JP2000345172A - Production of low sulfur light oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a low sulfur light oil, by which the low sulfur light oil having a high quality can efficiently be produced. SOLUTION: In this light oil-desulfurizing system for producing a low sulfur light oil, a light oil LGO as raw material is separated into a light distillate LLGO and a heavy distillate HLGO in a fractionator 10. The separated light distillate LLGO is hydrogenated in a first hydrogenation device 20 equipped with a hydrogenation catalyst 20B, and heavy distillate HLGO is also hydrogenated in a second hydrogenation device 30 equipped with hydrogenation catalyst 30B and 30D and a zeolite-based catalyst 30C, and is then mixed with the hydrogenated light distillate LLGO in a mixing device 40 to produce a desulfurized light oil DGO. Slightly desulfurized components contained in the light oil LGO as raw material are contained in the heavy distillate HLGO, and then acceleratedly isomerized, when the heavy distillate HLGO is selectively hydrogenated in the presence of the zeolite-based catalyst. Thereby, the desulfurized light oil DGO having a high quality can efficiently be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a steel sheet having a sulfur content of 0.5 to 0.5%.
2.5 wt%, a raw material light oil having a boiling point of 150 to 400 ° C.,
The present invention relates to a method for producing a low-sulfur gas oil, which is produced by hydrotreating to produce a low-sulfur gas oil.

[0002]

[Background Art] As air pollution worsens in urban areas,
Light oils used in diesel engines and the like are required to minimize the sulfur content in the light oils.
Light oils having a sulfur content of 500 ppm to 100 ppm, and even 50 ppm or less, have been desired. For this reason, conventionally, when hydrotreating light oil using a hydrotreating catalyst, a method for producing a low-sulfur light oil that obtains a light oil with a low sulfur content by raising the reaction temperature is known.

[0003]

However, in such a conventional method for producing a low-sulfur gas oil, since the reaction temperature is too high, the hue of the low-sulfur gas oil obtained by desulfurization deteriorates, and the quality of the product gas oil decreases. There is a problem that it cannot be secured.
In addition, when the hydrotreating is performed at an increased reaction temperature, the life of the hydrotreating catalyst used in the treatment is shortened. Therefore, the number of times of replacing the hydrotreating catalyst in the hydrotreating process increases, and the low sulfur gas oil is used. Cannot be produced efficiently. That is, the above-described conventional method for producing low-sulfur gas oil has a problem that it is difficult to efficiently produce high-quality low-sulfur gas oil.

[0004] An object of the present invention is to provide a method for producing low-sulfur gas oil that can efficiently produce high-quality low-sulfur gas oil.

[0005]

In order to achieve the above object, a method for producing a low-sulfur light oil according to the present invention comprises the steps of:
A separation step of separating a feed gas oil having a boiling point of 5 to 2.5 wt% and a boiling point of 150 to 400 ° C into a light fraction and a heavy fraction, and bringing the light fraction into contact with hydrogen in the presence of a hydrotreating catalyst. Light fraction hydrotreating step, a heavy fraction hydrotreating step of contacting the heavy fraction with hydrogen in this order in the presence of a hydrotreating catalyst, and a zeolite-based catalyst including zeolite, A mixing step of mixing the light product oil produced in the light fraction hydrotreating step and the heavy product oil produced in the heavy fraction hydrotreating step at an arbitrary ratio. It is characterized by.

Here, the aforementioned sulfur content of 0.5 to 2.5 w
As the feedstock gas oil having a boiling point of 150 to 400 ° C., a straight-run gas oil LGO obtained by atmospheric distillation of crude oil and a vacuum distillation obtained by further vacuum distillation of a residual oil obtained by atmospheric distillation of crude oil Light oil VGO, catalytic cracked light oil LCO obtained by catalytic cracking, pyrolyzed light oil CG obtained by thermal cracking
O, light oil VHLGO obtained from a vacuum desulfurization device, light oil DSGO obtained from a direct desulfurization device, and a mixture thereof can be used as a raw material gas oil. In short, various light oils produced as middle distillates in a petroleum refining system for refining crude oil to obtain various petroleum products can be used as the feedstock light oil.

