Synthesis, dynamic characterization, and modeling studies of an AM-3 membrane for light gases separation

authors	Cardoso, SP; Lin, Z; Portugal, I; Rodrigues, AE; Silva, CM
nationality	International
journal	MICROPOROUS AND MESOPOROUS MATERIALS
author keywords	Titanosilicate membrane; Gas permeation; Modeling; Permeation mechanism; Maxwell-Stefan approach
keywords	TITANOSILICATE ETS-10 MEMBRANES; SILICATE UMBITE MEMBRANES; MAXWELL-STEFAN EQUATIONS; ZEOLITE MEMBRANES; SILICALITE-1 MEMBRANES; COMPOSITE MEMBRANES; SURFACE-DIFFUSION; CO2 SEPARATION; MASS-TRANSFER; HIGH-PRESSURE
abstract	A new AM-3 membrane was prepared on a stainless-steel support for potential application in the separation of light gases, particularly hydrogen containing mixtures. It was dynamically characterized by permeation assays using H-2, He, N-2, CO2, and O-2 at fixed and programmed temperatures (between 304 and 394 K), and trans membrane pressure drops from 0.5 to 1.5 bar. The experimental results disclosed high selectivity of the AM-3 membrane towards hydrogen. In terms of transport mechanisms, they evidenced an activated behavior typical of surface diffusion, and a small contribution of macro-defects. The existence of intercrystalline micro-defects was revealed by the permeation of N-2, O-2, and CO2, whose kinetic diameters are larger than the pore diameter of AM-3. Gas permeation was accurately modeled based on the Maxwell-Stefan approach for surface diffusion in micropores, with additional terms for Knudsen and viscous fluxes through meso- and macro-defects. The global deviation achieved for the five gases was only 3.42%. The calculated results demonstrated that: viscous flow prevailed at low temperature (304 K), surface diffusion dominated when temperature increased, Knudsen transport was residual, the flux through defects predominated at 304 K (53.8-73.5% of total flux) but fell below 15% for temperatures above 370 K, and the influence of the support was negligible.
publisher	ELSEVIER SCIENCE BV
issn	1387-1811
year published	2018
volume	261
beginning page	170
ending page	180
digital object identifier (doi)	10.1016/j.micromeso.2017.11.008
web of science category	Chemistry, Applied; Chemistry, Physical; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary
subject category	Chemistry; Science & Technology - Other Topics; Materials Science
unique article identifier	WOS:000427668000022