JP4680520B2 - Low sulfur gas oil production method and environmentally friendly gas oil - Google Patents

Description

The present invention relates to a method for producing a low sulfur gas oil, and more particularly to a method for producing a low sulfur gas oil having a sulfur content reduced to 10 mass ppm or less.

  In recent years, the quality regulation value of light oil tends to be stricter worldwide in order to improve the air environment. In particular, the sulfur content in light oil may affect the durability of post-treatment devices such as oxidation catalysts, nitrogen oxide (NOx) reduction catalysts, and continuously regenerating diesel exhaust particulate removal filters that are expected as countermeasures for exhaust gases. For this reason, there is a demand for low sulfur in diesel oil. By further reducing the sulfur content in the gas oil to 50 ppm or less, particularly 10 ppm or less, the production of sulfate is suppressed, the deterioration of the nitrogen oxide reduction catalyst is suppressed, and the particulate matter on the post-treatment catalyst It can be expected to suppress the emission of nitrogen dioxide and particulate matter by reducing the production.

Under such circumstances, development of an ultra-deep desulfurization technology that significantly removes sulfur content in light oil is being emphasized. As a technique for reducing the sulfur content in light oil, it is usually considered that the operating conditions of hydrodesulfurization, for example, the reaction temperature, the liquid space velocity, etc., are severe. However, when the reaction temperature is raised, carbonaceous matter is deposited on the catalyst and the activity of the catalyst is rapidly reduced.When the liquid space velocity is lowered, the desulfurization ability is improved, but the purification treatment capacity is lowered. There is a need to scale. Therefore, one of the effective methods for achieving ultra-deep desulfurization of light oil without severe operating conditions is to develop a catalyst having excellent desulfurization activity. It has been proposed (Patent Documents 1 and 2). In particular, Patent Document 2 prepares a catalyst so that the average number of layers of molybdenum disulfide crystals contained in the catalyst is 2.5 to 5 in order to sufficiently secure the active point of the catalyst. However, Patent Document 2 does not disclose the aspect ratio of the molybdenum sulfide crystal as defined in the present invention, and the aspect ratio of the molybdenum disulfide crystal described in Patent Document 2 is outside the scope of the present invention. Conceivable.
Table 2000-62924 JP 2003-299960 A

When the gas oil fraction is hydrotreated, 4-methyldibenzothiophene (4-MDBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT) having an alkyl substituent at the 4-position or 6-position of dibenzothiophene (DBT). ), A sulfur compound having a steric hindrance to a sulfur atom selectively remains, and is known as a non-desulfurizable sulfur compound (Non-patent Document 1). It is also known that organic nitrogen compounds coexisting in the gas oil fraction, hydrogen sulfide and ammonia by-produced by the hydrogenation treatment inhibit the desulfurization reaction of sulfur compounds contained in the gas oil fraction (non- Patent Document 1).
T.A. Kabe, A .; Ishihara, W .; Quin, “Hydrodesulfurization and Hydrodentrogen”, Kodansha (1999)

Considering the characteristics of hydrotreatment of such a gas oil fraction, not only the development of a catalyst having an excellent desulfurization activity but also a process for efficiently performing ultra-deep desulfurization of gas oil, (1) a pre-stage catalyst layer And a method using a plurality of different catalysts in combination with the latter catalyst layer (Patent Document 3), (2) a gas-liquid separation mechanism is provided between the former catalyst layer and the latter catalyst layer, and the reaction product in the former catalyst layer is included in the reaction product A method for removing desulfurization reaction inhibiting substances such as hydrogen sulfide and ammonia by gas-liquid separation and reducing the concentration of hydrogen sulfide and ammonia supplied to the latter catalyst layer to perform the desulfurization reaction in the latter catalyst layer (patent Documents 4-6) have been devised. The catalyst used in the upstream catalyst layer in the case of applying such an improved process is not only excellent in desulfurization activity but also excellent in denitrification activity so that the desulfurization reaction in the downstream catalyst layer proceeds advantageously. It is also necessary.
No. 2002-10314 No. 2000-42130 International Publication No. 2002-31088 No. 2001-74973

There is a need to reduce the sulfur content in petroleum fractions, especially light oil. However, in the conventional technology, there is a limit to realizing low sulfur, and it has been necessary to select operation conditions with low productivity, particularly crude oil with low sulfur content. The present invention solves the above-mentioned problems, and the object of the present invention is to provide a low- sulfur gas oil that can be highly desulfurized by hydrotreating without using special crude oil and under highly productive operating conditions. It is in providing the manufacturing method of.

  The present inventor succeeded in obtaining a hydrotreating catalyst having both high desulfurization activity and denitrification activity by sulfiding a hydrotreating catalyst precursor containing cobalt, nickel and molybdenum in a specific composition. did. The present inventors have found that such a hydrotreating catalyst having both high desulfurization activity and denitrogenation activity is due to the presence of molybdenum sulfide crystals having a specific aspect ratio, thereby completing the present invention. It came to do.

That is, according to the first reference embodiment of the present invention, the inorganic porous oxide support is 10 to 25% by mass of molybdenum, 2 to 8% by mass in total of cobalt and nickel, and 0.5 to 2.0% of phosphorus. By sulfiding a hydrotreating catalyst precursor that is supported by mass%, the carbon content is less than 1 mass%, and the cobalt content is 60 mol% or more with respect to the total content of cobalt and nickel. There is provided a hydrotreating catalyst formed, comprising a molybdenum sulfide crystal, wherein the molybdenum sulfide crystal has an aspect ratio of 3 to 4.5.

According to a second reference aspect of the present invention, there is provided a hydrotreating method for hydrocarbon oil, characterized in that the hydrotreating catalyst is brought into contact with a hydrocarbon oil in the presence of hydrogen.

According to state-like of the present invention, there is provided a method for producing a sulfur content of 10 ppm by mass of low-sulfur diesel fuel which the gas oil fraction containing a sulfur content above 0.5 wt% as a raw material oil, inorganic porous oxide The carrier is supported by 10 to 25% by mass of molybdenum, 2 to 8% by mass of cobalt and nickel, 0.5 to 2.0% by mass of phosphorus, and the carbon content is less than 1% by mass; A hydrotreating catalyst formed by sulfiding a hydrotreating catalyst precursor having a cobalt content of 65 to 90 mol% with respect to the total content of cobalt and nickel is brought into contact with the feedstock in the presence of hydrogen. A first step of performing crude purification by hydrotreating, a second step of performing gas-liquid separation of the reaction mixture obtained in the first step, and a hydrotreating catalyst precursor containing tungsten, nickel and ethylenediaminetetraacetic acid Body And a third step of hydrotreating the hydrotreated catalyst subjected to sulfurization treatment with the crude refined oil obtained in the second step in the presence of hydrogen. Is provided. In this invention, the light oil obtained by this manufacturing method is also provided.

Furthermore, according to the present invention, the density is 0.795 g / cm ³ or more, the sulfur content is 5 ppm by mass or less, the monocyclic aromatic content is 5 to 18% by volume, and the polycyclic aromatic content is 2% by volume or less. In addition, an environmentally friendly light oil having a true calorific value per unit volume of 34500 J / cm ³ or more is provided. According to the present invention, the sulfur content in the environmentally friendly light oil can be 1 mass ppm or less.

