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

Efficient and convenient oxidation of cyclohexene to adipic acid with H₂O₂ catalyzed by H₂WO₄ in acidic ionic liquids

Bingtong Wang, Zongbin Zhang, Xinyu Zhang, Shixin Sun, Lin Wu, and Rong Xing

Yancheng Teachers University, Yancheng, China

E-mail: xingrr@126.com

Abstract: A simple, efficient, and eco-friendly catalytic system for the oxidation of cyclohexene to adipic acid with H₂O₂ catalyzed by H₂WO₄ in Brønsted acidic ionic liquids under solvent-free conditions has been developed. Reaction conditions such as the catalysts, the types of anions and cations for Brønsted acidic ionic liquids, reaction temperature, and the amount of hydrogen peroxide, were investigated. Moreover, the Hammett acidity functions (H ₀) of Brønsted acidic ionic liquids were determined using UV–visible spectrophotometry. The optimum reaction condition identified was n(H₂WO₄):n(Brønsted acidic ionic liquids):n(cyclohexene):n(H₂O₂) = 0.02:0.02:1:4.4, and the yield of adipic acid was 96% under the reaction scale of 10 mmol. The catalytic system can be easily recovered and reused for four reaction runs without significant loss of catalytic activity. Simple operation of the catalyst system and avoidance of the emission of nitrous oxide are the benefits of this work.

Keywords: Acidic ionic liquid ; H₂WO₄ ; Adipic acid ; Solvent-free oxidation 

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-017-0303-8

Chemical Papers 72 (3) 643–649 (2018)