JP7636213B2 - CON ZEOLITE, PROCESS FOR PRODUCING CON ZEOLITE, AND PROCESS FOR PRODUCING LOWER OLEFINS - Google Patents

Description

The present invention relates to CON-type zeolites, and more specifically to CON-type zeolites that can achieve a long life when used as a catalyst. The present invention also relates to a method for producing lower olefins using the zeolites as catalysts.

Conventionally, methods for producing lower olefins such as ethylene, propylene, and butene have commonly been used, such as steam cracking of naphtha and fluid catalytic cracking of vacuum diesel. In recent years, metathesis reactions using ethylene and 2-butene as raw materials and the MTO (methanol to olefins) process using methanol and/or dimethyl ether as raw materials have become well known.

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

Furthermore, Patent Document 2 proposes a CON-type zeolite having a signal intensity within a specific range in Al ²⁷ -MAS-NMR measurement as a CON-type zeolite catalyst capable of maintaining a high raw material conversion rate over a long period of time.

For example, Patent Documents 3 and 4 and Non-Patent Document 1 report that zeolite is mesostructured by hot water treatment in a pH-controlled medium in the presence of a surfactant, which increases the feedstock conversion rate and the selectivity of components such as gasoline in the catalytic cracking of crude oil. However, there is no mention of its application to CON-type zeolites or the catalyst life in the production of lower olefins.

JP 2013-245163 A International Publication No. 2017/090751 U.S. Patent No. 7,589,041 Patent No. 5481027

Catal. Sci. Technol. , 2, 987-994 (2012)

Patent Documents 1 and 2 disclose that lower olefins can be produced at a high yield and that a high raw material conversion can be maintained. However, the life of CON zeolite as a catalyst is not necessarily sufficient, and it is necessary to frequently switch between reaction gas and regeneration gas for catalyst regeneration.
The present invention is devised to solve the above problems, and has an object to provide a CON-type zeolite that can achieve a long life as a catalyst.

The inventors have conducted research to solve the above problems and have discovered that by optimizing the ratio of the BET specific surface area (A2) to the external surface area (A1) of CON zeolite, it is possible to provide a CON zeolite that can achieve a long life as a catalyst, thus completing the present invention.

The present invention includes the following gist.
[1] A CON-type zeolite in which, in a nitrogen adsorption/desorption measurement, the ratio (A2/A1) of the BET specific surface area (A2) calculated by BET plot to the external surface area (A1) calculated by t plot is 10 or less, and the BET specific surface area (A2) is 620 m ² /g or more.
[2] A CON-type zeolite in which, in a nitrogen adsorption/desorption measurement, the ratio (A2/A1) of the BET specific surface area (A2) calculated by BET plot to the external surface area (A1) calculated by t plot is 7 or less, and the BET specific surface area (A2) is 400 m ² /g or more.
[3] The CON-type zeolite according to [1] or [2], which contains silicon (Si) and aluminum (Al) as constituent elements.
[4] The CON-type zeolite according to [3], wherein the molar ratio (Si/Al) of silicon (Si) to aluminum (Al) is 10 or more.
[5] A method for producing CON zeolite, comprising the steps of:
A method for producing CON type zeolite, comprising an alkali treatment step of treating CON type zeolite under alkaline conditions in the presence of a surfactant.
[6] A method for producing CON zeolite, comprising the steps of:
A method for producing CON-type zeolite, comprising adding a surfactant to a gel that is a raw material for synthesizing zeolite.
[7] The CON-type zeolite according to any one of [1] to [4], which is a catalyst used in a reaction for producing lower olefins.
[8] A method for producing lower olefins, comprising a step of contacting a raw material containing methanol and/or dimethyl ether with the CON-type zeolite according to any one of [1] to [4] and [7].

In this specification, lower olefins refer to ethylene, propylene, and butene. In other words, olefins having 2 to 4 carbon atoms.

According to the present invention, it is possible to provide a CON-type zeolite that can achieve a long life as a catalyst. It is also possible to provide a method for producing a CON-type zeolite that can achieve a long life as a catalyst. Furthermore, it is also possible to provide a method for producing lower olefins using the zeolite as a catalyst.