The present invention provides a method for sulfur content efficiently producing 10 ppm by mass or less of low-sulfur diesel fuel. According to the catalyst and the hydrotreating method using the catalyst disclosed in the present specification , low-sulfur gas oil can be produced under mild conditions, and production can be efficiently increased. In addition, the present invention provides an environmentally-friendly light oil that has a sulfur content that is extremely low at 5 ppm by mass or less, and even 1 ppm by mass or less, and that secures a true calorific value per unit volume equivalent to that of conventionally marketed diesel oil. be able to.

[Hydroprocessing catalyst precursor]
Hydroprocessing catalyst precursor used in the production of water hydrogenation treatment catalyst as hydrogenation active metals, molybdenum 10 to 25 wt%, 2-8 wt% cobalt, and nickel in total phosphorus 0.5-2 0.0 mass%, the carbon content is less than 1 mass%, and the cobalt content is 60 mol% or more with respect to the total content of cobalt and nickel. The content of cobalt with respect to the total content of cobalt and nickel is preferably 65 to 90 mol%. If the cobalt content relative to the total content of cobalt and nickel is too high, the denitrification activity of the hydrotreating catalyst will decrease, and if the cobalt content is too low, the desulfurization activity of the hydrotreating catalyst will decrease. Further, the carbon content is preferably less than 0.5% by mass, particularly less than 0.1% by mass, because the aspect ratio of the molybdenum sulfide crystal is prevented from becoming smaller than a predetermined range. As other components, any of boron and fluorine or a combination of these elements may be used, and the total content thereof is preferably 1 to 10% by mass, particularly 2 to 6% by mass in terms of elements. .

Hydroprocessing catalyst precursor used in the production of water hydrogenation treatment catalyst preferably have a specific surface area of 100~450m ² / g, especially 150 to 300 m ² / g, a pore volume of 0.1~2cm ³ / g, in particular, 0.3 to 1.5 cm ³ / g, and the median pore diameter is preferably ³ to 20 nm, particularly 4 to 10 nm. Further, the hydrotreating catalyst precursor preferably has a spherical shape, a cylindrical shape, a trilobal type, or a four-leaf type. In particular, a columnar shape is preferable, and a cross-sectional dimension of 0.1 mm to 10 mm can be used, but 0.7 to 3 mm is preferable.

As the inorganic porous oxide carrier used for hydroprocessing catalyst precursor used in the production of water hydrogenation treatment catalyst, periodic table 2, 4, and 13, and oxides of Group 14 elements used (Periodic table according to IUPAC, 1990 recommendation). Among these, silica, alumina, magnesia, zirconia, boria, calcia and the like are preferable, and these may be used alone or in combination of two or more. In particular, alumina (having each crystal structure such as γ, δ, η, and χ), silica-alumina, silica, alumina-magnesia, silica-magnesia, and alumina-silica-magnesia are preferable.

Hydroprocessing catalyst precursor used in the production of water hydrogenation treatment catalyst is preferably prepared by supporting the metal component or the like to the inorganic porous oxide carrier. Method for producing a non-machine porous oxide support is not particularly limited, and production of inorganic hydrous oxide by a coprecipitation method or a kneading method or the like, after forming this, a method of performing drying and baking is preferably used.

  The method for supporting the metal component or the like is not particularly limited, but a commonly used spray impregnation method, dipping method, or the like is preferable, and a pore filling method in which a solution corresponding to the water absorption rate of the inorganic porous oxide carrier is impregnated is particularly preferable. In order to control the metal loading state, it is also preferable to use an organic compound or an organic salt in the metal loading liquid. After impregnating a solution containing a metal component or the like, it is dried at a temperature of 50 to 180 ° C., preferably 80 to 150 ° C., for 10 minutes to 24 hours. In order to carry more metal components and the like, drying and loading may be repeated. After supporting a desired metal component and the like, a hydrotreated catalyst precursor is produced by firing a dried product obtained by drying. This calcination treatment is preferably performed at a temperature range of 400 to 600 ° C., particularly 450 to 580 ° C., the temperature rising time to the calcination temperature is 10 to 240 minutes, and the holding time at the calcination temperature is 1 to 240 minutes. Is preferred.

[Sulfurization treatment of hydrotreating catalyst precursor]
The hydrotreating catalyst used in the present invention is produced by subjecting the above-mentioned hydrotreating catalyst precursor to a sulfiding treatment, and exhibits an active site as a hydrotreating catalyst. Usually, the sulfiding treatment is performed after filling the hydrotreating catalyst precursor into the reactor used for the hydrotreating. This sulfiding treatment is carried out by gradually raising the temperature of the sulfiding agent through the hydrotreating catalyst precursor, and the final sulfiding treatment temperature is 450 ° C. or lower, preferably 100 to 400 ° C. The reaction is carried out using a petroleum distillate containing a sulfur compound as a sulfiding agent, a sulfur-containing compound added thereto, or hydrogen sulfide under a hydrogen atmosphere at normal pressure or higher hydrogen partial pressure. The sulfur-containing compound in the case of adding a sulfur-containing compound to petroleum distillate is not particularly limited as long as it can be decomposed and converted into hydrogen sulfide under the sulfidizing treatment conditions. Carbon sulfide, thiophenes, dimethyl sulfide, dimethyl disulfide and various polysulfides. After filling the hydrotreating catalyst precursor into the reaction apparatus and before starting the sulfiding treatment, a drying process for removing water adhering to the hydrotreating catalyst precursor may be performed. This drying treatment is carried out at normal temperature to 220 ° C., preferably 200 ° C. or lower, under a hydrogen or inert gas atmosphere, with the gas flowing at normal pressure or higher.

  As the temperature of the catalyst is raised through the sulfiding agent, sulfur atoms in the sulfiding agent are taken into the catalyst at a certain temperature, and sulfiding begins. The temperature at which this sulfidation begins is referred to herein as the sulfidation start temperature. A lower desulfurization start temperature indicates higher desulfurization activity. The sulfidation start temperature is preferably 190 ° C. or lower, more preferably 185 ° C. or lower, particularly 180 ° C. or lower. Note that the amount of the hydrogenation active metal supported in the above-described hydrotreatment precursor is hardly changed even by the sulfidation treatment.

[Form of hydrotreating catalyst]
The present inventor controls the desulfurization activity and the denitrogenation activity after the sulfidation treatment by controlling the component and amount of the hydrogenation active metal supported on the hydrotreating catalyst precursor to the specific range as described above. We succeeded in obtaining a hydrotreating catalyst with both at very high levels. As a result of inspection of the properties and structure of such a high desulfurization / denitrogenation active hydrotreating catalyst by the present inventor, the form of molybdenum sulfide formed by sulfiding treatment is unique as described below. I found. It is known that molybdenum contained in the hydrotreating catalyst has a structure in which hexagons are stacked in layers by sulfidation, and forms molybdenum sulfide crystals. The plane parallel to the layer is called the Versal plane, and the plane perpendicular to the layer is called the edge plane. According to the present inventor, the average of the length (layer length) of the versal surface of the molybdenum sulfide crystal determined from the transmission electron micrograph is La (nm), and the average of the length of the edge surface (layer height). When Lb (nm) is a ratio La / Lb (aspect ratio) in a limited range of 3 to 4.5, desulfurization activity and denitrification activity may be extremely good at the same time. I understand. This is considered as follows.

