阅读说明：本技术 一种氮氧分离Li-LSX分子筛的制备方法 (Preparation method of nitrogen-oxygen separation Li-LSX molecular sieve ) 是由 张青 卓润生 刘新生 施宗波 何俊潼 周立旻 于 2021-09-23 设计创作，主要内容包括：本发明属于分子筛合成技术领域,具体涉及一种具有氮氧分离性能的Li-LSX分子筛的制备方法。本发明通过在超高温水热条件下,利用Li～(+)对LSX分子筛进行离子交换会发生质变,即Li～(+)容易进入到分子筛的方钠笼和六方柱笼中,仅需要交换两次就可达到90％以上的交换度。且本发明的方法在较大用量的生产表现出稳定的效果,更符合工业生产的实际情况,实施效果对于工业中的大规模生产具有可重复性。(The invention belongs to the technical field of molecular sieve synthesis, and particularly relates to a preparation method of a Li-LSX molecular sieve with nitrogen-oxygen separation performance. The invention utilizes Li under the condition of ultra-high temperature hydrothermal + Mass change occurs by ion exchange of LSX molecular sieves, i.e. Li + The catalyst can easily enter a sodium squarer cage and a hexagonal column cage of a molecular sieve, and the exchange degree of more than 90 percent can be achieved only by exchanging twice. The method of the invention shows stable effect in production with larger dosage, more accords with the actual situation of industrial production, and has repeatability for large-scale production in industry.)

1. A preparation method of a nitrogen-oxygen separation Li-LSX molecular sieve is characterized by comprising the following steps:

performing ion exchange on a lithium hydroxide aqueous solution and an LSX molecular sieve at the temperature of more than 180 ℃; the number of ion exchange is 2 or more; the product does not need to be roasted.

2. The method for preparing a nitrogen-oxygen separation Li-LSX molecular sieve according to claim 1, wherein the pH of the ion exchange is 7-8.

3. The method for preparing the Li-LSX molecular sieve for separating nitrogen and oxygen as claimed in claim 1, wherein the exchange time is 3-20 h.

4. The method for preparing a Li-LSX molecular sieve for nitrogen and oxygen separation according to claim 1, wherein Li is exchanged for the first time⁺The concentration is 1-1.5mol/L, and Li is exchanged for the second time⁺The concentration is 1.5-3 mol/L; li⁺At a concentration of Na⁺And K⁺1.1-10 times of the sum of the concentrations.

5. The method for preparing a nitrogen-oxygen separation Li-LSX molecular sieve according to claim 1, wherein Li⁺At a concentration of Na⁺And K⁺2-5 times of the sum of the concentrations.

6. The method for preparing a nitrogen-oxygen separation Li-LSX molecular sieve according to claim 1, wherein the first ion exchange of Li⁺The concentration is 1.2 mol/L; second ion exchange of Li⁺The concentration is 2 mol/L.

7. The method of claim 1, wherein the acid used to adjust the pH is selected from hydrochloric acid or acetic acid, and further selected from hydrochloric acid.

8. The method for preparing a nitrogen-oxygen separation Li-LSX molecular sieve as claimed in claim 1, wherein the exchange temperature is 200-220 ℃.

Technical Field

The invention belongs to the technical field of molecular sieve synthesis, and particularly relates to a preparation method of a Li-LSX molecular sieve with nitrogen-oxygen separation performance.

Background

The Li-LSX molecular sieve is a high-efficiency nitrogen-oxygen separation oxygen-making molecular sieve, and Li in the molecular sieve₂The oxygen-nitrogen separation efficiency is determined by the O content. The preparation method of the Li-LSX molecular sieve is mainly characterized in that Li is mixed with LSX⁺Exchanging into Na/K-LSX molecular sieve. The Li-LSX molecular sieve is an X-type molecular sieve, a unit cell of the Li-LSX molecular sieve consists of a supercage, a sodium squaraine and a hexagonal column cage, and hydrated lithium ions have large radius and are difficult to enter the sodium squaraine and the hexagonal column cage, so that the exchange rate of the lithium ions is generally low.

