Hydroprocessing process for crude benzol full range and / or coal-based light hydrocarbon feedstock

Abstract

The application discloses a kind of for crude benzene full fraction and / or coal-based light hydrocarbon hydrogenation processing method, under the condition of 4~15Mpa, make reaction raw material sequentially through first-stage hydrogenation reaction, secondary hydrogenation reaction and tertiary hydrogenation reaction step.Wherein, first-stage hydrogenation reaction is liquid phase prehydrogenation, selects first NiMo catalyst;Secondary hydrogenation reaction is gas-liquid two-phase hydrogenation, selects second NiMo catalyst;Tertiary hydrogenation reaction is gas-phase hydrogenation, selects at least one of third NiMo catalyst, CoMo catalyst and NiMoW catalyst.The application adopts reasonable catalyst grading scheme and appropriate process condition, without carrying out heavy removal pretreatment to crude benzene, reduce the energy consumption required in processing process.

Description

Technical Field

[0001] This invention relates to the field of hydrogenation treatment technology, and more specifically to the field of hydrogenation treatment technology for crude benzene full fraction and / or coal-based light hydrocarbons. Background Technology

[0002] Industrial crude benzene mainly comes from coking crude benzene and a small amount from petroleum crude benzene. Coking crude benzene is one of the important by-products in the coke production process, and its yield generally accounts for 0.9% to 1.2% of the coke output. As a primary chemical product, crude benzene has a complex and diverse composition. Its physicochemical indicators can refer to the requirements of "Crude Benzene YB / T5022-2016". Because it cannot be used directly in chemical production, it needs to be refined through deep processing to obtain pure benzene, toluene, xylene, and heavy benzene, etc., before it can be used downstream. The refining process generally includes acid washing and hydrorefining. Among them, the acid washing method was explicitly eliminated by the state in 2015. Currently, the mainstream crude benzene hydrogenation refining processes at home and abroad mainly include: the American Axens low-temperature gas-liquid two-phase hydrogenation technology, the German Uhde low-temperature gas-phase hydrogenation technology (KK method), the Litol process technology developed by Hudley for producing pure benzene by Asahi Kasei in Japan at high temperature thermal cracking, and the "proprietary combined process technology of low-temperature crude benzene hydrogenation and extractive distillation" independently developed by China based on the latter two.

[0003] However, regardless of the specific hydrorefining process described above, strictly speaking, they all belong to "light benzene hydrorefining," not true "crude benzene full-fraction hydrorefining." This is because they all require pre-treatment to remove the heavy benzene component—"heavy benzene"—from the crude benzene, either beforehand or during the hydrorefining process, before further hydrorefining the resulting "light benzene" to obtain high-quality pure benzene, toluene, xylene, and other aromatics. The removal of heavy benzene not only increases energy consumption but also results in the unrefined heavy benzene being sold as a cheap byproduct. Therefore, this type of technology, because it cannot process crude benzene of all components, increases plant energy consumption and reduces the resource and economic benefits of the product.

[0004] Coal-based light hydrocarbons are light hydrocarbon feedstocks rich in benzene and aromatic hydrocarbons, mainly derived from byproducts of coal gasification and coal liquefaction processes. Their physical properties are similar to crude benzene, but they contain slightly lower levels of aromatic hydrocarbons such as benzene, toluene, and xylene, and higher levels of olefins, sulfur and nitrogen impurities, and C5 and C4 light hydrocarbons. Therefore, coal-based light hydrocarbons, as a primary chemical product, cannot be directly used in chemical production and require hydrorefining. However, because their olefin content is much higher than that of crude benzene, a large amount of heat is released during hydrorefining, and equipment is highly susceptible to blockage due to olefin polymerization. Therefore, traditional crude benzene hydrorefining processes are not suitable for processing this feedstock. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for hydrogenation treatment of crude benzene whole fraction and / or coal-based light hydrocarbon feedstock.

[0006] A method for hydrogenation treatment of crude benzene fraction and / or coal-based light hydrocarbons includes the following steps: under conditions of 4–15 MPa, the reactants are sequentially subjected to a primary hydrogenation reaction, a secondary hydrogenation reaction, and a tertiary hydrogenation reaction; wherein the primary hydrogenation reaction is liquid-phase pre-hydrogenation, and a first NiMo catalyst is used in the primary hydrogenation reaction; the secondary hydrogenation reaction is gas-liquid two-phase hydrogenation, and a second NiMo catalyst is used in the secondary hydrogenation reaction; the tertiary hydrogenation reaction is gas-phase hydrogenation, and at least one of a third NiMo catalyst, a CoMo catalyst, and a NiMoW catalyst is used in the tertiary hydrogenation reaction. Optionally, a CoMo catalyst and a NiMoW catalyst are used in the tertiary hydrogenation reaction. Optionally, a triple NiMo catalyst, a CoMo catalyst, and a NiMoW catalyst are used in the tertiary hydrogenation reaction. Optionally, the tertiary hydrogenation reaction includes a prior reaction using a third NiMo catalyst and / or a CoMo catalyst, and a subsequent reaction using a NiMoW catalyst. Preferably, the reaction conditions are 5–12 MPa. More preferably, the reaction conditions are 5.5–11 MPa.

[0007] Preferably, the active metal content of the first NiMo catalyst is higher than that of the second NiMo catalyst.

[0008] Preferably, the temperature of the influent for the first-stage hydrogenation reaction is 95–160°C, the temperature of the influent for the second-stage hydrogenation reaction is 170–250°C, and the temperature of the influent for the third-stage hydrogenation reaction is 250–395°C.

