CHEMICAL COMPOSITION OF HYDROLITIC LIGNINS OF RICE HUSKS, WOOD SAWDUST, COTTON SEED HUSKS OF HYDROLYSIS PLANTS UZBEKISTAN AND OPTIMAL CONDITIONS FOR OBTAINING WATER-SOLUBLE NITROLIGNIN

The chemical composition of hydrolysis lignins of rice husks (HLRH), wood sawdust (HLWS), and cottonseed husks (HLCSH) taken from the dumps of hydrolysis plants in the Republic of Uzbekistan has been studied. It was found that in HLRH, the ash content (23.9%) is higher than in HLCSH (3.72%) and HLWS (3.83%), and the content of Klason lignin is lower (41.2%) than in HLCSH (79.3%) and HLWS (68.9%). The content of elemental carbon (C) minus the ash content in HLCSH turned out to be higher than in HLWS and HLRH. The content of H, O, S and N mainly varies depending on the plant source and the profile of the hydrolysis plant. Since HLCSH is obtained from cottonseed husks, which are a waste product of cottonseed oil production, it contains peptide and protein substances. Therefore, this is the main factor explaining the higher content of N than in other studied hydrolysis lignins (HL). It has been established that HLCSH has the highest content of -COOH groups than HLRH and HLWS, and it can be considered the most oxidized HL among those considered. In terms of the content of -OCH3 groups, HLWS is almost 1.35–1.56 times higher than HLRH and HLCSH, which indicates the predominance of hardwood sawdust, in which lignin structural units with guaiacyl and syringyl structures predominate. Oxidative nitration of HL was carried out by the wet method, using a mélange (nitrating mixture – nitric and sulfuric acids) solution in order to prevent the formation of hydrocyanic acid, the absence of an aggressive reaction medium, and the practicality of transferring the method to a production scale. The following parameters were chosen as optimal conditions: fraction size less than 2 mm; the concentration of melange for HLCSH and HLWS should be within 5%, and for HLRH 7%; ration solid : liquid phase 1 : 9; process time 3 hours for HLCSH and HLWS, 6 hours for HLRH. A method is proposed for obtaining water-soluble nitrolignin from HLCSH, HLWS, and HLRH, which can later be used for the production of various plant protection products with plant growth regulator activity.

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