Dedicated research on photochemical reactors is
fundamental to the application of this technology to real-life problems. In line
with this trend, we report a study of structural parameters of micro-structured
packed bed reactors (μPBR) regarding their ability to promote intensification. We
present an investigation on the effects of the size of spherical packings on
the developed flow regime, and its implications for the performance of the
reactor on a photochemical reaction in aqueous phase. Tubular reactors were
built with combinations of borosilicate glass tubes of two diameters (20 and 30
mm) packed with soda-lime glass spheres of three average diameters (1.0, 3.0
and 6.0 mm), alumina spheres of 6.0 mm diameter, and polished iron spheres of
5.0 mm diameter. Residence Time Distributions (RTD) were measured for each combination
of outer tube and glass sphere sizes. Results showed that as the packing size
decreases, the observed flow regime becomes closer to an ideal PFR, suggesting
that smaller packings are more suitable to applications that require precise
control of residence time. The aqueous-phase oxidation of benzoic acid by
oxygen radicals generated by UV-A irradiation of nitrite ions was used as model
photochemical reaction. We also observed that increasing the D/d<sub>p</sub> ratio
for narrower reactors faster specific reaction rates are achieved, suggesting that
intensification is possible in these reactors; however, the overall yield
decreases, probably due to increased photon loss. Lastly, we found that glass
spheres can be replaced by alumina spheres with little loss in light-collection
efficiency, indicating an attractive pathway for immobilized photocatalysis.
Determination of photochemical reaction rates using thermal lens spectrometry
