JPS63156890A - Conversion of heavy oil into light oil with carbonaceous matter formation suppressed - Google Patents

Abstract

PURPOSE:To provide such a process that an asphaltene-contg. heavy oil is hydrocracked, using a hydrogen-donating solvent, to convert into a light oil with carbonaceous matter formation suppressed, thus leading to alleviation of clogging problems caused by said carbonaceous matter. CONSTITUTION:(A) A raw heavy oil containing >=1.0wt% of asphaltene, (B) a hydrogen-donating solvent and (C) a hydrogen-contg. gas are introduced into a solid catalyst-contained hydrocracker in an upstream fixed bed state to carry out hydrocracking at a liquid space velocity <=1hr<-1> and hydrogen consumption >=1Nm<3>/kl-raw oil/%-cracking. Thence, part of the resulting reaction solution and the gas are introduced into a hydrogenation vessel packed with a solid catalyst to perform hydrogenation by feeding hydrogen so as to be <=0.5hr<-1> for liquid space velocity and >=3Nm<3>/kl-raw oil/%-cracking for hydrogen consumption, thus accomplishing the objective conversion of the heavy oil into a light oil.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is a method for hydrogenating heavy oil, particularly heavy oil containing 1.0 wt% or more of asphaltene content, that is, pentane insoluble content, using a hydrogen-donating solvent. It relates to a method of decomposing and making it lighter.

[Prior art and problems to be solved by the present invention] In recent years, the importance of lightening heavy oil has been increasing, and many methods have been proposed for thermal cracking, catalytic cracking, hydrocracking, etc. .

Here, heavy oil refers to 50wt of distillate with a boiling point of 350℃ or higher.
Hydrocarbon oil containing % or more, especially pentane insoluble content of 1.0w
Heavy oil containing t% or more refers to, for example, atmospheric distillation residue obtained from crude oil, vacuum distillation residue, or oil obtained from coal, oil shale, oil sand, bitumen, ultra-heavy crude oil, etc.

Furthermore, the term "lightening" here refers to the purpose of cracking the above-mentioned heavy oil with hydrogenation to obtain light oil containing naphtha, gasoline fraction, kerosene fraction, etc. be.

Generally, when heavy oil is cracked, the most important and troublesome problem is the formation of carbonaceous substances and the resulting clogging of various parts of the equipment. Furthermore, when heavy oil is decomposed using a catalyst, a decrease in the activity of the catalyst becomes an important problem. Furthermore, from an economic point of view, it is important to increase the amount of hydrogen consumed, and these problems become more serious as the feedstock oil becomes heavier and as it becomes lighter.

One known method for solving these problems is to use a hydrogen-donating solvent (for example, US Pat. No. 4,430,197). That is, it is well known that compounds obtained by hydrogenating polycyclic aromatic compounds, such as tetralin, have hydrogen-donating properties, and when heavy oil is hydrocracked using such hydrogen-donating solvents, It is well known that the reaction does not necessarily require a catalyst and that the reaction proceeds at relatively low hydrogen pressure (for example, U.S. Pat. No. 4,294,686 and Qil & (3as
Journal1 magazine, N'OV, 22.1982,
D, 111-116). Furthermore, many attempts have been made to utilize this industrially (for example, US Pat. No. 2,953,513). It is also well known that pyrolysis oil, catalytic cracking oil, hydrocracked oil, etc. contain such substances that have hydrogen donating properties, and that they themselves act as effective hydrogen donating solvents (e.g. U.S. Pat. No. 3,970,545).

However, in these methods, the decomposition reaction takes place efficiently only at relatively high temperatures, so carbonaceous substances or their precursors are produced during decomposition, which can clog various parts of the equipment and impede long-term stable operation. The biggest problem is hindrance.

