Method for producing aromatic compounds

Abstract

To provide a method for producing an aromatic compound, which can reduce an amount of coke adhering to a catalyst during the production of the aromatic compound.SOLUTION: The method for producing the aromatic compound according to the present disclosure includes: an aromatic compound production step of bringing a feedstock containing a hydrocarbon compound into contact with a catalyst containing zeolite to produce an aromatic compound; and a regeneration step of bringing the catalyst on which coke is adhered in the aromatic compound production step into contact with an oxygen-containing gas at 300°C or higher to remove the coke, and regenerating the catalyst, wherein the aromatic compound production step and the regeneration step are alternately repeated, and an amount of coke adhered to the catalyst regenerated by the regeneration step is 5 to 50% of an amount of coke adhered to the catalyst before the regeneration step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing an aromatic compound. [Background technology]

[0002] Aromatic compounds such as benzene, toluene, and xylene are often obtained by cracking feedstock oil (e.g., naphtha) obtained from petroleum refining in a thermal cracking reactor and separating and purifying the resulting thermal cracking products by distillation or extraction. In these methods for producing aromatic compounds, aliphatic hydrocarbons (paraffinic, olefinic, acetylenic, and alicyclic hydrocarbons) are by-produced as thermal cracking products other than aromatic compounds. Therefore, since aliphatic hydrocarbons are simultaneously produced in conjunction with the production of aromatic compounds, the production volume of aromatic compounds is adjusted in accordance with the production volume of aliphatic hydrocarbons, which naturally limits the production volume.

[0003] It has also been proposed to produce aromatic compounds by contacting a raw material containing an aliphatic or alicyclic hydrocarbon compound (hereinafter also referred to as a "hydrocarbon raw material") with a catalyst containing zeolite (hereinafter also referred to as a "zeolite catalyst") at a temperature of about 400°C to about 800°C (see, for example, Patent Documents 1 and 2, and Non-Patent Documents 1 to 4). These production methods have the advantage of being lower in added value than methods of producing aromatic compounds by thermal cracking, and that aromatic compounds can be produced from excess hydrocarbon raw materials.

[0004] Furthermore, the thermal cracking of feedstock oil also produces heavy aromatic compounds such as alkylnaphthalenes, which are difficult to separate and refine compared to light hydrocarbon compounds, and there is a need for their effective utilization. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3741455 [Patent Document 2] Patent No. 3264447 [Non-patent literature]

[0006] [Non-Patent Document 1] Industrial & Engineering Chemistry Research, Vol. 31, p. 995 (1992) [Non-patent document 2] Industrial & Engineering Chemistry Research, Vol. 26, p. 647 (1987) [Non-patent document 3] Applied Catalysis Vol. 78, p. 15 (1991) [Non-patent document 4] Microporous and Mesoporous Materials, Vol. 47, p. 253 (2001) Summary of the Invention [Problem to be solved by the invention]

[0007] A problem in the production of aromatic compounds using the above-mentioned zeolite catalyst is the accumulation of carbonaceous material (hereinafter also referred to as "coke") on the zeolite catalyst during the aromatization reaction, resulting in a decrease in catalytic activity, known as coking. To recover from this decrease in activity due to coking, industrial processes incorporate a process in which the coke is exposed to oxygen or steam to regenerate the catalytic activity. By alternately repeating the reaction (production of the target compound) and regeneration (combustion of the coke on the catalyst), the zeolite catalyst can be used for a long period of time.

[0008] Although coking causes a decrease in catalyst activity, it can be reversibly restored to a highly active state by performing a regeneration process. However, if excessive heat is generated during the regeneration process, which places a strain on the catalyst, there is a risk of irreversible loss of catalytic activity. Furthermore, because the regeneration process is an exothermic reaction, failure to control excessive heat generation can cause malfunctions in the reaction equipment. The heat generated during the regeneration process depends on the amount of coke removed during this process. In other words, reducing the amount of coke to be removed allows the catalyst to be used for a longer period of time.

