WO2018038169A1

WO2018038169A1 - Catalyst composition for producing c6-8 monocyclic aromatic hydrocarbon and method for producing c6-8 monocyclic aromatic hydrocarbon

Info

Publication number: WO2018038169A1
Application number: PCT/JP2017/030162
Authority: WO
Inventors: 泰之岩佐; 小林　正英; 賢小倉; 和奥村
Original assignee: Ｊｘｔｇエネルギー株式会社; 国立大学法人東京大学; 学校法人工学院大学
Priority date: 2016-08-26
Filing date: 2017-08-23
Publication date: 2018-03-01
Also published as: JP2018030112A

Abstract

A catalyst composition used for producing a C_6-8 monocyclic aromatic hydrocarbon characterized in: comprising a gallium-containing crystalline aluminosilicate; and the ratio (I/II) of a peak intensity I due to Ga-O to a peak intensity II due to Ga-Ga in a radial distribution function determined from an extended X-ray absorption fine structure (EXAFS) spectrum of a Ga-K absorption edge of said composition being greater than 0.25.

Description

Catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms and method for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms

The present invention relates to a catalyst composition for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms and a method for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms.
This application claims priority based on Japanese Patent Application No. 2016-165551 filed in Japan on August 26, 2016, the contents of which are incorporated herein by reference.

Conventionally, catalytic reforming of straight run naphtha using a platinum / alumina catalyst has been widely used commercially as a method for obtaining gasoline and aromatic hydrocarbons having a high octane number. As the raw material naphtha in the catalytic reforming, a fraction having a boiling point of 70 to 180 ° C. is mainly used for the purpose of producing gasoline for automobiles. In the case of the production of aromatic fractions such as benzene, toluene and xylene, so-called BTX, a fraction of 60 to 150 ° C. is used.
However, as the carbon number of the raw material hydrocarbons decreases, the conversion ratio to aromatics decreases, and the octane number of the product also decreases. Therefore, light hydrocarbons mainly composed of hydrocarbons having 7 or less carbon atoms are used as raw materials. As described above, it has been difficult to produce high-octane gasoline and aromatic hydrocarbons in a high yield by the conventional catalytic reforming method. For this reason, the use of such light hydrocarbons has been limited to petrochemical raw materials and raw materials for city gas production.
For this reason, attempts have been made to produce aromatic hydrocarbons from light hydrocarbons. For example, Patent Documents 1 to 3 describe an aromatic hydrocarbon production method using a gallium-containing crystalline aluminosilicate catalyst composition and a hydrocarbon having 2 to 7 carbon atoms as a main raw material.

JP 2008-37803 A JP 2008-38032 A JP 2009-233601 A

It is preferable that a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms with high added value can be produced in a high yield. Since the monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms with high yield and high added value is produced, the catalyst composition for producing monocyclic aromatic hydrocarbons as described in Patent Documents 1 to 3 has not been improved. There was room.
The present invention has been made in view of the above circumstances, and is a catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms that can produce monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms with high yield. The issue is to provide goods. It is another object of the present invention to provide a method for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms using the catalyst composition for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms.

As a result of intensive studies to solve the above problems, the present inventors have obtained high yields of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms by using crystalline aluminosilicates containing specific gallium atoms as catalyst compositions. We found that it can be obtained at a rate.
A first aspect of the present invention is a catalyst composition used for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms, comprising a crystalline aluminosilicate containing gallium, and the catalyst composition In the radial distribution function obtained from the wide-area X-ray absorption fine structure (EXAFS) spectrum at the K absorption edge of gallium, the ratio of the peak intensity I due to Ga—O to the peak intensity II due to Ga—Ga A catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms, wherein (I / II) is greater than 0.25.
According to a second aspect of the present invention, there is provided a single carbon atom having 6 to 8 carbon atoms, which is brought into contact with the catalyst composition for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms according to the first aspect of the present invention. This is a method for producing a ring aromatic hydrocarbon.

According to the present invention, it is possible to provide a catalyst composition for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms that can produce a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms with a high yield. In addition, it is possible to provide a method for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms using the catalyst composition for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms.

It is a figure explaining the principle of an extended X-ray absorption fine structure (EXAFS). It is a figure which shows the radial distribution function calculated | required from the spectrum of EXAFS.

<Catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms>
The present invention is a catalyst composition used for the production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms such as benzene, toluene, xylene and the like (hereinafter referred to as “BTX”).
The catalyst composition of the present invention is a catalyst composition containing a crystalline aluminosilicate containing gallium, and is determined from a broad X-ray absorption fine structure (EXAFS) spectrum of the K absorption edge of gallium for the catalyst composition. In the radial distribution function, the ratio (I / II) of the peak intensity I attributed to Ga—O and the peak intensity II attributed to Ga—Ga is characterized by being larger than 0.25.

