Process for refining low-quality diesel feedstocks and applications

Abstract

The present application relates to the field of hydroprocessing of aromatic-rich distillate oil, and particularly relates to a method for refining poor diesel raw material and application. The method comprises: sequentially subjecting the poor diesel raw material to at least two times of hydrofining, and the temperature of the first time of hydrofining is lower than that of the second time of hydrofining. Through the method of the present application, the denitrification rate of the hydrofining can be better controlled, and at the same time, a higher aromatic retention rate can be achieved, and the added value of the hydrofining product is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydroprocessing of aromatic-rich distillate oil, in particular to a method for refining poor-quality diesel feedstock and application thereof. BACKGROUND

[0002] The annual processing capacity of catalytic cracking devices in China has now exceeded 100 million tons, second only to the United States. Aromatic-rich heavy distillate oil, such as catalytic cracking diesel (LCO), has a high proportion in the diesel pool in China, accounting for about 30%, and is the main secondary processing diesel component. The total aromatic content of LCO is as high as 80%, naphthalene-based bicyclic aromatic hydrocarbons account for about 70%, and monocyclic and tricyclic aromatic hydrocarbons each account for about 15%. Ethylene tar is also a heavy distillate oil (>205℃) of aromatic-rich oil (aromatic content greater than 90%), which is the product of high-temperature condensation of steam cracking feedstock and product in steam cracking, and the main components are monocyclic and polycyclic aromatic hydrocarbon compounds, also containing N, S, O and other element heterocyclic compounds. Due to different cracking feedstocks, the yield of ethylene tar is also different, generally accounting for about 1 / 5 of the ethylene yield, and with the heavyization of ethylene feedstock, its yield is on the rise.

[0003] In the field of hydroprocessing of aromatic-rich distillate oil, since the 1970s, catalytic cracking feedstock hydrogenation pretreatment technology has been industrialized and applied, and has been applied in many refineries processing sulfur-containing or high-sulfur crude oil. At present, there is mature catalytic cracking feedstock pretreatment technology, in order to further improve product quality and conversion rate, catalytic feedstock hydrogenation pretreatment process gradually changes from traditional hydrodesulfurization refining (HDS) to mild hydrocracking (MHC) to improve denitrification, carbon residue and polycyclic aromatic hydrocarbon saturation capacity.

[0004] The sulfur content of LCO is high (0.2-1.5wt%) and the nitrogen content is generally greater than 400 ppm. In order to meet the new uses of LCO and the development of new processes suitable for the new uses (such as a new process for producing benzene (B), toluene (T) and xylene (X) by using catalytic LCO hydroconversion-selective transalkylation), the removal of impurities such as sulfur and nitrogen in LCO becomes the key to further development and application of LCO. Because a large amount of impurities such as sulfur and nitrogen in LCO have a toxic effect on subsequent catalysts for hydrogenation and selective ring opening, the impurities must be removed by a hydrofining process. LCO belongs to the diesel fraction, and it is difficult to deeply remove sulfur and nitrogen. The main reasons are as follows: (1) LCO contains sulfur compounds such as 4,6-dimethylbenzothiophene (4,6-DMDBT) and multi-substituted base ring nitrogen compounds, and due to the steric hindrance effect of the substituents, the reaction activity is low, and it is difficult to deeply remove sulfur and nitrogen; (2) polycyclic aromatic hydrocarbons and nitrogen-containing substances in the raw material and H2S in the product all have an inhibitory effect on deep desulfurization; (3) in the process of desulfurization and denitrification, transition hydrogenation is not allowed, because it will lead to a large amount of hydrogenation ring-opening reaction, which destroys the purpose of subsequent selective hydrogenation ring-opening for increasing the production of aromatic hydrocarbons; (4) in the process of hydrodesulfurization (HDS), methyis must be maximally retained to maximally produce xylene. Therefore, in order to remove these sulfur and nitrogen, a multifunctional, high-activity and high-selectivity hydrofining catalyst must be selected.

[0005] US4206036A uses titanium oxide as a carrier, loads active components, and is used as a hydrofining catalyst (desulfurization, denitrification), but the carrier has low mechanical strength, small specific surface area, and high price, and cannot be used in industrial applications.

[0006] US2006 / 0052235A1 introduces a hydrodesulfurization catalyst with mesoporous molecular sieve as a carrier, Co and Mo as active components, and silicone resin as a binder. The hydrofining catalyst has high hydrodesulfurization (HDS) / olefin saturation activity, but the patent does not give the absolute activity of HDS, and the mesoporous molecular sieve has poor stability and is difficult to be used for long-term operation in a harsh hydrodesulfurization environment.

