JP5744622B2 - Monocyclic aromatic hydrocarbon production method - Google Patents

Description

  The present invention relates to a method for producing monocyclic aromatic hydrocarbons, which produces monocyclic aromatic hydrocarbons from an oil rich in polycyclic aromatic hydrocarbons.

  Light cycle oil (hereinafter referred to as “LCO”), which is a cracked light oil produced by a fluid catalytic cracker, contains a large amount of polycyclic aromatic hydrocarbons and has been utilized as a light oil or heavy oil. However, in recent years, it has been proposed to obtain monocyclic aromatic hydrocarbons (for example, benzene, toluene, xylene, ethylbenzene, etc.) that can be used as a high octane gasoline base material or petrochemical raw material and have high added value from LCO. (For example, see Patent Documents 1 to 4).

JP-A-3-2128 Japanese Patent Laid-Open No. 3-52993 JP-A-3-26791 International Publication No. 2010/109899 Pamphlet

However, in the methods described in Patent Documents 1 to 4, it cannot be said that the yield of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms is necessarily high enough. That is, in the method, many by-products having relatively low added value other than the intended monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms were produced.
The present invention has been made to solve the above-described problems, and can produce monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms in high yield from a raw material oil containing polycyclic aromatic hydrocarbons. It aims at providing the manufacturing method of hydrocarbon.

As a result of intensive studies to achieve the above object, the present inventor has obtained the following knowledge.
In order to increase the yield of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms, heavy fractions other than the target product (monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms) in the reaction product, It is effective to circulate in the cracking and reforming reaction step, mix with the raw material oil, and cause repeated cracking and reforming reaction. Here, the cracking reforming reaction is a reaction for producing monocyclic aromatic hydrocarbons by cracking reforming using a fluidized bed.
Therefore, as a result of further investigation based on such knowledge, the present inventor has found that the yield of the target product can be further increased by adjusting the fraction to be circulated, thereby completing the present invention.

That is, in the method for producing a monocyclic aromatic hydrocarbon of the present invention, a monocyclic ring having 6 to 8 carbon atoms is obtained from a raw material oil having a 10 vol% distillation temperature of 140 ° C or higher and a 90 vol% distillation temperature of 380 ° C or lower. A method for producing a monocyclic aromatic hydrocarbon for producing an aromatic hydrocarbon, comprising:
The raw material oil is contacted with a catalyst for producing monocyclic aromatic hydrocarbons containing crystalline aluminosilicate and reacted to produce a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms and a heavy hydrocarbon having 9 or more carbon atoms. A cracking and reforming reaction step to obtain a product containing a fraction;
From the mixture of the product and the monocyclic aromatic hydrocarbon production catalyst entrained by the product, derived from the cracking and reforming reaction step, the monocyclic aromatic hydrocarbon production catalyst A catalyst separation step for separating and removing together with the tricyclic aromatic hydrocarbons contained in the product;
A separation step of separating at least a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms and a heavy fraction having 9 or more carbon atoms from a derived product derived from the catalyst separation step;
A purification and recovery step of purifying and recovering the monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms separated in the separation step;
A recycling step of returning the heavy fraction having 9 or more carbon atoms separated in the separation step to the cracking and reforming reaction step.

  The monocyclic aromatic hydrocarbon production method includes a hydrogenation reaction step of hydrogenating the heavy fraction having 9 or more carbon atoms separated in the separation step before the recycling step, In the recycling step, it is preferable that the hydrogenation reaction product of the heavy fraction having 9 or more carbon atoms obtained in the hydrogenation reaction step is returned to the cracking and reforming reaction step.

  In the method for producing the monocyclic aromatic hydrocarbon, a hydrogen recovery step for recovering hydrogen by-produced in the cracking and reforming reaction step from the product obtained in the cracking and reforming reaction step; And a hydrogen supply step for supplying the hydrogen recovered in the hydrogen recovery step to the hydrogenation reaction step.

  In the method for producing a monocyclic aromatic hydrocarbon, the separation step includes a three-ring aromatic hydrocarbon separated from a derivation derived from the catalyst separation step and supplied to the catalyst separation step. It is preferable to have an aromatic hydrocarbon supply step.

  According to the method for producing a monocyclic aromatic hydrocarbon of the present invention, it is possible to produce a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms in a high yield from a raw material oil containing a polycyclic aromatic hydrocarbon.

It is a schematic block diagram of the manufacturing plant which concerns on 1st Embodiment of the manufacturing method of the monocyclic aromatic hydrocarbon of this invention. It is a schematic block diagram of the manufacturing plant which concerns on 2nd Embodiment of the manufacturing method of the monocyclic aromatic hydrocarbon of this invention.

“First Embodiment”
1st Embodiment of the manufacturing method of the monocyclic aromatic hydrocarbon of this invention is described.
The manufacturing method of the monocyclic aromatic hydrocarbon of this embodiment is a method of manufacturing a C6-C8 monocyclic aromatic hydrocarbon from raw material oil, Comprising: The process of the following (a)-(i) is carried out. It is a method to have. FIG. 1 is a schematic configuration diagram of a manufacturing plant for explaining the first embodiment.

(A) The feedstock oil is brought into contact with the catalyst for monocyclic aromatic hydrocarbon production by the cracking reforming reactor 10 and reacted to produce a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms and 9 or more carbon atoms. A cracking and reforming reaction step for obtaining a product containing a heavy fraction; and (b) a catalyst for producing monocyclic aromatic hydrocarbons accompanied by the product derived from the cracking and reforming reaction step; A catalyst separation step (c) catalyst separation in which the monocyclic aromatic hydrocarbon production catalyst is separated and removed together with the tricyclic aromatic hydrocarbon contained in the product by a washing tower 12 and a catalyst separation device 14 from the mixture comprising From the derived product derived from the process, at least a monocyclic aromatic hydrocarbon (benzene / toluene / xylene) having 6 to 8 carbon atoms and a heavy fraction having 9 or more carbon atoms are separated into a first separation device 16 and a second separation. Separation step (d) for separation by apparatus 18 Purification and recovery step (e) for purifying and recovering monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms separated in the step by the purification and recovery device 20 (e) Hydrogenating heavy fractions having 9 or more carbon atoms separated in the separation step Hydrogenation reaction step of hydrogenating by reactor 28 (f) Recycling of hydrogenation reaction product of heavy fraction having 9 or more carbon atoms obtained by hydrogenation reaction step to cracking and reforming reaction step by recycle line 32 Step (g) In the separation step, a tricyclic aromatic hydrocarbon supply step (in which the tricyclic aromatic hydrocarbons separated from the derived product derived from the catalyst separation step are supplied to the catalyst separation step by the return lines 24 and 26 ( h) Hydrogen recovery process for recovering hydrogen by-produced in the cracking and reforming reaction process from the gas component separated in the separation process by the hydrogen recovery device 30 (i) Hydrogen recovered in the hydrogen recovery process is converted into hydrogen Hydrogen supply step of supplying to the hydrogenation reaction step by feeding line 34

Of the steps (a) to (i), the steps (a), (b), (c), (d), and (f) are essential steps in the invention according to claim 1, The steps e), (g), (h), and (i) are optional steps. Therefore, in the (f) recycling step, the heavy fraction having 9 or more carbon atoms separated in the separation step may be directly returned to the cracking and reforming reaction step without passing through the hydrogenation reaction step.
Hereinafter, each step will be specifically described.

