The important progress was attained by the Research Group No. 504 of the State Key Laboratory of Catalysis led by Prof. Weishen Yang. Their results were published as a communication in the journal of Angew. Chem. Int. Ed. （DOI: 10.1002/anie.201209077）
After analyzing thoroughly the basic principle of membrane permeability, and by combining experimental investigations with a number of characterizing techniques, this research group has studies three kinds of representative membrane materials (cf. AIChE Journal 2012，58, 1744-1754）, and discovered for the first time the enrichment of traces of sulfur impurities (< 20 ppm) on the permeable side of the membranes via directional migration under the action of chemical potential gradient of oxygen. They also found that due to this enrichment, the exchange rate of oxygen on the surface of the membrane would be decreased, and the permeability flux would be diminished. According to these observations, they proposed a mechanism for the migration of sulfur impurities. In addition, they put forward a simple and widely applicable method to solve the deteriorating problem caused by the sulfur impurities, namely, by coating the surface of the membrane with an oxygen activating porous layer to accommodate the sulfur impurities diffusing out from the bulk of the membrane. As a result, a long time and stable performance of the membrane under low temperature could be realized. It is anticipated that this accomplishment will push forward the development of oxygen permeable membranes as well as their applications in various important chemical processes.
DALIAN INSTITUTE OF CHEMICAL PHYSICS, CHINESE ACADEMY OF SCIENCES