Extension of a group contribution method to estimate the critical properties of ionic liquids of high molecular mass

The group contribution method proposed by Valderrama and Robles in 2007 and updated by Valderrama and co-workers 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.