Method and system for producing food-grade white oil and industrial white oil from coal tar hydrogenation tail oil

Abstract

The invention relates to a method and system for producing food-grade white oil and industrial white oil by using coal tar hydrogenation tail oil, and the method comprises the following steps: S1, enabling the coal tar hydrogenation tail oil to enter a solvent refining unit for solvent refining treatment to obtain raffinate oil and extract oil; s2, H2 and the raffinate oil enter a hydro-upgrading unit to be in contact with a hydro-upgrading catalyst, hydro-upgrading reaction is carried out, a hydro-upgrading reaction product is obtained, and the hydro-upgrading catalyst comprises a hydrotreating catalyst, a hydrodewaxing catalyst and a hydrofining catalyst; s3, enabling the hydro-upgrading reaction product to enter a steam stripping unit, and performing high-pressure steam stripping to obtain a gas-phase component and a liquid-phase component; s4, enabling the liquid-phase component to enter a post-hydrogenation refining unit to be in contact with a post-hydrogenation refining catalyst, and carrying out post-hydrogenation refining reaction to obtain a post-hydrogenation refining product; s5, allowing the hydrogenated refined product to enter a separation unit for separation treatment to obtain aviation kerosene, food-grade white oil and industrial white oil.

Description

TECHNICAL FIELD

[0001] The disclosure relates to the technical field of coal tar processing, in particular to a method and system for producing food-grade white oil and industrial white oil from coal tar hydrogenation tail oil. BACKGROUND

[0002] Currently, coal tar hydrogenation enterprises generally adopt a full-cycle process of hydrogenation tail oil. The process requires harsh reaction conditions, high temperature and high pressure operation, and the products are mainly naphtha and diesel oil fractions, which are single in type and have a low added value. Some enterprises use coal tar hydrogenation products to produce white oil, which is refined by multi-stage hydrogenation, isomerization and hydrogenation make-up. The reaction requires high pressure and multi-stage noble metal catalyst hydrogenation process. The present application proposes a combined processing process for coal tar hydrogenation tail oil to produce food-grade white oil and industrial white oil. SUMMARY

[0003] The purpose of the present disclosure is to provide a method and system for producing food-grade white oil and industrial white oil from coal tar hydrogenation tail oil.

[0004] To achieve the above-mentioned purpose, the first aspect of the present disclosure provides a method for producing food-grade white oil and industrial white oil from coal tar hydrogenation tail oil, comprising the following steps: S1, allowing the coal tar hydrogenation tail oil to enter a solvent refining unit for solvent refining treatment to obtain raffinate and extract oil; S2, allowing H2 and the raffinate to enter a hydro-upgrading unit to contact with a hydro-upgrading catalyst to perform a hydro-upgrading reaction, to obtain a hydro-upgrading reaction product, wherein the hydro-upgrading catalyst comprises a hydro-treating catalyst, a hydro-isomerization catalyst and a hydrofining catalyst; S3, allowing the hydro-upgrading reaction product to enter a stripping unit to obtain a gas phase component and a liquid phase component by high-pressure stripping; S4, allowing the liquid phase component to enter a post-hydrofining unit to contact with a post-hydrofining catalyst to perform a post-hydrofining reaction, to obtain a post-hydrofining product; S5, allowing the post-hydrofining product to enter a separation unit for separation treatment to obtain aviation kerosene, food-grade white oil and industrial white oil.

[0005] Optionally, in step S1, the conditions of the solvent refining treatment include: in the extraction tower, the mass ratio of solvent to coal tar hydrogenation tail oil is (0.5-5):1, and the top temperature of the extraction tower is 45-100℃; preferably, the mass ratio of solvent to coal tar hydrogenation tail oil is (1-3):1, and the top temperature of the extraction tower is 55-90℃; optionally, the solvent is at least one of furfural, NMP or phenol, and the contact mode of the solvent and the raw material is countercurrent or crossflow; preferably, the solvent is furfural or NMP, and the contact mode of the solvent and the raw material is countercurrent.

[0006] Optionally, the coal tar hydrogenation tail oil is from a coal tar fixed bed, ebullated bed-fixed bed, suspended bed-fixed bed hydrocracking tail oil or hydrofining tail oil, in particular, medium temperature coal tar fixed bed hydrocracking tail oil, medium-low temperature coal tar fixed bed hydrofining tail oil, medium-low temperature coal tar ebullated bed-fixed bed hydrofining tail oil, medium temperature coal tar ebullated bed-fixed bed hydrocracking tail oil, low temperature coal tar suspended bed-fixed bed hydrofining tail oil, medium-low temperature coal tar suspended bed-fixed bed hydrocracking tail oil. Preferably, the distillation range of the coal tar hydrogenation tail oil is 300-530°C, and more preferably 320-510°C.

[0007] The solvent refining process used in step S1 in the present disclosure has wide adaptability to raw materials, and provides a basis for producing high-value white oil using relatively poor hydrocracking tail oil raw materials. The solvent refining can partially remove heavy polycyclic aromatic hydrocarbons, gum, sulfur and nitrogen compounds, and condensed ring naphthenes in the raw oil, and the viscosity of the raffinate oil is reduced, the impurity content is reduced, and the severity of the subsequent hydro-upgrading unit is greatly reduced.

[0008] Optionally, in step S2, the hydroprocessing catalyst, the hydrodewaxing catalyst, and the hydrofining catalyst are sequentially arranged along the flow direction of H2 and the raffinate oil in the hydro-upgrading unit; step S2 comprises: The mixed raw material after mixing the raffinate oil with H2 enters the hydro-upgrading unit, and the mixed raw material is first contacted with the hydroprocessing catalyst to perform a hydroprocessing reaction, then contacted with the hydrodewaxing catalyst to perform a hydrodewaxing reaction, and finally contacted with the hydrofining catalyst to perform a hydrofining reaction, to obtain the hydro-upgrading reaction product. The volume ratio of the hydroprocessing catalyst: the hydrodewaxing catalyst: the hydrofining catalyst is (10-80): 100: (60-160), and preferably (20-60): 100: (80-120). The hydro-upgrading unit comprises a hydrodewaxing reactor and a hydrofining reactor, the hydrodewaxing reactor is filled with the hydroprocessing catalyst and the hydrodewaxing catalyst, and the hydrodewaxing reactor and the hydrofining reactor are combined in series without a fractionation device in between.

