Abstract
Lignin, a complex biopolymer found in vascular plants and as the byproduct of pulping, is anticipated to be one of the next generation�s resources for fuel and chemical feedstocks. To reach the point where lignin can efficiently be utilized, the products from its pyrolysis must be controlled, thus key factors in understanding what will maximize product yields and promote product selectivity must be investigated. We approach this problem through a systematic investigation starting with the simplest model compound that represents the dominant aryl glycerol--aryl ether interunit linkage in lignin, phenethyl phenyl ether, PhCH2CH2OPh (PPE). The decomposition of PPE at 375 �C in the gas and solution phases is now well understood, and occurs through a free-radical chain pathway involving competitive hydrogen abstraction at the  or carbon, which leads to different products and is described as the - product selectivity. This selectivity not only depends on relevant substituents, but it is also sensitive to interactions with metal oxide surfaces. Furthermore, covalent confinement in a nanoporous silica, hydrogen bonding interactions with the surface, and changes in the local environment with co-attached spacer molecules all can influence the product selectivity significantly. Here we will describe the impact of pore confinement and pore size, metal oxide surface acidity, hydrogen bonding of oxygen functional groups at the interface, and the influence of organic molecular structure at the interface on the pyrolysis product selectivity of this important lignin linkage.
