JP5457808B2 - Method for producing monocyclic aromatic hydrocarbons - Google Patents

Description

  In the present invention, high-value-added alkylbenzenes, particularly benzene, toluene, xylene (so-called BTX) are efficiently obtained from raw material hydrocarbon oil containing polycyclic aromatic hydrocarbons by nuclear hydrogenation, ring opening, and dealkylation. The present invention relates to a method for producing a selective monocyclic aromatic hydrocarbon, and in particular, the degradation of the catalyst is suppressed by reducing the poisoning substance of the hydrocracking catalyst to a specific amount or less, and the efficiency is stable over a long period of time. It relates to a method for producing monocyclic aromatic hydrocarbons.

  Alkylbenzenes represented by benzene, toluene, xylene (BTX) have been conventionally produced by a catalytic reforming method in petroleum refining. The catalytic reforming reaction is basically a reaction in which the carbon number does not change, but on the other hand, there is a large number of carbons, that is, the study to convert heavy oil into light oil such as gasoline fraction has long been studied. Has been tried. However, until now, the idea of extracting as a gasoline fraction has been exclusively made. That is, few methods have been reported for selectively obtaining BTX having high added value as a petrochemical raw material and monocyclic aromatic hydrocarbons that can be easily converted into them.

  As a method for selectively producing a monocyclic aromatic hydrocarbon from a polycyclic aromatic hydrocarbon, there is a method using a hydrocracking catalyst containing various zeolites (Patent Document 1). No information on the effects of toxic substances or limits was disclosed.

  Also known is a method of hydrocracking polycyclic aromatic hydrocarbons as raw materials and converting them to gasoline (Patent Documents 2 and 3), but the target product is gasoline, and alkylbenzenes such as BTX are selectively used. However, when it was considered to isolate alkylbenzenes as a product rather than a method for producing them, the level was still not sufficient. In addition, there are only performance results at the initial stage of the reaction, and no knowledge about catalyst poisoning or activity deterioration specific to hydrocracking is disclosed.

  Similarly, a method of hydrocracking a heavy hydrocarbon fraction into a monocyclic aromatic hydrocarbon is also known (Patent Document 4). However, here too, there are only performance results at the initial stage of the reaction with respect to the decomposition rate, BTX selectivity, etc., and no knowledge about catalyst poisoning or activity deterioration specific to hydrocracking has been disclosed.

International Publication No. 2007/135769 JP 2008-127541 A JP 2008-127542 A Special table 2009-508881

  When converting polycyclic aromatic hydrocarbons to monocyclic aromatic hydrocarbons as described above, the target BTXs and other monocyclic aromatic hydrocarbons can be selectively and stably maintained over a long period of time. The method of obtaining was not established. Under such circumstances, the present invention is a method for selectively and efficiently producing high-value-added monocyclic aromatic hydrocarbons, particularly BTX, from polycyclic aromatic hydrocarbons while suppressing excessive decomposition and excessive nuclear hydrogenation. It is an issue to provide. In addition, it is an object of the present invention to provide a method for efficiently producing the monocyclic aromatic hydrocarbons stably over a long period of time by suppressing a decrease in catalyst activity peculiar to hydrocracking reaction.

  As a result of intensive studies, the present inventor has maintained the selective and efficient production of monocyclic aromatic hydrocarbons by appropriately reducing the poisoning substances in the pretreatment step prior to the hydrocracking reaction. The present inventors have found that it is possible to suppress a decrease in the activity of the hydrocracking catalyst and to stably obtain a monocyclic aromatic hydrocarbon over a long period of time without causing a decrease in activity under mild conditions. The present invention has been conceived.

  That is, the present invention is as follows.

(1) (i) A raw material hydrocarbon oil having an aromatic ring constituent carbon ratio of 40 mol% or more is brought into contact with a hydrotreating catalyst in the presence of hydrogen to reduce the nitrogen content to 8.0 ppm by weight or less, A first step of converting a part or all of the polycyclic aromatic hydrocarbons to 1.5-ring and monocyclic aromatic hydrocarbons; and (ii) a first-step product oil obtained in the first step Including a second step of converting a part or all of the polycyclic and 1.5-ring aromatic hydrocarbons to monocyclic aromatic hydrocarbons in contact with the hydrocracking catalyst in the presence of the monocyclic aromatic hydrocarbons. Ratio of heavy naphtha yield when hydrocracking product oil having a content of 25% by volume or more is obtained, and when the amount of feed of hydrocarbon oil to the catalyst amount is 120 times or 12 times Special that _{(Y HN (120) / Y} HN (12)) is 0.90 or more (volume ratio) Method of manufacturing a selective monocyclic aromatic hydrocarbon to (although, Y _HN (120) is a heavy naphtha yield at equivalent course 120 times oil flow amount of the raw material hydrocarbon oil to the catalyst quantity, Y _HN (12) Indicates the yield of heavy naphtha when the feed amount of the raw material hydrocarbon oil with respect to the catalyst amount is equivalent to 12 times, and heavy naphtha indicates a fraction having a boiling point of 85 to 190 ° C.).
(2) The raw material hydrocarbon oil contains a fraction having a boiling point of 215 ° C. or higher of 30% by volume or more, and the hydrocracked product oil yield (reaction liquid yield) is 70% by volume or more. A method for producing a monocyclic aromatic hydrocarbon.
(3) The method for producing a selective monocyclic aromatic hydrocarbon according to (1) or (2) above, wherein the raw material hydrocarbon oil contains 60% by volume or more of hydrocarbons having a boiling point of 30 to 190 ° C.
(4) Ratio of conversion rate of a fraction having a boiling point of 215 ° C. or higher when the feed amount of the raw material hydrocarbon oil relative to the catalyst amount is equivalent to 120 times and when equivalent to 12 times (Conv. (120) / Conv. ( 12)) is a method for producing a selective monocyclic aromatic hydrocarbon according to any one of the above (1) to (3), wherein 0.92 or more (where Conv. (120) is a raw material carbonization relative to the catalyst amount) The conversion rate of a fraction having a boiling point of 215 ° C. or more when the passage amount of hydrogen oil is equivalent to 120 times, Conv. (12) is the boiling point of 215 when the passage amount of the raw hydrocarbon oil relative to the catalyst amount is equivalent to 12 times. Refers to conversion of fractions above ℃).

