RU2792150C2 - NaY MOLECULAR SIEVE WITH ALUMINUM-ENRICHED SURFACE AND ITS PRODUCTION METHOD - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: present invention relates to a NaY molecular sieve with an aluminum-enriched surface, a method for its production, a method for the production of a modified Y-type molecular sieve, and a modified Y-type molecular sieve. The NaY molecular sieve with an aluminum-enriched surface has an Al distribution index D: 1.01≤D≤10, where D=Al (S)/Al (C), Al (S) is an aluminum content on the surface and in the area from 2 to 6 nm below the surface of the molecular sieve, when measured by X-ray photoelectron spectroscopy (hereinafter – XPES), and Al (C) is an aluminum content of the entire molecular sieve, when measured by XPES; and it has a molar ratio of SiO₂/Al₂O₃ on the surface from 1 to 10 and SiO₂/Al₂O₃ in a volumetric phase from 2 to 20. The method for the production of a NaY molecular sieve includes following stages: a) mixing of structure-forming substance with the first silicon source to obtain the first mixture, wherein a molar composition of structure-forming substance is Na₂O:Al₂O₃:SiO₂:H₂O=(3-50):1:(3-50):(100-600); b) mixing of the first mixture with the second silicon source, an aluminum source, and water to obtain the second mixture, wherein a molar composition of the second mixture is Na₂O:Al₂O₃:SiO₂:H₂O=(1-10):1:(5-50):(100-600); c) implementation of hydrothermal crystallization of the second mixture and collection of a solid product; moreover, in terms of SiO₂, the mass ratio of the first silicon source and the second silicon source is 1:(0.001-20). The method for the production of a modified Y-type molecular sieve includes the above-mentioned stages (a), (b), and (c), as well as d. introduction of the NaY molecular sieve into reaction with ammonium, hydrothermal treatment, dealuminating, and addition of silicon dioxide. The resulting modified Y-type molecular sieve contains mesopores on a surface, has a molar ratio of SiO₂/Al₂O₃ in a volumetric phase from 10.0 to 13.0, the total pore volume according to the BET method of not less than 0.38 cm³/g, a volume of secondary pores according to the BET method of not less than 0.06 cm³/g, and unit cell parameters: a=b=c=2.44-2.46 nm.

EFFECT: provision of a NaY molecular sieve with an aluminum-enriched surface, which has a greater aluminum distribution gradient from a surface to a center of a particle than traditional NaY molecular sieves, as well as a simple and easy method for the production of a NaY molecular sieve.

32 cl, 3 dwg, 1 tbl, 16 ex

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a NaY molecular sieve with an aluminum enriched surface and a method for producing the same.

State of the art of the present invention

In the late 1950s, Milton and Breck successfully developed Y-type molecular sieves. Because the SiO ₂ /Al ₂ O ₃ ratio in the NaY molecular sieve structure is higher than in the X-type molecular sieve structure, NaY molecular sieves have higher heat resistance. and water resistance. In the early 1990s, Grace developed a structurant process for producing NaY molecular sieve, which uses water glass as a starting material to replace expensive silica sol, simplifying the process and shortening the growth cycle, and thus the NaY molecular sieve quickly found wide application in the petrochemical industry, in particular, in the catalytic cracking of oil. Among the hundreds of molecular sieves that have been developed up to now, the Y-type molecular sieve is the most widely used in the industry. At present, the crystal gel method is mainly used for the industrial production of NaY molecular sieve. Through the application and improvement of the crystal gel, the crystallization time of the Y-type molecular sieve is greatly shortened, which ensures the commercialization of the Y-type molecular sieve.

The Y-type molecular sieve has a FAU topology in which each unit cell consists of 192 TO ₄ units (T=Si, Al). The Y-type molecular sieve contains supercells with a diameter of 1.2 to 1.3 nm, and the twelve-membered ring of the Y-type molecular sieve has a large diameter opening of 0.74 to 0.75 nm. The ratio of silica to alumina in an industrial Y-type molecular sieve is typically less than 2.8. According to the Levenshtein mechanism, an atom in a tetrahedral position in close proximity to the framework Al atoms cannot be an Al atom, so for a given Al atom, the only possible closest position for another Al atom around a given Al atom is the para position in the adjacent quaternary ring with respect to to this Al atom. With respect to a given Al atom, aluminum atoms occupying the para position in neighboring quaternary rings are called NNN-Al. The number of NNN-Al atoms for each framework aluminum atom can be 0, 1, 2, and 3. Investigation of NNN-Al atoms in a dealuminated Y-type molecular sieve using magic angle spinning (MST) ²⁹ Si NMR shows that the less the number of Si(nAl) atoms (n ≥ 2) in the molecular sieve, the greater the relative content of 0-NNN-A1. Theoretical computational studies of framework aluminum in a molecular sieve show that as the number of NNN-Al atoms increases, the acidity of the molecular sieve gradually decreases, and only isolated aluminum atoms (0-NNN-Al) exhibit strong acidic properties. The hydrothermal stability of the molecular sieve is also related to the content of framework aluminum atoms in the molecular sieve, and when the content of framework aluminum atoms in the molecular sieve decreases, the unit cell of the molecular sieve also decreases, and thus the molecular sieve has improved thermal stability.

Directly produced industrial Y-type molecular sieves are typically of the Na type, have a framework silica to alumina (Si/Al) ratio of less than 2.8, and require sodium and aluminum to be removed before being added to the catalyst. For the application of the Y-type molecular sieve, the dealumination process is very important, by which it is possible not only to improve the hydrothermal stability and acidity of the Y-type molecular sieve, but also to create secondary pore channels in the molecular sieve. However, dealumination leads to a change in the distribution of skeleton aluminum atoms in the composition of the molecular sieve, which affects the acidity of the dealuminated Y-type molecular sieve. Studies have shown that when the molecular sieve is dealuminated, the acidity of the molecular sieve gradually increases, indicating that the skeleton aluminum atoms having weak acidic properties are easier to remove. As a rule, the ratio of silicon and aluminum atoms in the directly obtained NaY molecular sieve is lower. When the molecular sieve is moderately dealuminated, n-NNN-Al atoms (n=1, 2, 3) having weak acidity are preferably removed, and 0-NNN-Al atoms having strong acidity are retained to a greater extent; thus, dealumination increases the relative content of strong acid sites in the molecular sieve. When the number of aluminum atoms in the unit cell of the FAU type molecular sieve is more than 64, no 0-NNN-Al atoms are contained in the FAU molecular sieve, and there are no strong acid sites in the molecular sieve. When dealumination occurs, the number of 0-NNN-Al atoms in the FAU type molecular sieve increases and the number of acid sites increases. When the number of aluminum atoms in the unit cell of the FAU type molecular sieve is reduced to 29, the FAU type molecular sieve has the largest number of 0-NNN-Al atoms and the largest content of strong acid sites. On the other hand, as the dealumination of the Y-type molecular sieve continues, the number of 0-NNN-Al atoms decreases, and as a result, the number of strong acid sites decreases. Because the dealumination process selectively removes n-NNN-Al atoms, a dealuminated Y-type molecular sieve contains fewer n-NNN-Al atoms and a higher number of 0-NNN-Al atoms and strong acid sites compared to a directly produced Y-type molecular sieve at condition of the same ratio of silicon and aluminum atoms.

The molecular sieve dealumination process is a complex process that is difficult to control. The removal of aluminum turns out to be very sensitive to dealumination conditions, and it is also difficult to establish the degree of dealumination at the same level on the surface and in the bulk phase of the catalyst. In general, removal of aluminum at the surface of the molecular sieve is easier, while removal of aluminum in the bulk phase of the molecular sieve requires more severe dealumination conditions, which can, in turn, cause the molecular sieve framework to break down and damage the micropores, and thus Thus, the distribution of aluminum in the Y-type molecular sieve prior to modification by dealumination has a significant effect on the pore structure and acidic properties after dealumination.

The existing literature lacks a sufficient number of reports on the study of molecular sieves with an enriched aluminum surface, in particular NaY molecular sieves. CN1363517A discloses a process for producing an aluminum-rich AFI-type molecular sieve in which aluminum-rich gmelinite is crystallized by controlling the ratio of raw materials. CN101096274A and CN101096275A disclose a process for producing aluminium-enriched beta zeolite, comprising preparing silica aluminogel in the presence of a hydrolytic reagent, or impregnating a source of silica with a source of acidic aluminum to obtain a source of double silica and alumina, calcining and grinding the source of double silica and alumina to obtain aluminum enriched beta zeolite. In documents CN101274764A and CN101353168A, aluminum-enriched nanosized beta zeolite was prepared in a similar manner or in the presence of fluoride ions. All processes for producing aluminum-enriched molecular sieve are carried out in a one-step hydrothermal synthesis process. Although the early X-type molecular sieves that are described in USP2882244 are also faujasite-type molecular sieves with a very high aluminum content, they cannot be used in the catalytic process in place of Y-type molecular sieves and aluminium-enriched Y-type molecular sieves, because they do not belong to the Y type molecular sieve category and have poor structural stability under hydrothermal conditions. CN102173436 B discloses a process for producing an aluminium-enriched Y-type molecular sieve using a two-stage hydrothermal synthesis process and modification with rare earth elements. This method is characterized in that the molecular sieve is obtained by uniformly mixing a NaY type molecular sieve with an equal mass of colloid obtained from a silicon source and an aluminum source at molar ratios of Na ₂ O/SiO ₂ =0.3-0.5, SiO ₂ /Al ₂ O ₃ =5-7, H ₂ O/Na ₂ O=40-70, carrying out two-stage hydrothermal synthesis for 0.5 to 4 hours at a temperature of 60 to 110°C to obtain an aluminum-enriched NaY molecular sieve surface, carrying out a hydrothermal exchange reaction with rare earth ions, adjusting the pH value of the suspension at a level of 7 to 10 using an aqueous solution of ammonia, carrying out precipitation of oxides of rare earth elements, carrying out calcination in vacuum for 0.5 to 4 hours at a temperature of 450 up to 750°C and a pressure in the system from 0.001 to 0.09 MPa and subsequent exchange with an aqueous solution of ammonium salt until the content of Na2O is ≤1.0 wt. %, so as to obtain rare earth-containing molecular sieve type Y having a high surface area, the content of rare earth elements from 10 to 20 wt. % in terms of RE ₂ O ₃ and a specific surface area according to the Brunauer-Emmett-Teller (BET) method of at least 600 m ² /g. Considering the production method, due to the absence of any structure-forming substance, it is difficult to incorporate the aluminum element added in the two-stage hydrothermal synthesis process as framework aluminum atoms into the Y-type molecular sieve framework.