It is known that an active point having an activity with respect to a hydrotreating reaction exists only on the edge surface (Non-Patent Document 1 described above), and the active point on the edge surface is in the uppermost layer. If an active site is a rim site and an active site in another layer is an edge site, there is no hydrogenation activity for hydrocarbon double bonds or benzene rings at the edge site, and only a reaction that directly desulfurizes sulfur compounds proceeds. On the other hand, it is considered that desulfurization reaction involving hydrogenation or hydrogenation of the benzene ring occurs at the rim site (M. Daage, R. Chianelli, Journal of Catalysis, 149, 414). Page (1994)). On the other hand, it is known that the denitrification reaction proceeds as the hydrogenation activity increases (H. Topsoe, BS Clausen, FE Massoth, “HYDROTREATING CATALYSIS”, Springer (1996)). In the catalyst used in the present invention , the edge site relative to the rim site maintains a specific balance. Therefore, it is considered that high denitrification activity and high desulfurization activity are realized at the same time. Furthermore, the present inventor considers that such an aspect ratio that provides two types of activities is derived from the above-described components of the hydrogenation active metal, particularly the coexistence and composition of nickel and cobalt. Yes.

When the aspect ratio was obtained from a transmission electron micrograph, Lb was calculated by multiplying the average number of layers by subtracting 1 from 0.615 nm. The smaller the aspect ratio, the larger the area of the edge surface relative to the Versal surface. The aspect ratio of the hydrotreating catalyst used in the present invention is 3 to 4.5, preferably 3 to 4. Further, the rim crystal molybdenum sulfide, the hydrogen presence of high pressure, but is not effective to too much shorten the length of the layer for tend to aggregate during the reaction, even if too long a length of the layer This is not preferable because the number of sites and edge sites is reduced. The length of the layer of molybdenum sulfide crystals in hydrotreating catalyst after vulcanization of preferably 3.5～6Nm, particularly it has been found that it is preferable that 3.5～5Nm.

[Hydrocarbon hydrotreating method]
The hydrotreating catalyst provided by the present invention can perform hydrotreating of various hydrocarbon oils by contacting with the hydrocarbon oil in the presence of hydrogen. There are no particular restrictions on the reaction system such as batch type, flow type, fixed bed type, fluidized bed type, etc., but hydrogen and feedstock are continuously added to the hydrotreating catalyst packed in the fixed bed flow type reactor. The type of supplying and contacting is preferable. Preferred reaction conditions for the hydrotreating are: reaction temperature of 100 to 500 ° C., particularly 200 to 450 ° C., hydrogen pressure of 0.1 to 30 MPa, particularly 2 to 20 MPa, hydrogen / oil supply ratio of 50 to 2000 NL / L. In particular, it is 100 to 1000 NL / L, and the liquid space velocity (LHSV) is 0.05 to 20 h ⁻¹ , particularly 0.1 to 10 h ⁻¹ .

[Hydrocarbon oil]
The hydrocarbon oil used as the feedstock for the hydrotreating method used in the present invention is not particularly limited as long as it is a hydrocarbon oil having a total content of vanadium and nickel of 5 mass ppm or less, and crude oil and crude oil are distilled at atmospheric pressure. Or petroleum fractions such as LPG fraction, naphtha fraction, kerosene fraction, gas oil fraction, vacuum gas oil fraction, atmospheric residue, and vacuum residue obtained by distillation under reduced pressure, and pyrolysis of these petroleum fractions, Various petroleum fractions, such as catalytic cracking, hydrorefining, deleking, solvent dewaxing, solvent extraction with furfural, Fischer-Tropsch synthetic oil (FT synthetic oil), olefin polymer, coal liquefied oil, Plastic decomposition oil, oil sand or oil shale decomposition oil, etc. are preferably used. When a hydrocarbon oil having a total vanadium content and nickel content exceeding 5 ppm by mass is contacted with the hydrotreating catalyst used in the present invention in the presence of hydrogen, the vanadium content and the nickel content are deposited on the catalyst, and the catalyst is remarkably formed. Since it deactivates, it is not preferable.

[Light oil fraction]
The hydrotreating catalyst used in the present invention exhibits its effect particularly on desulfurization and denitrogenation of light oil fractions. The gas oil fraction to be the raw material hydrocarbon oil in the method for producing low sulfur gas oil of the present invention is preferably a gas oil fraction having a sulfur content of 1% by mass or more, usually having a sulfur content of 1 to 5% by mass, In particular, it is 1 to 3% by mass, the nitrogen content is 50 ppm by mass or more, particularly 80 to 500 ppm by mass, and the density (15 ° C.) is 0.75 g / cm ³ or more, particularly 0.80 to 0.0. 92 g / cm ³ . As the light oil fraction used as the raw material hydrocarbon oil, it is preferable to use a straight-run gas oil fraction, or a straight-run light oil fraction alone may be used, but a mixture obtained by mixing pyrolyzed oil or catalytic cracked oil into the straight-run light oil fraction. A light oil fraction may be used. This straight-run gas oil fraction is obtained by atmospheric distillation of crude oil, and approximately 10% by volume distillation temperature is 200 to 290 ° C., 50% by volume distillation temperature is 260 to 320 ° C., and 90% volume distillation temperature is 300-370 ° C. Pyrolysis oil is a light fraction oil obtained by applying heat to a heavy oil fraction and mainly using a radical reaction. For example, it can be obtained by the delayed coking method, visbreaking method or fluid coking method. Refers to the fraction to be made. Although these fractions may use the whole fraction obtained as a pyrolysis oil, it is suitable to use the fraction whose distillation temperature exists in the range of 150-520 degreeC. Catalytic cracked oil is a fraction obtained when catalytically cracking middle distillate and heavy distillate, especially vacuum gas oil distillate, atmospheric distillation residue, etc. with zeolitic catalyst, especially for the production of high octane gasoline This is a cracked gas oil fraction by-produced in the fluidized catalytic cracker. In general, a light catalytic cracked oil having a relatively low boiling point and a heavy catalytic cracked oil having a relatively high boiling point are separately collected from this fraction. In the present invention, any of these fractions can be used, but it is preferable to use the former light catalytic cracking oil, so-called light cycle oil (LCO). The LCO generally has a 10 vol% distillation temperature of 220 to 250 ° C, a 50 vol% distillation temperature of 260 to 290 ° C, and a 90 vol% distillation temperature of 310 to 355 ° C. In addition, heavy catalytic cracking oil, so-called heavy cycle oil (HCO), has a 10 vol% distillation temperature of 280 to 340 ° C, a 50 vol% distillation temperature of 390 to 420 ° C, and a 90 vol% distillation temperature of 450 ° C or higher. It is in.

