Developing an internally consistent set of theoretically based prediction models for the critical constants and normal boiling point of large n-alkanes

The normal boiling point (T_b), critical temperature (T_c), critical pressure (P_c), critical density (ρ_c), and critical compressibility factor (Z_c) are essential thermophysical properties for science and engineering. The long-chain-length trends for T_b, T_c, P_c, ρ_c, and Z_c of n-alkanes are of particular interest in petrochemical industries. For these and other reasons, the Design Institute for Physical Properties database (DIPPR 801) presents new prediction models that ensure thermodynamic consistency between the critical constants and the normal boiling point. This is accomplished by evaluating the quality of available experimental data, comparing the models with simulation results, and verifying that the infinite chain-length trends are consistent with polymer theory. A crucial aspect to the goals at DIPPR 801 is to provide appropriate estimates of uncertainty. We demonstrate how molecular simulation can be useful in this regard. In summary, the goal of this work is to present internally consistent models for predicting T_b, T_c, P_c, ρ_c, and Z_c of large n-alkanes. This study serves as an unique example of the DIPPR 801 methodology and provides a new algorithm for developing thermodynamically consistent prediction models for other families of compounds.