JP7600573B2 - METHOD FOR REGENERATING CATALYST AND METHOD FOR PRODUCING AROMATIC COMPOUND USING THE SAME - Google Patents

Description

The present invention relates to a method for efficiently regenerating a catalyst used in the production of aromatic compounds when aromatic compounds are produced, and also to a method for producing aromatic compounds from a hydrocarbon feedstock of aliphatic hydrocarbons and/or alicyclic hydrocarbons. In particular, the present invention relates to a method for producing aromatic compounds with excellent stability, which reduces the load on the catalyst by stably repeating the reaction and regeneration of the catalyst by adding a regeneration step.

Aromatic compounds such as benzene, toluene, and xylene are often obtained by decomposing feedstock oil (such as naphtha) obtained from petroleum refining in a thermal cracking reactor, and then isolating and refining the resulting thermal cracking products by distillation or extraction. In these methods of 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 produced simultaneously 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.

It has been proposed to produce aromatic compounds by contacting an aliphatic or alicyclic hydrocarbon feedstock with a catalyst that mainly contains medium pore size zeolite at a temperature of about 400°C to about 800°C (see, for example, Patent Documents 1-2 and Non-Patent Documents 1-4). Compared with the method of producing aromatic compounds by thermal decomposition, these production methods have the advantage that they have low added value and can produce aromatic compounds from surplus hydrocarbon feedstock.

Aromatic Compound Production A problem with the production of aromatic compounds using zeolite catalysts is the accumulation of carbonaceous matter on the zeolite catalyst during the aromatization reaction, which reduces its activity, known as coking. To recover from the reduced activity caused by this coking, a regeneration process is incorporated in which the carbonaceous matter is burned off, and the actual operation of the plant is continued by alternating between reaction and regeneration. Therefore, although the reduction in activity caused by coking results in an apparent reduction in activity, the activity can be reversibly restored by regeneration. However, repeated stress situations on the catalyst, such as excessive heat generation during the regeneration process, will irreversibly reduce the catalytic activity. Furthermore, because the regeneration process is an exothermic reaction, there is a possibility that the reactor will go into thermal runaway, damaging the reaction equipment.

Patent No. 3741455 Patent No. 3264447

Industrial & Engineering Chemistry Research, Vol. 31, p. 995 (1992) Industrial & Engineering Chemistry Research, Vol. 26, p. 647 (1987) Applied Catalysis Vol. 78, p. 15 (1991) Microporous and Mesoporous Materials, Vol. 47, p. 253 (2001)

The present invention provides a method for efficiently regenerating a catalyst for producing aromatic compounds when aromatic compounds are produced, and further provides a method for producing aromatic compounds with excellent stability, which reduces the load on the catalyst by stably repeating the reaction and regeneration of the catalyst when producing aromatic compounds from a hydrocarbon feedstock of aliphatic hydrocarbons and/or alicyclic hydrocarbons.

As a result of intensive research conducted by the inventors to solve the above problems, they discovered that when producing aromatic compounds from hydrocarbon compounds and burning off accumulated coke, controlling the oxygen concentration of the regeneration gas and recycling the exhaust gas enables safe and stable catalyst regeneration at low cost, resulting in a method for efficiently producing aromatic compounds stably over the long term, and thus completed the present invention.

That is, the present invention relates to a method for regenerating a catalyst for aromatic compound production, characterized in that when a catalyst for aromatic compound production having zeolite as an active ingredient, the performance of which has been reduced by coke adhesion, is contacted with a regeneration gas containing 2 to 5% by weight of oxygen to regenerate the catalyst for aromatic compound production, the contact temperature is controlled between 380 and 530°C so that the oxygen concentration of the exhaust gas after contact is 0.5 to 1.5% by weight, and a portion of the exhaust gas is mixed with air so that the oxygen concentration is 2 to 5% by weight, and circulated and supplied as the regeneration gas.

The present invention is described in detail below.

