JP5783724B2 - Integrated two-stage desulfurization / dewaxing using high temperature separator for stripping - Google Patents

Description

  The present invention relates to a two-stage hydroprocessing method using intermediate stripping. More specifically, the intermediate stripping is performed under high pressure and temperature by recycling the hot gas effluent from the stripping stage.

  North America, and more generally, the current regulations on diesel fuel standards around the world are a compilation of standards that must be met for properties such as cloud point and sulfur removal. The presence of factors such as topographical and environmental regional challenges often means that individual refineries consider a wide range of criteria in deciding how to set process conditions for producing diesel fuel. It means you have to. This is further complicated by fluctuations in the available crude feed.

  The conventional method for removing impurities such as nitrogen and sulfur from hydrocarbon feedstock in the production of diesel fuel is to convert the nitrogen and sulfur impurities to hydrogen sulfide and ammonia using a hydrotreating step. Then, after performing the hydrotreating step, a catalytic dewaxing step may be performed to improve flow characteristics such as cloud point of diesel fuel. Such a catalyst for the dewaxing step is usually susceptible to the presence of impurities sulfur and nitrogen.

  One conventional approach to producing diesel fuel is to perform the hydroprocessing and dewaxing steps in a single reactor. In this type of configuration, the hydrotreating step effluent is cascaded to the dewaxing step. Since the product from the first process step is sent in cascade, the process temperature of the hydroprocessing and dewaxing steps will be approximate. Usually, the temperature of the system is selected on the basis of the hydrotreating step to meet the sulfur specifications of the fuel, and as a result, the dewaxing step will be operated at an unnecessarily high temperature. For this reason, the diesel fuel is treated excessively, thereby reducing the cloud point more than necessary and correspondingly reducing the yield. In addition, this type of configuration tends to shorten the operating life of the dewaxing catalyst. In some cases, this situation may be reversed, such as when the dewaxing step is operated at a temperature higher than that required for hydroprocessing, such as when a new catalyst for hydroprocessing is charged to the reactor. As a result, the life of the hydrotreating catalyst is similarly shortened. The product sent in this cascade may be passed through a hot separator before being introduced into the dewaxing stage, but gases containing sulfur and nitrogen are usually not completely removed, resulting in desorption. Deterioration of the wax catalyst is accelerated.

  Another conventional approach is to use two separate reactors for the hydroprocessing and dewaxing steps. While this allows stripping between the hydroprocessing and dewaxing stages, the cost of building a configuration with two reactors is much higher.

  (Patent Document 1) provides a general system for contact treatment of a hydrocarbon raw material. In (Patent Document 1), the raw oil is hydrotreated to remove impurities, the first stripping step is performed at a pressure close to the operating pressure of the hydrotreating step, and then the second hydrotreating step is performed. Is done. The product from the second hydroprocessing step is then subjected to stripping, and at least a portion of the gas from the second hydroprocessing step is recycled to serve as a stripping gas for the first stripping step. Is done.

  (Patent Document 2) provides a system for processing a middle distillate for producing a product such as diesel fuel. In (Patent Document 2), the middle distillate is subjected to hydrogen treatment in two separate reactors, and stripping is performed in the middle of these. A portion of the product from the second hydrotreating step is then refluxed back to the beginning of the series of hydrotreating processes.

  (Patent Document 3) describes a method for producing diesel fuel from gas oil feedstock. This method includes hydroprocessing, hydrorefining, and catalytic dewaxing. Hydrorefining and catalytic dewaxing processes are carried out using a countercurrent of hydrogen.

  (Patent Document 4) describes another method for producing diesel fuel from gas oil. The method includes at least two hydroprocessing steps, during which the stripping and cleaning steps are performed. The washing step includes injecting additional hydrocarbon streams into the liquid product from the first hydroprocessing step. This additional hydrocarbon stream may be diesel, gasoline, and light vacuum gas oil.