・ EXAFS
Here, “EXAFS” means Extended X-ray Absorption Fine Structure, “extended X-ray absorption fine structure”. When the X-ray energy is plotted on the horizontal axis and the X-ray absorption intensity is plotted on the vertical axis, a steep rise (characteristic absorption edge) appears at a specific energy, but EXAFS is the characteristic absorption edge. Is a vibration of fine X-ray absorption that appears in an energy range higher than 50 eV.
EXAFS reflects a structure in the range of several tens of kilometers as viewed from the absorbing atoms (see Non-Patent Document: PETROTECH Vol. 30 No. 10 (2007)).

When performing EXAFS measurement on the catalyst composition of the present invention, when the catalyst composition of the present invention consists only of crystalline aluminosilicate containing gallium, the catalyst composition itself may be measured. In addition, when the catalyst composition of the present invention contains other components other than the crystalline aluminosilicate containing gallium, EXAFS is measured for the crystalline aluminosilicate containing gallium before being mixed with the other components. It is preferable.

The principle of EXAFS will be described with reference to FIG.
FIG. 1 schematically shows a crystalline aluminosilicate or gallium oxide containing gallium. When this is irradiated with X-ray 1, if the energy of X-ray 1 exceeds the binding energy of electrons of gallium atom 3, X-ray absorption occurs, and the electrons are excited to become free electrons (photoelectrons). Since electrons have wave properties as well as particle properties, the emitted photoelectron electron wave (w1) is scattered by surrounding atoms, the scattered photoelectron waves (w2, w3, w4) and the original photoelectron wave (w1). ) Cause interference. When this interference reinforces each other, the X-ray absorption intensity is slightly high, but when this interference weakens each other, the X-ray absorption intensity is low.
The way in which interference occurs depends on the number and distance of surrounding atoms (gallium atoms 5,

oxygen atoms

2 and 4 existing around gallium atom 3 in FIG. 1). Surrounding information can be obtained. Specifically, the distance to the surrounding atoms (inter-atomic distance), the type of surrounding atoms, and the number of surrounding atoms (coordination number) are known. This is the principle of EXAFS.

In the example shown in FIG. 1,

oxygen atoms

2 and 4 and a gallium atom 5 exist around the gallium atom 3. For this reason, when the gallium atom 3 is irradiated with the X-ray 1, the electron wave (w1) of the emitted photoelectrons is scattered by the

oxygen atoms

2 and 4 and the gallium atom 5, and the scattered photoelectron waves (w2, w3, w4). ) And the original photoelectron wave (w1) cause interference. In a radial distribution function obtained by analyzing EXAFS generated by interference by Fourier transform, a peak corresponding to the interatomic distance between the gallium atom 3 and the

oxygen atoms

2 and 4, and an atom between the gallium atom 3 and the gallium atom 5 Peaks according to the distance can be measured.

FIG. 2 shows a radial distribution obtained from EXAFS at the K absorption edge of a gallium atom for a catalyst composition containing a crystalline aluminosilicate containing gallium (Example 4 described later) and gallium oxide (Ga ₂ O ₃ ). Indicates a function. The radial distribution function obtained from EXAFS at the K absorption edge of a gallium atom has a Ga—O peak at an interatomic distance of about 1.5 と and a Ga—Ga peak at an interatomic distance of about 2.8 Å.

The catalyst composition of the present invention has a peak intensity I due to Ga—O (interatomic distance of about 1.5 mm shown in FIG. 2) and a peak intensity II attributable to Ga—Ga (interatomic distance 2 shown in FIG. 2). The ratio (I / II) to the vicinity of .8 cm is greater than 0.25. A small peak intensity II due to Ga—Ga means that the proportion of galliums close to each other is small, and a large peak intensity II means that a large proportion of galliums are close to each other. As shown in FIG. 2, the gallium present in the crystalline aluminosilicate containing gallium is considered the former, and the compound such as gallium oxide represented by Ga ₂ O ₃ is considered the latter. That is, the catalyst composition of the present invention means that the proportion of gallium present in the crystalline aluminosilicate is relatively high.

The ratio (I / II) between the peak intensity I and the peak intensity II is preferably 0.26 or more, and more preferably 0.28 or more. Moreover, although an upper limit is not specifically limited, For example, 2.0 or less is preferable and 1.0 is more preferable.

The present inventors paid attention to the principle of EXAFS, and used a catalyst composition comprising a crystalline aluminosilicate in which the intensity of a peak due to Ga—Ga is relatively small, in other words, a small proportion of gallium present in the vicinity of gallium. It has been found that monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms can be produced with a high yield when used in the above.
The gallium-containing crystalline aluminosilicate catalyst composition described in Patent Document 3 focuses on aluminum atoms in the gallium-containing crystalline aluminosilicate catalyst composition by MASNMR analysis. The present application focuses on gallium atoms and is an invention based on a new idea different from Patent Document 3.