[Method for hydrotreating gas oil fraction and method for producing low sulfur gas oil]
When the above-described hydrotreating catalyst is used for desulfurization of a light oil fraction, it may be used alone for desulfurization of the above-described light oil fraction, or may be used in combination with another hydrotreating catalyst. The above-mentioned hydrotreating catalyst is not necessarily suitable for desulfurization of sterically hindered sulfur-free sulfur compounds such as 4-MDBT and 4,6-DMDBT, but desulfurization of sulfur compounds with less steric hindrance is a short contact. Since it has high denitrification activity at the same time as effective, it can be combined with the above-mentioned hydrotreating catalyst as the pre-stage catalyst and another hydrotreating catalyst suitable for desulfurization of sterically hindered sulfur compounds as the post-stage catalyst. It is preferable to use it.

[Method for producing low sulfur gas oil including gas-liquid separation step]
A particularly preferred method for producing a low sulfur gas oil in the present invention is a method for producing a low sulfur gas oil having a sulfur content of 10 mass ppm or less using a gas oil fraction containing a sulfur content of 0.5 mass% or more as a feedstock, A first step of performing crude purification by hydrotreating the hydrotreating catalyst of the invention in contact with a feedstock in the presence of hydrogen; a second step of performing gas-liquid separation of the reaction mixture obtained in the first step; A third step is performed in which hydroprocessing catalyst containing molybdenum or tungsten and containing nickel is contacted with the crude oil obtained in the second step in the presence of hydrogen. When raw material oil is hydrotreated, desulfurization reaction and denitrogenation reaction proceed to produce hydrogen sulfide and ammonia. However, hydrogen sulfide and ammonia poison the hydrotreating catalyst and inhibit the desulfurization reaction. Therefore, the reaction mixture obtained in the first step is gas-liquid separated in the second step to remove hydrogen sulfide and ammonia, and the obtained crude refined oil is further hydrotreated in the third step. It is preferable because desulfurization can proceed efficiently and low sulfur gas oil can be produced under milder conditions, and production of low sulfur gas oil can be increased efficiently.

  The first step and the third step may be performed using different reactors, or the first step and the third step may be performed in the same reactor. In the case where the first step and the third step are performed using different reactors, the first step is provided between the reactor for the first step and the reactor for the third step. Gas-liquid separation device for performing gas-liquid separation of the reaction mixture obtained from the reactor for the gas, and a device for supplying the crude refined oil obtained from the gas-liquid separation device to the reactor for the third step together with hydrogen The hydrogenation treatment is preferably performed using a series of apparatuses. As the gas-liquid separator, a known separator such as a high-pressure separator, a stripper, a flasher, or a distillation tower is preferably used, and two or more separators may be used in combination. For example, it is particularly preferable to carry out gas-liquid separation of crude refined oil obtained by gas-liquid separation in a high-pressure separation tank using a stripper because hydrogen sulfide and ammonia can be effectively removed. The gas stream supplied for the stripping process by the stripper is preferably hydrogen, an inert gas or steam. On the other hand, when the first step and the third step are performed in the same reactor, it is preferable to use the apparatuses and methods disclosed in Patent Documents 4 to 5 described above. In the present invention, the ratio of the amount of hydrogen sulfide supplied per unit time to the second step from the first step, the amount of hydrogen sulfide supplied per unit time to the third step relative to the amount of ammonia, and the amount of ammonia in the present invention, The residual ratio of hydrogen sulfide and the residual ratio of ammonia are referred to as the residual ratio, and these residual ratios are preferably 0 to 50%. If the residual ratio is higher than 50%, the effect of reducing reaction inhibition in the third step by gas-liquid separation is reduced, which is not preferable. The lower these residual ratios, the higher the reaction inhibition reduction effect in the third step. However, when the residual ratio is brought close to 0%, the energy consumption in the production of low sulfur gas oil increases and the economic efficiency is impaired. The residual ratio is more preferably 1 to 40%, and particularly preferably 3 to 20%.

The hydrotreating catalyst used in the third step in the method for producing low-sulfur gas oil of the present invention is usually produced by sulfiding a hydrotreating catalyst precursor, and the sulphiding treatment is a hydrogenation used in the first step . A method similar to that for producing the treated catalyst is preferred. If the hydrotreating catalyst precursor in the stage before the sulfiding treatment of the hydrotreating catalyst used in the third step is a porous body containing molybdenum or tungsten and nickel, the hydrogen used in the first step The same hydrotreating catalyst precursor may be used, but a different hydrotreating catalyst precursor may be used and cobalt may be included. Known nickel-molybdenum-based hydrotreating catalyst precursors, nickel-cobalt-molybdenum-based hydrotreating catalyst precursors, and nickel-tungsten-based hydrotreating catalyst precursors are particularly preferably used. The composition of the hydrotreating catalyst precursor preferably has a total content of molybdenum and tungsten of 5 to 50% by mass and a total content of cobalt and nickel of 1 to 15% by mass. Further, it may contain an element such as phosphorus, boron or fluorine. Further, hydrogenation containing a chelating organic compound such as ethylenediaminetetraacetic acid (EDTA), trans-1,2-cyclohexanediamine-N, N, N ′, N′-tetraacetic acid, nitrilotriacetic acid, citric acid, etc. A treatment catalyst precursor is also preferably used. These chelating organic compounds are more preferably contained in the hydrotreating catalyst precursor in the form of a complex with cobalt or nickel. The hydrotreating catalyst precursor used in the method for producing low-sulfur gas oil of the present invention preferably has a mesopore central pore diameter of 4 to 20 nm, more preferably 4 to 15 nm. Furthermore, preferably, a specific surface area is 30-800 m < ² > / g, More preferably, it is 50-600 m < ² > / g. The hydrotreating catalyst precursor used in the method for producing low sulfur gas oil of the present invention is preferably not a powder but a molded body. Although there is no restriction | limiting in particular in the shape of a molded object, and a shaping | molding method, A spherical shape or a columnar shape is preferable. In the case of a spherical shape, the diameter is preferably 0.5 to 20 mm. The cross-sectional shape in the case of a columnar shape is not particularly limited, but a circular shape, a three-leaf shape, and a four-leaf shape are preferable cross-sectional shapes. The dimensions of the molded body in the case of a columnar shape are preferably about 0.25 to 400 mm ² in cross-sectional area and about 0.5 to 20 mm in length. Although there is no restriction | limiting in particular in the manufacturing method of a hydroprocessing catalyst precursor, It is preferable to include the above-mentioned active metal element, additional elements, such as phosphorus, and organic compounds, such as EDTA, in a porous inorganic oxide support | carrier. Examples of porous inorganic oxides include oxides such as alumina, silica, titania, magnesia, zirconia, silica-alumina, silica-titania, silica-zirconia, silica-magnesia, silica-alumina-titania, silica-alumina-zirconia, etc. Of these, a composite oxide, Y-type zeolite, stabilized Y-type zeolite, β-zeolite, mordenite-type zeolite, or one or more selected from zeolites such as MCM-22 is preferable.

  In the method for producing low sulfur gas oil according to the present invention, whether the first step and the third step are performed in the same reactor, or whether the first step and the third step are performed using different reactors. Regardless, the hydrotreating catalyst and reaction conditions are preferably selected as follows.

