JP5690623B2 - Monocyclic aromatic hydrocarbon production method - Google Patents

Description

  The present invention relates to a method for producing monocyclic aromatic hydrocarbons.

Light cycle oil (hereinafter referred to as “LCO”), which is a cracked light oil produced by fluid catalytic cracking (hereinafter referred to as “FCC”), contains a large amount of polycyclic aromatic hydrocarbons and is used as light oil or heavy oil. It was. However, in recent years, from LCO, high-octane gasoline base materials and petrochemical raw materials that can be used as high-value-added monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms (for example, benzene, toluene, xylene, ethylbenzene, etc.) Obtaining is being considered.
For example, Patent Documents 1 to 3 propose a method for producing monocyclic aromatic hydrocarbons from polycyclic aromatic hydrocarbons contained in a large amount in LCO or the like using a zeolite catalyst.

JP-A-3-2128 Japanese Patent Laid-Open No. 3-52993 JP-A-3-26791

However, in the methods described in Patent Documents 1 to 3, it cannot be said that the yield of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms is sufficiently high.
Therefore, in order to sufficiently increase the yield of monocyclic aromatic hydrocarbons, the LCO and the like are decomposed and reformed, and the resulting product is hydrogenated, and then the hydrogenated reactant is again used in the cracking and reforming reaction step. It can be recycled.

  Here, the product obtained by cracking and reforming LCO or the like contains a large amount (for example, 50 to 95% by mass) of polycyclic aromatic hydrocarbons in the heavy fraction. Polycyclic aromatic hydrocarbons are mainly composed of bicyclic aromatic hydrocarbons, although depending on the composition of the raw material oil, and are good raw materials for monocyclic aromatic hydrocarbons by partial hydrogenation. Therefore, as described above, the yield of monocyclic aromatic hydrocarbons can be sufficiently increased by recycling the hydrogenated reactants of polycyclic aromatic hydrocarbons and subjecting them again to the cracking and reforming reaction step. .

  However, the hydrogenation reaction of bicyclic aromatic (polycyclic aromatic) hydrocarbons is an exothermic reaction, and the calorific value is very large. Therefore, when the product containing a large amount of such polycyclic aromatic hydrocarbons is hydrogenated, the reaction temperature in the reactor becomes extremely high, and it is difficult to carry out an appropriate reaction with conventional equipment. . In addition, for example, by supplying hydrogen stepwise from the middle of the reactor (hydrogen quenching, etc.), it is possible to suppress an increase in the reaction temperature and to make an appropriate reaction. The device configuration becomes complicated, and the equipment cost increases significantly.

  This invention is made | formed in view of the said situation, The place made into the objective can manufacture a C6-C8 monocyclic aromatic hydrocarbon with a high yield from the raw material oil containing a polycyclic aromatic hydrocarbon. At the same time, an object is to provide a method for producing monocyclic aromatic hydrocarbons capable of suppressing extreme heat generation during the hydrogenation reaction and avoiding a significant increase in the equipment cost of the hydrogenation reactor.

The method for producing monocyclic aromatic hydrocarbons of the present invention comprises a monocyclic aromatic having 6 to 8 carbon atoms from a feedstock having a 10% by volume distillation temperature of 140 ° C. or higher and a 90% by volume distillation temperature of 380 ° C. or lower. A method for producing monocyclic aromatic hydrocarbons for producing hydrocarbons, 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;
A purification and recovery step of purifying and recovering the monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms separated from the product generated in the cracking and reforming reaction step;
A dilution step of adding a diluent consisting of hydrocarbons to a heavy fraction having 9 or more carbon atoms separated from the product produced in the cracking and reforming reaction step;
A hydrogenation reaction step of hydrogenating the mixture;
A recycling step of returning the hydrogenation reaction product of the mixture obtained in the hydrogenation reaction step to the cracking and reforming reaction step.

  In the method for producing the monocyclic aromatic hydrocarbon, the diluent is separated and removed from the hydrogenation reaction product of the mixture obtained in the hydrogenation reaction step, the diluent is recovered, and the carbon number of 9 is obtained. It is preferable to have a diluent recovery step for reuse as a diluent added to the above heavy fraction.

In the method for producing monocyclic aromatic hydrocarbons, it is preferable to use a hydrocarbon oil having a boiling point of less than 185 ° C. as the diluent.
In the method for producing monocyclic aromatic hydrocarbons, it is preferable to use a diluent having a polycyclic aromatic hydrocarbon concentration of 50% by mass or less.

  Further, in the method for producing monocyclic aromatic hydrocarbons, in the dilution step, a heavy hydrocarbon having 9 or more carbon atoms that is separated from the product generated in the cracking and reforming reaction step and used for the hydrogenation reaction step. It is preferable to adjust the amount of the diluent so that the mass ratio of the fraction and the diluent is in the range of 10:90 to 80:20.

  In the method for producing monocyclic aromatic hydrocarbons, in the dilution step, the concentration of polycyclic aromatic hydrocarbons in a mixture obtained by adding a diluent to a heavy fraction having 9 or more carbon atoms is 5 to 5 It is preferable to add a diluent so that it may become 50 mass%.

  In the method for producing monocyclic aromatic hydrocarbons, in the hydrogenation reaction step, the hydrogenation reaction pressure is preferably 0.7 MPa to 13 MPa.

  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. In addition, because it has a dilution step, it suppresses extreme heat generation due to hydrogenation of polycyclic aromatic hydrocarbons in the hydrogenation reaction step, enables stable hydrogenation reaction, and greatly increases the equipment cost of the hydrogenation reactor. Can be avoided.

It is a figure for demonstrating 1st Embodiment of the manufacturing method of the monocyclic aromatic hydrocarbon of this invention. It is a figure for demonstrating 2nd Embodiment of the manufacturing method of the monocyclic aromatic hydrocarbon of this invention.

“First Embodiment”
Hereinafter, 1st Embodiment of the manufacturing method of the monocyclic aromatic hydrocarbon of this invention is described.
FIG. 1 is a diagram for explaining a first embodiment of a method for producing monocyclic aromatic hydrocarbons according to the present invention. The method for producing monocyclic aromatic hydrocarbons according to this embodiment uses carbon from raw material oil. This is a method for producing a monocyclic aromatic hydrocarbon of formula 6-8.

That is, the method for producing monocyclic aromatic hydrocarbons of the present embodiment, as shown in FIG.
(A) A raw material oil is brought into contact with a catalyst for producing a monocyclic aromatic hydrocarbon and reacted to produce a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms and a heavy fraction having 9 or more carbon atoms. (B) Separation step for separating the product produced in the cracking and reforming reaction step into a plurality of fractions (c) Purifying monocyclic aromatic hydrocarbons separated in the separation step Obtained in the dilution step (e) dilution step in which a diluent is added to the heavy fraction having 9 or more carbon atoms separated from the product produced in the purification and reforming reaction step (d) decomposition reforming reaction step. Hydrogenation reaction step of hydrogenating the mixture (f) Recycling step of returning the hydrogenation reaction product of the mixture obtained in the hydrogenation reaction step to the cracking and reforming reaction step (g) From the gas components separated in the separation step , Hydrogen recovery process to recover by-produced hydrogen in the cracking reforming reaction process (h) Hydrogen recovery Hydrogen supply step for supplying hydrogen recovered in step (b) to the hydrogenation reaction step (a), (c), (d), (e), (f) among the steps (a) to (h) Is an essential step in the invention according to claim 1 of the present application, and the steps (b), (g), and (h) are optional steps.

