Abstract
Neutron scattering with isotopic substitution was used to study the structure of concentrated sulfuric acid, and two protic ionic liquids (PILs): a Brønsted-acidic PIL, synthesised using pyridine and excess of sulfuric acid, [Hpy][HSO4]·H2SO4, and a hydrated PIL, in which an equimolar mixture of sulfuric acid and pyridine has been doped with water, [Hpy][HSO4]·2H2O. Brønsted acidic PILs are excellent solvents/catalysts for esterifications, driving reaction to completion by phase-separating water and ester products. Water-doped PILs are efficient solvents/antisolvents in biomass fractionation. This study was carried out to provide an insight into the relationship between the performance of PILs in the two respective processes and their liquid structure. It was found that a persistent sulfate/sulfuric acid/water network structure was retained through the transition from sulfuric acid to PILs, even in the presence of 2 moles (∼17 wt%) of water. Hydrogen sulfate PILs have the propensity to incorporate water into hydrogen-bonded anionic chains, with strong and directional hydrogen bonds, which essentially form a new water-in-salt solvent system, with its own distinct structure and physico-chemical properties. It is the properties of this hydrated PIL that can be credited both for the good performance in esterification and beneficial solvent/antisolvent behaviour in biomass fractionation.
Original language | English |
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Pages (from-to) | 9785-9795 |
Number of pages | 11 |
Journal | Physical Chemistry Chemical Physics |
Volume | 25 |
Issue number | 14 |
Early online date | 10 Jan 2023 |
DOIs | |
Publication status | Published - 14 Apr 2023 |
Keywords
- General Physics and Astronomy
- Physical and Theoretical Chemistry
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Dive into the research topics of 'The structure of protic ionic liquids based on sulfuric acid, doped with excess of sulfuric acid or with water'. Together they form a unique fingerprint.Student theses
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New approaches to studying liquid structure and Lewis acidity
McGrogan, A. (Author), Swadzba-Kwasny, M. (Supervisor) & Holbrey, J. (Supervisor), Jul 2024Student thesis: Doctoral Thesis › Doctor of Philosophy
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