Method for producing lower olefins

Abstract

To provide CON-type zeolite which can achieve a long life as a catalyst.SOLUTION: There is provided a method for producing CON-type zeolite including a step of treating CON-type zeolite with an aqueous fluoride solution. Preferably, the CON-type zeolite is treated with an aqueous fluoride solution in the presence of an organic structure-directing agent. There is provided a method for producing lower olefin comprising a step of contacting a raw material containing methanol and / or dimethyl ether with a catalyst containing a CON-type zeolite produced by the method.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing CON-type zeolite, and more particularly to a method for producing CON-type zeolite capable of achieving a longer service life when used as a catalyst. The present invention also relates to a method for producing lower olefins using a catalyst containing CON-type zeolite produced by this method. In the present specification, lower olefins mean ethylene, propylene, and butene. In other words, they are olefins having 2 to 4 carbon atoms.

Background Art

[0002] As methods for producing lower olefins such as ethylene, propylene, and butene, steam cracking of naphtha and fluid catalytic cracking of vacuum gas oil have been generally carried out conventionally. In recent years, a metathesis reaction using ethylene and 2-butene as raw materials and an MTO (methanol to olefin) process using methanol and / or dimethyl ether as raw materials are known.

[0003] For example, as disclosed in Patent Document 1, by using a catalyst containing zeolite having a CON-type structure (CIT-1 zeolite) as an active ingredient with methanol and / or dimethyl ether as raw materials, propylene and butene can be produced in high yields, and furthermore, the by-production of ethylene during propylene production can be suppressed.

[0004] In addition, Patent Document 2 proposes a CON-type zeolite catalyst capable of maintaining a high raw material conversion rate over a long period of time. In nitrogen adsorption-desorption measurement, the ratio (A2 / A1) of the BET specific surface area (A2) calculated by the BET plot to the external surface area (A1) calculated by the t-plot is 10 or less, and the BET specific surface area (A2) is 620 m 2 / g or more, or a CON-type zeolite in which (A2 / A1) is 7 or less and the BET specific surface area (A2) is 400 m 2 / g or more. In Non-Patent Document 1, it is reported that by performing hydrothermal treatment on zeolite in the presence of ammonium fluoride and tetraethylammonium hydroxide, the hydrothermal stability at high temperatures is improved and the crystal structure is less likely to break. However, Non-Patent Document 1 does not mention applying this treatment to CON-type zeolite, nor does it mention the catalyst life in the production of lower olefins.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Patent Documents 1 and 2 disclose that lower olefins can be produced in high yields and that a high raw material conversion rate can be maintained for a long time. However, for CON-type zeolite, further improvement in life is required to reduce the frequency of catalyst regeneration. Also, a method for producing CON-type zeolite that can improve the life of relatively short-lived raw powder by post-treatment is needed.

[0008] The present invention aims to solve the above problems and has an object of providing a CON-type zeolite capable of achieving a long life as a catalyst.

Means for Solving the Problems

[0009] The inventors of the present invention have conducted studies to solve the above problems and found that by treating CON-type zeolite by contacting it with a fluoride, a CON-type zeolite capable of achieving a longer lifespan as a catalyst can be provided, thus completing the present invention.

[0010] The present invention includes the following gist. [1] A method for producing a CON-type zeolite, comprising a step of treating the CON-type zeolite with an aqueous fluoride solution. [2] The method for producing a CON-type zeolite according to [1], comprising a step of treating the CON-type zeolite with the aqueous fluoride solution in the presence of an organic structure-directing agent. [3] The method for producing a CON-type zeolite according to [1] or [2], comprising a step of treating the CON-type zeolite with the aqueous fluoride solution after subjecting the CON-type zeolite to pulverization and recrystallization treatment. [4] A method for producing a lower olefin, comprising a step of contacting a raw material containing methanol and / or dimethyl ether with a catalyst containing a CON-type zeolite produced by the production method according to any one of [1] to [3].

Effects of the Invention

[0011] According to the present invention, a method for producing a CON-type zeolite capable of achieving a longer lifespan as a catalyst can be provided. Furthermore, a method for producing a lower olefin using the zeolite as a catalyst can be provided.

Brief Description of the Drawings

[0012]

Figure 1

Modes for Carrying Out the Invention

[0013] The present invention will be described in detail below. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents, and various modifications can be made and implemented within the scope of the gist thereof.