Furthermore, Japanese Patent Application Laid-Open No. 61-235492 discloses that a partition made of a solid catalyst is installed inside the reaction tower to obtain the necessary liquid flow rate by generating a natural circulation flow and to avoid blockage caused by carbonaceous substances. At the same time, a method is disclosed in which a catalyst having a hydrogenation function is present in the reaction column to efficiently carry out the decomposition reaction and to significantly reduce the production of carbonaceous substances. However, in this method, although the production of carbonaceous matter and its precursors can be suppressed for the most part, a small amount of carbonaceous matter and its precursors are still produced, which causes the problem of clogging of subsequent equipment, piping, etc.

[Object of the Invention] The object of the present invention is to suppress the formation of carbonaceous substances in the decomposition of heavy oil containing asphaltene content of 1.0 wt% or more using a hydrogen-donating solvent, and to solve the problem of clogging caused by carbonaceous substances. The objective is to provide an efficient method for reducing weight.

That is, in the present invention, 50 vol% of the internal volume of the decomposition reactor
The asphaltene (asphaltenyl) Pentane insoluble matter) 1. A feedstock heavy oil containing Owt% or more, a hydrogen-donating solvent, and a hydrogen-containing gas are introduced, and the feedstock heavy oil is decomposed at a liquid hourly space velocity of 1 (hr-1) or less relative to the solid catalyst in the cracking reactor. A part of the liquid discharged from the decomposition reactor is used as the circulating liquid, and a part of the liquid and the gas are stored in a packed bed containing a solid catalyst of 50 vol% or more of the internal volume of the reactor, and are kept at a lower temperature than the decomposition reactor. The feedstock heavy oil is hydrogenated by passing it through the hydrogenation reactor at a liquid hourly space velocity of 0.5 (hrl) or less relative to the solid catalyst, and the hydrogen consumption in the cracking reactor is 1Nm3/kl-feedstock oil/ Hydrogen is added so that the hydrogen consumption in the hydrogenation reactor is 8.3 Nm3/kl-stock oil/%-decomposition rate or more, and the carbon precursor insoluble in toluene is added in the decomposition reactor. To provide a method for lightening heavy oil, which suppresses the formation of toluene and hydrogenates a carbon precursor insoluble in toluene in a hydrogenation reactor to convert it into a substance soluble in toluene. It is in.

[Means for Solving the Problems] The present invention relates to a method of decomposing heavy oil using a hydrogen-donating solvent, which suppresses the production of carbonaceous substances.

The present inventors conducted numerous experiments regarding the production of carbonaceous substances during heavy oil decomposition and discovered the following facts.

1) In order to suppress the production of carbonaceous substances in the decomposition reactor, it is most effective to coexist a hydrogen-donating solvent and a catalyst.

2) At this time, it is effective for the presence of a certain amount of catalyst in the decomposition reactor to suppress carbonaceous production.

3) The more active the catalyst is, the stronger it is and the more effective it is to have hydrogenation ability.

4) By suppressing the ratio of the raw material heavy oil throughput to the catalyst in the cracking reactor (ie, liquid hourly hourly velocity LH8V) to a certain level or more, the generation of carbonaceous substances is suppressed.

5) In order to avoid clogging due to carbonaceous matter in the decomposition reactor, it is effective to increase the linear velocity of the liquid passing through the catalyst layer in the decomposition reactor.

6) The most appropriate condition for the catalyst in the cracking reactor is a fixed bed.

7) By satisfying each of the above conditions, the production of carbonaceous matter and its precursors in the decomposition reactor was suppressed, but the small amount of carbonaceous matter and its precursors that were still produced were maintained under appropriate conditions. By being hydrogenated in the subsequent hydrogenation reactor, it is converted into a substance soluble in toluene.

8) Appropriate conditions for the hydrogenation reactor include the presence of a certain amount of catalyst relative to the internal volume of the reactor, the suppression of LH8V, the strong hydrogenation activity of the catalyst, and the temperature being close to the decomposition reactor temperature. The temperature is comparatively low.

The present inventors have completed the present invention based on these experimental facts. That is, the present invention was completed by organizing the results of many experiments and taking economic efficiency as an industrial device into consideration.