Hereinafter, each step will be specifically described.
<Decomposition and reforming reaction process>
In the cracking and reforming reaction step, the feedstock oil is brought into contact with the catalyst for producing monocyclic aromatic hydrocarbons, the saturated hydrocarbon contained in the feedstock oil is used as the hydrogen donor source, and the polycyclic aromatic is obtained by hydrogen transfer reaction from the saturated hydrocarbons. Group hydrocarbons are partially hydrogenated, ring-opened and converted to monocyclic aromatic hydrocarbons. It can also be converted to monocyclic aromatic hydrocarbons by cyclization and dehydrogenation of saturated hydrocarbons obtained in the feedstock or in the separation process. Furthermore, it is possible to obtain a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms by decomposing a monocyclic aromatic hydrocarbon having 9 or more carbon atoms. As a result, a product containing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms and a heavy fraction having 9 or more carbon atoms is obtained.

  This product includes hydrogen, methane, ethane, ethylene, LPG (propane, propylene, butane, butene, etc.), etc. in addition to monocyclic aromatic hydrocarbons and heavy fractions. The heavy fraction contains a large amount of bicyclic aromatic hydrocarbons such as naphthalene, methylnaphthalene, and dimethylnaphthalene, and also contains tricyclic or higher aromatic hydrocarbons such as anthracene depending on the feedstock. Yes. In the present application, these two-ring aromatic hydrocarbons and three or more ring aromatic hydrocarbons are collectively referred to as polycyclic aromatic hydrocarbons.

  In this cracking and reforming reaction step, most of the components such as naphthenobenzenes, paraffins and naphthenes in the feedstock oil are lost by producing monocyclic aromatic hydrocarbons. In addition, polycyclic aromatic hydrocarbons are partly converted to monocyclic aromatic hydrocarbons by decomposition and hydrogen transfer with saturated hydrocarbons, but at the same time the alkyl side chain is cleaved, mainly naphthalene, Bicyclic aromatic hydrocarbons with few side chains such as methylnaphthalene and dimethylnaphthalene are also by-produced. Therefore, in this cracking and reforming reaction step, monocyclic aromatic hydrocarbons are produced in high yield, and at the same time, bicyclic aromatic hydrocarbons are also by-produced as heavy fractions having 9 or more carbon atoms.

(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. With an oil having a 10% by volume distillation temperature of less than 140 ° C., a monocyclic aromatic hydrocarbon is produced from a light oil and does not meet the gist of the present invention. 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 feedstocks having a 10% by volume distillation temperature of 140 ° C. or more and a 90% by volume distillation temperature of 380 ° C. or less include LCO, LCO hydrorefined oil, coal liquefied oil, heavy oil hydrocracking refining Examples thereof include 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, but on the other hand, when hydrogenated in the hydrogenation reaction step, naphthe It can be converted into a monocyclic aromatic hydrocarbon by being converted into nobenzenes and recycled to the cracking reforming reaction step. Therefore, there are no particular restrictions on the feedstock oil containing a large amount of polycyclic aromatic hydrocarbons, but among the polycyclic aromatic hydrocarbons, aromatic hydrocarbons of 3 or more rings consume much hydrogen in the hydrogenation reaction step. However, even if it is a hydrogenation reaction product, it is not preferable to include a large amount since the reactivity in the cracking reforming reaction step is low. Therefore, the aromatic hydrocarbon of 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 format)
Examples of the reaction mode when the raw material oil is brought into contact with and reacted with the catalyst for producing a monocyclic aromatic hydrocarbon include a fixed bed, a moving bed, and a fluidized bed. In the present invention, since the heavy component is used as a raw material, a fluidized bed capable of continuously removing the coke adhering to the catalyst and capable of performing the reaction stably 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. When 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.

[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 / ZnO 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 catalyst for monocyclic aromatic hydrocarbon production contains gallium and / or zinc, the content of gallium and / or zinc in the catalyst for monocyclic aromatic hydrocarbon production is based on 100% by mass of the entire catalyst. It is preferable that it is 0.01-5.0 mass%, and it is more preferable that it is 0.05-2.0 mass%. If the content of gallium and / or 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 monocyclic aromatic hydrocarbons The yield can be higher.

[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 phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and other water-soluble phosphates are dissolved in water at an arbitrary concentration. What was prepared in this way can be used preferably.

  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 / or boron content in the monocyclic aromatic hydrocarbon production catalyst is preferably 0.1 to 10% by mass, based on 100% by mass of the entire catalyst, and 0.5 to 9% by mass. More preferably, it is 0.5-8 mass%. If the phosphorus and / or boron content is 0.1% by mass or more, the yield over time can be further prevented, and if it is 10% by mass or less, the yield of monocyclic aromatic hydrocarbons is increased. it can.

[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, it is in the form of powder, and in the case of a fixed bed, 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)
About the reaction pressure at the time of making a raw material oil contact and react with the catalyst for monocyclic aromatic hydrocarbon production, it is preferable to set it as 1.5 MPaG or less, and it is more preferable to set it as 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, gas passing over the catalyst for producing monocyclic aromatic hydrocarbons The time is preferably 1 to 300 seconds, more preferably 5 seconds for the lower limit and 150 seconds for the upper limit. 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.

<Separation process>
In the separation step, the product produced in the cracking and reforming reaction step is separated into a plurality of fractions.
In order to separate into a plurality of fractions, a known distillation apparatus or gas-liquid separation apparatus may be used. As an example of a distillation apparatus, what can distill and isolate | separate a some fraction with a multistage distillation apparatus like a stripper is mentioned. As an example of the gas-liquid separation device, a gas-liquid separation tank, a product introduction pipe for introducing the product into the gas-liquid separation tank, a gas component outflow pipe provided at the upper part of the gas-liquid separation tank, What comprises the liquid component outflow pipe | tube provided in the lower part of the said gas-liquid separation tank is mentioned.

  In the separation step, at least the gas component and the liquid fraction are separated, and the liquid fraction is further separated into a plurality of fractions. Examples of such a separation step include a form in which a gas component mainly containing a component having 4 or less carbon atoms (for example, hydrogen, methane, ethane, LPG, etc.) and a liquid fraction are separated, and a component having 2 or less carbon atoms ( For example, a form in which a gas component containing hydrogen, methane, ethane) and a liquid fraction are separated, and a form in which the liquid fraction is further separated into a fraction containing a monocyclic aromatic hydrocarbon and a heavy fraction. The liquid fraction is further separated into LPG, a fraction containing monocyclic aromatic hydrocarbons, and a heavy fraction, and the liquid fraction is further separated into LPG and a fraction containing monocyclic aromatic hydrocarbons, The form etc. which divide | segment and isolate | separate into a some heavy fraction are mentioned.

