On the isobaric specific heat capacity of natural gas

•A new set of isobaric heat capacity experimental data for a sour natural gas.•Generalized natural gas heat capacity model.•Validity in temperature from 250 to 414 K and pressures between 0.1 and 40 MPa.•AARE% of 2.61% in the comparison with experimental data.

A colorimeter equipped with a gas booster in conjunction with a PVT cell was used to measure the heat capacity of natural gas with different amounts of impurities. Based on new experimental and literature data, a general investigation of the isobaric specific heat capacity was carried out using the Jarrahian–Heidaryan equation of state (J–H-EOS). A model was obtained that is valid in wide ranges of pressures (0.1–40 MPa) and temperatures (250–414 K). The arithmetic average of the model’s absolute error is acceptable in engineering calculations and has superiority over other methods in its class.