The method for regenerating a catalyst for aromatic compound production of the present invention involves contacting a catalyst for aromatic compound production having zeolite as an active ingredient, the performance of which has been reduced by coke deposition, with a regeneration gas containing 2 to 5% oxygen by weight to regenerate the catalyst for aromatic compound production, controlling the contact temperature between 380 and 530°C so that the oxygen concentration of the exhaust gas after contact is 0.5 to 1.5% by weight, and mixing a portion of the exhaust gas with air while controlling the oxygen concentration to 2 to 5% by weight, and circulating and supplying it again as regeneration gas. This regeneration method makes it possible to regenerate a catalyst for aromatic compound production stably, safely, and efficiently. The proportion of exhaust gas to be mixed with air as regeneration gas can be any proportion as long as it is possible to obtain a regeneration gas containing 2 to 5% by weight of oxygen, and it is particularly preferable to mix 75 to 98% by weight of the exhaust gas discharged as exhaust gas.

(Catalyst for producing aromatic compounds)
The catalyst for producing aromatic compounds in the present invention contains zeolite as an active component. The zeolite is not particularly limited as long as it is within the category of zeolite. Preferably, the zeolite has a 10-membered ring framework structure, and specifically includes AEL, EUO, FER, MWW, HEU, MEL, MFI, NES, MRE, etc. In order to obtain a zeolite having excellent reaction selectivity and productivity for aromatic compounds, it is preferable to use an MFI type zeolite, and more preferably an MFI type zeolite that satisfies the following characteristics (i) to (iv). In this case, the MFI type refers to an aluminosilicate compound that belongs to the structure code MFI defined by the International Zeolite Association.

(i) The mesopore distribution curve has a peak, the half width (hw) of the peak is hw≦20 nm, the maximum value (μ) of the peak is 10 nm≦μ≦20 nm, and the mesopore volume (pv) of the mesopores corresponding to the peak is 0.05 ml/g≦pv.
(ii) In powder X-ray diffraction measurement at a diffraction angle of 2θ, there is no peak in the range of 0.1 to 3 degrees.
(iii) the average particle diameter (PD) is PD≦100 nm;
(iv) The differential pore volume value (dV _P /d(d _P ))-micropore distribution curve in the pore diameter range of 0.3 nm to 0.8 nm has a maximum value, and the pore diameter showing the largest differential pore volume value (dV _P /d(d _P )) is in the range of 0.4 to 0.5 nm.

Here, micropores are defined by IUPAC as pores with a pore diameter of 2 nm or less. Mesopores are defined by IUPAC as pores with a pore diameter of 2 to 50 nm. Micropores and mesopores can be measured by a general nitrogen adsorption method at liquid nitrogen temperature. By analyzing the measurement results obtained by the nitrogen adsorption method, the pore volume values of micropores and mesopores and the pore distribution curves can be obtained. For example, the following method can be used for this analysis.

For micropores, the adsorption process is analyzed by the Saito-Foley method (AIChE Journal, 1991, Vol. 37, pp. 429-436). For example, the total pore volume of the micropores can be obtained by integrating the amount of nitrogen gas desorbed in the range corresponding to a pore diameter of 2 nm or less. In addition, first, a cumulative curve is obtained in which the vertical axis represents the amount of nitrogen desorbed per unit mass V _P (mL/g) and the horizontal axis represents the micropore diameter d _P (nm), and then a differential pore volume value (dV _P /d(d _P ))-micropore distribution curve in which the vertical axis represents the differential value (dV _P /d(d _P )) of the amount of nitrogen gas desorbed from the micropore at the micropore diameter value can be obtained, thereby obtaining a peak of the increase in the amount of nitrogen desorbed per unit mass at the micropore diameter.

For mesopores, the desorption process is analyzed using the Barret-Joyner-Halenda method (Journal of the American Chemical Society, 1951, pp. 373-380). For example, the total pore volume of mesopores can be obtained by integrating the amount of nitrogen gas desorbed in the range corresponding to pore diameters of 2 nm to 50 nm.

In addition, by first obtaining a cumulative curve with the nitrogen desorption amount per unit mass _V (mL/g) on the vertical axis and the mesopore diameter _D (nm) on the horizontal axis, and then changing the vertical axis to the differential value (d( _V )/d( _D )) of the nitrogen gas desorption amount from the mesopores with respect to the mesopore diameter value, it is possible to obtain the peak of the increase in the nitrogen desorption amount per unit mass at the mesopore diameter.