<Decomposition and reforming reaction process>
In the cracking and reforming reaction step, the raw material oil is introduced into the cracking and reforming reactor 10 filled with the catalyst for producing monocyclic aromatic hydrocarbons, and brought into contact with the catalyst for producing monocyclic aromatic hydrocarbons to be reacted. . As a result, the saturated hydrocarbon contained in the feedstock is used as the hydrogen donor source, and the polycyclic aromatic hydrocarbon is partially hydrogenated by the hydrogen transfer reaction from the saturated hydrocarbon, and the ring is opened to form the monocyclic aromatic hydrocarbon. Convert. It can also be converted to monocyclic aromatic hydrocarbons by cyclization and dehydrogenation of saturated hydrocarbons obtained in the feedstock or in the cracking process. Furthermore, a C6-C8 monocyclic aromatic hydrocarbon can also be obtained by decomposing | disassembling a C9 or more monocyclic aromatic.

However, even if the tricyclic aromatic hydrocarbon is a hydrogenation reaction product, for example, since it has low reactivity in the cracking and reforming reaction step, it is hardly converted to a monocyclic aromatic hydrocarbon, and other products Derived with. In addition to monocyclic aromatic hydrocarbons, the product includes hydrogen, methane, ethane, LPG, heavy fractions having 9 or more carbon atoms, and the like.
In this cracking and reforming reaction step, when the product is derived, the catalyst for producing the monocyclic aromatic hydrocarbon is also slightly derived by being accompanied by the product. Therefore, in this cracking and reforming reaction step, a mixture of the product and the catalyst for producing monocyclic aromatic hydrocarbons is derived from the cracking and reforming reactor 10.

(Raw oil)
The feedstock oil used in the present invention is an oil having a 10 vol% distillation temperature of 140 ° C or higher and a 90 vol% distillation temperature of 380 ° C or lower. In the case of an oil having a 10% by volume distillation temperature of less than 140 ° C., a monocyclic aromatic hydrocarbon will be produced from a light oil, and a monocyclic aromatic will be produced from the feed oil containing the polycyclic aromatic hydrocarbon of the present invention. It becomes unsuitable for the purpose of manufacturing. In addition, when oil having a 90% by volume distillation temperature exceeding 380 ° C. is used, the yield of monocyclic aromatic hydrocarbons is lowered and coke deposition on the catalyst for producing monocyclic aromatic hydrocarbons The amount tends to increase and cause a sharp decrease in catalyst activity.
The 10 vol% distillation temperature of the feedstock oil is preferably 150 ° C or higher, and the 90 vol% distillation temperature of the feedstock oil is preferably 360 ° C or lower.

In addition, 10 volume% distillation temperature and 90 volume% distillation temperature here mean the value measured based on JISK2254 "petroleum product-distillation test method".
Examples of the feed oil having a 10% by volume distillation temperature of 140 ° C. or higher and a 90% by volume distillation temperature of 380 ° C. or lower include cracked light oil (LCO) produced by a fluid catalytic cracker, LCO hydrorefined oil, Examples include coal liquefied oil, heavy oil hydrocracked refined oil, straight-run kerosene, straight-run light oil, coker kerosene, coker light oil, and oil sand hydrocracked refined oil.
Polycyclic aromatic hydrocarbons are low in reactivity and are difficult to convert to monocyclic aromatic hydrocarbons in the cracking and reforming reaction step of the present invention. On the other hand, when they are hydrogenated in the hydrogenation reaction step, It can be converted into monocyclic aromatic hydrocarbons by being converted to naphthenobenzenes and then recycled to the cracking and reforming reaction step. However, among polycyclic aromatic hydrocarbons, aromatic hydrocarbons having 3 or more rings consume a large amount of hydrogen in the hydrogenation reaction step, and even in the hydrogenation reaction product, the reactivity in the cracking and reforming reaction step is low. Since it is low, it is not preferable to include a large amount. Therefore, the aromatic hydrocarbon having 3 or more rings in the feed oil is preferably 25% by volume or less, and more preferably 15% by volume or less.
In addition, as a feedstock for containing 2-ring aromatic hydrocarbons converted into naphthenobenzene in the hydrogenation reaction step and reducing aromatic hydrocarbons having 3 or more rings, for example, 90% by volume of the feedstock oil More preferably, the distillation temperature is 330 ° C. or lower.

  The polycyclic aromatic hydrocarbon referred to here is measured according to JPI-5S-49 “Petroleum products—Hydrocarbon type test method—High-performance liquid chromatograph method”, FID gas chromatograph method or two-dimensional gas chromatograph. It means the total value of the bicyclic aromatic hydrocarbon content (bicyclic aromatic content) and the tricyclic or higher aromatic hydrocarbon content (tricyclic or higher aromatic content) analyzed by the tograph method. Thereafter, when the content of polycyclic aromatic hydrocarbon, bicyclic aromatic hydrocarbon, tricyclic or higher aromatic hydrocarbon is indicated by volume%, it was measured according to JPI-5S-49. When it is shown by mass%, it is measured based on the FID gas chromatographic method or the two-dimensional gas chromatographic method.

(Reaction method)
Examples of the reaction method for contacting and reacting the raw material oil with the catalyst for producing monocyclic aromatic hydrocarbons, that is, the reaction method of the cracking reforming reactor 10, include a fixed bed, a moving bed, a fluidized bed and the like. In the present invention, since a heavy fraction is used as a raw material, a fluidized bed capable of continuously removing coke adhering to the catalyst and capable of performing a stable reaction is preferable. A continuous regenerative fluidized bed is particularly preferred in which the catalyst circulates between them and the reaction-regeneration can be repeated continuously. The feedstock oil in contact with the catalyst for producing monocyclic aromatic hydrocarbons is preferably in a gas phase. Moreover, you may dilute a raw material with gas as needed.

(Catalyst for monocyclic aromatic hydrocarbon production)
The catalyst for monocyclic aromatic hydrocarbon production contains crystalline aluminosilicate.

[Crystalline aluminosilicate]
The crystalline aluminosilicate is preferably a medium pore zeolite and / or a large pore zeolite because the yield of monocyclic aromatic hydrocarbons can be further increased.
The medium pore zeolite is a zeolite having a 10-membered ring skeleton structure. Examples of the medium pore zeolite include AEL type, EUO type, FER type, HEU type, MEL type, MFI type, NES type, and TON type. And zeolite having a WEI type crystal structure. Among these, the MFI type is preferable because the yield of monocyclic aromatic hydrocarbons can be further increased.
The large pore zeolite is a zeolite having a 12-membered ring skeleton structure. Examples of the large pore zeolite include AFI type, ATO type, BEA type, CON type, FAU type, GME type, LTL type, and MOR type. , Zeolites of MTW type and OFF type crystal structures. Among these, the BEA type, FAU type, and MOR type are preferable in terms of industrial use, and the BEA type is preferable because the yield of monocyclic aromatic hydrocarbons can be further increased.

The crystalline aluminosilicate may contain, in addition to the medium pore zeolite and the large pore zeolite, a small pore zeolite having a skeleton structure having a 10-membered ring or less, and a very large pore zeolite having a skeleton structure having a 14-membered ring or more. Good.
Here, examples of the small pore zeolite include zeolites having crystal structures of ANA type, CHA type, ERI type, GIS type, KFI type, LTA type, NAT type, PAU type, and YUG type.
Examples of the ultra-large pore zeolite include zeolites having CLO type and VPI type crystal structures.

