WO2016084651A1 - Process for producing para-xylene - Google Patents

Process for producing para-xylene Download PDF

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Publication number
WO2016084651A1
WO2016084651A1 PCT/JP2015/082234 JP2015082234W WO2016084651A1 WO 2016084651 A1 WO2016084651 A1 WO 2016084651A1 JP 2015082234 W JP2015082234 W JP 2015082234W WO 2016084651 A1 WO2016084651 A1 WO 2016084651A1
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Prior art keywords
xylene
zeolite
para
paraxylene
mixed fluid
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PCT/JP2015/082234
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French (fr)
Japanese (ja)
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松方　正彦
求 酒井
拓矢 金子
泰博 荒木
辰雄 濱松
信啓 木村
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学校法人早稲田大学
Ｊｘ日鉱日石エネルギー株式会社
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Publication of WO2016084651A1 publication Critical patent/WO2016084651A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/10—Supported membranes; Membrane supports
    • B01D69/108—Inorganic support material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/0215—Silicon carbide; Silicon nitride; Silicon oxycarbide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B37/00—Compounds having molecular sieve properties but not having base-exchange properties
    • C01B37/02—Crystalline silica-polymorphs, e.g. silicalites dealuminated aluminosilicate zeolites
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C15/00—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts
    • C07C15/02—Monocyclic hydrocarbons
    • C07C15/067—C8H10 hydrocarbons
    • C07C15/08—Xylenes
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/144—Purification; Separation; Use of additives using membranes, e.g. selective permeation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals

Definitions

  • the present invention relates to a method for producing para-xylene.
  • xylenes are extremely important compounds as starting materials for producing terephthalic acid, isophthalic acid, orthophthalic acid, etc., which are polyester raw materials. These xylenes are produced by, for example, transalkylation of toluene, disproportionation reaction, and the like, and the product contains structural isomers such as paraxylene, orthoxylene, and metaxylene.
  • Terephthalic acid obtained by oxidizing para-xylene is the main raw material for polyethylene terephthalate
  • phthalic anhydride obtained from ortho-xylene is used as a raw material for plasticizers
  • isophthalic acid obtained from meta-xylene is unsaturated. Used as a main raw material for polyester and the like. Therefore, a method for efficiently separating these structural isomers from the product is required.
  • inorganic films having good chemical resistance, oxidation resistance, heat stability, and pressure resistance have been proposed to solve these problems.
  • Separation and concentration using inorganic membranes can reduce the amount of energy used compared to separation by distillation or adsorbent, and can be separated and concentrated in a wider temperature range than polymer membranes. Further, it has an advantage that it can be applied to separation of a mixture containing an organic substance that cannot be separated by a polymer membrane due to deterioration.
  • zeolite membranes have regular sub-nanometer pores, so they function as molecular sieves, so they can selectively permeate specific molecules and are expected to exhibit high separation performance. .
  • Crystalline aluminosilicate which is collectively called zeolite, has a fine space (nanospace) of molecular size in one crystal, and is called “molecular sieve”.
  • molecular sieve Depending on the crystal structure, there are many types such as LTA (A type), MFI (ZSM-5 type), MOR, FER, and FAU (X type, Y type).
  • Zeolite with such a unique higher order structure exhibits shape selection function (molecular sieving function), adsorption / separation purification function, ion exchange function, solid acid function, catalytic function, etc., so it can be used in a wide range of industrial fields. Has been.
  • a zeolite membrane composite in which zeolite is formed into a membrane on a support is usually used.
  • Various methods for separating xylene isomers using such a zeolite membrane composite have been studied.
  • Patent Document 1 discloses a zeolite membrane containing a structure-directing agent such as tetrapropylammonium ion on the surface of a porous support as a method for producing a zeolite membrane capable of separating para-xylene from ortho-xylene and meta-xylene.
  • a method for producing a zeolite membrane is disclosed in which the structure-directing agent is removed by firing at a low temperature after forming the film.
  • Patent Document 2 discloses a technique for controlling shape selectivity by using a separation membrane in which a zeolite membrane and a silica membrane are sequentially laminated on a porous support.
  • Patent Document 3 discloses a technique for selectively separating paraxylene in a high temperature region by using a zeolite membrane composite in which a support is immersed in an impregnating material such as hydrocarbon wax and a crystalline molecular sieve layer (zeolite membrane) is formed. Is disclosed.
  • an object of the present invention is to provide a production method for selectively separating paraxylene from a mixed fluid containing xylene isomers, and to provide a method for producing paraxylene having high selectivity and high permeation rate. is there.
  • the present inventors have intensively studied the conditions for separating para-xylene from a mixed fluid containing xylene isomers using a zeolite membrane composite film formed on a porous support. As a result, it has been found that the separation selectivity and the permeation rate are greatly improved by allowing a predetermined amount of at least one selected from inorganic gas and lower hydrocarbon to coexist in the mixed fluid.
  • the present invention has been accomplished based on these findings.
  • the method for producing para-xylene according to the present invention selectively separates para-xylene from a mixed fluid containing at least ortho-xylene, meta-xylene and para-xylene, using a zeolite membrane composite film formed on a porous support.
  • paraxylene is produced by separating at least one selected from an inorganic gas and a lower hydrocarbon in the mixed fluid in an amount of 1 to 80 mol%.
  • the zeolite is preferably MFI-type zeolite.
  • the MFI-type zeolite is preferably silicalite-1.
  • the inorganic gas is any one or more selected from helium, argon, nitrogen, hydrogen, carbon monoxide, carbon dioxide, and oxygen, and the lower hydrocarbon is methane, ethane, ethylene, It is preferably at least one selected from propane, propylene, butane, butene and butadiene.
  • the purity of the obtained paraxylene with respect to the total xylene is preferably 84 mol% or more, and the permeation rate of the obtained paraxylene is preferably 50 g ⁇ m ⁇ 2 ⁇ h ⁇ 1 or more.
  • the separation is preferably performed at a temperature of 250 to 450 ° C. and a total pressure of 0.1 to 0.5 MPa.
  • the method for producing para-xylene according to the present invention is a method for selectively separating para-xylene from a mixed fluid containing xylene isomers, and has high selectivity and high permeation rate.
  • the type of zeolite constituting the zeolite membrane is preferably a zeolite having a pore size comparable to the size of the benzene ring.
  • a zeolite having a 10-membered oxygen pore is preferable.
  • MFI-type zeolite is particularly preferable because it has pores of almost the same size as the benzene ring.
  • MFI-type zeolite is mainly composed of oxides of Si and Al, and may contain other elements as long as the effects of the present invention are not impaired.
  • the MFI type zeolite also includes a silicalite-1 (silicalite-1) structure that substantially does not contain aluminum in the framework.
  • silicalite-1 is preferable because of easy film formation on a support.
  • the proportion of pores in the zeolite is preferably 20% or less with respect to the pores having a larger diameter than the pores derived from the crystal structure of the zeolite.
  • the proportion of pores larger than the zeolite pores is more preferably 5% or less.
  • the proportion of pores larger than the zeolite pores can be determined by measuring the pore distribution with a separation membrane defect structure analyzer.
  • the raw materials constituting the zeolite membrane are not particularly limited.
  • the silica source amorphous silica, amorphous silica, fumed silica, colloidal silica, tetraethyl orthosilicate (TEOS), sodium silicate, potassium silicate, lithium silicate and the like can be used.
  • TEOS tetraethyl orthosilicate
  • sodium silicate, potassium silicate, lithium silicate and the like can be used.
  • aluminum source sodium aluminate, potassium aluminate, aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum hydroxide, and the like can be used.
  • the structure directing agent used when forming the zeolite membrane may be variously selected depending on the desired zeolite.
  • the MFI type zeolite for example, tetrapropylammonium hydroxide (TPAOH) or tetrapropylammonium bromide (TPABr) is used.
  • TPAOH tetrapropylammonium hydroxide
  • TPABr tetrapropylammonium bromide
  • alkali metal or alkaline earth metal hydroxide specifically sodium hydroxide, potassium hydroxide, or the like may be used as a mineralizer.
  • an inorganic binder such as silica or alumina, an organic substance such as a polymer, a silylating agent for modifying the zeolite surface, or the like may be included as necessary in addition to zeolite.
  • the zeolite membrane may partially contain an amorphous component or the like, but is preferably a zeolite membrane substantially composed only of zeolite.
  • the thickness of the zeolite membrane is not particularly limited, but is usually 0.1 ⁇ m or more, preferably 0.6 ⁇ m or more, more preferably 1.0 ⁇ m or more. Moreover, it is 100 micrometers or less normally, Preferably it is 60 micrometers or less, More preferably, it is 20 micrometers or less. If the thickness of the zeolite membrane is too large, the permeation rate tends to decrease, and if it is too small, the selectivity tends to decrease or the membrane strength tends to decrease.
  • the thickness of the zeolite membrane can be determined by a field emission scanning electron microscope.
  • the particle diameter of the zeolite constituting the zeolite membrane is not particularly limited, but if it is too small, the grain boundary tends to increase and the selectivity tends to decrease. Therefore, it is usually 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more. Further, the upper limit of the particle diameter of zeolite is not more than the thickness of the membrane, for example, not more than 100 ⁇ m. Further, it is particularly preferable that the particle diameter of the zeolite is the same as the thickness of the zeolite membrane. When the particle size of the zeolite is the same as the thickness of the zeolite membrane, the grain boundary of the zeolite is the smallest. A zeolite membrane obtained by hydrothermal synthesis described later is preferable because the zeolite particle size and the zeolite membrane thickness may be the same. The particle diameter of zeolite can be determined by a field emission scanning electron microscope.
  • the crystal plane (101) / crystal plane (020) peak intensity ratio is preferably 1.10 or more.
  • the crystal plane (101) / crystal plane (020) peak intensity ratio is 1.10 or more, the paraxylene selectivity can be improved.
  • the peak intensity ratio of crystal plane (101) / crystal plane (020) is particularly preferably 2.0 or more.
  • An X-ray diffraction (XRD) spectrum can be obtained, for example, under the following conditions.
  • the X-ray diffraction spectrum is not limited as long as an X-ray diffraction spectrum can be obtained under the following conditions.
  • the porous support may be any porous inorganic substance having chemical stability that can crystallize zeolite in the form of a membrane on the surface thereof.
  • sintered ceramics such as silica, ⁇ -alumina, ⁇ -alumina, mullite, zirconia, titania, yttria, silicon nitride, silicon carbide, sintered metals such as iron, bronze, stainless steel, or glass And carbon moldings.
  • ⁇ -alumina ceramic sintered bodies and stainless sintered metals are preferred from the viewpoints of heat resistance, mechanical strength, chemical resistance, ease of preparation of the support, and availability.
  • the shape of the porous support is not particularly limited as long as it can effectively separate para-xylene from a mixed fluid of xylene isomers. Specifically, for example, a flat plate shape, a tubular shape, a honeycomb shape having a large number of cylindrical, columnar, or prismatic holes, a monolith, and the like can be given.
  • the average pore diameter of the porous support is not particularly limited, but those having a controlled average pore diameter are preferred. That is, it is usually 0.02 ⁇ m or more, preferably 0.05 ⁇ m or more, more preferably 0.1 ⁇ m or more. Moreover, it is 20 micrometers or less normally, Preferably it is 10 micrometers or less, More preferably, it is 5 micrometers or less. If the average pore diameter is too small, the permeation rate tends to be low, and if it is too large, the strength of the support itself is insufficient or a dense zeolite membrane tends to be difficult to form.
  • the average pore diameter of the porous support can be determined by a mercury intrusion method.
  • the porosity of the porous support is not particularly limited and does not need to be controlled in particular, but the porosity is usually preferably 20% or more and 60% or less. Porosity affects the permeation speed when separating gases and liquids, and if it is less than the lower limit, it tends to inhibit the diffusion of the permeate.
  • the porosity of the porous support can be determined by a mercury intrusion method.
  • the zeolite membrane composite is a membrane in which zeolite is fixed in the form of a membrane on the surface of a porous support, for example, hydrothermal synthesis of zeolite on the surface of a porous support or the like, What was crystallized into a film by treatment is used.
  • a zeolite membrane When forming a zeolite film on a porous support, it is preferable to form a zeolite membrane by hydrothermal synthesis after depositing a zeolite seed crystal on the porous support.
  • a dispersion obtained by dispersing zeolite seed crystal powder in a solvent onto the porous support In addition, the zeolite seed crystals can be attached to the porous support by mixing the zeolite seed crystals as a part of the raw material during the production of the porous support.
  • the dispersion containing the zeolite seed crystals may be simply dropped on the porous support, or the porous support may be immersed in the dispersion containing the zeolite seed crystals.
  • a widely used method such as spin coating, spray coating, roll coating, slurry coating, and filtration can also be used. From the viewpoint that the amount of seed crystals deposited on the porous support can be controlled with good reproducibility, a method of preparing a dispersion containing zeolite seed crystals and immersing the porous support in the dispersion is preferred.
  • Zeolite seed crystals may be commercially available or may be produced from raw materials.
