Using Volume Shifts To Improve the Description of Speed of Sound and Other Derivative Properties with Cubic Equations of State

• Published in: Industrial & engineering chemistry research Vol. 58; no. 20; pp. 8856 - 8870
• Main Authors: Palma, André M, Queimada, António J, Coutinho, João A. P
• Format: Journal Article
• Language: English
• Published: American Chemical Society 22.05.2019
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.9b00817

The simultaneous description of phase equilibria, volumetric properties, and derivative properties is of great relevance to industry. However, most thermodynamic models are unable to describe all these properties with the same set of parameters. Equations of state are no exception, especially cubic equations of state where this behavior is even more relevant. When considering the classic fitting of these equations to critical data, a volume shift is often required for an accurate description of density, but this approach fails to provide a satisfactory description of derivative properties. In this work, we analyze the influence of a volume shift within the modified Cubic-Plus-Association, Peng–Robinson, and Soave–Redlich–Kwong equations of state when fitted to speed of sound data instead of density data. An analysis is conducted on the effect on other derivative properties such as isothermal compressibility and isobaric expansivity. The analysis is based on water, alkanols/diols, and a group of hydrocarbons. A critical assessment is conducted on how this approach affects other properties.