Hydrodesulfurization method for diesel fuel fractions

Abstract

To provide a hydrodesulfurization method for a light oil fraction including a straight-run light oil and a cracked light oil, that can increase a hydrodesulfurization treatment capacity of the cracked light oil.SOLUTION: A hydrodesulfurization method for a light oil fraction comprises: starting a hydrodesulfurization reaction of straight-run light oil by supplying straight-run light oil to a hydrodesulfurization device; and stopping the hydrodesulfurization reaction of the straight-run light oil and starting the hydrodesulfurization reaction of a mixed oil of the straight-run light oil and a cracked light oil by further supplying the cracked light oil to the hydrodesulfurization device after a reaction t1 day has passed, wherein a content of the cracked light oil in the mixed oil is 0.5 to 30 vol.%, t1 satisfies 0.1×ttotal≤t1≤0.85×ttotal when a reaction completion time of the hydrodesulfurization reaction of the light oil fraction is a time when ttotal reaction days have elapsed, and a reaction temperature is equal to or lower than an upper limit temperature for use of the hydrodesulfurization device during an entire reaction period from 0 to ttotal days.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for hydrodesulfurization of a light oil fraction.

Background Art

[0002] In a light oil hydrodesulfurization apparatus filled with a desulfurization catalyst, usually, atmospheric distillation light oil obtained by treating crude oil with an atmospheric distillation apparatus is hydrodesulfurized. On the other hand, when there is a remaining desulfurization activity of the desulfurization catalyst, a fraction that is more difficult to desulfurize than atmospheric distillation light oil may be further mixed and hydrodesulfurized. Examples of such a fraction include catalytic cracked light oil obtained by catalytic cracking treatment of heavy oil with a fluid catalytic cracking unit.

[0003] Patent Document 1 discloses a method for producing a low-sulfur light oil base material in which straight-run light oil and catalytic cracked light oil having an initial boiling point of less than 220 ° C and a 90% distillation temperature of less than 325 ° C are mixed with the mixing ratio of the catalytic cracked light oil being 30% by volume or less, and the raw material oil is hydrodesulfurized to a sulfur content of 10 mass ppm or less. It is disclosed that by adopting such a production method, it is possible to obtain a low-sulfur light oil base material having a sulfur content of 10 mass ppm or less and satisfying a hue L1.5 while maintaining the activity of the desulfurization catalyst for a long period of time.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a result of investigations by the inventors of the present application, it was found that in the production method described in Patent Document 1, the amount of hydrodesulfurization treatment of cracked light oil is not sufficient and there is room for further improvement. The present invention has been made in view of the above circumstances, and aims to provide a method for hydrodesulfurizing a diesel fraction including straight-run diesel and cracked diesel, which can increase the amount of hydrodesulfurization treatment of cracked diesel. [Means for solving the problem]

[0006] To solve the above problems, the present invention has the following embodiments. [1] A method for hydrodesulfurizing a diesel fraction, comprising supplying a diesel fraction containing straight-run diesel and cracked diesel to a catalyst-filled hydrodesulfurization unit and performing a hydrodesulfurization reaction of the diesel fraction, wherein the hydrodesulfurization reaction of the straight-run diesel is started by supplying the straight-run diesel to the hydrodesulfurization unit, and after 1 day of reaction t, the hydrodesulfurization reaction of the straight-run diesel is stopped and the hydrodesulfurization reaction of the mixed oil of straight-run diesel and cracked diesel is started by supplying the cracked diesel to the hydrodesulfurization unit, wherein the content of the cracked diesel in the mixed oil is 0.5 to 30% by volume, and the end of the reaction of the hydrodesulfurization reaction of the diesel fraction is defined as reaction t total When the elapsed time is considered to be 0.1 × t, total ≤ t1 ≤ 0.85 × t total Satisfying the conditions, 0~t total A method for hydrodesulfurizing a diesel fuel fraction, wherein the reaction temperature is kept below the upper limit operating temperature of the hydrodesulfurization apparatus for the entire reaction period up to the elapsed day. [2] After t2 days of reaction, the supply of the cracked light oil to the hydrodesulfurization unit is stopped, thereby stopping the hydrodesulfurization reaction of the mixed oil and restarting the hydrodesulfurization reaction of the straight run light oil, t1 <t2≦0.9×t total A method for hydrodesulfurizing a diesel fuel fraction as described in [1], which satisfies the following conditions. [3] A method for producing a desulfurized light oil fraction, comprising supplying a light oil fraction containing straight-run light oil and cracked light oil to a hydrodesulfurization apparatus filled with a catalyst and producing a desulfurized light oil fraction by a hydrodesulfurization reaction of the light oil fraction, wherein by supplying the straight-run light oil to the hydrodesulfurization apparatus, starting a hydrodesulfurization reaction of the straight-run light oil, and at the time when t1 days have elapsed since the start of the reaction, further supplying the cracked light oil to the hydrodesulfurization apparatus to stop the hydrodesulfurization reaction of the straight-run light oil and start a hydrodesulfurization reaction of a mixed oil of the straight-run light oil and the cracked light oil, the content of the cracked light oil in the mixed oil is 0.5 to 30% by volume, and when the end of the hydrodesulfurization reaction of the light oil fraction is taken as the time when t total days have elapsed, 0.1×t total ≦t1≦0.85×t total is satisfied, and during the entire reaction period from 0 to t total days have elapsed, the reaction temperature is set to be not higher than the upper limit temperature of use of the hydrodesulfurization apparatus. [4] Further comprising stopping the supply of the cracked light oil to the hydrodesulfurization apparatus at the time when t2 days have elapsed since the start of the reaction to stop the hydrodesulfurization reaction of the mixed oil and restart the hydrodesulfurization reaction of the straight-run light oil, where t1 < t2 ≦ 0.9×t total is satisfied, the method for producing a desulfurized light oil fraction according to [1].

