A method for hydroprocessing of inferior oils

Abstract

The present application relates to the technical field of light diesel production, in particular to a method for hydrotreating inferior oil, comprising the following steps: mixing the inferior oil with a hydrocracking reaction product, hydrofining, stripping desulfurization, and fractionation treatment to obtain light diesel, light cycle oil and heavy cycle oil; the hydrocracking reaction product is obtained by hydrocracking a cycle oil formed by the light cycle oil and the heavy cycle oil; and the void fraction of the hydrofining catalyst in the reaction system is 50-80% during hydrofining. The catalyst with large voids is used as the catalyst during refining, which not only improves the adaptability of the reaction system to the inferior oil raw material, but also greatly improves the yield of the product and further reduces the impurity content in the product.

Description

Technical Field

[0001] This invention relates to the field of light diesel oil production technology, and more specifically to a method for hydrotreating inferior oil. Background Technology

[0002] Against the backdrop of increasingly stringent global environmental requirements and mounting pressure to reduce carbon emissions, the limitations of traditional fossil fuels are becoming increasingly apparent. Simultaneously, the gradual depletion of easily exploitable resources is prompting the oil and fuel industry to accelerate its transformation towards high-quality, low-carbon, and environmentally friendly practices, and to actively explore diversified development using renewable raw materials. However, this diversification of raw materials also brings new challenges. Compared to traditional petroleum-based raw materials, emerging renewable and waste-derived raw materials, such as waste oils, kitchen waste oils, swill oils, rancid oils, bio-asphalt, waste plastic oils, waste tire oils, waste lubricating oils, wood tar, coal tar, and heavy oil, generally possess characteristics such as high oxygen content, high acid value, enrichment of metal impurities, and excessive nitrogen and sulfur content, placing higher demands on processing technologies and catalyst systems.

[0003] Currently, when the industry uses traditional hydrorefining and cracking processes to process the above-mentioned raw materials, it is easy to encounter problems such as low efficiency, easy coking, blockage, catalysts being easily corroded and contaminated and losing their activity, and poor product quality. Even if cumbersome raw material pretreatment technologies such as desalination, water washing, acid washing, adsorption, and filtration are used, a large amount of energy consumption and waste will be generated. Hydrogenation units still cannot completely overcome the influence of impurities and cannot operate stably for a long period of time.

[0004] Existing technology discloses a method for combined hydrotreating of inferior distillate oils. This method involves hydrotreating catalytic cracking diesel fractions and hydrorefining coking distillate oils. The effluents from both hydrotreating and hydrorefining reactions are fed into a separation system. While maintaining a high diesel yield, this method reduces the content of impurities such as sulfur and nitrogen in the product. However, the product yield is low, the resource recovery effect is not ideal, and it fails to remove metallic impurities from the inferior oils, thus affecting the activity of the catalyst in the system. This not only results in high impurity levels in the final product but also makes it impossible for the system to operate stably for a long period of time. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect of low recovery rate of inferior oil in the prior art, thereby providing a hydrogenation treatment process for inferior oil.

[0006] Another technical problem that this invention aims to solve is to overcome the shortcomings of existing inferior oil treatment methods, which cannot effectively remove impurities, especially metallic impurities, from inferior oil, thereby providing a hydrogenation treatment process for inferior oil.

[0007] To this end, the present invention provides a method for hydrotreating inferior oil, comprising the following steps: mixing inferior oil with hydrocracking reaction products, hydrorefining, stripping desulfurization, and fractionation treatment to obtain light diesel oil, light circulating oil, and heavy circulating oil; wherein the hydrocracking reaction products are obtained by hydrocracking reaction of circulating oil formed from light circulating oil and heavy circulating oil; and during hydrorefining, the porosity of the hydrorefining catalyst in the reaction system is 50-80%.

[0008] This invention utilizes a large-porosity catalyst to refine inferior oil. The organic solid metals from the inferior oil are converted into inorganic metals, and then fed into a fractionation tower along with the oil product through a reactor. Qualified light products are separated by distillation at the top of the fractionation tower, while unqualified products are separated into light and heavy circulating oils. The heavy circulating oil, after being filtered and centrifuged to remove solid residues and asphaltenes, is then mixed with the light circulating oil to form a circulating oil. This mixed circulating oil is then heated by hydrogen in a heater and fed into a cracking reactor. The cracked products are mixed with fresh feedstock (i.e., untreated inferior oil) and fed into a large-porosity hydrorefining reactor for further reaction. The process provided by this invention uses a large-porosity solid catalyst as the refining catalyst, removing most impurities and solid contaminants. The unqualified circulating oil is further hydrocracking and mixed with the feedstock for crude refining, thereby enabling long-cycle processing of inferior oil products that are prone to coking, high in oxygen, high in metals, and high in sulfur and nitrogen, improving product quality and light oil yield, and extending the process lifespan.