1 is a graph showing the adsorption/desorption isotherms of CON-type zeolites according to Examples and Comparative Examples. For ease of viewing the graph, the vertical axis is +500, +400, +300, +200, and +100 [ml (STP)/g] for Examples 1 to 3 and Comparative Examples 1 and 2, respectively. The adsorption side is represented by a filled marker, and the desorption side is represented by an unfilled marker. 1 is a graph showing the transition of methanol conversion in the production of lower olefins using the CON-type zeolites according to the examples and comparative examples as catalysts.

The present invention will be described in detail below. However, the following description of the components is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents, and can be implemented in various modifications within the scope of the gist.

One embodiment of the present invention is a CON-type zeolite, in which, in a nitrogen adsorption/desorption measurement, the ratio (A2/A1) of the BET specific surface area (A2) calculated by a BET plot to the external surface area (A1) calculated by a t plot is 10 or less, and the BET specific surface area (A2) is 620 m ² /g or more.
Another embodiment of the present invention is a CON-type zeolite, in which, in a nitrogen adsorption/desorption measurement, the ratio (A2/A1) of the BET specific surface area (A2) calculated by a BET plot to the external surface area (A1) calculated by a t plot is 7 or less, and the BET specific surface area (A2) is 400 m ² /g or more.

CON-type zeolite is a zeolite with a three-dimensional pore structure in which two 12-membered ring structures and one 10-membered ring structure intersect as its constituent units. Compared with CHA-type zeolite, which is composed of only 8-membered ring structures, and MFI-type zeolite, which is composed of only 10-membered ring structures, CON-type zeolite with this 12-membered ring structure has an advantage in that the reaction products diffuse within the pores. In addition, CON-type zeolite has a structure in which 12-membered ring structures and 10-membered ring structures intersect in a zigzag pattern, and pores in three directions do not intersect at one point, so the intersection space is small, coke is unlikely to be generated due to the reaction, and it is thought that the reaction activity is unlikely to decrease significantly, and the catalyst has the advantage of a long life.

In the present embodiment, in a nitrogen adsorption/desorption measurement, the ratio (A2/A1) of the BET specific surface area (A2) calculated by a BET plot to the external surface area (A1) calculated by a t plot is 10 or less, and the BET specific surface area (A2) is 620 ^{m 2} /g or more, or (A2/A1) is 7 or less, and the BET specific surface area (A2) is 400 m ² /g or more.
By having the BET specific surface area (A2) be equal to or greater than the lower limit, sufficient catalytic efficiency can be obtained. Specifically, the BET specific surface area (A2) may be 400 m ² /g or more, in which case it is preferably 500 m ² /g or more, more preferably 550 m ² /g or more, and even more preferably 600 m ² /g or more, and the BET specific surface area (A2) may be 620 m ² /g or more, in which case it is preferably 630 m ² /g or more, and more preferably 640 m ² /g or more. The upper limit is not particularly limited, but is usually 2000 m ² /g or less.

In addition, by having the ratio (A2/A1) of the BET specific surface area (A2) to the external surface area (A1) be equal to or less than the upper limit mentioned above, the catalytic function of the CON-type zeolite is extended in life. (A2/A1) may be 10 or less, in which case it is preferably 9.5 or less, and may be 7 or less, in which case it is preferably 6 or less, more preferably 5 or less, and particularly preferably 4 or less. The lower limit is not particularly limited, but is usually 2 or more.

The BET specific surface area (A2), the ratio (A2/A1) of the BET specific surface area (A2) to the external surface area (A1), and the micropore volume (A3) can be calculated from nitrogen adsorption/desorption measurements, and can be performed using, for example, Belsorp-mini II manufactured by Microtrack-Bell. Data analysis can be performed using analysis software BELMaster manufactured by Microtrack-Bell. Here, the BET specific surface area (A2) is calculated by BET plotting measurement data with a relative pressure (P/P ₀ ) of 0.002 to 0.06. The external surface area (A1) and the micropore volume (A3) are calculated by t-plotting data with a relative pressure (P/P ₀ ) of 0.20 to 0.42. The Harkins-Jura is used as the standard isotherm.

The above value of (A2) and (A2/A1) can be set to a specific range, for example, by using CON-type zeolite as seed crystals, or by including an alkaline treatment step in the production process of CON-type zeolite, in which CON-type zeolite is treated under alkaline conditions in the presence of a surfactant, as described below.

In this embodiment, the CON-type zeolite is not particularly limited as long as it satisfies the above values of (A2) and (A2/A1), but is preferably a crystalline metallosilicate. The elements constituting the metallosilicate are not particularly limited, but may be, for example, one or more selected from aluminum (Al), boron (B), titanium (Ti), vanadium (V), iron (Fe), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), and tin (Sn).