[0009] An object of the present invention is to provide a method for producing an aromatic compound that can reduce the amount of coke that adheres to a catalyst during the production of an aromatic compound. [Means for solving the problem]

[0010] The present invention includes, for example, the following inventions. [1] an aromatic compound production step in which a raw material containing a hydrocarbon compound is brought into contact with a catalyst containing a zeolite to produce an aromatic compound; a regeneration step of contacting the catalyst to which coke has adhered in the aromatic compound production step with an oxygen-containing gas at 300°C or higher to remove the coke and regenerate the catalyst, the aromatic compound production step and the regeneration step are alternately repeated, A method for producing an aromatic compound, wherein the amount of coke adhering to the catalyst regenerated in the regeneration step is 5 to 50% of the amount of coke adhering to the catalyst before the regeneration step. [2] The method for producing an aromatic compound according to [1], wherein the amount of coke adhering to the catalyst before the regeneration step is 10 to 40 mass %. [3] An aromatic compound production apparatus having two or more reactors filled with the above catalyst is used, The aromatic compound production step is carried out in at least one of the reactors, and during the aromatic compound production step, the regeneration step is carried out in the other reactors; The method for producing an aromatic compound according to [1] or [2], wherein the aromatic compound production step and the regeneration step are alternately switched between different reactors at predetermined time intervals. [4] The method for producing an aromatic compound according to [3], wherein the conversion between the aromatic compound production step and the regeneration step is carried out every 10 to 100 hours. [5] The method for producing an aromatic compound according to any one of [1] to [4], wherein in the aromatic compound production step, the catalyst and the raw material are contacted at a reaction temperature of 400 to 800°C and a pressure of 0.05 to 5 MPa. [6] The method for producing an aromatic compound according to any one of [1] to [5], wherein the raw material is one or more hydrocarbon compounds selected from the group consisting of heavy aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds having 2 to 6 carbon atoms, and alicyclic hydrocarbon compounds. [7] The method for producing an aromatic compound according to any one of [1] to [6], wherein in the regeneration step, the oxygen-containing gas having an oxygen content of 1 to 25 mass % and at 400 to 450° C. is brought into contact with the catalyst. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a method for producing an aromatic compound, which can reduce the amount of coke that adheres to a catalyst during the production of an aromatic compound. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a flowchart of a manufacturing method according to one embodiment of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram illustrating an example of an aromatic compound production apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments and can be implemented in various modifications within the scope of the present disclosure. In this specification, the term "coke amount" refers to the mass percentage of the amount of coke adhering to the catalyst relative to the total amount of the catalyst and coke.

[0014] The method for producing an aromatic compound according to the present disclosure (hereinafter also simply referred to as the "production method according to the present disclosure") includes an aromatic compound production step in which a raw material containing a hydrocarbon compound is brought into contact with a catalyst containing zeolite to produce an aromatic compound, and a regeneration step in which an oxygen-containing gas is brought into contact with the catalyst to which coke has adhered in the aromatic compound production step at 300°C or higher to remove the coke and regenerate the catalyst. The aromatic compound production step and the regeneration step are carried out using a reactor. Here, the reactor is a container for contacting the raw material or the oxygen-containing gas with the catalyst inside. Focusing on one reactor, the aromatic compound production step and the regeneration step are carried out alternately and repeatedly. Note that the aromatic compound production apparatus may have one or more reactors. In addition, in this specification, the catalyst used in the production method according to the present disclosure is also referred to as a catalyst for producing aromatic compounds.

[0015] A flowchart of an example of the production method of the present disclosure is shown in Figure 1. Figure 1 is a flowchart of a production method using an aromatic compound production apparatus having two reactors (see Figure 2). Note that Figure 1 shows a case where reactor 20 is being started and then a regeneration step is started, and the reactor is filled with catalyst to which coke has adhered from a previous aromatic compound production step.

