An Investigation of Select Monomers and The Synthesis of Model Dimers Possessing the 4-O-5 Linkage and Their Ability to Undergo Electrocatalytic Hydrogenation

Abstract

While fossil fuels provide many advantages, our increased demand for them has driven up carbon dioxide concentrations in the atmosphere and has caused us to dig deeper in to the planet to obtain them. As we search for renewable, cleaner energy sources bio-oil, derived from biomass, is emerging as one of the possible replacements. Bio-oil itself is not suitable to use directly and must be upgraded. One of the components of bio-oil that is extremely difficult to cleave during fast pyrolysis is lignin. The 4-O-5 linkage in lignin, although not the most abundant, can tolerate 600°C pyrolysis while staying intact, indicating that the aryl-aryl ether bonds are very strong. However, electrocatalyric hydrogenation (ECH) may be able to cleave the strong ether bond under mild conditions. In this project, two 4-O-5 linkage dimer models were successfully synthesized in good overall (66% and 56%) yields. Further ECH on one of the 4-O-5 dimers proved that this strong 4-O-5 linkage could be cleaved by mild ECH conditions in high yields. While under the same mild conditions, lignin monomers can also readily undergo ECH and be upgraded to fuel-level molecules with good yields.