-Gallium-containing crystalline aluminosilicate The structure of the crystalline aluminosilicate containing gallium (hereinafter referred to as "gallium-containing crystalline aluminosilicate") contained in the catalyst composition of the present invention is not particularly limited, but is a pentasil-type zeolite. Zeolite having an MFI type and / or MEL type crystal structure is more preferable (a crystalline aluminosilicate having a three-dimensionally connected structure is called a zeolite). MFI-type and MEL-type zeolites belong to a known zeolite structure type of the kind published by “The Structure Commission of the International Zeolite Association” (Atlas of Zeolite Structure. 1978) Distributed by Polycrystalline Book Service, Pittsburgh, PA, USA). An example of an MFI type zeolite is ZSM-5, and an example of an MEL type zeolite is ZSM-11.

Examples of the gallium-containing crystalline aluminosilicate contained in the catalyst composition of the present invention include those in which gallium is present in the crystalline aluminosilicate, and those in which gallium is supported on the crystalline aluminosilicate (hereinafter referred to as “gallium-supporting crystalline aluminosilicate”). Silicate ") or a material containing both of them is used, but at least a crystalline aluminosilicate containing gallium is preferred. Further, it is more preferable that the crystalline aluminosilicate contains a gallium cation.

The gallium-containing crystalline aluminosilicate contained in the catalyst composition of the present invention is preferably produced by inserting gallium into the crystalline aluminosilicate by an ion exchange method. As an ion exchange method, a method in which a gallium source is used as a solution and a crystalline aluminosilicate is immersed (in many cases, an aqueous solution), or a crystalline aluminosilicate and a gallium source are physically mixed in a solid state. There is a method of performing ion exchange.
In this case, as the gallium source, gallium salts such as gallium nitrate and gallium chloride, gallium oxide and the like can be preferably used. In the case of a water-inhibiting substance such as gallium chloride or solid gallium oxide, a method of performing ion exchange by physically mixing crystalline aluminosilicate and a gallium source in a solid state is preferable. In addition, when ion exchange is performed, a method of heating in an atmosphere of a reducing gas, an inert gas, or a mixed gas containing them is preferable.

The particle diameter of the gallium-containing crystalline aluminosilicate contained in the catalyst composition of the present invention is preferably 0.05 to 20 μm, more preferably 0.1 to 10 μm, particularly preferably 0.5 to 5 μm, and 1 to 3 μm. Highly preferred.
Moreover, it is preferable that the content rate of the particle | grains which have said particle diameter is 80 mass% or more on the basis of the mass of all the particles.

When the size of the reaction molecule and the pore size of the crystalline aluminosilicate are almost the same, the diffusion rate of the molecule tends to be slow in the crystalline aluminosilicate pore. For this reason, when the particle diameter is 20 μm or less, the reactive molecule easily approaches the active site in the deep pores, and the active site is easily used effectively during the reaction.

When obtaining crystalline aluminosilicate by hydrothermal synthesis, factors affecting the size of the generated particles include the type of silica source, the amount of organic additives such as quaternary ammonium salts, and inorganic salts as mineralizers. And the amount of base, the amount of base in the gel, the pH of the gel, the heating rate during the crystallization operation, the temperature and the stirring rate, and the like. By appropriately adjusting these conditions, a crystalline aluminosilicate having the above-mentioned particle size range can be obtained.

The catalytic activity for the aromatization reaction of the gallium-containing crystalline aluminosilicate contained in the catalyst composition of the present invention is affected by the composition. In order to obtain a high reaction activity, it is preferable to contain 0.1 to 2.5% by mass of aluminum atoms based on the mass of the crystalline aluminosilicate, and 0.1 to 2.0% by mass. Is more preferable.
Further, on the same basis, the gallium atom is preferably contained in an amount of 0.1 to 5.0% by mass, more preferably 0.1 to 3.0% by mass.
The molar ratio of gallium to aluminum (atomic ratio, Ga / Al) is preferably from 0.1 to 2.0, more preferably from 0.2 to 1.9, and from 0.3 to 1 .8 or less is particularly preferable.

In the present invention, the content of gallium in the catalyst composition is preferably 0.02 parts by mass or more and 3.0 parts by mass or less.
The molar ratio of gallium to aluminum (atomic ratio, Ga / Al) is preferably from 0.1 to 2.0, more preferably from 0.2 to 1.9, and from 0.3 to 1 .8 or less is particularly preferable.