The above-mentioned separation step can be carried out by a fractionator, a gas-liquid separator or the like. In addition, in a normal-pressure distillation apparatus in which a light fraction and a heavy fraction among gas oil fractions are separated. A separation step may be performed. Further, the light fraction hydrotreating step and the heavy fraction hydrotreating step
It can be carried out by a hydrotreating apparatus equipped with a reaction tower for supplying a light fraction or a heavy fraction, and a hydrotreating catalyst disposed inside the reaction or the like.

When the heavy fraction hydrotreating step is carried out, the hydrotreating catalyst and the zeolite-based catalyst are arranged in a layer in the reaction tower in the hydrotreating apparatus, so that the hydrotreating catalyst and the zeolite are treated. The heavy fraction can be contacted with hydrogen in the order of the system catalyst. Further, as another method, even if a first hydrotreating catalyst and a catalyst obtained by mixing a zeolite-based catalyst and a second hydrotreating catalyst are arranged in layers, the first hydrotreating catalyst and the mixed catalyst may be mixed. In turn, the heavy fraction can be contacted with hydrogen.

The mixing step can be performed using a dedicated mixing device for mixing the light product oil and the heavy product oil. However, pipes for leading the light product oil and the heavy product oil are connected to each other. Alternatively, both can be mixed by providing a valve capable of adjusting the flow rate in each pipe.

Further, alumina, silica, titania, boria, zirconia, silica-alumina, and the like are used as the hydrotreating catalyst in the light fraction hydrotreating step and the hydrotreating catalyst in the heavy fraction hydrotreating step. A porous amorphous inorganic oxide such as alumina-boria, alumina-zirconia, or the like, on which an active metal is supported can be used.

As the active metal, at least one of a metal belonging to Group VI of the periodic table and a metal belonging to Group VIII can be employed. Specifically, cobalt (Co), molybdenum (Mo), Nickel (Ni), tungsten (W), chromium (Cr), and combinations thereof can be employed, but preferably the active metal / support combination is CoMo / alumina or NiMo.
/ Alumina is preferred.

As the above-mentioned zeolite-based catalyst, zeolite is mixed with any one of alumina, silica, and silica-alumina or a combination thereof,
A mixture in which an active metal is supported on this mixture or a mixture in which an active metal is not supported can be employed.

According to the present invention, since a separation step, a light fraction hydrotreating step, and a heavy fraction hydrotreating step are provided, the heavy fraction, that is, the high boiling fraction The hard-to-desulfurize component can be selectively isomerized (hydrogenated) with a zeolite-based catalyst in the heavy fraction hydrotreating step. Accordingly, by isomerizing the hard-to-desulfurize component, it is possible to easily remove the hard-to-desulfurize component in the heavy fraction by the subsequent hydrogenation treatment, so that the sulfur content of the light oil and the light oil obtained by mixing the heavy oil can be reduced. It becomes possible to make it extremely small.

Here, the structure of the hydrotreating catalyst and the hydrotreating catalyst in the heavy fraction hydrotreating step is derived based on the following knowledge.
That is, the sulfur content is 100 ppm or less, or 50 pp.
m or less so-called ultra-deep desulfurization for gas oil,
Desulfurization of non-desulfurizable sulfur alkyldibenzothiophenes contained in gas oil is a problem, and the point is how to efficiently react them. For example, when 4,6-dimethyldibenzothiophene is considered as the non-desulfurizable sulfur alkyldibenzothiophene, 4,6-dimethyldibenzothiophene has the following structure.

[0015]

Embedded image

Among such alkyldibenzothiophenes, those having an alkyl group at the substitution position 4 or the substitution position 6 in particular, because the steric hindrance of the alkyl prevents the contact between the sulfur atom and the catalytically active site. Is not desulfurized even if the hydrogenation treatment is performed, and as a result, the deep desulfurization reaction does not proceed.

Therefore, in the present invention, among the alkyldibenzothiophenes, attention is paid to the above-mentioned sterically hindered alkyldibenzothiophenes, and the position of the alkyl group is moved to a position where steric hindrance (contact hindrance) is small.
It was decided to improve the desulfurization reactivity of alkyldibenzothiophenes such as 4,6-dimethylbenzothiophene.
For example, the desulfurization reactivity is improved by moving the methyl group (Me-) of 4,6-dimethyldibenzothiophene having the above structure to a position represented by the following structural formula.