Then, PD can be calculated from the outer surface area using the following formula (1), for example.
PD=6/S (1/2.29×10 ⁶ +0.18×10 ⁻⁶ ) (1)
(Here, S indicates the external surface area (m ² /g).)
The external surface area (S (m ² /g)) in formula (1) can be determined by a t-plot method using a general nitrogen adsorption method at liquid nitrogen temperature. For example, when t is the thickness of the adsorption amount, measurement points in the range of 0.6 to 1 nm for t are linearly approximated, and the external surface area is determined from the slope of the obtained regression line.

Another method for measuring the particle size of zeolite is to randomly select 10 or more particles from a scanning electron microscope (SEM) or transmission electron microscope (TEM) photograph and determine their surface area average diameter.

The MFI zeolite can be produced, for example, by dealuminating the aluminum in the framework of MFI zeolite, which is a raw material that satisfies the above characteristics (i) to (iii), with steam or the like. The temperature of the steam treatment is preferably, for example, 400 to 900°C, particularly 450 to 800°C, and more preferably 500 to 700°C. The partial pressure of the steam is preferably 0.001 to 5 MPa, particularly 0.01 to 0.5 MPa, and more preferably 0.05 to 0.2 MPa. The concentration of the steam is preferably, for example, 0.01 to 100 vol% water vapor/dilution gas. The dilution gas may be an inert gas such as nitrogen, air, oxygen, carbon monoxide, carbon dioxide, or a mixture thereof. The steam treatment time can be selected arbitrarily. Furthermore, in order to enhance the effect of the steam treatment, it is preferable to perform ion exchange before and after the calcination treatment including the steam treatment.

The following method can be mentioned as an example of a method for producing MFI zeolite, a raw material that satisfies the above characteristics (i) to (iii).

Amorphous aluminosilicate gel is added to an aqueous solution of tetrapropylammonium (hereinafter sometimes referred to as "TPA") hydroxide and sodium hydroxide to form a suspension, MFI type zeolite is added to the resulting suspension as seed crystals to form a raw material composition, and the resulting raw material composition is crystallized and fired to obtain MFI type zeolite.

The form of the catalyst for producing aromatic compounds in the present invention is not limited, and it can be used in any form, such as using the zeolite powder as it is as a catalyst, compressing and molding it into a specific shape, or mixing it with a binder or the like and molding it into a specific shape.

(Regeneration of catalysts for aromatic compound production)
The method for regenerating a catalyst for aromatic compound production of the present invention regenerates a catalyst for aromatic compound production whose performance has deteriorated due to the adhesion of coke, for example, during the production of aromatic compounds from hydrocarbons, and when the catalyst for aromatic compound production to which coke has adhered is contacted with a regeneration gas containing 2 to 5% by weight of oxygen to regenerate the catalyst for aromatic compound production, the contact temperature is controlled between 380 and 530°C so that the oxygen concentration of the exhaust gas after the contact is 0.5 to 1.5% by weight, and a part of the exhaust gas is mixed with air while controlling the oxygen concentration to 2 to 5% by weight, and circulated and supplied as the regeneration gas. In this case, the exhaust gas is mixed with air in the weight percentage calculated by formula (2), thereby making it possible to control the oxygen concentration to 2 to 5% by weight.
(21 - regeneration gas oxygen concentration) / (21 - exhaust gas oxygen concentration) x 100 (2)
Here, the regeneration gas used in regenerating the catalyst for producing aromatic compounds has an oxygen content of 2 to 5% by weight, and may be prepared by mixing air or oxygen with an inert gas such as nitrogen, argon, or neon. In this case, it is preferable to use a dry gas in order to suppress the reduction in the specific surface area of the zeolite and the reduction in acid sites caused by the mixed water vapor and to eliminate the influence on the catalytic activity and catalyst life. The regeneration gas is further mixed with a part of the exhaust gas having an oxygen concentration of 0.5 to 1.5% by weight, and in this case, it is preferable to mix 75 to 98% by weight of the exhaust gas and prepare the gas. In addition, an inert gas may be mixed when the gas is circulated and supplied.

In the regeneration of the aromatic compound production catalyst of the present invention, the contact temperature is controlled between 380 and 530°C so that the oxygen concentration of the exhaust gas after contact with the regeneration gas is 0.5 to 1.5% by weight. The contact temperature can be appropriately selected between 380 and 530°C as long as the oxygen concentration of the exhaust gas is within the range of 0.5 to 1.5% by weight. Here, if the oxygen content of the regeneration gas is less than 2% by weight, or if the oxygen content of the exhaust gas is greater than 1.5% by weight, the efficiency of coke removal is poor, making it difficult to restore the catalytic performance. In addition, if the oxygen content of the regeneration gas exceeds 5% by weight, or if the oxygen content of the exhaust gas is less than 0.5% by weight, excessive coke combustion may cause deterioration of the zeolite contained in the catalyst itself or damage to the reactor.