Brief summary of the present invention

The purpose of the present invention is to provide an aluminum-rich surface NaY molecular sieve that has a larger aluminum distribution gradient from the surface to the center of the particle than conventional NaY molecular sieves, and to provide a method for producing NaY molecular sieve.

To achieve the object described above, the first aspect of the present application includes obtaining a NaY molecular sieve with an aluminum-rich surface, wherein the Al distribution index D of the molecular sieve satisfies the condition: 1.01 ≤ D ≤ 10, preferably 1.1 ≤ D ≤ 6, preferably 1.2 or 1.3 ≤ D ≤ 4, where D=Al(S)/Al(C), Al(S) means the aluminum content on the surface and in the region from 2 to 6 nm below the surface of the molecular sieve when measured by X-ray photoelectron spectroscopy (XPS), and Al (C) means the aluminum content of the entire molecular sieve when measured by XPS. According to a preferred embodiment, the aluminum-enriched surface molecular sieve has a SiO ₂ /Al ₂ O ₃ molar ratio on the surface of 1 to 10, preferably 2 to 8, and more preferably 2.5 to 5, and a SiO ₂ /Al ₂ O ₃ in the bulk phase, ranging from 2 to 20, preferably from 4 to 15, and more preferably from 6 to 10.

The NaY molecular sieve with an aluminum-rich surface according to the present invention has an Al content in terms of Al ₂ O ₃ from 18 to 26 wt. %, preferably from 21 to 25 wt. %.

The NaY molecular sieve with an aluminum-rich surface according to the present invention has an average particle size of 200 to 600 nm, preferably 400 to 500 nm.

The aluminium-enriched NaY molecular sieve of the present invention has a BET specific surface area of 640 to 790 m ² /g, preferably 690 to 780 m ² /g. The NaY molecular sieve with an aluminum-enriched surface according to the present invention has a BET pore volume of 0.34 to 0.50 ml/g, preferably 0.36 to 0.45 ml/g.

The second aspect of the present application includes the proposal of a method for producing NaY molecular sieve according to the first aspect of the present application, and the method includes the following steps:

a. mixing the structurant with the first source of silicon to form a first mixture, wherein the molar composition of the structurant is Na ₂ O:Al ₂ O ₃ :SiO ₂ :H ₂ O=(3-50):1:(3-50):( 100-600), preferably (6-25):1:(6-25):(200-400);

b. mixing the first mixture obtained in step (a) with a second source of silicon, a source of aluminum and water to form a second mixture;

c. carrying out hydrothermal crystallization of the second mixture obtained in step (b) and collecting the solid product;

moreover, in terms of SiO ₂ the mass ratio of the first source of silicon and the second source of silicon is 1:(0.001-20), preferably 1:(0.01-12).

Optionally, in step (a), the structurant is prepared by performing the following operations: mixing an aluminum source (such as sodium metaaluminate) for the structurant and soluble glass to form a third mixture, performing dynamic aging and static aging of the third mixture, and then mixing the third mixture with water to form a structure-forming substance.

Preferably, dynamic aging includes aging under agitation at 15 to 60° C. for 1 to 100 hours, preferably 3 to 60 hours, more preferably 5 to 48 hours, or 15 to 48 hours; and static aging includes aging by holding at 15 to 60° C. for 0.5 to 100 hours, preferably 3 to 60 hours, more preferably 5 to 48 hours, or 5 to 15 hours, or 15 to 48 hours.

Optionally, in step (a), the first silicon source is at least one selected from the group consisting of water glass, colloidal silicon dioxide, and silica sol.

Optionally, in step (a), mixing is carried out during mixing, and the mixing conditions are not limited in a certain way, if homogeneous mixing is achieved. In particular, when the first source of silicon is a solid source of silicon, mixing is carried out during mixing for, for example, from 30 to 180 minutes.

Optionally, in step (b), the amounts of the first mixture, the second source of silicon, the source of aluminum and water are not specifically limited, provided that the molar composition of the second mixture is Na ₂ O:Al ₂ O ₃ :SiO ₂ :H ₂ O= (1-10):1:(5-50):(100-600), preferably (2-6):1:(8-20):(200-400).

Optionally, in step (b), the second silicon source is at least one selected from the group consisting of soluble glass, silica alumina gel, and silica alum sol; preferably, the molar ratio of SiO ₂ /Al ₂ O ₂ silicaaluminum gel is from 3 to 30, preferably from 6 to 16; and the molar ratio of SiO ₂ /Al ₂ O ₃ of the silicaalumina sol is 3 to 30, preferably 6 to 16.

Optionally, in step (b), the aluminum source is at least one selected from the group consisting of sodium metaaluminate, aluminum sulfate, aluminum chloride, aluminum nitrate, and pseudoboehmite.

Optionally, the aluminum element from the structurant constitutes from 3 to 30% of the aluminum element in the second mixture, based on the element in moles.

Optionally, in step (b), the mixing is carried out during mixing, and the mixing conditions are not limited in a certain way, as long as homogeneous mixing is achieved.

Optionally, in step (c), the hydrothermal crystallization conditions are not particularly limited, and conventional hydrothermal crystallization conditions known in the art can be used, provided that the NaY molecular sieve of the present invention can be obtained. Optional hydrothermal crystallization conditions include, for example, a temperature of 40 to 100°C, preferably 90 to 100°C, and a duration of 10 to 60 hours, preferably 15 to 48 hours.

According to the above technical scheme, the structurant is first contacted with the first source of silicon to form a high local concentration of silicon, so that the formation of crystal nuclei with a high concentration of silicon atoms is facilitated. With the subsequent growth of crystal grains, the silicon source is consumed faster than the aluminum source, and the concentration of silicon atoms also decreases faster, so that the ratio of silicon and aluminum on the surface of the crystal nuclei gradually decreases, and finally a NaY molecular sieve with an aluminum-rich surface is obtained, moreover, the NaY molecular sieve has a larger distribution gradient of framework aluminum atoms from the surface to the center of the particle compared to traditional molecular sieves. The method of the present application does not require additional matrix agents or additives, the raw materials used are cheap and readily available, the synthesis can be successfully carried out by one-step hydrothermal crystallization, and the process is simple and easy to carry out.

The third aspect of the present application includes the preparation of a modified Y-type molecular sieve with a mesopore-enriched surface, characterized in that the modified Y-type molecular sieve has a SiO ₂ /Al ₂ O ₃ molar ratio in the bulk phase of 6 to 20, preferably 8 to 15 and preferably 10 to 13, and a total BET pore volume of not less than 0.35 cm3/g, preferably not less than 0.38 ^cm3 /g, or not less than 0.40 ^cm3 /g; a BET secondary pore volume of at least 0.06 cm ³ /g, preferably at least 0.08 cm ³ /g, or at least 0.09 cm ³ /g; and unit cell parameters: a=b=c=2.44-2.46 nm, and the content of sodium oxide in the modified Y-type molecular sieve is not more than 0.1 wt. % based on the total weight of the modified Y-type molecular sieve.

In addition, the modified Y-type molecular sieve may have a total BET pore volume of no more than 0.6 cm ³ /g, preferably no more than 0.55 cm ³ /g, or no more than 0.50 cm ³ / G; and a BET secondary pore volume of not more than 0.40 cm ³ /g, preferably not more than 0.3 cm ³ /g, or not more than 0.25 cm ³ /g.

According to the present application, the BET method for determining total pore volume and secondary pore volume, as well as the method for determining the unit cell parameters, Y-type molecular sieve are well known to those skilled in the art and will not be described in detail herein.

The modified Y-type molecular sieve according to the present invention has an Al content of 15 to 24 wt. %, preferably from 16 to 21 wt. %, in terms of Al ₂ O ₃ .

The modified Y type molecular sieve according to the present invention has an average particle size of 200 to 600 nm, preferably 400 to 500 nm.

The modified Y-type molecular sieve of the present invention has a BET specific surface area of 640 to 790 m ² /g, preferably 690 to 780 m ² /g.

The fourth aspect of the present application includes the provision of a method for producing a modified type Y molecular sieve, and the method is characterized in that it includes steps (a), (b) and (c) of the method according to the second aspect, and

d. reacting the NaY molecular sieve obtained in step (c) with ammonium to reduce the sodium content, hydrothermal treatment, dealumination, and addition of silica to obtain a modified Y-type molecular sieve.

