Method for producing DDR-type zeolite catalysts and lower olefins

Abstract

To provide a DDR-type zeolite catalyst capable of achieving a high yield of a lower olefin.SOLUTION: There is provided a DDR-type zeolite catalyst which contains silicon (Si) and aluminum (Al) as constituent elements, has a molar ratio (Si / Al) between silicon (Si) and aluminum (Al) of 60 or more and 150 or less and an average primary particle diameter of 1000 nm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a DDR-type zeolite catalyst, and more particularly to a DDR-type zeolite catalyst that can achieve high yield of ethylene when used as a catalyst. Furthermore, the invention relates to a method for producing lower olefins using a catalyst containing the zeolite. [Background technology]

[0002] Traditionally, methods for producing lower olefins such as ethylene, propylene, and butene have included steam cracking of naphtha and fluid catalytic cracking of vacuum diesel fuel. In recent years, metathesis reactions using ethylene and 2-butene as raw materials, and the MTO (methanol to olefin) process using methanol and / or dimethyl ether as raw materials have become known.

[0003] For example, Non-Patent Documents 1 to 3 disclose that by using methanol as a raw material and a zeolite having a DDR-type structure (Sigma-1, ZSM-58 zeolite) as a catalyst, the by-product formation of hydrocarbon components of C5 or higher can be suppressed, and ethylene and propylene can be produced in high yield. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Catal.Sci.Technol.,6,2663-2678(2016) [Non-Patent Document 2] ACS Catal., 7, 4033-4046 (2017) [Non-Patent Document 3] ACS Catal., 10, 3009-3017 (2020) [Overview of the project] [Problems that the invention aims to solve]

[0005] Non-patent document 1 reports the ethylene yield for DDR-type zeolite with a particle size of approximately 2.5 μm when the Si / Al2 ratio (calculated from NH3-TPD) is varied from 120 to 415. The results show that the higher the Si / Al2 ratio, the higher the ethylene yield, with the highest ethylene yield being around 43%. Furthermore, for a sample with a Si / Al2 ratio of 315, the ethylene yield when the particle size is varied is reported, and there is a tendency for the ethylene yield to be higher for samples with smaller particle sizes, with the highest ethylene yield being around 46%. Furthermore, Non-Patent Document 2 contains the results of a reaction evaluation of DDR-type zeolite with a Si / Al ratio of 50 and a particle size of approximately 500-1000 nm, showing that the maximum yield of ethylene was approximately 48%. Furthermore, Non-Patent Document 3 reports the results of a performance comparison for DDR-type zeolites with particle sizes of several μm and Si / Al ratios ranging from 22 to 172. The comparison is conducted in the range of methanol conversion rates of 45-55%, and the ethylene selectivity is maximized at Si / Al=22, showing a value of approximately 37%. However, sufficient research has not been conducted on the Si / Al ratio and particle size necessary to achieve high ethylene yield, and in particular, the optimal Si / Al ratio when the particle size is small remains unknown. For users who wish to selectively produce ethylene as a lower olefin, there is a need for zeolite catalysts that can achieve an ethylene yield exceeding 50%.

[0006] The present invention aims to solve the above problems and to provide a DDR-type zeolite catalyst that can achieve high yield of ethylene. [Means for solving the problem]

[0007] The inventors of the present invention conducted research to solve the above problems and found that by appropriately adjusting the molar ratio (Si / Al) of silicon (Si) and aluminum (Al) as constituent elements of the DDR-type zeolite, and the average primary particle size, it is possible to provide a DDR-type zeolite that can achieve a high yield of ethylene as a catalyst, thus completing the present invention.

