PRODUCTS OF NITROBENZENE OXIDATION FROM NON-WOOD LIGNIN ISOLATED BY SULPHURIC ACID

摘要

Lignin is a very attractive and promising raw material to produce vanillin. Lignin was isolated from black liquor by adding sulphuric acid at four levels of concentration (5, 25, 50 and 72 wt%) and subsequently adjusting the pH to 5. The alkaline nitrobenzene procedure for determining lignin structural units has been applied to non-wood lignin and qualitative and quantitative analyses of oxidative-cleavage reaction were evaluated. The total yield of the oxidation products ranged from 34.1 to 36.3 mu molesg(-1) pure lignin. The dominant phenolic compound was vanillin followed by syringaldehyde. For precipitated lignin samples, the G:S:H ratio varies between 9:3:1 and 7:3:1. It was confirmed that the yield of nitrobenzene oxidation and the contentof phenolic products depends on the isolation procedure.