JPH0135035B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method for converting coal into liquid hydrocarbon oil, and more specifically, after mixing finely pulverized coal with medium oil to form a slurry,
This invention relates to a method for efficiently liquefying water through stage hydrogenation treatment. In recent years, despite the remarkable increase in demand for oil, the discovery and development of new oil fields has shown a tendency to reach a plateau, and thus a global energy shortage is becoming a problem. For this reason, research and development on new or alternative energy has become active, and many processes are being considered for producing alternative fuels through gasification and liquefaction of coal, which has the largest reserves among fossil energy sources. There is. The production of natural gas alternative fuels through the gasification of coal is possible because coal with a high ash content and a wide range of properties can be used as a raw material, and it is also possible to apply coal gasification technology that has been developed for a long time. It is said to be the most technically complete and reliable. However, the large-scale production of alternative fuels from coal by or through the gasification process (1) consumes a large amount of expensive oxygen in the gasification process, and the consumed oxygen is reused as an energy source; (2) Coals contain large amounts of heteroelements such as N, O, and S, and therefore, it is extremely complicated and technically demanding to remove these compounds contained in the generated gas and obtain purified gas. Requires a difficult process; (3) Since the product is a gas, it is not suitable for storage and long-distance transportation; (4) A more complicated process is required to liquefy via gasification. It is not necessarily considered to be technically or economically advantageous. On the other hand, the direct liquefaction method by hydrotreating coal (1) consumes a large amount of hydrogen; (2) the hydrogenation reactivity of coal is low and varies widely depending on the type, production area, etc.; (3) The ash content in liquefied oil is extremely fine (several microns to several tens of microns), making solid-liquid separation technically difficult; It has been pointed out that the process has many disadvantages, such as the need to process the raw materials and products simultaneously; However, (1) a liquid fuel that is most similar in composition and properties to petroleum, whose resources are currently being depleted, can be obtained; Therefore, refining
Conventional systems for petroleum can be used almost unchanged in all aspects such as transportation, storage, and consumption, and the social and economic benefits of this are thought to be enormous; (2) Although coal contains a considerable amount of hydrogen, (H/C atomic ratio = 0.5 to 1.0), a considerable portion of these is contained in the liquefied oil along with the hydrogen “consumed” in the hydrogenation and liquefaction process, so it is effectively used as an energy source; (3 ) The hetero elements in coal can be easily separated into gas and liquid as H ₂ S, NH ₃ , H ₂ O, etc.;
For this reason, the direct coal liquefaction method is considered to be superior in principle to the gasification method, at least in terms of overall economic efficiency. For this reason, many processes have been proposed for direct liquefaction of coal since ancient times, and some have already been implemented industrially. Liquefaction methods based on direct hydrotreatment of coal are broadly classified into non-catalytic methods and catalytic methods. Although the former has features such as not requiring a catalyst and low hydrogen consumption, (1) the produced oil contains a lot of nitrogen, sulfur, oxygen, asphaltenes, etc., and has a large amount of residual carbon, so it is difficult to refine it into high-quality oil. There are many drawbacks mainly regarding the properties of the product, such as: (2) the product has a high proportion of pitch-like products and the yield of distillate is low; In order to compensate for these drawbacks, for example, in the SRC method developed in the United States, the ash-rich residue separated from the liquefied product is recycled to the hydrotreating process, thereby utilizing the catalytic action of coal ash. By doing so, it increases denitrification and desulfurization rates, etc.
Efforts are being made to improve the yield of liquefied oil. In addition, in the EDS method (exon donor solvent method), coal is extracted and liquefied using a so-called hydrogen donor solvent such as tetralin under hydrogen pressure, and the liquefied oil obtained by solid-liquid separation of ash and unreacted coal. is hydrogenated using a fixed catalyst bed. In this two-stage hydrotreating method, high-quality liquefied oil is separated from the hydrotreated oil, and the donor solvent is recovered and recycled as is to the extraction and liquefaction process. In this method, since the catalyst is used indirectly, deterioration due to ash in the coal can be avoided, and liquefied oil of relatively high quality can be obtained. However, these non-catalytic methods are not necessarily sufficient in terms of liquefaction rate and properties of liquefied oil. In contrast, so-called catalytic methods have been proposed in the past because they are expected to have a high yield of liquefied oil and provide high-quality oil.
Among these, the Bergius method has been proposed for the longest time and was temporarily implemented industrially. This method is a method for hydrocracking a coal-media oil slurry at high temperature and high hydrogen pressure in the presence of an inexpensive, disposable liquid-phase suspension catalyst. However, although this method is inexpensive, it requires a large amount of catalyst, and requires treatment to make the waste catalyst, along with the coal ash, non-polluting. On the other hand, H-coal method (H-
In the Coal process, a coal-media oil slurry is hydrocracked using a boiling catalyst bed to obtain synthetic crude oil or heavy fuel oil, depending on the severity of the reaction. This method is a development of the ebullated bed method, which has already been implemented industrially as a hydrodesulfurization method or hydrocracking method for heavy oil, but it requires separation of the catalyst from the ash in the coal or wear of the catalyst. There are many unresolved technical issues such as deterioration and deterioration. In the Synthoil process, a coal-media oil slurry is hydrocracked under highly turbulent conditions using a bed of fixed catalyst. One of the features of this process is that very high quality synthetic crude oil can be obtained directly.
The catalyst bed is easily blocked by ash in the coal,
Further, there are drawbacks such as significant wear and deterioration of the catalyst. As an improved method of the direct liquefaction of coal using the classical Bergius method, Japanese Patent Application Laid-Open No. 106709/1983 discloses a method using a catalyst smaller than coal ash particles. According to this method, coal ash and catalyst are separated and recovered from coal liquefied oil by utilizing differences in particle size, and mainly the liquefied oil containing the catalyst is recycled to the hydrotreating process. In connection with this, JP-A-53-106708 describes a method for producing a fine catalyst for coal liquefaction. However, since the catalyst obtained by this method is used in an unsupported state, the catalytic metal is not sufficiently dispersed, and therefore it is not necessarily expected to have sufficient activity and toxicity resistance. In JP-A-54-83908, in order to improve the donor solvent method, a slurry of donor solvent and coal powder was prepared at high temperature and under high hydrogen pressure.