US Pat. No. 6,635,170 US Pat. No. 6,623,628 US Patent Application Publication No. 2005/0269245 US Pat. No. 6,676,828

  What is needed is a flexible way to produce diesel fuel products without substantially adding capital costs so that oil refiners can meet various diesel standards.

  In one embodiment, a method for producing a diesel fuel product is provided. The method passes a first hydrocarbon feedstock having a first initial cloud point through a hydrotreating zone having a hydrotreating temperature and pressure to hydrogenate the feedstock under effective hydrotreating conditions. Treating to form a hydrotreated product having a sulfur content of 15 wppm or less. The hydrotreatment product is then passed through a stripping zone where the hydrotreatment product is subjected to stripping to form a gas effluent and a liquid effluent. The liquid effluent is then passed through a catalytic dewaxing treatment zone and dewaxed under effective catalytic dewaxing conditions including a first average catalytic dewaxing temperature that is at least 15 ° C. lower than the hydroprocessing temperature. A dewaxed product is formed having a cloud point at least 10 ° C. below the initial cloud point. Next, the temperature of the contact dewaxing treatment area is lowered to a second contact dewaxing temperature that is at least 5 ° C. lower than the first contact dewaxing temperature. Next, the second hydrocarbon feedstock having the second initial cloud point is passed through the hydrotreating zone, and the feedstock is hydrotreated at the same hydrotreating temperature, whereby the sulfur content is 15 wppm or less. A hydroprocessing product is formed. The second hydrotreating product is also passed through a stripping zone and subjected to stripping to form a second gas effluent and a second liquid effluent. The second liquid effluent is then passed through a catalytic dewaxing treatment zone and dewaxed at a second catalytic dewaxing temperature to produce a second dewaxing having a cloud point at least 10 ° C. lower than the second initial cloud point. Make things.

1 illustrates a suitable reaction system for carrying out the process according to the invention.

In one embodiment, the present invention provides a method for reducing capital costs while retaining the advantages of a two-stage configuration. This method takes advantage of the stripping hot separator between the hydrotreating stage and catalytic dewaxing steps within one reactor. The desulfurization reactor effluent is sent to a high temperature stripping separator where ammonia and hydrogen sulfide dissolved in the desulfurized liquid are removed and separated by stripping with make-up hydrogen. Also, only one common recycle compressor is required to serve as both a desulfurization and dewaxing reactor. Both the hydrotreating and dewaxing stages are operated in a cocurrent manner.

  Additional advantages are also provided by the various embodiments of the present invention. A high pressure stripper is not required after the dewaxing stage, one of which is that makeup gas is used in the stripping stage between the hydrotreating stage and the dewaxing stage. Furthermore, there is no need to reflux the product of any processing stage. More generally, it is not necessary to introduce additional hydrocarbon streams into the effluent from the hydroprocessing stage before passing the effluent through the catalytic dewaxing stage.

  Yet another advantage of various embodiments of the present invention is the ability to independently control the temperature of the hydroprocessing and dewaxing stages. This flexibility provides many advantages for diesel fuel production. For example, by adjusting only the temperature of the dewaxing stage while maintaining the temperature of the hydrotreating stage, diesel fuel that meets various standards can be produced from a single feedstock, The yield of diesel fuel is maximized.

  The method includes a first hydrogen treatment zone, a first separation zone following the first hydrogen treatment zone, and a second hydrogen treatment zone. Unlike typical practice in the art, the first separation zone is operated at the pressure of the previous hydrogen treatment zone. There is no vacuum separation between the first and second hydrogen treatment zones, i.e. no vacuum. The feedstock oil may be separated under reduced pressure after the second hydrogen treatment zone.

  For US diesel fuel, various requirements and standards are specified in ASTM D975 for location-based. Other similar regulations exist in Europe, Canada, and other countries. These standards typically include a requirement to reduce sulfur in diesel products to 15 wppm or less. Furthermore, although the cloud point standard varies widely, the cloud point is well below 0 ° C. for winter standards.

  Diesel boiling range feed streams suitable for use in the present invention are those having a boiling range of about 215 ° F to about 800 ° F. Preferably, the initial boiling point of the diesel boiling range feed stream is at least 250 ° F, or at least 300 ° F, or at least 350 ° F, or at least 400 ° F, or at least 451 ° F. Preferably, the diesel boiling range feedstock stream has an end point of 800 ° F or lower, or 775 ° F or lower, or 750 ° F or lower. In one embodiment, the boiling range of the diesel boiling range feedstock stream is from 451 ° F to about 800 ° F. In other embodiments, the diesel boiling range feed stream also includes a kerosene range compound, resulting in a feed stream having a boiling range of about 250 ° F. to about 800 ° F. Such feedstock streams may have a nitrogen content of about 50 to about 2000 wppm nitrogen, preferably about 50 to about 1500 wppm nitrogen, more preferably about 75 to about 1000 wppm nitrogen. In one embodiment, a feed stream suitable for use herein has a sulfur content of from about 100 to about 40,000 wppm sulfur, preferably from about 200 to about 30,000 wppm, more preferably from about 350 to about 25,000 wppm. Feedstock streams suitable for use may include synthetic feedstock streams such as Fischer-Tropsch hydrocarbons or feedstock streams derived from biological components such as animal or vegetable oils, fats, fatty acids and the like.

The main purpose of hydroprocessing is typically to reduce the sulfur, nitrogen, and aromatics of the feedstock and is not primarily aware of changing the boiling point of the feedstock. . Typically, the catalyst comprises at least one Group VIA and Group VIII metal supported on a support such as alumina or silica. Examples include Ni / Mo, Co / Mo, and Ni / W catalysts. Hydrotreatment conditions typically include a temperature of 315-425 ° C., a pressure of 300-3000 psig, a liquid space velocity (LHSV) of 0.2-10 h ⁻¹ , and a hydrogen treatment ratio of 500-10000 scf / bbl. Is included.

  In order to meet regulatory requirements, the sulfur present in the diesel product must be less than 15 wppm. In order to satisfy this standard, it is desirable to lower the target value of sulfur so as not to deviate from the standard due to process variations. In this way, a margin can be provided to compensate for errors that occur when diesel fuel is contaminated later, such as during transportation.

Catalytic dewaxing involves the removal and / or isomerization of paraffinic long chain molecules from the feedstock. Hydrodewaxing may be accomplished by selectively hydrocracking or hydroisomerizing these long chain molecules. The hydrodewaxing catalyst is preferably a molecular sieve such as crystalline aluminosilicate (zeolite) or silicoaluminophosphate (SAPO), such as zeolite beta. Preferably, the molecular sieve may be a 10-membered ring sieve such as ZSM-5, ZSM-22, ZSM-23, ZSM-35, ZSM-48, SAPO-11, SAPO-41. These catalysts may also have a metal hydrogenation component, preferably a Group VIII metal, in particular a Group VIII noble metal. Hydrodewaxing conditions include a temperature of 280-380 ° C., a pressure of 300-3000 psig, an LHSV of 0.1-5.0 h ⁻¹ , and a process gas ratio of 500-5000 scf / bbl.

  In a preferred embodiment, the dewaxing catalyst is selected to also perform desulfurization. In such embodiments, the sulfur in the feedstock can be reduced to a first level (such as about 12 wppm to about 25 wppm) by using a hydrotreating step. Additional sulfur is then removed during the dewaxing step to ensure a sulfur level of less than 15 wppm. By reducing the requirements for sulfur during the hydrotreating step, the severity of the conditions in the hydrotreating step can be relaxed, thereby improving yield. Suitable dewaxing catalysts may include bound molecular sieve catalysts comprising ZSM-48, ZSM-23, zeolite beta, and Group VIII noble metals such as Pt and Pd. ZSM-48, ZSM-23, or ZBM-30, EU-2, EU-11, etc., which are molecular sieves of the same shape as zeolite beta, may also be used.