[0018]

Embedded image

Specifically, by utilizing the solid acid property of the zeolite catalyst, an alkyl group (methyl group)
Can be transferred and eliminated. However, the zeolite catalyst has a problem that the catalyst is liable to be deteriorated when a large amount of polycyclic aromatic components and basic nitrogen are contained in the feedstock light oil to be isomerized. On the other hand, if the acid function of the zeolite catalyst is too strong, a cracking reaction of the feedstock gas oil occurs, generating unnecessary gas, naphtha, etc., and consequently hydrogen consumption, which leads to isomerization of the non-desulfurizable alkyldibenzothiophene. There is a problem that processing cannot be performed sufficiently. Further, since the desulfurization activity of the zeolite catalyst itself is weaker than that of a conventional catalyst (for example, an alumina oxide catalyst), there is a problem that the isomerization treatment cannot be performed sufficiently as described above.

Therefore, in the heavy fraction hydrotreating step, the easily desulfurized component is desulfurized in advance using a hydrotreating catalyst. The dibenzothiophenes are isomerized and the isomerized hardly-desulfurizable alkyldibenzothiophenes are desulfurized to obtain a sulfur content of 100 pp.
m or less deep desulfurization.

That is, according to the heavy fraction hydrotreating step, hydrogenation or denitrification of a polycyclic aromatic component is performed as a pretreatment for a zeolite catalyst using a hydrotreating catalyst. Hydrogenation of sulfur (alkyldibenzothiophene) and aromatics, which have become relatively easy to desulfurize, using a zeolite-based catalyst for isomerization of refractory sulfur (refractory alkyldibenzothiophenes) By doing so, a low-sulfur light oil with extremely low sulfur content can be obtained.

Further, since the aromatic components unevenly distributed in the feed gas oil are hydrogenated by the hydrotreating catalyst, it is possible to obtain a high-quality low sulfur gas oil in which the aromatic components are not unevenly distributed. In addition, since the target to be treated is determined by the hydrotreating catalyst and zeolite-based catalyst, and the gas oil is hydrotreated in stages, there is no need to raise the reaction temperature more than necessary, and low sulfur with good hue is obtained. Since gas oil can be obtained and the reaction temperature does not increase, the life of the catalyst can be prolonged, the number of replacements can be reduced, and low sulfur gas oil can be efficiently produced.

On the other hand, since the light fraction hardly contains the hardly desulfurizable sulfur, it is not necessary to carry out the above-mentioned stepwise hydrotreating, and the desulfurization rate necessary and sufficient in the ordinary hydrotreating step is reduced. Can be achieved.

In the above, alumina, silica, and the like are used as the zeolite-based catalyst in the heavy fraction hydrotreating step.
And zeolite are mixed with any one or combination of silica and alumina, and the mixture is mixed with Co, N
When a catalyst supporting an active metal such as i or Mo is used, the isomerization treatment and the hydrogenation treatment can be performed in the presence of a zeolite-based catalyst. However, if the second hydrotreating catalyst is disposed downstream of such a zeolite-based catalyst, the isomerized hardly desulfurizable sulfur can be more reliably removed.

That is, if the heavy fraction hydrotreating step is brought into contact with hydrogen in this order in the presence of the first hydrotreating catalyst, the zeolite catalyst and the second hydrotreating catalyst, the first Pre-desulfurization can be performed with the hydrotreating catalyst, isomerization can be performed exclusively with the zeolite-based catalyst, and hydrogenation of the isomerized hard-to-desulfurize sulfur can be performed with the second hydrotreating catalyst. Therefore, by sharing the role of each catalyst in this way, it is possible to reliably perform pre-desulfurization, isomerization treatment, and hydrogenation treatment, and it is possible to surely obtain a low-sulfur light oil with extremely low sulfur content.

The above-mentioned light fraction is preferably a fraction having an end point of 320 to 360 ° C. in the separation step. That is, by making the fraction at the end point of 320 to 360 ° C. a light fraction, most of the above-mentioned hard-to-desulfurize components are contained in the heavy fraction. Therefore, the desulfurization component in the light fraction hydrotreating step is improved by extremely reducing the amount of the hard-to-desulfurize component in the light fraction, and the sulfur content of the product gas oil can be further reduced.

Further, in the above-mentioned heavy fraction hydrotreating step, the sulfur content of the product oil treated with the hydrotreating catalyst preceding the zeolite catalyst is preferably 0.2 wt% or less. That is, the sulfur content of the product oil treated with the hydrotreating catalyst preceding the zeolite catalyst is reduced to 0.2 wt.
%, The isomerization treatment with the zeolite-based catalyst can be performed reliably and sufficiently, so that the desulfurization rate can be further improved.