The traditional method combines aqueous solution exchange and solid exchange, firstly, lithium ions are exchanged into an ultra-cage through the aqueous solution exchange, and then the lithium ions are exchanged into a sodium cubic cage and a hexagonal column cage through high-temperature roasting. The current commonly used method is an aqueous solution exchange method, the exchange temperature is usually low, for example, patent CN108675314A discloses a preparation method for industrially producing lithium type molecular sieve with low silica-alumina ratio, the exchange temperature is below 100 ℃, but the exchange process needs to be repeated for several times to obtain satisfactory ion exchange degree, and urea and ammonia water need to be added in the exchange process, which causes environmental pollution. In the literature report, the Li-LSX molecular sieve with high exchange degree can be obtained by 2-4 times of aqueous solution exchange at the temperature of below 100 ℃, and other auxiliary agents are not required to be added. However, the literature tests are laboratory tests, the dosage of the modified LSX molecular sieve is usually below 100g, and although the lithium ion exchange degree of the prepared molecular sieve is higher, the molecular sieve is not judged by a credible industrial performance test. The method is usually large-scale production in actual production, and the purity, the dosage accuracy and the environmental conditions of the method can not meet the laboratory standards, so that the reference of the laboratory effect in the actual production is poor.

Disclosure of Invention

Aiming at the problems in the process, the invention aims to provide the preparation method of the nitrogen-oxygen separation Li-LSX molecular sieve which is suitable for industrial production, has less exchange times and high lithium ion exchange degree.

The inventor finds that the ion exchange efficiency is low when the ion exchange is carried out below 100 ℃ in the actual production process, and the exchange degree of lithium ions in the prepared molecular sieve is not high, because the method is more from laboratory verification, and the small-scale experiment cannot simulate the large-scale production in the actual industrial production and has no repeatability. The inventor surprisingly finds that under the high-temperature hydrothermal condition, lithium ions can easily enter into the supercages of the molecular sieve and can also easily enter into the sodium squaring cages and the hexagonal column cages, so that the exchange efficiency of the lithium ions is greatly improved, and the Li-LSX molecular sieve with high exchange degree can be obtained only by carrying out two times of exchange through strict limitation on the exchange temperature. And the method passes the verification of a middle-sized experiment with the dosage of kilogram level, and compared with the small dosage of a laboratory, the method is more in line with the condition of industrial production.

The invention provides a preparation method of an oxygen-nitrogen separation Li-LSX molecular sieve, which comprises the following steps: performing ion exchange on a lithium hydroxide aqueous solution and an LSX molecular sieve at the temperature of more than 180 ℃; the number of ion exchange is 2 or more; the product does not need to be roasted.

The LSX molecular sieve is NaKLSX molecular sieve, and the LSX molecular sieve is composed of Na₇₃K₂₂Al₉₅Si₉₇O₃₈₄.wH2O。

Wherein the pH value of ion exchange is 7-8, and the exchange time is 3-20 h.

First exchange of Li⁺The concentration is 1-1.5mol/L, and Li is exchanged for the second time⁺The concentration is 1.5-3 mol/L; li + concentration is Na⁺And K⁺1.1-10 times of the sum of the concentrations.

Further, first ion-exchanging Li⁺The concentration is 1.2 mol/L; second ion exchange of Li⁺The concentration is 2 mol/L; li⁺At a concentration of Na⁺And K⁺2-5 times of the sum of the concentrations.

Wherein the acid used for adjusting the pH is selected from hydrochloric acid or acetic acid, and further selected from hydrochloric acid.

Further, the exchange temperature was 200-.

Compared with the prior art, the invention has the beneficial effects that:

through a large amount of researches, the invention discovers that under the condition of ultrahigh temperature hydrothermal (the temperature is more than or equal to 180 ℃), Li is utilized⁺Mass change occurs by ion exchange of LSX molecular sieves, i.e. Li⁺The catalyst can easily enter a sodium squarer cage and a hexagonal column cage of a molecular sieve, and the exchange degree of more than 90 percent can be achieved only by exchanging twice. The method of the invention shows stable effect in production with larger dosage, better accords with the actual situation of industrial production, can keep better implementation effect even if being scaled up to industrial production, and has repeatability for large-scale production in industry.

Drawings

FIG. 1 shows the cation content of the molecular sieve after primary ion exchange at different temperatures

Detailed Description

The technical solutions of the present invention are described clearly and completely below, and it is obvious that the described embodiments are some, not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Comparative example 1:

adding 230g of lithium hydroxide into 6000g of water, stirring uniformly, adding 210g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of LSX-1 molecular sieve, performing ion exchange at 20 ℃ for 20 hours, filtering, washing, and roasting at 550 ℃ for 2 hours to obtain Li-LSX-20-1; adding 280g of lithium hydroxide into 6000g of water, stirring uniformly, adding 245g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of Li-LSX-20-1 molecular sieve, performing ion exchange at 20 ℃ for 20 hours, filtering, washing, and roasting at 550 ℃ for 2 hours to obtain the Li-LSX-20-2 molecular sieve.

