Decoding Solvent Effects in Electrocatalytic Biomass Valorization: Levulinic Acid to γ‑Valerolactone.

Area of Science:

• Green Chemistry and Catalysis
• Electrochemical Engineering
• Biomass Conversion

Background:

• Electrocatalytic hydrogenation (ECH) of levulinic acid (LA) is a sustainable pathway to gamma-valerolactone (GVL), a valuable green solvent and fuel additive.
• Existing research often overlooks the critical influence of solvent choice on reaction outcomes, conflating substrate conversion with actual product yield.

Purpose of the Study:

• To systematically investigate the role of different solvent environments and temperatures in the ECH of LA to GVL.
• To decouple the effects of solvent properties and temperature on LA conversion and GVL selectivity.
• To establish design principles for optimizing GVL production via ECH.

Main Methods:

• Electrocatalytic hydrogenation of LA using various metal cathodes (GC, Cu, Ni, CuNi).
• Experiments conducted in three distinct solvents (methanol, DMSO, IPA) at two temperatures (15 °C and 35 °C).
• Analysis of solvent properties (viscosity, dielectric constant, ionic conductivity) and computational modeling (DFT).

Main Results:

• Solvent choice significantly impacts the maximum achievable LA conversion, while temperature governs selectivity towards GVL.
• At 15 °C, LA conversion occurs, but lactonization to GVL is suppressed. At 35 °C, GVL selectivity exceeds 90% in methanol, particularly with Ni-based catalysts.
• Methanol proved most effective due to low viscosity and high ionic conductivity, minimizing diffusion and ohmic losses. DMSO showed intermediate performance, while IPA yielded the lowest conversions.

Conclusions:

• Efficient LA-to-GVL ECH requires a synergistic interplay between catalyst, solvent properties, and temperature.
• Optimizing GVL production necessitates careful consideration of solvent effects on mass transport and reaction kinetics, alongside temperature control for thermally assisted lactonization.
• This study provides a clear design rule for maximizing GVL yield in ECH processes, emphasizing solvent and temperature optimization over mere conversion.