Recovery of vanillin from kraft lignin depolymerization with water as desorption eluent

In the concept of biorefineries, the production of added-value compounds from kraft lignin depolymerization is still hindered by the number of separation processes needed to purify the phenolic compounds. In this work, a sequence of oxidation, membrane filtration and chromatographic separation is proposed for the recovery of vanillin. The alkaline wet oxidation achieved a vanillin yield of 4.3% on lignin weight basis. The two-step membrane filtration reduced the initial organic load to 29.5 (+/- 1.8) g/L in the final permeate. The chromatographic step enriches solutions containing vanillin by alternating the feed phase with desorption utilizing only deionized water. In 22 cycles, 71% of the vanillin fed is recovered with at an average 1.5 g/cycle. Recovered fraction has a vanillin concentration of 4.7 g/L which can be further concentrated. This presents a major breakthrough for vanillin production from oxidized softwood lignin as it simplifies the purification procedure, reducing costs with desorption solvents and avoiding acid use.