JP2001089771A - Method for hydrodesulfurization of heavy hydrocarbon oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for hydrosulfurization of heavy hydrocarbon oil (hereafter called heavy oil), capable of producing a product oil having <=0.30 wt.% sulfur content stably for a long time by controlling the reaction temperature increase and catalyst degradation. SOLUTION: This method for hydrosulfurization of heavy oil is capable of producing a product oil having <=0.30 wt.% sulfur content (hereafter called PS portion) by bringing a heavy oil into contact with a catalyst together with hydrogen gas, and is characterized by using a heavy oil raw material wherein the sulfur content in asphaltene (hereafter called AS portion) of the raw material satisfies the following formula (1). Formula (1); AS portion (wt.%)<1.25×PS portion (wt.%)+0.10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hydrodesulfurization of heavy hydrocarbon oil (hereinafter sometimes referred to as "heavy oil"), and more particularly to a sulfur content containing asphaltenes in a heavy oil feedstock. Hereinafter, the content of AS may be regulated.) By controlling the generated oil whose sulfur content (hereinafter, sometimes referred to as PS content) is 0.30 wt% or less, the reaction temperature is increased and the catalyst is deteriorated. The present invention relates to a method for hydrodesulfurization of heavy oil, which can be suppressed and produced stably for a long period of time.

[0002]

2. Description of the Related Art In the hydrodesulfurization process of heavy oil, a residue of atmospheric distillation (AR), a residue of vacuum distillation (VR), or a mixed oil of these and light oil is used as a raw material oil. I have. In recent years, heavy oil feedstocks that can be supplied have a very large amount of sulfur, asphaltenes, and metals due to an increase in intermediate demand and crude oil resources. In order to desulfurize to the target sulfur content level, operation under severe conditions such as raising the reaction temperature is required. Therefore, these are severe raw materials for the heavy oil desulfurization unit due to severe deterioration of the catalyst.

[0003] On the other hand, heavy oil as a product is increasing in demand for heavy oils having a sulfur content of 0.3 wt% or less and further 0.2 wt% or less due to an increase in interest in environmental issues.
Conventionally, in order to produce such heavy oils with low sulfur content, to avoid severe operating conditions and to prevent rapid deterioration of the catalyst, high-quality sulfur-, asphaltene- and metal-free materials have been used. It has been required to use atmospheric distillation residue (AR), and it has been particularly difficult to use vacuum distillation residue (VR) as a raw material for producing such low sulfur heavy oil. Therefore, the production of low-sulfur heavy oil has been limited to those in which the feedstock oil is relatively expensive, and placed a heavy burden on the economy.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for hydrodesulfurization of heavy oil, which comprises reducing the reaction temperature and the deterioration of the catalyst to a product oil having a sulfur content of 0.30% by weight or less. It is an object of the present invention to provide a method capable of stably producing for a long period of time. Still another object of the present invention is to provide a method capable of producing a low-sulfur heavy oil using various feedstocks including a relatively inexpensive feedstock.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on the above-mentioned problems, and as a result, asphaltene-containing sulfur content in the heavy oil feedstock has been changed according to the target sulfur content (PS content) in the produced oil. It has been found that this problem can be achieved by regulating (AS content), and the present invention has been completed based on this finding.

That is, the present invention has the following gist. [1] A heavy hydrocarbon oil (hereinafter, referred to as heavy oil) is brought into contact with a catalyst together with hydrogen gas, and the sulfur content (hereinafter referred to as P
Called S minutes. ) Is a method for hydrodesulfurizing heavy oil to obtain a product oil of 0.30% by weight or less, wherein asphaltene-containing sulfur (hereinafter referred to as AS) is used as a heavy oil raw material.
Which satisfies the relationship of the following formula (1). AS content (wt%) <1.25 x PS content (wt%) + 0.10 ‥‥ (1)

[2] The method for hydrodesulfurization of heavy oil according to [1], wherein a heavy oil raw material whose AS content further satisfies the relationship of the following formula (2) is used. 0.7 × PS content (wt%) <AS content (wt%) ‥‥ (2) [3] As a heavy oil feedstock, a material whose AS content further satisfies the following formula (3) is used. 1) The method for hydrodesulfurization of heavy oil according to the above. 0.9 × PS content (wt%) <AS content (wt%) ‥‥ (3)