A method of hydroprocessing using a fixed catalyst bed with increased porosity is presented. However, all of these conventionally known direct liquefaction methods for coal are not necessarily sufficient in terms of liquid yield, properties of liquefied oil, catalyst deterioration, ash separation method, and the like. The inventors related to the direct liquefaction method of coal: (1) the structure of coal and the hydrocracking reaction mechanism; (2) the contribution or effect of the catalyst to each step of the coal liquefaction reaction;
(3) Deterioration mechanism of the catalyst; (4) Properties of ash in coal and liquefied oil; As a result of many studies, we have developed an improved method that has many advantages over conventional methods. It is something. One of the characteristics of the method of the present invention is that the coal-media oil slurry is hydrocracked in the presence of a metal-supported ultrafine particle catalyst, and the resulting oil is separated into solid-liquid, and then, if necessary, a metal-supported acidic carrier is used. Hydrotreating is performed using a fixed bed filled with a catalyst to remove nitrogen, sulfur, oxygen, etc. from the liquefied oil, and at the same time, the fine coal particles are hydrogenated and liquefied, and then the main product is separated from light oil, which is then turned into fine solids. The objective is to circulate at least a part of the heavy oil containing the oil to the hydrocracking process. Another feature is that in the solid-liquid separation step, at least a portion of the fine solids are contained in the treated oil with a reduced solid content concentration, and are substantially recycled to the hydrocracking step together with the heavy oil. The method of the present invention includes
It is characterized in that in the first hydrotreating step, a coal hydrocracking reaction is mainly carried out, and in the second hydrotreating step, a liquefied oil hydrorefining reaction is mainly carried out. Generally, in the hydrotreating process, the reaction tube is extremely prone to contamination due to adhesion of coke or pitch, but in the hydrotreating process of the method of the present invention, the heavy oil recycled from the light oil separation process is solidified. Since it contains fine solids that overflowed during the liquid separation process, this has the effect of significantly suppressing the adhesion of coke and the like to the reaction tube. Furthermore, the heavy oil that is circulated to the first hydrotreating step is
Since it has been substantially hydrotreated in advance in the second hydrotreating step, it improves the coal liquefaction rate together with the fine solid content contained therein, and further contributes to suppressing coke adhesion within the reaction column. One of the embodiments of carrying out the method of the present invention is one of the medium oils.
As a part, petroleum residue oil may be used together with the heavy oil recycled from the light oil separation process. In this method, by using petroleum-based residual oil as a part of the medium instead of coal-based oil, not only the difficult-to-process petroleum-based residual oil is simultaneously converted into high-quality light oil, but also solid-liquid separation is possible. Promoting effects are brought about.
Therefore, the use of petroleum-based residual oil as part of the medium oil can extend the plugging life of the fixed bed in the second hydrotreating process, and/or can reduce the solid content concentrated oil and recycled heavy oil from the solid-liquid separation process. The yield of light oil is improved because the amount of oil drawn out of the system is reduced. The inventors have found that in the presence of a metal-supported particulate catalyst, even under severe reaction conditions, slurry phase hydrogenation alone can reduce nitrogen, sulfur, oxygen, etc. in liquefied oil, especially heavy components. It is very difficult to reduce heteroelements. However, the produced oil from the first hydrotreatment step in the slurry phase,
Further hydrotreating using a fixed bed did not significantly increase the yield of light oil, but it was found that nitrogen, sulfur, oxygen, etc. were significantly reduced, and high-quality light oil was obtained. In particular, by using a metal-supported acidic carrier catalyst as a fixed bed catalyst, a significant reduction in nitrogen content, which is the most difficult to remove from liquefied oil, is observed.
As is well known, in the donor solvent method, etc.
Light components with a specific boiling point range recovered from the hydrotreated oil are recycled as a medium oil for extraction and liquefaction, but in the method of the present invention, the residual oil containing substantially fine solids is used as the medium in the first hydrotreatment step. This method circulates it as oil. The inventors found that compared to the heavy oil recovered from the product oil of the first hydrotreatment step,
The heavy oil separated and recovered from the product oil subjected to multi-stage hydrotreating has a low content of hetero elements such as nitrogen and sulfur and coke precursors such as asphaltenes,
It is acknowledged that the liquefaction rate in the first hydrogenation step is high and that there is little adhesion of coke, etc. to the inner wall of the reaction cylinder. Therefore, by circulating the heavy oil containing fine solids from the second hydrotreating process, it becomes possible to use harsh reaction conditions in the first hydrotreating process, and lightening is promoted. Then, the solid-liquid separation in the solid-liquid separation step could be substantially facilitated. Circulating the treated oil with reduced solid content from the solid-liquid separation process or the treated oil with finer solid content dispersed in it to the first hydrotreating process can greatly improve the coal liquefaction rate and light oil yield. Leads to. According to such a circulation process, the viscosity and specific gravity of the feedstock to the solid-liquid separation process are reduced, thereby facilitating the solid-liquid separation operation and substantially increasing the separation efficiency. In addition, clogging of the fixed bed in the second hydrotreating step can be suppressed by directly supplying a portion of the treated oil, which is subjected to solid-liquid separation and whose solid content can be reduced, to the light oil separation step. However, it is not necessarily preferable to supply the produced oil from the first hydrotreating step to the light oil separation step as it is without further hydrotreating it in the second hydrotreating step. If this happens, the properties and yield of light oil, which is the main product, will decrease, or the coal liquefaction rate in the first hydrotreatment process will decrease, the gas yield will increase, and the reaction tube will be more likely to be contaminated with coke. by causing undesirable consequences.
Therefore, the amount of treated oil supplied from the solid-liquid separation process to the first hydrotreating process and/or light oil separation process depends on the properties of raw coal, reactivity, ash content, and fixation of the second hydrotreating process. It is determined by considering many conditions such as the floor's occlusion life. The treated oil with reduced solid content from the solid-liquid separation process is separated into light oil and heavy oil in advance, and then at least a part of the heavy oil is transferred to the first or/and second oil.
