Vapor pressures and activity coefficients of 2,2,2-trifluoroethanol in binary mixtures with 1,3-dimethyl-2-imidazolidinone and 2-pyrrolidone Paris Chatzitakis a , Javid Safarov b, ⁎, Frank Opferkuch a , Belal Dawoud c , Egon Hassel b a Technische Hochschule Nürnberg Georg Simon Ohm, Nuremberg Campus of Technology, Fuerther Str. 246b, 90429 Nuremberg, Germany b Institute of Technical Thermodynamics, University of Rostock, Albert-Einstein-Str. 2, D-18059 Rostock, Germany c Laboratory of Sorption Processes, Ostbayerische Technische Hochschule Regensburg, Galgenberg Str. 30, 93053 Regensburg, Germany abstract article info Article history: Received 7 February 2020 Received in revised form 28 February 2020 Accepted 1 March 2020 Available online 5 March 2020 Keywords: 2-Trifluoroethanol 1,3-Dimethyl-2-imidazolidinone 2-Pyrrolidone Vapor pressure NRTL Clausius-Clapeyron The vapor pressures of two binary mixtures containing 2-trifluoroethanol (TFE) + 1,3-dimethyl-2- imidazolidinone (DMI) and TFE + 2-pyrrolidone (PYR), were investigated at temperatures T = (274.15 to 423.15) K using two different static method installations. Both combinations were modelled using an extended Clausius-Clapeyron equation with concentration dependent parameters and the NRTL equation with tempera- ture dependent parameters. The best fit was obtained using the NRTL equation. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Commercial vapor absorption heat pump systems are almost exclu- sively based on ammonia/water and water/lithium bromide (LiBr) working pairs. While the thermodynamic performance of these conven- tional working pairs has always been attractive, significant drawbacks, such as safety risks and operational limitations, have impeded wider adoption and commercialization. On one hand, ammonia is a toxic sub- stance, operating under high system pressures, and for that reason ex- cluded from residential or other sensitive environments. On the other hand, the aqueous electrolyte solutions pose no such risk, but are bound by corrosion issues and a limited temperature lift range, which when exceeded causes the solution concentration to cross the solubility limit, resulting in crystallization. This particular weakness has rendered such systems suitable only for cooling applications and in some cases as heat transformers [1]. The search for new working pairs and the development of new technology applications was previously not considered a top re- search priority. Currently, however, it is rapidly gaining interest, due to strict restrictions, and even prohibition, of the production and use of all high GWP/ODP conventional refrigerants for compres- sion heat pumps. The application of new environmentally benign, ozone friendly absorption heat pumps is becoming a rather attrac- tive prospect. The operation of an absorption heat pump cycle is largely dependent on the physical and chemical properties of the working pairs. Additionally, they must be thermally stable during all working temperature ranges, and reactions with metals and other structure materials should be minimal. Signi ficant efforts have been made towards mitigating some of these weaknesses. For instance, one of the common methods to reduce solution crys- tallization is the addition of small amounts of non-volatile organic substances with hygroscopic properties. Nevertheless, this ap- proach does not provide clear cut solutions, only incremental improvements. A number of studies have been published on the development of new working pairs for absorption heat pump systems, with the central focus being on replacements for water (regarding NH 3 +H 2 O) and LiBr (regarding H 2 O + LiBr), in an effort to reduce system cost and Journal of Molecular Liquids 305 (2020) 112828 ⁎ Corresponding author. E-mail addresses: paris.chatzitakis@th-nuernberg.de (P. Chatzitakis), javid.safarov@uni-rostock.de (J. Safarov). https://doi.org/10.1016/j.molliq.2020.112828 0167-7322/© 2020 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq