Abstract
Zirconia membranes were prepared on a porous alumina tube using sol-gel technique, and rhodium was then impregnated in the pores of the membranes by dipping in aqueous solution of RhCl3, followed by calcination in air. The permeation rates of unmodified zirconia membrane obeyed the Knudsen diffusion mechanism. However, hydrogen permeation changed from Knudsen diffusion to surface diffusion after the Rh modification. The Rh-loaded zirconia membrane showed a H2/CO2 separation factor of 10 at a permeation temperature of 100°C. A mixture of H2, CO (1%) and O2 (0-4%) was permeated through the Rh-loaded zirconia membrane in the range of 100-250°C. When the O2 concentration on the feed side exceeded the level of 1%, CO concentration on the permeate side was decreased to less than 50 ppm at 100°C. When the permeation temperature was raised to 200°C, the oxidation rate of CO was significantly decreased due to the consumption of O2 by the oxidation of H2.
