A process for the production of diesel components from coal tar by hydrogenation

Abstract

The present application provides a kind of coal tar hydrogenation production diesel component method, the method includes the following steps: (1) the pretreatment of coal tar raw material, after pretreatment, obtain purified coal tar;(2) in the presence of hydrogen, purified coal tar obtained after pretreatment enters hydrofining reaction zone and carries out hydrofining reaction, after separation, the effluent of hydrofining reaction obtains gas, naphtha, diesel fraction and unconverted oil;(3) in the presence of hydrogen, the unconverted oil obtained in step (2) enters hydrocracking reaction zone and carries out hydrocracking reaction, after separation, the effluent of hydrocracking reaction obtains gas and cracking oil, and the separation of cracking oil and the effluent of hydrofining reaction in step (2) is carried out.The present application can obtain high cetane number diesel component by the combination process of coal tar pretreatment and hydrogenation in the method of coal tar hydrogenation production diesel component, solves the problem that the cetane number of diesel component produced by coal tar does not meet the standard, and the total liquid yield is low.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals and relates to coal tar hydrogenation treatment technology, specifically to a method for producing diesel components from coal tar as raw material. Background Technology

[0002] Coal tar is a byproduct of coal dry distillation, coking, and gasification. As a petroleum alternative energy source with great development potential, coal tar can be used to produce clean vehicle fuels through hydrogenation technology. This can not only effectively alleviate the contradiction between oil supply and demand and reduce dependence on imported oil, but also effectively promote the clean and efficient utilization of coal and extend the coal chemical industry chain and value chain.

[0003] Unlike natural petroleum, coal tar contains high levels of polycyclic aromatic hydrocarbons and asphaltenes. When used as a raw material, coal tar is used in hydrogenation to produce diesel fractions, which have a very high aromatic content, severely affecting the cetane number of the diesel components. Currently, producing diesel fractions from coal tar through a two-stage process of hydrorefining and hydrocracking has become one of the main industrial routes for high-value-added processing and utilization of coal tar.

[0004] Patent CN1147575C discloses a method for producing diesel fuel by hydrogenating coal tar. This method separates coal tar into residual oil and distillate oil, which is then hydrogenated in a hydrorefining unit. The reaction products are then processed through a high-efficiency fractionation and stripping tower to obtain gasoline and diesel fuel. While this method provides a pathway for utilizing coal tar, it separates residual oil, affecting the total liquid yield of gasoline and diesel fuel and failing to maximize the production of fuel oil products.

[0005] Patent CN103059981A discloses a method for hydrogenating coal tar. This method first feeds coal tar with high impurity, gum, and asphaltenes content into a pre-hydrogenation reactor for pre-hydrogenation. Suspended fine impurities are then filtered out. Under a catalyst gradation system, hydrodemetallization and deep hydrorefining reactions are carried out sequentially. After separating the light components, the tar enters a hydrocracking reactor, where it is distilled to produce gasoline, diesel, and hydrocracking tail oil.

[0006] Patent CN116676105A discloses a catalyst gradation method for improving the yield of light oil products from coal tar hydrotreating. This method involves a system gradation method where a first reactor is loaded with two beds of refining catalyst from top to bottom; a second reactor is loaded with two beds of refining catalyst from top to bottom; a third bed is loaded with cracking catalyst; and a third reactor is loaded with a system gradation method where the upper part of the first and second beds is loaded with a more active cracking agent, the lower part of the second bed is loaded with refining agent, the upper part of the third bed is loaded with diesel pour point depressant, and the lower part is loaded with refining agent. This method achieves a yield of up to 90% for light oil products from coal tar hydrotreating. Although this method improves the oil yield, it uses a variety of catalysts and has a relatively complex gradation system. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for producing diesel components from coal tar by hydrogenation. Through a combination of coal tar pretreatment and hydrogenation processes, high cetane number diesel components can be obtained, solving the problems of substandard cetane number and low total liquid yield in existing coal tar diesel component production.

[0008] This invention provides a method for producing diesel fuel components by hydrogenating coal tar, the method comprising the following steps:

[0009] (1) Pre-treat the coal tar raw material to obtain purified coal tar;

[0010] (2) In the presence of hydrogen, the purified coal tar obtained after pretreatment enters the hydrorefining reaction zone for hydrorefining reaction. The hydrorefining reaction effluent is separated to obtain gas, naphtha, diesel fraction and unconverted oil.

[0011] (3) In the presence of hydrogen, the unconverted oil obtained in step (2) enters the hydrocracking reaction zone for hydrocracking reaction. After separation of the hydrocracking reaction effluent, gas and cracked oil are obtained. The cracked oil is separated together with the hydrorefining reaction effluent in step (2).

[0012] According to some specific embodiments of the present invention, the pretreatment process of coal tar raw material in step (1) includes the following steps:

[0013] (1.1) Coal tar feedstock is treated by contacting it with a pretreatment agent;

[0014] (1.2) The material stream obtained after the treatment in step (1.1) is separated to obtain pre-purified coal tar, aqueous phase and solid slag;

[0015] (1.3) The pre-purified coal tar obtained in step (1.2) enters the membrane separation unit and is separated into purified coal tar and leachate.