When the cracking and reforming reaction step is a fixed bed reaction, the content of the crystalline aluminosilicate in the monocyclic aromatic hydrocarbon production catalyst is 100% by mass based on the entire monocyclic aromatic hydrocarbon production catalyst. 60-100 mass% is preferable, 70-100 mass% is more preferable, 90-100 mass% is especially preferable. If the content of the crystalline aluminosilicate is 60% by mass or more, the yield of monocyclic aromatic hydrocarbons can be sufficiently increased.
When the cracking and reforming reaction step is a fluidized bed reaction, the content of crystalline aluminosilicate in the monocyclic aromatic hydrocarbon production catalyst is 100% by mass of the total monocyclic aromatic hydrocarbon production catalyst. 20-60 mass% is preferable, 30-60 mass% is more preferable, and 35-60 mass% is especially preferable. If the content of the crystalline aluminosilicate is 20% by mass or more, the yield of monocyclic aromatic hydrocarbons can be sufficiently increased. When the content of the crystalline aluminosilicate exceeds 60% by mass, the content of the binder that can be blended with the catalyst is reduced, which may be unsuitable for fluidized beds.

[Phosphorus, Boron]
The catalyst for producing monocyclic aromatic hydrocarbons preferably contains phosphorus and / or boron. If the catalyst for producing monocyclic aromatic hydrocarbons contains phosphorus and / or boron, it is possible to prevent the yield of monocyclic aromatic hydrocarbons from decreasing with time, and to suppress the formation of coke on the catalyst surface.

As a method for incorporating phosphorus into the monocyclic aromatic hydrocarbon production catalyst, for example, phosphorus is supported on crystalline aluminosilicate, crystalline aluminogallosilicate, or crystalline aluminodine silicate by an ion exchange method, an impregnation method, or the like. Examples thereof include a method, a method in which a phosphorus compound is contained during zeolite synthesis and a part of the skeleton of the crystalline aluminosilicate is replaced with phosphorus, and a method in which a crystal accelerator containing phosphorus is used during zeolite synthesis. The phosphate ion-containing aqueous solution used at that time is not particularly limited, but was prepared by dissolving phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and other water-soluble phosphates in water at an arbitrary concentration. Can be preferably used.
As a method for incorporating boron into the catalyst for monocyclic aromatic hydrocarbon production, for example, boron is supported on crystalline aluminosilicate, crystalline aluminogallosilicate, or crystalline aluminodine silicate by an ion exchange method, an impregnation method, or the like. Examples thereof include a method, a method in which a boron compound is contained at the time of zeolite synthesis and a part of the skeleton of the crystalline aluminosilicate is replaced with boron, a method in which a crystal accelerator containing boron is used at the time of zeolite synthesis, and the like.

  The phosphorus and boron contents in the monocyclic aromatic hydrocarbon production catalyst are preferably 0.1 to 10% by mass relative to the total weight of the catalyst, and more preferably the lower limit is 0.5% by mass or more. Preferably, the upper limit is more preferably 9% by mass or less, and particularly preferably 8% by mass or less. When the content of phosphorus with respect to the total weight of the catalyst is 0.1% by mass or more, a decrease in the yield of monocyclic aromatic hydrocarbons over time can be prevented, and when the content is 10% by mass or less, the monocyclic aromatics The yield of hydrocarbons can be increased.

[Gallium, zinc]
The catalyst for producing monocyclic aromatic hydrocarbons can contain gallium and / or zinc, if necessary. If gallium and / or zinc is contained, the production rate of monocyclic aromatic hydrocarbons can be increased.

The gallium-containing form in the monocyclic aromatic hydrocarbon production catalyst is one in which gallium is incorporated into the lattice skeleton of crystalline aluminosilicate (crystalline aluminogallosilicate), and gallium is supported on the crystalline aluminosilicate. And those containing both (gallium-supporting crystalline aluminosilicate).
In the catalyst for producing monocyclic aromatic hydrocarbons, the zinc-containing form is one in which zinc is incorporated in the lattice skeleton of crystalline aluminosilicate (crystalline aluminodine silicate), or zinc is supported on crystalline aluminosilicate. One (zinc-supporting crystalline aluminosilicate) and one containing both.

Crystalline aluminogallosilicate and crystalline aluminodine silicate have a structure in which SiO ₄ , AlO ₄ and GaO ₄ structures are present in the skeleton. In addition, crystalline aluminogallosilicate and crystalline aluminodine silicate are, for example, gel crystallization by hydrothermal synthesis, a method of inserting gallium or zinc into the lattice skeleton of crystalline aluminosilicate, or crystalline gallosilicate or crystalline It is obtained by inserting aluminum into the lattice skeleton of zincosilicate.

The gallium-supporting crystalline aluminosilicate is obtained by supporting gallium on a crystalline aluminosilicate by a known method such as an ion exchange method or an impregnation method. The gallium source used in this case is not particularly limited, and examples thereof include gallium salts such as gallium nitrate and gallium chloride, and gallium oxide.
The zinc-supporting crystalline aluminosilicate is obtained by supporting zinc on a crystalline aluminosilicate by a known method such as an ion exchange method or an impregnation method. Although it does not specifically limit as a zinc source used in that case, Zinc salts, such as zinc nitrate and zinc chloride, zinc oxide, etc. are mentioned.

  When the monocyclic aromatic hydrocarbon production catalyst contains gallium and / or zinc, the content of gallium and zinc in the monocyclic aromatic hydrocarbon production catalyst is 0. The content is preferably from 01 to 5.0% by mass, and more preferably from 0.05 to 2.0% by mass. If the content of gallium and zinc is 0.01% by mass or more, the production rate of monocyclic aromatic hydrocarbons can be increased, and if it is 5.0% by mass or less, the yield of monocyclic aromatic hydrocarbons Can be higher.

[shape]
The catalyst for monocyclic aromatic hydrocarbon production is, for example, in the form of powder, granules, pellets, etc., depending on the reaction mode. For example, in the case of a fluidized bed as in this embodiment, it is in the form of powder, and in the case of a fixed bed as in another embodiment, it is in the form of particles or pellets. The average particle size of the catalyst used in the fluidized bed is preferably 30 to 180 μm, more preferably 50 to 100 μm. The bulk density of the catalyst used in the fluidized bed is preferably 0.4 to 1.8 g / cc, more preferably 0.5 to 1.0 g / cc.
In addition, an average particle diameter represents the particle size used as 50 mass% in the particle size distribution obtained by the classification by a sieve, and a bulk density is the value measured by the method of JIS specification R9301-2-3.
When obtaining a granular or pellet-shaped catalyst, if necessary, an inert oxide may be blended into the catalyst as a binder and then molded using various molding machines.

  When the catalyst for monocyclic aromatic hydrocarbon production contains an inorganic oxide such as a binder, one containing phosphorus as the binder may be used.

(Reaction temperature)
The reaction temperature when the raw material oil is brought into contact with and reacted with the catalyst for producing a monocyclic aromatic hydrocarbon is not particularly limited, but is preferably 400 to 650 ° C. If the minimum of reaction temperature is 400 degreeC or more, raw material oil can be made to react easily, More preferably, it is 450 degreeC or more. Moreover, if the upper limit of reaction temperature is 650 degrees C or less, the yield of monocyclic aromatic hydrocarbon can be made high enough, More preferably, it is 600 degrees C or less.

(Reaction pressure)
The reaction pressure when the raw material oil and the recycled oil described below are brought into contact with and reacted with the catalyst for producing a monocyclic aromatic hydrocarbon is preferably 1.5 MPaG or less, and more preferably 1.0 MPaG or less. If the reaction pressure is 1.5 MPaG or less, the by-product of light gas can be suppressed and the pressure resistance of the reactor can be lowered.