Optionally, in step (d), the reaction with ammonium to reduce the sodium content comprises treating the NaY molecular sieve with an ammonium salt solution having an ammonium ion concentration of 0.1 to 1.0 mol/l, preferably 0.2 to 0.9 mol/l and more preferably from 0.4 to 0.8 mol/l, and the treatment includes, but is not limited to, impregnation of the NaY molecular sieve obtained in step (c) with an ammonium salt solution. The conditions used for this purpose include a temperature from room temperature to 100°C, preferably from 50 to 100°C, a mass ratio of liquid to solid phases (8-15):1 and a duration of 0.2 to 3 hours, preferably from 0.5 to 1.5 hours. Optionally, the treatment is carried out during the mixing process. The ammonium salt is at least one selected from the group consisting of ammonium nitrate, ammonium sulfate, ammonium chloride and ammonium acetate.

Optionally, in step (d), the hydrothermal treatment comprises treating the NaY molecular sieve, which has reacted with ammonium to reduce the sodium content, for 1 to 3 hours under 100% steam conditions at a pressure of 0.1 to 0.3 MPa, preferably from 0.1 to 0.2 MPa and a temperature of 400 to 700°C, preferably 500 to 650°C.

Optionally, in step (d), dealuminating and adding silica comprises pulping the NaY molecular sieve that has been hydrothermally treated to obtain a liquid-to-solid mass ratio (3-10):1 slurry, adding (NH ₄ ) ₂ SiF ₆ into suspension according to a dosage of 10 to 60 g, preferably 20 to 40 g (NH ₄ ) ₂ SiF ₆ per 100 g of NaY molecular sieve and stirring the mixture at a temperature of 80 to 120°C, preferably 85 to 99°C in for 0.5 to 5 hours, for example 1 to 3 hours to recover the product.

In a further step (d) according to a fourth aspect, the NaY molecular sieve with an aluminum-rich surface after treatment is subjected to modifications by ammonium reaction to reduce the sodium content, hydrothermal treatment, dealumination, and addition of silica to obtain a modified Y-type molecular sieve with a mesopore-rich surface.

Additional features and advantages of the present application will be presented in more detail in the following description.

Brief description of the drawings

The accompanying figures are presented to provide a better understanding of the present invention and form part of the present description; they are intended to illustrate embodiments of the present application and serve to clarify the present application along with the description, but do not limit the present application. Among the figures:

in fig. 1-2 are transmission electron microscopy (TEM) photographs of the modified Y-type molecular sieve obtained in Example 9; And

in fig. 3 is a TEM photograph of the Y-type molecular sieve obtained in Comparative Example 7.

Embodiments of the present invention

Embodiments of the present invention will be further illustrated below with reference to the figures. It should be understood that the embodiments are presented solely as an illustration and explanation without limiting the present invention.

All publications, patent applications, patents and other documents mentioned in the present description are incorporated herein in their entirety by reference. Unless otherwise specified, all technical and scientific terms used herein have the meanings commonly understood by those skilled in the art. In the event of conflict, including definitions, the present description shall prevail.

When materials, methods, components, devices, or devices are referred to in this specification with the term "known to those skilled in the art" or a similar term, this term means that the present description includes the specified items conventionally used in the art at the time of filing this application, and also includes items that are not currently in use but will become known in the art as being suitable for a similar purpose.

In addition, all ranges referred to herein include their respective endpoints, unless otherwise specifically specified. In addition, when a range, one or more preferred ranges, or a plurality of preferred upper and lower limits are given for an amount, concentration, or other value or parameter, it is to be understood that all ranges formed by any pair of any upper limits or corresponding preferred values and any lower limits or corresponding preferred values are considered to be specifically described, regardless of the fact that such pairs of values are individually described.

According to the present invention, when a technical solution is presented in a non-limiting sense, such as "comprising", "comprising", or similarly listing some relevant elements, it should be clear to those skilled in the art that an embodiment consisting or essentially consisting of these elements, can be obviously used to implement the technical solution. Thus, those skilled in the art should understand that the technical solution given in the present invention in a non-limiting sense also covers embodiments consisting of the listed elements or mainly consisting of the listed elements.

Finally, all percentages, parts, ratios, and other values included in the present description, are indicated in relation to the mass, unless otherwise specified in a certain way; but if the mass is not a base according to the traditional understanding of those skilled in the art, then the base is determined according to the traditional understanding of those skilled in the art.

The first aspect of the present application involves the preparation of a NaY molecular sieve with an aluminum-rich surface, wherein the Al distribution index D of the molecular sieve satisfies the condition 1.01 ≤ D ≤ 10, preferably 1.1 ≤ D ≤ 6, more preferably 1.2 or 1.3 ≤ D ≤ 4, while D=Al (S)/Al (C), Al (S) means the aluminum content on the surface and in the region from 2 to 6 nm below the surface of the molecular sieve when measured by XPS, and Al (C) means the content aluminum of the entire molecular sieve when measured by XPS. According to a preferred embodiment, the aluminum-enriched surface molecular sieve has a SiO ₂ /Al ₂ O ₃ molar ratio on the surface of 1 to 10, preferably 2 to 8, and more preferably 2.5 to 5, and a SiO ₂ /Al ₂ O ₃ molar ratio in the bulk phase 2 to 20, preferably 4 to 15 and more preferably 6 to 10.

The NaY molecular sieve with an aluminum-rich surface according to the present invention has an Al content in terms of Al ₂ O ₃ from 18 to 26 wt. %, preferably from 21 to 25 wt. %.

The NaY molecular sieve with an aluminum-rich surface according to the present invention has an average particle size of 200 to 600 nm, preferably 400 to 500 nm.

The aluminium-enriched NaY molecular sieve of the present invention has a BET specific surface area of 640 to 790 m ² /g, preferably 690 to 780 m ² /g. The NaY molecular sieve with an aluminum-enriched surface according to the present invention has a BET pore volume of 0.34 to 0.50 ml/g, preferably 0.36 to 0.45 ml/g.

According to the present application, the values and methods for studying the ratio of SiO ₂ /Al ₂ O ₃ on the surface and the ratio of SiO ₂ /Al ₂ O ₃ in the bulk phase of the molecular sieve are well known to those skilled in the art, and determining the aluminum content of the molecular sieve using the XPS method or X-ray fluorescence spectroscopy (XFS) is also well known to those skilled in the art and will not be described in detail herein.

The NaY molecular sieve with an aluminum-rich surface according to the present application has a larger aluminum distribution gradient from the surface to the center of the particle than conventional molecular sieves, as indicated by the Al distribution index D of the present invention. Thus, when the molecular sieve is obtained by the method of the present invention, the catalyst obtained after modification by dealumination will more easily have a larger mesoporous volume on the surface of the catalyst, and its preparation will be much easier.

The second aspect of the present application includes the proposal of a method for producing NaY molecular sieve according to the first aspect of the present application, and the method includes the following steps:

a. mixing the structurant with the first source of silicon to obtain the first mixture, wherein the molar composition of the structurant is Na ₂ O:Al ₂ O ₃ :SiO ₂ :H ₂ O=(3-50):1:(3-50):( 100-600), preferably (6-25):1:(6-25):(200-400);

b. mixing the first mixture obtained in step (a) with a second source of silicon, a source of aluminum and water to form a second mixture;

c. carrying out hydrothermal crystallization of the second mixture obtained in step (b) and collecting the solid product;

moreover, in terms of SiO ₂ the mass ratio of the first source of silicon and the second source of silicon is 1:(0.001-20), preferably 1:(0.01-12).

In the method according to the present invention, the structurant first comes into contact with the first source of silicon to form a high local concentration of silicon, so that the formation of crystal nuclei with a high concentration of silicon atoms is facilitated. With the subsequent growth of crystal grains, the silicon source is consumed faster than the aluminum source, and the concentration of silicon atoms also decreases faster, so that the ratio of silicon and aluminum on the surface of the crystal nuclei gradually decreases, and finally a NaY molecular sieve with an aluminum-rich surface is obtained, moreover, the NaY molecular sieve has a larger distribution gradient of framework aluminum atoms from the surface to the center of the particle compared to traditional molecular sieves.

According to the present invention, the structurant in step (a) is a conventional substance well known to those skilled in the art for the preparation of NaY molecular sieves, which can be prepared using prior art procedures. For example, the structurant can be obtained in steps comprising homogeneously mixing a silicon source (such as sodium silicate), an aluminum source (such as sodium metaaluminate) and optionally water according to a molar ratio, preferably representing, for example, (6-25)Na ₂ O:Al ₂ O ₃ :(6-25)SiO ₂ :(200-400)H ₂ O, in terms of oxides, holding for 0.5 to 48 hours at room temperature to 70°C to obtain structure-forming agent. According to a preferred embodiment of the present application, in order to obtain a more desirable effect, the steps for producing a structurant include mixing an aluminum source structurant (such as sodium metaaluminate) with water glass to form a third mixture, and subjecting the third mixture to dynamic aging and static aging, and then mixing with water to obtain a structure-forming substance. In addition, dynamic aging may include agitation and aging at 15 to 60°C for 1 to 100 hours, preferably 3 to 60 hours, preferably 5 to 48 hours, or 15 to 48 hours. hours; and static aging may include holding at 15 to 60°C for 0.5 to 100 hours, preferably 3 to 60 hours, more preferably 5 to 48 hours, or 5 to 15 hours, or 15 to 48 hours .