[0016] According to some specific embodiments of the present invention, the pretreatment agent in step (1.1) includes a first component, a second component, and a third component; based on the weight of the pretreatment agent, the content of the first component is 5% to 25%, preferably 10% to 20%, the content of the second component is 3% to 20%, preferably 5% to 15%, and the content of the third component is 55% to 90%, preferably 65% ​​to 80%; the amount of pretreatment agent added is 0.1% to 3.0% of the weight of the coal tar raw material, preferably 0.2% to 2.0%.

[0017] According to some specific embodiments of the present invention, the first component may be selected from one or more of hydroxyethyl ethylenediamine triacetic acid, dihydroxyethyl glycine, hypozinotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and sodium salts of the above compounds; preferably one or more of hydroxyethyl ethylenediamine triacetic acid, hypozinotriacetic acid, and ethylenediaminetetraacetic acid.

[0018] According to some specific embodiments of the present invention, the second component is further defined as an acidic compound, specifically selected from one or more of oxalic acid, glycolic acid, 2-hydroxypropionic acid, 2-hydroxysuccinic acid, tartaric acid, citric acid, salicylic acid, orthophosphoric acid, metaphosphoric acid, polyphosphoric acid, pyrophosphoric acid, methanesulfonic acid, benzenesulfonic acid, methylbenzenesulfonic acid, phenolsulfonic acid, and aminosulfonic acid, preferably one or more of glycolic acid, 2-hydroxysuccinic acid, and polyphosphoric acid.

[0019] According to some specific embodiments of the present invention, the third component is a polyhydroxy alcohol, specifically selected from one or more of diethylene glycol, glycerol, 2,2-dimethylolbutanol, and pentaerythritol, preferably one or more of glycerol and pentaerythritol.

[0020] According to some specific embodiments of the present invention, the residual liquid can be returned and separated again together with the material stream obtained after step (1.1). The weight ratio of the returned residual liquid to the material stream obtained after step (1.1) is 0.1:1 to 10:1, preferably 0.5:1 to 5:1.

[0021] According to some specific embodiments of the present invention, the coal tar feedstock can be further purified by the pretreatment agent, which can convert oil-soluble metals in the coal tar into water-soluble metals (mainly sodium, potassium and other metals) or insoluble salt residues (mainly iron, calcium and other metals).

[0022] According to some specific embodiments of the present invention, in step (1.1), the temperature at which the coal tar raw material is contacted with the pretreatment agent can be controlled to be 60-150°C, preferably 70-100°C.

[0023] According to some specific embodiments of the present invention, the separation temperature in step (1.2) is further 60-100°C, preferably 80-90°C.

[0024] According to some specific embodiments of the present invention, the separation in step (1.2) can be carried out by centrifugal separation, specifically by a three-phase centrifuge. The pre-purified coal tar (oil phase), aqueous phase, and solid slag after separation by the three-phase centrifuge can be discharged through the oil phase outlet, aqueous phase outlet, and solid phase outlet of the three-phase centrifuge, respectively. The centrifugal speed of the three-phase centrifuge can generally be controlled at 2000-5000 rpm, preferably 2500-3500 rpm.

[0025] According to some specific embodiments of the present invention, the membrane separation unit in step (1.3) further includes primary membrane separation and secondary membrane separation. The primary membrane separation uses an inorganic membrane filtration assembly, preferably with the pore size gradually increasing from the tube layer to the shell layer. The inorganic membrane filtration assembly can be a commercially available product, specifically selected from one or more of ceramic membranes, polymer metal complex membranes, and molecular sieve composite membranes. The coal tar feedstock flows rapidly parallel to the tube layer membrane surface and perpendicularly permeates through the membrane tube into the shell layer to form permeate. Metal and solid particles retained on the membrane surface in the permeate are carried away by the shear force generated by the permeate flowing across the membrane surface. The secondary membrane separation uses an oleophilic-hydrophobic membrane filtration assembly. The oleophilic-hydrophobic membrane filtration assembly can be made of organic membranes, hollow fiber membranes, or a combination of both. The coal tar permeate generated by the primary membrane separation flows through the secondary membrane filtration assembly, and water molecules in the permeate, upon contacting the hydrophobic membrane surface, cannot wet and accumulate, thus being discharged. The oleophilic and hydrophobic membrane filtration component can be selected from commercially available products, specifically one or more of polytetrafluoroethylene membranes, polyamide fiber membranes, polyvinylidene fluoride membranes, and mixed cellulose ester membranes.

[0026] According to some specific embodiments of the present invention, the operating temperature of the primary membrane separation is further 100-300°C, preferably 150-250°C.

[0027] According to some specific embodiments of the present invention, the operating temperature of the secondary membrane separation is further 70-100°C, preferably 80-90°C.