.. Activation treatment In addition, the gallium-containing crystalline aluminosilicate contained in the catalyst composition of the present invention is various activation treatments that are generally performed when crystalline aluminosilicate is used as a catalyst component, as desired. Can be applied. That is, the gallium-containing crystalline aluminosilicate contained in the catalyst composition of the present invention includes not only those produced by the method such as hydrothermal synthesis but also those obtained by modification or activation treatment thereof. It is.

For example, after a crystalline aluminosilicate is ion-exchanged in an aqueous solution containing ammonium salts such as ammonium chloride, ammonium fluoride, ammonium nitrate, and ammonium hydroxide to form an ammonium type, a metal ion other than alkali metal or alkaline earth metal is used. A desired metal other than an alkali metal or an alkaline earth metal can be introduced by ion exchange in an aqueous solution containing or impregnating the aqueous solution.
The ammonium-type gallium-containing crystalline aluminosilicate is heated in an atmosphere of air, nitrogen or hydrogen at a temperature of 200 to 800 ° C., preferably 350 to 700 ° C. for 3 to 24 hours to remove ammonia, thereby removing the acid type. The structure can be activated. The acid catalyst may be treated with hydrogen or a mixed gas of hydrogen and nitrogen under the above conditions. Furthermore, you may give the ammonia modification | denaturation which makes an acid type catalyst contact ammonia on dry conditions. In general, the catalyst composition of the present invention is preferably used after being subjected to the activation treatment before contacting with the hydrocarbon feedstock.

The active component of the catalyst composition of the present invention is the gallium-containing crystalline aluminosilicate, but for the purpose of facilitating molding or improving the mechanical strength of the catalyst, the catalyst composition is supported or molded. An auxiliary agent or the like may be included.
When the carrier or molding aid is included, the content of the gallium-containing crystalline aluminosilicate in the total mass of the catalyst composition is not particularly limited, but the gallium-containing crystalline aluminosilicate is based on the total mass of the catalyst composition. 40 to 95% by mass is preferable, 50 to 90% by mass is more preferable, and 60 to 80% by mass is further preferable.

Compositions containing gallium-containing crystalline aluminosilicate are various molded products such as granules, spheres, plates, pellets, etc. by methods such as extrusion, spray drying, tableting, rolling granulation, and granulation in oil. It can be. In molding, it is desirable to use an organic compound lubricant to improve moldability.

In general, the composition of a gallium-containing crystalline aluminosilicate can be formed prior to the ion-exchange step of the gallium-containing crystalline aluminosilicate with ammonium ions or the like, or after the gallium-containing crystalline aluminosilicate is ion-exchanged. It can also be done.

Additive The catalyst composition of the present invention may contain an additive in addition to the gallium-containing crystalline aluminosilicate described above. The additive is not particularly limited, and examples thereof include inorganic oxides such as alumina boria, silica, silica alumina, and aluminum phosphate, clay minerals such as kaolin and montmorillonite, inorganic phosphorus compounds, and organic phosphorus compounds. The addition amount is not particularly limited, but is added to the catalyst composition so as to be 50% by mass or less, more preferably 30% by mass or less, and further preferably 15% by mass or less.

Further, the catalyst composition of the present invention can be used with a metal component supported as an auxiliary component. The metal component as an auxiliary component may be supported on gallium-containing crystalline aluminosilicate, or may be supported on other additives, or both.
Examples of such auxiliary metal components include metals having dehydrogenation ability and metals having an effect of suppressing carbon deposition. Specific examples of the auxiliary metal component include those that improve catalytic activity, such as magnesium, calcium, strontium, barium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium. , Ytterbium, lutetium, titanium, vanadium, chromium, molybdenum, tungsten, manganese, rhenium, iron, ruthenium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, zinc, aluminum, indium, germanium, tin, lead , Phosphorus, antimony, bismuth, selenium and the like. These metals can be used alone or in combination of two or more, and the supported amount is 0.1 to 10% by mass in terms of metal. As the metal loading method, known techniques such as an ion exchange method, an impregnation method, and physical mixing can be used. Moreover, an auxiliary component metal can be contained by adding the metal component as an auxiliary component during the synthesis of the pentasil-type zeolite. In addition, as an auxiliary metal component having an effect of suppressing the deposition of coke during the reaction, magnesium, calcium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, One or more metals selected from ruthenium and iridium can be supported, and the supported amount is 0.01 to 5% by mass in terms of metal.

<Method for producing monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms>
In the method for producing an aromatic hydrocarbon of the present invention, the above-described catalyst composition of the present invention is brought into contact with a raw material oil containing a hydrocarbon having 2 to 7 carbon atoms to produce an aromatic hydrocarbon.
Here, the raw material used in the present invention contains a light hydrocarbon having 2 to 7 carbon atoms, and the content of the light hydrocarbon having 2 to 7 carbon atoms in the raw material is not particularly limited, but is preferably 20% by mass. Above, more preferably 40% by mass or more, particularly preferably 60 to 100% by mass.

