A new model with reduced number of virial coefficients for predicting heat capacity of homologous linear hydrocarbons over a 300 to 1,000 K temperature range based on molecular weight

Abstract

A new model for predicting heat capacity of linear hydrocarbons with a significantly reduced number of virial coefficients and based on molecular weight is presented for the first time. We show that the gas heat capacity, Cp, of three classes of homologous linear compounds can be accurately predicted from just one new empirical model over a wide range of temperature (300 to 1,000 K). This new model for Cp is a function of molecular weight (MW). It is synthesised from the widely used cubic virial temperature model. We illustrate its application with independent data from the widely consulted Yaws Database of 20-alkanes (methane to eicosane), 19-alkenes (ethylene to 1-eicosene) and 19-alkynes (ethyne to 1-eicosyne). The per cent discrepancy (%Df,g) and per cent bias (%Bf,g) overall between the new (f) and virial model (g) was, respectively, +3% and +1.0%. Discrepancy between the new model and the cubic virial model therefore is so small as to be negligible for practical purposes. The positive sign on the per cent bias indicates that on average the new model predicts greater values of Cp than the virial model. The new model is simple in form and is easy to use. A model for Cp based on MW does not appear to have been previously published. There is the possibility of this generalized form of the new model fitting further classes of compounds.