[0009] Traditional hydrorefining and cracking processes often suffer from low efficiency, coking, blockage, catalyst corrosion, catalyst deactivation due to contamination, and poor product quality. Even with complex pretreatment techniques such as desalination, washing, acid washing, adsorption, and filtration, significant energy consumption and waste are generated, and the hydrorefining unit still struggles to overcome the effects of impurities, hindering long-term stable operation. The method provided by this invention effectively combines large-pore catalyst hydrorefining with circulating oil hydrocracking, and optimizes the separation process. Within a single system, it achieves efficient, stepwise utilization of temperature and heat, separation of clean and contaminated materials, and continuous, stable production of clean products. This effectively solves the problem of processing inferior raw materials faced by traditional hydrorefining processes and catalysts, enabling both high-quality products and long-term operation.

[0010] In some embodiments, the hydrocracking catalyst includes at least one of cylindrical, cloverleaf, and spherical shapes.

[0011] In some embodiments, the hydrorefining catalyst includes at least one of gear type, Raschig ring type, hollow clover type, or four-blade type.

[0012] In some embodiments, the volume ratio of the hydrorefining catalyst to inferior oil is 2-5:1.

[0013] In some embodiments, the hydrorefining catalyst in the reaction system comprises at least three shapes, arranged from top to bottom within the reaction system, with the porosity of the hydrorefining catalyst in the reaction system being 70-80%, 65-70%, and 45-55% respectively. Preferably, the hydrorefining catalyst is arranged from top to bottom within the reaction system, with the porosity of the hydrorefining catalyst in the reaction system being 70-80%, 65-70%, and 50-55% respectively.

[0014] In some embodiments, the volume ratio of a hydrorefining catalyst with a porosity of 70-80%, a hydrorefining catalyst with a porosity of 65-70%, and a hydrorefining catalyst with a porosity of 45-55% is 10-30:30-70:10-40.

[0015] In some embodiments, the volume ratio of the hydrorefining catalyst with a porosity of 70-80%, the hydrorefining catalyst with a porosity of 65-70%, and the hydrorefining catalyst with a porosity of 50-55% is 10-30:30-70:10-40, preferably 10-30:30-70:20-40.

[0016] In some embodiments, the hydrogenation refining catalysts in the reaction system are, from top to bottom, a hollow cloverleaf-shaped catalyst with a porosity of 80%, a Raschig ring-shaped catalyst with a porosity of 70%, and a four-blade-shaped catalyst with a porosity of 50%.

[0017] In some embodiments, the hydrogenation refining catalysts in the reaction system are, from top to bottom, a Raschig ring catalyst with a porosity of 70%, a gear-type catalyst with a porosity of 65%, and a four-blade catalyst with a porosity of 55%.

[0018] In some embodiments, the heavy circulating oil obtained after fractionation is purified through solid-liquid separation and then participates in hydrocracking. The solid-liquid separation includes centrifugation and filtration.

[0019] In some embodiments, the temperature of the heavy circulating oil is reduced to 100-120°C before solid-liquid separation.

[0020] In some embodiments, the inferior oil includes at least one of waste grease, kitchen waste grease, swill oil, rancid oil, bio-asphalt, waste plastic oil, waste tire oil, waste lubricating oil, wood tar, coal tar, and heavy oil. The inferior oil provided in this invention embodiment is characterized by high oxygen content, high acid value, numerous metallic impurities, high nitrogen content, and high sulfur content. The process provided in this invention embodiment not only performs resource conversion on inferior oil with the above characteristics, but also eliminates the pretreatment step for inferior oil, while simultaneously increasing the yield of light biodiesel and reducing impurity content, thereby improving product qualification rate.

[0021] In some embodiments, the volume ratio of recycled oil to hydrogen in the hydrocracking reaction is 300-2000:1, preferably 800-1500:1.

[0022] In some embodiments, the volume ratio of light circulating oil to heavy circulating oil in the circulating oil is 8-9:1-2.

[0023] In some embodiments, the hydrogen to low-quality oil volume ratio in the hydrorefining reaction is 1500-2000:1.

[0024] In some embodiments, the volume ratio of circulating oil to inferior oil is 1-3:1.

[0025] In some of these embodiments, the temperature of the inferior oil before hydrorefining is 100-250°C, the temperature of the hydrocracking reaction products is 340-420°C, and the temperature during the refining reaction is 230-390°C.

[0026] In some of these embodiments, the temperature of the reactants is 330-360°C before the hydrocracking reaction, and the cracking rate is 10-70%.

[0027] In some embodiments, the inferior oil has a metal content of less than or equal to 200 ppm, an oxygen content of less than or equal to 13 vol%, a nitrogen content of less than or equal to 500 ppm, a sulfur content of less than or equal to 20,000 ppm, a water content of less than or equal to 20,000 ppm, and a phosphorus content of less than or equal to 100 ppm.

[0028] On the other hand, the present invention provides a light diesel oil, which is obtained by the above-described method for hydrotreating light oil.