Specific examples of zeolites that are preferred include crystalline aluminosilicates containing Al as a constituent element and crystalline gallosilicates containing Ga. These zeolites have excellent catalytic activity because the Al and Ga in the zeolite framework become acid sites and act as active sites for catalytic reactions. In particular, aluminosilicates containing Al are more desirable from the viewpoint of catalytic activity.

CON-type zeolite can be obtained more easily by adding a boron compound to the raw material gel described below, so it may contain B (boron) as a constituent element. Examples of such zeolite include crystalline boroaluminosilicate containing Al and B as constituent elements, and crystalline galloborosilicate containing Ga and B as constituent elements.

In the case of the crystalline aluminosilicate and crystalline gallosilicate, the ratio of the constituent elements is not particularly limited, but the Si/Al molar ratio or the Si/Ga molar ratio is usually 5 or more, preferably 10 or more, more preferably 25 or more, even more preferably 50 or more, particularly preferably 100 or more, and especially 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 the Si/Ga molar ratio in such a range, a zeolite catalyst having sufficient catalytic activity and further improved catalytic life can be obtained.

In the case of the crystalline boroaluminosilicate and crystalline galloborosilicate, the ratio of the constituent elements is not particularly limited, but like the crystalline aluminosilicate and crystalline gallosilicate, the Si/Al molar ratio or the Si/Ga molar ratio is usually 5 or more, preferably 10 or more, more preferably 25 or more, even more preferably 50 or more, particularly preferably 100 or more, and especially preferably 200 or more, and usually 5000 or less, preferably 1000 or less, and more preferably 500 or less. In addition, the Si/B molar ratio is not particularly limited, but is usually 3 or more, preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more, and the upper limit may be, for example, 100,000 or less, 50,000 or less, or 10,000 or less. The contents of Si, Al, Ga, B, etc. in this embodiment can usually be measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).

The ion exchange sites of CON-type zeolite are not particularly limited, and may be H-type or may be exchanged with metal ions. Here, the metal ions are specifically alkali metal ions, alkaline earth metal ions, etc.

The micropore volume (A3) of the CON-type zeolite used in this embodiment is not particularly limited, but is usually 0.1 ml/g or more, preferably 0.15 ml/g or more, more preferably 0.20 ml/g or more, and is usually 3 ml/g or less, preferably 2 ml/g or less.

The average particle size of the CON-type zeolite used in this embodiment is not particularly limited, but is usually 3 μm or less, preferably 1 μm or less, more preferably 700 nm or less, and particularly preferably 300 nm or less. It is also usually 20 nm or more, and preferably 40 nm or more.

Hereinafter, the method for producing the CON type zeolite of this embodiment will be described.
CON type zeolite can generally be prepared by hydrothermal synthesis. For example, a boron source, an aluminum source, a gallium source, a silica source, and the like are added to water to generate a uniform gel, to which a structure directing agent, preferably N,N,N-trimethyl-(-)-cis-myrtanylammonium hydroxide, is added and stirred, and the resulting raw gel is crystallized by holding it at 120 to 200°C in a pressurized and heated container. During crystallization, seed crystals may be added as necessary, and in terms of manufacturability, the addition of seed crystals is preferred in terms of improved operability. As the seed crystals, it is preferable to use CON type zeolite. In addition, it is preferable to add a surfactant to the raw gel. By adding a surfactant, the zeolite becomes fine particles, and it becomes easier to adjust the value of (A2) and the value of (A2/A1) to the desired range. As the surfactant, cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, and the like can be used alone or in combination. The surfactant is preferably a cationic surfactant that acts as a moderate crystal growth inhibitor, and examples thereof include hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride. The concentration of the surfactant is not particularly limited, but the molar ratio to Si is preferably 0.001 to 0.05. The crystallized raw gel is then filtered and washed, and the solid content is dried at 100 to 200°C, and subsequently calcined at 400 to 900°C to obtain zeolite powder.
Conventionally, CON-type zeolite has a slow nucleation and crystal growth rate, and has been synthesized over a relatively long period of time, about 5 to 21 days, so surfactants such as hexadecyltrimethylammonium bromide have not been introduced. This is because it has been thought that surfactants inhibit crystal growth, making crystallization difficult when surfactants are added. In this embodiment, by optimizing the synthesis conditions, crystallization can be achieved within a practical time, and the values of (A2) and (A2/A1) can be set within ranges that have not been achieved before, resulting in an especially excellent long life as a catalyst.

Here, one or more of boric acid, sodium borate, boron oxide, etc. can be used as the boron source. One or more of aluminum sulfate, aluminum nitrate, pseudoboehmite, aluminum alkoxide, aluminum hydroxide, alumina sol, sodium aluminate, etc. can be used as the aluminum source. One or more of gallium nitrate, gallium sulfate, gallium phosphate, gallium chloride, gallium bromide, gallium hydroxide, etc. can be used as the gallium source. One or more of silicates such as fumed silica, silica sol, silica gel, silicon dioxide, and water glass, silicon alkoxides such as tetraethoxyorthosilicate and tetramethoxysilane, silicon halides, etc. can be used as the silica source.

The amount of metal contained in CON-type zeolite can be adjusted by adjusting the amount of constituent elements (Al, Ga, B, etc.) during synthesis. It is also possible to use zeolites in which some of the constituent elements have been removed by steaming or acid treatment to adjust the content.

In this embodiment, it is preferable to have an alkali treatment step in which the prepared CON zeolite is treated with an alkali in the presence of a surfactant. The alkali treatment step causes the zeolite to have a mesostructure, making it easier to adjust the value of (A2) and the value of (A2/A1) to the desired range.
The surfactant used in the alkali treatment step may be a cationic surfactant, an anionic surfactant, a nonionic surfactant, an amphoteric surfactant, or the like, which may be used alone or in combination. Examples include hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride.
In the alkaline treatment step, the concentration of the surfactant is not particularly limited, and it may be contained in the treatment liquid at about 0.1 to 10% by mass.

The alkali for the alkali treatment is not particularly limited, and an ammonia solution, a sodium hydroxide solution, or the like can be used. The level of alkali is also not particularly limited, and the pH may be, for example, about 9 to 12.
The alkali treatment may be carried out by contacting the CON zeolite with an alkali, or by stirring the zeolite in an alkali solution. The temperature of the alkali treatment is not particularly limited, and may be, for example, about 100 to 200° C. The time of the alkali treatment is not particularly limited, and the zeolite may be immersed in the alkali solution for 0.1 to 24 hours.
After the alkali treatment, it is preferable to dry the product and then calcinate it again for use as a catalyst to remove the incorporated surfactant.

The CON-type zeolite of this embodiment can be used as a catalyst. When used as a catalyst, it may be a mixture with other substances, such as compounds containing alkaline earth metals or silicon.

The CON zeolite of the present embodiment is used as a catalyst for producing lower olefins. The raw material may be methanol or dimethyl ether, but is not limited thereto, and may be appropriately selected depending on the type of the target olefin.
The origin of methanol and dimethyl ether is not particularly limited. For example, they may be obtained by hydrogenation of a mixed gas of hydrogen/CO derived from coal and natural gas, and by-products in the steel industry, by reforming of alcohols derived from plants, by fermentation, or from organic materials such as recycled plastics and urban waste. In this case, they may be used as they are, or may be purified, in a state where compounds other than methanol and dimethyl ether are mixed as they are, resulting from each production method.
As the reaction raw material, only methanol or only dimethyl ether may be used, or a mixture of these may be used. When a mixture of methanol and dimethyl ether is used, there is no limitation on the mixing ratio.

The process for producing lower olefins using the above catalyst and raw material will be described below by taking as an example a case in which the raw material is methanol and/or dimethyl ether.
Another embodiment of the present invention, a method for producing lower olefins, comprises a step of contacting a raw material containing methanol and/or dimethyl ether with the above-mentioned CON-type zeolite. The reaction mode in this embodiment is not particularly limited 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. A fixed bed reactor is advantageous in terms of equipment costs including auxiliary equipment, catalyst costs, and operation management.
The process may be carried out in any of a batch, semi-continuous or continuous manner, but is preferably carried out in a continuous manner, and may be a process using a single reactor or a process using multiple reactors arranged in series or parallel.