  When producing monocyclic aromatic hydrocarbons from polycyclic aromatic hydrocarbons using a hydrocracking catalyst, the nitrogen compounds contained in the raw hydrocarbon oil are reduced to a specific amount or less in advance, and the hydrocracking catalyst is poisoned. By reducing substances such as sulfur compounds, nitrogen compounds, and aromatic hydrocarbons having 3 or more rings in advance, the catalyst of the most important hydrocracking process can be used under mild conditions. A ring aromatic hydrocarbon can be produced at a high concentration. As a result, it is possible to suppress the generation of carbon deposited on the catalyst and to maintain the catalytic activity for a long time.

  In the present invention, the monocyclic aromatic hydrocarbon means one obtained by substituting hydrogen of benzene with 0 to 6 saturated hydrocarbon groups, and the one other than unsubstituted is alkylbenzene. Accordingly, monocyclic aromatic hydrocarbons include benzene and alkylbenzene, which are sometimes referred to as benzenes. The saturated hydrocarbon group is preferably a lower alkyl group having 1 to 4 carbon atoms. A 1.5-ring aromatic hydrocarbon is saturated with one aromatic ring such as tetralin (1,2,3,4-tetrahydronaphthalene), indane (2,3-dihydroindene), and cyclohexylbenzene. A compound having one naphthene ring in one molecule, including those obtained by substituting hydrogen of the aromatic ring and naphthene ring with a chain hydrocarbon group, tetralin and alkyltetralin (also collectively referred to as tetralins) And indane and alkylindane (sometimes collectively referred to as indanes), cyclohexylbenzene and alkylcyclohexylbenzene (sometimes generically referred to as cyclohexylbenzenes), and the like. The polycyclic aromatic hydrocarbon is a hydrocarbon having two or more aromatic rings (one in which a plurality of condensed rings and single rings are bonded), and a hydrocarbon having two aromatic rings is a two-ring aromatic hydrocarbon. That's it.

  Hereinafter, with regard to the details of the method for producing a monocyclic aromatic hydrocarbon of the present invention, raw material hydrocarbon oil, pretreatment method, hydrocracking reaction, hydrocracking catalyst, hydrocracking catalyst manufacturing method, hydrocracking product oil The separation method and product hydrocarbon will be described in order.

[Raw material hydrocarbon oil]
The object of the present invention is to convert polycyclic aromatic hydrocarbons into monocyclic aromatic hydrocarbons, especially BTX. For this reason, the raw material hydrocarbon oil used contains 40% by volume or more, preferably 50% by volume or more, more preferably 60% by volume or more of polycyclic aromatic hydrocarbons. If the monocyclic aromatic hydrocarbon is contained in the raw material, it may be converted into a compound other than the monocyclic aromatic hydrocarbon by a decomposition reaction or a hydrogenation reaction. Less than 20% by volume, more preferably less than 15% by volume. Furthermore, since it is preferable that the total amount of BTX as the target product and the amount of aromatic hydrocarbon having 9 carbon atoms are also small, the total amount of BTX is less than 5% by volume, more preferably less than 3% by volume, still more preferably Is less than 2% by volume, and the aromatic hydrocarbon having 9 carbon atoms is preferably less than 20% by volume, more preferably less than 10% by volume, and particularly preferably less than 5% by volume.
Here, the amount contained in the raw material hydrocarbon oil is less than 40% by volume of polycyclic aromatic hydrocarbons, and the ratio of monocyclic aromatic hydrocarbons is 30% by volume or more and 30% by volume of bicyclic aromatic hydrocarbons. As described above, when BTX is 5% by volume or more and the aromatic hydrocarbon having 9 carbon atoms is 20% by volume or more, the desired monocyclic aromatic hydrocarbon (alkylbenzene) cannot be obtained in high yield. Absent.

  Furthermore, since the present invention aims to convert polycyclic aromatic hydrocarbons to monocyclic aromatic hydrocarbons, especially BTX, the raw material hydrocarbon oil used has a ratio of carbon constituting the aromatic ring. Higher is preferable. This aromatic ring-constituting carbon ratio can be measured by a nuclear magnetic resonance method and is also called an Fa value, but is preferably 40 mol% or more, more preferably 45 mol% or more, and particularly preferably 50 mol% or more. When the aromatic ring constituent carbon ratio is less than 40 mol%, the target monocyclic aromatic hydrocarbon cannot be obtained in the hydrocracking reaction, and the amount of gas produced increases, which is not preferable.

