Solar photochemical reactors

Reactions involving cycloalkanes as hydrogen donors and electron-poor alkynes e.g., methyl propiolate or dimethyl acetylenedicarboxylate) were carried out both in a photochemical reactor (350 nm) and under solar irradiation. 

The field of aquatic photochemistry encompasses a wide diversity of areas within environmental science. Natural waters receiving solar radiation are active photochemical reactors. Within these reactors, primary and secondary processes are occurring. Heterogeneous reactions are associated with both living and nonliving particulate matter. Naturally occurring humic substances are relatively efficient initiators of photochemical reactions. Many xenobiotic chemicals in natural waters undergo either direct or indirect photochemical transformations. 

Continuous xenon (Xe) arc lamps are very high intensity visible light emitters with good yield of UV which decreases in intensity from about 400 nm downwards emission also extends out into the near IR (Fig. 14.3c). Emission is a continuum with some high intensity emission lines from xenon, particularly around 420 80 nm and in the near IR, superimposed. Most fluorimeters use Xe-arc lamps as excitation source and these emission lines can be used for internal wavelength calibration e.g., the line at 467 nm can be used to calibrate the position of the excitation monochromator in a fluorimeter. Xe-arc lamps also make excellent high intensity irradiation sources for photochemical reactors. When fitted with a suitable Air Mass filter they give a reasonable approximation to the solar spectrum and are widely used in solar simulators. 

Xu J, Ao Y, Fu D, Lin J, Lin Y, Shen X, et al. Photocatalytic activity on Ti02-coated-side-glowing optical fiber reactor under solar light. J. Photochem. Photobiol. 2008 199 165-9. 

Regarding the photocatalyst structural configuration, thin-film powder layer and/or fluidized bed, coated wall-parallel, and honeycomb/foam monolithic reactors are probably the most representative. For photochemical water splitting, batch-type photoreactor is most frequently used configuration in lab-scale investigations. In the case of solar photoreactor systems, there are two of the major design issues (i) whether to use a suspended or a supported photocatalyst and (ii) whether to use concentrated or non-concentrated sunlight. 

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