Photochemical reactor bubble

Deposits at the lamp jacket can also be prevented in bubble photochemical reactors, where small rising gas bubbles of nearly uniform size and distribution create strong turbulences [2, 3, 18, 68]. This reactor is usually conceived as an annular photochemical reactor of relative small thickness (/R, Eq. 36). In principle, its use with reactive gas is rather limited, as the turbulence provoked by the bubbles must be maintained over the entire height of the reactor [69, 70]. Bubble characteristics may also change as a function of the flux of the substrate solution. 

A solution of 96 mg (65 mmol) of 85 in 60 mL of cyclohexane in a quartz tube is deoxygenated by argon bubbling. Irradiation is carried out by means of a Rayonet photochemical reactor using 254 nm irradiation lamps during 4 h. The solution is evaporated and the residue is separated by preparative HPLC (RSiL, 10 mm, 25 x 1 cm, 5mL/min) using hexane/ethyl acetate (30 1) as eluant. Compound 86 (30 mg) is obtained as colorless oil, while... 

In order to operate an immersion-well photochemical reactor effectively, first of all the air is removed finm the solvent by slowly allowing inert nitrogen or ai on gas to bubble through it via the sintered glass-disk. It is equally important to make sure that the correct choice of lamp is made for the reactor before starting the reaction. 

Another example of the OBRs use with solid particles is as a photochemical reactor with solids suspension, in this case the vortical flow patterns being used to suspend catalytic titania particles to convert organics in wastewater. The tita-nia needs to be activated by ultraviolet, and the reaction requires the presence of oxygen, so air is bubbled through. The gas-liquid mass transfer is enhanced by the oscillation of the fluid, as it increases hold-up time (bubble residence time) and reduces bubble size (increasing surface area and further increasing hold-up time). The flow patterns simultaneously ensure good exposure of the titania particles to the radiation from an axially located ultraviolet lamp. 

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