Carolin Regenbrecht

Highly selective generation of vanillin by anodic degradation of lignin: a combined approach of electrochemistry and product isolation by adsorption.

Summary The oxidative degradation of lignin into a variety of valuable products has been under investigation since the first half of the last century. Especially, the chance to claim this cheap, abundant and renewable source for the production of the important aroma chemical vanillin (1) was one of the major driving forces of lignin research. So far most of the developed methods fail in technical application since no viable concept for work-up is included. This work represents a combined approach of electrochemical conversion of Kraft lignin and product recovery by adsorption on a strongly basic anion exchange resin. Electrolysis conditions are optimized regarding reaction temperatures below 100 °C allowing operation of aqueous electrolytes in simple experimental set-up. Employing ion exchange resins gives rise to a selective removal of low molecular weight phenols from the strongly alkaline electrolyte without acidification and precipitation of remaining lignin. The latter represents a significant advantage compared with conventional work-up protocols of lignin solutions.

Treatment of black liquor (BL) by adsorption on AE resins and a subsequent electrochemical degradation of BL to obtain vanillin

Abstract The dominating kraft pulping process leads to kraft pulp and to black liquor (BL), which is incinerated for recovery of inorganic chemicals. A certain part of the BL can also be used as a source of organic chemicals without disturbing the recovery and energy balance of the mill. In this research, the removal of low molecular weight (MW) phenolic products from BL without disturbing the recovery process. Strongly basic anion exchange (AE) resin was utilized to deplete BL from different phenolic derivatives on a preparative scale. The adsorbed low MW phenols can be easily liberated by acidic treatment. Completely depleted BL was then electrochemically treated for further highly selective degradation of kraft lignin. This combined approach enabled the concentration of phenolic substances.

Efficient electroorganic synthesis of 2,3,6,7,10,11-hexahydroxytriphenylene derivatives.

Summary 2,3,6,7,10,11-Hexahydroxytriphenylene of good quality and purity can be obtained via anodic treatment of catechol ketals and subsequent acidic hydrolysis. The electrolysis is conducted in propylene carbonate circumventing toxic and expensive acetonitrile. The protocol is simple to perform and superior to other chemical or electrochemical methods. The key of the method is based on the low solubility of the anodically trimerized product. The shift of potentials is supported by cyclic voltammetry studies.