JP5330056B2 - Method for producing monocyclic aromatic hydrocarbons - Google Patents

Description

  The present invention relates to a method for producing high-value-added monocyclic aromatic hydrocarbons by subjecting surplus polycyclic aromatic hydrocarbons as feedstock to appropriate hydrogenolysis without excessively consuming expensive hydrogen. It is.

  It is common knowledge for those skilled in the art to suppress poisoning of the hydrocracking catalyst by pretreatment (mainly desulfurization) prior to the cracking reaction using the hydrocracking catalyst. At that time, considering protection of the hydrocracking catalyst, a catalyst having a higher desulfurization activity is preferable, and for that reason, it has been considered that increasing the hydrogenation activity as much as possible is a promising means (Non-patent Document 1).

  On the other hand, although a method for selectively producing alkylbenzenes that are monocyclic aromatic hydrocarbons from a fraction containing polycyclic aromatics is disclosed (Patent Document 1), as described above, hydrogen having enhanced hydrogenation activity. A hydrodesulfurization catalyst is used, which is not necessarily a method of suppressing excessive nuclear hydrogenation reaction.

International Publication No. 2007/135769 Pamphlet

Hydrocracking Science and Technology, J. et al. Scherzer and A.S. J. et al. Gruia, Marcel Dekker, Inc

  When selectively producing high-value-added monocyclic aromatic hydrocarbons from surplus polycyclic aromatic hydrocarbons, appropriate hydrorefining and hydrocracking reactions can be carried out without excessive consumption of expensive hydrogen. An effective method of applying has not been established. Under such circumstances, an object of the present invention is to provide a method for efficiently producing monocyclic aromatic hydrocarbons having high added value from polycyclic aromatic hydrocarbons while suppressing overdecomposition.

  By carrying out a selective nuclear hydrogenation reaction in which only one ring of the polycyclic aromatic hydrocarbon remains with a hydrorefining catalyst that suppresses the hydrogenation activity, an excessive It became possible to suppress the nuclear hydrogenation reaction.

  That is, the present invention is as follows.

[1] A raw material hydrocarbon oil in which the polycyclic aromatic hydrocarbon is 50 volume% or more and the total amount of the 1 ring aromatic hydrocarbon and the 1.5 ring aromatic hydrocarbon is less than 20 volume%,
(1) In the presence of hydrogen, the catalyst is brought into contact with a hydrorefining catalyst having a molybdenum content of 0.5% by weight or more and less than 8.0% by weight for desulfurization and denitrification, and polycyclic aromatic hydrocarbons are removed. Following the first step to convert to 1.5-ring aromatic hydrocarbons, (2) the intermediate oil obtained from the first step is contacted with a hydrocracking catalyst in the presence of hydrogen to convert to 1-ring aromatic hydrocarbons. By performing the second step to
A process for producing a monocyclic aromatic hydrocarbon, comprising producing a hydrocarbon having a monocyclic aromatic hydrocarbon content of 20% by volume or more and a polycyclic aromatic hydrocarbon content of less than 1.0% by volume.
[2] In the above first step and second step, the ratio of the residual degree of monocyclic aromatic hydrocarbons (1 RAsel) of the produced oil to the feedstock and the desulfurization rate (HDS) is 0.36 or more [1] The process for producing a monocyclic aromatic hydrocarbon according to [1].

  Use hydrorefining catalyst suitable for desulfurization and denitrification, suppress excessive nuclear hydrogenation under appropriate reaction conditions, and use efficiently without reducing unnecessary aromatic rings contained in the feedstock. Thus, high-value-added monocyclic aromatic hydrocarbons can be obtained at a high concentration, and consumption of expensive hydrogen can be suppressed.

  In the present invention, the polycyclic aromatic hydrocarbon refers to a hydrocarbon having two or more aromatic rings, and the one-ring aromatic hydrocarbon is obtained by substituting hydrogen of benzene with 0 to 6 chain hydrocarbon groups. It is also called alkylbenzenes. The 1.5-ring aromatic hydrocarbon is one saturated aromatic ring such as tetralin (1,2,3,4-tetrahydronaphthalene) or indane (2,3-dihydroindene). The compound which has the naphthene ring of 1 in 1 molecule.

  Hereinafter, for details of the method for producing a hydrocarbon fraction of the present invention, raw material hydrocarbon oil, first step, second step, hydrocracking catalyst, hydrocracking catalyst manufacturing method, hydrocracking product oil separation method The product hydrocarbons will be described in order.

[Raw material hydrocarbon oil]
In the present invention, the hydrocarbon oil used as a raw material is a polycyclic aromatic hydrocarbon of 50% by volume or more, preferably 55% by volume or more, particularly preferably 60% by volume or more. A feed hydrocarbon oil in which the total amount of 5-ring aromatic hydrocarbons is less than 20% by volume, preferably less than 15% by volume, particularly preferably 10% by volume. When the polycyclic aromatic hydrocarbon is less than 50% by volume, the desired monocyclic aromatic hydrocarbon (alkylbenzene) cannot be obtained in a high yield, which is not preferable. Further, when the total amount of the 1-ring aromatic hydrocarbon and the 1.5-ring aromatic hydrocarbon is 20% by volume or more, the hydrocracking reaction of the 1-ring aromatic hydrocarbon itself is promoted, which is not preferable.

  In addition, the larger the number of polycyclic aromatic rings, the better. It is preferable that the polycyclic aromatics in the raw material are bicyclic from the viewpoint of efficiently producing a single aromatic ring. . Among them, the polycyclic aromatics in the raw material are preferably those having 3 or more rings and more those having 2 rings. The content of three or more ring aromatic hydrocarbons is preferably 5.0% by volume or less, more preferably 3.0% by volume or less, and particularly preferably 1.0% by volume or less. Is preferably 30% by volume or more, more preferably 40% by volume or more, and particularly preferably 50% by volume or more.

  A preferable distillation property can be set based on the aromatic composition. That is, considering the boiling point (218 ° C.) of the bicyclic aromatic hydrocarbon naphthalene, the fraction of at least 160 ° C. and less than 280 ° C. is 10% by volume or more, and the fraction of 215 ° C. or more is 30% by volume or more. More preferably, 40% by volume or more is preferable. Therefore, as a preferable distillation property of the feedstock oil, a 10% distillation temperature is 100 ° C. or higher and lower than 230 ° C., more preferably 140 ° C. or higher and lower than 230 ° C., further preferably 150 ° C. or higher and lower than 220 ° C., and 90% distillation. The temperature is 230 ° C. or higher and lower than 400 ° C., more preferably 230 ° C. or higher and lower than 380 ° C., further 230 ° C. or higher and lower than 360 ° C., particularly 240 ° C. or higher and lower than 330 ° C.