There are no particular limitations on the amount of regeneration gas supplied and the contact time when regenerating a catalyst for aromatic compound production, so long as the catalyst can be regenerated. In particular, it is preferable to supply the regeneration gas at a volume ratio of 1:100 to 2000 to the catalyst volume, since this makes it possible to efficiently remove coke that has accumulated on the catalyst for aromatic compound production. In addition, the contact time is preferably 30 to 65 hours.

(Production of aromatic compounds)
The method for regenerating a catalyst for aromatic compound production of the present invention can be directly applied to the regeneration of a catalyst whose performance has been deteriorated due to coke adhesion.Furthermore, as a more preferred embodiment, it can be applied to a production method in which the production of aromatic compounds using a catalyst for aromatic compound production and the regeneration of the catalyst are repeated, and specifically, it can be applied to a production method of aromatic compounds, which includes a step of contacting a catalyst for aromatic compound production having zeolite as an active component with aliphatic hydrocarbons and/or alicyclic hydrocarbons having 2 to 6 carbon atoms at a temperature range of 400° C. to 800° C. to produce aromatic compounds, and the above-mentioned method for regenerating a catalyst for aromatic compound production as a step.

The aliphatic and/or alicyclic hydrocarbons having 2 to 6 carbon atoms may be any that fall within the category, such as 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. In addition, examples of the aliphatic and/or alicyclic hydrocarbons having 2 to 6 carbon atoms include C4 fraction, which is a distillation mixture of hydrocarbons having 4 carbon atoms obtained by cracking fractions of petroleum, such as naphtha, C5 fraction, which is a distillation mixture of hydrocarbons having 5 carbon atoms, and C6 fraction, which is a distillation mixture of hydrocarbons having 6 carbon atoms.

The temperature range for producing aromatic compounds by contacting with the aromatic compound production catalyst can be 400°C or higher and 800°C or lower, and is preferably 450°C or higher and 650°C or lower, as this provides particularly excellent production efficiency. The amount of raw material supplied to the aromatic compound production catalyst is preferably a gas volume ratio of 1:50 to 2000, particularly 1:100 to 1000, in order to achieve both production efficiency and aromatic yield. There is no restriction on the pressure during production, and it is preferable to produce the product at a pressure range of, for example, about 0.05 MPa to 5 MPa. When supplying the raw material, the hydrocarbon single gas, mixed gas, or a single or mixed gas diluted with an inert gas such as nitrogen, hydrogen, carbon monoxide, or carbon dioxide can be used.

There are no limitations on the reaction format used in the production, and for example, not only fixed bed, transport bed, fluidized bed, moving bed, and multi-tubular reactors, but also continuous flow, intermittent flow, and swing reactors can be used. Moreover, a reaction format using a swing reactor is preferable, as this is a particularly efficient method for producing aromatic compounds.

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

The present invention provides a method for efficiently regenerating a catalyst used in the production of aromatic compounds when aromatic compounds are produced, and also provides a method for producing aromatic compounds that can stably obtain a high aromatic yield over a long period of time by using the regeneration process as a step when producing aromatic compounds from aliphatic and/or alicyclic hydrocarbon raw materials, and is therefore highly productive, stable, and industrially useful.

The present invention will be explained in detail below with reference to examples.

The MFI zeolite and aromatic compound production catalysts used in the examples were measured and defined by the following methods.

- Measurement of pore distribution, pore diameter, and external surface area -
The pore distribution and pore diameter of the zeolite were measured by nitrogen adsorption measurements.

A general nitrogen adsorption apparatus (product name: BELSOAP-max, manufactured by BEL Japan) was used for the nitrogen adsorption measurement, and the adsorption side was measured at relative pressure (P/P ₀ ) intervals of 0.025. The desorption side was measured at relative pressure intervals of 0.05. The external surface area was determined by linear approximation of the thickness of the adsorption layer (t = 0.6 to 1.0 nm) using the t-plot method. BELMaster (ver. 2.3.1) manufactured by BEL Japan was used for the analysis of the pore distribution curve.