[0028] According to some specific embodiments of the present invention, a heat extraction device may be provided between the primary membrane separation and the secondary membrane separation.

[0029] According to some specific embodiments of the present invention, the total metal content in the purified coal tar obtained after pretreatment is not greater than 20 μg·g. -1 .

[0030] According to some specific embodiments of the present invention, the hydrorefining reaction zone in step (2) may be provided with one or more hydrorefining reactors, preferably two or three hydrorefining reactors, and even more preferably, two or more hydrorefining reactors are connected in series.

[0031] According to some specific embodiments of the present invention, the operating conditions of the hydrorefining reaction zone in step (2) are as follows: the reaction temperature is 220–420°C, preferably 280–380°C; the reaction pressure is 10–16 MPa, preferably 13–15 MPa; and the volume hourly space velocity is 0.3–1.0 h⁻¹. -1 Preferably, it is 0.5 to 0.8 h. -1 The hydrogen-to-oil volume ratio is 600–1600, preferably 700–1300.

[0032] According to some specific embodiments of the present invention, in step (2), the hydrorefining reaction zone is provided with a first hydroprotective agent bed, a first hydrorefining catalyst bed, a first hydrocracking catalyst bed, and a first supplementary hydrorefining catalyst bed in sequence according to the direction of liquid phase material flow; wherein, based on the total catalyst loading volume, the volume ratio of the first hydroprotective agent bed is 9% to 20%, preferably 12% to 17%; the volume ratio of the first hydrorefining catalyst bed is 62% to 78%, preferably 66% to 74%; the volume ratio of the first hydrocracking catalyst bed is 7% to 15%, preferably 9% to 13%; and the volume ratio of the first supplementary refining catalyst bed is 2% to 10%, preferably 4% to 8%.

[0033] According to some specific embodiments of the present invention, the first hydrogenation protective agent bed is filled with a hydrogenation protective catalyst, which can be selected from the FZC series protective agents developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. (FRIPP), and can be at least one of FGF-01, FGF-02, FZC-100B, and FZC-28; or it can be prepared according to common knowledge in the art as needed.

[0034] According to some specific embodiments of the present invention, the first hydrorefining catalyst bed is filled with a hydrorefining catalyst, preferably two or more types of hydrorefining catalysts, and more preferably, the pore size of the hydrorefining catalyst gradually decreases in the direction of liquid phase material flow, with the pore size difference between two adjacent hydrorefining catalyst layers being 2.0-7.0 nm; the active metal content of the hydrorefining catalyst gradually increases, with the active metal content difference between two adjacent hydrorefining catalyst layers being 3 wt%-9 wt%. The hydrorefining catalyst can be at least one of the FF-20, FF-32, FF-34, FF-22, and FF-66 series hydrorefining catalysts developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. (FRIPP); or it can be prepared according to common knowledge in the art as needed. Furthermore, the first hydrorefining catalyst generally includes a support and an active metal component. The support can be one or more inorganic metal oxides such as alumina and silicon oxide. The active metal can be at least one of Group VIB and Group VIII metals, preferably at least one of Mo, Co, and Ni. The active metal exists in oxide form, and the content of the active metal component in oxide form is 18 wt% to 28 wt% based on the weight of the first hydrorefining catalyst. The pore size of the first hydrorefining catalyst is 5-20 nm.

[0035] According to some specific embodiments of the present invention, the first hydrocracking catalyst bed is packed with a hydrocracking catalyst, which can be at least one of the FC-28, FC-20, FC-14, and FC-32 series hydrocracking catalysts developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. (FRIPP); or it can be prepared according to common knowledge in the art as needed. Further, the first hydrocracking catalyst generally includes a support and an active metal component, wherein the support can be one or more of amorphous silica-alumina, Y molecular sieves, etc.; the active metal can be at least one of Group VIB metals and Group VIII metals, preferably at least one of W and Ni; the active metal exists in oxide form. Based on the weight of the first hydrocracking catalyst, the content of the active metal component as oxide is 24m% to 33m%. The pore size of the first hydrocracking catalyst is 8-15nm.

[0036] According to some specific embodiments of the present invention, the first supplementary refining catalyst bed is filled with a hydrorefining catalyst, which can be at least one of the FF-20, FF-32, FF-34, FF-22 and FF-66 series hydrorefining catalysts developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. (FRIPP), or can be prepared according to common knowledge in the art as needed.

[0037] According to some specific embodiments of the present invention, in step (3), the hydrocracking reaction zone is provided with a second hydroprotective agent bed, a second hydrorefining catalyst bed, a second hydrocracking catalyst bed, and a second supplementary hydrorefining catalyst bed in sequence according to the direction of liquid phase material flow; wherein, based on the total catalyst bed volume, the volume ratio of the second hydroprotective agent bed is 1% to 5%, preferably 2% to 4%; the volume ratio of the second hydrorefining catalyst bed is 12% to 18%, preferably 14% to 16%; the volume ratio of the second hydrocracking catalyst bed is 68% to 80%, preferably 70% to 77%; and the volume ratio of the second supplementary refining catalyst bed is 5% to 10%, preferably 7% to 10%.