[0014] [CON-type zeolite] The present invention relates to a method for producing a CON-type zeolite, and more particularly, to a method for producing a CON-type zeolite capable of achieving a longer catalyst life as a catalyst and a method for producing a lower olefin using the same. Hereinafter, the CON-type zeolite applied to the method for producing the CON-type zeolite of the present invention may be referred to as "the CON-type zeolite of the present embodiment".

[0015] The CON-type zeolite is a zeolite having a three-dimensional pore structure in which two 12-membered ring structures and one 10-membered ring structure intersect as its structural unit. The CON-type zeolite having this 12-membered ring structure is advantageous in the intracrystalline diffusion of the reaction product as compared with the CHA-type zeolite composed only of 8-membered ring structures and the MFI-type zeolite composed only of 10-membered ring structures. In addition, the CON-type zeolite has a structure in which the 12-membered ring structure and the 10-membered ring structure intersect in a zigzag manner, and the three-directional pores do not intersect at one point, so the space of the intersection is small, coke generated by the reaction is less likely to be generated, and a significant decrease in reaction activity is less likely to occur. It has the advantage of a long catalyst life.

[0016] The composition of the CON-type zeolite of the present embodiment is not particularly limited, but it preferably contains silicon (Si) and aluminum (Al) as constituent elements. When it contains elements other than Si and Al, the other elements are not particularly limited, but for example, boron (B), titanium (Ti), vanadium (V), iron (Fe), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), tin (Sn) One or more selected from the group may be mentioned.

[0017] Specifically preferred examples include crystalline galloaluminosilicates containing Ga in addition to crystalline aluminosilicates containing Si and Al as constituent elements. In these zeolites, Al and Ga within the zeolite framework serve as acid sites and function as active sites for catalytic reactions, thus exhibiting excellent catalytic activity.

[0018] In addition, CON-type zeolites can be easily obtained by adding a boron compound to the raw material gel described later, so they may contain B (boron) as a constituent element. Examples of such zeolites include crystalline borosilicate aluminosilicates containing Si, Al, and B as constituent elements, and crystalline galloborosilicate aluminosilicates further containing Ga.

[0019] In the case of the crystalline aluminosilicates and crystalline galloaluminosilicates, the ratio of their constituent elements is not particularly limited. However, the Si / Al molar ratio or Si / Ga molar ratio is usually 5 or more, preferably 10 or more, more preferably 25 or more, still more preferably 50 or more, particularly preferably 100 or more, and most preferably 200 or more, and is usually 5000 or less, preferably 1000 or less, and more preferably 500 or less. By setting the Si / Al molar ratio or Si / Ga molar ratio within such a range, a zeolite catalyst having sufficient catalytic activity and an improved catalyst life can be obtained.

[0020] When the CON-type zeolite of this embodiment contains B, the Si / B molar ratio is not particularly limited, but is usually 3 or more, preferably 5 or more, more preferably 10 or more, still more preferably 20 or more, and the upper limit may be, for example, 100000 or less, 50000 or less, or 10000 or less.

[0021] It should be noted that the contents of Si, Al, Ga, B, etc. in the CON-type zeolite of this embodiment are usually values measured for CON-type zeolites produced by inductively coupled plasma atomic emission spectrometry (ICP-AES) or the like, and are not the ratios of the raw material charges.

[0022] The ion exchange sites of the CON-type zeolite of this embodiment are not particularly limited and may be of the H-type or exchanged with metal ions. Here, the metal ions are specifically alkali metal ions, alkaline earth metal ions, cerium, tungsten, manganese, iron, etc.

[0023] The micropore volume of the CON-type zeolite of this embodiment is not particularly limited, usually 0.1 ml / g or more, preferably 0.15 ml / g or more, more preferably 0.20 ml / g or more, and usually 3 ml / g or less, preferably 2 ml / g or less.

[0024] The average primary particle diameter of the CON-type zeolite of this embodiment is not particularly limited, usually 3 μm or less, preferably 1 μm or less, more preferably 700 nm or less, still more preferably 300 nm or less, and particularly preferably 200 nm or less. Also usually 20 nm or more, preferably 40 nm or more. Here, the average primary particle diameter of the CON-type zeolite can be determined by a scanning electron microscope (SEM).

[0025] [Method for Producing CON-Type Zeolite] Hereinafter, a method for producing the CON-type zeolite of this embodiment will be described.