  A typical distillate feedstock suitable for conversion to a diesel fuel product may have an initial cloud point in the range of about -20 ° C to about 5 ° C. In order to form a diesel fuel product suitable for winter conditions, the contact dewaxing conditions include a cloud point of at least about 10 ° C., or at least about 20 ° C., or at least about 30 ° C., or at least about 40 ° C., or at least about 50 You may select so that it may fall by ° C. To achieve this type of cloud point reduction, the dewaxing temperature may be 15 ° C., or 20 ° C., or 25 ° C., or 30 ° C. below the hydroprocessing temperature.

  The dewaxing temperature selected may also depend on the specifications of the diesel fuel product that is to be adapted. Since the temperature of the hydrotreatment and the dewaxing step can be controlled separately, it is also possible to adjust the dewaxing temperature so as to meet a desired standard. For example, producing a constant diesel fuel with a first cloud point specification and then producing a second batch of diesel fuel intended for different winter climates (with correspondingly changed cloud point regulations) It may be desirable. Since the dewaxing temperature is not governed by the hydroprocessing temperature, the dewaxing temperature can be optimized to produce a first cloud point standard diesel fuel. Once sufficient first cloud point grade diesel fuel is produced, the dewaxing temperature may be increased by at least about 5 ° C, or at least about 10 ° C, or at least about 15 ° C. Alternatively, the dewaxing temperature may be reduced by at least about 5 ° C, or at least about 10 ° C, or at least about 15 ° C. Even in this alternative embodiment of reducing the dewaxing temperature, it is desirable to dewax some diesel fuel, so changing the dewaxing temperature does not correspond to simply stopping the dewaxing step. Note that there is no. Therefore, the temperature decrease in the dewaxing stage is less than 100 ° C. By modifying the dewaxing temperature in this way, it is possible to improve the yield of diesel products with a more relaxed cloud point requirement, while at the same time reducing diesel fuel with a lower cloud point if necessary. It is still possible to manufacture.

Commonly practiced in the art is vacuum separation or vacuum between hydroprocessing steps. The reason for this vacuum separation is that the effluent from the first hydroprocessing step (or zone) is subjected to stripping before passing the effluent through the second hydroprocessing step. The intermediate stripping zone is used to remove gaseous impurities such as H ₂ S and NH ₃ produced in the first hydrotreating step, in order to strip light (low boiling) products from the effluent. Sometimes used. This type of gaseous impurity can adversely affect catalyst performance in the second hydroprocessing step or zone. However, it is usually necessary to pressurize and heat the effluent again before passing the stripped effluent through the second hydrotreating step.

  High pressure separators are well known in the art. These may include a flash drum, a pressurized stripper that includes a pressurized separator for separating liquids and gases at elevated temperatures, or a combination thereof. These devices are designed to operate at high temperatures, such as temperatures before the hydrogen treatment zone. The high pressure stripper may be operated in either a cocurrent or countercurrent manner with respect to the stripping gas.

  This method will be further described with reference to the representative method shown in FIG. By supplying unreacted feedstock to the hydrotreating device 20 through the line 15, hydrotreated product, hydrogen sulfide, ammonia, and light hydrocarbon gas are produced. Hydrogen for the first hydrogen treatment zone is supplied from the recycling apparatus 70 through the line 35. The product from the hydrotreating apparatus passes through a first separation zone 30 which is a stripping separator operated at a temperature and pressure close to the discharge temperature and pressure of the hydrotreating apparatus.

  The liquid hydrotreatment product is stripped with make-up hydrogen gas passing through the first separation zone 30 through line 25. Light hydrocarbons, hydrogen sulfide, and ammonia are separated from the hydroprocessing product and sent to the second separation zone 40. This separation zone may be a cooler conventional separator. The gas phase product from the second separation zone 40 is sent to the recycling device 70. The stripped hydroprocessing product is sent to the second catalytic dewaxing device 50. No vacuum separation is performed between the hydrotreating device 20 and the catalytic dewaxing device 50 (no pressure reduction). In order to balance the pressure, the catalytic dewaxing device 50 may be operated at a pressure close to the hydroprocessing device 20, although slightly higher or lower pressures are acceptable.