  A preferable distillation property can be set based on the aromatic composition. That is, since the boiling point of the bicyclic aromatic hydrocarbon naphthalene is 218 ° C., the fraction of 215 ° C. or higher is 30% by volume or more, more preferably 40% by volume or more, and particularly preferably 50% by volume or more. Therefore, as a preferable distillation property of the raw material hydrocarbon oil, a 10% distillation temperature is 140 ° C. or higher and lower than 260 ° C., more preferably 150 ° C. or higher and lower than 250 ° C., further 160 ° C. or higher and lower than 240 ° C., particularly 170 ° C. or higher. It is less than 235 ° C., and the 90% distillation temperature is 250 ° C. or more and less than 500 ° C., more preferably 250 ° C. or more and less than 400 ° C., further 255 ° C. or more and less than 390 ° C., particularly 260 ° C. or more and less than 380 ° C.

As a reaction inhibitor in the raw material hydrocarbon oil, usually, the nitrogen content is 0.01 wt% or more and less than 0.3 wt%, the sulfur content is 0.1 wt% or more and less than 5 wt%, or a tricyclic or more aromatic carbonization. Hydrogen is contained at about 10% by volume.
The main sulfur compounds present in the boiling point range of the raw material hydrocarbon oil of the present invention are benzothiophenes, dibenzothiophenes, and sulfides, but in the boiling point range of the raw material hydrocarbon oil used in the present invention, benzothiophenes And dibenzothiophenes. 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.

  Specifically, as raw material hydrocarbon oil, 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) Distillate obtained from a thermal cracking device, for example, a catalytic cracking oil obtained from a catalytic cracking device (particularly LCO), a thermal cracking oil obtained from a thermal cracking device (such as a coker or visbreaking), or an ethylene cracker. The resulting heavy residue of ethylene cracker, contact reformed oil obtained from catalytic reformer, and aromatic rich contact reformed oil and lubricating base oil obtained by extracting, distilling or membrane separating the contact reformed oil Examples thereof include a fraction obtained from an aromatic extraction apparatus to be produced and an 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, distillates such as intermediate products and by-products obtained by processing in an appropriate order using a plurality of the above-described refining apparatuses can also be used as the raw material hydrocarbon oil. Furthermore, these hydrocarbon oils may be used singly or as a mixture of two or more, and are adjusted to the above boiling range and aromatic ring constituent carbon ratio as the raw hydrocarbon oil 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 can be preferably used. ) Is preferred.

[Hydrogenation process (first process)]
In the present invention, first, a raw material hydrocarbon oil is brought into contact with a hydrorefining catalyst in the presence of hydrogen and subjected to desulfurization and denitrification treatment, thereby reducing the nitrogen content to 8.0 ppm by weight or less, The first step of converting part or all of the polycyclic aromatic hydrocarbons into fewer aromatic ring hydrocarbons, apparently from 1.5 to 1 ring aromatic hydrocarbons by addition or mild decomposition .
The indole, quinoline, and carbazole, which are main nitrogen compounds present in the raw hydrocarbon oil, are removed, and the nitrogen content of the first step product oil after the first step is 8 ppm by weight or less, preferably 7 ppm by weight In the following, it is more preferably reduced to 5 ppm by weight or less. If the nitrogen content of the first step product oil is not less than 8 ppm by weight, it is not preferable because rapid activity deterioration is caused in the subsequent hydrocracking step (second step).
The reaction conditions are preferably a temperature of 150 to 400 ° C., more preferably 200 to 380 ° C., still more preferably 250 to 360 ° C., and a pressure of 1.0 to 10 MPa, more preferably 2 to 8 MPa. speed (LHSV) is preferably from 0.1～10.0H ^-1, more preferably 0.1～8.0H ^-1, more preferably 0.2～5.0H ^-1 Not, hydrogen / hydrocarbon ratio It is preferably 100 to 5000 NL / L, more preferably 150 to 3000 NL / L.

  Although the above reaction conditions are related to each other, it is difficult to set them together.In general, however, when the reaction temperature is too high, it is effective for reducing sulfur and nitrogen contents, but polycyclic aromatics. Reduction of the group hydrocarbons involves a thermal condensation reaction, which may be undesirable. Increasing the reaction pressure and decreasing LHSV are also effective for reducing sulfur, nitrogen and polycyclic aromatic hydrocarbons, but are necessary to obtain the desired monocyclic aromatic hydrocarbons. Even a single aromatic ring portion may lead to complete nuclear hydrogenation, which is not necessarily preferable, and it is important to set an appropriate reaction condition range so that one aromatic ring remains.

