Highly selective conversion of guaiacol to tert-butylphenols in supercritical ethanol over a H2WO4 catalyst

Fuhang Mai; Kai Cui; Zhe Wen; Kai Wu; Fei Yan; Mengmeng Chen; Hong Chen; Yongdan Li

doi:10.1039/c8ra07962e

Highly selective conversion of guaiacol to tert-butylphenols in supercritical ethanol over a H₂WO₄ catalyst

RSC Adv. 2019 Jan 21;9(5):2764-2771. doi: 10.1039/c8ra07962e. eCollection 2019 Jan 18.

Authors

Fuhang Mai^{1

2}, Kai Cui^{1

2}, Zhe Wen^{1

2}, Kai Wu^{1

2}, Fei Yan^{1

2}, Mengmeng Chen^{1

2}, Hong Chen³, Yongdan Li^{1

2

4}

Affiliations

¹ State Key Laboratory of Chemical Engineering (Tianjin University), Tianjin Key Laboratory of Applied Catalysis Science and Technology, School of Chemical Engineering, Tianjin University Tianjin 300072 China.
² Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) Tianjin 300072 China.
³ School of Environmental Science and Engineering, Tianjin University Tianjin 300072 China chenhong_0405@tju.edu.cn +8613920176659.
⁴ Department of Chemical and Metallurgical Engineering, School of Chemical Engineering, Aalto University Kemistintie 1, Espoo, P. O. Box 16100, FI-00076 Aalto Finland.

Abstract

The conversion of guaiacol is examined at 300 °C in supercritical ethanol over a H₂WO₄ catalyst. Guaiacol is consumed completely, meanwhile, 16.7% aromatic ethers and 80.0% alkylphenols are obtained. Interestingly, tert-butylphenols are produced mainly with a high selectivity of 71.8%, and the overall selectivity of 2,6-di-tert-butylphenol and 2,6-di-tert-butyl-4-ethylphenol is as high as 63.7%. The experimental results indicate that catechol and 2-ethoxyphenol are the intermediates. Meanwhile, the WO₃ sites play an important role in the conversion of guaiacol and the Brønsted acid sites on H₂WO₄ enhance the conversion and favour a high selectivity of the tert-butylphenols. The recycling tests show that the carbon deposition on the catalyst surface, the dehydration and partial reduction of the catalyst itself are responsible for the decay of the H₂WO₄ catalyst. Finally, the possible reaction pathways proposed involve the transetherification process and the alkylation process during guaiacol conversion.