[0016] 1 , an aromatic compound production step S1 and a regeneration step S2 are alternately and repeatedly performed in each of the reactors 10 and 20. Then, while the aromatic compound production step S1 is being performed in the reactor 10, the regeneration step S2 is being performed in the reactor 20, and while the regeneration step S2 is being performed in the reactor 10, the aromatic compound production step S1 is being performed in the reactor 20. In this way, when the aromatic compound production step S1 is performed in at least one of the reactors and the regeneration step S2 is being performed in the other reactors during the aromatic compound production step S1, the aromatic compound production step S1 and the regeneration step S2 are alternately switched between the different reactors at predetermined time intervals, thereby enabling continuous production of aromatic compounds while maintaining the activity of the catalyst at a certain level or higher.

[0017] In the regeneration step of the production method of the present disclosure, the amount of coke after the regeneration step is reduced to 5 to 50% of the amount of coke before the regeneration step. As described above, in the regeneration step, the coke adhering to the catalyst after the aromatic compound production step is completed is not completely removed, but rather some of the coke is removed so that it remains, thereby making it possible to reduce the amount of coke adhering to the catalyst during aromatic compound production using the regenerated catalyst. This is thought to be because, during aromatic compound production, if the amount of coke adhering to the catalyst surface at the early stage of the reaction is small, coke is by-produced on excess acid sites on the catalyst surface. However, if the amount of coke is relatively large from the middle stage of the reaction onwards, coke has already adhered to the excess acid sites, making it difficult for the amount of coke to increase.

[0018] If the amount of coke after the regeneration step is 5% or more of the amount of coke before the regeneration step, excessive heat generation due to excessive coke combustion during regeneration is unlikely, and if it is 50% or less, the catalyst is likely to return to a highly active state. This configuration is believed to prevent excessive heat generation during the regeneration step in the production method of the present disclosure, allowing the zeolite catalyst to be used for a long period of time. The ratio of the amount of coke after the regeneration step to the amount of coke before the regeneration step is preferably 10 to 50%, more preferably 20 to 50%, and even more preferably 30 to 45%.

[0019] The amount of coke adhering to the catalyst before the regeneration step (after the aromatic compound production step is completed) is preferably 10 to 40% by mass. If the amount of coke adhering to the catalyst before the regeneration step is 10% by mass or more, it is thought that the amount of coke on the catalyst surface after regeneration will not be too small, making it difficult for the amount of coke to increase in the next aromatic compound production step. Furthermore, if the amount is 40% by mass or less, the catalyst will easily return to a highly active state in the regeneration step. The amount of coke adhering to the catalyst after the aromatic compound production step is completed is more preferably 15 to 40% by mass, even more preferably 20 to 40% by mass, and even more preferably 25 to 40% by mass.

[0020] Furthermore, the amount of coke adhering to the catalyst after the regeneration step is preferably 2 to 25 mass%. If the amount of coke adhering to the catalyst after the regeneration step is 2 to 25 mass%, an excellent balance is achieved between the reduction in the amount of coke adhering in the next aromatic compound production step and the activity of the catalyst. The amount of coke adhering to the catalyst after the regeneration step is preferably 6 to 22 mass%, more preferably 9 to 19 mass%, and even more preferably 9 to 16 mass%.

[0021] (Aromatic compound manufacturing equipment) In the production method of the present disclosure, for example, an aromatic compound production apparatus having one or more reactors filled with a zeolite catalyst can be used. FIG. 2 is a schematic diagram showing an example of an aromatic compound production apparatus used in the production method of the present disclosure. In FIG. 2, the aromatic compound production apparatus 100 has two reactors 10 and 20 filled with a catalyst. A raw material supply pipe 30 and an oxygen-containing gas supply pipe 40 are connected to the reactors 10 and 20, respectively. In addition, each of the reactors 10 and 20 can be provided with a temperature control device (not shown) to control the temperatures to be suitable for the aromatic compound production process and the regeneration process. This allows, for example, aromatic compound production in the reactor 10 and catalyst regeneration in the reactor 20 simultaneously. Then, when the catalyst activity decreases, the supply gas to the reactors 10 and 20 can be switched, and the catalyst can be regenerated in the reactor 10 while aromatic compound production in the reactor 20 can be performed simultaneously. By using the aromatic compound production apparatus 100, aromatic compounds can be continuously produced.

