Loponov, Konstantin Nikolayevich (2011) Development of a scalable photochemical reactor for syntheses of fine chemicals. PhD thesis, University of Warwick.

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Abstract

This study is in the area of sustainable chemical technology and is ultimately aimed at
developing a novel generic approach towards efficient, clean, safe and scalable synthesis
of important intermediates for pharmaceutical applications and catalysis using nonthermal
activation of chemical bonds. Current study is focused on molecular activation by
light, specifically addressing the class of singlet oxygen reactions.
A laboratory-scale annular recirculating photoreactor and a scalable microreactor unit
were designed, assembled and tested in oxygenation of α-pinene and stereoselective
oxygenation of homoallylic alcohols by the photogenerated singlet oxygen. Efficiencies
of light utilization and the quantum yields of the reactions for different sources of light in
various lamp-reactor geometries were quantified using actinometry. It was shown that
optimal thickness of the reaction layer, high intensity of light and elevated oxygen
pressures in continuous gas-liquid segmented flow are crucial for both safe and efficient
oxygenation. This study proved the viability of a novel concept of compact reactors with
embedded light emitting diodes. Finally, a methodology of efficient oxyfunctionalization
of allylic compounds was developed.
Following the developed methodology, the applicability of functional nanomaterials
based on pure and dye-modified porous silicon as heterogeneous photosensitizers of
singlet oxygen was studied in detail. It was demonstrated that the photosensitizing
efficiency of all the samples is much lower than that of conventional dye photosensitizers.
Low activity of the novel photosensitizers was attributed to quenching of the
photogenerated singlet oxygen by the surface quenching groups of porous silicon, low
quantum yield of photoluminescence in the case of pure porous silicon and to
thermodynamically favorable quenching of the photoexcited porphyrin states due to
energy/electron transfer to silicon nanocrystals in the case of dye modified porous silicon.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	T Technology > TP Chemical technology
Library of Congress Subject Headings (LCSH):	Drugs -- Synthesis, Active oxygen, Photochemistry
Official Date:	February 2011
Dates:	Date Event February 2011 Submitted
Institution:	University of Warwick
Theses Department:	School of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Lapkin, Alexei
Extent:	248 leaves : ill., charts
Language:	eng
URI:	http://wrap.warwick.ac.uk/id/eprint/35523

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