation without deep hydrogenation, thereby achieving a reduction in chemical reaction hydrogen consumption.

[0035] In the present invention, preferably, the method further comprises heat exchanging and cooling the gas phase desulfurization reaction product before the gas-liquid separation. The present invention has no particular limitation on the heat exchange conditions, and preferably can ensure that the macromolecular heavy substances in the gas phase desulfurization reaction product are liquefied.

[0036] The present invention has no particular limitation on the specific operation of the heat exchange, and any heat exchange medium commonly used in the art can be used for the heat exchange. The heat exchange can be performed in a heat exchange unit such as a heat exchanger, and the present invention has no particular limitation on the specific type of the heat exchanger, for example, it can be a commercial heat exchanger commonly defined in the art, or a tubular heat exchanger.

[0037] The present invention adopts a small amount of heat exchange under high temperature conditions for the gas phase desulfurization reaction product, retains a large amount of reaction heat under the condition of ensuring the liquefaction of macromolecules, realizes the feeding conditions of the liquid phase hydrogenation reactor, and saves energy consumption.

[0038] In the present invention, preferably, based on the total amount of the gas phase desulfurization reaction product, the mass percentage of the liquid phase component is 1-50%, and more preferably 10-30%. This preferred embodiment is more conducive to accurately controlling the liquefaction ratio, specifically hydrogenating the heavy components, and reducing chemical hydrogen consumption.

[0039] In the present invention, a hydrogenation catalyst with dearomatization function is loaded in the liquid phase hydrogenation reactor, and the present invention has a wide range of selection of types of hydrogenation dearomatization catalysts. Preferably, in step (3), the liquid phase dearomatization reaction is carried out in the presence of a hydrogenation dearomatization catalyst, and the hydrogenation dearomatization catalyst is a non-precious metal catalyst and / or a precious metal catalyst. In the present invention, the non-precious metal catalyst may include a carrier and a hydrogenation active metal, wherein the carrier is an inorganic refractory oxide, generally selected from at least one of alumina, amorphous silica-alumina, silicon dioxide and titanium oxide, preferably alumina; the hydrogenation active metal includes a VIB group metal component and / or a VIII group metal component. Preferably, in the hydrogenation dearomatization catalyst, the VIB group metal component is preferably selected from tungsten and / or molybdenum, and the content of the oxide in the catalyst is 5-30%, preferably 15-30%, and the VIII group metal component is preferably selected from nickel and / or cobalt, and the content of the oxide in the catalyst is 1-6%, 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, and the mass content of the auxiliary component in the hydrodearomatization catalyst is generally below 6wt%. The hydrodearomatization catalyst is preferably a Mo-Ni type catalyst.

[0040] In the present invention, there is no particular limitation on the source of the hydrodearomatization catalyst, and the catalyst may be prepared by any method or purchased commercially, and may be at least one of FHUDS-10, FHUDS-6 and FHUDS-8 developed by Fushun Research Institute of Petrochemical Industry (FRIPP) of Sinopec.

[0041] In the present invention, the noble metal catalyst preferably uses Pt, Pd or the like as the active metal, which can also be prepared by any method or can be a commercially available catalyst, such as the FHDA-10 catalyst developed by Fushun Research Institute of Petrochemicals (FRIPP) of Sinopec.

[0042] In the present invention, the conditions for the liquid phase dearomatization reaction are selected in a wide range. 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°C, preferably 260-360°C, for example, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C and values ​​between any two groups, and a volume space velocity of 0.1-5h -1 , preferably 0.1-0.45h -1 .

[0043] According to the present invention, in step (3), the specific operation and condition selection range for pressurizing and hydrogen mixing the liquid phase component is relatively wide. The pressurization and hydrogen mixing are used to supplement the hydrogen required for the reaction on the basis of pressurizing the liquid phase component. Preferably, the pressurization and hydrogen mixing are performed to meet the reaction conditions and hydrogen consumption requirements in the liquid phase hydrogenation reactor. In the present invention, there is no special limitation on the specific operation mode of pressurization and hydrogen mixing. The specific process may be that the liquid phase component is first pressurized by a pressurization unit, and then enters the hydrogen mixing unit, and the hydrogen is pressurized by a compressor (pressurization unit) to a pressure slightly higher than that of the liquid phase component (higher than the liquid phase component by 0.05-0.1MPa), and also enters the hydrogen mixing unit. The material flowing out of the hydrogen mixing unit is a liquid phase component dissolved with hydrogen.