  The catalytic dewaxing device removes and / or modifies the waxy paraffin from the hydrotreating product by selectively hydrocracking, isomerizing, or some combination thereof. The hydrogen for the catalytic dewaxing device 50 is supplied from the makeup hydrogen stream used in the first separation zone 30 and the hydrogen added from the recycling device. The resulting dewaxed product and any gases are then passed through the separation zone 60. The separator constituting the separation zone 60 separates the liquid product from the gas. Liquid product (dewaxed product is passed through line 65 for use as a diesel fuel product. The gaseous product from separator 60 is the same recycle loop used for the vapor phase product from separator 40. Therefore, a recycling apparatus common to all hydrogen in the system may be used.

  In the method shown in FIG. 1, most of the hydrogen sulfide and ammonia in the effluent from the first hydrogen treatment zone are removed in the separation zone 30 except for the equilibrium concentration determined by the partial pressure of these gases. This equilibrium amount is further reduced by adding make-up hydrogen required for the system as a stripping gas for the separator 30. Therefore, the liquid product flowing into the catalytic dewaxing device 50 contains almost no hydrogen sulfide or ammonia. This can be important when the catalyst used in the catalytic dewaxing device 50 is susceptible to these impurities. The equilibrium moves to favor the desorption of any hydrogen sulfide and ammonia remaining in the liquid product from the first hydroprocessing zone. Not only is the catalyst in the second hydrotreating zone better protected, but the reaction rate can also be increased. By not depressurizing between or after the hydrogen treatment zones, a gas stream for depressurization and repressurization is not required, thereby greatly reducing costs.

  The temperature used in the hydroprocessing and dewaxing steps can be controlled independently by the configuration used in the hydroprocessing apparatus and dewaxing apparatus. This makes it possible in particular to achieve the desired specifications by independently modifying the temperature of each reactor. As a result, reaction conditions can be easily modified in response to changes in product specifications or available feedstock types.

  As an example, the method of the present invention can be used to produce diesel fuel intended for various locations of use. Diesel fuel cloud point requirements vary greatly by month and region, as shown in ASTM D975 and / or the specification map specified in other national legislation. The ability to vary the severity of dewaxing to meet specific cloud point requirements is most economical to the user. Since the sulfur specification is constant, it may not be necessary to change the severity of the hydrotreatment for a given feedstock.

  When a single stage reactor is used, the ability to adjust the dewaxing temperature independently of the hydrotreatment stage is limited. Some hydrogen quenching may be performed between the hydrotreating and dewaxing catalyst, but the ability to adjust the temperature is very limited. Thus, if the feedstock is constant, the user may have to perform excessive hydroprocessing to reach a higher target value for the cloud point. Alternatively, the user may only compromise with an average cloud point improvement that is not the most economical.

  The method of the present invention overcomes the above-mentioned problems by allowing separate settings for hydroprocessing and dewaxing temperatures. This makes it possible to set the hydrotreating step to a higher first temperature. The temperature of the dewaxing step may then be set at least 10 ° C. lower, or at least 15 ° C., or at least 20 ° C., or at least 25 ° C. lower to meet the desired cloud point specification. Alternatively, the dewaxing step may be at a higher temperature, in which case the dewaxing step is at least 10 ° C higher, or at least 15 ° C, or at least 20 to meet the desired cloud point specification. Or higher by at least 25 ° C. By adapting to the desired cloud point specification, the yield of diesel fuel obtained by this method can be increased instead of simply operating at the temperature of the hydroprocessing stage.

  It should be noted that when referring to hydroprocessing and catalytic dewaxing temperatures, the temperatures herein refer to average temperatures. The average temperature is used for the catalyst bed (or reaction stage) since the temperature from the top of the catalyst bed / reaction stage to the bottom of the column should usually vary to some extent.