[0038] According to some specific embodiments of the present invention, the operating conditions of the hydrocracking reaction zone in step (3) are as follows: the reaction temperature is 320–420°C, preferably 340–400°C; the reaction pressure is 10–16 MPa, preferably 13–15 MPa; and the volume hourly space velocity is 0.5–1.4 h⁻¹. -1 Preferably, it is 0.6 to 1.2 hours. -1 The hydrogen-to-oil volume ratio is 700–1600, preferably 900–1500.

[0039] According to some specific embodiments of the present invention, the hydrocracking reaction zone in step (3) may be provided with one or more hydrocracking reactors, preferably two or three hydrocracking reactors, and even more preferably, two or more hydrocracking reactors are connected in series.

[0040] According to some specific embodiments of the present invention, the second hydrogenation protective agent bed is filled with a hydrogenation protective catalyst. The hydrogenation protective catalyst can be at least one of the protective agents FGF-01, FGF-02, FZC-100B, and FZC-28 developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. (FRIPP), or it can be prepared according to common knowledge in the art as needed.

[0041] According to some specific embodiments of the present invention, the second hydrorefining catalyst bed is filled with a hydrorefining catalyst. The hydrorefining catalyst can be at least one of the FF-20, FF-32, FF-34, FF-22, and FF-66 series hydrorefining catalysts developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. (FRIPP), or it can be prepared according to common knowledge in the art as needed. Further, the second hydrorefining catalyst generally includes a support and an active metal component. The support can be one or more inorganic metal oxides such as alumina and silicon oxide; the active metal can be at least one of Group VIB and Group VIII metals, preferably at least one of Mo, Co, and Ni; the active metal exists in oxide form, and the content of the active metal component, based on the weight of the second hydrorefining catalyst, is 18 wt% to 28 wt% in oxide form.

[0042] According to some specific embodiments of the present invention, the second hydrocracking catalyst bed is packed with hydrocracking catalyst, preferably with two or more types of hydrocracking catalyst, and more preferably with the pore size of the hydrocracking catalyst gradually decreasing in the direction of liquid phase material flow, and the pore size difference between two adjacent hydrocracking catalyst layers being 1.0-5.0 nm; the active metal content of the hydrocracking catalyst gradually increases, and the active metal content difference between two adjacent hydrocracking catalyst layers being 2 wt%-8 wt%. The hydrocracking catalyst can be at least one of the FC-28, FC-20, FC-14, and FC-32 series hydrocracking catalysts developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. (FRIPP), or it can be prepared according to common knowledge in the art as needed. Further, the second hydrocracking catalyst generally includes a support and an active metal component, wherein the support can be one or more of amorphous silica-alumina, Y molecular sieves, etc.; the active metal can be at least one of Group VIB metals and Group VIII metals, preferably at least one of W and Ni; the active metal exists in oxide form. Based on the weight of the second hydrocracking catalyst, the active metal component, calculated as oxides, comprises 24 wt% to 33 wt%. The pore size of the second hydrocracking catalyst is 8-15 nm.

[0043] According to some specific embodiments of the present invention, the second supplementary refining catalyst bed is filled with a hydrorefining catalyst, which can be at least one of the FF-20, FF-32, FF-34, FF-22 and FF-66 series hydrorefining catalysts developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. (FRIPP), or can be prepared according to common knowledge in the art as needed.

[0044] According to some specific embodiments of the present invention, the cracked oil produced in step (3) and the hydrorefining reaction effluent in step (2) are separated together using a common separation system. The separation system can be an atmospheric and vacuum distillation column, with gas separated at the top, naphtha fraction separated on the first side line, diesel fraction separated on the second side line, and unconverted oil separated at the bottom.

[0045] According to some specific embodiments of the present invention, the separated diesel fraction has a cetane number > 48.

[0046] According to some specific embodiments of the present invention, the total liquid product yield is >90%.

[0047] Compared with the prior art, the method for producing diesel components by hydrogenating coal tar provided by the present invention has the following advantages:

[0048] (1) The method provided by the present invention is based on the existing two-stage hydrotreating process of coal tar. The catalyst is graded in the hydrorefining reaction zone and the hydrocracking reaction zone. The hydrorefining reaction zone is graded and filled with a certain amount of hydrocracking catalyst, which helps to improve the macromolecular cracking reaction, aromatic saturation ring-opening reaction, cycloalkanes dealkylation and isomerization reaction in the refined product oil, thereby improving the cetane number of the diesel fraction obtained in the hydrorefining reaction zone. The hydrocracking reaction zone is graded and filled with a certain amount of hydrorefining catalyst and supplementary refining catalyst, which can saturate the olefin components in the cracked product oil with hydrogenation, and further remove sulfur and nitrogen elements.