[4] The method for hydrodesulfurizing heavy oil according to the above [1], wherein a heavy oil raw material whose AS content further satisfies the following formula (4) is used. 1.0 × PS content (wt%) <AS content (wt%) ‥‥ (4) [5] As the heavy oil feedstock, the one whose AS content satisfies the following formula (5) is used. ] The method for hydrodesulfurizing heavy oil according to any one of [4] to [4]. AS content (wt%) <1.25 x PS content (wt%) ‥‥ (5)

[6] The method for hydrodesulfurizing heavy oil according to any one of [1] to [5], wherein the heavy oil feedstock contains at least 0.5 wt% of asphaltenes which are insoluble in n-heptane. . [7] The method for hydrodesulfurizing heavy oil according to any one of the above [1] to [6], wherein the heavy oil feedstock contains a residue obtained by distillation under reduced pressure.

[0010]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a heavy hydrocarbon oil (heavy oil) is brought into contact with a catalyst together with hydrogen gas to obtain a product oil having a sulfur content (PS content) of 0.30 wt% or less. In the method of hydrodesulfurization of heavy oil, as a heavy oil feedstock,
It is necessary to use one whose asphaltene-containing sulfur content (AS content) satisfies the relationship of the following formula (1). AS content (wt%) <1.25 x PS content (wt%) + 0.10 ‥‥ (1)

The degradation (decrease in activity) of the heavy oil hydrodesulfurization catalyst is caused by the deposition of coke (polycondensed polycyclic aromatic carbonaceous material) and the deposition of metals (mainly vanadium and nickel) on the catalyst. As it happens, the precursor and metal content of coke are high in asphaltene in heavy oil feedstock. Therefore, conventionally, in order to suppress catalyst deterioration and perform long-term continuous operation, a heavy oil feedstock with a low asphaltene content should be selected, and in operation, the asphaltene decomposition rate should be used as an index. It was supposed to be.

In the present invention, as an index for selecting a heavy oil feedstock for producing a target low sulfur heavy oil, or as an index for estimating a possible desulfurization rate for a given heavy oil feedstock, Asphaltene-containing sulfur in heavy oil feedstock is used. That is, the present invention can be used as a raw material for producing a low-sulfur heavy oil even if the heavy oil having a high asphaltene content does not contain a large amount of sulfur contained in the asphaltene. It has been clarified that a heavy oil feedstock having a low sulfur content in asphaltene can suppress catalyst deterioration and perform long-term continuous operation even if the asphaltene decomposition rate is increased.

According to the present invention, the reaction temperature and the catalyst deterioration are significantly reduced by restricting the asphaltene-containing sulfur content (AS content) in the heavy oil feedstock so as to satisfy the following equation (1). The sulfur content (PS content) is 0.30
It is possible to stably produce the produced oil of not more than wt% for a long period of time. AS content (wt%) <1.25 x PS content (wt%) + 0.10 ‥‥ (1) When producing low sulfur heavy oil with a PS content of 0.30 wt% or less, the AS content of the heavy oil feedstock Is higher than the upper limit determined by the formula (1), the reaction temperature must be increased, and coke deposition and metal deposition occur frequently, resulting in a significant decrease in catalyst activity and catalyst life.

A more preferred heavy oil feedstock also satisfies the relationship of the following formula (5).
The reaction temperature can be further lowered, and the deterioration of the catalyst is further suppressed, so that the operation can be performed for a longer period. AS content (wt%) <1.25 × PS content (wt%) ‥‥ (5) Thus, from the viewpoint of lowering the reaction temperature and suppressing catalyst deterioration, the smaller the AS content of the heavy oil feedstock, the smaller the AS content. Although preferred, the effect levels off gradually as the AS content decreases. Further, considering that a heavy oil raw material having a small amount of AS is more valuable and expensive, the heavy oil raw material for fully exhibiting the advantages of the present invention has its AS component sequentially represented by the following formula ( As the relations of 2) to (4) are satisfied, a more preferable embodiment is obtained. 0.7 × PS content (wt%) <AS content (wt%) ‥‥ (2) 0.9 × PS content (wt%) <AS content (wt%) ‥‥ (3) 1.0 × PS content (wt%) <AS content (wt%) ‥‥ (4)

In the present invention, AS of heavy oil feedstock is used.
The term “part” refers to a ratio (unit: wt%) of sulfur contained in asphaltene in the heavy oil feed to the heavy oil feed.
Here, asphaltenes mean heavy oil raw material at 60 ° C.
-Means insolubles when dissolved in heptane.

