A method for adsorptive separation of n-alkanes in a c10-c25 distillate oil

Abstract

The present disclosure relates to a method for adsorptive separation of normal alkanes in C10-C25 distillate oil, comprising the following steps: S1, first contacting C10-C25 distillate oil with an adsorbent to obtain a desorption material containing C10-C25 normal alkanes and the adsorbent, and a raffinate containing C10-C25 isomeric alkanes, C10-C25 naphthenes, C10-C25 aromatics and a desorbent; S2, second contacting the desorbent with the desorption material to obtain an extract containing C10-C25 normal alkanes and the desorbent; the C10-C25 distillate oil comprises C10-C25 normal alkanes, C10-C25 isomeric alkanes, C10-C25 naphthenes and C10-C25 aromatics; the desorbent comprises C5-C8 normal alkanes, C6-C8 aromatics and optional C5-C8 isomeric alkanes; the particle size of the adsorbent is 0.3-0.6 mm, the adsorbent comprises 5A molecular sieve, and the crystal grain size of the 5A molecular sieve is 0.2-0.8 μm; the method can significantly improve the yield of normal alkanes above C14 and reduce the content of aromatics in normal alkanes.

Description

Technical Field

[0001] This disclosure relates to the field of adsorption separation, and specifically to a method for adsorption separation of n-alkanes from C10-C25 distillate oil. Background Technology

[0002] C10-C13 n-alkanes are mainly found in kerosene fractions, while C14-C25 n-alkanes are mainly found in diesel fractions. C10-C13 n-alkanes are the main component of light liquid waxes and are primarily used to produce straight-chain alkylbenzenes and fatty alcohols. C14-C20 n-alkanes are the main component of heavy liquid waxes and can be used to produce high-value-added products such as petroleum ester plasticizers, chlorinated paraffins, higher fatty alcohols, cosmetics, and synthetic petroleum proteins. N-alkanes above C20 are the main component of solid paraffins. High-purity n-alkanes in paraffins can be used as latent heat storage materials and are widely applied in high-tech systems such as aviation, aerospace, and microelectronics, as well as in energy-saving building applications. The dewaxed oil remaining after separating n-alkanes can be used as low-pour-point kerosene or diesel. Therefore, the separation of n-alkanes and non-n-alkanes in kerosene and diesel fractions has significant practical implications.

[0003] Kerosene and diesel oil have relatively wide boiling ranges, and the boiling point differences between their isomers are very small, making it impossible to separate liquid waxes using distillation. 5A molecular sieves have an effective pore size of approximately 0.51 nm, allowing n-alkanes with diameters smaller than 0.50 nm to pass through, while isoalkanes, cycloalkanes, and aromatics with diameters larger than 0.51 nm are rejected. Therefore, adsorption separation using 5A molecular sieves is an effective method for extracting liquid waxes.

[0004] Chinese industry standard NB / SH / T 0417-2013 stipulates that the aromatic content in light liquid wax should be less than 0.4% by mass, and the purity of n-alkanes should be greater than 98.5% by mass. Aromatic molecules have a relatively large diameter and will not enter the micropores of 5A molecular sieves. However, due to their strong polarity, a small amount of aromatics will be adsorbed on the surface of the adsorbent, which makes it difficult to reduce the aromatic content of n-alkanes. Furthermore, with increasingly stringent environmental protection requirements, the restrictions on aromatics in n-alkane products may become even stricter in the future.

[0005] n-Alkanes with different carbon numbers can be adsorbed by 5A molecular sieves. However, as the carbon number increases to more than 11, the mass transfer rate of n-alkanes shows a significant downward trend, which makes it difficult to improve the recovery rate of high carbon number n-alkanes.

[0006] CN91101507.8 discloses a method for improving the yield of long-chain n-alkanes. This method uses 5A molecular sieve adsorbent, C5-C8 n-alkanes as desorbents, and applies liquid-phase simulated moving bed technology to adsorb and separate C10-C35 n-alkanes. The key feature is the injection of low-carbon-number non-straight-chain hydrocarbons before or during feed to reduce the concentration of desorbent in the adsorbent bed, thereby mitigating competitive adsorption between the desorbent and long-chain n-alkanes in the feed and increasing the yield of the latter. However, the low-carbon-number non-straight-chain hydrocarbon stream introduced in this invention requires additional fractionation equipment for recovery, thus increasing investment and energy consumption.

[0007] CN201610825766.2 discloses a method for adsorbing and separating n-alkanes from C8-C22 n-alkanes and isoalkanes. This method involves passing the feedstock through a first adsorption separation zone, a second adsorption separation zone, and a third adsorption separation zone in a single pass. The first adsorption separation zone is filled with 5A molecular sieves, primarily adsorbing C8-C14 n-alkanes; the second adsorption separation zone is filled with HY molecular sieves, primarily adsorbing C15-C18 n-alkanes; and the third separation zone is filled with 13X molecular sieves, primarily adsorbing C19-C22 n-alkanes. However, the adsorption strength of HY and 13X molecular sieves for aromatics is much greater than that for alkanes; therefore, this method is not suitable for separating feedstocks containing aromatics. Summary of the Invention

[0008] The purpose of this disclosure is to provide a method for adsorption separation of n-alkanes from C10-C25 distillate oil. This method can separate n-alkanes from C10-C25 distillate oil, significantly improve the yield of n-alkanes with C14 and above, and reduce the content of aromatics in n-alkanes.

[0009] To achieve the above objectives, this disclosure provides a method for adsorption separation of n-alkanes from C10-C25 distillate oils, the method comprising the following steps:

[0010] S1. The C10-C25 distillate oil is brought into first contact with the adsorbent to obtain a material to be desorbed containing C10-C25 n-alkanes and the adsorbent, as well as a raffinate containing C10-C25 isoalkanes, C10-C25 cycloalkanes, C10-C25 aromatics and the desorbent.

[0011] S2. The desorbent is brought into a second contact with the material to be desorbed to obtain an extract containing C10-C25 n-alkanes and the desorbent.

[0012] The C10-C25 distillate oil includes C10-C25 n-alkanes, C10-C25 isoalkanes, C10-C25 cycloalkanes, and C10-C25 aromatics.

