Modified Y-type molecular sieve and preparation method thereof

Abstract

The invention provides a modified Y-type molecular sieve and a preparation method thereof. The modified Y-type molecular sieve is obtained by modifying a Y-type molecular sieve with a nitrogen-containing organic matter and then performing heat treatment, the mass content of nitrogen-containing organic matters in the modified Y-type molecular sieve is greater than or equal to 8%; the heat treatment is carried out in an inert atmosphere, and the temperature of the heat treatment is 450-600 DEG C; the nitrogen-containing organic matter is at least one of amino acid and amidino functional group-containing compounds. The nitrogen-containing organic matter is used for modifying the Y-type molecular sieve, and then heat treatment is performed, so that the B acid part in the Y-type molecular sieve can be converted into the L acid under the condition that the total acid amount is increased, the modification process is simple to operate, and the method has a positive effect on the adjustment of the performance of the molecular sieve.

Description

Technical Field

[0001] The present invention belongs to the field of molecular sieve modification, and particularly relates to a modified Y-type molecular sieve and a preparation method thereof. Background Art

[0002] Y molecular sieve is a synthetic molecular sieve, which has a supercage surrounded by β cages and hexagonal prismatic cages, and is composed of 18 four-membered rings, 4 six-membered rings and 4 twelve-membered rings, forming a structural pore orifice diameter of 0.74 nm and an inner diameter of 1.2 nm. Due to its rich pore structure and a large number of cracking active centers required for solid acid catalysts, when applied to hydrocracking reactions, its pore structure and acid distribution have a great influence on the selectivity, cracking activity and product distribution of the catalyst. The acidity of the molecular sieve (acid type, acid density, acid strength and acid distribution) directly determines the catalytic reaction performance of the catalyst applied. Generally, it is considered that the aluminum coordination state in the Y molecular sieve determines the acid type and acid strength. The framework four-coordinated aluminum corresponds to the B acid site, and the non-framework six-coordinated, five-coordinated and four-coordinated aluminum species all correspond to the L acid site. Corresponding to the hydrocracking reaction process, it is generally considered that the B acid active site is beneficial to the cracking reaction, and the L acid site is beneficial to the hydrogenation dehydrogenation reaction.

[0003] The influence of Y molecular sieve modification on its structure and acidity (Petrochemical Technology and Application) After performing three ammonium exchanges and two calcinations on NaY molecular sieve, HY molecular sieve with a sodium ion content of less than 0.2% is obtained; the ammonium-exchanged molecular sieve cake is placed in a high-temperature hydrothermal treatment furnace for hydrothermal treatment, and the hydrothermal treatment process is repeated for the obtained sample to obtain USY molecular sieve; the ammonium-exchanged molecular sieve is further modified with a mixed solution of oxalic acid and ammonium oxalate to obtain an acid-modified Y molecular sieve. In this technical solution, conventional calcination treatment and acid modification are used to investigate the influence of different treatment methods on the acid structure of the molecular sieve. Hydrothermal treatment can increase the amount of strong L acid, and the hydrothermal-oxalic acid combination can increase the amount of strong B acid.

[0004] CN106608643B discloses a modification method of Y-type molecular sieve. Aiming at the deficiency that the total acid amount of the molecular sieve decreases during the hydrothermal ultrastabilization process of the molecular sieve, affecting the cracking activity or selectivity, a modification method of Y-type molecular sieve with a high framework silicon-aluminum ratio, good stability and an appropriate increase in the number of acid centers is provided. Specifically, it includes (1) activating NaY molecular sieve with polyhydric alcohol at 80-200 °C for 1-10 h to obtain slurry A; (2) cooling slurry A and mixing it with an organic base to obtain slurry B; (3) adding a silicon source and an aluminum source in the order of adding the silicon source first and then the aluminum source, and subjecting the mixture to aging treatment to obtain slurry C; (4) performing hydrothermal crystallization on slurry C and recovering the product. In this technical solution, the molecular sieve is activated with polyhydric alcohol to Si-OH and Al-OH, and then a silicon source and an aluminum source are added to make it undergo hydrothermal crystallization again, aiming to increase the initial silicon-aluminum ratio and acid amount of the NaY molecular sieve, without realizing the change of the pore structure of the molecular sieve.

