Selecting Critical Properties of Terpenes and Terpenoids through Group-Contribution Methods and Equations of State


The knowledge of critical properties is fundamental in engineering process calculations for the estimation of thermodynamic properties and phase equilibria. A literature survey shows a large number of methods for predicting critical properties of different classes of compounds, but no previous study is available to evaluate their suitability for terpenes and terpenoids. In this work, the critical properties of terpenes and terpenoids were first estimated using the group contribution methods of Joback, Constantinou and Gani, and Wilson and Jasperson. These were then used to calculate densities and vapor pressure through the equations of state Peng-Robinson (PR) and Soave Redlich Kwong (SRK) and then compared with the experimental values. On other hand, density and vapor pressure experimental data were used to estimate the critical properties directly by the same equations of state (EoSs), allowing a comparison between the two estimation procedures. For this purpose densities for 17 pure terpenes and terpenoids were here measured at atmospheric,pressure in the temperature range (278.15 to 368.15) K. Using the first approach, the best combination is the Joback's method with the Peng Robinson EoS, despite the high relative deviations found for vapor pressure calculations and difficulties to predict density at low temperatures. Following the second approach, the set of critical properties and acentric factors estimated are able to adequately correlate the experimental data. Both equations show a similar capability to correlate the data with SRK EoS presenting a global %ARD of 3.16 and 0.62 for vapor pressure and density, respectively; while the PR EoS presented 3.61 and 0.66, for the same properties, both giving critical properties estimates also closer to those calculated by the Joback method, which is the recommended group-contribution method for this type of compounds.



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Martins, MAR; Carvalho, PJ; Palma, AM; Domanska, U; Coutinho, JAP; Pinho, SP

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This work was developed in the scope of the projects POCI-01-0145-FEDER-007679-CICECO-Aveiro Institute of Materials (ref. FCT UID/CTM/50011/2013), POCI-01-0145-FEDER-006984-Associate Laboratory LSRE-LCM both funded by European Regional Development Fund (ERDF) through COMPETE2020, Programa Operational Competitividade e Internacionalizacao (POCI), and by national funds through FCT (Fundacao para a Ciencia e a Tecnologia). This work is also a result of project "AlProcMat@N2020 (Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020)", with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through ERDF. M.A.R.M. acknowledges FCT for her Ph.D. grant (SFRH/BD/87084/2012) and COST for the STSM Grant from COST action CM1206. P. J. Carvalho also acknowledges FCT for a contract under the Investigador FCT 2015, Contract No. IF/00758/2015. A.M.P. acknowledges Infochem-KBC for his Ph.D. grant. The software Multiflash from Infochem-KBC was applied in some of the calculations

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