[0008] The present invention includes the following gist. [1] A DDR-type zeolite catalyst containing silicon (Si) and aluminum (Al) as constituent elements, with a molar ratio of silicon (Si) to aluminum (Al) (Si / Al) of 60 to 150, and an average primary particle diameter of 1000 nm or less. [2] In nitrogen adsorption / desorption measurements, 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 20 or less, the DDR-type zeolite catalyst according to claim 1. [3] A method for producing a lower olefin, comprising the step of contacting a raw material containing methanol and / or dimethyl ether with the DDR-type zeolite catalyst described in [1] or [2] above. [4] The reaction temperature is between 200°C and 750°C, the reaction pressure is between 0.1 kPa and 2 MPa, and the gravitational space velocity is 0.1 hr. -1 Over 10 hours -1 The method for producing the lower olefin described in [3] above is as follows: [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a DDR-type zeolite catalyst that can achieve a high yield of ethylene. Furthermore, it is possible to provide a method for producing lower olefins using this zeolite as a catalyst. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows the powder X-ray diffraction results of DDR-type zeolite (as-made type) according to Example 1 and Comparative Examples 1-3. [Figure 2] These are scanning electron microscope (SEM) images of DDR-type zeolite (as-made type) according to Example 1 and Comparative Examples 1-3. [Figure 3] This graph shows the changes in methanol conversion rate and selectivity in the production of lower olefins using DDR-type zeolite as a catalyst in Example 1 and Comparative Examples 1-3.

Embodiments for Carrying out the Invention

[0011] 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 can be variously modified and implemented within the scope of the gist.

[0012] [DDR-type zeolite] One embodiment of the present invention is a DDR-type zeolite catalyst, which contains silicon (Si) and aluminum (Al) as constituent elements, and the molar ratio (Si / Al) of silicon (Si) to aluminum (Al) is 60 or more and 150 or less, and the average primary particle size is 1000 nm or less.

[0013] DDR-type zeolite is a zeolite having a two-dimensional pore structure with a shape in which two 8-membered ring structures intersect as its structural unit. According to the IZA database, the pore diameter is 3.6×4.4 Å. Compared with the CHA-type zeolite (3.8×3.8 Å) represented by SAPO-34, which has been industrialized as an MTO catalyst, the pore structure is narrowed, so it is推测 that the by-production of hydrocarbon components with 5 or more carbons can be suppressed.

[0014] In this embodiment, the DDR-type zeolite contains silicon (Si) and aluminum (Al) as constituent elements, the molar ratio (Si / Al) of silicon (Si) to aluminum (Al) is 60 or more and 150 or less, and the average primary particle size is 1000 nm or less.

[0015] By having a molar ratio of silicon (Si) to aluminum (Al) (Si / Al) and an average primary particle size within the above range, ethylene can be obtained in high yield when producing lower olefins. Specifically, the molar ratio of silicon (Si) to aluminum (Al) (Si / Al) is preferably 70 or higher, more preferably 75 or higher, and even more preferably 80 or higher. Having a Si / Al ratio within this range suppresses the by-product formation of paraffins such as methane. Furthermore, the Si / Al ratio is preferably 140 or lower, more preferably 130 or lower. Having a Si / Al ratio within this range makes the cracking reaction that produces ethylene more likely to occur.

[0016] In addition, the average primary particle diameter must be 1000 nm or less, preferably 800 nm or less, more preferably 700 nm or less, and even more preferably 600 nm or less. Having the average primary particle diameter within this range suppresses the formation of paraffin by-products such as methane. The lower limit is not particularly limited, but is usually 20 nm or more, preferably 40 nm or more, and particularly preferably 60 nm or more.

[0017] Both "primary particle diameter" and "average primary particle diameter" can be calculated using a scanning electron microscope (SEM). Here, "primary particles" refer to the smallest particles in which no grain boundaries can be observed. In this invention, an SEM image of the zeolite catalyst is obtained, and the smallest particles in the portion corresponding to the zeolite included in the SEM image in which no grain boundaries can be observed are determined to be "primary particles." In this invention, primary particles do not necessarily exist as individual particles, and secondary particles may be formed by aggregation or the like. Even if secondary particles are formed, primary particles on the surface of the secondary particles can be identified in the SEM image. Note that DDR-type zeolites may show crack-like features on their surface, but these are not included in the definition of primary particles. The "average primary particle diameter" is measured as follows: 50 primary particles are randomly selected from the SEM image of the zeolite catalyst. For each of these 50 selected primary particles, the major axis (the length of the longest straight line connecting one end of the primary particle to the other) is measured. The arithmetic mean of these 50 major axes is defined as the "average primary particle diameter." However, if the zeolite catalyst contains fewer than 50 primary particles, the major axis of all primary particles in the zeolite catalyst is measured, and the average of these measurements is defined as the "average primary particle diameter."