[0022] The number of reactors may be three or more. For example, when an aromatic compound production apparatus has three or more reactors, two reactors can be operated, and the remaining reactors can be kept on standby as spare reactors to be used in place of the operating reactor when the catalytic activity of the reactor decreases. In addition, instead of a temperature control device, the reactors can be provided with a heat insulating material that has an insulating effect between the reactor and the external environment, and the temperature can be controlled by the temperature of the gas supplied.

[0023] (Catalyst for producing aromatic compounds) The production method of the present disclosure can use a catalyst containing a 10-membered ring and / or 12-membered ring pore zeolite. The 10-membered ring and / or 12-membered ring pore zeolite may be any zeolite within the scope of the present disclosure, such as 10-membered ring pore zeolites AEL, EUO, FER, HEU, MEU, MEL, MFI, and NES types; and 12-membered ring pore zeolites AFI, MTW, VFI, FAU, *BEA, and MWW types. Among these, 10-membered ring pore zeolites are preferred, and MFI zeolites are particularly preferred, as they enable efficient production of aromatic compounds. Furthermore, for example, MFI, *BEA, and MWW zeolites refer to aluminosilicate compounds with structure codes MFI, *BEA, and MWW, respectively, as defined by the International Zeolite Association. In this case, the zeolite may be a metal-containing zeolite, and the metal may be, for example, at least one metal selected from silver, calcium, magnesium, strontium, barium, gallium, and zinc, with zinc and / or gallium being particularly preferred. Here, if the zeolite is other than a 10-membered ring pore zeolite or a 12-membered ring pore zeolite, or if it contains components other than a 10-membered ring and / or a 12-membered ring pore zeolite, problems such as low selectivity to aromatic compounds and significant coke production are likely to occur.

[0024] The catalyst may have any of the following shapes: powder, cylinder, triangular prism, square prism, polygonal prism, hollow shape, honeycomb, cylinder, or (irregular) shape having independent pores or interconnected pores. When forming such a shape, the catalyst may contain binder or the like.

[0025] (Production of aromatic compounds) The aromatic compound production step included in the production method of the present disclosure can be, for example, a step of producing an aromatic compound by contacting the above-mentioned catalyst with a raw material containing one or more hydrocarbon compounds selected from the group consisting of heavy aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds having 2 to 6 carbon atoms, and alicyclic hydrocarbon compounds under predetermined temperature and pressure conditions. The raw material may be in the form of gas, liquid, or a mixture thereof.

[0026] The heavy aromatic hydrocarbon compound can be selected from aromatic hydrocarbon compounds having, for example, 8 to 15 carbon atoms and a boiling point of 130 to 250°C. Examples of heavy aromatic hydrocarbon compounds include monocyclic aromatic compounds having a paraffinic alkyl group, such as ethylbenzene, cumene, xylene, and triisopropylbenzene; monocyclic aromatic compounds having an olefinic alkyl group, such as styrene, allylbenzene, and divinylbenzene; and polycyclic aromatic hydrocarbon compounds, such as indane and indene. Among these, monocyclic aromatic compounds having an alkyl group with 8 to 15 carbon atoms are preferred because they allow for the selective and efficient production of benzene and toluene. Specific examples include monocyclic aromatic compounds having a paraffinic alkyl group, such as ethylbenzene, cumene, xylene, and triisopropylbenzene; and monocyclic aromatic compounds having an olefinic alkyl group, such as styrene, allylbenzene, and divinylbenzene. Here, aromatic hydrocarbon compounds having fewer than 8 carbon atoms or a boiling point of less than 130°C result in a raw material with a small carbon number, making the method less efficient as a method for producing aromatic compounds that can simultaneously produce benzene and toluene. On the other hand, aromatic hydrocarbon compounds with a carbon number of more than 15 or a boiling point of more than 250°C will produce coke due to side reactions during the reaction and will significantly reduce the production rates of the light components benzene and toluene, resulting in poor production efficiency. Heavy aromatic hydrocarbon compounds are generally more likely to produce coke during aromatic compound production than other hydrocarbon compounds, but in the production method of the present disclosure, it is preferable to include heavy aromatic hydrocarbon compounds as the raw material because this allows for a reduction in the amount of coke adhering to the catalyst.