  The ratio of the hydroprocessing catalyst used in the first step to the total amount of the hydroprocessing catalyst used in the first step and the third step is preferably 20 to 80% by volume, particularly 30 to 70% by volume. is there. If this ratio is less than 20% by volume, sulfur compounds other than the hard-to-desulfurize sulfur compound are supplied to the third step, and the hydrotreating catalyst used in the third step cannot exhibit sufficient desulfurization performance. If it exceeds 80% by volume, the reaction zone advantageous for the desulfurization reaction in which the coexisting concentration of hydrogen sulfide and ammonia is reduced is not preferable.

  In the case where different hydrotreating catalysts are used in the first step and the third step, the ratio of nickel in the total content of cobalt and nickel contained in the hydrotreating catalyst is determined in the first step. It is preferable to use a catalyst larger than the hydrotreating catalyst used in the third step. When the gas oil fraction is hydrotreated, the hard-to-desulfurize sulfur compound will remain selectively. However, for the desulfurization of the hard-to-desulfurize sulfur compound, a reaction route for directly desulfurizing sulfur atoms in the DBT skeleton (direct desulfurization). It is more advantageous to use a hydrotreating catalyst that can easily take a reaction route (hydrodesulfurization route) that desulfurizes after hydrogenating the benzene ring in the DBT skeleton to alleviate steric hindrance due to substituents. When the cobalt-molybdenum-based hydrotreating catalyst is compared with the nickel-molybdenum-based hydrotreating catalyst, it is known that the latter is more likely to take a hydrodesulfurization route (Takashi Hamada, Ryo Mabuchi, Isao Mochida, Journal of Petroleum Society, 37, 368-375 (1994)). The ratio of nickel in the total content of cobalt and nickel contained in the hydrotreating catalyst is larger than that of the hydrotreating catalyst used in the first step, so that it is difficult to desulfurize. Desulfurization of sulfur compounds is further promoted and preferable.

  Each of the hydrotreating catalysts used in the first step and the third step may be a single hydrotreating catalyst, or two or more types of catalysts may be combined and stacked. When two or more types of catalysts are combined and used in a stacked manner, a raw material oil or a crude refined one having a smaller proportion of nickel in the total content of cobalt and nickel contained in the hydrotreating catalyst It is preferable to arrange | position the thing with a larger ratio of the nickel which occupies for the total content of cobalt and nickel in the side near the reactor inlet to which oil is supplied, in the side nearer to the reactor outlet.

The reaction temperature in the first step and the third step is selected from the range of 280 to 450 ° C, preferably from the range of 300 to 420 ° C. The hydrogen pressure in the first step and the third step is preferably selected from the range of 3 to 10 MPa, and preferably selected from the range of 4 to 9 MPa. The reaction temperatures of the first step and the third step are not necessarily the same, and may be selected independently from the above range for each step. The total pressure in the first step is preferably higher than the total pressure in the third step, and is particularly preferably about 0.01 to 1 MPa higher than the total pressure in the third step. If the total pressure is the same as or lower than the total pressure in the third step, the fluid flow becomes unsatisfactory. The total liquid space velocity, which is the ratio of the feed amount on the volume basis of the feedstock to the total volume of the hydrotreating catalyst used in the first step and the third step, is preferably 0.1 to 5 h ⁻¹ , in particular 0.3 to 3h- ¹ . Further, the hydrogen / oil ratio in the first step and the third step is preferably 100 to 2000 NL / L, particularly 100 to 1000 NL / L, respectively. When hydrotreating in a fixed bed flow type reactor, each of the hydrotreating catalysts used in the first step and the third step may be packed in a single catalyst bed, or two or more The catalyst bed may be divided and filled. When the hydrotreatment catalyst is divided into two or more catalyst beds and charged with the hydrotreating catalyst, it is preferable to supply quench hydrogen between the catalyst beds. When quench hydrogen is supplied between the catalyst beds, the ratio of the total amount of hydrogen and quench hydrogen supplied together with the raw oil or the crude refined oil to the reactor inlet and the feed amount of the raw oil or the crude refined oil is 100. It is preferable to set it to -2000NL / L, especially 100-1000NL / L.

  In the method for producing low-sulfur gas oil of the present invention, DBT without an alkyl substituent contained in the crude refined oil supplied to the third step is preferably 10 ppm by mass or less, more preferably 5 masses as the sulfur content. It is preferably at most ppm, particularly at most 1 ppm by mass. If DBT is desulfurized to a very low concentration, the hardly-desulfurizable sulfur compound will remain selectively in the crude refined oil, and the difficult-to-desulfurize sulfur compound will become efficient under the reaction conditions of the third step. It is preferable because it is well desulfurized. Moreover, it is preferable that the sulfur content contained in the roughly refined oil supplied to the third step is preferably 2000 mass ppm or less, more preferably 1000 mass ppm or less, and particularly preferably 50 to 500 mass ppm. Usually, in the crude refined oil desulfurized to such a sulfur level, the hardly-desulfurizable sulfur compound remains selectively, and the hardly-desulfurizable sulfur compound is efficiently used under the reaction conditions of the third step. It is preferable because it is well desulfurized.

  The temperature of the liquid phase in the second step is not particularly limited, but is preferably selected from the range of 30 to 450 ° C., more preferably 200 to 420 ° C., which is the same as the outlet reaction temperature of the first step or 100 ° C. It is particularly preferred that the temperature is lower within the range of. If the temperature of the liquid phase in the second step is too low, the energy required for heating the crude refined oil or hydrogen supplied to the third step increases, which is not preferable. There is no particular limitation on the temperature of hydrogen, inert gas or steam supplied to the stripper when the stripping treatment is performed in the second step, but the temperature is preferably higher than room temperature, and is preferably from 100 ° C. to the first step. It is particularly preferable that the reaction temperature be within the range. When performing the stripping process in the second step, the flow rate of hydrogen, inert gas or steam supplied to the stripper is 0.01 to 2 times the flow rate of hydrogen supplied to the first step, and Is preferably selected from a range of 0.1 to 1 times.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this Example does not limit this invention.
[Reference Example 1]

As the support, a pellet having a cross-sectional shape of γ-alumina as a main component and a nominal size of 1/20 inch was used. The specific surface area measured by the nitrogen adsorption method was 259 m ² / g, the pore volume was 0.64 cm ³ / g, and the median pore diameter was 7.8 nm.

  50 g of ion-exchanged water, 31.8 g of molybdenum trioxide (manufactured by Taiyo Mining Co., Ltd.), 10.7 g of 45.6% cobalt carbonate (manufactured by Kansai Kagaku Kagaku Co., Ltd.), 3.6 g of 45.0% nickel carbonate (Nippon Chemical Industry Co., Ltd.) and 4.9 g of 85% phosphoric acid were added and dissolved at 80 ° C. with stirring. Furthermore, after naturally cooling to 60 ° C., 24 g of citric acid (manufactured by Kanto Chemical Co., Inc.) was added, dissolved while stirring, and naturally cooled to 40 ° C., and then 8 g of 35% hydrogen peroxide (Kanto Chemical ( Co., Ltd.) was added and allowed to cool to room temperature with stirring to prepare a support liquid. 120 g of this support liquid was impregnated with a pore filling method. The impregnated material was dried at 130 ° C. overnight and then calcined in air at 550 ° C. for 30 minutes in a ventilated rotary kiln to prepare a hydrotreating catalyst precursor 1.