[0018] Setting the average primary particle size within a specific range can be achieved, for example, by using DDR-type zeolite with a small particle size as a seed crystal, or by adding a surfactant to the zeolite synthesis raw material gel during the manufacturing process of DDR-type zeolite.

[0019] The elements other than silicon (Si) and aluminum (Al) included as constituent elements in the DDR-type zeolite of this embodiment are not particularly limited, but examples include one or more selected from boron (B), titanium (Ti), vanadium (V), iron (Fe), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), and tin (Sn).

[0020] Specifically, preferred examples include crystalline aluminosilicates containing Si and Al as constituent elements, as well as crystalline galloaluminosilicates containing Ga. These zeolites exhibit excellent catalytic activity because the Al and Ga within the zeolite framework act as acid sites, which are active sites in catalytic reactions.

[0021] In the case of a crystalline galloaluminosilicate containing Ga in addition to Si and Al as constituent elements, the content ratio of Ga is not particularly limited, but the Si / Ga molar ratio is preferably 50 or more, particularly 100 or more, especially 200 or more, and 4000 or less, particularly 2000 or less, especially 1000 or less. Further, the Ga / Al molar ratio is preferably 0.1 or more, particularly 0.2 or more, especially 0.4 or more, and 8 or less, particularly 4 or less, especially 2 or less. By setting the Si / Ga molar ratio and the Ga / Al molar ratio as described above, a zeolite catalyst having sufficient catalytic activity and extremely excellent catalyst life can be obtained, which is preferable.

[0022] Note that the contents of Si, Al, Ga, etc. of the DDR-type zeolite of the present embodiment are usually values measured for the produced DDR-type zeolite by inductively coupled plasma atomic emission spectrometry (ICP-AES) or the like, and are not the ratios of the raw material charges.

[0023] The ion exchange sites of the DDR-type zeolite of the present 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.

[0024] [Ratio of BET specific surface area (A2) to external surface area (A1)] The external surface area (A1) of the DDR-type zeolite of the present embodiment is usually 5 m 2 / g or more, preferably 10 m 2 / g or more, more preferably 15 m 2 / g or more, still more preferably 20 m 2 / g or more, and usually 500 m 2 / g or less, preferably 300 m 2 / g or less, more preferably 200 m 2 / g or less. The BET specific surface area (A2) of the DDR-type zeolite of the present embodiment is usually 150 m 2 / g or more, preferably 200 m 2 / g or more, more preferably 250 m 2 / g or more, more preferably 300m 2 / g or more, usually 1000m 2 Less than or equal to / g, preferably 800m 2 / g or less, more preferably 700m 2 It is less than / g. In this embodiment, the ratio of the BET specific surface area (A2) to the outer surface area (A1) (A2 / A1) is preferably 20 or less. When A2 / A1 is 20 or less, the diffusion of reaction products out of the pores is improved, and coking can be suppressed. From this viewpoint, A2 / A1 is more preferably 18 or less, even more preferably 17 or less, even more preferably 16 or less, and particularly preferably 15 or less. On the other hand, the lower limit is not particularly limited, but is usually 2 or more. The micropore volume (A3) of the DDR-type zeolite in this embodiment is not particularly limited, but is usually 0.05 ml / g or more, preferably 0.075 ml / g or more, more preferably 0.10 ml / g or more, and usually 3 ml / g or less, preferably 2 ml / g or less. The external surface area (A1), BET specific surface area (A2), and micropore volume (A3) can be calculated from nitrogen adsorption / desorption measurements, for example, using a Belsorp-miniII from Microtrac-Bell. Data analysis can then be performed using BELMaster, analysis software from Microtrac-Bell. Here, the BET specific surface area (A2) can be calculated by plotting BET data for relative pressure (P / P0) values ​​between 0.002 and 0.06. The external surface area (A1) and micropore volume (A3) can be calculated by plotting t-plot data for relative pressure (P / P0) values ​​between 0.20 and 0.42. Harkins-Jura is used as the standard isotherm.

[0025] [Method for manufacturing DDR-type zeolite] The following describes a method for manufacturing the DDR-type zeolite of this embodiment.

