X molecular sieve-based adsorbent, and preparation method therefor and use thereof

Abstract

The present invention relates to an X molecular sieve-based adsorbent. The adsorbent comprises at least 92 wt% of an X molecular sieve, and has a micropore volume of 0.18-0.30 mL / g and a mesopore volume of 0.01-0.1 mL / g. A pore size distribution curve of the adsorbent shows at least two mesopore distribution peaks, wherein the most probable pore size corresponding to one mesopore distribution peak ranges from 3.0 to 9.0 nm, and the most probable pore size corresponding to the other mesopore distribution peak ranges from 10.0 to 19.0 nm. The present invention further relates to a preparation method for the adsorbent, a use of the adsorbent, and a device comprising the adsorbent.

Description

Adsorbent based on X molecular sieve, its preparation method and application TECHNICAL FIELD

[0001] The present application relates to the technical field of adsorption separation, in particular to an adsorbent based on X molecular sieve and its preparation and application. BACKGROUND

[0002] Para-xylene is an important basic chemical raw material for producing polyester fiber. In industrial production, adsorption separation technology is usually used to separate para-xylene from C8 aromatic hydrocarbon mixture. Through the simulated moving bed process, mass transfer exchange is repeatedly carried out between C8 aromatic hydrocarbon mixture and adsorbent, so that para-xylene is enriched in the adsorbent, and then through desorption and rectification operation, para-xylene product is obtained. In the adsorption separation process, the development of high-performance adsorbent is the key to obtaining high-purity and high-yield para-xylene product.

[0003] The active component of para-xylene adsorption separation adsorbent is mainly X molecular sieve. In industry, X molecular sieve is generally mixed with clay as a binder in a certain proportion, and then the adsorbent is obtained after rolling ball molding, drying, calcination and cation exchange. Adsorption selectivity, adsorption capacity, mass transfer performance and mechanical strength are important indicators for evaluating adsorbents. High adsorption selectivity, high adsorption capacity, high mass transfer performance and high mechanical strength of adsorbents are beneficial to obtaining high-purity para-xylene product with high yield.

[0004] In order to improve the adsorption capacity of the adsorbent, in-situ crystallization method is usually used to convert the binder into X molecular sieve. CN1275926A discloses a coalesced molecular sieve adsorbent, the active component of which is X molecular sieve with Si / Al atomic ratio of 1-1.15, and the binder is a molecular sieveable clay. After alkaline treatment, the clay can be converted into X molecular sieve, thereby improving the adsorption capacity.

[0005] Hierarchical porous molecular sieve material has two types of pore structures, micropores and mesopores, and has unique advantages in mass transfer capacity, so it has great application prospect in the field of adsorption separation. However, when hierarchical porous X molecular sieve is used as the active component of the adsorbent, in-situ crystallization of the adsorbent pellets by alkaline treatment during the molding process often causes secondary crystallization of the mesopores in the hierarchical porous molecular sieve, thereby blocking the mesopores and losing their mass transfer advantages. Hydrothermal or acid treatment of the adsorbent pellets after molding to create mesopores will excessively damage the micropore channels, greatly reducing the adsorption capacity and compressive strength of the adsorbent.

[0006] However, the inventors found in the research that the mechanical strength, especially the compressive strength, of the adsorbent based on X molecular sieve known in the prior art still needs to be further improved to reduce the breakage of the adsorbent caused by filling the adsorbent during operation, thereby significantly prolonging its service life. SUMMARY

[0007] The object of the present application is to provide a new adsorbent based on X molecular sieve, which can have mesoporous channels of at least two different pore sizes and more cation-exchangeable sites, so as to have excellent mass transfer performance and excellent adsorption selectivity for para-xylene while having excellent mechanical strength, particularly compressive strength; and when used for the adsorptive separation of para-xylene, it has excellent adsorption selectivity, adsorption capacity, mass transfer performance and mechanical strength compared with adsorbents of the same type.

[0008] The object of the present application is to provide a new adsorbent based on X molecular sieve, which can have mesoporous channels of at least two different pore sizes and more cation-exchangeable sites, so as to have excellent mass transfer performance and excellent adsorption selectivity for para-xylene while having excellent mechanical strength, particularly compressive strength; and when used for the adsorptive separation of para-xylene, it has excellent adsorption selectivity, adsorption capacity, mass transfer performance and mechanical strength compared with adsorbents of the same type.

[0009] To achieve the above object, according to a first aspect, the present application provides a method for preparing an adsorbent based on X molecular sieve, comprising the following steps:

[0010] (1) mixing X molecular sieve with a binder, shaping and calcining to obtain a shaped body;

[0011] (2) optionally, treating the shaped body obtained in step (1) with an alkali solution to in-situ crystallize the binder contained therein to obtain a crystallized product;

[0012] (3) partially barium ion-exchanging the shaped body obtained in step (1) or the crystallized product obtained in step (2) with a barium salt solution and drying to obtain a dried product;

[0013] (4) ammonium ion-exchanging the dried product obtained in step (3) with an ammonium salt solution and calcining under a flowing gas atmosphere to obtain a calcined product; and

[0014] (5) barium ion-exchanging and optionally potassium ion-exchanging the calcined product obtained in step (4) and then drying to obtain the adsorbent.

[0015] According to a second aspect, the present application provides an X-zeolite based adsorbent comprising 92 to 99.8 mass-%, preferably at least 95 to 99.5 mass-%, for example 98.0 to 99.0 mass-% of X-zeolite; the micropore volume of the adsorbent is 0.18 to 0.30 mL / g, preferably 0.24 to 0.30 mL / g, the mesopore volume is 0.01 to 0.1 mL / g, preferably 0.04 to 0.098 mL / g, and the pore size distribution curve thereof shows at least two mesopore distribution peaks, wherein one of the mesopore distribution peaks corresponds to a most probable pore diameter in the range of 3.0 to 9.0 nm, and the other of the mesopore distribution peaks corresponds to a most probable pore diameter in the range of 10.0 to 19.0 nm. Preferably, the adsorbent further comprises at most 8 mass-%, preferably at most 5 mass-%, more preferably at most 2 mass-%, for example 1.0 to 2.0 mass-% of a matrix, wherein the matrix is a substance which has not been crystallized to X-zeolite after in-situ crystallization of a binder or adhesive.

[0016] Preferably, the X-zeolite based adsorbent is prepared according to the preparation method of the first aspect described above.

[0017] Preferably, at least a part of the cation sites of the X-zeolite are occupied by barium ions and optionally potassium ions; the Ba content in the adsorbent, measured as BaO, is 38.0 to 42.5 mass-%, and the K content, measured as K2O, is 0 to 3.0 mass-%, based on the total mass of the adsorbent, more preferably the Ba content in the adsorbent, measured as BaO, is 41.0 to 42.4 mass-%, and the K content, measured as K2O, is 0.1 to 1.0 mass-%.

[0018] Further preferably, the use of 29 Si and 27 Al high-resolution magic-angle spinning nuclear magnetic resonance, the sum of Si(OAl)4 and Si(OSi)1(OAl)3 structural tetrahedra in the framework structure of the adsorbent has a relative content of not less than 65 mol-%, preferably not less than 68 mol-%, of the total silicon species, and the non-framework aluminum has a relative content of not more than 3 mol-%, for example 2 mol-% or 1 mol-%, of the total aluminum species.

[0019] In this context, the term "silicon species" means a substance containing the element silicon, and the term "aluminum species" means a substance containing the element aluminum.

[0020] According to a third aspect, the present application provides the use of the adsorbent according to the present application for the adsorptive separation of xylene.

[0021] The preparation method of the X molecular sieve-based adsorbent according to the present application realizes the controllable breaking and tailoring of the Si-O-Al bonds of the adsorbent by the method of partial barium exchange, ammonium treatment and high-temperature calcination, thereby generating mesoporous channels with at least two different pore sizes in the adsorbent, improving the mass transfer performance of the adsorbent, and simultaneously speculating that the tailoring of the framework structure causes the opening of part of the β cages, so that Ba 2+ may occupy the type III exchange sites, and the higher Ba 2+ exchange amount can further improve the adsorption selectivity of the adsorbent, and the adsorbent exhibits excellent adsorption selectivity and excellent mass transfer performance when used for the adsorption separation of para-xylene.

[0022] Other features and advantages of the present application will be described in detail in the following specific embodiments.

[0023] According to a fourth aspect, the present application provides a method for adsorbing and separating para-xylene from a C8 aromatic hydrocarbon mixture containing para-xylene by liquid-phase adsorption separation, comprising the steps of contacting the C8 aromatic hydrocarbon mixture with the adsorbent of the present application or the adsorbent prepared by the method of the present application to adsorb para-xylene, and then contacting the adsorbent after adsorbing para-xylene with a desorption agent to desorb para-xylene.

[0024] According to a fifth aspect, the present application provides a device for separating para-xylene adsorption from a C8 aromatic hydrocarbon mixture by liquid-phase adsorption, which contains the adsorbent according to the present application, and preferably the device is selected from a fixed bed device, a moving bed device, a fluidized bed device or a simulated moving bed device. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, and together with the specific embodiments below, serve to explain the present application, but do not constitute a limitation on the present application. In the drawings:

[0026] Figure 1 shows the pore size distribution curve of the adsorbent A prepared according to Example 1 of the present application;

[0027] Figure 2 shows the solid-state nuclear magnetic 29 Si spectrum of the adsorbent A prepared according to Example 1 of the present application;

[0028] Figure 3 shows the solid-state nuclear magnetic 27 Al spectrum of the adsorbent A prepared according to Example 1 of the present application;

[0029] Figure 4 shows the pore size distribution curve of the adsorbent B prepared according to Example 2 of the present application;

[0030] Figure 5 shows the pore size distribution curve of the adsorbent G prepared according to Comparative Example 1;

[0031] Figure 6 shows the pore size distribution curve of adsorbent J prepared according to Comparative Example 4;

[0032] Figure 7 shows the solid state nuclear magnetic 29 Si spectrum of adsorbent K prepared according to Comparative Example 5;

[0033] Figure 8 shows the solid state nuclear magnetic 27 Al spectrum of adsorbent K prepared according to Comparative Example 5; and

[0034] Figure 9 shows a schematic diagram of the small-scale simulated moving bed adsorptive separation carried out in Example 7. DETAILED DESCRIPTION

[0035] The specific embodiments of the present application are described in detail below. However, it should be noted that the scope of the present application will not be limited by these specific embodiments, but will, instead, be defined by the claims.

[0036] Any specific numerical values (including the endpoints of numerical ranges) disclosed in this specification are not to be taken as limiting, but rather merely as describing the approximate values that are to be expected to be within the scope of the present application. Also, any numerical range recited in this specification is intended to include all derivatives (e.g., endpoints, increments) falling within the range, as well as all combinations of ranges.

[0037] As used in this specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a molecule" includes a mixture of molecules, reference to "an element" includes a combination of elements, and the like.