[0044] In the present 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, the 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 types of the pressurization unit and the hydrogen mixing unit, as long as the pressurization and hydrogen mixing of the liquid phase components can be achieved.

[0045] In the present invention, preferably, the boosting unit is a gas phase booster.

[0046] In the present invention, preferably, the hydrogen mixing unit is selected from at least one of a membrane-tube hydrogen dissolving assembly, a hydrogen mixer (for example, a high-efficiency hydrogen mixer), a microbubble generator, and a bubble fractalizer. For example, a hydrogen mixer with strong convection backmixing or a hydrogen mixer with micropores to generate microbubbles is used to increase solubility. Preferably, the hydrogen mixer is provided with a support plate with uniformly distributed pores and downcomers to improve gas phase dispersion.

[0047] In the present invention, preferably, during the hydrogen mixing process in step (3), relative to 1m 3 The liquid phase component, the hydrogen replenishment amount is 10-40Nm 3 .

[0048] In the present invention, preferably, the pressure of the liquid phase dearomatization reaction is at least 1 MPa higher than the pressure of the gas phase desulfurization reaction, preferably 2-6 MPa higher. The method provided by the present invention can be carried out at medium and low pressures, greatly reducing the severity of the reaction and saving energy consumption.

[0049] In the present invention, preferably, the temperature of the liquid phase dearomatization reaction is at least 15° C. lower than that of the gas phase desulfurization reaction, preferably 15-40° C. lower. This preferred embodiment is more conducive to liquefying macromolecules that need further reaction and retaining reaction heat.

[0050] In the present invention, there is no particular limitation on the application of the gas phase component (also referred to as hydrogenation light component) and the liquid phase hydrogenation reaction product obtained by gas-liquid separation, and they can be adaptively treated according to the specific needs of the product. Preferably, the method further comprises mixing the gas phase component and the liquid phase dearomatization reaction product in step (2) and then performing a dehydrosulfurization treatment. The gas phase component and the liquid phase dearomatization reaction product can be treated separately or together, preferably together. According to a preferred embodiment of the present invention, the method further comprises mixing the gas phase component and the liquid phase dearomatization reaction product, and then performing a dehydrosulfurization treatment to obtain a refined diesel product. The present invention does not particularly limit the specific operation and conditions of the dehydrosulfurization treatment, which can be carried out according to conventional technical means in the art, preferably by stripping. The stripping can be carried out in a stripping unit such as a stripping tower. In the present invention, preferably, the content of polycyclic aromatic hydrocarbons in the refined diesel product is less than 6wt%, and the content of S is less than 11μg / g.

[0051] In the present invention, there is no particular limitation on the types of the gas phase hydrogenation reactor and the liquid phase hydrogenation reactor. Preferably, the gas phase hydrogenation reactor and the liquid phase hydrogenation reactor are each independently a fixed bed reactor.

[0052] The second aspect of the present invention provides a diesel 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 which are connected in sequence; The liquid component outlet of the gas-liquid separation unit is connected to the inlet of the pressurization and hydrogen mixing unit; The gas phase hydrogenation reactor is used to carry out a gas phase desulfurization reaction on diesel and hydrogen to obtain a gas phase desulfurization reaction product; 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 logistics; The liquid phase hydrogenation reactor is used to carry out liquid phase dearomatization reaction on the pressurized and hydrogenated logistics to obtain a liquid phase dearomatization reaction product.

[0053] In the present invention, preferably, the gas phase hydrogenation reactor is filled with a hydrodesulfurization catalyst, and the liquid phase hydrogenation reactor is filled with a hydrodearomatization catalyst. The corresponding catalysts are matched in different reactors to achieve various hydrodesulfurization and hydrodearomatization reactions.

[0054] In the present invention, the types of gas phase hydrogenation reactor and liquid phase hydrogenation reactor have been described in the first aspect and will not be described in detail here.

[0055] In the present 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.

[0056] In the present invention, preferably, a liquid phase hydrogenation reaction product outlet is provided at the bottom of the liquid phase hydrogenation reactor.

[0057] In the present invention, preferably, the system further comprises a stripping unit, the inlet of which is connected to the outlet of the liquid phase dearomatization 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 perform hydrogen sulfide removal treatment on the liquid phase hydrogenation reaction product and / or the gas phase component obtained by the gas-liquid separation unit.