  As a reaction inhibitory substance in the raw material for hydrocracking reaction, the nitrogen content is usually 0.1 wt% or more and less than 3000 wt ppm, and the sulfur content is 0.1 wt% or more and less than 3 wt%. The main sulfur compounds are benzothiophenes, dibenzothiophenes, and sulfides, but there are many benzothiophenes and dibenzothiophenes in the boiling range of the raw material hydrocarbon oil used in the present invention. Since it is known that dibenzothiophene is electronically delocalized and is stable and hardly reacts, it is preferable that dibenzothiophene is not contained so much in the raw material hydrocarbon oil used in the present invention.

In the present invention, the hydrocarbon oil containing the polycyclic aromatic hydrocarbon used as a raw material is 50% by volume or more of the polycyclic aromatic hydrocarbon, and the total of the single ring aromatic hydrocarbon and the 1.5 ring aromatic hydrocarbon Any material can be used as long as the amount is less than 20% by volume.
Specifically, distillate obtained by atmospheric distillation of crude oil, vacuum gas oil obtained by vacuum distillation of atmospheric residue, lightening process of various heavy oils (catalytic cracking equipment, thermal cracking equipment, etc.) Distillates obtained from, for example, catalytic cracking oil (particularly LCO) obtained from catalytic cracking equipment, thermal cracking oil obtained from thermal cracking equipment (coker, visbreaking, etc.), ethylene cracker heavy obtained from ethylene cracker Aromatic extractor for producing residue, contact reformed oil obtained from catalytic reformer, and aromatic rich contact reformed oil, lubricating base oil obtained by extracting, distilling or membrane separating contact reformed oil And the aromatic-rich fraction obtained from a solvent dewaxing apparatus. Here, the aromatic rich refers to those having 10 or more carbon atoms obtained from the catalytic reformer and the content of the aromatic compound exceeding 50% by volume. In addition, desulfurization method or hydroconversion method to purify atmospheric distillation residue, vacuum distillation residue, dewaxed oil, oil sand, oil shale, coal, biomass, etc. (for example, heavy oil decomposition such as H-Oil process, OCR process, etc.) A distillate produced from a process or a cracking process of heavy oil with a supercritical fluid) can also be preferably used.

  In addition, a distillate obtained by processing in an appropriate order with a plurality of the above-described purification apparatuses can also be used as a hydrocarbon oil as a raw material for hydrocracking reaction. Furthermore, these hydrocarbon oils may be used singly or as a mixture of two or more, and may be adjusted to the above boiling range and aromatic ring constituent carbon ratio as a feedstock for hydrocracking. Can be used. Therefore, even if it is a hydrocarbon oil which remove | deviates said boiling point range and aromatic ring structure carbon ratio, it can also adjust and use the boiling point range and aromatic ring structure carbon ratio to said range. Among the above hydrocarbon oils, catalytic cracking oil, pyrolysis oil, vacuum gas oil, ethylene cracker heavy residue, catalytic reforming oil, and supercritical fluid cracking oil are preferable, and catalytic cracking gas oil (LCO) is particularly preferable.

[First step]
In the first step of the present invention, polycyclic aromatic hydrocarbons are converted to 1.5-ring aromatic hydrocarbons (tetralins and indanes) while reducing sulfur and nitrogen by performing hydrorefining treatment in advance. It is the process of converting.

The hydrorefining catalyst used for the hydrotreating treatment in the first step is a hydrorefining catalyst containing molybdenum in a refractory oxide carrier. In particular, it serves to reduce the sulfur content, so it is also called a desulfurization catalyst.
As such a catalyst, specifically, a carrier containing at least one selected from alumina, silica, boria, and zeolite, molybdenum, tungsten, nickel, and metals of Group 6 and Group 8 of the periodic table, Examples thereof include a catalyst supporting at least one metal selected from cobalt, platinum, palladium, iron, ruthenium, osmium, rhodium and iridium.

When the content of the metal is too large, an excessive nuclear hydrogenation reaction proceeds, and the balance between the desulfurization denitrogenation reaction and the nuclear hydrogenation reaction cannot be satisfied. Accordingly, the molybdenum content is 0.5 wt% or more and less than 8.0 wt%, preferably 1.0 wt% or more and less than 6.0 wt%, more preferably 2.0 wt% or more and less than 4.0 wt%. It is.
In addition, nickel, cobalt, and phosphorus may be appropriately added as a hydrorefining catalyst. However, in the present invention, it is not preferable to excessively improve the hydrogenation activity, so the total content of nickel and cobalt is 2. Less than 0.0% by weight, preferably less than 1.5% by weight, more preferably less than 1.0% by weight. Furthermore, the phosphorus content is less than 2.0% by weight, preferably less than 1.5% by weight, more preferably less than 1.0% by weight.

  The hydrorefining catalyst is used after treatment such as drying, reduction, sulfidation and the like before the hydrogenation reaction, if necessary. Moreover, it is preferable to use the quantity of the catalyst used for a 1st process in the range of 10-200 volume% with respect to the hydrocracking catalyst mentioned later. Here, when the amount is less than 10% by volume, the removal of the sulfur content is insufficient. On the other hand, when the amount exceeds 200% by volume, the apparatus becomes large and inefficient. Note that the first step and the second step described later may be configured as catalyst layers for each packed in one reaction tower, or may be configured from separate reaction towers. At this time, a reaction product gas extraction line may be installed upstream of the hydrogen supply line between the two catalyst layers to extract the reaction product gas and supply fresh hydrogen gas to promote the reaction. Moreover, it cannot be overemphasized that a separate individual apparatus may be sufficient as a 1st process and a 2nd process, respectively.