  By the above treatment, the sulfur content of the first step product oil is preferably 500 ppm by weight or less, more preferably 100 ppm by weight or less, and particularly preferably 50 ppm by weight or less. Along with the desulfurization and denitrogenation reactions by this hydrorefining treatment, the hydrogenation of the aromatic ring also proceeds partially. In the present invention, it is important to reduce the amount of polycyclic aromatic hydrocarbons, but it is also undesirable to reduce the amount of monocyclic aromatic hydrocarbons. Accordingly, it is preferable to treat the reaction conditions so that the polycyclic aromatic component can be hydrogenated to a 1-ring or 1.5-ring aromatic hydrocarbon, and the sulfur content contained in the feedstock oil, Depending on the nitrogen content, various reaction conditions (first step catalyst amount, reaction pressure, LHSV, reaction temperature, hydrogen / hydrocarbon ratio) can be adjusted by appropriate setting. In the first step, the total aromatic hydrocarbon amount after the reaction / the total aromatic hydrocarbon amount before the reaction (volume ratio) is preferably as high as possible, but specifically, it is preferably controlled to 0.85 or more, A more preferable residual ratio is 0.88 or more, and further preferably 0.90 or more.

  In the present invention, the remaining amount of 1.5 rings in the first step product oil is preferably equivalent to the amount converted from the total amount of two or more polycyclic aromatic hydrocarbons in the raw hydrocarbon oil. That is, it is preferable that the sum of the 1-ring aromatic hydrocarbon and the 1.5-ring aromatic hydrocarbon in the first step product oil is as much as possible with respect to the total aromatic hydrocarbon amount contained in the raw material hydrocarbon oil. Specifically, the amount of the 1.5 ring aromatic hydrocarbon in the first step product oil is preferably 35% by volume or more, more preferably 40% by volume or more, and particularly preferably 41% by volume or more. Further, the amount of monocyclic aromatic hydrocarbons in the first step product oil is preferably 10% by volume or more, more preferably 11% by volume or more, and particularly preferably 12% by volume or more.

  Furthermore, in the present invention, the presence of an aromatic hydrocarbon having 3 or more rings is not preferable because it can be a poisoning substance for the hydrocracking catalyst. Therefore, the content of the aromatic hydrocarbon of 3 or more rings in the first step product oil is preferably less than 5% by volume, more preferably less than 3% by volume, and particularly preferably less than 1% by volume.

  The hydrorefining catalyst used for hydrorefining is not particularly limited, but a catalyst in which at least one metal selected from Groups 6 and 8 of the Periodic Table is supported on a refractory oxide support. It can be used suitably. As such a catalyst, specifically, a support containing at least one selected from alumina, silica, boria and zeolite, molybdenum, tungsten, nickel as metals of Group 6 and Group 8 of the periodic table, Examples thereof include a catalyst on which at least one metal selected from cobalt, platinum, palladium, iron, ruthenium, osmium, rhodium and iridium is supported. For example, when molybdenum is used as the Group 6 metal, the content thereof is preferably 1% by weight or more and less than 20% by weight, particularly 5% by weight or more and 15% by weight in the hydrorefining catalyst. The total content of cobalt or nickel as the Group 8 metal is preferably 0.5 wt% or more and less than 10 wt%, particularly 1 wt% or more and less than 7 wt% in the hydrotreating catalyst. Further, phosphorus or boron may be added. 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 hydrotreating process in the range of 10 volume% or more and less than 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. The hydrotreating step and the hydrocracking step described later may be configured as a catalyst layer 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. Needless to say, the hydrotreating step and the hydrocracking step may be separate apparatuses.

[Hydrolysis reaction (second step)]
In the hydrocracking step (second step) in the present invention, in the presence of hydrogen, as will be described in detail later, the first step product oil and the hydrocracking catalyst are brought into contact with each other to convert the monocyclic aromatic hydrocarbons. It is a process of generating. That is, the decomposition of the bicyclic aromatics of the oil produced in the first step and the opening of only the naphthenic ring of the 1.5-ring aromatic hydrocarbon to convert it to a single-ring aromatic hydrocarbon. The hydrocracked product oil containing a fresh hydrocarbon fraction is produced.

  The reaction form of hydrocracking in the present invention is not particularly limited, and a reaction form widely used conventionally, 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 for hydrocracking is used after pretreatment such as drying, reduction, and sulfidation 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. The activation of the catalyst by sulfidation is generally carried out by treating the hydrocracking catalyst at a temperature of 150 to 800 ° C., preferably 200 to 500 ° C. under a hydrogen / hydrogen sulfide mixture stream.

In hydrocracking, for example, the operating conditions such as reaction temperature, reaction pressure, hydrogen flow rate, liquid space velocity, etc. are appropriately determined according to the properties of the raw material, the quality of the product oil, the production volume, and the capacity of the refinery / post-treatment facilities Adjust it.
The first step product oil obtained in the first step and the hydrocracking catalyst described below are reacted in the presence of hydrogen at a reaction temperature of 200 to 450 ° C, more preferably 250 to 430 ° C, more preferably 280 to 400 ° C, reaction pressure 2 to 10 MPa, more preferably 2 to 8 MPa, a liquid hourly space velocity (LHSV) 0.1~10.0h ^-1, more preferably 0.1~8.0h ^-1, more preferably 0.2 At 5.0 h ⁻¹ , the hydrogen / hydrocarbon ratio is 100 to 5000 NL / L, preferably 150 to 3000 NL / L. Through the above operation, part or all of the polycyclic aromatic hydrocarbons and 1.5-ring aromatic hydrocarbons in the raw hydrocarbon oil for hydrocracking reaction are decomposed to obtain the desired monocyclic aromatic hydrocarbons. Convert. 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 can be obtained by molding a support composed of a specific zeolite and a binder that binds the zeolite into pellets (columnar or irregular columnar), granules, or spheres. 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 based on ASTM standard D3663-78, more preferably 150 m ² / g or more and less than 700 m ² / g, more preferably 200 m ² / g or more and less than 600 m ² / g. It is. When the BET specific surface area is smaller than the above range, the active metal dispersion is insufficient and the activity is not improved. On the other hand, when the BET specific surface area is too large, sufficient pore volume cannot be maintained and the reaction product is not sufficiently diffused. It is not preferable because the progress of the reaction is rapidly inhibited.

