CN115970639A

CN115970639A - Molecular sieve, adsorbent, preparation method and application thereof

Info

Publication number: CN115970639A
Application number: CN202211346231.9A
Authority: CN
Inventors: 周君梦; 徐双; 胡晓倩; 刘禹; 湛洪丽; 王凤
Original assignee: Chia Tai Energy Materials Dalian Co ltd
Current assignee: Chia Tai Energy Materials Dalian Co ltd
Priority date: 2022-10-31
Filing date: 2022-10-31
Publication date: 2023-04-18

Abstract

The invention discloses a high-strength molecular sieve, an adsorbent, a preparation method and an application, wherein the adsorbent is provided with metal ions and a molecular sieve, and has a damage rate of less than 0.1% under 250N and 5 min.

Description

Molecular sieve, adsorbent, preparation method and application thereof

Technical Field

The invention belongs to the technical field of adsorbents, and particularly relates to a molecular sieve, an adsorbent, and preparation methods and applications thereof.

Background

The molecular sieve adsorption separation process is widely applied to industrial processes such as separation and purification of organic substances such as Paraxylene (PX), and the principle is that the separation is carried out by utilizing the difference of adsorption capacity of each component in a mixture on the solid surface of an adsorbent, and the performance of the adsorbent has an important influence on the adsorption separation effect. The adsorbent comprises activated carbon, silica gel, activated alumina, polymeric resin, molecular sieve and the like, wherein the molecular sieve adsorbent has the advantages of large specific surface area, high selectivity, high mechanical strength, stable chemical property and the like, and is commonly used in A type, X type, Y type, ZSM-5, mordenite and the like.

As described above, molecular sieves are a typical class of materials having adsorption capacity, which are widely used as catalysts or adsorbents in the fields of petroleum processing and fine chemicals. An ideal adsorbent should have a large adsorption capacity, high adsorption selectivity and a fast mass transfer rate, otherwise it is difficult to apply. Taking separation of Paraxylene (PX) as an example for illustration, the main application of PX (paraxylene) is to synthesize PTA (terephthalic acid) and further produce fine chemical products such as fibers, polyesters, resins, pesticides and fuels, and the performance of high-quality PX adsorbent depends on the separation effect of xylene mixed in the PX adsorbent. At present, the processes for separating mixed xylene mainly comprise: a rectification process, a cryogenic crystallization process, a complex extraction process and a simulated moving bed adsorption separation process. Because the boiling points of the components such as dimethylbenzene and the like are relatively close, a high-purity PX product is difficult to separate by adopting a rectification process, and the process has the advantages of large number of rectification tower plates, high energy consumption and low product profit. The complex extraction process needs to use an extractant with strong corrosivity and toxicity, has high requirements on equipment materials, has high construction cost, has certain potential safety hazards in operation, and is very limited in application at present. The cryogenic crystallization process has the problems of high early investment and high later maintenance cost, and the popularization and the application of the process are also influenced. The simulated moving bed adsorption separation of paraxylene is the process which is widely applied in China, has the best separation effect, low operation investment cost and can be continuously produced at present. The process adopts a mode of reverse contact of the adsorbent and the mixed liquid phase material, and continuously switches the flow of two phases, thereby improving the mass transfer driving force of the two phases and obtaining the high-purity PX product.

Besides adjusting the technological parameters of the simulated moving bed device, the performance of the PX adsorbent is another important factor determining the separation effect of the mixed xylene and the yield of the PX product. Furthermore, the technical characteristics of simulated moving bed adsorption separation show that the strength of the adsorbent plays a crucial role in the whole adsorption separation process, and if the strength of the adsorbent is insufficient, fine powder is generated in the device due to abrasion, so that the pipeline of the device is blocked, the system operation pressure of the adsorption tower device is influenced, frequent shutdown and maintenance are required, and the operation and maintenance cost is increased. Therefore, the preparation of high strength PX adsorbents has also become a focus of research in recent years.

The molecular sieve is generally powdery and cannot be directly applied to an adsorption device, so that the molecular sieve needs to be subjected to forming treatment, and is generally prepared into a granular formed molecular sieve by adding a binder and then applied to the field of adsorbents. In order to improve the mechanical strength of the adsorbent, the amount of the binder is usually increased or a strength aid is added. As in the first patent application, the aim of increasing the strength and bulk density of the adsorbent is achieved by increasing the amount of the binder used in the ball-rolling process. In the second patent application, it is mentioned that in order to enhance the strength of the titanium silicalite beads, a certain amount of boric acid, which is a strength aid, is added during rolling of the beads.