[0007] The carbon-hydrogen ratio of the rich-aromatic heavy distillate oil is high, the octane number and cetane number of the obtained gasoline and diesel by hydrogenation are low, the hydrogen consumption is high, and the economy is poor. CN102234539A completely saturates the aromatic hydrocarbons in the rich-aromatic oil and then hydrocracks to produce gasoline and diesel, and the production cost is high and there is no economy.

[0008] The existing technology for the rich-aromatic heavy distillate oil generally uses hydrogenation saturation and hydrocracking. For the rich-aromatic heavy distillate oil with an aromatic content of greater than 80%, not only the hydrogen consumption is high, but also the valuable aromatic resources are wasted.

[0009] The selective hydrofining process can selectively hydrogenate the heavy fraction oil rich in aromatic hydrocarbons, selectively hydrogenate the condensed ring aromatic hydrocarbons in the heavy fraction oil rich in aromatic hydrocarbons into benzene series aromatic hydrocarbons to prepare solvent oil or as a raw material for producing benzene, toluene and xylene aromatic hydrocarbons, can reduce hydrogen consumption and improve the added value. SUMMARY

[0010] The present application aims to overcome the problems of high hydrogen consumption and poor economic efficiency in the prior art of hydrogenation of fraction oil rich in aromatic hydrocarbons, and provides a method and application of refining of poor diesel oil raw material, which has low hydrogen consumption and can improve the added value of products.

[0011] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a method for refining poor diesel oil raw material, which comprises: sequentially passing the poor diesel oil raw material through at least two times of hydrofining, and the temperature of the first hydrofining of the adjacent two times of hydrofining is lower than the temperature of the second hydrofining.

[0012] The second aspect of the present application provides a two-stage hydrofining method for poor diesel oil raw material, which comprises:

[0013] (a) under the condition of a catalyst, mixing and contacting the poor diesel oil component with hydrogen to complete the first-stage hydrofining reaction, to obtain a first-stage hydrofining reaction product;

[0014] (b) without separation, the first-stage hydrofining reaction product is mixed and contacted with hydrogen under the condition of a catalyst after temperature reduction to complete the second-stage hydrofining reaction, to obtain a second-stage hydrofining reaction product.

[0015] The third aspect of the present application provides a three-stage hydrofining method for poor diesel oil raw material, which comprises:

[0016] (a) under the condition of a first catalyst, mixing and contacting the poor diesel oil component with hydrogen to complete the first-stage hydrofining reaction, to obtain a first-stage hydrofining reaction product;

[0017] (b) without separation, the first-stage hydrofining reaction product is mixed and contacted with hydrogen under the condition of the first catalyst after temperature reduction to complete the second-stage hydrofining reaction, to obtain a second-stage hydrofining reaction product;

[0018] (c) without separation, the second-stage hydrofining reaction product is mixed and contacted with hydrogen under the condition of a second catalyst after temperature reduction to complete the second-stage hydrofining reaction, to obtain a third-stage hydrofining reaction product.

[0019] The fourth aspect of the present application provides the application of the method in processing of poor diesel oil raw material.

[0020] Through the above technical solution, the present application has the following advantages:

[0021] The method of this invention for refining inferior diesel feedstock can better control the denitrification rate of hydrorefining, while achieving a higher aromatics retention rate, thereby increasing the added value of hydrorefined products. Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] The present invention provides a method for refining inferior diesel feedstock, the method comprising: subjecting the inferior diesel feedstock to at least two hydrorefining processes in sequence, wherein the temperature of the first hydrorefining process is lower than the temperature of the second hydrorefining process between two adjacent hydrorefining processes.

[0024] The method of this invention for refining inferior diesel feedstock can better control the denitrification rate of hydrorefining and achieve a higher aromatics retention rate.

[0025] In this invention, there is no particular limitation on the amount by which the temperature of the preceding hydrorefining process is lower than that of the subsequent hydrorefining process. According to a preferred embodiment of the invention, the temperature of the preceding hydrorefining process is 20-250°C lower than that of the subsequent hydrorefining process, preferably 20-100°C, more preferably 20-80°C, for example, 20°C, 30°C, 50°C, 80°C, 100°C, 150°C, 200°C, or 250°C. By adopting the aforementioned preferred scheme, the denitrification rate of the refining process can be further controlled, while the aromatic hydrocarbon retention rate can be further improved.

[0026] In this invention, as long as the objective of the invention can be achieved, there are no special requirements for the temperature of the first hydrogenation purification. According to a preferred embodiment of the invention, the temperature of the first hydrogenation purification is 200-450°C, preferably 210-400°C. By adopting the aforementioned preferred scheme, the denitrification rate of the purification can be further controlled, while the aromatic hydrocarbon retention rate can be further improved.