[0005] CN 105621444 A discloses a modified Y zeolite and a preparation method thereof. Aiming at the problem that the conventional modification method for the modification of Y zeolite simultaneously removes aluminum from the inside out during the modification process, reducing the number of acid sites and affecting the activity, a modified zeolite with a higher silica-aluminum ratio on the surface layer than that of the bulk phase and a preparation method thereof are provided. The modified Y zeolite is obtained by subjecting a NaY zeolite to ammonium exchange, hydrothermal treatment, acid modification, adsorbing an unsaturated olefin and then carrying out a carbon deposition reaction in an oxygen atmosphere, and then acid modification again. In this technical solution, carbonization is carried out after adsorbing the unsaturated olefin, and the unsaturated olefin is usually a dangerous chemical, and there are limitations in the processing process.

[0006] CN105498686B discloses a method for modifying a zeolite to improve its adsorption performance. Aiming at the problems of poor adsorption effect and desorption and reuse of the zeolite, a method for modifying the zeolite is provided, which specifically includes: loading or exchanging the zeolite with a soluble metal salt or a heteropolyacid, etc., and using the modified zeolite to adsorb 2-heptanone in the cyclohexanone product; this technology aims to enhance the adsorption and desorption performance of the zeolite, and does not perform directional modulation on the pore structure of the zeolite, thereby changing its performance in the hydrogenation reaction.

[0007] Therefore, further research on the modification of Y zeolite is still needed in the art. Summary of the Invention

[0008] The main object of the present invention is to provide a modified Y-type zeolite and a preparation method thereof to overcome the defects such as the introduction of impurities during the modification process of the Y-type zeolite in the prior art and the unsatisfactory performance of the modified Y zeolite.

[0009] To achieve the above object, the present invention provides a modified Y-type zeolite, which is obtained by modifying a Y-type zeolite with a nitrogen-containing organic compound and then performing heat treatment; the mass content of the nitrogen-containing organic compound in the modified Y-type zeolite is greater than or equal to 8%; the heat treatment is carried out in an inert atmosphere, and the temperature of the heat treatment is 450°C to 600°C; the nitrogen-containing organic compound is at least one of an amino acid and a compound containing a guanidino functional group.

[0010] For the modified Y-type zeolite of the present invention, before and after washing the modified Y-type zeolite with water, the content of the nitrogen-containing organic compound in the modified Y-type zeolite remains unchanged.

[0011] For the modified Y-type zeolite of the present invention, the nitrogen-containing organic compound is one or more of arginine, phenylalanine, methionine, ethylamidine hydrochloride, benzamidine hydrochloride, and 3-(guanidinothio)-1-propanesulfonic acid.

[0012] For the modified Y-type zeolite of the present invention, the Y-type zeolite is an H-type Y zeolite.

[0013] To achieve the above object, the present invention also provides a method for preparing the modified Y-type molecular sieve as described above, comprising the following steps:

[0014] Step 1: Mix the Y-type molecular sieve, the nitrogen-containing organic compound, and water, and react at 20 - 50 °C for 0.5 - 3 h;

[0015] Step 2: Heat-treat and calcine the modified Y-type molecular sieve obtained in Step 1 to obtain the modified Y-type molecular sieve.

[0016] In the method for preparing the modified Y-type molecular sieve according to the present invention, in Step 1, the Y-type molecular sieve and water are mixed first, and then mixed with the nitrogen-containing organic compound; in the mixture of the Y-type molecular sieve and water, the solid-liquid ratio is 1:5 - 10, and the mass ratio of the Y-type molecular sieve to the nitrogen-containing organic compound is 12.5 - 3:1.

[0017] In the method for preparing the modified Y-type molecular sieve according to the present invention, in the heat treatment, part of the nitrogen-containing organic compound on the modified Y-type molecular sieve decomposes to generate NO.

[0018] In the method for preparing the modified Y-type molecular sieve according to the present invention, the mass ratio of the Y-type molecular sieve to the nitrogen-containing organic compound is 10 - 5:1.

[0019] In the method for preparing the modified Y-type molecular sieve according to the present invention, the reaction temperature in Step 1 is 20 - 45 °C.

[0020] In the method for preparing the modified Y-type molecular sieve according to the present invention, the calcination temperature is less than or equal to 550 °C, and the calcination time is 3 - 6 h.