Comparative example 2:

adding 230g of lithium hydroxide into 6000g of water, stirring uniformly, adding 210g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of LSX-1 molecular sieve, carrying out ion exchange at 80 ℃ for 20 hours, filtering, washing, and roasting at 550 ℃ for 2 hours to obtain Li-LSX-80-1; adding 280g of lithium hydroxide into 6000g of water, stirring uniformly, adding 245g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of Li-LSX-80-1 molecular sieve, performing ion exchange at 80 ℃ for 20 hours, filtering, washing, and roasting at 550 ℃ for 2 hours to obtain the Li-LSX-80-2 molecular sieve.

Comparative example 3:

adding 230g of lithium hydroxide into 6000g of water, stirring uniformly, adding 210g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of LSX-1 molecular sieve, performing ion exchange at 120 ℃ for 20 hours, filtering, washing, and roasting at 550 ℃ for 2 hours to obtain Li-LSX 120-1; adding 280g of lithium hydroxide into 6000g of water, stirring uniformly, adding 245g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of Li-LSX-120-1 molecular sieve, performing ion exchange at 120 ℃ for 20 hours, filtering, washing, and roasting at 550 ℃ for 2 hours to obtain the Li-LSX-120-2 molecular sieve.

Comparative example 4:

adding 230g of lithium hydroxide into 6000g of water, stirring uniformly, adding 210g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of LSX-1 molecular sieve, performing ion exchange at 150 ℃ for 20 hours, filtering, washing, and roasting at 550 ℃ for 2 hours to obtain Li-LSX 150-1; adding 280g of lithium hydroxide into 6000g of water, stirring uniformly, adding 245g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of Li-LSX-150-1 molecular sieve, performing ion exchange at 150 ℃ for 20 hours, filtering, washing, and roasting at 550 ℃ for 2 hours to obtain the Li-LSX-150-2 molecular sieve.

Comparative example 5:

adding 230g of lithium hydroxide into 6000g of water, uniformly stirring, adding 210g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of LSX-1 molecular sieve, performing ion exchange at 150 ℃ for 20 hours, filtering, washing and drying to obtain Li-LSX-150-21; adding 280g of lithium hydroxide into 6000g of water, stirring uniformly, adding 245g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of Li-LSX-150-21 molecular sieve, performing ion exchange at 150 ℃ for 20 hours, filtering, washing and drying to obtain the Li-LSX-150-22 molecular sieve.

Example 1:

adding 230g of lithium hydroxide into 6000g of water, uniformly stirring, adding 210g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of LSX-1 molecular sieve, performing ion exchange at 180 ℃ for 20 hours, filtering, washing and drying to obtain Li-LSX-180-1; adding 280g of lithium hydroxide into 6000g of water, stirring uniformly, adding 245g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of Li-LSX-180-1 molecular sieve, performing ion exchange at 180 ℃ for 20 hours, filtering, washing and drying to obtain the Li-LSX-180-2 molecular sieve.

Example 2:

adding 230g of lithium hydroxide into 6000g of water, uniformly stirring, adding 210g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of LSX-1 molecular sieve, performing ion exchange at 200 ℃ for 20 hours, filtering, washing and drying to obtain Li-LSX-200-1; adding 280g of lithium hydroxide into 6000g of water, stirring uniformly, adding 245g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of Li-LSX-200-1 molecular sieve, performing ion exchange at 200 ℃ for 20 hours, filtering, washing and drying to obtain the Li-LSX-200-2 molecular sieve.

Example 3:

adding 230g of lithium hydroxide into 6000g of water, uniformly stirring, adding 210g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of LSX-1 molecular sieve, performing ion exchange at 220 ℃ for 20 hours, filtering, washing and drying to obtain Li-LSX-220-1; adding 280g of lithium hydroxide into 6000g of water, stirring uniformly, adding 245g of hydrochloric acid to adjust the pH value to 7-8, adding 1000g of Li-LSX-220-1 molecular sieve, performing ion exchange at 220 ℃ for 20 hours, filtering, washing and drying to obtain the Li-LSX-220-2 molecular sieve.

TABLE 1 cation content and Li in examples and comparative examples⁺Degree of exchange

Comparative examples 1 to 4 the molecular sieve Li obtained after repeating the conventional exchange-calcination method twice⁺The degree of exchange was still not high, and comparative example 5 employed a method of exchange with an aqueous solution at 150 ℃ but Li after repeating the exchange twice⁺The exchange degree is also lower, so the temperature of the exchange needs to be strictly controlled at the temperature of 180-220 ℃ in the invention, and Li can be obtained by only exchanging twice⁺The exchange degree is more than 90%.