Dynamic aging is beneficial to achieve sufficient mixing of sodium metaaluminate with water glass, and after aging and aging, water can be added during mixing until the desired molar ratio of structurant is reached. The structurant obtained according to the preferred embodiment is more favorable for producing NaY molecular sieve with an aluminum-rich surface.

According to the present application, in step (a), the first silicon source may be a variety of inorganic silicon sources commonly used to produce NaY molecular sieve, and be, for example, at least one substance selected from the group consisting of soluble glass, colloidal dioxide silicon and silica sol. According to one variant of implementation of the present application, the mixing is carried out in the mixing process. The mixing conditions are not particularly limited as long as homogeneous mixing is achieved. In particular, when the first source of silicon is a solid source of silicon (such as colloidal silicon dioxide), mixing is preferably carried out during mixing for, for example, 30 to 180 minutes. Thus, the solid source of silicon can be better mixed with the structurant, and as a result, the purpose of the present application is achieved. According to other embodiments of the present application, when the first silicon source is a liquid silicon source (e.g., water glass, silica sol, etc.), the mixing in step (a) may be a co-current mixing of the structurant with the first silicon source, and however, it can be carried out under conditions of high-speed mixing.

According to the present application, in step (b), the second silicon source may be the same as or different from the first silicon source. To obtain the desired effect, the second source of silicon is typically a liquid source of silicon, and may be, for example, at least one substance selected from the group consisting of water glass, silica aluminogel and silica aluminosol. More preferably, the molar ratio of SiO ₂ /Al ₂ O ₃ silicaaluminum gel is from 3 to 30, preferably from 6 to 16; the molar ratio of SiO ₂ /Al ₂ O ₃ of the silica aluminum sol is 3 to 30, preferably 6 to 16. carried out under conditions of high-speed mixing. In addition, the second source of silicon, the source of aluminum and water can be added in co-current mode with the first mixture at a point located at a distance from the first mixture.

According to the present application, in step (b), the aluminum source may be a conventional NaY molecular sieve material, for example, at least one selected from the group consisting of sodium metaaluminate, aluminum sulfate, aluminum chloride, aluminum nitrate, and pseudoboehmite. The water may be deionized or distilled water.

According to the present application, in step (b), the amounts of the first mixture, the second silicon source, the aluminum source and water are not specifically limited as long as the molar composition of the second mixture is Na ₂ O:Al ₂ O ₃ :SiO ₂ :H ₂ O=(1 -10):1:(5-50):(100-600), preferably (2-6):1:(8-20):(200-400). The element aluminum from the structure-forming substance is from 3 to 30 mol. % element aluminum in the second mixture, calculated on the element. Optionally in step (b), mixing is carried out during mixing; moreover, the mixing conditions are not limited in a certain way, if homogeneous mixing is achieved.

According to the present application, in step (c), the hydrothermal crystallization conditions are not specifically limited, and conventional hydrothermal crystallization conditions that are known in the art can be used as long as the NaY molecular sieve required by the present invention can be obtained as a result. Optional hydrothermal crystallization conditions include, for example, a temperature of 40 to 100°C, preferably 90 to 100°C, and a duration of 10 to 60 hours, preferably 15 to 48 hours.

The third aspect of the present application includes the preparation of a modified Y-type molecular sieve with a mesopore-enriched surface, characterized in that the modified Y-type molecular sieve has a molar ratio of SiO ₂ /Al ₂ O ₃ in the bulk phase from 6 to 20, preferably from 8 to 15, and more preferably from 10 to 13 and a total BET pore volume of not less than 0.35 cm ³ /g, preferably not less than 0.38 cm ³ /g or not less than 0.40 cm ³ /g; a BET secondary pore volume of not less than 0.06 cm3/g, preferably not less than 0.08 ^cm3 /g or not less than 0.09 ^cm3 /g; and unit cell parameters: a=b=c=2.44-2.46 nm, and the content of sodium oxide in the modified Y-type molecular sieve is not more than 0.1 wt. % based on the total weight of the modified Y-type molecular sieve.

In addition, the modified Y-type molecular sieve may have a total BET pore volume of 0.38 to 0.6 cm ³ /g, and a secondary BET pore volume of 0.06 to 0.4 cm ³ /g.

According to the present application, the BET method for determining total pore volume and secondary pore volume, as well as the method for determining the unit cell parameters, Y-type molecular sieve are well known to those skilled in the art and will not be described in detail herein.

The fourth aspect of the present application includes the provision of a method for producing a modified type Y molecular sieve, characterized in that the method includes steps (a), (b) and (c) of the method according to the second aspect and

d. reacting the NaY molecular sieve obtained in step (c) with ammonium to reduce the sodium content, hydrothermal treatment, dealumination, and addition of silica to obtain a modified Y-type molecular sieve.

According to the present application, after the hydrothermal crystallization, the NaY molecular sieve, which can be obtained through the conventional steps of filtering, washing and drying, is reacted with ammonium to reduce the sodium content, subjected to hydrothermal treatment and dealumination, and addition of silicon, so that a modified molecular sieve can be obtained. sieve NaY according to the present application.

According to the present application, in step (d), the reaction with ammonium to reduce the sodium content is well known to those skilled in the art, and the objective is to reduce the sodium oxide content of the molecular sieve, for example, to a level of 2.5 to 5.0 wt. %. In particular, the reaction with ammonium to reduce the sodium content may include treating the NaY molecular sieve with an ammonium salt solution having an ammonium ion concentration of 0.1 to 1.0 mol/L. Processing includes, but is not limited to, mixing the NaY molecular sieve obtained in step (c) with an ammonium salt solution. The conditions used for this treatment include a temperature of 50 to 100°C, a mass ratio of liquid to solid phases (8-15):1 and a duration of 0.5 to 1.5 hours. Processing can be carried out during mixing. The ammonium salt may be at least one selected from the group consisting of ammonium nitrate, ammonium sulfate, ammonium chloride and ammonium acetate. The process of reducing the sodium content by reaction with ammonium can be carried out one or more times using the same or different ammonium salts until the sodium oxide content of the molecular sieve NaY is brought to the target value.

According to the present application, the hydrothermal treatment, dealumination and addition of silicon carried out in step (d) are also well known to those skilled in the art. In particular, the hydrothermal treatment may include, for example, treating a NaY molecular sieve that has reacted with ammonium to reduce the sodium content for 1 to 3 hours under conditions of 100% steam, a gauge pressure of 0.1 to 0.2 MPa, and a temperature from 500 to 650°C. Dealuminizing and adding silicon may include, for example, pulping a NaY molecular sieve that has been hydrothermally treated to obtain a slurry with a liquid-to-solid mass ratio of (3-10):1, adding (NH ₄ ) ₂ SiF ₆ to the slurry according to the dosage of 10 to 60 g (NH ₄ ) ₂ SiF ₆ per 100 g of NaY molecular sieve, and stirring the mixture at 80 to 120° C. for 0.5 to 5 hours to recover the product. The method for recovering the product may include filtration and drying.

Examples

The present application will be further illustrated below by reference to examples and comparative examples, but the scope of the present application is not limited to these examples.

In each of the Examples and Comparative Examples, the relative crystallinity of the NaY molecular sieve was determined using an XRD6000 type X-ray diffractometer from Shimadzu under the following experimental conditions: CuKα radiation, tube voltage 40 kV, and tube current 40 mA. Relative crystallinity was determined according to the standard method SH/T0340-92 (Compendium of Chemical Industry Standards published by Standards Press of China, 2000).

The molar ratio of SiO ₂ /Al ₂ O ₃ on the surface of the molecular sieve was measured by XPS, this method was also used to measure the aluminum content on the surface and in the region from 2 to 6 nm below the surface of the sample (Al (S)). The instrument for this study was a PHI 5000 X-ray photoelectron spectrometer from Perkin-Elmer (electronic system for chemical analysis ESCA), where AlKα (1486.6 eV) was used as a radiation source, and the pressure in the analytical chamber was less than 10 ^-7 Pa during the measurement. The sample was etched with Ar ⁺ ions for 15 minutes prior to measurement to remove oxides formed during sample processing. The binding energies of all elements were corrected for carbon impurities (EC16=284.6 eV) and a specific test method is described in Chinese Journal of Catalysis, 11 (2), 1993: 127.

The molar ratio of SiO ₂ /Al ₂ O ₃ in the bulk phase of the molecular sieves and the total content of aluminum in the molecular sieves, i.e. Al (C) was determined using X-ray fluorescence spectroscopy (XFS). The research instrument was an X-ray fluorescence spectrometer model 3271E from Rigaku Industrial Corporation (Japan). In the research method, a rhodium target, a driving voltage of 50 kV and a driving current of 50 mA were used, and a scintillation counter and a proportional counter were used to determine the intensity of the spectral lines of each element, and the SiO ₂ content and the Al ₂ O ₃ content were quantitatively analyzed in the samples.

The unit cell parameters of the molecular sieve were determined according to the standard method SH/T0339-92 (Compendium of Chemical Industry Standards published by Standards Press of China, 2000).

The specific surface area and pore structure of the molecular sieve were examined using an ASAP2420 type automatic adsorption instrument and an ASAP2020 type automatic adsorption instrument from Micromeritics Instruments Corporation (USA), and the total pore volume and secondary pore volume of the molecular sieve were calculated according to the BET method including the following specific steps : BET specific surface area was determined for 3-5 selected values of nitrogen partial pressure ranging from 0.05 to 0.35, the actual nitrogen adsorption value was measured, and then the specific surface area was calculated by applying the BET equation. According to the plot of the curve t (statistical thickness of the adsorption film), the micropore volume and the total pore volume were calculated, and the secondary pore volume was calculated using the Barret-Joyner-Halenda (BDH) equation.