[0038] In the present application, micropore and mesopore volumes, specific surface areas and pore size distributions of the molecular sieves are determined by nitrogen physical adsorption method.

[0039] In the present specification, unless explicitly stated otherwise, any matter or matter not mentioned is directly applicable to the aspects known in the art without any change. Also, any embodiment described in the present specification can be freely combined with one or more other embodiments described in the present specification, and the technical solution or technical idea formed thereby is considered to be part of the original disclosure or original description of the present application, and should not be considered as new content that has not been disclosed or anticipated in the present specification, unless the combination is considered to be obviously unreasonable by those skilled in the art.

[0040] All patents and non-patent literature, including but not limited to textbooks and journal articles, mentioned in the present specification are incorporated by reference in their entirety into the present specification.

[0041] In the present specification, the term "comprising" is synonymous with "including" and "containing" and is inclusive or open-ended and does not exclude additional, unrecited elements. It is to be understood that the term "comprising" encompasses the terms "consisting of and "consisting essentially of. The term "based on" is synonymous with "comprising at least 80 wt% or at least 80 mol%". Percentages given are wt% unless explicitly stated.

[0042] As described above, in the first aspect, the present application provides a method for preparing an adsorbent based on X molecular sieve (hereinafter referred to as "preparation method"), which comprises the following steps:

[0043] (1) mixing, molding and calcining X molecular sieve with a binder to obtain a molded body;

[0044] (2) optionally, treating the molded body obtained in step (1) with an alkali solution to in-situ crystallize the binder contained therein to obtain a crystallized product;

[0045] (3) partially barium ion-exchanging the molded body obtained in step (1) or the crystallized product obtained in step (2) with a barium salt solution and drying to obtain a dried product;

[0046] (4) ammonium ion-exchanging the dried product obtained in step (3) with an ammonium salt solution and calcining under a flowing atmosphere to obtain a calcined product; and

[0047] (5) barium ion-exchanging and optionally potassium ion-exchanging the calcined product obtained in step (4) and then drying to obtain the adsorbent.

[0048] In the preparation method of the present application, after mixing, molding and calcining X molecular sieve with a binder, the binder is preferably treated with an in-situ crystallization process to form X molecular sieve from the binder, and then the molded body or the crystallized product (i.e. the molded body after the alkali solution treatment of step (2)) is partially barium ion-exchanged with a barium salt solution and dried, in which process part of the Na + ions in the molecular sieve are replaced by Ba 2+ ions, and then the dried product (i.e. the dried molded body after the partial ion-exchange with the barium salt solution of step (3)) is partially ammonium ion-exchanged with an ammonium salt solution, in which process part of the Na + ions and Ba 2+ ions in the molecular sieve are replaced by NH4 + ions, and then calcined under a flowing atmosphere. Without being bound by a particular theory, it is believed that during the calcination under a flowing atmosphere, the NH4 +will be converted into gaseous ammonia and hydrogen protons, Na + and Ba 2+ The difference in the distribution of the location and valence state of the ions in the molecular sieve framework leads to the breaking of Si-O-Al bonds at different locations after ammonium ion exchange and heat treatment, thereby forming a plurality of mesopores with different pore sizes, and the presence of such mesopores significantly improves the intracrystalline mass transfer capacity of the molecular sieve; in addition, during the calcination process in a flowing gas atmosphere, the high temperature promotes local rearrangement of the molecular sieve framework, the broken Si-O-Al bonds are reconnected with the surrounding silicon or aluminum atoms to form new bonding modes, and such local rearrangement of the molecular sieve framework will partially restore the mechanical strength of the molecular sieve while forming mesopores; in addition, due to the limited space steric hindrance, it is difficult for Ba 2+ to occupy the type III exchange sites on the β cage tetramer ring of the FAU molecular sieve, and through the breaking of Si-O-Al bonds after ammonium ion exchange and heat treatment, part of the β cage can be opened, so that Ba 2+ can occupy the type III exchange sites, so that a higher content of Ba 2+ occupies the exchange sites; a higher Ba 2+ exchange amount can improve the adsorption selectivity of the adsorbent. The inventors have also found that by adjusting the conditions for partial exchange of Ba 2+ in step (3), the exchange conditions of NH4 + ions in step (4), and the calcination treatment conditions, a plurality of mesopore channels with different pore sizes can be constructed while the micropore channels of the molecular sieve are maximally preserved, and the exchange amount of Ba 2+ in the subsequent steps is improved. The adsorbent as a whole has excellent adsorption selectivity, excellent compressive strength, and good mass transfer performance, thereby increasing the processing capacity of a separation device containing the adsorbent and improving the purity of the para-xylene product, and the higher compressive strength can also guarantee the operation cycle of the adsorption separation device.

[0049] According to an embodiment of the preparation method, the mass ratio of the X molecular sieve to the binder in step (1) is such that all the X molecular sieve can be shaped, and a shaped body can be obtained after calcination, and the mass ratio is usually 80:20 to 99:1, preferably 85:15 to 99:1, more preferably 90:10 to 99:1, preferably 95:5 to 99:1, and such mixing can be carried out by conventional methods in the art.

[0050] According to one embodiment of the preparation method, the X molecular sieve used in step (1) can be prepared by a conventional method in the art, as long as the method results in an X molecular sieve having the following properties: a SiO2 / Al2O3molar ratio of 2.0-2.6, for example 2.0, 2.1, 2.2, 2.3, 2.4, 2.5 or 2.6, a particle size of 0.8-2.5 μm, for example 0.8 μm, 0.9 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm or 2.5 μm, and any value within a range defined by any two of the above values; a Na mass fraction of 13-20% relative to the total weight of the X molecular sieve, preferably 14-19%, for example 15%, 16%, 17% or 18%, and any value within a range defined by any two of the above values, calculated as Na2O; a mesopore volume of 0.0015-0.0045 mL / g, preferably 0.002-0.004 mL / g, more preferably 0.0025-0.0035 mL / g, for example 0.003 mL / g; and a micropore volume generally not less than 0.1 mL / g, preferably not less than 0.15 mL / g, for example not less than 0.2 mL / g. Further preferably, the SiO2 / Al2O3molar ratio of the X molecular sieve used is 2.1-2.5, and the particle size is 0.8-1.5 μm.

[0051] According to one embodiment of the preparation method, the binder used in step (1) is selected from kaolinite, dickite, perlite, refractory stone, halloysite, hydromica, montmorillonite, or a combination thereof. Further preferably, the binder comprises 75-95% by mass of kaolinite and 5-15% by mass of halloysite, which can better convert into X molecular sieve during in-situ crystallization in step (2) using the binder having the composition, thereby improving the adsorption capacity and separation performance of the adsorbent.

[0052] According to one embodiment of the preparation method, in step (1), the shaped body obtained, for example by ball-rolling shaping, is dried at a temperature higher than 60°C, for example 75-120°C, preferably 80-110°C, to remove water in the shaped body; the drying can be performed in a drying device commonly used in the art, such as an oven, and the drying time is 1.0-20.0 hours, for example 1.5 hours, 2.5 hours, 4.0 hours, 5.5 hours, 6.5 hours, 7.5 hours, 9.0 hours, 11.5 hours or 12.0 hours, preferably 4.0-15.0 hours.

[0053] According to an embodiment of the preparation method, in step (1), the temperature of the calcination is 500-700°C, for example 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, 620°C, 640°C, 660°C, 680°C or 700°C; the time of the calcination is 0.5-6.0 hours, for example 0.5 hours, 1.0 hours, 1.5 hours, 2.0 hours, 2.5 hours, 3.0 hours, 3.5 hours, 4.0 hours, 4.5 hours, 5.0 hours, 5.5 hours or 6.0 hours; and the calcination can be carried out according to various ways known to those skilled in the art, which will not be described herein.

[0054] According to an embodiment of the preparation method, the shaping in step (1) can be achieved by various shaping methods commonly used in the art, which are not strictly limited in the present application. In some preferred embodiments, the shaping method in step (1) is balling, and the shaped body obtained is in the form of a sphere. In particular, the balling comprises gradually gathering and growing the shaped powder obtained by mixing the X molecular sieve and the binder in a rolling disc, and continuously spraying water to wet the surface of the sphere and adhere the powder.

[0055] According to an embodiment of the preparation method, the diameter of the shaped beads is 100-1300 μm, preferably 300-1000 μm, and the sphericity is greater than 0.85, preferably greater than 0.9. The expression "sphericity of the shaped beads" means the ratio of the surface area of a sphere having the same volume as the beads to the surface area of the beads, which is measured by conventional methods in the art, which will not be described herein.

[0056] According to an embodiment of the preparation method, in step (2), the shaped body after the calcination is treated with an alkaline solution to cause the in-situ crystallization of the binder in the shaped body into X molecular sieve, thereby increasing the content of the active component in the shaped body and improving the adsorption capacity of the adsorbent.

[0057] According to an embodiment of the preparation method, the alkaline solution used in step (2) is a mixed solution of sodium hydroxide and water glass, wherein the concentration of sodium hydroxide is 1.2-4.0 mol / L, for example 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2.0 mol / L, 2.4 mol / L, 2.8 mol / L, 3.2 mol / L, 3.6 mol / L or 4.0 mol / L, and any value within the range defined by any two of the above values, preferably 1.2-2.0 mol / L, and the concentration of silicon dioxide is 6-20 g / L, for example 6 g / L, 8 g / L, 10 g / L, 12 g / L, 14 g / L, 16 g / L, 18 g / L or 20 g / L, preferably 10-15 g / L.

[0058] According to an embodiment of the preparation method, the liquid to solid volume ratio of the base solution to the shaped body in the base solution treatment of step (2) is 1.2-3.0:1, for example, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1 or 3.0:1, and any value in the range between any two of the above-mentioned values, preferably 2.0-3.0:1.

[0059] According to an embodiment of the preparation method, the conditions of the base solution treatment in step (2) include: the treatment temperature is 90-100°C, for example, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C or 100°C, and any value in the range between any two of the above-mentioned values, and the treatment time is 1.5-6.0 hours, for example, 1.5 hours, 2.0 hours, 2.5 hours, 3.0 hours, 3.5 hours, 4.0 hours, 4.5 hours, 5.0 hours, 5.5 hours or 6.0 hours, and any value in the range between any two of the above-mentioned values.

[0060] According to an embodiment of the preparation method, in step (2), the shaped body obtained by in-situ crystallization can be washed with deionized water to remove metal ions deposited on the surface of the shaped body until the pH value of the deionized water is less than 8.0; then the washed shaped body is dried at a temperature higher than 80°C, for example, 90-130°C, preferably 100-120°C; the drying can be carried out in a drying device commonly used in the art, such as an oven, and the drying time is 1.0-20.0 hours, for example, 1.5 hours, 2.5 hours, 4.0 hours, 5.5 hours, 6.5 hours, 7.5 hours, 9.0 hours, 11.5 hours or 12.0 hours, preferably 4.0-15.0 hours.