[0026] CON-type zeolite can generally be prepared by a hydrothermal synthesis method. For example, an alkali source, an organic structure-directing agent, preferably N,N,N-trimethyl-(-)-cis-myrtanilammonium hydroxide, is added to water and stirred, and further, an aluminum source, a gallium source, a boron source, a silica source, etc. are added to generate a uniform gel. The obtained raw material gel is kept at 120 to 240 °C in a pressure heating container such as an autoclave for crystallization. During crystallization, a seed crystal may be added as needed, and from the viewpoint of productivity, it is preferable to add a seed crystal in terms of improving operability. As the seed crystal, it is preferable to use CON-type zeolite or BEA-type zeolite, and particularly preferably CON-type zeolite. Also, during this crystallization, it is preferable to add a surfactant to the raw material gel. By adding a surfactant, the zeolite is micronized, and it becomes easier to adjust the average primary particle diameter, etc. to a desired range.

[0027] As the surfactant, a cationic surfactant, an anionic surfactant, a nonionic surfactant, an amphoteric surfactant, etc. can be used alone or in combination. As the surfactant, a cationic surfactant that acts as a suitable crystal growth inhibitor is preferable. As an example, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium hydroxide, etc. can be mentioned.

[0028] The addition amount of the surfactant to the raw material gel is not particularly limited, but as a molar ratio to Si in the raw material gel, it is preferably 0.001 or more, more preferably 0.002 or more, particularly preferably 0.005 or more, and also preferably 0.05 or less, more preferably 0.03 or less, particularly preferably 0.015 or less.

[0029] After the crystallization of the raw material gel, the crystallized raw material gel is filtered and washed, then the solid content is dried at 100 - 200 °C, and subsequently calcined at 400 - 900 °C, whereby zeolite powder can be obtained.

[0030] As the silica source used for preparing the raw material gel, one or more of fumed silica, silica sol, silica gel, silicates such as silicon dioxide and water glass, alkoxides of silicon such as tetraethoxysilicate and tetramethoxysilane, and halides of silicon can be used. As the aluminum source, one or more of aluminum sulfate, aluminum nitrate, boehmite, aluminum alkoxide, aluminum hydroxide, alumina sol, sodium aluminate, etc. can be used. As the gallium source, one or more of gallium nitrate, gallium sulfate, gallium phosphate, gallium chloride, gallium bromide, gallium hydroxide, etc. can be used. As the boron source, one or more of boric acid, sodium borate, boron oxide, etc. can be used.

[0031] There is no particular limitation on the molar ratio (Si / Al) of silicon (Si) to aluminum (Al) in the CON-type zeolite used as the seed crystal, but it is preferably in the range of 25 to 10,000. Also, the seed crystal is preferably used in an amount of about 1 to 20% by mass based on the silica source to be added.

[0032] The content of the metal contained in the CON-type zeolite can be adjusted by adjusting the amounts of the constituent elements (Si, Al, Ga, B, etc.) during synthesis. Also, those in which the content is adjusted by removing a part of the constituent elements by steaming, acid treatment, etc. can also be used.

[0033] In this embodiment, an alkali treatment may be performed in which the CON-type zeolite prepared by hydrothermal synthesis is treated with an alkali in the presence of a surfactant. It is considered that the zeolite is mesostructured by the alkali treatment and its lifespan is improved.

[0034] As the surfactant used in the alkali treatment step, a cationic surfactant, an anionic surfactant, a nonionic surfactant, an amphoteric surfactant, etc. can be used alone or in combination. As an example, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium hydroxide, etc. can be mentioned. The concentration of the surfactant in the alkali treatment step is not particularly limited, and it can be contained in the treatment liquid at about 0.1 to 10% by mass.

[0035] The alkali for the alkali treatment is not particularly limited, and an ammonia solution, a sodium hydroxide solution, etc. can be used, and the degree of the alkali is not particularly limited either. For example, a pH of about 9 to 12 is sufficient. For the alkali treatment, the CON-type zeolite may be brought into contact with an alkali, or it may be stirred in an alkali solution containing a surfactant. Also, the temperature of the alkali treatment is not particularly limited, and for example, it may be about 100 to 200 °C. The time of the alkali treatment is not particularly limited either, and it may be immersed in an alkali solution containing a surfactant for 0.1 to 24 hours. It is desirable to dry after the alkali treatment, perform calcination again for use as a catalyst, and remove the incorporated surfactant.

