Photooxygenation in an advanced led-driven flow reactor module: Experimental investigations and modelling

• Published in: Chemical engineering and processing 2018-08, Vol.130, p.214-228
• Main Authors: Radjagobalou, Robbie, Blanco, Jean-François, Dechy-Cabaret, Odile, Oelgemöller, Michael, Loubière, Karine
• Format: Article
• Language: English
• Subjects: Chemical and Process Engineering; Chemical engineering; Chemical Sciences; Engineering Sciences; Flow photochemistry; Kinetic law; LED-driven flow reactor; Modelling; Photooxygenation; Sensitizer bleaching
• ISSN: 0255-2701; 1873-3204
• DOI: 10.1016/j.cep.2018.05.015

[Display omitted] •The two-phase photooxygenation of α-terpinene to ascaridole is investigated in an advanced LED-driven flow reactor.•The kinetics law is thoroughly established based all mechanistic steps.•The reaction conditions that enable minimization of sensitizer bleaching are identified.•Gas-liquid hydrodynamics can affect the conversion rates.•A model is proposed to predict the α-terpinene conversion when pure oxygen is used as reagent gas. The photooxygenation of  α-terpinene was investigated as a benchmark reaction in an advanced LED-driven flow reactor module, both from an experimental and modelling point of view. Ethanol was used as a green solvent and rose Bengal was chosen as a cheap sensitizer of industrial importance. Firstly, the kinetic law based on all mechanistic steps was established for the chosen photooxygenation. From this, the set of operating parameters potentially influencing the photoreaction rate were identified. Subsequently, experiments were carried out under continuous-flow conditions to screen these operating parameters, namely concentration of α-terpinene, concentration of photosensitizer, residence time, structure of the segmented gas-liquid flow and nature of the reagent gas phase (air versus pure oxygen). Finally, the conditions enabling minimization of sensitizer bleaching were established. It was also shown that the hydrodynamic characteristics of the gas-liquid flow can have an effect on the conversion levels. From this, a simplified model was proposed to predict the conversion at the reactor’s outlet when pure oxygen was used.