When the above-mentioned catalyst is packed into the fluidized bed reactor, in order to minimize the temperature distribution in the catalyst layer, granular materials inactive to the reaction, such as quartz sand, alumina, silica, silica-alumina, etc., may be mixed with the catalyst and packed. In this case, there is no particular restriction on the amount of granular materials inactive to the reaction, such as quartz sand, used. In addition, it is preferable that the granular materials have a particle size similar to that of the catalyst, from the viewpoint of uniform mixing with the catalyst.
In addition, the reaction substrate (reaction raw material) may be divided and fed to the reactor for the purpose of dispersing heat generated by the reaction.

There is no particular restriction on the total concentration (substrate concentration) of methanol and dimethyl ether in all the components fed to the reactor, but the sum of methanol and dimethyl ether is preferably 90 mol % or less of all the components fed. More preferably, it is 10 mol % or more and 70 mol % or less.

In addition to methanol and/or dimethyl ether, the reactor may contain gases inert to the reaction (also referred to as diluents), such as helium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, water, paraffins, hydrocarbons such as methane, aromatic compounds, and mixtures thereof. Among these, the coexistence of water (water vapor) is preferred because it is easily separated.
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. The diluent may also be mixed with the reaction raw materials before being placed in the reactor, or may be supplied to the reactor separately from the reaction raw materials.

The lower limit of the reaction temperature is usually about 200°C or higher, preferably 250°C or higher, and more preferably 300°C or higher, and the upper limit of the reaction temperature is usually 750°C or lower, and preferably 700°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 material 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 stable catalyst activity, and the yield of lower olefins drops significantly. Note that the reaction temperature here refers to the temperature at the inlet of the catalyst layer.

The upper limit of the reaction pressure is usually 5 MPa (absolute pressure, hereinafter the same) or less, preferably 2 MPa or less, more preferably 1 MPa or less, and particularly preferably 0.7 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 produced increases, and the yield of lower olefins tends to decrease. If the reaction pressure is too low, the reaction rate tends to be slow.

The reactor outlet gas (reactor effluent) is a mixed gas containing lower olefins as the reaction product, by-products and a diluent. The concentration of lower olefins in the mixed gas is usually 5 to 95% by weight.
Although the reaction product contains methanol and/or dimethyl ether as unreacted raw materials depending on the reaction conditions, it is preferable to carry out the reaction under reaction conditions that result in a 100% conversion of methanol and/or dimethyl ether, which makes it easy, and preferably unnecessary, to separate the reaction product from the unreacted raw materials.
The by-products include olefins having 5 or more carbon atoms, paraffins, aromatic compounds and water.

The reactor outlet gas, which is a mixed gas containing the reaction product lower olefins, unreacted raw materials, by-products and diluents, can be introduced into a known separation and purification facility and treated for recovery, purification, recycling and discharge according to the individual components.

In addition, the uses of the zeolite catalyst of the present invention are not limited to the production of lower olefins, but are also suitable for the production of p-xylene, ethylbenzene, and cumene, aromatization of light hydrocarbons, hydrocracking, hydrodewaxing, alkane isomerization, and automobile exhaust gas purification.

The present invention will be described in more detail below with reference to examples, but it goes without saying that the scope of the present invention is not limited to the examples.

[Example 1]
0.050 g of sodium hydroxide, 2.85 g of 30.0 wt % N,N,N-trimethyl-(-)-cis-myrtanylammonium hydroxide aqueous solution, and 2.90 g of demineralized water were mixed, to which 0.050 g of boric acid and 0.016 g of aluminum sulfate were added and stirred, and then 3.97 g of Cataloid SI-30 was added as a silica source and thoroughly stirred. Furthermore, 0.024 g of CON-type zeolite (Si/Al=270) was added as seed crystals and stirred to prepare a raw material gel.

The obtained raw gel was placed in an autoclave and heated at 170°C for 5 days at 15 rpm. The product was filtered, washed with water, and then dried at 100°C to obtain a white powder. The X-ray diffraction (XRD) pattern of the product confirmed that the product was CON-type zeolite. After drying, the product was calcined in an air atmosphere at 600°C for 6 hours to obtain a 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 an ammonium-type zeolite powder. It was then calcined in an air atmosphere at 500°C for 6 hours to obtain the proton-type zeolite powder of Example 1.

[Example 2]
0.200 g of the proton-type zeolite obtained in Example 1, 0.140 g of hexadecyltrimethylammonium bromide, 11.99 g of desalted water, and 0.81 g of 10% aqueous ammonia were mixed and thoroughly stirred. The resulting slurry was charged into an autoclave and heated at 150°C for 7 hours while standing. The product was filtered, washed with water, and then dried at 100°C to obtain a white powder. After drying, the product was calcined at 600°C for 6 hours in an air atmosphere to obtain the zeolite powder of Example 2.

