Degradation of lignosulfonate to vanillic acid using ferrate

Abstract

A new method is presented using electrochemically generated ferrate to degrade the technically relevant bio-based side-stream products, lignin and lignosulfonate. An exclusive degradation to vanillic acid is found, which was previously a reported by-product. As a natural resource, lignin can be utilized to substitute fossil-based chemicals in the industry to reduce greenhouse gas emissions and positively impact climate change. Ferrate is generated from grey cast iron sacrificial anodes in 40 wt% NaOH with a current efficiency of over 22% at a current density of up to 100 mA cm−2. Vanillic acid is obtained as the sole product after optimizing the reaction parameters, temperature, time, and ferrate concentration for the lignosulfonate degradation via the design of experiments. As a result, yields of 7.2 wt% of the flavoring agent and antioxidant vanillic acid are achieved. The presented two-step degradation provides an inexpensive path for the production of vanillic acid on a laboratory scale from a highly abundant bio-based side-stream.