Molecular sieves are synthetic crystalline aluminosilicates, as well as natural ones, commonly known as zeolite. There are many types of molecular sieves, and the three commonly used types are A-type, X-type and Y-type. ZSM35 Molecular Sieve told us that each type has different pore size and properties according to its cation, and there are many types, such as 3A Molecular Sieve, 4A Molecular Sieve, 5A Molecular Sieve, 10X Molecular Sieve, 13X Molecular Sieve , ZSM35 Molecular Sieve, Refrigerant Molecular Sieve and other models. There are strip and spherical shapes, with a particle size of 2-6mm.
The voids in the molecular sieve account for about 50% of the volume, and the average internal surface area per gram of molecular sieve is 700-800 m2. The adsorption process takes place inside the cavity. It can suck molecules smaller than the cavity into the pores, and block the molecules larger than the cavity out of the pores, playing the role of sieving molecules. The main characteristics of molecular sieves are:
1) The adsorption force is extremely strong, and the selective adsorption performance is also very good.
2) The degree of dryness is extremely high, and it has good drying ability for high temperature and high-speed airflow. The lower the water vapor content, that is, the lower the relative humidity, the more significant the adsorption capacity. However, when the relative humidity is high, the adsorption capacity is smaller than that of silica gel.
3) Good stability, and can maintain normal adsorption capacity below 200°C. The service life of molecular sieve is relatively long.
4) Molecular sieve has strong adsorption capacity for water, followed by acetylene and carbon dioxide.
Molecular sieve adsorbers (usually 5A molecular sieves) are used on the high and medium pressure devices to absorb moisture, carbon dioxide and acetylene at the same time, which greatly simplifies the process, simple operation and good purification effect. The molecular sieve process is adopted in the large-scale air separation unit of all low pressure, and the molecular sieve adsorber generally adopts 13X molecular sieve.