Catalysis

Vanillin

Engineering

Nitrobenzene

Kraft process

Raw material

Chemical engineering

Physical chemistry

Polymer

Biopolymer

Organic chemistry

Kraft paper

Chemistry

Electrode

Electrolyte

Pulp and paper industry

Electrolysis

Lignin

ACS Sustainable Chemistry & Engineering

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.

High-Temperature Electrolysis of Kraft Lignin for Selective Vanillin Formation