The raw hydrocarbon oil is a hydrorefining catalyst and hydrogen in the presence of hydrogen at a temperature of 150 ° C. or higher and lower than 400 ° C., more preferably 200 ° C. or higher and lower than 380 ° C., more preferably 250 ° C. or higher and lower than 360 ° C., and a pressure of 1 MPa or higher. Less than 10 MPa, more preferably 2 MPa or more and less than 8 MPa, liquid hourly space velocity (LHSV) 0.1 h ⁻¹ or more and less than 10.0 h ⁻¹ , more preferably 0.1 h ⁻¹ or more and less than 8.0 h ⁻¹ , more preferably 0 .2H ^-1 above 5.0h less than ^-1, hydrogen / hydrocarbon ratio 100 NL / L or more 5000 Nl / less L, preferably it is preferably contacted with less than 150 NL / L or more 3000NL / L.

  Through the above treatment, the sulfur content is preferably 500 ppm by weight or less, more preferably 100 ppm by weight or less, particularly preferably 50 ppm by weight or less, and the nitrogen content is preferably 50 ppm by weight or less, more preferably 20 ppm by weight or less. Preferably, it is reduced to 10 ppm by weight or less. Along with the desulfurization and denitrogenation reactions by this hydrorefining treatment, the hydrogenation of aromatics also proceeds partially.

  In the first step of the present invention, it is desirable to convert polycyclic aromatic hydrocarbons to 1.5 ring aromatic hydrocarbons as much as possible as described above. That is, the bicyclic aromatic hydrocarbon after the first step is preferably less than 20% by volume, more preferably less than 15% by volume, particularly preferably less than 10% by volume. Is less than 4% by volume, preferably less than 2% by volume, particularly preferably less than 1% by volume. The 1.5 ring aromatic hydrocarbon is 40% by volume or more, preferably 45% by volume or more, particularly preferably 50% by volume or more.

In the present invention, there is no problem in reducing the amount of polycyclic aromatic hydrocarbons, but it is not desirable to reduce the amount of monocyclic aromatic hydrocarbons. Therefore, it is preferable to treat the reaction conditions such that the polycyclic aromatic component can be hydrogenated to a single ring or 1.5 ring aromatic hydrocarbon. For this purpose, a predetermined desulfurization rate is required. It is desirable that the ratio of the remaining monocyclic aromatic hydrocarbons to be high.
In the second step to be described later, since the polycyclic aromatic component or the 1.5-ring aromatic hydrocarbon is mainly hydrogenated to the single-ring aromatic hydrocarbon, the raw material is used in all steps of the first step and the second step. Ratio of 1-ring aromatic hydrocarbon residualness (1RAsel) of product oil to oil and desulfurization rate (HDS) (1RAsel) / (HDS) is preferably 0.36 or more, more preferably 0.37 or more, especially It is preferable to set the reaction conditions in the first step so as to be 0.38 or more.

  The reaction form of the first step is not particularly limited, and a reaction form that has been widely used conventionally can be applied. Among them, the fixed floor type has a complicated apparatus configuration and is easy to operate.

[Second step]
The second step is a hydrocracking reaction and is carried out following the first step. The intermediate oil hydrotreated in the first step described above is brought into contact with a hydrocracking catalyst described later in the presence of hydrogen to produce various light hydrocarbon fractions such as monocyclic aromatic hydrocarbons. .

  The reaction mode of the second step in the present invention is not particularly limited, and conventionally used reaction modes, that is, a fixed bed, a boiling bed, a fluidized bed, a moving bed, etc. can be applied. Among them, the fixed bed type is preferable, the apparatus configuration is not complicated, and operation is easy.

  The hydrocracking catalyst used in the second step is used after pretreatment such as drying, reduction, and sulfurization after filling the reactor. These treatments are common to those skilled in the art, and can be carried out inside or outside the reaction column by well-known methods. Activation of the catalyst by sulfurization is generally performed by treating the hydrocracking catalyst at a temperature of 150 ° C. or higher and lower than 800 ° C., preferably 200 ° C. or higher and lower than 500 ° C., under a hydrogen / hydrogen sulfide mixed stream.

In the hydrocracking reaction of the second step, for example, the operating conditions such as reaction temperature, reaction pressure, hydrogen flow rate, liquid space velocity, etc. are the properties of the raw material, the quality of the product oil, the production volume, the refining equipment and the post-treatment capacity equipment. What is necessary is just to adjust suitably according to capability. The raw hydrocarbon oil and hydrocracking catalyst for hydrocracking reaction are reacted in the presence of hydrogen at a reaction temperature of 200 ° C. or higher and lower than 450 ° C., more preferably 250 ° C. or higher and lower than 430 ° C., more preferably 280 ° C. or higher and lower than 400 ° C. The reaction pressure is 2 MPa or more and less than 10 MPa, more preferably 2 MPa or more and less than 8 MPa, and the liquid space velocity (LHSV) is 0.1 h ⁻¹ or more and less than 10.0 h ⁻¹ , more preferably 0.1 h ⁻¹ or more and 8.0 h ^−. less than ^1, more preferably less than 0.2 h ^-1 or 5.0 h ^-1, hydrogen / hydrocarbon ratio (volume ratio) 100 NL / L or more 5000 Nl / less L, preferably the contact is less than 150 NL / L or more 3000NL / L Let By the above operation, the polycyclic aromatic or 1.5-ring aromatic hydrocarbon in the raw hydrocarbon oil for hydrocracking reaction is decomposed and converted into a desired single-ring aromatic hydrocarbon (alkylbenzene). Outside the range of the above operating conditions, it is not preferable for reasons such as insufficient cracking activity or rapid deterioration of the catalyst.

[Hydrolysis catalyst]
The hydrocracking catalyst of the present invention carries at least one metal component selected from Group 6 and Group 8 of the periodic table on a support composed of a composite oxide and a binder binding the composite oxide, and pellets It is formed into a shape (columnar shape, irregular columnar shape), granular shape, spherical shape or the like. Further, as its physical properties, the pore volume occupied by pores having a specific surface area of 100 m ² / g or more and less than 800 m ² / g, a central pore diameter of 3 nm or more and less than 15 nm, and a pore diameter of 2 nm or more and less than 60 nm is 0.1 mL / g or more and less than 1.0 mL / g.
The specific surface area is a value of the BET specific surface area determined by nitrogen adsorption according to ASTM standard D3663-78, preferably 150 m ² / g or more and less than 700 m ² / g, more preferably 200 m ² / g or more and 600 m ² / g. Is less than. When the BET specific surface area is smaller than 100 m ² / g, the active metal is not sufficiently dispersed and the activity is not improved. On the other hand, when the BET specific surface area is larger than 800 m ² / g, a sufficient pore volume cannot be maintained. This is not preferable because the diffusion of the product becomes insufficient and the progress of the reaction is rapidly inhibited.

