CN113694880B

CN113694880B - Rare earth-containing Li-LSX zeolite and preparation method and application thereof

Info

Publication number: CN113694880B
Application number: CN202111062068.9A
Authority: CN
Inventors: 卓润生; 杜爱华; 张明远; 刘新生
Original assignee: Runhe Catalyst Co ltd
Current assignee: Runhe Catalyst Co ltd
Priority date: 2021-09-10
Filing date: 2021-09-10
Publication date: 2023-10-10
Anticipated expiration: 2041-09-10
Also published as: CN113694880A

Abstract

A Li-LSX zeolite containing rare earth and a preparation method thereof belong to the technical field of chemical industry, and the preparation steps comprise: (1) According to M ₂ O/SiO ₂ ＝1～1.5、SiO ₂ /A1 ₂ O ₃ ＝2.5～5、H ₂ O/SiO ₂ The molar ratio of the silicon source, the aluminum source and the caustic alkali is 45-50, and the silicon source, the aluminum source and the caustic alkali are added, mixed and stirred and crystallized for 5-10 hours at the temperature of 80-100 ℃; (2) After filtration, the product is exchanged for 1 to 2 times by rare earth salt solution and baked for 0.5 to 3 hours at the temperature of 350 to 550 ℃ after the first exchange; (3) After grinding, adding silicon source, aluminum source and caustic alkali in proportion of 40-95% of total dry weight, and making the total mole ratio of material be M ₂ O/SiO ₂ =3.5 to 4 (Na/K molar ratio of alkali metal M2.5 to 3.5), siO ₂ /A1 ₂ O ₃ ＝1.5～2、H ₂ O/SiO ₂ After being stirred, the mixture is aged for 1 to 3 days and recrystallized for 10 to 25 hours at the temperature of between 60 and 80 ℃; (4) Filtering and exchanging ammonium salt, exchanging ion with lithium compound solution for 2-5 times, and roasting for 1-2 times at intervals of 300-430 ℃/0.5-3 hours; the lithium salt has high utilization rate, easy adjustment of product composition and performance, and better adsorption separation performance when being used as an oxygen-making adsorbent.

Description

Rare earth-containing Li-LSX zeolite and preparation method and application thereof

Technical Field

The invention relates to rare earth-containing Li-LSX zeolite and a preparation method and application thereof, in particular to cerium and lithium-containing X-type zeolite with low silicon-aluminum ratio and a preparation method thereof and application thereof in an oxygen production separation and purification process, and belongs to the technical field of chemical industry.

Background

The application fields of oxygen and nitrogen are wider and wider, and the demand is also larger and larger. Among them, oxygen is the basis on which human beings depend for survival, and is widely used as an important chemical raw material in various aspects of petrochemical industry, chemical synthesis, iron and steel smelting, nonferrous metallurgy, metal cutting welding, paper industry, fishery cultivation, altitude construction, tunnel construction, wastewater treatment, environmental protection and the like due to its strong oxidizing property and life-sustaining property. Along with the continuous improvement of the technological and industrial level, especially along with the emergence of new epidemic situations, the demand of oxygen in industries such as medical treatment also presents a trend of rapid rise.

The air contains a large amount of oxygen and nitrogen, and separation of oxygen and nitrogen from air is a common method for obtaining high-purity oxygen or nitrogen. Before the pressure swing adsorption technology appears, the air separation oxygen and nitrogen production is monopoly by the refrigeration separation technology, however, the method has the advantages of complex process, large equipment occupation, high investment, strict environmental requirement and long time consumption, is not suitable for preparing oxygen in a small oxygen production scale and rapidly and mechanically on site, and the condition is maintained until 70 years. After that, pressure swing adsorption technology has begun to be applied to the field of air separation and has been rapidly developed.

The pressure swing adsorption (Pressure Swing Adsorption, PSA) air separation oxygen production technology starts from the 60 th century, has the advantages of simple process, convenient operation, less investment, low energy consumption, high degree of automation and the like, and has been paid more attention to USP2944627, USP5176722, CN1196273A and the like at home and abroad. At present, the pressure swing adsorption air separation has been about 20% of the total duty cycle yield and is still growing rapidly.

Pressure Swing Adsorption (PSA) and Vacuum Pressure Swing Adsorption (VPSA) are common air separation means, and the preparation of efficient nitrogen-oxygen separation adsorbents is one of the keys of such variable pressure oxygen compression technologies. However, at present, there are many domestic oxygen generating devices, and in recent years, new technologies of pressure swing adsorption air separation oxygen generation using traditional 5A and 13X zeolite as oxygen-enriched adsorbents, novel efficient adsorbents and the like have been rapidly developed, and CN101524637B is also developed.

At present, the most studied adsorbents at home and abroad are mainly nitrogen adsorption materials, and representative are CaA, caX, naX, liX and the like, and the separation principle is based on the selective adsorption of the adsorbents on nitrogen and oxygen in air, and the nitrogen-oxygen separation is realized by utilizing the adsorption quantity, adsorption speed and adsorption capacity difference of the nitrogen and the oxygen and the characteristic that the adsorption quantity changes along with the pressure, and the pressure-increasing adsorption and the pressure-decreasing desorption.

The research of the adsorbent in China, especially in the research and development of novel adsorbent, has been rapidly developed, but still needs to be further improved. Chinese patent CN101524639a, for example, discloses a high strength adsorbent prepared from LSX zeolite for air, nitrogen, hydrogen and natural gas purification; chinese patent CN101766987B also discloses a novel Li-LSX zeolite adsorbent and a method for preparing the same, chinese patent CN101678314B also discloses a high rate and high crush strength adsorbent prepared with Li-LSX.

In order to further increase the zeolite content in the adsorbent to increase the adsorption performance of the adsorbent, there is a class of binderless adsorbent types that have attracted high attention, such as the methods disclosed in CN101524637B and CN109485058a for preparing binderless LSX zeolite adsorbents to further increase the adsorption performance by increasing the zeolite content.

Chinese patent CN107159105A discloses a non-binder 13X zeolite adsorbent and a preparation method thereof, wherein kaolin is used as a binder, the kaolin, the 13X zeolite raw powder and an additive are mixed and molded, and the mixture is subjected to primary roasting, crystallization in sodium hydroxide solution and secondary roasting to prepare the adsorbent with the binder content of less than 5 percent, and the adsorbent is mainly converted into the non-binder 13X zeolite adsorbent without A-type hetero-crystal peaks.

Chinese patent CN102513059A also discloses a preparation method of a binder-free 13X zeolite adsorbent, which comprises the steps of mixing 13X zeolite raw powder with a multi-water kaolin clay and an attapulgite clay, granulating, sieving, roasting at high temperature, immersing the roasted product into a sodium silicate mixed solution of sodium hydroxide and silicon dioxide for crystallization, washing, drying and roasting at high temperature to obtain the binder-free 13X zeolite, wherein the kaolin is converted into X zeolite mainly by adding a silicon source.

CN1234782a also discloses a process for the preparation of kaolin binders to LSX when the source of the transcrystalline alkali is a sodium/potassium mixture, the toluene adsorption amount of which can reach 22.5%, similar results being also disclosed in japanese patent JP 05163015. The prior art mainly adopts kaolin substances as a binder, and adopts sodium hydroxide or sodium silicate mixed solution for aging crystallization after high-temperature roasting, and the kaolin products are mainly converted into A-type zeolite or X-type zeolite, but the adsorption capacity of the kaolin products is smaller than that of LSX zeolite.

Chinese patent CN101524637a also discloses a preparation method of a binder-free adsorbent rich in LSX zeolite, in which NaLSX is used as an active component, kaolin is used as a binder, and the binder is formed and calcined by adding an alkali source and a silicon source (or not), and crystallized by adding sodium hydroxide alkali liquor, so that the kaolin binder is converted into X-type zeolite, but the silica-alumina ratio of the product is relatively high, and the adsorption capacity is affected.

Chinese patent CN1234782A discloses a method for producing LSX zeolite particles with low content of inert binding materials, which uses LSX powder and a zeolitizing binder, and adopts mixed alkali liquor of sodium hydroxide and potassium hydroxide to crystallize for 3-24 hours at 95 ℃ after molding, drying and calcining, thus preparing the binder-free adsorbent, but the zeolite contains more A-type zeolite, and the binder is mainly converted into A-type zeolite.