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a hydrodesulfurization method for a light oil fraction capable of increasing the hydrodesulfurization treatment amount of cracked light oil.

Brief Description of the Drawings

[0008] [Figure 1] It is a diagram showing the change over time of the reaction temperature in the hydrodesulfurization method of the light oil fraction of Examples 1 to 4.

Modes for Carrying Out the Invention

[0009] The embodiments of the present invention will be described in detail below, but the following description is merely one example of an embodiment of the present invention, and the present invention is not limited to these contents and can be modified and implemented within the scope of its gist.

[0010] In this specification, "straight-run diesel fuel" refers to atmospheric distilled diesel fuel obtained by processing crude oil in an atmospheric distillation unit. The properties of straight-run diesel fuel include, for example, a density of 0.84-0.87 g / mL at 15°C, a sulfur content of 0.5-1.5% by mass, a nitrogen content of 0.005-0.05% by mass, a 50% volume distillation temperature of 300-330°C, a 90% volume distillation temperature of 340-360°C, and an aromatic hydrocarbon content of 15-35% by volume. In this specification, "cracked diesel fuel" means catalytically cracked diesel fuel obtained by catalytic cracking heavy oil in a catalytic cracking apparatus. The properties of cracked diesel fuel include, for example, a density of 0.89 to 0.92 g / mL at 15°C, a sulfur content of 0.01 to 0.35 mass%, a nitrogen content of 0.01 to 0.1 mass%, a 50% volume distillation temperature of 260 to 290°C, a 90% volume distillation temperature of 320 to 365°C, and an aromatic hydrocarbon content of 30 to 80% volume. In this specification, straight-run diesel fuel and cracked diesel fuel are collectively referred to as "diesel fuel fractions."

[0011] The density at 15°C can be measured in accordance with JIS K 2249-1 (2011) "Crude oil and petroleum products - Method for determining density - Part 1: Vibration method". Sulfur content can be measured in accordance with JIS K 2541-4 (2003) "Crude oil and petroleum products - Test methods for sulfur content Part 4: Radiation excitation method". Nitrogen content can be measured in accordance with JIS K 2609 (1998) "Crude oil and petroleum products - Test method for nitrogen content". Aromatic hydrocarbon content can be measured in accordance with IP 548, "determination of aromatic hydrocarbon types in middle distillates - High performance liquid chromatography method with refractive index detection." The 50% volume distillation temperature and the 90% volume distillation temperature can be measured in accordance with JIS K2254 (2018) "Petroleum products - Method for determining distillation properties".

[0012] ≪Hydrodesulfurization Method for Diesel Fuel Fractions≫ The hydrogenation desulfurization method for the diesel fuel fraction of this embodiment involves supplying the diesel fuel fraction, including straight-run diesel fuel and cracked diesel fuel, to a hydrogenation desulfurization apparatus filled with a catalyst, and carrying out the hydrogenation desulfurization reaction of the diesel fuel fraction. The method for hydrodesulfurizing a diesel fraction includes supplying the straight-run diesel fuel to the hydrodesulfurization apparatus to initiate the hydrodesulfurization reaction of the straight-run diesel fuel, and, after 1 day of reaction time, further supplying the cracked diesel fuel to the hydrodesulfurization apparatus to stop the hydrodesulfurization reaction of the straight-run diesel fuel and initiate the hydrodesulfurization reaction of the mixed oil of the straight-run diesel fuel and the cracked diesel fuel. The content of the cracked light oil in the mixed oil is 0.5 to 30% by volume, and the reaction time at the end of the hydrogenation desulfurization reaction of the light oil fraction is t total When the elapsed time is considered to be 0.1 × t, total ≤ t1 ≤ 0.85 × t total It satisfies the condition. 0~t total Throughout the entire reaction period up to the day after the event, the reaction temperature shall be kept below the upper limit operating temperature of the hydrogenation desulfurization apparatus.

[0013] The hydrogenation desulfurization method for diesel fuel fractions in this embodiment includes a hydrogenation desulfurization reaction of straight-run diesel fuel and a hydrogenation desulfurization reaction of a mixed oil of straight-run diesel fuel and cracked diesel fuel (hereinafter also simply referred to as "hydrogenation desulfurization reaction of mixed oil").

[0014] (Maximum operating temperature of the hydrogen desulfurization unit) The upper limit operating temperature of a hydrodesulfurization apparatus is determined by factors such as the catalyst packed into the apparatus and the materials used in the apparatus. Typically, the upper limit operating temperature of a hydrodesulfurization apparatus is 370 to 450°C. In this embodiment, the upper limit operating temperature of the hydrodesulfurization apparatus can be set to, for example, 371.7°C.