[0027] Examples of the aliphatic hydrocarbon compounds and alicyclic hydrocarbon compounds having 2 to 6 carbon atoms include any compounds that fall within the scope of the category. For example, ethane, ethylene, propane, propylene, cyclopropane, n-butane, isobutane, 1-butene, 2-butene, isobutene, butadiene, cyclobutene, cyclobutane, n-pentane, 1-pentane, 2-pentane, 1-pentene, 2-pentene, 3-pentene, n-hexane, 1-hexane, 2-hexane, 1-hexene, 2-hexene, 3-hexene, hexadiene, cyclohexane, and mixtures thereof can be mentioned. Furthermore, examples include petroleum, for example, a C4 fraction, which is a distillation mixture of hydrocarbons having 4 carbon atoms obtained by cracking fractions of naphtha, a C5 fraction, which is a distillation mixture of hydrocarbons having 5 carbon atoms, and a C6 fraction, which is a distillation mixture of hydrocarbons having 6 carbon atoms.

[0028] The temperature range for producing aromatic compounds by contacting a raw material with a catalyst for aromatic compound production can be 400°C to 800°C, with 450°C to 650°C being preferred for particularly excellent production efficiency. The feed rate of the raw material to the catalyst for aromatic compound production is preferably a gas volume ratio of 1:50 to 2000, particularly 1:100 to 1000, to achieve both production efficiency and aromatic yield. There are no restrictions on the pressure during production, and production is preferably carried out within a pressure range of, for example, approximately 0.05 MPa to 5 MPa. In the aromatic compound production process, contacting the catalyst with the raw material at a reaction temperature of 400 to 800°C and a pressure of 0.05 to 5 MPa is preferred because aromatic compounds can be produced efficiently and catalyst degradation is unlikely to occur. When supplying raw materials, the hydrocarbon single gas, mixed gas, or a diluted version of these with a single or mixed gas selected from an inert gas such as nitrogen, hydrogen, carbon monoxide, and carbon dioxide can also be used.

[0029] The reaction type during production is not limited, and for example, not only a fixed bed, transport bed, fluidized bed, moving bed, or multi-tubular reactor, but also a continuous flow type, intermittent flow type, or swing type reactor can be used. The reaction type using a swing type reactor is preferred because it provides a particularly efficient method for producing aromatic compounds.

[0030] The aromatic compound to be produced is not particularly limited as long as it belongs to the category called aromatic compounds, and examples thereof include benzene, toluene, xylene, trimethylbenzene, ethylbenzene, propylbenzene, butylbenzene, naphthalene, and methylnaphthalene, with benzene and toluene being particularly preferred.

[0031] In the method for producing an aromatic compound of the present invention, ancillary steps such as a step of separating and purifying a product containing an aromatic compound, particularly a step of separating and purifying benzene and toluene, can be added as appropriate.

[0032] (Regeneration of catalysts for aromatic compound production) The regeneration step included in the production method of the present disclosure regenerates a catalyst containing zeolite as an active component, which is used in the production of aromatic compounds. This step can be, for example, a step of removing coke from a catalyst that has been coked during the aromatic compound production process by contacting the catalyst with an oxygen-containing gas having an oxygen content of 1 to 25% by mass at 300°C to 600°C. Contacting the catalyst with an oxygen-containing gas under these conditions efficiently removes coke and restores catalyst performance in a shorter time. From the perspectives of regeneration efficiency and suppressing temperature rise during regeneration, the oxygen content is preferably 2 to 20% by mass, and even more preferably 5 to 15% by mass. Furthermore, the temperature of the gas contacted with the catalyst is more preferably 380 to 530°C, and even more preferably 400 to 450°C.

