Photooxidation reactors

Drivers for Performing Photooxidation of Dienes in Micro Reactors... 

Beneficial Micro Reactor Properties for Photooxidation of Dienes... 

Photooxidation of Dienes Investigated in Micro Reactors Cas/liquid reaction 24 [CL 24] Oxidation of cyclopentadiene by singlet oxygen to 2-cyclopentene-1,4-diol... 

Photooxidation of CO was carried out with a flow reactor at room temperature (303 K). Prior to each experiment, the samples were calcinec at 473 K for 2 h in vacuo. The samples were hydoxylated by being exposed tc water vapor (20 Torr). UV irradiation was carried out with a UV lamp equipped with a UV-30 cut-off filter (< 300 nm). 

Prengle et al. (1996) studied the photooxidation by UV/H202 of waterborne hazardous Q-Q compounds in drinking water. Their work was conducted in a photochemical batch stirred-tank reactor, with medium pressure mercury arc immersion lamps of 100 and 450 W, covering the visible UV range, (578.0 to 222.4 nm). Tetrachloromethane, tetrachloroethane, dichloro-ethane, dichloroethene, trichloroethane, trichloroethene, and benzene were the compounds studied. Dark oxidation rates and photooxidation rates were determined. The latter rate constants were 104 to 10s greater than those under dark conditions. 

Martianov, I.N., Savinov, E.N., and Parmon, V.N., A comparative study of efficiency of photooxidation of organic contaminants in water solutions in various photochemical and photocatalytic systems. 1. Phenol photooxidation promoted by hydrogen peroxide in a flow reactor, /. Photochem. Photobiol. A Chem., 107, 227-231, 1997,... 

Obee TN. Photooxidation of sub-parts-per-million toluene and formaldehyde levels on titania using a glass-plate reactor. Environ Sci Technol 1996 30 3578-3584. 

Martyanov IN, Savinov EN, Parmon VN (1997) A Comparative Study of Efficiency of Photooxidation of Organic Contaminants in Water Solutions in Various Photochemical and Photocatalytic Systems. 1. Phenol Photooxidation Promoted by Hydrogen Peroxide in a Flow Reactor, J. Photochem. Photobiol. A Chem. 107 227-231. 

The reactivity of PO over titania-silica catalysts was tested in two ways. (a)Thermal isomerization of PO PO (20 pmol) was introduced to the reactor in the dark, then the sample was heated at 573 K to collect the products. (b)Photooxidation of PO PO (20 pmol) and O2 (200 pmol) were introduced to the reactor, then the sample was irradiated for 1 h. After collecting products in gas phase, the sample was heated at 573 K to collect the adsorbed products. 

The photoreactivity results showed that the reactor reaches steady state conditions after a long period of time (ca. 70 h) from the beginning of the irradiation. At steady state conditions the main photooxidation product was benzaldehyde but also benzyl alcohol and traces of benzoic acid and phenol were detected at all the experimental conditions used. During the transient period, benzene together with CO2 were also produced. No significant evidence of CO2 production was observed at steady state conditions. These results obviously indicate that at the experimental conditions used the photoprocess does not give rise to a complete degradation of toluene. 

Joshi et al. (EPA), Research Triangle Park 440 glass reactor photooxidant studies... 

Numerous results from kinetic and mechanistic studies using photo-reactors have been obtained which have contributed significantly to an increase in our knowledge on atmospheric chemistry, in particularly in the gas phase. Some open questions still remain, e.g. the mechanisms of the photooxidation of aromatic hydrocarbons and the process of gas-to-particle conversion. More recently also aerosol studies are being carried out in chambers. Some very recent work has led now to a much better understanding of the photochemieal wall effects in chambers which produce OH radicals (Rohrer et al., 2005). 

Most of the reactor designs tested for the photooxidation of organic pollutants by solar radiation are Ti02 slurry reactors. The implementation of solar photocatalytic reactors has occurred concurrently with advances in thedesign of solar thermal collectors, given the important characteristics shared by these units. There are, however, specific constraints for the design of solar photocatalytic reactors. 

In brief, it is shown that combined photooxidation and photoreduction of organic and inorganic species can considerably enhance the efficiency of photocatalytic reactors. It is also expected that a proper selection of the cation will optimize simultaneous oxidation-reduction processes. 

DSO via molybdate-catalyzed disproportionation of HjOj provides a readily scalable alternative to photooxidation. It can be carried out in commonly available stirred-tank reactors. However, the reaction does not work at low temperatures and organic media are limitedto alcoholic polar solvents (methanol or the safer ethylene glycol) or to microstructured media such as one-, two-, or three-phase microemulsion systems. The latter based on balanced catalytic surfactants advantageously combine low surfactant concentration with easy product isolation and catalyst recycling via simple phase separation. Safe processing may be further enhanced by microreactors, which minimize peroxide hold-up. 

The same group greatly improved this process by a novel continuous-flow reactor setup design (Figure 23.6) [47]. For the photooxidation reaction, the... 

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