  The central pore diameter of the hydrocracking catalyst is preferably 4.0 nm or more and less than 12 nm, more preferably 5.0 nm or more and less than 10 nm. The pore volume occupied by pores having a pore diameter of 2 nm or more and less than 60 nm is preferably 0.15 mL / g or more and less than 0.8 mL / g, more preferably 0.2 mL / g or more and less than 0.7 mL / g. is there. The central pore diameter and the pore volume are not preferable if they are too large or too small because there is an appropriate range from the relationship between the size of molecules involved in the reaction and diffusion.

  The so-called mesopore pore characteristics, that is, the pore diameter and the pore volume can be measured by a nitrogen gas adsorption method, and the relationship between the pore volume and the pore diameter can be calculated by the BJH method or the like. The median pore diameter is defined as V, where V is the cumulative pore volume occupied by pores having a pore diameter of 2 nm or more and less than 60 nm obtained under the condition of a relative pressure of 0.9667 in the nitrogen gas adsorption method. In the cumulative pore volume curve obtained by accumulating the volume amount, the pore diameter at which the cumulative pore volume becomes V / 2.

  As the hydrocracking catalyst in the present invention, those having macropores, mesopores and micropores can be used. Usually, since the pore characteristics of the mesopores of the composite oxide support are maintained until the formation of the catalyst, the pore characteristics of the mesopores of the hydrocracking catalyst are basically the above-mentioned pore characteristics of the composite oxide support. It can be adjusted by controlling the kneading conditions (time, temperature, torque) and firing conditions (time, temperature, type of flow gas and flow rate) so as to have mesopore pore characteristics.

  The pore characteristics of the macropores can be controlled by the space between the composite oxide particles and the filling rate with the binder. The space between the composite oxide particles can be controlled by the particle size of the composite oxide particles, and the filling rate can be controlled by the amount of the binder.

  The pore characteristics of micropores largely depend mainly on the pores inherent in composite oxides such as zeolite, but can also be controlled by dealumination treatment such as steaming.

  The pore characteristics of mesopores and macropores can also be influenced by the properties of the binder and the kneading conditions described below. The composite oxide is mixed with an inorganic oxide matrix (binder) to form a carrier.

[Composite oxide]
The composite oxide referred to in the present invention is a composite oxide having solid acidity. For example, in a binary composite oxide, K.I. Shibata, T .; Kiyoura, J. et al. Kitagawa, K .; Tanabé, Bull. Chem. Soc. Jpn. , 46, 2985 (1973), and many others are known. Among them, silica-alumina, silica-titania, silica-zirconia, and silica-magnesia can be preferably used as the composite oxide used in the present invention. As the ternary composite oxide, silica-alumina-titania and silica-alumina-zirconia can be preferably used. In addition, the composite oxide referred to in the present invention includes zeolite such as USY zeolite.

The composite oxide is selected from silica-alumina, silica-titania, silica-zirconia, silica-magnesia, silica-alumina-titania, silica-alumina-zirconia, tungsten oxide-zirconia, sulfated zirconia, alumina sulfate, zeolite 1 The species can be used alone, or two or more species can be used in combination. In particular, when silica-alumina is used as the composite oxide, it is preferably used such that the SiO ₂ / Al ₂ O ₃ ratio (molar ratio) is 1 to 20.

The zeolite is not particularly limited, but X-type, Y-type, β-type, MOR-type and MFI-type zeolites are preferable, and among them, Y-type, β-type and MFI-type zeolites can be suitably used. . Among the Y-type zeolite, an acidic type such as HY type obtained by ion-exchange of alkali metal is preferably used rather than an alkali metal type such as Na-Y type. Aluminum-treated USY-type zeolite (super stable Y-type zeolite) can also be used. This is obtained by acid treatment, high temperature treatment, steam treatment, etc., and has high resistance to crystallinity deterioration, and the content of alkali metal ions is less than 1.0% by weight, preferably 0.5%. It is characterized by a lattice constant of less than% by weight and not more than 2.46 nm and a SiO ₂ / Al ₂ O ₃ ratio (molar ratio) of 5 or more.

The H-Y zeolite and USY-type zeolite used in the present invention can be produced by any method as long as the molar ratio of aluminum to silicon is 1: 2.0 or more and less than 1: 10.0 and has a faujasite structure. Regardless of whether any of them can be used without any problem. In the present invention, it is preferable that the Y-type zeolite is first dealkalized and then steamed and / or acid treated to obtain a crystalline aluminosilicate having a lattice constant of 2.43 nm or more and less than 2.46 nm. In the case where the lattice constant exceeds 2.46 nm, the crystal structure collapses when it comes into contact with an aqueous solution having a pH of less than 3 during the acid treatment described later, the decomposition activity is lowered, and the yield of the target fraction is reduced. On the other hand, when the lattice constant is less than 2.43 nm, the crystallinity is poor and the amount of acid is small, so that the decomposition activity similarly decreases and the yield of the target fraction decreases. Note that the lattice constant is calculated from the value of the interplanar distance d obtained by the X-ray diffraction method by the following equation.
Lattice constant = d × (h ² + k ² + l ² ) ^1/2
Here, h, k, and l are Miller indices.

The above dealkalization treatment is performed by immersing the Y-type zeolite in an ammonia-containing solution or the like, exchanging alkali metal ions such as Na ⁺ with ammonium ions or the like, and firing the same. First, H-Y type zeolite is obtained, and further, this series of treatments is repeated several times to prepare USY (Ultra Stable Y) type zeolite having a further reduced alkali metal content through SY (Stable Y) type zeolite. be able to. The alkali metal content of the dealuminated USY zeolite is preferably less than 1.0% by weight, and more preferably less than 0.5% by weight.

  Further, the steam treatment may be performed by a method in which the dealkalized zeolite is brought into contact with steam at 500 to 800 ° C., preferably 550 to 750 ° C. Further, the acid treatment may be performed by immersing in an aqueous nitric acid solution having a pH of 3 or less. Either steam treatment or acid treatment may be used, but partial dealumination treatment is performed by using both treatments together, and a crystalline aluminosilicate having the above lattice constant is easily prepared by drying and firing. can do.

  In addition to Y-type zeolite, β-type, MOR type typified by mordenite, and MFI type zeolite typified by ZSM-5 can also be used. In this case, since these zeolites have a high silica / alumina ratio, they can be used without any special dealumination treatment.