[0015] (t total ) Reaction t is the point at the end of the hydrogenation desulfurization reaction of the diesel fuel fraction. total The elapsed time is substantially derived from the upper limit operating temperature of the hydrodesulfurization apparatus. In this embodiment, 0 to t total Throughout the entire reaction period up to the elapsed day, the reaction temperature shall be kept below the upper limit operating temperature of the hydrogenodesulfurization apparatus. That is, when the reaction temperature reaches the upper limit operating temperature of the hydrogenodesulfurization apparatus, the reaction t total This refers to the time elapsed in days. For example, when the reaction temperature reaches 0.93 times the maximum operating temperature of the hydrogenation desulfurization unit, it is considered to be the time elapsed in days. total The reaction time can also be measured in days, and the reaction time is defined as when the reaction temperature reaches 0.99 times the upper limit operating temperature of the hydrogenation desulfurization unit. total It may also be expressed as the time elapsed in days. If the reaction is temporarily stopped for reasons such as scheduled maintenance, and then restarted under substantially the same conditions as before the stoppage, the temporary stoppage of the reaction shall not be considered the end of the reaction. Substantially similar conditions mean that the reaction after restarting corresponds to the hydrodesulfurization reaction of straight-run diesel fuel or the hydrodesulfurization reaction of mixed oil in this embodiment. Furthermore, if the reaction is stopped when the reaction temperature is below the upper limit operating temperature of the hydrodesulfurization apparatus × 0.93, and the hydrodesulfurization reaction of straight-run diesel fuel or the hydrodesulfurization reaction of mixed oil in this embodiment is not subsequently restarted, the time of the stoppage shall not be considered the end of the reaction. total This will be the time elapsed in days. t total t can be a decimal number, for example, total A value of 100.5 indicates that 100 days + 12 hours have passed since the reaction (the same applies to t1 and t2, which will be discussed later).

[0016] (Time of onset of hydrogenation desulfurization reaction in mixed oil: after t1 day) In this embodiment, a hydrodesulfurization reaction of straight-run diesel fuel is carried out from the start of the reaction until the end of reaction day t1. After the end of reaction day t1, cracked diesel fuel is further supplied to the hydrodesulfurization unit, and a hydrodesulfurization reaction of the mixed oil is carried out.

[0017] The inventors of this invention have found that when the hydrodesulfurization reaction of the mixed oil is performed at the start of the reaction or in the early stages of the reaction, the deterioration of the catalyst progresses significantly. On the other hand, they have found that when the hydrodesulfurization reaction of straight-run diesel fuel is performed at the start of the reaction or in the early stages of the reaction, and then cracked diesel fuel is supplied to the hydrodesulfurization unit from the middle of the reaction onward to start the hydrodesulfurization reaction of the mixed oil, the deterioration of the catalyst is suppressed compared to the case described above.

[0018] Furthermore, the inventors of this invention have found that if the hydrodesulfurization reaction of the mixed oil is started in the later stages of the reaction to the end of the reaction, the total processing volume of straight-run diesel fuel and cracked diesel fuel decreases significantly. On the other hand, they have found that if the hydrodesulfurization reaction of the mixed oil is started in the middle to later stages of the reaction, the total processing volume of straight-run diesel fuel and cracked diesel fuel improves compared to the aforementioned case. This finding is due to the fact that the reaction temperature needs to be set higher for the hydrodesulfurization reaction of mixed oil than for the hydrodesulfurization reaction of straight-run diesel fuel. In other words, if the hydrodesulfurization reaction of the mixed oil is started in the later stages of the reaction to the end of the reaction, it is easy to exceed the upper limit operating temperature of the hydrodesulfurization equipment, and the reaction has to be terminated.

[0019] The above relationship can be expressed by the following equation (1). 0.1 × t total ≤ t1 ≤ 0.85 × t total (1) In the above formula (1), t1, t total As stated above.

[0020] t1 is 0.10 × t total That is all, 0.15 × t total Preferably, it is 0.18 × t total It is more preferable that the value be greater than or equal to the lower limit. If t1 is greater than or equal to the lower limit, significant deterioration of the catalyst is suppressed, and as a result, the processing capacity of cracked diesel fuel can be increased.

[0021] t1 is preferably 60 or greater, more preferably 90 or greater, and even more preferably 110 or greater. When t1 is above the lower limit, significant deterioration of the catalyst is suppressed, and as a result, the processing capacity of cracked diesel fuel can be increased.

[0022] The reaction temperature at the time elapsed 1 day t1 (the day before the time elapsed 1 day t1) is preferably -75°C or higher, more preferably -70°C or higher, and even more preferably -65°C or higher. When the reaction temperature is above the above lower limit, significant deterioration of the catalyst is suppressed, and as a result, the processing capacity of cracked diesel fuel can be increased.

[0023] t1 is 0.85 × t total The following is true: 0.70 × t total Preferably, the following is true: 0.50 × t total It is more preferable that the following conditions are met: If t1 is less than or equal to the upper limit, the hydrodesulfurization reaction of the mixed oil can be carried out for a longer period of time, and as a result, the total processing capacity of straight-run diesel and cracked diesel can be increased.

[0024] The reaction temperature at the time elapsed t1-1 day (the day before the time elapsed t1 day) is preferably 10°C or less below the upper limit temperature of the hydrodesulfurization apparatus, more preferably 20°C or less below the upper limit temperature of the hydrodesulfurization apparatus, and even more preferably 25°C or less below the upper limit temperature of the hydrodesulfurization apparatus. When the reaction temperature is below the above upper limit, it becomes possible to carry out the hydrodesulfurization reaction of the mixed oil for a longer period of time, and as a result, the total processing volume of straight run diesel fuel and cracked diesel fuel can be increased.

[0025] The content of cracked diesel fuel in the mixed oil is 0.5 to 30% by volume, preferably 0.5 to 20% by volume, and more preferably 0.5 to 10% by volume. If the content of cracked diesel fuel is above the lower limit of the above range, the processing capacity of cracked diesel fuel can be increased. If the content of cracked diesel fuel is below the upper limit of the above range, significant deterioration of the catalyst is suppressed, and as a result, the processing capacity of cracked diesel fuel can be increased.