It may also be supplied to a hydrogenation process. By circulating the heavy oil from the separation step to the first hydrotreating step, lightening can be further promoted. However, such a separation process reduces the viscosity and specific gravity of the feedstock to the solid-liquid separation process by circulating a portion of the separated light oil to the first hydrotreating process or the solid-liquid separation process, thereby reducing the viscosity and specific gravity of the feedstock to the solid-liquid separation process. This is particularly preferred for promoting solid-liquid separation. Similarly, solid-liquid separation can be facilitated by circulating the light oil separated from the produced oil in the second hydrotreating step and distilled under normal pressure to the solid-liquid separation step. The circulating amount and fraction of light oil for such solid-liquid separation are determined depending on the solid-liquid separation method, the properties of the solids to be separated, and the properties of the light oil to be circulated. When petroleum-based residual oil is used as part of the medium oil of coal slurry, it is recognized that at least a large solid-liquid separation promoting effect can be obtained by circulating the amount of these light oils. In addition, naphtha to
Light oil fractions, especially kerosene gas oil fractions, are used, but depending on the solid-liquid separation method, conditions, etc., vacuum light oil may be added to these. The product oil from the second hydrotreating step is fed to a light oil separation step. The light oil separation method is not particularly limited, but usually one or more methods selected from atmospheric or reduced pressure distillation and solvent deasphalting methods, particularly a combination of normal pressure and reduced pressure distillation, is preferred. However, in addition to these methods, more favorable results may of course be obtained by combining known methods such as stripping of light oil with a hydrogen stream. As already mentioned, the naphtha to gas oil fractions, especially the kerosene and gas oil fractions separated in this step may be recycled to the solid-liquid separation step. Furthermore, among the separated light oils, those with a boiling point of 300° C. or higher, such as vacuum gas oil and deasphalted oil, may be circulated to the second hydrotreating step. It goes without saying that such circulation of light oil is preferable for further hydrorefining and converting it into high-quality oil, but it is particularly advantageous for extending the plugging life of the fixed catalyst bed in the second hydrotreating step. It is valid. That is, since the feedstock to the second hydrotreating step contains fine ash particles and/or metal-supported ultrafine particle catalysts that are not separated in the solid-liquid separation step, most of them pass through the fixed catalyst layer, but a portion of them is It has been found that these substances accumulate within the catalyst layer and eventually lead to blockage. However, the inventors have proposed that the feedstock containing fine solids be added to a heavy oil, at least a portion of which remains liquid under the hydrogenation reaction conditions, and which does not contain any solids, such as vacuum gas oil or deasphalted oil. It has been found that the addition of solid content not only reduces the amount of solid content deposited on the solid-liquid catalyst layer, but also changes the deposition distribution and significantly extends the plugging life of the catalyst layer. The heavy oil separated in the light oil separation process is
It contains fine solids that overflowed in the solid-liquid separation step, and at least a portion of these is recycled to the first hydrotreating step to effectively prevent coking or improve the coal liquefaction rate. However, if the ash in the coal is extremely fine and contains a large amount, the solid content concentration in the circulating oil will gradually increase, and the fixed catalyst bed in the second hydrotreating process will become clogged in a short period of time. Since continuous operation is not possible due to such reasons, a method is in place to extract a portion of the heavy oil from the system and use it separately.
Similarly, in the solid-liquid separation process, the solid content concentration in the treated oil, which is supplied to the second hydrotreating process, is reduced and the clarity is increased, thereby extending the plugging life of the fixed catalyst bed. If you try to extend the time period, you will have to produce a large amount of waste liquid with a high solid content concentration. Although such waste liquid may be used as fuel, etc., it is thermally decomposed together with a part of the circulating heavy oil or separately at a temperature of 400 to 600°C, and the resulting light oil is subjected to a solid-liquid separation process or/and It may be circulated to the second hydrogenation step. Thermal cracking is carried out by known methods, such as the delayed coker process, in which a portion of the feedstock is converted to light hydrocarbon gas and distillate and the remainder to coke or pitch.
Although the coke or pitch obtained here contains a large amount of ash, it can be effectively used as a fuel or as a raw material for hydrogen production. The distillate oil recycled to the solid-liquid separation step promotes solid-liquid separation, and is then refined into a high-quality light oil in the second hydrotreating step. Adding a pyrolysis step to the method of the present invention
This is very suitable for substantially increasing the yield of light oil and further extending the plugging life of the fixed catalyst bed in the second hydrotreating step. In the method of the present invention, when the light oil separation step consists of a multistage treatment, the residue from the final treatment may be recycled to the first hydrotreating step, but only the residue from the intermediate treatment may be recycled and the residue obtained from the final treatment may be recycled. The resulting residue may be extracted from the system for separate use, or may be supplied to the above-mentioned thermal decomposition process. Specifically, when the light oil separation process consists of a combined process of atmospheric or/and vacuum distillation and a solvent deasphalting process, a part of the distillation residue oil is recycled to the first hydrotreating process, and the remainder is recycled to the solvent. This means supplying to the descaling process. A portion of the deasphalted oil obtained in such a combined step may be recycled as it is to the first and/or second hydrotreating step, thereby substantially converting it into a higher quality oil. The process of the invention converts virtually all carbon-containing solid organic matter, especially coal, into liquid oil. However, in general, materials with extremely low carbon content have a low yield of liquid oil and consume a large amount of chemical hydrogen per liquefied oil, so they are not necessarily suitable liquefaction raw materials. Conversely, materials with extremely high carbon content, such as anthracite, coke, or charcoal, generally have extremely low hydrogenation reactivity and are not preferred raw materials. The most preferred coals include bituminous coal, subbituminous coal, brown coal, and lignite having a carbon content of 60 to 90% by weight on an anhydrous and ashless basis. However, all of these coals contain a considerable amount of moisture and ash, which makes solid-liquid separation difficult or reduces the hydrogen partial pressure in the hydrotreating process, so it is necessary to carry out drying and coal washing processes in advance. Preferably, it is removed.
In the method of the present invention, these pretreated coals are usually pulverized to an average single particle diameter of 200 microns or less, preferably 30 to 100 microns, and then fed to the first hydrotreating step. The pulverization of coals is carried out under an inert gas atmosphere or in water or oil to avoid oxidation or dust explosions.
Particularly in the first pulverization step, it is preferable to knead and pulverize while mixing with medium oil. As the medium oil, heavy oil from the light oil separation process is usually used, but in addition to this, oil produced in the first and/or second hydrotreating process, waste liquid with concentrated solids from the solid-liquid separation process, etc. , vacuum gas oil or deasphalted oil from a light oil separation process or/and a pyrolysis process may be used. Alternatively, petroleum residue oil may be added to facilitate separation of ash in the solid-liquid separation step. The mixing ratio of medium oil and coal can be arbitrarily determined within a range that allows easy handling of the mixture slurry. However, if the mixing ratio of coal becomes small, the coal liquefaction efficiency decreases and the circulating oil ratio increases, which is not necessarily preferable. On the other hand, a higher mixing ratio of coal is preferable from the viewpoint of liquefaction efficiency, but the fluidity of the mixture slurry, especially in the preheating tube, decreases, and furthermore, the fluidity in the reaction tube in the first hydrotreating step decreases. Contamination due to caulking, etc. may occur, which is not necessarily desirable. Therefore, the weight mixing ratio of coal to medium oil is usually in the range of 0.05 to 2:1, preferably 0.2 to 0.6:1 on an anhydrous and ashless basis. It is highly preferred to use petroleum residue oil as part of the medium oil for preparing the coal slurry in the method of the invention. That is, as already mentioned, this results in (1) conversion of difficult-to-process residual oil into high-quality oil; (2) improvement of the liquefaction rate of coal; and (3) improvement of the oil produced in the first hydrotreatment step. Very favorable effects such as facilitating solid-liquid separation can be obtained. Among these effects, (2) varies depending on the properties and type of petroleum residue, but generally the greater the content of soluble metals, the greater the effect. In addition, the effect of (3) is not very large for coal-based heavy oil, coal tar, anthracene oil, etc., so (1) and
Rather than thinking that it is due to an interaction with (2), it is reasonable to think that it is related to the composition of petroleum residue or its cracked oil. In other words, compared to coal-based heavy oil, the aromatic carbon ratio of petroleum-based residual oil is at most 20%.