[0033] If the oxygen content of the gas is less than 1% by mass or the temperature is less than 300°C, the coke removal efficiency is low and it becomes difficult to recover the catalytic performance. If the oxygen content of the gas exceeds 25% by mass or the temperature exceeds 600°C, the zeolite contained in the catalyst itself deteriorates, making it difficult to recover the catalytic performance.

[0034] The oxygen-containing gas has an oxygen content of 1 to 25% by mass, and can be prepared by mixing air or oxygen with an inert gas such as nitrogen, argon, or neon. However, gas prepared with water vapor is not preferred because it reduces the specific surface area of ​​the zeolite and the acid sites, adversely affecting the catalytic activity and catalyst life. Dry gas with no water vapor adjustment, or with only a trace amount of water vapor or no water vapor at all is preferred.

[0035] The amount of gas supplied during regeneration and the regeneration time are not particularly limited as long as the catalyst can be regenerated. In particular, since this allows for efficient removal of coke deposited on the aromatic production catalyst, it is preferable to supply gas under conditions where the gas volume per hour / aromatic production catalyst volume is 200 to 700, and more preferably 300 to 600. From the viewpoint of aromatic compound productivity, the regeneration time is preferably 10 to 100 hours, more preferably 30 to 100 hours, and even more preferably 50 to 100 hours. A regeneration time of 10 hours or more can further enhance the catalytic activity. Furthermore, a regeneration time of 100 hours or less can prevent excessive reduction in the amount of coke during the regeneration step, thereby further reducing the amount of coke adhering to the catalyst in the subsequent aromatic compound production step.

[0036] When aromatic compounds are continuously produced by switching between an aromatic compound production process and a regeneration process between different reactors at predetermined intervals using an aromatic compound production apparatus having two or more reactors, it is preferable to switch between each process (time for the aromatic compound production process, time for the regeneration process) every 10 to 100 hours. In this case, aromatic compounds can be produced with high catalytic activity, and the amount of coke after the regeneration process can be kept within an appropriate range, which contributes to extending the catalyst's life. [Example]

[0037] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0038] The test conditions and evaluation methods used in the examples are shown below.

[0039] ~Aromatic compound manufacturing equipment~ A fixed-bed gas-phase flow reactor using a stainless steel reaction tube (inner diameter 16 mm, length 600 mm) was used. The reaction tube was filled with the catalyst described below, and a heat pretreatment was performed under a dry air flow. A raw material supply pipe and an oxygen-containing gas supply pipe were connected to the reactor, respectively, so that the raw material and oxygen-containing gas could be supplied alternately. The reaction tube was insulated with heat insulating material.

[0040] ~Analysis of reaction products~ In the aromatic compound production process, the reaction outlet gas and reaction liquid were collected and analyzed individually using a gas chromatograph. The gas components were analyzed using a gas chromatograph (Shimadzu Corporation, product name GC-14B) equipped with a TCD detector. The packing material used was either PorapakQ (product name) manufactured by Waters or MS-5A (product name) manufactured by GL Sciences. The liquid components were analyzed using a gas chromatograph (Shimadzu Corporation, product name GC-2025) equipped with an FID detector. The separation column used was a capillary column (GL Sciences, product name TC-1).

[0041] ~Analysis of regeneration gas during regeneration process~ During the regeneration process, component analysis at the reactor outlet was constantly performed using a zirconia oxygen analyzer (Yokogawa Electric, product name: ZS8) and a laser gas analyzer (Yokogawa Electric, product name: TDLS8000). A portion of the exhaust gas at the reactor outlet was circulated to the reactor inlet, and the flow rate and oxygen concentration of the oxygen-containing gas were controlled by adjusting the mixture ratio of air, circulating gas, and nitrogen gas.

[0042] ~How to calculate conversion rate~ The amount of aliphatic hydrocarbon compounds consumed in the aromatic compound production process described in Preparation Example 2 below (the mass of the aliphatic hydrocarbon compounds supplied minus the mass of the aliphatic hydrocarbon compounds obtained from the reactor outlet) and the amount of heavy aromatic hydrocarbon compounds consumed (the mass of the heavy aromatic hydrocarbon compounds supplied minus the mass of the heavy aromatic hydrocarbon compounds obtained from the reactor outlet) were calculated as the sum of these two amounts, and the amount of the total feedstock consumed in the aromatic compound production process was calculated. This amount was then divided by the mass of the total feedstock, and the resulting value, expressed as a percentage, was evaluated as the conversion rate.