  The center pore diameter of the hydrocracking catalyst is more preferably 3.5 nm or more and less than 12 nm, and particularly preferably 4.0 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 more preferably 0.15 mL / g or more and less than 0.8 mL / g, and particularly preferably 0.2 mL / g or more and less than 0.7 mL / g. It is. 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.

[Zeolite]
Zeolite as used in the present invention needs to have a specific acid strength, and β-type zeolite can be suitably used in order to suppress excessive decomposition and excessive nuclear hydrogenation. Na-type, H-type, and NH ₄ type are widely available as β-type zeolite, and Na-type is usually obtained by synthesis, and can be easily converted into H-type and NH ₄ -type by ion exchange thereafter. Specifically, the strength of Bronsted acid is particularly important, and a Bronsted acid having a specific acid strength is required.

The acid strength of Bronsted acid refers to the heat of adsorption of ammonia, and is 110 kJ / Mol or more and less than 150 kJ / Mol, more preferably 115 kJ / Mol or more and less than 140 kJ / Mol, and particularly preferably 120 kJ / Mol or more and less than 135 kJ / Mol. As a specific measurement method, N.I. Katada, T .; Tsubaki, M .; Niwa, Appl. Cat. A: Gen. 340, (2008) p. 76 or Katano Naobu, Niwa Miki, Zeolite, Vol. 21, (2004) p. 45, the method of ammonia adsorption-temperature desorption (NH ₃ -TPD method) and Fourier transform. It can be determined by infrared spectroscopy (FT-IR method). That is, the amount of acid is obtained from the difference in absorption temperature at each temperature due to the bending vibration (1430 cm ⁻¹ ) of Bronsted acid. Assuming that the heat of adsorption of ammonia is constant, the acid strength distribution is determined from the temperature dependence. Of the obtained distribution, the strong acid side peak of Bronsted acid was read and defined as the maximum acid strength.

  The β-type zeolite as a zeolite, transition metal such as iron, cobalt, nickel, molybdenum, tungsten, copper, zinc, chromium, titanium, vanadium, zirconia, cadmium, tin, lead, lanthanum, cerium, ytterbium, europium, A catalyst supporting one or more metals selected from rare earths such as dysprosium can be preferably used. The supporting method can be carried out by an ordinary method. These metal ions are introduced by immersing the support in a solution containing the metal salt, and a transition metal-containing crystalline aluminosilicate or a rare earth-containing crystalline alumino is introduced. It may be a silicate. When subjected to the hydrocracking reaction described later, the transition metal-containing crystalline aluminosilicate or the rare earth-containing crystalline aluminosilicate may be used alone or in combination of two or more thereof.

[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 zeolite and have 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 zeolite, thereby improving the strength of the catalyst. The specific surface area of the binder is desirably 30 m ² / g or more.

  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 zeolite 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. The weight of the zeolite relative to the total weight of the zeolite part and the binder part is preferably 1% by weight or more and less than 80% by weight, particularly preferably 10% by weight or more and less than 70% by weight. If the amount is less than 1% by weight, the effect of improving the decomposition activity due to the use of 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% by weight or more and 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 0.1% by weight, a sufficient hydrogenation function cannot be obtained, and if it exceeds 5% by weight, the addition efficiency is poor and it is not economical, which is not preferable.

[Method for producing hydrocracking catalyst]
The hydrocracking catalyst of the present invention can be prepared by kneading and forming a zeolite and a binder, then drying and firing to prepare a carrier, and further impregnating and supporting a metal component, followed by drying and firing. .

  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.

[Properties of hydrocracked oil]
In the hydrocracking step, the hydrocracked product oil produced is more preferable as the ratio of monocyclic aromatic hydrocarbons increases as compared to the raw hydrocarbon oil. Specifically, as an increase with respect to the raw material hydrocarbon oil, the monocyclic aromatic hydrocarbon is preferably 13% by volume or more, more preferably 14% by volume or more, and particularly preferably 15% by weight. It is preferably 8% by volume or more, more preferably 9% by volume or more, and particularly preferably 10% by volume or more. Similarly, the increase in aromatic hydrocarbons having 9 carbon atoms is 4% by volume or more, preferably 5% by volume or more, particularly preferably 6% by volume or more, and two or more rings remaining in the hydrocracked product oil. The total amount of the polycyclic aromatic hydrocarbons is 7.0% by volume or less, preferably 6.0% by volume or less, particularly preferably 5.5% by volume or less. The total amount is 2.0% by volume or less, preferably 1.5% by volume or less, particularly preferably 1.0% by volume or less.