The above-mentioned zeolite-based catalyst includes amorphous inorganic oxides of 40 to 99 wt% and zeolite 1
A zeolite-based catalyst in which at least one metal of Group VI metal and Group VIII metal is supported at 0 to 25 wt% in terms of oxide on a support containing ６０60 wt% of the metal. Is preferred.

The zeolite used in the zeolite-based catalyst includes a silica / alumina ratio (SiO 2).
₂ / Al ₂ O ₃ ) is preferably ₂ to 500 zeolite, more preferably, the silica / alumina ratio is 5
It is preferred to employ ~ 50 zeolites. In particular,
Examples of the zeolite include Y-type zeolite, β-type zeolite, X-type zeolite, L-type zeolite, mordenite,
Pentasil-type zeolites, A-type zeolites and the like can be employed, and silicalite can also be suitably used.

Further, when an active metal is supported on the above-mentioned zeolite, a metal belonging to Group VI of the periodic table is applied to the zeolite;
At least one metal of Group VIII metal can be supported, and for example, an active metal such as cobalt, molybdenum, and nickel can be supported.

Specific examples of suitable zeolite catalysts include zeolite catalysts (CoMo / Y zeolite to alumina) in which cobalt and molybdenum are supported on a carrier in which Y type zeolite and alumina are mixed, or pentasil type catalyst. A zeolite-based catalyst (Ni / pentasil-type zeolite to silica-alumina) in which nickel is supported on a carrier in which zeolite and silica-alumina are mixed is exemplified.

In the heavy distillate hydrotreating step, the above-mentioned zeolite catalyst is combined with the first zeolite catalyst.
Preferably, the volume ratio is 5 to 60% based on the total amount of the catalyst including the second hydrotreating catalyst. By specifically limiting the composition, volume ratio, etc. of the zeolite-based catalyst in this way, it is possible to promote the isomerization of the hardly desulfurized component in the heavy fraction of the feedstock light oil, and to carry out the hydrotreatment efficiently. ,
Light oil with extremely low sulfur content can be produced more efficiently.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a gas oil production system for carrying out a method for producing low sulfur gas oil according to an embodiment of the present invention. This light oil production system
As shown in FIG. 1, a fractionator 10, a first hydrotreating device 20, a second hydrotreating device 30, and a mixing device 40 are provided.

The fractionator 10 converts the straight-run gas oil LGO, which is a feed gas oil, into a light fraction LLGO and a heavy fraction H
This is a part where a separation step for separating into LGO is performed, and by setting the cut temperature of the fractionator 10 to a predetermined value, the light fraction LLGO and the heavy fraction HLG
O can be separated.

The straight-run gas oil LGO is supplied to a normal-pressure distillation apparatus (not shown) installed as a pre-process of the fractionator 10.
Is a gas oil fraction having a sulfur content of 0.5 to 2.5 wt%, a total aromatic content of 10 to 50 wt%, and a boiling point of 150 to 400 ° C. In the present embodiment, the gas oil fraction of the atmospheric distillation apparatus is used as the feed gas oil, but the present invention is not limited to this. VGO, catalytic cracking gas oil LCO, pyrolysis gas oil CGO, vacuum desulfurized gas oil VHLGO, direct desulfurized gas oil D
Various light oils such as SGO, and also a mixed light oil thereof can be used as the raw material light oil. The light fraction LL
GO is collected by setting the cut temperature of the fractionator 10 so that a fraction having an end point of 320 to 360 ° C is distilled, and the heavy fraction HLGO is collected as residual oil.

The first hydrotreating unit 20 is provided with a light fraction LL
This is a part for performing a light fraction hydrotreating step for hydrotreating GO, in which a light fraction LLGO is supplied and a hydrogenation treatment is performed on a reaction tower 20A, and a hydrogen disposed inside the reaction tower 20A. And a conversion catalyst 20B.

The second hydrotreating unit 30 is provided with a heavy fraction HL
It is a part for performing a heavy fraction hydrotreating step for hydrotreating GO, and includes a reaction tower 30A similarly to the first hydrotreating apparatus 20, and inside the reaction tower 30A,
Hydrotreating catalyst 30B, zeolite-containing catalyst 30C containing zeolite, and second hydrotreating catalyst 30D are arranged in layers. The reaction conditions of the hydrotreating in the first hydrotreating apparatus 10 and the second hydrotreating apparatus 20 can be appropriately set for each apparatus within the range shown in Table 1 below.

