Method for producing faujasite-type zeolite

Abstract

To provide a method for producing a faujasite-type zeolite that retains high crystallinity while being hydrophobic.SOLUTION: A method for producing faujasite-type zeolite, includes: a first step in which a faujasite-type zeolite is steam-treated at a temperature of 500 to 800°C to obtain a zeolite for acid treatment by pulling aluminum from the skeleton of the faujasite-type zeolite; and a second step in which the resulting zeolite is subjected to acid treatment one or more times for removing extra-skeletal aluminum to obtain an acid-treated zeolite. In the second step, the acid treatment is preferably performed multiple times. It is preferred that the number of moles of aluminum contained in the zeolite after the first acid treatment be 0.05 or more and 0.10 or less per 1 mole of aluminum contained in the zeolite for acid treatment. It is also preferred that the subsequent acid treatment be performed at a temperature of 50-98°C, and that the number of moles of aluminum contained in the zeolite after the subsequent acid treatment be 0.35 or more relative to 1 mole of aluminum contained in the zeolite before the subsequent acid treatment.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a faujasite-type zeolite that is hydrophobic yet maintains high crystallinity by suppressing crystal collapse. [Background technology]

[0002] The substance zeolite is a general term for crystalline porous aluminosilicates. Zeolites have been widely used as catalysts, adsorbents, and separation membranes in many industrial processes, including oil refining and petrochemicals. For example, the fluid catalytic cracking process is an important process that uses catalysts to crack heavy oil in petroleum and obtain high-value fractions such as gasoline. Faujasite-type zeolites, porous materials with strong solid acidity, have long been used as catalysts in this process. Faujasite-type zeolites have also long been used as adsorbents.

[0003] It is known that the properties of faujasite-type zeolites are significantly affected by the ratio of Si to Al. This ratio, commonly referred to as the silica-alumina ratio (SAR), is expressed as the SiO2 / Al2O3 molar ratio. For example, it is known that increasing the silica-alumina ratio reduces the amount of Al in the zeolite framework, thereby reducing the solid acidity derived from the Al in the framework and resulting in hydrophobicity (low affinity for water). Conversely, decreasing the silica-alumina ratio increases the solid acidity derived from the Al in the framework, resulting in hydrophilicity.

[0004] Methods for increasing the framework silica-aluminum ratio of faujasite-type zeolites are widely known (Non-Patent Document 1). For example, 1) a dealumination method by heat treatment with water vapor (Patent Document 1), 2) a dealumination method by acid treatment (Patent Document 2), or 3) a dealumination method such as treatment with a fluoride (Patent Document 3) are known. It has also been reported that a zeolite with a very high silica-aluminum ratio can be obtained by combining two of these treatments (Patent Document 2, Non-Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 09-173853 [Patent Document 2] Patent Publication No. 2021-080132 [Patent Document 3] Japanese Patent Application Publication No. 62-216913 [Non-patent literature]

[0006] [Non-Patent Document 1] Takae Kawai, "Thermal Measurement" 1992,19(2),70-75. [Non-patent document 2] PKMaher et al., Adv. Chem. Ser., 1971, 101, 266. Summary of the Invention [Problem to be solved by the invention]

[0007] When hydrophobic faujasite-type zeolite is synthesized using the above-described production method, aluminum is removed from the framework, which causes the zeolite to collapse, resulting in low crystallinity despite the hydrophobic nature of the zeolite.

[0008] In light of these circumstances, an object of the present invention is to provide a faujasite-type zeolite that is hydrophobic yet maintains high crystallinity by suppressing crystal collapse. [Means for solving the problem]

[0009] The inventors have found that faujasite-type zeolite that is both hydrophobic and crystalline can be obtained by treating faujasite-type zeolite with steam and removing aluminum extracted from the framework of the zeolite (hereinafter simply referred to as "extraframework") by acid treatment.