  • raw materials for example, sodium silicate, silica gel, silica sol or silica powder as silica raw material, sodium aluminate or aluminum hydroxide as alumina raw material, TPAOH, TPABr as structure directing agent, sodium hydroxide as mineralizer, etc.
  • TPAOH, TPABr as structure directing agent
  • sodium hydroxide as mineralizer, etc.
  • zeolite seed crystal When a commercially available zeolite seed crystal is used, it is pulverized to a desired size with a pulverizer and then dispersed in water to prepare a dispersion.
  • the prepared dispersion is appropriately attached to the porous support by the above method.
  • the dispersion may be in any state such as a slurry, a sol, or a solution, and can be appropriately prepared according to the coating method employed.
  • a slurry-like dispersion is preferable because of easy adhesion.
  • the amount of zeolite seed crystals deposited on the porous support is preferably 0.5 to 20 g / m 2 .
  • the amount of zeolite seed crystals deposited on the porous support is particularly preferably 1 to 10 g / m 2 .
  • the amount of zeolite seed crystals attached to the porous support can be determined from the difference in the weight of the support before and after the seed crystals are attached.
  • the particle diameter of the zeolite seed crystal attached to the porous support is 200 nm or more. If the seed crystal particle size is less than 200 nm, the seed crystal is likely to enter the porous support and the voids of the porous support are blocked. Further, when the particle diameter of the zeolite seed crystal attached to the porous support is 200 nm or more, the support is made of an impregnating material as described in Patent Document 3 in the process of forming a film on the porous support. An impregnation step is also unnecessary.
  • the particle size of the zeolite seed crystals attached to the porous support is more preferably 200 to 1,000 nm, and particularly preferably 200 to 500 nm.
  • a zeolite membrane can be formed on a porous support by hydrothermal synthesis using a porous support to which a zeolite seed crystal obtained by the above method is attached.
  • a general method can be used for forming a zeolite film by hydrothermal synthesis.
  • a silica source, an aluminum source, a mineralizer, and a structure-directing agent are mixed with water or an aqueous alcohol solution to form a precursor solution, and a porous support having a zeolite seed crystal attached thereto is immersed in the obtained precursor solution.
  • hydrothermal synthesis may be performed by heating in an autoclave or the like.
  • the temperature of the hydrothermal synthesis treatment is preferably 80 to 130 ° C., for example, and more preferably 80 to 120 ° C. At a temperature lower than 80 ° C., crystallization of zeolite is difficult to proceed. On the other hand, at a temperature higher than 130 ° C., the crystal gap of the zeolite crystal becomes large. This is because the proportion of pores having a larger diameter than the pores derived from the crystal structure of zeolite is increased.
  • the hydrothermal synthesis treatment time is preferably 80 to 240 hours, more preferably 100 to 200 hours. If it is shorter than 80 hours, the selectivity of para-xylene may be lowered, and if it is longer than 240 hours, the permeation rate may be lowered.
  • the zeolite membrane film is fired in air at 450 to 700 ° C. in an oxygen atmosphere or nitrogen atmosphere for 2 to 10 hours to obtain a zeolite membrane composite. .
  • the temperature is raised to a desired temperature at a temperature rising rate of 0.1 to 10 ° C./min. It is preferable to remove the structure directing agent. By setting the rate of temperature rise and the rate of temperature fall within the above ranges, the proportion of pores having a larger diameter than pores derived from the crystal structure of zeolite can be reduced.
  • the rate of temperature increase to the firing temperature is more preferably 0.5 to 5 ° C./min, and the temperature decrease rate is more preferably 0.5 to 5 ° C./min.
  • the zeolite membrane composite in which the proportion of pores larger than the pores derived from the crystal structure in the proportion of pores of the zeolite membrane is 20% or less is the amount of zeolite seed crystals deposited on the porous support, hydrothermal
  • the zeolite can be produced by appropriately adjusting the temperature during synthesis, the time, the heating rate during firing, the cooling rate, and the like.
  • the zeolite membrane composite is preferably immersed in an aqueous solution or an alcohol solution containing an orthosilicate ester after forming a zeolite film on the porous support. Grain boundaries and pinholes can be repaired by immersing the zeolite membrane composite in an orthosilicate solution.
  • the orthosilicate ester is not particularly limited, and examples thereof include tetramethyl orthosilicate and tetraethyl orthosilicate.
  • the restoration treatment with the orthosilicate ester solution is preferably performed by stirring the zeolite membrane composite in an orthosilicate ester solution at a temperature of 40 to 90 ° C. for 1 to 48 hours. It is preferable that the zeolite membrane composite is washed and fired after the repair treatment with the orthosilicate solution.
  • the shape of the zeolite membrane composite is not particularly limited, and any shape such as a tubular shape, a hollow fiber shape, a monolith type, and a honeycomb type can be adopted.
  • the size is not particularly limited.
  • a tubular shape a length of 2 cm to 200 cm, an inner diameter of 0.05 cm to 2 cm, and a thickness of 0.5 mm to 4 mm are practical and preferable.
  • the method for producing para-xylene according to the present invention is a mixed fluid containing at least ortho-xylene, meta-xylene and para-xylene using a zeolite membrane composite film formed on a porous support (hereinafter referred to as “xylene mixed fluid”).
  • xylene mixed fluid a mixed fluid containing at least ortho-xylene, meta-xylene and para-xylene using a zeolite membrane composite film formed on a porous support
  • xylene mixed fluid may contain ethylbenzene, trimethylbenzene or the like in addition to orthoxylene, metaxylene and paraxylene.
  • the xylene mixed fluid is a gas or a liquid.
  • VP vapor permeation
  • PV pervaporation
  • the xylene mixed fluid is separated by coexisting 1 to 80 mol% of at least one selected from inorganic gas and lower hydrocarbon.
  • 1 to 80 mol% of at least one selected from inorganic gas and lower hydrocarbon hereinafter sometimes referred to as “inorganic gas / lower hydrocarbon”
  • the inorganic gas / lower hydrocarbon is 1 to 80 mol% means that the combined inorganic gas / lower hydrocarbon and xylene mixed fluid is 100 mol%, so that the xylene mixed fluid is 99 to 20 mol%. Means.
  • molecules of the xylene mixed fluid to be separated may be adsorbed on the surface of the pores of the zeolite. Since the pores of zeolite are on the order of sub-nanometers, permeation of xylene molecules is hindered and separation of xylene isomers cannot be performed effectively by adsorbing molecules of xylene mixed fluid to the pore surface. Sometimes. In particular, ortho-xylene and meta-xylene are larger than para-xylene in terms of molecular structure, and when adsorbed and coated on the separation membrane surface on the raw material supply side, there is a concern that they may remain on the membrane surface and block pores.
  • the present inventors have found that mixing and diluting an xylene mixed fluid with an inorganic gas / lower hydrocarbon greatly improves both the separation selectivity and permeation rate of paraxylene. This can be considered to be because the partial pressure of ortho-xylene and meta-xylene is reduced, and these xylene molecules are moderately relaxed and suppressed from adsorbing to the pore surface.
  • the content of the inorganic gas / lower hydrocarbon is less than 1 mol%, the effect of moderately mitigating / suppressing the adsorption of xylene molecules on the pore surface is not sufficient. On the other hand, if the content of the inorganic gas / lower hydrocarbon exceeds 80 mol%, the transmission rate of para-xylene is not sufficient.
  • the content of the inorganic gas / lower hydrocarbon is preferably 5 mol% or more, more preferably 10 mol% or more, and further preferably 20 mol% or more.
  • the content of inorganic gas / lower hydrocarbon is preferably less than 70 mol%, more preferably less than 60 mol%, still more preferably less than 50 mol%, and most preferably less than 45 mol%.
  • the inorganic gas is a gas having little polarity, and is preferably one or more selected from helium, argon, nitrogen, hydrogen, carbon monoxide, carbon dioxide and oxygen. Any one of them may be used alone, or any two or more of them may be mixed.
  • the lower hydrocarbon is a gas that is a gas at normal temperature and pressure and has 4 or less carbon atoms. The lower hydrocarbon is preferably at least one selected from methane, ethane, ethylene, propane, propylene, butane, butene and butadiene. Any one of them may be used alone, or any two or more of them may be mixed.
  • FIG. 1 is a schematic view of a vapor permeation apparatus using a zeolite membrane composite. It shows as one of the examples of the apparatus for performing the manufacturing method of the paraxylene of this invention.
  • the xylene mixed fluid in the supply liquid tank 22 is supplied into the separation cell 10 held at a predetermined pressure by the pump 21. At that time, inorganic gas / lower hydrocarbon is supplied from the cylinder 20 and mixed with the xylene mixed fluid.
  • the separation cell 10 is installed in an oven (not shown), and is heated to a predetermined temperature during the separation.
  • a zeolite membrane composite 11 in which a zeolite is formed on a cylindrical porous support is installed.
  • the xylene mixed fluid and the inorganic gas / lower hydrocarbon mixture are vaporized and supplied to the outer surface of the zeolite membrane composite 11.
  • argon gas is allowed to flow from the cylinder 23 as a carrier gas inside the cylindrical zeolite membrane composite 11.
  • the xylene mixed fluid is selectively separated when passing through the cylindrical zeolite membrane composite 11 from the outside to the inside.
  • the separated paraxylene exits from the inner surface of the zeolite membrane composite 11 and is discharged to the outside together with the carrier gas. Thereafter, the separated para-xylene is separated from the carrier gas by being cooled and liquefied, and can be obtained as para-xylene.
  • a part of the separated and discharged para-xylene is collected, and components are analyzed by a gas chromatograph 26 equipped with a FID as a detector.
  • the xylene mixed fluid that has not passed through the cylindrical zeolite membrane composite 11 passes through the back pressure valve 25 and is discharged to the outside.
  • a mixed gas of argon and methane is supplied from the cylinder 24 as an internal standard substance for the gas chromatograph.
  • methane is used as the lower hydrocarbon
  • a mixed gas of argon and ethane is used as the internal standard substance.
  • the total pressure of the xylene mixed fluid and the inorganic gas / lower hydrocarbon when the xylene mixed fluid is separated is preferably 0.1 to 0.5 MPa.
  • the total pressure is less than 0.1 MPa, the paraxylene permeation rate decreases.
  • the selectivity (purity) of paraxylene decreases.
  • the lower limit of the total pressure is more preferably 0.2 MPa.
  • the upper limit of the total pressure is more preferably 0.4 MPa.
  • the temperature at which the xylene mixed fluid is separated is preferably 250 to 450 ° C.
  • the temperature at which the xylene mixed fluid is separated means the temperature of the zeolite membrane composite. Outside this temperature range, the paraxylene permeation rate decreases.
  • the lower limit of the temperature is more preferably 300 ° C.
  • the upper limit of the temperature is more preferably 400 ° C, further preferably 350 ° C.
  • the purity of the obtained para-xylene with respect to the total xylene is preferably 84 mol% or more.
  • the purity of the obtained para-xylene with respect to the total xylene is the ratio of the para-xylene component to the total xylene component in the xylene mixed fluid obtained by permeating the zeolite membrane composite.
  • the purity of para-xylene with respect to all xylenes is 84 mol% or more, it becomes easy to obtain high-purity para-xylene on an industrial scale. More preferably, it is 88 mol% or more, More preferably, it is 90 mol% or more, Most preferably, it is 92 mol% or more.
  • the permeation rate of the obtained paraxylene is preferably 50 g ⁇ m ⁇ 2 ⁇ h ⁇ 1 or more.
  • the permeation rate of para-xylene can be determined by multiplying the permeation rate of the xylene mixed fluid by the purity of para-xylene with respect to all xylenes.
  • the permeation rate is 50 g ⁇ m ⁇ 2 ⁇ h ⁇ 1 or more, it becomes easy to produce high-purity paraxylene on an industrial scale. More preferably, it is 80 g ⁇ m ⁇ 2 ⁇ h ⁇ 1 or more, and further preferably 100 g ⁇ m ⁇ 2 ⁇ h ⁇ 1 or more.
  • the paraxylene / metaxylene separation factor is preferably 16 or more.
  • the para-xylene / ortho-xylene separation factor is preferably 17 or more.
  • the separation factor is the ratio of component A (mol%) and component B (mol%) in the permeate gas to the ratio of component A (mol%) and component B (mol%) in the supply gas. Value. At this time, it becomes easy to produce high purity para-xylene on an industrial scale. More preferably, it is 20 or more, More preferably, it is 30 or more.
  • TEOS tetraethyl orthosilicate
  • TPAOH tetrapropylammonium hydroxide
  • pure water a synthetic solution.
  • the composition of the solution was 0.004Na 2 O: SiO 2 : 0.176TPAOH: 43.9H 2 O.
  • the obtained synthesis solution was hydrothermally synthesized under stirring conditions at 100 ° C. for 24 hours.
  • the synthesized solution was filtered, and the recovered powder was baked at 530 ° C. for 8 hours to obtain seed crystals of silicalite-1.
  • the seed crystal particle size was 270 nm. The particle diameter was measured by a dynamic light scattering method.
