Lithium-containing modified low silicon-aluminum X type molecular sieve adsorbent and preparation method thereof

Abstract

The invention relates to a lithium-containing modified low silicon-aluminum X type molecular sieve adsorbent and a preparation method thereof. The molecular sieve adsorbent comprises the following components in parts by weight: 80-90 parts of Li-LSX molecular sieve raw powder, 10-20 parts of binder and 1-5 parts of forming adjuvant; the method comprises following steps: modifying the merchant low-silicon molecular sieve raw powder by the processes of once exchange and once roasting, twice exchange and twice roasting and third lithium exchange to obtain the Li-LSX molecular sieve raw powder, and then mixing with the binder and the forming adjuvant for shaping to obtain the product. Compared with the prior art, the exchange roasting modification process provided by the invention can improve the stability of LSX molecular sieve framework, reduce the damage on the LSX molecular sieve framework caused by the subsequent process, obtain the LSX molecular sieve the Li+ exchange degree of which is more than 95%, and lower production cost, thus making large-scale industrial production possible.

Description

technical field [0001] The invention relates to a molecular sieve adsorbent and a preparation method thereof, in particular to a lithium-containing modified low-silicon aluminum X-type molecular sieve adsorbent and a preparation method thereof. Background technique [0002] Faujasite molecular sieves with a silicon / aluminum ratio (n(Si) / n(Al)) of 1.0-1.5 belong to X-type molecular sieves. When n(Si) / n(Al) is regulated at 1.0-1.1, it is called Low silica aluminum X type molecular sieve (LSX). With the increase of the Al content in the framework, the number of negatively charged cations in the balanced Al-O tetrahedral framework increases correspondingly, and the exchange modification capacity of the LSX molecular sieve increases accordingly; 2 The Li-LSX molecular sieve modified by Li ion exchange with the strongest molecular interaction shows superior nitrogen adsorption capacity and nitrogen-oxygen separation ability in gas separation. Therefore, it has been widely used a...

AI Technical Summary

Problems solved by technology

However, this method needs to consume a large amount of high-concentration exchange fluid, the exchange time is long and the number of exchanges is low, the exchange efficiency is low, the waste is serious, the production process is complicated and the cost is high, and it is difficult to industrialize production.

[0004] Patents US 5916836 (1999) and CN 101289196A (2008) disclose a method for preparing Li-LSX molecular sieves with substantially the same processing steps, the method is to pass LSX through K + The aqueous solution was exchanged several times (optimized 5 times) into K-LSX, and then passed through NH 4 + The aqueous solution is exchanged multiple times (preferably 5 times) into NH 4 -LSX, and finally NH 4 -LSX for Li + exchange, and deNH through the system 3 Drag balance promotes Li + exchange; the method uses NH 4 + The transitional exchange method improves the utilization rate of Li, but also increases the treatment process, and due to the poor hydrothermal stability of the low-silicon-alumina molecular sieve framework itself, in the frequent hydrothermal ion exchange process (not less than 10 times) there is a possibility of destroying the molecular sieve framework, and additional NH 3 Recycling Process Unit

[0005] In the patent CN 101125664A, Li + In the exchange method, the Na-LSX zeolite molecular sieve is first roasted, then exchanged by Li ion aqueous solution, and finally the LiNa-LSX molecular sieve with a certain lithium exchange degree is mixed with solid lithium salt powder for solid phase exchange to obtain an exchange degree of 96%. The above lithium-type low-silicon-aluminum X-type zeolite molecular sieve; this method uses solid phase exchange to avoid the huge waste of lithium salt caused by traditional aqueous solution exchange, but it is difficult to achieve the uniformity of ion exchange scale in powder mixing, which will directly lead to lithium exchange in this method. Inhomogeneous, and in addition to the cation exchange reaction in the solid-state high-temperature roasting process, anions will be occluded to varying degrees in the zeolite supercage. In addition, the solid phase exchange requires 1°C / min, 2°C / min and 4°C / min. Programmed temperature operation is difficult to achieve in large-scale industrial roasting and activation production

[0006] Patent CN 101380565A discloses a method for preparing an active molecular sieve adsorbent. In this method, FAU-type molecular sieves and kaolin-based binders are formed and calcined, and then ion-exchanged with the flowing lithium ion exchange liquid in a multi-stage serial exchange column. , through drying and activation to obtain an adsorbent containing high lithium exchange degree and low silicon X-type molecular sieve; this method uses high concentration (2.2M) high flux ion exchange liquid (1.7M 3 / H) Ion exchange also has the problem of low utilization rate of lithium exchange, and the formed adsorbent undergoes high temperature (99°C) high flow rate (1.7M 3 / H) The exchange liquid is washed repeatedly, and the patent embodiment does not point out whether this treatment process will affect some macroscopic physical properties of the adsorbent in the use of engineering equipment, such as compressive strength, wear rate and service life, etc.