Lignin Source
Paper mills may use either coniferous or deciduous trees as feedstock. Mature plant cells need to stiffen cell walls to support the plant, and this is done by the production of a structure containing linked aromatic rings, a material known as lignin. The weight of a tree means a lot has to be produced. Lignin is also involved in water transport.
Coniferous trees produce lignin with a different structure to deciduous trees. The difference is small, but concerns the number of methoxy groups present on the aromatic rings and so affects the amount of vanillin that can be made.

diagram: comparing lignin types diagram: comparing lignin types
diagram: comparing lignin types
diagram: comparing lignin types
diagram: comparing lignin types
diagram: comparing lignin types

Production Method 1: Lignin Route

Route to Vanillin
Specialist paper, with a higher content of fibrous cellulose, is made using the sulphite process. After the paper pulping process (which produces cellulose), a rather unpleasant black liquor remains containing lignin, sugars and process chemicals. The sugars can be fermented, and the remaining lignin is treated with alkali and oxidising agents to break apart the tough lignin structure. The resulting mixture contains vanillin, which is separated from other products by solvent extraction and purified. Purity is important if the vanillin is to be used in food products.


equation: vanillin from lignin


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