(Contact time)
The contact time between the feedstock and the catalyst for producing monocyclic aromatic hydrocarbons is not particularly limited as long as the desired reaction proceeds substantially. For example, the gas passage time on the catalyst for producing monocyclic aromatic hydrocarbons The lower limit is more preferably 5 seconds or more, and the upper limit is more preferably 150 seconds or less. If the contact time is 1 second or longer, the reaction can be performed reliably, and if the contact time is 300 seconds or shorter, accumulation of carbonaceous matter in the catalyst due to coking or the like can be suppressed. Or the generation amount of the light gas by decomposition | disassembly can be suppressed.

<Catalyst separation step>
In the catalyst separation step, the product derived from the cracking and reforming reaction step (cracking reforming reactor 10) and the catalyst for the production of monocyclic aromatic hydrocarbons accompanying the product (hereinafter simply referred to as catalyst) The catalyst is removed from the mixture consisting of: In addition, tricyclic aromatic hydrocarbons contained in the product are also separated and removed.

That is, the catalyst separation step includes a washing tower 12 to which the mixture is supplied, and a catalyst separator 14 that separates and removes the catalyst by solid-liquid separation of a heavy fraction derived from the washing tower 12. It is configured.
The operation in the cleaning tower 12 will be described.
The product vapor from the partial reforming reactor 10 is supplied to the lower part of the washing tower 12. In the washing tower 12, the bottom liquid of the washing tower 12 is extracted, pressurized by a pump, cooled by a heat exchanger, and then circulated to the middle stage of the washing tower 12. In the washing tower 12, the vapor reaction product and the circulating liquid come into countercurrent contact with each other, whereby the entrained catalyst particles slightly contained in the reaction product from the cracking reforming reactor 10 are trapped in the circulating liquid. Thus, the catalyst particles from the reaction product can be removed. However, since the circulating liquid itself is also circulated, a trace amount of catalyst is also present in the circulating liquid in the middle stage of the washing tower 12. When the gas-liquid countercurrent contact is made, it is inevitable that the droplets are accompanied, and the catalyst is also contained in the droplets. As a result, a very small amount of catalyst remains in the vapor of the reaction product. In order to capture and separate the droplets containing the entrained catalyst particles, the heavy fraction separated in the first separation device 16 containing no catalyst at the top of the washing tower 12 and / or the heavy fraction separated in the purification and recovery step is used. A mass fraction (containing a large amount of tricyclic aromatic hydrocarbons) is supplied. In this way, most of the catalyst is removed at the bottom of the washing tower 12 by the circulating liquid at the bottom of the column, and the reaction product of the vapor containing a very small amount of catalyst and the heavy fraction from the first separator 16 containing no catalyst at all. The catalyst particles are removed by a two-step process in which the minute portion is brought into countercurrent contact with the upper portion to capture droplets containing the catalyst.
For example, the washing tower 12 is provided with a buckle tray inside and has a theoretical plate set to about three, and the mixture supplied in a high temperature state (for example, 550 ° C.) is externally cooled (not shown). The catalyst is separated from the cooled and partially liquefied product while being circulated and cooled. The washing tower 12 is supplied with tricyclic aromatic hydrocarbons as a washing liquid from a separation step described later. This washing liquid wash | cleans the said product in the gas-liquid mixed state in the washing tower 12, and transfers a catalyst contained in this product in a washing | cleaning liquid, thereby efficiently separating the catalyst from the product. Remove.

  In addition, the washing tower 12 contains a part of gas such as hydrogen, methane and ethane, a light part such as LPG, a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms, and a heavy fraction having 9 or more carbon atoms. On the other hand, the heavy fraction such as polycyclic aromatic hydrocarbons mainly composed of tricyclic aromatic hydrocarbons and the catalyst are led out from the tower top. However, since the tricyclic aromatic hydrocarbons are supplied to the washing tower 12 as a washing liquid from the separation step described later, the heavy fraction derived from the bottom of the washing tower 12 contains the inside of the washing tower 12. All the tricyclic aromatic hydrocarbons in the mixture are not included, but only a part thereof is included. That is, only a part of the tricyclic aromatic hydrocarbons in the mixture in the cleaning tower 12 is derived without being derived from the bottom of the tower. It should be noted that the heavy fraction derived from the tower bottom includes a heavy fraction such as a bicyclic aromatic hydrocarbon in addition to the tricyclic aromatic hydrocarbon.

  The catalyst separator 14 is configured to have, for example, a filter, and separates and removes the heavy fraction containing the catalyst derived from the washing tower 12 by solid-liquid separation and separates and removes the catalyst from the heavy fraction. is there. The separated catalyst may be sent to, for example, a catalyst regeneration tower (not shown), regenerated here, and then recycled to the cracking and reforming reaction step. May be. The heavy fraction after removal of the catalyst, that is, polycyclic aromatic hydrocarbons mainly composed of tricyclic aromatic hydrocarbons, can be used as fuel (torch oil) for heating the catalyst regeneration tower, for example. it can.

<Separation process>
In the separation step, a monocyclic aromatic hydrocarbon having at least 6 to 8 carbon atoms and a heavy fraction having 9 or more carbon atoms are obtained from a derived product derived from the top of the washing tower 12 (catalyst separation step) by a plurality of separation devices. Separate the minutes.
That is, this separation step is configured to include the first separation device 16 and the debutizer (second separation device) 18 in the present embodiment. However, the separation step of the present invention does not necessarily require these two separation devices, and can be constituted by, for example, a single distillation device. Therefore, the debutizer (second separator) 18 can be omitted. Moreover, you may comprise a separation process including the 3rd separation apparatus 22 mentioned later as needed.

The first separation device 16 separates a gas component such as hydrogen, methane, ethane and the liquid fraction from the derived product. A known gas-liquid separator is used as the first separator 16. As an example of the gas-liquid separation device, a gas-liquid separation tank, a product introduction pipe for introducing a product into the gas-liquid separation tank, a gas component outflow pipe provided at an upper part of the gas-liquid separation tank, What comprises the liquid component outflow pipe | tube provided in the lower part of the gas-liquid separation tank is mentioned.
In the present embodiment, gas-liquid separation devices are arranged in two stages, cooled in the front stage 16a, and a heavy fraction mainly composed of tricyclic aromatic hydrocarbons in the liquid fraction (hereinafter referred to as tricyclic aromatic hydrocarbons). And the pressure is increased in the subsequent stage 16b to separate the gas component and the liquid fraction after separation of the tricyclic aromatic hydrocarbon.
The debutizer 18 (second separator) includes an LPG fraction containing butane and the like from the liquid fraction separated by the first separator 16 and a crude aromatic fraction containing a large amount of monocyclic aromatic hydrocarbons having 6 or more carbon atoms. And to separate.