  Crystalline aluminosilicates with adjusted silica / alumina ratios in this way are used for transition metal salts such as iron, cobalt, nickel, molybdenum, tungsten, copper, zinc, chromium, titanium, vanadium, zirconia, cadmium, tin, and lead. In addition, these metal ions are introduced by dipping in a solution containing a rare earth salt such as lanthanum, cerium, ytterbium, europium, dysprosium, etc. Good. When the hydrocracking reaction described later is used, the crystalline aluminosilicate, the transition metal-containing crystalline aluminosilicate, or the rare earth-containing crystalline aluminosilicate may be used alone or in combination. May be.

[binder]
As the binder, porous and amorphous ones such as alumina, silica-alumina, titania-alumina, zirconia-alumina, and boria-alumina can be suitably used. Of these, alumina, silica-alumina, and boria-alumina are preferred because they have a strong ability to bind complex oxides and a high specific surface area. These inorganic oxides function as a substance that supports an active metal and also serve as a binder that binds the composite oxide, thereby improving the strength of the catalyst. The specific surface area of the binder is desirably 30 m ² / g or more.

  The binder which is one of the constituent components of the carrier is a powder made of aluminum hydroxide and / or hydrated oxide (hereinafter also simply referred to as alumina powder), in particular, an oxide having a boehmite structure such as pseudoboehmite. Aluminum monohydrate (hereinafter also simply referred to as alumina) can be preferably used because it can improve hydrocracking activity and selectivity. The binder is also a powder of aluminum hydroxide and / or hydrated oxide containing boria (boron oxide), particularly aluminum oxide monohydrate having a boehmite structure such as pseudoboehmite containing boria. Since it can improve the chemical decomposition activity and selectivity, it can be preferably used.

  As aluminum oxide monohydrate, commercially available alumina sources (for example, PURAL (registered trademark), CATAPAL (registered trademark), DISPERAL (registered trademark), DISPAL (registered trademark), commercially available from SASOL, from UOP Commercially available VERSAL (registered trademark) or HIQ (registered trademark) commercially available from ALCOA, etc.) can be used. Alternatively, it can be prepared by a known method of partially dehydrating aluminum oxide trihydrate. When the aluminum oxide monohydrate is in the form of a gel, the gel is dissolved with water or acidic water. When alumina is synthesized by a precipitation method, the acidic aluminum source can be selected from aluminum chloride, aluminum sulfate, aluminum nitrate, and the like, and the basic aluminum source can be selected from sodium aluminate, potassium aluminate, and the like.

  The blending ratio of the binder is preferably 5% by weight or more and less than 70% by weight, particularly 10% by weight or more and less than 60% by weight, based on the total weight of the composite oxide and the binder constituting the catalyst. If it is less than 5% by weight, the mechanical strength of the catalyst tends to be lowered, and if it exceeds 70% by weight, the hydrocracking activity and selectivity are relatively lowered. When USY zeolite is used as the composite oxide, the weight of the USY zeolite with respect to the total weight of the composite oxide part and the binder part constituting the catalyst is 1% by weight or more and less than 80% by weight, particularly 10% by weight or more and less than 70% by weight. It is preferable to do. If it is less than 1% by weight, the effect of improving the cracking activity due to the use of USY zeolite is hardly exhibited, and if it exceeds 80% by weight, the middle distillate selectivity is relatively lowered.

[Metal component]
The hydrocracking catalyst of the present invention preferably contains a metal selected from Group 6 and Group 8 of the periodic table as an active component. Of the Group 6 and Group 8 metals, molybdenum, tungsten, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, and platinum are particularly preferably used. These metals can be used alone or in combination of two or more. The amount of these metals added is such that the total amount of Group 6 and Group 8 metal elements in the hydrocracking catalyst is 0.05% by weight or more and less than 35% by weight, particularly 0.1% by weight or more and 30% by weight. It is preferable to contain so that it may become less. When molybdenum is used as the metal, the content thereof is preferably 5% by weight or more and less than 20% by weight, particularly 7 to 15% by weight in the hydrocracking catalyst. When tungsten is used as the metal, the content thereof is preferably 5% by weight or more and less than 30% by weight, particularly 7% by weight or more and less than 25% by weight in the hydrocracking catalyst. If the addition amount of molybdenum or tungsten is less than the above range, the hydrogenation function of the active metal necessary for the hydrocracking reaction is insufficient, which is not preferable. On the other hand, when the amount is larger than the above range, the added active metal component tends to aggregate and is not preferable.

  When molybdenum or tungsten is used as the metal, it is more preferable to add cobalt or nickel to improve the hydrogenation function of the active metal. In this case, the total content of cobalt or nickel is preferably 0.5 wt% or more and less than 10 wt%, particularly 1 wt% or more and less than 7 wt% in the hydrocracking catalyst. When one or more of rhodium, iridium, platinum, and palladium are used as the metal, the content is 0.1 wt% or more and less than 5 wt%, particularly 0.2 wt% or more and less than 3 wt%. It is preferable to do. If it is less than this range, a sufficient hydrogenation function cannot be obtained, and if it exceeds this range, the addition efficiency is poor and it is not economical, which is not preferable.

The Group 6 metal component supported as an active component is an aqueous solution of a compound such as ammonium paramolybdate, molybdic acid, ammonium molybdate, phosphomolybdic acid, ammonium tungstate, tungstic acid, tungstic anhydride, or tungstophosphoric acid. It can be impregnated and added.
Group 8 metal components include nickel and cobalt nitrates, sulfates, chlorides, fluorides, bromides, acetates, carbonates, phosphates, aqueous solutions such as chloroplatinic acid, dichlorotetraammineplatinum, tetrachloro Hexammineplatinum, platinum chloride, platinum iodide, potassium chloroplatinate, palladium acetate, palladium chloride, palladium nitrate, palladium acetylacetonate, rhodium acetate, rhodium chloride, rhodium nitrate, ruthenium chloride, osmium chloride, iridium chloride, etc. May be used as an aqueous solution.
Further, phosphorus, boron, potassium, and rare earth such as lanthanum, cerium, ytterbium, europium, dysprosium may be added as the third component.

