The properties of zeolite(2)

Many reactions catalyzed by zeolites are of the positive carbon ion type, and the reactions occur via positive carbon ion intermediates. Zeolites also have considerable catalytic activity for some free radical reactions and oxidation-reduction reactions.

Natural zeolites generally cannot be used as catalysts, and can only be used as catalysts after being modified to H-type zeolites by ion exchange. Natural zeolite can be used as a carrier to carry catalytically active metals (such as Bi, Sb, Ag, Cu and rare earths, etc.), which show good catalytic performance through metal action.

Stability

The thermal stability of zeolite mainly depends on the ratio of Si+Al to balanced cations in it. Within the range of its composition change, generally the higher the Si content, the better the thermal stability.

Natural zeolite has good acid resistance, and its lattice is basically not damaged when it acts with strong acid for 2h at less than 100℃, and filigree zeolite can also remain stable in aqua regia. Therefore, natural zeolites are commonly used in acid treatment methods for activation, regeneration and utilization for other purposes.

The alkaline resistance of zeolite is much less than the acid resistance, which is caused by the presence of acidic sites in the zeolite crystal lattice. When it is placed in a low concentration of strong alkaline medium, the zeolite structure is destroyed.

Agriculture and livestock industry

The ion-exchange and adsorption properties of zeolite can be used to improve the ion-exchange and adsorption properties of soil, thus achieving the effect of fertilization, water retention and soil improvement.

According to reports, many areas in Japan are in the farmland to neutralize the acidic volcanic soil zeolite powder, the application of zeolite powder, rice, wheat can increase yields by 5%-10%. In Zhejiang Province, China, the application of 450-900μm zeolite powder, rice yield increased by 10%-20%.

Zeolite is also used as additive for feed and adsorbent for deodorization in feedlot.

Building materials

Zeolite is mainly used as active mix in cement and as admixture in concrete to reduce the amount of cement and to improve various functions.

Zeolite is mainly used as a cement mixer because it contains soluble active aluminum components and has volcanic ash activity. Therefore, it can partially replace cementitious materials without affecting the performance of cement.

By using the volcanic ash activity of zeolite as an admixture in concrete, especially in high-performance concrete, zeolite can react with Ca(OH)2 (no hardening strength), a by-product formed after hydration of cement, to produce substances with hardening strength, thus improving the strength of concrete.

Zeolite in concrete as admixture, there is a unique significance and role, due to the ion exchange properties of zeolite, it can absorb the Na+ and K+ brought in by cement and other components in the concrete system, thus eliminating or reducing the alkali aggregate reaction between Na+ and K+ and the aggregates with active SiO2 components, improving the durability and safety of concrete use.

Natural zeolite has good foaming properties at 110°C, so it is also a raw material for producing light-aggregate concrete and other lightweight building materials.