[0038]

[Table 1]

As the hydrotreating catalysts 20B, 30B, and 30D, an active metal is added to a porous amorphous inorganic oxide such as alumina, silica, titania, boria, zirconia, silica-alumina, alumina-boria, and alumina-zirconia. What is carried is adopted. As the active metal, at least one of a metal belonging to Group VI of the periodic table and a metal belonging to Group VIII is employed. For example, cobalt (Co), molybdenum (Mo), nickel (Ni), tungsten (W) , Chromium (Cr), and combinations thereof. In the case of the present embodiment, a CoMo / alumina catalyst is used as the preferred hydrotreating catalysts 20B and 30B.
A NiMo / alumina catalyst is employed as the second hydrotreating catalyst 30D.

As the zeolite-based catalyst 30C, zeolite is mixed with any one of alumina, silica, and silica-alumina, or a combination thereof, and an active metal is supported on the mixture or no active metal is supported. Things are adopted. The zeolite has a silica / alumina ratio (SiO ₂ / Al ₂ O ₃ ) of 2 to 2.
A zeolite having a silica / alumina ratio of 5 to 50, preferably 5 to 50, is used.
Zeolite, β zeolite, X zeolite, L zeolite, mordenite, pentasil zeolite,
A type zeolite is employed. Also, silicalite can be suitably used.

Further, when an active metal is supported on the above-mentioned zeolite, a metal of Group VI of the periodic table is applied to the zeolite;
At least one metal among the Group VIII metals can be supported, and for example, an active metal such as cobalt, molybdenum, and nickel is supported. In the case of the present embodiment, a zeolite catalyst (Co) in which cobalt and molybdenum are supported on a carrier in which Y-type zeolite and alumina are mixed is used as a preferable zeolite catalyst.
Mo / Y-type zeolite to alumina) or a zeolite-based catalyst (Ni / pentasil-type zeolite to silica-alumina) in which nickel is supported on a mixture of pentasil-type zeolite and silica-alumina is employed.

In the second hydrotreating apparatus 30, the filling ratio of the catalysts 30B, 30C, and 30D is such that the zeolite-based catalyst 30C is 5 to 60 vol% (more preferably, the total amount of the catalysts 30B, 30C, and 30D). Is 1
(5 to 40 vol%). That is, the amount of the zeolite-based catalyst 30C is equal to that of the catalysts 30B, 30B.
If the content is 5 vol% or less based on the total amount of C and 30D, the isomerization of the hardly-desulfurizable alkyldibenzothiophene is not sufficiently performed, so that ultra-depth desulfurization cannot be achieved.

If the amount of the zeolite-based catalyst 30B is at least 60 vol% with respect to the total amount of the catalysts 30B, 30C and 30D, a cracking reaction of the straight-run gas oil LGO, which is a feed gas oil, will occur, and hydrogen Since this causes consumption, ultra-deep desulfurization cannot be achieved because the isomerization treatment of the non-desulfurizable alkyldibenzothiophene is not performed as described above.
Furthermore, when the amount of the zeolite-based catalyst 30B is too large,
As a result, the amounts of the first hydrotreating catalyst 30B and the second hydrotreating catalyst 30D in the pretreatment are relatively reduced, so that sufficient pretreatment and posttreatment cannot be performed, and ultra-depth desulfurization is performed. Cannot be achieved.

The mixing device 40 includes the first hydrotreating device 20
And a pipeline 42 for guiding the light product oil treated by the second hydrotreating apparatus 30 and the heavy product oil treated by the second hydrotreating apparatus 30. Although not shown, the pipeline 41 and the pipeline 42 are each provided with a valve on the upstream side of the connection portion, and the valves can adjust the flow rates of the light product oil and the heavy product oil. ing.

Next, the operation of the above-described gas oil desulfurization system will be described. (1) The straight-run gas oil LGO fractionated by the atmospheric distillation unit (not shown) is separated into a light fraction LLGO and a heavy fraction HLGO by the fractionator 10 as a feed gas light oil. (2) The light fraction LLGO is supplied to the reaction tower 20A of the first hydrotreating apparatus 20, where it is brought into contact with hydrogen in the presence of the hydrotreating catalyst 20B to be desulfurized and turned into light product oil.

