This work continues the systematic study of global phase diagrams in binary systems relevant for the description of natural gases using the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EOS). Reservoirs frequently contain non-hydrocarbon compounds such as CO2, N-2, or H2S that have strong effects upon the thermodynamic properties of natural gases. Thus, we study the behavior of their binary mixtures with n-alkanes over wide pressure and temperature ranges to get a deeper insight into the intermolecular pair interactions reflected in the phase behavior of the mixtures. These systems show complex patterns within the van Konynenburg classification, and the theoretical model accurately reproduces them. In the case of H2S containing mixtures (H2S is a compound that has autoassociation hydrogen-bonding ability), we analyze several association models to obtain the most reliable approach by comparing the predicted association degree of H2S to available experimental data. A conclusion from this series of papers is that PC-SAFT is a reliable and accurate model to predict the behavior of the different types of binary mixtures involved in complex multicomponent natural gases, with the ability to describe the different patterns of fluid-phase behavior presented by the studied systems over wide pressure and temperature ranges.