[0058] In the present invention, preferably, the system further comprises a heat exchange unit disposed between the gas phase hydrogenation reactor and the gas-liquid separation unit, the heat exchange unit being used to perform heat exchange on the gas phase desulfurization reaction product and then perform gas-liquid separation. In the present invention, the heat exchange unit is not particularly limited and can be a conventional choice in the art, such as a heat exchanger.

[0059] In the present invention, there is no particular limitation on the gas-liquid separation unit, and it can be a conventional choice in the art, for example, it can be a gas-liquid separator.

[0060] In the present invention, preferably, the pressurizing and hydrogen mixing unit is used to supplement the hydrogen required for the reaction on the basis of pressurizing the liquid phase components, preferably pressurizing and mixing the hydrogen to meet the reaction conditions and hydrogen consumption requirements in the liquid phase hydrogenation reactor. The types of the pressurizing and hydrogen mixing unit have been described in the first aspect and will not be repeated here.

[0061] The present invention will be described in detail below through examples.

[0062] In the present invention, unless otherwise explicitly stated, percentages and contents are all based on mass.

[0063] Combine the following Figure 1 The method and system of the present invention are described in detail. Diesel feedstock and hydrogen 1 enter the gas phase hydrogenation reactor 2, gas phase desulfurization reaction occurs, and gas phase desulfurization reaction product 3 is obtained; enter the heat exchange unit 4 (heat exchanger), after cooling by the heat exchanger, enter the gas-liquid separation unit 5 (gas-liquid separator) to obtain liquid phase component 6 and gas phase component 7. The gas phase component 7 is discharged upward from the gas-liquid separator, and the liquid phase component 6 is discharged downward from the gas-liquid separator, and then enters the liquid phase hydrogenation reactor 9 through the pressurization and hydrogen mixing unit 8 for liquid phase hydrogenation reaction to obtain hydrogenated heavy component 10, and the gas phase component 7 is mixed with the hydrogenated heavy component 10 and enters the stripping unit 11 (stripping tower), and finally obtains the refined diesel product 12.

[0064] In the following examples and comparative examples, chemical hydrogen consumption refers to the mass percentage of hydrogen consumed per unit mass of raw material.

[0065] Examples 1-3 Use Figure 1 The process diagram is as follows. Two 100mL fixed-bed hydrogenation reactors are connected in series, namely a gas phase hydrogenation reactor and a liquid phase hydrogenation reactor. A heat exchanger, a gas-liquid separator, a supercharger and a hydrogen mixer are arranged between the reactors. The gas phase hydrogenation reactor is loaded with 50mL Mo-Co type diesel hydrogenation catalyst A, and the liquid phase hydrogenation reactor is loaded with 50mL Mo-Ni type diesel hydrogenation catalyst B. A gas phase component outlet is arranged above the gas-liquid separator, which is connected to the bottom effluent of the liquid phase hydrogenation reactor and then enters the stripping tower together to obtain a refined diesel product.

[0066] A mixture of straight-run diesel, coking diesel and catalytic diesel was used as the raw material oil. The properties of the catalyst are shown in Table 1, the properties of the raw material oil are shown in Table 2, and the reaction process conditions and results are shown in Table 3.

[0067] Example 4 The same process flow as in Example 1-3 was adopted, except that the hydrogen-to-oil volume ratio at the inlet of the gas phase reactor was increased. The properties of the catalyst are shown in Table 1, the properties of the feed oil are shown in Table 2, and the reaction process conditions and results are shown in Table 3.

[0068] Example 5 The same process flow as in Example 1-3 was used, except that the separation conditions for gas-liquid separation were changed. The properties of the catalyst are shown in Table 1, the properties of the feedstock oil are shown in Table 2, and the reaction process conditions and results are shown in Table 3.

[0069] Comparative Example 1 The conventional diesel fixed bed hydrogenation process was adopted, and two hydrogenation reactors were set in series, namely a gas phase hydrogenation reactor and a liquid phase hydrogenation reactor, and a stripping tower was set between the two reactors to remove hydrogen sulfide. The gas phase hydrogenation reactor was filled with 50mL Mo-Co type diesel hydrogenation catalyst A, and the liquid phase hydrogenation reactor was filled with 50mL Mo-Ni type diesel hydrogenation catalyst B. After the reactor, high-fraction, low-fraction, stripping and other processes were conventionally set to obtain a refined diesel product. After removing hydrogen sulfide, the hydrogen was pressurized and recycled by a circulating hydrogen compressor. The raw materials and catalyst properties are the same as those in Example 1-3, and the reaction process conditions and results are shown in Table 3.