  • Silicalite-1 powder prepared as a seed crystal was dispersed in pure water to prepare seed crystal suspension 1 so that the concentration of the seed crystal in the slurry was 10 g / L.
  • a cylindrical ⁇ -alumina support having a diameter of 1 cm and a length of 3 cm was prepared as a porous support.
  • the average pore diameter of the support was 150 nm, and the porosity was 37%.
  • the ⁇ -alumina support was immersed in the seed slurry for 1 minute to obtain a seed support porous support 1. It was 5.6 g / m ⁇ 2 > when the seed-crystal load of the porous support 1 with a seed crystal was measured.
  • the seed crystal was mainly supported on the support.
  • zeolite membrane composite A synthetic solution was obtained by mixing tetraethyl orthosilicate (TEOS), tetrapropylammonium hydroxide (TPAOH), ethanol, and pure water and aging at 60 ° C. for 4 hours.
  • the composition of the solution was SiO 2 : 0.12TPAOH: 66H 2 O: 8 EtOH.
  • the seed support porous support 1 was immersed in the resultant synthesis solution, and hydrothermal synthesis was performed at 100 ° C. for 7 days. Then, it baked at 500 degreeC for 8 hours, and the zeolite membrane composite 1 was obtained. The firing was performed at 1 ° C./min, held at 500 ° C. for 8 hours, and then cooled at 1 ° C./min.
  • the structure of the zeolite of the zeolite membrane composite 1 was determined to be silicalite-1 from the peak pattern in XRD measurement.
  • a xylene mixed fluid separation test was performed using the vapor permeation apparatus shown in FIG.
  • Tables 1 to 4 show the types of inorganic gas / lower hydrocarbon, the mixing ratio of xylene mixed fluid (A) and inorganic gas / lower hydrocarbon (B) (A / B ratio), separation membrane temperature, and total pressure. Tests 1 to 43 were performed as described below under various conditions.
  • the xylene mixed fluid in the supply liquid tank 22 was heated to a gas by a heater and supplied to the separation cell 10 held at a predetermined pressure by the pump 21.
  • the separation cell 10 was installed in an oven (not shown) and heated to a predetermined temperature during the permeation test.
  • a xylene mixed fluid to be separated was supplied to the outer surface of the cylindrical zeolite membrane composite 1 to obtain a permeate gas from the inner surface of the cylindrical zeolite membrane composite 1.
  • Argon gas was flowed as a carrier gas at a rate of 300 mL / min on the permeate side.
  • the recovered gas containing the gas that permeated the zeolite membrane composite 1 was collected and analyzed by the gas chromatograph 26.
  • the permeation rate of the xylene mixed fluid (g ⁇ m ⁇ 2 ⁇ h ⁇ 1 ), the purity of paraxylene (mol%), the permeation rate of paraxylene (g ⁇ m ⁇ 2 ⁇ h ⁇ 1 )
  • the para-xylene / meta-xylene separation factor and the para-xylene / ortho-xylene separation factor were determined.
  • the separation factor is the value of the ratio of component A (mol%) and component B (mol%) in the permeate gas to the ratio of component A (mol%) and component B (mol%) in the supply gas.
  • the measurement formula is shown below.
  • Para-xylene / meta-xylene separation factor (PP-X / PM-X) / (FP-X / FM-X)
  • PM-X meta-xylene concentration in permeate gas
  • FP-X para-xylene concentration in feed gas
  • FM-X meta-xylene concentration in feed gas
  • FIG. 2 is a graph showing the relationship between the transmission rate and purity of paraxylene at 300 ° C. in the presence of hydrogen gas based on the results in Table 1.
  • FIG. 3 is a diagram showing the relationship between the permeation rate and purity of paraxylene at 350 ° C. in the presence of hydrogen gas based on the results in Table 2.
  • FIG. 4 is a diagram showing the relationship between the transmission rate and purity of paraxylene at 400 ° C. in the presence of hydrogen gas based on the results in Table 3.
  • Each curve is obtained by plotting the data in the table with dots and connecting with approximate curves. The plot on each curve shows the total pressure increasing from top to bottom.
  • the purity tends to decrease uniformly as the total pressure increases, whereas the permeation rate may have a maximum value when the temperature of the separation membrane is 350 ° C.
  • FIG. 5 is a diagram showing the relationship between the transmission rate and purity of paraxylene at 350 ° C. in the presence of hydrogen gas, argon gas or methane gas based on a part of Table 2 and the results of Table 4.
  • the mixing ratio of xylene mixed fluid (A) and inorganic gas / lower hydrocarbon (B) is 50/50, which shows the difference in separation performance of paraxylene due to the difference in inorganic gas. It can be seen that hydrogen gas is superior in purity to argon gas or methane gas.

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Abstract

Provided is a para-xylene production process for selectively separating para-xylene from a mixed fluid including xylene isomers, the production process having high selectivity and a high permeation rate. Disclosed is a process for producing para-xylene by selectively separating para-xylene from a mixed fluid including at least ortho-xylene, meta-xylene, and para-xylene by using a zeolite membrane composite in which a membrane is formed on a porous support body, wherein the separation is performed by making 1-80 mol% of at least one substance selected from inorganic gases and lower hydrocarbons coexist in said mixed fluid.

Description

パラキシレンの製造方法Method for producing para-xylene
　本発明は、パラキシレンの製造方法に関する。 The present invention relates to a method for producing para-xylene.
　芳香族化合物の中でも、キシレン類は、ポリエステルの原料となるテレフタル酸、イソフタル酸、オルソフタル酸などを製造する出発原料として、極めて重要な化合物である。これらのキシレン類は、例えば、トルエンのトランスアルキル化、不均化反応などによって製造されるが、生成物中には構造異性体であるパラキシレン、オルトキシレン、メタキシレンが存在する。パラキシレンを酸化することによって得られるテレフタル酸は、ポリエチレンテレフタレートの主要原料として、オルトキシレンから得られる無水フタル酸は、可塑剤などの原料として、また、メタキシレンから得られるイソフタル酸は、不飽和ポリエステルなどの主要原料としてそれぞれ使用される。そのため、生成物の中からこれらの構造異性体を効率的に分離する方法が求められている。 Among aromatic compounds, xylenes are extremely important compounds as starting materials for producing terephthalic acid, isophthalic acid, orthophthalic acid, etc., which are polyester raw materials. These xylenes are produced by, for example, transalkylation of toluene, disproportionation reaction, and the like, and the product contains structural isomers such as paraxylene, orthoxylene, and metaxylene. Terephthalic acid obtained by oxidizing para-xylene is the main raw material for polyethylene terephthalate, phthalic anhydride obtained from ortho-xylene is used as a raw material for plasticizers, and isophthalic acid obtained from meta-xylene is unsaturated. Used as a main raw material for polyester and the like. Therefore, a method for efficiently separating these structural isomers from the product is required.
　従来、有機物を含有する気体または液体の混合物からの含有成分の分離、濃縮は、対象となる物質の性質に応じて、蒸留法、共沸蒸留法、溶媒抽出／蒸留法、吸着剤などにより行われている。
　しかしながら、これらの方法は、多くのエネルギーを必要とする、あるいは分離、濃縮対象の適用範囲が限定的であるといった欠点がある。 Conventionally, separation and concentration of components from a gas or liquid mixture containing organic substances is performed by distillation, azeotropic distillation, solvent extraction / distillation, adsorbent, etc., depending on the properties of the target substance. It has been broken.
However, these methods have drawbacks that they require a lot of energy or have a limited application range for separation and concentration.
　これらの方法に代わる分離方法として、高分子膜や無機膜などの膜を用いた膜分離、濃縮方法が提案されている。しかし、高分子膜は加工性に優れる特徴をもつ一方で、熱や化学物質、圧力により劣化して性能が低下することが問題であった。 As an alternative to these methods, a membrane separation and concentration method using a membrane such as a polymer membrane or an inorganic membrane has been proposed. However, while the polymer film has the characteristics of excellent processability, it has been a problem that the performance deteriorates due to deterioration due to heat, chemicals, and pressure.
　近年、これらの問題を解決すべく耐薬品性、耐酸化性、耐熱安定性、耐圧性が良好な種々の無機膜が提案されてきている。無機膜を用いた分離、濃縮は、蒸留や吸着剤による分離に比べ、エネルギーの使用量を削減できるほか、高分子膜よりも広い温度範囲で分離、濃縮を実施できる。更に劣化の問題により高分子膜では分離できない有機物を含む混合物の分離にも適用できるという利点を有している。その中でもゼオライト膜は、サブナノメートルの規則的な細孔を有しているため、分子ふるいとしての働きをもつので選択的に特定の分子を透過でき、高分離性能を示すことが期待されている。 In recent years, various inorganic films having good chemical resistance, oxidation resistance, heat stability, and pressure resistance have been proposed to solve these problems. Separation and concentration using inorganic membranes can reduce the amount of energy used compared to separation by distillation or adsorbent, and can be separated and concentrated in a wider temperature range than polymer membranes. Further, it has an advantage that it can be applied to separation of a mixture containing an organic substance that cannot be separated by a polymer membrane due to deterioration. Among them, zeolite membranes have regular sub-nanometer pores, so they function as molecular sieves, so they can selectively permeate specific molecules and are expected to exhibit high separation performance. .
　ゼオライトと総称される結晶性アルミノケイ酸塩は、一つの結晶内に分子サイズの微空間（ナノスペース）を有しており、「分子ふるい」の名で呼ばれている。また、その結晶構造により、ＬＴＡ（Ａ型）、ＭＦＩ（ＺＳＭ－５型）、ＭＯＲ、ＦＥＲ、ＦＡＵ（Ｘ型、Ｙ型）といった数多くの種類が存在する。このような特異な高次構造を備えたゼオライトは、形状選択機能（分子ふるい機能）、吸着／分離精製機能、イオン交換機能、固体酸機能、触媒機能などを発揮するので、広い産業分野で利用されている。 Crystalline aluminosilicate, which is collectively called zeolite, has a fine space (nanospace) of molecular size in one crystal, and is called “molecular sieve”. Depending on the crystal structure, there are many types such as LTA (A type), MFI (ZSM-5 type), MOR, FER, and FAU (X type, Y type). Zeolite with such a unique higher order structure exhibits shape selection function (molecular sieving function), adsorption / separation purification function, ion exchange function, solid acid function, catalytic function, etc., so it can be used in a wide range of industrial fields. Has been.
　ゼオライト膜を分離、濃縮に使用する場合、通常、支持体上に膜状にゼオライトを形成させたゼオライト膜複合体が用いられている。こうしたゼオライト膜複合体を用いたキシレン異性体の分離方法が種々検討されてきている。 When a zeolite membrane is used for separation and concentration, a zeolite membrane composite in which zeolite is formed into a membrane on a support is usually used. Various methods for separating xylene isomers using such a zeolite membrane composite have been studied.
　例えば、特許文献１には、パラキシレンをオルトキシレン、メタキシレンから分離することが可能なゼオライト膜の製造方法として、多孔質支持体の表面にテトラプロピルアンモニウムイオン等の構造規定剤を含むゼオライト膜を形成した後に、低温で焼成することにより当該構造規定剤を除去するゼオライト膜の製造方法が開示されている。 For example, Patent Document 1 discloses a zeolite membrane containing a structure-directing agent such as tetrapropylammonium ion on the surface of a porous support as a method for producing a zeolite membrane capable of separating para-xylene from ortho-xylene and meta-xylene. A method for producing a zeolite membrane is disclosed in which the structure-directing agent is removed by firing at a low temperature after forming the film.
　また、特許文献２には、多孔質支持体上にゼオライト膜とシリカ膜が順次積層された分離膜とすることにより、形状選択性を制御する技術が開示されている。特許文献３には、支持体を炭化水素ワックス等の含浸材料に浸漬後に結晶性モレキュラーシーブ層（ゼオライト膜）を成膜したゼオライト膜複合体によって、高温領域でパラキシレンを選択的に分離する技術が開示されている。 Patent Document 2 discloses a technique for controlling shape selectivity by using a separation membrane in which a zeolite membrane and a silica membrane are sequentially laminated on a porous support. Patent Document 3 discloses a technique for selectively separating paraxylene in a high temperature region by using a zeolite membrane composite in which a support is immersed in an impregnating material such as hydrocarbon wax and a crystalline molecular sieve layer (zeolite membrane) is formed. Is disclosed.
特許第５４８１０７５号公報Japanese Patent No. 5481075 特開２００７－２０３２４１号公報JP 2007-203241 A 特表２００２－５３７９９０号公報JP 2002-537990 Gazette
　しかしながら、特許文献１によるゼオライト膜の製造方法では、膜形成後の焼成温度が低いものであり、パラキシレンの透過速度が満足できるレベルではない。特許文献２の分離膜においても、パラキシレンの選択率を向上しうるものの、透過速度が満足できるレベルではない。また、特許文献３のゼオライト膜では、透過速度（パーミアンス）と選択性のバランスが劣り、低分圧においても選択性は必ずしも十分なものではない。 However, in the method for producing a zeolite membrane according to Patent Document 1, the firing temperature after film formation is low, and the permeation rate of paraxylene is not at a satisfactory level. Even in the separation membrane of Patent Document 2, although the paraxylene selectivity can be improved, the permeation rate is not at a satisfactory level. Moreover, the zeolite membrane of Patent Document 3 has a poor balance between permeation rate (permeance) and selectivity, and the selectivity is not always sufficient even at a low partial pressure.