[0009] Optionally, in step S2, the treatment conditions of the hydro-upgrading unit include: the temperature of the hydroprocessing reaction is 300-400°C, the hydrogen partial pressure is 3-15 MPa, the volume space velocity is 0.5-6 h -1 , and the hydrogen / oil volume ratio is (200-2000): 1; preferably, the temperature of the hydroprocessing reaction is 320-380°C, the hydrogen partial pressure is 5-12 MPa, the volume space velocity is 1.0-5.0 h -1The hydrogen-to-oil volume ratio is (300-1200):1; The temperature for the decondensation reaction under hydrogen conditions is 300–390℃, the partial pressure of hydrogen is 3–15 MPa, and the volume hourly space velocity is 0.4–4.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (200–2000):1; preferably, the temperature of the hydrogen dewaxing reaction is 320–370°C, the hydrogen partial pressure is 5–12 MPa, and the volume hourly space velocity is 0.5–2.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is (300-1200):1; The hydrogenation purification reaction is carried out at temperatures of 290–390 °C, hydrogen partial pressures of 3–15 MPa, and volume hourly space velocities of 0.4–4.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (200–2000):1; preferably, the hydrogenation refining reaction temperature is 310–380°C, the hydrogen partial pressure is 5–12 MPa, and the volume hourly space velocity is 0.5–2.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is (300-1200):1.

[0010] Optionally, in step S2, the hydrotreating catalyst is an active metal catalyst for desulfurization, denitrification, saturation of olefins and aromatics, with a support of porous oxides of aluminum and silicon or a combination thereof, and boron or phosphorus as the promoter, wherein the phosphorus content is not greater than 3% of the total mass of the hydrotreating catalyst, the boron content is not greater than 1% of the total mass of the hydrotreating catalyst, and the active metal is a combination of W and Ni, or a combination of Mo and Ni, or a combination of Mo and Ni and W.

[0011] Optionally, in step S2, the hydrodewaxing catalyst is a bifunctional catalyst with both shape-selective cracking and hydrogenation functions. This hydrodewaxing catalyst contains a molecular sieve, a hydrogenation active metal component, and an inert support. The molecular sieve is at least one of ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-35, ZSM-48, SAPO-11, β-zeolite, USY, or mordenite, preferably ZSM-5 molecular sieve. The hydrogenation active metal component is selected from at least one of Group VIB metals and Group VIII non-precious metals, preferably Ni. The inert support includes at least one of alumina, silica, and titanium oxide.

[0012] Optionally, in step S2, the hydrorefining catalyst is a metal refining catalyst for saturated olefins and aromatics, and its support is a porous oxide of aluminum, silicon, or titanium or a combination thereof, and the metal is a combination of Mo and Ni, or a combination of Mo and Ni, or a combination of Mo, Ni, W, or Co; preferably, the support of the hydrorefining catalyst is phosphorus-modified alumina, and the metal is a combination of Mo and Ni, or W.

[0013] In step S2 of this disclosure, a hydrotreating unit is set up, employing a two-stage series process of hydrotreating-hydrodewaxing-hydrorefining reactors. Hydrotreating can further remove impurities such as sulfur (S), nitrogen (N), and oxygen (O), partially saturate aromatics, improve the composition of the feedstock, and reduce the severity of subsequent reactions. Hydrodewaxing can selectively crack long-chain hydrocarbons, perform shallow cracking and partial ring-opening reactions, and improve the low-temperature fluidity of the product. Hydrorefining can perform aromatic saturation, olefin saturation, and other reactions on the products of hydrodewaxing. By adjusting the operating conditions (temperature, pressure, space velocity, hydrogen-to-oil ratio) and catalyst formulation, the hydrotreating unit can, to a certain extent, control the key indicators of the product such as pour point and aromatic content to meet the production needs of different grades of white oil. At the same time, it provides the required feedstock for the post-hydrorefining unit, enabling the post-hydrorefining unit to conduct reactions at a higher space velocity and lower pressure.

[0014] Optionally, in step S3, the hydrogenation reforming reaction product enters the stripping unit, and the hydrogen obtained after high-pressure stripping and hot-high-pressure separation enters the hydrogenation refining unit for recycling, and the liquid phase component is controlled at 180-280°C; wherein, the high-pressure stripping temperature is 320°C-370°C and the pressure is 5-12 MPa.

[0015] In this disclosure, the method and conditions for step S3 to enter the stripping unit for stripping processing are conventional methods and conditions.

[0016] Optionally, in step S4, the post-hydrogenation refining unit includes a post-hydrogenation refining reactor, which is filled with a post-hydrogenation refining catalyst. The post-hydrogenation refining catalyst is a noble metal catalyst, and its support is at least one of alumina, silicon oxide, and titanium oxide. The noble metal is reduced Pt, a combination of Pt and Ni, a combination of Pt and Pd, or a combination of Pt, Pd, and Ni. The weight content of the noble metal in the post-hydrogenation refining catalyst is 0.5% to 1.0%. Preferably, the support of the post-hydrogenation refining catalyst is Al2O3 or Al2O3-SiO2, and the noble metal is Pt and Pd.

[0017] Optionally, in step S4, based on the hydrodecondensation catalyst of the hydrotreating unit in step S2, the amount of the post-hydrotreating refining catalyst is 50-150% by volume, preferably 75-120% by volume. The processing conditions for the post-hydrogenation purification reaction include: a temperature of 180–280°C, a hydrogen partial pressure of 8–20 MPa, and a volume hourly space velocity of 0.5–6 h⁻¹. -1 The hydrogen-to-oil volume ratio is (200–2000):1; preferably, the refining reaction temperature after hydrogenation is 210–250°C, the hydrogen partial pressure is 12–18 MPa, and the volume hourly space velocity is 0.8–3 h⁻¹. -1The hydrogen-to-oil volume ratio is (300-1200):1.