[0029] The present invention provides the application of light diesel oil in renewable fuels or biofuel.

[0030] The technical solution of this invention has the following advantages:

[0031] 1. This invention provides a method for hydrotreating inferior oil, comprising the following steps: mixing inferior oil with hydrocracking reaction products, refining, desulfurizing, and fractionating to obtain light diesel oil, light cycle oil, and heavy cycle oil; wherein the hydrocracking reaction products are obtained by hydrocracking light cycle oil and heavy cycle oil, and during refining, the porosity of the catalyst in the reaction system is 50-80%. The tolerance of the hydrotreating process to impurities in the feedstock directly affects the system stability, catalyst life, and product quality. This invention utilizes a catalyst with large porosity as the catalyst during refining, which not only improves the adaptability of the reaction system to inferior oil feedstock but also significantly increases the product yield and further reduces the impurity content in the product. In particular, this invention uses the product of hydrocracking after fractionation of light cycle oil and heavy cycle oil as the hydrocracking reaction products, which not only improves the recovery rate of inferior oil resources but also effectively reduces the impurity content in the product.

[0032] 2. This invention provides a method for hydrotreating inferior oil, wherein the hydrorefining catalyst comprises at least one of gear-type, Raschig ring-type, hollow clover-type, or four-blade-type. By selecting at least one of gear-type, Raschig ring-type, hollow clover-type, or four-blade-type catalysts as the hydrorefining catalyst, this invention can improve the adaptability of the reaction system to inferior oil, increase reaction efficiency, accelerate the reaction process, and effectively reduce the impurity content in the product.

[0033] 3. This invention provides a method for hydrotreating inferior oil, wherein the hydrorefining catalyst in the reaction system comprises at least three shapes. By selecting catalysts of different shapes, not only can the porosity be increased, but the contact area of ​​the catalyst can also be considered to improve the utilization rate, while also ensuring good strength, thereby increasing the material throughput.

[0034] 4. This invention provides a method for hydrotreating inferior oil. The heavy cycle oil obtained after fractionation is subjected to solid-liquid separation before participating in a hydrocracking reaction. The solid-liquid separation includes centrifugation and filtration. This invention separates inferior oil into light diesel oil, light cycle oil, and heavy cycle oil through the reaction of inferior oil with hydrocracking products. The light cycle oil does not contain impurities such as asphalt or metals. Only solid-liquid separation of the heavy cycle oil is needed to obtain relatively pure cycle oil. This not only simplifies the separation steps for impurities, especially metal impurities, but also effectively reduces the impurity content. Furthermore, by reducing the metal impurity content in the mixed oil, the activity of the catalyst is maintained, the stability of the reaction system is improved, and the service life of the reaction system is extended.

[0035] 5. The present invention provides a method for hydrotreating inferior oil, wherein the temperature of the heavy circulating oil is reduced to 100-120℃ before solid-liquid separation. By reducing the temperature of the heavy circulating oil to 100-120℃, the present invention improves the fluidity of the heavy circulating oil, facilitating solid-liquid separation, and further removes the water content from the heavy circulating oil through high-temperature treatment, thereby further reducing the amount of impurities.

[0036] 5. This invention provides a method for hydrotreating inferior oil. Before hydrorefining, the temperature of the inferior oil is 100-250℃, the temperature of the hydrocracking reaction products is 340-420℃, and the temperature during the refining reaction is 230-390℃. This invention fully utilizes the heat from the hydrocracking reaction to raise the temperature of the inferior oil feedstock, resulting in good thermal energy utilization efficiency and effective use of thermal energy. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a process flow diagram of a method for treating inferior oil by hydrogenation provided in Embodiment 1 of the present invention. Detailed Implementation

[0039] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0040] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0041] The catalyst used in this embodiment of the invention is the hydrogenation catalyst provided in Example 7 of the specification published in CN117463311A.

[0042] Example 1

[0043] Please see Figure 1 As shown in the figure, this embodiment provides a method for hydrotreating inferior oil, and the specific steps and methods are as follows:

[0044] (1) Using catering swill oil as raw material, the swill oil is heated to 150°C and mixed with hydrocracking reaction products and hydrogen at 390°C. After mixing, the temperature is 245°C, and the mixture enters the first and second large-pore refining reactors for refining reaction. The catalysts in the first and second large-pore refining reactors are arranged in the following order from top to bottom: a hollow plum blossom-shaped catalyst with a porosity of 80%, a Raschig ring-shaped catalyst with a porosity of 70%, and a four-leaf catalyst with a porosity of 50%. The catalyst is a wheel-shaped catalyst with five catalyst beds. The total catalyst loading and the volume ratio of swill oil are 4:1. The volume ratio of hollow clover-shaped catalyst with 80% porosity, Raschig ring catalyst with 70% porosity, and four-blade wheel-shaped catalyst with 50% porosity is 20:40:20. The swill oil contains 180 ppm metal, 11 wt% oxygen, 350 ppm sulfur, 280 ppm nitrogen, 500 ppm water, and 60 ppm phosphorus.

