Experimental Evidence for Azeotrope Formation from Protic Ionic Liquids

Filipe M S Ribeiro; Carlos F R A C Lima; Artur M S Silva; Luís M N B F Santos

doi:10.1002/cphc.201800335

Experimental Evidence for Azeotrope Formation from Protic Ionic Liquids

Chemphyschem. 2018 Sep 18;19(18):2364-2369. doi: 10.1002/cphc.201800335. Epub 2018 Jun 20.

Authors

Filipe M S Ribeiro¹, Carlos F R A C Lima^{1

2}, Artur M S Silva², Luís M N B F Santos¹

Affiliations

¹ Department of Chemistry and Biochemistry, Faculty of Science of University of Porto, Rua do Campo Alegre, 4169-007, Porto, Portugal.
² Department of Chemistry & QOPNA, University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal.

PMID: 29799151
DOI: 10.1002/cphc.201800335

Abstract

Herein, we present experimental evidence that protic ionic liquids (PILs), derived from 1 : 1 liquid mixtures of the organic superbases 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) with carboxylic acids, form azeotropic mixtures with acid/base molar fractions different from 1 : 1. The ability of the carboxylic acids to form strong hydrogen bonds with the PIL ion pair leads to an azeotropic composition richer in the acid component. The results show that the azeotropic composition is ruled by the extent of acid-base equilibrium and the relative volatility of the neutral species in the PIL medium. The PILs show marked negative deviations from Raoult's Law with the stronger superbase (DBU) leading to an azeotropic composition closer to the equimolar 1 : 1 ratio.

Keywords: activity coefficients; carboxylic acids; organic superbases; speciation; volatility.

Publication types

Research Support, Non-U.S. Gov't

Abstract

Publication types

Grants and funding