Timothy N. Obee

The viability of photocatalysis for air purification.

Photocatalytic oxidation (PCO) air purification technology is reviewed based on the decades of research conducted by the United Technologies Research Center (UTRC) and their external colleagues. UTRC conducted basic research on the reaction rates of various volatile organic compounds (VOCs). The knowledge gained allowed validation of 1D and 3D prototype reactor models that guided further purifier development. Colleagues worldwide validated purifier prototypes in simulated realistic indoor environments. Prototype products were deployed in office environments both in the United States and France. As a result of these validation studies, it was discovered that both catalyst lifetime and byproduct formation are barriers to implementing this technology. Research is ongoing at the University of Connecticut that is applicable to extending catalyst lifetime, increasing catalyst efficiency and extending activation wavelength from the ultraviolet to the visible wavelengths. It is critical that catalyst lifetime is extended to realize cost effective implementation of PCO air purification.

Computational and Experimental Studies of UV/Titania Photocatalytic Oxidation of VOCs in Honeycomb Monoliths

Abstract The use of honeycombs as monolith supports for UV/Titania photocatalysis of volatile organic compounds (VOCs) has been investigated theoretically and experimentally. A theoretical model based on analysis of the UV intensity distribution, transport of gaseous contaminants to the catalyzed surface, and surface photocatalytic destruction has been developed. Both diffuse and specular reflection models have been developed for the UV illumination calculations. The model uses measured intrinsic photocatalytic destruction rates determined in a research reactor which gives the concentration-, humidity-, and UV intensity-dependences of the rates. Model predictions have been compared to measurements in a high-flow, staged monolith, demonstration purifier for several gaseous contaminants of interest. Agreement between modeling and experiment is generally quite good. The sensitivity of purifier efficiency to monolith pore size and illuminated contact time is discussed. The performance obtained with honeycombs is comparable to that with porous foams, but with much reduced weight, pressure drop, and cost. The conclusion of this research is that honeycomb monoliths are attractive for use in practical UV/Titania photocatalytic devices, particularly at very high flow rates where pressure drop is a concern, and for those situations where monolith weight is an important design constraint.