[0045] (2) The refined product obtained after processing by the first and second large-void refining reactors is heat-treated and then passed through a stripping tower to remove hydrogen sulfide acid gas. It is then fed into a fractionation tower. The fraction in the middle of the fractionation tower at 175-330℃ is used as light diesel oil, the fraction in the lower part of the fractionation tower at 330-360℃ is used as light circulating oil, and the fraction at the bottom of the fractionation tower at more than 360℃ is used as heavy circulating oil. The temperature of the heavy circulating oil is reduced to below 120℃. The heavy circulating oil is then centrifuged (2500 rpm, 10 min) to remove asphaltenes and metals. Finally, it is filtered through a ceramic filter with a pore size of 5 nanometers to reduce the metal content of the heavy circulating oil to 8 ppm.

[0046] (3) Light and heavy circulating oils are mixed to obtain a mixed oil. After heat exchange treatment, the temperature of the mixed oil is 335℃. Hydrogen (purity 99 vol%) is mixed with the mixed oil. The volume ratio of light to heavy circulating oil is 9:1, and the volume ratio of hydrogen to mixed oil is 800:1. The mixture is heated to 360℃ in a heating furnace and then fed into a hydrocracking reactor for cracking reaction (the catalyst is a silicon-aluminum catalyst). The cracking rate is 30%, and the outlet temperature of the hydrocracking reactor is 370℃. The circulating oil after cracking treatment is mixed with swill oil feedstock. The mixture is then mixed with circulating hydrogen, with a volume ratio of circulating hydrogen to swill oil of 1500:1. The volume of the circulating oil is twice that of the inferior oil. The inlet temperature of the first and second large-void refining reactors is controlled at 245℃. The mixture of circulating oil, swill oil feedstock, and hydrogen is sequentially fed into the first and second large-void refining reactors for refining reaction. After heat exchange treatment and removal of hydrogen sulfide acid gas by the stripping tower, it is fed into the fractionation tower to obtain light diesel oil. The heavy circulating oil and light circulating oil continue to undergo this step, reacting with the swill oil in a circulating cycle.

[0047] The yield of light biodiesel obtained in this embodiment is 84% ​​(yield of light biodiesel = mass of light biodiesel / mass of feedstock oil × 100%). The quality indicators of the light biodiesel meet the test results of NB / T10897-2021 "Hydrocarbon-based Biodiesel" and the light biodiesel has the following characteristics: metal content ≤1ppm (analytical method: ICP-AES), oxygen content ≤200ppm (analytical method: EN 17351), aromatic content <0.1wt% (analytical method: SH / T 0806), sulfur ≤5ppm (analytical method: SH / T 0689), and nitrogen content ≤3ppm (analytical method: SH / T 0657). The stable operation cycle of the entire system can reach 2 years. The obtained light biodiesel can be used as a high-quality renewable fuel for transportation vehicles, or it can be subsequently used in conjunction with an isomerization dewaxing unit to produce biojet fuel.

[0048] Example 2

[0049] This embodiment provides a method for hydrotreating inferior oil, the specific steps and methods are as follows:

[0050] (1) Using waste plastic pyrolysis oil as raw material, the pyrolysis oil is heated to 200℃ and mixed with hydrocracking reaction products at 415℃. After mixing, the temperature is 260℃, and the mixture enters the first and second large-void refining reactors for refining. The catalysts in the first and second large-void refining reactors are, from top to bottom, a Raschig ring catalyst with a porosity of 70%, a gear-type catalyst with a porosity of 65%, and a four-blade catalyst with a porosity of 55%. The catalyst bed is 6... The total amount of catalyst and the volume ratio of waste plastic pyrolysis oil are 2.5:1. Among them, the volume ratio of Raschig ring catalyst with 70% porosity, gear catalyst with 65% porosity and four-blade catalyst with 55% porosity is 20:40:20. The pyrolysis oil has a metal content of 65 ppm, an oxygen content of 1.2 wt%, a sulfur content of 217 ppm, a nitrogen content of 642 ppm, a water content of 60 ppm, a phosphorus content of 1.5 ppm, an olefin content of 28% wt, and an aromatic content of 13% wt.

[0051] (2) The refined product obtained after processing in the first and second large-void refining reactors is heat-treated and then, after removing hydrogen sulfide acid gas, fed into a fractionation tower. The fraction from the middle section of the fractionation tower at 175-330℃ is used as light diesel oil, the fraction from the lower section at 330-360℃ is used as light circulating oil, and the fraction from the bottom section above 360℃ is used as heavy circulating oil. The heavy circulating oil is then centrifuged (1900 rpm, 15 min) at temperatures below 90℃ to remove asphaltenes and metals, and then filtered through a ceramic filter to reduce the metal content of the heavy circulating oil to 4 ppm.