[Method for producing hydrocracking catalyst]
The hydrocracking catalyst of the present invention is prepared by kneading and molding a composite oxide and a binder, followed by drying and firing to prepare a carrier, and further impregnating and supporting a metal component, followed by drying and firing. Can do. The production method of the hydrocracking catalyst of the present invention will be described in detail below, but is not limited to the following method, and other methods capable of producing a catalyst having predetermined pore characteristics and performance may be used. it can.

  For kneading, a kneader generally used for catalyst preparation can be used. Usually, a method of adding raw materials, adding water and mixing with a stirring blade is preferably used, but there is no particular limitation on the order of adding raw materials and additives. Water is usually added at the time of kneading, but it is not particularly necessary to add water when the raw material is in the form of a slurry. In addition to water or instead of water, an organic solvent such as ethanol, isopropanol, acetone, methyl ethyl ketone, or methyl isobutyl ketone may be added. The kneading temperature and kneading time vary depending on the composite oxide and binder used as raw materials, but are not particularly limited as long as a preferable pore structure is obtained. Similarly, as long as the properties of the catalyst of the present invention are maintained, an acid such as nitric acid, a base such as ammonia, an organic compound such as citric acid and ethylene glycol, a water-soluble property such as cellulose ethers and polyvinyl alcohol. A high molecular compound, ceramic fiber, etc. may be added and kneaded.

  After kneading, it can be molded using a known molding method generally used for catalyst preparation. In particular, extrusion using a screw-type extruder that can be efficiently molded into any shape such as pellets (columnar, irregular columnar), granules, and spheres, and molding by an oil drop method that can be efficiently molded into spheres. Preferably used. Although there is no restriction | limiting in particular in the size of a molded object, For example, if it is a column-shaped pellet, a thing about 0.5-20 mm in diameter and 0.5-15 mm in length can be obtained easily.

  The molded product obtained as described above is used as a carrier by drying and baking treatment. This firing process may be performed at a temperature of 300 to 900 ° C. for 0.1 to 20 hours in a gas atmosphere such as air or nitrogen.

  There is no particular limitation on the method for supporting the metal component on the carrier. Prepare an aqueous solution of metal oxides or their salts, such as nitrates, acetates, carbonates, phosphates, halides, etc. that you want to support, and support them by spraying, impregnation by immersion, ion exchange, etc. . More metal components can be supported by repeating the supporting process and the drying process.

  For example, the carrier is impregnated with an aqueous solution containing a Group 6 metal component, and then dried at room temperature to 150 ° C., preferably 100 to 130 ° C. for 0.5 hour or more, or without drying, the Group 8 is left as it is. After impregnating with an aqueous solution containing the above metal components and drying at room temperature to 150 ° C., preferably 100 to 130 ° C. for 0.5 hours or more, 350 to 800 ° C., preferably 450 to 600 ° C. for 0.5 hours or more. The catalyst can be prepared by calcination.

  The Group 6 and Group 8 metals supported on the catalyst of the present invention may be in any form such as metals, oxides, and sulfides.

[Mechanical strength of hydrocracking catalyst and support]
The higher the mechanical strength of the hydrocracking catalyst, the better. For example, the side crushing strength of a cylindrical pellet having a diameter of 1.6 mm is preferably 3 kg or more, and more preferably 4 kg or more. In the case of producing a catalyst by impregnating and supporting a metal component after producing a molded carrier, it is preferable that the molded carrier also has sufficient mechanical strength in order to produce the catalyst with good yield. Specifically, the mechanical strength of the molded carrier in the present invention is preferably 3 kg or more, and more preferably 4 kg or more, as the side crushing strength of a cylindrical pellet having a diameter of 1.6 mm.

The bulk density of the catalyst is preferably 0.4 g / cm ³ or more and less than 2.0 g / cm ³ , more preferably 0.5 g / cm ³ or more and less than 1.5 g / cm ³ , particularly preferably 0.6 g / cm ^3. Above 1.2 g / cm ³ .

[Properties of hydrocracked oil]
In the second step, 40% by volume or more of the fraction corresponding to a boiling point of 215 ° C. or higher in the raw hydrocarbon oil is converted into a fraction of less than 215 ° C. The hydrocracked product oil has a hydrocarbon having a boiling point of 215 ° C. or lower, that is, a hydrocarbon lighter than naphthalene, in an amount of 40% by volume or more, preferably 50% by volume or more, more preferably 60% by volume or more, particularly Preferably it is 75 volume% or more. The hydrocracked product oil obtained by hydrocracking treatment preferably contains 20% by volume or more of monocyclic aromatic hydrocarbons (alkylbenzenes), more preferably 30% by volume or more, and still more preferably 40% by volume. %, Preferably containing less than 30% by volume of 1.5 ring aromatic hydrocarbons, more preferably less than 28% by volume, and preferably containing less than 1% by volume of polycyclic aromatic hydrocarbons. More preferably, it is less than 0.7 volume%, and further less than 0.5 volume%.

[Post-processing process]
In this invention, it is also possible to install the post-processing process which refine | purifies the hydrocracked product oil obtained as needed. Although a post-processing process is not specifically limited, The catalyst kind, catalyst amount, and operation conditions similar to a 1st process can be set. The post-treatment step may be installed immediately after the second step to treat the hydrocracked product oil, or may be installed after the subsequent separation step to individually treat each separated hydrocarbon fraction. Also good. By installing this post-treatment step, impurities in the product can be greatly reduced. For example, the sulfur content and the nitrogen content can be reduced to 0.1 ppm by weight or less.

[Method for separating hydrocracked product oil]
The resulting hydrocracked product oil is subjected to an appropriate separation step to products such as LPG fraction, gasoline fraction, kerosene fraction, light oil fraction, non-aromatic naphtha fraction and monocyclic aromatic hydrocarbons. Can be separated. These products can be used as they are as LPG, gasoline, kerosene, light oil and petrochemical raw materials as long as they satisfy the standards for petroleum products, etc. Used as a substrate. The separation process is not particularly limited, and any known method such as precision distillation, adsorption separation, sorption separation, extraction separation, membrane separation, or the like can be employed according to the product properties for the purpose. Moreover, what is necessary is just to set those operating conditions suitably.

  In general, a distillation method is widely used, which uses a difference in boiling points to separate, for example, an LPG fraction, a gasoline fraction, a kerosene fraction, and a light oil fraction. Specifically, the portion lighter than the boiling point of 0 to 30 ° C. is the LPG fraction, the portion having a higher boiling point to 150 to 215 ° C. is the gasoline fraction, and the portion having a higher boiling point to 215 to 260 ° C. The kerosene fraction, and the higher boiling point up to about 260-370 ° C can be used as the light oil fraction, and the heavier fraction is treated as an unreacted product in the hydrocracking reaction step again. Alternatively, it may be used for a base material such as A heavy oil.