[0010] The method for producing faujasite-type zeolite according to the present invention, which advantageously solves the above-mentioned problems, includes a first step of steam-treating faujasite-type zeolite at a temperature of 500 to 800°C to obtain zeolite for acid treatment by extracting aluminum from the framework of the zeolite, and a second step of treating the zeolite for acid treatment obtained in the first step with acid one or more times to remove aluminum outside the framework and obtain acid-treated zeolite.

[0011] The method for producing faujasite-type zeolite according to the present invention is as follows: (a) in the second step, acid treatment is performed multiple times, and the number of moles of aluminum contained in the zeolite after the first acid treatment is in the range of 0.05 to 0.10 per mole of aluminum contained in the zeolite for acid treatment; (b) in the second step, acid treatment is performed multiple times, and the treatment conditions for the subsequent acid treatment are that the temperature is in the range of 50 to 98°C, and the number of moles of aluminum contained in the zeolite after the subsequent acid treatment is in the range of 0.35 or more per mole of aluminum contained in the zeolite before the subsequent acid treatment; This is thought to be a more preferable solution. [Effects of the Invention]

[0012] According to the present invention, a method for producing a faujasite-type zeolite that is hydrophobic yet maintains high crystallinity by suppressing crystal collapse can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0013] The faujasite-type zeolite of the present invention will be described in detail below.

[0014] The faujasite-type zeolite of the present invention (hereinafter also simply referred to as "zeolite") ensures hydrophobicity by increasing the silica-alumina ratio. The silica-alumina ratio of the zeolite is preferably 80 to 300. This silica-alumina ratio is calculated from the composition ratio of the zeolite. The higher this silica-alumina ratio, the higher the silica-alumina ratio of the framework tends to be, and therefore the affinity of the zeolite with water tends to decrease (become more hydrophobic). However, if this silica-alumina ratio is too high, the amount of aluminum in the framework tends to decrease, and the solid acidity tends to decrease.

[0015] The lattice constant of the zeolite of the present invention is preferably 2.428 nm or more. This lattice constant is an index showing the silica-aluminum ratio of the zeolite framework. As the amount of aluminum in the framework increases (as the silica-aluminum ratio of the framework decreases), the lattice constant increases, and as the amount of aluminum in the framework decreases (as the silica-aluminum ratio of the framework increases), the lattice constant decreases. If the lattice constant of the zeolite is too low, the amount of aluminum in the framework is small, which tends to reduce the solid acidity. Furthermore, if the lattice constant is too large, the affinity with water tends to increase. Therefore, it is more preferable that the zeolite of the present invention has a lattice constant of 2.428 to 2.433 nm.

[0016] The crystallinity of the zeolite of the present invention is preferably high. The crystallinity of a zeolite affects the durability and solid acidity of the zeolite. The intensity of the diffraction peaks derived from the faujasite structure obtained by X-ray diffraction measurement was used as an index of the crystallinity of the zeolite (JIS K0131 General Rules for X-ray Diffraction Analysis). Specifically, a faujasite-type zeolite obtained by a specific method was used as a reference material, and the intensity ratio of the peaks derived from the faujasite structure obtained by X-ray diffraction measurement was used as an index of the crystallinity of the zeolite. The intensity ratio of the zeolite is preferably 0.95 or more, and more preferably 1.00 or more. It is obvious to those skilled in the art that the higher the crystallinity, the better. For zeolites, the upper limit may be 1.50 or less.

[0017] The specific surface area of ​​the zeolite of the present invention is 650 m2 / g or more. Zeolites generally have a very large specific surface area due to the pore structure derived from their skeleton. 2 If the specific surface area is lower than 800 m / g, the pore structure derived from the framework of the zeolite may not be sufficiently developed, and the solid acidity may be low. The higher the specific surface area of ​​the faujasite zeolite, the better. 2 More specifically, the specific surface area may be 700 m / g or less. 2 / g or more, 770m 2 / g or less.

