Unwanted conversion of monoterpenes during industrially relevant conditions
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Journal Title
Journal ISSN
Volume Title
Kemian tekniikan korkeakoulu |
Master's thesis
Authors
Date
2024-08-29
Department
Major/Subject
Chemistry
Mcode
CHEM3023
Degree programme
Master's Programme in Chemical, Biochemical and Materials Engineering
Language
en
Pages
76+7
Series
Abstract
Methanol is a widely used fuel that can be produced from renewable sources such as biomass, helping to reduce fossil fuel consumption and environmental impact. However, the purification of raw methanol produced during kraft pulping poses some challenges. Therefore, this thesis investigated the unwanted conversion of monoterpenes during the methanol purification process in a kraft pulp mill. In the experimental part, native from deposits were obtained and analysed, along with deposits produced at the laboratory scale. Soxhlet extraction yielded 46% of acetone-soluble deposits. Native and acetone-soluble deposits were analysed using NMR and GC-MS, which identified the presence of monoterpenes such as alpha-pinene incorporated by sulphur and nitrogen containing compounds. It shows non-volatile organic compounds (VOCs) might play important role in polymerization. Elemental analysis, XPS and FTIR provided complementary information indicating the presence of carbon-nitrogen and carbon-sulphur bonds. Solubility tests revealed that the precipitates have moderate polarity, and black precipitates were reproduced at the laboratory scale using in-methanol sample from the mill. Based on the analytical results and literature study, it is hypothesized that a general reaction mechanism involving the acid-catalysed polymerization of monoterpenes in the presence of H2SO4. The mechanism involves protonation, nucleophilic attack by sulphur compounds, oxidation, and nitrogen incorporation. Key parameters in the polymerization process include the presence of nucleophile, acidity, and residence time. Results indicated that monoterpenes, such as alpha-pinene, incorporated with nitrogen and sulphur, are the main precursors for the unwanted precipitates formed during the methanol purification process. These findings can further help in developing strategies to mitigate polymerization and optimize the process.Description
Supervisor
Vuorinen, TapaniThesis advisor
Dou, JinzeKyllönen, Pia
Keywords
monoterpenes, methanol, distillation, polymerization, sulphur