FIG. 1 shows an example of the form of the reaction part when carrying out the present invention. Raw material heavy oil 1 , hydrogen-donating solvent 2 and hydrogen-containing gas 3 are introduced into cracking reactor 4 . The decomposition reactor contains a solid catalyst in an amount of 50 yo1% or more of the internal volume of the reactor. A part of the decomposed liquid, carbonaceous material and hydrogen-containing gas are not separated and are converted into decomposition reaction products 5.
It is introduced into the hydrogenation reactor 6 as a hydrogenation reactor.

On the other hand, in order to avoid an increase in pressure loss within the decomposition reactor, it is necessary to maintain the linear velocity of the liquid passing through the fixed bed at 2 cm/sec or more, preferably at 3.5 cm/sec or more. This is accomplished by providing an external circulating liquid stream to the cracking reactor.

Therefore, a part of the liquid decomposed in the decomposition reactor 4 is preferably introduced into the decomposition reactor 4 as a circulating liquid by a forced means such as a circulation pump 8 after separating the hydrogen-containing gas. Note that if the hydrogen-containing gas is small, it is not necessary to separate it from the circulating liquid stream.

A catalyst occupying 50 vol% or more of the internal volume of the reactor is housed in the hydrogenation reactor. Although the carbonaceous substances and their precursors produced in the cracking reactor are suppressed by the coexistence effect of the hydrogen-donating solvent and the catalyst, a small amount is still produced. Carbonaceous substances and their precursors produced in this decomposition reactor are hydrogenated and solubilized in a hydrogenation reactor. Therefore, the hydrogenation reactor reaction product 7 does not substantially contain carbon or its precursor. In industrial equipment, the hydrogenation reactor reaction product 7 is separated into various fractions by a rectification device, etc., and the hydrogen-donating solvent is recovered.
It is generally used cyclically.

The type of cracking reactor of the present invention is a conventional fixed bed containing a solid catalyst with upward flow of gas and liquid.

Moreover, the reactor described in JP-A-61-235492 can be used.

The type of hydrogenation reactor of the present invention is a conventional fixed bed containing a solid catalyst in the form of a packed bed.

In the present invention, the amount of catalyst in the decomposition reactor is 20 vol% or more of the internal volume of the reactor, preferably 30 to 95 vol%.
It is in the range of 1%. If the amount is less than 20 vol%, the effect of adding the catalyst is small, and the effect of suppressing carbonaceous production is small.

On the other hand, in a hydrogenation reactor, 50 vol% of the reactor internal volume
As mentioned above, it is preferably in the range of 60 to 95 vol%.

If it is less than 50 vol%, the reactor volume will be wasted, which is not preferable from the economic point of view.

Generally, when cracking heavy oil, the most serious problem is the formation of carbonaceous matter and the resulting clogging.

Although the problem can be alleviated to some extent by using a hydrogen-donating solvent, carbonaceous substances are still generated, which clog the inside of the reaction vessel, each device, and the piping, and prevent stable operation. Generally, when a hydrogen-donating solvent is used, decomposition is carried out without a catalyst. However, by using a catalyst having a hydrogenation function at this time, the production of carbonaceous substances and their precursors can be significantly suppressed. Further, as the catalyst used at this time, a catalyst having a hydrodemetalization function is preferable. In other words, at the same time as heavy oil is decomposed, heavy metals such as vanadium and nickel contained in the heavy oil are removed and adhere to the catalyst, reducing the amount of heavy metals entering the subsequent hydrogenation reactor, thereby increasing the activity of the catalyst in the hydrogenation reactor. Deterioration is largely prevented.

Further, at this time, it is necessary that the activity of the catalyst in the decomposition reactor is higher than a certain level. In other words, it is effective in suppressing carbonaceous production to have a relatively large amount of catalyst in the cracking reactor and to keep the ratio of the amount of feedstock heavy oil processed to the amount of catalyst in the cracking reactor, that is, the liquid hourly space velocity, to a relatively low level. be.