The adsorption process of the nitrogen adsorption measurement was analyzed using the Saito-Foley method (AIChE Journal, 1991, Vol. 37, pp. 429-436), and a micropore distribution curve was obtained in which the horizontal axis represents the constant of the micropore microdiameter and the vertical axis represents the differential value of the desorption amount of nitrogen gas.

The desorption process of the nitrogen adsorption measurement was analyzed using the Barret-Joyner-Halenda method (Journal of the American Chemical Society, 1951, pp. 373-380), and a mesopore distribution curve was obtained in which the horizontal axis represents the pore diameter constant and the vertical axis represents the differential value of the amount of desorbed nitrogen gas. The total pore volume of the mesopores was calculated by integrating the amount of desorbed nitrogen gas in the range of 2 nm to 50 nm.

The maximum peak of the differential value (d(V/m)/d(D)) of the amount of nitrogen gas desorbed from the mesopores with respect to the mesopore diameter value was analyzed using the intensity approximation of a Gaussian function, and mesopores with diameters within a range of twice the standard deviation (2σ) (=μ±2σ) from the center value (μ) of the Gaussian function were defined as uniform mesopores. The pore volume of uniform mesopores was calculated by integrating the amount of nitrogen gas desorbed within a range of ±2σ based on the center value (μ).

～Measurement of average particle size～
The average particle diameter was calculated from the external surface area using the above formula (1). In formula (1), S is the external surface area (m ² /g) and PD is the average particle diameter (m). The external surface area (S (m ² /g)) in formula (1) was determined by the t-plot method using a nitrogen adsorption method at liquid nitrogen temperature.

~Measurement of _SiO2 / _{Al2O3 molar} ratio~
The SiO ₂ /Al ₂ O ₃ molar ratio of the zeolite was determined by dissolving MFI zeolite in a mixed aqueous solution of hydrofluoric acid and nitric acid, and measuring the resultant by inductively coupled plasma atomic emission spectrometry (ICP-AES) using a general ICP apparatus ((trade name) OPTIMA 3300DV, manufactured by PerkinElmer).

～Measurement of aggregate size～
The volume average diameter (D ₅₀ ) of the aggregate particle diameter was measured by a dynamic scattering method. A Microtrac HRA (Model 9320-x100) (manufactured by Nikkiso Co., Ltd.) (trade name) was used for the measurement. In the measurement, the particle refractive index was 1.66, the particles were set to transparent non-spherical particles, and the liquid refractive index of the solvent was 1.33.

~ Powder X-ray diffraction measurement ~
Measurements were performed in air using an X-ray diffraction measurement device (Spectris Corporation, product name: X'pert PRO MPD) with a tube voltage of 45 kV and a tube current of 40 mA using CuKα1. The range of 0.04 to 5 degrees was analyzed at 0.08 degrees/step and 200 seconds/step. In addition, background correction based on the absorption rate of the direct beam was removed.

The presence or absence of a peak can be confirmed visually, or a peak search program can be used. A common peak search program can be used. For example, the measurement results, with the horizontal axis being 2θ (degrees) and the vertical axis being intensity (a.u.), were smoothed using the SAVITSKY & GOLAY formula and a sliding polynomial filter, and then the second derivative was performed. If there were three or more consecutive negative values, it was determined that a peak was present.

~Aromatic compound manufacturing equipment~
A fixed-bed gas-phase flow-type reactor using a stainless steel reaction tube (inner diameter 38 mm, length 4000 mm) was used. The reaction tube was filled with a catalyst for aromatic compound production, and a heat pretreatment was performed under a dry air flow. After that, the raw material gas was fed and the reaction for producing aromatic compounds was carried out. The reaction tube was insulated with a heat-insulating material, and the temperature was controlled by introducing gas heated in a heating furnace. The apparatus conditions and operating conditions of the reactor are not limited to those described in this embodiment, and can be appropriately selected. In the aromatic compound production process, the reaction outlet gas and the reaction liquid are sampled and analyzed by gas chromatography. The gas components were analyzed using a gas chromatograph equipped with a TCD detector (manufactured by Shimadzu Corporation, product name GC-14B). PorapakQ (trade name) manufactured by GL Sciences or MS-5A (trade name) manufactured by GL Sciences was used. The liquid components were analyzed using a gas chromatograph equipped with an FID detector (Shimadzu Corporation, product name: GC-2025). The separation column was a capillary column (GL Sciences, product name: TC-1). In the aromatic compound production catalyst regeneration process, the components at the reactor outlet were analyzed using a zirconia oxygen analyzer (manufactured by Yokogawa Electric Corporation, product name: ZS8 model) and a laser gas analyzer (Yokogawa A part of the exhaust gas from the reactor outlet was circulated to the reactor inlet, and the regeneration gas flow rate and oxygen concentration were controlled by the mixture ratio of air, circulating gas, and nitrogen gas. .