[0026] (Completion time of the hydrodesulfurization reaction of the mixed oil: after 2 days t) The hydrodesulfurization reaction of the mixed oil may be carried out continuously until the completion of the hydrodesulfurization reaction of the diesel fraction. In this embodiment, it is preferable to stop the hydrodesulfurization reaction of the mixed oil by stopping the supply of cracked diesel fuel to the hydrodesulfurization unit at the 2nd day of reaction t, before the completion of the reaction, and to restart the hydrodesulfurization reaction of the straight-run diesel fuel. That is, the hydrodesulfurization reaction of the mixed oil is carried out from the 1st day of reaction t to the 2nd day of reaction t, and from the 2nd day of reaction t to the 2nd day of reaction t total It is preferable to carry out the hydrodesulfurization reaction of straight-run diesel fuel until the end of the day. In this case, the total processing volume of straight-run diesel fuel and cracked diesel fuel can be increased compared to when the hydrodesulfurization reaction of the mixed oil is carried out continuously until the end of the hydrodesulfurization reaction of the diesel fuel fraction.

[0027] As mentioned above, the hydrodesulfurization reaction of mixed oils requires a higher reaction temperature than the hydrodesulfurization reaction of straight-run diesel fuel. In other words, if the hydrodesulfurization reaction of mixed oils is carried out in the later stages of the reaction or towards the end of the reaction, the operating temperature of the hydrodesulfurization equipment is likely to be exceeded, forcing the reaction to be terminated. On the other hand, by stopping the supply of cracked diesel fuel to the hydrodesulfurization equipment in the later stages of the reaction or towards the end of the reaction, the hydrodesulfurization reaction of the mixed oil is stopped, and the hydrodesulfurization reaction of straight-run diesel fuel is restarted, making it possible to set a lower reaction temperature and continue the reaction for a longer period. As a result, the total processing capacity of straight-run diesel fuel and cracked diesel fuel can be increased.

[0028] The above relationship can be expressed by equation (2) below. t1 <t2≦0.9×t total (2) In the above formula (2), t1, t2, t total As stated above.

[0029] t² is 0.9 × t total Preferably, the following is true: 0.82 × t total It is more preferable that the following conditions are met: 0.65 × t totalIt is even more preferable that the following conditions are met: If t2 is less than or equal to the upper limit, the hydrogenation desulfurization reaction of the diesel fraction can be carried out for a longer period of time, and as a result, the total processing capacity of straight-run diesel and cracked diesel can be increased.

[0030] The reaction temperature at 1 day after reaction t2 (the day before t2) is preferably 0.97°C or less multiplied by the upper limit temperature of the hydrodesulfurization unit, more preferably 0.95°C or less multiplied by the upper limit temperature of the hydrodesulfurization unit, and even more preferably 0.93°C or less multiplied by the upper limit temperature of the hydrodesulfurization unit. When the reaction temperature is below the above upper limit, the hydrodesulfurization reaction of the diesel fraction can be carried out for a longer period of time, and as a result, the total processing volume of straight-run diesel and cracked diesel can be increased.

[0031] The period from the time t1 to t2 (t2-t1), that is, the period during which the hydrodesulfurization reaction of the mixed oil takes place, is t total ×0.1~t total It is preferable that the number of days be 0.80, total ×0.15~t total It is more preferable that it be 0.65 days, total ×0.20~t total It is even more preferable that the period be 0.40 days. If the period is greater than or equal to the lower limit of the range, the processing capacity of cracked diesel fuel can be increased. If the period is less than or equal to the upper limit of the range, significant deterioration of the catalyst is suppressed, and as a result, the processing capacity of cracked diesel fuel can be increased.

[0032] In this embodiment, the combination of t1, t2, and (t2-t1) is such that t1 is 0.18 × t total ~0.65 × t total Therefore, t2 is 0.35 × t total ~0.85 × t total And (t2-t1) is 0.10 × t total ~0.30 × t total It is preferable that the duration is (days), and t1 is 0.18 × t total ~0.30 × t total Therefore, t2 is 0.30 × t total ~0.50 × ttotal And (t2-t1) is 0.10 × t total ~0.30 × t total (days) is more preferable. By using such combinations of t1, t2, and (t2-t1), catalyst degradation is suppressed under the reaction conditions described later, and as a result, the content of cracked diesel in the mixed oil can be made to a very high percentage of 18-30% by volume. In this case, when the supply amount of straight-run diesel in the hydrodesulfurization reaction of straight-run diesel and the hydrodesulfurization reaction of the mixed oil is kept constant, 0-t total In the case where only the hydrodesulfurization reaction of straight-run diesel fuel is carried out during the entire reaction period up to the day elapsed, and in the case where 0-t total When the hydrogenation desulfurization method for the diesel fraction of the present invention is carried out during the entire reaction period up to the day elapsed, total It was found that the lengths are substantially equivalent. In other words, it is possible to increase the total processing capacity of straight-run diesel and cracked diesel by the amount of cracked diesel processed in the hydrodesulfurization reaction of the mixed oil.

