RKJZ interaction parameters

Figure 3. RKJZ interaction parameters for the H20-hydrocarbon systems...

Figure 5. RKJZ interaction parameters for methane-C10+ hydrocarbons...

One example will serve to underscore the reason for the advantage over Chao-Seader at high pressure. Figure 1 shows the convergence of RKJZ K-values to unity as the mixture critical pressure is approached, for a temperature and composition on the mixture critical locus for the methane-ethane-butane ternary (20). This mixture was chosen in order to check RKJZ apparent critical pressure vs. the 1972 corresponding-states correlation of Teja and Rowlinson (21), which presumably has a better theoretical basis than the RKJZ method. In these comparisons, the Teja and Rowlinson correlation uses two interaction parameters per binary pair, based primarily on fits to binary critical loci the RKJZ method uses Cij = 0 for all binaries, based on binary VLE data. 

---