~30%, and for this reason, the cracked oil from now on will have a high content of paraffinic hydrocarbons, so it will have low compatibility with asphaltenes or pitch-like products, and it will also have a low specific gravity, making it less compatible with the coal ash contained in the first hydrotreating step. Alternatively, it is presumed that unreacted charcoal becomes more likely to coagulate, promoting solid-liquid separation. According to the inventors' study results, petroleum-based residual oil is usually preferably a residual oil with a boiling point of 300°C or higher;
Of course, it is also possible to use heavy oils containing a small amount of distillate oil, such as these heavy oils containing a large amount of residue. As mentioned above, petroleum-based residual oils include crude oil, which contains 100 ppm or more, preferably 200 ppm or more of soluble metals.
Atmospheric distillation residue oil, vacuum distillation residue oil, solvent deasphalting residue, etc. obtained from tar sand bits, tar, and shale oil are used. These residual oils are usually used without treatment, but they can also be used after being subjected to a hydrotreating process in advance, or after being hydrodemetalized and then subjected to solvent deasphalting to increase the aromatic carbon ratio. All of these petroleum-based residual oils simply contain a large amount of sulfur, nitrogen, asphaltene, etc., and have a high residual carbon content, making them easy to colk, as well as containing small amounts of soluble metals and/or fine solids. Therefore, although it is virtually impossible to perform hydrogenation treatment using a conventional fixed bed, it is possible to produce high-quality light oil with a high yield (virtually 100%).
In addition to the conversion (estimated to be close to 100%), it is recognized that, as mentioned above, it provides a very favorable additive effect for the coal liquefaction process. Here, soluble metals are dissolved in petroleum residue as organometallic compounds. V, Ni, Fe, Cu, Cr, Mo, etc., and these are known to be concentrated in heavy components such as asphaltene. Although a residual oil containing few soluble metals can also be used as a medium oil for coal slurry, it is preferable that the residual oil contains as many metals as possible in order to increase the coal liquefaction rate in the first hydrotreating step. The ratio of petroleum residue oil added as part of the media oil to coals varies depending on their properties, the ratio of recycled heavy oil, the method of solid-liquid separation process, etc., but is usually 3 to 3. 1000%
The range is preferably about 10 to 300%. Or the ratio of soluble metals to coal is 20~
5000ppm, usually in the range of 100-500ppm. The produced oil from the first hydrotreating step is supplied to a solid-liquid separation step. In the method of the present invention, any known solid-liquid separation method may be used. The solid content dispersed in the produced oil is mainly coal ash, unreacted coal particles, and metal-supported ultrafine catalyst particles, and many of them are fine particles of 10μ or less. For this purpose, known solid-liquid separation methods such as hyperseparation method, centrifugation method, hydrocyclone method, and anti-solvent method may be used alone, but even more efficient separation is possible by combining these methods. Become. As a method for separating these fine solids, the inventor has disclosed in Japanese Patent Application No. 105208/1983 a method for extracting solids using water containing a trace or small amount of surfactant, but this method is different from the method of the present invention. Of course, it is also suitably applied to. Furthermore, as already mentioned, by circulating the light oil, especially the kerosene and gas oil fraction, separated in each step of the method of the present invention as a feedstock to the solid-liquid separation step, the difference in specific gravity between the solid content and the dispersed oil can be improved. The solid-liquid separation may be promoted by spreading the liquid, reducing the viscosity, and/or coagulating the solid particles. Coal liquefied oil contains fine solids that are extremely difficult to separate into solid and liquid, and it is recognized that at least a part of these overflows into the treated oil with a reduced solid content concentration. However, these fine solids pass through the fixed bed in the second hydrotreating step without being deposited, and are concentrated into heavy oil in the light oil separation step and recycled to the first hydrotreating step. . As already mentioned, one of the characteristics of the method of the present invention is that the fine solid content containing the ultrafine catalyst is first mixed with heavy oil.
By circulating it in the hydrotreating process, it is possible to suppress contamination caused by coking inside the reaction cylinder and improve the coal liquefaction rate. It is recognized that the solid content deposited on the fixed catalyst layer in the second hydrotreating step mainly consists of coarse particles. Therefore, in the solid-liquid separation step, measures are taken to remove as many coarse particles as possible. The degree of separation of these coarse particles varies depending on the properties or concentration of the solid content, the porosity of the fixed catalyst bed, the shape of the catalyst, etc., but usually 20% of the coarse solid content with a volume average particle diameter of 10μ or more is used. %, preferably more than 50% by weight, is removed in the solid-liquid separation step. In the method of the present invention, the reaction conditions for the first and second hydrogenation steps are usually 300 to 500°C and a hydrogen partial pressure of 50°C.
Kg/ ^cm2 or more. More specifically, in the first hydrogenation step, the temperature is 350 to 500°C, preferably 400 to 480°C,
Hydrogen partial pressure 50-500Kg/cm ² Preferably 100-350Kg/
cm ² , and in the second hydrogenation step, the hydrogen partial pressure is 300 to 460°C, preferably 350 to 440°C, and 100 Kg/cm ² or more, preferably 150 to 400 Kg/cm ² . In the first hydrotreating step, a decomposition and lightening reaction is mainly carried out, and the decomposition of the coal into asphaltene and heavy oil by the liquefaction reaction of the coal and the lightening of the medium oil proceed, but the elimination of hetero elements does not progress very much. The second hydrotreating step mainly involves hydrogenation of coal liquefied oil and medium oil, hydrogenation of unsaturated compounds, and hydrogenation of heteroelements.
