Composite catalyst, method for producing the composite catalyst, and method for producing a lower olefin

Abstract

To provide a composite catalyst having a high conversion rate and high lower olefin selectivity in combination when manufacturing lower olefins from a hydrocarbon raw material.SOLUTION: A composite catalyst contains a zeolite that is a crystalline aluminosilicate containing gallium and iron and having a skeleton structure with 8 to 12 membered rings, or a zeolite that is a crystalline aluminosilicate having a skeleton structure that contains iron but does not contain gallium and has 8 to 12 membered rings, silicon dioxide as a binder, and diphosphorus pentoxide. By using this composite catalyst, a high reaction conversion rate and a high selectivity for lower olefins can be provided at the same time.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a composite catalyst, a method for producing a composite catalyst, and a method for producing a lower olefin. [Background technology]

[0002] Lower olefins (ethylene and propylene), which are important basic raw materials in petrochemicals, are expected to continue to see steady demand growth. Currently, more than 50% of propylene is produced by steam cracking (steam cracking) of naphtha and other materials. However, this technology is catalyst-free, requiring high temperatures of 800-900°C for decomposition, and is an energy-intensive process that involves the input of excess steam.

[0003] Furthermore, since the main product of the above technology is ethylene and propylene is produced as a by-product, the production ratio is almost fixed at ethylene / propylene = 2 / 1 when naphtha is used as a raw material. This means that supply may not be able to keep up with future increases in demand for propylene. From these perspectives, there is a strong desire for an alternative process that can efficiently produce propylene from naphtha raw material with the least possible energy consumption.

[0004] Currently, research and development is underway on energy-saving propylene production methods that apply fixed-bed naphtha catalytic cracking using zeolite catalysts as an alternative to steam crackers. For example, it has been proposed to use crystalline aluminosilicates having an MFI-type structure that does not contain gallium but contains iron, or contains iron and gallium, as catalysts when producing lower olefins from low-boiling-point hydrocarbon raw materials such as light naphtha (see, for example, Patent Documents 1-3). According to the zeolite catalysts described in Patent Documents 1-3, it is possible to increase the amount of propylene produced relative to ethylene at relatively low reaction temperatures, and to extend the catalyst life. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-24005 [Patent Document 2] Japanese Patent Publication No. 2014-24006 [Patent Document 3] Japanese Patent Publication No. 2014-24007 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] When commercializing the production of lower olefins using zeolite catalysts, it is desirable to use a fixed-bed system, which has lower equipment costs than a fluidized-bed system. In this case, it is preferable to be able to stably and continuously produce lower olefins over a long period of time using a fixedly positioned zeolite catalyst, and further extension of the zeolite catalyst's lifespan is required. In order to further reduce manufacturing costs for commercialization, in addition to having a long lifespan, a zeolite catalyst is needed that can produce lower olefins with a high conversion rate and high selectivity.

[0007] This disclosure is made in view of the above circumstances and aims to provide a composite catalyst that has both a high conversion rate and a high selectivity for lower olefins in the production of lower olefins from hydrocarbon raw materials. [Means for solving the problem]

[0008] One aspect of the present disclosure is a composite catalyst. This composite catalyst comprises a zeolite which is a crystalline aluminosilicate containing gallium and iron and having a skeletal structure with 8 to 12 membered rings, or a zeolite which does not contain gallium but contains iron and has a skeletal structure with 8 to 12 membered rings, silicon dioxide as a binder, and phosphorus pentoxide.

[0009] Another aspect of this disclosure is a method for producing the above-mentioned composite catalyst. This method includes a hydrothermal synthesis step, a molding step, an ion exchange step, and a phosphorus modification step.

[0010] Still another aspect of the present disclosure is a method for producing lower olefins. In this production method, a hydrocarbon raw material is supplied to the inlet of a catalyst layer containing the above composite catalyst, lower olefins are obtained from the outlet of the catalyst layer, and the temperature difference between the inlet and the outlet is 20°C to 150°C.

Advantages of the Invention

[0011] According to the present disclosure, in the production of lower olefins, a composite catalyst having both a high conversion rate and a high lower olefin selectivity can be provided.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic diagram of a reactor used in the performance evaluation test of each composite catalyst of Examples 1 to 10 and Comparative Example 1. [Figure 2] It is a diagram showing the composition of each composite catalyst of Examples 1 to 8 and Comparative Example 1. [Figure 3] It is a diagram showing the performance evaluation test results of each composite catalyst of Examples 1 to 3 and Comparative Example 1. [Figure 4] It is a diagram showing the temperature distribution of the catalyst layer in the performance evaluation test of each composite catalyst of Examples 2, 4 to 8. [Figure 5] It is a diagram showing the performance evaluation test results of each composite catalyst of Examples 2, 4 to 8. [Figure 6] It is a diagram showing the performance evaluation test results of each composite catalyst of Examples 2, 4 to 8. [Figure 7] It is a diagram showing the composition of each composite catalyst of Examples 8 to 10. [Figure 8] It is a diagram showing the performance evaluation test results of each composite catalyst of Examples 8 to 10.

Modes for Carrying Out the Invention

[0013] (Composite Catalyst) The composite catalyst of the present disclosure is a composite catalyst for producing lower olefins from a hydrocarbon raw material, and includes a zeolite which is a crystalline aluminosilicate containing gallium and iron or iron and having a framework structure with a ring member number of 8 to 12, silicon dioxide, and diphosphorus pentoxide. According to such a configuration, by compounding the zeolite having catalytic action, silicon dioxide, and diphosphorus pentoxide as a binder, it is possible to increase the conversion rate of the hydrocarbon raw material while suppressing a decrease in the selectivity of ethylene and propylene.

[0014] In Patent Documents 1 to 3, aluminum oxide (alumina powder) is used as a binder, but it has been found that the catalyst life is clearly extended by using silicon dioxide (silica) as a binder. That is, it has been found that the catalyst life can be extended by mixing silicon dioxide with the above-mentioned zeolite. This is presumably because silicon dioxide coexisting with at least a part of the acid sites present on the outer surface of the zeolite affects, for example, by reducing the acid strength of the acid sites, suppressing the formation of aromatic hydrocarbons from lower olefins on the outer surface of the zeolite, and inhibiting the formation of coke which causes the shortening of the catalyst life. Furthermore, by including diphosphorus pentoxide in the catalyst, the conversion rate of the hydrocarbon raw material can be increased. As a result, it becomes possible to produce lower olefins from a hydrocarbon raw material in a fixed bed system, which can be sufficiently efficiently produced over a long period of time.

[0015] The zeolite which is a crystalline aluminosilicate has a framework structure with a ring member number of 8 to 12. The framework structure of the zeolite is database-ized by the International Zeolite Association, and a structure code consisting of three capital letters of the alphabet is given. This structure code specifies only the geometric structure of the framework.

[0016] For example, LTA is a structural code for an 8-membered ring skeleton structure, FER, MWW, MFI are examples of structural codes for a 10-membered ring skeleton structure, and MOR, LTL, FAU, BEA are examples of structural codes for a 12-membered ring skeleton structure. Note that only some structural codes for zeolites with each number of member rings are shown here. The pore diameter of a zeolite is influenced by the number of member rings in its skeleton structure, and the pore diameter is determined to some extent by whether the number of member rings is 8 to 12. For example, the pore diameter of zeolites in general is about 0.2 to 1.0 nm, and for zeolites with a typical skeleton structure of 8 to 12 member rings, the pore diameter is about 0.40 nm to 0.75 nm. In this embodiment, the pore size of the zeolite is preferably such that it is suitable for use when producing propylene (ethylene) using the catalytic function of the zeolite with, for example, a lower olefin of C4 to C8 as a hydrocarbon raw material. For example, it is preferably about 0.40 nm to 0.75 nm as described above, but is not limited to this range.

