Abstract

ABSTRACT: The majority of nanocomposite olefin/paraffin separation membranes use silver nanoparticles or silver ions as the olefin binding agent. In this theoretical study, we character-ize the olefin interaction with silver nanoparticles and show that silver is special in that it chemisorbs ethylene more weakly than other metals. Some variation with particle size is found; small 79 atom nanoparticles tend to bind ethylene more strongly than larger 140 atom particles, which in turn are well approxi-mated by facets of bulk crystal surfaces. The effect of replacing cores of nanoparticles with different metals is demonstrated to selectively tune binding based on the relative d-band centers of the twometals.We identify silver-cored, gold-shelled nanoparticles as potentially more effective for olefin/paraffin separations. Random alloys of gold and silver were also considered. We find that 25%-75 % Au-Ag random alloys are strong candidates for use in olefin/paraffin separation membranes due to the presence of reactive (111) faces without the cost of a strong increase in the binding energies on edges and corners. Nanocomposite membranes containing these nanoparticles hold promise for more efficiently separating olefins from paraffins.