[0033] The hydrodesulfurization reaction of the mixed oil, which is carried out between day t1 and day t2 of the reaction, may be performed only once, or it may be performed multiple times as long as the above formulas (1) and (2) are satisfied. In the case where it can be performed multiple times, the completion of the first hydrodesulfurization reaction of the mixed oil is t 2(1回目) Check and t 2(1回目) Thereafter, the start time of the hydrogenosulfurization reaction of the second mixed oil satisfying the above formulas (1) and (2) is t. 1(2回目) and the completion time of the second hydrodesulfurization reaction of the mixed oil is t 2(2回目) This is the case when it is possible to configure this. The hydrodesulfurization reaction of the mixed oil is preferably carried out 1 to 20 times, more preferably 1 to 10 times, and even more preferably 1 time. When the hydrodesulfurization reaction of the mixed oil is carried out multiple times, the total period for carrying out the hydrodesulfurization reaction of the mixed oil is t total ×0.15 (days) or more total It is preferable that the number of days is less than 0.80. total ×0.18 (days) ~ t total It is more preferable that it be ×0.75 (days), total×0.20 (days) ~ t total It is even more preferable that the period be ×0.70 (days). If the period is greater than or equal to the lower limit of the range, the processing rate of cracked diesel fuel can be increased. If the period is less than or equal to the upper limit of the range, significant deterioration of the catalyst is suppressed, and as a result, the processing rate of cracked diesel fuel can be increased.

[0034] (catalyst) In this embodiment, the catalyst is not particularly limited, and any diesel fuel desulfurization catalyst known in the art can be used. Various inorganic oxides can be used as the catalyst support, such as silica, alumina, boria, magnesia, titania, zeolite, silica-alumina, silica-magnesia, silica-zirconia, silica-tria, silica-beryllia, silica-titania, silica-boria, alumina-zirconia, alumina-titania, alumina-boria, alumina-chromia, alumina-zeolite, titania-zirconia, silica-alumina-tria, silica-alumina-zirconia, silica-alumina-magnesia, silica-magnesia-zirconia, or mixtures of two or more of these. Among these inorganic oxides, preferred ones include alumina, silica-alumina, alumina-titania, alumina-boria, alumina-zirconia, and alumina-zeolite, with alumina and alumina-zeolite being particularly preferred, and γ-alumina being particularly preferred among alumina. These inorganic oxides may be used individually or in combination of two or more.

[0035] The metal to be included as an active component in the carrier is at least one metal selected from Group 6 and Groups 8-10 of the periodic table, preferably molybdenum, tungsten, cobalt, and nickel. These metals are effective in any form, such as metallic, metal oxide (including composite metal oxides), or metal sulfide (including composite metal sulfide), and may also exist in a form in which the metal is bonded to the catalyst carrier by ion exchange or the like. The content of this metal component is usually in the range of about 10 to 35% by mass, based on the catalyst and in terms of oxides. If the metal content is 10% by mass or more, the absolute amount of metal acting as active sites increases, and hydrogenation activity, including desulfurization activity, is exhibited. If the metal content is 35% by mass or less, metal aggregation is suppressed, the decrease in the number of active sites is suppressed, and as a result, the decrease in hydrogenation activity is suppressed. Furthermore, if necessary, in addition to the active metals consisting of Group 6 and Groups 8-10 of the periodic table, phosphorus, boron, zinc, zirconia, carbon, etc., can be included. Examples of such catalysts include the catalyst described in International Publication No. 2004 / 054712, the catalyst described in Japanese Patent Application Publication No. 2005-305418, and the catalyst described in Japanese Patent Application Publication No. 2000-342976. When applying the method of the present invention, there are no restrictions on the form of the catalyst layer, and it can be applied to reactors with catalyst layers such as fixed beds, moving beds, and fluidized beds.

[0036] (Reaction conditions) The following reaction conditions are preferable for the hydrodesulfurization reaction of straight-run diesel fuel and the hydrodesulfurization reaction of mixed oils. The hydrogen partial pressure is preferably 3 to 8 MPa, and more preferably 4 to 8 MPa. If the hydrogen partial pressure is above the lower limit of the above range, the hydrodesulfurization reaction of straight-run diesel fuel and the hydrodesulfurization reaction of mixed oil proceed more easily.

[0037] The reaction temperature is preferably 300 to 420°C, more preferably 320 to 400°C, and even more preferably 330 to 380°C. If the reaction temperature is above the lower limit of the above range, the hydrodesulfurization reaction of straight-run diesel fuel and the hydrodesulfurization reaction of the mixed oil proceed more easily. If the reaction temperature is below the upper limit of the above range, catalyst degradation is suppressed. The reaction temperature refers to the average temperature of the catalyst layer.

[0038] The liquid space velocity is 0.3 to 5.0 hours. -1 Preferably, 0.5 to 5.0 hours -1 It is more preferable that the time is 0.8 to 5.0 hours. -1 It is even more preferable that the liquid space velocity is above the lower limit of the range, which improves the processing rate of straight-run diesel fuel and mixed oil per unit time. If the liquid space velocity is below the upper limit of the range, the hydrodesulfurization reaction of straight-run diesel fuel and the hydrodesulfurization reaction of mixed oil proceed more easily.

[0039] The hydrogen / oil ratio is 150-400 Nm³. 3 Preferably, it is / kL, and 200-400 Nm 3 It is more preferable that the value be / kL, and 250-400 Nm 3 It is even more preferable that the value be / kL.

[0040] The density of straight-run diesel fuel at 15°C is preferably 0.84 to 0.87 g / mL, more preferably 0.84 to 0.86 g / mL, and even more preferably 0.84 to 0.85 g / mL.

