Tubular photoreactor “Tube”

Batch or discontinuous reactors have their main drawback in the lack of precise temperature control. Additionally, photon penetration depth can be limited by changes in the medium’s absorbance, meaning that achieving optimal reaction conditions is not always easy.

The Tube tubular or loop photoreactor was developed by UV-Consulting Peschl GmbH in 1995 as part of a pharmaceutical process development in Basel (Switzerland) and belongs to the group of so-called microreactors. Basically, it consists of a UV-transparent fluoropolymer tube through which the liquid to be irradiated circulates, wrapped around a thermally insulated support and irradiation system. This tube can have different diameters and lengths and can be wound in several layers as long as transmittance allows.

This tubular photoreactor operates continuously until the reaction is complete. This implies that reaction kinetics can be optimally adjusted and controlled, while being accurately analyzed throughout the entire circuit. The latter, combined with its continuous mode operation, makes the optimization of existing photochemical processes relatively simple. For example, the potential appearance of by-products due to over-irradiation can be studied and located without great difficulty.

The main advantages of this design compared to flat-plate microreactors lie in the fact that all emitted photons have access to the reaction medium and that the flow channels can be cleaned or replaced with extreme ease. Similarly, the selection of the tube diameter and associated adjustments for the optical path or flow rate represent an advantage when a wide range of reactions is desired (multipurpose continuous flow).

Scale-up is not achieved by increasing the size of the reactor, but by increasing the number of reactors until the desired production volume per unit of time is reached. Consequently, the use of these reactors in industrial processes has considerable limitations and is primarily intended for basic research to avoid errors in subsequent industrial-scale processes.