[0052] (3) Light and heavy circulating oils are mixed to obtain a mixed oil. After heat exchange treatment, the temperature of the mixed oil is 325℃. The mixed oil is then mixed with hydrogen (purity 99 vol%), wherein the volume ratio of light to heavy circulating oil is 9:1 and the volume ratio of hydrogen to mixed oil is 1200:1. The mixture is then heated to 340℃ in a heating furnace and fed into a hydrocracking reactor for cracking reaction. The cracking rate is 60%, and the outlet temperature of the hydrocracking reactor is 415℃. The circulating oil after cracking treatment is mixed with pyrolysis oil feedstock and fed into the circulating oil system. The volume ratio of hydrogen, recycled hydrogen, and pyrolysis oil is 2000:1. The volume of recycled oil is twice the volume of waste plastic pyrolysis oil feedstock. The inlet temperature of the first and second large-void refining reactors is controlled at 260℃. The mixture formed by recycled oil, swill oil feedstock, and hydrogen is sequentially fed into the first and second large-void refining reactors for refining reaction. After heat exchange treatment and removal of hydrogen sulfide acid gas, it is fed into a fractionation tower to obtain light diesel oil. The heavy recycled oil and light recycled oil continue to undergo this step, reacting with the pyrolysis oil in a cycle.

[0053] Using the detection method of Example 1, the yield of light diesel oil obtained in this example is 92%; the metal content in the light diesel oil is less than 0.5 ppm, the oxygen content is less than 10 ppm, the sulfur content is less than 10 ppm, and the nitrogen content is less than 30 ppm; the stable operating cycle of the entire system can reach 2.0 years. The obtained light diesel oil can be used as a high-quality renewable fuel for transport vehicles.

[0054] Example 3

[0055] This embodiment provides a method for treating inferior oil with hydrogenation. The specific steps and methods are the same as in embodiment 1. The difference is that in step (1), the catalysts from top to bottom are a hollow plum blossom-shaped catalyst with a porosity of 80%, a Raschig ring-shaped catalyst with a porosity of 70%, and a four-blade-shaped catalyst with a porosity of 50%, with a volume ratio of 30:50:30.

[0056] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 84.5%. The light biodiesel contains metal content ≤1ppm, oxygen content ≤150ppm, aromatic content <0.1wt% (analytical method is SH / T 0806), sulfur ≤5ppm, and nitrogen content ≤2ppm. The stable operation cycle of the entire system can reach 1.3 years.

[0057] Example 4

[0058] This embodiment provides a method for treating inferior oil with hydrotreating. The specific steps and methods are the same as in embodiment 1. The difference is that in step (1), the catalysts from top to bottom are a hollow plum blossom-shaped catalyst with a porosity of 80%, a Raschig ring-shaped catalyst with a porosity of 70%, and a four-blade-shaped catalyst with a porosity of 50%, with a volume ratio of 10:30:40.

[0059] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 83.7%; the light biodiesel contains ≤1 ppm metal content, ≤260 ppm oxygen content, <0.1 wt% aromatic content, ≤6 ppm sulfur content, and ≤3 ppm nitrogen content; the stable operation cycle of the entire system can reach 1.6 years.

[0060] Example 5

[0061] This embodiment provides a method for treating inferior oil with hydrotreating. The specific steps and methods are the same as in embodiment 1. The difference is that in step (1), the catalysts from top to bottom are a hollow plum blossom-shaped catalyst with a porosity of 80%, a Raschig ring-shaped catalyst with a porosity of 70%, and a four-blade-shaped catalyst with a porosity of 50%, with a volume ratio of 20:40:10.

[0062] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 79.8%; the metal content in the light biodiesel is ≤3ppm, the oxygen content is ≤350ppm, the aromatic content is <0.1wt%, the sulfur content is ≤10ppm, and the nitrogen content is ≤5ppm; the stable operation cycle of the entire system can reach 1.1 years.

[0063] Example 6

[0064] This embodiment provides a method for hydrotreating inferior oil. The specific steps and methods are the same as in Example 1. The difference is that in step (1), the porosity of the hollow plum blossom catalyst is 70%, the porosity of the Raschig ring catalyst is 65%, and the porosity of the four-blade catalyst is 45%. The volume ratio of the hollow plum blossom catalyst with a porosity of 70%, the Raschig ring catalyst with a porosity of 65%, and the four-blade catalyst with a porosity of 45% is 20:40:20.

[0065] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 81.6%; the metal content in the light biodiesel is ≤2ppm, the oxygen content is ≤370ppm, the aromatic content is <0.1wt%, the sulfur content is ≤15ppm, and the nitrogen content is ≤5ppm; the stable operation cycle of the entire system can reach 1.0 year.

[0066] Example 7

[0067] This embodiment provides a method for treating inferior oil by hydrogenation. The specific steps and methods are the same as in embodiment 1, except that the volume ratio of hydrogen to mixed oil in step (3) is 1500:1.