[0013] The desorbent includes C5-C8 n-alkanes, C6-C8 aromatics, and optionally C5-C8 isoalkanes;

[0014] The adsorbent has a particle size of 0.3-0.6 mm, and the adsorbent includes 5A molecular sieve with a crystal size of 0.2-0.8 μm.

[0015] Optionally, the grain size of the 5A molecular sieve is 0.2-0.7 μm;

[0016] Optionally, the water content of the adsorbent is less than 3% by weight.

[0017] Optionally, relative to the total volume of the desorbent, the content of the C5-C8 n-alkanes is 50-95% by volume, the content of the C6-C8 aromatics is 5-20% by volume, and the content of the C5-C8 isoalkanes is 0-30% by volume.

[0018] Optionally, the temperatures of the first contact and the second contact are 185-230°C and the pressures are 1.0-2.5 MPa, respectively.

[0019] Optionally, a liquid-phase simulated moving bed process is used to adsorb and separate n-alkanes from C10-C25 distillate oils. The simulated moving bed contains 12-24 adsorbent beds.

[0020] Step S1 includes: bringing the C10-C25 distillate oil into the adsorbent bed for the first contact to obtain a raffinate containing the C10-C25 isoalkanes, the C10-C25 cycloalkanes, the C10-C25 aromatics and a desorbent, and the adsorbent bed containing the C10-C25 n-alkanes as the material to be desorbed;

[0021] Step S2 includes: making the desorbent contact with the material to be desorbed in the second contact to obtain the extract.

[0022] Optionally, the method further includes:

[0023] The extract was separated to obtain the C10-C25 n-alkanes and the desorbent;

[0024] The raffinate is separated to obtain the C10-C25 isoalkanes, the C10-C25 cycloalkanes, the C10-C25 aromatics, and the desorbent.

[0025] Optionally, the method further includes: subjecting the material containing the C10-C25 n-alkanes obtained from the extraction liquid to a third contact with an X-type molecular sieve adsorbent and / or a Y-type molecular sieve adsorbent.

[0026] The temperature of the third contact is 100-120℃, the pressure is 0.5-1.5MPa, and the volumetric hourly space velocity is 0.5-5.0h. -1 ;

[0027] The water content of the X-type molecular sieve adsorbent and the Y-type molecular sieve adsorbent is less than 5% by weight, respectively.

[0028] Optionally, the method for preparing the adsorbent includes the following steps:

[0029] (1) Mix molecular sieve raw materials, binder and additives and perform molding treatment to obtain the first product;

[0030] (2) The first product is subjected to heat treatment to obtain the second product;

[0031] (3) The second product is contacted with an alkaline solution to obtain a third product;

[0032] (4) The third product is contacted with a solution containing a calcium source to carry out an ion exchange reaction to obtain a fourth product;

[0033] (5) The fourth product is activated;

[0034] The molecular sieve raw material has a crystal size of 0.2-0.8 μm, and the molecular sieve raw material includes NaA molecular sieve powder.

[0035] Optionally, in step (1), the adhesive includes one or more of clay-based adhesives, silica sol, and alumina sol;

[0036] The clay-based binder includes one or more of kaolin, halloysite, and attapulgite;

[0037] The additives include one or more of lignin, guar gum powder, corn starch, bayberry tannin, and methylcellulose.

[0038] Optionally, in step (1), the weight ratio of the molecular sieve raw material to the binder is (85-95):(5-15) on a dry basis.

[0039] On a dry basis, the amount of the additive is 1-6% by weight relative to the total weight of the molecular sieve raw material and the binder.

[0040] Optionally, step (1) further includes: forming the product of the molding process into particles with a particle size of 0.30-0.60 mm, and subjecting the particles to a first drying process to obtain the first product;

[0041] The conditions for the first drying process include: a temperature of 80-200℃ and a time of 1-4 hours.

[0042] Optionally, in step (2), the heat treatment conditions include: a temperature of 500-740℃ and a time of 1-4h.

[0043] Optionally, in step (3), the contact conditions include: a temperature of 80-99°C and a time of 1-5 hours;

[0044] The alkaline solution includes sodium hydroxide solution and / or potassium hydroxide solution;

[0045] The concentration of the alkaline solution is 0.5-2 mol / L, and the volume ratio of the second product to the alkaline solution is 1:(1-5).

[0046] Optionally, step (3) further includes: washing the solid obtained from the contact until the pH of the washing solution is below 10.0 to obtain the third product.

[0047] Optionally, in step (4), the conditions for the ion exchange reaction include: a time of 1-4 h and a temperature of 10-99 °C;

[0048] The calcium source includes calcium chloride and / or calcium nitrate;

[0049] The volume ratio of the third product to the solution is 1:(2-6);

[0050] In the solution, the concentration of the calcium source is 0.1-2.0 mol / L;

[0051] Step (4) further includes: subjecting the solid product obtained from the ion exchange reaction to a second drying treatment to obtain the fourth product;

[0052] The conditions for the second drying process include: a time of 1-4 hours and a temperature of 80-200℃.

[0053] Optionally, in step (5), the activation reaction conditions include: a time of 1-4 hours and a temperature of 250-350°C.

[0054] Through the above technical solution, this application effectively adsorbs and separates n-alkanes in C10-C25 distillate oil by using an adsorbent containing 5A molecular sieves with specific properties and a specific desorbent. The method disclosed herein is simple and can significantly improve the yield of n-alkanes with C14 and above. The desorbent used for adsorption and separation is supplemented with aromatics with low carbon number and low boiling point, which can significantly reduce the aromatic content in the n-alkane product.

[0055] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0056] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0057] Figure 1 This is a schematic diagram of the process for adsorption and separation of n-alkanes in C10-C25 distillate oil using a liquid-phase simulated moving bed process, as described in the embodiments of this disclosure.

[0058] Explanation of reference numerals in the attached figures

[0059] 101-112 Adsorption Column Detailed Implementation

[0060] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0061] This disclosure provides a method for adsorption separation of n-alkanes from C10-C25 distillate oils, the method comprising the following steps:

[0062] S1. The C10-C25 distillate oil is brought into first contact with the adsorbent to obtain a material to be desorbed containing C10-C25 n-alkanes and the adsorbent, as well as a raffinate containing C10-C25 isoalkanes, C10-C25 cycloalkanes, C10-C25 aromatics and the desorbent.

[0063] S2. The desorbent is brought into a second contact with the material to be desorbed to obtain an extract containing C10-C25 n-alkanes and the desorbent.