The light hydrocarbon having 2 to 7 carbon atoms is not particularly limited, and may be linear, branched or cyclic, and may be paraffin or olefin. Furthermore, a mixture thereof may be used. Specific examples of such hydrocarbons include linear aliphatic saturated hydrocarbons having 2 to 7 carbon atoms (ethane, propane, normal butane, normal pentane, normal hexane, normal heptane), branched aliphatic saturated hydrocarbons. (Isobutane, 2-methylbutane, 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane, 2-methylhexane, 3-methylhexane, 2,2-dimethylpentane, 2, 3-dimethylpentane, 2,4-dimethylpentane, 2,2,3-trimethylbutane), cycloaliphatic saturated hydrocarbon (cyclopropane, cyclobutane, cyclopentane, 1-methylcyclopentane, 1,1-dimethylcyclopentane 1,2-dimethylcyclopentane, 1,3-dimethylcyclopentane, cyclohexa , Methylcyclohexane, etc.), linear aliphatic unsaturated hydrocarbons (ethylene, propylene, normal butene, normal pentene, normal hexene, normal heptene, etc.), branched aliphatic unsaturated hydrocarbons (isobutene, 2-methylbutene, 2- Liquefied petroleum mainly composed of methylpentene, 3-methylpentene, 2-methylhexene, 3-methylhexene, etc.), cycloaliphatic unsaturated hydrocarbons (cyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, etc.), propane and butane Gas, light fraction (light naphtha) with a boiling point of 100 ° C. or less in naphtha fraction mainly composed of paraffin having 5 to 7 carbon atoms, C4 fraction from fluid catalytic cracker (FCC), raffinate of ethylene cracker, etc. Is mentioned.

Next, although the process of the manufacturing method of the monocyclic aromatic hydrocarbon of this invention is not specifically limited, It is preferable to mainly have the following 5 processes.
(A) Conversion reaction step (b) Gas-liquid separation step of reaction bed effluent (c) Hydrogen separation step from separation gas (d) Aromatic hydrocarbon separation step from separation liquid (e) Raw material light hydrocarbon And mixing process of recycled gas

(Conversion reaction process)
In this step, at least n reaction layers holding the above-described catalyst composition are arranged in series, and a heating furnace or the like is provided between the reaction layers as means for heating the effluent from the reaction layer. In this step, a mixture of a light hydrocarbon as a raw material and a recycle gas, which will be described later, is passed through a reaction layer to convert the mixture into an aromatic hydrocarbon. Preferred reaction conditions in this step are a reaction layer inlet temperature of 350 to 650 ° C., a hydrogen partial pressure of 0.5 MPa or less, and a raw material gas space velocity of 100 to 2000 hr ⁻¹ .

The reaction layer inlet temperature in the conversion reaction step according to the present invention is generally in the preferred range of 350 to 650 ° C., but 450 to 650 ° C. when the light hydrocarbon as the main component is normal paraffin. When isoparaffin is the main component, 400 to 600 ° C. and when olefin is the main component, 350 to 550 ° C. are more preferable temperature ranges.

The reactor used in the conversion reaction step is not particularly limited, and examples thereof include a fixed bed reactor, a CCR reactor, and a fluidized bed reactor. When using a fixed bed or a CCR type reactor, at least n reaction layers holding the catalyst composition described above (n is an integer of 2 or more) are arranged in series, and further between the reaction layers or in the reaction layer, A heating device such as a heating furnace is preferably provided as means for heating the effluent from the previous reaction layer. Of the n reaction layers arranged in series, the catalyst amount in the first-stage reaction layer is 30% by volume or less, preferably 1-30% by volume, more preferably 2-30% by volume of the total catalyst amount. %, More preferably 2 to 28% by volume. When the number n of reaction layers arranged in series is 3 or more, the amount of catalyst in the first-stage reaction layer is preferably 60 / n volume% or less of the total amount of catalyst. Thereby, the aromatic yield finally obtained improves. Further, the number n of the reaction layers is not particularly limited as long as it is 2 or more. However, if the number is too large, the effect is not changed and the economical efficiency is deteriorated. Accordingly, n is preferably 2 or more and 8 or less, more preferably 3 or more and 6 or less.