[Example 3]
5.522 g of 30.9 wt % N,N,N-trimethyl-(-)-cis-myrtanylammonium hydroxide aqueous solution, 0.642 g of 8 M sodium hydroxide aqueous solution, and 17.321 g of demineralized water were mixed, to which 0.247 g of boric acid and 0.026 g of aluminum sulfate were added and stirred, and then 2.404 g of Cab-O-sil M7D was added as a silica source and thoroughly stirred. Further, 0.146 g of hexadecyltrimethylammonium bromide was added and stirred, and then 0.049 g of CON-type zeolite (Si/Al=270) was added as seed crystals and stirred to prepare a raw gel.
The obtained raw gel was placed in an autoclave and heated at 170° C. for 7 days at 40 rpm. The product was filtered, washed with water, and then dried at 100° C. to obtain a white powder. After drying, the product was calcined at 600° C. for 6 hours in an air atmosphere to obtain a sodium-type zeolite powder.
The obtained powder was subjected to ion exchange in a 2.5N ammonium nitrate aqueous solution at 80°C for 2 hours, then filtered and dried. The dried powder was again subjected to ion exchange in a 2.5N ammonium nitrate aqueous solution at 80°C for 3 hours, then filtered and dried to obtain an ammonium type zeolite powder. The powder was then calcined in an air atmosphere at 600°C for 3 hours to obtain a proton type zeolite powder of Example 3.

[Comparative Example 1]
1.29 g of 1.0 M sodium hydroxide aqueous solution, 2.88 g of 30.0 wt % N,N,N-trimethyl-(-)-cis-myrtanylammonium hydroxide aqueous solution, and 1.67 g of demineralized water were mixed, and 0.049 g of boric acid and 0.010 g of aluminum sulfate were added thereto and stirred, and then 4.02 g of Cataloid SI-30 was added as a silica source and thoroughly stirred. Furthermore, 0.025 g of BEA type zeolite (Si/Al=20) was added as seed crystals and stirred to prepare a raw material gel. The obtained raw material gel was heated and post-treated in the same manner as in Example 1 to obtain a proton type zeolite powder of Comparative Example 1.

[Comparative Example 2]
0.052 g of sodium hydroxide, 2.77 g of 30.8 wt % N,N,N-trimethyl-(-)-cis-myrtanylammonium hydroxide aqueous solution, and 3.00 g of demineralized water were mixed, and 0.049 g of boric acid and 0.008 g of aluminum sulfate were added thereto and stirred, and then 3.93 g of Cataloid SI-30 was added as a silica source and thoroughly stirred. Furthermore, 0.024 g of BEA type zeolite (Si/Al=15) was added as seed crystals and stirred to prepare a raw material gel. The obtained raw material gel was heated and post-treated in the same manner as in Example 1 to obtain a proton type zeolite powder of Comparative Example 2.

[Comparative Example 3]
0.45 g of 1.0 M sodium hydroxide aqueous solution, 0.79 g of 1.05 M N,N,N-trimethyl-(-)-cis-myrtanylammonium hydroxide aqueous solution, and 1.43 g of demineralized water were mixed, to which 0.011 g of boric acid and 0.0082 g of zinc acetate were added and stirred, and then 0.27 g of fumed silica (Cab-O-Sil M-7D, manufactured by CABOT) was added as a silica source and thoroughly stirred. Furthermore, 0.0054 g of BEA-type borosilicate was added as seed crystals and stirred to prepare a raw material gel.
The obtained raw gel was placed in an autoclave and heated at 170° C. for 7 days under a rotation speed of 40 rpm. The product was filtered, washed with water, and then dried overnight at 100° C. After drying, it was calcined at 600° C. for 6 hours in an air atmosphere to obtain a sodium-type zeolite powder.

0.2 g of the obtained powder was added to 20 ml of 2N aqueous nitric acid solution and stirred at 100°C under reflux for 20 hours. The zeolite was then filtered, washed with water, and dried overnight at 100°C to obtain proton-type zeolite powder. The entire amount of the obtained powder was added to 20 g of an aqueous solution in which 0.0031 g of aluminum nitrate nonahydrate had been dissolved, and stirred at 100°C under reflux for 2 days. The zeolite was then filtered, washed with water, and dried overnight at 100°C to obtain the proton-type zeolite powder of Comparative Example 3.