  The method according to the invention makes it possible to obtain the further advantage of being able to accommodate multiple types of product standards. For example, during the transition from summer to winter, it would be desirable to be able to continue to produce this fuel for as long as possible for any location where summer diesel is allowed, as this would improve yield. On the other hand, switching to a lower cloud point requirement would be earlier at other locations of use. The method of the present invention allows the dewaxing temperature to be varied to produce multiple types of diesel products, thus allowing it to still meet desired product specifications while maximizing yield. The cloud point variation depending on the location of use may be at least 5 ° C, or at least 10 ° C, or at least 15 ° C, or at least 20 ° C.

  Another example of the flexibility of the method provided by the present invention relates to the type of initial feedstock that can be used. Depending on the origin of the feedstock, it may be desirable to carry out the hydrotreatment under somewhat severe conditions. For example, Fischer-Tropsch feedstocks may require little processing, while feedstocks containing biological components may become more severe to meet the desired sulfur target. May be necessary. Alternatively, one mineral-based feedstock and another feedstock may have similar overall profiles except that the sulfur or nitrogen content varies. The method according to the invention makes it possible to modify the severity of the hydrotreatment without compromising the ability to meet the desired cloud point specification.

  Applicants have discovered that the impact of impurities on the catalytic dewaxing process is more severe than previously predicted. The performance with respect to the cloud point of a dewaxing catalyst composed of ZSM-48 bound to alumina containing about 0.6 wt% Pt was investigated using a pilot plant. A middle distillate feed having a cloud point of about −5 ° C. was dewaxed using a catalyst. This roughly corresponds to the type of feedstock that will be obtained after the hydroprocessing and stripping steps of the present invention. After dewaxing at 610 ° F., the catalyst reduced the cloud point of the hydrocarbon stream to about −65 ° C.

Several days later, various impurities were added to the feedstock to confirm the effect on the cloud point and the processing temperature required to achieve a given cloud point. First, 50 ppm NH ₃ was added to the feed. After about 5 days, the cloud point of the resulting product rose to about −50 ° C. The amount of NH _{3 was} then increased to about 250 ppm over 3 days. As a result, the cloud point slightly exceeded −20 ° C. The ammonia was then removed from the feed for about a week, and the cloud point of the product of this process was restored to about -40 ° C.

  Next, 25 ppm of aniline was added for 3 days. This again increased the cloud point and exceeded -20 ° C. The temperature was then raised to 630 ° F. and the amount of aniline was increased to 50 ppm in about 7 days. The resulting product had a cloud point that was stable around -25 ° C. The aniline was then removed while maintaining the temperature at 630 ° F. After about 2 weeks, the cloud point recovered to the initial value of about -65 ° C.

  Subsequently, the influence of the sulfur content was investigated. The same feedstock was mixed with 5000 wppm sulfur and treated at 630 ° F. for 5 days. The cloud point of the product immediately stabilized to a value slightly below -10 ° C. Raising the temperature to 650 ° F. lowered the cloud point to about −25 ° C., and further increasing the temperature to 680 ° F. resulted in a cloud point of about −40 ° C.

Claims (12)