[0018] The hydrorefining unit in step S4 of this disclosure aims at deep aromatic saturation and decolorization of the product oil. The catalyst used is a well-known noble metal hydrorefining catalyst in the art. These can be commercially available or prepared using existing methods. In the hydrorefining unit, a dedicated noble metal hydrorefining catalyst is used to perform final deep refining of the hydrotreated product, which can deeply remove aromatics (especially carcinogenic polycyclic aromatic hydrocarbons), trace amounts of sulfur and nitrogen, improve color, and ensure that the product meets the specifications of relevant standards.

[0019] In step S5 of this disclosure, the method and conditions for the hydrogenated purified product to enter the separation unit for separation processing are conventional methods and conditions. For example, separation is performed by distillation, a method known in the art, which typically includes one or more flash distillation, atmospheric distillation, and vacuum distillation operation units to achieve the desired separation.

[0020] A second aspect of this disclosure provides a system for producing food-grade white oil and industrial white oil from coal tar hydrogenation tail oil. The system includes a solvent refining unit, a hydrotreating unit, a stripping unit, a post-hydrotreating refining unit, and a separation unit, sequentially connected in series. The solvent refining unit is configured to perform solvent refining treatment on the coal tar hydrogenation tail oil to obtain raffinate oil and extracted oil. The hydrotreating unit includes a hydrotreating catalyst and is configured to contact hydrogen gas with the raffinate oil from the solvent refining unit and the hydrotreating catalyst for further processing. The hydrogenation reaction yields the hydrogenation reaction product; wherein the hydrogenation catalyst includes a hydrotreating catalyst, a hydrodecondensation catalyst, and a hydrorefining catalyst; the stripping unit is configured to perform gas-liquid separation treatment on the hydrogenation reaction product from the hydrogenation unit to obtain a gas phase component and a liquid phase component, and to remove H2S and NH3 from the liquid phase component; the post-hydrorefining unit is configured to contact the liquid phase component from the stripping unit with the post-hydrorefining catalyst to carry out a post-hydrorefining reaction to obtain the post-hydrorefining product; The separation unit is configured to separate the hydrorefined products from the hydrorefining unit to obtain aviation kerosene, food-grade white oil, and industrial white oil.

[0021] This disclosure has the following advantages compared to the prior art: Through the above technical solutions, this disclosure provides a method and system for producing food-grade white oil and industrial white oil from coal tar hydrogenation tail oil. The coal tar hydrogenation tail oil is first subjected to solvent refining treatment, which effectively removes heavy aromatics, gums, and polycyclic cycloalkanes from the tail oil. This allows the hydrorefining unit to operate at a higher space velocity and lower pressure, effectively reducing the operational severity of the hydrorefining unit. By subjecting the raffinate obtained from solvent refining in the hydrorefining unit to hydrodewaxing reaction, the composition and low-temperature fluidity of the product are effectively improved. The hydrorefining reaction enhances the aromatic saturation function of the hydrorefining unit, further reducing the aromatic content of the hydrogenated oil, providing a suitable feedstock for the downstream refining unit. Furthermore, the hydrorefining unit employs a two-reactor, one-stage series process, resulting in a shorter process flow. The use of a hydrogenation catalyst gradation scheme improves the quality of the obtained product while maintaining a good liquid yield, and to a certain extent, alleviates the operational severity of the downstream refining unit. Finally, in the post-hydrogenation refining unit, a larger space velocity and a special precious metal catalyst are used to catalytically hydrogenate the products of the hydrorefining reaction. This achieves the goal of deep removal of aromatics (especially carcinogenic polycyclic aromatic hydrocarbons), trace amounts of sulfur and nitrogen, improvement of color, and production of food-grade white oil and industrial white oil, thereby improving the quality of the oil.

[0022] Using whole-fraction medium-temperature coal tar fixed-bed hydrocracking tail oil, medium-low temperature coal tar fixed-bed hydrorefining tail oil, and low-temperature coal tar fluidized bed-fixed-bed hydrocracking tail oil as feedstocks, the method provided in this disclosure is adopted: (1) The solvent refining-hydrogenation combined technology is adopted. The solvent refining unit in the front end removes sulfur, nitrogen impurities and non-ideal components such as polycyclic aromatic hydrocarbons from the raw materials in advance, which significantly reduces the operational severity of the subsequent hydrogenation process. This allows the hydrogenation process to achieve the deep refining and saturation effect that can only be achieved by the traditional single high-pressure hydrogenation process by using only medium or medium-high pressure conditions. This combined process not only greatly reduces operating costs such as equipment investment and hydrogen consumption, but also effectively improves the technical economy and operational safety of the entire process while ensuring high product quality.

[0023] (2) The hydrorefining catalyst is used in the hydrorefining unit. Compared with the process in which the hydrorefining unit only contains hydrorefining-hydrogenation dewaxing catalyst, the percentage of aromatic hydrocarbons in the liquid phase obtained by the hydrorefining-stripping unit is reduced by 15%, 23%, and 20%, respectively, and the saturated hydrocarbon content is higher. The final food-grade white oil and industrial white oil products are of better quality, and the color number of the No. 2 food-grade white oil is increased by more than +1, +4, and +3, respectively.

[0024] (3) The solvent refining process of coal tar hydrogenation tail oil reduces the percentage content of aromatics in the liquid phase component by 15%, 23% and 20% respectively compared with the solventless refining process, and reduces the percentage content of aromatics in the industrial white oil by 8.7%, 10.8% and 8.9% respectively.

[0025] (4) When using a precious metal hydrogenation refining catalyst in the hydrogenation refining unit, the total yield of food-grade white oil and industrial white oil (relative to the feed of the hydrogenation refining unit) increases by 7.5%, 8.6% and 6.6% respectively, and the aromatic content of the industrial white oil decreases by 3%, 5% and 2% respectively.

[0026] (5) In the hydrotreating unit, a series process of hydrotreating-hydrodewaxing-hydrorefining is adopted. Compared with the series process of hydrotreating-hydrorefining-hydrodewaxing, the percentage content of aromatics in the liquid phase of the hydrotreating-stripping unit is reduced by 7%, 5%, and 6%, respectively. The total yield of the final food-grade white oil and industrial white oil products (relative to the feed of the hydrotreating unit) increases by 5.6%, 10.8%, and 7.5%, respectively.