[0061] In the above-mentioned preferred embodiments, the optionally implemented step (2) can better achieve the transformation of the binder into X molecular sieve, thereby improving the adsorption capacity and separation performance of the obtained adsorbent.

[0062] According to an embodiment of the preparation method, in step (3), Ba 2+ According to an embodiment of the preparation method, in step (3), the barium salt is selected from barium chloride, barium nitrate, or a combination thereof.

[0063] According to an embodiment of the preparation method, in step (3), the concentration of the barium salt solution is 0.05-1.0 mol / L, for example, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1.0 mol / L, and any value in the range between any two of the above values, preferably 0.05-0.2 mol / L.

[0064] According to an embodiment of the preparation method, in step (3), the liquid-to-solid volume ratio of the barium salt solution to the shaped body obtained in step (1) or the crystallized product obtained in step (2) in the barium ion exchange process is 1-10:1, for example, 1:1, 2:1, 4:1, 6:1, 8:1 or 10:1, preferably 2-5:1.

[0065] According to an embodiment of the preparation method, in step (3), the conditions of the barium ion exchange include a temperature of 25-95°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or 95°C, preferably 80-95°C, and a time of 0.5-5.0 hours, for example, 0.5 hour, 1.0 hour, 1.5 hours, 2.0 hours, 2.5 hours, 3.0 hours, 3.5 hours, 4.0 hours, 4.5 hours or 5.0 hours, preferably 2.0-5.0 hours. At least a part of the cation sites of the obtained partial barium ion exchange product is occupied by barium ions, and the Ba content, in terms of BaO, in the partial barium ion exchange product is 1.0-30.0 mass%, preferably 5.0-25.0 mass%, more preferably 10.0-23.0 mass%, for example, 10.0 mass%, 12.0 mass%, 15.0 mass%, 18.0 mass%, 20.0 mass% or 22.0 mass%, based on the mass of the product.

[0066] According to one embodiment of the preparation method, in step (3), the barium ion-exchanged shaped body can be washed with deionized water to remove metal ions deposited on the surface of the shaped body, wherein the liquid-to-solid volume ratio of the deionized water used to the shaped body is greater than 3:1, for example, 4:1, 6:1, 8:1, or 15:1, preferably 5-13:1. The washed shaped body is dried at a temperature higher than 80°C, for example, 95-120°C, preferably 100-110°C, to remove water from the shaped body and to enhance the interaction between barium ions and the molecular sieve at the exchange sites; the drying can be performed in a drying device commonly used in the art, such as an oven, and the drying time is 1.0-20.0 hours, for example, 1.5 hours, 2.5 hours, 4.0 hours, 5.5 hours, 6.5 hours, 7.5 hours, 9.0 hours, 11.5 hours, or 12.0 hours, and any value in the range between any two of the above-mentioned values, preferably 4.0-15.0 hours.

[0067] According to one embodiment of the preparation method, in step (4), NH4 + The cation-exchangeable sites of the X molecular sieve in the barium ion-exchanged shaped body are exchanged with NH4

[0068] According to one embodiment of the preparation method, in step (4), the concentration of the ammonium salt solution is 0.2-5.0 mol / L, for example, 0.2 mol / L, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, 4.5 mol / L, or 5.0 mol / L, and any value in the range between any two of the above-mentioned values, preferably 0.2-2.0 mol / L.

[0069] According to one embodiment of the preparation method, in step (4), the liquid-to-solid volume ratio of the ammonium salt solution to the barium ion-exchanged shaped body during the ammonium ion exchange is 2-10:1, for example, 2:1, 4:1, 6:1, 8:1, or 10:1, preferably 2-5:1.

[0070] According to one embodiment of the preparation method, in step (4), the conditions for the ammonium ion exchange include a temperature of 25-95 °C, such as 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, or 95 °C, preferably 50-75 °C, and a time period of 0.5-5.0 hours, such as 0.5 hour, 1.0 hour, 1.5 hour, 2.0 hour, 2.5 hour, 3.0 hour, 3.5 hour, 4.0 hour, 4.5 hour, or 5.0 hour, and any value in a range defined by any two of the above values, preferably 0.5-2.0 hour.

[0071] According to one embodiment of the preparation method, in step (4), the ammonium ion exchanged shaped body can be washed with deionized water to remove metal ions deposited on the surface of the shaped body, wherein the liquid to solid volume ratio of the deionized water used to the shaped body is greater than 3:1, such as 4:1, 6:1, 8:1, or 15:1, preferably 5-13:1. The washed shaped body is optionally dried at a temperature higher than 80 °C, such as 95-130 °C, preferably 100-120 °C, to remove water from the shaped body; the drying can be performed in a drying device commonly used in the art, such as an oven, and the drying time is 2.0-20.0 hours, such as 2.5 hour, 4.0 hour, 5.5 hour, 6.5 hour, 7.5 hour, 9.0 hour, 11.5 hour, or 12.0 hour, preferably 4.0-15.0 hour.

[0072] In step (4) of the preparation method, the purpose of the calcination treatment under a flowing atmosphere is to selectively destroy the framework structure of the molecular sieve to form mesoporous channels while avoiding significant destruction of the microporous channels of the molecular sieve. According to one embodiment of the preparation method, in step (4), the temperature of the calcination is 130-500 °C, such as 160 °C, 200 °C, 250 °C, 300 °C, 350 °C, 400 °C, 450 °C, or 500 °C, and any value in a range defined by any two of the above values, preferably 160-350 °C, more preferably 180-300 °C; and the calcination time is 0.5-8.0 hours, such as 0.5 hour, 1.0 hour, 1.5 hour, 2.0 hour, 2.5 hour, 3.0 hour, 3.5 hour, 4.0 hour, 4.5 hour, 5.0 hour, 5.5 hour, 6.0 hour, 6.5 hour, 7.0 hour, 7.5 hour, or 8.0 hour, and any value in a range defined by any two of the above values, preferably 1.0-6.0 hour, more preferably 1.0-2.0 hour.

[0073] According to an embodiment of the preparation method, in step (4), the flowing gas atmosphere can be a flowing air atmosphere or a flowing inert gas atmosphere (such as a flowing nitrogen gas or a flowing argon gas atmosphere), and is more preferably a flowing nitrogen gas atmosphere.

[0074] According to an embodiment of the preparation method, in step (4), the gas flow rate of the flowing gas atmosphere is 0.1-1.5 L / h / g adsorbent, such as 0.1 L / h / g adsorbent, 0.3 L / h / g adsorbent, 0.5 L / h / g adsorbent, 0.7 L / h / g adsorbent, 0.9 L / h / g adsorbent, 1.1 L / h / g adsorbent, 1.3 L / h / g adsorbent or 1.5 L / h / g adsorbent, and is preferably 0.1-0.5 L / h / g adsorbent.

[0075] In step (4) of the preparation method according to the present application, the calcination treatment allows better avoiding significant damage to the molecular sieve framework structure, so that the resulting adsorbent has both higher micropore volume, adsorption capacity and separation performance while opening the beta cage of the X molecular sieve and forming mesoporous channels.

[0076] According to an embodiment of the preparation method, in step (5), the calcination product obtained in step (4) is subjected to cation exchange, so that at least part of the cation sites of the X molecular sieve contained therein are occupied by Ba 2+ and optionally K + ions. Preferably, the ratio of the total moles of cations (Ba 2+ and optionally K + ) in the exchange solution used to the moles of Na + ions in the molecular sieve, i.e. the exchange ratio, is 1.5-3.0:1, such as 1.7:1, 1.9:1, 2.1:1, 2.3:1, 2.5:1 or 2.7:1, and any value in the range between any two of the aforementioned values.

[0077] Without being bound to a particular theory, it is believed that the cation exchange treatment of step (5) allows the barium ions or barium ions and potassium ions to coordinate with the oxygen ions in the molecular sieve framework, so that a high PX selective adsorption field with symmetry of D2 group is generated in the X molecular sieve, and the resulting adsorbent has higher separation performance.

[0078] According to a preferred embodiment, in step (5), only barium ion exchange is performed, and the barium ion exchange is performed using a solution of a soluble barium salt, which is preferably selected from barium chloride, barium nitrate, or a combination thereof.

[0079] According to a preferred embodiment, in step (5), barium ion exchange is performed first, followed by potassium ion exchange, or potassium ion exchange is performed first, followed by barium ion exchange; or a mixed solution of potassium and barium ions is used for exchange; the barium ion exchange is performed using a solution of soluble barium salt, preferably selected from barium chloride, barium nitrate, or a combination thereof; the potassium ion exchange is performed using a potassium salt solution, preferably selected from potassium chloride, potassium nitrate, or a combination thereof.

[0080] According to a preferred embodiment, in step (5), barium ion and potassium ion exchange are performed simultaneously using a mixed solution containing soluble barium salt and potassium salt, the selection of which is as described above.

[0081] According to one embodiment of the preparation method, the conditions for performing the barium ion exchange and optionally potassium ion exchange in step (5) include: a temperature of 30-95°C, for example, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or 95°C, and any value within the range of any two of the above values, preferably 80-95°C; and a time of 2.0-48.0 hours, for example, 2.0 hours, 6.0 hours, 10.0 hours, 14.0 hours, 18.0 hours, 22.0 hours, 26.0 hours, 30.0 hours, 34.0 hours, 38.0 hours, 42.0 hours, 46.0 hours, or 48.0 hours, and any value within the range of any two of the above values, preferably 12.0-36.0 hours. More preferably, in step (5), the volume hourly space velocity (VHSV) of the barium salt solution, potassium salt solution, and their mixture in the ion exchange is independently 1.0-20.0 h⁻¹. -1 For example, 1.0h -1 2.0h -1 3.0h -1 4.0h -1 5.0h - 1 6.0h -1 7.0h -1 8.0h -1 9.0h -1 10.0h -1 12.0h -1 14.0h -1 16.0h - 1 18.0h -1 or 20.0h -1 And any value within the range formed by any two of the above values, preferably 1.0-10.0h. -1 .

[0082] According to the present application, the product after ion exchange in step (5) can be washed with deionized water to remove the metal ions deposited on the surface of the shaped body, wherein the deionized water used has a liquid to solid volume ratio of greater than 3:1, for example 4:1, 6:1, 8:1 or 15:1, preferably 5-13:1. The washed shaped body is optionally purged with an inert gas for a period of time, for example 5-30 hours, and then dried to obtain the X molecular sieve-based adsorbent, the drying temperature is preferably 100-120°C and the time is preferably 6.0-24.0 hours; the drying can be carried out in a drying device commonly used in the art, such as an oven.