Further, in the conversion reaction step according to the present invention, it is possible to operate at a constant reaction layer inlet temperature, and to increase the reaction layer inlet temperature continuously or stepwise so as to obtain a predetermined aromatic yield. You can also drive. When the aromatic yield falls below the specified range, or when the reaction bed inlet temperature exceeds the specified temperature range, the reactor is switched to a reactor filled with new catalyst or a reactor filled with regenerated catalyst. Continue the reaction. The regeneration of the catalyst can be performed by heat treatment at 200 to 800 ° C., preferably 350 to 700 in an air stream such as air, nitrogen, hydrogen, or a nitrogen / hydrogen mixed gas. The method for producing aromatic hydrocarbons of the present invention is preferably carried out using two series of fixed bed reactors including a reaction layer holding the catalyst composition. In this case, each series of reaction apparatuses is composed of a plurality of reaction layers arranged in series. While the raw material containing light hydrocarbons is introduced into one series of reactors and the reaction proceeds, the catalyst in the other series of reactors is subjected to a regeneration treatment. By performing the reaction / regeneration alternately at intervals of 1 to 10 days in these two series of reactors, for example, continuous operation for one year can be performed. Further, like the cyclic operation, it is possible to continuously perform the reaction by switching a part or all of the series of reactors used for the reaction to another series. It is preferable to keep the aromatic yield within a predetermined range of 40 to 75% by weight by continuously or stepwise increasing the reaction temperature for each cycle of the reaction for 1 to 10 days.

The aromatic yield R is represented by the following formula (1).
R = A / B × 100 (%) (1)
A: Mass of C6-C8 aromatic hydrocarbon in the conversion reaction product B: Mass of all converted reaction product and unreacted hydrocarbon raw material

When aliphatic and / or alicyclic hydrocarbons are converted to aromatic hydrocarbons, a reaction involving dehydrogenation proceeds. Therefore, under the reaction conditions, a hydrogen partial pressure suitable for the reaction is set without adding hydrogen. Will have. Intentional addition of hydrogen has the advantage of suppressing coke deposition and reducing the frequency of regeneration, but the yield of aromatics is not necessarily advantageous because it decreases rapidly with increasing hydrogen partial pressure. Therefore, the hydrogen partial pressure is preferably suppressed to 0.5 MPa or less.
In the conversion reaction step according to the present invention, it is desirable to have a light gas containing methane and / or ethane circulated as a recycle gas from the subsequent separation step. By performing the conversion reaction in the presence of the light gas containing methane and / or ethane, coke deposition on the catalyst can be suppressed, and the aromatic yield can be kept high over a long period of time. The total amount of light gas (recycle gas) circulated to the reaction system is desirably 0.1 to 10 parts by mass, preferably 0.5 to 3 parts by mass, per 1 part by mass of the hydrocarbon feedstock.

(Gas-liquid separation process of reaction bed effluent)
In this step, the effluent from the conversion reaction step is introduced into a gas-liquid separation zone composed of one or more gas-liquid separators, and gas-liquid separation is performed under relatively high pressure, and aromatic hydrocarbons are removed. This is a step of separation into a liquid component (high pressure separation liquid) contained as a main component and a light gas (high pressure separation gas) such as hydrogen, methane, ethane, propane, or butane. As separation conditions, the temperature is usually 10 to 50 ° C., preferably 20 to 40 ° C., and the pressure is usually 0.5 to 8 MPa, preferably 1 to 3 MPa. The reaction bed effluent is cooled by indirect heat exchange with low-temperature raw hydrocarbons before being introduced into the gas-liquid separation process, and, if necessary, hydrogen from the gas-liquid separation process and light gas is separated. In order to reduce the process load, a part of the light gas can be separated.

(Hydrogen separation process from separated gas)
This step is a step of selectively separating hydrogen from the high-pressure separation gas separated in the gas-liquid separation step to obtain a recycle gas containing methane and / or ethane. As a hydrogen separation method in this case, a conventionally known method such as a membrane separation method or a cryogenic separation method is used. From the viewpoint of selective hydrogen separation efficiency, it is preferable to use a membrane separation method. However, when off gas from a cryogenic separation method is used as a recycle gas, unreacted propane is maximized compared to off gas from the membrane separation method. Therefore, there is an advantage that the aromatic hydrocarbon yield can be increased by 1 to 3% by mass. Which method to use is judged from an economic point of view. As the membrane separation device, for example, a device using polyimide, polysulfone, a blend of polysulfone and polydimethylsiloxane as a separation membrane is commercially available. Part of the recycled gas obtained in this step is discharged out of the system in order to keep the total amount of circulating gas within a certain range. In order to recover high-purity hydrogen, a membrane separation device or a PSA (absorption / desorption separation device) is preferably installed as a recovery system in the subsequent stage of the membrane separation device. The selection of the latter device is determined from an economic point of view.

(Separation process of aromatic hydrocarbons from the separation liquid)
This step is a step of separating aromatic hydrocarbon and low boiling point hydrocarbon gas from the high-pressure separation liquid obtained in the gas-liquid separation step, and a stabilizer (distillation tower) is used as the apparatus. The low-boiling point hydrocarbon gas separated as the top fraction is composed of C3 to C4 hydrocarbons and is used as a recycle gas.

