The closed system pyrolysis of β-O-4 lignin substructure model compounds

Lignin substructure model compounds having a β-O-4 linkage were synthesized. These were guaiacylglycerol-β-guaiacyl ether (GGE) and guaiacylglycerol-β-syringyl ether (GSE) which model guaiacyl and syringyl units respectively. Closed system microscale pyrolysis of GGE and GSE was carried out at 300 °C both in the presence and absence of water vapour. The laboratory degradation of GSE occurred predominantly by breaking the Cβ–O bond of the β-O-4 linkage to form the ring B fragment of the model compound. This was followed by demethylation of the aromatic methoxyl groups. Char formation was another significant process during pyrolysis. There are structural features of the char formed during the heating of GGE which indicate incorporation of the remaining fragment of the model compound (ring A coupled with the propyl segment of the aryl ether linkage).