The LSX mentioned in the prior art is Si/Al=1.0-1.15 low silica alumina ratio X-type zeolite, which is a novel adsorption separation material, and artificially synthesized faujasite (FAU structure type) is generally divided into X-type zeolite and Y-type zeolite according to different silica alumina ratio, wherein the chemical formula of the X-type zeolite is Na ₉₆ (A1 ₉₆ Si ₉₆ O ₃₈₄ )264H ₂ O, where SiO ₂ /Al ₂ O ₃ The molar ratio of (2) to (3.0), and the faujasite with the silicon-aluminum molar ratio of (2.0) to (2.2) is called low-silicon faujasite, also called low-silicon X zeolite LSX.

Related researches find that LSX is an excellent adsorbent, which makes it applicable in the fields of oxygen enrichment, hydrogen storage, gas purification and drying, tail gas treatment, environmental protection, liquid phase adsorption separation of hydrocarbon and the like. The LSX has wide application prospect, and promotes each organization to continuously optimize and improve the production process flow, and reduces the process cost while improving the product quality, thereby meeting the application requirements. If the LSX zeolite with higher adsorption capacity and low silica-alumina ratio is used in the traditional air pre-purification process, the carbon dioxide in the air flow can be reduced to 0.3 microgram/gram under the same condition, and the dynamic water adsorption capacity is improved to 3.5, which is far higher than that of the common 13X molecular sieve.

The LSX zeolite is an air separating agent with wide application, and has the advantages of large nitrogen adsorption capacity, high nitrogen-oxygen separation coefficient, easy desorption and the like. It has wide application in pressure swing adsorption separation and vacuum pressure swing adsorption separation. Baksh et al found that LiX molecular sieves have a much higher adsorption capacity for nitrogen than NaX; when the X zeolite has a lower silica to alumina ratio, more cations may be exchanged, thus exhibiting better adsorption performance. Due to Li ⁺ Minimum radius, maximum charge density compared to Na ⁺ 、Mg ²⁺ And Ag ⁺ The Li-LSX zeolite has better oxygen-enriched performance and nitrogen-oxygen separation capability.

U.S. Pat. Nos. 5268023 and 5962358 disclose that Li-LSX has a larger nitrogen adsorption capacity and oxygen-nitrogen adsorption capacity than ordinary zeolite X, thus exhibiting superior performance in gas separation and thus being widely used in the process fields of PSA pressure swing adsorption separation, VSA vacuum pressure swing adsorption separation, and the like, as disclosed in European patent EP0769320B 1. When LiLSX zeolite is used as pressure swing adsorption air separation oxygen-making adsorbent, the oxygen-nitrogen separation coefficient is 2-3 times that of traditional 5A and 13X, and the large pressure swing adsorption air separation oxygen-making device made of said adsorbent has the adsorbent loading quantity of only 1/5 of 5A molecular sieve, and its oxygen-making power consumption is also lower by above 20%, and said nitrogen-oxygen separation process is disclosed in U.S. patent No. 3140 933 and U.S. patent No. 4859217.

There are many literature reports at home and abroad that LSX zeolite is prepared by synthesizing low-silicon type X zeolite as described in classical technical literature of Guter H.Kuhl. Crystallization of low-silicon faujasite. Zeolite (1987) No.7, p 451) with a feed molar ratio of SiO ₂ /A1 ₂ O ₃ ＝2、(K ₂ O+Na ₂ O)/A1 ₂ O ₃ ＝1、K ₂ O/(K ₂ O+Na ₂ O) =0.2 to 0.25; preparing potassium-sodium type low-silicon X-type zeolite with a silicon-aluminum ratio of 2; the product had a cyclohexane saturation adsorption capacity of 17% at 25℃P/Po=0.21, a water absorption capacity of 30% at 50% relative humidity and a carbon dioxide adsorption capacity of 20% at 250 mmHg.

The foreign patent documents FR2357482, GB1580928 disclose that a mixture comprising sodium hydroxide, potassium hydroxide, sodium aluminate and sodium silicate is crystallized at a temperature below 50 ℃ without stirring or is matured at a temperature below 50 ℃ without stirring and then is subjected to still crystallization at a temperature of 60-100 ℃. To obtain a high crystallinity (. Gtoreq.90%) LSX zeolite, the total synthesis time takes about 50 hours. The preparation of US4859217 also comprises the steps of cryocongealing, re-crystallization after ageing at normal temperature and the like.

A great deal of LSX zeolite synthesis technology is also disclosed in Chinese patent, for example, CN101717094A discloses a sodium type low-silicon X zeolite raw powder and a preparation method thereof, and the product has higher adsorption capacity and adsorption rate to water and carbon dioxide; CN101289197B discloses a preparation method of low silicon X-type zeolite raw powder which can be produced industrially; CN107021505a adopts a seed crystal method to efficiently synthesize LSX-type zeolite with low silica-alumina ratio, which comprises adding LSX seed crystal to obtain LSX-type zeolite; CN110627087a is a low-silicon faujasite raw powder synthesized by a liquid-phase seed crystal method, and can be directly synthesized by conventional raw materials to prepare high-quality LSX zeolite raw powder.

Chinese patent CN111268692A discloses a synthesis method of high-crystallinity LSX zeolite, which replaces NaOH and KOH used in the traditional method by adding NaCl in the process of synthesizing the LSX zeolite, reduces the alkalinity of a synthesis system, fully utilizes the structure guiding action of anions and synthesizes the high-purity LSX zeolite.

Chinese patent CN103055805B discloses a synthesis method of LSX zeolite with mesoporous layer sequence structure used as air separation oxygen-enriched adsorbent, which uses macromolecule with dual properties of oleophylic and hydrophilic as zeolite synthesis template agent, and adopts one-step synthesis process to prepare zeolite with mesoporous structure; chinese patent CN111960430a discloses a synthesis method and application of high crystallinity hierarchical porous LSX zeolite, in which different pore-forming templates are used in hydrothermal synthesis process to prepare hierarchical porous LSX zeolite with controllable pore diameter and surface area, but the application is mainly in the process of glycerol hydrogenation reaction.

Chinese patents CN107352553a and CN101903291a also disclose the preparation of LSX type zeolites with controlled particle size distribution. This is also reported in foreign European patents EP-A-0818418, EP-B1-0922673 and EP-B1-0960854 for the synthesis of faujasite LSX with a predominant particle size distribution.

In order to reduce the cost, chinese patent CN105600803A, CN101704533A also discloses a technology for synthesizing LSX zeolite by using kaolin, which takes inner Mongolia coal-series kaolin as a raw material, and directly synthesizes the low silica alumina ratio X zeolite with high water absorption rate under a hydrothermal condition; chinese patent CN102874837B solves the problem that pure LSX zeolite can be synthesized by adding seed crystals when raw materials come from kaolin by adopting the steps of roasting and activating the kaolin; CN 102826567A discloses a method for preparing lithium type low-silicon aluminum type X zeolite from potassium feldspar, but the preparation of LSX zeolite from natural raw materials tends to result in a decrease in product quality and performance.

In order to make the synthesis process simpler and more convenient, chinese patent CN106698458A and ZL201010023049.0 also disclose that 13X zeolite is used as a raw material, and mixed alkali liquor of sodium hydroxide and potassium hydroxide is used for converting the 13X zeolite into low-silicon zeolite, so that the silicon aluminum of the product is still relatively large, and the oxygen adsorption capacity of the modified material is still relatively low.

In addition to the extensive research on synthesis of low-silica LSX zeolite, a great deal of research work is also faced in terms of ion exchange, such as Chinese patent CN1311713A discloses a low silica to alumina ratio 13X air separation adsorbent which focuses on the influence of the exchange degree of low silica to alumina ratio zeolite on adsorption; chinese patent CN1230452a considers that in KNaLSX, the adsorption amount is maximum when the mass fraction of potassium ions is at the minimum and maximum exchangeable values, and in the conventional synthesis method, the mass fraction of potassium ions is 5-50, so that it is necessary to exchange the potassium ions to meet the requirement as an adsorbent.