[0018] The alkali metal content of the zeolite of the present invention is preferably low. Alkali metals may poison the solid acid contained in the zeolite. Therefore, the alkali metal content of the zeolite is preferably 0.2 mass% or less, and more preferably 0.1 mass% or less, calculated as MO, where M is the alkali metal. The zeolite of the present invention is particularly susceptible to poisoning by Na among alkali metals, so a low Na content is preferred.

[0019] The zeolite of the present invention can be used, for example, as a component of a catalyst used in the fields of petroleum refining and petrochemicals, or as an adsorbent.

[0020] The method for producing faujasite-type zeolite of the present invention will be described in detail below.

[0021] The method for producing a faujasite-type zeolite of the present invention (hereinafter also referred to as the "production method of the present invention") comprises the steps of: a first step of treating faujasite-type zeolite with steam at a temperature of 500 to 800°C to extract aluminum from the framework of the zeolite to obtain a zeolite for acid treatment; and a second step of treating the zeolite for acid treatment obtained in the previous step with an acid at least once to remove extraframework aluminum and obtain an acid-treated zeolite. In the second step, multiple acid treatments may be performed.

[0022] (First step: Steaming to obtain zeolite for acid treatment) The production method of the present invention includes a dealumination step in which faujasite-type zeolite is treated with steam at a temperature of 500 to 800°C to extract aluminum from the zeolite framework. While it is possible to extract aluminum from the zeolite framework using only the acid treatment step, this method significantly damages the zeolite framework and tends to result in low crystallinity. Therefore, it is important to perform this step before the acid treatment step described below. The extracted aluminum remains on the surface of the zeolite as an aluminum compound, also known as extra-framework aluminum.

[0023] The faujasite-type zeolite used in this step may be commercially available or may be synthesized by a conventionally known method. For example, the zeolite can be obtained by adding a Si raw material, an Al raw material, and then a Na raw material and water, followed by hydrothermal treatment at a temperature of 80 to 120°C. The silica-aluminum ratio of the zeolite used as a raw material is preferably in the range of 2 to 10. Zeolites with silica-aluminum ratios in this range are easy to mass-produce industrially. It is more preferable that the zeolite be ion-exchanged with ammonium ions.

[0024] In this step, the faujasite-type zeolite is preferably treated with steam at a temperature of 500 to 800° C. When the steam treatment is carried out in this temperature range, aluminum can be efficiently extracted from the zeolite framework.

[0025] In this step, the steam treatment time is preferably about 1 to 24 hours. Although it depends on the steam treatment temperature, if the treatment time is too short, aluminum may not be sufficiently extracted from the skeleton by the steam treatment. On the other hand, if the steam treatment time is too long, productivity may be hindered.

[0026] The steam concentration in this step is 50% or more of the saturated steam amount, and preferably 90% or more. If steam treatment is performed when the saturated steam amount is low, the zeolite framework tends to be easily broken. This is thought to be because the framework becomes unstable due to defects that occur when extraframework aluminum is generated. In this state, the zeolite framework is easily broken by heat. On the other hand, if the saturated steam amount is within the above-mentioned range, the zeolite framework tends to be less broken.

[0027] The zeolite for acid treatment obtained in this step preferably has a lattice constant of 2.430 to 2.440 nm.

[0028] (Second step: First acid treatment step) The method further comprises an acid treatment step of treating the zeolite for acid treatment with an acid to remove extra-framework aluminum, in which extra-framework aluminum remaining on the surface of the zeolite after the steam treatment is removed using an acid.

[0029] In this step, any known acid can be used, such as sulfuric acid, nitric acid, or hydrochloric acid.

[0030] The temperature for the acid treatment in this step is preferably in the range of 50 to 98° C., more preferably 65 to 95° C. In this step, it is preferable to perform the acid treatment at a higher temperature to remove as much extraframework aluminum remaining on the surface of the zeolite as possible.

