The solubility and diffusivity of ethylene in a polymer-filled nanopore is investigated. The goal is to ascertain whether the thermodynamic and transport properties of the ethylene-polyethylene system are influenced by the confinement in the nanopore. The nanopore is representative of the smallest pores present in current supported polyethylene catalysts. Advanced modeling techniques are used to generate a single atomistic polyethylene chain confined in the pore. Subsequently, Monte Carlo and Molecular techniques are employed to determine thermodynamic (phase equilibrium) and transport properties of the ethylene-polyethylene system for two different pore sizes. For the smallest pore, both types of properties differ from their values in macroscopic bulk systems. Such differences are shown to be a consequence of confinement in the nanopore and can be of relevance in catalyst design and in mesoscopic and macroscopic modeling of heterogenous polyolefin catalysis.