<Tricyclic aromatic hydrocarbon supply process>
The tricyclic aromatic hydrocarbons separated in the first stage 16a (first separation device 16) in the first separation device 16 are returned to the washing tower 12 (catalyst separation step) as a washing liquid by the first return line 24. That is, the first return line 24 constitutes a tricyclic aromatic hydrocarbon supply process for supplying the tricyclic aromatic hydrocarbon as a cleaning liquid to the catalyst separation process. In addition, the tricyclic aromatic hydrocarbon supply process of the present invention may be configured not only by the first return line 24 but also by, for example, a second return line 26 described later. The second return line 26 may be configured. Further, the tricyclic aromatic hydrocarbon may be separated in another process after the first separator 16 and supplied to the catalyst separation step as a cleaning liquid. In this case, the tricyclic aromatic carbonization may be performed. The hydrogen supply process is also a tricyclic aromatic hydrocarbon supply process.
By supplying the tricyclic aromatic hydrocarbon as a cleaning liquid to the cleaning tower 12, the product in a gas-liquid mixed state is cleaned in the cleaning tower 12, and the catalyst contained in the product is placed in the cleaning liquid. The catalyst can be efficiently separated and removed from the product. A part of the tricyclic aromatic hydrocarbons supplied to the washing tower 12 is led to the catalyst separator 14 together with the catalyst. Further, the remaining portion stays in the washing tower 12 or is sent to the first separation device 16.

<Purification and recovery process>
In the purification and recovery step, the monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms separated in the separation step is purified and recovered by the purification and recovery device 20.
The purification and recovery device 20 is composed of a monocyclic aromatic hydrocarbon (benzene / toluene / xylene) having 6 to 8 carbon atoms and a heavy fraction, that is, mainly having 9 or more carbon atoms, from the crude aromatic fraction obtained by the debutizer 18. Into heavy fractions. The separated monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms is further purified to recover benzene, toluene and xylene, respectively. As such a purification and recovery apparatus 20, a known distillation apparatus, for example, a multistage distillation apparatus such as a stripper is used.

  The third separation device 22 separates the heavy fraction separated from the purification and recovery device 20 into a heavy fraction having 9 carbon atoms and a heavy fraction having 10 or more carbon atoms. And about the heavy fraction of carbon number 9, this is collect | recovered and used as a base material etc. of various products. On the other hand, the heavy fraction having 10 or more carbon atoms is sent back to the recycle process to be returned to the cracking and reforming reaction process and used for the cracking and reforming reaction in the cracking and reforming reactor 10 together with the raw material oil. However, the third separation device 22 is not essential in the present invention, and may be omitted, and the heavy fraction having 9 or more carbon atoms separated from the purification and recovery device 20 may be directly sent to the recycling process. Good.

  Here, the heavy fraction separated from the monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms by the purification and recovery apparatus 20 is a heavy fraction having 9 or more carbon atoms, and is a polycyclic aromatic hydrocarbon. As a main component, it contains a large amount of naphthalene and alkylnaphthalenes. It also contains a small amount of tricyclic aromatic hydrocarbons. That is, tricyclic aromatic hydrocarbons that could not be separated by the washing tower 12 or the first separation device 16 are contained in the heavy fraction. Therefore, the tricyclic aromatic hydrocarbons are separated by the third separator 22 as a heavy fraction having 10 or more carbon atoms.

As described above, tricyclic aromatic hydrocarbons are low in reactivity in the cracking and reforming reaction process even if they are, for example, hydrogenation reactants, and are hardly converted into monocyclic aromatic hydrocarbons. Recycling to the reaction process does not contribute to improving reaction efficiency.
Therefore, the third separation device 22 not only separates the heavy fraction separated from the monocyclic aromatic recovery device 20 into a heavy fraction having 9 carbon atoms and a heavy fraction having 10 or more carbon atoms. Further, the tricyclic aromatic hydrocarbon may be separated from the heavy fraction having 9 or more carbon atoms. The separated tricyclic aromatic hydrocarbons are returned to the cleaning tower 12 (catalyst separation step) as a cleaning liquid by the second return line 26. In this case, the second return line 26 also constitutes a three-ring aromatic hydrocarbon supply step for supplying the three-ring aromatic hydrocarbon as a cleaning liquid to the catalyst separation step together with the first return line 24 as described above. It will be a thing.

  However, the amount of tricyclic aromatic hydrocarbons separated by the third separation device 22 is not so large. Therefore, considering the increase in equipment cost and operating cost due to separation of tricyclic aromatic hydrocarbons, the third separation is performed when there is little economic effect by separating and returning the tricyclic aromatic hydrocarbons. Separation of tricyclic aromatic hydrocarbons in the apparatus 22 may be omitted.

<Hydrogenation reaction process>
In the hydrogenation reaction step, the heavy fraction having 10 or more carbon atoms separated by the third separation device 22 (separation step) is hydrogenated by the hydrogenation reactor 28. Specifically, the heavy fraction and hydrogen are supplied to the hydrogenation reactor 28, and a polycyclic aromatic hydrocarbon (mainly bicyclic aromatic carbonization) contained in the heavy fraction is obtained using a hydrogenation catalyst. Hydrogen) is at least partially treated.
The polycyclic aromatic hydrocarbon is preferably hydrogenated until the average number of aromatic rings is 1 or less. For example, naphthalene is preferably hydrogenated to tetralin (naphthenobenzene). If the hydrogenation is carried out until the average number of aromatic rings is 1 or less, it is easily converted into monocyclic aromatic hydrocarbons when returned to the cracking reforming reaction step (cracking reforming reactor 10).

  In addition, in order to further improve the yield of monocyclic aromatic hydrocarbons in the cracking and reforming reaction step, in the hydrogenation reaction step, inclusion of polycyclic aromatic hydrocarbons in the hydrogenation reaction product of the heavy fraction obtained The amount is preferably 40% by mass or less, more preferably 25% by mass or less, and further preferably 15% by mass or less. The polycyclic aromatic hydrocarbon content in the hydrogenation reaction product is preferably less than the polycyclic aromatic hydrocarbon content in the feedstock, and decreases by increasing the amount of hydrogenation catalyst or increasing the reaction pressure. Can be made. However, it is not necessary to hydrogenate all the polycyclic aromatic hydrocarbons until they become saturated hydrocarbons. Excessive hydrogenation tends to increase hydrogen consumption and heat generation.

  In the present embodiment example, hydrogen by-produced in the cracking / reforming reaction step (cracking / reforming reactor 10) is used. That is, hydrogen is recovered from a gas component obtained in the separation step (first separation device 16) in a hydrogen recovery step (hydrogen recovery device 30) described later, and recovered in a hydrogen supply step (hydrogen supply line 34). The hydrogen thus supplied is supplied to a hydrogenation reaction step (hydrogenation reactor 28).

A preferred example of the reaction system of the hydrogenation reactor 28 (hydrogenation reaction step) is a fixed bed.
As the hydrogenation catalyst, a known hydrogenation catalyst (eg, nickel catalyst, palladium catalyst, nickel-molybdenum catalyst, cobalt-molybdenum catalyst, nickel-cobalt-molybdenum catalyst, nickel-tungsten catalyst, etc.) should be used. Can do.
The hydrogenation reaction temperature varies depending on the hydrogenation catalyst used, but is usually in the range of 100 to 450 ° C, more preferably 200 to 400 ° C, and even more preferably 250 to 380 ° C.

The hydrogenation reaction pressure varies depending on the hydrogenation catalyst and raw materials used, but is preferably in the range of 0.7 MPa to 13 MPa, more preferably 1 MPa to 10 MPa, and particularly preferably 1 MPa to 7 MPa. preferable. If the hydrogenation reaction pressure is set to 13 MPa or less, a hydrogenation reactor having a low service pressure can be used, and the equipment cost can be reduced.
On the other hand, the hydrogenation reaction pressure is preferably 0.7 MPa or more from the viewpoint of the yield of the hydrogenation reaction.