[0027] This disclosure utilizes low-quality coal tar hydrogenation tail oil to produce food-grade white oil and industrial white oil, exhibiting broad raw material adaptability and high product added value. It employs a combined process of solvent refining, hydroreforming, stripping, and post-hydrorefining, which, while ensuring product quality, allows for milder operating conditions in the hydroreforming unit and reduces catalyst usage in the post-hydrorefining unit. The results achieved under relatively low operating conditions can be attained using a traditional single high-pressure hydrogenation process. Attached Figure Description

[0028] Figure 1 This is an exemplary flowchart of a method and system for producing food-grade white oil and industrial white oil from coal tar hydrogenation tail oil provided in this disclosure. Detailed Implementation

[0029] In the following examples and comparative examples, the hydrotreating catalyst is referred to as I, the hydrodewaxing catalyst as II, the hydrorefining catalyst as III, and the post-hydrorefining catalyst as IV; the catalysts used are from the following sources. Hydrotreating catalyst I is commercially available as FF-20, developed by Sinopec Fushun Research Institute, with W-Mo-Ni as the active metal component; hydrodewaxing catalyst II is commercially available as JN-63, developed by Jiangsu Yangzi Catalyst Co., Ltd., with Ni and ZSM-5 molecular sieve as the active components; hydrorefining catalyst III is a self-made hydrorefining catalyst with W-Mo-Ni as the active metal component; and post-hydrorefining catalyst IV is commercially available as FHDA-10, developed by Sinopec Fushun Research Institute, with Pt and Pd as the active metal components. Other catalysts were used in the examples and comparative examples, which are described below.

[0030] Preparation Example 1 The hydrorefining catalyst III used in the examples was prepared by the following method: Weigh 1000g of pseudoboehmite powder (produced by Zibo Honghe Chemical Co., Ltd.), add 15g of guar gum powder and mix well, then add 1100mL of 2% dilute nitric acid solution and knead evenly. Extrude the mixture into clover-shaped strips with a diameter of 1.5 mm on an extruder, air dry at room temperature, dry at 120℃ for 6 hours, and calcine at 550℃ for 4 hours under air circulation to obtain carrier S-1. Weigh 100g of carrier S-1, immerse the carrier in an aqueous solution containing 6.7g of diammonium hydrogen phosphate for 2 hours, air dry at room temperature for 12 hours, and then dry at 110℃ for 12 hours to obtain a phosphorus-containing alumina carrier.

[0031] Weigh 25.5 g of nickel nitrate and 35.0 g of ammonium metatungstate and dissolve them in an appropriate amount of deionized water. Weigh 16.2 g of ammonium heptamolybdate and dissolve it in an appropriate amount of deionized water. Add a small amount of ammonia to promote dissolution. Mix the solutions containing nickel nitrate, ammonium metatungstate, and ammonium heptamolybdate. Add a small amount of ammonia to adjust the pH to 8-9 and control the total volume of the mixture to 75-80 mL. Slowly add the mixture to the phosphorus-containing alumina support and let it stand for 2 hours. Then, air dry at room temperature for 12 hours, and then dry at 110℃ for 6 hours. Finally, calcine it in a muffle furnace at 450℃ for 4 hours (heating rate 2℃ / min) to obtain the hydrorefining catalyst III-A. Its composition was determined by X-ray fluorescence method.

[0032] Based on the dry weight of hydrorefining catalyst III-A, the mass fraction of nickel oxide is 4%, the mass fraction of tungsten oxide is 20%, the mass fraction of molybdenum oxide is 8%, and the remainder is phosphorus-containing alumina support. Based on the dry weight of hydrorefining catalyst A, the mass fraction of phosphorus is 1.0% by element.

[0033] Preparation Example 4 The hydrorefining catalyst was prepared according to Preparation Example 1. The difference between this comparative example and Preparation Example 1 is that phosphorus is not introduced. The support is directly impregnated with a prepared co-impregnation solution containing nickel, molybdenum and tungsten. Hydrorefining catalyst III-B was thus prepared.

[0034] Based on the dry weight of hydrorefining catalyst III-B, the mass fraction of nickel oxide is 4%, the mass fraction of tungsten oxide is 20%, the mass fraction of molybdenum oxide is 8%, and the remainder is alumina support.

[0035] Examples 1 to 3 according to Figure 1 The process shown uses coal tar hydrotreating tail oil as raw material to produce food-grade white oil and industrial white oil. The properties of the raw materials are listed in Table 1. The hydrotreating catalyst used is FF-20, the hydrodewaxing catalyst is JN-63, the hydrorefining catalyst is the hydrorefining catalyst III-A from Preparation Example 1, and the post-hydrotreating refining catalyst is FHDA-10.

[0036] (1) In the solvent refining unit: Coal tar hydrogenation tail oil and furfural are introduced from the bottom and top of the extraction tower, respectively, and are subjected to countercurrent contact within the extraction tower for solvent refining of the coal tar hydrogenation tail oil.

[0037] (2) In the hydrogenation unit: The raffinate obtained from solvent refining is mixed with hydrogen and then enters the hydrorefining unit for catalytic reaction. The catalyst is a graded combination of catalyst I (hydrotreatment catalyst), II (hydrogenation dewaxing catalyst), and III (hydrorefining catalyst). The hydrorefining unit adopts a two-reactor, one-stage series configuration.

[0038] (3) In the stripping unit: Hot high-pressure stripping was used to separate the hydrogenation reaction products into gas and liquid phases to obtain gas phase and liquid phase components.

[0039] (4) In the post-hydrogenation refining unit: The hydrogenation refining reactor is filled with catalyst IV (hydrogenation refining catalyst). The relative volume of catalyst IV is based on the volume of hydrogenation dewaxing catalyst II in the hydrogenation reforming unit. In Examples 1 to 3, the catalyst volume ratio IV:II is 75:100, 100:100, and 90:100, respectively.

[0040] The hydrogenated and refined products are then distilled to obtain aviation kerosene, food-grade white oil, and industrial white oil.

[0041] The specific process conditions used in the production of food-grade white oil and industrial white oil are shown in Table 2. The properties of the raffinate oil obtained from the solvent refining unit are listed in Table 3. The properties of the liquid phase components obtained from the hydrorefining-stripping unit are listed in Table 4. The product oil yield (based on the feed oil from the hydrorefining unit) and properties are listed in Tables 5-6.