In other words, when currently available catalysts are used, the liquid hourly space velocity in the decomposition reactor must be set to below Bhr-+), preferably from 0.1 to 0.8 (hr-+). In addition, in the hydrogenation reactor, the liquid hourly space velocity is set to 0.5 (
hr-+) or less.

In the present invention, hydrogen consumption is the best indicator of the degree of suppression of carbonaceous production. That is, a large amount of hydrogen consumption means that decomposition products are hydrogenated and stabilized, and this is considered to represent the function of the catalyst.

In general, carbonaceous substances and their precursors are toluene insoluble (w
t%). As a standard for stable operation without the problem of clogging due to carbonaceous matter, the toluene insoluble content in the cracking reactor outlet liquid is 1 wt% or less, and the toluene insoluble content in the hydrogenation reactor outlet liquid is 0.05 wt% or less. Then, the hydrogen consumption in the decomposition reactor is 1Nm3
/kl - feedstock oil / % - cracking rate (hydrogen consumption per 1% cracking rate) or more, preferably 1.2 to 1 ONm 3 /
It is necessary to add hydrogen of kJ - feedstock oil/% - cracking rate, and the hydrogen consumption in the hydrogenation reactor is 3Nm3/kl -stockstock oil/% - cracking rate or more, preferably 5 to 15 ONm It is necessary to add 3/kJ-feedstock oil/%-decomposition rate of hydrogen.

Here, the decomposition rate is defined as follows.

[Total amount of decomposition products (a) - ff1 (q) of the boiling point higher than the initial boiling point of the feedstock oil in the decomposition products]/Feedstock oil (g) x 100 In order to prevent clogging in the decomposition reactor, it is necessary to Fluidizing the catalyst in the reactor is also effective, but is undesirable because it complicates the equipment and reduces catalyst concentration. When heavy oil is cracked in the presence of a hydrogen-donating solvent and a catalyst, the carbonaceous substances or their precursors produced are fine particles and are easily carried away by the liquid flow. Therefore, in order to avoid clogging in the decomposition reactor, it is not necessary to fluidize the catalyst particles, and clogging can be avoided by maintaining the linear velocity of the liquid in the decomposition reactor at 2 cm/sec or more.

Further, the carbonaceous material or its precursor carried out from the decomposition reactor in this manner is solubilized by being subjected to hydrogen treatment in a subsequent hydrogenation reactor. This is a very important fact experimentally discovered by the present inventors, and is characterized in that the decomposition in the first stage is carried out in the coexistence of a hydrogen-donating solvent and a catalyst. By combining these facts, it has become possible to substantially eliminate the production of carbonaceous matter, which was unavoidable during conventional heavy oil cracking.

When decomposition is carried out in the presence of a hydrogen-donating solvent and catalyst,
The reaction proceeds at relatively low temperatures and low pressures. Therefore, unlike conventional decomposition using hydrogen-donating solvents, high temperatures are not required, and in the case of the method of the present invention, the temperature of the decomposition reactor can be in the range of 380°C to 470°C. Further, since the hydrogen-donating solvent is present, it is not necessary to increase the hydrogen pressure too much, and 30 to 150 kg/cIi·g is sufficient.

On the other hand, the temperature inside the hydrogenation reactor needs to be kept lower (10 to 80°C) than the temperature of the decomposition reactor. The reason for this is to hydrogenate and solubilize a small amount of carbon precursor produced in the decomposition reactor, and to prevent the production of carbon precursor in the hydrogenation reactor.

The temperature inside the hydrogenation reactor is 330-440 °C, and the reaction pressure is 30-150 kGl/ci-(l).

In the present invention, the amount of the hydrogen-donating solvent added is in the range of 0.3 to 3 (wt ratio), preferably 0.5 to 2 (wt ratio) as a solvent ratio (solvent/raw oil).

In the subsequent hydrogenation reactor, hydrogenation of the cracked oil and the hydrogen-donating solvent are mainly carried out. This hydrogenation reaction hydrogenates and solubilizes the carbonaceous material or its precursor produced by the previous decomposition reaction, and at the same time hydrodesulfurizes the oil lightened by the decomposition, and hydrorefines the hydrogenated membrane containing nitrogen. will be held.

