| Hydrocarbons, made from fossil petroleum, currently remain the most practical energy sources for transportation. But with current energy crisis and the implication of burning fossil fuels as one of the major contributors to climate change, the production of fuels from biomass has become a possible alternative to displace fossil-based fuels. Unfortunately, biomass suffers from two flaws: (1) Inefficiency: at best, plants only capture and store about 1% of the sun's energy in chemical form; and (2) Energy density: biomass has about one third of the energy that of hydrocarbons. So, deriving value from all components of biomass including lignin, optimizing conversion processes that can harness the chemical energy stored in biomasses efficiently, and converting biomass to fuels that are energy dense is essential.;To this end, conventional biomass to ethanol conversion strategies utilize pretreatment methods such as extractive ammonia pretreatment (EA) and alkaline hydrogen peroxide pretreatment (AHP), to improve the rates and extents of subsequent hydrolysis of sugars and maximize biofuel yields. As part of the pretreatment method, EA and AHP also enable the recovery of lignin which is often combusted for heat and power production. Lignin however accounts for 40% of the energy of biomass and is one of the largest natural sources of renewable aromatic compounds so it can be an ideal candidate for the production of higher-value products that would otherwise be derived from petrochemical feedstocks. The challenges in lignin valorization however come from lignin's complex structure that is naturally designed to be resistant to biological degradation. Thermochemical conversion processes such as fast pyrolysis offer a strategy for lignin depolymerization.;During fast pyrolysis the feedstock (biomass, lignin, etc.) is liquefied by heating in an oxygen free environment to form biochar, combustible gas and bio-oil. The biochar co-product has potential for use in soil amendment and carbon sequestration. The combustible gas is often burned for heat and power production. The major product, bio-oil, has the potential to displace liquid hydrocarbon fuels. However, bio-oil's reactive and corrosive nature along with its low energy content are major barriers for the adaption of this system. Classical catalytic upgrading is usually used to hydrogenate and deoxygenate bio-oil, often at high temperature and very high pressure. These severe conditions can result in barriers, such as catalyst deactivation. To avoid these conditions, electrocatalytic hydrogenation (ECH) can be used to stabilize bio-oil via hydrogenation and deoxygenation of reactive components under mild conditions (25--80 °C and 1 atm).;As lignin is converted to phenolic monomers, dimers, and oligomers upon pyrolysis, the transformation of lignin model compounds exhibiting similar bonding arrangements indicates the potential for lignin valorization using ECH. In this study, conversion, yield, and faradaic efficiency of ECH of model compounds derived from pyrolysis of lignins extracted from pretreated biomass are examined. ECH of these compounds is carried out using an activated carbon cloth supported ruthenium cathode. Having uncovered surprisingly easy aryl ether cleavages, the outcome of this research will provide understanding to further integrate biomass pretreatment, pyrolysis, and electrocatalysis systems for bio-oil stabilization and lignin valorization. |