[0027] In this invention, as long as the objective of the invention can be achieved, there are no special requirements for the temperature of the final hydrorefining. According to a preferred embodiment of the invention, the temperature of the final hydrorefining is 240-520°C, preferably 240-460°C. By adopting the aforementioned preferred scheme, the denitrification rate of the purification can be further controlled, while the aromatic hydrocarbon retention rate can be further improved.

[0028] In this invention, the conditions for hydrorefining can be conventionally chosen in the art. According to a preferred embodiment of this invention, the conditions for hydrorefining include a reaction pressure of 3.5-7.5 MPa, preferably 4-7 MPa.

[0029] According to a preferred embodiment of the present invention, the conditions for hydrorefining include: a weight hourly space velocity (WHSV) of 0.5-3 h⁻¹ for the hydrocarbon feedstock. -1 Preferably 0.5-2h -1 .

[0030] According to a preferred embodiment of the present invention, the conditions for hydrorefining include: a hydrogen-to-oil volume ratio of 600-5000:1, preferably 800-4000:1.

[0031] By adopting the aforementioned preferred hydrorefining conditions, the denitrification rate of the refining process can be further controlled, while the aromatic hydrocarbon retention rate can be further improved.

[0032] In this invention, as long as the objective of the invention can be achieved, there is no particular requirement regarding the number of hydrorefining cycles performed on the inferior diesel feedstock. According to a preferred embodiment of the invention, the method includes performing hydrorefining on the inferior diesel feedstock 2-5 times, preferably 2-3 times. By adopting the aforementioned preferred scheme, the denitrification rate of the refining process can be further controlled, while the aromatics retention rate can be further improved.

[0033] In this invention, inferior diesel fuel can be used. In order to further improve the processing effect, according to a preferred embodiment of the invention, the initial boiling point of the inferior diesel fuel is 150-250℃ and the final boiling point is 300-380℃.

[0034] According to a preferred embodiment of the present invention, the sulfur content of the inferior diesel feedstock is 500-7000 ug / mL, preferably 800-5000 ug / mL; the nitrogen content is 100-1000 ug / mL, preferably 200-800 ug / mL; and the aromatic content is >60 wt%, preferably >70 wt%. By adopting the aforementioned preferred embodiment, the denitrification rate of the refining process can be further controlled, while the aromatic retention rate can be further improved.

[0035] According to a preferred embodiment of the present invention, the inferior diesel feedstock is selected from at least one of catalytic cracking diesel, coking diesel, hydrotreated diesel, straight-run diesel, coal tar, direct coal liquefaction oil, and indirect coal liquefaction oil.

[0036] In this invention, the hydrorefining catalyst can be a commonly used catalyst in the art. According to a preferred embodiment of the invention, the active component of the hydrorefining catalyst is selected from oxides of Group VIB and / or Group VIII metal elements, preferably selected from Group VIB and Group VIII metal elements.

[0037] According to a preferred embodiment of the present invention, the hydrorefining catalyst further includes a lanthanide metal as an auxiliary agent. By adopting the aforementioned preferred embodiment, the denitrification rate of the refining process can be further controlled, while the aromatic hydrocarbon retention rate can be further improved.

[0038] According to a preferred embodiment of the present invention, the weight ratio of Group VIB metals, Group VIII metals, and lanthanide metals (based on oxides) in the active component of the hydrorefining catalyst is 1:0.1-0.9:0-0.1; preferably 1:0.2-0.8:0-0.1; more preferably 1:0.2-0.8:0.01-0.06. By adopting the aforementioned preferred scheme, the denitrification rate of the refining process can be further controlled, while the aromatic hydrocarbon retention rate can be further improved.

[0039] According to a preferred embodiment of the present invention, the Group VIB metal element is molybdenum and / or tungsten.

[0040] According to a preferred embodiment of the present invention, the Group VIII metal element is nickel and / or cobalt.

[0041] According to a preferred embodiment of the present invention, the lanthanide element is praseodymium.

[0042] According to a preferred embodiment of the present invention, when hydrorefining is performed twice, the weight content of the active component of the catalyst in the second hydrorefining, based on metal oxides, is not higher than the weight content of the active component of the catalyst in the first hydrorefining, preferably 0-5% lower. By adopting the aforementioned preferred scheme, the denitrification rate of the refining process can be further controlled, while the aromatic hydrocarbon retention rate can be further improved.

[0043] According to a preferred embodiment of the present invention, when hydrorefining is performed at least three times, the weight content of the active component in the catalyst for the third and subsequent hydrorefining processes is lower than the weight content of the active component in the catalyst for the first and second hydrorefining processes. By adopting the aforementioned preferred scheme, the denitrification rate of the refining process can be further controlled, while the aromatic hydrocarbon retention rate can be further improved.