[0064] The C10-C25 distillate oil includes C10-C25 n-alkanes, C10-C25 isoalkanes, C10-C25 cycloalkanes, and C10-C25 aromatics.

[0065] The desorbent includes C5-C8 n-alkanes, C6-C8 aromatics, and optionally C5-C8 isoalkanes;

[0066] The adsorbent has a particle size of 0.3-0.6 mm, and the adsorbent includes 5A molecular sieve with a crystal size of 0.2-0.8 μm.

[0067] In this disclosure, in step S1, the desorbent in the raffinate does not originate from the first contact, but rather from the upstream of the simulated moving bed, or it may originate from the desorbent in the downstream adsorbent bed.

[0068] In this disclosure, an adsorbent containing a 5A molecular sieve with specific properties is used for the adsorption and separation of n-alkanes in C10-C25 distillate oil. The 5A molecular sieve has a small crystal size, which can significantly improve the intracrystalline diffusion rate of long-chain n-alkanes. The adsorbent also has a small particle size, which can significantly improve the external diffusion rate of long-chain n-alkanes, thereby improving the adsorption efficiency.

[0069] To further improve the mass transfer rate of high carbon number n-alkanes, according to one embodiment of this disclosure, the grain size of the 5A molecular sieve is 0.2-0.7 μm, which can improve the intracrystalline diffusion rate of n-alkanes.

[0070] According to one embodiment of this disclosure, before adsorption separation, the C10-C25 distillate oil is hydrogenated to convert the olefins therein into alkanes, and sulfur-containing and nitrogen-containing compounds need to be removed to avoid poisoning the adsorbent.

[0071] According to one embodiment of the present disclosure, the water content of the adsorbent is 3% by weight or less, wherein "water content of the adsorbent" refers to the water content relative to the total weight of the adsorbent; when the water content of the adsorbent is within the range of the present disclosure, a higher adsorption capacity of n-alkane can be obtained.

[0072] According to one embodiment of this disclosure, in the 5A molecular sieve, Ca 2+ The degree of exchange is 67-97%, and the above degree of exchange represents Ca 2+ The percentage of ions relative to exchangeable cation sites in the molecular sieve. Specific measurement methods include: analyzing the mass fraction of Na₂O and CaO in the adsorbent using X-ray fluorescence spectrometry (XRF), denoted as m. N and m C Then Ca 2+ Degree of ion exchange = m C / M C / (m C / M C +m N / M N M N and M C These are the molar masses of Na₂O and CaO, respectively.

[0073] In this disclosure, the C5-C8 n-alkanes in the desorbent have a better desorption effect on C10-C25 n-alkanes in C10-C25 distillate oils, especially C14-C25 n-alkanes, and do not affect the adsorption of C10-C25 n-alkanes. Using them as desorbents can achieve a higher recovery rate of n-alkanes. Furthermore, the desorbent of this disclosure also contains C6-C8 aromatics, which can effectively elute C10-C25 aromatics adsorbed on the surface of the adsorbent and improve product purity. The C5-C8 isoalkanes can adjust the adsorption strength and desorption capacity of the desorbent.

[0074] According to one embodiment of this disclosure, relative to the total volume of the desorbent, the content of C5-C8 n-alkanes is 50-95% by volume, the content of C6-C8 aromatics is 5-20% by volume, and the content of C5-C8 isoalkanes is 0-30% by volume; wherein, the C5-C8 n-alkanes may include, for example, n-hexane (nC6), n-heptane (nC7), etc., the C5-C8 isoalkanes may include, for example, isooctane (iC8), etc., and the C6-C8 aromatics may include, for example, benzene, toluene, ethylbenzene, xylene, etc.

[0075] In order to balance high adsorption capacity and mass transfer and diffusion of long-chain n-alkanes, according to one embodiment of the present disclosure, the temperatures of the first contact and the second contact are 185-230°C and the pressures are 1.0-2.5 MPa, respectively. The above conditions can ensure that the stream is in the liquid phase at the adsorption temperature and can ensure the mass transfer and diffusion of long-chain n-alkanes.

[0076] According to one embodiment of the present disclosure, a liquid-phase simulated moving bed process is used to adsorb and separate n-alkanes from C10-C25 distillate oils. The simulated moving bed contains 12-24 adsorbent beds.

[0077] Step S1 includes: making the C10-C25 distillate oil into the adsorbent bed in the first contact to obtain a raffinate containing C10-C25 isoalkanes, C10-C25 cycloalkanes, C10-C25 aromatics and desorbent, and an adsorbent bed containing C10-C25 n-alkanes as the material to be desorbed;

[0078] Step S2 includes: making the desorbent contact with the material to be desorbed in the second contact to obtain the extract.

[0079] According to one embodiment of this disclosure, the method further includes: separating the extract to obtain C10-C25 n-alkanes and a desorbent; the separation method is conventional in the art, such as fractional distillation, the separated desorbent can be recycled, and the fractional distillation material containing C10-C25 n-alkanes has a C10-C25 n-alkane content of 99.5% by weight or more and an aromatic hydrocarbon content of 0.1% by weight or less.

[0080] To further reduce the aromatic content in n-alkane products, according to one embodiment of this disclosure, the method includes: subjecting the material containing C10-C25 n-alkanes obtained from the extract to a third contact with an X-type molecular sieve and / or a Y-type molecular sieve; the temperature of the third contact is 100-120°C, the pressure is 0.5-1.5 MPa, and the volume hourly space velocity is 0.5-5 h⁻¹. -1 The water content of the X-type molecular sieve and the Y-type molecular sieve is less than 5% by weight. There are at least two adsorption towers for the above treatment, including adsorption and regeneration, which are used alternately. After the third treatment, the aromatic content of C10-C25 in the n-alkane product is less than 0.01% by weight.

[0081] According to one embodiment of this disclosure, the method further includes: separating the raffinate to obtain C10-C25 isoalkanes, C10-C25 cycloalkanes, C10-C25 aromatics and a desorbent, wherein the separated desorbent can be recycled; the separation method is conventional in the art, such as fractional distillation.

