High-pressure fluid-phase equilibria: Experimental methods, developments and systems investigated (2013–2016)

Abstract

With this article we extend our review series on high-pressure (above 1 MPa) phase equilibrium data to articles published between 2013 and 2016, including a compilation of systems investigated, recent developments, and trends. We considered phase equilibria of vapor, liquid, and solid phases, hydrates, critical points, solubility of high-boiling substances in supercritical fluids, solubility of gases in liquids, and solubility (sorption) of volatile components in ionic liquids and in polymers. In total, we found 1400 relevant articles in the four-year period 2013–2016 which means a 40 % increase as compared to the previous review period 2009–2012. This can be explained by a more elaborated search strategy, new publication strategies of the authors, and by the ongoing scientific interest in high-pressure phase equilibria. We summarize scientific areas that drive the measurement of high-pressure phase equilibria, and we give examples of review articles, which focus on a specific topic related to experimental high-pressure phase equilibrium data.Apart from 14 systematically searched journals, we observed a tremendous increase in the number of articles found in other journals, rising from 59 articles (2009–2012) to 473 articles (2013–2016). Until the late 1990s, the average number of authors per article was approximately 3. From then on, it has been increasing almost linearly and has reached a value of 4.7 in 2016. More than one third of the articles contain data on only one system. While the average number of systems per article is close to 3, the median value is 2.For more than 4000 systems, the reference, the temperature and pressure range of the data, and the experimental method used for the measurements is given in 41 tables. Information on hydrate systems and systems containing ionic liquids are given in 6 additional tables. 47.1 % of all systems of the review period 2013–2016 contain CO2 as one of the components. Other frequently measured components are water (32 %), methane (12.3 %), nitrogen (5.1 %), propane (3.7 %), ethane (3 %), hydrogen (2.7 %), and ethanol (2.2 %). In the period 2013–2016, 18 % of the data sets involve hydrate equilibria, 15.4 % of the systems include an ionic liquid, and 7.7 % contain a refrigerant. In the period from 1988 to 2016, we observed a clear shift in the investigated systems from chlorofluorocarbon to hydrofluorocarbon and then to hydrofluoroolefin refrigerants.The number of investigations at very high temperatures and pressures has increased, since a higher number of data sets from the Earth and planetary sciences have been found and included in the period of this review. The average internal volume of all cells used for measurements in the review period is 141 mL. Many different methods for the measurements of high-pressure phase equilibrium data exist. We discuss the main advantages and challenges of the methods and give examples of their use in the period 2013–2016. The percentage of the use of synthetic methods constantly rose from 29 % in the first period (1988–1993) to 62 % in the fourth period (2005–2008). Since then, it has stayed almost constant. Analytical–isobaric–isothermal (flow) methods have been used less and less, from 22 % (1988–1993) to 5 % (2013–2016). Synthetic-nonvisual methods are used more and more often, rising from 3 % (1988–1993) to 23 % (2013–2016).