Preparation Example 1 (Preparation of Raw Zeolite)
MFI type zeolite was produced by the method described in JP 2013-227203 A.

Amorphous aluminosilicate gel was added to an aqueous solution of tetrapropylammonium (hereinafter sometimes abbreviated as TPA) hydroxide and sodium hydroxide and suspended. MFI type zeolite was added as seed crystals to the resulting suspension to prepare a raw material composition. The amount of seed crystals added was 0.7% _by weight based on the weight of _Al2O3 and _SiO2 in the raw material composition.

The composition of the raw material composition is as follows:
_SiO2 / _Al2O3 molar ratio=48, TPA/Si molar ratio=0.05, Na/Si molar ratio=0.16, OH _/ Si molar ratio=0.21, _H2O /Si molar ratio=10.

The obtained raw material composition was sealed in a stainless steel autoclave and crystallized for 4 days while stirring at 115°C to obtain a slurry-like mixed liquid. The crystallized slurry-like mixed liquid was subjected to solid-liquid separation using a centrifugal settler, and the solid particles were washed with a sufficient amount of pure water and dried at 110°C to obtain a dry powder. The obtained dry powder was dispersed in 1 mol/L hydrochloric acid, filtered, and dried. After calcination at 550°C for 1 hour in air, a calcination treatment including steam treatment at 600°C with 50% water vapor for 2 hours was performed. The obtained powder was dispersed in 1 mol/L hydrochloric acid, filtered, and washed to obtain MFI-type zeolite.

The obtained MFI zeolite had an average particle size of 38 nm, a SiO ₂ /Al ₂ O ₃ molar ratio of 55, and a total mesopore volume of 0.45 ml/g. The micropore distribution curve had a maximum value with the largest differential pore volume value at a pore diameter of 0.4125 nm. The half-width of the peak of the uniform mesopores in the mesopore distribution curve was 16 nm, and the center value was 15 nm. The pore volume of the uniform mesopores was 0.40 ml/g, and the ratio of the pore volume of the uniform mesopores to the total pore volume of the mesopores was 89%. In addition, the powder X-ray diffraction of the obtained MFI zeolite showed that there was no peak in the range of 0.1 to 3 degrees, indicating that the mesopores were irregularly connected.

Preparation Example 2 (Forming of raw zeolite)
43 parts by weight of silica (product name Snowtex N-30G, manufactured by Nissan Chemical Industries, Ltd.), 4 parts by weight of cellulose, and 30 parts by weight of pure water were added to 100 parts by weight of the MFI zeolite obtained in Preparation Example 1 and kneaded. The kneaded product was then formed into a cylindrical molded body having a diameter of 3.0 mm and a length of 2.0 to 5.5 mm (average length 4.5 mm). This was dried overnight at 100°C and then sintered at 600°C for 2 hours to prepare a catalyst for producing aromatic compounds.

Example 1
2.0 kg of the aromatic compound production catalyst obtained in Preparation Example 2 was loaded into the aromatic compound production apparatus described above, and a mixed gas of butenes (60% 1-butene + 15% trans-butene + 15% isobutene + 10% cis-butene) was used as the aliphatic hydrocarbon raw material to produce aromatic compounds under the following conditions. Thereafter, the catalyst for aromatic compound production on which coke had been deposited was contacted with a regeneration gas in which air was diluted with nitrogen so that the oxygen concentration was 3% by weight, while controlling the temperature of the regeneration gas between 450 and 520°C so that the oxygen concentration of the exhaust gas (oxygen concentration at the reactor outlet) was 0.7 to 1.3%, and 80 to 95% by weight of the exhaust gas was mixed with air and circulated as a regeneration gas to maintain an oxygen concentration of 3% by weight, thereby regenerating the catalyst for aromatic compound production. The regeneration conditions for the catalyst for aromatic compound production are shown below. Then, the production of aromatic compounds and the regeneration of the catalyst for aromatic compound production were repeated, and the evaluation of the production of aromatic compounds was performed 10 times. The aromatics production catalyst, which had been repeatedly subjected to aromatic compound production and catalyst regeneration, showed stable butenes conversion, benzene yield, toluene yield, and xylene yield, and was capable of stable operation without thermal runaway during regeneration. The results are shown in Table 1.

