Abstract: In order to investigate the adsorption characteristics of molecular sieve adsorbents used in the interspace of cryogenic vessels, the adsorption isotherms of the 4A, 5A and 13X molecular sieves for N₂, O₂ single components and air were obtained by static expansion method. In the range of 10^-3~10³Pa, the differences in adsorption capacity of different molecular sieves for gases were compared, and the adsorption mechanism of molecular sieves was explored. The results show that the 5A and 13X molecular sieves have strong adsorption performance for N₂ and O₂ under vacuum conditions at liquid nitrogen temperature, the absorption capacity can reach 10⁴Pa·L/g magnitude. The adsorption capacity of O₂ in the 4A molecular sieve can also reach 10⁴Pa·L/g magnitude, while the 4A molecular sieve has poor nitrogen adsorption ability when the equilibrium pressure is higher, the saturated adsorption capacity reaches only about 300Pa·L/g. The adsorption capacity of the three molecular sieves for air follows 13X molecular sieve>5A molecular sieve>4A molecular sieve, and at liquid nitrogen temperature, the adsorption rate of 5A molecular sieve on air is higher than that of 13X molecular sieve. Studying the vacuum adsorption characteristics of molecular sieves at low temperatures helps to guide the application of molecular sieves in cryogenic vessels, which also provides a reference for the design of low temperature molecular sieves.

Key words: molecular sieves, cryogenic vessels, static expansion method, adsorption isotherm, adsorption capacity