Microwave Photochemistry and Photocatalysis. Part 1: Principles and Overview

Vladimir      Cirkva; Stanislav      Relich

Abstract

The coupled activation of photochemical and photocatalytic reactions by using of two different types of radiation, microwave and UV/Vis, is covered by the new discipline called microwave photochemistry and photocatalysis. Such a connection might have a synergic effect on reaction efficiencies or, at least, enhance them by summing up the individual effects. The objective of this discipline is frequently, but not necessarily, connected to the electrodeless discharge lamp (EDL) as a novel light source which generates efficiently UV/Vis radiation when placed into a microwave field. This review article is focused on the general principles of microwave photochemistry and photocatalysis, i.e. generation of UV/Vis discharge in EDL (theory of the microwave discharges, construction of EDL, preparation of the thin titania films on EDL, spectral characteristics of EDL, and performance of EDL). Likewise, the various microwave photochemical and photocatalytic reactor types (batch with external or internal light source, flow-through with external light source, annular flow-through with internal EDL, and cylindrical flow-through surrounded with EDL) with different arrangement of the lamps are described. The concept of microwave photochemistry and photocatalysis as an important issue in synthetic chemistry and material science is presented in several tables.

Keywords: Batch and flow-through photoreactor, electrodeless discharge lamp, microwave, photocatalysis, photochemistry, thin titania films, photochemical, photocatalytic reactions, synthetic chemistry, material science, thin titania, Organic Syntheses, Or-ganic Reactions, photoactivation, ultrasound, high pressure, mechanical activation, supercritical fluids, electro-chemistry, microwave chemistry, ultrasound (US)-assisted chemical proc-esses, photocatalytic reactors, plasma chemistry, electrotechnics, avalanche, mercury, argon, electromagnetic spectrum, magnetron, aqueous 10 hydrofluoric acid, sol-gel methods, nanosized metallic oxide, polycondensation, oxopolymers, gelization, crystallization, surfactants, calcination, acetylacetonate, X-ray diffraction, Raman spectroscopy, X-ray photoelectron, spectroscopy, scanning electron microscopy (SEM), atomic force micros-copy (AFM), absorption spectroscopy, monochroma-tors, electrode lamp, spectrometer, line emission peaks, continuous bands, quartz, Pyrex Hg-EDLs, buffer noble gas, cis-trans photoi-somerization, electromagnetic energy, magnetron oscillator, MICROWAVE PHOTOCHEMICAL AND PHOTOCATA-LYTIC REACTORS, fiber optic spectral probe, cylindrical photoreactor, Photo-hydrolysis, mono-chloroacetic acid, pH electrode, Batch Photocatalytic Reactors, semiconductor photocatalyst, Flow-through Photocatalytic Reactors