Selective defunctionalization by TiO_2 of monomeric phenolics from lignin pyrolysis into simple phenols

摘要

This study is focused on defunctionalizing monomeric phenolics from lignin into simple phenols for applications such as phenol/formaldehyde resins, epoxidized novolacs, adhesives and binders. Towards this goal, Titanium dioxide (TiO_2) was used to selectively remove hydroxyl, methoxy, carbonyl and carboxyl functionalities from the monomeric phenolic compounds from lignin to produce mainly phenol, cresols and xylenols. The results showed that anatase TiO_2 was more selective and active compared to rutile TiO_2. Catechols were found to be the most reactive phenolics and 4-ethylguaiacol the least reactive with anatase TiO_2. An overall conversion of about 87% of the phenolics was achieved at 550°C with a catalyst-to-feed ratio of 5w/w. Over 97% conversion of phenolics is achievable at moderate temperatures (550°C or ≤600°C) and a moderate catalyst-to-feed ratio of 6.5:1. The reactivity of catechols on TiO_2 suggests that titania is a promising catalyst in the removal of hydroxyl moiety.