[0017] In this case, the number of member rings in the zeolite skeleton structure is preferably 8 to 12, and more preferably 10 to 12. For example, ZSM-5 (Zeolite Socony Mobil-5) is known as an MFI type zeolite having a 10-membered ring structure, and beta-type zeolite is known as a BEA type zeolite having a 12-membered ring structure. MFI type zeolites and beta-type zeolites can be suitably used as zeolites with 8 to 12 member rings. In particular, MFI type zeolites can be suitably used.

[0018] Furthermore, in this embodiment, the zeolite used is, for example, a crystalline aluminosilicate that does not contain gallium (Ga) but contains iron (Fe), or a crystalline aluminosilicate that contains both gallium (Ga) and iron. Fe has the function of suppressing the acidity of the acid sites of the zeolite. Ga has the function of promoting the dehydrogenation reaction of alkanes. The zeolite catalyst in this embodiment is a composite catalyst obtained by molding and calcination with the addition of a binder, and by phosphorus modification, with silicon dioxide used as the binder.

[0019] In this embodiment, the phosphorus pentoxide content in the composite catalyst is preferably 0.1 to 5.0 wt%, and more preferably 0.1 to 3.0 wt%. By setting the phosphorus pentoxide content within this range, the conversion rate of hydrocarbon raw materials can be further improved.

[0020] In a zeolite that is an MFI-type crystalline aluminosilicate containing iron (but not gallium), the elemental molar composition ratio of iron (iron / (iron + aluminum (Al))) is preferably 0.4 to 0.7, and more preferably 0.4 to 0.6.

[0021] In a zeolite that is an MFI-type crystalline aluminosilicate containing iron (but not gallium), the acid density (silicon (Si) / (iron + aluminum) element ratio) is preferably 75.0 to 200.0, and more preferably 80.0 to 200.0. The element ratio refers to the composition ratio based on the number of moles of each element as described above.

[0022] Furthermore, in a zeolite that is an MFI-type crystalline aluminosilicate containing iron and gallium elements, the elemental molar composition ratio of iron (iron / (iron + gallium + aluminum)) is preferably 0.2 to 0.6, and more preferably 0.3 to 0.5.

[0023] Furthermore, in a zeolite which is an MFI-type crystalline aluminosilicate containing iron and gallium elements, the elemental molar composition ratio of gallium (gallium / (iron + gallium + aluminum)) is preferably 0.1 to 0.4, and more preferably 0.2 to 0.4.

[0024] Furthermore, in MFI-type zeolite catalysts containing iron and gallium elements, the acid density (silicon element / (iron element + gallium element + aluminum element) element ratio) is preferably 75.0 to 200.0, and more preferably 80.0 to 200.0.

[0025] As described above, by using the zeolite of this embodiment, which is an MFI-type crystalline aluminosilicate containing iron, the acid strength can be adjusted from the iron content and acid density. Furthermore, by adding gallium, the dehydrogenation-promoting effect of alkanes can be improved. At the acid site of the zeolite, alkanes are catalytically decomposed, generating carbon double bonds and producing lower olefins. However, if the acid strength at the acid site is too strong, for example, the lower olefins will not detach from the acid site after becoming lower olefins, and the reaction will proceed further, leading to cyclization and dehydrogenation to produce aromatic hydrocarbons. A large amount of aromatic hydrocarbons will result in a large amount of coke precipitation, which shortens the lifespan of the composite catalyst. Therefore, adjusting the acid strength is important in reducing the amount of coke precipitation.

[0026] By setting the molar composition ratio of iron element, the molar composition ratio of gallium element, and the acid density within the above-mentioned ranges, the yield of propylene can be further improved, and the generation of aromatic carbons that cause coke formation can be further suppressed.

[0027] In the composite catalyst according to this embodiment, the zeolite is preferably a crystalline aluminosilicate that does not contain gallium but contains iron, and the acid density, as the composition ratio of the number of moles of silicon to the sum of the number of moles of iron and aluminum, is 75.0 to 200.0, and the composition ratio of the number of moles of iron to the sum of the number of moles of iron and aluminum is preferably 0.4 to 0.7. With such a configuration, by setting the acid density and the molar composition ratio of iron within the above ranges, the amount of propylene produced relative to ethylene can be increased, and the effect of suppressing the production of aromatic hydrocarbons in the presence of silicon dioxide as a binder can be further enhanced.

[0028] In the composite catalyst according to this embodiment, the zeolite is a crystalline aluminosilicate containing iron and gallium, and preferably the acid density, as the composition ratio of the number of moles of silicon to the sum of the number of moles of iron, gallium, and aluminum, is 75.0 to 200.0, the composition ratio of the number of moles of gallium to the sum of the number of moles of iron, gallium, and aluminum is 0.1 to 0.4, and the composition ratio of the number of moles of iron to the sum of the number of moles of iron, gallium, and aluminum is 0.2 to 0.6. With such a configuration, by setting the acid density, the molar composition ratio of iron (Fe), and the molar composition ratio of gallium (Ga) within the above ranges, the amount of propylene produced relative to ethylene can be increased, and the production of aromatic hydrocarbons can be further suppressed in the presence of silicon dioxide, which is a binder. Here, iron has the function of suppressing the acid strength of the acid sites of the zeolite, and gallium has the function of promoting the dehydrogenation reaction of alkanes.

[0029] In the composite catalyst according to this embodiment, the silicon dioxide (silica) content is preferably 5 to 50 wt%, and more preferably 5 to 40 wt%. By setting the silicon dioxide content within this range, the amount of aromatic hydrocarbons produced can be reduced more efficiently while suppressing the decrease in the amount of propylene produced. This makes it possible to more effectively extend the catalytic function of the zeolite in the composite catalyst. To increase the yield of lower olefins, it is preferable to reduce the silicon dioxide content and increase the zeolite content, and to suppress the production of aromatic hydrocarbons, it is preferable to increase the silicon dioxide content. Furthermore, it is presumed that silicon dioxide as a binder has a stronger effect than aluminum oxide (alumina) as a binder in coating and inactivating acid sites on the outer surface of the zeolite.

[0030] The BET specific surface area of ​​silicon dioxide is 50-500 m². 2 It is preferable that it be / g, and 100-400m 2 It is more preferable that the BET specific surface area is within this range. By setting the BET specific surface area within this range, it is possible to further improve the raw material conversion rate while maintaining a high selectivity for lower olefins.

[0031] (Method for manufacturing composite catalysts) The composite catalyst according to the above embodiment is manufactured through four steps: 1. hydrothermal synthesis, 2. molding, 3. ion exchange, and 4. phosphorus modification. Each step will be described below.

[0032] 1. Hydrothermal synthesis process Hydrothermal synthesis is a general term for methods of synthesizing substances in the presence of high-temperature, high-pressure water, and many zeolites, as crystalline aluminosilicates, are synthesized using this method. Common raw materials used in synthesis include silica sources (sodium silicate, colloidal silica, fumed silica, etc.), alumina sources (aluminum hydroxide, sodium aluminate, etc.), structure-regulating agents (amines, etc.), mineralizing agents (alkali metal hydroxides, etc.), and water.

[0033] In this embodiment, an iron source (e.g., iron nitrate, iron oxide, iron sulfate, iron phosphate, iron chloride, iron bromide, metallic iron (iron powder), organic iron acid, etc.) is added to the raw materials. When producing a composite catalyst containing iron and gallium, in addition to the iron source, a gallium source (e.g., gallium nitrate, gallium oxide, gallium sulfate, gallium phosphate, gallium chloride, gallium bromide, gallium hydroxide, etc.) is added to the raw materials. These are mixed to prepare a highly reactive amorphous hydrogel (mother gel), which is then packed into an autoclave, a pressure-resistant reactor, and heated at approximately 150°C for a predetermined time to synthesize zeolite. After the hydrothermal synthesis reaction, powdered zeolite is obtained through steps such as separation of the product, washing with water, drying, and calcination (performed to decompose and remove structural defining agents).