[0009] Preferably, the process further includes the step of: the influent of the secondary hydrogenation reaction first undergoes a protective reaction treatment step to remove substances prone to coking, and then the secondary hydrogenation reaction is carried out.

[0010] Preferably, the process further includes the step of heating the influent of the primary hydrogenation reaction to 145°C to 160°C at the beginning or end of the process flow before it enters the primary hydrogenation reaction.

[0011] Preferably, the process further includes the step of: sequentially exchanging heat between the effluent from the tertiary hydrogenation reaction and the influent from the tertiary hydrogenation reaction, the influent from the secondary hydrogenation reaction, and the influent from the primary hydrogenation reaction.

[0012] Preferably, the process further includes the step of: exchanging heat with the effluent from the primary hydrogenation reaction, and then passing the effluent from the tertiary hydrogenation reaction through a steam generator for heat exchange and cooling, so as to transfer the excess heat in the effluent to water to generate low-pressure steam, thereby achieving the purpose of full heat recovery.

[0013] Preferably, the process further includes the following steps: dechlorinating the effluent after the three-stage hydrogenation reaction; performing high-pressure separation on the dechlorinated effluent to separate excess hydrogen; performing low-pressure separation on the effluent after high-pressure separation to separate hydrogen sulfide; performing a first distillation on the effluent after low-pressure separation to obtain gaseous and liquid fractions; performing a second distillation on the gaseous fraction after the first distillation to obtain liquefied petroleum gas (LPG) components; and performing fractionation on the liquid fraction after the first distillation to obtain refined light aromatics and diesel blending components.

[0014] Preferably, the process further includes the step of subjecting the side-stream effluent of the fractionation treatment to a third distillation treatment to obtain hydrogenated naphtha and further refined light aromatics.

[0015] Preferably, the process further includes the step of stripping the side stream effluent of the fractionation process using steam or nitrogen as the stripping medium to obtain diesel blending components.

[0016] The hydrotreating method disclosed herein uses crude benzene whole fraction and / or coal-based light hydrocarbon feedstock, and employs advanced process flow selection and a reasonable catalyst gradation scheme, which can have the following significant characteristics and advantages:

[0017] 1. This method overcomes the limitations of traditional crude benzene hydrogenation technology, which cannot process the entire crude benzene fraction and coal-based light hydrocarbons, and can only process the components remaining after the removal of heavy benzene (i.e., light benzene). This method can directly process one or more of the crude benzene fraction and coal-based light hydrocarbons, or a mixture of both in a certain proportion, thus achieving diversity in raw material processing. Furthermore, it hydrogenates and refines the heavy benzene component in the crude benzene to obtain high-value-added hydrogenated naphtha / diesel blending components, improving the resource and economic efficiency of raw material processing.

[0018] 2. In this method, there is no need to perform heavy weight removal pretreatment on crude benzene, which further reduces the energy consumption required for the processing. Therefore, compared with the traditional crude benzene hydrogenation refining process, the energy consumption per unit of raw material processed by this method is lower.

[0019] 3. Due to the advanced process flow and reasonable catalyst gradation scheme of this method, under appropriate process conditions (temperature, pressure, space velocity and hydrogen-to-oil ratio), the aromatic loss rate during raw material processing is comparable to that of the traditional crude benzene hydrogenation process, ensuring a high yield of the target product.

[0020] 4. This method, through liquid-phase pre-hydrogenation and reactor protection in the pre-hydrogenation process, as well as a reasonable heat exchange process, can reduce the frequency of local blockages in the unit, increase the operating cycle of the unit, and reduce the economic losses caused by unit shutdown and maintenance.

[0021] 5. In this method, liquefied gas (C4 and C5) recovery towers are set up in reasonable process sections to maximize the liquid phase recovery rate during the processing and significantly improve the economic benefits of the equipment. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A flowchart of the hydrogenation treatment method for crude benzene whole fraction and / or coal-based light hydrocarbon feedstock disclosed herein is shown. Detailed Implementation

[0024] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this disclosure.

[0025] This invention discloses a hydrotreating method for crude benzene whole fraction and / or coal-based light hydrocarbons. This method can process crude benzene whole fraction and / or coal-based light hydrocarbon feedstock into products such as liquefied petroleum gas, pure benzene, toluene, xylene, hydrotreated naphtha, and diesel blending components. This hydrotreating method employs a three-stage hydrotreating process under high pressure, effectively removing heavy metals and impurities such as sulfur, nitrogen, and oxygen from the feedstock. It also effectively alleviates coking and blockage during the hydrotreating process and allows for deep hydrotreating of heavy benzene in the crude benzene.

[0026] raw material

[0027] According to the present invention, the raw materials used are those containing crude benzene and / or coal-based light hydrocarbons.

[0028] In some embodiments, the feedstock consists essentially of the crude benzene fraction. For example, the density of the crude benzene is 0.871–0.900 g / cm³. 3 The distillation range is as follows: initial boiling point > 70℃, distillate > 93% before 180℃, total distillate > 85% for benzene, toluene, and xylene, and benzene > 68%.

[0029] In some embodiments, the raw material is substantially composed of heavy benzene. For example, the density of heavy benzene is 0.960–1.050 g / cm³. 3The distillation range is 130℃~300℃, the total nitrogen content is ≤8000mg / kg, and the total sulfur content is ≤8000mg / kg.

[0030] In some embodiments, the raw material consists primarily of coal-based light hydrocarbons. For example, the density of the coal-based light hydrocarbons is 0.760–0.820 g / cm³. 3 The distillation range is 35℃~185℃, the content of benzene, triphenylene and terephthalic acid is ≥35%, and the content of diene is <11gI2 / 100g.