[0042] According to the data from Examples 1 to 3, the method provided in this disclosure can produce No. 1 food-grade white oil, No. 2 food-grade white oil, and Class I industrial white oil. Specifically, the No. 1 food-grade white oil product can also be used as No. 15 cosmetic white oil; the No. 2 food-grade white oil product can also be used as No. 40 cosmetic white oil, or the fraction can be further distilled and fractionated to remove some high-boiling-point fractions to produce No. 36 cosmetic white oil, or to remove some low-boiling-point fractions to produce No. 50 cosmetic white oil.

[0043] Table 1 Properties of Coal Tar Hydrogenation Tail Oil Table 2. Process conditions used in the preparation of white oil in Examples 1-3 Table 3 Properties of the raffinate oil obtained from the solvent refining unit in Examples 1-3 Table 4 Properties of liquid phase components obtained from the hydrotreating-stripping unit in Examples 1-3 Table 5. Product yields from Examples 1-3 (relative to feed to the hydrotreating unit) Table 6 Properties of food-grade white oil and industrial white oil products obtained in Examples 1-3 Comparative Examples 1 to 3 Referring to the process flow of Examples 1-3, the difference between Comparative Examples 1-3 and Examples 1-3 is that: no hydrorefining catalyst is added to the hydrotreating unit; the remaining processes, catalysts used, and conditions of Comparative Examples 1-3 are the same as those of Examples 1-3. The properties of the raw materials are the same as in Table 1; the properties of the raffinate oil obtained from the solvent refining unit are the same as those of Examples 1-3, as shown in Table 3; the operating conditions of the hydrotreating unit are shown in Table 7; the operating conditions of the remaining units are the same as those of Examples 1-3; the properties of the liquid phase components obtained from the hydrotreating-stripping unit are listed in Table 8; and the product oil yield (based on the feed oil of the hydrotreating unit) and properties are listed in Tables 9-10.

[0044] Table 7. Process conditions in the hydrotreating unit for each experiment in the preparation of white oil in Comparative Examples 1 to 3. Table 8 Properties of liquid phase components obtained from the hydrogenation-stripping unit of Comparative Examples 1 to 3 Table 9 Product yields of Comparative Examples 1 to 3 (relative to feed to the hydrotreating unit) Table 10 Properties of food-grade and industrial white oil products obtained from Comparative Examples 1 to 3 Comparing Comparative Examples 1-3 with Examples 1-3, it can be seen that Examples 1-3, which use the method provided in this disclosure, employed a hydrorefining catalyst in the hydrorefining unit. The liquid phase components obtained from the hydrorefining-stripping unit of Examples 1-3 had lower aromatic content (reduced by 15%, 23%, and 20% respectively compared to the aromatic percentage of the liquid phase components of Comparative Examples 1-3) and higher saturated hydrocarbon content. The resulting food-grade white oil and industrial white oil products were of better quality (e.g., lower aromatic content, higher Cépernity color, and lower sulfur content). For example, the color number of the No. 2 food-grade white oil obtained in Examples 1-3 increased by +1, +4, and +3 respectively compared to Comparative Examples 1-3. However, the key properties of the food-grade white oil and industrial white oil prepared by Comparative Examples 1-3 (e.g., UV absorbance of polycyclic aromatic hydrocarbons, easily carbonizable substances, aromatic content, etc.) did not meet the specified requirements.

[0045] Comparative Examples 4 to 6 The difference between Comparative Examples 4-6 and Examples 1-3 is that, compared with the process flow of Examples 1-3, no solvent refining unit is set up, while the remaining processes, catalysts, and conditions are the same as those of Examples 1-3. The properties of the raw materials are the same as in Table 1. The operating conditions of the hydrotreating unit, stripping unit, and post-hydrotreating refining unit are the same as those of Examples 1-3, as shown in Table 3. The properties of the liquid phase components obtained from the hydrotreating-stripping unit are listed in Table 11, and the product oil yield (based on the feed oil of the hydrotreating unit) and properties are listed in Tables 12-13.

[0046] Table 11 Properties of liquid phase components obtained from the hydrogenation-stripping unit of Comparative Examples 4 to 6 Table 12 Product yields of Comparative Examples 4 to 6 (relative to feed to the hydrotreating unit) Table 13 Properties of food-grade and industrial white oil products obtained from Comparative Examples 4 to 6 Comparing Comparative Examples 4-6 with Examples 1-3, it can be seen that Examples 1-3, which employ the method provided in this disclosure, use solvent refining to remove some polycyclic aromatic hydrocarbons and heteroatom compounds from the feedstock oil. This allows the hydrotreating unit to produce feedstocks that meet the requirements for refining precious metals after hydrotreating, even with a higher space velocity and lower reaction temperature. The liquid phase components obtained from the hydrotreating-stripping units of Examples 1-3 have even lower aromatic hydrocarbon content (reduced by 13% compared to the aromatic hydrocarbon percentage in the liquid phase components of Comparative Examples 4-6, respectively). The higher content of saturated hydrocarbons (15%, 11%) resulted in better quality food-grade and industrial white oil products (e.g., lower aromatic content, higher saturated hydrocarbon content, and lower sulfur content). Examples 1 to 3 showed a reduction of 8.7%, 10.8%, and 8.9% in aromatic content compared to Comparative Examples 4 to 6, respectively. However, the key properties of the food-grade and industrial white oils prepared in Comparative Examples 4 to 6 (e.g., UV absorbance of polycyclic aromatic hydrocarbons, easily carbonizable substances, and aromatic content) did not all meet the specified requirements.

[0047] Comparative Examples 7 to 9 Referring to the process flow of Examples 1-3, the difference between Comparative Examples 7-9 and Examples 1-3 is that the commercial brand of the hydrorefining catalyst used in the post-hydrogenation refining unit is RJW-3. This catalyst was developed by the Petrochemical Research Institute of Sinopec and belongs to the non-precious metal hydrorefining catalyst, with Ni and W as the active metal components. The remaining processes and conditions of Comparative Examples 7-9 are the same as those of Examples 1-3. The properties of the raw materials are shown in Table 1, the operating conditions of each unit are shown in Table 2, the properties of the raffinate oil obtained from the solvent refining unit are shown in Table 3, the properties of the liquid phase components obtained from the hydrorefining-stripping unit are shown in Table 4, and the product oil yield (based on the feed oil of the hydrorefining unit) and properties are listed in Tables 14-15.