[0026] DDR-type zeolites can generally be prepared by hydrothermal synthesis. For example, an alkali source, an organic structure-determining agent (preferably 1-adamantylamine, methyltropinium iodide, quinuclidinium hydroxide, etc.) is added to water and stirred. Further, an aluminum source, a gallium source, a boron source, a silica source, etc., are added to produce a homogeneous gel. The resulting raw material gel is then held at 100-220°C in a pressurized heating vessel such as an autoclave to crystallize. Seed crystals may be added as needed during crystallization, and adding seed crystals is preferable as it facilitates the crystallization of DDR-type zeolites. It is preferable to use DDR-type zeolites as seed crystals. It is preferable to use pulverized zeolites as seed crystals, as this makes it easier to obtain DDR-type zeolites with small particle sizes.

[0027] After the crystallization of the raw material gel, the crystallized raw material gel is filtered and washed, the solid components are dried at 100-200°C, and then calcined at 400-900°C to obtain zeolite powder.

[0028] As silica sources used in the preparation of the raw material gel, one or more types of silicates such as fumed silica, silica sol, silica gel, silicon dioxide, and water glass, as well as silicon alkoxides such as tetraethoxyorthosilicate and tetramethoxysilane, and silicon halides can be used. As an aluminum source, one or more of the following can be used: aluminum sulfate, aluminum nitrate, boehmite pseudo, aluminum alkoxide, aluminum hydroxide, alumina sol, sodium aluminate, etc. One or more of the following can be used as the gallium source: gallium nitrate, gallium sulfate, gallium phosphate, gallium chloride, gallium bromide, gallium hydroxide, etc. One or more boron sources can be used, such as boric acid, sodium borate, or boron oxide.

[0029] There are no particular restrictions on the molar ratio (Si / Al) of silicon (Si) to aluminum (Al) in the DDR-type zeolite used as seed crystal, but it is preferably in the range of 25 to 10000. Furthermore, it is preferable to use about 1 to 20% by mass of the seed crystal relative to the silica source added.

[0030] DDR-type zeolites allow for adjustment of the metal content by controlling the amounts of constituent elements (Si, Al, Ga, B, etc.) during synthesis. Alternatively, zeolites with adjusted content can be used by removing some of the constituent elements through methods such as steaming or acid treatment.

[0031] [catalyst] The DDR-type zeolite of this embodiment can be used as a catalyst. In particular, the DDR-type zeolite of this embodiment is useful as a catalyst used in reactions that produce lower olefins. However, the applications of the zeolite catalyst of this embodiment are not limited to catalysts for the production of lower olefins, and it can also be suitably used in the production of p-xylene, ethylbenzene, cumene, aromatization of light hydrocarbons, hydrocracking, dewaxing, isomerization of alkanes, and automobile exhaust gas purification. In this specification, lower olefins refer to ethylene, propylene, and butene. In other words, olefins having 2 to 4 carbon atoms.

[0032] The DDR-type zeolite of this embodiment may be used as a catalyst in the reaction as is, or it may be used as a mixture with other substances that are inert to the reaction, such as alkaline earth metals or silicon-containing compounds. Alternatively, it may be granulated or molded using a binder before being used in the reaction. Examples of substances that are inert to the reaction or binders include alumina or alumina sol, silica, silica gel, silicates, quartz, and mixtures thereof. Among these, silica is preferred because it is expected to have excellent strength and catalytic performance as an industrial catalyst. Mixing with these substances is also effective in reducing the overall cost of the catalyst, increasing the density of the catalyst, and increasing the catalytic strength.

[0033] [Method for producing lower olefins] In the method for producing lower olefins using the catalyst containing DDR-type zeolite of this embodiment, methanol and dimethyl ether are examples of raw materials, but are not limited to these, and can be appropriately selected depending on the type of olefin to be produced.

[0034] The following describes a method for producing lower olefins using the above catalyst, with an example where the raw materials are methanol and / or dimethyl ether.

[0035] Another embodiment of the present invention, a method for producing a lower olefin, comprises the step of contacting a catalyst containing the above-mentioned DDR-type zeolite with a raw material containing methanol and / or dimethyl ether.