  In the present embodiment, the liquid fraction is separated into a gas component containing a component having 4 or less carbon atoms (for example, hydrogen, methane, ethane, LPG, etc.) and a liquid fraction. A form that is separated into a fraction containing a cyclic aromatic hydrocarbon and a heavier fraction (heavy fraction having 9 or more carbon atoms) separated therefrom is suitably employed. Here, the heavy fraction having 9 or more carbon atoms separated in the separation step varies depending on the properties of the feedstock, the cracking reforming reaction step, the separation step, etc., but the concentration of polycyclic aromatic hydrocarbons Is as high as 50 to 95% by mass.

<Purification and recovery process>
In the purification and recovery step, the monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms obtained in the separation step is purified and recovered.
In this purification and recovery step, since a fraction heavier than a monocyclic aromatic hydrocarbon is separated in the separation step, a benzene / carbon is produced from a fraction containing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms. A process for recovering toluene / xylene is employed. Here, the heavier fraction than the monocyclic aromatic hydrocarbon is a heavy fraction having 9 or more carbon atoms, mainly composed of a polycyclic aromatic hydrocarbon, and particularly a bicyclic aromatic such as naphthalenes. Contains a lot of hydrocarbons.

In the case where a form in which the liquid fraction is not fractionated is adopted as the separation step, a fraction heavier than the monocyclic aromatic hydrocarbon is separated and removed in this purification and recovery step, and the monocyclic aromatic is removed. A step of recovering hydrocarbons or benzene / toluene / xylene (monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms) is employed.
In addition, the liquid fraction is not well fractionated in the separation step, and when a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms is recovered, a large amount of fraction other than the monocyclic aromatic hydrocarbon is contained. In this case, the fraction may be separated and supplied to, for example, a hydrogenation reaction step described later. The fraction heavier than the monocyclic aromatic hydrocarbon is mainly composed of polycyclic aromatic hydrocarbons, and particularly contains a large amount of bicyclic aromatic hydrocarbons such as naphthalenes.

<Dilution process>
In the dilution step, a diluent made of hydrocarbons prepared separately in advance is added to the heavy fraction having 9 or more carbon atoms separated from the product produced in the cracking and reforming reaction step, and the above-mentioned heavy weight having 9 or more carbon atoms is added. The polycyclic aromatic hydrocarbon concentration in the mixture comprising the mass fraction and the diluent is set lower than the polycyclic aromatic hydrocarbon concentration in the heavy fraction. That is, the polycyclic aromatic hydrocarbon concentration in the heavy fraction subjected to the hydrogenation reaction step described later is lowered to an appropriate concentration.

The heavy fraction (heavy fraction obtained by removing the diluent from the mixture) separated in the separation step and directly used for the hydrogenation reaction step described later is the polycyclic aromatic hydrocarbon as described above. The concentration is very high, for example 50 to 95% by mass.
Here, the polycyclic aromatic hydrocarbons, for example, the bicyclic aromatic hydrocarbons occupying most of them, have a very large calorific value during the hydrogenation reaction as described above, and the content ratio of the polycyclic aromatic hydrocarbons is high. In the case of a raw material, it is desirable to take a technique for suppressing an excessive increase in reaction temperature in order to carry out a stable reaction. Also in the present invention, as a method for suppressing the reaction temperature, a general method can be adopted, and a method such as hydrogen quenching can be used. However, the heavy fraction separated in the separation step and directly used in the hydrogenation reaction step has a very high polycyclic aromatic hydrocarbon concentration of, for example, 50 to 95% by mass as described above. Therefore, if it is attempted to suppress the heat generation only by hydrogen quenching, the apparatus configuration for suppressing the heat generation becomes very complicated as compared with a normal kerosene oil desulfurization apparatus or the like.

  Therefore, in this embodiment, the concentration of the polycyclic aromatic hydrocarbon in the oil (mixture) to be subjected to the hydrogenation reaction step in advance by the dilution step is adjusted, and the heat generated by the hydrogenation of the polycyclic aromatic hydrocarbon is suppressed, Even a conventional general hydrogenation reactor can sufficiently perform a proper hydrogenation reaction.

  Diluents include hydrocarbons that are less likely to be hydrogenated than polycyclic aromatic hydrocarbons in the hydrogenation reaction step described below, specifically monocyclic rings such as trimethylbenzene and tetramethylbenzene (including various isomers). Aromatic hydrocarbons, naphthenes such as cyclohexanes and decalins, and hydrocarbons including paraffins are preferably used. At that time, it is necessary to select a raw material in which the diluent and the heavy fraction are compatible. When the concentration of the polycyclic aromatic hydrocarbon is extremely high, it is desirable to select a monocyclic aromatic hydrocarbon or the like. On the other hand, when the hydrogenation reaction conditions are set to a high pressure of 7 MPa or more, for example, the monocyclic aromatic hydrocarbon itself as the diluent may be hydrogenated. Thus, it is necessary to select an appropriate solvent in accordance with actual hydrogenation reaction conditions. In the case of recovery / reuse as a diluent, monocyclic aromatic hydrocarbons can also be used as diluents as saturated hydrocarbons, so there is no problem and the diluent can be used as it is in the cracking and reforming reaction step. Although there is no problem, it should be noted that a sufficient exothermic suppression effect may not be obtained in the hydrogenation reaction step. Further, the diluent may contain the polycyclic aromatic hydrocarbon as long as the concentration (content) of the polycyclic aromatic hydrocarbon is lower than that of the heavy fraction. Compared to a diluent that does not contain a ring aromatic hydrocarbon, the effect of suppressing heat generation is reduced. Specifically, refinery bases containing the monocyclic aromatic hydrocarbons, naphthenes, paraffins, etc. and also containing polycyclic aromatic hydrocarbons, for example, the cracking also used as the feedstock Various cracked base materials such as light oil (LCO), straight-run base materials and the like can also be used.

Further, the polycyclic aromatic hydrocarbon concentration of such a diluent may be any concentration that can lower the polycyclic aromatic hydrocarbon concentration in the mixture to be formed to an appropriate concentration, and is preferably 50% by mass. Hereinafter, it is more preferably 30% by mass or less, and further preferably 20% by mass or less.
Such a diluent is stored, for example, in a separately prepared storage tank, and is supplied to a line for transferring the heavy fraction from there and mixed with the heavy fraction. This reduces the polycyclic aromatic hydrocarbon concentration in the resulting mixture to an appropriate concentration.

