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

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.

Facile Preparation of Haggite by Reducing V2O5 in Guaiacol/Methanol Solution.

Haggite-structured V4O6(OH)4 is prepared via a one-step reduction of V2O5 in a mixture of guaiacol and methanol. Guaiacol delays the overreduction of Haggite to V2O3. The time window for the stable existence of the Haggite phase is enlarged at low temperature.