[0021] Advantages of the present invention:

[0022] The present invention modifies the Y-type molecular sieve with a nitrogen-containing organic compound and then performs heat treatment, enabling the Y-type molecular sieve to convert part of the B acid in the molecular sieve into L acid under the condition that the total acid amount increases. The modification process is simple and has a positive effect on adjusting the performance of the molecular sieve.

[0023] In addition, during the modification process, the functional groups in the nitrogen-containing organic compound react with the surface structure of the Y molecular sieve. During the heat treatment at 450 °C - 600 °C, the nitrogen-containing organic compound decomposes to sequentially generate H 2 O, CO 2In addition, part of the oxygen element on the surface of the Y zeolite will also be removed. Since the microporous specific surface area accounts for the main component in the specific surface area of the Y zeolite, the focus of the removal of this oxygen element is the removal of the oxygen element in the micropores. Therefore, the modification of the Y zeolite in the present invention can also achieve the effect of expanding the micropores of the Y zeolite, overcoming the disadvantage that the microporous structure modification degree is relatively weak when the outer surface of the Y zeolite is modified in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the ultraviolet-visible spectrogram of the aqueous solution at the initial stage of the preparation of the Y-A1 zeolite in Example 1 and the solution after washing the Y-A1 zeolite.

[0025] Figure 2 For the Y-A2 zeolite in Example 2, the release curves of H 2 O, CO 2 , and NO. DETAILED DESCRIPTION OF THE INVENTION

[0026] The technical solutions of the present invention will be described in detail below. The following embodiments are implemented on the premise of the technical solutions of the present invention, and the detailed implementation processes are given. However, the protection scope of the present invention is not limited to the following embodiments. For the structures or experimental methods without specific conditions noted in the following embodiments, they are usually in accordance with conventional conditions.

[0027] The present invention provides a modified Y-type zeolite, which is obtained by modifying a Y-type zeolite with a nitrogen-containing organic substance and then performing heat treatment; the mass content of the nitrogen-containing organic substance in the modified Y-type zeolite is greater than or equal to 8%; the heat treatment is carried out in an inert atmosphere, and the temperature of the heat treatment is 450°C to 600°C; the nitrogen-containing organic substance is at least one of an amino acid and a compound containing a guanidino functional group.

[0028] For the modification of Y zeolite, it is generally mainly through hydrothermal treatment combined with acid modification or alkali modification, that is, high-temperature hydrothermal treatment causes partial collapse of the silicon-aluminum framework, and then assisted by acid treatment or alkali treatment to remove the unstable non-framework structure, so as to realize the adjustment of the pore structure and acid distribution of the zeolite. In this way, a certain amount of impurity ions such as acid anions or alkali cations will be introduced. If the subsequent washing or removal is not clean, it will affect the long-term use of the zeolite.

[0029] The Y-type molecular sieve of the present invention is modified with a nitrogen-containing organic compound and heat-treated at 450°C to 600°C to obtain a modified Y-type molecular sieve. Specifically, the Y-type molecular sieve is modified with a nitrogen-containing organic compound, that is, after adsorbing the nitrogen-containing organic compound under certain conditions, it is then heat-treated at 450°C to 600°C in an inert atmosphere to obtain a modified Y-type molecular sieve. This heat treatment process enables the nitrogen element in the modified organic compound to escape as NO, thereby changing the molecular sieve framework structure. By converting the framework aluminum in the molecular sieve into non-framework aluminum, it is possible to convert the B acid in the molecular sieve into L acid under the condition of increasing the total acid amount, realizing the regulation of the molecular sieve performance. The present invention realizes the modulation of the acid type of the molecular sieve while introducing no impurities and having a simple operation.

[0030] In addition, the functional groups in the nitrogen-containing organic compound react with the surface structure of the molecular sieve. In the specific surface area of the molecular sieve, the micropore specific surface area accounts for the main component. Therefore, the oxygen element removed from the Y-type molecular sieve structure mainly comes from the micropore oxygen element. Therefore, the modification process of the present invention can achieve the effect of micropore expansion of the Y-type molecular sieve.

[0031] The Y-type molecular sieve of the present invention is not particularly limited, and it can be prepared according to the prior art methods or can be a commercially available product. In one embodiment, the Y-type molecular sieve of the present invention is an H-type Y-type molecular sieve.