[0082] The method disclosed herein can be used for both batch and continuous operations. According to one embodiment, a liquid-phase simulated moving bed process is employed to adsorb and separate n-alkanes from C10-C25 distillate oils. The simulated moving bed comprises 12-24 adsorbent beds. To achieve continuous operation of the industrial separation unit, the adsorption separation process is carried out in a simulated moving bed device with multiple adsorbent beds. The adsorbent is packed in a columnar container in the form of a fixed bed. The adsorbent beds can be multiple adsorption columns connected in series, or they can be divided into multiple adsorbent beds by a screen or grid inside an adsorption tower. The liquid stream flows from top to bottom between the adsorbent beds. Several streams entering or leaving the adsorbent bed divide the adsorbent into at least four regions: adsorption zone, purification zone, desorption zone, and isolation zone, for adsorption and separation operations. The n-alkanes in the C10-C25 distillate oil undergo adsorption, purification, and desorption processes in different regions. Figure 1As shown, in the liquid-phase simulated moving bed device, the adsorbent bed between the raw material to be separated entering the simulated moving bed adsorption tower and the raffinate stream leaving the adsorption tower is the adsorption zone. The raw material stream containing n-alkanes enters the adsorption chamber from the upstream of the adsorption zone and contacts the adsorbent. The C10-C25 n-alkanes are adsorbed into the crystal pores of the 5A molecular sieve. The unadsorbed isoalkanes, cycloalkanes, and aromatics flow out of the adsorbent bed from the downstream of the adsorption zone along with a portion of the desorbent to form the raffinate stream. The area between the raffinate stream leaving the adsorption tower and the raw material stream entering the adsorption tower is called the purification zone. In this zone, the flow from top to bottom washes the non-n-alkanes outside the micropores of the adsorbent to the downstream. The upstream of this zone is rich in C10-C25 n-alkanes, and the raffinate stream containing the desorbent leaves the adsorption bed. The region between the desorbent stream entering the adsorption tower and the evaporator stream leaving the adsorption tower is called the desorption zone. The desorbent enters from the upstream of this zone, displacing the n-alkanes within the micropores of the adsorbent, allowing the adsorbent to be reused. There is also an isolation zone between the desorbent stream and the evaporator stream; this zone is designed to prevent non-n-alkanes from entering the desorption zone and contaminating the evaporator. Each adsorption column or adsorbent bed is connected to at least one feed line to transport several feed streams entering or leaving the adsorption separation unit. The positions of these feed streams entering or leaving the adsorbent bed are periodically changed from top to bottom, simulating a countercurrent flow between the liquid and adsorbent phases, with the liquid flowing downwards and the adsorbent moving upwards. The step time is 50-300 s. For small-scale experimental devices, the inlet and outlet positions remain unchanged; the same countercurrent flow effect can be achieved by moving the adsorbent bed. The evaporator stream and evaporator stream leaving the adsorption tower enter a fractionation tower to separate the products and recycle the desorbent.

[0083] In this disclosure, the adsorbent containing 5A molecular sieve can be formed from 4A molecular sieve, binder, and additives, and then the formed body is obtained through calcination, binder crystallization, Ca exchange, and activation. The forming process can be carried out according to various techniques well known to those skilled in the art, such as mixing the molecular sieve, binder, and additives, and then agglomerating them by extrusion, pressing, or rolling into spheres. Silicon-aluminum oxide binders with no adsorption capacity are commonly used in the forming process. To improve the adsorption capacity of the adsorbent, this type of binder needs to be crystallized to obtain a binder-free 4A molecular sieve formed body; the cell composition of the 5A molecular sieve in this disclosure is Ca4Na4[Al 12 Si 12 O 48 ]·20H2O. The micropores within the 5A molecular sieve can selectively adsorb C10-C25 n-alkanes.

[0084] According to one embodiment of this disclosure, a method for preparing the adsorbent includes the following steps:

[0085] (1) Mix molecular sieve raw materials, binder and additives and perform molding treatment to obtain the first product;

[0086] (2) The first product is subjected to heat treatment to obtain the second product;

[0087] (3) The second product is contacted with an alkaline solution to obtain a third product;

[0088] (4) The third product is contacted with a solution containing a calcium source to carry out an ion exchange reaction to obtain the fourth product;

[0089] (5) The fourth product is activated;

[0090] The molecular sieve raw material has a crystal size of 0.2-0.8 μm, and the molecular sieve raw material includes NaA molecular sieve powder.

[0091] According to one embodiment of this disclosure, the crystal size of the molecular sieve raw material is 0.2-0.7 μm.

[0092] According to one embodiment of this disclosure, in step (1), the binder includes one or more of clay-based binders, silica sol, and alumina sol; the clay-based binder includes one or more of kaolin, halloysite, and attapulgite; the additives include one or more of lignin, guar gum, corn starch, bayberry tannin, and methylcellulose; when there are two or more types of binders or additives, this disclosure does not impose specific restrictions on their proportions.

[0093] According to one embodiment of this disclosure, in step (1), the weight ratio of the molecular sieve raw material to the binder, on a dry basis, is (85-95):(5-15), preferably (90-95):(5-10). When the weight ratio of the molecular sieve raw material to the binder is within the above range, the problems of high adsorbent bulk density and decreased active component content due to excessive binder content and poor adsorbent strength due to excessively low binder content can be avoided.

[0094] According to one embodiment of this disclosure, in step (1), the amount of the additive, on a dry basis, is 1-6% by weight, preferably 2-4% by weight, relative to the total weight of the molecular sieve raw material and the binder.

[0095] In this disclosure, the forming process can be, for example, ball forming, extrusion forming, or tablet forming. The forming process can be carried out in equipment such as a high-speed granulator, a coating machine, a disc granulator, an extruder, or a tablet press. For example, in ball forming, the mixed powder is placed in a ball forming device, and water is added to the material in a spray form while it is rolling. Simultaneously, the mixed powder is added in a scattering form, causing the fine powder to agglomerate, round, and form small balls, which are then compacted to obtain spherical granules. In extrusion forming, the mixed powder is placed in an extrusion device, and a certain amount of water is added for kneading before extrusion to obtain strips. The strips are then dried, crushed, and sieved to obtain granules. In tablet forming, the mixed powder is placed in a tablet pressing device and pressed into shape, then crushed and sieved to obtain granules.