[Comparative Example 1]
50 g of ion-exchanged water, 31.8 g of molybdenum trioxide (manufactured by Taiyo Mining Co., Ltd.), 7.2 g of 45.6% cobalt carbonate (manufactured by Kansai Catalysts Chemical Co., Ltd.), 7.3 g of 45.0% nickel carbonate (Nippon Chemical Industry Co., Ltd.), 4.9 g of 85% phosphoric acid was added, dissolved with stirring at 80 ° C., and allowed to cool naturally to 60 ° C., then 24 g of citric acid (manufactured by Kanto Chemical Co., Ltd.) ) And dissolved with stirring. After naturally cooling to 40 ° C., 8 g of 35% hydrogen peroxide (manufactured by Kanto Chemical Co., Inc.) was added, and the mixture was allowed to cool to room temperature with stirring to prepare a support liquid. 120 g of the carrier used in Reference Example 1 was impregnated with this supporting liquid by a pore filling method. The impregnated product was dried at 130 ° C. overnight and then calcined in the air at 500 ° C. for 30 minutes with a ventilated rotary kiln to prepare the hydrotreating catalyst precursor 2.

[Comparative Example 2]
To 50 g of ion-exchanged water, 31.3 g of molybdenum trioxide (manufactured by Taiyo Mining Co., Ltd.), 10.6 g of 45.6% cobalt carbonate (manufactured by Kansai Catalysts Chemical Co., Ltd.), and 4.8 g of 85% phosphoric acid are added. Then, the mixture was dissolved at 80 ° C. with stirring, and further allowed to cool to 60 ° C., and then 24 g of citric acid (manufactured by Kanto Chemical Co., Inc.) was added and dissolved with stirring. After naturally cooling to 40 ° C., 8 g of 35% hydrogen peroxide (manufactured by Kanto Chemical Co., Inc.) was added, and the mixture was allowed to cool to room temperature with stirring to prepare a support liquid. The carrier used in Reference Example 1 was impregnated with this support liquid by a pore filling method. The impregnated product was dried at 130 ° C. overnight, and then calcined in the air at 550 ° C. for 30 minutes in a ventilated rotary kiln to prepare a hydrotreating catalyst precursor 3.

[Comparative Example 3]
As the carrier, a pellet having a cross-sectional shape mainly composed of γ-alumina and having a three-leaf type and a nominal size of 1/20 inch was used. The specific surface area measured by the nitrogen adsorption method is 293 m ² / g, the pore volume is 0.64 cm ³ / g, and the central pore diameter is 7.6 nm.

  To 50 g of ion-exchanged water, 24.9 g of molybdenum trioxide (manufactured by Taiyo Mining Co., Ltd.), 10.4 g of 45.6% cobalt carbonate (manufactured by Kansai Catalysts Chemical Co., Ltd.), and 11.8 g of 85% phosphoric acid are added. After dissolving at 80 ° C. with stirring and further naturally cooling to 60 ° C., 24 g of citric acid (manufactured by Kanto Chemical Co., Inc.) was added, dissolved with stirring, allowed to cool to room temperature, Prepared. 120 g of this support liquid was impregnated with a pore filling method. The impregnated material was dried at 130 ° C. overnight, and then calcined in the air at 550 ° C. for 30 minutes in a ventilated rotary kiln to prepare a hydrotreating catalyst precursor 4.

  Table 1 shows the analysis results and composition analysis results of the specific surface area, pore volume, and median pore diameter of these hydrotreating catalyst precursors 1 to 4 measured by the nitrogen adsorption method.

[Analysis of hydrotreating catalyst precursor and hydrotreating catalyst]
The hydrogenation catalyst precursors 1 to 4 were heated at a constant rate in a hydrogen sulfide / hydrogen stream, and consumption amounts of hydrogen sulfide and hydrogen were examined (TPS analysis). In this TPS measurement (manufactured by Okura Riken), about 100 mg of a hydroprocessing catalyst precursor pulverized and having a particle size of 32-64 mesh was collected and charged into a reaction tube, and the reaction tube was attached to the apparatus. After pretreatment at 400 ° C. for 2 hours in an air atmosphere and cooling to room temperature, the mixture was stabilized at 28 ° C. for 1 hour or more. After confirming that the hydrogen sulfide UV detector (wavelength 215 nm) and hydrogen TCD detector are stable, switch to hydrogen sulfide / hydrogen gas, hold at 28 ° C. for 2 hours, and then continue to 6 ° C./min up to 400 ° C. At a temperature program of 2 hours at 400 ° C. An example of the measurement result is shown in FIG. FIG. 1 shows the results for the hydrotreating catalyst precursor 1. In FIG. 1, it is assumed that the consumption of hydrogen sulfide (H ₂ S) increases in the lower part of the figure, and the consumption of hydrogen (H ₂ ) increases in the upper part of the figure. As is clear from FIG. 1, two consumption peaks of hydrogen sulfide were recognized in the measurement results. The low-temperature peak is due to the formation of molybdenum oxysulfide and molybdenum trisulfide-like compounds coordinated by nickel and cobalt by the exchange of oxygen and sulfur, and the high-temperature peak changes from oxysulfide to the sulfide state It is. In addition, a peak of hydrogen consumption was observed at the temperature between these peaks, which was generated by hydrogen sulfide being generated by hydrogen being hydrogenated at the same time as part of S of oxysulfide was released. it is conceivable that. Therefore, this peak top temperature was treated as the sulfidation start temperature, and is shown in Table 1 together. There exists a tendency for the desulfurization activity and denitrogenation activity of the hydrotreating catalyst obtained from the hydrotreating catalyst precursor having a low sulfidation start temperature to be higher.

The form of molybdenum sulfide of the hydrotreating catalyst obtained by sulfiding the hydrotreating catalyst precursors 1 to 4 was measured. The above-mentioned TPS measurement was carried out to pulverize the sulfurized hydroprocessing catalyst, and it was put in heptane and dispersed for several minutes with an ultrasonic cleaner. One drop of the suspension was dropped on the mesh of the microgrid, dried, and then observed with a transmission electron microscope (TEM). In this TEM observation, the acceleration voltage is 200 kV, the observation direct magnification is 300,000 times, and the photographic magnification is 1.5 million times. The length was measured. An example of a TEM photograph is shown in FIG. This operation was performed on at least 100 Mo sulfides, and the average number of layers and the average length (La) were determined. Table 1 shows the aspect ratio (La / Lb) of Mo sulfide calculated by multiplying the average number of layers by the distance between layers of 0.615 nm as the average height (Lb) .