[0036] In the present invention, the CON-type zeolite thus obtained is treated with an aqueous fluoride solution (hereinafter, this treatment may be referred to as "fluoride treatment"). By performing the fluoride treatment, it is presumed that defects are repaired, coking of the catalyst is suppressed, and the lifetime is improved. Specifically, the fluoride treatment can be performed by putting the CON-type zeolite of the present embodiment into an aqueous fluoride solution and performing heat treatment.

[0037] Note that the CON-type zeolite to be subjected to the fluoride treatment according to the present invention is the CON-type zeolite produced as described above. However, the fluoride treatment according to the present invention may be performed on the as-made type zeolite before calcination and removal of the organic structure directing agent, or may be performed on zeolites such as Na type, NH4 type, and H type after calcination and removal of the organic structure directing agent. From the viewpoint of simplifying the catalyst production process, it is preferable to perform the treatment on the as-made type zeolite. Hereinafter, the CON-type zeolite to be subjected to the fluoride treatment according to the present invention may be referred to as "the CON-type zeolite to be treated".

[0038] In the present invention, the fluoride used for the fluoride treatment is not particularly limited as long as it is a compound containing fluorine, but those that generate fluoride ions in the liquid as an aqueous solution, such as ammonium fluoride, hydrogen fluoride, sodium fluoride, and potassium fluoride, are preferable. These fluorides may be used alone or in combination of two or more. Among these fluorides, ammonium fluoride is preferable from the viewpoints of solubility and safety.

[0039] There is no particular limitation on the fluoride concentration in the aqueous fluoride solution, but it is preferably 0.001 or more, more preferably 0.005 or more, and still more preferably 0.01 or more in terms of the molar ratio of fluoride to water. If the fluoride concentration is at or above the above lower limit, the above effects by performing the fluoride treatment can be obtained more effectively. On the other hand, the molar ratio of fluoride to water is preferably 1 or less, more preferably 0.3 or less, and still more preferably 0.1 or less. If the fluoride concentration is at or below the above upper limit, the above effects can be effectively obtained while maintaining crystallinity.

[0040] There is no particular limitation on the treatment temperature (the temperature of the aqueous fluoride solution) with the aqueous fluoride solution, but it is preferably 70°C or higher, more preferably 100°C or higher, and still more preferably 150°C or higher. If the treatment temperature is at or above the above lower limit, the above effects by performing the fluoride treatment can be obtained more effectively. On the other hand, the treatment temperature is preferably 200°C or lower, more preferably 180°C or lower, and still more preferably 170°C or lower. If the treatment temperature is at or below the above upper limit, the above effects can be effectively obtained while maintaining crystallinity.

[0041] There is no particular limitation on the treatment time with the aqueous fluoride solution, but it is preferably 3 hours or more, more preferably 10 hours or more, and still more preferably 15 hours or more. If the treatment time is at or above the above lower limit, the above effects by performing the fluoride treatment can be obtained more effectively. On the other hand, the treatment time is preferably 100 hours or less, more preferably 50 hours or less, and still more preferably 30 hours or less. If the treatment time is at or below the above upper limit, the above effects can be effectively obtained while maintaining crystallinity.

[0042] The amount of the fluoride aqueous solution used for the fluoride treatment is not particularly limited, but it is preferably 1 g or more, more preferably 1.5 g or more, and still more preferably 2 g or more as the amount of the aqueous solution containing fluoride per 1 g of the CON-type zeolite to be treated. If the amount of the fluoride aqueous solution is not less than the above lower limit, the above effects by performing the fluoride treatment can be obtained more effectively. On the other hand, the amount of the fluoride aqueous solution is preferably 100 g or less, more preferably 50 g or less, and still more preferably 10 g or less as the amount of the aqueous solution containing fluoride per 1 g of the CON-type zeolite to be treated. If the amount of the fluoride aqueous solution is not more than the above upper limit, the above effects can be effectively obtained while maintaining the crystallinity.

[0043] In addition, in the fluoride treatment, it is preferable to coexist an organic structure-directing agent and perform the fluoride treatment in the presence of the organic structure-directing agent. By performing the fluoride treatment in the presence of the organic structure-directing agent, the above effects can be effectively obtained while maintaining the crystallinity. Examples of the organic structure-directing agent used in this case include ammonium salts or amines having 1 to 50 carbon atoms such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-propylammonium hydroxide, N,N,N-trimethyl-(-)-cis-myrtanilammonium hydroxide. These organic structure-directing agents may be used alone or in combination of two or more.