The morphology and grain size of the molecular sieve was determined by electron microscopy. A scanning electron microscope (SEM) model S-4300 from Hitachi with an accelerating voltage of 10 kV and an attachment for energy dispersive spectroscopy (EDS) was used, and a layer of gold was galvanically deposited on the surface of the sample before the study. The catalyst was examined using a field emission transmission electron microscope Tecnai G2F 20 from the company FEI, carrying out the suspension method of sample preparation, for which the catalyst sample was dispersed in absolute ethanol, shaking to a homogeneous state, the mixture was applied dropwise onto a copper grid and observed after complete evaporation of ethyl alcohol.

The sodium oxide content of the molecular sieve was determined using X-ray fluorescence spectroscopy (XRF). The research instrument was an X-ray fluorescence spectrometer model 3271E from Rigaku Industrial Corporation (Japan). In the research method, a rhodium target, a drive voltage of 50 kV and a drive current of 50 mA were used, and a scintillation counter and a proportional counter were used to determine the intensity of the spectral lines of each element, and a quantitative or semi-quantitative analysis was carried out.

Below are some raw materials used in the examples and comparative examples:

a highly alkaline sodium metaaluminate solution from Sinopec Changling Refining & Chemical Company having an Al ₂ O ₃ content of 40.2 g/l, a Na ₂ O content of 255 g/l, and a density of 1.324; water glass from Sinopec Changling Refining & Chemical Company, having a SiO ₂ content of 260.6 g/l, a Na ₂ O content of 81.6 g/l, a density of 1.2655, and a modulus of 3.3; colloidal silicon dioxide from Sinopharm Chemical Reagent Co., Ltd. having a SiO ₂ content of 90%; a low alkaline sodium metaaluminate solution from Sinopec Changling Refining & Chemical Company having an Al ₂ O ₃ content of 194 g/l, a Na ₂ O content of 286.2 g/l, and a density of 1.413; aluminum sulfate from Sinopec Changling Refining & Chemical Company, having an Al ₂ O ₃ content of 88.9 g/l and a density of 1.2829; alkaline silica sol from Sinopharm Chemical Reagent Co., Ltd. in ammonium form, having a Na ₂ O content of 0.2 to 0.4%, a pH value of 9 to 10 and a SiO ₂ content of 40%; silica aluminum gel A from Sinopharm Chemical Reagent Co., Ltd., having a SiO ₂ content of 90%, an Al ₂ O ₃ content of 10%, and a SiO ₂ /Al ₂ O ₃ molar ratio of 15.3; and silica aluminum gel B from Sinopharm Chemical Reagent Co., Ltd. having a SiO ₂ content of 85%, an Al ₂ O ₃ content of 15%, and a SiO ₂ /Al ₂ O ₃ molar ratio of 9.6.

Examples 1-8 are presented to illustrate the NaY molecular sieve obtained according to steps (a)-(c) of the method of the second aspect of the present application.

Example 1

642.44 g of a highly alkaline sodium metaaluminate solution was added to 866.51 g of water glass, the mixture was stirred for dynamic aging for 48 hours at room temperature of 20°C, then the mixture was kept and aged for 5 hours at 60°C, and finally, 195 g of deionized water was added during mixing, so as to obtain a structure-forming substance having a molar composition of 15Na ₂ O:Al ₂ O ₃ :15SiO ₂ :320H ₂ O.

348.4 g of the structurant described above and 12.63 g of the first source of silicon, which is colloidal silicon dioxide, were mixed under high-speed stirring conditions (rotation speed was 900 rpm) at room temperature, and stirring was continued for 30 minutes to obtain the first mixture. Then the first mixture, 508.14 g of the second source of silicon, which is soluble glass, 43.10 g of the aluminum source, which is a low alkaline solution of sodium metaaluminate, 286.5 g of the aluminum source, which is aluminum sulfate, and 166.5 g of water were added into the mixing tank in direct-flow mode also under high-speed mixing at room temperature to obtain a second mixture having a molar composition of 2.7Na ₂ O:Al ₂ O ₃ :8.6SiO ₂ :259H ₂ O. The mass ratio of the first source of silicon and the second source silicon was 1:8.3, and the structurant was added in such an amount that the number of moles of the aluminum element in the structurant was 15% of the moles of the aluminum element in the second mixture. After stirring until homogeneous, the mixture was placed in a stainless steel reactor and subjected to static crystallization for 24 hours at a temperature of 100°C, and then a NaY molecular sieve, which is an Al product, was obtained after filtration, drying washing. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

Example 2

642.44 g of a highly alkaline sodium metaaluminate solution was mixed with 866.51 g of water glass, the mixture was stirred for dynamic aging for 48 hours at room temperature of 20°C, then the mixture was kept and aged for 5 hours at 60°C, and finally, 195 g of deionized water was added during mixing, so as to obtain a structure-forming substance having a molar composition of 15Na ₂ O:Al ₂ O ₃ :15SiO ₂ :320H ₂ O.

311.6 g of the structurant described above and 12.63 g of the first source of silicon, which is colloidal silicon dioxide, were mixed under high-speed stirring conditions (rotation speed was 900 rpm) at room temperature, and stirring was continued for 60 minutes to obtain the first mixture. Then the first mixture, 441.37 g of the second source of silicon, which is soluble glass, 40.00 g of the aluminum source, which is a low alkaline solution of sodium metaaluminate, 251.00 g of the aluminum source, which is aluminum sulfate, and 200.63 g of water were added into the mixing tank in direct-flow mode also under high-speed stirring at room temperature to obtain a second mixture having a molar composition of 2.7Na ₂ O:Al ₂ O ₃ :8.6SiO ₂ :269H ₂ O. The mass ratio of the first source of silicon and the second source silicon was 1:7.1 in terms of SiO ₂ and the structure-forming substance was added in such an amount that the number of moles of the aluminum element in the structure-forming substance was 15% of the number of moles of the aluminum element in the second mixture. After stirring until homogeneous, the mixture was placed in a stainless steel reactor and subjected to static crystallization for 24 hours at a temperature of 100°C, and then a NaY molecular sieve, which is the A2 product, was obtained after filtering, washing, drying. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

Example 3

164.54 g of a highly alkaline sodium metaaluminate solution was mixed with 291.37 g of water glass, the mixture was stirred for dynamic aging for 20 hours at 30°C, then the mixture was held and aged for 15 hours at 40°C, and finally 60 g of deionized water was added during stirring, so as to obtain a structure-forming substance having a molar composition of 20Na ₂ O:Al ₂ O ₃ :20SiO ₂ :380H ₂ O.

515.91 g of the structurant described above and 592.62 g of the first water glass silicon source were mixed in co-current mode under high-speed mixing conditions (rotation speed was 900 rpm) at room temperature to obtain a first mixture. Then 500 g of the second source of silicon, which is water glass, 166.31 g of the aluminum source, which is a low alkaline solution of sodium metaaluminate, 332.87 g of the aluminum source, which is aluminum sulfate, and 479.4 g of water, were added in co-current mode at the point , located at a great distance from the first mixture, under conditions of high-speed mixing (rotation speed was 900 rpm) to obtain a mixture having a molar composition of 4Na ₂ O:Al ₂ O ₃ :9SiO ₂ :220H ₂ O. The mass ratio of the first source of silicon and the second source of silicon was 1:0.83 in terms of SiO ₂ , and the structurant was added in such an amount that the number of moles of the aluminum element in the structurant was 10% of the moles of the aluminum element in the second mixture. After stirring until homogeneous, the mixture was placed in a stainless steel reactor and subjected to static crystallization for 24 hours at a temperature of 95°C, and then the NaY molecular sieve, which is the A3 product, was obtained after filtering, washing, drying. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

Example 4

251.76 g of a highly alkaline solution of sodium metaaluminate was mixed with 349.64 g of water glass, the mixture was stirred for dynamic aging for 15 hours at 40°C, then the mixture was kept and aged for 20 hours at 15°C, and finally 78 g deionized water was added during stirring, so as to obtain a structure-forming substance having a molar composition of 6Na ₂ O:Al ₂ O ₃ :16SiO ₂ :290H ₂ O.

679.4 g of the structurant described above and 1000 g of the first silica source, which is water glass, were co-currently mixed under high speed stirring conditions at room temperature to obtain a first mixture. Then the first mixture, 129.04 g of the second source of silicon, which is soluble glass, 55.90 g of the aluminum source, which is a low alkaline solution of sodium metaaluminate, 514.81 g of the aluminum source, which is aluminum sulfate, and 489.2 g of water in succession was added to the mixing tank to form a second mixture having a molar composition of 3Na ₂ O:Al ₂ O ₃ :10SiO ₂ :250H ₂ O. The weight ratio of the first silicon source to the second silicon source was 1:0.13 in terms of SiO ₂ , and the structurant was added in such an amount that the number of moles of the aluminum element in the structurant was 15% of the number of moles of the aluminum element in the second mixture. After stirring until homogeneous, the mixture was placed in a stainless steel reactor and subjected to static crystallization for 36 hours at a temperature of 95°C, and then a NaY molecular sieve, which is an A4 product, was obtained after filtering, washing, drying. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

Example 5

642.44 g of a highly alkaline sodium metaaluminate solution was added to 866.51 g of water glass, the mixture was stirred for dynamic aging for 48 hours at room temperature of 20°C, then the mixture was held and aged for 5 hours at 60°C, and, finally, 195 g of deionized water was added during stirring, so as to obtain a structure-forming substance having a molar composition of 15Na ₂ O:Al ₂ O ₃ :15SiO ₂ :320H ₂ O.