[0083] According to an embodiment of the preparation method, the preparation method comprises the following steps:

[0084] (1) uniformly mixing X molecular sieve with a binder to obtain a shaped powder, placing the shaped powder in a rolling shaping device, rolling while spraying water until the powder is completely gathered into small balls, drying the shaped small balls, and calcining at a temperature of 500-700°C, wherein the content of the binder is 1-8 mass%, preferably 3-6 mass%, and the content of the X molecular sieve is 99-92 mass%, preferably 97-94 mass%, relative to the total mass of the shaped powder;

[0085] (2) treating the shaped and calcined small balls obtained in step (1) with an alkali solution to in-situ crystallize the binder contained therein;

[0086] (3) contacting the in-situ crystallized small balls obtained in step (2) with a barium salt solution to perform partial barium ion exchange for 0.5-5.0 hours, and drying;

[0087] (4) contacting the dried product obtained in step (3) with an ammonium salt solution to perform ammonium ion exchange for 0.5-5.0 hours, and performing calcination treatment under a flowing air atmosphere; and

[0088] (5) performing barium ion exchange or barium-potassium ion exchange on the calcined product obtained in step (4), and then drying to obtain the adsorbent.

[0089] In a second aspect, the present application provides an adsorbent based on X molecular sieve, comprising 98.0-99.0 mass% of X molecular sieve and 1.0-2.0 mass% of matrix, relative to the total mass of the adsorbent, the matrix being a substance which is not crystallized into X molecular sieve after in-situ crystallization of the binder, the micropore volume of the adsorbent is 0.18-0.30 mL / g, preferably 0.24-0.30 mL / g, the mesopore volume is 0.01-0.1 mL / g, preferably 0.04-0.098 mL / g, and the pore size distribution curve thereof shows at least two mesopore distribution peaks, wherein one of the mesopore distribution peaks corresponds to a most probable pore size in the range of 3.0-9.0 nm, preferably in the range of 3.5-8.5 nm, such as 4.5 nm, 5.5 nm, 6.5 nm or 7.5 nm, and any value in the range composed of any two of the above-mentioned values, and the other of the mesopore distribution peaks corresponds to a most probable pore size in the range of 10.0-19.0 nm, preferably in the range of 11.0-18.0 nm, such as 12 nm, 13 nm, 15 nm or 17 nm, and any value in the range composed of any two of the above-mentioned values.

[0090] In the present text, the micropores of the X molecular sieve generally refer to the pores with a pore size of less than 2 nm in the X molecular sieve; the mesopores generally refer to the pores with a pore size of 2 nm to 50 nm.

[0091] According to an embodiment of the adsorbent of the present application, the binder can be selected from the group consisting of kaolinite, dickite, perlite, refractory stone, halloysite, hydromica, montmorillonite, or a combination thereof.

[0092] According to an embodiment of the adsorbent of the present application, the 250N compression crushing strength of the adsorbent is less than 5.5%, such as less than 5.0%, less than 4.0% or less than 3.0%, and the bulk density of the calcined base is 0.91-1.20 g / cm 3 , such as 0.92 g / cm 3 , 0.95 g / cm 3 , 0.98 g / cm 3 , 1.01 g / cm 3 , 1.04 g / cm 3 , 1.07 g / cm 3 , 1.10 g / cm 3 , 1.13 g / cm 3 , 1.16 g / cm 3 , 1.19 g / cm 3 or 1.20 g / cm 3 , and any value in the range composed of any two of the above-mentioned values.

[0093] According to one embodiment of the adsorbent of the present application, at least part of the cation sites of the X molecular sieve contained in the adsorbent are occupied by barium ions and optionally potassium ions, the content of Ba in terms of BaO in the adsorbent is 38.0 to 42.5 mass% based on the mass of the adsorbent, for example 38.0 mass%, 38.5 mass%, 39.0 mass%, 39.5 mass%, 40.0 mass%, 40.5 mass% or 41.0 mass%, and any value within a range defined by any two of the above values, and the content of K in terms of K2O is 0 to 3.0 mass%, for example 0.5 mass%, 1.0 mass%, 1.5 mass%, 2.0 mass%, 2.5 mass% or 3.0 mass%, and any value within a range defined by any two of the above values.

[0094] According to one embodiment of the adsorbent of the present application, the adsorbent has a framework structure in which the sum of Si(OAl)4and Si(OSi)1(OAl)3structural tetrahedra is not less than 65 mol% of the total silicon species, for example 65 to 85 mol%, such as 65 mol%, 70 mol%, 75 mol%, 80 mol% or 85 mol%, and any value within a range defined by any two of the above values, and the non-framework aluminum is not more than 3 mol% of the total aluminum species, for example 1 to 3 mol%, such as 1.0 mol%, 1.5 mol%, 2.0 mol%, 2.5 mol% or 3.0 mol%, and any value within a range defined by any two of the above values. 29 Si and 27 Al high-resolution magic-angle spinning nuclear magnetic resonance measurement, the sum of Si(OAl)4and Si(OSi)1(OAl)3structural tetrahedra in the framework structure of the adsorbent is not less than 65 mol% of the total silicon species, for example 65 to 85 mol%, such as 65 mol%, 70 mol%, 75 mol%, 80 mol% or 85 mol%, and any value within a range defined by any two of the above values, and the non-framework aluminum is not more than 3 mol% of the total aluminum species, for example 1 to 3 mol%, such as 1.0 mol%, 1.5 mol%, 2.0 mol%, 2.5 mol% or 3.0 mol%, and any value within a range defined by any two of the above values. Further preferably, the sum of Si(OAl)4and Si(OSi)1(OAl)3structural tetrahedra in the framework structure of the adsorbent is not less than 70 mol% of the total silicon species, for example 70 to 85 mol%, and the non-framework aluminum is not more than 1 mol% of the total aluminum species, for example 0.5 to 1 mol%.

[0095] According to one embodiment of the adsorbent of the present application, the external specific surface area of the adsorbent is 15 to 50 m 2 / g, for example 20 m 2 / g, 30 m 2 / g or 40 m 2 / g, and any value within a range defined by any two of the above values; and the micropore specific surface area is 540 to 600 m 2 / g, for example 550 m 2 / g, 560 m 2 / g, 570 m 2 / g or 580 m 2 / g, and any value in a range bounded by any of the above values; an average particle size D50 of 425-600 pm, such as 450 pm, 480 pm, 500 pm, 530 pm, or 550 pm, and any value in a range bounded by any of the above values; a 250N crush strength of less than 5.5%, such as less than 5.0%, less than 4.5%, or less than 4.0%; a tap density of 0.91-1.20 g / cm 3 , such as 0.95 g / cm 3 , 1.0 g / cm 3 , 1.1 g / cm 3 , or 1.15 g / cm 3 , and any value in a range bounded by any of the above values.

[0096] In a particularly preferred embodiment, the X molecular sieve based adsorbent according to the second aspect described above can be prepared by the method according to the first aspect described above.

[0097] In a third aspect, the present application provides the use of the X molecular sieve based adsorbent described above for the adsorptive separation of para-xylene, in particular for the adsorptive separation of para-xylene from a C8aromatic hydrocarbon mixture comprising para-xylene.

[0098] The adsorbents according to the present application and the adsorbents prepared by the method according to the present application are particularly suitable for use in a liquid phase adsorptive separation process of aromatic hydrocarbon isomers, in particular for the adsorptive separation of para-xylene from a C8aromatic hydrocarbon mixture, such as a mixture comprising o-xylene, m-xylene, para-xylene, and ethylbenzene.

[0099] In a fourth aspect, the present application provides a method for the adsorptive separation of para-xylene from a C8aromatic hydrocarbon mixture comprising para-xylene by liquid phase adsorptive separation, comprising the steps of contacting the C8aromatic hydrocarbon mixture with an adsorbent of the present application or an adsorbent prepared by the method of the present application to adsorb para-xylene, and contacting the adsorbent after adsorption of para-xylene with a desorbent to desorb para-xylene.

[0100] According to a preferred embodiment, the liquid phase adsorptive separation can be carried out in a multi-column series mode, or in a simulated moving bed mode realized by means of a rotary valve or solenoid valve group.

[0101] According to a preferred embodiment, the desorbent is selected from the group consisting of para-diethylbenzene, toluene, or a combination thereof.

[0102] According to a preferred embodiment, the operating pressure of the adsorption separation is 0.3-1.5 MPa, for example 0.3 MPa, 0.5 MPa, 0.8 MPa, 1.0 MPa, 1.2 MPa, 1.4 MPa or 1.5 MPa, and the operating temperature is 120-190℃, for example 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃ or 190℃.

[0103] In a fifth aspect, the present invention provides an apparatus for separating p-xylene adsorbed from a mixture of C8 aromatics by liquid-phase adsorption, comprising an adsorbent according to the present invention.

[0104] According to a preferred embodiment, the device is selected from a fixed bed device, a moving bed device, a fluidized bed device, or a simulated moving bed device.

[0105] Example

[0106] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0107] In the following examples and comparative examples, unless otherwise specified, all parameters were measured according to conventional methods in the art:

[0108] The total pore volume, micropore volume, mesopore volume, specific surface area, and pore size distribution of the adsorbent were determined by nitrogen physical adsorption method using a Micromeritics ASAP 2020 physical adsorption instrument. Prior to testing, the samples were kept at a temperature of 300-450℃ and <10 -2 Degassing was performed at a pressure of Pa for 6.0–16.0 hours, preferably at 300 °C for 10.0 hours. Nitrogen physical adsorption was carried out at 77 K. The total specific surface area and average adsorption pore size of the molecular sieve were calculated using the BET (Brunauer-Emmett-Teller) equation; with P0 at 0.1 MPa, the total pore volume of the sample was determined using the nitrogen adsorption amount when the relative adsorption amount P / P0 = 0.975. The micropore specific surface area, external specific surface area, and micropore volume were calculated using the t-plot method, and the mesopore size distribution was calculated using the Barrett-Joyner-Halenda method.

[0109] The elemental chemical composition of the adsorbent was characterized by X-ray fluorescence spectrometry (XRF) using a Shimadzu XRF-1800 XRF spectrometer. Qualitative analysis of BaO, K₂O, and Na₂O was performed based on the correspondence between characteristic X-ray fluorescence wavelengths and atomic numbers. Quantitative analysis of BaO, K₂O, and Na₂O was performed by comparing the peak intensities at the X-ray fluorescence wavelengths with those of standard samples.

[0110] The coordination number and existing form of silicon atoms and aluminum atoms in the adsorbent are used 29 Si and 27 Al high-resolution magic angle nuclear magnetic resonance technology (MAS NMR) characterization, 29 Si nucleus and 27 The single pulse spectrum of the Al nucleus is completed using a Bruker Avance III 500WB spectrometer, 29 Si nucleus and 27 The resonance frequencies of the Si and Al nuclei are 500.1 MHz and 89.6 MHz, respectively. The relative content of the sum of Si (OAl) 4 and Si (OSi) 1 (OAl) 3 structure tetrahedrons in the total silicon species in the adsorbent skeleton structure is 29 The ratio of the sum of the peak areas corresponding to the chemical shifts of -86 ppm and -90 ppm to the sum of all peak areas corresponding to -70 ppm to -120 ppm in the Si MAS NMR spectrum; the relative content of non-framework aluminum in the total aluminum species is 27 The ratio of the peak area corresponding to 0 ppm to the sum of all peak areas corresponding to -20 ppm to 100 ppm in the Al MAS NMR spectrum

[0111] The adsorption capacity of the adsorbent is determined by contacting nitrogen carrying toluene (toluene partial pressure is 0.5 MPa) with a certain mass of adsorbent at 35°C until toluene reaches adsorption equilibrium. The adsorption capacity of the measured adsorbent is calculated according to the mass difference of the adsorbent before and after toluene adsorption.