[0044] Among these, tetraethylammonium hydroxide (TEAOH), N,N,N-trimethyl-(-)-cis-myrtanilammonium hydroxide (TMMAOH), etc. are preferable because they make it easier to maintain the crystallinity of the CON-type zeolite.

[0045] When performing the fluoride treatment in the presence of the organic structure-directing agent, the organic structure-directing agent may be added to the fluoride aqueous solution to use a fluoride aqueous solution containing the organic structure-directing agent. In this case, there is no particular limitation on the concentration of the organic structure-directing agent in the aqueous fluoride solution, but it is preferably 0.001 or more, more preferably 0.003 or more, and still more preferably 0.005 or more in terms of the molar ratio of the organic structure-directing agent to water. If the concentration of the organic structure-directing agent is at or above the above lower limit, the above effects by the presence of the organic structure-directing agent can be obtained more effectively. On the other hand, the concentration of the organic structure-directing agent is preferably 1 or less, more preferably 0.2 or less, and still more preferably 0.07 or less in terms of the molar ratio of the organic structure-directing agent to water. If the concentration of the organic structure-directing agent is at or below the above upper limit, the above effects can be effectively obtained while maintaining crystallinity. From the same viewpoint as above, the organic structure-directing agent is preferably 0.01 to 10, particularly 0.05 to 5, and especially 0.1 to 1 in terms of the molar ratio to the fluoride in the aqueous solution.

[0046] In the present invention, it is also preferable to perform the above fluoride treatment after pulverizing and recrystallizing the CON-type zeolite to be treated. By performing the pulverizing and recrystallizing treatment, the crystallinity can be enhanced while reducing the primary particle size.

[0047] In this case, for the pulverization of the CON-type zeolite to be treated, a ball mill, a bead mill, a jet mill, or the like can be used. Among these, a bead mill is preferable because it is suitable for the refinement of the CON-type zeolite. That is, the average primary particle size of the dried CON-type zeolite usually produced by the above-described method is in the range of 20 nm to 3 μm as described above. However, by pulverizing the average primary particle size of such CON-type zeolite to preferably 300 nm or less, more preferably 200 nm or less, the external surface area of the CON-type zeolite can be increased. The lower limit of the average primary particle size of the pulverized CON-type zeolite is usually about 20 nm, and if it is pulverized more finely than this, the crystallinity may decrease.

[0048] The recrystallization treatment of the pulverized CON-type zeolite can be carried out by filtering the slurry after the hydrothermal synthesis of the zeolite into a solid phase and a liquid phase (hereinafter referred to as the supernatant), adding the pulverized CON-type zeolite to the supernatant, and performing a heat treatment under the recrystallization treatment conditions described below, for example. The aqueous solution used for recrystallization may be the supernatant as it is, or an aqueous solution separately prepared by adding a silica source, an aluminum source, an organic structure-directing agent, etc. In addition, the recrystallization treatment may be carried out two or more times to improve the crystallinity.

[0049] <Recrystallization treatment conditions> Temperature: Usually 100~220 °C, preferably 140~200 °C Treatment time: Usually 1~120 hours, preferably 10~24 hours Treatment container: There is no particular limitation, but when the temperature is 100 °C or higher, it is preferable to use a sealed pressure-resistant container, for example, a sealed autoclave. The amount of the pulverized CON-type zeolite in the supernatant is preferably about 5~50 g with respect to 100 mL of the supernatant.

[0050] [Catalyst] The CON-type zeolite produced by performing a fluoride treatment by the method for producing a CON-type zeolite of the present invention can be used as a catalyst. In particular, the CON-type zeolite produced by the method for producing a CON-type zeolite of the present invention is useful as a catalyst used in a reaction for producing lower olefins (hereinafter, the catalyst containing the CON-type zeolite produced by the method for producing a CON-type zeolite of the present invention may be referred to as the "CON-type zeolite catalyst of the present invention"). The uses of the CON-type zeolite catalyst of the present invention are not limited to the catalyst for producing lower olefins, and it is also preferably used for the production of p-xylene, the production of ethylbenzene and cumene, the aromatization of light hydrocarbons, hydrocracking, hydrodewaxing, the isomerization of alkanes, and the purification of automobile exhaust gases.

