Abstract:

The performance of various types of zeolites for N2/O2 and CH4/N2 separation has been studied. The separation factors αN2/O2 and αCH4/N2 for all the Na-form zeolites are < 1. Compared with Na-form zeolites, H-form zeolites adsorb larger quantities of O2 and smaller quantities of N2, so αN2/O2 is increased, but αCH4/N2 is reduced. On the contrast, Ca-form zeolites adsorb larger quantities of N2, so αN2/O2 is reduced but αCH4/N2 is increased. However the αN2/O2 and αCH4/N2 for both H- and Ca- form zeolites are ＜1.The changes in adsorption behavior can be explained in the light of energetics of sorption in zeolites. Chemical vapor deposition with silicon methoxide has been used to control the pore-opening size of the zeolites. As the amount of SiO2 deposition on NaA is increased, the adsorption of the bulkier component in the binary gas mixture is suppressed, so the values of αN2/O2 and αCH4/N2 for SiNaA zeolites are increased quickly to >1. Experimental results show that if the right type of zeolite is chosen fine control of zeolites pore-opening size through chemical vapor deposition has a potential as a good method for preparing high selective adsorbent in gas separation.

Key words: N₂/O₂ separation, CH₄/N₂ separation, Zeolites, Chemical vapor deposition, Controlled pore-opening size