ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Efficient cyclodehydration of diethylene glycol in Brønsted acidic ionic liquids

Yuan-Yuan Wang, Wei Li, and Li-Yi Dai

Shanghai Key Laboratory of Green Chemistry and Chemical Process, Department of Chemistry, East China Normal University, 200062 Shanghai, China

E-mail: lydai@chem.ecnu.edu.cn

Received: 2 August 2007  Revised: 15 October 2007  Accepted: 29 October 2007

Abstract: Cyclodehydration of diethylene glycol using various Brønsted acidic ionic liquids as dual solvent-catalysts has been studied for the first time. Better results were obtained in the presence of 1-butyl-3-methylimidazolium hydrogen sulfate ([PSmim]HSO₄) compared with other Brønsted acidic ionic liquids. Effects of the reaction conditions such as reaction temperature, reaction time and molar ratio of ionic liquid to diethylene glycol have been investigated. High diethylene glycol conversion, 97.0 %, and high 1,4-dioxane selectivity, 89.3 %, were obtained in [PSmim]HSO₄ under optimum conditions. Hammett method was used to determine the acidity order of these ionic liquids and the results were consistent with the catalytic activities observed in the cyclodehydration reaction. Utilization of Brønsted acidic ionic liquids as dual solvent-catalysts has some advantages, e.g. high conversion of DEG, easy preparation and reuse of ionic liquids, avoiding toxic catalysts and solvents.

Keywords: Brønsted acidic ionic liquids - cyclodehydration - diethylene glycol - 1,4-dioxane - acidity characterization

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-008-0028-9

Chemical Papers 62 (3) 313–317 (2008)