348.4 g of the structurant described above and 31.57 g of the first silicon source, which is an alkaline silica sol, were mixed under high-speed stirring conditions at room temperature to obtain a first mixture. Then 508.14 g of the second source of silicon, which is water glass, 43.10 g of the aluminum source, which is a low alkaline sodium metaaluminate solution, 286.5 g of the aluminum source, which is aluminum sulfate, and 147.55 g of water, were added in co-current mode at a point far away from the first mixture under high-speed stirring (rotation speed was 900 rpm) to obtain a mixture having a molar composition of 2.7Na ₂ O:Al ₂ O ₃ :8.6SiO ₂ :259H ₂ O The weight ratio of the first silicon source to the second silicon source was 1:10.9 in terms of SiO ₂ , and the structurant was added in such an amount that the number of moles of the aluminum element in the structurant was 15% of the moles of the aluminum element in the second mixture. After stirring until homogeneous, the mixture was placed in a stainless steel reactor and subjected to static crystallization for 24 hours at a temperature of 100°C, and then a NaY molecular sieve, which is an A5 product, was obtained after filtering, washing, drying. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

Example 6

642.44 g of a highly alkaline sodium metaaluminate solution was mixed with 866.51 g of water glass, the mixture was stirred for dynamic aging for 48 hours at room temperature of 20°C, then the mixture was kept and aged for 5 hours at 60°C, and finally, 195 g of deionized water was added during mixing, so as to obtain a structure-forming substance having a molar composition of 15Na ₂ O:Al ₂ O ₃ :15SiO ₂ :320H ₂ O.

311.6 g of the structurant described above, 6.63 g of the first source of silicon, which is colloidal silicon dioxide, and 15 g of alkali silica sol were mixed under high-speed stirring conditions (rotation speed was 900 rpm) at room temperature and stirred for 170 minutes at a rotation speed of 900 rpm to obtain the first mixture. Then the first mixture, 441.37 g of the second source of silicon, which is water glass, 40 g of the aluminum source, which is a low alkaline sodium metaaluminate solution, 251 g of the aluminum source, which is aluminum sulfate, and 191.63 g of water, were added to the mixing tank in direct-flow mode also under conditions of high-speed mixing (at a rotation speed of 900 rpm) at room temperature to obtain a second mixture having a molar composition of 2.7Na ₂ O:Al ₂ O ₃ :8.6SiO ₂ :269H ₂ O. The mass ratio of the first the silicon source and the second silicon source was 1:8.1 in terms of SiO ₂ , and the structurant was added in such an amount that the number of moles of the aluminum element in the structurant was 15% of the moles of the aluminum element in the second mixture. After stirring until homogeneous, the mixture was placed in a stainless steel reactor and subjected to static crystallization for 24 hours at a temperature of 100°C, and then a NaY molecular sieve, which is an A6 product, was obtained after filtering, washing, drying. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

Example 7

251.76 g of a highly alkaline solution of sodium metaaluminate was added to 349.64 g of water glass, the mixture was stirred for dynamic aging for 48 hours at room temperature of 20°C, then the mixture was kept and aged for 5 hours at 60°C, and, finally, 78 g of deionized water was added during stirring, so as to obtain a structure-forming substance having a molar composition of 16Na ₂ O:Al ₂ O ₃ 16SiO ₂ :290H ₂ O.

679.4 g of the structurant described above and 1000 g of the first silica source, which is water glass, were mixed in co-current mode under high-speed mixing conditions (rotation speed was 900 rpm) at room temperature to obtain a first mixture. Then, 29.36 g of the second source of silicon, which is silica aluminum gel A, 62.41 g of the source of aluminum, which is a low alkaline solution of sodium metaaluminate, 533.44 g of the source of aluminum, which is aluminum sulfate, and 479 g of water, were added in co-current mode at the point located at a great distance from the first mixture, under conditions of high-speed mixing (rotation speed was 1200 rpm) to obtain a mixture having a molar composition of 3Na ₂ O:Al ₂ O ₃ 10SiO ₂ :250H ₂ O. The mass ratio of the first source of silicon and the second the source of silicon was 1:0.13 in terms of SiO ₂ and the structurant was added in such an amount that the number of moles of the aluminum element in the structurant was 15% of the moles of the aluminum element in the second mixture. After stirring until homogeneous, the mixture was placed in a stainless steel reactor and subjected to static crystallization for 24 hours at a temperature of 95°C, and then a NaY molecular sieve, which is an A7 product, was obtained after filtering, washing, drying. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

Example 8

The NaY molecular sieve was obtained by carrying out the method in Example 7, except that silica alumino gel A was replaced with an equal amount of silica alumino gel B. The results of the study of relative crystallinity and other parameters of the resulting NaY molecular sieve, which is the product A8, are shown in Table 1.

Comparative examples 1-6 are presented to illustrate the method.

Comparative Example 1

348.4 g of the same structurant as in example 1, 12.63 g of colloidal silicon dioxide, 508.14 g of silica, which is a source of soluble glass, 43.10 g of a source of aluminum, which is a low alkaline solution of sodium metaaluminate, 286 .5 g of an aluminum source, which is aluminum sulfate, and 166.5 g of water were added to a mixing tank at room temperature under high speed stirring conditions to obtain a reaction mixture having a molar composition

2.7Na ₂ O:Al ₂ O38.6SiO ₂ :259H ₂ O. After stirring until homogeneous, the mixture was placed in a stainless steel reactor and subjected to static crystallization for 24 hours at a temperature of 100°C, and then a NaY molecular sieve representing product B1 was obtained after filtration, washing and drying. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

Comparative Example 2

348.4 g of the same structurant as in Example 1, 508.14 g of water glass, 43.10 g of a low alkaline sodium metaaluminate solution, 286.5 g of aluminum sulfate and 166.5 g of water were added in co-current mode to the mixing tank at room temperature under high speed stirring. After stirring until homogeneous, the above mixture was further homogeneously stirred with 12.63 g of colloidal silica, also at room temperature under high-speed stirring conditions, to obtain a reaction mixture having a molar composition of 2.7Na ₂ O:Al ₂ O38.6SiO ₂ : 259H ₂ O. After stirring until homogeneous, the mixture was placed in a stainless steel reactor and subjected to static crystallization for 24 hours at a temperature of 100°C, and then a NaY molecular sieve, which is a B2 product, was obtained after filtering, washing, drying. The results, which are relative crystallinity and other parameters of the product, are shown in Table 1. Comparative Example 3

515.9 g of structurant (same as in Example 3), 166.31 g of a low alkaline sodium metaaluminate solution, 332.87 g of aluminum sulfate, 1092.62 g of water glass and 479.4 g of water were successively added to the mixing tank at room temperature under high-speed stirring to obtain a mixture having a molar composition of 4Na ₂ O:Al ₂ O ₃ :9SiO ₂ :220H ₂ O. After stirring until homogeneous, the mixture was placed in a stainless steel reactor and subjected to static crystallization for 24 hours at temperature of 95°C, and then the NaY molecular sieve, which is the product of B3, was obtained after filtration, washing, drying. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

Comparative Example 4

1129.04 g of water glass, 55.90 g of a low alkaline sodium metaaluminate solution, 514.81 g of aluminum sulfate, 679.4 g of structurant (same as in Example 4) and 489.2 g of water were successively added to the mixing tank at room temperature under high-speed stirring conditions, to obtain a reaction mixture having a molar composition of 3Na ₂ O:Al ₂ O ₃ :10SiO ₂ :250H ₂ O. After stirring until a homogeneous state, the mixture was placed in a stainless steel reactor and subjected to static crystallization for 24 hours at 95°C, and then the NaY molecular sieve, which is the B4 product, was obtained after filtration, washing, drying. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

Comparative Example 5

348.4 g of structurant (same as in Example 5), 43.10 g of a low alkaline sodium metaaluminate solution, 286.5 g of aluminum sulfate, 31.57 g of alkali silica sol, 508.14 g of water glass and 147.55 g water was added simultaneously to the mixing tank at room temperature under high-speed stirring conditions to obtain a mixture having a molar composition of 2.7Na ₂ O:Al ₂ O ₃ :8.6SiO ₂ :259H ₂ O. After stirring until homogeneous, the mixture was placed in a reactor from stainless steel and subjected to static crystallization for 24 hours at a temperature of 95°C, and then the NaY molecular sieve, which is the B5 product, was obtained after filtering, washing, drying. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

Comparative Example 6

311.6 g of structurant (same as in example 6), 441.37 g of water glass, 40 g of a low alkaline sodium metaaluminate solution, 251 g of aluminum sulfate, 6.63 g of colloidal silicon dioxide, 15 g of alkaline silica sol and 191. 63 g of water was simultaneously added to the mixing tank at room temperature under high-speed mixing conditions to obtain a mixture having a molar composition of 2.7Na ₂ O:Al ₂ O ₃ :8.6SiO ₂ :269H ₂ O. After stirring until homogeneous, the mixture was placed in stainless steel reactor and subjected to static crystallization for 48 hours at a temperature of 90°C, and then NaY molecular sieve, which is a B6 product, was obtained after filtering, washing, drying. The results, representing relative crystallinity and other product parameters, are shown in Table 1.

As can be seen in Table 1, the NaY molecular sieves produced using the method of the present application were enriched in aluminum at the surface and had a larger aluminum distribution gradient from the surface to the center of the particle compared to conventional molecular sieves.