[0041] The sulfur content relative to the total mass of straight-run diesel fuel is preferably 0.5 to 1.5% by mass, more preferably 0.5 to 1.3% by mass, and even more preferably 0.5 to 1.1% by mass. The nitrogen content relative to the total mass of straight-run diesel fuel is preferably 0.005 to 0.05% by mass, more preferably 0.005 to 0.025% by mass, and even more preferably 0.005 to 0.02% by mass. The aromatic compound content relative to the total volume of straight-run diesel fuel is preferably 15 to 35% by volume, more preferably 15 to 33% by volume, and even more preferably 15 to 30% by volume.

[0042] The 50% volume distillation temperature of straight-run diesel fuel is preferably 300-330°C, more preferably 300-320°C, and even more preferably 300-310°C. The 90% volume distillation temperature of straight-run diesel fuel is preferably 340-360°C, more preferably 340-358°C, and even more preferably 340-356°C.

[0043] In the hydrodesulfurization reaction of straight-run diesel fuel, the feed oil, which mainly consists of straight-run diesel fuel, may contain other fractions in addition to straight-run diesel fuel. For example, cracked diesel fuel may be present in an amount of less than 0.5 volumes relative to the total volume of the feed oil. Other fractions other than cracked diesel fuel that may be present in the feed oil include, for example, diesel fuel fractions obtained from a direct desulfurization unit. The content of other fractions relative to the total volume of the feed oil is preferably 30% by volume or less, and more preferably 10% by volume or less. That is, in the hydrodesulfurization reaction of straight-run diesel fuel, the content of straight-run diesel fuel relative to the total volume of the feed oil is preferably 70% by volume or more, more preferably 90% by volume or more, and even more preferably 99.5% by volume or more.

[0044] The density of cracked diesel fuel at 15°C is preferably 0.89 to 0.92 g / mL, more preferably 0.89 to 0.915 g / mL, and even more preferably 0.89 to 0.910 g / mL.

[0045] The sulfur content relative to the total mass of the cracked diesel fuel is preferably 0.01 to 0.35% by mass, more preferably 0.01 to 0.30% by mass, and even more preferably 0.01 to 0.25% by mass. The nitrogen content relative to the total mass of the cracked diesel fuel is preferably 0.01 to 0.1% by mass, more preferably 0.01 to 0.07% by mass, and even more preferably 0.01 to 0.05% by mass. The aromatic compound content relative to the total volume of cracked diesel fuel is preferably 30 to 80% by volume, more preferably 30 to 75% by volume, and even more preferably 30 to 70% by volume.

[0046] The 50% volume distillation temperature of the cracked diesel fuel is preferably 260-290°C, more preferably 260-285°C, and even more preferably 270-280°C. The 90% volume distillation temperature of the cracked diesel fuel is preferably 320-365°C, more preferably 320-360°C, and even more preferably 330-355°C. The above range of 90% volume distillation temperature indicates that the cracked diesel fuel in this embodiment is relatively heavy cracked diesel fuel. Heavy cracked diesel fuel tends to accelerate catalyst degradation, so when performing a hydrodesulfurization reaction of a mixture of straight-run diesel fuel and cracked diesel fuel, relatively light cracked diesel fuel (cracked diesel fuel with a low 90% volume distillation temperature) has conventionally been used to increase the processing volume of cracked diesel fuel. On the other hand, the inventors of this application have found that by adopting the hydrodesulfurization method for diesel fuel fractions of the present invention, catalyst degradation can be suppressed even when using heavier cracked diesel fuel than before, and it becomes possible to process a larger amount of heavy cracked diesel fuel, as will be specifically shown in the examples described later.

[0047] In the hydrodesulfurization reaction of mixed oil, the mixed oil, which mainly consists of straight-run diesel fuel and cracked diesel fuel, may also contain other fractions in addition to straight-run diesel fuel and cracked diesel fuel. In the hydrodesulfurization reaction of mixed oil, the content of the mixed oil relative to the total volume of the raw materials is preferably 75% by volume or more, more preferably 85% by volume or more, and even more preferably 99.5% by volume or more.

[0048] The density of the resulting oil (desulfurized light oil fraction) at 15°C is preferably 0.81 to 0.85 g / mL, more preferably 0.81 to 0.845 g / mL, and even more preferably 0.81 to 0.84 g / mL.

[0049] The sulfur content relative to the total mass of the produced oil is preferably 0.0001 to 0.0008% by mass, more preferably 0.0004 to 0.0008% by mass, and even more preferably 0.0006 to 0.0008% by mass.

[0050] The distillation temperature of the 50% by volume of the produced oil is preferably 270-320°C, more preferably 280-310°C, and even more preferably 285-310°C. The distillation temperature of the 90% by volume of the generated oil is preferably 320-360°C, more preferably 325-360°C, and even more preferably 325-355°C.

[0051] To carry out the hydrogenation desulfurization method for light oil fractions according to this embodiment on a commercial scale, a fixed bed, moving bed, or fluidized bed catalyst layer of the catalyst described above can be formed in a reactor in a hydrogenation desulfurization unit, the light oil fraction can be introduced into this reactor, and the hydrogenation desulfurization reaction of the light oil fraction can be carried out under the above conditions. Most commonly, a fixed bed catalyst layer is formed in the reactor, the light oil fraction can be introduced to the top of the reactor, the light oil fraction can be passed from top to bottom of the fixed bed, and the product oil can be discharged from the bottom of the reactor, or conversely, the light oil fraction can be introduced to the bottom of the reactor, the light oil fraction can be passed from bottom to top of the fixed bed, and the product oil can be discharged from the top of the reactor.