[0044] According to a preferred embodiment of the present invention, the active component weight content of the catalysts in the third and subsequent hydrorefining processes is 1-9% lower than that of the active component weight content of the catalysts in the first and second hydrorefining processes. By adopting the aforementioned preferred embodiment, the denitrification rate of the refining process can be further controlled, while the aromatic hydrocarbon retention rate can be further improved.

[0045] According to a preferred embodiment of the present invention, the support for the hydrorefining catalyst is selected from at least one of alumina, silicon dioxide, titanium dioxide, and activated carbon.

[0046] According to a preferred embodiment of the present invention, the hydrogenation catalyst contains 0-30% by weight of Group VIB metal elements as oxides, preferably 6-25%, 0-18% by weight of Group VIII metal elements as oxides, preferably 1.5-15%, and 0-1% by weight of lanthanide metal elements as oxides, preferably 0.1-0.8%.

[0047] This invention provides a two-stage hydrorefining method for inferior diesel fuel, comprising:

[0048] (a) Under the conditions of the first hydrorefining catalyst, the component containing inferior diesel oil is mixed and contacted with hydrogen to complete the first stage of hydrorefining reaction, and the first stage of hydrorefining product is obtained.

[0049] (b) The product of the first stage hydrogenation reaction is not separated. Under the conditions of the second hydrogenation refining catalyst, it is cooled and mixed with hydrogen to complete the second stage hydrogenation refining reaction, and the product of the second stage hydrogenation reaction is obtained.

[0050] According to a preferred embodiment of the present invention, the conditions for the first-stage hydrorefining reaction include: a reaction pressure of 3.5-7.5 MPa, preferably 4-7 MPa; and / or a weight hourly space velocity (WHSV) of 0.5-3 h⁻¹ for the hydrocarbon feedstock. -1 Preferably 0.5-2h -1 The hydrogen-to-oil volume ratio is 600-5000:1, preferably 800-4000:1; the inlet temperature is 200-450℃, preferably 210-400℃.

[0051] According to a preferred embodiment of the present invention, the conditions for the second-stage hydrorefining reaction include: a reaction pressure of 3.5-7.5 MPa, preferably 4-7 MPa; and / or a weight hourly space velocity (WHSV) of 0.5-3 h⁻¹ for the hydrocarbon feedstock. -1 Preferably 0.5-2h -1 The hydrogen-to-oil volume ratio is 600-5000:1, preferably 800-4000:1; the inlet temperature is 220-520℃, preferably 220-440℃.

[0052] This invention provides a three-stage hydrorefining method for inferior diesel fuel, comprising:

[0053] (a) Under the conditions of the first hydrorefining catalyst, the component containing inferior diesel oil is mixed and contacted with hydrogen to complete the first stage of hydrorefining reaction, and the first stage of hydrorefining product is obtained.

[0054] (b) The products of the first stage hydrogenation reaction are not separated. Under the conditions of the second hydrogenation refining catalyst, after cooling, they are mixed with hydrogen to complete the second stage hydrogenation refining reaction and obtain the products of the second stage hydrogenation reaction.

[0055] (c) The products of the second stage hydrogenation reaction are not separated. Under the conditions of the third hydrogenation refining catalyst, they are cooled and mixed with hydrogen to complete the second stage hydrogenation refining reaction, and the products of the third stage hydrogenation reaction are obtained.

[0056] According to a preferred embodiment of the present invention, the conditions for the first-stage hydrorefining reaction include: a reaction pressure of 3.5-7.5 MPa, preferably 4-7 MPa; and / or a weight hourly space velocity (WHSV) of 0.5-3 h⁻¹ for the hydrocarbon feedstock. -1 Preferably 0.5-2h -1 The hydrogen-to-oil volume ratio is 600-5000:1, preferably 800-4000:1; the inlet temperature is 200-450℃, preferably 210-400℃.

[0057] According to a preferred embodiment of the present invention, the conditions for the second-stage hydrorefining reaction include: a reaction pressure of 3.5-7.5 MPa, preferably 4-7 MPa; and / or a weight hourly space velocity (WHSV) of 0.5-3 h⁻¹ for the hydrocarbon feedstock. -1 Preferably 0.5-2h -1 The hydrogen-to-oil volume ratio is 600-5000:1, preferably 800-4000:1; the inlet temperature is 220-520℃, preferably 220-440℃.

[0058] According to a preferred embodiment of the present invention, the conditions for the third-stage hydrorefining reaction include: a reaction pressure of 3.5-7.5 MPa, preferably 4-7 MPa; and / or a weight hourly space velocity (WHSV) of 0.5-3 h⁻¹ for the hydrocarbon feedstock. -1 Preferably 0.5-2h -1 The hydrogen-to-oil volume ratio is 600-5000:1, preferably 800-4000:1; the inlet temperature is 240-520℃, preferably 240-460℃.