[0016] The PS content of the produced oil is the sulfur content in the oil component (spilled oil) produced by the hydrodesulfurization reaction. This product oil is then usually separated by distillation into heavy oil and other light fractions. The sulfur content in the produced oil is higher in heavy oil. Therefore, the sulfur content in the heavy oil is somewhat higher than the PS content in each formula of the present invention.

The heavy oil feedstock used in the present invention is not particularly limited as long as the above formula (1) is satisfied. Typically, the content of n-heptane-insoluble matter (asphaltenes) is 0.5% by weight or more, preferably 0.5% by weight or more. Is a hydrocarbon oil containing 1.0 wt% or more, more preferably 2.0 to 7.0 wt%. Typical examples thereof include atmospheric distillation residue oil, vacuum distillation residue oil, asphalt oil, pyrolysis oil, Tar sand oil, etc., and if necessary, these are "lighter hydrocarbon oils" such as straight run (atmospheric distillation) kerosene, catalytic cracked gas oil, straight run gas oil, catalytic cracked heavy gas oil, straight run heavy A mixture of light oil, vacuum distilled light oil, and the like may be used.

In particular, according to the present invention, the vacuum distillation residue oil which has been considered difficult to use in the production of low-sulfur heavy oils is also used as long as the oil satisfies the above formula (1) as a whole. Can be used as all or part of As the mixture with the vacuum distillation residual oil, the above-mentioned "lighter hydrocarbon oil" is preferable in that the AS content of the feedstock oil and the like can be easily adjusted. The mixing amount of the “lighter hydrocarbon oil” is not particularly limited, but is determined according to the properties (such as the AS content) of the vacuum distillation residue oil to be mixed, the viscosity of the target product oil, the sulfur content, and the like. As a practical mixing amount of the “lighter hydrocarbon oil”, 1 to 50% by volume, preferably 10 to 4% by volume of the whole feedstock oil is used.
It is appropriate to set the range to 0% by volume. Particularly preferred among "lighter hydrocarbon oils" are catalytic cracking gas oils. Since the catalytic cracking gas oil has a large amount of aromatic components and a small amount of asphaltenes, the accumulation of carbonaceous material during the desulfurization reaction is small, and the effect of dissolving and removing carbonaceous material is expected.

The hydrodesulfurization catalyst used in the present invention is:
There is no particular limitation as long as it has a hydrodesulfurization function,
In addition, those having functions such as hydrodemetallization, hydrocracking, hydrodenitrogenation, and descaling may be used. Typically, a metal-supported inorganic oxide catalyst supporting at least one metal selected from Group 6 and Groups 8 to 10 of the periodic table can be used.

Examples of the inorganic oxide carrier include alumina, alumina-phosphorus, and alumina-boron carriers (phosphorus, boron and the like mean oxides thereof), those containing alumina as a carrier component, silica, and the like. A carrier such as magnesia, silica-magnesia, zirconia, titania, silica-titania and the like can be used. In particular, those containing alumina as a carrier component can be suitably used.
Further, as the supported metal, molybdenum, tungsten, chromium, nickel, cobalt, iron, platinum, or the like can be used. In particular, those containing molybdenum and nickel can be suitably used. It should be noted that phosphorus and boron are used as carrier components for convenience, but the case where they act as carrier components is not excluded.

Among these, a catalyst in which nickel-molybdenum is supported on an alumina carrier, a catalyst in which nickel-molybdenum is supported in an alumina-phosphorus carrier, and a catalyst in which nickel-molybdenum is supported on an alumina-boron carrier are particularly preferable. When phosphorus is contained as a carrier, the content of phosphorus is desirably 0.1 to 10% by weight, preferably 0.2 to 8% by weight.

The amount of supported metal is from 1 to 25 molybdenum.
wt.%, preferably 4-15 wt%, and 0.5-10 wt%, preferably 1.5 wt%, of cobalt or nickel.
It is desirable that the content of the metal in the catalyst be expressed by w
expressed as t%).

