Upgrading Kolbe Electrolysis—Highly Efficient Production of Green Fuels and Solvents by Coupling Biosynthesis and Electrosynthesis

Abstract

The chemical industry is transitioning to more sustainable and biobased processes. One key element of this transition is coupling energy fluxes and feedstock utilization for optimizing processes, routes and efficiencies. Here, we show for the first time the coupling of the Kolbe electrolysis at the anode with a subsequent microbial conversion of the cathodically produced coproduct hydrogen. Kolbe electrolysis of valeric acid yields the liquid drop-in fuel additive n-octane. Subsequently, the solvent isopropanol is produced by resting Cupriavidus necator cells using gaseous electrolysis products (esp. CO 2 and H 2 ). The resting microbial cells show carbon efficiencies of up to 41 % and Coulombic/ Faradaic efficiencies of 60 % and 80 % for anodic and cathodic reactions, respectively. The implementation of a paired electrolyser resulted in superior process performances with overall efficiencies of up to 64.4 %.

Killing Two Birds with One Stone: Upgrading Organic Compounds via Electrooxidation in Electricity-Input Mode and Electricity-Output Mode

“…Besides the desired Kolbe-product, a co-product of CO 2 with a double-molar fraction was generated at the anode and usually stoichiometric amounts of H 2 from water electrolysis at the cathode. Therefore, in an undivided electrolyzer, the respective gaseous electrolysis products of CO 2 and H 2 are to be obtained, and these can be directly utilized without further purification [ 82 ]. Recently, Markus Stöckl and co-workers [ 82 ] reported the first coupling of the anodic Kolbe electrolysis with a subsequent microbial conversion of the produced coproduct hydrogen at the cathode.…”

“…Therefore, in an undivided electrolyzer, the respective gaseous electrolysis products of CO 2 and H 2 are to be obtained, and these can be directly utilized without further purification [ 82 ]. Recently, Markus Stöckl and co-workers [ 82 ] reported the first coupling of the anodic Kolbe electrolysis with a subsequent microbial conversion of the produced coproduct hydrogen at the cathode. Kolbe electrolysis of valeric acid yielded n-octane.…”

“…The resulted efficiencies of the process steps and the overall efficiency are shown (CE = Carbon efficiency, FE = Faradaic efficiency). Reproduced with permission [ 82 ], Copyright 2022, Wiley Publishing Group.…”