Examples 9-16 are presented to illustrate modified Y-type molecular sieves obtained by reacting the NaY molecular sieves obtained in Examples 1-8 with ammonium to reduce the sodium content, followed by hydrothermal treatment, dealumination and addition of silica according to step d of method four aspect of the present application.

Example 9

Sample A1 obtained in Example 1 was reacted with ammonium to reduce the sodium content, hydrothermally treated, dealuminated, and added with silicon to obtain a modified Y-type molecular sieve with a mesopore-enriched surface by performing the following steps:

10 L of an aqueous solution of ammonium nitrate with a concentration of 0.5 mol/L was obtained, 1000 g of Al molecular sieve was weighed and added to 10 L of the obtained aqueous solution of ammonium nitrate during stirring at a rotation speed of 300 rpm, stirring at a constant temperature of 90 ° C for one hour, then the molecular sieve was filtered off, and the operation was repeated until the content of Na ₂ O in the molecular sieve was 4.5 wt. %. The dried sample was subjected to hydrothermal treatment at a temperature of 500°C, 100% steam and a gauge pressure of 0.1 MPa for 1.5 hours. Then, 200 g of the sample was placed in 1 L of deionized water, heated rapidly and stirred at a temperature of 95°C and a stirring speed of 300 rpm. An aqueous solution of ammonium hexafluorosilicate was added rapidly to the molecular sieve suspension, a total of 50 g of ammonium hexafluorosilicate was added, then stirred at constant temperature and constant speed for 2 hours, filtered and dried to obtain a modified NaY molecular sieve. The product was designated NY-1, its properties are shown in Table 1, and a transmission electron microscopy (TEM) photograph is shown in FIG. 1-2, where a mesoporous structure was observed for the modified NaY molecular sieve.

Example 10

Sample A2 obtained in Example 2 was reacted with ammonium to reduce the sodium content, hydrothermally treated, dealuminated, and added with silicon to obtain a modified Y-type molecular sieve with a mesopore-enriched surface by performing the following steps:

10 L of an aqueous solution of ammonium sulfate with a concentration of 0.2 mol/L was obtained, 1000 g of A2 molecular sieve was weighed and added to 10 L of the obtained aqueous solution of ammonium nitrate during stirring at a rotation speed of 300 rpm, stirring at a constant temperature of 90 ° C for one hour, then the molecular sieve was filtered off, and the operation was repeated until the content of Na ₂ O in the molecular sieve was 5.0 wt. %. The dried sample was subjected to hydrothermal treatment at a temperature of 570°C, 100% steam and a gauge pressure of 0.2 MPa for 2.0 h. mixing speed 300 rpm. An aqueous solution of ammonium hexafluorosilicate was rapidly added to the molecular sieve suspension, a total of 50 g of ammonium hexafluorosilicate was added, then stirred at constant temperature and constant speed for 2 hours, filtered and dried to obtain a modified Y-type molecular sieve. The product was designated by the number NY-2, its properties are presented in table 1.

Example 11

Sample A3 obtained in Example 3 was reacted with ammonium to reduce the sodium content, hydrothermally treated, dealuminated, and added with silicon to obtain a modified Y-type molecular sieve with a mesopore-enriched surface by performing the following steps:

10 L of an aqueous solution of ammonium chloride with a concentration of 0.5 mol/L was obtained, 1000 g of A3 molecular sieve was weighed and added to 10 L of the obtained aqueous solution of ammonium nitrate during stirring at a rotation speed of 300 rpm, stirring at a constant temperature of 90° C for one hour, then the molecular sieve was filtered off, and the operation was repeated until the content of Na ₂ O in the molecular sieve was from 2.5 to 5 wt. %. The dried sample was subjected to hydrothermal treatment at a temperature of 550°C, 100% steam and a gauge pressure of 0.2 MPa for 2.5 hours. mixing speed 300 rpm. An aqueous solution of ammonium hexafluorosilicate was rapidly added to the molecular sieve suspension, a total of 60 g of ammonium hexafluorosilicate was added, then stirred at constant temperature and constant speed for 2 hours, filtered and dried to obtain a modified Y-type molecular sieve. The product was designated by the number NY-3, its properties are presented in table 1.

Example 12

Sample A4 obtained in Example 4 was reacted with ammonium to reduce the sodium content, hydrothermally treated, dealuminated, and added with silicon to obtain a modified Y-type molecular sieve with a mesopore-enriched surface by performing the following steps:

10 L of an aqueous solution of ammonium nitrate with a concentration of 0.7 mol/L was obtained, 1000 g of A4 molecular sieve was weighed and added to 10 L of the obtained aqueous solution of ammonium nitrate during stirring at a rotation speed of 300 rpm, stirring at a constant temperature of 90 ° C for one hour, then the molecular sieve was filtered off, and the operation was repeated until the content of Na ₂ O in the molecular sieve was 4.0 wt. %. The dried sample was subjected to hydrothermal treatment at a temperature of 600°C, 100% steam and a gauge pressure of 0.1 MPa for 1.0 h. mixing speed 300 rpm. An aqueous solution of ammonium hexafluorosilicate was added rapidly to the molecular sieve suspension, a total of 50 g of ammonium hexafluorosilicate was added, then stirred at a constant temperature and constant speed for 2 hours, filtered and dried to obtain a modified Y-type molecular sieve. The product was designated by the number NY-4, its properties are presented in table 1.

Example 13

Sample A5 obtained in Example 5 was reacted with ammonium to reduce the sodium content, hydrothermally treated, dealuminated, and added with silicon to obtain a modified Y-type molecular sieve with a mesopore-enriched surface by performing the following steps:

10 L of an aqueous solution of ammonium nitrate with a concentration of 0.7 mol/L was obtained, 1000 g of A5 molecular sieve was weighed and added to 10 L of the obtained aqueous solution of ammonium nitrate during stirring at a rotation speed of 300 rpm, stirring at a constant temperature of 90 ° C for one hour, then the molecular sieve was filtered off, and the operation was repeated until the content of Na ₂ O in the molecular sieve was 3.0 wt. %. The dried sample was subjected to hydrothermal treatment at a temperature of 600°C, 100% steam and a gauge pressure of 0.1 MPa for 1.0 h. mixing speed 300 rpm. An aqueous solution of ammonium hexafluorosilicate was rapidly added to the molecular sieve suspension, a total of 60 g of ammonium hexafluorosilicate was added, then stirred at constant temperature and constant speed for 2 hours, filtered and dried to obtain a modified Y-type molecular sieve. The product was designated by the number NY-5, its properties are presented in table 1.

Example 14

Sample A6 obtained in Example 6 was reacted with ammonium to reduce the sodium content, hydrothermally treated, dealuminated, and added with silicon to obtain a modified Y-type molecular sieve with a mesopore-enriched surface through the following steps:

10 L of an aqueous solution of ammonium nitrate with a concentration of 0.7 mol/L was obtained, 1000 g of A6 molecular sieve was weighed and added to 10 L of the obtained aqueous solution of ammonium nitrate during stirring at a rotation speed of 300 rpm, stirring at a constant temperature of 90 ° C for one hour, then the molecular sieve was filtered off, and the operation was repeated until the content of Na ₂ O in the molecular sieve was 4.5 wt. %. The dried sample was subjected to hydrothermal treatment at a temperature of 600°C, 100% steam and a gauge pressure of 0.1 MPa for 1.0 h. mixing speed 300 rpm. An aqueous solution of ammonium hexafluorosilicate was added rapidly to the molecular sieve suspension, a total of 60 g of ammonium hexafluorosilicate was added, then stirred at constant temperature and constant speed for 2 hours, filtered and dried to obtain a modified Y-type molecular sieve. The product was designated as NY-6, its properties are presented in table 1.

Examples 15 and 16

The samples prepared in Examples 7-8 were reacted with ammonium to reduce sodium content, hydrothermally treated, dealuminated, and added silicon according to the method of Example 9 to obtain modified Y-type molecular sieves with a mesopore-enriched surface.

Modified Y-type molecular sieves are numbered NY-7 and NY-8 and their properties are shown in Table 1.

Comparative Example 7

The sample obtained in Comparative Example 1 was subjected to reaction with ammonium to reduce sodium content, hydrothermal treatment, dealumination, and silicon addition according to the method of Example 9 to obtain a comparative product designated as DB-1, the properties of which are shown in Table 1, and a photograph of which obtained by TEM is shown in Fig. 3, where no mesoporous structure was found.

Comparative Example 8

The sample obtained in Comparative Example 2 was subjected to reaction with ammonium to reduce sodium content, hydrothermal treatment, dealumination and addition of silicon according to the method of Example 9 to obtain a comparative product designated as DB-2, the properties of which are shown in Table 1.

Comparative Example 9

The sample obtained in Comparative Example 3 was subjected to reaction with ammonium to reduce sodium content, hydrothermal treatment, dealumination, and addition of silicon according to the method of Example 11 to obtain a comparative product designated as DB-3, the properties of which are shown in Table 1.

Comparative Example 10

The sample obtained in Comparative Example 4 was reacted with ammonium to reduce the sodium content, hydrothermally treated, dealuminated, and added silicon according to the method of Example 12 to obtain a comparative product designated as DB-4, the properties of which are shown in Table 1.

Comparative Example 11

The sample obtained in Comparative Example 5 was subjected to reaction with ammonium to reduce sodium content, hydrothermal treatment, dealumination, and addition of silicon according to the method of Example 13 to obtain a comparative product designated as DB-5, the properties of which are shown in Table 1.

