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Dalligos, Desiree (2024) Continuous reaction monitoring by dielectric spectroscopy. PhD thesis, University of Nottingham.

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Abstract

Off-line monitoring is a valuable method in research and industrial processes for obtaining important information of a process or chemical reaction. Unfortunately, it is time consuming, inefficient and challenging for reactions that use toxic reagents and high temperature/ pressure conditions. Furthermore, this method consists of safety hazards to the operators. An alternative approach is to continuously monitor the reaction in situ by employing the appropriate process analytical technique. There are many analytical techniques available, however, there is no single analytical technique that can be applied to every system.

This work demonstrates the potential of dielectric spectroscopy (DS) as a process analytical technique for monitoring chemical synthesis. Different types of reaction systems were monitored by DS to observe any changes to the dielectric properties throughout the course of the reaction. The results were then corroborated with other well established techniques such as NMR spectroscopy and FTIR spectroscopy.

A univariate method was developed to select a single frequency which gave the best prediction for following the concentration of the starting material of the monitored reaction. The use of multivariate methods to analyse the data such as Principal Component Analysis (PCA) and Partial Least Squares (PLS) regression were also applied. It was found that PLS was more advantageous compared to univariate analysis and PCA.

Temperature fluctuations of the monitored reaction caaffect the dielectric measurements as DS is a highly temperature dependent technique. Therefore, any temperature changes throughout the reaction could affect the quality of the results. The robustness of the PLS model was investigated by changing the reaction condition by 5°C and the new data was tested on the PLS model which was built from the original reaction conditions. The results showed that a 5°C difference in temperature was tolerable and did not show any significant difference to the results.

A method for gauging the sensitivity of the instrument was also developed to test the suitability of a new reaction to be analysed by DS as a monitoring technique. Additionally, DS was able to monitor a fluorescent reaction which is advantageous compared to Raman spectroscopy due to broad fluorescent peaks. The availability of a commercial probe and fibre optic cable for DS also means that it can easily be implemented in reaction processes.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Ball, Liam T. Dimitrakis, Georgios Pilling, Michael J.
Keywords:	dielectric spectroscopy, on-line/ in-line reaction monitoring, process analytical technology, multivariate data analysis
Subjects:	Q Science > QD Chemistry > QD 71 Analytical chemistry
Faculties/Schools:	UK Campuses > Faculty of Science > School of Chemistry
Item ID:	77036
Depositing User:	Dalligos, Desiree
Date Deposited:	24 Jul 2024 04:40
Last Modified:	24 Jul 2024 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/77036

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