[0096] According to one embodiment of this disclosure, step (1) further includes: forming the product of the molding treatment into particles with a particle size of 0.30-0.60 mm, and subjecting the particles to a first drying treatment to obtain the first product; the particles can be, for example, spherical particles, which have good flowability, are easy to fill evenly, and have good fluid distribution uniformity; the conditions for the first drying treatment include: a temperature of 80-200°C and a time of 1-4 hours. The method of the first drying treatment is conventional in the art and is not specifically required; the above drying treatment can remove water from the macropores inside the particles.

[0097] According to one embodiment of this disclosure, in step (2), the heat treatment conditions include: a temperature of 500-740°C and a time of 1-4 hours, and the heat treatment method may be, for example, roasting.

[0098] According to one embodiment of this disclosure, in step (3), the contact conditions include: a temperature of 80-99°C and a time of 1-5 hours; the alkaline solution includes sodium hydroxide solution and / or potassium hydroxide solution; the concentration of the alkaline solution is 0.5-2 mol / L, and the volume ratio of the second product to the alkaline solution is 1:(1-5).

[0099] According to one embodiment of this disclosure, step (3) further includes: washing the solid obtained from the contact until the pH value of the washing liquid is below 10.0 to obtain a third product.

[0100] According to one embodiment of this disclosure, in step (4), the conditions for the ion exchange reaction include: a time of 1-4 h and a temperature of 10-99 °C; the calcium source includes a calcium-soluble compound, preferably including calcium chloride and / or calcium nitrate. When the calcium source includes two or more, there is no specific limitation on their ratio, that is, any ratio can achieve the technology of this disclosure; the volume ratio of the third product to the solution is 1:(2-6); and the concentration of the calcium source in the solution is 0.1-2.0 mol / L.

[0101] According to one embodiment of this disclosure, step (4) further includes: subjecting the solid product obtained by the ion exchange reaction to a second drying treatment to obtain the fourth product; the conditions for the second drying treatment include: time of 1-4 hours and temperature of 80-200°C; the method of the second drying treatment is conventional in the art and is not specifically required.

[0102] In this disclosure, all pH values ​​are test values ​​under conditions of 25°C and standard atmospheric pressure.

[0103] In this disclosure, the ion exchange reaction can be carried out, for example, by immersing the third product in a solution containing a calcium source.

[0104] According to one embodiment of this disclosure, the activation treatment temperature is 250-350°C, preferably 270-320°C; the activation treatment time is 1-4 hours, preferably 2-3 hours; the activation treatment can be carried out in a dry air atmosphere, under vacuum conditions, or in a nitrogen atmosphere to reduce the degree of hydrothermal damage to the molecular sieve at higher temperatures; the activation treatment method and steps are conventional in the art.

[0105] In this disclosure, 98% of the binder is converted into molecular sieves during the preparation process, meaning that the adsorbent contains almost no binder.

[0106] The following examples use, for example Figure 1 The small simulated moving bed device shown was tested to verify the effectiveness of this disclosure.

[0107] The effectiveness of the invention was verified by using a small-scale simulated moving bed device with continuous countercurrent flow. The small-scale simulated moving bed device comprises 12 adsorption columns connected in series, each column being 195 mm long and 30 mm in inner diameter, with a total adsorbent loading of 1650 ml. The 12 columns are connected at both ends by a circulating pump to form a closed loop. The four streams of material to be separated—the raw material, desorbent, extractant, and raffinate—divide the 12 adsorption columns into four zones: the three adsorption columns between the raw material stream and the raffinate stream form the adsorption zone; the four adsorption columns between the extractant stream and the raw material stream form the purification zone; the three adsorption columns between the desorbent stream and the extractant stream form the desorption zone; and the two adsorption columns between the raffinate stream and the desorbent stream form the isolation zone.

[0108] During operation, a micro-pump continuously injects the desorbent and adsorption feed streams into the simulated moving bed apparatus. The extract stream flows out of the apparatus continuously through the micro-pump, while the raffinate stream flows out of the apparatus under pressure control. The flow rate in each zone is adjusted by setting the circulation pump flow rate and the four inlet and outlet streams. At regular intervals, one adsorption column is moved in the opposite direction to the liquid flow to achieve continuous countercurrent chromatography of the adsorbent and fluid. Chromatographic analysis of the extract and raffinate composition, combined with the flow rates of each stream, calculates the purity and yield of the extract.

[0109] Unless otherwise specified, all reagents used in the examples and comparative examples were commercially available.

[0110] Gas chromatography instrument model and test conditions: An Agilent 7890 gas chromatograph was used to test the composition of the liquid sample. HP-5 column, injection volume 0.3 μL, injection temperature 290℃, split ratio 45:1, column flow rate 3.9 mL / min, FID detection, detection temperature 290℃, H2 flow rate 35 mL / min, air flow rate 350 mL / min, N2 flow rate 20 mL / min, initial column temperature 50℃, held for 3 min, then increased to 150℃ at a rate of 2℃ / min, held for 6 min.

[0111] Particle size testing method: Select 0.3-0.6 mm particles by screening using a US standard sieve.

[0112] The method for testing moisture content is as follows: the sample is calcined at 600℃ for more than 2 hours, and the percentage decrease in mass is the moisture content.

[0113] Grain size testing method: The molecular sieve morphology was observed using a Hitachi S4800 scanning electron microscope and the grain size was measured using SMile View software.

[0114] The method for testing the degree of exchange was as follows: X-ray fluorescence spectrometry (XRF) was used to analyze the mass fractions of Na₂O and CaO in the adsorbent, and the values ​​were recorded as m. N and m C Then Ca 2+ Degree of ion exchange = m C / M C / (m C / M C +m N / M N M N and M CThese are the molar masses of Na₂O and CaO, respectively. The XRF instrument model and testing conditions are: a 3013 X-ray fluorescence spectrometer (XRF) manufactured by Nippon Kikka Electric Co., Ltd. After drying the test sample at 100-120℃, it is ground into powder of approximately 200 mesh. The fine powder is poured into a tablet mold and placed on a hydraulic press to be pressed into tablets. The applied pressure is generally above 30 MPa and held for 5 seconds. The size of the pressed tablets is Φ30 mm.

[0115] In the examples and comparative examples, the crystal size of the molecular sieve was the same as that of the original molecular sieve powder.