[0032] In the present invention, the nitrogen-containing organic compound is at least one of an amino acid and a compound containing a guanidino functional group. The nitrogen-containing organic compound of the present invention is a non-hazardous chemical, and the modification process of the Y-type molecular sieve is safe, environmentally friendly, and convenient for production. In another embodiment, the nitrogen-containing organic compound also contains functional groups such as benzyl and mercapto. In yet another embodiment, the nitrogen-containing organic compound of the present invention is one or more of arginine, phenylalanine, methionine, ethylamidine hydrochloride, benzamidine hydrochloride, and 3-(formamidothio)-1-propanesulfonic acid.

[0033] The modification of the Y-type molecular sieve with the nitrogen-containing organic compound is, for example, reacting the nitrogen-containing organic compound and the Y-type molecular sieve at 20 - 50°C, and the reaction time is, for example, 0.5 - 3 h. After the reaction, the slurry is filtered, washed, and dried. The drying temperature is, for example, 100 - 120°C, and the drying time is, for example, 1 - 5 h.

[0034] The functional groups of the nitrogen-containing organic compound of the present invention tend to react with the surface structure of the Y-type molecular sieve, and washing the modified Y-type molecular sieve will not cause a change in its nitrogen-containing organic compound content, indicating that the specific functional groups in the nitrogen-containing organic compound have reacted with the surface structure of the molecular sieve to form a stable nitrogen-containing organic compound - Y-type molecular sieve structure.

[0035] In the present invention, the molecular sieve after drying is subjected to heat treatment. The heat treatment is carried out in an inert atmosphere, and the temperature of the heat treatment is 450 °C to 600 °C. During the heat treatment under this temperature condition, the nitrogen-containing organic matter in the modified Y-type molecular sieve decomposes, and H 2 O, CO 2 and NO can be successively released. Since the released oxygen element is greater than the total amount of oxygen element in the nitrogen-containing organic matter in the modified Y-type molecular sieve, a part of the oxygen contained in the Y-type molecular sieve is removed, resulting in the destruction of the framework of the Y molecular sieve after heat treatment. H 2 O, CO 2 Among O and NO, the escape temperature of NO is the highest, indicating that the reaction potential energy required for the escape of NO is the largest. The escape of NO represents the destruction of the framework of the Y molecular sieve during the heat treatment process, thereby realizing the conversion of framework aluminum in the Y molecular sieve into non-framework aluminum, and further realizing the process of converting B acid in the Y molecular sieve into L acid. The aluminum element in the Y molecular sieve is the main content providing the acidity of the molecular sieve. In the modification process of the Y molecular sieve of the present invention, only the reduction of the oxygen element in the molecular sieve is involved, and the loss of the aluminum element is not involved, so that the content of the aluminum element in the Y molecular sieve is increased to a certain extent, and thus the total acid amount of the modified Y molecular sieve can be moderately increased.

[0036] Moreover, since the specific functional groups in the nitrogen-containing organic matter have reacted with the surface structure of the Y molecular sieve, the nitrogen-containing organic matter will fully realize the removal of the oxygen element on the surface of the molecular sieve. Since the microporous specific surface area accounts for the main component in the specific surface area of the molecular sieve. Therefore, in the process of removing this oxygen element, the key is the process of removing the oxygen element in the micropores. Therefore, the present invention can also realize the function of expanding the micropores of the Y molecular sieve, overcoming the disadvantage that the prior art focuses on modifying the outer surface of the molecular sieve and the degree of modification of the microporous structure is weak.

[0037] In one embodiment, the present invention also provides a method for preparing the above-mentioned modified Y-type molecular sieve, including the following steps:

[0038] Step 1, mixing the Y-type molecular sieve, the nitrogen-containing organic matter and water, and reacting at 20 - 50 °C for 0.5 - 3 h;

[0039] Step 2, subjecting the modified Y-type molecular sieve obtained in Step 1 to heat treatment and roasting to obtain the modified Y-type molecular sieve.

[0040] For the selection of the Y-type molecular sieve and the nitrogen-containing organic matter, detailed descriptions have been given above and will not be repeated here. In one embodiment, in Step 1, the Y-type molecular sieve and water are mixed, and then mixed with the nitrogen-containing organic matter. In the mixture of the Y-type molecular sieve and water, the solid-liquid ratio is 1:5 to 10, and the mass ratio of the Y-type molecular sieve to the nitrogen-containing organic matter is 12.5 to 3:1, preferably 10 to 5:1.

