Scale-up of visible light organo-photocatalytic synthesis reactions in a spinning disc reactor
Alba Acevedo Fernández, Emma A. C. Emanuelsson
Abstract
Visible light photocatalysis uses sunlight or low energy lighting; and recently a range of chemical transformations using organic dye catalysts have been discovered, which can replace toxic and expensive metal catalysts. The challenge is how to scale-up visible light photocatalytic reactors, as they require large surface area to volume ratios, as light penetration is reduced with solution depth. This suggests the use of a high surface area reactor, like a spinning disc reactor (SDR). This article reports the first in-depth study that compares the performance of a visible light SDR to a batch reactor, with the aim of establishing the key scale-up parameters. Two oxidation reactions using cheap organic dye catalysts were studied (mass-transfer-limited & photon-flux-limited) using a specifically designed solar simulator. The key variables influencing the rate constant (s−1) and productivity (kg/s) were disc surface area, light intensity and flowrate. Light uptake was 900% higher for the mass-transfer-limited reaction and 400% higher for the photon-limited-reaction in the SDR in comparison to the batch reactor and a disc pattern study identified optimal flow patterns. Outdoor experiments showed similar results. This study offers a new way to scale-up visible light photocatalytic reactions, thereby reducing energy demand and moving industrial chemistry away from fossil fuels.