[Reference Example 2]
[Hydrotreatment of diesel oil fraction using fixed bed flow reactor]
Using the hydrotreating catalyst precursor 1 obtained in Reference Example 1 , a hydrotreating experiment was conducted using a Middle East straight-run gas oil (light oil fraction A) having properties shown in Table 2 as a feedstock. A fixed bed flow reactor was charged with 10 mL of the hydrotreating catalyst precursor 1, and the temperature was raised from room temperature to 150 ° C. in 2 hours while flowing hydrogen at a hydrogen pressure of 5.0 MPa. Thereafter, the hydrotreating catalyst 1 was subjected to sulfurization treatment in the following procedure. A sulfiding agent (commercial light oil mixed with 1% by mass of carbon disulfide) was passed for 2 hours under conditions of hydrogen pressure 5.0 MPa, hydrogen / oil ratio 200 NL / L, LHSV 2.0 h ⁻¹ , 150 ° C. . Thereafter, the supply of the sulfiding agent and hydrogen was continued under constant conditions other than temperature, the temperature was raised to 230 ° C. at 20 ° C./h, and the temperature was kept constant at 230 ° C. for 4 hours. Thereafter, the temperature was further increased to 300 ° C. at 17.5 ° C./h, and the temperature was kept constant at 300 ° C. for 7 hours. Then, the hydrorefining reaction of the light oil fraction was performed using this hydrotreated catalyst treated with sulfur. The hydrorefining reaction conditions were as follows: hydrogen purity: 99.9% or more, hydrogen pressure: 5.0 MPa, liquid space velocity: 4.5 h ⁻¹ , hydrogen / oil ratio: 200 NL / L. Analyzing sulfur and nitrogen in the product oil sampled at reaction temperatures of 330 ° C, 340 ° C, 350 ° C and 360 ° C, desulfurization is performed with a reaction order of 1.5 for the raw oil sulfur, The desulfurization reaction rate constant and the denitrification reaction rate constant were determined with the reaction order relative to the feedstock nitrogen content being 1.0 order.

[Comparative Example 4]
Instead of hydroprocessing catalyst precursor as obtained in Reference Example 1 hydroprocessing catalyst precursor 1, except for using hydrotreating catalyst precursor 2-4 obtained in Comparative Example 1-3, Reference A hydrotreatment experiment was performed in the same manner as in Example 2 to determine a desulfurization reaction rate constant and a denitrogenation reaction rate constant, respectively.

Relative desulfurization activity and relative denitrogenation activity of the desulfurization reaction rate constants and denitrogenation reaction rate constants obtained in Reference Example 2 and Comparative Example 4 were compared using the hydrotreating catalyst precursor 4 as a reference (100). Is also shown in Table 1. The aspect ratio (La / Lb) desulfurization activity and denitrogenation activity have small water hydrogenation treatment catalyst of molybdenum sulfide, it is clear that much higher than in the hydrotreating catalyst of Comparative Example.

[Example 1]
[Production of low-sulfur gas oil by hydrotreating gas oil fractions using a reactor equipped with a gas-liquid separation mechanism]
A carrier mainly composed of silica alumina was impregnated with an impregnating solution obtained by mixing ammonia water, EDTA, nickel nitrate hexahydrate, and ammonium metatungstate aqueous solution, and then dried at 130 ° C. for 24 hours. Nickel-tungsten hydrotreatment catalyst precursor A was obtained. The elemental analysis results of the nickel-tungsten-based hydrotreating catalyst precursor A are as follows: Ni: 3.06 mass%, W: 17.4 mass%, C: 3.06 mass%, N: 2.76 mass%, Si : 13.8% by mass, Al: 12.0% by mass. The pore characteristics measured by the nitrogen adsorption method were a pore volume of 0.117 mL / g, a specific surface area of 63 m ² / g, and a median pore diameter of 6.3 nm.

  A schematic flow of the reactor used is shown in FIG. This reactor comprises two reactors, reactor 1 and reactor 2, with a high pressure separation tank 3 and a stripper 4 between them, and the reactor 2 is connected to a high pressure separation tank 5, a mist separation tank 6 and a stripper 7. They are connected by piping 16-42. Hydrogen supply to the reactors 1 and 2 is performed from the pipe 14 and the pipes 29 and 30, respectively. The raw material oil is sent to the reactor 1 through the pipes 13 and 15. Hydrogen gas can be supplied to the stripper 4 from the pipe 23 and brought into gas-liquid contact with the liquid staying in the stripper 4. From the high-pressure separation tank 3 and the stripper 4, the gas (off-gas) containing hydrogen sulfide and ammonia generated by the hydrorefining reaction can be removed from the reaction system through the pipe 21 and the pipe 24, respectively. The liquid taken out from the stripper 4 is supplied to the reactor 2 through the pipes 26 to 28 and 31. The reaction mixture hydrotreated in the reactor 2 is gas-liquid separated in the high-pressure separation tank 5 and the mist separation tank 6, and the liquid component is sent to the stripper 7 and stripped, and then taken out as product oil.

The reactor 1 is filled with 50 mL of the hydrotreating catalyst precursor 1, the reactor 2 is filled with 50 mL of the nickel-tungsten hydrotreating catalyst precursor A, the on-off valves 8 and 10 are closed, and the on-off valve 9 is opened. The temperature was raised from room temperature to 120 ° C. in 2 hours while flowing hydrogen at a hydrogen pressure of 5.0 MPa and 40 L / h. Thereafter, the hydrotreating catalyst precursor 1 was subjected to sulfiding treatment in the following procedure to obtain a sulfurized hydrotreating catalyst. Sulfurizing agent (commercial light oil mixed with 1% by mass of carbon disulfide) was passed for 2 hours under the conditions of hydrogen pressure 5.0 MPa, hydrogen / oil ratio 200 NL / L, LHSV 2.0 h ⁻¹ , 120 ° C. . Thereafter, the supply of the sulfiding agent and hydrogen was continued under the conditions other than the temperature, the temperature was raised to 230 ° C. at 27.5 ° C./h, and the temperature was kept constant at 230 ° C. for 4 hours. Thereafter, the temperature was further increased to 300 ° C. at 42.5 ° C./h, and the temperature was kept constant at 300 ° C. for 7 hours. Then, hydrorefining reaction of the light oil fraction A was performed using the hydrotreating catalyst subjected to sulfurization treatment. Open / close valves 8 and 10 are opened and open / close valve 9 is closed, hydrogen pressure of reactor 1 is 5.1 MPa, hydrogen pressure of reactor 2 is 5.0 MPa, hydrogen / feed oil supply ratio to each of reactor 1 and reactor 2 200 NL / L, LHSV = 1.5 h ^{−1 with} respect to the total catalyst charge of reactor 1 and reactor 2, and hydrogen supply 30 L / h from pipe 23 to stripper 4, reactor 1, reactor 2, high pressure separation tank The reaction was carried out at a temperature of 330 ° C. for both 3 and stripper 4. The sulfur content of the product oil obtained from the pipe 38 was 9 ppm by mass. Further, when the on-off valve 11 was closed and the on-off valve 12 was opened, the sampled intermediate product oil was stripped with nitrogen gas and analyzed for the sulfur content of the intermediate product oil. As a result, the sulfur content was 369 ppm by mass. Other reaction conditions and operations were the same as described above, and the reaction was carried out with the temperature of the reactor 1, the reactor 2, the high-pressure separation tank 3 and the stripper 4 all set to 340 ° C. The resulting product oil had a sulfur content of 4 mass ppm, and the intermediate product oil had a sulfur content of 157 mass ppm. The other reaction conditions were the same as described above, and the reaction was carried out with the reactor 1, the reactor 2, the high-pressure separation tank 3 and the stripper 4 each having a temperature of 345 ° C. The sulfur content of the obtained product oil was 0.4 mass ppm, and the sulfur content of the intermediate product oil was 121 mass ppm. The properties of the product oil are as follows. Hydrocarbon composition: saturated content 85.0%, olefin content 0.0%, 1 ring aromatic content 13.9%, 2 ring aromatic content 0.99%, 3 or more ring aromatic content 0.10%, Polycyclic aromatic content 1.09%, total aromatic content 15.0%, true calorific value: 35400 J / cm ³ , density (15 ° C.): 0.8218 g / cm ³ .