[0031] In some embodiments, the feedstock is any one, two, or three of crude benzene fraction, heavy benzene, and coal-based light hydrocarbons.

[0032] Three-stage hydrotreating

[0033] Reference Figure 1 The hydrotreating method of the present invention includes subjecting the aforementioned raw materials to three-stage hydrotreating, namely, the raw materials sequentially undergoing a first-stage hydrotreating reaction, a second-stage hydrotreating reaction, and a third-stage hydrotreating reaction to perform hydrorefining of the raw materials, completing the removal of heavy metals, olefin saturation, desulfurization, denitrification, and deoxygenation, etc., to form a product stream that includes at least the following substances: liquefied petroleum gas (containing butane, pentane, and a small amount of propane, etc.), refined light aromatics (containing a mixture of benzene, toluene, and xylene), hydrotreated naphtha, and diesel blending components.

[0034] Specifically, feedstock 11 is mixed with recycled hydrogen after replenishment and used as influent 12 for the first-stage hydrogenation reaction, which is a liquid-phase pre-hydrogenation reaction using a first NiMo catalyst. Effluent 14 from the first-stage hydrogenation reaction is used as influent for the second-stage hydrogenation reaction, which is a gas-liquid two-phase hydrogenation reaction using a second NiMo catalyst. Effluent 15 from the second-stage hydrogenation reaction is used as influent for the tertiary hydrogenation reaction, which is a gas-phase hydrogenation reaction using at least one of a third NiMo catalyst, a CoMo catalyst, and a NiMoW catalyst. The hydrogen added to the feedstock includes recycled hydrogen 64 and replenishment hydrogen 62, where recycled hydrogen 64 refers to excess hydrogen separated from the effluent 16 of the tertiary hydrogenation reaction after three stages of hydrogenation treatment.

[0035] More specifically, the operating conditions for the three-stage hydrogenation process are as follows: the system pressure is 4–15 MPa, preferably 5–12 MPa, and more preferably 5.5–11 MPa; the temperature of the influent for the first-stage hydrogenation reaction is 95–160°C, the temperature of the influent for the second-stage hydrogenation reaction is 170–250°C, and the temperature of the influent for the third-stage hydrogenation reaction is 250–395°C.

[0036] refer to Figure 1After the raw material enters the hydrotreating system 100, it is pressurized to 5-15 MPa by the feed pump P-1. The raw material is mixed with excess hydrogen and then heated to 95-160°C before entering the primary hydrotreating reactor R-1. The first NiMo catalyst is placed in the primary hydrotreating reactor R-1. In some embodiments, the primary hydrotreating reactor R-1 can be a tubular fixed-bed reactor or an adiabatic fixed-bed reactor, preferably an adiabatic fixed-bed reactor. The raw material contacts the first NiMo catalyst in the primary hydrotreating reactor R-1, achieving liquid-phase pre-hydrogenation. Under the action of the first NiMo catalyst, substances that are prone to polymerization and coking, such as dienes, styrene, indene, and cyclopentadiene, are hydrogenated to saturation or converted into monoolefins. In some embodiments, the primary hydrotreating reactor R-1 also contains a protective agent, which is a catalyst with a special structure containing a small amount of active metal. This protective agent is used to adsorb solid impurities and a small amount of asphaltenes in the material, preventing the main catalyst used in the hydrotreating reaction from clogging and deactivating. The raw material passes through the protective agent first and then through the first NiMo catalyst.

[0037] The effluent from the primary hydrogenation reaction is heated to 170–250°C and enters the secondary hydrogenation reactor R-2, where a second NiMo catalyst is disposed. In some embodiments, the secondary hydrogenation reactor R-2 can be a fixed-bed, moving-bed, or fluidized-bed reactor, preferably a fixed-bed reactor, and more preferably an adiabatic fixed-bed reactor. The effluent from the primary hydrogenation reaction contacts the second NiMo catalyst in the secondary hydrogenation reactor R-2, achieving gas-liquid two-phase hydrogenation. Under the action of the second NiMo catalyst, monoolefins are hydrogenated to saturation, and small compounds containing heteroatoms such as sulfur, nitrogen, and oxygen undergo hydrogenation and de-impurification reactions. In some embodiments, the secondary hydrogenation reactor R-2 also contains a protective agent and / or a demetallizing agent. In a preferred embodiment, the effluent from the primary hydrogenation reaction sequentially passes through a protective agent, a demetallizing agent, and the second NiMo catalyst, thus removing trace impurities before undergoing the secondary hydrogenation reaction. This demetallizing agent is a catalyst with a special structure containing a certain amount of active metal. It is used to adsorb heavy metal elements rich in materials and prevent the main catalyst used in the hydrogenation reaction from being poisoned and deactivated.

[0038] The effluent from the secondary hydrogenation reaction is heated to 250–395°C and enters the tertiary hydrogenation reactor R-3, in which CoMo and NiMoW catalysts are disposed. In some embodiments, the tertiary hydrogenation reactor R-3 may be a fixed-bed, moving-bed, or fluidized-bed reactor, preferably a fixed-bed reactor, and more preferably an adiabatic fixed-bed reactor.

[0039] In some embodiments, the three-stage hydrogenation reactor R-3 is entirely composed of CoMo catalyst, and the effluent 15 from the second-stage hydrogenation reaction undergoes deep hydrogenation at a relatively high temperature (above 330°C) to remove sulfur, nitrogen, and oxygen impurities from all components.

[0040] In some embodiments, a third NiMo catalyst and a NiMoW catalyst are selected in the three-stage hydrogenation reactor R-3, and the effluent 15 from the second-stage hydrogenation reaction is hydrogenated at a relatively low temperature (below 350°C) to complete the deep hydrogenation of all components to remove sulfur, nitrogen and oxygen impurities.