U.S. Pat. No. 3,182,62 believes that due to Li ⁺ Minimum radius, maximum charge density compared to Na ⁺ 、Ca ⁺⁺ 、Mg ⁺⁺ The plasma zeolite, liX zeolite has better oxygen-enriched performance, the adsorption capacity to nitrogen is much higher than that of common X-type zeolite, while Li-LSX zeolite has larger nitrogen adsorption capacity and nitrogen-oxygen separation capability than that of common X-type zeolite, and shows superior separation performance. However, practice in the separation process of PSA and VSA has proven that Li is only present in zeolite ⁺ The exchange degree is more than 70 percent, and the nitrogen adsorption capacity is rapidly increased.

U.S. Pat. No. 3,182 also discloses that Li-LSX zeolite is only Li ⁺ At an exchange degree of more than 75%, the nitrogen adsorption capacity thereof increases rapidly, and Li, which plays a key role in nitrogen adsorption and desorption, increases rapidly ⁺ Mainly located at specific positions in the framework structure of FAU-type zeolite, but because of the difficulty in exchanging the cations, a great deal of lithium salt resources with high price are inevitably wasted in the preparation of the Li-LSX zeolite with high exchange degree.

U.S. Pat. No. 3,379 and U.S. Pat. No. 3, 5932509 disclose that Li-LSX zeolite with different exchange degrees can be obtained by a multiple exchange method, and in the process of carrying out lithium ion exchange modification by using KNA-LSX zeolite as a raw material, high-concentration lithium salt aqueous solution is generally used for multiple continuous exchanges to achieve higher exchange degree.

New Li is disclosed in U.S. Pat. No. 3,182 ⁺ Switching method, passing LSX through K ⁺ Exchange to KLSX and go through NH ₄ ⁺ Exchange to NH ₄ LSX, finally NH ₄ LSX Li Process ⁺ Exchange to LiLSX, li utilization greater than 90%, in this preparation method K is carried out with potassium sulphate ⁺ Exchanging at 80deg.C for 1 hr each time for 3 times, NH with ammonium sulfate ₄ ⁺ The process is carried out by repeating the process for 4 times every 2 hours at 80 ℃ for preparing LiLSX zeolite, the period is quite long, the industrial production is difficult, moreover, the pH value of potassium sulfate solution is=3-4, the LSX zeolite skeleton is damaged to a certain extent after being soaked for a long time at 80 ℃, and KLSX is exchanged into NH ₄ LSX also has a certain degree of damage at 80 ℃, and after being finally exchanged into LiLSX, the crystallinity of the LSX obviously decreases, and the adsorption performance and the service life of the LiLSX zeolite are affected.

Domestic Cui Yicheng et al (journal of chemistry 2003,61 (3): 350-353) also reported that lithium modified LSX-type zeolites are useful in>At high exchange degree of 88, nitrogen adsorption capacity and nitrogen-oxygen separation coefficient representing air separation performance are obviously improved, and the exchange degree of lithium ions is researched to reach more than 98%. Guo Daidan et al in their studies (ion exchange and adsorption 2002,18 ] &): 516-521) also yields a degree of exchange of about 96%. Liu Zonghui et al (Petroleum journal (Petroleum processing), 2008, 1001-8719 journal: 47-50) repeatedly exchange Li with a high-concentration lithium salt aqueous solution ⁺ The degree of exchange of (2) reaches approximately 100%.

However, the methods all need to consume a large amount of high-concentration exchange liquid, and have the advantages of long exchange time, multiple times, low exchange efficiency, serious waste, complex production process, high cost and adverse industrial production. Therefore, in the case where the price of Li salt is continuously increased and sodium ions are difficult to exchange at individual positions in the LSX zeolite framework, how to obtain a higher ion exchange degree with low production cost and reasonable process conditions is one of the research focuses in the art.

Also disclosed in chinese patent CN101289196a is a process for preparation having substantially the same processing steps, first subjecting LSX to K ⁺ Multiple replacement, reuse of NH ₄ ⁺ Multiple replacement of the solution, followed by Li with 1-10 wt% LiOH solution ⁺ And (3) exchanging, and introducing air in a proper amount to finally obtain the LiLSX zeolite with high crystallinity. In the Li modified X molecular sieve and the preparation method thereof disclosed in the Chinese patent ZL201110305323.8, X zeolite raw powder is exchanged with ammonium salt, then lithium salt solution is soaked on zeolite by adopting a soaking method, and LiX is obtained by drying and roasting, but the Li modified X molecular sieve still belongs to X zeolite, and has poorer adsorption performance.

In chinese patent CN101125664A, CN100556808C, ZL200710121786.2, an ion exchange method for preparing lithium-type low-silicon aluminum X-type zeolite is disclosed, first, through lithium ion aqueous solution exchange, sodium-type low-silicon aluminum X-type zeolite has a certain lithium ion exchange degree, and then, the lithium-type low-silicon aluminum X-type zeolite is obtained by using a solid phase exchange method, so that the final lithium ion exchange degree is greater than 96%, but the oxygen adsorption performance is poor.

In the report of preparing zeolite into adsorbent, chinese patent CN101766987B discloses a lithium-containing modified low-silicon aluminum X-type zeolite adsorbent and a preparation method thereof, which is characterized in that zeolite raw powder is subjected to one-to-one baking, two-to-two baking and three-to-one lithium modification to obtain Li-LSX zeolite raw powder, and then the Li-LSX zeolite raw powder is mixed with a binder and a forming additive to form a product, wherein the exchange baking modification process improves the stability of LSX zeolite framework, reduces the damage of subsequent treatment process to the LSX zeolite framework, and obtains Li ⁺ LSX zeolite with exchange degree above 95%.

In chinese patent CN101380565a, an ion exchange method on an adsorbent is disclosed, firstly, faujasite zeolite and kaolin binder are molded and calcined, then exchanged with flowing lithium ion exchange liquid in a multistage series exchange column, and dried and activated to obtain the adsorbent containing low-silicon X zeolite with high lithium exchange degree.

With the rapid development of the lithium ion battery energy storage industry, the demand of lithium is continuously increased, the consumption is gradually increased, the reserve is gradually reduced, the price is steadily increased, and the trend is maintained in the foreseeable future. Thus, li is partially replaced by a large amount of other ions of low cost, such as alkaline earth, rare earth cations ⁺ There is a certain interest in developing a zeolite adsorbent for air separation that is relatively low in lithium content.

Use of alkaline earth metal ions Sr in U.S. Pat. No. 3,182 ²⁺ Modifying Ca-LSX zeolite to obtain Ca ²⁺ Exchange degree 5% -45% and Sr ²⁺ (Ca, sr) -LSX zeolite with 60-95% exchange degree, and the nitrogen adsorption capacity of the LSX zeolite can be improved by introducing alkaline earth metal; chinese patent CN108862303A also discloses an alkaline earth cation Sr-LSX zeolite, a preparation method and application thereof.

Domestic Guan Lili et al (Acta Phys. -Chim. Sin., "2002, 18:998-1004) was prepared by Ca on Na-LSX zeolite ²⁺ Exchange, the results show that with Ca ²⁺ The adsorption amount of the prepared (Ca, na) -LSX zeolite to nitrogen is in a linear increasing trend, and Ca at different positions in the zeolite framework ²⁺ The influence on the nitrogen adsorption performance is not obvious.

Further ion exchange of Na-LSX zeolite with alkaline earth cations such as magnesium, calcium, strontium and barium is also performed in U.S. patent USP4481081, and the results show that although these cations can improve the adsorption performance to nitrogen, compared with the zeolite such as Li-LSX and Ag-LSX, alkaline earth metal type LSX zeolite has a certain limitation on practical application because it is difficult to desorb nitrogen, thereby increasing energy consumption in the air separation process.

Hutson et al (AIChE Journal, 1999,45 (4): 724-734) prepared by incorporating small amounts of Ag into Li-LSX zeolite ⁺ The (Li, ag) -LSX zeolite is obtained, and the result shows that the zeolite has higher selectivity under high pressure and lower selectivity under low pressure, and the silver salt has higher price and complex exchange process, so that the zeolite is difficult to realize industrial production and industrial application in practice.

Chinese patent CN103549150A, CN107486146B and CN108854947A both disclose the preparation method and application of mixed cationic LiCa-LSX and AgCa-LSX zeolite, respectively, and it is considered that the mixed cationic zeolite can be used as selective adsorbent for nitrogen and oxygen in PSA/VPSA oxygen production process, reducing lithium salt consumption, simplifying process, and improving N of whole sample ₂ The adsorption capacity, and also overcomes the problems that sodium ions are difficult to exchange at individual positions in the Na-LSX zeolite framework, the price of lithium salt is continuously increased, and the like.