　本発明は、上記事情に鑑みてなされたものである。すなわち、本発明の課題は、キシレン異性体を含む混合流体からパラキシレンを選択的に分離する製造方法であって、高い選択性と高い透過速度とを有するパラキシレンの製造方法を提供することである。 The present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide a production method for selectively separating paraxylene from a mixed fluid containing xylene isomers, and to provide a method for producing paraxylene having high selectivity and high permeation rate. is there.
　本発明者らは、多孔質支持体上に成膜したゼオライト膜複合体を用いて、キシレン異性体を含む混合流体からパラキシレンを分離する際の条件について鋭意検討を重ねた。その結果、混合流体中に無機ガスおよび低級炭化水素から選ばれる少なくとも１つを所定量共存させることによって、分離の選択性と透過速度とが共に大きく向上することを見出した。本発明はこれらの知見に基づいて成し遂げられたものである。 The present inventors have intensively studied the conditions for separating para-xylene from a mixed fluid containing xylene isomers using a zeolite membrane composite film formed on a porous support. As a result, it has been found that the separation selectivity and the permeation rate are greatly improved by allowing a predetermined amount of at least one selected from inorganic gas and lower hydrocarbon to coexist in the mixed fluid. The present invention has been accomplished based on these findings.
　すなわち、本発明のパラキシレンの製造方法は、多孔質支持体上に成膜したゼオライト膜複合体を用いて、少なくともオルトキシレン、メタキシレンおよびパラキシレンを含む混合流体からパラキシレンを選択的に分離してパラキシレンを製造する方法であって、前記混合流体に無機ガスおよび低級炭化水素から選ばれる少なくとも１つを１～８０ｍｏｌ％共存させて分離を行うものである。 That is, the method for producing para-xylene according to the present invention selectively separates para-xylene from a mixed fluid containing at least ortho-xylene, meta-xylene and para-xylene, using a zeolite membrane composite film formed on a porous support. In this method, paraxylene is produced by separating at least one selected from an inorganic gas and a lower hydrocarbon in the mixed fluid in an amount of 1 to 80 mol%.
　また、本発明は、前記ゼオライトが、ＭＦＩ型ゼオライトであることが好ましい。 In the present invention, the zeolite is preferably MFI-type zeolite.
　また、本発明は、前記ＭＦＩ型ゼオライトが、ｓｉｌｉｃａｌｉｔｅ－１であることが好ましい。 In the present invention, the MFI-type zeolite is preferably silicalite-1.
　また、本発明は、前記無機ガスが、ヘリウム、アルゴン、窒素、水素、一酸化炭素、二酸化炭素および酸素から選ばれるいずれか１つ以上であり、前記低級炭化水素が、メタン、エタン、エチレン、プロパン、プロピレン、ブタン、ブテンおよびブタジエンから選ばれるいずれか１つ以上であることが好ましい。 Further, in the present invention, the inorganic gas is any one or more selected from helium, argon, nitrogen, hydrogen, carbon monoxide, carbon dioxide, and oxygen, and the lower hydrocarbon is methane, ethane, ethylene, It is preferably at least one selected from propane, propylene, butane, butene and butadiene.
　また、本発明は、得られたパラキシレンの全キシレンに対する純度が８４ｍｏｌ％以上であり、かつ得られたパラキシレンの透過速度が５０ｇ・ｍ－２・ｈ－１以上であることが好ましい。 In the present invention, the purity of the obtained paraxylene with respect to the total xylene is preferably 84 mol% or more, and the permeation rate of the obtained paraxylene is preferably 50 g · m −2 · h −1 or more.
　また、本発明は、前記分離を、温度２５０～４５０℃、全圧０．１～０．５ＭＰａで行うことが好ましい。 In the present invention, the separation is preferably performed at a temperature of 250 to 450 ° C. and a total pressure of 0.1 to 0.5 MPa.
　本発明のパラキシレンの製造方法は、キシレン異性体を含む混合流体からパラキシレンを選択的に分離する製造方法であって、高い選択性と高い透過速度とを有している。 The method for producing para-xylene according to the present invention is a method for selectively separating para-xylene from a mixed fluid containing xylene isomers, and has high selectivity and high permeation rate.
ゼオライト膜複合体を用いたベーパーパーミエーション装置の概略図である。It is the schematic of the vapor permeation apparatus using a zeolite membrane composite. 水素ガス共存下の３００℃におけるパラキシレンの透過速度と純度との関係を示す図である。It is a figure which shows the relationship between the permeation | transmission rate and purity of paraxylene in 300 degreeC under hydrogen gas coexistence. 水素ガス共存下の３５０℃におけるパラキシレンの透過速度と純度との関係を示す図である。It is a figure which shows the relationship between the permeation | transmission rate of paraxylene in 350 degreeC under hydrogen gas coexistence, and purity. 水素ガス共存下の４００℃におけるパラキシレンの透過速度と純度との関係を示す図である。It is a figure which shows the relationship between the permeation | transmission rate and purity of paraxylene in 400 degreeC under hydrogen gas coexistence. 水素ガス、アルゴンガスまたはメタンガス共存下の３５０℃におけるパラキシレンの透過速度と純度との関係を示す図である。It is a figure which shows the relationship between the permeation | transmission rate and purity of paraxylene in 350 degreeC under hydrogen gas, argon gas, or methane gas coexistence.
　本発明に係るパラキシレンの製造方法の好適な実施形態について、更に詳細に説明する。但し、以下に記載する構成要件の説明は、本発明の実施態様の一例であり、本発明はこれらの内容に限定されるものではなく、その要旨の範囲内で種々変形して実施することができる。 A preferred embodiment of the method for producing paraxylene according to the present invention will be described in more detail. However, the description of the constituent requirements described below is an example of embodiments of the present invention, and the present invention is not limited to these contents, and various modifications can be made within the scope of the invention. it can.
（ゼオライト）
　本発明において、ゼオライト膜を構成するゼオライトの種類は、ベンゼン環の大きさと同程度の細孔径を持つゼオライトが好ましい。具体的には酸素１０員環の細孔を持つゼオライトが好ましい。その中でもＭＦＩ型ゼオライトは、ベンゼン環とほぼ同じ大きさの細孔を持つため特に好ましい。ＭＦＩ型ゼオライトは、ＳｉとＡｌの酸化物を主成分とするものであり、本発明の効果を損なわない限り、それ以外の元素が含まれていてもよい。
　ＭＦＩ型ゼオライトには、ＺＳＭ－５以外に実質的に骨格内にアルミニウムを含まないｓｉｌｉｃａｌｉｔｅ－１（シリカライト－１）構造なども含まれる。ＭＦＩ型ゼオライトの中でも、支持体上への成膜の容易さから、ｓｉｌｉｃａｌｉｔｅ－１が好ましい。 (Zeolite)
In the present invention, the type of zeolite constituting the zeolite membrane is preferably a zeolite having a pore size comparable to the size of the benzene ring. Specifically, a zeolite having a 10-membered oxygen pore is preferable. Among these, MFI-type zeolite is particularly preferable because it has pores of almost the same size as the benzene ring. MFI-type zeolite is mainly composed of oxides of Si and Al, and may contain other elements as long as the effects of the present invention are not impaired.
In addition to ZSM-5, the MFI type zeolite also includes a silicalite-1 (silicalite-1) structure that substantially does not contain aluminum in the framework. Among MFI-type zeolites, silicalite-1 is preferable because of easy film formation on a support.
　ゼオライト中の細孔の割合は、ゼオライトの結晶構造に由来する細孔より大きな径の細孔の割合が２０％以下であることが好ましい。ゼオライトの結晶構造に由来する細孔より大きな径の細孔、すなわち、ゼオライトの結晶構造に由来する細孔より大きな粒界やピンホールの割合を２０％以下とすることにより、パラキシレンをより選択的に分離することができる。ゼオライト細孔より大きな細孔の割合は、５％以下であることがより好ましい。ゼオライト細孔より大きな細孔の割合は、分離膜欠陥構造解析装置による細孔分布の測定によって求めることができる。 The proportion of pores in the zeolite is preferably 20% or less with respect to the pores having a larger diameter than the pores derived from the crystal structure of the zeolite. By selecting less than 20% of grain boundaries and pinholes larger in diameter than pores derived from the crystal structure of zeolite, that is, pores derived from the crystal structure of zeolite, para-xylene is more selected Can be separated. The proportion of pores larger than the zeolite pores is more preferably 5% or less. The proportion of pores larger than the zeolite pores can be determined by measuring the pore distribution with a separation membrane defect structure analyzer.
（ゼオライト膜）
　本発明において、ゼオライト膜を構成する原料は、特に限定されるものではない。シリカ源としては、無定形シリカ、アモルファスシリカ、ヒュームドシリカ、コロイダルシリカ、オルトケイ酸テトラエチル（ＴＥＯＳ）、ケイ酸ナトリウム、ケイ酸カリウム、ケイ酸リチウム等を使用することができる。また、アルミニウム源としては、アルミン酸ナトリウム、アルミン酸カリウム、塩化アルミニウム、硝酸アルミニウム、硫酸アルミニウム、水酸化アルミニウム等を使用することができる。 (Zeolite membrane)
In the present invention, the raw materials constituting the zeolite membrane are not particularly limited. As the silica source, amorphous silica, amorphous silica, fumed silica, colloidal silica, tetraethyl orthosilicate (TEOS), sodium silicate, potassium silicate, lithium silicate and the like can be used. As the aluminum source, sodium aluminate, potassium aluminate, aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum hydroxide, and the like can be used.
　また、ゼオライト膜を形成する際に使用される構造規定剤は、所望のゼオライトによって種々選択すればよい。ＭＦＩ型ゼオライトの場合は、例えば、テトラプロピルアンモニウムヒドロキシド（ＴＰＡＯＨ）、テトラプロピルアンモニウムブロミド（ＴＰＡＢｒ）が使用される。また、目的とするゼオライトの種類に応じて、鉱化剤として、例えば、アルカリ金属またはアルカリ土類金属の水酸化物、具体的には水酸化ナトリウム、水酸化カリウム等を使用してもよい。 Further, the structure directing agent used when forming the zeolite membrane may be variously selected depending on the desired zeolite. In the case of the MFI type zeolite, for example, tetrapropylammonium hydroxide (TPAOH) or tetrapropylammonium bromide (TPABr) is used. Further, according to the type of the target zeolite, for example, alkali metal or alkaline earth metal hydroxide, specifically sodium hydroxide, potassium hydroxide, or the like may be used as a mineralizer.
　ゼオライト膜を構成する成分としては、ゼオライト以外にシリカ、アルミナなどの無機バインダー、ポリマーなどの有機物、あるいはゼオライト表面を修飾するシリル化剤などを必要に応じて含んでいてもよい。ゼオライト膜は、一部にアモルファス成分などが含有されていてもよいが、好ましくは実質的にゼオライトのみで構成されるゼオライト膜である。 As a component constituting the zeolite membrane, an inorganic binder such as silica or alumina, an organic substance such as a polymer, a silylating agent for modifying the zeolite surface, or the like may be included as necessary in addition to zeolite. The zeolite membrane may partially contain an amorphous component or the like, but is preferably a zeolite membrane substantially composed only of zeolite.
　ゼオライト膜の厚さは、特に限定されないが、通常０．１μｍ以上、好ましくは０．６μｍ以上、より好ましくは１．０μｍ以上である。また、通常１００μｍ以下、好ましくは６０μｍ以下、より好ましくは２０μｍ以下である。ゼオライト膜の膜厚が大き過ぎると透過速度が低下する傾向があり、小さ過ぎると選択性が低下したり、膜強度が低下する傾向がある。ゼオライト膜の厚さは電界放出形走査電子顕微鏡により求めることができる。 The thickness of the zeolite membrane is not particularly limited, but is usually 0.1 μm or more, preferably 0.6 μm or more, more preferably 1.0 μm or more. Moreover, it is 100 micrometers or less normally, Preferably it is 60 micrometers or less, More preferably, it is 20 micrometers or less. If the thickness of the zeolite membrane is too large, the permeation rate tends to decrease, and if it is too small, the selectivity tends to decrease or the membrane strength tends to decrease. The thickness of the zeolite membrane can be determined by a field emission scanning electron microscope.