  In the case of the extraction method for separating the aromatic component, it can be separated into an aromatic component and a non-aromatic component using an appropriate solvent, but may be used in appropriate combination with the above distillation method. In this case, the gasoline fraction and / or kerosene fraction obtained from the distillation separation is used to mix a solvent for selectively extracting aromatics, for example, sulfolane (tetrahydrothiophene dioxide), and the temperature is set to 20-100. Extraction fraction in which aromatic compounds are selectively extracted with sulfolane and raffinate in which paraffinic hydrocarbons that are not extracted into sulfolane are concentrated by processing under the conditions of extraction from normal pressure to 1.0 MPa. It is separated into fractions. In the extract fraction containing a boiling point component of at least 80 ° C. obtained by this extraction treatment, the aromatic compound is selectively extracted. Can be used for products. In addition, since the raffinate fraction contains a relatively large amount of isoparaffin and naphthene, it can be used as it is as a gasoline base material for producing a high octane gasoline composition, and further used as a feedstock for a catalytic reforming process. Can also be converted to aromatic hydrocarbons.

  The aromatic fraction of the extract fraction extracted with sulfolane and sulfolane are easily separated by distillation operation, and the separated sulfolane is reused as an extraction solvent. The separated aromatic component can be converted into paraxylene, benzene, or the like having higher added value through a transalkylation treatment, an isomerization treatment, or the like.

[Product hydrocarbon]
The hydrocarbon products obtained through the above separation step include an LPG fraction having a boiling point of -10 to 30 ° C, a gasoline fraction having a boiling point of 30 to 215 ° C, a kerosene fraction having a boiling point of 215 to 260 ° C, and a boiling point of 260 to 370 ° C. And the residue remaining after separating the above fraction. In the present invention, the smaller the residue, the better, and it can be recycled to the second step to reduce the weight.
In addition, an extract fraction and a raffinate fraction can be obtained by extracting a gasoline fraction with a solvent such as sulfolane. The raffinate fraction is a non-aromatic naphtha fraction and is useful as a gasoline base material, a solvent raw material and the like. The extract fraction is a monocyclic aromatic hydrocarbon (alkylbenzenes) useful as a petrochemical raw material.

Hereafter, the manufacturing method of the hydrocarbon fraction of this invention is demonstrated in detail and concretely using an Example and a comparative example.
[Hydropurification catalysts A to D]

  Aqueous boehmite powder was kneaded with ammonia water and water, and then extruded into a columnar product having a diameter of 1.4 mm. This molded body was dried at 130 ° C. for 6 hours and calcined at 800 ° C. for 1 hour to obtain a γ-alumina carrier. This γ-alumina carrier was impregnated with a molybdic acid aqueous solution by a spray method and dried at 130 ° C. for 6 hours. Then, the desulfurization catalyst A was obtained by baking at 600 degreeC for 30 minutes. Table 1 shows the composition (supported metal content) and typical physical properties of the desulfurization catalyst A.

  Nitric acid and water were added to and kneaded with commercially available pseudo boehmite powder, and then extruded into a columnar product having a diameter of 1.4 mm. This molded body was dried at 130 ° C. for 6 hours and calcined at 600 ° C. for 1 hour to obtain a γ-alumina carrier. This γ-alumina support was impregnated with a molybdic acid aqueous solution by a spray method and dried at 130 ° C. for 6 hours. Further, an aqueous nickel nitrate solution was impregnated by a spray method and dried at 130 ° C. for 6 hours. Then, desulfurization catalyst B was obtained by baking at 500 degreeC for 30 minutes. Table 1 shows the composition (supported metal content) and typical physical properties of the desulfurization catalyst B.

  Nitric acid and water were added to and kneaded with commercially available pseudo boehmite powder, and then extruded into a columnar product having a diameter of 1.4 mm. This molded body was dried at 130 ° C. for 6 hours and calcined at 600 ° C. for 1 hour to obtain a γ-alumina carrier. This γ-alumina carrier was impregnated with a molybdic acid aqueous solution by a spray method and dried at 130 ° C. for 6 hours. Further, a mixed aqueous solution of nickel nitrate and phosphoric acid was impregnated with a spray method and dried at 130 ° C. for 6 hours. Then, the desulfurization catalyst C was obtained by baking at 500 degreeC for 30 minutes. Table 1 shows the composition of the desulfurization catalyst C (supported metal content) and typical physical properties.

In the method for preparing the desulfurization catalyst C, a desulfurization catalyst D was obtained by the same method except that cobalt nitrate was used instead of nickel nitrate. Table 1 shows the composition (supported metal content) and representative physical properties of the desulfurization catalyst D.
[Preparation of hydrocracking catalyst]

1684 g of NH ₄ -Y type zeolite (HSZ-341NHA manufactured by Tosoh Corporation) having a SiO ₂ / Al ₂ O ₃ ratio of 6.9 and a specific surface area of 697 m ² / g, 834 g of alumina powder (alumina Versal 250 manufactured by UOP), Add 500 mL of 4.0% by weight dilute nitric acid solution and 50 g of ion-exchanged water, knead, extrude into a cylindrical shape (pellet), dry at 130 ° C. for 6 hours, and then calcined at 600 ° C. for 2 hours. It was.
This support was spray impregnated with an aqueous ammonium molybdate solution and dried at 130 ° C. for 6 hours, and then spray-impregnated with an aqueous nickel nitrate solution and dried at 130 ° C. for 6 hours. Subsequently, decomposition catalyst E was obtained by calcining at 500 ° C. for 30 minutes under an air stream. Table 1 shows the composition of the cracking catalyst E (supported metal content) and typical physical properties.

The measuring apparatus and method used in the above-mentioned catalyst physical property measurement are shown below.
[Measurement method of pore characteristics]

  For measurement of pore characteristics (specific surface area, pore volume occupied by pores having a pore diameter of 2 nm or more and less than 60 nm, central pore diameter) by a nitrogen gas adsorption method, an ASAP2400 type measuring instrument manufactured by Micromeritics was used.