(Mixing process of raw light hydrocarbons and recycled gas)
In this step, the raw material light hydrocarbon is mixed with the recycle gas containing methane and / or ethane obtained in the hydrogen gas separation step and the low boiling point hydrocarbon gas separated in the aromatic hydrocarbon separation step. It is a process, and this mixing can be performed in a pipe. This mixture is introduced into the conversion reaction step. The mixing ratio of the recycle gas and the low boiling point hydrocarbon gas per 1 part by mass of the raw light hydrocarbon is 0.1 to 10 parts by mass, preferably 0.5 to 3 parts by mass. Thus, the following effects are acquired by using methane and / or ethane as recycle gas. That is, the aromatization reaction by dehydrocyclization is an endothermic reaction, and therefore the catalyst layer temperature is lowered, which is disadvantageous for the aromatization reaction. Methane and / or ethane is considered an inert gas because it does not aromatize under the reaction conditions. By heating methane and / or ethane, this acts as a heat supply medium, suppresses the temperature drop of the catalyst layer, favorably advances the aromatization reaction, and improves the aromatic hydrocarbon yield. Moreover, the partial pressure of the hydrogen produced | generated by the conversion reaction of a raw material can be reduced by recycling, and an aromatization reaction can be advanced advantageously, As a result, an aromatic hydrocarbon yield can be improved. Furthermore, since the gas velocity in the reaction layer is increased (GHSV is increased), the contact time between the reaction substrate and the catalyst active site is shortened, and the excessive reaction that gives the coke-like substance can be suppressed. As a result, it is possible to suppress the decrease in activity that occurs with the elapsed time of the reaction and maintain the aromatic hydrocarbon yield at a high level. In commercial equipment, the recycle gas ratio must be determined from an economic point of view.

Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to the following examples.

≪Synthesis example≫
(Example 1)
Using ZSM-5 (ammonium type, Si / Al = 35 mol / mol) 5 g made by Tosoh, it was calcined at 500 ° C. for 5 hours under air flow to obtain ZSM-5 (proton type). Subsequently, 0.06 g of gallium chloride was added in a dry nitrogen atmosphere so that 0.5% by mass (value in which the total mass of ZSM-5 was 100% by mass) was ion-exchanged (or impregnated). The gallium-containing ZSM is obtained by mixing 4.8 g of the ZSM-5 (proton type) in an agate mortar for 10 minutes, then drying at 150 ° C. for 12 hours in a dry nitrogen atmosphere, and further heat treating at 500 ° C. for 12 hours -5 was obtained. Tableting was performed by applying a pressure of 39.2 MPa (400 kgf), coarsely pulverized to a size of 20 to 28 mesh, and granulated to obtain crystalline aluminosilicate 1 containing gallium. This crystalline aluminosilicate 1 was used as the catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms of Example 1.

(Example 2)
3. 0.12 g of gallium chloride and the above ZSM-5 (proton type) so that 1.0% by mass (value with the total mass of crystalline aluminosilicate being 100% by mass) is ion-exchanged (or impregnated). A crystalline aluminosilicate 2 containing gallium was prepared in the same manner as in Example 1 except that the amount was 8 g. This crystalline aluminosilicate 2 was used as the catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms of Example 2.

(Example 3)
Example 1 except that Tosoh ammonium type crystalline aluminosilicate (Si / Al = 100 mol / mol) was used instead of Tosoh ZSM-5 (ammonium type, Si / Al = 35 mol / mol). In the same manner, crystalline aluminosilicate 3 containing gallium was obtained. This crystalline aluminosilicate 3 was used as the catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms of Example 3.

Example 4
Example 2 was used except that Tosoh ammonium type crystalline aluminosilicate (Si / Al = 100 mol / mol) was used instead of Tosoh ZSM-5 (ammonium type, Si / Al = 35 mol / mol). In the same manner, crystalline aluminosilicate 4 containing gallium was obtained. This crystalline aluminosilicate 4 was used as the catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms of Example 4.

(Example 5)
3. 0.25 g of gallium chloride and ZSM-5 (proton type) so that 2.0% by mass (a value obtained when the total mass of crystalline aluminosilicate is 100% by mass) is ion-exchanged (or impregnated). A crystalline aluminosilicate 5 containing gallium was prepared in the same manner as in Example 3 except that the amount was 8 g. This crystalline aluminosilicate 5 was used as the catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms of Example 5.

(Example 6)
Example 1 except that Tosoh ammonium type crystalline aluminosilicate (Si / Al = 200 mol / mol) was used instead of Tosoh ZSM-5 (ammonium type, Si / Al = 35 mol / mol). In the same manner, crystalline aluminosilicate 6 containing gallium was obtained. This crystalline aluminosilicate 6 was used as the catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms of Example 6.