(3) The heavy fraction HLGO is supplied to the reaction tower 30A of the second hydrotreating apparatus 30, and is first contacted with hydrogen in the presence of the first hydrotreating catalyst 30B to perform the hydrotreating. Done. Next, the hydrogenated heavy fraction HLG
O comes into contact with hydrogen in the presence of the zeolite-based catalyst 30C, so that the hard-to-desulfurize component in the heavy fraction HLGO is isomerized and the aromatic components unevenly distributed in the heavy fraction HLGO are also hydrogenated. . Then, the isomerized hardly-desulfurized component is contacted with hydrogen in the presence of the second hydrotreating catalyst 30D to be desulfurized.

(4) The light product oil treated in the first hydrotreating unit 20 is sent from the pipeline 41, and the heavy product oil treated in the second hydrotreating unit 30 is sent from the pipeline 42 to the mixing unit 40. , Where the two are mixed. In mixing, by adjusting the opening and closing of valves provided on the upstream side of each pipeline,
By adjusting the mixing ratio of the light product oil and the heavy product oil, desulfurized light oil DGO having desired properties can be obtained.

According to the above embodiment, the following effects can be obtained. That is, the above-described gas oil desulfurization system includes the fractionator 10 for performing the separation step and the first hydrotreating apparatus 2 for performing the light fraction hydrotreatment step.
0, and the second hydrotreating apparatus 30 for performing the heavy fraction hydrotreating step, the hard-to-desulfurize component contained in the straight-run gas oil LGO is a zeolite-based catalyst in the second hydrotreating apparatus 30. It can be selectively isomerized at 30C. After that, by treating with the second hydrotreating catalyst 30D, the components that are difficult to desulfurize can be removed, and the sulfur content in the heavy product oil can be extremely reduced.

On the other hand, the light fraction LLGO containing almost no hard-to-desulfurize component is efficiently desulfurized by performing a normal desulfurization treatment in the first hydrotreating unit 20. Then, the light fraction LLGO and the heavy fraction HLGO are mixed at a desired ratio by the mixing device 40, so that desulfurized light oil DGO with extremely low sulfur content can be efficiently produced.

Since the heavy fraction HLGO is hydrotreated in the presence of the zeolite catalyst 30C, the heavy fraction H
The aromatic component contained in the LGO can also be hydrogenated, and a high-quality desulfurized light oil DGO in which the aromatic component is not unevenly distributed can be obtained.

Further, the first hydrotreating unit 20 and the second hydrotreating unit 30 are provided according to the light fraction LLGO and the heavy fraction HLGO. It is not necessary to set higher than necessary, and high quality desulfurized light oil DGO with good hue can be obtained.

Since the reaction temperature in each of the hydrotreaters 20 and 30 can be appropriately set according to the light fraction LLGO and the heavy fraction HLGO, the catalysts 20B, 30B, 3
By extending the life of 0C and 30D and reducing the number of replacements, desulfurized light oil DGO can be produced more efficiently.

Since the fraction at the end point of 320 to 360 ° C. is used as the light fraction LLGO in the fractionator 10, the hardly desulfurized component contained in the straight-run gas oil LGO is almost contained in the heavy fraction HLGO. Becomes Therefore,
By making the hard-to-desulfurize component in the light fraction LLGO extremely small, the desulfurization efficiency in the first hydrotreating unit 20 is improved, and the sulfur content of the desulfurized light oil DGO can be further reduced.

Further, since the configuration and the filling ratio of the zeolite catalyst 30C in the second hydrotreating apparatus 30 are set as described above, the isomerization of the hardly desulfurized component in the heavy fraction HLGO is promoted. Hydrogenation can be performed efficiently, and the sulfur content of the desulfurized gas oil DGO can be further reduced.

The present invention is not limited to the above-described embodiment, but includes the following modifications. In the above embodiment, the separation step is performed by the fractionator 10, but is not limited to this. That is, in the atmospheric distillation apparatus set as a pre-process of the fractionator of the embodiment, the straight-run gas oil LGO is allowed to be fractionated from the beginning into the light fraction LLGO and the heavy fraction HLGO, The fractionator 10 in the embodiment may be omitted. This eliminates the need for the fractionator 10, thereby simplifying the structure of the gas oil desulfurization system.

