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Transformations of pine wood during exposure to ozone were studied. The content of lignin and cellulose in the cellulose-containing material (CCM) from ozonated wood was determined. The polymerization degree (PD) of cellulose from CCM was determined. The CCM samples were examined by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and X-ray diffraction (XRD) analysis. HPLC analysis of water-soluble lignin ozonolysis products was performed. Wood ozonation leads to lignin destruction; 40–42% delignification degree is achieved. The destruction of aromatic components is confirmed by DRIFT spectra. A decrease in the intensity of skeletal vibrations of aromatic ring at 1511 and 1598 cm–1, bands at 1662 cm–1, and an increase in the intensity of stretching C=O vibrations of lignin and hemicelluloses (HCs) at 1736 cm–1 were observed. The stoichiometric ratio of the amount of absorbed ozone and the destroyed guaiacyl units, as well as the composition of water-soluble products, shows that ozonolysis is the main mode of wood lignin destruction. The XRD data and a decrease in PD of cellulose show that, in addition to lignin, HCs and amorphous cellulose are also destroyed during ozonation. It has been found that the region of ozone specific absorption ≤1.5 mmol O3/g corresponds to the most efficient destruction of lignin with the lowest degradation of cellulose fiber.

Ozonation has been considered as a method for the pretreatment of plant biomass to obtain cellulose and monosaccharides. Ozone consumption by aspen wood with various moisture contents has been investigated. We have considered the gradual transformation of the substrate: wood to ozonated wood to cellulose-containing product (CP) to holocelluloze (HC) and to cellulose. Yields of ozonated wood (OW), the (CP), water-soluble ozonation products, HC, and cellulose have been determined. The lignin content in the CP has been estimated. Both HC and cellulose samples have been studied by IR spectroscopy. The degree of polymerization and molecular mass distribution of cellulose obtained from ozonated wood have been determined. It has been shown that wood destruction by ozone is accompanied by degradation of lignin, hemicelluloses, and cellulose. It has been found that physicochemical properties of cellulose obtained from ozonated wood can be regulated by the variation of the initial moisture content in the substrate. Both molecular ozone and radical species, which are generated in the course of ozone reactions with water present in the substrate structure, participate in wood destruction.