  Further, the conversion rate of a fraction having a boiling point of 215 ° C. or more is preferably 50% by volume or more, more preferably 60% by volume or more, and particularly preferably 70% by volume or more. About the yield of hydrocracked product oil (reaction liquid yield) 70 volume% or more, more preferably 75 volume% or more, and particularly preferably 80 volume% or more. A low conversion rate is not preferable because the desired monocyclic aromatic hydrocarbon is difficult to obtain. When the reaction liquid yield is less than 70% by volume, that is, when the decomposition reaction is excessive, it is not preferable economically, and it is not preferable because the problem of activity deterioration accompanying carbon deposition on the catalyst caused by the decomposition reaction is caused. . The reaction liquid yield is expressed as volume% when the raw material hydrocarbon oil is set to 100, and in the cracking reaction, a large amount of gas is by-produced and is often smaller than 100 volume%, but gas generation is suppressed. When selective decomposition without nuclear hydrogenation or gas generation occurs preferentially, it may exceed 100% by volume.

  In the present invention, it is important to convert more from a polycyclic aromatic hydrocarbon to a naphtha fraction which is a monocyclic aromatic hydrocarbon. In the present invention, the naphtha fraction is a fraction having a boiling point of 30 ° C. or more and less than 190 ° C., and the yield obtained is preferably 60% by volume or more, more preferably 67% by volume or more, and particularly preferably 70%. It is more than volume%. In particular, a fraction having a boiling point of 85 to 190 ° C. can be referred to as a heavy naphtha fraction, but is particularly useful because it includes BTX itself and can be used as a raw material hydrocarbon oil for a catalytic reforming reaction. Therefore, the heavy naphtha is preferably 40% by volume or more, more preferably 43% by volume or more, and particularly preferably 45% by volume or more.

  Furthermore, in this invention, the hydrocracking catalyst which is the main reaction can be protected by performing an appropriate hydrotreating in advance, and the decrease in the activity of the hydrocracking catalyst can be suppressed. In general, in a hydrocracking apparatus, a bottom decomposition rate constant operation or a middle distillate yield constant operation is performed. Therefore, in the present invention, the conversion rate of the fraction having a boiling point of 215 ° C. or higher corresponding to the bottom decomposition rate and the heavy naphtha yield corresponding to the middle distillate yield are stably maintained and not lowered over a long period of time. It is extremely important in actual operation. That is, the conversion rate (Conv. (120)) of the boiling point of 215 ° C. or higher when the feed rate of oil is 120 times the catalyst amount and the fraction of boiling point of 215 ° C. or more when the feed rate is 12 times. Conversion ratio (Conv. (12)) ratio (Conv. (120) / Conv. (12)) is assumed to be 0.92 or more when the conversion rate of 215 ° C. or higher fraction is the residual degree of conversion. Is more preferably 0.93 or more, and particularly preferably 0.95 or more.

Similarly, the ratio of the heavy naphtha yield (Y _HN (120)) when the feed amount of the raw material to the catalyst amount is 120 times the ratio of the heavy naphtha yield (Y _HN (12)) when the equivalent of 12 times (Y _HN When (120) / Y _HN (12)) is the residual degree of heavy naphtha yield, it is preferably 0.90 or more, more preferably 0.93 or more, and particularly preferably 0.95 or more. .
When the residual degree of conversion of the 215 ° C. or higher fraction is less than 0.92 and the residual degree of heavy naphtha yield is less than 0.90, the activity of the catalyst is drastically reduced and the catalyst can be stably operated over a long period of time. This becomes impossible and is not preferable.

[Post-processing process]
In the present invention, as in the pretreatment step, a post-treatment step for refining the hydrocracked product oil obtained as necessary can be installed. Although a post-processing process is not specifically limited, The catalyst kind, catalyst amount, and operation conditions similar to a pre-processing process can be set. The post-treatment process may be installed immediately after the hydrocracking process to treat the hydrocracked product oil, or may be installed after the subsequent separation process to treat each separated hydrocarbon fraction individually. May be. 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 adopted according to the product properties. Moreover, what is necessary is just to set those operating conditions suitably.

  The distillation method uses a difference in boiling points to separate, for example, into 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. A kerosene fraction, and a portion having a higher boiling point up to about 260 to 370 ° C. can be used as a light oil fraction. A heavier fraction is combined with the kerosene fraction as an unreacted product, You may process by a hydrocracking reaction process and may use it for base materials, such as A heavy oil.

  Hereafter, the manufacturing method of the hydrocarbon fraction of this invention is demonstrated in detail and concretely using an Example and a comparative example.

[Preparation of hydrocracking catalyst]
13.4 g of H-β type zeolite (HSZ-940HOA manufactured by Tosoh Corporation) having a SiO ₂ / Al ₂ O ₃ ratio of 39.6 and a specific surface area of 746 m ² / g is 834 g of alumina powder (alumina Versal 250 manufactured by UOP). Mix, add 500 mL of 4.0 wt% dilute nitric acid solution and 100 g of ion-exchanged water, knead, extrude into a cylindrical shape (pellet), dry at 130 ° C for 6 hours, and then fire at 600 ° C for 2 hours And used as a carrier. Here, the dry weight of zeolite and alumina contained in the support (when dried at 130 ° C.) was set to 70% by weight and 30% by weight, respectively.
In addition, when this zeolite was measured by ammonia TPD, the maximum acid strength was 125 kJ / mol as ammonia adsorption heat.