　ゼオライト膜を構成するゼオライトの粒子径は、特に限定されないが、小さ過ぎると粒界が大きくなるなどして選択性などを低下させる傾向がある。それ故、通常３０ｎｍ以上、好ましくは５０ｎｍ以上、より好ましくは１００ｎｍ以上である。また、ゼオライトの粒子径の上限は膜の厚さ以下、例えば、１００μｍ以下である。さらに、ゼオライトの粒子径がゼオライト膜の厚さと同じである場合が特に好ましい。ゼオライトの粒子径がゼオライト膜の厚さと同じであるとき、ゼオライトの粒界が最も小さくなる。後に述べる水熱合成で得られたゼオライト膜は、ゼオライトの粒子径とゼオライト膜の厚さが同じになる場合があるので好ましい。ゼオライトの粒子径は電界放出形走査電子顕微鏡により求めることができる。 The particle diameter of the zeolite constituting the zeolite membrane is not particularly limited, but if it is too small, the grain boundary tends to increase and the selectivity tends to decrease. Therefore, it is usually 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more. Further, the upper limit of the particle diameter of zeolite is not more than the thickness of the membrane, for example, not more than 100 μm. Further, it is particularly preferable that the particle diameter of the zeolite is the same as the thickness of the zeolite membrane. When the particle size of the zeolite is the same as the thickness of the zeolite membrane, the grain boundary of the zeolite is the smallest. A zeolite membrane obtained by hydrothermal synthesis described later is preferable because the zeolite particle size and the zeolite membrane thickness may be the same. The particle diameter of zeolite can be determined by a field emission scanning electron microscope.
　また、ゼオライト膜のＸ線回折スペクトルにおいて、結晶面(101)/結晶面(020)ピーク強度比は１．１０以上であることが好ましい。ゼオライト膜複合体のゼオライト膜のＸ線回折スペクトルにおいて、結晶面(101)/結晶面(020)ピーク強度比が１．１０以上であると、パラキシレンの選択性を向上させることができる。結晶面(101)/結晶面(020)ピーク強度比が２．０以上であると特に好ましい。 Further, in the X-ray diffraction spectrum of the zeolite membrane, the crystal plane (101) / crystal plane (020) peak intensity ratio is preferably 1.10 or more. In the X-ray diffraction spectrum of the zeolite membrane of the zeolite membrane composite, if the crystal plane (101) / crystal plane (020) peak intensity ratio is 1.10 or more, the paraxylene selectivity can be improved. The peak intensity ratio of crystal plane (101) / crystal plane (020) is particularly preferably 2.0 or more.
　Ｘ線回折（ＸＲＤ）スペクトルは、例えば、下記の条件によって取得することができる。なお、下記条件でＸ線回折スペクトルを取得できればよく、Ｘ線回折装置を限定するものではない。
　装置：Ｒｉｇａｋｕ　Ｕｌｔｉｍａ　ＩＶ
　Ｘ線源：Ｃｕ－Ｋ
　管電圧：４０ｋＶ
　管電流：４０ｍＡ
　スキャン速度：３°／ｍｉｎ An X-ray diffraction (XRD) spectrum can be obtained, for example, under the following conditions. The X-ray diffraction spectrum is not limited as long as an X-ray diffraction spectrum can be obtained under the following conditions.
Device: Rigaku Ultimate IV
X-ray source: Cu-K
Tube voltage: 40 kV
Tube current: 40 mA
Scan speed: 3 ° / min
（多孔質支持体）
　多孔質支持体は、その表面などにゼオライトを膜状に結晶化できるような化学的安定性がある多孔質の無機物質であれば如何なるものであってもよい。具体的には、例えば、シリカ、α－アルミナ、γ－アルミナ、ムライト、ジルコニア、チタニア、イットリア、窒化珪素、炭化珪素などのセラミックス焼結体、鉄、ブロンズ、ステンレスなどの焼結金属、またはガラス、カーボン成型体などが挙げられる。これらのうち、耐熱性、機械的強度、耐薬品性、支持体作成の容易さや、入手容易性の点から、α－アルミナのセラミックス焼結体、ステンレスの焼結金属が好ましい。 (Porous support)
The porous support may be any porous inorganic substance having chemical stability that can crystallize zeolite in the form of a membrane on the surface thereof. Specifically, for example, sintered ceramics such as silica, α-alumina, γ-alumina, mullite, zirconia, titania, yttria, silicon nitride, silicon carbide, sintered metals such as iron, bronze, stainless steel, or glass And carbon moldings. Of these, α-alumina ceramic sintered bodies and stainless sintered metals are preferred from the viewpoints of heat resistance, mechanical strength, chemical resistance, ease of preparation of the support, and availability.
　多孔質支持体の形状は、キシレン異性体の混合流体からパラキシレンを有効に分離できるものであれば特に限定されない。具体的には、例えば、平板状、管状のもの、または円筒状、円柱状や角柱状の孔が多数存在するハニカム状のものやモノリスなどが挙げられる。 The shape of the porous support is not particularly limited as long as it can effectively separate para-xylene from a mixed fluid of xylene isomers. Specifically, for example, a flat plate shape, a tubular shape, a honeycomb shape having a large number of cylindrical, columnar, or prismatic holes, a monolith, and the like can be given.
　多孔質支持体が有する平均細孔径は特に制限されないが、平均細孔径が制御されているものが好ましい。すなわち、通常０．０２μｍ以上、好ましくは０．０５μｍ以上、より好ましくは０．１μｍ以上である。また、通常２０μｍ以下、好ましくは１０μｍ以下、より好ましくは５μｍ以下である。平均細孔径が小さ過ぎると透過速度が小さくなる傾向があり、大き過ぎると支持体自体の強度が不十分になったり、緻密なゼオライト膜が形成されにくくなる傾向がある。多孔質支持体が有する平均細孔径は、水銀圧入法によって求めることができる。 The average pore diameter of the porous support is not particularly limited, but those having a controlled average pore diameter are preferred. That is, it is usually 0.02 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more. Moreover, it is 20 micrometers or less normally, Preferably it is 10 micrometers or less, More preferably, it is 5 micrometers or less. If the average pore diameter is too small, the permeation rate tends to be low, and if it is too large, the strength of the support itself is insufficient or a dense zeolite membrane tends to be difficult to form. The average pore diameter of the porous support can be determined by a mercury intrusion method.
　また、多孔質支持体の気孔率は特に制限されず、また特に制御する必要は無いが、気孔率は、通常２０％以上６０％以下であることが好ましい。気孔率は、気体や液体を分離する際の透過速度を左右し、前記下限未満では透過物の拡散を阻害する傾向があり、前記上限を超えると支持体の強度が低下する傾向がある。多孔質支持体の気孔率は、水銀圧入法によって求めることができる。 Further, the porosity of the porous support is not particularly limited and does not need to be controlled in particular, but the porosity is usually preferably 20% or more and 60% or less. Porosity affects the permeation speed when separating gases and liquids, and if it is less than the lower limit, it tends to inhibit the diffusion of the permeate. The porosity of the porous support can be determined by a mercury intrusion method.
（ゼオライト膜複合体）
　本発明において、ゼオライト膜複合体とは、多孔質支持体の表面などにゼオライトが膜状に固着しているものであり、例えば、多孔質支持体の表面などにゼオライトを水熱合成や、水蒸気処理により膜状に結晶化させたものが用いられる。 (Zeolite membrane composite)
In the present invention, the zeolite membrane composite is a membrane in which zeolite is fixed in the form of a membrane on the surface of a porous support, for example, hydrothermal synthesis of zeolite on the surface of a porous support or the like, What was crystallized into a film by treatment is used.
　多孔質支持体上にゼオライトを成膜する場合、多孔質支持体上にゼオライト種晶を付着させた後、ゼオライト膜を水熱合成により形成することが好ましい。一般的に、多孔質支持体にゼオライト種晶を付着させるためには、ゼオライト種晶の粉末を溶剤に分散させた分散液を多孔質支持体上に塗布することが好ましい。その他、多孔質支持体製造時に原料の一部としてゼオライト種晶粉末を混入させることで、多孔質支持体にゼオライト種晶を付着させることもできる。塗布の方法としては、ゼオライト種晶を含む分散液を多孔質支持体に単純に滴下するだけでもよく、ゼオライト種晶を含む分散液に多孔質支持体を浸漬することでもよい。また、スピンコート、スプレーコート、ロールコート、スラリーの塗布、濾過など汎用されている方法を用いることもできる。多孔質支持体上の種晶の付着量を再現性よく制御できるという観点から、ゼオライト種晶を含む分散液を調製し、該分散液に多孔質支持体を浸漬する方法が好ましい。 When forming a zeolite film on a porous support, it is preferable to form a zeolite membrane by hydrothermal synthesis after depositing a zeolite seed crystal on the porous support. In general, in order to attach a zeolite seed crystal to a porous support, it is preferable to apply a dispersion obtained by dispersing zeolite seed crystal powder in a solvent onto the porous support. In addition, the zeolite seed crystals can be attached to the porous support by mixing the zeolite seed crystals as a part of the raw material during the production of the porous support. As a coating method, the dispersion containing the zeolite seed crystals may be simply dropped on the porous support, or the porous support may be immersed in the dispersion containing the zeolite seed crystals. In addition, a widely used method such as spin coating, spray coating, roll coating, slurry coating, and filtration can also be used. From the viewpoint that the amount of seed crystals deposited on the porous support can be controlled with good reproducibility, a method of preparing a dispersion containing zeolite seed crystals and immersing the porous support in the dispersion is preferred.
　ゼオライト種晶は、市販のものを用いてもよく、原料から製造してもよい。原料から製造する場合には、例えばシリカ原料としてケイ酸ナトリウム、シリカゲル、シリカゾルまたはシリカ粉末、アルミナ原料としてアルミン酸ナトリウムまたは水酸化アルミニウム、構造規定剤としてＴＰＡＯＨ、ＴＰＡＢｒ、鉱化剤として水酸化ナトリウムなどを使用して、既知の方法で製造することができる。 Zeolite seed crystals may be commercially available or may be produced from raw materials. When manufacturing from raw materials, for example, sodium silicate, silica gel, silica sol or silica powder as silica raw material, sodium aluminate or aluminum hydroxide as alumina raw material, TPAOH, TPABr as structure directing agent, sodium hydroxide as mineralizer, etc. Can be produced in a known manner.
　ゼオライト種晶として市販のものを用いる場合には、所望の大きさに粉砕機で粉砕した後、水に分散させ、分散液を調製する。調製した分散液は、適宜上記の方法で多孔質支持体に付着させる。該分散液は、スラリー、ゾル、溶液など、いずれの状態としても良く、採用する塗布方法に応じて適宜調製することができる。多孔質支持体を浸漬してゼオライト種晶を付着させる方法を採用する場合には、付着の容易性からスラリー状の分散液であることが好ましい。 When a commercially available zeolite seed crystal is used, it is pulverized to a desired size with a pulverizer and then dispersed in water to prepare a dispersion. The prepared dispersion is appropriately attached to the porous support by the above method. The dispersion may be in any state such as a slurry, a sol, or a solution, and can be appropriately prepared according to the coating method employed. In the case of adopting a method of immersing the porous support and adhering the zeolite seed crystal, a slurry-like dispersion is preferable because of easy adhesion.
　多孔質支持体上へのゼオライト種晶の付着量は、０．５～２０ｇ／ｍ２とすることが好ましい。多孔質支持体上へのゼオライト種晶の付着量を上記範囲とすることにより、ゼオライトの結晶構造に由来する細孔より大きな径の細孔の割合を低減させることができる。ゼオライト種晶の付着量は、１～１０ｇ／ｍ２であることが特に好ましい。多孔質支持体へのゼオライト種晶の付着量は、種晶付着前後の支持体重量の差より求めることができる。 The amount of zeolite seed crystals deposited on the porous support is preferably 0.5 to 20 g / m 2 . By setting the amount of zeolite seed crystals deposited on the porous support in the above range, the proportion of pores having a larger diameter than the pores derived from the crystal structure of the zeolite can be reduced. The adhesion amount of the zeolite seed crystal is particularly preferably 1 to 10 g / m 2 . The amount of zeolite seed crystals attached to the porous support can be determined from the difference in the weight of the support before and after the seed crystals are attached.
　また、多孔質支持体に付着させるゼオライト種晶の粒子径は２００ｎｍ以上であることが好ましい。種晶の粒子径が２００ｎｍ未満であると多孔質支持体に種晶が入り込みやすくなって多孔質支持体の空隙が塞がれてしまい好ましくない。また、多孔質支持体に付着させるゼオライト種晶の粒子径が２００ｎｍ以上であると、多孔質支持体上に成膜する過程において、特許文献３に記載されているような含浸材料で支持体を含浸する工程も不要となる。多孔質支持体に付着させるゼオライト種晶の粒子径は２００～１，０００ｎｍであることがより好ましく、２００～５００ｎｍであることが特に好ましい。 Moreover, it is preferable that the particle diameter of the zeolite seed crystal attached to the porous support is 200 nm or more. If the seed crystal particle size is less than 200 nm, the seed crystal is likely to enter the porous support and the voids of the porous support are blocked. Further, when the particle diameter of the zeolite seed crystal attached to the porous support is 200 nm or more, the support is made of an impregnating material as described in Patent Document 3 in the process of forming a film on the porous support. An impregnation step is also unnecessary. The particle size of the zeolite seed crystals attached to the porous support is more preferably 200 to 1,000 nm, and particularly preferably 200 to 500 nm.