[0070] Comparative Example 2 The same process flow as in Example 1-3 was adopted, except that the hydrogen-oil volume ratio at the gas phase reactor inlet was increased, the hydrogen mixer before the liquid phase hydrogenation reactor was cancelled, and a liquid phase booster pump was used instead. 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 raw materials and catalyst properties were the same as in Example 1-3, and the reaction process conditions and results are shown in Table 3.

[0071] Table 1 Table 2 Table 3 Note: In Table 3, the amount of hydrogen replenished refers to the amount relative to 1m 3 The amount of hydrogen required for the liquid phase component.

[0072] As can be seen from the above table, 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 is low and liquefaction is difficult during the heat exchange process, the liquefaction ratio (liquid phase component content) is reduced, and a portion of polycyclic aromatic hydrocarbons and large molecular sulfides enter the gas phase component and cannot undergo further hydrogenation reaction, resulting in a poor saturated desulfurization effect of polycyclic aromatic hydrocarbons.

[0073] In Example 5, since the liquefaction ratio (liquid phase component content) after heat exchange is high, the liquid phase temperature does not meet the feed reaction temperature and needs to be reheated, which increases energy consumption. In addition, since unnecessary nitrides and monocyclic aromatic hydrocarbons enter the liquid phase components, the hydrogen consumption of the chemical reaction is increased.

[0074] Comparative Example 1 adopts conventional fixed bed hydrogenation technology and traditional catalyst loading system, and the pressure of gas phase hydrogenation reactor 1 is relatively high, resulting in desulfurization, denitrogenation and dearomatization occurring simultaneously and affecting each other. The reaction conditions of the two reactors cannot be optimized for a certain reaction, resulting in poor reaction effect and high hydrogen consumption, hydrogen recycling, and high energy consumption. However, under the premise that the pressure of the gas phase hydrogenation reactor is significantly reduced, the reaction system of the present invention divides desulfurization and dearomatization and denitrogenation into two reaction systems, optimizes the reaction conditions in a targeted manner, obtains better dearomatization effect, and better retains nitrides that do not need hydrogenation, avoids the limitation of nitrides on hydrogenation reaction, and improves reaction efficiency; sulfides are removed through the hydrogenolysis path, and nitrides are hydrogenated in small amounts to reduce hydrogen consumption; hydrogen does not need to be recycled, reducing energy consumption.

[0075] In Comparative Example 2, no hydrogen mixer is provided in front of the liquid phase hydrogenation reactor, and sufficient hydrogen source is 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 will lead to low oil phase partial pressure in the separator and insufficient liquefaction, that is, it is difficult for all polycyclic aromatic hydrocarbons to enter the liquid phase components for liquid phase hydrogenation reaction, resulting in a high content of polycyclic aromatic hydrocarbons in the refined diesel product. In addition, a compressor is required for hydrogen circulation, and the energy consumption is still higher than that of the embodiment.

[0076] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for hydrogenating diesel, characterized in that: The method comprises the following steps: (1) In the presence of hydrogen, diesel is subjected to a gas-phase desulfurization reaction in a gas-phase hydrogenation reactor to obtain a gas-phase desulfurization reaction product; (2) separating the gas-phase desulfurization reaction product into gas-liquid components to obtain a gas-phase component and a liquid-phase component; (3) The liquid phase components are pressurized and mixed with hydrogen, and then a liquid phase dearomatization reaction is carried out in a liquid phase hydrogenation reactor to obtain a liquid phase dearomatization reaction product.

2. The method according to claim 1, wherein: In step (1), the diesel is selected from at least one of straight-run diesel, catalytic diesel, coker diesel and ebullated-bed residue hydrogenated diesel; Preferably, in step (1), the diesel has an initial distillation point of 140-200°C, a final distillation point of 300-400°C, an S content of ≯20000 μg / g, preferably ≯15000 μg / g, an N content of ≯1000 μg / g, preferably ≯800 μg / g, and a polycyclic aromatic hydrocarbon content of ≯50 wt%.