In the above embodiment, a CoMo / alumina catalyst is used as the hydrotreating catalysts 20B, 30B and 30D, and a CoMo / Y-type zeolite to alumina catalyst or a Ni / pentasil-type zeolite to silica-alumina catalyst is used as the zeolite-based catalyst 30C. , But is not limited to these. That is, the hydrotreating catalysts 20B, 30B
B, 30D, and zeolite-based catalyst 30C can be constituted by appropriately combining the above-mentioned applicable amorphous inorganic oxide carrier and active metal, and each catalyst also efficiently produces light oil having extremely low sulfur content. In order to do so, they may be appropriately combined. In addition, specific structures, shapes, and the like at the time of carrying out the present invention may be other structures and the like as long as the object of the present invention can be achieved.

[0057]

EXAMPLE 1 In the gas oil desulfurization system shown in FIG. 1, a straight gas oil LGO, which is a feed gas oil, is subjected to light fraction LLGO and heavy fraction H by a fractionator 10.
After being separated into LGO, the light fraction LLGO is hydrotreated in the first hydrotreating apparatus 20 and the heavy fraction is hydrotreated in the second hydrotreating apparatus 30, respectively. DGO was obtained.

The straight-run gas oil LGO is supplied to the fractionator 10
Atmospheric gas oil obtained as an extraction fraction of an atmospheric distillation apparatus set in the previous step, which has a boiling point of 180 to
380 ° C, sulfur content 1.4 wt%, polycyclic aromatic content 12.0
wt% (polycyclic aromatic: 2 + 3-ring aromatic).

In the fractionation in the fractionator 10, the fraction at IBP to 330 ° C. is used as a light fraction LLGO,
The residue at 330 ° C. to 380 ° C. was used as a heavy fraction HLGO, and when the above straight-run gas oil LGO was fractionated, the heavy fraction HLGO was 40 vol% of the straight-run gas oil LGO.

Type and filling of hydrotreating catalyst 20B in first hydrotreating apparatus 20, first hydrotreating catalyst 30B, zeolite-based catalyst 30C, and second hydrotreating catalyst 30D in second hydrotreating apparatus 30 Table 2 shows the ratio.
As shown in FIG.

[0061]

[Table 2]

Under the reaction conditions shown in Table 2, the LHSV per total straight gas oil / total catalyst amount was 2.5 h ^-1 . The weight average reaction temperature of all catalysts was 316.
° C. Further, the first hydrotreating apparatus 20 and the second
The reaction conditions inside the reaction towers 20A and 30A of the hydrotreating apparatus 30 are as shown in Table 3.

[0063]

[Table 3]

(Example 2) In the gas oil desulfurization system described in the embodiment, as shown in FIG. 2, the catalyst configuration in the reaction tower 130A of the second hydrotreating apparatus 130 is changed to the first hydrotreating catalyst 130B. And zeolite-based catalyst 130C
In this system, the straight-run gas oil LGO as the feed gas oil was hydrotreated in the same procedure as in the first embodiment to obtain a desulfurized gas oil DGO.

The straight-run gas oil LGO used is the same as in the first embodiment, and the individual reaction conditions in the first hydrotreating unit 20 and the second hydrotreating unit 130 are as shown in Table 3 of the first embodiment. The same is true. Note that the LHSV per total straight gas oil / total catalyst amount in this example was 2.5 h ⁻¹ and the hydrogen / oil ratio was 320 nm ³ / kl. The weight average reaction temperature of all the catalysts was 316 ° C.

The hydrotreating catalyst 20B in the first hydrotreating apparatus 20, the first hydrotreating catalyst 130B in the second hydrotreating apparatus 130, and the zeolite-based catalyst 13
The type and filling ratio of 0C are as shown in Table 4.

[0067]

[Table 4]

(Comparative Example 1) Straight-run gas oil L similar to that in Example 1
GO was desulfurized by the usual hydrotreating apparatus 120 shown in FIG. 3 to obtain desulfurized light oil DGO. Hydrotreating unit 120
Conditions and Catalyst 120 in Reaction Tower 120A
B is as shown in Table 5.