[0052] The hydrogenation desulfurization method for the diesel fuel fraction in this embodiment may be a single-stage hydrogenation desulfurization method in which the above-mentioned catalyst is packed into a single reactor, or it may be a multi-stage continuous hydrogenation desulfurization method in which the catalyst is packed into multiple reactors.

[0053] It is preferable to activate the catalyst by sulfidation treatment in the reactor before use (i.e., before the hydrodesulfurization reaction of straight-run diesel fuel). Sulfidation treatment can be carried out by passing hydrogen sulfide through a hydrogen atmosphere at atmospheric pressure or a hydrogen partial pressure of at least that pressure using petroleum distillates containing sulfur compounds, a mixture of petroleum distillates and sulfiding agents such as dimethyl sulfide or carbon disulfide, or hydrogen sulfide. The temperature during sulfidation treatment is preferably 200 to 400°C, and more preferably 250 to 350°C. [Examples]

[0054] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Note that Example 4 is for reference only.

[0055] As a catalyst, an alumina-HY zeolite support (alumina:HY zeolite mass ratio = 95:5) was used, on which cobalt was supported at a rate of 6.0 mass% based on catalyst load and oxide equivalent, molybdenum at a rate of 27.0 mass% based on catalyst load and oxide equivalent, phosphorus at a rate of 4.0 mass% based on catalyst load and oxide equivalent, and carbon at a rate of 4.0 mass% based on catalyst load and elemental equivalent.

[0056] The catalyst was activated by sulfidation treatment in the reactor before use. The sulfidation treatment was performed by circulating hydrogen and straight-run diesel fuel at approximately 22°C through the catalyst layer packed in the reactor, raising the temperature to 300°C at 20°C / hr, holding at 300°C for 24 hours, and then raising the temperature to 350°C at 20°C / hr. The flow conditions for hydrogen and straight-run diesel fuel were: hydrogen partial pressure of 4.9 MPa, and straight-run diesel fuel with the properties described in Table 1 at a liquid space velocity of 1.5 hours. -1 It was distributed as follows: Hydrogen / oil ratio: 200 Nm 3 / kL

[0057] (Reaction conditions) Table 1 shows the properties of the straight-run diesel fuel and cracked diesel fuel used in the reaction. In Table 1, T50 represents the 50% distillation temperature, and T90 represents the 90% distillation temperature. Density (15°C), sulfur content, nitrogen content, T50, T90, and aromatic content were measured using the method described above. The reaction conditions for Examples 1 to 4 are shown in Table 2. Note that "(straight-run diesel)" in Table 2 refers to the reaction conditions for the hydrodesulfurization reaction of straight-run diesel. The mixed fluid of the generated oil and gas was discharged from the reactor outlet, the generated oil was separated using a gas-liquid separator, and the sulfur content was measured using the method described above. The maximum operating temperature for the hydrodesulfurization apparatus was set at 371.7°C. The reaction was considered complete when the temperature reached 0.99°C multiplied by the maximum operating temperature of the hydrodesulfurization apparatus (i.e., 367.4°C).

[0058] [Table 1]

[0059] [Table 2]

[0060] [Example 1] The hydrodesulfurization reaction of straight-run diesel fuel was initiated by supplying it to the hydrodesulfurization unit. After 121 days of reaction, the hydrodesulfurization reaction of the straight-run diesel fuel was stopped by supplying cracked diesel fuel to the hydrodesulfurization unit, and the hydrodesulfurization reaction of the mixed oil of straight-run diesel fuel and cracked diesel fuel was initiated. After 241 days of reaction, the hydrodesulfurization reaction of the mixed oil was stopped by ceasing the supply of cracked diesel fuel to the hydrodesulfurization unit, and the hydrodesulfurization reaction of the straight-run diesel fuel was restarted. After 600 days of reaction, the supply of straight-run diesel fuel to the hydrodesulfurization unit was stopped, and the reaction was terminated. The supply amount of straight-run diesel fuel in the hydrodesulfurization reaction of the straight-run diesel fuel and the hydrodesulfurization reaction of the mixed oil was 30,000 BPD. The supply amount of cracked diesel fuel in the hydrodesulfurization reaction of the mixed oil was 8,600 BPD. That is, t1=121, t2=241, t total= 600, and the content of the cracked diesel fuel in the mixed oil was 22% by volume. This information, as well as the amount of straight-run diesel fuel processed during the entire reaction period (total straight-run diesel fuel in Table 3) and the amount of cracked diesel fuel processed (total cracked diesel fuel in Table 3) are shown in Table 3 (the same applies to Examples 2 to 4 below). The change in reaction temperature over time is shown in Figure 1 (the same applies to Examples 2 to 4 below).

[0061] [Example 2] The hydrodesulfurization reaction of straight-run diesel fuel was initiated by supplying it to the hydrodesulfurization unit. After 241 days of reaction, the hydrodesulfurization reaction of the straight-run diesel fuel was stopped by supplying cracked diesel fuel to the hydrodesulfurization unit, and the hydrodesulfurization reaction of the mixed oil of straight-run diesel fuel and cracked diesel fuel was initiated. After 361 days of reaction, the hydrodesulfurization reaction of the mixed oil was stopped by ceasing the supply of cracked diesel fuel to the hydrodesulfurization unit, and the hydrodesulfurization reaction of the straight-run diesel fuel was restarted. After 600 days of reaction, the supply of straight-run diesel fuel to the hydrodesulfurization unit was stopped, and the reaction was terminated. The supply amount of straight-run diesel fuel in the hydrodesulfurization reaction of the straight-run diesel fuel and the hydrodesulfurization reaction of the mixed oil was 30,000 BPD. The supply amount of cracked diesel fuel in the hydrodesulfurization reaction of the mixed oil was 7,500 BPD.