[0031] The acid used in this step is preferably contained in the solution in an amount such that the number of moles of protons derived from the acid per mole of aluminum contained in the zeolite for acid treatment is 2.6 to 5.0. For example, when a zeolite containing 1 mole of aluminum (Al) is treated with sulfuric acid (H2SO4), it is preferable to adjust the amount of sulfuric acid contained in the acid solution to 1.3 to 2.5 moles.

[0032] The time for the acid treatment in this step is preferably about 0.5 to 24 hours, although it depends on the temperature of the acid treatment or the amount of acid. If the time for the acid treatment is within this range, the purpose of the acid treatment step can be sufficiently achieved. Although there is no problem if the time for the acid treatment is longer, an upper limit may be set from the viewpoint of productivity.

[0033] After the acid treatment, the acid solution and zeolite can be separated into solid and liquid by filtration or other methods. Components derived from the acid solution may remain in the separated zeolite. Therefore, it is preferable to wash the separated zeolite by suspending it again in ion-exchanged water and pouring hot water below 75°C onto the filter cloth. This washing process can be repeated until the electrical conductivity of the filtrate reaches 0.2 mS / cm or less. The separated zeolite, i.e., the acid-treated zeolite, may be heat-treated. Heat treatment here refers to drying and calcination (including steaming).

[0034] The number of moles of aluminum contained in the acid-treated zeolite obtained in this step is preferably in the range of 0.05 to 0.10 per mole of aluminum contained in the zeolite for acid treatment. If the number of moles of aluminum contained in the zeolite after acid treatment is less than 0.05, many aluminum atoms will be extracted in the acid treatment step, which may make the crystalline structure of the zeolite more susceptible to destruction. If the number of moles of aluminum contained in the zeolite after acid treatment is more than 0.10, the amount of aluminum removed in the subsequent acid treatment step will increase, which may make the crystalline structure of the zeolite more susceptible to destruction in the subsequent acid treatment step.

[0035] The lattice constant of the acid-treated zeolite obtained in this step is preferably 2.428 to 2.433 nm.

[0036] (Second step: subsequent acid treatment step) The method may further include a step of subjecting the acid-treated zeolite obtained in the first acid treatment step to one or more acid treatments, in which aluminum contained in the acid-treated zeolite is further removed while preventing the crystal structure from collapsing.

[0037] In these acid treatment steps, any known acid can be used, such as sulfuric acid, nitric acid, or hydrochloric acid.

[0038] The temperature of the acid treatment in these acid treatment steps is preferably 50 to 98° C., more preferably 65 to 95° C. In these steps, it is preferable to perform the acid treatment at a higher temperature to remove as much extraframework aluminum remaining on the surface of the zeolite as possible.

[0039] The pH in these acid treatment steps is preferably 0.50 or higher. If the pH is lower than 0.50, the crystalline structure of the zeolite is likely to be destroyed.

[0040] The acid treatment time in these acid treatment steps varies depending on the temperature of the acid treatment or the amount of acid, but is preferably in the range of about 0.5 hours to 24 hours. If the acid treatment time is roughly within this range, the purpose of the acid treatment step can be fully achieved. Although a longer acid treatment time is not a problem, it is not preferable from the viewpoint of productivity.

[0041] After the acid treatment, the acid solution and zeolite can be separated into solid and liquid by filtration or other methods. Components derived from the acid solution may remain in the separated zeolite. Therefore, it is preferable to resuspend the separated zeolite in ion-exchanged water and wash it by pouring hot water below 75°C onto the filter cloth. This washing process can be repeated until the electrical conductivity of the filtrate reaches 0.2 mS / cm or less. The separated zeolite can be heated to obtain faujasite-type zeolite. Heat treatment here refers to drying and calcination (including steaming).

[0042] The faujasite-type zeolite obtained by these steps preferably has a lattice constant in the range of 2.428 nm or more and 2.433 nm or less.