[0059] In this invention, the catalyst needs to undergo pre-sulfurization treatment before activity evaluation. According to a preferred embodiment of this invention, the pre-sulfurization treatment conditions are as follows: wet sulfidation in a cyclohexane solution containing 500-5000 ppm CS2, starting sulfidation at 130-200℃, with programmed temperature increase at a rate of 5-30℃ / h, and holding at 280-380℃ for 4-30h.

[0060] This invention provides an application of the method described in this invention in the processing of inferior diesel fuel.

[0061] The present invention will be described in detail below through embodiments. In the following embodiments, all raw materials are commercially available products;

[0062] Aromatic protection rate:

[0063] Desulfurization rate:

[0064] Denitrification rate:

[0065] In the formula,

[0066] R A The percentage of aromatics is %.

[0067] X S The percentage of sulfur conversion rate;

[0068] X N Nitrogen conversion rate (%);

[0069] C A in The mass percentage of total aromatics in the raw materials

[0070] C A out The mass percentage of total aromatic hydrocarbons in the product

[0071] C S in The mass percentage of sulfur in the raw material;

[0072] C S out The mass percentage of sulfur in the product;

[0073] C N in The mass percentage of nitrogen in the raw material;

[0074] C N out This represents the mass percentage of nitrogen in the product.

[0075] Example 1

[0076] Hydrorefining reactor I and hydrorefining reactor II are each filled with 30 ml of hydrorefining catalyst. The reaction is carried out on a pressurized fixed adiabatic bed reactor. The inferior diesel feedstock and hydrogen are hydrorefined together in two separate processes.

[0077] The catalyst is as follows: It is a supported catalyst with alumina as the support. The active components, by weight of the total catalyst, are: NiO 4.5%, MoO3 12.5%, and Co2O3 5.5%.

[0078] Inferior diesel feedstock: distillation range 203℃-340℃, total aromatics 84%, sulfur content 2800ppm, nitrogen content 450ppm;

[0079] The catalyst needs to be pre-sulfurized before the reaction. The conditions are: wet sulfidation in a cyclohexane solution containing 2000 ppm CS2, starting sulfidation at 160℃, with programmed temperature increase at a rate of 15℃ / h, and holding at 330℃ for 20h.

[0080] Reaction conditions: The weight hourly space velocity (WHSV) of the hydrocarbon feedstock is 1.0 h⁻¹. -1 The reaction pressure was 5.8 MPa; the hydrogen-to-oil volume ratio was 1500:1; the inlet temperature of refining reactor I was 270℃; and the inlet temperature of refining reactor II was 300℃.

[0081] Catalyst evaluation results:

[0082] First stage of hydrorefining: desulfurization rate 85.71%, denitrification rate 82.22%, aroma retention rate 97.62%;

[0083] The second stage of hydrorefining achieves a desulfurization rate of 99.64%, a denitrification rate of 98.89%, and an aromaticity retention rate of 94.05%.

[0084] Example 2

[0085] Hydrorefining reactor I and hydrorefining reactor II are each filled with 30 ml of hydrorefining catalyst. The reaction is carried out on a pressurized fixed adiabatic bed reactor. The inferior diesel feedstock and hydrogen are hydrorefined together in two separate processes.

[0086] The catalyst is as follows: It is a supported catalyst with alumina as the support. The active components, by total weight of the catalyst, are: NiO 4.5%, MoO3 12.5%, and WO3 5.5%.

[0087] Inferior diesel feedstock: distillation range 155℃-305℃, total aromatics 72%, sulfur 1000ppm, nitrogen 220ppm;

[0088] Pre-sulfurization treatment is required before the catalyst reacts. The conditions are as follows: wet sulfidation in a cyclohexane solution containing 2000 ppm CS2, starting sulfidation at 140℃, with programmed temperature increase at a rate of 20℃ / h, and holding at 320℃ for 22h.

[0089] Reaction conditions: The weight hourly space velocity (WHSV) of the hydrocarbon feedstock was 0.6 h⁻¹. -1 The reaction pressure was 4.5 MPa; the hydrogen-to-oil volume ratio was 900:1; the inlet temperature of refining reactor I was 240℃; and the inlet temperature of refining reactor II was 290℃.

[0090] Catalyst evaluation results:

[0091] First stage of hydrorefining: desulfurization rate 85%, denitrification rate 81.82%, aroma retention rate 97.92%;

[0092] The second stage of hydrorefining achieves a desulfurization rate of 99%, a denitrification rate of 97.73%, and an aromaticity retention rate of 94.44%.

[0093] Example 3

[0094] Hydrorefining reactor I and hydrorefining reactor II are each filled with 30 ml of hydrorefining catalyst. The reaction is carried out on a pressurized fixed adiabatic bed reactor. The inferior diesel feedstock and hydrogen are hydrorefined together in two separate processes.

