Christopher M. Saffron

Bio-oil derived from lignocellulosic biomass represents an alternative to fossil fuels as an energy source and chemical feedstock. Fast pyrolysis of lignocellulosic biomass yields a rich mixture of oxygenated organic species with low energy density and low stability, which can be electrochemically upgraded to increase energy density and stability and produce value-added chemicals. Here, we focus on electrocatalytic hydrotreatment of furfural (FF) and 4-propylphenol (4-PP), two constituents of raw bio-oil. In a binary mixture, the presence of FF has been shown to inhibit the reduction of 4-PP. The underlying mechanisms of these competing reactions are probed using density functional theory (DFT) and experimental electrochemical deposition techniques. The binding energies of FF and 4-PP, as well as their respective reduction products and associated reaction thermodynamics, are examined comparatively on multiple facets of single-crystal platinum and ruthenium catalysts. FF is shown to bind competitively compared to 4-PP, particularly on Pt(111) and Ru(0001), and hydrogenation products such as tetrahydrofurfuryl alcohol (THFA) and 4-propylcyclohexanol (4-PCOL) were found to bind less strongly to the surfaces than the reactants. FF reduction side products, including dimers furoin (FUI) and hydrofuroin (HF), were also found to bind competitively with 4-PP. No thermodynamic barriers were observed for FF hydrogenation to THFA, whereas 4-PCOL formation is favored on Pt facets, and propylcyclohexane (PC) formation is favored on Ru. The presence of barriers to 4-PP hydrogenation indicates that FF hydrogenation is thermodynamically favored on Pt and Ru. Further, limiting potential calculations suggest that the FF reduction pathways are generally favorable around 0 V vs. RHE. In contrast, the 4-PP reduction pathways require a more cathodic bias, achieved at potentials less than -0.1 V vs. RHE. The adsorption behavior of FF-derived reduction products on polycrystalline Pt is experimentally validated using a Quartz Crystal Microbalance (QCM). Such experiments yield estimates of aqueous-phase free energies of adsorption, which are compared with computational results that are correlated to the aqueous phase. Overall, the DFT model results suggest that the observed inhibition of 4-PP by FF is due to competitive adsorption and favorable FF reaction thermodynamics.

Bio-oil derived from lignocellulosic biomass represents a sustainable alternative to fossil fuels as an energy source and chemical feedstock. Fast pyrolysis of lignocellulosic biomass yields a rich mixture of oxygenated organic species with low energy density and low stability, which can be electrochemically upgraded to increase energy density and stability and produce value-added chemicals. Here, we focus on electrocatalytic hydrotreatment of furfural (FF) and 4-propylphenol (4-PP), two constituents of raw bio-oil. In a binary mixture, the presence of FF has been shown to inhibit the reduction of 4-PP. The underlying mechanisms of these competing reactions are probed using density functional theory (DFT) and experimental electrochemical deposition techniques. The binding energies of FF and 4-PP, as well as their respective reduction products and associated reaction thermodynamics, are examined comparatively on multiple facets of single-crystal platinum and ruthenium catalysts. FF is shown to bind competitively compared to 4-PP, particularly on Pt(111) and Ru(0001), and hydrogenation products such as tetrahydrofurfuryl alcohol (THFA) and 4-propylcyclohexanol (4-PCOL) were found to bind less strongly to the surfaces than the reactants. FF reduction side products, including dimers furoin (FUI) and hydrofuroin (HF), were also found to bind competitively with 4-PP. No thermodynamic barriers were observed for FF hydrogenation to THFA, whereas 4-PCOL formation is favored on Pt facets, and propylcyclohexane (PC) formation is favored on Ru. The presence of barriers to 4-PP hydrogenation indicates that FF hydrogenation is thermodynamically favored on Pt and Ru. Further, limiting potential calculations suggests that the FF reduction pathways are generally favorable around 0 V vs. RHE. In contrast, the 4-PP reduction pathways require a more cathodic bias, achieved at potentials less than -0.1 V vs. RHE. Adsorption behavior of FF-derived reduction products on polycrystalline Pt is experimentally validated using a Quartz Crystal Microbalance (QCM). Such experiments yield estimates of aqueous-phase free energies of adsorption, which are correlated with the gas phase for comparison with computational results. Overall, the DFT model results suggest that the observed inhibition of 4-PP by FF is due to competitive adsorption and favorable FF reaction thermodynamics.

