Evaluation of photocatalysis for gas-phase air cleaning - Part 1 : process, technical, and sizing considerations

The results of a literature survey and an engineering analysis are presented that evaluate the process, technical, and sizing considerations of photocatalytic oxidation (PCO) as a commercial technology to treat (i.e., remove) low-level contaminants in feed streams of air. PCO uses the energy of photons from light sources to activate a catalyst. Upon activation, adsorbed gases, particularly molecular oxygen (O2), water vapor (H2O), and contaminant species, can participate in surface-mediated reactions that, under appropriate operating conditions, can produce and desorb product species, notably carbon dioxide (CO2) and H2O. Approximately 60 organic compounds have been studied in heterogeneous gasphase PCO, while only a few inorganic compounds have been
studied. With regard to commercial-scale applications, the present challenge is to design hotocatalytic treatment devices that have low pressure drop, make efficient use of light, and
employ a stable catalyst that can be readily regenerated if it becomes poisoned or deactivated. Presently, gas-phase heterogeneous photocatalysis will likely find application wherein (1) the gas-phase contaminants have been identified in a feed stream and demonstrated to be removed when the feed is passed through the PCO device and (2) reaction by-products have been studied and not found to be of concern.