As the hydrogen-donating solvent used in the present invention, a hydride of a polycyclic aromatic hydrocarbon or a hydrocarbon containing 30 wt % or more of a hydride of a polycyclic aromatic hydrocarbon can be used.

The polycyclic aromatic hydrocarbons mentioned here are 2 to 6 rings, preferably 2 to 4 rings, such as naphthalene, anthracene, phenanthrene, pyrene, naphthacene, chrysene, benzopyrene, perylene, bicene, etc., or derivatives thereof. Examples include aromatic hydrocarbons and derivatives thereof.

Furthermore, those with a boiling point of 150 to 500°C and containing 30 wt% or more of polycyclic aromatic hydrocarbon hydrides are also effective as hydrogen-donating solvents, such as those used in catalytic cracking equipment (FCC).
Various products obtained from petroleum refining equipment such as cycle oil, bottom oil of catalytic reforming equipment, bottom oil of naphtha pyrolysis equipment, and various products obtained from coal such as tar oil, anthracene oil, creosote oil, coal liquefied oil, etc. Examples include products obtained from tar sands, oil shale, bitumen, and the like.

The catalyst used in the present invention is not particularly limited, and commonly used catalysts can be used, but the catalyst used in the decomposition reactor must have a hydrodemetalization function, It is preferable that the activity is less likely to decrease due to attachment of heavy metals such as nickel. Further, the catalyst used in the subsequent hydrogenation reactor must have a hydrodesulfurization function, and a so-called desulfurization catalyst can be used. These solid catalysts include alumina, silica, silica-alumina, alumina-boria, and silica-alumina.
Inorganic substances such as magnesia, silica-alumina-titania, natural and synthetic zeolites, Group II such as nickel and cobalt, and Group VIB such as molybdenum and tungsten.
Examples include catalysts supporting group metal oxides or sulfides.

Although the shape of the solid catalyst particles is not particularly limited, for example, a spherical catalyst, an extrusion molded catalyst, a compression molded catalyst, etc. are used.

The particle diameter of the catalyst is 0.01 to iomm, preferably o
, i to 5# are desirable.

The hydrogen-containing gas used in the present invention refers to 70wt of hydrogen gas.
% or more is preferable, and for example, a hydrogen-containing gas from a reformer is used.

[Example 7] The present invention will be specifically described below based on Examples and Comparative Examples.

Example 1 An experiment was conducted using the system diagram shown in FIG. 1 for the purpose of lightening Arabian Heavy vacuum residual oil by the method of the present invention. The cracking reactor was an upflow fixed bed with external circulation of liquid, and the hydrogenation reactor was a downflow fixed bed. The properties of the raw oil are shown in Table 1, the shape of the reactor is shown in Table 2, and the operating conditions are shown in Table 3.
Shown in the table.

Tetralin was used as the hydrogen-donating solvent, and the raw oil and tetralin were charged into the decomposition reactor at a wt ratio of 1:1. After collecting the reaction product and separating the tetralin, the properties of the product were measured. It was operated continuously for 720 hours,
There was no increase in pressure loss.

The properties of the products at the exits of the cracking reactor and hydrogenation reactor are shown in Table 1 together with the properties of the raw oil. In addition, since it is difficult to measure carbonaceous substances, the toluene-insoluble content is shown.

The catalyst used was a commercially available 1/32-inch extruded catalyst in which cobalt and molybdenum were supported on a silica-alumina carrier. Furthermore, after the experiment was completed, the apparatus was opened and inspected, but no accumulation of carbonaceous substances was observed in the reactor or piping.

