Effect of bleaching on the transformation of wood stilbenes
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School of Chemical Engineering |
Master's thesis
Authors
Date
2024-09-30
Department
Major/Subject
Biomass Refining
Mcode
Degree programme
Master's Programme in Chemical, Biochemical and Materials Engineering
Language
en
Pages
74
Series
Abstract
This study aimed to investigate the mechanism of the reaction of polydatin, resveratrol, and pinosylvin with chlorine dioxide, focusing on studying the effects of reaction time and relative molar concentration of chlorine dioxide on stilbene's oxidation and chlorination. The proposed reaction mechanism compared the reactivity of polydatin, resveratrol, and pinosylvin based on their functional groups, such as meta-OH, para-OH, and -glucoside. In the experimental part, polydatin, resveratrol, and pinosylvin model compounds reacted with chlorine dioxide in an aqueous solution. The secondary form products were analyzed by GC-MS to study the effect of reaction time (ranging from 0.1 to 60 minutes) between stilbenes and chlorine dioxide (and HClO). The identified portfolio of products conforms to the predicted reaction mechanism. Glucoside oxidized products were detected from polydatin, along with oxidized and chlorinated polydatin and the monomeric components. For resveratrol, the higher oxidized and chlorinated monomeric compounds were identified. Additionally, unreacted pinosylvin, benzoic acid, and mono-, di-, and tri-chlorinated pinosylvin were identified from reactions of pinosylvin and ClO2. The product com-position and quantities between the 0.1- and 60-minute reactions remained very similar, indicating that the majority of reactions were completed within just 0.1 minutes (six seconds). However, some minor reactions were observed in polydatin, like the increased amount of chlorinated polydatin and chlorinated monomeric compounds. The large error bars in triplicate data can be attributed to the fact that stilbenes and chlorine dioxide still react when the reaction is quenched under zero degrees. The total amount of pinosylvin and its chlorinated pinosylvin decreased along with the increase in the relative molar ratio of chlorine dioxide. The concentration of highly chlorinated products was also increased, such as di-chlorinated pinosylvin and tri-chlorinated pinosylvin, along with the decreased concentration of pinosylvin and monochlorinated pinosylvin. The study on the reaction mechanism between hypochlorous acid and pinosylvin confirmed the chlorination reaction that is triggered by hypochlorous acid.Description
Supervisor
Vuorinen, TapaniThesis advisor
Dou, JinzeKeywords
wood extractives, stilbene, polydatin, resveratrol, pinosylvin, chlorinated stilbene, hypochlorous acid