Demethylation of model lignin to polyphenols catalyzed by solid acid in halogen-free aqueous system

In this study, different solid acids were used as catalysts for demethylation of model compound 2-methoxy-4-methylphenol (creosol) to produce 4-methylcatechol (4-MeCat) in halogen-free aqueous system. The results showed that a high 4-MeCat yield of 48.5% was achieved over TiO 2 supported on activated carbon, while the Nb 2 O 5 catalyst with suitable Brønsted/Lewis acid site exhibited the highest average production rate of 0.053 min −1 . The high total acidity improves the 4-MeCat yield and a suitable ratio of Brønsted to Lewis acid sites benefits the catalytic activity over unit acid sites. The stable crystal and acid sites of Nb 2 O 5 catalyst result in high activity stability, while the supported TiO 2 catalyst is deactivated much faster. The loss of acid sites and acid site coverage are the main deactivation reasons for demethylation in aqueous medium.