As a process used for the hydrodesulfurization reaction, a fixed bed reactor is generally used, but there is no problem even in a reaction type such as a moving bed or a boiling bed. The flow of the reaction may be an upward flow or a downward flow. The reaction conditions for heavy oil hydrodesulfurization are not particularly limited, and ordinary conditions may be selected. For example, the reaction temperature is 150 to 4
50 ° C, preferably 300 to 430 ° C, reaction pressure is 7 to
22 MPa, preferably 9 to 20 MPa, liquid hourly space velocity (LHSV) of 0.05 to 3.0 / hr, preferably 0.1 to 1.0 / hr, and hydrogen / oil ratio of 100 to 3,000.
0 Nm ³ / kl, preferably 200 to 1,500 Nm ³
/ Kl. In order to keep the sulfur content (PS content) of the produced oil constant during operation, it is usual to increase the reaction temperature in accordance with the deterioration (decrease in activity) of the catalyst.

[0024]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples. Example 1 Vacuum distillation residue (VR) as a heavy oil feedstock
Mixed oil of oil and catalytic cracking light oil (LCO) (mixing ratio VR: LC
O = 85: 15 (volume ratio), sulfur content 3.47 wt%, asphaltene-containing sulfur content (AS content) 0.38 wt%), and a hydrodesulfurization catalyst (alumina carrier with nickel 4 wt% on an oxide basis, molybdenum) In a heavy oil hydrodesulfurization unit packed with a catalyst supporting 10 wt%), continuous operation was performed while adjusting reaction conditions such as reaction temperature so that the sulfur content (PS content) of the produced oil was 0.24 wt%. Carried out.
According to the above formula (1) in the present invention, a feedstock oil suitable for obtaining a product oil having a PS content of 0.24 wt% has an AS content of less than 0.40 wt%. Table 1 shows the properties of the feedstock, Table 2 shows the reaction conditions at the start of operation and the properties of the desulfurized product oil, Table 3 shows the reaction conditions and the properties of the desulfurized product oil on the 30th day of operation start, and Table 4 The table shows the reaction conditions 60 days after the start of operation and the properties of the desulfurized oil.

Comparative Example 1 A mixed oil of vacuum distillation residue (VR) and catalytic cracking light oil (LCO) (mixing ratio VR: LCO = 85: 15 (volume ratio), sulfur content 3.4) as a heavy oil feedstock
A continuous operation was performed in the same manner as in Example 1 except that 5 wt% and an AS content of 0.42 wt%) were used. Table 1 shows the properties of the feedstock, and Tables 2 to 4 at the time of operation start, on the 30th day of operation start,
The respective reaction conditions and properties of the desulfurized product oil on the 60th day from the start of operation are shown.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[Comparison of the results of Example 1 and Comparative Example 1] At the start of the operation, Example 1 using a heavy oil feedstock having a lower AS content and satisfying the above-mentioned formula (1) is better The reaction temperature for producing a product oil having the same PS can be lowered by 10 ° C. as compared with Comparative Example 1 using a heavy oil feedstock that does not satisfy the above formula (1). On the 60th day from the start of the operation, the increase in the reaction temperature required to maintain the PS content of the produced oil at the same level (compared with that at the start of the operation) indicates that the temperature was 10 ° C. in Example 1. On the other hand, in Comparative Example 1, the temperature was 20 ° C., and the reaction temperature at this time was 20 ° C. lower in Example 1. From this, in Example 1 using a stock oil whose AS content satisfies the formula (1) of the present invention,
The difference in AS content is slight (Example 1: 0.38 wt
%, Comparative Example 1: 0.42 wt%), it is understood that the deterioration of the catalyst is much more effectively suppressed.

Example 2 Same as Example 1 except that atmospheric distillation residue oil (AR) (sulfur content: 1.85 wt%, asphaltene-containing sulfur content (AS content): 0.29 wt%) was used as a heavy oil feedstock. In the heavy oil hydrodesulfurization unit, continuous operation was performed while adjusting reaction conditions such as reaction temperature so that the sulfur content (PS content) of the produced oil was 0.16 wt%. In addition,
According to the formula (1) of the present invention, the PS content is 0.16 wt.
% Of the resulting oil has an AS content of 0.3%.
It is less than 0 wt%. Table 5 shows the properties of the feedstock,
Tables 6 to 8 show the respective reaction conditions and the properties of the desulfurized oil at the start of operation, on the 30th day of operation, and on the 60th day of operation.