[0068] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 83.4%; the metal content in the light biodiesel is ≤1ppm, the oxygen content is ≤109ppm, the aromatic content is <0.1wt%, the sulfur content is ≤4ppm, and the nitrogen content is ≤2ppm; the stable operation cycle of the entire system can reach 1.8 years.

[0069] Example 8

[0070] This embodiment provides a method for treating inferior oil by hydrogenation. The specific steps and methods are the same as in embodiment 1, except that the volume ratio of hydrogen to mixed oil in step (3) is 300:1.

[0071] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 78.7%; the metal content in the light biodiesel is ≤2ppm, the oxygen content is ≤450ppm, the aromatic content is <0.2wt%, the sulfur content is ≤7ppm, and the nitrogen content is ≤5ppm; the stable operation cycle of the entire system can reach 1.0 year.

[0072] Example 9

[0073] This embodiment provides a method for treating inferior oil by hydrogenation. The specific steps and methods are the same as in embodiment 1, except that the volume ratio of hydrogen to mixed oil in step (3) is 2000:1.

[0074] The yield of light biodiesel obtained in this embodiment is 79.2%; the light biodiesel contains ≤2ppm metal content, ≤380ppm oxygen content, <0.25wt% aromatic hydrocarbon content, ≤6ppm sulfur content, and ≤4ppm nitrogen content; the stable operation cycle of the entire system can reach 1.2 years.

[0075] Example 10

[0076] This embodiment provides a method for hydrotreating inferior oil, the specific steps and methods are as follows:

[0077] (1) Using catering swill oil as raw material, the swill oil is heated to 100°C and mixed with hydrocracking reaction products and hydrogen at 415°C. After mixing, the temperature is 330°C, and the mixture enters the first and second large-pore refining reactors for refining reaction. The catalysts in the first and second large-pore refining reactors are arranged in the following order from top to bottom: a hollow plum blossom-shaped catalyst with a porosity of 80%, a Raschig ring-shaped catalyst with a porosity of 70%, and a four-leaf catalyst with a porosity of 50%. The catalyst is a wheel-shaped catalyst with five catalyst beds. The total catalyst loading and the volume ratio of swill oil are 2:1. The volume ratio of hollow clover-shaped catalyst with 80% porosity, Raschig ring catalyst with 70% porosity, and four-blade wheel-shaped catalyst with 50% porosity is 20:40:20. The swill oil contains 180 ppm metal, 11 wt% oxygen, 350 ppm sulfur, 280 ppm nitrogen, 500 ppm water, and 60 ppm phosphorus.

[0078] (2) The refined product obtained after processing in the first and second large-void refining reactors is heat-treated, and then passed through a stripping tower to remove hydrogen sulfide acid gas before being fed into a fractionation tower. The fraction in the middle of the fractionation tower at 175-330℃ is used as light diesel oil, the fraction in the lower part of the fractionation tower at 330-360℃ is used as light circulating oil, and the fraction oil at the bottom of the fractionation tower at a temperature greater than 360℃ is used as heavy circulating oil. The temperature of the heavy circulating oil is reduced to below 120℃, and the heavy circulating oil is centrifuged (2000 rpm, 20 min) to remove asphaltenes and metals. Then it is filtered through a ceramic filter with a pore size of 5 nanometers to reduce the metal content of the heavy circulating oil to 8 ppm.

[0079] (3) Light and heavy circulating oils are mixed to obtain a mixed oil. After heat exchange treatment, the temperature of the mixed oil is 320℃. Hydrogen (purity 99 vol%) is mixed with the mixed oil, wherein the volume ratio of light to heavy circulating oil is 8:2 and the volume ratio of hydrogen to mixed oil is 800:1. The mixture is heated to 360℃ in a heating furnace and then fed into a hydrocracking reactor for cracking reaction (the catalyst is a silicon-aluminum catalyst). The cracking rate is 40%, and the outlet temperature of the hydrocracking reactor is 415℃. The circulating oil after cracking treatment is the hydrocracking product. The product is mixed with gutter oil feedstock and then mixed with recycled hydrogen at a volume ratio of 2000:1. The volume of recycled oil is three times that of the inferior oil. The inlet temperature of the first and second large-void refining reactors is controlled at 330°C. The mixture of recycled oil, gutter oil feedstock, and hydrogen is sequentially fed into the first and second large-void refining reactors for refining. After heat exchange treatment to remove hydrogen sulfide acid gas, the mixture is fed into a fractionation tower to obtain light diesel oil. The heavy and light recycled oils continue to undergo this step, reacting with the recycled gutter oil.

[0080] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 80.2%; the metal content in the light biodiesel is ≤1ppm, the oxygen content is ≤110ppm, the aromatic content is <0.12wt%, the sulfur content is ≤4ppm, and the nitrogen content is ≤2ppm; the stable operation cycle of the entire system can reach 1.7 years.