[0095] The catalyst is as follows: It is a supported catalyst with alumina as the support. The active components, by weight of the total catalyst, are: NiO 4.5%, MoO3 12.5%, and Co2O3 5.5%.

[0096] Inferior diesel feedstock: distillation range 160℃-310℃, total aromatics 86%, sulfur 4500ppm, nitrogen 780ppm;

[0097] Pre-sulfurization treatment is required before the catalyst reacts. The conditions are as follows: wet sulfidation in a cyclohexane solution containing 2000 ppm CS2, starting sulfidation at 150℃, with programmed temperature increase at a rate of 15℃ / h, and holding at 340℃ for 18h.

[0098] Reaction conditions: The weight hourly space velocity (WHSV) of the hydrocarbon feedstock was 1.8 h⁻¹. -1 The reaction pressure was 6.8 MPa; the hydrogen-to-oil volume ratio was 3800:1; the inlet temperature of refining reactor I was 300℃; and the inlet temperature of refining reactor II was 320℃.

[0099] Catalyst evaluation results:

[0100] First stage of hydrorefining: desulfurization rate 88.89%, denitrification rate 89.74%, aroma retention rate 95.35%;

[0101] The second stage of hydrorefining achieves a desulfurization rate of 99.78%, a denitrification rate of 98.97%, and an aromaticity retention rate of 93.72%.

[0102] Example 4

[0103] Same as Example 1, except that the inlet temperature of refining reactor I is 270°C and the inlet temperature of refining reactor II is 280°C.

[0104] Catalyst evaluation results:

[0105] First stage of hydrorefining: desulfurization rate 85.71%, denitrification rate 82.22%, aroma retention rate 97.62%;

[0106] The second stage of hydrorefining achieves a desulfurization rate of 90%, a denitrification rate of 93.33%, and an aromaticity retention rate of 95.24%.

[0107] Example 5

[0108] Same as Example 1, except that the inlet temperature of refining reactor I is 230°C and the inlet temperature of refining reactor II is 320°C.

[0109] Catalyst evaluation results:

[0110] First stage of hydrorefining: desulfurization rate 83.57%, denitrification rate 81.56%, aroma retention rate 97.98%;

[0111] The second stage of hydrorefining achieves a desulfurization rate of 99.61%, a denitrification rate of 98.22%, and an aromaticity retention rate of 93.57%.

[0112] Example 6

[0113] Same as Example 1, except that the inferior diesel feedstock has an S content of 6000ppm.

[0114] Catalyst evaluation results:

[0115] First stage of hydrorefining: desulfurization rate 83.33%, denitrification rate 80%, aroma retention rate 96.43%;

[0116] The second stage of hydrorefining achieved a desulfurization rate of 91.67%, a denitrification rate of 93.33%, and an aromaticity retention rate of 93.21%.

[0117] Example 7

[0118] Same as Example 1, except that the hydrorefining reactor II is filled with 30 ml of hydrorefining catalyst, which is as follows: the catalyst is a supported catalyst, the support is alumina, and the active component, by weight of the total catalyst, is 18.5% NiO.

[0119] Catalyst evaluation results:

[0120] First stage of hydrorefining: desulfurization rate 78.57%, denitrification rate 73.33%, aroma retention rate 95.24%;

[0121] The second stage of hydrorefining resulted in a desulfurization rate of 90.36%, a denitrification rate of 92.89%, and an aromaticity retention rate of 91.67%.

[0122] Example 8

[0123] Similar to Example 1, except that a third stage of hydrorefining is added. Hydrorefining reactor III is filled with 30 ml of hydrorefining catalyst, and the reaction is carried out on a pressurized fixed adiabatic bed reactor. The inferior diesel feedstock is hydrorefined three times in sequence.

[0124] The third-stage hydrorefining catalyst is as follows: the catalyst is a supported catalyst, the support is alumina, and the active components, by total catalyst weight, are NiO 4.5%, MoO3 10.5%, and Co2O3 3%.

[0125] Reaction conditions: The weight hourly space velocity (WHSV) of the hydrocarbon feedstock is 1.0 h⁻¹. -1 The reaction pressure was 5.8 MPa; the hydrogen-to-oil volume ratio was 1500:1; the inlet temperature of refining reactor I was 260℃; the inlet temperature of refining reactor II was 290℃; and the inlet temperature of refining reactor III was 310℃.

[0126] Catalyst evaluation results:

[0127] First stage of hydrorefining: desulfurization rate 84.64%, denitrification rate 80.44%, aroma retention rate 97.98%;

[0128] Second-stage hydrorefining: desulfurization rate 99.61%, denitrification rate 98.67%, aroma retention rate 94.64%;

[0129] The third stage of hydrogenation refining achieves a desulfurization rate of 99.75%, a denitrification rate of 99%, and an aromaticity retention rate of 90.48%.