Electrocatalytic transformation of a phenolic compound on activated carbon cloth-supported Ru and Pt was inhibited in the presence of furfural. Reduction of furfural to furfuryl alcohol prior to electrolytic treatment mitigates the inhibitory effect.

Electrocatalytic transformation of oxygenated aromatics to cycloalkanes on activated carbon cloth-supported ruthenium and platinum under mild conditions (≤60°, atmospheric pressure) using hydrogen equivalents produced in situ by water splitting.

In this paper, we examine how traditional life-cycle assessment (LCA) for bio-based and compostable plastics overlooks issues surrounding carbon sequestration and microplastic persistence. To outline biased comparisons drawn from these omitted environmental impacts, we provide, as an example, a comparative LCA for compostable biobased vs. non-compostable fossil-based materials. In doing so we (1) demonstrate the proper way to capture carbon footprints to make fair comparisons and (2) identify the overlooked issues of microplastics and the need for non-persistent alternatives. By ensuring accurate biogenic carbon capture, key contributors to CO₂ evolution are properly identified, allowing well-informed changes to formulations that can reduce the environmental impact of greenhouse gas emissions. In a complimentary manner, we summarize the growing research surrounding microplastic persistence and toxicity. We highlight the fundamental ability and the growing number of studies that show that industrial composting can completely mineralize certified compostable materials. This mineralization exists as a viable solution to combat microplastic persistence, currently an absent impact category in LCA. In summary, we propose a new paradigm in which the value proposition of biobased materials can be accurately captured while highlighting compostables as a solution for the increasing microplastic accumulation in the environment.

Electrocatalytic transformation of furfural to tetrahydrofurfuryl alcohol on activated carbon cloth-supported ruthenium at mild conditions (≤ 50 °C under atmospheric pressure) using hydrogen equivalents produced in situ by water splitting.

This study presents a technoeconomic analysis (TEA) for a novel ionic polybutylene adipate-co-terephthalate (PBAT), CPBAT, as a paper coating material, showcasing excellent water and oil resistance. This TEA determined total capital investment, operating costs, and minimum selling prices for a production capacity of 1,000 kg of CPBAT per day. The minimum selling prices of CPBAT coated on Kraft paper (CPBAT-K) and CPABT coated on starch-coated Kraft paper (CPBAT-S) are estimated to be $1.327/m² and $1.864/m², respectively. Additionally, the results of a sensitivity analysis show that the production of CPBAT-K and CPBAT-S is highly sensitive to the production capacity, raw material costs, energy efficiency of the coating process, reaction energy, and reaction yield. Recovery of the ionization solvent only marginally increases the selling prices of CPBAT-K and CPBAT-S, and hence, it is highly favorable. By increasing production capacity, lowering raw material costs, using energy-efficient coating machines, and partially recovering energy from reactions, the prices of CPBAT-K and CPBAT-S can be reduced to $0.588/m² and $0.914/m², respectively. Given that commercial polyethylene-coated paper prices range from $0.94/m² to $1.850/m², CPBAT-based coated papers with comparable mechanical and barrier properties along with biodegradability and recyclability are positioned as highly competitive and sustainable alternatives in the market.

Microalgae could be sustainably used to sequester CO₂ and processed to fuels and chemicals.

Quantification of environmental impacts through life cycle assessment is essential when evaluating bioenergy systems as potential replacements for fossil-based energy systems. Bioenergy systems employing localized fast pyrolysis combined with electrocatalytic hydrogenation followed by centralized hydroprocessing (Py-ECH) can have higher carbon and energy efficiencies than traditional cellulosic biorefineries. A cradle-to-grave life cycle assessment was performed to compare the performance of Py-ECH versus cellulosic fermentation in three environmental impact categories: climate change, water scarcity, and eutrophication. Liquid hydrocarbon production using Py-ECH was found to have much lower eutrophication potential and water scarcity footprint than cellulosic ethanol production. Greater amounts of renewable electricity led to lower greenhouse gas emissions for the Py-ECH processing. When the renewable fraction of grid electricity is higher than 87%, liquid hydrocarbon production using Py-ECH has lower greenhouse gas emissions than cellulosic ethanol production. A sensitivity analysis illustrates the major role of annual soil carbon sequestration in determining system-wide net greenhouse gas emissions.