A New Group-Contribution Approach for Ideal Gas Heat Capacity, Critical Temperature and Normal Boiling Point

We propose two new group-contribution models for the ideal gas heat capacity cpig(T), one for the critical temperature Tc, and the normal boiling point Tb. For all properties the model is based on a decomposition into base and second-order groups, which are simultaneously parametrized to experimental data. For the critical temperature and normal boiling point, each group is assigned one or two parameters based on data availability. For the critical temperature, 1454 substances were used for optimization, resulting in a mean absolute relative deviation (MARD) from experimental data of 2.46%. For the normal boiling point 5591 substances were used for optimization with a MARD of 2.26%. For the ideal gas heat capacity we propose two new group-contribution models based on the Aly-Lee equation and a reparameterization of the Joback and Reid model. The models are parametrized for the temperature range 50–3000 K for 1009 substances, where the MARD to the experimental data for the best model is 1.73%. In addition, we individually parametrize 1162 substances with a deviation to the experimental data of 0.54%. As Supporting Information, we provide Python code to estimate the critical temperature, the normal boiling point, and the ideal gas heat capacity based on the proposed models.