However, even though all nitrogen is adsorbed by the zeolite, the adsorption isotherms of the prior art for oxygen and argon in the air are nearly identical, resulting in a substantial lack of selectivity for oxygen and argon, and the separated oxygen-enriched product gas also contains about 5% argon, making it difficult to produce oxygen concentrations greater than 95% by pressure swing adsorption using nitrogen adsorbents. For this reason, in recent years, research has been focused on improving the adsorption capacity of an adsorbent material for oxygen and the adsorption separation selectivity of oxygen/argon, and it is desired to better produce high purity oxygen, such as CN201930684U, by changing the separation adsorption mode, using an oxygen adsorbent instead of the conventional nitrogen adsorbent; along with the demand of oxygen in the medical field after new coronary epidemic situation, the application of the oxygen is emphasized.

Chinese patent CN1071592C reports an oxygen selective adsorbent capable of separating oxygen from a gas mixture, which comprises a high surface area matrix supporting a complex of uniformly spaced transition elements, an oxygen adsorption capacity of greater than 0.3 mmol/g and an oxygen absorption rate of greater than 0.3 mmol/g per minute, and which can produce oxygen with a purity of greater than 99% by pressure swing adsorption; however, such transition element absorbents are difficult to manufacture, are expensive, are sensitive to trace impurities in the gas, and are difficult to apply in practice.

The prior art which is relatively similar to the invention is a Ce-LiX high-performance oxygen adsorption material disclosed in China patent CN103933933A and a preparation method thereof, wherein the oxygen adsorption amount is 10-15 ml/g. The lithium exchange degree is not high, and the composition and the stable control are not easy to adjust because of the ion competition adsorption process in the hydrothermal exchange process of different ions; in addition, the repeated acid exchange and roasting processes can damage the structure of zeolite and increase the silicon-aluminum ratio, and the utilization rate of lithium ions is low.

The research breakthrough direction in the field is gradually focused on how to improve the utilization rate of Li ions under the trend that the price of lithium salt is continuously high so as to save the production cost; how to increase Li under the premise of ensuring that the lattice structure of the LSX zeolite is not destroyed and the silicon-aluminum ratio is not increased ⁺ To fully exert the superior performance of the Li-LSX zeolite adsorbent in the air adsorption separation process; in addition, how to modify and improve the zeolite adsorption separation characteristics to provide oxygen/argon adsorption separation capability and the like.

Accordingly, although a great deal of prior art has been disclosed in the art relating to the preparation of Li-LSX zeolite, there remains a need in the art to continuously improve the performance, characteristics and preparation techniques of LSX zeolite in terms of improving adsorption capacity, separation selectivity, desorption performance, zeolite structural stability and service life; in addition, the preparation process is optimized continuously according to the environmental protection requirement, so that the preparation process is more efficient, low in consumption and environment-friendly.

Disclosure of Invention

Aiming at the characteristics of the prior art in the preparation method and the product performance, the invention aims to provide an improved preparation technology, a rare earth-containing Li-LSX zeolite product with improved oxygen adsorption performance and an application method.

The invention provides a preparation method of rare earth-containing Li-LSX zeolite, which comprises the following preparation steps:

(1) According to M ₂ O/SiO ₂ =1 to 1.5 (alkali metal M is Na and/or K), siO ₂ /A1 ₂ O ₃ ＝2.5～5、H ₂ O/SiO ₂ The molar ratio of the silicon source, the aluminum source and the caustic alkali is 45-50, and the silicon source, the aluminum source and the caustic alkali are added, mixed and stirred and crystallized for 5-10 hours at the temperature of 80-100 ℃;

(2) After filtration, the product is exchanged for 1 to 2 times by rare earth salt solution, and is baked for 0.5 to 3 hours at 350 to 550 ℃ after one exchange;

(3) After grinding the product, adding silicon source, aluminum source and caustic alkali in a mass ratio of 40-95 wt% of the total dry basis, and making the total molar ratio of the materials be M ₂ O/SiO ₂ =3.5 to 4 (molar ratio Na/K in alkali metal M2.5 to 3.5), siO ₂ /A1 ₂ O ₃ ＝1.5～2、H ₂ O/SiO ₂ 70-75, ageing for 1-3 days after uniformly mixing and stirring, and recrystallizing at 60-80 ℃ for 10-25 hours;

(4) After filtering the product, exchanging 1-5 times by ammonium salt solution, filtering, then, introducing air, exchanging 2-5 times by lithium compound solution, and roasting 1-3 times between two adjacent lithium ion exchanges at 300-430 ℃/0.5-3 hours.

The content and operation of zeolite synthesis techniques and aging and hydrothermal crystallization processes are well known to those of ordinary skill in the art and routinely practiced, and knowledge of such aspects is well known from many technical monographs published in the art, such as "Breck, d.w." Zeolite Molecular Sieves ", wiley, new York, 1974.

The invention prepares a framework SiO containing rare earth Li-LSX zeolite products ₂ /Al ₂ O ₃ The molar ratio is 1.9-2.3, the BET specific surface area is 450-700 m ² Gram/g, saturated Water absorption>30wt%, cyclohexane saturated adsorption quantity>18wt% of lithium oxide and 0.2wt% to 10wt% of rare earth oxide.

Those skilled in the art will readily appreciate that the present invention is well defined and limited by the foregoing description of the features of the invention, namely, the preparation process, the compositional range of the product elements, structural features, and performance features; at the same time, the most important content and characteristics in the preparation process of the invention are defined and limited; these are all features and contents that are quite different from the prior art and are also difficult to obtain and reference directly from the teaching of the prior art.

The preparation method of the rare earth-containing Li-LSX zeolite is characterized in that the silicon source is one or more selected from water glass, silica sol, silica gel, diatomite and silica-aluminum gel, and the water glass is preferred due to the factors of low cost, convenience and easy availability; these silicon source materials are commercially available for convenience.

The preparation method of the rare earth-containing Li-LSX zeolite is characterized in that the aluminum source is selected from one or more of sodium aluminate, aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum oxide, aluminum hydroxide, aluminum sol, aluminum gel and silicon-aluminum gel, and sodium aluminate is preferred due to the factors of low cost, convenience and easy availability; these aluminum source materials are readily available by commercial procurement.

The preparation method of the rare earth-containing Li-LSX zeolite is characterized in that the metal element M is selected from sodium and potassium, and the corresponding caustic alkali is selected from sodium hydroxide and potassium hydroxide; in the first hydrothermal crystallization process, sodium hydroxide is preferable; these caustic bases are conveniently available in a commercially available manner.

LSX is a low silica alumina ratio X-type zeolite with a silica alumina ratio of 1.0-1.1, and the unit cell structure is four-membered or six-membered ring formed by connecting aluminum oxide tetrahedron and silicon oxide tetrahedron through oxygen bridge. The multiple rings are recombined to form a hexagonal cylinder cage and a sodalite cage, thereby forming the octahedral zeolite cage. The octahedral zeolite cages are mutually communicated through a twelve-membered ring to form a main pore canal of the LSX zeolite, and the pore diameter of the octahedral zeolite cages is 0.9-l.0 nanometers; information and knowledge concerning zeolite framework structure, pore channels may be obtained by reference to the zeolite monographs or other zeolite works described above, and the like.

The preparation method of the rare earth-containing Li-LSX zeolite is characterized in that the rare earth salt solution is subjected to ion exchange, preferably, the filtered primary crystallization product Na-LSX zeolite is subjected to hydrothermal exchange for 2 times according to the liquid/solid mass ratio of 5-20 and 75-95 ℃/1-2 hours, and is baked for 1-2 hours at 450-500 ℃ after one exchange, so that rare earth ions are promoted to migrate from an supercage to a sodalite cage, and the method is shown in figure 2.

The preparation method of the rare earth-containing Li-LSX zeolite is characterized in that rare earth elements in a zeolite framework are loaded in a manner of replacing alkali metal ions such as sodium ions and potassium ions in the zeolite framework by ion hydrothermal exchange; and through exchange and migration after roasting, the zeolite exists in a hexagonal column cage of the silicon-aluminum zeolite in an ionic form, so that the aim of stabilizing the zeolite structure and improving the stability is fulfilled.