[0116] Example 1

[0117] Adsorbent X-1 was prepared using the following steps, and then used for the adsorption and separation of n-alkanes in C10-C25 distillate oil:

[0118] 50 kg of NaA molecular sieve powder, 3 kg of halloysite (all on a dry basis), and 1 kg of corn starch were mixed evenly to prepare a mixed powder, wherein the NaA molecular sieve crystal size was 0.8 μm. The mixed powder was rolled into small balls with a diameter of 0.3-0.6 mm in a sugar-coating pan, and then dried at 85 °C for 4 h and calcined at 550 °C for 4 h. 40 L of the calcined small balls were soaked in 80 L of 1.0 mol / L NaOH aqueous solution at 97 °C for 4 h, and then washed with deionized water until the pH value was below 10.0 to obtain NaA small balls. 40 L of NaA microspheres were immersed in 200 L of 1.0 mol / L CaCl2 aqueous solution for ion exchange. The temperature of the exchange solution was maintained at 95 °C for 4 h. The microspheres were then washed with deionized water and dried (for 4 h at 150 °C). The microspheres were then activated in dry air at a programmed temperature of 280 °C for 2 h to obtain 5A microsphere adsorbent X-1. The parameters are listed in Table 1.

[0119] use Figure 1 The experiment was conducted using a small-scale simulated moving bed. Twelve adsorption columns were packed with the aforementioned adsorbent. The composition of the C10-C25 distillate oil is shown in Table 2. The desorbent consisted of 80 vol% nC7 and 20 vol% toluene. The adsorption zone consisted of 3 columns, the purification zone of 4 columns, the desorption zone of 3 columns, and the isolation zone of 2 columns. Adsorption separation was performed at a temperature of 235℃, a pressure of 2.5 MPa, a feed flow rate of 1158 mL / h, a desorbent flow rate of 1734 mL / h, an extract flow rate of 1015 mL / h, a raffinate flow rate of 1877 mL / h, and a step time of 150 s. Chromatographic analysis yielded the composition of the extract and raffinate. The calculated content of n-alkanes in the extract (excluding the desorbent) was 99.6 wt%, and the aromatic content was 0.07 wt%. The yields of nC10-nC25 n-alkanes are shown in Table 3.

[0120] Example 2

[0121] Adsorbent X-2 was prepared using the steps of Example 1, except that the crystal size of the NaA molecular sieve powder was 0.3 μm, the activation temperature after ion exchange drying was 300 °C, and the water content of the adsorbent was 1.5% by weight. The parameters of adsorbent X-2 are listed in Table 1.

[0122] A small-scale simulated moving bed experiment was conducted according to the method in Example 1, except that the desorbents were 60% by volume nC6, 20% by volume iC8, and 20% by volume benzene. Adsorption separation was carried out at a temperature of 200°C, a pressure of 2.5 MPa, a feed flow rate of 1158 mL / h, a desorbent flow rate of 2000 mL / h, an extract flow rate of 1381 mL / h, a raffinate flow rate of 1777 mL / h, and a step time of 150 s. Chromatographic analysis yielded the composition of the extract and raffinate. The calculated content of n-alkanes in the extract (excluding the desorbent) was 99.6% by weight, and the content of aromatics was 0.05% by weight. The yields of nC10-nC25 n-alkanes are shown in Table 3.

[0123] Example 3

[0124] Adsorbent X-1 was used, and the adsorption and separation of n-alkanes in C10-C25 distillate oil was carried out using a method similar to that in Example 1.

[0125] A small-scale simulated moving bed experiment was conducted according to the method in Example 1, except that the desorbents were 60% by volume nC5, 20% by volume iC8, and 20% by volume benzene. Adsorption separation was performed at a temperature of 185°C, a pressure of 2.5 MPa, a feed flow rate of 1158 mL / h, a desorbent flow rate of 1891 mL / h, an extract flow rate of 1172 mL / h, a raffinate flow rate of 1877 mL / h, and a step time of 150 s. Chromatographic analysis yielded the composition of the extract and raffinate. The calculated content of n-alkanes in the extract (excluding the desorbent) was 99.5% by weight, and the content of aromatics was 0.06% by weight. The yields of nC10-nC25 n-alkanes are shown in Table 3.

[0126] Example 4

[0127] Adsorbent X-1 was used, and the adsorption and separation of n-alkanes in C10-C25 distillate oil was carried out using a method similar to that in Example 1.

[0128] A small-scale simulated moving bed experiment was conducted according to the method in Example 1, except that the desorbent was 95% by volume nC7 and 5% by volume toluene. Adsorption separation was performed at a temperature of 235°C, a pressure of 2.5 MPa, a feed flow rate of 1158 mL / h, a desorbent flow rate of 1734 mL / h, an extract flow rate of 1015 mL / h, a raffinate flow rate of 1877 mL / h, and a step time of 150 s. Chromatographic analysis yielded the composition of the extract and raffinate. The calculated content of n-alkanes in the extract (excluding the desorbent) was 99.5% by weight, and the content of aromatics was 0.1% by weight. The yields of nC10-nC25 n-alkanes are shown in Table 3.

[0129] Example 5

[0130] The adsorption separation of n-alkanes in C10-C25 distillate oil was performed using the method described in Example 4. 13000 mL of the obtained nC10-nC25 n-alkane product was injected into an adsorption column containing 1000 mL of NaX molecular sieve adsorbent (water content 3% by weight). The temperature was 100°C, the pressure was atmospheric pressure, and the volume hourly space velocity (VHSV) was 5 h⁻¹. -1 The aromatic hydrocarbon content detected at the outlet was 0.01% by weight.

[0131] Example 6

[0132] Adsorbent X-6 was prepared using the following steps, and then used for the adsorption and separation of n-alkanes in C10-C25 distillate oil:

[0133] 58 kg of NaA molecular sieve powder, 10 kg of kaolin (all dry basis weight), and 2 kg of guar gum powder were mixed evenly to prepare a mixed powder, wherein the NaA molecular sieve crystal size was 0.2 μm. The mixed powder was rolled into small balls with a diameter of 0.3-0.6 mm in a sugar-coating pan, and then dried at 150℃ for 3 h and calcined at 600℃ for 4 h. 40 L of the calcined small balls were soaked in 60 L of 2 mol / L NaOH aqueous solution at 90℃ for 5 h, then washed with deionized water until the pH value was below 10.0, and dried (for 2 h at 200℃) to obtain NaA small balls. 30 L of NaA microspheres were immersed in 150 L of 1.5 mol / L CaCl2 aqueous solution for ion exchange. The temperature of the exchange solution was maintained at 80 °C for 3 h. Then, the microspheres were washed with deionized water and dried (for 2 h at 200 °C). The microspheres were then activated in a dry air atmosphere by programmed heating to 290 °C for 2 h to obtain 5A microsphere adsorbent X-6. The parameters are listed in Table 1.