[0034] To explain the zeolite manufacturing method in more detail, a mother liquor gel A is prepared, consisting of colloidal silica with a particle size of 8-11 nm as a silicon source and sodium hydroxide (NaOH) for pH adjustment, and a mother liquor gel B is prepared, containing Al2(SO4)-nH2O as an aluminum source, Ga(NO3)3-nH2O as a gallium source, Fe(NO3)3-nH2O as an iron source, and tetrapropylammonium bromide (TPrABr) as a structure-controlling agent. It is preferable to reduce the amount of TPrABr added as a structure-controlling agent.

[0035] Next, mother liquor gel A and mother liquor gel B are stirred and mixed (for example, for 15 minutes). This prepares a highly reactive amorphous hydrogel. Next, the mixed and stirred mother liquor gel is aged (for example, overnight at 60°C). Then, as described above, the mixture is stirred at 110°C to 200°C and at a rotation speed of 150 rpm to 1000 rpm (for example, hydrothermal synthesis under self-pressure in an autoclave). That is, the hydrogel is crystallized under high temperature and high pressure. However, the reaction temperature is relatively low, and the generation of coarse particles is suppressed by nucleation at low temperatures. Also, the stirring speed is relatively high to increase the amount of nucleation. Crystals are obtained by stirring under these conditions for, for example, 24 hours. The obtained crystals are washed with water and dehydrated by centrifugation. After that, the crystals are dried for 3 hours at, for example, 120°C and then calcined for 3 hours at 550°C to remove TPrABr. Note that if gallium is not present, no gallium source is added to mother liquor gel B.

[0036] 2. Molding process Generally, when zeolites are used industrially as catalysts, they are often molded into cylindrical shapes or other forms to improve mechanical properties and reduce pressure loss. This process mainly involves steps such as kneading the zeolite synthesized as described above with silicon dioxide as a binder, molding, drying, and firing. For molding, methods such as extrusion molding are used.

[0037] For example, powdered zeolite obtained through the hydrothermal synthesis process (or ion exchange process) described above is mixed with silica powder and starch as a molding aid, and then mixed with an aqueous sodium hydroxide solution (alkaline aqueous solution) to obtain a lump-shaped mixture. Note that the molding aid is not limited to starch; for example, any substance that increases viscosity when water is added, which can form a lump when the zeolite powder and silica powder are mixed with water, and which, during firing, is almost entirely converted into water and carbon dioxide and disappears from the molded body, such as PVP (polyvinylpyrrolidone). This mixture is processed into a cylindrical shape by, for example, extrusion molding and dried at 120°C for about 3 hours. Next, a molded body can be obtained by firing at 550°C for 3 hours under air circulation.

[0038] In the molding process, it is preferable to use an alkaline aqueous solution containing starch as a molding aid when molding the mixture of zeolite and silicon dioxide. By adding an alkaline aqueous solution containing starch when kneading the zeolite and silicon dioxide, it becomes easier to form a lump-like mixture.

[0039] In addition, the molding process may be performed after the ion exchange process, or the ion exchange process may be performed after the molding process, but it is preferable to perform the ion exchange process after the molding process.

[0040] 3. Ion exchange process Many chemical reactions that utilize zeolites as catalysts take advantage of their properties as solid acids, and these acidic properties are manifested by introducing acidic OH groups (Brønsted acid sites) into the zeolite. To manifest these acidic properties, ion exchange reactions are generally applied. Typically, zeolites obtained by hydrothermal synthesis have sodium cations (Na) added to maintain charge balance. + It contains ), but by ion exchange, protons (H + ) is replaced with ammonium ions (NH4) using NH4NO3 solution. +) is ion-exchanged, and then dried and calcined to remove ammonia, thereby removing protons (H + Sometimes, a method is used to convert it to a proton-type zeolite catalyst. For example, a proton-type zeolite catalyst can be obtained by repeating ion exchange with an aqueous ammonium nitrate solution under boiling reflux and subsequent water washing four times, followed by drying at 120°C for 3 hours and calcination at 550°C for 3 hours under air circulation.

[0041] When an ion exchange process is performed after the molding process, it may be possible to suppress the generation of aromatic hydrocarbons, which cause coke formation, in the production of lower olefins using the composite catalyst finally obtained via the phosphorus modification process. Furthermore, the molded zeolite catalyst after the molding process is easier to handle than the powdered crystalline aluminosilicate used in the hydrothermal synthesis process, improving the workability of the ion exchange process.

[0042] 4. Phosphorus modification process After the molding and ion exchange processes, the obtained zeolite catalyst is impregnated with an aqueous solution of phosphorus precursor, dried, and calcined to modify it with phosphorus. This phosphorus modification process yields a composite catalyst containing phosphorus pentoxide (hereinafter also referred to as the phosphorus-modified composite catalyst). Examples of phosphorus precursors include diammonium hydrogen phosphate ((NH4)2HPO4) and phosphoric acid (H3PO4). The reaction conditions in the phosphorus modification process can be appropriately determined by those skilled in the art. For example, the composite catalyst is impregnated with an aqueous solution of phosphorus precursor for 5 minutes under boiling reflux. Subsequently, the phosphorus-modified composite catalyst can be obtained by washing with purified water, drying, and calcining at 550°C for 3 hours under air circulation.

[0043] In the production of the composite catalyst, the process sequence can, for example, be carried out in the order of hydrothermal synthesis, molding, ion exchange, and phosphorus modification, although it is also possible to perform the molding process after the ion exchange process. Performing the ion exchange process on a composite catalyst molded into a predetermined shape is more efficient than performing the ion exchange process on powdered zeolite obtained in the hydrothermal synthesis process. Furthermore, it may be possible to suppress the generation of aromatic hydrocarbons by forming the composite catalyst with silicon dioxide as a binder and then exposing acid sites through the ion exchange process.

[0044] (Method for producing lower olefins) The method for producing lower olefins according to this embodiment involves supplying hydrocarbon raw materials to the inlet of a catalyst layer containing the composite catalyst according to the above embodiment, obtaining lower olefins from the outlet of the catalyst layer, and maintaining a temperature difference of 20°C to 150°C between the inlet and outlet. With this configuration, the generation of aromatic hydrocarbons can be suppressed, and the production volume of lower olefins can be increased, that is, the selectivity of lower olefins can be increased.

[0045] In this embodiment, for example, a catalyst layer containing the above-described composite catalyst is placed as a fixed bed in the reactor. The hydrocarbon raw material supplied to the reactor passes through the catalyst layer in contact with it. As a result, the hydrocarbon raw material is converted into lower olefins such as ethylene and propylene. The generated lower olefins are obtained from the outlet of the catalyst layer. When the hydrocarbon raw material passes through the catalyst layer, the temperature difference between the inlet and outlet of the catalyst layer is 10 to 200°C, preferably 20 to 100°C. This temperature difference can suppress the generation of aromatic hydrocarbons and increase the selectivity of lower olefins.

[0046] The reaction between the hydrocarbon raw material and the catalyst layer is preferably carried out in a mild temperature range of 530°C to 650°C, more preferably 550°C to 640°C. Since this temperature is lower than that of the steam cracking method, it offers superior energy efficiency and reduces costs. Furthermore, by generating lower olefins at relatively low temperatures, the generation of aromatic hydrocarbons can be suppressed, thereby extending the lifespan of the composite catalyst.