[0112] The adsorption selectivity of the adsorbent is determined using a dynamic pulse test device: the device is composed of a feed system, an adsorption column, a heating furnace, a pressure control valve, etc. The adsorption column is a Ф6x1800mm stainless steel tube, and the adsorbent loading is 50ml. The inlet at the lower end of the adsorption column is connected to the feed and nitrogen system, and the outlet at the upper end is connected to the pressure control valve, which is then connected to the effluent collector. The desorbent used in the experiment is 30% by volume of p-diethylbenzene (PDEB) and 70% by volume of n-heptane. The pulse feed liquid composition is 5% by volume of each of ethylbenzene (EB), p-xylene (PX), m-xylene (MX), o-xylene (OX), n-nonane (NC9), and 75% by volume of p-diethylbenzene.

[0113] The adsorption selectivity of the adsorbent is determined by weighing the measured adsorbent particles with a particle size of 300-850μm, filling them into the adsorption column, and vibrating them, and then dehydrating and activating them at 160-190°C in a nitrogen atmosphere; then the gas in the desorbent removal system is introduced. The system pressure is raised to 0.8MPa, and the temperature is raised to 177°C, and the desorbent is stopped, and the desorbent is introduced at a rate of 1.0h -18 mL of pulsed feed solution was introduced at a volume hourly space velocity (VHSV), followed by the introduction of desorbent at the same VHSV. Three drops of desorbate were collected every 2 minutes and analyzed by gas chromatography. Desorption curves for each component were plotted with the volume of desorbent on the x-axis and the concentrations of NC9, EB, PX, MX, and OX on the y-axis. NC9, being unadsorbed, can be used as a tracer to obtain the dead volume of the adsorption system. The midpoint of the tracer's half-peak width (WHM) was taken as the zero point. The net retention volume R from the midpoint of the WHM width of each component (EB, PX, MX, and OX) to the zero point was measured. The net retention volume of any component is proportional to the partition coefficient at adsorption equilibrium, reflecting the interaction force between each component and the adsorbent material. The ratio of the net retention volumes of two components is the selectivity β. For example, the ratio of the net retention volume of PX to the net retention volume of EB represents the ratio of the adsorption performance of the adsorbent material for PX and EB, i.e., the adsorption selectivity of the adsorbent material for PX relative to EB, denoted as β. P / E Similarly, the adsorption selectivity of the adsorbent material for PX relative to MX and OX is denoted as β. P / M and β P / O The volume of desorbent required for the concentration of MX in the effluent to increase from 10% to 90% at the leading edge of the pulse desorption curve of MX is defined as the adsorption rate [S]. A ] 10-90 The desorbent volume required for the MX concentration to decrease from 90% to 10% after the desorption curve is defined as the desorption rate [S]. D ] 90-10 [S] A ] 10-90 With [S] D ] 90-10 The smaller the value, the higher the mass transfer performance of the adsorption material.

[0114] The method for determining the relative content of the active component and the matrix of the adsorbent is as follows: the toluene adsorption capacity of the adsorbent and the same mass of X zeolite are measured separately, and the ratio of the two is the content of the active component (X molecular sieve). The matrix content = 1 - percentage content of active component.

[0115] The adsorbent particle size was determined by laser diffraction using a Masterizer-2000 X-ray fluorescence spectrometer from MALVERN, UK. The particle size distribution of the sample was obtained based on the difference in laser scattering angle caused by different particle sizes. The average particle size of the sample was taken as the particle size (D50) corresponding to the cumulative particle size distribution of a sample reaching 50%.

[0116] Method for measuring the bulk density of the adsorbent: 50 mL of the adsorbent was added to a 100 mL measuring cylinder, and was vibrated for 5 minutes on a vibrating densitometer (produced by Liaoning Instrument Research Co., Ltd.), then 50 mL of the adsorbent was added and vibrated for 5 minutes, and the ratio of the mass of the adsorbent to the volume in the measuring cylinder was the bulk density of the adsorbent; a certain mass of the adsorbent was calcined at 600℃ for 2 hours, and was cooled to room temperature in a desiccator, and the ratio of the mass of the adsorbent after calcination to the mass of the adsorbent before calcination was the ignition base, and the bulk density of the ignition base = ignition base x bulk density of the adsorbent.

[0117] The compressive strength of the adsorbent was represented by the breakage rate of the adsorbent pellets under 250N, and the lower the breakage rate, the higher the compressive strength. The method for measuring was as follows: after the adsorbent pellets passed through a 300 μm sieve, the adsorbent pellet particles with a particle size greater than 300 μm were taken, and about 1.5 mL was loaded into a stainless steel cylinder. A top pin was installed in interference fit with the stainless steel cylinder, and after being pressed once under a pressure of 250N, the adsorbent was poured out, then passed through a 300 μm sieve, and the adsorbent pellet particles with a particle size greater than 300 μm were weighed. The decrease in the adsorbent with a particle size greater than 300 μm before and after being pressed was the breakage rate of the adsorbent.

[0118] In the following examples and comparative examples, various reagents and raw materials used were commercially available products, unless otherwise specified.

[0119] In the examples according to the present application, the X molecular sieve was prepared by the following method:

[0120] (1) 41.98 g of water glass (silicon source, the mass fraction of Si in SiO2 in the water glass was 19.85 wt%, the mass fraction of Na in Na2O was 6.25 wt%, and the mass fraction of water was 73.90 wt%), 26.83 g of low-alkalinity sodium metavanadate (aluminum source, the mass fraction of Na in Na2O was 22.97 wt%, the mass fraction of Al in Al2O3 was 20.99 wt%, and the mass fraction of water was 56.04 wt%), 2.23 g of sodium hydroxide (inorganic base, the mass fraction of Na in Na2O was 77.5 wt%, and the mass fraction of water was 22.5 wt%), and 102.43 g of deionized water were added to a reaction kettle and stirred and mixed for 1 hour at a temperature of 30℃ to obtain a mixture;

[0121] In the mixture, the molar ratio of silicon element in SiO2 to aluminum element in Al2O3 was 2.75:1, the molar ratio of sodium element in Na2O to silicon element in SiO2 was 1.16:1, and the molar ratio of H2O to aluminum element in Al2O3 was 165.0:1;

[0122] (2) The mixture prepared in step (1) is transferred into a closed reactor, and is aged at 35°C for 12 hours to obtain an aged product;

[0123] (3) The aged product prepared in step (2) is subjected to crystallization treatment at 95°C for 24 hours. After the crystallization is completed, solid-liquid separation is performed by reduced pressure filtration, and the obtained solid is washed with deionized water until the pH of the filtrate is neutral, and is dried at 90°C for 12 hours to obtain X molecular sieve, which has a SiO2 / Al2O3 molar ratio of 2.35, a particle size of 1.0 μm, a Na mass fraction of 16.7% in terms of Na2O, and a mesopore volume of 0.003 mL / g.

[0124] Example 1

[0125] Preparation of adsorbent:

[0126] (1) 92 kg (mass on ignition, the same below) of the X molecular sieve (SiO2 / Al2O3 molar ratio of 2.35, particle size of 1.0 μm, Na mass fraction of 16.7% in terms of Na2O, and mesopore volume of 0.003 mL / g) prepared above is mixed with 8 kg of binder (containing 90 mass% of kaolinite and 10 mass% of halloysite) uniformly, and is put into a rotating disc. While rotating, an appropriate amount of deionized water is sprayed to make the solid powder gather into small balls. The amount of water sprayed during the balling is 8 mass% of the solid powder. After screening, small balls having a particle size of 300-1000 μm are taken, dried at 80°C for 10.0 hours, and calcined at 540°C for 4.0 hours to obtain adsorbent small balls;

[0127] (2) The calcined small balls obtained in step (1) are subjected to in-situ crystallization treatment using a mixed solution of sodium hydroxide and water glass. The concentration of sodium hydroxide in the mixed solution is 1.5 mol / L, the concentration of silica is 12 g / L, and the liquid-to-solid volume ratio is 3.0:1. After treatment at 95°C for 4.0 hours, the product is washed with deionized water until the pH is less than 8.0, and is dried at 100°C for 8.0 hours;

[0128] (3) The crystallized small balls obtained in step (2) are treated with a 0.05 mol / L barium chloride solution. The liquid-to-solid volume ratio is 5.0:1, and the treatment is performed at 95°C for 4.0 hours. After washing with deionized water, the product is dried at 120°C for 10.0 hours. The Ba content in the partially barium-exchanged intermediate product is 18.5 mass% in terms of BaO, relative to the weight of the partially barium-exchanged intermediate product;

[0129] (4) The dried spheres obtained in step (3) were treated with 0.8 mol / L ammonium chloride solution with a liquid-to-solid volume ratio of 5.0:1. The spheres were treated at 50°C for 2.0 hours, washed with deionized water, and dried at 120°C for 10.0 hours. The resulting product was then calcined in a flowing nitrogen atmosphere with a flow rate of 0.01 L / h / g adsorbent at 200°C for 2.0 hours.

[0130] (5) 130 mL of the pellets obtained after calcination in step (4) were loaded into an ion exchange column for cation exchange, using a mixed solution of 0.18 mol / L barium nitrate and 0.07 mol / L potassium nitrate at a concentration of 8.0 h. -1 The volume hourly space velocity (VHSV) was continuously exchanged at 0.1 MPa and 95 °C for 6.0 hours, with a total volume of 5000 mL of mixed solution. After ion exchange, the solid was washed with 700 mL of deionized water at 70 °C, purged under nitrogen atmosphere at 70 °C for 24.0 hours, and dried at 100 °C for 8.0 hours to obtain adsorbent A.

[0131] The obtained adsorbent A had a Ba content of 41.70% (BaO) and a K content of 0.59% (K₂O). Nitrogen physisorption analysis revealed that the micropore volume of adsorbent A was 0.252 mL / g, the mesopore volume was 0.052 mL / g, and the most probable pore sizes corresponding to the two mesopore distribution peaks on the pore size distribution curve were 5.5 nm and 11.4 nm, respectively. In the framework structure, the sum of Si(OAl)₄ and Si(OSi)₁(OAl)₃ tetrahedra accounted for 74 mol% of the total silicon species, while non-framework aluminum accounted for 1.5 mol% of the total aluminum species.