(Example 7)
Example 2 except that Tosoh ammonium type crystalline aluminosilicate (Si / Al = 200 mol / mol) was used instead of Tosoh ZSM-5 (ammonium type, Si / Al = 35 mol / mol). In the same manner, crystalline aluminosilicate 7 containing gallium was obtained. This crystalline aluminosilicate 7 was used as the catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms of Example 7.

(Comparative Example 1)
5 g of ammonium-type crystalline aluminosilicate (Si / Al = 35 mol / mol) was ion-exchanged (or impregnated) with 2.0% by mass (value in which the total mass of crystalline aluminosilicate was 100% by mass). As such, it was suspended in an aqueous solution in which 0.57 g of gallium nitrate was dissolved in 70 ml of distilled water and stirred at 80 ° C. for 24 hours. Then, gallium containing crystalline aluminosilicate was obtained by baking at 500 degreeC for 3 hours under air circulation. Tableting was performed by applying a pressure of 39.2 MPa (400 kgf), coarsely pulverized to a size of 20 to 28 mesh, and granulated to obtain crystalline aluminosilicate 8 containing gallium.
This crystalline aluminosilicate 8 was used as the catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms of Comparative Example 1.

≪EXAFS measurement≫
For the catalyst compositions for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms of Examples 1 to 7 and Comparative Example 1, the K absorption edge of gallium was measured under the following measurement conditions.
The obtained EXAFS spectrum was subjected to Fourier transform using the following data analysis (Fourier transform) program to obtain a radial distribution function.
The radial distribution function of Example 4, Comparative Example 1, and Ga ₂ O ₃ is shown in FIG.
From this radial distribution function, the peak intensity I of the peak attributed to the Ga—O bond (peak in the range of 1.5 ± 0.02Å) is obtained, and the peak attributed to the Ga—Ga bond (2.8). Peak intensity II of a peak in the range of ± 0.02 mm was determined. The results are shown in Table 2.

〔Measurement condition〕
X-ray source: Continuous X-ray spectroscopic crystal: Si (111)
Beam size: 1mm x 5mm
Detector: Ionization chamber Measurement atmosphere: Atmospheric measurement time: 5 minutes Dwell time: 1 sec
Measurement range: Ga K absorption edge (10000 to 10500 eV)

[Data analysis]
Data analysis (Fourier transform) program: REX2000 (manufactured by Rigaku)

≪BTX yield≫
Using the flow reactors in which the catalyst compositions of Examples 1 to 7 and Comparative Example 1 were filled in 5 mL reactors, the properties shown in Table 1 below were obtained under the conditions of reaction temperature: 550 ° C. and reaction pressure: 0.1 MPaG. The raw material oil was brought into contact with and reacted with the catalyst composition. At that time, nitrogen was introduced as a diluent so that the contact time between the raw material oil and the catalyst was 6.4 seconds.
The reaction is carried out for 30 minutes under these conditions to produce a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms, and the composition of the product is analyzed by an FID gas chromatograph directly connected to the reaction apparatus to obtain 6 to 8 carbon atoms. The yield of monocyclic aromatic hydrocarbons was measured. The measurement results are shown in Table 2.

As shown in Table 2 above, Examples 1 to 7 using the catalyst composition to which the present invention was applied had higher BTX yield than the case of using the catalyst composition of Comparative Example 1 to which the present invention was not applied. .

Claims

A catalyst composition used for the production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms,
Containing crystalline aluminosilicate containing gallium,
In the radial distribution function obtained from the broad X-ray absorption fine structure (EXAFS) spectrum of the K absorption edge of gallium for the catalyst composition, the peak intensity I due to Ga—O and the peak due to Ga—Ga A catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms, wherein the ratio (I / II) to strength II is greater than 0.25.
The catalyst composition for producing monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms according to claim 1, wherein the crystalline aluminosilicate is pentasil-type zeolite.
The catalyst composition for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms according to claim 1 or 2, wherein the crystalline aluminosilicate is MFI type zeolite.
The monocyclic aromatic carbon atom having 6 to 8 carbon atoms according to any one of claims 1 to 3, wherein the content of gallium in the catalyst composition is 0.02 parts by mass or more and 3.0 parts by mass or less. Catalyst composition for hydrogen production.
The monocyclic aromatic having 6 to 8 carbon atoms according to any one of claims 1 to 4, wherein a molar ratio of gallium to aluminum (atomic ratio, Ga / Al) is 0.1 or more and 2.0 or less. Catalyst composition for hydrocarbon production.
A monocyclic ring having 6 to 8 carbon atoms, wherein the feedstock oil is brought into contact with the catalyst composition for producing a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms according to any one of claims 1 to 5. A method for producing aromatic hydrocarbons.