[0049] (2) The method provided by this invention has good feedstock adaptability. By combining pretreatment and hydrotreating, it can process coal tar feedstock with high aromatic, high nitrogen, and high oxygen content, and directly produce high cetane number diesel fractions. The cracking product oil is fully recycled back to the fractionation system, with no cracking tail oil discharged externally, which improves the utilization rate of coal tar feedstock and maximizes total liquid recovery. Moreover, the hydrorefining reaction zone and the hydrocracking reaction zone share a single fractionation system, which can reduce equipment investment and control costs.

[0050] (3) The coal tar pretreatment method provided by the present invention carries out a phase transfer reaction on the metal impurities that exist in the coal tar in the form of oil-soluble metals, transferring the metal impurities from the originally stable coal tar colloidal system to the aqueous phase or forming insoluble salt residue. Furthermore, through the use of compound component pretreatment agent, component C in the pretreatment agent can provide multiple hydroxyl groups to combine with the chelate ligands of the complex formed by coal tar and pretreatment agent to stabilize the complex. At the same time, it makes the complex have a certain degree of hydrophilicity, so that the water-soluble metals can be more stably dissolved in the aqueous phase. In addition, the use of pretreatment agent can achieve densification and solubilization of the aqueous phase, promote the precipitation of salt residue into the aqueous phase and make it easy to separate, and avoid the formation of a three-phase liquid state of oil on water, aqueous phase and oil under water during the demetallization process. Furthermore, this method combines with primary separation and coarse slag removal, and membrane filtration for fine slag removal, to achieve gradual slag removal according to the size of solid slag particles. This is suitable for continuous operation and avoids the downtime for maintenance and cleaning caused by clogging of solid-liquid separation equipment, which is common when using only one solid-liquid separation method. Simultaneously with slag removal, water in the coal tar can be removed, eliminating the need for additional dewatering units. This invention can efficiently remove metals, water, and solid impurities from coal tar, avoiding the formation of a three-phase liquid state (water above oil, water phase, and water below oil) during metal removal, which is difficult to separate. It has advantages such as wide applicability, mild operating conditions, and high resource utilization.

[0051] (4) The pretreatment purification method provided by the present invention is more adaptable to coal tar from different sources. By adjusting the feed ratio of membrane separation returned to the three-phase centrifugal separation unit, it can adapt to coal tar raw materials of different quality levels, so as to achieve the best purification effect. Moreover, the entire process can be completed without discharging residual liquid. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of a coal tar pretreatment method.

[0053] Figure 2 A schematic diagram of the process flow for producing diesel components from coal tar by hydrogenation. Detailed Implementation

[0054] The method of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments to ensure that those skilled in the art can fully understand the technical solution. However, this does not limit the scope of protection of the technical solution of this application; the specific scope of protection is determined by the content of the claims.

[0055] Figure 1The process flow diagram of the coal tar pretreatment process of the present invention is as follows: Coal tar raw material 1 and pretreatment agent 2 are continuously added to preprocessor 3, and after being fully mixed, they enter three-phase centrifuge 4. After centrifugation, pre-purified coal tar 5, aqueous phase 6 and solid slag 7 are obtained. The pre-purified coal tar 5 is cross-flowed through primary membrane separation 8 and secondary membrane separation 9 to obtain purified coal tar 10 and leachate 11. The leachate 11 is returned to three-phase centrifuge 4 for metal slag removal and dehydration operations again.

[0056] Figure 2 The process flow diagram for producing diesel components from coal tar by hydrogenation is as follows: In the presence of hydrogen 27, the pretreated purified coal tar 10 enters the hydrorefining reaction zone 12 for hydrorefining. The hydrorefining reaction effluent 13 enters the first gas-liquid separator 14, where it is separated to obtain a gaseous effluent 15 and a liquid effluent 16. The gaseous effluent 15, after being pressurized by the circulating hydrogen compressor 26, can be used as circulating hydrogen for the hydrorefining reaction. Zone 12 and / or hydrocracking reaction zone 22 are reused; the liquid effluent 16 further enters the fractionation tower 17 for fractionation to obtain gas 18, naphtha 19, diesel fraction 20, and unconverted oil 21; the unconverted oil 21 enters the hydrocracking reaction zone 22 for hydrocracking reaction, and the hydrocracking reaction effluent enters the second gas-liquid separator 23 for separation to obtain gaseous material 25 and cracked product oil 24. The cracked product oil 24 is recycled back to the fractionation tower 17 for further separation. The gaseous material 25, after being pressurized by the circulating hydrogen compressor 26, can be used as circulating hydrogen to enter the hydrorefining reaction zone 12 and / or hydrocracking reaction zone 22 for reuse.

[0057] In the context of this specification, during the coal tar pretreatment process, the membrane module used for primary membrane separation is a cylindrical zirconia ceramic membrane with a filtration pore size of 0.05 μm and a specification of φ4 mm × φ6 mm × 700 mm, and the membrane module used for secondary membrane separation is a mixed cellulose membrane with a filtration pore size of 0.02 μm and a specification of 254 mm width.