The invention synthesizes rare earth-containing LSX zeolite with more stable structure through a hydrothermal recrystallization process, and the adopted secondary hydrothermal treatment process is more beneficial to forming high crystallinity and complete structure in the process of synthesizing and preparing rare earth-lithium composite metal cation-containing zeolite, avoids the generation of impurity phases and the mutual competitive interference in the hydrothermal exchange process of the composite metal cation, is beneficial to the adjustment of composition and performance, and the related processes and contents are not mentioned and disclosed in the prior art, and are difficult to obtain enlightenment and reference through experience.

The preparation method of the rare earth-containing Li-LSX zeolite is characterized in that the rare earth elements are selected from rare earth elements such as lanthanum, cerium, praseodymium, neodymium and the like and mixed rare earth, preferably cerium, and the rare earth-containing Li-LSX zeolite has better oxygen adsorption performance and oxygen and argon separation effect, and the adsorption characteristics and performance can be obviously changed by the method; these rare earth element compounds are readily available by commercial procurement.

Due to Li ⁺ Small radius, extremely high hydration capacity, usually with tetrahydrated ions of Li (H) ₂ O) ₄ ⁺ Cation exchange with Kna-LSX zeolite; the LSX zeolite framework comprises a supercage and a sodalite cage, and cations in the framework are positioned in S in the supercage _III 、S _II Position and S near both sides of sodalite cage _I S with cage center _I Bits.

Referring to the accompanying drawings of the specification 2 to 3, the tetrahydrate ion Li (H ₂ O) ₄ ⁺ The exchange LSX zeolite cations were:

first, S in super cage is exchanged _III 、S _II The positive ions with positions and parts close to SI' positions on two sides of the sodalite cage account for about 80 percent of the total positive ions, and the positive ions are convenient for Li (H) due to larger super cage radius ₂ O) ₄ ⁺ And K is equal to ⁺ 、Na ⁺ The diffusion exchange of the lithium ion can be basically completed by one-step exchange of aqueous solution under milder conditions, and the lithium ion utilization rate is high.

Next, S of the exchange portion near both sides of the sodalite cage _I Center S of' position and hexagonal column cage _I The cations in the positions account for about 20% of the total cations. Due to Li ⁺ The radius after hydration is larger (0.382 nanometers), and the six-membered ring (0.25 to 0.26 nanometers) of the sodalite cage cannot pass through and must pass through the S outside the sodalite cage _I Li (H) ₂ O) ₄ ⁺ Dissociation into Li ⁺ After that, can exchange S _I Cation at the position, li (H) ₂ O) ₄ ⁺ Is a critical control step of the exchange process.

Due to the water solution exchange characteristics and the protection of the LSX zeolite framework, the exchange system temperature and severity should be as low as possible, such that Li (H ₂ O) ₄ ⁺ The hydrolysis process is very slow, and ion migration is difficult to carry out, so that the high exchange degree can be achieved only by repeated high-temperature and multiple exchanges for a long time, the utilization rate of lithium ions is very low, and the zeolite framework is damaged to different degrees, thereby belonging to the field ofDifficulties in LiLSX preparation.

The LiKNA-LSX zeolite after the primary exchange is roasted to promote Li (H) ₂ O) ₄ ⁺ Hydrolysis of (2) and Li ⁺ With the center S of the hexagonal column cage _I Exchange of the cation at the position and also promote S which is difficult to exchange at two side parts of the sodalite cage _I The cation at the' position and the cation exchanged from the center of the hexagonal column cage migrate to the super cage S which is easy to exchange in the aqueous solution _III 、S _II The position provides favorable conditions for the next step of water solution exchange; and then high exchange degree is achieved through multiple exchanges and roasting. However, the calcination process itself is liable to cause damage to the zeolite framework, and particularly, the LSX-type zeolite having a low silica-alumina ratio is more serious. Accordingly, the present invention addresses these problems with the preparation method described above and some more specific steps and matters as follows.

The preparation process of RE-containing Li-LSX zeolite features that the ammonium salt solution is ion exchanged in the hydrothermal condition of liquid/solid mass ratio of 5-20 and 75-95 deg.c/1-2 hr and ammonia water to control the pH value of the slurry to 8-9 for 1-5 times.

The preparation method of the rare earth-containing Li-LSX zeolite is characterized in that the ammonium salt solution is selected from ammonium sulfate solution, ammonium nitrate solution, ammonium chloride solution, ammonium oxalate solution, ammonium phosphate solution, ammonium acetate solution, ammonium carbonate solution and acid absorption recovery solution for ammonia gas, and the ammonium salt, the ammonia and the acid can be obtained commercially.

The preparation method of the rare earth-containing Li-LSX zeolite is characterized in that the recovery liquid is ammonia gas which escapes from the exchange process of the lithium compound solution under the ventilation condition, the ammonia gas is absorbed and neutralized by an acid solution to generate a recovery ammonium salt solution, and the recovery ammonium salt solution is recycled to the exchange process of the ammonium salt solution of the crystallized product sodium-type rare earth-containing LSX; preferably, the ammonium sulfate solution with lower price and the dilute sulfuric acid are adopted as exchange liquid, and the dilute sulfuric acid is used for absorbing and recycling ammonia gas to form ammonium sulfate recycling liquid; ammonium sulfate, sulfuric acid are commercially available.

The preparation method of the rare earth-containing Li-LSX zeolite is characterized in that the lithium compound solution is selected from lithium nitrate solution, lithium sulfate solution, lithium chloride solution, lithium phosphate solution, lithium carbonate solution, lithium oxalate solution, lithium fluoride solution, lithium hydroxide solution and recovery solution of lithium-containing compound; preferably a recovery solution selected from lithium nitrate, lithium chloride, lithium hydroxide, and lithium-containing compounds; most preferred are recovery solutions of lithium hydroxide and lithium-containing compounds to reduce cost and control the extent of damage to the zeolite framework.

The invention provides a preparation method of rare earth-containing Li-LSX zeolite, which is characterized in that the lithium ion exchange is to make the synthesized intermediate product after ammonium exchange contain rare earth NH ₄ -slurry of LSX zeolite, under the preferred conditions, controlling the pH value of the slurry to be 10-12, introducing air into the slurry, and carrying out hydrothermal ion exchange for 3-4 times by using lithium-containing compound solution under the conditions of 40-95 ℃/0.5-2 hours; between the two hydrothermal ion exchanges, roasting is carried out for 1-2 times at a time interval of 350-430 ℃/0.5-2 hours so as to promote the migration of lithium ions.

Under the most preferred conditions, the intermediate product obtained after the ammonium sulfate exchange by the lithium hydroxide solution contains rare earth NH ₄ The LSX zeolite is subjected to lithium ion exchange, the pH value of the slurry is controlled to be 11.5 under the condition that air is introduced into the slurry, the hydrothermal ion exchange is carried out for 2 times at the speed of 50-85 ℃ for 1-1.5 hours, the slurry is roasted for 1 time at the time interval of 360-375 ℃ for 1-1.5 hours in the middle of the two hydrothermal ion exchanges, the ammonia gas escaping along with the air is absorbed by dilute sulfuric acid, and the filtrate containing lithium ions and the ammonium sulfate-containing recovery liquid are returned to the lithium exchange liquid and the ammonium salt exchange liquid for recycling.

According to the preparation method, the invention also provides a rare earth-containing Li-LSX zeolite, which is prepared by dissolving the compound involved in the preparation process of the zeolite, stirring and mixing, hydrothermal crystallization, ion-water heat exchange, filtering, absorption, recycling, drying, roasting and other chemical operation processes, and dissolving the compound by using nitric acid, oxalic acid, acetic acid and other acid solutions when the compound is prepared into a solution, wherein the acids can be conveniently obtained in a commercial purchasing mode, are well known and mastered by those of ordinary skill in the art, and are applied to daily scientific research and production work.

The invention also provides an adsorbent applied to the oxygen production adsorption separation and purification process, which is characterized in that the rare earth-containing Li-LSX zeolite provided by the invention is mixed with 5-25 wt% of binder and 1-5 wt% of forming auxiliary agent according to the mass ratio of 75-95 wt% of the total amount on a dry basis to form spherical or strip-shaped particles with the crushing strength of more than 25 newtons/particle; preferably the adsorbent particles have a crush strength >40 newtons per particle; the adsorbent is formed, dried and baked at 250-550 deg.c to form solid adsorbent particle.

