Statistical design of experiments for production and purification of vanillin and aminophenols from commercial ligninElectronic supplementary information (ESI) available. See DOI: 10.1039/d0gc01234c

Lignin is a complex polyphenolic substance that collectively represents the largest renewable source of aromatic carbon on Earth. Despite low yield and purity from depolymerized lignin, bio-derived vanillin (4-hydroxy-3-methoxybenzaldehyde) is a desirable molecule in the food/beverage and fragrance industries. To maximize vanillin yield from commercially-available softwood lignin, a series of oxidation reactions were conducted using a Box-Behnken statistical design. By varying time, temperature and O 2 pressure, optimal conditions were selected using the Response Surface Method, and a maximum vanillin yield of 5.3 wt% was achieved. Flash chromatography of depolymerized lignin was investigated by comparing anion exchange and reversed-phase resins and fractions were characterized by GC-MS, GPC-HPLC, FT-IR and NMR. Anion exchange separations using 1M NaCl as the sole mobile phase reached a vanillin purity of 55 wt %. Lastly, the vanillin mixture was reacted via reductive amination, and facile acid-base work up led to the formation of 4-((diethylamino)methyl)-2-methoxyphenol at 94.3 wt % purity. The aminophenol is an intermediate in the synthesis of pharmaceutical agents, ionic liquids and benzalkonium salts. Production and purification of vanillin from lignin using ion exchange, and subsequent conversion to aminophenol ionic liquid precursors.