Gas chromatographic measurements of activity coefficients at infinite dilution for refrigerants with a polyol ester oil as a stationary phase

Activity coefficients at infinite dilution have been measured by gas chroma tography for 14 refrigerants (R12, R22, R32, R124, R125, R134a, R142b, R143 a, RE170, R236ea, R290, R600, R600a, and R236fa) as solutes, using a polyol ester oil (POE), EMKARATE by ICI, as a stationary phase (solvent). Instrum ental analysis (NMR, IR) showed that the main components of the oil are pen taerithritol esters of carboxylic acids, and electrospray ionization spectr ometry revealed an average molecular mass of the POE of 618 g.mol(-1). The measurements were performed within a temperature range of 244 K to 313 K, b ut a specific temperature range for each refrigerant was adopted depending on its retention data. The experimental findings are well-represented by th e equation: In gamma(i)(infinity) = a(i) - b(i)/T. Some refrigerants, i.e., R22, R124, R125, R236ea, and R236fa, show quite a considerable positive te mperature dependence of their activity coefficients at infinite dilution, w hich can be attributed to hydrogen bonding with the POE, unlike other refri gerants that show a small, either positive or negative temperature dependen ce. To our knowledge, there are no data in the literature on activity coeff icients at infinite dilution for refrigerant and oil (lubricant) systems, a nd details on the solubility of refrigerants in oils are also extremely sca rce.