Local environment effects on the pyrolysis of a tethered, nanoconfined lignin model compound

Lignin is viewed as an alternative feedstock for renewable energy, however there is a lack of thermochemical kinetic data to predict reaction pathways and kinetics involved in the decomposition of this very complex, cross-linked macromolecular structure. Here we are interested in describing the effects of restricted diffusion and interfacial structure by conducting a systematic investigation into the reaction pathways of silica-immobilized phenethyl phenyl ether (=PPE), the simplest model compound that represents the dominant arylglycerol-β-aryl ether (β-O-4) interunit linkage in lignin. It is known that PPE decomposes through two competitive pathways as a result of hydrogen abstraction from either the α-carbon or β-carbon, with product selectivity described as α/β. However, on a surface, the rearrangement pathway that follows the abstraction at the β-carbon, involves an O, C-phenyl shift rearrangement that is largely influenced by the local environment. Our recent studies show that during the pyrolysis of tethered PPE in a mesoporous silica, the selectivity is also influenced by pore confinement, tailoring the pore with inert spacer molecules, and controlling grafting density. Here we will discuss the effects that grafting density, varying the characteristics of spacers, and alterations in surface environment have on the product selectivity and rates on the pyrolysis of tethered PPE in mesoporous MCM41 (2.8 nm pore) at 375°C.