[0047] In this embodiment, the composite catalyst can be used for a long period of time, but a gradual decrease in the amount of lower olefin produced occurs due to catalyst degradation over time. Therefore, for example, by gradually increasing the contact temperature between the hydrocarbon raw material and the catalyst layer over time, the production amount of lower olefin can be stabilized over a long period of time, and the replacement or regeneration period of the composite catalyst can be postponed.

[0048] When supplying hydrocarbon raw materials to the catalyst layer as a gas, the gas can contain 15 wt% or more, more preferably 50 wt% or more of the hydrocarbon raw materials. The contact time between the hydrocarbon raw materials and the catalyst layer is preferably 0.08 to 1.0 hours, more preferably 0.08 to 0.4 hours. By setting the contact time within this range, lower olefins can be produced more efficiently, and the amount of aromatic hydrocarbons produced can be suppressed, thereby extending the lifespan of the composite catalyst. In other words, if the contact time is short, the amount of lower olefins produced decreases, but the amount of aromatic hydrocarbons produced also decreases, and the lifespan of the composite catalyst is extended. If the contact time is long, the amount of lower olefins produced increases, but the amount of aromatic hydrocarbons produced also increases, and the lifespan of the composite catalyst is shortened. Therefore, it is preferable to set the contact time considering the amount of lower olefins produced and the lifespan of the composite catalyst.

[0049] For example, when using a raw material gas such as light naphtha as a hydrocarbon raw material, the raw material gas is supplied to the reactor without dilution with an inert gas such as nitrogen or a diluent such as water vapor. That is, the hydrocarbon raw material is brought into contact with the composite catalyst and reacted. The raw material gas may contain a diluent, and in this case, the gas supplied to the composite catalyst preferably contains 15 wt% or more of the hydrocarbon material such as light naphtha, and more preferably 50 wt% or more. The above-mentioned composite catalyst is placed as a fixed bed in the reactor, and the raw material gas supplied to the reactor is passed through it in contact with the composite catalyst. In this case, the reaction proceeds in a mild temperature range of 530°C to 650°C, more preferably 550°C to 640°C, to produce ethylene and propylene.

[0050] Hydrocarbon raw materials include low-boiling-point hydrocarbon raw materials such as light naphtha. Naphtha (full-range naphtha) is a product obtained by distilling crude oil using an atmospheric distillation unit, with a boiling point range of approximately 30 to 200°C. Of this naphtha, those with a boiling point range of approximately 30 to 100°C are called light naphtha, and those with a boiling point range of approximately 100 to 200°C are called heavy naphtha. Light naphtha corresponds to a fraction mainly composed of pentane (5 carbon atoms) and hexane (6 carbon atoms).

[0051] The low-boiling-point hydrocarbon raw material is basically light naphtha, but it may also contain some heavy naphtha or be full-range naphtha. Furthermore, the low-boiling-point hydrocarbon raw material may be something other than naphtha; for example, natural gas other than petroleum or other hydrocarbon raw materials with fractions equivalent to light naphtha can be used. By-products from the production of various products from petroleum and natural gas can also be used as hydrocarbon raw materials, and basically, hydrocarbons with relatively low boiling points can be used as raw materials. In this embodiment, lower olefins are sometimes defined as olefins with a small number of carbon atoms, such as ethylene, propylene, butene, or olefins with more carbon atoms (e.g., 5 to 8 carbon atoms), but here, lower olefins include at least ethylene with 2 carbon atoms and propylene with 3 carbon atoms.

[0052] In the reaction to produce lower olefins, the contact time, which is the reciprocal of the LHSV (Liquid Hourly Space Velocity) of the hydrocarbon raw material, is preferably 0.08 to 1.0 h, and more preferably 0.08 to 0.4 h. The LHSV is preferably 1.0 to 12.5 h⁻¹, and more preferably 2.5 to 12.5 h⁻¹. Here, LHSV is the rate at which the hydrocarbon raw material is supplied to the catalyst layer as a liquid, and contact time is the time it takes for the hydrocarbon raw material to pass through the catalyst layer as a liquid. When the raw material is supplied to the catalyst layer, as described above, the raw material is in a gaseous state from a liquid, but here, the space velocity of the raw material as a liquid before gasification supplied to the reaction vessel is used. Note that the space velocity may be the space velocity of the raw material gas (GHSV) or the space velocity of weight (WHSV).

[0053] In the production of lower olefins, increasing the reaction temperature increases the conversion rate of hydrocarbon raw materials, resulting in a larger production volume of lower olefins and also a larger production volume of aromatic hydrocarbons. Therefore, it is necessary to determine the reaction temperature by balancing the energy efficiency during heating, the production volume of lower olefins, and the lifespan of the composite catalyst due to the increase in aromatic hydrocarbons. By setting the temperature within the range described above, it is possible to ensure a long lifespan for the composite catalyst and stable production of lower olefins.

[0054] In the production of lower olefins, increasing the contact time increases the conversion rate of hydrocarbon raw materials, leading to a larger production volume of lower olefins and also a larger production volume of aromatic hydrocarbons. Therefore, it is necessary to determine the contact time by balancing the production volume of lower olefins with the lifespan of the composite catalyst due to the increase in aromatic hydrocarbons. By setting the contact time within the range described above, it is possible to ensure a long lifespan for the composite catalyst and stable production of lower olefins.

[0055] In this embodiment, when the composite catalyst is used continuously, the amount of aromatic hydrocarbons produced is less than in the conventional method, and consequently the amount of precipitated carbon is also less, thus extending the lifespan of the composite catalyst. In the long-term production of lower olefins, for example, if the composite catalyst is replaced or regenerated when the yield of lower olefins falls to a set lower limit, the yield of lower olefins will gradually decrease over time. Therefore, by increasing the reaction temperature or lengthening the contact time (decreasing the LHSV (space velocity)) in response to the passage of time, the decrease in the yield of lower olefins can be suppressed, and the yield of lower olefins can be stabilized over a long period of time.

[0056] In this case, there is a risk that the amount of aromatic hydrocarbons produced may increase due to the rise in reaction temperature and decrease in space velocity. However, the amount of aromatic hydrocarbons produced also decreases over time, and the rise in reaction temperature and decrease in space velocity do not significantly alter the decreasing trend in the amount of aromatic hydrocarbons produced over time, making it unlikely that the amount of aromatic hydrocarbons will increase. Note that the rise in reaction temperature and the deceleration of the space velocity of the raw materials (increase in contact time) may be performed individually or in combination. Furthermore, when combining the rise in reaction temperature and the deceleration of space velocity, these may be performed at the same time or at different times. For example, in continuous production, the space velocity may be decelerated in the initial stages and the reaction temperature may be increased in the later stages, or vice versa. Alternatively, the rise in reaction temperature and the deceleration of space velocity may be performed alternately, or at different frequencies, for example, the reaction temperature may be increased three times, followed by the deceleration of space velocity once.

[0057] In the composite catalyst, the method for producing this composite catalyst, and the method for producing lower olefins according to the above-described embodiment, silica is used as a binder for forming powdered zeolite, and phosphorus pentoxide is also used to suppress coke formation and increase the conversion rate while maintaining a high selectivity for lower olefins. Therefore, in the production of lower olefins using the composite catalyst, it becomes possible to efficiently and continuously produce lower olefins for a long period of time of 1000 hours or more in a mild temperature range of about 530 to 650°C (a low temperature range in the production of lower olefins). [Examples]

[0058] Next, embodiments of the present disclosure will be described. These embodiments are not intended to limit the present disclosure in any way.