[0058] Table 1 Properties of Coal Tar Raw Materials

[0059]

[0060]

[0061] Example 1

[0062] The coal tar pretreatment method is carried out according to the following steps:

[0063] (1) Coal tar feedstock A is continuously fed into the mixing container of the pre-processor at a feed rate of 50 kg / h along with the coal tar pretreatment agent. The coal tar pretreatment agent consists of component A, component B, and component C. Component A is hydroxyethyl ethylenediamine triacetic acid, component B is glycolic acid and orthophosphoric acid (glycolic acid: orthophosphoric acid = 1:1), and component C is 2,2-dihydroxymethylbutanol. The weight percentage composition of the three components is 10% for component A, 15% for component B, and 75% for component C. The amount of pretreatment agent added is 0.3 wt% of the coal tar feedstock. The heating temperature of the mixing container is 90℃, and the mixing time is 30 min.

[0064] (2) The material flow obtained after step (1) is fed into a three-phase centrifuge at a centrifugal temperature of 90°C and a centrifugal speed of 3000 rpm. The centrifugation separates the pre-purified coal tar, aqueous phase and solid slag.

[0065] (3) The pre-purified coal tar cross-flows through primary membrane separation and secondary membrane separation. The filtration temperature of the membrane filter in the primary membrane separation is set to 150℃, and the filtration temperature of the membrane filter in the secondary membrane separation is set to 90℃, to obtain purified coal tar permeate and residual liquid to be purified.

[0066] (4) The leachate to be purified is returned to the three-phase centrifuge for metal slag removal and dehydration again. The weight ratio of the leachate to be purified to the feed into the three-phase centrifuge upstream is 1:1. The analysis results of the purified coal tar are shown in Table 2.

[0067] Example 2

[0068] (1) Coal tar raw material A is continuously fed into the stirring container of the pre-processor at a feed rate of 50 kg / h along with the coal tar pretreatment agent. The coal tar pretreatment agent consists of component A, component B, and component C. Component A is hydroxyethyl ethylenediamine triacetic acid, component B is tartaric acid and metaphosphoric acid (tartaric acid: metaphosphoric acid = 7:3), and component C is pentaerythritol. The weight percentage composition of the three components is 10% for component A, 15% for component B, and 75% for component C. The amount of pretreatment agent added is 0.5 wt% of the coal tar raw material. The heating temperature of the stirring container is 100℃, and the stirring time is 30 min.

[0069] (2) The coal tar treated in step (1) is fed into a three-phase centrifuge at a centrifuge temperature of 95°C and a centrifuge speed of 3000 rpm. The centrifugation separates the pre-purified coal tar, aqueous phase and solid residue.

[0070] (3) The pre-purified coal tar cross-flows through primary membrane separation and secondary membrane separation. The filtration temperature of the membrane filter in the primary membrane separation is set to 175℃, and the filtration temperature of the membrane filter in the secondary membrane separation is set to 90℃, to obtain purified coal tar permeate and residual liquid to be purified.

[0071] (4) The leachate to be purified is returned to the three-phase centrifuge for metal slag removal and dehydration again. The weight ratio of the leachate to be purified to the feed into the three-phase centrifuge upstream is 0.5:1. The analysis results of the purified coal tar are shown in Table 2.

[0072] Comparative Example 1

[0073] The process is basically the same as in Example 1, except that component C, 2,2-dihydroxymethylbutanol, is not added to the coal tar pretreatment agent. The analysis results of the purified coal tar are shown in Table 2.

[0074] Comparative Example 2

[0075] The process is basically the same as in Example 1, except that the material flow obtained in step (1) does not enter the three-phase centrifuge, but directly enters the membrane separation unit for processing. The leachate to be purified after separation is not circulated. The analysis results of the coal tar after purification are shown in Table 2.

[0076] Comparative Example 3

[0077] Compared with Example 1, no membrane separation unit was set up, but the other steps were the same as in Example 1. The analysis results of the purified coal tar are shown in Table 2.

[0078] Comparative Example 4

[0079] Compared with Example 2, no component C, namely pentaerythritol, was added to the pretreatment agent. The results of the purified coal tar analysis are shown in Table 2.

[0080] Table 2 Results of purified coal tar

[0081]

[0082]

[0083] Example 3

[0084] Hydrogenation treatment was performed using the purified coal tar from Example 1 as raw material. Figure 2 The process is shown in Table 3. The operating conditions of the hydrorefining reaction zone and the hydrocracking reaction zone are shown in Table 4. The catalyst gradation schemes of the hydrorefining reaction zone and the hydrocracking reaction zone are shown in Table 5.

[0085] Example 4

[0086] Hydrogenation treatment was performed using the purified coal tar from Example 1 as raw material. Figure 2 The process is shown in Table 3. The operating conditions of the hydrorefining reaction zone and the hydrocracking reaction zone are shown in Table 4. The catalyst gradation schemes of the hydrorefining reaction zone and the hydrocracking reaction zone are shown in Table 5.