Although the two methods can improve the strength of the adsorbent to a certain extent, the performance of the obtained adsorbent is still not ideal in practice, and for the method represented in the patent application document I, because the proportion of the binder is too large, great pressure is brought to subsequent crystal transformation work, the conditions that crystal transformation is incomplete, crystal transformation time is long, and the binder can be completely transformed by multiple crystal transformation are easily caused, so that the production cost and the sewage discharge amount are directly improved, and the environmental protection pressure is increased greatly.

For the method represented in the patent application document two, applying the method to the preparation process of PX adsorbent will undoubtedly increase the production cost, and simultaneously introduce impurities, and the subsequent cation exchange process will be affected accordingly, resulting in low cation content of the adsorbent, and finally causing the decrease of the separation performance of the adsorbent to mixed xylene.

Patent application document one:

name: a paraxylene adsorbent and a preparation method thereof;

application No.: 03137917.6;

patent application document two:

name: a rolling ball forming method of a high-strength TS-1 titanium silicalite molecular sieve catalyst;

application No.: 201210509211.9.

disclosure of Invention

1. Problems to be solved

When the existing formed molecular sieve is applied to the field of catalysts or adsorbents, the problem of insufficient strength exists,

the invention provides a molecular sieve with high strength;

based on the molecular sieve, the invention also provides a preparation method of the molecular sieve;

in addition, the present invention provides an adsorbent having high strength;

based on the method, the invention also provides a preparation method of the adsorbent with high strength.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

in a first aspect of the present invention, there is provided a molecular sieve having high strength (i.e., low breakage rate), the molecular sieve having:

a burned basis bulk density of not less than 1.5 g/ml;

under the condition of 250N,5min, the breakage rate is less than 0.1 percent.

The high strength molecular sieve according to any one of the embodiments of the first aspect of the present invention, wherein the molecular sieve has a packing density of 1.50 to 1.80g/ml, preferably 1.60 to 1.80g/ml, more preferably 1.65 to 1.80g/ml, and even more preferably 1.70 to 1.80g/ml;

the micropore specific surface area of the molecular sieve is 800-950 square meters per gram, preferably 850-950 square meters per gram, more preferably 870-950 square meters per gram, and even more preferably 885-950 square meters per gram;

the micropore volume of the molecular sieve is 0.380-0.450 cm ³ A/g, preferably 0.385 to 0.450cm ³ Per g, more preferably 0.390 to 0.450cm ³ (ii) more preferably 0.395 to 0.450cm ³ /g；

The damage rate of the molecular sieve is less than 0.1%, preferably less than 0.08%, and more preferably less than 0.05% under 250N,5min.

Based on the above, the molecular sieve provided by the first aspect of the invention has high strength and high packing density, and when the molecular sieve is directly used as an adsorbent or used as an adsorbent after metal ion exchange, the molecular sieve can effectively ensure that the unit volume of the device has large filling amount, and obviously improve the processing capacity of the device. And the strength of the adsorption tower in the use process can be ensured to the greatest extent, the phenomenon that the pressure drop of the adsorption tower is increased due to abrasion, breakage and the like in the application process of the existing molecular sieve or the adsorbent prepared by taking the molecular sieve as the raw material is avoided to the greatest extent, and the adverse factors in the operation process of the device are effectively reduced.

In a second aspect of the present invention, a method for preparing a high-strength molecular sieve is provided, which can prepare the above molecular sieve structure with high strength; the preparation method comprises the following steps:

s1, performing (primary) granulation treatment on a powder raw material to obtain a granular product A;

the powder raw material contains a molecular sieve and a binder; or the powder raw material contains a sub-sieve, a binder and a pore-forming agent;

s2, crushing the blend containing the granular product A and the powder raw material to obtain a crushed product B;

s3, adjusting the humidity of the crushed product B, and then carrying out (secondary) granulation treatment to obtain a granular product C;

s4, sequentially carrying out roasting treatment, in-situ crystallization treatment and roasting treatment on the granular product C;

wherein, the damage rate of the obtained molecular sieve is less than 0.1 percent under the condition of 250N and 5 min.

Based on the above, further explanation is;

i) As used herein, "Raw-molecular sieve" refers to a molecular sieve that has not been treated with a flocculant. Different types of Raw-molecular sieves can be selected for different purposes of application, such as depending on the target substance adsorbed:

for example, if the target substance is p-xylene, the type X molecular sieve is preferable, and further, the type 13X molecular sieve is preferable.