　上記方法により得られるゼオライト種晶を付着させた多孔質支持体を用いて水熱合成することで、多孔質支持体上にゼオライト膜を形成することができる。 A zeolite membrane can be formed on a porous support by hydrothermal synthesis using a porous support to which a zeolite seed crystal obtained by the above method is attached.
　本発明において、水熱合成によるゼオライトの成膜は、一般的な方法をとることができる。例えば、シリカ源、アルミニウム源、鉱化剤、構造規定剤を水またはアルコール水溶液と混合して前駆液とし、得られた前駆液中にゼオライト種晶を付着させた多孔質支持体を浸漬させた状態で、オートクレーブ等で加熱して水熱合成すればよい。 In the present invention, a general method can be used for forming a zeolite film by hydrothermal synthesis. For example, a silica source, an aluminum source, a mineralizer, and a structure-directing agent are mixed with water or an aqueous alcohol solution to form a precursor solution, and a porous support having a zeolite seed crystal attached thereto is immersed in the obtained precursor solution. In this state, hydrothermal synthesis may be performed by heating in an autoclave or the like.
　水熱合成処理の温度は、例えば、８０～１３０℃とすることが好ましく、８０～１２０℃で水熱合成することがより好ましい。８０℃より低い温度では、ゼオライトの結晶化が進行しにくい。一方、１３０℃より高い温度では、ゼオライト結晶の結晶間隙が大きくなる。これは、ゼオライトの結晶構造に由来する細孔より大きな径の細孔の割合が大きくなるためである。 The temperature of the hydrothermal synthesis treatment is preferably 80 to 130 ° C., for example, and more preferably 80 to 120 ° C. At a temperature lower than 80 ° C., crystallization of zeolite is difficult to proceed. On the other hand, at a temperature higher than 130 ° C., the crystal gap of the zeolite crystal becomes large. This is because the proportion of pores having a larger diameter than the pores derived from the crystal structure of zeolite is increased.
　また、水熱合成処理の時間は、８０～２４０時間とすることが好ましく、１００～２００時間とすることがより好ましい。８０時間より短いとパラキシレンの選択性が低下するおそれがあり、２４０時間より長いと透過速度が低下するおそれがある。 The hydrothermal synthesis treatment time is preferably 80 to 240 hours, more preferably 100 to 200 hours. If it is shorter than 80 hours, the selectivity of para-xylene may be lowered, and if it is longer than 240 hours, the permeation rate may be lowered.
　多孔質支持体上にゼオライトを成膜後、ゼオライト膜成膜体を４５０～７００℃の空気下、酸素雰囲気下または窒素雰囲気下で、２～１０時間焼成することによりゼオライト膜複合体が得られる。焼成処理は、０．１～１０℃／分の昇温速度で所望の温度まで昇温し、所定時間焼成の後、０．１～１０℃／分の降温速度で降温して、細孔内の構造規定剤を除去することが好ましい。昇温速度および降温速度を上記範囲とすることにより、ゼオライトの結晶構造に由来する細孔より大きな径の細孔の割合を低減することができる。焼成温度への昇温速度は、０．５～５℃／分とすることがより好ましく、降温速度は０．５～５℃／分とすることがより好ましい。 After forming a zeolite film on a porous support, the zeolite membrane film is fired in air at 450 to 700 ° C. in an oxygen atmosphere or nitrogen atmosphere for 2 to 10 hours to obtain a zeolite membrane composite. . In the firing treatment, the temperature is raised to a desired temperature at a temperature rising rate of 0.1 to 10 ° C./min. It is preferable to remove the structure directing agent. By setting the rate of temperature rise and the rate of temperature fall within the above ranges, the proportion of pores having a larger diameter than pores derived from the crystal structure of zeolite can be reduced. The rate of temperature increase to the firing temperature is more preferably 0.5 to 5 ° C./min, and the temperature decrease rate is more preferably 0.5 to 5 ° C./min.
　ゼオライト膜の細孔の割合において、結晶構造に由来する細孔より大きな細孔の割合が２０％以下であるゼオライト膜複合体は、多孔質支持体上へのゼオライト種晶の付着量、水熱合成時の温度、時間、焼成時の昇温速度、降温速度等を適宜調整してゼオライトを成膜することにより製造することができる。 The zeolite membrane composite in which the proportion of pores larger than the pores derived from the crystal structure in the proportion of pores of the zeolite membrane is 20% or less is the amount of zeolite seed crystals deposited on the porous support, hydrothermal The zeolite can be produced by appropriately adjusting the temperature during synthesis, the time, the heating rate during firing, the cooling rate, and the like.
　また、本発明において、ゼオライト膜複合体は、多孔質支持体にゼオライトを成膜後に、オルトケイ酸エステルを含有する水溶液やアルコール溶液に浸漬させることが好ましい。ゼオライト膜複合体をオルトケイ酸エステル溶液に浸漬することによって、粒界やピンホールを修復することができる。 In the present invention, the zeolite membrane composite is preferably immersed in an aqueous solution or an alcohol solution containing an orthosilicate ester after forming a zeolite film on the porous support. Grain boundaries and pinholes can be repaired by immersing the zeolite membrane composite in an orthosilicate solution.
　オルトケイ酸エステルとしては、特に制限されないが、オルトケイ酸テトラメチル、オルトケイ酸テトラエチルなどが挙げられる。オルトケイ酸エステル溶液による修復処理は、ゼオライト膜複合体をオルトケイ酸エステル溶液に浸漬した状態で、温度４０～９０℃で、１～４８時間撹拌することにより行うことが好ましい。オルトケイ酸エステル溶液による修復処理後、ゼオライト膜複合体を洗浄、焼成することが好ましい。 The orthosilicate ester is not particularly limited, and examples thereof include tetramethyl orthosilicate and tetraethyl orthosilicate. The restoration treatment with the orthosilicate ester solution is preferably performed by stirring the zeolite membrane composite in an orthosilicate ester solution at a temperature of 40 to 90 ° C. for 1 to 48 hours. It is preferable that the zeolite membrane composite is washed and fired after the repair treatment with the orthosilicate solution.
　本発明において、ゼオライト膜複合体の形状は特に限定されず、管状、中空糸状、モノリス型、ハニカム型などあらゆる形状を採用できる。また大きさも特に限定されず、例えば、管状の場合は、通常長さ２ｃｍ以上２００ｃｍ以下、内径０．０５ｃｍ以上２ｃｍ以下、厚さ０．５ｍｍ以上４ｍｍ以下が実用的で好ましい。 In the present invention, the shape of the zeolite membrane composite is not particularly limited, and any shape such as a tubular shape, a hollow fiber shape, a monolith type, and a honeycomb type can be adopted. Also, the size is not particularly limited. For example, in the case of a tubular shape, a length of 2 cm to 200 cm, an inner diameter of 0.05 cm to 2 cm, and a thickness of 0.5 mm to 4 mm are practical and preferable.
（パラキシレンの製造方法）
　本発明のパラキシレンの製造方法は、多孔質支持体上に成膜したゼオライト膜複合体を用いて、少なくともオルトキシレン、メタキシレンおよびパラキシレンを含む混合流体（以下、「キシレン混合流体」と記載することもある。）からパラキシレンを選択的に分離してパラキシレンを製造する方法である。分離対象のキシレン混合流体としては、オルトキシレン、メタキシレン、パラキシレンのほかに、エチルベンゼン、トリメチルベンゼンなどを含んでいてもよい。キシレン混合流体は、気体または液体である。多孔質支持体上に成膜したゼオライト膜複合体を用いて、ベーパーパーミエーション（ＶＰ）法やパーベーパレーション（ＰＶ）法等の手法によって、キシレン混合流体からパラキシレンを選択的に分離することができる。 (Method for producing para-xylene)
The method for producing para-xylene according to the present invention is a mixed fluid containing at least ortho-xylene, meta-xylene and para-xylene using a zeolite membrane composite film formed on a porous support (hereinafter referred to as “xylene mixed fluid”). In this method, para-xylene is produced by selectively separating para-xylene from the para-xylene. The xylene mixed fluid to be separated may contain ethylbenzene, trimethylbenzene or the like in addition to orthoxylene, metaxylene and paraxylene. The xylene mixed fluid is a gas or a liquid. Using a zeolite membrane composite film formed on a porous support, the paraxylene is selectively separated from the xylene mixed fluid by a vapor permeation (VP) method or a pervaporation (PV) method. Can do.
　本発明のパラキシレンの製造方法では、前記キシレン混合流体に無機ガスおよび低級炭化水素から選ばれる少なくとも１つを１～８０ｍｏｌ％共存させて分離を行うものである。キシレン混合流体に対して、無機ガスおよび低級炭化水素から選ばれる少なくとも１つ（以下、「無機ガス／低級炭化水素」と記載することもある。）を１～８０ｍｏｌ％共存させることによって、キシレン混合流体からパラキシレンを高い選択性と高い透過速度で分離することができる。ここで、無機ガス／低級炭化水素が１～８０ｍｏｌ％であるとは、無機ガス／低級炭化水素とキシレン混合流体とを合わせて１００ｍｏｌ％であるので、キシレン混合流体が９９～２０ｍｏｌ％であることを意味している。 In the method for producing para-xylene according to the present invention, the xylene mixed fluid is separated by coexisting 1 to 80 mol% of at least one selected from inorganic gas and lower hydrocarbon. By mixing 1 to 80 mol% of at least one selected from inorganic gas and lower hydrocarbon (hereinafter sometimes referred to as “inorganic gas / lower hydrocarbon”) in the xylene mixed fluid, Para-xylene can be separated from the fluid with high selectivity and high permeation rate. Here, the inorganic gas / lower hydrocarbon is 1 to 80 mol% means that the combined inorganic gas / lower hydrocarbon and xylene mixed fluid is 100 mol%, so that the xylene mixed fluid is 99 to 20 mol%. Means.
　ゼオライト膜複合体を用いてキシレン混合流体を分離する際に、分離対象であるキシレン混合流体の分子が、ゼオライトの細孔の表面に吸着することがある。ゼオライトの有する細孔は、サブナノメートルのオーダーであるため、キシレン混合流体の分子が細孔表面に吸着することによって、キシレン分子の透過が阻害されたり、キシレン異性体の分離が有効に行われなくなることがある。特に、オルトキシレンやメタキシレンは分子構造上パラキシレンに比べて大きく、原料供給側の分離膜表面に吸着・被覆すると、膜表面に留まって細孔を塞ぐ懸念がある。本発明者らは、キシレン混合流体に無機ガス／低級炭化水素を混合して希釈することによって、結果として、パラキシレンの分離の選択性と透過速度とが共に大きく向上することを見出した。これは、オルトキシレンやメタキシレンの分圧が減少し、これらのキシレン分子が細孔表面に吸着することを適度に緩和・抑制しているためと考えることができる。 When the xylene mixed fluid is separated using the zeolite membrane composite, molecules of the xylene mixed fluid to be separated may be adsorbed on the surface of the pores of the zeolite. Since the pores of zeolite are on the order of sub-nanometers, permeation of xylene molecules is hindered and separation of xylene isomers cannot be performed effectively by adsorbing molecules of xylene mixed fluid to the pore surface. Sometimes. In particular, ortho-xylene and meta-xylene are larger than para-xylene in terms of molecular structure, and when adsorbed and coated on the separation membrane surface on the raw material supply side, there is a concern that they may remain on the membrane surface and block pores. The present inventors have found that mixing and diluting an xylene mixed fluid with an inorganic gas / lower hydrocarbon greatly improves both the separation selectivity and permeation rate of paraxylene. This can be considered to be because the partial pressure of ortho-xylene and meta-xylene is reduced, and these xylene molecules are moderately relaxed and suppressed from adsorbing to the pore surface.
　無機ガス／低級炭化水素の含有量が１ｍｏｌ％未満であると、キシレン分子が細孔表面に吸着することを適度に緩和・抑制する効果が十分ではない。また、無機ガス／低級炭化水素の含有量が８０ｍｏｌ％を超えると、パラキシレンの透過速度が十分ではない。無機ガス／低級炭化水素の含有量は、好ましくは５ｍｏｌ％以上、より好ましくは１０ｍｏｌ％以上、さらに好ましくは２０ｍｏｌ％以上である。また、無機ガス／低級炭化水素の含有量は、好ましくは７０ｍｏｌ％未満、より好ましくは６０ｍｏｌ％未満、さらに好ましくは５０ｍｏｌ％未満、最も好ましくは４５ｍｏｌ％未満である。 If the content of the inorganic gas / lower hydrocarbon is less than 1 mol%, the effect of moderately mitigating / suppressing the adsorption of xylene molecules on the pore surface is not sufficient. On the other hand, if the content of the inorganic gas / lower hydrocarbon exceeds 80 mol%, the transmission rate of para-xylene is not sufficient. The content of the inorganic gas / lower hydrocarbon is preferably 5 mol% or more, more preferably 10 mol% or more, and further preferably 20 mol% or more. The content of inorganic gas / lower hydrocarbon is preferably less than 70 mol%, more preferably less than 60 mol%, still more preferably less than 50 mol%, and most preferably less than 45 mol%.