[0041] In one embodiment, the reaction temperature of the mixture of Y-type zeolite, nitrogen-containing organic matter and water is 20-45 °C.

[0042] Step 1: The modified Y-type zeolite is heat-treated and calcined to obtain a modified Y-type zeolite.

[0043] The heat treatment of the present invention is carried out in an inert atmosphere. The present invention does not particularly limit the type of inert atmosphere, such as nitrogen atmosphere, argon atmosphere, etc. The heat treatment temperature is 450 °C to 600 °C, preferably 480 °C to 530 °C. At this heat treatment temperature, the nitrogen-containing organic matter on the modified Y-type zeolite will decompose, resulting in weight loss, and the main component released during the weight loss process is NO.

[0044] The present invention does not particularly limit the calcination temperature, for example, it is less than or equal to 550 °C, and the calcination time is 3-6 h.

[0045] The mass content of the nitrogen-containing organic matter in the modified Y-type zeolite obtained by the present invention is greater than or equal to 8%, for example, 8%-30%.

[0046] The modified Y-type zeolite obtained by the method of the present invention has an increased acid amount, a directional modulation of the acid type, a moderate pore expansion of the pore channels, and the modifying reagent is environmentally friendly, the modification operation is simple, and there is no impurity residue during the modification process.

[0047] The modified Y-type zeolite of the present invention can be used in hydrocracking reactions and has high cracking activity and good selectivity.

[0048] The technical solution of the present invention will be further described in detail below through specific examples. The Y zeolite used in the examples of the present invention is HY zeolite (SiO 2 and Al 2 O 3 molar ratio 12.3), and the Na 2 O content is less than 0.1 wt%, hereinafter referred to as Y zeolite.

[0049] Example 1:

[0050] Weigh 10 g of Y zeolite, add it to 100 g of deionized water, stir evenly, then add 3.0 g of arginine, and carry out the reaction at 25 °C for 3 h. Then, filter and wash the formed slurry, and dry it at 120 °C for 3 h to obtain the organically modified Y-A1 zeolite. Heat-treat it at 480 °C in a nitrogen atmosphere, and then calcine it at 550 °C in an air atmosphere for 3 h to obtain the modified Y1 zeolite.

[0051] Use ultraviolet-visible spectroscopy to characterize the arginine detachment of Y-A1 zeolite before and after water washing. The results are as Figure 1As shown, washing with water does not cause a change in the arginine content on the Y-A1 molecular sieve. Specifically, as Figure 1 shown, at the initial stage of preparation, 3.0 g of arginine was dissolved in 100 g of water, and at this time, the aqueous solution had an obvious ultraviolet-visible absorption spectrum; the Y-A1 molecular sieve was added to 100 g of water, stirred, filtered, and the washed solution was taken for ultraviolet-visible light determination, and it did not have a significant ultraviolet-visible absorption spectrum, indicating that the structure of the modified Y molecular sieve was stable and washing with water would not cause arginine to fall off from the Y molecular sieve.

[0052] Example 2:

[0053] Weigh 10 g of Y molecular sieve and add it to 80 g of deionized water, stir evenly, then add 0.4 g of arginine and 0.4 g of benzamidine hydrochloride, and react at room temperature of 23 °C for 3 h. Then, filter and wash the formed slurry, and dry it at 120 °C for 3 h to obtain the organically modified Y-A2 molecular sieve. Heat-treat it at 450 °C in a nitrogen atmosphere, and then calcine it at 550 °C in an air atmosphere for 6 h to obtain the modified Y2 molecular sieve. Use a thermogravimetry-infrared-chromatography-mass spectrometry combined instrument to characterize the modified Y-type molecular sieve Y-A2, and focus on the release of H 2 O, CO 2 and NO molecules under the condition of programmed temperature rise. Therefore, the combined instrument detects the release of molecules with molecular masses of 18, 44, and 30 with temperature changes, and the results are as Figure 2 shown. As Figure 2 shown, as the temperature rises, the organic matter in the Y molecular sieve decomposes, and H 2 O, CO 2 and NO are released in turn, and the escape temperature of NO is the highest, mainly concentrated in the range of 450 °C to 600 °C.