[0134] A small-scale simulated moving bed experiment was conducted according to the method in Example 1. Chromatographic analysis was performed to obtain the composition of the extract and the residue. The content of n-alkanes in the extract (excluding the desorbent) was calculated to be 99.5% by weight, the content of aromatics was 0.08% by weight, and the yield of nC10-nC25 n-alkanes is shown in Table 3.

[0135] Comparative Example 1

[0136] Adsorbent Y-1 was prepared using the following steps, and then used for the adsorption and separation of n-alkanes in C10-C25 distillate oil:

[0137] 50 kg of NaA molecular sieve powder, 3 kg of halloysite (all on a dry basis), and 1 kg of corn starch were mixed evenly to prepare a mixed powder, wherein the NaA molecular sieve crystal size was 2.5 μm. The mixed powder was rolled into small balls with a diameter of 0.3-0.6 mm in a sugar-coating pan, and then dried at 85 °C for 8 h and calcined at 550 °C for 4 h. 40 L of the calcined small balls were soaked in 80 L of 1.0 mol / L NaOH aqueous solution at 97 °C for 4 h, then washed with deionized water until the pH value was below 10.0, and dried to obtain NaA small balls. 40 L of NaA microspheres were immersed in 200 L of 1.0 mol / L CaCl2 aqueous solution for ion exchange. The temperature of the exchange solution was maintained at 95 °C for 4 h. The microspheres were then washed with deionized water and dried (for 4 h at 150 °C). The microspheres were then activated in a dry air atmosphere by a programmed temperature increase to 500 °C for 2 h to obtain 5A microsphere adsorbent Y-1. The parameters are listed in Table 1.

[0138] use Figure 1 The small-scale simulated moving bed experiment was conducted, with 12 adsorption columns packed with the aforementioned adsorbent. The composition of the adsorbent feedstock is shown in Table 2. The desorbent consisted of 80% by volume nC7 and 20% by volume toluene. The adsorption zone consisted of 3 columns, the purification zone of 4 columns, the desorption zone of 3 columns, and the isolation zone of 2 columns. Adsorption separation was performed under the following conditions: column temperature 235℃, pressure 2.5MPa, feed flow rate 1158mL / h, desorbent flow rate 1734mL / h, extract flow rate 1015mL / h, raffinate flow rate 1877mL / h, and step time 150s. Chromatographic analysis yielded the composition of the extract and raffinate. The calculated content of n-alkanes in the extract (excluding the desorbent) was 99.6% by weight, and the aromatic content was 0.07% by weight. The yields of nC10-nC25 n-alkanes are shown in Table 3.

[0139] Comparative Example 2

[0140] Adsorbent Y-2 was prepared using the steps of Example 1, except that the particle size of the 5A molecular sieve adsorbent was 0.9-1.0 mm. The parameters of adsorbent Y-2 are listed in Table 1.

[0141] use Figure 1 The small-scale simulated moving bed experiment was conducted, with 12 adsorption columns packed with the aforementioned adsorbent. The composition of the adsorbent feedstock is shown in Table 2. The desorbent consisted of 80% by volume nC7 and 20% by volume toluene. The adsorption zone consisted of 3 columns, the purification zone of 4 columns, the desorption zone of 3 columns, and the isolation zone of 2 columns. Adsorption separation was performed under the following conditions: column temperature 235℃, pressure 2.5MPa, feed flow rate 1158mL / h, desorbent flow rate 1734mL / h, extract flow rate 1015mL / h, raffinate flow rate 1877mL / h, and step time 150s. Chromatographic analysis yielded the composition of the extract and raffinate. The calculated content of n-alkanes in the extract (excluding the desorbent) was 99.6% by weight, and the aromatic content was 0.07% by weight. The yields of nC10-nC25 n-alkanes are shown in Table 3.

[0142] Comparative Example 3

[0143] Adsorbent X-1 was used to separate n-alkanes from C10-C25 distillate oils.

[0144] The above-mentioned adsorbent was packed into 12 adsorption columns, and a small-scale simulated moving bed experiment was conducted according to Example 1, except that the desorbent was 80% by volume n-heptane and 20% by volume isooctane. Adsorption separation was carried out at a temperature of 200°C, a pressure of 2.5 MPa, a feed flow rate of 1158 mL / h, a desorbent flow rate of 2000 mL / h, an extract flow rate of 1381 mL / h, a raffinate flow rate of 1777 mL / h, and a step time of 150 s. Chromatographic analysis revealed the composition of the extract and raffinate, and the calculated content of n-alkanes in the extract (excluding the desorbent) was 99.2% by weight, and the content of aromatics was 0.5% by weight.

[0145] Comparative Example 4

[0146] Adsorbent X-1 was used to separate n-alkanes from C10-C25 distillate oils.

[0147] A small-scale simulated moving bed experiment was conducted according to Example 3, except that the desorbents were 60% by volume nC5 and 40% by volume iC8. Adsorption separation was performed at a temperature of 185°C, a pressure of 2.5 MPa, a feed flow rate of 1158 mL / h, a desorbent flow rate of 1891 mL / h, an extract flow rate of 1172 mL / h, a raffinate flow rate of 1877 mL / h, and a step time of 150 s. Chromatographic analysis yielded the composition of the extract and raffinate, and the calculated content of n-alkanes (excluding the desorbent) in the extract was 99.1% by weight, and the content of aromatics was 0.5% by weight.

[0148] Comparative Example 5

[0149] Adsorbent Y-3 was prepared using the method described in Example 1, except that the crystal size of the NaA molecular sieve powder was 1.2 μm. The parameters of adsorbent Y-3 are listed in Table 1.