[0081] Example 11

[0082] This embodiment provides a method for hydrotreating inferior oil, the specific steps and methods are as follows:

[0083] (1) Using catering swill oil as raw material, the swill oil is heated to 250°C and mixed with hydrocracking reaction products and hydrogen at 350°C. After mixing, the temperature is 280°C, and the mixture enters the first and second large-pore refining reactors for refining reaction. The catalysts in the first and second large-pore refining reactors are arranged in the following order from top to bottom: a hollow plum blossom-shaped catalyst with a porosity of 80%, a Raschig ring-shaped catalyst with a porosity of 70%, and a four-leaf catalyst with a porosity of 50%. The catalyst is a wheel-shaped catalyst with five catalyst beds. The total catalyst loading and the volume ratio of swill oil are 5:1. The volume ratio of hollow clover-shaped catalyst with 80% porosity, Raschig ring catalyst with 70% porosity, and four-blade wheel-shaped catalyst with 50% porosity is 20:40:20. The swill oil contains 180 ppm metal, 11 wt% oxygen, 350 ppm sulfur, 280 ppm nitrogen, 500 ppm water, and 60 ppm phosphorus.

[0084] (2) The refined product obtained after processing by the first and second large-void refining reactors is heat-treated and then passed through a stripping tower to remove hydrogen sulfide acid gas. It is then fed into a fractionation tower. The fraction in the middle of the fractionation tower at 175-330℃ is used as light diesel oil, the fraction in the lower part of the fractionation tower at 330-360℃ is used as light circulating oil, and the fraction at the bottom of the fractionation tower at more than 360℃ is used as heavy circulating oil. The temperature of the heavy circulating oil is reduced to below 120℃. The heavy circulating oil is then centrifuged (2500 rpm, 10 min) to remove asphaltenes and metals. Finally, it is filtered through a ceramic filter with a pore size of 5 nanometers to reduce the metal content of the heavy circulating oil to 8 ppm.

[0085] (3) Light and heavy circulating oils are mixed to obtain a mixed oil. After heat exchange treatment, the temperature of the mixed oil is 340°C. Hydrogen (purity 99 vol%) is mixed with the mixed oil. The volume ratio of light to heavy circulating oil is 8:2, and the volume ratio of hydrogen to mixed oil is 800:1. The mixture is heated to 360°C in a heating furnace and then fed into a hydrocracking reactor for cracking (the catalyst is a silicon-aluminum catalyst). The cracking rate is 38%, and the outlet temperature of the hydrocracking reactor is 350°C. The circulating oil after cracking treatment is the hydrocracking product. The product is mixed with gutter oil feedstock and then mixed with recycled hydrogen at a volume ratio of 2000:1. The volume of recycled oil is twice that of the inferior oil. The inlet temperature of the first and second large-void refining reactors is controlled at 280°C. The mixture of recycled oil, gutter oil feedstock, and hydrogen is sequentially fed into the first and second large-void refining reactors for refining. After heat exchange treatment to remove hydrogen sulfide acid gas, the mixture is fed into a fractionation tower to obtain light diesel oil. The heavy recycled oil and light recycled oil continue to undergo this step, reacting with the recycled gutter oil.

[0086] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 81.3%; the light biodiesel has a metal content ≤2ppm, an oxygen content ≤160ppm, an aromatic content <0.14wt%, a sulfur content ≤4ppm, and a nitrogen content ≤3ppm; the entire system can operate stably for 1.5 years.

[0087] Comparative Example 1

[0088] This comparative example provides a method for hydrotreating inferior oil, and the specific steps and methods are as follows:

[0089] (1) Using catering swill oil as raw material, the swill oil is heated to 245°C and enters the first large-void refining reactor and the second large-void refining reactor for refining reaction. The catalysts in the first large-void refining reactor and the second large-void refining reactor are arranged in the following order from top to bottom: hollow plum blossom type catalyst with 80% porosity, Raschig ring type catalyst with 70% porosity, and four-blade type catalyst with 50% porosity. There are 5 catalyst beds. The total amount of catalyst and the volume ratio of swill oil are 4:1. The volume ratio of hollow plum blossom type catalyst with 80% porosity, Raschig ring type catalyst with 70% porosity, and four-blade type catalyst with 50% porosity is 20:40:20. The metal content in the swill oil is 180 ppm, the oxygen content is 11 wt%, the sulfur content is 350 ppm, the nitrogen content is 280 ppm, the water content is 500 ppm, and the phosphorus content is 60 ppm.

[0090] (2) The refined product obtained after processing by the first and second large-void refining reactors is heat-treated and then passed through a stripping tower to remove hydrogen sulfide acid gas. It is then fed into a fractionation tower. The fraction in the middle of the fractionation tower at 175-330℃ is used as light diesel oil, the fraction in the lower part of the fractionation tower at 330-360℃ is used as light circulating oil, and the fraction at the bottom of the fractionation tower at more than 360℃ is used as heavy circulating oil. The temperature of the heavy circulating oil is reduced to below 120℃. The heavy circulating oil is then centrifuged (2500 rpm, 10 min) to remove asphaltenes and metals. Finally, it is filtered through a ceramic filter with a pore size of 5 nanometers to reduce the metal content of the heavy circulating oil to 8 ppm.