[0054] Example 3:

[0055] Weigh 10 g of Y molecular sieve and add it to 50 g of deionized water, stir evenly, then add 1.8 g of methionine and 0.2 g of ethylamidine hydrochloride, and react at 30 °C for 3 h. Then, filter and wash the formed slurry, and dry it at 120 °C for 3 h to obtain the organically modified Y-A3 molecular sieve. Carry out a thermal reaction at 530 °C in a nitrogen atmosphere, and then calcine it at 550 °C in an air atmosphere for 4 h to obtain the modified Y3 molecular sieve.

[0056] Example 4:

[0057] Weigh 10 g of Y zeolite and add it to 100 g of deionized water. Stir evenly, then add 1.0 g of phenylalanine and 0.67 g of 3-(formamidinothio)-1-propanesulfonic acid, and carry out the reaction at 40 °C for 2 h. Then filter and wash the formed slurry, and dry it at 120 °C for 3 h to obtain organically modified Y-A4 zeolite. Carry out a thermal reaction at 450 °C in a nitrogen atmosphere, and then calcine it at 550 °C for 3 h in an air atmosphere to obtain modified Y4 zeolite.

[0058] Comparative Example 1:

[0059] Weigh 3.0 g of glycine and 10 g of Y zeolite. After preparing a solution of the weighed glycine with 4 g of water, carry out equal-volume impregnation with the Y zeolite, and dry it at 120 °C for 3 h to obtain Y-D1 zeolite impregnated with glycine. Carry out a thermal reaction at 480 °C in a nitrogen atmosphere, and then calcine it at 550 °C for 3 h in an air atmosphere to obtain modified D1 zeolite.

[0060] Comparative Example 2:

[0061] Weigh 10 g of Y zeolite and put it into a hydrothermal treatment device. Slowly heat it up to 550 °C in an air atmosphere, and carry out hydrothermal treatment for 3 h with a water inlet rate of 4 g / min to obtain hydrothermally treated D2 zeolite.

[0062] Carry out NH 3 -TPD characterization on Y, Y1, Y2, Y3, Y4, D1, and D2 zeolites. Use the total NH 3 adsorption amount of the zeolite to characterize the total acid amount of the zeolite. The characterization results are shown in Table 1. From the data in Table 1, it can be seen that compared with the original Y-type zeolite, the total NH 3 adsorption amount of the Y1, Y2, Y3, and Y4 zeolites modified in the present invention has increased to a certain extent. The reason is that after the zeolite is modified with nitrogen-containing organic matter and combined with the heat treatment process, the nitrogen element combines with oxygen element and is released, causing changes in the framework structure of the zeolite, and the coordination structure of aluminum element will also change accordingly. Therefore, it affects the total acid amount of the modified zeolite. Since only impregnation of nitrogen-containing compounds is achieved in Comparative Example 1, which is not the stable adsorption in the organic matter modification process of the present invention, the nitrogen element in the nitrogen-containing compound in Comparative Example 1 does not form a stable organic matter-Y-type zeolite structure on the surface of the zeolite. Therefore, during the thermal reaction process, the impregnated organic matter has little effect on the elements in the zeolite, and the total acid amount changes little compared with the original Y-type zeolite. Comparative Example 2 is a hydrothermal process, and the total acid amount of the obtained zeolite D1 is almost unchanged compared with the Y zeolite.

[0063] Table 1 NH 3 -TPD characterization data of zeolites

[0064] Molecular sieve <![CDATA[Adsorption capacity (cm 3 / g)]]> Y 33.1 Y1 34.2 Y2 33.9 Y3 34.5 Y4 34.9 D1 33.4 D2 33.2

[0065] The pyridine adsorption infrared characterization results of Y, Y1, Y2, Y3, D1, and D2 molecular sieves are shown in Table 2. At room temperature, pyridine is adsorbed on the surface of the molecular sieve, and then the system temperature is raised to 200 °C. The peak areas of the infrared absorption peaks at wavenumbers of 1540 cm -1 and 1450 cm -1 represent the amounts of B acid sites and L acid sites in the total acid amount of the molecular sieve, respectively. The ratio of the two values is the total B acid amount / total L acid amount. From the data in Table 2, it can be seen that compared with the Y molecular sieve, the total B acid amount / total L acid amount of Y1, Y2, and Y3 shows a significant decrease, indicating that the invention modification can convert framework aluminum in the molecular sieve into non-framework aluminum, thereby realizing the conversion of B acid in the molecular sieve into L acid, resulting in a decrease in the B acid amount and an increase in the L acid amount, and thus leading to a decrease in the total B acid amount / total L acid amount. The total B / L acid ratio of D1 and D2 molecular sieves also decreases compared with the Y molecular sieve. The decrease of D1 is not as obvious as that of D2, because a stable organic matter-Y type molecular sieve structure was not formed in Comparative Example 1; in Comparative Example 2, the change in the acid type was mainly brought about by the hydrothermal treatment process, but the degree of change was limited and did not achieve the technical effect of the present invention.

