Platinized Titanium as Alternative Cost‐Effective Anode for Efficient Kolbe Electrolysis in Aqueous Electrolyte Solutions

Abstract

Five commercial materials were assessed for electrochemical conversion of n‐hexanoic acid by Kolbe electrolysis. Platinized titanium performed best, achieving a coulombic efficiency (CE) of 93.1±6.7 % (n=6) for the degradation of n‐hexanoic acid and 48.3±3.2 % (n=6) for the production of n‐decane, which is close to the performance of pure platinum (89.7±14.4 and 55.5±3.5 %; n=6). 56.7 mL liquid fuel was produced per mole n‐hexanoic acid, converting to an energy demand of 6.66 kWh and 1.22 € per L. Using optical profilometry and scanning electron microscopy coupled with energy‐dispersive X‐ray spectroscopy, it was shown that the degree of coverage of the titanium surface with platinum played the most important role. An uncovered surface of as little as 1–3 % already led to a deterioration of the CE of approximately 50 %. Using platinized titanium requires >36 times less capital expenditure at only <10 % increased operational expenditure; an electrode lifetime of 10000 h can be expected.

Study on the Effect of Electrolyte pH during Kolbe Electrolysis of Acetic Acid on Pt Anodes

“…It was shown that at extreme cell voltages above 20 V a yield of 64.7 % of n‐triacontane was obtained in a basic electrolyte (1.3 M KOH) and at a cell temperature of 55 °C. Besides pure platinum electrodes, platinized titanium electrodes were investigated for the conversion of n‐hexanoic acid to n‐decane [28] . Qui et al [10] .…”

“…Besides pure platinum electrodes, platinized titanium electrodes were investigated for the conversion of n-hexanoic acid to n-decane. [28] Qui et al [10] demonstrated the catalytic activity of RuO 2 and IrO 2 thin films for the conversion of valeric acid. The two latter studies report promising activity and selectivity to both Kolbe and (non)-Kolbe products, while platinum (e. g. platinum foil) was revealed as the most effective electrode for Kolbe electrolysis.…”

“…Conversion of these more complex acid structures appears extremely sensitive to the applied process conditions and electrode composition. Specifically, the influence of electrode material, [10,27,28] solvent type and reactant concentration, [29] reactor configuration [30] and potential [22] are crucial. This is illustrated by, for example Zhang et al [29] for the conversion of palmitic acid to n-triacontane.…”

3D Printed Microreactors for the Continuous Non‐Kolbe Electrolysis

“…These olefins include important monomers like propylene [12,13] or ethyl acrylate [3], whereas oxygenated products show promising applications in fuel design [4] or fine chemical industry [6]. While the general reaction con-ditions of (Non-)Kolbe electrolysis were thoroughly studied [7,8], current research focuses on the substrate scope [14,15], economical and ecologically improved anodes [3,16], and sophisticated reaction engineering like in situ product separation [3,9,10] or continuous processes [10,17,18]. The Non-Kolbe electrolysis of monomethyl succinic acid enables a sustainable pathway to methyl acrylate, which is used in textile industry.…”

Bio-Electrocatalytic Conversion of Food Waste to Ethylene via Succinic Acid as the Central Intermediate

“…Several approaches are known to convert carboxylic acids (e.g., levulinic acid, hexanoic acid) into longer-chain aliphatic compounds (fuels) or high-value organic chemicals, ,,− but the carboxylic acids need to be produced and purified before electrochemical conversion. Electro-biorefinery concepts combine biological and electrochemical processes to facilitate the conversion of complex renewable feedstocks into high-value chemicals. ,, Long-chain alkanes, such as decane, obtained from the Kolbe reaction, are suitable transportation fuels, but they are not ideal substrates for the chemical industry, due to their lack of chemical functional groups . Therefore, other non-Kolbe products, such as alkenes are more desirable.…”