[0059] (Example 1) Method for synthesizing Fe-Ga-Al-MFI zeolite Solution A consisted of 58.9 g of colloidal silica (SiO2 30.6 wt%, Na2O 0.4 wt%, H2O 69.0 wt%) and 2.26 g of sodium hydroxide. Solution B consisted of 0.19 g of aluminum sulfate n hydrate, 0.11 g of gallium nitrate n hydrate, 0.24 g of iron nitrate nonahydrate, 3.10 g of tetrapropylammonium bromide, and 187.8 g of purified water. Solutions A and B were gradually mixed at room temperature with stirring, and then vigorously stirred in a mixer for 15 minutes. The mixed solution was kept warm at 60°C and allowed to stand overnight. After that, a hydrothermal synthesis reaction was carried out in an autoclave under self-pressure at 115°C for 72 hours at 900 rpm. After cooling, the product was thoroughly washed with purified water. Subsequently, a powdered Na-type MFI zeolite containing Fe, Ga, and Al (hereinafter referred to as Fe-Ga-Al-MFI zeolite) was synthesized by drying at 120°C for 3 hours and then calcining at 550°C for 3 hours under air circulation. The elemental molar composition of this zeolite was determined by X-ray fluorescence analysis to be Si / (Fe+Ga+Al)=91.5, Fe / (Fe+Ga+Al)=0.6, Ga / (Fe+Ga+Al)=0.1, and Al / (Fe+Ga+Al)=0.3 (see Figure 2).

[0060] Method for preparing Fe-Ga-Al-MFI / AE200 catalyst Powdered Na-type Fe-Ga-Al-MFI zeolite synthesized according to the above procedure, and silica powder as a binder (AEROSIL® 200, Nippon Aerosil Co., Ltd., BET specific surface area 200 m²) 2After mixing a predetermined amount of starch as a molding aid with the mixture ( / g), the mixture was kneaded while adding an appropriate amount of sodium hydroxide aqueous solution (NaOH concentration 4.5 wt%) to obtain a granular zeolite / silica mixture. Subsequently, it was processed into a cylindrical shape (1.0 mmφ) using an extruder, dried at 120°C for 3 hours, and calcined at 550°C for 3 hours under air circulation to obtain an Fe-Ga-Al-MFI zeolite / silica composite. This composite was subjected to ion exchange with a 2.2 mol / L ammonium nitrate aqueous solution under boiling reflux, followed by water washing four times (each ion exchange lasting 2 hours, with fresh 2.2 mol / L ammonium nitrate aqueous solution used each time), dried at 120°C for 3 hours, and calcined at 550°C for 3 hours under air circulation to prepare a proton-type Fe-Ga-Al-MFI zeolite / silica composite catalyst (hereinafter referred to as Fe-Ga-Al-MFI / AE200 catalyst). The weight composition of this catalyst was determined by X-ray fluorescence analysis to be Fe-Ga-Al-MFI / AE200 = 65 / 35 [wt% / wt%] (see Figure 2).

[0061] Method for preparing P(0.2)-Fe-Ga-Al-MFI / AE200 catalyst (P2O5 loading rate 0.2 wt%) A cylindrical Fe-Ga-Al-MFI / AE200 catalyst prepared according to the above procedure was impregnated with a 0.5 mol / L aqueous solution of diammonium hydrogen phosphate under boiling reflux for 5 minutes. After heating was stopped, the catalyst was allowed to stand overnight and cooled naturally. After washing with a sufficient amount of purified water, the catalyst was dried at 120°C for 3 hours and calcined at 550°C for 3 hours under air circulation to prepare a phosphorus-modified Fe-Ga-Al-MFI / AE200 catalyst (hereinafter referred to as P(0.2)-Fe-Ga-Al-MFI / AE200 catalyst). The loading rate (weight composition) of the phosphorus compound was determined to be 0.2 wt% as phosphorus pentoxide (P2O5) by X-ray fluorescence analysis (see Figure 2).

[0062] Performance evaluation test method for P(0.2)-Fe-Ga-Al-MFI / AE200 catalyst The cylindrical P(0.2)-Fe-Ga-Al-MFI / AE200 catalyst prepared according to the above procedure was sized to a length of 1.0 - 2.0 mm to obtain a catalyst sample for performance evaluation. The performance evaluation test was carried out using a fixed-bed flow reactor for the catalytic cracking reaction of a light hydrocarbon raw material (a mixture of 50 wt% n-pentane (n-C5H 12 ) and 50 wt% n-hexane (n-C6H 14 )) (see Figure 1). 3.5 mL of the catalyst was filled into a stainless steel reaction tube (made of SUS316) with an inner diameter of 8.0 mm so that the bed height of the catalyst layer was 30 mm. Glass wool was filled before and after the catalyst layer, and alumina beads were further filled before and after the glass wool. The reaction conditions were as follows: the average temperature of the catalyst layer was about 650 °C (maintained so that the entire catalyst layer was about 650 °C, see Figures 3 and 4), the pressure was 0.15 MPa, and the LHSV (Liquid Hourly Space Velocity) of the light hydrocarbon raw material was 6.0 h -1 (the supply flow rate of the light hydrocarbon was 0.35 mL / min), and the catalytic cracking reaction was carried out. Two hours after the start of the reaction, the gas-phase and liquid-phase products were collected for gas chromatography analysis, and the one-pass conversion rate (wt%) of the light hydrocarbon raw material and the selectivity (wt%) of the products were determined as indicators of the catalyst performance. In the present disclosure, the one-pass conversion rate is defined as (the amount of supplied raw material - the amount of unreacted raw material) / the amount of supplied raw material x 100 [wt%], and the selectivity of the product is defined as the amount of product generated / (the amount of supplied raw material - the amount of unreacted raw material) x 100 [wt%].

[0063] (Example 2) Synthesis method of Fe-Ga-Al-MFI zeolite In the same manner as in Example 1, Na-type Fe-Ga-Al-MFI zeolite was synthesized. The elemental molar composition of this zeolite was determined by fluorescence X-ray analysis to be Si / (Fe + Ga + Al) = 91.5, Fe / (Fe + Ga + Al) = 0.6, Ga / (Fe + Ga + Al) = 0.1, and Al / (Fe + Ga + Al) = 0.3 (see Figure 2).

[0064] Preparation method of Fe-Ga-Al-MFI / AE200 catalyst Fe-Ga-Al-MFI / AE200 catalysts were prepared in the same manner as in Example 1. The weight composition of this catalyst was determined by X-ray fluorescence analysis to be Fe-Ga-Al-MFI / AE200 = 65 / 35 [wt% / wt%] (see Figure 2).

[0065] Method for preparing P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst (P2O5 loading rate 1.0 wt%) A phosphorus-modified Fe-Ga-Al-MFI / AE200 catalyst was prepared in the same manner as in Example 1, except that the concentration of the diammonium hydrogen phosphate aqueous solution used for impregnation was 2.0 mol / L (hereinafter referred to as P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst). The loading rate (weight composition) of the phosphorus compound was determined to be 1.0 wt% as phosphorus pentoxide (P2O5) by X-ray fluorescence analysis (see Figure 2).

[0066] Performance evaluation test method for P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst The cylindrical P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst prepared according to the procedure described above was granulated to a length of 1.0 to 2.0 mm to prepare a catalyst sample for performance evaluation. The performance evaluation test was carried out in the same manner as in Example 1 (see Figure 1).

[0067] (Example 3) Method for synthesizing Fe-Ga-Al-MFI zeolite Na-type Fe-Ga-Al-MFI zeolite was synthesized in the same manner as in Example 1. The elemental molar composition of this zeolite was determined by X-ray fluorescence analysis to be Si / (Fe+Ga+Al)=91.5, Fe / (Fe+Ga+Al)=0.6, Ga / (Fe+Ga+Al)=0.1, and Al / (Fe+Ga+Al)=0.3 (see Figure 2).