(Aromatic compound production conditions)
Reaction (catalysis) temperature: 570°C.
Feed gas: butenes mixed gas 3.0 kg/hour.
Ratio of the volume of the feed gas to the volume of the catalyst: 1:480.
Reaction time: 48 hours.

(Catalyst regeneration conditions for aromatic compound production)
Regeneration temperature: 450℃~520℃.
Regeneration gas oxygen concentration: 3% by weight.
Reactor outlet oxygen concentration: 0.7 to 1.3% by weight.
Ratio of regeneration gas volume to catalyst volume: 1:720.
Pressure: 0.1MPaG.
Play time: 35 hours.

Example 2
Except for the aromatic compound production conditions and aromatic compound production catalyst regeneration conditions being as follows, the aromatic compound production and aromatic compound production catalyst regeneration were repeated 10 times in the same manner as in Example 1, and evaluation was performed. The aromatic compound production catalyst that had been repeatedly subjected to aromatic compound production and catalyst regeneration showed stable butenes conversion, benzene yield, toluene yield, and xylene yield, and no thermal runaway occurred during regeneration, allowing stable operation. The results are shown in Table 2.

(Aromatic compound production conditions)
Reaction (catalysis) temperature: 585°C.
Feed gas: butenes mixed gas 4.0 kg/hour.
Ratio of the volume of the feed gas to the volume of the catalyst: 1:650.
Reaction time: 48 hours.

(Catalyst regeneration conditions for aromatic compound production)
Regeneration temperature: 430℃~520℃.
Regeneration gas oxygen concentration: 3% by weight.
Reactor outlet oxygen concentration: 0.7 to 1.3% by weight.
Ratio of regeneration gas volume to catalyst volume: 1:980.
Pressure: 0.15MPaG.
Playback time: 40 hours

Example 3
Except for the aromatic compound production conditions and aromatic compound production catalyst regeneration conditions being as follows, the aromatic compound production and aromatic compound production catalyst regeneration were repeated 10 times in the same manner as in Example 1, and evaluation was performed. The aromatic compound production catalyst that had been repeatedly subjected to reaction and regeneration showed stable butenes conversion, benzene yield, toluene yield, and xylene yield, and no thermal runaway occurred during regeneration, allowing stable operation. The results are shown in Table 3.

(Aromatic compound production conditions)
Reaction (catalysis) temperature: 600°C.
Feed gas: butenes mixed gas 2.0 kg/hour.
Ratio of the volume of the feed gas to the volume of the catalyst: 1:310.
Reaction time: 48 hours.

(Catalyst regeneration conditions for aromatic compound production)
Regeneration temperature: 470℃~520℃.
Regeneration gas oxygen concentration: 4.5% by weight.
Reactor outlet oxygen concentration: 0.8 to 1.5% by weight
Ratio of regeneration gas volume to catalyst volume: 1;470.
Pressure: 0.2MPaG.
Play time: 42 hours.

Comparative Example 1
The production of aromatic compounds and the regeneration of the catalyst for producing aromatic compounds were repeated 10 times in the same manner as in Example 1, except that the oxygen concentration of the regeneration gas was set to 7% by weight, and evaluation was performed.

The butenes conversion rate began to decrease from the fifth cycle, and from the sixth cycle the total benzene yield, toluene yield, and xylene yield began to decrease significantly. The evaluation results are shown in Table 4.

Comparative Example 2
The production of aromatic compounds and the regeneration of the catalyst for producing aromatic compounds were repeated 10 times in the same manner as in Example 1, except that the regeneration temperature was not controlled but was set at 550°C.

