Isolation and characterization of vanillin from coconut husk lignin via alkaline nitrobenzene oxidation

Abstract

Isolation of vanillin from lignin extracted from coconut husk is presented in this study. Phosphoric acid (20%) is employed to precipitate the lignin from the black liquor produced by cooking the mixture of coconut husk and 1M NaOH in steam autoclave at 121°C for one hour. Separation of vanillin from lignin was carried out via oxidation by adding 0.1 g of coconut husk lignin into a mixture of 2M NaOH (10 ml) and nitrobenzene (0.4 ml) in steel capillary bomb heated at 160°C for 2.5 hours. Detection and quantification of vanillin presents in the lignin oxidized mixture was performed by liquid and gas chromatography. The recovery of vanillin from the mixture was done via crystallization process by dissolving the mixture in acetone and heats up to 60°C with periodic stirring. Vanillin crystal appeared by rapidly cooled the heated mixture in the ice bath. The vanillin obtained was characterized by Infrared Spectroscopy (FTIR) for component verification. Component isolation by HPLC and GC-FID denoted the retention time of vanillin appeared around 18.852 minutes and 16.913 minutes respectively. A yield of 2.83% vanillin was isolated from 0.1 g lignin sample and the result of FTIR characterization has suggested that the isolated compound is vanillin