  For example, in this dilution step, a mixture comprising a heavy fraction having 9 or more carbon atoms separated from the product produced in the cracking reforming reaction step and a diluent, that is, a mixture that is actually used in the hydrogenation reaction step. It is preferable to add the diluent to the heavy fraction so as to form a mixture so that the concentration of the polycyclic aromatic hydrocarbon is 5% by mass or more and 50% by mass or less. Moreover, it is more preferable to add a diluent so that it may become 15 to 35 mass%.

  By setting the polycyclic aromatic hydrocarbon concentration in the mixture to 50% by mass or less, heat generation due to the hydrogenation reaction in the hydrogenation reaction step, which will be described later, is suppressed, and an extreme increase in the reaction temperature in the hydrogenation reactor is prevented. Thus, an appropriate hydrogenation reaction (for example, conversion from a bicyclic aromatic hydrocarbon to naphthenobenzenes) can be performed. In addition, a general hydrogenation reactor can be used. Furthermore, by setting it as 5 mass% or more, the conversion from the polycyclic aromatic hydrocarbon which is the main purpose of the hydrogenation reaction step to naphthenobenzenes can be performed with a desired efficiency.

  However, if the polycyclic aromatic hydrocarbon concentration in the mixture is too low, the conversion efficiency from polycyclic aromatic hydrocarbons to naphthenobenzenes will not be sufficiently profitable in terms of cost. It is necessary to increase the size of the chemical reactor. Therefore, in order to further increase the conversion efficiency, it is more preferably set to 15% by mass or more as described above. Further, in order to sufficiently suppress the heat generation due to the hydrogenation reaction, the content is more preferably 35% by mass or less.

  In this dilution step, the amount of diluent to be supplied is appropriately determined in order to adjust the polycyclic aromatic hydrocarbon concentration in the mixture to the above-described concentration. At that time, the amount of the diluent is greatly influenced by the polycyclic aromatic hydrocarbon concentration in the heavy fraction having 9 or more carbon atoms separated from the product produced in the cracking and reforming reaction step. That is, if the polycyclic aromatic hydrocarbon concentration in the heavy fraction is high, it is necessary to relatively increase the amount of the diluent, and if the polycyclic aromatic hydrocarbon concentration in the heavy fraction is low. The amount of diluent can be relatively reduced. It is also greatly affected by the concentration of polycyclic aromatic hydrocarbons in the diluent. That is, if the polycyclic aromatic hydrocarbon concentration in the diluent is high, the amount of the diluent needs to be relatively large, and if the polycyclic aromatic hydrocarbon concentration in the diluent is low, the amount of the diluent Can be relatively reduced.

Usually, as described above, the polycyclic aromatic hydrocarbon concentration in the heavy fraction separated from the product in the separation step is 50 to 95% by mass.
Therefore, in diluting the heavy fraction, the polycyclic aromatic hydrocarbon concentration in the heavy fraction (product) and the polycyclic aromatic hydrocarbon concentration in the diluent are, for example, JPI-5S-49 “ Petroleum products-hydrocarbon type test method-high-performance liquid chromatographic method "or polycyclic in the mixture after confirmation by FID gas chromatographic method or two-dimensional gas chromatographic method and diluting with a diluent The mixing ratio of the heavy fraction and the diluent is determined so that the aromatic hydrocarbon concentration is 5 to 50% by mass, preferably 15 to 35% by mass as described above. Usually, when the concentration of the polycyclic aromatic hydrocarbon in the diluent is, for example, 20% by mass or less, the heavy fraction separated in the separation step (separated from the product produced in the cracking and reforming reaction step, hydrogen The mass ratio (mixing ratio) of the heavy fraction having 9 or more carbon atoms to be used in the chemical reaction step) and the diluent is adjusted to be in the range of 10:90 to 80:20.

  In addition, when the flow rate per unit time of the heavy fraction supplied from the separation step to the hydrogenation reaction step is constant, the diluent is also united under the conditions within the above mass ratio range. A constant flow rate per hour is added to the heavy fraction. When the flow rate per unit time of the heavy fraction changes, the diluent also changes its flow rate in response to this change.

<Hydrogenation reaction process>
In the hydrogenation reaction step, the mixture formed by adding a diluent to the heavy fraction having 9 or more carbon atoms in the dilution step is hydrogenated. Specifically, the mixture and hydrogen are supplied to a hydrogenation reactor, and at least a part of the polycyclic aromatic hydrocarbons contained in the mixture is hydrotreated using a hydrogenation catalyst. Here, a bicyclic aromatic hydrocarbon such as naphthalene is used for the heavy fraction separated in the separation step and further in the purification and recovery step and used for the hydrogenation reaction step, that is, the heavy fraction having 9 or more carbon atoms. (Polycyclic aromatic hydrocarbons) are contained in large quantities. Further, although it is less than the heavy fraction, the diluent also contains bicyclic aromatic (polycyclic aromatic) hydrocarbons depending on the type.

  Therefore, in the hydrogenation reaction step, it is preferable to hydrogenate this polycyclic aromatic hydrocarbon until the average number of aromatic rings is 1 or less. For example, naphthalene is preferably hydrogenated until it becomes tetralin (naphthenobenzene). Alkylnaphthalenes such as methylnaphthalene and dimethylnaphthalene also have naphthenobenzene, an aromatic hydrocarbon having a tetralin skeleton. It is preferable that Similarly, indene may be an aromatic hydrocarbon having an indane skeleton, anthracene may be an aromatic hydrocarbon having an octahydroanthracene skeleton, and phenanthrene may be an aromatic hydrocarbon having an octahydrophenanthrene skeleton. preferable.

  If hydrogenation is carried out until the average number of aromatic rings is 1 or less, when the hydrogenation reaction product is returned to the cracking and reforming reaction step in the recycling step described later, the hydrogenation reaction product, particularly an aromatic compound having a tetralin skeleton. Group hydrocarbons are easily converted to monocyclic aromatic hydrocarbons. Thus, in order to increase the yield of monocyclic aromatic hydrocarbons in the cracking and reforming reaction step, the polycyclic aromatic hydrocarbon content in the hydrogenation reaction product obtained in the hydrogenation reaction step is set to 40%. It is preferable to set it as mass% or less, It is more preferable to set it as 25 mass% or less, It is further more preferable to set it as 15 mass% or less.

  Moreover, it is preferable that content of the polycyclic aromatic hydrocarbon in the obtained hydrogenation reaction product is less than the content of the polycyclic aromatic hydrocarbon in the raw material oil. Regarding the polycyclic aromatic hydrocarbon content in the hydrogenation reaction product, that is, the concentration of the polycyclic aromatic hydrocarbon, the concentration may be decreased by increasing the amount of the hydrogenation catalyst or increasing the reaction pressure. it can. However, it is not necessary to hydrotreat all the polycyclic aromatic hydrocarbons until they become saturated hydrocarbons. Excessive hydrogenation causes an increase in hydrogen consumption and an excessive increase in calorific value.

