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Platinum Metals Rev., 2003, 47, (4), 183

Magnetic Field Effects on Benzene Photodegradation


Since nuclear and electronic spin polarisation phenomena during chemical reactions were discovered, magnetic field effects on the kinetics of chemical reactions, especially those with free radicals, have been examined. As heterogeneous photocatalytic reactions in the presence of O2 produce free radicals and radical ions the reactions may be affected by magnetic fields.

Scientists from Fuzhou University, P. R. China, have now reported the effects of magnetic fields on the UV photocatalytic degradation at 65°C, of benzene using a synthesised 0.5% Pt/TiO2 catalyst (W. Zhang, X. Wang and X. Fu, Chem. Commun., 2003, (17), 2196–2197).

The catalyst was placed in a quartz tube, surrounded by an electromagnetic field vertical to the axes in the photoreactor, and benzene was supplied at 20 ml min−1. Benzene conversion and CO2 production were monitored. On application of magnetic field (59.42 mT) benzene conversion increased from 15.5 to 18%, and CO2 production increased from 52 to 175 ppm. On removing the field benzene conversion fell to 4%, and CO2 production fell to its initial value. Low field intensities suppressed benzene conversion, but at fields > 52 mT benzene conversion increased rapidly. CO2 production increased over the whole field range.

Removal and reapplication of the field produced a similar result, but putting fresh catalyst into a field produced little improvement. Without UV, Pt or catalyst, no reaction occurred. The results may be linked to decomposition of intermediate species on Pt. Reasons for the phenomena are unknown; further studies are in progress.

[In addition these are metals of very considerable industrial importance with a wide variety of applications; this will continue to be the case for a long time to come, and many new important applications will be found for them.]