Conversion to H ₂ S, NH _3, etc. takes place, but decomposition and lightening do not progress much. The most important purpose of the second hydrotreating step is to reduce the amount of solvent-insoluble residue by hydrogenating the fine unreacted coal particles and fine ash that overflowed in the solid-liquid separation step, or the coke deposited on the catalyst fine particles. Examples include catalyst regeneration and activation. In particular, the inventors discovered for the first time that a fine particle catalyst deteriorated due to coke precipitation during the hydrocracking process is rehydrogenated, where the coke on the fine particle catalyst returns to oil and the catalyst is activated. This is a fact, and the method of the present invention is one example of application of this new phenomenon. The fine solid content contained in the heavy oil that was previously separated from the oil produced in the second hydrotreating process is extremely effective in suppressing coke contamination in the reaction tube and promoting the coal liquefaction reaction in the first hydrotreating process. However, it is presumed that these are all due to the decoking and activation of the fine solid content in the second hydrotreating step. Although it is possible to carry out the reactions in each hydrogenation process under the same conditions, it is usually preferable to use low hydrogen pressure and high temperature in the first hydrogenation process to promote the decomposition reaction, and in the second hydrogenation process, a fixed catalyst is used. High hydrogen pressure and low temperature are desirable in order to suppress the deterioration of the layer and to remove coke from the fine solid content. These reaction conditions can be arbitrarily changed depending on other factors, such as the properties of coal or the properties and ratio of medium oil, but usually the reaction in the second hydrotreating step is faster than that in the first hydrotreating step. The conditions are set such that the hydrogen partial pressure is higher by 10 Kg/cm ² or more, preferably 30 Kg/cm ² or more, and/or the reaction temperature is lower by 10° C. or more, preferably 20° C. or more. In the method of the present invention, a fixed bed filled with a conventional hydrotreating catalyst can also be used in the second hydrotreating step. However, in this method, since the feedstock contains a small amount of fine solids and a large amount of heavy components such as asphaltenes, a catalyst layer and catalyst are required that prevent solids from accumulating and that can sufficiently hydrogenate the heavy components. It is preferable to use According to the inventors' study, such a catalyst has a diameter of 0.3~
Substantially spherical catalysts of 20 mm, preferably 0.5 to 10 mm, can be used. By using such a catalyst, a sufficiently high catalyst packing density can be obtained, and while maintaining a high activity per reactor volume, the solid content accumulation ratio in the catalyst layer is small and a relatively long blockage can be achieved. It is possible to obtain longevity. Alternatively, a catalyst having a thickness of 0.3 to 20 mm, preferably 0.5 to 5 mm at the thinnest part, is placed in the reaction tube.
The plugging life of the catalyst layer can also be extended by filling the reactor so that the porosity based on the volume of the reactor is substantially increased. Porosity is usually 40-90% preferably
The catalyst shape and packing method are selected to be in the range of 40-70%. The shape of such a catalyst may be arbitrarily selected, such as a honeycomb shape, a cylindrical shape, or a Raschig ring shape. The feedstock for the second hydrotreating step may include Ti, Fe, or
May contain soluble metals such as V and Ni.
These soluble metals may accumulate on the surface of the hydrotreating catalyst in the second hydrotreating step, degrading the catalyst or causing clogging of the catalyst layer.
In order to prevent deterioration of the catalyst layer due to such soluble metals, these feed materials may be subjected to demetallization treatment in advance. As the hydrodemetalization catalyst, those generally known for demetalization of heavy oil may be used as they are. The present invention has already studied demetalization catalysts, and these technical details are disclosed in, for example, Japanese Patent Application Laid-Open No.
53-98308, 53-115703, 54-31099, etc. However, in the method of the present invention, it has been found that among these known demetalization catalysts for heavy oil, those using fibrous magnesium silicate having a double-chain structure as a carrier are particularly preferred because they have particularly high activity. Ta. As the magnesium silicate carrier, in particular, one or more selected from sepiolite, palygorskite, and attapulgite, a porous body obtained by modifying these, or a composite porous body with alumina sol, silica sol, titania sol, alumina silica sol, etc. are used. , these porous carriers are usually molded and then processed according to periodic table b, b,
a, a, a, a, and one or more metals selected from group metals, preferably Zn, Cu, Ni, Co, V, Mo, and W, and carry out the same reaction as the second hydrogenation step. used under conditions. In the second hydrotreating step, any known heavy oil hydrotreating catalyst may be used. However, since the raw material to be treated contains larger amounts of nitrogen and oxygen, as well as asphaltenes and coke than normal heavy oil, it is extremely difficult to remove these impurities by hydrogenation while preventing catalyst deterioration. Have difficulty. According to studies by the present inventors, the activity and deterioration of the catalyst in this process are most strongly influenced by the physical structure. Therefore, as a catalyst in this step,
Supports one or more selected from V, Mo, W, Ni, and Co, preferably Mo, Ni, and Co, and has a specific surface area of 50
m ² /g, preferably 150 m ² /g or more, and an average pore diameter of 20 to 150 Å, preferably 50 to 120 Å. As a carrier for such a catalyst, alumina or alumina-silica is usually used because it provides high desulfurization and hydrogenation activities and is easy to obtain desired catalyst physical properties, shape, and strength. Therefore, as the fixed bed catalyst in the second hydrotreating step in the method of the present invention, a catalyst for hydrodesulfurization of heavy oil is usually used as it is or after being formed into various shapes so as to increase the porosity of the reaction tube. . However, when we further investigated the catalyst carrier used in the second hydrotreating step, we found that although sufficiently high desulfurization and hydrogenation activities can be obtained by using ordinary alumina or alumina-silica carrier catalysts, It was found that the nitrogen content, which is often contained in a larger amount than petroleum residue oil, did not decrease much, especially in the heavy content recycled to the first hydrotreating process. Ta. In addition, the higher the reduction rate of nitrogen content in heavy oil and the higher the atomic ratio of hydrogen to carbon, the more preferable it is to be used as a medium oil in the first hydrotreating process. After searching, we found that an acidic carrier catalyst having almost the same pore structure as an alumina catalyst and a supported metal is suitable. Examples of porous acidic carriers include TiO ₂ , ZrO ₂ , TiO ₂・SiO ₂ , ZrO ₂・
SiO ₂ , MgO・SiO ₂ , Al ₂ O ₃・MgO, Al ₂ O ₃・
_TiO2 , _Al2O3・_SiO2・_MgO , _TiO2・_ZrO2 ,
SiO ₂ / rare earth oxides, aluminum phosphate, acidic metal phosphates, mineral acid treatment viscosity and these and
One or more selected from the group consisting of Al ₂ O ₃ or Al ₂ O ₃ ·SiO ₂ treated with acidic fluorine compounds such as HF and BF ₃ is used. Particularly preferred acidic carrier catalysts have a specific surface area of 50 m ² /g or more, preferably 150 m ² /g or more, an average pore diameter of 20 to 150 Å,
Preferably it is 50 to 120 Å, and the supported metal is V,
One or more selected from Mo, W, Ni, and Co, preferably 5 to 20% of Mo or W each as an oxide.