[0091] Using the detection method of Example 1, the yield of light biodiesel obtained in this comparative example was 58.3%; the metal content in the light biodiesel was ≤15ppm, the oxygen content was ≤1200ppm, the aromatic content was <0.3wt%, the sulfur content was ≤15ppm, and the nitrogen content was ≤8ppm; the stable operation cycle of the entire system could only reach 0.8 years.

[0092] Comparative Example 2

[0093] This comparative example provides a method for treating inferior oil with hydrogenation. The specific steps and methods are the same as in Example 1, except that the catalyst in step (1) contains only a hollow plum blossom-shaped catalyst with a porosity of 90%.

[0094] Using the detection method of Example 1, the yield of light biodiesel obtained in this comparative example was 63.4%; the metal content in the light biodiesel was ≤21ppm, the oxygen content was ≤800ppm, the aromatic content was <0.4wt%, the sulfur content was ≤22ppm, and the nitrogen content was ≤9ppm; the stable operation cycle of the entire system could only reach 0.9 years.

[0095] Comparative Example 3

[0096] This comparative example provides a method for treating inferior oil with hydrogenation. The specific steps and methods are the same as in Example 1, except that the catalyst in step (1) contains only a hollow plum blossom-shaped catalyst with a porosity of 40%.

[0097] The yield of light biodiesel obtained in this comparative example was 83.4%; the metal content in the light biodiesel was ≤10ppm, the oxygen content was ≤190ppm, the aromatic content was <0.2wt%, the sulfur content was ≤6ppm, and the nitrogen content was ≤3ppm; the stable operation cycle of the entire system could only reach 0.4 years.

[0098] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for hydrotreating inferior oil, characterized in that, Includes the following steps, Inferior oil is mixed with hydrocracking reaction products, and then subjected to hydrorefining, stripping desulfurization and fractionation treatment in sequence to obtain the fraction with a temperature of 175-330℃ as light diesel oil, the fraction with a temperature of 330-360℃ as light cycle oil, and the fraction with a temperature greater than 360℃ as heavy cycle oil. The heavy circulating oil obtained after fractionation is mixed with the light circulating oil obtained after fractionation after solid-liquid separation to obtain a mixed oil. This mixed oil is then subjected to hydrocracking to obtain circulating oil, which is the hydrocracking product. During hydrorefining, the hydrorefining catalyst is arranged from top to bottom in the reaction system. The catalysts in the reaction system are, in order, a hollow cloverleaf type catalyst with a porosity of 70-80%, a Raschig ring type catalyst with a porosity of 65-70%, and a four-blade type catalyst with a porosity of 45-55%, with a volume ratio of 10-30:30-50:20-40. In the hydrocracking reaction, the volume ratio of light cycle oil to heavy cycle oil after solid-liquid separation is 8-9:1-2. In the hydrorefining reaction, the volume ratio of recycled oil to inferior oil is 1-3:

1. The substandard oil includes at least one of swill oil and waste plastic oil.

2. The method for hydrotreating inferior oil according to claim 1, characterized in that, The volume ratio of the hydrorefining catalyst to the inferior oil is 2-5:

1.

3. The method for hydrotreating inferior oil according to claim 2, characterized in that, The hydrogenation refining catalysts in the reaction system, from top to bottom, are a hollow plum blossom-shaped catalyst with a porosity of 80%, a Raschig ring-shaped catalyst with a porosity of 70%, and a four-blade-shaped catalyst with a porosity of 50%.

4. The method for hydrotreating inferior oil according to claim 1, characterized in that, The heavy circulating oil obtained after fractionation is subjected to solid-liquid separation before participating in hydrocracking. The solid-liquid separation includes centrifugation and filtration.

5. The method for hydrotreating inferior oil according to claim 4, characterized in that, Before solid-liquid separation, the temperature of the heavy circulating oil is reduced to 100-120℃.

6. The method for hydrotreating inferior oil according to claim 1, characterized in that, In the hydrorefining reaction, the volume ratio of hydrogen to low-quality oil is 1500-2000:

1.

7. The method for hydrotreating inferior oil according to claim 1, characterized in that, Before hydrorefining, the temperature of inferior oil is 100-250℃, the temperature of hydrocracking reaction products is 340-420℃, and the temperature during the hydrorefining reaction is 230-390℃.

8. The method for hydrotreating inferior oil according to claim 1, characterized in that, Before hydrocracking, the temperature of the mixed oil is 330-360℃, and the cracking rate of the hydrocracking reaction is 10-70%; and / or, The inferior oil has a metal content ≤200ppm, an oxygen content ≤13vol%, a nitrogen content ≤500ppm, a sulfur content ≤20000ppm, a water content ≤20000ppm, and a phosphorus content ≤100ppm.

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