Hydrogen consumption is preferably not more than ^{3000scfb (506Nm 3 / m 3)} , more preferably less ^{2500scfb (422Nm 3 / m 3)} , more preferably not more than 1500scfb (253Nm ³ / ^{m 3)} .
On the other hand, the hydrogen consumption is preferably 300 scfb (50 Nm ³ / m ³ ) or more from the viewpoint of the yield of the hydrogenation reaction.
The liquid hourly space velocity (LHSV) is preferably set to below 0.1 h ^-1 or ^{20h -1,} and more preferably to 0.2 h ^-1 or ^{10h -1} or less. When LHSV is 20 h ⁻¹ or less, polycyclic aromatic hydrocarbons can be sufficiently hydrogenated at a lower hydrogenation reaction pressure. On the other hand, by setting 0.1 ^-1 or more, it is possible to avoid an increase in size of the hydrogenation reactor.

<Recycling process>
In the recycling process, the hydrogenation reaction product of the heavy fraction obtained in the hydrogenation reaction process is mixed with the raw material oil through the recycling line 32 and returned to the cracking and reforming reaction process.
By returning the hydrogenation reaction product of the heavy fraction to the cracking and reforming reaction step, a monocyclic aromatic hydrocarbon can be obtained using the heavy fraction that was a by-product as a raw material. Therefore, the amount of by-products can be reduced, and the production amount of monocyclic aromatic hydrocarbons can be increased, whereby the production efficiency of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms can be increased. Moreover, since saturated hydrocarbons are also produced by hydrogenation, the hydrogen transfer reaction in the cracking and reforming reaction step can be promoted.
Furthermore, the hydrogenation reaction product of the heavy fraction that is returned to the cracking and reforming reaction step in the recycling process (recycling line 32) includes tricyclic aromatics that are not easily converted to monocyclic aromatic hydrocarbons in the cracking and reforming reaction process. Since hydrocarbons are hardly contained, the conversion efficiency of the recycled hydrogenation reactant into monocyclic aromatic hydrocarbons is improved.
From these, it is possible to improve the overall yield of monocyclic aromatic hydrocarbons relative to the amount of feedstock supplied, and thus increase the yield of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms.

In the recycling process, it is not always necessary to recycle the entire amount of the hydrogenation reactant into the raw material oil for the cracking and reforming reaction process. In that case, the hydrogenated reactant that has not been recycled can be used, for example, as a fuel substrate.
In the above embodiment, the heavy fraction having 10 or more carbon atoms obtained in the third separation device 22 (separation step) is hydrotreated, and then returned to the cracking and reforming reaction step. The heavy fraction may be directly returned to the cracking and reforming reaction step without being performed. Even in this case, since this recycled oil contains almost no tricyclic aromatic hydrocarbons, the conversion efficiency of the recycled oil to monocyclic aromatic hydrocarbons is improved.
Further, the heavy fraction separated from the purification / recovery device 20 is not separated into a heavy fraction having 9 carbon atoms and a heavy fraction having 10 or more carbon atoms by the third separation device 22, and this purification / recovery is performed. The heavy fraction having 9 or more carbon atoms separated from the apparatus 20 may be directly supplied to the hydrogenation reactor 28 (hydrogenation reaction step) or to the cracking reforming reactor 10 (cracking reforming reaction step). Good.

<Hydrogen recovery process>
In the hydrogen recovery step, hydrogen produced as a by-product in the cracking and reforming reaction step (cracking reforming reactor 10) from the gas component obtained in the separating step (the rear stage 16b of the first separator 16) is converted into a hydrogen recovery device 30. Recover by.
The method for recovering hydrogen is not particularly limited as long as hydrogen contained in the gas component obtained in the separation step and other gas can be separated. For example, the pressure fluctuation adsorption method (PSA method), the cryogenic separation method, Examples thereof include a membrane separation method. Therefore, as the hydrogen recovery apparatus 30, an apparatus (for example, a PSA apparatus) that recovers hydrogen based on these methods is used.
Usually, the amount of hydrogen recovered in the hydrogen recovery step is larger than the amount necessary for hydrogenating a heavy fraction having 9 or more carbon atoms.

<Hydrogen supply process>
In the hydrogen supply step, the hydrogen obtained in the hydrogen recovery step (hydrogen recovery device 30) is supplied to the hydrogenation reaction step (hydrogenation reactor 28) through the hydrogen supply line 34. The hydrogen supply amount at that time is adjusted according to the heavy fraction supplied to the hydrogenation reaction step. If necessary, the hydrogen pressure is adjusted.
If there is a hydrogen supply step as in this embodiment, the heavy fraction can be hydrogenated using hydrogen by-produced in the cracking and reforming reaction step (cracking reforming reactor 10). Therefore, part or all of the hydrogen supply from the outside can be reduced by covering part or all of the hydrogen used in the production method of the present embodiment with by-product hydrogen.

In the method for producing monocyclic aromatic hydrocarbons of the present embodiment, by returning a heavy fraction having 10 or more carbon atoms or 9 or more carbon atoms to the cracking and reforming reaction step, A monocyclic aromatic hydrocarbon can be obtained using a fraction as a raw material. Therefore, the amount of by-products can be reduced, and the production amount of monocyclic aromatic hydrocarbons can be increased, whereby the production efficiency of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms can be increased.
In addition, hydrogenation of heavy fractions in the hydrogenation reaction step and return to the cracking reforming reaction step also produces saturated hydrocarbons by hydrogenation, thus promoting the hydrogen transfer reaction in the cracking reforming reaction step. it can.

  Furthermore, tricyclic aromatic hydrocarbons are separated and removed from the mixture derived from the cracking and reforming reaction process in the catalyst separation process, and then the resulting heavy fraction having 10 (9) carbon atoms or more is cracked and reformed. Since the process is returned to the process, the heavy fraction returned to the cracking and reforming reaction process contains almost all the tricyclic aromatic hydrocarbons that are difficult to be converted into monocyclic aromatic hydrocarbons in the cracking and reforming reaction process. Therefore, the conversion efficiency of the recycled heavy fraction (or its hydrogenation reactant) to a monocyclic aromatic hydrocarbon is improved. Therefore, the yield of the general monocyclic aromatic hydrocarbon with respect to the supply amount of raw material oil can be improved, and the yield of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms can be increased.

In addition, since the tricyclic aromatic hydrocarbons are separated in the separation step, the tricyclic aromatic hydrocarbon content of the heavy fraction to be recycled (or the hydrogenation reaction product thereof) can be reduced, Thereby, the conversion efficiency of the heavy fraction into monocyclic aromatic hydrocarbons can be improved.
Further, since the tricyclic aromatic hydrocarbons separated in the separation step are supplied to the catalyst separation step as a cleaning liquid by the tricyclic aromatic hydrocarbon supply step by the first return line 24 and the second return line 26, in the catalyst separation step The catalyst can be separated and removed more efficiently.

“Second Embodiment”
2nd Embodiment of the manufacturing method of the monocyclic aromatic hydrocarbon of this invention is described.
FIG. 2 is a schematic configuration diagram of a manufacturing plant for explaining the second embodiment. The manufacturing method of the monocyclic aromatic hydrocarbon of this embodiment is a method of manufacturing a C6-C8 monocyclic aromatic hydrocarbon from raw material oil similarly to 1st Embodiment.