[0048] Table 14 Product yields of Comparative Examples 7 to 9 (relative to feed to the hydrotreating unit) Table 15 Properties of food-grade and industrial white oil products obtained from Comparative Examples 7 to 9 Comparing Comparative Examples 7-9 with Examples 1-3, it can be seen that Examples 1-3, which use the method provided in this disclosure, employ a precious metal hydrogenation refining catalyst in the hydrogenation refining unit. This catalyst has a strong aromatic saturation capacity, resulting in higher yields of food-grade white oil and industrial white oil products (e.g., the total yield of food-grade white oil and industrial white oil obtained in Examples 1-3 (relative to the feed of the hydrogenation reforming unit) increased by 7.5%, 8.6%, and 6.6%, respectively, compared to Comparative Examples 7-9), and better quality (e.g., lower aromatic content, higher cerbutyric acid content, and lower sulfur content). For example, the percentage of aromatics in the industrial white oil obtained in Examples 1-3 decreased by 3%, 5%, and 2%, respectively, compared to Comparative Examples 7-9, thus improving the quality of the oil. However, the key properties of the food-grade white oil and industrial white oil prepared by Comparative Examples 7-9 (e.g., UV absorbance of polycyclic aromatic hydrocarbons, easily carbonizable substances, lead, arsenic, heavy metals, aromatic content, etc.) did not all meet the specified requirements.

[0049] Comparative Examples 10 to 12 Referring to the process flow of Examples 1-3, the difference between Comparative Examples 10-12 and Examples 1-3 is that in the hydrotreating unit, along the flow direction of the mixed feedstock, a hydrotreating catalyst, a hydrorefining catalyst, and a hydrodewaxing catalyst are sequentially arranged. The remaining processes and conditions are the same as in Examples 1-3. The properties of the feedstock are as shown in Table 1. The operating conditions of the hydrotreating unit are shown in Table 16. The operating conditions of the other units are the same as in Examples 1-3. The properties of the raffinate oil obtained from the solvent refining unit are the same as in Table 3. The properties of the liquid phase components obtained from the hydrotreating-stripping unit are shown in Table 17. The product oil yield (based on the feed oil of the hydrotreating unit) and properties are listed in Tables 18-19.

[0050] Table 16. Process conditions in the hydrotreating unit for each experiment in the preparation of white oil in Comparative Examples 10-12. Table 17 Properties of liquid phase components obtained from the hydrotreating-stripping unit of Comparative Examples 10-12 Table 18 Product yields of Comparative Examples 10 to 12 (relative to feed to the hydrotreating unit) Table 19 Properties of food-grade and industrial white oil products obtained from Comparative Examples 10 to 12 Comparing Comparative Examples 10-12 with Examples 1-3, it can be seen that Examples 1-3, which use the method provided in this disclosure, employ a series process of hydrotreating-hydrodewaxing-hydrorefining in the hydrotreating unit. This process can significantly reduce the pour point of the feedstock oil under lower pressure and higher space velocity conditions. At the same time, the aromatic components after partial saturation dewaxing provide the required feedstock for the hydrorefining unit. Compared to Comparative Examples 10-12, the liquid phase components obtained from the hydrotreating-stripping units in Examples 1-3 had lower aromatic content (7%, 5%, and 6% lower than the aromatic percentage of the liquid phase components in Comparative Examples 10-12, respectively) and higher saturated hydrocarbon content, resulting in higher yields of the final food-grade white oil and industrial white oil products. For example, the total yields of the food-grade white oil and industrial white oil obtained in Examples 1-3 (relative to the feed from the hydrotreating unit) increased by 5.6%, 10.8%, and 7.5% respectively compared to Comparative Examples 10-12, and the white oil quality was better (e.g., lower aromatic content and higher Cépermont brand). However, some properties of the food-grade white oil and industrial white oil prepared in Comparative Examples 10-12 (e.g., UV absorbance of polycyclic aromatic hydrocarbons, easily carbonizable substances, aromatic content, etc.) did not meet the specified requirements.

[0051] Examples 4 to 6 The raw materials used in Examples 4 to 6 were all full-fraction medium-temperature coal tar fixed-bed hydrocracking tail oil, and the properties of the raw materials were the same as in Example 1, as shown in Table 1.

[0052] Example 4 follows the same process as Example 1, except that the hydrorefining catalyst III is replaced with the hydrorefining catalyst III-B used in Example 4. The remaining processes and conditions are the same as in Example 1. The operating conditions for each unit are shown in Table 2 (Example 1). The properties of the raffinate oil obtained from the solvent refining unit are shown in Table 3 (Example 1). The properties of the liquid phase components obtained from the hydrorefining-stripping unit are shown in Table 20. The product oil yield (based on the feed oil from the hydrorefining unit) and properties are listed in Tables 21 and 22.

[0053] Example 5 follows the process of Example 1, except that hydrorefining catalyst III is replaced with a commercially available hydrorefining catalyst, FH-5A (developed by Sinopec Fushun Research Institute, with Mo-Ni as the active metal component). The remaining processes and conditions are the same as in Example 1. The operating conditions for each unit are shown in Table 2 (Example 1), the properties of the raffinate oil obtained from the solvent refining unit are shown in Table 3 (Example 1), the properties of the liquid phase components obtained from the hydroreforming-stripping unit are shown in Table 20, and the product oil yield (based on the feed oil from the hydroreforming unit) and properties are listed in Tables 21 and 22.