The adsorbent applied to the oxygen production adsorption separation and purification process is characterized in that the binder is one or more selected from attapulgite, sheep liver soil, kaolin, swelling upper material, montmorillonite, alumina sol and silica sol; the preferred amount is 10 to 20wt% on a dry basis. These binders are one of the common binders for construction materials, which are part of the composition of the binder and the carrier in the adsorbent, and which can increase the binding strength of the adsorbent and improve the mechanical properties, and these materials are commercially available.

The rare earth-containing Li-LSX zeolite adsorbent is characterized in that the forming auxiliary agent is selected from sesbania powder, methyl cellulose, sodium carboxymethyl cellulose and starch, and is used as a pore-forming agent and a lubricant, the dosage of the pore-forming agent and the lubricant is 1-5wt%, and the auxiliary agent in the forming preparation can be obtained in a commercial mode.

Before the adsorbent is molded and prepared, raw material powder is generally subjected to chemical operations such as grinding and sieving with 40-200 meshes, sieving, mixing, acidification, kneading, extruding, rolling ball/extruding, drying, roasting and the like which are well known to those of ordinary skill in the art, and is used daily; screening and ball and strand molding devices are commercially available.

The invention also provides an air adsorption separation and oxygen adsorption purification method, which comprises the step of applying the adsorbent prepared by the method in the air adsorption separation and oxygen purification process; the isolated transformation and purification procedures involved are well known to those of ordinary skill in the art and are employed in routine scientific research and production.

Compared with the prior art, the invention has the technical effects that: in the preparation process, rare earth ions can more effectively stabilize the framework structure of zeolite only by migrating from the super cage to the sodalite cage and the hexagonal column cage, and the process is difficult to carry out in the preparation process of the zeolite with low silicon-aluminum ratio; the exchange and the counter exchange processes of different ions have mutual competitive interference and influence, so that the composition ratio of the exchange processes of different ions is not easy to control and adjust, the exchange degree of each ion is difficult to master and control and avoid mutual interference, and the problems of dissociation and migration of hydrated ions are promoted by roasting, and the framework collapse of zeolite with low silicon-aluminum ratio is easy to bring.

The preparation method of the invention effectively solves the problem of mutual competition interference in the ion exchange process, can very effectively and conveniently align and control the cationic composition on the zeolite framework, and plays roles of respectively supporting the zeolite framework structure by the modified metals and improving the adsorption performance.

The method of the invention has the advantages that the operation flexibility of the synthesis and ion exchange process is enhanced, the condition control requirement of each working section is reduced, and the problems that the synthesis and exchange conditions are required to be strictly controlled in the traditional process and the requirement on deviation control is particularly high in the process of amplifying production are solved.

The RE of the rare earth-containing Li-LSX zeolite provided by the technical proposal of the invention ³⁺ Better migration effect of exchange position, li ⁺ The ion exchange degree is high, the final crystallization degree of zeolite is more complete, and the preparation process is relatively simple and easy to control. And the recycling degree of the working solution is high, and the consumption and the cost are reduced.

The invention has the beneficial technical effects that the oxygen-enriched adsorbent prepared by the rare earth-containing Li-LSX zeolite has larger adsorption capacity and higher adsorption rate on oxygen, has better capability of adsorbing and separating oxygen and nitrogen in air, is more superior as raw powder of the adsorbent for preparing the LiLSX zeolite for air separation oxygen or purifying, is particularly suitable for pressure swing adsorption separation process of industrial air, and has better stability and service life due to more stable modified zeolite framework.

Additional features and advantages of the invention will be set forth in the detailed description which follows. The following examples are provided to further illustrate the contents and effects of the present invention and are illustrative of the embodiments of the present invention, but are not to be construed as limiting the broad interpretation of the invention.

Drawings

FIG. 1 is an X-ray diffraction pattern of example 1 of a rare earth-containing Li-LSX zeolite of the invention.

Figure 2 is a schematic representation of the unit cell and extra-framework cation positions in LSX zeolite of faujasite structure.

FIG. 3 is a nitrogen adsorption isotherm at 30℃for the rare earth-containing Li-LSX of the present invention and a comparative LSX zeolite.

The figures are illustrated in the order 1-comparative example 3, 2-examples 1, 3-examples 2, 4-examples 3, 5-comparative examples 1, 6-comparative example 2.

Detailed Description

The following describes specific embodiments of a rare earth-containing Li-LSX zeolite and a preparation method thereof with reference to the accompanying drawings. As shown in figures 2-3, RE with strong hydration capability is used in the respective exchange process of rare earth ions and lithium ions ³⁺ 、Li ⁺ Ions are difficult to pass and migrate in a six-ring window with smaller radius due to larger radius of hydrated examples, and S in the super cage is exchanged firstly _III 、S _II Position, and Na partially near SI' positions on both sides of sodalite cage (beta cage) ⁺ 、K ⁺ And (3) cations. Because the RE is conveniently hydrated by being carried out in a super cage with larger radius ³⁺ 、Li ⁺ Ions and K ⁺ 、Na ⁺ And the diffusion exchange of the (C) is high in exchange efficiency and utilization rate.

The damage degree to the zeolite framework with low silicon-aluminum ratio is reduced by controlling the conditions of the hydrothermal exchange and the thermal roasting treatment, so that S outside the sodalite cage is promoted _I Dissociation of hydrated ions at the' position into RE of smaller radius ³⁺ 、Li ⁺ After the cation, the cation is easier to pass through the six-membered ring of the sodalite cage, and the S near two sides of the sodalite cage is partially replaced by a plurality of exchange steps _I Position and hexagonal column cage center S _I Na of the position ⁺ 、K ⁺ A cation; at the same time promote S which is difficult to exchange at two side parts of sodalite cage _I Cation at position and Na exchanged from center of hexagonal column cage ⁺ 、K ⁺ Cations migrate to the supercage S which is easily exchanged in aqueous solution _III 、S _II The position is convenient for the next replacement.

Ion exchange in this section has an important influence on zeolite framework stability and adsorption separation performance of zeolite; the combination of the secondary crystallization step improves the mutual competitive interference and the damage to the framework in the ion exchange process, ensures that the composition and the performance of the zeolite are more convenient to adjust and control, and repairs the damage caused by the dealumination, the collapse and the like of the framework.

In the examples of the preparation method and the application of the rare earth-containing Li-LSX zeolite provided by the invention, the phases, the crystallinity, the unit cell and the framework silicon-aluminum ratio of the components in the zeolite and the adsorbent are analyzed and measured by an X-ray diffractometer; the element composition content is measured by an X-ray fluorescence method; measuring the specific surface area of the catalyst by adopting a low-temperature nitrogen adsorption method; measuring the mechanical strength of the adsorbent by using a pressure measuring instrument; the adsorption amount was measured by a static capacity method.

Other analytical tests can be found in (national standard for Petroleum and Petroleum products testing methods, chinese Standard Press publication 1989) and (petrochemical analytical method (RIPP test method), scientific Press publication 1990).

Example 1

This example is intended to illustrate the implementation of the preparation process of the present invention and the rare earth-containing Li-LSX zeolite prepared.

Into 0.6 liter of deionized water, 0.4 liter of water glass (technical grade, siO) was added with stirring ₂ =250 g/L, modulus 3.2, le shan division, inc. Of run and catalyst, and 0.5L of sodium metaaluminate with low basicity (technical grade, al ₂ O ₃ =100 g/l, na ₂ O=150 g/l, the same as above), after stirring uniformlyStatic crystallization was carried out at 95℃for 6 hours.

After filtration, a 4wt% cerium nitrate solution (technical grade cerium nitrate formulation, supra) was used at a liquid/solid ratio of 5:1 for 1 hour at 85 ℃, drying, roasting for 1 hour at 450 ℃, exchanging once under the same condition, and collecting filtrate for the next recycling.

After filtration, the mixture was milled for 2 hours in a mini-mixer mill after mixing with 800 g of zirconium beads having a diameter of 1 mm at a rotation speed of 80 rpm, after sieving out the zirconium beads, 2 liters of water glass (as above) and 5 liters of sodium metaaluminate having a low basicity (as above), 2.5 kg of 30% by weight sodium hydroxide solution (technical grade, as above) and 3 kg of 30% by weight potassium hydroxide solution (technical grade, as above) were added, and after stirring uniformly, they were aged at room temperature for 2 days and subjected to static crystallization at 70℃for 16 hours.