As described herein, the "binder" functions primarily to bind the molecular sieve and is capable of being converted to an X molecular sieve by crystal transformation; illustratively, the type of the binder can be one or more of kaolin, halloysite, attapulgite, dextrin and silica-alumina sol;

as described herein, the "pore-forming agent" functions primarily to introduce a mesoporous structure to the molecular sieve; illustratively, the type of the pore-forming agent can be one or more of superfine carbon fiber, sesbania powder, polyethylene glycol and sodium carboxymethylcellulose;

II) as described herein, "granular" is not limited to "granules" or "blocks" of "round, near round" or the like, but may also be strips, sheets, or the like formed by extrusion or kneading with a certain "force"; preferably "particles" or "blocks" of "round, near round" or the like.

As described herein, the "granulation treatment" may be a conventionally known molding method, such as a known oil column molding method, a known bar extrusion molding method, a known spray molding method, or a known roll molding method.

III) As used herein, "crushing treatment" means a treatment in which the aforementioned "granular product A" having a certain particle diameter or a large size is treated to obtain a fine powder; on the basis of this, the method is suitable for the production,

in some embodiments, the "crushing treatment" may be that the "granular product a" is put into a high-speed crusher, crushed at a certain rotation speed until it is crushed into fine powder with micron-level particle size, and the operation is repeated for 1 to 3 times according to the actual material condition and the target particle strength; based on the method, through the treatment of a certain rotating speed, the hydrogen bond action among the Raw-molecular sieve, the binder and water molecules is enhanced by centrifugal force, and the interaction force of the molecules is correspondingly enhanced, so that the strength of the molecular sieve or the strength of the adsorbent prepared by taking the molecular sieve as a Raw material is greatly improved, the phenomenon of pipeline blockage caused by fine powder generated by abrasion in the actual production process of the device can be solved, and the overhaul frequency of the device is reduced. Meanwhile, in the rotating speed interval adopted by the invention, the Raw-molecular sieve, the binder and the pore-expanding agent can be further mixed and dispersed uniformly, and the crystal structure of the Raw-molecular sieve can be ensured not to be damaged;

in some embodiments, the rotation speed of the high-speed pulverizer is required to be 3000-4000 r/min; in practice, the magnitude of the rotation speed influences the strength of the subsequent products. The reason is that the magnitude of the rotation speed determines whether the crushed product B having the target particle diameter or size can be obtained; if the rotating speed is too low, for example, less than 3000r/min, the crushing effect of the granular product a is poor, and the crushed product does not reach the target particle size range, so that the phenomenon that the crushed product is not easy to form balls in the secondary ball rolling process or the strength of the crushed product with larger particle size is greatly reduced after the crushed product is formed balls for the second time occurs; if the rotating speed is too high, for example, higher than 4000r/min, the water adsorbed by the molecular sieve is greatly separated out, and surrounding particles are rapidly bonded to form larger particles.

Iv) as described herein, in s4,

the purpose of the roasting treatment is to treat the binder in the molecular sieve into a state capable of carrying out in-situ crystal transformation, and simultaneously remove the pore-forming agent through roasting to form a mesoporous structure; based on this, in some embodiments, the temperature of the roasting treatment is 450 to 800 ℃; the temperature is further preferably 550-750 ℃; the treatment time is 1 to 6 hours;

the in-situ crystallization treatment aims at converting all the binders in the molecular sieve into the molecular sieve capable of being used for separating mixed xylene; based on this, in some embodiments, the in situ crystallization process is generally performed in an alkaline solution. As a preferred scheme, the in-situ crystallization temperature is 90-120 ℃, and the crystallization time is 4-12 hours; the alkaline solution is generally at a concentration of 1 to 3mol/L and the alkaline type is generally hydrogenSodium oxide, potassium hydroxide, based on which Na is contained ⁺ 、K ⁺ And the like metal cations.

Based on the above, the preparation of the molecular sieve provided by the invention does not need to increase the dosage of the binder for improving the strength of the obtained molecular sieve. In fact, the preparation method of the molecular sieve provided by the invention can prepare a product with high strength, and meanwhile, in the preparation process, the consumption of the binder is small, so that the consumption of raw materials required by subsequent in-situ crystallization (crystal transformation) can be reduced, the crystal transformation time is shortened, the success rate of one-time complete crystal transformation is improved, the discharge amount of washing wastewater after crystal transformation is correspondingly reduced, the burden of environmental protection of enterprises is reduced, and the production cost is also reduced.