[0069]

[Table 5]

The components of the desulfurized light oil DGO obtained in Example 1, Example 2 and Comparative Example 1 were analyzed.
The result was as shown in the figure. The desulfurized light oil DGO obtained in Example 1 had a sulfur content of 0.005 wt%, a polycyclic aromatic content of 1.2 vol%, and a hue (ASTM) of 0.2.
The DGO obtained in Example 2 has a sulfur content of 0.010 wt.
%, Polycyclic aromatic content 1.5 vol%, hue (ASTM)
0.3. Compared with Comparative Example 1 which is a normal desulfurization method, the desulfurized gas oil DGO obtained in Example 2 also shows an improvement in the desulfurization rate, but the desulfurized gas oil DGO obtained in Example 1 has extremely high quality and low desulfurization. It was found to be sulfur gas oil, confirming the effects of the present invention.

[0071]

[Table 6]

[0072]

According to the present invention as described above, since a separation step, a light fraction hydrotreating step and a heavy fraction hydrotreating step are provided, the heavy fraction, that is, the high boiling fraction The hard-to-desulfurize component in the fraction can be selectively isomerized (hydrogenated) with a zeolite-based catalyst in the heavy fraction hydrotreating step. Accordingly, by isomerizing the hard-to-desulfurize component, it is possible to easily remove the hard-to-desulfurize component in the heavy fraction by the subsequent hydrogenation treatment, so that the sulfur content of the light oil and the light oil obtained by mixing the heavy oil can be reduced. It can be extremely small.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a structure of a gas oil desulfurization system according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a structure of a gas oil desulfurization system according to a second embodiment.

FIG. 3 is a block diagram illustrating a structure of a gas oil desulfurization system in Comparative Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fractionator (separation process) 20 1st hydrotreating device (light fraction hydrotreating process) 20B Hydrotreating catalyst 30 2nd hydrotreating device (heavy fraction hydrotreating process) 30B 1st hydrogen Catalyst 30C Zeolite catalyst 30D Second hydrotreating catalyst 40 Mixer (mixing process) LGO Straight run gas oil (feed oil light oil) LLGO Light fraction HLGO Heavy fraction

Claims (7)

[Claims] 1. A sulfur content of 0.5 to 2.5 wt% and a boiling point of 150
A separation step of separating a feedstock gas oil at ~ 400 ° C into a light fraction and a heavy fraction; a light fraction hydrotreating step of contacting the light fraction with hydrogen in the presence of a hydrotreating catalyst; In the presence of a hydrotreating catalyst, and a zeolite-based catalyst containing zeolite, the heavy fraction is contacted with hydrogen in this order in a heavy fraction hydrotreating step, and in the light fraction hydrotreating step Light product oil
A mixing step of mixing the heavy product oil generated in the heavy fraction hydrotreating step at an optional ratio. 2. The method for producing a low-sulfur gas oil according to claim 1, wherein the heavy fraction hydrotreating step comprises treating the heavy fraction with a first hydrotreating catalyst, the zeolite-based catalyst, and (2) A method for producing a low sulfur gas oil, comprising contacting hydrogen in this order in the presence of a hydrotreating catalyst. 3. The method for producing a low-sulfur gas oil according to claim 1, wherein the light fraction comprises an end point of 320 to 3 in the separation step.
A method for producing a low sulfur gas oil, which is a fraction at 60 ° C. 4. The method for producing a low-sulfur gas oil according to any one of claims 1 to 3, wherein the sulfur content of the product oil treated with the hydrotreating catalyst preceding the zeolite catalyst is 0.2 wt. % Or less. 5. The method for producing a low-sulfur gas oil according to claim 1, wherein the zeolite-based catalyst is an amorphous inorganic oxide 40 to 99.
a carrier containing at least one metal of Group VI and / or Group VIII of the periodic table in an amount of 0 to 25 wt% in terms of oxide on a carrier containing 1 wt% and 60 wt% of zeolite. A method for producing a low-sulfur gas oil, comprising: 6. The method for producing a low-sulfur gas oil according to claim 1, wherein the zeolite contained in the zeolite-based catalyst has a silica / alumina ratio of 2 to 500. Method for producing low sulfur gas oil. 7. The method for producing a low-sulfur gas oil according to claim 1, wherein the zeolite-based catalyst is obtained by adding the zeolite-based catalyst and the first and second hydrotreating catalysts. 5-6 volume ratio to the total amount of catalyst in the heavy fraction hydrotreating process
A method for producing low-sulfur gas oil, which is 0%.