Volumetric properties of three nonylphenol ethoxylated nonionic surfactant mixtures with methanol: Experimental study and modeling with Tammann-Tait and PC-SAFT equation of state

Abstract

Although physicochemical properties are essential for production and equipment design in oil and gas industries, there is still a lack of data for some systems because of hazardous temperature and pressure conditions. This work provides a volumetric behavior study of three different mixtures composed of nonylphenol ethoxylated nonionic surfactant (IGEPAL CO-520, CO-630, and CO-720) + methanol in the entire mole fraction composition range for temperatures from 313.15 K to 413.15 K and pressures up to 100.0 MPa. These systems behave as a regular liquid, with a volume contraction predominance. It was observed that for high methanol molar content, there is an increase in the cohesive forces because of the ethoxylated chain increases in oxyethylene units. Nevertheless, it was observed that the hydrogen bonds between ether oxygens and hydroxyl hydrogens decrease by increasing temperature, as given by internal pressure data and PC-SAFT modeling. Besides, a new set of parameters for the PC-SAFT equation of state is provided to calculate volumetric and second-order derivative properties.