[0043] The number of moles of aluminum contained in the faujasite-type zeolite obtained in the subsequent acid treatment step is preferably in the range of 0.35 or more per mole of aluminum contained in the zeolite before the subsequent acid treatment. If the number of moles of aluminum contained in the faujasite-type zeolite is less than 0.35, many aluminum atoms will be extracted in the acid treatment step, which may make the zeolite crystal structure more fragile. The upper limit is less than 1. [Example]

[0044] The zeolite of the present invention and its production method will be described in detail below using examples, but the present invention is not limited to these examples in any way.

[0045] Measurements and evaluations in the examples of the present invention were carried out by the following methods.

[0046] (composition analysis) The Si and Al contents of the samples were measured using a fluorescent X-ray analyzer (RIX-3000). From the measurement results, the Si and Al contents were converted into SiO2 and Al2O3, respectively, and the silica-aluminum ratio (SiO2 / Al2O3 molar ratio) was calculated.

[0047] (Confirmation of crystal structure) The mortar-ground sample was placed in an X-ray diffractometer (Rigaku MiniFlex600, CuKα source) and scanned from 2θ = 5 to 50° for X-ray diffraction measurements. Samples were determined to have a faujasite structure if peaks were identified in the diffraction planes attributable to the faujasite structure (FAU) from the X-ray diffraction pattern. Specifically, the presence or absence of diffraction peaks attributable to the (331), (511), (440), (533), (642), (660), and (555) planes was confirmed. The positions of the peaks attributable to these diffraction planes can be found in the technical literature (MMJ Treacy, JB Higgins, COLLECTION OF SIMULATED XRD POWDERPATTERNS FOR ZEOLITES, Fifth Revised Edition, Elsevier). The peak position may vary slightly depending on the measurement conditions, and if it is within ±0.5° from the peak position described in the above document, it can be considered that the peak is derived from the faujasite structure.

[0048] (Water adsorption evaluation) 1.0 g of sample powder was pretreated at 300°C for 3 hours, and then allowed to absorb moisture for 5 hours in an atmosphere of 40°C and 40% humidity using a thermo-hygrostat "KCL-2000" manufactured by Tokyo Rikaki Co., Ltd. The amount of water adsorbed was calculated from the sample weight before and after moisture absorption as follows: Water adsorption amount (%) = (sample weight after moisture absorption - sample weight before moisture absorption) / sample weight before moisture absorption × 100

[0049] (Lattice constant measurement) Approximately 2 / 3 weight parts of the sample powder and approximately 1 / 3 weight part of anatase-type TiO powder (Kanto Chemical, titanium(IV) oxide (anatase type)) as an internal standard were weighed and mixed in a mortar. This powder was placed in an X-ray diffractometer (Rigaku Corporation, "RINT-Ultima," radiation source: CuKα) and the X-ray diffraction pattern was measured by scanning from 2θ = 23 to 33°. From the obtained pattern, the lattice constants were calculated from the following formulas (1) to (3) using 2θ, which indicates the center of the half-width of the peaks of the (533) and (642) planes of TiO anatase and faujasite zeolites.

[0050]

number

[0051] (X-ray diffraction intensity ratio, X-ray diffraction half-width) The powder sample was crushed in a mortar and placed in an X-ray diffractometer (Rigaku MiniFlex600, CuKα source) and scanned from 2θ = 5 to 50° to measure the X-ray diffraction pattern. The intensities of the diffraction peaks attributable to the (331), (511), (440), (533), (642), (660), and (555) planes of the faujasite structure (FAU) were summed, and the ratio of this sum to the total peak intensity of the faujasite-type zeolite (JRC-Z-Y5.3, listed as "USY-F" in Table 3) used as the Catalysis Society reference catalyst was calculated. The average value of the half-width of these peaks was used as the X-ray diffraction half-width.

