Deoxyalkylation of guaiacol using haggite structured V4O6(OH)4

Abstract

When V₂O₅ is used for the deoxygenation of guaiacol in methanol, it is reduced in situ to haggite structured V₄O₆(OH)₄. Guaiacol prevents further reduction of the haggite phase in methanol and haggite catalyzes the partial deoxygenation of guaiacol. Haggite is a metastable redox catalyst for the deoxygenation of guaiacol, which follows the reverse Mars–van Krevelen mechanism. In addition, haggite is also a Lewis acid catalyst and catalyzes the alkylation of guaiacol with methanol as the alkylation reagent. The main products of the guaiacol deoxyalkylation are 2,6-dimethylphenol, 2-methoxy-6-methylphenol, 2,4,6-trimethylphenol, 2,3,6-trimethylphenol, 2,3,5,6-tetramethylphenol and 6-methyl-2-tert-butylphenol. Oligomerization takes place during the reaction but it is reversible. When the reaction is performed at 300 °C for 6 h, the 83.5% total selectivity for alkylphenols is achieved with a 99.0% conversion.