From the fourth cycle onwards, the butenes conversion rate and the total benzene yield, toluene yield and xylene yield began to clearly decline. The evaluation results are shown in Table 5.

Comparative Example 3
An attempt was made to repeatedly produce aromatic compounds and regenerate the catalyst for producing aromatic compounds in the same manner as in Example 2, except that the oxygen concentration in the regeneration gas was set to 1.5% by weight and the oxygen concentration at the reactor outlet was controlled to be 0.5 to 1.0% by weight. However, coke removal was insufficient, and it was not possible to continue evaluating the production of aromatic compounds.

Comparative Example 4
An attempt was made to repeatedly produce aromatic compounds and regenerate the catalyst for producing aromatic compounds in the same manner as in Example 3, except that the oxygen concentration in the regeneration gas was set to 10% by weight and the oxygen concentration at the reactor outlet was controlled to be 7.0 to 8.0% by weight. However, a problem occurred in which the temperature inside the reactor exceeded 650°C during regeneration, making stable regeneration impossible and making it impossible to evaluate the production of aromatic compounds.

The present invention provides a method for efficiently regenerating a catalyst for producing aromatic compounds when aromatic compounds are produced, and by using the regeneration method as a process for producing aromatic compounds from aliphatic and/or alicyclic hydrocarbon raw materials, the reaction and regeneration of the catalyst are repeated, making the method highly productive, stable, and safe and extremely useful industrially.

Claims (8)

A method for regenerating a catalyst for producing aromatic compounds, comprising contacting a catalyst for producing aromatic compounds having zeolite as an active ingredient, the performance of which has been reduced by the adhesion of coke, with a regeneration gas containing 2 to 5% by weight of oxygen to regenerate the catalyst, the method comprising controlling the contact temperature between 380 and 530°C so that the oxygen concentration of the exhaust gas after the contact is 0.5 to 1.5% by weight, and mixing 75 to 98% by weight of the exhaust gas with air so that the oxygen concentration is 2 to 5% by weight, and circulating and supplying the mixed gas as the regeneration gas. The method for regenerating a catalyst for producing aromatic compounds according to claim 1, characterized in that the zeolite is an MFI type zeolite. 3. The method for regenerating a catalyst for aromatic compound production according to claim 1, wherein the zeolite is an MFI type zeolite that satisfies the following characteristics (i) to (iv):
(i) The mesopore distribution curve has a peak, the half width (hw) of the peak is hw≦20 nm, the center value (μ) of the peak is 10 nm≦μ≦20 nm, and the mesopore volume (pv) of the mesopores corresponding to the peak is 0.05 ml/g≦pv.
(ii) In powder X-ray diffraction measurement at a diffraction angle of 2θ, there is no peak in the range of 0.1 to 3 degrees.
(iii) the average particle diameter (PD) is PD≦100 nm;
(iv) The differential pore volume value (dV _P /d(d _P ))-micropore distribution curve in the pore diameter range of 0.3 nm to 0.8 nm has a maximum value, and the pore diameter showing the largest differential pore volume value (dV _P /d(d _P )) is in the range of 0.4 to 0.5 nm. 4. The method for regenerating a catalyst for aromatic compound production according to claim 1, wherein the zeolite is one that has been subjected to a calcination treatment in which steam treatment is added during the calcination treatment in the production of the zeolite . A method for regenerating a catalyst for producing aromatic compounds according to any one of claims 1 to 4, characterized in that the regeneration gas is supplied to the catalyst for producing aromatic compounds at a volume ratio of 1:100 to 2000. A method for producing aromatic compounds, comprising the steps of: contacting an aromatic compound production catalyst having zeolite as an active ingredient with an aliphatic hydrocarbon and/or alicyclic hydrocarbon having 2 to 6 carbon atoms at a temperature range of 400°C to 800°C to produce aromatic compounds; and a method for regenerating the aromatic compound production catalyst according to any one of claims 1 to 5. The method for producing aromatic compounds according to claim 6, characterized in that aliphatic hydrocarbons and/or alicyclic hydrocarbons having 2 to 6 carbon atoms are supplied to the catalyst for producing aromatic compounds in a volume ratio of 1:50 to 2000. The method for producing an aromatic compound according to claim 6 or 7, characterized in that the aromatic compound contains at least one of the group consisting of benzene, toluene, and xylene.