[0087] Example 5

[0088] Hydrogenation treatment was performed using the purified coal tar from Example 2 as raw material. Figure 2 The process is shown in Table 3. The operating conditions of the hydrorefining reaction zone and the hydrocracking reaction zone are shown in Table 4. The catalyst gradation schemes of the hydrorefining reaction zone and the hydrocracking reaction zone are shown in Table 5.

[0089] Comparative Example 5

[0090] Compared to Example 3, the hydrorefining reaction zone was not loaded with hydrocracking catalyst, and the hydrocracking reaction zone was not loaded with hydrorefining catalyst or supplementary refining catalyst. The operating conditions of the hydrorefining reaction zone and the hydrocracking reaction zone are shown in Table 3, the catalyst gradation schemes of the hydrorefining reaction zone and the hydrocracking reaction zone are shown in Table 4, and the product properties are shown in Table 5.

[0091] Comparative Example 6

[0092] The process is basically the same as in Example 3, except that the coal tar feedstock was not pretreated and was directly fed into the hydrorefining and hydrocracking reaction zones for processing. The operating conditions of the hydrorefining and hydrocracking reaction zones are shown in Table 3, the catalyst gradation schemes of the hydrorefining and hydrocracking reaction zones are shown in Table 4, and the product properties are shown in Table 5.

[0093] Comparative Example 7

[0094] The process is basically the same as in Example 3, except that the purified coal tar obtained in Comparative Example 1 is used as the raw material. The operating conditions of the hydrorefining reaction zone and the hydrocracking reaction zone are shown in Table 3, the catalyst gradation schemes of the hydrorefining reaction zone and the hydrocracking reaction zone are shown in Table 4, and the product properties are shown in Table 5.

[0095] Table 3 Operating conditions for hydrorefining and hydrocracking reactions

[0096]

[0097] Table 4 Catalyst gradation scheme for hydrorefining and hydrocracking reaction zones

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[0099] Table 5 Product Properties

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Claims

1. A method for producing diesel fuel components by hydrogenating coal tar, the method comprising the following steps: (1) Pre-treatment of coal tar raw material to obtain purified coal tar. The pre-treatment process of coal tar raw material includes the following steps: (1.1) Coal tar feedstock is treated by contacting a pretreatment agent; (1.2) The material stream obtained after the treatment in step (1.1) is separated to obtain pre-purified coal tar, aqueous phase and solid slag; (1.3) The pre-purified coal tar obtained in step (1.2) enters the membrane separation unit, and after membrane separation, purified coal tar and leachate are obtained; (2) In the presence of hydrogen, the purified coal tar obtained after pretreatment enters the hydrorefining reaction zone for hydrorefining reaction. The hydrorefining reaction effluent is separated to obtain gas, naphtha, diesel fraction and unconverted oil. (3) In the presence of hydrogen, the unconverted oil obtained in step (2) enters the hydrocracking reaction zone for hydrocracking reaction. After separation of the hydrocracking reaction effluent, gas and cracked oil are obtained. The cracked oil is separated together with the hydrorefining reaction effluent in step (2).

2. The method according to claim 1, wherein, The pretreatment agent in step (1.1) includes a first component, a second component and a third component; based on the weight of the pretreatment agent, the content of the first component is 5% to 25%, preferably 10% to 20%, the content of the second component is 3% to 20%, preferably 5% to 15%, and the content of the third component is 55% to 90%, preferably 65% ​​to 80%.

3. The method according to claim 1, wherein, The amount of pretreatment agent added is 0.1% to 3.0% of the weight of the coal tar raw material, preferably 0.2% to 2.0%.

4. The method according to claim 2, wherein, The first component is selected from one or more of the sodium salts of hydroxyethyl ethylenediamine triacetic acid, dihydroxyethyl glycine, hypozinotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and the above compounds; preferably one or more of hydroxyethyl ethylenediamine triacetic acid, hypozinotriacetic acid, and ethylenediaminetetraacetic acid.

5. The method according to claim 2, wherein, The second component is an acidic compound selected from one or more of oxalic acid, glycolic acid, 2-hydroxypropionic acid, 2-hydroxysuccinic acid, tartaric acid, citric acid, salicylic acid, orthophosphoric acid, metaphosphoric acid, polyphosphoric acid, pyrophosphoric acid, methanesulfonic acid, benzenesulfonic acid, methylbenzenesulfonic acid, phenolsulfonic acid, and aminosulfonic acid, preferably one or more of glycolic acid, 2-hydroxysuccinic acid, and polyphosphoric acid.

6. The method according to claim 2, wherein, The third component is a polyhydroxy alcohol, which is selected from one or more of diethylene glycol, glycerol, 2,2-dimethylolbutanol, and pentaerythritol, preferably one or more of glycerol and pentaerythritol.

