Frequency Response Study of Adsorbate Mobilities of Different Character in Various Commercial Adsorbents

Abstract

The sorption of strong basic ammonia, acidic carbon dioxide, and apolar propane in different commercial adsorbents: activated alumina, charcoal, and silica gel porous particles and 4A, 5A, and 13X zeolite pellets has been investigated using the frequency response (FR) method. Despite differences in the sorption and diffusion processes of the sorbates in 4A, 5A, and 13X zeolite crystals, in the pelletized samples, intercrystalline diffusion was found to be the rate-controlling process with macropore diffusivities being the same within 1 order of magnitude for NH3 or CO2. The mass transport rates of the apolar propane seemed to be more sensitive to differences in the meso- and macropore size distributions of the zeolitic pellets. The micropore adsorption capacity played a significant role in the uptakes controlled by macropore diffusion. For ammonia and carbon dioxide, sorption proved to be the rate-determining process inside the zeolite crystals, but for propane, intracrystalline diffusion was rate contro...