[0043] Preparation Example 1 (Catalyst Preparation) 100 parts by mass of 10-membered ring pore zeolite (manufactured by Tosoh Corporation, product name HSZ-840HOA; Si / Al2 ratio = 40, MFI type) were mixed with 43 parts by mass of silica (manufactured by Nissan Chemical Industries, Ltd., product name Snowtex N-30G), 4 parts by mass of cellulose, and 30 parts by mass of pure water, and the mixture was then formed into cylindrical molded bodies with a diameter of 1.5 mm and lengths of 1.0 to 7.0 mm (average length 3.5 mm). These were then dried overnight at 100°C to prepare a catalyst.

[0044] Preparation Example 2 (Production of aromatic compounds) The catalyst obtained in Preparation Example 1 was packed into the middle section of a stainless steel reaction tube of a fixed-bed gas-phase flow reactor, and the temperature was raised to 525°C while flowing air at 50 ml / min, and the flow gas was switched to nitrogen at 50 ml / min. A ceramic tubular furnace was used for heating, and the temperature of the catalyst layer was controlled.

[0045] Aromatic compounds were produced under the following conditions using a mixture of aliphatic hydrocarbon compounds (a mixed solution of 40% by mass of methylcyclopentane, 24% by mass of hexane, 10% by mass of cyclohexane, 8% by mass of pentane, 6% by mass of methylcyclohexane, 4% by mass of heptane, 2% by mass of ethylcyclohexane, 2% by mass of octane, and 1% by mass of nonane) and heavy aromatic hydrocarbon compounds (a mixture of 30% by mass of styrene, 20% by mass of allylbenzene, 20% by mass of ethylbenzene, 20% by mass of triisopropylbenzene, and 10% by mass of indane) in a mass ratio of 4:1 as feedstock. The amount of coke adhering to the catalyst during aromatic compound production increased to 13.5% by mass 24 hours after the start of aromatic compound production, 17.5% by mass after 48 hours, and 24.5% by mass after 96 hours. The increase in coke amount tended to slow over time. In other words, as the amount of coke increased, coke tended to adhere less easily to the catalyst. Furthermore, the conversion rate was 92.0% by mass 24 hours after the start of aromatic compound production, 91.9% by mass 48 hours later, and 91.6% by mass 96 hours later, confirming that a high conversion rate was maintained.

[0046] (Production conditions for aromatic compounds) Reaction temperature: 525°C. Catalyst weight: 3.75g. Weight space velocity: 1.56h -1 . Reaction pressure: 0.1 MPa. Reaction time: 96 hours.

[0047] Example 1 The coked aromatic production catalyst obtained in Preparation Example 2 was regenerated under the conditions described below, and aromatic compounds were again produced under the conditions shown in Preparation Example 2.

[0048] (Regeneration conditions for aromatic compound production catalysts) Playback temperature: 400℃~450℃. Regeneration gas oxygen concentration: 1 to 5 mass%. Ratio of regeneration gas volume to catalyst volume: 500 / hour. Pressure: 0.1MPa. Playback time: 45 hours.

[0049] Example 2 The coked catalyst for aromatic compound production obtained in Preparation Example 2 was regenerated under the same conditions as in Example 1, except that the regeneration time was 32.5 hours. Thereafter, aromatic compounds were produced again under the conditions shown in Preparation Example 2.

[0050] Example 3 The coked catalyst for aromatic compound production obtained in Preparation Example 2 was regenerated under the same conditions as in Example 1, except that the regeneration time was 38 hours. Thereafter, aromatic compounds were produced again under the conditions shown in Preparation Example 2.

[0051] Comparative Example 1 Aromatic compounds were produced under the conditions shown in Preparation Example 2 using the coke-free aromatic compound production catalyst obtained in Preparation Example 1 (assuming the catalyst was completely free of coke).