[0054] Example 6 follows the process of Example 1, except that the top temperature of the solvent refining unit is 50°C, the solvent-to-oil ratio is 3.5:1, and the remaining processes and conditions are the same as in Example 1. The operating conditions for the remaining units are shown in Table 2 (Example 1). The properties of the raffinate obtained from the solvent refining unit are as follows: Raffinate yield: 67% by weight, Density (20°C): 892.8 kg·m³ -3 Kinematic viscosity at 100℃: 3.85 mm 2 •s-1, pour point: 30℃, residual carbon: 0.03 wt%, sulfur content: 2 mg / kg, nitrogen content: 16 mg / kg, saturated hydrocarbon content: 78.4 wt%, aromatic hydrocarbon content: 21.6 wt%. The properties of the liquid phase components obtained from the hydrotreating-stripping unit are shown in Table 20, and the product oil yield (based on the feed oil of the hydrotreating unit) and properties are listed in Tables 21 and 22.

[0055] Table 20 Properties of liquid phase components obtained from the hydrotreating-stripping unit in Examples 4-6 Table 21 Product yields from Examples 4-6 (relative to feed to the hydrotreating unit) Table 22 Properties of food-grade white oil and industrial white oil products obtained in Examples 4-6 Comparing Example 4 with Example 1, it can be seen that the hydrorefining catalyst used in Example 1 is a phosphorus-modified catalyst; comparing Example 5 with Example 1, it can be seen that the hydrorefining catalyst used in Example 1 contains three active metal elements: nickel, molybdenum, and tungsten, while the hydrorefining catalyst in Example 5 contains two active metal elements: nickel and molybdenum; comparing Example 6 with Example 1, it can be seen that in the process of producing food-grade white oil and industrial white oil, the solvent refining process in Example 1 is carried out in the solvent refining unit according to the process conditions of the preferred embodiment of this disclosure; compared with Examples 4 to 6, the liquid phase component obtained by the hydrorefining-stripping unit of Example 1 has a lower aromatic content (reduced by 1.4%, 2.8%, and 2% respectively compared with the liquid phase component aromatic content of Examples 4 to 6) and a higher saturated hydrocarbon content, resulting in better quality white oil (e.g., lower aromatic content and higher cerbert-specific content).

[0056] Examples 7 to 9 The raw materials used in Examples 7 to 9 were all full-fraction medium-temperature coal tar fixed-bed hydrocracking tail oil, and the properties of the raw materials were the same as in Example 1, as shown in Table 1.

[0057] Examples 7-9 follow the same process as Example 1, except that the reaction conditions for the hydrotreating unit, stripping unit, or post-hydrotreating refining unit are listed in Table 23. The remaining processes, catalysts, and conditions are the same as in Example 1. The operating conditions for the solvent refining unit in Examples 7-9 are the same as in Example 1, as shown in Table 2. The properties of the raffinate oil obtained from the solvent refining unit are the same as in Example 1, as shown in Table 3. The properties of the liquid phase components obtained from the hydrotreating-stripping unit are shown in Table 24. The product oil yield (based on the feed oil from the hydrotreating unit) and properties are listed in Tables 25-26.

[0058] Table 23 Process conditions for the hydrotreating unit, stripping unit, and post-hydrotreating refining unit in Examples 7-9 Table 24 Properties of liquid phase components obtained from the hydrotreating-stripping unit in Examples 7-9 Table 25 Product yields from Examples 7-9 (relative to feed to the hydrotreating unit) Table 26 Properties of food-grade white oil and industrial white oil products obtained in Examples 7-9 According to Tables 23 to 26 above: Comparing Example 7 with Example 1, Example 1, in the process of producing food-grade white oil and industrial white oil, carried out the reaction according to the catalyst loading volume ratio of the preferred embodiment of this disclosure (the volume ratio of hydrotreating catalyst: hydrodewaxing catalyst: hydrorefining catalyst is 20~60:100:80~120); comparing Example 8 with Example 1, Example 1, in the process of producing food-grade white oil and industrial white oil, was processed in the hydrotreating unit according to the process conditions of the preferred embodiment of this disclosure; comparing Example 9 with Example 1, Example 1, in the process of producing food-grade white oil and industrial white oil, was processed in the post-hydrotreating refining unit according to the process conditions of the preferred embodiment of this disclosure; compared with Example 7, the total yield of food-grade white oil and industrial white oil obtained by Example 1 (relative to the feed of the hydrotreating unit) increased by 6.5% compared with Example 7; compared with Examples 7 to 9, the quality of the food-grade white oil and industrial white oil products obtained by Example 1 is better (e.g., lower aromatic content, higher cerbutyric acid content).

[0059] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0060] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0061] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for producing food-grade white oil and industrial white oil from coal tar hydrogenation tail oil, characterized in that, Includes the following steps: S1. The coal tar hydrogenation tail oil is fed into the solvent refining unit for solvent refining treatment to obtain raffinate oil and extract oil. S2. H2 and the raffinate oil are introduced into the hydrotreating unit and contacted with the hydrotreating catalyst to carry out the hydrotreating reaction and obtain the hydrotreating reaction product. The hydrotreating catalyst includes a hydrotreatment catalyst, a hydrodewaxing catalyst and a hydrorefining catalyst. S3. The hydrogenation reforming reaction product is fed into the stripping unit and stripped under high pressure to obtain gas phase and liquid phase components. S4. The liquid phase component is introduced into the post-hydrogenation purification unit and comes into contact with the post-hydrogenation purification catalyst to carry out the post-hydrogenation purification reaction and obtain the post-hydrogenation purification product. S5. The hydrogenated refined product is fed into a separation unit for separation processing to obtain aviation kerosene, food-grade white oil and industrial white oil.

2. The method according to claim 1, characterized in that, In step S1, the conditions for the solvent purification treatment include: In the extraction tower, the mass ratio of solvent to coal tar hydrogenation tail oil is 0.5~5:1, and the temperature at the top of the extraction tower is 45~100℃. The solvent is at least one of furfural, NMP or phenol, and the contact mode between the solvent and the raw material is countercurrent or crosscurrent. The coal tar hydrocracking tail oil comes from the hydrocracking tail oil or hydrorefining tail oil of coal tar fixed bed, fluidized bed-fixed bed, or suspension bed-fixed bed, specifically medium-temperature coal tar fixed bed hydrocracking tail oil, medium-low temperature coal tar fixed bed hydrorefining tail oil, medium-low temperature coal tar fluidized bed-fixed bed hydrorefining tail oil, medium-temperature coal tar fluidized bed-fixed bed hydrocracking tail oil, low temperature coal tar suspension bed-fixed bed hydrorefining tail oil, and medium-low temperature coal tar suspension bed-fixed bed hydrocracking tail oil. The distillation range of the coal tar hydrogenated tail oil is 280~550℃.