According to the preparation method of the high-strength molecular sieve in any embodiment of the second aspect of the invention, in the S1, the addition amount of the Raw-molecular sieve is not less than 95wt% calculated by the total weight of the powder Raw material; the addition amount of the binder is not more than 5wt%;

preferably, the addition amount of the Raw-molecular sieve is 95 to 98 weight percent; the addition amount of the binder is 2-5 wt%.

According to the preparation method of the high-strength molecular sieve in any embodiment of the second aspect of the present invention, in the step S1, the powder raw material may further contain a pore-forming agent; calculated by the total weight of the powder Raw materials, the addition amount of the Raw-molecular sieve is not less than 95wt%; the addition amount of the binder is not more than 5wt%; the addition amount of the pore-forming agent is not more than 3wt%;

preferably, the addition amount of the Raw-molecular sieve is 95-98 wt%; the addition amount of the binder is 2-5 wt%; the addition amount of the pore-forming agent is 0-3 wt%.

According to the method for preparing a high-strength molecular sieve in any embodiment of the second aspect of the invention, in the case of S1, the particle size of the granular product a is required to be 1 to 2cm;

as described herein, the particle size of the product a affects the strength of the subsequent product, and in fact, if the particle size of the granular product a is too small, for example, less than 1cm, the granular product a may have insufficient binding force due to insufficient contact between the material and water;

if the particle size of the granular product a is too large, for example, higher than 2cm, the granular product a is too dense due to too large caking of the material, and the subsequent crystal transformation effect is finally affected.

In the method for producing a high strength molecular sieve according to any one of the embodiments of the second aspect of the present invention, in S2, the particle size of the crushed product B is not more than 10 μm.

As described herein, the particle size of the crushed product B affects the strength of the subsequent product, and in fact, if the particle size of the crushed product B is too large, for example, more than 10 μm, the particles are not easy to be combined into spheres again.

According to the method for preparing a high-strength molecular sieve in any embodiment of the second aspect of the invention, in S2, the addition amount of the powder raw material is 3 to 15wt% of the granular product a.

In fact, if the addition amount of the powder raw material is too low, water can be continuously separated out at a high speed to form larger particles; and the addition of excessive powder can reduce the proportion of the powder after the particle is crushed and influence the strength of secondary balling.

According to the preparation method of the high-strength molecular sieve in any embodiment of the second aspect of the invention, water is added to the crushed product B in the amount of 5-20 wt% of the powder raw material in the crushed product B in S3, so as to achieve the purposes of adjusting the humidity of the crushed product B and performing secondary granulation.

In fact, if the addition amount of water is too low, secondary balling is not easy to occur; if the amount of water added is high, the viscosity of the material is too high, and the particle size of the pellets exceeds the range of the target interval.

The high strength molecular sieve according to any of the embodiments of the first aspect of the present invention may be prepared by the method of preparing a high strength molecular sieve according to any of the embodiments of the second aspect of the present invention.

According to a third aspect of the present invention, there is provided a high-strength adsorbent having a molecular sieve structure and metal ions, and having:

a burned basis bulk density of not less than 1.5 g/ml;

not less than 800 square meters per gramSpecific surface area of micropores, and/or, not less than 0.38cm ³ A micropore volume per gram;

under the condition of 250N and 5min, the breakage rate is less than 0.1 percent.

The high-strength adsorbent according to any one of the embodiments of the third aspect of the present invention, which has a packing density of 1.50 to 1.80g/ml, preferably 1.60 to 1.80g/ml, more preferably 1.65 to 1.80g/ml, and still more preferably 1.70 to 1.80g/ml;

the micropore specific surface area of the adsorbent is 800-950 square meters per gram, preferably 850-950 square meters per gram, more preferably 870-950 square meters per gram, and even more preferably 885-950 square meters per gram;

the micropore volume of the adsorbent is 0.380-0.450 cm ³ A/g, preferably 0.385 to 0.450cm ³ Per g, more preferably 0.390 to 0.450cm ³ A concentration of 0.395 to 0.450cm ³ /g；

The breakage rate of the adsorbent is less than 0.1%, preferably less than 0.08%, and more preferably less than 0.05% under 250N,5min conditions.