7. The method according to claim 1, wherein, The residual liquid is returned and separated together with the material stream obtained after step (1.1); the weight ratio of the returned residual liquid to the material stream obtained after step (1.1) is 0.1:1 to 10:1, preferably 0.5:1 to 5:

1.

8. The method according to claim 1, wherein, In step (1.1), the temperature for contact treatment of coal tar raw material with pretreatment agent is controlled at 60-150℃, preferably 70-100℃.

9. The method according to claim 1, wherein, The separation temperature in step (1.2) is 60-100℃, preferably 80-90℃.

10. The method according to claim 1, wherein, The membrane separation unit in step (1.3) includes primary membrane separation and secondary membrane separation. The primary membrane separation uses an inorganic membrane filter assembly, preferably with the pore size of the inorganic membrane filter assembly gradually increasing from the tube layer to the shell layer. The secondary membrane separation uses an oleophilic and hydrophobic membrane filter assembly.

11. The method according to claim 10, wherein, The operating temperature for primary membrane separation is 100–300℃, preferably 150–250℃.

12. The method according to claim 10, wherein, The operating temperature for secondary membrane separation is 70–100℃, preferably 80–90℃.

13. The method according to claim 1, wherein, The total metal content in the purified coal tar obtained after pretreatment is no greater than 20 μg·g. -1 .

14. The method according to claim 1, wherein, The operating conditions of the hydrorefining reaction zone in step (2) are as follows: reaction temperature is 220–420℃, preferably 280–380℃; reaction pressure is 10–16 MPa, preferably 13–15 MPa; volume hourly space velocity is 0.3–1.0 h⁻¹. -1 Preferably, it is 0.5–0.8 h. -1 The hydrogen-to-oil volume ratio is 600–1600, preferably 700–1300.

15. The method according to claim 1, wherein, In step (2), the hydrorefining reaction zone is sequentially arranged with a first hydroprotective agent bed, a first hydrorefining catalyst bed, a first hydrocracking catalyst bed, and a first supplementary hydrorefining catalyst bed according to the direction of liquid phase material flow. Based on the total catalyst loading volume, the volume ratio of the first hydroprotective agent bed is 9%–20%, preferably 12%–17%; the volume ratio of the first hydrorefining catalyst bed is 62%–78%, preferably 66%–74%; the volume ratio of the first hydrocracking catalyst bed is 7%–15%, preferably 9%–13%; and the volume ratio of the first supplementary refining catalyst bed is 2%–10%, preferably 4%–8%.

16. The method according to claim 1, wherein, The first hydrorefining catalyst bed is filled with hydrorefining catalyst, preferably with two or more types of hydrorefining catalyst. More preferably, the pore size of the hydrorefining catalyst gradually decreases in the direction of liquid phase material flow, and the pore size difference between two adjacent hydrorefining catalyst layers is 2.0-7.0 nm. The active metal content of the hydrorefining catalyst gradually increases, and the active metal content difference between two adjacent hydrorefining catalyst layers is 3 wt%-9 wt%.

17. The method according to claim 1, wherein, In step (3), the hydrocracking reaction zone is sequentially arranged with a second hydroprotective agent bed, a second hydrorefining catalyst bed, a second hydrocracking catalyst bed, and a second supplementary hydrorefining catalyst bed according to the direction of liquid phase material flow. Among them, based on the total catalyst bed volume, the volume ratio of the second hydroprotective agent bed is 1% to 5%, preferably 2% to 4%; the volume ratio of the second hydrorefining catalyst bed is 12% to 18%, preferably 14% to 16%; the volume ratio of the second hydrocracking catalyst bed is 68% to 80%, preferably 70% to 77%; and the volume ratio of the second supplementary refining catalyst bed is 5% to 10%, preferably 7% to 10%.

18. The method according to claim 1, wherein, The operating conditions of the hydrocracking reaction zone in step (3) are as follows: reaction temperature is 320–420℃, preferably 340–400℃; reaction pressure is 10–16 MPa, preferably 13–15 MPa; volume hourly space velocity is 0.5–1.4 h⁻¹. -1 Preferably, the time is 0.6 to 1.2 h. -1 The hydrogen-to-oil volume ratio is 700–1600, preferably 900–1500.

19. The method according to claim 1, wherein, The second hydrocracking catalyst bed is filled with hydrocracking catalyst, preferably with two or more types of hydrocracking catalyst. More preferably, the pore size of the hydrocracking catalyst gradually decreases in the direction of liquid phase material flow, and the pore size difference between two adjacent hydrocracking catalyst layers is 1.0-5.0 nm; the active metal content of the hydrocracking catalyst gradually increases, and the active metal content difference between two adjacent hydrocracking catalyst layers is 2wt%-8wt%.

20. The method according to claim 1, wherein, The cracked oil produced in step (3) and the hydrorefining effluent from step (2) are separated together using a common separation system. The separation system can be an atmospheric and vacuum distillation column, with gas separated at the top, naphtha fraction separated on the first side line, diesel fraction separated on the second side line, and unconverted oil separated at the bottom.

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