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

4 years ago

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

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 H2, He, N2, CO2, and O2 at fixed and programmed temperatures (between 304 and 394 K), and transmembrane 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 N2, O2, 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 URL: www.sciencedirect.com/science

DOI: S1387181117307291