Purification Of Attapulgite And Its Application As Binder In Adsorbent For Air Separation

Attapulgite is a kind of natural clay minerals with fibrous texture layer-chain structure. Its plentiful porosity structure and high surface provide a large number of adsorption center. With regulated the force between adsorption quality and adsorbent, surface electricity negative improved adsorption performance. So it directly used for the adsorbent or the binder of the zeolite adsorbent.As a natural mineral clay, impurities will weaken its original adsorption, colloidal and viscous properties. Furthermore its structure not only has the rod-like single crystal, but also has the crystal beam and aggregates for the Van Der Waals Forces and hydrogenbond. It is bound to reduce its surface area, thereby affecting the adsorption and bonding properties. So, before using the attapulgite, it is need to adopt appropriate methods to remove impurities and dissociation crystal aggregates to realize the purification and refinement. This can improve its microstructure, and then improve the adsorption and adhesive properties.With attapulgite’s unique structural features,the previous used it as a binder in separating oxygen from air molecular sieve adsorbent. But the adsorbent has low strength, high abrasion and low nitrogen-oxygen separation performance. In this study, we make natural attapulgite dissolved in aqueous solution of dispersant, with hydration and ultrasonic oscillation to be processed. Then we prepared a binder of the zeolite adsorbent with high purity and high dispersion. And at the same time, we improve its surface electricity negative, further improve its adsorption performance. We completed the purification, decentralized and surface modification by one step. Then we get molecular sieve adsorbent with high mechanical strength, low abrasion and high adsorption. It improved the adsorption capacity of nitrogen and nitrogen-oxygen separation ability. The main results are as follows:1、Using slice attapulgite as crude material, tetrasodiun pyrophosphatete、 trasodiun pyrophosphate and sodium hexametaphosphate as dispersant, we decentralized purify in the mechanical agitation and ultrasonic oscillation alternately. The results show:purified by different dispersant, the purity of attapulgite increased greatly and the dispersion properties improved. Purified by tetrasodiun pyrophosphatete and sodium hexametaphosphate, the purity of attapulgite achieved 100%. Purified by trasodiun pyrophosphate, the dispersion properties of attapulgite is better than another.2、We Take the 13X as a molecular sieve adsorbent body and take the attapulgite clay purified by different dispersent as binder. Mixing ratio of 13X: attapulgite=4:1, we prepared adsorbent. Calcining at 500℃, CO2 adsorption capacity of molecular sieve adsorbents is increased in 10%～20% more than unpurified,and the water adsorption capacity is increased largely.Using the attapulgite clay purified by tetrasodiun pyrophosphatete as binder, we prepared molecular sieve adsorbents. Mechanical strength and abrasion of this adsorbent is well and the nitrogen-oxygen separation performance is steady.So it can be used as adsorbent for air separation. Using the attapulgite clay purified by sodium hexametaphosphate as binder, we prepared molecular sieve adsorbents. Mechanical strength and abrasion of this adsorbent is not very well and the nitrogen and oxygen separation performance is not stable. So when we use the sodium hexametaphosphate as dispersant, the content should be controlled within 2%～3%.