1. Introduction
Moisture contamination in industrial media is the primary cause of equipment corrosion, catalyst poisoning, product performance degradation, and shortened service life of precision components. Traditional desiccants including silica gel, activated alumina, and conventional low-silicon molecular sieves are only suitable for neutral and weakly alkaline environments. In typical acidic working conditions represented by lithium battery carbonate electrolyte, HFE hydrofluoroether, PFPE perfluoropolyether fluid, and fluorinated etching specialty gas, trace acidic substances generated by medium hydrolysis will rapidly destroy the aluminum-oxygen skeleton of common molecular sieves, resulting in sodium ion precipitation, powder shedding, and complete loss of adsorption capacity.
Acid-resistant molecular sieves represented by high-silicon ZSM-5, modified AW/AS series, and full-silicon zeolites feature adjustable silica-alumina ratio, stable microscopic framework, and strong resistance to acidic erosion. They can maintain efficient and stable selective water adsorption in long-term acidic working environments, achieving deep dehydration to low ppm or even ppb level, which fully meets the purification requirements of high-purity electronic chemicals and semiconductor process gases.
2. Acid-Resistant Mechanism of Molecular Sieves
The acid resistance of zeolite molecular sieves is fundamentally determined by the silica-alumina ratio (SiO₂/Al₂O₃). The lower the aluminum content in the crystal framework, the fewer acid-sensitive Al-O bonds, and the stronger the structural stability in acidic media.
Conventional 3A, 4A and 13X molecular sieves belong to low-silicon aluminosilicates. Their abundant framework aluminum is easily hydrolyzed and detached by HF, HCl and organic acids, leading to skeleton collapse and pulverization. In contrast, high-silicon acid-resistant zeolites reduce the number of vulnerable aluminum active sites by increasing the silica-alumina ratio. Full-silicon ZSM-5 zeolite completely removes framework aluminum, achieving extreme resistance to hydrofluoric acid corrosion.
In addition, acid-resistant molecular sieves retain uniform microporous structure. The pore diameter is precisely matched with the kinetic diameter of water molecules (2.8 Å), realizing 100% selective adsorption of water without adsorbing fluorinated fluids, carbonate solvents, and high-purity process gases, avoiding medium loss and component ratio deviation.
3. Classification and Performance Characteristics of Industrial Acid-Resistant Molecular Sieves
According to acid resistance grade and applicable medium types, industrial acid-resistant drying molecular sieves are divided into four categories, covering weak acid, medium acid, and strong HF acidic working conditions.