Comparative Example 2 Atmospheric distillation residue (AR) (1.80 wt% sulfur content, 0.35 AS content) as a heavy oil feedstock
wt%), except that the same continuous operation as in Example 2 was performed. Table 5 shows the properties of the feedstock, and Tables 6 to 8 show the reaction conditions and the properties of the desulfurized product oil at the start of operation, on the 30th day of operation start, and on the 60th day of operation start.

[0033]

[Table 5]

[0034]

[Table 6]

[0035]

[Table 7]

[0036]

[Table 8]

[Comparison of the results of Example 2 and Comparative Example 2] At the start of operation, Example 2 using a heavy oil feedstock having a lower AS content and satisfying the above-mentioned formula (1) has a lower AS content. The reaction temperature for producing a product oil having the same PS can be lowered by 5 ° C. as compared with Comparative Example 2 using a heavy oil feedstock that does not satisfy the above formula (1). On the 60th day from the start of the operation, the reaction temperature required to maintain the PS content of the produced oil at the same level as at the start of the operation is shown. In Example 2, the temperature was 12 ° C., and the reaction temperature at this point was 11 ° C. in Example 2.
° C lower. From this, the difference in the AS content is smaller in Example 2 using the stock oil satisfying the formula (1) of the present invention (Example 2: 0.29 wt%, Comparative Example 2). :
(0.35 wt%), it is understood that deterioration of the catalyst is much more effectively suppressed as compared with Comparative Example 2.

Example 3 A mixed oil of vacuum distillation residue (VR) and catalytic cracking light oil (LCO) (mixing ratio VR: LCO = 85: 15 (volume ratio), sulfur content 3.5) as a heavy oil feedstock
0 wt%, sulfur content containing asphaltene (AS content) 0.2
The same continuous operation as in Example 1 was performed except that 6 wt%) was used. The sulfur content (PS content) of the generated oil is also 0.24wt
%, And the reaction conditions such as the reaction temperature were adjusted. According to the formula (5) of the present invention, a raw material oil suitable for obtaining a product oil having a sulfur content (PS content) of 0.24 wt% is an asphaltene-containing sulfur content (AS content) of 0.30 wt%. Less than. Table 9 shows the properties of the feed oil,
Table 2 shows the reaction conditions and properties of the desulfurized oil at the start of operation, on the 30th day of operation, and on the 60th day of operation.

[0039]

[Table 9]

[0040]

[Table 10]

[0041]

[Table 11]

[0042]

[Table 12]

[Comparison of the results of Example 3 and Example 1] At the start of operation, an example using a heavy oil feedstock having a lower AS content and satisfying not only the expression (1) but also the expression (5). In Example 3, the reaction temperature for producing a product oil having the same PS was higher than that in Example 1 using a heavy oil feedstock in which the AS component satisfied the expression (1) but did not satisfy the expression (5). It can be further lowered by 2 ° C. On the 60th day of operation, the P
Looking at the increase in the reaction temperature required to maintain the S content at the same level as at the start of the operation, the temperature was 10 ° C. in Example 1 but was 9 ° C. in Example 3; Is lower by 3 ° C. in Example 3. From this,
It is understood that in Example 3 using a feed oil having a PS content that also satisfies the formula (5) of the present invention, deterioration of the catalyst was further suppressed.

Example 4 A mixed oil of vacuum distillation residue (VR) and catalytic cracking gas oil (LCO) (mixing ratio VR: LCO = 85: 15 (volume ratio), sulfur content 3.4) as a heavy oil feedstock
A continuous operation was performed in the same manner as in Example 3 except that 6 wt% and an AS content of 0.15 wt%) were used. The reaction conditions such as the reaction temperature were adjusted so that the PS content of the produced oil was also 0.24 wt%. According to the formula (2) of the present invention, PS
A feedstock that is advantageous for obtaining a product oil having a content of 0.24 wt% is one having an AS content of more than 0.16 wt%. Ninth
The table shows the properties of the raw material oil, and Tables 10 to 12 show the respective reaction conditions and the properties of the desulfurized product oil at the start of operation, the 30th day of operation start, and the 60th day of operation start.