The high strength sorbent according to any one of the embodiments of the third aspect of the invention, the sorbent having:

the framework structure of faujasite;

the framework structure further comprises metal cations, and the metal cations comprise one or two of Ba and K;

i) the kind of the metal ion can be arbitrarily selected according to the purpose, as described herein; preferably, the metal ion is at least one of barium and potassium, based on which:

in some embodiments, the metal cation may be Ba ²⁺ The adsorbent can be applied to adsorption separation of mixed xylene; the adsorbent can also be applied to adsorption separation of any one of o-xylene, m-xylene and p-xylene;

in some embodiments, the metal cation may be K ⁺ The adsorbent can be applied to adsorption separation of mixed xylene; the adsorbent in this case can also be applied to the ortho-diAdsorption separation of any one of toluene, m-xylene and p-xylene;

in some other embodiments, the metal cation may be Ba ²⁺ And K ⁺ The adsorbent can be applied to adsorption separation of mixed xylene; the adsorbent can also be applied to the adsorption separation of any one of o-xylene, m-xylene and p-xylene;

wherein the mixed xylene is a mixture of two or more of o-xylene, m-xylene and p-xylene.

Based on this, the adsorbent provided by the third aspect of the invention has high strength, high packing density of the adsorbent per unit volume of the device, and can effectively improve the processing capacity of the device. Meanwhile, the cation exchange degree of the adsorbent is high, the specific surface area and pore volume of micropores of the adsorbent are large, and the yield of a target product is further improved.

In a fourth aspect of the present invention, there is provided a method for preparing a high-strength adsorbent, which can prepare the high-strength adsorbent according to the third aspect of the present invention, the method comprising the steps of:

and (3) exchanging metal ions by using a solution containing metal ions for the molecular sieve provided by the first aspect or the molecular sieve prepared by any method of the second aspect, so as to obtain the high-strength adsorbent.

A method of making a high strength adsorbent according to any one of the embodiments of the fourth aspect of the present invention, comprising the steps of:

a step of preparing the high-strength molecular sieve according to any one of the embodiments of the second aspect; and

and (3) carrying out metal cation exchange treatment on the molecular sieve. Contacting a solution containing a metal ion, which may be Na, with the high strength molecular sieve, as described herein, with the high strength molecular sieve ⁺ The exchange occurs and then a load is formed on the high strength molecular sieve. In some embodiments, a conventional cation exchange method is used, and the specific steps are to use metal-containingIons (e.g. Ba) ²⁺ And/or K ⁺ ) The solution of (2) is used for dipping the molecular sieve after crystal transformation at a certain temperature until Na is added ⁺ All substitutions. Based on the advantages of the molecular sieve provided by the first aspect or the molecular sieve prepared by any one of the methods of the second aspect, the exchange treatment of metal cations can be ensured to enable Ba to be adsorbed ²⁺ Or K ⁺ Or Ba ²⁺ And K ⁺ Na with molecular sieves ⁺ The exchange rate reaches more than 99.5 percent.

According to the high-strength adsorbent of the third aspect of the present invention, the adsorbent can be obtained by the method for producing a high-strength adsorbent provided in any one of the above-described fourth aspects.

The high-strength molecular sieve of the first aspect above, or the high-strength molecular sieve prepared according to any one of the embodiments of the fourth aspect of the present invention, or the high-strength adsorbent provided by the third aspect above, or the high-strength adsorbent prepared according to any one of the embodiments of the fourth aspect of the present invention, or the high-strength adsorbent according to the fifth aspect of the present invention, is applied to the separation of an object from a mixture by adsorption;

the target comprises one or more of o-xylene, m-xylene and p-xylene; preferably comprising only para-xylene.

Based on the molecular sieve and the adsorbent provided by the invention, the molecular sieve and the adsorbent have wide application prospects, and can effectively fill the gap of the PX capacity expansion in China for the increase of the demand of the adsorbent. Meanwhile, the preparation method of the adsorbent is simple and easy to master, is beneficial to large-scale production of products, and has low production device investment, low later maintenance cost and good economy.

Drawings

FIG. 1 is a cross-sectional electron microscope picture of the PX adsorbent prepared in example 1;

fig. 2 is a morphology chart of PX adsorbent pellets prepared in example 1.

Detailed Description

The disclosure may be understood more readily by reference to the following description taken in conjunction with the accompanying drawings and examples, all of which form a part of this disclosure. It is to be understood that this disclosure is not limited to the particular products, methods, conditions or parameters described and/or illustrated herein. Further, the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting unless otherwise specified.

It is also to be understood that certain features of the disclosure may be described herein, for clarity, in the context of separate embodiments, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or specifically excluded, each individual embodiment is considered combinable with any other embodiment, and the combination is considered to represent another different embodiment. Conversely, various features of the disclosure that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination. Finally, while a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or sub-structure may itself be considered a separate embodiment.

Unless otherwise indicated, it is to be understood that each individual element of a list and each combination of individual elements in the list is to be construed as a different embodiment. For example, a list of embodiments denoted as "A, B or C" should be interpreted to include embodiments "a", "B", "C", "a or B", "a or C", "B or C", or "A, B or C".