  The second embodiment is different from the first embodiment shown in FIG. 1 in that the cleaning step is composed of the cleaning tower 12 and the catalyst separator 16 in the first embodiment, and the separation step is the same as the first separation device 16. Whereas the debutizer 18 (second separation device), the purification / recovery device 20 and the third separation device 22 are configured, in the second embodiment, as shown in FIG. 2, the washing process is performed by the fractionator 40 and the catalyst separator. 14, and the separation step is composed of the fractionator 40, the debutizer 18 (second separation device), the purification / recovery device 20, and the third separation device 22. That is, in the present embodiment, a fractionator 40 is used in place of the cleaning tower 12 and the first separation device 16 of the first embodiment.

Therefore, the method for producing monocyclic aromatic hydrocarbons of this embodiment is also a method having the steps (a) to (i) basically as in the first embodiment.
Hereinafter, processes using an apparatus different from the first embodiment will be described. In addition, description is abbreviate | omitted about the same process using the same apparatus as 1st Embodiment.

<Catalyst separation step>
In the catalyst separation step, as in the first embodiment, the catalyst (a catalyst for producing monocyclic aromatic hydrocarbons) is removed from the mixture derived from the cracking reforming reaction step (cracking reforming reactor 10). Further, tricyclic aromatic hydrocarbons contained in the product obtained in the cracking and reforming reaction step are also separated and removed.

  However, in this embodiment, the fractionator 40 fulfills its function in place of the washing tower 12 in the first embodiment. The fractionator 40 is a known distillation tower configured in multiple stages, and separates a heavy fraction mainly composed of a catalyst and a tricyclic aromatic hydrocarbon in the mixture on the bottom side of the tower, and on the top side of the tower. The gas component in the mixture (in the product of the cracking reforming reaction step) is separated. In the intermediate part, an intermediate fraction (liquid fraction) is separated between the gas component and the heavy fraction mainly composed of the 3-ring aromatic hydrocarbon.

At the tower bottom of the fractionator 40, a heavy fraction having a high boiling point, that is, a heavy fraction mainly composed of a tricyclic aromatic hydrocarbon is liquefied. Thereby, a heavy fraction mainly composed of tricyclic aromatic hydrocarbons is led out together with the catalyst from the bottom of the column.
The derived heavy fraction is supplied to the catalyst separator 14 as in the first embodiment, where the catalyst is separated and removed. In addition, polycyclic aromatic hydrocarbons (heavy fraction) mainly composed of tricyclic aromatic hydrocarbons after removing the catalyst are used as fuel (torch oil) for heating the catalyst regeneration tower, for example. Is done.

<Separation process>
Further, from the middle part of the fractionator 40 to the top of the column, as in the first separation device 16 of the first embodiment, hydrogen, methane, ethane, etc. are obtained by distillation from the fraction from which the catalyst has been separated (derived product). Gas components and liquid fractions are separated. Then, as described above, an intermediate fraction (liquid fraction) separated from the intermediate portion is derived, and a gas component is derived from the top of the column.
When the gas component and the liquid fraction are separated from the middle part of the fractionator 40 to the top of the tower, the tricyclic aromatic hydrocarbon is liquefied as part of the liquid fraction. This liquefied tricyclic aromatic hydrocarbon flows down to the bottom of the column as a heavy fraction and functions as a cleaning liquid in the catalyst separation performed at the bottom of the column. Therefore, the fractionator 40 also has a tricyclic aromatic hydrocarbon supplying step therein.

The middle fraction (liquid fraction) derived from the middle part of the fractionator 40 is supplied to the debutizer 18 (second separation device) and subjected to separation treatment. Hereinafter, the purification / recovery device 20 is the same as in the first embodiment. The third separation device 22 sequentially performs separation processing. Then, after the heavy fraction having 10 or more carbon atoms is sent to the hydrogenation reaction step (hydrogenation reactor 28) and subjected to the hydrogenation reaction, it is mixed with the raw material oil by the recycling step (recycling line 32), The process is returned to the cracking and reforming reaction step. In the case of separating the tricyclic aromatic hydrocarbons (heavy fraction mainly composed of tricyclic aromatic hydrocarbons) from the heavy fraction having 10 or more carbon atoms in the third separator 22, the separated tricyclic aromatics are separated. The hydrocarbons are returned to the bottom of the fractionator 40 as a cleaning liquid by the second return line 26. Also in the present embodiment, the third separation device 22 can be omitted.
On the other hand, the gas component derived from the top of the fractionator 40 is sent to the hydrogen recovery device 30 (hydrogen recovery step), and is then processed in the same manner as in the first embodiment.

Even in the method for producing monocyclic aromatic hydrocarbons of the present embodiment, by returning the heavy fraction having 10 or more carbon atoms or 9 or more carbon atoms to the cracking and reforming reaction step, A monocyclic aromatic hydrocarbon can be obtained using a fraction as a raw material. Therefore, the amount of by-products can be reduced, and the production amount of monocyclic aromatic hydrocarbons can be increased, whereby the production efficiency of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms can be increased.
In addition, hydrogenation of heavy fractions in the hydrogenation reaction step and return to the cracking reforming reaction step also produces saturated hydrocarbons by hydrogenation, thus promoting the hydrogen transfer reaction in the cracking reforming reaction step. it can.

Furthermore, tricyclic aromatic hydrocarbons are separated and removed from the mixture derived from the cracking and reforming reaction process in the catalyst separation process, and then the resulting heavy fraction having 10 (9) carbon atoms or more is cracked and reformed. Since the process is returned to the process, the heavy fraction returned to the cracking and reforming reaction process contains almost all the tricyclic aromatic hydrocarbons that are difficult to be converted into monocyclic aromatic hydrocarbons in the cracking and reforming reaction process. Therefore, the conversion efficiency of the recycled heavy fraction (or its hydrogenation reactant) to a monocyclic aromatic hydrocarbon is improved. Therefore, the yield of the general monocyclic aromatic hydrocarbon with respect to the supply amount of raw material oil can be improved, and the yield of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms can be increased.
In addition, since the tricyclic aromatic hydrocarbons are separated in the separation step, the tricyclic aromatic hydrocarbon content of the heavy fraction to be recycled (or the hydrogenation reaction product thereof) can be reduced, Thereby, the conversion efficiency of the heavy fraction into monocyclic aromatic hydrocarbons can be improved.

“Other embodiment examples”
The present invention is not limited to the first and second embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, the hydrogen used in the hydrogenation reaction step is not a by-product generated in the cracking and reforming reaction step, but hydrogen obtained by a known hydrogen production method may be used. Hydrogen produced as a by-product may be used.

[Experimental example]
(Comparative Test Example 1)
In the production plant shown in FIG. 1, LCO having the properties shown in the following table was used as a raw material oil, and this was supplied to the cracking and reforming reactor 10 to carry out the reaction. Thereafter, the treatment was performed in the same manner as in the first embodiment, and the heavy fraction after removal of the catalyst by the catalyst separator 14, that is, the polycyclic aromatic hydrocarbon mainly composed of tricyclic aromatic hydrocarbons was recovered. . Then, the recovered heavy fraction was supplied to the hydrogenation reactor 28 to perform a hydrogenation reaction, thereby obtaining a hydrogenation reaction product of the heavy fraction. Thereafter, the obtained hydrogenation reaction product was supplied to the cracking and reforming reactor 10 in place of the raw material oil, and the cracking and reforming reaction was performed. When the amount (content) of the tricyclic aromatic hydrocarbon in the heavy fraction was examined, it was about 42.8% by mass, and most of the other was bicyclic aromatic hydrocarbon.