[0066] Table 2 Pyridine adsorption infrared characterization results of molecular sieves

[0067]

[0068]

[0069] The physical adsorption characterization results of Y, Y1, Y2, Y3, Y4, D1, and D2 molecular sieves are shown in Table 3. Among them, the most probable pore diameter of the micropores is calculated by the Horvath-Kawazoe method. From the data in Table 3, it can be seen that the most probable pore diameter of the micropores of Y1, Y2, Y3, and Y4 molecular sieves has a certain degree of increase compared with the Y molecular sieve, indicating that the modification of the present invention realizes the function of expanding the micropores of the molecular sieve. Since D1 and D2 did not form a stable organic matter-Y type molecular sieve structure during the modification process, and the D2 modification process is prone to generate a non-framework structure resulting in a pore blocking effect, the most probable pore diameter of its micropores has not changed significantly compared with the Y molecular sieve.

[0070] Table 3 Physical adsorption characterization results of molecular sieves

[0071] Molecular sieve Micropore most probable pore diameter nm Y 0.817 Y1 0.837 Y2 0.831 Y3 0.836 Y4 0.833 D1 0.822 D2 0.819

[0072] Of course, the present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the claims of the present invention.

Claims

1. A modified Y-type molecular sieve, characterized in that, it is obtained by modifying a Y-type molecular sieve with a nitrogen-containing organic compound and then performing heat treatment; the mass content of the nitrogen-containing organic compound in the modified Y-type molecular sieve is greater than or equal to 8%; the heat treatment is carried out in an inert atmosphere, and the temperature of the heat treatment is 450°C to 600°C; the nitrogen-containing organic compound is at least one of amino acids and compounds containing amidino functional groups.

2. The modified Y-type molecular sieve according to claim 1, characterized in that, before and after washing the modified Y-type molecular sieve with water, the content of the nitrogen-containing organic compound in the modified Y-type molecular sieve remains unchanged.

3. The modified Y-type molecular sieve according to claim 1, characterized in that, the nitrogen-containing organic compound is one or more of arginine, phenylalanine, methionine, ethylamidine hydrochloride, benzamidine hydrochloride, and 3-(amidinosulfanyl)-1-propanesulfonic acid.

4. The modified Y-type molecular sieve according to claim 1, characterized in that, the Y-type molecular sieve is an H-type Y molecular sieve.

5. A preparation method of the modified Y-type molecular sieve according to any one of claims 1-4, characterized in that, it comprises the following steps: Step 1, mixing a Y-type molecular sieve, a nitrogen-containing organic compound, and water, and reacting at 20-50°C for 0.5-3 h; Step 2, performing heat treatment and roasting on the modified Y-type molecular sieve obtained in Step 1 to obtain a modified Y-type molecular sieve.

6. The preparation method of the modified Y-type molecular sieve according to claim 5, characterized in that, in Step 1, the Y-type molecular sieve and water are mixed, and then mixed with the nitrogen-containing organic compound; in the mixture of the Y-type molecular sieve and water, the solid-liquid ratio is 1:5 to 10, and the mass ratio of the Y-type molecular sieve to the nitrogen-containing organic compound is 12.5 to 3:

1.

7. The preparation method of the modified Y-type molecular sieve according to claim 5, characterized in that, in the heat treatment, part of the nitrogen-containing organic compound on the modified Y-type molecular sieve decomposes to generate NO.

8. The preparation method of the modified Y-type molecular sieve according to claim 6, characterized in that, the mass ratio of the Y-type molecular sieve to the nitrogen-containing organic compound is 10 to 5:

1.

9. The preparation method of the modified Y-type molecular sieve according to claim 5, characterized in that, the reaction temperature in Step 1 is 20-45°C.

10. The preparation method of the modified Y-type molecular sieve according to claim 5, characterized in that, the roasting temperature is less than or equal to 550°C, and the roasting time is 3-6 h.

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