[Comparison of the results of Examples 4 and 3] At the start of operation, the reaction temperature of Example 4 using a heavy oil feedstock in a region not satisfying the expression (2) because the AS content was further lower. Is only 1 ° C. lower than that of Example 3 using a heavy oil feedstock in which the AS content is in a range not satisfying the expression (2). On the 60th day of the operation, the increase in the reaction temperature required to maintain the PS content of the produced oil at the same level as at the start of the operation was 6 ° C. in both Examples. The temperature difference is also 1 ° C. From this, AS
In Example 4 using a feed oil whose component is less than the lower limit of the formula (5) of the present invention, the difference in AS component (Example 4: 0.1
(5 wt%, Example 3: 0.26 wt%), it can be understood that the effect of suppressing catalyst deterioration as compared with Example 3 has leveled off. Here, in consideration of the price of the base oil in both cases (the embodiment 4 is about 10% more expensive), it is more advantageous to select the base oil of the embodiment 3 from the viewpoint of economy.

Comparative Example 3 Using the same feed oil and the same heavy oil hydrodesulfurization apparatus as in Example 2, the sulfur content (PS
) Was 0.32 wt% (out of the scope of the present invention), and the continuous operation was performed while adjusting reaction conditions such as reaction temperature. Table 13 shows the properties of the feedstock, and Tables 14 to 16 show the reaction conditions and properties of the desulfurized product oil at the start of operation, on the 30th day of operation, and on the 60th day of operation.

[0047]

[Table 13]

[0048]

[Table 14]

[0049]

[Table 15]

[0050]

[Table 16]

[Comparison of the results of Comparative Example 3 and Example 2] At the start of the operation, the reaction temperature of Comparative Example 3 for the purpose of producing oil having a PS content of 0.32 wt% was 0.16 wt% of the PS content.
Only 5 ° C. lower than that of Example 2 aimed at the oil produced from

On the 60th day from the start of operation, the PS
The rise in reaction temperature required to keep the minutes the same is 6 ° C. for both, and the difference in reaction temperature at this point is also 5 ° C. With this difference, the operation of Example 2 in which a much more valuable product oil having a PS content of 0.16 wt% is obtained from this raw material oil produces a product oil having a PS content of 0.32 wt%. It is understood that the operation is much more economical than the operation of Comparative Example 3.

[0053]

According to the present invention, in a method for hydrodesulfurization of heavy oil, a product oil having a sulfur content (PS content) of 0.30% by weight or less can be used to prevent an excessive rise in reaction temperature and deterioration of a catalyst. It is possible to produce stably for a long period of time without occurrence. Furthermore, low-sulfur oils can be produced economically using a variety of raw oils, including vacuum distillation residual oils.

Claims (7)

[Claims] 1. A heavy hydrocarbon oil (hereinafter referred to as "heavy oil") is brought into contact with a catalyst together with hydrogen gas to obtain a product oil having a sulfur content (hereinafter referred to as "PS content") of 0.30 wt% or less. A method for hydrodesulfurization of heavy oil, characterized by using, as a heavy oil feedstock, one whose asphaltene-containing sulfur content (hereinafter, referred to as AS content) satisfies the relationship of the following formula (1). A method for hydrodesulfurization of heavy oil. AS content (wt%) <1.25 x PS content (wt%) + 0.10 ‥‥ (1) 2. The method for hydrodesulfurization of heavy oil according to claim 1, wherein a heavy oil feedstock whose AS content further satisfies the following formula (2) is used. 0.7 × PS content (wt%) <AS content (wt%) ‥‥ (2) 3. The method for hydrodesulfurizing heavy oil according to claim 1, wherein a heavy oil feedstock whose AS content further satisfies the relationship of the following formula (3) is used. 0.9 × PS content (wt%) <AS content (wt%) ‥‥ (3) 4. The method for hydrodesulfurization of heavy oil according to claim 1, wherein a heavy oil raw material whose AS content further satisfies the relationship of the following formula (4) is used. 1.0 × PS content (wt%) <AS content (wt%) ‥‥ (4) 5. The method for hydrodesulfurizing heavy oil according to claim 1, wherein a heavy oil feedstock whose AS content satisfies the relationship of the following formula (5) is used. AS content (wt%) <1.25 x PS content (wt%) ‥‥ (5) 6. The method for hydrodesulfurizing heavy oil according to claim 1, wherein the heavy oil feedstock contains at least 0.5% by weight of asphaltenes, which are insolubles in n-heptane. 7. The method for hydrodesulfurizing heavy oil according to claim 1, wherein the heavy oil feedstock contains a residue obtained by distillation under reduced pressure.