　ここで、無機ガスとは、極性の少ないガスであり、ヘリウム、アルゴン、窒素、水素、一酸化炭素、二酸化炭素および酸素から選ばれるいずれか１つ以上であることが好ましい。いずれかの単独であっても、いずれか２つ以上の混合物であってもよい。また、低級炭化水素とは、常温常圧で気体であるものであり、炭素数が４以下の炭化水素である。低級炭化水素としては、メタン、エタン、エチレン、プロパン、プロピレン、ブタン、ブテンおよびブタジエンから選ばれるいずれか１つ以上であることが好ましい。いずれかの単独であっても、いずれか２つ以上の混合物であってもよい。 Here, the inorganic gas is a gas having little polarity, and is preferably one or more selected from helium, argon, nitrogen, hydrogen, carbon monoxide, carbon dioxide and oxygen. Any one of them may be used alone, or any two or more of them may be mixed. The lower hydrocarbon is a gas that is a gas at normal temperature and pressure and has 4 or less carbon atoms. The lower hydrocarbon is preferably at least one selected from methane, ethane, ethylene, propane, propylene, butane, butene and butadiene. Any one of them may be used alone, or any two or more of them may be mixed.
　図１は、ゼオライト膜複合体を用いたベーパーパーミエーション装置の概略図である。本発明のパラキシレンの製造方法を行うための装置の具体例の１つとして示されている。供給液タンク２２内のキシレン混合流体は、ポンプ２１により所定の圧力に保持された分離セル１０内に供給される。その際、無機ガス／低級炭化水素がボンベ２０から供給され、前記のキシレン混合流体と混合される。分離セル１０は、図示しないオーブン内に設置されており、分離中所定温度に加熱されている。分離セル１０内には、円筒型の多孔質支持体上にゼオライトが成膜されたゼオライト膜複合体１１が設置されている。キシレン混合流体と無機ガス／低級炭化水素の混合物は、気化されて、ゼオライト膜複合体１１の外側表面に供給される。また、円筒型のゼオライト膜複合体１１の内側には、キャリアガスとして、ボンベ２３からアルゴンガスが流されている。キシレン混合流体は、円筒型のゼオライト膜複合体１１を外側から内側へ透過する際に、選択的に分離される。分離されたパラキシレンは、ゼオライト膜複合体１１の内側表面から出て、キャリアガスとともに、外部へ排出される。その後、分離されたパラキシレンは、冷却して液化させることによって、キャリアガスと分離され、パラキシレンとして得ることができる。なお、分離され、排出されたパラキシレンの一部は採取されて、ＦＩＤを検出器として備えたガスクロマトグラフ２６によって、成分が分析される。一方、円筒型のゼオライト膜複合体１１を内側へ透過しなかったキシレン混合流体は、背圧弁２５を通過して、外部へ排出される。また、ガスクロマトグラフの内部標準物質として、ボンベ２４からアルゴンとメタンの混合ガスを供給する。なお、低級炭化水素としてメタンを使用する場合は、内部標準物質としてアルゴンとエタンの混合ガスを使用する。 FIG. 1 is a schematic view of a vapor permeation apparatus using a zeolite membrane composite. It shows as one of the examples of the apparatus for performing the manufacturing method of the paraxylene of this invention. The xylene mixed fluid in the supply liquid tank 22 is supplied into the separation cell 10 held at a predetermined pressure by the pump 21. At that time, inorganic gas / lower hydrocarbon is supplied from the cylinder 20 and mixed with the xylene mixed fluid. The separation cell 10 is installed in an oven (not shown), and is heated to a predetermined temperature during the separation. In the separation cell 10, a zeolite membrane composite 11 in which a zeolite is formed on a cylindrical porous support is installed. The xylene mixed fluid and the inorganic gas / lower hydrocarbon mixture are vaporized and supplied to the outer surface of the zeolite membrane composite 11. In addition, argon gas is allowed to flow from the cylinder 23 as a carrier gas inside the cylindrical zeolite membrane composite 11. The xylene mixed fluid is selectively separated when passing through the cylindrical zeolite membrane composite 11 from the outside to the inside. The separated paraxylene exits from the inner surface of the zeolite membrane composite 11 and is discharged to the outside together with the carrier gas. Thereafter, the separated para-xylene is separated from the carrier gas by being cooled and liquefied, and can be obtained as para-xylene. A part of the separated and discharged para-xylene is collected, and components are analyzed by a gas chromatograph 26 equipped with a FID as a detector. On the other hand, the xylene mixed fluid that has not passed through the cylindrical zeolite membrane composite 11 passes through the back pressure valve 25 and is discharged to the outside. Further, a mixed gas of argon and methane is supplied from the cylinder 24 as an internal standard substance for the gas chromatograph. When methane is used as the lower hydrocarbon, a mixed gas of argon and ethane is used as the internal standard substance.
　キシレン混合流体を分離させる際のキシレン混合流体と無機ガス／低級炭化水素とを合わせた全圧については、０．１～０．５ＭＰａとすることが好ましい。全圧が０．１ＭＰａ未満であると、パラキシレンの透過速度が低下する。全圧が０．５ＭＰａを超えると、パラキシレンの選択性（純度）が低下する。また、全圧の下限は、０．２ＭＰａがより好ましい。全圧の上限は、０．４ＭＰａがより好ましい。 The total pressure of the xylene mixed fluid and the inorganic gas / lower hydrocarbon when the xylene mixed fluid is separated is preferably 0.1 to 0.5 MPa. When the total pressure is less than 0.1 MPa, the paraxylene permeation rate decreases. When the total pressure exceeds 0.5 MPa, the selectivity (purity) of paraxylene decreases. Further, the lower limit of the total pressure is more preferably 0.2 MPa. The upper limit of the total pressure is more preferably 0.4 MPa.
　キシレン混合流体を分離させる際の温度については、２５０～４５０℃とすることが好ましい。ここで、キシレン混合流体を分離させる際の温度とは、ゼオライト膜複合体の温度を意味している。この温度範囲から外れると、パラキシレンの透過速度が低下する。また、温度の下限は、３００℃がより好ましい。温度の上限は、４００℃がより好ましく、３５０℃がさらに好ましい。 The temperature at which the xylene mixed fluid is separated is preferably 250 to 450 ° C. Here, the temperature at which the xylene mixed fluid is separated means the temperature of the zeolite membrane composite. Outside this temperature range, the paraxylene permeation rate decreases. Further, the lower limit of the temperature is more preferably 300 ° C. The upper limit of the temperature is more preferably 400 ° C, further preferably 350 ° C.
　得られたパラキシレンの全キシレンに対する純度は、８４ｍｏｌ％以上であることが好ましい。ここで、得られたパラキシレンの全キシレンに対する純度とは、ゼオライト膜複合体を透過して得られたキシレン混合流体中の全キシレン成分に対するパラキシレン成分の比率のことである。パラキシレンの全キシレンに対する純度が８４ｍｏｌ％以上であれば、工業規模のスケールで高純度のパラキシレンを得ることが容易となる。より好ましくは８８ｍｏｌ％以上であり、さらに好ましくは９０ｍｏｌ％以上であり、最も好ましくは９２ｍｏｌ％以上である。 The purity of the obtained para-xylene with respect to the total xylene is preferably 84 mol% or more. Here, the purity of the obtained para-xylene with respect to the total xylene is the ratio of the para-xylene component to the total xylene component in the xylene mixed fluid obtained by permeating the zeolite membrane composite. When the purity of para-xylene with respect to all xylenes is 84 mol% or more, it becomes easy to obtain high-purity para-xylene on an industrial scale. More preferably, it is 88 mol% or more, More preferably, it is 90 mol% or more, Most preferably, it is 92 mol% or more.
　また、得られたパラキシレンの透過速度は、５０ｇ・ｍ－２・ｈ－１以上であることが好ましい。ここで、パラキシレンの透過速度とは、キシレン混合流体の透過速度にパラキシレンの全キシレンに対する純度を掛け合わせることによって求めることができる。５０ｇ・ｍ－２・ｈ－１以上の透過速度であれば、工業規模のスケールで高純度のパラキシレンを製造することが容易となる。より好ましくは８０ｇ・ｍ－２・ｈ－１以上であり、さらに好ましくは１００ｇ・ｍ－２・ｈ－１以上である。 Further, the permeation rate of the obtained paraxylene is preferably 50 g · m −2 · h −1 or more. Here, the permeation rate of para-xylene can be determined by multiplying the permeation rate of the xylene mixed fluid by the purity of para-xylene with respect to all xylenes. When the permeation rate is 50 g · m −2 · h −1 or more, it becomes easy to produce high-purity paraxylene on an industrial scale. More preferably, it is 80 g · m −2 · h −1 or more, and further preferably 100 g · m −2 · h −1 or more.
　また、パラキシレン／メタキシレン分離係数は、１６以上であることが好ましい。同様に、パラキシレン／オルトキシレン分離係数は、１７以上であることが好ましい。ここで、分離係数とは、供給ガス中の成分Ａ（ｍｏｌ％）と成分Ｂ（ｍｏｌ％）との比に対する透過ガス中の成分Ａ（ｍｏｌ％）と成分Ｂ（ｍｏｌ％）との比の値をいう。このとき、工業規模のスケールで高純度のパラキシレンを製造することが容易となる。より好ましくは２０以上であり、さらに好ましくは３０以上である。 Also, the paraxylene / metaxylene separation factor is preferably 16 or more. Similarly, the para-xylene / ortho-xylene separation factor is preferably 17 or more. Here, the separation factor is the ratio of component A (mol%) and component B (mol%) in the permeate gas to the ratio of component A (mol%) and component B (mol%) in the supply gas. Value. At this time, it becomes easy to produce high purity para-xylene on an industrial scale. More preferably, it is 20 or more, More preferably, it is 30 or more.
　以下、本発明を実施例により具体的に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples.
（種晶の調製）
　水酸化ナトリウム、オルトケイ酸テトラエチル(ＴＥＯＳ)、テトラプロピルアンモニウムヒドロキシド（ＴＰＡＯＨ）、純水を混合し、２４時間室温で撹拌することで、合成溶液を得た。溶液の組成は０．００４Ｎａ２Ｏ：ＳｉＯ２：０．１７６ＴＰＡＯＨ：４３．９Ｈ２Ｏであった。得られた合成溶液を１００℃で２４時間、撹拌条件下で水熱合成を行った。合成後の溶液をろ過し、回収した粉末を５３０℃で８時間焼成を行うことでｓｉｌｉｃａｌｉｔｅ－１の種晶を得た。種晶の粒子径は、２７０ｎｍであった。なお、粒子径は動的光散乱法により測定した。 (Preparation of seed crystals)
Sodium hydroxide, tetraethyl orthosilicate (TEOS), tetrapropylammonium hydroxide (TPAOH), and pure water were mixed and stirred at room temperature for 24 hours to obtain a synthetic solution. The composition of the solution was 0.004Na 2 O: SiO 2 : 0.176TPAOH: 43.9H 2 O. The obtained synthesis solution was hydrothermally synthesized under stirring conditions at 100 ° C. for 24 hours. The synthesized solution was filtered, and the recovered powder was baked at 530 ° C. for 8 hours to obtain seed crystals of silicalite-1. The seed crystal particle size was 270 nm. The particle diameter was measured by a dynamic light scattering method.
（種晶付多孔質支持体の調製）
　種晶として準備したｓｉｌｉｃａｌｉｔｅ－１粉末を純水中に分散させ、スラリー中の種晶の濃度が１０ｇ／Ｌとなるように種晶懸濁液１を調製した。次に、多孔質支持体として、直径１ｃｍ、長さ３ｃｍの円筒型のα－アルミナ支持体を準備した。支持体の平均細孔径は１５０ｎｍであり、気孔率は３７％であった。α－アルミナ支持体を種晶スラリーに１分間浸漬し、種晶付多孔質支持体１を得た。種晶付多孔質支持体１の種晶担持量を測定したところ５．６ｇ／ｍ２であった。種晶付多孔質支持体１の表面及び断面をＳＥＭにて観察したところ、種晶は支持体上に主に担持されていた。 (Preparation of seed support porous support)
Silicalite-1 powder prepared as a seed crystal was dispersed in pure water to prepare seed crystal suspension 1 so that the concentration of the seed crystal in the slurry was 10 g / L. Next, a cylindrical α-alumina support having a diameter of 1 cm and a length of 3 cm was prepared as a porous support. The average pore diameter of the support was 150 nm, and the porosity was 37%. The α-alumina support was immersed in the seed slurry for 1 minute to obtain a seed support porous support 1. It was 5.6 g / m < 2 > when the seed-crystal load of the porous support 1 with a seed crystal was measured. When the surface and cross section of the seed crystal-attached porous support 1 were observed with an SEM, the seed crystal was mainly supported on the support.