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. Next, catalyst A was obtained by calcination at 500 ° C. for 30 minutes under an air stream. The metal composition of catalyst A was 7.8% by weight of Mo, 3.0% by weight of Ni, 26.6% by weight of Si, and 13.4% by weight of Al.
When the pore characteristics of this catalyst A were measured by a nitrogen gas adsorption method, the specific surface area was 359 m ² / g, the pore volume occupied by pores having a pore diameter of 2 nm or more and less than 60 nm was 0.312 mL / g, the center pore The diameter was 4.1 nm.

  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.

Example 1
A raw material oil A is used as a raw material hydrocarbon oil, a commercially available NiMo / alumina-based desulfurization catalyst is arranged in the reaction tower A tower, the catalyst A is arranged in the reaction tower B tower so as to have a catalyst capacity of 1: 2, and a table As shown in FIG. 2, the reaction pressure = 7.0 MPa, LHSV = 0.5 h ⁻¹ , hydrogen / raw hydrocarbon oil ratio = 1,400 NL / L, A tower reaction temperature = 320 ° C., B tower reaction temperature = 355 ° C. Then, a hydrogenolysis reaction was performed. Table 1 shows the properties of the raw material oil A used in the reaction, and Tables 2a and 2b show the properties of the resulting product oil. The metal composition of the commercially available NiMo / alumina-based desulfurization catalyst used in the reaction tower A was 12.3% by weight for Mo, 3.5% by weight for Ni, 2.0% by weight for P, and 38.% for Al. It was 2% by weight.

  Here, the gas yield is a vaporized component at normal pressure and room temperature, the light naphtha yield is a component in the boiling range of normal pressure to 85 ° C, and the heavy naphtha yield is a component in the boiling range of 85 to 190 ° C. The kerosene oil yield means a component having a boiling range of 190 ° C. or higher.

The reaction liquid yield is the residual ratio (volume%) of the fraction having 5 or more carbon atoms after the reaction with the raw material hydrocarbon oil, and the conversion rate of the fraction having a boiling point of 215 ° C. or higher is a value obtained by the following formula. is there.
Conversion rate (%) of a fraction having a boiling point of 215 ° C. or higher = 100− (fraction having a boiling point of 215 ° C. or higher in the produced oil (volume%) / fraction having a boiling point of 215 ° C. or higher in the raw hydrocarbon oil (volume%)) × 100

The residual degree of conversion of the fraction of 215 ° C. or higher is the feed of the raw material to the amount of catalyst with respect to the conversion of the fraction having a boiling point of 215 ° C. or higher (Conv. This refers to the ratio of the conversion rate (Conv. (120)) of a fraction having a boiling point of 215 ° C. or higher when the amount corresponds to 120 times. (120) / Conv. It is represented by (12).
Also, the ratio of the heavy naphtha yield (Y _HN (120)) when the feed oil is 120 times to the heavy naphtha yield (Y _HN (12)) when the feed degree is 12 times the feed rate Y _HN (120) / Y _HN (12).

(Comparative Example 1)
As shown in Table 3, the raw oil B was used as the raw material hydrocarbon oil, the tower naphtho reaction temperature = 320 ° C., the tower B reaction temperature = 370 to 375 ° C., and the LHSV = 0.644 h ^−1. The hydrocracking reaction was carried out under the same conditions as in Example 1 except that the conditions were set so as to be the same level. Table 1 shows the properties of the raw material oil B used in the reaction, and Tables 3a and 3b show the properties of the resulting product oil.

(Example 2)
The hydrocracking reaction was carried out under the same conditions as in Example 1 except that the raw material oil C was used as the raw material hydrocarbon oil, and the tower A reaction temperature = 350 ° C. and the tower B reaction temperature = 365 ° C. as shown in Table 2. . Table 1 shows the properties of the raw material oil C used in the reaction, and Tables 2a and 2b show the properties of the resulting product oil.

(Comparative Example 2)
As shown in Table 3, the hydrocracking reaction was performed under the same conditions as in Example 2 except that the tower A reaction temperature was 340 ° C. The properties of the resulting product oil are shown in Tables 3a and 3b.

As is clear from Tables 2a and b and Tables 3a and b, in Examples 1 and 2, a desired pretreatment was performed prior to the hydrocracking reaction to obtain the desired value from the 1.5-ring aromatic hydrocarbon. Conversion to monocyclic aromatic hydrocarbons proceeds efficiently, and the feed rate of feedstock corresponding to 10 times the feed rate of feedstock compared to when the feed rate of feedstock to the catalyst is equivalent to 12 times. It can be seen that there is almost no decrease in activity even after 120 times. On the other hand, when an appropriate pretreatment is not performed (Comparative Examples 1 and 2), a large amount of poisonous substances are brought into the hydrocracking process, resulting in a decrease in catalytic activity. Under this circumstance, it is necessary to increase the reaction temperature to increase the yield of monocyclic aromatic hydrocarbons. As a result, the coke deterioration of the catalyst accompanying the high temperature reaction further progresses, which is not preferable from the viewpoint of economic deterioration due to a decrease in catalyst life and an increase in input energy.
In general, in a hydrocracking apparatus, a bottom decomposition rate constant operation or a middle distillate yield constant operation is performed. Accordingly, the conversion rate of the fraction having a boiling point of 215 ° C. or more corresponding to the bottom decomposition rate and the heavy naphtha yield corresponding to the middle fraction yield are stably maintained over a long period of time as in Examples 1 and 2. It is extremely beneficial for practical operation not to decrease.