[0051] The CON-type zeolite produced by the method for producing a CON-type zeolite of the present invention may be directly used in the reaction as the CON-type zeolite catalyst of the present invention, or may be used as a mixture with other substances inert to the reaction, such as compounds containing alkaline earth metals or silicon, or may be granulated or formed using a binder and then used in the reaction. Examples of the substances inert to the reaction and the binder include alumina or alumina sol, silica, silica gel, silicate, quartz, and mixtures thereof. Among these, silica is preferred in that it is expected to have excellent strength and catalyst performance as an industrial catalyst. Mixing with these substances is also effective for reducing the cost of the entire catalyst, increasing the density of the catalyst, and increasing the catalyst strength.

[0052] In the method for producing lower olefins using the CON-type zeolite catalyst of the present invention, examples of the raw materials include, but are not limited to, methanol and dimethyl ether, and can be appropriately selected according to the type of the target olefin.

[0053] Hereinafter, the method for producing lower olefins using the above catalyst will be described by way of example when the raw materials are methanol and / or dimethyl ether.

[0054] [Method for Producing Lower Olefins] Another embodiment of the method for producing lower olefins of the present invention comprises a step of bringing the above-mentioned CON-type zeolite catalyst of the present invention into contact with a raw material containing methanol and / or dimethyl ether.

[0055] The origin of the methanol and dimethyl ether used as raw materials is not particularly limited. For example, those obtained by the hydrogenation reaction of a mixed gas of hydrogen / CO derived from coal, natural gas, and by-products in the iron and steel industry, those obtained by the reforming reaction of plant-derived alcohols, those obtained by the fermentation method, those obtained from organic substances such as recycled plastics and municipal waste, those obtained by the methanol synthesis reaction using carbon dioxide as a raw material, etc. may be mentioned. At this time, those in a state where compounds other than methanol and dimethyl ether resulting from each production method are arbitrarily mixed may be used as they are, or purified ones may be used. In addition, as the reaction raw material, only methanol may be used, only dimethyl ether may be used, or these may be mixed and used. When methanol and dimethyl ether are mixed and used, there is no limitation on the mixing ratio.

[0056] As the reaction mode in this embodiment, there is no particular limitation as long as the methanol and / or dimethyl ether feedstock is in the gas phase in the reaction zone, and a known gas-phase reaction process using a fluidized bed reactor, a moving bed reactor, or a fixed bed reactor can be applied. In the case of a fixed bed reactor, it is particularly advantageous in terms of equipment cost including auxiliary equipment, catalyst cost, and operation management. Also, it can be carried out in any form of batch, semi-continuous, or continuous, but it is preferably carried out in a continuous manner, and the method may be a method using a single reactor or a method using a plurality of reactors arranged in series or parallel.

[0057] When filling the above-mentioned catalyst into a fixed bed reactor, in order to suppress the temperature distribution of the catalyst layer to a small extent, particulate matter inert to the reaction such as quartz sand, alumina, silica, silica-alumina, etc. may be mixed with the catalyst and filled. In this case, the amount of particulate matter inert to the reaction such as quartz sand is not particularly limited. In addition, this particulate matter preferably has a particle size similar to that of the catalyst in terms of uniform mixing property with the catalyst. In addition, the reactor may supply the reaction substrate (reaction raw material) in a divided manner for the purpose of dispersing the heat generated by the reaction.

[0058] There is no particular limitation regarding the total concentration (substrate concentration) of methanol and dimethyl ether in all the feed components supplied to the reactor, but the sum of methanol and dimethyl ether is preferably 90 mol% or less in all the feed components. More preferably, it is 10 mol% or more and 70 mol% or less.

[0059] In the reactor, in addition to methanol and / or dimethyl ether, gases inert to the reaction (also referred to as diluents), such as helium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, water, hydrocarbons such as paraffins and methane, aromatic compounds, and mixtures thereof, can be present. Among these, it is preferable that water (steam) coexists because the separation is good. As such a diluent, the impurities contained in the reaction raw materials may be used as they are, or a separately prepared diluent may be mixed with the reaction raw materials and used. Also, the diluent may be mixed with the reaction raw materials before being put into the reactor, or may be supplied to the reactor separately from the reaction raw materials.