3. The method according to claim 1, characterized in that, In step S2, the hydrotreating catalyst, the hydrodewaxing catalyst, and the hydrorefining catalyst are sequentially arranged along the flow direction of H2 and raffinate oil in the hydrotreating unit; step S2 includes: The mixture of the raffinate oil and H2 is fed into a hydrotreating unit. The mixture is first contacted with the hydrotreating catalyst for hydrotreating reaction, then with the hydrodewaxing catalyst for hydrodewaxing reaction, and finally with the hydrorefining catalyst for hydrorefining reaction to obtain the hydrotreating reaction product. The volume ratio of the hydrotreating catalyst, the hydrodewaxing catalyst, and the hydrorefining catalyst is 10~80:100:60~160. The hydrotreating unit includes a hydrodewaxing reactor and a hydrorefining reactor. The hydrodewaxing reactor is filled with a hydrotreating catalyst and a hydrodewaxing catalyst. The hydrodewaxing reactor and the hydrorefining reactor are connected in series in one section, without a fractionation device in between.

4. The method according to claim 3, characterized in that, In step S2, the processing conditions of the hydrotreating unit include: The hydrogenation reaction was carried out at a temperature of 300–400 °C, a hydrogen partial pressure of 3–15 MPa, and a volume hourly space velocity of 0.5–6 h⁻¹. -1 The hydrogen-to-oil volume ratio is 200–2000:1; The temperature for the decondensation reaction under hydrogen conditions is 300–390℃, the partial pressure of hydrogen is 3–15 MPa, and the volume hourly space velocity is 0.4–4.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 200–2000:1; The hydrogenation purification reaction is carried out at temperatures of 290–390 °C, hydrogen partial pressures of 3–15 MPa, and volume hourly space velocities of 0.4–4.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 200–2000:

1.

5. The method according to claim 1, characterized in that, In step S2, the hydrotreating catalyst is an active metal catalyst for desulfurization, denitrification, saturation of olefins and aromatics. Its support is a porous oxide of aluminum or silicon or a combination thereof. The promoter is boron or phosphorus, wherein the phosphorus content is not greater than 3% of the total mass of the hydrotreating catalyst, the boron content is not greater than 1% of the total mass of the hydrotreating catalyst, and the active metal is a combination of W and Ni, or a combination of Mo and Ni, or a combination of Mo, Ni and W.

6. The method according to claim 1, characterized in that, In step S2, the hydrodewaxing catalyst is a bifunctional catalyst with both shape-selective cracking and hydrogenation functions. This hydrodewaxing catalyst contains a molecular sieve, a hydrogenation active metal component, and an inert support. The molecular sieve is at least one of ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-35, ZSM-48, SAPO-11, β-zeolite, USY, or mordenite. The hydrogenation active metal component is selected from at least one of Group VIB metals and Group VIII non-precious metals. The inert support includes at least one of alumina, silica, and titanium oxide. The hydrogenation refining catalyst is a metal refining catalyst for saturated olefins and aromatics. Its support is a porous oxide of aluminum, silicon, or titanium, or a combination thereof. The auxiliary agent is phosphorus, and the metal is a combination of Mo and Ni or W, or a combination of Mo and Ni or Co, or a combination of Mo, Ni, W, and Co.

7. The method according to claim 1, characterized in that, In step S3, the hydrogenation reforming reaction product enters the stripping unit, and the hydrogen obtained after high-pressure stripping and hot-high-pressure separation enters the hydrogenation refining unit for recycling. The liquid phase component is controlled at 180-280°C; wherein, the high-pressure stripping temperature is 320°C-370°C and the pressure is 5-12 MPa.

8. The method according to claim 1, characterized in that, In step S4, the post-hydrogenation refining unit includes a post-hydrogenation refining reactor, which is filled with a post-hydrogenation refining catalyst. The post-hydrogenation refining catalyst is a noble metal catalyst, and its support is at least one of alumina, silicon dioxide, and titanium dioxide. The noble metal is reduced Pt, a combination of Pt and Ni, a combination of Pt and Pd, or a combination of Pt, Pd, and Ni. The weight content of the noble metal in the post-hydrogenation refining catalyst is 0.5% to 1.0%. Based on the hydrodecondensation catalyst of the hydrotreating unit in step S2, the amount of the post-hydrotreating refining catalyst is 50-150% by volume.

9. The method according to claim 1, characterized in that, In step S4, the processing conditions for the post-hydrogenation purification reaction include: The purification reaction after hydrogenation is carried out at a temperature of 180–280 °C, a hydrogen partial pressure of 8–20 MPa, and a volume hourly space velocity of 0.5–6 h⁻¹. -1 The hydrogen-to-oil volume ratio is 200–2000:

1.

10. A system for producing food-grade white oil and industrial white oil from coal tar hydrogenation tail oil, characterized in that, The system includes a solvent refining unit, a hydrotreating unit, a stripping unit, a post-hydrotreating refining unit, and a separation unit, which are connected in sequence. The solvent refining unit is configured to perform solvent refining on coal tar hydrogenation tail oil to obtain raffinate oil and extract oil. The hydrotreating unit includes a hydrotreating catalyst, and the hydrotreating unit is configured to contact hydrogen gas and raffinate oil from the solvent refining unit with the hydrotreating catalyst to carry out a hydrotreating reaction and obtain hydrotreating reaction products; wherein the hydrotreating catalyst includes a hydrotreatment catalyst, a hydrodewaxing catalyst, and a hydrorefining catalyst. The stripping unit is configured to perform gas-liquid separation processing on the hydroreforming reaction products from the hydroreforming unit to obtain gas phase components and liquid phase components. The post-hydrogenation refining unit is configured to contact the liquid phase component from the stripping unit with the post-hydrogenation refining catalyst to carry out the post-hydrogenation refining reaction and obtain the post-hydrogenation refining product. The separation unit is configured to separate the hydrorefined products from the hydrorefining unit to obtain aviation kerosene, food-grade white oil, and industrial white oil.

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