[0052] (Specific surface area measurement) The sample powder was pretreated at 500°C for 1 hour in an inert gas atmosphere and placed in a measurement cell. A mixed gas of 30 vol% nitrogen and 70 vol% helium was passed through the measurement device (MR-6, manufactured by Nippon Bell Co., Ltd.) at -196°C to adsorb nitrogen onto the sample powder. The ambient temperature was then raised to 25°C to desorb the nitrogen adsorbed onto the sample powder. The amount of desorbed nitrogen was detected using a thermal conductivity detector (TCD). The specific surface area per gram of sample powder was calculated by converting the detected amount of desorbed nitrogen into specific surface area using the cross-sectional area of ​​the nitrogen molecule.

[0053] (Solid acidity evaluation (NH3 temperature-programmed desorption amount)) After pretreatment at 500°C for 1 hour, 0.05 g of sample powder was weighed and the amount of NH3 thermal desorption was measured using a MicrotrackBell "BELCAT II" device. The sample was heated to 500°C over 1 hour while flowing He, held at 500°C for 1 hour, then cooled to 100°C, and held at 100°C for 30 minutes while flowing 5 vol% NH3-He. The sample was then held at 100°C for 30 minutes while flowing He. While flowing He, the sample was heated from 100°C to 700°C at a rate of 10°C / min, and the desorbed NH3 was detected using a TCD detector.

[0054] [Example 1] (dealuminization process) The silica-aluminum ratio is 5.2, the lattice constant is 2.466 nm, and the specific surface area is 720 m 2 A faujasite-type zeolite (hereinafter referred to as "NaY") having a Na content of 13.0 mass% in terms of Na2O was prepared. 50.0 kg of this NaY was added to 500 L of water at a temperature of 60°C, and 14.0 kg of ammonium sulfate was further added to obtain a suspension. This suspension was stirred at 70°C for 1 hour and filtered. The solid obtained by filtration was washed with water. Next, this solid was washed with an ammonium sulfate solution prepared by dissolving 14.0 kg of ammonium sulfate in 500 L of water at a temperature of 60°C, and further washed with 500 L of water at 60°C, and then dried at 130°C for 20 hours, whereby approximately 65 mass% of the Na contained in the NaY was converted to ammonium ions (NH4 +Approximately 45 kg of faujasite-type zeolite (hereinafter referred to as "65NH4Y") ion-exchanged with 65NH4Y was obtained. The Na content of this 65NH4Y was 4.5 mass% in terms of Na2O. 40 kg of this 65NH4Y was subjected to steam treatment in a saturated steam atmosphere at 670°C for 1 hour to obtain dealuminated faujasite-type zeolite.

[0055] The entire amount of this dealuminated faujasite-type zeolite was added to 400 L of water at 60°C, followed by the addition of 49.0 kg of ammonium sulfate to obtain a suspension. This suspension was stirred at 90°C for 1 hour and then filtered. The solid obtained by filtration was washed with 2400 L of water at 60°C. The solid was then dried at 130°C for 20 hours to obtain approximately 37 kg of faujasite-type zeolite (hereinafter referred to as "93NH4USY") in which approximately 93 mass% of the Na contained in the original NaY was ion-exchanged with NH4. Composition analysis of this 93NH4USY revealed a silica-alumina ratio of 5.2 and a Na content of 1.1 mass% calculated as Na2O. 10.0 kg of this 93NH4USY was subjected to steam treatment in a saturated steam atmosphere at 670°C for 2 hours to obtain approximately 2.7 kg of zeolite for acid treatment (hereinafter referred to as "USY(5)").