[0068] Method for preparing Fe-Ga-Al-MFI / AE200 catalyst Fe-Ga-Al-MFI / AE200 catalysts were prepared in the same manner as in Example 1. The weight composition of this catalyst was determined by X-ray fluorescence analysis to be Fe-Ga-Al-MFI / AE200 = 65 / 35 [wt% / wt%] (see Figure 2).

[0069] Method for preparing P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst (P2O5 loading rate 1.0 wt%) A phosphorus-modified Fe-Ga-Al-MFI / AE200 catalyst was prepared in the same manner as in Example 2 (hereinafter referred to as P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst). The loading rate (weight composition) of the phosphorus compound was determined to be 1.0 wt% as phosphorus pentoxide (P2O5) by X-ray fluorescence analysis (see Figure 2).

[0070] Performance evaluation test method for P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst The cylindrical P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst prepared according to the procedure described above was granulated to a length of 1.0 to 2.0 mm to prepare a catalyst sample for performance evaluation. The performance evaluation test was carried out in the same manner as in Example 1, except that steam (25 wt%) was added in addition to the light hydrocarbon raw material (see Figure 1).

[0071] (Comparative Example 1) Method for synthesizing Fe-Ga-Al-MFI zeolite Na-type Fe-Ga-Al-MFI zeolite was synthesized in the same manner as in Example 1. The elemental molar composition of this zeolite was determined by X-ray fluorescence analysis to be Si / (Fe+Ga+Al)=91.5, Fe / (Fe+Ga+Al)=0.6, Ga / (Fe+Ga+Al)=0.1, and Al / (Fe+Ga+Al)=0.3 (see Figure 2).

[0072] Method for preparing Fe-Ga-Al-MFI / AE200 catalyst Fe-Ga-Al-MFI / AE200 catalysts were prepared in the same manner as in Example 1. The weight composition of this catalyst was determined by X-ray fluorescence analysis to be Fe-Ga-Al-MFI / AE200 = 65 / 35 [wt% / wt%] (see Figure 2).

[0073] Performance evaluation test method for Fe-Ga-Al-MFI / AE200 catalyst The cylindrical Fe-Ga-Al-MFI / AE200 catalyst prepared according to the procedure described above was granulated to a length of 1.0 to 2.0 mm to prepare a catalyst sample for performance evaluation. The performance evaluation test was carried out in the same manner as in Example 1 (see Figure 1).

[0074] Figure 3 shows the catalyst performance test results for Comparative Example 1 and Examples 1-3. For the Fe-Ga-Al-MFI / AE200 catalyst without phosphorus compound modification (Comparative Example 1), the one-pass conversion rate of light hydrocarbon feedstocks was 71.5 wt%, the selectivity for lower olefins was 51.0 wt% (total of ethylene, propylene, and butenes), and the selectivity for BTX was 17.5 wt% (total of benzene, toluene, and xylene). On the other hand, for the P(0.2)-Fe-Ga-Al-MFI / AE200 catalyst with 0.2 wt% of P2O5 supported (Example 1), the one-pass conversion rate improved to 75.5 wt%, while maintaining the same level of lower olefin selectivity (50.3 wt%) as Comparative Example 1. In the P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst (Example 2), in which the P2O5 loading rate was increased to 1.0 wt%, the one-pass conversion rate improved to 79.9 wt%, and the lower olefin selectivity (49.4 wt%) was at the same level as Comparative Example 1. Furthermore, the BTX selectivity was 18.0-19.9 wt%, which was only a slight increase compared to Comparative Example 1.

[0075] From the above, it was found that applying a phosphorus-modified Fe-Ga-Al-MFI / SiO2 composite catalyst to the catalytic cracking reaction of light hydrocarbon raw materials has the effect of increasing the raw material conversion rate without significantly affecting the selectivity of the product. Furthermore, when a reaction test was conducted using the phosphorus-modified Fe-Ga-Al-MFI / SiO2 composite catalyst with the addition of 25 wt% steam to lower the partial pressure of the raw materials (Example 3), it was confirmed that the formation of lower olefins was further promoted and the selectivity improved to 58.2 wt%.

[0076] (Example 4) Method for synthesizing Fe-Ga-Al-MFI zeolite Na-type Fe-Ga-Al-MFI zeolite was synthesized in the same manner as in Example 1. The elemental molar composition of this zeolite was determined by X-ray fluorescence analysis to be Si / (Fe+Ga+Al)=91.5, Fe / (Fe+Ga+Al)=0.6, Ga / (Fe+Ga+Al)=0.1, and Al / (Fe+Ga+Al)=0.3 (see Figure 2).

[0077] Method for preparing Fe-Ga-Al-MFI / AE200 catalyst Fe-Ga-Al-MFI / AE200 catalysts were prepared in the same manner as in Example 1. The weight composition of this catalyst was determined by X-ray fluorescence analysis to be Fe-Ga-Al-MFI / AE200 = 65 / 35 [wt% / wt%] (see Figure 2).

[0078] Method for preparing P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst (P2O5 loading rate 1.0 wt%) A phosphorus-modified Fe-Ga-Al-MFI / AE200 catalyst was prepared in the same manner as in Example 2 (hereinafter referred to as P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst). The loading rate (weight composition) of the phosphorus compound was determined to be 1.0 wt% as phosphorus pentoxide (P2O5) by X-ray fluorescence analysis (see Figure 2).

[0079] Performance evaluation test method for P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst The cylindrical P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst prepared according to the procedure described above was granulated to a length of 1.0 to 2.0 mm to prepare a catalyst sample for performance evaluation. The performance evaluation test was carried out in the same manner as in Example 1, except that the average temperature of the catalyst layer was set to approximately 631°C (maintaining the inlet temperature of the catalyst layer to approximately 624°C and the outlet temperature to approximately 648°C, see Figure 4) (see Figure 1).

[0080] (Example 5) Method for synthesizing Fe-Ga-Al-MFI zeolite Na-type Fe-Ga-Al-MFI zeolite was synthesized in the same manner as in Example 1. The elemental molar composition of this zeolite was determined by X-ray fluorescence analysis to be Si / (Fe+Ga+Al)=91.5, Fe / (Fe+Ga+Al)=0.6, Ga / (Fe+Ga+Al)=0.1, and Al / (Fe+Ga+Al)=0.3 (see Figure 2).

[0081] Method for preparing Fe-Ga-Al-MFI / AE200 catalyst Fe-Ga-Al-MFI / AE200 catalysts were prepared in the same manner as in Example 1. The weight composition of this catalyst was determined by X-ray fluorescence analysis to be Fe-Ga-Al-MFI / AE200 = 65 / 35 [wt% / wt%] (see Figure 2).

[0082] Method for preparing P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst (P2O5 loading rate 1.0 wt%) A phosphorus-modified Fe-Ga-Al-MFI / AE200 catalyst was prepared in the same manner as in Example 2 (hereinafter referred to as P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst). The loading rate (weight composition) of the phosphorus compound was determined to be 1.0 wt% as phosphorus pentoxide (P2O5) by X-ray fluorescence analysis (see Figure 2).

[0083] Performance evaluation test method for P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst The cylindrical P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst prepared according to the procedure described above was granulated to a length of 1.0 to 2.0 mm to prepare a catalyst sample for performance evaluation. The performance evaluation test was carried out in the same manner as in Example 1, except that the average temperature of the catalyst layer was set to approximately 627°C (maintaining the inlet temperature of the catalyst layer to approximately 614°C and the outlet temperature to approximately 648°C, see Figure 4) (see Figure 1).