%, Ni and Co in total from 0.5 to 10%, and further contains 1 to 15% by weight, preferably 2 to 8% by weight of boron or/and phosphorus as a co-catalyst. These acidic carrier catalysts have sufficiently high denitrification ability, high desulfurization and deoxygenation ability, and high hydrogenation ability, and are therefore extremely preferred as fixed bed catalysts in the second hydrogenation step in the process of the present invention. One of the characteristics of the method of the present invention is that a considerable portion of nitrogen, sulfur, and oxygen contained in the medium oil supplied to the second hydrotreating step is eliminated, and coke or pitch, etc., are deposited on the fine solids. is removed by hydrogenation,
Alternatively, since it is activated, a part of it is recycled and used, thereby suppressing contamination or clogging due to coke or pitch deposits inside the reaction column in the first hydrotreating step, and further improving the coal liquefaction rate. It's about doing. Although the fine solids recycled to the first hydrotreating step have a coking suppressing effect, the composition of these fine solids and the amount recycled to the first hydrotreating step vary depending on the production area of the coking coal. varies widely, and this changes the coal liquefaction rate and coking prevention effect. Therefore, in order to keep the catalytic effect of these fine solids constant regardless of the type of coal or production area in the first hydrotreating step, it is necessary to add a powdered catalyst in the same manner as in the Bergius method mentioned above. You can also do it. However, in general, it is practically very difficult to obtain a particulate catalyst of the order of the finest ash particles (diameter of several microns or less) in coal liquefied oil by mere pulverization using known methods. JP-A-53-106708 discloses a method for producing such a fine catalyst for coal liquefaction, but as mentioned earlier, this catalyst is an unsupported catalyst, so it has sufficiently high activity and resistance to poisoning. I can't expect that. In the first hydrotreating step, a known fine catalyst can be used, but the average single particle diameter is 200 mm.
The ultrafine powder made of a heat-resistant inorganic substance with a particle size of mμ or less, preferably 100 mμ or less, contains periodic table b, b,
0.1% by weight of one or more selected from a, a, a, a, and group metals based on the powder carrier
As mentioned above, it is preferable to use a metal-supported ultrafine particle catalyst which is substantially supported, preferably at least 0.5% by weight. The average single particle diameter of such a metal-supported fine catalyst is desirably 200 mμ or less, preferably 100 mμ or less. This is because in the method of the present invention, the finest ash particles in coal liquefied oil are distributed with a single particle diameter of 0.1 to several microns, so fine particles are used as catalyst particles, and the catalyst particles are used in the solid-liquid separation process. This is to cause the ash to mainly overflow into the treated oil and to cause the ash to remain mainly in the waste oil. Metals supported on the catalyst include H ₂ S,
Those that can maintain high activity in the hydrocracking reaction of coal and heavy oil in a high-pressure hydrogen atmosphere containing NH ₃ , H ₂ O, etc. are preferred, and in particular Zn, Cu,
Ni, Co, V, Cr, Mo, W especially Cu, Ni, Co,
One or more selected from Mo and V are preferred.
These metals can be supported on an ultrafine powder carrier by any known method, or they can also be obtained by impregnating a non-aqueous solution containing these metal compounds. In addition, various known fine powders can be used as powder carriers made of heat-resistant inorganic materials, such as white carbon, or fine powders of silicic acid, aluminum silicate, calcium silicate, alumina, titania, and silica obtained in substantially the same process as white carbon. One or more selected from titania, especially silicic anhydride or anhydrous alumina having an average single particle diameter of 20 mμ or less are particularly suitable. In the first hydrotreating step in the method of the present invention, the ratio of the metal-supported particulate catalyst to the slurry consisting of coal and medium oil depends on the properties of the coal,
Although it can be varied within a wide range depending on the reaction conditions, it is usually 0.01 to 10% by weight, preferably 0.2 to 2% by weight based on the new catalyst. In addition, since the particulate catalyst is made up of even more fine particles than coal ash, a considerable portion of the catalyst is distributed to the feedstock side of the second hydrotreating process in the solid-liquid separation process and used while being circulated, so it is not added to the raw coal. Of course, the ratio is extremely small. The properties of the light oil obtained as the main product by the method of the present invention vary widely depending on the properties of the raw coal, reaction conditions, etc. Therefore, depending on the use of the light oil, it may be further hydrorefined, hydrocracked or reformed by known methods. In particular, in order to obtain a gasoline fraction, catalytic cracking may be carried out after further hydrodenitrogenation and desulfurization in advance, or as it is. In addition, waste oil with concentrated solid content produced as a by-product from the solid-liquid separation process and/or a portion of the recycled heavy oil are normally supplied to the pyrolysis process, and only the distillate oil is supplied to each hydrotreating process. However, the ash-concentrated residue of by-product coke or pitch is used separately as a raw material for hydrogen production. However, the waste oil or heavy oil from these solid-liquid separation processes may be recycled to any process after solid content is removed by a known method such as supercritical extraction. Next, the processing steps of a preferred embodiment of the present invention will be further explained with reference to the drawings. These processing steps are merely examples, and the method of the present invention is not limited thereto, and it goes without saying that various changes can be made. Figure 1 is a flow sheet showing the most basic steps of the method of the present invention. In the figure, coal powder is supplied to a mixing tank 1 together with heavy oil containing fine solids circulated from a line 37, where the coal powder is mixed and, if necessary, pulverized. Mixing tank 1
The coal slurry mixed in passes through line 21,
Together with the hydrogen-containing gas supplied from line 31,
It is sent to the hollow reactor 2. The product is subsequently sent via line 22 to the first gas-liquid separator 3. The gaseous products separated in the gas-liquid separator 3 are sent from the line 23 to the circulating gas treatment device 4, where they are
Separates C1 _{- C2} components, hydrogen sulfide and ammonia,
It is recovered as a hydrogen-containing gas and used together with fresh hydrogen from the line 24 as a hydrogen source for the subsequent hydrogenation reaction column 6. The liquid product separated in the gas-liquid separator 3 is sent to the solid-liquid separator 5 via a line 25, and the solid content including ash and unreacted charcoal is extracted through a line 27. At least a part of the extremely fine solids in the coal ash is not separated by the solid-liquid separator 15 and overflows as it is, passing through the line 26 to the hydrogen supplied from the line 28 and, if necessary, from the line 34. A fixed bed hydrotreating reactor 6 along with the vacuum gas oil supplied
sent to. Further, a portion of the treated oil from the solid-liquid separator 5 bypasses the hydrogenation reaction column 6 and is directly sent to the atmospheric distillation column 8 through a line 29.