In this disclosure, the singular forms of the articles "a", "an" and "the" also include the corresponding plural reference, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Thus, for example, reference to "a substance" is a reference to at least one of such substance and its equivalents.

Terms including ordinal numbers such as "first" and "second" may be used to explain various components or fluids, but these components or fluids are not limited by these terms. Thus, these terms are only used to distinguish one component/fluid from another component/fluid without departing from the teachings of the present disclosure.

When items are described by using the conjunctive terms "… … and/or … …", and the like, the description is to be understood as including any and all combinations of one or more of the associated listed items.

In general, use of the term "about" denotes an approximation that may vary depending on the desired characteristics obtained by the disclosed subject matter and will be interpreted in a context-dependent manner based on functionality. Thus, one of ordinary skill in the art will be able to account for some degree of variation on a case-by-case basis. In some cases, the number of significant digits used in expressing a particular value may be a representative technique for determining the difference allowed by the term "about". In other cases, a gradual change in a series of values may be used to determine the range of differences allowed by the term "about". Further, all ranges disclosed herein are inclusive and combinable, and reference to a value recited in a range includes each value within the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; as used herein, the term and/or includes any and all combinations of one or more of the associated listed items.

The present invention is further illustrated by the following specific examples, which are not intended to limit the invention in any way. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated. The essential features and the remarkable effects of the present invention can be obtained from the following examples, which are a part of the examples of the present invention, but not all of them, and therefore they do not limit the present invention, and those skilled in the art should make some insubstantial modifications and adjustments according to the contents of the present invention, and fall within the scope of the present invention.

The following specific examples:

the specific method for testing the adsorption separation performance of the sample comprises the following steps: the method adopts a single-column test method, the filling amount of the adsorbent is 50ml, nitrogen is firstly introduced to heat, activate and dehydrate, the system pressure is 0.85MPa, the system temperature is 177 ℃, and the separated product after condensation is collected and analyzed by using gas chromatography.

The specific method for measuring the burning base bulk density of the sample comprises the following steps: 50g of the adsorbent is placed in a 100ml measuring cylinder, the measuring cylinder is filled until the volume of the adsorbent in the measuring cylinder is not changed, and the volume value V is read, so that the bulk density rho =50/V g/ml of the adsorbent, the packing density rho (f) = rho S of the adsorbent is read, and S is the solid content of the adsorbent measured after the adsorbent is roasted at 650 ℃ for 1 hour.

The specific method for measuring the breakage rate of the sample comprises the following steps: accurately weighing 1.5ml of the adsorbent mass M1 after compaction, putting the adsorbent mass M1 into a customized cylindrical sample cell for compaction, applying 250N pressure to the adsorbent downwards and keeping the pressure for 5min, pouring all samples into a 30 mu M standard sieve for sieving, and weighing the sample mass M2 on the sieve, so that the pellet breakage rate R =100% 1 (M1-M2)/M1 can be calculated.

Example 1

Uniformly mixing 2000g X molecular sieve Raw powder (namely Raw-molecular sieve) and 57g kaolin, transferring the mixture into a rolling granulator, uniformly spraying 679g deionized water on the surface of the mixed powder under a rolling state, and stopping rolling when the small balls grow to about 1-2 cm.

Crushing the small balls and the supplemented 200g of mixed dry powder in the same proportion into powder of 1-2 mu m by a high-speed crusher at the speed of 3200r/min, and pouring the powder into a rolling granulator again for secondary rolling forming, wherein 31g of supplemented deionized water needs to be sprayed in the process. After molding, the pellets of 200-1100 μm are sieved and dried, and then are roasted at 700 ℃ for standby.

Carrying out in-situ crystal transformation treatment on the roasted adsorbent pellets, wherein the solid-to-liquid ratio (by volume ratio) is 1.3:1, the concentration of caustic soda is 1.2mol/L, the concentration of active silica sol is 0.2mol/L, the treatment temperature is 70 ℃, 2 hours, 92 ℃ and 2 hours, and after crystal transformation is finished, the molecular sieve balls are washed and dried for standby.

And (3) performing cation exchange on the crystallized adsorbent pellet for 7 hours at 90 ℃ under normal pressure by using a 0.1mol/L barium acetate solution, washing and drying after the exchange is finished to prepare a PX adsorbent pellet product S1, activating in a nitrogen atmosphere, and detecting the adsorption performance.

The section electron microscope of the prepared PX adsorbent is shown in figure 1;

the morphology of the prepared PX adsorbent beads is shown in fig. 2.