[0132] The pore size distribution curve of adsorbent A is shown in Figure 1. Solid-state NMR 29 The Si spectrum is shown in Figure 2. Solid-state NMR. 27 The Al spectrum is shown in Figure 3.

[0133] The composition and properties of adsorbent A are shown in Table 1.

[0134] Adsorbent performance testing

[0135] 1.0 g of adsorbent A was used for gas phase adsorption experiment to determine its adsorption capacity and saturation. 50 mL of adsorbent A was used for liquid phase pulse experiment to determine its adsorption selectivity and adsorption and desorption rates. The results are shown in Table 3.

[0136] Example 2

[0137] Adsorbent B was prepared according to the method of Example 1, but the difference was that the concentration of ammonium chloride solution in step (4) was 0.2 mol / L.

[0138] The Ba mass content of the obtained adsorbent B is 41.20% as BaO, the K mass content is 0.58% as K2O, the micropore volume is 0.274 mL / g, the mesopore volume is 0.021 mL / g, and the two mesopore distribution peaks on the pore size distribution curve correspond to the most probable pore diameters of 5.3 nm and 11.3 nm, respectively. The sum of Si(OAl)4 and Si(OSi)1(OAl)3 structure tetrahedra in the framework structure accounts for 79 mol% of the total silicon species, and the non-framework aluminum accounts for 0.8 mol% of the total aluminum species.

[0139] The pore size distribution curve of the adsorbent B is shown in FIG. 4, and the composition and properties of the adsorbent B are shown in Table 1.

[0140] The adsorbent performance test is carried out according to the method of Example 1, and the test results are shown in Table 3.

[0141] Example 3

[0142] The adsorbent C is prepared according to the method of Example 1, but the difference is that the concentration of the barium chloride solution in step (3) is 0.2 mol / L, and the Ba content in the partial barium exchanged intermediate product obtained in step (3) is 24.5 mass% as BaO.

[0143] The Ba mass content of the obtained adsorbent C is 40.90% as BaO, the K mass content is 0.61% as K2O, the micropore volume is 0.261 mL / g, the mesopore volume is 0.033 mL / g, and the two mesopore distribution peaks on the pore size distribution curve correspond to the most probable pore diameters of 4.8 nm and 12.7 nm, respectively. The sum of Si(OAl)4 and Si(OSi)1(OAl)3 structure tetrahedra in the framework structure accounts for 77 mol% of the total silicon species, and the non-framework aluminum accounts for 1.0 mol% of the total aluminum species.

[0144] The composition and properties of the adsorbent C are shown in Table 1.

[0145] The adsorbent performance test is carried out according to the method of Example 1, and the test results are shown in Table 3.

[0146] Example 4

[0147] The adsorbent D is prepared according to the method of Example 1, but the difference is that the calcination temperature in step (4) is 300°C, and the calcination time is 1.0 hour.

[0148] The Ba mass content of the obtained adsorbent D is 39.10% as BaO, the K mass content is 0.57% as K2O, the micropore volume is 0.231 mL / g, the mesopore volume is 0.079 mL / g, and the two mesopore distribution peaks on the pore size distribution curve correspond to the most probable pore diameters of 6.1 nm and 13.7 nm, respectively. The sum of Si(OAl)4 and Si(OSi)1(OAl)3 structure tetrahedra in the framework structure accounts for 68 mol% of the total silicon species, and the non-framework aluminum accounts for 2.2 mol% of the total aluminum species.

[0149] The composition and properties of the adsorbent D are shown in Table 1.

[0150] The adsorbent performance test was performed according to the method of Example 1, and the test results are shown in Table 3.

[0151] Example 5

[0152] The adsorbent E was prepared according to the method of Example 1, but the difference is that the barium ion exchange temperature in step (3) is 80°C, and the Ba content in the obtained intermediate product after partial barium exchange in step (3) is 16.8% as BaO.

[0153] The Ba mass content of the obtained adsorbent E is 41.3% as BaO, the K mass content is 0.57% as K2O, the micropore volume is 0.251 mL / g, the mesopore volume is 0.028 mL / g, and the mesopore most probable pore diameters are 5.9 nm and 12.6 nm. The sum of Si(OAl)4 and Si(OSi)1(OAl)3 structure tetrahedra in the framework structure accounts for 76 mol% of the total silicon species, and the non-framework aluminum accounts for 1.2 mol% of the total aluminum species.

[0154] The composition and properties of the adsorbent E are shown in Table 1.

[0155] The adsorbent performance test was performed according to the method of Example 1, and the test results are shown in Table 3.

[0156] Example 6

[0157] The adsorbent F was prepared according to the method of Example 1, but the difference is that the ammonium ion exchange temperature in step (4) is 75°C, and the exchange time is 4.0 hours.

[0158] The obtained adsorbent F has a Ba content of 39.8% (BaO by mass) and a K content of 0.60% (K₂O by mass). Its micropore volume is 0.231 mL / g, mesopore volume is 0.071 mL / g, and the most probable mesopore diameters are 4.9 nm and 13.1 nm. In its framework structure, the sum of Si(OAl)₄ and Si(OSi)₁(OAl)₃ tetrahedra accounts for 69 mol% of the total silicon species, while non-framework aluminum accounts for 2.5 mol% of the total aluminum species.

[0159] The composition and properties of adsorbent F are shown in Table 1.

[0160] The adsorbent performance was tested according to the method in Example 1, and the test results are shown in Table 3.

[0161] Comparative Example 1

[0162] Take 10.9 kg of sodium aluminate solution (containing 17.3% by mass of Al2O3 and 21.0% by mass of Na2O), 48.3 kg of deionized water and 13.1 kg of sodium hydroxide, stir to completely dissolve the solid alkali, then add 66.8 kg of water glass (containing 28.3% by mass of SiO2 and 8.8% by mass of Na2O), stir until uniform, and let stand at 25°C for 20.0 hours to obtain the directing agent. The molar ratio of each material is: SiO2 / Al2O3 = 17, Na2O / SiO2 = 0.95, H2O / SiO2 = 17.6.

[0163] Take 174 kg of water glass, 768 kg of deionized water, and 13 kg of sodium hydroxide. Stir thoroughly at 25°C. While stirring, add 178 kg of sodium aluminate and mix well. Then add 0.8 kg of a guiding agent and stir evenly. Finally, add 9.5 kg of 60% by mass dimethylhexadecyl[3-(trimethoxysilyl)propyl]ammonium chloride [(CH3O)3Si(CH2)3N(CH3)2(CH2)]. 15 The CH3Cl aqueous solution was used as the template agent (R) solution. The mixture was stirred until homogeneous to obtain the synthesis system. The molar ratios of the materials were: SiO2 / Al2O3 = 2.8, Na2O / SiO2 = 1.23, H2O / SiO2 = 65, and the mass ratio of R / SiO2 was 0.06. The amount of the directing agent added was 0.2% of the mass of SiO2 in the synthesis system, calculated based on the SiO2 content.

[0164] The above-described synthesis system was heated to 100°C and hydrothermally crystallized for 8.0 hours under static conditions. The crystallized product was washed with deionized water until the pH of the washing solution was less than 10. The resulting solid was dried at 80°C for 12.0 hours, calcined in air at 200°C for 1.0 hour, then calcined at 380°C for 1.0 hour, and then calcined at 540°C for 4.0 hours to obtain mesoporous NaX molecular sieve.

[0165] 92 kg (assay, same below) of the above mesoporous NaX molecular sieve (molar ratio of SiO2 / Al2O3 was 2.35, particle size was 1.0 μm, mass fraction of Na in terms of Na2O was 16.7%, mesopore volume was 0.027 mL / g) was mixed with 8 kg of a binder (containing 90 mass% of kaolinite and 10 mass% of halloysite) uniformly, and was put into a rotating disc, and while rotating, a proper amount of deionized water was sprayed to make the solid powder gather into small pellets. The amount of water sprayed while rotating was 8 mass% of the solid powder. After sieving, the pellets with a particle size of 300-1000 μm were dried at 80°C for 10.0 hours and calcined at 540°C for 4.0 hours to obtain adsorbent pellets.

[0166] The adsorbent pellets after calcination were subjected to in-situ crystallization treatment using a mixed solution of sodium hydroxide and water glass, the concentration of sodium hydroxide in the mixed solution was 1.5 mol / L, the concentration of water glass was 12 g / L, and the liquid-to-solid volume ratio was 3.0:1. After treatment at 95°C for 4.0 hours, the pellets were washed with deionized water until the pH value was less than 8.0, and were dried at 100°C for 8.0 hours.

[0167] The 130 mL of the pellets after in-situ crystallization were loaded into an ion exchange column for cation exchange, and a mixed solution of 0.18 mol / L barium nitrate and 0.07 mol / L potassium nitrate was used to continuously exchange the pellets at a space velocity of 8.0 h"1 at 0.1 MPa and 94°C for 6.0 hours, and the total amount of the mixed solution used was 5000 mL. After the ion exchange was completed, the solid was washed with 700 mL of deionized water at 70°C, was purged with nitrogen at 70°C for 24.0 hours, and was dried at 100°C for 8.0 hours to obtain adsorbent G. -1

[0168] The mass content of Ba in the obtained adsorbent G was 39.10% in terms of BaO, the mass content of K was 0.60% in terms of K2O, the micropore volume was 0.238 mL / g, the mesopore volume was 0.009 mL / g, and the pore size distribution curve is shown in Fig. 5, and no obvious mesopore distribution peak was observed. The sum of the relative contents of Si(OAl)4 and Si(OSi)1(OAl)3 structure tetrahedra in the framework structure of the adsorbent G was 82 mol% of the total silicon species, and the relative content of non-framework aluminum was 0.9 mol% of the total aluminum species.

[0169] The composition and properties of the adsorbent G are shown in Table 2.

[0170] The performance of the adsorbent G was tested according to the method of Example 1, and the test results are shown in Table 3.

[0171] Comparative Example 2

[0172] ​Adsorbent H was prepared according to the method of Example 1, except that in step (4) the ammonium chloride solution treatment was not performed, but calcination was performed directly.

[0173] The Ba mass content of the obtained adsorbent H was 40.80% as BaO, the K mass content was 0.59% as K2O, the micropore volume was 0.249 mL / g, the mesopore volume was 0.007 mL / g, and no obvious mesopore distribution peak was observed in the pore size distribution curve, indicating that there was no mesopore channel with regular pore size in the adsorbent H within the measured amount, and the small amount of mesopore volume might be caused by irregular pores formed by crystal packing. The sum of Si(OAl)4and Si(OSi)1(OAl)3structure tetrahedra in the framework structure accounted for 79 mol% of the total silicon species, and the non-framework aluminum accounted for 0.7 mol% of the total aluminum species.

[0174] The composition and properties of adsorbent H are shown in Table 2.

[0175] The performance test of adsorbent H was performed according to the method of Example 1, and the test results are shown in Table 3.