As the reaction format in the hydrogenation reaction step, a fixed bed is preferably employed.
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 is preferably 0.7 MPa or more and 13 MPa or less. In particular, it is more preferably 1 MPa or more and 10 MPa or less, and further preferably 1 MPa or more and 7 MPa or less. If the hydrogenation pressure is 13 MPa or less, a hydrogenation reactor having a relatively low service pressure can be used, and the equipment cost can be reduced. Moreover, since the pressure of the hydrogen recovered in the hydrogen recovery step is usually 13 MPa or less, the recovered hydrogen can be used without increasing the pressure. On the other hand, if the pressure is 0.7 MPa or more, the yield of the hydrogenation reaction can be maintained sufficiently appropriately.

Hydrogen consumption may vary depending on the amount of diluent oil to be returned in the dilution step described later, is preferably not more than ^{2000scfb (337Nm 3 / m 3)} , more not more than 1500scfb (253Nm ³ / ^{m 3)} Preferably, it is more preferably 1000 scfb (169 Nm ³ / m ³ ) or less.
On the other hand, the hydrogen consumption is preferably 100 scfb (17 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.

  Here, the polycyclic aromatic hydrocarbons, for example, the bicyclic aromatic hydrocarbons occupying most of them, have a very large calorific value during the hydrogenation reaction as described above, and the content ratio of the polycyclic aromatic hydrocarbons is high. In the case of a raw material, it is desirable to take a technique for suppressing an excessive increase in reaction temperature in order to carry out a stable reaction. Also in the present invention, as a method for suppressing the reaction temperature, a general method can be adopted, and a method such as a circulating hydrogen gas quench adopted in a normal kerosene oil desulfurization apparatus can be used. However, the heavy fraction separated in the separation step has a very high polycyclic aromatic hydrocarbon concentration of, for example, 50 to 95% by mass as described above. When trying to do so, a quenching facility close to two digits is required, and the configuration around the reactor for suppressing heat generation becomes very complicated. Moreover, since it becomes a reactor with a very large calorific value, it is evaluated as a device having a large risk in an emergency operation. However, in this embodiment, as described above, a diluent is added to the heavy fraction to form a mixture, and the concentration of polycyclic aromatic hydrocarbons in the mixture is 5 to 50% by mass, preferably 15 to Since the content is 35% by mass, it is possible to suppress heat generation caused by hydrogenation of polycyclic aromatic hydrocarbons and to perform a sufficiently appropriate hydrogenation reaction even in a conventional general hydrogenation reactor.

<Hydrogen recovery process>
In the hydrogen recovery step, hydrogen is recovered from the gas component obtained in the separation step.
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.

<Hydrogen supply process>
In the hydrogen supply step, the hydrogen obtained in the hydrogen recovery step is supplied to the hydrogenation reactor in the hydrogenation reaction step. The hydrogen supply amount at that time is adjusted according to the amount of the mixture to be subjected to the hydrogenation reaction step. If necessary, the hydrogen pressure is adjusted.
By having a hydrogen supply step as in this embodiment, the mixture can be hydrogenated using hydrogen by-produced in the cracking and reforming reaction step. Covering part or all of the hydrogen with by-product hydrogen makes it possible to reduce part or all of the external hydrogen supply.

<Recycling process>
In the recycling process, the hydrogenation reaction product of the mixture obtained in the hydrogenation reaction process is mixed with the raw material oil and returned to the cracking and reforming reaction process.
By returning the hydrogenation reaction product of the mixture to the cracking and reforming reaction step, it is possible to obtain a monocyclic aromatic hydrocarbon from the heavy fraction that was a byproduct as a raw material. Therefore, the amount of by-products can be reduced and the amount of monocyclic aromatic hydrocarbons produced 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. From these facts, it is possible to improve the overall yield of monocyclic aromatic hydrocarbons with respect to the amount of feedstock supplied.
In the recycling step, the entire hydrogenation reaction product does not necessarily have to be recycled to the raw material oil in the cracking and reforming reaction step. In that case, the hydrogenated reactant that has not been recycled can also be used as a fuel substrate.

In addition, monocyclic aromatic hydrocarbons, naphthenes, and paraffins in the diluent also contribute to the production of monocyclic aromatic hydrocarbons in the cracking and reforming reaction step. Therefore, this diluent also contributes to the improvement of the yield of monocyclic aromatic hydrocarbons.
If the heavy fraction is directly returned to the cracking and reforming reaction step without hydrotreating, the yield of monocyclic aromatic hydrocarbons is almost zero because the reactivity of polycyclic aromatic hydrocarbons is low. Does not improve.

In the method for producing aromatic hydrocarbons of the present embodiment, since it has a hydrogenation reaction step and a recycling step, a monocyclic aromatic hydrocarbon can be obtained using a heavy fraction that is a by-product as a raw material. Can do. Therefore, the amount of by-products can be reduced and the amount of monocyclic aromatic hydrocarbons produced can be increased. Therefore, a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms can be produced from a raw material oil containing polycyclic aromatic hydrocarbons with a high yield.
In addition, a diluent is added to the heavy fraction having 9 or more carbon atoms separated from the product produced in the cracking and reforming reaction step, and the polycyclic aromatic hydrocarbon concentration in the resulting mixture is determined as the heavy fraction. Because it has a dilution step that lowers the polycyclic aromatic hydrocarbon concentration of, it suppresses extreme heat generation due to the hydrogenation of the polycyclic aromatic hydrocarbon in the hydrogenation reaction step, enabling a stable hydrogenation reaction, A significant increase in the equipment cost of the hydrogenation reactor can be avoided.

“Second Embodiment”
A second embodiment of the method for producing monocyclic aromatic hydrocarbons of the present invention will be described.
FIG. 2 is a diagram for explaining a second embodiment of the method for producing monocyclic aromatic hydrocarbons of the present invention, and the method for producing monocyclic aromatic hydrocarbons of this embodiment is also based on carbon from raw material oil. This is a method for producing a monocyclic aromatic hydrocarbon of formula 6-8.

That is, the method for producing a monocyclic aromatic hydrocarbon of the present embodiment, as shown in FIG.
(I) A raw material oil is brought into contact with a catalyst for producing a monocyclic aromatic hydrocarbon and reacted to produce a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms and a heavy fraction having 9 or more carbon atoms. (J) Separation step for separating the product produced in the cracking and reforming reaction step into a plurality of fractions (k) Purifying monocyclic aromatic hydrocarbons separated in the separation step Obtained in the dilution step (m) dilution step in which a diluent is added to the heavy fraction having 9 or more carbon atoms separated from the product produced in the cracking reforming reaction step. Hydrogenation reaction step of hydrogenating the mixture (n) The diluent is separated and removed from the hydrogenation reaction product of the mixture obtained in the hydrogenation reaction step, and the diluent is recovered and used as the diluent in the dilution step. Diluent recovery process to be reused (o) The hydrogenation reaction product of the mixture obtained in the hydrogenation reaction process is separated. Recycle process to return to the reforming reaction process (p) Hydrogen recovery process for recovering hydrogen by-produced in the cracking reforming reaction process from the gas components separated in the separation process (q) Hydrogen recovered in the hydrogen recovery process Step of supplying hydrogen to the hydrogenation reaction step Among the steps (i) to (q) above, the steps (i), (k), (l), (m), (n), (o) are the present application. It is an essential step in the invention according to claim 2, and the steps (j), (p) and (q) are optional steps.