[0041] Optionally, two catalysts, CoMo and NiMoW, are used in the three-stage hydrogenation reactor R-3. Alternatively, three catalysts are used in the three-stage hydrogenation reactor R-3: a third NiMo catalyst, a CoMo catalyst, and a NiMoW catalyst. Preferably, the third NiMo catalyst and / or CoMo catalyst are placed in the upper layer of the three-stage hydrogenation reactor R-3, and the NiMoW catalyst is placed in the lower layer. The effluent 15 from the second-stage hydrogenation reaction, under the action of the third NiMo catalyst and / or CoMo catalyst, undergoes the removal of sulfur, nitrogen, and oxygen impurities from light benzene and some heavy benzene; under the action of the NiMoW catalyst, the remaining heavy benzene undergoes the removal of sulfur, nitrogen, and oxygen impurities. In some embodiments, the three-stage hydrogenation reactor R-3 also contains a protective agent and / or a demetallizing agent. In a preferred embodiment, the effluent 15 from the second-stage hydrogenation reaction sequentially passes through a protective agent, a demetallizing agent, the third NiMo and / or CoMo catalyst, and the NiMoW catalyst, so that the effluent is first removed of trace impurities before undergoing the third-stage hydrogenation reaction.

[0042] In some embodiments, the active metal content of the first NiMo catalyst and the second NiMo catalyst is not limited; for example, they can be the same or different. In a preferred embodiment, the first NiMo catalyst has a high active metal content, while the second NiMo catalyst has a slightly lower active metal content. The former, with its high active metal content, facilitates a more complete primary hydrogenation reaction of unsaturated compounds such as dienes at low temperatures; the latter, with its slightly lower active metal content, ensures both the smooth progress of the secondary hydrogenation reaction and a lower aromatic hydrocarbon loss rate.

[0043] In the three-stage hydrogenation process disclosed herein, the hydrogenation reaction is carried out gradually, stepwise, and segmentally to achieve hydrogenation refining. The first-stage NiMo catalyst has a high active metal content, giving it relatively high reactivity and a low activation temperature (80–120°C). Therefore, under appropriate conditions, the feedstock, such as diolefins, styrene, indene, and cyclopentadiene, which are prone to polymerization and coking, are pre-hydrogenated or converted into monoolefins through the first-stage hydrogenation reaction. The second-stage NiMo catalyst has a slightly lower active metal content, ensuring both smooth progress of the feedstock in the second-stage hydrogenation reaction and a lower aromatic hydrocarbon loss rate. The second-stage hydrogenation reaction mainly focuses on the further saturation of monoolefins and the removal of small-molecule sulfur, nitrogen, and oxygen impurities from the feedstock. The upper stage employs a highly reactive third NiMo catalyst and / or a CoMo catalyst with optimal aromatic selectivity to perform hydrogenation refining of light benzene and some heavy benzene, including desulfurization, denitrification, and deoxygenation, while ensuring minimal aromatic loss. Simultaneously, a more reactive NiMoW catalyst is arranged below to ensure sufficient hydrogenation depth for the refining and purification of macromolecules in heavy benzene.

[0044] The feedstock contains numerous impurities and is rich in dienes. Conventional processes are prone to clogging the hydrogenation reactor or other equipment, leading to plant shutdowns for maintenance. The hydrogenation treatment method disclosed herein optimizes the catalyst gradation scheme, reducing the frequency of localized blockages and thus extending the plant's operating cycle while minimizing economic losses from downtime.

[0045] In some embodiments, the effluent from the primary hydrogenation reaction undergoes a protective reaction treatment step to remove easily coking substances before proceeding to the secondary hydrogenation reaction. The hydrogenation treatment system 100 includes a protective reactor MR-1, which is filled with ceramic balls and a porous protective agent to effectively remove easily coking substances, such as asphaltenes and gums inherent in the feedstock and olefin polymers formed by small amounts of side reactions during hydrogenation heating, thereby extending the coking time of the secondary hydrogenation reactor. In some embodiments, the hydrogenation treatment system 100 has two parallel protective reactors MR-1, one in operation and the other on standby, further reducing the frequency of localized blockages in the unit and allowing for online treatment of blockage locations without affecting production.

[0046] In some embodiments, the hydrotreating method further includes dechlorination treatment of the effluent from the tertiary hydrotreating reaction. The hydrotreating system 100 includes a dechlorination reactor R-4, which is filled with a dechlorinating agent to remove hydrogen chloride produced after the hydrotreating reaction, effectively preventing hydrogen chloride corrosion of pipelines and equipment. Since the dechlorination reactor R-4 effectively solves the problem of excessive chlorine content, it can normally process raw materials with a chlorine content below 50 ppm, and can process raw materials with a chlorine content exceeding 100 ppm for a short period. Therefore, this method can handle raw materials with high chlorine content. Generally, raw materials with higher chlorine content are cheaper, thus improving the economic efficiency of the plant.

[0047] In some embodiments, the effluent from the tertiary hydrogenation reaction exchanges heat with at least one of the influents from the primary, secondary, and tertiary hydrogenation reactions. In the three-stage hydrogenation process, the temperature increases progressively at each stage, and since the hydrogenation reaction is exothermic, the effluent temperature from the tertiary hydrogenation reaction can reach 320-395°C. Therefore, this effluent can provide heat energy for the influents of each stage of the hydrogenation reaction. In a preferred embodiment, the effluent from the tertiary hydrogenation reaction provides heat energy for the influents of the primary, secondary, and tertiary hydrogenation reactions. In a more preferred embodiment, the effluent from the tertiary hydrogenation reaction first exchanges heat with the influent of the tertiary hydrogenation reaction, then with the influent of the secondary hydrogenation reaction, and finally with the influent of the primary hydrogenation reaction. In some embodiments, the effluent from the tertiary hydrogenation reaction undergoes dechlorination treatment before exchanging heat with the influents of each stage of the hydrogenation reaction.