[0130] Example 9

[0131] Similar to Example 8, except that the catalyst in the refining reactor III is as follows: the catalyst is a supported catalyst, the support is alumina, and the active components, by total weight of the catalyst, are NiO 4.5%, MoO3 12.5%, and Co2O3 5.5%.

[0132] Catalyst evaluation results:

[0133] First stage of hydrorefining: desulfurization rate 84.64%, denitrification rate 80.44%, aroma retention rate 97.98%;

[0134] Second-stage hydrorefining: desulfurization rate 99.61%, denitrification rate 98.67%, aroma retention rate 94.64%;

[0135] The third stage of hydrorefining achieves a desulfurization rate of 99.68%, a denitrification rate of 98.78%, and an aroma retention rate of 88.1%.

[0136] Example 10

[0137] Similar to Example 8, except that the inlet temperature of refining reactor I is 270°C; the inlet temperature of refining reactor II is 280°C; and the inlet temperature of refining reactor III is 290°C.

[0138] Catalyst evaluation results:

[0139] First stage of hydrorefining: desulfurization rate 85.71%, denitrification rate 82.22%, aroma retention rate 97.62%;

[0140] Second-stage hydrorefining: desulfurization rate 90%, denitrification rate 93.33%, aroma retention rate 95.24%;

[0141] The third stage of hydrorefining achieves a desulfurization rate of 95.36%, a denitrification rate of 94.44%, and an aromaticity retention rate of 92.86%.

[0142] Example 11

[0143] Same as Example 1, except that the catalyst for the second hydrorefining is as follows: the catalyst is a supported catalyst, the support is alumina, and the active components, by total weight of the catalyst, are NiO 6.5%, MoO3 14.5%, and Co2O3 6.5%;

[0144] Catalyst evaluation results:

[0145] First-stage hydrorefining: desulfurization rate 83.93%, denitrification rate 78.89%, aroma retention rate 97.02%;

[0146] The second stage of hydrorefining achieves a desulfurization rate of 99.36%, a denitrification rate of 97.78%, and an aromaticity retention rate of 92.86%.

[0147] Example 12

[0148] Same as Example 1, except that the catalyst for the second hydrorefining is as follows: the catalyst is a supported catalyst, the support is alumina, and the active components, by weight of the total catalyst, are 10% NiO and 12.5% ​​MoO3.

[0149] Catalyst evaluation results:

[0150] First stage of hydrorefining: desulfurization rate 83.57%, denitrification rate 77.78%, aroma retention rate 96.43%;

[0151] The second stage of hydrorefining achieves a desulfurization rate of 99.29%, a denitrification rate of 97.33%, and an aromaticity retention rate of 92.38%.

[0152] Example 13

[0153] Similar to Example 1, except that the two-stage hydrorefining catalyst has an added active additive. The catalyst is as follows: the catalyst is a supported catalyst, the support is alumina, and the active components, by total weight of the catalyst, are: NiO 4.5%, MoO3 12.5%, Co2O3 5.5%, and praseodymium oxide 0.5%.

[0154] Catalyst evaluation results:

[0155] First stage of hydrorefining: desulfurization rate 86.36%, denitrification rate 84.44%, aroma retention rate 97.38%;

[0156] The second stage of hydrorefining achieves a desulfurization rate of 99.71%, a denitrification rate of 99.11%, and an aroma retention rate of 94.4%.

[0157] Comparative Example 1

[0158] Same as Example 1, except that the inlet temperature of refining reactor I is 300°C and the inlet temperature of refining reactor II is 270°C.

[0159] Catalyst evaluation results:

[0160] First stage of hydrorefining: desulfurization rate 89.29%, denitrification rate 86.67%, aroma retention rate 92.86%;

[0161] The second stage of hydrorefining resulted in a desulfurization rate of 92.86%, a denitrification rate of 91.11%, and an aromaticity retention rate of 90.48%.

[0162] Comparative Example 2

[0163] Same as Example 1, except that the inlet temperature of refining reactor I is 280°C; the inlet temperature of refining reactor II is 280°C.

[0164] Catalyst evaluation results:

[0165] First stage of hydrorefining: desulfurization rate 86.43%, denitrification rate 83.33%, aroma retention rate 96.43%;

[0166] The second stage of hydrorefining achieved a desulfurization rate of 88.93%, a denitrification rate of 88.89%, and an aromaticity retention rate of 94.76%.

[0167] Comparative Example 3

[0168] Same as Example 1, except that only hydrorefining reactor I is used, and the reactor inlet temperature is 280°C.

