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The aerobic, partial oxidation of THPMI for the production of cashmeran

MacGinley, Joseph 2021. The aerobic, partial oxidation of THPMI for the production of cashmeran. PhD Thesis, Cardiff University.
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The industrial production of Cashmeran is of vital importance to the fragrance industry. This is due to Cashmeran being the only molecule with a floral-fruity musky odour with conifer woody aspects, that also has a low odour threshold. The current process to produce Cashmeran is an aerobic, partial oxidation of the bicyclic alkene, tetrahydropentamethyl indane (THPMI); this process is currently limited by low selectivity at high conversion. This thesis explores the effect the current industrial catalyst, Co�bis(2-ethylhexanoate), has on this reaction. Although without any catalyst the oxidation occurs rapidly, inclusion of Co-bis(2-ethylhexanoate) improves overall selectivity to the desired products (Cashmeran and Cashmeran-alcohol), increases the Cashmeran to Cashmeran-alcohol ratio, and slightly increases the rate of reaction. The catalyst supresses build-up of the primary oxidation product, tetrahydropentamethyl indane hydroperoxide (THPMI-HP), which is likely the cause of increased selectivity as undesired radical reaction routes are supressed. The catalyst also causes reaction quenching, which is related to the temperature of reaction and strongly to the loading of catalyst in the reaction. This quenching phenomenon is likely a result of free cobalt ions causing radical termination reactions, drastically slowing down the rate of THPMI oxidation. Alternative catalysts were tested including supported cobalt oxide on aminated silica (CoO/SiO2), cobalt (II, III) oxide (Co3O4), Molybdenum blue and various acid catalysts. The cobalt�based catalysts demonstrate catalytic activity to convert THPMI into THPMI-HP, but not for the decomposition of THPMI-HP into the desired products. Molybdenum blue, glutaric acid, and Amberlyst-15 supress conversion and selectivity significantly. Small amounts of cobalt leaching occurs when using heterogeneous cobalt catalysts which was shown to have minimal impact on the reaction. It was also demonstrated that ppm levels of Co-bis(2-ethylhexanoate) are capable of initiating oxidation of THPMI into THPMI-HP, although do not facilitate THPMI-HP decomposition into the desired products. This work has demonstrated the complex, radical-mediated nature of the oxidation of THPMI into Cashmeran and the subtle yet vital effect Co-bis(2-ethylhexanoate) has on the reaction. Although no superior alternative catalyst has been demonstrated, this work builds the foundation for further research into this reaction and how to control selectivity and so improve yield of Cashmeran.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Chemistry
Date of First Compliant Deposit: 23 May 2022
Last Modified: 24 May 2022 10:02

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