(I) The cracking and reforming reaction step can be performed in the same manner as the (a) cracking and reforming reaction step in the first embodiment.
(J) The separation step can be performed in the same manner as the (b) separation step in the first embodiment.
The (k) purification / recovery step can be performed in the same manner as the (c) purification / recovery step in the first embodiment.
The (m) hydrogenation reaction step can be performed in the same manner as the (e) hydrogenation reaction step in the first embodiment.
The (p) hydrogen recovery step can be performed in the same manner as the (g) hydrogen recovery step in the first embodiment.
The (q) hydrogen supply step can be performed in the same manner as the (h) hydrogen supply step in the first embodiment.

In the (l) dilution step in the present embodiment, in the same manner as the (d) dilution step in the first embodiment, hydrocarbons are separated from hydrocarbons into the heavy fraction having 9 or more carbon atoms separated in the separation step. The concentration of polycyclic aromatic hydrocarbons in the mixture consisting of the heavy fraction having 9 or more carbon atoms and the diluent is determined from the concentration of polycyclic aromatic hydrocarbons in the heavy fraction. make low.
As the diluent used in this embodiment, instead of using hydrocarbons stored in a separately prepared storage tank as in the first embodiment, the diluent recovered in the diluent recovery step described later is reused. And use. However, hydrocarbons are supplied from a separately prepared storage tank or the like when starting up or in a case where the diluent cannot be recovered in the diluent recovery process and the diluent is insufficient.

  Therefore, as the diluent, unlike the first embodiment, the diluent can be easily separated and recovered from the hydrogenation reaction product in the diluent recovery step, specifically, hydrogen of polycyclic aromatic hydrocarbons by distillation operation. Those which are easily separated from the compounds (especially naphthenobenzene) are used. Further, as this diluent, hydrocarbons that are difficult to be hydrogenated are used as in the first embodiment. Therefore, polycyclic aromatic hydrocarbons having a boiling point higher than that of naphthenobenzene and easily subjected to a hydrogenation reaction are not mainly contained. As shown in FIG. 2, the diluent of this embodiment circulates the hydrogenation reaction process, the diluent recovery process, and the dilution process many times, so that a part of the diluent cannot be recovered from the recovery process, etc., and the diluent is reduced. In some cases, the heavy fraction is partially decomposed and recovered as a diluent in the diluent recovery step, and the diluent increases. Therefore, it is necessary to control the diluent circulation amount as necessary. However, in any case, a material that is less susceptible to hydrogenation and decomposition than necessary in the hydrogenation reaction step is preferable.

Therefore, as such a hydrocarbon, for example, a hydrocarbon having a boiling point lower than that of t-decalin (t-decahydronaphthalene) having a boiling point of 185 ° C. generated in the hydrogenation reaction step is preferably used. That is, naphthene, paraffin, or monocyclic aromatic compounds that are easily separated from polycyclic aromatic hydrocarbons or naphthenobenzene by distillation and are not easily hydrogenated are suitably used as diluents.
In addition, the dilution process of this embodiment is the same as the dilution process of 1st Embodiment except using such a diluent. That is, the polycyclic aromatic hydrocarbon concentration of the mixture formed by diluting with a diluent is the same as in the dilution step of the first embodiment. In addition, regarding the dilution rate by the diluent, that is, the mass ratio (mixing ratio) between the heavy fraction and the diluent, the present embodiment basically uses a diluent that does not contain polycyclic aromatic hydrocarbons. Compared to the mass ratio in one embodiment, the amount of diluent added can be reduced.

<Diluent recovery process>
In the diluent recovery step, the diluent is separated and removed from the hydrogenation reaction product of the mixture obtained in the hydrogenation reaction step, and the diluent is recovered. The recovered diluent is reused as a diluent to be added to the heavy fraction having 9 or more carbon atoms in the dilution step.
As a method for separating and removing the diluent from the hydrogenation reaction product of the mixture, the distillation operation is preferably employed as described above. That is, in this diluent recovery step, for example, the distillation tower separates into components having a boiling point lower than 185 ° C. and components higher than this. Thereby, for example, a component having a boiling point lower than 185 ° C. can be separated from a component having a boiling point higher than 185 ° C. Therefore, the diluent can be regenerated by cooling and condensing the separated component having a boiling point lower than 185 ° C., that is, the diluent component.
Therefore, this is sent to the dilution step, added to the heavy fraction to form a mixture, and then the hydrogenation reaction step, the diluent recovery step, and the dilution step are sequentially circulated.

  (O) Unlike the first embodiment, in the recycling process, instead of directly returning the total amount of the hydrogenation reaction product of the mixture obtained in the hydrogenation reaction process to the cracking reforming reaction process, a diluent recovery process The fraction from which the diluent has been separated is mixed with the raw material oil and returned to the cracking and reforming reaction step.

Even in the method for producing monocyclic aromatic hydrocarbons of the present embodiment, since it has a hydrogenation reaction step and a recycling step, it has 6 to 8 carbon atoms in a high yield from a raw material oil containing polycyclic aromatic hydrocarbons. The monocyclic aromatic hydrocarbon can be produced.
Moreover, since it has a dilution process, the extreme heat_generation | fever of the polycyclic aromatic hydrocarbon in a hydrogenation reaction process can be suppressed, and the raise of the installation cost of a hydrogenation reactor can be avoided.
Furthermore, since it has a diluent recovery step of separating and removing the diluent from the hydrogenation reaction product of the mixture, and recovering and reusing the diluent, a new diluent can be obtained by circulating the diluent. The process of continuing to supply is unnecessary, and the operating conditions can be simplified.

"Other embodiments"
It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention.
For example, the hydrogen used in the hydrogenation reaction step is not produced as a by-product in the cracking and reforming reaction step, and hydrogen obtained by a known hydrogen production method may be used. Further, hydrogen produced as a by-product in other catalytic cracking methods may be used. Further, the monocyclic aromatic hydrocarbons may be combined and sent to the hydrogenation reaction step and then separated. In that case, you may serve as a C6-C8 monocyclic aromatic hydrocarbon collection | recovery process and a diluent collection process.

  Moreover, in the said embodiment, the heavy fraction discharge process of extracting a fixed amount of a part of heavy fractions having 9 or more carbon atoms obtained from the fraction separated in the separation step and discharging it out of the system. It may be provided. Specifically, when the heavy fraction is directly supplied from the separation step to the hydrogenation reaction step, a part of the heavy fraction is extracted and discharged out of the system before the diluent is mixed in the dilution step. You may do it.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to these Examples.