[0084] (Example 6) Method for synthesizing Fe-Ga-Al-MFI zeolite Na-type Fe-Ga-Al-MFI zeolite was synthesized in the same manner as in Example 1. The elemental molar composition of this zeolite was determined by X-ray fluorescence analysis to be Si / (Fe+Ga+Al)=91.5, Fe / (Fe+Ga+Al)=0.6, Ga / (Fe+Ga+Al)=0.1, and Al / (Fe+Ga+Al)=0.3 (see Figure 2).

[0085] Method for preparing Fe-Ga-Al-MFI / AE200 catalyst Fe-Ga-Al-MFI / AE200 catalysts were prepared in the same manner as in Example 1. The weight composition of this catalyst was determined by X-ray fluorescence analysis to be Fe-Ga-Al-MFI / AE200 = 65 / 35 [wt% / wt%] (see Figure 2).

[0086] Method for preparing P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst (P2O5 loading rate 1.0 wt%) A phosphorus-modified Fe-Ga-Al-MFI / AE200 catalyst was prepared in the same manner as in Example 2 (hereinafter referred to as P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst). The loading rate (weight composition) of the phosphorus compound was determined to be 1.0 wt% as phosphorus pentoxide (P2O5) by X-ray fluorescence analysis (see Figure 2).

[0087] Performance evaluation test method for P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst The cylindrical P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst prepared according to the procedure described above was granulated to a length of 1.0 to 2.0 mm to prepare a catalyst sample for performance evaluation. The performance evaluation test was carried out in the same manner as in Example 1, except that the average temperature of the catalyst layer was set to approximately 621°C (maintaining the inlet temperature of the catalyst layer to approximately 599°C and the outlet temperature to approximately 649°C, see Figure 4) (see Figure 1).

[0088] (Example 7) Method for synthesizing Fe-Ga-Al-MFI zeolite Na-type Fe-Ga-Al-MFI zeolite was synthesized in the same manner as in Example 1. The elemental molar composition of this zeolite was determined by X-ray fluorescence analysis to be Si / (Fe+Ga+Al)=91.5, Fe / (Fe+Ga+Al)=0.6, Ga / (Fe+Ga+Al)=0.1, and Al / (Fe+Ga+Al)=0.3 (see Figure 2).

[0089] Method for preparing Fe-Ga-Al-MFI / AE200 catalyst Fe-Ga-Al-MFI / AE200 catalysts were prepared in the same manner as in Example 1. The weight composition of this catalyst was determined by X-ray fluorescence analysis to be Fe-Ga-Al-MFI / AE200 = 65 / 35 [wt% / wt%] (see Figure 2).

[0090] Method for preparing P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst (P2O5 loading rate 1.0 wt%) A phosphorus-modified Fe-Ga-Al-MFI / AE200 catalyst was prepared in the same manner as in Example 2 (hereinafter referred to as P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst). The loading rate (weight composition) of the phosphorus compound was determined to be 1.0 wt% as phosphorus pentoxide (P2O5) by X-ray fluorescence analysis (see Figure 2).

[0091] Performance evaluation test method for P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst The cylindrical P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst prepared according to the procedure described above was granulated to a length of 1.0 to 2.0 mm to prepare a catalyst sample for performance evaluation. The performance evaluation test was carried out in the same manner as in Example 1, except that the average temperature of the catalyst layer was set to approximately 616°C (maintaining the inlet temperature of the catalyst layer to approximately 588°C and the outlet temperature to approximately 648°C, see Figure 4) (see Figure 1).

[0092] (Example 8) Method for synthesizing Fe-Ga-Al-MFI zeolite Na-type Fe-Ga-Al-MFI zeolite was synthesized in the same manner as in Example 1. The elemental molar composition of this zeolite was determined by X-ray fluorescence analysis to be Si / (Fe+Ga+Al)=91.5, Fe / (Fe+Ga+Al)=0.6, Ga / (Fe+Ga+Al)=0.1, and Al / (Fe+Ga+Al)=0.3 (see Figure 2).

[0093] Method for preparing Fe-Ga-Al-MFI / AE200 catalyst Fe-Ga-Al-MFI / AE200 catalysts were prepared in the same manner as in Example 1. The weight composition of this catalyst was determined by X-ray fluorescence analysis to be Fe-Ga-Al-MFI / AE200 = 65 / 35 [wt% / wt%] (see Figure 2).

[0094] Method for preparing P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst (P2O5 loading rate 1.0 wt%) A phosphorus-modified Fe-Ga-Al-MFI / AE200 catalyst was prepared in the same manner as in Example 2 (hereinafter referred to as P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst). The loading rate (weight composition) of the phosphorus compound was determined to be 1.0 wt% as phosphorus pentoxide (P2O5) by X-ray fluorescence analysis (see Figure 2).

[0095] Performance evaluation test method for P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst The cylindrical P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst prepared according to the procedure described above was granulated to a length of 1.0 to 2.0 mm to prepare a catalyst sample for performance evaluation. The performance evaluation test was carried out in the same manner as in Example 1, except that the average temperature of the catalyst layer was set to approximately 607°C (maintaining the inlet temperature of the catalyst layer to approximately 564°C and the outlet temperature to approximately 649°C, see Figure 4) (see Figure 1).

[0096] Figures 5 and 6 summarize the catalyst performance in Example 2 and Examples 4-8. In Example 2, the catalyst layer temperature was maintained at around 650°C throughout the entire layer (layer height 3 cm), resulting in a reaction test under near-isothermal conditions (see Figure 4). On the other hand, in Examples 4-8, while the catalyst layer outlet temperature was maintained at approximately 650°C, the inlet temperature was set lower than the outlet temperature within the range of 564-624°C, resulting in a reaction test under conditions where a temperature gradient was intentionally created. In all cases, the one-pass conversion rate was at the same level, ranging from 77.4 to 79.9 wt%, but differences were observed in the product distribution. Lowering the inlet temperature improved the selectivity of the lower olefin, while suppressing the selectivity of BTX (see Figures 5 and 6).

[0097] From the above, it was found that when applying a phosphorus-modified Fe-Ga-Al-MFI / SiO2 composite catalyst in the catalytic cracking reaction of light hydrocarbon raw materials, lower olefins can be more selectively produced by setting a lower inlet temperature and creating a temperature gradient in the catalyst layer.

[0098] (Example 9) Method for synthesizing Fe-Ga-Al-MFI zeolite Na-type Fe-Ga-Al-MFI zeolite was synthesized in the same manner as in Example 1. The elemental molar composition of this zeolite was determined by X-ray fluorescence analysis to be Si / (Fe+Ga+Al)=91.5, Fe / (Fe+Ga+Al)=0.6, Ga / (Fe+Ga+Al)=0.1, and Al / (Fe+Ga+Al)=0.3 (see Figure 7).

[0099] Method for preparing Fe-Ga-Al-MFI / AE380 catalyst Silica powder used as a binder (AEROSIL® 380, Nippon Aerosil Co., Ltd., BET specific surface area 380 m²) 2 Fe-Ga-Al-MFI / AE380 catalysts were prepared in the same manner as in Example 1, except that the weight composition was set to ( / g). The weight composition of this catalyst was determined by X-ray fluorescence analysis to be Fe-Ga-Al-MFI / AE380 = 65 / 35 [wt% / wt%] (see Figure 7).

[0100] Method for preparing P(1.0)-Fe-Ga-Al-MFI / AE380 catalyst (P2O5 loading rate 1.0 wt%) Using the cylindrical Fe-Ga-Al-MFI / AE380 catalyst prepared according to the procedure described above, a phosphorus-modified Fe-Ga-Al-MFI / AE380 catalyst was prepared in the same manner as in Example 2 (hereinafter referred to as P(1.0)-Fe-Ga-Al-MFI / AE380 catalyst). The loading rate (weight composition) of the phosphorus compound was determined to be 1.0 wt% as phosphorus pentoxide (P2O5) by X-ray fluorescence analysis (see Figure 7).