Sending a first hydrocarbon feedstock having a first initial cloud point to a hydrotreating zone having a hydrotreating temperature and pressure and hydrotreating the feedstock under effective hydrotreating conditions; A step of forming a hydrotreated product having a sulfur content of 15 wppm or less by
Sending the hydroprocessing product to a stripping zone;
Forming a gas effluent and a liquid effluent by subjecting the hydroprocessing product to stripping;
Sending the liquid effluent to a catalytic dewaxing treatment zone and dewaxing the liquid effluent under effective catalytic dewaxing conditions including a first catalytic dewaxing temperature that is at least 10 ° C. lower than the hydrotreating temperature. Forming a dewaxed product having a cloud point at least 10 ° C. lower than the first initial cloud point;
Lowering the temperature of the contact dewaxing treatment zone to a second contact dewaxing temperature that is at least 5 ° C. lower than the first contact dewaxing temperature;
By sending a second hydrocarbon feedstock having a second initial cloud point to the hydrotreating zone and hydrotreating the second hydrocarbon feedstock at the hydrotreating temperature, the sulfur content is 15 wppm. Forming a second hydrotreating product that is:
Sending the second hydrotreating product to the stripping zone;
Forming a second gas effluent and a second liquid effluent by subjecting the second hydrotreating product to stripping; and bringing the second liquid effluent into the catalytic dewaxing treatment zone. Feeding and dewaxing the second liquid effluent at the second catalytic dewaxing temperature to form a second dewaxed product having a cloud point at least 10 ° C. lower than the second initial cloud point. Including steps,
A method for producing diesel fuel, characterized in that no depressurization is performed between the hydrotreating zone and the catalytic dewaxing zone. By sending a first hydrocarbon feedstock having a first initial cloud point to a hydrotreating zone having a hydrotreating temperature and pressure and hydrotreating the feedstock under effective hydrotreating conditions. Forming a hydrotreated product having a sulfur content of 15 wppm or less,
Sending the hydroprocessing product to a stripping zone;
Forming a gas effluent and a liquid effluent by subjecting the hydroprocessing product to stripping;
Sending the liquid effluent to a catalytic dewaxing treatment zone and dewaxing the liquid effluent under effective catalytic dewaxing conditions including a first catalytic dewaxing temperature that is at least 10 ° C. lower than the hydrotreating temperature. Forming a dewaxed product having a cloud point at least 10 ° C. lower than the first initial cloud point;
Raising the temperature of the contact dewaxing treatment zone to a second contact dewaxing temperature that is at least 5 ° C. higher than the first contact dewaxing temperature;
By sending a second hydrocarbon feedstock having a second initial cloud point to the hydrotreating zone and hydrotreating the second hydrocarbon feedstock at the hydrotreating temperature, the sulfur content is 15 wppm. Forming a second hydrotreating product that is:
Sending the second hydrotreating product to the stripping zone;
Forming a second gas effluent and a second liquid effluent by subjecting the second hydrotreating product to stripping; and bringing the second liquid effluent into the catalytic dewaxing treatment zone. Feeding and dewaxing the second liquid effluent at the second catalytic dewaxing temperature to form a second dewaxed product having a cloud point at least 10 ° C. lower than the second initial cloud point. Including steps,
A method for producing diesel fuel, characterized in that no depressurization is performed between the hydrotreating zone and the catalytic dewaxing zone.   The method according to claim 1 or 2, characterized in that the hydroprocessing product and the second hydroprocessing product are subjected to stripping using make-up hydrogen. The method according to claim 1 or 2 , characterized in that the method is carried out without circulating the product from the catalytic dewaxing treatment zone to the hydrotreatment zone or the stripping zone.   The method according to claim 1 or 2, wherein the stripping of the first hydroprocessing product comprises stripping at a temperature and pressure corresponding to the outlet temperature and pressure of the hydroprocessing zone. .   The method according to claim 1 or 2, characterized in that the first catalytic dewaxing temperature is at least 15 ° C lower than the hydroprocessing temperature.   The method according to claim 1 or 2, characterized in that the first catalytic dewaxing temperature is at least 25 ° C lower than the hydroprocessing temperature.   The method of claim 1, wherein the second contact dewaxing temperature is at least 10 ° C. less than the first contact dewaxing temperature.   The method of claim 1, wherein the second contact dewaxing temperature is at least 15 ° C. lower than the first contact dewaxing temperature.   The method of claim 2, wherein the second contact dewaxing temperature is at least 10 ° C. higher than the first contact dewaxing temperature.   The method of claim 2, wherein the second contact dewaxing temperature is at least 15 ° C. higher than the first contact dewaxing temperature.   The method of claim 2, wherein the second contact dewaxing temperature is 100 ° C. or less higher than the first contact dewaxing temperature.

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