[Catalyst preparation example for monocyclic aromatic hydrocarbon production]
Preparation of catalyst containing gallium and phosphorus supported crystalline aluminosilicate:
From 1706.1 g of sodium oxalate (J sodium silicate No. 3, SiO ₂ : 28 to 30% by mass, Na: 9 to 10% by mass, balance water, manufactured by Nippon Chemical Industry Co., Ltd.) and 2227.5 g of water Solution (A), Al ₂ (SO ₄ ) ₃ · 14 to 18H ₂ O (special reagent grade, manufactured by Wako Pure Chemical Industries, Ltd.), 64.2 g, tetrapropylammonium bromide, 369.2 g, H ₂ SO ₄ (97% by mass) of 152.1 g, NaCl (326.6 g), and 2975.7 g of water (B) were prepared.
Next, the solution (B) was gradually added to the solution (A) while stirring the solution (A) at room temperature. The resulting mixture was vigorously stirred with a mixer for 15 minutes to break up the gel into a milky homogeneous fine state.

Next, this mixture was put into a stainless steel autoclave, and a crystallization operation was performed under self-pressure under the conditions of a temperature of 165 ° C., a time of 72 hours, and a stirring speed of 100 rpm. After completion of the crystallization operation, the product was filtered to recover the solid product, and washing and filtration were repeated 5 times using about 5 liters of deionized water. The solid substance obtained by filtration was dried at 120 ° C., and further calcined at 550 ° C. for 3 hours under air flow.
As a result of X-ray diffraction analysis (model name: Rigaku RINT-2500V), the obtained fired product was confirmed to have an MFI structure. The fluorescent X-ray analysis (model name: Rigaku ZSX101e) _by, SiO 2 / _Al 2 _{O 3} ratio (molar ratio) was 64.8. Moreover, the aluminum element contained in the lattice skeleton calculated from this result was 1.32% by mass.

Subsequently, 30 mass% ammonium nitrate aqueous solution was added at a rate of 5 mL per 1 g of the obtained fired product, heated and stirred at 100 ° C. for 2 hours, filtered, and washed with water. This operation was repeated 4 times, followed by drying at 120 ° C. for 3 hours to obtain an ammonium type crystalline aluminosilicate. Thereafter, baking was performed at 780 ° C. for 3 hours to obtain a proton-type crystalline aluminosilicate.
Next, 120 g of the obtained proton-type crystalline aluminosilicate was impregnated with 120 g of an aqueous gallium nitrate solution so that 0.4% by mass (a value obtained by setting the total mass of the crystalline aluminosilicate to 100% by mass) was supported, Dry at 120 ° C. Then, it baked at 780 degreeC under air circulation for 3 hours, and obtained the gallium carrying | support crystalline aluminosilicate.
Next, 30 g of the obtained gallium-supporting crystalline aluminosilicate was mixed with 30 g of diammonium hydrogenphosphate aqueous solution so that 0.7% by mass of phosphorus (the value with the total mass of the crystalline aluminosilicate being 100% by mass) was supported. Impregnation and drying at 120 ° C. Then, it baked at 780 degreeC under air circulation for 3 hours, and obtained the catalyst A containing crystalline aluminosilicate, gallium, and phosphorus.

  The following Examples 1 to 3 were obtained in the cracking and reforming reaction step based on the first embodiment shown in FIG. 1 and Examples 4 to 7 were based on the second embodiment shown in FIG. Diluent was added to the heavy fraction separated from the product to dilute the heavy fraction.

Example 1
LCO (10% by volume distillation temperature 215 ° C., 90% by volume distillation temperature 318 ° C.) shown in Table 1 as a raw material oil is included in the reaction temperature: 538 ° C., reaction pressure: 0.3 MPaG, LCO and catalyst. Contact and reaction with catalyst A (MFI type zeolite carrying 0.4% by mass of gallium and 0.7% by mass of phosphorus) in a fluidized bed reactor under the condition of contact time with zeolite component of 12 seconds, and cracking and reforming Reaction was performed. Subsequently, the obtained monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms was recovered by distillation. The content of polycyclic aromatic hydrocarbons in the heavy fraction having 9 or more carbon atoms after the removal of the monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms was calculated using a two-dimensional gas chromatograph (ZTEX KT2006 GC It was 87 mass% when it measured using (* GC system).
Subsequently, 1,3,5-trimethylbenzene (TMB) as a diluent was added to the heavy fraction so as to have a mass ratio of 17:83 (heavy fraction: diluent). Thereafter, a mixed oil of a heavy fraction and a diluent (polycyclic aromatic hydrocarbon content is 15% by mass) using a commercially available nickel-molybdenum catalyst, reaction temperature 350 ° C., reaction pressure 5 MPa, LHSV = Hydrogenation was performed under the condition of 0.5 h- ¹ . The hydrogen used in the hydrogenation reaction step was hydrogen separated from the hydrogen recovery step.
Further, the hydrogenation reaction product obtained by treating the mixed oil of the heavy fraction and the diluent in the hydrogenation reaction step is recycled to the cracking and reforming reaction step, and the number of carbon atoms is 6 under the cracking and reforming reaction conditions. ˜8 monocyclic aromatic hydrocarbons were produced. The quantity of the obtained C6-C8 monocyclic aromatic hydrocarbon was 62 mass%.

(Example 2)
In the dilution step, monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms were produced in the same manner as in Example 1 except that the light oil having the properties shown in Table 2 was used as the diluent. In addition, content of the polycyclic aromatic hydrocarbon of the mixed oil of a heavy fraction and a diluent was 18 mass%. The quantity of the obtained C6-C8 monocyclic aromatic hydrocarbon was 45 mass%.

(Example 3)
In the diluting step, the same as in Example 1 except that a mixture of 50% by mass of 1,3,5-trimethylbenzene (TMB) and 50% by mass of normal decane was used as a diluent. A ring aromatic hydrocarbon was produced. In addition, content of the polycyclic aromatic hydrocarbon of the mixed oil of a heavy fraction and a diluent was 15 mass%. The quantity of the obtained C6-C8 monocyclic aromatic hydrocarbon was 53 mass%.