The synthesis conditions for Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 1. Comparative Examples 1 and 2 are examples in which the feed composition is the same as that of Example 1, except that the seed crystals were changed from CON-type zeolite to BEA-type zeolite.

The zeolites according to Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated as follows.
<Nitrogen adsorption/desorption measurement>
Nitrogen adsorption and desorption measurements of the synthesized proton-type zeolite powder were performed using a Belsorp-mini II manufactured by Microtrack-Bell. In the measurement, the zeolite was heated and dried at 400°C under vacuum for 2 hours, and then nitrogen adsorption and desorption measurements were performed at liquid nitrogen temperature. Figure 1 shows the adsorption and desorption isotherms of the zeolites according to Examples 1 and 2 and Comparative Examples 1 to 3. Data analysis was performed using analysis software BELMaster manufactured by Microtrack-Bell. The BET specific surface area (A2) was calculated by BET plotting the measurement data with a relative pressure (P/P ₀ ) of 0.002 to 0.06. The external surface area (A1) and the micropore volume (A3) were calculated by t-plotting the data with a relative pressure (P/P ₀ ) of 0.20 to 0.42. The standard isotherm used was Harkins-Jura.

<Production of lower olefins>
The zeolites obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were used to produce lower olefins. A fixed-bed flow reactor was used for the reaction, and 33 mg of premixed proton-type zeolite powder and 470 mg of quartz sand were filled in a quartz reaction tube with an inner diameter of 6 mm. A mixed gas of 50 mol % methanol and 50 mol % nitrogen was supplied to the reactor so that the weight space velocity of methanol was 15 h ^-1 , and the reaction was carried out at 500°C and 0.1 MPa (absolute pressure). The product was analyzed by gas chromatography every hour from the start of the reaction. Figure 2 shows a graph showing the progress of the 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 of reaction. The catalyst life was defined as the time during which the methanol conversion rate was maintained at 99% or more.

As shown in Table 1, the ratio (A2/A1) of the BET specific surface area (A2) to the external surface area (A1) is small, and the zeolites of Examples 1 to 3, which have a large BET specific surface area (A2), maintain a high raw material conversion rate for a long period of time.

Claims (7)

In a nitrogen adsorption/desorption measurement, the ratio (A2/A1) of the BET specific surface area (A2) calculated by BET plot to the external surface area (A1) calculated by t plot is 10 or less, and the BET specific surface area (A2) is 620 m ² /g or more;
The molar ratio (Si/Al or Si/Ga) of the constituent elements silicon (Si) and aluminum (Al), or silicon (Si) and gallium (Ga) is 200 or more;
CON type zeolite. In a nitrogen adsorption/desorption measurement, the ratio (A2/A1) of the BET specific surface area (A2) calculated by BET plot to the external surface area (A1) calculated by t plot is 7 or less, and the BET specific surface area (A2) is 400 m ² /g or more;
The molar ratio (Si/Al or Si/Ga) of the constituent elements silicon (Si) and aluminum (Al), or silicon (Si) and gallium (Ga) is 200 or more;
CON type zeolite. A method for producing the CON zeolite according to claim 1 or 2 ,
The method includes an alkali treatment step of treating CON zeolite under alkaline conditions in the presence of a surfactant,
An ammonia solution is used as the alkali for the alkaline treatment,
The concentration of the surfactant in the treatment solution is 0.1 to 10% by mass,
The temperature of the alkali treatment is 100 to 200°C.
A method for producing CON type zeolite. A method for producing the CON zeolite according to claim 1 or 2 ,
A cationic surfactant is added to the zeolite synthesis raw material gel,
The method includes a step of crystallizing the zeolite synthesis raw material gel by holding the gel at 120 to 200° C. in a pressurized and heated container,
The concentration of the cationic surfactant is 0.001 to 0.05 in terms of a molar ratio to Si;
A method for producing CON type zeolite. The method for producing CON-type zeolite according to claim 3 or 4, wherein the surfactant is hexadecyltrimethylammonium bromide or hexadecyltrimethylammonium chloride. The CON-type zeolite according to claim 1 or 2, which is a catalyst used in a reaction for producing lower olefins. A method for producing lower olefins, comprising a step of contacting a raw material containing methanol and/or dimethyl ether with the CON zeolite according to any one of claims 1, 2 and 6.

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