Viscosity, second pVT-virial coefficient, and diffusion of pure and mixed small alkanes CH4, C2H6, C3H8, n-C4H10, i-C4H10, n-C5H12, i-C5H12, and C(CH3)(4) calculated by means of an isotropic temperature-dependent potential. I. Pure alkanes

摘要

Reference tables of second pVT-virial coefficients B(T), viscosity eta(T), and self-diffusion rho D(T) are given for all neat alkanes CnH2n+2, n < 6, for temperatures T <= 1200 K starting at 100 K for CH4, 150 K for C2H6, and 180 K for C3H8, n-C4H10, i-C4H10, n-C5H12, i-C5H12, and C(CH3)(4). Restricting ourselves to low densities the thermophysical properties are calculated by means of an isotropic (n-6) Lennard-Jones temperature dependent potential (LJTDP). In this model the potential well depth epsilon(eff)(T) and the separation at minimum energy R-m((eff))(T) are explicitly temperature dependent, whereas the repulsive term n > 12 is independent of T. The LJTDP has been used before in order to construct reference tables of thermophysical properties of neat gases [Zarkova and Hohm, J. Phys. Chem. Ref. Data 31, 183 (2002)] and binary mixtures [Zarkova, Hohm, and Damyanova, J. Phys. Chem. Ref. Data 32, 1591 (2003)]. However, those studies were restricted to atoms and globularly shaped nondipolar molecules. Here the approach is extended to elongated, not necessarily spherically symmetric, and in part slightly dipolar molecules. As in previous works the potential parameters epsilon((eff))(T), R-m((eff))(T), and n are determined by minimizing the root-mean-square deviation between calculated and experimentally obtained thermophysical properties B(T), eta(T), rho D(T), and the second acoustic virial coefficient beta(T) normalized to their experimental error. In extension of our previous efforts we present a thorough statistical analysis of the experimental input data which gives us the possibility to select primary data which could be used to build up a database. (c) 2006 American Institute of Physics.