|Title||Laser‐Mediated Photo‐High‐p,T Intensification of Vitamin D3 Synthesis in Continuous Flow|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||M. Escriba‐Gelonch, A. Halpin, T. Noël, V. Hessel|
A new reactor design for photosynthesis in microflow is presented based on spatial overlap of a laser beam through a capillary tube. A conical Archimedean spiral facilitates exposure of the entire volume of the reaction solution to the irradiation beam. In this fashion, photo‐high‐p,T intensification of the photolysis of 7‐dehydrocholesterol is achieved using either a pulsed ultraviolet (UV) laser excitation (in the order of femtoseconds) alone or in tandem with a conventional UV lamp. The goal is to control the kinetics of the side photoreactions under pulsed photolysis, as well as to reduce the reaction time and enhance the vitamin D3 yield. Three kinds of effects are targeted: a) Utilizing a very large and spatially homogeneous photon flux inside the flowing solution; b) the novel process window of combining photo‐ with thermal intensification to promote the final, irreversible thermal step to vitamin D3; and c) the use of sub‐ps laser pulses to supply excitation energy on a timescale shorter than the formation of side photoproducts. Finally, photo‐processing with the laser alone is compared to the tandem irradiation by the laser‐UV lamp.
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