Example 4
LCO (10% by volume distillation temperature 215 ° C., 90% by volume distillation temperature 318 ° C.) shown in Table 1 as a raw material oil is included in the reaction temperature: 538 ° C., reaction pressure: 0.3 MPaG, LCO and catalyst. Contact and reaction with catalyst A (MFI type zeolite carrying 0.4% by mass of gallium and 0.7% by mass of phosphorus) in a fluidized bed reactor under the condition of contact time with zeolite component of 12 seconds, and cracking and reforming Reaction was performed. Subsequently, the obtained monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms was recovered by distillation. The content of polycyclic aromatic hydrocarbons in the heavy fraction having 9 or more carbon atoms after the removal of the monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms was calculated using a two-dimensional gas chromatograph (ZTEX KT2006 GC It was 87 mass% when it measured using (* GC system).
Subsequently, 1,3,5-trimethylbenzene (TMB) as a diluent was added to the heavy fraction so as to have a mass ratio of 5:95 (heavy fraction: diluent) (dilution step). Thereafter, a mixed oil of heavy fraction and diluent (polycyclic aromatic hydrocarbon content is 8% by mass) using a commercially available nickel-molybdenum catalyst, reaction temperature 350 ° C., reaction pressure 5 MPa, LHSV = Hydrogenation was performed under the condition of 0.5 h- ¹ . The hydrogen used in the hydrogenation reaction step was hydrogen separated from the hydrogen recovery step.
Further, the hydrogenation reaction product obtained by treating the mixed oil of heavy fraction and diluent in the hydrogenation reaction step is fractionated into a fraction having a boiling point higher than 185 ° C and a fraction having a boiling point of 185 ° C or lower. The fraction having a boiling point of less than 185 ° C. was returned before the hydrogenation reaction step and reused as a diluent. A fraction having a boiling point of 185 ° C. or higher was recycled to the cracking and reforming reaction step, and monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms were produced under the cracking and reforming reaction conditions. The quantity of the obtained C6-C8 monocyclic aromatic hydrocarbon was 44 mass%.

(Example 5)
In the dilution step, a mixture of 50% by mass of 1,3,5-trimethylbenzene (TMB) and 50% by mass of normal decane was used as a diluent, and the mixing ratio of the heavy fraction and the diluent was 50:50 by mass ratio. Thus, a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms was produced in the same manner as in Example 4 except that the reaction pressure was 3 MPa in the hydrogenation reaction step. In addition, content of the polycyclic aromatic hydrocarbon of the mixed oil of a heavy fraction and a diluent was 44 mass%. The quantity of the obtained C6-C8 monocyclic aromatic hydrocarbon was 46 mass%.

(Example 6)
A monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms was produced in the same manner as in Example 4, except that the mixing ratio of the heavy fraction and the diluent was 33:67 in the dilution step. . In addition, content of the polycyclic aromatic hydrocarbon of the mixed oil of a heavy fraction and a diluent was 32 mass%. The quantity of the obtained C6-C8 monocyclic aromatic hydrocarbon was 45 mass%.

(Example 7)
In the dilution step, the mixing ratio of the heavy fraction and the diluent was set to 17:83 by mass ratio, and the reaction pressure was set to 7 MPa in the hydrogenation reaction step. 8 monocyclic aromatic hydrocarbons were produced. In addition, content of the polycyclic aromatic hydrocarbon of the mixed oil of a heavy fraction and a diluent was 15 mass%. The amount of the obtained monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms was 43% by mass.

(Comparative Example 1)
A monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms was produced in the same manner as in Example 1 except that the heavy fraction was not diluted. The quantity of the obtained C6-C8 monocyclic aromatic hydrocarbon was 44 mass%.

Table 3 shows the following results.
"Diluent": Type of diluent (in the case of a mixture, the lower part shows the mass ratio of each component)
“Heavy fraction / diluent”: Mass ratio of heavy fraction to diluent “Polycyclic aromatics after dilution”: Polycyclic aromatic hydrocarbon concentration of the mixture after dilution in the dilution step (mass) %)
“Reaction pressure”: Reaction pressure (MPa) in hydrogenation reaction process
“Polycyclic aromatics after hydrogenation reaction”: Polycyclic aromatic hydrocarbon concentration (mass%) in the hydrogenated product after the hydrogenation reaction step
"Hydrogen conversion of diluent": Ratio of hydrogenated diluent (%)
"Heavy fraction treatment rate per unit time": Treatment rate of heavy fraction per unit time (comparative example 1 that is undiluted is assumed to be 100)
“Heat generation amount”: Calculated value of the heat generation amount per kg of oil to be subjected to the hydrogenation reaction step (comparative example 1 which is undiluted is 100)
“Diluent separation by distillation”: presence or absence of diluent recovery step “monocyclic aromatic having 6 to 8 carbon atoms”: monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms obtained in the cracking and reforming reaction step Amount (mass%)

  From the results shown in Table 3, in Examples 1 to 7 in which dilution was performed compared to Comparative Example 1 in which the heavy fraction was directly hydrogenated without dilution (undiluted), the oil used for the hydrogenation reaction step It was confirmed that the calorific value per kg was reduced. This indicates that by adding a diluent to the heavy fraction, the concentration of polycyclic aromatic hydrocarbons was reduced and heat generation was relatively suppressed. Thus, the hydrogenation operation can be stably performed. Further, it was found that the hydrogenation conversion rate of the diluent is very low, and even when the diluent is recovered, the diluent can be reused and effectively used.

Claims (7)

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;
A purification and recovery step of purifying and recovering the monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms separated from the product generated in the cracking and reforming reaction step;
A diluent consisting of hydrocarbons is added to the heavy fraction having 9 or more carbon atoms separated from the product produced in the cracking and reforming reaction step , and the polycyclic aromatic hydrocarbons in the mixture thus obtained are added . A dilution step in which the concentration is lower than the concentration of polycyclic aromatic hydrocarbons in the heavy fraction ;
A hydrogenation reaction step of hydrogenating the mixture;
A recycle step of returning the hydrogenation reaction product of the mixture obtained in the hydrogenation reaction step to the cracking and reforming reaction step, and producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms Method.   Dilution that separates and removes the diluent from the hydrogenation reaction product of the mixture obtained in the hydrogenation reaction step, recovers the diluent, and reuses it as a diluent to be added to the heavy fraction having 9 or more carbon atoms The method for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms according to claim 1, further comprising an agent recovery step.   The method for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms according to claim 2, wherein a hydrocarbon oil having a boiling point of less than 185 ° C is used as the diluent.   The monocyclic aromatic carbon having 6 to 8 carbon atoms according to any one of claims 1 to 3, wherein the diluent has a polycyclic aromatic hydrocarbon concentration of 50% by mass or less. A method for producing hydrogen.   In the dilution step, the mass ratio of the heavy fraction having 9 or more carbon atoms separated from the product produced in the cracking reforming reaction step and used for the hydrogenation reaction step and the diluent is 10 The amount of diluent is adjusted so that it may become in the range of: 90 to 80:20, The C6-C8 monocyclic aromatic carbonization as described in any one of Claims 1-4 characterized by the above-mentioned. A method for producing hydrogen.   In the dilution step, the diluent is added so that the polycyclic aromatic hydrocarbon concentration in the mixture obtained by adding the diluent to the heavy fraction having 9 or more carbon atoms is 5 to 50% by mass. The manufacturing method of the C6-C8 monocyclic aromatic hydrocarbon as described in any one of Claims 1-5.   In the said hydrogenation reaction process, hydrogenation reaction pressure shall be 0.7 Mpa-13 Mpa, The C6-C8 monocyclic aromatic hydrocarbon of any one of Claims 1-6 characterized by the above-mentioned. Production method.

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