[0048] In some embodiments, the influents of each stage of the hydrogenation reaction can be heated to the corresponding temperature by a heater before the hydrogenation reaction. For example, the influent of the first-stage hydrogenation reaction can be heated to 95–160°C by a heater. Preferably, at the beginning or end of the process flow, the influent of the first-stage hydrogenation reaction is heated by heater E-2 before the first-stage hydrogenation reaction is carried out. At the beginning or end of the process flow, when the effluent of the tertiary hydrogenation reaction cannot provide sufficient heat energy for the influent of the first-stage hydrogenation reaction, heat energy can be provided by heater E-2.

[0049] See Figure 1The hydrotreating system 100 further includes a first heat exchanger E-1, a second heat exchanger E-3, and a third heat exchanger E-4. The first heat exchanger E-1 exchanges heat between the influent of the primary hydrotreating reaction and the effluent of the tertiary hydrotreating reaction; the second heat exchanger E-3 exchanges heat between the influent of the secondary hydrotreating reaction and the effluent of the tertiary hydrotreating reaction; and the third heat exchanger E-4 exchanges heat between the influent of the tertiary hydrotreating reaction and the effluent of the tertiary hydrotreating reaction. The effluent of the tertiary hydrotreating reaction passes sequentially through the third heat exchanger E-4, the second heat exchanger E-3, and the first heat exchanger E-1. In some embodiments, the hydrotreating system 100 also includes a heater E-2 to provide heat energy to the influent of the primary hydrotreating reaction. Specifically, the heater E-2 is an electric heater or an externally supplied heat source heater, which is started at the beginning or end of the process flow.

[0050] In some embodiments, the effluent from the secondary hydrogenation reaction is heated by a heating device before flowing into the tertiary hydrogenation reactor R-3. Specifically, the hydrogenation treatment system 100 includes a hydrogenation heater F-1, and the effluent from the secondary hydrogenation reaction first passes through a third heat exchanger E-4, and then is heated by the hydrogenation heater F-1 before flowing into the tertiary hydrogenation reactor R-3.

[0051] In some embodiments, the hydrotreating system 100 further includes a feed buffer tank D-1, and the raw material enters the feed buffer tank D-1 and is then pressurized by the feed pump P-1.

[0052] High and low pressure separation

[0053] After high-pressure and low-pressure separation steps on the effluent from the three-stage hydrogenation reaction, a product stream is obtained. Specifically, the effluent from the three-stage hydrogenation reaction undergoes high-pressure separation to remove excess hydrogen, and the effluent after high-pressure separation undergoes low-pressure separation to remove hydrogen sulfide. The effluent after low-pressure separation is the product stream. The excess hydrogen can be used as recycled hydrogen 64 and mixed with the feedstock for further hydrogenation reactions, while the hydrogen sulfide is discharged from the system. The pressure range for high-pressure separation is 5.0–12 MPa, and the pressure range for low-pressure separation is 0.8–2.5 MPa.

[0054] See also Figure 1 The hydrotreating system 100 is equipped with a high-pressure separator D-2 and a low-pressure separator D-3. The effluent 16 from the three-stage hydrotreating reaction passes through the high-pressure separator D-2 to separate excess hydrogen. The effluent 18 from the high-pressure separator D-2 enters the low-pressure separator D-3 to separate hydrogen sulfide 37 and obtain product stream 21. More specifically, the excess hydrogen separated by the high-pressure separator D-2 is mixed with the feedstock after passing through the circulating hydrogen compressor K-1.

[0055] In some embodiments, the effluent from the tertiary hydrogenation reaction undergoes heat exchange in a fourth heat exchanger E-5 before entering the high-low pressure separation step. In some embodiments, the fourth heat exchanger E-5 is a steam generator (waste heat boiler), and the cold source medium is water. The water carries away most of the heat from the effluent of the tertiary hydrogenation reaction, causing its temperature to drop to 30–60°C.

[0056] Product stream separation

[0057] The effluent (product stream) after low-pressure separation is further separated into liquefied petroleum gas (LPG), refined light aromatics (a mixture containing benzene, toluene, and xylene), hydrotreated naphtha, and diesel blending components through multiple distillations, fractionations, or stripping. Specifically, in some embodiments, the effluent after low-pressure separation undergoes a first distillation to obtain gaseous and liquid fractions; the gaseous fraction after the first distillation undergoes a second distillation to obtain LPG; and the liquid fraction after the first distillation undergoes fractionation to obtain refined light aromatics, hydrotreated naphtha, and diesel blending components. In the prior art, the gaseous fraction after the first distillation mainly consists of butane, pentane, hydrogen sulfide, and small amounts of propane and recycled hydrogen components (methane, hydrogen, etc.). This fraction can be liquefied to form LPG, which includes components such as propane, butane, and pentane. Compared with the prior art, the present invention, through a second distillation process, can not only further remove dissolved hydrogen sulfide from liquefied petroleum gas (LPG) and improve the quality requirements of LPG, but also effectively recover this component material as a high-value product, thereby increasing the overall target yield of raw materials in the processing process and thus improving the economic benefits of processing and production.

