High-Temperature Electrolysis of Kraft Lignin for Selective Vanillin Formation

Abstract

Lignin represents the largest renewable resource of aromatic moieties on earth and harbors a huge potential as a sustainable feedstock for the synthesis of biobased aromatic fine chemicals. Due to the complex, heterogeneous, and robust chemical structure of the biopolymer, the valorization is associated with significant challenges. Unfortunately, technical lignins, which are a large side stream of the pulp and paper industries, are mainly thermally exploited. In this study, technical Kraft lignin was selectively electrochemically depolymerized to the aroma chemical vanillin. Using electricity, toxic and/or expensive oxidizers could be replaced. The electrodegradation of Kraft lignin was performed at 160 °C in a simple undivided high-temperature electrolysis cell and studied in respect to several reaction parameters. At optimized electrolytic conditions vanillin could be obtained in high selectivity with 67% efficiency compared to the common nitrobenzene oxidation. Additionally, the established high-temperature electrolysis indicated a reliable process and could be easily adapted to a variety of different Kraft lignins.

Electrochemical Degradation of Lignin by ROS

“…To increase the products selectivity on the Ni anode, a simple undivided high-temperature electrolytic cell for the electrooxidation of lignin at 160 • C has been designed recently. Under the optimized electrolysis conditions, the vanillin can be obtained with a yield of 4.2 wt%, which in high selectivity with 67% efficiency compared to the common nitrobenzene oxidation [63]. However, the degradation of lignin through electro-generated *OH on the anode is accompanied by a strong oxygen evolution reaction (OER).…”

Biogene Produkte: Guter Geschmack aus Holz

“…Ein elektrochemisches Verfahren arbeitet nun mit Kraft-Lignin als Rohstoff, um Vanillin zu produzieren, dessen Qualität aufgrund reagenzfreier Umsetzung die Bezeichnung "natürliches Vanillin" zulässt. 4 der Substitutionsmuster am aromatischen Kern bezeichnet als H-, Gbeziehungsweise S-Einheit, Abbildung oben rechts).…”

“…18) Diese elektrokatalytisch aktive Schicht ist schwerlös- Die Methode ist robust: Angewendet auf technisch relevante Kraft-Lignine verschiedener Qualität ergaben sich Ausbeuten zwischen 2,2 Gewichtsprozent und 4,2 Gewichtsprozent. 4) Durch den simplen, preiswerten Zweielektrodenaufbau ist dieser Prozess bestehenden Verfahren wirtschaftlich überlegen.…”

Lignin-Assisted Water Electrolysis for Energy-Saving Hydrogen Production With Ti/PbO2 as the Anode

“…At low temperatures, the conversion rate of lignin and the rate of hydrogen evolution reaction (HER) is generally low (Caravaca et al, 2019;Li et al, 2020). But both of them can be promoted evidently when the temperature is increased from ambient temperature to about 100 °C (Zirbes and Quadri, 2020). Temperature can change the intrinsic reaction rate of the chemical reaction and the mass transfer rate of reactants/ products, so it can have a great influence on the LAWE.…”