A study of packing induced selectivity effects in the liquid phase adsorption of alkane/alkene mixtures on NaY

The adsorption of liquid alkane/alkene mixtures on NaY (Si/Al 2.79) was investigated using a batch technique. The adsorption of alkenes with different chain lengths (hexene, octene, decene, dodecene) from hexane, heptane, octane, decane, dodecane and tetradecane was measured at room temperature. Already at low concentrations, the alkenes are selectively adsorbed on NaY from their binary mixture with an alkane. In the investigated alkene concentration range between 0 and 20 mol%, a maximum pore filling of 0.32 ml/g is reached depending on the chain length of both the alkene and the alkane. Two remarkable effects were observed: (1) shorter alkenes are preferentially adsorbed compared to longer alkenes, (2) the adsorption of the alkene depends strongly on the chain length of the alkane solvent. With shorter alkanes, the alkene selectivity decreases. However, the shorter the alkene, the smaller the influence of the alkane solvent. The observed effects can be explained by a more favorable packing of smaller molecules compared to larger molecules inside the supercages of NaY. (c) 2005 Elsevier Inc. All rights reserved.