[0058] Specifically, in some embodiments, the top gaseous distillate from the fractionation process is classified as light aromatics, the first-side effluent from the fractionation process becomes hydrotreated naphtha, and the second-side and / or bottom effluent from the fractionation process becomes diesel blending components. In some embodiments, the first-side effluent from the fractionation process may undergo a third distillation process to obtain hydrotreated naphtha and further separated high-purity refined light aromatics. This third distillation process further separates the light aromatics from the hydrotreated naphtha, which not only improves the purity of the hydrotreated naphtha to meet its requirements for aromatic content (especially benzene content), but also helps to increase the yield of refined light aromatics.

[0059] In some embodiments, the side stream effluent from the fractionation process is stripped to obtain a diesel blend component. Stripping removes light components from the side stream effluent, effectively increasing the flash point of the diesel blend component, and recovers the removed light components into the hydrotreated naphtha. The stripping medium can be superheated steam or a superheated inert stripping medium (e.g., nitrogen), preferably superheated nitrogen. Compared to superheated steam, superheated nitrogen achieves the same stripping removal of light components without introducing steam, which would cause water turbidity or even emulsification in the fractionation column top product. Furthermore, steam stripping generates a large amount of oily wastewater, causing secondary pollution, and wastewater treatment adds additional energy and economic costs. Finally, the production cost of nitrogen is significantly lower than that of steam.

[0060] Continue to refer to Figure 1 The hydrotreating system 100 includes a stabilization tower C-1, a liquefied petroleum gas (LPG) tower C-2, and a fractionation tower C-3. The effluent 21 from the low-pressure separation process flows into the stabilization tower C-1 for a first rectification process, resulting in a gaseous fraction flowing from the top and a liquid fraction flowing from the bottom. The liquid formed from the cooled gaseous fraction at the top of the stabilization tower C-1 flows into the LPG tower C-2, where it undergoes a second rectification process, resulting in a liquid fraction (LPG) flowing from the bottom. The liquid fraction at the bottom of the stabilization tower C-1 flows into the fractionation tower C-3 for fractionation, resulting in refined light aromatics flowing from the top and diesel blending components obtained from the side stream and / or bottom effluent 44. In some embodiments, the liquid fraction 22 at the bottom of the stabilization tower C-1 undergoes fractionation in the fractionation tower C-3, directly flowing out hydrotreated naphtha (not shown in the figure) from its side stream. (See reference...) Figure 1 The hydrotreating system 100 also includes a mixed aromatics cut-off tower C-5. In other embodiments, the bottom liquid fraction of the stabilizing tower C-1 is fractionated in the fractionating tower C-3, and the effluent 24 from its side line flows into the mixed aromatics cut-off tower C-5 for a third rectification process. Refined light aromatics flow from the top of the mixed aromatics cut-off tower C-5, and hydrotreated naphtha flows from its bottom. In some embodiments, the hydrotreating system 100 includes a stripping tower C-4. The effluent 27 from the second side line of the fractionating tower C-3 flows into the stripping tower C-4 for stripping to obtain diesel blending components, while the effluent 28 from the top of the stripping tower C-4 returns to the fractionating tower C-3.

[0061] Specifically, the hydrogenation treatment system 100 also includes a first reflux tank D-6, a second reflux tank D-7, a third reflux tank D-4, and a fourth reflux tank D-5. The first reflux tank D-6 is connected to the top of the fractionation column C-3 and is used to cool and reflux the overhead effluent 25 (refined light aromatics) of the fractionation column C-3. The second reflux tank D-7 is connected to the top of the mixed aromatics cut-off column C-5 and is used to cool and reflux the overhead effluent 26 (refined light aromatics) of the mixed aromatics cut-off column C-5. The third reflux tank D-4 is connected between the top of the stabilization column C-1 and the liquefied gas column C-2 and is used to cool and reflux the overhead effluent 23 of the stabilization column C-1. The fourth reflux tank D-5 is connected to the top of the liquefied gas column C-2 and is used to cool and reflux the overhead effluent 29 of the liquefied gas column C-2.

[0062] In some embodiments, the bottom effluent of the stabilization column C-1 is heated before flowing into the fractionation column C-3. The hydrogenation treatment system 100 is equipped with a fractionation heater F-2, and the bottom effluent of the stabilization column C-1 is heated to 250-350°C by the fractionation heater F-2 before flowing into the fractionation column C-3.

[0063] Specifically, refer to Figure 1 The product stream separation module of the hydrotreating system 100 is equipped with a first product outflow pipeline 31, a second product outflow pipeline 32, a third product outflow pipeline 33, a fourth product outflow pipeline 34, a fifth product outflow pipeline 35, and a sixth product outflow pipeline 36. Specifically, the first product outflow pipeline 31 provides an outflow channel for the hydrotreated naphtha product; the second product outflow pipeline 32 provides an outflow channel for the liquefied petroleum gas product; the third product outflow pipeline 33 provides an outflow channel for the diesel blending components product; the fourth product outflow pipeline 34 provides an outflow channel for the non-aromatic / raffinate oil product; the fifth product outflow pipeline 35 provides an outflow channel for the toluene and xylene products; and the sixth product outflow pipeline 36 provides an outflow channel for the pure benzene product.

[0064] In some embodiments, the hydrotreating system 100 is equipped with an aromatics extraction unit L-1. The sixth product outflow line 36, the fifth product outflow line 35, and the fourth product outflow line 34 are respectively connected to the aromatics extraction unit L-1. Refined light aromatics 42 flow into the aromatics extraction unit L-1, pure benzene flows out from the sixth product outflow line 36, toluene and xylene flow out from the fifth product outflow line 35, and non-aromatics / raffinate flows out from the fourth product outflow line 34.