(Examples 1-4)
Catalytic cracked light oil as raw material oil (sulfur content: 1740 ppm by weight, nitrogen content: 293 ppm by weight, monocyclic aromatic hydrocarbons (including 1.5 rings): 16.5% by volume, bicyclic aromatic hydrocarbons: 41 .2% by volume, aromatic hydrocarbons having 3 or more rings: 12.4% by volume, total amount of aromatic compounds: 70.1% by volume, 10% by volume distillation temperature: 222.5 ° C., 50% by volume distillation temperature : 279.5 ° C, 90 vol% distillation temperature: 342.0 ° C), desulfurization catalyst A as hydrotreating catalyst in the first column, cracking catalyst E as hydrocracking catalyst in the second column, etc. As shown in Table 2, the reaction pressure was 7.0 MPa, LHSV = 0.5 h ⁻¹ , hydrogen / raw oil ratio = 1400 NL / L, first tower reaction temperature 320 to 400, second tower reaction temperature 360. The hydrogenolysis reaction was performed under the condition of ° C. The properties of the resulting oil obtained are shown in Table 2.

(Comparative Examples 1-7)
In place of the desulfurization catalyst A, the desulfurization catalyst B (Comparative Examples 1 to 3), the desulfurization catalyst C (Comparative Examples 4 to 5), and the desulfurization catalyst D (Comparative Examples 6 to 7) are used as the catalyst charged in the first column. Then, under the reaction conditions described in Table 3 and Table 4, the hydrogenolysis reaction was performed in the same manner as in Examples 1 to 4.

1 RAsel. Is the residual degree of monocyclic aromatic hydrocarbons in the product oil relative to the feedstock oil, and is a value obtained from the following formula.
1 RAsel. (%) = Content of monocyclic aromatic hydrocarbons in the product oil (volume%) / total aromatic hydrocarbon content in the feed oil (volume%) × 100

HDS represents the desulfurization rate and is a value obtained by the following equation.
HDS (%) = 1− (sulfur concentration of product oil (ppm by weight) / sulfur concentration of feedstock oil (weight ppm)) × 100

  The reaction liquid yield was defined as the residual rate (% by weight) of the fraction having 5 or more carbon atoms after the reaction.

  As shown in Tables 2-4, as is clear from Examples 1-4, by hydrotreating and hydrocracking under suitable reaction conditions using a suitable hydrorefining catalyst in the first column, Compared with the case of using hydrorefining catalysts that have been widely used in the past (Comparative Examples 1 to 7), the hydrogen consumption can be reduced and the bicyclic aromatic hydrocarbons can be consumed without excessive consumption of expensive hydrogen. Is efficiently converted to desired monocyclic aromatic hydrocarbons (alkylbenzenes). It can be seen that particularly high-value-added BTX fractions such as benzene and toluene can be obtained with high yield and high selectivity under low hydrogen consumption conditions.

  The method for analyzing the raw material oil and product oil properties used in the above Examples and Comparative Examples is as follows.

  The composition of monocyclic aromatic hydrocarbons (alkylbenzenes) (benzene, toluene, xylenes) and the composition of 1.5-ring aromatic hydrocarbons (tetralins) were measured using a hydrocarbon total component analyzer manufactured by Shimadzu Corporation. Measured and calculated according to JIS K2536.

  For the type analysis (ring analysis) of aromatic compounds, a high-performance liquid chromatograph is used in accordance with the Petroleum Institute method JPI-5S-49-97, normal hexane is used for the mobile phase, and RI is used for the detector. Carried out.

  The sulfur content was measured using the fluorescent X-ray method in the high concentration region and the microcoulometric titration method in the low concentration region according to the sulfur content test method of JIS K2541. The nitrogen content was measured using a chemiluminescence method according to the nitrogen content test method of JIS K2609.

  By carrying out a selective nuclear hydrogenation reaction in which only one ring of the polycyclic aromatic hydrocarbon remains with a hydrorefining catalyst that suppresses the hydrogenation activity, an excessive It becomes possible to suppress the nuclear hydrogenation reaction, and the obtained hydrocracked product oil is subjected to an appropriate separation step, and the LPG fraction, gasoline fraction, kerosene fraction, light oil fraction, non-aromatic naphtha It can be separated into products such as distillates and monocyclic aromatic hydrocarbons, and these products can be used as raw materials for LPG, gasoline, kerosene, light oil and petrochemicals as long as they satisfy the standards for petroleum products. Furthermore, they can be used as a base material for preparing and purifying them.

Claims (2)

A raw material hydrocarbon oil in which the total amount of polycyclic aromatic hydrocarbons is 50% by volume or more, monocyclic aromatic hydrocarbons and 1.5 ring aromatic hydrocarbons is less than 20% by volume,
(1) In the presence of hydrogen, the temperature is 150 ° C. or more and less than 400 ° C., the pressure is 1 MPa or more and less than 10 MPa, the liquid space velocity (LHSV) is 0.1 h ⁻¹ or more and less than 10.0 h ⁻¹ , and the hydrogen / hydrocarbon ratio is 100 NL / L or more. It is less than 5000 NL / L, the molybdenum content is 0.5 wt% or more and less than 8.0 wt%, is brought into contact with a hydrorefining catalyst that does not contain nickel, cobalt, or phosphorus, and performs desulfurization and denitrification treatment. Next to the first step of converting ring aromatic hydrocarbons to 1.5 ring aromatic hydrocarbons, (2) the intermediate oil obtained from the first step is reacted in the presence of hydrogen at a reaction temperature of 200 ° C. or higher and lower than 450 ° C. Contacting the hydrocracking catalyst at a pressure of 2 MPa or more and less than 10 MPa, a liquid space velocity (LHSV) of 0.1 h ^-1 or more and less than 10.0 h ^-1 and a hydrogen / hydrocarbon ratio (volume ratio) of 100 NL / L or more and less than 5000 NL / L. Let, many By carrying out the second step of converting a ring aromatic or 1.5 ring aromatic hydrocarbon to a 1 ring aromatic hydrocarbon, 1 ring aromatic hydrocarbon is 20% by volume or more, and polycyclic aromatic hydrocarbon is 1%. A method for producing a monocyclic aromatic hydrocarbon, comprising producing a hydrocarbon of less than 0.0% by volume.   2. The ratio of the residual single-ring aromatic hydrocarbon (1 RAsel) of the produced oil to the feedstock and the desulfurization rate (HDS) is 0.36 or more in all of the first and second steps. A method for producing a monocyclic aromatic hydrocarbon.