[0176] Comparative Example 3

[0177] Adsorbent I was prepared according to the method of Example 3, except that in step (4) the calcination treatment was not performed.

[0178] The Ba mass content of the obtained adsorbent I was 40.50% as BaO, the K mass content was 0.59% as K2O, the micropore volume was 0.246 mL / g, the mesopore volume was 0.011 mL / g, and no obvious mesopore distribution peak was observed in the pore size distribution curve, indicating that there was no mesopore channel with regular pore size in the adsorbent H within the measured amount, and the small amount of mesopore volume might be caused by irregular pores formed by crystal packing. The sum of Si(OAl)4and Si(OSi)1(OAl)3structure tetrahedra in the framework structure accounted for 80 mol% of the total silicon species, and the non-framework aluminum accounted for 1.1 mol% of the total aluminum species.

[0179] The composition and properties of adsorbent I are shown in Table 2.

[0180] The performance test of adsorbent I was performed according to the method of Example 1, and the test results are shown in Table 3.

[0181] Comparative Example 4

[0182] Adsorbent J was prepared according to the method of Example 3, except that step (3) was not performed.

[0183] The Ba mass content of the obtained adsorbent J was 41.20% as BaO, the K mass content was 0.57% as K2O, the micropore volume was 0.251 mL / g, the mesopore volume was 0.039 mL / g, and the most probable mesopore diameter was 4.8 nm. The sum of Si(OAl)4and Si(OSi)1(OAl)3structure tetrahedra in the framework structure accounted for 69 mol% of the total silicon species, and the non-framework aluminum accounted for 2.2 mol% of the total aluminum species.

[0184] The pore size distribution curve of the adsorbent J is shown in FIG. 6, and the composition and properties of the adsorbent J are shown in Table 2.

[0185] The performance test of the adsorbent J was carried out according to the method of Example 1, and the test results are shown in Table 3.

[0186] Comparative Example 5

[0187] The adsorbent K was prepared according to the method of Example 3, except that 66 kg (mass on ignition, the same below) of X molecular sieve (SiO2 / Al2O3molar ratio of 2.35, particle size of 1.0 μm, and Na mass fraction of 16.7% as Na2O) and 34 kg of binder (containing 90% by mass of kaolinite and 10% by mass of halloysite) were used as raw materials in step (1), and the calcination temperature in step (4) was 600°C.

[0188] The Ba mass content of the obtained adsorbent K was 33.50% as BaO, the K mass content was 0.43% as K2O, the micropore volume was 0.142 mL / g, the mesopore volume was 0.089 mL / g, and the most probable mesopore diameters were 6.1 nm and 16.2 nm. The sum of Si(OAl)4and Si(OSi)1(OAl)3structure tetrahedra in the framework structure accounted for 56 mol% of the total silicon species, and the non-framework aluminum accounted for 7.8 mol% of the total aluminum species.

[0189] Solid-state NMR of adsorbent K 29 The Si spectrum is shown in FIG. 7, and the solid-state NMR 27 Al spectrum is shown in FIG. 8. The composition and properties of the adsorbent K are shown in Table 2.

[0190] The performance test of the adsorbent K was carried out according to the method of Example 1, and the test results are shown in Table 3.

[0191] Comparative Example 6

[0192] The adsorbent L was prepared according to the method of Example 3, except that step (3) was not performed, and step (4) was only ammonium ion exchange and drying, without calcination in a flowing air atmosphere.

[0193] The Ba mass content of the obtained adsorbent L is 41.20% as BaO, the K mass content is 0.57% as K2O, the micropore volume is 0.251 mL / g, the mesopore volume is 0.009 mL / g, and no obvious mesopore distribution peak is observed in the pore size distribution curve, indicating that there is no mesopore channel with regular pore size in the adsorbent H in the measured amount. The sum of Si(OAl)4 and Si(OSi)1(OAl)3 structure tetrahedra in the framework structure accounts for 80 mol% of the total silicon species, and the non-framework aluminum accounts for 1.1 mol% of the total aluminum species.

[0194] The composition and properties of the adsorbent L are shown in Table 2.

[0195] The performance test of the adsorbent L is carried out according to the method of Example 1, and the test results are shown in Table 3.

[0196] Comparative Example 7

[0197] The adsorbent M is prepared according to the method of Example 1, but the difference is that in step (3), the obtained small balls after crystallization in step (2) are treated with a barium chloride solution of 0.23 mol / L, the liquid-solid volume ratio is 5.0:1, the treatment is carried out at 95°C for 4.0 hours, and after washing with deionized water, drying is carried out at 120°C for 10.0 hours, and step (5) is not carried out.

[0198] The Ba mass content of the obtained adsorbent M is 37.70% as BaO, and it does not contain K. By nitrogen physical adsorption determination, the micropore volume of the adsorbent A is 0.254 mL / g, the mesopore volume is 0.003 mL / g, and no obvious mesopore distribution peak is observed in the pore size distribution curve, indicating that there is no mesopore channel with regular pore size in the adsorbent H in the measured amount. The sum of Si(OAl)4 and Si(OSi)1(OAl)3 structure tetrahedra in the framework structure accounts for 77 mol% of the total silicon species, and the non-framework aluminum accounts for 1.2 mol% of the total aluminum species.

[0199] The composition and properties of the adsorbent M are shown in Table 2.

[0200] The performance test of the adsorbent M is carried out according to the method of Example 1, and the test results are shown in Table 3.

[0201] Comparative Example 8

[0202] The adsorbent N is prepared according to the method of Example 3, but the difference is that the calcination treatment in step (4) is not carried out under a flowing inert atmosphere.

[0203] The Ba mass content of the obtained adsorbent N is 40.20% as BaO, the K mass content is 0.59% as K2O, the micropore volume is 0.241 mL / g, the mesopore volume is 0.015 mL / g, the mesopore most probable pore diameter is 5.6 nm and 12.5 nm. The sum of Si(OAl)4 and Si(OSi)1(OAl)3 structure tetrahedra in the framework structure accounts for 76 mol% of the relative content of total silicon species, and non-framework aluminum accounts for 2.7 mol% of the relative content of total aluminum species.

[0204] The composition and properties of the adsorbent N are shown in Table 2.

[0205] The performance test of the adsorbent N was carried out according to the method of Example 1, and the test results are shown in Table 3.

[0206] Comparative Example 9

[0207] The X molecular sieve was synthesized according to Example 1 of the patent application CN114425297A:

[0208] (1) Preparation of an aluminum source: 200 kg of aluminum hydroxide, 180.68 kg of sodium hydroxide and 157.11 kg of deionized water were added to a reaction kettle, heated to 100°C, and stirred for 6 hours to form a clear and transparent low-alkalinity sodium metaaluminate solution as an aluminum source. The Al2O3 content in the aluminum source is 23.93 mass%, the Na2O content is 26.09 mass%, and the molar ratio of Na2O to Al2O3 is 1.79.

[0209] (2) Preparation of a directing agent: 4.02 kg of sodium hydroxide, 10.90 kg of deionized water, 2.22 kg of the aluminum source prepared in step (1), and 23.24 kg of water glass (the SiO2 content in the water glass is 20.17 mass%, the Na2O content is 6.32 mass%, and the same below) were added to a reaction kettle under stirring, wherein the molar ratio of each material is SiO2 / Al2O3 = 15, Na2O / SiO2 = 1.07, H2O / SiO2 = 21, and then the directing agent was obtained by aging at 35°C for 16 hours.

[0210] (3) Cooling of raw materials: 100 kg of water glass and 50 kg of the aluminum source prepared in step (1) were cooled to 0°C, respectively.

[0211] (4) Preparation of X molecular sieve: under stirring, 8.17 kg of deionized water, 3.67 kg of potassium hydroxide, 46.94 kg of aluminum source cooled to 0°C in step (3), and 91.32 kg of water glass cooled to 0°C in step (3), 0.85 kg of directing agent prepared in step (2) were added into a reaction kettle to obtain a X molecular sieve synthesis system, wherein the molar ratio of each material was SiO2 / Al2O3=2.80, (Na2O+K2O) / SiO2=1.05, H2O / SiO2=18, K + / (K + +Na + )=0.1, the molar ratio of Al2O3 contained in the directing agent to Al2O3 contained in the X molecular sieve synthesis system was 0.10%, and the temperature of the synthesis system was 3°C.

[0212] The above-mentioned molecular sieve synthesis system was transferred into a closed reaction kettle, heated to 100°C for static crystallization for 2 hours, stirred for 5 minutes, continued static crystallization for 10 hours, then filtered, the obtained solid was washed with deionized water until the pH of the filtrate was 8-9, and dried at 80°C for 12 hours to obtain X molecular sieve a. SEM analysis showed that the crystal grain size was 50-400 nm, the molar ratio of SiO2 / Al2O3 was 2.42 (X-ray fluorescence spectroscopy was used, the same below), the total pore volume was 0.43 cm 3 / g, the micropore volume was 0.32 cm 3 / g, and the mesopore volume was 0.11 cm 3 / g.

[0213] Preparation of adsorbent:

[0214] The adsorbent was prepared according to the method in Example 1, but different in that: the powdered X molecular sieve a prepared in the present comparative example was used instead of the X molecular sieve used in Example 1; and after the ball-rolling and in-situ crystallization, the following ion exchange was directly carried out: 130 ml of dried small balls were loaded into an ion exchange column for cation exchange, a mixed solution of 0.18 mol / L barium nitrate and 0.12 mol / L potassium chloride was used to continuously exchange at a volume space velocity of 6.0 h -1 -1 at 0.1 MPa and 94°C for 8 hours, the total amount of barium nitrate solution was 5000 ml, and the exchange ratio was 1.6. After the ion exchange was completed, the solid was washed with 700 ml of deionized water at 70°C, dried in a nitrogen atmosphere at 70°C for 30 hours, and dehydrated and activated in a nitrogen atmosphere at 180°C for 6 hours to obtain adsorbent O. The pore size distribution curve showed that the most probable pore diameters were 16 nm and 45 nm, respectively; the composition, toluene adsorption capacity, physical property parameters, and adsorption performance of adsorbent O determined by liquid phase pulse experiment are shown in Tables 2 and 3.

[0215] Table 1. Composition and properties of adsorbents prepared in each example

[0216] Table 2. Composition and properties of adsorbents prepared in each comparative example

[0217] Table 3. Test results of adsorbents prepared in each example and comparative example

[0218] As shown in the data in Tables 1 and 2, the adsorbents according to the present application have both increased active component X molecular sieve content and improved compressive strength, ignition base bulk density and adsorption capacity compared with the comparative adsorbents. As shown in the data in Table 3, the adsorbents according to the present application exhibit both more optimal xylene adsorption selectivity and more optimal mass transfer performance than the comparative adsorbents.

[0219] Example 7

[0220] Separation experiments of p-xylene were carried out with adsorbent A on a continuous countercurrent small-scale simulated moving bed.