[0150] According to the method in Example 1, using Figure 1 The small-scale simulated moving bed experiment was conducted, with 12 adsorption columns packed with the aforementioned adsorbent. The composition of the C10-C25 distillate oil is shown in Table 2. The desorbent consisted of 80 vol% nC7 and 20 vol% toluene. The adsorption zone consisted of 3 columns, the purification zone of 4 columns, the desorption zone of 3 columns, and the isolation zone of 2 columns. Adsorption separation was performed at a temperature of 235℃, a pressure of 2.5 MPa, a feed flow rate of 1158 mL / h, a desorbent flow rate of 1734 mL / h, an extract flow rate of 1015 mL / h, a raffinate flow rate of 1877 mL / h, and a step time of 150 s. Chromatographic analysis yielded the composition of the extract and raffinate. The calculated content of n-alkanes in the extract (excluding the desorbent) was 99.5 wt%, and the aromatic content was 0.08 wt%. The yields of nC10-nC25 n-alkanes are shown in Table 3.

[0151] Table 1

[0152]

[0153] Table 2

[0154]

[0155] Table 3

[0156]

[0157] Based on the above data, it can be seen that the method disclosed herein can adsorb and separate n-alkanes from C10-C25 distillate oils. This method can significantly improve the yield of n-alkanes with C14 and above and reduce the content of aromatics in n-alkanes.

[0158] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0159] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0160] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for adsorption and separation of n-alkanes from C10-C25 distillate oils, characterized in that, This method involves using a liquid-phase simulated moving bed process to adsorb and separate n-alkanes from C10-C25 distillate oils. The simulated moving bed comprises 12-24 adsorbent beds. Step S1 includes: making the C10-C25 distillate oil into a first contact with the adsorbent bed to obtain a raffinate containing C10-C25 isoalkanes, C10-C25 cycloalkanes, C10-C25 aromatics and a desorbent, and the adsorbent bed containing C10-C25 n-alkanes as the material to be desorbed; Step S2 includes: making a second contact between the desorbent and the material to be desorbed to obtain an extract; The desorbent includes C5-C8 n-alkanes and C6-C8 aromatics; Relative to the total volume of the desorbent, the content of C5-C8 n-alkanes is 50-95% by volume, and the content of C6-C8 aromatics is 5-20% by volume. The adsorbent has a particle size of 0.3-0.6 mm, and the adsorbent includes 5A molecular sieve with a crystal size of 0.2-0.8 μm.

2. The method according to claim 1, wherein, The desorbent includes C5-C8 n-alkanes, C6-C8 aromatics, and C5-C8 isoalkanes; The content of the C5-C8 isoalkanes is 0-30% by volume relative to the total volume of the desorbent.

3. The method according to claim 1, wherein, The crystal size of the 5A molecular sieve is 0.2-0.7 μm.

4. The method according to claim 1, wherein, The water content of the adsorbent is less than 3% by weight.

5. The method according to claim 1, wherein, The temperatures of the first contact and the second contact are 185-230℃ and the pressures are 1.0-2.5MPa, respectively.

6. The method according to claim 1, wherein, The method further includes: The extract was separated to obtain the C10-C25 n-alkanes and the desorbent; The raffinate is separated to obtain the C10-C25 isoalkanes, the C10-C25 cycloalkanes, the C10-C25 aromatics, and the desorbent.

7. The method according to claim 6, wherein, The method further includes: subjecting the material containing the C10-C25 n-alkanes obtained by separating the extract to a third contact with an X-type molecular sieve adsorbent and / or a Y-type molecular sieve adsorbent; The temperature of the third contact is 100-120℃, the pressure is 0.5-1.5MPa, and the volumetric hourly space velocity is 0.5-5.0h. -1 ; The water content of the X-type molecular sieve adsorbent and the Y-type molecular sieve adsorbent is less than 5% by weight, respectively.

8. The method according to claim 1, wherein, The method for preparing the adsorbent includes the following steps: (1) The molecular sieve raw material, binder and additives are mixed and molded to obtain the first product; (2) The first product is subjected to heat treatment to obtain the second product; (3) The second product is contacted with an alkaline solution to obtain a third product; (4) The third product is contacted with a solution containing a calcium source to carry out an ion exchange reaction to obtain the fourth product; (5) Activate the fourth product; The molecular sieve raw material has a crystal size of 0.2-0.8 μm, and the molecular sieve raw material includes NaA molecular sieve powder.

9. The method according to claim 8, wherein, In step (1), the adhesive includes one or more of clay-based adhesives, silica sol, and alumina sol; The clay-based binder includes one or more of kaolin, halloysite, and attapulgite; The additives include one or more of lignin, guar gum powder, corn starch, bayberry tannin, and methylcellulose.

10. The method according to claim 8, wherein, In step (1), the weight ratio of the molecular sieve raw material to the binder is (85-95):(5-15) on a dry basis. On a dry basis, the amount of the additive is 1-6 by weight relative to the total weight of the molecular sieve raw material and the binder.

11. The method according to claim 8, wherein, Step (1) further includes: forming the product of the molding process into particles with a particle size of 0.30-0.60 mm, and subjecting the particles to a first drying process to obtain the first product; The conditions for the first drying process include: a temperature of 80-200℃ and a time of 1-4 hours.

12. The method according to claim 8, wherein, In step (2), the heat treatment conditions include: a temperature of 500-740℃ and a time of 1-4h.

13. The method according to claim 8, wherein, In step (3), the contact conditions include: a temperature of 80-99℃ and a time of 1-5h; The alkaline solution includes sodium hydroxide solution and / or potassium hydroxide solution; The concentration of the alkaline solution is 0.5-2 mol / L, and the volume ratio of the second product to the alkaline solution is 1:(1-5).

14. The method according to claim 13, wherein, Step (3) further includes: washing the solid obtained from the contact until the pH of the washing solution is below 10.0 to obtain the third product.

15. The method according to claim 8, wherein, In step (4), the conditions for the ion exchange reaction include: time of 1-4 h and temperature of 10-99 °C; The calcium source includes calcium chloride and / or calcium nitrate; The volume ratio of the third product to the solution is 1:(2-6). In the solution, the concentration of the calcium source is 0.1-2.0 mol / L; Step (4) further includes: subjecting the solid product obtained from the ion exchange reaction to a second drying treatment to obtain the fourth product; The conditions for the second drying process include: a time of 1-4 hours and a temperature of 80-200℃.

16. The method according to claim 8, wherein, In step (5), the activation treatment conditions include: time of 1-4 hours and temperature of 250-350℃.

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