（ゼオライト膜複合体の調製）
　オルトケイ酸テトラエチル(ＴＥＯＳ)、テトラプロピルアンモニウムヒドロキシド（ＴＰＡＯＨ）、エタノール、純水を混合し、６０℃で４時間エージングすることで、合成溶液を得た。溶液の組成はＳｉＯ２：０．１２ＴＰＡＯＨ：６６Ｈ２Ｏ：８ＥｔＯＨであった。得られた合成溶液に種晶付多孔質支持体１を浸漬し、１００℃で７日間、水熱合成を行った。その後、５００℃で８時間焼成を行い、ゼオライト膜複合体１を得た。焼成は１℃/ｍｉｎで昇温し、５００℃で８時間保持した後、１℃/ｍｉｎで降温した。ゼオライト膜複合体１のゼオライトの構造は、ＸＲＤ測定におけるピークパターンからｓｉｌｉｃａｌｉｔｅ－１と決定した。 (Preparation of zeolite membrane composite)
A synthetic solution was obtained by mixing tetraethyl orthosilicate (TEOS), tetrapropylammonium hydroxide (TPAOH), ethanol, and pure water and aging at 60 ° C. for 4 hours. The composition of the solution was SiO 2 : 0.12TPAOH: 66H 2 O: 8 EtOH. The seed support porous support 1 was immersed in the resultant synthesis solution, and hydrothermal synthesis was performed at 100 ° C. for 7 days. Then, it baked at 500 degreeC for 8 hours, and the zeolite membrane composite 1 was obtained. The firing was performed at 1 ° C./min, held at 500 ° C. for 8 hours, and then cooled at 1 ° C./min. The structure of the zeolite of the zeolite membrane composite 1 was determined to be silicalite-1 from the peak pattern in XRD measurement.
（ベーパーパーミエーション試験）
　ゼオライト膜複合体１を用い、図１に示すベーパーパーミエーション装置によりキシレン混合流体の分離試験を行った。キシレン混合流体として、キシレン異性体混合物（パラキシレン／メタキシレン／オルトキシレン＝１／２／１（ｍｏｌ比））を用いた。無機ガス／低級炭化水素の種類、キシレン混合流体（Ａ）と無機ガス／低級炭化水素（Ｂ）の混合比率（Ａ／Ｂ比）、分離膜の温度、全圧を表１～表４に記載の条件に種々変えて、下記のようにして試験１～４３を行った。 (Vapor permeation test)
Using the zeolite membrane composite 1, a xylene mixed fluid separation test was performed using the vapor permeation apparatus shown in FIG. As the xylene mixed fluid, a xylene isomer mixture (paraxylene / metaxylene / orthoxylene = 1/2/1 (mol ratio)) was used. Tables 1 to 4 show the types of inorganic gas / lower hydrocarbon, the mixing ratio of xylene mixed fluid (A) and inorganic gas / lower hydrocarbon (B) (A / B ratio), separation membrane temperature, and total pressure. Tests 1 to 43 were performed as described below under various conditions.
　供給液タンク２２内のキシレン混合流体をヒーターによって加熱して気体とし、ポンプ２１によって所定の圧力に保持された分離セル１０内に供給した。分離セル１０は、図示しないオーブン内に設置されており、透過試験中所定の温度に加熱した。円筒型のゼオライト膜複合体１の外側表面に分離するキシレン混合流体を供給し、円筒型のゼオライト膜複合体１の内側表面から透過ガスを得た。透過側にはキャリアガスとしてアルゴンガスを３００ｍＬ／ｍｉｎの速度で流した。ゼオライト膜複合体１を透過したガスを含む回収ガスを分取し、ガスクロマトグラフ２６にて分析を行なった。分析の結果を基に、キシレン混合流体の透過速度（ｇ・ｍ－２・ｈ－１）、パラキシレンの純度（ｍｏｌ％）、パラキシレンの透過速度（ｇ・ｍ－２・ｈ－１）、パラキシレン／メタキシレン分離係数、パラキシレン／オルトキシレン分離係数を求めた。 The xylene mixed fluid in the supply liquid tank 22 was heated to a gas by a heater and supplied to the separation cell 10 held at a predetermined pressure by the pump 21. The separation cell 10 was installed in an oven (not shown) and heated to a predetermined temperature during the permeation test. A xylene mixed fluid to be separated was supplied to the outer surface of the cylindrical zeolite membrane composite 1 to obtain a permeate gas from the inner surface of the cylindrical zeolite membrane composite 1. Argon gas was flowed as a carrier gas at a rate of 300 mL / min on the permeate side. The recovered gas containing the gas that permeated the zeolite membrane composite 1 was collected and analyzed by the gas chromatograph 26. Based on the analysis results, the permeation rate of the xylene mixed fluid (g · m −2 · h −1 ), the purity of paraxylene (mol%), the permeation rate of paraxylene (g · m −2 · h −1 ) The para-xylene / meta-xylene separation factor and the para-xylene / ortho-xylene separation factor were determined.
　試験の結果を表１～４に示した。なお、分離係数とは、供給ガス中の成分Ａ（ｍｏｌ％）と成分Ｂ（ｍｏｌ％）との比に対する透過ガス中の成分Ａ（ｍｏｌ％）と成分Ｂ（ｍｏｌ％）との比の値をいう。パラキシレン／メタキシレン分離係数を例に取って、下記に測定式を示した。
　パラキシレン／メタキシレン分離係数＝（ＰＰ-Ｘ／ＰＭ-Ｘ）／（ＦＰ-Ｘ／ＦＭ-Ｘ）
　　ＰＰ-Ｘ：透過ガス中のパラキシレン濃度
　　ＰＭ-Ｘ：透過ガス中のメタキシレン濃度
　　ＦＰ-Ｘ：供給ガス中のパラキシレン濃度
　　ＦＭ-Ｘ：供給ガス中のメタキシレン濃度 The test results are shown in Tables 1-4. The separation factor is the value of the ratio of component A (mol%) and component B (mol%) in the permeate gas to the ratio of component A (mol%) and component B (mol%) in the supply gas. Say. Taking the para-xylene / meta-xylene separation factor as an example, the measurement formula is shown below.
Para-xylene / meta-xylene separation factor = (PP-X / PM-X) / (FP-X / FM-X)
PP-X: para-xylene concentration in permeate gas PM-X: meta-xylene concentration in permeate gas FP-X: para-xylene concentration in feed gas FM-X: meta-xylene concentration in feed gas
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　図２は、表１の結果をもとに、水素ガス共存下の３００℃におけるパラキシレンの透過速度と純度との関係を示した図である。図３は、表２の結果をもとに、水素ガス共存下の３５０℃におけるパラキシレンの透過速度と純度との関係を示す図である。図４は、表３の結果をもとに、水素ガス共存下の４００℃におけるパラキシレンの透過速度と純度との関係を示す図である。各曲線は、表のデータを点でプロットして、近似曲線で結んだものである。各曲線上のプロットは、上から下に行くにつれて、全圧が増大している。 FIG. 2 is a graph showing the relationship between the transmission rate and purity of paraxylene at 300 ° C. in the presence of hydrogen gas based on the results in Table 1. FIG. 3 is a diagram showing the relationship between the permeation rate and purity of paraxylene at 350 ° C. in the presence of hydrogen gas based on the results in Table 2. FIG. 4 is a diagram showing the relationship between the transmission rate and purity of paraxylene at 400 ° C. in the presence of hydrogen gas based on the results in Table 3. Each curve is obtained by plotting the data in the table with dots and connecting with approximate curves. The plot on each curve shows the total pressure increasing from top to bottom.
　これらの図において、全圧０．３ＭＰａの水素ガスを共存していない比較例（×印の点）と対比してみると、キシレン混合流体に水素ガスを共存させて分離を行うことによって、パラキシレンの純度において、またはパラキシレンの純度と透過速度の両者において、性能が向上することが分かる。 In these figures, when compared with the comparative example in which hydrogen gas with a total pressure of 0.3 MPa does not coexist (points marked with x), the separation is performed by allowing hydrogen gas to coexist in the xylene mixed fluid. It can be seen that performance improves in xylene purity or in both paraxylene purity and permeation rate.
　また、全圧が増大するに従って、純度は一様に低下する傾向があるのに対して、分離膜の温度が３５０℃のときに、透過速度は極大値を有する場合があることが分かる。 Also, it can be seen that the purity tends to decrease uniformly as the total pressure increases, whereas the permeation rate may have a maximum value when the temperature of the separation membrane is 350 ° C.
　図５は、表２の一部と表４の結果をもとに、水素ガス、アルゴンガスまたはメタンガス共存下の３５０℃におけるパラキシレンの透過速度と純度との関係を示す図である。キシレン混合流体（Ａ）と無機ガス／低級炭化水素（Ｂ）の混合比率は５０／５０として、無機ガスの違いによるパラキシレンの分離性能の差を示している。水素ガスの方がアルゴンガスまたはメタンガスよりも純度に優れていることが分かる。 FIG. 5 is a diagram showing the relationship between the transmission rate and purity of paraxylene at 350 ° C. in the presence of hydrogen gas, argon gas or methane gas based on a part of Table 2 and the results of Table 4. The mixing ratio of xylene mixed fluid (A) and inorganic gas / lower hydrocarbon (B) is 50/50, which shows the difference in separation performance of paraxylene due to the difference in inorganic gas. It can be seen that hydrogen gas is superior in purity to argon gas or methane gas.
　また、表１～表４から分かるように、パラキシレン／メタキシレン分離係数、パラキシレン／オルトキシレン分離係数はいずれも、同一の圧力のときで比較すると、キシレン混合流体に水素ガスまたはアルゴンガスを共存させて分離を行うことによって、性能が向上していることが分かる。 As can be seen from Tables 1 to 4, the paraxylene / metaxylene separation factor and the paraxylene / orthoxylene separation factor were compared with each other at the same pressure. It can be seen that the performance is improved by performing the separation in the coexistence.
　１０　分離セル
　１１　ゼオライト膜複合体
　２０　ボンベ
　２１　ポンプ
　２２　供給液タンク
　２３　ボンベ
　２４　ボンベ
　２５　背圧弁
　２６　ガスクロマトグラフ DESCRIPTION OF SYMBOLS 10 Separation cell 11 Zeolite membrane composite 20 Cylinder 21 Pump 22 Supply liquid tank 23 Cylinder 24 Cylinder 25 Back pressure valve 26 Gas chromatograph

Claims (6)

  1. 　多孔質支持体上に成膜したゼオライト膜複合体を用いて、少なくともオルトキシレン、メタキシレンおよびパラキシレンを含む混合流体からパラキシレンを選択的に分離してパラキシレンを製造する方法であって、前記混合流体に無機ガスおよび低級炭化水素から選ばれる少なくとも１つを１～８０ｍｏｌ％共存させて分離を行うパラキシレンの製造方法。 A method for producing para-xylene by selectively separating para-xylene from a mixed fluid containing at least ortho-xylene, meta-xylene and para-xylene using a zeolite membrane composite film formed on a porous support, A method for producing para-xylene, wherein the mixed fluid is separated in the presence of 1 to 80 mol% of at least one selected from inorganic gas and lower hydrocarbon.
  2. 　前記ゼオライトが、ＭＦＩ型ゼオライトである請求項１に記載のパラキシレンの製造方法。 The method for producing paraxylene according to claim 1, wherein the zeolite is MFI type zeolite.
  3. 　前記ＭＦＩ型ゼオライトが、ｓｉｌｉｃａｌｉｔｅ－１である請求項２に記載のパラキシレンの製造方法。 The method for producing paraxylene according to claim 2, wherein the MFI-type zeolite is silicalite-1.
  4. 　前記無機ガスが、ヘリウム、アルゴン、窒素、水素、一酸化炭素、二酸化炭素および酸素から選ばれるいずれか１つ以上であり、前記低級炭化水素が、メタン、エタン、エチレン、プロパン、プロピレン、ブタン、ブテンおよびブタジエンから選ばれるいずれか１つ以上である請求項１～３のいずれか１項に記載のパラキシレンの製造方法。 The inorganic gas is one or more selected from helium, argon, nitrogen, hydrogen, carbon monoxide, carbon dioxide and oxygen, and the lower hydrocarbon is methane, ethane, ethylene, propane, propylene, butane, The method for producing para-xylene according to any one of claims 1 to 3, which is at least one selected from butene and butadiene.
  5. 　得られたパラキシレンの全キシレンに対する純度が８４ｍｏｌ％以上であり、かつ得られたパラキシレンの透過速度が５０ｇ・ｍ－２・ｈ－１以上である請求項１～３のいずれか１項に記載のパラキシレンの製造方法。 The purity of the obtained paraxylene with respect to the total xylene is 84 mol% or more, and the permeation rate of the obtained paraxylene is 50 g · m -2 · h -1 or more. The manufacturing method of the para-xylene of description.
  6. 　前記分離を、温度２５０～４５０℃、全圧０．１～０．５ＭＰａで行う請求項１～３のいずれか１項に記載のパラキシレンの製造方法。 The method for producing para-xylene according to any one of claims 1 to 3, wherein the separation is performed at a temperature of 250 to 450 ° C and a total pressure of 0.1 to 0.5 MPa.
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