The produced oil treated in the hydrotreating reactor 6 is sent to the second gas-liquid separator 7 via a line 30. The gaseous product separated here is supplied to the cavity reactor 2 as a hydrogen-containing gas via the line 31, the liquid product is supplied to the atmospheric pressure reactor 2 via the line 32, and the liquid product is supplied via the line 32 to the atmospheric reactor 2. After that, atmospheric distillation column 8
The C ₃ to light oil components are separated. The residual oil from the atmospheric distillation column 8 is directly circulated to the mixing tank 1 via lines 38 and 37, and is also sent to the vacuum distillation column 9, where it is separated into a vacuum residue and vacuum gas oil. A portion of the reduced pressure residue is drawn out of the system via lines 35 and 36, and the remainder is circulated to the mixing tank 1 via line 37. The process shown in Figure 2 is basically the same as that shown in Figure 1, but the waste oil with concentrated solid content separated in the solid-liquid separator 5 and the vacuum distillation column are A part of the vacuum residue separated in step 9 is
The difference is that they are supplied to the pyrolysis apparatus 10 for treatment via line 27 and lines 35 and 36, respectively. Distillate oil produced in the thermal cracker 10 is circulated to the fixed bed hydrotreating reactor 6 and is essentially hydrorefined into high-quality oil. The process shown in Figure 3 shows an example in which petroleum residue is used as part of the medium oil of coal slurry. This method uses a solvent deasphalting device 10 instead of the pyrolysis device 10 in FIG. 2.
Also, compared to the method shown in FIG. 1, the difference is that the atmospheric distillation column 8 is located between the solid-liquid separation device 5 and the hydrogenation treatment device 6. A part of the kerosene obtained in the atmospheric distillation column 8 is used in a line 40 to promote solid-liquid separation. FIG. 4 shows an example of using an ultrafine particle catalyst as the catalyst used in the cavity reactor 2. This method shows a method in which the solid-concentrated waste liquid from the solid-liquid separation device 5 and a portion of the residue separated in the vacuum distillation column 10 are treated in the thermal decomposition device 11 in the same way as the method shown in FIG. The solvent deasphalting device 10 uses C ₃ to _{C 8} as a solvent,
Preferably, a paraffinic hydrocarbon solvent consisting of _C5 to _C7 is used, and the temperature is normal temperature to 300°C, preferably
Light oil is extracted and separated at 120 to 250°C and at normal pressure to about 50 kg/cm ² . A part of the deasphalted oil from the solvent deasphalting device 10 is extracted outside the system, but if necessary, it is circulated to the fixed bed hydrotreating reaction column 6 or the mixing tank 1. Next, the method of the present invention will be explained in more detail with reference to Examples. In the examples, all parts and percentages are by weight unless otherwise specified. Example 1 As an experimental device, the hollow reaction tube 2 and the fixed bed hydrogenation reaction tube 6 shown in Figure 1 each had an inner diameter of 25 mm, and the length of the constant temperature part excluding the preheating section was about 1 m, and a bypass line 29 was used. and 34 is not used,
In addition, the vacuum residue was not circulated to the mixing tank 1, but was completely extracted from the system through the line 36. Australian coal having the properties shown below was used as a raw material, and about 500 c.c. of a desulfurization catalyst having the properties shown below was charged into a fixed bed hydrogenation reaction tube 6 to cause a reaction. Elemental analysis of raw material coal properties ^* Carbon 81.2% Hydrogen 5.8% Nitrogen 1.6% Sulfur 0.62% Oxygen 10.8% Hydrogen/carbon atomic ratio 0.86 Moisture 2.75% Ash 7.53% *Ashless/anhydrous standard Desulfurization catalyst properties support Body γ-alumina Supported metal MoO ₃ 15.7% CoO 3.8% Nio 1.8% Specific surface area 289 m ² /g Pore volume (mercury intrusion method) 0.49 cc / g Raw coal was crushed in a nitrogen stream, and only the amount that passed through a 100-mesh sieve was placed in a mixing tank 1 together with about three times the weight of creosote oil having the following properties, and thoroughly mixed and kneaded to obtain a slurry liquid. Creosote oil properties Initial boiling point 164℃ 50% distillation temperature 321℃ End point 391℃ Impurities Nitrogen 0.68% Sulfur 0.44% Creosote oil is needed only at the start of the reaction, and after the operation reaches steady state. is atmospheric distillation column 8
Use the residue from After the slurry liquid is sent to the hollow reaction tube 2 and subjected to hydrogenation treatment under the following conditions, hydrogen and gaseous products (methane, ethane, H ₂ S, H ₂ O, NH ₃ etc.) and light hydrocarbons (propane, butane including pentane and hexane fractions), a large excess of distillate from the atmospheric distillation column is added to the liquid component, and the coarse solids are removed using a centrifuge. Most of it was removed. It was observed that the solid content in the separated clarified liquid was reduced to about 70% of the feedstock with particles larger than 0.1μ, and in particular about 80% of coarse particles with a particle diameter of 10μ or more were removed. . The clarified liquid was again hydrotreated in a fixed bed hydrogenation reactor under the following conditions. Hydrotreating conditions

[Table] The hydrotreated oil was subsequently subjected to atmospheric distillation to recover the distillate oil, a portion of the residual oil was circulated to a mixing tank, and the remainder was sent to a vacuum distillation column to separate vacuum gas oil. Table 4 below shows the yield and main properties of the light components recovered in the atmospheric distillation column and the vacuum distillation column. The total yield of methane, ethane and light hydrocarbons (propane, butane) is approximately 11%, the yield of vacuum residue containing solids is approximately 23%, and the yield of centrifuged residue (distillate oil is approximately 10%). The yield (including %) was about 18%. Atmospheric pressure distillation Vacuum distillation yield % 23 13 (Naphtha~light oil) (vacuum light oil) Properties Sulfur % 0.03 0.08 Nitrogen % 0.23 0.45 Oxygen 0.17 0.62 Example 2 In the method of Example 1, the same raw material coal was treated in detail below. The method of Example 1 was repeated, except that 1.0% by weight of ultrafine catalyst supporting metals was added. The ultrafine catalyst uses commercially available white carbon as a carrier with a specific surface area of 380 m ² /g and an average single particle diameter of 7 mμ obtained by treating silicon tetrachloride with a high-temperature gas phase decomposition method, and molybdenum and nickel as catalyst metals. This is a catalyst supported as . Predetermined amount of acetylacetone molybdenum oxide [MoO ₂ (C ₅ H ₇ O ₂ ) ₂ ]