(Experimental example 1)
In the manufacturing plant shown in FIG. 1, LCO having the same properties as Comparative Test Example 1 was used as a raw material oil, and this was supplied to the cracking and reforming reactor 10 to cause the reaction. Thereafter, processing was performed in the same manner as in the first embodiment, and a heavy fraction having 10 or more carbon atoms derived from the third separation device 22 was recovered. Then, the recovered heavy fraction was supplied to the hydrogenation reactor 28 to perform a hydrogenation reaction, thereby obtaining a hydrogenation reaction product of the heavy fraction. Thereafter, the obtained hydrogenation reaction product was supplied to the cracking and reforming reactor 10 in place of the raw material oil, and the cracking and reforming reaction was performed. In this third separation device 22, the tricyclic aromatic hydrocarbons were not separated, and the recovered heavy fraction was supplied to the cracking reforming reactor 10 as it was. When the amount (content) of the tricyclic aromatic hydrocarbon in the heavy fraction was examined, it was about 3.1% by mass, and most of the other was bicyclic aromatic hydrocarbon.

(Comparative Test Example 2)
In Comparative Test Example 1, the heavy fraction recovered after removing the catalyst by the catalyst separator 14 and the heavy fraction having 10 or more carbon atoms derived from the third separator 22 and recovered in Experimental Example 1 Were mixed. Then, the mixed heavy fraction was supplied to the hydrogenation reactor 28 to cause a hydrogenation reaction to obtain a hydrogenation reaction product of the mixed heavy fraction. Thereafter, the obtained hydrogenation reaction product was supplied to the cracking and reforming reactor 10 in place of the raw material oil, and the cracking and reforming reaction was performed. Note that the mixing ratio (mass ratio) of the heavy fraction used in Comparative Test Example 1 and the heavy fraction used in Experimental Example 1 (Comparative Test Example 1: Experimental Example 1) was approximately 1: 9. . Therefore, in calculation, the amount (content) of the tricyclic aromatic hydrocarbon in the mixed heavy fraction is about 7.0% by mass.

(Comparative Test Example 3)
LCO having the same properties as those in Comparative Test Example 1 and Experimental Example 1 was used as a feed oil and supplied to the cracking and reforming reactor 10.

In Comparative Test Example 1, Experimental Example 1, Comparative Test Example 2, and Comparative Test Example 3, BTX (benzene, benzene in the obtained product after the decomposition product reaction was performed in the cracking reforming reactor 10, respectively. Toluene, xylene), ie, BTX yield was examined. The results are shown below. In addition, the following BYX yield is the mass%.
Comparative Test Example 1 Experimental Example 1 Comparative Test Example 2 Comparative Test Example 3
(3RA) (42.8) (3.1) (7.0)
BTX yield; 26% 48% 45% 37%
However, (3RA) is a tricyclic aromatic hydrocarbon, and the numerical value in () is the amount (content) of the tricyclic aromatic hydrocarbon in the heavy fraction before the hydrogenation reaction used in each example. Show.

From the above results, first, in Comparative Test Example 1, the heavy fraction mainly composed of tricyclic aromatic hydrocarbons after the removal of the catalyst by the catalyst separator 14 is subjected to a hydrogenation reaction through the cracking and reforming reactor 10. However, the yield of BTX is significantly lower than that of Comparative Test Example 3. For this reason, it was found that it is not preferable to use recycled oil for the heavy fraction after the catalyst is removed by the catalyst separator 14.
On the other hand, in Experimental Example 1 in which the heavy fraction having 10 or more carbon atoms derived and recovered from the third separator 22 is supplied to the cracking reforming reactor 10 after the hydrogenation reaction, and the cracking reforming reaction is performed, Even compared with Comparative Test Example 3, the BTX yield is sufficiently improved. Furthermore, it can be seen that the BTX yield is sufficiently improved as compared with Comparative Test Example 2. In Comparative Test Example 2, a heavy fraction mainly composed of tricyclic aromatic hydrocarbons once separated was mixed with a heavy fraction having 10 or more carbon atoms derived from and recovered from the third separator 22. Yes, BTX yield is improved by removing heavy fractions mainly composed of tricyclic aromatic hydrocarbons, because BTX yield is higher in Experimental Example 1 than in Comparative Test Example 2. I understand that.
Therefore, after extracting the tricyclic aromatic hydrocarbons together with the catalyst by the catalyst separator 14, the heavy fraction having 10 or more carbon atoms derived and recovered from the third separator 22 is used as a recycle oil as a raw oil. In addition, it was confirmed that the yield of BTX can be improved by using it for the cracking and reforming reaction step as compared with the case of using only the raw material oil for the cracking and reforming reaction step (Comparative Test Example 3).

  INDUSTRIAL APPLICABILITY The present invention is useful for the production of monocyclic aromatic hydrocarbons using, as raw materials, LCO obtained from an FCC device and kerosene, light oil obtained from a crude oil distillation device.

DESCRIPTION OF SYMBOLS 10 ... Decomposition | reformation reforming reactor, 12 ... Washing tower, 14 ... Catalyst separation apparatus, 16 ... 1st separation apparatus, 18 ... Debutizer (2nd separation apparatus), 20 ... Purification and recovery apparatus, 22 ... 3rd separation apparatus, 24 ... 1st return line, 26 ... 2nd return line, 28 ... Hydrogenation reactor, 30 ... Hydrogen recovery device, 32 ... Recycle line, 34 ... Hydrogen supply line, 40 ... Fractionator

Claims (4)

Monocyclic aromatic hydrocarbon production method for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms from a raw material oil having a 10 vol% distillation temperature of 140 ° C or higher and a 90 vol% distillation temperature of 380 ° C or lower Because
The raw material oil is contacted with a catalyst for producing monocyclic aromatic hydrocarbons containing crystalline aluminosilicate and reacted to produce a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms and a heavy hydrocarbon having 9 or more carbon atoms. A cracking and reforming reaction step to obtain a product containing a fraction;
From the mixture of the product and the monocyclic aromatic hydrocarbon production catalyst entrained by the product, derived from the cracking and reforming reaction step, the monocyclic aromatic hydrocarbon production catalyst A catalyst separation step for separating and removing together with the tricyclic aromatic hydrocarbons contained in the product;
A separation step of separating at least a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms and a heavy fraction having 9 or more carbon atoms from a derived product derived from the catalyst separation step;
A purification and recovery step of purifying and recovering the monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms separated in the separation step;
And a recycling step of returning the heavy fraction having 9 or more carbon atoms separated in the separation step to the cracking and reforming reaction step. A method for producing monocyclic aromatic hydrocarbons, comprising: Before the recycling step, it has a hydrogenation reaction step of hydrogenating a heavy fraction having 9 or more carbon atoms separated in the separation step,
2. The single recycling process according to claim 1, wherein in the recycling step, the hydrogenation reaction product of the heavy fraction having 9 or more carbon atoms obtained in the hydrogenation reaction step is returned to the cracking and reforming reaction step. A method for producing ring aromatic hydrocarbons.   A hydrogen recovery step for recovering hydrogen by-produced in the cracking and reforming reaction step from the product obtained in the cracking and reforming reaction step, and hydrogen recovered in the hydrogen recovery step to the hydrogenation reaction step. The method for producing monocyclic aromatic hydrocarbons according to claim 2, further comprising a hydrogen supply step of supplying.   The separation step includes a tricyclic aromatic hydrocarbon supply step of supplying a tricyclic aromatic hydrocarbon separated from a derivative derived from the catalyst separation step to the catalyst separation step. The manufacturing method of the monocyclic aromatic hydrocarbon as described in any one of claim | item 1 -3.

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