[0056] (First acid treatment process) 8.0 kg of this zeolite for acid treatment was suspended in 62 L of water at room temperature, and after heating to 90°C, 29.6 kg of 25% by mass sulfuric acid was gradually added to prepare an acid solution. This acid solution was stirred for 4 hours to perform the acid treatment. After stirring was completed, the acid solution was filtered, and the obtained solid was washed with 160 L of ion-exchanged water at 60°C and further dried at 110°C for 20 hours to obtain acid-treated USY zeolite (hereinafter referred to as "acid-treated product-1"). The obtained acid-treated product-1 was subjected to the above measurements and evaluations. Its properties are shown in Table 1.

[0057] (Subsequent acid treatment step) 1.0 kg of the acid-treated product-1 was suspended in 7.8 L of water at room temperature, and the temperature was raised to 75°C. 0.4 kg of 25% by mass sulfuric acid was gradually added to prepare an acid solution. This acid solution was stirred for 4 hours for re-acidification. After stirring, the acid solution was filtered, and the resulting solid was washed with 20 L of ion-exchanged water at 60°C and further dried at 110°C for 20 hours to obtain USY zeolite (hereinafter referred to as "USY-1"). The obtained USY-1 was subjected to the above measurements and evaluations. Its properties are shown in Table 2.

[0058] [Example 2] USY zeolite (hereinafter referred to as "USY-2") was obtained in the same manner as in Example 1, except that in the subsequent acid treatment step, the amount of 25 mass% sulfuric acid was changed to 0.7 kg. This USY-2 was subjected to the same measurements and evaluations as in Example 1. The results are shown in Table 2.

[0059] [Example 3] USY zeolite (hereinafter referred to as "USY-3") was obtained in the same manner as in Example 1, except that in the subsequent acid treatment step, the amount of 25 mass% sulfuric acid was changed to 1.0 kg. This USY-3 was subjected to the same measurements and evaluations as in Example 1. The results are shown in Table 2.

[0060] [Example 4] USY zeolite (hereinafter referred to as "USY-4") was obtained in the same manner as in Example 3, except that in the subsequent acid treatment step, the temperature of the acid solution was raised to 90°C. This USY-4 was subjected to the same measurements and evaluations as in Example 1. The results are shown in Table 1.

[0061] [Example 5] USY zeolite (hereinafter referred to as "USY-5") was obtained in the same manner as in Example 4, except that in the subsequent acid treatment step, the amount of 25 mass% sulfuric acid was changed to 2.0 kg. This USY-5 was subjected to the same measurements and evaluations as in Example 1. The results are shown in Table 2.

[0062] [Example 6] Acid-treated USY zeolite (hereinafter referred to as "acid-treated product-2") was obtained in the same manner as in Example 1, except that the temperature in the first acid treatment step was set to 50°C. USY zeolite (hereinafter referred to as "USY-6") was obtained in the same manner as in Example 4, except that the acid-treated product-2 was used and the amount of 25% sulfuric acid was set to 0.9 kg in the subsequent acid treatment step. The acid-treated products-2 and USY-6 were subjected to the same measurements and evaluations as in Example 1. The results are shown in Tables 1 and 2, respectively.

[0063] [Example 7] USY zeolite (hereinafter referred to as "USY-7") was obtained in the same manner as in Example 6, except that in the subsequent acid treatment step, the temperature was 50°C and the amount of 25% sulfuric acid was 1.2 kg. This USY-7 was subjected to the same measurements and evaluations as in Example 1. The results are shown in Table 2.

[0064] [Example 8] An acid-treated USY zeolite (hereinafter referred to as "acid-treated product-3") was obtained in the same manner as in Example 1, except that in the first acid treatment step, the amount of 25% by mass sulfuric acid was 35.2 kg. In the subsequent acid treatment step, USY zeolite (hereinafter referred to as "USY-8") was obtained in the same manner as in Example 4, except that the amount of 25% by mass sulfuric acid was 2.0 kg using the acid-treated product-3. The acid-treated products-3 and USY-8 were subjected to the same measurements and evaluations as in Example 1. The results are shown in Tables 1 and 2, respectively.