[0101] P(1.0)-Fe-Ga-Al-MFI / AE380 Catalyst performance evaluation test method The cylindrical P(1.0)-Fe-Ga-Al-MFI / AE380 catalyst prepared according to the procedure described above was granulated to a length of 1.0 to 2.0 mm to prepare a catalyst sample for performance evaluation. The performance evaluation test was carried out in the same manner as in Example 1, except that the average temperature of the catalyst layer was set to approximately 604°C (maintaining the inlet temperature of the catalyst layer to approximately 564°C and the outlet temperature to approximately 650°C) (see Figure 1).

[0102] (Example 10) Method for synthesizing Fe-Ga-Al-MFI zeolite Na-type Fe-Ga-Al-MFI zeolite was synthesized in the same manner as in Example 1. The elemental molar composition of this zeolite was determined by X-ray fluorescence analysis to be Si / (Fe+Ga+Al)=91.5, Fe / (Fe+Ga+Al)=0.6, Ga / (Fe+Ga+Al)=0.1, and Al / (Fe+Ga+Al)=0.3 (see Figure 7).

[0103] Method for preparing Fe-Ga-Al-MFI / HDK-T40 catalyst Silica powder used as a binder (HDK(registered trademark)-T40, Wacker Chemicals (China) Ltd., BET specific surface area 387 m²) 2A proton-type Fe-Ga-Al-MFI zeolite / silica composite catalyst was prepared in the same manner as in Example 1, except that it was specified as ( / g). (Hereafter referred to as Fe-Ga-Al-MFI / HDK-T40 catalyst). The weight composition of this catalyst was determined by X-ray fluorescence analysis to be Fe-Ga-Al-MFI / HDK-T40 = 65 / 35 [wt% / wt%] (see Figure 7).

[0104] Method for preparing P(1.0)-Fe-Ga-Al-MFI / HDK-T40 catalyst (P2O5 loading rate 1.0 wt%) The cylindrical Fe-Ga-Al-MFI / prepared according to the procedure described above HDK-T40 Using a catalyst, phosphorus modification Fe-Ga-Al-MFI / was performed in the same manner as in Example 2. HDK-T40 The catalyst was prepared (hereinafter referred to as P(1.0)-Fe-Ga-Al-MFI / HDK-T40 (Described as a catalyst). The loading rate (weight composition) of the phosphorus compound was determined to be 1.0 wt% as phosphorus pentoxide (P2O5) by X-ray fluorescence analysis (see Figure 7).

[0105] Performance evaluation test method for P(1.0)-Fe-Ga-Al-MFI / HDK-T40 catalyst The cylindrical P(1.0)-Fe-Ga-Al-MFI / HDK-T40 catalyst prepared according to the procedure described above was granulated to a length of 1.0 to 2.0 mm to prepare a catalyst sample for performance evaluation. The performance evaluation test was carried out in the same manner as in Example 1, except that the average temperature of the catalyst layer was set to approximately 606°C (maintaining the inlet temperature of the catalyst layer to approximately 565°C and the outlet temperature to approximately 648°C) (see Figure 1).

[0106] Figure 8 is a table summarizing the catalyst performance test results for Examples 8, 9, and 10. The BET specific surface area was 200 m². 2 Compared to the P(1.0)-Fe-Ga-Al-MFI / AE200 catalyst using a silica binder of / g (Example 8), it showed a higher BET specific surface area (380~387m²). 2In the P(1.0)-Fe-Ga-Al-MFI / AE380 catalyst (Example 9) and P(1.0)-Fe-Ga-Al-MFI / HDK-40 catalyst (Example 10) using a silica binder containing ( / g), the one-pass conversion rate improved to 83.2-83.9 wt%, while the lower olefin selectivity (53.2-55.0 wt%) and BTX selectivity (13.5-16.0 wt%) were maintained at the same level.

[0107] From the above, it was found that in the catalytic cracking reaction of light hydrocarbon raw materials, applying a phosphorus-modified Fe-Ga-Al-MFI / SiO2 composite catalyst using a silica binder with a high specific surface area has the effect of increasing the raw material conversion rate without significantly affecting the selectivity of the product.

[0108] The embodiments of this disclosure have been described in detail above. The embodiments described above are merely examples of how to implement this disclosure. The contents of the embodiments do not limit the technical scope of this disclosure, and many design changes, such as changes, additions, and deletions of components, are possible as long as they do not depart from the spirit of the invention as defined in the claims. In the embodiments described above, the contents in which such design changes are possible are emphasized with notations such as "in this embodiment" or "in this embodiment," but design changes are also permitted even if there are no such notations. Any combination of the above components is also valid as an embodiment of this disclosure.

Claims

1. The material comprises a zeolite which is a crystalline aluminosilicate having a skeletal structure with 8 to 12 member rings and containing gallium and iron in the skeletal structure, silicon dioxide as a binder, and phosphorus pentoxide, The zeolite has an acid density of 75.0 to 200.0 as the composition ratio of the number of moles of silicon to the sum of the number of moles of iron, gallium, and aluminum, a composition ratio of the number of moles of gallium to the sum of the number of moles of iron, gallium, and aluminum of 0.1 to 0.4, and a composition ratio of the number of moles of iron to the sum of the number of moles of iron, gallium, and aluminum of 0.2 to 0.

6. A composite catalyst for producing lower olefins from hydrocarbon raw materials, characterized by containing 0.1 to 1.0 wt% of the aforementioned phosphorus pentoxide.

2. The composite catalyst according to claim 1, characterized in that the composite catalyst contains 5 to 50 wt% of silicon dioxide.

3. The BET surface area of ​​the aforementioned silicon dioxide is 50 to 500 m². ２ The composite catalyst according to claim 1 or 2, characterized in that it is / g.

4. A hydrothermal synthesis process is performed to synthesize powdered zeolite by mixing a silica source, an alumina source, an iron source, a gallium source, a structure-regulating agent, a mineralizing agent, and water to prepare an amorphous hydrogel, and then filling the hydrogel into an autoclave and heating it at 110°C to 200°C. A molding process is performed to obtain molded zeolite by mixing the aforementioned powdered zeolite with a binder, molding it, drying it, and firing it. An ion exchange step is performed to introduce acidic OH groups into the molded zeolite by an ion exchange reaction. A method for producing a composite catalyst according to any one of claims 1 to 3, comprising a phosphorus modification step in which the zeolite catalyst obtained in the ion exchange step is impregnated with an aqueous phosphorus precursor solution, dried, and calcined to modify it with phosphorus.

5. A hydrothermal synthesis process is performed to synthesize powdered zeolite by mixing a silica source, an alumina source, an iron source, a gallium source, a structure-regulating agent, a mineralizing agent, and water to prepare an amorphous hydrogel, and then filling the hydrogel into an autoclave and heating it at 110°C to 200°C. An ion exchange step is performed to introduce acidic OH groups into the powdered zeolite by an ion exchange reaction. A molding step is performed to obtain a molded zeolite catalyst by mixing the zeolite catalyst obtained in the ion exchange step with a binder, molding it, drying it, and firing it. A method for producing a composite catalyst according to any one of claims 1 to 3, comprising a phosphorus modification step of impregnating the molded zeolite catalyst with an aqueous phosphorus precursor solution, drying it, and calcining it to modify it with phosphorus.

6. A method for producing a lower olefin, characterized by supplying a hydrocarbon raw material to the inlet of a catalyst layer containing a composite catalyst according to any one of claims 1 to 3, obtaining a lower olefin from the outlet of the catalyst layer, and having a temperature difference of 10°C to 200°C between the inlet and the outlet.

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