[0062] [Example 3] The hydrodesulfurization reaction of straight-run diesel fuel was initiated by supplying it to the hydrodesulfurization unit. After 361 days of reaction, the hydrodesulfurization reaction of the straight-run diesel fuel was stopped by supplying cracked diesel fuel to the hydrodesulfurization unit, and the hydrodesulfurization reaction of the mixed oil of straight-run diesel fuel and cracked diesel fuel was initiated. After 479 days of reaction, the hydrodesulfurization reaction of the mixed oil was stopped by ceasing the supply of cracked diesel fuel to the hydrodesulfurization unit, and the hydrodesulfurization reaction of the straight-run diesel fuel was restarted. After 600 days of reaction, the supply of straight-run diesel fuel to the hydrodesulfurization unit was stopped, and the reaction was terminated. The supply amount of straight-run diesel fuel in the hydrodesulfurization reaction of the straight-run diesel fuel and the hydrodesulfurization reaction of the mixed oil was 30,000 BPD. The supply amount of cracked diesel fuel in the hydrodesulfurization reaction of the mixed oil was 5,200 BPD.

[0063] [Example 4] The hydrodesulfurization reaction of straight-run diesel fuel was initiated by supplying it to the hydrodesulfurization unit. After 481 days of reaction, the hydrodesulfurization reaction of the straight-run diesel fuel was stopped by supplying cracked diesel fuel to the hydrodesulfurization unit, and the hydrodesulfurization reaction of the mixed oil of straight-run diesel fuel and cracked diesel fuel was initiated. After 600 days of reaction, the supply of the mixed oil of straight-run diesel fuel and cracked diesel fuel to the hydrodesulfurization unit was stopped, and the reaction was terminated. The supply amount of straight-run diesel fuel in the hydrodesulfurization reaction of the straight-run diesel fuel and the hydrodesulfurization reaction of the mixed oil was 30,000 BPD. The supply amount of cracked diesel fuel in the hydrodesulfurization reaction of the mixed oil was 3,000 BPD.

[0064] [Table 3]

[0065] In the hydrogenation desulfurization method for diesel fuel fractions of the present invention, it was found that even when the hydrogenation desulfurization reaction of the mixed oil was started after 1 day of reaction t, there was no significant deterioration of the catalyst (no rapid increase in reaction temperature), and as a result, the amount of cracked diesel fuel processed was increased. As mentioned above, the inventors of this application have determined that t1 is 0.1 × t total It has already been confirmed that if the hydrodesulfurization reaction of the mixed oil is started before a certain temperature, catalyst degradation occurs and the reaction temperature rises. In this case, the duration of the hydrodesulfurization reaction of the mixed oil is set to approximately 120 days (t2-t1), similar to that in Examples 1-4, and the time until the temperature reaches 367.4°C (t total If the processing time is set to the same 600 days as in Examples 1-4, the content of cracked diesel fuel in the mixed oil will have to be kept low, and if the processing volume of straight-run diesel fuel is the same as in Examples 1-4, the processing volume of cracked diesel fuel will be lower.

[0066] Furthermore, in Examples 1-3, where the hydrodesulfurization reaction of the mixed oil was stopped by ceasing the supply of cracked diesel fuel to the hydrodesulfurization unit after 2 days of reaction t, and the hydrodesulfurization reaction of the straight-run diesel fuel was restarted, it was found that the amount of cracked diesel fuel processed was higher than in Example 4. [Industrial applicability]

[0067] The hydrogenation desulfurization method for diesel fuel fractions according to the present invention is useful because it can be used to reduce the sulfur content in diesel fuel fractions.

Claims

[Claim 1] A method for hydrodesulfurizing a diesel fuel fraction, comprising supplying a diesel fuel fraction including straight-run diesel fuel and cracked diesel fuel to a catalyst-filled hydrodesulfurization unit and carrying out a hydrodesulfurization reaction of the diesel fuel fraction, By supplying the straight-run diesel fuel to the hydrodesulfurization apparatus, the hydrodesulfurization reaction of the straight-run diesel fuel is initiated. reaction t １ After a certain number of days, by further supplying the cracked light oil to the hydrodesulfurization apparatus, the hydrodesulfurization reaction of the straight-run light oil is stopped, and the hydrodesulfurization reaction of the mixed oil of straight-run light oil and cracked light oil is started. The reaction includes stopping the supply of the cracked diesel fuel to the hydrodesulfurization apparatus after 2 days, thereby stopping the hydrodesulfurization reaction of the mixed oil, restarting the hydrodesulfurization reaction of the straight-run diesel fuel, and continuing the hydrodesulfurization reaction of the straight-run diesel fuel until the hydrodesulfurization reaction of the diesel fuel fraction is completed. The content of the cracked light oil in the mixed oil is 0.5 to 30% by volume. The reaction t is defined as the time when the hydrogenation desulfurization reaction of the light oil fraction is completed. ｔｏｔａｌ When considering the time elapsed in days, 0.1 × t ｔｏｔａｌ ≤ t １ ≤ 0.85 × t ｔｏｔａｌ The following conditions are met: t1 < t2 ≤ 0.9 × t total, and 0 to t ｔｏｔａｌ A method for hydrodesulfurizing a diesel fuel fraction, wherein the reaction temperature is kept below the upper limit operating temperature of the hydrodesulfurization apparatus for the entire reaction period up to the elapsed day.

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