A novel green preparation process for N-acetyl-L-cysteine: More efficient, economical and environmentally friendly

N-acetyl-L-cysteine (NAC) is widely used in the biochemistry, pharmaceuticals and food additives. At present, the synthesis methods of NAC are difficult to achieve high-quality NAC production due to multi-step separation, poor product quality and heavy pollution. In this study, a new green process was developed combined with organic synthesis, electrochemical reduction and electrodialysis technology to efficiently produce high quality NAC. This new process adopted the strategy of acylation followed by electrolysis. Firstly, L-cystine was acetylated to N, N'-diacetyl-L-cystine (DiNAC), and then DiNAC was electrochemically directly reduced to NAC using carbon cathode. Finally, the high quality NAC was extracted after desalting by electrodialysis. The novel preparation process avoids racemization and oxidation of intermediate products, achieves the removal of impurities, desalting and recycling of electrolyte, and largely reduces wastes discharge. The pilot scale test showed that the total yield was 73.1%, the electrochemical yield was 96.2%, and the energy consumption was 2.56 kW·h kg−1. The brief environmental and tech-economic analysis demonstrated that the process had the advantages of mild reaction conditions, short synthesis steps, high product quality, low waste emissions. It indicates that this novel process is efficient, economical, environmentally friendly, and suitable for the industrial production.