[0060] The lower limit of the reaction temperature is usually about 200°C or higher, preferably 300°C or higher, more preferably 400°C or higher, still more preferably 450°C or higher, and particularly preferably 500°C or higher. The upper limit of the reaction temperature is usually 750°C or lower, preferably 700°C or lower, and more preferably 600°C or lower. If the reaction temperature is too low, the reaction rate is low, and there is a tendency for a large amount of unreacted raw materials to remain, and the yield of lower olefins also decreases. On the other hand, if the reaction temperature is too high, it is difficult to obtain the stable activity of the catalyst, and the yield of lower olefins decreases significantly. Here, the reaction temperature refers to the temperature at the outlet of the catalyst layer.

[0061] The upper limit of the reaction pressure is usually 5 MPa (absolute pressure, the same hereinafter) or less, preferably 1 MPa or less, more preferably 0.7 MPa or less, still more preferably 0.5 MPa or less, and particularly preferably 0.3 MPa or less. The lower limit of the reaction pressure is not particularly limited, but is usually 0.1 kPa or more, preferably 7 kPa or more, and more preferably 50 kPa or more. If the reaction pressure is too high, the amount of undesirable by-products such as paraffins and aromatic compounds increases, and the yield of lower olefins tends to decrease. If the reaction pressure is too low, the reaction rate tends to be slow.

[0062] As the reactor outlet gas (reactor effluent), a mixed gas containing lower olefins as reaction products, by-products, and diluents can be obtained. The lower olefin concentration in the mixed gas is usually 5 to 95% by mass. Depending on the reaction conditions, methanol and / or dimethyl ether may be contained as unreacted raw materials in the reaction product, but it is preferable to carry out the reaction under reaction conditions such that the conversion rates of methanol and / or dimethyl ether reach 100%. Thereby, the separation of the reaction product and the unreacted raw materials becomes easy, preferably unnecessary. Examples of the by-products include olefins having 5 or more carbon atoms, paraffins, aromatic compounds, and water.

[0063] The mixed gas containing lower olefins as reaction products, unreacted raw materials, by-products, and diluents as the reactor outlet gas may be introduced into known separation and purification equipment, and recovery, purification, recycling, and discharge treatments may be carried out according to each component.

Examples

[0064] Hereinafter, the present invention will be described in more detail with reference to examples, but it goes without saying that the scope of the present invention is not limited to the following examples only.

[0065] [Example 1] <Preparation of raw material gel> 3.17 g of sodium hydroxide, 177.81 g of an aqueous solution of N,N,N-trimethyl-(-)-cis-myrtanilammonium hydroxide (TMMAOH) with a mass percentage of 30%, and 181.10 g of water were mixed. To this, 3.09 g of boric acid (H3BO3) and 1.00 g of aluminum sulfate were added and stirred. After that, 247.91 g of Cataloid SI-30 (colloidal silica manufactured by JGC Catalysts and Chemicals Ltd., 30.3 mass% SiO2, 0.41 mass% Na2O, 69.29 mass% H2O) was added as a silica source and stirred well. Further, 1.51 g of CON-type zeolite was added as a seed crystal, and the raw material gel was prepared by stirring.

[0066] <Preparation of Zeolite Powder (A)> The obtained raw material gel was charged into an autoclave and heated at 170 °C for 4 days. The product was separated into a solid phase and a liquid phase (hereinafter, supernatant) by filtration. The solid was washed with water and then dried at 100 °C to obtain a white powder. From the X-ray diffraction (XRD) pattern of the product, it was confirmed that the obtained product was CON-type zeolite. This white powder was designated as "zeolite powder (A)".

[0067] <Grinding and Recrystallization> 100 g of water was added to 20 g of zeolite powder (A), and bead milling was performed for 30 minutes using LMZ05 manufactured by Asizawa Fine Tech Co., Ltd. and zirconia beads with a particle size of 300 μm. To 0.2 g of the obtained powder, 2.0 g of the supernatant concentrated 1.25-fold by a rotary evaporator was added, and it was heated at 170 °C for 16 hours using an autoclave. Further, to 0.2 g of the separated and recovered powder, 2.0 g of the supernatant concentrated 1.67-fold was added, and it was heated at 140 °C for 20 hours using an autoclave. The obtained product was filtered, washed with water, and then dried at 100 °C to obtain a white powder. From the X-ray diffraction (XRD) pattern of the white powder obtained by this grinding and recrystallization, it was confirmed that the obtained white powder was CON-type zeolite. This white powder was designated as "zeolite powder (B)".