[0036] The origin of methanol and dimethyl ether used as raw materials is not particularly limited. Examples include those obtained by hydrogenation reactions of hydrogen / CO mixed gases derived from coal, natural gas, and by-products in the steel industry; those obtained by reforming reactions of plant-derived alcohols; those obtained by fermentation; those obtained from organic materials such as recycled plastics and municipal waste; and those obtained by methanol synthesis reactions using carbon dioxide as a raw material. In this case, methanol and dimethyl ether may be used as is, or purified methanol may be used, as they may contain any mixture of other compounds resulting from each manufacturing method. The reaction materials may consist of methanol alone, dimethyl ether alone, or a mixture of both. When methanol and dimethyl ether are used as a mixture, there are no restrictions on the mixing ratio.

[0037] The reaction mode in this embodiment is not particularly limited as long as the methanol and / or dimethyl ether feedstocks are in the gas phase in the reaction zone, and known gas-phase reaction processes using fluidized bed reactors, moving bed reactors, or fixed bed reactors can be applied. Using a fluidized bed reactor makes it possible to operate even with catalysts that have a short single-pass life. Furthermore, the process can be carried out in batch, semi-continuous, or continuous form, but continuous is preferred, and this method may involve using a single reactor or using multiple reactors arranged in series or parallel.

[0038] Furthermore, when filling the fixed-bed reactor with the aforementioned catalyst, in order to minimize the temperature distribution of the catalyst layer, granular material that is inert to the reaction, such as quartz sand, alumina, silica, or silica-alumina, may be mixed with the catalyst before filling. In this case, there are no particular restrictions on the amount of granular material that is inert to the reaction, such as quartz sand, used. However, it is preferable that the particle size of this granular material is similar to that of the catalyst, in terms of uniform mixing with the catalyst. Furthermore, the reaction substrate (reaction raw material) may be supplied to the reactor in divided portions in order to disperse the heat generated by the reaction.

[0039] There are no particular restrictions on the total concentration (substrate concentration) of methanol and dimethyl ether in the total feed components supplied to the reactor, but the sum of methanol and dimethyl ether is preferably 90 mol% or less of the total feed components. More preferably it is 10 mol% to 70 mol%. The above range is preferable in terms of reaction rate and lower olefin yield.

[0040] In addition to methanol and / or dimethyl ether, the reactor may contain other gases that are inert to the reaction (hereinafter 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 presence of water (water vapor) is preferable because it allows for good separation. As such a diluent, the impurities contained in the reaction raw materials may be used as is, or a separately prepared diluent may be mixed with the reaction raw materials before use. Furthermore, the diluent may be mixed with the reaction raw materials before being placed in the reactor, or it may be supplied to the reactor separately from the reaction raw materials.

[0041] The lower limit of the reaction temperature is usually about 200°C or higher, preferably 250°C or higher, more preferably 300°C or higher, and particularly preferably 400°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, a large amount of unreacted raw materials tend 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 decreases significantly. Here, the reaction temperature refers to the temperature at the outlet of the catalyst layer.

[0042] The upper limit of the reaction pressure is usually preferably 5 MPa (absolute pressure, the same applies hereinafter) or less, more preferably 2 MPa or less, even more preferably 1 MPa or less, even more preferably 0.7 MPa or less, and particularly preferably 0.4 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 below the above upper limit, the amount of undesirable by-products such as paraffins and aromatic compounds is suppressed, and the yield of lower olefins increases. On the other hand, if the reaction pressure is above the above lower limit, a sufficient reaction rate can be obtained.

[0043] The weight-space velocity of the reaction raw materials is 0.1hr -1 Preferably, it should be 0.5hr -1 The above is more preferable. On the other hand, the gravitational space velocity is 10hr -1 The following is preferable: 5hr -1 The following is more preferable: When the gravimetric space velocity is within this range, the yield of lower olefins is improved.

[0044] The reactor outlet gas (reactor effluent) is a mixed gas containing the reaction product, a lower olefin, a by-product, and a diluent. The concentration of the lower olefin in the mixed gas is typically 5 to 95% by mass. Depending on the reaction conditions, the reaction product may contain unreacted methanol and / or dimethyl ether as raw materials. However, it is preferable to carry out the reaction under conditions where the conversion rate of methanol and / or dimethyl ether is high. This facilitates the separation of the reaction product from the unreacted raw materials. In particular, it is preferable to carry out the reaction under conditions where the conversion rate of methanol and / or dimethyl ether is 100%, as this eliminates the need to separate the reaction product from the unreacted raw materials. By-products include olefins with 5 or more carbon atoms, paraffins, aromatic compounds, and water.

