Interaction model for the critical pressures of aliphatic hydrocarbon mixtures

An interaction model is proposed for the prediction of the critical pressures of multicomponent aliphatic hydrocarbon mixtures which may include methane. This model utilizeg a series consisting of terms of increasing order which has been truncated beyond the fifth interaction term. After a number of algebraic manipulations, the excess critical pressure for these multicomponent mixtures has been represented as follows\documentclass{article}\pagestyle{empty}\begin{document}\begin{array}{cl}{P_c - P_c^t } & { = \sum\limits_{i,j} {\left[{A_{ij} + B_{ij} n_i + C_{ij} n_i^2 } \right]n_i n_j + } } \\ {} & {1 \ne i < j} \\ {} & {n_1 \sum\limits_{i > 1} {\left[ {A_{1j} + B_{1j} n_1 + C_{1j} n_1^2 + D_{1j} n_1^3 } \right]n_j + } } \\ {} & {\sum\limits_{\begin{array}{*{20}c} {i,j,k} \\ {1 \ne i < j < k} \\ \end{array} } {\beta _{ijk} n_i n_j n_k + \left( {\frac{3} {n}} \right)n_1 \sum\limits_{\begin{array}{*{20}c} {j,k} \\ {1 \ne j < k} \\ \end{array} } {\beta _{1jk} n_j n_k } } } \\ \end{array}\end{document}The nonmethane interaction coefficients A ij , B ij , C ij and β ijk and the methane interaction coefficients A 1 j , B 1 j , C 1 j , D 1 j and β 1 jk have been expressed as functions of the critical pressure parameter, π ij . The resulting relationships permit the evaluation of these interaction coefficients for a multicomponent system and from its composition, the critical pressure of the mixture is calculated. The critical pressures of several binary and multicomponent aliphatic hydrocarbon mixtures have been calculated and have been compared with experimental values. For 99 binary methane‐free mixtures representing 11 systems, the average deviation is 3.23%. For 46 binary mixtures representing six methane systems, the average deviation becomes 4.41 %. For 36 multicomponent aliphatic hydrocarbon mixtures containing from three to six components, the average deviation is found to be 3.18%.