[0065] In some embodiments, the fourth product outlet line 34 is connected to the first product outlet line 31 via the first connecting line 52. One end of the first product outlet line 31 is connected to the bottom of the mixed aromatics cutting tower C-5, and the first product outlet line 31 is used to transport hydrotreated naphtha. A first switching valve 71 is provided on the first connecting line 52, and a second switching valve 72 is provided at the end of the fourth product outlet line 34 away from the aromatics extraction unit L-1. Depending on the condition of the aromatics extraction unit L-1, one of the first switching valve 71 and the second switching valve 72 is selectively opened, while the other remains closed.

[0066] In some embodiments, the fifth product outlet line 35 is connected to the first product outlet line 31 via a second connecting line 54. A third switching valve 73 is provided on the second connecting line 54, and a fourth switching valve 74 is provided at the end of the fifth product outlet line 35 furthest from the aromatics extraction device L-1. Depending on the condition of the aromatics extraction device L-1, one of the third switching valve 73 and the second switching valve 74 is selectively opened, while the other remains closed.

[0067] Example 1

[0068] The raw materials are at least one of coking crude benzene and coal-based light hydrocarbons.

[0069] The composition and mass fraction of crude benzene from coking are as follows: total aromatics 88.14%, diene value 1.9 gI2 / 100g, bromine value 13.3 gBr2 / 100g, total sulfur 5071 mg / kg, total nitrogen content 853 mg / kg, and total chlorine content 8.2 mg / kg.

[0070] The composition and mass fraction of coal-based light hydrocarbons are as follows: total aromatics 49.53%, diene value 9.2 gI2 / 100g, bromine value 70 gBr2 / 100g, total sulfur 2808 mg / kg, total nitrogen content 1736 mg / kg, and total chlorine content 17.9 mg / kg.

[0071] The hydrogenation reaction conditions are as follows: first-stage hydrogenation reaction temperature 110℃, pressure 6.0MPa, and space velocity 2.0h⁻¹. -1 The hydrogen-to-oil ratio was 500:1; the secondary hydrogenation reaction temperature was 170℃, the pressure was 5.8 MPa, and the space velocity was 1.5 h⁻¹. -1 The hydrogen-to-oil ratio was 800:1; the three-stage hydrogenation reaction was carried out at a temperature of 270℃, a pressure of 5.5 MPa, and a space velocity of 0.65 h⁻¹. -1 The hydrogen-to-oil ratio was 1000:1. The results of continuous hydrogenation reactions for feedstocks 1.1 and 1.2 for 90 days are shown in Table 1.

[0072] Table 1 describes the results of the following hydrogenation reactions, and Table 2 describes the yields obtained for the following reactions.

[0073] #1.1 The raw material is coking crude benzene.

[0074] #1.2 The raw materials are 40% wt coking crude benzene and 60% wt coal-based light hydrocarbons.

[0075] Table 1

[0076]

[0077] Table 2

[0078]

[0079]

[0080] As can be seen from the above embodiments, after 90 days of continuous operation, the pressure drop from the outlet of the tertiary hydrogenation reactor to the inlet of the primary hydrogenation reactor is less than 15 kPa, especially the pressure drop of the processing condition of feedstock #1.1 is less than 10 kPa, indicating that there is basically no coking or blockage in the hydrogenation reactor and the entire system, thus demonstrating that the process conditions can be operated for a long period. After primary hydrogenation, the content of diolefins in feedstocks #1.1 and #1.2 is reduced to below 1.0 g I2 / 100 g, indicating that the diolefins most prone to polymerization and coking in the feedstock at lower temperatures have been basically removed by the hydrogenation reaction. After secondary hydrogenation, the content of monoolefins and other unsaturated hydrocarbons in feedstocks #1.1 and #1.2 is reduced to below 5 g Br2 / 100 g, indicating that the substances that are relatively prone to polymerization and coking have been basically removed by the hydrogenation reaction at this stage, providing sufficient favorable conditions for the subsequent high-temperature hydrogenation refining reaction—tertiary hydrogenation, and effectively solving the problem of reactor and system blockage caused by polymerization and coking of feedstock during hydrogenation. After three-stage hydrogenation, the total sulfur and total nitrogen in the products of feedstock schemes #1.1 and #1.2 are both below 0.5 mg / kg, indicating that the present invention has good desulfurization, denitrification, and purification capabilities. Meanwhile, the aromatic hydrocarbon loss rate of each reaction product relative to the feedstock in the examples is all <1.5%, indicating that the present invention achieves good aromatic hydrocarbon product recovery while simultaneously addressing the hydrogenation of heavy benzene, demonstrating significant advantages.

[0081] Example 2

[0082] The raw materials were the raw material scheme #1.2 in Example 1. According to the reaction conditions in Example 1, Table 3 describes the comparison of yields obtained from the following items, and Table 4 describes the comparison of the benzene, toluene, and xylene content of refined light aromatics and hydrogenated naphtha obtained from the following items.

[0083] #2.1 (Prior Art) The gaseous distillate at the top of the stabilizer column C-1 enters the third reflux tank D-4 and becomes liquefied gas after cooling, i.e., it does not undergo a second rectification process; the effluent from the side line of the fractionation column C-3 becomes hydrotreated naphtha, i.e., it does not undergo a third rectification process.

[0084] #2.2 (Invention) The gaseous fraction at the top of the stabilizer C-1 enters the third reflux tank D-4, and the liquid formed after cooling enters the LPG tower C-2. In the LPG tower C-2, it undergoes a second rectification process to obtain LPG. The effluent from the side line of the fractionation tower C-3 enters the mixed aromatics cutting tower C-5. In the mixed aromatics cutting tower C-5, it undergoes a third rectification process to separate light aromatics and hydrogenated naphtha.

