This research deals with a process of catalytic oxidation of flax shives to vanillin and pulp. Catalytic oxidation of flax shives with molecular oxygen allows two main products to be obtained—vanillin with a yield of up to 12 wt.% of lignin, and pulp. Final forms of the catalyst particles (Cu₂O and CuO) are agglomerates or monocrystals 0.5–5 µm in size. Acid prehydrolysis of the shives does not affect the oxidation, in contrast to pine-wood oxidation. Lignin prehydrolysis and oxidation was suggested as illustrate this difference. The dependence of the vanillin formation rate on stirring speed was studied. Minimum alkali consumption in the process was attained with a mild stirring speed of the reaction mass.

Agrotechnical wastes from processing herbaceous plants consist of lignin and polysaccharides, which can be processed into monomers – phenols and carbohydrates. The prospects of chemical processing of several agrotechnical waste types with a high lignin content (flax shives, sunflower seed husks and buckwheat husks) into vanillin, pulp, and glucose by oxidation and acid hydrolysis were studied. It has been shown that despite the distant phylogenetic relationship of the studied plants, their lignins have a similar structure: they contain a similar amount of methoxyl groups (10–13 wt.% per lignin) and give close yields of aromatic aldehydes upon oxidation with nitrobenzene (17–19%) and oxygen (14–16%). In general, the suitability of agrotechnical wastes for oxidation to aromatic aldehydes determines by the lignin content. Among the studied wastes, flax shives are the most promising feedstock for chemical processing into vanillin and glucose. Cellulose-containing solid residues of oxidation process are more easily hydrolyzed compared to the initial lignocellulosic biomass. The inversion of glucose oligomers during the hydrolysis of cellulose with H2SO4 is limited by the hydrolysis of the tetra- and octamers.