Example 2

2000g X molecular sieve raw powder, 38.4g kaolin and 51g halloysite are mixed uniformly, transferred to a rolling granulator, 710g deionized water is sprayed uniformly on the surface of the mixed powder in a rolling state, and the rolling is stopped when the small balls grow to about 1-2 cm.

Crushing the small balls and the supplementary 170g of dry powder mixed in the same proportion into powder of 1-2 mu m by a high-speed crusher at the speed of 3000r/min, and pouring the powder into a rolling granulator again for secondary rolling forming, wherein 16g of supplementary deionized water needs to be sprayed in the process. After molding, the pellets of 200-1100 μm are sieved and dried, and then are roasted at 700 ℃ for standby.

The conditions of crystal transformation and cation exchange of the molecular sieve beads are the same as those of example 1, and a PX adsorbent bead product S2 is prepared.

Example 3

2000g 13X molecular sieve Raw powder (namely Raw-molecular sieve), 77g kaolin and 17g sesbania powder are uniformly mixed, the mixture is transferred into a rolling granulator, 670g deionized water is uniformly sprayed on the surface of the mixed powder in a rolling state, and the rolling is stopped when small balls grow to about 1-2 cm.

Crushing the small balls and the supplemented 200g of mixed dry powder in the same proportion into powder of 1-2 mu m by a high-speed crusher at the speed of 3500r/min, and repeating the rolling ball crushing action once. And pouring the crushed materials into a rolling granulator again for rolling forming, wherein 28g of supplementary deionized water needs to be sprayed in the rolling granulator. After molding, the pellets of 200-1100 μm are sieved and dried, and then are roasted at 700 ℃ for standby.

The conditions of crystal transformation and cation exchange of the molecular sieve beads are the same as those of example 1, and a PX adsorbent bead product S3 is prepared.

Example 4

2000g 13X molecular sieve raw powder and 40g halloysite are uniformly mixed, the mixture is transferred to a rolling granulator, 714g deionized water is uniformly sprayed on the surface of the mixed powder in a rolling state, and the rolling is stopped when small balls grow to about 1-2 cm.

The small balls and the supplemented 230g of dry powder mixed in the same proportion are crushed into 1-2 mu m powder by a high-speed crusher at the speed of 3500 r/min. And pouring the crushed materials into a rolling granulator again for rolling forming again, wherein 30g of supplementary deionized water needs to be sprayed in the process. After molding, the pellets of 200-1100 μm are sieved and dried, and then are roasted at 700 ℃ for standby.

The conditions of crystal transformation and cation exchange of the molecular sieve beads are the same as those of example 1, and a PX adsorbent bead product S4 is prepared.

Example 5

2000g of 13X molecular sieve raw powder, 48g of kaolin and 25g of sodium carboxymethylcellulose are uniformly mixed, the mixture is transferred to a rolling granulator, 694g of deionized water is uniformly sprayed on the surface of the mixed powder in a rolling state, and the rolling is stopped when the small balls grow to about 1-2 cm.

Crushing the small balls and the supplemented 185g of mixed dry powder in the same proportion into powder of 1-2 mu m by a high-speed crusher at the speed of 3500r/min, and repeating the rolling ball crushing action twice. And pouring the crushed materials into a rolling granulator again for rolling forming again, wherein 35g of supplementary deionized water needs to be sprayed in the process. After molding, the pellets of 200-1100 μm are sieved and dried, and then are roasted at 700 ℃ for standby.

The conditions of crystal transformation and cation exchange of the molecular sieve beads are the same as those of example 1, and a PX adsorbent bead product S5 is prepared.

Comparative example 1

2000g 13X molecular sieve raw powder and 403g kaolin are uniformly mixed, the mixture is transferred into a rolling granulator, 1100g deionized water is uniformly sprayed on the surface of the mixed powder under a rolling state, the rolling is stopped when the small balls grow to a target particle size range, the small balls with the particle size of 200-1100 microns are sieved after the mixture is formed, and the small balls are dried and roasted at 700 ℃ for standby application.

The conditions of crystal transformation and cation exchange of the molecular sieve beads are the same as those of example 1, and a PX adsorbent bead product M1 is prepared.

Comparative example 2

The relevant parameters involved in the preparation of the adsorbent in this comparative example are the same as those in example 1, and the differences only lie in the differences in the preparation methods, which are specifically as follows:

adsorbent pellet product M2: mixing the molecular sieve raw powder and kaolin uniformly, transferring the mixture into a rolling granulator, spraying deionized water on the surface of the mixed powder uniformly in a rolling state, and stopping rolling when the small balls grow to be about 0.8cm in particle size. The rest of the process was the same as in example 1.