[0045] The mixed gas, which is the reaction product (lower olefin), unreacted raw materials, by-products, and diluents, is introduced into a known separation and purification facility and treated by recovery, purification, recycling, or discharge according to each component. [Examples]

[0046] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to the following examples.

[0047] [Example 1] 3.63 g of 1 M sodium hydroxide aqueous solution, 0.30 g of 1-adamantylamine (an organic structure-determining agent), and 9.62 g of water were mixed. 0.062 g of aluminum sulfate was added and stirred, and then 3.95 g of Cataloid SI-30 (manufactured by JGC Catalysts & Chemicals Co., Ltd.) was added as a silica source and stirred thoroughly. Furthermore, 0.072 g of pulverized DDR-type zeolite was added as a seed crystal and stirred to prepare the raw material gel.

[0048] The obtained raw material gel was placed in an autoclave and heated at 160°C for one day. After filtering and washing the product with water, it was dried at 100°C to obtain an as-made type white powder. X-ray diffraction (XRD) patterns of the product confirmed that the obtained product was a DDR type zeolite. Note that "as-made type" means the state after drying and before calcination of the organic structure-controlling agent.

[0049] The obtained zeolite powder was calcined 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. Subsequently, it was calcined at 500°C for 6 hours in an air atmosphere to obtain the proton-type zeolite of Example 1.

[0050] [Comparative Example 1] 3.65 g of 1 M sodium hydroxide aqueous solution, 0.30 g of 1-adamantylamine, and 9.61 g of water were mixed, and 0.125 g of aluminum sulfate was added and stirred. Then, 3.96 g of Cataloid SI-30 (manufactured by JGC Catalysts & Chemicals Co., Ltd.) was added as a silica source and stirred thoroughly. Furthermore, 0.072 g of pulverized DDR-type zeolite was added as a seed crystal and stirred to prepare the raw material gel. The obtained raw material gel was heated and post-treated in the same manner as in Example 1 to obtain the proton-type zeolite powder of Comparative Example 1.

[0051] [Comparative Example 2] 3.62 g of 1 M sodium hydroxide aqueous solution, 0.30 g of 1-adamantylamine, and 9.61 g of water were mixed, and 0.015 g of aluminum sulfate was added and stirred. Then, 3.95 g of Cataloid SI-30 (manufactured by JGC Catalysts & Chemicals Co., Ltd.) was added as a silica source and stirred thoroughly. Furthermore, 0.072 g of pulverized DDR-type zeolite was added as a seed crystal and stirred to prepare the raw material gel. The obtained raw material gel was heated and post-treated in the same manner as in Example 1 to obtain the proton-type zeolite powder of Comparative Example 2.

[0052] [Comparative Example 3] 8.37 g of 1 M aqueous sodium hydroxide solution, 0.61 g of 1-adamantylamine and 23.73 g of water were mixed, 0.124 g of aluminum sulfate was added thereto and stirred, and then 2.40 g of aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.) as a silica source was added and sufficiently 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 except that it was heated at 160 °C for 5 days, and a proton-type zeolite powder of Comparative Example 3 was obtained.

[0053] The synthesis conditions according to Example 1 and Comparative Examples 1 to 3 are summarized in Table 1.

[0054] [Evaluation of Zeolite] The following evaluations were performed on the zeolites according to Example 1 and Comparative Examples 1 to 3.

[0055] <X-ray Diffraction Measurement> X-ray diffraction (XRD) measurement of the synthesized zeolite was performed using "D2 PHASER" manufactured by BRUKER. The XRD pattern obtained by the measurement is shown in FIG. 1. From FIG. 1, it was confirmed that the zeolites according to Example 1 and Comparative Examples 1 to 3 all have a DDR-type structure.