[0068] <Fluoride Treatment> To 2.0 g of zeolite powder (B), which is the obtained pulverized and recrystallized zeolite, 4.0 g of an aqueous solution of ammonium fluoride / tetraethylammonium hydroxide (0.1 tetraethylammonium hydroxide / 0.74 ammonium fluoride / 15.19 water in molar ratio) was added, and the mixture was heated at 170 °C for 24 hours while rotating at 22 rpm. The product was filtered, washed with water, and then dried at 100 °C to obtain a white powder. From the X-ray diffraction (XRD) pattern of the product, it was confirmed that the obtained product was a CON-type zeolite.

[0069] <Firing and Ion Exchange Treatment> After drying the obtained product, it was fired at 600 °C for 6 hours in an air atmosphere to obtain sodium-type zeolite powder. The obtained powder was subjected to ion exchange in a 1N ammonium nitrate aqueous solution at 80 °C for 1 hour, and then filtered. The filtered powder was again subjected to ion exchange in a 1N ammonium nitrate aqueous solution at 80 °C for 1 hour, and then filtered and dried to obtain ammonium-type zeolite powder. Then, it was fired at 500 °C for 6 hours in an air atmosphere to obtain the proton-type zeolite powder of Example 1.

[0070] [Comparative Example 1] Zeolite powder (A) was subjected to firing and ion exchange treatment in the same manner as in Example 1 to obtain the proton-type zeolite powder of Comparative Example 1.

[0071] [Comparative Example 2] Zeolite powder (B) was subjected to firing and ion exchange treatment in the same manner as in Example 1 to obtain the proton-type zeolite powder of Comparative Example 2.

[0072] The synthesis conditions according to Example 1 and Comparative Examples 1 and 2 were summarized in Table 1.

[0073] [Evaluation of Zeolite] The following evaluations were performed on the CON-type zeolites according to Example 1 and Comparative Examples 1 and 2.

[0074] <Elemental Analysis> Elemental analysis was performed by inductively coupled plasma atomic emission spectrometry (ICP-AES). For the measurement of the CON-type zeolites in Example 1 and Comparative Examples 1 and 2, "iCAP6300" manufactured by Thermo Fisher Scientific was used. The Si / Al molar ratio of the synthesized CON-type zeolite is shown in the column of the elemental analysis results in Table 1.

[0075] <Production of lower olefins> Using the CON-type zeolites obtained in Examples 1 and 2 and Comparative Example 1, the production of lower olefins was carried out. For the reaction, a fixed-bed flow reactor was used, and a quartz reaction tube with an inner diameter of 6 mm was filled with 33 mg of pre-mixed proton-type zeolite powder and 470 mg of quartz sand. A mixed gas of 50 mol% methanol and 50 mol% nitrogen was fed to the reactor so that the weight hourly space velocity of methanol was 15 h -1 -1, and the reaction was carried out at 500 °C and 0.1 MPa (absolute pressure). The products were analyzed by gas chromatography every hour from the start of the reaction. Figure 1 shows a graph representing the change in methanol conversion rate. Table 1 shows the methanol conversion rate (%), ethylene selectivity (C-mol%), propylene selectivity (C-mol%), butene selectivity (C-mol%), and catalyst life (hr) after 2 hours from the start of the reaction. The catalyst life was defined as the time during which the methanol conversion rate was maintained at 99% or more.

[0076]

Table 1

[0077] As shown in Table 1, it can be seen that the CON-type zeolite of Example 1 including the step of treating with an aqueous fluoride solution maintains a high raw material conversion rate for a long period of time.

Claims

1. A method for producing lower olefins, comprising a step of contacting a catalyst containing a CON-type zeolite produced by a method for producing a CON-type zeolite, the method including a step of treating a raw material containing methanol and / or dimethyl ether with an aqueous fluoride solution with respect to the CON-type zeolite.

2. In the method for producing lower olefins according to Claim 1, A method for producing lower olefins, comprising a step of contacting a catalyst containing a CON-type zeolite produced by a method for producing a CON-type zeolite, the method including a step of treating the CON-type zeolite with the aqueous fluoride solution in the presence of an organic structure-directing agent.

3. In the method for producing lower olefins according to Claim 1 or 2, A method for producing lower olefins, comprising a step of contacting a catalyst containing a CON-type zeolite produced by a method for producing a CON-type zeolite, the method including a step of treating the CON-type zeolite with the aqueous fluoride solution after subjecting the CON-type zeolite to pulverization and recrystallization treatment.

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