[0065] [Comparative Example 1] USY zeolite (hereinafter referred to as "USY-R1") was obtained in the same manner as in Acid-treated Product-1, except that the amount of 25% by mass sulfuric acid was 48.0 kg in the first acid treatment step of Example 1. This USY-R1 was subjected to the same measurements and evaluations as in Example 1. The results are shown in Table 3.

[0066] Comparative Example 2 USY zeolite (hereinafter referred to as "USY-R2") was obtained in the same manner as in Acid-treated Product-1, except that the amount of 25% by mass sulfuric acid was 64.0 kg in the first acid treatment step of Example 1. This USY-R2 was subjected to the same measurements and evaluations as in Example 1. The results are shown in Table 3.

[0067] Comparative Example 3 USY zeolite (hereinafter referred to as "USY-R3") was obtained in the same manner as in Example 4, except that in the subsequent acid treatment step, the amount of 25 mass% sulfuric acid was changed to 2.8 kg. This USY-R3 was subjected to the same measurements and evaluations as in Example 1. The results are shown in Table 1.

[0068] Comparative Example 4 USY zeolite (hereinafter referred to as "USY-R4") was obtained in the same manner as in Example 8, except that in the reacid treatment step, the amount of 25 mass% sulfuric acid was changed to 2.5 kg. This USY-R4 was subjected to the same measurements and evaluations as in Example 1. The results are shown in Table 3.

[0069] Comparative Example 5 An acid-treated USY zeolite (hereinafter referred to as "acid-treated product-4") was obtained in the same manner as in Example 1, except that in the first acid treatment step, the amount of 25% sulfuric acid was changed to 19.2 kg. In the subsequent acid treatment step, USY zeolite (hereinafter referred to as "USY-R5") was obtained in the same manner as in Example 4, except that the amount of 25% sulfuric acid was changed to 2.1 kg using the acid-treated product-4. The acid-treated products-4 and USY-R5 were subjected to the same measurements and evaluations as in Example 1. The results are shown in Tables 1 and 3, respectively.

[0070] Comparative Example 6 An acid-treated USY zeolite (hereinafter referred to as "acid-treated product-5") was obtained in the same manner as in Example 1, except that the temperature in the first acid treatment step was 40°C. USY zeolite (hereinafter referred to as "USY-R6") was obtained in the same manner as in Example 2, except that the acid-treated product-5 was used and the temperature in the re-acid treatment step was 40°C. The acid-treated products-5 and USY-R6 were subjected to the same measurements and evaluations as in Example 1. The results are shown in Tables 1 and 3, respectively.

[0071] [Table 1]

[0072] [Table 2]

[0073] [Table 3]

[0074] USY-1 to 8 have higher X-ray diffraction intensity ratios than USY-R1 to USY-R6, and can be evaluated as zeolites with high durability. The water adsorption amount of zeolite is an index of hydrophobicity, and the smaller the amount, the more hydrophobic it is. Based on the above water adsorption amount evaluation, it has been confirmed that USY-1 to 8 have water adsorption amounts of 5% or less.

Claims

[Claim 1] a first step of treating faujasite-type zeolite with steam at a temperature of 500 to 800°C to extract aluminum from the framework of the zeolite to obtain a zeolite for acid treatment; a second step of treating the zeolite for acid treatment obtained in the step with an acid at least once to remove aluminum outside the framework and obtain an acid-treated zeolite; In the second step, acid treatment is performed multiple times, and the number of moles of aluminum contained in the zeolite after the first acid treatment is in the range of 0.05 to 0.10 per mole of aluminum contained in the zeolite for acid treatment, The treatment conditions for the subsequent acid treatment are that the temperature is in the range of 50 to 98°C, and the number of moles of aluminum contained in the zeolite after the subsequent acid treatment is in the range of 0.35 or more per mole of aluminum contained in the zeolite before the subsequent acid treatment. A method for producing faujasite-type zeolite.

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