[0056] <Elemental Analysis> Elemental analysis was performed by inductively coupled plasma optical emission spectrometry (ICP-AES). "iCAP7600 Duo" manufactured by Thermo Fisher Scientific was used for the measurement of the zeolites of Example 1 and Comparative Examples 1 to 3. The Si / Al molar ratios of the synthesized zeolites are shown in Table 1.

[0057] <Scanning Electron Microscope> Scanning electron microscope (SEM) measurements for Example 1 and Comparative Examples 1 and 2 were performed using a Zeiss "ULTRA55". SEM measurements for Comparative Example 3 were performed using a Hitachi High-Technologies "S-4800". Figure 2 shows SEM images of the zeolite catalysts for Example 1 and Comparative Examples 1-3. Figure 2 is a 10,000x magnification image. Fifty primary particles were randomly selected from the obtained SEM images, and their major axis was measured to determine the particle diameter. For Comparative Example 3, due to its larger particle diameter, a 4,000x magnification image was used to measure the particle diameter. The arithmetic mean of the obtained particle diameters was used as the average primary particle diameter. The results are shown in Table 1. <Nitrogen adsorption / desorption measurement> Nitrogen adsorption and desorption measurements of the synthesized zeolite were performed using the "Belsorp-miniII" manufactured by Microtrac-Bell. For the measurements, the zeolite was heated and dried under vacuum at 400°C for 2 hours, and then nitrogen adsorption and desorption measurements were performed at liquid nitrogen temperature. Data analysis was performed using BELMaster, analysis software manufactured by Microtrac-Bell. The BET specific surface area (A2) was calculated by plotting the BET data for relative pressures (P / P0) of 0.002 to 0.06. The external surface area (A1) and micropore volume (A3) were calculated by plotting the data for relative pressures (P / P0) of 0.20 to 0.42. Harkins-Jura was used as the standard isotherm.

[0058] <Manufacturing of lower olefins> Lower olefins were produced using the zeolites obtained in Example 1 and Comparative Examples 1-3. A fixed-bed flow reactor was used for the reaction, and 100 mg of pre-mixed proton-type zeolite powder and 400 mg of quartz sand were packed into a 6 mm inner diameter quartz reaction tube. A mixed gas of 50 mol% methanol and 50 mol% nitrogen was introduced at a methanol weight space velocity of 1 hr. -1The mixture was supplied to the reactor as described above, and the reaction was carried out at 450°C and 0.1 MPa (absolute pressure). The product was analyzed by gas chromatography every hour from the start of the reaction. Figure 3 shows a graph illustrating the changes in methanol conversion rate and selectivity. Table 1 shows the methanol conversion rate (%), ethylene yield (C-mol%), propylene yield (C-mol%), butene yield (C-mol%), and catalyst lifetime (hr) after 3 hours from the start of the reaction. Catalyst lifetime was defined as the time during which the methanol conversion rate remained above 90%. In addition, the average values ​​for methanol conversion rate (%), ethylene yield (C-mol%), propylene yield (C-mol%), and butene yield (C-mol%) from 2 hours to 4 hours after the start of the reaction are also shown.

[0059] [Table 1]

[0060] As shown in Table 1, the zeolite according to Example 1 exhibited a high ethylene yield and maintained a high raw material conversion rate over a long period of time.

Claims

1. It contains silicon (Si) and aluminum (Al) as constituent elements, with a molar ratio of silicon (Si) to aluminum (Al) (Si / Al) of 75 to 140, and an average primary particle diameter of 60 nm to 700 nm. A DDR-type zeolite catalyst for ethylene production, wherein, in nitrogen adsorption / desorption measurements, the ratio of the BET specific surface area (A2) calculated by the BET plot to the external surface area (A1) calculated by the t plot (A2 / A1) is 20 or less.

2. A mixture comprising the DDR-type zeolite catalyst for ethylene production described in Claim 1 and a substance or binder that is inert to the reaction.

3. A method for producing ethylene, comprising the step of contacting a raw material containing methanol and / or dimethyl ether with the DDR-type zeolite catalyst for ethylene production described in claim 1 or the mixture described in claim 2.

4. The reaction temperature is between 200°C and 750°C, the reaction pressure is between 0.1 kPa and 2 MPa, and the gravitational space velocity is 0.1 hr －１ Over 10 hours －１ The method for producing ethylene according to claim 3, as described below.

Images