The group contribution method proposed by Valderrama and Robles in 2007 and extended by Valderrama and Rojas in 2009 to estimate the critical properties of ionic liquids is revised and an additional test for determining the consistency of the estimated properties is proposed. The new testing method includes the calculation of the saturation pressure at the normal boiling temperature using an equation of state and an accurate model to represent the temperature function of the attractive term in the equation of state. In determining the vapor pressure, the critical temperature, the critical pressure, the critical volume, and the acentric factor determined by group contribution are included. The proposed method complements the previous density test of the authors that tested the critical temperature, the critical volume, and the normal boiling temperature only. A total of 1130 ionic liquids are considered in this work, and double checking, using the density and the normal vapor pressure, is applied. Also, a spreadsheet file that allows any reader to calculate and check the critical properties of other ionic liquids containing any of the 44 groups defined by the method is provided.

The group contribution method proposed by Valderrama and Robles in 2007 and updated by Valderrama and coworkers in 2012 to estimate the critical properties of ionic liquids is extended to evaluate these properties for ionic liquids of higher molecular mass. The modifications are done to follow the behavior that these properties have for other type of substances, such as the asymptotic tendency of the normal boiling temperature as the molecular mass M increases. The magnitudes of the modifications are found so that the pressure test and the density test previously defined by the authors are fulfilled for most substances. The proposed extension does not change anything of the original method already in use which is valid for ILs with M < 500 g/mol. A total of 316 ionic liquids with M > 500 g/mol are considered in this work. Of these, 310 passed the pressure test. Also, 111 of these ILs have experimental density values and 103 pass the density test, with absolute average deviation of 4.1 %. A spreadsheet for calculating the critical properties and performing the tests is provided as Supporting Information. The spreadsheet file includes at present the properties for 1630 ionic liquids of molecular mass going from 77 to 1730.

No abstract

No abstract

No abstract

ResumenSe aplica un modelo para el cálculo de la viscosidad del tipo ecuación cúbica de estado de Peng-Robinson. El modelo ha sido empleado para correlacionar y predecir viscosidades de sustancias puras y mezclas en especial en la región de saturación. Los parámetros del modelo han sido generalizados en términos de la masa molar. Las expresiones generalizadas son estimadas mediante el ajuste de datos experimentales de alcanos y alcoholes. Las desviaciones absolutas promedio para la viscosidad, entre los valores correlacionados y los experimentales, son 6.26% y 7.21% para alcanos y alcoholes, respectivamente. Se realizan cálculos predictivos con desviaciones absolutas promedio de 3.99% para alcanos y 13.76% para alcoholes. Para viscosidades de mezclas se utilizaron tres enfoques de reglas de mezclado. Las desviaciones promedio calculadas son 18.66%, 10.31% y 3.85% para las reglas simples, de uno y dos parámetros respectivamente. Los resultados indican que el modelo propuesto proporciona resultados adecuados y consistentes, teniendo en cuenta la simplicidad de las expresiones generalizadas desarrolladas. Palabras clave: viscosidad; ecuaciones cúbicas de estado; sustancias puras; mezclas Modeling the Viscosity Based on Peng-Robinson Type Cubic TP Equation AbstractA viscosity model based on the Peng-Robinson cubic equation of state is applied. The model has been used to correlate and predict viscosities of pure substances and mixtures especially in the saturation zone. The parameters of the model are generalized in terms of the molar mass. The generalized expressions are estimated by fitting the experimental data for a group of alkanes and alcohols. Average deviations between calculated values and experimental data for alkanes and alcohols are 6.26% and 7.21%. Some predictive calculations are performed for alkanes and alcohols finding average absolute deviation of 3.99% and 13.76%. To extend the model to mixtures, some binary mixtures calculations are performed using three mixing rule approaches. The results obtained with the simple, one and two interaction parameters mixing rules are 18.66%, 10.31% and 3.85%. The results indicate that the new viscosity model provides results that can be considered adequate and consistent taking in account the simplicity of the generalized expressions.

No abstract

A group contribution method developed by Valderrama and Robles in 2007 is updated and extended to calculate the critical properties, the normal boiling temperature, and the acentric factor of metal-containing ionic liquids (MILs). The proposed extension is valid for all types of ionic liquid, including MILs, for which the values of the contributions are reported in this paper. Values of 29 new metal groups are determined, and the estimated properties of 2574 new ionic liquids are tested for consistency using two independent tests, one for density and another for vapor pressure, as previously proposed by the authors. A spreadsheet for calculating the critical properties and performing the tests is provided as Supporting Information. The spreadsheet file includes at present the properties for 4156 ionic liquids of molar mass going from 77 to 1730, including MILs.