After filtration and water washing, the product was washed with 4wt% ammonium sulfate solution (technical grade, same as above) in a liquid to solid mass ratio of 5: exchanging at 1, 75 ℃ for 0.5 hour, adding ammonia water to control the pH value of the slurry to be about 8.5, repeating for 4 times, filtering, and recovering the filtrate.

The filtered product was prepared with 1wt% lithium hydroxide solution (technical grade lithium hydroxide, same as above) at 10 liquid/solid: 1, and exchanging for 2 hours at 50 ℃ under the condition of introducing air, controlling the pH value of the slurry to be about 11.5 by adding ammonia water, and absorbing ammonia gas escaping with the air by 5wt% of dilute sulfuric acid (prepared by industrial grade sulfuric acid, the same as the above) to form an ammonium salt recovery liquid. Drying, roasting at 375 deg.c for 1 hr, adding 1wt% concentration lithium hydroxide solution, introducing air to control the pH value of the slurry to 11.5, exchange at 75 deg.c for 2 hr, recovering ammonia gas, filtering and drying to obtain RE-containing Li-LSX zeolite of example 1.

Comparative example 1

This comparative example is used to illustrate the preparation of a low silica to alumina ratio LiRE-LSX zeolite according to the prior art process.

Potassium sodium low silica type X zeolite having a silica to alumina ratio of 2 was prepared as described in the literature of Gunter H.Kuhl. Crystallization of low-silica faujasite. Zeolite (1987) No.7, p 451).

Rare earth-containing LiRE-LSX zeolite was prepared as described in USP 5916836.

Comparative example 2

This comparative example is intended to illustrate the preparation of a low silica to alumina ratio Ce-LiX zeolite according to a representative procedure in the prior art.

Potassium sodium low silica type X zeolite having a silica to alumina ratio of 2 was prepared as described in the literature Gunter H.Kuhl. Crystallization of low-silica faujasite. Zeolite (1987) No.7, p 451.

The product after washing and filtering is put into a vacuum drying oven, pretreated for 2 hours at 120 ℃, and then is mixed with lithium chloride solution with the concentration of 2 weight percent according to the liquid-solid ratio of 20:1 ml/g, placing in a stirring tank, performing ion exchange reaction at 75 ℃ for 3 hours, filtering and washing with deionized water, and drying the obtained sample at room temperature to obtain the intermediate product Li-LSX zeolite.

The intermediate Li-LSX zeolite was mixed with a 1.5wt% cerium chloride solution at a liquid to solid ratio of 50:1 ml/g, and placing in a stirring tank, performing ion exchange reaction at 55 ℃ for 2 hours, filtering and washing with deionized water. And drying the washed sample at room temperature, putting the dried sample into a muffle furnace, slowly heating to 350 ℃, keeping the temperature for 3 hours, and cooling to obtain the Ce-LiX zeolite.

Comparative example 3

This comparative example is intended to illustrate the preparation of a low silica to alumina ratio Li-LSX zeolite in accordance with a more typical prior art process.

And according to Li of USP5916836 ⁺ Ion exchange method using K ⁺ 、NH ₄ ⁺ 、Li ⁺ Is used for preparing the crystallized product KNA-LSX zeolite into Li ⁺ Li-LSX zeolite with high ion exchange degree.

Example 2

This example illustrates the convenient and controllable increase of rare earth content of rare earth-containing Li-LSX zeolite at high lithium ion exchange using the process of the present invention.

Adding 0.7 liter of water glass (the same as above) and 1 liter of low-alkalinity sodium metaaluminate (the same as above) into 1.5 liter of deionized water, uniformly mixing, adding at room temperature, mixing and stirring, and carrying out static crystallization at 92 ℃ for 8 hours.

After filtration, the filtrate containing cerium nitrate was recovered by liquid/solid ratio of 20:1 for 2 hours at 80 ℃, drying, roasting at 400 ℃ for 2 hours, exchanging with 4wt% cerium nitrate solution (same as above) for 2 hours at 80 ℃, and recovering rare earth exchanged filtrate.

After filtration, the mixture was milled in a small stirred mill with 1.5 kg of zirconium beads of 1 mm diameter for 2 hours at a rotation speed of 75 revolutions per minute, after which the zirconium beads were removed by sieving, 1 liter of water glass (as above) and 2.5 liters of low-alkalinity sodium metaaluminate (as above) were added, and 1.2 kg of 30wt% sodium hydroxide solution (as above) and 1.5 kg of 30wt% potassium hydroxide solution (as above) were added, and after uniform mixing and stirring, they were aged at room temperature for 3 days and then subjected to static crystallization at 70℃for 16 hours.

After filtration, liquid/solid 10:1, carrying out primary exchange and secondary exchange on filtrate after ammonium exchange recovery, and then carrying out liquid/solid 5:1, performing three-phase exchange by using ammonium salt recovery liquid of ammonia gas absorbed by dilute sulfuric acid; finally, according to liquid/solid 5:1, 4wt% ammonium sulfate solution is used for 4 th exchange, the exchange temperature is 70 ℃, the exchange time is 1 hour each time, the pH value of slurry in the exchange process is controlled to be about 8-9, and filtrate after ammonium exchange is recovered for the next use.

After filtration, the filtrate was exchanged with recovered lithium salt at liquid/solid 10:1 for 2 hours at 80 ℃, repeating the process, roasting for 1 hour at 380 ℃ after drying, exchanging for 2 hours under the same condition of 1wt% lithium hydroxide solution, introducing air in the exchanging process, absorbing ammonia gas escaping with the air by using 5wt% dilute sulfuric acid or recovered ammonium salt filtrate, and controlling the pH value of slurry in the exchanging process to be about 11-12; and (5) filtering and drying. Li-LSX zeolite with increased rare earth content of example 2 was prepared.

Example 3

This example is intended to illustrate the process of the present invention for the convenient and controlled preparation of Li-LSX zeolite with higher rare earth content at high lithium ion exchange.

1.5L of water glass (the same as above) and 2L of low-alkalinity sodium metaaluminate (the same as above) are added into 2.5L of deionized water, uniformly mixed and stirred, and then statically crystallized for 5 hours at 96 ℃.

After filtration, the filtrate was exchanged with recovered cerium ions at a liquid/solid ratio of 10:1 for 1 hour at 90 ℃ and repeating the exchange once, drying and roasting for 1.5 hours at 420 ℃, and then adding 4wt% cerium nitrate solution according to the liquid/solid ratio of 5:1 for 1 hour under the same temperature conditions.

After filtration, the mixture was milled in a small stirred mill with 3 kg of zirconium beads of 1 mm diameter for 2 hours at a rotation speed of 60 rpm, after which 0.8 l of water glass (as above) and 2 l of sodium metaaluminate of low basicity (as above) were added, and 1 kg of 30wt% sodium hydroxide solution (as above) and 1.2 kg of 30wt% potassium hydroxide solution (as above) were added, and after mixing and stirring uniformly, they were aged at room temperature for 2 days and subjected to static crystallization at 70℃for 16 hours.

After filtration, liquid/solid 20:1, carrying out primary exchange on filtrate after ammonium exchange recovery according to the proportion, and then carrying out primary exchange according to the liquid/solid ratio of 10:1, performing secondary exchange and tertiary exchange by using ammonium salt recovery liquid of ammonia gas absorbed by dilute sulfuric acid; finally, according to liquid/solid 5:1, 4wt% ammonium sulfate solution is used for 4 th exchange, the exchange temperature is 75 ℃, the exchange time is 1 hour each time, the pH value of slurry in the exchange process is controlled to be about 8-9, and filtrate after ammonium exchange is recovered for the next use.

After filtration, the filtrate was exchanged with recovered lithium salt at 20 liquid/solid: 1 is exchanged for 2 hours at 80 ℃ and is repeated once; drying and roasting for 2 hours at 365 ℃, and then carrying out liquid/solid 10:1, exchanging for 2 hours at the same temperature by using 1wt% lithium hydroxide solution, introducing air in the exchange process, absorbing ammonia gas escaping with the air by using 5wt% dilute sulfuric acid or recovered ammonium salt filtrate, and controlling the pH value of slurry in the exchange process to be about 11-12; and (5) filtering and drying. Li-LSX zeolite with higher rare earth content of example 3 was prepared.