Adsorbent pellet product M3: mixing the molecular sieve raw powder and kaolin uniformly, transferring the mixture into a rolling granulator, spraying deionized water on the surface of the mixed powder uniformly in a rolling state, and stopping rolling when the small balls grow to have the particle size of about 3 cm. The rest is the same as in example 1.

Comparative example 3

adsorbent pellet product M4: the pellets and the supplemented dry mixed powder were crushed at 2000r/min using a high-speed pulverizer, and the rest was the same as in example 1.

The performance test data of the adsorbent beads prepared in examples 1 to 5 and comparative examples 1 to 4 are shown in Table 1.

TABLE 1 data for performance testing of examples 1-5 and comparative examples 1-4

As can be seen from table 1, the PX adsorbent provided by the present invention has excellent packing density, cation exchange degree, specific micropore surface area and pore volume, and separation performance for mixed xylenes.

Claims

1. A preparation method of a molecular sieve is characterized in that,

the preparation method comprises the following steps:

s1, processing a powder raw material to obtain a granular product A;

the powder Raw material contains a Raw-molecular sieve and a binder;

s2, crushing the blend containing the granular product A and the powder raw materials to obtain a crushed product B;

wherein the addition amount of the powder raw material is 3-15 wt% of the granular product A;

s3, adjusting the humidity of the crushed product B, and then performing granulation treatment to obtain a granular product C;

wherein, the damage rate of the obtained molecular sieve is not higher than 0.1% under the condition of 250N,5 min.

2. A method of preparing a molecular sieve according to claim 1,

in the S1, the addition amount of the Raw-molecular sieve is 95-98 wt%;

the addition amount of the binder is 2-5 wt%;

the particle size of the granular product A is 1-2 cm.

3. A process for the preparation of a molecular sieve according to any one of claims 1 to 2,

s2, crushing the blend containing the granular product A and the powder raw material at the rotating speed of 3000-4000 r/min; and/or the presence of a gas in the gas,

in S2, the particle size of the crushed product B is not more than 10 μm.

4. A process for the preparation of a molecular sieve according to any one of claims 1 to 2,

and S3, adding water into the crushed product B, wherein the addition amount of the water is 5-20 wt% of the powder raw material in the S2, so as to achieve the purpose of adjusting the humidity of the crushed product B.

5. A molecular sieve, characterized in that it is prepared by the process according to any one of claims 1 to 4.

6. A preparation method of an adsorbent is characterized in that,

the adsorbent has a molecular sieve structure and metal ions,

the preparation of the adsorbent comprises the following steps:

enabling the solution containing the metal ions to contact with a molecular sieve, and carrying out metal ion exchange treatment on the molecular sieve to obtain the adsorbent;

wherein the molecular sieve is prepared by the method of any one of claims 1 to 4; alternatively, the first and second electrodes may be,

the molecular sieve is according to claim 5.

7. An adsorbent having a molecular sieve structure and metal ions, comprising:

a burned basis bulk density of not less than 1.5 g/ml; preferably a fired bulk density of 1.50 to 1.80g/ml; further preferably a burned basis bulk density of 1.60 to 1.80g/ml; more preferably a burned base bulk density of 1.65 to 1.80g/ml;

a breakage rate of less than 0.1% under 250N,5 min; preferably, the breakage rate is less than 0.08 percent;

the specific surface area of the micropores is not less than 800 square meters per gram, preferably 800 to 950 square meters per gram; more preferably 850-950 square meters per gram of micropore specific surface area; more preferably 870-950 square meters per gram of micropore specific surface area;

and/or the presence of a gas in the atmosphere,

not less than 0.38cm ³ A micropore volume per gram; preferably 0.380 to 0.450cm ³ A micropore volume per gram; more preferably 0.390 to 0.450cm ³ A micropore volume per gram; more preferably 0.395-0.450 cm ³ Micropore volume per gram.

8. The sorbent according to claim 7, characterized in that it has:

the framework structure of faujasite;

the framework structure further comprises metal ions;

the metal ions comprise one or two of Ba and K.

9. The adsorbent according to any one of claims 7 to 8, wherein the high-strength molecular adsorbent is produced by the method according to claim 6.

10. Use of the adsorbent prepared according to claim 6 or the adsorbent according to any one of claims 7 to 9,

separating the mixture to obtain target substance by adsorption;

the target comprises one or more of o-xylene, m-xylene and p-xylene.