Comparative Example 1 As in Example 1, an experiment was conducted to lighten Arabian Heavy vacuum residual oil. The reactor and other experimental equipment are as in Example 1.
However, no catalyst was present in the decomposition reactor, and decomposition was performed using only a hydrogen-donating solvent (tetralin). External circulation of the liquid was carried out in the same manner as in Example 1, but after 120 hours of operation, the cracking reactor outlet piping became clogged with the hydrogenation reactor catalyst layer, and the pressure loss increased, so the experiment was discontinued. Table 1 shows the properties of the products at the exits of the cracking reactor and hydrogenation reactor.

Furthermore, when the apparatus was opened and inspected after the experiment was completed, carbonaceous substances were found to have accumulated in the piping after the hydrogenation reactor.

=19- The following is considered from Example 1 and Comparative Example 1.

1) In the cracking reactor, by coexisting a hydrogen-donating solvent and a catalyst, increasing the catalyst occupancy in the reactor, and reducing the liquid hourly space velocity of the feedstock heavy oil relative to the catalyst,
The addition of hydrogen to the decomposition products is promoted, and the generation of toluene-insoluble matter (carbon precursor) is significantly suppressed. That is, from Table 1: As is clear, the toluene insoluble content in the decomposition reactor was Example 1 <Comparative Example 1.

2) By introducing the reaction product of the cracking reactor into the subsequent hydrogenation reactor, toluene insoluble matter is reduced.

As is clear from Table 1, in Example 1 and Comparative Example 1, the toluene insoluble matter at the hydrogenation reactor outlet is reduced compared to the cracking reactor outlet.

3) According to the method of the present invention, the production of carbonaceous precursors in the decomposition reactor can be suppressed, and the amount of toluene insoluble matter at the outlet of the hydrogenation reactor can be reduced to zero (see Table 1).

4) A small amount of carbonaceous material or its precursor is produced in the decomposition reactor, but by keeping the linear velocity of the liquid at 2 cm/sec or more, no increase in pressure loss occurs in the decomposition reactor (Example 1 Experiment) result).

5) There is no increase in pressure loss in the hydrogenation reactor catalyst layer.

There is no increase in pressure loss within the hydrogenation reactor because carbonaceous production is suppressed in the cracking reactor and the carbonaceous precursor is solubilized within the hydrogenation reactor.

As is clear from the above results, the method of the present invention suppresses the formation of carbonaceous matter, eliminates the problem of clogging, and enables stable operation over a long period of time.

[Effects of the Invention] The effects of implementing the present invention are as follows: 1) Generation of carbonaceous material or its precursor in the decomposition reactor is suppressed.

As mentioned above, by allowing a hydrogen-donating solvent and a catalyst to coexist, allowing a certain amount of catalyst to be present, and keeping LH8V low, the production of carbonaceous substances or their precursors is improved compared to the case where no catalyst is present. It is possible to suppress it to 1/10 or less.

2) Clogging in the cracking reactor is avoided.

As mentioned above, since the generation of carbonaceous substances or their precursors in the decomposition reactor is small and the particles are fine,
By keeping the linear velocity of the liquid at 2 cm/sec or more, increased pressure loss is avoided.

3) Clogging of piping and equipment between the decomposition reactor and hydrogenation reactor is avoided.

In conventional methods, it was necessary to remove solid particles (carbonaceous material) after the cracking reactor.

However, in the method of the present invention, carbonaceous material or its precursor may be introduced into the subsequent hydrogenation reactor, so removal of solid particles is not necessarily required as in conventional methods. This simplifies the piping between the decomposition reactor and the hydrogenation reactor and prevents clogging.

4) No clogging in the hydrogenation reactor.

A catalyst is housed in a packed bed in the hydrogenation reactor. Therefore, in the conventional method, an increase in pressure loss in the catalyst layer was a problem, but in the method of the present invention, the pressure loss in the hydrogenation reactor is reduced because the carbonaceous material or its precursor is solubilized. Does not increase.

