1. Photocatalytic oxidation of toluene at indoor air levels (ppbv): Towards a better assessment of conversion, reaction intermediates and mineralization
- Author
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Sleiman, Mohamad, Conchon, Pierre, Ferronato, Corinne, and Chovelon, Jean-Marc
- Subjects
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PHOTOCATALYSIS , *OXIDATION , *TOLUENE , *INTERMEDIATES (Chemistry) , *CHEMICAL reactors , *TITANIUM dioxide , *THERMAL desorption , *VOLATILE organic compounds - Abstract
Abstract: We report here a new analytical methodology for the investigation of toluene photocatalytic removal at indoor-relevant concentration level (ppbv). Experiments were performed using an annular flow-through reactor with TiO2 as photocatalyst, toluene as a model VOC and under different ranges of relative humidity (RH: 0–70%), inlet concentration (20–400ppbv) and flow rate (70–350mLmin−1). Analysis of reaction intermediates was conducted using an automated thermal desorption technique coupled to GC–MS instrument (ATD–GC–MS) whereas a GC coupled to pulsed discharge helium ionization detector (GC–PDPID) was used for the first time for on-line measurements of CO and CO2 at ppbv level. Under these conditions, toluene conversion was up to 90–100% with a slight influence of inlet concentration and RH, whereas flow rate was found to be a prevalent factor. Mineralization (%) varied from 55 to 95% and has shown to be strongly inhibited by the increase of RH whereas flow rate and inlet concentration exhibited a negligible effect. The reaction intermediates were found to be different according to the RH level: in absence of water vapor, traces of low molecular weight carbonyls (formaldehyde, methyl glyoxal, etc.) were detected and quantified in the gas phase whereas at RH 40%, hydroxylated intermediates such as cresols and benzyl alcohol were observed. On the basis of identification results, a reaction mechanism was proposed involving mainly direct hole oxidation at dry conditions and hydroxylation by OH radicals at high RH level. [Copyright &y& Elsevier]
- Published
- 2009
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