[0221] The small-scale simulated moving bed device comprises 24 adsorption columns connected in series, each column being 195 mm long and having an inner diameter of 30 mm, and the total loading amount of adsorbent being 3300 mL. The 24 columns connected in series are connected at both ends by a circulating pump to form a closed loop, as shown in Figure 9. Four streams of material in or out, including adsorption feedstock, desorbent, extract, and raffinate, divide the 24 adsorption columns into four sections, i.e. 7 adsorption columns between the adsorption feedstock (column 15) and the raffinate (column 21) are the adsorption zone, 9 adsorption columns between the extract (column 6) and the adsorption feedstock (column 14) are the purification zone, 5 adsorption columns between the desorbent (column 1) and the extract (column 5) are the desorption zone, and 3 adsorption columns between the raffinate (column 22) and the desorbent (column 24) are the buffer zone. The temperature control of the entire adsorption system is 177°C, and the pressure is 0.8 MPa.

[0222] During operation, the desorbent p-diethylbenzene and the feedstock were continuously injected into the above simulated moving bed at flow rates of 1420 mL / h and 1310 mL / h, respectively, and the extract and the raffinate were extracted from the device at flow rates of 734 mL / h and 1996 mL / h, respectively. The composition of the feedstock was: ethylbenzene 9.3 mass%, p-xylene 18.5 mass%, m-xylene 45.5 mass%, o-xylene 17.4 mass%, non-aromatic component 9.4 mass%.

[0223] The circulating pump flow rate was set to 3720 mL / h, and every 80 seconds, four streams of material moved simultaneously in the same direction as the liquid flow to one adsorption column (in Figure 9, from the solid line to the dashed line position, and so on). The purity of the para-xylene obtained by the adsorbent A was 99.83% by mass, and the yield was 98.46% by mass under the stable operating state.

[0224] Example 8

[0225] The adsorbent B was packed in a small simulated moving bed device, and the adsorption separation of para-xylene was carried out according to the method of Example 7. The purity of the para-xylene obtained under the stable operating state was 99.88% by mass, and the yield was 98.26% by mass.

[0226] Comparative Example 10

[0227] The comparative adsorbent G was packed in a small simulated moving bed device, and the adsorption separation of para-xylene was carried out according to the method of Example 7. The purity of the para-xylene obtained under the stable operating state was 98.63% by mass, and the yield was 95.35% by mass.

[0228] By comparing the results of Examples 7-8 and Comparative Example 10, it can be seen that the adsorbent of the present application can obtain a higher purity of para-xylene product in the simulated moving bed device, and a higher yield of para-xylene product per unit time.

[0229] The above describes the preferred embodiments of the present application in detail, but the present application is not limited to the specific details in the above-described embodiments. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, and these simple modifications all belong to the protection scope of the present application.

[0230] In addition, it should be noted that each specific technical feature described in the above-described specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0231] In addition, various different embodiments of the present application can also be combined in any appropriate manner, as long as they do not deviate from the technical concept of the present application, and they should also be considered as disclosed by the present application.

Claims

1. An adsorbent based on X molecular sieve, comprising 92-99.8 mass%, preferably at least 95-99.5 mass%, preferably 98.0-99.0 mass% of X molecular sieve, the micropore volume of the adsorbent being 0.18-0.30 mL / g, preferably 0.24-0.30 mL / g, the mesopore volume being 0.01-0.1 mL / g, preferably 0.04-0.1 mL / g, and the pore size distribution curve thereof showing at least two mesopore distribution peaks, one of which has a most probable pore size in the range of 3.0-9.0 nm and the other has a most probable pore size in the range of 10.0-19.0 nm.

2. The adsorbent of claim 1, wherein At least a portion of the cation sites of the X molecular sieve are occupied by barium ions and optionally potassium ions, the Ba content in the adsorbent, calculated as BaO, being 38.0-42.5 mass% and the K content, calculated as K2O, being 0-3.0 mass% based on the total mass of the adsorbent; preferably, the Ba content in the adsorbent, calculated as BaO, is 41.0-42.4 mass% and the K content, calculated as K2O, is 0.1-1.0 mass%.

3. The adsorbent according to claim 1 or 2, characterized in that By using 29 Si and 27 Al high-resolution magic-angle nuclear magnetic resonance determination, the sum of Si(OAl)4 and Si(OSi)1(OAl)3 structure tetrahedra in the framework structure of the adsorbent is not less than 65 mol%, preferably not less than 70 mol%, relative content of total silicon species, and the relative content of non-framework aluminum in total aluminum species is not higher than 3 mol%, preferably not higher than 1 mol%.

4. The adsorbent according to any one of claims 1 to 3, characterized in that The adsorbent has an external specific surface area of 15-50 m 2 / g, a micropore specific surface area of 540-600 m 2 / g, an average particle size D50 of 425-600 μm, a 250N compression breakage of less than 5.5%, and / or a tared bulk density of 0.91-1.20 g / cm 3 .

5. A method of preparing an adsorbent based on X molecular sieves, comprising the steps of : (1) mixing, shaping and calcining X molecular sieve with a binder to obtain a shaped body; (2) optionally, treating the shaped body obtained in step (1) with an alkali solution to effect in situ crystallization of the binder contained therein to obtain a crystallized product; (3) subjecting the shaped body obtained in step (1) or the product obtained in step (2) to partial barium ion exchange with a barium salt solution and drying to obtain a dried product; (4) subjecting the dried product obtained in step (3) to ammonium ion exchange with an ammonium salt solution and calcining under a flowing gas atmosphere to obtain a calcined product; and (5) subjecting the calcined product obtained in step (4) to barium ion exchange and optional potassium ion exchange and then drying to obtain the adsorbent.

6. The method of claim 5, wherein In step (1): the SiO2 / Al2O3 molar ratio of the X molecular sieve is 2.0-2.6, preferably 2.2-2.4, the particle size is 0.8-2.5 μm, preferably 0.8-1.5 μm, and preferably the Na mass fraction of the X molecular sieve, calculated as Na2O, is 15.0-17.0%; and / or the binder is selected from the group consisting of kaolinite, dickite, perlite, refractory stone, halloysite, hydromica, montmorillonite, or a combination thereof, preferably the binder consists of 75-95 mass% of kaolinite and 5-15 mass% of halloysite; and / or the X molecular sieve is mixed with the binder at a mass ratio of 80:20 to 99:1, preferably 95:5 to 99:1; and / or the shaping is performed by rolling; and / or the calcination is performed at a temperature of 500-700°C for 2.0-6.0 hours.

7. The method according to claim 5 or 6, characterized in that In step (2): The alkali solution used is a mixed solution of sodium hydroxide and water glass, wherein the concentration of sodium hydroxide is 1.2-4.0 mol / L, the concentration of silicon dioxide is 6-20 g / L, preferably, the concentration of sodium hydroxide is 1.2-2.0 mol / L, the concentration of silicon dioxide is 10-15 g / L; and / or The liquid-solid volume ratio of the alkali solution to the shaped body in the alkali solution treatment is 1.2-3.0:1, preferably 1.2-2.0:1; and / or The conditions of the alkali solution treatment include: the treatment temperature is 90-100℃, the treatment time is 1.5-6.0 hours.

8. The method according to any one of claims 5-7, characterized by In step (3): The barium salt is selected from barium chloride, barium nitrate, or a combination thereof; and / or The concentration of the barium salt solution is 0.05-1.0 mol / L, preferably 0.05-0.2 mol / L; and / or The liquid-solid volume ratio of the barium salt solution to the dried product in the partial barium ion exchange process is 1-10:1, preferably 2-5:1; and / or The conditions of the partial barium ion exchange include: the temperature is 25-95℃, preferably 80-95℃, the time is 0.5-5.0 hours, preferably 2.0-5.0 hours; and / or The obtained partial barium ion exchange product has at least part of the cation sites occupied by barium ions, and the Ba content, calculated as BaO, in the partial barium ion exchange product is 1.0-30.0 mass% based on the mass of the product.

9. The method according to any one of claims 5-8, characterized by In the ammonium ion exchange process of step (4): The ammonium salt is selected from ammonium chloride, ammonium sulfate, ammonium nitrate, or a combination thereof; and / or The concentration of the ammonium salt solution is 0.2-5.0 mol / L, preferably 0.2-2.0 mol / L; and / or The liquid-solid volume ratio of the ammonium salt solution to the crystallized product in the ammonium ion exchange process is 2-10:1, preferably 2-5:1; and / or The conditions of the ammonium ion exchange include: the temperature is 25-95℃, preferably 50-75℃, the time is 0.5-5.0 hours, preferably 0.5-2.0 hours.

10. The method according to any one of claims 5-9, characterized by In the calcination process of step (4): The temperature of the calcination is 130-500℃, preferably 150-300℃; and / or The time of the calcination is 0.5-8.0 hours, preferably 1.0-6.0 hours; and / or The flow atmosphere is a flow air atmosphere or a flow inert gas atmosphere, preferably a flow air atmosphere; and / or The gas flow rate of the flow atmosphere is 0.1-1.5 L / h / g adsorbent, preferably 0.1-0.5 L / h / g adsorbent.

11. The method according to any one of claims 5-10, characterized by In step (5): The barium ion exchange is carried out using a solution of a soluble barium salt, preferably the soluble barium salt is selected from barium chloride, barium nitrate, or a combination thereof; the potassium ion exchange is carried out using a solution of a potassium salt, preferably the potassium salt is selected from potassium chloride, potassium nitrate, or a combination thereof; or, the barium ion exchange and the potassium ion exchange are carried out using a mixed solution comprising a soluble barium salt and a potassium salt; preferably, the conditions for the barium ion exchange and the optional potassium ion exchange comprise a temperature of 30-95 °C, preferably 80-95 °C, a time of 2.0-48.0 hours, preferably 12.0-36.0 hours, and a volume hourly space velocity of 1.0-20.0 h -1 , preferably 1.0-10.0 h -1 .

12. Use of the adsorbent according to any one of claims 1-4 or prepared by the method according to any one of claims 5-11 for adsorptive separation of para-xylene.

13. A process for separating para-xylene from a C8 aromatics mixture comprising para-xylene by liquid phase adsorption separation, comprising the steps of contacting the C8 aromatics mixture with the adsorbent according to any one of claims 1-4 or the adsorbent prepared by the process of any one of claims 8-13 to adsorb para-xylene, and contacting the adsorbent after adsorbing para-xylene with a desorbent to desorb para-xylene.

14. The method of claim 13, wherein The desorbent is selected from para-diethylbenzene, toluene, or a combination thereof.

15. The method according to claim 13 or 14, characterized in that The adsorption separation is operated at a pressure of 0.3-1.5 MPa and a temperature of 120-190 °C.

16. An apparatus for separating para-xylene adsorption from a C8 aromatics mixture comprising para-xylene by liquid phase adsorption, comprising the adsorbent according to any one of claims 1-4 or the adsorbent prepared by the process according to any one of claims 5-11.

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