[0169] Catalyst evaluation results:

[0170] First stage of hydrorefining: desulfurization rate 86.43%, denitrification rate 83.33%, aroma retention rate 96.46%.

[0171] The results from the examples and comparative examples show that the technical solution of the present invention can achieve high desulfurization rate, denitrification rate and aroma retention rate in the refining of inferior diesel feedstock.

[0172] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for refining inferior diesel fuel, characterized in that, The method includes: subjecting inferior diesel feedstock to at least two hydrorefining processes in sequence, wherein the temperature of the first hydrorefining process is lower than the temperature of the second hydrorefining process between two adjacent processes; The temperature of the first hydrorefining step in a series of adjacent hydrorefining processes is 20-250°C lower than the temperature of the second hydrorefining step. The temperature for the first hydrogenation refining is 200-450℃; The final hydrorefining temperature is 240-520℃; The active component of the hydrorefining catalyst is selected from Group VIB and Group VIII metal elements, and the hydrorefining catalyst further includes lanthanide metal elements; the Group VIB metal element is molybdenum and / or tungsten; the Group VIII metal element is nickel and / or cobalt; and the lanthanide metal element is praseodymium. When hydrorefining is performed twice, the weight content of the active component of the catalyst in the second hydrorefining, based on metal oxides, shall not be higher than the weight content of the active component of the catalyst in the first hydrorefining. When hydrorefining is performed at least three times, the weight content of the active component of the catalyst in the third and subsequent hydrorefining processes, based on metal oxides, is lower than the weight content of the active component of the catalyst in the first and second hydrorefining processes. The catalyst for hydrorefining contains 6-30% by weight of Group VIB metals (calculated as oxides), 1.5-18% by weight of Group VIII metals (calculated as oxides), and 0.1-1% by weight of lanthanides (calculated as oxides). In the active component of the hydrorefining catalyst, the weight ratio of Group VIB metals, Group VIII metals, and lanthanide metals, calculated as oxides, is 1:0.2-0.8:0.01-0.

06.

2. The method according to claim 1, wherein, The temperature of the first hydrorefining step in a two-step process is 20-100°C lower than the temperature of the second hydrorefining step; and / or The temperature for the first hydrorefining is 210-400℃; and / or The final hydrogenation purification temperature is 240-460℃.

3. The method according to claim 1, wherein, The temperature of the first hydrogenation process in two consecutive hydrogenation processes is 20-80°C lower than the temperature of the second hydrogenation process.

4. The method according to claim 1, wherein, The conditions for the hydrorefining include: The reaction pressure is 3.5-7.5 MPa; and / or The heavy hourly space velocity is 0.5-3 h. -1 ; and / or The hydrogen-to-oil volume ratio is 600-5000:

1.

5. The method according to claim 1, wherein, The conditions for the hydrorefining include: The reaction pressure is 4-7 MPa; and / or The heavy hourly space velocity is 0.5-2 h. -1 ; and / or The hydrogen-to-oil volume ratio is 800-4000:

1.

6. The method according to claim 1, wherein, The method involves sequentially hydrorefining inferior diesel feedstock 2-5 times.

7. The method according to claim 1, wherein, The method involves sequentially hydrorefining inferior diesel feedstock 2-3 times.

8. The method according to claim 1, wherein, The initial boiling point of the inferior diesel feedstock is 150-250℃, and the final boiling point is 300-380℃.

9. The method according to claim 1, wherein, The inferior diesel feedstock contains 500-7000 ug / mL of sulfur, 100-1000 ug / mL of nitrogen, and >60 wt% of aromatics.

10. The method according to claim 9, wherein, The inferior diesel feedstock contains 800-5000 ug / mL of sulfur, 200-800 ug / mL of nitrogen, and >70 wt% of aromatics.

11. The method according to claim 1, wherein, The inferior diesel feedstock is selected from at least one of catalytic cracking diesel, coking diesel, hydrotreated diesel, and straight-run diesel.

12. The method according to claim 1, wherein, When hydrorefining is performed twice, the active component weight content of the catalyst in the second hydrorefining, based on metal oxides, shall not be higher than the active component weight content of the catalyst in the first hydrorefining by 0-5%. When hydrorefining is performed at least three times, the weight content of the active component of the catalyst in the third and subsequent hydrorefining processes, calculated as metal oxides, is 1-9% lower than the weight content of the active component of the catalyst in the first and second hydrorefining processes.

13. The method according to any one of claims 1-12, wherein, The hydrogenation catalyst contains 6-25% by weight of Group VIB metals (calculated as oxides), 1.5-15% by weight of Group VIII metals (calculated as oxides), and 0.1-0.8% by weight of lanthanides (calculated as oxides).

14. The application of the method according to any one of claims 1-13 in the processing of inferior diesel fuel.