[Example 2]
The nickel-tungsten hydrotreatment catalyst precursor A described in Example 1 was calcined at 500 ° C. for 30 minutes to obtain a nickel-tungsten hydrotreatment catalyst precursor B. The elemental analysis results of the nickel-tungsten-based hydrotreating catalyst precursor B are as follows: Ni: 3.67% by mass, W: 20.8% by mass, C: 0.13% by mass, N: 0.08% by mass, Si : 16.4% by mass, Al: 14.2% by mass. The pore characteristics measured by the nitrogen adsorption method were a pore volume of 0.297 mL / g, a specific surface area of 238 m ² / g, and a median pore diameter of 4.5 nm.

The same method as in Example 1 except that in Example 1 , the reactor 2 was charged with the nickel-tungsten hydroprocessing catalyst precursor A instead of being charged with the nickel-tungsten hydroprocessing catalyst precursor A. The hydrorefining reaction of the light oil fraction A was performed using the hydrotreating catalyst that had been subjected to the sulfuration treatment in (1). Open / close valves 8 and 10 are opened and open / close valve 9 is closed, hydrogen pressure of reactor 1 is 5.1 MPa, hydrogen pressure of reactor 2 is 5.0 MPa, hydrogen / feed oil supply ratio to each of reactor 1 and reactor 2 200 NL / L, LHSV = 1.5 h ^{−1 with} respect to the total catalyst charge of reactor 1 and reactor 2, and hydrogen supply 30 L / h from pipe 23 to stripper 4, reactor 1, reactor 2, high pressure separation tank The reaction was carried out at a temperature of 340 ° C. for both 3 and stripper 4. The sulfur content of the product oil obtained from the pipe 38 was 7 ppm by mass. Further, when the open / close valve 11 was closed and the open / close valve 12 was opened, the sampled intermediate product oil was stripped with nitrogen gas, and the sulfur content of the intermediate product oil was analyzed. As a result, the sulfur content was 157 ppm by mass.

[Comparative Example 5]
A hydrotreating catalyst that has been subjected to a sulfiding treatment in the same manner as in Example 2 except that the reactor 1 is filled with the hydrotreating catalyst precursor 3 instead of the hydrotreating catalyst precursor 1. The hydrorefining reaction of the light oil fraction A was performed. Open / close valves 8 and 10 are opened and open / close valve 9 is closed, hydrogen pressure of reactor 1 is 5.1 MPa, hydrogen pressure of reactor 2 is 5.0 MPa, hydrogen / feed oil supply ratio to each of reactor 1 and reactor 2 200 NL / L, LHSV = 1.5 h ^{−1 with} respect to the total catalyst charge of reactor 1 and reactor 2, and hydrogen supply 30 L / h from pipe 23 to stripper 4, reactor 1, reactor 2, high pressure separation tank The reaction was carried out at a temperature of 340 ° C. for both 3 and stripper 4. The sulfur content of the product oil obtained from the pipe 38 was 24 mass ppm. Further, when the open / close valve 11 was closed and the open / close valve 12 was opened, the sampled intermediate product oil was stripped with nitrogen gas, and the sulfur content of the intermediate product oil was analyzed. As a result, the sulfur content was 439 ppm by mass.

The following methods were used as measurement methods in Examples , Reference Examples and Comparative Examples.

[Measurement method of pore characteristics]
For measurement of pore characteristics by the nitrogen gas adsorption method, an ASAP2400 type measuring instrument manufactured by Micromeritics was used.

[Method for measuring sulfur content]
The sulfur content of the light oil fraction was measured using a ZSX101e type fluorescent X-ray analyzer manufactured by Rigaku Corporation.

According to the hydrotreating method using the catalysts of the present invention, a low sulfur diesel fuel, particularly a sulfur content of 5 mass ppm or less, further to produce the following gas oil 1 mass ppm under mild conditions, also efficiently increased production can do. Since the environmentally friendly light oil of the present invention has a sulfur content as low as 5 ppm by mass or less and further as 1 ppm by mass or less, and secures a true calorific value per unit volume equivalent to that of conventionally marketed diesel oil, It is possible to simultaneously reduce emissions of environmental pollutants and reduce carbon dioxide emissions from diesel vehicles, thereby contributing to the protection of the global environment.

It is a figure which shows the TPS measurement result of the hydrotreating catalyst precursor 1. It is a TEM photograph of a hydrotreating catalyst obtained by hydrotreating a hydrotreating catalyst precursor. It is a figure which shows the general | schematic flow of the reaction apparatus provided with the gas-liquid separation mechanism between the reactors used for the Example of this invention , the reference example, and the comparative example.

Explanation of symbols

1 and 2: reactor, 3: high pressure separation tank, 4: stripper, 5: high pressure separation tank, 6: mist separation tank, 7: stripper, 8-12: open / close valve, 13-42: piping

Claims (3)

  A method for producing a low sulfur gas oil having a sulfur content of 10 ppm by mass or less using a gas oil fraction containing a sulfur content of 0.5% by mass or more as a feedstock,
  The inorganic porous oxide support carries 10 to 25% by mass of molybdenum, 2 to 8% by mass in total of cobalt and nickel, and 0.5 to 2.0% by mass of phosphorus, and the carbon content is 1 mass. And a hydrotreating catalyst formed by sulfiding a hydrotreating catalyst precursor having a cobalt content of 65 to 90 mol% with respect to the total content of cobalt and nickel in the presence of hydrogen. A first step in which rough purification is performed by hydrotreating with a raw material oil;
  A second step of performing gas-liquid separation of the reaction mixture obtained in the first step;
A hydrotreating treatment is performed in which a hydrotreating catalyst obtained by sulfiding a hydrotreating catalyst precursor containing tungsten, nickel and ethylenediaminetetraacetic acid is brought into contact with the crude oil obtained in the second step in the presence of hydrogen. A process for producing a low sulfur gas oil, comprising: The reaction temperature in the first step and the third step is 280 to 450 ° C., the hydrogen pressure in the first step and the third step is 3 to 10 MPa, and the total pressure in the first step is The manufacturing method of the low sulfur gas oil of Claim 1 higher than the total pressure of a 3rd process.   A light oil having a sulfur content of 5 ppm by mass or less obtained by the method according to claim 1 or 2 and a monocyclic aromatic content of 5 to 18% by volume and a polycyclic aromatic content of 2% by volume or less.