Example 4

This example is intended to illustrate the process of the present invention and shows the properties of rare earth-containing Li-LSX zeolites of examples 1-3, and LSX zeolites of comparative examples 1-3, prepared in the prior art, as shown in Table 1.

Table 1 physicochemical Properties of the zeolite products of examples 1 to 3 and comparative examples 1 to 3

Project	Example 1	Example 2	Example 3	Comparative example 1	Comparative example 2	Comparative example 3
							CeO ₂ /wt％	1.94	4.09	7.79	2.09	2.82	-
Li ₂ O/wt％	6.96	6.53	6.02	5.95	6.34	7.52
							BET/m ² /g	572	568	565	490	440	585

From the point of view of ion balance, rare earth exists in the zeolite products of the examples and the comparative examples to a certain extent in nonionic morphology deposition phenomenon. Table 2 shows the static saturated adsorption of the rare earth-containing Li-LSX zeolite prepared in the example and the LSX zeolite prepared in the comparative example.

Table 2, adsorption properties of the zeolite products of examples 1 to 3 and comparative examples 1 to 3

/>

Shown in FIG. 3 of the specification are nitrogen adsorption isotherms at 30℃for the LSX zeolites of examples 1-3 and comparative examples 1-3, li ⁺ Has advantages in improving the nitrogen adsorption capacity.

Example 5

This example is intended to illustrate the process of preparing an adsorbent using the method of the present invention and the application to the adsorption purification separation of oxygen.

The LSX zeolite powders of examples 1 to 3 and comparative examples 1 to 3 were kneaded with 1.2wt% sesbania powder, 14.8wt% attapulgite clay in a mass ratio of 84wt% for 0.5 hours with an appropriate amount of deionized water, and the products were extruded in the form of 1.6 mm extrudates. Drying the extruded material at 110 ℃ for 4 hours, and roasting at 480 ℃ for 6 hours; the adsorbents prepared from the LSX zeolites of sample examples 1 to 3 and comparative examples 1 to 3 were obtained and were designated as adsorbents-examples 1 to 3 and adsorbents-comparative examples 1 to 3.

TABLE 3 adsorbents-examples 1 to 3 and adsorbents-comparative examples 1 to 3 strength cases

The oxygen adsorption properties of the adsorbents, examples 1 to 3 and comparative examples 1 to 3, were measured by a static capacity method at 25℃and a pressure of 1atm, as shown in Table 4.

Table 4, adsorbent-oxygen adsorption properties of the zeolite products of examples 1 to 3 and comparative examples 1 to 3

The adsorbents, examples 1 to 3 and comparative examples 1 to 3, were sequentially charged into a small separation experimental apparatus for oxygen and argon, and their adsorption separation performance was tested.

Raw material gas composition: 90% -95% of oxygen, 4% -5% of argon and the balance of nitrogen.

TABLE 5 adsorbents-examples 1 to 3 and adsorbents-comparative examples 1 to 3 argon oxygen separation cases

It should be understood that the above embodiments are merely for illustrating the technical solution of the present invention and not for limiting the same, and that although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A preparation method of rare earth-containing Li-LSX zeolite is characterized in that the preparation steps of the zeolite comprise:

(1) According to M ₂ O/SiO ₂ = 1～1.5、SiO ₂ /A1 ₂ O ₃ =2.5～5、H ₂ O/ SiO ₂ The molar ratio of the aluminum source and the caustic alkali is 45-50, and the silicon source, the aluminum source and the caustic alkali are added, mixed and stirred to 80-100 ^o Crystallizing for 5-10 hours; wherein, the alkali metal M is Na and/or K;

(2) Filtering, exchanging the product with rare-earth salt solution for 1-2 times, and after one exchange, adding the rare-earth salt solution into the solution at 450-550 ^o Roasting the mixture for 0.5 to 3 hours;

(3) After grinding the product, adding silicon source, aluminum source and caustic alkali in a mass ratio of 40-95 wt% of the total dry basis, and making the total molar ratio of the materials be M ₂ O/SiO ₂ = 3.5～4、SiO ₂ /A1 ₂ O ₃ =1.5～2、H ₂ O/SiO ₂ 70 to 75, wherein the molar ratio of Na/K in the alkali metal M is 2.5 to 3.5, and the mixture is aged for 1 to 3 days after being evenly mixed and stirred, and the mixture is aged for 60 to 80 days ^o C, recrystallizing for 10-25 hours;

(4) Filtering the product, exchanging with ammonium salt solution for 1-5 times, filtering, introducing air, exchanging with lithium compound solution for 2-5 times, and exchanging between adjacent lithium ions for 300-430 times ^o Roasting for 1-3 times at the time of C/0.5-3 hours.

2. The process for preparing rare earth-containing Li-LSX zeolite as claimed in claim 1, wherein said zeolite product has a skeleton of SiO ₂ /Al ₂ O ₃ The molar ratio is 1.9-2.3, the BET specific surface area is 450-700 m ² Gram/g, saturated Water absorption>30wt%, cyclohexane saturated adsorption quantity>18 wt% of lithium oxide and 0.2wt% to 10wt% of rare earth oxide.

3. The method for preparing rare earth-containing Li-LSX zeolite according to claim 1, wherein the silicon source is one or more selected from the group consisting of water glass, silica sol, silica gel, diatomaceous earth, and silica-alumina gel, and the aluminum source is one or more selected from the group consisting of sodium aluminate, aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum oxide, aluminum hydroxide, alumina sol, aluminum gel, and silica-alumina gel.

4. The method for preparing rare earth-containing Li-LSX zeolite as in claim 1, wherein the metal element M is sodium and potassium and the rare earth element is cerium.

5. The method for preparing rare earth-containing Li-LSX zeolite according to claim 1, wherein the ammonium salt solution is selected from the group consisting of ammonium sulfate solution, ammonium nitrate solution, ammonium chloride solution, ammonium oxalate solution, ammonium phosphate solution, ammonium acetate solution, ammonium carbonate solution, and acid-absorbed recovery solution of ammonia gas; the lithium compound solution is selected from lithium nitrate solution, lithium sulfate solution, lithium chloride solution, lithium phosphate solution, lithium carbonate solution, lithium oxalate solution, lithium fluoride solution, lithium hydroxide solution, and recovery solution of lithium compound.

6. The process for preparing Li-LSX zeolite containing rare earth as set forth in claim 1, wherein said solution of lithium compound is ion-exchanged by subjecting the slurry of the synthesized and ammonium-exchanged zeolite product to hydrothermal ion exchange for 3-4 times under the condition of introducing air, controlling the pH value of the slurry to 8-9 and between the two hydrothermal ion exchanges to 350-400 ^o And C/treatment conditions of 0.5-2 hours, and roasting for 1-2 times at intervals.

7. The process of preparing RE-containing Li-LSX zeolite as in claim 6, wherein the ion exchange of the solution of lithium compound is to introduce air into the slurry to exchange the ammonium-exchanged intermediate product with lithium hydroxide solution to obtain RE-containing NH ₄ The LSX zeolite is subjected to ion exchange, the escaped ammonia gas is absorbed and recovered by acid solution, the filtrate and the recovery liquid are recycled, and the pH value of the slurry is controlled to be 10-12.

8. The method for preparing rare earth-containing Li-LSX zeolite as defined in claim 7, wherein ammonia gas evolved during the exchange of the lithium compound solution under aeration is absorbed by a dilute sulfuric acid solution, and the ammonium sulfate solution produced by neutralization is recycled to the exchange of the ammonium salt solution of the crystallized product.

9. A rare earth-containing Li-LSX zeolite, characterized in that the zeolite is prepared according to the preparation method of any one of claims 1 to 8.

10. An adsorbent applied to the oxygen-making adsorption separation and purification process is characterized in that the rare earth-containing Li-LSX zeolite of claim 9 is mixed with 5 to 25 weight percent of binder and 1 to 5 weight percent of forming auxiliary agent according to the mass ratio of 75 to 95 weight percent of the total amount on a dry basis to form spherical or bar-shaped particles with the crushing strength of more than 25 newtons/particle.