[0052] For Examples 1 to 3, the amount of coke adhering to the catalyst after the initial aromatic compound production under the conditions of Preparation Example 2, the amount of coke adhering to the catalyst after regeneration, and the amount of coke adhering to the catalyst after a second aromatic compound production under the conditions of Preparation Example 2 were measured at each stage. These values ​​are shown in Table 1 as the amount of coke before regeneration, the amount of coke after regeneration, and the amount of coke after aromatic compound production. Note that for Comparative Example 1, only the amount of coke adhering to the catalyst after aromatic compound production was measured. Table 1 also shows the difference between the amount of coke before regeneration and the amount of coke after regeneration as the "amount of coke removed in the regeneration step," the difference between the amount of coke after aromatic compound production and the amount of coke after regeneration as the "amount of coke produced," and the ratio (percentage) of the amount of coke after regeneration to the amount of coke before regeneration as the "coke reduction rate before and after the regeneration step." The conversion rate during the second aromatic compound production is also shown.

[0053] [Table 1]

[0054] Compared to Comparative Example 1, which uses a catalyst with no coke (which has been regenerated so that any coke adhering thereto is completely removed, i.e., a catalyst with a coke reduction rate of 0% before and after the regeneration process), Examples 1 to 3, which use catalysts with a coke reduction rate of 5 to 50% before and after the regeneration process so that some coke remains, were confirmed to have a reduced amount of coke produced. Furthermore, the average conversion rates of Examples 1 to 3 all exceeded 80%, and the conversion rates were also good. [Industrial Applicability]

[0055] The present invention can reduce the amount of coke that adheres to the catalyst during the aromatic compound production process when aromatic compounds are produced by alternately repeating a process of producing aromatic compounds by contacting a raw material with a catalyst and a process of regenerating the catalyst, thereby contributing to extending the catalyst's lifespan and reducing the maintenance burden on the equipment. [Explanation of symbols]

[0056] 10, 20... reactor, 30, 40... supply pipe, 100... aromatic compound production apparatus

Claims

1. an aromatic compound production step in which a raw material containing a hydrocarbon compound is brought into contact with a catalyst containing a zeolite to produce an aromatic compound; a regeneration step of contacting the catalyst to which coke has adhered in the aromatic compound production step with an oxygen-containing gas at 300°C or higher to remove the coke and regenerate the catalyst, the aromatic compound production step and the regeneration step are alternately repeated, A method for producing an aromatic compound, wherein the amount of coke adhering to the catalyst regenerated in the regeneration step is 5 to 50% of the amount of coke adhering to the catalyst before the regeneration step.

2. 2. The method for producing an aromatic compound according to claim 1, wherein the amount of coke adhering to the catalyst before the regeneration step is 10 to 40 mass %.

3. An aromatic compound production apparatus having two or more reactors filled with the catalyst is used, The aromatic compound production step is carried out in at least one of the reactors, and during the aromatic compound production step, the regeneration step is carried out in the other reactors; 3. The method for producing an aromatic compound according to claim 1, wherein the aromatic compound production step and the regeneration step are alternately switched between different reactors at predetermined time intervals.

4. The method for producing an aromatic compound according to claim 3, wherein the conversion between the aromatic compound production step and the regeneration step is carried out every 10 to 100 hours.

5. 3. The method for producing an aromatic compound according to claim 1, wherein in the aromatic compound production step, the catalyst and the raw material are contacted at a reaction temperature of 400 to 800°C and a pressure of 0.05 to 5 MPa.

6. 3. The method for producing an aromatic compound according to claim 1, wherein the raw material is one or more hydrocarbon compounds selected from the group consisting of heavy aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds having 2 to 6 carbon atoms, and alicyclic hydrocarbon compounds.

7. 3. The method for producing an aromatic compound according to claim 1, wherein the regeneration step brings the oxygen-containing gas, which has an oxygen content of 1 to 25 mass % and is at 400 to 450° C., into contact with the catalyst.

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