The raw hydrocarbon oil used in the above Examples and Comparative Examples and the method for analyzing the properties of the product oil are as follows.
The composition of monocyclic aromatic hydrocarbons (benzene, toluene, xylenes) and the composition of 1.5 ring aromatic hydrocarbons (tetralins, etc.) were measured using a hydrocarbon total component analyzer manufactured by Shimadzu Corporation. It measured according to JIS K2536.

The aromatic ring constituent carbon ratio was measured using a JSX G270 type nuclear magnetic resonance apparatus using deuterated chloroform as a solvent and tetramethylsilane (0 ppm) as an internal standard.
Quantification of aromatic ring constituent carbon and aliphatic constituent carbon for each carbon species classification is SGNNE mode, with data points of 32768 points, observation frequency region width of 27027 Hz, pulse width of 2 μs, pulse waiting time of 30 S, and integration number of 2,000 times. The measured and Fourier-transformed spectrum signal was calculated from the integral ratio. In the obtained spectrum shift value, those in the range of 120 to 150 ppm were attributed to aromatic carbon and expressed as mol% with respect to the total carbon.

  According to the present invention, polycyclic aromatic hydrocarbons are used as a raw material hydrocarbon oil, and poisoning of the hydrocracking catalyst is suppressed by reducing poisonous substances to an appropriate predetermined amount or less, and excessive hydrogenation hydrogenation. By carrying out an appropriate hydrocracking reaction without carrying out the above, a method for efficiently producing a high-value-added monocyclic aromatic hydrocarbon, particularly BTX (benzene, toluene, xylene) is provided. From the hydrocracked product oil obtained by the present invention, through an appropriate separation step, LPG fraction, gasoline fraction, kerosene fraction, light oil fraction, non-aromatic naphtha fraction and monocyclic aromatic hydrocarbon Products (including BTX) can be obtained. Therefore, the present invention can be effectively used for petroleum refining and the production of various petroleum products and petrochemical raw materials by directly or appropriately combining the above petroleum fractions.

Claims (4)

(1) A raw material hydrocarbon oil having an aromatic ring constituent carbon ratio of 40 mol% or more and a boiling point of 215 ° C or more containing 30 vol% or more is heated in the presence of hydrogen at a temperature of 150 to 400 ° C and a pressure of 1.0 to 1.0. Under conditions of 10 MPa, liquid hourly space velocity (LHSV) of 0.1 to 10.0 h ⁻¹ , hydrogen / hydrocarbon ratio of 100 to 5000 NL / L, the nitrogen content is reduced to 8.0 ppm by weight or less by contacting with the hydrorefining catalyst. At the same time, the first step of converting part or all of the polycyclic aromatic hydrocarbons to 1.5-ring and monocyclic aromatic hydrocarbons, and (2) the first-step product oil obtained in the first step In the presence of hydrogen under the conditions of a temperature of 200 to 450 ° C., a pressure of 2 to 10 MPa, a liquid space velocity (LHSV) of 0.1 to 10.0 h ⁻¹ , and a hydrogen / hydrocarbon ratio of 100 to 5000 NL / L. Polycyclic aromatic hydrocarbons and 1.5 ring aromatics in contact with cracking catalyst A hydrocracked product oil having a content of 1-ring aromatic hydrocarbon of 25% by volume or more, comprising a second step of converting a part or all of the hydrocarbon into a 1-ring aromatic hydrocarbon, and a catalyst The ratio of heavy naphtha yield (Y _HN (120) / Y _HN (12)) is 0.90 or more (capacity) when the feed amount of the feed hydrocarbon oil is 120 times and 12 times method of manufacturing a selective monocyclic aromatic hydrocarbon, which is a ratio) (wherein, Y _HN (120) is a heavy naphtha yield at equivalent course 120 times oil flow amount of the raw material hydrocarbon oil to the catalyst weight Y _HN (12) indicates a heavy naphtha yield when the feed amount of the raw material hydrocarbon oil with respect to the catalyst amount is equivalent to 12 times, and heavy naphtha indicates a fraction having a boiling point of 85 to 190 ° C.). Method of manufacturing a selective monocyclic aromatic hydrocarbons according to claim 1 wherein the water hydride decomposition product oil yield is 70% by volume or more.   The method for producing a selective one-ring aromatic hydrocarbon according to claim 1 or 2, wherein the raw material hydrocarbon oil contains 60 vol% or more of hydrocarbons having a boiling point of 30 to 190 ° C.   Ratio of conversion rate of fractions with boiling points of 215 ° C. or higher when the flow rate of feed hydrocarbon oil relative to the catalyst amount is equivalent to 120 times or 12 times (Conv. (120) / Conv. (12)) Is a method for producing a selective monocyclic aromatic hydrocarbon according to any one of claims 1 to 3, wherein Conv. (120) is the amount of feed of raw material hydrocarbon oil relative to the amount of catalyst. Is the conversion rate of the fraction with a boiling point of 215 ° C. or higher when the time is equivalent to 120 times, and Conv. (12) Refers to rate).