3. 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, wherein the hydrodesulfurization catalyst comprises a carrier and a hydrogenation component; Preferably, the carrier is an inorganic refractory oxide, and the inorganic refractory oxide is selected from at least one of alumina, amorphous silica-alumina, silicon dioxide and titanium oxide; Preferably, the hydrogenation component comprises a Group VIII metal component and / or a Group VIIB metal component; Preferably, the hydrodesulfurization catalyst is a Mo-Co type hydrodesulfurization catalyst; Preferably, based on the total amount of the Mo-Co type hydrodesulfurization catalyst, the content of Mo calculated as oxide is 15-30wt%, and the content of Co calculated as oxide is 2-6wt%; Preferably, in step (1), the sulfur content in the gas phase desulfurization reaction product is 1-25wt% of the sulfur content of diesel fuel, more preferably 5-15wt%, and even more preferably 5-10wt%; 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°C, preferably 300-380°C, hydrogen to oil volume ratio of 50-500, preferably 50-300, volume space velocity of 0.5-3h -1 , preferably 0.8-2h -1 .

4. The method according to any one of claims 1 to 3, wherein: The method further comprises, before performing the gas-liquid separation, subjecting the gas-phase desulfurization reaction product to heat exchange and cooling; Preferably, based on the total amount of the gas-phase desulfurization reaction product, the mass percentage of the liquid phase component is 1-50%, more preferably 10-30%.

5. The method according to any one of claims 1 to 4, wherein: In step (3), the liquid phase dearomatization reaction is carried out in the presence of a hydrodearomatization catalyst, and the hydrodearomatization catalyst is a non-precious metal catalyst and / or a precious metal catalyst; Preferably, in step (3), the conditions of the liquid phase dearomatization reaction include: a pressure of 2-10 MPa, preferably 3-7 MPa, a temperature of 200-400°C, preferably 260-360°C, and a volume space velocity of 0.1-5 h -1 , preferably 0.1-0.45h -1 ; Preferably, during the hydrogen mixing process in step (3), relative to 1m 3 The liquid phase component, the hydrogen replenishment amount is 10-40Nm 3 ; Preferably, the pressure of the liquid phase dearomatization reaction is at least 1 MPa higher than the pressure of the gas phase desulfurization reaction, preferably 2-6 MPa higher; Preferably, the temperature of the liquid phase dearomatization reaction is at least 15°C lower than the temperature of the gas phase desulfurization reaction, preferably 15-40°C lower.

6. The method according to any one of claims 1 to 5, wherein: The method further comprises mixing the gas phase component in step (2) with the liquid phase dearomatization reaction product and then performing a dehydrosulfurization treatment to obtain a refined diesel product; Preferably, the polycyclic aromatic hydrocarbons content in the refined diesel product is less than 6 wt %, and the S content is less than 11 μg / g.

7. The method according to any one of claims 1 to 6, wherein: The gas phase hydrogenation reactor and the liquid phase hydrogenation reactor are each independently a fixed bed reactor.

8. A diesel hydrogenation system, characterized in that: 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 which are connected in sequence; The liquid component outlet of the gas-liquid separation unit is connected to the inlet of the pressurization and hydrogen mixing unit; The gas phase hydrogenation reactor is used to carry out a gas phase desulfurization reaction on diesel and hydrogen to obtain a gas phase desulfurization reaction product; The pressurization and hydrogen mixing unit is used to pressurize and hydrogen mix the liquid phase component obtained by the gas-liquid separation unit to obtain a pressurized and hydrogen mixed logistics; The liquid phase hydrogenation reactor is used to carry out liquid phase dearomatization reaction on the pressurized and hydrogenated logistics to obtain a liquid phase dearomatization reaction product.

9. The hydrogenation system according to claim 8, wherein: The gas phase hydrogenation reactor is filled with a hydrodesulfurization catalyst, and the liquid phase hydrogenation reactor is filled with a hydrodearomatization catalyst; Preferably, the gas phase hydrogenation reactor and the liquid phase hydrogenation reactor are each independently a fixed bed reactor.

10. The hydrogenation system according to claim 8 or 9, wherein: The system further comprises a stripping unit, the inlet of which is connected to the outlet of the liquid phase dearomatization reaction product of the liquid phase hydrogenation reactor and / or to the outlet of the gas phase component of the gas-liquid separation unit.

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