Examining the Adsorption (Vapor−Liquid Equilibria) of Short-Chain Hydrocarbons in Low-Density Polyethylene with the SAFT-VR Approach

The versatility of the SAFT-VR approach in the prediction of fluid-phase equilibria of complex fluids is illustrated for systems of short and long hydrocarbons. In particular, we examine the vapor−liquid equilibrium of a mixture of methane + hexatriacontane (C36H74) and the adsorption and coadsorption of light alkanes on low-density polyethylene. The molecules are modeled as chains of square-well segments, and the approach incorporates separate contributions to take into account the effect of monomer−monomer interactions and the bonding of the segments to form chains. In previous work (McCabe, C.; Jackson, G. Phys. Chem. Chem. Phys. 1999, 1, 2057), the phase behavior of pure long-chain n-alkane molecules was examined using the SAFT-VR approach; the intermolecular potential parameters were found to tend to a limiting value as the chain length of the n-alkane increases. Linear relationships with molecular weight for these parameters are used to model the polyethylene polymer in this work.