5) There is no problem of clogging in equipment and piping after the hydrogenation reactor. As described above, since the carbonaceous material or its precursor is solubilized in the hydrogenation reactor, substantially no solid matter is present in the subsequent piping and equipment. therefore,
The problem of clogging, which was a serious problem in the past, is resolved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the invention in detail. 1: Feedstock heavy oil, 2: Hydrogen-donating solvent, 3: Hydrogen-containing gas, 4: Cracking reactor, 5: Cracking reactor reaction product, 6: Hydrogenation reactor, 7: Hydrogenation reactor reaction product Item 8.9: Circulation pump. Procedural amendment stamp November 24, 1985 Director General of the Patent Office Kunio Ogawa 1, Indication of the case 1986 Patent Application No. 301724 2, Name of the invention Heavy oil that suppresses the formation of carbonaceous substances Relation to the case of the person making the amendment 3. Patent applicant address: 3-12 Nishi-Shinbashi-chome, Minato-ku, Tokyo Name (
444) Japan Oil Co., Ltd. Representative Yasuoki Kenuchi 4, Agent 105 Address Toranomon Electric Building, 2-8-1 Toranomon, Minato-ku, Tokyo Telephone (501) 9370 Name (6899) Patent Attorney Tatsuo Ito 5, Amendment In the subject specification, "Detailed Description of the Invention" and [5 of Drawings]
, Contents of amendment 1, page 11, line 15 and line 16 of the specification “20
Correct ``vol%'' to ``r50vol%''. 2. Change “30-95” from page 11, line 15 of the same book to “50-95”.
Corrected to 95. 3. “8, 9: Circulation pump” on page 27, line 18 of the same book.
Correct it to "8: Circulating pump, 9: Circulating fluid."that's all

Claims (1)

[Claims] 1. A solid catalyst containing 50 vol% or more of the internal volume of the decomposition reactor in the form of an upward flow fixed bed, and the linear velocity of the liquid passing through the fixed bed is 2 cm/sec or more. A raw material heavy oil containing 1.0 wt% or more of asphaltene (pentane insoluble matter), a hydrogen-donating solvent, and a hydrogen-containing gas are introduced into a cracking reactor having an external circulating liquid flow, and the raw material heavy oil is decomposed into the reactor. The liquid hourly space velocity for the solid catalyst is 1 (hr^-^1)
A part of the liquid decomposed below and discharged from the decomposition reactor is used as the circulating liquid, and a part of the liquid and the gas are stored in a packed bed with a solid catalyst of 50 vol% or more of the internal volume of the reactor,
In the hydrogenation reactor, which is kept at a lower temperature than the cracking reactor, the liquid hourly space velocity of the feedstock heavy oil relative to the solid catalyst is set to 0.5 (hr^-^
1) Hydrogenation is performed through the following steps, and the hydrogen consumption in the cracking reactor is 1Nm^3/kl-feedstock oil/%-decomposition rate or more, and the hydrogen consumption in the hydrogenation reactor is 3Nm^3/
kl - Feedstock oil / % - Hydrogen is added to achieve a cracking rate or higher, suppressing the production of toluene-insoluble carbon precursors in the cracking reactor, and suppressing the toluene-insoluble carbon precursors in the hydrogenation reactor. A method for lightening heavy oil, which is characterized by hydrogenating it and converting it into a substance soluble in toluene. 2. The method according to claim 1, wherein the hydrogen-donating solvent is a hydride of a polycyclic aromatic hydrocarbon. 3. The method according to claim 1, wherein the hydrogen-donating solvent is a hydride of a hydrocarbon oil having a boiling point of 150 to 500°C and a polycyclic aromatic hydrocarbon content of 30 wt% or more. 4. The method according to claim 1, wherein the catalyst accommodated in the decomposition reactor has a hydrodemetalization function. 5. The method according to claim 1, wherein the catalyst accommodated in the hydrogenation reactor has a hydrodesulfurization function. 6. The method according to claim 1, wherein the temperature in the decomposition reactor is 380 to 470°C and the reaction pressure is 30 to 150 Kg/cm^2·g. 7. The temperature in the hydrogenation reactor is 330 to 440 °C,
The method according to claim 1, wherein the reaction pressure is 30 to 150 Kg/cm^2.g.