Comparative Example 12

The sample obtained in Comparative Example 6 was subjected to reaction with ammonium to reduce sodium content, hydrothermal treatment, dealumination, and silicon addition according to the method of Example 14 to obtain a comparative product designated as DB-6, the properties of which are shown in Table 1.

The preferred embodiments of the present application have been described in detail above with reference to the figures, however, the present application is not limited to the specific details of the above embodiments, and various simple modifications can be made in the technical solution according to the present application within the technical idea of the present application, and all of these simple modifications belong to the scope of patent protection of the present application.

It should be noted that in the above embodiments, the various specific features described in these embodiments may be combined in any suitable manner unless there is conflict, and in order to avoid unnecessary repetition, the various possible combinations need not be detailed herein.

In addition, any combination can be made within the various embodiments of the present application, and these combinations should also be considered as a disclosure of the present application, provided that they do not go beyond the spirit of the present application.

Claims (42)

1. A NaY molecular sieve with an aluminum-enriched surface, characterized in that the Al distribution index D of the molecular sieve satisfies the condition: 1.01≤D≤10, and D=Al(S)/Al(C), Al (S) means the aluminum content on the surface and in the region from 2 to 6 nm below the surface of the molecular sieve as measured by X-ray photoelectron spectroscopy (XPS), and Al (C) means the aluminum content of the total molecular sieve as measured by XPES, in which the molecular sieve with an aluminum-enriched surface has a SiO ₂ /Al ₂ O ₃ molar ratio in the surface from 1 to 10 and a SiO ₂ /Al ₂ O ₃ molar ratio in bulk phase from 2 to 20. 2. Molecular sieve NaY according to claim 1, characterized in that the distribution index D Al of the molecular sieve satisfies the condition: 1.3≤D≤4. 3. NaY molecular sieve according to claim 1, characterized in that the molar ratio of SiO ₂ /Al ₂ O ₃ on the surface is from 2.5 to 5 and the molar ratio of SiO ₂ /Al ₂ O ₃ in the bulk phase is from 6 to 10. 4. NaY molecular sieve according to claim 1, characterized in that the NaY molecular sieve with an aluminum-enriched surface has an Al content in terms of Al ₂ O ₃ from 18 to 26 wt. %. 5. NaY molecular sieve according to claim 4, characterized in that the NaY molecular sieve with an aluminum-enriched surface has an Al content in terms of Al ₂ O ₃ from 21 to 25 wt. %. 6. NaY molecular sieve according to claim 1, characterized in that the NaY molecular sieve with an aluminum-enriched surface has an average particle size of 200 to 600 nm. 7. NaY molecular sieve according to claim 1, characterized in that the NaY molecular sieve with an aluminum enriched surface has an average particle size of 400 to 500 nm. 8. A method for producing a NaY molecular sieve according to claim 1, characterized in that it includes the following steps: a) mixing the structurant with the first source of silicon to obtain the first mixture, wherein the molar composition of the structurant is Na ₂ O:Al ₂ O ₃ :SiO ₂ :H ₂ O=(3-50):1:(3-50) :(100-600); b) mixing the first mixture obtained in step (a) with a second source of silicon, a source of aluminum and water to obtain a second mixture; c) carrying out hydrothermal crystallization of the second mixture obtained in step (b) and collecting the solid product; moreover, in terms of SiO ₂ , the mass ratio of the first source of silicon and the second source of silicon is 1:(0.001-20), and moreover, the molar composition of the second mixture is Na ₂ O:Al ₂ O ₃ :SiO ₂ :H ₂ O=(1 -10):1:(5-50):(100-600). 9. The method according to claim 8, in which in step a) the molar composition of the structure-forming substance is Na ₂ O:Al ₂ O ₃ :SiO ₂ :H ₂ O=(6-25):1:(6-25): (200-400), and in terms of SiO ₂ the mass ratio of the first source of silicon and the second source of silicon is 1:(0.01-12). 10. The method according to claim 8, wherein in step (a) the structurant is obtained by performing the following operations: mixing the source of aluminum for the structurant with soluble glass to obtain a third mixture, performing dynamic aging and static aging of the third mixture, and then mixing the third mixtures with water to obtain a structure-forming substance; dynamic aging includes aging while stirring at 15 to 60°C for 1 to 100 hours, and static aging includes aging while holding at 15 to 60°C for 0.5 to 100 hours. 11. The method of claim 10 wherein the aluminum source is sodium metaaluminate. 12. The method of claim 10, wherein the stirring aging is carried out for 5 to 48 hours and the holding aging is carried out for 5 to 48 hours. 13. The method of claim 8, wherein in step (a) the first silicon source is at least one selected from the group consisting of soluble glass, colloidal silicon dioxide, and silica sol. 14. The method of claim 8, wherein in step (a) the first silicon source is a solid silicon source and the mixing is carried out during mixing for 30 to 180 minutes. 15. The method according to claim 8, wherein in step (b) the second mixture has the molar composition Na ₂ O:Al ₂ O ₃ :SiO ₂ :H ₂ O=(2-6):1:(8-20): (200-400). 16. The method according to p. 8, in which in stage (b) the second source of silicon is at least one substance selected from the group consisting of soluble glass, silica aluminogel and silica aluminosol; the molar ratio of SiO ₂ /Al ₂ O ₃ of the silicaaluminum gel is from 3 to 30, and the molar ratio of SiO ₂ /Al ₂ O ₃ of the silicaaluminum sol is from 3 to 30. 17. The method according to claim 16, in which the molar ratio of SiO ₂ /Al ₂ O ₃ silicaaluminum gel is from 6 to 16, and the molar ratio of SiO ₂ /Al ₂ O ₃ of silicaaluminum sol is from 6 to 16. 18. The method of claim 8, wherein in step (b) the aluminum source is at least one selected from the group consisting of sodium metaaluminate, aluminum sulfate, aluminum chloride, aluminum nitrate, and pseudoboehmite. 19. The method of claim. 8, wherein the element aluminum in the structure-forming substance is from 3 to 30% of the aluminum element in the second mixture, calculated on the element in moles. 20. The method of claim 8, wherein in step (c) the hydrothermal crystallization conditions comprise a temperature of 40 to 100° C. and a duration of 10 to 60 hours. 21. The method of claim 20 wherein in step (c) the hydrothermal crystallization conditions comprise a temperature of 90 to 100° C. and a duration of 15 to 48 hours. 22. A method for producing a modified Y-type molecular sieve, comprising steps (a), (b) and (c) according to claim 8, and also d) reacting the NaY molecular sieve obtained in step (c) with ammonium to reduce the sodium content, hydrothermal treatment, and dealuminating and adding silica to form a modified Y-type molecular sieve. 23. The method of claim 22 wherein the reaction with ammonium to reduce the sodium content in step (d) comprises treating the NaY molecular sieve with an ammonium salt solution having an ammonium ion concentration of 0.1 to 1.0 mol/l, wherein the conditions treatments include a temperature from room temperature to 100°C, a mass ratio of liquid and solid phases (8-15):1 and a duration of 0.2 to 3 hours. 24. The method of claim. 23, in which the concentration of ammonium ions is from 0.4 to 0.8 mol/l, and the processing conditions include a temperature of from 50 to 100°C and a duration of from 0.5 to 1.5 hours. 25. The method of claim 22, wherein the ammonium salt is at least one selected from the group consisting of ammonium nitrate, ammonium sulfate, ammonium chloride, and ammonium acetate. 26. The method of claim 22, wherein in step (d) the hydrothermal treatment comprises treating the NaY molecular sieve that has reacted with ammonium to reduce the sodium content for 1 to 3 hours under conditions of 100% steam, a gauge pressure of 0, 1 to 0.3 MPa and temperatures from 400 to 700°C. 27. The method according to p. 26, in which the gauge pressure is 0.1 to 0.2 MPa, and the temperature is from 500 to 650°C. 28. The method of claim 22, wherein in step (d) the dealumination and addition of silica comprises slurrying the NaY molecular sieve that has been hydrothermally treated to form a slurry with a liquid to solid mass ratio of (3-10): 1, adding (NH ₄ ) ₂ SiF ₆ to the suspension according to the dosage of 10 to 60 g (NH ₄ ) ₂ SiF ₆ per 100 g NaY molecular sieve, stirring the mixture at 80 to 120°C for 0.5 to 5 hours and product extraction. 29. The method according to p. 28, in which (NH ₄ ) ₂ SiF ₆ is added to the suspension according to a dosage of from 20 to 40 g, while stirring the mixture is carried out at a temperature of from 85 to 99°C. 30. Modified molecular sieve type Y containing mesopores on the surface and obtained by the method according to any one of paragraphs. 22-28, wherein the modified Y-type molecular sieve has a SiO ₂ /Al ₂ O ₃ molar ratio in the bulk phase from 10.0 to 13.0, and wherein the modified Y-type molecular sieve has a BET total pore volume of not less than 0 .38 cm ³ /g; the volume of secondary pores according to the BET method is not less than 0.06 cm ³ /g; and unit cell parameters: a=b=c=2.44-2.46 nm. 31. Modified Y-type molecular sieve according to claim 30, which has a total pore volume according to the BET method of not less than 0.40 cm ³ /g; the volume of secondary pores according to the BET method is not less than 0.09 cm ³ /g. 32. Modified Y-type molecular sieve according to claim 30, characterized in that the Y-type modified molecular sieve has a sodium oxide content of not more than 0.1 wt. % based on the total weight of the modified Y-type molecular sieve.

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