[0085] Table 3

[0086]

[0087]

[0088] Table 4

[0089]

[0090] As can be seen from the above embodiments, the treatment by LPG tower C-2 effectively recovered 2.82% of the LPG component in the total product, and the sulfur content of the LPG was reduced to below 0.1 ppm. This indicates that the treatment by LPG tower C-2 in this invention not only ensures the qualified quality of the product, but also improves the overall processing yield of the unit through the aftereffect recovery of the LPG component, thereby improving resource and economic benefits. After the effluent from the first line of the fractionation tower C-3 is treated by the mixed aromatics cutting tower C-5, the benzene content in the hydrotreated naphtha is reduced from 32.73% to ≤0.01%. This not only makes the hydrotreated naphtha meet the requirement of ≤0.8% benzene content in GB 17930-2016, but also shows that the proportion of the total content of benzene, toluene, and xylene in the refined light aromatics relative to the total raw material increases from 46.48% to 69.10%, significantly improving the overall recovery rate of benzene, toluene, and xylene in the refined light aromatics. Therefore, it can be seen that the mixed aromatics cutting tower C-5 in this invention has achieved effective separation of each target product while ensuring that the index requirements of each target product are met, so it is necessary and beneficial.

[0091] It should be further clarified that, in the above-disclosed inventions, the term "in sequence" mainly indicates a temporal or spatial order of precedence, and does not necessarily indicate a temporal continuation or spatial adjacency. For example, between two steps that are sequentially defined by "in sequence," there may be other steps; between two components that are connected by "in sequence," there may be other components connected to each other.

[0092] The above descriptions are merely a few embodiments of this disclosure. Those skilled in the art can make various modifications or variations to the embodiments of this disclosure based on the content disclosed in the application documents without departing from the spirit and scope of this disclosure.

Claims

1. A method for hydrogenation treatment of crude benzene whole fraction and / or coal-based light hydrocarbons, characterized in that, The method includes the following steps: Under conditions of 4–15 MPa, the reactants are subjected to a first-stage hydrogenation reaction, a second-stage hydrogenation reaction, and a third-stage hydrogenation reaction in sequence; The effluent from the three-stage hydrogenation reaction is subjected to high-pressure separation to remove excess hydrogen. The effluent after the high-pressure separation treatment is subjected to low-pressure separation treatment to separate hydrogen sulfide; The effluent after the low-pressure separation process is subjected to a first distillation process to obtain gaseous and liquid fractions; The gaseous fraction after the first distillation treatment is subjected to a second distillation treatment to obtain a liquefied gas component. as well as The liquid fraction after the first distillation process is fractionated to obtain light aromatics and diesel blending components; in: The primary hydrogenation reaction is a liquid-phase pre-hydrogenation reaction. The temperature of the influent to the primary hydrogenation reaction is 95–160°C. The primary hydrogenation reaction is carried out in an adiabatic fixed-bed reactor. The primary hydrogenation reaction uses a first NiMo catalyst. The secondary hydrogenation reaction is a gas-liquid two-phase hydrogenation reaction. The temperature of the influent to the secondary hydrogenation reaction is 170-250°C. The influent to the secondary hydrogenation reaction is fed from top to bottom. The secondary hydrogenation reaction uses a second NiMo catalyst. The active metal content of the second NiMo catalyst is lower than that of the first NiMo catalyst. The three-stage hydrogenation reaction is a gas-phase hydrogenation reaction. The temperature of the influent in the three-stage hydrogenation reaction is 250-395°C. The influent in the three-stage hydrogenation reaction first reacts through the upper layer of the third NiMo catalyst and / or CoMo catalyst, and then reacts through the lower layer of the NiMoW catalyst.

2. The hydrogenation treatment method according to claim 1, characterized in that, It also includes the step of: subjecting the influent of the secondary hydrogenation reaction to a protective reaction treatment step to remove substances prone to coking before carrying out the secondary hydrogenation reaction.

3. The hydrogenation treatment method according to claim 2, characterized in that, It also includes the step of heating the influent of the first-stage hydrogenation reaction to 95°C to 160°C at the beginning or end of the process flow before it enters the first-stage hydrogenation reaction.

4. The hydrogenation treatment method according to claim 3, characterized in that, It also includes the following steps: The effluent after the three-stage hydrogenation reaction is sequentially heat-exchanged with the influent of the three-stage hydrogenation reaction, the influent of the two-stage hydrogenation reaction, and the influent of the one-stage hydrogenation reaction.

5. The hydrogenation treatment method according to claim 4, characterized in that, It also includes the following steps: The effluent from the tertiary hydrogenation reaction, after exchanging heat with the effluent from the primary hydrogenation reaction, is then cooled again by passing it through a steam generator. This process transfers excess heat from the effluent to water to generate low-pressure steam, thereby achieving full heat recovery.

6. The hydrogenation treatment method according to any one of claims 1 to 5, characterized in that, It also includes the following steps: Prior to the high-pressure separation process, the effluent from the three-stage hydrogenation reaction is subjected to dechlorination treatment.

7. The hydrogenation treatment method according to claim 6, characterized in that, It also includes the following steps: The side effluent from the fractionation process is subjected to a third distillation process to obtain hydrogenated naphtha and further light aromatics.

8. The hydrogenation treatment method according to claim 7, characterized in that, It also includes the following steps: Using steam or nitrogen as the stripping medium, the effluent from the second side of the fractionation process is stripped to obtain diesel blending components.

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