and acetylacetone nickel [Ni
(C ₅ H ₇ O ₂ ) ₂ ] was dissolved in about 100 times the amount of 1,4-dioxane to obtain a homogeneous solution. Separately, white carbon (ultrafine silicic anhydride) was added to the same solvent and kneaded, followed by vigorous stirring to uniformly suspend the mixture, which was then mixed with the previously prepared solution containing molybdenum and nickel. The mixed solution was transferred to a container equipped with a reflux condenser and maintained at a temperature near the boiling point of the solvent for about 3 hours to prevent bumping, and then most of the solvent was evaporated under reduced pressure. The gel-like residue thus obtained is further
After drying under reduced pressure at 100-150℃, 300℃, then
The mixture was fired at 500°C for 1 hour each to obtain an ultrafine catalyst supporting metal. The main properties are as follows. Catalyst properties Specific surface area (m ² /g) 270 Average single particle diameter (mμ) 9 Amount of metal supported MoO ₃ (%) 1.4 NiO (%) 0.5 The above catalyst is very well dispersed in oil, and the particle diameter is It was confirmed that it was almost the same as the raw material white carbon. The yield and main properties of the naphtha to gas oil fraction and vacuum gas oil separated in the atmospheric distillation column 8 and the vacuum distillation column 9 in this example are shown below. Product yield and properties Atmospheric distillation column Vacuum distillation column product Naphtha to gas oil Vacuum gas oil yield (%) 25 16 Properties Sulfur (%) 0.03 0.06 Nitrogen (%) 0.24 0.49 Oxygen (%) 0.20 0.42 Example 3 In order to improve the liquefaction rate of coal and facilitate the solid-liquid separation operation, the method of Example 1 was repeated except that 50% by weight of extra heavy crude oil having the following properties was added to the raw coal. Ultra-heavy oil distillation 350℃ ^- Distillation 15% by volume 500℃ ^- Distillation 30% by volume Properties Sulfur 5.18% Nitrogen 0.59% Vanadium 1130ppm Nickel 106ppm N-heptane insolubles 11.5% Conradson residual carbon 15.9% Reaction tube Hydrotreating conditions in Nos. 2 and 6 are shown below. Hydrotreating conditions

【table】

[Table] Furthermore, the yields and main properties of the naphtha to gas oil fraction and vacuum gas oil separated in the atmospheric distillation column 8 and the vacuum distillation column 9 in this example are shown below. Product yield and properties Atmospheric distillation column Vacuum distillation column product Naphtha to gas oil Vacuum gas oil Yield (%) 35 15 Properties Sulfur (%) 0.14 0.31 Nitrogen (%) 0.31 0.52 Oxygen (%) 0.15 0.40 Methane , the total yield of ethane and light hydrocarbons (propane, butane) is 11%, the yield of the vacuum residue containing solids is 11%, and the yield of the centrifuged residue containing about 20% distillate is It was about 20%. Furthermore, after the reaction was completed, we analyzed the iron deposited on the used demetalization catalyst and desulfurization catalyst filled in the reaction tube 6, and found that most of the iron was deposited in the demetalization catalyst layer, and the desulfurization catalyst layer was made up of iron sulfide. It was observed that there was almost no deterioration due to precipitation on the surface of the catalyst particles.

[Brief explanation of drawings]

Figures 1 to 4 are flow sheets showing various aspects of the method of the present invention. Distillation column, 9 is a vacuum distillation column, 10
1 and 2 respectively indicate solvent deasphalting equipment.

Claims (1)

[Claims] 1 (a) Pulverize coal to 200 μm or less and mix it with a medium oil containing fine solids to form a slurry phase;
By treating the slurry phase under high hydrogen pressure and high temperature, most of the coal is converted into liquid, and at the same time, the medium oil is converted into light oil.
Hydrotreating process; (B) Solid-liquid separation process in which the produced oil containing solids from step (A) is separated into a part with concentrated solids and a part containing fine solids; (C) Process (B) ) A second hydrotreating step in which the portion containing fine solids is treated under high hydrogen pressure and high temperature in the presence of a substantially fixed hydrotreating catalyst to denitrify and desulfurize; (d) step; Separation step of separating the oil produced from step (c) into light oil that does not substantially contain fine solids and heavy oil that contains fine solids; (e) Contains fine solids from step (d) A circulation process in which at least a portion of heavy oil is supplied as a medium oil in step (a); A multistage hydrotreating method for converting coal into light oil with reduced nitrogen and sulfur, characterized by comprising the above steps; . 2. The method according to claim 1, wherein the separation step in step (d) comprises a combination of atmospheric distillation and/or reduced pressure distillation and solvent deasphalting treatment. 3. The method according to claim 1 or 2, wherein the concentrated solid fraction separated in step (b) is recycled to step (a) or/and (d). 4 The second hydrogenation treatment conditions in step (c) are the same as the first in step (a).
The method according to claim 1, 2 or 3, wherein the hydrogen partial pressure is higher by 10 kg/cm ² or more and the reaction temperature is lower by 10° C. or more compared to the hydrogenation treatment conditions. 5. The hydrotreating catalyst of step (c) supports a compound of one or more metals selected from groups b, b, a, a, a, a and groups of the periodic table,
5. The method according to claim 1, 2, 3, or 4, which comprises a porous carrier made of one or more selected from sepiolite, palygorskite, and attapulgite, or a modified product thereof. 6 The catalyst for hydrogenation in step (c) is (a) alumina silica, boric acid, HF or phosphoric acid impregnated alumina,
TiO ₂ , ZrO ₂ , TiO ₂・SiO ₂ , ZrO ₂・SiO ₂ ,
MgO・SiO ₂ , Al ₂ O ₃・MgO, Al ₂ O ₃・SiO ₂・
MgO, _Al2O3・_TiO2 , _{Al2O3 ・ SiO2 ・ B2O3 ,}
One or more selected from the group consisting of TiO ₂ / ZrO ₂ , SiO ₂ / rare earth oxides, aluminum phosphate, acidic metal phosphates, mineral acid treated clays, and products of these treated with HF, BF ₃ or acidic fluorine compounds (b) One or more of V, Mo, W, Ni, Co and Cu is supported on a carrier consisting of (c) an average pore diameter of 20 to 150 Å,
The method according to claim 1, 2, 3 or 4, wherein the specific surface area is 50 m ² /g or more. 7. The method according to claim 1, 2, 3, 4, 5 or 6, wherein a part of the medium oil is petroleum heavy oil with a boiling point of 300°C or higher. 8. The method according to claim 1, 2, 3, 4, 5, 6, or 7, wherein the weight ratio of coal to circulating oil is 0.05 to 2:1 on an ashless and anhydrous basis. 9 Claim 1, in which a fine particle catalyst is suspended in a slurry phase consisting of coal and circulating oil;
The method according to item 2, 3, 4, 5, 6, 7 or 8.