Catalytic hydrolysis of lignin-derived aryl methyl ethers over zeolites

Promovendus/a: Xian Wu

Promotor(en): Prof. dr. ir. Bert Sels

Global warming, boosted by the substantial carbon dioxide (CO2) emissions resulting from fossil fuel consumption, poses a grave threat to our planet. Addressing this urgent issue requires the development of sustainable technologies independent of traditional fossil feedstocks and fuels. Biomass, alongside plastic waste and CO2, presents itself as a compelling contender for realizing a minimized carbon footprint in the production of carbon-based chemicals and materials. Lignin, a primary constituent of lignocellulosic biomass and the predominant aromatic carbon reservoir in plants, bears substantial promise as a renewable reservoir for bioaromatics and cyclic hydrocarbons within the circular bioeconomy paradigm.

However, the chemical reactivity and broad applicability of technical lignins and lignin-derived chemicals are hindered by the methoxy groups of the native aryl methyl ethers. Overcoming this limitation requires selectively unlocking the phenolic hydroxyl functionality through O-demethylation, offering expanded possibilities for application. Notably, a recently developed lignin-first biorefinery, particularly the reductive catalytic fractionation (RCF) approach, has demonstrated success in producing substantial quantities of functionalized monomeric phenolics, known as guaiacols and syringols. In this context, our research explores the potential of acid catalysis for O-demethylation, transforming guaiacols into corresponding catechols—an industrially appealing compound with versatile applications. Commercialized zeolites, with unique microporous systems, serve as catalysts in this process, surpassing other types of catalysts, such as metal oxides and aqueous mineral acids, in hot liquid water.